In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been st...In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.展开更多
The E-plane waveguide branch directional couplers are analyzed by a method which combines the multimode network theory with rigorous mode-matching approach. The electromagnetic field components are expanded by the sup...The E-plane waveguide branch directional couplers are analyzed by a method which combines the multimode network theory with rigorous mode-matching approach. The electromagnetic field components are expanded by the superposition of LSEx modes rather than TE and TM modes in the mode-matching procedure. Meanwhile, the electromagnetic problem is transferred into the network problem through the mode-matching treatment. It is shown that the present method has the advantages of simplicity and less computation without affecting the accuracy of the calculation.展开更多
Three dimensional(3D)echocardiogram enables cardiologists to visua-lize suspicious cardiac structures in detail.In recent years,this three-dimensional echocardiogram carries important clinical value in virtual surgica...Three dimensional(3D)echocardiogram enables cardiologists to visua-lize suspicious cardiac structures in detail.In recent years,this three-dimensional echocardiogram carries important clinical value in virtual surgical simulation.However,this 3D echocardiogram involves a trade-off difficulty between accu-racy and efficient computation in clinical diagnosis.This paper presents a novel Flip Directional 3D Volume Reconstruction(FD-3DVR)method for the recon-struction of echocardiogram images.The proposed method consists of two main steps:multiplanar volumetric imaging and 3D volume reconstruction.In the crea-tion of multiplanar volumetric imaging,two-dimensional(2D)image pixels are mapped into voxels of the volumetric grid.As the obtained slices are discontin-uous,there are some missing voxels in the volume data.To restore the structural and textural information of 3D ultrasound volume,the proposed method creates a volume pyramid in parallel with theflip directional texture pyramid.Initially,the nearest neighbors of missing voxels in the multiplanar volumetric imaging are identified by 3D ANN(Approximate Nearest Neighbor)patch matching method.Furthermore,aflip directional texture pyramid is proposed and aggregated with distance in patch matching tofind out the most similar neighbors.In the recon-struction step,structural and textural information obtained from differentflip angle directions can reconstruct 3D volume well with the desired accuracy.Com-pared with existing 3D reconstruction methods,the proposed Flip Directional 3D Volume Reconstruction(FD-3DVR)method provides superior performance for the mean peak signal-to-noise ratio(40.538 for the proposed method I and 39.626 for the proposed method II).Experimental results performed on the cardi-ac datasets demonstrate the efficiency of the proposed method for the reconstruc-tion of echocardiogram images.展开更多
