With the evolution of new manufacturing technologies such as multi-material 3D printing, one can think of new type of objects that consist of considerably less, yet heterogeneous, material, consequently being porous, lighter and cheaper, while having the very same functionality as the original object when manufactured from one single solid material. We aim at questioning five decades of traditional paradigms in geometric CAD and focus at new generation of CAD objects that are not solid, but contain heterogeneous free-form internal microstructures. We propose a unified manufacturing pipeline that involves all stages, namely design, optimization, manufacturing, and inspection of microstructured free-form geometries. We demonstrate our pipeline on an industrial test case of a blisk blade that sustains the desired pressure limits, yet requires significantly less material when compared to the solid counterpart.

This study was aimed at enhancing the thermal properties of unidirectional chopped carbon fiber (CCF)/high-density polyethylene (HDPE) composites for applications requiring unidirectional heat dissipation. CCF/HDPE composite samples were fabricated using a special post-extrusion tension alignment method. The influence of different manufacturing variables, including fiber content, length, and draw ratio (DR, representing the tension), on the thermal conductivity was examined. Moreover, the response surface methodology (RSM) was used to investigate the influence of the manufacturing process variables. Results indicated that the thermal conductivity increased with increasing CCF wt.% and DR. The increase in DR promoted fiber alignment, contributing to enhanced thermal conductivity in the aligned direction. Additionally, the thermal conductivity increased with the increase in the CCF length. The proposed approach can facilitate efficient heat management in automotive and aerospace industries.

Undeclared nuclear activities are challenging given the lack of information from the sites involved in such activities. Wide-area environmental sampling (WAES) can be an effective method to detect undeclared nuclear activities. However, it is crucial to address the potential risks during the WAES, including sample tampering or extortions. Therefore, tracking and monitoring of various on-site data is imperative to accurately interpret the status of samples and workers throughout the WAES process. 'Environmental and Geographical Data Transfer (EGDT)' was developed for the real-time monitoring of integrated on-site data. EGDT module is equipped with various sensors and can be attached to a worker's uniform or a sample storage box. This study demonstrated the technical effectiveness of EGDT by exploring three experimental methodologies for feasibility assessment. Compared to the Normal Operation case, the inference of the Sample Extortion case was predominantly based on changes in lux and dose rate. The inference of the Out-of-Work-Area case primarily relied on changes in dose rate and acceleration. Finally, the preliminary evaluation of the performance of the developed prototype was conducted, and a foundation was established for enhancing the application in the WAES process.

The study suggests that GB-CNT/PA6 multiscale hybrid composite can be used to create a network structure with controllable electrical conductivity, making it a promising material for various practical applications. The paper introduces a new method for controlling electrical conductivity of composite materials by creating a segregated network morphology (SNM) using a glass bubble (GB)-carbon nanotube (CNT)/polyamide 6 (PA6) multiscale hybrid composite. Instead of relying solely on CNTs, the addition of GB allows for a more economical process by reducing the required CNT concentration to achieve the desired electrical conductivity. The paper also analyzes the effects of varying GB and CNT content on electrical conductivity based on percolation theory. The results demonstrate an 18.8 times increase in electrical conductivity with the SNM approach. The study proposes that this approach could be used to create composite materials with controllable electrical conductivity, making them suitable for various applications.

In this study, a carbon nanotube-glass bubble/polyamide 6 (CNT-GB/PA6) multiscale hybrid composite was manufactured. Through a coagulation process including CNT and GB, a segregated network was formed to produce a composite structure with tunable thermal conductivity. Within the segregated network structure, a complex phenomenon of decrease and increase in thermal conductivity owing to the interaction by CNT and GB, and an equation to predict thermal conductivity through the contents of GB and CNT was formulated. A model to predict the thermal conductivity using the RSM analysis was presented, and the contents of GB and CNT were adjusted according to the required thermal conductivity. It was confirmed through the LFA thermal conductivity measurement that the thermal conductivity increased with GB and CNT contents. Moreover, when 30% of GB was added to the 5 wt% CNT composite, the thermal conductivity increased by about 17%. However, in the experiment to confirm the effect of GB alone, it was confirmed that the thermal conductivity decreased as the GB content increased. Thus, the size of the structural path, which was controlled by the GB content through which electrons pass, played an important role in this study. The results of this study can be used in astronautic fields that require insulation to save energy and in construction engineering where thermal insulation and heat emission are important.

The tensor product parametric representations are the most commonly used representation in geometric modeling. Yet, other representations have advantages in certain aspects, and in this work, we focus on employing implicit representations in the construction of microstructures. An implicit function, either functionally precise, or spline trivariate-based, is used to populate a macro-shape trivariate parametric form, and construct a conforming microstructure. Either the implicit tile or the macro-shape can be functionally graded or be heterogeneous, carrying graded properties such as material, translucency, or color alongside the geometry. Further, the implicit tiles can be parametrized and hence their geometry can vary across the macro-shape. The representation is locally precise and we demonstrate that in a slicing process that employs no (piecewise-linear) approximation. Finally, we demonstrate this framework on several 3D printed heterogeneous models.

