bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability and identifiability of parameters in Galerkin approximation of distributed systems under multiple inputs
Authors: Kunisch K. , White L. 
Published: July 2007

AbstractIn this communication we consider conditions for stability and identifiability of parameters in initial value problems governed by systems of ordinary differential equations that are obtained as Galerkin approximations of parabolic initial boundary value problems. Of particular interest are problems in which multiple inputs are allowed to obtain multiple outputs. These input—output relations are used to obtain the desired identifiability results.
Multipurpose controller design in multivariable stochastic control systems
Authors: Baṅka S. 
Published: July 2007

AbstractThe paper presents a computer‐aided procedure for multipurpose controller design which in multivariable (linearized) stochastic systems simultaneously ensures (1) complete dynamic decoupling of control loops, (2) arbitrary closed‐loop pole placement and internal stability of the control system, (3) steady state output rejection of non‐zero mean values of disturbances as well as zero steady state regulation and/or tracking errors, (4) reduction of amplitude modulation of the control signals and (5) optimal steady state estimation of the plant's state and output vectors. The polynomial matrix approach in the frequency s‐domain is used to solve the stochastic control problem. Numerical results and simulations for a simplified version of a ship‐positioning control system design are presented to illustrate characteristics of the problem.
A modified optimal load‐frequency controller for interconnected power systems
Authors: Liaw C. M. 
Published: July 2007

AbstractThis paper presents a modified optimal load‐frequency controller for interconnected hydrothermal power systems. The weighting matrix of the optimal controller is sequentially modified to let the dominant energy open‐loop poles or poles in a conventional optimal feedback system be located in the desired region. The poles selected to be shifted are determined using the concept of dominant energy modes rather than those located closer to the imaginary axis. Improper pole placement can be avoided and very good system frequency and tie‐line power dynamic responses can be achieved by the proposed controller.
Optimization of a photocell
Authors: Achdou Y. , Pironneau O. 
Published: July 2007

AbstractPhotocells contain a silicon‐based solar energy absorbing material. An optimal design of the interface between this material and the exterior medium is desired. The problem is modelled by the Helmholtz equation. The interface is assumed to be periodic and thus only one period is considered. It is shown that the problem has a solution if the interface is not allowed to oscillate too much. An approximation of the solution is computed with the finite element method coupled with an integral Fourier method for the radiation condition. The numerical simulations show fairly large improvements in the efficiency of the photocell.
Minimum variance control for repetitive disturbances with application to active noise control
Authors: Costin Mark H. 
Published: July 2007

AbstractUsing minimum variance control theory, a controller is designed to reduce noise that contains a repetitive component of measurable time‐varying frequency. The particular application for which the controller is designed is the active cancellation of both road and engine noise in a vehicle passenger compartment. The controller is appropriate for this case because engine noise can be shown to be expressed as a summation of harmonically related sine waves whose frequency is determined by the engine rotational speed. An example is presented where a controller is developed for active noise control in a station‐wagon with road noise caused by striking a tyre and engine noise represented by the noise spectrum of a diesel engine. Computer simulations show that the developed controller significantly reduces the noise from both sources.
Stability margins of singularly perturbed discrete‐time systems based on state feedback and linear quadratic optimal control
Authors: Cheng Chiu‐Pin , Li Tzuu‐Hseng S. , Sun York‐Yih 
Published: July 2007

AbstractMathematical descriptions of the stability margins of discrete singularly perturbed systems are proposed. These descriptions are carried out on the basis of state feedback control and the major results are as follows: (1) the stability margins of a composite controlled system appear to be bounded by those of its subsystems; (2) the solution of the ∞‐bound for the desired stability margins is obtained; (3) some properties of linear quadratic optimal control for singularly perturbed systems are provided; (4) the effect of ϵ on the robustness is also presented under linear quadratic optimal control.
Optimal open‐loop/closed‐loop control for one‐dimensional structures with several state variables
Authors: Bruch J. C. , Sadek I. S. , Adali S. , Sloss J. M. 
Published: July 2007

