基于SAFETI模拟的大气条件对天然气扩散影响的研究

为了确定在大气条件影响下天然气泄漏的燃烧影响和毒性影响,采用高斯模型对天然气泄漏后的扩散进行分析,确定了大气对其浓度分布影响的两大因素:风速和大气稳定度。通过SAFETI软件对容器内天然气瞬时泄漏的场景进行模拟,并结合控制变量法对模拟结果"泄漏发生18.75 s时,浓度4.4×10~(-2)天然气云的水平分布情况"、"下风向最大爆炸半径天然气浓度随时间变化的关系"进行分析,研究了天然气扩散过程中受风速和大气稳定度影响的浓度变化趋势和扩散分布规律。研究得出:天然气在泄漏的过程中,以聚集再分散的方式进行扩散,天然气总体分布的几何中心向下风向移动;泄漏天然气在扩散过程中,扩散速度随着风速和大气稳定度的增大而增大;天然气聚集的饱和浓度,随着风速的增大而增大,随着大气稳定度的增大而减小;在一定的时间内,风速越大,大气稳定度越大,天然气的扩散范围越大。     

自然通风条件下室内CO2扩散浓度变化的数值模拟

探究室内危险性气体泄漏后的扩散特性及危害区域的影响,采用CFD软件FLUENT对室内自然通风条件下CO2连续泄漏扩散浓度的变化过程进行了数值模拟,研究CO2扩散过程的浓度场分布和危害区域变化规律,并比较CO2连续泄漏的风洞实验结果与数值模拟结果。结果表明:CO2在重力的作用下,泄漏后向空间的下方扩散,形成气体积聚,浓度逐渐延长,梯度变化较大,出现分层现象,并形成危害区域。随着时间的延长,室内各点的浓度增加,危害区域逐渐变大,并向上方移动;实验数据和模拟结果吻合较好,证明FLUENT可以较准确地模拟室内CO2的扩散过程。     

基于FLUENT的天然气管道微量泄漏数值模拟

为了降低天然气管道泄漏对环境造成的危害,采用FLUENT软件对高压天然气管道微量泄漏后甲烷扩散特性进行数值模拟,模拟了非稳态时甲烷浓度分布情况;探究不同管道压力和泄漏方式以及不同时间下天然气泄漏扩散过程的变化规律,并通过甲烷浓度分布图分析天然气的扩散特性和区域。结果表明:管内压力越大,甲烷扩散区域越大;泄漏方式为细缝泄漏时,扩散范围就相对小孔泄漏较大;甲烷泄漏出去的扩散浓度变化在前几分钟内就已达到稳定。     

舱室有害气体泄漏数值模拟

为研究舱室内害气体泄露过程,减少有害气体对乘载员的危害。采用Navier-Stokes方程与RNG k-ε湍流模型,利用计算流体力学(CFD)理论方法,建立有害气体泄漏的数值计算模型。以某型车辆为例,对车舱内有害气体泄漏扩散过程进行数值模拟,计算得到舱室内有害气体各组分在舱内空间分布及舱室内有害气体泄漏扩散的一般规律。分析结果表明,文中计算方法有效地捕捉到舱内有害气体运动过程以及浓度变化过程,可为舱室有害气体控制设计与评价提供理论基础。     

厂房内液体化学品泄漏相变扩散数值模拟

针对有限空间中易发生相变的液体化学品意外泄漏的情况,运用Fluent软件对其泄漏扩散进行数值模拟。湍流模型选用RNGk-ε模型,考虑液体发生相变时的蒸发潜热,分析了不同时刻的危害区域范围,数值预测其在有限空间的温度场、速度场及浓度场的时空分布。结果表明,在风的下游和地面附近化学品浓度较高,并且液体蒸发相变导致温度降低,化学品浓度越高,温度越低;液体蒸发相变是一个渐变过程,在刚开始泄漏时空间气相质量浓度较低,随时间继续气相质量浓度逐渐升高,并且在水平和垂直方向其扩散呈不同特点。     

