Distribution by Scientific Domains
Distribution within Engineering

Terms modified by Guaranteed

  • guaranteed cost
  • guaranteed cost controller

  • Selected Abstracts


    EVOLUTION, Issue 9 2005
    Hanna Kokko
    Abstract Much of the theory of sexual selection assumes that females do not generally experience difficulties getting their eggs fertilized, yet sperm limitation is occasionally documented. How often does male limitation form a selection for female traits that improve their mating rate? The question is difficult to test, because if such traits evolve to be efficient, sperm limitation will no longer appear to be a problem to females. Here, we suggest that changes in choosiness between populations, and in particular between virgin and mated females, offer an efficient way to test this hypothesis. We model the "wallflower effect," that is, changes in female preferences due to time and mortality costs of remaining unmated (for at least some time). We show that these costs cause adaptive reductions of female choice, even if mate encounter rates appear high and females only rarely end their lives unfertilized. We also consider the population consequences of plastic or fixed mate preferences at different mate encounter rates. If mate choice is plastic, we confirm earlier verbal models that virgins should mate relatively indiscriminately, but plastic increase of choosiness in later matings can compensate and intensify sexual selection on the male trait, particularly if there is last male sperm precedence. Plastic populations will cope well with unusual conditions: eagerness of virgins leads to high reproductive output and a relaxation of sexual selection at low population densities. If females lack such plasticity, however, population-wide reproductive output may be severely reduced, whereas sexual selection on male traits remains strong. [source]

    Guaranteed a posteriori error estimation for fully discrete solutions of parabolic problems

    T. Strouboulis
    Abstract This paper addresses the construction of guaranteed computable estimates for fully discrete solutions of parabolic problems. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    On the modelling of publish/subscribe communication systems

    R. Baldoni
    Abstract This paper presents a formal framework of a distributed computation based on a publish/subscribe system. The framework abstracts the system through two delays, namely the subscription/unsubscription delay and the diffusion delay. This abstraction allows one to model concurrent execution of publication and subscription operations without waiting for the stability of the system state and to define a Liveness property which gives the conditions for the presence of a notification event in the global history of the system. This formal framework allows us to analytically define a measure of the effectiveness of a publish/subscribe system, which reflects the percentage of notifications guaranteed by the system to subscribers. A simulation study confirms the validity of the analytical measurements. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Conservation Alliances with Indigenous Peoples of the Amazon

    The future of Amazonian indigenous reserves is of strategic importance for the fate of biodiversity in the region. We examined the legislation governing resource use on indigenous lands and summarize the history of the Kayapo people's consolidation of their >100,000 km2 territory. Like many Amazonian indigenous peoples, the Kayapo have halted the expansion of the agricultural frontier on their lands but allow selective logging and gold mining. Prospects for long-term conservation and sustainability in these lands depend on indigenous peoples' understandings of their resource base and on available economic alternatives. Although forest conservation is not guaranteed by either tenure security or indigenous knowledge, indigenous societies' relatively egalitarian common-property resource management regimes,along with adequate incentives and long-term partnerships with conservation organizations,can achieve this result. Successful initiatives include Conservation International's long-term project with the A'ukre Kayapo village and incipient large-scale territorial monitoring and control in the Kayapo territory, and the Instituto SocioAmbiental (ISA) 15-year partnership with the peoples of the Xingu Indigenous Park, with projects centered on territorial monitoring and control, education, community organization, and economic alternatives. The recent agreement on ecological restoration of the Xingu River headwaters between ranchers and private companies, indigenous peoples, and environmentalists, brokered by ISA, marks the emergence of an indigenous and conservation alliance of sufficient cohesiveness and legitimacy to negotiate effectively at a regional scale. Resumen:,Las alianzas actuales entre indígenas y organizaciones de conservación en el Amazonas Brasileño han ayudado a obtener el reconocimiento oficial de ,1 millón de km2 en áreas indígenas. El futuro del as reservas indígenas amazónicas es de importancia estratégica para el futuro de la biodiversidad en la región. Examinamos la legislación que rige a la utilización de recursos en zonas indígenas y sintetizamos la historia de la consolidación del territorio > 100,000 km2 de la etnia Kayapo. Como muchos grupos Amazónicos, los Kayapo han detenido la expansión de la frontera agrícola en sus tierras pero permiten actividades madereras y mineras selectivas. Las perspectivas de conservación y sustentabilidad a largo plazo en estas tierras dependen del entendimiento de su base de recursos y de las alternativas económicas disponibles por parte de los grupos indígenas. A pesar de que ni la seguridad en la posesión ni el conocimiento indígena garantizan la conservación de los bosques, los regímenes indígenas de gestión de recursos de propiedad común relativamente igualitarios en conjunto con incentivos adecuados y asociaciones con organizaciones de conservación pueden obtener este resultado. Iniciativas exitosas incluyen el proyecto a largo plazo de Conservation International con el pueblo A'ukre Kayapo y el incipiente monitoreo y control territorial a gran escala en el territorio Kayapo y la asociación durante 15 años del Instituto Socioambiental (ISA) con habitantes del Parque Indígena Xingu, con proyectos enfocados al monitoreo y control territorial, a la educación, a la organización comunitaria y a alternativas económicas. El reciente acuerdo, negociado por ISA, entre rancheros y compañías privadas, grupos indígenas y ambientalistas para la restauración ecológica del Río Xingu marca el surgimiento de una alianza indígena y de conservación con la cohesión y legitimidad suficientes para negociar efectivamente a escala regional. [source]

