THERMODYNAMIC VARIATIONAL APPROACH FOR CLIMB OF AN EDGE DISLOCATION

A general thermodynamic variational approach is applied to study the force on an edge dislocation, which drives the dislocation to climb. Our attention is focused on the physical mechanism responsible for dislocation climb. A dislocation in a material element climbs as a result of vacancies diffusing into or out from the dislocation core, with the dislocation acting as a source or a sink for vacancy diffusion in the material element. The basic governing equations for dislocation climb and the climb forces on the dislocation are obtained naturally as a result of the present thermodynamic variational approach.

西宁市耕地利用变化及其驱动力研究

以西宁市地区为例,以耕地为研究对象,运用特尔斐法、相关分析和主成分分析法对2000～2008年耕地数量变化相关的社会、经济、农业驱动力进行定量分析,并将定量分析结果与专家对西宁市以往的研究结果结合进行探讨。结果表明,社会发展、经济投资、农业科技进步及人口因素对耕地利用变化产生很大影响,并据此提出西宁市合理利用保护耕地的建议。