Search

Personalization is an emerging manufacturing paradigm towards meeting diversified customer needs. This paper proposes a framework for producing personalized products efficiently. An approach for optimal mix of different module types is proposed in order to construct a proper assembly architecture. Sketch-based modeling, which facilitates easy model creation and modification by customers, is presented as a key to personalized design. A cyber physical system provides the platform for the collaborative design and co-creation of personalized products. A case study on personalized bicycles based on the proposed framework is presented. Such a framework enables open product realization through active customer participation. [ABSTRACT FROM AUTHOR]

We describe the iterative design and evaluation of a geometric interaction technique for bare-hand mid-air virtual pottery. We model the shaping of a pot as a gradual and progressive convergence of the pot-profile to the shape of the user׳s hand represented as a point-cloud (PCL). Our pottery-inspired application served as a platform for systematically revealing how users use their hands to express the intent of deformation during a pot shaping process. Our approach involved three stages: (a) clutching by proximal-attraction, (b) shaping by proximal-attraction, and (c) shaping by grasp+motion. The design and implementation of each stage was informed by user evaluations of the previous stage. Our work evidently demonstrates that it is possible to enable users to express their intent for shape deformation without the need for a fixed set of gestures for clutching and deforming a shape. We found that the expressive capability of hand articulation can be effectively harnessed for controllable shaping by organizing the deformation process in broad classes of intended operations such as pulling, pushing, and fairing. After minimal practice with the pottery application, users could figure out their own strategy for reaching, grasping, and deforming the pot. Users particularly enjoyed using day-to-day physical objects as tools for shaping pots. [ABSTRACT FROM AUTHOR]

The advent of depth cameras has enabled mid-air interactions for shape modeling with bare hands. Typically, these interactions employ a finite set of pre-defined hand gestures to allow users to specify modeling operations in virtual space. However, human interactions in real world shaping processes (such as pottery or sculpting) are complex, iterative, and continuous. In this paper, we show that the expression of user intent in shaping processes can be derived from the geometry of contact between the hand and the manipulated object. Specifically, we describe the design and evaluation of a geometric interaction technique for bare-hand mid-air virtual pottery. We model the shaping of a pot as a gradual and progressive convergence of the pot’s profile to the shape of the user’s hand represented as a point-cloud (PCL). Thus, a user does not need to learn, know, or remember any gestures to interact with our system. Our choice of pottery simplifies the geometric representation, allowing us to systematically study how users use their hands and fingers to express the intent of deformation during a shaping process. Our evaluations demonstrate that it is possible to enable users to express their intent for shape deformation without the need for a fixed set of gestures for clutching and deforming a shape. [ABSTRACT FROM AUTHOR]

Abstract: Product design is a highly involved, often ill-defined, complex and iterative process, and the needs and specifications of the required artifact get more refined only as the design process moves toward its goal. An effective computer support tool that helps the designer make better-informed decisions requires efficient knowledge representation schemes. In today’s world, there is a virtual explosion in the amount of raw data available to the designer, and knowledge representation is critical in order to sift through this data and make sense of it. In addition, the need to stay competitive has shrunk product development time through the use of simultaneous and collaborative design processes, which depend on effective transfer of knowledge between teams. Finally, the awareness that decisions made early in the design process have a higher impact in terms of energy, cost, and sustainability, has resulted in the need to project knowledge typically required in the later stages of design to the earlier stages. Research in design rationale systems, product families, systems engineering, and ontology engineering has sought to capture knowledge from earlier product design decisions, from the breakdown of product functions and associated physical features, and from customer requirements and feedback reports. VR (Virtual reality) systems and multidisciplinary modeling have enabled the simulation of scenarios in the manufacture, assembly, and use of the product. This has helped capture vital knowledge from these stages of the product life and use it in design validation and testing. While there have been considerable and significant developments in knowledge capture and representation in product design, it is useful to sometimes review our position in the area, study the evolution of research in product design, and from past and current trends, try and foresee future developments. The goal of this paper is thus to review both our understanding of the field and the support tools that exist for the purpose, and identify the trends and possible directions research can evolve in the future. [Copyright &y& Elsevier]

