Design of a reverberant chamber for noise exposure experiments with small animals

Previous work on the acoustic design of small reverberant chambers for studies on laboratory animals has paid, in general, more attention to the frequency response at certain points in their interior. These designs aimed to provide a frequency response as flat as possible at the receivers, thus avoiding unpleasant spectral coloration effects. However, an equally important, and frequently neglected, aspect is to set an acoustic field as spatially uniform as possible inside the zone where the animals are to be placed during the exposure to noise. Here, an optimization procedure is described to calculate the proportions of the chamber dimensions that confers the highest sound level with the minimum mean squared deviation averaged in a given area inside the chamber. In addition, new stimuli have been designed with a high-pass filtering and linear with frequency gain. These stimuli were intended to adapt the characteristics of the exposing noise to the rodent hearing spectrum, displaced toward higher frequencies than the hearing frequency band of humans.     

Broadband shock noise reduction in turbulent jets by water injection

The concept of effective jet properties introduced by the author (Kandula M. Prediction of turbulent jet mixing noise reduction by water injection. AIAA J 2008;46(11):2714-22) has been extended to the estimation of broadband shock noise reduction by water injection in supersonic jets. Comparison of the predictions with the test data for cold and hot underexpanded supersonic nozzles shows a satisfactory agreement. The results also reveal the range of water mass flow rates over which saturation of mixing noise reduction and existence of parasitic noise are manifest.     

光电混合机器人视觉系统中光寻址空间光调制器的噪音处理

分析了光寻址空间光调制器对连续图像采样产生的噪音和假频,利用采样理论,提出设置光学去假频前置滤波器抑制噪音和假频的方法.理论分析得出去假频前置滤波器为矩形窗函数的基础上,根据视觉系统中光寻址空间光调制器的参量,计算出了本系统所用的去假频前置滤波器的结构尺寸.视觉系统图像特征提取试验结果表明效果良好.     

Stochastic and coherence resonance in lasers: homoclinic chaos and polarization bistability

We report Stochastic Resonance and Coherence Resonance phenomena in experiments using CO₂ lasers. First, we consider a polarized laser with feedback; for suitable feedback parameters, the laser intensity undergoes homoclinic chaos consisting in the return to a saddle focus, where noise controls the permanence time around the saddle. Second, we discuss a quasi-isotropic laser where noise induces switching between two intensity components with mutually orthogonal polarization.     

Robustness of NRZ, RZ, CSRZ and CRZ modulation on fiber nonlinearities and amplifier noise at 40 Gbps for (OC-786) long haul link

In this paper, the robustness of NRZ, RZ, carrier-suppressed RZ (CSRZ) and chirped RZ (CRZ) modulation formats at 40 Gbps for (OC-786) long haul link on the amplifier noise figure and fiber nonlinearities has been investigated. The investigations reveals that highest Q²(dB) of the order of [20, 25]; [19, 20]; [18, 19] and [16, 18] has been obtained in case of RZ, CSRZ, CRZ and NRZ modulation formats, respectively, in the presence of fiber nonlinearities and with and without amplifier noise figure of 6 dB. It has been observed that Q²(dB) in case of CRZ fluctuate between 18 and 14 at power variation of −10 to 4 dBm and NF of 6 dB, while it is between 19-9, 20-0 and 16-0 in case of CSRZ, RZ and NRZ. It has been identified that CRZ and CSRZ have shown the robustness on fiber nonlinearity and noise at 40 Gbps up to the transmission distance of 450 km. The wide eye opening in case of CRZ modulation also proved the robustness on fiber nonlinearity and noise.     

Noise removal in three-fringe photoelasticity by median filtering

In three-fringe photoelasticity, the total fringe order is obtained by comparing the colour of the unknown photoelastic fringe pattern with a calibration specimen. Comparison is conventionally done by minimising the colour difference error using the least square method. This can give the total fringe order from a single-colour isochromatic field. This technique, however, leads to misidentification of fringe order in some regions. Some researches have proposed boundary identification technique to remove this error. Whilst this ensures continuity of fringe order data over the domain, this does not provide accurate results for every region. A simpler method has been proposed in this paper using median filtering which can be easily undertaken using any standard image processing software. The method is demonstrated with the help of a simple example of disc under diametral compression.     

基于人眼视觉特性的彩色图像自适应增强算法

针对有些图像增强算法对噪声比较敏感,提出了一种自适应图像增强算法.利用原算法的基本原理,结合人眼的视觉特性自适应地生成算法的参数,这样首先保留了原算法实现容易、运算速度快等特点,其次,对噪声具有一定的抑制作用,再次,可以增强和保留图像细节信息.通过实验比较,所提算法能够自适应地生成算法的参数,并在保持了原算法原有的容易实现的优点的基础上,提高了算法抑制噪声方面的性能,将该算法应用于彩色图像增强也取得了相当理想的结果.     

Denseness of volatile and nonvolatile sequences of functions

In a recent paper by Jonasson and Steif, definitions to describe the volatility of sequences of Boolean functions, $f_n:{\{?1,1\}}^n\to \{?1,1\}$ were introduced. We continue their study of how these definitions relate to noise stability and noise sensitivity. Our main results are that the set of volatile sequences of Boolean functions is a natural way “dense” in the set of all sequences of Boolean functions, and that the set of non-volatile Boolean sequences is not “dense” in the set of noise stable sequences of Boolean functions.     

A novel adaptive algorithm of CPE correction for OFDM systems

On the basis of the analysis of the effect of PHase Noise (PHN) and Common Phase Error (CPE) on Orthogonal Frequency Division Multiplexing (OFDM) systems, a cost function is constructed. By the cost function and the idea of Least-Mean-Square (LMS) adaptive algorithm, the adaptive algorithm for the correction of CPE is presented. The simulations have been performed to investigate the performance for tracking PHN and estimating CPE, the results show that the algorithm performs soundly.     

印制电路板的抗干扰设计

以印制电路板的电磁兼容性为核心,分析了电磁干扰的产生机理,详细介绍了在设计、装配印制电路板时的抗干扰措施.