Fast and accurate covariance matrix reconstruction for adaptive beamforming using Gauss-Legendre quadrature

Most of the reconstruction-based robust adaptive beamforming(RAB)algorithms require the covariance matrix reconstruction(CMR)by high-complexity integral computation.A Gauss-Legendre quadrature(GLQ)method with the highest algebraic precision in the interpolation-type quadrature is proposed to reduce the complexity.The interference angular sector in RAB is regarded as the GLQ integral range,and the zeros of the threeorder Legendre orthogonal polynomial is selected as the GLQ nodes.Consequently,the CMR can be efficiently obtained by simple summation with respect to the three GLQ nodes without integral.The new method has significantly reduced the complexity as compared to most state-of-the-art reconstruction-based RAB techniques,and it is able to provide the similar performance close to the optimal.These advantages are verified by numerical simulations.

Frequency-invariant robust adaptive beamforming based on interference covariance matrix reconstruction

Consider the problems of frequency-invariant beampattern optimization and robustness in broadband beamforming.Firstly,a global optimization algorithm,which is based on phase compensation of the array manifolds,is used to construct the frequency-invariant beampattern.Compared with some methods presented recently,the proposed algorithm is not only available to get the global optimal solution,but also simple for physical realization.Meanwhile,a robust adaptive broadband beamforming algorithm is also derived by reconstructing the covariance matrix.The essence of the proposed algorithm is to estimate the space-frequency spectrum using Capon estimator firstly,then integrate over a region separated from the desired signal direction to reconstruct the interference-plus-noise covariance matrix,and finally caleulate the adaptive beamformer weights with the reconstructed matrix.The design of beamformer is formulated as a convex optimization problem to be solved.Simulation results show that the performance of the proposed algorithm is almost always close to the optimal value across a wide range of signal to noise ratios.

Porcine vesical acellular matrix graft of tunica albuginea for penile reconstruction

Aim： To characterize the feasibility of the surgical replacement of the penile tunica albuginea （TA） and to evaluate the value of a porcine bladder acellular matrix （BAM） graft. Methods： Acellular matrices were constructed from pigs＇ bladders by cell lysis, and then examined by scanning electron microscopy （SEM）. Expression levels of the mRNA of the vascular endothelial growth factor （VEGF） receptor, fibroblast growth factor （FGF）-1 receptor, neuregulin, and brain-derived neurotrophic factor （BDNF） in the acellular matrix and submucosa of the pigs＇ bladders were determined through the reverse transcription-polymerase chain reaction （PCR）. A 5 mm× 5 mm square was excised from the penile TA of nine rabbits. The defective TA was then covered in porcine BAM. Equal numbers of animals were sacrificed and histochemically examined at 2, 4 and 6 months after implantation. Results： SEM of the BAM showed collagen fibers with many pores. VEGF receptor, FGF-1 receptor and neuregulin mRNA were expressed in the porcine BAM; BDNF mRNA was not detected. Two months after implantation, the graft sites exhibited excellent healing without contracture, and the fusion between the graft and the neighboring normal TA appeared to be well established. There were no significant histological differences between the implanted tunica and the normal control tunica at 6 months after implantation. Conclusion： The porcine BAM graft resulted in a structure which was sufficiently like that of the normal TA. This implantation might be considered applicable to the reconstruction of the TA in conditions such as trauma or Peyronie＇s disease.

Oversample Reconstruction Based on a Strong Inter-Diagonal Matrix for an Optical Microscanning Thermal Microscope Imaging System

Based on a strong inter-diagonal matrix and Taylor series expansions,an oversample reconstruction method was proposed to calibrate the optical micro-scanning error. The technique can obtain regular 2 ×2 microscanning undersampling images from the real irregular undersampling images,and can then obtain a high spatial oversample resolution image. Simulations and experiments show that the proposed technique can reduce optical micro-scanning error and improve the system＇s spatial resolution. The algorithm is simple,fast and has low computational complexity. It can also be applied to other electro-optical imaging systems to improve their spatial resolution and has a widespread application prospect.

