Modifying CAD/CAM surfaces according to displacements prescribed at a finite set of points

This article presents a method for modifying CAD/CAM surfaces automatically in accordance with displacements prescribed at a finite set of points in R³, such as node displacements predicted by finite-element analysis. The method is based on the ‘morphing’ approach introduced by Sederberg and Parry in 1986. The input to the process consists of (a) a CAD/CAM model containing trimmed polynomial B-spline surfaces and (b) a set of points and associated displacement vectors in R³. These points are assumed to be close to, but not necessarily on, the objects of the CAD/CAM model. A rectangular volume, enclosing the CAD/CAM model and the input points in R³, is represented as a volume spline, i.e. a trivariate tensor-product spline. A modified volume spline is computed using (a) a least-squares fit based on the given point displacements, and (b) a smoothing functional. The modified CAD/CAM objects are defined as compositions of the original parametric functions and the modified volume spline (i.e. a morphing). In order to ensure compatibility with standard commercial CAD/CAM systems, the modified surfaces are fitted with appropriate splines using any standard, reasonably shape-preserving, fitting procedure applied in the parameter domains of the original surfaces.     

Fast parallel polynomial division via reduction to triangular toeplitz matrix inversion and to polynomial inversion modulo a power

It is known that division with a remainder of two polynomials of degree at most s can be performed over an arbitrary field F of constants using uniform arithmetic and Boolean circuits of depth O(log s log log s) and polynomial size. A new algorithm is presented that yields those bounds via reduction to triangular Toeplitz matrix inversion and to polynomial inversion modulo a power. (If|F| > (s?1)² or if P-uniform computation is allowed, then the depth can be reduced to O(log s).) This approach is new and makes the result conceptually simpler.     

A geometric model correctly reproducing both the regular term and the configurational entropy of a ternary solution

The historically first geometrical method pioneered by Bonnier and Caboz to evaluate the Gibbs energy of a ternary solution from the Gibbs energies of binary solutions correctly reproduces the configurational entropy, but not the regular term. In contrast, the constructs suggested by Toop, Kohler, Colinet and Muggianu result in the correct zero-order interaction parameter, but underestimate the configurational entropy. It is demonstrated that it is always possible to select compositions of the binary solutions reproducing both the regular term and the ideal entropy of mixing. A consistent method of finding these compositions is developed.     

Ensuring compatibility of G-continuous surface patches around a nodepoint

The problem of ensuring compatibility of mixed partial derivative vectors of surface patches joining G²-continuously around a common nodepoint is essential in modelling G²-continuous n-sided surfaces. Although the compatibility constraints can be removed by using C² Gregory patches, these patches have singularities at their corner points. This paper presents conditions for ensuring the compatibility of the mixed partial derivative vectors of surface patches joining G²-continuously around a common nodepoint. After investigating the solvability of these compatibility conditions, a new solution method exploiting G³-continuity of surface patches at a common nodepoint is given. Example surfaces based on this solution method are also provided.     

On the convex combination of TD and continuous triangular norms

The problem of when is a triangular norm, where T_D is the drastic product and T is a continuous triangular norm, is studied. It is shown that T_λ cannot be a triangular norm when T is nilpotent. It is also shown that T_λ is a triangular norm if T is strict and its additive generator f satisfies f(λx)=f(x)+f(λ) for all x∈[0,1]. The cases that T=T_M and T is the ordinal sum of continuous Archimedean summands are also discussed. Some left-continuous t-norms which can be combined with each other are given.     

On the shape of a set of points and lines in the plane

Detailed geometric models of the real world are in increasing demand. LiDAR data is appropriate to reconstruct urban models. In urban scenes, the individual surfaces can be reconstructed and connected to form the scene geometry. There are various methods for reconstructing the free‐form shape of a point sample on a single surface. However, these methods do not take the context of the surface into account. We present the guided α‐shape: an extension of the well known α‐shape that uses lines (guides) to indicate preferred locations for the boundary of the shape. The guided α‐shape uses (parts of) these lines as boundary where the points suggest that this is appropriate. We prove that the guided α‐shape can be constructed in O((n + m) log (n + m)) time, from an input of n points and m guides. We apply guided α‐shapes to urban reconstruction from LiDAR, where neighboring surfaces can be connected conveniently along their intersection lines into adjacent surfaces of a 3D model. We analyze guided α‐shapes of both synthetic and real data and show they are consistently better than α‐shapes for this application.     