In this study, we investigated a novel method of mechanical alignment to enhance the tensile properties of chopped carbon fiber (CCF)/high-density polyethylene (HDPE) composites. By utilizing a novel extruder and take-up system based on the melt spinning technique, we successfully controlled the alignment of CCF at various thicknesses using mechanical tension. This facilitated the production of extruded profiles with controlled tensile conditions. Experimental measurements were conducted to evaluate the tensile strength and modulus of the composites. The results demonstrate the effectiveness of the proposed CCF alignment method, which involves adjusting the thickness of the extruded profiles, in controlling the mechanical properties of the composites. As a result, the ultimate tensile strength increased by 50%, and the tensile modulus increased by 130%. Additionally, we developed a numerical model that predicts the tensile modulus based on randomly generated fibers and the Mori-Tanaka model for property estimation. The fiber orientation distribution was influenced by the fiber shape and manufacturing conditions. Scanning electron microscope (SEM) images revealed that the fibers aligned more along the extrusion direction with increased draw ratio. The orientation distribution of the randomly generated fibers varied significantly based on the fiber length and draw ratio, indicating a narrowed distribution range along the extrusion direction with increased fiber length or draw ratio. These findings demonstrate that the proposed CCF alignment method, which involves changing the thickness of the extruded profiles, can effectively control the mechanical properties of the composite.

We present a simple and effective method for the interactive segmentation of feature regions in a triangular mesh. From the user‐specified radius and click position, the candidate region that contains the desired feature region is defined as geodesic disc on a triangle mesh. A concavity‐aware harmonic field is then computed on the candidate region using the appropriate boundary constraints. An initial isoline is chosen by evaluating the uniformly sampled ones on the harmonic field based on the gradient magnitude. A set of feature points on the initial isoline is selected and the anisotropic geodesics passing through them are then determined as the final segmentation boundary, which is smooth and locally shortest. The experimental results show several segmentation results for various 3D models, revealing the effectiveness of the proposed method.

Background: Increasing demand for liver transplantation has led adequate donor expansion as a primary important issue.Surgeons are trying to solve the absolute shortage of supply by broadening the donor spectrum.As western centers relatively have more obese potential donors with steatosis, these centers have published several studies about application of weight loss donor in living donor liver transplantation which shows no significant difference comparing with normal graft.This study aims to compare outcomes of weight loss graft with normal graft to confirm actual outcomes in Korea.Methods: We retrospectively reviewed all the cases of living donor liver hepatectomy for liver transplantation from 2014 to 2021.Eighty donor with weight loss due to steatosis and 533 non-obese liver donors were included.Perioperative outcomes were compared between two groups.Liver volume assessment results about before and after weight loss were compared additionally to confirm trends of volume change.Results: The two groups did not differ significantly with respect to perioperative outcomes measured in terms of estimated blood loss, liver insufficiency, recovery of liver function, perioperative complication rates, and length of hospital stay.Non-obese liver donor had more chance for minimally invasive techniques than weight loss group (p = 0.008).Total liver volume and graft volume decreased with weight loss (p < 0.001) However, residual volume itself showed no significant difference between before and after weight loss (mean, 35.20 ± 4.68 vs. 36.35± 5.25, p = 0.112).Conclusions: Liver graft with weight loss produced similar perioperative outcomes and recovery rates of liver function.It allowed donor pool expansion with feasible and safe with comparable outcomes.

Objective: To investigate the feasibility and safety of RLDRH Summary of Background Data: Data for minimally invasive living-donor right hepatectomy, especially RLDRH, from a relatively large donor cohort that have not been reported yet. Methods: From March 2016 to March 2019, 52 liver donors underwent RLDRH. The clinical and perioperative outcomes of RLDRH were compared with those of CODRH (n = 62) and LADRH (n = 118). Donor satisfaction with cosmetic results was compared between RLDRH and LADRH using a body image questionnaire. Results: Although RLDRH was associated with longer operative time (minutes) (RLDRH, 493.6; CODRH, 404.4; LADRH, 355.9; P < 0.001), mean estimated blood loss (mL) was significantly lower (RLDRH, 109.8; CODRH, 287.1; LADRH, 265.5; P = 0.001). Postoperative complication rates were similar among the 3 groups (RLDRH, 23.1%; CODRH, 35.5%; LADRH, 28.0%; P = 0.420). Regarding donor satisfaction, body image and cosmetic appearance scores were significantly higher in RLDRH than in LADRH. After propensity score matching, RLDRH showed less estimated blood loss compared to those of CODRH (RLDRH, 114.7 mL; CODRH, 318.4 mL; P < 0.001), but complication rates were similar among the three groups (P = 0.748). Conclusions: RLDRH resulted in less blood loss compared with that of CODRH and similar postoperative complication rates to CODRH and LADRH. RLDRH provided better body image and cosmetic results compared with those of LADRH. RLDRH is feasible and safe when performed by surgeons experienced with both robotic and open hepatectomy.

