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Nonlinearity
Kinds of Nonlinearity Terms modified by Nonlinearity Selected AbstractsREASSESSING NONLINEARITY IN THE URBAN DISADVANTAGE/VIOLENT CRIME RELATIONSHIP: AN EXAMPLE OF METHODOLOGICAL BIAS FROM LOG TRANSFORMATION,CRIMINOLOGY, Issue 4 2003LANCE HANNON Sociologists and criminologists have become increasingly concerned with nonlinear relationships and interaction effects. For example, some recent studies suggest that the positive relationship between neighborhood disadvantage and violent crime is nonlinear with an accelerating slope, whereas other research indicates a nonlinear decelerating slope. The present paper considers the possibility that this inconsistency in findings is partially caused by lack of attention to an important methodological concern. Specifically, we argue that researchers have not been sensitive to the ways in which logarithmic transformation of the dependent variable can bias tests for nonlinearity and statistical interaction. We illustrate this point using demographic and violent crime data for urban neighborhoods, and we propose an alternative procedure to log transformation that involves the use of weighted least-squares regression, heteroscedasticity consistent standard errors, and diagnostics for influential observations. [source] A General Misspecification Test for Spatial Regression Models: Dependence, Heterogeneity, and NonlinearityJOURNAL OF REGIONAL SCIENCE, Issue 2 2001Thomas De Graaff There is an increasing awareness of the potentials of nonlinear modeling in regional science. This can be explained partly by the recognition of the limitations of conventional equilibrium models in complex situations, and also by the easy availability and accessibility of sophisticated computational techniques. Among the class of nonlinear models, dynamic variants based on, for example, chaos theory stand out as an interesting approach. However, the operational significance of such approaches is still rather limited and a rigorous statistical-econometric treatment of nonlinear dynamic modeling experiments is lacking. Against this background this paper is concerned with a methodological and empirical analysis of a general misspecification test for spatial regression models that is expected to have power against nonlinearity, spatial dependence, and heteroskedasticity. The paper seeks to break new research ground by linking the classical diagnostic tools developed in spatial econometrics to a misspecification test derived directly from chaos theory,the BDS test, developed by Brock, Dechert, and Scheinkman (1987). A spatial variant of the BDS test is introduced and applied in the context of two examples of spatial process models, one of which is concerned with the spatial distribution of regional investments in The Netherlands, the other with spatial crime patterns in Columbus, Ohio. [source] Testing for Neglected Nonlinearity in Cointegrating Relationships,JOURNAL OF TIME SERIES ANALYSIS, Issue 6 2007Andrew P. Blake C32; C45 Abstract., This article proposes pure significance tests for the absence of nonlinearity in cointegrating relationships. No assumption of the functional form of the nonlinearity is made. It is envisaged that the application of such tests could form the first step towards specifying a nonlinear cointegrating relationship for empirical modelling. The asymptotic and small sample properties of our tests are investigated, where special attention is paid to the role of nuisance parameters and a potential resolution using the bootstrap. [source] Organometallic Complexes for Nonlinear Optics, 47 , Synthesis and Cubic Optical Nonlinearity of a Stilbenylethynylruthenium Dendrimer,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2010Christopher J. Jeffery Abstract The synthesis of the 1st generation dendrimer 1,3,5-{trans -[Ru(C,C-3,5-(trans -[Ru(C,CPh)(dppe)2(C,CC6H4 -4-(E)-CHCH)])2C6H3)(dppe)2(C,CC6H4 -4-(E)-CHCH)]}3C6H3 proceeds by a novel route that features Emmons-Horner-Wadsworth coupling of 1,3,5-C6H3(CH2PO(OEt)2)3 with trans -[Ru(C,CC6H4 -4-CHO)Cl(dppe)2] and 1-I-C6H3 -3,5-(CH2PO(OEt)2)2 with trans -[Ru(C,CPh)(C,CC6H4 -4-CHO)(dppe)2] as key steps. The stilbenylethynylruthenium dendrimer is much more soluble than its ethynylated analog 1,3,5-{trans -[Ru(C,C-3,5-(trans -[Ru(C,CPh)(dppe)2(C,CC6H4 -4-C,C)])2C6H3)(dppe)2(C,CC6H4 -4-C,C)]}3C6H3 and, in contrast to the ethynylated analog, is a two-photon absorber at telecommunications wavelengths. [source] Peculiarities of soliton motion in molecular systems with high dispersionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004V. V. Krasilnikov Abstract In this work, features of propagating protons along molecular chain of hydrogen bonds are described from position of soliton dynamics with taking into account interaction of first and second neighbors of a proton sublattice. It is proposed extension of the model that is an endless chain of water molecules in which formation of hydrogen bonds is due to participating one proton of every water molecule, a second proton no participating in hydrogen bond and being confined by covalent bond of an oxygen atom. Nonlinearity is due to peculiar properties of proton sublattice potential. The model used to obtain continual equations which contain the spatial derivatives of the fourth order that is related with dispersion of longwave oscillations. The availability of such a dispersion changes essentially dynamics of the molecular chain, which allows of manifesting new peculiarities of propagating nonlinear excitations. It is shown there are two new sorts of charge density excitations transferred by solitons determined as exact analytic dependences in such a system. