基于 Beta信誉系统的无线传感网络鲁棒安全自定位

针对现实应用中各种不利因素干扰而严重影响无线传感网络的定位性能的问题,提出一种鲁棒安全定位算法. 首先在Beta信誉系统的基础上建立信任评估框架;然后,传感器节点在多跳通信范围内将锚节点的最终信任值与所存储的阈值进行比较;最后,采用基于泰勒级数展开的加权最小二乘法估算普通传感器节点的坐标. 仿真结果验证了该算法的有效性和鲁棒性,相比其他几种定位算法,该算法具有更高的定位精度,不仅能够很好地识别出无线传感网络中的恶意锚节点,同时大大地提高了节点自定位技术的定位精度.     

固定延迟的流水线双精度浮点除法电路

除运算采用泰勒级数展开,用5级流水线结构,查找表大小缩小为2.5kB,并获得固定延迟.FPGA综合结果表明,与其他设计电路相比,面积减小了33%.     

基于泰勒级数线性插值的DDFS研究

直接数字频率合成器是信号源的核心,也是目前的一个研究热点。本文介绍了直接数字频率合成器(direct digital frequency synthesizer,DDFS)的工作原理;详细介绍了基于泰勒级数的线性插值法减少ROM使用量的原理,研究了基于该方法的直接数字频率合成器的实现电路。对电路原理进行了分析并进行了仿真,仿真结果验证了基于泰勒级数的线性插值法可有效的减少ROM的使用量。最后分析并讨论了电路各参数对DDFS频谱纯度的影响。     

Discretization of nonlinear systems with delayed multi-input via Taylor series and scaling and squaring technique

An input time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via digital computers. In this paper a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed. The mathematical structure of the new discretization method is analyzed. On the basis of this structure the sampled-data representation of nonlinear systems with time-delayed multi-input is presented. The delayed multi-input general equation has been derived. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. Additionally, hybrid discretization schemes that result from a combination of the scaling and squaring technique (SST) with the Taylor series expansion are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method’s parameters to meet CPU time and accuracy requirements, are examined as well. A performance of the proposed method is evaluated using a nonlinear system with time delay: maneuvering an automobile.     

Research on modified Newton and Taylor-series methods in TDOA

In the Time Difference Of Arrival (TDOA) source localization model, based on the Taylor-series (TS) method and Newton (NT) method, this paper presents the Modified Taylor-series(MTS) method and the Modified Newton method(MNT), which solve the critical convergent problem caused by the bad initial value in the original algorithms. The proposed algorithms modify the ill-condition Hessian matrix caused by the bad initial value using the Tikhonov (TI) or the Diagonal Singular Value Decomposition technique (DSVD) in the Regularization theory. The regularization parameter which controls the properties of the regularized solution is determined by the L-curve method. Simulation results show that compared with the TS and NT methods, the proposed methods ensure that the solution of the iterative methods converges on the source location, improves the convergent probability and has a better capability to remove the local minima. The proposed methods also give superior performances of the location accuracy comparing with the closed-form algorithms in low SNR environment.     

Investigation of non-Taylor-series based positioning method for hybrid GPS

This article discusses equation derivation and computation of the conventional Taylor-series based and the proposed non-Taylor-series based positioning methods for hybrid GPS systems, namely hybrid E-OTD/GNSS and GPS/cellphone systems. The proposed positioning method is less complicated and yet it is able to provide more accurate positioning results. Furthermore, it does not require initial estimation of an A-GPS receiver's position. However, the proposed positioning method requires additional ranging information which can be made available by the surrounding base stations. Positioning accuracy is calculated and compared between the conventional and the proposed positioning methods. The obtained results show that the proposed direct method can achieve better accuracy as compared with the approximate method.     

校正源条件下基于双星序列观测量的地面运动目标定位算法及理论性能分析

The method for locating a moving source on earth using a sequence of time difference of arrival(TDOA)and frequency difference of arrival(FDOA)measurements pairs obtained by dual-satellites was presented in the presence of calibration sources with accurate positions.First,the difference calibration(DC)location algorithm aiming to the mobile target was derived,and its theoretical performance was also analytically derived.The result demonstrates that the DC localization variance could not reach the CRB,although it could eliminate the location bias produced by the position and velocity errors of the dual-satellites.For this reason,a two-step optimal association location algorithm was proposed,and its theoretical performance was proved to be equal to the CRB.Finally,a variety of numerical experiments are performed to corroborate the superiority of the geolocation algorithms and the effectiveness of the performance analysis.     

PARTICLE SIZE DISTRIBUTION IN A PLANAR JET FLOW UNDERGOING SHEAR-INDUCED COAGULATION AND BREAKAGE

A CFD simulation is performed for a particle-laden planar jet flow.The Reynolds number is 8300,and the initial particle diameter is 1 μm.Large Eddy Simulation(LES) is employed to calculate the flow field,and the Taylor-series expansion moment method(TEMOM) is adopted to deal with the balance equation of particle coagulation and breakage.The shear-induced coagulation kernel,power-law breakage kernel and symmetric fragment distribution function are involved.The prediction of the distribution of the mean streamwise velocity of the jet is in good agreement with experimental data.The evolution of particle number concentration,volume concentration,polydispersity,particle diameter and standard geometric deviation is discussed in detail.The results show that as the jet travels downstream,the particle number concentration and volume concentration decrease,while their spans become wider.The polydispersity and particle diameter are very large in the shear layers at the upstream and in the core of vortex structures at the downstream.The particle standard geometric deviation changes within the range of 1.32 ≤σg≤ 1.96,and increases sharply in the shear layers.All variables approach the steady-state as time progresses.