安全壳空气中放射性与燃材元件破损的关系

核燃料元件包壳发生破损后,裂变产物放射性就进入主载热剂,然后从主回路系统漏向安全壳,使安全壳空气中出现放射性,文章计算了在安全壳空气中出现的裂变气体及其衰变产物的放射性浓度,并和国家规定的工作场所的在空气中最大允许浓度作比较,最后找出了在不超过最大允许浓度(MPC)的限制下,燃料元件的总破损面积,棒数与允许泄漏率之间的关系。     

低微水的体积分数对SF_6局部放电及分解特性的影响

为了研究交流电压、低体积分数(1 350×10-6)条件下水分对SF6气体局部放电及分解特性的影响,搭建了SF6绝缘电力设备实验及检测平台,详细描述了金属突出物缺陷下局部放电量及SOF2、SO2F2、SO2、CO2等4种气体分解产物随微水的体积分数的变化规律。结果表明,平均局部放电量和总体放电量都随微水的体积分数呈现先下降后上升的趋势;微水的体积分数的增加对几种产物均有促进作用,且对3种含硫产物的促进作用强于对CO2的促进作用。气体产物体积分数比值φ(SOF2+SO2)/φ(SO2F2)随微水的体积分数的变化表现出较好的稳定性,最终稳定在3~4之间;φ(SOF2+SO2+SO2F2)/φ(CO2)则随着φ(H2O)的增加呈现总体增长的趋势,其低微水的体积分数下的值在2.5~3之间。因此,SF6气体分解检测法应用过程中需要充分考虑微水的体积分数的影响。     

基于蒙特卡罗模拟的α能谱拖尾分析

α能谱测量是通过对放射性核素释放α粒子能量的测量来实现核素识别和定量分析的技术.α能谱易受测量样品形态的影响,存在着向低能拖尾的现象,这降低了α能谱测量的准确性.为了分析α能谱谱形特点,采用蒙特卡罗程序Geant4模拟了~(241)Am源的α能谱,并对可能造成~(241)Amα能谱峰拖尾的因素进行了模拟分析.结果表明,~(241)Am源上沉积的灰尘是其α能谱峰拖尾的主要原因;采用最小二乘法拟合可以对沉积灰尘的粒径分布进行估计.这项工作也表明基于蒙特卡罗模拟的α能谱分析可获得测量样品更多特性(如形状),有助于提高α能谱的分析能力.     

多巴胺修饰聚乙二醇的合成及与Fe~(3+)配位研究

利用对硝基苯基氯甲酸酯活化方法合成多巴胺(DOPA)末端修饰的线型聚乙二醇PEG-(DOPA)_2,通过核磁共振技术、紫外-可见分光光度法和动态流变学技术对产物结构和性质进行表征。实验结果表明,多巴胺与PEG-10000的偶联率高达98.0%;随着pH值增大(3.5~12),多巴胺基团与金属Fe~(3+)发生从一配位到稳定三配位结构的转变;在一定聚合物浓度下(≥9%(w/v,重量/体积比),多巴胺基团与Fe~(3+)的物质的量比为3:1)和pH=12时,PEG-(DOPA)_2与Fe~(3+)发生配位,引起PEG聚合物之间的交联,形成PEG-DOPA-Fe~(3+)水凝胶。该凝胶具有pH敏感性和自愈性等多功能性,在生物医学工程和水下机械涂层材料等领域具有潜在应用。     

热核聚变等离子中氩注入过程辐射特性的时间演化

通过假定一定的等离子体温度、密度分布,数值求解了一维等离子体的连续性方程,获得了杂质氩电离态分布,其辐射功率随空间位置和时间而变化。结果显示：在杂质注入时间较短时,由于离子输运及各种损失机制,总杂质密度在空间分布尚未达到平衡,电离态离子主要分布在等离子体周边,完全电离离子所占份额很小;当时间达到0．25s时,氩在等离子体中完全达到平衡状态,体积辐射功率趋于一个稳定的数值;辐射功率在空间的分布随时间变化较小,主要分布在等离子体周边及边界层一个狭小的辐射带内,说明氩引起的辐射主要由低电离态离子引起。     

