基于改进粒子群算法的地震标量波方程反演   总被引：4，自引：2，他引：2       下载免费PDF全文

朱童  李小凡  李一琼  张美根 《地球物理学报》2011,54(11):2951-2959

针对标准粒子群优化(PSO)算法存在易出现早熟而陷入局部最优以及进化后期收敛速度慢等缺陷,通过考虑粒子所处位置间相互作用,提出了一种改进的并行粒子群优化算法.由于引入粒子位置间的相互影响,减少了粒子搜索过程盲目性,因此能有效提高算法的收敛速度.数值试验表明,这种改进的粒子群算法适用于二维标量波方程的速度反演,且算法具有...  相似文献   

顾及邻近点的改进PSO-SVM模型在基坑沉降预测的应用研究     

袁志明  李沛鸿  刘小生 《大地测量与地球动力学》2021,41(3):313-318

针对SVM模型在基坑沉降预测领域存在参数选择困难和基于单点数据建模的缺点,建立顾及邻近点的PSO-SVM模型。采用PSO-SVM模型进行最优训练样本数量研究,结果表明短期样本的预测效果最优。将邻近点沉降变形值作为影响基坑沉降的因素引入到改进的PSO-SVM模型中,实例表明,在短期样本数据下顾及邻近点的PSO-SVM模型的拟合精度优于PSO-SVM模型,而在中长期样本条件下预测精度不佳。针对该缺点提出组合多尺度一维小波分解函数和柯西分布函数来改进顾及邻近点的PSO-SVM模型,实验结果表明,顾及邻近点的改进PSO-SVM模型可有效解决参数选择困难和单点建模的问题,适用于不同样本数量下的沉降变形预测,具有较高的预测精度。  相似文献   

不同因素影响下层间错动带颗粒破碎和剪切强度特性试验研究   总被引：2，自引：0，他引：2  

赵阳  周辉  冯夏庭  邵建富  江权  闵弘  江亚丽  黄可 《岩土力学》2013,34(1):13-22

为了获得不同初始颗粒粒径分布和含水率对层间错动带颗粒破碎和剪切强度特性的影响,通过对比泥夹碎屑、泥夹粉砂、全泥型3种不同层间错动带类型与现场3种不同含水率（10%、7%和3%）试样在法向压力2～10 MPa作用下的反复直剪试验和剪切面颗粒粒径分析试验结果,可得出以下结论：①粗颗粒越多（d60越大）,采用相对颗粒破碎势Br量化的颗粒破碎程度越大;②较干颗粒（低含水率）由于磨损产生了更多的细小颗粒,而较湿颗粒（高含水率）由于破裂和摩擦产生了较大颗粒;③粗颗粒仅对峰值抗剪强度产生一定的影响,且粗颗粒越多,残余强度包线非线性越强;④黏聚力和内摩擦角随含水率线性减小,且低含水率试样残余强度包线非线性最强;⑤残余内摩擦角随颗粒破碎后的黏粒含量（<2 μm）线性减小。提出的残余内摩擦角初步预测公式可供实际工程参考。  相似文献   

真空加载方式对吹填流泥加固效果及土颗粒移动的影响研究   总被引：2，自引：0，他引：2  

武亚军  杨建波  张孟喜 《岩土力学》2013,34(8):2129-2135

考虑加载方式的影响开展室内模型试验,对4组相同性质的泥浆试样（含水率为100%）分别采用不同的加载方式,即-80 kPa、-60 kPa→80 kPa、-40 kPa→-80 kPa、-20 kPa→-80 kPa进行加载,加载过程中对试样的出水量、沉降量和侧向变形进行跟踪监测,并对处理后土体的含水率、塑性指数和十字板剪切强度等的空间分布与变化规律进行研究。试验结果表明,（1）真空加载方式对吹填流泥的固结具有比较明显的影响;（2）初始真空荷载为-20 kPa时所得到的土体沉降量最大、强度最高,始终保持-80 kPa荷载情况下所得到的土体沉降量最小、强度最低;（3）从塑性指数的分布特征来看,土颗粒随着土中水的排出发生移动,初始真空荷载越大,这种趋势越明显,部分土颗粒会聚积在排水板周围而导致土体渗透性能的降低,严重时会影响土体的后续固结。建议在流泥淤泥的真空固结过程中采用低初始荷载方式进行加载。  相似文献   

基于指标规范化的水安全评价组合极值公式          下载免费PDF全文

汪嘉杨  张碧  李祚泳  张雪乔 《水文》2013,33(3):5-9

在选取各项指标参照值并设定相应规范变换式的基础上,将参数多元组合算子加以改进,提出适用于多区域、多项指标的、具有普适性的水安全评价组合极值公式,并采用粒子群算法优化公式中的参数。将优化好的具有普适性的组合极值公式应用于实例分析计算,评价结果与其他多种方法的评价结果一致,表明该公式的实用性和可行性。由于基于指标规范化的组合极值公式不受评价指标数目多少的限制,为水安全评价模型的普适化、简单化提供了一条途径。  相似文献   

