Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the perf...Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the performance of direct-path signal is important to system performance for this type of radar. While the Signal to Noise Ratio (SNR) of direct-path signal is low, it will deteriorate the detection performance. In this paper, how SNR of direct-path signal induces degradation on the SNR of CAF, and how the integration gain affects by integration time are analyzed, both with theoretical analysis and numerical simulation, which are valuable for the R&D of passive radar.展开更多
Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modula...Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modulated.The experiment results show that the signal to noise ratio has been improved by 32.64 dB when the modulation depth(converted to laser frequency)and frequency are optimized to 4 MHz and 6 kHz,respectively.This technique enables us to perform a highly sensitive non-destructive detection of Rydberg atoms.展开更多
为了解决红外制导研究中舰船图像样本数量不足的问题,提出一种面向舰船图像的改进的生成对抗网络(generative adversarial network,GAN),能够生成高质量的红外图像。首先转换可见光图像颜色空间以更好地捕捉夜间低亮度下图像的轮廓信息...为了解决红外制导研究中舰船图像样本数量不足的问题,提出一种面向舰船图像的改进的生成对抗网络(generative adversarial network,GAN),能够生成高质量的红外图像。首先转换可见光图像颜色空间以更好地捕捉夜间低亮度下图像的轮廓信息,然后引入残差块生成网络降低低像素的可见光图像对生成的红外图像的影响并加深网络层数以更好地学习深层映射关系,最后引入更平滑的损失函数加快收敛速度,提高生成红外图像目标边缘清晰程度。在制作的无人机拍摄的红外可见光配对的数据集进行测试,改进后的方法平均生成图像峰值信噪比(peak signal to noiseratio,PSNR)提升20.3%,结构相似性度量(structural similarity,SSIM)提升30.4%。结果表明改进的网络可以生成质量更高的红外仿真图像,用于目标检测等任务有更好的效果。展开更多
空时自适应处理(Space-Time Adaptive Processing,STAP)技术可以实现对机载雷达杂波的有效抑制,显著提高机载雷达对运动目标的检测性能。但在实际工程应用过程中,STAP技术不可避免地会受到各种空时误差的影响,导致其性能严重下降。本文...空时自适应处理(Space-Time Adaptive Processing,STAP)技术可以实现对机载雷达杂波的有效抑制,显著提高机载雷达对运动目标的检测性能。但在实际工程应用过程中,STAP技术不可避免地会受到各种空时误差的影响,导致其性能严重下降。本文首先给出了各种空时误差的数学模型,然后从目标导向矢量失配和杂波自由度增加两方面系统分析了误差影响STAP性能的内在机理,并以信杂噪比(Signal to Clutter plus Noise Ratio,SCNR)损失为指标分析了不同误差对STAP性能的影响,最后通过仿真实验对相关分析进行了验证。本文工作量化了不同误差对STAP性能的影响程度,可为机载脉冲多普勒雷达空时误差补偿提供重要的理论支撑。展开更多
目的评价同反相位成像在胶质瘤分级中的诊断价值。材料与方法回顾性分析74例经病理证实的胶质瘤患者的病例资料,术前行MR同反相位增强成像,在同反相位图像上计算胶质瘤实体部分信号下降比率(signal loss ratio,SLR),比较高级别胶质瘤(hi...目的评价同反相位成像在胶质瘤分级中的诊断价值。材料与方法回顾性分析74例经病理证实的胶质瘤患者的病例资料,术前行MR同反相位增强成像,在同反相位图像上计算胶质瘤实体部分信号下降比率(signal loss ratio,SLR),比较高级别胶质瘤(high grade glioma,HGG)和低级别胶质瘤(low grade glioma,LGG)SLR的差异,并利用受试者工作特征(receiver operating characteristic,ROC)曲线评价SLR值的分级效能。结果HGG的SLR值高于LGG,差异具有统计学意义(P<0.05),SLR鉴别HGG和LGG的曲线下面积(area under the curve,AUC)值为0.895。结论同反相位成像能帮助进行胶质瘤的分级,且简便易行,具有很好的临床实用价值。展开更多
文摘Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the performance of direct-path signal is important to system performance for this type of radar. While the Signal to Noise Ratio (SNR) of direct-path signal is low, it will deteriorate the detection performance. In this paper, how SNR of direct-path signal induces degradation on the SNR of CAF, and how the integration gain affects by integration time are analyzed, both with theoretical analysis and numerical simulation, which are valuable for the R&D of passive radar.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304203 and 2016YFF0200104)the National Natural Science Foundation of China(Grant Nos.61505099,61827824,91536110,and 61975104)the Fund for Shanxi ‘1331 Project’ Key Subjects Construction,Bairen Project of Shanxi Province,China
文摘Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modulated.The experiment results show that the signal to noise ratio has been improved by 32.64 dB when the modulation depth(converted to laser frequency)and frequency are optimized to 4 MHz and 6 kHz,respectively.This technique enables us to perform a highly sensitive non-destructive detection of Rydberg atoms.
文摘为了解决红外制导研究中舰船图像样本数量不足的问题,提出一种面向舰船图像的改进的生成对抗网络(generative adversarial network,GAN),能够生成高质量的红外图像。首先转换可见光图像颜色空间以更好地捕捉夜间低亮度下图像的轮廓信息,然后引入残差块生成网络降低低像素的可见光图像对生成的红外图像的影响并加深网络层数以更好地学习深层映射关系,最后引入更平滑的损失函数加快收敛速度,提高生成红外图像目标边缘清晰程度。在制作的无人机拍摄的红外可见光配对的数据集进行测试,改进后的方法平均生成图像峰值信噪比(peak signal to noiseratio,PSNR)提升20.3%,结构相似性度量(structural similarity,SSIM)提升30.4%。结果表明改进的网络可以生成质量更高的红外仿真图像,用于目标检测等任务有更好的效果。
文摘空时自适应处理(Space-Time Adaptive Processing,STAP)技术可以实现对机载雷达杂波的有效抑制,显著提高机载雷达对运动目标的检测性能。但在实际工程应用过程中,STAP技术不可避免地会受到各种空时误差的影响,导致其性能严重下降。本文首先给出了各种空时误差的数学模型,然后从目标导向矢量失配和杂波自由度增加两方面系统分析了误差影响STAP性能的内在机理,并以信杂噪比(Signal to Clutter plus Noise Ratio,SCNR)损失为指标分析了不同误差对STAP性能的影响,最后通过仿真实验对相关分析进行了验证。本文工作量化了不同误差对STAP性能的影响程度,可为机载脉冲多普勒雷达空时误差补偿提供重要的理论支撑。
文摘目的评价同反相位成像在胶质瘤分级中的诊断价值。材料与方法回顾性分析74例经病理证实的胶质瘤患者的病例资料,术前行MR同反相位增强成像,在同反相位图像上计算胶质瘤实体部分信号下降比率(signal loss ratio,SLR),比较高级别胶质瘤(high grade glioma,HGG)和低级别胶质瘤(low grade glioma,LGG)SLR的差异,并利用受试者工作特征(receiver operating characteristic,ROC)曲线评价SLR值的分级效能。结果HGG的SLR值高于LGG,差异具有统计学意义(P<0.05),SLR鉴别HGG和LGG的曲线下面积(area under the curve,AUC)值为0.895。结论同反相位成像能帮助进行胶质瘤的分级,且简便易行,具有很好的临床实用价值。
