一种改进的人工鱼群聚类算法     

李小培  张洪伟  邹书蓉 《成都信息工程学院学报》2014,29(5):485-490

为了克服K-Means算法对初始类簇中心、噪声点、孤立点敏感缺点,将K-Means算法和人工鱼群算法结合,提出了改进的人工鱼群聚类算法。在该算法中将类簇中心看作一条人工鱼,让每条人工鱼执行随机、觅食、聚群、追尾行为中的一种,并将更新后的位置作为K-Means算法的初始值,不断重复人工鱼的位置更新和K-Means操作,直到算法结束。由于在算法中加入了动态移动步长和全局人最优人工鱼位置,聚类的收敛精度和速度都得到提高。使用iris和glass数据集进行聚类时,与其他算法相比,文中的收敛时间缩短2.6%,精度提高1.36%。  相似文献   

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卢祥  袁运彬  蒋振伟 《大地测量与地球动力学》2014,34(3):137-141

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独立接闪杆闪击次生的负面效应及减负方法     

包炳生  廖必军  杨安良 《气象科技》2014,42(5):906-911

由于设置在建筑物天面或者建筑物附近的独立接闪杆在引雷入地过程中将产生瞬态高电位,电磁感应经传导、耦合可能致损电气或电子设备,造成跨步电压可能危害路经行人。根据电磁场理论、借鉴建筑物引下线分流技术等,给出跨步电压的计算公式和安全门限、为了降低独立接闪杆负面效应,提出了在独立接闪杆空心钢管内使用多股阻燃铜缆的多路分流技术,并在文物防雷工程中实施应用。  相似文献   

地球内部应变与应力固体潮   总被引：5，自引：0，他引：5       下载免费PDF全文

周江存  孙和平  徐建桥  陈晓东 《地球物理学报》2013,56(11):3779-3787

本文详细介绍了地球内部应变和应力固体潮的计算理论,基于PREM地球模型计算了地球内部的Love数,并计算了地球内部的应力和应变的6个独立分量在不同深度和纬度处的时间变化序列.结果表明:应力潮汐的振幅达到10³Pa,应变潮汐振幅达到10^-8;不管应力或是应变潮汐,其振幅随深度的不同都有较大的变化;6个应力和应变分量对纬度依赖较大,但没有表现出南北纬度上的严格的对称性,与纬度的对应关系由引潮位展开的大地系数确定.本文结果可有效应用于地球内部应变或应力潮汐观测的固体潮改正;另外,将本文结果应用于研究潮汐触发地震问题,给出了中国中部地区的一个算例,结果表明地震断层正应力潮汐和应力张量第一不变量潮汐与发震时刻具有明显的相关性,而这种相关性并未在其他如剪切应力以及库伦破坏应力潮汐中表现出来.  相似文献   

Evaluating channel response to an extreme sedimentation event in the context of historical range of variability: Upper Colorado River,USA   总被引：1，自引：0，他引：1  

Sara L. Rathburn  Zan K. Rubin  Ellen E. Wohl 《地球表面变化过程与地形》2013,38(4):391-406

In May 2003, a breach in a large irrigation ditch within Rocky Mountain National Park (RMNP) initiated a debris flow that entered Lulu Creek and the Colorado River, where 36 000 m³ of sediment substantially altered channel forms and processes. We present a proof of concept to understand whether the 2003 disturbance is within the historical range of variability (HRV), and whether the recovery potential of the system is sufficient to adapt to the disturbance. Flow and sediment regimes, and channel morphology and stability were monitored on Lulu Creek and the Colorado River from 2004 to 2011. Dominant channel response following the debris flow within Lulu Creek included step development, bed armoring, and channel widening. Step height‐to‐length ratios (H/L) for three reaches on Lulu Creek are outside the HRV of reference channels, with one reach approaching reference conditions. Erosion of approximately 23% of the debris fan volume occurred as a result of the long duration 2011 peak flow. Sediment within the Lulu Creek fan will persist for ~30–190 years, assuming current maximum and mean removal rates. Planform changes on the Colorado River since the debris flow include an increase in single‐thread geometries, with braided reaches where bar deposition occurred. Bedload transport and grain‐size analysis of bedload indicate translational spreading of a sand wave front with a dispersive component in steeper reaches. Lulu Creek is returning to a condition of natural variability, but the Colorado River is outside the HRV expected for steep‐gradient, pool‐riffle channels. Applying HRV to a situation where management questions require a longer term perspective, and pre‐disturbance baseline data are limited, is a useful approach. The HRV analysis facilitates a better understanding of site variability and delineates the range of possibilities of channel form and process to achieve management goals. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Simulating sub-daily hydrological process with SWAT: a review     

Tássia Mattos Brighenti  Nadia Bernardi Bonumá  Raghavan Srinivasan  Pedro Luiz Borges Chaffe 《水文科学杂志》2013,58(12):1415-1423