针对工业机械设备实时监测中不可控因素导致的振动信号数据缺失问题,提出一种基于自适应二次临近项交替方向乘子算法(adaptive quadratic proximity-alternating direction method of multipliers, AQ-ADMM)的压缩感知缺失信号重构方法...针对工业机械设备实时监测中不可控因素导致的振动信号数据缺失问题,提出一种基于自适应二次临近项交替方向乘子算法(adaptive quadratic proximity-alternating direction method of multipliers, AQ-ADMM)的压缩感知缺失信号重构方法。AQ-ADMM算法在经典交替方向乘子算法算法迭代过程中添加二次临近项,且能够自适应选取惩罚参数。首先在数据中心建立信号参考数据库用于构造初始字典,然后将K-奇异值分解(K-singular value decomposition, K-SVD)字典学习算法和AQ-ADMM算法结合重构缺失信号。对仿真信号和两种真实轴承信号数据集添加高斯白噪声后作为样本,试验结果表明当信号压缩率在50%~70%时,所提方法性能指标明显优于其它传统方法,在重构信号的同时实现了对含缺失数据机械振动信号的快速精确修复。展开更多
背景:关节置换是治疗老年移位性股骨颈骨折的主要手段,全髋关节置换与半髋关节置换的选择是目前具有较大争论的焦点。目的:基于倾向性评分匹配法对比直接前入路下全髋与半髋关节置换治疗老年移位性股骨颈骨折的中远期生存状态。方法:选...背景:关节置换是治疗老年移位性股骨颈骨折的主要手段,全髋关节置换与半髋关节置换的选择是目前具有较大争论的焦点。目的:基于倾向性评分匹配法对比直接前入路下全髋与半髋关节置换治疗老年移位性股骨颈骨折的中远期生存状态。方法:选择2016年1月至2021年1月收治的147例老年移位性股骨颈骨折患者(≥65岁),其中88例行全髋关节置换,59例行人工股骨头置换(半髋关节置换)。对于患者术前合并症采用年龄校正Charlson合并症评分表,计算患者虚弱度,并采用倾向性评分匹配法对两组患者进行1∶1匹配,比较匹配后两组患者的手术时间、出血量、术后住院时间、住院费用、营养指标、术后并发症、死亡率和术后生存时间,其中术后生存时间采用Kaplan-Meier生存分析。结果与结论:①倾向性评分匹配后,两组共有42对匹配成功,匹配后两组患者术前资料均衡可比(P>0.05);②与半髋关节置换组相比,全髋关节置换组手术时间(79.71 min vs.59.07 min,P<0.001)、出血量(839.64 mL vs.597.83 mL,P=0.001)、住院费用(56508.15元vs.41702.85元,P<0.001)明显增加,但全髋关节置换组死亡率低于半髋关节置换组(36%vs.57%,HR=0.44,95%CI:0.23-0.87,P=0.018),平均生存时间长于半髋关节置换组(59.4个月vs.43.7个月,P=0.024);③两组患者在术后住院时间、术前术后营养指标、术后整体并发症发生率上,差异均无显著性意义(P>0.05);但在术后疼痛方面,半髋关节置换组疼痛发生率明显高于全髋关节置换组(24%vs.7%,P=0.035);④整体来看,全髋关节置换具有更好的长期预后生存效果,但对于身体素质差的患者则更适合行半髋关节置换;同时,术后的疼痛可能很大程度上会对患者髋关节置换后的生活质量及存活时间产生影响。展开更多
近年来,无人机因体积小、灵活性好等优势被广泛应用在车辆跟踪领域。当无人机在高空飞行时,其捕捉的图像中车辆目标存在像素点少、拥挤以及被遮挡的情况。现有的多目标跟踪研究方法在车辆被遮挡过程中发生非线性运动时,使用卡尔曼滤波预...近年来,无人机因体积小、灵活性好等优势被广泛应用在车辆跟踪领域。当无人机在高空飞行时,其捕捉的图像中车辆目标存在像素点少、拥挤以及被遮挡的情况。现有的多目标跟踪研究方法在车辆被遮挡过程中发生非线性运动时,使用卡尔曼滤波预测,会出现车辆位置预测不准确的问题。为了解决这些问题,采用先检测后跟踪(tracking by detection,TBD)范式,对YOLOv8检测算法进行改进,在网络结构中引入了BiFormer稀疏动态注意力模块,用于提取小目标特征信息。同时使用轻量级上采样算子CARAFE替换原最近邻插值上采样,减少上采样过程中小目标特征丢失的问题。提出一种轻量化跟踪模型FA-SORT,针对SORT算法提出三点改进:改进KF、添加速度方向一致性匹配和检测值匹配。在自制地组合了多个车辆数据集上验证改进的YOLOv8算法。实验结果表明,与YOLOv8相比,精确率(precision)提高了0.97%,召回率(recall)提高了0.898%。对所提出的FA-SORT算法使用UAVDT数据集进行验证,结果表明,与现有的多目标跟踪算法相比,HOTA指标首个达到70.05%,IDF1达到87.45%,跟踪速度达到29.93 FPS。验证了FA-SORT跟踪算法在多车辆跟踪任务中的优越性。展开更多
探讨如何优化营商环境以促进外商直接投资(foreign direct investment,FDI)的流入及FDI对企业创新具有怎样的影响对中国经济社会发展具有重大现实意义。基于组态视角,采用fsQCA和PSM研究方法,检验不同营商环境要素对FDI的组态效应,以及...探讨如何优化营商环境以促进外商直接投资(foreign direct investment,FDI)的流入及FDI对企业创新具有怎样的影响对中国经济社会发展具有重大现实意义。基于组态视角,采用fsQCA和PSM研究方法,检验不同营商环境要素对FDI的组态效应,以及不同营商环境组态对企业创新的影响。研究发现,单个营商环境要素不构成高FDI的必要条件,各要素相互结合以“殊途同归”的方式产生高FDI。产生高FDI的营商环境组态有创新环境主导型、市场-人文环境驱动型、市场-政务-创新环境驱动型和综合驱动型4条;产生非高FDI的营商环境组态有3条,概括为多要素抑制型和人文环境抑制型;产生高FDI的营商环境组态与产生非高FDI的营商环境组态呈现非对称性特征;东部发达地区营商环境组态引入的FDI能够促进当地企业创新,中部地区营商环境组态引入的FDI对当地企业创新影响存在差异性,西部地区营商环境组态引入的FDI抑制了当地企业创新。在“双循环”新发展格局背景下,基于组态视角为优化营商环境引入FDI及促进企业创新提供理论指导。展开更多
基金supported by the Foundation of Key Laboratory for Underwater Test & Control Technology under Grant No.9140C260201110C26
文摘In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.
