基于VRML的三维地下管网信息系统的实现     

张小萍  瞿畅  王君泽 《测绘科学》2009,34(4)

针对目前广泛使用的地下管网系统在三维描述方面的欠缺,本文利用虚拟现实技术和VRML语言,构建了基于VRML的三维地下管网信息系统。这一系统的实现,用户可通过网络异地浏览地下管网的三维虚拟模型和查询相关数据信息,大大提高了工作效率和城市数字化管理水平。  相似文献   

THE APPLICATION OF FRACTAL STUDY IN FORECASTING FLOOD CALAMITIES IN WUZHOU, GUANGXI     

常疆  王良健 《中国地理科学(英文版)》1999,9(2):184-188

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Reply to discussion on “Application of probabilistic neural network to design breakwater armor blocks” by Zekai Şen,Tarkan Erdik,Yavuz Karsavran     

Dookie Kim  Dong Hyawn Kim  Seongkyu Chang 《Ocean Engineering》2008,35(11-12):1284

  相似文献   

Hydrogeochemistry and environmental isotopes of ground water in Jeju volcanic island,Korea: implications for nitrate contamination     

Dong‐Chan Koh  Ho‐Wan Chang  Kwang‐Sik Lee  Kyung‐Seok Ko  Yongje Kim  Won‐Bae Park 《水文研究》2005,19(11):2225-2245

Ground water from springs and public supply wells was investigated for hydrochemistry and environmental isotopes of ³H, ¹⁸O and D in Jeju volcanic island, Korea. The wells are completed in a basaltic aquifer and the upper part of hydrovolcanic sedimentary formation. Nitrate contamination is conspicuous in the coastal area where most of the samples have nitrate concentrations well above 1 mg NO₃ N/l. Agricultural land use seems to have a strong influence on the distribution of nitrate in ground water. Comparison of stable isotopic compositions of precipitation and ground water show that ground water mostly originates from rainy season precipitation without significant secondary modification and that local recharge is dominant. ³H concentration of ground water ranged from nearly zero to 5 TU and is poorly correlated with vertical location of well screens. The occurrence of the ³H‐free, old ground water is due to the presence of low permeability layers near the boundary of the basaltic aquifer and the hydrovolcanic sedimentary formation, which significantly limits ground water flow from the upper basaltic aquifer. The old ground water exhibited background‐level nitrate concentrations despite high nitrate loadings, whereas young ground water had considerably higher nitrate concentrations. This correlation of ³H and nitrate concentration may be ascribed to the history of fertilizer use that has increased dramatically since the early 1960s in the island. This suggests that ³H can be used as a qualitative indicator for aquifer vulnerability to nitrate contamination. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

日照市矿产资源优化配置探析     

贺兆成  庄华 《山东国土资源》2009,25(7):9-10

近年来，日照市高度重视矿产资源优化配置工作，紧紧以整顿和规范矿产资源开发秩序工作为契机，全面推广开采新技术，积极推动小矿整合，促进矿山企业规模化经营，有效提高了矿产资源利用率，取得了良好的社会效益和经济效益。1日照市矿产资源优化配置现状（1）推动资源整合，优化矿山企业空间布局。为解决矿山布局不合理和矿产开发中的“小、散、乱”问题，提高矿产资源节约集约利用水平，该市积极推动小矿整合，切实提高规模化经营水平。按照矿产资源总体规划和整合方案的规定，对限采区、宜采区内的勘查开采实行统一规划、统一管理，确定了矿山整合范围和具体名单，灵活采取兼并、  相似文献   

Copula‐based flood frequency (COFF) analysis at the confluences of river systems     

Cheng Wang  Ni‐Bin Chang  Gour‐Tsyh Yeh 《水文研究》2009,23(10):1471-1486

Many civil infrastructures are located near the confluence of two streams, where they may be subject to inundation by high flows from either stream or both. These infrastructures, such as highway bridges, are designed to meet specified performance objectives for floods of a specified return period (e.g. the 100 year flood). Because the flooding of structures on one stream can be affected by high flows on the other stream, it is important to know the relationship between the coincident exceedence probabilities on the confluent stream pair in many hydrological engineering practices. Currently, the National Flood Frequency Program (NFF), which was developed by the US Geological Survey (USGS) and based on regional analysis, is probably the most popular model for ungauged site flood estimation and could be employed to estimate flood probabilities at the confluence points. The need for improved infrastructure design at such sites has motivated a renewed interest in the development of more rigorous joint probability distributions of the coincident flows. To accomplish this, a practical procedure is needed to determine the crucial bivariate distributions of design flows at stream confluences. In the past, the copula method provided a way to construct multivariate distribution functions. This paper aims to develop the Copula‐based Flood Frequency (COFF) method at the confluence points with any type of marginal distributions via the use of Archimedean copulas and dependent parameters. The practical implementation was assessed and tested against the standard NFF approach by a case study in Iowa's Des Moines River. Monte Carlo simulations proved the success of the generalized copula‐based joint distribution algorithm. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Polyploidy induction by hydrostatic pressure shock and embryo development of sea cucumber Apostichopus japonicus     

