A New Class of Nonlinear Error Control Codes Based on Neural Networks

By mcans of stable attractors of discret Hopfield neural network (DHNN) , anew class of nonlinear error control codes is sugsested and some relativetheorems are presented. A kind of single error control codes is also given forillustrating this new approach.

TRELLIS STRUCTURES OF BLOCK CODES AND THEIR DECODING

Trellis structures of block codes are discussed. L-section trellis structures of some BCH codes are presented. A fast maximum likelihood decoding algorithm for BCH codes is proposed correspondingly, the decoding problem of q-ary images of qm-ary block codes is also discussed. The direct-sum partition and the associated decoding algorithms are given for the images.

Assessment of cortical bone fatigue using coded nonlinear ultrasound

Bone fatigue accumulation is a factor leading to bone fracture,which is a progressive process of microdamage deteriorating under long-term and repeated stress.Since the microdamage of the early stage in bone is difficult to be investigated by linear ultrasound,the second harmonic generation method in nonlinear ultrasound technique is employed in this paper,which is proved to be more sensitive to microdamage.To solve the deficiency that the second harmonic component is easily submerged by noise in traditional nonlinear measurement,a weighted chirp coded sinusoidal signal was applied as the ultrasonic excitation,while pulse inversion is implemented at the receiving side.The effectiveness of this combination to improve the signal-to-noise ratio has been demonstrated by in vitro experiment.Progressive fatigue loading experiments were conducted on the cortical bone plate in vitro for microdamage generation.There was a significant increase in the slope of the acoustic nonlinearity parameter with the propagation distance(increased by 8%and 24%respectively)when the bone specimen was at a progressive level of microdamage.These results indicate that the coded nonlinear ultrasonic method might have the potential in diagnosing bone fatigue.

A Comparative Analysis between the Spanish and Portuguese Seismic Codes: Application to a Border RC Primary School

The Iberian Peninsula is close to the Eurasia-Africa plate boundary resulting in a considerable seismic hazard.In fact,the southwestern Iberian Peninsula is affected by far away earthquakes of long-return period with large-very large magnitude.A project named PERSISTAH(Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva,in Portuguese)aims to cooperatively assess the seismic vulnerability of primary schools located in the Algarve(Portugal)and Huelva(Spain).Primary schools have been selected due to the considerable amount of similar buildings and their seismic vulnerability.In Portugal,the Decreto Lei 235/83(RSAEEP)is mandatory while in Spain,the mandatory code is the Seismic Building Code(NCSE-02).In both countries,the Eurocode-8(EC-8)is recommended.Despite the fact that both regions would be equally affected by an earthquake,both seismic codes are significantly different.This research compares the seismic action of Ayamonte(Huelva)and Vila Real de Santo António(Portugal).Both towns are very close and located at both sides of the border.Moreover,they share the same geology.This analysis has been applied considering a reinforced concrete(RC)primary school building located in Huelva.To do so,the performance-based method has been used.The seismic action and the damage levels are compared and analysed.The results have shown considerable differences in the seismic actions designation,in the performance point values and in the damage levels.The values considered in the Portuguese code are significantly more unfavourable.An agreement between codes should be made for border regions.

BLIND ADAPTIVE MULTIUSER DETECTOR FOR NONLINEARLY MODULATED SATELLITE MOBILE CDMA SYSTEMS

This paper presents a novel blind adaptive noncoherent decorrelative multiuser detector for nonlinearly modulated satellite mobile Code Division Multiple Access (CDMA) systems. By using the known signature waveforms of the counterpart earth station in the blind adaptive multiuser detector, the system performance has been improved obviously. The computation results about the convergence properties of the new detector and the previous detectors demonstrate that the proposed multiuser detector has better performance than previous multiuser detectors for nonlinearly modulated CDMA systems.

Computation of Error in Estimation of Nonlinearity in ADC Using Histogram Technique

Computation of error in estimation of nonlinearity in ADC using histogram test are reported in this paper. Error determination in estimation of Differential Nonlinearity (DNL) and Integral Nonlinearity (INL) of an ADC is done by taking deviation of estimated value from actual value. Error in estimated INL and DNL is determined to check the usefulness of basic histogram test algorithm. Arbitrary error is introduced in ideal simulated ADC transfer characteristics and full scale simulated sine wave is applied to ADC for computation of error in estimation of transition levels and nonlinearity. Simulation results for 5 and 8 bit ADC are pre-sented which show effectiveness of the proposed method.

