Passive Attack Detection for a Class of Stealthy Intermittent Integrity Attacks

This paper proposes a passive methodology for detecting a class of stealthy intermittent integrity attacks in cyber-physical systems subject to process disturbances and measurement noise. A stealthy intermittent integrity attack strategy is first proposed by modifying a zero-dynamics attack model. The stealthiness of the generated attacks is rigorously investigated under the condition that the adversary does not know precisely the system state values. In order to help detect such attacks, a backward-in-time detection residual is proposed based on an equivalent quantity of the system state change, due to the attack, at a time prior to the attack occurrence time. A key characteristic of this residual is that its magnitude increases every time a new attack occurs. To estimate this unknown residual, an optimal fixed-point smoother is proposed by minimizing a piece-wise linear quadratic cost function with a set of specifically designed weighting matrices. The smoother design guarantees robustness with respect to process disturbances and measurement noise, and is also able to maintain sensitivity as time progresses to intermittent integrity attack by resetting the covariance matrix based on the weighting matrices. The adaptive threshold is designed based on the estimated backward-in-time residual, and the attack detectability analysis is rigorously investigated to characterize quantitatively the class of attacks that can be detected by the proposed methodology. Finally, a simulation example is used to demonstrate the effectiveness of the developed methodology.      

爆破成井装药结构与中心孔药量的模拟与实践

为研究小断面急倾斜天井采用VCR法一次爆破成井的中心孔药量问题,采用ANSYS/LS-DYNA对成井过程进行了数值模拟。根据C·W利文斯顿球状药包理论,采用5孔布置、单孔中心掏槽、同分层中心孔与边孔不等高装药模拟成井过程。通过观察爆炸作用下岩石塑性应变场的变化,确定该方法能够很好地解决岩石夹制性问题。进而,改变中心孔药量进行多组模拟,发现不同中心孔药量与井壁上不同位置的单元应力对岩石抗拉强度的二阶矩的值呈非线性关系,并由此总结出中心孔药量的确定方法。工程实例验证了采用不等高装药与使用合理的药量能够达到理想的成井效果。     

基于粒子群算法的彩报印刷墨量计算方法研究

着墨量的精确计算和自动控制是提高彩色报纸图像质量的主要因素;针对目前彩报印刷计算不准确及自动化程度低等不足,主要对基于粒子群算法的彩报印刷CMYK四色油墨墨量计算方法进行研究;在分析基本粒子群算法原理的基础上,通过引入自适应惯性权重和收缩因子,改善了算法的收敛性能,应用改进粒子群算法对求解本问题进行研究,验证了算法的有效性,该墨量预置方法能较精确地控制墨层厚度,为彩报印刷自动配色提供了可参考的方法.     

一类控制量非负的新型脉冲随机控制模型

提出并研究了一类新型的脉冲随机控制模型,其状态结构由关于半鞅的线性随机微分方程所确定,其控制费用函数为关于控制前状态与控制量的二元函数且其控制量保持非负.首先建立了一类新型的变分方程并证明了其解的存在性.通过对变分方程的解函数进行一系列随机分析处理,证明了最佳控制的存在性且对其结构进行了深入分析.此外,由于本文模型与以往文献中的随机控制模型有着重大差异,因而在分析手法上与以往文献相比颇多差异之处.可以预期,本文不仅在随机控制的研究中将具有重要的理论意义,而且在金融控制及证券管理方面也将有着广泛的应用价值.     

基于实时操作系统的低成本捷联惯导系统

针对捷联惯导系统低成本、小体积的要求,给出提出一种利用微机械惯性传感器,、以ARM芯片作为导航计算机的硬件方案。设计基于嵌入式实时操作系统的实时多任务导航计算机软件系统。测试结果表明,姿态角度的短期误差可保持在2o范围内,软件系统能合理分配硬件资源,提高导航计算机的整体性能,软件的模块化设计使导航计算机的软件系统具备良好可移植性。     

电压输出型传感器高精度数字转换模块的研制

传感器输出信号的数字采集是工业检测系统数字化的关键技术,通过对各种传感器的分析和研究,采用能适应0～100mV宽动态模拟输入信号范围、24位显示分辨率的数字采集技术,研制出电压输出型传感器高精度数字转换模块.该模块具有功耗低、体积小、可靠性高、使用安装方便的特点,解决了工业现场各种类型传感器输出信号的数字量转换问题,它为企业新产品研发和传统设备数字化改造提供了前端数字信息采集的硬件支持.     

Inventory models for multi-warehouse systems under fixed and flexible space leasing contracts

In this paper, we analyze a practical situation in which an inventory manager is faced with several options to store excess stocks whenever the storage capacity of his/her warehouse is insufficient. The manager can choose from either storage space providers through fixed long term or flexible leasing contracts, or the manager can acquire the extra required space from the spot market. We formulate this inventory problem with multiple storage facilities as a nonlinear program and show that it has a global optimal solution. We then provide closed-form solutions for the optimal ordering quantity and leased spot market space depending on the value of the unconstrained economic order quantity. In addition, we develop some structural properties for the optimal ordering policy and include several examples to illustrate the formulated models.     

Economic lot sizing in a production system with random demand

An extended economic production quantity model that copes with random demand is developed in this paper. A unique feature of the proposed study is the consideration of transient shortage during the production stage, which has not been explicitly analysed in existing literature. The considered costs include set-up cost for the batch production, inventory carrying cost during the production and depletion stages in one replenishment cycle, and shortage cost when demand cannot be satisfied from the shop floor immediately. Based on renewal reward process, a per-unit-time expected cost model is developed and analysed. Under some mild condition, it can be shown that the approximate cost function is convex. Computational experiments have demonstrated that the average reduction in total cost is significant when the proposed lot sizing policy is compared with those with deterministic demand.     

闸坝对河流水质水量影响评估及调控能力识别研究框架

针对重污染河流闸坝众多、水污染事故多发、防洪防污矛盾突出等问题,评估闸坝对河流水质水量影响,识别闸坝调控能力,是解决河流突发性水污染事故的科学基础和前提条件。探讨了当前闸坝对河流水质水量影响评估及调控能力识别技术研究面临的关键科学问题,包括闸坝对河流水质水量影响评估技术方法,闸坝调控、入河污染负荷和河流水质变化之间量化关系模拟技术方法,闸坝对河流水质水量调控能力识别技术;并以淮河流域为例,结合淮河重大水专项国家需求和科技需求,初步提出闸坝对河流水质水量影响评估及调控能力识别技术研究框架,旨在为闸坝水质水量联合调度提供理论支持。     

Assessing the performance of normal-based and REML-based confidence intervals for the intraclass correlation coefficient

Using normal distribution assumptions, one can obtain confidence intervals for variance components in a variety of applications. A normal-based interval, which has exact coverage probability under normality, is usually constructed from a pivot so that the endpoints of the interval depend on the data as well as the distribution of the pivotal quantity. Alternatively, one can employ a point estimation technique to form a large-sample (or approximate) confidence interval. A commonly used approach to estimate variance components is the restricted maximum likelihood (REML) method. The endpoints of a REML-based confidence interval depend on the data and the asymptotic distribution of the REML estimator. In this paper, simulation studies are conducted to evaluate the performance of the normal-based and the REML-based intervals for the intraclass correlation coefficient under non-normal distribution assumptions. Simulated coverage probabilities and expected lengths provide guidance as to which interval procedure is favored for a particular scenario. Estimating the kurtosis of the underlying distribution plays a central role in implementing the REML-based procedure. An empirical example is given to illustrate the usefulness of the REML-based confidence intervals under non-normality.