核供热堆正常运行时气载放射性释放的计算方法

核供热堆要建在城市附近为城市居民供热，因而做好环境影响评价十分重要。正常 运行工况下气载放射性流出物向环境释放量的计算是环境影响评价的基础。本文根据壳式低 温核供热堆的结构设计特点，提出了该种堆型在正常运行工况下气载放射性流出物向环境释 放的６种主要来源，即元件破裂监测系统定期取样监测排放、反应堆压力容器上部气空间的泄 漏、主回路水的泄漏、反应堆舱室中空气的活化、安全壳中气体的活化、废气系统的排放。并推 导出它们的计算公式。     

Oxygen isotope variation in the water cycle of the Yamzho lake Basin in southern Tibetan Plateau

Given the potential use of stable isotope in the paleoclimate reconstruction from lacustrine records as well as in the local hydrology cycle, it is crucial to understand the processes of stable isotope evolution in catchment in the Tibetan Plateau region. Here we present a detailed study on the water oxygen isotope based on 2 years observation including precipitation, river water and lake water in the Yamzho Lake, south of the Tibetan Plateau. Temporal variation of local precipitation 5180 shows an apparent ＂monsoon cycle＂. In monsoon season, 5180 in waters is lower. In non-monsoon season, δ^18O in precipitation and lake water is higher and higher river δ^18O exists in spring, probably reflecting the effect of land surface evaporation, together with the higher δ^18O values in spring precipitation. It is also found that the surface lake water δ^18O varies seasonally and annually. The lower lake water δ^18O in the late summer is apparently related to the summer monsoon precipitation. The mean δ^18O value of lake water in 2007 is 1.2‰ higher than that in 2004, probably due to the less monsoon precipitation in summer of 2007, as can be confirmed from the precipitation data at the Langkazi meteorological data. It is also found that an obvious shift of vertical lake water δ^18O reflects the fast mixture of lake water. δ^18O values of lake water are over 10‰ higher than those of precipitation and river water in this region due to the evaporation fractionation. The modeled results show that the evaporation process of the lake water is sensitive to relative humidity, and the present lake water δ^18O reflects a relative humidity of 51% in the Yamzho Lake. It shows that the lake will take 30.5 years to reach present lake water δ^18O given a large shift in the input water δ^18O. The modeled results also reveal that surface lake water temperature and inflow δ^18O have slight effect on the isotopic balance process of lake water in the Yamzho Lake.     

抑制off-gel分离中18O标记回标的方法研究

off-gel分离法和¹⁸O标记是蛋白质组学研究中常用的分离和标记方法,通过对大鼠纹状体蛋白酶解后的肽段进行off-gel分离,以及基于超滤后的¹⁸O标记与off-gel分离的结果表明,off-gel对复杂生物样品具有良好的聚焦和分离效果,超滤去除游离酶后,¹⁸O标记的肽段没有发现明显回标现象,¹⁶O与¹⁸O标记的肽段1:1混合后,90%以上的蛋白¹⁶O/¹⁸O比值为1.04±0.16,因此,对复杂样品的考察结果说明基于超滤的¹⁸O标记可以与off-gel分离联合使用,扩大了¹⁸O标记在分离方法中的选择范围,能够应用于定量蛋白质组学的研究中.     

Characteristics of U-pattern distribution of highconcentration <Superscript>210</Superscript>Pb in surface air at central Guizhou,China

