Geometric modeling and processing

The EU-DEMO is one of the most ambitious projects of EUROfusion, aimed at designing a prototype of a nuclear fusion power plant. In 2025 a new Low-Aspect-Ratio (LAR) configuration has been introduced, replacing the past baseline by changing the aspect ratio (A) of the tokamak from 3.1 to 2.8. The LAR has several benefits from the divertor point of view, the main one is the lower heat load on the plasma facing components (PFCs). The peak heat flux to the divertor during reattachment decreased, with respect to the previous EU-DEMO configuration, by about 45%, from ≈82 MW/m2 to ≈44 MW/m2. This work presents the design of the divertor system in the LAR configuration by adopting System Engineering (SE) approach. Starting from previous baseline, the current design is updated with aim of improving the manufacturing, shielding and structural performances. Using the SE approach, previously implemented features can be transferred and modified in a rational way in the new LAR configuration. New PFCs have been proposed as well as new cooling layout for the cassette body. The inboard vertical target design has been modified based on the results obtained from the previous baseline, aiming to improve the shielding performance and reduce the temperature of the supports in normal operations.

Keywords: Divertor , EU-DEMO , Eurofer97 , Systems engineering , Virtual prototyping

In the context of EUROfusion activities for the development of the DEMO reactor design, the divertor configuration is a major challenge. The current conceptual divertor design is based on the use of EUROFER97 for the divertor cassette body, while tungsten monoblocks bonded to CuCrZr pipes are used for plasma-facing targets. The evaluations developed to identify the best water coolant thermal–hydraulic conditions avoiding material embrittlement (for EUROFER 97) and softening/hardening (for copper alloy pipes) led to the identification of a new divertor baseline solution, based on the new cooling water operating conditions, named Divertor Single Null High-Temperature (SNHT). Such conditions require water at relatively high temperature (295 °C) and pressure (15.5 MPa), posing new challenging issues related to the general layout of the divertor cassette, its structural robustness and the manufacturing technologies. This work presents a comparative assessment between two different solutions proposed for the design and manufacturing of the divertor cassette body. A preliminary structural assessment and technological parameters are considered, as well as shielding and thermo-hydraulic performances.

Keywords: Divertor , EU-DEMO , Eurofer97

The lack of a standardized methodology complicates accuracy assessment in computer-assisted mandibular reconstruction. Existing landmark-based methods are susceptible to operator variability, while surface-based comparisons can mask local deviations. This study validates a novel, automated protocol, the Global Positioning Layout (GPL), to quantify the 3D discrepancy between the virtual surgical plan and the postoperative outcome, by comparing its performance and reliability against Methods A and B. A retrospective cohort of 17 patients was analysed, with three operators performing all measurements on two occasions. The GPL method demonstrated complete reproducibility, with no inter- or intra-operator variability, providing a detailed, spatially-oriented assessment of deviations. In contrast, the landmark-based method showed poor reproducibility and systematic bias and was often inapplicable due to the absence of landmarks after resection. The surface-based method, while objective for its mean error metric, was operator-dependent for initial alignment and its non-directional output masked significant localized deviations. This study validates GPL as a robust and fully reproducible tool that overcomes the critical limitations of established techniques. The GPL method provides a strong foundation for a standardized protocol, essential for the reliable comparison of surgical outcomes, refinement of surgical techniques, and improvement of long-term patient outcomes.

Keywords: Accuracy assessment, Validation , Computer-Aided Manufacturing , Mandibular reconstruction, Computer-Aided Design , Prosthesis

AbstractA feasibility study of a new testing facility, i.e., the Volumetric Neutron Source (VNS) in a tokamak configuration, was initiated in 2023 and is now under way to address potential showstoppers. Key outcomes of the engineering activities are presented in [1] and the latest improvements in [2]. The main goal of the VNS is to provide a realistic environment to test the in-vessel components of fusion reactors, in particular the tritium-breeding blanket. Lessons learned during previous years of DEMO development point to the need for thorough nuclear design integration already at the level of the basic machine design; hence, issues related to the maintenance of the in-vessel components have been addressed at a basic level. The work presented here describes the remote maintenance strategy for VNS blanket segments, which is an adaptation of the concept proposed for DEMO in previous years [3]. The work discusses the basic approach for the development of an integrated remote blanket strategy for the VNS blanket. Consistent with the initial requirements of the machine, the remote replacement sequence of the blankets, the potential list of the required tools and transporter, and the conceptual design of some of the main tools are presented and discussed in this article.

