非光滑边界的一阶椭圆型复方程的Riemann－Hilbert边值问题

非光滑边界的一阶椭圆型复方程的Ｒｉｅｍａｎｎ－Ｈｉｌｂｅｒｔ边值问题杨广武（河北轻化工学院石家庄市０５００１８）在［１－３］中已较详细地研究了平面上具有光滑边界区域Ｄ上椭圆型复方程的各种基本边值问题。本文将讨论具有非光滑边界区域Ｄ上非线性一阶椭圆型复...     

扩展桥联双核铜（Ⅱ）体系的磁耦合机理

应用密度泛函理论，采用对称性破损方法研究了草酸根桥联及草酰胺桥联双核铜（Ⅱ）体系的磁耦合作用机理。结果表明：两磁中心的自旋布居大小相等，符号相反，二者之间为反铁磁耦合。而且，与磁中心相联的配体原子与磁中心具有相同符号的自旋布居，磁中心的自旋具有显著的离域效应。HOMO中磁中心未成对电子的占据轨道之间对称性和能级的匹配程度是影响磁耦合强弱的关键。当对称性匹配时，改变桥联基团占据轨道的能级，例如通过改变桥接原子的电负性， 即可改变磁耦合作用的强度，电负性愈低，磁耦全作用愈强。当对称性不匹配时，体系中存在较弱的磁耦合。     

Analysis of Pyrolysates for Phenol Formaldehyde Resin by Py-GC/MS

Pyrolysis of phenol formaldehyde resin has been investigated by Pyrolysis Gas Chromatography-Mass Spectroscopy at the different temperatures from 500℃ to 750℃. Its composition of pyrclysates has been analyzed. Several compounds, especially benzene, toluene, p-xylene could only be formed above 500-550℃. Howerver, peak intensities for some pbend derivatives were decreased at the higher temperature. During pyrolysis, for thermo-setting phenol formaldehyde resins, polymeric chain scissions take place as a successive removal of the monomer units from the polymeric chain. The chain scissions are followed by secondary reactions, which leads to a variety of compounds. Addition reactions can also take place among the double-bond compounds during pyrolysis.     

规范经济行为是珠江上游生态建设的根本途径

江河上游的规划和治理是建设生态环境的基础和关键。珠江上游生态环境建设要从规范现实经济行为入手，以便遏制日趋恶化的生态环境，进一步拓展生态环境对经济发展的承载能力。规范珠江上游各经济主体的行为，要以可持续发展观为价值标准，以分析实际情况为出发点，采用切实可行的对策措施。