小波降噪与粒子群优化综合回归爆破震动参数

爆破震动测试得到的数据常常具有较大的离散性,采用剔除错误数据和小波降噪对爆破震动检测数据进行预处理,以标准残差平方和作为爆破振动实测数据与萨道夫斯基公式拟合值偏差大小的判断依据,应用小波降噪对实测数据进行处理的方法,优化了粒子群算法对萨道夫斯基公式中的k和 的回归分析。研究结果表明,小波降噪和粒子群优化算法结合使用,能够较真实地反映爆破震动测试的真实情况,从而提高了对爆破震动测试模拟的精度。研究结果对爆破振动测试理论和工程实践具有一定的参考价值。     

基于颗粒破碎的钙质沉积物高压固结变形分析

采用高压固结试验,研究珊瑚礁沉积碎屑物试样在固结、回弹过程中的变形特性以及在不同加载方式、含水条件下的颗粒破碎情况,分析含砂量对变形的影响以及不同试验条件下的颗粒破碎规律。研究结果表明,不同的含砂量使砂、砾在试样固结时起到的作用不同,导致试样变形规律存在差异;加载方式、含水条件等对颗粒破碎影响显著,并在颗粒破碎结果分析中发现,0.25 mm是颗粒破碎时相对稳定的粒径,是研究钙质砂颗粒破碎的一个重要粒径界限,其结果对于将钙质碎屑物作为稳定的填筑材料、提高珊瑚礁地基稳定性等具有实用价值。     

断层三维滑动速率反演的算法对比

将微粒群优化算法与位错理论模型相结合,采用模拟重力测量数据反演断层三维滑动速率,并比较了该算法与蒙特卡洛法和蚁群算法的反演结果。利用河西地区2001~2004年的GPS数据,对祁连山断层的三维滑动速率进行反演,并与蚁群算法进行比较。结果表明,微粒群优化算法可有效求解断层的三维滑动速率,收敛快、精度高。     

Particle velocity and concentration profiles in bedload experiments on a steep slope

Depth profiles of particle streamwise velocity, concentration and bedload sediment transport rate were measured in a turbulent and supercritical water flow. One‐size 6 mm diameter spherical glass beads were transported at equilibrium in a two‐dimensional 10% steep channel with a mobile bed. Flows were filmed from the side by a high‐speed camera. Particle tracking algorithms made it possible to determine the position, velocity and trajectory of a very large number of particles. Approximately half of the sediment transport rate was composed by rolling grains, and the other half by saltation. This revealed a complex structure, with several concentration and flux peaks due to rolling, and one peak due to saltation. With an increase of the sediment transport rate, the depth structure remained the same at the water/granular interface, with peak value increases but with no shift in elevations. The saltation region expanded towards higher elevations with an increase of the particle velocity commensurate to the water velocity. The proportion of the sediment transport rate in saltation did not vary significantly. The particle streamwise velocity profiles exhibited three segments: an exponential decay in the bed, a linear increase where rolling and saltation co‐existed, and above this, a logarithmic‐like shape due to saltating particles. These results are comparable to profiles measured and modelled in dry granular free surface flows and in more intense bedload such as sheet flows. Copyright © 2014 John Wiley & Sons, Ltd.     

楚科奇海悬浮体含量分布及其颗粒组分特征

对中国第四次北极科学考察在楚科奇海获取的悬浮体样品进行悬浮体及其颗粒组分特征的分析,旨在了解楚科奇海悬浮体分布、成因特征以及其沉积学意义。研究发现,楚科奇海中部悬浮体浓度最低,而在靠近白令海峡的南部海域和中北部海域,中下层海水中发现两个悬浮体浓度高值区。楚科奇海阿拉斯加沿岸和巴罗峡谷底层海水中,悬浮体浓度相对较高。扫描电镜分析结果显示,楚科奇海南部和中北部中下层海水中的悬浮体,主要以硅藻为主,但这两个海域的硅藻优势种明显不同。阿拉斯加沿岸和巴罗峡谷中的悬浮体,以生物碎屑为主。结合楚科奇海温度、盐度资料,楚科奇海南部和中北部高浓度悬浮体分别受经白令海峡夏季入侵的太平洋海水和楚科奇海冬季残留水的控制,而阿拉斯加沿岸和巴罗峡谷中下层的悬浮体,则受阿拉斯加沿岸流的控制。     

