[Elenco soci]


Di Angelo Luca

Professore Ordinario


Università degli Studi dell'Aquila
luca.diangelo@univaq.it

Sito istituzionale
SCOPUS ID: 57201549035
Orcid: 0000-0002-5341-0500



Pubblicazioni scientifiche

[1] Di Angelo L., Di Stefano P., Governi L., Marzola A., Volpe Y., Can MaWR-Method for Symmetry Plane Detection be Generalized for Complex Panfacial Fractures?, Lecture Notes in Mechanical Engineering, 148-158, (2023). Abstract
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Abstract: When dealing with craniofacial impairments, restoring the morphological condition is as crucial as restoring the functional ones to avoid psychosocial disabilities for the patient. For this aim, the accurate location of the midsagittal plane is essential for performing reliable symmetry analyses and guiding effective surgery planning. To provide a fully automatic and landmark-independent approach, capable of providing a midsagittal plane for craniofacial skeleton even from anatomical models with high asymmetries, an innovative method, called MaWR-method, was developed by the authors in a previous work. This paper further investigates the MaWR-method by evaluating its capacity to produce a successful outcome even in the worst-case scenario that may be considered in maxillofacial surgery, namely panfacial fractures. In all the test cases considered in this work, the method proved robust and reliable in its original design. It provided a consistent result requiring no user involvement, even when dealing with extreme asymmetries because of extensive and complex fractures.

Keywords: Feature recognition | Mid-sagittal plane | Symmetry analysis | Symmetry plane detection

[2] Di Angelo L., Di Stefano P., Guardiani E., The Morphological and Geometrical Segmentation of Human Thoracic and Lumbar Vertebrae: An Automatic Computer-Based Method, Lecture Notes in Mechanical Engineering, 306-317, (2023). Abstract
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Abstract: These authors presented an automatic computer-based method for morphological feature segmentation and recognition for thoracic and lumbar human vertebrae in a previous paper. The method analyses high-density discretized models by segmentation and recognition rules codifying the vertebra morphology information, which does not change between different subjects. The methodology has been demonstrated to be valid and repeatable in segmenting and recognizing morphological features of vertebrae. The proposed one gives repeatable and reproducible results concerning the traditional manual methods. Nonetheless, the method has been tested only on human lumbar and thoracic vertebrae without distinctive pathologies. This paper aims to extend this methodology for much wider use by analyzing single vertebrae affected by common defectiveness in archaeological and medical fields. The results of the experimentations, analyzed by a skilled anthropologist and radiologist, show that the method correctly segments the analyzed morphological features, also for thoracic and lumbar vertebrae with defectiveness: in particular, defects that alter the shape of features or the symmetry of the vertebra, determine the absence of a feature, or heavily change the spatial distribution of the anterior part respect to the posterior one, have been analyzed.

Keywords: 3D medical image analysis | Feature recognition | Thoracic and lumbar vertebrae analysis | Vertebrae analysis computer-based methods

[3] Alicandro M., Di Angelo L., Di Stefano P., Dominici D., Guardiani E., Zollini S., Fast and Accurate Registration of Terrestrial Point Clouds Using a Planar Approximation of Roof Features, Remote Sensing, 14(13), (2022). Abstract
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Abstract: 3D reconstructed models are becoming more diffused daily, especially in the Cultural Heritage field. These geometric models are typically obtained from elaborating a 3D point cloud. A significant limit in using these methods is the realignment of different point clouds acquired from different acquisitions, particularly for those whose dimensions are millions of points. Although several methodologies have tried to propose a solution for this necessity, none of these seems to solve definitively the problems related to the realignment of large point clouds. This paper presents a new and innovative procedure for the fine registration of large point clouds. The method performs an alignment by using planar approximations of roof features, taking the roof’s extension into account. It looks particularly suitable for the alignment of large point clouds acquired in urban and archaeological environments. The proposed methodology is compared in terms of accuracy and time with a standard photogrammetric reconstruction based on Ground Control Points (GCPs) and other ones, aligned by the Iterative Closest Point method (ICP) and markers. The results evidence the excellent performance of the methodology, which could represent an alternative for aligning extensive photogrammetric reconstructions without the use of GCPs.

Keywords: multi-UAV scanning registration | particle swarm optimization | point cloud registration | shape features recognition

[4] Di Angelo L., Di Stefano P., Guardiani E., A review of computer-based methods for classification and reconstruction of 3D high-density scanned archaeological pottery, Journal of Cultural Heritage, 56, 10-24, (2022). Abstract
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Abstract: Ceramics analysis, classification, and reconstruction are essential to know an archaeological site's history, economy, and art. Traditional methods used by the archaeologists for their investigation are time-consuming and are neither reproducible nor repeatable. The results depend on the operator's subjectivity, specialization, personal skills, and professional experience. Consequently, only a few indicative samples with characteristic components are studied with wide uncertainties. Several automatic methods for analysing sherds have been published in the last years to overcome these limitations. To help all the involved researchers, this paper aims to provide a complete and critical analysis of the state-of-the-art until the end of 2021 of the most important published methods on pottery analysis, classification, and reconstruction from a 3D discrete manifold model. To this end, papers in English indexed by the Scopus database are selected by using the following keywords: “computer methods in archaeology”, “3D archaeology”, “3D reconstruction”, “3D puzzling”, “automatic feature recognition and reconstruction”. Additional references complete the list found through the reading of selected papers. The 125 selected papers, referring to only archaeological potteries, are divided into six groups: 3D digitalization, virtual prototyping, Fragment features processing, geometric model processing of whole-shape pottery, 3D Vessel reconstruction from its fragments, classification, and 3D information systems for archaeological pottery visualization and documentation. In the present review, the techniques considered for these issues are critically analysed to highlight their pros and cons and provide recommendations for future research.

Keywords: Automatic features recognition | Computer methods in archaeology | Computer-based methods for sherds classification and reconstruction | Mesh segmentation | Pottery profile detection | Pottery profile dimensions

[5] Di Angelo L., Di Stefano P., Morabito A.E., Measurement of constant radius swept features in cultural heritage, Journal of Physics: Conference Series, 2204(1), (2022). Abstract
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Abstract: The dimensional characterization of archaeological fragment is a very complex operation and could prove to be useful for identifying the presence of standard attributes in the ceramics found from a specific archaeological site, or for making comparisons and analysis of similarities or for studying ancient technologies used for manufacture of objects. The dimensional analysis of the fragments is now carried out manually with traditional measuring devices. Typically, the results obtained are inaccurate and non-repeatable measurements. This paper focuses on the dimensional characterization of a specific geometric class of features: the constant radius swept features (called here CRS features). Several archaeological features, such as rims, bases, decorative motifs, processing marks and grooves are referable from a geometric point of view to the class of CRS features. These are detail features, which may be very interesting for the investigation of some aspects related to the historical-archaeological classification of the find. CRS features are often found on worn, damaged (e.g. chipped) or fragmented objects; they are frequently characterized, from a geometric point of view, by free form surfaces and by a limited cross sectional extension. In some cases, CRS features can be of axially symmetrical geometry: this occurs quite frequently in the case of archaeological pottery. For all these reasons, it is often difficult to apply traditional manual methods for the quantitative dimensional characterization of CRS features. This paper describes an original methodology for the measurement of CRS features acquired by scanning technologies. The algorithmic implementation of this methodology, consisting of a suitable processing of the feature nodes, allows to carry out automatically the dimensional characterization of the feature.

[6] Di Angelo L., Di Stefano P., Forgione A., Guardiani E., Pane C., A computer-based method for the accurate analysis of the trilobate spouts found in the cathedral of Amiternum, Journal of Physics: Conference Series, 2204(1), (2022). Abstract
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Abstract: The traditional manual method of analysis of ceramic finds involves expert operators in long and routine activities whose results depend on their subjectivity, specialization, and professional experience. This implies that the analysis of sherds is carried out using few data affected by high uncertainty. These limitations are even more clear with fragments with small axially symmetric portions whose elements of the investigation are not axially symmetric, such as handles, spouts, decorations. In this way both the axis of symmetry of the original object and the reference planes and/or axes of the characteristic dimensions of the elements are identified with such approximations as to compromise subsequent analyses and comparisons. To overcome these limitations, in this paper a new computer-based procedure is proposed. As a case study, the analysis fragments of jugs/bowls with trilobed spouts found in the site of Amiternum, coming from 12th-13th century contexts are considered; their analysis is fundamental to analyze the site where they were found since there is no archival documentation about their use.

[7] Di Angelo L., Mancini E., Di Stefano P., Numerical methodology for design and optimization of a connecting rod for very high speed engines, International Journal on Interactive Design and Manufacturing, 16(1), 109-134, (2022). Abstract
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Abstract: Motorsports equipment design is a complex and evolving engineering discipline, whose driving factor for each component is maximizing the weight reduction, ensuring its operation and in-service life imposed by the regulations. The design complexity in this field is because all key components are subject to high and time-varying stresses. Top teams in high-tech categories can invest large amounts of money in developing and applying sophisticated CAE systems. Such economic commitment is not sustainable for all those teams operating in strategic categories where the production of vehicles and their components are in the hands of small realities, such as karts or mini-motorcycles. In these fields, the most common design approach is the trial and error on physical prototypes. Such an inefficient approach leads to high costs, and, for the rough exploration of the design space, a very low innovation for every component. To overcome these limitations, the presented paper proposes a systematic methodology for the structural design of high-speed engine parts, accessible also to small artisan teams. The method is based on the use of commercial CAD and CAE software; it analyses a 3D CAD model comprising all the components of the whole kinematic chain to which the element to be considered belongs. The FE model is built by setting appropriate boundary conditions on all the components of the above-mentioned chain and imposing, on the element to be studied, for each kinematic configuration, all the acting loads, including the inertial ones. This methodology is here applied to the redesign of a connecting rod of the engine for go-kart competitions. The obtained results are critically discussed and compared with the key methods available in the literature: static analysis and quasi-dynamic analysis. The results evidence methods presented in the literature do no work in presence of high inertia loads: for some crank angles, the stress level got is higher than the yield stress. Instead, by using the proposed method, the consistency of safety coefficient values with those available in the literature is obtained. The proposed methodology could lead to an increase in innovation and in a time and cost reduction during the development process of the motorsport engines having a high specific power obtained with high rotation speeds. This could determine a decrease in the cost of race vehicles with an expansion of potential practitioners of these strategic categories.

Keywords: Connecting rod optimization | Fatigue | FE model | High inertia loads

[8] Romano D., Di Angelo L., Kovacevic-Badstubner I., Grossner U., Parise M., Antonini G., Efficient partial elements computation for the non-orthogonal PEEC method including conductive, dielectrics and magnetic materials, IEEE Transactions on Magnetics, (2022). Abstract
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Abstract: The partial element equivalent circuit method is a well-known numerical technique that is used to solve Maxwell’s equations in their integral equation form. The application of the PEEC method to modeling domains with non-orthogonal three-dimensional geometries requires the computation of the interaction integrals to be performed numerically, thus slowing down the overall computation. This work presents a new technique that allows improving the computation of the interaction integrals of the PEEC method for non-orthogonal geometries under the quasi-static hypothesis. To this purpose, a voxelization approach that automatically decomposes non-orthogonal volumes in elementary parallelepipeds is used, allowing the implementation of closed-form formulas for the interaction integrals and completely avoiding numerical integration. The proposed approach is applied to three example problems exhibiting very good accuracy and excellent speed-up compared to the standard one using the numerical integration.

