一种新柱式

文章介绍了在计算机的帮助下产生的一种全新的柱式。它基于一种基本的折叠手法,其结果所呈现的极其丰富的细节超越了传统cAD工具能够绘制的极限,也超越了肉眼所能观察的极限。这些出乎意料的形式与极其微小的细节来自计算机程序的反复迭代,它们超出了建筑师的经验、教育和历史认知,无论从手法还是结果来看,都是一种彻底的创新。文章还指出,建造如此复杂的细节需要现代化的数字加工技术与独特的加工技巧。     

基于神经网络的压块机生产率预测研究

在对生产率影响因子分析的基础上,提出了应用正交试验法确定影响生产率的主要因子的快速方法。通过对主要影响因子与生产率的正交试验数据进行分析,得到用于BP神经网络预测模型的输入、输出变量以及训练神经网络所需的数据样本,多次试取隐含层和各隐含单元,并选取trainhn作为最优训练函数,建立了压块机生产率预测的人工神经网络系统。在试验结果中随机选取6组试验样本,进行连续5次挠度预测,预测值和试验实测值最大相对误差为0．14mm,解析结果表明：压块机预测结果与实验值吻合的较好,建立的人工神经网络预测模型具有较高的预测精度。     

An adjusted temperature wall function for turbulent forced convective heat transfer for bluff bodies in the atmospheric boundary layer

Accurate convective heat transfer predictions are required in building engineering and environmental studies on urban heat islands, building energy performance, building-envelope durability or conservation and (natural) ventilation of buildings. When applying computational fluid dynamics (CFD) for these computationally-expensive studies at high-Reynolds numbers, wall functions are mostly used to model the boundary-layer region. In this study, an adjustment to the standard temperature wall function is proposed for forced convective heat transfer at surfaces of typical wall-mounted bluff bodies in turbulent boundary layers, such as the atmospheric boundary layer, at moderate to high Reynolds numbers. The methodology to determine this customised temperature wall function (CWF) from validated numerical data of CFD simulations using low-Reynolds number modelling (LRNM) is explained, where a logarithmic- law behaviour is found. The performance of this CWF is evaluated for several bluff-body configurations. Standard wall functions (SWFs) yield deviations of about 40% for the convective heat transfer coefficient, compared to LRNM. With the CWF however, these deviations are reduced to about 10% or lower. The CWF therefore combines increased (wall-function) accuracy for convective heat transfer predictions with the typical advantage of wall functions compared to LRNM, being a lower grid resolution in the near-wall region, which increases computational economy and facilitates grid generation. Furthermore, this CWF can be easily implemented in existing CFD codes, and is implemented in the commercial CFD code Fluent in this study.     

复杂环境下雷达三维探测范围

构建虚拟战场系统,为实现雷达在复杂自然环境和复杂电子干扰环境影响下的雷达探测范围,根据高级传播模型(APM)的基本原理,并综合考虑电子干扰环境的影响,提出了一个改进的支援式干扰模型。该模型混合了APM和电子干扰模型,重点考虑了大气折射率的影响,可描述复杂自然环境和复杂电子干扰环境的双重影响。在可视化时,利用点绘制代替面绘制和中点代替插值点改进了移动立方体(MC)方法,提高了渲染速度。根据数据获取、数据处理和数据渲染的流程,利用可视化软件包(VTK)实现了对雷达探测范围的三维显示。     

一种基于实时语义维层次链的OLAP查询算法

目前,P2P环境下的OLAP查询策略都是基于从客户端获取查询结果集,如DSCD算法和DQDC算法等主要是研究怎样快速地从客户端获取查询结果集,由于客户端的Data Cube的实时数据更新效率低,易导致查询结果失真,从而影响OLAP的查询效率。为了提高P2P网络中OLAP的实时查询效率,提出了一种RTOS（Real-time Semantic OLAP Search,实时语义的OLAP查询）算法,并结合查询速度和失真率两方面的实验证明,该算法能有效地提高P2P环境下OLAP的决策分析性能。     