Estimation of high-spatial resolution clear-sky longwave downward and net radiation over land surfaces from MODIS data

Surface downwelling longwave radiation (LWDN) and surface net longwave radiation (LWNT) are two components in the surface radiation budget. In this study, we developed new linear and nonlinear models using a hybrid method to derive instantaneous clear-sky LWDN over land from the Moderate Resolution Imaging Spectroradiometer (MODIS) TOA radiance at 1 km spatial resolution. The hybrid method is based on extensive radiative transfer simulation (physical) and statistical analysis (statistical). Linear and nonlinear models were derived at 5 sensor view zenith angles (0°, 15°, 30°, 45°, and 60°) to estimated LWDN using channels 27-29 and 31-34. Separate models were developed for daytime and nighttime observations. Surface pressure effect was considered by incorporating elevation in the models. The linear LWDN models account for more than 92% of variations of the simulated data sets, with standard errors less than 16.27 W/m² for all sensor view zenith angles. The nonlinear LWDN models explain more than 93% of variations, with standard errors less than 15.20 W/m². The linear and nonlinear LWDN models were applied to both Terra and Aqua TOA radiance and validated using ground data from six SURFRAD sites. The nonlinear models outperform the linear models at five sites. The averaged root mean squared errors (RMSE) of the nonlinear models are 17.60 W/m² (Terra) and 16.17 W/m² (Aqua), with averaged RMSE ~ 2.5 W/m² smaller than that of the linear models. LWNT was estimated using the nonlinear LWDN models and the artificial neural network (ANN) model method that predicts surface upwelling longwave radiation. LWNT was also validated using the same six SURFRAD sites. The averaged RMSEs are 17.72 (Terra) and 16.88 (Aqua) W/m²; the averaged biases are − 2.08 (Terra) and 1.99 (Aqua) W/m². The LWNT RMSEs are less than 20 W/m² for both Terra and Aqua observations at all sites.     

Fair, G- and C-continuous circle splines for the interpolation of sparse data points

This paper presents a carefully chosen curve blending scheme between circles, which is based on angles, rather than point positions. The result is a class of circle splines that robustly produce fair-looking G²-continuous curves without any cusps or kinks, even through rather challenging, sparse sets of interpolation points. With a simple reparameterization the curves can also be made C²-continuous. The same method is usable in the plane, on the sphere, and in 3D space.     

C3连续的单位四元数插值样条曲线

目的 构造一类C³连续的单位四元数插值样条曲线,证明它的插值性和连续性,并把它应用于刚体关键帧动画设计中。方法 利用R³空间中插值样条曲线的5次多项式调配函数的累和形式构造了S³空间中单位四元数插值样条曲线,它不仅能精确通过一系列给定的方向,而且能生成C³连续的朝向曲线。结果 与Nielson的单位四元数均匀B样条插值曲线的迭代构造方法相比,所提方法避免了为获取四元数B样条曲线控制顶点对非线性方程组迭代求解的过程,提高了运算效率;与单位四元数代数三角混合插值样条曲线的构造方法（Su方法）相比,所提方法只用到多项式基,运算速度更快。本例中创建关键帧动画所需的时间与Nielson方法和Su方法相比平均下降了73%和33%。而且,相比前两种方法,所提方法产生的四元数曲线连续性更高,由C²连续提高到C³连续,这意味着动画中刚体的朝向变化更加自然。结论 仿真结果表明,本文方法对刚体关键帧动画设计是有效的,对实时性和流畅性要求高的动画设计场合尤为适用。     

Effects of interaction parameters and melting points of pure metals on the phase diagrams of the binary alloy nanoparticle systems: A classical approach based on the regular solution model

The effects of thermodynamic properties on the phase stability of an imaginary A–B binary alloy nanoparticle system were examined using a regular solution model based on the CALPHAD method. When the two components of an alloy had the same melting points, both the liquidus and solidus temperatures decreased across the whole composition range, regardless of the sign of the interaction parameter. When the two substances had different melting points and , similar behavior was observed. However, when , the solidus and solvus lines, and the eutectic composition move to the pure substance side that has the lower melting point.     

