检索结果-南通市图书馆

Spatio-temporal changes in the six major glaciers of the Chitral River basin(Hindukush Region of Pakistan)between 2001 and 2018

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2020年第3期17卷 572-587页

作者： Jawaria GUL Sher MUHAMMAD LIU Shi-yin Siddique ULLAH Shakeel ahmad Huma HAYAT adnan ahmad tahir Department of Environmental Sciences COMSATS University Islamabad(CUI)Abbottabad Campus22060AbbottabadPakistan International Center for Integrated Mountain Development(ICIMOD) KathmanduNepal Institute of International Rivers and Eco-Security Yunnan UniversityKunmingChina Division of Environmental System Analysis School of EnvironmentTsinghua UniversityBeijing 100084 China

Glaciers in the northern Pakistan are a distinctive source of freshwater for the irrigation,drinking and industrial water supplies of the people living in those regions and downstream. These glaciers are under a direct global warming impact as indicated in many previous studies. In this study, we estimated the glacier dynamics in terms of Equilibrium Line Altitude(ELA), mass balance and the snout position variation using remote sensing data between 2001 and 2018. Six glaciers, having area≥ 20 km2 each, situated in the Chitral region(Hindukush Mountains) were investigated in this study. Digital Elevation Model(DEM) and available cloud-free continuous series of Landsat and Sentinel satellite images from minimum snow cover season were used to monitor the variability in the studied glaciers by keeping the status of glaciers in year 2001 as a reference. The annual climatic trends of mean temperature and total precipitation from Chitral weather station were detected using the nonparametric Mann-Kendall’s test. Results revealed a general increase in the ELA, decrease in the glacier mass balance and the retreat of snout *** upward shift in the ELA for the entire study area and data period was ~345 ± 93 m at a rate of^13 m.a-1 from the reference year’s position i.e.~4803 m asl. Estimated mean mass balance for the entire study area indicated a decline of-0.106 ± 0.295 m w.e. a-1. Periods of snout retreat and advance in different glaciers were found but the mean value over the entire study area was a retreat of-231 ± 140 *** obvious relationship was found between the glacier variation trends and the available gauged climatic data possibly due to the presence of debris cover in ablation zones of all the studied glaciers which provides insulation and reduces the immediate climatic effects.

关键词： Glacier dynamics Hindukush region Sentinel Landsat Mass balance Equilibrium Line Altitude Snout position

Remote Sensing Data Application to Monitor Snow Cover Variation and Hydrological Regime in a Poorly Gauged River Catchment—Northern Pakistan

在线全文

学校读者我要写书评

暂无评论

International Journal of Geosciences 2014年第1期5卷 27-37页

作者： Samreen Abdul Hakeem Muhammad Bilal Arshid Pervez adnan ahmad tahir Department of Environmental Sciences COMSATS Institute of Information Technology Abbottabad Pakistan

Snow- and glacier-nourished river basins located in the Himalaya-Karakoram-Hindukush (HKH) ranges supply a significant amount of discharge in River Indus upstream Tarbela Dam. It is, hence, important to comprehend the cryosphere variation and its relationship to the stream flow in these high-altitude river catchments. The MODIS remotely sensed database of snow products was chosen to examine the average annual snow and glacier cover (cryosphere) variations in the Shigar River basin (poorly gauged mountainous sub-catchment of the Indus River). Hydrological regime in the area was investigated through monthly database of observed stream fluxes and climate variables (precipitation and mean temperature) for the Shigar River catchment. Analysis indicated the usefulness of remote sensing techniques for estimation of the snow cover variation in the poorly or un-gauged high-elevation catchments of the HKH zone. Results also showed that Shigar River discharge was influenced mainly by the seasonal and annual snow cover area (SCA) variation and the temperature seasonality. Moreover, it is important to uncover such inter-relationship of stream flow, climate variables and snow cover in the poorly gauged high-altitude catchments of Karakoram region for better water resource management and accurate flood hazards predictions at Tarbela.

关键词： Shigar River Basin Satellite Remote Sensing MODIS Snow Products Water Resources Management ASTER-GDEM

Erratum to:Spatio-temporal changes in the six major glaciers of the Chitral River basin(Hindukush Region of Pakistan)between 2001 and 2018

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2020年第8期17卷 2048-2048页

作者： Jawaria GUL Sher MUHAMMAD LIU Shi-yin Siddique ULLAH Shakeel ahmad Huma HAYAT adnan ahmad tahir Department of Environmental Sciences COMSATS University Islamabad(CUI)Abbottabad Campus22060AbottabadPakistan International Center for Integrated Mountain Development(ICIMOD) KathmanduNepal Institute of International Rivers and Eco-Security Yunnan UniversityKunmingChina Division of Environmental System Analysis School of EnvironmentTsinghua UniversityBeijing 100084 China

The article Spatio-temporal changes in the six major glaciers of the Chitral River basin(Hindukush Region of Pakistan)between 2001 and 2018,written by Jawaria GUL,Sher MUHAMMAD,LIU Shi-yin,Siddique ULLAH,Shakeel ahmad,Huma HAYAT and adnan ahmad tahir,was originally published Online First without Open *** publication in volume 17,issue 3,page 572-587,the author decided to opt for Open Choice and to make the article an Open Access ***,the copyright of the article has been changed to C The Author(s)2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License(http://***/licenses/by/4.0/),which permits use,duplication,adaptation,distribution and reproduction in any medium or format,as long as you give appropriate credit to the original author(s)and the source,provide a link to the Creative Commons license,and indicate if changes were *** original version of this article has been revised due to a retrospective Open Access order.