Keywords: Equivalent circuits | Geometry | Integral equations | Integral equations | Magnetic circuits | Magnetic domains | magnetic fields | magnetic material modeling | Mathematical models | partial element equivalent circuit (PEEC) method | Standards | voxel

[9] Di Angelo L., Di Stefano P., Morabito A., Automatic Segmentation of Sweep Features of Constant Radius from Archaeological Artifacts, Lecture Notes in Mechanical Engineering, 901-908, (2022). Abstract
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Abstract: The sweep features of constant radius are particularly significant for the purposes of the historical-archaeological investigation and classification of ancient artifacts. The paper focuses on the automatic recognition of this specific class of features from triangulated 3D models experimentally acquired from cultural heritage objects. This is not a trivial problem. The ancient artifacts, although repeatable, are unique handmade pieces with a geometry commonly characterized by complex and non-analytical shapes. Their surfaces are also usually damaged and worn, so that the related geometric properties are altered or lost. The methodology proposed here is inspired by the one previously developed by the authors for the automatic segmentation of fillets, rounds and grooves from high-density triangulated models of mechanical components. The paper, in particular, focuses on the aspects of this methodology that must be tuned to allow the recognition of the sweep features of constant radius from archaeological finds. The methodology has been implemented and finally applied to an archaeological find acquired by a laser scanner.

Keywords: 3D archaeology | 3D digital models | Computer methods in archaeology | Feature recognition | Laser scanning

[10] Di Angelo L., Di Stefano P., Guardiani E., Pane C., A Review on Computer-Based Methods for Archeological Pottery Classification and Reconstruction, Lecture Notes in Mechanical Engineering, 909-919, (2022). Abstract
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Abstract: The knowledge of the history, economy, and art of an archeological site is based on information that can be taken from ceramics analysis, classification, and reconstruction. The traditional methods used by the archeologists for their investigation are time-consuming, not reproducible, and repeatable, and the results depend on the subjectivity, specialization, personal skills, and professional experience of the operator. An as consequence, only a few indicative samples that have characteristic components are analyzed with wide uncertainties. In order to overcome these limitations, in the last years, some automatic methods for studying archeological pottery’s findings are proposed in the literature. To help all the researchers involved in this field, this paper aims to provide a complete and critical analysis of the state-of-the-art until the end of 2020 of the published methods on pottery classification and reconstruction from a 3D discrete manifold model. For this purpose, papers in English by the Scopus database are collected by using the following keywords: “computer methods in archaeology”, “3D archaeology”, “3D reconstruction”, “automatic feature recognition and reconstruction”, “3D puzzling”. The list is completed by additional references found through the reading of selected papers. The 35 selected papers are divided into three groups: Geometric model fragment processing, 3D information systems for archaeological pottery visualization and documentation, 3D puzzling of archaeological fragments. The results of the present review are focused on the presentation of the pros and cons of the techniques used on these different issues.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Computer-based methods for sherd classification and reconstruction | Surface segmentation

[11] Di Angelo L., Di Stefano P., Guardiani E., A Photogrammetry Reconstruction of Emissario Romano in Capistrello, Lecture Notes in Mechanical Engineering, 920-929, (2022). Abstract
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Abstract: UAV Photogrammetry is a quite widely use technology for 3D reconstruction of territory, thanks to its satisfying results in many fields of applications and its low cost. Most of researches that addressed this topic use Ground Control Points (GCPs) for scaling and georeferencing the acquired point-cloud. In this paper, due to the particular morphology of the surveyed territory that makes very difficult to define GCPs in the region of interest, an innovative technique based on geometrical features was used for orienting, scaling and georeferencing the 3D point-cloud. The case is the ancient Roman outlet of the Fucino emissary, sited in a very steep and not accessible area, near Capistrello (AQ) city, Italy. The obtained results show that the proposed methodology, although less accurate than standard one using GCPs, provides quite good results, so that it can be used where the use of GCPs is difficult or impossible.

Keywords: Archaeology | Feature-based alignment | UAV photogrammetry

[12] Di Angelo L., Di Stefano P., Guardiani E., An automatic method for feature segmentation of human thoracic and lumbar vertebrae, Computer Methods and Programs in Biomedicine, 210, (2021). Abstract
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Abstract: Background and objective: Because of the three-dimensional distribution of morphological features of human vertebrae and the whole spine, in recent years, to make more precise diagnoses and to design optimized surgical procedures, new protocols have been proposed based on analysing their three-dimensional (3D) models. In the related literature, processes of segmentation and morphological features recognition are essentially performed by a skilled operator that selects the interesting areas. So, being affected by the preparation and experience of the operator, this produces an evaluation that is poorly reproducible and repeatable for the uncertainties of a typical manual measurement process. Methods: To overcome this limitation, in this paper a new automatic method is proposed for feature segmentation and recognition of human vertebrae. The proposed computer-based method, starting from 3D high density discretized models of thoracic and lumbar vertebrae, automatically performs both the semantic and geometric segmentation of their morphological features. The segmentation and recognition rules codify some important definitions used in the traditional manual method, considering all the vertebra morphology information that is invariant inter-subject. Results: The automatic method proposed here is verified by analysing many real vertebrae, both acquired using a 3D scanner and coming from Computerized Tomography (CT) scans. The obtained results are critically discussed and compared with the traditional manual methods for vertebra analysis. The method has proven to be robust and reliable in the segmentation and recognition of morphological features of vertebrae. Furthermore, the proposed automatic method avoids the blurring of quantitative parameters get from vertebrae, resulting from poor repeatability and reproducibility of manual methods used in the state-of-the-art. Conclusions: Starting from the automatic segmentation and recognition here proposed, it is possible to automatically calculate the parameters of thoracic or lumbar vertebrae used in archaeology, medicine, or biomechanics or define their new ones.

Keywords: 3D medical image analysis | Computer methods for vertebra analysis | Shape segmentation | Thoracic and lumbar vertebrae | Three-dimensional measurement

[13] Angelo L.D., Romano D., Antonini G., Kovacevic-Badstubner I., Grossner U., Efficient computation of partial elements for non-orthogonal PEEC meshes, 2021 Joint IEEE International Symposium on Electromagnetic Compatibility Signal and Power Integrity, and EMC Europe, EMC/SI/PI/EMC Europe 2021, 692-696, (2021). Abstract
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Abstract: The partial element equivalent circuit (PEEC) method has proven to be able to provide a valid solution method of the Maxwell's equations in the time as well as the frequency domain. The extension of the basic PEEC approach to non-orthogonal geometries has significantly expanded the applicability of the method. The computation of interaction integrals is typically performed numerically and it results to be time-consuming. This work presents a new flexible and accurate computational method for determining the partial inductances in the quasi-static limit. More specifically, an automatic decomposition of the non-orthogonal geometries into parallelepipeds is proposed so that analytical formulas which are available in this case can be used. The accuracy, and speed of the proposed method is compared with standard integration routines exhibiting a satisfactory accuracy and reduced computation time.

[14] Di Angelo L., Duronio F., De Vita A., Di Mascio A., Cartesian mesh generation with local refinement for immersed boundary approaches, Journal of Marine Science and Engineering, 9(6), (2021). Abstract
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Abstract: In this paper, an efficient and robust Cartesian Mesh Generation with Local Refinement for an Immersed Boundary Approach is proposed, whose key feature is the capability of high Reynolds number simulations by the use of wall function models, bypassing the need for accurate boundary layer discretization. Starting from the discrete manifold model of the object to be analyzed, the proposed model generates Cartesian adaptive grids for a CFD simulation, with minimal user interactions; the most innovative aspect of this approach is that the automatic generation is based on the segmentation of the surfaces enveloping the object to be analyzed. The aim of this paper is to show that this automatic workflow is robust and enables to get quantitative results on geometrically complex configurations such as marine vehicles. To this purpose, the proposed methodology has been applied to the simulation of the flow past a BB2 submarine, discretized by non-uniform grid density. The obtained results are comparable with those obtained by classical body-fitted approaches but with a significant reduction of the time required for the mesh generation.

Keywords: Cartesian adaptive grids | Immersed boundaries | LES simulation

[15] Di Angelo L., Di Stefano P., Guardiani E., Morabito A.E., A 3d informational database for automatic archiving of archaeological pottery finds, Sensors (Switzerland), 21(3), 1-18, (2021). Abstract
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Abstract: From archaeological excavations, huge quantities of material are recovered, usually in the form of fragments. Their correct interpretation and classification are laborious and time-consuming and requires measurement, analysis and comparison of several items. Basing these activities on quantitative methods that process 3D digital data from experimental measurements allows optimizing the entire restoration process, making it faster, more accurate and cheaper. The 3D point clouds, captured by the scanning process, are raw data that must be properly processed to be used in automatic systems for the analysis of archeological finds. This paper focuses on the integration of a shape feature recognizer, able to support the semantic decomposition of the ancient artifact into archaeological features, with a structured database, able to query the large amount of information extracted. Through the automatic measurement of the dimensional attributes of the various features, it is possible to facilitate the comparative analyses between archaeological artifacts and the inferences of the archaeologist and to reduce the routine work. Here, a dedicated database has been proposed, able to store the information extracted from huge quantities of archaeological material using a specific shape feature recognizer. This information is useful for making comparisons but also to improve the archaeological knowledge. The database has been implemented and used for the identification of pottery fragments and the reconstruction of archaeological vessels. Reconstruction, in particular, often requires the solution of complex problems, especially when it involves types of potsherds that cannot be treated with traditional methods.

Keywords: 3D archaeology | Computer methods in archaeology | Information search and retrieval | Measurement precision in archaeol-ogy | Similarity metric

[16] Eslami D., Di Angelo L., Di Stefano P., Guardiani E., A semi-automatic reconstruction of archaeological pottery fragments from 2D images using wavelet transformation, Heritage, 4(1), 76-90, (2021). Abstract
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Abstract: The problem of matching fragments of three-dimensional (3D) objects has gained increasing attention, and several approaches have been developed to solve this problem. To date, however, to the best knowledge of the authors, there is no computer-based method supporting archaeologists in this activity. For this purpose, in this paper, a semi-automatic approach is proposed for the reconstruction of archaeological pottery fragments based on two-dimensional (2D) images. Firstly, the method, considering the curves as features, involves the extraction of edge curves by applying the Canny filter algorithm to the fragments’ image. Next, the wavelet transformation method is used to fit the edge curves and obtain the approximation coefficients. Then, the correlation coefficients between fragments are computed and the matching of fragments is done by comparing their values. The proposed approach is tested on some real cases. The results of the experimentation show, if compared with the state-of-the-art, that the method seems to be efficient and accurate in the reconstruction of pottery from 2D images of their fragments.

Keywords: Edge detection | Pottery fragment | Reconstruction | Wavelet transformation

[17] Di Angelo L., Di Stefano P., Guardiani E., An advanced GCode analyser for predicting the build time for additive manufacturing components, Acta IMEKO, 9(4), 30-38, (2020). Abstract
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Abstract: Additive manufacturing is a technology for quickly fabricating physical models, functional prototypes, and small batches of parts by stacking two-dimensional layered features directly from computer-aided design data. One of the most important challenges in this sector relates to the capability to predict the build time in advance, since this is crucial to evaluating the production costs. In this paper, an accurate method for obtaining build-time is proposed. This method is based on an advanced GCode analyzer written in Python following an object-oriented paradigm for scalability and maintainability. Various examples are used to demonstrate the reliability of the algorithm, while its potential applications are also illustrated.

Keywords: Additive manufacturing | Build time estimation | Manufacturing costs | Process planning

[18] Angelo L.D., Stefano P.D., Guardiani E., Pane C., Automatic shape feature recognition for ceramic finds, Journal on Computing and Cultural Heritage, 13(3), (2020). Abstract
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Abstract: Ceramic sherds are the most common finds in archaeology. They are complex to analyze and onerous to process. A large number of indistinct sherds coming from excavations must be preliminarily grouped in some categories. This clusterization helps the next phase, in which archaeologists classify the ceramics. Due to the difficulty of these preliminary, repetitive, and routine phases, a great deal of archaeological material remains unstudied in museum repositories or archaeological sites. An effective method to automate these routine phases is presented in this article. The proposed method performs a shape feature segmentation of the sherds, which is fundamental to undertake any further analysis, such as potsherds classification, reconstruction, or cataloging. A set of specific shape features, useful to understand the find properties, is defined and methods for recognizing them are proposed. The method's performance is tested in the analysis of some real, critical cases.

