This paper presents a technique for creating a smooth, closed surface from a set of 2D contours, which have been extracted from a 3D scan. The technique interprets the pixels that make up the contours as points in ℝ(3) and employs Multi-level Partition of Unity (MPU) implicit models to create a surface that approximately fits to the 3D points. Since MPU implicit models additionally require surface normal information at each point, an algorithm that estimates normals from the contour data is also described. Contour data frequently contains noise from the scanning and delineation process. MPU implicit models provide a superior approach to the problem of contour-based surface reconstruction, especially in the presence of noise, because they are based on adaptive implicit functions that locally approximate the points within a controllable error bound. We demonstrate the effectiveness of our technique with a number of example datasets, providing images and error statistics generated from our results.

In this paper we present MUG, a collaborative 3D environment to support knowledge-based conceptual design. This work integrates Computer-Aided and Collaborative Design methods with representation framework being developed for the Semantic Web. In this work, we have created a unique environment that allows a group of users, working together over the Internet, to create both a 3D layout and a knowledge-based description of a conceptual product design. MUG accepts domain-specific engineering ontologies described with the DARPA Agent Markup Language (DAML) and provides a multi-modal collaborative 3D environment, supporting shared audio and shared 3D manipulation, for users to define product structures. MUG is written entirely in the Java language and runs across a wide wide variety of hardware and operating system platforms.

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This paper provides a framework for information assurance within collaborative design based on a technique we call rolebased viewing. Role-based viewing enables role-based access control through geometric partitioning of 3D models. The partitioning is used to create variable level-of-detail (LOD) meshes, across both individual parts and assemblies, to provide a model suitable for access rights for individual actors within a collaborative design environment. We show how this technique can be used to implement a hierarchical set of security access privileges based on the Bellla Padula model. The partitioning is derived from a set of access specifications for an assembly model and its parts. The authors believe that this work is the first of its kind in the field of computer-aided design and collaborative engineering.

The microstructure and mechanical properties of ultrafine-grain (UFG) commercial-grade Al obtained by equichannel angular pressing (ECAP) are study in the temperature range 4.2–295K. Transmission electron microscopy and x-ray diffraction methods are used to show that as the number of passes increases, the grain size decreases, the grain shape becomes increasingly equiaxial, and the dislocation density inside a grain and the character of the intergrain boundaries change. An increase of the coherent scattering region and a decrease of the level of microdeformations indicate that pressing decreases the total density of imperfections of the crystal structure inside grains. As temperature decreases, the yield stress, plasticity, and strain hardening rate of UFG and coarse-grain polycrystals increase substantially. The deformation of UFG polycrystals at 4.2K becomes unstable (abrupt). The temperature dependences of the yield stress σy(T) of UFG and coarse-grain polycrystals, where the form of these dependences is characteristic for thermally activated detachment of dislocations from short-range potential barriers, are studied. The differences observed in the dependences σy(T) for UFG polycrystals are explained by a change in the nature of such barriers and the mechanism by which glide dislocations overcome them. The dependences of the yield stress σy and the coefficient of strain hardening θ on the grain size d are obtained. It is determined that the Hall–Petch relation describes the function σy(d) in the temperature interval 4.2–295K. The Hall–Petch coefficient increases as temperature decreases. The function θ(d) is monotonically decreasing at 295 and 77K but θ is independent of d at 4.2K. The experimental data are discussed within the framework of existing notions about the influence of the microstructure produced by ECAP on the evolution of the dislocation density during subsequent deformation.