New Codes with Finite Length for a Wiretap Channel

In this paper, an equivocation scheme with finite code length is proposed for a wiretap channel. The proposed coding scheme is composed of two constituent codes, an outer code and an inner code, which are used efficiently for various channel conditions. A Hamming code and its cosets are used for an outer code and bit-extension mapping is adopted for an inner code. The average equivocation is discussed for small messages and the probability of causing imperfect secrecy is defined to investigate the performance of outer and inner codes. The results show that usage of inner codes increases the equivocation capability of wiretap channels.     

红外仿真中像面最大温差的计算方法

针对红外仿真系统中杂散辐射会影响模拟像面温度均匀性的问题,提出了像面温度偏差这一概念,并给出了像面最大温度偏差值的计算方法.建立了用于计算像面最大温差的红外仿真系统简化模型.定义了能反映像面温度变化的局部辐照度偏差系数.推导了局部辐照度偏差系数与像面最大温差的表达式,给出了红外仿真系统像面最大温差的一般计算步骤.通过实际算例演示了该计算方法,并设计了验证实验.结果表明,测试得到的像面最大温差均在理论计算数值范围内,从而验证了该方法的正确性和有效性.     

An adaptive pre-distorter for the compensation of HPA nonlinearity

A high power amplifier (HPA) is used for the amplification of transmitting communication signals. However, it produces distortions by creating AM/AM and AM/PM modulations in the transmitting signal, Accordingly, this nonlinearity results in bandwidth expansion and nonlinear distortion in the in-band signal. This paper proposes an algorithm for the operation of a pre-distorter, which is composed of a look-up table (LUT), that can compensate for the distortion produced by an HPA. For the fast initialization of the LUT, an estimation algorithm is also proposed for the HPA characteristics. Furthermore, an adaptive algorithm based on the minimization of the mean square error is proposed to compensate for the time-varying property of an HPA. The performance of the proposed algorithm is analyzed by applying the algorithm to an 8-level vestigial sideband (VSB) modulation to be used in the ATSC terrestrial digital TV system     

Optimum Detection of Quantized PAM Data Signals

The degree of complexity of a digital signal processor is closely related to the precision with which samples of an incoming analog waveform are represented. There is considerable interest in determining how coarse this representation can be without seriously degrading performance from that of an ideal processor of unquantized samples. This question is examined for a receiver of noisy, linearly distorted pulse amplitude modulation (PAM) signals. An optimum [maximum likelihood (ML)] detector, analogous to the Viterbi detector for unquantized samples, is derived for the case of a quantized sample sequence. Performance is evaluated under the assumption of high signal-to-noise ratio (SNR), and the resultant error probability is a good approximation for coarse quantization, and an upper bound for any degree of quantization. For a specified error probability, the degree of quantization suggested by this approach is conservative. Since receiver complexity is closely associated with the length of the digital representation of an input sample, an upper bound on receiver complexity is also suggested. Numerical evaluation of the error probability is quite tedious for an arbitrary channel; however, system performance may be readily evaluated for partial-response (PR) signaling. For the PR channels     

Multiple-symbol differential detection with interference suppression

A multiple-symbol differential detector is formulated for M-ary differential phase-shift keying modulation where the channel state information is unknown to the receiver. The maximum-likelihood decision statistic is derived for the detector, and its performance is demonstrated by analysis and simulation. Under the Gaussian assumption for the aggregate interference plus noise, an exact expression for the symbol pairwise error probability is developed for M-ary differential phase-shift keying modulation over a diversity, slow-fading Rayleigh channel in the presence of an interference source. A simpler expression of the pairwise error probability is developed for the asymptotic case of large signal-to-noise ratio and small signal-to-interference ratio. It is shown that with an increasing observation interval, the performance of the differential detector over an unknown channel approaches that of optimum combining with known channel.     

CPEF:一种用于人脸识别的图像择优方法

针对人脸识别的输入图像信息量高低不均的问题,提出了一种多参数图像择优的评分机制CPEF主要有三点贡献:第一点是提出了一种新颖的基于主动形状模型(ASM)定位的人脸水平旋转程度评估方法;第二点是采用递归的方式计算权重;第三点是提出了一组参数定量地描述了图像择优方法.过程如下:首先,计算图像质量;其次基于二分类器判断人眼是否处于睁开状态;然后以颜色直方图信息判定人是否处于张嘴状态;最后,综合水平旋转程度及其他参数,配合权重,给出评分.在FERET人脸库上的实验结果证明,CPEF有效地将人脸图像按照入主观感受做出排名,准确率高达92％.并且按得分高低排序采用Gabor配合SVM做人脸识别对比测试,对比实验证明,经CPEF处理后的图像在人脸识别中的准确率显著提升.     