    Stability and identification for rational approximation of frequency response function of unbounded soil

    Xiuli Du
    Abstract Exact representation of unbounded soil contains the single output,single input relationship between force and displacement in the physical or transformed space. This relationship is a global convolution integral in the time domain. Rational approximation to its frequency response function (frequency-domain convolution kernel) in the frequency domain, which is then realized into the time domain as a lumped-parameter model or recursive formula, is an effective method to obtain the temporally local representation of unbounded soil. Stability and identification for the rational approximation are studied in this paper. A necessary and sufficient stability condition is presented based on the stability theory of linear system. A parameter identification method is further developed by directly solving a nonlinear least-squares fitting problem using the hybrid genetic-simplex optimization algorithm, in which the proposed stability condition as constraint is enforced by the penalty function method. The stability is thus guaranteed a priori. The infrequent and undesirable resonance phenomenon in stable system is also discussed. The proposed stability condition and identification method are verified by several dynamic soil,structure-interaction examples. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Applications of PAT-Process Analytical Technology in Recombinant Protein Processes with Escherichia coli

    C. Kaiser
    Abstract Monitoring of bioprocesses and thus observation and identification of such processes is one of the main aims of bioprocess engineering. It is of vital importance in bioprocess development to improve the overall productivity by avoiding unintentional limitations to ensure not only optimal process conditions but also the observation of established production processes. Furthermore, reproducibility needs to be improved and final product quality and quantity be guaranteed. Therefore, an advanced monitoring and control system has been developed, which is based on different in-line, on-line and at-line measurements for substrates and products. Observation of cell viability applying in-line radio frequency impedance measurement and on-line determination of intracellular recombinant target protein using the reporter protein T-Sapphire GFP based on in-line fluorescence measurement show the ability for the detection of critical process states. In this way, the possibility for the on-line recognition of optimal harvest times arises and disturbances in the scheduled process route can be perceived. [source]

    Path-dependent climate policy: the history and future of emissions trading in Europe

    Edwin Woerdman
    At the end of the 1990s, the EU was still sceptical towards emissions trading, but in 2003 it adopted a directive that enables such trading in the EU from 2005 onwards. Instead of presenting ad hoc explanations, we develop and apply the path dependence approach to clarify this remarkable attitude change. Sunk costs, switching costs and learning explain why politicians were initially tempted to add credit trading to existing, sub-optimal policy. Permit trading, however, is more efficient and effective. An institutional lock-in was bound to occur, but attitudes changed as a result of internal pressures, such as the pioneering role of the European Commission, and external ,shocks', such as the withdrawal of the US from the Kyoto Protocol. A full-scale institutional break-out towards efficiency is not guaranteed, though, because elements of credit trading can still enter the permit trading directive. The risk is that these elements become locked in, from which it may be difficult to escape. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment. [source]

