为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特...为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特征,构造三阶张量表示的阵列接收数据模型;接着,借鉴二维空间平滑算法的思想,在张量接收数据模型中构建三阶张量子阵块,再使该子阵块在张量域进行前向空间平滑,继而得到平滑后的张量协方差矩阵;最后,通过高阶奇异值分解(Higher-order Singular Value Decomposition,HOSVD)得到信号子空间,利用降维MUSIC算法对相干信号源的二维波达方向(Direction of Arrival,DOA)进行估计,并根据已经获得的DOA信息求解出相干信号的极化参数。仿真结果表明,在信噪比为0 dB以及快拍数为100的情况下,该算法的估计精度比空间平滑算法提高了约70%,成功分辨概率提高了约89%,且无需进行四维谱峰搜索,降低了算法的复杂度,对相干信号具有更高的估计精度和分辨能力。展开更多
目的探究体素内不相干运动成像定量参数联合超声评分法对产前前置胎盘伴胎盘植入的诊断价值。方法选取江苏省南通市妇幼保健院2017年3月至2021年9月收治的84例产前前置胎盘患者作为研究对象,所有受试者于孕35~38周时接受产前超声检查及...目的探究体素内不相干运动成像定量参数联合超声评分法对产前前置胎盘伴胎盘植入的诊断价值。方法选取江苏省南通市妇幼保健院2017年3月至2021年9月收治的84例产前前置胎盘患者作为研究对象,所有受试者于孕35~38周时接受产前超声检查及MRI检查,分析患者产前体素内不相干运动成像定量参数及超声评分,另以患者产后病理或手术观察结果为金标准,根据患者是否合并胎盘植入将其分为植入组和非植入组。比较两组体素内不相干运动成像定量参数及超声评分、妊娠结局,以受试者操作特征曲线评价体素内不相干运动成像定量参数及超声评分诊断产前前置胎盘伴胎盘植入的诊断效能。结果84例前置胎盘患者中伴有胎盘植入31例(36.47%)。植入组产后出血、出生后1 min Apgar评分≤7分占比高于非植入组(P<0.05)。植入组超声评分高于非植入组,灌注分数(f值)低于非植入组(P<0.05)。f值及超声评分单一及联合诊断产前前置胎盘伴胎盘植入的诊断灵敏度分别为77.42%、80.65%、87.09%,特异度分别为71.70%、71.70%、75.47%。结论体素内不相干运动成像定量参数及超声评分对产前前置胎盘伴胎盘植入均具有较高的临床诊断效能。展开更多
目的:探讨体素内不相干运动(IVIM)参数与直肠癌组织学类型、病理分级的相关性。方法:收集经病理证实的直肠普通腺癌29例(普通组)和黏液性腺癌12例(黏液组),术前行常规MR及10个b值(0、10、20、50、100、200、400、800、1200、2000 s/mm 2...目的:探讨体素内不相干运动(IVIM)参数与直肠癌组织学类型、病理分级的相关性。方法:收集经病理证实的直肠普通腺癌29例(普通组)和黏液性腺癌12例(黏液组),术前行常规MR及10个b值(0、10、20、50、100、200、400、800、1200、2000 s/mm 2)IVIM序列扫描,比较2组肿瘤实质区标准扩散系数(ADC)、真扩散系数(D)、假扩散系数(D*)、灌注分数(f值),采用受试者工作特征曲线(ROC)评价各参数诊断效能。结果:普通组标准ADC、D、f值均明显低于黏液性腺癌(P<0.01)。普通组不同病理分级病人间标准ADC、D、D*、f值差异均无统计学意义(P>0.05)。ROC曲线分析显示,标准ADC、D、f值鉴别诊断普通腺癌和黏液性腺癌的阈值、敏感性、特异性及ROC曲线下面积依次为0.998×10-3 mm 2/s、88.3%、55.7%、0.748,0.81×10-3 mm 2/s、91.7%、72.9%、0.814,43.00%、75.0%、72.9%、0.758。结论:IVIM参数能定量反映不同组织学类型直肠癌细胞密集度及灌注特征,其中以D值诊断与鉴别价值最佳,有助于术前预测和治疗方案制定。展开更多
The first generation coherence algorithm(namely C1 algorithm) is based on the statistical cross-correlation theory, which calculates the coherency of seismic data along both in-line and cross-line. The work, based on ...The first generation coherence algorithm(namely C1 algorithm) is based on the statistical cross-correlation theory, which calculates the coherency of seismic data along both in-line and cross-line. The work, based on texture technique, makes full use of seismic information in different directions and the difference of multi-traces, and proposes a novel methodology named the texture coherence algorithm for seismic reservoir characterization, for short TEC algorithm. Besides, in-line and cross-line directions, it also calculates seismic coherency in 45° and 135° directions deviating from in-line. First, we clearly propose an optimization method and a criterion which structure graylevel co-occurrence matrix parameters in TEC algorithm. Furthermore, the matrix to measure the difference between multi-traces is constructed by texture technique, resulting in horizontal constraints of texture coherence attribute. Compared with the C1 algorithm, the TEC algorithm based on graylevel matrix is of the feature that is multi-direction information fusion and keeps the simplicity and high speed, even it is of multi-trace horizontal constraint, leading to significantly improved resolution. The practical application of the TEC algorithm shows that the TEC attribute is superior to both the C1 attribute and amplitude attribute in identifying faults and channels, and it is as successful as the third generation coherence.展开更多
