The Numerical Solution by the Method of Boundary Element to the Question of Solid-liquid Variation

相变问题的数值计算方法有多种，本文用边界元法解应用工程中常见的相变导热问题。There are many numerical caculation methods to the varition problem.This thesis uses the boundery element method to solve some common variation heat conduction problem

北京春季亚微米气溶胶的化学组分特性及有机气溶胶来源解析

基于颗粒物化学组分监测仪(Aerosol Chemical Speciation Monitor, ACSM)的在线实时观测,对北京春季亚微米气溶胶(PM_1)的化学组分和特性进行分析,并利用PMF & ME-2 (Positive Matrix Factorization & Multilinear Engine)源解析模式对其中的有机物进行来源解析。结果表明,在观测期间PM_1的浓度变化范围为2.40-249.10 μg·m~(-3),平均浓度58.0 μg·m~(-3),其中有机物为主要组分,占比41.4%。有机物的来源包括四个一次源:机动车排放源(hydrocarbon-like organic aerosol, HOA)、烹饪源(cooking organic aerosol,COA)、燃煤燃烧源(coal combustion organic aerosol,CCOA)、生物质燃烧源(biomass burning organic aerosol, BBOA)和一个二次有机源(oxygenated organic aerosol,OOA)。通过不同污染事件的对比结果表明,二次气溶胶在重污染期所占比重会明显上升,并且静稳气象条件也对污染的形成产生重要影响