文摘The E-plane waveguide branch directional couplers are analyzed by a method which combines the multimode network theory with rigorous mode-matching approach. The electromagnetic field components are expanded by the superposition of LSEx modes rather than TE and TM modes in the mode-matching procedure. Meanwhile, the electromagnetic problem is transferred into the network problem through the mode-matching treatment. It is shown that the present method has the advantages of simplicity and less computation without affecting the accuracy of the calculation.
文摘Three dimensional(3D)echocardiogram enables cardiologists to visua-lize suspicious cardiac structures in detail.In recent years,this three-dimensional echocardiogram carries important clinical value in virtual surgical simulation.However,this 3D echocardiogram involves a trade-off difficulty between accu-racy and efficient computation in clinical diagnosis.This paper presents a novel Flip Directional 3D Volume Reconstruction(FD-3DVR)method for the recon-struction of echocardiogram images.The proposed method consists of two main steps:multiplanar volumetric imaging and 3D volume reconstruction.In the crea-tion of multiplanar volumetric imaging,two-dimensional(2D)image pixels are mapped into voxels of the volumetric grid.As the obtained slices are discontin-uous,there are some missing voxels in the volume data.To restore the structural and textural information of 3D ultrasound volume,the proposed method creates a volume pyramid in parallel with theflip directional texture pyramid.Initially,the nearest neighbors of missing voxels in the multiplanar volumetric imaging are identified by 3D ANN(Approximate Nearest Neighbor)patch matching method.Furthermore,aflip directional texture pyramid is proposed and aggregated with distance in patch matching tofind out the most similar neighbors.In the recon-struction step,structural and textural information obtained from differentflip angle directions can reconstruct 3D volume well with the desired accuracy.Com-pared with existing 3D reconstruction methods,the proposed Flip Directional 3D Volume Reconstruction(FD-3DVR)method provides superior performance for the mean peak signal-to-noise ratio(40.538 for the proposed method I and 39.626 for the proposed method II).Experimental results performed on the cardi-ac datasets demonstrate the efficiency of the proposed method for the reconstruc-tion of echocardiogram images.
