367 results on '"Induced oscillations"'
Search Results
2. Oscillation modes of a linear oscillator, induced by frequency fluctuations in the form of non-Markovian dichotomous noise
- Author
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Sirotkin, O. L.
- Subjects
non-markovian processes ,supplementary variables ,linear oscillator ,induced oscillations ,beating oscillations ,Physics ,QC1-999 - Abstract
Background and Objectives: A set of differential equations is derived for the probability density functions of the phase coordinates of dynamic systems featuring parametric fluctuations in the form of non-Markovian dichotomous noise having arbitrary distribution functions for life at the states ± 1. As an example, the first moment of the phase coordinate of an oscillator was calculated, its perturbed motion being described by a stochastic analogue of the Mathieu–Hill equation. It is intended to show that linear dynamical systems subjected to parametric fluctuations are capable of producing states not appropriate to deterministic modes. Materials and Methods: The problem is solved using the method of supplementary variables which facilitates, through an expansion of the phase space, transformation of the non-Markovian dichotomous noise into a Markovian one. Results: It has been established that sustained beating oscillations of the amplitudes are observed provided the dichotomous noise structure contains the life time distribution function as a sum of two weighted exponents describing two states of the system, i.e. ±1. Conclusion: As a matter of fact, a Markovian simulation of the oscillator features only damped oscillations. Properties of the process in question being delta-correlated or Gaussian are not utilized. The calculations are made using ordinary differential equations with no integral operators being involved.
- Published
- 2021
- Full Text
- View/download PDF
3. Calculation of the Vibration Parameters of Steam-Generator Tube Systems to Validate the Vibration Strength and Lifetime.
- Author
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Fesenko, T. N., Koretskii, S. A., and Shitova, L. I.
- Abstract
A mathematical model of the vibrations of an elastic tube bundle in a crossflow is considered. The model is applicable to predict the reaction of the tube bundle components under the action of the vortex and hydroelastic excitation mechanisms considering the intermediate supports placed with gaps between them and the tube components—the presence of the gaps is a necessary precondition for assembling the structure. The impact of the tubes–intermediate supports is taken into account by the oblique impact model with the normal and tangential components of the reaction force of the supports. The proposed mathematical model was implemented in the Matlab programming environment. The parameters of the induced vibrations of the steam-generator-tube model such as the frequency content and the root-mean-square (rms) values of the vibration-induced displacements and accelerations were calculated. The dependences of the above parameters on the design and operating characteristics were studied. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
4. Role of top-down language control in bilingual production and comprehension: Evidence from induced oscillations.
- Author
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Xie, Ning, Li, Baike, Zhang, Man, and Liu, Huanhuan
- Subjects
- *
BILINGUALISM , *COGNITIVE ability , *LANGUAGE acquisition , *COMPREHENSION , *LANGUAGE ability - Abstract
Aims: The present study was designed to investigate the role of language control during simultaneous production and comprehension. Design: Participants completed a set of language background and cognitive skills questionnaires and were randomly divided into pairs. Then, the pairs of participants were asked to finish a joint language switching task while their electroencephalogram was recorded. When one participant was naming pictures, the other one was listening. The language to be used in each trial was specified by cues. Data and Analysis: Response latencies were obtained. An analysis was conducted on induced oscillations in a cue-locked period and a stimulus-locked period. Findings: An analysis of induced oscillations showed that production and comprehension exhibited different delta and theta oscillations, suggesting that cross-modality interference may be caused by joint language switching, and bilinguals employed different degrees of language control in comprehension and production. Furthermore, the cross-person condition exhibited stronger oscillations than the within-person condition, indicating that joint language switching involves cross-person interference and that bilinguals use additional oscillations to inhibit such interference. Importantly, the stimulus-locked period showed larger delta and theta oscillations in second language switch trials than in first language switch trials in the within-person condition, indicating that delta and theta may index the inhibition of cross-language interference. Originality: The current study revealed the top-down language control mechanism by analysing induced oscillations, which reflected a mainly cognitively driven process. Significance: Bilinguals' language control might be used to inhibit complex interference during daily life. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
5. Induced Oscillations in Worm-Gear Drives of Rotary-Type Manufacturing Machines.
- Author
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Kryukov, V. A. and Preis, V. V.
- Abstract
Induced oscillations in the electromechanical worm-gear drives of rotary-type manufacturing machines are investigated. Using two design models, viz., a model with rigid linkages and a model that accounts for elastic linkages, natural frequencies have been determined and amplitude-frequency characteristics have been constructed. An asynchronous drive motor is described by the dynamic characteristic. A comparison of the results calculated using two models has established the range of the initial parameters within which the dependences can be used that were obtained from the simplest design model with rigid linkages. This will allow considerable simplification and reduction in the time of synthesizing the drive under consideration. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
6. The Spectrum of Bio-electric Activity in Response to Taste Adjectives.
- Author
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Klochkova, Olga, Pogorelova, Irina, Startseva, Marina, Alexandrov, Yuri, and Shabanov, Gennady
- Subjects
BRAIN function localization ,NEUROPHYSIOLOGY ,BIOPOTENTIALS (Electrophysiology) ,ELECTRIC stimulation ,ANALYSIS of variance - Abstract
Frequency spectra of the induced brain activity function in the range of 0.13 to 27 Hz of 16 female subjects aged 18-20 were studied. The activity was caused by reading of taste adjectives from the screen. The function significantly differs for different hemispheres in the studied frequency range. Frequency shifts ranges in the stimulation (maxima) and inhibition (minima) zones of the brain activity differential function were determined. ANOVA model implemented within the Statistica 10.0 software was used for statistical analysis of the measured data. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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- View/download PDF
7. Haptic recognition memory following short-term visual deprivation: Behavioral and neural correlates from ERPs and alpha band oscillations.
- Author
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Santaniello, Gerardo, Sebastián, Manuel, Carretié, Luis, Fernández-Folgueiras, Uxia, and Hinojosa, José Antonio
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RECOGNITION (Psychology) , *MEMORY , *EVOKED potentials (Electrophysiology) , *BRAIN waves , *VISION disorders - Abstract
In the current study, we investigated the effects of short-term visual deprivation (2 h) on a haptic recognition memory task with familiar objects. Behavioral data, as well as event-related potentials (ERPs) and induced event-related oscillations (EROs) were analyzed. At the behavioral level, deprived participants showed speeded reaction times to new stimuli. Analyses of ERPs indicated that starting from 1000 ms the recognition of old objects elicited enhanced positive amplitudes only for the visually deprived group. Visual deprivation also influenced EROs. In this sense, we observed reduced power in the lower-1 alpha band for the processing of new compared to old stimuli between 500 and 750 ms. Overall, our data showed improved haptic recognition memory after a short period of visual deprivation. These effects were thought to reflect a compensatory mechanism that might have developed as an adaptive strategy for dealing with the environment when visual information is not available. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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8. Amplified induced neural oscillatory activity predicts musicians’ benefits in categorical speech perception.
- Author
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Bidelman, Gavin M.
- Subjects
- *
EVOKED potentials (Electrophysiology) , *NEUROPLASTICITY , *MUSICIANS , *TIME-frequency analysis , *SPEECH processing systems - Abstract
Event-related brain potentials (ERPs) reveal musical experience refines neural encoding and confers stronger categorical perception (CP) and neural organization for speech sounds. In addition to evoked brain activity, the human EEG can be decomposed into induced (non-phase-locked) responses whose various frequency bands reflect different mechanisms of perceptual-cognitive processing. Here, we aimed to clarify which spectral properties of these neural oscillations are most prone to music-related neuroplasticity and which are linked to behavioral benefits in the categorization of speech. We recorded electrical brain activity while musicians and nonmusicians rapidly identified speech tokens from a sound continuum. Time-frequency analysis parsed evoked and induced EEG into alpha- (∼10 Hz), beta- (∼20 Hz), and gamma- (>30 Hz) frequency bands. We found that musicians’ enhanced behavioral CP was accompanied by improved evoked speech responses across the frequency spectrum, complementing previously observed enhancements in evoked potential studies (i.e., ERPs). Brain-behavior correlations implied differences in the underlying neural mechanisms supporting speech CP in each group: modulations in induced gamma power predicted the slope of musicians’ speech identification functions whereas early evoked alpha activity predicted behavior in nonmusicians. Collectively, findings indicate that musical training tunes speech processing via two complementary mechanisms: (i) strengthening the formation of auditory object representations for speech signals (gamma-band) and (ii) improving network control and/or the matching of sounds to internalized memory templates (alpha/beta-band). Both neurobiological enhancements may be deployed behaviorally and account for musicians’ benefits in the perceptual categorization of speech. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
9. Active Inceptor Failure as a Trigger for Pilot-Induced Oscillations
- Author
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Michael Jones and Miles Barnett
- Subjects
Pilot-Induced Oscillation ,Computer science ,Control theory ,Rotorcraft ,Induced oscillations ,Failures ,Oscillation (cell signaling) ,Isometric exercise ,Active Control Inceptor ,Active control - Abstract
The use of active inceptor systems allows for control of the aircraft even following mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor "freezes" in position, a virtual force-displacement model is used to continue to provide control input. Testing on DLR's experimental helicopter (active control technology/flying helicopter simulator) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using this mode. This paper presents results from a simulation campaign undertaken to determine whether PIOs could be exposed through this use of control and/or the resultant severity. The results show that isometric failure caused severe PIOs. Unacceptable failure characteristics were reported by all four pilots. PIO incipience was predicted through the use of offline tools. It is recommended that specific PIO investigations be undertaken during the evaluation of active inceptor failure modes.