Abstract: When existing parts are re-used for the development of a new product or business-to-business transactions, a method for searching parts from a database that best meet user’s requirements is essential. The core of a part search method is to measure the similarity between parts’ specifications and the user’s input data in an efficient manner. In this paper, the authors suggest a new method for part similarity measurement using ontology and multi-criteria decision making (MCDM) technique and discuss its technical details. This method ensures interoperability with existing engineering information management systems, represents part specifications in a formal manner, and has generality in search procedure. A case study with ejector pins has also been conducted for the demonstration of the proposed method. [Copyright &y& Elsevier]

Abstract: A robust technique for determining the principal axes of a 3D shape represented by a point set, possibly with noise, is presented. We use techniques from robust statistics to guide the classical principal component analysis (PCA) computation. Our algorithm is based on a robust statistics method: least median of squares (LMS), for outlier detection. Using this method, an outlier-free major region of the shape is extracted, which ignores the effect on other minor regions regarded as the outliers of the shape. In order to effectively approximate the LMS optimization, the forward search technique is utilized. We start from a small outlier-free subset robustly chosen as the major region, where an octree is used for accelerating computation. Then the region is iteratively increased by adding samples at a time. Finally, by treating the points on minor regions as outliers, we are able to define the principal axes of the shape as one of the major region. One of the advantages of our algorithm is that it automatically disregards outliers and distinguishes the shape as the major and minor regions during the principal axes determination without any extra segmentation procedure. The presented algorithm is simple and effective and gives good results for point-based shapes. The application on shape alignment is considered for demonstration purpose. [Copyright &y& Elsevier]

The replacement therapy using recombinant human FVIII (rFVIII) is the first line of therapy for hemophilia A. Approximately 15–30% of the patients develop inhibitory antibodies. Recently, we reported that liposomes composed of phosphatidylserine (PS) could reduce the immunogenicity of rFVIII. However, PS containing liposomal-rFVIII is likely to reduce the systemic exposure and efficacy of FVIII due to rapid uptake of the PS containing liposomes by the reticuloendothelial system (RES). Here, we investigated whether phosphatidylserine (PS) liposomes containing Polyethylene glycol (PEG) (PEGylated), could reduce the immunogenicity of rFVIII and reverse the reduction in systemic exposure of rFVIII. Animals given PEGylated liposomal-rFVIII had lower total and inhibitory anti-rFVIII antibody titers, compared to animals treated with rFVIII alone. The mean stimulation index of CD4+ T-cells from animals given PEGylated liposomal-rFVIII also was lower than for animals that were given rFVIII alone. Pharmacokinetic studies following intravenous dosing indicated that the systemic exposure (area under the activity curve, AUAC0–24h) of PEGylated liposomal-rFVIII was ∼59 IU/mL × h and significantly higher than that of non-PEGylated liposomal-rFVIII (AUAC0–24h ∼ 36 IU/mL × h). Based on these studies, we speculate that PEGylated PS-containing liposomal rFVIII may improve efficacy of rFVIII. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:3753–3764, 2008 [ABSTRACT FROM AUTHOR]

Factor VIII (FVIII) is a multidomain protein that is deficient in hemophilia A, a clinically important bleeding disorder. Replacement therapy using recombinant human FVIII (rFVIII) is the main therapy. However, approximately 15–30% of patients develop inhibitory antibodies that neutralize rFVIII activity. Antibodies to epitopes in C2 domain, which is involved in FVIII binding to phospholipids, are highly prevalent. Here, we investigated the effect of phosphatidylserine (PS)-containing liposomes, which bind to C2 domain with high affinity and specificity, upon the immunogenicity of rFVIII. Circular dichroism studies showed that PS-containing liposomes interfered with aggregation of rFVIII. Immunogenicity of free- versus liposomal-rFVIII was evaluated in a murine model of hemophilia A. Animals treated with s.c. injections of liposomal-rFVIII had lower total- and inhibitory titers, compared to animals treated with rFVIII alone. Antigen processing by proteolytic enzymes was reduced in the presence of liposomes. Animals treated with s.c. injections of liposomal-rFVIII showed a significant increase in rFVIII plasma concentration compared to animals that received rFVIII alone. Based on these studies, we hypothesize that specific molecular interactions between PS-containing bilayers and rFVIII may provide a basis for designing lipidic complexes that improve the stability, reduce the immunogenicity of rFVIII formulations, and permit administration by s.c. route. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1386–1398, 2008 [ABSTRACT FROM AUTHOR]