Keywords: CAD , Conceptual design , FEM , Remote handling , Volumetric neutron source

Articulated total body models have proved to be a useful tool for multibody analyses focused on human body behaviour. Historically, they have found wide applications in vehicle crash analyses, while the respective use in forensic biomechanics is less common and is hampered by the use of generic, simplified geometries and mechanical properties. The article introduces one advancement in these models aimed to replicate the outer geometry more faithfully as this aspect is crucial whenever the expected scenario includes one or more impacts between the human body and the environment. This accurate replication of the outer geometry has been made possible by the development of statistical shape models of the human body which can be shaped according to a limited set of anthropometric measurements. The anthropomorphic model was the basis to create a subject-specific articulated total body android, whose behaviour was validated against experimental tests obtained on cadavers, simulating pedestrian-to-car impacts. The correspondence between numerical and experimental data was checked making use of metrics (EARTH and EEARTH) specifically developed for time histories comparison. This activity has led to the optimization of contact parameters, differentiating the behaviour of the head versus all other body segments. On the whole, a validated model for forensic applications has been set up. This model is characterised by a high geometric accuracy and can be used, for example, to analyse fall scenarios. Further effort will be dedicated to set up a methodology for subject-specific parametrization of joint properties in terms of range of movement and passive stiffness.

Keywords: Articulated Total Body (ATB) , Contact properties , Crash tests , Forensic biomechanics , Multibody analysis , Time histories

Mandibular reconstruction, particularly with temporomandibular joint (TMJ) involvement, is a challenging procedure where precise evaluation of condylar displacement is critical for assessing functional and anatomical outcomes. The complexity of this evaluation stems from anatomical variability, surgical techniques, and post-surgical changes, making consistent and reliable assessments difficult. To address this issue, we developed an innovative, standardized procedure for the evaluation of condylar displacement following mandibular reconstruction. The proposed procedure starts from biomedical image analysis and integrates precise segmentation with an innovative standardized alignment technique, ensuring reproducibility across different reconstructive approaches, regardless of the surgical method used. This procedure was validated through a retrospective study of 18 patients, employing a consistent 3D model reconstruction and analysis workflow. The results demonstrate that the developed procedure provides a reliable framework for comparing different reconstructive methods, regardless of whether they employ CAD/AM techniques or conventional approaches, offering a repeatable and adaptable approach for assessing mandibular reconstruction outcomes. This methodology lays the groundwork for future improvements in surgical planning and post-operative evaluation, ultimately contributing to the optimization of both functional and aesthetic results in mandibular reconstruction.

Keywords: 3D model reconstruction , condylar displacement evaluation , mandibular reconstruction , standardized alignment procedure

Background: Pediatric surgical tracheotomy is a high-risk procedure demanding specialized training due to the unique anatomical and physiological characteristics of children. A key challenge in surgical education is the limited availability of high-fidelity simulators that provide a safe environment for skill development. Methods: We developed an innovative pediatric task trainer for surgical tracheotomy using 3D printing and silicone casting. This simulator features a modular design with a replaceable cartridge replicating critical anatomical structures, including the trachea, thyroid gland, cervical fascia, vessels, and musculature. To enhance realism, it also simulates bleeding upon incision. Results: Expert physicians evaluated the trainer's anatomical accuracy, procedural realism, and overall training effectiveness. Feedback was highly positive, confirming that the device closely replicates pediatric tracheotomy conditions and offers a realistic training experience. Conclusion: The positive expert feedback highlights the simulator's potential as a valuable tool for improving surgical proficiency and reducing the risk of complications in live procedures. This task trainer represents a significant advancement in pediatric airway management training and an essential asset for surgical simulation.

