Nonlinear analysis of cardiac rhythm fluctuations using DFA method

An approach by which the detrented fluctuation analysis (DFA) method can be used to help diagnose heart failure was demonstrated. DFA was applied to patients suffering from congestive heart failure (CHF) to check correlations between DFA indices and CHF, and determine a correlation between DFA indices and mortality, with a particular attention to the residue parameter, which is a measure of the departure of the DFA from its power law approximation. DFA parameters proved to be useful as a complement to the physiological parameters weber and FE to sort out the patients into three prognostic group.

Fishtail effects and improved critical current density in polycrystalline bulk MgB2 containing carbon nanotubes

Bulk, polycrystalline MgB2 samples containing 2.5 wt.% multi-walled carbon nanotubes (CNTs) have been prepared by conventional solid state reaction at 800 °C. The effect of Mg precursor powders composed of two different particle sizes on the critical current density (Jc) of the as-sintered samples has been investigated. An enhancement of Jc at high field has been observed in MgB2 samples containing CNTs prepared with fine Mg powders, whereas the values of Jc in the sample prepared using the coarser Mg powders was slightly decreased. These results contrast significantly with measurements on pure, undoped, MgB2 samples prepared from the same Mg precursor powders. They suggest that carbon substitution into the MgB2 lattice, which accounts for increased flux pinning, and therefore Jc, is more effective in precursor Mg powders with a larger surface area. Rather surprisingly, the so-called fishtail effect, observed typically in MgB2 single crystals and in the (RE)BCO family of high temperature superconductors (HTSs), was observed in both sets of CNT-containing polycrystalline samples as a result of lattice defects associated with C substitution. Significantly, analytical fits to the data for each sample suggest that the same flux pinning mechanism accounts for the fishtail effect in polycrystalline MgB2 and (RE)BCO. © 2013 Elsevier B.V. All rights reserved.

A power optimised narrowband power-line communication system

Narrowband Power-line Communication (NPLC) technology uses a narrow bandwidth to transmit information. Its major applications include control, smart home systems and security. This paper proposes a power optimised NPLC system to minimise its systemic power consumption without compromising its communication ability. By using the proposed Smart Energy Conservation Layer which reads the signal strength from the PLC channel, a power optimised system is achieved to provide the essential transmitting power to secure the communications. Compared to commercial systems, the potential power saving could be up to 99% in a household environment, as demonstrated by the experimental results. © 2013 IEEE.

Magnetic characterisation of large grain, bulk Y-Ba-Cu-O superconductor-soft ferromagnetic alloy hybrid structures

Large grain, bulk Y-Ba-Cu-O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell's algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the superconductor alone below this saturation level, and especially when the applied field is removed. The results of the study show further that the beneficial effects on the trapped field are enhanced when the ferromagnet covers the entire surface of the superconductor for different ferromagnetic components of various shapes and fixed volume. © 2014 Elsevier B.V. All rights reserved.

Stochastic resonance for modulated gain in a single-mode laser

Stochastic resonance (SR) induced by the signal modulation is investigated, by introducing the signal-modulated gain into a single-mode laser system. Using the linear approximation method, we detailedly calculate the signal-to-noise ratio (SNR) of a gain-noise model of the single-mode laser, taking the cross-correlation between the quantum noise and pump noise into account. We find that, SR appears in the dependence of the SNR on the intensities of the quantum and the pump noises when the correlation coefficient between both the noises is negative; moreover, when the cross-correlation between the two noises is strongly negative, SR exhibits a resonance and a suppression versus the gain coefficient, meanwhile, the single-peaked SR and multi-peaked SR occur in the behaviors of the SNR as functions of the loss coefficient and the deterministic steady-state intensity. (c) 2005 Elsevier B.V. All rights reserved.

