Search results for "Linear analysis"

showing 10 items of 23 documents

Experimental observations of upstream overdeepening

2005

The issue of morphodynamic influence in meandering streams is investigated through a series of laboratory experiments on curved and straight flumes. Both qualitative and quantitative observations confirm the suitability of the recent theoretical developments (Zolezzi & Seminara 2001) that indicate the occurrence of two distinct regimes of morphodynamic influence, depending on the value of the width ratio of the channel β. The threshold value βR separating the upstream from the downstream influence regimes coincides with the resonant value discovered by Blondeaux & Seminara (1985). Indeed it is observed that upstream influence may occur only in relatively wide channels, while narrower stream…

BedformMechanics of MaterialsMechanical EngineeringOverdeepeningThe issue of morphodynamic influence in meandering streams is investigated through a series of laboratory experiments on curved and straight flumes. Both qualitative and quantitative observations confirm the suitability of the recent theoretical developments (Zolezzi & Seminara 2001) that indicate the occurrence of two distinct regimes of morphodynamic influence depending on the value of the width ratio of the channel β. The threshold value βR separating the upstream from the downstream influence regimes coincides with the resonant value discovered by Blondeaux & Seminara (1985). Indeed it is observed that upstream influence may occur only in relatively wide channels while narrower streams are dominated by downstream influence. A series of experiments has been carried out in order to check the above theoretical predictions and show for the first time evidence of the occurrence of upstream overdeepening. Two different sets of experiments have been designed where a discontinuity in channel geometry was present such that the channel morphodynamics was influenced in the upstream direction under super-resonant conditions (β >βR) and in the downstream direction under sub-resonant conditions (β <βR). Experimental results give qualitative and quantitative support to the theoretical predictions and allow us to clarify the limits of the linear analysis.MechanicsLinear analysisCondensed Matter PhysicsWidth ratioGeology
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Stability of charge-pump phase-locked loops : the hold-in and pull-in ranges

2020

The problem of design and analysis of synchronization control circuits is a challenging task for many applications: satellite navigation, digital communication, wireless networks, and others. In this article the Charge-Pump Phase-Locked Loop (CP-PLL) electronic circuit, which is used for frequency synthesis and clock generation in computer architectures, is studied. Analysis of CP-PLL is not trivial: full mathematical model, rigorous definitions, and analysis still remain open issues in many respects. This article is devoted to development of a mathematical model, taking into account engineering aspects of the circuit, interpretation of core engineering problems, definition in relation to m…

CP-PLLPFDcontrol of phase synchronizationsäätöteoriaphase-frequency detectorcharge-pumpsäätötekniikkaphase-locked loopselektroniset piiritnonlinear analysispull-in rangematemaattiset mallithold-in range
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Entropy-Based Detection of Complexity and Nonlinearity in Short-Term Heart Period Variability under different Physiopathological States

2020

We compare different estimators of a popular en-tropy-based nonlinear dynamic measure, i.e. the conditional entropy (CE), as regards their ability to assess the complexity and nonlinearity of short-term heart rate variability (HRV). The CE is computed using binning, kernel and nearest neighbor entropy estimators in HRV time series measured from young, old and post-myocardial infarction patients studied at rest and during orthostatic stress. We find that the three estimators yield similar patterns of CE, but different patterns of nonlinear dynamics, across groups and conditions. These results suggest that the strategy for CE estimation is not crucial for the quantification of complexity, but…

Conditional entropynearest neighborHeart period variabilityEstimatork-nearest neighbors algorithmConditional entropy (CE)Nonlinear systemStatisticsSettore ING-INF/06 - Bioingegneria Elettronica E InformaticaEntropy (information theory)Heart rate variabilitynonlinear analysis methodTime seriescomplexityheart rate variability (HRV)Mathematics
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Nonlinear dynamical model of Costas loop and an approach to the analysis of its stability in the large

2015

The analysis of the stability and numerical simulation of Costas loop circuits for highfrequency signals is a challenging task. The problem lies in the fact that it is necessary to simultaneously observe very fast time scale of the input signals and slow time scale of phase difference between the input signals. To overcome this difficult situation it is possible, following the approach presented in the classical works of Gardner and Viterbi, to construct a mathematical model of Costas loop, in which only slow time change of signal's phases and frequencies is considered. Such a construction, in turn, requires the computation of phase detector characteristic, depending on the waveforms of the…

Costas loopphase detector characteristicstability in the largenonlinear analysisphase comparatorsimulointiphase-locked loop (PLL)BPSK
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Nonlinear dynamical model of Costas loop and an approach to the analysis of its stability in the large

2015

The analysis of the stability and numerical simulation of Costas loop circuits for high-frequency signals is a challenging task. The problem lies in the fact that it is necessary to simultaneously observe very fast time scale of the input signals and slow time scale of phase difference between the input signals. To overcome this difficult situation it is possible, following the approach presented in the classical works of Gardner and Viterbi, to construct a mathematical model of Costas loop, in which only slow time change of signal?s phases and frequencies is considered. Such a construction, in turn, requires the computation of phase detector characteristic, depending on the waveforms of th…