Keywords: 3D printing , CAD modeling , Clinical simulation , Pediatric task trainer , Surgical tracheotomy

This article presents the preliminary results of a numerical study on the heat and mass transport properties of lattice-periodic strut-based cores. The lattice structures considered are the typical Body-Centered Cubic (BCC) and an original variant, WBCC, characterized by waved struts. A fully parametric CAD model of the lattice solid has been created, allowing the diameter of the struts and their waviness to be varied. The model is then shared with the Finite Element solver and the Computational Fluid Dynamics (CFD) solver to obtain the average thermal flux coming from an imposed thermal gradient and the pressure drop occurring when the unit cell is subjected to a fluid flow. From the post-processing of the numerical data, the effective thermal conductivity and permeability have been calculated to quantify these phenomena. Initial results show that the numerical method correctly determines the properties of unit cells, and that waviness directly induces an orthotropic behavior of both thermal and fluid dynamic properties.

Keywords: Body-Centered Cubic , Permeability , Thermal Conductivity , Waviness

Background: Mandibular reconstruction, with temporomandibular joint (TMJ) involvement, is a challenging procedure where precise evaluation of condylar displacement is critical for assessing functional and aesthetic outcomes. The complexity of this evaluation stems from anatomical variability, surgical techniques, and post-surgical changes, making consistent and reliable assessments difficult. This study assessed condylar displacement following mandibular reconstruction using a standardized protocol for reproducibility. Methods: A retrospective analysis of patients treated at AOU Careggi, Florence (2019–2023), was conducted, with preoperative, immediate postoperative, and long-term CT scans analyzed across four groups: customized microvascular bone flaps, conventional bone flaps, customized plate implants, and soft tissue-only reconstructions. Results: Customized bone flaps and plate implants minimized condylar displacement, while conventional bone flaps had initial misalignment, stabilizing over time. Soft tissue-only reconstructions led to complete condylar resorption after two years. Conclusion: The study introduced a standardized protocol for assessing condylar shifts, highlighting the advantages of CAD/CAM-based techniques in preserving TMJ integrity, and suggesting further research for refining reconstructive strategies.

Keywords: CAD-CAM technology , Condylar displacements , Fibula free flap , Mandibular reconstruction , Temporomandibular joint

In tumor resection surgery, an approach to the reconstruction of the bone anatomy, after removal of the tumor, is represented by allografts. A good match between the donor and recipient is crucial in enhancing integration and minimizing failure rate. However, the recipient bone is often altered by the tumor, making the comparison unreliable. Moreover, evaluating multiple donors is often a complex and time-consuming process. Thus, in this work, an algorithm is proposed that is able to automatically reconstruct the virtual healthy bone anatomy of the recipient and to use this reconstruction to select the most suitable donor. The proposed algorithm first reconstructs the healthy anatomy by aligning the bone to the mirrored contralateral using the Iterative Closest Point (ICP) algorithm. Then, to select the optimal donor, the algorithm queries a digital bone bank by aligning the reconstructed template to donor candidates using a localized search strategy. Finally, L1-Chamfer Distance and a newly devised metric called Surface Distance are computed to evaluate the similarity and assess the optimal donor. The algorithm was validated on a dataset of 49 healthy femurs by creating 980 simulated resections. A retrospective study on two real cases was also conducted. The algorithm achieved a median L1-Chamfer Distance of 0.7217 mm and a Surface Distance of 0.3225 mm for the reconstruction of the healthy anatomy and 0.8621 mm and 0.5338 mm, respectively, for the best donor. The retrospective studies showed how the algorithm was able to outperform the manual procedure in both time and accuracy of the allograft. These case studies highlighted how the algorithm performs efficiently even in real case scenarios, enhancing the shape matching between the recipient and donor bone and thus possibly improving post-operative outcomes.