Abstract: Conventional shape matching for engineering models primarily considers rigid shape similarity. They do not seek global shape similarity while considering large local deformations. However, engineering models created by some parametric-based design can involve large parametric changes. As a result, they do not share similarity in their global shape. Hence our goal is to develop shape representations for global matching of part models that can have large dissimilarity through stretching and/or bending. This paper presents a strategy of an integrated shape matching for contours of engineering drawings inspired by the divide-and-conquer paradigm. The original shape is decoupled into two levels of shape representations namely, higher-level structure and lower-level geometry. The higher-level structure matching is then achieved driven by optimal integrated solutions from matching of lower-level local geometry. Feature points are first extracted using curve evolution to attain the two levels of representations. In order to suit engineering semantics, a new significance function for a point is defined to suppress small features using discrete curve evolution. To conduct the integrated shape matching, a mechanism of using lookup tables is employed to associate these two levels of representations. Dynamic Time Warping and Elastic Matching are employed at different levels of shape representations in order to achieve the optimal integration. To demonstrate the advantages of the proposed work for engineering shapes, experiments for contour evolution, feature point registration, and shape-based similarity for retrieval are conducted. They are also compared with the existing methods. The experimental results show that the structure-oriented contour representation and matching are more meaningful and consistent from an engineering perspective. [Copyright &y& Elsevier]

In this paper, we present a search method with multi-class probability estimates for sketch-based 3D engineering part retrieval. The purpose of using probabilistic output from classification is to support high-quality part retrieval by motivating user relevance feedback from a ranked list of top categorical choices. Given a free-hand user sketch, we use an ensemble of classifiers to estimate the likelihood of the sketch belonging to each predefined category by exploring the strengths of various individual classifiers. Complementary shape descriptors are used to generate classifiers with probabilistic output using support vector machines (SVM). A weighted linear combination rule, called adapted minimum classification error (AMCE), is developed to concurrently minimize the classification errors and the log likelihood errors. Experiments are conducted using our Engineering Shape Benchmark database to evaluate the proposed combination rule. User studies show that users can easily identify the desired classes and then the parts under the proposed method and algorithms. Compared with the best individual classifier, the classification accuracy using AMCE increased by 7% for 3D models, and the average best rank improved by 11.6% for sketches. [Copyright &y& Elsevier]

Abstract: A large amount of 2D drawings have been produced in engineering fields. To reuse and share the available drawings efficiently, we propose two methods in this paper, namely 2.5D spherical harmonics transformation and 2D shape histogram, to retrieve 2D drawings by measuring their shape similarity. The first approach represents a drawing as a spherical function by transforming it from a 2D space into a 3D space. Then a fast spherical harmonics transformation is employed to get a rotation invariant descriptor. The second statistics-based approach represents the shape of a 2D drawing using a distance distribution between two randomly sampled points. To allow users to interactively emphasize certain local shapes that they are interested in, we have adopted a flexible sampling strategy by specifying a bias sampling density upon these local shapes. The two proposed methods have many valuable properties, including transform invariance, efficiency, and robustness. In addition, their insensitivity to noise allows for the user''s causal input, thus supporting a freehand sketch-based retrieval user interface. Experiments show that a better performance can be achieved by combining them together using weights. [Copyright &y& Elsevier]

The physical phenomenon of aggregation can have profound impact on the stability of therapeutic proteins. This study focuses on the aggregation behavior of recombinant human FVIII (rFVIII), a multi-domain protein used as the first line of therapy for hemophilia A, a bleeding disorder caused by the deficiency or dysfunction of factor VIII (FVIII). Thermal denaturation of rFVIII was investigated using circular dichroism (CD) spectroscopy and size exclusion chromatography (SEC). The dependence of unfolding on heating rate indicated that the thermal denaturation of the protein was at least partly under kinetic control. The data was interpreted in terms of a simple two-state kinetic model, $N(Native)\buildrel k \over\longrightarrow A({\rm Aggregated})$, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation. Analysis of the data in terms of the above scheme suggested that under the experimental conditions used in this study, the rate-controlling step in the aggregation of rFVIII may be a unimolecular reaction involving conformational changes. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2023–2029, 2005 [ABSTRACT FROM AUTHOR]

