AM60镁合金在汽车发动机冷却液中的腐蚀电化学行为

研究AM60镁合金在3种(A、B、C)市售汽车发动机冷却液中的腐蚀电化学行为.极化曲线、电化学阻抗谱测试表明,冷却液A对AM60镁合金的腐蚀性最强,B腐蚀性略低于A,C腐蚀性最弱,最适于镁合金汽车发动机使用.冷却液对发动机镁合金材料的腐蚀性与其电阻有关系,电阻越大,腐蚀性越小;冷却液中的乙二醇和添加剂组分在镁合金表面的竞争吸附对镁合金的腐蚀行为也有重要影响.     

有限理性企业市场占有率的混沌分析

在企业占有市场的模型分析中,运用分支理论和动力学系统理论,发现企业在等价的同一产品中对科研投资和广告宣传产品的力度进行调整时,会导致企业在一定的市场中所占有的市场份额出现分支;并随科研投资和宣传产品资金的增加,企业所占市场份额会进入混沌状态.     

民用航空煤油的化学组分分析

采用气相色谱-质谱联用法检测民用航空煤油溶液和蒸汽的化学组分,通过检索NIST 17.L标准谱库和比对标准物质的保留时间定性,使用峰面积归一化法确定各组分的相对含量并分析其健康效应.结果 表明,民用航空煤油溶液和蒸汽中的化学组分有差异,溶液中的碳数分布为C7-C15,主要包括烷烃,环烷烃,芳香烃,含氧、含氮化合物,会引...     

Traffic of Molecular Motors Through Tube-Like Compartments

The traffic of molecular motors through open tube-like compartments is studied using lattice models. These models exhibit boundary-induced phase transitions related to those of the asymmetric simple exclusion process (ASEP) in one dimension. The location of the transition lines depends on the boundary conditions at the two ends of the tubes. Three types of boundary conditions are studied: (A) Periodic boundary conditions which correspond to a closed torus-like tube. (B) Fixed motor densities at the two tube ends where radial equilibrium holds locally; and (C) Diffusive motor injection at one end and diffusive motor extraction at the other end. In addition to the phase diagrams, we also determine the profiles for the bound and unbound motor densities using mean field approximations and Monte Carlo simulations. Our theoretical predictions are accessible to experiments.     

D-~3He商用堆工作物理参数的空间分析

由于D-~3He聚变堆不要求厚的包层和大的内侧空间,中子壁负载小得多,第一壁几乎是永久性的,维修更换问题减轻。采用低径比有利于电流驱动和较大的等离子体变形和好的垂直稳定性,以便得到大的等离子体电流,因而得到高的β和好的约束。本文从目前普遍采用的堆芯等离子体物理规律为基础,编制了DHE3TOK程序。研究了以D-~3He为燃料,低径比A=2.5工作在第一稳定区的商用堆特点。对它的工作物理参数空间范围进行广泛调查的基础上,提出了需要研究和发展的关键工程技术问题。     

Development of an Improved Liquid Chromatographic Method for the Analysis of Doxycycline

Summary An improved LC method is described for the separation of doxycycline and its impurities. The separation of 2-acetyl-2-decarboxamidodoxycycline from the main peak doxycycline is much better than that obtained with official pharmacopoeia methods. The method is robust and shows good selectivity, repeatability, linearity and sensitivity. Eight commercial samples were examined using the method developed. The method uses an XTerra RP-18, 5 m (25 cm × 4.6 mm I. D.) column kept at a temperature of 35 °C. UV detection is performed at 280 nm. The mobile phase consists of acetonitrile – 0.2 M tetrabutylammonium hydrogen sulphate pH 7.0 – 0.3 M ethylenediaminetetraacetate pH 7.0 – water (130:350:350:170, v/v/v/v).     

商品住宅购买决策涉入对购买意愿的影响：顾客参与和顾客感知价值的链式中介作用

营销是房地产开发全过程中一个重要的环节,为更好地实现销售目标,需要尽可能提升购房者的购买意愿。为探究商品住宅购买意愿的影响机制,构建了以购买决策涉入为自变量、购买意愿为因变量、顾客参与和顾客感知价值为中介变量的结构方程模型。采用方便抽样方法进行问卷调查,使用SPSS 19.0和AMOS 23.0对437个有效样本进行数据分析。实证结果表明,购买决策涉入、顾客参与、顾客感知价值均对购买意愿有显著正向影响;顾客参与、顾客感知价值在购买决策涉入对购买意愿的影响中起到链式中介作用。研究可为房地产企业制定营销策略和改善营销行为提供理论指导。     

Lattice models of traffic flow considering drivers' delay in response

This paper proposes two lattice traffic models by taking into account the drivers' delay in response. The lattice versions of the hydrodynamic model are described by the differential-difference equation and difference-difference equation, respectively. The stability conditions for the two models are obtained by using the linear stability theory. The modified KdV equation near the critical point is derived to describe the traffic jam by using the reductive perturbation method, and the kink--antikink soliton solutions related to the traffic density waves are obtained. The results show that the drivers' delay in sensing headway plays an important role in jamming transition.     

Investigation of performances of commercial diesel oxidation catalysts for CO,C3H6, and NO oxidation

Four commercial monolithic diesel oxidation catalysts (DOCs) with two different platinum group metal (PGM) loadings and Pt:Pd ratios of 1:0, 2:1, 3:1 (w/w) were investigated systematically for CO, C₃H₆, and NO oxidation, CO-C₃H₆ co-oxidation, and CO-C₃H₆-NO oxidation reactions via transient activity measurements in a simulated diesel engine exhaust environment. As PGM loading increased, light-off curves shifted to lower temperatures for individual and co-oxidation reactions of CO and C₃H₆. CO and C₃H₆ were observed to inhibit theoxidation of themselves and each other. Addition of Pd to Pt was found to enhance CO and C₃H₆ oxidation performance of the catalysts while the presence and amount of Pd was found to increase the extent of self-inhibition of NO oxidation. NO inhibited CO and C₃H₆ oxidation reactions while NO oxidation performance was enhanced in the presence of CO and C₃H₆ probably due to the occurrence of reduced Pt and Pd sites during CO and C₃H₆ oxidations. The optimum Pt:Pd ratio for individual and co-oxidations of CO, C₃H₆, and NO was found to be Pt:Pd = 3:1 (w/w) in the range of experimental conditions investigated in this study.     

The Use of an Automated Device in the Direct Simultaneous Determination of Heavy Metals in Commercial Coca Cola By DPASV

Abstract

The performance of a polarographic analyser equipped with a long-lasting, sessile-drop mercury electrode is described in the direct, simultaneous determination of heavy metals (cadmium, copper and lead) in some Coca Cola samples (drawn from commercial bottles or tins). The determinations were performed by the differential pulse anodic stripping voltammetric technique using a programmed fully automated sequence (i.e., deposition-stripping-recording). The results obtained (1-3, 6-25 and 1.5-3.3 ppb for cadmium, copper and lead, respectively) as well as those previously obtained in the stripping analysis of some sea-waters and mineral-waters samples suggest that the proposed automated device ensures sufficient sensitivity and accuracy to be employed in the DPASV determination of toxic metals (at trace and subtrace levels) in natural waters and beverages.