Extraction of Singular Points from Dense Motion Fields: An Analytic Approach

In this paper we propose a new method to extract the vortices, sources, and sinks from the dense motion field preliminary estimated between two images of a fluid video. This problem is essential in meteorology for instance to identify and track depressions or convective clouds in satellite images. The knowledge of such points allows in addition a compact representation of the flow which is very useful in both experimental and theoretical fluid mechanics. The method we propose here is based on an analytic representation of the flow. This approach has the advantage of being robust, simple, fast and requires few parameters.     

皮带布料机在龙滩大坝碾压混凝土施工中的应用

以美国ROTEC公司的塔带机、供料线为代表的皮带布料机已成功应用于三峡工程常态混凝土浇筑,而用于大坝主体工程碾压混凝土浇筑是个新事物;碾压混凝土施工具有连续、快速、高强度的特点,势必要求混凝土输送各个环节与之匹配、相适应。从拌和楼放料、供料线接料设计、供料线保温、塔（顶）带机仓面布料等方面入手对皮带布料机进行了分析,总结了皮带布料机在浇筑碾压混凝土施工中的经验。     

Production of biodiesel from waste fryer grease using mixed methanol/ethanol system

Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester. To untangle this problem, two-stage (acid and alkali catalyzed) method was used for biodiesel synthesis. More than 90% ester was obtained when two-stage method was used compared to ∼ 50% ester in single stage alkaline catalyst. In the case of mixed alcohol, a relatively smaller amount of ethyl esters was formed along with methyl esters. Acid value, viscosity, and cetane number of all the esters prepared from WFG were within the range of the ASTM standard. Esters obtained from WFG showed good performance as a lubricity additive.     

纵向零序电压保护新方案及其应用

由于结构设计的原因，综合性能较好的一些保护方案如横差保护和不完全纵差保护等将不能应用于大型超临界汽轮发电机。文中重点讨论了纵向零序电压保护方案的改进及其在应用中的问题。研究表明，发电机发生匝间短路故障时3次谐波电势减小，而机组外部故障时发电机3次谐波电势增大。因此，为了提高纵向零序电压保护方案的性能，可以根据故障时3次谐波电压增量的特性作为选取制动量的依据，从而提高保护性能。亦即:当3次谐波电压表现为负增量时，制动量取为0或接近0;而当3次谐波电压表现为正增量时，以该增量值作为制动量。此外，对匝间保护纵向零序电压元件增加一个小延时是可行的，它可以提高保护躲暂态3次谐波影响的能力。仿真计算表明，比例制动式纵向零序电压保护能可靠区分内外部故障，符合大型超临界汽轮发电机的保护要求。     

金平水电站沥青混凝土心墙堆石坝设计

金平水电站沥青混凝土心墙堆石坝坝高91.5 m,坝址覆盖层很厚,设计中对坝基进行振冲碎石桩加固,采用一道全封闭混凝土墙防渗.坝坡稳定采用毕肖普法和瑞典圆弧法计算,坝体和坝基的应力和变形采用三维有限元增量法计算.     

隔壁精馏塔分离芳烃混合物的模拟研究

采用隔壁精馏塔分离苯-甲苯-对二甲苯物系,用Aspen Plus软件模拟了隔壁精馏塔内温度分布及液相组成分布,考察了汽相和液相分配比对产品纯度的影响。对隔壁精馏塔模拟得到的优化操作条件为:隔壁精馏塔的理论板数为30块,侧线采出在第14块理论板,进料段为15块理论板,在进料段的第7块理论板进料,进料组成n(苯)∶n(甲苯)∶n(对二甲苯)为1∶3∶1,回流比为8.8,液相分配比为2.96,汽相分配比为0.83。在此条件下,各组分的摩尔分数大于98.5%,与实验结果基本吻合。当进料组成n(苯)∶n(甲苯)∶n(对二甲苯)为1∶3∶1时,采用隔壁精馏塔可比常规两塔流程节能27.18%。     

A Dynamic Dictionary for Priced Information with Application

In this paper we design a dynamic dictionary for the priced information model initiated by Charikar et al. Assume that a set S consisting of n elements is given such that each element has an associated price, a positive real number. The cost of performing an operation on elements of S is a function of their prices. The cost of an algorithm is the sum of the costs of all operations it performs. The objective is to design algorithms which incur low cost. In this model we propose a dynamic dictionary, supporting search, insert and delete, for keys drawn from a linearly ordered set. As an application we show that the dictionary can be used in computing the trapezoidal map of a set of line segments, a fundamental problem in computational geometry.     

基于WebGIS的粗泥沙集中来源区电子地图系统研究

基于WebGIS的粗泥沙集中来源区电子地图系统建设，以粗泥沙集中来源区作为研究区域，以黄河中游粗泥沙集中来源区水土保持工作流程（包括规划设计、计划管理、综合治理、预防监督和淤地坝管理等）为主线，依托黄河流域水土保持生态与环境监测系统网络、黄河流域水土保持监测系统数据库，建立覆盖黄河流域、黄土高原区、多沙粗沙区、粗泥沙集中来源区，面向不同水土保持管理层的水土保持监测与管理信息系统。     

再论异重流和均质流动的一些相似关系

在对上层静止下层流动的异重流和均质明渠流之间相似关系研究的基础上，本文将这一成果推广，给出了上层流动下层静止的异重流和均质明渠流之间的一些相似关系，并将结果应用于二维重叠式排取水口的水深计算，结果与前人的实验一致。考虑到实际的重叠式排取水口都是三维的，所以本文利用前人的实验结果，进一步给出了三维重叠式排取水口高度及水深的计算方法，所得结果揭示了排水口温差水跃的形成机理和形成条件。     

测定地下水流向的多计数管探头的研制

多计数管流向探头;;单孔;;总流向;;局部流向;;滤水管 掌握地下水的流动方向,有助于研究地下水的运动规律。利用放射性单孔法可以测定地下水流某一点流动方向。 应用放射性指示剂在单孔中测定地下水流向的方法由奥地利的梅尔霍费于1963年首先提出,1964年波兰的鲍劳斯齐克等把这种方法用于现场测量。放射性单孔流向测量方法有若干种,其原理基本相同,仅测量装置结构有区别,早期有单管旋转式探头。我们从1983年7月