Bangladesh is prone to severe flooding as being located at the confluence of three mighty rivers named the Ganges, Brahmaputra, and Meghna. As a consequence, river flooding and erosion are common natural disasters tha...Bangladesh is prone to severe flooding as being located at the confluence of three mighty rivers named the Ganges, Brahmaputra, and Meghna. As a consequence, river flooding and erosion are common natural disasters that severely affect the landscape, lives and economy of the country. Dharla River, one of the trans-boundary rivers originated in the Himalayas, along with Brahmaputra River has a great influence on the recurring floods and erosion in north-western Bangladesh. Almost in every year, excessive erosion and embankment damages caused by Dharla render a thousand of people homeless with massive loss of crops and poultries. As per the environmentalists, this is a matter of huge concern as development of accurate flood maps and erosion prediction for Dharla River has been very challenging. In this study, the flood map and Dharla River bank shifting study have been developed by using HEC-RAS 4.1.0 hydrodynamic model and Landsat satellite images. In addition, the HEC-GeoRAS was used to establish the river reach for HEC-RAS. The calibration and validation have been performed using the observed and simulated water levels for the years of 2013 and 2014 respectively. The HEC-RAS flood water level output was used in HEC-GeoRAS for raster interpolation followed by overlain onto the land surface elevation of the study area. Then, the difference between water level interpolation and land elevation surfaces has been considered as a depth of inundation which is performed in Arc-Map 10.2. Flood maps have been generated for the years 2010, 2013, and 2014 for highest water level of each year. The erosion prone areas have been indicated by analyzing bank shifting of Dharla River for the years 1987, 1997, 2007, and 2017 by digitizing the satellite images in Arc-GIS 10.2. From the observation it has been found that the course of the Dharla River has been shifted vastly since 1987 to 2017 due to erosion.展开更多
文摘Bangladesh is prone to severe flooding as being located at the confluence of three mighty rivers named the Ganges, Brahmaputra, and Meghna. As a consequence, river flooding and erosion are common natural disasters that severely affect the landscape, lives and economy of the country. Dharla River, one of the trans-boundary rivers originated in the Himalayas, along with Brahmaputra River has a great influence on the recurring floods and erosion in north-western Bangladesh. Almost in every year, excessive erosion and embankment damages caused by Dharla render a thousand of people homeless with massive loss of crops and poultries. As per the environmentalists, this is a matter of huge concern as development of accurate flood maps and erosion prediction for Dharla River has been very challenging. In this study, the flood map and Dharla River bank shifting study have been developed by using HEC-RAS 4.1.0 hydrodynamic model and Landsat satellite images. In addition, the HEC-GeoRAS was used to establish the river reach for HEC-RAS. The calibration and validation have been performed using the observed and simulated water levels for the years of 2013 and 2014 respectively. The HEC-RAS flood water level output was used in HEC-GeoRAS for raster interpolation followed by overlain onto the land surface elevation of the study area. Then, the difference between water level interpolation and land elevation surfaces has been considered as a depth of inundation which is performed in Arc-Map 10.2. Flood maps have been generated for the years 2010, 2013, and 2014 for highest water level of each year. The erosion prone areas have been indicated by analyzing bank shifting of Dharla River for the years 1987, 1997, 2007, and 2017 by digitizing the satellite images in Arc-GIS 10.2. From the observation it has been found that the course of the Dharla River has been shifted vastly since 1987 to 2017 due to erosion.
文摘嵌入式多核结构的共享资源冲突是硬实时任务最差情况执行时间(worst-case execution time,WCET)估算的难点,而且通过减少共享资源冲突延迟的估算可以减少硬实时任务的WCET估算值,提高硬实时任务的可调度性。针对带有冲突感知总线(interference-aware bus arbiter,IABA)的嵌入式多核结构,提出了一种基于bank-column缓存划分的访存请求冲突延迟上限优化方法,根据bank冲突次数和冲突延迟上限的关系,该方法通过优化bank到核映射来减少bank冲突发生次数,从而减小冲突延迟上限和WCET估算值。实验结果表明,与现有冲突延迟上限界定方法相比,提出的方法能减少约29%的WCET估算值。
