透明和吸收介质非线性参数n2,X^（3）及其时间响应特性研究

对透明和吸收介质的简并四波混频理论作了处理,实验上给出了掺半导体玻璃,无机和有机材料的三阶非线性极化率x~(3)和非线性折射率n_2的值,而且确定了非线性参数x~(3)的时间响应特性,实验装置的时间分辨率为5ps.     

不同权矢量下水声低频相控垂直阵远程探测性能的研究

理论分析水声低频相控垂直线阵不同权矢量远程探测性能并仿真研究。文中首先依据绝热简正波理论,导出相控垂直线阵远程探测的声传播理论模型。在此基础上,给出了相控阵权矢量与目标参数估计方差理论下限Cramer-Rao界(CRB)之间的对应关系。其次,利用KRAKEN软件求解仿真环境下波动方程的本征值和本征函数,数值计算比较相控阵七种发射权矢量下远程探测效能。结果表明,相控垂直阵在发送1号模权矢量时,具有较优的远程探测性能和参数估计方差下限。     

Using the system function to analyze the performance of transducer’s impedance measurement method

Prom investigation of the advantages and disadvantages of conventional tri-voltage method,a method for the measurement of the transmitting transducer’s impedance was presented to solve the difficult problem of examining the consistency of the transmitting phased array on the single-mode excitation sea spot.In the method based on the system function, the circuit structure of tri-voltage method was used but new parameters were measured.The principle of the method was given first.Then when resistors with different nominal values were used in the circuit,the measured results for the impedance of transducers were reported.The results were compared with the higher precision impedance analyzer.Finally,the error analysis was performed according to the impedance formula and the equivalent circuit parameters were fitted.Under the condition of guaranteeing the sampling precision,by performance analyzing, the resistor value in series was chosen relatively smaller than the impedance of transducer,the measurement of impedance could achieve the same precision as the higher precision impedance analyzer.Finally,the least squares curve-fitting of measured curves indicated that the transducer equivalent electrical parameters could be extracted accurately and used to design the matching network.     

实时超声引导经会阴/直肠前列腺系统精准活检在前列腺癌诊断中的应用价值

为探讨实时超声引导经会阴/直肠前列腺系统精准活检在前列腺癌诊断中的应用价值,本研究回顾性分析2016年1月~2018年12月于我院接受前列腺穿刺活检的150例疑似前列腺癌患者的完整临床资料,将行实时超声引导经会阴前列腺活检的74例患者纳入A组,其中前列腺特异性抗原(PSA)灰区患者26例;将行实时超声引导经直肠前列腺系统精准活检的76例患者纳入B组,其中PSA灰区患者28例,比较各组患者一般资料、前列腺癌检出率、PSA灰区前列腺癌检出率,以及术后并发症情况。结果显示,两组年龄、PSA水平、前列腺体积比较,差异无统计学意义(P>0.05);A组穿刺针数及手术时间均高于B组(P<0.05);A组PSA灰区患者前列腺癌检出率高于B组(P<0.05);A组血便发生率低于B组(P<0.05)。实时超声引导经会阴与经直肠前列腺系统精准活检在前列腺癌诊断中的检出率相当,但针对PSA灰区患者而言,经会阴穿刺活检的检出率更高,且术后血便等并发症发生率低,安全性更高。     

应用相移技术和迭代算法的综合鉴别联合变换相关器

把相移技术和迭代算法应用到综合鉴别联合变换相关中,计算机模拟结果表明,运用了相移技术和迭代算法后这种相关器的光能效率和鉴别率得到了很大提高,实现了高鉴别率和高光能效率的综合鉴别光学模式识别.进一步研究了输入噪声对相关器性能的影响,相关的抗噪声能力有待提高.     

彩色负片的颗粒性能研究-印片颗粒指数

彩色负片的颗粒性能是一个重要的质量指标。以往颗粒性能的度量采用均方根颗粒度的方法。均方根颗粒度建立在只对彩色负片进行灰密度(白光调制)采样的基础之上,难以保证所测数值与实际扩印照片效果相符合。采用对彩色负片进行红、绿、蓝三色光调制密度采样的方法,从三色均方根颗粒度出发,结合扩印过程中颗粒性能的传递特性以及观察照片时人眼的视觉生理和心理特性等诸多因素,形成一个代表最终照片颗粒效果的知觉颗粒度,称为彩色负片的印片颗粒指数(PGI)。实际测试和观测比较表明,所测彩色负片印片颗粒指数数值与其扩印效果相符合,印片颗粒指数方法能够反应彩色负片颗粒性的实用效果。     

浅海声场单模闭环发射的最佳估计算法

提出了一种浅海声场单模闭环发射的最佳估计算法。通过对声场格林函数矩阵估计协方差的分析,设计了一种对格林函数矩阵作最佳估计的最佳发射阵权系数矩阵,此权系数矩阵为酉矩阵且各元素绝对值相等。基于此矩阵的单模发射算法可以使得单模激发过程以最快的速度收敛,并且发射稳定。算法的优势在模拟计算中得到了验证。最后给出了海上实验的结果,单模含量高达97%。      

压电陶瓷发射换能器的Butterworth匹配定理

提出并证明了压电陶瓷发射换能器的Butterworth匹配定理。定理的显公式形式使复杂的宽带匹配问题变成为简单的算术问题．举例说明经过匹配之后,换能器带宽明显提高,而功率增益却接近于1。     

Radial basis function interpolation supplemented lattice Boltzmann method for electroosmotic flows in microchannel

Large gradients of physical variables near the channel walls are characteristic of EOF. The previous numerical simulations of EOFs with the lattice Boltzmann method (LBM) utilize uniform lattice and are not efficient, especially when the electric double layer (EDL) thickness is significantly smaller than the channel height. The efficient LBM simulation of EOF in microchannel calls for a nonuniform mesh which is dense in the EDL region and sparse in the bulk region. In this article, we formulate a radial basis function (RBF)-based interpolation supplemented LBM (ISLBM) to solve the governing equations of EOF, that is, the Poisson, Nernst–Planck, and Navier–Stokes equations, in a nonuniform mesh system. Unlike the conventional ISLBM, the RBF-ISLBM determines the prestreaming distribution functions by using the local RBF-based interpolation over circular supporting regions and is particularly suitable for nonuniform meshes. The RBF-ISLBM is validated by the EOFs in infinitely long and finitely long microchannels. The results show that the RBF-ISLBM possesses excellent robustness and accuracy. Finally, we use the RBF-ISLBM to simulate the EOFs with the hitherto highest electrokinetic parameter, κa, defined by the ratio of channel height a to EDL thickness κ⁻¹, in LBM simulations of EOF.     

An optimal algorithm for single-mode close-loop excitation in shallow water

An optimal algorithm for single-mode close-loop excitation in shallow water is presented.By analyzing the covariance of estimation value of Green’s function matrix,an optimal source array weights matrix is presented to estimate Green’s function matrix.The weights matrix is a unitary matrix,and absolute values of the matrix elements are equal. Algorithm based on the weights matrix makes single-mode excitation converge at maximum speed and be steady.Advantages of the algorithm are confirmed by numerical simulations. Finally,results of shallow water experiment are presented,and the energy ratio of single mode is higher than 97 percent.