A time-domain frequencydependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference(im...A time-domain frequencydependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference(image interference)in preamble are separated by correlation and used to estimate I/Q imbalance parameters.After that, a Least Square(LS) estimation of compensation filter is obtained and adopted in the compensation structure. Two applications of the presented algorithm are discussed: we could either estimate the channel along with I/Q imbalance or estimate the imbalance parameter only to maintain a lower cost. Both applications are testified by simulation. The results show that the image interference is significantly suppressed even in poor SNR condition, and the computation cost of the algorithms is low.展开更多
As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the paramete...As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the parameter, connector rotating-π method, is proposed. With the method, the apex offset of a common connector end face is measured. The result is compared with that measured by a Norland 3000 fiber connector end face interferometer. It is found that the difference between two results is 1.8μm. Meantime, the influences of relevant error resources on apex offset measurement under rotating-π method and apex-core method are respectively analyzed, and two error equations are derived. The analytical result shows that, compared with apex-core method, if two additional sub-tilts of axis within and in the direction perpendicular to principal plane caused by its rotation are not bigger than the original axis tilt angle, the max. measurement error will then be reduced by at least 22.5% with rotating-π method. The practicability of the method is confirmed by the experiments.展开更多
We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through s...We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum.展开更多
For the diagnosis of glaucoma,optical coherence tomography(OCT)is a noninvasive imaging technique for the assessment of retinal layers.To accurately segment intraretinal layers in an optic nerve head(ONH)region,we pro...For the diagnosis of glaucoma,optical coherence tomography(OCT)is a noninvasive imaging technique for the assessment of retinal layers.To accurately segment intraretinal layers in an optic nerve head(ONH)region,we proposed an automatic method for the segmentation of three intraretinal layers in eye OCT scans centered on ONH.The internal limiting membrane,inner segment and outer segment,Bruch’s membrane surfaces under vascular shadows,and interaction of multiple high-reflectivity regions in the OCT image can be accurately segmented through this method.Then,we constructed a novel spatial-gradient continuity constraint,termed spatial-gradient continuity constraint,for the correction of discontinuity between adjacent image segmentation results.In our experiment,we randomly selected 20 B-scans,each annotated three retinal layers by experts.Signed distance errors of?0.80μm obtained through this method are lower than those obtained through the state-of-art method(?1.43μm).Meanwhile,the segmentation results can be used as bases for the diagnosis of glaucoma.展开更多