MRI CS-3D-MATRIX序列在膝关节前交叉韧带损伤诊断中的应用研究

目的:探讨CS-3D-MATRIX序列结合多平面重建(multiplanar reconstruction,MPR)技术在膝关节前交叉韧带(anterior cruciate ligament,ACL)损伤诊断中的应用价值。方法:选取44例因膝关节疼痛来院进行MRI扫描的患者,分别行2D-FSE序列和CS-3D-MATRIX序列扫描,将采用CS-3D-MATRIX序列扫描得到的原始图像传至后处理工作站进行MPR。比较2组序列图像的信噪比(signal to noise ratio,SNR)、膝关节ACL显示完整度,以及膝关节图像的运动伪影、ACL边缘的锐利度及图像整体质量。采用SPSS 20.0软件进行数据处理。结果:2组序列的SNR值比较差异无统计学意义(P=0.124>0.05),2组序列图像的运动伪影(P=0.467>0.05)和图像综合质量评分(P=0.617>0.05)比较差异无统计学意义,CS-3D-MATRIX序列的ACL显示完整度例数(43例)高于2D-FSE序列(19例)(P=0.000<0.05),CS-3D-MATRIX序列的ACL锐利度略低于2D-FSE序列(P=0.025<0.05)。结论:CS-3D-MATRIX序列扫描速度快、分辨力高,结合MPR技术可以完整显示ACL图像的形态和结构,尤其是在显示ACL完整度方面更具优势,在膝关节ACL损伤诊断中具有较高的应用价值。

金属表面Data Matrix条码高光区域的信息重构

为实现工业产品的可追溯性,直接将条码加工在零件表面的直接零件标识(Direct Part Marking,DPM)技术,在国内外受到了越来越多的关注。对于金属零件,由于其具有较高的反光性,由相机捕获的金属表面的条码图像常常产生局部高光现象,影响条码的正确读取。为此,针对金属表面激光标刻二维条码出现的局部高光现象,提出了基于五步重构模型的条码重构法,以重构高光区域的条码信息。对获得的条码图像进行倾斜校正,使"L"型实线边界位于图像左下角,对条码进行网格划分实现各个模块的定位。基于Modified Specular-Free(MSF)图像对高光区域进行检测。采用五步重构模型对条码的各个模块进行数值填充,对条码进行读取。实验表明,该算法能达到去除金属表面上条码局部高光的目的,并取得了较高的识读正确率。

组织工程化口腔黏膜等效物的血管化特征

背景:前期研究中三维细胞重建组织工程化口腔黏膜等效物结构类似于正常口腔黏膜,即存在类上皮样结构、类固有层样结构、类血管腔样结构,并已初步实现了等效物的血管化建立,但其血管化特征尚不十分明确。目的:采用血管内皮细胞特异性标志物表达谱关联激光捕获显微切割系统靶向获取血管化口腔黏膜等效物的血管样结构,评价其成血管能力,揭示其血管化特征。方法:分别从人牙龈上皮组织和固有层组织原代培养人牙龈上皮细胞、人牙龈成纤维细胞、人牙龈间充质干细胞,人牙龈间充质干细胞经单克隆扩增培养后诱导分化形成血管内皮样细胞。将人牙龈上皮细胞、人牙龈成纤维细胞、血管内皮样细胞分层负载于脱细胞血管基质-0.25%类人Ⅰ型胶原支架上,构建血管化口腔黏膜等效物。将血管化口腔黏膜等效物(实验组)与脱细胞血管基质-0.25%类人Ⅰ型胶原支架(对照组)分别植入裸鼠背部皮下,14 d后两组切口表面涂布生物胶,实验组生物胶表面接种人牙龈上皮细胞,对照组不接种细胞,继续饲养14 d后取材,利用形态学观察口腔黏膜等效物分层结构;采用较为全面的血管内皮细胞特异性标志物表达谱对口腔黏膜等效物中的新生血管样结构进行免疫组化、免疫荧光标记,进行血管化特征分析;采用激光捕获显微切割系统靶向捕获免疫组化特异性标记的口腔黏膜等效物中新生血管样结构,靶向分析其血管化特征。结果与结论:(1)形态学观察显示口腔黏膜等效物细胞层次清晰,结构类似于正常口腔黏膜,即存在类上皮样结构、类固有层样结构、类血管腔样结构,类血管腔样结构内存在散在红细胞;(2)口腔黏膜等效物组中EdU Apollo示踪种子细胞结果显示:EdU Apollo 488标记的人牙龈上皮细胞呈绿色荧光表达;DAPI标记的人牙龈成纤维细胞呈蓝色荧光表达,体内形成类固有层样结构;Ed U Apollo 567标记的血管内皮样细胞呈红色荧光表达,体内形成类血管样结构;(3)血管内皮细胞特异性标志物表达谱免疫荧光标记血管结构显示,与正常口腔黏膜相比,口腔黏膜等效物中CD31、CD51、CD54、CD105、Tie-2、VWF、血管内皮生长因子受体1、血管内皮生长因子受体2表达升高(P<0.0001),CD34表达无明显变化(P>0.05);(4)与特异性标记的口腔黏膜血管结构相比,激光捕获显微切割系统靶向捕获的口腔黏膜等效物血管样结构中CD51、CD54、CD105、Tie-2、VWF、血管内皮生长因子受体1、血管内皮生长因子受体2表达升高(P<0.0001),CD31、CD34表达无明显变化(P>0.05);(5)结果表明,通过三维细胞分层重建的口腔黏膜等效物能够实现良好的血管化,其血管化特征符合新生血管生成的免疫学功能及特点;血管化助力三维细胞分层重建的口腔黏膜等效物再生。

