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Scaling Parameters (scaling + parameter)
Selected AbstractsDual high-gain-based adaptive output-feedback control for a class of nonlinear systems,INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2008P. Krishnamurthy Abstract We propose an adaptive output-feedback controller for a general class of nonlinear triangular (strict-feedback-like) systems. The design is based on our recent results on a new high-gain control design approach utilizing a dual high-gain observer and controller architecture with a dynamic scaling. The technique provides strong robustness properties and allows the system class to contain unknown functions dependent on all states and involving unknown parameters (with no magnitude bounds required). Unlike our earlier result on this problem where a time-varying design of the high-gain scaling parameter was utilized, the technique proposed here achieves an autonomous dynamic controller by introducing a novel design of the observer, the scaling parameter, and the adaptation parameter. This provides a time-invariant dynamic output-feedback globally asymptotically stabilizing solution for the benchmark open problem proposed in our earlier work with no magnitude bounds or sign information on the unknown parameter being necessary. Copyright © 2007 John Wiley & Sons, Ltd. [source] 3-D viscous Cahn,Hilliard equation with memoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2009Monica Conti Abstract We deal with the memory relaxation of the viscous Cahn,Hilliard equation in 3-D, covering the well-known hyperbolic version of the model. We study the long-term dynamic of the system in dependence of the scaling parameter of the memory kernel , and of the viscosity coefficient ,. In particular we construct a family of exponential attractors, which is robust as both , and , go to zero, provided that , is linearly controlled by ,. Copyright © 2008 John Wiley & Sons, Ltd. [source] QRS Amplitude and Shape Variability in MagnetocardiogramsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2000MARKUS HUCK In magnetocardiography, averaging of QRS complexes is often used to improve the signal-to-noise ratio. However, averaging of QRS complexes ignores the variation in amplitude and shape of the signals caused, for example, by respiration. This may lead to suppression of signal portions within the QRS complexes. Furthermore, for inverse source, reconstructions of dipoles and of current density distributions errors in the special arrangement may occur. To overcome these problems we developed a method for separating and selective averaging QRS complexes with different shapes and amplitudes. The method is based on a spline interpolation of the QRS complex averaged by a standard procedure. This spline function then is fitted to each QRS complex in the raw data by means of nonlinear regression (Levenberg-Marquardt method). Five regression parameters are applied: a linear amplitude scaling, two parameters describing the baseline drift, a time scaling parameter, and a time shift parameter. We found that both amplitude and shape of the QRS complex are influenced by respiration. The baseline shows a weaker influence of the respiration. The regression parameters of two neighboring measurement channels correlate linearly. Thus, selective averaging of a larger number of sensors can be performed simultaneously. [source] An Activation-Based Model of Sentence Processing as Skilled Memory RetrievalCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 3 2005Richard L. Lewis Abstract We present a detailed process theory of the moment-by-moment working-memory retrievals and associated control structure that subserve sentence comprehension. The theory is derived from the application of independently motivated principles of memory and cognitive skill to the specialized task of sentence parsing. The resulting theory construes sentence processing as a series of skilled associative memory retrievals modulated by similarity-based interference and fluctuating activation. The cognitive principles are formalized in computational form in the Adaptive Control of Thought,Rational (ACT,R) architecture, and our process model is realized in ACT,R. We present the results of 6 sets of simulations: 5 simulation sets provide quantitative accounts of the effects of length and structural interference on both unambiguous and garden-path structures. A final simulation set provides a graded taxonomy of double center embeddings ranging from relatively easy to extremely difficult. The explanation of center-embedding difficulty is a novel one that derives from the model' complete reliance on discriminating retrieval cues in the absence of an explicit representation of serial order information. All fits were obtained with only 1 free scaling parameter fixed across the simulations; all other parameters were ACT,R defaults. The modeling results support the hypothesis that fluctuating activation and similarity-based interference are the key factors shaping working memory in sentence processing. We contrast the theory and empirical predictions with several related accounts of sentence-processing complexity. [source] Hysteretic energy spectrum and damage controlEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2001Rafael Riddell Abstract The inelastic response of single-degree-of-freedom (SDOF) systems subjected to earthquake motions is studied and a method to derive hysteretic energy dissipation spectra is proposed. The amount of energy dissipated through inelastic deformation combined with other response parameters allow the estimation of the required deformation capacity to avoid collapse for a given design earthquake. In the first part of the study, a detailed analysis of correlation between energy and ground motion intensity indices is carried out to identify the indices to be used as scaling parameters and base line of the energy dissipation spectrum. The response of elastoplastic, bilinear, and stiffness degrading systems with 5 per cent damping, subjected to a world-wide ensemble of 52 earthquake records is considered. The statistical analysis of the response data provides the factors for constructing the energy dissipation spectrum as well as the Newmark,Hall inelastic spectra. The combination of these spectra allows the estimation of the ultimate deformation capacity required to survive the design earthquake, capacity that can also be presented in spectral form as an example shows. Copyright © 2001 John Wiley & Sons, Ltd. [source] Dynamic scaling for Eley-Rideal reactions over rough surfaceINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2004Ajay Chaudhari Eley-Rideal reaction mechanism is studied over rough surface of random deposition model. Two types of rough surface are considered: (1) different rough surface with same surface density and (2) different rough surface with different surface density. Dynamic scaling theory, which is generally applied to the growing surface, is applied for this reaction mechanism to obtain the temporal and spatial scaling parameters , and ,. The scaling parameters are found to be negative in contrast to the positive scaling parameters in surface growth model. The values of , are the same for both types of surface whereas the values of , are different. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 286,292, 2004 [source] Thermodynamics of Phase Behavior in PEO/P(EO- b -DMS) Homopolymer and Block Co-Oligomer Mixtures under PressureMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2003Shichun Jiang Abstract The cloud-point temperatures (Tcl's) of poly(ethylene oxide) (PEO) and poly(ethylene oxide)- block -polydimethylsiloxane (P(EO- b -DMS)) homopolymer and block-oligomer mixtures were determined by turbidity measurements over a range of temperatures (105 to 130,°C), pressures (1 to 800 bar), and compositions (10,40 wt.-% PEO). The system phase separates upon cooling and Tcl was found to decrease with an increase in pressure for a constant composition. In the absence of special effects, this finding indicates negative excess volumes. Special attention was paid to the demixing temperatures as a function of the pressure for the different polymer mixtures and the plots in the T - , plane (where , signifies volume fractions). The cloud-point curves of the polymer mixture under pressures were observed for different compositions. The Sanchez-Lacombe (SL) lattice fluid theory was used to calculate the spinodals, the binodals, the Flory-Huggins (FH) interaction parameter, the enthalpy of mixing, and the volume changes of mixing. The calculated results show that modified P(EO- b -DMS) scaling parameters with the new combining rules can describe the thermodynamics of the PEO/P(EO- b -DMS) system well with the SL theory. Cloud point curves for various PEO/P(EO- b -DMS) polymer mixtures at various pressures on the T - ,PEO plane. [source] The challenge of tree height in Eucalyptus regnans: when xylem tapering overcomes hydraulic resistanceNEW PHYTOLOGIST, Issue 4 2010Giai Petit Summary ,Recent research suggests that increasing conduit tapering progressively reduces hydraulic constraints caused by tree height. Here, we tested this hypothesis using the tallest hardwood species, Eucalyptus regnans. ,Vertical profiles of conduit dimensions and vessel density were measured for three mature trees of height 47, 51 and 63 m. ,Mean hydraulic diameter (Dh) increased rapidly from the tree apex to the point of crown insertion, with the greatest degree of tapering yet reported (b > 0.33). Conduit tapering was such that most of the total resistance was found close to the apex (82,93% within the first 1 m of stem) and the path length effect was reduced by a factor of 2000. Vessel density (VD) declined from the apex to the base of each tree, with scaling parameters being similar for all trees (a = 4.6; b = ,0.5). ,Eucalyptus regnans has evolved a novel xylem design that ensures a high hydraulic efficiency. This feature enables the species to grow quickly to heights of 50,60 m, beyond the maximum height of most other hardwood trees. [source] Multipole electron-density modelling of synchrotron powder diffraction data: the case of diamondACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2010H. Svendsen Accurate structure factors are extracted from synchrotron powder diffraction data measured on crystalline diamond based on a novel multipole model division of overlapping reflection intensities. The approach limits the spherical-atom bias in structure factors extracted from overlapping powder data using conventional spherical-atom Rietveld refinement. The structure factors are subsequently used for multipole electron-density modelling, and both the structure factors and the derived density are compared with results from ab initio theoretical calculations. Overall, excellent agreement is obtained between experiment and theory, and the study therefore demonstrates that synchrotron powder diffraction can indeed provide accurate structure-factor values based on data measured in minutes with limited sample preparation. Thus, potential systematic errors such as extinction and twinning commonly encountered in single-crystal studies of small-unit-cell inorganic structures can be overcome with synchrotron powder diffraction. It is shown that the standard Hansen,Coppens multipole model is not flexible enough to fit the static theoretical structure factors, whereas fitting of thermally smeared structure factors has much lower residuals. If thermally smeared structure factors (experimental or theoretical) are fitted with a slightly wrong radial model (s2p2 instead of sp3) the radial scaling parameters (`,' parameters) are found to be inadequate and the `error' is absorbed into the atomic displacement parameter. This directly exposes a correlation between electron density and thermal parameters even for a light atom such as carbon, and it also underlines that in organic systems proper deconvolution of thermal motion is important for obtaining correct static electron densities. [source] A robust bulk-solvent correction and anisotropic scaling procedureACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2005Pavel V. Afonine A reliable method for the determination of bulk-solvent model parameters and an overall anisotropic scale factor is of increasing importance as structure determination becomes more automated. Current protocols require the manual inspection of refinement results in order to detect errors in the calculation of these parameters. Here, a robust method for determining bulk-solvent and anisotropic scaling parameters in macromolecular refinement is described. The implementation of a maximum-likelihood target function for determining the same parameters is also discussed. The formulas and corresponding derivatives of the likelihood function with respect to the solvent parameters and the components of anisotropic scale matrix are presented. These algorithms are implemented in the CCTBX bulk-solvent correction and scaling module. [source] | |||||||||||||