A better understanding of the variation of ²¹⁰Pb concentrations in the surface air is the key to trace lake sedimentation and catchment erosion, to establish and validate the global diffusion model of contaminants, and to assess the impact of natural radiation on the ecological system. Basing on the study progresses of the sedimentation, the atmospheric model and the unique environmental background in the Yunnan-Guizhou Plateau, and starting from December 20, 2001, we made use of a 500 NE Type aerosol sampler to collect filter samples, once a week in the past consecutive two years, in the surface air at Mt. Guanfeng, Guiyang City, China. Synchronous detailed γ-energy spectrometric observations of ²¹⁰Pb concentrations at both Chinese and U.S. laboratories have shown that the average monthly ²¹⁰Pb concentration displays a regular U-patterns distribution of annual variations, with high values appearing in winter and low values in late spring and summer. The average annual ²¹⁰Pb concentrations are estimated to be 2.77±0.63 mBq/m³, about 4 times the average maximum concentrations reported from quite a number of monitoring stations throughout the world. The possible factors affecting the sources of ²¹⁰Pb in the surface air in the central part of Guizhou Province are: Release of ²²²Rn from the U-Ra series enriched in the soils; chemical weathering of carbonate rocks; the exploitation, processing and utilization of coal and phosphorous resources. The principal factor controlling the high ²¹⁰Pb concentrations in the surface air in the central Guizhou and their annual U-pattern distribution is the release of ²²²Rn. The average monthly ²¹⁰Pb concentrations show a good negative powerfunction relationship with increasing precipitation and also show a good negative linear-function relationship with the rise of air temperature in month grouping. Group No.1 (June to November) reflects a relatively low release of ²²²Rn from soils in relatively high temperature seasons; Group No.2 (December to May) mirrors a relatively high release of ²²²Rn from soils in relatively low temperature seasons. The average monthly ²¹⁰Pb concentrations simulated in terms of the precipitation and air temperature are in good consistency with the measured values, revealing that the regular U-pattern distribution characteristics of ²¹⁰Pb concentrations in the surface air in the central Guizhou are controlled predominantly by regional precipitation and air temperature. Meanwhile, it is also indicated that the magnitude of variation of air temperature and precipitation within the same year also constrains the ratio of high values over low values of average monthly ²¹⁰Pb concentrations. On a month time scale, precipitation and air temperature are a main factor affecting the release of ²²²Rn from soils (rocks). In this aspect strong evidence has been obtained.     

Distribution of <Emphasis Type="Italic">δ</Emphasis><Superscript>18</Superscript>O in surface snow along a transect from Zhongshan Station to Dome A,East Antarctica

Surface snow samples were collected during the 14th (1997/1998) and 24th (2007/2008) Chinese National Antarctica Research Expeditions along a transect from Zhongshan Station to Dome A. The stable oxygen isotope ratios of these samples were measured to investigate their relationships with temperature and geographical parameters (latitude, longitude, altitude and distance to the coast). The results reveal a strong positive correlation (R=0.945) between δ¹⁸O and mean annual temperature, with a gradient of 0.84‰°C ^–1, which is a little higher than that in Terre Adelie Land. Regression analyses also show that the δ¹⁸O of surface snow is strongly correlated with distance to the coast (R=0.942), latitude (R=0.942), and altitude (R=0.941). But no significant correlation was found between δ¹⁸O and longitude in study area. Altitude should be the most important factor influencing the δ¹⁸O distribution because of distinctive topography. The δ¹⁸O-altitude and T-altitude gradients along this transect are determined to be –1.1‰/100 m and 1.31°C/100 m, respectively.     

桶型3He中子探测器探测效率标定装置设计分析研究

基于后处理生产的³He中子探测器,开展了桶型中子探测效率标定装置的材料选择及功能结构设计分析,使用MCNP程序构建了装置及³He探测器的相关计算模型,根据生产过程及设计需求,分别分析了桶型中子探测效率标定装置慢化层的慢化效果,及不同位置多根³He管中子探测器的探测效率,并计算了源管、探测器上方及屏蔽体周围的剂量,结果表明该装置的慢化能力及屏蔽效果良好,放射性剂量水平满足辐射防护要求。     

非饱和煤矸石淋滤仪改进及应用

为提升非饱和煤矸石室内淋滤试验的可靠性与准确性,对传统非饱和煤矸石淋滤仪的降雨模拟系统进行改良,实现了随机降雨路径的模拟,并增大了煤矸石有效淋滤体积。同时,以韩城桑树坪煤矿煤矸石为研究对象,揭示了不同降雨强度和风化程度组合条件下煤矸石淋滤特征,试验结果是：(1)淋滤液电导率(EC)及SO4_^2-浓度(c)均随淋滤时间呈整体下降趋势,且可划分为快速下降和缓降趋稳两个阶段;(2)采用指数型函数、傅里叶函数及幂函数对不同试验条件下EC-t和c-t关系曲线进行拟合,拟合函数R_²介于0.87~1.00;(3)167mm/h降雨强度下,淋滤液电导率及SO_4^2-浓度对风化程度的敏感性指数最大,分别为3.14和7.64;(4)相较其它条件下淋滤液电导率及SO_4^2-浓度,83mm/h降雨强度和风化3a矸石条件下淋滤液EC值和c值更高。分析得到三点结论：(1)煤矸石可溶元素释放量主要呈指数型函数衰减,并在试验进行3~5h后趋于稳定;(2)风化程度为影响煤矸石可溶元素释放能力的主控因素;(3)较小的降雨强度和较高的风化程度有利于煤矸石元素持续淋滤释放。     