AbstractAn optimal control problem for one‐dimensional structures described by a system of partial differential equations is formulated. Open‐ and closed‐loop control mechanisms are incorporated into the formulation and a general method of solution is presented in the context of a structural vibration problem. The expenditure of control force is restricted by penalizing a functional of the open‐loop control force in the performance index and by imposing a constraint on the magnitude of the closed‐loop control force. The optimality condition for the open‐loop control is derived by using the methods of eigenfunction expansion and variational calculus. The closed‐loop control parameters are obtained from the minimization of the energy of the system. The theory is illustrated by solving a vibration control problem for a beam undergoing torsional and flexural vibrations. Numerical results are presented in a graphical form in which the behaviours of the controlled and uncontrolled beams at different terminal times are compared. The numerical results indicate the effectiveness of the proposed control mechanism for reducing excessive vibrations as measured by the energy of the beam. The minimizing value of the closed‐loop control parameter associated with displacement feedback is shown to be a function of the terminal time.
Dynamic disturbance minimization control for discrete non‐linear stochastic systems
Authors: Azemi Asad , Yaz Engin 
Published: July 2007

AbstractA dynamic feedback control scheme is proposed to reduce the effect of process and measurement disturbances of known wave‐form for a class of discrete non‐linear stochastic systems. A Lyapunovbased non‐linear filter developed previously by the authors is utilized for the estimation of the disturbance state and combined with a least‐squares‐type control action in a certainty equivalence manner for disturbance reduction. In order to illustrate the performance of the proposed dynamic disturbance rejection technique, three examples which address some important cases are provided.
Suboptimal control for bilinear systems
Authors: Ying Y. Q. , Rao M. , Sun Y. X. 
Published: July 2007

AbstractSuboptimal control for bilinear systems is discussed by use of an extension of the linear‐quadratic optimal control index. The design method of this bilinear suboptimal control system is presented. Its application to the moisture control of a paper‐making process is given as an example. The simulation results show that this suboptimal control system functions very well.
Optimal advertising in growing‐stabilizing markets
Authors: Dorroh J. R. , Ferreyra Guillermo 
Published: July 2007

AbstractThe method of dynamic programming is used to determine the optimal synthesis of an advertising problem. The market of the product in question grows exponentially up to a time when it stabilizes at a constant value. The problem is singular and with an unbounded control. A parametrization of time is introduced to deal with these difficulties.
A linear programming approach to on‐line constrained optimal terrain‐tracking systems
Authors: Rehbock V. , Teo K. L. , Jennings L. S. 
Published: July 2007

AbstractThe idea of an optimal decision strategy is applied to a class of tracking problems. The resulting pointwise optimization problem is posed as a linear programming problem, in contrast to previous work where it is posed as a quadratic programming problem. A useful result concerning the convergence of the tracking error in the presence of control constraints is derived and applied to an aircraft terrain‐following system.
The determination of feedback gains for uncertain linear systems using higher‐order sensitivity minimization
Authors: Fabien Brian C. 
Published: July 2007

AbstractTo reduce the influence of large parameter variation on the response of linear systems, this paper considers the design of controllers that minimize the higher‐order sensitivities. Here the higher‐order sensitivities are defined as the second‐order, third‐order, etc. partial derivatives of the state and control vectors with respect to the uncertain parameter. The feedback gains are obtained by minimizing a quadratic cost function that includes state and control sensitivities of arbitrary order. The paper also presents an efficient numerical procedure for solving the resultant system of non‐linear matrix equations. The effectiveness of the approach is demonstrated by the design of an output feedback controller for an electromagnetic suspension. By comparison with standard design approaches it is shown that higher‐order sensitivity minimization can be used to reduce the deviation from the nominal trajectory caused by parameter variation.
Linear optimal control for an aircraft model
Authors: Frangos C. 
Published: July 2007

AbstractA linear optimal proportional plus integral (PI) controller is designed for a lateral aircraft model such that an approximately decoupled closed‐loop step response is obtained for the roll angle and side‐slip angle while the linear optimal feedback gains are simultaneously minimized. A standard mathematical programming algorithm is employed to calculate the diagonal state weighting matrix Q such that the specifications are satisfied. The synthesis procedure consists of the iterative minimization of a functional where at each iteration step a linear optimal control problem is solved.
Stochastic adaptive control of multivariable systems with a class of amplitude‐dependent non‐linearities
Authors: Xiong Y. F. , Unbehauen H. 
Published: July 2007