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal Structure and Excited Optical Nonlinearity of a 1D Polymeric [W2O2S6Cu4(NCMe)4] n Cluster.CHEMINFORM, Issue 38 2004Hegen Zheng Abstract For Abstract see ChemInform Abstract in Full Text. [source] Nonlinearity and Chaos in Molecular Vibrations.CHEMPHYSCHEM, Issue 4 2007By Guozhen Wu. No abstract is available for this article. [source] Dynamic Wavelet Neural Network for Nonlinear Identification of Highrise BuildingsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2005Xiaomo Jiang Compared with conventional neural networks, training of a dynamic neural network for system identification of large-scale structures is substantially more complicated and time consuming because both input and output of the network are not single valued but involve thousands of time steps. In this article, an adaptive Levenberg,Marquardt least-squares algorithm with a backtracking inexact linear search scheme is presented for training of the dynamic fuzzy WNN model. The approach avoids the second-order differentiation required in the Gauss,Newton algorithm and overcomes the numerical instabilities encountered in the steepest descent algorithm with improved learning convergence rate and high computational efficiency. The model is applied to two highrise moment-resisting building structures, taking into account their geometric nonlinearities. Validation results demonstrate that the new methodology provides an efficient and accurate tool for nonlinear system identification of high-rising buildings. [source] Sensitivity Analyses of Spatial Population Viability Analysis Models for Species at Risk and Habitat Conservation PlanningCONSERVATION BIOLOGY, Issue 1 2009ILONA R. NAUJOKAITIS-LEWIS análisis de sensibilidad; análisis de viabilidad poblacional; incertidumbre; metapoblación; planificación de la conservación Abstract:,Population viability analysis (PVA) is an effective framework for modeling species- and habitat-recovery efforts, but uncertainty in parameter estimates and model structure can lead to unreliable predictions. Integrating complex and often uncertain information into spatial PVA models requires that comprehensive sensitivity analyses be applied to explore the influence of spatial and nonspatial parameters on model predictions. We reviewed 87 analyses of spatial demographic PVA models of plants and animals to identify common approaches to sensitivity analysis in recent publications. In contrast to best practices recommended in the broader modeling community, sensitivity analyses of spatial PVAs were typically ad hoc, inconsistent, and difficult to compare. Most studies applied local approaches to sensitivity analyses, but few varied multiple parameters simultaneously. A lack of standards for sensitivity analysis and reporting in spatial PVAs has the potential to compromise the ability to learn collectively from PVA results, accurately interpret results in cases where model relationships include nonlinearities and interactions, prioritize monitoring and management actions, and ensure conservation-planning decisions are robust to uncertainties in spatial and nonspatial parameters. Our review underscores the need to develop tools for global sensitivity analysis and apply these to spatial PVA. Resumen:,El análisis de viabilidad poblacional (AVP) es un marco de referencia efectivo para los esfuerzos de recuperación de especie y de hábitat, pero la incertidumbre en las estimaciones de parámetros y la estructura del modelo pueden llevar a predicciones no confiables. La integración de información compleja y a menudo incierta a los modelos de AVP espaciales requiere la aplicación de análisis de sensibilidad para explorar la influencia de parámetros espaciales y no espaciales sobre las predicciones de los modelos. Revisamos 87 análisis de modelos de AVP demográficos espaciales de plantas y animales para identificar métodos comunes de análisis de sensibilidad en publicaciones recientes. En contraste con las mejores prácticas recomendadas por la comunidad de modeladores, los análisis de los sensibilidad de AVP típicamente fueron ad hoc, inconsistentes y difíciles de comparar. La mayoría de los estudios aplicaron métodos locales a los análisis de sensibilidad, pero pocos variaron parámetros múltiples simultáneamente. La falta de estándares para los análisis de sensibilidad y descripción en los AVP espaciales tiene el potencial de comprometer la habilidad de aprender colectivamente