- Published
- 2020
10. Description of the Fields of Vibration in 2D Latticed Structures with Triangular (Hexagonal) Cells
- Author
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V. L. Krupenin
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Physics ,Hexagonal crystal system ,Mechanical Engineering ,Equations of motion ,02 engineering and technology ,01 natural sciences ,Industrial and Manufacturing Engineering ,Action (physics) ,Vibration ,020303 mechanical engineering & transports ,Sine wave ,Classical mechanics ,0203 mechanical engineering ,0103 physical sciences ,Broadband ,Induced oscillations ,C++ string handling ,Safety, Risk, Reliability and Quality ,010301 acoustics - Abstract
This article deals with the problem of describing the fields of vibration in string lattices with triangular (centered hexagonal) cells. The problems of this kind have not been adequately studied despite the fact that the required models find application in the dynamic analysis of various machines and structures as well as in crystallography and materials science. Equations of motion are provided. Problems of propagation of sinusoidal waves and induced oscillations under a random broadband force action are considered.
- Published
- 2019
11. Pilot-Induced Oscillations Prevention During Aircraft Flight in Formation
- Author
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Iuliia Zaitceva and Boris Andrievsky
- Subjects
Circular motion ,business.industry ,Computer science ,Induced oscillations ,Pilot model ,Statistics::Other Statistics ,Aerospace engineering ,business ,Actuator saturation - Abstract
The paper is devoted to preventing oscillations in the angular motion of piloted aircraft by the pseudo-linear correcting device. The prime cause of this event is the unfavorable interaction between the pilot and the vehicle or the so-called pilot-induced oscillations. In this connection, it becomes necessary to consider the human influence on the piloting process to preserve the formation.
- Published
- 2021
12. Detection of Cortical Oscillations Induced by SCS Using Power Spectral Density
- Author
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P. Sovka, A. Stancak, and L. Svoboda
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Power spectral density ,failed-back surgery syndrome ,spinal cord stimulation ,induced oscillations ,EEG ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
Chronic, intractable pain of lower back and lower extremity might develop as the result of unsuccessful surgery of back. This state called failed-back surgery syndrome (FBSS) cannot be effectively treated by pharmacotherapy. Electric stimulation of the dorsal spinal cord is applied to relieve the pain. According to the medical hypothesis, oscillatory activity, which might be related to the analgesic effects, may occur in the cortex during the stimulation. To confirm the presence of the SCS induced oscillations, a new method of detection was designed for this purpose. The analysis of EEG data was performed using power spectral density, confidence intervals, visualization and group statistic for its verification. Parameters of the method were experimentally optimized to maximize its reliability. During ongoing SCS, statistically significant changes were detected and localized at the stimulation frequency and/or its subharmonic or upper harmonic over central midline electrodes in eight patients.
- Published
- 2007
13. Localization of Cortical Oscillations Induced by SCS Using Coherence
- Author
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P. Sovka, A. Stancak, and L. Svoboda
- Subjects
Magnitude squared coherence ,z-coherence ,failedback surgery syndrome ,spinal cord stimulation ,induced oscillations ,EEG ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
This paper suggests a method based on coherence analysis and scalp mapping of coherence suitable for more accurate localization of cortical oscillations induced by electric stimulation of the dorsal spinal cord (SCS), which were previously detected using spectral analysis. While power spectral density shows the increase of power during SCS only at small number of electrodes, coherence extends this area and sharpens its boundary simultaneously. Parameters of the method were experimentally optimized to maximize its reliability. SCS is applied to suppress chronic, intractable pain by patients, whom pharmacotherapy does not relieve. In our study, the pain developed in lower back and lower extremity as the result of unsuccessful vertebral discotomy, which is called failed-back surgery syndrome (FBSS). Our method replicated the results of previous analysis using PSD and extended them with more accurate localization of the area influenced by SCS.
- Published
- 2007
14. Application of Quantitative Measures for Analysing Aircraft Handling Qualities.
- Author
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Hebbar, Archana and Pashilkar, Abhay A.
- Subjects
HANDLING characteristics of airplanes ,FLIGHT ,AIRPLANE piloting ,PERFORMANCE ,STANDARD deviations - Abstract
The ease and precision with which pilot is able to handle the designated task determines the aircraft's handling qualities. Accordingly, the most common methodology for determining aircraft's handling qualities is through pilot opinions or through questionnaires. These subjective means of analysis is not reliable as the sole source of judgments. Quantitative metrics to analyse the task difficulty based on pilot's performance, supplemented with subjective decision, can provide better insight into pilot workload levels and in turn the aircraft's handling qualities. Application of few objective performance measurement techniques to flight data of a high performance fighter aircraft is discussed in this paper. Pilot/aircraft's performance under different configurations is analysed. Analysis results show that pilots usually tend to give more priority to pitch axis in case of dual axis tracking task. And pilots are therefore more aggressive in accomplishing pitch axis tracking task than in roll. Workload assessments were also performed by comparing the results of single axis tracking experiments conducted using a high fidelity flight simulator with the flight data. It is seen that when roll axis control task is exercised as the primary task, pilot's aggressiveness levels in controlling the roll control inceptor is significantly less, along with improved tracking accuracy levels. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
15. Numerical Simulation and Experiments of Flow-Induced Oscillations of Single-Cylinder With Large Passive Turbulence Control
- Author
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Hai Sun, Michael M. Bernitsas, Hongrae Park, and Ningyu Li
- Subjects
Physics ,Computer simulation ,Turbulence ,Quantitative Biology::Tissues and Organs ,Flow (psychology) ,STRIPS ,Mechanics ,Cylinder (engine) ,law.invention ,Physics::Fluid Dynamics ,Vortex-induced vibration ,law ,Fluid–structure interaction ,Induced oscillations - Abstract
Passive turbulence control (PTC) is being used in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan to enhance flow induced oscillations (FIO) of cylinders in the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter. Large PTC triggers VIV and galloping at lower flow speeds for energy harvesting. Currently, FIO of cylinders with large PTC for high Re has received limited attention and, particularly, the effect of variable PTC height on FIO of cylinders. The vast majority of ocean currents, rivers, and tides are too slow for Marine Hydro Kinetic (MHK) energy technologies to harness it. In order to enhance FIO and to initiate galloping earlier, a circular cylinder is geometrically modified using straight strips placed on the cylinder surface symmetrically PTC strips on the cylinder effectively change the flow properties. In the present study, the FIO of a single-cylinder with large PTC, on end linear-springs, is modelled and simulated using a Fluid-Structure Interaction (FSI) code. Results are verified by corresponding experimental data. Results show that VIV onset occurs at lower Re for large-PTC cylinder in comparison with lower-PTC cylinder. Contrary to smooth cylinders for which the amplitude ratio is small in the transition region between VIV and galloping, application of large PTC leads to high amplitude response in the transition region. The mechanism behind this observation is the further departure of the geometry from the smooth circular cylinder. The latter does not exhibit galloping due to flow and geometric symmetry in all directions. Moreover, in the galloping region, the amplitude ratio increases with the height of PTC. Earlier onset of galloping and enhancement of geometric asymmetry support this observation as well.