北京及周边地区2004年8、9月层积云结构及谱分析飞机探测研究

2004年8～9月利用机载粒子测量系统 (Particle Measuring System, 简称PMS) 对我国北京及周边地区的三次锋面云系进行了探测, 本文分析了三次降水性层积云中各种粒子的垂直、水平和谱分布。结果表明, 三次降水云系基本是冷锋或者暖锋系统下形成的层积混合云系。云内以直径5～9 μm、200 μm和400～1000 μm的云和降水粒子为主。9月14日暖锋层积云系的粒子浓度最大, FSSP-100 (前向散射粒子谱探头)、 GA2(二维灰度云粒子图像探头)、 GB2(二维灰度降水粒子探头)分别探测的最大粒子浓度为318.97 cm-3、0.03 cm-3、0.0065 cm-3。8月12日和8月15日的冷锋层积云系有多个干层。GA2探测的平均浓度谱基本为单峰分布, 并找出了合适的拟合函数。冷锋层积云系的负温云层中存在着相同浓度量级的过冷云水和雨水、霰粒、柱状和针状冰晶, 过冷水含量可达到0.26 g/m3, 暖锋云系中则以霰粒、结淞粒子和冰雪晶聚合体为主, 也存在少量柱状、针状冰晶和过冷水滴。与我国北方地区13架次飞行探测结果比较, 北京及周边地区2003年8月15日、2004年8月12日和9月14日层积云0 ℃层以上的冰雪晶粒子直径最大, 浓度居中, 过冷水含量因云系结构不同而变化较大。     

雷达-雨量计-粒子激光探测仪联合估算降水量

为了提高区域降水量观测的空间分辨率, 提出了雷达-雨量计-粒子激光探测仪联合校准法。首先, 利用粒子激光探测仪观测到的滴谱资料建立实时的Z-I关系, 然后, 利用变分法对同时有雷达回波和雨量计资料的点的实测校准因子进行校准, 获得最优校准因子分析场, 最后, 对有雨量计的点取雨量计实际观测值, 没有雨量计的点利用最优校准因子分析场估算降水。利用此方法对辽宁省2007年5月15日一次天气过程进行降水量估算, 结果表明: 雷达-雨量计-粒子激光探测仪联合校准法结合了雨量站观测资料单点精度高和雷达资料时空分辨率高的优点, 提高了降水量的估算精度, 更好地反映了降水的空间分布。     

Intelligent optimization algorithms to VDA of models with on/off parameterizations

Some variational data assimilation (VDA) problems of time- and space-discrete models with on/off parameterizations can be regarded as non-smooth optimization problems. Same as the sub-gradient type method, intelligent optimization algorithms, which are widely used in engineering optimization, can also be adopted in VDA in virtue of their no requirement of cost functions gradient (or sub-gradient) and their capability of global convergence. Two typical intelligent optimization algorithms, genetic algorithm (GA) and particle swarm optimization (PSO), are introduced to VDA of modified Lorenz equations with on-off parameterizations, then two VDA schemes are proposed, that is, GA based VDA (GA-VDA) and PSO based VDA (PSO-VDA). After revealing the advantage of GA and PSO over conventional adjoint methods in the ability of global searching at the existence of cost functions discontinuity induced by on-off switches, sensitivities of GA-VDA and PSO-VDA to population size, observational noise, model error and observational density are detailedly analyzed. Its shown that, in the context of modified Lorenz equations, with proper population size, GA-VDA and PSO-VDA can effectively estimate the global optimal solution, while PSO-VDA consumes much less computational time than GA-VDA with the same population size, and requires a much lower population size with nearly the same results, both methods are not very sensitive to observation noise and model error, while PSO-VDA shows a better performance with observational noise than GA-VDA. It is encouraging that both methods are not sensitive to observational density, especially PSO-VDA, using which almost the same perfect assimilation results can be obtained with comparatively sparse observations.     

专业气象服务产品自动制作与发布系统

利用地面雨滴谱的连续观测资料,可以分析降水特征和降水的形成机制。对于人工增雨的效果检验工作,雨滴谱资料的分析研究也具有重要的参考价值。目前,山西省人工降雨防雹办公室建设了6300km^2的人工影响天气效果检验示范基地,并且引进了4部德国OTT公司的Parsivel激光降水粒子谱测量系统,分别布设在太谷、汾阳、介休和祁县,这为进行雨滴谱观测研究提供了有利的条件。本文对Parsivel降水粒子谱仪的功能、产品以及在气象领域的应用作简单的介绍,旨在给我们使用此仪器进行降水微结构特征研究提供参考。     

Condensation particle counting below 2 nm seed particle diameter and the transition from heterogeneous to homogeneous nucleation

Particle detection by condensation particle counters (CPCs) is ultimately limited by the onset of homogeneous nucleation. At vapour supersaturations around the homogeneous nucleation limit the diameter of critical clusters is typically about 2 nm. It is widely assumed that only particles larger than critical clusters can be activated by vapour condensation and the general detection limit of CPCs is therefore currently accepted to be around 2 nm particle diameter. Using an expansion type CPC with n-propanol as working fluid we investigated the transition from heterogeneous to homogeneous nucleation, clearly showing that particles are activated much before the onset of homogeneous nucleation, even at particle diameters as small as 1.4 nm. For particle diameters below 2 nm we have usually found condensation particle counting to be influenced by the simultaneous presence of ions as generated in a bipolar diffusion charger. In this paper we illustrate how the presence of ions influences particle number concentration measurement and how ions can be removed in order to obtain accurate seed particle number concentrations for particle diameters down to 1 nm.