    Co-Cultures of Primary Cells on Self-Supporting Nanoporous Alumina Membranes,

    Andreas Hoess
    Due to their unique properties, self-supporting nanoporous aluminum oxide (alumina) membranes are useful substrates for the indirect co-cultivation of cells. The membrane can act as a physical barrier between different cell types, whereas the cell-to-cell communication is guaranteed by the diffusion of soluble molecules or factors through the pores. With the help of such membranes the mRNA expression of hepatic genes can be induced in human adipose-derived mesenchymal stem cells (hASCs) during an indirect co-cultivation with primary mouse hepatocytes under different culture conditions. This proof of concept shows that such a cultivation approach is beneficial for different issues in the field tissue engineering or cell therapy. [source]

    Judicial Review of European Anti-Terrorism Measures,The Yusuf and Kadi Judgments of the Court of First Instance

    EUROPEAN LAW JOURNAL, Issue 1 2008
    Christina Eckes
    It accepted that the Community uses its competence to adopt state sanctions in combination with Article 308 EC to freeze the assets of civil persons, including European citizens. The court also reduced its jurisdiction to a basic scrutiny of whether jus cogens was violated. The Court of First Instance's decisions can be criticised on various grounds. First, the application of these Articles is contrary to the wording of the Treaty and the case-law of the European Court of Justice (ECJ). Further, as a consequence of the Court of First Instance's judgments, decisions of the UN Sanctions Committee become the supreme law within the EU, provided they meet the requirements of jus cogens as defined by the Court of First Instance. In addition, the individual is deprived of all fundamental rights guaranteed under European law. [source]

    The Cocoon of Power: Democratic Implications of Interinstitutional Agreements

    EUROPEAN LAW JOURNAL, Issue 1 2007
    Sonja Puntscher Riekmann
    It starts from the premise that democratic rules as developed in the national context may be used as a yardstick for supranational governance as well. Thus, parliamentarisation of the Union is defined as an increase in democracy, although relating problems such as weak European party systems, low turnouts, and remoteness are not to be neglected. The article evaluates several case studies on IIAs in this vein and asks whether they strengthen the European Parliament or not, and why. It arrives at conclusions that allow for differentiation: empowerment of the European Parliament occurs in particular when authorisation to conclude an IIA stems from the Treaty or from the power that the European Parliament has in crucial fields such as the budget and is willing to use for this purpose. Success is, however, not guaranteed in every case, and is sometimes more symbolic than real. However, a democratic critique must also stress negative consequences of IIAs in terms of responsivity, accountability, and transparency. [source]

    QoS in IntServ-based IP networks: the peak rate policing

    Lorenzo Battaglia
    In the last few years, IP has moved towards resource reservation, with the task to guarantee in the future Quality of Service (QoS). This has led to flow admission control algorithms based on the negotiation of standardised traffic parameters. QoS can be guaranteed in any network, a priori from the used technology, only if the used admission control algorithm wisely shares the network's resources among the users. Any admission control algorithm on its turn can do so, only if every user respects the negotiated traffic parameters. Since any user could, maliciously or not, send at a higher rate than negotiated, i.e. use a higher share of resources than the negotiated one, in every network in which admission control is performed, a policing algorithm is used. An ideal policer should guarantee to reject no packet of a well-behaved user and police contract violation as rigidly as possible. All this independently of the characteristics of the monitored stream and of the background traffic. This holds also for Integrated Services (IS) based IP networks. In these networks, every user negotiates a peak and an average rate. In this paper we present the solution to the peak rate policing issue. We adapt the Generic Cell Rate Algorithm (GCRA), well-known policer used in ATM networks, to police the peak rate of flows of packets with variable length. We intuitively call this modified GCRA Generic Packet Rate Algorithm (GPRA) and dimension its parameters so that independently of the characteristics of the policed flow and of the background traffic, no packets of a well-behaved user are rejected and that the flows of any misbehaving user are rigidly policed. Copyright © 2003 AEI. [source]

