基于改进的CV模型的医学图像分割

基于CV模型的水平集分割是医学图像分割的一个重要的分割手段。医学图像分割要求精度高,速度快。传统的处理方式效率比较低,不能满足医学图像的分割要求。针对这一缺点,本文提出新的分割模式。首先,在分割过程中间断的对图像进行窗口化处理,减少演化过程所需计算的数据量。同时使活动轮廓的演化速度伴随窗口规模进行调整,减少演变所需的迭代次数。实验表明,改进之后分割方法能够极大的提高分割速度,同时图像细节部分的分割也有更高的精度。     

基于全网业务模型和蒙特卡洛仿真的电力通信网可靠性评估

传统的电力通信网可靠性研究基于网络的拓扑结构和业务流向,没有考虑电力通信业务复杂的组网方式。基于烟台电力通信网在运业务的实际情况,提出了复杂的系统级仿真模型。在此基础上,提出了光缆可靠度和设备可靠度的概念。另外,本文提出了可靠性破坏代价的概念,通过蒙特卡洛系统级仿真,给出电力通信网全网的可靠性数据。     

Comparative Assessment of Adaptive Body-Bias SOI Pass-Transistor Logic

A very low voltage transconductor for video frequency range applications and compatible with standard CMOS technology is described. In the proposed transconductor, except the DC level shifter circuit (DCLS), the whole transconductor uses the main supply voltage [which can be as low as 1.5 V in a standard 0.6 μm CMOS technology] while the DCLS uses a simple charge-pump circuit as its supply voltage and has a very low current consumption. In addition, proper common-mode sense and charge-pump circuits are developed for this low-voltage application. Meanwhile, some techniques to improve the frequency response, linearity, and noise performance of the proposed transconductor are described. In a standard 0.6 μm CMOS technology and single 1.5 V supply, simulations show that the proposed transconductor futures a THD of −50 dB for 1.4 V_pp and 10 MHz input signal and −60 dB for 1.4 V_pp and 1 MHz signal where the threshold voltage of MOS transistors could be as high as 1 V. Based on the proposed transconductor, a lowpass filter with 700 kHz to 8 MHz programmable cutoff frequency and a bandpass 10.7 MHz second order filter were implemented. Armin Tajalli received the B.Sc. from Sharif University of Technology (SUT), Tehran, Iran, in 1997, and M.Sc. from Tehran Polytechnic University, Tehran, Iran, in 1999. From 1998 he has joint Emad Co. as a senior design engineer were he has worked on several industrial and R&D projects on analog and mixed-mode ICs. He received the award of the Best Design Engineer from Emad Co., 2001, the Kharazmi Award of Industrial Research and Development, Iran, 2002, and Presidential Award of the Best Iranian Researchers, in 2003. He is now working toward his PhD degree at SUT. His current interests are design of high speed circuits for telecommunication systems. Mojtaba Atarodi received the B.S.E.E. from Amir Kabir University of Technology (Tehran Polytechnic) in 1985, and M.Sc. degree in electrical engineering from the University of California, Irvine, in 1987. He received the Ph.D. degree from the University of Southern California (USC) on the subject of analog IC design in 1993. From 1993 to 1996 he worked with Linear Technology Corporation as a senior analog design engineer. Since then, he has been consulting with different IC companies. He is currently a visiting professor at Sharif University of Technology. He has published more than 30 technical papers in the area of analog and mixed-signal integrated circuit design as well as analog CAD tools.     

Minimum Duration Outage for CDMA Cellular Systems: A Level Crossing Analysis

Traditionally, outage for CDMA cellular systems has been defined as the signal level (or, more precisely, the signal-to-interference ratio (SIR)) falling below a required threshold. In real cellular environments, it is not the instantaneous drop of the signal strength below the threshold that determines outage. It is, in fact, the duration of time below a threshold that determines outage for cellular systems. Moreover, the static analysis of outage precludes the time correlation in the signals which is important in real systems owing to mobility, fading and power control. In this paper, we analyze minimum duration outages for such systems, where outage is defined as an excursion of the SIR below a level for a certain minimum duration. We formulate the outage condition as a level crossing problem and extend asymptotic results from the theory of level crossings to derive analytical results for the probability of outage. This method enables us to include the time correlation of signals in the analysis as well. The validity of the asymptotic results is verified using some exact results as well as simulations. These minimum duration outages have implications in redefining user capacity and handoff performance.     

