一种基于时空拥挤度的应急疏散路径优化方法   总被引：3，自引：1，他引：2  

李清泉  李秋萍  方志祥 《测绘学报》2011,40(4):517-523

提出时空拥挤度的概念来描述时间与空间维上的移动对象的拥挤程度,并以此提出一种基于拥挤度的应急疏散路径优化方法,该方法能够为大型公共场所的人员疏散提供从建筑物内部经由路网离开危险区域的一个完整疏散路径方案。分析在疏散路径分配的过程中以最短路径为基础的疏散路径分配方案的拥堵情形,然后以缓解拥堵、减少疏散总时间为目标,设计疏散路径分配方案的优化方法。试验结果表明优化后的方案能够减轻整个疏散方案的拥堵程度,同时能够为每个疏散个体提供一条相对合理的疏散路径。  相似文献   

空间信息剖分组织的全球离散格网理论与方法   总被引：1，自引：0，他引：1  

童晓冲 《测绘学报》2011,40(4):536

随着对地观测手段的不断进步,在广大区域甚至全球范围应用遥感和其他类型空间数据的机率大大增加。构建具有连续性、层次性和动态性的全球数据模型已成为广受关注的重要研究方向。目前,全球空间数据组织处理模型的研究已经取得了可喜进展,其中构建＂全球离散格网系统＂（discrete global grid systems,DGGS）,正是针对该问题提出的一种解决方案。  相似文献   

Association of polycyclic aromatic hydrocarbons (PAHs) and metallic species in a tropical urban atmosphere – Delhi,India     

Sayantan?Sarkar  P.?S.?KhillareEmail author 《Journal of Atmospheric Chemistry》2011,68(2):107-126

Ambient respirable particles (PM₁₀; aerodynamic diameter ≤10 μm) collected in a tropical urban environment (Delhi, India) during December 2008-November 2009 were characterized with respect to 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) and 8 major and trace metals (Fe, Mn, Cd, Cu, Ni, Pb, Zn and Cr). Concentrations of Σ₁₆PAHs (annual mean: 74.7 ± 50.7 ng m⁻³, range 22.1–258.4 ng m⁻³) and most metallic species were at least an order of magnitude greater than values reported from similar locations worldwide. Seasonal variations in Σ₁₆PAHs were significant (p < 0.001) with highest levels in winter while crustal and anthropogenic metals showed significant but mutually opposite seasonal dependence. Statistically significant associations were observed between chemical species and various meteorological parameters. The PAH profile was dominated by combustion-derived large-ring species (~85%) that were essentially local in origin. Principal component analysis–multiple linear regression (PCA-MLR) apportioned four sources: crustal dust (73%), vehicular emission (21%), coal combustion (4%) and industrial emission (2%) that was further validated by hierarchical cluster analysis (HCA). Temporal trend analysis showed that crustal sources were predominant in summer (p < 0.05) while the remaining sources were most active in winter. Summertime intrusions of Saharan dust were identified with the help of aerosol maps and air parcel backward trajectories. Inhalation cancer risk assessment showed that up to 3,907 excess cancer cases (357 for PAHs, 122 for Cd, 2040 for Cr (VI) and 1387 for Ni) are likely in Delhi considering lifetime inhalation exposure to these chemicals at their current concentrations.  相似文献   

Comparisons of Two Ensemble Mean Methods in Measuring the Average Error Growth and the Predictability   总被引：1，自引：0，他引：1       下载免费PDF全文

丁瑞强  李建平 《Acta Meteorologica Sinica》2011,25(4):395-404

In this paper, taking the Lorenz system as an example, we compare the influences of the arithmetic mean and the geometric mean on measuring the global and local average error growth. The results show that the geometric mean error (GME) has a smoother growth than the arithmetic mean error (AME) for the global average error growth, and the GME is directly related to the maximal Lyapunov exponent, but the AME is not, as already noted by Krishnamurthy in 1993. Besides these, the GME is shown to be more appropriate than the AME in measuring the mean error growth in terms of the probability distribution of errors. The physical meanings of the saturation levels of the AME and the GME are also shown to be different. However, there is no obvious difference between the local average error growth with the arithmetic mean and the geometric mean, indicating that the choices of the AME or the GME have no influence on the measure of local average predictability.  相似文献   