de los resultados de AVP, de interpretar con precisión los resultados en casos en que las relaciones de los modelos sean no lineales e incluyan interacciones, para priorizar las acciones de monitoreo y manejo y para asegurar que la planificación de las decisiones de conservación sean robustas ante la incertidumbre en los parámetros espaciales y no espaciales. Nuestra revisión subraya la necesidad de desarrollar herramientas para análisis de sensibilidad globales y aplicarlos a AVP espaciales. [source] The Wealth Effect on New Business Startups in a Developing EconomyECONOMICA, Issue 291 2006ALICE MESNARD The paper tests for nonlinearities in the wealth effect on self-employment, as can arise from startup costs or liquidity constraints. Using both nonparametric and parametric methods, we show that the relationship between the probability of a return migrant to Tunisia starting up a business and the stock of his savings repatriated at return is concave for almost the entire range of our data, though we find weak evidence of a convex relationship at very low wealth levels. Our results suggest that the aggregate self-employment rate is an increasing function of aggregate wealth, but a decreasing function of wealth inequality. [source] Cavity QED with a trapped ionFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2003W. Vogel A trapped ion in a leaky cavity is studied in the regime of strong atom-field coupling. Particular emphasis is paid on nonlinearities due to smooth localization of the ion's wavefunction and on decoherence effects caused by spontaneous emission and cavity losses. Possibilities of quantum-state preparation are analyzed and single-ion lasing is considered. [source] Synergy between small- and large-scale feedbacks of vegetation on the water cycleGLOBAL CHANGE BIOLOGY, Issue 7 2005Marten Scheffer Abstract Predictions of the effects of climate change on the extent of forests, savannas and deserts are usually based on simple response models derived from actual vegetation distributions. In this review, we show two major problems with the implicitly assumed straightforward cause,effect relationship. Firstly, several studies suggest that vegetation itself may have considerable effects on regional climate implying a positive feedback, which can potentially lead to large-scale hysteresis. Secondly, vegetation ecologists have found that effects of plants on microclimate and soils can cause a microscale positive feedback, implying that critical precipitation conditions for colonization of a site may differ from those for disappearance from that site. We argue that it is important to integrate these nonlinearities at disparate scales in models to produce more realistic predictions of potential effects of climate change and deforestation. [source] On the intertemporal value relevance of conventional financial accounting in AustraliaACCOUNTING & FINANCE, Issue 4 2007Mark Brimble G10; G14; M41 Abstract This paper examines whether the relevance of conventional (earnings focused) accounting information for valuation has declined in Australia over a recent period of 28 years. Motivation is provided by the anecdotal concerns of financial analysts, accounting regulators, and a cluster of US centric academic research papers that conclude that the relevance of financial accounting (and earnings in particular) has declined over time. After controlling for nonlinearities and stock price inefficiencies, we find that the value relevance of core accounting earnings has not declined. A possible exception is found for small stocks. We also observe that net book values are relatively less important in Australia when compared to the USA. Our results are informative for investors who require feedback on valuation issues and the International Accounting Standards Board regulators in any further moves towards a balance sheet focus. [source] A dual mortar approach for 3D finite deformation contact with consistent linearizationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2010Alexander Popp Abstract In this paper, an approach for three-dimensional frictionless contact based on a dual mortar formulation and using a primal,dual active set strategy for direct constraint enforcement is presented. We focus on linear shape functions, but briefly address higher order interpolation as well. The study builds on previous work by the authors for two-dimensional problems. First and foremost, the ideas of a consistently linearized dual mortar scheme and of an interpretation of the active set search as a semi-smooth Newton method are extended to the 3D case. This allows for solving all types of nonlinearities (i.e. geometrical, material and contact) within one single Newton scheme. Owing to the dual Lagrange multiplier approach employed, this advantage is not accompanied by an undesirable increase in system size as the Lagrange multipliers can be condensed from the global system of equations. Moreover, it is pointed out that the presented method does not make use of any regularization of contact constraints. Numerical examples illustrate the efficiency