丁君  常亚青  王子臣  宋坚 《中国海洋湖沼学报》2007,25(2):184-190

The manipulation of the chromosome set for commercially valuable marine animals is important for enhancing aquacultural production. In this study, triploid and tetraploid sea cucumber Apostichopus japonicus were induced by hydrostatic pressure shock, and the conditions of appropriate induction were tested with different starting times, and hydrostatic pressure intensities and durations. The highest rate of triploid induction reached 20% and that of tetraploid was 60%. In consideration of the survival rate and hatch rate, the appropriate treatment for triploid was 55 Mpa of hydrostatic pressure for 5 min at 55 min after fertilization (a.f.), while for tetraploid it was 60 Mpa for 5 min at 61 min a.f. The triploid of the sea cucumber could survive through the pelagic larval stage and attachment stage, and develop like the control group of the experiment. The tetraploid, however, could not survive the attachment stage.  相似文献   

A study on one‐dimensional consolidation of layered structured soils          下载免费PDF全文

Kang‐He Xie  Chang‐Qing Xia  Ran An  Hong‐Wei Ying  Hao Wu 《国际地质力学数值与分析法杂志》2016,40(7):1081-1098

The governing equations for one‐dimensional consolidation of layered structured soils under time‐dependent loading are established. Using simplified k‐σ′ and m_v‐σ′ models, n‐layered structured soils are transformed into (n + 1) or (n + 2)‐layered soils in which the thickness of upper and lower layers are gradually changing. The approximate solutions for the governing equations are then obtained under two types of boundary conditions, and the computer program is developed. Based on the solutions and computer program, the consolidation behavior of layered structured soils with soft interlayer is studied. It is shown that the permeability and compressibility of the soft interlayer have the greatest influences on the rate of settlement and rate of the dissipation of excess pore water pressure. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Latitudinal distribution of mesozooplankton in the off-equatorial northeastern Pacific before and after the 1998/99 La Niña event     

Kang JH  Kim WS  Chang KI 《Marine environmental research》2008,65(3):218-234

Factors affecting mesozooplankton distributions in the northeastern tropical Pacific Ocean were investigated using data obtained along a meridian line (5 degrees -12 degrees N, 131.5 degrees W) in the summers of 1998, 1999, and 2003. The survey periods corresponded to a sharp transition between the 1997-1998 El Ni?o and 1998-1999 La Ni?a events, the 1999 La Ni?a event, and near-normal conditions after the moderate 2002-2003 El Ni?o in the equatorial Pacific. A strong upwelling in the divergence zone from 10.5 degrees to 11 degrees N caused a shoaling of the thermocline depth (approximately 30 m), resulting in increases in nitrate and phytoplankton chlorophyll a (chl-a) concentrations, and, in turn, mesozooplankton abundance during the La Ni?a in 1999. In contrast, in 1998, remnants of El Ni?o characteristics, deeper thermocline depth (60-150 m) and warm surface water (>28 degrees C), led to low concentrations of nitrate, chl-a and low mesozooplankton abundance, except in the convergence zone around 7 degrees N. The thermocline depth and nitrate concentration obtained during the near-normal period in 2003 corresponded to intermediate values as compared to those obtained during El Ni?o and La Ni?a conditions. Interannual changes in the position and strength of ecotones, such as divergence and convergence zones, affected mesozooplankton community structure and cyclopoid-to-calanoid ratios along the 131.5 degrees W meridian line. The clustering pattern of the mesozooplankton community was mostly characterized by calanoid (mainly Clausocalanus sp.) and cyclopoid (mainly Oncaea sp.) copepods, accounting for most of the observed differences among groups during the study period. Cyclopoids and calanoids were more abundant in 1999 than in 1998 or 2003, with a sharp increase to the north, while they were less abundant to the north in 1998 and 2003. The cyclopoid-to-calanoid ratio peaked in the convergence zone in 1998 and the divergence zones in 1999 and 2003, apparently due to the strength and location of the ecotones. Principal component analysis (PCA) with environmental factors and dominant mesozooplankton groups showed that dominant groups were affected by nitrate and chl-a concentrations in 1998, by sigma-t (water density), nitrate and chl-a concentrations in 1999, and by sigma-t, salinity and chl-a concentration (except siphonophores) in 2003. Latitudinal distribution of thermocline depth before and after the 1998/99 La Ni?a event showed a distinct interannual difference. The abundance of mesozooplankton in the divergence zone in 1999 was distinctively higher than abundances found in the convergence and divergence zones in 1998 and 2003, which resulted from the shallow thermocline depth due to an intensified upwelling during the strong 1998-1999 La Ni?a event.  相似文献   

Propagation of a solitary wave over rigid porous beds   总被引：1，自引：0，他引：1  

Ching-Jer Huang  Mao-Lin Shen  Hsing-Han Chang 《Ocean Engineering》2008,35(11-12):1194-1202

The unsteady two-dimensional Navier–Stokes equations and Navier–Stokes type model equations for porous flows were solved numerically to simulate the propagation of a solitary wave over porous beds. The free surface boundary conditions and the interfacial boundary conditions between the water region and the porous bed are in complete form. The incoming waves were generated using a piston type wavemaker set up in the computational domain. Accuracy of the numerical model was verified by comparing the numerical results with the theoretical solutions. The main characteristics of the flow fields in both the water region and the porous bed were discussed by specifying the velocity fields. Behaviors of boundary layer flows in both fluid and porous bed regions were also revealed. Effects of different parameters on the wave height attenuation were studied and discussed. The results of this numerical model indicate that for the investigated incident wave as the ratio of the porous bed depth to the fluid depth exceeds 10, any further increase of the porous bed depth has no effect on wave height attenuation.  相似文献