Quaternion rational surfaces: Rational surfaces generated from the quaternion product of two rational space curves

A quaternion rational surface is a surface generated from two rational space curves by quaternion multiplication. The goal of this paper is to demonstrate how to apply syzygies to analyze quaternion rational surfaces. We show that we can easily construct three special syzygies for a quaternion rational surface from a μ-basis for one of the generating rational space curves. The implicit equation of any quaternion rational surface can be computed from these three special syzygies and inversion formulas for the non-singular points on quaternion rational surfaces can be constructed. Quaternion rational ruled surfaces are generated from the quaternion product of a straight line and a rational space curve. We investigate special μ-bases for quaternion rational ruled surfaces and use these special μ-bases to provide implicitization and inversion formulas for quaternion rational ruled surfaces. Finally, we show how to determine if a real rational surface is also a quaternion rational surface.     

Crossing the Border: From Keto- to Imine Reduction in Short-Chain Dehydrogenases/Reductases

The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes.     

基于NURBS算法的工业机器人轨迹规划研究

轨迹规划是工业机器人研究领域的重要内容之一。为解决使用直线与圆弧逼近不规则曲线方法带来较大误差的问题,提出使用NURBS拟合自由曲线,并使用S形速度曲线来控制机器人末端的运动速度和加速度,使各个插补点的位置、速度和加速度能够连续,将之反推到关节空间可以得到各个关节的角度、角速度和角加速度。最后以IRB2600工业机器人为仿真本体,通过MATLAB仿真证明:NURBS和S形速度曲线相结合的方法可以得到在关节空间连续、平稳的运行轨迹、速度曲线、加速度曲线,减弱了因各关节角度、角速度、角加速度突变带来的冲击影响,优化了机器人运行轨迹。     

日本东京都都民住宅

文章介绍了日本东京都都民住宅的建筑设计、内部布局、建筑材料、装修设计、细部设计、物业管理等,以及与国内住宅设计布局上的不同之处.     

新建地区排水系统应因地制宜选用分流或合流制

提出排水制度的选择应因地制宜 ,根据各种因素综合考虑 ,而不应盲目的采用分流制。介绍了荷兰发明的合流制的优点。建议《室外排水设计规范》(GBJ 14 87)应该修正。     

生态建筑理性化表达的多样性

通过对生态建筑的本质与视觉表达多样性的挥讨,并举相应实例加以说明,从而认识到生态建筑多样化的表达方式正逐渐走向理性和科学。     

浅议城中村建筑和规划的现状与未来

面对在中国城市普遍存在“城中村”的现象,调查了“城中村”目前的人居现状及人居环境中存在的大量问题,提出改造城中村的思路与模式,揭示“城中村”实现合理城市化的重要意义。     

住房抵押贷款的理性违约及其风险的规避

分析了住房抵押贷款中借款人的理性违约，认为因住房贬值而导致的借款人理性违约，实质上是住房的价格风险在供款人和贷款人之间的重新再分配。基于对我国住房抵押贷款市场中缺乏违约风险规避机制的分析，作者提出了建立我国由政府性质的担保机构和商业保险公司共同提供保险的综合违约风险规避机制的设想。此外，就建立政府性质担保机构的问题进行了着重探讨，通过对美国联邦住房管理局（FHA）的住房抵押贷款互助保险基金（MMIF）的分析，并结合中国实际，得出了中国有必要设立政府性质担保机构的结论。     

运用合理低价评标法搞好招标管理

通过对合理低价评标法的分析,阐述了其在工作实践中所发挥的优势及运用该方法加强招标管理所要采取的必要措施,从而使投资效益在工程建设中得到充分发挥,并在激烈的竞争中使企业立于不败之地。     

广州卷烟二厂的设计规划与改造

在我国加入WTO后,国际化竞争日益加剧,国内卷烟厂为了迎接挑战相继进行异地技术改造,为厂前区规划及单体设计带来契机。通过介绍广州卷烟二厂异地技改项目的投标中标方案,旨在进一步探索烟厂厂前区规划及单体设计的创新思路。