首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8篇
  免费   2篇
测绘学   1篇
大气科学   1篇
地球物理   2篇
地质学   5篇
海洋学   1篇
  2022年   1篇
  2018年   2篇
  2017年   3篇
  2016年   1篇
  2014年   1篇
  2011年   1篇
  1992年   1篇
排序方式: 共有10条查询结果,搜索用时 31 毫秒
1
1.
The usefulness of coal petrography for assessing and evaluating the properties of coal is well established. Such study is particularly helpful for evaluating Indian coals which are conspicuously heterogenous in nature. In a comparative study on the various schemes of classification and codification of coal using petrographic parameters, the importance of an international petrographic classification has been stressed. In the light of such a scheme—originally suggested for categorising Indian coals using vitrinite and exinite contents and reflectance of vitrinite as parameters—an attempt has been made to define the various important coal deposits of the subcontinent. They appear to be remarkably amenable to national planning from the standpoint of coal utilization.  相似文献   
2.
Shoreline is the dynamic interfaces of both terrestrial and marine environment, which constantly affected by natural coastal processes includes wave, tide, littoral drift and cyclonic storms as well as coastal development. Wave induced littoral drift and fluvial discharge causing the gradual inlet migration and has the concurrent impact on shoreline of Chilika lagoon. This study is to determine the long-term shoreline changes along the coast of Chilika lagoon. Historical satellite images were used to analyse the shoreline erosion and accretion based on statistical approach. The satellite data from 1975 to 2015 were processed by using ERDAS Imagine and the shorelines are extracted. The shoreline oscillation was analysed at an interval of 100 m along the coast of Chilika lagoon using DSAS software. Most commonly used statistical methods such as end point rate and linear regression rate are used. The shoreline change analysis for entire coast of the lagoon since 40 years (1975–2015) indicates that 62% is of accretion, 25% is under stable coast and erosion is 13%. The result reveals that the lagoon coast shows high accretion of 9.12 m/year at updrift side of the lagoon inlet whereas the downdrift side shows high erosion of ??10.73 m/year due to the wave induced northeasterly longshore sediment transport round the year and riverine discharge. This study would provide the potential erosion and accretion area at Chilika lagoon coast and would help in adaptive shoreline management plan.  相似文献   
3.

Poverty is the most important metric for determining the nature and sense of wellbeing in a given area. Most economists consider poverty to be an economic criterion for assessing many aspects of human development as well as overall social development; yet, society is multi-faceted in its many forms. To address this pressing societal issue, the current study used the Multidimensional poverty index (MPI). To analyse urban poverty among slum communities, the researchers used the Global MPI of the Oxford Poverty and Human Development Initiative and UNDP (following Alkire and Foster) techniques. Researchers attempted to create a Multidimensional poverty index (MPI) for impoverished households in Purulia's designated slums in this study. In the second phase, the multidimensional poverty of Purulia's urban poor households was assessed based on (a) location, (b) social groupings, and (c) length of stay. Finally, researchers have attempted to identify the factors that contribute to multidimensional poverty. Two indicators, the Head Count Ratio (H) and Intensity of Poverty, have been offered to better explain the nature of MPI (A). Based on slum population density and areal density, eight urban slum areas with 320 households has been taken from 8 selected slums based on Yamane’s methodology from Purulia Municipality's wards. A structured questionnaire, an oral history interview, and a focus group discussion were used as primary data sources, with secondary data acquired from several officially published sources. The study displays a decomposed multidimensional poverty picture in terms of overall condition, socioeconomic groups, and household age, with a quantitative methodology that is transparent. When the locations have been considered, a qualitative approach has been used to determine that the slums closest to the railway track are the most multidimensionally disadvantaged of the eight slums. Furthermore, the schedule caste population has been found to be more deprived across many socioeconomic groups, with Scheduled tribe (ST) households being the most deprived in terms of health on one hand (applied quantitative methodology) and multi-nominal regression (applied qualitative methodology) indicating a mix mode approach. This form of analysis, which combines quantitative and qualitative approaches, can aid stakeholders and policymakers in developing specific poverty-reduction policies at the regional level.

  相似文献   
4.
