An alternative approach to ascertain the rate-determining steps of TiO2 photoelectrocatalytic reaction by electrochemical impedance spectroscopy

In an attempt to ascertain the rate-determining steps (RDS) of TiO2 photoelectrocatalytic (PEC) reaction, the PEC oxidation of sulfosalicylic acid (SSA) solution in a TiO2-coated electrode reactor system was monitored by applying the electrochemical impedance spectroscopy (EIS) method. In the meantime, an EIS mathematical model was first established to theoretically simulate the PEC reaction. Based on the EIS model, the theoretical simulation indicates three typical reactions in a PEC oxidation process, which include the charge-transfer-dominated reaction, both the charge-transfer- and adsorption-dominated reaction, and the adsorption-dominated reaction. The experimental results of EIS measurement showed that there was only one arc/semicircle on the EIS plane display when the external bias applied was below 200 mV (vs SCE) in the SSA PEC degradation whereas there were two arcs/semicircles when the externally applied bias exceeded 200 mV (vs SCE). The experimental results have a good agreement with the model simulation. The EIS method in this study provides an easier way to determine the RDS in a PEC oxidation process, which would be helpful to better control the reaction in practice.

Modeling and optimization for separation of ionic solutes in pressurized flow capillary electrochromatography

By manipulation of applied pressure or voltage, pressurized flow capillary electrochromatography (P-CEC) permits unique control of selectivity for ionic solutes. A simple mathematical model has been developed to describe the quantitative relationship between the electrochromatographic retention factor (k(*)) of charged solutes and the applied voltage and pressure. The validity of the model was verified experimentally with hydrophilic interaction mode CEC (HI-CEC). On the basis of the model developed, it was found that the value of k(*) could be predicted accurately using only a limited number of data points from the initial experiments at different voltages or pressures. Correlation between the experimentally measured and calculated k(*) was excellent, with a correlation coefficient greater than 0.999. Optimization for the separation of peptides by P-CEC was also performed successfully on the basis of the proposed model.

黄土区考虑滞后作用的坡地水量转化模型

建立了考虑滞后作用的坡地水量转化数学模型，并对模型不同情况下的定解条件进行了分析。利用陕西长武王东沟小流域坡地天然降雨－入渗－产流的实测资料对模型进行了系统检验，结果表明该模型具有较高精度，考虑滞后作用时的模拟值更加接近实测值。在降雨入渗过程中，滞后作用对土壤含水率、入渗速率、径流过程、产流量都有相当大的影响。

基于GIS的区域水土流失评价研究

以黄土高原为研究区，对该区的水土流失进行系统、宏观、综合的分析，确定了一套适于该区水土流失宏观定量评价的指标体系，并运用ＧＩＳ技术，对该区影响水土流失的各个因素进行空间分析，实现了多源数据的空间集成和专题信息的提取，建立了适于该区水土流失评价的宏观定量数学模型，并对研究区一定评价年限内的水土流失状况进行了应用评价。

Enhancements of the simulation method on the edge effect in resin transfer molding processes

In resin transfer molding processes, small clearances exist between the fiber preform and the mold edges, which result in a preferential resin flow in the edge channel and then disrupt the flow patterns during the mold filling stage. A mathematical model including the effect of cavity thickness on resin flow was developed for flow behavior involving the interface between an edge channel and a porous medium. According to the mathematical analysis of momentum equations in a fully developed rectangular duct and formulations of the equivalent edge permeability, comparing with three-dimensional Navier-Stokes equations, the governing equations were modified in the edge channel. The volume of fluid (VOF) method was applied to track the flow front. A simple case is numerically simulated using the modified governing equations. The effects of edge channel width and cavity thickness on flow front and inlet pressure are analyzed, and the evolution characteristics of simulated results are in agreement with the experimental results. (c) 2007 Elsevier B.V. All rights reserved

Combined Effects of Hot Curing Conditions and Reaction Heat on Rubber Vulcanization Efficiency and Vulcanizate Uniformity

A mathematical model of the chemical kinetics of silicone rubber Vulcanization is developed, with the thermal effects being computed using the increment method, and the hot Vulcanization process estimated with the finite element method. The results show that the reaction heat of rubber vulcanization is important for energy saving, and that a proper curing medium temperature is important when considering both vulcanization efficiency and vulcanizate uniformity. The results also indicate that increases in the forced convective heat transfer coefficient have no significant effect above a certain level. The validity of the numerical model is indirectly proven by comparison with existing data.