Keywords: 3D archaeology | Automatic feature recognition | computer methods in archaeology | surface segmentation

[19] Di Angelo L., Di Stefano P., Guardiani E., Search for the optimal build direction in additive manufacturing technologies: A review, Journal of Manufacturing and Materials Processing, 4(3), (2020). Abstract
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Abstract: By additive manufacturing technologies, an object is produced deposing material layer by layer. The piece grows along the build direction, which is one of the main manufacturing parameters of Additive Manufacturing (AM) technologies to be set-up. This process parameter affects the cost, quality, and other important properties of the manufactured object. In this paper, the Objective Functions (OFs), presented in the literature for the search of the optimal build direction, are considered and reviewed. The following OFs are discussed: part quality, surface quality, support structure, build time, manufacturing cost, and mechanical properties. All of them are distinguished factors that are affected by build direction. In the first part of the paper, a collection of the most significant published methods for the estimation of the factors that most influence the build direction is presented. In the second part, a summary of the optimization techniques adopted from the reviewed papers is presented. Finally, the advantages and disadvantages are briefly discussed and some possible new fields of exploration are proposed.

Keywords: Build orientation factors | Cost analysis | Multi objective optimization | Part build orientation

[20] Eslami D., Di Angelo L., Di Stefano P., Pane C., Review of computer-based methods for archaeological ceramic sherds reconstruction, Virtual Archaeology Review, 11(23), 34-49, (2020). Abstract
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Abstract: Potteries are the most numerous finds found in archaeological excavations; they are often used to get information about the history, economy, and art of a site. Archaeologists rarely find complete vases but, generally, damaged and in fragments, often mixed with other pottery groups. By using the traditional manual method, the analysis and reconstruction of sherds are performed by a skilled operator. Reviewed papers provided evidence that the traditional method is not reproducible, not repeatable, time-consuming and its results have great uncertainties. To overcome the aforementioned limits, in the last years, researchers have made efforts to develop computer-based methods for archaeological ceramic sherds analysis, aimed at their reconstruction. To contribute to this field of study, in this paper, a comprehensive analysis of the most important available publications until the end of 2019 is presented. This study, focused on pottery fragments only, is performed by collecting papers in English by the Scopus database using the following keywords: "computer methods in archaeology", "3D archaeology", "3D reconstruction", "automatic feature recognition and reconstruction", "restoration of pottery shape relics". The list is completed by additional references found through the reading of selected papers. The 53 selected papers are divided into three periods of time. According to a detailed review of the performed studies, the key elements of each analyzed method are listed based on data acquisition tools, features extracted, classification processes, and matching techniques. Finally, to overcome the actual gaps some recommendations for future researches are proposed.

Keywords: 3D archaeology | 3D reconstruction | Automatic feature recognition and reconstruction | Computer methods in archaeology | Restoration of pottery shape relics

[21] Di Angelo L., Di Stefano P., Dolatnezhadsomarin A., Guardiani E., Khorram E., A reliable build orientation optimization method in additive manufacturing: the application to FDM technology, International Journal of Advanced Manufacturing Technology, 108(1-2), 263-276, (2020). Abstract
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Abstract: Additive manufacturing (AM) is a group of processes which manufacture a part by adding sequential layers of material on each other. In the last decade, these processes have been extensively applied in industry for constructing small volumes of complex, customized parts. Since parts are built layer-by-layer, the build orientation affects the surface quality and the total cost of the part. The search for optimal build orientation is not trivial since these factors are, typically, in conflict with each other. The major limitation of the methods described in the literature to choose the optimal build direction is in the insufficient accuracy of the estimates of the manufacturing cost and of the surface quality. These factors are very complex to be estimated, and accuracy in their evaluation requires methods that are very time-consuming. On the contrary, in practical use, a multi-objective optimization process requires an objective function that is reliable and easy to be evaluated. In order to overcome these problems, in this paper, original methods to estimate the manufacturing cost and surface quality as a function of build orientation are presented. They are implemented, for the fused deposition modeling (FDM) technology, in a multi-objective optimization problem that is solved by an S-metric selection evolutionary multi-objective algorithm (SMS-EMOA), obtaining an approximation of the Pareto front. The final selection of the recommended orientation is performed by the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Properly designed case studies are used to evaluate the reliability of the proposed method, and the results are compared with the state-of-the-art method to find optimal build orientation.

Keywords: Additive manufacturing | Build orientation | Multi-objective optimization | Surface quality

[22] Angelo L.D., Gherardini F., Stefano P.D., Leali F., Design for visual quality enhancement of artificial infrastructure facilities: An application to electricity pylons, Applied Sciences (Switzerland), 10(3), (2020). Abstract
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Abstract: (1) Background: The visual impact of artificial infrastructures on natural landscapes generates a common negative perception in public opinion. However, as in the case of electrical energy, the increasing demand for power supply and its need for capillary distribution require the installation of new lines, commonly overhead lines with tall tower-like pylons. In most countries, this situation is faced with many attempts of solutions, as participatory workshops and design contests. Nevertheless, the solutions are usually not further developed into real structures due to many limitations (e.g., regulatory, safety, lack of feasibility). (2) Methods: This paper presents a systematic method for the design of tower-like pylons (e.g., electric ones) able to improve the visual quality on the landscape areas in which they will be installed. The method identifies a design strategy that advantageously exploits the inevitable visual impact of pylons on the landscape by integrating the symbolic morphology and the topologically optimized pylon structure from the earliest design phases. (3) Results: The resulting structure is designed in three steps. First, a concept is morphologically developed by integrating symbolic references to the landscape, environment, or cultural society. Second, the concept is topologically optimized, by reducing the structural weight and its visual impact, and respecting regulatory requirements. Third, the resulting structure is engineered and embodied into an industrially feasible layout. (4) Conclusions: The method is able to develop an original, brand new tower-like pylon integrating all the types of requirements, such as regulatory, industrial feasibility, and social components' needs. The resulting electricity pylon presents an enhanced visual quality according to the citizens' feedback.

Keywords: Electricity pylon | Integrated design method | Topology optimization | Visual impact improvement

[23] Di Angelo L., Di Stefano P., Morabito A.E., Guardiani E., Point clouds registration based on constant radius features for large and detailed cultural heritage objects, 2020 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage, 168-173, (2020). Abstract
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Abstract: The registration permits to positioning in a single reference system point clouds acquired from different points of view. Since this is typically obtained with an iterative numerical method, it represents an important source of error in the entire reverse engineering process. As all iterative methods, such errors depend on the choice of the initial solution; therefore, this process requires an expert user who, by using dedicated software, choices the sequence of clouds to be registered, imposes for each pairwise the first attempt registration, launches the iterative method, and verifies the final result. With the aim to minimize the error and the user's interaction, some devices are proposed in the market (turntable or the anthropomorphic arm, etc.). The above-mentioned hardware and software tools cannot be used in the cultural heritage applications involving large and detailed objects. In this paper, an automatic alignment method of point clouds is proposed. The method uses as inputs the constant radius features, which are frequently detectable on cultural heritage objects. The automatic alignment of the point clouds is based on the recognition, the segmentation, and the registration of the sweep lines identifiable from these features.

[24] Renzi C., Di Angelo L., Leali F., Automotive Design Engineering: Material and Processes Selection Problems, Lecture Notes in Mechanical Engineering, 373-384, (2020). Abstract
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Abstract: Multicrieria Decision-making methods (MCDM) are efficiently used as a support to engineering design, even if tested procedures and experience-based approaches are often preferred in SMEs and several industrial contexts. An extended critical review investigates how decision-making methods can help solving engineering design problems in automotive design. In particular, in this work, a classification of decision-making methods related to engineering design, is proposed, in which decisional techniques are matched with the design phases, and to corresponding automotive industry design problems. In literature a large amount of paper is dedicated to the selection of materials and manufacturing processes in the detail design phase. Also, hybrid methods, namely a combination of decision-making methods with other mathematical methods will be investigated to overcome some methodological drawbacks in MCDM methods. Due to the high impact of the problem in both industrial and research field, this work could help increasing production rate by reducing redesign errors related to material/processes selection problems, and concurrently transferring the knowledge of decision-making methods within the industrial context.

Keywords: Automotive design | Detail design | Material selection | Multicriteria decision making

[25] Di Angelo L., Di Stefano P., Guardiani E., A Build-Time Estimator for Additive Manufactured Objects, Lecture Notes in Mechanical Engineering, 925-935, (2020). Abstract
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Abstract: Additive Manufacturing is a very time consuming technology. An estimation of the build time is fundamental to: Evaluate the production cost in budgeting process.Make use of optimization methods, which use as parameter the build time, for determining optimal build direction. In both these cases a fast and valid build time estimator, which can work with a few input data deducible from geometric model, is required. In the proposed paper a reliable parametric-based method to determine the build time for additive manufactured objects is provided. The implemented method is based on a back-propagation artificial neural network, which gives the possibility to implement the complex functions that elapse some driving build-time factors and the build time. The neural network training is based on data provided by a properly developed analyzer of the list of commands given to AM machines, which performs an analytical estimation of the build time. The implementation of the proposed methodology is illustrated and some comparisons between the real and estimated build-time are provided, then the results are critically analyzed.

Keywords: Adaptive model | Additive Manufacturing | Build time estimation | Process planning

[26] Di Angelo L., Di Stefano P., Morabito A.E., Automatic Segmentation of Constant Radius Secondary Features from Real Objects, Lecture Notes in Mechanical Engineering, 201-212, (2020). Abstract
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Abstract: Secondary features, such as fillets, rounds, chamfers and grooves, are simple transitions between primary features, generally introduced in order to remove the sharp edges created by the intersection of primary features. Being able to distinguish secondary from primary features is important in various application contexts, such as reverse engineering, automatic geometric inspection of real scanned objects, and for preparation of models for FEM analysis and CNC tool-path generation. The process for the recognition of secondary features from high-density tessellated models of real work-pieces is intrinsically complex for several reasons. This explains why, currently, there are no methodologies able to recognize automatically secondary features and the investigation on secondary features is mostly focused on B-Rep models. In a previous paper, the authors proposed a method for secondary features recognition from discrete geometric models synthetically generated. Here the methodology is extended to discrete geometric models experimentally acquired, for which the recognition is a very complex process, due to the object discretization, to its non-ideal geometry and to measurement errors.

Keywords: Blending features | Feature recognition | Fuzzy logic | Point cloud segmentation

[27] Angelo L.D., Di Stefano P., Renzi C., Leali F., A design methodology for an innovative racing mini motorcycle frame, Computer-Aided Design and Applications, 17(6), 1116-1129, (2020). Abstract
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Abstract: Sports equipment design is a young and evolving engineering discipline focused on the best simultaneous optimization of user and product as a system. In motorsports, in particular, the final performance during a race depends on many parameters related to the vehicle, circuit, weather, and tyres and the personal feelings of every single driver. Top teams in high-tech categories can invest huge amounts of money in developing simulators, but such economic commitment is not sustainable for all those teams that operate in minor but very popular categories, such as karts or mini-motorcycles. In these fields, the most common design approach is trial and error on physical prototypes. Such an approach leads to high costs, long optimization times, poor innovation, and inefficient management of the design knowledge. The present paper proposes a driver centred methodology for the design of an innovative mini racing motorcycle frame. It consists of two main phases: the drivers’ feelings translation into engineering requirements and constraints, and the exploration of the design solution space. Expected effects of the application of the proposed methodology are an overall increase in the degree of innovation, time compression, and cost reduction during the development process, with a significant impact on the competitiveness of small racing teams in minor categories.

