Effects of human activities on migratory waterbirds at Lashihai Lake, China

Surveys on migratory waterbirds and their habitats at Lashihai Lake, China, were conducted from October 1999 to April 2000. Five fixed points, representing different degrees of habitat disturbance and quality, were selected around the lake. We used counts (n = 30) to compare diversity and abundance of waterbirds at each point and evaluate the effects of habitat disturbance. The distribution of waterbirds was affected by disturbance, with snore than one-third of the total species and nearly half of the total individuals occurring at the least disturbed point. Species richness was weakly and abundance was strongly correlated to habitat disturbance, but not to habitat quality. Habitat destruction and use of canoes were prominent at the lake. Naxi ethnic fishermen (n = 37) were interviewed. They caught 570 waterbirds between October 1999 and March 2000 in fishing nets. An estimation of the total number of waterbirds been trapped on the lake is 6164. Diving species were most susceptible. Conservation measures that should implement immediately include the cessation of habitat destruction, better plan for the development of tourism, a reduction in the number of canoes and zoning of the non-fishing area. (C) 2002 Elsevier Science Ltd. All rights reserved.

The Category-Theoretic Solution of Recursive Domain Equations

Recursive specifications of domains plays a crucial role in denotational semantics as developed by Scott and Strachey and their followers. The purpose of the present paper is to set up a categorical framework in which the known techniques for solving these equations find a natural place. The idea is to follow the well-known analogy between partial orders and categories, generalizing from least fixed-points of continuous functions over cpos to initial ones of continuous functors over $\omega $-categories. To apply these general ideas we introduce Wand's ${\bf O}$-categories where the morphism-sets have a partial order structure and which include almost all the categories occurring in semantics. The idea is to find solutions in a derived category of embeddings and we give order-theoretic conditions which are easy to verify and which imply the needed categorical ones. The main tool is a very general form of the limit-colimit coincidence remarked by Scott. In the concluding section we outline how compatibility considerations are to be included in the framework. A future paper will show how Scott's universal domain method can be included too.

Microsatellite-centromere distances and microsatellite diversity in different ploidy classes of Chinese shrimp (Fenneropenaeus Chinensis)

This is the first report of microsatellite-centromere mapping in this commercial species Fenneropenaeus Chinensis, and will be important for providing fixed points in the linkage groups of genetic maps. Triploid Chinese shrimp was induced by heat shock. The fertilized eggs were treated either by retention of the first polar body or the second polar body to produce Meiosis I (MI) or Meiosis II (MII) triploid. The triploidy status in each Chinese shrimp could be confirmed by nine polymorphic microsatellite loci, in which the parents with different alleles and the female parents were each heterozygous. The nine loci were mapped in relation to their centromeres in three MII triploid families, which were induced by retention of the second polar bodies after fertilization with sperm. Microsatellite-centromere (M-C) distances ranged from 9.6 cM to 37 cM under the assumption of complete interference. Information on the positions of centromeres in relation to the microsatellite loci will represent a contribution towards assembly of genetic maps in F. chinensis. Twelve polymorphic microsatellites were used to assess the heterozygosity and allelic diversity in different ploidy classes. As expected, triploids were significantly more polymorphic than diploids. The diploids had an average heterozygosity and allelic diversity value of 0.86, whereas the triploids heterozygosity averaged 0.93 and had allelic diversity value of 1.29. However, MI triploids were not significantly more polymorphic than MII in the microsatellite loci.

基于最大不动点模型的描述逻辑系统FLε的有穷基

研究了描述逻辑的有穷基问题,分析了有穷基在描述逻辑中的重要意义及其研究现状,并研究了形式概念分析中的属性蕴含和Duguenne-Guigues基问题.利用形式概念分析中Duguenne-Guigues基存在的证明结果,在F.Baader工作基础上设置了描述逻辑的描述背景,重新定义了描述背景下的属性蕴含,证明了带循环术语的描述逻辑系统FLε存在最大不动点语义(greatest fixed-points,gfp)模型,给出了带循环术语的描述逻辑系统FLε在最大不动点模型下的有穷基的存在性定理,并证明有穷基的可靠性和完备性.描述逻辑有穷基可以帮助知识工程师构建一个更适用于推理的描述逻辑知识库.

