Accuracy of the kinematic wave and diffusion wave approximations for time-independent flows with infiltration included     

V. P. Singh  V. Aravamuthan 《水文研究》1998,12(12):1951-1979

Errors in the kinematic wave and diffusion wave approximation for time-independent (or steady-state) cases of channel flow with infiltration were derived for three types of boundary conditions: zero flow at the upstream end, and critical flow depth and zero depth gradient at the downstream end. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with errors of less than 1·4% for KF²₀≥7·5, and up to 14% for KF²₀≤0·75 for the upstream boundary condition of zero discharge and finite depth, where K is the kinematic wave number and F₀ is the Froude number. The kinematic wave approximation was reasonably accurate except at the channel boundaries and for small values of KF²₀ (≤1). The accuracy of these approximations was significantly influenced by the downstream boundary, both in terms of the magnitude of the error and the segment of the channel reach for which these approximations would be applicable. © 1998 John Wiley & Sons, Ltd.  相似文献   

Flood frequency analysis     

Baidya  S.  Singh  Ajay  Panda  Sudhindra N. 《Natural Hazards》2020,100(3):1137-1158

Natural Hazards - The recurring flooding causes loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways and canals. It also frequently damages power...  相似文献   

Development of Proxy Model for Hydraulic Fracturing and Seismic Wave Propagation Processes     

Singh  Manik  Srinivasan  Sanjay 《Mathematical Geosciences》2020,52(1):81-110

Mathematical Geosciences - Characterization of discrete fracture networks is necessary for unconventional reservoir development, as they control the flow of fluids toward the hydraulically...  相似文献   

Triangular Grid-Based Fuzzy Cross-Update Inversion of Gravity Data: Case Studies from Mineral Exploration     

Singh  Anand 《Natural Resources Research》2020,29(1):459-471

Natural Resources Research - In mineral exploration, geophysical inversion is a common mathematical tool to obtain reliable information on subsurface density properties based on gravity...  相似文献   

Impact of cropping pattern changes on the exploitation of water resources: A remote sensing and GIS approach     

Anil Sood  B. U. Choudhury  S. S. Ray  S. K. Jalota  P. K. Sharma  Shushma Panigrahy 《Journal of the Indian Society of Remote Sensing》2009,37(3):483-491

A remote sensing-based approach was applied to study the impact of changes in cropping system on the exploitation of water resources in two districts namely Ludhiana in central Punjab and Muktsar in South-Western Punjab. Rice-wheat remained dominant rotation in Ludhiana while cottonwheat rotation was replaced partially by rice-wheat in Muktsar within a span of over five years (1998–99 to 2003–04). The solo rice-wheat system in Ludhiana district has resulted in large-scale ground water exploitation as is evident from the faster decline in water table (up to 0.9m year⁻¹) and higher tube-wells density (440 per 1000 ha). As a result, nearly 60 per cent of the total area of Ludhiana district has the water table depth greater than 10m and in some blocks, it has reached to a depth of 22 m. In Muktsar district, corresponding rise in water table is 0.2m per year and tube well density is 114 per 1000 ha. Irrigation water associated with paddy cultivation in Ludhiana and adjoining areas moves laterally through the buried paleo-channels of Sutlaj in the deeper soil profile and gets accumulated in the basin lands of Muktsar and adjoining areas and causes an extra water flux and subsequent rise in water table, recorded at 3 to 7m depth. To minimize the hydrological imbalance of the state, it is suggested to diversify some of the area in the central districts from irrigation water intensive rice-wheat system to less water intensive cropping system.  相似文献   

Geospatial approach for tiger habitat evaluation and distribution in Corbett Tiger reserve,India     

G. Singh  A. Velmurugan  M. P. Dakhate 《Journal of the Indian Society of Remote Sensing》2009,37(4):573-585

India has a rich repository of flora and fauna, but the rapid decline of wildlife and threat to its habitat has been a serious cause of concern. Hence, protected areas have been set up to achieve specific conservation objectives to facilitate timely and reliable information on forest types and its composition, degradation status and their suitability for different species of flora and fauna. In the present study, evaluation of tiger habitat in Corbett Tiger reserve is carried out using remote sensing, ground and other ancillary sources and is integrated using GIS using multi-criteria model. The results indicated that sal, mixed sal, miscellaneous forest, plantation, grassland, agriculture and scrub land are the major land use/land cover types and majority of the study area is covered under dense forest. Tiger habitat suitability analysis showed that large proportion of the area (51.4%) was found to be highly suitable followed by moderately suitable area (31%). Further, the correlation drawn between range-wise suitability area and actual tiger population in Corbett Tiger Reserve CTR indicated a positive correlation of 0.73. Disturbance to wildlife habitat, vegetation degradation and shrinking passage corridor are the major concern in CTR.  相似文献   

Design of a neuro fuzzy model for image compression in wavelet domain     

Vipula Singh  Navin Rajpal  K. Srikanta Murthy 《Journal of the Indian Society of Remote Sensing》2009,37(2):185-199

