Optimization techniques and inverse problems: Reconstruction of conductivity profiles in the time domain

The iterative probing of an inhomogeneous lossy dielectric slab, whose conductivity is unknown, is discussed. The probing is done in the time domain from the measurements of the field on the interface when this slab is illuminated by a known field. An exact integral formulation is used. Minimization of a cost function, characteristic of the discrepancy between the measured field and the field which would be scattered by a known slab, is specified by the optimization theory. The notion of the adjoint state of the field is introduced. The influence of some parameters of this minimization is studied. Great importance is given to the sensitivity of the probing as function of the amplitude of errors in the data. Such an iterative probing appears fast, accurate, and efficient, even in the case of large errors.     

Transition from Electromagnetic to Hot-gas Driver in an Electric Shock Experiment†

It is not possible with any electrode system to produce a perfectly uniform electric field and the departures from uniformity may producer errors in the measured values of Townsend's first and second ionization coefficients. Calculations are reported giving the magnitude of the errors in the first coefficient,α, for helium, hydrogen, nitrogen and methane at low E/p, where the errors reach a maximum, for Bruce and other electrode systems. An experimental method of detecting errors in α from this source is proposed and a theoretical equation is presented relating the error in α. to the maximum field non-uniformity.     

Joint Angle and Array Gain-Phase Errors Estimation Using PM-like Algorithm for Bistatic MIMO Radar

This paper discusses the problem of the direction of departure (DOD) and the direction of arrival (DOA) estimation for multi-input multi-output (MIMO) radar with array gain-phase errors. In this paper, we propose a propagator method (PM)-like algorithm for joint angle and array gain-phase errors estimation in MIMO radar. The proposed method not only yields automatically paired estimates of the angles and gain-phase errors but also has much better gain-phase errors estimation performance than the estimation of signal parameters via rotational invariance techniques (ESPRIT)-like algorithm; this has higher computational cost than the proposed algorithm. Furthermore, the proposed algorithm has angle estimation performance very close to ESPRIT-like algorithm. We also derive the Cramér–Rao bound (CRB) for MIMO radar with array gain-phase errors. Simulation results present the usefulness of our approach.     

MEMS惯性测量单元航姿更新中的测量误差估算方法

利用MEMS惯性测量单元测量载体的航姿,需要借助精密转台且较难精确估算测量误差,导致成本高误差大.针对该问题,该文利用卡尔曼滤波器在线估算载体的姿态和陀螺仪的偏置,提出一种优化航姿精度的测量误差估算方法.通过推导测量误差的数学模型,分析航姿精度随测量误差变化的关系,得到最优航姿时的测量误差值.采用一种MEMS惯性测量单...     

基于Huber范数和概率运动场的鲁棒图像超分辨重建算法

传统超分辨(SR)算法对配准误差、模型误差以及噪声过于敏感,这限制了其在实际中的应用。为了提高算法的鲁棒性,该文从配准和重建两方面对传统算法进行了改进。在配准阶段,通过引入概率运动场避免了算法对配准精度的依赖,同时利用Heaviside函数实现权重映射,进一步提高了算法的自适应性;在重建阶段,采用基于Huber范数的正则化估计,在提高重建鲁棒性的同时也保证了算法数值解的稳定性。实验表明该算法具有很好的鲁棒性,其重构性能优于现有的一些超分辨重建方法。     

一种均匀线阵幅相误差校正算法

阵列幅相误差会严重影响MUSIC算法的测向性能,为此基于均匀线阵,给出了一种新的幅相误差校正算法。首先根据协方差矩阵的关系式构造了一种二次代价函数,然后利用理想条件下均匀线阵协方差矩阵具有Toeplitz结构的性质,通过交替迭代的方法对此二次代价函数进行优化求解,从而估计出了幅相误差和理想条件下的协方差矩阵,最后利用MUSIC算法即可估计出信源方位。计算机仿真结果验证了文中的算法是有效的,并且具有较高的参数估计精度。     

减小平面近场测量中多次反射误差的新方法

本文给出了用平面近场技术测量超低副瓣天线时,平面近场测量总误差与天线远场方向图副瓣电平的误差方程,并进行了计算机仿真;提出了减小平面近场测量中探头天线与待测天线间多次反射误差和微波暗室电特性误差对超低副瓣天线所引入的测量误差的"自校准法",实验结果说明该方法是解决平面近场测量中多次反射和微波暗室电特性误差较为理想的方法.     

A Bimodal Approach for Land Vehicle Localization

In this paper, we present a novel idea to integrate a low cost inertial measurement unit (IMU) and Global Positioning System (GPS) for land vehicle localization. By taking advantage of positioning data calculated from an image based on photogrammetry and stereo‐vision techniques, errors caused by a GPS outage for land vehicle localization were significantly reduced in the proposed bimodal approach. More specifically, positioning data from the photogrammetric approach are fed back into the Kalman filter to reduce and compensate for IMU errors and improve the performance. Experimental results are presented to show the robustness of the proposed method, which can be used to reduce positioning errors caused by a low cost IMU when a GPS signal is not available in urban areas.     

