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151.
This article introduces the new Indian 2 m telescope which has been designed by MT Mechatronics in a detailed conceptual design study for the Indian Institute of Astrophysics, Bangalore. We describe the background of the project and the science goals which shall be addressed with this telescope. NLST is a solar telescope with high optical throughput and will be equipped with an integrated Adaptive Optics system. It is optimized for a site with the kind of seeing and wind conditions as they are expected at a lake site in the Himalayan mountains. The telescope can also be used for certain night time applications. We also give the scientific rationale for this class of telescope (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
152.
This study focuses on the evaluation of seismic safety of unreinforced masonry buildings in Turkey by using fragility curves generated for two behavior modes of load bearing walls: in-plane and out-of-plane. During generation of fragility curves, a force-based approach has been used. There exist two limit states in terms of base shear strength for in-plane behavior mode and flexural strength for out-of-plane behavior mode. To assess the seismic vulnerability of unreinforced masonry buildings in Turkey, fragility curves generated for in-plane behavior were verified by the observed damage during the 1995 Dinar (Turkey) earthquake and fragility curves generated for out-of-plane behavior were verified by the observed damage during the 2010 Elaz?? (Turkey) earthquake. The verification results reveal that the proposed fragility-based procedure can provide an alternative for the seismic safety evaluation of unreinforced masonry buildings in Turkey. Using this procedure, it becomes possible to investigate a large population of masonry buildings located in regions of high seismic risk in a short period of time. The obtained results are valuable in the sense that they can be used as a database during the development of strategies for pre-earthquake planning and risk mitigation for earthquake prone regions of Turkey. 相似文献
153.
A simple analytical solution is developed for computing the dynamic interaction tensor for floating pile groups with batter piles. For this purpose, the governing differential equations are derived for an unloaded batter floating pile closely spaced to another loaded pile with the same properties. The reaction of soil against pile deformation is modeled by the springs and dashpots along the length of the pile. The soil is assumed linear viscous elastic and the pile behavior is linear elastic. The closed form solutions of governing equations are obtained using appropriate boundary conditions. The results are verified and compared with rigorous and approximate analytical solutions for vertical piles. The proposed method can be readily applied by engineers in the design of pile groups with batter piles. 相似文献
154.
In this study, we present a newly developed method for the estimation of surface flow paths on a digital elevation model (DEM). The objective is to use a form‐based algorithm, analyzing flow over single cells by dividing them into eight triangular facets and to estimate the surface flow paths on a raster DEM. For each cell on a gridded DEM, the triangular form‐based multiple flow algorithm (TFM) was used to distribute flow to one or more of the eight neighbor cells, which determined the flow paths over the DEM. Because each of the eight facets covering a cell has a constant slope and aspect, the estimations of – for example – flow direction and divergence/convergence are more intuitive and less complicated than many traditional raster‐based solutions. Experiments were undertaken by estimating the specific catchment area (SCA) over a number of mathematical surfaces, as well as on a real‐world DEM. Comparisons were made between the derived SCA by the TFM algorithm with eight other algorithms reported in the literature. The results show that the TFM algorithm produced the closest outcomes to the theoretical values of the SCA compared with other algorithms, derived more consistent outcomes, and was less influenced by surface shapes. The real‐world DEM test shows that the TFM was capable of modeling flow distribution without noticeable ‘artefacts’, and its ability to track flow paths makes it an appropriate platform for dynamic surface flow simulation. 相似文献
155.
A desert in the delta: Participatory assessment of changing livelihoods induced by commercial shrimp farming in Southwest Bangladesh 总被引:2,自引:0,他引:2
In recent years, shrimp aquaculture, which is undertaken largely in the tropical countries, has experienced spectacular growth in response to expanding global demand and higher economic return. Shrimp exports bring substantial foreign exchange to the producing countries and also generate employment for various stakeholders related to this industry. Despite a number positive aspects (e.g., foreign exchange, employment and food) of shrimp farming, the industry has serious negative environmental impacts. Because of the degradation of natural resources, commercial shrimp farming imposes socio-economic costs on rural resource-reliant communities as their traditional means of food production and livelihoods are displaced. Bangladesh produces 2.5 percent of the global production of shrimp. The country earned about 400 million dollars (U.S.) from shrimp exports during 2004-2005, up from only US$3.17 million in 1971-72. Bangladesh is suffering because of unplanned expansion of this aquaculture and increasingly called as “a desert in the delta”. The purpose of this paper is to identify the impact of commercial saltwater shrimp farming on rural livelihood patterns in southwest Bangladesh using different Participatory Research methods. The authors suggest that vulnerabilities in livelihoods of the rural communities increased due to narrowing down agricultural production, income sources and natural supply of food. Other socio-economic impacts (e.g., landuse patterns, homestead and family structure, daily movement pattern and activities, drinking water, and law and order) also followed as a reaction to the changing ecological conditions. It is also found that economic benefits from shrimp cultivation to the communities was minimal or even negative due to the polarization and outflow of profits, which is augmenting the threat of poverty. 相似文献
156.