    Psychiatric endophenotypes and the development of valid animal models

    T. D. Gould
    Endophenotypes are quantifiable components in the genes-to-behaviors pathways, distinct from psychiatric symptoms, which make genetic and biological studies of etiologies for disease categories more manageable. The endophenotype concept has emerged as a strategic tool in neuropsychiatric research. This emergence is due to many factors, including the modest reproducibility of results from studies directed toward etiologies and appreciation for the complex relationships between genes and behavior. Disease heterogeneity is often guaranteed, rather than simplified, through the current diagnostic system; inherent benefits of endophenotypes include more specific disease concepts and process definitions. Endophenotypes can be neurophysiological, biochemical, endocrine, neuroanatomical, cognitive or neuropsychological. Heritability and stability (state independence) represent key components of any useful endophenotype. Importantly, they characterize an approach that reduces the complexity of symptoms and multifaceted behaviors, resulting in units of analysis that are more amenable to being modeled in animals. We discuss the benefits of more direct interpretation of clinical endophenotypes by basic behavioral scientists. With the advent of important findings regarding the genes that predispose to psychiatric illness, we are at an important crossroads where, without anthropomorphizing, animal models may provide homologous components of psychiatric illness, rather than simply equating to similar (loosely analogized) behaviors, validators of the efficacy of current medications or models of symptoms. We conclude that there exists a need for increased collaboration between clinicians and basic scientists, the result of which should be to improve diagnosis, classification and treatment on one end and to increase the construct relevance of model organisms on the other. [source]

    Isolation of Solid Solution Phases in Size-Controlled LixFePO4 at Room Temperature

    Genki Kobayashi
    Abstract State-of-the-art LiFePO4 technology has now opened the door for lithium ion batteries to take their place in large-scale applications such as plug-in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room-temperature phase diagram is essential to understand the facile electrode reaction of LixFePO4 (0,<,x,<,1), but it has not been fully understood. Here, intermediate solid solution phases close to x,=,0 and x,=,1 have been isolated at room temperature. Size-dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid-solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two-phase equilibrium potential is largely due to the bulk solid solution, and thus support the size-dependent miscibility gap model. [source]

    The grobal in the sporting glocal

    GLOBAL NETWORKS, Issue 2 2007
    Abstract This article provides a counterpoint to analyses of contemporary sport culture that falsely polarize the global and the local, in a manner that tends to privilege, and indeed romanticize, expressions of the sporting local. Rather than treating them as mutually exclusive categories, this discussion seeks to further the understanding of the constitutive interdependence linking the (sporting) global and the (sporting) local. In looking to further the understanding of the contemporary sporting landscape, we offer an alternative approach that reinscribes the influence of the global in shaping structures, practices, and experiences of the sporting local. The processual and empirical continuum through which we conceptualize globalization is bounded by grobalization (the imperialistic ambitions of nations, corporations, organizations, and the like and their desire, indeed need, to impose themselves on various geographic areas) and glocalization (the interpenetration of the global and the local, resulting in unique outcomes in different geographic areas): the grobal and the glocal. We discuss four sport scenarios, and illustrate the manner in which they exhibit , in varying inflections and to varying intensities , the necessary, but never guaranteed, interpenetrative relationship between the grobal and the glocal. This is achieved by both problematizing the very possibility of the sporting local within conditions of intensive and extensive globalization (leading to the concept of the glocal), and simultaneously explicating the importance of the global (through the concept of the grobal) to the structure and experience of everyday sport cultures. [source]

    The geography of hospital admission in a national health service with patient choice