AbstractThis paper presents a novel direct stochastic adaptive control scheme for a non‐linear multivariable system which is given by a cascade connection of a two‐segment piecewise‐linear asymmetric non‐linear matrix followed by a linear multivariable system with a general interactor matrix. An optimal control law for the non‐linear multivariable system is derived from a cost function in which the non‐linear parameter matrix of the discussed model is included. This control law results in the closed‐loop dynamic property of the non‐linear system being the same as that of its linear portion. A switching gain sequence matrix is introduced to overcome parameter estimation problems. The scheme can deal with systems whose linear portions are open‐loop unstable and/or non‐minimum phase processes. The algorithm will ensure that the closed‐loop system is globally stable and convergent.
A decomposition approach to suboptimal control of discrete‐time systems
Authors: Nardini Andrea , Piccardi Carlo , Soncini‐Sessa Rodolfo 
Published: July 2007

AbstractA suboptimal controller for a class of discrete‐time systems is presented. The controller is derived by first solving ‘off‐line’ a simplified optimal control problem obtained by neglecting part of the system state and by considering a larger time step, then by solving ‘on‐line’ at each time step an optimization problem based on the results of the previously solved ‘off‐line’ problem. A simple numerical example is presented to illustrate the control scheme.
Differential dynamic programming technique for optimal control
Authors: Lin T. C. , Arora J. S. 
Published: July 2007

AbstractContinuous‐ and discrete‐time differential dynamic programming (DDP) approaches to solve general optimal control problems are described and analysed. A comparison of the two approaches shows the continuous‐time approach to be more general and flexible compared with the discrete‐time approach, since it is not tied to any discretization scheme. A comparison of DDP with the non‐linear programming (NLP) approach is also given. Three structural control problems — a linear model of a space structure, a single degree of freedom non‐linear impact absorber and a non‐linear flexible beam subjected to an impulsive load — are used to numerically evaluate the continuous‐ and discrete‐time DDP approaches. Several grid sizes are used to show that the continuous‐time approach with a reasonable number of grid points is more accurate and efficient (in most cases) than the discrete‐time approach. It is therefore recommended to fully develop and evaluate the technique for the optimal control of large‐scale systems.
Terrain tracking based on optimal aim strategies
Authors: Barnard R. 
Published: July 2007

AbstractThis short communication discusses two recently proposed terrain‐tracking schemes, reformulates both schemes as special cases of a previously proposed optimal aim strategy, outlines a more precise and explicit continuous‐time control law based on a fixed‐point neural network, describes a more rapid and effective discrete‐time control law based on a fixed‐point iteration process, and derives criteria for matching reference models to the dynamical characteristics of individual systems.
Optimization and control of a fedbatch fermentation process
Authors: Queinnec I. , Dahhou B. 
Published: July 2007

AbstractThis paper describes the optimization problem of a fedbatch fermentation process for alcohol production which initially consists of minimizing a time‐optimal global criterion. Dynamic programming methods have previously allowed one to solve this global optimization problem and to deduce a local criterion to be maximized at each sampling step by using non‐linear programming techniques. It is then stated that under a few realistic constraints the optimization problem can be translated into the regulation problem of the substrate concentration in the fermentor. The optimal value is a function of a certain growth model. A control law based on the quotient between measurement and optimal value is then implemented. Simulation results and real‐life experiments validate the problem transformation.
Optimization of the protrusion shape for a couette‐type flow
Authors: Kacimov A. R. 
Published: July 2007

AbstractA study is made of the longitudinal 2D viscous steady flow and heat flux between two plates. Optimal shape design problems are solved in explicit form and shown to have unique global extrema. Conformal mappings are used to bring the problems into a fixed domain and solve them as Dirichlet boundary value problems in the form of Cauchy integrals and series expansions. For the simplest problem statement the optimum is shown to coincide with the well‐known concrete dam outline of constant hydraulic gradient.
Optimal pulsing in an advertising diffusion model
Authors: Feichtinger Gustav , Novak Andreas 
Published: July 2007

