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111.
Interception loss, I, was determined by continuous concurrent measurements of the canopy precipitation balances of a mature seed orchard tree of Pinus radiata, and a dominant tree of Eucalyptus viminalis at a mountainous high rainfall site (900 m a.s.l.) in Tallaganda State Forest of the Upper Shoalhaven Catchment. Approximate canopy storage capacity (Sc) of the pine was 54 l, and that of the eucalypt was 11·3 l. Gross pine I was 26·5 per cent and eucalypt I was 8·3 per cent of total incident rainfall over a period of 18 months, from June 1975 to December 1976. The exponential model that provided the best fit to overall data relating I to gross rainfall (Pg) was of good precision for the pine (r2 = 0·73) but rather poor precision for the eucalypt (r2 = 0·27). A consistent pattern in interception data of the two canopy types suggested that variation in I was related to change in pervasive conditions influencing rates of evaporation from wet canopies during rainfall. Multiple regression analyses confirmed that factors such as rainfall intensity and windspeed explained some of the variation in eucalypt I but little in pine I. Negative eucalypt I and corresponding low values of pine I over a wide range of Pg (up to 20 mm) suggest that capture of wind-borne precipitation (cloud, mist, or fog) had also complicated the canopy precipitation balances. 相似文献
112.
在分析J2EE体系结构及EJB组件技术的基础上，提出一种基于EJB组件的分布式电子商务应用系统框架；并对其中各部分所采用技术进行了分析及合理选择；最后讨论了应用服务器选取、负载均衡等关键技术问题。该系统框架具有较好的可扩展性、可重用性、开放性和兼容性。 相似文献
113.
《The Professional geographer》1988,40(1):116-131
Books reviewed in this article: Boundary Control and Legal Priniciples . Curtis M. Brown , Walter G. Robillard and Donald A. Wilson . Lost Initiatives: Canada's Forest Industries, Forest Policy, and Forest Conservation . R. Peter Gillis and Thomas R. Roach . The Navajo Atlas: Resources, People, and History of the Dine Bikeyah . James M. Goodman . The City and the Sign . M. Gottdiener AND Alexandros Ph . Lagopoulos , EDS. The Comfortable House: North American Suburban Architecture 1890–1930 . Alan Gowans . Arabic-Islamic Cities. Building and Planning Principles . Besim Salim Hakim . Contemporary Climatology . Ann Henderson -Sellers and Peter J. Robinson . A Trace of Desert Waters . Samuel G. Houghton . Geography, Resources and Environment. Vol. 1: Selected Writings of Gilbert F. White. Vol. 2: Themes from the Work of Gilbert F. White . Robert W. Kates AND Ian Burton , ED. Spatial Dimensions of Unemployment and Underemployment (A Case Study of Rural Punjab) . Gopal Krishan . Maps of the Holy Land: Cartobibliography of Printed Maps, 1475–1900 . Compiled by Eran Laor , assisted by Shoshana Klein . The Geography of Third World Cities . Stella Lowder . A Perspective on U.S. Farm Problems and Agricultural Policy . Lance Mc Kinzie , Timothy G. Baker AND Wallace E. Tyner . Soil Erosion and Its Control. R.P.C . Morgan , ED Geopolitics . Patrick O'Sullivan . Landscape, Meanings and Values . Edmund C. Penning -Rowsell AND David Lowenthal , EDS. 相似文献
114.
分析了当前地理信息系统运用和功能现状,提出了网格地理信息系统的4点技术特征,并在此基础上提出了一种以服务为中心的体系结构.针对面向对象空间数据模型无法描述许多广泛存在却无法用属性、方法和事件来描述的地理逻辑,以及空间数据语意不一致带来的数据集成和综合应用问题,提出了一种基于规则的空间数据组织模式.针对网格环境下空间信息的深度共享问题,提出了一种结合Multi-Agents和Web Services这两种分布式计算技术的空间信息服务模式. 相似文献
115.