局地大气能量有效性中的表面扰动位能特征   总被引：2，自引：0，他引：2  

高丽  李建平 《气象学报》2011,69(4):664-671

在局地扰动位能理论工作基础上,进一步研究了与实际地形有关的表面扰动位能部分,理论推导了数学表达式,表明地形和表面热状况是其决定因素。利用再分析资料考察了其气候学和气候变率特征。研究表明,表面扰动位能具有独特的热动力学意义,它的量值与地球表面高大地形密切联系,而其季节变动特点则与表面热状况的季节变化息息相关。高纬度极地地形区域为明显的全年基本不变的负扰动位能分布区,低纬度热带区域则呈现季节变动非常小的正扰动位能分布。表面扰动位能的季节变动和年际变率的极值区都位于北半球中纬度的高大地形区域,夏季达到正的极大值,而冬季则转变成负值区。这一特征在青藏高原区最为典型,其表面扰动位能在时域和频域上均表现出明显的年代际特征,年际变率以2—4a周期为主。  相似文献   

Influence of the Saharan Air Layer on Atlantic Tropical Cyclone Formation during the Period 1-12 September 2003     

潘维玉  吴立广 《大气科学进展》2011,(1)

Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated ...  相似文献   

一种复杂海天背景下的红外舰船目标自动检测方法   总被引：3，自引：0，他引：3  

王鹏  吕高杰  龚俊斌  田金文 《武汉大学学报(信息科学版)》2011,36(12):1438-1441

提出了一种红外舰船目标检测算法。首先,利用设计好的频域组合高通滤波器对原始红外图像进行处理,以得到舰船目标可能存在的区域即目标潜在区;然后,对获得的目标潜在区进行尺度自适应的局部阈值分割,进而提取出较为完整的舰船目标或者虚假目标;最后通过检测吃水线特征来筛选出正确的舰船目标。实验结果表明,此算法能够有效地检测出复杂海天背景条件下的红外舰船目标,且具有一定的时效性。  相似文献   

南华北盆地晚石炭世—早二叠世层序地层学及古地理研究     

刁玉杰  魏久传  李增学  曹红  李旭峰 《地层学杂志》2011,(1):88-94

南华北盆地晚石炭世—早二叠世主要为陆表海充填沉积。通过层序界面识别和层序地层划分,建立层序地层格架,将研究区晚石炭世—早二叠世地层划分为1个Ⅱ级陆表海充填层序,3个Ⅲ级层序(Sq1—Sq3),分别对应晚石炭世巴什基尔-格舍尔期、早二叠世紫松期和隆林期,同时对3个层序的特征及演化进行了分析。根据层序地层学研究对Sq1~Sq3进行古地理重建,发现陆表海充填总体上为海退序列,物源主要来自北缘阴山隆起;同时也证实了海侵转换面的存在,全球海平面上升和板缘构造运动共同塑造了南华北盆地晚石炭世—早二叠世特殊的古地理演化过程。  相似文献   

Local particle traps in the high latitude magnetosphere and the acceleration of relativistic electrons     

E.E. Antonova  I.M. Myagkova  M.V. Stepanova  M.O. Riazantseva  I.L. Ovchinnikov  B.V. Mar’in  M.V. Karavaev 《Journal of Atmospheric and Solar》2011,73(11-12):1465-1471

Variations of electron fluxes with energies 300–600 keV in the region of quasitrapping are analyzed using data of the low orbiting Coronas-F satellite. Enhancements in the electron fluxes with energies above 300 keV are observed at the polar boundary of the outer radiation belt. Meteor-3M satellite data, OVATION and AP models of the position of the auroral oval are used to determine the position of analyzed increases in the energetic electrons with respect to the position of the auroral oval. There is a significant number of events when these increases were observed at a few consequent orbits crossing the outer radiation belt boundary. Studied increases in relativistic electron fluxes are localized at the latitudes of the auroral oval. Different mechanisms of formation of observed enhancements are discussed. The possibility of the appearance of increases due to formation of local particle traps is analyzed using Tsyganenko geomagnetic field models. The role of the formation of local particle traps at the boundary of the outer radiation belt and its possible influence to the formation of the outer radiation belt is discussed.  相似文献   

Chemical Characteristics of Snow-Firn Pack in Altai Mountains and Its Environmental Significance     

王飞腾  王林  康剑  寇福堂 《中国地质大学学报(英文版)》2011,(4)

In order to study the chemical characteristics of snow-firn pack in Altai Mountains and its environmental significance, a 1.5-m deep snow-firn pack was dug in the accumulation zone (3 300 m a.s.l.) of the Kanas Glacier in August 2009. A total of 15 samples were analyzed for major ions. Results show that the concentrations of major ions in the snow-firn pack are NH4+>SO42->Ca2+>NO3-> Na+>Cl->K+>Mg2+. NH4+ is the dominant cation with a medium value of 4.7 ueq·L-1, accounting for 39.8% of the total cations, an...  相似文献