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Sample records for finite impulse response

  1. Recursive Inversion By Finite-Impulse-Response Filters

    NASA Technical Reports Server (NTRS)

    Bach, Ralph E., Jr.; Baram, Yoram

    1991-01-01

    Recursive approximation gives least-squares best fit to exact response. Algorithm yields finite-impulse-response approximation of unknown single-input/single-output, causal, time-invariant, linear, real system, response of which is sequence of impulses. Applicable to such system-inversion problems as suppression of echoes and identification of target from its scatter response to incident impulse.

  2. Recursive Inversion By Finite-Impulse-Response Filters

    NASA Technical Reports Server (NTRS)

    Bach, Ralph E., Jr.; Baram, Yoram

    1991-01-01

    Recursive approximation gives least-squares best fit to exact response. Algorithm yields finite-impulse-response approximation of unknown single-input/single-output, causal, time-invariant, linear, real system, response of which is sequence of impulses. Applicable to such system-inversion problems as suppression of echoes and identification of target from its scatter response to incident impulse.

  3. Optical Implementation Of Systolic Finite Impulse Response Filters

    NASA Astrophysics Data System (ADS)

    Ramamoorthy, P. A.; Govind, G.; Antony, S.

    1987-11-01

    An optical systolic finite impulse response (FIR) filter (or convolution operation) implementation using barrel shifters and a modified signed digit (MSD) adder is discussed. The computational element used in systolic FIR filters in electronics consists of a multiplier and an accumulator. A speedup in the throughput data rate along with a high degree of regularity and concurrency can be achieved by replacing the multiplier with barrel shifters and accumulators. The optical implementation of this architecture offers reconfigurability together with the inherent speed and massive parallelism of optics. It is shown that an FIR filter of order eight can be implemented by using one liquid crystal light valve (LCLV) and one optical MSD adder. All barrel shifters in the architecture are implemented using different areas in the same LCLV structure. The MSD adder is implemented using symbolic substitution logic (SSL), and the input operands in the various cells are arranged on the same input data plane to give all required summation terms.

  4. A Finite-Element Method Model of Soft Tissue Response to Impulsive Acoustic Radiation Force

    PubMed Central

    Palmeri, Mark L.; Sharma, Amy C.; Bouchard, Richard R.; Nightingale, Roger W.; Nightingale, Kathryn R

    2010-01-01

    Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson’s ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue’s dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers. PMID:16382621

  5. Vibration suppression of structures with densely spaced modes using maximally robust minimum delay digital finite impulse response filters

    NASA Astrophysics Data System (ADS)

    Glossiotis, G. N.; Antoniadis, I. A.

    2007-03-01

    Due to the inherent flexibility of engineering structures, transient and residual vibrations occur when a motion command is applied, thus raising several practical restrictions concerning their fast, accurate and safe motion. Although various command-preconditioning techniques have been proposed for the effective suppression of the excited vibrations, their application has been limited only to structures with a few distinct and well-separated modes. This paper further considers the applicability of motion preconditioning methods for a large class of lightweight flexible structures, which present multiple densely spaced natural modes, existing even at relatively low frequencies. Properly designed finite impulse response (FIR) filters can lead to an effective motion preconditioning method, suppressing drastically the excited vibrations over the entire excited frequency band. Compared to other alternative preconditioning methods, such as input shapers or infinite impulse response (IIR) filters, FIR filters present the most efficient behavior in terms of vibration suppression efficiency, or in terms of the delay introduced in the motion command, as verified by numerical simulations and experimental results involving multibay trusses, with tenths of densely spaced modes in a range from 0.4 Hz up to 75 Hz.

  6. A Methodology for Rapid Prototyping Peak-Constrained Least-Squares Bit-Serial Finite Impulse Response Filters in FPGAs

    NASA Astrophysics Data System (ADS)

    Carreira, Alex; Fox, Trevor W.; Turner, Laurence E.

    2003-12-01

    Area-efficient peak-constrained least-squares (PCLS) bit-serial finite impulse response (FIR) filter implementations can be rapidly prototyped in field programmable gate arrays (FPGA) with the methodology presented in this paper. Faster generation of the FPGA configuration bitstream is possible with a new application-specific mapping and placement method that uses JBits to avoid conventional general-purpose mapping and placement tools. JBits is a set of Java classes that provide an interface into the Xilinx Virtex FPGA configuration bitstream, allowing the user to generate new configuration bitstreams. PCLS coefficient generation allows passband-to-stopband energy ratio (PSR) performance to be traded for a reduction in the filter's hardware cost without altering the minimum stopband attenuation. Fixed-point coefficients that meet the frequency response and hardware cost specifications can be generated with the PCLS method. It is not possible to meet these specifications solely by the quantization of floating-point coefficients generated in other methods.

  7. Detecting Structural Failures Via Acoustic Impulse Responses

    NASA Technical Reports Server (NTRS)

    Bayard, David S.; Joshi, Sanjay S.

    1995-01-01

    Advanced method of acoustic pulse reflectivity testing developed for use in determining sizes and locations of failures within structures. Used to detect breaks in electrical transmission lines, detect faults in optical fibers, and determine mechanical properties of materials. In method, structure vibrationally excited with acoustic pulse (a "ping") at one location and acoustic response measured at same or different location. Measured acoustic response digitized, then processed by finite-impulse-response (FIR) filtering algorithm unique to method and based on acoustic-wave-propagation and -reflection properties of structure. Offers several advantages: does not require training, does not require prior knowledge of mathematical model of acoustic response of structure, enables detection and localization of multiple failures, and yields data on extent of damage at each location.

  8. Finite-element nonlinear transient response computer programs PLATE 1 and CIVM-PLATE 1 for the analysis of panels subjected to impulse or impact loads

    NASA Technical Reports Server (NTRS)

    Spilker, R. L.; Witmer, E. A.; French, S. E.; Rodal, J. J. A.

    1980-01-01

    Two computer programs are described for predicting the transient large deflection elastic viscoplastic responses of thin single layer, initially flat unstiffened or integrally stiffened, Kirchhoff-Lov ductile metal panels. The PLATE 1 program pertains to structural responses produced by prescribed externally applied transient loading or prescribed initial velocity distributions. The collision imparted velocity method PLATE 1 program concerns structural responses produced by impact of an idealized nondeformable fragment. Finite elements are used to represent the structure in both programs. Strain hardening and strain rate effects of initially isotropic material are considered.

  9. Identification of Experimental Unsteady Aerodynamic Impulse Responses

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.; Piatak, David J.; Scott, Robert C.

    2003-01-01

    The identification of experimental unsteady aerodynamic impulse responses using the Oscillating Turntable (OTT) at NASA Langley's Transonic Dynamics Tunnel (TDT) is described. Results are presented for two configurations: a Rigid Semispan Model (RSM) and a rectangular wing with a supercritical airfoil section. Both models were used to acquire unsteady pressure data due to pitching oscillations on the OTT. A deconvolution scheme involving a step input in pitch and the resultant step response in pressure, for several pressure transducers, is used to identify the pressure impulse responses. The identified impulse responses are then used to predict the pressure response due to pitching oscillations at several frequencies. Comparisons with the experimental data are presented.

  10. Temporal Preparation, Response Inhibition and Impulsivity

    ERIC Educational Resources Information Center

    Correa, Angel; Trivino, Monica; Perez-Duenas, Carolina; Acosta, Alberto; Lupianez, Juan

    2010-01-01

    Temporal preparation and impulsivity involve overlapping neural structures (prefrontal cortex) and cognitive functions (response inhibition and time perception), however, their interrelations had not been investigated. We studied such interrelations by comparing the performance of groups with low vs. high non-clinical trait impulsivity during a…

  11. Temporal Preparation, Response Inhibition and Impulsivity

    ERIC Educational Resources Information Center

    Correa, Angel; Trivino, Monica; Perez-Duenas, Carolina; Acosta, Alberto; Lupianez, Juan

    2010-01-01

    Temporal preparation and impulsivity involve overlapping neural structures (prefrontal cortex) and cognitive functions (response inhibition and time perception), however, their interrelations had not been investigated. We studied such interrelations by comparing the performance of groups with low vs. high non-clinical trait impulsivity during a…

  12. Anatomy of a SAR impulse response.

    SciTech Connect

    Doerry, Armin Walter

    2007-08-01

    A principal measure of Synthetic Aperture Radar (SAR) image quality is the manifestation in the SAR image of a spatial impulse, that is, the SAR's Impulse Response (IPR). IPR requirements direct certain design decisions in a SAR. Anomalies in the IPR can point to specific anomalous behavior in the radar's hardware and/or software.

  13. Temporal preparation, response inhibition and impulsivity.

    PubMed

    Correa, Angel; Triviño, Mónica; Pérez-Dueñas, Carolina; Acosta, Alberto; Lupiáñez, Juan

    2010-08-01

    Temporal preparation and impulsivity involve overlapping neural structures (prefrontal cortex) and cognitive functions (response inhibition and time perception), however, their interrelations had not been investigated. We studied such interrelations by comparing the performance of groups with low vs. high non-clinical trait impulsivity during a temporal preparation go no-go task. This task measured, in less than 10 min, how response inhibition was influenced both by temporal orienting of attention (guided by predictive temporal cues) and by sequential effects (produced by repetition/alternation of the duration of preparatory intervals in consecutive trials). The results showed that sequential effects produced dissociable patterns of temporal preparation as a function of impulsivity. Sequential effects facilitated both response speed (reaction times - RTs - to the go condition) and response inhibition (false alarms to the no-go condition) selectively in the low impulsivity group. In the high impulsivity group, in contrast, sequential effects only improved RTs but not response inhibition. We concluded that both excitatory and inhibitory processing may be enhanced concurrently by sequential effects, which enables the temporal preparation of fast and controlled responses. Impulsivity could hence be related to less efficient temporal preparation of that inhibitory processing. 2010 Elsevier Inc. All rights reserved.

  14. The thermal impulse response of Escherichia coli

    PubMed Central

    Paster, Eli; Ryu, William S.

    2008-01-01

    Swimming Escherichia coli responds to changes in temperature by modifying its motor behavior. Previous studies using populations of cells have shown that E. coli accumulate in spatial thermal gradients, but these experiments did not cleanly separate thermal responses from chemotactic responses. Here we have isolated the thermal response by studying the behavior of single, tethered cells. The motor output of cells grown at 33°C was measured at constant temperature, from 10° to 40°C, and in response to small, impulsive increases in temperature, from 23° to 43°C. The thermal impulse response at temperatures < 31°C is similar to the chemotactic impulse response: Both follow a similar time course, share the same directionality, and show biphasic characteristics. At temperatures > 31°C, some cells show an inverted response, switching from warm- to cold-seeking behavior. The fraction of inverted responses increases nonlinearly with temperature, switching steeply at the preferred temperature of 37°C. PMID:18385380

  15. Controller reduction by preserving impulse response energy

    NASA Technical Reports Server (NTRS)

    Craig, Roy R., Jr.; Su, Tzu-Jeng

    1989-01-01

    A model order reduction algorithm based on a Krylov recurrence formulation is developed to reduce order of controllers. The reduced-order controller is obtained by projecting the full-order LQG controller onto a Krylov subspace in which either the controllability or the observability grammian is equal to the identity matrix. The reduced-order controller preserves the impulse response energy of the full-order controller and has a parameter-matching property. Two numerical examples drawn from other controller reduction literature are used to illustrate the efficacy of the proposed reduction algorithm.

  16. Subjective field study of response to impulsive helicopter noise

    NASA Technical Reports Server (NTRS)

    Powell, C. A.

    1981-01-01

    Subjects, located outdoors and indoors, judged the noisiness and other subjective noise characteristics of flyovers of two helicopters and a propeller driven airplane as part of a study of the effects of impulsiveness on the subjective response to helicopter noise. In the first experiment, the impulsive characteristics of one helicopter was controlled by varying the main rotor speed while maintaining a constant airspeed in level flight. The second experiment which utilized only the helicopters, included descent and level flight operations. The more impulsive helicopter was consistently judged less noisy than the less impulsive helicopter at equal effective perceived noise levels (EPNL). The ability of EPNL to predict noisiness was not improved by the addition of either of two proposed impulse corrections. A subjective measure of impulsiveness, however, which was not significantly related to the proposed impulse corrections, was found to improve the predictive ability of EPNL.

  17. SAR impulse response with residual chirps.

    SciTech Connect

    Doerry, Armin Walter

    2009-06-01

    A Linear Frequency-Modulated (LFM) chirp is a function with unit amplitude and quadratic phase characteristic. In a focused Synthetic Aperture Radar (SAR) image, a residual chirp is undesired for targets of interest, as it coarsens the manifested resolution. However, for undesired spurious signals, a residual chirp is often advantageous because it spreads the energy and thereby diminishes its peak value. In either case, a good understanding of the effects of a residual LFM chirp on a SAR Impulse Response (IPR) is required to facilitate system analysis and design. This report presents an analysis of the effects of a residual chirp on the IPR. As reference, there is a rich body of publications on various aspects of LFM chirps. A quick search reveals a plethora of articles, going back to the early 1950s. We mention here purely as trivia one of the earlier analysis papers on this waveform by Klauder, et al.

  18. Causal impulse response for circular sources in viscous media

    PubMed Central

    Kelly, James F.; McGough, Robert J.

    2008-01-01

    The causal impulse response of the velocity potential for the Stokes wave equation is derived for calculations of transient velocity potential fields generated by circular pistons in viscous media. The causal Green’s function is numerically verified using the material impulse response function approach. The causal, lossy impulse response for a baffled circular piston is then calculated within the near field and the far field regions using expressions previously derived for the fast near field method. Transient velocity potential fields in viscous media are computed with the causal, lossy impulse response and compared to results obtained with the lossless impulse response. The numerical error in the computed velocity potential field is quantitatively analyzed for a range of viscous relaxation times and piston radii. Results show that the largest errors are generated in locations near the piston face and for large relaxation times, and errors are relatively small otherwise. Unlike previous frequency-domain methods that require numerical inverse Fourier transforms for the evaluation of the lossy impulse response, the present approach calculates the lossy impulse response directly in the time domain. The results indicate that this causal impulse response is ideal for time-domain calculations that simultaneously account for diffraction and quadratic frequency-dependent attenuation in viscous media. PMID:18397018

  19. Trait impulsivity and response inhibition in antisocial personality disorder.

    PubMed

    Swann, Alan C; Lijffijt, Marijn; Lane, Scott D; Steinberg, Joel L; Moeller, F Gerard

    2009-08-01

    Impulsive behavior is a prominent characteristic of antisocial personality disorder. Impulsivity is a complex construct, however, representing distinct domains of cognition and action. Leading models refer to impulsivity as an inability to evaluate a stimulus fully before responding to it (rapid-response impulsivity), and as an inability to delay responding despite a larger reward (reward-delay impulsivity). We investigated these models in terms of the diagnosis and severity of antisocial personality disorder. Thirty-four male subjects on probation/parole who met DSM-IV criteria for ASPD, and 30 male healthy comparison subjects, matched by ethnicity, were recruited from the community. The Barratt Impulsiveness Scale (BIS-11) provided an integrated measure of trait impulsivity. Rapid-response impulsivity was assessed using the Immediate Memory Task (IMT), a continuous performance test. Reward delay impulsivity was assessed using the Two-choice Impulsivity Paradigm (TCIP), where subjects had the choice of smaller-sooner or larger-delayed rewards, and the Single Key Impulsivity Paradigm (SKIP), a free-operant responding task. Compared to controls, subjects with ASPD had higher BIS-11 scores (Effect Size (E.S.)=0.95). They had slower reaction times to IMT commission errors (E.S.=0.45). Correct detections, a measure of attention, were identical to controls. On the SKIP, they had a shorter maximum delay for reward (E.S.=0.76), but this was not significant after correction for age and education. The groups did not differ on impulsive choices on the TCIP (E.S.<0.1). On probit analysis with age and education as additional independent variables, BIS-11 score, IMT reaction time to a commission error, and IMT positive response bias contributed significantly to diagnosis of ASPD; SKIP delay for reward did not. Severity of ASPD, assessed by the number of ASPD symptoms endorsed on the SCID-II, correlated significantly with commission errors (impulsive responses) on the IMT, and

  20. Associations between trait impulsivity and prepotent response inhibition.

    PubMed

    Aichert, Désirée S; Wöstmann, Nicola M; Costa, Anna; Macare, Christine; Wenig, Johanna R; Möller, Hans-Jürgen; Rubia, Katya; Ettinger, Ulrich

    2012-01-01

    This study addresses the relationship between trait impulsivity and inhibitory control, two features known to be impaired in a number of psychiatric conditions. While impulsivity is often measured using psychometric self-report questionnaires, the inhibition of inappropriate, impulsive motor responses is typically measured using experimental laboratory tasks. It remains unclear, however, whether psychometrically assessed impulsivity and experimentally operationalized inhibitory performance are related to each other. Therefore, we investigated the relationship between these two traits in a large sample using correlative and latent variable analysis. A total of 504 healthy individuals completed the Barratt Impulsiveness Scale (BIS-11) and a battery of four prepotent response inhibition paradigms: the antisaccade, Stroop, stop-signal, and go/no-go tasks. We found significant associations of BIS impulsivity with commission errors on the go/no-go task and directional errors on the antisaccade task, over and above effects of age, gender, and intelligence. Latent variable analysis (a) supported the idea that all four inhibitory measures load on the same underlying construct termed "prepotent response inhibition" and (b) revealed that 12% of variance of the prepotent response inhibition construct could be explained by BIS impulsivity. Overall, the magnitude of associations observed was small, indicating that while a portion of variance in prepotent response inhibition can be explained by psychometric trait impulsivity, the majority of variance remains unexplained. Thus, these findings suggest that prepotent response inhibition paradigms can account for psychometric trait impulsivity only to a limited extent. Implications for studies of patient populations with symptoms of impulsivity are discussed.

  1. Understanding the impulse response method applied to concrete bridge decks

    NASA Astrophysics Data System (ADS)

    Clem, D. J.; Popovics, J. S.; Schumacher, T.; Oh, T.; Ham, S.; Wu, D.

    2013-01-01

    The Impulse Response (IR) method is a well-established form of non-destructive testing (NDT) where the dynamic response of an element resulting from an impact event (hammer blow) is measured with a geophone to make conclusions about the element's integrity, stiffness, and/or support conditions. The existing ASTM Standard C1740-10 prescribes a set of parameters that can be used to evaluate the conditions above. These parameters are computed from the so-called `mobility' spectrum which is obtained by dividing the measured bridge deck response by the measured impact force in the frequency domain. While applying the test method in the laboratory as well as on an actual in-service concrete bridge deck, the authors of this paper observed several limitations that are presented and discussed in this paper. In order to better understand the underlying physics of the IR method, a Finite Element (FE) model was created. Parameters prescribed in the Standard were then computed from the FE data and are discussed. One main limitation appears to be the use of a fixed upper frequency of 800 Hz. Test data from the real bridge deck as well as the FE model both show that most energy is found above that limit. This paper presents and discusses limitations of the ASTM Standard found by the authors and suggests ways for improving it.

  2. Impulse source versus dodecahedral loudspeaker for measuring parameters derived from the impulse response in room acoustics.

    PubMed

    San Martín, Ricardo; Arana, Miguel; Machín, Jorge; Arregui, Abel

    2013-07-01

    This study investigates the performance of dodecahedral and impulse sources when measuring acoustic parameters in enclosures according to ISO 3382-1 [Acoustics-Measurement of room acoustic parameters. Part 1: Performance spaces (International Organization for Standardization, Geneva, Switzerland, 2009)]. In general, methods using speakers as a sound source are limited by their frequency response and directivity. On the other hand, getting impulse responses from impulse sources typically involves a lack of repeatability, and it is usually necessary to average several measurements for each position. Through experiments in different auditoriums that recreate typical situations in which the measurement standard is applied, it is found that using impulse sources leads to greater variation in the results, especially at low frequencies. However, this prevents subsequent dispersions due to variables that this technique does not require, such as the orientation of the emitting source. These dispersions may be relevant at high frequencies exceeding the established tolerance criteria for certain parameters. Finally, a new descriptor for dodecahedral sources reflecting the influence their lack of omnidirectionality produces on measuring acoustic parameters is proposed.

  3. Assessment of Community Response to High-Energy Impulsive Sounds

    DTIC Science & Technology

    1981-07-01

    10M --0 -- f·· ’ " .. ~’ 82. ol o~l41 ASSESSIENT OF COMMUNITY RESPONSE ( TO HIGH - ENERGY IMPtLSIVE SOUNDS Report of Working Group 84 Committee on...SOUNDS 4 SUBJECTIVE RESPONSE TO HIGH - ENERGY IMPULSIVE SOUNDS 5 SOUND LEVEL-WEIGHTED POPULATION 17 LAND-USE PLANNINC FOR COMBINED ENVIRONMENTS 18...Listening 13 4 Recomhmended Relationships for Predicting Coummunity Response to High - Energy Impulsive Sounds and to Other Sounds 15 ix MOuOM PA 60LN UM

  4. A finite element study of the EIDI system. [Electro-Impulse De-Icing System

    NASA Technical Reports Server (NTRS)

    Khatkhate, A. A.; Scavuzzo, R. J.; Chu, M. L.

    1988-01-01

    This paper presents a method for modeling the structural dynamics of an Electro-Impulse De-Icing System, using finite element analyses procedures. A guideline for building a representative finite element model is discussed. Modeling was done initially using four noded cubic elements, four noded isoparametric plate elements and eight noded isoparametric shell elements. Due to the size of the problem and due to the underestimation of shear stress results when compared to previous analytical work an approximate model was created to predict possible areas of shedding of ice. There appears to be good agreement with the test data provided by The Boeing Commercial Airplane Company. Thus these initial results of this method were found to be encouraging. Additional analytical work and comparison with experiment is needed in order to completely evaluate this approach.

  5. The (p,2p) reaction in finite range relativistic distorted-wave impulse approximation

    NASA Astrophysics Data System (ADS)

    Kushwaha, Mahendra

    The (p,2p) reaction on 40Ca at incident proton energy of 300MeV is examined in the formalism of finite-range relativistic distorted-wave impulse approximation (FR-RDWIA). In comparison to conventional t-matrix model of Love-Franey, a new form of nucleon-nucleon t-matrix effective interaction is derived at 300MeV using Reid soft core potentials for isotopic spin one and taking into account the finite-range effects in the p -p interaction at knockout vertex. In comparison to the conventional finite range nonrelativistic and relativistic formalism, the present formalism with a new version of p-p t-matrix is effectively reproducing the shape of cross-section energy distributions for 1d3/2, 1d5/2 and 2s1/2 states for asymmetric angle pair of 30∘-55∘. Discrepancies between the experimental cross-section data and finite range theoretical calculations at Ep = 300MeV are reasonably resolved in the present approach. Without any adjustable parameter of bound state, the obtained spectroscopic factors are in reasonably good agreement with the relativistic and nonrelativistic theoretical predictions by (p,2p), (e,e‧p) and (d,3He) analysis.

  6. Volterra network modeling of the nonlinear finite-impulse reponse of the radiation belt flux

    SciTech Connect

    Taylor, M.; Daglis, I. A.; Anastasiadis, A.; Vassiliadis, D.

    2011-01-04

    We show how a general class of spatio-temporal nonlinear impulse-response forecast networks (Volterra networks) can be constructed from a taxonomy of nonlinear autoregressive integrated moving average with exogenous inputs (NAR-MAX) input-output equations, and used to model the evolution of energetic particle f uxes in the Van Allen radiation belts. We present initial results for the nonlinear response of the radiation belts to conditions a month earlier. The essential features of spatio-temporal observations are recovered with the model echoing the results of state space models and linear f nite impulse-response models whereby the strongest coupling peak occurs in the preceding 1-2 days. It appears that such networks hold promise for the development of accurate and fully data-driven space weather modelling, monitoring and forecast tools.

  7. Self-reported impulsivity, but not behavioral choice or response impulsivity, partially mediates the effect of stress on drinking behavior

    PubMed Central

    HAMILTON, KRISTEN R.; ANSELL, EMILY B.; REYNOLDS, BRADY; POTENZA, MARC N.; SINHA, RAJITA

    2013-01-01

    Stress and impulsivity contribute to alcohol use, and stress may also act via impulsivity to increase drinking behavior. Impulsivity represents a multi-faceted construct and self-report and behavioral assessments may effectively capture distinct clinically relevant factors. The present research investigated whether aspects of impulsivity mediate the effect of stress on alcohol use. A community-based sample of 192 men and women was assessed on measures of cumulative stress, alcohol use, self-reported impulsivity, and behavioral choice and response impulsivity. Data were analyzed using regression and bootstrapping techniques to estimate indirect effects of stress on drinking via impulsivity. Cumulative adversity exhibited both direct effects and indirect effects (via self-reported impulsivity) on drinking behavior. Additional models examining specific types of stress indicated direct and indirect effects of trauma and recent life events, and indirect effects of major life events and chronic stressors on drinking behavior. Overall, cumulative stress was associated with increased drinking behavior, and this effect was partially mediated by self-reported impulsivity. Self-reported impulsivity also mediated the effects of different types of stress on drinking behavior. These findings highlight the value of mediation models to examine the pathways through which different types of stress increase drinking behavior. Treatment and prevention strategies should focus on enhancing stress management and self-control. PMID:22376044

  8. Self-reported impulsivity, but not behavioral choice or response impulsivity, partially mediates the effect of stress on drinking behavior.

    PubMed

    Hamilton, Kristen R; Ansell, Emily B; Reynolds, Brady; Potenza, Marc N; Sinha, Rajita

    2013-01-01

    Stress and impulsivity contribute to alcohol use, and stress may also act via impulsivity to increase drinking behavior. Impulsivity represents a multi-faceted construct and self-report and behavioral assessments may effectively capture distinct clinically relevant factors. The present research investigated whether aspects of impulsivity mediate the effect of stress on alcohol use. A community-based sample of 192 men and women was assessed on measures of cumulative stress, alcohol use, self-reported impulsivity, and behavioral choice and response impulsivity. Data were analyzed using regression and bootstrapping techniques to estimate indirect effects of stress on drinking via impulsivity. Cumulative adversity exhibited both direct effects and indirect effects (via self-reported impulsivity) on drinking behavior. Additional models examining specific types of stress indicated direct and indirect effects of trauma and recent life events, and indirect effects of major life events and chronic stressors on drinking behavior. Overall, cumulative stress was associated with increased drinking behavior, and this effect was partially mediated by self-reported impulsivity. Self-reported impulsivity also mediated the effects of different types of stress on drinking behavior. These findings highlight the value of mediation models to examine the pathways through which different types of stress increase drinking behavior. Treatment and prevention strategies should focus on enhancing stress management and self-control.

  9. Understanding Computation of Impulse Response in Microwave Software Tools

    ERIC Educational Resources Information Center

    Potrebic, Milka M.; Tosic, Dejan V.; Pejovic, Predrag V.

    2010-01-01

    In modern microwave engineering curricula, the introduction of the many new topics in microwave industrial development, or of software tools for design and simulation, sometimes results in students having an inadequate understanding of the fundamental theory. The terminology for and the explanation of algorithms for calculating impulse response in…

  10. Understanding Computation of Impulse Response in Microwave Software Tools

    ERIC Educational Resources Information Center

    Potrebic, Milka M.; Tosic, Dejan V.; Pejovic, Predrag V.

    2010-01-01

    In modern microwave engineering curricula, the introduction of the many new topics in microwave industrial development, or of software tools for design and simulation, sometimes results in students having an inadequate understanding of the fundamental theory. The terminology for and the explanation of algorithms for calculating impulse response in…

  11. Impulse and Frequency Response of a Moving Coil Galvanometer.

    ERIC Educational Resources Information Center

    McNeill, D. J.

    1985-01-01

    Describes an undergraduate laboratory experiment in which a moving coil galvanometer is studied and the electromotive force generated by the swinging coil provides the impulse response information in a form suitable for digitizing and inputing to a microcomputer. Background information and analysis of typical data are included. (JN)

  12. Impulse and Frequency Response of a Moving Coil Galvanometer.

    ERIC Educational Resources Information Center

    McNeill, D. J.

    1985-01-01

    Describes an undergraduate laboratory experiment in which a moving coil galvanometer is studied and the electromotive force generated by the swinging coil provides the impulse response information in a form suitable for digitizing and inputing to a microcomputer. Background information and analysis of typical data are included. (JN)

  13. Neural response to reward anticipation is modulated by Gray's impulsivity.

    PubMed

    Hahn, Tim; Dresler, Thomas; Ehlis, Ann-Christine; Plichta, Michael M; Heinzel, Sebastian; Polak, Thomas; Lesch, Klaus-Peter; Breuer, Felix; Jakob, Peter M; Fallgatter, Andreas J

    2009-07-15

    According to the Reinforcement Sensitivity Theory (RST), Gray's dimension of impulsivity, reflecting human trait reward sensitivity, determines the extent to which stimuli activate the Behavioural Approach System (BAS). The potential neural underpinnings of the BAS, however, remain poorly understood. In the present study, we examined the association between Gray's impulsivity as defined by the RST and event-related fMRI BOLD-response to anticipation of reward in twenty healthy human subjects in brain regions previously associated with reward processing. Anticipation of reward during a Monetary Incentive Delay Task elicited activation in key components of the human reward circuitry such as the ventral striatum, the amygdala and the orbitofrontal cortex. Interindividual differences in Gray's impulsivity accounted for a significant amount of variance of the reward-related BOLD-response in the ventral striatum and the orbitofrontal cortex. Specifically, higher trait reward sensitivity was associated with increased activation in response to cues indicating potential reward. Extending previous evidence, here we show that variance in functional brain activation during anticipation of reward is attributed to interindividual differences regarding Gray's dimension of impulsivity. Thus, trait reward sensitivity contributes to the modulation of responsiveness in major components of the human reward system which thereby display a core property of the BAS. Generally, fostering our understanding of the neural underpinnings of the association of reward-related interindividual differences in affective traits might aid researchers in quest for custom-tailored treatments of psychiatric disorders, further disentangling the complex relationship between personality traits, emotion, and health.

  14. Evaluation of bridge foundations by impulse response methods

    NASA Astrophysics Data System (ADS)

    Finno, Richard J.; Gassman, Sarah L.

    1998-03-01

    This paper summarizes the results of a series of impulse response tests on inaccessible drilled shafts constructed at the National Geotechnical Experimentation Site (NGES) at Northwestern University. The drilled shafts are 610 to 910 mm in diameter and 12 to 27 m long, and are covered by pile caps up to 1.5 m thick. Results of tests on drilled shafts obscured by the pile caps have shown that useful information can be obtained below a 'cutoff frequency' which is defined by the propagation velocity and the geometries of the intervening structure and the deep foundation. An extension of the conventional impulse response method using multiple geophones is described which makes interpretation of responses from the foundation easier by minimizing the effects of surface waves on the processed signals. Superposing the velocity responses from each geophone allows the reflections from the deep foundation to be more easily identified.

  15. Finite Element Modeling of Impulsive Excitation and Shear Wave Propagation in an Incompressible, Transversely Isotropic Medium

    PubMed Central

    Rouze, Ned C.; Wang, Michael H.; Palmeri, Mark L.; Nightingale, Kathy R.

    2013-01-01

    Elastic properties of materials can be measured by observing shear wave propagation following localized, impulsive excitations and relating the propagation velocity to a model of the material. However, characterization of anisotropic materials is difficult because of the number of elasticity constants in the material model and the complex dependence of propagation velocity relative to the excitation axis, material symmetries, and propagation directions. In this study, we develop a model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle. Wave motion is described in terms of three propagation modes identified by their polarization relative to the material symmetry axis and propagation direction. Phase velocities for these propagation modes are expressed in terms of five elasticity constants needed to describe a general TI material, and also in terms of three constants after the application of two constraints that hold in the limit of an incompressible material. Group propagation velocities are derived from the phase velocities to describe the propagation of wave packets away from the excitation region following localized excitation. The theoretical model is compared to the results of finite element (FE) simulations performed using a nearly incompressible material model with the five elasticity constants chosen to preserve the essential properties of the material in the incompressible limit. Propagation velocities calculated from the FE displacement data show complex structure that agrees quantitatively with the theoretical model and demonstrates the possibility of measuring all three elasticity constants needed to characterize an incompressible, TI material. PMID:24094454

  16. Retrieving impulse response function amplitudes from the ambient seismic field

    NASA Astrophysics Data System (ADS)

    Viens, Loïc; Denolle, Marine; Miyake, Hiroe; Sakai, Shin'ichi; Nakagawa, Shigeki

    2017-07-01

    Seismic interferometry is now widely used to retrieve the impulse response function of the Earth between two distant seismometers. The phase information has been the focus of most passive imaging studies, as conventional seismic tomography uses traveltime measurements. The amplitude information, however, is harder to interpret because it strongly depends on the distribution of ambient seismic field sources and on the multitude of processing methods. Our study focuses on the latter by comparing the amplitudes of the impulse response functions calculated between seismic stations in the Kanto sedimentary basin, Japan, using several processing techniques. This region provides a unique natural laboratory to test the reliability of the amplitudes with complex wave propagation through the basin, and dense observations from the Metropolitan Seismic Observation network. We compute the impulse response functions using the cross correlation, coherency and deconvolution techniques of the raw ambient seismic field and the cross correlation of 1-bit normalized data. To validate the amplitudes of the impulse response functions, we use a shallow Mw 5.8 earthquake that occurred on the eastern edge of Kanto Basin and close to a station that is used as the virtual source. Both S and surface waves are retrieved in the causal part of the impulse response functions computed with all the different techniques. However, the amplitudes obtained from the deconvolution method agree better with those of the earthquake. Despite the expected wave attenuation due to the soft sediments of the Kanto Basin, seismic amplification caused by the basin geometry dominates the amplitudes of S and surface waves and is captured by the ambient seismic field. To test whether or not the anticausal part of the impulse response functions from deconvolution also contains reliable amplitude information, we use another virtual source located on the western edge of the basin. We show that the surface wave amplitudes

  17. Auditorium acoustics evaluation based on simulated impulse response

    NASA Astrophysics Data System (ADS)

    Wu, Shuoxian; Wang, Hongwei; Zhao, Yuezhe

    2001-05-01

    The impulse responses and other acoustical parameters of Huangpu Teenager Palace in Guangzhou were measured. Meanwhile, the acoustical simulation and auralization based on software ODEON were also made. The comparison between the parameters based on computer simulation and measuring is given. This case study shows that auralization technique based on computer simulation can be used for predicting the acoustical quality of a hall at its design stage.

  18. Inhibition and impulsivity: behavioral and neural basis of response control.

    PubMed

    Bari, Andrea; Robbins, Trevor W

    2013-09-01

    In many circumstances alternative courses of action and thoughts have to be inhibited to allow the emergence of goal-directed behavior. However, this has not been the accepted view in the past and only recently has inhibition earned its own place in the neurosciences as a fundamental cognitive function. In this review we first introduce the concept of inhibition from early psychological speculations based on philosophical theories of the human mind. The broad construct of inhibition is then reduced to its most readily observable component which necessarily is its behavioral manifestation. The study of 'response inhibition' has the advantage of dealing with a relatively simple and straightforward process, the overriding of a planned or already initiated action. Deficient inhibitory processes profoundly affect everyday life, causing impulsive conduct which is generally detrimental for the individual. Impulsivity has been consistently linked to several types of addiction, attention deficit/hyperactivity disorder, mania and other psychiatric conditions. Our discussion of the behavioral assessment of impulsivity will focus on objective laboratory tasks of response inhibition that have been implemented in parallel for humans and other species with relatively few qualitative differences. The translational potential of these measures has greatly improved our knowledge of the neurobiological basis of behavioral inhibition and impulsivity. We will then review the current models of behavioral inhibition along with their expression via underlying brain regions, including those involved in the activation of the brain's emergency 'brake' operation, those engaged in more controlled and sustained inhibitory processes and other ancillary executive functions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Rapid-Response Impulsivity: Definitions, Measurement Issues, and Clinical Implications

    PubMed Central

    Hamilton, Kristen R.; Littlefield, Andrew K.; Anastasio, Noelle C.; Cunningham, Kathryn A.; Fink, Latham H.; Wing, Victoria C.; Mathias, Charles W.; Lane, Scott D.; Schutz, Christian; Swann, Alan C.; Lejuez, C.W.; Clark, Luke; Moeller, F. Gerard; Potenza, Marc N.