    HEALTH ECONOMICS, Issue 9 2010
    Daniele Fabbri
    Abstract Each year about 20% of the 10 million hospital inpatients in Italy get admitted to hospitals outside the Local Health Authority of residence. In this paper we carefully explore this phenomenon and estimate gravity equations for ,trade' in hospital care using a Poisson pseudo-maximum likelihood method. Consistency of the PPML estimator is guaranteed under the null of independence provided that the conditional mean is correctly specified. In our case we find that patients' flows are affected by network autocorrelation. We correct for it by relying upon spatial filtering. Our results suggest that the gravity model is a good framework for explaining patient mobility in most of the examined diagnostic groups. We find that the ability to restrain patients' outflows increases with the size of the pool of enrollees. Moreover, the ability to attract patients' inflows is reduced by the size of pool of enroless for all LHAs except for the very big LHAs. For LHAs in the top quintile of size of enrollees, the ability to attract inflows increases with the size of the pool. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Recent role of splenectomy in chronic hepatic disorders

    HEPATOLOGY RESEARCH, Issue 12 2008
    Toru Ikegami
    For years splenectomy in hepatic disorders has been indicated only for the treatment of gastro-esophageal varices. However, with recent advances in medical and surgical treatments for chronic hepatic disorders, the use of splenectomy has been greatly expanded, such that splenectomy is used for reversing hypersplenism, for applying interferon treatment for hepatitis C, for treating hyperdynamic portal circulation associated with intractable ascites, and for controlling portal pressure during small grafts in living donor liver transplantation. Such experiences have shown the importance of portal hemodynamics, even in cirrhotic livers. Recent advances in surgical techniques have enabled surgeons to perform splenectomy more safely and less invasively, but the procedure still has considerable clinical outcomes. Splenectomy in hepatic disorders may become a more common procedure with expanded indications. However, it should also be noted that the long-term effects of splenectomy, in terms of improved hematological or hepatic function, is still not guaranteed. Moreover, the impact of splenectomy on immunologic status remains unclear and needs to be elucidated in both experimental and clinical settings. [source]

    Performance analysis of IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems

    Dong-Liang Sun
    Abstract Recently, an efficient segregated algorithm for incompressible fluid flow and heat transfer problems, called inner doubly iterative efficient algorithm for linked equations (IDEAL), has been proposed by the present authors. In the algorithm there exist inner doubly iterative processes for pressure equation at each iteration level, which almost completely overcome two approximations in SIMPLE algorithm. Thus, the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate and stability of solution process. However, validations have only been conducted for two-dimensional cases. In the present paper the performance of the IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems is analyzed and a systemic comparison is made between the algorithm and three other most widely used algorithms (SIMPLER, SIMPLEC and PISO). By the comparison of five application examples, it is found that the IDEAL algorithm is the most robust and the most efficient one among the four algorithms compared. For the five three-dimensional cases studied, when each algorithm works at its own optimal under-relaxation factor, the IDEAL algorithm can reduce the computation time by 12.9,52.7% over SIMPLER algorithm, by 45.3,73.4% over SIMPLEC algorithm and by 10.7,53.1% over PISO algorithm. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Positivity-preserving, flux-limited finite-difference and finite-element methods for reactive transport

    Robert J. MacKinnon
    Abstract A new class of positivity-preserving, flux-limited finite-difference and Petrov,Galerkin (PG) finite-element methods are devised for reactive transport problems. The methods are similar to classical TVD flux-limited schemes with the main difference being that the flux-limiter constraint is designed to preserve positivity for problems involving diffusion and reaction. In the finite-element formulation, we also consider the effect of numerical quadrature in the lumped and consistent mass matrix forms on the positivity-preserving property. Analysis of the latter scheme shows that positivity-preserving solutions of the resulting difference equations can only be guaranteed if the flux-limited scheme is both implicit and satisfies an additional lower-bound condition on time-step size. We show that this condition also applies to standard Galerkin linear finite-element approximations to the linear diffusion equation. Numerical experiments are provided to demonstrate the behavior of the methods and confirm the theoretical conditions on time-step size, mesh spacing, and flux limiting for transport problems with and without nonlinear reaction. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Robust adaptive output-feedback control for a class of nonlinear systems with time-varying actuator faults

