方向性麦克风的极性图特性及增益变化特征研究

在传统的电子耳蜗体外机中,信号采集采用的是全向性麦克风。近年来的研究和产业中逐渐出现了方向性麦克风的使用以及麦克风阵列语音增强算法的研究。本文基于实际的方向性麦克风的尺寸及信号输出模式来探讨其信号采集特点、波束形成特征和增益变化的特性,研究正增益变化和负增益变化的系统响应曲线及变化特征,分析增益变化对高低频信号的不同影响,有助于方向性麦克风的进一步应用及电子耳蜗前端语音增强的研究。

电流互感器极性确定及极性引出图绘制研究

文章主要针对电流互感器调试阶段的重难点问题提供了准确可靠的极性确定方法,详细介绍了电流互感器极性确认的步骤,提出了一种确认极性的新方法。在此基础上,提供了极性引出图的绘制方法和验证步骤。可以为减少调试工作量、确保继电保护的可靠性、优化投运工作提供保障,有利于提高一次通流试验和复校带负荷试验的正确性。

一些关于C4对星的Set Ramsey 数

运用参数坐标构造出一个有限射影平面,由射影平面与射影平面上一个极性映射导出极性图. 根据 极性图, 对于一些 n,能够构造出 C4 对星 K1,n 的 set Ramsey 数 Ms(C4, K1,n) 的极值图。 由此 得到了关于这部分 n 的 Ms(C4, K1,n) 的下界并确定了一些新的精确值。

VEHICLE SEGMENTATION AND SHADOW HANDLER BASED ON EXTREMUM IMAGE

The shadows similar to the vehicle and the spots caused by vehicle lamps need to be accurately detected in the vehicle segmentation involved in the video-based traffic parameter measurement. Generally, the road surface is different from the vehicle surface in the gray-level architecture. An invariant gray-level architecture-the extremum image in the changing illumination environment is derived and a novel algorithm is presented for detecting shadows and spots. The gray-level structure that is not sensitive to the illumination is employed in the algorithm and the road surface mistaken as vehicles can be removed.

Forming limit of textured AZ31B magnesium alloy sheet at different temperatures

Repeated unidirectional bending （RUB） was carried out to improve the texture of commercial AZ31B magnesium alloy sheets. All specimens were prepared in the rolling direction. The forming limit diagrams （FLDs） of AZ31B magnesium alloy sheet were determined experimentally by conducting stretch-forming tests at room temperature, 100, 200 and 300 ℃ Compared with the as-received sheet, the lowest limited strain of AZ31B magnesium alloy sheet with tilted texture in the FLD increased by 79% at room temperature and 104% at 100 ℃. The texture also affected the extension of the forming limit curves （FLC） in the FLD. However, the FLCs of two kinds of sheets almost overlapped at temperature above 200 ℃. It can be concluded that the reduction of （0002） texture intensity is effective to the improvement of formability not only at room temperature but also at low-and-medium temperature. The effect of texture on FLDs becomes weak with increasing temperature.

Formability of AA5052/polyethylene/AA5052 sandwich sheets

The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the hot pressing adhesive method. Then, the uniaxial tensile tests were conducted to investigate the mechanical properties of AA5052/polyethylene/ AA5052 sandwich sheets, and the stretching tests were carried out to investigate the influences of polymer core thickness on the limit dome height of the sandwich sheet. The forming limit curves for three kinds of sandwich sheets were obtained. The experimental results show that the forming limit of the AA5052/polyethylene/AA5052 sandwich sheet is higher than that of the monolithic AA5052 sheet, and it increases with increasing the thickness of polyethylene core.

Stress based forming limit diagram for formability characterization of 6061 aluminum

Two numerical criteria of forming limit diagram（FLD） criterion and ductile fracture criterion（DFC） are presented for FLD prediction of 6061 aluminum. The numerical results are compared with the experimental FLD and also punch＇s load-displacement curve of experimental samples. Experimental FLD of this study is calculated using hemispherical punch test of Hecker. Experimental FLD is converted to FLSD and imported to the Abaqus software to predict necking of samples. Numerical results for FLSD prediction were compared with experimental FLSD. Results show that ductile fracture criterion has higher accuracy for FLD and FLSD prediction of 6061 aluminum. Comparison of numerical and experimental results for force-displacement curve of punch shows that numerical results have a good agreement with experiment.