    2015-01-01

    Impulsivity is a multi-faceted construct that is a core feature of multiple psychiatric conditions and personality disorders. However, progress in understanding and treating impulsivity in the context of these conditions is limited by a lack of precision and consistency in its definition and assessment. Rapid-response-impulsivity (RRI) represents a tendency toward immediate action that occurs with diminished forethought and is out of context with the present demands of the environment. Experts from the International Society for Research on Impulsivity (InSRI) met to discuss and evaluate RRI-measures in terms of reliability, sensitivity, and validity with the goal of helping researchers and clinicians make informed decisions about the use and interpretation of findings from RRI-measures. Their recommendations are described in this manuscript. Commonly-used clinical and preclinical RRI-tasks are described, and considerations are provided to guide task selection. Tasks measuring two conceptually and neurobiologically distinct types of RRI, “refraining from action initiation” (RAI) and “stopping an ongoing action” (SOA) are described. RAI and SOA-tasks capture distinct aspects of RRI that may relate to distinct clinical outcomes. The InSRI group recommends that: 1) selection of RRI-measures should be informed by careful consideration of the strengths, limitations, and practical considerations of the available measures; 2) researchers use both RAI and SOA tasks in RRI studies to allow for direct comparison of RRI types and examination of their associations with clinically relevant measures; and, 3) similar considerations should be made for human and non-human studies in an effort to harmonize and integrate pre-clinical and clinical research. PMID:25867840

  20. Subtypes of trait impulsivity differentially correlate with neural responses to food choices.

    PubMed

    van der Laan, Laura N; Barendse, Marjolein E A; Viergever, Max A; Smeets, Paul A M

    2016-01-01

    Impulsivity is a personality trait that is linked to unhealthy eating and overweight. A few studies assessed how impulsivity relates to neural responses to anticipating and tasting food, but it is unknown how impulsivity relates to neural responses during food choice. Although impulsivity is a multi-faceted construct, it is unknown whether impulsivity subtypes have different underlying neural mechanisms. We investigated how impulsivity correlates with brain responses during food choice and in how far different impulsivity subtypes modulate brain responses during food choice differently. Twenty weight-concerned females performed an fMRI task in which they indicated for high and low energy snacks whether or not they wanted to eat them. Impulsivity subtypes were measured by the monetary delay discounting task and the Barratt Impulsiveness Scale (total BIS-11 and subscales). Only temporal subtypes of impulsivity, namely delay discounting and the BIS-11 non-planning subscale, modulated responses to food choice; both measures correlated positively with striatum activation during high versus low energy choices. However, only delay discounting predicted high energy choices, whereas BIS-11 non-planning independently related to a striatum region that reflects subjective stimulus value. To conclude, the brain mechanisms underlying subtypes of impulsivity have a common ground but differ in specific aspects of food-related decision-making. The findings advance our understanding of the neural correlates of different impulsivity subtypes in the food domain. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Acoustic radiation force impulse imaging of vulnerable plaques: a finite element method parametric analysis

    PubMed Central

    Doherty, Joshua R.; Dumont, Douglas M.; Trahey, Gregg E.; Palmeri, Mark L.

    2012-01-01

    Plaque rupture is the most common cause of complications such as stroke and coronary heart failure. Recent histopathological evidence suggests that several plaque features, including a large lipid core and a thin fibrous cap, are associated with plaques most at risk for rupture. Acoustic Radiation Force Impulse (ARFI) imaging, a recently developed ultrasound-based elasticity imaging technique, shows promise for imaging these features noninvasively. Clinically, this could be used to distinguish vulnerable plaques, for which surgical intervention may be required, from those less prone to rupture. In this study, a parametric analysis using Finite-Element Method (FEM) models was performed to simulate ARFI imaging of five different carotid artery plaques across a wide range of material properties. It was demonstrated that ARFI could resolve the softer lipid pool from the surrounding, stiffer media and fibrous cap and was most dependent upon the stiffness of the lipid pool component. Stress concentrations due to an ARFI excitation were located in the media and fibrous cap components. In all cases, the maximum Von Mises stress was < 1.2 kPa. In comparing these results with others investigating plaque rupture, it is concluded that while the mechanisms may be different, the Von Mises stresses imposed by ARFI are orders of magnitude lower than the stresses associated with blood pressure. PMID:23122224

  2. Direction Finding Using an Antenna with Direction Dependent Impulse Response

    NASA Technical Reports Server (NTRS)

    Foltz, Heinrich; Kegege, Obadiah

    2016-01-01

    Wideband antennas may be designed to have an impulse response that is direction dependent, not only in amplitude but also in waveform shape. This property can be used to perform direction finding using a single fixed antenna, without the need for an array or antenna rotation. In this paper direction finding is demonstrated using a simple candelabra-shaped monopole operating in the 1-3 GHz range. The method requires a known transmitted pulse shape and high signal-to-noise ratio, and is not as accurate or robust as conventional methods. However, it can add direction finding capability to a wideband communication system without the addition of any hardware.

  3. Loss Factor Estimation Using the Impulse Response Decay Method on a Stiffened Structure

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph; Schiller, Noah; Allen, Albert; Moeller, Mark

    2009-01-01

    High-frequency vibroacoustic modeling is typically performed using energy-based techniques such as Statistical Energy Analysis (SEA). Energy models require an estimate of the internal damping loss factor. Unfortunately, the loss factor is difficult to estimate analytically, and experimental methods such as the power injection method can require extensive measurements over the structure of interest. This paper discusses the implications of estimating damping loss factors using the impulse response decay method (IRDM) from a limited set of response measurements. An automated procedure for implementing IRDM is described and then evaluated using data from a finite element model of a stiffened, curved panel. Estimated loss factors are compared with loss factors computed using a power injection method and a manual curve fit. The paper discusses the sensitivity of the IRDM loss factor estimates to damping of connected subsystems and the number and location of points in the measurement ensemble.

  4. Impulse response method for characterization of echogenic liposomesa)

    PubMed Central

    Raymond, Jason L.; Luan, Ying; van Rooij, Tom; Kooiman, Klazina; Huang, Shao-Ling; McPherson, David D.; Versluis, Michel; de Jong, Nico; Holland, Christy K.

    2015-01-01

    An optical characterization method is presented based on the use of the impulse response to characterize the damping imparted by the shell of an air-filled ultrasound contrast agent (UCA). The interfacial shell viscosity was estimated based on the unforced decaying response of individual echogenic liposomes (ELIP) exposed to a broadband acoustic impulse excitation. Radius versus time response was measured optically based on recordings acquired using an ultra-high-speed camera. The method provided an efficient approach that enabled statistical measurements on 106 individual ELIP. A decrease in shell viscosity, from 2.1 × 10−8 to 2.5 × 10−9 kg/s, was observed with increasing dilatation rate, from 0.5 × 106 to 1 × 107 s−1. This nonlinear behavior has been reported in other studies of lipid-shelled UCAs and is consistent with rheological shear-thinning. The measured shell viscosity for the ELIP formulation used in this study [κs = (2.1 ± 1.0) × 10−8 kg/s] was in quantitative agreement with previously reported values on a population of ELIP and is consistent with other lipid-shelled UCAs. The acoustic response of ELIP therefore is similar to other lipid-shelled UCAs despite loading with air instead of perfluorocarbon gas. The methods described here can provide an accurate estimate of the shell viscosity and damping for individual UCA microbubbles. PMID:25920822

  5. Deriving a dosage-response relationship for community response to high-energy impulsive noise

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.

    1994-01-01

    The inability to systematically predict community response to exposure to sonic booms (and other high energy impulsive sounds) is a major impediment to credible analyses of the environmental effects of supersonic flight operations. Efforts to assess community response to high energy impulsive sounds are limited in at least two important ways. First, a paucity of appropriate empirical data makes it difficult to infer a dosage-response relationship by means similar to those used in the case of general transportation noise. Second, it is unclear how well the 'equal energy hypothesis' (the notion that duration, number, and level of individual events are directly interchangeable determinants of annoyance) applies to some forms of impulsive noise exposure. Some of the issues currently under consideration by a CHABA working group addressing these problems are discussed. These include means for applying information gained in controlled exposure studies about different rates of growth of annoyance with impulsive and non-impulsive sound exposure levels, and strategies for developing a dosage-response relationship in a data-poor area.

  6. A useful approximation for the flat surface impulse response

    NASA Technical Reports Server (NTRS)

    Brown, Gary S.

    1989-01-01

    The flat surface impulse response (FSIR) is a very useful quantity in computing the mean return power for near-nadir-oriented short-pulse radar altimeters. However, for very small antenna beamwidths and relatively large pointing angles, previous analytical descriptions become very difficult to compute accurately. An asymptotic approximation is developed to overcome these computational problems. Since accuracy is of key importance, a condition is developed under which this solution is within 2 percent of the exact answer. The asymptotic solution is shown to be in functional agreement with a conventional clutter power result and gives a 1.25-dB correction to this formula to account properly for the antenna-pattern variation over the illuminated area.

  7. Influence of "omnidirectional" loudspeaker directivity on measured room impulse responses.

    PubMed

    Knüttel, Tobias; Witew, Ingo B; Vorländer, Michael

    2013-11-01

    Measured room impulse responses (RIR) strongly depend on the directivity of the sound source used for the measurement. An analysis method is presented that is capable of pinpointing the influence of the loudspeaker's directivity on a set of RIRs. Taking into account the rotational symmetries of a dodecahedron loudspeaker, it detects the effects that the changing directional pattern induces in the RIR. The analysis of RIRs measured in completely different acoustical environments reveals that the influence of the loudspeaker's directivity can still be observed in the very late part of the RIR-even in very reverberant rooms. These results are presented and the consistency with general room acoustical theory is revised and discussed.

  8. Response of the night aurora to a negative sudden impulse

    NASA Astrophysics Data System (ADS)

    Belakhovsky, V. B.; Vorobjev, V. G.

    2016-11-01

    Data from the meridian scanning photometers of the NORSTAR network and all-sky cameras of the THEMIS network were used for a detailed study of the response of night auroras to the sharp decrease of the solar wind dynamic pressure on September 28, 2009. The decrease in dynamic pressure was accompanied by a corresponding depression of the magnetic field in the SYM-H index and the origin of a negative sudden impulse ( SI) with a duration of 5-8 min and amplitude of 150-200 nT in the horizontal component of the magnetic field at stations of the night sector of the auroral zone. The magnetic impulse was preceded by a long calm magnetic period, although the IMF Bz-component was negative for 1.5 hour before the SI -. The commencement of the SI -, which was determined by variations in the magnetic field at 0650 UT, was accompanied by a sharp increase in the intensity of discrete forms of polar auroras in the midnight sector of the auroral zone and their fast propagation to the pole. Approximately 6-8 min after the SI -, the auroral intensity in the emissions, which were excited by the fluxes of precipitated electrons and protons, quickly began to decrease in the night sector. Analysis of the optical observations showed the two-stage character of the response of the night auroras to the SI - in the considered event: first, fast movement of the discrete aurora forms to the pole with a significant increase in their intensity, and a further fast decrease in auroral intensity with a delay of 6-8 min relative to the SI -. The possible reasons for such aurora behavior are discussed.

  9. The Temporal Impulse Response Function during Smooth Pursuit

    PubMed Central

    Tong, Jianliang; Ramamurthy, Mahalakshmi; Patel, Saumil S.; Vu-Yu, Lan-Phuong; Bedell, Harold E.

    2009-01-01

    Recent studies indicate that the extent of perceived motion smear is attenuated asymmetrically during smooth pursuit eye movements, based on the relative directions of the target and eye motion. We conducted two experiments to determine if the reduction of perceived smear during pursuit might be associated with an acceleration of the temporal impulse response function (TIRF). In Experiment 1, two-pulse increment sensitivity was determined during fixation and rightward pursuit for sequential flashes of a long horizontal line, presented with stimulus-onset asynchronies between 5.9 and 234 ms. In Experiment 2, temporal contrast sensitivity was measured during fixation and rightward pursuit for a vertical 1 cpd grating with retinal image velocities between 4 and 30 Hz. During pursuit, grating motion was either in the same or the opposite direction as the eye movement. TIRFs were modeled as the impulse responses of a second-order, low-pass linear system, fit to the two-pulse increment sensitivity data by an optimization procedure and to the temporal contrast sensitivity results by iterative Fourier synthesis. The results indicate that the natural temporal frequency of the fitted TIRFs was approximately 10% higher during pursuit than fixation. In experiment 2, the increased natural frequency of the TIRF was restricted to the condition in which the grating moved spatially in the opposite direction of the pursuit eye movement. The results are consistent with the hypothesis that extra-retinal signals reduce the extent of perceived motion smear during pursuit, in part by increasing the speed of visual processing preferentially for one direction of image motion. PMID:19706304

  10. Using crosscorrelation techniques to determine the impulse response of linear systems

    NASA Technical Reports Server (NTRS)

    Dallabetta, Michael J.; Li, Harry W.; Demuth, Howard B.

    1993-01-01

    A crosscorrelation method of measuring the impulse response of linear systems is presented. The technique, implementation, and limitations of this method are discussed. A simple system is designed and built using discrete components and the impulse response of a linear circuit is measured. Theoretical and software simulation results are presented.

  11. Responsibility and impulsivity and their interaction in relation to obsessive-compulsive symptoms.

    PubMed

    Smári, Jakob; Bouranel, Guethrún; Thornóra Eiethsdóttir, Sigríethur

    2008-09-01

    In the present study, the role of responsibility and impulsivity and their interaction in obsessive-compulsive symptoms was investigated. The obsessive-compulsive inventory-revised (OCI-R), an attention deficit and hyperactivity/impulsivity self-report scale (AD/HD-SR), the responsibility attitudes scale (RAS), Eysenck's impulsiveness/venturesomeness/empathy questionnaire (IVE), the community epidemiological survey-depression (CES-D) and the Penn State worry questionnaire (PSWQ) were administered to a sample of 405 Icelandic university students. Responsibility attitudes (RAS) and impulsivity measures were significantly related to scores on the OCI-R total scale, even when depression had been taken into consideration. The interaction between responsibility and hyperactivity/impulsivity added to the prediction of OCI-R scores over and above simple effects.

  12. Response of end tidal CO2 pressure to impulse exercise.

    PubMed

    Yano, T; Afroundeh, R; Yamanak, R; Arimitsu, T; Lian, C-S; Shirkawa, K; Yunoki, T

    2014-03-01

    The purpose of the present study was to examine how end tidal CO(2) pressure (PETCO(2)) is controlled in impulse exercise. After pre-exercise at 25 watts for 5 min, impulse exercise for 10 sec with 200 watts followed by post exercise at 25 watts was performed. Ventilation (VE) significantly increased until the end of impulse exercise and significantly re-increased after a sudden decrease. Heart rate (HR) significantly increased until the end of impulse exercise and then decreased to the pre-exercise level. PETCO(2) remained constant during impulse exercise. PETCO(2) significantly increased momentarily after impulse exercise and then significantly decreased to the pre-exercise level. PETCO(2) showed oscillation. The average peak frequency of power spectral density in PETCO(2) appeared at 0.0078 Hz. Cross correlations were obtained after impulse exercise. The peak cross correlations between VE and PETCO(2), HR and PETCO(2), and VE and HR were 0.834 with a time delay of -7 sec, 0.813 with a time delay of 7 sec and 0.701 with a time delay of -15 sec, respectively. We demonstrated that PETCO(2) homeodynamics was interactively maintained by PETCO(2) itself, CO(2) transportation (product of cardiac output and mixed venous CO(2) content) into the lungs by heart pumping and CO(2) elimination by ventilation, and it oscillates as a result of their interactions.

  13. An Item Response Theory Analysis of the Impulsive Behaviors Checklist for Adolescents

    ERIC Educational Resources Information Center

    You, Jianing; Leung, Freedom; Lai, Ching-man; Fu, Kei

    2011-01-01

    This study used item response theory (IRT) to examine the Impulsive Behaviors Checklist for Adolescents (IBCL-A) among 6,276 (67.7% girls) Chinese secondary school students. The IBCL-A included 15 maladaptive impulsive behaviors adapted from the Revised Diagnostic Interview for Borderlines. The authors obtained the severity and discrimination…

  14. Subjective diffuseness of music signals convolved with binaural impulse responses

    NASA Astrophysics Data System (ADS)

    Shimokura, Ryota; Tronchin, Lamberto; Cocchi, Alessandro; Soeta, Yoshiharu

    2011-07-01

    The spatial impression of sound in a hall can be quantified using sound field factors such as the interaural cross-correlation coefficient (IACC) calculated from binaural impulse response (BIR), henceforth denoted by IACC IR. The subjective diffuseness for the listener is a spatial attribute which depends on factors associated both with the source signal and with the actual sound field, and is quantified using the IACC of the signal received by the listener, henceforth denoted by IACC SR. Therefore, the subjective diffuseness in a given hall may change with the music. The aims of this study are to estimate the IACC SR from the IACC IR and the factors, which is obtained from autocorrelation function (ACF) of music signal, and to evaluate the subjective diffuseness by these factors. First, the relationship between the IACC IR and IACC SR was investigated. Second, subjective diffuseness was measured by a psycho-acoustical experiment. As a result, the IACC SR could be estimated from the IACC IR of the BIR and the effective duration ( τe) from the ACF of music signal. It was found that the effects of BIRs on subjective diffuseness could be evaluated by IACC IR for almost all subjects, while the effects of music signals could be evaluated by the τe and the width of the peak at τ=0 ( Wϕ(0) ) of the ACF.

  15. Modeling of localized impulsive injection of neutrals and plasma response

    NASA Astrophysics Data System (ADS)

    Tokar, M. Z.

    2017-05-01

    Neutral particles of hydrogen isotopes, released locally and impulsively into the plasma of fusion devices, can significantly affect local plasma properties. A model, allowing to describe self-consistently the spreading of neutrals from the source and their effect on the local and global plasma conditions is developed. It is based on the separation on each flux surface of two zones, the ‘cold’ cloud, comprising neutral molecules injected and atoms generated in collisions of molecules with electrons and ions, and the ‘hot’ environment affected by flows along the magnetic field of newly produced charged particles outward and heat conduction toward the cloud. Computations are done for the conditions of laser induced desorption spectroscopy applied in Ohmically heated plasmas in the TEXTOR tokamak and foreseen for the ITER fusion reactor. In both cases the local plasma state is strongly changed by the desorption pulse, and this effect is increasing with the growing isotope mass. As a result the total number of photons emitted is reduced noticeably, up to 4 times in the case of tritium injection in ITER, and the necessity to take into account the plasma response by interpreting measurements is demonstrated.

  16. Two-Meter Laser Material Response Impulse Measurements

    DTIC Science & Technology

    1988-02-11

    The initial MLi impulse studies used a Fotonic gauge as a velocity sensor. As a check on its accuracy, impulse was measured using a simple pendulum...the results agreed with the Fotonic gauge data. A careful investigation of the pendulum experimental technique followed; no problems were found. The S...been taken at different pressures. The MLI data were taken over a range of 0.05 to 0.50 torr, with the exception of two Fotonic gauge shots, which were

  17. A negative relationship between ventral striatal loss anticipation response and impulsivity in borderline personality disorder.

    PubMed

    Herbort, Maike C; Soch, Joram; Wüstenberg, Torsten; Krauel, Kerstin; Pujara, Maia; Koenigs, Michael; Gallinat, Jürgen; Walter, Henrik; Roepke, Stefan; Schott, Björn H

    2016-01-01

    Patients with borderline personality disorder (BPD) frequently exhibit impulsive behavior, and self-reported impulsivity is typically higher in BPD patients when compared to healthy controls. Previous functional neuroimaging studies have suggested a link between impulsivity, the ventral striatal response to reward anticipation, and prediction errors. Here we investigated the striatal neural response to monetary gain and loss anticipation and their relationship with impulsivity in 21 female BPD patients and 23 age-matched female healthy controls using functional magnetic resonance imaging (fMRI). Participants performed a delayed monetary incentive task in which three categories of objects predicted a potential gain, loss, or neutral outcome. Impulsivity was assessed using the Barratt Impulsiveness Scale (BIS-11). Compared to healthy controls, BPD patients exhibited significantly reduced fMRI responses of the ventral striatum/nucleus accumbens (VS/NAcc) to both reward-predicting and loss-predicting cues. BIS-11 scores showed a significant positive correlation with the VS/NAcc reward anticipation responses in healthy controls, and this correlation, while also nominally positive, failed to reach significance in BPD patients. BPD patients, on the other hand, exhibited a significantly negative correlation between ventral striatal loss anticipation responses and BIS-11 scores, whereas this correlation was significantly positive in healthy controls. Our results suggest that patients with BPD show attenuated anticipation responses in the VS/NAcc and, furthermore, that higher impulsivity in BPD patients might be related to impaired prediction of aversive outcomes.

  18. Impulse Response Measurements Over Space-Earth Paths Using the GPS Coarse/Acquisition Codes

    NASA Technical Reports Server (NTRS)

    Lemmon, J. J.; Papazian, P. B.

    1995-01-01

    The impulse responses of radio transmission channels over space-earth paths were measured using the course/acquisition code signals from the Global Positioning System of satellites. The data acquisition system and signal processing techniques used to develop the impulse responses are described. Examples of impulse response measurements are presented. The results indicate that this measurement approach enables detection of multipath signals that are 20 dB or more below the power of the direct arrival. Channel characteristics that could be investigated with additional measurements and analyses are discussed.

  19. Approximation of the impulse response of an ultra-wide band antenna

    NASA Astrophysics Data System (ADS)

    Tamas, R.; Chilo, J.; Saguet, P.

    2007-08-01

    Ultra-wide band antennas can be characterized by the time-domain impulse response. This paper introduces an approximate form of the impulse response that can be calculated by applying the method of moments to the Freedholm integral equation of convolution. Numerical results are compared to those obtained using the traditional frequency-domain approach. The validity of the approximate impulse response and the application constraints are also discussed. It is shown that the time-domain approach is faster than the frequency-domain approach while the accuracy is preserved.

  20. Relationships between Impulsivity and Subjective Response in an IV Ethanol Paradigm

    PubMed Central

    Leeman, Robert F.; Ralevski, Elizabeth; Limoncelli, Diana; Pittman, Brian; O’Malley, Stephanie S.; Petrakis, Ismene L.

    2014-01-01

    Rationale: Impulsivity and individual differences in subjective response to alcohol are risk factors for alcohol problems and possibly endophenotypes for alcohol dependence. Few prior studies have addressed relationships between the two constructs. Objectives: To predict subjective responses to ethanol, we tested self-reported impulsiveness, ethanol dose condition (high dose, low dose or placebo) and time (7 timepoints) along with interactions among these variables. Methods: The present study is a secondary analysis of data from a within subject, placebo-controlled, dose-ranging ethanol administration study using IV infusion with a clamping technique to maintain steady-state breath alcohol concentration. The sample consisted of healthy, non-alcohol dependent social alcohol drinkers between the ages of 21-30 (N=105). Participants at varying levels of impulsivity were compared with regard to stimulant and subjective responses to three ethanol dose conditions over time. Results: Individuals with higher impulsivity reported stronger stimulant and weaker sedative response to alcohol, particularly at the higher dose. Higher impulsivity was associated with a steeper increase in stimulant effects during the first half of clamped ethanol infusion with the higher dose. Conclusions: These results suggest that impulsive individuals may experience enhanced reinforcing, stimulant effects and relatively muted aversive, sedative effects from alcohol. These subjective responses may relate to enhanced risk of alcohol problems among more impulsive individuals. PMID:24553574

  1. Relationships between impulsivity and subjective response in an IV ethanol paradigm.

    PubMed

    Leeman, Robert F; Ralevski, Elizabeth; Limoncelli, Diana; Pittman, Brian; O'Malley, Stephanie S; Petrakis, Ismene L

    2014-07-01

    Impulsivity and individual differences in subjective response to alcohol are risk factors for alcohol problems and possibly endophenotypes for alcohol dependence. Few prior studies have addressed relationships between the two constructs. To predict subjective responses to ethanol, we tested self-reported impulsiveness, ethanol dose condition (high dose, low dose, or placebo), and time (seven time points) along with interactions among these variables. The present study is a secondary analysis of data from a within-subject, placebo-controlled, dose-ranging ethanol administration study using IV infusion with a clamping technique to maintain steady-state breath alcohol concentration. The sample consisted of healthy, non-alcohol dependent social alcohol drinkers between the ages of 21 and 30 (N=105). Participants at varying levels of impulsivity were compared with regard to stimulant and subjective responses to three ethanol dose conditions over time. Individuals with higher impulsivity reported elavated stimulant and dampened sedative response to alcohol, particularly at the higher dose. Higher impulsivity was associated with a steeper increase in stimulant effects during the first half of clamped ethanol infusion with the higher dose. These results suggest that impulsive individuals may experience enhanced reinforcing, stimulant effects, and relatively muted aversive sedative effects from alcohol. These subjective responses may relate to enhanced risk of alcohol problems among more impulsive individuals.

  2. Response of structural concrete elements to severe impulsive loads

    NASA Astrophysics Data System (ADS)

    Krauthammer, T.; Shanaa, H. M.; Assadi, A.

    1994-10-01

    The behavior and response of structural concrete elements under severe short duration dynamic loads was investigated numerically. The analytical approach utilized the Timoshenko beam theory for the analysis of reinforced concrete beams and one-way slabs. Nonlinear material models were used to derive the flexural and shear resistances, and the differential equations of the Timoshenko beam theory were solved numerically by applying the finite difference technique. A simplified approach was developed for estimating the strain rate in structural concrete members, and the corresponding strain rate effects on the strength of the steel and concrete were incorporated into the analysis. Detailed failure criteria were established for predicting the collapse of structural concrete members. Five cases subjected to localized impact loads and eleven cases subjected to distributed explosive loads were analyzed, and the results were compared to experimental data obtained by other investigators.

  3. [Biodynamic response of the human shank subjected to impulse load].

    PubMed

    Wang, X; Bai, R; Tumer, S T

    2000-06-01

    This paper reported the establishment of biodynamic modelling of the human shank in the sagittal palne while the human thigh is fixed. And when the shank is subjected to the two types of externally applied impulse loads, the forces associated with the four main ligaments, as well as the bone-to-bone contact forces in the knee joint are numerically obtained. The contact point locations are also presented together with the angular motions of the lower limb segments.

  4. Response Due To Impulsive Force In Generalized Thermomicrostretch Elastic Solid

    NASA Astrophysics Data System (ADS)

    Kumar, V.; Singh, R.

    2015-08-01

    A two dimensional Cartesian model of a generalized thermo-microstretch elastic solid subjected to impulsive force has been studied. The eigen value approach is employed after applying the Laplace and Fourier transforms on the field equations for L-S and G-L model of the plain strain problem. The integral transforms have been inverted into physical domain numerically and components of normal displacement, normal force stress, couple stress and microstress have been illustrated graphically.

  5. A conditioned response as a measure of impulsive-compulsive behaviours in Parkinson's disease.

    PubMed

    Evans, Andrew H; Kettlewell, Jade; McGregor, Sarah; Kotschet, Katya; Griffiths, Robert I; Horne, Malcolm

    2014-01-01

    Parkinson's Disease patients wore a device on the wrist that gave reminders to take levodopa and also measured bradykinesia and dyskinesia. Consumption of medications was acknowledged by placing the thumb on the device. Some patients performed this acknowledgement repeatedly and unconsciously. This study examines whether this behaviour reflected increased impulsivity. Twenty five participants were selected because they had i) excess acknowledgements described above or ii) Impulsive-Compulsive Behaviours or iii) neither of these. A blinded assessor applied clinical scales to measure Impulsive-Compulsive Behaviours, cognition, depression, anxiety and apathy. A Response Ratio, representing the number of acknowledgements/number of doses (expressed as a percentage) was tightly correlated with ratings of Impulsive-Compulsive Behaviours (r² = 0.79) in 19/25 subjects. Some of these patients had dyskinesia, which was higher with extraneous responses than with response indicating medication consumption. Six of the 25 subjects had high Impulsive-Compulsive Behaviour Scores, higher apathy scores, low levels of dyskinesia and normal Response Ratios. Patients without ICB (low RR) also had low dyskinesia levels regardless of the relevance of the response. An elevated Response Ratio is a specific measure of a type of ICB where increased incentive salience is attributed to cues by the presence of high striatal dopamine levels, manifested by high levels of dyskinesia. This study also points to a second form of ICBs which occur in the absence of dyskinesia, has normal Response Ratios and higher apathy scores, and may represent prefrontal pathology.

  6. Impulsivity and aggression mediate regional brain responses in Borderline Personality Disorder: An fMRI study.

    PubMed

    Soloff, Paul H; Abraham, Kristy; Burgess, Ashley; Ramaseshan, Karthik; Chowdury, Asadur; Diwadkar, Vaibhav A

    2017-02-28

    Fronto-limbic brain networks involved in regulation of impulsivity and aggression are abnormal in Borderline Personality Disorder (BPD). However, it is unclear whether, or to what extent, these personality traits actually modulate brain responses during cognitive processing. Using fMRI, we examined the effects of trait impulsivity, aggression, and depressed mood on regional brain responses in 31 female BPD and 25 control subjects during a Go No-Go task using Ekman faces as targets. First-level contrasts modeled effects of negative emotional context. Second-level regression models used trait impulsivity, aggression and depressed mood as predictor variables of regional brain activations. In BPD, trait impulsivity was positively correlated with activation in the dorsal anterior cingulate cortex, orbital frontal cortex (OFC), basal ganglia (BG), and dorsolateral prefrontal cortex, with no areas of negative correlation. In contrast, aggression was negatively correlated with activation in OFC, hippocampus, and BG, with no areas of positive correlation. Depressed mood had a generally dampening effect on activations. Effects of trait impulsivity on healthy controls differed from effects in BPD, suggesting a disorder-specific response. Negative emotional context and trait impulsivity, but not aggression or depression, diminished task performance across both groups. Negative emotional context may interfere with cognitive functioning in BPD through interaction with the neurobiology of personality traits.

  7. Impulsivity and Stress Response in Pathological Gamblers During the Trier Social Stress Test.

    PubMed

    Maniaci, G; Goudriaan, A E; Cannizzaro, C; van Holst, R J

    2017-03-18

    Gambling has been associated with increased sympathetic nervous system output and stimulation of the hypothalamic-pituitary-adrenal axis. However it is unclear how these systems are affected in pathological gambling. This study aimed to investigate the effect of the Trier Social Stress Test (TSST) on cortisol and on cardiac interbeat intervals in relation to impulsivity, in a sample of male pathological gamblers compared to healthy controls. In addition, we investigated the correlation between the TSST, duration of the disorder and impulsivity. A total of 35 pathological gamblers and 30 healthy controls, ranging from 19 to 58 years old and all male, participated in this study. Stress response was measured during and after the TSST by salivary cortisol and cardiac interbeat intervals; impulsivity was assessed with the Barratt Impulsiveness Scale (BIS-11). Exposure to the TSST produced a significant increase in salivary cortisol and interbeat intervals in both groups, without differences between groups. We found a negative correlation between baseline cortisol and duration of pathological gambling indicating that the longer the duration of the disorder the lower the baseline cortisol levels. Additionally, we found a main effect of impulsivity across groups on interbeat interval during the TSST, indicating an association between impulsivity and the intensity of the neurovegetative stress response during the TSST. Involvement of the hypothalamic-pituitary-adrenal axis in pathological gambling was confirmed together with evidence of a correlation between length of the disorder and diminished baseline cortisol levels. Impulsivity emerged as a personality trait expressed by pathological gamblers; however the neurovegetative response to the TSST, although associated with impulsivity, appeared to be independent of the presence of pathological gambling.

  8. Viscoelastic damped response of cross-ply laminated shallow spherical shells subjected to various impulsive loads

    NASA Astrophysics Data System (ADS)

    Şahan, Mehmet Fatih

    2017-02-01

    In this paper, the viscoelastic damped response of cross-ply laminated shallow spherical shells is investigated numerically in a transformed Laplace space. In the proposed approach, the governing differential equations of cross-ply laminated shallow spherical shell are derived using the dynamic version of the principle of virtual displacements. Following this, the Laplace transform is employed in the transient analysis of viscoelastic laminated shell problem. Also, damping can be incorporated with ease in the transformed domain. The transformed time-independent equations in spatial coordinate are solved numerically by Gauss elimination. Numerical inverse transformation of the results into the real domain are operated by the modified Durbin transform method. Verification of the presented method is carried out by comparing the results with those obtained by the Newmark method and ANSYS finite element software. Furthermore, the developed solution approach is applied to problems with several impulsive loads. The novelty of the present study lies in the fact that a combination of the Navier method and Laplace transform is employed in the analysis of cross-ply laminated shallow spherical viscoelastic shells. The numerical sample results have proved that the presented method constitutes a highly accurate and efficient solution, which can be easily applied to the laminated viscoelastic shell problems.

  9. A theoretical and experimental investigation of the linear and nonlinear impulse responses from a magnetoplasma column

    NASA Technical Reports Server (NTRS)

    Grody, N. C.

    1973-01-01

    Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.

  10. Spatio-Temporal Dynamics of Impulse Responses to Figure Motion in Optic Flow Neurons

    PubMed Central

    Lee, Yu-Jen; Jönsson, H. Olof; Nordström, Karin

    2015-01-01

    White noise techniques have been used widely to investigate sensory systems in both vertebrates and invertebrates. White noise stimuli are powerful in their ability to rapidly generate data that help the experimenter decipher the spatio-temporal dynamics of neural and behavioral responses. One type of white noise stimuli, maximal length shift register sequences (m-sequences), have recently become particularly popular for extracting response kernels in insect motion vision. We here use such m-sequences to extract the impulse responses to figure motion in hoverfly lobula plate tangential cells (LPTCs). Figure motion is behaviorally important and many visually guided animals orient towards salient features in the surround. We show that LPTCs respond robustly to figure motion in the receptive field. The impulse response is scaled down in amplitude when the figure size is reduced, but its time course remains unaltered. However, a low contrast stimulus generates a slower response with a significantly longer time-to-peak and half-width. Impulse responses in females have a slower time-to-peak than males, but are otherwise similar. Finally we show that the shapes of the impulse response to a figure and a widefield stimulus are very similar, suggesting that the figure response could be coded by the same input as the widefield response. PMID:25955416

  11. Mechanical response of single nerve cells estimated by femtosecond laser-induced impulsive force

    NASA Astrophysics Data System (ADS)

    Iino, Takanori; Furuno, Tadahide; Hagiyama, Man; Ito, Akihiko; Hosokawa, Yoichiroh

    2015-03-01

    Single nerve cell's mechanical response is an important issue for understanding function of nerve system, though, the response has been rarely clear. One of the factors is difficulty to stimulate the single cells by quantitative and controllable mechanical stress with subcellular spatial selectivity. As such mechanical stimulator, our group has focused on shock and stress waves generated by focusing the femtosecond laser under a microscope. When those waves impact on the biological cell, they act as an impulsive force. Although the impulsive force is available as a mechanical manipulator of the single cells, it was not confirmed that it could stimulate the nerve cells. Here we investigated the issue using neuro2a cells extending their neurite as an experimental model of nerve cell. Our results indicated that the impulsive force could be available as the stimulator to cause the mechanical response of the neuro2a cell.

