高压线走廊下建设大型公共绿地的探索

通过闵行经济技术开发区范围内高压线走廊下的40万m~2非生产性用地建设成大型公共绿地的实践,提出了“以绿养园,以园养园”的新思路,充分体现“谁种养,谁保护,谁得益”的原则,给上海地区乃至全国开发利用高压线走廊下的土地资源,提供了借鉴。     

受控离散事件过程（CDEP）的一种代数分析方法

本文在文［１～３］的基础上，提出了受控离散事件过程（ＣＤＥＰ）的一种代数分析方法，弥补了Ｒａｍａｄｇｅ和Ｗｏｎｈａｍ［１～３］的理论对具体系统的应用缺乏可操作性的缺陷，使得对ＣＤＥＰ动态过程的分析变得更为直观，同时也使控制器的设计过程更具可操作性．     

Experimental evaluation of fishway modifications on the passage behaviour of adult Chinook salmon and steelhead at Lower Granite Dam,Snake River,USA

Previous studies of Pacific salmonid passage over Snake River dams indicated slowed passage at transition pools, the transition area between the fishway entrance and the fish ladder. In 2001 and 2002, we conducted an experiment to determine if modified weirs affected adult salmon and steelhead passage times and route selection through the Lower Granite Dam transition pool. Fish attraction flows through the lower ladder weirs were experimentally increased using removable panels. During the experiment we monitored radio‐tagged adult Chinook salmon and steelhead to determine passage routes and times through the transition pool. The weir treatment increased the number of spring–summer Chinook salmon passing straight through the transition pool compared to those exiting the transition pool to the collection channel or tailrace. Mean passage times through the transition pool differed among routes and were significantly lower during treatment periods for the exit‐to‐collection channel route in spring‐summer Chinook salmon, but not for other routes. Passage times among routes differed in steelhead, but there was no evidence of treatment effects on route use or passage time. Fall Chinook exhibited similar trends in route use and passage time to spring–summer Chinook, but differences were not significant, perhaps because of relatively small sample size. Total dam passage times did not differ by treatment or route for any run. Fish depth during passage of the transition pool suggested that most fish passed through submerged orifices and supported the hypothesis that increased water velocity through these orifices caused the increase in straight‐through passage in spring–summer Chinook. Collectively, the results suggested the weir modifications provided improvement to passage through the transition pool for spring–summer Chinook and no evidence of negative effects on other runs. The results from this study were used to develop new design criteria and modifications of the Lower Granite Dam fishway. Copyright © 2006 John Wiley & Sons, Ltd.     

高效辐射换热器的研制

本文所介绍的高效辐射换热器是指在其环缝通道中安装有网状二次传热面的辐射换热器，用对比实验方法研究了它们在空气预热温度、给热系数和阻力系数上的差别．实验表明：高效辐射换热器可强化空气侧的传热，其综合传热系数达５９Ｗ／（ｍ２·℃），而阻力系数可控制在３０００Ｐａ以内．     

伪随机流场法在堤坝渗漏探测中的应用与研究

伪随机流场法具有快捷、直接、精确有效等优点,逐步成为堤坝渗漏探测的主流方法。利用该方法,在漏水区域、库区无穷远段进行高压供电,库区内网格状布置测点,可查找渗漏入水点。通过对各异常区域的区域面积、异常区域内各测点的异常平均值以及对于严重渗漏的临界值进行计算,可判断水库渗漏通道和各渗漏点的渗漏量比例。此外,由于该方法快速便捷的特点,可以运用该方法进行实时监测。应用于某混凝土面板堆石坝的探测结果表明,利用堤坝周边已经存在的监测孔或在灌浆帷幕下游进行钻孔,进行伪随机电位差或者电流测试,可在无损条件下判断渗漏来源和通道发育方向,检测防渗处理效果。该方法可为堤坝渗漏监测预警、拟定防渗处理方案提供依据。     

Turbulent flow field comparison and related suitability for fish passage of a standard and a simplified low‐gradient vertical slot fishway

Fishways are hydraulic structures that allow passage of fish across obstructions in rivers. Vertical slot fishways—VSFs—are considered the most efficient and least selective type of technical fishway solutions, especially due to their ability to remain effective even when significant upstream and/or downstream water level fluctuations occur. The scope of the present study is to perform numerical simulations in order to investigate and compare the hydraulic turbulent flow field in a standard and a simplified version of the most common VSF design. Implications in relation to fish swimming behaviour and fish passage performance are discussed. Different water depths (as well as discharges) were investigated, using a bed slope of 5%, as a reference for low‐gradient VSFs with a very limited selectivity that can be used in multispecies rivers in grayling‐barbel regions. Results show that maximum values of velocity, turbulent kinetic energy, and Reynolds stresses are higher in the standard design. However, corresponding to slot geometry and orientation, the direction of the main jet in the simplified design is more inclined towards the left side of the pool. This causes the eddy to split into 2 smaller ones; the minimum eddy dimension is reduced from 0.4–0.5 to 0.2–0.3 m. These dimensions are detrimental for fish passage efficiency, being more comparable with fish length (0.15–0.40 m), thus affecting migrating fish stability and orientation. Furthermore, the standard design provides a more straightforward upstream path and wider areas of low flow velocities and turbulence, useful for fish resting. Therefore, it is recommended that the standard design should be preferred over its simplified version, even if its construction costs are around 10–15% higher than the simplified one.     

Stochastic defect diffusion model for relaxation effects in crystalline polyethylene

It is suggested that some relaxation processes observed in crystalline polyethylene are consequences of the diffusive motion of a particular defect called a point dislocation or twist dispiration loop along the polyethylene stems in lamellar crystals. The motion of the defect, characterized by a diffusion coefficient and a mobility, is described by solutions of the Smoluchowski diffusion equation with boundary conditions that constrain the defect to move along routes that produce experimentally observable results. The fact that passage of the defect causes both a 180° rotation of the chain and moves an extra CH₂ group in the direction of the chain axis is important to the interpretation of the data according to this model. The diffusion coefficient for a defect is estimated to be around 2 × 10^?9 cm² s^?1 at 70°C. This value is shown to be reasonable both from the viewpoint of detailed computer modelling of defect motion and contemporary ideas about scaling.     

大规模认知无线电网络的时延分析

时延作为无线网络的最基本的性能之一,对网络信息分发、路由协议设计、节点部署等都具有重要意义。与传统的无线网络不同,认知无线电网络的频谱资源具有动态变化性,该特性会对网络时延产生极大的影响。因此,如何对动态频谱环境下的大规模认知无线电网络进行时延分析,是一项很具挑战性的课题。为此,首先对动态频谱环境进行建模,将认知用户的频谱接入过程建模为一个连续时间的马尔可夫链,并建立认知用户的生存函数来量化授权用户活动以及信道数量对频谱环境的影响;其次,将上述模型与首次通过渗流理论结合起来,研究了大规模认知无线电网络时延的伸缩规律,并获取了更为精确的时延与距离比的上限值。理论分析及仿真结果表明,动态频谱环境与密度一样会对时延产生极大影响。研究结论对认知无线电网络的设计具有重要的指导意义。     

热塑性弹性体SBS异型材挤出模具设计

本文通过对异型材截面形状及原材料挤出成型性能分析，设计了正确的口模形状及合理的流线形流道，设计的模具能够生产出符合尺寸精度要求的型材。