- Published
- 2021
16. Process‐induced cell cycle oscillations in CHO cultures: Online monitoring and model‐based investigation
- Author
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M��ller, Johannes, Bhat, Krathika, Riecken, Kristoffer, P��rtner, Ralf, Zeng, An-Ping, and Jandt, Uwe
- Subjects
0106 biological sciences ,0301 basic medicine ,repeated-batch ,Cell ,Population ,Ingenieurwissenschaften [620] ,Bioengineering ,CHO Cells ,Models, Biological ,01 natural sciences ,Applied Microbiology and Biotechnology ,Flow cytometry ,03 medical and health sciences ,Cricetulus ,fed-batch ,Biological Clocks ,Cricetinae ,010608 biotechnology ,medicine ,Animals ,feeding strategy ,education ,Cell synchronization ,FUCCI ,education.field_of_study ,medicine.diagnostic_test ,Chemistry ,Cell Cycle ,Cell cycle ,620: Ingenieurwissenschaften ,030104 developmental biology ,medicine.anatomical_structure ,automated flow cytometry ,Cell culture ,Induced oscillations ,Biophysics ,ddc:620 ,Experimental methods ,Biotechnology - Abstract
�� 2019 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals, Inc. The influence of process strategies on the dynamics of cell population heterogeneities in mammalian cell culture is still not well understood. We recently found that the progression of cells through the cell cycle causes metabolic regulations with variable productivities in antibody-producing Chimese hamster ovary (CHO) cells. On the other hand, it is so far unknown how bulk cultivation conditions, for example, variable nutrient concentrations depending on process strategies, can influence cell cycle-derived population dynamics. In this study, process-induced cell cycle synchronization was assessed in repeated-batch and fed-batch cultures. An automated flow cytometry set-up was developed to measure the cell cycle distribution online, using antibody-producing CHO DP-12 cells transduced with the cell cycle-specific fluorescent ubiquitination-based cell cycle indicator (FUCCI) system. On the basis of the population-resolved model, feeding-induced partial self-synchronization was predicted and the results were evaluated experimentally. In the repeated-batch culture, stable cell cycle oscillations were confirmed with an oscillating G1 phase distribution between 41% and 72%. Furthermore, oscillations of the cell cycle distribution were simulated and determined in a (bolus) fed-batch process with up to 25 �� 106 cells/ml. The cell cycle synchronization arose with pulse feeding only and ceased with continuous feeding. Both simulated and observed oscillations occurred at higher frequencies than those observable based on regular (e.g., daily) sample analysis, thus demonstrating the need for high-frequency online cell cycle analysis. In summary, we showed how experimental methods combined with simulations enable the improved assessment of the effects of process strategies on the dynamics of cell cycle-dependent population heterogeneities. This provides a novel approach to understand cell cycle regulations, control cell population dynamics, avoid inadvertently induced oscillations of cell cycle distributions and thus to improve process stability and efficiency.
- Published
- 2019
17. Bragg-induced oscillations in non-PT complex photonic lattices
- Author
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P. A. Brandão and Solange B. Cavalcanti
- Subjects
Physics ,Quantum electrodynamics ,Induced oscillations ,Plane wave ,General Physics and Astronomy ,Initial value problem ,Parity (physics) ,Trapping ,Optical field ,Gaussian beam ,Numerical integration - Abstract
We investigate Bragg-induced oscillations in complex non-PT periodic structures, that is, a periodic medium with gain and loss and not necessarily symmetric under the combined action of parity and time reversal operations. We compare our analytic results based on the expansion of the optical field in Bragg-resonant plane waves with a direct numerical integration of the paraxial wave equation beyond the shallow potential approximation and using a wide Gaussian beam as initial condition. In particular, we study under which conditions a mode trapping phenomenon may still be observed and to inspect how the energy exchange between the spectral modes takes place during propagation in this more general class of asymmetric complex potentials.
- Published
- 2019
18. Influence of Airframe Flexibility on Pilot-Induced Oscillations
- Author
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Antônio B. Guimarães Neto, Flavio J. Silvestre, and Daniel Drewiacki
- Subjects
Flexibility (engineering) ,020301 aerospace & aeronautics ,0209 industrial biotechnology ,Computer science ,Applied Mathematics ,Pilot-induced oscillation ,Aerospace Engineering ,02 engineering and technology ,Flight control surfaces ,Automotive engineering ,020901 industrial engineering & automation ,0203 mechanical engineering ,Flight dynamics ,Space and Planetary Science ,Control and Systems Engineering ,Induced oscillations ,Airframe ,Hardware_INTEGRATEDCIRCUITS ,Oscillation (cell signaling) ,Electrical and Electronic Engineering - Abstract
The advent of fly-by-wire technology brought many advantages to aircraft design, but also increased the number of occurrences of the undesirable pilot-induced oscillation phenomena. To analyze such...
- Published
- 2019
19. Induced Oscillations in Worm-Gear Drives of Rotary-Type Manufacturing Machines
- Author
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V. V. Preis and V. A. Kryukov
- Subjects
Worm drive ,business.product_category ,Computer science ,Mechanical Engineering ,02 engineering and technology ,Type (model theory) ,01 natural sciences ,Industrial and Manufacturing Engineering ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Control theory ,Asynchronous communication ,0103 physical sciences ,Induced oscillations ,Range (statistics) ,Safety, Risk, Reliability and Quality ,Reduction (mathematics) ,business ,010301 acoustics ,Drive motor - Abstract
Induced oscillations in the electromechanical worm-gear drives of rotary-type manufacturing machines are investigated. Using two design models, viz., a model with rigid linkages and a model that accounts for elastic linkages, natural frequencies have been determined and amplitude-frequency characteristics have been constructed. An asynchronous drive motor is described by the dynamic characteristic. A comparison of the results calculated using two models has established the range of the initial parameters within which the dependences can be used that were obtained from the simplest design model with rigid linkages. This will allow considerable simplification and reduction in the time of synthesizing the drive under consideration.
- Published
- 2019
20. Blood-pressure-induced oscillations of cerebral hemodynamics during hemodialysis
- Author
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Angelo Sassaroli, Thao Pham, Daniel E. Weiner, Sergio Fantini, Cristianne Fernandez, Giles Blaney, and Arushi Agarwal
- Subjects
medicine.medical_specialty ,Mean arterial pressure ,Chemistry ,medicine.medical_treatment ,Hemodynamics ,Venous blood ,Cerebral autoregulation ,Blood pressure ,Cerebral hemodynamics ,Internal medicine ,Induced oscillations ,medicine ,Cardiology ,Hemodialysis - Abstract
In a study on one patient during hemodialysis, we used near-infrared spectroscopy (NIRS) to measure coherent oscillations of cerebral concentrations of oxyhemoglobin ([HbO2]), deoxyhemoglobin ([Hb]), and total-hemoglobin ([HbT]) induced by systemic oscillations in mean arterial pressure (MAP) at a frequency of 0.07 Hz. During hemodialysis, we observed that the phase of [Hb] versus [HbO2] becomes less negative, whereas the phase of [HbT] versus MAP becomes more negative. By applying a quantitative hemodynamic model, we assign these phase changes to an increase in venous blood transit time and a less effective cerebral autoregulation during the hemodialysis process.
- Published
- 2021
21. Robustness of behaviorally induced oscillations in epidemic models under a low rate of imported cases
- Author
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David Juher, David Rojas, and Joan Saldaña
- Subjects
Oscillations ,Inflow ,Anàlisi funcional no lineal ,01 natural sciences ,Communicable Diseases ,Quantitative Biology - Quantitative Methods ,010305 fluids & plasmas ,Epidemic models ,0103 physical sciences ,Infection transmission ,Applied mathematics ,Humans ,Bifurcation theory ,Differentiable dynamical systems ,Sustained oscillations ,Teoria de la bifurcació ,Models estocàstics ,010306 general physics ,Robustness (economics) ,Epidemics ,Quantitative Biology - Populations and Evolution ,Quantitative Methods (q-bio.QM) ,Mathematics ,Behavior ,Stochastic simulations ,Models, Statistical ,High amplitude ,Ode ,Populations and Evolution (q-bio.PE) ,Sistemes dinàmics diferenciables ,Awareness ,Nonlinear functional analysis ,Stochastic models ,FOS: Biological sciences ,Induced oscillations - Abstract
This paper is concerned with the robustness of the sustained oscillations predicted by an epidemic ODE model defined on contact networks. The model incorporates the spread of awareness among individuals and, moreover, a small inflow of imported cases. These cases prevent stochastic extinctions when we simulate the epidemics and, hence, they allow to check whether the average dynamics for the fraction of infected individuals are accurately predicted by the ODE model. Stochastic simulations confirm the existence of sustained oscillations for different types of random networks, with a sharp transition from a non-oscillatory asymptotic regime to a periodic one as the alerting rate of susceptible individuals increases from very small values. This abrupt transition to periodic epidemics of high amplitude is quite accurately predicted by the Hopf-bifurcation curve computed from the ODE model using the alerting rate and the infection transmission rate for aware individuals as tuning parameters., Comment: 17 pages, 11 figures
- Published
- 2021
22. Mathematical modeling of self-induced oscillations of a segmental-conical body with free movement in the pitch angle
- Author
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E. A. Chasovnikov
- Subjects
Physics ,symbols.namesake ,Mach number ,Computer simulation ,Induced oscillations ,Process (computing) ,symbols ,Mechanics ,Pitch angle ,Transient (oscillation) ,Pitching moment ,Conical surface - Abstract
Numerical simulation of self-induced pitch oscillations of a segmental-conical body at Mach number M = 2.0 is performed using the mathematical model of the pitching moment, which includes an ordinary linear differential equation of the first order. The parameters of the mathematical model were determined from the condition of the best agreement between the calculated and experimental transient processes pitch angle in time. Numerical modeling of self-induced oscillations was also carried out using the time-lag hypothesis and concepts of aerodynamic derivatives. It is shown that the proposed mathematical model is not only satisfactory describes the experimental transient process like the other two, but also explains the known experimental effects.