Keywords: Design methodology | Racing motorcycle frame design | Topological optimization

[28] Morabito A.E., Di Angelo L., Di Stefano P., Guardiani E., Pane C., 3D virtual reconstruction of the ancient Roman incile of the fucino lake, Sensors (Switzerland), 19(16), (2019). Abstract
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Abstract: The construction of the artificial emissary of Fucino Lake is one of the most ambitious engineering buildings of antiquity. It was the longest tunnel ever made until the 19th century and, due to the depth of the adduction inlet, it required a monumental and complex incile, which, for functionality, cannot be compared to other ancient emissaries. The Roman emissary and its "incile" (Latin name of the inlet structure) were almost completely destroyed in the 19th century, when Fucino Lake was finally dried. Today, only few auxiliary structures such as wells, tunnels, and winzes remain of this ancient work. As evidence of the ancient incile remains a description made by those who also destroyed it and some drawings made by travelers who, on various occasions, visited the site. This paper presents a virtual reconstruction of the Roman incile, obtained both through the philological study of the known documentation, interpreting iconographic sources that represent the last evidence of this structure, and through the survey on the territory. The main purpose is to understand its technical functionalities, the original structures, and its evolution during the time, taking into account the evolution of the Fucino Lake water levels, technological issues, and finally o_ering its visual reconstruction.

Keywords: 3D virtual reconstruction This research received no external funding | Archaeology | Monumental heritage | Remote sensing

[29] Di Angelo L., Di Stefano P., Guardiani E., A build time estimator for Additive Manufacturing, 2019 IEEE International Workshop on Metrology for Industry 4.0 and IoT, MetroInd 4.0 and IoT 2019 - Proceedings, 344-349, (2019). Abstract
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Abstract: Additive Manufacturing (AM) is a technology for quickly fabricating physical models, functional prototypes and small batches of parts, by stacking two-dimensional layered features, directly from computer-aided design (CAD) data. One of the most important challenges in this sector is represented by the capacity to predict in advance build time required for manufacturing a part because it's crucial to evaluate production cost. In this paper, an accurate method for obtaining build time is proposed. This method is based on an advanced GCode reader written in Python following an Object Oriented paradigm for scalability and maintainability. Some examples were used to demonstrate the reliability of the algorithm and possible uses of it are illustrated.

[30] Di Angelo L., Di Stefano P., Morabito A.E., Fillets, rounds, grooves and sharp edges segmentation from 3D scanned surfaces, CAD Computer Aided Design, 110, 78-91, (2019). Abstract
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Abstract: Fillets, rounds, chamfers and grooves are secondary features which are typically present in real manufactured mechanical components to satisfy some manufacturing and functional requirements. Despite the broad array of research conducted on feature recognition, the investigation of secondary features is a relatively new topic. All of the pertinent studies have been focusedonly on the recognition of secondary features from B-Rep models. The recognition and segmentation of secondary features from a discrete model is a non-trivial problem due to the same geometric descriptors that may be applied to both primary and secondary features. Moreover, although in real-world mechanical parts primary features are planes, cylinders or cones, the secondary features may be non-analytical and complex-shaped geometries. Further sources of uncertainty are the measurement errors and non-ideal geometries of the real objects to which the method is applied. To overcome these problems, a new and original method to segment secondary features of tessellated geometric models is proposed. The method is based on the analysis of geometric-differential properties and provides specific strategies that reduce its sensitivity to all of the above-mentioned uncertainties without affecting its selectivity. The proposed method, described in detail in this paper, is tested in some very critical cases, and the results are presented and discussed.

Keywords: 3D mesh segmentation | 3D scanning | Blending features | Features recognition | Fuzzy logic | STL

[31] Di Angelo L., Di Stefano P., Governi L., Marzola A., Volpe Y., A robust and automatic method for the best symmetry plane detection of craniofacial skeletons, Symmetry, 11(2), (2019). Abstract
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Abstract: The accurate location of the mid-sagittal plane is fundamental for the assessment of craniofacial dysmorphisms and for a proper corrective surgery planning. To date, these elaborations are carried out by skilled operators within specific software environments. Since the whole procedure is based on the manual selection of specific landmarks, it is time-consuming, and the results depend on the operators' professional experience. This work aims to propose a new automatic and landmark-independent technique which is able to extract a reliable mid-sagittal plane from 3D CT images. The algorithm has been designed to perform a robust evaluation, also in the case of large defect areas. The presented method is an upgraded version of a mirroring-and registration technique for the automatic symmetry plane detection of 3D asymmetrically scanned human faces, previously published by the authors. With respect to the published algorithm, the improvements here introduced concern both the objective function formulation and the method used to minimize it. The automatic method here proposed has been verified in the analysis of real craniofacial skeletons also with large defects, and the results have been compared with other recent technologies.

Keywords: Cranio-maxillofacial | Feature recognition | Medical imaging | Mid-sagittal plane | Symmetry analysis

[32] Di Angelo L., Di Stefano P., Guardiani E., Morabito A.E., A 3D information framework for automated archaeological pottery archival, 2019 IMEKO TC4 International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2019, 178-183, (2019). Abstract
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Abstract: The classification of ceramic archaeological fragments is based on shape, dimensions, decorations, technological elements, color and material. Nowadays, all of these features are still recognized and analyzed by a skilled operator. It follows that the resulting characterization of shape and sizes of archaeological fragments is poorly reproducible and repeatable. With a view to overcome these limitations, a computer-based methodology, able to extract automatically several quantitative information from high-density discrete geometric models acquired by the laser scanning of archaeological fragments, was proposed. In this paper, the set of quantitative information obtainable is furtherly broadened, by including the segmentation of some types of morphological features, the identification of the fragment shape type, the evaluation of the longitudinal profile and the estimation of a larger set of dimensional features. Finally, a new 3D information framework is proposed to store the large variety of quantitative information extracted.

[33] Di Angelo L., Di Stefano P., Morabito A.E., Pane C., Constant radius geometric features segmentation in archeological pottery, IMEKO International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2017, 69-74, (2019). Abstract
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Abstract: This paper gives a contribution to the automatic recognition of significant features of ancient ceramics, useful for the historical and/or archeological investigation. These very common type geometric features are obtained by a sweeping action that leaves negative or positive traces, characterized by a cross section with one or more constant radii. The paper proposes a novel methodology that, analyzing the principal curvatures at the points of high-density geometric models of ceramic vessels, acquired by laser scanning, identifies the nodes potentially attributable to these features of constant radius. The recognition process is not trivial since it is affected by uncertainties. To overcome the limits of a recognition based on crisp sets, the recognition rule, proposed for the feature segmentation, is implemented by a fuzzy approach. The method has been tested in the identification of embossed decorations in an ancient olla and it proves to be promising for further applications on other types of geometric features of constant radius.

[34] Di Angelo L., Di Stefano P., Pane C., A new 3D information system for archeological pottery, IMEKO International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2017, 57-63, (2019). Abstract
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Abstract: The study of the immense patrimony of ceramic finds is still performed by the traditional manual archaeological approach. So that, the information of the shape and dimensions of the sherds have high uncertainties, are expensive and time consuming to be obtained. With the aim to overcome these limitations, for several years our research group has directed efforts to the development of an automatic computer-based method for the morphological and dimensional characterization of axially-symmetric shards. In this paper, the salient points of this method are reported, as well as the management system of all gathered information. The 3D information system is designed for its future use for pottery classification and reconstruction of ancient ceramics.

[35] Di Angelo L., Di Stefano P., Fasciani R., Gaudenzi D., Pane C., The virtual reconstruction of the lake Fucino's emissary, IMEKO International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2017, 116-121, (2019). Abstract
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Abstract: The Lake Fucino's emissary represents one of the most important hydraulic construction realized in antiquity. Unfortunately, little remains of the original structure of the Roman emissary, obliterated by the Torlonia building and the definitive drying of the lake. This article presents its virtual reconstruction, in order to understand survey and technological issues met by Romans and to visually offer reconstruction theories, interpreting a partially lost evidence of the Roman technology. The engineering resource becomes the means for a deeper comprehension of archaeological questions, combining the tools of engineering and archeology.

[36] Di Angelo L., Di Stefano P., Pane C., An automatic method for pottery fragments analysis, Measurement: Journal of the International Measurement Confederation, 128, 138-148, (2018). Abstract
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Abstract: With the aim to reduce the uncertainties of the traditional archaeological approach and reduce costs for ceramic investigation, in this paper a computer-based method is proposed. A discrete geometric model of a pottery fragment is the starting input, from which a first distinction in axially and not-axially symmetric surfaces can be done. Geometrical and morphological features are then recognized. Only once that all this information is obtained, it is possible to proceed with the dimensional analysis. The analysis carried on the test case here illustrated proves that the automatic method presents accuracy and robustness not achievable even using the best application of the archaeological method. This method seems to be functional to other goals, such as for pottery classification and reconstruction of ancient ceramics.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Surface segmentation

[37] Di Angelo L., Di Stefano P., Fratocchi L., Marzola A., An AHP-based method for choosing the best 3D scanner for cultural heritage applications, Journal of Cultural Heritage, 34, 109-115, (2018). Abstract
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Abstract: In this paper, a method for determining the best choice of the 3D scanner for cultural heritage applications is presented. Generally speaking, this activity is not trivial since a 3D scanner that matches all the requirements of a typical preservation activity in cultural heritage does not exist. Thus, to the best of the authors’ knowledge, the choice of compromise is typically performed in an unstructured way. In order to structure this choice, a method based on the Analytic Hierarchy Process (AHP) is proposed. In the proposed method, the three levels of the AHP hierarchy structure are the selection of the best 3D scanner for a specific cultural heritage application (goal), the most important technical parameters that mainly affect the choice of a 3D scanner (criteria), and the devices matching the required resolution (alternatives). Having defined the goal, prioritization of the type and quality of information is performed by the team leader of the research group (typically a skilled archaeologist), while the priority of the pairwise comparison among alternatives is decided by an expert on 3D scanners. The application of the proposed method in two contrasting situations concerning pottery fragments highlights its ease of use, its robustness (confirmed by the consistency analysis), and the completeness of the technical and economic assessment (since all relevant elements are taken into account), which put together, in a structured way, competences in very different fields (archaeology and 3D digital devices).

Keywords: 3D archaeology | Analytic Hierarchy Process (AHP) | Choice of best 3D scanners

[38] Di Angelo L., Di Stefano P., Morabito A.E., Pane C., Measurement of constant radius geometric features in archaeological pottery, Measurement: Journal of the International Measurement Confederation, 124, 138-146, (2018). Abstract
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Abstract: Constant radius geometric features are a common type of manufacturing features of ancient ceramics. They are obtained by a sweeping action of a tool, which leaves negative or positive traces characterized by a cross-section with one or more constant radii. The automatic recognition and dimensional characterization of these features could be useful for understanding the technology used to manufacture ceramics. Thus, a new perspective in archaeological investigations can be furnished. For this purpose, in this paper a new computer-based methodology suited to segmenting constant radius geometric features and measuring their dimensional parameters is proposed. Starting from a 3D discrete geometric model of the ceramic, the region pertaining to these features is determined and measurements of their radii are performed. Due to the uncertainties of various sources, which affect the investigated object, the required process is not trivial. In order to solve this problem, the segmentation phase is conducted using a non-conventional logic suitable for exploring the object with a fuzzy sensitivity, and the measurement is performed by a robust fitting method applied to the segmented entities. The methodology has been tested in the identification of embossed decorations of an ancient olla. The combined effects of the feature segmentation process together with the measure detection approach on the obtained results are critically analyzed and discussed.

