测井岩性识别新方法研究

为了更好地解决测井岩性识别问题,引入了一种基于粒子群优化的支持向量机算法.通过实际测井资料和岩性剖面资料进行学习训练支持向量机,并利用粒子群优化算法对支持向量机参数进行优化,建立了测井岩性识别的支持向量机模型,应用该方法对准噶尔盆地某井的测井岩性进行识别,并将该方法的识别结果与BP神经网络方法的识别结果进行了比较,结果表明该方法优于BP神经网络方法,具有识别正确率高、收敛速度快、推广能力强等优点.     

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。     

含AgI人工冰核粒子的电镜分析

为深入认识当前人工影响天气作业中广泛使用的AgI焰剂的成冰特性, 利用电子显微镜对含AgI焰剂产生的人工冰核粒子尺度特征进行分析研究。利用环境场扫描电镜对焰剂颗粒的尺度分布和形态学特征进行研究, 利用场发射高分辨透射电镜纳米区域的X射线成分分析 (EDS) 对实验样品的颗粒结构特点和主要组成成分进行研究。实验结果表明:不同配方焰剂燃烧产生的颗粒谱分布特征有明显差异, 所取5种焰剂产生的颗粒平均谱分布, 其直径在0.02~0.50 μm之间的粒子数占98.96%, 即产生粒子绝大部分都可直接参加云内的成冰核化过程, 但其谱宽、峰值直径, 分布特征都不相同。透射电镜结果表明:焰剂颗粒的主要组成是KCl, 其表面附着AgI小颗粒, 该结构特征可能更有利于焰剂颗粒的成冰核化。利用中国气象科学研究院1 m3等温冷云室对AgI焰剂阈温对比实验表明:5种焰剂的成冰阈温在-3.5~-4.4 ℃范围内, 不同焰剂配方的阈温不同, 最大相差1 ℃。焰剂成冰核化速率主要由颗粒的大小 (均立方根直径) 决定, 同时受到谱宽、主峰位置等多种分布特征量影响, 改进配方时应综合考虑。同时, 由于高于-4.4 ℃时, 焰剂产生颗粒接触过冷水滴缺少活性, 即含AgI焰剂不适于云中较暖区的催化。     

Decoupling of Aerosol Absorption Coefficient in the Spring of 2006 at an Urban Site in Beijing

 A statistic regression approach was used to estimate the wavelength exponents of black carbon (BC) and dust particles, and further to separate the contributions of the two types of aerosols to the total light absorption coefficient measured in the Beijing urban area in the spring of 2006. The results show that the wavelength exponent (a) of black carbon aerosol at urban site was approximately -0.92, which is in agreement with the value of -0.8±0.2 reported in related studies. The decoupling analysis of the measured light absorption coefficients during the three floating dust periods ( March 25, March 27, and April 9) demonstrates that, on average, the light absorption caused by dust particles took up about 32.8% of the total light absorption at 520 nm wavelength, and by black aerosol more than 60%. This indicates that the black carbon was still the major contributor to the total aerosol light absorption in Beijing urban area even during the floating dust periods.     

南极中山站电离层的极区特征

本文利用1996年的电离层数字测高仪DPS-4所测的f0F2、f0E以及美国NOAA和DMSP卫星观测估算的半球功率指数和午夜极光区赤道侧边界纬度等资料,考察中山站电离层的极区特征。结果表明,在太阳和地磁宁静环境下,冬季极夜磁正午中山站处于极隙区中心时,电离层内的电离密度达全天的最大值;上、下午各有数小时间隔位极光带内时,高能粒子的电离作用也很重要;夜间进入极差区后,电子密度则很低。夏季极昼时,太阳EUV辐射的电离效应使电离层电离密度比冬季值大许多,而且,日变化的最大值时间也提前了1~2h,强磁扰时,极隙区和极光带均向低纬侧移动;中山站上空的电子密度会大幅度下降。在中等扰动环境下情况要加复杂：磁正午前后极隙区内软粒子沉降的电离强度有所减小,而上、下午极光区的高能粒子电离则有较大增加。     