关键词： Open Region license

Hypsometric properties of mountain landscape of Hunza River Basin of the Karakoram Himalaya

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2018年第9期15卷 1881-1891页

作者： BAIG Siddique Ullah tahir adnan ahmad DIN ahmad KHAN Humaira High Mountain Research Center Development Studies COMSATS University Islamabad (Abbottabad Campus) Environmental Sciences COMSATS University Islamabad (Abbottabad Campus) Computer Sciences COMSATS University Islamabad (Abbottabad Campus)

Within Karakoram Himalaya, Hunza River Basin(study area) is unique for a number of reasons: 1) potential impacts of highly concentrated highpitched mountains and glacial ice; 2) the glaciated portions have higher mean altitude as compared to other glaciated landscapes in the Karakoram; 3) this basin occupies varieties of both clean and debriscovered glaciers and/or ice. Therefore, it is imperative to understand the stability of topographic surface and potential implications of fluctuating glacial-ice causing variations in the movement of material from higher to lower elevations. This paper advocates landscape-level hypsometric investigations of glaciated landscape lies between 2280–7850 m elevation above sea level and non-glaciated landscape between 1461–7570 m. An attempt is made to understand intermediate elevations, which disguise the characteristics of glaciated hypsometries that are highly correlated with the Equilibrium Line Altitude(ELA). However, due to data scarcity for high altitude regions especially above 5000 m elevation, literature values for climatic conditions are used to create a relationship between hypsometry and variations in climate and ELA. The largest glaciated area(29.22%) between 5047 to 5555 m lies in the vertical regime of direct snow-accumulation zone and in the horizontal regime of net-accumulation zone(low velocity, net freezing, and no-sliding). In both landscapes, the hypsometric curves are ‘slow beginning' followed by ‘steep progress' and finally reaching a ‘plateau', reflecting the rapid altitudinal changes and the dominance of fluvial transport resulting in the denudation of land-dwelling and the transport of rock/debris from higher to lower altitudes. Reported slight differences in the average normalized bin altitudes against the cumulative normalized area between glaciated and non-glaciated landscapes are an indicator of slightly different land-forms and landform changes.

关键词： Karakoram Hypsometry Glaciation Equilibrium Line Altitude

Performance improvement of complementary feeders using static transfer switch system

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第2期10卷 189-200页

作者： tahir MAHMOOD Mohammad ahmad CHOUDHRY Department of Electrical Engineering University of Engineering and Technology

The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.

关键词： Complementary feeder Cross current Static transfer switch (STS) Sensitive load Voltage sag PSCAD/EMTDC

Influence of accelerated curing on the compressive strength of polymer-modified concrete

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2022年第5期16卷 589-599页

作者： Izhar ahmad Kashif Ali KHAN tahir ahmad Muhammad ALAM Muhammad Tariq BASHIR College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China Department of Civil Engineering Muslim Youth UniversityIslamabad 44000Pakistan Department of Civil Engineering CECOS University of IT&Emerging SciencesPeshawar 25000Pakistan Department of Civil Engineering University of Engineering&TechnologyMardan 23200Pakistan

In recent building practice,rapid construction is one of the principal ***,in designing concrete structures,compressive strength is the most significant of all *** 3-d and 7-d compressive strength reflects the strengths at early phases,the ultimate strength is *** effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate(EVA)at the later ***-Smirnov(KS)goodness-of-fit test was used to examine distribution of the *** compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28,56,90,120,210,and 365 *** accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression *** on the results of KS goodness-of-fit test,it was concluded that KS test statistics value(D)in each case was lower than the critical value 0.521 for a significance level of 0.05,which demonstrated that the data was normally *** on the results of compressive strength test,it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16%***,it was concluded that predicted compressive strength values lies within a 6%difference from the actual strength values for all the mixes,which indicates the practicability of the regression *** research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.

