An Algebraic Detection Approach for Control Systems under Multiple Stochastic Cyber-attacks

In order to compromise a target control system successfully,hackers possibly attempt to launch multiple cyberattacks aiming at multiple communication channels of the control system.However,the problem of detecting multiple cyber-attacks has been hardly investigated so far.Therefore,this paper deals with the detection of multiple stochastic cyber-attacks aiming at multiple communication channels of a control system.Our goal is to design a detector for the control system under multiple cyberattacks.Based on frequency-domain transformation technique and auxiliary detection tools,an algebraic detection approach is proposed.By applying the presented approach,residual information caused by different attacks is obtained respectively and anomalies in the control system are detected.Sufficient and necessary conditions guaranteeing the detectability of the multiple stochastic cyber-attacks are obtained.The presented detection approach is simple and straightforward.Finally,two simulation examples are provided,and the simulation results show that the detection approach is effective and feasible.

连续Domain的遗传性及其不变性

引入Domain子空间的概念,得到Scott开集和闭集都是Domain的子空间。证明连续Domain或代数Domain对开子空间和闭子空间都是可遗传的。证明连续Domain或代数Domain在保Waybelow序的Scott连续映射下保持不变。

相容双有限domain及相关范畴性质

将建立在dcpo上的双有限domain等概念推广到相容定向完备偏序集上,定义了相容定向完备偏序集上的逼近单位、有限分离、相容双有限domain等概念,给出了相容双有限domain的等价命题.并从范畴学的角度考察证明了以相容双有限domain为对象,Scott连续映射为态射的范畴CBF是笛卡儿闭范畴.还讨论了相容定向完备偏序集及相容代数domain上的几个性质.

Z-连续Domain关于Z-子空间的遗传性

利用Z-Domain中的Z-子空间的概念,得出Z-Scott开集和Z-Scott闭集都是Z-子空间结论.利用Z-连续子空间、Z-代数子空间的定义,得出Z-连续Domain、Z-代数Domain关于闭Z-子空间遗传这一结论.

代数L-domain的表示定理及其相关范畴性质

引入局部条件并半格 (简记为 L cusl)及其理想完备化等概念 .证明了 :任一代数 L domain的紧元集是 L cusl;任一代数 L domain是其紧元集赋予 Alexandrov拓扑时的 Sober化 ;任一 L cusl的理想完备化是代数 L domain,从而得到了代数 L domain的表示定理 .还证明了 Scott连续映射为态射的代数 L domain范畴为 L cusl与单调映射作成的范畴的反射子范畴 .

相容连续Domain的遗传性

定义相容Domain的子Domain与子空间等概念,得到Scott开集和Scott闭集都是相容Domain的子Domain与子空间的结论,证明了相容连续Domain或相容代数Domain对开子空间和闭子空间都是可遗传的。

两类代数Domain范畴的等价

首先证明了一个Domain范畴与它的等价范畴有相同的笛卡儿闭性,其次通过引入两类新的偏序集即L-偏序集和B-偏序集,构造了范畴LPOSA(由L-偏序集与逼近关系组成)和范畴BPOSA(由B-偏序集与逼近关系组成),并证明了它们分别与代数L-domain范畴ALD和代数bc-domain范畴ABD等价．

关于代数L-domain的一个刻画定理

引入了强core紧拓扑空间的概念,给出了代数L-domain的刻画定理,其主要结果是:偏序集D是代数L-domain当且仅当对每个强core紧拓扑空间X,函数空间[X→D]是代数L-domain.

相容连续Domain的不变性

引入了Scott相容连续映射与商相容Domain等概念,研究了Scott相容连续映射保局部基与保waybelow序及保局部基与保紧元之间的关系,证明了相容连续Domain或相容代数Domain在保局部基的Scott相容连续满映射下保持不变.

拟Z-代数domain

基于一般子集系统Z,引入拟Z-代数domain的概念,研究了拟Z-代数domain的一些映射性质,并讨论了拟Z-代数domain与拟Z-连续domain之间的关系及拟Z-代数domain的乘积。

连通代数domain上相容紧元及范畴的研究

基于连通集的定义,引入了c-理想的概念,得出了连通代数domain中每一个元都是相容紧元,当且仅当它的每个c-理想都是主c-理想,给出了连通代数domain满足升链条件。研究了连通完备偏序集A中的每个元是相容紧元的充要条件是A与A的c-理想格同构。最后,证明了连通代数domain范畴与偏序集范畴等价。

几乎代数基与有界完备domain

研究几乎代数dcpo的性质,并得到如下主要结果:1)具有可数几乎代数弱闭基的有界完备domain构成的范畴是Cartesian闭的;2)对每个具有(可数)几乎代数基的dcpo,其相容下幂domain是一个具有可数几乎代数弱闭基的有界完备domain.