Prediction of fracture limits of Ni-Cr based alloy under warm forming condition using ductile damage models and numerical method

The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit diagram(FFLD)was transformed into a stress-based(σ-FFLD)and effective plastic strain(EPS)vs triaxiality(η)plot to remove the excess dependency of fracture limits over the strains.For the prediction of fracture limits,seven different damage models were calibrated.The Oh model displayed the best ability to predict the fracture locus with the least absolute error.Though the experimentally obtained fracture limits have only been used for the numerical analysis,none of the considered damage models predicted the fracture strains over the entire considered range of stress triaxiality(0.33<η<0.66).The deep drawing process window helped to determine wrinkling,safe and fracture zones while drawing the cylindrical cups under different temperature and lubricating conditions.Further,the highest drawing ratio of 2 was achieved at 673 K under the lubricating condition.All the numerically predicted results of both stretch forming and deep drawing processes using the Hill 1948 anisotropic yielding function were found to be good within the acceptable range of error.

江西吉泰盆地晚白垩世红层的磁性地层学

根据古地磁极性柱状图和国际极性柱状图的对比，吉盆盆地钻孔所穿透的红色地层应该是晚白垩世。其持续时间是前100Ma-前65Ma，在其上统南雄组（K2n)与赣州组（K2g)之间有一短暂的反向期，可作为两者划分的极性依据。此外，还推算出南雄组的沉积速率从薄至厚是0．038mm/a→0.109mm/a→0.152mm/a；赣州组则为0.023mm/a→0.039mm/a→0.043mm/a。

UNSUPERVISED POLINSAR CLASSIFICATION BASED ON OPTIMAL COHERENCE SET

Aiming to solve the misclassification problems of unsupervised polarimetric Wishart clas- sification algorithm based on Freeman decomposition, an unsupervised Polarimetric Synthetic Aper- ture Radar （SAR） Interferotnery （PolInSAR） classification algorithm based on optimal coherence set parameters is studied and proposed. This algorithm uses the result of Freeman decomposition to divide the image into three basic categories including surface scattering, volume scattering, and double-bounce Then, the PolInSAR optimal coherence set parameters are used to finely divide each of the three basic categories into 9 categories, and the whole image is divided into 27 categories. Because both the Freeman decomposition result and optimal coherence set parameters indicate specific scattering characteristics, the whole image is merged into 16 categories based on physical meaning. At last, the Wishart cluster is employed to obtain the final classification result. To preserve the purity of scattering characteristics, pixels with similar scattering characteristics are restricted to be classified with other pixels. The final classification results effectively resolve the misclassification problem, not only the buildings can be effectively distinguished from vegetation in urban areas, but also the road is well distinguished from grass. In this paper, the E-SAR PolInSAR data of German Aerospace Center （DLR） are used to verify the effectiveness of the algorithm.

Full polarization scattering characteristics of sea fractal surface

In the conventional single polarization SAR system, only the scattering information of HH polarization or VV polarization can be obtained. Only co-polarizaion scattering cases are considered and cross-polarizaiton （HV and VH polarization） scattering cases are neglected. Therefore, much important information must be lost. Research on full polarization SAR system is an important approach to extract more useful information from SAR imaging. In this paper, the authors derived the full polarization scattering coefficients of 2-D sea fractal surface and simulated the radar cross section （RCS） of different polarizations. They also gave the exact theoretical explanations of the fully polarization scattering characteristics of sea fractal surface, and confirmed that the depolarization can be neglected. The result is the basis of the full SAR system design and SAR imaging.

Formability of the AMS 5596 Sheet in Comparison with EDDQ Steel Sheet

Some materials form better than others, moreover, a material that has the best formability for one stamping may behave very poorly in a stamping of another Configuration. The forming limit of a metal sheet is generally given in terms of the limiting principal strains under different loading conditions and represented by the so-called FLD （forming limit diagram）. In view of the difficulty to experimentally determine the forming limits, many researchers have sought to predict FLD. The formability of sheet metal has frequently been expressed by the value of strain hardening exponent and plastic anisotropy ratio. The stress-strain and hardening behaviour of a material is very important in determining its resistance to plastic instability. For these reasons, extensive test programs are often carried out in an attempt to correlate material formability with value of some mechanical properties. In this study, mechanical properties and the FLD of the AMS 5596 sheet metal was determined by using uniaxial tensile test and Marciniak＇s flat bottomed punch test respectively.

CHAOS AND ORDER OF INVERSE LIMIT SPACE FOR A GRAPH MAP

With the method of inverse limit, the author obtains several criteria of chaos of piecewise monotone continuous maps on finite graphs.