Factor VIII (FVIII) is a multi-domain protein that is important in the clotting cascade. Its deficiency causes Hemophilia A, a bleeding disorder. The unfolding of protein domains can lead to physical instability such as aggregation, and hinder their use in replacement therapy. It has been shown that the aggregation of rFVIIII is initiated by small fluctuations in the protein's tertiary structure (Grillo et al., 2001, Biochemistry 40:586–595). We have investigated the domain(s) involved in the initiation of aggregation using circular dichroism (CD), size exclusion chromatography (SEC), fluorescence anisotropy, domain specific antibody binding, and clotting activity studies. The studies indicated that aggregation may be initiated as a result of conformational change in the C2 domain encompassing the lipid-binding region (2303–2332). The presence of O-phospho-L-Serine (OPLS), which binds to the lipid-binding region of FVIII, prevented aggregation of the protein. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1288–1299, 2005 [ABSTRACT FROM AUTHOR]

Factor VIII is a multidomain protein composed of Al, A2, B, A3, C1, and C2 domains. Deficiency or dysfunction of factor VIII causes hemophilia A, a bleeding disorder. Administration of exogenous recombinant factor VIII as a replacement leads to development of inhibitory antibodies against factor VIII in 15-30% of hemophilia A patients. Hence, less immunogenic preparations of factor VIII are highly desirable. Inhibitory antibodies against factor VIII are mainly directed against immunodominant epitopes in C2, A3, and A2 domains. Further, several universal epitopes for CD4+ T-cells have been identified within the C2 domain. The C2 domain is also known to interact specifically with phosphatidylserine-rich lipid vesicles. Here, we have investigated the hypothesis that complexation of O-phospho-L-serine, the head group of phosphatidylserine, with the C2 domain can reduce the overall immunogenicity of factor VIII. The biophysical (circular dichroism and fluorescence) and biochemical studies (ELISA and size exclusion chromatography) showed that O-phospho-L-serine binds to the phospholipid-binding region in the C2 domain, and this interaction causes subtle changes in the tertiary structure of the protein. O-Phospho-L-serine also prevented aggregation of the protein under thermal stress. The immunogenicity of the factor VIII-O-phospho-L-serine complex was evaluated in hemophilia A mice. The total and inhibitory antibody titers were lower for factor VIII-O-phospho-L-serine complex compared with factor VIII alone. Moreover, factor VIII administered as a complex with O-phospho-L-serine retained in vivo activity in hemophilia A mice. Our results suggest that factor VIII-O-phospho-L-serine complex may be beneficial to increase the physical stability and reduce immunogenicity of recombinant factor VIII preparations. [ABSTRACT FROM AUTHOR]

Cochleates are lipid-based delivery system that have found application in drug and gene delivery. They are precipitates, formed as a result of interaction between cations (e.g. Ca2+) and negatively charged phospholipids such as phosphatidylserine (PS). In the present study, we investigated the utility of fluorescent probe Laurdan (6-dodecanoyl-2-dimethylamino naphthalene) to monitor cochleate phase formation. Following addition of Ca2+ to Laurdan labeled lipid vesicles comprised of brain phosphatidylserine (BPS), a significant blue shift in the emission peak maximum of Laurdan was observed and the spectral features were distinct from those observed for the gel and liquid-crystalline (LC) phases. This is consistent with the formation of anhydrous cochleate cylinders that was further confirmed by electron microscopy studies. Due to dipolar relaxation, excitation and emission generalized polarization (GPEx and GPEm) indicate transition from a LC to a rigid and dehydrated (RD) cochleate phase. These spectral changes were utilized to monitor the influence of lipid composition, ionic strength and lamellarity on the formation of cochleate phase. The results indicated that the presence of phosphatidylcholine (PC) and bulk Na+ concentration influenced the formation of cochleate structures from small unilamellar vesicles (SUV) and multilamellar vesicles (MLV) composed of PS. The presence of PC and higher bulk Na+ concentration stabilized the PS vesicles against collapse and total loss of contents, intermediate molecular events in the formation of cochleate structures. From these studies, we conclude that Laurdan fluorescence is a sensitive and a rapid method to detect cochleate phase formation. [Copyright &y& Elsevier]

