Experimental study of acoustic characteristics of expansion chamber with mean flows

For the measurement of transmission loss of the silencers which have mean flow, the noise levels of signals depicted by microphone usually prohibit accurate measurements of the transmission loss. To overcome this difficulty, static pressure compensation technique has been developed to increase the dynamic range of the microphones, resulting accurate measurement of transmission loss in the presence of high noise level. Series of experiments to investigate the acoustic characteristics of expansion chamber with mean flow has been performed using the pressure compensated microphones. Results demonstrate: (1) frequency shift due to the presence of mean flow, (2) effect of length, diameter, offset length and twisting angles to the transmission loss of expansion chamber with and without mean flow (up to 50m/sec), (3) relation between the proposed parameter ‘aspect ratio’ and number of peaks of transmission loss in low frequency region.     

Automatic Contrast Enhancement by Transfer Function Modification

In this study, we propose an automatic contrast enhancement method based on transfer function modification (TFM) by histogram equalization. Previous histogram‐based global contrast enhancement techniques employ histogram modification, whereas we propose a direct TFM technique that considers the mean brightness of an image during contrast enhancement. The mean point shifting method using a transfer function is proposed to preserve the mean brightness of an image. In addition, the linearization of transfer function technique, which has a histogram flattening effect, is designed to reduce visual artifacts. An attenuation factor is automatically determined using the maximum value of the probability density function in an image to control its rate of contrast. A new quantitative measurement method called sparsity of a histogram is proposed to obtain a better objective comparison relative to previous global contrast enhancement methods. According to our experimental results, we demonstrated the performance of our proposed method based on generalized measures and the newly proposed measurement.     

移动相机下基于三维背景估计的运动目标检测

室内环境中的运动目标检测是计算机视觉领域的研究热点,而移动相机造成的动态背景是运动目标检测的难点。本文提出一种基于同步定位与地图创建(ORB-SLAM)三维背景估计的运动目标检测算法,首先使用移动相机遍历整个室内环境,采用ORB-SLAM技术建立当前全局环境的三维背景特征点云模型;然后基于局部视频建立局部三维特征点云,根据定位信息将当前局部三维特征点云与环境三维背景特征点云进行嵌入,基于环境背景信息,采用三维均值漂移(3DMS)算法,对局部三维特征点云进行前景特征点提取;运用深度卷积神经网络,对提取的前景特征点所在候选区域进行运动目标确认。通过多个室内场景的实际实验进行验证,结果表明本文方法具有较高的运动目标检测准确率和召回率,提出的运动目标检测算法充分利用了三维背景信息,采用深度卷积神经网络进行确认,有效地改善了检测的准确性和鲁棒性。     

基于SOR-PCG的低复杂度信号检测算法研究

针对最小均方误差信号检测算法复杂度随着天线数量增加呈指数增长的问题,提出低复杂度的预处理共轭梯度信号检测算法.该算法通过灵活调整松弛因子,运用预处理技术降低矩阵条件数,从而加快共轭梯度信号检测算法的收敛速度.仿真结果显示,该算法在小数量的迭代中能够达到和最小均方误差检测算法相似的误码率,算法复杂度下降了一个数量级.通过选择适当的松弛因子,相比直接用共轭梯度法,能够更快收敛到最佳值.     

光寻址电位传感器的噪声分析与信号处理方法研究

鉴于光寻址电位传感器(LAPS)的响应信号较弱,传统的抽取频域基波分量的方法易受信号漂移和随机噪声的影响,提出了一种基于频域分量均方根和卡尔曼滤波的两步信号处理方法。基于光寻址电位传感器件的理论模型构建了其等效电路模型,推导得到输出信号的表达式,分析了漂移与噪声产生的原因及其抑制方法。通过实验检测了不同pH值的溶液,并采集了系统输出的光电流信号。求取信号傅里叶变换后频域中的基波分量、二次谐波分量、三次谐波分量的谱线幅值的均方根,然后对归一化电流-偏压(I-V)特性曲线进行卡尔曼滤波。实验结果表明,相对于单纯抽取基波分量的方法,基于频域分量均方根和卡尔曼滤波的两步信号处理方法使检测结果的均方差(MSE)降低了97%,显著减少了信号漂移和随机噪声对检测结果的影响。     

Experimental Research on Erbium-doped Superfluorescent Fiber Source

The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ～20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ～0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems.     

Expanding the MOS: Development and Psychometric Evaluation of the MOS-R and MOS-X

The Mean Opinion Scale (MOS) is a questionnaire used to obtain listeners' subjective assessments of synthetic speech. This paper documents the motivation, method, and results of six experiments conducted from 1999 to 2002 that investigated the psychometric properties of the MOS and expanded the range of speech characteristics it evaluates. Our initial experiments documented the reliability, validity, sensitivity, and factor structure of the P.L. Salza et al. (Acta Acustica, Vol. 82, pp. 650–656, 1996) MOS and used psychometric principles to revise and improve the scale. This work resulted in the MOS-Revised (MOS-R). Four subsequent experiments expanded the MOS-R beyond its previous focus on Intelligibility and Naturalness, to include measurement of the Prosody and Social Impression of synthetic voices. As a result of this work, we created the MOS-Expanded (MOS-X), a rating scale shown to be reliable, valid, and sensitive for high-quality evaluation of synthetic speech in applied industrial settings.     

谈皎然文论中儒家中庸之道与佛家中道思想的沟通

中唐诗僧皎然的诗歌理论著作《诗式》立足于儒学,由儒而入佛,并试图通过儒学来沟通佛学。其诗学理论体现了儒家中庸之道与佛家中道思想的融合与沟通。     

EM procedures using mean field-like approximations for Markov model-based image segmentation

Image segmentation using Markov random fields involves parameter estimation in hidden Markov models for which the EM algorithm is widely used. In practice, difficulties arise due to the dependence structure in the models and approximations are required. Using ideas from the mean field approximation principle, we propose a class of EM-like algorithms in which the computation reduces to dealing with systems of independent variables. Within this class, the simulated field algorithm is a new stochastic algorithm which appears to be the most promising for its good performance and speed, on synthetic and real image experiments.     

Cryptosporidium Log-inactivation with Ozone Using Effluent CT10, Geometric Mean CT10, Extended Integrated CT10 and Extended CSTR Calculations

The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit.