多信息水声传输方式及其应用研究

介绍“抗强噪声水层深度遥测装置”专利中,采用频分PPM(Pulse-Position modulation)方式进行多信息水声传输的研究和工程设计,并着重阐述产生PPM数字信号的新方法和应用特殊的数字选频滤波接收的先进技术,并提出所设计的有关电路。     

Features and origin of the dynamic and the nonlinear piezoelectricity in poly(vinylidene fluoride)

Some of the piezoelectric coefficients of poly(vinylidene fluoride) are distinctly stress dependent. We report on their dependence on the frequency of an oscillatory stress excitation, on the amount of the remanent polarization in the sample materials, and on the magnitude of an offset stress. In order to explain the observed dynamic and nonlinear piezoelectric properties, a model is developed that attributes them to changes in the local polarization in an interphase between the crystalline and amorphous phases in this semicrystalline polymer.     

用最小均方误差对数短时谱幅值估计法增强语音信号

本文主要研究语音增强系统在短时频域内,以对数最小均方误差作为语音幅值估计的准则.对含噪语音进行消噪处理。首先推导了公式,并从理论上作了分析研究.在此基础上作了大量实验,与类似的最小均方误差短时谱幅值估计法(MMSE STSA)作了性能比较.实验结果表明,由MMSE LOG-STSA增强方法得到的语音输出的质量优于由MMSA STSA方法得到的质量.语音的失真度和清晰度均有显著改善,同时大大降低了语音中的“音乐噪声”.     

含信号调制噪声和频率波动的时滞分数阶振子的随机共振

本文研究了含信号调制噪声和频率波动的小时滞线性分数阶振子的随机共振. 利用分数阶Shapiro-Loginov公式和Laplace变换技巧,本文首先推导了系统响应的一阶稳态矩和稳态响应振幅增益（Output Amplitude Gain, OAG）的解析表达式,然后讨论了分数阶、时滞及噪声参数对OAG的影响. 结果显示,各参数对OAG的影响均呈现出非单调变化的特点,表明系统出现广义随机共振. 特别地,分数阶与时滞的协同作用可能诱导随机共振的多样化,这就为在一定范围内调控随机共振提供了可能.     

百米跑模式在教学中的应用

百米跑模式对于教学和训练具有很高的价值;本文根据百米跑模式原理,结合教学实例论述了模式在教学中的应用,对教师尽快发现及解决百米成绩较差学生存在的主要问题,颇有帮助,并在教学实践中取得了显著地效果。     

高速公路自动收费系统

本文介绍一种通过红外方式传输智能卡内数据的自动收费系统,实现了高速公路不停车收费。它能有效的解决高速公路收费处车辆堵塞问题,具有较强的实用性。     

Phase separation and disorder in half metallic ferromagnetic manganite thin films: A theoretical study looking forward low noise nano-devices

The resistivity of thin La_0.7Sr_0.3MnO₃ films was first investigated in a wide temperature (T) range (10–750 K). Films grown by different techniques and on several substrates enabled to analyze samples with different amounts of disorder. The aim of this work was to elucidate the nature of the metal–insulator (M–I) transition occurring at T = T_p in these films and its relation with the different kinds of inhomogeneities they could present like intrinsic electric disorder and co-existence of two different electrical and/or magnetic phases. The low-temperature resistivity state was described mostly by a law which scales as T with  ≈ 2.5. This supports the theoretical proposal of single magnon scattering in presence of minority spin states localized by the disorder. In the whole range of temperatures the experimental data are found to be consistent with a phase separation (PS) scenario. In order to go through the origin of the characteristic length scale of inhomogeneity found, preliminarily low frequency noise measurements as a function of T in a range of temperature around the M–I transition were made. The samples used were patterned using photolithography into bridges with various widths and lengths. No clear sign of separation phase dynamic has been observed in our noise measurements. Unexpectedly the normalized Hooge parameter _H/n was found not to be volume (Ω) independent. The LSMO electrical properties may strongly be driven by disorder and new design for magnetoresistance sensors may have to take into account their intrinsic PS.     

A Background and noise elimination method for quantitative calibration of near infrared spectra

A new hybrid algorithm is proposed to eliminate the varying background and noise simultaneously for multivariate calibration of near infrared (NIR) spectral signals. The method is based on the use of multi-resolution, which is one of the main advantages provided by wavelet transform. The signals are firstly split into different frequency components, which keep the same data points of the original signals. In conjunction with a modified uninformative variable elimination (mUVE) criterion, the new method can be used to remove the low-frequency varying background and the high-frequency noise simultaneously. The method is successfully applied to simulated spectral data set and experimental NIR spectral data, resulting in more parsimonious multivariate models with higher precision. In addition, the proposed strategy can be applied to other spectral signals as well.