A NEW ESTIMATION METHOD OF SPATIAL PEAK TEMPORAL AVERAGE INTENSITY AND SPATIAL PEAK PULSE AVERAGE INTENSITY IN HIFU FIELD

High intensity focused ultrasound( HIFU) inmedicine has been developed rapidly for more thanten years.It changes the situation of slowly ad-vancing in ultrasonic therapy. HIFU has become anew character of ultrasound in medicine.The ex-tracorporal lithotriptor,the pyrothrapy,the HIFUsurgery,the HIFU hemostasis,and the HIFUabortion are the most important progresses.Theyshow that the applications of ultrasound in therapywill have greater project than that in diagnosis[1] .China has made m…     

基于灰色关联的数字图像去噪研究

在图像去噪过程中为了既能获得较好的去噪效果，又能更好地保护图像细节，运用灰色系统理论的灰关联度的思想提出了一种基于灰色关联的加权均值滤波器．尝试了将灰色理论中的灰色关联用于图像的均值去噪，对均值滤波器的权值加以优化．实验表明，该算法使图像处理效果比传统的均值滤波效果有所提高。     

复合噪声图像去噪

在现实的图像处理中,图像往往含有加法均匀或者高斯分布噪声的干扰.如果只使用邻域平均法或中值滤波法都不能很好的对图像进行去噪.提出了一种复合型去噪法.该算法首先利用分离像素法把不同噪声污染的像素区别开来,然后分别再用中值滤波或邻域平均法去噪.实验结果表明,此方法具有很强的可信度.     

某型变速器箱体振动噪声分析研究

以某新开发的变速器箱体为研究对象,利用HyperWorks软件建立该变速器箱体的有限元模型。对变速器箱体做自由模态分析和频率响应分析,得到其模态频率分布和相应振型,避开共振点,获得箱体表面振动的速度响应云图。最后对变速器箱体进行辐射噪声分析,提取箱体表面的噪声分布图以得到声辐射敏感区域,提出改进箱体结构的措施。该研究为变速器减震降噪提供重要参考。     

Human machine collaborative support scheduling system of intelligence information from multiple unmanned aerial vehicles based on eye tracker

Many human-machine collaborative support scheduling systems are used to aid human decision making by providing several optimal scheduling algorithms that do not take operator’s attention into consideration. However, the current systems should take advantage of the operator’s attention to obtain the optimal solution. In this paper, we innovatively propose a human-machine collaborative support scheduling system of intelligence information from multi-UAVs based on eye-tracker. Firstly, the target recognition algorithm is applied to the images from the multiple unmanned aerial vehicles (multi-UAVs) to recognize the targets in the images. Then, the support system utilizes the eye tracker to gain the eye-gaze points which are intended to obtain the focused targets in the images. Finally, the heuristic scheduling algorithms take both the attributes of targets and the operator’s attention into consideration to obtain the sequence of the images. As the processing time of the images collected by the multi-UAVs is uncertain, however the upper bounds and lower bounds of the processing time are known before. So the processing time of the images is modeled by the interval processing time. The objective of the scheduling problem is to minimize mean weighted completion time. This paper proposes some new polynomial time heuristic scheduling algorithms which firstly schedule the images including the focused targets. We conduct the scheduling experiments under six different distributions. The results indicate that the proposed algorithm is not sensitive to the different distributions of the processing time and has a negligible computational time. The absolute error of the best performing heuristic solution is only about 1%. Then, we incorporate the best performing heuristic algorithm into the human-machine collaborative support systems to verify the performance of the system.     

城市轨道交通轨道减振降噪设计研究

城市轨道交通的快速发展在创造良好的经济、社会和环境效益的同时,也不可避免地给城市带来了振动和噪声问题。通过对噪声源进行分析,得出轮轨噪声是城市轨道交通的主要噪声源。因此,合理选择轨道结构的型式是最为有效的减振降噪措施。通过对各种轨道结构减振型式的分析比选,得出轨道减振设计中合理、有效的减振降噪措施。     

单矢量水听器改进MUSIC算法的噪声抑制性能研究

针对MUSIC算法在相干噪声背景下估计目标方位性能下降的问题,利用酉变换的空时相关矩阵（unitary spatio-temporal correlation matrice—USTCM）,替代MUSIC算法中的数据协方差矩阵,设计了单矢量水听器的USTC-MUSIC算法,通过仿真验证了新方法不论噪声是不相干或相干,其噪声抑制能力和目标分辨能力均优于原方法.     