万安水电站汛期运行研究

万安水电站位于赣江中游，肩负有上下游防洪任务，下游防洪控制点为吉安、石上两站．电站正常运行后，正常蓄水位和防洪高水位均为100．00m，防洪限制水位和死水位均为90．00m．受移民条件限制，初期运行上述特征水位均降低，主汛期4～6月库水位控制在85．00m，发电水头比正常运行降低5m，机组出力受阻达40％以上，致使电站效益不能充分发挥，而4～6月恰为用电高峰期，电网缺电十分严重．为解决主汛期发电和防洪的矛盾，提出了汛期采用预泄办法提高运行水位的方法，即在水文气象预报的有效预见期（18～24h）内，按8800m3／s控制下泄，使库水位从8800m或90．00m泄至85．00m，可满足万安水电站防洪的两个约束条件，即回水对赣州市的影响既不超过0．3m，也不会加重下游的防洪负担．经过1993年6月的实际运行，证明此方法是可行和有效的，提高万安水电站的运行水位，既增加了经济效益，又提高了运行水头，改善了机组工况．     

Majority and minority carrier traps in monocrystalline CulnSe2

Electron and hole traps in Bridgman-grown monocrystalline CuInSe₂ were investigated by carrying out deep level transient spectroscopy measurements on homojunctions, Al-CuInSe₂ (p-type), and Au-CuInSe₂ (n-type) Schottky junctions. Three hole trap levels and two electron trap levels were observed on these devices. Effects of oxygen and etching on the electron trap level at 182 ±15 meV from the conduction band edge were specifically studied. It was found that the election trap densities in the homojunctions prepared using the CuInSe₂ samples treated in NH₂NH₂ solution, which absorbes oxygen atoms in the samples, were larger than the electron trap densities in the homojunctions prepared using untreated samples. Moreover, the electron trap densities in the homojunctions after prolonged heat treatment in O₂ were less than that without prolonged heat treatment. The results thus suggested that oxygen atoms in CuInSe₂ can reduce the electron trap density of p-type CuInSe₂. The effects of chemical etching on these electron traps were also studied. The excess indium atoms in the CuInSe₂ were considered to affect the electron traps.     

New privilege-based visual cryptography with arbitrary privilege levels

Recently, Hou et al. introduced a novel (2, n) privilege-based visual cryptography scheme (PVCS) with various privilege levels of shadow images. In this scheme, a shadow with a higher privilege contributes more recovered information, while a lower privileged shadow has the less recovery capability. Moreover, the visual quality of stacked result depends on the total sum of privilege levels for all involved shadows in reconstruction. Unfortunately, the PVC scheme has the inconsistency of the contrast of recovered image and the sum of privilege levels. Accordingly, an enhanced Hou et al.’s (2, n)-PVC scheme (EPVCS) is proposed to solve this inconsistency problem. However, the EPVCS is not a general solution to implement all PVCSs with arbitrary privilege levels, and it also has the unequal whiteness of shadows. In this paper, we first extend Hou et al.’s (2, n)-EPVCS with a correct privilege levels achieving the consistency of the contrast and the sum of privilege levels. Then we construct a (2, n)-PVCS to allow arbitrary privilege levels and provide the equal whiteness for each shadow.     

基于LabVIEW的闪变仪软件设计

LabVIEW是虚拟仪器中的一种图形化编程语言,不但能够完成一半的数学运算与逻辑运算和输入输出功能,还带有专门用于数据采集和仪器控制的库函数和开发工具,以及专业的数学分析程序包,基本上可以满足复杂的工程计算和分析要求.由电网电压波动引起的照明灯光闪烁现象,即闪变,给人们的日常工作和生活带来了许多不便.为了统一国际上闪变测试方法与评价标准,国际电工委员会(IEC)制定了闪变仪的测试功能和设计规范.采用低级通用的运算模式,分析了IEC闪变仪灯-眼-脑环节各部分的输入输出信号.根据IEC制定的闪变仪的设计规则,利用LabVIEW建立了数字式闪变仪灯-眼-脑环节的模型,使之能对电压数字信号进行分析处理,得到电压瞬时闪变视感度.仿真结果验证了用灯-眼-脑传递函数形式来逼近视感度系数,能够得到正确的结果.     

基于市县一体平台的县（区）数字电视整转的实践

在基于市县一体的技术业务平台实施县（区）级有线电视数字化整转和运维中,充分结合武进自身管理和个性需求特点,在分前端建设、网络改造、大功率中波台的干扰问题、节目授权、机卡配对、整转断模、机顶盒维修等方面有许多创新举措,使全区30万用户的整转和运维工作取得了快速高效、平稳有序、安全运行的良好成效。     

Reliability assessment of principal point estimates for forensic applications

Although quite recent as a forensic research domain, computer vision analysis of scenes is likely to become more and more important in the near future, thanks to its robustness to image alterations at the signal level, such as image compression and filtering. However, the experimental assessment of vision-based forensic algorithms is a particularly critical task, since they cannot be tested on massive amounts of data, and their performance can heavily depend on user skill. In this paper we investigate on the accuracy and reliability of a vision-based, user-supervised method for the estimation of the camera principal point, to be used in cropping and splicing detection. Results of an extensive experimental evaluation show how the estimation accuracy depends on perspective conditions as well as on the selected image features. Such evidence led us to define a novel visual feature, referred to as Minimum Vanishing Angle, which can be used to assess the reliability of the method.