Modelling the effects of dam removal on migratory walleye (Sander vitreus) early life‐history stages

Many dams in the USA have outlived their intended purpose and an increasing number are being considered for removal. Yet, quantitative studies of the potential physical, biological and ecological responses are needed to assess dam removal decisions. In this paper, the responses of migratory walleye (Sander vitreus) to increased spawning habitat availability as a result of dam removal was studied by comparing scenarios with and without a high‐head dam in the Sandusky River (Ohio), a major tributary to Lake Erie. A conceptual, ecological model was proposed to define the relationship between hydrodynamics and walleye spawning, egg hatching, larval drift and survival. A mathematical, ecological model of the early life‐history stages was then developed and coupled with time series of depth and velocity predictions over the spawning grounds from a 1‐D hydrodynamic model. Model simulations were run for 1984–1993 for both the with‐ and without‐dam scenarios to assess the potential benefit of dam removal. The simulation results demonstrated that velocity, depth and water temperature are major factors influencing adult walleye spawning success. Without the dam, 10 times the amount of spawning habitat would be available for walleye to spawn. This increase in spawning habitat area resulted in up to five times the total egg deposition and seven times the larval output to the nursing grounds, based on the assumption that 5% of the walleye population of Lake Erie migrated up the Sandusky River to spawn. We concluded that the spawning habitat in the current condition (with the dam) is limiting and additional spawning habitat upstream could significantly increase the number of larval walleye drifting to Lake Erie. The model sensitivity analysis showed that the number of walleye migrating up the river in spring is the dominant factor for larval recruitment to the lake. Copyright © 2006 John Wiley & Sons, Ltd.     

一氯胺消毒剂检测新技术及应用

讨论了传统一氯胺测定方法在应用中的局限性,并介绍了一种新的检测技术.实际应用表明该技术可以使水厂饮用水消毒中产生尽可能多的一氯胺,还可以使污水处理厂出水消毒中一氯胺的检测精确,而不受有机氯胺、亚硝酸盐和锰的干扰;帮助水厂控制过量投加氯和氨,从而降低成本.     

二维多波束蜂窝网覆盖方法研究

提出一种基于二维多波束形成的蜂窝网覆盖方法,该方法旨在通过对平面阵阵元权矢量的控制,使所形成的波束在空域上呈非均匀蜂窝网结构,达到重点地区覆盖密度高,非重点区域覆盖密度低的目的,减小资源利用率,并重点分析了波束设计思路和权值的计算方法,仿真结果表明:该覆盖方法是有效的.     

憎水性栀子蓝色素制备的研究

以浓盐酸为催化剂,采用乙酸酐酯化处理水溶性栀子蓝色素,制备了憎水性栀子蓝色素.探讨了栀子蓝色素与乙酸酐料液比、反应时间和反应温度等因素对憎水性栀子蓝色素色价的影响.结果表明:采用料液比1:20,在常温下反应4 h,为制备憎水性栀子蓝色素的最优条件.同时,通过红外光谱、可见吸收光谱及溶解性对栀子蓝色素的酯化改性进行了初步的探讨.     

基体温度对磁控溅射沉积ZAO薄膜性能的影响

利用中频交流磁控溅射方法 ,采用氧化锌铝陶瓷靶材 [w(ZnO) =98%、w(Al2 O3 ) =2 % ]制备了ZAO(ZnO∶Al)薄膜 ,观察了基体温度对ZAO薄膜的晶体结构、电学和光学性能的影响 ,采用X射线衍射仪对薄膜的结构进行了分析 ,采用光学分度计和电阻测试仪测量了薄膜的光学、电学特性 ,采用霍尔测试仪测量了薄膜的载流子浓度和霍尔迁移率。结果表明 :沉积薄膜时的基体温度对薄膜的结构、结晶状况、可见光透射率以及导电性有较大的影响。当基体温度为 2 5 0℃ ,Ar分压为 0 8Pa时 ,薄膜的最低电阻率为 4 6× 10 -4Ω·cm ,方块电阻为 35Ω时 ,可见光 (λ =5 5 0nm)透射率高达 92 0 %。     

Local residence time,residence revolution,and residence volume distributions in twin‐screw extruders

This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers     

碾压混凝土抗裂性能的几个影响因素研究

影响碾压混凝土抗裂性能的因素很多，本文主要从水泥矿物成分、石粉含量、掺和料（氧化镁等）、骨料特性（弹性模量）及砂率等方面影响因素开展试验研究，分析各因素对碾压混凝土抗裂性能的影响效果。试验结果表明，砂率和石粉含量均存在碾压混凝土抗裂能力最大的最优含量；掺入适量的氧化镁掺和料和合理增加水泥熟料中的C，S和C4AF两种矿物成分含量，对提高碾压混凝土的抗裂能力非常有利；骨料的弹性模量是影响混凝土弹性模量的重要因素，使用低弹性模量骨料可以大大降低混凝土的弹性模量，增大极限拉伸值，提高混凝土的抗裂能力。     

变频器在暖通空调行业中的应用

本文提出中央空调系统的一种变频调速改造方案，介绍了该系统的结构组成及运行原理，对系统各部分的作用进行了讨论。     

当代建筑源自通神学

通神学是西方社会科学发展的产物.当科学和人们信仰的宗教产生冲突时,人们的精神该何去何从？最终,人们的精神从通神学那里获得了安宁.本文通过研究通神学的产生,以及它对艺术,包括建筑艺术的影响,探索当代建筑的本原和发展方向--表达情感、激起情感.     

Global practical stabilization of planar linear systems in the presence of actuator saturation and input additive disturbance

In this note, we revisit the problem of global practical stabilization for planar linear systems subject to actuator saturation and input additive disturbances. A parameterized linear state feedback law is designed such that, by tuning the value of the parameter, all trajectories of the closed-loop system converge to an arbitrarily small neighborhood of the origin in a finite time and remain in there.