二维不规则图形排样算法的优化

寻求二维不规则图形零件在排样区域上的最优排列 ,也就是对二维不规则图形的计算机自动排样算法进行优化 ,将在工业应用中有很广阔的前景。采用矩形包络和状态搜索相结合的排样算法对二维不规则图形零件进行排样 ,从而得到优化的排样结果     

装配式钢框架-减震围护墙的构造与机理研究

针对装配式钢框架结构存在的带门窗洞口围护墙体系易遭受地震破坏以及围护墙的附加刚度和约束效应对结构抗震不利等问题,提出一种开设门窗洞口的减震墙体——减震围护墙。为验证装配式钢框架-减震围护墙的工作机制,采用ABAQUS软件对减震围护墙（开洞）-框架单元、普通围护墙（开洞）-框架单元和减震墙板（未开洞）-框架单元进行建模分析,对比研究不同墙体对框架附加刚度、墙板应力和洞口变形的影响。结果表明：与普通围护墙相比,减震围护墙为框架提供的附加抗侧刚度和水平承载力大大减小,解决了普通围护墙过强的约束作用和附加刚度效应对结构抗震不利问题;在大位移加载工况下,减震围护墙一方面可避免墙体破坏,另一方面可减小或避免门、窗洞口变形,起到保护门、窗部件作用,从而保证地震时逃生和震后开展应急救援工作;减震围护墙对框架的附加作用主要由减震层提供,门窗开洞对框架受力性能影响较小;设置减震围护墙可避免门洞或窗洞洞口角部发生局部破坏;装配式钢框架-减震围护墙的“墙-梁”型连接构造合理可靠,门窗开洞对连接件受力影响较小。     

屏蔽机箱设计分析

一个好的机箱对于避免或减小电磁干扰、电磁辐射等具有重要作用,为此主要就设计屏蔽机箱时应全面考虑的问题进行了详细分析,并给出了一些实际建议。     

A comparison of tenurial change and privatization in two Garden City communities: Sunnyside Gardens,New York City and Garbatella,Rome

The paper problematizes public housing privatization. It compares the trajectory of tenure change in two garden communities – Garbatella, Rome and Sunnyside Gardens, New York City – which privileged public and private ownership, respectively. The cases are currently dealing with tenure change. Sunnyside experienced the enclosure of gardens and citizens’ attempt to reclaim what was held in common in order to bring back the communal spaces. Garbatella is a place where growth over time of rights, powers, immunities, and privileges is manifested in long-lasting processes of appropriation of public housing goods. Despite their different stories, Sunnyside helps to problematize the process of public housing privatization in Garbatella which is further complicated by tenure complexity, State-induced rent gap and institutional displacement. The analysis of tenure change, done by using the ‘incidents of ownership’ notion developed by Marcuse, contributes to the understanding of what public housing privatization means in social and spatial terms. Housing privatization leads to an erosion of the in-between space where individual and collective aspiration meet as a precondition for the reproduction of what is held in common: spatial goods such as open spaces and housing – a fundamental aspect of our citizenship.     

Study on flashover in a single chamber lined with combustible materials

With the theories of fire dynamics and relevant parameters of combustible lining materials, a predicted model of hot gas layer temperature during pre‐flashover stage of enclosure fires was established, and the effects of lining materials on the likelihood of flashover were theoretically analyzed. By using common commercial lining materials, such as wall papers, foam plastics, wood‐based panels, and fabric‐upholstered wall panel, the phenomenon of flashover was reproduced in a small‐scale firebox of 1/4 sizes of ISO 9705 test chamber. By comparing the theoretical results with experimental data, the equation predicting the hot gas layer of quasi‐steady enclosure fires was gained; an indicator I_FO to reflect overall the hazards of flashover and to classify flashover fires was proposed, and its application was initially studied. The study results can be helpful to explain further and overall the effects of lining materials on enclosure fires and can be used to guide the prevention of flashover by choosing appropriate interior decoration materials. Copyright © 2012 John Wiley & Sons, Ltd.     

输煤栈桥结构中主要构件的设计

输煤栈桥长期以来由于没有专门的栈桥结构规范可依,其布置、构件形式和材料选用等多种多样。本文将在栈桥设计中对整个结构体系的布置原则、主要构件的形式和选择,特别是楼板不同形式做法等相关问题进行总结,以供设计人员在今后的工作中参考。     

关于电梯设备接地问题的讨论

介绍了电气系统接地的几个概念,讨论了接地系统中导线截面的选择,设备外壳接地及保护线与防雷装置共地问题,提出了电梯设备的做法.     

试论中央空调系统中节能的几个途径

针对中央空调系统的节能方法进行了探讨,分别阐述了工艺设计、围护结构、风系统控制、暖通空调系统的运行管理等方面的节能潜力及其可行性,以期指导实践,有效地利用和节约能源,实现可持续发展。     

Finite element simulation of magnetoconvection inside a sinusoidal corrugated enclosure with discrete isoflux heating from below

A numerical investigation of the steady magnetoconvection in a sinusoidal corrugated enclosure has been performed. In this analysis, two vertical sinusoidal corrugated walls are maintained at a constant low temperature whereas a constant heat flux source whose length is varied from 20 to 80% of the reference length of the enclosure is discretely embedded at the bottom wall. The Penalty finite element method has been used to solve the governing Navier–Stokes and energy conservation equation of the fluid medium in the enclosure in order to investigate the effect of discrete heat source sizes on heat transfer for different values of Grashof number and Hartmann number. The values of the governing parameters are the Grashof number Gr (10³ to 10⁶), Hartmann number Ha (0 to 100) and Prandtl number Pr (0.71). The present numerical approach is found to be consistent and the solution is obtained in terms of stream functions and isotherm contours.     

Optimization and temperature mapping of an ultra-high thermal stability environmental enclosure

Precision metrology, lithography and machining systems will soon require sub-nanometer tolerances in order to meet the evolving needs of industry. This, in turn, requires thermal control of large environmental enclosures with sub-millidegree single-point stability and control of temperature gradients to several millidegrees. In order to optimize the system's thermal controls, it is essential to measure the open-loop transfer function. We report a technique that obtains the open-loop transfer function by utilizing a dynamic signal analyzer to perform a closed-loop frequency response measurement of the thermal system. Based on the transfer function, we designed a PI-lead compensation controller and achieved one-sigma air temperature stability of less than 1 m°C at a single point over 2 h. In order to rapidly map temperature gradients over large regions inside the 7 m³-volume enclosure, we have developed a measurement scheme that involves mechanically scanning a network of thermistors. Accurate cross calibration of the thermistors and a study of self-heating effects on temperature measurement in moving air have also been performed, which assures the relative accuracy of the thermistors is less than 1 m°C. Comparing temperature gradient maps taken before and after control improvements shows improved temperature stability over the mapped volumes.