ABSTRACT

The Soil and Water Assessment Tool (SWAT) is a watershed-scale hydrologic model that integrates water quantity and quality modules. Despite the large amount of knowledge on the SWAT model, specific understanding of sub-daily applications remains limited. In this review, we identify the shortcomings and possible ways forward in simulating sub-daily processes with the model. A literature review was conducted, along with a participatory method based on a questionnaire. We reviewed 28 scientific articles and categorized them into: (i) model development, (ii) streamflow methods comparison, (iii) water quality, and (iv) other applications. We found that using sub-daily data improves hydrograph peak simulation, while for medium flows use of daily data was better. From all the reviewed studies, a 1-hour time step was the most suitable time scale for the sub-daily model application. The participatory questionnaire confirmed the hypothesis that the main challenge for using the sub-daily routine was the lack of high-resolution data.  相似文献   

Vortex evolution due to straining: a mechanism for dominance of strong,interior anticyclones     

Lee Paul Graves  Michael T. Montgomery 《地球物理与天体物理流体动力学》2013,107(3):151-183

In this article we address two questions: Why do freely evolving vortices weaken on average, even when the viscosity is very small? Why, in the fluid's interior, away from vertical boundaries and under the influence of Earth's rotation and stable density stratification, do anticyclonic vortices become dominant over cyclonic ones when the Rossby number and deformation radius are finite? The context for answering these questions is a rotating, conservative, Shallow-water model with Asymmetric and Gradient-wind Balance approximations. The controlling mechanisms are vortex weakening under straining deformation (with a weakening that is substantially greater for strong cyclones than strong anticyclones) followed by a partially compensating vortex strengthening during a relaxation phase dominated by Vortex Rossby Waves (VRWs) and their eddy–mean interaction with the vortex. The outcome is a net, strain-induced vortex weakening that is greater for cyclones than anticyclones when the deformation radius is not large compared to the vortex radius and the Rossby number is not small. Furthermore, when the exterior strain flow is sustained, the vortex changes also are sustained: for small Rossby number (i.e., the quasigeostrophic limit, QG), vortices continue to weaken at a relatively modest rate, but for larger Rossby number, cyclones weaken strongly and anticyclones actually strengthen systematically when the deformation radius is comparable to the vortex radius. The sustained vortex changes are associated with strain-induced VRWs on the periphery of the mean vortex. It therefore seems likely that, in a complex flow with many vortices, anticyclonic dominance develops over a sequence of transient mutual straining events due to the greater robustness of anticyclones (and occasionally their net strengthening).  相似文献   

张渤带洞体应变参数解算及结果分析   总被引：3，自引：1，他引：2  

马栋  晏锐  武艳强  范强  陈建国 《中国地震》2013,29(1):97-106

采用张渤带2002年以来的洞体应变观测资料,首先利用Venedikov调和分析方法计算带内各个台站洞体应变测项的潮汐因子和相位滞后,并以潮汐因子的稳定性对观测资料进行了质量评价.其后,以怀来台伸缩仪为例讨论了3分量和2分量观测解算平面应变参数的模型及其适用性,结果表明二者的相关系数在0.9以上.在此基础上,选取张渤带上资料较稳定的16个洞体应变台站资料进行了应变参数时间序列计算,并对华北M5.0地震前应变参数同步变化现象进行了总结.最后对比了洞体应变与GPS应变的差异,并分析了可能的原因.  相似文献   

An Unusual, Three-Dimensionally Preserved, Large Hadrosauriform Pes Track from “Mid”-Cretaceous Jiaguan Formation of Chongqing, China     

Xing Lid  Phil R. Bell  Jerald D. Harris  Philip J. Currie 《《地质学报》英文版》2012,86(2):304-312

Three-dimensional tracks provide unique insights into the locomotor mechanics of their track makers. An isolated, large hadrosauriform print attributable to Caririchnium lotus from the “mid”-Cretaceous Lotus track site (Jiaguan Formation) in China permits reconstruction of the footfall, weight-bearing, and kick-off phases of the step cycle. Large-scale modifications of the pes during the step cycle indicate C. lotus trackmakers were capable of locomotory modifications in response to substrate consistency beyond the “expected” shift between bipedal and quadrupedal postures. An unusual curvature to the trace of one of the outer digits indicates substantial transverse mobility. The remaining digits demonstrate lesser degrees of transverse movement accompanied by extension of the digits during footfall. The absence of overprinted scale-scratch marks and toe drags are consistent with a vertical kick-off of the pes and concomitant flexion of the digits. This track suggests that pedal mobility in C. lotus track makers was greater than previously suspected and has implications for reconstructions of hadrosauriform locomotion.  相似文献   

斜向波对台阶地形上有限吃水半无限长弹性板的散射作用     

郭云霞  刘勇  孟珣 《海洋学报(英文版)》2016,35(7):113-121

基于线性势流理论和欧拉-伯努利梁理论,采用匹配特征函数展开法建立斜向波对台阶地形上有限吃水半无限长弹性板散射的解析解。与以往研究不同,本文同时考虑波浪入射角度、弹性板吃水、三种不同板端条件（自由板端、简支板端、固定板端）以及海底地形的影响。本文还直接将板端条件引入匹配边界条件,建立线性方程组求解速度势中的展开系数,计算过程简单、高效。计算结果表明：本文方法收敛性好,并满足能量守恒方程。将本文计算结果与文献中的特例结果进行对比,吻合良好。分析了波浪入射角度、弹性板吃水、不同板端条件以及海底地形对弹性板水动力参数的影响,研究结果可以为工程设计提供参考。  相似文献