Modelling and control of an acetylene converter

In this paper, the modelling and control of an industrial acetylene converter are examined. A kinetic model of the key reactions is proposed, and incorporated in a dynamic model of the converter. Plant data are used to tune the model, and values for the activation energies are shown to agree with values obtained from the literature. In addition, the estimated reaction rates are shown to decrease with increasing run length. A linear, low order model is developed from the full dynamic model. The process is shown to possess a significant delay time which made control of the outlet conditions difficult. The linear model is used to design a controller for the outlet temperature, and it is shown that a model based controller can satisfactorily control the outlet temperature, while a PID controller cannot.     

Nonlinear Modeling and Control of a Unicycle

A unicycle system is composed of a unicycle and a rider. This system is inherently unstable, but together with a skilled rider can be autonomously controlled and stabilized. A dynamical investigation, a control design and a numerical solution of a nonlinear unicycle autonomous model are presented. The use of a nonlinear model for the control design is shown in this paper to be of great importance. A three-rigid-body physical model was selected for the dynamical study of the system. In a linearized model important physical characteristics of the unicycle system disappear (e.g. interactions between the longitudinal and lateral systems are being neglected), and therefore it is not recommended to be used for the control design. A nonlinear control law, which replaces the rider in stabilizing the model, was derived in the present work, using a nonlinear unicycle model. A simulation study shows good performance of this controller. Time spectral element methods are developed and used for integrating the nonlinear equations of motion. The approach employs the time discontinuous Galerkin method which leads to A-stable high order accurate time integration schemes.     

Modeling of web conveyance systems for multivariable control

A distributed parameter model of the lateral dynamic behavior of a moving web in an n-roller system is proposed. A span of web moving longitudinally and under tension is modeled as a beam with shear flexibility (Timoshenko beam). A quasistatic simplification of the model is made on the basis of spectral separation. Boundary conditions at the web-roller interface are considered. Actuator dynamics are introduced through the formulation of the boundary conditions. Closed-loop simulations using a state-space version of the simplified model are in agreement with experimental results     

Parameter identification of damping models in multibody dynamic simulation of mechanical systems

To reduce vibration and noise, a damping mechanism is often required in mechanical systems. Many types of dampers are currently used. In this paper, several typical damping models, i.e., structural damping, frictional damping, and viscoelastic damping, are illustrated, and their parameters are identified for multibody dynamic simulation. Linear damping, widely adopted for structural damping, is applied to beam deflection. Quadratic damping including air resistance is applied to plate deflection. To model stick phenomenon in mechanical dampers, a STV (stick-transition velocity) model was first introduced. To identify parameters, an optimization process is applied to the damping parameters. A new MSTV (modified stick-transition velocity) model is proposed for a friction damper. A modified Kelvin–Voight model is suggested for a rubber bushing model used in vehicle dynamics, and its parameters are identified. A modified Bouc–Wen model is also proposed; it includes the hysteretic behavior of an elastomer, and optimized results with parameter identification are compared to test results.     

反例引导的模型检验工具的设计

针对模型组合中常见的"状态空间爆炸"问题,分析了抽象和组合两种方法各自的优缺点,采用"反例引导的抽象精化"框架和模型检验思想,将抽象和组合结合起来,为模型组合的检验提出了一种新的方法.设计了模型的抽象、组合、检验和精化算法,开发了一款基于反例引导的、图形化的模型检验工具,使用Kripke结构建立模型,用LTL描述性质,从而表明了反例引导的模型检验方法的过程.     

基于BSP的并行事务处理模型

BSP模型独立于并行体系结构,既可作为并行计算模型,又可作为并行程序设计模型。提出了基于BSP模型的H－V事务模型,适用于长、短事务和长短事务混杂的情况。给出了在无共享结构下实现并行事务处理的进程结构。该结构不仅实现了事务内及事务间并行性,而且使人有可用性（availability）和可扩充性（scalability）,而后给出了适用于该模型的基于时间戳的多版本并发控制协议,最后描述了事务在超步结构下的运行过程。性能测试表明,使用该模型进行事务处理时可获得良好的事务响应时间和加速比。     

A multi-granularity locking model for concurrency control inobject-oriented database systems

A locking model adopting a multi-granularity approach is proposed for concurrency control in object-oriented database systems. The model is motivated by a desire to provide high concurrency and low locking overhead in accessing objects. Locking in schemas and locking in instances are developed separately and then are integrated. Schema changes and composite objects are also taken into account. A dual queue scheme for efficient scheduling of lock requests is developed. The model consists of a rich set of lock modes, a compatibility matrix, and a locking protocol. Characteristic query examples on single class, class lattice, and composite objects are used to illustrate the comparison between the ORION model and the proposed model. It is shown that our locking model has indeed made some improvements and is suitable for concurrency control in object-oriented databases     

A model for deployment of a freefall lifeboat from a moving ramp into waves

The equations of motion of a freefall lifeboat are formulated using Kane’s method. Deployment from a moving ramp is assumed to occur in a known plane and a 2D model suffices. A segmented approach is used to model ramp contact. A separate 3D model is presented for the water entry phase. The hydrodynamic loads at water entry are also modeled using a segmented approach. The equations are solved numerically using a standard Runge–Kutta MATLAB routine.     

Multi-national capital budgeting using chance-constrained goal programming

A chance-constrained goal programming model is developed for the direct foreign investment decisions of U.S.-based multi-national companies. Goals, objectives and constraints, which are unique to direct foreign investment decisions, are included in the model. The model also considers economic exposure of exchange-rate risk. A solution procedure is suggested. The model is illustrated by a numerical example that includes sensitivity analysis.     