If a coherent perturbation field is used to couple the excited level of the coupling transition in the five-level K-type atom with another higher excited level, the two-photon electromagnetically induced transparency ...If a coherent perturbation field is used to couple the excited level of the coupling transition in the five-level K-type atom with another higher excited level, the two-photon electromagnetically induced transparency can be locally modulated by altering the parameters of the additional perturbation field. With different detunings of the coherent perturbation field, the absorption peak or transparency window with sharp and high-contrast speetrM feature can be generated in the two-photon absorption spectrum. The physical interpretation of these phenomena is given in terms of the dressed states.展开更多
文摘为了提高传统空间平滑算法对相干信号的估计精度,提出了一种张量域空间平滑多重信号分类(Multiple Signal Classification,MUSIC)解相干算法。首先,利用四元数的正交特性重新构造极化域导向矢量;其次,考虑阵列接收数据固有的多维结构特征,构造三阶张量表示的阵列接收数据模型;接着,借鉴二维空间平滑算法的思想,在张量接收数据模型中构建三阶张量子阵块,再使该子阵块在张量域进行前向空间平滑,继而得到平滑后的张量协方差矩阵;最后,通过高阶奇异值分解(Higher-order Singular Value Decomposition,HOSVD)得到信号子空间,利用降维MUSIC算法对相干信号源的二维波达方向(Direction of Arrival,DOA)进行估计,并根据已经获得的DOA信息求解出相干信号的极化参数。仿真结果表明,在信噪比为0 dB以及快拍数为100的情况下,该算法的估计精度比空间平滑算法提高了约70%,成功分辨概率提高了约89%,且无需进行四维谱峰搜索,降低了算法的复杂度,对相干信号具有更高的估计精度和分辨能力。
文摘目的探究体素内不相干运动成像定量参数联合超声评分法对产前前置胎盘伴胎盘植入的诊断价值。方法选取江苏省南通市妇幼保健院2017年3月至2021年9月收治的84例产前前置胎盘患者作为研究对象,所有受试者于孕35~38周时接受产前超声检查及MRI检查,分析患者产前体素内不相干运动成像定量参数及超声评分,另以患者产后病理或手术观察结果为金标准,根据患者是否合并胎盘植入将其分为植入组和非植入组。比较两组体素内不相干运动成像定量参数及超声评分、妊娠结局,以受试者操作特征曲线评价体素内不相干运动成像定量参数及超声评分诊断产前前置胎盘伴胎盘植入的诊断效能。结果84例前置胎盘患者中伴有胎盘植入31例(36.47%)。植入组产后出血、出生后1 min Apgar评分≤7分占比高于非植入组(P<0.05)。植入组超声评分高于非植入组,灌注分数(f值)低于非植入组(P<0.05)。f值及超声评分单一及联合诊断产前前置胎盘伴胎盘植入的诊断灵敏度分别为77.42%、80.65%、87.09%,特异度分别为71.70%、71.70%、75.47%。结论体素内不相干运动成像定量参数及超声评分对产前前置胎盘伴胎盘植入均具有较高的临床诊断效能。
文摘目的:探讨体素内不相干运动(IVIM)参数与直肠癌组织学类型、病理分级的相关性。方法:收集经病理证实的直肠普通腺癌29例(普通组)和黏液性腺癌12例(黏液组),术前行常规MR及10个b值(0、10、20、50、100、200、400、800、1200、2000 s/mm 2)IVIM序列扫描,比较2组肿瘤实质区标准扩散系数(ADC)、真扩散系数(D)、假扩散系数(D*)、灌注分数(f值),采用受试者工作特征曲线(ROC)评价各参数诊断效能。结果:普通组标准ADC、D、f值均明显低于黏液性腺癌(P<0.01)。普通组不同病理分级病人间标准ADC、D、D*、f值差异均无统计学意义(P>0.05)。ROC曲线分析显示,标准ADC、D、f值鉴别诊断普通腺癌和黏液性腺癌的阈值、敏感性、特异性及ROC曲线下面积依次为0.998×10-3 mm 2/s、88.3%、55.7%、0.748,0.81×10-3 mm 2/s、91.7%、72.9%、0.814,43.00%、75.0%、72.9%、0.758。结论:IVIM参数能定量反映不同组织学类型直肠癌细胞密集度及灌注特征,其中以D值诊断与鉴别价值最佳,有助于术前预测和治疗方案制定。
基金Project(2013CB228600)supported by the National Basic Research Program of ChinaProject(2011A-3606)supported by the CNPC "12.5" Program of China
文摘The first generation coherence algorithm(namely C1 algorithm) is based on the statistical cross-correlation theory, which calculates the coherency of seismic data along both in-line and cross-line. The work, based on texture technique, makes full use of seismic information in different directions and the difference of multi-traces, and proposes a novel methodology named the texture coherence algorithm for seismic reservoir characterization, for short TEC algorithm. Besides, in-line and cross-line directions, it also calculates seismic coherency in 45° and 135° directions deviating from in-line. First, we clearly propose an optimization method and a criterion which structure graylevel co-occurrence matrix parameters in TEC algorithm. Furthermore, the matrix to measure the difference between multi-traces is constructed by texture technique, resulting in horizontal constraints of texture coherence attribute. Compared with the C1 algorithm, the TEC algorithm based on graylevel matrix is of the feature that is multi-direction information fusion and keeps the simplicity and high speed, even it is of multi-trace horizontal constraint, leading to significantly improved resolution. The practical application of the TEC algorithm shows that the TEC attribute is superior to both the C1 attribute and amplitude attribute in identifying faults and channels, and it is as successful as the third generation coherence.