Keywords: Computer methods in archaeology | Fuzzy logic | Geometric features recognition | Metrology for cultural heritage

[39] Di Angelo L., Di Stefano P., Morabito A.E., Secondary features segmentation from high-density tessellated surfaces, International Journal on Interactive Design and Manufacturing, 12(3), 801-809, (2018). Abstract
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Abstract: A new method for secondary features segmentation, performed on high-density tessellated geometric models, is proposed. Four types of secondary features are considered: fillets, rounds and grooves. Sharp edges are also recognised. The method is based on an algorithm that analyses the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for the maximum principal curvature. Since the deterministic application of this simple working principle shows several problems, due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model belonging to secondary features of a given radius, an appropriate set of membership functions is defined and evaluated based on some parameters, which affect the quality of the curvature estimation. A region-growing algorithm connects the nodes pertaining to a same secondary feature so that, for a given radius, one or more secondary features may be recognized. The method is applied and verified in some test cases.

Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm

[40] Di Angelo L., Di Stefano P., Pane C., The 3D virtual reconstruction of an engineering work of the past, IOP Conference Series: Materials Science and Engineering, 364(1), (2018). Abstract
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Abstract: The construction of artificial emissary of Lake Fucino's represents one of the most significant engineering challenges that took place in antiquity. Unfortunately, the imposing structure of the Roman emissary was almost completely erased from the building of the late nineteenth century, constructed for the final drying of the lake. This article presents its virtual reconstruction, to understand the technological issues met by Romans and to visually offer reconstruction theories starting from interpreting of the few Roman remains. So that, engineering resources are used to try to understand unresolved issues in archaeology.

[41] Angelo L.D., Stefano P.D., Axis estimation of thin-walled axially symmetric solids, Pattern Recognition Letters, 106, 47-52, (2018). Abstract
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Abstract: In this paper, a new method for axis detection of discrete thin-walled axially symmetric surfaces is presented. This method is based on the property of thin-walled axially symmetric surfaces that the minimum path of a point on the external wall to the internal wall is on a straight line passing through the axis. This working principle, since it does not require the evaluation of differential geometrical properties, makes the method robust to noise. The proposed method has been applied in a very critical application area: axially symmetric archaeological pottery fragments, for which the evaluation of the axis is complex because of manufacturing error and of modification of the surface properties due to the action of time and weather. The trueness of the proposed method is compared with those of the five methods presented in the literature in the analysis of real sherds of various dimensions and conditions. The proposed method demonstrates greater robustness than these methods and is shown to be promising to improve the number of sherds that can be successfully analyzed.

Keywords: 3D archeology | Axis estimation | Computer | Geometric inspection | Methods in archaeology

[42] Di Angelo L., Di Stefano P., Marzola A., Surface quality prediction in FDM additive manufacturing, International Journal of Advanced Manufacturing Technology, 93(9-12), 3655-3662, (2017). Abstract
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Abstract: Additive manufacturing technologies produce objects which present a characteristic surface texture. This is an inevitable and systematic error and has a predictable shape feature which depends on certain process parameters. In order to reduce manufacturing costs and obtain the best results from the point of view of quality, it is essential to predict this error in advance and choose the process parameters which minimise it. For the purpose of measuring the surface quality, the index Ra (ISO 4287, 1997) is used in the related literature. In this paper, it is first demonstrated that the use of roughness parameters in FDM-manufactured surfaces is not adequate to quantify the surface error. The parameter Pa (ISO 4287) is proposed as a more appropriate index to evaluate the surface quality; it is investigated and critically analysed in comparison with the Ra index. A new original model to predict Pa for FDM-manufactured surfaces is presented. The model prediction is compared with experimental data and with the estimation performed by the models described in the literature, within the limits of their capability to predict Pa.

Keywords: Additive manufacturing | Fused deposition modelling | Surface quality

[43] Di Angelo L., Di Stefano P., Pane C., Automatic dimensional characterisation of pottery, Journal of Cultural Heritage, 26, 118-128, (2017). Abstract
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Abstract: The dimensional characterisation of pottery is usually necessary to typify finds and also to recognise sherds pertaining to the same object. With the aim of reducing the uncertainties that typically affect the measurement carried out by the approach traditionally performed by archaeologists, we propose a new automatic method for dimensional characterisation of pottery fragments. The method, starting from a 3D-scanned high point density model, takes advantages from the preventive segmentation and recognition of its significant geometric features; the corresponding characteristic dimensions are evaluated by dedicated procedures. The dimensions measured are also those typically evaluated by archaeologists. In order to quantify the performances of the proposed method, a comparison of its repeatability and reproducibility is made with respect to the traditional manual approach. The proposed method, tested in some real critical cases, demonstrates better performances and lower uncertainties with respect to the traditional approaches.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Measurement precision in archaeology | Pottery profile | Surface segmentation

[44] Renzi C., Leali F., Di Angelo L., A review on decision-making methods in engineering design for the automotive industry, Journal of Engineering Design, 28(2), 118-143, (2017). Abstract
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Abstract: Decision-making methods have proven to be an effective support to engineering design. However, it is proved that very often designers prefer tested procedures and experience-based approaches. Many reasons have been discussed in the literature, dealing with consolidated design habits of people and companies, high cost in terms of time consumption, and lack of tools and knowledge. The paper systematically investigates, through an extended critical review, how decision-making methods can be used by automotive designers to solve the most common engineering problems involved along the design process. In particular, the paper proposes an original classification of the most widely used decision-making methods in engineering design, a match between such techniques with the typical design phases, and a mapping of their application into the automotive field. This research can be considered as a further step to transfer the state-of-the-art knowledge on decision-making methods to the industrial context, establishing a common background for practitioners and researchers.

Keywords: automotive industry | Decision-making methods | engineering design | industrial design | product development

[45] Di Angelo L., Di Stefano P., Pane C., Automatic Features Recognition for Anthropometry, Procedia Manufacturing, 11, 1667-1674, (2017). Abstract
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Abstract: For the purpose of reducing uncertainties in the measurements of morphologically complex biological objects, the authors present a new automatic method, which takes advantage from the representation of the object in the form of the 3D geometric model obtained from CT-scans or 3D scanning. In this paper, the method is verified in real cases and compared with the traditional approaches.

Keywords: 3D biomedical image analysis | measurement accuracy | measurement protocols in biomedicine | shape segmentation

[46] Di Angelo L., Di Stefano P., Morabito A.E., Product model for dimensioning, tolerancing and inspection, Lecture Notes in Mechanical Engineering, 0, 1033-1040, (2017). Abstract
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Abstract: This paper presents a new methodology whose goals are on the one hand the formulation of a tolerance specification that is consistent with the functional, technological and control needs and, on the other, the automatic control of tolerance. The key aspect of the methodology is the digital model of the product, referred to as GMT (Geometric Model of Tolerancing), which gives a complete, consistent and efficient description of its geometrical and dimensional properties with the aim of being able to specify, simulate, manufacture and inspect them. By means a real test case, the potentialities of a first implementation of the proposed methodology are critically discussed.

Keywords: CAT (Computer-Aided Tolerancing) | GD&T (Geometric Dimensioning and Tolerancing) | Geometric inspection | GPS (Geometric Product Specification)

[47] Di Angelo L., Di Stefano P., Morabito A.E., Segmentation of secondary features from high-density acquired surfaces, Lecture Notes in Mechanical Engineering, 0, 1043-1051, (2017). Abstract
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Abstract: A new method for secondary features segmentation, performed in highdensity acquired geometric models, is proposed. Four types of secondary features are considered: fillets, rounds, grooves and sharp edges. The method is based on an algorithm that analyzes the principal curvatures. The nodes, potentially attributable to a fillet of given geometry, are those with a certain value for maximum principal curvature. Since the deterministic application of this simple wor king principle shows several problems due to the uncertainties in the curvature estimation, a fuzzy approach is proposed. In order to segment the nodes of a tessellated model that pertain to the same secondary features, proper membership functions are evaluated as function of some parameters, which affect the quality of the curvature estimation. A region growing algorithm connects the nodes pertaining to the same secondary feature. The method is applied and verified for some test cases.

Keywords: Computational geometry | Features extractions | Fuzzy logic | Mechanical engineering computing | Region growing algorithm

[48] Di Angelo L., Leali F., Di Stefano P., Can open-source 3D mechanical CAD systems effectively support university courses?, International Journal of Engineering Education, 32(3), 1313-1324, (2016). Abstract
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Abstract: Most universities have introduced 3D CAD education and training in their engineering courses in recent years so as to respond to the actual needs of the industrial world for high-skilled design engineers. It is well demonstrated that the effectiveness of such courses depends on teaching an effective design approach rather than training for the use of specific commercial CAD tools. Since open-source CAD software has emerged in many fields as a promising alternative to commercial off-the-shelf systems, the present paper investigates the possibility for universities to adopt open-source instruments to effectively support their educational goals. Open-source 3D CAD systems are quantitatively evaluated by an original Compliance Index which considers the design tools typically used to model and draw industrial products and their weights in accomplishing the design tasks. The results obtained for the evaluation of a set of open-source CAD systems are presented and critically discussed.

Keywords: 3D CAD | CAD teaching | Open source 3D CAD | Software evaluation

[49] Di Angelo L., Di Stefano P., A method for posture prediction of the upper trunk of video terminal operators, Computer-Aided Design and Applications, 14(1), 28-37, (2016). Abstract
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Abstract: This paper presents a method for posture prediction of the upper trunk of video terminal (VDT) operators, which is then verified by means of some test cases. The prediction of the upper trunk posture is, in fact, a very difficult task to carry out due mainly to the complexity of the anatomy of the spine and the surrounding muscles. The method being proposed in this paper is based on the integration of the knowledge which is obtained experimentally through the posture analysis of real cases into a configured human multi-body kinematic model which has been implemented in a commercial CAD system. A trained artificial neural network retains the knowledge concerning the VDT operator’s postures detected in different working positions. The posture simulations obtained with the proposed method are subsequently compared with the real ones determined by a 3D scanner. The results obtained confirm the effectiveness of such a method, which is deemed promising to implement other anthropometric data and further human poses.

Keywords: Artificial neural network | Ergonomics | Multi-body virtual human models | Posture prediction

[50] Di Angelo L., Di Stefano P., Bernardi S., Continenza M.A., A new computational method for automatic dental measurement: The case of maxillary central incisor, Computers in Biology and Medicine, 70, 202-209, (2016). Abstract
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Abstract: This paper proposes a new automatic approach to determine the accurate measure of human teeth. The aim of the proposed computer based method is to reduce inaccuracy of measurement with respect to traditional approaches. Starting from a 3D model of the teeth which is obtained from 3D scanning, the method algorithmically evaluates the most important dimensional features detectable in central incisors. For this purpose, specific rules are put forward and implemented in original software with a view to identifying repere points, from which to detect dimensional features both unambiguously and accurately. The automatic method which is proposed here is verified by means of the analysis of real teeth and is then compared with the current state-of-the-art methods for teeth measurement.

Keywords: 3D biomedical image analysis | Computer methods for tooth analysis | Dental dimensions | Measurement accuracy | Measurement protocols in biomedicine

[51] Di Angelo L., Di Stefano P., Pane C., An automatic method for dimensional and shape characterization of pottery, IMEKO International Conference on Metrology for Archeology and Cultural Heritage, MetroArcheo 2016, 2016-October, 16-22, (2016). Abstract
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Abstract: With the aim to improve the quality of the traditional archaeological approach and reduce costs for ceramic investigation, in this paper a computer-based method is proposed. A discrete geometric model of a pottery fragment is the starting input, from which a first distinction in axially and not-axially symmetric surfaces can be done. Geometrical and morphological features are then recognized. Only once that all these information are obtained, it is possible to proceed with the dimensional analysis. The method here proposed allows reducing the uncertainties of the traditional archaeological approach. The analysis carried on the test case here presented, proves that the automatic method presents repeatability and reproducibility that cannot be obtained even using the best application of the archaeological method. This method seems to be functional to other scopes such as for pottery classification and reconstruction of ancient ceramics.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Surface segmentation

[52] Di Angelo L., Di Stefano P., Performance evaluation and experimental characterization of a new automatic method for measuring vertebrae, IMEKO International Conference on Metrology for Archeology and Cultural Heritage, MetroArcheo 2016, 2016-October, 230-235, (2016). Abstract
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Abstract: In this paper performance evaluation and experimental characterization of a new automatic method for measuring vertebrae are analysed. Starting to a discrete valid geometric model of the vertebra, obtained from CT-scans or 3D scanning, the method measures algorithmically vertebrae. The proposed study is performed by analysing the most used dimensional features of lumbar and thoracic real vertebrae in anthropological investigations. The results are compared with the state-of-the-art methods for vertebra measurement.

