为进一步提高压缩感知重构算法的重构成功率和重构精度,从原子匹配准则和预选阶段原子选择方式的角度出发,提出一种基于Dice系数的弱选择回溯匹配追踪(weak-selection backtracking matching pursuit based on Dice coefficient,DWBMP)...为进一步提高压缩感知重构算法的重构成功率和重构精度,从原子匹配准则和预选阶段原子选择方式的角度出发,提出一种基于Dice系数的弱选择回溯匹配追踪(weak-selection backtracking matching pursuit based on Dice coefficient,DWBMP)算法.首先,采用Dice系数匹配准则度量两个向量之间的相似性,选出最匹配的原子,以优化支撑集;然后,结合回溯思想和弱选择思想剔除相似性较小的原子,完成预选阶段原子的二次筛选.MATLAB仿真结果显示,相同条件下,DWBMP算法较经典的压缩感知重构算法具有更优的重构精度和重构成功率.展开更多
Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the...Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.展开更多
In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship...In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship of candidate sequences in the PTS method under the interleaved partition method, it has been discovered that some candidate sequences generated by phase factor sequences have the same peak average power ratio（PAPR）. Hence, phase factor sequences can be optimized to reduce their searching times. Then, the computational process of generating candidate sequences can be simplified by improving the utilization of data and minimizing the calculations of complex multiplication. The performance analysis shows that, compared with the conventional PTS scheme, the proposed approach significantly decreases the computational complexity and has no loss of PAPR performance.展开更多
2024年2月20日06:00—21日08:00(北京时)京津冀地区发生一次伴随对流的暴雪天气,造成河北中南部极端暴雪,过程最大降水量为25.6 mm。利用京津冀176个国家气象观测站降水资料,雷达、卫星等多源观测资料,结合ERA5再分析资料对此次过程进...2024年2月20日06:00—21日08:00(北京时)京津冀地区发生一次伴随对流的暴雪天气,造成河北中南部极端暴雪,过程最大降水量为25.6 mm。利用京津冀176个国家气象观测站降水资料,雷达、卫星等多源观测资料,结合ERA5再分析资料对此次过程进行诊断分析。结果表明:此次过程是地面冷高压扩散南下携带冷空气经东北平原转向从渤海湾进入华北地区形成的回流暴雪过程。500~700 h Pa异常偏强的偏南风为京津冀地区暴雪提供充足水汽。极端暴雪发生在强切变、低对流有效位能环境,150 m~4 km高度的垂直风切变超过35 m·s^(-1),600~750 h Pa冷锋锋面存在条件对称不稳定层结,锋面次级环流在逆温层之上导致条件对称不稳定能量释放,形成高架对流,产生雷电、短时强降雪天气。展开更多
为提升欠定盲源分离问题中混合矩阵的估计精度,在噪声环境下基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法的基础上,提出一种自适应确定输入参数的DBSCAN算法(adaptive DBSCAN,A-DBSCAN...为提升欠定盲源分离问题中混合矩阵的估计精度,在噪声环境下基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法的基础上,提出一种自适应确定输入参数的DBSCAN算法(adaptive DBSCAN,A-DBSCAN)用于混合矩阵估计。针对DBSCAN算法邻域半径(Eps)及邻域点数(MinPts)依赖人为设定的问题,首先利用曲线拟合方法得出Eps,然后通过分析聚类输出类别数与噪声点数关系确定MinPts,并将其与混合矩阵估计模型相结合,最后通过最短路径算法实现源信号恢复。实验结果表明,提出的算法在估计混合矩阵和恢复源信号时,相关性能与对比算法相较均有明显提升。展开更多
文摘为进一步提高压缩感知重构算法的重构成功率和重构精度,从原子匹配准则和预选阶段原子选择方式的角度出发,提出一种基于Dice系数的弱选择回溯匹配追踪(weak-selection backtracking matching pursuit based on Dice coefficient,DWBMP)算法.首先,采用Dice系数匹配准则度量两个向量之间的相似性,选出最匹配的原子,以优化支撑集;然后,结合回溯思想和弱选择思想剔除相似性较小的原子,完成预选阶段原子的二次筛选.MATLAB仿真结果显示,相同条件下,DWBMP算法较经典的压缩感知重构算法具有更优的重构精度和重构成功率.
基金Project(51974278)supported by the National Natural Science Foundation of ChinaProject(E2018203446)supported by the Natural Science Foundation of Hebei Province Distinguished Young Fund Project,ChinaProject(2018YFA0707303)supported by the National Key Research and Development Project of China。
文摘Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.
基金supported by the National Natural Science Foundation of China(6167309361370152)the Science and Technology Project of Shenyang(F16-205-1-01)
文摘In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship of candidate sequences in the PTS method under the interleaved partition method, it has been discovered that some candidate sequences generated by phase factor sequences have the same peak average power ratio（PAPR）. Hence, phase factor sequences can be optimized to reduce their searching times. Then, the computational process of generating candidate sequences can be simplified by improving the utilization of data and minimizing the calculations of complex multiplication. The performance analysis shows that, compared with the conventional PTS scheme, the proposed approach significantly decreases the computational complexity and has no loss of PAPR performance.
文摘2024年2月20日06:00—21日08:00(北京时)京津冀地区发生一次伴随对流的暴雪天气,造成河北中南部极端暴雪,过程最大降水量为25.6 mm。利用京津冀176个国家气象观测站降水资料,雷达、卫星等多源观测资料,结合ERA5再分析资料对此次过程进行诊断分析。结果表明:此次过程是地面冷高压扩散南下携带冷空气经东北平原转向从渤海湾进入华北地区形成的回流暴雪过程。500~700 h Pa异常偏强的偏南风为京津冀地区暴雪提供充足水汽。极端暴雪发生在强切变、低对流有效位能环境,150 m~4 km高度的垂直风切变超过35 m·s^(-1),600~750 h Pa冷锋锋面存在条件对称不稳定层结,锋面次级环流在逆温层之上导致条件对称不稳定能量释放,形成高架对流,产生雷电、短时强降雪天气。
文摘为提升欠定盲源分离问题中混合矩阵的估计精度,在噪声环境下基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法的基础上,提出一种自适应确定输入参数的DBSCAN算法(adaptive DBSCAN,A-DBSCAN)用于混合矩阵估计。针对DBSCAN算法邻域半径(Eps)及邻域点数(MinPts)依赖人为设定的问题,首先利用曲线拟合方法得出Eps,然后通过分析聚类输出类别数与噪声点数关系确定MinPts,并将其与混合矩阵估计模型相结合,最后通过最短路径算法实现源信号恢复。实验结果表明,提出的算法在估计混合矩阵和恢复源信号时,相关性能与对比算法相较均有明显提升。