采用多Agent的网络攻防仿真模型

采用多Agent技术对网络攻防仿真进行建模。提出了一种描述网络攻防任务的通用方式。利用角色来承担任务的某个子集,角色中工作类型和管理地位得到分离,使得逻辑上更清晰。建立了一个多层次的Agent团队结构模式,并为团队结构的调整提供了算法。最后通过DDoS攻防模拟验证了模型。     

Complexity measure evaluation and selection

A formal model of program complexity developed earlier by the authors is used to derive evaluation criteria for program complexity measures. This is then used to determine which measures are appropriate within a particular application domain. A set of rules for determining feasible measures for a particular application domain are given, and an evaluation model for choosing among alternative feasible measures is presented. This model is used to select measures from the classification trees produced by the empirically guided software development environment of R.W. Selby and A.A. Porter, and early experiments show it to be an effective process     

基于概率和条件逻辑的PKI信任模型推理

提出一种基于概率和条件谓词逻辑来表示和推导PKI信任模型的方法．该方法用3个二元条件谓词表示不同个体之间的关系,并给出了实体认证规则、信任规则和信任扩展规则，对信任度定义了一个概率模型，该模型能反映约束条件如何影响信任度．概率模型加条件谓词逻辑能够对一个PKI信任模型进行更精确的描述．     

Gain-scheduled controller synthesis for a nonlinear PDE

Linear parameter-varying (LPV) modelling and control of a nonlinear partial differential equation (PDE) is considered in this article. The one-dimensional viscous Burgers' equation is discretised using a finite difference scheme; the boundary conditions are taken as control inputs and the velocities at two grid points are assumed to be measurable. A nonlinear high-order state space model is generated and proper orthogonal decomposition is used for model order reduction. After assessing the accuracy of the reduced model, a low-order functional observer is designed to estimate the reduced states which are linear combinations of the velocities at all grid points. A discrete-time quasi-LPV model that is affine in scheduling parameters is derived based on the reduced model. A polytopic LPV controller is synthesised based on a generalised plant containing the LPV model and the functional observer. More generally, the proposed method can be used to design an LPV controller for a quasi-LPV system with non-measurable scheduling parameters. Simulation results demonstrate the high tracking performance and disturbance and measurement noise rejection capabilities of the designed LPV controller compared with a linear quadratic Gaussian (LQG) controller based on a linearised model.     

An Inspection Policy for Deteriorating Processes Using Delay-Time Concept

A method for determining the discrete time points of inspection for a deteriorating single-unit system under condition-based maintenance is developed. The system is in a normal state, a symptom state or a failed state. A delay-time model is utilized to describe the transition of the states. The transition time from a normal state to a symptom state and that from a symptom state to a failed state are derived assuming continuous deteriorating processes based on a reaction rate model which is categorized as a failure physics model. Failed-dangerous and failed-safe probabilities of an imperfect inspection are considered. A method for minimizing the long-run average cost per unit time is formulated. The characteristics and sensitivity of the proposed method are investigated.     

A non-smooth optimization model for a two-tiered supply chain network

A non-smooth optimization model is established for a two-tiered supply chain network where manufacturers are at the upper level and consumers are at the lower level. A supply chain equilibrium model is considered at the lower level while policy interventions are taken into account at the upper level. A mathematical program with equilibrium constraints (MPEC) is established for the two-tiered supply chain network. Numerical illustrations are carried out using a 9-node network and preliminary results are reported.     

基于BP神经网络的模糊参数辨识

提出一种与TSK模糊模型相似的模糊模型—M-2模型,证明了M-2模型与一个4层前向神经网络是等价的,在此基础上提出基于BP神经网络的模糊模型参数辨别算法,即通过BP神经网络对样本数据的学习,直接从样本数据获取模型参数,建立M-2模糊模型,通过仿真实例验证了该算法的有效性。     

Dynamic modeling and linear model predictive control of gas pipeline networks

A linear model predictive control (LMPC) strategy is developed for large-scale gas pipeline networks. A nonlinear dynamic model of a representative pipeline is derived from mass balances and the Virial equation of state. Because the full-order model is ill-conditioned, reduced-order models are constructed using time-scale decomposition arguments. The first reduced-order model is used to represent the plant in closed-loop simulations. The dimension of this model is reduced further to obtain the linear model used for LMPC design. The LMPC controller is formulated to regulate certain pipeline pressures by manipulating production setpoints of cryogenic air separation plants. Both input and output variables are subject to operational constraints. Three methods for handling output constraint infeasibilities are investigated.     

一个基于角色的Web安全访问控制系统

对基于角色的访问控制模型进行了分析并定义了相关的概念，给出了实现模型和算法设计；对现行的web安全认证和访问控制中存在的问题和隐患进行了分析，给出了一种新的可行的安全解决方案；最终实现了一个基于角色访问控制策略的web资源安全管理系统，它在实际应用中取得稳定、可靠和有效的结果．     

一种可重构的工作流执行模型

为提高工作流系统的适应性和可维护性,提出了一种可重构的工作流执行模型。该模型面向活动行为的相异性和动态性,把活动状态作为描述过程状态的特征,给出了过程状态的形式化定义,建立了过程状态间的层次化关系与优先级关系。在该基础上,严格地给出了基于基本特征集和基于相容特征集的过程状态精化方法,设计了自动生成过程状态转移关系的算法。最后,结合实际应用讨论了一种基于规则的执行模型可重构性实现方法。应用该方法能够提高工作流管理系统适应企业业务过程需求快速变化的能力。