Quantum chemical SINDO1 study of vanadium pentoxide

An improved set of parameters for vanadium in the semiempirical quantum chemical SCF MO method SINDO1 is presented. It is shown that both the geometries and heats of formation of a number of vanadium-containing compounds calculated by this method are in good agreement with available experimental data. Model clusters of increasing size are used for the study of geometric and energetic properties of vanadium pentoxide. Both hydrogen atom and proton adsorption on the (010) surface of vanadium pentoxide and a subsequent formation of different oxygen vacancies have been investigated. Based on these computational results the reactivities of V₂O₅-surface oxygen atoms for adsorption are discussed.     

高温超高压处理HDPE的WAXD及FT－IR研究

用ＷＡＸＤ和ＦＴ－ＩＲ对高温超高压处理前后的ＨＤＰＥ进行了研究。发现经５．０ＧＰａ的高压处理或２００℃下４．０ＧＰａ的高压同时处理后的ＨＤＰＥ分子链的化学结构未发生变化。ＨＤＰＥ晶体中（２００）面与（１１０）面衍射峰的峰高比（γ）随着压力的升高而增大，表明ＨＤＰＥ分子链在超高压作用下发生了取向排列，且升高温度更有利于这种取向排列，但当压力增大至５．０ＧＰａ及温度升高至２００℃时，γ反而大幅度下降。     

Synthesis of polyurethane elastomers hypercross-linked by partially hydrated polyhydroxylated C60

Utilization of polyhydroxylated C₆₀ (fullerenols) in a condensation reaction with diisocyanated oligo(tetramethylene oxide) led to the successful fabrication of elastomeric poly (urethane-ether) networks. These polymer networks exhibit interesting thermal behavior at low temperatures, improved tensile strength and elongation at ambient temperatures, and enhanced thermal mechanical stability at high temperatures, as compared with those of the parent linear polyurethane analogues; or with the conventional oligo (tetramethylene oxide)-derived polyurethane elastomers cross-linked by trihydroxylated reagents (1,I,1-trismethylol propane) or tetrahydroxylated reagents (pentaerythritol). The presence of a limited quantity of water molecules in the condensation reaction of fullerenols with diisocyanated prepolymers modified the physical properties of the resulting elastomeric products with a notable increase in tensile strength, modulus, and Ts over those of elasotmers prepared under anhydrous conditions. These water molecules contributed effectively to the increase of the number of cross-linking centers during the reaction.     

快速凝固Al—Li—Cu—Mg—Zr合金中H相的Z相的TEM研究

用ＨＲＴＥＭ、ＴＥＭ及ＥＤＡＸ分析研究了Ａｌ－Ｌｉ－Ｃｕ－Ｚｒ合金中的一种新相（暂名Ｈ相）和六角Ｚ相的结构，确定Ｈ相具有四方点阵，点阵参数为ａ＝２．８ｎｍ，ｃ＝２．４ｎｍ，ＥＤＡＸ分析表明Ｈ明和Ｚ相均含有Ａｌ，Ｍｇ，Ｃｕ。发现Ｈ相与Ｚ相的共存取向关系为［１００］ｈ｜｜［１１２０］ｚ，［０１０］｜｜［０００１］Ｚ。还观察到Ｚ相中一种特有有的旋转畴结构。     

Efficient Reflectance and Visibility Approximations for Environment Map Rendering

We present a technique for approximating isotropic BRDFs and precomputed self-occlusion that enables accurate and efficient prefiltered environment map rendering. Our approach uses a nonlinear approximation of the BRDF as a weighted sum of isotropic Gaussian functions. Our representation requires a minimal amount of storage, can accurately represent BRDFs of arbitrary sharpness, and is above all, efficient to render. We precompute visibility due to self-occlusion and store a low-frequency approximation suitable for glossy reflections. We demonstrate our method by fitting our representation to measured BRDF data, yielding high visual quality at real-time frame rates.     

Boundary Constrained Swept Surfaces for Modelling and Animation

Due to their simplicity and intuitiveness, swept surfaces are widely used in many surface modelling applications. In this paper, we present a versatile swept surface technique called the boundary constrained swept surfaces. The most distinct feature is its ability to satisfy boundary constraints, including the shape and tangent conditions at the boundaries of a swept surface. This permits significantly varying surfaces to be both modelled and smoothly assembled, leading to the construction of complex objects. The representation, similar to an ordinary swept surface, is analytical in nature and thus it is light in storage cost and numerically very stable to compute. We also introduce a number of useful shape manipulation tools, such as sculpting forces, to deform a surface both locally and globally. In addition to being a complementary method to the mainstream surface modelling and deformation techniques, we have found it very effective in automatically rebuilding existing complex models. Model reconstruction is arguably one of the most laborious and expensive tasks in modelling complex animated characters. We demonstrate how our technique can be used to automate this process.     

水平连铸-冷轧法生产H65黄铜带工艺研究

本文主要论述采用水平连铸一冷轧工艺生产H65黄铜带的技术特点、易产生的质量问题与解决办法，以及产品的机械性能、尺寸公差及表面质量。     

Fast Voronoi modeling

The common way to construct Voronoi tessellations is to compare the distances between given reference points using a given distance function. To generalize this distance-function concept we expand an existing approach which defines distance functions by their ``unit circles'. Our new approach allows modeling the ``unit circles' by a closed Spline curve. Changing the control polygon directly affects the tessellation's appearance. Typically generalized Voronoi diagrams are represented by Voronoi vertices and curves separating the individual tiles. To obtain interactive modeling we extended an existing hardware accelerated rendering approach computing a bitmap-representation using different colors for individual tiles. With our extension, we are able to use our Spline distance representations as input for a growing process. This growing process easily takes into account weighting approaches like multiplicative, additive, and even free functional weighting.     

Consistent Viewing and Interaction for Multiple Users in Projection-Based VR Systems

In projection-based Virtual Reality (VR) systems, typically only one headtracked user views stereo images rendered from the correct view position. For other users, who are presented a distorted image, moving with the first user's head motion, it is difficult to correctly view and interact with 3D objects in the virtual environment. In close-range VR systems, such as the Virtual Workbench, distortion effects are especially large because objects are within close range and users are relatively far apart. On these systems, multi-user collaboration proves to be difficult. In this paper, we analyze the problem and describe a novel, easy to implement method to prevent and reduce image distortion and its negative effects on close-range interaction task performance. First, our method combines a shared camera model and view distortion compensation. It minimizes the overall distortion for each user, while important user-personal objects such as interaction cursors, rays and controls remain distortion-free. Second, our method retains co-location for interaction techniques to make interaction more consistent. We performed a user experiment on our Virtual Workbench to analyze user performance under distorted view conditions with and without the use of our method. Our findings demonstrate the negative impact of view distortion on task performance and the positive effect our method introduces. This indicates that our method can enhance the multi-user collaboration experience on close-range, projection-based VR systems.