血管数字减影图象中的结构特征提取

基于Ｘ线数字减影图象的三维血管结构重建很大程度上依赖于图象中血管的有效检测和结构关系描述。本文给出一个在局部特征检测基础上的结构特征提取和组织方法，涉及结构分析之前的中间视觉处理层次，即将图象中主要结构分离出来供结构分析之用。首先用一个突出结构检测算法独立地组织和选择中轴曲线片断和边缘曲线片断，然后将两者信号相结合以验证突出结构算法获得的结果并滤除噪声结构。     

一种获取摄像机安装高度及倾角的简易标定方法

提出了一种在摄像机内参数已知的情况下,通过地面上已知的4个及以上共面点求解出摄像机安装高度和安装倾角的标定方法.选定地面为X-O-Y面,则Z轴方向的平移因子即为摄像机的安装高度.方法借鉴了利用共面点进行标定的方法,在计算过程中利用投影矩阵元素间的比值关系,巧妙地消除了深度因子的影响,求解出了旋转角度和摄像机的安装高度,进而得到了摄像机的外参数矩阵.将多组实验计算出的安装高度结果和实际测量值相对比,得到的误差非常小,证明了该算法计算简便且具有较高的准确性.     

格的归约理论和它在密码学中的应用

介绍和讨论了格理论在公钥密码体制中的应用.利用格的归约技术可以分析研究计算部分密钥位与整个密钥位的计算复杂性.在均匀模式下,计算基于公钥系统的Okamoto协议的2loglogp密钥位与计算整个密钥的难度是相同的.用格的理论建立了一个公钥密码系统,且该系统是安全的,除非能够在多项式时间内从n维格L中找到最短的非零向量.     

零电压开关预燃电源的研究

本文提出了在脉冲氙灯预燃电路中将着火电压与预燃电流由不同电路来提供的设计思想 ,并采用了零电压开关技术。对逆变器的工作过程进行了数学分析 ,对功率开关管实现零电压开通的条件进行了讨论。实验证明该预燃电源在负载断路和短路情况下都能正常工作 ,功率开关管的开关损耗非常小 ,开关频率可达 10 0 k Hz,减小了电源体积 ,提高了电源效率 ,适用于各种尺寸的脉冲氙灯。     

卫星传感器网络的定位算法及在应急通信中应用

针对应急通信系统的需求,提出了一种基于卫星传感器网络的应急监测与通信系统.介绍了卫星传感器网络的基本概念和网络结构,基于RSSI信息的多重覆盖策略,提出了一种适于卫星传感器网络的非测距定位算法-MOLA.仿真结果表明,该定位算法能够满足应急通信与监测系统对定位性能的需要.     

Modulation instability of dispersion-shifted fiber couplers

The nonlinear coupled-mode equations are rewritten by even and odd modes. We study modulation instability (MI) of dispersion-shifted fiber couplers when either even or odd mode is launched alone by using zero-dispersion waveleng threlatively long (quasi-cw) pulses. The result shows that there are new types of MI in both the normal-dispersion and the anomalous-dispersion regimes. MI is concerned with forth-order dispersion and has no relation with third-order dispersion.Quasi-cw can be changed into pulses array under certain conditions. We can extract super short pulse from this. Furthermore,the bandwidth of gain spectra widens and its strength accretes as the input power increases.     

Prediction of the pipe buckling by using broadening factor with distributed Brillouin fiber sensors

We successfully measured longitudinal strains in two full-scale steel pipe specimens subjected to loading combinations of internal pressure, axial tensile force and bending moments undergoing local buckling under controlled laboratory conditions. Carbon-coated fibers, for the first time, and standard communication fibers were used. By using the broadening factor of the Brillouin spectrum width, we can successfully predict the location and progression sequence of buckling patterns, prior their visual detection in the laboratory. The broadening factor processing time is more efficient than multiple-peak fitting of the Brillouin spectrum method. Thus, it is capable of proving real-time deformation progression in structural health monitoring applications. High strength carbon-coated fibers are found to be superior to standard communication fibers in two respects: they provide more accurate readings and are able to measure significantly larger strains.     

Continuous and Damped Vibration Detection Based on Fiber Diversity Detection Sensor by Rayleigh Backscattering

An optical fiber vibration sensor based on a polarization diversity scheme has been developed to study structural vibration properties under external disturbance. The polarization diversity scheme has improved signal-to-noise ratio (SNR) by over 13 dB with capability of detection frequency of sub-hertz to tens of kilo- hertz. The minimum dynamic strain we have detected is 3 nepsiv, and the SNR of the sensor is >37 dB without any averaging. For the first time, Rayleigh backscattering has been utilized to detect continuous and damped vibration generated by a piezo fiber stretcher and vibrating cantilever with a frequency range of sub-hertz to 16 kHz. We also use this sensor and polarization analyzer to characterize the polarization state change and phase shift of the piezo fiber stretcher in transmission and Rayleigh backscattering up to kilohertz frequency, both results agrees quantitatively.     

基模螺旋天线的研究

本文提出了一种计算基模螺旋天线的新方法.该方法采用螺旋线段对基模螺旋天线进行划分,只需少量分段就可用矩量法对其进行精确模拟分析.文中求出了螺旋天线上的电流分布和远场方向图,与直线段模拟计算结果吻合良好.求阻抗矩阵 Z时,利用螺旋天线的对称性和周期性,只需求出一小部分元素就可得到Z 矩阵的其它元素的值.该方法分段数少,使得计算时间和计算所需存储量大大减小,计算速度和精度显著提高.     

Toward better wireload models in the presence of obstacles

Wirelength estimation techniques typically contain a site density function that enumerates all possible path sites for each wirelength in an architecture and an occupation probability function that assigns a probability to each of these paths to be occupied by a wire. In this paper, we apply a generating polynomial technique to derive complete expressions for site density functions which take effects of layout region aspect ratio and the presence of obstacles into account. The effect of an obstacle is separated into two parts: the terminal redistribution effect and the blockage effect. The layout region aspect ratio and the obstacle area are observed to have a much larger effect on the wirelength distribution than the obstacle's aspect ratio and location. Accordingly, we suggest that these two parameters be included as indices of lookup tables in wireload models. Our results apply to a priori wirelength estimation schemes in chip planning tools to improve parasitic estimation accuracy and timing closure; this is particularly relevant for system-on-chip designs where IP blocks are combined with row-based layout