文摘针对工业机械设备实时监测中不可控因素导致的振动信号数据缺失问题,提出一种基于自适应二次临近项交替方向乘子算法(adaptive quadratic proximity-alternating direction method of multipliers, AQ-ADMM)的压缩感知缺失信号重构方法。AQ-ADMM算法在经典交替方向乘子算法算法迭代过程中添加二次临近项,且能够自适应选取惩罚参数。首先在数据中心建立信号参考数据库用于构造初始字典,然后将K-奇异值分解(K-singular value decomposition, K-SVD)字典学习算法和AQ-ADMM算法结合重构缺失信号。对仿真信号和两种真实轴承信号数据集添加高斯白噪声后作为样本,试验结果表明当信号压缩率在50%~70%时,所提方法性能指标明显优于其它传统方法,在重构信号的同时实现了对含缺失数据机械振动信号的快速精确修复。
文摘背景:关节置换是治疗老年移位性股骨颈骨折的主要手段,全髋关节置换与半髋关节置换的选择是目前具有较大争论的焦点。目的:基于倾向性评分匹配法对比直接前入路下全髋与半髋关节置换治疗老年移位性股骨颈骨折的中远期生存状态。方法:选择2016年1月至2021年1月收治的147例老年移位性股骨颈骨折患者(≥65岁),其中88例行全髋关节置换,59例行人工股骨头置换(半髋关节置换)。对于患者术前合并症采用年龄校正Charlson合并症评分表,计算患者虚弱度,并采用倾向性评分匹配法对两组患者进行1∶1匹配,比较匹配后两组患者的手术时间、出血量、术后住院时间、住院费用、营养指标、术后并发症、死亡率和术后生存时间,其中术后生存时间采用Kaplan-Meier生存分析。结果与结论:①倾向性评分匹配后,两组共有42对匹配成功,匹配后两组患者术前资料均衡可比(P>0.05);②与半髋关节置换组相比,全髋关节置换组手术时间(79.71 min vs.59.07 min,P<0.001)、出血量(839.64 mL vs.597.83 mL,P=0.001)、住院费用(56508.15元vs.41702.85元,P<0.001)明显增加,但全髋关节置换组死亡率低于半髋关节置换组(36%vs.57%,HR=0.44,95%CI:0.23-0.87,P=0.018),平均生存时间长于半髋关节置换组(59.4个月vs.43.7个月,P=0.024);③两组患者在术后住院时间、术前术后营养指标、术后整体并发症发生率上,差异均无显著性意义(P>0.05);但在术后疼痛方面,半髋关节置换组疼痛发生率明显高于全髋关节置换组(24%vs.7%,P=0.035);④整体来看,全髋关节置换具有更好的长期预后生存效果,但对于身体素质差的患者则更适合行半髋关节置换;同时,术后的疼痛可能很大程度上会对患者髋关节置换后的生活质量及存活时间产生影响。
文摘近年来,无人机因体积小、灵活性好等优势被广泛应用在车辆跟踪领域。当无人机在高空飞行时,其捕捉的图像中车辆目标存在像素点少、拥挤以及被遮挡的情况。现有的多目标跟踪研究方法在车辆被遮挡过程中发生非线性运动时,使用卡尔曼滤波预测,会出现车辆位置预测不准确的问题。为了解决这些问题,采用先检测后跟踪(tracking by detection,TBD)范式,对YOLOv8检测算法进行改进,在网络结构中引入了BiFormer稀疏动态注意力模块,用于提取小目标特征信息。同时使用轻量级上采样算子CARAFE替换原最近邻插值上采样,减少上采样过程中小目标特征丢失的问题。提出一种轻量化跟踪模型FA-SORT,针对SORT算法提出三点改进:改进KF、添加速度方向一致性匹配和检测值匹配。在自制地组合了多个车辆数据集上验证改进的YOLOv8算法。实验结果表明,与YOLOv8相比,精确率(precision)提高了0.97%,召回率(recall)提高了0.898%。对所提出的FA-SORT算法使用UAVDT数据集进行验证,结果表明,与现有的多目标跟踪算法相比,HOTA指标首个达到70.05%,IDF1达到87.45%,跟踪速度达到29.93 FPS。验证了FA-SORT跟踪算法在多车辆跟踪任务中的优越性。
文摘探讨如何优化营商环境以促进外商直接投资(foreign direct investment,FDI)的流入及FDI对企业创新具有怎样的影响对中国经济社会发展具有重大现实意义。基于组态视角,采用fsQCA和PSM研究方法,检验不同营商环境要素对FDI的组态效应,以及不同营商环境组态对企业创新的影响。研究发现,单个营商环境要素不构成高FDI的必要条件,各要素相互结合以“殊途同归”的方式产生高FDI。产生高FDI的营商环境组态有创新环境主导型、市场-人文环境驱动型、市场-政务-创新环境驱动型和综合驱动型4条;产生非高FDI的营商环境组态有3条,概括为多要素抑制型和人文环境抑制型;产生高FDI的营商环境组态与产生非高FDI的营商环境组态呈现非对称性特征;东部发达地区营商环境组态引入的FDI能够促进当地企业创新,中部地区营商环境组态引入的FDI对当地企业创新影响存在差异性,西部地区营商环境组态引入的FDI抑制了当地企业创新。在“双循环”新发展格局背景下,基于组态视角为优化营商环境引入FDI及促进企业创新提供理论指导。