Stabilized Multi-domain Simulation Algorithms and Their Application in Simulation Platform for Forging Manipulator

Most researches focused on the analytical stabilized algorithm for the modular simulation of single domain, e.g., pure mechanical systems. Only little work has been performed on the problem of multi-domain simulation stability influenced by algebraic loops. In this paper, the algebraic loop problem is studied by a composite simulation method to reveal the internal relationship between simulation stability and system topologies and simulation unit models. A stability criterion of multi-domain composite simulation is established, and two algebraic loop compensation algorithms are proposed using numerical iteration and approximate function in multi-domain simulation. The numerical stabilized algorithm is the Newton method for the solution of the set of nonlinear equations, and it is used here in simulation of the system composed of mechanical system and hydraulic system. The approximate stabilized algorithm is the construction of response surface for inputs and outputs of unknown unit model, and it is utilized here in simulation of the system composed of forging system, mechanical and hydraulic system. The effectiveness of the algorithms is verified by a case study of multi-domain simulation for forging system composed of thermoplastic deformation of workpieces, mechanical system and hydraulic system of a manipulator. The system dynamics simulation results show that curves of motion and force are continuous and convergent. This paper presents two algorithms, which are applied to virtual reality simulation of forging process in a simulation platform for a manipulator, and play a key role in simulation efficiency and stability.

Domain函数空间代数性的一个注记

利用步函数讨论了domain函数空间的代数性,证明了当D是Lawson紧的代数domain,L是一个特定的非L-domain的连续domain时,函数空间[D→L]是代数的.

Variational Formulations Yielding High-Order Finite-Element Solutions in Smooth Domains without Curved Elements

One of the reasons for the great success of the finite element method is its versatility to deal with different types of geometries. This is particularly true of problems posed in curved domains. Nevertheless it is well-known that, for standard variational formulations, the optimal approximation properties known to hold for polytopic domains are lost, if meshes consisting of ordinary elements are still used in the case of curved domains. That is why method’s isoparametric version for meshes consisting of curved triangles or tetrahedra has been widely employed, especially in case Dirichlet boundary conditions are prescribed all over a curved boundary. However, besides geometric inconveniences, the isoparametric technique helplessly requires the manipulation of rational functions and the use of numerical integration. In this work we consider a simple alternative that bypasses these drawbacks, without eroding qualitative approximation properties. More specifically we work with a variational formulation leading to high order finite element methods based only on polynomial algebra, since they do not require the use of curved elements. Application of the new approach to Lagrange methods of arbitrary order illustrates its potential to take the best advantage of finite-element discretizations in the solution of wide classes of problems posed in curved domains.

CLASSIFICATION OF A CLASS OF HYPERBOLIC REINHARDT DOMAINS

In this article, the author discusses the dimension of holomorphic automorphism groups on hyperbolic Reirihardt domains. and classifies those hyperbolic Reinhardt domains whose automorphism group has prescribed dimension n2 - 2 (where n is the dimension of domain).

Harmonic Balance Methods:A Review and Recent Developments

The harmonic balance(HB)method is one of the most commonly used methods for solving periodic solutions of both weakly and strongly nonlinear dynamical systems.However,it is confined to low-order approximations due to complex symbolic operations.Many variants have been developed to improve the HB method,among which the time domain HB-like methods are regarded as crucial improvements because of their fast computation and simple derivation.So far,there are two problems remaining to be addressed.i)A dozen of different versions of HB-like methods,in frequency domain or time domain or in hybrid,have been developed;unfortunately,misclassification pervades among them due to the unclear borderlines of different methods.ii)The time domain HB-like methods suffer from non-physical solutions,which have been shown to be caused by aliasing(mixture of the high-order into the low-order harmonics).Although a series of dealiasing techniques have been developed over the past two decades,the mechanism of aliasing and the final solution to dealiasing are still not well known to the academic community.This paper aims to provide a comprehensive review of the development of HB-like methods and enunciate their principal differences.In particular,the time domain methods are emphasized with the famous aliasing phenomenon clearly addressed.

一种计算机代数系统的设计与实现

为利用计算机对数学表达式进行自动推理,实现自主可控的计算机代数系统,提出了基于抽象语法树模式匹配的计算机代数系统设计方法。在对计算机代数系统设计过程进行认知与分解的基础上建立了总体设计模型,并利用F#强大的函数式编程语言能力,快速实现解析器和表达式模式匹配,从而提高开发效率。通过设计一个可实现表达式化简、展开、求导、极限、泰勒级数和积分等功能的计算机代数系统,验证了该设计的准确性和有效性。

有损伤框架结构中的波动分析

基于回传射线矩阵法 ,研究了有损伤框架结构在水平方波脉冲作用下脉冲作用点的速度波 ,结构的局部损伤用减小受损单元的横截面面积来模拟。结果表明 :改变脉冲作用点位置 ,通过脉冲作用点横向速度波首波波幅的变化可以确定受损单元的起始位置 ;当脉冲作用点在受损单元的起始位置时 ,脉冲作用点横向速度波首波波幅变化越大 ,损伤越大 ,脉冲作用点横向速度波的第一个波谷到达时间越晚 ,损伤单元越长。

复阻尼结构动力方程的增维精细积分法

为了避开求解复阻尼结构强迫激励动力学方程的积分运算,引入增维精细积分方法。根据复阻尼系统复化对偶原则,将动力学方程和激励波对偶复化为实部和虚部的形式,推导出增维矩阵的精细积分求解过程。结果表明,由于不用求解迭代矩阵H的逆矩阵,避免了矩阵奇异带来的计算解的不稳定性。在计算矩阵仅增加一维的情况下,化积分运算为代数运算,扩大了精细积分法的应用范围。通过对比增维精细积分法和频域法计算结果,二者结果保持较高的一致性。