    Zhengqiang Zhang
    Abstract A robust adaptive output-feedback control scheme is proposed for a class of nonlinear systems with unknown time-varying actuator faults. Additional unmodelled terms in the actuator fault model are considered. A new linearly parameterized model is proposed. The boundedness of all the closed-loop signals is established. The desired control performance of the closed-loop system is guaranteed by appropriately choosing the design parameters. The properties of the proposed control algorithm are demonstrated by two simulation examples. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Robust diagnosis and fault-tolerant control of distributed processes over communication networks

    Sathyendra Ghantasala
    Abstract This paper develops a robust fault detection and isolation (FDI) and fault-tolerant control (FTC) structure for distributed processes modeled by nonlinear parabolic partial differential equations (PDEs) with control constraints, time-varying uncertain variables, and a finite number of sensors that transmit their data over a communication network. The network imposes limitations on the accuracy of the output measurements used for diagnosis and control purposes that need to be accounted for in the design methodology. To facilitate the controller synthesis and fault diagnosis tasks, a finite-dimensional system that captures the dominant dynamic modes of the PDE is initially derived and transformed into a form where each dominant mode is excited directly by only one actuator. A robustly stabilizing bounded output feedback controller is then designed for each dominant mode by combining a bounded Lyapunov-based robust state feedback controller with a state estimation scheme that relies on the available output measurements to provide estimates of the dominant modes. The controller synthesis procedure facilitates the derivation of: (1) an explicit characterization of the fault-free behavior of each mode in terms of a time-varying bound on the dissipation rate of the corresponding Lyapunov function, which accounts for the uncertainty and network-induced measurement errors and (2) an explicit characterization of the robust stability region where constraint satisfaction and robustness with respect to uncertainty and measurement errors are guaranteed. Using the fault-free Lyapunov dissipation bounds as thresholds for FDI, the detection and isolation of faults in a given actuator are accomplished by monitoring the evolution of the dominant modes within the stability region and declaring a fault when the threshold is breached. The effects of network-induced measurement errors are mitigated by confining the FDI region to an appropriate subset of the stability region and enlarging the FDI residual thresholds appropriately. It is shown that these safeguards can be tightened or relaxed by proper selection of the sensor spatial configuration. Finally, the implementation of the networked FDI,FTC architecture on the infinite-dimensional system is discussed and the proposed methodology is demonstrated using a diffusion,reaction process example. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Adaptive TS-FNN control for a class of uncertain multi-time-delay systems: The exponentially stable sliding mode-based approach

    Tung-Sheng Chiang
    Abstract This paper presents an adaptive Takagi,Sugeno fuzzy neural network (TS-FNN) control for a class of multiple time-delay uncertain nonlinear systems. First, we develop a sliding surface guaranteed to achieve exponential stability while considering mismatched uncertainty and unknown delays. This exponential stability result based on a novel Lyapunov,Krasovskii method is an improvement when compared with traditional schemes where only asymptotic stability is achieved. The stability analysis is transformed into a linear matrix inequalities problem independent of time delays. Then, a sliding mode control-based TS-FNN control scheme is proposed to achieve asymptotic stability for the controlled system. Since the TS-FNN combines TS fuzzy rules and a neural network structure, fewer numbers of fuzzy rules and tuning parameters are used compared with the traditional pure TS fuzzy approach. Moreover, all the fuzzy membership functions are tuned on-line even in the presence of input uncertainty. Finally, simulation results show the control performance of the proposed scheme. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Neural network-based adaptive control of piezoelectric actuators with unknown hysteresis

    Wen-Fang Xie
    Abstract This paper proposes a neural network (NN)-based adaptive control of piezoelectric actuators with unknown hysteresis. Based on the classical Duhem model described by a differential equation, the explicit solution to the equation is explored and a new hysteresis model is constructed as a linear model in series with a piecewise continuous nonlinear function. An NN-based dynamic pre-inversion compensator is designed to cancel out the effect of the hysteresis. With the incorporation of the pre-inversion compensator, an adaptive control scheme is proposed to have the position of the piezoelectric actuator track the desired trajectory. This paper has three distinct features. First, it applies the NN to online approximate complicated piecewise continuous unknown nonlinear functions in the explicit solution to Duhem model. Second, an observer is designed to estimate the output of hysteresis of piezoelectric actuator based on the system input and output. Third, the stability of the controlled piezoelectric actuator with the observer is guaranteed. Simulation results for a practical system validate the effectiveness of the proposed method in this paper. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Adaptive critic design using non-linear network structures