Factor VIII (FVIII), a plasma glycoprotein, is an essential cofactor in the blood coagulation cascade. It is a multidomain protein, known to bind to phosphatidylserine (PS)-containing membranes. Based on X-ray and electron crystallography data, binding of FVIII to PS-containing membranes has been proposed to occur only via the C2 domain. Based on these models, the molecular topology of membrane-bound FVIII can be envisioned as one in which only a small fraction of the protein interacts with the membrane, whereas the majority of the molecule is exposed to an aqueous milieu. We have investigated the topology of the membrane-bound FVIII using biophysical and biochemical techniques. Circular dichroism (CD) and fluorescence studies indicate no significant changes in the secondary and tertiary structure of FVIII associated with the membranes. Acrylamide quenching studies show that the protein is predominantly present on the surface of the membrane, exposed to the aqueous milieu. The light scattering and electron microscopy studies indicate the absence of vesicle aggregation and fusion. Binding studies with antibodies directed against specific epitopes in the A1, A2 and C2 domains suggest that FVIII binds to the membrane primarily via C2 domain including the specific phospholipid binding epitope (2303–2332) and may involve subtle conformational changes in this epitope region. [Copyright &y& Elsevier]

A thermoplastic adhesive bonding process with a high-density polyethylene (HDPE)-based adhesive has been developed for galvanized steel to polypropylene (PP) composite. The processing temperature significantly affects the strength of the adhesively bonded lap joints. Melting of the surface of the PP composite prior to bonding was found helpful for interdiffusion between adhesive and PP composite during the bonding process. Cataplasma aging tests showed that use of a polyester–melamine-based primer on the galvanized steel before preparation of the PP composite/galvanized steel joints reduced durability. However, the primer did not cause significant adhesion loss under cyclic moisture/temperature condition. It was established that the loss in adhesion of joints made from galvanized steel treated with primer was due to the blistering of the primer in Cataplasma environment. [Copyright &y& Elsevier]

This paper explores improving sketching skills and reducing the inhibition to sketch for student designers. In the first study, students were taught sketching skills through an in-class workshop. The effect was evaluated using a pre-mid-post test ( n = 40). In the second study, students were led through art activities to reduce their inhibition to sketch. The effect was tested using another pre-mid-post test ( n = 26). The first study found sketching skills increased, but declined with disuse. The second study found reduced inhibition immediately after the workshop, an increase after the sketch skills workshop, and a decrease over the semester. This suggests that sketch training and inhibition-reducing exercises are effective in the short term, but must be emphasized over time for a permanent change. [ABSTRACT FROM AUTHOR]

Abstract: Customers often present certain preferences relative to the same product, such as function, shape, color, and cost. The ideas in the mind of the customer can be represented by higher level concepts. However, the actual shape, color, and cost embodied in the product can only be viewed as lower-level features. In this paper, a model of preference elicitation from customers is proposed to bridge the gap between low-level features and high-level concepts. First, the attributes of customer preferences are classified using preference taxonomies that we develop. These taxonomies are represented using unstructured documents that are directly collected from customer descriptions. Second, the documents or catalogs of design requirements, containing some textual descriptions and survey reports, are then normalized by using an ontology-based semantic representation. Some semantic rules are developed to describe the low-level features of customer preferences to build an ontological knowledge base. Third, customer preferences are mapped to domain ontologies for driving high-level concept generation. A customer preference modeling framework is developed to construct a vector space model to measure the similarity between two preference concept ontologies. Finally, an empirical study is implemented, and five different customer groups are surveyed about the cell phone preferences. The query results are analyzed to deeply understand the validity of concept generation from the customer preferences. [Copyright &y& Elsevier]

Abstract: 3D shape retrieval and clustering is of current interest in several different fields, including mechanical engineering. Several new shape representations for 3D objects are continuing to emerge. Most shape representations are embedded in a variety of feature spaces. However, some of the recently reported shape representations are embedded in arbitrary metric spaces, i.e. distance spaces, rather than in multi-dimensional feature space. For such representations, the only operations available on the data objects are distance calculations between the objects. In addition, some of the view-based representations are embedded in non-metric spaces where the representations and the corresponding distances do not follow the triangle inequality. For shape clustering applications, most existing algorithms assume the shape representations either to be embedded in a multi-dimensional feature space or a metric distance space, making it difficult to evaluate several shape representations that do not conform to these assumptions. Therefore, two different approaches were evaluated for using the distance features of a shape to obtain clustering results. In the first method, the original distances are transformed into feature space using a multi-dimensional scaling approach for use with -means clustering. The second approach directly uses the original distances with a distance-based clustering algorithm. We compared the clustering effectiveness of these two approaches using a classified benchmark database of 3D models. The effect of using different shape descriptors and number of clusters was studied using four measures of clustering effectiveness. Several statistical methods, including the Rand Index and Mutual Information Index, were used to objectively evaluate the clustering efficacy. [Copyright &y& Elsevier]