提出了一种基于多图形处理器(graphic processing unit,GPU)设计思想的Harris角点检测并行算法,使用众多线程将计算中耗时的影像高斯卷积平滑滤波部分改造成单指令多线程(single instruction multi-ple thread,SIMT)模式,并采用GPU中共享存储器、常数存储器和锁页内存机制在统一计算设备架构(com-pute unified device archetecture,CUDA)上完成影像角点检测的全过程。实验结果表明,基于多GPU的Har-ris角点检测并行算法比CPU上的串行算法可获得最高达60倍的加速比,其执行效率明显提高,对于大规模数据处理呈现出良好的实时处理能力。 相似文献
116.
城市地质灾害应急管理平台的设计与研究 总被引：1，自引：0，他引：1
我国地质灾害多发,严重威胁到山地城市安全.城市地质灾害应急管理的首要环节是应急部门对信息的及时沟通和决策部门对信息的高效管理.因此,设计具有完善的数据共享模式,并具备良好服务架构的信息平台是科学应急管理的必要手段.本文研究了城市地质灾害应急管理平台设计中的关键技术,提出了基于地理网络和元数据管理的数据共享模式;建立了基于SOA的平台架构,并描述了分布式环境下的平台配置结构.通过引入先进的软件技术和GIS技术,可以为城市地质灾害救援指挥提供必要的信息和技术支撑,最终实现减轻城市突发性地质灾害损失的目的. 相似文献
117.
MARCIN SŁOWIK 《Geografiska Annaler: Series A, Physical Geography》2012,94(3):301-320
GPR and aerial surveys were conducted to study changes of channel pattern in the lower course of the Obra River (western Poland). The river is an example of an intensive anthropogenic transformation, however, the origin of the river pattern changes in its lower course is not obvious. The GPR measurements were done using a georadar MALÅ ProEx equipped with a shielded 250 MHz antenna. A 3D analysis of the GPR data supported with lithologic information indicated traces of a multi‐channel pattern. A variable orientation of sediment layering within channel bars and differences in channels depth and width pointed to changes of direction of the river bed migration. Analysis of aerial photographs and a satellite image indicated that only a few of the channels inferred from GPR could be discerned. The reason could be the more than 1 m thick fine sands layer covering all the alluvial structures. Analysis of historical maps from the eighteenth and the nineteenth centuries showed that 250 years ago the Obra was a meandering river. The maps illustrate also several meander cutoffs and decreased wetlands surface. The following transformations of the river bed pattern were discerned: 1. From braided to meandering channel pattern which could be a natural process caused by climatic and sediment transport rate changes that was also observed in case of other lowland rivers. 2. From meandering to sinuous pattern with channel islands and then to sinuous with oxbow lakes. However, further research is needed to study reasons and timing of the observed changes. 相似文献
118.
MICAPS预报业务平台现状与发展 总被引：10，自引：1，他引：9
文章介绍了气象信息综合分析处理系统(MICAPS)系统开发的过程和MICAPS未来发展计划,重点介绍了MICAPS第三版开发的基本情况、系统构架和系统中使用的关键技术和算法。MICAPS第三版采用开放式构架,基本框架负责系统主界面、地图投影、图层控制等基本功能,各种功能模块通过扩展功能模块实现,对系统二次开发提供最大限度的支持。MICAPS第三版实现了MICAPS定义的各类数据,如地面观测、高空观测、离散点数据、标量和矢量格点场、城市预报台风路径、地理信息等的显示,并增加了雷达主要PUP产品、雷达基数据、卫星GPF数据、卫星AWX格式数据、GPS水汽、闪电定位、AMDAR资料、风廓线数据等资料的显示,增强了网络资料检索、菜单资料检索、综合图检索等数据检索能力,增加雨量累加、会商支持、历史资料检索应用等实用功能。 相似文献
119.