基金supported in part by the National High Technology Research and Development Program of China(863 Program)(No.2011AA010201)National Science and Technology Major Project(No.2013ZX03005010)+1 种基金the National Natural Science Foundation of China(NSFC)(No.61371103 and No.60902025)Key Science and Technology Program of Sichuan Province of China(No.2012FZ0119 and No.2012FZ0029)
文摘A time-domain frequencydependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference(image interference)in preamble are separated by correlation and used to estimate I/Q imbalance parameters.After that, a Least Square(LS) estimation of compensation filter is obtained and adopted in the compensation structure. Two applications of the presented algorithm are discussed: we could either estimate the channel along with I/Q imbalance or estimate the imbalance parameter only to maintain a lower cost. Both applications are testified by simulation. The results show that the image interference is significantly suppressed even in poor SNR condition, and the computation cost of the algorithms is low.
基金Research Projects of Nanjing University of Science and Technology
文摘As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the parameter, connector rotating-π method, is proposed. With the method, the apex offset of a common connector end face is measured. The result is compared with that measured by a Norland 3000 fiber connector end face interferometer. It is found that the difference between two results is 1.8μm. Meantime, the influences of relevant error resources on apex offset measurement under rotating-π method and apex-core method are respectively analyzed, and two error equations are derived. The analytical result shows that, compared with apex-core method, if two additional sub-tilts of axis within and in the direction perpendicular to principal plane caused by its rotation are not bigger than the original axis tilt angle, the max. measurement error will then be reduced by at least 22.5% with rotating-π method. The practicability of the method is confirmed by the experiments.
基金Supported by the Teaching and Research Foundation for the Outstanding Young Faculty of Southeast University
文摘We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum.
基金Projects(61672542,61573380)supported by the National Natural Science Foundation of China
文摘For the diagnosis of glaucoma,optical coherence tomography(OCT)is a noninvasive imaging technique for the assessment of retinal layers.To accurately segment intraretinal layers in an optic nerve head(ONH)region,we proposed an automatic method for the segmentation of three intraretinal layers in eye OCT scans centered on ONH.The internal limiting membrane,inner segment and outer segment,Bruch’s membrane surfaces under vascular shadows,and interaction of multiple high-reflectivity regions in the OCT image can be accurately segmented through this method.Then,we constructed a novel spatial-gradient continuity constraint,termed spatial-gradient continuity constraint,for the correction of discontinuity between adjacent image segmentation results.In our experiment,we randomly selected 20 B-scans,each annotated three retinal layers by experts.Signed distance errors of?0.80μm obtained through this method are lower than those obtained through the state-of-art method(?1.43μm).Meanwhile,the segmentation results can be used as bases for the diagnosis of glaucoma.
基金Supported by National Natural Science Foundation of China under Grant Nos.10775100 and 10974137
文摘If a coherent perturbation field is used to couple the excited level of the coupling transition in the five-level K-type atom with another higher excited level, the two-photon electromagnetically induced transparency can be locally modulated by altering the parameters of the additional perturbation field. With different detunings of the coherent perturbation field, the absorption peak or transparency window with sharp and high-contrast speetrM feature can be generated in the two-photon absorption spectrum. The physical interpretation of these phenomena is given in terms of the dressed states.