The increasing use of geopolymers in the construction industry, driven by the need for eco-friendly production processes and the gradual replacement of Portland cement in such applications, leads to new scientific challenges. In particular, the availability of reliable tools to predict the mechanical response of this class of materials is becoming increasingly crucial for their application in a wider range of engineering solutions. In the context of this research work, and as a contribution to addressing these needs, a modeling framework based on a morphologically informed Representative Volume Element was developed and proposed. To this end, an X-ray tomographic technique was employed on geopolymer samples, and internal defects were quantified through morphometric image analysis. The resulting data were subsequently integrated into a Finite Element Method (FEM) code to build a Representative Volume Element incorporating a distribution of equivalent porosity. Therefore, numerical simulations were carried out using an explicit FEM code to reproduce a compressive mechanical test, and the results were compared with experimental data. Good agreement was observed between the experimental and numerical results, both in the linear elastic regime and during the damage initiation and failure phases of the specimens.

Keywords: CT scan , FEM , Geopolymers , morphometry , Representative Volume Element

Hollow Fiber Membrane Bioreactors (HFMBs) support mammalian cell culture at high cell density by enabling effective transport of nutrients, gases and metabolites to/from cells and by offering high membrane surface area-to-bioreactor volume ratios, scalability and flexibility in design. A recent study showed that shell-and-tube HFMBs with cells in the extracapillary space (ECS) for medicine may be designed to mimic the bone architecture for bone tissue engineering (TE). A more transport-efficient HFMB, the BRx-HFMB, consists of a 3D stack of alternating cross-woven mats of microporous and gas-permeable hollow fiber membranes with cells in the ECS and medium flowing inside the membranes. This design was shown to support the culture of a large mass of densely packed cells with high oxygen and nutrient metabolic demands similar to bone cells. Its biomimicry and rationale for good performance are poorly characterized, hindering exploitation of its characteristics for bone TE. Herein, we report the architectural and biomimetic characterization of pore/void distribution in the ECS of laboratory BRx-HFMBs using non-invasive non-destructive micro-computed tomography and advanced image analysis to minimize artifacts. The results suggest that the ECS pore architecture and specific surface area of BRx-HFMBs mimic those of bone tissue, favoring cell migration around, and adhesion on, membranes at clinical cell densities. The membrane network architecture enables cell perfusion with medium, and membranes act as spatially distributed oxygen sources promoting oxygen transport through the cell construct over longer distances than in static bioreactors. This supports the use of BRx-HFMBs to develop cellular models of bone tissue for drug testing and precision medicine. This journal is

This paper proposes a path planning algorithm, the Constrained Delaunay Triangulation Rapidly-exploring Random Tree Star (CDT-RRT*), for determining a feasible path between a start and goal node on a 2D map. While exploiting the advantages of Constrained Delaunay Triangulation (CDT) for the discretization of the map, the algorithm manages to find an optimized sequence of triangles and sequence of points belonging to some edges of this set of triangles. The resulting geometrical path is computationally faster than RRT* but with lower performances in terms of length. To improve the aspect related to path length, a final version of CDT-RRT* is presented in this paper. The addition of backtracking leads to high performances in terms of computational time while improving the path length parameter, making the resulting CDT-RRT* average value comparable to the one of RRT*. One of the main advantages of CDT-RRT* is its scalability, thus, although the nuclear fusion scenario constitutes the primary case study, the proposed methodology is also generalizable to industrial warehouses and other constrained environments.