Development of Beam Optics Code LEADS-v5

To calculate nonlinear transport of space charge dominated beam in 6D phase spaces, a computer code package LEADS-v5 (Linear and Electrostatic Accelerator Dynamics Simulations) has been developed. The codes calculate particle motions in the beam transport systems consisting of electrostatic and magnetic focusing lenses, ion analyzers, multipoles and RF accelerating structures. The nonlinear forces of external electric/magnetic fields are analyzed by the Lie algebraic method, and the space charge forces are obtained by the particle in cell (PIC) scheme. In the codes, Uniform and Gaussian particle distributions can be chosen to generate randomly the particle initial coordinates. The optimization procedures are provided to make the beam optics designs reasonable and fast. Graphically displays of calculated results are provided.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

单极性ADC静态参数的测试方法

模数转换器(ADC)的静态指标包括微分非线性(DNL)和积分非线性(INL),测量静态参数的主要方法为码密度直方图法。传统的码密度直方图法对输入正弦波的幅值的计算精度有较高的要求,提出了一种基于码密度直方图的归一化处理的平台方案。根据测试要求,选取符合要求的测试激励幅值输入,从而对归一化处理后的方案有效性进行验证。实验结果表明进行归一化处理降低了正弦波幅值的变化对于码密度直方图法的影响,提高了码密度直方图法测试的稳定性。

双稳态压电超结构的超传输滞回效应与非互易编码特性

利用超结构的非线性效应能够实现新颖的振动能量传输调控现象.双稳态超结构存在非线性超传输特性,即在超结构线性化带隙内,当激励幅值超过某个临界值时,传输的振动能量将突变到很大值.文章针对含双稳态分流电路的压电超结构梁,建立了力电耦合非线性动力学数值模型,并采用伽辽金法对数值模型进行降阶处理以提升计算效率.基于上述模型研究了双稳态压电超结构的振动能量非线性传输特性,发现超结构线性局域共振带隙内的超传输特性存在滞回效应,也即向上扫幅激励和向下扫幅激励两种工况下超传输临界值不同.通过改变双稳态电路两个稳定平衡点的间距或者电路在稳定平衡点的共振强度可以移动超传输滞回区间.进一步通过在双稳态压电超结构一侧布置线性共振电路来引入系统非对称性,可使得正方向和反方向的超传输滞回区间发生偏离,利用这种非互易的超传输滞回效应可以在不同激励幅值区间实现不同模式的非互易编码.增强系统非对称性可使得正方向和反方向的超传输滞回区间偏离更加显著,故非互易编码区间具有可调性.文章极大地拓展了超材料的非互易模式,正方向和反方向能量传输性能不再局限于传统超材料固定的“传输”或“非传输”状态,通过合适的非互易编码设计可以实现弹性信息的单向传输功能.

Nonlinear codes with asymptotic parameters better than the Gilbert-Varshamov and the Xing Bounds

In this paper, we show that the Gilbert-Varshamov and the Xing bounds can be improved significantly around two points where these two bounds intersect by nonlinear codes from algebraic curves over finite fields.

基于非线性编码的叠加概率整形20QAM星座方案

针对多输入多输出可见光通信系统计算复杂度高、相邻星座点容易相互交叠的问题,提出一种基于非线性编码的叠加概率整形(PS)20阶正交幅度调制(20QAM)星座方案。首先,基于提出的非线性编码方程,将等概率的4级电平信号编码为PS 5级电平信号。然后,将PS 5级电平信号映射为梯形形状的PS 5QAM信号以最大化叠加星座的欧氏距离。最后,将PS 5QAM信号与等概率的4QAM信号进行翻转叠加得到PS 20QAM信号。实验结果证明:所提出的叠加20QAM星座方案对系统的非线性失真有较强的鲁棒性,比叠加16QAM、叠加24QAM星座方案的误码率性能更优。

On the constructions of constant-composition codes from perfect nonlinear functions

A new construction of constant-composition codes based on all known perfect nonlinear functions from Fqm to itself is presented, which provides a kind of unified constructions of constant-composition codes based on all known perfect nonlinear functions from F qm to itself.It is proved that the new constant-composition codes are optimal with respect to the Luo-Fu-Vinck-Chen bound, when m is an odd positive integer greater than 1.Finally, we point out that two constructions of constant-composition codes, proposed by Ding Cunsheng et al.in 2005, are equivalent to two special types of the new constant-composition codes.

Error-detecting abilities of binary nonlinear constant weight codes

CONSTANT weight codes are very important in coding theory for its application to communication. In refs. [1—5], the undetected error probabilities (UEP)of binary nonlinear constant weight codes (BNCW) were studied, and Wang et al. showed that when n】8, BNCW codes (n, 2, ω) were not proper, Wang proposed a conjecture that when n】4δ and δ】 1, BNCW codes (n, 2δ, ω) are not proper. in this note, the error-detecting abilities

