On computing the worst-case peak gain of linear systems

Based on the bounds due to Doyle and Boyd, we present simple upper and lower bounds for the l¹-norm of the ‘tail’ of the impulse response of finite-dimensional discrete-time linear time-invariant systems. Using these bounds, we may in turn compute the l^∞-gain of these systems to any desired accuracy. By combining these bounds with results due to Khammash and Pearson, we derive upper and lower bounds for the worst-case l^∞-gain of discrete-time systems with diagonal perturbations.     

一种基于彩色编码技术的基序发现算法

从DNA序列中发现基序是生物计算中的一个重要问题,序列条数K=20包含基序用例的序列条数k=16的(l,d)-(K-k)问题(记作(l,d)-(20-16)问题)是目前生物学家十分关注的基序发现问题.针对该问题提出了一种基于彩色编码技术的SDA(sample-driven algorithm)搜索算法--彩色编码基序搜索算法(color coding motif finding algorithm,简称CCMF算法).它利用彩色编码技术将该问题转化为(l,d)-(16-16)问题,再采用分治算法和分支定界法来求解.在解决将(l,d)-(20-16)问题转化为(l,d)-(16-16)问题时,CCMF算法利用彩色编码技术将4 845个组合降低到403个着色,这将极大地提高算法的整体运行效率.使用模拟数据和生物数据进行测试的结果表明,CCMF算法能够快速发现所有(l,d)-(20-16)问题的基序模型和基序用例,具有优于其他算法的综合性能评价,能够用于真实的基序发现问题.同时,通过修改着色方案,CCMF算法可以用于求解一般的(l,d)-(K-k)问题,其中,k＜K.     

基于观测器的l1鲁棒故障检测方法

基于参数化的控制系统输出观测器,将鲁棒控制理论中l^1最优化方法用于故障检测技术,提出一种新的控制系统鲁棒故障检测方法,通过求解一个混合0－1型整数线性规划问题,可得出l^1优化残差函数,仿真结果验证了所提方法的有效性。     

参数曲面上的插值与混合

如何表示曲面上的曲线,在处理诸如数控加工中的路径设计以及CAD/CAM等领域频繁出现的曲面裁剪问题时显得日益重要.给出了数据点的切方向(切方向及曲率向量或测地曲率值)指定而G¹连续(G²连续)插值曲面上任意点列的方法.作为曲面上曲线插值问题的特例,还讨论了曲面上曲线的混合问题.基本思想是借助于微分几何的有关结论,曲面上曲线的插值问题被转化为其参数平面上类似的曲线插值问题.该方法能够用二维隐式方程来表示曲面上的插值曲线,从而把在显示该曲线时所面对的曲面求交的几何问题转化为计算隐式曲线的代数问题.实验证明该方法是可行的,而且适用于CAD/CAM及计算机图形学等领域.     

On pure H reduced-order dynamic controllers: an erratum

There are at least two approaches advocated to obtain a pure H^∞ reduced-order dynamic controller for a given augmented plant. One approach is to eliminate completely the H² aspect from a standard H²/H^∞ setting. A second approach is to equate the H² aspect with the H^∞ aspect in that same setting. This paper invalidates the first approach but affirms the second approach and produces the correct equations resulting therefrom.     

A minimum-area circuit forl-selection

We prove tight upper and lower bounds on the area of semelective, when-oblivious VLSI circuits for the problem ofl-selection. The area required to select thelth smallest ofn k-bit integers is found to be heavily dependent on the relative sizes ofl,k, andn. Whenl<2 ^k , the minimal area isA = (minn,l(k-logl)). Whenl2 ^k ,A = (2 ^k (logl-k + 1)).This work was supported in part by National Science Foundation Grant DMC 84-06408 and by the Slovak Academy of Sciences.     

Supervisory control of hybrid systems within a behavioural framework

This contribution addresses the synthesis of supervisory control for hybrid systems Σ with discrete external signals. Such systems are in general neither l-complete nor can they be represented by finite state machines. We find an l-complete approximation (abstraction) Σ_l for Σ, represent it by a finite state machine, and investigate the control problem for the approximation. If a solution exists, we synthesize the maximally permissive supervisor for Σ_l. We show that it also solves the control problem for the hybrid system Σ. If no solution exists, approximation accuracy can be increased by computing a k-complete abstraction Σ_k, k>l. This paper is entirely set within the framework on Willems’ behavioural systems theory.     

MIMO离散时间系统混合l1/H2控制

研究了MIMO(多输入多输出)离散时间系统的混合l₁/H₂优化问题,该问题可描述为最优化一个传递函数矩阵的l₁范数同时保证另一个传递函数矩阵的H₂范数满足预定的指标.研究了最优目标函数值关于H₂范数指标的连续性.证明了MIMO系统混合l₁/H₂控制问题最优解的存在性.由于基于标定-Q(scaled-Q)方法求解MIMO混合l₁/H₂问题,避免了进行零点插值运算的困难.通过求解有限维非线性规划问题可得到最优目标值的收敛的上下界.     