工业机器人的小脑模型控制

本文为动力学控制工业机器人提出了一种综合学习算法,这种学习算法可将以前所学的信息用于新的控制输入.这种控制方法不需要事先知道机器人动力学,它易于应用于特殊的控制问题或修改以适应实际系统中的变化,控制方法在时间上是有效的,且很适合于定点实现.学习控制算法的有效性通过4自由度的直接驱动机器人前两个关节在重复运动中的计算机仿真实验得到了验证.

工业机器人机械手的小脑模型自适应控制

本文为动力学控制工业机器人机械手提出一种综合控制算法。该控制算法,利用小脑模型算术计算机模块模拟机器人机械手的动力学方程并计算实现期望运动所需力矩作为前馈力矩控制项;利用自适应控制器实现反馈控制,以消除由输入扰动和参数变化而引起的机器人机械手运动误差。这种控制方法在时间上是有效的,且很适合于定点实现。控制方法的有效性通过四自由度的直接驱动机器人前两个关节的计算机仿真实验得到验证。

Scattering of linear water waves by a fixed and infinitely long rectangular structure parallel to a vertical wall in oblique seas

The scattering of linear water waves by an infinitely long rectangular structure parallel to a vertical wall in oblique seas is investigated. Analytical expressions for the diffracted potentials are derived using the method of separation of variables. The unknown coefficients in the expressions are determined through the application of the eigenfunction expansion matching method. The expressions for wave forces on the structure are given. The calculated results are compared with those obtained by the boundary element method. In addition, the influences of the wall, the angle of wave incidence, the width of the structure, and the distance between the structure and the wall on wave forces are discussed. The method presented here can be easily extended to the study of the diffraction of obliquely incident waves by multiple rectangular structures.

THE EFFECT OF RADIATION-INDUCED CROSS-LINKING ON THE RELAXATION OF TAUT TIE MOLECULES DURING ANNEALING OF DRAWN LDPE

Shrinkage, retractive stress, and infrared dichroism of the drawn low-density polyethylene (LDPE) as-drawn and irradiated by Co-60-ray have been measured under different annealing conditions. The shrinkage and the disorientation of the irradiated sample was undergone more rapidly than that of unirradiated one as the temperature was continuously increased, surpassing a certain value, and a higher degree of shrinkage and disorientation was achieved finally for the irradiated sample when the samples were annealed with free ends. For the samples heated isothermally with fixed ends, the retractive stress went through a maximum and then attenuated to a limited value, and the degree of such a stress attenuation for the unirradiated sample was much more than that for the irradiated sample. These results show that the taut tie molecules (TTMs) in drawn PE can relax by the pulling of chain segments out of crystal blocks that they anchored in at elevated temperatures higher than the a transition and also by the displacing of microfibrils if the samples were annealed with free ends. The cross-links produced by irradiation prohibit the former process. It was further observed that the dependence of the average extinction coefficient of the band at 2016 cm-1 on that of the band at 1894 cm-1 is related to irradiation and annealing conditions, which has also been explained by the relaxation of TTMs and the function of irradiation-induced cross-linking on the relaxation.

Protocol of capillary isoelectric focusing to separate extremely acidic and basic proteins

A new set-up was constructed for capillary isoelectric focusing (CIEF) involving a sampling capillary as a bypass fixed to the separation capillary. Sample solutions were subjected to a previously established pH gradient from the sample capillary. Besides performing conventional CIEF, the separation of ampholytic compounds with isoelectric points (p/s) beyond the pH gradient was carried out on this system. This method was termed as pH gradient driven electrophoresis (PGDE) and the basic mathematical expressions were derived to express the dynamic fundamentals. Proteins such as lysozyme, cytochrome C, and pepsin with p/s higher than 10 or below 3 were separated in a pH gradient provided by Pharmalyte (pH 3-10). Finally, this protocol convincingly exhibited its potential in the separation of a solution of chicken egg white.