水源热泵抽灌井布局及其运行过程中地下温度变化

本文以某水源热泵空调系统为例,建立了抽灌场地及周边地下水动力场与温度场的耦合数学模型,运用数值法求得系统运行过程中地下水的温度变化,分析了场地"热短路"效应和不同含水层中温度场的影响范围,以定量化的手段科学评价了场地抽灌井的布局及其可行性。分析结果表明,由于抽灌井之间的"热短路"程度较轻,场地的抽灌井布局可保证系统的高效运行。     

Lightning and climate: A review

Research on regional and global lightning activity and the global electrical circuit is summarized. This area of activity has greatly expanded through observations of lightning by satellite and through increased use of the natural (Schumann) resonances of the Earth–ionosphere cavity. The global electrical circuit provides a natural framework for monitoring global change on many time scales. Lightning is responsive to temperature on many time scales, but the sensitivity to temperature appears to diminish at the longer time scales.     

几种生态因子对尖刀蛏幼贝存活率和生长率的影响

2008～2009年,在浙江省海洋水产养殖研究所永兴基地研究了底质、饵料、温度和盐度对平均壳长为32.28±3.98mm的尖刀蛏（Cultelles scalprum）幼贝存活率和生长率的影响.结果表明：尖刀蛏幼贝以软泥底质最佳,实验条件下存活率达到76.7%,其次为沙底质,存活率为71.7%,最差为硬泥底质,存活率仅为60.0%;几种易于大规模培养的微藻中,最适宜的饵料为牟氏角毛藻,实验条件下存活率达到90.0%,生长率达到25.9%,其次为球等鞭金藻和亚心形扁藻;尖刀蛏幼贝存活的适宜温度为10～30℃,最适生长温度为26～30℃;存活的适宜盐度为18～26,最适生长盐度为22.尖刀蛏与其他大多数沿岸贝类一样属于广温广盐性品种,其幼贝更适宜于在盐度较低的环境中生存.     

鲈鱼对组氨酸需求量的研究

鲈鱼的生长受饲料中组氨酸(His)的含量变化显著(P<0.05)。当饲料中组氨酸含量过低或过高时,鲈鱼的终末体质量和特定生长率显著低于其它处理组,而处理组2(组氨酸含量为0.45%)、处理组3(组氨酸含量为0.57%)和处理组4(组氨酸含量为0.66%)之间差异不显著。终末体重、特定生长率和饲料效率在处理组3(组氨酸含量为0.57%)达到最大值,分别为21.0 g,1.72%d-1和0.81。以上结果表明,His是鲈鱼生长的必需氨基酸之一,且鲈鱼能有效利用晶体His。根据饲料中组氨酸的含量与鲈鱼特定生长的关系,经计算求得鲈鱼饲料中组氨酸含量为0.54%饲料干物质(即1.29%蛋白)时,鲈鱼的生长达到最佳状态。     

基于GNSS差分定位的天气雷达坐标精确定位研究

天气雷达天线馈源的精确定位关系到雷达数据的精确使用和天气雷达全网拼图的使用效果.目前,国内新一代天气雷达天线馈源坐标基本都是使用GNSS(GLobal Navigation Satellite System)系统中的美国GPS(Global Position System)系统接收机,在雷达塔楼楼顶单点瞬时定位测量得到的,误差一般大于30 m.为了提高定位精度,将GPS精确定位技术与全站仪测量相对高度结合起来,提出了一种测量天气雷达的馈源坐标的方法,可使天线馈源的海拔高度测量精度达到10 m以内.使用这种方法对北京市气象局S波段新一代天气雷达天线馈源坐标进行了实地测量,精度达到设计要求.     

关于场论和路论关系问题的探讨

电磁场与电路是电子类学生的必修基础课,希望通过讨论来改变重路轻场的现象.     

Predicting and forecasting flow discharge at sites receiving significant lateral inflow

Two models, one linear and one non‐linear, were employed for the prediction of flow discharge hydrographs at sites receiving significant lateral inflow. The linear model is based on a rating curve and permits a quick estimation of flow at a downstream site. The non‐linear model is based on a multilayer feed‐forward back propagation (FFBP) artificial neural network (ANN) and uses flow‐stage data measured at the upstream and downstream stations. ANN predicted the real‐time storm hydrographs satisfactorily and better than did the linear model. The results of sensitivity analysis indicated that when the lateral inflow contribution to the channel reach was insignificant, ANN, using only the flow‐stage data at the upstream station, satisfactorily predicted the hydrograph at the downstream station. The prediction error of ANN increases exponentially with the difference between the peak discharge used in training and that used in testing. ANN was also employed for flood forecasting and was compared with the modified Muskingum model (MMM). For a 4‐h lead time, MMM forecasts the floods reliably but could not be applied to reaches for lead times greater than the wave travel time. Although ANN and MMM had comparable performances for an 8‐h lead time, ANN is capable of forecasting floods with lead times longer than the wave travel time. Copyright © 2007 John Wiley & Sons, Ltd.     

Turbot Scophthalmus maximus：stocking density on growth, pigmentation and feed conversion

1 INTRODUCTION Turbot is a type of marine flatfish naturally distributing along the coastal area of European. It is highly demanded for good taste. The price therefore, is very expensive. To meet the consump- tion, large-scale turbot cultures were perform…     

Model Validation and Performance Evaluation for The Multi-Tethered Aerostat Subsystem of the Large Adaptive Reflector

The Canadian design for the Square Kilometre Array radio telescope includes a large multi-tethered aerostat to support the telescope’s receiver. To validate this design concept, two parallel tracks have been undertaken: a numerical simulation of the multi-tethered aerostat system has been assembled, and a one-third scale prototype of the system has been constructed. This paper describes the experimental facility, presents results from initial tests of the uncontrolled system and compares these results to the predictions of the computer model of the system. Generally, the results compare very favourably. Using the simulation, we arrive at two important design philosophies to be used in the design of the full-scale system: (a) perturbations on the confluence point should be minimized, and (b) the system stiffness should be maximized to ensure minimum response to disturbances.     

Reduced growth in hybrid tilapia (Oreochromis mossambicus ×O. Niloticus) at intermediate stocking density

Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density. This project was financially supported by the State Key Laboratory of Freshwater Ecology and Biotechnology of China and by Shanghai Fisheries University (Project SFU. 200003).