    Ognjen Kuljaca
    Abstract A neural net (NN)/fuzzy logic (FL) adaptive critic controller is described. This structure takes advantage of the decision-making properties of a FL system to critique and tune a NN action-generating network. The stability of the proposed structure is proven. NN and fuzzy weight tuning algorithms are given that do not require complicated initialization procedures or any off-line learning phase. Tracking and bounded NN weights and control signals are guaranteed. The adaptive fuzzy critic controller given here is a model-free controller' in the sense that it works for any system in a prescribed class without the need for extensive modeling and preliminary analysis to find a regression matrix'. There is no linearity in the parameter (LIP) requirement. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Control of induction motors: an adaptive passivity MIMO perspective

    Manuel A. Duarte-Mermoud
    The design of two multiple-input multiple-output (MIMO) controllers for induction motors, based on adaptive passivity, is presented in this paper. The controller design method is based on concepts of equivalence passivity via adaptive feedback, previously developed by the authors. Robustness under variations of the motor-load parameters is guaranteed and the knowledge of such a parameters is not needed in the design. Simple proportional controllers for the torque, rotor flux and stator current control loops are used, due to the control simplification introduced by the use of feedback passive equivalence. A principle called ,Torque-Flux Control Principle' is used in this article introducing a considerable simplification in the resultant controller. Because of the employment of this principle, the control efforts are diminished and rotor flux estimation (or measurement) is avoided. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Closed-loop iterative learning control for non-linear systems with initial shifts

    Mingxuan Sun
    Abstract This paper is concerned with the problem of the iterative learning control with current cycle feedback for a class of non-linear systems with well-defined relative degree. The tracking error caused by a non-zero initial shift is detected as extended D-type learning algorithm is applied. The defect is overcome by adding terms including the output error, its derivatives as well as integrals. Asymptotic tracking of the final output to the desired trajectory is guaranteed. As an alternative approach, an initial rectifying action is introduced in the extended D-type learning algorithm and shown effective to achieve the desired trajectory jointed smoothly with a transitional trajectory from the starting position. Also these algorithms with adjustable tracking interval ensure better robustness performance in the presence of initial shifts. Numerical simulation is conducted to demonstrate the theoretical results. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Guaranteed recursive non-linear state bounding using interval analysis

    Michel Kieffer
    Abstract The problem considered here is state estimation in the presence of unknown but bounded state perturbations and measurement noise. In this context, most available results are for linear models, and the purpose of the present paper is to deal with the non-linear case. Based on interval analysis and the notion of set inversion, a new state estimator is presented, which evaluates a set estimate guaranteed to contain all values of the state that are consistent with the available observations, given the perturbation and noise bounds and a set containing the initial value of the state. To the best of our knowledge, it is the first estimator for which this claim can be made. The precision of the set estimate can be improved, at the cost of more computation. Theoretical properties of the estimator are studied, and computer implementation receives special attention. A simple illustrative example is treated. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Experts, dialects, and discourse

    Rakesh Mohan Bhatt
    This paper examines "expert" discourse , complexes of signs and practices that organize and legitimize social existence and social reproduction , to demonstrate the ideological processes involved in the manufacture of Standard English ideology and its continual duplication as necessitated by the three axiomatic conceptions of the English-sacred imagined community (cf. Anderson 1991). It is argued that the hierarchical structure needed to sustain the sacred imagined community can only be guaranteed if Standard English is accepted by all members as inevitable and the speakers of this standard accepted as uncontested authorities of English language use. How is this ideological manipulation and indoctrination in fact accomplished? This paper focuses on two sites of ideological manipulation , the learning and teaching of English in post-colonial contexts , and argues that expert promulgations enable what Foucault has called régimes of truth to be organized around the language. Expert discourse establishes a habit of thought which makes the standard variety of English (British/American) desirable, necessary, normal, natural, universal, and essential, and all other varieties instances of deficit and deviation. The key ideological process is a naturalizing move that drains the conceptual of its historical content, making it seem universal and timelessly true (Woolard & Schieffelin 1994). [source]