Preparation and simulation of an additional catalyst layer for direct methanol fuel cell

An additional anode catalyst layer with PtRu/C was hot pressed between two Nafion (R) 112 membranes and a conventional direct methanol fuel cell (DMFC) cathode/membrane/anode assembly with the above membranes as separator was fabricated. The additional catalyst layer formed an assistant cell with the cathode to prevent methanol crossover. A simple one-dimensional mathematical model was presented to describe the performance of this new type of membrane electrode assembly system. As seen from both experimental result and model analysis, the additional catalyst layer can not only effectively prevent the methanol crossover, but also generate electrical power with the crossover methanol. The percentage of output power of the assistant cell to the total power analyzed by the model is about 40% under usual condition, which is much higher than that from experimental result, indicating the potential of the development in the DMFC designing. It was also discovered that the electrical power generated from the assistant cell with crossover methanol could take higher percentage in total electrical power when the main DMFC current density became lower.

Simulation of characteristic electrochemical behavior of azobenzene derivative self-assembled monolayers

The characteristic electrochemical mechanics of azobenzene derivative self-assembled monolayers is discussed in present paper. It is presented that the structure inhibition is one of the most important factors in the increase of electrochemical reactive energy. A corresponding mathematical model was established based on Levich and Marcus's theory. Moreover, computational program was written to simulate the decrease of apparent rate constant (k(app)) of electron transfer with increasing surface concentration.

Quantitative structure-property relationship research to the analysis of photoionization sensitivity of organic compounds in gas chromatography

The A(m) index and molecular connectivity index were used for studying the photoionization sensitivity of some organic compounds in gas chromatography. The analysis of structure-property relationship between the photoionization sensitivity of the compounds and the A(m) indices or molecular connectivity indices has been carried out. The genetic algorighm was used to build the correlation model in this field. The results demonstrate that the property of compounds can be described by both A(m) indices and molecular connectivity indices, and the mathematical model obtained by the genetic algorithm was better than that by multivariate regression analysis.

Atom space distance and computing of molecular similarity

A mathematical model on computation of molecular similarity was suggested, The algorithmic techniques for measuring the degree of similarity between pairs of three-dimensional chemical molecules was represented by modified interatomic distance matrices. Current work was carried out on Indigo 2 work station with Sybyl software. Four groups of molecules were used to compute the molecules similarity to testing the mathematical model with satisfactory results.

Simultaneous determination of four phases of copper in geological samples

According to the specific property of respective phases in copper ore, optimal extracting condition for, tour phases of copper with five infusion was examined. After a series of experiments, for example, different weight Of sample, artificial mixed single phases sample and repeated experiment, the extracting ratio constants foil all phases in different infusions were obtained. The mathematical model which is on the basis of the stable extracting constant is established. Based on the purpose-control genetic algorithms, we only need to determine the total copper in the sample in different infusions under the selected condition, then the value of respective phase could be calculated. The-relative standard deviation are (%) free oxidized copper phase:1.5, conjunction oxidized copper phase: 17.6,, secondary copper sulfide phase: 1.9, primary copper sulfide phase : 2.7,total copper: 0.8.

投喂策略对工厂化养殖半滑舌鳎的效应特征与投喂模型构建

1、在封闭循环水工厂化养殖条件下，进行为期44天的6×2双因素随机设计动物试验，即6个体重阶段（45-550g）和2种养殖密度水平（高密度比正常密度提高20-30%），探寻我国北方工厂化养殖半滑舌鳎生长、摄食和水质的变化特征及规律。结果如下： （1）日增重、日均摄食量、饲料系数等绝对指标与体重阶段呈正相关，对应的增重率、特定生长率和摄食率等相对指标与其呈负相关；氨氮、COD等水生态指标相对浓度与体重阶段呈负相关。（2）新发现半滑舌鳎的日摄食率为0.43-0.92%，对常规鱼类投饲率推荐范围（2-5%）提出了质疑，为现代海水养殖精准饲喂和清洁生产提供了科学依据。 2、在封闭循环水养殖条件下，通过56天的4×2双因素随机设计动物试验，探寻月饱食度和和日粮次喂比例对工厂化养殖半滑舌鳎幼鱼（291.47±4.23g）生长与免疫的影响。结果如下： （1）月饱食度显著影响鱼的生长、摄食和水氨氮相对浓度，对饲料系数、水质其它指标和血液免疫无显著影响。 （2）日次喂比例显著影响鱼生长、饲料系数和水氨氮指标等，对水质其它指标、摄食量及免疫指标无显著影响。等量投喂组的生长和水氨氮指标显著高于差量投喂，饲料系数低于差量投喂。 （3）确定90%月饱食度与差量投喂为兼顾生长和水环境的生态适宜投喂组合模式，100%月饱食度与等量投喂为获得最快生长的投喂组合模式。 3、通过对实验数据进行对数化处理、多 元线性拟合、变量替代等方法，初步建立了封闭循环水养殖半滑舌鳎的投喂模型、总有害氮排泄和日增重预测模型。本模型的建立和完善，可初步实现最佳生长、最 少饲料浪费、并向生物滤器提供稳定代谢物的新型工厂化养殖清洁投喂目的，使封闭循环水养殖半滑舌鳎的饲料投喂和水环境调控步入数字、精准、动态的层次。