Speckle reduction based on contourlet transform using scale adaptive threshold for medical ultrasound image

A new speckle suppression method in contourlet domain was presented. By modeling the subband contourlet coefficients of the ultrasound images after logarithmic transform as generalized Gaussian distribution (GGD), we gave a scale-adaptive threshold in Bayesian framework. Experimental results of both synthetic and clinical ultrasound images show that our method has a better performance on speckle suppressing than the wavelet-based method while well preserving the feature details.     

基于邻域相关的自适应中值滤波算法

为改善图像效果,在对现有的椒盐噪声自适应中值滤波算法分析的基础上,提出了基于邻域相关的自适应中值偏移滤波算法。算法对自适应中值滤波算法的处理过程进行改进。当滤波窗口大于设定的最大值时,根据像素点邻域内的像素点灰度值分布在不同的区间,将像素点灰度值的复原分为偏大或偏小两种情况。受污染像素点的滤波输出值为偏移的中值,偏移的距离根据改进的自适应中值滤波算法运行时滤波窗口的大小来决定。从仿真结果可见:该算法滤波后的图像具有较高的峰值信噪比,对图像细节的保留能力和抑制椒盐噪声的能力都有一定的提高。     

基于小波变换和自适应直方图均衡的红外图像增强

针对实际应用中红外图像的对比度较低、存在噪声的缺点,结合人的视觉特征,在已有图像增强方法的基础上,采用小波变换与自适应直方图均衡相结合的方法对红外图像进行增强.该方法不但解决了红外图像对比度低的问题,而且降低了噪声,突出了图像细节.     

超低频接收信号降噪研究

在建立超低频接收信号模型的基础上,对超低频接收信号误码率性能进行了分析。将小波降噪算法应用于超低频噪声处理中,通过Monte Carlo计算机仿真试验,对基于小波降噪和传统数字滤波的方法对模拟的超低频接收信号进行噪声处理,并对降噪后的误码率性能进行分析,结果表明,应用小波降噪的方法对超低频接收信号进行非线性噪声处理,比传统数字滤波的方法能带来更高的信噪比增益。     

跳跃扩散模型外汇重置期权定价

在完全外汇市场环境下讨论了外汇汇率过程受Brown运动和Possion过程共同驱动时外汇重置期权的定价问题.利用等价鞅测度和标准正态分布函数给出了这一模型下单时点重置外汇看涨期权的定价公式,最后在常系数条件下导出了一种特殊形式外汇重置期权的Black-Scholes公式.     

超低频接收信号降噪研究

在建立超低频接收信号模型的基础上,对超低频接收信号误码率性能进行了分析。将小波降噪算法应用于超低频噪声处理中,通过Monte Carlo计算机仿真试验,对基于小波降噪和传统数字滤波的方法对模拟的超低频接收信号进行噪声处理,并对降噪后的误码率性能进行分析,结果表明,应用小波降噪的方法对超低频接收信号进行非线性噪声处理,比传统数字滤波的方法能带来更高的信噪比增益。     

超声清洗槽内声场分布的研究

从一维平面波理论入手分析了超声清洗槽内的声场分布特性,用水听器法和染色法测量了超声清洗槽内的声场分布.结果表明,清洗槽内液面水平方向上的声压分布比较均匀,垂直方向上的声压由槽底到液面呈起伏变化,显示了驻波特性,总体上有逐渐减小的趋势,这说明了声波在传播过程中有一定的衰减.实验测量的声压分布和理论分析的结果比较一致.     

智能车牌识别系统中消除图像干扰的方法

在智能车牌识别系统中,经过汽车图像的初分割,可从复杂的汽车及背景图像中分割出汽车图像,但复杂灰度图像经二值化处理后存在许多干扰白点.提出一种＂高斯滤波＂的方法去除这些白点,使二值化图像变得平滑、少毛刺,并具有较好的连通性.     

一种基于卡尔曼数据平滑的分段曲线拟合室内定位算法

室内定位技术的关键在于获取距离参数,在这一问题的研究中运用RSSI信号获得距离参数一直是比较通行的方法.本文针对室内环境复杂,接收RSSI信号存在较大噪声的情况,提出了一种运用卡尔曼滤波器对信号数据进行平滑预处理,随后利用最小二乘法进行分段曲线拟合从而实现定位的算法.通过实验测试结果表明,本文所提出的算法平均定位精度可达0.9 m,与普通数据平均值预处理算法和曲线直接拟合方法相比较,定位精度更高;比直接应用对数距离损耗路径模型的定位算法更为合理可靠,能够在一定程度上满足无线传感器网络室内定位需求.     

