氯气瞬时泄漏浓度演化过程模拟研究

以高斯烟团模型为基础,建立氯气瞬时泄漏气体扩散浓度分布数值模型,利用MATLAB软件求解该模型,对求解结果以可视化图形进行数值模拟,分别模拟了大气稳定度为A、C、E,风速为1.5,2.5,3.5 m/s,泄漏时间为30,60,90,120,150,180 s的演化结果,其仿真结果很好的显示了氯气瞬时泄漏浓度动态演化过程,为评估氯气泄漏事故风险,划分应急疏散范围提供了数据支持。

基于晶体相场模型二元合金凝固过程的晶粒形貌模拟

基于相场模型研究了二元合金在不同过冷速率下的晶粒形貌演化。结果表明,形核数量随着冷却速率的提高而不断提高,晶粒尺寸随着冷却速率的增加而降低。当冷却速率达到某个极限值时,晶界迁移速率明显变慢,凝固组织粗化现象受到抑制。

氢气/氧气混合气体等离子体放电动力学机理

针对绿色无毒推进剂航天器火箭发动机真空低温条件下点火困难等问题,提出通过放电产生非平衡等离子体,利用其活化效应改善发动机点火性能。为了研究氢、氧混合气体放电产生的活性粒子的时间演化特性,利用Bolsig+求解器计算得到不同电子碰撞反应能量损失分数随约化场强变化规律;利用ZDplaskin程序包对氢、氧混合气体放电过程进行零维仿真;研究了不同约化场强下混合气体活性粒子随时间变化规律。结果表明,不同约化场强下,氢、氧混合气体中各类电子碰撞反应消耗能量占比不同。约化场强较小的情况下,电子能量大部分被分子的碰撞激发所消耗;而约化场强较大的情况下,电子能量主要用于分子的离解与电离;约化场强大于100 Td时,放电过程电子浓度快速增大,更有利于活性粒子的生成与积累。

Quantitative characterization of lamellarαprecipitation behavior of IMI834 Ti-alloy in isothermal and non-isothermal heat treatments

To reveal the affecting mechanism of cooling rate on lamellarαprecipitation,the precipitation behaviors of lamellarαphase in IMI834 titanium alloy during isothermal and non-isothermal heat treatments were quantitatively characterized using experimental analysis.Critical precipitation temperatures at various cooling rates were obtained using thermal dilatation testing.Using metallographic microscopy,electron microprobe analysis,and data fitting methods,the quantitative evolution models of average width,volume fraction,and solute concentration in theαandβphases were built for different temperatures or cooling rates.A comparison between the two precipitation behaviors showed that the average width and volume fraction of lamellarαphase under non-isothermal conditions were smaller than those under isothermal conditions.With increasing cooling rate,the average width and volume fraction were decreased significantly,and the critical precipitation temperatures were reduced.This phenomenon is mainly attributed to the decreased diffusion velocity of solutes Al,Mo,and Nb with increasing cooling rate.

Paleoproductivity evolution in the West Philippine Sea during the last 700 ka

In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka, the vertical gradient of Δδ13C in dissolved inorganic carbon Δδ13C between those of foraminifera Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi） and planktonic foraminiferal assemblages were analysed in piston Core MD06-3047 retrieved from the Benham Rise （east of the Luzon Island）. Paleoproductivity evolution in the West Philippine Sea during the last 700 ka is closely related to glacial-interglacial cycles and precession-controlled insolation. Controlling factors ofpaleoproductivity could have been both thermocline fluctuations related with ENSO-Iike processes and eolian input associated with East Asian winter monsoon, and the former could have been the primary factor. A higher productivity and a shallower thermocline coeval with the occurrence of low CO2 concentrations in the EPICA Dome C ice core might indicate that biological export production in the low-latitude could act as a significant sink in the global carbon cycle, and modify atmospheric CO2 concentrations. Spectral analysis further reveals that the paleoproductivity is mainly controlled by thermocline fluctuations subjected to ENSO processes responding to processional variability of insolation. High coherences in eccentricity, obliquity and precession periods fiuther revealing the close link between thermocline fluctuations, paleoproductivity and atmospheric CO2 levels.

Aggregation Behaviors of a Two-Species System with Lose-Lose Interactions

We propose an aggregation evolution model of two-species （A- and B-species） aggregates to study the prevalent aggregation phenomena in social and economic systems. In this model, A- and B-species aggregates perform self-exchange-driven growths with the exchange rate kernels K（k, l） = Kkl and L（k, l） = Lkl, respectively, and the two species aggregates perform self-birth processes with the rate kernels J1（k） = J1 k and J2（ k ） = J2k, and meanwhile the interaction between the aggregates of different species A and B causes a lose-lose scheme with the rate kernel H（k,l） = Hkl. Based on the mean-field theory, we investigated the evolution behaviors of the two species aggregates to study the competitions among above three aggregate evolution schemes on the distinct initial monomer concentrations A0 and B0 of the two species. The results show that the evolution behaviors of A- and B-species are crucially dominated by the competition between the two self-birth processes, and the initial monomer concentrations Ao and Bo play important roles, while the lose-lose scheme play important roles in some special cases.

Model-Simulated Atmospheric Carbon Dioxide: Comparisons with Satellite Retrievals and Ground-Based Observations

Atmospheric CO2 concentrations from January 2010 to December 2010 were simulated using the GEOS-Chem(Goddard Earth Observing System-Chemistry) model and the results were compared to satellite Gases Observing Satellite(GOSAT) and ground-based the Total Carbon Column Observing Network(TCCON) data. It was found that CO2 concentrations based on GOSAT satellite retrievals were generally higher than those simulated by GEOS-Chem. The differences over the land area in January and April ranged from 1 to 2 ppm, and there were major differences in June and August. At high latitudes in the Northern Hemisphere in June, as well as south of the Sahara, the difference was greater than 5 ppm. In the high latitudes of the Northern Hemisphere the model results were higher than the GOSAT retrievals, while in South America the satellite data were higher. The trend of the difference in the high latitudes of the Northern Hemisphere and the Saharan region in August was opposite to June. Maximum correlation coefficients were found in April, reaching 0.72, but were smaller in June and August. In January, the correlation coefficient was only 0.36. The comparisons between GEOS-Chem data and TCCON observations showed better results than the comparison between GEOS and GOSAT. The correlation coefficients ranged between 0.42(Darwin) and 0.92(Izana). Analysis of the results indicated that the inconsistency between satellite observations and model simulations depended on inversion errors caused by data inaccuracies of the model simulation's inputs, as well as the mismatch of satellite retrieval model input parameters.