Modelling the dynamical behaviour of a paper web. Part II

In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid–solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called “edge-flutter” is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension.     

Non-linear impulsive dynamical systems. Part I: Stability and dissipativity

In this paper we develop Lyapunov and invariant set stability theorems for non-linear impulsive dynamical systems. Furthermore, we generalize dissipativity theory to non-linear dynamical systems with impulsive effects. Specifically, the classical concepts of system storage functions and supply rates are extended to impulsive dynamical systems providing a generalized hybrid system energy interpretation in terms of stored energy, dissipated energy over the continuous-time system dynamics and dissipated energy over the resetting instants. Furthermore, extended Kalman‐Yakubovich‐Popov conditions in terms of the impulsive system dynamics characterizing dissipativeness via system storage functions are derived. Finally, the framework is specialized to passive and non-expansive impulsive systems to provide a generalization of the classical notions of passivity and non-expansivity for non-linear impulsive systems. These results are used in the second part of this paper to develop extensions of the small gain and positivity theorems for feedback impulsive systems as well as to develop optimal hybrid feedback controllers.     

Optimal Selection of the Regularization Function in a Weighted Total Variation Model. Part I: Modelling and Theory

A weighted total variation model with a spatially varying regularization weight is considered. Existence of a solution is shown, and the associated Fenchel predual problem is derived. For automatically selecting the regularization function, a bilevel optimization framework is proposed. In this context, the lower-level problem, which is parameterized by the regularization weight, is the Fenchel predual of the weighted total variation model and the upper-level objective penalizes violations of a variance corridor. The latter object relies on a localization of the image residual as well as on lower and upper bounds inspired by the statistics of the extremes.     

Modelling the behaviour of a control-element blade during irradiation

The control-rod elements in a boiling-water reactor contain natural boron carbide (B₄C) powder, used as neutron-absorber material and clad in stainless-steel blades. During in-reactor service, the internal production of helium gas and point defects in neutron-irradiated boron carbide cause swelling which can induce significant contact stresses in the blade causing, eventually, stress-corrosion cracking of the blades. In this work, a finite-element analysis of a control-rod blade consisting of B₄C powder and stainless-steel cladding has been performed using ADINA. An algorithm for the finite-element calculation of a porous material such as B₄C powder has been developed and which models both swelling and consolidation behaviour of B₄C powder. The Drucker-Prager constitutive law has been used to model the consolidation effect. The model has been verified with an analytical solution for a simple geometry. A number of cases with B₄C powder in contact with stainless steel and using the actual blade design have been studied for which contact stresses, the displacements and the effective stresses are calculated. Finally, the model has been used to predict the deformation of the blade during irradiation under B₄C swelling and irradiation-induced creep of stainless steel.     

Consumer web search behaviour: diagrammatic illustration of wayfinding on the web

External information search behaviour has long been of interest to consumer researchers. Experimental and post hoc survey research methodologies have typically used a large number of variables to record search activity. However, as these are usually considered in aggregate, there is little opportunity for the researcher to overview the search style of a consumer. To date, the diagrammatic illustration of search behaviour has been limited to experimental environments in which the available information was strictly bounded, for example, within databases or when information display boards have been used. This paper, which focuses largely on inter-site world wide web (WWW) search behaviour, discusses web search paradigms and the variables used to capture WWW search. It also provides a conceptual framework for the representation of external information search behaviour in diagrammatic form. The technique offers researchers an opportunity to holistically interpret information search data and search styles. The benefits include the identification of particular search styles, more precise interpretation of web search activity numeric data and the potential application for the training of web users to improve their search effectiveness.     

On dynamical behaviour of two-dimensional biological reactors

The dynamical behaviour for a generic two-dimensional model of a continuous bioreactor is studied in this article. The state variables for the bio-reacting system are restricted to concentrations of substrate and biomass, where the specific growth rate is a smooth function of the substrate concentration, which can be a kinetic function, monotone or non-monotone (as Monod, Haldane, Teissier, etc.). The effect of input (dilution rate) on multiplicity and bifurcation of equilibrium is shown in open-loop configuration. The absence of limit cycles on open-loop configuration and through state-feedback on the dilution rate are demonstrated. The aim of analysing oscillations under state feedback control is related to the possible improvement of reactor yields under this operation regime. An example for a cell-producing bioreactor illustrates the analytical results.     

Diagnosis model for dynamical systems Part 1. Discrete system

Many static diagnosis models, which express the static relation between faults and syndrome, have been studied extensively. However, it is difficult to apply these static models to dynamical systems in which the syndrome changes dynamically. In order to construct diagnostic systems for dynamical systems, a dynamic diagnosis model that can express the dynamic relation of fault propagation should be studied. In this paper, we propose a failure propagation model which explicitly expresses some dynamic aspects of failure propagation in a system. Two concepts of dynamic diagnosabilities are defined for the model. Algorithms are presented which are designed to evaluate these diagnosabilities of the model as well as to locate a primary failure from a syndrome.     