Costas loopta213phase detector characteristicstability in the largeta111phase comparatorsimulationPhase detectorphase-locked loop (PLL)Loop (topology)Phase-locked loopNonlinear systemControl and Systems EngineeringControl theoryCostas loopPhase spaceSignal Processingnonlinear analysisPhase detector characteristicComputer Vision and Pattern RecognitionLinear approximationElectrical and Electronic EngineeringSoftwareBPSKMathematicsSignal Processing
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ChemInform Abstract: Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds.

2010

In this work we carry out a study of pattern recognition to detect the microbiological activity in a group of heterogeneous compounds. The structural descriptors utilized are the topological connectivity indexes. The methods followed are stepwise linear discriminant analysis (linear analysis) and artificial neural network (nonlinear analysis). Although both methods are appropriate to differentiate between active and inactive compounds, the artificial neural network is, in this case, more adequate, since it shows in a test set a prediction success of 98%, versus 92% obtained with linear discriminant analysis.

Heterogeneous groupArtificial neural networkbusiness.industryChemistryTest setPattern recognition (psychology)Pattern recognitionGeneral MedicineArtificial intelligenceLinear analysisLinear discriminant analysisbusinessAntimicrobialChemInform
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Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds

1998

In this work we carry out a study of pattern recognition to detect the microbiological activity in a group of heterogeneous compounds. The structural descriptors utilized are the topological connectivity indexes. The methods followed are stepwise linear discriminant analysis (linear analysis) and artificial neural network (nonlinear analysis). Although both methods are appropriate to differentiate between active and inactive compounds, the artificial neural network is, in this case, more adequate, since it shows in a test set a prediction success of 98%, versus 92% obtained with linear discriminant analysis.

Heterogeneous groupMolecular StructureArtificial neural networkbusiness.industryLinear modelDiscriminant AnalysisPattern recognitionGeneral ChemistryLinear analysisAntimicrobialLinear discriminant analysisPattern Recognition AutomatedComputer Science ApplicationsAnti-Infective AgentsNonlinear DynamicsComputational Theory and MathematicsTest setPattern recognition (psychology)Linear ModelsNeural Networks ComputerArtificial intelligencebusinessInformation SystemsMathematicsJournal of Chemical Information and Computer Sciences
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Theoretical elastoplastic buckling of stringer stiffened cylindrical shells

1985

Abstract A linear analysis method is offered to predict the theoretical elastoplastic buckling of stringer stiffened cylindrical shells subjected to longitudinal loading. Welding residual stresses are taken into account in the calculation, but effects of geometrical imperfections and pre-buckling displacements are ignored. The examples analysed show a good correlation between the analytical results and those obtained experimentally with stocky models of moderate geometrical imperfections.

Materials scienceStringerBucklingMechanics of Materialsbusiness.industryMetals and AlloysWelding residual stressBuilding and ConstructionStructural engineeringComposite materialLinear analysisbusinessCivil and Structural EngineeringJournal of Constructional Steel Research
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A non-linear Ritz method for progressive failure analysis of variable angle tow composite laminates

2022

A Ritz formulation for non-linear analysis of damage initiation and evolution in variable angle tow composite plates under progressive loading is presented. The model is built on a few key items. It assumes first order shear deformation theory kinematics and non-liner strains in the von Karman sense. The constitutive relationships are formulated in the framework of continuum damage mechanics at the ply level, so that each laminate layer can experience in-plane damage initiation and evolution, then reflected in material softening and loss of local stiffness. A Ritz polynomial expansion of the primary variables and the minimization of the total potential energy provide the discrete solution e…

Mechanics of MaterialsContinuum damage mechanics failure analysis variable angle tow composites Ritz method non-linear analysisMechanical EngineeringGeneral MathematicsGeneral Materials ScienceSettore ING-IND/04 - Costruzioni E Strutture AerospazialiCivil and Structural Engineering
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Sul controllo del meccanismo di collasso di controventi eccentrici

2007

The effectiveness of different non-linear static procedures, for the detection of the collapse mechanism of eccentric braced frames, is investigated. EBFs introduced into truss frame structures are considered. For such a typology of structures, plastic deformations are concen-trated in a single resistant element at each floor, greatly increasing the risk of the formation of soft storey mechanisms, even if the structure is designed according to the capacity design. The results of different non-linear static procedures are compared to those obtained by incremental dynamic non-linear analysis, considering a meaningful set of artificially generated stationary accelerograms, compatible with a ta…

Non linear static analysis Incremental dynamic non-linear analysis STEEL STRUCTURES EBF: ECCENTRIC BEAM FRAMES
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