  12. Modeling and parameter identification of impulse response matrix of mechanical systems

    NASA Astrophysics Data System (ADS)

    Bordatchev, Evgueni V.

    1998-12-01

    A method for studying the problem of modeling, identification and analysis of mechanical system dynamic characteristic in view of the impulse response matrix for the purpose of adaptive control is developed here. Two types of the impulse response matrices are considered: (i) on displacement, which describes the space-coupled relationship between vectors of the force and simulated displacement, which describes the space-coupled relationship between vectors of the force and simulated displacement and (ii) on acceleration, which also describes the space-coupled relationship between the vectors of the force and measured acceleration. The idea of identification consists of: (a) the practical obtaining of the impulse response matrix on acceleration by 'impact-response' technique; (b) the modeling and parameter estimation of the each impulse response function on acceleration through the fundamental representation of the impulse response function on displacement as a sum of the damped sine curves applying linear and non-linear least square methods; (c) simulating the impulse provides the additional possibility to calculate masses, damper and spring constants. The damped natural frequencies are used as a priori information and are found through the standard FFT analysis. The problem of double numerical integration is avoided by taking two derivations of the fundamental dynamic model of a mechanical system as linear combination of the mass-damper-spring subsystems. The identified impulse response matrix on displacement represents the dynamic properties of the mechanical system. From the engineering point of view, this matrix can be also understood as a 'dynamic passport' of the mechanical system and can be used for dynamic certification and analysis of the dynamic quality. In addition, the suggested approach mathematically reproduces amplitude-frequency response matrix in a low-frequency band and on zero frequency. This allows the possibility of determining the matrix of the

  13. Numeric Solution of Plasma Impulse Response with Model Fokker-Planck Operator

    NASA Astrophysics Data System (ADS)

    Klein, Kristopher; Skiff, Fred

    2009-11-01

    Using a model Fokker-Planck collision operatorfootnotetextJ. P. Dougherty Phys. Fluids 7 (1964) we have investigated the impulse response of a kinetic plasma, in prescribed external electric and magnetic fields, due to several types of perturbations in phase space. The one-dimensional case is treated numerically as a solution of a Fredholm-Volterra Equation of the Second Kind. We also provide motivation for using the same numeric method for finding solutions of the higher dimensional cases. By comparing the numeric impulse response to measured two-point correlation functions in a magnetized plasma, we hope to test Onsager's regression hypothesis.

  14. Anomalous signed passive fathometer impulse response when using adaptive beam forming (L).

    PubMed

    Harrison, Chris H

    2009-06-01

    The impulse response of the seabed can be extracted from sea surface ambient noise by cross-correlating the time series from an upward and a downward steered beam. When the steering for each beam is standard minimum variance adaptive beam forming it has been found that the impulse response for significant echoes appears to have the same amplitude but opposite sign. A mathematical explanation is offered for this strange phenomenon. Crucial contributing factors are that the cross-spectral density matrix for the vertical array typically consists of the sum of a Toeplitz matrix and a much weaker Hankel matrix and that it is ill-conditioned.

  15. Ablative Thermal Response Analysis Using the Finite Element Method

    NASA Technical Reports Server (NTRS)

    Dec John A.; Braun, Robert D.

    2009-01-01

    A review of the classic techniques used to solve ablative thermal response problems is presented. The advantages and disadvantages of both the finite element and finite difference methods are described. As a first step in developing a three dimensional finite element based ablative thermal response capability, a one dimensional computer tool has been developed. The finite element method is used to discretize the governing differential equations and Galerkin's method of weighted residuals is used to derive the element equations. A code to code comparison between the current 1-D tool and the 1-D Fully Implicit Ablation and Thermal Response Program (FIAT) has been performed.

  16. Where the ocean influences the impulse response and its effect on synchronous changes of acoustic travel time.

    PubMed

    Spiesberger, John L

    2011-12-01

    In 1983, sounds at 133 Hz, 0.06 s resolution were transmitted in the Pacific for five days at 2 min intervals over 3709 km between bottom-mounted instruments maintained with atomic clocks. In 1989, a technique was developed to measure changes in acoustic travel time with an accuracy of 135 microseconds at 2 min intervals for selected windows of travel time within the impulse response. The data have short-lived 1 to 10 ms oscillations of travel time with periods less than a few days. Excluding tidal effects, different windows exhibited significant synchronized changes in travel time for periods shorter than 10 h. In the 1980s, this phenomenon was not understood because internal waves have correlation lengths of a few kilometers which are smaller than the way sound was thought to sample the ocean along well-separated and distinct rays corresponding to different windows. The paradox's resolution comes from modern theories that replace the ray-picture with finite wavelength representations that predict sound can be influenced in the upper ocean over horizontal scales such as 20 km or more. Thus, different windows are influenced by the same short-scale fluctuations of sound speed. This conclusion is supported by the data and numerical simulations of the impulse response. © 2011 Acoustical Society of America

  17. A Conditioned Response as a Measure of Impulsive-Compulsive Behaviours in Parkinson's Disease

    PubMed Central

    McGregor, Sarah; Kotschet, Katya; Griffiths, Robert I.; Horne, Malcolm

    2014-01-01

    Objectives Parkinson's Disease patients wore a device on the wrist that gave reminders to take levodopa and also measured bradykinesia and dyskinesia. Consumption of medications was acknowledged by placing the thumb on the device. Some patients performed this acknowledgement repeatedly and unconsciously. This study examines whether this behaviour reflected increased impulsivity. Methods and Results Twenty five participants were selected because they had i) excess acknowledgements described above or ii) Impulsive-Compulsive Behaviours or iii) neither of these. A blinded assessor applied clinical scales to measure Impulsive-Compulsive Behaviours, cognition, depression, anxiety and apathy. A Response Ratio, representing the number of acknowledgements/number of doses (expressed as a percentage) was tightly correlated with ratings of Impulsive-Compulsive Behaviours (r2 = 0.79) in 19/25 subjects. Some of these patients had dyskinesia, which was higher with extraneous responses than with response indicating medication consumption. Six of the 25 subjects had high Impulsive-Compulsive Behaviour Scores, higher apathy scores, low levels of dyskinesia and normal Response Ratios. Patients without ICB (low RR) also had low dyskinesia levels regardless of the relevance of the response. Conclusion An elevated Response Ratio is a specific measure of a type of ICB where increased incentive salience is attributed to cues by the presence of high striatal dopamine levels, manifested by high levels of dyskinesia. This study also points to a second form of ICBs which occur in the absence of dyskinesia, has normal Response Ratios and higher apathy scores, and may represent prefrontal pathology. PMID:24586685

  18. Impulse Response of a Density Contrast Wedge Using Normal Coordinates.

    NASA Astrophysics Data System (ADS)

    Chu, Dezhang

    The exact impulse solutions of a point source for a penetrable wedge (rhonerho ', upsilon = upsilon ') and a shallow water wedge using normal coordinates are presented. This is the extension of Biot and Tolstoy's exact solution in normal coordinates for a rigid wedge. Our solutions reduce to known solutions for rigid (rho'toinfty ), free (rho'to 0), and homogeneous (rho' = rho) wedges. The direct, reflected, transmitted and diffracted waves are well separated in time domain. The reflected (transmitted) part can be described by the direct waves traveling from the images around the image circle to the receiver, the amplitude depends on the number of times that the actual wave is reflected from the wedge walls. The diffracted part of the solution is not the solution for an ideal wedge (rigid or free) multiplied by an impedance factor. Transmission of acoustic wave in a wedge shaped waveguide (shallow water wedge) can also be solved in a normal mode formulation. An array of sources can excite single mode transmission in the waveguide. Alternatively, a combination of the wedge solution for a set of source positions can also be chosen to excite a single mode. The normal mode technique and wedge solution using normal coordinates give the same signal amplitudes. We compare our wedge solutions with the laboratory experimental measurements given by Tindle et al. The good agreements of the theoretical predictions with their experimental data suggests that the exact solution of an isovelocity wedge can be applied for a more general penetrable wedge by incorporating the total reflections if the velocity contrast is as close enough to 1.0.

  19. Linear Ordinary Differential Equations with Constant Coefficients. Revisiting the Impulsive Response Method Using Factorization

    ERIC Educational Resources Information Center

    Camporesi, Roberto

    2011-01-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as well as of…

  20. Dynamic response of mechanical systems to impulse process stochastic excitations: Markov approach

    NASA Astrophysics Data System (ADS)

    Iwankiewicz, R.

    2016-05-01

    Methods for determination of the response of mechanical dynamic systems to Poisson and non-Poisson impulse process stochastic excitations are presented. Stochastic differential and integro-differential equations of motion are introduced. For systems driven by Poisson impulse process the tools of the theory of non-diffusive Markov processes are used. These are: the generalized Itô’s differential rule which allows to derive the differential equations for response moments and the forward integro-differential Chapman-Kolmogorov equation from which the equation governing the probability density of the response is obtained. The relation of Poisson impulse process problems to the theory of diffusive Markov processes is given. For systems driven by a class of non-Poisson (Erlang renewal) impulse processes an exact conversion of the original non-Markov problem into a Markov one is based on the appended Markov chain corresponding to the introduced auxiliary pure jump stochastic process. The derivation of the set of integro-differential equations for response probability density and also a moment equations technique are based on the forward integro-differential Chapman-Kolmogorov equation. An illustrating numerical example is also included.

  1. Linear Ordinary Differential Equations with Constant Coefficients. Revisiting the Impulsive Response Method Using Factorization

    ERIC Educational Resources Information Center

    Camporesi, Roberto

    2011-01-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as well as of…

  2. Reverberation time measurement using integrated impulse response and sweep sine excitation

    NASA Astrophysics Data System (ADS)

    Nabuco, Marco; Brando, Paulo

    2002-11-01

    As the capacity and speed of digital processing systems becomes much higher, the integrated impulsive response for reverberation time measurements by the indirect method also becomes more feasible and faster. The MLS technique to obtain the impulse response for LTI has been developed during the last several years and it is very well reported by the bibliography. Some frequency analyzers available in the market are capable to generate and process MLS to get the impulse responses very easily. Sometimes, when the room to be tested is very reverberant, sequences of higher order and a certain number of average are necessary to assure acceptable signal-to-noise ratio. The sweep sine technique or the deconvolution method to obtain impulsive responses presents many new advantages, most of them still reported in various technical documents. This paper presents the results of application of this technique to measure the reverberation time in two different reverberation rooms. Comparisons with MLS, ensemble, and reverberation time averages are presented. The sweep sine technique repeatability was verified in a reverberation chamber for a polyurethane foam sample and showed smaller standard deviations when compared with other techniques. (To be presented in Portuguese.)

  3. Impulsivity in women with eating disorders: problem of response inhibition, planning, or attention?

    PubMed

    Rosval, Lindsay; Steiger, Howard; Bruce, Kenneth; Israël, Mimi; Richardson, Jodie; Aubut, Melanie

    2006-11-01

    Impulsivity is generally believed to be more characteristic of individuals with bulimic than with restrictive eating disorders (EDs). However, studies have not exhaustively explored the association between EDs and various component dimensions of the impulsivity construct. We conducted a multidimensional assessment of impulsivity in 84 women with bulimia nervosa (BN), 37 with anorexia nervosa (AN: 19 restricters and 18 bingers-purgers), and 61 normal-control participants. To assess multiple components of impulsivity, participants completed a battery of self-report questionnaires and a performance test. Compared with normal-control participants, all ED groups showed attentional problems. However, only women suffering BN or AN-binge purge subtype showed elevations on motoric forms of impulsivity, whereas women with BN were the only group to report tendencies toward reckless behavior. These findings suggest that binge-eating behavior coincides with problems of response inhibition, whereas a risk-taking attitude may be a unique characteristic of individuals with BN. (c) 2006 by Wiley Periodicals, Inc.

  4. Reduced Prefrontal Cortex Hemodynamic Response in Adults with Methamphetamine Induced Psychosis: Relevance for Impulsivity

    PubMed Central

    Yamamuro, Kazuhiko; Kimoto, Sohei; Iida, Junzo; Kishimoto, Naoko; Nakanishi, Yoko; Tanaka, Shohei; Ota, Toyosaku; Makinodan, Manabu; Kishimoto, Toshifumi

    2016-01-01

    Patients with methamphetamine abuse/dependence often exhibit high levels of impulsivity, which may be associated with the structural abnormalities and functional hypoactivities observed in the frontal cortex of these subjects. Although near-infrared spectroscopy (NIRS) is a simple and non-invasive method for characterizing the clinical features of various psychiatric illnesses, few studies have used NIRS to directly investigate the association between prefrontal cortical activity and inhibitory control in patients with methamphetamine-induced psychosis (MAP). Using a 24-channel NIRS system, we compared hemodynamic responses during the Stroop color-word task in 14 patients with MAP and 21 healthy controls matched for age, sex and premorbid IQ. In addition, we used the Barrett Impulsivity Scale-11 (BIS-11) to assess impulsivity between subject groups. The MAP group exhibited significantly less activation in the anterior and frontopolar prefrontal cortex accompanied by lower Stroop color-word task performance, compared with controls. Moreover, BIS-11 scores were significantly higher in the MAP group, and were negatively correlated with the hemodynamic responses in prefrontal cortex. Our data suggest that reduced hemodynamic responses in the prefrontal cortex might reflect higher levels of impulsivity in patients with MAP, providing new insights into disrupted inhibitory control observed in MAP. PMID:27050450

  5. Finite Post Synaptic Potentials Cause a Fast Neuronal Response

    PubMed Central

    Helias, Moritz; Deger, Moritz; Rotter, Stefan; Diesmann, Markus

    2011-01-01

    A generic property of the communication between neurons is the exchange of pulses at discrete time points, the action potentials. However, the prevalent theory of spiking neuronal networks of integrate-and-fire model neurons relies on two assumptions: the superposition of many afferent synaptic impulses is approximated by Gaussian white noise, equivalent to a vanishing magnitude of the synaptic impulses, and the transfer of time varying signals by neurons is assessable by linearization. Going beyond both approximations, we find that in the presence of synaptic impulses the response to transient inputs differs qualitatively from previous predictions. It is instantaneous rather than exhibiting low-pass characteristics, depends non-linearly on the amplitude of the impulse, is asymmetric for excitation and inhibition and is promoted by a characteristic level of synaptic background noise. These findings resolve contradictions between the earlier theory and experimental observations. Here we review the recent theoretical progress that enabled these insights. We explain why the membrane potential near threshold is sensitive to properties of the afferent noise and show how this shapes the neural response. A further extension of the theory to time evolution in discrete steps quantifies simulation artifacts and yields improved methods to cross check results. PMID:21427776

  6. Derivation of a new parametric impulse response matrix utilized for nodal wind load identification by response measurement.

    PubMed

    Kazemi Amiri, A; Bucher, C

    2015-05-26

    This paper provides new formulations to derive the impulse response matrix, which is then used in the problem of load identification with application to wind induced vibration. The applied loads are inversely identified based on the measured structural responses by solving the associated discrete ill-posed problem. To this end - based on an existing parametric structural model - the impulse response functions of acceleration, velocity and displacement have been computed. Time discretization of convolution integral has been implemented according to an existing and a newly proposed procedure, which differ in the numerical integration methods. The former was evaluated based on a constant rectangular approximation of the sampled data and impulse response function in a number of steps corresponding to the sampling rate, while the latter interpolates the sampled data in an arbitrary number of sub-steps and then integrates over the sub-steps and steps. The identification procedure was implemented for a simulation example as well as an experimental laboratory case. The ill-conditioning of the impulse response matrix made it necessary to use Tikhonov regularization to recover the applied force from noise polluted measured response. The optimal regularization parameter has been obtained by L-curve and GCV method. The results of simulation represent good agreement between identified and measured force. In the experiments the identification results based on the measured displacement as well as acceleration are provided. Further it is shown that the accuracy of experimentally identified load depends on the sensitivity of measurement instruments over the different frequency ranges.

  7. Comparison of New Methods for Assessing Community Response to High Energy Impulsive Sounds

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.

    1996-01-01

    The latest CHABA Working Group to have reviewed published information about the effects of high energy impulsive sounds (such as sonic booms) on communities has recommended abandonment of the dosage-response relationship identified by its predecessor in favor of two alternate prediction method. Both of the new assessment methods continue to rely on C-weighted measurements of impulsive sounds One of the two assessment methods retains the standard assumptions of the 'equal energy hypothesis' (the notion that annoyance is governed simply by the product of level, duration, and number noise events), and further assumes that the rate of growth of the prevalence of annoyance is proportional to the rate of growth of loudness with level. The other assessment method, however, assumes a level dependent (non-equal energy) summation of the C-weighted sound exposure levels of individual impulsive events. Since predictions of the second method are distribution-dependent, they are not readily represents graphically in the form of a single dosage-response function. The effects on annoyance predictions of variance in distributions of CSEL values of impulsive sounds are explored in this presentation.

  8. Comparison of New Methods for Assessing Community Response to High Energy Impulsive Sounds

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.

    1996-01-01

    The latest CHABA Working Group to have reviewed published information about the effects of high energy impulsive sounds (such as sonic booms) on communities has recommended abandonment of the dosage-response relationship identified by its predecessor in favor of two alternate prediction method. Both of the new assessment methods continue to rely on C-weighted measurements of impulsive sounds One of the two assessment methods retains the standard assumptions of the 'equal energy hypothesis' (the notion that annoyance is governed simply by the product of level, duration, and number noise events), and further assumes that the rate of growth of the prevalence of annoyance is proportional to the rate of growth of loudness with level. The other assessment method, however, assumes a level dependent (non-equal energy) summation of the C-weighted sound exposure levels of individual impulsive events. Since predictions of the second method are distribution-dependent, they are not readily represents graphically in the form of a single dosage-response function. The effects on annoyance predictions of variance in distributions of CSEL values of impulsive sounds are explored in this presentation.

  9. Neonatal handling causes impulsive behavior and decreased pharmacological response to methylphenidate in male adult wistar rats.

    PubMed

    Lazzaretti, Camilla; Kincheski, Grasielle Clotildes; Pandolfo, Pablo; Krolow, Rachel; Toniazzo, Ana Paula; Arcego, Danusa Mar; Couto-Pereira, Natividade de Sá; Zeidán-Chuliá, Fares; Galvalisi, Martin; Costa, Gustavo; Scorza, Cecilia; Souza, Tadeu Mello E; Dalmaz, Carla

    2016-03-01

    Neonatal handling has an impact on adult behavior of experimental animals and is associated with rapid and increased palatable food ingestion, impaired behavioral flexibility, and fearless behavior to novel environments. These symptoms are characteristic features of impulsive trait, being controlled by the medial prefrontal cortex (mPFC). Impulsive behavior is a key component of many psychiatric disorders such as attention deficit hyperactivity disorder (ADHD), manic behavior, and schizophrenia. Others have reported a methylphenidate (MPH)-induced enhancement of mPFC functioning and improvements in behavioral core symptoms of ADHD patients. The aims of the present study were: (i) to find in vivo evidence for an association between neonatal handling and the development of impulsive behavior in adult Wistar rats and (ii) to test whether neonatal handling could have an impact on monoamine levels in the mPFC and the pharmacological response to MPH in vivo. Therefore, experimental animals (litters) were classified as: "non-handled" and "handled" (10[Formula: see text]min/day, postnatal days 1-10). After puberty, they were exposed to either a larger and delayed or smaller and immediate reward (tolerance to delay of reward task). Acute MPH (3[Formula: see text]mg/Kg. i.p.) was used to suppress and/or regulate impulsive behavior. Our results show that only neonatally handled male adult Wistar rats exhibit impulsive behavior with no significant differences in monoamine levels in the medial prefrontal cortex, together with a decreased response to MPH. On this basis, we postulate that early life interventions may have long-term effects on inhibitory control mechanisms and affect the later response to pharmacological agents during adulthood.

  10. Assessing personal financial management in patients with bipolar disorder and its relation to impulsivity and response inhibition.

    PubMed

    Cheema, Marvi K; MacQueen, Glenda M; Hassel, Stefanie

    2015-01-01

    Impulsivity and risk-taking behaviours are reported in bipolar disorder (BD). We examined whether financial management skills are related to impulsivity in patients with BD. We assessed financial management skills using the Executive Personal Finance Scale (EPFS), impulsivity using the Barratt Impulsiveness Scale (BIS) and response inhibition using an emotional go/no-go task in bipolar individuals (N = 21) and healthy controls (HC; N = 23). Patients had fewer financial management skills and higher levels of impulsivity than HC. In patients and controls, increased impulsivity was associated with poorer personal financial management. Patients and HC performed equally on the emotional go/no-go task. Higher BIS scores were associated with faster reaction times in HC. In patients, however, higher BIS scores were associated with slower reaction times, possibly indicating compensatory cognitive strategies to counter increased impulsivity. Patients with BD may have reduced abilities to manage personal finances, when compared against healthy participants. Difficulty with personal finance management may arise in part as a result of increased levels of impulsivity. Patients may learn to compensate for increased impulsivity by modulating response times in our experimental situations although whether such compensatory strategies generalize to real-world situations is unknown.

  11. Discrete-time linear and nonlinear aerodynamic impulse responses for efficient CFD analyses

    NASA Astrophysics Data System (ADS)

    Silva, Walter Arturo

    This dissertation discusses the mathematical existence and the numerical identification of linear and nonlinear aerodynamic impulse response functions. Differences between continuous-time and discrete-time system theories, which permit the identification and efficient use of these functions, will be detailed. Important input/output definitions and the concept of linear and nonlinear systems with memory will also be discussed. It will be shown that indicial (step or steady) responses (such as Wagner's function), forced harmonic responses (such as Theodorsen's function or those from doublet lattice theory), and responses to random inputs (such as gusts) can all be obtained from an aerodynamic impulse response function. This will establish the aerodynamic discrete-time impulse response function as the most fundamental and computationally efficient aerodynamic function that can be extracted from any given discrete-time, aerodynamic system. The results presented in this dissertation help to unify the understanding of classical two-dimensional continuous-time theories with modern three-dimensional, discrete-time theories. Nonlinear aerodynamic impulse responses are identified using the Volterra theory of nonlinear systems. The theory is described and a discrete-time kernel identification technique is presented. The kernel identification technique is applied to a simple nonlinear circuit for illustrative purposes. The method is then applied to the nonlinear viscous Burger's equation as an example of an application to a simple CFD model. Finally, the method is applied to a three-dimensional aeroelastic model using the CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code and then to a two-dimensional model using the CFL3D Navier-Stokes code. Comparisons of accuracy and computational cost savings are presented. Because of its mathematical generality, an important attribute of this methodology is that it is applicable to a wide range of nonlinear

  12. Fluoxetine response in impulsive-aggressive behavior and serotonin transporter polymorphism in personality disorder.

    PubMed

    Silva, Hernán; Iturra, Patricia; Solari, Aldo; Villarroel, Juana; Jerez, Sonia; Jiménez, Marco; Galleguillos, Felipe; Bustamante, Maria Leonor

    2010-02-01

    Disturbances in central serotonin function have been implicated in impulsive and aggressive behavior. A deletion/insertion polymorphism within the 5-HT transporter promoter gene (5-HTTLPR) is thought to be associated with disturbed impulse control, anxiety, and depression. The serotonin transporter (5-HTT) is the primary action site for selective serotonin reuptake inhibitors (SSRIs). Several studies of major depression have shown that the l allele of 5-HTTLPR is associated with better SSRI antidepressant effects than the s allele. This study investigates the association between response of impulsivity to treatment with fluoxetine and 5-HTTLPR polymorphism in 49 personality disordered patients. Additionally, we studied TPH1, 5HT1B and 5HT2C receptor polymorphisms as predictors of response in this population. Results reveal that patients with the l/l genotype of 5-HTTLPR had a significantly better response to fluoxetine when compared to s allele carriers, as evaluated on the basis of total (P<0.05) and Aggression subscale (P<0.01) Overt Aggression Scale Modified-score percentage change. There were no significant associations between fluoxetine response and TPH1 (A218C) (-6525 A>G) (-5806 G>T), HTR1B (G861C) and HTR2C (G68C) genotype groups. This is the first study assessing the association between these polymorphisms and anti-impulsive response to fluoxetine in personality disorder. As the s genotype is associated with a poorer selective serotonin reuptake inhibitors response in major depression, bulimia nervosa and borderline personality disorder, it could represent a common biological background for SSRI response.

  13. Does Impulsiveness Moderate Response to Financial Incentives for Smoking Cessation Among Pregnant and Newly Postpartum Women?

    PubMed Central

    Lopez, Alexa A.; Skelly, Joan M.; White, Thomas J.; Higgins, Stephen T.

    2015-01-01

    We examined whether impulsiveness moderates response to financial incentives for cessation among pregnant smokers. All participants were randomized to either a condition wherein financial incentives were delivered contingent on smoking abstinence or to a control condition wherein incentives were delivered independent of smoking status. The study was conducted in two steps: First, we examined associations between baseline impulsiveness scores and abstinence at late pregnancy and 24-weeks postpartum as part of a planned prospective study of this topic using data from a recently completed, randomized controlled clinical trial (N = 118). Next, to increase statistical power, we conducted a second analysis collapsing results across that recent trial and two prior trials involving the same contingent incentive and control conditions (N = 236). Impulsivity was assessed using a delay discounting (DD) of hypothetical monetary rewards task in all three trials and Barratt Impulsiveness Scale (BIS) in the most recent trial. Neither DD nor BIS predicted antepartum or postpartum smoking status in the single or combined trials. Receiving abstinence-contingent incentives, lower baseline smoking rate (cigs/day), and a history of quit attempts pre-pregnancy predicted greater odds of antepartum abstinence across the single and combined trials. No variable predicted postpartum abstinence across the single and combined trials, although a history of antepartum quit attempts and receiving abstinence-contingent incentives predicted in the single and combined trials, respectively. Overall, this study provides no evidence that impulsiveness as assessed by DD or BIS moderates response to this treatment approach while underscoring a substantial association of smoking rate and prior quit attempts with abstinence across the contingent incentives and control treatment conditions. PMID:25730417

  14. Does impulsiveness moderate response to financial incentives for smoking cessation among pregnant and newly postpartum women?

    PubMed

    Lopez, Alexa A; Skelly, Joan M; White, Thomas J; Higgins, Stephen T

    2015-04-01

    We examined whether impulsiveness moderates response to financial incentives for cessation among pregnant smokers. Participants were randomized to receive financial incentives delivered contingent on smoking abstinence or to a control condition wherein incentives were delivered independent of smoking status. The study was conducted in two steps: First, we examined associations between baseline impulsiveness and abstinence at late pregnancy and 24-weeks-postpartum as part of a planned prospective study of this topic using data from a recently completed, randomized controlled clinical trial (N = 118). Next, to increase statistical power, we conducted a second analysis collapsing results across that recent trial and two prior trials involving the same study conditions (N = 236). Impulsivity was assessed using a delay discounting (DD) of hypothetical monetary rewards task in all three trials and Barratt Impulsiveness Scale (BIS) in the most recent trial. Neither DD nor BIS predicted smoking status in the single or combined trials. Receiving abstinence-contingent incentives, lower baseline smoking rate, and a history of quit attempts prepregnancy predicted greater odds of antepartum abstinence across the single and combined trials. No variable predicted postpartum abstinence across the single and combined trials, although a history of antepartum quit attempts and receiving abstinence-contingent incentives predicted in the single and combined trials, respectively. Overall, this study provides no evidence that impulsiveness as assessed by DD or BIS moderates response to this treatment approach while underscoring a substantial association of smoking rate and prior quit attempts with abstinence across the contingent incentives and control treatment conditions. (c) 2015 APA, all rights reserved).

  15. Relationships between trait impulsivity and cognitive control: the effect of attention switching on response inhibition and conflict resolution.

    PubMed

    Leshem, Rotem

    2016-02-01

    This study examined the relationship between trait impulsivity and cognitive control, as measured by the Barratt Impulsiveness Scale (BIS) and a focused attention dichotic listening to words task, respectively. In the task, attention was manipulated in two attention conditions differing in their cognitive control demands: one in which attention was directed to one ear at a time for a whole block of trials (blocked condition) and another in which attention was switched pseudo-randomly between the two ears from trial to trial (mixed condition). Results showed that high impulsivity participants exhibited more false alarm and intrusion errors as well as a lesser ability to distinguish between stimuli in the mixed condition, as compared to low impulsivity participants. In the blocked condition, the performance levels of the two groups were comparable with respect to these measures. In addition, total BIS scores were correlated with intrusions and laterality index in the mixed but not the blocked condition. The findings suggest that high impulsivity individuals may be less prone to attentional difficulties when cognitive load is relatively low. In contrast, when attention switching is involved, high impulsivity is associated with greater difficulty in inhibiting responses and resolving cognitive conflict than is low impulsivity, as reflected in error-prone information processing. The conclusion is that trait impulsivity in a non-clinical population is manifested more strongly when attention switching is required than during maintained attention. This may have important implications for the conceptualization and treatment of impulsivity in both non-clinical and clinical populations.

  16. Association of COMT and SLC6A3 polymorphisms with impulsivity, response inhibition and brain function.

    PubMed

    Kasparbauer, Anna-Maria; Merten, Natascha; Aichert, Désirée S; Wöstmann, Nicola; Meindl, Thomas; Rujescu, Dan; Ettinger, Ulrich

    2015-10-01

    Evidence of the genetic correlates of inhibitory control is scant. Two previously studied dopamine-related polymorphisms, COMT rs4680 and the SLC6A3 3' UTR 40-base-pair VNTR (rs28363170), have been associated with response inhibition, however with inconsistent findings. Here, we investigated the influence of these two polymorphisms in a large healthy adult sample (N = 515) on a response inhibition battery including the antisaccade, stop-signal, go/no-go and Stroop tasks as well as a psychometric measure of impulsivity (Barratt Impulsiveness Scale) (Experiment 1). Additionally, a subsample (N = 144) was studied while performing the go/no-go, stop-signal and antisaccade tasks in 3T fMRI (Experiment 2). In Experiment 1, we did not find any significant associations of COMT or SLC6A3 with inhibitory performance or impulsivity. In Experiment 2, no association of COMT with BOLD was found. However, there were consistent main effects of SLC6A3 genotype in all inhibitory contrasts: Homozygosity of the 10R allele was associated with greater fronto-striatal BOLD response than genotypes with at least one 9R allele. These findings are consistent with meta-analyses showing that the 10R allele is associated with reduced striatal dopamine transporter expression, which in animal studies has been found to lead to increased extracellular dopamine levels. Our study thus supports the involvement of striatal dopamine in the neural mechanisms of cognitive control, in particular response inhibition.

  17. Impulse responses of automaticity in the Purkinje fiber.

    PubMed

    Chay, T R; Lee, Y S

    1984-04-01

    We examined the effects of brief current pulses on the pacemaker oscillations of the Purkinje fiber using the model of McAllister , Noble, and Tsien (1975. J. Physiol. [Lond.]. 251:1-57). This model was used to construct phase-response curves for brief electric stimuli to find "black holes," where rhythmic activity of the Purkinje fiber ceases. In our computer simulation, a brief current stimulus of the right magnitude and timing annihilated oscillations in membrane potential. The model also revealed a sequence of alternating periodic and chaotic regimes as the strength of a steady bias current is varied. We compared the results of our computer simulations with experimental work on Purkinje fibers and pointed out the importance of modeling results of this kind for understanding cardiac arrhythmias.

  18. Impulse Response Estimation for Spatial Resolution Enhancement in Ultrasonic NDE Imaging

    SciTech Connect

    Clark, G A

    2004-06-25

    This report describes a signal processing algorithm and MATLAB software for improving spatial resolution in ultrasonic nondestructive evaluation (NDE) imaging of materials. Given a measured reflection signal and an associated reference signal, the algorithm produces an optimal least-squares estimate of the impulse response of the material under test. This estimated impulse response, when used in place of the raw reflection signal, enhances the spatial resolution of the ultrasonic measurements by removing distortion caused by the limited-bandwidth transducers and the materials under test. The theory behind the processing algorithms is briefly presented, while the reader is referred to the bibliography for details. The main focus of the report is to describe how to use the MATLAB software. Two processing examples using actual ultrasonic measurements are provided for tutorial purposes.

  19. Free segmentation in rendered 3D images through synthetic impulse response in integral imaging

    NASA Astrophysics Data System (ADS)

    Martínez-Corral, M.; Llavador, A.; Sánchez-Ortiga, E.; Saavedra, G.; Javidi, B.

    2016-06-01

    Integral Imaging is a technique that has the capability of providing not only the spatial, but also the angular information of three-dimensional (3D) scenes. Some important applications are the 3D display and digital post-processing as for example, depth-reconstruction from integral images. In this contribution we propose a new reconstruction method that takes into account the integral image and a simplified version of the impulse response function (IRF) of the integral imaging (InI) system to perform a two-dimensional (2D) deconvolution. The IRF of an InI system has a periodic structure that depends directly on the axial position of the object. Considering different periods of the IRFs we recover by deconvolution the depth information of the 3D scene. An advantage of our method is that it is possible to obtain nonconventional reconstructions by considering alternative synthetic impulse responses. Our experiments show the feasibility of the proposed method.

  20. Quality of sound in large rooms: Alteration of room impulse responses

    NASA Astrophysics Data System (ADS)

    Linusson, Per

    1993-02-01

    Psychoacoustic testing of Room Impulse Responses (RIR), using editing techniques and listening tests with help of auralization is considered. Using these techniques the question of when the reverberation tail is subjectively diffuse was studied. This question is of great interest, for example for auralization techniques. Binaural Room Impulse Responses (BRIR's) were measured in two positions in a concert hall. Their respective reverberation tails were substituted by editing. Listening tests indicated that even with a connection time of 400 ms, some test persons could consistently detect differences with speech as source signal. With music (piano) as source signal the 'limit' of the diffuse part was somewhere between 200 to 400 ms. In the second listening test an individual reflection was substituted with a diffuse one by editing. Three types of diffuse reflections were used. The results indicated that it is possible to improve the subjective quality with a diffuse reflection. Furthermore the character of the diffuse reflection is significant.

  1. Acoustic impulse response method as a source of undergraduate research projects and advanced laboratory experiments.

    PubMed

    Robertson, W M; Parker, J M

    2012-03-01

    A straightforward and inexpensive implementation of acoustic impulse response measurement is described utilizing the signal processing technique of coherent averaging. The technique is capable of high signal-to-noise measurements with personal computer data acquisition equipment, an amplifier/speaker, and a high quality microphone. When coupled with simple waveguide test systems fabricated from commercial PVC plumbing pipe, impulse response measurement has proven to be ideal for undergraduate research projects-often of publishable quality-or for advanced laboratory experiments. The technique provides important learning objectives for science or engineering students in areas such as interfacing and computer control of experiments; analog-to-digital conversion and sampling; time and frequency analysis using Fourier transforms; signal processing; and insight into a variety of current research areas such as acoustic bandgap materials, acoustic metamaterials, and fast and slow wave manipulation. © 2012 Acoustical Society of America

  2. Tomographic reconstruction of indoor spatial temperature distributions using room impulse responses

    NASA Astrophysics Data System (ADS)

    Bleisteiner, M.; Barth, M.; Raabe, A.