Land subsidence susceptibility mapping at Kinta Valley (Malaysia) using the evidential belief function model in GIS 总被引:4,自引:0,他引:4
Biswajeet Pradhan Mohammed Hasan Abokharima Mustafa Neamah Jebur Mahyat Shafapour Tehrany 《Natural Hazards》2014,73(2):1019-1042
Land subsidence is one of the frequent geological hazards worldwide. Urban areas and agricultural industries are the entities most affected by the consequences of land subsidence. The main objective of this study was to estimate the land subsidence (sinkhole) hazards at the Kinta Valley of Perak, Malaysia, using geographic information system and remote sensing techniques. To start, land subsidence locations were observed by surveying measurements using GPS and using the tabular data, which were produced as coordinates of each sinkhole incident. Various land subsidence conditioning factors were used such as altitude, slope, aspect, lithology, distance from the fault, distance from the river, normalized difference vegetation index, soil type, stream power index, topographic wetness index, and land use/cover. In this article, a data-driven technique of an evidential belief function (EBF), which is in the category of multivariate statistical analysis, was used to map the land subsidence-prone areas. The frequency ratio (FR) was performed as an efficient bivariate statistical analysis method in order compare it with the acquired results from the EBF analysis. The probability maps were acquired and the results of the analysis validated by the area under the (ROC) curve using the testing land subsidence locations. The results indicated that the FR model could produce a 71.16 % prediction rate, while the EBF showed better prediction accuracy with a rate of 73.63 %. Furthermore, the success rate was measured and accuracies of 75.30 and 79.45 % achieved for FR and EBF, respectively. These results can produce an understanding of the nature of land subsidence as well as promulgate public awareness of such geo-hazards to decrease human and economic losses. 相似文献
157.
Using TDR and modeling tools to investigate effects of interactive factors on preferential flow and transport in field sandy clay soil 总被引:2,自引:0,他引:2
Hasan Merdun 《Environmental Earth Sciences》2014,71(4):1821-1838
Investigation of the extent of preferential flow and transport affected by several factors and their interactions in the vadose zone using the advanced measurement and modeling techniques is crucial for protection of groundwater from agricultural chemicals like fertilizers and pesticides. The objectives of this study were to investigate the interactive effects of factors like soil structure, initial soil water content (SWC), and application rate on preferential flow and transport using the time domain reflectometry (TDR) measurements of SWC and electrical conductivity (EC) in the plots of 12 treatments in a sandy clay field soil, applying the models (HYDRUS-1D and MACRO) to the measured data, performing Tukey test statistical analysis, and relating model parameters to basic soil properties, consequently, flow and transport characteristics. Analysis of response times and the changes in SWC and EC with time during the experiments in the profiles of the treatments confirmed the existence of preferential flow and transport at the site. As long as the other factors or conditions were constant; undisturbed versus disturbed soil, wet versus dry initial SWC, and high versus low application rate caused preferential flow and transport in the soil based on the TDR measurements. Overall HYDRUS-1D had better performance than MACRO in the simulations of the measured data. These results suggest that different scales of these factors in different field soils need to be further studied for better understanding the flow and transport processes in the vadose zone. 相似文献
158.
Ali Sungur Mustafa Soylak Selehattin Yilmaz Hasan Özcan 《Environmental Earth Sciences》2014,72(9):3293-3305
Utilizing the sequential extraction procedure (acid soluble, reducible, oxidizable, and residual) proposed by The European Community Bureau of Reference (BCR), the trace metals present in the sediments of the Ergene River, Turkey, were determined. The sediment samples were collected from 10 sampling sites and analyzed to identify the concentrations of cadmium, cobalt, chromium, copper, manganese, nickel, lead and zinc. The flame atomic absorption spectrometer was used for metal determination. The validation of the results was checked by the analysis of the BCR-701 standard reference material. The relationship existing between the sediment characteristics and metal fractions was identified using the correlation analysis. Hierarchical cluster analysis was performed to find out the grouping of the sampling sites based on the similarities of the heavy metals in the bioavailable fraction. When the extractable amounts of heavy metals are considered, the quantity of the mobile fractions (viz., acid soluble, reducible, and oxidizable) of the heavy metals is observed to be higher when compared with that of the immobile fraction (residual). This might be caused by the anthropogenic sources. Besides, it was statistically discovered that the organic matter, pH and clay contents could influence the bonding of the analyte metals in various forms. The cluster analysis revealed three clusters of the sampling stations, with group I (S5-8) and group II (S3, S4 and S9) showing higher environmental risks. The risk assessment code indicated that the highly mobile soluble fractions of Mn, Zn, Cd and Co created a high environmental risk which could result in negative impacts on the aquatic biota. 相似文献
159.
The longitudinal fast solitary waves induced by weakly relativistic positron showers of astrophysical origin are studied in a plasma system contaminated with some massive impurities in presence of superthermal effects. The superthermal effects are due to the high energy electrons. The impurities are dust corpuscles with positive and negative charges. It is noticed that increase in the kappa parameter of electrons and relativistic streaming factor of weakly relativistic positron shower, negative dust concentration invoke an enhancement in the strength of solitary wave. On the other hand increase in the shower’s temperature as well as positive dust concentration diminish the solitary hump strength. It is worth to mention that only hump type compressive fast solitary waves are predicted by our model, for the given set of plasma parameters, because the convective coefficient of the nonlinear governing equation for solitary wave remains positive in considered regime of interaction for plasma and positron shower. Our calculations in linear regime predict both the fast and slow positron shower induced longitudinal, electrostatic perturbations. Our results may be of importance in understanding the nonlinear propagation of waves in doped astrophysical superthermal plasmas with relativistic positron showers. 相似文献
160.
Sabeeh R. Jabbar Hasan A. Fleyeh Jinan M. Al Razzaz 《Astrophysics and Space Science》1986,123(2):325-333
The aim of this paper is to present a general method for computation of the geometrical elements of totally eclipsing W UMa (close, or in actual contact) binary systems in the frequency-domain.This method has been done using a new technique (two minima with the improved values of the photometric perturbation effects). The results are compared with the results calculated by different methods, that have used the same observation references.The improved photometric perturbation terms have been discussed and its effects are computed for both (primary and secondary) minima. 相似文献