基于.Net的三层Client/Server结构及其应用

三层Client／Server结构是数据库应用开发的新趋势。对三层Client／Server的体系结构、主要特点进行了分析，提出了三层结构设计的框架，介绍了在．NET平台下数据库应用的实现，并结合一个实例——门诊挂号子系统，探讨了基于组件的逻辑上三层结构的数据库应用的实现过程。说明了三层结构具有较好的灵活性、易维护和可重用性。     

基于.net & B/S架构的NET-OA研究与开发

通过对办公自动化现状及趋势的分析,从企事业单位的用户需求、系统的设计原则、运行架构、三层体系及实现方案出发,构建一个基于.net & B/S的企事业通用网络OA系统的平台,达到加快企事业内部信息传输、提高办事效率、整合各种资源的目的。     

The convex hull of a regular set of integer vectors is polyhedral and effectively computable

Number Decision Diagrams (NDD) provide a natural finite symbolic representation for regular set of integer vectors encoded as strings of digit vectors (least or most significant digit first). The convex hull of the set of vectors represented by a NDD is proved to be an effectively computable convex polyhedron.     

An algorithm for uniform random sampling of points in and on a hypersphere

A new algorithm, based on a set of generalized polar coordinates, is given for uniform random sampling of points in the interior or on the surface of an N-dimensional hypersphere. Computation times are compared for a variety of algorithms on several high-speed computers.     

一类活性Petri网控制器的冗余检测及结构简化

S4R(systems of sequential systems with shared resources)网是分析和解决柔性制造系统死锁现象常用的一种重要的Petri网子类模型,现有的基于S4R网的死锁预防方法通常采用对部分或者全部严格极小信标添加控制库所来实现.此类方法的不足在于得到的活性S4R控制器中往往存在冗余控制库所.针对已为网中每一个严格极小信标都逐一添加了控制库所和相关连接弧的活性S4R控制器,本文提出并设计了一种基于整数规划技术的冗余检测及结构简化方法,由此得到结构更简单、行为允许度更高的活性S4R控制器.该方法的核心思想是:如果网中已经存在一个p-不变式使得某个严格极小信标满足最大受控条件,那么为该严格极小信标添加的控制库所就是冗余的.由于该方法无需进行Petri网的可达性分析,避免了状态组合爆炸问题,因此具有较高的可行性和计算效率.最后用实验验证了本文方法的正确性和有效性.     

两阶段灰色综合测度决策模型与三角白化权函数的改进

首先将中心点三角白化权函数中对应于灰类1 和灰类s的三角白化权函数分别取为下限测度白化权函数和上限测度白化权函数. 这一改进避免了将各聚类指标的取值范围向左、右延拓的困扰. 针对灰色聚类系数向量delta_i  的各分量均衡取值或灰色聚类系数向量delta_i 有若干个位于前列的主分量取值相近, 难以判定决策对象归属的问题, 构建一种新的两阶段灰色综合测度决策模型, 以解决灰色聚类系数向量delta_i 的各分量取值趋于均衡或delta_i 有若干个位于前列的主分量取值相近情形下的综合决策问题, 并通过应用实例验证了模型的有效性.

     

Asp．net和B／S架构的档案信息管理系统应用

按照档案管理信息化的要求,以山东某通信档案信息数字化管理为例,介绍采用B／s模式和基于ASP．net技术开发档案信息数字化管理系统的系统结构、实现技术、模块设计和实现方案。该管理系统能完整、准确、迅速地提供档案管理相关信息与资源的检索、精确查询、信息更新等功能,为信息化建设更好地发展提供服务