- Published
- 2021
23. Quenching friction‐induced oscillations in multibody‐systems by the use of high‐frequency excitation
- Author
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Simon Keller and Wolfgang Seemann
- Subjects
Materials science ,Quenching (fluorescence) ,Induced oscillations ,ddc:620 ,Molecular physics ,Excitation ,Engineering & allied operations - Abstract
Dry friction can be a cause of undesired self-excited oscillations. One way to suppress this underlying mechanism is the superposition of high-frequency vibrations whereby the effective friction characteristics is changed and a quasi-equilibrium can be stabilized. This damping effect is analyzed in detail for single-degree-of-freedom systems [1] and experiments and simulations show a good accordance [2]. In this work, the analytical approach from [1] is used to analyze the stabilizing effect of superposed oscillations for a two-degree-of-freedom system subject to friction.
- Published
- 2021
- Full Text
- View/download PDF
24. New eclipsing binaries with mercury-manganese stars
- Author
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J. Labadie-Bartz, Oleg Kochukhov, Viktor Khalack, and Matt Shultz
- Subjects
media_common.quotation_subject ,FOS: Physical sciences ,Context (language use) ,Astrophysics ,01 natural sciences ,early-type [stars] ,chemically peculiar [stars] ,Astronomi, astrofysik och kosmologi ,0103 physical sciences ,Binary star ,Astrophysics::Solar and Stellar Astrophysics ,Astronomy, Astrophysics and Cosmology ,Eccentricity (behavior) ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,media_common ,Eclipse ,Physics ,010308 nuclear & particles physics ,White dwarf ,Astronomy and Astrophysics ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Induced oscillations ,binaries: eclipsing [stars] ,Astrophysics::Earth and Planetary Astrophysics ,binaries: spectroscopic [stars] - Abstract
Eclipsing binary stars are rare and extremely valuable astrophysical laboratories that make possible precise determination of fundamental stellar parameters. Investigation of early-type chemically peculiar stars in eclipsing binaries provides important information for understanding the origin and evolutionary context of their anomalous surface chemistry. In this study we discuss observations of eclipse variability in six mercury-manganese (HgMn) stars monitored by the TESS satellite. These discoveries double the number of known eclipsing HgMn stars and yield several interesting objects requiring further study. In particular, we confirm eclipses in HD 72208, thereby establishing this object as the longest-period eclipsing HgMn star. Among five other eclipsing binaries, reported here for the first time, HD 36892 and HD 53004 stand out as eccentric systems showing heartbeat variability in addition to eclipses. The latter object has the highest eccentricity among eclipsing HgMn stars and also exhibits tidally induced oscillations. Finally, we find evidence that HD 55776 may be orbited by a white dwarf companion., Comment: 5 pages, 5 figures; accepted for publication in MNRAS
- Published
- 2021
25. Modal contribution of bundle oscillation to induced flow.
- Author
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Capanna, Roberto, Sarrouy, Emmanuelle, Ricciardi, Guillaume, and Bardet, Philippe M.
- Subjects
- *
PRESSURIZED water reactors , *POTENTIAL flow , *PROPER orthogonal decomposition , *PULSATILE flow , *AXIAL flow , *PARTICLE image velocimetry - Abstract
Bundle motion of a pressurized water reactor core under seismic excitation induces a pulsatile oscillatory flow which can strongly affect the behaviour of the whole reactor. Understanding these phenomena is thus a primary concern for the nuclear industry. An index matched experimental facility was recently built allowing the study of a surrogate fuel bundle under axial flow undergoing a seismic excitation. The use of a fluid which is refractive index matched with the transparent surrogate bundle allows to perform non-intrusive particle image velocimetry measurements over the whole fluid domain. This paper focuses on experiments performed with a shaking table frequency close to the first resonance mode of the bundle under otherwise stagnant water. The local flow induced by the oscillation of the fuel bundle is then observed. Three significant dataset are analysed to understand how very small changes in the structural behaviour of the fuel bundle can lead to important changes in the flow field. A proper orthogonal decomposition of the bundle excitation shows that the higher modes (even if they have small amplitudes) can contribute significantly to the flow induced in the channel. A numerical simulation based on the potential flow theory simulates the experimental conditions and provides a physical interpretation of the observed phenomena. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
26. Modeling of a Hydrokinetic Energy Converter With Two Tandem Cylinders in Flow-Induced Oscillations
- Author
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Michael M. Bernitsas, Yanfang Lv, and Sun Hai
- Subjects
Physics ,Tandem ,Flow (mathematics) ,Energy converter ,Induced oscillations ,Mechanics - Abstract
Flow Induced Oscillations (FIO) of tandem cylinders can be enhanced to harness hydrokinetic energy by varying the system parameters. In general, the Converter consists of two mass–spring–damper oscillators subjected to transverse FIOs and specifically Vortex Induced Vibrations and galloping. These FIOs are strongly influenced by variations of the inflow velocity, damping, stiffness, mass and in-flow center-to-center spacing L between two tandem cylinders. In turn, those influence the harnessed power and efficiency of the Converter. In previous experiments, the interactions between the cylinders were proven to be beneficial for the synergy of the cylinders. In this paper, modeling of tandem-cylinder converters is studied considering the Converter parameters, aiming at enhancing the cylinder synergy resulting in increased harnessed power by using a backpropagation (BP) neural network. The main conclusions are: (1) The surrogate model is constructed by a BP network using the experimental data to reduce excessive experimentation or computational inaccuracy. The harnessed power at different flow velocities is computed by the present model and is found to be consistent with experimental results not included in the modeling. (2) Increasing the damping ratio (0.20–0.30) of two tandem cylinders is conducive to improve the power efficiency, but has little effect on power harvesting. (3) In galloping, the harnessed power and its corresponding efficiency for the case of L/D = 1.57 perform at a higher level than that of bigger spacing ratios.
- Published
- 2020
27. Reconstruction of Process Forces in a Five-Axis Milling Center with a LSTM Neural Network in Comparison to a Model-Based Approach
- Author
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Berend Denkena, Benjamin Bergmann, and Dennis Stoppel
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Artificial neural network ,0209 industrial biotechnology ,business.product_category ,Mean squared error ,Computer science ,media_common.quotation_subject ,Dewey Decimal Classification::600 | Technik::620 | Ingenieurwissenschaften und Maschinenbau ,02 engineering and technology ,010501 environmental sciences ,Inertia ,01 natural sciences ,Industrial and Manufacturing Engineering ,020901 industrial engineering & automation ,process monitoring ,ddc:650 ,0105 earth and related environmental sciences ,media_common ,lcsh:T58.7-58.8 ,machine tools ,Machine tools ,Dynamometer ,Mechanical Engineering ,Process (computing) ,Dewey Decimal Classification::600 | Technik::650 | Management ,Machine tool ,Mechanics of Materials ,Test set ,Induced oscillations ,Process monitoring ,ddc:620 ,business ,lcsh:Production capacity. Manufacturing capacity ,Algorithm ,artificial neural network - Abstract
Based on the drive signals of a milling center, process forces can be reconstructed. Therefore, a novel approach is presented to reconstruct the process forces with a long short-term memory neural network (LSTM) using drive signals as an input. The LSTM is evaluated and compared to a model-based approach. The latter compensates nonlinearities and disturbances such as friction and inertia. For training of the LSTM, multiple milling processes are considered to enhance the generalizability. Training data is generated by recording drive signals and process forces measured by a dynamometer. The LSTM is then evaluated using a test set, which comprises new process parameters. It is shown that the LSTM has a lower root mean square error (RMSE) in comparison to the model-based approach. Especially, when changing the feed motion direction during milling, the neural network clearly outperforms the model-based approach. Nevertheless, there are processes, where the LSTM induced oscillations, which do not correspond to the measured forces. © 2020 MDPI Multidisciplinary Digital Publishing Institute. All rights reserved.