Development of a 50,000-gate programmable logic device for gate array prototyping

Systems designers want the cost and integration benefits from custom-logic solutions, but must mange the risk and cost of design errors. Several strategies have evolved to address this problem, with the two most common being design simulation, where a software model of the design is tested with simulated test vectors in an attempt to find error conditions, and emulation, where a hardware model of the design is tested with the same vectors, to attempt to find any errors. The principle difference between the two validation methods is how quickly they can identify errors in a design.     

基于SCKF和姿态估计的SINS/GPS在线对准方法

该文提出了基于平方根容积卡尔曼滤波和初始姿态估计的捷联惯导/全球定位系统组合在线对准法。构建平方根容积卡尔曼滤波器来对初始姿态估计的非线性量测模型进行滤波,估计代表初始姿态转换矩阵的罗德里格参数,并以此求出当前时刻的姿态转换矩阵,从而求出当前时刻准确的姿态。该文分别对制导武器系统和车载系统进行了半实物仿真。仿真结果表明,此方法可在25 s左右完成在线对准。其中短距离制导武器仿真结果航向角及俯仰角误差在0.1°内,横滚角误差在0.3°内;低成本车载导航系统仿真结果航向角误差在0.2°内,俯仰角及横滚角误差在1°内,可满足制导武器及低成本民用车辆的对准需求。     

单片机矩阵大面积测温及远程通讯系统

文中给出了一种利用矩阵结构进行多点测温的方法，它能充分利用计算硬件资源，降低系统成本，扩展了单片机在大面积多点测量领域里的应用，系统设计有效了克服通迅中信号的碰撞问题和传输错误，具有可靠性高，抗干扰性能等优点。     

双面阵CCD实时测量激光发散角的系统

针对目前激光光束发散角测试速度慢,实时性差的问题,提出采用两个面阵CCD同时测量激光远场区域两个不同位置的光束宽度,用两点拟合的方法计算激光光束发散角的方法。该方法装置简单,可快速实时准确地测量激光光束发散角。测试结果表明,系统测量误差<0.1 mrad,重复测量误差均±1%之内。该测量方法研制的仪器成本低、测试效率高、便于携带,适合设备生产现场和空间有限的快速实时检测需求。     

一种均匀线阵互耦和幅相误差校正算法

阵列互耦和幅相误差会严重影响MUSIC算法的测向性能,为此该文基于均匀线阵,给出了一种新的阵列互耦和幅相误差校正算法．文中首先根据阵列协方差矩阵的关系式构造了一种二次代价函数,然后利用理想条件下均匀线阵协方差矩阵具有Toeplitz结构的性质,通过交替迭代的方法对该代价函数进行优化求解,从而估计出了阵列互耦、幅相误差以及理想条件下的协方差矩阵,最后利用MUSIC算法即可得到信源方位的估计值．计算机仿真结果验证了文中算法的有效性．      

Obtaining FPGA soft error rate in high performance information systems

Soft errors due to cosmic particles are a growing reliability threat for VLSI systems. The vulnerability of FPGA-based designs to soft errors is higher than ASIC implementations since the majority of chip real estate is dedicated to memory bits, configuration bits, and user bits. Moreover, Single Event Upsets (SEUs) in the configuration bits of SRAM-based FPGAs result in permanent errors in the mapped design.FPGAs are widely used in the implementation of high performance information systems. Since the reliability requirements of these high performance information sub-systems are very stringent, the reliability of the FPGA chips used in the design of such systems plays a critical role in the overall system reliability. In this paper, we compare and validate the soft error rate of FPGA-based designs used in the Logical Unit Module board of a commercial information system with the field error rates obtained from actual field failure data. This comparison confirms that our analytical tool is very accurate (there is an 81% overlap in FIT rate range obtained with our analytical modeling framework and the field failure data studied). It can be used for identifying vulnerable modules within the FPGA for cost-effective reliability improvement.     

Explicit Ziv–Zakai bound for analysis of DOA estimation performance of sparse linear arrays

Sparse linear arrays (SLAs) provide similar direction-of-arrival estimation performance to filled linear arrays in terms of angular accuracy and resolution with reduced size, weight, power consumption, and cost. However, they are subject to significant ambiguities due to high sidelobes in the array beampattern, which give rise to large estimation errors. In this paper, we develop an explicit closed-form expression for the Ziv–Zakai bound on the mean square estimation error in order to quantify the degradation in estimation performance due to the sidelobe ambiguities. The bound consists of three terms which correspond to the three types of estimation errors: small mainlobe errors, errors due to sidelobe ambiguities, and random errors. The bound is used to analyze the performance of different SLA configurations. Maximum likelihood estimation simulations confirm the contribution of the different types of estimation errors predicted by the bound. The analysis shows that much of the performance degradation due to ambiguities are from random errors that cannot be controlled by array design, while additional degradation due to sidelobe errors depends strongly on the array configuration. Isolating the contributions of the three types of errors provides greater understanding of the behavior of sparse arrays, allowing for more effective system design and analysis.     