Keywords: CDT , DT , Path planning , RRT*

Non-invasive assessment of spinal morphology traditionally relies on subjective manual palpation or data-driven deep learning models that often lack metrological interpretability. This study presents a fully automated, purely geometric framework for the localization and morphometric characterization of spinous processes directly from 3D dorsal surface scans. Leveraging continuous differential geometry and the scale-invariant properties of the shape index, the proposed algorithm operates independently of training data, physical markers, and ionizing radiation. Validation against expert clinical palpation demonstrated high spatial reliability, yielding a mean spatial deviation of 3.7 mm and a 98.6% Confidence Index in matching manually identified landmarks. Notably, the computational framework exhibited heightened morphological sensitivity, consistently extracting mathematically valid geometric signatures in spinal regions conservatively bypassed by the clinician. This resulted in a theoretical algorithmic False Negative Rate bounded between 13.5% and 14.6%, compared to a 33.1% manual rate. Furthermore, the system autonomously evaluated morphometric parameters, such as basal width, symmetry index, and local apical prominence, successfully classifying 327 apophyses into “prominent” (19%) and “masked” (81%) morphotypes across complex, soft-tissue-mediated topographies. While these findings highlight the method's capability to standardize and objectify dorsal surface assessment, definitive anatomical fidelity requires future radiological correlation. Ultimately, this robust topographic profiling lays the foundation for autonomously quantifying structural asymmetries in clinical spinal deformities.

Keywords: 3D surface topography , Automated detection , Differential geometry , Morphometrics , Non-invasive spinal assessment , Spinous process localization

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The shift toward electrification is pushing mechanical components to operate at higher rotational speeds, where fluid interactions significantly impact system efficiency due to load-independent power losses. While experimental methods and Computational Fluid Dynamics (CFD) simulations offer insights into these losses, the latter has become a fundamental design tool, especially for lubricated Rolling Element Bearings (REB) and gear systems. Recent studies highlight that solver selection, boundary conditions, and mesh quality, strongly affect simulation accuracy and computational cost. High-quality meshing, although time-consuming in the pre-processing phase, is widely recognized as a strategic investment, reducing computational efforts in simulations that can extend over weeks or months. This paper reviews and discusses meshing strategies for CFD simulations of lubricated mechanical components, focusing on open-source environments like OpenFOAM®. It examines techniques for modeling cylindrical roller bearings, tapered roller bearings, ball bearings, spur gears, helical gears, planetary gear systems, and bevel gears. It further presents mesh manipulation methods for rigid geometries under complex motions and systems involving time-dependent topological changes. A detailed literature review is provided, alongside original case studies demonstrating meshing methodologies. This work addresses a critical gap in CFD literature, offering a structured and practical guide to meshing lubricated mechanical systems.

Keywords: Grid , Multi-phase lubrication , Tribology

Percutaneous tracheotomy represents a critical airway procedure, yet training opportunities in pediatric patients remain limited due to the low incidence and high risk associated with the procedure. Simulation-based training plays a key role in enabling physicians to develop procedural skills in a safe environment. This study presents the design, fabrication, and validation of a high-fidelity physical simulator for pediatric percutaneous tracheotomy using the Frova screw technique. The simulator reproduces the anatomy of an eight-year-old patient in a hyperextended neck position, allowing rigid bronchoscope insertion, and includes relevant anatomical landmarks. The presence of a blood pocket enhances procedural realism. The modular design, with a reusable base and disposable cartridge, enables rapid reset between sessions while minimizing maintenance costs. Soft tissues were reproduced through silicone molding, while rigid components were fabricated using fused deposition modeling 3D printing. Validation was performed by 39 physicians using a structured five-point Likert scale questionnaire. The simulator achieved a mean score of 4.2/5, with item scores ranging from 3.6 to 4.7, indicating a high level of perceived realism, procedural fidelity, and educational value, as well as highlighting potential areas of improvement. These findings suggest that the proposed simulator is a useful tool for simulation-based education, with the potential to improve operator confidence and patient safety in complex airway emergencies.

Keywords: 3D printing , CAD modeling , Frova screw technique , pediatric simulator , percutaneous tracheotomy