IRFPA非均匀性校正数学机理与仿真技术研究

针对红外成像系统的实际工程应用,阐述了红外焦平面阵列(Infrared Focal PlaneArray,IRFPA)非均匀性校正辐射定标的基本原理,推导出了红外焦平面阵列非均匀性校正属于函数插值或拟合的数学机理,给出了适于工程应用的相关非均匀性校正算法。同时,为了克服实际工作中研究设备不足等条件的限制,详细研究了红外焦平面阵列非均匀性校正的仿真技术,给出了有效的仿真算法。该仿真技术能够有效地满足实际工程中对非均匀性校正算法的验证与评估要求。     

Atmospheric correction for ocean color remote sensing: opticalproperties of aerosols derived from CZCS imagery

A procedure for an accurate atmospheric correction for ocean color remote sensing is described. It is shown that an appropriate aerosol model is the key factor for pursuing the atmospheric correction, including multiple scattering light in the atmosphere-ocean system. An algorithm for estimating the aerosol models suitable for the Nimbus-7 CZCS image of interest is proposed. As a result, phytoplankton pigment concentration near the sea surface is derived through the atmospheric correction and biooptical algorithms. The treatment is found to provide an improved pigment map of the sea surface near Japan     

A theoretical model for the current-voltage characteristics of afloating-gate EEPROM cell

A model for current-voltage characteristics of an EEPROM cell has been developed and used in the simulation of an EEPROM test structure. It provides an explanation for the observed strong drain-induced barrier lowering effect and the role of trapped charge in the floating gate. In this model, the surface potential is related to the terminal voltages through an equivalent electrical circuit. Charge sheet and depletion approximation are used to describe the charge distribution in the semiconductor. Gradual approximation is assumed in deriving the drain current equation. A simplified drain current equation under a strong inversion condition is derived. An expression defining the extrapolated threshold voltage is obtained. It is useful in parameter extraction. A new method for extracting the drain coupling ratio and the channel coupling ratio is proposed. Finally, it is shown that extrapolated threshold voltage is a convenient quantity for classifying the threshold voltage of an EEPROM cell     

故障的收集处理与系统应用

加强对故障的收集,并建立一个妥善保存、快速传递、有效利用的应用信息系统,是研制高质量装备的有效保证手段.结合该单位质量管理与控制的实际运行情况,以收集故障信息管理工作为基础,从故障的分类管理、收集处理以及应用实例等方面,阐述了有效的控制质量信息管理是质量体系有效运行的长效机制,是企业实现组织战略目标的必经之路,是产品可...     

On the design of an optimal quantizer

The problem of designing an optimal quantizer with a fixed number of levels for a wide class of error weighting functions and an arbitrary distribution function is discussed. The existence of an optimal quantizer is proved, and a two-stage algorithm for its design is suggested. In this algorithm, at the first stage, Lloyd's iterative Method I is applied for reducing the region where, at the second stage, the search for an optimal quantizer is performed using a hybrid of the dynamic programming algorithm and the Lloyd-Max algorithm, which achieves the absolute optimality of dynamic programming with much less computational effort. For a continuous distribution with log-concave density and an increasing convex weighting function of the absolute quantization error, a reliable method is presented to compute the parameters of the optimal quantizer with a known precision using a generalization either of Lloyd's Method I or of the Lloyd-Max algorithm     

Peak-to-average power ratio analysis in multicarrier DS-CDMA

Multicarrier direct-sequence code-division multiple access (MC-DS-CDMA) is an attractive technique for achieving high-bit-rate wireless data transmission. Although the potentially large peak-to-average power ratio (PAPR) is an important factor for its application, there is no theoretical PAPR analysis of the transmitted signal in an MC-DS-CDMA system in the literature. The purpose of this paper is to fill such a gap. We derive a general formula for the complementary cumulative distribution function (CCDF) of the PAPR of an MC-DS-CDMA signal, giving a possible lower bound of CCDF. To achieve the lowest bound of CCDF, a criterion is proposed for optimal interleaver design in an MC-DS-CDMA system. By using two interleaver design methods as examples, simulation results demonstrate the effectiveness of the new criterion in interleaver design.     

Faster Impedance Estimation for Coupled Microstrips with an Overrelaxation Method (Short Papers)

Using the Frankel-Young method, fast estimation of the potential distribution for a microstrip structure is obtained when an accelerating factor /spl omega/ is introduced in the finite-differences (relaxation) method. It is possible to calculate such a factor by an iterative technique, but the time of computation needed to find /spl omega/ annihilates the theoretical gain. In this short paper, the authors present a method which gives an analytical expression for /spl omega/. The realistic case examined here, as an illustration, is that of the suspended microstrip couplers for which odd and even impedances are the interesting parameters. Given an analytical expression for /spl omega/, the overrelaxation method appears as a very powerful and attractive method for finding the solution of any type of microstrip structure.     