基于克里金插值的井网优化方案设计 ——以沈阳市浑河李官堡水源地为例     

尹慧  王新民 《世界地质》2013,32(4):820-824

傍河型水源地具有水量稳定、水质清洁的优点,因此水源地水井肩负采水和检测水质双重作用。结合李官堡水源地实例,基于克里金空间插值方法,建立关于三氮污染物多目标监测井网优化模型; 以李官堡水源地近十年的地下水监测井网观测数据为依据,利用多目标粒子群优化算法提出一种较为合理的监测井网分布方案。  相似文献   

宇宙线“膝区”物理简介及国内观测研究进展     

厉海金  陈天禄  刘茂元 《天文学进展》2013,(3)

宇宙线发现100年来极大地推动了粒子物理学、天体物理学的发展,然而其起源、加速和传播的问题依然是宇宙线研究的三个根本问题。宇宙线“膝区”物理的研究是解决宇宙线这些基本问题的途径之一。简要回顾了宇宙线研究的历史和能谱特点;重点阐述了宇宙线“膝区”的实验观测数据以及重要实验组测量的差异和争论的焦点;归纳讨论了解释宇宙线“膝区”成因的四种主要理论模型,并结合最新实验数据说明了第四种成因(新物理过程)的可能性不大;叙述了国内研究者对宇宙线“膝区”物理研究的贡献;最后对宇宙线“膝区”物理研究的前景进行了展望。  相似文献   

北太平洋和北冰洋大气中多氯联苯的浓度与气固分配行为     

王震  那广水  高会  王艳洁  姚子伟 《海洋学报(英文版)》2014,33(12):32-39

Polychlorinated biphenyls(PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteristics of PCBs and their gas/particle partitioning. The mean concentration of 26 ∑PCBs(vapor plus particulate phase)(∑PCBs) was 19.116 pg/m3 with a standard deviation of 13.833 pg/m3. Three most abundant congeners were CB-28,-52 and-77, accounting for 43.0% to ∑PCBs. The predominance of vapor PCBs(79.0% to ∑PCBs) in the atmosphere was observed. PCBs were negative correlated with the latitudes and inverse of the absolute temperature(1/T). The significant correlation for most congeners was also observed between the logarithm of gas/particle partition coefficient(log KP) and 1/T. Shallower slopes(from-0.15 to-0.46, average-0.27) were measured from the regression of the logarithm of sub-cooled liquid vapor pressures(logpo L) and log KP for all samples. The difference of the slopes and intercepts among samples was insignificant(p0.1), implying adsorption and/or absorption processes and the aerosol composition did not differ significantly among different samples. By comparing three models, the J-P adsorption model, the octanol/air partition coefficient(KOA) based model and the soot-air model, the gas/particle partitioning of PCBs in the Arctic atmosphere was simulated more precisely by the soot-air model, and the adsorption onto elemental carbon is more sensitive than the absorption into organic matters of aerosols, especially for lowchlorinated PCB congeners.  相似文献   

Characteristics from a hydrodynamic model of a trapezoidal artificial reef   总被引：1，自引：0，他引：1  

姜昭阳  梁振林  黄六一  刘扬  唐衍力 《中国海洋湖沼学报》2014,32(6):1329-1338

Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef. Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices; and forces for the reef model were measured by load cell. The results of flume experiments agree well with the numerical data. In addition, the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes, showing a more complicated flow structure than that of a stand-alone reef. Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef. The role of the reef in water flow is to reduce flow velocity and generate turbulence.  相似文献   

Effect of spatial and temporal scales on habitat suitability modeling: A case study of Ommastrephes bartramii in the northwest pacific ocean     

Caixia Gong  Xinjun Chen  Feng Gao  Siquan Tian 《中国海洋大学学报(英文版)》2014,13(6):1043-1053

Temporal and spatial scales play important roles in fishery ecology, and an inappropriate spatio-temporal scale may result in large errors in modeling fish distribution. The objective of this study is to evaluate the roles of spatio-temporal scales in habitat suitability modeling, with the western stock of winter-spring cohort of neon flying squid(Ommastrephes bartramii) in the northwest Pacific Ocean as an example. In this study, the fishery-dependent data from the Chinese Mainland Squid Jigging Technical Group and sea surface temperature(SST) from remote sensing during August to October of 2003–2008 were used. We evaluated the differences in a habitat suitability index model resulting from aggregating data with 36 different spatial scales with a combination of three latitude scales(0.5°, 1° and 2°), four longitude scales(0.5°, 1°, 2° and 4°), and three temporal scales(week, fortnight, and month). The coefficients of variation(CV) of the weekly, biweekly and monthly suitability index(SI) were compared to determine which temporal and spatial scales of SI model are more precise. This study shows that the optimal temporal and spatial scales with the lowest CV are month, and 0.5° latitude and 0.5° longitude for O. bartramii in the northwest Pacific Ocean. This suitability index model developed with an optimal scale can be cost-effective in improving forecasting fishing ground and requires no excessive sampling efforts. We suggest that the uncertainty associated with spatial and temporal scales used in data aggregations needs to be considered in habitat suitability modeling.  相似文献