Data Gathering in Wireless Sensor Networks Via Regular Low Density Parity Check Matrix

A great challenge faced by wireless sensor networks(WSNs) is to reduce energy consumption of sensor nodes. Fortunately, the data gathering via random sensing can save energy of sensor nodes. Nevertheless, its randomness and density usually result in difficult implementations, high computation complexity and large storage spaces in practical settings. So the deterministic sparse sensing matrices are desired in some situations. However,it is difficult to guarantee the performance of deterministic sensing matrix by the acknowledged metrics. In this paper, we construct a class of deterministic sparse sensing matrices with statistical versions of restricted isometry property(St RIP) via regular low density parity check(RLDPC) matrices. The key idea of our construction is to achieve small mutual coherence of the matrices by confining the column weights of RLDPC matrices such that St RIP is satisfied. Besides, we prove that the constructed sensing matrices have the same scale of measurement numbers as the dense measurements. We also propose a data gathering method based on RLDPC matrix. Experimental results verify that the constructed sensing matrices have better reconstruction performance, compared to the Gaussian, Bernoulli, and CSLDPC matrices. And we also verify that the data gathering via RLDPC matrix can reduce energy consumption of WSNs.

THE STATE SPACE RECONSTRUCTION TECHNOLOGY OF DIFFERENT KINDS OF CHAOTIC DATA OBTAINED FROM DYNAMICAL SYSTEM

Certain deterministic nonlinear systems may show chaotic behavior. We consider the motion of qualitative information and the practicalities of extracting a part from chaotic experimental data. Our approach based on a theorem of Takens draws on the ideas from the generalized theory of information known as singular system analysis. We illustrate this technique by numerical data from the chaotic region of the chaotic experimental data. The method of the singular-value decomposition is used to calculate the eigenvalues of embedding space matrix. The corresponding concrete algorithm to calculate eigenvectors and to obtain the basis of embedding vector space is proposed in this paper. The projection on the orthogonal basis generated by eigenvectors of timeseries data and concrete paradigm are also provided here. Meanwhile the state space reconstruction technology of different kinds of chaotic data obtained from dynamical system has also been discussed in detail.

A 3-D RECONSTRUCTION METHOD BASED ON THE CONSTRAINT OF EPIPOLAR GEOMETRY

This paper combines the least-square method and iteration method to get the fundamental matrix and develops a new evaluation function based on the epipolar geometry. During the iteration, with the evaluation function as a measurment, the points which bring larger noise are deleted, and the points with smaller noise are retained, thus the precision of our method is increased. The experiment results indicate the new method is precise in calculation, stable in performance and resistant to noise.