AbstractEmpirical evidence indicates that a given moderate number of ads per year may achieve higher effect when concentrated in flights than when spread equally. In the control‐theoretic literature a few approaches have been developed for which the optimal policy is a pulsing schedule. The present communication analyses a two‐state diffusion advertising model for repeat purchasing. Recognizing the interaction between customers and potential buyers, the optimal advertising policy turns out to be a persistent periodic oscillation. This provides a further interesting example in marketing for the existence of a stable limit cycle.
Crosstalk between NF‐κB/p65 and β‐catenin/TCF4/p300 signalling pathways through alterations in GSK‐3β expression during trans‐differentiation of endometrial carcinoma cells
Authors: Saegusa M , Hashimura M , Kuwata T , Hamano M , Okayasu I 
Published: July 2007

Abstractβ‐Catenin/TCF4/p300 signalling loops play an important role in trans‐differentiation towards the morular phenotype of endometrial carcinomas. Crosstalk between NF‐κB and β‐catenin pathways has been proposed and we focused here on associations between these two pathways during trans‐differentiation. In normal endometrium, nuclear phosphorylated p65 (pp65), the active form NF‐κB subunit, was found to be significantly increased in the secretory phase, correlating positively with vimentin and E‐cadherin and inversely with Snail mRNA expression. On transfection of p65, vimentin, E‐cadherin, and Snail were transcriptionally altered, indicating possible roles in establishment and maintenance of the secretory phenotype. In endometrial carcinomas with morules, levels of nuclear pp65, Snail mRNA, vimentin, and cytoplasmic TNF‐α were reduced during trans‐differentiation, correlating inversely with nuclear β‐catenin. Nuclear accumulation of GSK‐3β, along with β‐catenin, was observed in morules. In cell lines, overexpression of p65 inhibited β‐catenin/TCF4‐mediated transcription, while transfection of GSK‐3β resulted in repression of TNF‐α‐induced NF‐κB activity. Moreover, nuclear GSK‐3β was increased by overexpression of β‐catenin, as well as induction of G1‐cell cycle arrest. These findings provide evidence that a shift from NF‐κB to β‐catenin signalling pathways through alterations in GSK‐3β expression may be essential for the induction of trans‐differentiation of endometrial carcinoma cells, leading to a shut‐down of mesenchymal markers. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Simulation and validation of resin flow during manufacturing of composite panels containing embedded impermeable inserts with the VARTM process
Authors: Lawrence Jeffrey M. , Frey Pierre , Obaid Ahmad Abu , Yarlagadda Shridhar , Advani Suresh G. 
Published: July 2007

AbstractModern composite materials are becoming more and more advanced as engineers are better able to take advantage of their properties. In addition to their lighter weight and net‐shape manufacturing, current interest is to make these materials multifunctional. This may require one to insert various objects into the composite to achieve a variety of different goals. It is important to understand how these embedded objects will affect both the manufacturing and the structural integrity of the component. In this work, the effects of impermeable embedded inserts on the infusion stage of vacuum‐assisted resin transfer molding (VARTM) will be explored. In VARTM, one places a distribution media on top of the preform to aid the filling as the resin will first fill the face of the preform in contact with the distribution media and will then infuse the preform in the thickness direction. However, if one has an embedded impermeable insert in the thickness direction, it will obstruct the flow in the region below the embedded object. Several case studies are conducted to understand the effect of the geometry and placement of the embedded insert and the distribution media lay out and properties on the impregnation of the resin into the fiber preform. Finally, an approach is outlined to modify the layout of the distribution media in order to ensure a complete saturation of the preform under all but the most extreme conditions. The approach is validated with experiments. POLYM. COMPOS., 28:442–450, 2007. © 2007 Society of Plastics Engineers
Characterization of composites for use in the ball‐joints of the Maeslant storm surge barrier
Authors: Van Paepegem W. , Degrieck J. , Samyn P. , De Baets P. , Van Schepdael L. , Leendertz J.S. 
Published: July 2007