Abstract: A global visibility map is a spherical image built to describe the complete set of global visible view directions for a surface. In this paper, we consider the computation of global visibility maps for regions on the boundary of a polyhedron. Both the self-occlusions introduced by a region and the global occlusions introduced by the rest of the surfaces on the boundary of the polyhedron are considered for computing a global visibility map. We show that the occluded view directions introduced between a pair of polyhedral surfaces can be computed from the spherical projection of the Minkowski sum of one surface and the reflection of the other. A suitable subset of the Minkowski sum, which shares the identical spherical projection with the complete Minkowski sum, is constructed to obtain the spherical images representing global occlusions. Our method has been successfully tested on many CAD models. It extends the previous methods for computing global visibility maps using convex decomposition, and it exhibits a better performance. [Copyright &y& Elsevier]

Abstract: The paper proposes a methodology to assist the designer at the initial stages of the design synthesis process by enabling him/her to employ knowledge and algorithms existing in graph network theory. The proposed method comprises three main stages: transforming the synthesis problem into a graph theoretic problem; devising the topology possessing special engineering properties corresponding to the system requirements; finding the geometric configuration of that topology that will possess the desired properties. To clarify the idea and to demonstrate its generality, the approach is presented through three synthesis case studies from different engineering domains: electrical networks, statics and kinematics. As is highlighted in the paper, the approach of employing graph theory in the synthesis process offers several unique advantages. Among these advantages are: gaining a general perspective on different synthesis problems from different engineering domains by transforming them into the same graph problem; employing the same graph algorithms for different synthesis problems; establishing the existence of configurations with special properties solely from the topology of the system; transferring knowledge and methods between different engineering disciplines for both the topology and the geometry generation steps. [Copyright &y& Elsevier]

Results of a combined experimental and numerical study of the rate-dependent fracture behavior of thermoplastic bonded joints are presented. Double cantilever beam joints bonded with a high-density polyethylene based adhesive were investigated, and a rate-dependent crack growth behavior was found in tests under constant loading rates. In tests with variable loading rate, stress relaxation effects had considerable influence on the crack growth behavior. A rate-dependent cohesive zone model is applied to the analysis of these rate effects during crack growth. [Copyright &y& Elsevier]

Rate effects in the failure behavior are investigated for adhesive bonds in which the source of time- dependence is the rate of the material separation in the fracture process zone. A rate-dependent cohesive zone model (CZM) is described and used to analyze rate effects during debonding. The model consists of a rate-independent CZM in parallel to a Maxwell element. General implications derived for the model with respect to rate effects in the failure behavior of adhesives are presented. The application of the model to the analysis of crack growth is described in a companion paper. [Copyright &y& Elsevier]

The mechanical interlocking of a thermoplastic adhesive and wood substrate is studied with scanning electron microscopy. A thermoplastic/glass composite is bonded to oak (Quercus) using a polypropylene based adhesive. The wood is etched away using a combination of chromic, nitric, and sulfuric acids, leaving the morphology of the adhesive interface intact. The revealed surface is examined with environmental scanning electron microscopy. We have shown for the first time that a thermoplastic adhesive conforms to features of the wood as small as 1 μm across. The adhesive penetrates the vascular tissues of the wood for more than 150 μm through openings 15 μm across, and invades hundreds of microns through larger channels. [Copyright &y& Elsevier]

