Neural networks-based simulation of land cover scenarios in Doon valley,India     

Sandeep Maithani 《国际地球制图》2015,30(2):163-185

Land cover transformation is one of the foremost aspects of human-induced environmental change, having an extensive history dating back to antiquity. The present study aims to simulate the process of land cover change based on different policy-based scenarios so as to provide a basis for sustainable development in Doon valley, India. For this purpose, an artificial neural network-based spatial predictive model was developed for the Doon valley. The predictive model generated future land cover patterns under three policy scenarios, i.e. baseline scenario, compact growth scenario and hierarchical growth scenario (HGS). The simulated land cover patterns mirror where land cover patterns are headed in the valley by year 2021. The result suggests that unabated continuation of the present pattern of land cover transformation will result in a regional imbalance. However, this skewed development can be corrected by altering the current growth trend as revealed in the compact growth and HGSs.  相似文献   

南京蒋庙岩体的年代学、地球化学及其地质意义   总被引：1，自引：1，他引：0  

洪文涛  徐夕生  贺振宇  闫峻 《岩石学报》2010,26(5):1577-1588

南京蒋庙侵入岩体的主体为辉长岩-闪长岩,并伴有少量的二长岩。LA-ICP-MS锆石U-Pb定年表明,其形成于118±1.1Ma,为长江中下游地区中生代最晚的一次岩浆活动。岩石地球化学资料表明,在岩浆上升及结晶过程中无明显的地壳物质混染。蒋庙岩体的εNd(t)值为-0.49～-2.29,介于DMM及EMII之间。简单二单元混合计算表明,其源区中有较高比例的软流圈物质加入。综合其它年龄资料,长江中下游地区中生代岩浆活动可分为3期:早期为151～133Ma,中期为131～126Ma,晚期为125～118Ma。中生代时期该区总体处于板内伸展的构造环境,经历了岩石圈拉张、软流圈持续上涌的地幔过程。  相似文献   

Spectral characteristics of high shallow water waves     

V. Sanil Kumar  K. Ashok Kumar 《Ocean Engineering》2008,35(8-9):900-911

The spectral characteristics of shallow water waves with significant wave height more than 2 m based on the data collected along the Indian coast is examined. It was found that the value of Joint North Sea Wave Project (JONSWAP) parameters (α and γ) increases with significant wave height and mean wave period and decreases with spectral peak period. The estimated average value (0.0027 and 1.63) of the JONSWAP parameters, α and γ were less than the generally recommended values of 0.0081 and 3.3, respectively. By carrying out a multi-regression analysis, an empirical equation is arrived relating the JONSWAP parameters with significant wave height, peak wave period and mean wave period. It was found that the Scott spectra underestimate the maximum spectral energy of high waves. The study shows that the measured wave spectra can be represented by JONSWAP spectra with the JONSWAP parameters estimated based on the equation proposed in this paper.  相似文献   

Natural vibration characteristics of gravity structures     

Ashok K. Chugh 《国际地质力学数值与分析法杂志》2007,31(4):607-648

A forced vibration procedure is presented to estimate fundamental and higher frequencies of vibrations and associated mode shapes of gravity structures. The gravity structures considered are retaining walls and gravity dams. The validity of the proposed procedure is tested on three test problems of varying complexity for which the natural vibration frequencies and mode shapes either have known analytical solutions or have been determined via numerical means/field tests by others. Also included are the results of natural vibration frequencies and associated mode shapes for a spillway control structure located near the abutment end of an embankment dam obtained using the proposed procedure. For all problems considered, fundamental frequency and mode shape results using the proposed procedure are compared with the results obtained using an alternative procedure in which static deflections due to the structure's own weight are used as the starting point for free vibrations by setting the gravity vector to zero. All results compare well. The merits of the proposed procedure are discussed. Published in 2006 by John Wiley & Sons, Ltd.  相似文献   

Announcement     

Ashok Kauhsal 《Journal of the Indian Society of Remote Sensing》1999,27(2):xiii-xiii

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Simulation of Tropical Cyclone Circulation Over the Bay of Bengal Using the Arakawa-Schubert Cumulus Parameterization. Part II: Some Sensitivity Experiments     