Indian monsoon influences altitude effect of δ~(18)O in precipitation/river water on the Tibetan Plateau

The δ^18O variation in precipitation acquired from 28 stations within the network of Tibetan Observation and Research Platform （TORP） is studied, with the focus on the altitude effect of δ^18O in river water during monsoon precipitation in an effort to understand the monsoon influence on isotopic composition in annual river water. It is found that δ^18O in precipitation on the Plateau is influenced by different moisture sources, with significant Indian monsoon influence on δ^18O composition in plateau precipitation and river water. The δ^18O of water bodies in the monsoon domain is generally more depleted than that in the westerly domain, suggesting gradual rainout of southwesterly borne marine moisture in the course of long-distance transportation and lifting over the Himalayas. The lapse rate of δ^18O in river water with altitude is the largest during monsoon precipitation, due to the increased temperature vertical gradient over the southern Plateau region controlled by monsoon circulation. The combination of δ^18O in river water in monsoon （wet） and non-monsoon （dry） seasons shows a larger lapse rate than that in non-monsoon （dry） season alone. As the altitude effect of δ^18O in precipitation and river water on the Tibetan Plateau results from the combined effect of monsoon moisture supply and westerly moisture supply, the δ^18O composition and its altitude effect on the Plateau during monsoon seasons should be considered in the reconstruction of paleoelevation of the Tibetan Plateau.     

π介子凝聚对中子星物质的影响

在相对论平均场理论框架下研究了π^-介子凝聚对包括Δ共振态的中子星物质状态方程及其粒子分布的影响. 研究表明, π^-介子凝聚的存在对中子星物质的粒子分布有明显影响, 使Δ^-粒子出现推迟, Δ⁺粒子出现提前. π^-介子凝聚的出现还使中子星物质的状态方程变软. 尽管这种改变很小, 但这种变软的趋势仍具有重要的意义.     

Characteristics of δ 18O in precipitation over Eastern Monsoon China and the water vapor sources

Monsoon circulation is an important carrier of water vapor transport, and it impacts the precipitation of the monsoonal regions through the constraints and controls of large-scale water vapor transport and distributions as well as the water vapor balance. An overall research on stable Hydrogen and Oxygen isotopes in precipitation over Eastern Monsoon China could benefit a compre-hensive understanding of the monsoonal precipitation mechanism. Seventeen field stations of the Chinese Network of Isotopes in Precipitation (CHNIP) have been selected to collect monthly composite precipitation samples during the years 2005―2006. Components of δD and δ¹⁸O have been analyzed to achieve the spatiotemporal distributions. The established Local Meteoric Water Line δD=7.46 δ¹⁸O+0.90 based on the 274 obtained monthly samples could be treated as isotope input functions across the region, due to basically reflecting the specific regional meteorological conditions over Eastern Monsoon China. The δ-value de-pleted from coastal to inner area. In Southern China and Northeastern China there were typical periodic patterns of δ¹⁸8O. Differ-ent dominant affecting metrological factors have been raised with different regions. From south to north, the temperature effect of δ¹⁸18O enhanced, while the amount effect changed from existing at an all-year-scale in Southern China to being only remarkable during the main rainy seasons in North China and Northeastern China. Main geographical controls varied from altitude in South-ern China and North China to latitude in Northeastern China. Furthermore, δ¹⁸O had an implication of advance and retreat of the monsoon as well as rainfall belt transfer δ¹⁸O was also a tracer for the movement path of typhoon and tropical storms.