This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved ...This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient （CG） algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.展开更多
Image fusion based on the sparse representation(SR)has become the primary research direction of the transform domain method.However,the SR-based image fusion algorithm has the characteristics of high computational com...Image fusion based on the sparse representation(SR)has become the primary research direction of the transform domain method.However,the SR-based image fusion algorithm has the characteristics of high computational complexity and neglecting the local features of an image,resulting in limited image detail retention and a high registration misalignment sensitivity.In order to overcome these shortcomings and the noise existing in the image of the fusion process,this paper proposes a new signal decomposition model,namely the multi-source image fusion algorithm of the gradient regularization convolution SR(CSR).The main innovation of this work is using the sparse optimization function to perform two-scale decomposition of the source image to obtain high-frequency components and low-frequency components.The sparse coefficient is obtained by the gradient regularization CSR model,and the sparse coefficient is taken as the maximum value to get the optimal high frequency component of the fused image.The best low frequency component is obtained by using the fusion strategy of the extreme or the average value.The final fused image is obtained by adding two optimal components.Experimental results demonstrate that this method greatly improves the ability to maintain image details and reduces image registration sensitivity.展开更多
Histogram of collinear gradient-enhanced coding （HCGEC）, a robust key point descriptor for multi-spectral image matching, is proposed. The HCGEC mainly encodes rough structures within an image and suppresses detaile...Histogram of collinear gradient-enhanced coding （HCGEC）, a robust key point descriptor for multi-spectral image matching, is proposed. The HCGEC mainly encodes rough structures within an image and suppresses detailed textural information, which is desirable in multi-spectral image matching. Experiments on two multi-spectral data sets demonstrate that the proposed descriptor can yield significantly better results than some state-of- the-art descriptors.展开更多
The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodica...The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodically time-varying mesh stiffness, the nonlinear tooth backlash, the lump-parameter model of the gear system is developed with one rotational and two translational freedoms of each gear. The eigen-values and eigenvectors are derived and analyzed on the basis of the real modal theory. The sensitivities of natural frequencies to design parameters including supporting and meshing stiffnesses, gear masses, and moments of inertia by the direct differential method are also calculated. The results show the quantitative and qualitative impact of the parameters to the natural characteristics of the gear system. Furthermore, the periodic steady state solutions are obtained by the numerical approach based on the nonlinear model. These results are employed to gain insights into the primary controlling parameters, to forecast the severity of the dynamic response, and to assess the acceptability of the gear design.展开更多
目的突发感音神经性耳聋是耳科急症之一,常诱发焦虑-抑郁样情绪障碍,但是突发感音神经性耳聋如何促进情绪障碍的发生尚不清楚。本研究利用脑功能梯度技术探索突发感音神经性耳聋与情绪障碍的关系。材料与方法我们对44名突发感音神经性...目的突发感音神经性耳聋是耳科急症之一,常诱发焦虑-抑郁样情绪障碍,但是突发感音神经性耳聋如何促进情绪障碍的发生尚不清楚。本研究利用脑功能梯度技术探索突发感音神经性耳聋与情绪障碍的关系。材料与方法我们对44名突发感音神经性耳聋患者和40名健康对照组的听力、多维度神经功能及静息状态脑功能梯度进行了评估。采用脑功能连接梯度来识别双侧突发感音神经性耳聋引起的大脑皮层连接梯度的变化。采用统计参数图软件包(statistical parametric mapping 12,SPM12)处理功能磁共振成像(functional magnetic resonance imaging,fMRI)数据,采用社会科学统计软件包(statistical package for the social sciences 22.0,SPSS 22.0)计算fMRI数据与焦虑-抑郁样情绪障碍评分的皮尔森相关性。结果患者与健康对照在年龄、性别和受教育程度上匹配良好。患者组两耳的平均听阈明显高于健康对照组,且突发感音神经性耳聋患者的焦虑和抑郁评分显著增高。结果显示两组间的主梯度没有显著差异。在网络水平,突发感音神经性耳聋在初级梯度上差异无统计学意义,但在节点水平,患者左侧楔前叶的梯度值显著高于健康对照组,而左侧、右侧距状裂周围皮层,右侧海马旁回及左内侧额上回的主梯度值显著低于健康对照组(P<0.001)。突发感音神经性耳聋患者的右侧距状裂周围皮层梯度值与焦虑自评量表得分呈负相关(r=-0.413,P=0.005)。结论突发感音神经性耳聋患者脑区的功能梯度变化有助于阐明突发感音神经性耳聋患者出现情绪障碍的神经病理学基础。展开更多
基金supported partly by the State Key Program of National Natural Science Foundation of China(60632020)the Youth Science Foundation of University of Electronic Science and Technology of China(JX0823).
文摘This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient （CG） algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.
基金the National Natural Science Foundation of China(61671383)Shaanxi Key Industry Innovation Chain Project(2018ZDCXL-G-12-2,2019ZDLGY14-02-02,2019ZDLGY14-02-03).
文摘Image fusion based on the sparse representation(SR)has become the primary research direction of the transform domain method.However,the SR-based image fusion algorithm has the characteristics of high computational complexity and neglecting the local features of an image,resulting in limited image detail retention and a high registration misalignment sensitivity.In order to overcome these shortcomings and the noise existing in the image of the fusion process,this paper proposes a new signal decomposition model,namely the multi-source image fusion algorithm of the gradient regularization convolution SR(CSR).The main innovation of this work is using the sparse optimization function to perform two-scale decomposition of the source image to obtain high-frequency components and low-frequency components.The sparse coefficient is obtained by the gradient regularization CSR model,and the sparse coefficient is taken as the maximum value to get the optimal high frequency component of the fused image.The best low frequency component is obtained by using the fusion strategy of the extreme or the average value.The final fused image is obtained by adding two optimal components.Experimental results demonstrate that this method greatly improves the ability to maintain image details and reduces image registration sensitivity.
