In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pear...In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pearl River Estuary （Delft3D） has been applied to the study of the physical hydrography of Hong Kong waters and its relationship with algal bloom transport patterns in the dry and wet seasons. The general 3D hydrodynamic circulation and salinity structure in the partially-mixed estuary are presented. Extensive numerical surface drogue tracking experiments are performed for algal blooms that are initiated in the Mirs Bay under different seasonal, wind and tidal conditions. The probability of bloom impact on the Victoria Harbour and nearby urban coastal waters is estimated. The computations show that： i） In the wet season （May - August）, algal blooms initiated in the Mirs Bay will move in a clockwise direction out of the bay, and be transported away from Hong Kong due to SW monsoon winds which drive the SW to NE coastal current; ii） In the dry season （November- April）, algal blooms initiated in the northeast Mirs Bay will move in an anti-clockwise direction and be carried away into southern waters due to the NE to SW coastal current driven by the NE monsoon winds; the bloom typically flows past the east edge of the Victoria Harbeur and nearby waters. Finally, the role of hydrodynamic transport in an important episodic event -- the spring 1998 massive red tide -- is quantitatively examined. It is shown that the strong NE to E wind during late March to early April, coupled with the diurnal tide at the beginning of April, significantly increased the probability of bloom transport into the Port Shelter and East Lamma Channel, resulting in the massive fish kill. The results provide a basis for risk assessment of harmful algal bloom （HAB） impact on urban coastal waters around the Victoria Habour.展开更多
加油锥套检测与跟踪是无人机自主空中加油得以实现的前提,提出一种锥套检测算法,通过添加人工标记,结合颜色通道相减的方法对锥套标记进行提取,利用最大类间方差法进行阈值分割,结合中值滤波、形态学操作完成锥套检测。对原始图像进行...加油锥套检测与跟踪是无人机自主空中加油得以实现的前提,提出一种锥套检测算法,通过添加人工标记,结合颜色通道相减的方法对锥套标记进行提取,利用最大类间方差法进行阈值分割,结合中值滤波、形态学操作完成锥套检测。对原始图像进行噪声、对比度、亮度干扰,验证检测算法的鲁棒性。在该检测算法的基础上,结合上一帧锥套的图像尺寸和锥套运动速度确定锥套的ROI(region of interest)区域,提出一种锥套跟踪算法,在ROI区域内完成对锥套的检测和定位。仿真实验结果表明,引入跟踪后,帧处理速度大大提高,能很好的满足实时性需求。展开更多
基金This study was supported by a Hong Kong Research Grants Council Group Research Project (RGC//HKU1/02C) ,and partially by a grantfromthe University Grants Committee of the Hong Kong Special Administrative Region,China(Project No. AoE/P-04/04 and P-04/02) tothe Area of Excellencein Marine Environment Research andInnovativeTechnology (MERIT)
文摘In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pearl River Estuary （Delft3D） has been applied to the study of the physical hydrography of Hong Kong waters and its relationship with algal bloom transport patterns in the dry and wet seasons. The general 3D hydrodynamic circulation and salinity structure in the partially-mixed estuary are presented. Extensive numerical surface drogue tracking experiments are performed for algal blooms that are initiated in the Mirs Bay under different seasonal, wind and tidal conditions. The probability of bloom impact on the Victoria Harbour and nearby urban coastal waters is estimated. The computations show that： i） In the wet season （May - August）, algal blooms initiated in the Mirs Bay will move in a clockwise direction out of the bay, and be transported away from Hong Kong due to SW monsoon winds which drive the SW to NE coastal current; ii） In the dry season （November- April）, algal blooms initiated in the northeast Mirs Bay will move in an anti-clockwise direction and be carried away into southern waters due to the NE to SW coastal current driven by the NE monsoon winds; the bloom typically flows past the east edge of the Victoria Harbeur and nearby waters. Finally, the role of hydrodynamic transport in an important episodic event -- the spring 1998 massive red tide -- is quantitatively examined. It is shown that the strong NE to E wind during late March to early April, coupled with the diurnal tide at the beginning of April, significantly increased the probability of bloom transport into the Port Shelter and East Lamma Channel, resulting in the massive fish kill. The results provide a basis for risk assessment of harmful algal bloom （HAB） impact on urban coastal waters around the Victoria Habour.
文摘加油锥套检测与跟踪是无人机自主空中加油得以实现的前提,提出一种锥套检测算法,通过添加人工标记,结合颜色通道相减的方法对锥套标记进行提取,利用最大类间方差法进行阈值分割,结合中值滤波、形态学操作完成锥套检测。对原始图像进行噪声、对比度、亮度干扰,验证检测算法的鲁棒性。在该检测算法的基础上,结合上一帧锥套的图像尺寸和锥套运动速度确定锥套的ROI(region of interest)区域,提出一种锥套跟踪算法,在ROI区域内完成对锥套的检测和定位。仿真实验结果表明,引入跟踪后,帧处理速度大大提高,能很好的满足实时性需求。