New construction of highly nonlinear resilient S-boxes via linear codes

Highly nonlinear resilient functions play a crucial role in nonlinear combiners which are usual hardware oriented stream ciphers.During the past three decades,the main idea of construction of highly nonlinear resilient functions are benefited from concatenating a large number of affine subfunctions.However,these resilient functions as core component of ciphers usually suffered from the guess and determine attack or algebraic attack since the n-variable nonlinear Boolean functions can be easily given rise to partial linear relations by fixing at most nil variables of them.How to design highly nonlinear resilient functions(S-boxes)without concatenating a large number of nil variables affine subfunctions appears to be an important task.In this article,a new construction of highly nonlinear resilient functions is proposed.These functions consist of two classes subfunctions.More specially,the first class(nonlinear part)contains both the bent functions with 2k variables and some affine subfUnctions with n/2-k variables which are attained by using[n/2-k,m,d]disjoint linear codes.The second class(linear part)includes some linear subfunctions with nil variables which are attained by using[n/2,m,d]disjoint linear codes.It is illustrated that these resilient functions have high nonlinearity and high algebraic degree.In particular,It is different from previous well-known resilient S-boxes,these new S-boxes cannot be directly decomposed into some affine subftinctions with nil variables by fixing at most nil variables.It means that the S-boxes(vectorial Boolean functions)which use these resilient functions as component functions have more favourable cryptography properties against the guess and determine attack or algebraic attacks.

Subfield Codes of Linear Codes from Perfect Nonlinear Functions and Their Duals

Let F_(p)^(m) be a finite field with p^(m) elements,where p is an odd prime and m is a positive integer.Recently,[17]and[35]determined the weight distributions of subfield codes with the form C f={((T r(a f(x)+b x)+c)_(x∈F_(p)^(m)),T r(a)):a,b∈F_(p)^(m),c∈F_(p)}for f(x)=x^(2) and f(x)=x p k+1,respectively,where Tr(⋅)is the trace function from F_(p)^(m) to F_(p),and k is a nonnegative integer.In this paper,we further investigate the subfield code C f for f(x)being a known perfect nonlinear function over F_(p)^(m) and generalize some results in[17,35].The weight distributions of the constructed codes are determined by applying the theory of quadratic forms and the properties of perfect nonlinear functions over finite fields.In addition,the parameters of the duals of these codes are also determined.Several examples show that some of our codes and their duals have the best known parameters according to the code tables in[16].The duals of some proposed codes are optimal according to the Sphere Packing bound if p≥5.

The Determination on Weight Hierarchies of q-Ary Linear Codes of Dimension 5 in Class IV

The weight hierarchy of a linear[n;k;q]code C over GF(q) is the sequence(d_1,d_2,…,d_k)where d_r is the smallest support of any r-dimensional subcode of C. "Determining all possible weight hierarchies of general linear codes" is a basic theoretical issue and has important scientific significance in communication system.However,it is impossible for g-ary linear codes of dimension k when q and k are slightly larger,then a reasonable formulation of the problem is modified as: "Determine almost all weight hierarchies of general g-ary linear codes of dimension k".In this paper,based on the finite projective geometry method,the authors study g-ary linear codes of dimension 5 in class IV,and find new necessary conditions of their weight hierarchies,and classify their weight hierarchies into6 subclasses.The authors also develop and improve the method of the subspace set,thus determine almost all weight hierarchies of 5-dimensional linear codes in class IV.It opens the way to determine the weight hierarchies of the rest two of 5-dimensional codes(classes III and VI),and break through the difficulties.Furthermore,the new necessary conditions show that original necessary conditions of the weight hierarchies of k-dimensional codes were not enough(not most tight nor best),so,it is important to excogitate further new necessary conditions for attacking and solving the fc-dimensional problem.

采用单工循环编码解码的分布式光纤喇曼温度传感器

针对连续脉冲编码解码技术在分布式光纤喇曼温度传感器应用中出现被测光纤非线性峰值阀值光功率变低、编码过程较复杂等问题,提出了一种将光脉冲码均匀分布在整条被测光纤的单工循环编码解码技术和应用方案,并在27km单模系统中与传统单脉冲技术系统做了对比实验.结果表明:相比连续编码解码技术,单工循环编码解码技术不仅保持了编码解码技术相对于传统单脉冲技术的信噪比改善能力,而且有效地提高了光纤的非线性峰值阀值光功率.在编码时只需循环发送一组码,就可使系统的信噪比和测量距离获得极大的提高.采用211位循环编码解码技术的多模系统经16万次重复测量后,可在25km处获得±1.5℃的温度不确定度,空间分辨率为3m.

最佳非线性等重检错码的存在性问题

本文分析了二进制（２ｍ，２，ｍ）非线性等重码的不可检错误概率，证明了当ｍ≥５时，它不是最佳检错码，从而完全证明了作者提出的：当ｎ≥９时，不存在最佳二进制非线性等重码的猜想．

高精度数据驱动型TDC在高能物理实验中应用的研究

目前国际国内高能物理方面时间数字转换的发展趋势是使用集成的、高精度、多次击中型TDC,数据驱动型TDC(DataDrivenTDC)是其中的热点。研究高性能TDC的具体指标以及改进的方法对高能物理实验中的应用具有指导作用。我们对北京谱仪(BESIII)中考虑使用的一种新型高精度TDC进行了测量研究。本文介绍了我们为此建立的测量平台,和对该TDC进行非线性、分辨率、双脉冲分辨等测量的手段和结果,探讨了对其进行甚高精度(24.4ps)修正的方法,给出了修正的效果。