Contribution à l'étude Électrochimique de Dérivés de l'Acide Mercapto-2 Pyridinecarboxylique-5. II

Abstract

Electrochemical caracteristics of 2-mercaptopyridine-5-carboxylic acid and its methylic ester have been determined using recent polarographic techniques. Measurements have been carried out as a function of parameters such as frequency, others surimposed signals and as a function of concentration and pH. Results are compared to those obtained for selectively methylated on sulfur or nitrogen atoms derivatives. Interpretations of the data are given. The optimal conditions for a quantitative determination by D.C. and differential pulse polarography are fixed.     

一种任意起始位姿的连续曲率泊车路径在线规划方法

针对目前泊车路径规划算法对起始位姿要求严格，且难以兼顾最终位姿精度、路径质量及计算效率等问题，提出了一种任意起始位姿的连续曲率路径在线规划方法。该方法将整个泊车路径规划分为库位内调整与入库过程两部分。库位内调整采用以最终位姿高精度与调整次数最少为目标函数的最优化方法进行逐段规划；入库过程采用连续曲率曲线组用于混合A*算法的状态节点扩展以直接生成无需后处理的可执行路径。设计考虑路径的曲率变化与方向改变次数的估价函数；采用由路径几何形状特征点构建特征多边形的碰撞检测方法以提高计算效率。离线仿真与实车试验结果验证了该方法的有效性。     

北京城市物流业碳排放及驱动因素研究

估算了1998-2012年北京城市物流业的碳排放量,建立了北京城市物流业碳排放影响因素的通径分析模型.结果表明:物流基础设施的建设是该阶段碳排放增长的决定性因素,经济发展水平、以石油为主的能源结构、城镇化是促进碳排放的重要因素,能源效率对碳排放的正向影响较弱,产业结构对碳排放具有负向影响.最后提出了北京城市物流业低碳化发展的对策.     

Zur kepplimg eines exakten verfahrens mit einem heuristiscieb verfahren für die lösung ganzzahliger linearer optimierungsprobleme

Combining an exact method with a heuristic approach possibilities for solving linear mixed integer optimization problems are investigated. For the considered exact method numerical results with problems from the practice are given. Proper heuristic methods are the interior path methods [2] for which numerical experiences are well-known or the so-called geometric approach [8], Deriving of sufficient conditions for the existence of feasible solutions is possible.     

中学生学习自我效能感、学习策略与学业成就的关系

以学习自我效能感和学习策略量表为工具,通过方差分析、相关分析和路径分析等方法,重点考察了学习自我效能感和学习策略这两个因素对学业成就的影响路径以及相互间的关系.发现中学生的学习自我效能感与学习策略间存在着显著的相关关系;学习自我效能感和学习策略对初中生的学业成就有显著回归效应,而学习策略对高中生的学业成就有显著回归效应;学习自我效能感可通过影响学习策略来间接影响学业成就.     

职业教育校地合作分析与合作路径构建研究

通过分析职业教育与地方的"粘度",剖析当前校地合作存在的"雾区",构建校地合作的路径,指出职业教育校地合作应从战略上实施"学校与政府对接,专业与企业对接,师生与农村家庭对接"宏观、中观、微观三个层面的对接,开发"政府,学校,企业,学生"四方主体的内在驱动,开展"低、小、微"合作。     

A novel synthetic strategy for preparing semi‐aromatic components modified polyamide 6 polymer

In this work, a novel synthetic path for preparing semi‐armotic components modified polyamide 6 was developed by caprolactam as solvent of purified terephthalic acid and 1,6‐hexanediamine. First, the ring opening reaction and poly‐addition of caprolactam were initiated by 1,6‐hexanediamine to generate a prepolymer containing amino groups in both ends, then followed by the poly‐condensation reaction with purified terephthalic acid, a long chain copolymer was produced, which the reaction time was reduced by 4 h compared with conventional hydrolytic ring‐opening polymerization of pure caprolactam. By varying the ratio of terephthalic acid and 1,6‐hexanediamine, a series of copolymers with different number average molecular weight and physical properties were prepared. Analytical results showed that the conversion percentage of caprolactam is significantly increased by the proposed method. Furthermore, this new copolymers exhibited excellent transparence and high decomposition temperature. Besides, the copolymers with average molecular weight ≥15,000 present good mechanical properties, making it a potentially useful application in plastics, textile yarn, and membranes. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 959–967     

Roe‐type Riemann solvers for general hyperbolic systems

We present a Roe‐type weak formulation Riemann solver where the average coefficient matrix is computed numerically. The novelty of this approach is that it is general enough that can be applied to any hyperbolic system while retaining the accuracy of the original Roe solver. We show applications to the compressible Euler equations with general equation of state. An alternative version of the method uses directly the eigenvectors in the averaging process, simplifying the algorithm. These new solvers are applied in conservative and path‐conservative schemes with high‐order accuracy and on unstructured meshes. Copyright © 2014 John Wiley & Sons, Ltd.     

基于知识图谱的我国农产品品牌研究述评

依据科学知识图谱相关理论，利用CiteSpace软件对农产品品牌相关文献进行可视化分析，再利用Netdraw软件描绘主要研究内容的网络关系，对我国农产品品牌研究的热点内容、演进历程和趋势进行分析.结果表明，农产品品牌研究内容主要集中在农产品品牌属性结构及效应、品牌评价、品牌建设运营及区域品牌/地理标志品牌等方面.研究内容的演进路径反映了不同阶段的研究特色，也契合了国家政策调整和经济社会发展需求变化.我国专注于农产品品牌研究的学者和机构较少，学者间或机构间也未建立起紧密的合作关系.未来研究应进一步完善农产品品牌基本理论及研究方法，拓展农产品品牌研究的深度与广度，建立合作紧密的学术研究网络.