Fiber-optic reflection measurements using OCWR and OTDR techniques

A method for determining the backscatter and reflection responses of an optical fiber and reflector to an arbitrary input is developed. Two cases are specifically considered: a continuous-wave input and a rectangular pulse input. From the rectangular pulse input response, the equation is derived for computing the reflectance of a discrete component from an optical time-domain reflectometer (OTDR) measurement. Precautions are given for accurately performing reflectance measurements using an OTDR. Two methods are presented for determining the backscatter level of the fiber type under test, and its importance in reflection measurements is shown     

Relationships for Green's function spectral dyadics involvinganisotropic imperfect conductors embedded in layered anisotropic media

The Green's function spectral dyadic that characterizes a perfectly conducting patch antenna or propagating line can be modified to account for noninfinite conductivity. This is done through a relationship for a single planar interface imbedded in an anisotropic medium. A relationship for an arbitrary number of planar interfaces imbedded in an anisotropic medium is also derived. The imperfect conductor is represented by an anisotropic impedance     

Electromagnetic Pulse Coupling Through an Aperture into a Two-Parallel-Plate Region

Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.     

Universally ideal secret-sharing schemes

Given a set of parties {1, ···, n}, an access structure is a monotone collection of subsets of the parties. For a certain domain of secrets, a secret-sharing scheme for an access structure is a method for a dealer to distribute shares to the parties. These shares enable subsets in the access structure to reconstruct the secret, while subsets not in the access structure get no information about the secret. A secret-sharing scheme is ideal if the domains of the shares are the same as the domain of the secrets. An access structure is universally ideal if there exists an ideal secret-sharing scheme for it over every finite domain of secrets. An obvious necessary condition for an access structure to be universally ideal is to be ideal over the binary and ternary domains of secrets. The authors prove that this condition is also sufficient. They also show that being ideal over just one of the two domains does not suffice for universally ideal access structures. Finally, they give an exact characterization for each of these two conditions     

Diffraction from an abruptly terminated dielectric slab waveguide in the presence of a cylindrical scatterer

The efficiency of using an adaptor lens in front of an abruptly terminated symmetric slab optical waveguide is examined analytically in this paper. The adaptor lens is assumed to be of cylindrical shape with a constant refractive index. The coupling of the modes propagating inside the slab guide into radiation waves in the presence of the lens is treated by integral equation methods. In the first step an integral equation is derived for the Green's functionG(r/r')of an abruptly terminated slab waveguide. The integral equation is solved approximately by an iterative procedure giving accurate results when the difference of the refractive indices between the slab waveguide and substrate-cover regions is small. The Green's function is then used to formulate another integral equation for the unknown field inside the adaptor lens. The latter integral equation for the cylindrical lens cross section area is solved by adopting a cylindrical partial wave expansion for the unknown interior field. After determining this field, the reflection-coupling coefficients for the guided modes propagating in the opposite direction of the incident wave, are computed by using the Green's functionG(r/r'). Radiation patterns are also derived in the far field region for an incident slab guided mode. Numerical results are computed and presented for several guide dimensions, lens radii, and refractive indices.     

Theoretical Study of a Two-Section Ultrawideband Antenna Array

The paper presents a theoretical consideration of a two-dimensional array consisting of two series-connected parts: an infinite system of one-dimensional arrays of strip horns and an array of planar horns. The eigenwave problem for an infinite one-dimensional array of strip transmission lines k]which reduces to a singular integral equation with respect to the current on the strip k]is solved. An analytical solution for the current and an expression for the characteristic impedance of the principal T-wave of the array k]which is valid in the scanning mode k]are found. A model of an array with smoothly varying parameters that describes the operation of a one-dimensional array of strip horns in the approximation of a microwave transmission line is developed. In the same approximation k]a model of an array of planar horns and the entire two-dimensional two-section array is developed and its numerical study is performed.     

A correction and an addendum for “Variable-rate coding formeteor-burst communications”

A correction is presented in this note for an error which appears in the subject paper (see ibid., vol.37, p.1105-12, 1989). In addition, attached as an addendum is a proof that a modified version of an algorithm presented in the subject paper produces an optimal packet configuration for variable-rate coding in meteor-burst communications. The proof of optimality for the original algorithm is quite tedious, and was not included in the subject paper