POPs can stay long enough to diffuse and transfer sufficiently in the environment. Researches indicate that it's inadequate to study POPs' fate and environmental behavior, in order to get comprehensive knowled...POPs can stay long enough to diffuse and transfer sufficiently in the environment. Researches indicate that it's inadequate to study POPs' fate and environmental behavior, in order to get comprehensive knowledge of the POPs' fate and transfer processes in an area, experiment should be combined with model simulation. Recently multimedia models have become the primary choice in simulating organic pollutant's fate and assessing exposure risk to ecosystem for they can nearly represent the real environment. Among all models, with simple structure, less required parameters, fugacity model has been an efficient tool used widely on simulating the fate and transport of POPs and put into practice in many countries and areas successfully. On the basis of achievements in scientific research, this paper will emphatically take up the following three questions one by one that consist of fugacity model's principle, pivotal questions and application prospects in china.展开更多
本文以太湖为研究对象 ,应用逸度方法研究不同藻类生物量对 p,p′- DDT、六氯苯和六六六在太湖沉积相和水相中分布的影响。计算中选取多介质环境模型中的 L evel 模型 ,并把该模型中悬浮相中的藻类分离出来作为一个生物相。计算结果能...本文以太湖为研究对象 ,应用逸度方法研究不同藻类生物量对 p,p′- DDT、六氯苯和六六六在太湖沉积相和水相中分布的影响。计算中选取多介质环境模型中的 L evel 模型 ,并把该模型中悬浮相中的藻类分离出来作为一个生物相。计算结果能真实反映 POPs在太湖中的分布。藻类生物量的变化对太湖中 POPs在水相和沉积相的分布影响非常大。通过对计算结果的分析 ,得出除去太湖水团中的POPs的最佳时机是每次藻华后藻类大量死亡时。展开更多
Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants(POPs), however, quantitative studies on these combined factors are scarce. In t...Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants(POPs), however, quantitative studies on these combined factors are scarce. In this study, dichlorodiphenyltrichloroethane(DDTs), polycyclic aromatic hydrocarbons(PAHs), and polychlorinated biphenyls(PCBs)were used as examples to identify how and when those factors may be related to the deposition of POPs in the sediment of Lake Chaohu, China, using generalized additive models(GAMs). Three historical trends of DDT, PAH, and PCB deposition were delineated in a dated sediment core encompassing ~100 years of historical record: a steady state or gradually increasing stage, a rapidly increasing stage, and a declining stage. The GAM results showed that aquatic total phosphorus(TP) concentrations and regional GDP(anthropogenic factors) were dominant contributors to POP accumulation rates in the lake sediment. The fitted relationships between air temperature and sedimentary DDT and PAH concentrations were linear and negative, while a positive linear relationship was found for PCBs, suggesting that Lake Chaohu may have become a net source for DDTs and PAHs, and a sink for PCBs, under a progressively warming climate.展开更多
随着电子元器件产业的发展,对封装的集成性和可靠性也提出了更高的要求。作为一种典型失效形式,翘曲引发的芯片脱层、脱焊和开裂等问题,往往对成品率及封装可靠性产生重要影响。为了探究芯片的翘曲演变规律,基于ANSYS有限元软件,建立了...随着电子元器件产业的发展,对封装的集成性和可靠性也提出了更高的要求。作为一种典型失效形式,翘曲引发的芯片脱层、脱焊和开裂等问题,往往对成品率及封装可靠性产生重要影响。为了探究芯片的翘曲演变规律,基于ANSYS有限元软件,建立了叠层封装(Package on Package,PoP)结构热翘曲的仿真模型,考虑了焊料的Anand黏塑性本构模型,讨论了灌封胶膨胀系数、芯片厚度、焊球弹性模量对结构热翘曲的影响,并针对芯片的翘曲控制提出了优化建议。结果表明,芯片受热时的主要翘曲形态为弓曲,在从高温到低温变化的过程中,其翘曲形态逐渐由上凸转变为下凹。上层封装芯片的翘曲相对较大,灌封胶的热膨胀系数及芯片厚度是翘曲的主要影响因素。展开更多
基金Supponed by the National Natural sdence Foundation of China(49971070, 40031010, 40024101)
文摘POPs can stay long enough to diffuse and transfer sufficiently in the environment. Researches indicate that it's inadequate to study POPs' fate and environmental behavior, in order to get comprehensive knowledge of the POPs' fate and transfer processes in an area, experiment should be combined with model simulation. Recently multimedia models have become the primary choice in simulating organic pollutant's fate and assessing exposure risk to ecosystem for they can nearly represent the real environment. Among all models, with simple structure, less required parameters, fugacity model has been an efficient tool used widely on simulating the fate and transport of POPs and put into practice in many countries and areas successfully. On the basis of achievements in scientific research, this paper will emphatically take up the following three questions one by one that consist of fugacity model's principle, pivotal questions and application prospects in china.
基金supported by the National Key Research and Development Program of China(No.2017YFA0605003)the National Natural Science Foundation of China(No.91751114,41521003)
文摘Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants(POPs), however, quantitative studies on these combined factors are scarce. In this study, dichlorodiphenyltrichloroethane(DDTs), polycyclic aromatic hydrocarbons(PAHs), and polychlorinated biphenyls(PCBs)were used as examples to identify how and when those factors may be related to the deposition of POPs in the sediment of Lake Chaohu, China, using generalized additive models(GAMs). Three historical trends of DDT, PAH, and PCB deposition were delineated in a dated sediment core encompassing ~100 years of historical record: a steady state or gradually increasing stage, a rapidly increasing stage, and a declining stage. The GAM results showed that aquatic total phosphorus(TP) concentrations and regional GDP(anthropogenic factors) were dominant contributors to POP accumulation rates in the lake sediment. The fitted relationships between air temperature and sedimentary DDT and PAH concentrations were linear and negative, while a positive linear relationship was found for PCBs, suggesting that Lake Chaohu may have become a net source for DDTs and PAHs, and a sink for PCBs, under a progressively warming climate.
文摘随着电子元器件产业的发展,对封装的集成性和可靠性也提出了更高的要求。作为一种典型失效形式,翘曲引发的芯片脱层、脱焊和开裂等问题,往往对成品率及封装可靠性产生重要影响。为了探究芯片的翘曲演变规律,基于ANSYS有限元软件,建立了叠层封装(Package on Package,PoP)结构热翘曲的仿真模型,考虑了焊料的Anand黏塑性本构模型,讨论了灌封胶膨胀系数、芯片厚度、焊球弹性模量对结构热翘曲的影响,并针对芯片的翘曲控制提出了优化建议。结果表明,芯片受热时的主要翘曲形态为弓曲,在从高温到低温变化的过程中,其翘曲形态逐渐由上凸转变为下凹。上层封装芯片的翘曲相对较大,灌封胶的热膨胀系数及芯片厚度是翘曲的主要影响因素。