关键词： compressive strength prediction polymer-modified concrete linear regression fit early age strength ethylene vinyl acetate

Using machine learning to predict habitat suitability of sloth bears at multiple spatial scales

在线全文

学校读者我要写书评

暂无评论

Ecological Processes 2021年第1期10卷 634-645页

作者： tahir Ali Rather Sharad Kumar Jamal ahmad Khan Department of Wildlife Sciences Aligarh Muslim UniversityAligarhUttar Pradesh 202002India The Corbett Foundation 81-88Atlanta BuildingNariman PointMumbaiMaharashtra 400021India

Background:Habitat resources occur across the range of spatial scales in the *** environmental resources are characterized by upper and lower limits,which define organisms’distribution in their *** respond to these resources at the optimal spatial ***,multi-scale assessments are critical to identifying the correct spatial scale at which habitat resources are most influential in determining the specieshabitat *** study used a machine learning algorithm random forest(RF),to evaluate the scaledependent habitat selection of sloth bears(Melursus ursinus)in and around Bandhavgarh Tiger Reserve,Madhya Pradesh,***:We used 155 spatially rarified occurrences out of 248 occurrence records of sloth bears obtained from camera trap captures(n=36)and scats located(n=212)in the *** calculated focal statistics for 13 habitat variables across ten spatial scales surrounding each presence-absence record of sloth ***(>5000 m)and small(1000–2000 m)spatial scales were the most dominant scales at which sloth bears perceived the habitat *** the habitat covariates,farmlands and degraded forests were the essential patches associated with sloth bear occurrences,followed by sal and dry deciduous *** final habitat suitability model was highly accurate and had a very low out-of-bag(OOB)error *** high accuracy rate was also obtained using alternate validation ***:Human-dominated landscapes are characterized by expanding human populations,changing landuse patterns,and increasing habitat *** and degraded habitats constitute~40%of the landform in the buffer zone of the *** of the management implications may be identifying the highly suitable bear habitats in human-modified landscapes and integrating them with the existing conservation landscapes.

关键词： Bandhavgarh Melursus ursinus Multi-scale Habitat selection Random forest Sloth bear Species distribution models

Multi-scale habitat selection and impacts of climate change on the distribution of four sympatric meso-carnivores using random forest algorithm

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Ecological Processes 2020年第1期9卷 709-725页

Background:The habitat resources are structured across different spatial scales in the environment,and thus animals perceive and select habitat resources at different spatial *** to adopt the scale-dependent framework in species habitat relationships may lead to biased ***-scale species distribution models(SDMs)can thus improve the predictive ability as compared to single-scale *** study outlines the importance of multi-scale modeling in assessing the species habitat relationships and may provide a methodological framework using a robust algorithm to model and predict habitat suitability maps(HSMs)for similar multi-species and multi-scale ***:We used a supervised machine learning algorithm,random forest(RF),to assess the habitat relationships of Asiatic wildcat(Felis lybica ornata),jungle cat(Felis chaus),Indian fox(Vulpes bengalensis),and golden-jackal(Canis aureus)at ten spatial scales(500-5000 m)in human-dominated *** calculated out-of-bag(OOB)error rates of each predictor variable across ten scales to select the most influential spatial scale *** scale optimization(OOB rates)indicated that model performance was associated with variables at multiple spatial *** species occurrence tended to be related strongest to predictor variables at broader scales(5000 m).Multivariate RF models indicated landscape composition to be strong predictors of the Asiatic wildcat,jungle cat,and Indian fox *** the same time,topographic and climatic variables were the most important predictors determining the golden jackal *** models predicted range expansion in all four species under future climatic ***:Our results highlight the importance of using multiscale distribution models when predicting the distribution and species habitat *** wide adaptability of meso-carnivores allows them to persist in human-dominated regions and may even thrive in disturbed habi

关键词： Multiple-scale Multi-species Sympatric carnivores Species distribution modeling Bandhavgarh Climate change

Lead isotope signatures of Pb-Zn sulfide mineralization in the Reshian-Lamnian area of Azad Jammu and Kashmir,Pakistan

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal Of Geochemistry 2010年第1期29卷 65-74页

作者： Mohammad tahir Shah Tazeem Khan ahmad Khan National Centre of Excellence in Geology University of Peshawar Department of Earth Sciences University of Sargodha

The Reshian-Lamnian area within the Hazara-Kashmir syntaxis in Pakistan is composed mainly of the rocks of the Salkhala,Panjal and Murree *** metal sulfide mineralization in the form of sphalerite and galena with lesser amounts of chalcopyrite and pyrite is present within the Salkhala Formation of the study *** all these ore phases are homogeneous in *** Pb isotopic composition of galena from the area suggests that there is very little or negligible variation in the ratios of 206Pb/204Pb,207Pb/204Pb and 208Pb/*** ages ranging from 509 to 562 Ma and the μ values of 10.71 to 10.93 have been calculated for the studied Pb-Zn *** the basis of field features,mineralogy and Pb-isotope signatures,it is concluded that the Pb-Zn sulfide mineralization in the Reshian-Lamnia area is pre-Himalayan in age and can be correlated with the Cambro-Ordovician(Pan-African) orogenic event.

关键词：铅同位素组成铅锌硫化矿克什米尔巴基斯坦签名边境地区化学成分喜马拉雅