Image compression forms the backbone for several applications such as storage of images in a database, picture archiving, TV and facsimile transmission, and video conferencing. Compression of images involves taking advantage of the redundancy in the data present within an image. This work evaluates the performance of an image compression system based on fuzzy vector quantization, wavelet-based sub band decomposition and neural network. The vector quantization is often used when high compression ratios are required. The implementation consists of three steps: first, the image is decomposed into a set of sub bands with different resolutions corresponding to different frequency bands. Different quantization and coding schemes are used for different sub bands based on their statistical properties. In the second step, wavelet coefficients corresponding to the lowest frequency band are compressed by differential pulse code modulation (DPCM) and the coefficients corresponding to higher frequency bands are compressed using neural network. Finally, the result of the second step was used as input to fuzzy vector quantizer. Image quality was compared objectively using mean squared error and peak signal to noise ratio along with the visual appearance. The simulation results show clear performance improvement with respect to decoded picture quality when compared with other image compression techniques (Liu, 2005; Premaraju, 1996).  相似文献   

Global GPS data analysis at the National Geodetic Survey     

William G. Kass  Robert L. Dulaney  Jake Griffiths  Stephen Hilla  Jim Ray  James Rohde 《Journal of Geodesy》2009,83(3-4):289-295

NOAA’s National Geodetic Survey (NGS) has been one of the Analysis Centers (ACs) of the International GNSS Service (IGS) since its inception in 1994. Solutions for daily GPS orbits and Earth orientation parameters are regularly contributed to the IGS Rapid and Final products, as well as solutions of weekly station positions. These solutions are combined with those of the other ACs and then the resultant IGS products are distributed to users. To perform these tasks, NGS has developed and refined the Program for the Adjustment of GPS EphemerideS (PAGES) software. Although PAGES has continuously evolved over the past 15 years, recent efforts have focused mostly on updating models and procedures to conform more closely to IGS and the International Earth Rotation Service (IERS) conventions. Details of our processing updates and demonstrations of the improvements will be provided.  相似文献   

Species diversity and population status of threatened plants in different landscape elements of the Rohtang Pass,western Himalaya     

K. N. Singh  Gopichand  Amit Kumar  Brij Lal  N. P. Todaria 《山地科学学报》2008,5(1):73-83

This paper highlights the quantitative estimates of plant species diversity and ecosystems of the Rohtang Pass,which is one of the most preferred visiting spots by tourists in Himachal Pradesh （H.P.）,India. In spite of high pressure of anthropogenic activities,the Rohtang Pass still harbours a variety of flowering plants with economic value,including various medicinal herbs. In order to observe species diversity in different landscape elements （LSEs）,ground surveys were conducted in nine unique LSEs within the elevation range between 3624 m and 4332 m. Plant community structure in each LSE was studied using stratified random sampling where a total 56 quadrats of 1 m^2 in size for herbs and 7 quadrats of 25 m^2 for shrubs were made. Of the total 50 plant species belonging to 15 families recorded in different random quadrats,24 species were found of medicinal value. Maximum species richness （18） and value of Shannon diversity （H＇=2.2648） were observed on northeast-facing slope in Picrorhiza kurrooa dominated LSE in moist area,followed by Rheum emodi LSE （species richness = 17 and H＇ = 2.4141） distributed on south-facing slope. Maximum values of species richness and Shannon diversity in Rheum emodi LSE were observed between 8 ～ 12 and 1.4797 ～ 2.1911,respectively. Rhododendron anthopogon dominated LSE on northwest-facing slope was found least diverse in terms of species richness where the Simpson index of dominance （D） was 0.4205. The species were equal in abundance in P. kurrooa LSE on east-facing slope and Pleurospermum candollii LSE on north-facing slope,showing the maximum similarity in terms of species distribution between the two LSEs. Low turnover of species across common LSEs gives an idea regarding their limited distribution. Five species of threatened category according to the IUCN criteria were observed in seven LSEs. The largest population of threatened medicinal plants was recorded on northeast and northwest-facing slopes where population density of Bergenia stracheyi （  相似文献   

长江口南支-南港沙波的稳定域   总被引：9，自引：1，他引：9  

程和琴  时钟  Kostaschuk Ray  董礼先 《海洋与湖沼》2004,35(3):214-220

1997年枯季和1998年特大洪水后期,在长江口南支一南港用直读式海流计和Endeco／YSI Inc．174SSM流速仪定点测量近底和表层流速大小和方向,并采集床面泥沙样品经室内分析得到底沙粒径,用声学测深仪和Ultra Electronics旁侧声纳仪走航测量床面形态。结果表明：1)枯、洪季时落潮流近底和表层流速比涨潮流流速大,落潮流周期比涨潮流周期长,且洪季落潮流表层流速大于枯季时,洪季落潮流周期比枯季时长;2)床面泥沙枯季时为粗粉砂至极细砂,而洪季时为极细砂至细砂;3)枯、洪季床面上的沙波形态受落潮流控制,波高与波长之比值以及背流面坡度较小,洪季时沙波波高比枯季时高,波长比枯季时长。显然,长江口南支-南港落、涨潮流和床面泥沙粒径及沙波形态的特征均与季节性变化的径流有关。此外,在Van den Berg and Van Gelder(1993)底形稳定相图中,作者提出了一个新的沙纹与沙波间的转化边界。  相似文献