Interactions between the bloom-forming dinoflagellates Prorocentrum donghaiense and Alexandrium tamarense in laboratory cultures

Interactions between Prorocentrum donghaiense and Alexandrium tamarens, two bloom-forming dinoflagellates, were investigated using bi-algal cultures. All R donghaiense died, but A. tamarense was hardly affected by the end of the experiment when the initial cell density was set at 1.0 X 10(4) cells mL(-1) for P. donghaiense and 0.28 x 10(4) cells mL(-1) for A. tamarense. However, significant growth suppression occurred in either species when the initial cell density of P donghaiense increased to I. 0 X 105 Cells mL(-1) in the bi-algal culture, but no out-competement was observed. The simultaneous assay on the culture filtrates showed that P donghaiense filtrate prepared at a lower initial density (1.0 X 10(4) cells mL(-1)) stimulated growth of the co-cultured A. tanzarense (0.28 x 10(4) cells mL(-1)), but filtrate at a higher initial density (1.0 x 10(5) cells mL(-1)) depressed its growth. The filtrate of A. tamarense at a density of 0.28 x 10(4) cells mL(-1) killed all R donghaiense at a lower density (1.0 x 10(4) cells mL(-1)), but only exhibited an inhibitory effect on it at a higher density (1.0 x 10(5) cells mL(-1)). It is likely that these two species of microalgae interfere with each other mainly by releasing allelochemical substance(s) into the culture medium, and a direct cell-to-cell contact was not necessary for their mutual interaction. The allelopathic test further proved that A. tamarense could affect the growth of co-cultured P. donghaiense by producing allelochemical(s); moreover, A. tamarense culture filtrate at the stationary growth phase (SP) had a strongly inhibitory effect on P donghaiense compared to that at the exponential phase (EP). Results also demonstrated a dose-dependent relationship between the microalgal initial cell density and the degree of the allelopathic effect. The growth of R donghaiense and A. tamarense in the bi-algal cultures was simulated using a mathematical model to quantify the interaction. The estimated parameters from the model showed that the inhibition exerted by A. tamarense on P. donghaiense was about 17 and 8 times stronger than the inhibition P. donghaiense exerted on A. tamarense, when the initial cell density was set at 1.0 X 10(4) and 1.0 X 10(5) cells mL(-1) for P donghaiense, respectively. and 0.28 x 10(4) cells mL(-1) for A. tamarense in the bi-algal cultures. A. tamarense seems to have a survival strategy that is superior to that of P. donghaiense in bi-algal cultures under controlled laboratory conditions. (c) 2006 Elsevier B.V. All rights reserved.

一种可变形移动机器人协同构形变换方法

提出了一种可变形移动机器人AMOEBA-I的协同构形变换方法,建立了机器人系统的数学模型,对各个模块之间的协同变换及运动特性进行了分析.研究了机器人3个模块在协同变换过程中的电流变化情况,实现了3种特殊构形之间的变换.通过理论分析和实验比较了协同构形变换方法的特点,实验验证了在多种地面条件下机器人协同构形变换方法的有效性.

可变形机器人协同转向运动研究

可变形机器人AMOEBA-I具有多种构形和多种转向方式.为实现机器人转向性能的优化,提出了可变形机器人的协同转向方法,并建立了相应的数学模型,对不同构形下的协同转向方式进行了理论分析.设定了机器人三个模块在协同转向过程中的运动关系,在此基础上给出了可变形机器人协同转向性能的评价指标.通过理论和实验比较了不同构形下的协同转向方式,实验验证了协同转向方法的有效性.