Development of cube-type SOFC stacks using anode-supported tubular cells

Tubular SOFCs have shown many desirable characteristics such as high thermal stability during rapid heat cycling and large electrode area per unit volume, which can accelerate to realize SOFC systems applicable to portable devices and auxiliary power units for automobile. So far, we have developed anode-supported tubular SOFCs with 0.8–2 mm diameter using Gd-doped CeO₂ (GDC) electrolyte, NiO-GDC anode and (La, Sr)(Co, Fe)O₃ (LSCF)-GDC cathode. In this study, a newly developed cube-type SOFC stack which consists of three SOFC bundles was designed and examined. The bundle consists of three 2 mm diameter tubular SOFCs and a rectangular shaped cathode support where these tubular cells are arranged in parallel. The performance of the stack whose volume is less than 1 cm³ was shown to be 2.8 V OCV and over 1 W at 1.6 V under 500 °C. Cathode loss factor due to current collection from cathode matrix was also estimated using a proposed model.     

基于魔方的并联机构运动支链构造及综合方法

提出了1种基于魔方的并联机构运动支链构造及综合方法,该方法不仅能够直观反映出运动支链中运动副的数量,还能展现出相邻运动副之间的轴线关系,有利于机构创新工作者,根据具体的需求综合出最优的机构构型。首先介绍了并联机构,魔方以及魔方与运动副和运动副轴线之间的相互联系;其次通过魔方的各种变换来构造出各种运动支链,并借助螺旋理论分析运动支链的末端运动特征;而后根据运动支链的末端运动特征状况进行整理、分类,组建运动支链库;最后,根据实际的需求,在运动支链库中选择合适的运动支链,构造出一系列同等运动形式的并联机构,并对其进行评估,从而得到最优的并联机构构型。     

On the role of constitutive model in the forming limit of FCC sheet metal with cube orientations

The effect on forming-limit diagrams (FLD) of an initial cube texture and its evolution was studied using the well-known M-K approach in conjunction with a viscoplastic crystal plasticity model (VPSC). We focused on how the strength of the cube texture affects localized necking. In particular, we addressed the results of Wu et al. [Effect of cube texture on sheet-metal formability. Materials Science and Engineering A 2004;364:182-7] who found that a spread about cube exhibits unexpectedly high limit strains. The FLD and yield loci were determined for several spreads about {1 0 0}〈0 0 1〉 with uniform or Gaussian distributions. A smooth transition in predicted limit strains from the ideal cube, through textures with increasing cut-off angles, to a random texture was calculated using the MK-VPSC approach. Results indicate that the constitutive model selected has a critical importance for predicting the behavior of materials that exhibit a qualitative change in the crystallographic texture, and hence, evolve anisotropically during mechanical deformation.     

Real time discrete shading

A shading technique for voxel-based images, termedcongradient shading, is presented. As the surface information is not available in voxel representation, the surface normal must be recovered from the 3D discrete voxel map itself. The technique defines the normal as one of a finite set of neighborhood-estimated gradients and can thus employ precalculated look-up tables. Furthermore, a table-driven mechanism permits changing the light source parameters by merely redefining the look-up table. The technique uses only simple arithmetic operations and is thus suitable for hardware implementation. Since it has been implemented not as a post-processor, but as part of the projection pipeline of the cube architecture, congradient shading can be executed in real time. Two versions of the technique in real time. Two versions of the technique have been conceived and implemented:unidirectional shading, in which the gradient is estimated only from neighborhoods along the scan-lines;bidirectional shading, in which both horizontal and vertical components of the gradient are considered. In spite of the simplicity of the technique, the results are practically indistinguishable from images generated by conventional techniques.This work was supported by the National Science Foundation under grants DCR 8603603, CCR 8743478, CCR 8717016, and MIP 8805130     

角锥棱镜阵列式反射镜反光性能及其评价的研究

角锥棱镜阵列式反射镜由角锥棱镜列阵构成，是用光学塑料注塑制造的。本文论述了这种反向镜反射光发散角的形成和反射光有效通光口径与入射角的系统等理论，提出了应从制造和使用角度考虑分别用新单项参数和综合参数来评定其反光性能，同时还提出了对各项参数的测量方法。