    2016-03-01

    Temperature can be estimated by acoustic travel time measurements along known sound paths. By using a multitude of known sound paths in combination with a tomographic reconstruction technique a spatial and temporal resolution of the temperature field can be achieved. Based on it, this article focuses on an experimental method in order to determine the spatially differentiated development of room temperature with only one loudspeaker and one microphone. The theory of geometrical room acoustics is being used to identify sound paths under consideration of reflections. The travel time along a specific sound path is derived from the room impulse response. Temporal variances in room impulse response can be attributed primarily to a change in air temperature and airflow. It is shown that in the absence of airflow a 3D acoustic monitoring of the room temperature can be realized with a fairly limited use of hardware.

  3. Scattering Impulse Response Synthesis Using Random Noise Illumination: Initial Concept Evaluation.

    DTIC Science & Technology

    1988-03-01

    CONCEPT . 2 C. OVERVIEWV OF THESIS.....................................5 11. TEORY OF NOIS.ESOLRtCE IMP1ULSIE RLS1IONSE MIE--ASURL.NIEN F .7 A...INTRODUCTION A. OVERVIEW The objective of this research is to demonstrate the viability of performing high- resolution impulse response scattering... marketing of this technology. The second advan- taue is related to the use of noise-source illunlination for tactical and strategic radar applications

  4. The Right Superior Frontal Gyrus and Individual Variation in Proactive Control of Impulsive Response.

    PubMed

    Hu, Sien; Ide, Jaime S; Zhang, Sheng; Li, Chiang-Shan R

    2016-12-14

    A hallmark of cognitive control is the ability to rein in impulsive responses. Previously, we used a Bayesian model to describe trial-by-trial likelihood of the stop signal or p(Stop) and related regional activations to p(Stop) to response slowing in a stop signal task. Here, we characterized the regional processes of conflict anticipation in association with intersubject variation in impulse control in 114 young adults. We computed the stop signal reaction time (SSRT) and a measure of motor urgency, indexed by the reaction time (RT) difference between go and stop error trials or "GoRT - SERT," where GoRT is the go trial RT and SERT is the stop error RT. Motor urgency and SSRT were positively correlated across subjects. A linear regression identified regional activations to p(Stop), each in correlation with SSRT and motor urgency. We hypothesized that shared neural activities mediate the correlation between motor urgency and SSRT in proactive control of impulsivity. Activation of the ventromedial prefrontal cortex, posterior cingulate cortex and right superior frontal gyrus (SFG) during conflict anticipation correlated negatively with the SSRT. Activation of the right SFG also correlated negatively with GoRT - SERT. Therefore, activation of the right SFG was associated with more efficient response inhibition and less motor urgency. A mediation analysis showed that right SFG activation to conflict anticipation mediates the correlation between SSRT and motor urgency bidirectionally. The current results highlight a specific role of the right SFG in translating conflict anticipation to the control of impulsive response, which is consistent with earlier studies suggesting its function in action restraint.

  5. Impulsivity in binge eating disorder: food cues elicit increased reward responses and disinhibition.

    PubMed

    Schag, Kathrin; Teufel, Martin; Junne, Florian; Preissl, Hubert; Hautzinger, Martin; Zipfel, Stephan; Giel, Katrin Elisabeth

    2013-01-01

    Binge eating disorder (BED) represents a distinct eating disorder diagnosis. Current approaches assume increased impulsivity to be one factor leading to binge eating and weight gain. We used eye tracking to investigate both components of impulsivity, namely reward sensitivity and rash-spontaneous behaviour towards food in BED for the first time. Overweight and obese people with BED (BED+; n = 25), without BED (BED-; n = 26) and healthy normal-weight controls (NWC; n = 25) performed a free exploration paradigm measuring reward sensitivity (experiment 1) and a modified antisaccade paradigm measuring disinhibited, rash-spontaneous behaviour (experiment 2) using food and nonfood stimuli. Additionally, trait impulsivity was assessed. In experiment 1, all participants located their initial fixations more often on food stimuli and BED+ participants gazed longer on food stimuli in comparison with BED- and NWC participants. In experiment 2, BED+ participants had more difficulties inhibiting saccades towards food and nonfood stimuli compared with both other groups in first saccades, and especially towards food stimuli in second saccades and concerning sequences of first and second saccades. BED- participants did not differ significantly from NWC participants in both experiments. Additionally, eye tracking performance was associated with self-reported reward responsiveness and self-control. According to these results, food-related reward sensitivity and rash-spontaneous behaviour, as the two components of impulsivity, are increased in BED in comparison with weight-matched and normal-weight controls. This indicates that BED represents a neurobehavioural phenotype of obesity that is characterised by increased impulsivity. Interventions for BED should target these special needs of affected patients.

  6. Impulsivity in Binge Eating Disorder: Food Cues Elicit Increased Reward Responses and Disinhibition

    PubMed Central

    Schag, Kathrin; Teufel, Martin; Junne, Florian; Preissl, Hubert; Hautzinger, Martin; Zipfel, Stephan; Giel, Katrin Elisabeth

    2013-01-01

    Background Binge eating disorder (BED) represents a distinct eating disorder diagnosis. Current approaches assume increased impulsivity to be one factor leading to binge eating and weight gain. We used eye tracking to investigate both components of impulsivity, namely reward sensitivity and rash-spontaneous behaviour towards food in BED for the first time. Methods Overweight and obese people with BED (BED+; n = 25), without BED (BED−; n = 26) and healthy normal-weight controls (NWC; n = 25) performed a free exploration paradigm measuring reward sensitivity (experiment 1) and a modified antisaccade paradigm measuring disinhibited, rash-spontaneous behaviour (experiment 2) using food and nonfood stimuli. Additionally, trait impulsivity was assessed. Results In experiment 1, all participants located their initial fixations more often on food stimuli and BED+ participants gazed longer on food stimuli in comparison with BED− and NWC participants. In experiment 2, BED+ participants had more difficulties inhibiting saccades towards food and nonfood stimuli compared with both other groups in first saccades, and especially towards food stimuli in second saccades and concerning sequences of first and second saccades. BED− participants did not differ significantly from NWC participants in both experiments. Additionally, eye tracking performance was associated with self-reported reward responsiveness and self-control. Conclusions According to these results, food-related reward sensitivity and rash-spontaneous behaviour, as the two components of impulsivity, are increased in BED in comparison with weight-matched and normal-weight controls. This indicates that BED represents a neurobehavioural phenotype of obesity that is characterised by increased impulsivity. Interventions for BED should target these special needs of affected patients. PMID:24146885

  7. Multi-input Multi-output System Identification Using Impulse Responses

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Isao; Kasai, Tokio; Igawa, Hirotaka

    This paper presents a new algorithm for multi-input multi-output (MIMO) system identification in the time domain using impulse responses. The algorithm is suitable for the on-orbit system identification of spacecraft using the responses to thruster impulse inputs measured by typical satellite on-board sensors. The Eigensystem Realization Algorithm (ERA) realizes a multi-input multi-output (MIMO) system using asynchronous impulse responses in the time domain. Our new method identifies the input and output matrices of a MIMO collocated system by applying a recursive least-squares iteration scheme to refine the matrices obtained from conventional ERA. In this manner, the input matrix is considered to be constructed by the mode shape vectors and the actuator sensitivity matrix. A numerical simulation of an actual spacecraft, the Engineering Test Satellite-VI (ETS-VI), is performed to verify the algorithm. The nominal dynamics model of ETS-VI, which has six rigid body modes and fourteen elastic modes due to large flexible solar panels, is excited by six body-mounted thrusters, and the translational velocities and attitude rates are measured simultaneously. Our method successfully identifies all of the fourteen natural frequencies, damping ratios and mode shape vectors, confirming its validity.

  8. On the interpretation of kernels - Computer simulation of responses to impulse pairs

    NASA Technical Reports Server (NTRS)

    Hung, G.; Stark, L.; Eykhoff, P.

    1983-01-01

    A method is presented for the use of a unit impulse response and responses to impulse pairs of variable separation in the calculation of the second-degree kernels of a quadratic system. A quadratic system may be built from simple linear terms of known dynamics and a multiplier. Computer simulation results on quadratic systems with building elements of various time constants indicate reasonably that the larger time constant term before multiplication dominates in the envelope of the off-diagonal kernel curves as these move perpendicular to and away from the main diagonal. The smaller time constant term before multiplication combines with the effect of the time constant after multiplication to dominate in the kernel curves in the direction of the second-degree impulse response, i.e., parallel to the main diagonal. Such types of insight may be helpful in recognizing essential aspects of (second-degree) kernels; they may be used in simplifying the model structure and, perhaps, add to the physical/physiological understanding of the underlying processes.

  9. A new algorithm for spatial impulse response of rectangular planar transducers.

    PubMed

    Cheng, Jiqi; Lu, Jian-Yu; Lin, Wei; Qin, Yi-Xian

    2011-02-01

    Previous solutions for spatial impulse responses of rectangular planar transducers require either approximations or complex geometrical considerations. This paper describes a new, simplified and exact solution using only trigonometric functions and simple set operations. This solution, which can be numerically implemented with a straightforward algorithm, is an exact implementation of the Rayleigh integral without any far field or paraxial approximation. Additionally, a nonlinear relationship was also established for spatial impulse responses from two field points which share the same projection point on the transducer surface plane. By incorporating this relationship in the algorithm, the computational efficiency of spatial impulse responses and continuous fields is improved about 20-folds and 14-folds, respectively. This algorithm has practical applications in designing l-D linear/phased arrays, 1.5-D arrays and 2-D arrays, as demonstrated through numerical simulations with array transducers. Experiments were also conducted to verify the new solution and results show that the algorithm is both accurate and efficient. The application of this method may include development of ultrasound imaging system for hard and soft tissue nondestructive assessment.

  10. Rod-cone interactions and the temporal impulse response of the cone pathway

    PubMed Central

    Zele, Andrew J.; Cao, Dingcai; Pokorny, Joel

    2008-01-01

    Dark-adapted rods suppress cone-mediated flicker detection. This study evaluates the effect that rod activity has on cone temporal processing by investigating whether rod mediated suppression changes the cone pathway impulse response function, regardless of the form of the temporal signal. Stimuli were generated with a 2-channel photostimulator that has four primaries for the central field and four primaries for the surround. Cone pathway temporal impulse response functions were derived from temporal contrast sensitivity data with periodic stimuli, and from two-pulse discrimination data in which pairs of briefly pulsed stimuli were presented successively at a series of stimulus onset asynchronies. Dark-adapted rods altered the amplitude and timing of cone pathway temporal impulse response functions, irrespective of whether they were derived from measurements with temporally periodic stimuli or in a brief presentation temporal resolution task with pulsed stimuli. Rod-cone interactions are a fundamental operation in visual temporal processing under mesopic light levels, acting to decrease the temporal bandwidth of the visual system. PMID:18486960

  11. Epithelial transport pathways of rat colon determined in vivo by impulse response analysis.

    PubMed

    Edmonds, C J; Smith, T

    1979-11-01

    1. A method is described for studying transepithelial pathways for the movement of different solutes and water. Using the blood and the secretory curves of changing tracer activity following an intravenous bolus, the rate of transit of molecules together with their impulse response functions, which reflect the transfer processes can be examined. 2. Movements of Na, Cl, I, urea and water from blood to lumen across rat colonic epithelium were all consistent with simple diffusion through a paracellular route. Most of the secreted K, however, passed through a K selective route associated with a significant K epithelial pool. 3. Adding cyanide to the luminal solution caused a reversible fall of transepithelial potential difference associated with changes in the impulse response functions of water, urea and K indicating reduction of the restriction on diffusion. Cellular K content was unaffected. 4. K entered the bulk of the epithelial cellular K almost exclusively from the blood side. A small epithelial K pool, identified by studies with a miniature GM counter, had kinetic characteristics like those of the K selective pathway observed in the studies of impulse response functions.

  12. A new algorithm for spatial impulse response of rectangular planar transducers

    PubMed Central

    Cheng, Jiqi; Lu, Jian-yu; Lin, Wei; Qin, Yi-Xian

    2010-01-01

    Previous solutions for spatial impulse responses of rectangular planar transducers require either approximations or complex geometrical considerations. This paper describes a new, simplified and exact solution using only trigonometric functions and simple set operations. This solution, which can be numerically implemented with a straightforward algorithm, is an exact implementation of the Rayleigh integral without any far field or paraxial approximation. Additionally, a nonlinear relationship was also established for spatial impulse responses from two field points which share the same projection point on the transducer surface plane. By incorporating this relationship in the algorithm, the computational efficiency of spatial impulse responses and continuous fields is improved about 20 folds and 14 folds, respectively. This algorithm has practical applications in designing 1-D linear/phased arrays, 1.5-D arrays and 2-D arrays, as demonstrated through numerical simulations with array transducers. Experiments were also conducted to verify the new solution and results show that the algorithm is both accurate and efficient. The application of this method may include development of ultrasound imaging system for hard and soft tissue nondestructive assessment. PMID:20863543

  13. Quantifying viscoelasticity of gelatin phantoms by measuring impulse response using compact optical sensors.

    PubMed

    Qiang, Bo; Greenleaf, James; Zhang, Xiaoming

    2010-07-01

    Tissue elastography measures tissue mechanical properties, which contain important physiological information and help medical diagnosis. Instead of tracking shear wave propagation inside tissue as do magnetic resonance elastography and ultrasound based techniques, this study focuses on monitoring the propagation of surface Raleigh waves stimulated by short impulses. The method is noncontact, noninvasive, and low cost and has a potential for clinical applications. A customized device designed to measure surface wave propagation is constructed based on a laser displacement sensor (LDS). Experiments are carried out on two porcine skin gelatin phantoms of different concentrations. For each phantom, the phase velocities of specific frequencies are extracted using a cross-spectrum method and then the material elasticity and viscosity are found by fitting the phase velocities with the Voigt's model. The results suggest that measuring viscoelasticity by monitoring the response to a surface impulse is an efficient method because of the richness of frequency content of impulse responses. The results are validated with a standard continuous wave (CW) method.

  14. Dose-response relationship of autonomic nervous system responses to individualized training impulse in marathon runners.

    PubMed

    Manzi, Vincenzo; Castagna, Carlo; Padua, Elvira; Lombardo, Mauro; D'Ottavio, Stefano; Massaro, Michele; Volterrani, Maurizio; Iellamo, Ferdinando

    2009-06-01

    In athletes, exercise training induces autonomic nervous system (ANS) adaptations that could be used to monitor training status. However, the relationship between training and ANS in athletes has been investigated without regard for individual training loads. We tested the hypothesis that in long-distance athletes, changes in ANS parameters are dose-response related to individual volume/intensity training load and could predict athletic performance. A spectral analysis of heart rate (HR), systolic arterial pressure variability, and baroreflex sensitivity by the sequences technique was investigated in eight recreational athletes during a 6-mo training period culminating with a marathon. Individualized training load responses were monitored by a modified training impulse (TRIMP(i)) method, which was determined in each athlete using the individual HR and lactate profiling determined during a treadmill test. Monthly TRIMP(i) steadily increased during the training period. All the ANS parameters were significantly and very highly correlated to the dose of exercise with a second-order regression model (r(2) ranged from 0.90 to 0.99; P < 0.001). Variance, high-frequency oscillations of HR variability (HRV), and baroreflex sensitivity resembled a bell-shaped curve with a minimum at the highest TRIMP(i), whereas low-frequency oscillations of HR and systolic arterial pressure variability and the low frequency (LF)-to-high frequency ratio resembled an U-shaped curve with a maximum at the highest TRIMP(i). The LF component of HRV assessed at the last recording session was significantly and inversely correlated to the time needed to complete the nearing marathon. These results suggest that in recreational athletes, ANS adaptations to exercise training are dose related on an individual basis, showing a progressive shift toward a sympathetic predominance, and that LF oscillations in HRV at peak training load could predict athletic achievement in this athlete population.

  15. Convergence of finite difference transient response computations for thin shells.

    NASA Technical Reports Server (NTRS)

    Sobel, L. H.; Geers, T. L.

    1973-01-01

    Numerical studies pertaining to the limits of applicability of the finite difference method in the solution of linear transient shell response problems are performed, and a computational procedure for the use of the method is recommended. It is found that the only inherent limitation of the finite difference method is its inability to reproduce accurately response discontinuities. This is not a serious limitation in view of natural constraints imposed by the extension of Saint Venant's principle to transient response problems. It is also found that the short wavelength limitations of thin shell (Bernoulli-Euler) theory create significant convergence difficulties in computed response to certain types of transverse excitations. These difficulties may be overcome, however, through proper selection of finite difference mesh dimensions and temporal smoothing of the excitation.

  16. Identification of Linear and Nonlinear Aerodynamic Impulse Responses Using Digital Filter Techniques

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1997-01-01

    This paper discusses the mathematical existence and the numerically-correct identification of linear and nonlinear aerodynamic impulse response functions. Differences between continuous-time and discrete-time system theories, which permit the identification and efficient use of these functions, will be detailed. Important input/output definitions and the concept of linear and nonlinear systems with memory will also be discussed. It will be shown that indicial (step or steady) responses (such as Wagner's function), forced harmonic responses (such as Theodorsen's function or those from doublet lattice theory), and responses to random inputs (such as gusts) can all be obtained from an aerodynamic impulse response function. This paper establishes the aerodynamic impulse response function as the most fundamental, and, therefore, the most computationally efficient, aerodynamic function that can be extracted from any given discrete-time, aerodynamic system. The results presented in this paper help to unify the understanding of classical two-dimensional continuous-time theories with modern three-dimensional, discrete-time theories. First, the method is applied to the nonlinear viscous Burger's equation as an example. Next the method is applied to a three-dimensional aeroelastic model using the CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code and then to a two-dimensional model using the CFL3D Navier-Stokes code. Comparisons of accuracy and computational cost savings are presented. Because of its mathematical generality, an important attribute of this methodology is that it is applicable to a wide range of nonlinear, discrete-time problems.

  17. Identification of Linear and Nonlinear Aerodynamic Impulse Responses Using Digital Filter Techniques

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1997-01-01

    This paper discusses the mathematical existence and the numerically-correct identification of linear and nonlinear aerodynamic impulse response functions. Differences between continuous-time and discrete-time system theories, which permit the identification and efficient use of these functions, will be detailed. Important input/output definitions and the concept of linear and nonlinear systems with memory will also be discussed. It will be shown that indicial (step or steady) responses (such as Wagner's function), forced harmonic responses (such as Tbeodorsen's function or those from doublet lattice theory), and responses to random inputs (such as gusts) can all be obtained from an aerodynamic impulse response function. This paper establishes the aerodynamic impulse response function as the most fundamental, and, therefore, the most computationally efficient, aerodynamic function that can be extracted from any given discrete-time, aerodynamic system. The results presented in this paper help to unify the understanding of classical two-dimensional continuous-time theories with modem three-dimensional, discrete-time theories. First, the method is applied to the nonlinear viscous Burger's equation as an example. Next the method is applied to a three-dimensional aeroelastic model using the CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code and then to a two-dimensional model using the CFL3D Navier-Stokes code. Comparisons of accuracy and computational cost savings are presented. Because of its mathematical generality, an important attribute of this methodology is that it is applicable to a wide range of nonlinear, discrete-time problems.

  18. Comparison of methods of predicting community response to impulsive and nonimpulsive noise

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.

    1994-01-01

    Several scientific, regulatory, and policy-coordinating bodies have developed methods for predicting community response to sonic booms. The best known of these is the dosage-response relationship of Working Group 84 of the National Academy of Science's Committee on Hearing, Bioacoustics and Biomechanics. This dosage-response relationship between C-weighted DayNight Average Sound Level and the prevalence of annoyance with high energy impulsive sounds was derived from limited amounts of information about community response to regular, prolonged, and expected exposure to artillery and sonic booms. U.S. Army Regulation 201 adapts this approach to predictions of the acceptability of impulsive noise exposure in communities. This regulation infers equivalent degrees of effect with respect to a well known dosage-response relationship for general (nonimpulsive) transportation noise. Differences in prevalence of annoyance predicted by various relationships lead to different predictions of the compatibility of land uses with sonic boom exposure. An examination of these differences makes apparent several unresolved issues in current practice for predicting and interpreting the prevalence of annoyance due to sonic boom exposure.

  19. Using a signal cancellation technique involving impulse response to assess directivity of hearing aids.

    PubMed

    Wu, Yu-Hsiang; Bentler, Ruth A

    2009-12-01

    The directional microphone systems of modern digital hearing aids are capable of changing their spatial directivity pattern and/or the microphone mode in response to changes in the properties of environmental sounds. These adaptive/automatic features make measurement of a hearing aid's directivity in a given test environment very difficult. Assessing the directivity of such systems requires a signal that can record the system's response while not changing the system's directivity. This paper proposes a method using a signal cancellation technique involving impulse responses to acoustically assess a hearing aid's directivity (referred to as the IR method). The impulse is presumed to be undetectable to the adaptive/automatic system because it contains little energy and a short response could be recorded before the system actually reacts. In the current study, the IR method was evaluated by testing five adaptive/automatic directional hearing aids in noise of various intensities. The results revealed that the IR method was an accurate and repeatable way to assess slow-acting directional systems in noise of varying intensities and fast-acting systems in noise of high intensities.

  20. Reduced Order Models Based on Linear and Nonlinear Aerodynamic Impulse Responses

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1999-01-01

    This paper discusses a method for the identification and application of reduced-order models based on linear and nonlinear aerodynamic impulse responses. The Volterra theory of nonlinear systems and an appropriate kernel identification technique are described. Insight into the nature of kernels is provided by applying the method to the nonlinear Riccati equation in a non-aerodynamic application. The method is then applied to a nonlinear aerodynamic model of an RAE 2822 supercritical airfoil undergoing plunge motions using the CFL3D Navier-Stokes flow solver with the Spalart-Allmaras turbulence model. Results demonstrate the computational efficiency of the technique.

  1. Linear ordinary differential equations with constant coefficients. Revisiting the impulsive response method using factorization

    NASA Astrophysics Data System (ADS)

    Camporesi, Roberto

    2011-06-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as well as of the other more advanced approaches: Laplace transform, linear systems, the general theory of linear equations with variable coefficients and the variation of constants method. The approach presented here can be used in a first course on differential equations for science and engineering majors.

  2. Arbitrary magnetic field gradient waveform correction using an impulse response based pre-equalization technique.

    PubMed

    Goora, Frédéric G; Colpitts, Bruce G; Balcom, Bruce J

    2014-01-01

    The time-varying magnetic fields used in magnetic resonance applications result in the induction of eddy currents on conductive structures in the vicinity of both the sample under investigation and the gradient coils. These eddy currents typically result in undesired degradations of image quality for MRI applications. Their ubiquitous nature has resulted in the development of various approaches to characterize and minimize their impact on image quality. This paper outlines a method that utilizes the magnetic field gradient waveform monitor method to directly measure the temporal evolution of the magnetic field gradient from a step-like input function and extracts the system impulse response. With the basic assumption that the gradient system is sufficiently linear and time invariant to permit system theory analysis, the impulse response is used to determine a pre-equalized (optimized) input waveform that provides a desired gradient response at the output of the system. An algorithm has been developed that calculates a pre-equalized waveform that may be accurately reproduced by the amplifier (is physically realizable) and accounts for system limitations including system bandwidth, amplifier slew rate capabilities, and noise inherent in the initial measurement. Significant improvements in magnetic field gradient waveform fidelity after pre-equalization have been realized and are summarized.

  3. The Dynamic Effects of Changes in Prices and Affordability on Alcohol Consumption: An Impulse Response Analysis.

    PubMed

    Jiang, Heng; Livingston, Michael

    2015-11-01

    To investigate how changes in alcohol price and affordability are related to aggregate level alcohol consumption in Australia to help to inform effective price and tax policy to influence consumption. Annual time series data between 1974 and 2012 on price and per-capita consumption for beer, wine and spirits and average weekly income were collected from the Australian Bureau of Statistics. Using a Vector Autoregressive model and impulse response analysis, the dynamic responses of alcohol consumption to changes in alcohol prices and affordability were estimated. Alcohol consumption in Australia was negatively associated with alcohol price and positively associated with the affordability of alcohol. The results of the impulse response analysis suggest that a 10% increase in the alcohol price was associated with a 2% decrease in the population-level alcohol consumption in the following year, with further, diminishing, effects up to year 8, leading to an overall 6% reduction in total consumption. In contrast, when alcohol affordability increased, per-capita alcohol consumption increased over the following 6 years. Our findings suggest that increasing alcohol prices or taxes can help to reduce alcohol consumption at the population level in Australia. However, the impact of affordability in our findings highlights that pricing policies need to consider increases in income to ensure effectiveness. Alcohol price policy should only cautiously focus on individual beverage types, because increasing the price of one beverage generally leads to an increase in consumption of substitutes. © The Author 2015. Medical Council on Alcohol and Oxford University Press. All rights reserved.

  4. Auditory Responses in the Barn Owl's Nucleus Laminaris to Clicks: Impulse Response and Signal Analysis of Neurophonic Potential

    PubMed Central

    Wagner, Hermann; Brill, Sandra; Kempter, Richard; Carr, Catherine E.

    2009-01-01

    We used acoustic clicks to study the impulse response of the neurophonic potential in the barn owl's nucleus laminaris. Clicks evoked a complex oscillatory neural response with a component that reflected the best frequency measured with tonal stimuli. The envelope of this component was obtained from the analytic signal created using the Hilbert transform. The time courses of the envelope and carrier waveforms were characterized by fitting them with filters. The envelope was better fitted with a Gaussian than with the envelope of a gamma-tone function. The carrier was better fitted with a frequency glide than with a constant instantaneous frequency. The change of the instantaneous frequency with time was better fitted with a linear fit than with a saturating nonlinearity. Frequency glides had not been observed in the bird's auditory system before. The glides were similar to those observed in the mammalian auditory nerve. Response amplitude, group delay, frequency, and phase depended in a systematic way on click level. In most cases, response amplitude decreased linearly as stimulus level decreased, while group delay, phase, and frequency increased linearly as level decreased. Thus the impulse response of the neurophonic potential in the nucleus laminaris of barn owls reflects many characteristics also observed in responses of the basilar membrane and auditory nerve in mammals. PMID:19535487

  5. Impulse responses of visible phototubes used in National Ignition Facility neutron time of flight diagnostics.

    PubMed

    Datte, P S; Eckart, M; Moore, A S; Thompson, W; Vergel de Dios, G

    2016-11-01

    Neutron-induced visible scintillation in neutron time of flight (NToF) diagnostics at the National Ignition Facility (NIF) is measured with 40 mm single stage micro-channel plate photomultipliers and a 40 mm vacuum photodiode, outside the neutron line of sight. In NIF experiments with 14 MeV neutron yields above Y > 10 × 10(15) these tubes are configured to deliver of order 1 nC of charge in the nominally 5 ns NToF into a 50 Ω load. We have examined a number of 40 mm tubes manufactured by Photek Ltd. of St. Leonards on Sea, UK, to determine possible changes in the instrument impulse response as a function of signal charge delivered in 1 ns. Precision NToF measurements at approximately 20 m require that we characterize changes in the impulse response moments to <40 ps for the first central moment and ∼2% rms for the square root of the second central moment with ∼500 ps value. Detailed results are presented for three different diode configurations.

  6. Impulse responses of visible phototubes used in National Ignition Facility neutron time of flight diagnostics

    NASA Astrophysics Data System (ADS)

    Datte, P. S.; Eckart, M.; Moore, A. S.; Thompson, W.; Vergel de Dios, G.

    2016-11-01

    Neutron-induced visible scintillation in neutron time of flight (NToF) diagnostics at the National Ignition Facility (NIF) is measured with 40 mm single stage micro-channel plate photomultipliers and a 40 mm vacuum photodiode, outside the neutron line of sight. In NIF experiments with 14 MeV neutron yields above Y > 10 × 1015 these tubes are configured to deliver of order 1 nC of charge in the nominally 5 ns NToF into a 50 Ω load. We have examined a number of 40 mm tubes manufactured by Photek Ltd. of St. Leonards on Sea, UK, to determine possible changes in the instrument impulse response as a function of signal charge delivered in 1 ns. Precision NToF measurements at approximately 20 m require that we characterize changes in the impulse response moments to <40 ps for the first central moment and ˜2% rms for the square root of the second central moment with ˜500 ps value. Detailed results are presented for three different diode configurations.

  7. Image reconstruction using a gradient impulse response model for trajectory prediction.

    PubMed

    Vannesjo, S Johanna; Graedel, Nadine N; Kasper, Lars; Gross, Simon; Busch, Julia; Haeberlin, Maximilian; Barmet, Christoph; Pruessmann, Klaas P

    2016-07-01

    Gradient imperfections remain a challenge in MRI, especially for sequences relying on long imaging readouts. This work aims to explore image reconstruction based on k-space trajectories predicted by an impulse response model of the gradient system. Gradient characterization was performed twice with 3 years interval on a commercial 3 Tesla (T) system. The measured gradient impulse response functions were used to predict actual k-space trajectories for single-shot echo-planar imaging (EPI), spiral and variable-speed EPI sequences. Image reconstruction based on the predicted trajectories was performed for phantom and in vivo data. Resulting images were compared with reconstructions based on concurrent field monitoring, separate trajectory measurements, and nominal trajectories. Image reconstruction using model-based trajectories yielded high-quality images, comparable to using separate trajectory measurements. Compared with using nominal trajectories, it strongly reduced ghosting, blurring, and geometric distortion. Equivalent image quality was obtained with the recent characterization and that performed 3 years prior. Model-based trajectory prediction enables high-quality image reconstruction for technically challenging sequences such as single-shot EPI and spiral imaging. It thus holds great promise for fast structural imaging and advanced neuroimaging techniques, including functional MRI, diffusion tensor imaging, and arterial spin labeling. The method can be based on a one-time system characterization as demonstrated by successful use of 3-year-old calibration data. Magn Reson Med 76:45-58, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  8. Application of damage detection methods using passive reconstruction of impulse response functions.

    PubMed

    Tippmann, J D; Zhu, X; Lanza di Scalea, F

    2015-02-28

    In structural health monitoring (SHM), using only the existing noise has long been an attractive goal. The advances in understanding cross-correlations in ambient noise in the past decade, as well as new understanding in damage indication and other advanced signal processing methods, have continued to drive new research into passive SHM systems. Because passive systems take advantage of the existing noise mechanisms in a structure, offshore wind turbines are a particularly attractive application due to the noise created from the various aerodynamic and wave loading conditions. Two damage detection methods using a passively reconstructed impulse response function, or Green's function, are presented. Damage detection is first studied using the reciprocity of the impulse response functions, where damage introduces new nonlinearities that break down the similarity in the causal and anticausal wave components. Damage detection and localization are then studied using a matched-field processing technique that aims to spatially locate sources that identify a change in the structure. Results from experiments conducted on an aluminium plate and wind turbine blade with simulated damage are also presented. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  9. Impulsive response of an automatic transmission system with multiple clearances: Formulation, simulation and experiment

    NASA Astrophysics Data System (ADS)

    Crowther, Ashley R.; Singh, Rajendra; Zhang, Nong; Chapman, Chris

    2007-10-01

    Impulsive responses in geared systems with multiple clearances are studied when the mean torque excitation and system load change abruptly, with application to a vehicle driveline with an automatic transmission. First, torsional lumped-mass models of the planetary and differential gear sets are formulated using matrix elements. The model is then reduced to address tractable nonlinear problems while successfully retaining the main modes of interest. Second, numerical simulations for the nonlinear model are performed for transient conditions and a typical driving situation that induces an impulsive behaviour simulated. However, initial conditions and excitation and load profiles have to be carefully defined before the model can be numerically solved. It is shown that the impacts within the planetary or differential gears may occur under combinations of engine, braking and vehicle load transients. Our analysis shows that the shaping of the engine transient by the torque converter before reaching the clearance locations is more critical. Third, a free vibration experiment is developed for an analogous driveline with multiple clearances and three experiments that excite different response regimes have been carried out. Good correlations validate the proposed methodology.

  10. Repeated exposure reduces the response to impulsive noise in European seabass.

    PubMed

    Radford, Andrew N; Lèbre, Laurie; Lecaillon, Gilles; Nedelec, Sophie L; Simpson, Stephen D

    2016-10-01

    Human activities have changed the acoustic environment of many terrestrial and aquatic ecosystems around the globe. Mounting evidence indicates that the resulting anthropogenic noise can impact the behaviour and physiology of at least some species in a range of taxa. However, the majority of experimental studies have considered only immediate responses to single, relatively short-term noise events. Repeated exposure to noise could lead to a heightened or lessened response. Here, we conduct two long-term (12 week), laboratory-based exposure experiments with European seabass (Dicentrarchus labrax) to examine how an initial impact of different sound types potentially changes over time. Naïve fish showed elevated ventilation rates, indicating heightened stress, in response to impulsive additional noise (playbacks of recordings of pile-driving and seismic surveys), but not to a more continuous additional noise source (playbacks of recordings of ship passes). However, fish exposed to playbacks of pile-driving or seismic noise for 12 weeks no longer responded with an elevated ventilation rate to the same noise type. Fish exposed long-term to playback of pile-driving noise also no longer responded to short-term playback of seismic noise. The lessened response after repeated exposure, likely driven by increased tolerance or a change in hearing threshold, helps explain why fish that experienced 12 weeks of impulsive noise showed no differences in stress, growth or mortality compared to those reared with exposure to ambient-noise playback. Considering how responses to anthropogenic noise change with repeated exposure is important both when assessing likely fitness consequences and the need for mitigation measures.

  11. Surface response of a fluid-loaded solid to impulsive line and point forces: Application to scanning acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Every, A. G.; Briggs, G. A. D.

    1998-07-01

    Algorithms are presented for calculating the two- and three-dimensional time domain dynamic Green's functions of a pair of joined semi-infinite anisotropic elastic continua. They are used to calculate the normal surface displacement response of fluid-loaded solids to impulsive line and point forces. Particular attention is given to the resonant and singular features in the response associated with the Stoneley-Scholte interfacial wave, leaky Rayleigh and pseudosurface acoustic waves, and lateral waves, i.e., surface skimming bulk waves of the solid and of the liquid. The various regimes are explored, in which the fluid sound speed and acoustic impedance range from small to large as compared to those of the solid. The effects of elastic anisotropy of the solid are illustrated with results for a carbon fiber composite and for the principal crystallographic cuts of a number of cubic crystals of anisotropy coefficient η=2C44/(C11-C12) greater and less than unity. Calculated images, representing the dependence of the normal displacement response on time and direction, are in good agreement with published acoustic microscopy images of a number of anisotropic solids that have been measured with a configuration of two line focus or two point focus lenses. These images display prominent features due to leaky Rayleigh and pseudosurface waves, as well as sharper lateral wave structures. The mode of excitation and detection does not, however, couple into the water lateral wave and Sholte wave, which are absent from the measured images. This effect is simulated by setting a finite cutoff, determined by the aperture angles of the lenses, to the spatial Fourier transform of the surface Green's function.

  12. fMRI investigation of response inhibition, emotion, impulsivity, and clinical high-risk behavior in adolescents

    PubMed Central

    Brown, Matthew R. G.; Benoit, James R. A.; Juhás, Michal; Dametto, Ericson; Tse, Tiffanie T.; MacKay, Marnie; Sen, Bhaskar; Carroll, Alan M.; Hodlevskyy, Oleksandr; Silverstone, Peter H.; Dolcos, Florin; Dursun, Serdar M.; Greenshaw, Andrew J.