Diagnosis model for dynamical systems Part 2. Continuous system

While most existing systems requiring diagnosis are dynamical, most models proposed for diagnosis are static. Consequently, a mathematical model of differential equations is used for a model-based diagnosis of dynamical systems. Although this model-based diagnosis has been well studied, it is not used much in practice owing to the computational difficulty and the difficulty of obtaining the mathematical model. We propose a diagnosis model for continuous dynamical systems. The model can be expressed by a signed directed-graph, which has been studied extensively in qualitative matrix theory. We interpret these qualitative results in terms of the diagnosis model, and also present new results for the model. The dynamic aspects of the qualitative stabilities of the model are mainly discussed. The distinguishability of the sign pattern is also studied with a new concept of invariant fault pattern defined in the model. Strategies for monitoring as well as for the diagnosis of the dynamical systems are derived by these qualitative results.     

Rethinking the semantic Web. Part I

The semantic Web is a compelling vision, in which the World Wide Web will include a notion of meaning in data and services. Intelligent agents will exchange information and rules for how to interact with that information, with or without human intervention; appointments will be automatically scheduled; and automated agents will select and invoke services. Information will be easy to find without depending solely on keywords. In part one of this column, the author propose several reasons that this vision hasn't yet been adopted despite substantial research funding in the US and European Union (EU). These reasons will provide the foundation for a new approach, which propose in part two.     

Modelling hypermedia and web applications: the Ariadne Development Method

The development process of hypermedia and web systems poses very specific problems that do not appear in other software applications, such as the need for mechanisms to model sophisticated navigational structures, interactive behaviors, interfaces with external applications, security constraints and multimedia compositions. Even though experience, modelling skills and abstractions can be borrowed from existing software design methods, such as object-oriented modelling, hypermedia developers need specific mechanisms to analyze and design using entities that belong to the hypermedia domain (such as nodes, links, anchors and space and time-based relationships). Moreover, hypermedia methods should provide mechanisms to deal with all the aforementioned features in a progressive and integrated way. In this paper, we present the Ariadne Development Method (ADM), a software engineering method that proposes a systematic, flexible, integrative and platform-independent process to specify and evaluate hypermedia and web applications. ADM has been shown particularly useful in complex systems involving a huge number of users with different abilities to access information, with a complex structure where a huge number of nodes have to be organized in a clear way to produce specifications that are discussed by people with an heterogeneous background. This is the case of ARCE, a Latin American project where 21 countries are cooperating to produce a web platform to improve assistance in disaster mitigation situations.     

Control and observation for dynamical queueing networks. I

For the optimal control problem for a queueing network state, we write the Bellman equation and give examples of its analytic and numerical solutions. In the first part, we give examples of solving optimal control problems for elementary network structures. In the second part, we give a solution of the optimal control problem for the network state and observations that gives an answer to the question of what, when, where, and how to measure in the network while solving dynamic routing problems. We give examples of solving synthesis problems for optimal controls and optimal network informational structures for modern telecommunicational systems.     

Numerical experiments on the statistical behaviour of dynamical systems with a few degrees of freedom

Numerical experiments concerning the arising statistical laws in a system of nonlinear interacting waves are described. A chain of particles coupled by nonlinear springs has been used as a model. Various statistical properties of the chain have been investigated numerically. A comparison with the theory of the Korteweg-de Vries equation is given.     

Modelling chaotic behaviour of SIP retransmission mechanism

The Session Initiation Protocol (SIP) retransmission mechanism can cause SIP network collapse with short-term overload. In this paper, we investigate with a fluid modelling approach the chaotic behaviour of the SIP retransmission mechanism in SIP networks. We capture the complex correlation structure in SIP systems through a detailed and novel queuing analysis. To dimension a buffer size which can avoid unnecessary message drop in a SIP server, we develop a sufficient condition for a stable SIP system analytically based on our fluid model. We also apply our fluid model to the simulation of a complex SIP system. We compare the simulation results achieved through our fluid models with those based on OPNET^® event-driven approach to demonstrate the validity of our approach.     

Modelling a telescopic boom – the 3D case: Part II

In this paper, we shall extend an idea of the modelling flexible telescopic boom using a non-linear finite element method to the three-dimensional case. The boom is assembled by Reissner’s geometrically exact beam elements. The sliding boom parts are coupled together by the element, where a slide-spring is coupled to beam with the aid of a master–slave technique. A special element with a revolute joint and an element with offset are developed. Telescopic movement is achieved by the element with varying length and the connector expressing the chains. This technique yields system equations without algebraic constraints.     

Modelling methods for web application verification and testing: state of the art

Models are considered an essential step in capturing different system behaviours and simplifying the analysis required to check or improve the quality of software. Verification and testing of web software requires effective modelling techniques that address the specific challenges of web applications. In this study we survey 24 different modelling methods used in web site verification and testing. Based on a short catalogue of desirable properties of web applications that require analysis, two different views of the methods are presented: a general categorization by modelling level, and a detailed comparison based on property coverage. Copyright © 2008 John Wiley & Sons, Ltd.     

张力控制在纸机传动控制系统中的研究

介绍了张力控制在造纸机变频传动控制系统中的程序设计与应用。配合速度控制，张力控制更有效的解决成品纸生产的质量状况。更好的提高了系统的精确性和稳定性。