- Published
- 2020
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28. Differences in visually induced MEG oscillations reflect differences in deep cortical layer activity
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Earl K. Miller and Dimitris A. Pinotsis
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0301 basic medicine ,Visual perception ,genetic structures ,Computer science ,QH301-705.5 ,Models, Neurological ,Medicine (miscellaneous) ,Sensory system ,Bayesian inference ,Article ,General Biochemistry, Genetics and Molecular Biology ,Neural activity ,03 medical and health sciences ,0302 clinical medicine ,Neuroimaging ,Psychology ,Humans ,Layer (object-oriented design) ,Biology (General) ,030304 developmental biology ,Cerebral Cortex ,0303 health sciences ,Computational model ,Magnetoencephalography ,Bayes Theorem ,Laminar flow ,030104 developmental biology ,Synapses ,Induced oscillations ,Visual Perception ,RC0321 ,Nerve Net ,General Agricultural and Biological Sciences ,Neuroscience ,030217 neurology & neurosurgery - Abstract
Neural activity is organized at multiple scales, ranging from the cellular to the whole brain level. Connecting neural dynamics at different scales is important for understanding brain pathology. Neurological diseases and disorders arise from interactions between factors that are expressed in multiple scales. Here, we suggest a new way to link microscopic and macroscopic dynamics through combinations of computational models. This exploits results from statistical decision theory and Bayesian inference. To validate our approach, we used two independent MEG datasets. In both, we found that variability in visually induced oscillations recorded from different people in simple visual perception tasks resulted from differences in the level of inhibition specific to deep cortical layers. This suggests differences in feedback to sensory areas and each subject’s hypotheses about sensations due to differences in their prior experience. Our approach provides a new link between non-invasive brain imaging data, laminar dynamics and top-down control., Pinotsis and Miller present a simplified neural mass model for estimating the laminar dynamics that contribute to non-invasively recorded time frequency data. Using two independent MEG datasets, they give evidence for deep cortical layers contributing to inter-individual variability in visually induced oscillations. Their study links non-invasive brain imaging data, laminar dynamics and top-down control.
- Published
- 2020
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29. The use of the Open-Loop Onset Point (OLOP) to predict rotorcraft pilot-induced oscillations
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Michael Jones
- Subjects
020301 aerospace & aeronautics ,Pilot-Induced Oscillations ,Computer science ,Open-loop controller ,Aerospace Engineering ,Boundary (topology) ,Transportation ,Hubschrauber ,PIO ,02 engineering and technology ,01 natural sciences ,010305 fluids & plasmas ,Task (project management) ,APC ,OLOP ,0203 mechanical engineering ,Control theory ,Rotorcraft ,0103 physical sciences ,Induced oscillations ,Pilot model ,HQ ,Point (geometry) ,Category II ,Simulation - Abstract
The Open-Loop Onset Point (OLOP) criterion has, for many years, been successfully used as a method to predict quasi-non-linear pilot-induced oscillations (PIOs) for fixed-wing aircraft. Only limited research has been conducted using the criterion for prediction of PIOs occurring in rotorcraft. This paper details a study to extend the application of OLOP to rotorcraft, using the combination of control inputs appropriate for the task and a suitable pilot model. Results are compared between pilot subjective opinion and OLOP predictions, from tests performed in a ground-based simulation facility. Using ‘task-specific’ application of OLOP, results obtained in the investigation are encouraging, whereby the objective predictions reflect subjective pilot assessment. From results obtained, a modified boundary is presented.
- Published
- 2020
30. Upscaling Low Salinity Water Flooding in Heterogenous Reservoirs
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Hasan Al-Ibadi, Karl Dunbar Stephen, and Eric James Mackay
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Permeability (earth sciences) ,Low salinity ,Random field ,Induced oscillations ,Soil science ,Water flooding ,Relative permeability ,Grid ,Scale model ,Geology - Abstract
Summary Modelling the dynamic fluid behaviour of Low Salinity Water Flooding (LSWF) at the reservoir scale is a challenge which requires a coarse grid enable prediction in a feasible timescale. However, evidence shows that using low resolution models will result in a considerable mismatch compared with an equivalent fine scale model with the potential of strong numerically induced oscillations. This work examines two new upscaling methods in a heterogenous reservoir where viscous crossflow takes place to improve the precision of predictions. We apply two approaches to upscaling of the flow to improve precision. In the first upscaling method, we shift the effective salinity range for the coarse model based on algorithms that we have developed to correct for numerical dispersion. The second upscaling method uses appropriate pseudo relative permeability curves that we derive. The shape of this new set of relative permeability is designed based on a modified fractional flow analysis of LSWF that we have developed and captures the relationship between dispersion and the waterfront velocities. This approach removes the need for explicit simulation of salinity transport. We applied these approaches in layered models and for permeability distributed as a correlated random field. Upscaling by shifting the effective salinity range of the coarse model gave a good match to the fine case scenario, while considerable mismatch was observed for traditional upscaling of the absolute permeability only using averaging methods. For highly coarsened models, this method of upscaling reduces the oscillations appear, but they can be apparent. On the other hand, upscaling by using a single (pseudo) relative permeability produced more robust results with a very promising match to the fine scale scenario. These methods of upscaling showed promising results where they were used to upscale fully communicating and non-communicating layers as well as models with randomly correlated permeability. Unlike documented methods in literate, these newly derived methods take into account the crucial effect of numerical dispersion and effective concentration on fluid dynamic using mathematical tools. These methods could be applied for other models where the phase mobilities change as a result of an injected solute, such as surfactant flooding and alkaline flooding. Usually these models use two sets of relative permeability and switch from one to another as a function of the concentration of the solute.
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- 2020
31. Nonlinear phase-amplitude reduction of delay-induced oscillations
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Kiyoshi Kotani, Akihiko Akao, Sho Shirasaka, Yutaro Ogawa, Yasuhiko Jimbo, and Hiroya Nakao
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Physics ,Bistability ,Quantitative Biology::Molecular Networks ,Dynamics (mechanics) ,Phase (waves) ,FOS: Physical sciences ,Amplitude reduction ,Nonlinear Sciences - Adaptation and Self-Organizing Systems ,Intensity (physics) ,Reduction (complexity) ,Nonlinear system ,Quantum electrodynamics ,Induced oscillations ,Adaptation and Self-Organizing Systems (nlin.AO) - Abstract
Spontaneous oscillations induced by time delays are observed in many real-world systems. Phase reduction theory for limit-cycle oscillators described by delay-differential equations (DDEs) has been developed to analyze their synchronization properties, but it is applicable only when the perturbation applied to the oscillator is sufficiently weak. In this study, we formulate a nonlinear phase-amplitude reduction theory for limit-cycle oscillators described by DDEs on the basis of the Floquet theorem, which is applicable when the oscillator is subjected to perturbations of moderate intensity. We propose a numerical method to evaluate the leading Floquet eigenvalues, eigenfunctions, and adjoint eigenfunctions necessary for the reduction and derive a set of low-dimensional nonlinear phase-amplitude equations approximately describing the oscillator dynamics. By analyzing an analytically tractable oscillator model with a cubic nonlinearity, we show that the asymptotic phase of the oscillator state in an infinite-dimensional state space can be approximately evaluated and non-trivial bistability of the oscillation amplitude caused by moderately strong periodic perturbations can be predicted on the basis of the derived phase-amplitude equations. We further analyze a model of gene-regulatory oscillator and illustrate that the reduced equations can elucidate the mechanism of its complex dynamics under non-weak perturbations, which may be relevant to real physiological phenomena such as circadian rhythm sleep disorders.
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- 2020
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32. Switching induced oscillations in discrete one-dimensional systems
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Enrique Peacock-López and Steve A. Mendoza
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General Mathematics ,Applied Mathematics ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,01 natural sciences ,010305 fluids & plasmas ,Ecosystem model ,0103 physical sciences ,Attractor ,Induced oscillations ,Statistical physics ,Alternation (linguistics) ,010306 general physics ,Mathematics - Abstract
In ecological modeling, seasonality can be represented as an alternation between environmental conditions. We consider a switching strategy that alternates between two undesirable dynamics and find that they can yield a desirable periodic behavior in the case of the Beverton–Holt, Ricker, and modified Ricker maps, which have been extensively used to model ecological populations. For the Ricker and modified Ricker models, we observe coexistence of attractors, which, under the same conditions, define basin of attractions, and the final dynamic behavior depends on the initial conditions.
- Published
- 2018
33. Reducing Quantization Effects in Motion Control via Dual-Stage Actuators and Induced Oscillations
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Aurelio T. Salton, Jinchuan Zheng, Jeferson Vieira Flores, and Minyue Fu
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Harmonic analysis ,Physics ,Quantization (physics) ,Control theory ,Induced oscillations ,Estimator ,Kalman filter ,Motion control ,Actuator ,Dual stage - Abstract
This paper explores the concept of dual-stage actuators in order to reduce the errors generated by output quantization in motion systems. Oscillations are induced upon the quantized actuator such that its trajectory is reconstructible by a model-free estimator. Based on the nature of these oscillations and on intermittent measurements that indicate when the output crossed from one quantization region to another, the exact value of the actuator output is computed. The micro actuator is then used to compensate the error generated by these oscillations and achieve an improved steady-state response. Simulation results show a promising perspective for the proposed approach.