Polar parameterizations of star-shaped domains are based on the line segments that connect a suitably chosen center point with the points on the domain's boundary. Valid (i.e., regular everywhere except at the center point) polar parameterizations are obtained when choosing a center from the kernel of the domain. Recently, the flexibility of these polar parameterizations has been enhanced by considering so-called arc fibrations ( Jüttler et al., 2019 ), which are polar parameterizations that use circular arcs in order to connect the center with the boundary points. We propose and analyze another generalization of polar parameterizations, which uses parabolic arcs instead of lines or circular arcs. This class of curves is simultaneously simpler (since admitting polynomial parameterizations) and more flexible.

We present an efficient algorithm for computing the precise Hausdorff Distance (HD) between two freeform surfaces. The algorithm is based on a hybrid Bounding Volume Hierarchy (BVH), where osculating toroidal patches (stored in the leaf nodes) provide geometric properties essential for the HD computation in high precision. Intrinsic features from the osculating geometry resolve computational issues in handling the cross-boundary problem for composite surfaces, which leads to the acceleration of HD algorithm with a solution (within machine precision) to the exact HD. The HD computation for general freeform surfaces is discussed, where we focus on the computational issues in handling the local geometry across surface boundaries or around surface corners that appear as the result of gluing multiple patches together in the modeling of generic composite surfaces. We also discuss how to switch from an approximation stage to the final step of computing the precise HD using numerical improvements and confirming the correctness of the HD computation result. The main advantage of our algorithm is in the high precision of HD computation result. As the best cases of the proposed torus-based approach, we also consider the acceleration of HD computation for freeform surfaces of revolution and linear extrusion, where we can support real-time computation even for deformable surfaces. The acceleration is mainly due to a fast biarc approximation to the planar profile curves of the simple surfaces, each generated by rotating or translating a planar curve. We demonstrate the effectiveness of the proposed approach using experimental results.

This research aims to optimize the mechanical properties of woven fabric composites, especially the elastic modulus. A micromechanics model of woven fabric composites was used to obtain the mechanical properties of the fiber composite, and a genetic algorithm (GA) was employed for the optimization tool. The structure of the fabric fiber was expressed using the width, thickness, and wave pattern of the fiber strands in the woven fabric composites. In the GA, the chromosome string consisted of the thickness and width of the fill and warp strands, and the objective function was determined to maximize the elastic modulus of the composite. Numerical analysis showed that the longitudinal mechanical properties of the strands contributed significantly to the overall elastic modulus of the composites because the longitudinal property was notably larger than the transverse property. Therefore, to improve the in-plane elastic modulus, the resulting geometry of the composites possessed large volumes of related strands with large cross-sectional areas and small strand waviness. However, the numerical results of the out-of-plane elastic modulus generated large strand waviness, which contributed to the fiber alignment in the out-of-plane direction. The findings of this research are expected to be an excellent resource for the structural design of woven fabric composites.

We present a simple algorithm for synthesizing 3D jigsaw puzzles from arbitrary 3D freeform 2-manifold geometric models represented with trimmed NURBS surfaces. The construction algorithm is based on a few conventional geometric operations on freeform curves and surfaces. In particular, we need to compute the offset of freeform NURBS surfaces (for thickening the 2-manifold surfaces) and the functional composition of a univariate curve representation to a bivariate rational surface (for breaking up a 3D model into curved jigsaw tiles). It is thus almost straightforward to convert the proposed algorithm to a practical system using standard tools available in B-rep based geometric modeling systems, that employ trimmed NURBS surfaces. We demonstrate the effectiveness of the proposed approach by fabricating several test sets of 3D jigsaw puzzles for freeform solids consisting of trimmed NURBS surface models.

We present an efficient and robust algorithm for computing the self-intersection of a freeform surface, based on a special representation of miter points, using sufficiently small quadrangles in the parameter domain. A self-intersecting surface changes its normal direction quite dramatically around miter points, located at the open endpoints of the self-intersection curve. This undesirable behavior causes serious problems in the stability of geometric algorithms on the surface. To facilitate a stable detection of miter points, we employ osculating toroidal patches and their intersections, and consider a gradual change to degenerate intersections as a signal for the detection of miter points. The exact location of each miter point is bounded by a tiny ball in the Euclidean space and is also represented as a small quadrangle in the parameter space. The surface self-intersection curve is then constructed, using a hybrid Bounding Volume Hierarchy (BVH), where the leaf nodes contain osculating toroidal patches and miter quadrangles. We demonstrate the effectiveness of our approach by using test examples of computing the self-intersection of freeform surfaces.

