Density functional study of Au_nCu (n=1-7) clusters     

郭建军  魏成富  杨继先  迭东 《海洋学报(英文版)》2010,29(11)

The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copper-doped gold clusters, Au_nCu (n=1-7), are investigated using the density functional theory. Several low-lying isomers are determined. The results indicate that the ground-state Au_nCu clusters have planar structures for n = 1-7. The stability trend of the Au_nCu clusters (n=1-7), shows that odd-numbered Au_nCu clusters are more stable than the neighbouring even-numbered ones, thereby indicating the Au₅Cu clusters are magic cluster with high chemical stability.  相似文献   

基于GIS的滁州市旅游资源功能分区及旅游线路设计   总被引：2，自引：0，他引：2  

尹乐  王永明 《测绘与空间地理信息》2010,33(1):31-33,41

通过对滁州市旅游资源的调查和分类,分析得出其总体特征,提出了滁州市旅游功能分区,结合GIS相关技术,利用MapInfo软件制成旅游功能分区图。同时,为了开拓旅游客源市场,扩大滁州市旅游业的影响力,进行了旅游线路设计并绘制成图。  相似文献   

Developing an empirical model of canopy water flux describing the common response of transpiration to solar radiation and VPD across five contrasting woodlands and forests     

Rhys Whitley  Daniel Taylor  Catriona Macinnis‐Ng  Melanie Zeppel  Isa Yunusa  Anthony O'Grady  Ray Froend  Belinda Medlyn  Derek Eamus 《水文研究》2013,27(8):1133-1146

A modified Jarvis–Stewart model of canopy transpiration (E_c) was tested over five ecosystems differing in climate, soil type and species composition. The aims of this study were to investigate the model's applicability over multiple ecosystems; to determine whether the number of model parameters could be reduced by assuming that site‐specific responses of E_c to solar radiation, vapour pressure deficit and soil moisture content vary little between sites; and to examine convergence of behaviour of canopy water‐use across multiple sites. This was accomplished by the following: (i) calibrating the model for each site to determine a set of site‐specific (SS) parameters, and (ii) calibrating the model for all sites simultaneously to determine a set of combined sites (CS) parameters. The performance of both models was compared with measured E_c data and a statistical benchmark using an artificial neural network (ANN). Both the CS and SS models performed well, explaining hourly and daily variation in E_c. The SS model produced slightly better model statistics [R² = 0.75–0.91; model efficiency (ME) = 0.53–0.81; root mean square error (RMSE) = 0.0015–0.0280 mm h^‐1] than the CS model (R² = 0.68–0.87; ME = 0.45–0.72; RMSE = 0.0023–0.0164 mm h^‐1). Both were highly comparable with the ANN (R² = 0.77–0.90; ME = 0.58–0.80; RMSE = 0.0007–0.0122 mm h^‐1). These results indicate that the response of canopy water‐use to abiotic drivers displayed significant convergence across sites, but the absolute magnitude of E_c was site specific. Period totals estimated with the modified Jarvis–Stewart model provided close approximations of observed totals, demonstrating the effectiveness of this model as a tool aiding water resource management. Analysis of the measured diel patterns of water use revealed significant nocturnal transpiration (9–18% of total water use by the canopy), but no Jarvis–Stewart formulations are able to capture this because of the dependence of water‐use on solar radiation, which is zero at night. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Transformation method of exterior orientation angular elements obtained via position and orientation system under Gauss-Kruger projection coordinate system     

Xiuxiao Yuan  Xueping Zhang  Jianhong Fu 《地球空间信息科学学报》2010,13(3):157-165

Data obtained via airborne position and orientation system (POS) is in WGS 84 global geocentric reference frame, while the national coordinate reference system for topographic mapping in China is generally Gauss-Kruger projection coordinate system. Therefore, data obtained via a POS must be transformed to national coordinate system. Owing to the effects of earth curvature and meridian deviation, there are some errors in the process of angle transformation from roll, pitch, and heading (Φ ,Θ ,Ψ )obtained dir...  相似文献   

Contribution of different functional groups to the diet of major predatory fishes at a seagrass meadow in northeastern Japan     

Katsumasa Yamada  Masakazu Hori  Yoshiyuki Tanaka  Natsuki Hasegawa  Masahiro Nakaoka 《Estuarine, Coastal and Shelf Science》2010

