Determination of appropriate RF blocking impedance for MRI surface coils and arrays

Surface and phased array receiving coils in MRI typically require that RF excitation be accomplished using the body coil. This process requires that the receiving coils contain blocking circuitry to increase the overall circuit impedance during RF excitation and withstand the electromotive force induced by the applied electromagnetic field. The aim of this study was to determine the optimal impedance range required during RF excitation based on an assessment of image quality. The experimental results are fit by an exponential model and establish criteria that can be applied for general receiver coil design.     

应用在混合式光电电流互感器中的Rogowski线圈

介绍了光电式电流互感器的一种类型－混合式光电电流互感器的传感头采样线圈,即Ｒｏｇｏｗｓｋｉ线圈的原理,结构及实验结果。     

Self-insurance of investor under repeating catastrophic risks

A decision-making problem of investment into a profitable object in a catastrophic risk area is considered. By a catastrophic risk is meant the probability of severe yet unlikely losses. As a risk hedging mechanism, an insurance fund is considered that is replenished by a part of profit and is used for object renewal. It is shown that methods of insurance mathematics can be used to assess the risk to lose the object. For the plant loss probability as a function of the insurance reserve, integral equations are derived. They can be solved by successive approximations. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 74–83, May–June 2007.     

Information properties of the simplest feedback operator and certain conclusions

A study of the response to a random input signal of the simplest operator with constant transfer factor in a direct channel where there is negative feedback present is carried out. It is shown that feedback in the channel exerts a positive influence on the information properties of the output quantity. It is suggested that the results of the study can be recommended for the construction of reliable computations in future computers and other information systems.     

Robust correlation coefficients as the initial data for the solution of problems of confluent analysis

A technology for the solution of problems of confluent analysis of noisy technological processes is developed based on the technologies used in calculation of the variance of interference, the degree of robustness of estimators of the auto-and cross-correlation functions, robust correlation matrices, and balance algorithms for the relative errors of their elements.     

一种面向主动服务的情境觉察计算方法

We focus on modeling and computing of aware con- text with uncertainty for making dynamic decision during seam- less mobile service.We re-examine formalism of random set, which is not finite-set statistics (FISST),argue the limitations of the direct numerical approaches,give new modeling mode based on random sets theory (RST) for aware context,and propose our computing approach of modeled aware context.In addition, we extend classic D-S evidence theory after considering relia- bility,time efficiency,relativity of context,and compare these two kinds of relative computing methods for uncertain context. By comparing,the validity of new context-aware computing ap- proach based on improved random set theory (IRST) or extended D-S evidence theory (EDS) for proactive service has been tested.     

计算机病毒的随机传染模型

传染是计算机病毒的主要特征之一,病毒的传染不仅提高了病毒的存活率,而且对计算机系统资源造成破坏和威胁。为了分析计算机病毒在计算机内的微观传染规律,在分析病毒传染机制的基础上,结合当前操作系统的特点,建立和分析了计算机病毒在单个计算机系统内的随机传染模型。得出结论:在单进程操作系统环境下,病毒的感染数量呈线性增长,感染强度相对稳定;在多进程操作系统环境下,病毒的感染数量和感染强度都呈e的指数级增长。最后提出了反病毒传染技术的发展趋势。     

新型巨磁阻抗传感器的特性研究

研究了非线性非对角化GMI传感器的信号拾取线圈参数对传感器灵敏度的影响.这些参数包括线圈的长度,线圈的直径,线圈的匝数以及线圈所用漆包线直径.结果显示传感器灵敏度正比于驱动频率和线圈匝数,同时线径变小和线圈直径变小有利于提高灵敏度.使用1 000匝的线圈时获得了最佳效果,该传感器测量范围在±400 A/m,灵敏度为3.518×10-2V/Am-1,分辨率为10-7 A/m,可在室温至150℃间正常工作,显示了其在弱磁测量上的巨大潜力.实验结果利用法拉第定律和线圈参数得以解释.     

微硬盘时变线性系统的随机扰动衰减研究

针对微硬盘伺服系统中音圈马达驱动器的不确定时变线性模型，利用李亚普诺夫稳定性理论及线性矩阵不等式，提出一种非线性观测器及其相应的含饱和项的反馈控制器．从理论上论证了系统在所设计的控制器作用下能全局一致毕竟有界，并实现了扰动衰减．应用多种类型的扰动测试该控制器，结果显示磁头的输出能快速进入和保持在指定磁道所容许的范围内，而且，在该控制器作用下，扰动衰减速度快.     

随机中文汉字验证码的生成及应用

介绍了验证码的应用优势和生成原理.分析了汉字的编码和处理原理.详述了还处于发展阶段的中文验证码以及噪音图片的生成和应用.