基于二维混合模型和状态观测器的重复控制设计

针对一类正则线性系统, 提出一种基于状态观测器和二维混合模型的重复控制系统设计方法. 首先, 通过构造一个状态观测器来重构系统的状态, 建立基于重构状态的线性控制律. 然后, 通过独立地考虑重复控制系统的连续控制过程与离散学习行为, 给出基于状态观测器和重构状态反馈的连续/离散二维混合模型. 针对这个混合模型, 运用二维Lyapunov泛函方法, 以线性矩阵不等式(Linear matrix inequality, LMI)的形式给出重复控制系统存在重复控制器和状态观测器的充分条件, 所给条件可用Matlab工具箱方便地求解. 数值仿真验证了本文所提方法的有效性.     

非均匀采样系统的一种递推辨识方法

在非均匀采样系统辨识方法中, 通常利用重采样、数值积分等方法来处理非均匀采样数据, 所用模型多为连续有理分式传递函数, 在递推形式下非均匀采样对象又常局限于``数据缺失'的情况. 本文研究更为一般的异步非均匀采样的多变量系统, 采用连续时间状态空间模型描述, 推导了模型参数、参数梯度和系统状态之间的相互递推关系, 构成一种可变迭代间隔的递推辨识算法, 在每次输出采样点上仅更新模型中受当前采样数据影响的参数. 这种辨识方法可以适用于任意非均匀采样系统, 多采样率系统也可作为一种特例适用于本算法. 仿真结果表明, 所提的方法是可行有效的.     

非相称多时滞奇异系统的有记忆状态反馈控制

针对一类非相称多时滞奇异系统, 研究其时滞相关稳定性问题. 给出了易于数值检验的时滞无关正则条件. 基于Lyapunov-Krasovskii泛函方法和广义积分引理给出了系统时滞相关稳定的充分条件. 本文的主要思想是利用矩阵不等式方法, 设计有记忆状态反馈控制器, 使相应的闭环系统时滞无关正则、无脉冲、渐进稳定, 并直接给出了有记忆状态反馈控制器参数化的表达形式. 最后通过数值仿真验证了所提方法的有效性.     

基于收发平衡判定的TCP流量回放方法

基于真实网络流量的互动式回放测试是当前针对防火墙、IPS等串接型安全设备进行测评的最新方法.文中在分析现有基于状态判定的TCP流量互动式回放方法基础之上,引入收发平衡机制,提出了一种基于收发平衡和状态判定相结合的新的TCP流量回放方法.通过在发送TCP数据包前优先进行收发平衡判定将数据包发送出去,提出的方法能够有效减少TCP流量在发送过程中的状态判定开销,提高回放性能.对引入收发平衡机制前后的TCP流量回放方法的差异进行了分析比较.从单个TCP会话特性、并发会话流量特性、网络传输延迟与丢包等角度分析验证了影响引入收发平衡机制后的算法有效性的因素.实际流量实验表明,文中所提方法在回放TCP流量时性能有显著提升,适用于在更大规模的流量环境下对防火墙、IPS等串接型网络安全设备进行测评.     

Colon segmentation and colonic polyp detection using cellular neural networks and three-dimensional template matching

Abstract: In this study, an automatic three-dimensional computer-aided detection system for colonic polyps was developed. Computer-aided detection for computed tomography colonography aims at facilitating the detection of colonic polyps. First, the colon regions of whole computed tomography images were carefully segmented to reduce computational burden and prevent false positive detection. In this process, the colon regions were extracted by using a cellular neural network and then the regions of interest were determined. In order to improve the segmentation performance of the study, weights in the cellular neural network were calculated by three heuristic optimization techniques, namely genetic algorithm, differential evaluation and artificial immune system. Afterwards, a three-dimensional polyp template model was constructed to detect polyps on the segmented regions of interest. At the end of the template matching process, the volumes geometrically similar to the template were emhanced.     