of our method and the high quality of results in 3D finite deformation contact analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] Coupled solution of the species conservation equations using unstructured finite-volume methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2010Ankan Kumar Abstract A coupled solver was developed to solve the species conservation equations on an unstructured mesh with implicit spatial as well as species-to-species coupling. First, the computational domain was decomposed into sub-domains comprised of geometrically contiguous cells,a process similar to additive Schwarz decomposition. This was done using the binary spatial partitioning algorithm. Following this step, for each sub-domain, the discretized equations were developed using the finite-volume method, and solved using an iterative solver based on Krylov sub-space iterations, that is, the pre-conditioned generalized minimum residual solver. Overall (outer) iterations were then performed to treat explicitness at sub-domain interfaces and nonlinearities in the governing equations. The solver is demonstrated for both two-dimensional and three-dimensional geometries for laminar methane,air flame calculations with 6 species and 2 reaction steps, and for catalytic methane,air combustion with 19 species and 24 reaction steps. It was found that the best performance is manifested for sub-domain size of 2000 cells or more, the exact number depending on the problem at hand. The overall gain in computational efficiency was found to be a factor of 2,5 over the block (coupled) Gauss,Seidel procedure. All calculations were performed on a single processor machine. The largest calculations were performed for about 355 000 cells (4.6 million unknowns) and required 900,MB of peak runtime memory and 19,h of CPU on a single processor. Copyright © 2009 John Wiley & Sons, Ltd. [source] Temporal accuracy analysis of phase change convection simulations using the JFNK-SIMPLE algorithmINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2007Katherine J. Evans Abstract The incompressible Navier,Stokes and energy conservation equations with phase change effects are applied to two benchmark problems: (1) non-dimensional freezing with convection; and (2) pure gallium melting. Using a Jacobian-free Newton,Krylov (JFNK) fully implicit solution method preconditioned with the SIMPLE (Numerical Heat Transfer and Fluid Flow. Hemisphere: New York, 1980) algorithm using centred discretization in space and three-level discretization in time converges with second-order accuracy for these problems. In the case of non-dimensional freezing, the temporal accuracy is sensitive to the choice of velocity attenuation parameter. By comparing to solutions with first-order backward Euler discretization in time, it is shown that the second-order accuracy in time is required to resolve the fine-scale convection structure during early gallium melting. Qualitative discrepancies develop over time for both the first-order temporal discretized simulation using the JFNK-SIMPLE algorithm that converges the nonlinearities and a SIMPLE-based algorithm that converges to a more common mass balance condition. The discrepancies in the JFNK-SIMPLE simulations using only first-order rather than second-order accurate temporal discretization for a given time step size appear to be offset in time. Copyright © 2007 John Wiley & Sons, Ltd. [source] Sequential Monte Carlo methods for multi-aircraft trajectory prediction in air traffic managementINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 10 2010I. Lymperopoulos Abstract Accurate prediction of aircraft trajectories is an important part of decision support and automated tools in air traffic management. We demonstrate that by combining information from multiple aircraft at different locations and time instants, one can provide improved trajectory prediction (TP) accuracy. To perform multi-aircraft TP, we have at our disposal abundant data. We show how this multi-aircraft sensor fusion problem can be formulated as a high-dimensional state estimation problem. The high dimensionality of the problem and nonlinearities in aircraft dynamics and control prohibit the use of common filtering methods. We demonstrate the inefficiency of several sequential Monte Carlo algorithms on feasibility studies involving multiple aircraft. We then develop a novel particle filtering algorithm to exploit the structure of the problem and solve it in realistic scale situations. In all studies we assume that aircraft fly level (possibly at different altitudes) with known, constant, aircraft-dependent airspeeds and estimate the wind forecast errors based only on ground radar measurements. Current work concentrates on extending the algorithms to non-level flights, the joint estimation of wind forecast errors and the airspeed and mass of the different aircraft and the simultaneous fusion of airborne and ground radar measurements. Copyright © 2010 John Wiley & Sons, Ltd. [source] Nonlinear adaptive tracking-control synthesis for functionally uncertain systemsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2010Zenon Zwierzewicz Abstract The paper is concerned with the problem of adaptive tracking system control synthesis. It is assumed that a nonlinear, feedback linearizable object dynamics (model structure) is (partially) unknown and some of its nonlinear characteristics can be approximated by a sort of functional approximators. It has been proven that proportional state feedback plus parameter adaptation are able to assure its asymptotic stability. This form of controller permits online compensation of unknown model nonlinearities and exogenous disturbances, which results in satisfactory tracking performance. An interesting feature of the system is that the whole process control is performed without requisite asymptotic convergence of approximator parameters to the postulated ,true' values. It has been noticed that the parameters play rather a role of slack variables on which potential errors (that otherwise would affect the state variables) cumulate. The system's performance has been tested via Matlab/Simulink simulations via an example of ship path-following problem. Copyright © 2009 John Wiley & Sons, Ltd. [source] Improved adaptive control for the discrete-time parametric-strict-feedback formINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 12 2009Graciela Adriana González Abstract Adaptive control design for a class of single-input single-output nonlinear discrete-time systems in parametric-strict-feedback form is re-visited. No growth restrictions are assumed on the nonlinearities. The control objective is to achieve tracking of a reference signal. As usual, the algorithm derives from the combination of a control law and a parameter estimator (certainty equivalence principle). The parameter estimator strongly lies on the regressor subspace identification by means of an orthogonalization process. Certain drawbacks of previous schemes are analyzed. Several modifications on them are considered to improve the algorithm complexity, control performance and numerical stability. As a result, an alternative control scheme is proposed. When applied to the proposed class of systems, global boundedness and convergence remain as achieved objectives while improving the performance issues of previous schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Robust stabilization of a class of non-minimum-phase nonlinear systems in a generalized output feedback canonical formINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2009Jun Fu Abstract In this paper, a globally robust stabilizer for a class of uncertain non-minimum-phase nonlinear systems in generalized output feedback canonical form is designed. The system contains unknown parameters multiplied by output-dependent nonlinearities and output-dependent nonlinearities enter such a system both additively and multiplicatively. The proposed method relies on a recently developed novel parameter estimator and state observer design methodology together with a combination of backstepping and small-gain approach. Our design has three distinct features. First, the parameter estimator and state observer do not necessarily follow the classical certainty-equivalent principle any more. Second, the design treats unknown parameters and unmeasured states in a unified way. Third, the technique by combining standard backstepping and small-gain theorem ensures robustness with respect to dynamic uncertainties. Finally, two numerical examples are given to show that the proposed method is effective, and that it can be applied to more general systems that do not satisfy the cascading upper diagonal dominance conditions developed in recent papers, respectively. Copyright © 2008 John Wiley & Sons, Ltd. [source] Experimental modelling and intelligent control of a wood-drying kilnINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2001Givon Chuen Kee Yan Abstract Proper control of the wood-drying kiln is crucial in ensuring satisfactory quality of dried wood and in minimizing drying time. This paper presents the development, implementation, and evaluation of a control system for a lumber drying kiln process incorporating sensory feedback from in-wood moisture content sensors and intelligent control such that the moisture content of lumber will reach and stabilize at the desired set point without operator interference. The drying process is difficult to model and control due to complex dynamic nonlinearities, coupling effects among key variables, and process disturbances caused by the variation of lumber sizes, species, and environmental factors. Through system identification scheme using experimental data and recursive least-squares algorithm for parameter estimation, appropriate models are developed for simulation purpose and controller design. Two different control methodologies are employed and compared: a conventional proportional-integral-derivative (PID) controller and a direct fuzzy logic controller (FLC), and system performance is evaluated through simulations. The developed control system is then implemented in a downscaled industrial kiln located at