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- 2019
34. Pilot-Induced Oscillations and Their Prevention
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Iuliia Zaitceva, Dmitry G. Arseniev, Nikolay Kuznetsov, and Boris Andrievsky
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High rate ,0209 industrial biotechnology ,020901 industrial engineering & automation ,Computer science ,Control theory ,parasitic diseases ,Induced oscillations ,technology, industry, and agriculture ,02 engineering and technology ,human activities - Abstract
The paper is devoted to such an important problem of piloted aircraft control as an unfavorable aircraft-pilot coupling. Mainly, the so-called Pilot-Induced Oscillations, i.e., long uncontrolled irregular oscillations which may happen due to the controlling surface magnitude and rate limitations when pilot attempts to control the aircraft with the high rate and accuracy. The simulation and in-flight test results of several PIO events are described, and the literature overview of the PIO prevention method is given.
- Published
- 2019
35. Torsional behavior of multistory RC frame structures due to asymmetric seismic interaction
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Maria C. Naoum and Chris G. Karayannis
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021110 strategic, defence & security studies ,business.industry ,0211 other engineering and technologies ,Torsion (mechanics) ,020101 civil engineering ,02 engineering and technology ,Structural engineering ,Reinforced concrete ,0201 civil engineering ,Seismic analysis ,Nonlinear system ,Induced oscillations ,Interaction type ,business ,Geology ,Civil and Structural Engineering - Abstract
Collisions between structures due to seismic oscillations have been reported many times in literature as a common case of damage. Further it is quite usual seismically induced oscillations of a structure in a city center block of buildings to be partly restrained in lateral displacements and therefore torsional behavior to be introduced in the structure. Two different types of structural interaction may be defined: (a) Diaphragm-to-diaphragm collisions (Type A). (b) The floor levels of the two structures are different. Consequently during the seismic oscillations the diaphragms of the first one impact the columns of the other (Τype B or interstory pounding). In this work the cases of an 8-story reinforced concrete building that suffers pounding with an adjacent structure that has 1, 2, 3, 4, 5, 6, 7 or 8 stories are studied. Pounding occurs only in one (Case 1) or in two (Case 2) columns of the structures and since the other columns are free to move without restrictions a torsional behavior is introduced (asymmetric pounding). Moreover in Type B interaction these columns of the 8-story frame structure undergo impacts at a height equal to 2/3 of their deformable length from the diaphragms of the other structure. The influence of an initial distance between the two interacting structures on the torsion effect is investigated too. Nonlinear seismic step-by-step analyses are performed. More than two hundred pounding cases with torsional effect each one for three natural seismic excitations are studied. Results in terms of shear and ductility demands of the columns are presented and commented. Both types A and B yielded high torsional structural rotation. In interaction Type B it can be deduced from the cases under examination that the column that is endured the impact from the top floor of the other structure develops high shear demands that exceed the available capacity many times during the step-by-step seismic analysis. Moreover high ductility demands have been observed for this column. Finally it is concluded that for buildings that may undergo asymmetric pounding not taking it into account may lead under certain conditions to non-secure design or even critical situations.
- Published
- 2018
36. Influence of chest compression artefact on capnogram-based ventilation detection during out-of-hospital cardiopulmonary resuscitation
- Author
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Luis A. Leturiondo, James K. Russell, Jesus Ruiz, Mikel Leturiondo, Dana Zive, Digna M. González-Otero, Mohamud Daya, Sofía Ruiz de Gauna, and José Julio Gutiérrez
- Subjects
medicine.medical_specialty ,medicine.medical_treatment ,Electric Countershock ,Heart Massage ,030204 cardiovascular system & hematology ,Emergency Nursing ,Sensitivity and Specificity ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,Capnography ,law ,Internal medicine ,Hyperventilation ,medicine ,Humans ,Cardiopulmonary resuscitation ,Out of hospital ,medicine.diagnostic_test ,business.industry ,Respiration ,030208 emergency & critical care medicine ,Compression (physics) ,Cardiopulmonary Resuscitation ,Ventilation (architecture) ,Induced oscillations ,Emergency Medicine ,Cardiology ,medicine.symptom ,Artifacts ,Cardiology and Cardiovascular Medicine ,business ,Algorithms ,Defibrillators - Abstract
Background Capnography has been proposed as a method for monitoring the ventilation rate during cardiopulmonary resuscitation (CPR). A high incidence (above 70%) of capnograms distorted by chest compression induced oscillations has been previously reported in out-of-hospital (OOH) CPR. The aim of the study was to better characterize the chest compression artefact and to evaluate its influence on the performance of a capnogram-based ventilation detector during OOH CPR. Methods Data from the MRx monitor–defibrillator were extracted from OOH cardiac arrest episodes. For each episode, presence of chest compression artefact was annotated in the capnogram. Concurrent compression depth and transthoracic impedance signals were used to identify chest compressions and to annotate ventilations, respectively. We designed a capnogram-based ventilation detection algorithm and tested its performance with clean and distorted episodes. Results Data were collected from 232 episodes comprising 52 654 ventilations, with a mean (±SD) of 227 (±118) per episode. Overall, 42% of the capnograms were distorted. Presence of chest compression artefact degraded algorithm performance in terms of ventilation detection, estimation of ventilation rate, and the ability to detect hyperventilation. Conclusion Capnogram-based ventilation detection during CPR using our algorithm was compromised by the presence of chest compression artefact. In particular, artefact spanning from the plateau to the baseline strongly degraded ventilation detection, and caused a high number of false hyperventilation alarms. Further research is needed to reduce the impact of chest compression artefact on capnographic ventilation monitoring.
- Published
- 2018
37. Haptic recognition memory following short-term visual deprivation: Behavioral and neural correlates from ERPs and alpha band oscillations
- Author
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Manuel Sebastián, José A. Hinojosa, Luis Carretié, Gerardo Santaniello, and Uxía Fernández-Folgueiras
- Subjects
Adult ,Male ,medicine.medical_specialty ,genetic structures ,Audiology ,050105 experimental psychology ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Reaction Time ,medicine ,Humans ,0501 psychology and cognitive sciences ,Evoked Potentials ,Recognition memory ,Haptic technology ,Neural correlates of consciousness ,General Neuroscience ,05 social sciences ,Electroencephalography ,Recognition, Psychology ,Term (time) ,Haptic memory ,Alpha Rhythm ,Memory, Short-Term ,Neuropsychology and Physiological Psychology ,Behavioral data ,Alpha band ,Induced oscillations ,Female ,Psychology ,Photic Stimulation ,030217 neurology & neurosurgery - Abstract
In the current study, we investigated the effects of short-term visual deprivation (2 h) on a haptic recognition memory task with familiar objects. Behavioral data, as well as event-related potentials (ERPs) and induced event-related oscillations (EROs) were analyzed. At the behavioral level, deprived participants showed speeded reaction times to new stimuli. Analyses of ERPs indicated that starting from 1000 ms the recognition of old objects elicited enhanced positive amplitudes only for the visually deprived group. Visual deprivation also influenced EROs. In this sense, we observed reduced power in the lower-1 alpha band for the processing of new compared to old stimuli between 500 and 750 ms. Overall, our data showed improved haptic recognition memory after a short period of visual deprivation. These effects were thought to reflect a compensatory mechanism that might have developed as an adaptive strategy for dealing with the environment when visual information is not available.
- Published
- 2018
38. Power extraction from stall-induced oscillations of an airfoil
- Author
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Daniel Pereira, Muhammad R. Hajj, Flávio D. Marques, and Mohamed Y. Zakaria
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Physics ,Airfoil ,Mechanical Engineering ,Limit cycle oscillation ,Stall (fluid mechanics) ,Aerodynamics ,Mechanics ,Aeroelasticity ,01 natural sciences ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Nonlinear system ,0103 physical sciences ,Induced oscillations ,General Materials Science ,010301 acoustics ,Energy harvesting - Abstract
Aerodynamic and structural nonlinearities of aeroelastic systems control different aspects of their limit cycle oscillations and bifurcations. One strong nonlinear unsteady aerodynamic effect that results in self-induced oscillations of airfoils is the dynamic stall. So, the concept of power extraction from stall-induced oscillations of a pitching airfoil is investigated. Experiments are performed to explore and enhance the conversion of the oscillations of a NACA0012 airfoil that is restrained elastically in pitching to electrical power. Wind tunnel tests are performed on an airfoil model connected to a DC electric motor to harvest the energy. The effects of varying the position of the axle, which defines the elastic axis, are investigated. Bifurcation diagrams as the air speed is increased and average power estimates for different experimental conditions are used to analyze the power extraction features. The results show an aerodynamic efficiency of about 40% indicating that an airfoil oscillating under the effects of dynamic stall is an adequate platform for energy harvesting.