Intuitionistic fuzzy transformation semigroups

The idea of (faithful) intuitionistic fuzzy transformation semigroup, intuitionistic admissible relation, and intuitionistic (strong) homomorphism are introduced and their basic properties are examined.     

Full mobile agent interoperability in an IEEE-FIPA context

The existence of heterogeneous mobile agent systems hinders the interoperability of mobile agents. Several solutions exist, but they are limited in some aspects. This article proposes a full interoperability solution, in the context of the IEEE-FIPA agent standards, composed of three parts. The first part is a simple language-independent agent interface that enables agents to visit locations with different types of middlewares. The second part is a set of design models for the middlewares to support agents developed for different programming languages and architectures. And the third part is a method based on agents with multiple codes and a common agent data encoding mechanism to enable interoperability between middlewares that do not support the same programming languages. Furthermore two agent interoperability implementations, and its corresponding performance comparison, carried out over the JADE and AgentScape agent middlewares are presented.     

Exploring alternatives for transition verification

When an implementation under test (IUT) is state-based, and its expected abstract behavior is given in terms of a finite state machine (FSM), a checking sequence generated from a specification FSM and applied to an IUT for testing can provide us with high-level confidence in the correct functional behavior of our implementation. One of the issues here is to generate efficient checking sequences in terms of their lengths. As a major characteristics, a checking sequence must contain all β-sequences for transition verification. In this paper, we discuss the possibility of reducing the lengths of checking sequences by making use of the invertible transitions in the specification FSM to increase the choice of β-sequences to be considered for checking sequence generation. We present a sufficient condition for adopting alternative β-sequences and illustrate typical ways of incorporating these alternative β-sequences into existing methods for checking sequence generation to reduce the lengths. Compared to the direct use of three existing methods, our experiments show that most of the time the saving gained by adopting alternative β-sequences falls in the range of 10–40%.     

Structural and electrical properties of mixed oxides of manganese and vanadium: A new semiconductor oxide thermistor material

Binary oxides of manganese and vanadium have been synthesized by solid state sintering, in which the mass ratio of the individual components Mn₂O₃ and VO₂ have been varied from 90:10 to 5:95. The bulk ceramic samples were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive X-ray analysis. The initial compositions either rich in Mn₂O₃ or in equi-proportion by mass with VO₂ yield β-Mn₂V₂O₇ or a new crystalline form of Mn₂V₂O₇, with unit cell parameters: a = 7.73091 Å, b = 6.640788 Å, c = 6.70779 Å α = γ = 90° and β = 98.7086° which is designated as γ-Mn₂V₂O₇. The compositions, richer in VO₂ produce MnV₂O₆ co-existing with V₂O₅ the proportion of which increases with increase in VO₂. The surface microanalysis shows a spherical-granular morphology in Mn₂V₂O₇ structure and plate/rod-like structures co-existing with granular morphology in case of MnV₂O₆ together with V₂O₅. The electrical parameters of the negative temperature coefficient thermistors were determined. Depending on the constituent oxide composition, the NTC thermistors showed room temperature resistivity in the range of 6.52 × 10² to 6.1 × 10⁶ Ω-cm. The thermistor constant and activation energy are in the range of 0.12–0.458 eV and 1393–4801 K, respectively.     

可信平台模块自动化测试研究

可信平台模块(trusted platform module,TPM)是信息安全领域新发展趋势可信计算的关键部件,对其进行规范符合性测试非常有必要.由于传统测试方法与经验无法满足精确、易被机器处理的测试要求,状态机理论可为符合性测试的正确性提供理论基础,但易于产生状态爆炸问题.因此,基于TPM规范进行了一致性测试建模,提出相应策略提高测试效率,建立了TPM自动化测试工具.该工具能基于数据库自动生成测试用例,根据状态图进行一致性测试或自定义测试,达到过程可视化的效果.针对待测试产品得出了较为全面一致性结论和基本安全分析,为今后的可信产品安全性测试打下基础.