The lower Apalachicola–Chattahoochee–Flint River Basin in the Southeast United States represents a major agricultural area underlain by the highly productive karstic Upper Floridan aquifer (UFA). During El Niño Southern Oscillation‐induced droughts, intense groundwater withdrawal for irrigation lowers streamflow in the Flint River due to its hydraulic connectivity with the UFA and threatens the habitat of the federally listed and endangered aquatic biota. This study assessed the compounding hydrologic effects of increased irrigation pumping during drought years (2010–2012) on stream–aquifer water exchange (stream–aquifer flux) between the Flint River and UFA using the United States Geological Survey modular finite element groundwater flow model. Principal component and K‐means clustering analyses were used to identify critical stream reaches and tributaries that are adversely affected by irrigation pumping. Additionally, the effectiveness of possible water restriction scenarios on stream–aquifer flux was also analysed. Moreover, a cost–benefit analysis of acreage buyout procedure was conducted for various water restriction scenarios. Results indicate that increased groundwater withdrawal in Water Year 2011 decreased baseflow in the lower Apalachicola–Chattahoochee–Flint River Basin, particularly, in Spring Creek, where irrigation pumping during April, June, and July changed the creek condition from a gaining to losing stream. Results from sensitivity analysis and simulated water restrictions suggest that reducing pumping in selected sensitive areas is more effective in streamflow recovery (approximately 78%) than is reducing irrigation intensity by a prescribed percentage of current pumping rates, such as 15% or 30%, throughout the basin. Moreover, analysis of acreage buyout indicates that restrictions on irrigation withdrawal can have significant impacts on stream–aquifer flux in the Basin, especially in critical watersheds such as Spring and Ichawaynochaway Creeks. The proposed procedure for ranking of stream reaches (sensitivity analysis) in this study can be replicated in other study areas/models. This study provides useful information to policymakers for devising alternate irrigation water withdrawal policies during droughts for maintaining flow levels in the study area.  相似文献   
5.
ABSTRACT

Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening.  相似文献   
6.
The study makes a probabilistic assessment of drought risks due to climate change over the southeast USA based on 15 Global Circulation Model (GCM) simulations and two emission scenarios. The effects of climate change on drought characteristics such as drought intensity, frequency, areal extent, and duration are investigated using the seasonal and continuous standard precipitation index (SPI) and the standard evapotranspiration index (SPEI). The GCM data are divided into four time periods namely Historical (1961–1990), Near (2010–2039), Mid (2040–2069), and Late (2070–2099), and significant differences between historical and future time periods are quantified using the mapping model agreement technique. Further, the kernel density estimation approach is used to derive a novel probability-based severity-area-frequency (PBS) curve for the study domain. Analysis suggests that future increases in temperature and evapotranspiration will outstrip increases in precipitation and significantly affect future droughts over the study domain. Seasonal drought analysis suggest that the summer season will be impacted the most based on SPI and SPEI. Projections based on SPI follow precipitation patterns and fewer GCMs agree on SPI and the direction of change compared to the SPEI. Long-term and extreme drought events are projected to be affected more than short-term and moderate ones. Based on an analysis of PBS curves, especially based on SPEI, droughts are projected to become more severe in the future. The development of PBS curves is a novel feature in this study and will provide policymakers with important tools for analyzing future drought risks, vulnerabilities and help build drought resilience. The PBS curves can be replicated for studies around the world for drought assessment under climate change.  相似文献   
7.
The sediments of the raw sewage-fed fishpond system at East Kolkata Wetland (EKW) were analyzed for heavy metal content in a comprehensive way. Various indices of contamination like enrichment factor (EF), geo-chemical index (I geo), modified degree of contamination (mDC), and pollution load index (PLI) were assessed. In all cases, instead of literature values, the metal concentrations of less contaminated sites, separated by the statistical approach of the hierarchical cluster analysis, were used as baseline values. In the present study, about 70% of the pond sediments are found uncontaminated, 5% display low degree of contamination and 25% are designated as moderate degree of contamination. Both the EF and I geo indices highlighted that the metals lead (Pb), cadmium (Cd), and chromium (Cr) are responsible for the contamination while there is little anthropogenic input in cases of Cu, Zn, and Ni. Most of the ponds situated near the main sewage flowing canals as well as the main traffic highway and close to the solid waste dumping areas recorded higher degree of metal contamination as evident from spatial variation of mDC and PLI indices in the study area. Indices comparison study clearly indicates that although these are calculated using different methods, these may or may not produce the same indices values and hence the values should neither be compared nor be averaged. But all the above indices are directly related to a common term contamination factor (CF). Classification of contamination levels based on these CF values is found to be similar and this classification is only valid up to the level of high degree of contamination. Thus, the use of any one of these indices is sufficient to classify the degree of contamination of an area. However, to evaluate the contamination per metal, both I geo and EF are effective while, to assess the composite effect of all the metals, PLI is preferable to mDC.  相似文献   
8.