    2015-01-01

    High-risk behavior in adolescents is associated with injury, mental health problems, and poor outcomes in later life. Improved understanding of the neurobiology of high-risk behavior and impulsivity shows promise for informing clinical treatment and prevention as well as policy to better address high-risk behavior. We recruited 21 adolescents (age 14–17) with a wide range of high-risk behavior tendencies, including medically high-risk participants recruited from psychiatric clinics. Risk tendencies were assessed using the Adolescent Risk Behavior Screen (ARBS). ARBS risk scores correlated highly (0.78) with impulsivity scores from the Barratt Impulsivity scale (BIS). Participants underwent 4.7 Tesla functional magnetic resonance imaging (fMRI) while performing an emotional Go/NoGo task. This task presented an aversive or neutral distractor image simultaneously with each Go or NoGo stimulus. Risk behavior and impulsivity tendencies exhibited similar but not identical associations with fMRI activation patterns in prefrontal brain regions. We interpret these results as reflecting differences in response inhibition, emotional stimulus processing, and emotion regulation in relation to participant risk behavior tendencies and impulsivity levels. The results are consistent with high impulsivity playing an important role in determining high risk tendencies in this sample containing clinically high-risk adolescents. PMID:26483645

  13. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general rules-of-thumb'' for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  14. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general ``rules-of-thumb`` for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  15. State-space models of impulse hemodynamic responses over motor, somatosensory, and visual cortices.

    PubMed

    Hong, Keum-Shik; Nguyen, Hoang-Dung

    2014-06-01

    THE PAPER PRESENTS STATE SPACE MODELS OF THE HEMODYNAMIC RESPONSE (HR) OF FNIRS TO AN IMPULSE STIMULUS IN THREE BRAIN REGIONS: motor cortex (MC), somatosensory cortex (SC), and visual cortex (VC). Nineteen healthy subjects were examined. For each cortex, three impulse HRs experimentally obtained were averaged. The averaged signal was converted to a state space equation by using the subspace method. The activation peak and the undershoot peak of the oxy-hemoglobin (HbO) in MC are noticeably higher than those in SC and VC. The time-to-peaks of the HbO in three brain regions are almost the same (about 6.76 76 ± 0.2 s). The time to undershoot peak in VC is the largest among three. The HbO decreases in the early stage (~0.46 s) in MC and VC, but it is not so in SC. These findings were well described with the developed state space equations. Another advantage of the proposed method is its easy applicability in generating the expected HR to arbitrary stimuli in an online (or real-time) imaging. Experimental results are demonstrated.

  16. State-space models of impulse hemodynamic responses over motor, somatosensory, and visual cortices

    PubMed Central

    Hong, Keum-Shik; Nguyen, Hoang-Dung

    2014-01-01

    The paper presents state space models of the hemodynamic response (HR) of fNIRS to an impulse stimulus in three brain regions: motor cortex (MC), somatosensory cortex (SC), and visual cortex (VC). Nineteen healthy subjects were examined. For each cortex, three impulse HRs experimentally obtained were averaged. The averaged signal was converted to a state space equation by using the subspace method. The activation peak and the undershoot peak of the oxy-hemoglobin (HbO) in MC are noticeably higher than those in SC and VC. The time-to-peaks of the HbO in three brain regions are almost the same (about 6.76 76 ± 0.2 s). The time to undershoot peak in VC is the largest among three. The HbO decreases in the early stage (~0.46 s) in MC and VC, but it is not so in SC. These findings were well described with the developed state space equations. Another advantage of the proposed method is its easy applicability in generating the expected HR to arbitrary stimuli in an online (or real-time) imaging. Experimental results are demonstrated. PMID:24940540

  17. Vaporization response of evaporating drops with finite thermal conductivity

    NASA Technical Reports Server (NTRS)

    Agosta, V. D.; Hammer, S. S.

    1975-01-01

    A numerical computing procedure was developed for calculating vaporization histories of evaporating drops in a combustor in which travelling transverse oscillations occurred. The liquid drop was assumed to have a finite thermal conductivity. The system of equations was solved by using a finite difference method programmed for solution on a high speed digital computer. Oscillations in the ratio of vaporization of an array of repetitivity injected drops in the combustor were obtained from summation of individual drop histories. A nonlinear in-phase frequency response factor for the entire vaporization process to oscillations in pressure was evaluated. A nonlinear out-of-phase response factor, in-phase and out-of-phase harmonic response factors, and a Princeton type 'n' and 'tau' were determined. The resulting data was correlated and is presented in graphical format. Qualitative agreement with the open literature is obtained in the behavior of the in-phase response factor. Quantitatively the results of the present finite conductivity spray analysis do not correlate with the results of a single drop model.

  18. Finite response time of shock wave modulation by turbulence

    NASA Astrophysics Data System (ADS)

    Inokuma, Kento; Watanabe, Tomoaki; Nagata, Koji; Sasoh, Akihiro; Sakai, Yasuhiko

    2017-05-01

    Response time of the post-shock wave (SW) overpressure modulation by turbulence is investigated in wind tunnel experiments. A peak-overpressure fluctuation, observed on a wall, is induced by turbulence around the SW ray, but away from the wall, demonstrating finite response time of the modulation. We propose a model of the modulation based on the SW deformation by a local flow disturbance, which yields the response time being proportional to the product of the large-eddy turnover time and (MT/MS0)0.5 (MT: turbulent Mach number and MS0: shock Mach number), in consistent with the experiments.

  19. Response inhibition in the parametric go/no-go task and its relation to impulsivity and subclinical psychopathy.

    PubMed

    Weidacker, Kathrin; Whiteford, Seb; Boy, Frederic; Johnston, Stephen J

    2017-03-01

    The current study utilizes the parametric go/no-go task (PGNG), a task that examines changes in inhibitory performance as executive function load increases, to examine the link between psychopathic traits, impulsivity, and response inhibition in a cohort of healthy participants. The results show that as executive function load increased, inhibitory ability decreased. High scores on the Cognitive Complexity subscale of the Barratt Impulsivity Scale (BIS-11) predict poor inhibitory ability in the PGNG. Similarly, high scores on the Psychopathy Personality Inventory-Revised (PPI-R) Blame Externalization subscale predict response inhibition deficits in the PGNG, which loads more on the executive functions than the standard go/no-go task. The remaining BIS-11 as well as PPI-R subscales did not interact with inhibitory performance in the PGNG highlighting the specificity of associations between aspects of personality and impulsivity with inhibitory performance as cognitive load is increased. These data point towards the sensitivity of the PGNG in studying response inhibition in the context of highly impulsive populations and its utility as a measure of impulsivity.

  20. An indirect time-of-flight measurement technique for sub-mm range resolution using impulse photocurrent response

    NASA Astrophysics Data System (ADS)

    Usui, Takahiro; Yasutomi, Keita; Man, Han San; Takasawa, Taishi; Kagawa, Keiichiro; Kawahito, Shoji

    2014-03-01

    This paper presents a new ToF measurement technique using an impulse photocurrent response. In the proposed technique, a laser with a short pulse width for light source, which can be regarded as an impulse input for a detector. As a result, the range calculation is determined only by photocurrent response of the detector. A test chip fabricated in a 0.11um CIS technology employs a draining-only modulation pixel, which enables a high speed charge modulation. The measurable range measured to be 50 mm within nonlinear error of 5% and the average range resolution of 0.21 mm is achieved.

  1. The generation of shared cryptographic keys through channel impulse response estimation at 60 GHz.

    SciTech Connect

    Young, Derek P.; Forman, Michael A.; Dowdle, Donald Ryan

    2010-09-01

    Methods to generate private keys based on wireless channel characteristics have been proposed as an alternative to standard key-management schemes. In this work, we discuss past work in the field and offer a generalized scheme for the generation of private keys using uncorrelated channels in multiple domains. Proposed cognitive enhancements measure channel characteristics, to dynamically change transmission and reception parameters as well as estimate private key randomness and expiration times. Finally, results are presented on the implementation of a system for the generation of private keys for cryptographic communications using channel impulse-response estimation at 60 GHz. The testbed is composed of commercial millimeter-wave VubIQ transceivers, laboratory equipment, and software implemented in MATLAB. Novel cognitive enhancements are demonstrated, using channel estimation to dynamically change system parameters and estimate cryptographic key strength. We show for a complex channel that secret key generation can be accomplished on the order of 100 kb/s.

  2. The relation between the waveguide invariant, multipath impulse response, and ray cycles.

    PubMed

    Harrison, Chris H

    2011-05-01

    The waveguide invariant, β, that manifests itself as interference fringes or "striations" in a plot of frequency vs source-receiver separation, is usually thought of as a modal phenomenon. This paper shows that striations can be explained simply through the variation of the eigenray arrival times with range, in short, the variation of the multipath impulse response. It is possible to calculate β for a number of sound speed profiles analytically and to find what β depends on, why it switches from one value to another, how it depends on source-receiver depth, how it depends on variable bathymetry, and how smooth the sound speed profile needs to be for clear fringes. The analytical findings are confirmed by calculating striation patterns numerically starting from eigenray travel times in various stratified environments. Most importantly the approach throws some light on what can be deduced from β alone and the likelihood and utility of striations in reverberation.

  3. A Variable Step-Size Proportionate Affine Projection Algorithm for Identification of Sparse Impulse Response

    NASA Astrophysics Data System (ADS)

    Liu, Ligang; Fukumoto, Masahiro; Saiki, Sachio; Zhang, Shiyong

    2009-12-01

    Proportionate adaptive algorithms have been proposed recently to accelerate convergence for the identification of sparse impulse response. When the excitation signal is colored, especially the speech, the convergence performance of proportionate NLMS algorithms demonstrate slow convergence speed. The proportionate affine projection algorithm (PAPA) is expected to solve this problem by using more information in the input signals. However, its steady-state performance is limited by the constant step-size parameter. In this article we propose a variable step-size PAPA by canceling the a posteriori estimation error. This can result in high convergence speed using a large step size when the identification error is large, and can then considerably decrease the steady-state misalignment using a small step size after the adaptive filter has converged. Simulation results show that the proposed approach can greatly improve the steady-state misalignment without sacrificing the fast convergence of PAPA.

  4. Nonlinear filtering of noisy interference fringes with the 2D spatially dependent filter impulse response

    NASA Astrophysics Data System (ADS)

    Gurov, Igor P.; Volkov, Mikhail V.

    2002-04-01

    Image enhancement and evaluation play an important role in modern information and measurement technologies. An important image kind is obtained in coherent systems in holography and interferometry in the form of fringe patterns. Because of the physical and technical limitations fringe patterns are often distorted under the noise influence. It is proposed new noise-immune method for fringe pattern enhancement and evaluation. Unlike conventional filtering methods, in this method a filter impulse response is formed by the local empirical histogram modification with the spatial weighting function inside a dimensionally-varied area dependent on the local fringe intensity distribution. High efficiency of the method was verified experimentally when processing real noisy distorted fringe patterns.

  5. Estimating and removing colorations from the deconvolved impulse response of an underwater acoustic channel.

    PubMed

    Gemba, Kay L; Nosal, Eva-Marie; Reed, Todd R

    2017-01-01

    The impulse response (IR) of an acoustic channel can be obtained by cross-correlating the received signal with the broadband excitation signal in unfavorable noise conditions. However, the deconvolved IR is colored by the IRs of the combined electrical equipment. This letter presents a time domain approach using pre-computed filters to whiten the unknown coloration in order to obtain the channel's time domain waveform. The method is validated with an image-source model and the IR of the channel is recovered with spectral root mean square error of -27 dB. Data results obtained from a pool experiment with non-calibrated equipment yield a whitened IR with standard deviation of 0.9 dB (30-68 kHz band).

  6. A no a priori knowledge estimation of the impulse response for satellite image noise reduction

    NASA Astrophysics Data System (ADS)

    Benbouzid, A. B.; Taleb, N.

    2015-04-01

    Due to launching vibrations and space harsh environment, high resolution remote sensing satellite imaging systems require permanent assessment and control of image quality, which may vary between ground pre-launch measurements, after launch and over satellite lifetime. In order to mitigate noise, remove artifacts and enhance image interpretability, the Point Spread Function (PSF) of the imaging system is estimated. Image deconvolution can be performed across the characterization of the actual Modulation Transfer Function (MTF) of the imaging system. In this work we focus on adapting and applying a no reference method to characterize in orbit high resolution satellite images in terms of geometrical performance. Moreover, we use natural details contained in images as edges transitions to estimate the impulse response via the assessment of the MTF image. The obtained results are encouraging and promising.

  7. Responses of free-living coastal pelagic fish to impulsive sounds.

    PubMed

    Hawkins, Anthony D; Roberts, Louise; Cheesman, Samuel

    2014-05-01

    The behavior of wild, pelagic fish in response to sound playback was observed with a sonar/echo sounder. Schools of sprat Sprattus sprattus and mackerel Scomber scombrus were examined at a quiet coastal location. The fish were exposed to a short sequence of repeated impulsive sounds, simulating the strikes from a pile driver, at different sound pressure levels. The incidence of behavioral responses increased with increasing sound level. Sprat schools were more likely to disperse and mackerel schools more likely to change depth. The sound pressure levels to which the fish schools responded on 50% of presentations were 163.2 and 163.3 dB re 1 μPa peak-to-peak, and the single strike sound exposure levels were 135.0 and 142.0 dB re 1 μPa(2) s, for sprat and mackerel, respectively, estimated from dose response curves. For sounds leading to mackerel responses, particle velocity levels were also estimated. The method of observation by means of a sonar/echo sounder proved successful in examining the behavior of unrestrained fish exposed to different sound levels. The technique may allow further testing of the relationship between responsiveness, sound level, and sound characteristics for different types of man-made sound, for a variety of fish species under varied conditions.

  8. Development of a fast sampling system for estimation of impulse responses of mobile radio channels

    NASA Astrophysics Data System (ADS)

    Melancon, Pierre

    1994-07-01

    This paper describes the features of measurement equipment developed to measure impulse response estimates of mobile radio channels in less than a ms per measurement. The development of such equipment was required to measure mobile radio channels in realistic operating scenarios, in a normal sized vehicle moving at typical speeds in different environments. Up to speeds of 70 km/hr, the measurement period is short enough to assume the equipment is measuring the same channel during the whole sampling interval. AT the transmitter end of the measurement system, a wideband signal (10 MHz) is produced by modulating a carrier frequency with a 511 bit pseudo random sequence at 5 Mb/s and transmitted through the radio channel. The received signal is down-converted to 70 MHz and demodulated by a complex demodulator. The quadrature baseband signals at the demodulator outputs are then filtered and sampled at high speed by two fast digitizers. During this process, the data are stored in large memory banks to allow a fast sampling rate during a long period of time. Data are transferred to laser disks for further processing in the laboratory. Impulse response of radio channels are estimated by performing a software correlation between a measurement system back to back reference and real time measurements. A minivan was modified to hold the receiver, digitizers, memory banks and the computer. A shaft encoder was attached to its rear left wheel to trigger measurements while moving. Features of the system are discussed along with the effects of data block length, signal to noise ratio, sampling rate, memory size and phase stability on the design of the measurement equipment. Finally, some measurement results are presented and discussed.

  9. Impulsivity in the supermarket. Responses to calorie taxes and subsidies in healthy weight undergraduates.

    PubMed

    Giesen, Janneke C A H; Havermans, Remco C; Nederkoorn, Chantal; Jansen, Anita

    2012-02-01

    The present study investigated the effect of taxing high-energy dense products and subsidizing low-energy dense products on changes in calorie consumption. More specifically, we hypothesized that 'more impulsive' individuals were less influenced by such pricing strategies compared to 'less impulsive' individuals. Contrary to our hypothesis, results showed that 'more impulsive' individuals adjusted their calorie consumption with regard to price changes whereas 'less impulsive' participants were less influenced by price changes. Furthermore, taxing high-energy dense products was more successful in reducing calorie consumption than subsidizing low-energy dense products.

  10. A Fresh Look at Linear Ordinary Differential Equations with Constant Coefficients. Revisiting the Impulsive Response Method Using Factorization

    ERIC Educational Resources Information Center

    Camporesi, Roberto

    2016-01-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations of any order based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as…

  11. A Fresh Look at Linear Ordinary Differential Equations with Constant Coefficients. Revisiting the Impulsive Response Method Using Factorization

    ERIC Educational Resources Information Center

    Camporesi, Roberto

    2016-01-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations of any order based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as…

  12. Differentiating Tower of Hanoi performance: interactive effects of psychopathic tendencies, impulsive response styles, and modality.

    PubMed

    Salnaitis, Christina L; Baker, Crystal A; Holland, James; Welsh, Marilyn

    2011-01-01

    Previous research has demonstrated that performance on the computerized Tower of Hanoi is lower than performance on the manual Tower of Hanoi. The present study was conducted to elucidate potential factors that contribute to performance differences across modalities. Personality characteristics related to psychopathy and impulsive response styles were hypothesized to be correlates of poor performance on the computerized version of the Tower of Hanoi, which is a problem-solving task that requires working memory, planning, and inhibition. Eighty-four college students from a mid-sized university participated. Participants were grouped as low, middle, or high psychopathy based on their total scores on the Psychopathic Personality Inventory. A 2 (Modality) × 3 (Psychopathy) analysis of covariance, controlling for visuospatial working memory, yielded a significant interaction, in which the high psychopathy group did not differ in performance across modality, whereas the low and middle psychopathy groups performed more poorly on the computerized version. Subsequent analyses on reaction time and accuracy for the computerized modality indicated that a reflective, methodical approach to the computerized task was more productively utilized in the low psychopathy group, whereas the fast and accurate approach was more productively utilized in the high psychopathy group. These results suggest that individuals with elevated psychopathic tendencies within a normal population are not necessarily deficient in problem-solving performance on the Tower of Hanoi. Impulsive responding is associated with poor performance in the computerized version of the Tower of Hanoi, irrespective of psychopathic tendencies. Caution should be exercised in interpreting scores on the computerized Tower of Hanoi because the psychometric properties required for comparability with the manual version have not been sufficiently demonstrated.

  13. Increased impulsivity in response to food cues after sleep loss in healthy young men

    PubMed Central

    Cedernaes, Jonathan; Brandell, Jon; Ros, Olof; Broman, Jan-Erik; Hogenkamp, Pleunie S; Schiöth, Helgi B; Benedict, Christian

    2014-01-01

    Objective To investigate whether acute total sleep deprivation (TSD) leads to decreased cognitive control when food cues are presented during a task requiring active attention, by assessing the ability to cognitively inhibit prepotent responses. Methods Fourteen males participated in the study on two separate occasions in a randomized, crossover within-subject design: one night of TSD versus normal sleep (8.5 hours). Following each nighttime intervention, hunger ratings and morning fasting plasma glucose concentrations were assessed before performing a go/no-go task. Results Following TSD, participants made significantly more commission errors when they were presented “no-go” food words in the go/no-go task, as compared with their performance following sleep (+56%; P<0.05). In contrast, response time and omission errors to “go” non-food words did not differ between the conditions. Self-reported hunger after TSD was increased without changes in fasting plasma glucose. The increase in hunger did not correlate with the TSD-induced commission errors. Conclusions Our results suggest that TSD impairs cognitive control also in response to food stimuli in healthy young men. Whether such loss of inhibition or impulsiveness is food cue-specific as seen in obesity—thus providing a mechanism through which sleep disturbances may promote obesity development—warrants further investigation. PMID:24839251

  14. Current impulse response of thin InP p+-i-n+ diodes using full band structure Monte Carlo method

    NASA Astrophysics Data System (ADS)

    You, A. H.; Cheang, P. L.

    2007-02-01

    A random response time model to compute the statistics of the avalanche buildup time of double-carrier multiplication in avalanche photodiodes (APDs) using full band structure Monte Carlo (FBMC) method is discussed. The effect of feedback impact ionization process and the dead-space effect on random response time are included in order to simulate the speed of APD. The time response of InP p+-i-n+ diodes with the multiplication region of 0.2μm is presented. Finally, the FBMC model is used to calculate the current impulse response of the thin InP p+-i-n+ diodes with multiplication lengths of 0.05 and 0.2μm using Ramo's theorem [Proc. IRE 27, 584 (1939)]. The simulated current impulse response of the FBMC model is compared to the results simulated from a simple Monte Carlo model.

  15. Neurophysiological correlates of altered response inhibition in internet gaming disorder and obsessive-compulsive disorder: Perspectives from impulsivity and compulsivity.

    PubMed

    Kim, Minah; Lee, Tak Hyung; Choi, Jung-Seok; Kwak, Yoo Bin; Hwang, Wu Jeong; Kim, Taekwan; Lee, Ji Yoon; Lim, Jae-A; Park, Minkyung; Kim, Yeon Jin; Kim, Sung Nyun; Kim, Dai Jin; Kwon, Jun Soo

    2017-01-30

    Although internet gaming disorder (IGD) and obsessive-compulsive disorder (OCD) represent opposite ends of the impulsivity and compulsivity dimensions, the two disorders share common neurocognitive deficits in response inhibition. However, the similarities and differences in neurophysiological features of altered response inhibition between IGD and OCD have not been investigated sufficiently. In total, 27 patients with IGD, 24 patients with OCD, and 26 healthy control (HC) subjects participated in a Go/NoGo task with electroencephalographic recordings. N2-P3 complexes elicited during Go and NoGo condition were analyzed separately and compared among conditions and groups. NoGo-N2 latency at the central electrode site was delayed in IGD group versus the HC group and correlated positively with the severity of internet game addiction and impulsivity. NoGo-N2 amplitude at the frontal electrode site was smaller in OCD patients than in IGD patients. These findings suggest that prolonged NoGo-N2 latency may serve as a marker of trait impulsivity in IGD and reduced NoGo-N2 amplitude may be a differential neurophysiological feature between OCD from IGD with regard to compulsivity. We report the first differential neurophysiological correlate of the altered response inhibition in IGD and OCD, which may be a candidate biomarker for impulsivity and compulsivity.

  16. Neurophysiological correlates of altered response inhibition in internet gaming disorder and obsessive-compulsive disorder: Perspectives from impulsivity and compulsivity

    PubMed Central

    Kim, Minah; Lee, Tak Hyung; Choi, Jung-Seok; Kwak, Yoo Bin; Hwang, Wu Jeong; Kim, Taekwan; Lee, Ji Yoon; Lim, Jae-A; Park, Minkyung; Kim, Yeon Jin; Kim, Sung Nyun; Kim, Dai Jin; Kwon, Jun Soo

    2017-01-01

    Although internet gaming disorder (IGD) and obsessive-compulsive disorder (OCD) represent opposite ends of the impulsivity and compulsivity dimensions, the two disorders share common neurocognitive deficits in response inhibition. However, the similarities and differences in neurophysiological features of altered response inhibition between IGD and OCD have not been investigated sufficiently. In total, 27 patients with IGD, 24 patients with OCD, and 26 healthy control (HC) subjects participated in a Go/NoGo task with electroencephalographic recordings. N2-P3 complexes elicited during Go and NoGo condition were analyzed separately and compared among conditions and groups. NoGo-N2 latency at the central electrode site was delayed in IGD group versus the HC group and correlated positively with the severity of internet game addiction and impulsivity. NoGo-N2 amplitude at the frontal electrode site was smaller in OCD patients than in IGD patients. These findings suggest that prolonged NoGo-N2 latency may serve as a marker of trait impulsivity in IGD and reduced NoGo-N2 amplitude may be a differential neurophysiological feature between OCD from IGD with regard to compulsivity. We report the first differential neurophysiological correlate of the altered response inhibition in IGD and OCD, which may be a candidate biomarker for impulsivity and compulsivity. PMID:28134318

  17. Effects of body position on the ventilatory response following an impulse exercise in humans.

    PubMed

    Haouzi, Philippe; Chenuel, Bruno; Chalon, Bernard

    2002-04-01

    The aim of this study was to identify some of the mechanisms that could be involved in blunted ventilatory response (VE) to exercise in the supine (S) position. The contribution of the recruitment of different muscle groups, the activity of the cardiac mechanoreceptors, the level of arterial baroreceptor stimulation, and the hemodynamic effects of gravity on the exercising muscles was analyzed during upright (U) and S exercise. Delayed rise in VE and pulmonary gas exchange following an impulselike change in work rate (supramaximal leg cycling at 240 W for 12 s) was measured in seven healthy subjects and six heart transplant patients both in U and S positions. This approach allows study of the relationship between the rise in VE and O2 uptake (VO2) without the confounding effects of contractions of different muscle groups. These responses were compared with those triggered by an impulselike change in work rate produced by the arms, which were positioned at the same level as the heart in S and U positions to separate effects of gravity on postexercising muscles from those on the rest of the body. Despite superimposable VO2 and CO2 output responses, the delayed VE response after leg exercise was significantly lower in the S posture than in the U position for each control subject and cardiac-transplant patient (-2.58 +/- 0.44 l and -3.52 +/- 1.11 l/min, respectively). In contrast, when impulse exercise was performed with the arms, reduction of ventilatory response in the S posture reached, at best, one-third of the deficit after leg exercise and was always associated with a reduction in VO2 of a similar magnitude. We concluded that reduction in VE response to exercise in the S position is independent of the types (groups) of muscles recruited and is not critically dependent on afferent signals originating from the heart but seems to rely on some of the effects of gravity on postexercising muscles.

  18. Subthalamic deep brain stimulation restores automatic response activation and increases susceptibility to impulsive behavior in patients with Parkinson's disease.

    PubMed

    Plessow, Franziska; Fischer, Rico; Volkmann, Jens; Schubert, Torsten

    2014-06-01

    Repeatedly reported deficits of patients with Parkinson's disease (PD) in selecting an appropriate action in the face of competing response alternatives has led to the conclusion of a basal ganglia (BG) involvement in response selection and impulse control. Despite capacious research, it remains elusive how BG dysfunction affects processes subserving goal-directed behavior. Even more problematically, since PD pathology transcends a BG dysfunction due to dopamine depletion in the nigrostriatal DA system (by also comprising alterations in extrastriatal dopamine availability and other neurotransmitter systems), it is not yet clear which aspects of these deficits are actually caused by BG dysfunction. To address this question, the present study investigated 13 off-medication PD patients with bilateral therapeutic subthalamic deep brain stimulation (DBS) both with and without stimulation (DBSON and DBSOFF, respectively) and 26 healthy controls. All participants performed a task that tests the relation between automatic response impulses and goal-directed action selection. Results show an improvement of automatic response activation under DBSON, increasing the susceptibility to impulsive responses, and a reduced impact of automatic response activation under DBSOFF. We argue that the BG determine the efficiency of the regulation and transmission of stimulus-driven bottom-up response activation required for efficient response selection.

  19. Finite Element Modeling of the Buckling Response of Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Rose, Cheryl A.; Moore, David F.; Knight, Norman F., Jr.; Rankin, Charles C.

    2002-01-01

    A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.

  20. Depressive-type emotional response pattern in impulsive-aggressive patients with borderline personality disorder.

    PubMed

    Jayaro, C; De La Vega, I; Bayon-Palomino, C; Díaz-Marsá, M; Montes, A; Tajima, K; López-Ibor, J J; Carrasco, J L

    2011-12-01

    Borderline personality disorder (BPD) is typically characterized by severe affective dysregulation leading to impulsive behaviors. Accordingly, preliminary data suggest the hypothesis that BPD patients could have a specific and altered pattern of subjective emotional response to stimuli. The nature of the emotional response in BPD can be compared with other affective disorders and provide further insight on the nosological proximity with other psychiatric disorders. Subjective emotional response was investigated in 19 patients with DSM-IV BPD with no current depressive episode and in 19 healthy control subjects by using the International Affective Picture System (IAPS). The intensity of arousal, valence and dominance was rated in response to 60 images categorized as pleasant, unpleasant and neutral by using a self-assessment instrument. ANOVA of multiple factors was used for between-groups comparisons. The obtained pattern showed that BPD patients considered the unpleasant and neutral images as less aversive than controls, but the activation that these images induced was higher. Patients showed significantly greater arousal than controls for unpleasant and neutral images (p<0.05) but presented greater valence (more positive emotion) for these images (p<0.05). In addition, BPD patients showed lower dominance (greater insecurity and dyscomfort) for positive images (p<0.05). The subjective emotional response pattern of BPD patients suggests a trait of vulnerability to pleasant stimuli and is similar to the pattern found in depressive patients in previous studies. This supports the evidence that BPD could in part be related with the spectrum of the affective temperament and affective disorders. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Digital high-pass filter deconvolution by means of an infinite impulse response filter

    NASA Astrophysics Data System (ADS)

    Födisch, P.; Wohsmann, J.; Lange, B.; Schönherr, J.; Enghardt, W.; Kaever, P.

    2016-09-01

    In the application of semiconductor detectors, the charge-sensitive amplifier is widely used in front-end electronics. The output signal is shaped by a typical exponential decay. Depending on the feedback network, this type of front-end electronics suffers from the ballistic deficit problem, or an increased rate of pulse pile-ups. Moreover, spectroscopy applications require a correction of the pulse-height, while a shortened pulse-width is desirable for high-throughput applications. For both objectives, digital deconvolution of the exponential decay is convenient. With a general method and the signals of our custom charge-sensitive amplifier for cadmium zinc telluride detectors, we show how the transfer function of an amplifier is adapted to an infinite impulse response (IIR) filter. This paper investigates different design methods for an IIR filter in the discrete-time domain and verifies the obtained filter coefficients with respect to the equivalent continuous-time frequency response. Finally, the exponential decay is shaped to a step-like output signal that is exploited by a forward-looking pulse processing.

  2. An Iterative Technique for Designing Finite Impulse Response Chebyshev MTI Filters with Nonlinear Delay

    DTIC Science & Technology

    1978-03-01

    Passband Ripple Passband Lower Passbaisd Ripple Passband Lower in Passband Weights N Edge IHz) fPASS (d8) RPe Edge ( Hzj fPASS (dB) RpB Edge (Hz) Ripple (dB...NN IIV 24 THIS PAGE IS BtST QUALITY MR&QXCABLE RhM COrY R±albH.Md TD DDC . w u- w F-ii W _jL 4 0 W X Z-C :1[M (’ ’ ’ 𔃻(4C z z3 z 11 z k-i I 1’ t...L~ THIS PAGE IS BEST QUALITY PRACTICABLE 31 EFOM OPY FUlRNISIE TD DDQ .~ x z S. < w W, w r -c N 0 r z~’ Nr Z-C14c;L ciw I-- ED w w. w’ ;= ’L 0 to CC

  3. Optical implementation of a single-layer finite impulse response neural network

    NASA Astrophysics Data System (ADS)

    Silveira, Paulo E. X.; Pati, G. S.; Wagner, Kelvin H.

    2000-05-01

    This paper demonstrates a space integrating optical implementation of a single-layer FIRNN. A scrolling spatial light modulator is used for representing the spatio-temporal input plane, while the weights are implemented by the adaptive grating formation in a photorefractive crystal. Differential heterodyning is used for low-noise bipolar output detection and an active stabilization technique using a lock-in amplifier and a piezo-electric actuator is adopted for long term interferometric stability. Simulations and initial experimental results for adaptive sonar broadband beamforming are presented.

  4. Computer Algorithms for the Design and Implementation of Linear Phase Finite Impulse Response Digital Filters

    DTIC Science & Technology

    1981-07-01

    341—1 * U. 4 4 « * 4 4 « 4 4 4 4 4 4 4 n^jr^oc^ TDh - X)in 4^mru—•o-^x>^- (n^on^O!Vf^JM■\\l’^J’M’^i^u(\\J^M—•—>-< r r r X X X c X r r r X...3310 Willett Drive Laramie, WY 82070 CALSPAN Corp. ATTN: E. Fisher P. 0. Box 400 Buffalo, NY 14225 SSD Dynamics , Inc. ATTN: Dr. M. Soifer 755

  5. Unbiased identification of finite impulse response linear systems operating in closed-loop.

    PubMed

    Westwick, David T; Perreault, Eric J

    2006-01-01

    The force and position data issued to construct models of joint dynamics are often obtained from closed-loop experiments, where the joint position is perturbed using an actuator configured as a position servo. If the position servo is orders of magnitude staffer than the joint, as is often the case, it is possible to treat the data as if they were obtained in open loop. It may be more relevant to study joint dynamics in compliant environments. This can be accomplished by adding an admittance controller, programmed to simulate a compliant environment, into the servo. Under these conditions, the presence of feedback cannot be ignored. Unbiased estimates of a system can be directly obtained from closed-loop data using the prediction error method. However, this is not true, in general, when linear regression or correlation-based analysis is used to fit nonparametric time- or frequency domain models. We develop a prediction error minimization based identification method for a nonparametric time-domain model, augmented with a parametric noise model. Simulations suggest that the method produces unbiased estimates of the dynamics of a system operating inside a feedback loop, even though linear regression results in substantial biases.

  6. Window-Based Channel Impulse Response Prediction for Time-Varying Ultra-Wideband Channels

    PubMed Central

    Al-Samman, A. M.; Azmi, M. H.; Rahman, T. A.; Khan, I.; Hindia, M. N.; Fattouh, A.

    2016-01-01

    This work proposes channel impulse response (CIR) prediction for time-varying ultra-wideband (UWB) channels by exploiting the fast movement of channel taps within delay bins. Considering the sparsity of UWB channels, we introduce a window-based CIR (WB-CIR) to approximate the high temporal resolutions of UWB channels. A recursive least square (RLS) algorithm is adopted to predict the time evolution of the WB-CIR. For predicting the future WB-CIR tap of window wk, three RLS filter coefficients are computed from the observed WB-CIRs of the left wk−1, the current wk and the right wk+1 windows. The filter coefficient with the lowest RLS error is used to predict the future WB-CIR tap. To evaluate our proposed prediction method, UWB CIRs are collected through measurement campaigns in outdoor environments considering line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Under similar computational complexity, our proposed method provides an improvement in prediction errors of approximately 80% for LOS and 63% for NLOS scenarios compared with a conventional method. PMID:27992445

  7. Localizing nearby sound sources in a classroom: Binaural room impulse responses

    NASA Astrophysics Data System (ADS)

    Shinn-Cunningham, Barbara G.; Kopco, Norbert; Martin, Tara J.

    2005-05-01

    Binaural room impulse responses (BRIRs) were measured in a classroom for sources at different azimuths and distances (up to 1 m) relative to a manikin located in four positions in a classroom. When the listener is far from all walls, reverberant energy distorts signal magnitude and phase independently at each frequency, altering monaural spectral cues, interaural phase differences, and interaural level differences. For the tested conditions, systematic distortion (comb-filtering) from an early intense reflection is only evident when a listener is very close to a wall, and then only in the ear facing the wall. Especially for a nearby source, interaural cues grow less reliable with increasing source laterality and monaural spectral cues are less reliable in the ear farther from the sound source. Reverberation reduces the magnitude of interaural level differences at all frequencies; however, the direct-sound interaural time difference can still be recovered from the BRIRs measured in these experiments. Results suggest that bias and variability in sound localization behavior may vary systematically with listener location in a room as well as source location relative to the listener, even for nearby sources where there is relatively little reverberant energy. .

  8. Extracting the frequencies of the pinna spectral notches in measured head related impulse responses

    NASA Astrophysics Data System (ADS)

    Raykar, Vikas C.; Duraiswami, Ramani; Yegnanarayana, B.

    2005-07-01

    The head related impulse response (HRIR) characterizes the auditory cues created by scattering of sound off a person's anatomy. The experimentally measured HRIR depends on several factors such as reflections from body parts (torso, shoulder, and knees), head diffraction, and reflection/diffraction effects due to the pinna. Structural models (Algazi et al., 2002; Brown and Duda, 1998) seek to establish direct relationships between the features in the HRIR and the anatomy. While there is evidence that particular features in the HRIR can be explained by anthropometry, the creation of such models from experimental data is hampered by the fact that the extraction of the features in the HRIR is not automatic. One of the prominent features observed in the HRIR, and one that has been shown to be important for elevation perception, are the deep spectral notches attributed to the pinna. In this paper we propose a method to robustly extract the frequencies of the pinna spectral notches from the measured HRIR, distinguishing them from other confounding features. The method also extracts the resonances described by Shaw (1997). The techniques are applied to the publicly available CIPIC HRIR database (Algazi et al., 2001c). The extracted notch frequencies are related to the physical dimensions and shape of the pinna.