文摘Histogram of collinear gradient-enhanced coding （HCGEC）, a robust key point descriptor for multi-spectral image matching, is proposed. The HCGEC mainly encodes rough structures within an image and suppresses detailed textural information, which is desirable in multi-spectral image matching. Experiments on two multi-spectral data sets demonstrate that the proposed descriptor can yield significantly better results than some state-of- the-art descriptors.
文摘The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodically time-varying mesh stiffness, the nonlinear tooth backlash, the lump-parameter model of the gear system is developed with one rotational and two translational freedoms of each gear. The eigen-values and eigenvectors are derived and analyzed on the basis of the real modal theory. The sensitivities of natural frequencies to design parameters including supporting and meshing stiffnesses, gear masses, and moments of inertia by the direct differential method are also calculated. The results show the quantitative and qualitative impact of the parameters to the natural characteristics of the gear system. Furthermore, the periodic steady state solutions are obtained by the numerical approach based on the nonlinear model. These results are employed to gain insights into the primary controlling parameters, to forecast the severity of the dynamic response, and to assess the acceptability of the gear design.
文摘目的突发感音神经性耳聋是耳科急症之一,常诱发焦虑-抑郁样情绪障碍,但是突发感音神经性耳聋如何促进情绪障碍的发生尚不清楚。本研究利用脑功能梯度技术探索突发感音神经性耳聋与情绪障碍的关系。材料与方法我们对44名突发感音神经性耳聋患者和40名健康对照组的听力、多维度神经功能及静息状态脑功能梯度进行了评估。采用脑功能连接梯度来识别双侧突发感音神经性耳聋引起的大脑皮层连接梯度的变化。采用统计参数图软件包(statistical parametric mapping 12,SPM12)处理功能磁共振成像(functional magnetic resonance imaging,fMRI)数据,采用社会科学统计软件包(statistical package for the social sciences 22.0,SPSS 22.0)计算fMRI数据与焦虑-抑郁样情绪障碍评分的皮尔森相关性。结果患者与健康对照在年龄、性别和受教育程度上匹配良好。患者组两耳的平均听阈明显高于健康对照组,且突发感音神经性耳聋患者的焦虑和抑郁评分显著增高。结果显示两组间的主梯度没有显著差异。在网络水平,突发感音神经性耳聋在初级梯度上差异无统计学意义,但在节点水平,患者左侧楔前叶的梯度值显著高于健康对照组,而左侧、右侧距状裂周围皮层,右侧海马旁回及左内侧额上回的主梯度值显著低于健康对照组(P<0.001)。突发感音神经性耳聋患者的右侧距状裂周围皮层梯度值与焦虑自评量表得分呈负相关(r=-0.413,P=0.005)。结论突发感音神经性耳聋患者脑区的功能梯度变化有助于阐明突发感音神经性耳聋患者出现情绪障碍的神经病理学基础。
文摘目的探讨二维相位对比(2D phase contrast,2D PC)磁共振成像(magnetic resonance imaging,MRI)序列在定量分析髂静脉压迫综合征(iliac vein compression syndrome,IVCS)患者静脉管腔内血液平均流速(mean blood flow velocity,MV)的应用价值。材料与方法前瞻性招募2023年12月到2024年7月在本院经数字减影血管造影(digital subtraction angiography,DSA)诊断明确为IVCS且需要血管腔内介入治疗的患者30例(试验组)及10名健康志愿者(对照组),收集患者临床资料并行1.5 T飞利浦超导MRI检查,在自由稳态进动(balance fast field echo,B-FFE)序列图像基础上分别在下腔静脉、双侧髂外静脉的冠状位、矢状位及轴位图上垂直扫描2D PC MRI序列,使用定量流量(quantitative flow,Q_FLOW)后处理软件得到血管垂直横切面感兴趣区(region of interest,ROI)内MV值。所有2D PC MRI检查进行两次,通过分析两次扫描结果的一致性(Bland-Altman图)来验证序列稳定性;分别比较IVCS试验组与对照组双侧髂外静脉MV值,评估IVCS患者髂总静脉受压对远端血流的影响;比较IVCS试验组(健侧髂外MV-患侧髂外MV)与对照组(右侧髂外MV-左侧髂外MV)髂外静脉MV差值,分析流速差诊断IVCS的效能;术中通过中心静脉导管(central venous catheter,CVC)测量IVCS患者组髂-下腔静脉压力梯度,并与患侧髂外静脉MV值进行相关性分析。结果两次2D PC MRI扫描结果一致性良好(P均<0.001);试验组患侧髂外静脉血液流速低于健侧(P<0.001),对照组双侧髂外静脉MV值差异没有统计学意义(P=0.518);使用双侧髂外静脉MV差值诊断IVCS效能高,AUC为0.939(95%CI:0.887~0.991),敏感度为81.7%,特异度为100.0%;术中CVC测量压力梯度结果与狭窄静脉远心端MV呈负相关(r=-0.951,P<0.001)。结论2D PC MRI定量分析IVCS患者静脉血液流速结果稳定、可靠,双侧髂外静脉MV差值诊断IVCS特异性高,IVCS患者髂外静脉MV值与髂-下腔静脉压力梯度符合伯努利原理,2D PC MRI可作为一种无创诊断IVCS及间接评估静脉血流压力的工具,为IVCS患者血管腔内介入治疗的手术指征提供重要参考。