[53] Di Angelo L., Di Stefano P., A new method for the automatic identification of the dimensional features of vertebrae, Computer Methods and Programs in Biomedicine, 121(1), 36-48, (2015). Abstract
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Abstract: In this paper a new automatic approach to determine the accurate measure of human vertebrae is proposed. The aim is to speed up the measurement process and to reduce the uncertainties that typically affect the measurement carried out by traditional approaches. The proposed method uses a 3D model of the vertebra obtained from CT-scans or 3D scanning, from which some characteristic dimensions are detected. For this purpose, specific rules to identify morphological features, from which to detect dimensional features unambiguously and accurately, are put forward and implemented in original software. The automatic method which is here proposed is verified by analysing real vertebrae and is then compared with the state-of-the-art methods for vertebra measurement.

Keywords: 3D medical-image analysis | Computer methods for vertebra analysis | Measurement accuracy | Measurement protocols in biomedicine | Shape segmentation | Vertebral dimensions

[54] Di Angelo L., Di Stefano P., Geometric segmentation of 3D scanned surfaces, CAD Computer Aided Design, 62, 44-56, (2015). Abstract
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Abstract: The geometric segmentation of a discrete geometric model obtained by the scanning of real objects is affected by various problems that make the segmentation difficult to perform without uncertainties. Certain factors, such as point location noise (coming from the acquisition process) and the coarse representation of continuous surfaces due to triangular approximations, introduce ambiguity into the recognition process of the geometric shape. To overcome these problems, a new method for geometric point identification and surface segmentation is proposed. The point classification is based on a fuzzy parameterization using three shape indexes: the smoothness indicator, shape index and flatness index. A total of 11 fuzzy domain intervals have been identified and comprise sharp edges, defective zones and 10 different types of regular points. For each point of the discrete surface, the related membership functions are dynamically evaluated to be adapted to consider, point by point, those properties of the geometric model that affects uncertainty in point type attribution. The methodology has been verified in many test cases designed to represent critical conditions for any method in geometric recognition and has been compared with one of the most robust methods described in the related literature.

Keywords: Discrete differential geometry | Discrete surfaces | Geometric segmentation

[55] Di Angelo L., Di Stefano P., Morabito A.E., A robust method for axis identification, Precision Engineering, 39, 194-203, (2015). Abstract
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Abstract: The present paper proposes a new method for axis identification in discrete axially symmetrical geometric models. This method is based on-a-never-used-before property of the axially symmetrical surfaces for which the symmetry line of any section curve of the surface (or of a portion of it in the case of an incomplete axially symmetrical surface) always intersects the axis of symmetry of the surface. Thus the working principle of the method makes it very robust to local defectiveness, measurement noise and outliers. In order to compare it with the most cited methods presented in literature, several types of tests have been designed and performed. The robustness of those methods, on the one hand, has been evaluated by defining the Statistical Confidence Boundary at 1σ confidence level. The trueness of the method, on the other hand, has been evaluated on geometric models obtained by measuring real objects. The high robustness, which characterizes the proposed method, makes it particularly suitable for product geometric inspection where high accuracy is required.

Keywords: Axis identification | Geometric inspection

[56] Di Angelo L., Di Stefano P., Morabito A.E., Comparison of methods for axis detection of high-density acquired axially-symmetric surfaces, International Journal on Interactive Design and Manufacturing, 8(3), 199-208, (2014). Abstract
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Abstract: Axis evaluation is a fundamental preliminary step for several applications, from archaeology to geometric inspection of mechanical workpieces. The axis of symmetry is the situation feature of axially-symmetric surfaces, but also a reference for the evaluation of specific geometric properties (roundness, cylindricity and straightness of the axis). Since it is a non-physical geometric entity, it is not directly measurable from the surface, but can nevertheless be derived from the surface. For discretised models, defined by point clouds or triangular meshes, the axis of symmetry detection is a very complex task to accomplish. In this paper three methods for axis estimation of high-density acquired axially-symmetric surfaces are reviewed and compared in the common cases. The methods comparison, performed in this work, doesn't consist just in an ordinary implementation of methods already described in the literature. These methods involve some auxiliary processing tools (mainly devoted to evaluate geometric differential properties) which characterise the implemented version and its performances. For each of these methods various versions have been considered and implemented which diversify each other for the criterion used for geometrical differential properties of the tessellated model. The methods for axis estimation are compared in the interpretation of the axes of axially-symmetric geometries (analytical and generic, partial and complete) for several types of discretization (size and regularity of the mesh). The results show that in the case of complete axially-symmetric features (analytical or generic), the three analysed methods perform similar results. In presence of not complete axially-symmetric features the methods show very different performances. The methods for axes estimation are of particular interest in several applications where precision and reliability are required. In this paper the main characteristics of the most important methods are identified and some guidelines for their use are given. © 2014 Springer-Verlag France.

Keywords: Axis of rotation | Discretised surfaces | Geometric features recognition | Reverse engineering

[57] Di Angelo L., Di Stefano P., A computational Method for Bilateral Symmetry Recognition in Asymmetrically Scanned Human Faces, Computer-Aided Design and Applications, 11(3), 275-283, (2014). Abstract
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Abstract: This paper presents a new mirroring-and-registration method for the automatic symmetry plane detection of 3D asymmetrically scanned human faces. Once the mirroring of the original data is carried out with respect to the first-attempt symmetry plane, which is estimated by the PCA method, the source point cloud and the mirrored data are registered by the ICP algorithm that minimises a new weighted function. The final symmetry plane obtained approximates in the least-squares sense the midpoints of the lines connecting homologous points randomly chosen. This method is validated by analysing some specifically-designed test cases. The obtained results show that the method is quite insensitive to asymmetries of data resulting from the acquisition process. © 2013 © 2013 CAD Solutions, LLC.

Keywords: iterative closest points | mirroring | rasterstereography | registration | symmetry plane

[58] Di Angelo L., Di Stefano P., An evolutionary geometric primitive for automatic design synthesis of functional shapes: The case of airfoils, Advances in Engineering Software, 67, 164-172, (2014). Abstract
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Abstract: A novel self-adaptive geometric primitive for functional geometric shape synthesis is presented. This novel geometric primitive, for CAD use, is specifically designed to reproduce geometric shapes with functional requirements, such as the aerodynamic and hydrodynamic ones, once the functional parameters are furnished. It produces a typical CAD representation of a functional profile: a set of Bézier curves. The proposed primitive follows a generate-and-test approach and takes advantage of the use of a properly designed artificial neural network (BNN). It combines the properties of a geometric primitive and the capability to manage the engineering knowledge in a specific field of application. The proposed evolutionary primitive is applied to a real engineering application: the automatic synthesis of airfoils. Some examples are simulated in order to test the effectiveness of the proposed method. The results obtained by an original prototypal software are presented and critically discussed. © 2013 Elsevier Ltd. All rights reserved.

Keywords: Airfoils design | Artificial neural networks | Automatic design synthesis | Functional shape synthesis | Geometric primitive | Self-adaptive geometric primitive

[59] Di Angelo L., Di Stefano P., Morabito A.E., Recognition of intrinsic quality properties for automatic geometric inspection, International Journal on Interactive Design and Manufacturing, 7(4), 203-215, (2013). Abstract
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Abstract: In the last few years the need for methodologies capable of performing an automated geometric inspection has increased. These methodologies often use 3D high-resolution optical digitisers to acquire points from the surface of the object to be inspected. It is expected that, in the near future, geometric inspection will be requiring more and more the use of these instruments. At present geometric inspection is not profiting from all the opportunities attainable by 3D high-resolution optical scanners or from the numerous tools which can be used for processing the point cloud acquired from the inspected product. For some years now, these authors have been working on a new methodology for automatic tolerance inspection working from a 3D model acquired by optical digitisers. In this paper all the information recognisable in a scanned object is organised into a new data structure, called Recognised Geometric Model (RGM). The final aim is to define a representation of the inspected object for the automatic evaluation of the non-idealities pertaining to the form, orientation and location of the non-ideal features of the acquired object. The key concept of the proposed approach is the capability to recognise some intrinsic nominal properties of the acquired model. These properties are assumed as references to evaluate the non-idealities of the inspected object. With this approach the references of geometric inspection are searched for in the inspected object independently of a tolerance specification and of the availability of a 3D nominal representation. The high-level geometric information within RGM depends on the rules used for its identification. The capability to recognise specific categories of nominal references offers the possibility of introducing new tolerances to be specified. The proposed approach has been implemented in original software by means of which a specific test case has been analysed. © 2012 Springer-Verlag France.

Keywords: Automated inspection | ISO tolerancing | Three-dimensional metrology

[60] Di Angelo L., Di Stefano P., Spezzaneve A., Symmetry line detection for non-erected postures, International Journal on Interactive Design and Manufacturing, 7(4), 271-276, (2013). Abstract
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Abstract: In this work, a new technique for symmetry line detection for non-erected postures, which can not be investigated with the other methods presented in the literature, is proposed. It evaluates the symmetry line by means an adaptive process in which a first attempt is modified step by step until the solution converges to the best estimation. The method here proposed is validated by analysing four different non-erected postures in which the spine does not lie onto sagittal plane, by the comparison with the traditional approach to symmetry line detection, having as reference the cutaneous marking. Results are analysed and critically discussed. © 2012 Springer-Verlag France.

Keywords: Anatomical landmarks | Back shape analysis | Posture prediction | Rasterstereography | Symmetry line

[61] Di Angelo L., Di Stefano P., Bilateral symmetry estimation of human face, International Journal on Interactive Design and Manufacturing, 7(4), 217-225, (2013). Abstract
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Abstract: This paper proposes a new method for the identification of the symmetry plane of the human face, working from 3D high-density scanned data. The method being proposed is an original variant of a typical mirroring and registration method. This method is validated by analysing some specifically designed test cases. The obtained results show that the method is quite insensitive to local asymmetries, whether they be near or far from the symmetry plane, and is also repeatable and slightly conditioned by the acquisition process. © 2012 Springer-Verlag France.

Keywords: Asymmetry | Mirroring | Rasterstereography | Registration | Symmetry plane

[62] Di Angelo L., Di Stefano P., Spezzaneve A., A method for 3D detection of symmetry line in asymmetric postures, Computer Methods in Biomechanics and Biomedical Engineering, 16(11), 1213-1220, (2013). Abstract
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Abstract: The methods for symmetry line detection presented in the literature are typically suited to analyse symmetric upright postures, both standing and seated. The proposed method focuses on the symmetry line detection in subjects assuming asymmetric postures in which this line falls far outside the sagittal plane. The proposed approach evaluates the symmetry line by means of an autoregressive process in order to determine the set of planes suited to slice the back coherently with its geometric spatial configuration. The method is analysed assuming the cutaneous marking as reference and it is compared with a previous one, also developed by these authors. Results are analysed and critically discussed. © 2013 Taylor & Francis.