the Innovation Centre of National Research Council (NRC) of Canada. This experimental set-up is equipped with a variety of sensors, including thermocouples for temperature feedback, an air velocity transmitter for measuring airflow speed in the plenum, relative humidity sensors for measuring the relative humidity inside the kiln, and in-wood moisture content sensors for measuring the moisture content of the wood pieces. For comparison, extensive experimental studies are carried out on-line using the two controllers, and the results are evaluated to tune the controller parameters to achieve good performance in the wood-drying kiln. The combination of conventional control with the intelligent control promises improved performance. The control system developed in this study may be applied in industrial wood-drying kilns, with a clear potential for improved quality and increased speed of drying. Copyright © 2001 John Wiley & Sons, Ltd. [source] Envelope tracking power amplifier with static predistortion linearizationINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2009Timo Rautio Abstract This paper presents the design method, properties and driving techniques of a linear 0.5,W 1,GHz LDMOS power amplifier used in a supply modulated envelope tracking transmitter with real-time predistortion. Causes of nonlinearities are identified, and various supply voltage drives are experimented. Measured results show that the power efficiency can be improved while maintaining high linearity. Copyright © 2008 John Wiley & Sons, Ltd. [source] A modularized framework for solving an economic,environmental power generation mix problemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2004Haoxiang Xia Abstract This paper presents a modularized simulation modelling framework for evaluating the impacts on economic cost and CO2 emissions resulting from the introduction of a solid oxide fuel cell (SOFC) system into the existing mix of centralized power generation technologies in Japan. The framework is comprised of three parts: a dual-objective linear programming model that solves the generation best-mix problem for the existing power generation technologies; a nonlinear SOFC system model in which the economic cost and CO2 emissions by the SOFC system can be calculated; and the Queuing Multi-Objective Optimizer (QMOO), a multi-objective evolutionary algorithm (MOEA) developed at the EPFL in Switzerland as the overall optimizer of the combined power supply system. Thus, the framework integrates an evolutionary algorithm that is more suitable for handling nonlinearities with a calculus-based method that is more efficient in solving linear programming problems. Simulation experiments show that the framework is successful in solving the stated problem. Moreover, the three components of the modularized framework can be interconnected through a platform-independent model integration environment. As a result, the framework is flexible and scalable, and can potentially be modified and/or integrated with other models to study more complex problems. Copyright © 2004 John Wiley & Sons, Ltd. [source] The real exchange rate and real interest differentials: the role of nonlinearitiesINTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 4 2005Nelson C. Mark Abstract Recent empirical work has shown the importance of nonlinear adjustment in the dynamics of real exchange rates and real interest differentials. This work suggests that the tenuous empirical linkage between the real exchange rate and the real interest differential might be strengthened by explicitly accounting for these nonlinearities. We pursue this strategy by pricing the real exchange rate by real interest parity. The resulting first-order stochastic difference equation gives the real exchange rate as the expected present value of future real interest differentials which we compute numerically for three candidate nonlinear processes. Regressions of the log real US dollar prices of the Canadian dollar, deutschemark, yen and pound on the fundamental values implied by these nonlinear models are used to evaluate the linkage. The evidence for linkage is stronger when these present values are computed over shorter horizons than for longer horizons. Copyright © 2005 John Wiley & Sons, Ltd. [source] First hyperpolarizabilities of vinylogue organometallic sesquifulvalene chromophores: A DFT studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 12 2006Chaoyong Mang Abstract Static first hyperpolarizabilities of vinylogue mono- and bimetallic sesquifulvalene chromophores, [(,5 -C5H5)M{,,(,5 -C5H4)CHCH(,6 -C7H7)}]+ (M = Fe, Ru, and Os) and [(,5,C5H5)M{,,(,5 -C5H4)CHCH(,6 -C7H7)}Cr(CO)3]+ (M = Fe, Ru, and Os) have been calculated within DFT theoretical approach. The results agree well with the recent Hyper-Rayleigh scattering (HRS) measurements. The coordinated transition metals reduced the magnitude of dipole moment and first hyperpolarizability. The metal-to-ligand charge-transfer contributes to the first hyperpolarizability and, as a result, the rational substitution of coordinated metal could modulate