  9. The integration of periodic truss bridge design and impulse response method

    NASA Astrophysics Data System (ADS)

    Can, Onur; Ozevin, Didem

    2017-04-01

    Global structural monitoring strategies for steel truss bridges have the challenges as the influence of boundary conditions on the comparison of predicted and measured properties, and the insensitivity of current methods to small flaws. It is important to consider the damage mechanisms and their influences to structural behavior in the design process. In this paper, the truss optimization is linked with periodic structure design such that each periodic unit (repetitive truss section) has distinct dispersion curve that can be monitored in time for the presence of damage. The numerical model of periodic unit is performed for pristine and cracked conditions. The changes in dispersion behavior with the increase of damage are noted. A section of the truss is built in the laboratory, and the dispersion of periodic unit is obtained using impulse response method in order to reduce the influence of boundary conditions. The changes of dispersion curve of periodic cell with the increase of damage are compared with the numerical results. The proposed design strategy integrates the damage detection philosophy to the design stage, and increases the reliability of nondestructive evaluation method.

  10. Impulse response of an S-cone pathway in the aging visual system.

    PubMed

    Shinomori, Keizo; Werner, John S

    2006-07-01

    Age-related changes in the temporal properties of an S-cone pathway were characterized by the psychophysical impulse-response function (IRF). Participants included 49 color-normal observers ranging in age from 16.8 to 86.3 years. A double-pulse method was used to measure the IRF with S-cone modulation at constant luminance. Stimuli were presented as a Gaussian patch (+/-1SD = 2.3 degrees ) in one of four quadrants around a central fixation cross on a CRT screen. The test stimulus was modulated from the equal-energy white of the background toward the short-wave spectrum locus. Each of the two pulses (6.67 ms) was separated by an interstimulus interval (ISI) from 20 to 720 ms. Chromatic detection thresholds were determined by a four-alternative forced-choice method with staircases for each ISI in one session. IRFs were calculated from the threshold data using a model with four parameters of an exponentially damped sine wave. S-cone IRFs have only an excitatory phase and a much longer time course compared with IRFs for luminance modulation measured with the same apparatus. The results demonstrated significant age-related losses in IRF amplitude, but the latency (time to peak) of the IRF was stable with age.

  11. Dynamic response of clamped corrugated sandwich plates subjected to underwater impulsive loads

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Zhang, Wei; Ye, Nan; Li, Dacheng

    2017-01-01

    Corrugated sandwich plates are widely used in marine industry because such plates have high strength-to-weight ratios and blast resistance. The laboratory-scaled fluid-structure interaction experiments are performed to demonstrate the shock resistance of corrugated sandwich plates by quantifying the permanent transverse deflection at mid-span of the plates as a function of impulsive loadings per areal mass. Sandwich structures with 6mm-thick 3003 H18 aluminum corrugated core and 5A06 face sheets subjected to underwater impulsive loadings are studied experimentally in this paper. The dynamic deformations of plates are captured with the the 3D digital imaging correlation method (DIC). The results affirm the peak deflection during the processes of dynamic deformation and the residual maximum deflection for post-mortem plates show a linear trend with the impulses per areal mass, and show sensitivity to the change of impulses. Inhomogeneous deformation for corrugated sandwich plates are show uneven rather than the perfect parabolic shapes reported in previous studies. With the increasing of intensities for impulsive loadings, the failure modes can be observed more complicated from the initial plastic deformation to debonding and crack. This paper provides valid data to quantify the peak deflection, residual deflection and failure modes as functions of impulses and geometric parameters in the future work.

  12. Preamplifier impulse-response shape-driven shot-noise in direct-detection photon-counting laser radars

    NASA Astrophysics Data System (ADS)

    Youmans, Douglas G.

    2001-09-01

    The number of photons returning form a target in a given time interval is well described by a negative-binomial distributed random variable. A photomultipler tube (PMT) photon-counting detector is optimal for direct detection, and the number of detected-photon 'electron pulses' produced is also negative-binomially distributed per time bin, with a reduced mean due to the device quantum efficiency. These time distributed electron pulses are amplified and filtered by the preamplifier electronics prior to digitization and signal processing. The voltage output pulse per individual photo-electron event is known as the 'impulse-response- function' of the detector and preamplifier. In this study we employ a typical analog preamplifier filter response, modeled as a Butterworth lowpass filter of order two, which filters a 200 ps wideband PMT input voltage pulse. The random summation of these lowpass voltage impulse-responses, as created by the negative-binomial photon arrival times and random photo-electron creation, is the classical electronic 'shot-noise' random process. We derive numerically the voltage probability density function of this negative- binomial/impulse-response driven shot-noise random process following the stochastic process literature. We also show a technique to include PMT variations in gain, known as the 'pulse height distribution,' and to incorporate Gaussian baseline-noise voltage. Agreement with AMOR experiments is shown to be excellent. In addition, a Monte Carlo realization is presented, using the same impulse-response temporal shape, which also gives excellent agreement with AMOR data and with the analytical/numerical calculations.

  13. Structural and acoustic response of a finite stiffened submarine hull

    NASA Astrophysics Data System (ADS)

    Wang, Xian-zhong; Jiang, Chen-ban; Xu, Rui-yang

    2016-12-01

    After borrowing the idea of precise integration method, a precise integration transfer matrix method (PITMM) is proposed by modifying traditional transfer matrix method. The submarine hull can be modeled as joined conicalcylindrical-spherical shells. By considering the effect of the ring-stiffeners, the field transfer matrixes of shells of revolution are obtained accurately by PITMM. After assembling the field transfer matrixes into an entire matrix, the dynamic model is established to solve the dynamic responses of the joined shell. By describing the sound pressure in fluid by modified wave superposition method (MWSM) and collocating points along the meridian line of the joined shell, finally the structural and acoustic responses of a finite stiffened submarine hull can be predicted by coupled PITMM and MWSM. The effectiveness of the present method has been verified by comparing the structural and acoustic responses of the spherical shell with existing results. Furthermore, the effects of the model truncation, stiffness and thickness on the structural and acoustic responses of the submarine hull are studied.

  14. An indirect time-of-flight measurement technique with impulse photocurrent response for sub-millimeter range resolved imaging.

    PubMed

    Yasutomi, Keita; Usui, Takahiro; Han, Sang-Man; Takasawa, Taishi; Kagawa, Keiichiro; Kawahito, Shoji

    2014-08-11

    This paper presents an indirect time-of-flight (TOF) measurement technique with an impulse photocurrent response of a lock-in pixel. By using a short-pulse laser, the generated photocurrent can be presumed to be an impulse response. This facilitates the utilization of the full high-speed performance of the photodetector and gives high range resolution. As a proof-of-concept, a test chip with a lock-in pixel based on draining-only modulation was implemented using 0.11 μm CMOS image-sensor technology. The test chip achieved a range resolution of 0.29 mm in a 50-mm measurable range, which corresponds to a time resolution of 1.9 ps and the successful acquisition of a 3-mm example step.

  15. Computation of Schenberg response function by using finite element modelling

    NASA Astrophysics Data System (ADS)

    Frajuca, C.; Bortoli, F. S.; Magalhaes, N. S.

    2016-05-01

    Schenberg is a detector of gravitational waves resonant mass type, with a central frequency of operation of 3200 Hz. Transducers located on the surface of the resonating sphere, according to a distribution half-dodecahedron, are used to monitor a strain amplitude. The development of mechanical impedance matchers that act by increasing the coupling of the transducers with the sphere is a major challenge because of the high frequency and small in size. The objective of this work is to study the Schenberg response function obtained by finite element modeling (FEM). Finnaly, the result is compared with the result of the simplified model for mass spring type system modeling verifying if that is suitable for the determination of sensitivity detector, as the conclusion the both modeling give the same results.

  16. Lagrangian and energy forms for retrieving the impulse response of the Earth due to random electromagnetic forcing.

    PubMed

    Slob, Evert; Weiss, Chester J

    2011-08-01

    We distinguish between trivial and nontrivial differences in retrieving the real or imaginary parts of the Green's function. Trivial differences come from different Green's function definitions. The energy and lagrangian forms constitute nontrivial differences. Magnetic noise sources suffice to extract the quasistatic electromagnetic-field Earth impulse response in the lagrangian form. This is of interest for Earth subsurface imaging. A numerical example demonstrates that all source vector components are necessary to extract a single-field vector component.

  17. Instantaneous Impulses.

    ERIC Educational Resources Information Center

    Erlichson, Herman

    2000-01-01

    Describes an experiment that extends Newton's instantaneous-impulse method of orbital analysis to a graphical method of orbit determination. Discusses the experiment's usefulness for teaching both horizontal projectile motion and instantaneous impulse. (WRM)

  18. Instantaneous Impulses.

    ERIC Educational Resources Information Center

    Erlichson, Herman

    2000-01-01

    Describes an experiment that extends Newton's instantaneous-impulse method of orbital analysis to a graphical method of orbit determination. Discusses the experiment's usefulness for teaching both horizontal projectile motion and instantaneous impulse. (WRM)

  19. A Fast Method to Calculate the Spatial Impulse Response for 1-D Linear Ultrasonic Phased Array Transducers.

    PubMed

    Zou, Cheng; Sun, Zhenguo; Cai, Dong; Muhammad, Salman; Zhang, Wenzeng; Chen, Qiang

    2016-11-08

    A method is developed to accurately determine the spatial impulse response at the specifically discretized observation points in the radiated field of 1-D linear ultrasonic phased array transducers with great efficiency. In contrast, the previously adopted solutions only optimize the calculation procedure for a single rectangular transducer and required approximation considerations or nonlinear calculation. In this research, an algorithm that follows an alternative approach to expedite the calculation of the spatial impulse response of a rectangular linear array is presented. The key assumption for this algorithm is that the transducer apertures are identical and linearly distributed on an infinite rigid plane baffled with the same pitch. Two points in the observation field, which have the same position relative to two transducer apertures, share the same spatial impulse response that contributed from corresponding transducer, respectively. The observation field is discretized specifically to meet the relationship of equality. The analytical expressions of the proposed algorithm, based on the specific selection of the observation points, are derived to remove redundant calculations. In order to measure the proposed methodology, the simulation results obtained from the proposed method and the classical summation method are compared. The outcomes demonstrate that the proposed strategy can speed up the calculation procedure since it accelerates the speed-up ratio which relies upon the number of discrete points and the number of the array transducers. This development will be valuable in the development of advanced and faster linear ultrasonic phased array systems.

  20. A Fast Method to Calculate the Spatial Impulse Response for 1-D Linear Ultrasonic Phased Array Transducers

    PubMed Central

    Zou, Cheng; Sun, Zhenguo; Cai, Dong; Muhammad, Salman; Zhang, Wenzeng; Chen, Qiang

    2016-01-01

    A method is developed to accurately determine the spatial impulse response at the specifically discretized observation points in the radiated field of 1-D linear ultrasonic phased array transducers with great efficiency. In contrast, the previously adopted solutions only optimize the calculation procedure for a single rectangular transducer and required approximation considerations or nonlinear calculation. In this research, an algorithm that follows an alternative approach to expedite the calculation of the spatial impulse response of a rectangular linear array is presented. The key assumption for this algorithm is that the transducer apertures are identical and linearly distributed on an infinite rigid plane baffled with the same pitch. Two points in the observation field, which have the same position relative to two transducer apertures, share the same spatial impulse response that contributed from corresponding transducer, respectively. The observation field is discretized specifically to meet the relationship of equality. The analytical expressions of the proposed algorithm, based on the specific selection of the observation points, are derived to remove redundant calculations. In order to measure the proposed methodology, the simulation results obtained from the proposed method and the classical summation method are compared. The outcomes demonstrate that the proposed strategy can speed up the calculation procedure since it accelerates the speed-up ratio which relies upon the number of discrete points and the number of the array transducers. This development will be valuable in the development of advanced and faster linear ultrasonic phased array systems. PMID:27834799

  1. Database of Multichannel In-Ear and Behind-the-Ear Head-Related and Binaural Room Impulse Responses

    NASA Astrophysics Data System (ADS)

    Kayser, H.; Ewert, S. D.; Anemüller, J.; Rohdenburg, T.; Hohmann, V.; Kollmeier, B.

    2009-12-01

    An eight-channel database of head-related impulse responses (HRIRs) and binaural room impulse responses (BRIRs) is introduced. The impulse responses (IRs) were measured with three-channel behind-the-ear (BTEs) hearing aids and an in-ear microphone at both ears of a human head and torso simulator. The database aims at providing a tool for the evaluation of multichannel hearing aid algorithms in hearing aid research. In addition to the HRIRs derived from measurements in an anechoic chamber, sets of BRIRs for multiple, realistic head and sound-source positions in four natural environments reflecting daily-life communication situations with different reverberation times are provided. For comparison, analytically derived IRs for a rigid acoustic sphere were computed at the multichannel microphone positions of the BTEs and differences to real HRIRs were examined. The scenes' natural acoustic background was also recorded in each of the real-world environments for all eight channels. Overall, the present database allows for a realistic construction of simulated sound fields for hearing instrument research and, consequently, for a realistic evaluation of hearing instrument algorithms.

  2. Harmonic response of a class of finite extensibility nonlinear oscillators

    NASA Astrophysics Data System (ADS)

    Febbo, M.

    2011-06-01

    Finite extensibility oscillators are widely used to simulate those systems that cannot be extended to infinity. For example, they are used when modelling the bonds between molecules in a polymer or DNA molecule or when simulating filaments of non-Newtonian liquids. In this paper, the dynamic behavior of a harmonically driven finite extensibility oscillator is presented and studied. To this end, the harmonic balance method is applied to determine the amplitude-frequency and amplitude-phase equations. The distinguishable feature in this case is the bending of the amplitude-frequency curve to the frequency axis, making it asymptotically approach the limit of maximum elongation of the oscillator, which physically represents the impossibility of the system reaching this limit. Also, the stability condition that defines stable and unstable steady-state solutions is derived. The study of the effect of the system parameters on the response reveals that a decreasing value of the damping coefficient or an increasing value of the excitation amplitude leads to the appearance of a multi-valued response and to the existence of a jump phenomenon. In this sense, the critical amplitude of the excitation, which means here a certain value of external excitation that results in the occurrence of jump phenomena, is also derived. Numerical experiments to observe the effects of system parameters on the frequency-amplitude response are performed and compared with analytical calculations. At a low value of the damping coefficient or at a high value of excitation amplitude, the agreement is poor for low frequencies but good for high frequencies. It is demonstrated that the disagreement is caused by the neglect of higher-order harmonics in the analytical formulation. These higher-order harmonics, which appear as distinguishable peaks at certain values in the frequency response curves, are possible to calculate considering not the linearized frequency of the oscillator but its actual

  3. Finite-strain large-deflection elastic-viscoplastic finite-element transient response analysis of structures

    NASA Technical Reports Server (NTRS)

    Rodal, J. J. A.; Witmer, E. A.

    1979-01-01

    A method of analysis for thin structures that incorporates finite strain, elastic-plastic, strain hardening, time dependent material behavior implemented with respect to a fixed configuration and is consistently valid for finite strains and finite rotations is developed. The theory is formulated systematically in a body fixed system of convected coordinates with materially embedded vectors that deform in common with continuum. Tensors are considered as linear vector functions and use is made of the dyadic representation. The kinematics of a deformable continuum is treated in detail, carefully defining precisely all quantities necessary for the analysis. The finite strain theory developed gives much better predictions and agreement with experiment than does the traditional small strain theory, and at practically no additional cost. This represents a very significant advance in the capability for the reliable prediction of nonlinear transient structural responses, including the reliable prediction of strains large enough to produce ductile metal rupture.

  4. Eysenck personality inventory: impulsivity/neuroticism and social desirability response set.

    PubMed

    Kumari, V

    1996-02-01

    The Hindi version of the Eysenck Personality Inventory and the Trait scale of the Hindi version of the State-Trait Anxiety Inventory were administered to 945 female Indian students (M age = 20.4 yr., SD = 1.4) to study the personalities of those scoring low and high on the Lie scale, and the association of Lie scale scores in the intercorrelation between Impulsivity and Neuroticism under no motivation to fake good. The group with low scores on the Lie scale had lower scores on Impulsivity and higher scores on Neuroticism and Trait Anxiety than a group scoring high on the Lie scale. No association of Lie scale scores was observed with scores on Extraversion. Lie scale scores were differentially associated with scores on Impulsivity and Neuroticism. The need to consider the Lie scale in addition to other scales in studies of personality is emphasised.

  5. The Latent Structure of Impulsivity: Impulsive Choice, Impulsive Action, and Impulsive Personality Traits

    PubMed Central

    MacKillop, James; Weafer, Jessica; Gray, Joshua; Oshri, Assaf; Palmer, Abraham; de Wit, Harriet

    2016-01-01

    Rationale Impulsivity has been strongly linked to addictive behaviors, but can be operationalized in a number of ways that vary considerably in overlap, suggesting multidimensionality. Objective This study tested the hypothesis that the latent structure among multiple measures of impulsivity would reflect three broad categories: impulsive choice, reflecting discounting of delayed rewards; impulsive action, reflecting ability to inhibit a prepotent motor response; and impulsive personality traits, reflecting self-reported attributions of self-regulatory capacity. Methods The study used a cross-sectional confirmatory factor analysis of multiple impulsivity assessments. Participants were 1252 young adults (62% female) with low levels of addictive behavior who were assessed in individual laboratory rooms at the University of Chicago and the University of Georgia. The battery comprised a delay discounting task, Monetary Choice Questionnaire, Conners Continuous Performance Test, Go/NoGo Task, Stop Signal Task, Barratt Impulsivity Scale, and the UPPS-P Impulsive Behavior Scale. Results The hypothesized three-factor model provided the best fit to the data, although Sensation Seeking was excluded from the final model. The three latent factors were largely unrelated to each other and were variably associated with substance use. Conclusions These findings support the hypothesis that diverse measures of impulsivity can broadly be organized into three categories that are largely distinct from one another. These findings warrant investigation among individuals with clinical levels of addictive behavior and may be applied to understanding the underlying biological mechanisms of these categories. PMID:27449350

  6. Measurement of the responses of polyurethane and CONFOR(TM) foams and the development of a system identification technique to estimate polyurethane foam parameters from experimental impulse responses

    NASA Astrophysics Data System (ADS)

    Sundaram, Vaidyanadan

    Flexible polyurethane foam is the main cushioning element used in car seats. Optimization of an occupied seat's static and dynamic behavior requires models of foam that are accurate over a wide range of excitation and pre-compression conditions. Experiments were conducted to measure the response of foam over a wide range of excitation which include slowly varying uniaxial compression tests on a 3 inch cube foam sample, base excitation and impulse excitation test on a foam-mass system. The foam used was the same in all of the experiments, thus obtaining all the responses on the same foam sample which helps eliminate the sample to sample variation. Similar efforts were taken to conduct impulse and base excitation tests on CONFOR(TM) foam to help in future modeling efforts of CONFOR(TM) foam. All the experimental protocols and data pre-processing protocols along with results are presented. Previous researcher developed a linear model for a single-degree of freedom foam-mass system subjected to an impulsive excitation. Free response data from impulse tests on a foam-mass system with different masses was used to identify model parameters at various pre-compression levels (settling points). The free response of the system was modeled as a Prony series (sum of exponentials) whose parameters can be related to the parameters in the foam-mass system model. Models identified from tests at one settling point performed poorly when used to predict the response at other settling points. In this research, a method is described to estimate the parameters of a global model of the foam behavior from data gathered in a series of impulse tests at different settling points. The global model structure includes a nonlinear elastic term and a hereditary viscoelastic term. The model can be used to predict the settling point for each mass used and, by expanding the model about that settling point, local linear models of the response to impulsive excitation can be derived. From this analysis

  7. Groundwater recharge and time lag measurement through Vertosols using impulse response functions

    NASA Astrophysics Data System (ADS)

    Hocking, Mark; Kelly, Bryce F. J.

    2016-04-01

    Throughout the world there are many stressed aquifers used to support irrigated agriculture. The Condamine River catchment (southern Queensland, Australia) is one example of a globally significant agricultural region where groundwater use has exceeded recharge over the last 50 years. There is a high dependence on groundwater in this catchment, because yearly rainfall is highly variable, and actual evapotranspiration often exceeds rainfall. To better manage the aquifer there is a need to correctly conceptualise the primary inputs and outputs of the system, and characterise the lags in system response to all forcings. In catchment models it is particularly important to correctly proportion diffuse (areal) rainfall recharge and to account for the lag between rainfall and recharge at the water table. Throughout large portions of the Condamine Catchment, groundwater levels are now 20 or more metres below the ground surface. This study aimed to better quantify the lag between rainfall and recharge at the water table using the predefined impulse response function in continuous time method (PIRFICT; von Asmuth et al., 2002; von Asmuth, 2012). The PIRFICT method was applied to 255 multi-decadal groundwater level data sets throughout the catchment. Inputs into the modelling include rainfall, irrigation deep drainage, stream water level, evapotranspiration, and groundwater extractions. As an independent check the PIRFICT model derived diffuse recharge estimates are compared to point lysimeter and geochemical recharge estimates in the Vertosol soils within this catchment. It is estimated using the PIRFICT method that in the Condamine Catchment between 1990 and 2012, the mean rain-derived groundwater recharge is 4.4 mm/year. Mean groundwater response from rainfall was determined to be 5.3 years: range 188 days to 48 years. The recharge estimates are consistent with both geochemical and lysimeter point measurements of recharge. It is concluded that where extensive groundwater

  8. Comparison of several methods for obtaining the time response of linear systems to either a unit impulse or arbitrary input from frequency-response data

    NASA Technical Reports Server (NTRS)

    Donegan, James J; Huss, Carl R

    1957-01-01

    Several methods of obtaining the time response of Linear systems to either a unit impulse or an arbitrary input from frequency-response data are described and compared. Comparisons indicate that all the methods give good accuracy when applied to a second-order system; the main difference is the required computing time. The methods generally classified as inverse Laplace transform methods were found to be most effective in determining the response to a unit impulse from frequency-response data of higher order systems. Some discussion and examples are given of the use of such methods as flight-data-analysis techniques in predicting loads and motions of a flexible aircraft on the basis of simple calculations when the aircraft frequency response is known.

  9. Examination of trait impulsivity on the response to a brief mindfulness intervention among college student drinkers

    PubMed Central

    Vinci, Christine; Peltier, MacKenzie; Waldo, Krystal; Kinsaul, Jessica; Shah, Sonia; Coffey, Scott F.; Copeland, Amy L.

    2016-01-01

    Mindfulness-based strategies show promise for targeting the construct of impulsivity and associated variables among problematic alcohol users. This study examined the moderating role of intervention (mindfulness vs relaxation vs control) on trait impulsivity and three outcomes examined post-intervention (negative affect, positive affect, and urge to drink) among 207 college students with levels of at-risk drinking. Moderation analyses revealed that the relationship between baseline impulsivity and the primary outcomes significantly differed for participants who underwent the mindfulness versus relaxation interventions. Notably, simple slope analyses revealed that negative urgency was positively associated with urge to drink following the mindfulness intervention. Among participants who underwent the relaxation intervention, analysis of simple slopes revealed that negative urgency was negatively associated with urge to drink, while positive urgency was positively associated with positive affect following the relaxation intervention. Findings suggest that level (low vs high) and subscale of impulsivity matter with regard to how a participant will respond to a mindfulness versus relaxation intervention. PMID:27344030

  10. Auditory and behavioral responses of California sea lions (Zalophus californianus) to single underwater impulses from an arc-gap transducer

    NASA Astrophysics Data System (ADS)

    Finneran, James J.; Dear, Randall; Carder, Donald A.; Ridgway, Sam H.

    2003-09-01

    A behavioral response paradigm was used to measure underwater hearing thresholds in two California sea lions (Zalophus californianus) before and after exposure to underwater impulses from an arc-gap transducer. Preexposure and postexposure hearing thresholds were compared to determine if the subjects experienced temporary shifts in their masked hearing thresholds (MTTS). Hearing thresholds were measured at 1 and 10 kHz. Exposures consisted of single underwater impulses produced by an arc-gap transducer referred to as a ``pulsed power device'' (PPD). The electrical charge of the PPD was varied from 1.32 to 2.77 kJ; the distance between the subject and the PPD was varied over the range 3.4 to 25 m. No MTTS was observed in either subject at the highest received levels: peak pressures of approximately 6.8 and 14 kPa, rms pressures of approximately 178 and 183 dB re: 1 μPa, and total energy fluxes of 161 and 163 dB re: 1 μPa2s for the two subjects. Behavioral reactions to the tests were observed in both subjects. These reactions primarily consisted of temporary avoidance of the site where exposure to the PPD impulse had previously occurred.

  11. Finite orbit energetic particle linear response to toroidal Alfven eigenmodes

    NASA Astrophysics Data System (ADS)

    Berk, H. L.; Breizman, B. N.; Ye, Huanchun

    1992-03-01

    The linear response of energetic particles of the TAE modes is calculated taking into account their finite orbit excursion from the flux surfaces. The general expression reproduces the previously derived theory for small banana width; when the banana width Δ b is much larger than the mode thickness Δ m, we obtain a new compact expression for the linear power transfer. When Δm/ Δb≪1, the banana orbit effect reduces the power transfer by a factor Δm/ Δb from that predicted by the narrow orbit theory. A comparison is made of the contribution to the TAE growth rate of energetic particles with a slowing-down distribution arising from an isotropic source, and a balanced-injected beam source when the source speed is close to the Alfven speed. For the same stored energy density, the contribution from the principal resonances (| v‖|= vA) is substantially enhanced in the beam case compared to the isotropic case, while the contribution at the higher sidebands (| v‖|= vA/(2 l-1) with l⩾2) is substantially reduced.

  12. Finite orbit energetic particle linear response to toroidal Alfven Eigenmodes

    NASA Astrophysics Data System (ADS)

    Berk, H. L.; Ye, Huanchun; Breizman, B. N.

    1991-07-01

    The linear response of energetic particles to the toroidal Alfven eigenmodes (TAE) modes is calculated taking into account their finite orbit excursion from the flux surfaces. The general expression reproduces the previously derived theory for small banana width: when the banana width delta(sub b) is much larger than the mode thickness delta(sub m), we obtain a new compact expression for the linear power transfer. When delta(sub m)/delta(sub b) is much less than 1, the banana orbit effect reduces the power transfer by a factor of delta(sub m)/delta(sub b) from that predicted by the narrow orbit theory. A comparison is made of the contribution to the TAE growth rate of energetic particles with a slowing-down distribution arising from an isotropic source, and a balance-injected beam source when the source speed is close to the Alfven speed. For the same stored energy density, the contribution from the principal resonances (absolute value of upsilon(parallel) = upsilon(sub A) is substantially enhanced in the beam case compared to the isotropic case, while the contribution at the higher sidebands (absolute value of upsilon(parallel) = upsilon(sub A)/(2l - 1) with l greater than or = 2) is substantially reduced.

  13. Finite orbit energetic particle linear response to toroidal Alfven eigenmodes

    SciTech Connect

    Berk, H.L.; Ye, Huanchun . Inst. for Fusion Studies); Breizman, B.N. . Inst. Yadernoj Fiziki)

    1991-07-01

    The linear response of energetic particles to the TAE modes is calculated taking into account their finite orbit excursion from the flux surfaces. The general expression reproduces the previously derived theory for small banana width: when the banana width {triangle}{sub b} is much larger than the mode thickness {triangle}{sub m}, we obtain a new compact expression for the linear power transfer. When {triangle}{sub m}/{triangle}{sub b} {much lt} 1, the banana orbit effect reduces the power transfer by a factor of {triangle}{sub m}/{triangle}{sub b} from that predicted by the narrow orbit theory. A comparison is made of the contribution to the TAE growth rate of energetic particles with a slowing-down distribution arising from an isotropic source, and a balance-injected beam source when the source speed is close to the Alfven speed. For the same stored energy density, the contribution from the principal resonances ({vert bar}{upsilon}{sub {parallel}}{vert bar} = {upsilon}{sub A} is substantially enhanced in the beam case compared to the isotropic case, while the contribution at the higher sidebands ({vert bar}{upsilon}{sub {parallel}}{vert bar}) = {upsilon}{sub A}/(2{ell} {minus} 1) with {ell} {ge} 2) is substantially reduced. 10 refs.

  14. Vibration Response of Multi Storey Building Using Finite Element Modelling

    NASA Astrophysics Data System (ADS)

    Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.

    2016-07-01

    Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.

  15. Response of a grounded dielectric slab to an impulse line source using leaky modes

    NASA Technical Reports Server (NTRS)

    Duffy, Dean G.

    1994-01-01

    This paper describes how expansions in leaky (or improper) modes may be used to represent the continuous spectrum in an open radiating waveguide. The technique requires a thorough knowledge of the life history of the improper modes as they migrate from improper to proper Riemann surfaces. The method is illustrated by finding the electric field resulting from an impulsively forced current located in the free space above a grounded dielectric slab.

  16. Dietary restraint and impulsivity modulate neural responses to food in adolescents with obesity and healthy adolescents.

    PubMed

    Hofmann, Johannes; Ardelt-Gattinger, Elisabeth; Paulmichl, Katharina; Weghuber, Daniel; Blechert, Jens

    2015-11-01

    Despite alarming prevalence rates, surprisingly little is known about neural mechanisms underlying eating behavior in juveniles with obesity. To simulate reactivity to modern food environments, event-related potentials (ERP) to appetizing food images (relative to control images) were recorded in adolescents with obesity and healthy adolescents. Thirty-four adolescents with obesity (patients) and 24 matched healthy control adolescents watched and rated standardized food and object images during ERP recording. Personality (impulsivity) and eating styles (trait craving and dietary restraint) were assessed as potential moderators. Food relative to object images triggered larger early (P100) and late (P300) ERPs. More impulsive individuals had considerably larger food-specific P100 amplitudes in both groups. Controls with higher restraint scores showed reduced food-specific P300 amplitudes and subjective palatability ratings whereas patients with higher restraint scores showed increased P300 and palatability ratings. This first ERP study in adolescents with obesity and controls revealed impulsivity as a general risk factor in the current obesogenic environment by increasing food-cue salience. Dietary restraint showed paradoxical effects in patients, making them more vulnerable to visual food-cues. Salutogenic therapeutic approaches that deemphasize strict dietary restraint and foster healthy food choice might reduce such paradoxical effects. © 2015 The Obesity Society.

  17. Linking impulse response functions to reaction time: Rod and cone reaction time data and a computational model

    PubMed Central

    Cao, Dingcai; Zele, Andrew J.; Pokorny, Joel

    2007-01-01

    Reaction times for incremental and decremental stimuli were measured at five suprathreshold contrasts for six retinal illuminance levels where rods alone (0.002–0.2 Trolands), rods and cones (2–20 Trolands) or cones alone (200 Trolands) mediated detection. A 4-primary photostimulator allowed independent control of rod or cone excitations. This is the first report of reaction times to isolated rod or cone stimuli at mesopic light levels under the same adaptation conditions. The main findings are: 1) For rods, responses to decrements were faster than increments, but cone reaction times were closely similar. 2) At light levels where both systems were functional, rod reaction times were ~20 ms longer. The data were fitted with a computational model that incorporates rod and cone impulse response functions and a stimulus-dependent neural sensory component that triggers a motor response. Rod and cone impulse response functions were derived from published psychophysical two-pulse threshold data and temporal modulation transfer functions. The model fits were accomplished with a limited number of free parameters: two global parameters to estimate the irreducible minimum reaction time for each receptor type, and one local parameter for each reaction time versus contrast function. This is the first model to provide a neural basis for the variation in reaction time with retinal illuminance, stimulus contrast, stimulus polarity, and receptor class modulated. PMID:17346763

  18. Ice Sheet Roughness Estimation Based on Impulse Responses Acquired in the Global Ice Sheet Mapping Orbiter Mission

    NASA Astrophysics Data System (ADS)

    Niamsuwan, N.; Johnson, J. T.; Jezek, K. C.; Gogineni, P.

    2008-12-01

    The Global Ice Sheet Mapping Orbiter (GISMO) mission was developed to address scientific needs to understand the polar ice subsurface structure. This NASA Instrument Incubator Program project is a collaboration between Ohio State University, the University of Kansas, Vexcel Corporation and NASA. The GISMO design utilizes an interferometric SAR (InSAR) strategy in which ice sheet reflected signals received by a dual-antenna system are used to produce an interference pattern. The resulting interferogram can be used to filter out surface clutter so as to reveal the signals scattered from the base of the ice sheet. These signals are further processed to produce 3D-images representing basal topography of the ice sheet. In the past three years, the GISMO airborne field campaigns that have been conducted provide a set of useful data for studying geophysical properties of the Greenland ice sheet. While topography information can be obtained using interferometric SAR processing techniques, ice sheet roughness statistics can also be derived by a relatively simple procedure that involves analyzing power levels and the shape of the radar impulse response waveforms. An electromagnetic scattering model describing GISMO impulse responses has previously been proposed and validated. This model suggested that rms-heights and correlation lengths of the upper surface profile can be determined from the peak power and the decay rate of the pulse return waveform, respectively. This presentation will demonstrate a procedure for estimating the roughness of ice surfaces by fitting the GISMO impulse response model to retrieved waveforms from selected GISMO flights. Furthermore, an extension of this procedure to estimate the scattering coefficient of the glacier bed will be addressed as well. Planned future applications involving the classification of glacier bed conditions based on the derived scattering coefficients will also be described.

  19. Impulse generation by detonation tubes

    NASA Astrophysics Data System (ADS)

    Cooper, Marcia Ann

    Impulse generation with gaseous detonation requires conversion of chemical energy into mechanical energy. This conversion process is well understood in rocket engines where the high pressure combustion products expand through a nozzle generating high velocity exhaust gases. The propulsion community is now focusing on advanced concepts that utilize non-traditional forms of combustion like detonation. Such a device is called a pulse detonation engine in which laboratory tests have proven that thrust can be achieved through continuous cyclic operation. Because of poor performance of straight detonation tubes compared to conventional propulsion systems and the success of using nozzles on rocket engines, the effect of nozzles on detonation tubes is being investigated. Although previous studies of detonation tube nozzles have suggested substantial benefits, up to now there has been no systematic investigations over a range of operating conditions and nozzle configurations. As a result, no models predicting the impulse when nozzles are used exist. This lack of data has severely limited the development and evaluation of models and simulations of nozzles on pulse detonation engines. The first experimental investigation measuring impulse by gaseous detonation in plain tubes and tubes with nozzles operating in varying environment pressures is presented. Converging, diverging, and converging-diverging nozzles were tested to determine the effect of divergence angle, nozzle length, and volumetric fill fraction on impulse. The largest increases in specific impulse, 72% at an environment pressure of 100 kPa and 43% at an environment pressure of 1.4 kPa, were measured with the largest diverging nozzle tested that had a 12° half angle and was 0.6 m long. Two regimes of nozzle operation that depend on the environment pressure are responsible for these increases and were first observed from these data. To augment this experimental investigation, all data in the literature regarding

  20. Extensions of the scattering-object function and the pulser-receiver impulse response in the field II formalism.

    PubMed

    Bloomfield, Philip E

    2005-05-01

    The pulse-echo impulse-response format in the Field II formalism is generalized to separately located transmitter and receiver. To first order in sound velocity and density perturbations, identical results for the scattering-object function are obtained for the Morse-Ingard and the Chernov formulation in both the temporal and frequency domains: f(s)=-[2Delta(c/c)+(Delta(rho/rho))(1-cos(theta))] where for ultrasonic pulse-echo or transmission modality, cos(theta) approximately -1 or +1, respectively.

