针对多种处理痕迹的数字语音取证算法

现有的数字语音取证研究主要集中于对单一的某种操作进行检测，无法对不相关的操作进行判断。针对该问题，提出了一种能够同时检测经过变调、低通滤波、高通滤波和加噪这四种操作的数字语音取证方法。首先，计算语音的归一化梅尔频率倒谱系数（MFCC）统计矩特征；然后通过多个二分类器对特征进行训练，并组合投票得到多分类器；最后使用该多分类器对待测语音进行分类。在TIMIT以及UME语音库上的实验结果表明，归一化MFCC统计矩特征在库内实验中均达到了97%以上的检测率，且在对MP3压缩鲁棒性测试的实验中，检测率仍能保持在96%以上。     

Depth-Averaged Drag Coefficient for Modeling Flow through Suspended Canopies

Aquatic suspended canopies are porous obstacles that extend down from the free-surface but have a gap between the canopy and bed. Examples of suspended canopies include those formed by aquaculture structures or floating vegetation. The major difference between suspended canopies and the more common submerged canopies, which are located on the bottom boundary, is the influence of the bottom boundary layer beneath the suspended canopy. Data from laboratory experiments are presented which explore aspects of the flow through and beneath suspended canopies constructed from rigid cylinders. The experiments, using both acoustic Doppler and two-dimensional (2D) particle tracking velocimetry, give details of the flow structure that may be divided vertically into a bottom boundary layer, a canopy shear layer, and an internal canopy layer. The experimental data show that the penetration of the shear layer into the canopy is limited by the distance between the canopy and bottom boundary layer. Peaks in velocity spectra indicate an interaction between the bottom boundary and canopy shear layer. An analytical model is also developed that can be used to calculate a drag coefficient that includes the effect of both canopy drag and bed friction. This drag coefficient is suitable for use in 2D (depth-averaged) hydrodynamic modeling. The model also allows the average velocity within and beneath the canopy to be calculated, and is used to investigate the effect of canopy density and thickness on both total drag and bottom friction.     

Exploratory Study of Submerged Hydraulic Jumps with Blocks

A preliminary study on submerged jumps with baffle walls and blocks downstream of a sluice gate was conducted. Two series of experiments were carried out on baffle walls and baffle blocks. The momentum equation was utilized to derive a relation for the drag coefficient that was validated by the experimental data of the baffle wall series. The baffle block series consisted of five Froude numbers and a range of submergence factors with one configuration of baffle blocks. The inlet depth factor was found to be a function of the submergence and Froude number. It was observed that the energy dissipation efficiency was a function of submergence with the maximum efficiency being in excess of that of the corresponding free jump.     

Role of Energy Loss on Discharge Characteristics of Sluice Gates

A theoretical method was used to derive an equation for the discharge coefficient of sluice gates in rectangular channels under orifice-flow (both free and submerged) conditions. The proposed equation allows for the effects of energy dissipation between the upstream section of the gate and the vena contracta. The hydraulic energy loss in the upstream pool is attributable to the induced turbulence by the recirculating region and to the growth of bottom boundary layer. For the submerged-flow condition, turbulent shear-layer entrainment is also responsible for the energy loss. This energy loss is introduced into the equations through a coefficient k that has been conventionally assumed to be negligible. Experimental data from the literature were used to validate the equation, which showed good agreement with the measured values. It is also shown that the magnitude of the energy-loss factor is a function of the geometry of the gate and can modify the discharge coefficient. An equation for the distinguishing condition between free and submerged flows is also presented. The new equations can be used to predict the performance of sluice gates with different edge shapes under free- and submerged-flow situations.     

基于CMN和PMC算法的语音增强失真补偿方法研究

语音增强技术在低信噪比情况下,由于语音增强带来的失真使得系统的识别性能严重下降.因此提出一种结合特征空间的倒谱均值归一化算法(CMN)和模型空间的并行模型合并算法(PMC)的语音增强失真补偿技术.实验结果表明,该方法有效提高了低信噪比情况下的语音信号识别率.     

缠绕螺旋线斜拉索气动性能的数值模拟

为研究螺旋线对斜拉索气动性能的影响,采用Fluent软件的LES模块对光拉索和缠绕螺旋线拉索进行数值模拟。首先,建立了光拉索和缠绕螺旋线拉索的数值计算模型,并在拉索轴向布置9个截面的风压和风速监测点;然后,采用Fluent软件的大涡模拟模块进行了数值计算;最后,在数值模拟数据的基础上,研究了螺旋线对拉索平均阻力系数、脉动升力系数、旋涡脱落频率、风压和风速的轴向相关性、绕流流场等的影响。研究结果表明:在风雨激振发生的雷诺数范围内,缠绕螺旋线能减小拉索的平均阻力系数;破坏规则的旋涡脱落,减小脉动升力系数,降低气动力在拉索轴向方向的相关性。     

Some Transient Thermoelastic Plate Problems

The purpose of the present paper is to study the development of temperature and thermal stress fields, and this paper consists of two problems. First, a generalized thermoelastic homogeneous isotropic plate of unit thickness that is initially at temperature T _o , is studied. Second, the development of these fields in each layer of a multilayered plate using coupled thermoelastic theory is investigated. Each layer of the medium is assumed to be of isotropic elastic thermally conducting homogeneous material. Perfect mechanical bonding at the interface between the different layers is assumed. The numerical computations are carried out for a plate of stainless steel and for one-, two- and three layered plates of stainless steel and copper to display the variation of the stress and temperature fields. The computed results are illustrated graphically for each problem.     

Improved subband-forward algorithm for acoustic noise reduction and speech quality enhancement

This paper addresses the problem of speech enhancement and acoustic noise reduction by adaptive filtering algorithms. Recently, we have proposed a new Forward blind source separation algorithm that enhances very noisy speech signals with a subband approach. In this paper, we propose a new variable subband step-sizes algorithm that allows improving the previous algorithm behaviour when the number of subband is selected high. This new proposed algorithm is based on recursive formulas to compute the new variable step-sizes of the cross-coupling filters by using the decorrelation criterion between the estimated sub-signals at each subband output. This new algorithm has shown an important improvement in the steady state and the mean square error values. Along this paper, we present the obtained simulation results by the proposed algorithm that confirm its superiority in comparison with its original version that employs fixed step-sizes of the cross-coupling adaptive filters and with another fullband algorithm.     

再谈地基应力系数的配套问题

指出了应力系数表“不配套”现象的严重问题，讨论了应力系数的两类组合和应力系数公式的统一系列等问题。     

Optimal Operating Conditions For Lab-Scale Ozonation Reactors

A method for the assessment of the optimal operating conditions for a mechanically stirred gas–liquid reactor is presented. The method exploits both fluid dynamic and chemical information. First, the behavior of the specific stirring power as a function of the stirrer speed allows singling out the dispersion region, in which the most efficient gas–liquid mass transfer is achieved. Inside this region, the analysis of experimental data obtained when considering a chemical system reacting at moderate Hatta numbers (i.e., Ha < about 2) allows determination of the rate constants and the fluid dynamic parameters (i.e., the mass transfer coefficient in the absence of chemical reaction and the characteristic diffusion time).