Keywords: anatomical landmarks | back shape analysis | posture prediction | rasterstereography | symmetry line

[63] Di Angelo L., Di Stefano P., Giaccari L., A fast mesh-growing algorithm for manifold surface reconstruction, Computer-Aided Design and Applications, 10(2), 197-220, (2013). Abstract
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Abstract: In a previous paper these authors presented a new mesh- growing approach based on the Gabriel 2 - Simplex (G2S) criterion. If compared with the Cocone family and the Ball Pivoting methods, G2S demonstrated to be competitive in terms of tessellation rate, quality of the generated triangles and defectiveness produced when the surface to be reconstructed was locally flat. Nonetheless, its major limitation was that, in the presence of a mesh which was locally non - flat or which was not sufficiently sampled, the method was less robust and holes and non-manifold vertices were generated. In order to overcome these limitations, in this paper, the performance of the G2S mesh-growing method is fully improved in terms of robustness. The performances of the new version of the G2S approach (in the following Robust G2S) has been compared with that of the old one, and that of the Cocone family and the Ball Pivoting methods in the tessellation of some benchmark point clouds and artificially noised test cases. The results obtained show that the use of the Robust G2S is advantageous, as opposed to the other methods here considered, even in the case of noised point clouds. Unlike the other methods, the one which is proposed preserves manifoldness and geometric details of the point cloud to be meshed. © 2013 CAD Solutions, LLC.

Keywords: Reverse engineering | Surface reconstruction | Triangular meshes

[64] Di Angelo L., Di Stefano P., Spezzaneve A., An iterative method to detect symmetry line falling far outside the sagittal plane, International Journal on Interactive Design and Manufacturing, 6(4), 233-240, (2012). Abstract
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Abstract: In this work, a new technique for symmetry line detection for asymmetric postures, which can not be investigated with the other methods presented in the literature, is proposed. It evaluates the symmetry line by means an adaptive process in which a first attempt is modified step by step until the solution converges to the best estimation. The method here proposed is validated by analysing four different asymmetric postures in which the spine lies far outside the sagittal plane, having as reference the cutaneous marking. Results are analysed and critically discussed. © 2012 Springer-Verlag.

Keywords: Anatomical landmarks | Back shape analysis | Posture prediction | Raster stereography | Symmetry line

[65] Angelo L.D., Stefano P.D., Morabito A.E., The RGM data structure: A nominal interpretation of an acquired high point density model for automatic tolerance inspection, International Journal of Production Research, 50(12), 3416-3433, (2012). Abstract
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Abstract: In a previous paper (Di Angelo, L., Di Stefano, P. and Morabito, A., 2011. Automatic evaluation of form errors in high-density acquired surfaces. International Journal of Production Research, 49 (7), 2061-2082) we proposed an original methodology for the automation of the geometric inspection, starting from an acquired high-density surface. That approach performed a recognition process on the acquired data aiming at the identification of some intrinsic nominal references. An intrinsic nominal reference was detected when a geometric property was recognised to be common to a set of adjacent points in the 3D data set representing the acquired object. The recognition of these properties was carried out based on some rules. Starting from these concepts, a new specification language was defined, which is based on recognisable geometric entities. This paper expands the category of intrinsic nominal references to include new mutual intrinsic orientation, location and dimensional properties pertaining to 3D features. This approach involves the automatic construction of a geometric reference model for a scanned workpiece, called recognised geometric model (RGM). The domain of the representable entities within the RGM strictly depends on the rules used for the recognition of the intrinsic properties. In particular, this paper focuses on the rules for the recognition of the orientation and location properties between non-ideal features. When using the RGM, tolerances are specified according to the set of available and recognisable intrinsic nominal references. Based on the geometric product specification, the RGM data structure can be queried to capture some quantitative information concerning special intrinsic geometric parameters and/or non-idealities. © 2012 Copyright Taylor and Francis Group, LLC.

Keywords: automated inspection | ISO tolerancing | shape recognition | three dimensional metrology | triangular meshes

[66] Di Angelo L., Di Stefano P., A neural network-based build time estimator for layer manufactured objects, International Journal of Advanced Manufacturing Technology, 57(1-4), 215-224, (2011). Abstract
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Abstract: A correct prediction of build time is essential to calculate the accurate cost of a layer manufactured object. The methods presented in literature are of two types: detailed-analysis- and parametric-based approaches. The former require that a lot of data, related to the kinematic and dynamic performance of the machine, should be known. Parametric models, on the other hand, are of general use and relatively simple to implement; however, the parametric methods presented in literature only provide a few of the components of the total build time. Therefore, their performances are not properly suited in any case. In order to overcome these limitations, this paper proposes a parametric approach which uses a more complete set of build-time driving factors. Furthermore, considering the complexity of the parametric build time function, an artificial neural network is used so as to improve the method flexibility. The analysis of the test cases shows that the proposed approach provides a quite accurate estimation of build time even in critical cases and when supports are required. © 2011 Springer-Verlag London Limited.

Keywords: Artificial neural network | Build-time estimation | Rapid prototyping

[67] di Angelo L., di Stefano P., Vinciguerra M.G., Experimental validation of a new method for symmetry line detection, Computer-Aided Design and Applications, 8(1), 71-86, (2011). Abstract
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Abstract: In this work a new method for symmetry line recognition, from 3D scanned data of a subject's back, is presented. The new method is validated by comparison with traditional techniques based on cutaneous marking. For this purpose, the upright standing and sitting postures of a sample of 75 subjects, who usually perform different sports activities, are analysed. Error in symmetry line detection is measured as the distance between the estimated symmetry line and the position of the markers. The proposed method is compared with another one described in literature which has been validated in clinical field. Results are analysed and critically discussed. © 2011 CAD Solutions, LLC.

Keywords: Back shape analysis | Posture prediction | Symmetry line

[68] di Angelo L., di Stefano P., Experimental comparison of methods for differential geometric properties evaluation in triangular meshes, Computer-Aided Design and Applications, 8(2), 193-210, (2011). Abstract
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Abstract: This paper deals with the investigation of the stability and the accuracy of the most important methods to estimate the parameters that are involved in the shape recognition process of tessellated surfaces. For this purpose, four approaches to estimate the differential geometric properties of tessellated surfaces are systematically examined (namely, simple and extended quadric fitting methods, Rusinkiewicz's method and Meyer discrete method). A set of test cases has been designed in order to investigate the sensitivity of those methods to factors such as noise in point location, surface typology (chosen between those types that usually define the boundary of mechanical parts such as: planes, cylinders, spheres, cones and tori), mesh resolution and mesh regularity. Based on the results obtained, some criticism of the analyzed methods is made and some guidelines are provided in order to choose the most robust and reliable method in relation to the surface typology, quality of the mesh and noise in point location. © 2011 CAD Solutions, LLC.

Keywords: Curvature estimation | Shape recognition | Triangular meshes

[69] Di Angelo L., Di Stefano P., Giaccari L., A new mesh-growing algorithm for fast surface reconstruction, CAD Computer Aided Design, 43(6), 639-650, (2011). Abstract
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Abstract: This paper presents a new high-performance method for triangular mesh generation based on a mesh-growing approach. Starting from a seed triangle, the algorithm grows the triangular mesh by selecting a new point based on the Gabriel 2Simplex criterion. This criterion can be considered to be a good approximation of the 2D Delaunay if the point cloud is well-sampled and not too rough. The performance of the proposed method is compared with that of the Cocone family and that of Ball Pivoting as regards the tessellation rate and the quality of the surface being generated from some benchmark point clouds and artificially noised test cases. The results are analysed and critically discussed. © 2011 Elsevier Ltd. All rights reserved.

Keywords: Reverse engineering | Surface reconstruction | Triangular meshes

[70] Di Angelo L., Di Stefano P., Morabito A.E., Automatic evaluation of form errors in high-density acquired surfaces, International Journal of Production Research, 49(7), 2061-2082, (2011). Abstract
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Abstract: In this paper the authors present an original methodology aiming at the automation of the geometric inspection, starting from a high-density acquired surface. The concept of intrinsic nominal reference is herein introduced in order to evaluate geometric errors. Starting from these concepts, a new specification language, which is based on recognisable geometric entities, is defined. This work also proposes some surface differential properties, such as the intrinsic nominal references, from which new categories of form errors can be introduced. Well-defined rules are then necessary for the unambiguous identification of these intrinsic nominal references. These rules are an integral part of the tolerance specification. This new approach requires that a recognition process be performed on the acquired model so as to automatically identify the already-mentioned intrinsic nominal references. The assessable errors refer to recognisable geometric entities and their evaluation leaves the nominal reference specification aside since they can be intrinsically associated with a recognised geometric shape. Tolerance specification is defined based on the error categories which can be automatically evaluated and which are an integral part of the specification language. © 2011 Taylor & Francis.

Keywords: automated inspection | form error evaluation | GPS tolerancing

[71] Di Angelo L., Di Stefano P., C<sup>1</sup> continuities detection in triangular meshes, CAD Computer Aided Design, 42(9), 828-839, (2010). Abstract
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Abstract: The identification of C1 continuities is important in many applications involving point clouds or triangular meshes, such as surface segmentation, inspection and rendering. The methods in literature have some limitations which make them strongly dependent on some properties of the mesh (point typology, mesh resolution, uniformity of the shape of triangles and error in point location). Furthermore, some of them do not discriminate non-regular points from those that are inside a band around them. In this work, a new method for automatic detection of C1 continuities in triangular meshes is presented. The method introduces an original function, called sharpness indicator, which enables us to evaluate properties related to surface smoothness. The performance of the new method is compared with that of four methods presented in literature as regards the recognition of C1 continuities both in synthetic and real meshes. Results are analysed and critically discussed. © 2010 Elsevier Ltd. All rights reserved.

Keywords: C continuities detection 1 | Reverse engineering | Triangular meshes

[72] Di Angelo L., Di Stefano P., Vinciguerra M.G., Experimental validation of a new method for symmetry line detection, Computer-Aided Design and Applications, 7, 1-17, (2010). Abstract
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Abstract: In this work a new method for symmetry line recognition, from 3D scanned data of a subject’s back, is presented. The new method is validated by comparison with traditional techniques based on cutaneous marking. For this purpose, the upright standing and sitting postures of a sample of 75 subjects, who usually perform different sports activities, are analysed. Error in symmetry line detection is measured as the distance between the estimated symmetry line and the position of the markers. The proposed method is compared with another one described in literature which has been validated in clinical field. Results are analysed and critically discussed. © 2010 Taylor & Francis Group, LLC.

Keywords: Back shape analysis | Posture prediction | Symmetry line

[73] Di Angelo L., Di Stefano P., Parametric cost analysis for web-based e-commerce of layer manufactured objects, International Journal of Production Research, 48(7), 2127-2140, (2010). Abstract
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Abstract: Web-based e-commerce of rapid prototyping services is going to be a widely diffused methodology used to compete in a global market. A competitive market imposes a very accurate estimation of prototyping price. Prototype costs depend on many factors, some of which may be easily deduced, while some others consist in a complex function of the geometric model properties and of the specific technology employed to build a physical model. Build time, which affects some components of the prototype's build cost, is a critical factor to deduce. Build time depends not only on the prototype dimensions but also on the complexity of the shape that, in turn, affects the movement of the tool to form the object. A parametric approach to build cost estimation, suited for web-based e-commerce, is presented in this paper. Significant cost driving factors of layer manufactured objects are identified and instruments to evaluate them are proposed. Special attention has been paid to define a parametric approach to build time estimation. The proposed parametric approach analyses the geometrical features, which typically affect the build time of the main layer manufacturing technologies. The method is verified in some test cases related to FDM technology. © 2010 Taylor & Francis.

Keywords: Cost estimating | E-commerce | Rapid prototyping

[74] Bianconi F., Conti P., Di Angelo L., Interoperability among CAD/CAM/CAE systems: A review of current research trends, Geometric Modeling and Imaging New Trends, 2006, 2006, 82-89, (2006). Abstract
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Abstract: Interoperability among CAD/CAM/CAE systems is a well known problem in product design and development. At present geometrical data exchange among different software packages is usually carried out through neutral file formats (IGES or STEP) or through proprietary formats. Data exchange processes are usually afflicted by several problems, such as: information loss, redundancy, one-way data exchange and static data exchange. These drawbacks do not permit a really geometric-centric design, and even if the model is transmitted without loss of information, the exchanged data do not incorporate details such as sketches, constraints and features, which represent the designer's intent. As a result, the model can hardly be modified, and the original intent of the designer may be misunderstood. During the last five years various solutions have been proposed to solve the above mentioned problems. The aim of this work is to investigate and discuss recent research trends in this topic. © 2006 IEEE.

[75] Di Stefano P., Bianconi F., Di Angelo L., An approach for feature semantics recognition in geometric models, CAD Computer Aided Design, 36(10), 993-1009, (2004). Abstract
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Abstract: This paper describes a method for the recognition of the semantics of parts (features) of a component from a pure geometric representation. It is suitable for verifying product life-cycle requirements from the early stages of the design process. The proposed method is appropriate to analyse B-rep geometric models, and it is not limited to models described by planar and cylindrical surfaces, but it can handle several types of face shapes. In this work the concept of semanteme is introduced. A semanteme represents the minimal element of engineering meaning that can be recognised in a geometric model. The semantemes recognised in a part of the model, which are potentially of engineering significance, are used to associate an engineering meaning to the part. This approach gives a wide flexibility to the proposed system, which is suitable to be used in different contexts of application, since it is possible to describe the reference context using the semanteme that the system can manage. In the paper the implemented prototype system is briefly described. The prototype system takes advantage of neutral interfaces that allow geometrical and topological information to be retrieved from a commercial CAD system. © 2003 Elsevier Ltd. All rights reserved.

Keywords: Feature recognition | Intermediate geometric model | Semantics recognition

[76] Di Stefano P., Di Angelo L., Neural network based geometric primitive for airfoil design, Proceedings - SMI 2003: Shape Modeling International 2003, 201-206, (2003). Abstract
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Abstract: A geometric primitive for CAD implementation is presented in this paper (Bèzier Neural Network BNN). It is specifically designed to reproduce geometric shapes with functional requirements such as aerodynamic and hydrodynamic profiles. This primitive can be useful when a known and well defined map between functional requirements and geometric data does not exist, and it have to be deduced by a physical or numerical experimental analysis. BNN gives rise to a typical CAD representation, a Bèzier curve, of a functional profile, once the functional parameters are supplied. In BNN the capability of neural network to approximate very complex and non-linear function has been combined with the capability of Bèzier functions to describe geometry, in a unique neural network. In this work BNN is used in the representation of aerodynamic profiles starting to their typical functional parameters: lift and drag coefficients, Reynolds number and angle of attack. BNN is tested in reproducing the wing profile of the 4-digit NACA series. The output of BNN is compared with the results of a fluiddynamic analysis performed by commercial software. © 2003 IEEE.

[77] De Vita A., Di Angelo L., Andreassi L., CFD analysis of engines: An advanced approach based on codes dynamically coupled, Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division, 585-594, (2003). Abstract
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Abstract: An advanced approach to evaluate the gas flow in internal combustion engines has been carried out. It is based on an interactive procedure which dynamically couples one-dimensional (1D) and three dimensional (3D) computational fluid dynamics codes. Direct feedback between the codes has been assured allowing 3D fluid flow effects to be fed back into the 1D system. A cycle-by-cycle convergence of results in the data exchange sections has been guaranteed. The capability of describing physical phenomena increases and some numerical problems, as the reflection of pressure waves on the 3D grid boundaries, can be avoided. The procedure has been applied to a simple test case and to a typical engine application where 3D effects are not negligible: flow field definition within an air box for race cars. The procedure has proven effective and could be easily adapted for further different applications. Copyright © 2003 by ASME.

[78] De Vita A., Di Angelo L., Andreassi L., CFD analysis of engines: An advanced approach based on codes dynamically coupled, American Society of Mechanical Engineers, Internal Combustion Engine Division (Publication) ICE, 40, 585-594, (2003). Abstract
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Abstract: An advanced approach to evaluate the gas flow in internal combustion engines has been carried out. It is based on an interactive procedure which dynamically couples one-dimensional (ID) and three dimensional (3D) computational fluid dynamics codes. Direct feedback between the codes has been assured allowing 3D fluid flow effects to be fed back into the ID system. A cycle-by-cycle convergence of results in the data exchange sections has been guaranteed. The capability of describing physical phenomena increases and some numerical problems, as the reflection of pressure waves on the 3D grid boundaries, can be avoided. The procedure has been applied to a simple test case and to a typical engine application where 3D effects are not negligible: flow field definition within an air box for race cars. The procedure has proven effective and could be easily adapted for further different applications.

[79] De Vita A., Di Angelo L., Allocca L., Early-injection and time-resolved evolution of a spray for GDI engines, American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED, 257(2 A), 135-146, (2002). Abstract
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Abstract: An experimental study was carried out to analyze the temporal and spatial evolutions of a high pressure swirled spray from an electronically controlled single-hole injector for Direct Injection of fuel in Spark Ignition engines. As such, the experimental set up and the image processing technique have proven to be effective in describing the time- and space-evolution of the spray and they can be easily adapted to further application for different injection systems. The results have provided useful information for a better understanding of the phenomena related to the high-pressure swirled-injector sprays.

[80] Allocca L., Bella G., De Vita A., Di Angelo L., Experimental validation of a GDI spray model, SAE Technical Papers, (2002). Abstract
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Abstract: A computational model and an experimental analysis have been performed to study the atomisation processes of hollow cone fuel sprays from a high pressure swirl injector for gasoline direct injection (GDI) engines. The objective has been to obtain reliable simulations and better understood structure and evolution of the spray and its interaction with air the flow field. The 3D computations are based on the KIVA 3 code in which basic spray sub models have been modified to simulate break-up phenomena and evaporation process. Spray characteristics have been measured using a system, able to gather and to process spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 80 μm). The readout system has been triggered by a TTL signal synchronized with the start of injection. A digital image processing software has been used to analyse the collected pictures. Computed and measured spray characteristics, such pre-spray and main-spray structure, tip penetration and break-up phenomena, have been compared, achieving good levels of agreement. Copyright © 2002 Society of Automotive Engineers, Inc.

[81] De Vita A., Di Angelo L., Andreassi L., Romagnuolo S., CFD-aided design of an airbox for race cars, SAE Technical Papers, (2002). Abstract
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Abstract: The design of a "high-performance" airbox for a naturally aspirated internal combustion engine (ICE) of a car racing in prototype sport competitions is described. A computational approach to achieve optimum airbox geometry in terms of fluid dynamical losses reduction and engine volumetric efficiency improvement is proposed. Experiments on race track have been carried out to test the car performances improvement. The numerical calculations have been done using a 3D numerical code. The code solves finite-difference approximation of the fluid dynamic governing equations (continuity, momentum and energy balance). The solution has been performed numerically by an integration both in space and time by means of the Arbitrarian Lagrangian Eulerian (ALE) technique. The numerical simulations have been carried out imposing steady and unsteady boundary conditions. The first ones allow to define the fluid dynamic losses and the airbox fluid dynamic behavior in order to identify an "optimum" design; the last ones, defined by means of a 1D code which takes into account the whole engine fluid dynamic scheme, contribute to describe the airbox behavior under more realistic operating conditions. The developed procedure has allowed to define the airbox geometry to be tested on race track. Tests show that there is a great improvement of car performances in comparison to the ones obtained with the unmodified airbox which originally equipped the car. Copyright © 2002 Society of Automotive Engineers, Inc.

[82] De Vita A., Di Angelo L., Allocca L., Alfuso S., Evolution of a high-pressure spray from a swirled gasoline injector, SAE Technical Papers, 2001-September(September), (2001). Abstract
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Abstract: An extensive experimental work has been made in order to analyze the structure of the spray of a large-angle single-hole high-pressure swirl injector for direct-injection spark-ignited (DISI) gasoline engines. Spatial and temporal evolution measurements of the spray have been carried out in an optically accessible vessel. The spray has been lighted by an 80 mm thickness and 12 ns duration pulsed laser sheet, generated by a 532 nm Nd-YAG laser, both along the spray axis and in cross sections perpendicularly to it. The scattered light has been collected at 90° from the laser sheet direction by a digital CCD camera with a frame grabber synchronized to the single-shot injection command and the laser start pulse. A digital image processing system has allowed analyzing the images collected by the CCD camera. It has been possible to visualize the formation and the spatial and temporal evolution of the initial liquid slug (pre-spray) and of the hollow-cone and solid-cone stray structure. Many changes in the internal spray structure at different distances from the nozzle have been observed.

[83] De Vita A., Di Angelo L., Rotondi R., Numerical and experimental investigation of an impinging gasoline low- pressure spray, SAE Technical Papers, 2001-September(September), (2001). Abstract
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Abstract: Wall film formation by gasoline low-pressure spray and the droplet rebound are important processes to be taken into account in the design of the inlet ducts and in the control optimization. Numerical simulations are nowadays the only tool able to give some information on the evolution of liquid film in the inlet duct or in the combustion chamber of gasoline engines. This paper presents an extensive numerical and experimental study of the behavior of a low- pressure gasoline injector impinging spray. Spray impingement process was analyzed using an experimental setup that is capable to elaborate spray images gathered in different time steps before and after the impact. Calculations were performed using a modified version of the KIVA3V code. New spray, wall film and post-impingement sub-models were introduced in the code. The numerical and experimental results are expressed in terms of impact velocity, spray morphology and radial and axial evolution of the post-impingement jet, as a function of characteristic parameters such as injector-wall distance and impact angle. The results provide useful information for a better understanding of the impinging of a jet on a solid wall, and for the validation of physical models implemented in the CFD code, in order to obtain more reliable simulations of the injection process.

[84] De Vita A., Di Angelo L., On the Performance of Car Interior Air Filters, SAE Technical Papers, 2001-September(September), (2001). Abstract
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Abstract: In this study, the performances of two filter media, (Cellulose single layer and dual layered wool non wool/cellulose with electrically charged fibre) for automotive cabin air cleaning application, are investigated. Pressure drops of "clean" and dust loaded filter, fractional efficiencies and behaviour of dust loading were measured. The measurements were carried out in a panel filter housing like that specified by the Society of Automotive Engineers SAE J726 Air Cleaner Test Code. Dual-layered filter, as expected, has filtration efficiency and pressure drops very higher than single layer filter. The flow fields inside the test housing were, also, measured using a Pitot tube. The filter in the housing is exposed to non uniform velocity with very high velocities in the center and lower velocities toward the edge. These velocity variations may be expected to affect the performance of the filter, in terms of efficiency, pressure drops and dust holding capacity. Simple filter efficiency model based on single fibre inertial interception was applied in order to show the influence of non uniform velocities on the filter efficiency.

[85] De Vita A., Andreassi L., Di Angelo L., Experimental and computational study for the optimization of race car intake air flow, SAE Technical Papers, (2001). Abstract
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Abstract: The performances increasing of internal combustion engines for race car has driven to develop special systems in order to improve the volumetric efficiency. To this aim, in the last years, a great effort has been done especially in studying geometries for airbox, turbo-compressors, special exhaust systems, etc. In this paper, the project of a "high-performance" airbox for a naturally aspirated internal combustion engine (ICE) of a car racing in prototype sport competitions is described. In order to optimize the airbox geometry under extremely complex operative conditions, the fluid dynamic phenomena inside the airbox have been studied by means of a three dimensional computational code (3D CFD). This approach has allowed to study different airbox geometry and to define the one to be realized and tested on race track. The new airbox geometry, defined in this way, has brought to good results. In fact, the tests on race-track, show that there is great improvement of car performances in comparison to the ones obtained with the unmodified airbox. Copyright © 2001 ATA, SAE International and SAE of Japan.