本文针对传统SURF(Speeded Up Robust Features)算法精度和速度较低的问题,提出一种优化的图像匹配算法.在特征点提取阶段引入局部二维熵来刻画特征点的独特性,通过计算特征点的局部二维熵并设置合适的阈值来剔除一部分误点;在匹配阶段...本文针对传统SURF(Speeded Up Robust Features)算法精度和速度较低的问题,提出一种优化的图像匹配算法.在特征点提取阶段引入局部二维熵来刻画特征点的独特性,通过计算特征点的局部二维熵并设置合适的阈值来剔除一部分误点;在匹配阶段用曼哈顿距离代替欧式距离,并引入最近邻和次近邻的概念,提取出模板图像中特征点与待匹配图像中特征点曼哈顿距离最近的前两个点,如果最近的距离除以次近的距离得到的比值小于设定的阈值T,则接受这一对匹配对,以此减少错误匹配.实验结果表明该算法优于传统算法,精度和速度均有一定程度的提高.展开更多
The shape parameter and scale parameter of generalized Pareto distribution are estimated by hybrid of genetic algorithm and pattern search.The volality of the return is obtained by GARCH model.VaR and CVaR are compute...The shape parameter and scale parameter of generalized Pareto distribution are estimated by hybrid of genetic algorithm and pattern search.The volality of the return is obtained by GARCH model.VaR and CVaR are computed respectively under GPD model and GARCH-GPD model.The experimental results show that VaR and CVaR based on GARCH-GPD are more effectively measure the financial risks.展开更多
GARCH model under the assumption of generalized error distribution(GED) is used to obtain the daily-volatility of log-return.The parameters are estimated by adaptive genetic algorithm.The tests of VaR and CVaR show th...GARCH model under the assumption of generalized error distribution(GED) is used to obtain the daily-volatility of log-return.The parameters are estimated by adaptive genetic algorithm.The tests of VaR and CVaR show that GARCH-GED model is valid for financial risk measure.展开更多
The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location an...The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location and large defects.The bending of energy band between AlGaN electron blocking layer and conduction layer obstructs transport of holes to multiple quantum wells.In this paper,we propose a gradual Al-composition p-type AlGaN(p-AlGaN)conduction layer to improve the light emitting properties of AlGaN-based DUV-LED.Increased carrier concentration in the active region enhances the effective radiative recombination rate of the LED.Consequently,the IQE of our optimazited DUV-LED is increased by 162%in comparison with conventional DUV-LEDs.展开更多
文摘本文针对传统SURF(Speeded Up Robust Features)算法精度和速度较低的问题,提出一种优化的图像匹配算法.在特征点提取阶段引入局部二维熵来刻画特征点的独特性,通过计算特征点的局部二维熵并设置合适的阈值来剔除一部分误点;在匹配阶段用曼哈顿距离代替欧式距离,并引入最近邻和次近邻的概念,提取出模板图像中特征点与待匹配图像中特征点曼哈顿距离最近的前两个点,如果最近的距离除以次近的距离得到的比值小于设定的阈值T,则接受这一对匹配对,以此减少错误匹配.实验结果表明该算法优于传统算法,精度和速度均有一定程度的提高.
文摘The shape parameter and scale parameter of generalized Pareto distribution are estimated by hybrid of genetic algorithm and pattern search.The volality of the return is obtained by GARCH model.VaR and CVaR are computed respectively under GPD model and GARCH-GPD model.The experimental results show that VaR and CVaR based on GARCH-GPD are more effectively measure the financial risks.
文摘GARCH model under the assumption of generalized error distribution(GED) is used to obtain the daily-volatility of log-return.The parameters are estimated by adaptive genetic algorithm.The tests of VaR and CVaR show that GARCH-GED model is valid for financial risk measure.
基金supported by the Key Research and Development Program of Shandong Province(Nos.2018GGX101027,2017GGX201002 and 2016GGX4101)the Union Funds of Guizhou Science and Technology Department and Guizhou Minzu University China(No.LH20157221)+1 种基金the Yantai“13th Five-Year”Marine Economic Innovation and Development Demonstration City Project(No.YHCXZB-L-201703)Fundamental Research Funds of Shandong University in China(Nos.2018WLJH87,2018JCG01 and 2017TB0021)。
文摘The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location and large defects.The bending of energy band between AlGaN electron blocking layer and conduction layer obstructs transport of holes to multiple quantum wells.In this paper,we propose a gradual Al-composition p-type AlGaN(p-AlGaN)conduction layer to improve the light emitting properties of AlGaN-based DUV-LED.Increased carrier concentration in the active region enhances the effective radiative recombination rate of the LED.Consequently,the IQE of our optimazited DUV-LED is increased by 162%in comparison with conventional DUV-LEDs.