Flow regularity and optimality conditions with controls inL p

In this paper we study theC ^p regularity of the flow of a nonlinear nonautonomous control system with respect to control maps belonging toL ^p withp≥r. The results obtained are applied to get first- and second-order optimality conditions when the control space isL ^p . The problem which we consider is in the Mayer form and includes endpoint constraints. We present first-order necessary conditions for a wide class of control systems. Moreover, we show that the usual second-order sufficient conditions are effective only if the mapf that defines the control system is a polynomial of degree two in the control variable and the controls belong toL ².     

面向关系-事务数据的数据匿名方法

在发布同时包含关系和事务属性的数据（简称为关系-事务数据）时,由于关系数据和事务数据均有可能受到链接攻击,需要同时匿名这两部分的数据.现有的数据匿名技术在匿名化关系-事务数据时会造成严重的数据缺损,无法保障数据可用性.针对此问题,提出了（k,l）-多样化模型,通过等价类上的l-多样化约束和事务数据上的k-匿名约束来保证用户隐私不被泄露.在此基础上,设计并实现了APA和PAA两种满足该模型的匿名算法,以不同的顺序对关系-事务数据进行匿名,并提出了相应的数据缺损评估方法.实际公开数据集上的实验结果表明,与现有的数据匿名技术相比,APA和PAA能够在保护用户隐私的前提下,以更低的数据缺损和更高的效率完成对关系-事务数据的匿名.     

G 2 interpolation and blending on surfaces

We introduce a method for curvature-continuous (G ²) interpolation of an arbitrary sequence of points on a surface (implicit or parametric) with prescribed tangent and geodesic curvature at every point. The method can also be used forG ² blending of curves on surfaces. The interpolation/blending curve is the intersection curve of the given surface with a functional spline (implicit) surface. For the construction of blending curves, we derive the necessary formulas for the curvature of the surfaces. The intermediate results areG ² interpolation/blending methods in IR².     

New approaches to robust l2?l∞ and H∞ filtering for uncertain discrete-time systemsfiltering for uncertain discrete-time systems

The problems of robust l ₂−l _∞ and H _∞ filtering for discrete-time systems with parameter uncertainty residing in a polytope are investigated in this paper. The filtering strategies are based on new robust performance criteria derived from a new result of parameter-dependent Lyapunov stability condition, which exhibit less conservativeness than previous results in the quadratic framework. The designed filters guaranteeing a prescribed l ₂−l _∞ or H _∞ noise attenuation level can be obtained from the solution of convex optimization problems, which can be solved via efficient interior point methods. Numerical examples have shown that the filter design procedures proposed in this paper are much less conservative than earlier results.     

宽带噪声激励下带有分数阶控制器的强非线性系统的随机平均技术

运用随机平均法研究了宽带噪声激励下带有分数阶PI~λD~μ控制器的强非线性系统.首先,应用广义谐波平衡技术,将分数阶PI~λD~μ控制力分解为幅值依赖的等效拟线性阻尼力和拟线性回复力,得到了受控整数阶等效非线性系统.然后,运用基于广义谐和函数的随机平均法得到关于幅值的平均伊藤微分方程.最后,建立并求解相应的简化Fokker-Planck-Kolmogorov(FPK)方程,得到稳态概率密度函数.作为算例,考察了Duffing-van de Pol振子.数值结果表明随机平均法能够达到较高的精度,分数阶PI~λD~μ控制器能够对系统响应进行有效的控制.此外,宽带噪声参数ξ_i、ω_i及D_i改变时,本文提出的方法仍具有较好的适用性,分数阶控制器仍同样具有非常好的控制效果.     

Bounded size dictionary compression: SC-completeness and NC algorithms

We study the parallel complexity of a bounded size dictionary version (LRU deletion heuristic) of the LZ2 compression algorithm. The unbounded version was shown to be P-complete. When the size of the dictionary is O(log^kn), the problem of computing the LZ2 compression is shown to be hard for the class of problems solvable simultaneously in polynomial time and O(log^kn) space (that is, SC^k). We also introduce a variation of this heuristic that turns out to be an SC^k-complete problem (the original heuristic belongs to SC^k+1). In virtue of these results, we argue that there are no practical parallel algorithms for LZ2 compression with LRU deletion heuristic or any other heuristic deleting dictionary elements in a continuous way. For simpler heuristics (SWAP, RESTART, FREEZE), practical parallel algorithms are given.     