Background and objective: Accurately measuring cervical vertebrae dimensions is crucial for diagnosing conditions, planning surgeries, and studying morphological variations related to gender, age, and ethnicity. However, traditional manual measurement methods, due to their labour-intensive nature, time-consuming process, and susceptibility to operator variability, often fall short in providing the objectivity required for reliable measurements. This study addresses these limitations by introducing a novel computer-based method for automatically identifying the dimensional features of human cervical vertebrae, leveraging 3D geometric models obtained from CT or 3D scanning. Methods: The proposed approach involves defining a local coordinate system and establishing a set of rules and parameters to evaluate the typical dimensional features of the vertebral body, foramen, and spinous process in the sagittal and coronal planes of the high-density point cloud of the cervical vertebra model. This system provides a consistent measurement reference frame, improving the method's reliability and objectivity. Based on this reference system, the method automates the traditional standard protocol, typically performed manually by radiologists, through an algorithmic approach. Results: The performance of the computer-based method was compared with the traditional manual approach using a dataset of nine complete cervical tracts. Manual measurements were conducted following a defined protocol. The manual method demonstrated poor repeatability and reproducibility, with substantial differences between the minimum and maximum values for the measured features in intra- and inter-operator evaluations. In contrast, the measurements obtained with the proposed computer-based method were consistent and repeatable. Conclusions: The proposed computer-based method provides a more reliable and objective approach for measuring the dimensional features of cervical vertebrae. It establishes a procedural standard for deducing the morphological characteristics of cervical vertebrae, with significant implications for clinical applications, such as surgical planning and diagnosis, as well as for forensic anthropology and spinal anatomy research. Further refinement and validation of the algorithmic rules and investigations into the influence of morphological abnormalities are necessary to improve the method's accuracy.

Keywords: Biomedical engineering , Cervical vertebrae , CT measures standardization

The qualification of in-vessel components for a fusion power plant requires a test environment with a high flux of 14 MeV neutrons over a sufficiently large surface and volume. Performance testing and qualification of the complex design and technologies of fusion nuclear components is needed, in particular that of the tritium breeding blanket (BB). Testing in relevant conditions over a relevant time will also allow gaining the necessary confidence regarding the build-up and control of tritium inventories inside the BB, which will be an important radioactive source. An option of such a volumetric neutron source (VNS) is a beam-driven tokamak. A feasibility study of the main machine components and associated plant systems is described in this article. The machine has a major radius of 2.53 m, a single-null divertor configuration, and four tangential 120 keV beamlines that generate a fusion power of approximately 30 MW and provide current drive for a steady-state plasma scenario. The plasma is small with a minor radius of a = 0.55 m to maximize the neutron wall load, up to 0.5 MW/m², similar to what is targeted in ITER. Approximately 25 m² are available for blanket testing including 4 port plugs, which offer flexibility regarding the test module operating conditions and the implementation of instrumentation. Given the small plasma, much of the tokamak's volume is made up by the neutron shielding structures that are similarly sized as in ITER. To reduce the construction risk, ITER-like concepts were adopted for many components. In some cases, however, lessons learned from ITER led to the development of customized or innovative concepts. Due to the modest fusion power the plasma will burn <1 kg of tritium per year, which can be provided from external sources.

Keywords: Breeding blanket testing , Demo , Remote maintenance , Tokamak , VNS , Volumetric neutron source

Building energy consumption constitutes a significant share of global energy demand. This study examines how a prefabricated building, often subject to challenges in maintaining comfort, can meet the nearly zero-energy building (nZEB) standards in Italy. This study fills the gap in the literature on prefabricated buildings that meet nZEB standards, proposing an innovative approach that integrates vacuum insulated panels (VIP) and photovoltaic systems with storage to optimize energy efficiency and thermal comfort. The paper examines an existing prefabricated building and assesses the most effective solutions to implement, along with their respective impacts on comfort and energy consumption. The model of the building is developed in EnergyPlus and verified with experimental data. The results indicate significant energy savings, demonstrating the feasibility of prefabricated buildings in achieving nZEB goals. In particular, if the building is equipped with solar shading, controlled mechanical ventilation, free cooling, and vacuum insulated panels, the thermal savings is 60 %. If the maximum photovoltaic power possible is installed on the roof the energy demand coverage is 63 %, which increases to 95 % with a storage system with a nominal capacity of 10 kWh. This paper aims to provide insights for designers, researchers and policymakers by exposing the potential for prefabricated solutions to meet stringent energy standards and promote sustainability in the construction industry.

Keywords: Dynamic simulation , Energy saving systems , nZEB building , Photovoltaic and storage systems , Prefabricated building