CT大重建矩阵联合重建算法对肺结节的诊断价值

目的探讨CT大重建矩阵1024×1024联合Karl迭代重建算法对肺结节的诊断价值。资料与方法前瞻性收集2021年10月—2022年5月于大连医科大学附属第一医院行胸部CT检查的500例患者,对CT扫描图像原始数据进行分组重建。A组采用常规512×512矩阵结合Karl 5级重建;B组采用1024×1024大重建矩阵结合不同等级Karl算法重建,获得B1(Karl 6)、B2(Karl 7)、B3(Karl 8)、B4(Karl 9)4个亚组。测量主动脉弓上方的气管腔内(气管区)及左肺上叶无血管区(肺实质)的CT值和噪声值,计算信噪比。由2位医师评价A、B组肺部总体图像质量。比较B组中图像质量最佳亚组与A组病灶显示情况,依据手术病理结果,分析诊断效能。结果B组组内随Karl等级升高,气管和肺实质标准差值逐渐下降,信噪比逐渐升高(F=675.002~2020.903,P<0.05)。B组各项主观评分均高于A组(Z=-15.361~-6.465,P<0.05),B4组主观评分最高。A组和B4组部分实性结节(≤3 mm)和实性结节(6.1 mm~≤3 cm)显示清晰度差异无统计学意义(Z=-2.000、-0.378,P>0.05);与A组相比,B4组结节显示清晰率提升12%~100%;胸膜凹陷征显示差异无统计学意义(χ^(2)=2.143,P>0.05)。以43例手术病理结果为诊断金标准,B4组诊断准确度为65.12%,优于A组的41.86%(χ^(2)=4.674,P<0.05)。结论大重建矩阵联合Karl算法可以获得较好的图像质量,有利于诊断肺结节。

基于对抗自编码填补网络的MIMO雷达故障阵元缺失数据重构

多输入多输出(Multiple In Multiple Out,MIMO)雷达的阵元故障会导致其协方差矩阵出现整行整列数据缺失,从而降低其角度估计性能。为此,提出一种对抗自编码填补网络(Adversarial Autoencoder Imputation Network,AAEIN)来重构故障阵元的缺失数据。该网络由负责重构缺失数据的自动编码(Autoencoder,AE)网络和负责分辨数据来源的鉴别器组成。在二者的对抗训练中,AE网络的重构能力和鉴别器的分辨能力不断得到提升,直至两者收敛。为避免网络训练过程中参数量大和计算复杂度高的问题,文中结合MIMO雷达协方差矩阵的Hermitian特性,使用协方差矩阵上三角部分构建数据集用于网络训练。仿真结果表明,文中方法可以有效地重构故障阵元的缺失数据且具有较高的重构精度。

基于实数化的均匀圆阵矩阵重构方法

为了减小低快拍数和低信噪比下采样协方差矩阵误差,并降低其运算复杂度,提出了一种基于实数化的均匀圆阵采样协方差矩阵重构方法。针对均匀圆阵的特点,通过组建特殊的基向量,构成特殊的重构矩阵。通过将采样协方差矩阵实数化,进一步降低了重构矩阵的复杂度。考虑到多通道不一致性对重构矩阵的影响,引入0位校正算法,提高了重构方法的稳健性。最后应用重构后的协方差矩阵进行子空间类波达方向估计(direction of arrival,DOA)。实验仿真证明,该特殊重构矩阵在实数化下与原矩阵重构能力相同;当快拍数为100、信噪比为0 dB时,双信源分辨力较重构前由74%提高到95%以上;理论重构运算复杂度降低到原来的53.99%。

基于矩阵分布式重构的正交极化阵DOA估计

对于子空间类算法而言,协方差矩阵估计的准确性将很大程度的影响到算法的性能,理想的协方差矩阵估计为无限长的信号运算得到,实际中大多使用有限快拍数的采样数据进行协方差矩阵估计。有学者研究表明,阵列协方差矩阵位于由接收信号的所有可能导向矢量构成的子空间中,可以利用子空间组成的完备重构矩阵对协方差矩阵进行重构,此类方法需要对阵列的所有可能接收信号进行积分,并获得由其主成分构成的重构矩阵。为了减小低快拍数和低信噪比下采样协方差矩阵误差,并降低其运算复杂度,提出了一种基于正交偶极子组成的均匀圆阵的采样协方差矩阵重构方法。将整体阵列划分为子阵1和子阵2,子阵内部仅存在空域相位差而没有极化敏感特性,子阵间空域相位差相同,极化敏感特性不同。并基于均匀圆阵的结构特点,给出了特殊的重构矩阵,特殊的重构矩阵不依赖信号特性,仅与圆阵结构相关,通过理论分析和仿真测试可以得到,特殊的重构矩阵在维度和复杂度方面均优于全角度域和极化域积分的重构矩阵。该方法将重构算法应用到了极化敏感阵列领域同时减少了运算的复杂度,通过后续对低信噪比和低快拍数的仿真测试表明,重构后的协方差矩阵可以有效提高信号子空间和理想噪声子空间的正交性,使用重构的协方差矩阵进行极化空间谱估计提高了在恶劣环境下的信源分辨力。