On the strict logic foundation of fuzzy reasoning

This paper focuses on the logic foundation of fuzzy reasoning. At first, a new complete first-order fuzzy predicate calculus system K^* corresponding to the formal system L^* is built. Based on the many-sort system K_ms^* corresponding to K^*, the triple I methods of FMP and FMT for fuzzy reasoning and their consistency are formalized, thus fuzzy reasoning is put completely and rigorously into the logic framework of fuzzy logic.The author is indebted to anonymous referee for his useful comments which have helped to improve the paper.     

l1优化在网格去噪中的应用

目的 网格去噪是计算机图形学中的经典问题,而如何在去除噪声的同时保持网格的特征结构是这一研究方向所面临的最大挑战。方法 提出一种具有稀疏性的全局网格去噪方法,该方法源于信号处理理论中稀疏表示的基本思想,通过优化全局能量函数来去除网格模型的噪声,同时能够保持网格模型的特征结构。该方法共分为两个步骤,第1步为网格面法向量的滤波,首先建立全局优化模型,对噪声网格的面法向量进行滤波优化,其中引入l₁范数来保证解的稀疏性,使得优化后新的面法向量能够保持网格的特征结构;第2步为网格曲面的重建,根据第1步得到的新的面法向量,按照面法向量的定义,建立最小二乘意义下的网格顶点的重建模型,求解得到新的网格曲面。结果 由于该模型是全局方法,避免了现有滤波方法可能出现的不收敛等问题,能够取得比较满意的去噪效果。结论 大量实验结果表明,本文方法在去除噪声的同时,能较好地保持网格的特征结构,尤其对于CAD模型有很好的实验效果。     

Structure-Texture Image Decomposition—Modeling, Algorithms, and Parameter Selection

This paper explores various aspects of the image decomposition problem using modern variational techniques. We aim at splitting an original image f into two components u and ρ, where u holds the geometrical information and ρ holds the textural information. The focus of this paper is to study different energy terms and functional spaces that suit various types of textures. Our modeling uses the total-variation energy for extracting the structural part and one of four of the following norms for the textural part: L², G, L¹ and a new tunable norm, suggested here for the first time, based on Gabor functions. Apart from the broad perspective and our suggestions when each model should be used, the paper contains three specific novelties: first we show that the correlation graph between u and ρ may serve as an efficient tool to select the splitting parameter, second we propose a new fast algorithm to solve the TV − L¹ minimization problem, and third we introduce the theory and design tools for the TV-Gabor model. First online version published in February, 2006     

Achievable H performance in sampled-data smoothing: beyond the -barrier

The lifting technique is a powerful tool for handling the periodically time-varying nature of sampled-data systems. Yet all known solutions of sampled-data H^∞ problems are limited to the case when the feedthrough part of the lifted system, , satisfies , where γ is the required H^∞ performance level. While this condition is always necessary in feedback control, it might be restrictive in signal processing applications, where some amount of delay or latency between measurement and estimation can be tolerated. In this paper, the sampled-data H^∞ fixed-lag smoothing problem with a smoothing lag of one sampling period is studied. The problem corresponds to the a-posteriori filtering problem in the lifted domain and is probably the simplest problem for which a smaller than performance level is achievable. The necessary and sufficient solvability conditions derived in the paper are compatible with those for the sampled-data filtering problem. This result extends the scope of applicability of the lifting technique and paves the way to the application of sampled-data methods in digital signal processing.     

On decoupling the H-optimal sensitivity problem for products of plants

In this note we show how to solve the H^∞-optimal sensitivity problem for a SISO plant P(s) = P₁(s)P₂(s), given the solutions for P₁(s), P₂(s). This allows us to solve the problem for systems of the form e^−hsP₀(s), where P₀(s) is the transfer function of a stable, LTI, finite dimensional system.     

Direct amperometric determination of l-ascorbic acid (Vitamin C) at octacyanomolybdate-doped-poly(4-vinylpyridine) modified electrode in fruit juice and pharmaceuticals

The glassy carbon electrode (GCE) modified with Mo(CN)₈⁴⁻-incorporated-poly(4-vinylpyridine) (PVP/Mo(CN)₈⁴⁻), which has been recently shown to possess several attractive attributes as an efficient electrocatalytic electrode for l-ascorbic acid oxidation and its estimation, is used for l-ascorbic acid estimation directly in orange fruit juice and Celin tablet in a 0.1 M H₂SO₄ acid solution without any special treatment. Constant potential amperometry at 570 mV (saturated calomel electrode, SCE) in stirred solutions is used for this purpose. A good correlation is attained with the official titrametric method. To understand the possible electrocatalytic reaction mechanism for the electro-oxidation of l-ascorbic acid, calibration graphs over the range 1 × 10⁻⁵ to 1 × 10⁻² mol dm⁻³ l-ascorbic acid are compared for the three electrodes, ca. PVP/Mo(CN)₈⁴⁻, undoped PVP, and GCE; the curvature at high ascorbic acid concentration for the PVP/Mo(CN)₈⁴⁻ electrode is explained in terms of Michaelis–Menten (MM) saturation kinetics. The apparent MM constant (K_M), the maximum catalytic current (i_M), the complex decomposition rate constant (k_c), and the heterogeneous modified electrode rate constant (k^′_ME) are calculated from three different approaches. A reasonably high value of ≈1 × 10⁻² cm s⁻¹ is obtained for k^′_ME, indicating efficient l-ascorbic acid mediation at the PVP/Mo(CN)₈⁴⁻ electrode, thus accounting for quite a high sensitivity of this modified film electrode compared to several other modified electrodes.