基于网格划分的无线传感器网络节点冗余分析     

黄守志  赵学增  Bilen S G  张中华 《东北石油大学学报》2013,37(3):112-116,122,130

在无线传感器网络中,节点的大量随机部署导致冗余节点的存在,寻找冗余节点并使它定时休眠,可以减少网络冗余数据和信道拥塞、降低节点能耗,从而延长网络的生命周期.现有的CCP算法、圆周覆盖算法在去除冗余节点后网络产生覆盖盲区;基于Voronoi图的算法计算量大且只能用于同构网络;节点时间表制定算法在判定过程中只考虑部分邻居节点,不能完全消除冗余节点.提出基于网格划分的冗余节点判定方法,并且将网格算法与EECRS协议结合,建立基于冗余节点消除的路由协议.仿真分析结果表明,网格算法冗余节点判定的准确性优于圆周覆盖算法和CCP算法的;网络生命周期比圆周覆盖算法的延长22.2%,比CCP算法的延长30.5%,该路由协议能够有效延长网络生命周期.  相似文献   

基于栅格尺度的沙漠化预警模型研究——以塔里木河下游中段区域为例   总被引：2，自引：0，他引：2  

孟现勇  刘志辉  李诚志  蔡磊  刘敦利 《中国沙漠》2013,33(1):24-32

以塔里木河下游为研究区,基于沙漠化在气候、地表和人文3方面的成因构建沙漠化预警指标体系,并建立预警模型;基于研究区1990年、2000年和2006年的遥感、气候、地表和人文数据,利用ArcGIS对各因子数据进行量化和栅格化处理,通过预警模型实现了研究区3个时期在栅格尺度上（30 m×30 m）的沙漠化程度分布,分别利用前两期和第3期的结果进行参数修正和验证;在此基础上预测研究区“间歇输水”和“无输水”情况下2015年的沙漠化发展趋势。通过参数修正、预警模型对研究区沙漠化程度分布模拟正确率达90%以上,预警模型适用性较好。间歇输水对塔里木河下游沙漠化逆转起到一定的作用,是防止其完全沙漠化的必要措施,但此逆转作用基本上只局限于沿河道有限范围内,无法彻底改变研究区的沙漠化现状。  相似文献   

Regional differences in hydrological response to canopy interception schemes in a land surface model   总被引：1，自引：0，他引：1       下载免费PDF全文

Chi Zhang  Dagang Wang  Guiling Wang  Weitao Yang  Xiaoping Liu 《水文研究》2014,28(4):2499-2508

Two different canopy interception schemes are applied to the parameterization of the hydrological processes in the Community Land Model version 3. One scheme treats rainfall and canopy water storage as spatially uniform within each model grid cell, and the other scheme considers sub‐grid variability of rainfall and water storage in the parameterization of canopy hydrological processes. The hydrological responses to differences between these two schemes in different regions are studied. It is found that the impact of the sub‐grid variability in the tropical regions is generally greater than the extra‐tropical regions. However, such impact can't be negligible for the extra‐tropical regions. Soil water in the total 3.4 m soil depth increases by 3% for Central‐South Europe, and vegetation temperature increases by 0.14 °C for Southeastern United States if the regional averages are considered. The magnitude of the impact is greater if the analysis focuses on the specific grid cells in these regions. The impact is tightly correlated with rainfall amount and vegetation density. The correlation coefficient between such impact and rainfall amount and vegetation density varies with regions and hydrological variables, with the largest value of 0.92 for interception loss in Amazonia. Our results indicate that the impact of the sub‐grid variability on hydrological processes in the extra‐tropical areas is also important, although rainfall amount and vegetation density in these areas are not as high as in the tropical areas. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

二维三分量TTI 介质Lebedev 网格正演模拟     

李娜  黄建平  李振春  李庆洋  郭振波  田坤 《中国地震》2014,30(2):289-297

鉴于三维各向异性介质(TTI、单斜等)正演模拟在计算量与内存上的巨大消耗以及标准交错网格机制波场插值带来的数值频散,本文采用二维三分量Lebedev交错网格有限差分方法对TTI介质进行波场模拟,利用二维介质便可得到3个相互垂直分量的弹性波场,并利用余弦相似度将其与完全三维正演波场进行对比,分析了该方法的模拟精度。对比测试结果表明,本文方法避免了插值误差,能够精确反映地震波在二维观测平面内的运动学特征,并且平面内质点的偏振速度、振幅能量与三维结果具有较高的相似度,而模拟占用的计算机资源却只相当于三维模拟中的一个二维剖面,是一种高效、准确的各向异性介质数值模拟方法。  相似文献   

虚拟化技术在地震信息网络业务中的应用   总被引：1，自引：0，他引：1  

吴晨  王方建  李永红  董晓娜  吴丹桐 《地震地磁观测与研究》2012,33(3):252-256

根据VMware公司的虚拟机组件ESX3．5及管理组件Virtual Center2．5,结合现有硬件技术平台,在山东省地震局实现虚拟化技术的实际部署和应用。结果发现,将虚拟化技术应用到地震行业信息网络业务,可以提高工作效率,具有重要的实际意义。  相似文献   

SRC框格复合墙抗剪承载力计算及影响因素分析     

钱坤  郭猛  李挺  袁泉 《世界地震工程》2012,28(1):62-68

SRC框格复合墙是在普通RC密肋复合墙基础上结合型钢混凝土概念而提出来的一种复合墙板,以轻钢龙骨代替框格内原有纵向受力钢筋,通过焊接或螺栓连接在梁柱轻钢龙骨节点处实现刚性或半刚性连接.在SRC框格复合墙模型试验基的础上,利用ANSYS程序对墙体受力过程进行了非线性有限元分析,提出了SRC框格复合墙抗剪承载力的实用计算公式,并对框格含钢率、轻钢强度等影响因素进行了有限元分析.研究结果表明:所提出的SRC框格复合墙抗剪承载力计算公式,与非线性有限元计算结果吻合较好,能够适应框格含钢率等不同因素变化的计算精度要求;提高肋梁中轻钢强度或含钢率可以有效提高墙体抗剪承载力,而不宜单独采用提高混凝土强度的方法.  相似文献   