基于小快拍场景的联合校正稳健波束形成算法

针对传统的自适应波束形成算法在目标导向矢量失配及接收数据的协方差矩阵存在误差时,性能急剧下降的问题,提出了一种基于小快拍场景的联合协方差矩阵重构,及导向矢量优化的稳健波束形成算法。对不确定集约束求解得到干扰导向矢量,根据稀疏干扰来向的导向矢量近似正交,求出干扰导向矢量对应的干扰功率,从而完成协方差矩阵重构;对期望信号来向及其邻域进行权值求解,对加权后的数据特征分解,利用多信号分类(Multiple Signal Classification, MUSIC)谱估计算法对信号区域积分得到信号协方差矩阵,将其主特征值近似为期望信号的导向矢量完成重新估计。仿真结果表明,在无误差时,算法输出信干噪比(Signal to Interference Plus Noise Ratio, SINR)接近理论最优;在多种误差环境下输出性能随信噪比(Signal to Noise Ratio, SNR)的变化均具有较好的稳健性,并且在信号来向可精准形成波束;在小快拍时可以较快收敛至理论最优值。

Lessons Learned from Three Different Acellular Dermal Matrices in Direct-to-Implant Breast Reconstruction

The aim of the study was to show significant differences regarding postoperative complications and outcomes using three different Acellular Dermal Matrices (ADM), namely Epiflex®, Strattice® and Braxon®, in immediate implant-based subpectoral breast reconstruction cases. Background: The use of Acellular Dermal Matrices for implant-based breast reconstruction cases continues to evolve. There is a wide variety of products which differ significantly in their biological features. It remains unclear if and how these differences manifest in clinical practice. Methods: 82 cases of primary breast reconstruction in the Department of Plastic and Aesthetic Surgery of HELIOS Clinics Schwerin, Germany between 2010 and 2018 were analyzed. 25 patients received Strattice® acellular dermal matrix (SADM), 22 cases Epiflex® acellular dermal matrix (EADM) and the remaining 35 cases Braxon® acellular dermal matrix (BADM). The mean follow-up was 1.8 years. Cases were analyzed regarding minor or major complications and rate of capsular contracture grade III or IV (Baker Classification). Results: The overall complication rate was 34.1% for all groups (SADM = 40%, EADM = 50%, BADM = 20%, p-value = 0.051). Of all cases, 6 patients underwent implant exchange or secondary autologous reconstruction due to capsular contracture (7.3%). The mean time between revision due to capsular contracture and reconstruction was 35.8 ± 14.4 months. 50% of patients, who developed capsular contracture, received postoperative radiation. Mean hospitalization time was 8.2 ± 3 days (SADM = 8 ± 3.2 days, EADM = 10 ± 2.8 days, BADM = 6 ± 1.3 days). There were no significant differences between all three groups for demographics, overall complication rate or capsular contracture. However, patients receiving Braxon® matrix showed significantly fewer minor complications (p-value = 0.01). Moreover, patients receiving Braxon® ADM showed a significantly lower time of hospitalization (p < 0.001). Conclusion: No significant differences regarding the overall complication rate were found between the three groups. Different biological features of ADM showed a weak influence on overall results. However, patients receiving Braxon® ADM showed significantly lower minor complication rates and hospitalization time. In addition, these matrices showed a trend towards lower capsular contracture rates. The low rate of capsular contracture hints at possible advantages of ADM-use in direct-to-implant cases.