D. V. Bhaskar Rao  K. Ashok 《Pure and Applied Geophysics》2001,158(5-6):1017-1046

—?The role of sea-surface temperature (SST) and Coriolis parameter in the evolution and intensification of tropical cyclones has been examined using the ten-level axi-symmetric primitive equation model described in the companion paper (Bhaskar Rao and Ashok, 1999). Two experiments have been conducted using the ten-level model to assess the role of Coriolis parameter “f” in tropical cyclone intensity and the size of the storm generated. Six experiments have been performed to assess the importance of Sea-Surface Temperature (SST) in tropical cyclogenesis and intensification. The initial thermodynamic field and the initial vortex are the same as that used to simulate the Bay of Bengal tropical cyclone discussed in the companion paper. Further sensitivity experiments indicated a strong dependency of the model on SSTs. The model initial vortex could not intensify with an SST of 299?K but could with an SST of 300?K. The increase of SST from 300?K to 300.5?K shows rapid intensification with a minimum central surface pressure of 910?hPa and a maximum tangential wind of 80?m/s. Further increase of SST only shows a marginal increase in intensity and a larger radius of maximum wind. Sensitivity experiments to assess the role of the Coriolis parameter suggest that tropical cyclones develop more intensity and are faster at relatively lower latitudes.  相似文献   

Effective strength eccentricity concept for inelastic analysis of asymmetric structures     

A. K. Mittal  Ashok K. Jain 《地震工程与结构动力学》1995,24(1):69-84

A large number of parameters affect the inelastic response of an eccentric system. The centre of resistance no longer remains constant due to continuous loading and unloading of various elements of the system in and out of the inelastic region. The objective of this study is to develop the concept of strength eccentricity for asymmetrical structures excited well into the inelastic region in the event of a severe earthquake. A single mass monosymmetric three-element system is selected. The torsional flexibility parameter is varied so as to obtain nine eccentric configurations covering the entire spectrum of such systems. These models were subjected to S00E component of the El Centro earthquake of 1940 which is considered to be a very severe earthquake. The concept of effective strength eccentricity is introduced which is defined as strength eccentricity at the point of intersection of ductility ratio curves of REE and FEE. It is proposed to provide additional strength in the elements of a torsionally unbalanced system independent of the design eccentricity. Empirical equations are proposed to account for design eccentricity and additional strength as well as distribution of the design strength. The proposed formulation is compared with the torsional provisions of UBC 1991, NBCC 1990 and NZC 1992. It is concluded that additional ductility demand on the REE and FEE designed based on the proposed formulation is almost nil as compared to that given by the three codes. The NZC and UBC require maximum ductility on the REE. The increase in overall strength of the system is least for the proposed formulation as compared to that given by the three codes. NBCC consistently requires the maximum total strength ratio.  相似文献   

Book reviews     

Juha J. Uitto  A. K. P. Mochtan  Ashok K. Dutt  Anindita Pari 《GeoJournal》1993,31(2):213-214

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An evaluation of national economic planning in the People's Republic of China     

Ashok K. Dutt  Frank J. Costa 《Geoforum》1980,11(1):1-15

The People's Republic of China has sought, since its inception in 1949, to develop through economic planning at the national level rather than rely on traditional free market mechanisms. This paper examines the changing characteristics of this economic planning over time, including the shifting balance between centralizing and decentralizing policies. The disruptive effects of the “Great Leap Forward” and the Cultural Revolution are also discussed and the general features of the contemporary situation are examined.  相似文献   

GIS assisted inverse geochemical modeling for plausible phase transfers in aquifers     

S. D. Dhiman  Ashok K. Keshari 《Environmental Geology》2006,50(8):1211-1219

A geographical information system (GIS) assisted approach that couples a groundwater flow model and an inverse geochemical model is presented to quantify the phase mole transfers between two points on the flow path within a groundwater system. It is used to investigate the plausible phase transfers in the unconfined aquifer of Mehsana district of Gujarat State, India. X-ray diffraction analysis of soil samples is carried out for mineral characterization. The groundwater flow field is simulated using MODFLOW and flow paths used for inverse geochemical modeling are traced using PMPATH, a particle tracking algorithm. The plausible phase mole transfers in the flow path are quantified using PHREEQC geochemical code. The different scenarios generated by inverse modeling routine are used as input to the geochemical model and simulation runs are taken as forward models. The obtained results are compared to the target solution chemistry by using the square of the Pearson product moment correlation coefficient. Results reveal that the groundwater is undersaturated with anhydrite, carbon dioxide (gas), fluorite, gypsum, halite, jarosite-K, and siderite. It is oversaturated with aragonite, calcite, dolomite, ferrihydrite, goethite, and hematite. Results further reveal that calcite is precipitating, while dolomite, gypsum, carbon dioxide, and fluorite are dissolving together with ion exchange in the flow path.  相似文献