A critical state model for sands dependent on stress and density

An elastoplastic model for sands is presented in this paper, which can describe stress–strain behaviour dependent on mean effective stress level and void ratio. The main features of the proposed model are: (a) a new state parameter, which is dependent on the initial void ratio and initial mean stress, is proposed and applied to the yield function in order to predict the plastic deformation for very loose sands; and (b) another new state parameter, which is used to determine the peak strength and describe the critical state behaviour of sands during shearing, is proposed in order to predict simply negative/positive dilatancy and the hardening/softening behaviour of medium or dense sands. In addition, the proposed model can also predict the stress–strain behaviour of sands under three-dimensional stress conditions by using a transformed stress tensor instead of ordinary stress tensor. Copyright © 2004 John Wiley & Sons, Ltd.     

A neural network approach to ship track-keeping control

This paper presents an on-line trained neural net work controller for ship track-keeping problems. Following a brief review of the ship track-keeping control development since the 1980's, an analysis of various existing backpropagation-based neural controllers is provided. We then propose a single-input multioutput (SIMO) neural control strategy for situations where the exact mathematical dynamics of the ship are not available. The aim of this study is to build an autonomous neural controller which uses rudder to regulate both the tracking error and heading error. During the whole control process, the proposed SIMO neural controller adapts itself on-line from a direct evaluation of the control accuracy, and hence the need for a “teacher” or an off-line training process can be removed. With a relatively modest amount of quantitative knowledge of the ship behavior, the design philosophy enables real time control of a nonlinear ship model under random wind disturbances and measurement noise. Three different track-keeping tasks have been simulated to demonstrate the effectiveness of the training method and the robust performance of the proposed neural control strategy     

COORDINATING DEVELOPMENT OF AGRICULTURAL RESOURCES AND ENVIRONMENT OF THE TROPIC REGION IN YUNNAN PROVINCE

（姚建衢）（杨焕宗）ＣＯＯＲＤＩＮＡＴＩＮＧＤＥＶＥＬＯＰＭＥＮＴＯＦＡＧＲＩＣＵＬＴＵＲＡＬＲＥＳＯＵＲＣＥＳＡＮＤＥＮＶＩＲＯＮＭＥＮＴＯＦＴＨＥＴＲＯＰＩＣＲＥＧＩＯＮＩＮＹＵＮＮＡＮＰＲＯＶＩＮＣＥ￥ＹａｏＪｉａｎｑｕ（Ｉｎｓｔｉｔｕｔｅｏｆ...     

利用降水平均递增率求山地最大降水高度

本文引入降水平均递增率的概念,改进了文献中的计算方法,可以一次求出山地降水量与海拔的经验关系式中全部参数的最佳值,其中包括山地最大降水高度。并用实例说明了本法的步骤及特点。     

Studies on the distribution and antibacterial properties of Streptomyces in the intertidal zone of Southern Fujian

The oceans have rich resources of microbes. In recent years, searching for antibiotic of new structure and special biological activity from marine microbes has received great attention. This paper reports the results of the studies on the distribution and the antibacterial properties of Streptomyces in the intertidal zone of Southern Fujian. These studies have important significance to further investigate     

厦门筼筜港的形成与演变

本文根据实际调查的资料,概述了筼筜港区的地质地貌特征,重点论述了第四纪沉积物的成因和时代,阐述了该区的形成与演变过程,把它划分为5个发育阶段。     

病毒膜蛋白及其表达和纯化技术的研究进展

病毒囊膜是包膜病毒除核衣壳外的另一主要成分。它主要由多种蛋白质构成，称为膜蛋白，膜蛋白以单聚体，二聚体，三聚体，甚至更多的聚合体的形式存在，具有中和抗体，与靶细胞受体结合，凝集红细胞，诱导细胞融合等多种功能，膜蛋白可采用将其基因整合入载体，并在昆虫细胞，哺乳细胞或细菌中获得体外表达，膜蛋白可在去污剂的作用下形成蛋白质－脂－去污剂的复合物而被溶解，其中去污剂的临界微团浓度，亲水物－亲脂物平衡值，荷电、紫外穿透性等是选择合适去污剂的主要参考因子，溶解后的膜蛋白多利用聚丙烯酰胺凝胶电泳、凝胶过滤层析，离子交换层析，亲和层析，高效液相层析等技术并结合梯度离心；分级沉淀等进行分离、纯化。     

不同树龄桐花树茎上白条地藤壶分布特征的研究

研究了广西英罗港红树林区向海林带不同树龄的桐花树茎上白条地藤壶的分布特征。结果表明，白条地藤壶在茎上的附着高度（h)随树龄和树高增大而增大。在最大树龄17龄植株上平均达到182cm，此高度为潮高约512cm海水才能浸及，在一年中约有将近90％的时间暴露在空气中。附着高度（h)与树高（H）比值h/H以5龄树最大，达91．9％。树层最大密度达46600Ind/m^2，最小为172Ind/m^2。在同一树龄的不同树层，密度表现为先随树高增大逐渐增大，达到最大密度后又下降。在不同树龄的同一树层，密度高低变化，分布一般出现多个峰。白条地藤壶最适宜附着和生长在桐花树茎上100－120cm树层（浸及此树层的海水潮高约为430－450cm)。树层最大生物量为1719．05g/m^2，最小为5．39g/m^2。生物量分布与密度的相似。     

南海西沙西南海域表层沉积物特征

西沙西南海域表层沉积物样品矿物成分，地球化学，微体古生物分析测试结果表明：沉积物可分为７种类型，沉积环境主要是陆坡，部分为深海平原，海洋生物，海洋化学以及火山物质的沉积起到了积极的作用，陆源物质的影响较小，它们主要来源于北部大陆和南部岛礁等物源区。     

Modeling the seismic response of basin-edge structure by a sequential waveform method

A sequential waveform method is developed to simulate the seismic response of basin-edge structure excited by a plane incident P-wave. The full procedure involves: (a) a previous parameterization of the investigated model using the seismic wave velocities and depths of the sedimentary stratifications; (b) an input motion determined from the records at stations installed on hard rock; (c) forward computation of the P-SV elastic wave field by means of a two-dimensional finite difference (FD) method; (d) the optimization of the model vector using simulated annealing technique and comparing the simulated seismic response of the tested structure with the observed wave field; (e) the correction of the initial model by trial-and-error by testing the differences between synthetics and observed data, and (f) the final solution obtained by iteration using the conjugate gradient algorithm. The search of an optimal basin-edge model has been parallel processed by varying the shapes and velocities of strata on the basis of the fitting of relative timing, amplitude and phase between the output and the observed data. The input motion and sensitivity have been checked and the validity of the method has been demonstrated by numeric analysis. Using the teleseismic records generated by 7 earthquakes recorded at 26 broadband seismic stations, we have studied the seismic velocity structure of the southern edge of the Jiyang depression located in the Bohai Bay basin, northern China. Two cross sections show an agreement between the velocity results and the geological sections available in the region. In addition, we obtain evidence of three hidden faults under the sections and features that suggest major extensions at the Paleogene.