  1. A fresh look at linear ordinary differential equations with constant coefficients. Revisiting the impulsive response method using factorization

    NASA Astrophysics Data System (ADS)

    Camporesi, Roberto

    2016-01-01

    We present an approach to the impulsive response method for solving linear constant-coefficient ordinary differential equations of any order based on the factorization of the differential operator. The approach is elementary, we only assume a basic knowledge of calculus and linear algebra. In particular, we avoid the use of distribution theory, as well as of the other more advanced approaches: Laplace transform, linear systems, the general theory of linear equations with variable coefficients and variation of parameters. The approach presented here can be used in a first course on differential equations for science and engineering majors.

  2. Fractionating impulsivity: neuropsychiatric implications.

    PubMed

    Dalley, Jeffrey W; Robbins, Trevor W

    2017-02-17

    The ability to make decisions and act quickly without hesitation can be advantageous in many settings. However, when persistently expressed, impulsive decisions and actions are considered risky, maladaptive and symptomatic of such diverse brain disorders as attention-deficit hyperactivity disorder, drug addiction and affective disorders. Over the past decade, rapid progress has been made in the identification of discrete neural networks that underlie different forms of impulsivity - from impaired response inhibition and risky decision making to a profound intolerance of delayed rewards. Herein, we review what is currently known about the neural and psychological mechanisms of impulsivity, and discuss the relevance and application of these new insights to various neuropsychiatric disorders.

  3. Impulse Pump

    DTIC Science & Technology

    2016-06-17

    APPLICATIONS [0002] None. BACKGROUND OF THE INVENTION (1) Field of the Invention [0003] The present invention relates to an impulse pump for generating...impulse pump 15. The sleeve bearings 98 are affixed to the head block 90 to ease axial motion while the plunger 72 is under torsional loads. [0041

  4. The vibrational mode of the tibia and assessment of bone union in experimental fracture healing using the impulse response method.

    PubMed

    Nakatsuchi, Y; Tsuchikane, A; Nomura, A

    1996-10-01

    This study attempts to clarify the use of the impulse response method in the assessment of fracture healing. The vibrational mode as well as the effect of simulated callus consolidation on the vibrational parameters of excised human tibia were studied. Two separate vibrations were found, one vibrating strongly in the lateral direction and the other vibrating weakly in the antero-posterior direction. The ability to identify the primary vibrational mode in the lateral direction would make the impulse response method suitable for use in clinical practice. The callus consolidation process was simulated by the sequential consolidation of an adhesive material in an experimentally produced fracture gap. The change in hardness of the epoxy was found to correlate well with the change of resonant frequency of the bone. The resonant frequency demonstrated a steady increase during the initial phase of consolidation of the adhesive, up to about 40% of its final hardness. With the addition of various constructs for fracture fixation to the in vitro model such as a plate, Ender's pins, a Russell-Taylor intramedullary nail, or an Orthofix external fixator, the relationship between the consolidation of the 'callus' and the change in resonant frequency of the bone was not disturbed.

  5. Determining arterial wave transit time from a single aortic pressure pulse in rats: vascular impulse response analysis

    PubMed Central

    Chang, Ru-Wen; Chang, Chun-Yi; Lai, Liang-Chuan; Wu, Ming-Shiou; Young, Tai-Horng; Chen, Yih-Sharng; Wang, Chih-Hsien; Chang, Kuo-Chu

    2017-01-01

    Arterial wave transit time (τw) in the lower body circulation is an effective biomarker of cardiovascular risk that substantially affects systolic workload imposed on the heart. This study evaluated a method for determining τw from the vascular impulse response on the basis of the measured aortic pressure and an assumed triangular flow (Qtri). The base of the unknown Qtri was constructed with a duration set equal to ejection time. The timing of the peak triangle was derived using a fourth-order derivative of the pressure waveform. Values of τws obtained using Qtri were compared with those obtained from the measure aortic flow wave (Qm). Healthy rats (n = 27), rats with chronic kidney disease (CKD; n = 22), and rats with type 1 (n = 22) or type 2 (n = 11) diabetes were analyzed. The cardiovascular conditions in the CKD rats and both diabetic groups were characterized by a decrease in τws. The following significant relation was observed (P < 0.0001): τwtriQ = −1.5709 + 1.0604 × τwmQ (r2 = 0.9641). Our finding indicates that aortic impulse response can be an effective method for the estimation of arterial τw by using a single pressure recording together with the assumed Qtri. PMID:28102355

  6. Determining arterial wave transit time from a single aortic pressure pulse in rats: vascular impulse response analysis.

    PubMed

    Chang, Ru-Wen; Chang, Chun-Yi; Lai, Liang-Chuan; Wu, Ming-Shiou; Young, Tai-Horng; Chen, Yih-Sharng; Wang, Chih-Hsien; Chang, Kuo-Chu

    2017-01-19

    Arterial wave transit time (τw) in the lower body circulation is an effective biomarker of cardiovascular risk that substantially affects systolic workload imposed on the heart. This study evaluated a method for determining τw from the vascular impulse response on the basis of the measured aortic pressure and an assumed triangular flow (Q(tri)). The base of the unknown Q(tri) was constructed with a duration set equal to ejection time. The timing of the peak triangle was derived using a fourth-order derivative of the pressure waveform. Values of τws obtained using Q(tri) were compared with those obtained from the measure aortic flow wave (Q(m)). Healthy rats (n = 27), rats with chronic kidney disease (CKD; n = 22), and rats with type 1 (n = 22) or type 2 (n = 11) diabetes were analyzed. The cardiovascular conditions in the CKD rats and both diabetic groups were characterized by a decrease in τws. The following significant relation was observed (P < 0.0001): τw(triQ) = -1.5709 + 1.0604 × τw(mQ) (r(2) = 0.9641). Our finding indicates that aortic impulse response can be an effective method for the estimation of arterial τw by using a single pressure recording together with the assumed Q(tri).

  7. Impulse control disorders in frontotemporal dementia: spectrum of symptoms and response to treatment.

    PubMed

    Pompanin, Sara; Jelcic, Nela; Cecchin, Diego; Cagnin, Annachiara

    2014-01-01

    To describe a patient with behavioral variant frontotemporal dementia (bvFTD) presenting with impulse control disorders (ICDs) which responded to fluvoxamine and topiramate. A 64-year-old woman was affected by several ICDs. At disease onset, she suffered from impulsive smoking and overeating which caused a body weight increase of 20 kg in 6 months. Later on she manifested binge-eating behavior and skin-picking compulsion. Presence of progressive frontal cognitive impairment (Mini Mental State Examination 24/30) and evidence of hypoperfusion of the anterior cingulate and dorsolateral frontal cortex with brain single-photon emission computed tomography scan contributed to the diagnosis of bvFTD. Use of combination treatment with selective serotonin reuptake inhibitor drugs and topiramate improved all these symptoms. This case extends the clinical phenotype of repetitive and compulsive habits in bvFTD to encompass symptoms suggestive of ICDs. It is proposed that fluvoxamine and topiramate may be considered as treatment options in these conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Millennial scale system impulse response of polar climates - deconvolution results between δ 18O records from Greenland and Antarctica

    NASA Astrophysics Data System (ADS)

    Reischmann, E.; Yang, X.; Rial, J. A.

    2013-12-01

    Deconvolution has long been used in science to recover real input given a system's impulse response and output. In this study, we applied spectral division deconvolution to select, polar, δ 18O time series to investigate the possible relationship between the climates of the Polar Regions, i.e. the equivalent to a climate system's ';impulse response.' While the records may be the result of nonlinear processes, deconvolution remains an appropriate tool because the two polar climates are synchronized, forming a Hilbert transform pair. In order to compare records, the age models of three Greenland and four Antarctica records have been matched via a Monte Carlo method using the methane-matched pair GRIP and BYRD as a basis for the calculations. For all twelve polar pairs, various deconvolution schemes (Wiener, Damped Least Squares, Tikhonov, Kalman filter) give consistent, quasi-periodic, impulse responses of the system. Multitaper analysis reveals strong, millennia scale, quasi-periodic oscillations in these system responses with a range of 2,500 to 1,000 years. These are not symmetric, as the transfer function from north to south differs from that of south to north. However, the difference is systematic and occurs in the predominant period of the deconvolved signals. Specifically, the north to south transfer function is generally of longer period than the south to north transfer function. High amplitude power peaks at 5.0ky to 1.7ky characterize the former, while the latter contains peaks at mostly short periods, with a range of 2.5ky to 1.0ky. Consistent with many observations, the deconvolved, quasi-periodic, transfer functions share the predominant periodicities found in the data, some of which are likely related to solar forcing (2.5-1.0ky), while some are probably indicative of the internal oscillations of the climate system (1.6-1.4ky). The approximately 1.5 ky transfer function may represent the internal periodicity of the system, perhaps even related to the

  9. Response of personal noise dosimeters to continuous and impulse-like signals

    NASA Astrophysics Data System (ADS)

    Evans, D. J.; Flynn, D. R.; Nedzelnitsky, V.; Burnett, E. D.

    1991-06-01

    A study of the capabilities of noise dosimeters to measure personal exposure to time varying and impulse-like noises was carried out. Ten commercial noise dosimeters were obtained. A laboratory reference noise dosimeter was constructed to provide a demonstrably accurate basis with which to compare the commercial noise dosimeters. Each commercial dosimeter, when ordered from the manufacturer, was specified to have a threshold A-weighted sound level of 80 dB, a criterion sound level of 90 dB, and an exchange rate of 5 dB and/or 3 dB. The performance of the commercial dosimeters was compared with theory and with results obtained from the reference dosimeter. Except in a few isolated cases, the commercial dosimeters were in general agreement with the performance specification of the appropriate American National Standard and with the Occupational Safety and Health Administration (OSHA) regulations.

  10. Vibration testing based on impulse response excited by pulsed-laser ablation: Measurement of frequency response function with detection-free input

    NASA Astrophysics Data System (ADS)

    Hosoya, Naoki; Kajiwara, Itsuro; Hosokawa, Takahiko

    2012-03-01

    We have developed a non-contact vibration-measurement system that is based on impulse excitation by laser ablation (i.e. laser excitation) to measure the high-frequency-vibration characteristics of objects. The proposed method makes it possible to analyse the frequency response function just by measuring the output (acceleration response) of a test object excited by pulsed-laser ablation. This technique does not require detection of the input force. Firstly, using a rigid block, the pulsed-laser-ablation force is calibrated via Newton's second law. Secondly, an experiment is conducted in which an object whose natural frequency lies in the high-frequency domain is excited by pulsed-laser ablation. The complex frequency spectrum obtained by Fourier transform of the measured response is then divided by the estimated pulsed-laser-ablation force. Finally, because of the error involved in the trigger position of the response with respect to the impulse arrival time, the phase of the complex Fourier transform is modified by accounting for the response dead time. The result is the frequency response function of the object. The effectiveness of the proposed method is demonstrated by a vibration test of an aluminium block.

  11. Methodology to determine skull bone and brain responses from ballistic helmet-to-head contact loading using experiments and finite element analysis.

    PubMed

    Pintar, Frank A; Philippens, Mat M G M; Zhang, JiangYue; Yoganandan, Narayan

    2013-11-01

    The objective of the study was to obtain helmet-to-head contact forces from experiments, use a human head finite element model to determine regional responses, and compare outputs to skull fracture and brain injury thresholds. Tests were conducted using two types of helmets (A and B) fitted to a head-form. Seven load cells were used on the head-form back face to measure helmet-to-head contact forces. Projectiles were fired in frontal, left, right, and rear directions. Three tests were conducted with each helmet in each direction. Individual and summated force- and impulse-histories were obtained. Force-histories were inputted to the human head-helmet finite element model. Pulse durations were approximately 4 ms. One-third force and impulse were from the central load cell. 0.2% strain and 40 MPa stress limits were not exceeded for helmet-A. For helmet-B, strains exceeded in left, right, and rear; pressures exceeded in bilateral directions; volume of elements exceeding 0.2% strains correlated with the central load cell forces. For helmet-A, volumes exceeding brain pressure threshold were: 5-93%. All elements crossed the pressure limit for helmet-B. For both helmets, no brain elements exceeded peak principal strain limit. These findings advance our understanding of skull and brain biomechanics from helmet-head contact forces. Published by Elsevier Ltd.

  12. Effect of Neck Muscle Strength and Anticipatory Cervical Muscle Activation on the Kinematic Response of the Head to Impulsive Loads

    PubMed Central

    Eckner, James T.; Oh, Youkeun K.; Joshi, Monica S.; Richardson, James K.; Ashton-Miller, James A.

    2015-01-01

    Background Greater neck strength and activating the neck muscles to brace for impact are both thought to reduce an athlete's risk of concussion during a collision by attenuating the head's kinematic response after impact. However, the literature reporting the neck's role in controlling postimpact head kinematics is mixed. Furthermore, these relationships have not been examined in the coronal or transverse planes or in pediatric athletes. Hypotheses In each anatomic plane, peak linear velocity (DV) and peak angular velocity (Dv) of the head are inversely related to maximal isometric cervical muscle strength in the opposing direction (H1). Under impulsive loading, DV and Dv will be decreased during anticipatory cervical muscle activation compared with the baseline state (H2). Study Design Descriptive laboratory study. Methods Maximum isometric neck strength was measured in each anatomic plane in 46 male and female contact sport athletes aged 8 to 30 years. A loading apparatus applied impulsive test forces to athletes' heads in flexion, extension, lateral flexion, and axial rotation during baseline and anticipatory cervical muscle activation conditions. Multivariate linear mixed models were used to determine the effects of neck strength and cervical muscle activation on head DV and Dv. Results Greater isometric neck strength and anticipatory activation were independently associated with decreased head DV and Dv after impulsive loading across all planes of motion (all P\\.001). Inverse relationships between neck strength and head DV and Dv presented moderately strong effect sizes (r = 0.417 to r = 0.657), varying by direction of motion and cervical muscle activation. Conclusion In male and female athletes across the age spectrum, greater neck strength and anticipatory cervical muscle activation (“bracing for impact”) can reduce the magnitude of the head's kinematic response. Future studies should determine whether neck strength contributes to the observed sex and

  13. A family of variable step-size affine projection adaptive filter algorithms using statistics of channel impulse response

    NASA Astrophysics Data System (ADS)

    Shams Esfand Abadi, Mohammad; AbbasZadeh Arani, Seyed Ali Asghar

    2011-12-01

    This paper extends the recently introduced variable step-size (VSS) approach to the family of adaptive filter algorithms. This method uses prior knowledge of the channel impulse response statistic. Accordingly, optimal step-size vector is obtained by minimizing the mean-square deviation (MSD). The presented algorithms are the VSS affine projection algorithm (VSS-APA), the VSS selective partial update NLMS (VSS-SPU-NLMS), the VSS-SPU-APA, and the VSS selective regressor APA (VSS-SR-APA). In VSS-SPU adaptive algorithms the filter coefficients are partially updated which reduce the computational complexity. In VSS-SR-APA, the optimal selection of input regressors is performed during the adaptation. The presented algorithms have good convergence speed, low steady state mean square error (MSE), and low computational complexity features. We demonstrate the good performance of the proposed algorithms through several simulations in system identification scenario.

  14. The atomic oxygen green and red line emission response to sudden impulses of the solar wind dynamic pressure.

    NASA Astrophysics Data System (ADS)

    Leonovich, Ludmila; Leonovich, Vitaly; Tashchilin, Anatoly

    The atomic oxygen green and red line emission response to sudden impulses of the solar wind dynamic pressure was revealed at mid-latitudes. The paper presents the study results of the dependence of the observed emissions intensity from the sudden variations in the solar wind and the geomagnetic field. These results show a relationship of the emissions disturbance amplitude with the solar wind speed, as well as with the geomagnetic field variations. We used the zenith photometer optical data, the geomagnetic field and the total electron content variations obtained for the Eastern Siberia region (52(°) N, 103(°) E). The investigation was supported by the RFFI grants № 12-05-00024-а, № 13-05-00733.

  15. Finite-element impact response of debonded composite turbine blades

    NASA Astrophysics Data System (ADS)

    Dey, Sudip; Karmakar, Amit

    2014-02-01

    This paper investigates on the transient behavior of debonded composite pretwisted rotating shallow conical shells which could be idealized as turbine blades subjected to low velocity normal impact using finite-element method. Lagrange's equation of motion is used to derive the dynamic equilibrium equation and the moderate rotational speeds are considered neglecting the Coriolis effect. An eight-noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the impact parameters. The time-dependent equations are solved by using Newmark's time integration scheme. Parametric studies are performed to investigate the effects of triggering parameters like angle of twist, rotational speed, laminate configuration and location of debonding considering low velocity normal impact at the center of eight-layered graphite-epoxy composite cantilevered conical shells with bending stiff ([0o2/{±} 30o]s), torsion stiff ([45°/-45°/-45°/45°]s) and cross-ply ([0°/90°/0°/90°]s) laminate configurations.

  16. Comparative analysis of the bronchodilator response measured by impulse oscillometry (IOS), spirometry and body plethysmography in asthmatic children.

    PubMed

    Olaguíbel, J M; Alvarez-Puebla, M J; Anda, M; Gómez, B; García, B E; Tabar, A I; Arroabarren, E

    2005-01-01

    Asthma is common among young children. The assessment of respiratory resistance by the impulse oscillometry system (IOS), based on the superimposition of respiratory flow by short-time impulses, requires no patient active collaboration. We evaluated the baseline repeatability and bronchodilator response of IOS indices in preschool children, their correlation with spirometry and whole body plethysmography, and differences between atopic and nonatopic children. Thirty-three asthmatic children (3-6 yrs.) underwent IOS measurement (R5rs, R20rs and X5rs) by triplicate at the baseline, after placebo and after salbutamol inhalation. Spirometry (FEV1) and whole body plethysmography (sRaw) were made at the baseline and after salbutamol. Baseline within-test (coefficient of variation: CV%) and between-test repeatability (baseline-placebo) were addressed. Bronchodilator response was evaluated by the SD index (change in multiples of the between-test repeatability). Baseline repeatability for R5rs was 4.1%. Its values decreased by 2SD after salbutamol inhalation, and correlated with FEV1 and sRaw at both, baseline (r=-0.51 and r=0.49) and post-salbutamol (r=-0.63 and r=0.54). A trend towards correlation between salbutamol-induced changes in R5rs and in sRaw (r=0.33) was observed. Atopic and non-atopic children showed no differences in lung function. IOS was well accepted by young asthmatic children and provided reproducible and sensitive indices of lung function. Resistance values obtained by IOS at low frequency (R5rs) were reproducible and correlated with spirometry and plethysmographic values.

  17. Field-Aligned Current Reconfiguration and Magnetospheric Response to an Impulse in the Interplanetary Magnetic Field BY Component

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Eriksson, S.; Korth, H.; Hairston, M. R.; Baker, J. B.; Heinselman, C. J.

    2013-12-01

    When the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, flow channels in the ionosphere with velocities in excess of 2 km/s have been observed, which can deposit large amounts of energy into the high-latitude thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from the Sondrestrom incoherent scatter radar and the DMSP spacecraft were used to investigate ionospheric convection during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field-Aligned Current (FAC) system. Additionally, data from AMPERE were used to investigate the time response of the dawn-side FAC pair. We find there is a delay of approximately 1.25 hours between the arrival of the dawnward IMF impulse at the magnetopause and strength of the dawnward FAC pair, which is comparable to substorm growth and expansion time scales under southward IMF. Additionally, we find at the time of the peak FAC, there is evidence of a reconfiguring four-sheet FAC system in the morning local time sector of the ionosphere. Additionally, we find an inverse correlation between the dawn FAC strength and both the solar wind Alfvénic Mach number and the SYM-H index. No statistically significant correlation between the FAC strength and the solar wind dynamic pressure was found.

  18. The Ionospheric Convection and Birkeland Current Response to an Impulse in the Interplanetary Magnetic Field BY Component

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Eriksson, S.; Korth, H.; Baker, J. B.; Hairston, M. R.; Heinselman, C. J.; Anderson, B. J.

    2013-05-01

    When the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, sunward flow channels on open field lines with velocities in excess of 2 km/s are generated in the polar ionosphere, which can deposit large amounts of energy into the cusp-region thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from ground based radars and the DMSP spacecraft were assimilated to investigate the global convection pattern during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field-Aligned Current (FAC) system. Additionally, data from AMPERE and the Sondrestrom Incoherent Scatter Radar were used to investigate the time response of the flow channel and its associated FAC pair. We find that there is a delay of approximately 1.25 hours between the arrival of the dawnward IMF impulse at the magnetopause and the speed of the flow channel and strength of the FACs flanking it. In addition to correlation between the dawnward component of the IMF and the flanking FAC strength, we also find that there is inverse correlation between the flanking FAC strength and both the SYM-H index and Solar Wind Alfvenic Mach Number. No statistically significant correlation is found between the flanking FAC strength and solar wind dynamic pressure.

  19. Field-aligned current reconfiguration and magnetospheric response to an impulse in the interplanetary magnetic field BY component

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Eriksson, S.; Korth, H.; Baker, J. B. H.; Hairston, M. R.; Heinselman, C.; Anderson, B. J.

    2013-06-01

    the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, flow channels in the ionosphere with velocities in excess of 2 km/s have been observed, which can deposit large amounts of energy into the high-latitude thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from the Sondrestrom incoherent scatter radar and the Defense Meteorological Satellite Program spacecraft were used to investigate ionospheric convection during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field-Aligned Current (FAC) system. Additionally, data from AMPERE were used to investigate the time response of the dawnside FAC pair. We find there is a delay of approximately 1.25 h between the arrival of the dawnward IMF impulse at the magnetopause and strength of the dawnward FAC pair, which is comparable to substorm growth and expansion time scales under southward IMF. Additionally, we find at the time of the peak FAC, there is evidence of a reconfiguring four-sheet FAC system in the morning local time sector of the ionosphere. Additionally, we find an inverse correlation between the dawn FAC strength and both the solar wind Alfvénic Mach number and the SYM-H index. No statistically significant correlation between the FAC strength and the solar wind dynamic pressure was found.

  20. Filter design of eight order butterworth infinite impulse response for earthquake sign

    NASA Astrophysics Data System (ADS)

    Perdana, Yusuf Hadi; Marsono, Agus

    2017-07-01

    Filtering is an important procedure in modern seismology analysis to obtain the best quality result in advanced process. There are many programs of signal processing consisting of signal filtering features, for example Seismic Analysis Code (SAC). Unfortunately, the basic mathematical equations in signal processing are not explained in detail. This research has purposes to design a Butterworth filter and to examine the influence of increasing order on the arrival time, polarity, and first motion amplitude of seismic wave. Filter design was done by computing eight order lowpass analog transfer functions and transforming them into lowpass, highpass, and bandpass digital using bilinear transformation so we have recursive and causal filters. The designed filter was then validated by the result of SAC. Based on the research we have found that the method and algorithm of designed filter are consistent with SAC. Increasing filter order can clarify the phases of seismic wave positions. On the other hand, it can influence the phase delay and impulse attenuation of seismic waves. The implication of this effects are error on computation of earthquake parameter and source mechanism. Filter instability due to increasing order will quickly occur if the cutoff frequency range is short or the sampling frequency is high. An appropriate passband frequency at low filter order can optimally generate earthquake filtered waves.

  1. A responsive finite element method to aid interactive geometric modeling.

    PubMed

    Umetani, N; Takayama, K; Mitani, J; Igarashi, T

    2011-01-01

    Current computer-aided engineering systems use numerical-simulation methods mainly as offline verification tools to reject designs that don't satisfy the required constraints, rather than as tools to guide users toward better designs. However, integrating real-time finite element method (FEM) into interactive geometric modeling can provide user guidance. During interactive editing, real-time feedback from numerical simulation guides users toward an improved design without tedious trial-and-error iterations. Careful reuse of previous computation results, such as meshes and matrices, on the basis of speed and accuracy trade-offs, have helped produce fast FEM analysis during interactive editing. Several 2D example applications and informal user studies show this approach's effectiveness. Such tools could help nonexpert users design objects that satisfy physical constraints and help those users understand the underlying physical properties.

  2. On impulse response functions computed from dynamic contrast-enhanced image data by algebraic deconvolution and compartmental modeling.

    PubMed

    Brix, Gunnar; Salehi Ravesh, Mona; Zwick, Stefan; Griebel, Jürgen; Delorme, Stefan

    2012-04-01

    Concentration-time courses measured by dynamic contrast-enhanced (DCE) imaging can be described by a convolution of the arterial input with an impulse response function, Q(T)(t), characterizing tissue microcirculation. Data analysis is based on two different approaches: computation of Q(T)(t) by algebraic deconvolution (AD) and subsequent evaluation according to the indicator dilution theory (IDT) or parameterization of Q(T)(t) by analytical expressions derived by compartmental modeling. Pitfalls of both strategies will be addressed in this study. Tissue data acquired by DCE-CT in patients with head-and-neck cancer and simulated by a reference model (MMID4) were analyzed by a two-compartment model (TCM), a permeability-limited two-compartment model (PL-TCM) and AD. Additionally, MMID4 was used to compute the 'true' response function that corresponds to the simulated tumor data. TCM and AD yielded accurate fits, whereas PL-TCM performed worse. Nevertheless, the corresponding response functions diverge markedly. The response curves obtained by TCM decrease exponentially in the early perfusion phase and overestimate the tissue perfusion, Q(T)(0). AD also resulted in response curves starting with a negative slope and not - as the 'true' response function in accordance with the IDT - with a horizontal plateau. They are thus not valid responses in the sense of the IDT that can be used unconditionally for parameter estimation. Response functions differing considerably in shape can result in virtually identical tissue curves. This non-uniqueness makes a strong argument not to use algebraic but rather analytical deconvolution to reduce the class of solutions to representatives that are in accordance with a-priori knowledge. To avoid misinterpretations and systematic errors, users must be aware of the pitfalls inherent to the different concepts. Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  3. A touch screen based Stop Signal Response Task in rhesus monkeys for studying impulsivity associated with chronic cocaine self-administration.

    PubMed

    Liu, Shijing; Heitz, Richard P; Bradberry, Charles W

    2009-02-15

    Among a range of cognitive deficits, human cocaine addicts display increased impulsivity and decreased performance monitoring. In order to establish an animal model that can be used to study the underlying neurobiology of these deficits associated with addiction, we have developed a touch screen based Stop Signal Response Task for rhesus monkeys. This task is essentially identical to the clinically used Stop Signal Task employed for diagnostic and research purposes. In this task, impulsivity is reflected in the amount of time needed to inhibit a response after it has been initiated, the Stop Signal Response Time (SSRT). Performance monitoring is reflected by the slowing of response times following Stop trials (Post-Stop Slowing, PSS). Herein we report on the task structure, the staged methods for training animals to perform the task, and a comparison of performance values for control and cocaine experienced animals. Relative to controls, monkeys that had self-administered cocaine, followed by 18 months abstinence, displayed increased impulsivity (increased SSRT values), and decreased performance monitoring (decreased PSS values). Our results are consistent with human data, and thereby establish an ideal animal model for studying the etiology and underlying neurobiology of cocaine-induced impulse control and performance monitoring deficits.

  4. Low Pretreatment Acoustic Radiation Force Impulse Imaging (ARFI) Values Predict Sustained Virological Response in Antiviral Hepatitis C Virus (HCV) Therapy

    PubMed Central

    Zopf, Steffen; Rösch, Lara; Konturek, Peter C.; Goertz, Ruediger S.; Neurath, Markus F.; Strobel, Deike

    2016-01-01

    Background Non-invasive procedures such as acoustic radiation force impulse imaging (ARFI) shear-wave elastography are currently used for the assessment of liver fibrosis. In the course of chronic hepatitis C, significant liver fibrosis or cirrhosis develops in approximately 25% of patients, which is a negative predictor of antiviral treatment response. Cirrhosis can be prevented by successful virus elimination. In this prospective study, a pretreatment ARFI cutoff value of 1.5 m/s was evaluated in relation to sustained virological response to anti-HCV therapy. Material/Methods In 23 patients with chronic hepatitis C, liver stiffness was examined with ARFI at defined times before and under antiviral triple therapy (peginterferon, ribavirin in combination with a first-generation protease inhibitor, and telaprevir or boceprevir). Patients were stratified into 2 groups based on pretreatment ARFI values (<1.5 m/s and ≥1.5 m/s) for the assessment of virological response. Results The liver stiffness at baseline for all patients was 1.57±0.79 m/s (ARFI median ± standard deviation; margin: 0.81 m/s to 3.45 m/s). At week 4 of triple therapy, patients with low pretreatment ARFI values had higher rates of HCV-RNA negativity (69% vs. 43%), reflecting an early rapid virological response (eRVR). Sustained virological response (SVR) was found in 75% (12/16) of patients with an ARFI value <1.5 m/s and only 57% (4/7) of patients with ARFI value ≥1.5 m/s. Conclusions Patients with chronic hepatitis C and pretreatment ARFI <1.5 m/s showed earlier virus elimination and better response to treatment. PMID:27690214

  5. Preventing (impulsive) errors: Electrophysiological evidence for online inhibitory control over incorrect responses

    PubMed Central

    van den Wildenberg, Wery P. M.; Spieser, Laure; Ridderinkhof, K. Richard

    2016-01-01

    Abstract In a rich environment, with multiple action affordances, selective action inhibition is critical in preventing the execution of inappropriate responses. Here, we studied the origin and the dynamics of incorrect response inhibition and how it can be modulated by task demands. We used EEG in a conflict task where the probability of compatible and incompatible trials was varied. This allowed us to modulate the strength of the prepotent response, and hence to increase the risk of errors, while keeping the probability of the two responses equal. The correct response activation and execution was not affected by compatibility or by probability. In contrast, incorrect response inhibition in the primary motor cortex ipsilateral to the correct response was more pronounced on incompatible trials, especially in the condition where most of the trials were compatible, indicating a modulation of inhibitory strength within the course of the action. Two prefrontal activities, one medial and one lateral, were also observed before the response, and their potential links with the observed inhibitory pattern observed are discussed. PMID:27005956

  6. Cultural Consensus Theory: Aggregating Continuous Responses in a Finite Interval

    NASA Astrophysics Data System (ADS)

    Batchelder, William H.; Strashny, Alex; Romney, A. Kimball

    Cultural consensus theory (CCT) consists of cognitive models for aggregating responses of "informants" to test items about some domain of their shared cultural knowledge. This paper develops a CCT model for items requiring bounded numerical responses, e.g. probability estimates, confidence judgments, or similarity judgments. The model assumes that each item generates a latent random representation in each informant, with mean equal to the consensus answer and variance depending jointly on the informant and the location of the consensus answer. The manifest responses may reflect biases of the informants. Markov Chain Monte Carlo (MCMC) methods were used to estimate the model, and simulation studies validated the approach. The model was applied to an existing cross-cultural dataset involving native Japanese and English speakers judging the similarity of emotion terms. The results sharpened earlier studies that showed that both cultures appear to have very similar cognitive representations of emotion terms.

  7. Narrow Band Susceptibility Prediction from the Impulse Scatter Response of a Pseudomissile (Case I),

    DTIC Science & Technology

    1998-04-01

    State University. [2] Comparison of Results Since the prediction of the coupled signal is pertinent to this discussion, the narrow band coupling...1300 to 1500 MHz susceptibility response band. It is not clear based on this method how the probe response was perturbed by the local boundary...scaling property for linear systems dependent upon the local region’s resonant modes, it is appropriate to consider developing better analysis tools and

  8. Adolescent Impulsivity: Findings from a Community Sample

    ERIC Educational Resources Information Center

    d'Acremont, Mathieu; Van der Linden, Martial

    2005-01-01

    Impulsivity is central to several psychopathological states in adolescence. However, there is little consensus concerning the definition of impulsivity and its core dimensions. In response to this lack of consensus, Whiteside and Lynam (2001, "Pers. Individ. Differ." 30, 669-689) have developed the UPPS Impulsive Behavior Scale, which is able to…

  9. Adolescent Impulsivity: Findings from a Community Sample

    ERIC Educational Resources Information Center

    d'Acremont, Mathieu; Van der Linden, Martial

    2005-01-01

    Impulsivity is central to several psychopathological states in adolescence. However, there is little consensus concerning the definition of impulsivity and its core dimensions. In response to this lack of consensus, Whiteside and Lynam (2001, "Pers. Individ. Differ." 30, 669-689) have developed the UPPS Impulsive Behavior Scale, which is able to…

  10. Wave spectral response to sudden changes in wind direction in finite depth waters

    DTIC Science & Technology

    2015-11-14

    Virtual Special Issue Ocean Surface Waves Wave spectral response to sudden changes in wind direction in finite-depth waters Saima Aijaz a , ∗, W...Revised 22 October 2015 Accepted 2 November 2015 Available online 14 November 2015 Keywords: Wave modelling Wind shift Wave response...Whitecapping dissipation Swell dissipation Bottom friction a b s t r a c t The response of a wind -sea spectrum to sudden changes in wind directions of 180

  11. The Development of a 3D LADAR Simulator Based on a Fast Target Impulse Response Generation Approach

    NASA Astrophysics Data System (ADS)

    Al-Temeemy, Ali Adnan

    2017-09-01

    A new laser detection and ranging (LADAR) simulator has been developed, using MATLAB and its graphical user interface, to simulate direct detection time of flight LADAR systems, and to produce 3D simulated scanning images under a wide variety of conditions. This simulator models each stage from the laser source to data generation and can be considered as an efficient simulation tool to use when developing LADAR systems and their data processing algorithms. The novel approach proposed for this simulator is to generate the actual target impulse response. This approach is fast and able to deal with high scanning requirements without losing the fidelity that accompanies increments in speed. This leads to a more efficient LADAR simulator and opens up the possibility for simulating LADAR beam propagation more accurately by using a large number of laser footprint samples. The approach is to select only the parts of the target that lie in the laser beam angular field by mathematically deriving the required equations and calculating the target angular ranges. The performance of the new simulator has been evaluated under different scanning conditions, the results showing significant increments in processing speeds in comparison to conventional approaches, which are also used in this study as a point of comparison for the results. The results also show the simulator's ability to simulate phenomena related to the scanning process, for example, type of noise, scanning resolution and laser beam width.

  12. From the channel model of an InSb-based superresolution optical disc system to impulse response and resolution limits.

    PubMed

    Hepper, Dietmar

    2011-06-10

    The signal model of a superresolution optical channel can be an efficient tool for developing components of an associated high-density optical disc system. While the behavior of the laser diode, aperture, lens, and detector are properly described, a general mathematical model of the superresolution disc itself has not yet been available until recently. Different approaches have been made to describe the properties of a mask layer, mainly based on temperature- or power-dependent nonlinear effects. A complete signal-based or phenomenological optical channel model--from non-return-to-zero inverted input to disc readout signal--has recently been developed including the reflectivity of a superresolution disc with InSb used for the mask layer. In this contribution, the model is now extended and applied to a moving disc including a land-and-pit structure, and results are compared with data read from real superresolution discs. Both impulse response and resolution limits are derived and discussed. Thus the model provides a bridge from physical to readout signal properties, which count after all. The presented approach allows judging of the suitability of a mask layer material for storage density enhancement already based on static experiments, i.e., even before developing an associated disc drive.

