基于盲解卷积的水声信号恢复技术

信号在环境复杂多途严重的水声波导中传输后,接收到的信号时间长度被拉长,信号是失真的。在许多实际应用中,常常希望从已失真的接收信号中把原始信号波形恢复出来。本文利用盲解卷积技术对水声信号恢复进行研究。理论推演表明,在垂直阵条件下用人造的格林函数可成功地代替水声信道真实的格林函数,可以把非线性关系化解为线性关系,从而推导出依靠基阵记录下的信息去确定声源宽带信号原始波形和环境传播特征的公式和步骤。声场数值计算对6种海底类型进行,恢复后的宽带信号与原始信号的归一化相关系数均大于0.945,对硬海底多途严重的情况,收效特别明显,证明该方法的有效性。在青岛海试中恢复后信号的相关系数平均值为0.933,在青岛海试中利用这种解卷积技术去恢复信号是成功的。     

Analysis of ultrasonic guided waves propagating in long bones and cortical thickness based on time-frequency methods

The ultrasonic signals in long bones contain multiple guided modes which are mutual superposed.The velocities of guided waves in long bones are very sensitive to cortical thickness (CTh).In this paper,Hilbert-Huang transform(HHT) was proposed to analyze multi-mode guided waves,which can decompose superposed waves into many independent modes.Then the group velocity of each mode was obtained at corresponding frequency,which was compared with the results of short time Fourier transform(STFT).The CTh was also obtained by comparing with the theoretical calculation.The results showed that the experimental determined thickness was in agreement with the actual CTh,indicating that measuring the velocity of the guided mode can be used to estimate the CTh.The HHT is an effective method to identify multimode guided waves.     

Eigenspace-based source number estimation for direction-of-arrival estimation

A eigenspace-based source number estimation was presented.It projects the estimated covariance matrix of array signal into signal eigen-subspace and noise eigen-subspace, respectively.Using the orthogonality between signal eigen-subspace and noise eigen-subspace, it is easy to differentiate the contribution of signal and noise by using the criterion value,or the magnitude of projection.Like the Direction-of-Arrival(DOA) estimation algorithm,the estimator uses the eigenvalue decomposition of covariance matrix with order M×M,where M is the number of elements,and hence can save much computational burden.To reduce more computational burden,the estimation can be implemented by the decomposition in the real-value space.Computer simulation demonstrates the distribution of criterion value and the performance of the estimation method.The estimation method was also tested with the sonar data,which shows good performances.     

湍流信号分析中小波基的对比和选取

采用小波分析处理湍流脉动信号时,不同的小波基往往会带来不同的分析结果.为了尽可能准确地提取湍流流动的多尺度特征,研究并建立湍流信号处理中适宜小波基选取的合理方法是十分必要的.基于湍流时频特性,结合信息熵理论,建立了以品质因数和特征谱熵值为评价指标的小波基选取方法.以计算分析三组不同湍流信号的小波基为例,结果进一步验证了...     

输入方波信号的过阻尼谐振子的随机共振

计算了在输入方波信号情况下过阻尼谐振子的输出功率谱和信噪比,详细讨论了相应的随机共振现象,并与输入余弦信号情况进行对比.研究发现:它们均出现随机共振现象,且均存在共振和抑制并存的现象.但这一并存现象,在两模型中分别出现于不同的共振曲线. 关键词： 过阻尼谐振子 随机共振 方波信号     

纳米材料在蛋白磷酸化分析中的应用研究

蛋白质磷酸化修饰是一种重要的蛋白质翻译后修饰,在细胞代谢过程中发挥着重要作用。当蛋白质的正常磷酸化调节发生异常时,会导致癌症、糖尿病、心脏病等各种疾病的发生。因此,蛋白磷酸化分析对于疾病的早期快速诊断、药物筛选和治疗等方面具有重大的意义。由于蛋白质磷酸化过程是动态的,并且磷酸化肽段或蛋白在生物样品中的含量较低,因此高灵敏的蛋白磷酸化分析面临着巨大的挑战。该文依据在检测过程中,选择性识别或捕获磷酸化的肽段或蛋白的主要机理,综述了近几年纳米材料对磷酸化肽段的富集和信号放大作用在蛋白磷酸化分析中的研究进展,并对其未来研究方向进行了展望。     

Sensitive detection of DNA methyltransferase activity based on rolling circle amplification technology

This work develops a fluorescence approach for sensitive detection of DNA methyltransferase activity based on endonuclease and rolling circle amplification （RCA） technique. In the presence of DNA adenine methylation （Dam） MTase, the methylation-responsive sequence of hairpin probe is methylated and cleaved by the methylation-sensitive restriction endonuclease Dpn 1. The products cleaved by restriction endonuclease Dpn I then function as a signal primer to initiate RCA reaction by hybridizing with the circular DNA template. Each RCA product containing thousands of repeated sequences might hybridize with a large number of molecular beacons （detection probes）, resulting in an enhanced fluorescence signal. In the absence of Dam MTase, neither methylation/cleavage nor RCA reaction can be initiated and no fluorescence signal is observed. The proposed method exhibits a dynamic range from 0.5 U/mL to 30 U/mL and a detection limit of 0.18 U/mL. This method can be used for the screening of antimicrobial drugs and has a great potential to be further applied in early clinical diagnosis.     

恢复蛋白Recoverin正则模式分析的理论研究

采用旋转平移块方法对Ca2+/豆蔻酰基开关进行了正则模式分析(NMA). 研究结果表明, 恢复蛋白(Recoverin)的T态的N-末端与C-末端易于发生刚体逆向旋转, 一旦结合Ca2+, 很容易发生构象变化, 形成具有双向构象转变特征的I态. I态是一个中间结构, 既可以发生构象回转到T态, 又可以继续相对旋转到R态, 使豆蔻酰基完全暴露, 从而行使其信号传导生物功能. 从低频振动模式分析可以看出, 恢复蛋白具有构象转变这一本质属性.     

酸性络蓝K双波长信号系数光度法测定钙镁

基于在氢氧化钠溶液中,钙、镁均与酸性络蓝K(ACBK)形成暗红色配合物,提出了测定钙和镁的双波长信号系数光度法.该法不仅消除了钙、镁之间的吸收干扰,且消除了一定量的共存离子的干扰.利用褪色法与生色法的吸光度之和作为信号吸光度,使方法的灵敏度大为提高.测定钙、镁总量时,分别用钙、镁吸收曲线正峰与负峰上的等吸收波长470.5 nm(λPa)及559.5 nm(λNa)处测定吸光度APa和ANa,求得总量的信号系数fs为2.439.于λPa470.5 nm处测得任一浓度钙、镁试液的吸光度APa′,其信号吸光度As=fsAλPa′.测定镁时,以试剂ACBK褪色对钙配合物生色的完全相消干扰的波长539 nm(Pa)作为测定波长,负峰波长583 nm为Na.按相同方法测得镁的信号系数fs为4.148.     

基于IGA-小波软阈值的MEMS矢量水听器信号去噪方法

提出了将使用新的遗传策略,将与当前进化迭代和种群平均适应度变化趋势相关的惩罚因子引入到遗传算法的自适应交叉、变异概率中,依据种群适应度集中分散程度自主调节遗传操作顺序的改进的遗传算法,并用此改进的遗传算法自适应获取最佳小波阈值,然后结合小波软阈值去噪方法对信号去噪.仿真实验和实测实验说明提出的基于改进遗传算法的小波软阈值去噪方法具有良好的去噪性能,且具有一定的稳定性.