    QoS-aware fair packet scheduling in IEEE 802.16 wireless mesh networks

    Yajun Li
    Abstract In this paper, we address the problem of heterogeneous quality-of-service (QoS) provisioning in IEEE 802.16-based wireless mesh networks. Our objective is to provide a novel service differentiation scheme based on distributed scheduling in the IEEE 802.16-based mesh mode, thereby offering QoS guarantees. We first devise a novel scheme for the traffic class differentiation, which can be implemented at the medium access control layer. We then present a QoS-aware fair packet scheduling (QFPS) algorithm to fulfill the QoS provisioning. With QFPS, a traffic flow with urgent QoS demand is guaranteed to be given priority in wireless resource allocation over those ones with mild QoS requirements. A shorter end-to-end delay is therefore expected to be offered for the traffic flows with time-urgent requirements. Moreover, we propose a new fairness model among different traffic flows traversing the same node. All traffic flows passing through a node are served by the Deficit Round-Robin scheduling algorithm to achieve fairness within the same priority group. The experimental results of the QFPS demonstrate that various traffic flows are provided with a differentiated service that offers QoS guarantees. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Expedited forwarding end-to-end delay and jitter in DiffServ

    Hamada Alshaer
    Abstract The scheduling disciplines and active buffer management represent the main components employed in the differentiated services (DiffServ) data plane, which provide qualitative per-hop behaviors corresponding to the QoS required by supported traffic classes. In the first part of this paper, we compute the per-hop delay bound that should be guaranteed by the different multiservice scheduling disciplines, so that the end-to-end (e2e) delay required by expedited forwarding (EF) traffic can be guaranteed. Consequently, we derive the e2e delay bound of EF traffic served by priority queuing,weighted fair queuing (PQ,WFQ) at every hop along its routing path. Although real-time flows are principally offered EF service class, some simulations on DiffServ-enabled network show that these flows suffer from delay jitter and they are negatively impacted by lower priority traffic. In the second part of this paper, we clarify the passive impact of delay jitter on EF traffic, where EF flows are represented by renewal periodic ON,OFF flows, and the background (BG) flows are characterized by the Poisson process. We analyze through different scenarios the jitter effects of these BG flows on EF flow patterns when they are served by a single class scheduling discipline, such as first-input first-output, and a multiclass or multiservice scheduling discipline, such as static priority service discipline. As a result, we have found out that the EF per-hop behaviors (PHBs) configuration according to RFCs 2598 and 3246 (IETF RFC 2598, June 1999; RFC 3246, IETF, March 2002) cannot stand alone in guaranteeing the delay jitter required by EF flows. Therefore, playout buffers must be added to DiffServ-enabled networks for handling delay jitter problem that suffers from EF flows. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Dynamic bandwidth recycle algorithm for OVSF,CDMA systems

    Peng-Jung Wu
    Abstract This paper presents a dynamic bandwidth recycle algorithm in the downlink of a WCDMA system using orthogonal variable spreading factor codes (OVSF). It consists of a bandwidth recycle algorithm and a bandwidth reservation algorithm. The bandwidth recycle algorithm is used to recycle bandwidth from current serviced connections when the system does not have enough available bandwidth to support a bandwidth request. The bandwidth reservation algorithm is used to reduce transmission delay caused by suddenly increasing bandwidth requests. Four traffic classes, conversational, streaming, interactive, and background classes, defined by universal mobile telecommunication system (UMTS) are considered. Simulation results show that the bandwidth utilization and block rate are improved, the bandwidth guaranteed to conversational and streaming classes are protected, and the delay time of interactive and background classes are kept under an acceptable value even when the traffic load is heavy. Copyright © 2005 John Wiley & Sons, Ltd. [source]