A novel image restoration algorithm based on high-dimensional space geometry

A novel image restoration approach based on high-dimensional space geometry is proposed, which is quite different from the existing traditional image restoration techniques. It is based on the homeomorphisms and "Principle of Homology Continuity" (PHC), an image is mapped to a point in high-dimensional space. Begin with the original blurred image, we get two further blurred images, then the restored image can be obtained through the regressive curve derived from the three points which are mapped form the images. Experiments have proved the availability of this "blurred-blurred-restored" algorithm, and the comparison with the classical Wiener Filter approach is presented in final.

Stochastic resonance in single-mode semiconductor lasers

Owing to the considerable virtues of semiconductor lasers for applications, they have become the main optical source for fiber communication systems recently. The behavior of stochastic resonance (SR) in direct-modulated semiconductor laser systems is investigated in this article. Considering the carrier and photon noises and the cross-correlation between the two noises, the power spectrum of the photon density and the signal-to-noise ratio (SNR) of the modulated laser system were calculated using the linear approximation method. We found that the SR always appears in the dependence of the SNR upon the bias current density, and is strongly affected by the cross-correlation coefficient of the carrier and photon noises, the frequency of modulation signal and the photon lifetime in the laser cavity. Hence, it is promising to use the SR mechanism to enhance the SNR of direct-modulated semiconductor laser systems and improve the quality of optical communication. (c) 2006 Elsevier B.V. All rights reserved.

A novel image restoration algorithm based on high-dimensional space geometry

A novel image restoration approach based on high-dimensional space geometry is proposed, which is quite different from the existing traditional image restoration techniques. It is based on the homeomorphisms and "Principle of Homology Continuity" (PHC), an image is mapped to a point in high-dimensional space. Begin with the original blurred image, we get two further blurred images, then the restored image can be obtained through the regressive curve derived from the three points which are mapped form the images. Experiments have proved the availability of this "blurred-blurred-restored" algorithm, and the comparison with the classical Wiener Filter approach is presented in final.

Complex networks constructed from irrational number sequences

In this paper, we construct (d, r) networks from sequences of different irrational numbers. In detail, segment an irrational number sequence of length M into groups of d digits which represent the nodes while two consecutive groups overlap by r digits (r = 0,1,...,d-1), and the undirected edges indicate the adjacency between two consecutive groups. (3, r) and (4, r) networks are respectively constructed from 14 different irrational numbers and their topological properties are examined. By observation, we find that network topologies change with different values of d, r and even sequence length M instead of the types of irrational numbers, although they share some similar features with traditional random graphs. We make a further investigation to explain these interesting phenomena and propose the identical-degree random graph model. The results presented in this paper provide some insight into distributions of irrational number digits that may help better understanding of the nature of irrational numbers.

针对C语言的自动微分系统及其应用

采用切线性模式和代码转换策略,开发了C语言自动微分转换系统(DTC),用于牛顿法求解非线性方程中Jacobi矩阵—向量乘积计算。介绍系统计算模型、功能、特色,并讨论系统的设计与实现技术,包括编译技术、微分代码转换及输入/输出(I/O)相关分析。最后给出了几个具有说服力的测试与应用。