We examined the variation in habitat use and diet of three dominant fish species (Myoxocephalus brandti, Pholidapus dybowskii, and Pholis crassispina) in a seagrass meadow in the Akkeshi-ko estuary in northeastern Japan, where broad and dense Zostera marina beds exist, using a semi-quantitative census of the fishes and analyses of their stomach contents. Differences among the three fish species in the temporal variation in abundance of each age class (mainly 1- and 2-year age classes) indicated that the temporal pattern of utilization of the seagrass meadow were different among them. In the semi-quantitative dietary analysis, two prey categories, i.e., taxonomic group (order and suborder) and functional group, were used to explain the variation in prey composition with size-dependent changes. The six prey functional groups were classified based on the ecological traits of the prey, i.e., trophic level, size, and life type (habitat and behavior). Ontogenetic shifts in prey of the three fish species could be fully explained by a combination of the two prey categories, and not by the use of only one category (taxonomic or functional group). The pattern of ontogenetic shifts in prey differed among the fish species and size (age) classes. These results indicate that segregation of habitat (seagrass meadow) and prey group (taxonomic and functional group) is performed among the three species, which may contribute to their coexistence in this estuary.  相似文献   

大旋角影像的绝对定向方法研究     

张永军  胡丙华  张剑清 《武汉大学学报(信息科学版)》2010,(4)

针对近景摄影测量中影像与地面坐标系间存在大旋转角的问题,在分析现有绝对定向算法的基础上,提出了一种适合大旋转角影像的绝对定向方法,采用奇异矩阵分解获取较准确的角元素初值,并结合最小二乘平差进行粗差剔除和绝对定向精确参数解算。试验表明,本算法计算简单、收敛速度快,具有很好的实用价值。  相似文献   

GPS/IMU用于航空遥感直接对地定位的原理与方法   总被引：1，自引：0，他引：1       下载免费PDF全文

王冬红  范永弘  王慧  刘军 《海洋测绘》2010,30(2):11-14

阐述了GPS/IMU系统进行位置与姿态测量的基本原理,推导了利用GPS/IMU的导航解计算遥感器瞬时外方位元素的数学模型,并利用机载三线阵影像验证了GPS/IMU辅助直接对地定位的精度潜力。三组ADS40数据直接定位的试验结果表明,GPS/IMU提供的外方位元素具有较高的定位精度,平面精度优于2.5个像元,高程优于5.1个像元,但存在系统性的测量误差,在大比例尺遥感测绘作业中引入少量控制点参与平差仍是必须的。  相似文献   

一类推广的Leslie-Gower型捕食-被捕食模型的动力学性质研究     

刘华祥 《广东海洋大学学报》2009,29(3):53-58

探讨了一类推广的Leslie-Gower型捕食-被捕食模型的动力学性质。以HollingII型功能反应和推广的Leslie-Gower模式为基础建立了无时滞和有时滞的捕食-被捕食种间作用模型;分析了无时滞模型共生平衡点的稳定性和Hopf分支,得到了共生平衡点的稳定性条件,找到了使系统发生Hopf分支的参数临界值,建立了系统存在稳定极限环的条件;分析了时滞模型系统共生平衡点的渐近稳定性以及孕育时滞参数值变化对模型系统共生平衡点稳定性的影响,找到了时滞模型系统发生Hopf分支的参数临界值,证明了当时滞参数在临界值附近变化时,系统也将发生Hopf分支。  相似文献   

Spatial patterns in community structure of motile epibenthic fauna in coastal habitats along the Skagerrak – Baltic salinity gradient     

Emma Nohrén  Leif Pihl  Håkan Wennhage 《Estuarine, Coastal and Shelf Science》2009

Patterns in community structure and functioning of motile epibenthic fauna were investigated in shallow (0–1 m) sediment habitats along the Skagerrak–Baltic estuarine gradient (salinity range from 4 to 34). The study area was divided into five regions, reflecting different sea-basins along the 1260 km coastline, and fauna was collected at six sites within each region. Ten replicate samples of motile epibenthic fauna were taken randomly at each site with a portable drop trap (bottom area 1 m²) in June and September in 2004.  相似文献   

LBS中多尺度空间方位的自然语言描述     

应申  李霖  高玉荣  甘莉  姜文亮  余建伟 《地理信息世界》2008,6(1):28-33

位置服务是地理信息系统(GIS)应用的重要领域,GIS提供关于空间位置的坐标描述,但这不符合人们的认知和日常习惯。地理空间中人们日常的交流通常使用方位描述。基于自然语言的空间方位的描述对移动目标(如驾驶员)是十分重要的,通过规范的地点描述语言进行快速的地理定位,可提高人的空间反应和处理能力。本文依据人的多尺度空间认知,分析空间参考和定位习惯,结合自然语言描述知识,利用GIS分析功能,给出多尺度环境下空间方位的自然语言描述。  相似文献