Investigating a Hierarchy of Eulerian Closure Models for Scalar Transfer Inside Forested Canopies 总被引：3，自引：3，他引：0
Jehn-Yih Juang Gabriel G. Katul Mario B. Siqueira Paul C. Stoy Heather R. McCarthy 《Boundary-Layer Meteorology》2008,128(1):1-32
Modelling the transfer of heat, water vapour, and CO2 between the biosphere and the atmosphere is made difficult by the complex two-way interaction between leaves and their immediate microclimate. When simulating scalar sources and sinks inside canopies on seasonal, inter-annual, or forest development time scales, the so-called well-mixed assumption (WMA) of mean concentration (i.e. vertically constant inside the canopy but dynamically evolving in time) is often employed. The WMA eliminates the need to model how vegetation alters its immediate microclimate, which necessitates formulations that utilize turbulent transport theories. Here, two inter-related questions pertinent to the WMA for modelling scalar sources, sinks, and fluxes at seasonal to inter-annual time scales are explored: (1) if the WMA is to be replaced so as to resolve this two-way interaction, how detailed must the turbulent transport model be? And (2) what are the added predictive skills gained by resolving the two-way interaction vis-à-vis other uncertainties such as seasonal variations in physiological parameters. These two questions are addressed by simulating multi-year mean scalar concentration and eddy-covariance scalar flux measurements collected in a Loblolly pine (P. taeda L.) plantation near Durham, North Carolina, U.S.A. using turbulent transport models ranging from K-theory (or first-order closure) to third-order closure schemes. The multi-layer model calculations with these closure schemes were contrasted with model calculations employing the WMA. These comparisons suggested that (i) among the three scalars, sensible heat flux predictions are most biased with respect to eddy-covariance measurements when using the WMA, (ii) first-order closure schemes are sufficient to reproduce the seasonal to inter-annual variations in scalar fluxes provided the canonical length scale of turbulence is properly specified, (iii) second-order closure models best agree with measured mean scalar concentration (and temperature) profiles inside the canopy as well as scalar fluxes above the canopy, (iv) there are no clear gains in predictive skills when using third-order closure schemes over their second-order closure counterparts. At inter-annual time scales, biases in modelled scalar fluxes incurred by using the WMA exceed those incurred when correcting for the seasonal amplitude in the maximum carboxylation capacity (V cmax, 25) provided its mean value is unbiased. The role of local thermal stratification inside the canopy and possible computational simplifications in decoupling scalar transfer from the generation of the flow statistics are also discussed.
相似文献
“The tree, tilting its leaves to capture bullets of light; inhaling, exhaling; its many thousand stomata breathing, creating the air”. Ruth Stone, 2002, In the Next Galaxy
120.
Turbulent Intensities and Velocity Spectra for Bare and Forested Gentle Hills: Flume Experiments 总被引：1，自引：1，他引：0
To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume
experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted
above a bare surface while the second experiment was conducted within and above a densely arrayed rod canopy. The velocity
variances and spectra from these two experiments were compared in the middle, inner, and near-surface layers. In the middle
layer, and for the canopy surface, longitudinal and vertical velocity variances () were in phase with the hill-induced spatial mean velocity perturbation (Δu) around the so-called background state (taken here as the longitudinal mean at a given height) as predicted by rapid distortion
theory (RDT). However, for the bare surface case, and remained out of phase with Δu by about L/2, where L is the hill half-length. In the canopy layer, wake production was a significant source of turbulent energy for , and its action was to re-align velocity variances with Δu in those layers, a mechanism completely absent for the bare surface case. Such a lower ‘boundary condition’ resulted in longitudinal
variations of to be nearly in phase with Δu above the canopy surface. In the inner and middle layers, the spectral distortions by the hill remained significant for the
background state of the bare surface case but not for the canopy surface case. In particular, in the inner and middle layers
of the bare surface case, the effective exponents derived from the locally measured power spectra diverged from their expected
− 5/3 value for inertial subrange scales. These departures spatially correlated with the hill surface. However, for the canopy
surface case, the spectral exponents were near − 5/3 above the canopy though the minor differences from − 5/3 were also
correlated with the hill surface. Inside the canopy, wake production and energy short-circuiting resulted in significant departures
from − 5/3. These departures from − 5/3 also appeared correlated with the hill surface through the wake production contribution
and its alignment with Δu. Moreover, scales commensurate with Von Karman street vorticies well described wake production scales inside the canopy,
confirming the important role of the mean flow in producing wakes. The spectra inside the canopy on the lee side of the hill,
where a negative mean flow delineated a recirculation zone, suggested that the wake production scales there were ‘broader’
when compared to their counterpart outside the recirculation zone. Inside the recirculation zone, there was significantly
more energy at higher frequencies when compared to regions outside the recirculation zone. 相似文献