1024×1024重建矩阵结合迭代重建算法在胃部CT血管成像中的应用

目的 探究1 024×1 024重建矩阵结合迭代重建(Karl)算法在胃部血管及肿瘤供血动脉CT血管成像中的应用价值。资料与方法 前瞻性收集大连医科大学附属第一医院2022年3—6月行胃部CT血管成像的胃部肿瘤患者30例,对CT扫描图像原始数据进行分组重建。A组采用常规512×512矩阵结合Karl 5级重建;B组采用1 024×1 024大重建矩阵结合不同等级Karl算法重建,分为B1(Karl 5)、B2(Karl 7)及B3(Karl 9)3个亚组。在轴位图像上测量胃左动脉起始部的腹主动脉、腹腔干、脾动脉、肝动脉及同层面腹壁皮下脂肪组织的CT值和SD值,计算信噪比(SNR)、对比噪声比(CNR)。由2名观察者采用5分法评估各组图像质量。结果 2名观察者主观评价一致性较好(Kappa=0.782~0.789,P<0.05),B1~B3组图像主观评分均优于A组,B2组得分最高(二维评分:χ^(2)=27.309、24.250;三维评分:χ^(2)=21.964、21.294;P均<0.05),30例患者中25例见胃动脉系统参与肿瘤供血,B2组各血管的清晰显示率均优于A组;A与B1、B2组各血管CT值差异无统计学意义(t=-1.918~2.720,P>0.05),B2组较A组血管SD值、SNR、CNR和背景噪声值,除腹主动脉SD、肝动脉CNR外差异均无统计学意义(t=-5.909~5.768,P>0.05);B1~3组图像随着Karl算法等级提高,SD值逐渐降低(F=2.881~27.109,P<0.05),SNR、CNR逐渐升高(F=3.612~12.149,P<0.05)。结论 1 024×1 024重建矩阵结合Karl 7级算法可以改善图像质量,增强胃部微细血管及肿瘤供血动脉分支的显示效果,在临床上有很好的应用价值。

修正-联合正则化的冲击载荷识别与响应重构

针对传统结构响应重构中正则化方法对冲击载荷峰值识别精度低、非加载区识别结果振荡且识别精度易受噪声干扰等问题,提出基于修正-联合正则化的冲击载荷识别与结构响应重构方法.基于状态空间模型,推导冲击载荷及结构响应的重构方程.对测量响应降噪,利用降噪后响应与识别响应的差值修正L2正则化解.联合L1正则化解的稀疏性优势,在保证冲击载荷非加载区域识别稳定的同时,获得更高精度的峰值识别结果,实现结构动态响应的重构.通过数值和实验案例验证了所提方法的有效性,对比了传递矩阵法和粒子滤波法的响应重构效果.结果表明,所提方法具有良好的抗噪性,能够较准确地识别冲击载荷,有效地重构结构动态响应.

基于改进型LBP译码的LDPC码稀疏校验矩阵重建

针对LDPC码稀疏校验矩阵重建问题,基于改进型LBP译码的思想提出了一种高误码率下的LDPC码稀疏校验矩阵重建算法。首先,从码字矩阵中随机抽取部分比特构建码字分析矩阵,并对其做高斯消元求对偶空间;其次,通过判定对偶空间向量是否稀疏,提高了后续疑似校验向量判定的效率;最后,在接收码字个数不足时,利用已知校验向量结合改进型LBP译码方法纠正错误码字,加快LDPC码稀疏校验矩阵的重建速度,提高重建性能。仿真结果表明,所提算法在高误码率0.0045的条件下,对于IEEE802.11n协议下的(648,324)LDPC码,相比于现有算法,稀疏校验矩阵重建率提升了52.16%,可达到92.28%。

基于混合正则化方法的结构载荷识别与响应重构

针对结构载荷识别与响应重构问题中存在的不适定性,提出一种最小平方残差(least square minimal residual,LSMR)算法与Tikhonov正则化方法相结合的混合正则化方法,实现利用结构有限测点的加速度响应识别载荷并重构未知的各类型响应。首先,基于时域状态空间模型构建结构的传递矩阵,并建立载荷识别与响应重构方程;其次,采用混合正则化方法改善载荷识别问题的不适定性,得到载荷的正则化解,并结合响应重构方程的传递矩阵对结构的位移、速度和加速度响应进行重构;最后,通过简支梁数值仿真和试验分析验证所提方法的可行性。结果表明,所提方法能改善重构方程的不适定性,从而对结构未知载荷和各类型响应进行有效重构。