大直径钻孔灌注桩的承载力发挥特征分析

以某工程大直径桩为研究对象,采用现场试桩、理论分析计算相结合的方法,对大直径深长钻孔灌注桩的承载力发挥特征进行了研究,主要包括以下几个内容：（1）进行了4根大直径桩静载荷试验,获得了各试桩的极限承载力;（2）通过在桩身埋设钢弦式钢筋计,量测得各级荷载下桩身的内力变化情况;（3）通过计算得出桩身轴力和桩侧摩阻力沿桩身的分布规律以及桩侧摩阻力和桩端阻力的发挥情况,并以此为基础研究了桩基荷载传递特性及侧摩阻力发挥规律。     

汽车交流发电机端盖栅格对其气动噪声和温度特性的综合影响

为了同步提高目前新能源汽车发电机的气动噪声性能和散热效果，满足更严苛的噪声、振动与声振粗糙度需求，以某型汽车交流发电机为研究对象，基于台架试验和数值仿真方法探究端盖栅格对气动噪声和温度场分布的综合影响规律；基于五点法获得了噪声声压级分布，基于多热电偶测点获得了关键部件的温度分布，基于计算流体动力学仿真软件和电磁场Maxwell仿真软件获得了发电机内部的流场、声场和温度场分布，采用试验结果验证数值计算模型的正确性；在分析原始发电机气动噪声特性和温度场特性的基础上，设计了具有不同倾角的端盖栅格侧壁以降低冷却气流冲击的动能损失，探讨了端盖栅格倾角和扇叶气流出口角的合理匹配，并基于牛顿冷却理论研究了波状端盖栅格对增加换热表面面积和降低气动噪声的影响。研究结果表明:端盖栅格结构对气动噪声有较大贡献，同时也对冷却效果产生显著影响；端盖栅格侧壁倾斜40°时能够和扇叶气流出口角更合理地匹配，有效减少冷却气流冲击的能量损失，三相定子绕组最高温度降低9.63 K，12阶次气动噪声降低3 dB(A)以上；波纹状端盖栅格增加对流换热面积和气流速度的同时降低了气动冲击作用，使得端盖散热量增加7.72 W，定子铁芯、端盖和三相定子绕组温度分别降低了5.12、4.94和5.29 K，栅格对涡流的改善以及气流对栅格的冲击削弱使12和24阶次气动噪声降低3 dB(A)以上。      

Analysis of through-the-thickness stress distribution in thick laminate multi-bolt joints using global-local method

The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain the stress state around the fastener hole in multi-bolt thick laminate joints, a global-local approach is introduced. In the method, the most seriously damaged zone is 3D modeled by taking the displacement field got from the 2D global model as boundary conditions. Through comparison and analysis there are the following findings: the global-local finite element method is a reliable and efficient way to solve the stress distribution problem; the stress distribution around the fastener hole is quite uneven in through-the-thickness direction, and the stresses of the elements close to the shearing plane are much higher than the stresses of the elements far away from the shearing plane; the out-of-plane stresses introduced by the single-lap joint cannot be ignored due to the delamination failure; the stress state is a useful criterion for further more complex studies involving failure analysis.     

Logit模型的改进及其在客流分担率预测中的应用——以成渝城际铁路为例

为了进一步提高Logit模型效用函数的准确性、适时性和适用性,增加了Logit模型的衡量指标,充分考虑新指标对总效用的影响,重新定义了效用函数.运用改进后的Logit模型,以成渝城际铁路全长352 km的东线方案实施并通车为背景,在成渝城际铁路实施公交化运营、公路运输进一步缩短旅行时间的新一轮公铁竞争中,估算出铁路、公路和民航的分担率.预测结果显示,铁路客流分担率仍能上升11%,从而达到87.8%,在未来成渝客运市场中占有绝对优势,而公路的份额将减少至10.7%.通过分析构建的效用函数中各个因素变化的灵敏度,作者提出建议:为了提高成渝城际铁路客流分担率,最关键的因素是提高购票成功率和增加旅行舒适度.