We present a maximum-clearance motion planning algorithm for planar geometric models with three degrees of freedom (translation and rotation). This work is based on recent developments in real-time algorithms for computing the Minkowski sums and Voronoi diagrams of planar geometric models bounded by G1-continuous sequences of circular arcs. Compared with their counterparts using polygons with no G1-continuity at vertices, the circle-based approach greatly simplifies the Voronoi structure of the collision-free space for the motion planning in a plane with three degrees of freedom. We demonstrate the effectiveness of the proposed approach by test sets of maximum-clearance motion planning through narrow passages in a plane. CCS Concepts • Computing methodologies → Motion planning; planar geometric models; circle-based algorithm; maximum-clearance; Minkowski sum; Voronoi diagram; medial axis;

Obtaining spatially continuous, high resolution thermal images is crucial in order to effectively analyze heat-related phenomena in urban areas and the inherent high spatial and temporal variations. Spatiotemporal Fusion (STF) methods can be applied to enhance spatial and temporal resolutions simultaneously, but most STF approaches for the generation of Land Surface Temperature (LST) have not focused specifically on urban regions. This study therefore proposes a two-phase approach using Landsat 8 and MODIS images acquired on a study area in Beijing to first, investigate the sharpening of the fine resolution image input with urban-related spectral indices and second, to explore the potential of implementing the sharpened results into the Spatiotemporal Adaptive Data Fusion Algorithm for Temperature Mapping (SADFAT) to generate high spatiotemporal resolution LST images in urban areas. For this test, five urban indices were selected based on their correlation with brightness temperature. In the thermal sharpening phase, the Fractional Urban Cover (FUC) index was able to delineate spatial details in urban regions whilst maintaining its correlation with the original brightness temperature image. In the STF phase however, FUC sharpened results returned relatively high levels of correlation coefficient values up to 0.689, but suffered from the highest Root Mean Squared Error (RMSE) and Average Absolute Difference (AAD) values of 4.260 K and 2.928 K, respectively. In contrast, Normalized Difference Building Index (NDBI) sharpened results recorded the lowest RMSE and AAD values of 3.126 K and 2.325 K, but also the lowest CC values. However, STF results were effective in delineating fine spatial details, ultimately demonstrating the potential of using sharpened urban or built-up indices as a means to generate sharpened thermal images for urban areas, as well as for input images in the SADFAT algorithm. The results from this study can be used to further improve STF approaches for daily and spatially continuous mapping of LST in urban areas.

We present an efficient and robust algorithm for computing the intersection curve of two freeform surfaces using a Bounding Volume Hierarchy (BVH), where the leaf nodes contain osculating toroidal patches. The covering of each surface by a union of tightly fitting toroidal patches greatly simplifies the geometric operations involved in the surface–surface-intersection computation, i.e., the bounding of surface normals, the detection of surface binormals, the point projection from one surface to the other surface, and the intersection of local surface patches. Moreover, the hierarchy of simple bounding volumes (such as rectangle-swept spheres) accelerates the geometric search for the potential pairs of surface patches that may generate some curve segments in the surface–surface-intersection. We demonstrate the effectiveness of our approach by using test examples of intersecting two freeform surfaces, including some highly non-trivial examples with tangential intersections. In particular, we test the intersection of two almost identical surfaces, where one surface is obtained from the same surface, using a rotation around a normal line by a smaller and smaller angle θ=10−k degree, k=0,…,5. The intersection results are often given as surface subpatches in some highly tangential areas, and even as the whole surface itself, when θ=0.00001∘.

We present a highly efficient algorithm for computing the minimum distance between two solids of revolution, each of which is defined by a planar cross‐section region and a rotation axis. The boundary profile curve for the cross‐section is first approximated by a bounding volume hierarchy (BVH) of fat arcs. By rotating the fat arcs around the axis, we generate the BVH of fat tori that bounds the surface of revolution. The minimum distance between two solids of revolution is then computed very efficiently using the distance between fat tori, which can be boiled down to the minimum distance computation for circles in the three‐dimensional space. Our circle‐based approach to the solids of revolution has distinctive features of geometric simplification. The main advantage is in the effectiveness of our approach in handling the complex cases where the minimum distance is obtained in non‐convex regions of the solids under consideration. Though we are dealing with a geometric problem for solids, the algorithm actually works in a computational style similar to that of handling planar curves. Compared with conventional BVH‐based methods, our algorithm demonstrates outperformance in computing speed, often 10–100 times faster. Moreover, the minimum distance can be computed very efficiently for the solids of revolution under deformation, where the dynamic reconstruction of fat arcs dominates the overall computation time and takes a few milliseconds.