DMR +: An efficient alternative to TMR to protect registers in Xilinx FPGAs

Registers are one of the circuit elements that can be affected by soft errors. To ensure that soft errors do not affect the system functionality, Triple Modular Redundancy (TMR) is commonly used to protect registers. TMR can effectively protect against errors affecting a single flip-flop and has a low overhead in terms of circuit delay. The main drawback of TMR is that it requires more than three times the original circuit area as the flip-flops are triplicated and additional voting logic is inserted. Another alternative is to protect registers using Error Correction Codes (ECCs), but those typically require a large circuit delay overhead and are not suitable for high speed implementations. In this paper, DMR + an alternative to TMR to protect registers in FPGAs, is presented. The proposed scheme exploits the FPGA structure to achieve a reduction in the FPGA resources (LUTs and Flip-Flops) at the cost of a certain overhead in delay. DMR + can correct all single bit errors like TMR but is more vulnerable to multiple bit errors. To evaluate the benefits, the DMR + technique has been implemented and compared with TMR considering standalone registers and also some simple designs.     

Fault Tolerance Analysis of Communication System Interleavers: the 802.11a Case Study

The study of Multiple Soft errors on memory modules caused by radiation effects represents an interesting field of current research. The fault tolerance of these devices in radiation environments is traditionally analyzed and increased by means of soft error protection mechanisms as EDAC codes or physical interleaving. As Communication System interleavers are mainly implemented using memories, a similar protection against soft errors to the one used for memory devices could be performed, as a conventional solution, when they are used in critical missions. In this paper, the knowledge of the system is used to apply the communication interleaving pattern as physical interleaving employing the inherent redundancy (added by previous modules of the Communication System) of the data processed by the interleaver as an error correction mechanism. Therefore a similar protection to the conventional solutions is obtained but with a reduced cost.

Low cost and highly reliable hardened latch design for nanoscale CMOS technology

With technology node shrinking, the susceptibility of a single chip to soft errors increases. Hence, the critical charge (Qcrit) of circuit decreases and this decrease is expected to continue with further technology scaling. In this paper previous hardened latch circuits are analyzed and it is found that previous designs offer limited protection against soft error especially for soft error caused by high energy particles and not all the nodes are under soft error protection. Therefore, in this paper we propose a low cost hardened latch design in 45 nm CMOS technology with full protection for all internal nodes as well as output node against soft error. Moreover, the proposed hardened approach is technology independent. Compared to previous hardened latch designs, the proposed design reduces cost in terms of power delay product (PDP) 59% on average.     

Application of the Kalman Filter in Linearity Testing of Analog-to-Digital Converters

This work introduces application of the Kalman Filter in linearity test of Analog-to-Digital Converters (ADCs). The Kalman Filter can be used to suppress errors in the histogram counts, based on characteristics of the test environment and the device under test, and achieve high accuracy within short test time. In this paper, appropriate system and noise models, and a corresponding form of the Kalman Filter are developed, while all necessary parameters are obtained from experimental measurements. Simulation and experiment results show that the INL _k test errors are reduced by more than 50% by applying the proposed method. Consequently, this method can achieve desired accuracy with significantly fewer samples as compared to the conventional algorithm, and shorten the linearity test time by a factor of four or higher. This method is valuable for effectively reducing the production test time and cost for ADCs.     

Numerical analysis of effects of measurement errors on ultrasonic-measurement-integrated simulation

Ultrasonic-measurement-integrated (UMI) simulation, in which feedback signals are applied to the governing equations based on errors between ultrasonic measurement and numerical simulation, has been investigated for reproduction of the blood flow field. However, ultrasonic measurement data inherently include some errors. In this study, the effects of four major measurement errors, namely, errors due to gaussian noise, aliasing, wall filter, and lack of data, on UMI simulation were examined by a numerical experiment dealing with the blood flow field in the descending aorta with an aneurysm, the same as in our previous study. While solving the governing equations in UMI simulation, gaussian noise did not prevent the UMI simulation from effectively reproducing the blood flow field. In contrast, aliasing caused significant errors in UMI simulation. Effects of wall filter and lack of data appeared in diastole and in the whole period, respectively. By detecting significantly large feedback signals as a sign of aliasing and by not adding feedback signals where measured Doppler velocities were aliasing or zero, the computational accuracy substantially improved, alleviating the effects of measurement errors. Through these considerations, UMI simulation can provide accurate and detailed information on hemodynamics with suppression of four major measurement errors.