We propose a conditional generative model, named Part Geometry Network (PG-Net), which synthesizes realistic objects and can be used as a robust feature descriptor for object reconstruction and classification. Surface and volumetric representations of objects have complementary properties of three-dimensional objects. Combining these modalities is more informative than using one modality alone. Therefore, PG-Net utilizes complementary properties of surface and volumetric representations by estimating curvature, surface area, and occupancy in voxel grids of objects with a single decoder as a multi-task learning. Objects are combinations of multiple parts, and therefore part geometry (PG) is essential to synthesize each part of the objects. PG-Net employs a part identifier to learn the part geometry. Additionally, we augmented a dataset by interpolating individual functional parts such as wings of an airplane, which helps learning part geometry and finding local/global minima of PG-Net. To demonstrate the capability of learning object representations of PG-Net, we performed object reconstruction and classification tasks on two standard large-scale datasets. PG-Net outperformed the state-of-the-art methods in object synthesis, classification, and reconstruction in a large margin. • Learning surface and volumetric geometry for more effective model training and shape prediction. • Synthesizing objects with the parametric model given conditional information. • Developed a feature descriptor for shape classification and reconstruction. • Learning shape distribution with a conditional generative model with multi-task learning. [ABSTRACT FROM AUTHOR]

Most three-dimensional (3D) computer-aided design (CAD) models of mechanical parts, created during the design stage, have high shape complexity. The shape complexity required of CAD models reduces according to the field of application. Therefore, it is necessary to simplify the shapes of 3D CAD models, depending on their applications. Traditional simplification methods recognize simplification target shape based on a pre-defined algorithm. Such algorithm-based methods have difficulty processing unusual partial shapes not considered in the CAD model. This paper proposes a method that uses a network based on a generative adversarial network (GAN) to simplify the 3D CAD models of mechanical parts. The proposed network recognizes and removes simplification target shapes included in the 3D CAD models of mechanical parts. A 3D CAD model dataset was constructed to train the 3D CAD model simplification network. 3D CAD models are represented in voxel form in the dataset. Next, the constructed training dataset was used to train the proposed network. Finally, a 3D voxel simplification experiment was performed to evaluate the performance of the trained network. The experiment results showed that the network had an average error rate of 3.38% for the total area of the mechanical part and an average error rate of 14.61% for the simplification target area. • We present a learning-based method for simplifying mechanical 3D CAD models. • The proposed method utilizes an adversarial learning approach. • The generator generates a simplified CAD model from the original model. • The discriminator classifies the data created by the generator as either false or true. • Our method achieved a simplification performance of around 15% error rate. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a “positive feedback loop” effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the “print-it-all” paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. [ABSTRACT FROM AUTHOR]

Laser direct deposition provides an attractive and cost effective means for repairing or remanufacturing high value engineering components. This study demonstrates the successful repair of defective voids in turbine airfoils based on a new semi-automated geometric reconstruction algorithm and a laser direct deposition process. A Boolean difference between the original defective model and the final reconstructed model yields a parameterized geometric representation of the repair volume. The experimental results of this method demonstrate the effectiveness of laser direct deposition in remanufacturing and its potential to adapt to a wide range of part defects. A Life Cycle Assessment (LCA) on the energy and environmental impacts by remanufacturing is also presented. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel interaction system, “Shape-It-Up”, for creative expression of 3D shapes through the naturalistic integration of human hand gestures with a modeling scheme dubbed intelligent generalized cylinders (IGC). To achieve this naturalistic integration, we propose a novel paradigm of shape–gesture–context interplay (SGCI) wherein the interpretation of gestures in the spatial context of a 3D shape directly deduces the designer’s intent and the subsequent modeling operations. Our key contributions towards SGCI are threefold. Firstly, we introduce a novel representation (IGC) of generalized cylinders as a function of the spatial hand gestures (postures and motion) during the creation process. This representation allows for fast creation of shapes while retaining their aesthetic features like symmetry and smoothness. Secondly, we define the spatial contexts of IGCs as proximity functions of their representational components, namely cross-sections and the skeleton with respect to the hands. Finally, we define a natural association of modification and manipulation of the IGCs by combining the hand gestures with the spatial context. Using SGCI, we implement intuitive hand-driven shape modifications through skeletal bending, sectional deformation and sectional scaling schemes. The implemented prototype involves human skeletal tracking and hand posture classification using the depth data provided by a low-cost depth sensing camera (Kinect™). With Shape-It-Up, our goal is to make the designer an integral part of the shape modeling process during early design, in contrast to the case for current CAD tools which segregate 3D sweep geometries into procedural 2D inputs in a non-intuitive and onerous process requiring extensive training. We conclusively demonstrate the modeling of a wide variety of 3D shapes within a few seconds. [Copyright &y& Elsevier]