针对复杂地形的三种地震波走时算法及对比   总被引：3，自引：2，他引：1       下载免费PDF全文

孙章庆  孙建国  韩复兴 《地球物理学报》2012,55(2):560-568

复杂地形条件下地震波走时算法对于研究复杂地形地区的成像问题有着重要的意义.为了得到精度高且适应于复杂地形的走时算法,首先提出阶梯网格迎风差分法.然后将该方法与不等距网格有限差分法和混合网格线性插值法进行对比研究,得出如下结论:混合网格线性插值法的计算精度最高,但其计算效率最低;阶梯网格迎风差分法的计算精度最低,但其计算效率最高;不等距网格有限差分法的计算精度和计算效率均居中;而究竟选取哪种算法作为给定复杂地形模型的地震波走时算法,应该综合考虑地形的特点、所研究问题对计算精度及计算效率的要求等因素.最后通过一个计算实例验证了三种算法在面对复杂地形、近地表及地下复杂介质等复杂地质条件时均有很好的适应性和稳定性.  相似文献   

贴体网格各向异性对坐标变换法求解起伏地表下地震初至波走时的影响   总被引：3，自引：3，他引：0       下载免费PDF全文

兰海强  张智  徐涛  白志明 《地球物理学报》2012,55(10):3355-3369

笛卡尔坐标系中的经典程函方程在静校正、叠前偏移、走时反演、地震定位、层析成像等很多地球物理工作中都有应用,然而用其计算起伏地表的地震波走时却比较困难.本文通过把曲线坐标系中的矩形网格映射到笛卡尔坐标系的贴体网格,推导出曲线坐标中的程函方程,而后,用Lax-Friedrichs快速扫描算法求解曲线坐标系的程函方程.研究表明本文方法能有效处理地表起伏的情况,得到准确稳定的计算结果.由于地表起伏,导致与之拟合的贴体网格在空间上的展布呈各向异性,且这种各向异性的强弱对坐标变换法求解地震初至波的走时具有重要影响.本文研究表明,随着贴体网格的各向异性增强,用坐标变换法求解地表起伏区域的走时计算误差增大,且计算效率降低,这在实际应用具有指导意义.  相似文献   

A hybrid absorbing boundary condition for elastic staggered‐grid modelling     

Yang Liu  Mrinal K. Sen 《Geophysical Prospecting》2012,60(6):1114-1132

We recently proposed an efficient hybrid scheme to absorb boundary reflections for acoustic wave modelling that could attain nearly perfect absorptions. This scheme uses weighted averaging of wavefields in a transition area, between the inner area and the model boundaries. In this paper we report on the extension of this scheme to 2D elastic wave modelling with displacement‐stress formulations on staggered grids using explicit finite‐difference, pseudo‐implicit finite‐difference and pseudo‐spectral methods. Numerical modelling results of elastic wave equations with hybrid absorbing boundary conditions show great improvement for modelling stability and significant absorption for boundary reflections, compared with the conventional Higdon absorbing boundary conditions, demonstrating the effectiveness of this scheme for elastic wave modelling. The modelling results also show that the hybrid scheme works well in 2D rotated staggered‐grid modelling for isotropic medium, 2D staggered‐grid modelling for vertically transversely isotropic medium and 2D rotated staggered‐grid modelling for tilted transversely isotropic medium.  相似文献   

Reconstructing the historical spatial land use pattern for Jiangsu Province in mid-Qing Dynasty   总被引：1，自引：1，他引：0  

Xiaobin Jin  Qian Pan  Xuhong Yang  Qing Bai  Yinkang Zhou 《地理学报(英文版)》2016,26(12):1689-1706

This study is proposed to reconstruct a high-resolution spatial distribution of historical land use pattern with all land use types to overcome low-accuracy and/or the monotonic land use type in current historical land use reconstruction studies. The year of 1820 is set as the temporal section and the administrative area of Jiangsu Province is the study area. Land use types being reconstructed include farmland, residential land (including both urban land and rural residential land), water body, and other land (including forest land, grassland, and unused land). Data sources mainly refer to historical documents, historical geographic research outcomes, contemporary statistics, and natural environmental data. With great considerations over regional natural resources and social and economic conditions, a few theoretical assumptions have been proposed to facilitate the adjustment on prefecture farmland, urban land, and rural residential land. Upholding the idea that the contemporary land use pattern has been inherently in sequence with the historical land use pattern as well as the land use pattern shall be consistent to its accessibility, this study reconstructs the land use pattern in Jiangsu Province in 1820 with 100 m*100 m grids based on accessibility analysis and comprehensive evaluation. The outcome has been tested as valid by regionalization and correlation analysis. The resulted spatial distribution shows that back in 1820 in Jiangsu Province: (1) farmland, urban land, rural residential land, water body, and other land take about 48.49%, 4.46%, 0.16%, 15.03%, and 31.86% of the total land area respectively; (2) the land use pattern features high proportion of land in farming while low-proportion land in non-farming uses while population, topography, and the density of water body lead to great spatial variations; and (3) the reconstruction methodology has been tested as reasonable based on significant positive correlations between 1820 data and 1985 for both farmland and rural residential land at the prefecture level.  相似文献