Retention modeling and simultaneous optimization of pH value and gradient steepness in RP-HPLC using feed-forward neural networks

A novel approach is proposed for the simultaneous optimization of mobile phase pH and gradient steepness in RP-HPLC using artificial neural networks. By presetting the initial and final concentration of the organic solvent, a limited number of experiments with different gradient time and pH value of mobile phase are arranged in the two-dimensional space of mobile phase parameters. The retention behavior of each solute is modeled using an individual artificial neural network. An "early stopping" strategy is adopted to ensure the predicting capability of neural networks. The trained neural networks can be used to predict the retention time of solutes under arbitrary mobile phase conditions in the optimization region. Finally, the optimal separation conditions can be found according to a global resolution function. The effectiveness of this method is validated by optimization of separation conditions for amino acids derivatised by a new fluorescent reagent.

浑太流域洪涝灾害及其治理方略

Hunhe, Taizihe rivers originating from the east mountain areas of Liaoning Province are the biggest tributaries of the left bank of Liaohe River. From the initial stage of New China to the early 1990s, the frequency of flood damage had decreased, but recently the disasters have upgraded and changed from trunk stream to tributary basins. In July 1995, Dongzhouhe, a tributary of Hunhe River, suffered from a heaviest flood since establishing the document of floods in Hunhe basin. Meanwhile, a peak discharge, almost beyond double defending ability, occurred at Dadongshanpu Station of Beishahe River, a tributary of Taizihe River. Besides the continued heavy rainstorm, no controllable water conservancy projects and ecological damages caused by quickly decreasing forest cover and water and soil loss are the two main causes of flood damage. In addition, the low flood protection standard is also one of causes. According to the above analyses, some strategies of synthetic controlling for flood damages were put forward: 1) Establishing the system of ecological engineering to defend floods and reduce disasters; 2)Setting up storage and detention areas; 3) Establishing flood controlling information system; 4) Improving the accuracy of media short period and short period rainstorm forecast and flood forecast; 5) Insurance of flood protection.

Application of coupling model for stress relaxation of phenolphthalein polyether ketone

According to stress relaxation curves of phenolphthalein polyether ketone (PEK-C) at different temperatures and the principle of the time-temperature equivalence, the master curve of PEK-C at arbitrary reference temperature is obtained. A coupling model is applied to explain quantitatively stress relaxation behaviour of PEK-C at different temperatures. The parameters obtained from the coupling model have important physical meaning. Copyright (C) 1996 Elsevier Science Ltd.

SIMPLE-MODELS FOR STRESS-RELAXATION AND YIELD PHENOMENON OF PHENOLPHTHALEIN POLY(ETHER KETONE)

According to stress relaxation curves of phenolphthalein poly(ether ketone) (PEK-C) at different temperatures and the principle of time-temperature equivalence, the master curves of PEK-C at arbitrary reference temperatures are obtained. A coupling model (Kohlrausch-Williams-Watts) is applied to explain quantitatively the different temperature dependence of stress relaxation behavior and the relationship between stress relaxation and yield phenomenon is established through the coupling model.

Generation of internal and surface waves by seafloor movement in a two layer fluid system

Internal and surface waves generated by the deformations of the solid bed in a two layer fluid system of infinite lateral extent and uniform depth are investigated. An integral solution is developed for an arbitrary bed displacement on the basis of a linear approximation of the complete description of wave motion using a transform method (Laplace in time and Fourier in space) analogous to that used to study the generation of tsunamis by many researchers. The theoretical solutions are presented for three interesting specific deformations of the seafloor; the spatial variation of each seafloor displacement consists of a block section of the seafloor moving vertically either up or down while the time-displacement history of the block section is varied. The generation process and the profiles of the internal and surface waves for the case of the exponential bed movement are numerically illustrated, and the effects of the deformation parameters, densities and depths of the two layers on the solutions are discussed. As expected, the solutions derived from the present work include as special cases that obtained by Kervella et al. [Theor Comput Fluid Dyn 21:245-269, 2007] for tsunamis cased by an instantaneous seabed deformation and those presented by Hammack [J Fluid Mech 60:769-799, 1973] for the exponential and the half-sine bed displacements when the density of the upper fluid is taken as zero.

Strongly nonlinear long interfacial waves in uniform basic flows and their dispersion relationship

In this paper, long interfacial waves of finite amplitude in uniform basic flows are considered with the assumption that the aspect ratio between wavelength and water depth is small. A new model is derived using the velocities at arbitrary distances from the still water level as the velocity variables instead of the commonly used depth-averaged velocities. This significantly improves the dispersion properties and makes them applicable to a wider range of water depths. Since its derivation requires no assumption on wave amplitude, the model thus can be used to describe waves with arbitrary amplitude.

Effective ac dielectric response of graded cylindrical composites

Under an external alternating current (ac) field, the effective ac dielectric response of graded composites consisting of the graded cylindrical inclusion having complex permittivity profiles has been investigated theoretically. A model that the dielectric function is assumed to be a constant while the conductivity has a power-law dependence on the radial variable r, namely epsilon(i)(r) = A + cr(k)/i omega. is studied and the local analytical potentials of the inclusion and the host regions are derived in terms of hyper-geometric function. In the dilute limit, the effective ac dielectric response is predicted. Meanwhile, we have given the exact proof of the differential effective dipole approximation (DEDA) method, which is suitable to arbitrary graded profiles. Furthermore, we have given the analytical potentials and the effective ac dielectric responses of coated graded cylindrical composites for two cases, case (a) graded core and case (b) graded coated layer, having the graded dielectric profiles, respectively. (c) 2005 Elsevier B.V. All rights reserved.