Abstract: The process of re-creating CAD models from actual physical parts, formally known as digital shape reconstruction (DSR) is an integral part of product development, especially in re-design. While, the majority of current methods used in DSR are surface-based, our overarching goal is to obtain direct parameterization of 3D meshes, by avoiding the actual segmentation of the mesh into different surfaces. As a first step towards reverse modeling physical parts, we extract (1) locally prominent cross-sections (PCS) from triangular meshes, and (2) organize and cluster them into sweep components, which form the basic building blocks of the re-created CAD model. In this paper, we introduce two new algorithms derived from Locally Linear Embedding (LLE) (Roweis and Sauk, 2000 ) and Affinity Propagation (AP) (Frey and Dueck, 2007 ) for organizing and clustering PCS. The LLE algorithm analyzes the cross-sections (PCS) using their geometric properties to build a global manifold in an embedded space. The AP algorithm, then clusters the local cross sections by propagating affinities among them in the embedded space to form different sweep components. We demonstrate the robustness and efficiency of the algorithms through many examples including actual laser-scanned (point cloud) mechanical parts. [Copyright &y& Elsevier]

Abstract: A novel method for projecting points onto a point cloud, possibly with noise, is presented based on the point directed projection (DP) algorithm proposed by Azariadis P., Sapidis N. [Drawing curves onto a cloud of points for point-based modelling. Computer-Aided Design 2005; 37(1): 109–22]. The new method operates directly on the point cloud without any explicit or implicit surface reconstruction procedure. The presented method uses a simple, robust, and efficient algorithm: least-squares projection (LSP), which projects points onto the point cloud in a least-squares sense without any specification of the projection vector. The main contribution of this novel method is the automatic computation of the projection vector. Furthermore, we demonstrate the effectiveness of this approach through a number of application examples including thinning a point cloud, point normal estimation, projecting curves onto a point cloud and others. [Copyright &y& Elsevier]

Abstract: Three-dimensional shape retrieval is a problem of current interest in several different fields, especially in the mechanical engineering domain. There exists a large body of work in developing representations for 3D shapes. However, there has been limited work done in developing domain-dependent benchmark databases for 3D shape searching. We propose a benchmark database for evaluating shape-based search methods relevant to the mechanical engineering domain. Twelve different shape descriptors belonging to three categories, namely: (1) feature vector-based, (2) histogram-based, and (3) view-based, are compared using the benchmark database. The main contributions of this paper are the development of a new engineering shape benchmark and an understanding of the effectiveness of different shape representations for classes of engineering parts. Overall, it was found that view-based representations yielded better retrieval results for a majority of shape classes, while no single method performed best for all shape categories. [Copyright &y& Elsevier]

Abstract: Estimates suggest that more than 75% of engineering design activity comprises reuse of previous design knowledge to address a new design problem. Reusing design knowledge has great potential to improve product quality, shorten lead time, and reduce cost. However, PLM systems, which address the issue of reuse by searching for keywords in filenames, part numbers or context attached to CAD models, do not provide a robust tool to search reusable knowledge. This paper presents a brief overview of a novel approach to search for 3D models. The system is built on a client–server–database architecture. The client takes in the query input from the user along with his search preferences and passes it to the server. The server converts the shape input into feature vectors and a unique skeletal graph representation. Details of the algorithms to perform these steps are presented here. Principal advantages of our graph representation are: (i) it preserves geometry and topology of the query model, (ii) it is considerably smaller than the B-Rep graph, and (iii) it is insensitive to minor perturbations in shape, but sensitive enough to capture the major features of a shape. The combined distance of feature vectors and skeletal graphs in the database provide an indirect measure of shape similarity between models. Critical database issues such as search system efficiency, semantic gap reduction and the subjectivity of the similarity definition are addressed. This paper reports our initial results in designing, implementing and running the shape search system. [Copyright &y& Elsevier]

Abstract: Three-dimensional shape searching is a problem of current interest in several different fields. Most techniques have been developed for a particular domain and reduce a shape into a simpler shape representation. The techniques developed for a particular domain will also find applications in other domains. We classify and compare various 3D shape searching techniques based on their shape representations. A brief description of each technique is provided followed by a detailed survey of the state-of-the-art. The paper concludes by identifying gaps in current shape search techniques and identifies directions for future research. [Copyright &y& Elsevier]