粒子群优化神经网络的土壤有机质高光谱估测

针对提高土壤有机质高光谱估测精度的问题,该文对山东省泰安市的92个棕壤样本进行光谱去噪,剔除异常样本处理后,对光谱反射率进行11种变换,发现一阶微分变换最佳;然后计算土壤有机质含量与变换后光谱反射率的相关系数,选取5个特征波段,分别利用多元线性回归、BP神经网络、支持向量机、粒子群优化神经网络4种方法建立土壤有机质含量高光谱估测模型并进行精度比较。实验结果表明,多元线性回归、BP神经网络、支持向量机和粒子群优化神经网络模型的决定系数R2分别为0.520 3、0.665 4、0.735 0和0.853 0,均方根误差分别为2.12、1.99、1.45和1.08。研究结果表明,粒子群优化神经网络的反演精度高、稳定性强,可有效提高土壤有机质的光谱估测能力。     

A generalized rigid particle contact model for fracture analysis

Rigid particle models taking directly into consideration the physical mechanisms and the influence of the material meso‐structure have recently been developed for fracture studies of quasi‐brittle material such as concrete. The formulation of a generalized contact model for rigid particle simulations is presented in which the contact discretization is a model parameter. The contact model performance for different discretizations is evaluated for uniaxial tensile tests, for uniaxial compression tests and for a notched beam in mode I. Copyright © 2005 John Wiley & Sons, Ltd.     

Impedances of rigid cylindrical foundations embedded in transversely isotropic soils

A complete formulation and implementation for assessment of the response to dynamic loads of cylindrical rigid structures embedded in transversely isotropic elastic half‐spaces is presented. The analysis is performed in the frequency domain and the steady‐state structure response is obtained. The method is based on a non‐singular version of the indirect boundary element method which uses influence functions, instead of Green's functions, as fundamental solutions. These influence functions are the response of an elastic half‐space to distributed, internally applied loads. The proposed method imposes full bonding contact between the foundation and the surrounding soil. Numerical results for displacement (vertical and horizontal) and rotation (twisting and rocking) impedances, showing the influence of the soil anisotropy, are presented. Results for the soil–structure interface tractions and for the displacement field throughout the half‐space are also shown. Copyright © 2006 John Wiley & Sons, Ltd.     

Multi‐objective particle swarm optimization for generating optimal trade‐offs in reservoir operation

A multi‐objective particle swarm optimization (MOPSO) approach is presented for generating Pareto‐optimal solutions for reservoir operation problems. This method is developed by integrating Pareto dominance principles into particle swarm optimization (PSO) algorithm. In addition, a variable size external repository and an efficient elitist‐mutation (EM) operator are introduced. The proposed EM‐MOPSO approach is first tested for few test problems taken from the literature and evaluated with standard performance measures. It is found that the EM‐MOPSO yields efficient solutions in terms of giving a wide spread of solutions with good convergence to true Pareto optimal solutions. On achieving good results for test cases, the approach was applied to a case study of multi‐objective reservoir operation problem, namely the Bhadra reservoir system in India. The solutions of EM‐MOPSOs yield a trade‐off curve/surface, identifying a set of alternatives that define optimal solutions to the problem. Finally, to facilitate easy implementation for the reservoir operator, a simple but effective decision‐making approach was presented. The results obtained show that the proposed approach is a viable alternative to solve multi‐objective water resources and hydrology problems. Copyright © 2007 John Wiley & Sons, Ltd.     

Leica AT960激光跟踪仪测量精度分析

粒子加速器的高精度准直要求对测量技术提出很大挑战,由于激光跟踪仪具有大尺寸、高精度及三维空间测量的优势,因此需要开展激光跟踪仪对粒子加速器的测量精度研究。首先,针对激光跟踪仪的标称测量精度,介绍了激光跟踪仪标称测量精度的表达方法、测试方法,对标称精度指标的计算方法进行推导,并对其具体含义进行解释,为激光跟踪仪的测量应用及数据处理提供了理论基础。然后,以直线控制网为代表开展激光跟踪仪对粒子加速器控制网的测量方法和测量精度分析,在中国散裂中子源大科学装置直线加速器进行了实际测量,采用激光跟踪仪分两组在同一时间内进行观测,通过对控制网单组的平差精度以及两组的坐标对比分析,全面准确地评价其测量精度,发现200 m长直线控制网点位横向最弱精度优于0.2 mm。同时,以导线网为简化模型对直线控制网的精度进行理论估算,发现直线控制网中部点位横向精度与控制网长度的三次方开根号成正比,从而可快速推算出其他规模的直线控制网的的测量精度,为陆续建设的粒子加速器的准直精度分析以及准直方案决策提供指导。