Community structure of macrobenthos in coastal water off Rushan, southern Shandong Peninsula, and the relationships with environmental factors

To understand the present actuality of the marine ecosystem in the southern coastal water region of the Shandong Peninsula and the impact of the global change and the human activities to the marine ecosystem of the region, the macrobenthic community structure was researched based on data from 26 sampling stations carried out on four seasonal cruises from December 2006 to November 2007. The data was analyzed using PRIMER 6.0 and SPSS 15.0 software packages. The results showed that 236 macrobenthic species in total were collected from the research region by the field works. Most of the species belong to Polychaeta (76 species), Mollusca (75) and Crustacea (60). Of which, 33 species were common species by the four cruises. The dominant species were different among the four seasons, however, the polychaete species Nephtys oligobranchia and Sternaspis scutata were always dominant in the four seasons. The abundances and biomasses of the macrobenthos from the research region were variable in tire four seasons. The results of CLUSTER and MDS analysis showed that the similarities of macrobenthic structures among the stations were low, most of the similarities were at about 40% of similarity values, only that of two stations were up to 60%. In accordance with the similarity values of the macrobenthic structures, the 26 stations were clustered as six groups at arbitrary similarity level of 30%. The ABC curve indicated that the marcofauna communities in the research region had riot been disturbed distinctly. The results of BIOENV and BVSTEP (Spearman) analysis implied that the concentrations of organic matter in bottom water and heavy metal copper in sediment, water depth and temperature of bottom were the most significant environmental factors to affect the macrobentic community.

Summertime community structure of intertidal macrobenthos in Changdao Archipelago, Shandong Province, China

The community structure of intertidal macrobenthos in Changdao Archipelago (north of Shandong Peninsula, between Bohai Bay and the northern Yellow Sea) was examined based on samples collected from 14 stations in five transects in June 2007. Three stations corresponding to high, medium and low tidal areas were set up for each transect. A total of 68 macrobenthic species were found in the research region, most of which belonged to Mollusca and Crustacea. The average abundance and biomass of the macrobenthos was 1383 ind./m(2) and 372.41 g/m(2), respectively. The use of an arbitrary similarity level of 20% resulted in identification of five groups among the 14 stations in the research region. There were remarkable differences in the biomass, abundance and Shannon-Wiener diversity index of the different sediments. Specifically, the order of biomass was rocky shores > gravel > mud-sand > coarse sand > stiff mud, while the order of abundance was rocky shores > coarse sand > mud-sand > gravel > stiff mud, and that of the diversity index was mud-sand > gravel > stiff mud > rocky shores > coarse sand. The above results revealed that the sediment type was the most important factor affecting the structure of the macrobenthic community of the intertidal zone.

迭代法求解P3P问题的成立条件研究

迭代方法求解P3P问题的成立条件一直困扰着基于P3P的模型定位方法在实际中的应用。本文对于迭代方法求解P3P问题的成立条件做了比较完整的分析,在对于P3P问题的参数方程和目标方程进行介绍后给出了针对任意三角形用迭代方法求解P3P问题的成立条件。

基于摇臂-转向架结构月球车的越障能力判断准则

对轮式移动系统进行越障分析时,常以垂直越障作为评价标准。但是,月球车在凹凸不平的月面上行驶时,垂直越障模型不具有一般性。为此,本文对基于摇臂-转向架结构月球车在任意路面的越障进行了研究。一般情况下,由于任意路面越障模型相对复杂,可以建立的独立平衡方程数目少于未知变量数,因此无法得到越障能力与路面参数的函数关系式。针对上述问题,文中将最大有效牵引力假设引入越障模型中,得到了一种任意路面越障能力的判断准则。通过算例分析,表明了所提方法的有效性。

一类非完整约束动力学系统的人工场导向控制

对于一类具有轮式移动机构的非完整动力学系统，本文通过建立人工场的方法来实现其位姿镇定、轨迹跟踪和路径跟踪等控制问题。人工场用于导向和控制方向角，而通过辅助的线速度控制以获取最佳收敛路径。控制器设计中同时兼顾动力学扰动及实际系统速度和输出力矩的饱和限制，所得控制器对于跟踪问题仅需知道期望位姿，而且结构简单、鲁棒性强、便于实现。

非完整约束轮式移动机器人人工场导向控制研究

导向控制在非完整约束轮式移动机器人的运动控制中具有重要作用，该文通过建立人工场的方法来引导和控制方向角，通过辅助的线速度控制前进或后退，以获得最佳收敛路径；同时考虑到实际系统速度饱和限制，从而设计出一种新的非连续位姿镇定律，并将该结果扩展，使得平面内任意点-点镇定、轨迹跟踪和路径跟踪问题均可得以实现，且对于跟踪问题仅需知道期望位姿，所得控制器不权设计简单，鲁棒性强，收敛速度快，还具有一定的普遍性。

基于分层控制的移动机器人最优运动规划

研究移动机器人在带有多移动障碍物的动态环境中的运动规划问题．基于分层最优控制理论，提出了一种新的运动规划方法来解决移动机器人的导航与避障问题．仿真实例证明了该方法的有效性。

强化学习算法中启发式回报函数的设计及其收敛性分析

回报函数设计的好与坏对学习系统性能有着重要作用,按回报值在状态-动作空间中的分布情况,将回报函数的构建分为两种形式:密集函数和稀疏函数,分析了密集函数和稀疏函数的特点.提出启发式回报函数的基本设计思路,利用基于保守势函数差分形式的附加回报函数,给学习系统提供更多的启发式信息,并对算法的最优策略不变性和迭代收敛性进行了证明.启发式回报函数能够引导学习,加快学习进程,从而可以实现强化学习在实际大型复杂系统应用中的实时控制和调度.