- Published
- 2017
39. Oscillatory characteristics of the visual mismatch negativity: what evoked potentials aren't telling us.
- Author
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Stothart, George and Kazanina, Nina
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EVOKED potentials (Electrophysiology) ,YOUNG adults ,BIOPOTENTIALS (Electrophysiology) ,ELECTROENCEPHALOGRAPHY ,TRANSCRANIAL magnetic stimulation - Abstract
The visual mismatch negativity (vMMN) response is typically examined by subtracting the average response to a deviant stimulus from the response to the standard. This approach, however, can omit a critical element of the neural response, i.e., the non-phase-locked ("induced") oscillatory activity. Recent investigations of the oscillatory characteristics of the auditory mismatch negativity (aMMN) identified a crucial role for theta phase locking and power. Oscillatory characteristics of the vMMN from 39 healthy young adults were investigated in order to establish whether theta phase locking plays a similar role in the vMMN response. We explored changes in phase locking, overall post-stimulus spectral power as well as non-phase-locked spectral power compared to baseline (-300 to 0ms). These were calculated in the frequency range of 4-50 Hz and analysed using a non-parametric cluster based analysis. vMMN was found intermittently in a broad time interval 133-584 ms post-stimulus and was associated with an early increase in theta phase locking (75-175ms post-stimulus) that was not accompanied by an increase in theta power. Theta phase locking in the absence of an increase in theta power has been associated with the distribution and flow of information between spatially disparate neural locations. Additionally, in the 450-600ms post-stimulus interval, deviant stimuli yielded a stronger decrease in non-phase-locked alpha power than standard stimuli, potentially reflecting a shift in attentional resources following the detection of change. The examination of oscillatory activity is crucial to the comprehensive analysis of a neural response to a stimulus, and when combined with evoked potentials (EPs) provide a more complete picture of neurocognitive processing. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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40. Increasing the reactant conversion through induced oscillations in a continuous stirred tank reactor by using PI control.
- Author
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Pérez-Polo, Manuel F. and Pérez-Molina, Manuel
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- *
OSCILLATIONS , *PROPORTIONAL control systems , *TANKS , *CURVES , *GRAPHIC arts , *PROCESS control systems - Abstract
Highlights: [•] Complete model of a PI controlled CSTR to research its self-oscillating behavior. [•] Incorporation of two PI controllers to produce sustained oscillations. [•] Determination of cusp point and lobe curves as a function of the PI parameters. [•] Reactant conversion increment through oscillations generated by the PI controllers. [•] Graphics to choose the PI controller parameters to analyze the reactant conversion. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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41. Self-oscillating chaotic behavior and induced oscillations of a continuous stirred tank reactor with nonlinear control
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Pérez-Polo, Manuel F. and Pérez-Molina, Manuel
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- *
CHAOS theory , *OSCILLATIONS , *STORAGE tanks , *CHEMICAL reactors , *NONLINEAR control theory , *PROPYLENE oxide , *PROPYLENE glycols , *LYAPUNOV exponents , *SULFUR acids , *WATER - Abstract
Abstract: We analyze the dynamical properties of a continuous stirred tank reactor (CSTR) to produce propylene glycol from propylene oxide with an excess of water containing sulfur acid and methanol assuming an exothermic pseudo-first order reaction. The self-oscillation behavior is briefly treated, and when this state is achieved, it is shown that a sinusoidal variation of the reactor coolant flow rate may produce chaotic behavior. The chaotic oscillations are researched from the bifurcation diagrams, whereas sensitive dependence, Lyapunov exponents and power spectral density and surrogate computations allow to corroborate the presence of chaos. The chaotic behavior is used in connection with a nonlinear control law (based on differential geometry methods) which is applied to reach an arbitrary set point with very small control signals, even in the presence of random noise. On the basis of the nonlinear control law, new control signals are deduced to obtain induced oscillations both in the concentration and reactor temperature. In this case two new dynamical behaviors have been obtained by means of two different strategies: choosing an oscillation frequency with arbitrary amplitude or choosing the amplitude with arbitrary frequency. [Copyright &y& Elsevier]
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- 2012
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42. Lateralization of Frequency-Specific Networks for Covert Spatial Attention to Auditory Stimuli.
- Author
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Thorpe, Samuel, D'Zmura, Michael, and Srinivasan, Ramesh
- Abstract
We conducted a cued spatial attention experiment to investigate the time-frequency structure of human EEG induced by attentional orientation of an observer in external auditory space. Seven subjects participated in a task in which attention was cued to one of two spatial locations at left and right. Subjects were instructed to report the speech stimulus at the cued location and to ignore a simultaneous speech stream originating from the uncued location. EEG was recorded from the onset of the directional cue through the offset of the inter-stimulus interval (ISI), during which attention was directed toward the cued location. Using a wavelet spectrum, each frequency band was then normalized by the mean level of power observed in the early part of the cue interval to obtain a measure of induced power related to the deployment of attention. Topographies of band specific induced power during the cue and inter-stimulus intervals showed peaks over symmetric bilateral scalp areas. We used a bootstrap analysis of a lateralization measure defined for symmetric groups of channels in each band to identify specific lateralization events throughout the ISI. Our results suggest that the deployment and maintenance of spatially oriented attention throughout a period of 1,100 ms is marked by distinct episodes of reliable hemispheric lateralization ipsilateral to the direction in which attention is oriented. An early theta lateralization was evident over posterior parietal electrodes and was sustained throughout the ISI. In the alpha and mu bands punctuated episodes of parietal power lateralization were observed roughly 500 ms after attentional deployment, consistent with previous studies of visual attention. In the beta band these episodes show similar patterns of lateralization over frontal motor areas. These results indicate that spatial attention involves similar mechanisms in the auditory and visual modalities. [ABSTRACT FROM AUTHOR]
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- 2012
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43. Intertrial coherence and causal interaction among independent EEG components
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Zervakis, M., Michalopoulos, K., Iordanidou, V., and Sakkalis, V.
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- *
ALZHEIMER'S disease , *EVOKED potentials (Electrophysiology) , *ELECTROENCEPHALOGRAPHY , *ATTENTION , *COGNITION , *SHORT-term memory - Abstract
Abstract: Over the past few years there has been an increased interest in studying the underlying neural mechanism of attention and cognitive brain activity. This paper aims towards identifying and analyzing distinct responses in an auditory working memory paradigm, as independent components with variable latency, frequency and phase characteristics. The event-related nature of components (either phase or non-phase-locked) over multiple trials is thoroughly examined through intertrial coherence measures. Furthermore, the functional coupling of independent components is investigated through the concept of partial directed coherence depicted as a directed graph. Using these tools, the paper compares issues of activation, connectivity and directionality in the synchronization maps of two populations, of control and Alzheimer''s subjects. The results on real data from an oddball experiment verify and further enhance the findings of previous studies and illustrate the potential of the proposed analysis framework. [Copyright &y& Elsevier]
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- 2011
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44. Induced theta oscillations as biomarkers for alcoholism
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Andrew, Colin and Fein, George
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- *
ALCOHOLISM , *EVOKED potentials (Electrophysiology) , *OSCILLATIONS , *BIOMARKERS , *ELECTROENCEPHALOGRAPHY , *SYNCHRONIZATION , *ANALYSIS of covariance , *STIMULUS generalization , *TEMPERANCE - Abstract
Abstract: Objective: Studies have suggested that non-phase-locked event-related oscillations (ERO) in target stimulus processing might provide biomarkers of alcoholism. This study investigates the discriminatory power of non-phase-locked oscillations in a group of long-term abstinent alcoholics (LTAAs) and non-alcoholic controls (NACs). Methods: EEGs were recorded from 48 LTAAs and 48 age and gender comparable NACs during rest with eyes open (EO) and during the performance of a three-condition visual target detection task. The data were analyzed to extract resting power, ERP amplitude and non-phase-locked ERO power measures. Data were analyzed using MANCOVA to determine the discriminatory power of induced θ ERO vs. resting θ power vs. P300 ERP measures in differentiating the LTAA and NAC groups. Results: Both groups showed significantly more θ power in the pre-stimulus reference period of the task vs. the resting EO condition. The resting θ power did not discriminate the groups, while the LTAAs showed significantly less pre-stimulus θ power vs. the NACs. The LTAAs showed a significantly larger θ event-related synchronization (ERS) to the target stimulus vs. the NACs, even after accounting for pre-stimulus θ power levels. ERS to non-target stimuli showed smaller induced oscillations vs. target stimuli with no group differences. Alcohol use variables, a family history of alcohol problems, and the duration of alcohol abstinence were not associated with any θ power measures. Conclusions: While reference θ power in the task and induced θ oscillations to target stimuli both discriminate LTAAs and NACs, induced θ oscillations better discriminate the groups. Induced θ power measures are also more powerful and independent group discriminators than the P3b amplitude. Significance: Induced frontal θ oscillations promise to provide biomarkers of alcoholism that complement the well-established P300 ERP discriminators. [Copyright &y& Elsevier]
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- 2010
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45. Impulsivity, anxiety, and individual differences in evoked and induced brain oscillations
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Knyazev, Gennady G., Levin, Evgenij A., and Savostyanov, Alexander N.
