边角后方交会的精度分析及布设方案选择

在推出边角后方会简捷精度估算式的基础上,分析并给出了待定点较优的选择区域,还讨论了其解的多值性问题及实质,针对边角后方交会应用中有较严格的布点限制,提出了双边单角后方交会的布设方案;文中给出了其点位与精度计算的固定公式,并附有实例难证。     

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.     

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).     

黑水虻在水产饲料中的应用进展

总结黑水虻的生物特性、营养成分含量及其在水产饲料中的应用,简述黑水虻幼虫不同产品形式(干虫/虫粉、脱脂虫粉、虫油、鲜虫/虫浆)在草食性、杂食性、肉食性和甲壳动物饲料中的应用进展,阐述在水产动物饲料中适量添加黑水虻可提高所饲动物的生长性能,过量添加则引起动物发生病理性变化,综述在不同水生动物中黑水虻的最适添加量,提出黑水虻在产业化生产及水产饲料中的应用前景及问题。     

Breeding and mass scale rearing of clownfish Amphiprion percula: feeding and rearing in brackishwater

Breeding and mass scale larval rearing of clownfish Amphiprion percula is very limited in brackishwater. We designed an indoor program of A. percula culture in brackishwater with a salinity of 24±1, during which the impacts of feed type, water temperature, and light intensity, on the efficiency of its reproduction, were revealed. The fish were accommodated along with sea anemones in fibre glass tanks to determine the influence of brooder diet on breeding efficiency. Higher reproductive efficiency [number of eggs laid (276 22.3 eggs)] was observed when fish were fed live Acetes sp. rather than clam (204 16.4 eggs), trash fish (155 12 eggs) and formulated feed (110 10 eggs). The spawning rate was increased during September and October (water temperature, 28.74 0.55°C) on average of 2.4 spawning per month; and low spawning rate was in January (water temperature, 24.55 0.45°C) on average of 1 spawning per month. Among three light intensities (100, 500, and 900 lx) set to evaluate larval survival rate, larvae showed the highest survival rate (65.5%) at 900 lx. The breeding method specifically in brackishwater developed in the present study is a new approach, will help the people from the regions of estuary and backwater to enhance their livelihood and it will lead to reduce the exploitation from the wild habitat.