the first hyperpolarizability of the organometallic chromophores. The study would be helpful to understand optical nonlinearities in organometallic complexes. © 2006 Wlley Periodicals, Inc. Int J Quantum Chem, 2006 [source] A coupled FDTD-artificial neural network technique for large-signal analysis of microwave circuitsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2002S. Goasguen Abstract We propose a first-order global modeling approach of Monolithic Microwave Integrated Circuits (MMIC) by modeling the active device with a neural network based on a full hydrodynamic model. This neural network describes the nonlinearities of the equivalent circuit parameters of an MESFET implemented in an extended Finite Difference Time Domain mesh to predict large-signal behaviors of the circuits. We successfully represented the transistor characteristics with a one-hidden-layer neural network, whose inputs are the gate voltage Vgs and the drain voltage Vds. The trained neural network shows excellent accuracy and dramatically reduces the computational time in comparison with the hydrodynamic model. Small-signal simulation is performed and validated by comparison with HP-Libra. Then large-signal behaviors are obtained, which demonstrates the successful use of the artificial neural network. © 2002 John Wiley & Sons, Inc. Int J RF and Microwave CAE 12: 25,36, 2002. [source] Nonlinear predictive control of smooth nonlinear systems based on Volterra models.INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 16 2010Application to a pilot plant Abstract There is a large demand to apply nonlinear algorithms to control nonlinear systems. With algorithms considering the process nonlinearities, better control performance is expected in the whole operating range than with linear control algorithms. Three predictive control algorithms based on a Volterra model are considered. The iterative predictive control algorithm to solve the complete nonlinear problem uses the non-autoregressive Volterra model calculated from the identified autoregressive Volterra model. Two algorithms for a reduced nonlinear optimization problem are considered for the unconstrained case, where an analytic control expression can be given. The performance of the three algorithms is analyzed and compared for reference signal tracking and disturbance rejection. The algorithms are applied and compared in simulation to control a Wiener model, and are used for real-time control of a chemical pilot plant. Copyright © 2009 John Wiley & Sons, Ltd. [source] A dual-observer design for global output feedback stabilization of nonlinear systems with low-order and high-order nonlinearitiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 15 2009Ji Li Abstract This paper employs a dual-observer design to solve the problem of global output feedback stabilization for a class of nonlinear systems whose nonlinearities are bounded by both low-order and high-order terms. We show that the dual-observer comprised of two individual homogeneous observers, can be implemented together to estimate low-order and high-order states in parallel. The proposed dual observer, together with a state feedback controller, which has both low-order and high-order terms, will lead to a new result combining and generalizing two recent results (Li J, Qian C. Proceedings of the 2005 IEEE Conference on Decision and Control, 2005; 2652,2657) and (Qian C. Proceedings of the 2005 American Control Conference, June 2005; 4708,4715). Copyright © 2008 John Wiley & Sons, Ltd. [source] Boundedness in Lurie system with stiffening nonlinearitiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2008Abdallah Ben Abdallah Abstract In this paper, we deal with the problem of boundedness of solutions in single-input single-output Lurie system. We prove the boundedness of solutions from the stability of zero dynamics under a restriction on the nonlinearity. The linear block is supposed to be of relative degree one or two, stabilizable by high-gain output feedback and not necessary minimum phase. The nonlinearity is required to have the stiffening property. Copyright © 2007 John Wiley & Sons, Ltd. [source] Lur'e Lyapunov functions and absolute stability criteria for Lur'e systems with multiple nonlinearitiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 9 2007Chunyu Yang Abstract In this paper, the absolute stability problem of Lur'e systems with multiple nonlinearities is investigated. Popov-type absolute stability criteria are surveyed and classified by distinguishing the Lur'e Lyapunov function upon which the criteria are based. A modified Lur'e Lyapunov function is presented. Some necessary and sufficient conditions for the existence of the Lyapynov function to guarantee the absolute stability of Lur'e systems are derived. By these conditions, LMI-based stability criteria are presented. The obtained criteria are expected to be less conservative than the existing ones. Finally, numerical examples are given to illustrate the advantages and effectiveness of our results. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||