- Subjects
- *
IMPULSIVE personality , *ANXIETY , *INDIVIDUAL differences , *BRAIN function localization - Abstract
Abstract: There is much evidence to confirm the view that slow waves of delta and theta ranges are linked to activation whereas alpha oscillations are somehow related to inhibition processes. In the domain of individual differences, impulsive behavior is frequently associated with increased spectral power of slow oscillations whereas Behavioral Inhibition (BI) may be associated with higher reactivity within alpha band. Here it is hypothesized that Impulsivity would predispose to higher responding in low frequencies whereas BI would predispose to higher responding within alpha band. In a sample of 51 subjects, evoked and induced responses to auditory stimuli were studied in two experimental sessions: 1) in a simple discrimination task and 2) in a stop-signal task in which subjects had to be ready to withdraw the prepared motor response. Impulsive subjects showed higher baseline delta, theta and alpha power and higher magnitude of induced responses in low frequencies. They also showed lower phase-locking in low frequencies to auditory stimuli and higher phase-locking to the overt behavioral response onset. High BI scorers showed higher baseline alpha power and higher desynchronization in this frequency band in response to stimuli. The reported findings appear to support the idea that low frequency oscillations are associated with behavioral approach and alpha with behavioral inhibition tendencies but these associations are only valid for induced responses to stimuli. [Copyright &y& Elsevier]
- Published
- 2008
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46. How the tide influences dangerous level rises on the coast of the Sea of Okhotsk and adjacent areas in cases of tsunami and storm surges
- Author
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G. V. Shevchenko
- Subjects
geography ,East coast ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Storm surge ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Ridge ,Induced oscillations ,Period (geology) ,Tide gauge ,Surge ,Geology ,Sea level ,0105 earth and related environmental sciences - Abstract
A long-term sea level series were analyzed, recorded at 12 coastal tide gauges located on the coast of the Sea of Okhotsk and the Pacific coast of the Kuril Islands and Kamchatka. Estimates for the maximum heights of the tidal level, storm surges, and tsunamis were obtained separately, as well as for the rare recurrence of the total sea level height with the probability of these individual components superposition. The maximum total height of the sea level without a tsunami were obtained for the Magadan station, where the main factor is anomalously large tides, as well as for Iturup and Matua islands, where the highest storm surges were recorded. The minimum values were obtained for Ust’-Kamchatsk and Malokuril’sk (Shikotan Island) on different flanks of the study area. When a tsunami is included, the maximum values of possible total sea level rises were observed on the Pacific coast of the Kuril Ridge and the influence of tides and meteorologically induced oscillations are small. On the east coast of Kamchatka adjacent to the considered closed area, the role of tsunamis is much smaller. At the Kuril’sk station, where the height of the largest tsunami (Chilean, May 1960) was about a half the strongest surge height, the contribution of the tsunami scarcely affected the resulting estimates. As a rule, the contribution of a tsunami becomes significant at other stations on the coast of the Sea of Okhotsk with a recurrence period of 100 years.
- Published
- 2017
47. An Investigation on Three Point Explicit Schemes and Induced Numerical Oscillations
- Author
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Ritesh Kumar Dubey and Sabana Parvin
- Subjects
Conservation law ,Applied Mathematics ,Mathematical analysis ,Scalar (mathematics) ,01 natural sciences ,Stencil ,010101 applied mathematics ,Numerical approximation ,0103 physical sciences ,Induced oscillations ,0101 mathematics ,Spurious relationship ,010301 acoustics ,Data dependent ,Analysis ,Mathematics - Abstract
Spurious induced oscillations have been one of the fundamental problem associated with numerical approximation of the solution of hyperbolic conservation laws. In this note, using notion of data dependent stability, generic three point schemes for scalar case are analysed to show that the induced oscillations depend on initial data too. Further, it is concluded that it is not possible to have an initial data independent, ’uniformly’ non-oscillatory three point fixed stencil scheme irrespective of its accuracy.
- Published
- 2017
48. Gamma Band Oscillations Reveal Neural Network Cortical Coherence Dysfunction in Schizophrenia Patients
- Author
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Light, Gregory A., Hsu, Jung Lung, Hsieh, Ming H., Meyer-Gomes, Katrin, Sprock, Joyce, Swerdlow, Neal R., and Braff, David L.
- Subjects
- *
GAMMA globulins , *COGNITIVE ability , *SCHIZOPHRENIA , *BIOLOGICAL neural networks , *PSYCHOSES - Abstract
Background: Gamma band activity has been associated with many sensory and cognitive functions, and is important for cortico-cortical transmission and the integration of information across neural networks. The aims of the present study were to determine if schizophrenia patients have deficits in the generation and maintenance of coherent, synchronized oscillations in response to steady-state stimulation, and to examine the clinical and cognitive correlates of the electroencephalography (EEG) oscillatory dynamics. Methods: Schizophrenia patients (n = 100) and nonpsychiatric subjects (n = 80) underwent auditory steady-state event-related potential testing. Click trains varying in rate of stimulation (20, 30, and 40 Hz) were presented; EEG-evoked power and intertrial phase synchronization were obtained in response to each stimulation frequency. Subjects also underwent clinical and neurocognitive assessments. Results: Patients had reductions in both evoked power and phase synchronization in response to 30- and 40-Hz stimulation but normal responsivity to 20-Hz stimulation. Maximal deficits were detected in response to 40-Hz stimulation. A modest association of reduced working memory performance and 40-Hz intertrial phase synchronization was present in schizophrenia patients (r = .32, p <.01). Conclusions: Schizophrenia patients have frequency-specific deficits in the generation and maintenance of coherent gamma-range oscillations, reflecting a fundamental degradation of basic integrated neural network activity. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
49. A Delay Vector Variance based Approach for Detecting and Isolating the Non-linearity Induced Oscillations in Control Loops * *Financial support to the first author from Siemens AS, Norway, is gratefully acknowledged
- Author
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Muhammad Aftab, Selvanathan Sivalingam, and Morten Hovd
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0209 industrial biotechnology ,Engineering ,Operations research ,business.industry ,Non linearity ,02 engineering and technology ,Variance (accounting) ,01 natural sciences ,020901 industrial engineering & automation ,Control and Systems Engineering ,Control theory ,Control system ,0103 physical sciences ,Induced oscillations ,Embedding ,Time series ,010306 general physics ,business ,Control (linguistics) - Abstract
Non-linear time series analysis based methods are a popular choice for industrial control loop data analysis. In this paper a delay vector variance (DVV) based approach is presented to analyze the source of oscillations in an industrial control loop. The method is capable of differentiating between the linear and non-linear causes of oscillations and can also help in isolating the source of non-linearity. The automatic determination of embedding dimensions is augmented with the DVV analysis to make it more robust and reliable. The efficacy of the proposed method is established using simulation as well as industrial case studies.
- Published
- 2017
50. Modeling Walking with an Inverted Pendulum Not Constrained to the Sagittal Plane. Numerical Simulations and Asymptotic Expansions
- Author
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Guillermo H. Goldsztein
- Subjects
0209 industrial biotechnology ,Plane (geometry) ,Point particle ,Mathematical analysis ,Motion (geometry) ,02 engineering and technology ,General Medicine ,01 natural sciences ,Stability (probability) ,Sagittal plane ,010305 fluids & plasmas ,Inverted pendulum ,Computer Science::Robotics ,020901 industrial engineering & automation ,medicine.anatomical_structure ,Control theory ,0103 physical sciences ,Induced oscillations ,Perpendicular ,medicine ,Mathematics - Abstract
Inverted pendulum models are commonly used to study the bio-mechanics of biped walkers. In its simplest form, the inverted pendulum consists of a point mass attached to two straight mass-less legs. Most works constrain the motion of the mass to the sagittal plane, i.e. the plane perpendicular to the ground that contains the direction toward the biped is walking. In this article, we remove this constrain to study the oscillations, the mass experiences in the direction perpendicular to the sagittal plane as the biped walks. While small, these lateral oscillations are unavoidable and of importance in the understanding of balance and stability of walkers, as well as walkers induced oscillations in pedestrian bridges.
- Published
- 2017
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