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Forest cover dynamics in Palas Valley Kohistan, Hindu Kush-Himalayan Mountains, Pakistan 被引量:1
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作者 Noor ul HAQ Fazlur RAHMAN +1 位作者 Iffat TABASSUM mehran 《Journal of Mountain Science》 SCIE CSCD 2021年第2期416-426,共11页
Forest cover change in the mountainous region is driven by a variety of anthropogenic and natural factors.The Hindu Kush-Himalayan Mountains has experienced a considerable vegetation cover change due to intensive huma... Forest cover change in the mountainous region is driven by a variety of anthropogenic and natural factors.The Hindu Kush-Himalayan Mountains has experienced a considerable vegetation cover change due to intensive human activities,such as population growth,proximate causes,accessibility,unstable political situations,government policy failure and poverty.The present study seeks to find out the impact of population growth and road network expansion on forest cover of Palas valley based on remotely sensed data and employing geospatial techniques.Changes in forest cover were determined by classifying time-series satellite images of Landsat and Sentinel 2 A.The images of October 1980,2000,2010 and 2017 were classified into six land cover classes and then the impact of population growth and accessibility on forest cover was analyzed.Furthermore,forest cover and land-use change detection map was prepared using classified images of 1980 and 2017.The data were collected mainly from field visits(ground verification),census reports,Communication and Works Department,Kohistan.Satellite imageries were obtained from the United States Geological Survey’s websites and classified in ERDAS imagine 2014 and ESRI ArcGIS 10.2.1 using supervised classification-maximum likelihood algorithm.Result of this study revealed that a substantial reduction in forest cover has taken place mainly in the proximity of human settlements.On the average,during the study period,annually more than 460 hectares of forest area has been converted into other uses. 展开更多
关键词 Forest cover changes Population growth Road networks DEFORESTATION Palas Valley Pakistan
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角膜微切刀辅助的角膜内人工角膜植入的机械稳定性
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作者 Melanie H. +13 位作者 Erb mehran Taban Charles A. Barsam Paula M. Sweet Roy S. Chuck 许珂(译) 李子良(校) 《美国医学会眼科杂志(中文版)》 2005年第3期F0003-F0003,共1页
目的:建立一种实验室模型来研究角膜内人工角膜植入术。方法:用一种联合角膜微切刀和人工前房的系统在13例成人角膜中开发一种带蒂角膜板层切除术。掀开角膜瓣后.对角膜后基质层行2.5或3mm的环钻。一个模型人工角膜定位于植床。角... 目的:建立一种实验室模型来研究角膜内人工角膜植入术。方法:用一种联合角膜微切刀和人工前房的系统在13例成人角膜中开发一种带蒂角膜板层切除术。掀开角膜瓣后.对角膜后基质层行2.5或3mm的环钻。一个模型人工角膜定位于植床。角膜瓣用缝线闭合。增加前房内压,伤口漏水时的压力被记录。对前部角膜板层行3或3.5mm的环钻用于暴露人工角膜。漏水时的压力再次确定。 展开更多
关键词 人工角膜植入术 机械稳定性 角膜板层切除术 人工前房 室模型 角膜瓣 人角膜 角膜后 膜定位
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