In the Apalachicola-Chattahoochee-Flint (ACF) river basin in Alabama, Georgia, and Florida (USA), population growth in the city of Atlanta and increased groundwater withdrawal for irrigation in southwest Georgia are greatly affecting the supply of freshwater to downstream regions. This study was conducted to understand and quantify the effect of irrigation pumpage on the karst Upper Floridan Aquifer and river–aquifer interactions in the lower ACF river basin in southwest Georgia. The groundwater MODular Finite-Element model (MODFE) was used for this study. The effect of two drought years, a moderate and a severe drought year, were simulated. Comparison of the results of the irrigated and non-irrigated scenarios showed that groundwater discharge to streams is a major outflow from the aquifer, and irrigation can cause as much as 10 % change in river–aquifer flux. The results also show that during months with high irrigation (e.g., June 2011), storage loss (34 %), the recharge and discharge from the upper semi-confining unit (30 %), and the river–aquifer flux (31 %) are the major water components contributing towards the impact of irrigation pumpage in the study area. A similar scenario plays out in many river basins throughout the world, especially in basins in which underlying karst aquifers are directly connected to a nearby stream. The study suggests that improved groundwater withdrawal strategies using climate forecasts needs to be developed in such a way that excessive withdrawals during droughts can be reduced to protect streams and river flows.  相似文献   
9.
In this study, ten best management practices (BMP) were implemented on agricultural areas in the Saginaw River Watershed using the Soil and Water Assessment Tool model based on four targeting methods (Load per Subbasin Area Index (LPSAI), Load per Unit Area Index (LPUAI), Concentration Impact Index (CII), and Load Impact Index (LII)). The effective BMPs both for targeting and non‐targeting pollutants were contour farming (CF) (except total nitrogen reduction during total phosphorus targeting scenario), residue management 1000 kg/ha and 2000 kg/ha, strip cropping, recharge structures, terracing, and native grass (NG). In contrast, conservation tillage and no tillage did not reduce significant amount of pollutants for any combination of targeting methods and priority areas. In regard to spatial correlation between targeting methods, a strong relationship was found between the LPSAI and LPUAI methods both for the sediment and total nitrogen targeting scenarios. In addition, a similar result was found between the CII and LPSAI targeting methods. Regarding the spatiotemporal variability of BMP implementation plan, distinct change in priority area was observed in the case of NG implementation by the end of the second year; however, this impact was minimal for CF due to less pollutant reduction efficiency compared to NG. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
10.
Spatiotemporal variability of meteorological droughts in southeastern USA   总被引:1,自引:0,他引:1  
Droughts in the southeast USA have been linked to economic losses and intractable water conflicts. The region has witnessed several severe droughts events during the period from 1901 to 2005. In this study, spatiotemporal variability in meteorological drought characteristics in the southeast were analyzed using two different datasets by the means of standard precipitation index and standard precipitation evapotranspiration index for the period 1901–2005 for agricultural and non-agricultural seasons. The study periods were divided into three epochs 1901–1935, 1936–1970, and 1971–2005 and drought characteristics, in terms of severity, frequency, number, and trends were analyzed. Additionally, areal extent, drought severities and return periods associated with three severe drought years 1904, 1954, and 2000 were analyzed. Except for the state of Florida, results indicate decrease in drought severity during the recent epoch of 1970–2005 in the study domain. Trend analysis confirms that the study domain has become wetter over the last 105 years. Wetting trends were more prominent in the agricultural season. Additionally, droughts seem to have migrated from the western part of the study area encompassing the states of Alabama, Tennessee, Louisiana, and Mississippi to the Florida panhandle region during the recent epoch. Droughts exhibited higher spatiotemporal variability during the agricultural season compared to the non-agricultural seasons. Results also showed that early to mid-1950s experienced some of the most severe droughts in the study domain. Some of the drought events, such as the drought of 1954 and 2000, have been equivalent to a 100-year drought event in the southeast. The results from this study form the benchmark for studying the impacts of future climate change projections on meteorological droughts in the southeast.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号