AbstractIn 2004, the rehabilitation works of the Maeslant storm surge barrier in the Netherlands were finished. The two gates of the barrier are attached to a pivotal point on both banks. The pivotal points are designed as two large ball‐joints (10 m diameter) that must allow for both horizontal and vertical movements of the gates. Five hundred individual composite material discs provide a low friction sliding contact with the ball. Two designs for the composite material discs are discussed in this article: (i) a polyester/polyester disc with a Teflon coating and (ii) an UHMWPE (ultra‐high molecular weight polyethylene) disc with a reinforcing carbon/epoxy ring. The test methods for characterization of the composite materials are presented. It is shown that internationally standardized test methods do not provide all necessary information and that additional measurements have to be made. Based on the results of these tests, the best design has been integrated in the storm surge barrier. POLYM. COMPOS., 28:470–478, 2007. © 2007 Society of Plastics Engineers
The effect of antihypertensive drugs and drug combinations on the incidence of new‐onset type‐2 diabetes mellitus
Authors: Burke Thomas A. , Sturkenboom Miriam C. , Ohman‐Strickland Pamela A. , Wentworth Charles E. , Rhoads George G. 
Published: July 2007

AbstractPurposeTo evaluate the effect of antihypertensive drugs on new‐onset type‐2 diabetes.MethodsThis was a cohort study using the UK General Practice Research Database (GPRD). Patients newly diagnosed with hypertension between 1991 and 2001, and treated with antihypertensive drugs, were included. Type‐2 diabetes mellitus was identified based on a physician diagnosis or an anti‐diabetic drug prescription. Antihypertensive treatments were classified as: ACE inhibitors (ACE‐Is), β blockers, calcium channel blockers (CCB), thiazides, all other drugs, and their combinations.ResultsA total of 2706 incident diabetes cases were identified in 98 629 hypertensive patients during 307 356 patient years (8.8/1000 patient years). New‐onset diabetes was lower for ACE‐I regimens compared with non‐ACE inhibitor regimens (HR = 0.90; 95%CI: 0.82–0.99). CCB monotherapy (HR = 1.27; 95%CI: 1.07–1.51) had an increased risk of diabetes compared with ACE‐I monotherapy. ACE‐I plus thiazide had the lowest risk of diabetes among double combinations, followed by ACE‐I plus β blocker, and ACE‐I plus CCB. Double combinations with an ACE‐I had 0.79 (95%CI: 0.67–0.92) times the risk compared with non‐ACE inhibitor combinations. The risk of new‐onset diabetes was significantly higher for β blocker plus thiazide (HR = 1.37; 1.10–1.70), CCB plus thiazide (HR = 1.44; 95%CI: 1.13–1.83), but not β blocker plus CCB (HR = 1.30; 95%CI: 0.99–1.70) compared with ACE‐I plus thiazide.ConclusionsAntihypertensive drug combinations including an ACE‐I had a significantly lower risk of new‐onset diabetes than antihypertensive drug combinations without an ACE‐I. Copyright © 2007 John Wiley & Sons, Ltd.
Theoretical consideration on the glass transition behavior of polymer nanocomposites
Authors: Lee Kyung Ju , Lee Do Kyoung , Kim Yong Woo , choe Woo‐Seok , Kim Jong Hak 
Published: July 2007

AbstractWe have developed a new molecular thermodynamic model to predict the glass transition temperature (Tg) of nanocomposites consisting of polymer (1) and nanoparticle (2) based on the configurational entropy model and the Flory–Huggins theory. Four configurational entropies have been taken into account in this study: the disorientation entropy of the polymer (Sdis‐1), the confinement entropy of the nanoparticle (Scon‐2), the mixing (Smix‐12), and the specific interaction entropies (Sspe‐12) of the polymer/nanoparticle. Quantitative descriptions according to the proposed model are consistent with experimental Tg data of polymer nanocomposites. Our results demonstrate that Tg values of polymer nanocomposites can be enhanced or depressed relative to neat polymer depending on the intensity of specific interaction between polymer and nanoparticles, which is quantitatively identified by a physical parameter (γspe) in this model. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2232–2238, 2007