限界模型检测方法及其应用

形式化验证主要是通过精确的分析来证明或证伪硬件或软件系统中一些明确的声明或者性质。形式化验证方法在广义上可以分成两大类：模型检测和定理证明。模型检测由对模型的所有状态和迁移做详尽访问的自动检测机制组成。这种机制是通过对适当的抽象模型进行直接或间接的状态枚举技术来实现的，从而证明模型中存在或者不存在所谓的“瑕疵”状态。定理证明则是运用数学推理和逻辑推论来证明系统的正确性。本文所讨论的就是模型检测方法中的限界模型检测方法及其相关的改进和应用。近些年来，基于可满足性求解（SAT）的限界模型检测方法作为基于BDD的模型检测方法的一种有效的补充，已经有了一定的发展。A. Biere等人最先提出了对于线性时序逻辑公式（LTL）的限界模型检测方法，进而，W.Penczek又提出了对于全局计算树逻辑（ACTL）的限界模型检测方法。由于模型检测方法具有很高的复杂性，因此，其效率问题始终倍受关注。论文第一个方面的重要贡献就体现在提高限界模型检测效率方面的相关研究上。我们对Penczek提出的限界模型检测方法进行了两方面的改进，以提高其求解效率。第一方面的改进是通过改进所需路径条数计算函数，将时序操作符EX和其它时序操作符区分开来，以减少编码时所需的迁移关系和变量数目；第二方面的改进则是采用统一路径编码的方式来简化公式的编码。通过这两方面的改进，公式在最坏情况下的编码复杂度得到了有效的降低。同时，我们还在工具BMV中实现了改进后的方法。随着实时系统的应用日益广泛，在对全局计算树逻辑的限界模型检测方法做了改进，提高了其求解效率以后，我们又将目光转移到了对实时系统的限界模型检测上。如何将限界模型检测方法高效的运用到对实时系统的检测当中成为了本文第二个方面的重要贡献。基于SAT的限界模型检测方法在对实时系统的模型和描述性质的公式进行编码时，需要对时间变量和时钟约束进行布尔编码，由于时间的连续性和不确定性，使得在对它进行布尔编码时，往往会相当的复杂，不仅耗费大量的时间，而且还不利于SAT的求解，即使是使用改进后的限界模型检测方法，整个验证过程的效率还是很低。所以，在对实时系统进行限界模型检测方面，我们转而考虑采用基于可满足性模块理论（SMT）的方法来对实时系统的模型和描述性质的公式进行编码。由于SMT可以直接处理基于整数或者实数的线性算术表达式，因此，我们可以直接用整型或者实型变量来表示时间变量，用线性算术表达式来表示时钟约束。与基于SAT的限界模型检测方法相比，基于SMT的限界模型检测方法在处理实时系统方面，不仅简化了编码过程，而且大大提高了求解效率。在此基础上，我们运用基于SAT的对全局计算树逻辑的限界模型检测方法中的改进思想，对基于SMT的实时系统的限界模型检测方法也做了相应的改进，使其求解效率较之改进前有了较大的提升。最后，我们就基于SAT的限界模型检测方法和基于SMT的限界模型检测方法以及它们的改进方法进行了一系列的实验对比。从实验结果可以看出，改进后的方法比改进前的方法在时间效率和空间效率上都有明显的提升，同时就实时系统来说，采用了SMT和限界模型检测相结合的方法以后，效率也比没有采用这两者的方法要高很多。

on lin-bose problem

This paper study generalized Serre problem proposed by Lin and Bose in multidimensional system theory context [Multidimens. Systems and Signal Process. 10 (1999) 379; Linear Algebra Appl. 338 (2001) 125]. This problem is stated as follows. Let F ∈ Al×m be a full row rank matrix, and d be the greatest common divisor of all the l × l minors of F. Assume that the reduced minors of F generate the unit ideal, where A = K[x 1,...,xn] is the polynomial ring in n variables x 1,...,xn over any coefficient field K. Then there exist matrices G ∈ Al×l and F1 ∈ A l×m such that F = GF1 with det G = d and F 1 is a ZLP matrix. We provide an elementary proof to this problem, and treat non-full rank case.

认证字典及其在PKI中的应用研究

认证字典是一类重要的数据结构,它在众多研究领域都具有重要的理论和应用价值.文中介绍了认证字典的基本概念和原理,引入了时间约束,给出了一种新的认证字典分类方法.从认证字典在PKI中的应用出发,分析了其实现技术;并简单地分析和比较了基于不同认证字典实现的证书撤销方案.

服务自适应模型及其应用

提出了一个基于模糊理论的服务自适应模型。完整地形式化了服务自适应选择过程,使用模糊语言变量和隶属度方程定义了上下文状态和服务策略选择规则。基于当前上下文与服务实现策略标准上下文之间的模糊距离概念,提出了计算服务实现策略合适程度的合适度方程。结合名为“校园助理”的上下文敏感应用场景,阐述了该模型的有效性和具体应用。