  13. Mathematical Model of the Ear’s Response to Weapons Impulses

    DTIC Science & Technology

    2015-04-01

    NOTICES Disclaimers The findings in this report are not to be construed as an official Department of the Army position unless so designated ... sounds (over 120 dB) that starts with pressure in the free- field, accounts for the effects of the head, external ear, middle ear, and cochlea, and...the ear’s response to intense sounds (over 120 dB) that starts with pressure in the free-field, accounts for the effects of the head, external ear

  14. Directional impulse response of a large cavity inside a sonic crystal.

    PubMed

    Spiousas, Ignacio; Eguia, Manuel C

    2012-10-01

    Both temporal and directional responses of a cavity inside a two-dimensional sonic crystal are investigated. The size of the cavity is large compared to the lattice parameter and the wavelength for the frequency range of interest. Hence, a hybrid method to compute the response is proposed, combining multiscattering theory for the calculation of the reflective properties of the sonic crystal with a modified ray-tracing algorithm for the sound propagation within the cavity. The response of this enclosure displays resonances for certain frequency bands that depend on the geometry of the lattice and the cavity. When a full band gap exists in the sonic crystal, rays cannot propagate through the medium and total reflection occurs for all incidence angles, leading to strong resonances with an isotropic intensity field inside the cavity. When only some propagation directions are forbidden, total reflection occurs for certain ranges of incidence angles, and resonances can also be elicited but with a highly anisotropic intensity field. The spectrum of resonances of the cavity is strongly affected by changes in the lattice geometry, suggesting that they can be tailored to some extent, a feature that can lead to potential applications in architectural acoustics.

  15. Experimental measurement of tympanic membrane response for finite element model validation of a human middle ear.

    PubMed

    Ahn, Tae-Soo; Baek, Moo-Jin; Lee, Dooho

    2013-01-01

    The middle ear consists of a tympanic membrane, ligaments, tendons, and three ossicles. An important function of the tympanic membrane is to deliver exterior sound stimulus to the ossicles and inner ear. In this study, the responses of the tympanic membrane in a human ear were measured and compared with those of a finite element model of the middle ear. A laser Doppler vibrometer (LDV) was used to measure the dynamic responses of the tympanic membrane, which had the measurement point on the cone of light of the tympanic membrane. The measured subjects were five Korean male adults and a cadaver. The tympanic membranes were stimulated using pure-tone sine waves at 18 center frequencies of one-third octave band over a frequency range of 200 Hz ~10 kHz with 60 and 80 dB sound pressure levels. The measured responses were converted into the umbo displacement transfer function (UDTF) with a linearity assumption. The measured UDTFs were compared with the calculated UDTFs using a finite element model for the Korean human middle ear. The finite element model of the middle ear consists of three ossicles, a tympanic membrane, ligaments, and tendons. In the finite element model, the umbo displacements were calculated under a unit sound pressure on the tympanic membrane. The UDTF of the finite element model exhibited good agreement with that of the experimental one in low frequency range, whereas in higher frequency band, the two response functions deviated from each other, which demonstrates that the finite element model should be updated with more accurate material properties and/or a frequency dependent material model.

  16. Impulsive control for hypervelocity missiles

    NASA Astrophysics Data System (ADS)

    Magness, R. W.

    1981-05-01

    A hypervelocity agile interceptor/quickshot is being developed for defense of ballistic missile launch sites. A guidance and control system is required to achieve the missile guidance accuracy necessary for direct target impact. Attitude control systems evaluated for the agile interceptor included aerodynamic controls, thrust vector controls and impulsive motor controls. The solid squib impulsive control motion was selected because of high response rate, low weight and low volume. A baseline motor configuration was designed and a solid propellant squib was developed for use in the control system. Ballistic pendulum and bench tests were conducted with a test impulsive control motor to measure nominal performance, establish the standard deviation of performance, and define requirements to prevent sympathetic ignition. A dynamic control wind tunnel test was also conducted to determine the impulse augmentation due to the impulsive motor jet interaction with the missile boundary layer. The degree and direction of augmentation was measured for variations in Mach number and angle of attack.

  17. Stimulus-Response Theory of Finite Automata, Technical Report No. 133.

    ERIC Educational Resources Information Center

    Suppes, Patrick

    The central aim of this paper and its projected successors is to prove in detail that stimulus-response theory, or at least a mathematically precise version, can give an account of the learning of many phrase-structure grammars. Section 2 is concerned with standard notions of finite and probabilistic automata. An automaton is defined as a device…

  18. The response of monoenergetic gamma rays in finite media are investigated

    NASA Technical Reports Server (NTRS)

    Snow, W. J.

    1969-01-01

    In a study of the transport of radiation in matter, the response parameters of monoenergetic gamma rays incident on various materials with finite geometries were calculated on a CDC 3600 computer. The report includes results for gamma rays normal to cyclindrical germanium and silicon detectors.

  19. Negative urgency and ventromedial prefrontal cortex responses to alcohol cues: fMRI evidence of emotion-based impulsivity

    PubMed Central

    Cyders, Melissa A.; Dzemidzic, Mario; Eiler, William J.; Coskunpinar, Ayca; Karyadi, Kenny; Kareken, David A.

    2013-01-01

    Background Recent research has highlighted the role of emotion-based impulsivity (negative and positive urgency personality traits) for alcohol use and abuse, but has yet to examine how these personality traits interact with the brain’s motivational systems. Using functional magnetic resonance imaging (fMRI), we tested if urgency traits and mood induction affected medial prefrontal responses to alcohol odors (AcO). Methods Twenty seven social drinkers (mean age = 25.2, 14 males) had six fMRI scans while viewing negative, neutral, or positive mood images (3 mood conditions) during intermittent exposure to AcO and appetitive control (AppCo) aromas. Results Voxel-wise analyses (p < 0.001) confirmed [AcO > AppCo] activation throughout medial (mPFC) and ventromedial prefrontal regions (vmPFC). Extracted from a priori mPFC and vmPFC regions, and analyzed in Odor (AcO, AppCo) × Mood factorial models, AcO activation was greater than AppCo in left vmPFC (p < 0.001), left mPFC (p = 0.002), and right vmPFC (p = 0.01) regions. Mood did not interact significantly with activation but the covariate of trait negative urgency accounted for significant variance in left vmPFC (p = 0.01) and right vmPFC (p = 0.01) [AcO > AppCo] activation. Negative urgency also mediated the relationship between vmPFC activation and both (1) subjective craving and (2) problematic drinking. Conclusion The trait of negative urgency is associated with neural responses to alcohol cues in the vmPFC, a region involved in reward value and emotion-guided decision-making. This suggests that negative urgency might alter subjective craving and brain regions involved in coding reward value. PMID:24164291

  20. An automatic damage detection algorithm based on the Short Time Impulse Response Function

    NASA Astrophysics Data System (ADS)

    Auletta, Gianluca; Carlo Ponzo, Felice; Ditommaso, Rocco; Iacovino, Chiara

    2016-04-01

    Structural Health Monitoring together with all the dynamic identification techniques and damage detection techniques are increasing in popularity in both scientific and civil community in last years. The basic idea arises from the observation that spectral properties, described in terms of the so-called modal parameters (eigenfrequencies, mode shapes, and modal damping), are functions of the physical properties of the structure (mass, energy dissipation mechanisms and stiffness). Damage detection techniques traditionally consist in visual inspection and/or non-destructive testing. A different approach consists in vibration based methods detecting changes of feature related to damage. Structural damage exhibits its main effects in terms of stiffness and damping variation. Damage detection approach based on dynamic monitoring of structural properties over time has received a considerable attention in recent scientific literature. We focused the attention on the structural damage localization and detection after an earthquake, from the evaluation of the mode curvature difference. The methodology is based on the acquisition of the structural dynamic response through a three-directional accelerometer installed on the top floor of the structure. It is able to assess the presence of any damage on the structure providing also information about the related position and severity of the damage. The procedure is based on a Band-Variable Filter, (Ditommaso et al., 2012), used to extract the dynamic characteristics of systems that evolve over time by acting simultaneously in both time and frequency domain. In this paper using a combined approach based on the Fourier Transform and on the seismic interferometric analysis, an useful tool for the automatic fundamental frequency evaluation of nonlinear structures has been proposed. Moreover, using this kind of approach it is possible to improve some of the existing methods for the automatic damage detection providing stable results

  1. A Zero Extraction and Separation Technique for Surface Acoustic Wave and Digital Signal Processing FIR (Finite Impulse Response) Filter Implementation.

    DTIC Science & Technology

    1986-01-01

    situations and is discussed briefly. Factoring Methods Several unique approaches to zero extraction exist. The first was by none other than Sir Issac ... Newton (1642-1727). Since that 34 time, other algorithms by Bairstow, Lin, Muller and Birge-Vieta have arrived (Ralston and Wilf 1960). These

  2. Finite element simulation of rate-dependent magneto-active polymer response

    NASA Astrophysics Data System (ADS)

    Haldar, K.; Kiefer, B.; Menzel, A.

    2016-10-01

    This contribution is concerned with the embedding of constitutive relations for magneto-active polymers (MAP) into finite element simulations. To this end, a recently suggested, calibrated, and validated material model for magneto-mechanically coupled and rate-dependent MAP response is briefly summarized in its continuous and algorithmic settings. Moreover, the strongly coupled field equations of finite deformation magneto-mechanics are reviewed. For the purpose of numerical simulation, a finite element model is then established based on the usual steps of weak form representation, discretization and consistent linearization. Two verifying inhomogeneous numerical examples are presented in which a classical ‘plate with a hole’ geometry is equipped with MAP properties and subjected to different types of time-varying mechanical and magnetic loading.

  3. Adaptive infinite impulse response system identification using modified-interior search algorithm with Lèvy flight.

    PubMed

    Kumar, Manjeet; Rawat, Tarun Kumar; Aggarwal, Apoorva

    2017-03-01

    In this paper, a new meta-heuristic optimization technique, called interior search algorithm (ISA) with Lèvy flight is proposed and applied to determine the optimal parameters of an unknown infinite impulse response (IIR) system for the system identification problem. ISA is based on aesthetics, which is commonly used in interior design and decoration processes. In ISA, composition phase and mirror phase are applied for addressing the nonlinear and multimodal system identification problems. System identification using modified-ISA (M-ISA) based method involves faster convergence, single parameter tuning and does not require derivative information because it uses a stochastic random search using the concepts of Lèvy flight. A proper tuning of control parameter has been performed in order to achieve a balance between intensification and diversification phases. In order to evaluate the performance of the proposed method, mean square error (MSE), computation time and percentage improvement are considered as the performance measure. To validate the performance of M-ISA based method, simulations has been carried out for three benchmarked IIR systems using same order and reduced order system. Genetic algorithm (GA), particle swarm optimization (PSO), cat swarm optimization (CSO), cuckoo search algorithm (CSA), differential evolution using wavelet mutation (DEWM), firefly algorithm (FFA), craziness based particle swarm optimization (CRPSO), harmony search (HS) algorithm, opposition based harmony search (OHS) algorithm, hybrid particle swarm optimization-gravitational search algorithm (HPSO-GSA) and ISA are also used to model the same examples and simulation results are compared. Obtained results confirm the efficiency of the proposed method.

  4. Response to Cognitive impulsivity and the behavioral addiction model of obsessive–compulsive disorder: Abramovitch and McKay (2016)

    PubMed Central

    Grassi, Giacomo; Figee, Martjin; Stratta, Paolo; Rossi, Alessandro; Pallanti, Stefano

    2016-01-01

    In our recently published article, we investigated the behavioral addiction model of obsessive–compulsive disorder (OCD), by assessing three core dimensions of addiction in patients with OCD healthy participants. Similar to the common findings in addiction, OCD patients demonstrated increased impulsivity, risky decision-making, and biased probabilistic reasoning compared to healthy controls. Thus, we concluded that these results support the conceptualization of OCD as a disorder of behavioral addiction. Here, we answer to Abramovitch and McKay (2016) commentary on our paper and we support our conclusions by explaining how cognitive impulsivity is also a typical feature of addiction and how our results on decision-making and probabilistic reasoning tasks reflect cognitive impulsivity facets that are consistently replicated in OCD and addiction. PMID:27677325

  5. The effect of loading time on flexible pavement dynamic response: a finite element analysis

    NASA Astrophysics Data System (ADS)

    Yin, Hao; Solaimanian, Mansour; Kumar, Tanmay; Stoffels, Shelley

    2007-12-01

    Dynamic response of asphalt concrete (AC) pavements under moving load is a key component for accurate prediction of flexible pavement performance. The time and temperature dependency of AC materials calls for utilizing advanced material characterization and mechanistic theories, such as viscoelasticity and stress/strain analysis. In layered elastic analysis, as implemented in the new Mechanistic-Empirical Pavement Design Guide (MEPDG), the time dependency is accounted for by calculating the loading times at different AC layer depths. In this study, the time effect on pavement response was evaluated by means of the concept of “pseudo temperature.” With the pavement temperature measured from instrumented thermocouples, the time and temperature dependency of AC materials was integrated into one single factor, termed “effective temperature.” Via this effective temperature, pavement responses under a transient load were predicted through finite element analysis. In the finite element model, viscoelastic behavior of AC materials was characterized through relaxation moduli, while the layers with unbound granular material were assumed to be in an elastic mode. The analysis was conducted for two different AC mixtures in a simplified flexible pavement structure at two different seasons. Finite element analysis results reveal that the loading time has a more pronounced impact on pavement response in the summer for both asphalt types. The results indicate that for reasonable prediction of dynamic response in flexible pavements, the effect of the depth-dependent loading time on pavement temperature should be considered.

  6. Impulsivity and comorbid traits: a multi-step approach for finding putative responsible microRNAs in the amygdala

    PubMed Central

    Pietrzykowski, Andrzej Z.; Spijker, Sabine

    2014-01-01

    Malfunction of synaptic plasticity in different brain regions, including the amygdala plays a role in impulse control deficits that are characteristics of several psychiatric disorders, such as ADHD, schizophrenia, depression and addiction. Previously, we discovered a locus for impulsivity (Impu1) containing the neuregulin 3 (Nrg3) gene, of which the level of expression determines levels of inhibitory control. MicroRNAs (miRNAs) are potent regulators of gene expression, and have recently emerged as important factors contributing to the development of psychiatric disorders. However, their role in impulsivity, as well as control of Nrg3 expression or malfunction of the amygdala, is not well established. Here, we used the GeneNetwork database of BXD mice to search for correlated traits with impulsivity using an overrepresentation analysis to filter for biologically meaningful traits. We determined that inhibitory control was significantly correlated with expression of miR-190b, -28a, -340, -219a, and -491 in the amygdala, and that the overrepresented correlated traits showed a specific pattern of coregulation with these miRNAs. A bioinformatics analysis identified that miR-190b, by targeting an Nrg3-related network, could affect synaptic plasticity in the amygdala, targeting bot impulsive and compulsive traits. Moreover, miR-28a, -340, -219a, and possibly -491 could act on synaptic function by determining the balance between neuronal outgrowth and differentiation. We propose that these miRNAs are attractive candidates of regulation of amygdala synaptic plasticity, possibly during development but also in maintaining the impulsive phenotype. These results can help us to better understand mechanisms of synaptic dysregulation in psychiatric disorders. PMID:25561905

  7. The Neurobiology of Impulsive Aggression

    PubMed Central

    2016-01-01

    Abstract This selective review provides a model of the neurobiology of impulsive aggression from a cognitive neuroscience perspective. It is argued that prototypical cases of impulsive aggression, those associated with anger, involve the recruitment of the acute threat response system structures; that is, the amygdala, hypothalamus, and periaqueductal gray. It is argued that whether the recruitment of these structures results in impulsive aggression or not reflects the functional roles of ventromedial frontal cortex and dorsomedial frontal and anterior insula cortex in response selection. It is also argued that impulsive aggression may occur because of impaired decision making. The aggression may not be accompanied by anger, but it will reflect disrupted evaluation of the rewards/benefits of the action. PMID:26465707

  8. The Neurobiology of Impulsive Aggression.

    PubMed

    Blair, Robert J R

    2016-02-01

    This selective review provides a model of the neurobiology of impulsive aggression from a cognitive neuroscience perspective. It is argued that prototypical cases of impulsive aggression, those associated with anger, involve the recruitment of the acute threat response system structures; that is, the amygdala, hypothalamus, and periaqueductal gray. It is argued that whether the recruitment of these structures results in impulsive aggression or not reflects the functional roles of ventromedial frontal cortex and dorsomedial frontal and anterior insula cortex in response selection. It is also argued that impulsive aggression may occur because of impaired decision making. The aggression may not be accompanied by anger, but it will reflect disrupted evaluation of the rewards/benefits of the action.

  9. Concussion in professional football: brain responses by finite element analysis: part 9.

    PubMed

    Viano, David C; Casson, Ira R; Pellman, Elliot J; Zhang, Liying; King, Albert I; Yang, King H

    2005-11-01

    Brain responses from concussive impacts in National Football League football games were simulated by finite element analysis using a detailed anatomic model of the brain and head accelerations from laboratory reconstructions of game impacts. This study compares brain responses with physician determined signs and symptoms of concussion to investigate tissue-level injury mechanisms. The Wayne State University Head Injury Model (Version 2001) was used because it has fine anatomic detail of the cranium and brain with more than 300,000 elements. It has 15 different material properties for brain and surrounding tissues. The model includes viscoelastic gray and white brain matter, membranes, ventricles, cranium and facial bones, soft tissues, and slip interface conditions between the brain and dura. The cranium of the finite element model was loaded by translational and rotational accelerations measured in Hybrid III dummies from 28 laboratory reconstructions of NFL impacts involving 22 concussions. Brain responses were determined using a nonlinear, finite element code to simulate the large deformation response of white and gray matter. Strain responses occurring early (during impact) and mid-late (after impact) were compared with the signs and symptoms of concussion. Strain concentration "hot spots" migrate through the brain with time. In 9 of 22 concussions, the early strain "hot spots" occur in the temporal lobe adjacent to the impact and migrate to the far temporal lobe after head acceleration. In all cases, the largest strains occur later in the fornix, midbrain, and corpus callosum. They significantly correlated with removal from play, cognitive and memory problems, and loss of consciousness. Dizziness correlated with early strain in the orbital-frontal cortex and temporal lobe. The strain migration helps explain coup-contrecoup injuries. Finite element modeling showed the largest brain deformations occurred after the primary head acceleration. Midbrain strain

  10. Time Course Analysis of Motor Excitability in a Response Inhibition Task According to the Level of Hyperactivity and Impulsivity in Children with ADHD

    PubMed Central

    Hoegl, Thomas; Heinrich, Hartmut; Barth, Wolfgang; Lösel, Friedrich; Moll, Gunther H.; Kratz, Oliver

    2012-01-01

    Short interval intracortical inhibition (SICI) of motor cortex, measured by transcranial magnetic stimulation (TMS) in a passive (resting) condition, has been suggested as a neurophysiological marker of hyperactivity in attention-deficit/hyperactivity disorder (ADHD). The aim of this study was to determine motor excitability in a go/nogo task at stages of response preparation, activation and suppression in children with ADHD, depending on the level of hyperactivity and impulsivity. Motor evoked potentials were recorded in 29 typically developing children and 43 children with ADHD (subdivided in two groups with higher and lower levels of hyperactivity/impulsivity; H/I-high and H/I-low). In the H/I-high group, SICI was markedly reduced in the resting condition and during response preparation. Though these children were able to increase SICI when inhibiting a response, SICI was still reduced compared to typically developing children. Interestingly, SICI at rest and during response activation were comparable, which may be associated with their hypermotoric behaviour. In the H/I-low group, response activation was accompanied by a pronounced decrease of SICI, indicating reduced motor control in the context of a fast motor response. In summary, different excitability patterns were obtained for the three groups allowing a better understanding of dysfunctional response activation and inhibition processes within the motor cortex in children with ADHD. PMID:23049936

  11. Chaotic (as a one-dimensional map) laser cavity: influence of finite response time

    SciTech Connect

    Hnilo, A.A.; de Sousa Vieira, M.C.

    1988-05-01

    A laser cavity whose output is a train of pulses of intensities given by a one-dimensional recurrence map with a sharp extremum was presented in a previous paper. In this paper we study the road to chaos that is obtained when finite response times are taken into account. The scenario changes smoothly from the sharp map's scenario (undefined universality class) to the Fiegenbaum's scenario (logistic-map universality class) as the response time increases. We also discuss the feasibility of using the device as a new method for measuring short response times.

  12. Simulation of Electromagnetic Wave Logging Response in Deviated Wells Based on Vector Finite Element Method

    NASA Astrophysics Data System (ADS)

    Lv, Wei-Guo; Chu, Zhao-Tan; Zhao, Xiao-Qing; Fan, Yu-Xiu; Song, Ruo-Long; Han, Wei

    2009-01-01

    The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles.

  13. Estimating the pi* goodness of fit index for finite mixtures of item response models.

    PubMed

    Revuelta, Javier

    2008-05-01

    Testing the fit of finite mixture models is a difficult task, since asymptotic results on the distribution of likelihood ratio statistics do not hold; for this reason, alternative statistics are needed. This paper applies the pi* goodness of fit statistic to finite mixture item response models. The pi* statistic assumes that the population is composed of two subpopulations - those that follow a parametric model and a residual group outside the model; pi* is defined as the proportion of population in the residual group. The population was divided into two or more groups, or classes. Several groups followed an item response model and there was also a residual group. The paper presents maximum likelihood algorithms for estimating item parameters, the probabilities of the groups and pi*. The paper also includes a simulation study on goodness of recovery for the two- and three-parameter logistic models and an example with real data from a multiple choice test.

  14. Finite-element simulation of transient heat response in ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Ando, Ei'ichi; Kagawa, Yukio

    1992-05-01

    The application of the finite-element method to a transient heat response problem in electrostrictive ultrasonic transducers during their pulsed operation is described. The temperature and thermal stress distribution are of practical importance for the design of the ultrasonic transducers when they are operated at intense levels. Mechanical vibratory loss is responsible for heat in the elastic parts while dielectric loss in the ferroelectric parts. A finite-element computer model is proposed for the temperature change evaluation in the transducers with time. Natural and forced cooling convection and heat radiation from the transducers' boundaries are included. Simulation is made for Langevin-type transducer models, for which comparison is made with experimental data.

  15. Implementation of structural response sensitivity calculations in a large-scale finite-element analysis system

    NASA Technical Reports Server (NTRS)

    Giles, G. L.; Rogers, J. L., Jr.

    1982-01-01

    The implementation includes a generalized method for specifying element cross-sectional dimensions as design variables that can be used in analytically calculating derivatives of output quantities from static stress, vibration, and buckling analyses for both membrane and bending elements. Limited sample results for static displacements and stresses are presented to indicate the advantages of analytically calclating response derivatives compared to finite difference methods. Continuing developments to implement these procedures into an enhanced version of the system are also discussed.

  16. A nonstandard finite difference scheme for a basic model of cellular immune response to viral infection

    NASA Astrophysics Data System (ADS)

    Korpusik, Adam

    2017-02-01

    We present a nonstandard finite difference scheme for a basic model of cellular immune response to viral infection. The main advantage of this approach is that it preserves the essential qualitative features of the original continuous model (non-negativity and boundedness of the solution, equilibria and their stability conditions), while being easy to implement. All of the qualitative features are preserved independently of the chosen step-size. Numerical simulations of our approach and comparison with other conventional simulation methods are presented.

  17. Auditory and behavioral responses of bottlenose dolphins (Tursiops truncatus) and a beluga whale (Delphinapterus leucas) to impulsive sounds resembling distant signatures of underwater explosions.

    PubMed

    Finneran, J J; Schlundt, C E; Carder, D A; Clark, J A; Young, J A; Gaspin, J B; Ridgway, S H

    2000-07-01

    A behavioral response paradigm was used to measure masked underwater hearing thresholds in two bottlenose dolphins and one beluga whale before and after exposure to impulsive underwater sounds with waveforms resembling distant signatures of underwater explosions. An array of piezoelectric transducers was used to generate impulsive sounds with waveforms approximating those predicted from 5 or 500 kg HBX-1 charges at ranges from 1.5 to 55.6 km. At the conclusion of the study, no temporary shifts in masked-hearing thresholds (MTTSs), defined as a 6-dB or larger increase in threshold over pre-exposure levels, had been observed at the highest impulse level generated (500 kg at 1.7 km, peak pressure 70 kPa); however, disruptions of the animals' trained behaviors began to occur at exposures corresponding to 5 kg at 9.3 km and 5 kg at 1.5 km for the dolphins and 500 kg at 1.9 km for the beluga whale. These data are the first direct information regarding the effects of distant underwater explosion signatures on the hearing abilities of odontocetes.

  18. Interindividual variability of arterial impulse response to intravenous injection of nonionic contrast agent (Iohexol) in DCE-CT study

    SciTech Connect

    Kim, S. M.; Haider, M. A.; Milosevic, M.; Yeung, I. W. T.

    2009-10-15

    Purpose: It is known that the arterial input function (AIF) in dynamic contrast-enhanced (DCE)-CT differs among patients even for fixed contrast injection protocols. Therefore, a study has been performed to investigate the interindividual variability of the AIF with respect to patient factors (such as weight, height, and age). In addition, it has been demonstrated that the relations from the interindividual variability investigation can be further used for the estimation of AIF for a patient without the requirement of measurement. Methods: DCE-CT data for a cohort of 34 patients with cervical carcinoma were used for the investigation of interindividual variability of the AIF. To dissociate the effect of different durations of contrast injection, the arterial impulse response (AIR) to intravenous contrast injection was calculated and examined for its correlations with these patient factors. An empirical functional form was proposed to model the AIR with temporal intensity of a first pass of contrast agent followed by recirculation and quasiequilibrium state of contrast concentration. Specific features (onset time, peak time, and amplitudes) of the AIR were tested for correlations with the patient factors. Linear regression was applied to cases that show significant strong correlation between the AIR amplitudes and patient factors. The results were then used to predict the AIR for any given patient based on the patient factors. It was shown that using the predicted AIR, the AIF of the patient can be estimated without the requirement of measurement given the injection protocol is known. The method of AIF estimation was tested in DCE-CT data from another group of 14 patients. The efficacy of individually estimated AIF on pharmacokinetic analysis was assessed against the use of measured AIF and population-averaged AIF as the latter is another possible strategy for AIF generation if AIF measurement is not available. Results: It was found that the amplitudes of AIR

  19. [Impulse control in addiction: a translational perspective].

    PubMed

    Schmaal, L; Broos, N; Joos, L; Pattij, T; Goudriaan, A E

    2013-01-01

    Impulsivity is a hallmark of addiction and predicts treatment response and relapse. Impulsivity is, however, a complex construct. Translational cross-species research is needed to give us greater insight into the neurobiology and the role of impulsivity in addiction and to help with the development of new treatment strategies for improving patients' impulse control. To review recent evidence concerning the concept of impulsivity and the role of impulsivity in addiction. The concept and neurobiology of impulsivity are reviewed from a translational perspective. The role of impulsivity in addiction and implications for treatment are discussed. Our recent translational cross-species study indicates that impulsivity is made up of several, separate independent features with partly distinct underlying neurobiological substrates. There are also indications that these features make a unique and independent contribution to separate stages of the addiction cycle. In addition, the improvement of impulse control is a promising new target area for treatments that could lead to better results. However, those involved in developing new treatment strategies will have to take into account the complexity and multidimensional character of impulsivity.

  20. Callous-unemotional, impulsive-irresponsible, and grandiose-manipulative traits: Distinct associations with heart rate, skin conductance, and startle responses to violent and erotic scenes.

    PubMed

    Fanti, Kostas A; Kyranides, Melina N; Georgiou, Giorgos; Petridou, Maria; Colins, Olivier F; Tuvblad, Catherine; Andershed, Henrik

    2017-05-01

    The present study aimed to examine whether callous-unemotional, grandiose-manipulative, and impulsive-irresponsible dimensions of psychopathy are differentially related to various affective and physiological measures, assessed at baseline and in response to violent and erotic movie scenes. Data were collected from young adults (N = 101) at differential risk for psychopathic traits. Findings from regression analyses revealed a unique predictive contribution of grandiose-manipulative traits in particular to higher ratings of positive valence for violent scenes. Callous-unemotional traits were uniquely associated with lower levels of sympathy toward victims and lower ratings of fear and sadness during violent scenes. All three psychopathy dimensions and the total psychopathy scale showed negative zero-order correlations with heart rate at baseline, but regression analyses revealed that only grandiose manipulation was uniquely predictive of lower baseline heart rate. Grandiose manipulation was also significantly associated with lower baseline skin conductance. Regarding autonomic activity, findings resulted in a unique negative association between grandiose manipulation and heart rate activity in response to violent scenes. In contrast, the impulsive-irresponsible dimension was positively related with heart rate activity to violent scenes. Finally, findings revealed that only callous-unemotional traits were negatively associated with startle potentiation in response to violent scenes. No associations during erotic scenes were identified. These findings point to unique associations between the three assessed dimensions of psychopathy with physiological measures, indicating that grandiose manipulation is associated with hypoarousal, impulsive irresponsibility with hyperarousal, and callous-unemotional traits with low emotional and fear responses to violent scenes. © 2017 Society for Psychophysiological Research.

  1. Dynamic Response of a Planetary Gear System Using a Finite Element/Contact Mechanics Model

    NASA Technical Reports Server (NTRS)

    Parker, Robert G.; Agashe, Vinayak; Vijayakar, Sandeep M.

    2000-01-01

    The dynamic response of a helicopter planetary gear system is examined over a wide range of operating speeds and torques. The analysis tool is a unique, semianalytical finite element formulation that admits precise representation of the tooth geometry and contact forces that are crucial in gear dynamics. Importantly, no a priori specification of static transmission error excitation or mesh frequency variation is required; the dynamic contact forces are evaluated internally at each time step. The calculated response shows classical resonances when a harmonic of mesh frequency coincides with a natural frequency. However, peculiar behavior occurs where resonances expected to be excited at a given speed are absent. This absence of particular modes is explained by analytical relationships that depend on the planetary configuration and mesh frequency harmonic. The torque sensitivity of the dynamic response is examined and compared to static analyses. Rotation mode response is shown to be more sensitive to input torque than translational mode response.

  2. Dynamic Response of a Planetary Gear System Using a Finite Element/Contact Mechanics Model

    NASA Technical Reports Server (NTRS)

    Parker, Robert G.; Agashe, Vinayak; Vijayakar, Sandeep M.

    2000-01-01

    The dynamic response of a helicopter planetary gear system is examined over a wide range of operating speeds and torques. The analysis tool is a unique, semianalytical finite element formulation that admits precise representation of the tooth geometry and contact forces that are crucial in gear dynamics. Importantly, no a priori specification of static transmission error excitation or mesh frequency variation is required; the dynamic contact forces are evaluated internally at each time step. The calculated response shows classical resonances when a harmonic of mesh frequency coincides with a natural frequency. However, peculiar behavior occurs where resonances expected to be excited at a given speed are absent. This absence of particular modes is explained by analytical relationships that depend on the planetary configuration and mesh frequency harmonic. The torque sensitivity of the dynamic response is examined and compared to static analyses. Rotation mode response is shown to be more sensitive to input torque than translational mode response.

  3. Simulation of the ultrasonic array response from real branched cracks using an efficient finite element method

    NASA Astrophysics Data System (ADS)

    Felice, Maria V.; Velichko, Alexander; Wilcox, Paul D.; Barden, Tim J.; Dunhill, Tony K.

    2014-02-01

    A hybrid model to simulate the ultrasonic array response from stress corrosion cracks is presented. These cracks are branched and difficult to detect so the model is required to enable optimization of an array design. An efficient frequency-domain finite element method is described and selected to simulate the ultrasonic scattering. Experimental validation results are presented, followed by an example of the simulated ultrasonic array response from a real stress corrosion crack whose geometry is obtained from an X-ray Computed Tomography image. A simulation-assisted array design methodology, which includes the model and use of real crack geometries, is proposed.

  4. Simulation of the ultrasonic array response from real branched cracks using an efficient finite element method

    SciTech Connect

    Felice, Maria V.; Velichko, Alexander; Wilcox, Paul D.; Barden, Tim J.; Dunhill, Tony K.

    2014-02-18

    A hybrid model to simulate the ultrasonic array response from stress corrosion cracks is presented. These cracks are branched and difficult to detect so the model is required to enable optimization of an array design. An efficient frequency-domain finite element method is described and selected to simulate the ultrasonic scattering. Experimental validation results are presented, followed by an example of the simulated ultrasonic array response from a real stress corrosion crack whose geometry is obtained from an X-ray Computed Tomography image. A simulation-assisted array design methodology, which includes the model and use of real crack geometries, is proposed.

  5. A double expansion method for the frequency response of finite-length beams with periodic parameters

    NASA Astrophysics Data System (ADS)

    Ying, Z. G.; Ni, Y. Q.

    2017-03-01

    A double expansion method for the frequency response of finite-length beams with periodic distribution parameters is proposed. The vibration response of the beam with spatial periodic parameters under harmonic excitations is studied. The frequency response of the periodic beam is the function of parametric period and then can be expressed by the series with the product of periodic and non-periodic functions. The procedure of the double expansion method includes the following two main steps: first, the frequency response function and periodic parameters are expanded by using identical periodic functions based on the extension of the Floquet-Bloch theorem, and the period-parametric differential equation for the frequency response is converted into a series of linear differential equations with constant coefficients; second, the solutions to the linear differential equations are expanded by using modal functions which satisfy the boundary conditions, and the linear differential equations are converted into algebraic equations according to the Galerkin method. The expansion coefficients are obtained by solving the algebraic equations and then the frequency response function is finally determined. The proposed double expansion method can uncouple the effects of the periodic expansion and modal expansion so that the expansion terms are determined respectively. The modal number considered in the second expansion can be reduced remarkably in comparison with the direct expansion method. The proposed double expansion method can be extended and applied to the other structures with periodic distribution parameters for dynamics analysis. Numerical results on the frequency response of the finite-length periodic beam with various parametric wave numbers and wave amplitude ratios are given to illustrate the effective application of the proposed method and the new frequency response characteristics, including the parameter-excited modal resonance, doubling-peak frequency response

  6. Linear response, fluctuation-dissipation, and finite-system-size effects in superdiffusion

    NASA Astrophysics Data System (ADS)

    Godec, Aljaž; Metzler, Ralf

    2013-07-01

    Lévy walks (LWs) are a popular stochastic tool to model anomalous diffusion and have recently been used to describe a variety of phenomena. We study the linear response behavior of this generic model of superdiffusive LWs in finite systems to an external force field under both stationary and nonstationary conditions. These finite-size LWs are based on power-law waiting time distributions with a finite-time regularization at τc, such that the physical requirements are met to apply linear response theory and derive the power spectrum with the correct short frequency limit, without the introduction of artificial cutoffs. We obtain the generalized Einstein relation for both ensemble and time averages over the entire process time and determine the turnover to normal Brownian motion when the full system is explored. In particular, we obtain an exact expression for the long time diffusion constant as a function of the scaling exponent of the waiting time density and the characteristic time scale τc.

  7. Implementation of an ANCF beam finite element for dynamic response optimization of elastic manipulators

    NASA Astrophysics Data System (ADS)

    Vohar, B.; Kegl, M.; Ren, Z.

    2008-12-01

    Theoretical and practical aspects of an absolute nodal coordinate formulation (ANCF) beam finite element implementation are considered in the context of dynamic transient response optimization of elastic manipulators. The proposed implementation is based on the introduction of new nodal degrees of freedom, which is achieved by an adequate nonlinear mapping between the original and new degrees of freedom. This approach preserves the mechanical properties of the ANCF beam, but converts it into a conventional finite element so that its nodal degrees of freedom are initially always equal to zero and never depend explicitly on the design variables. Consequently, the sensitivity analysis formulas can be derived in the usual manner, except that the introduced nonlinear mapping has to be taken into account. Moreover, the adjusted element can also be incorporated into general finite element analysis and optimization software in the conventional way. The introduced design variables are related to the cross-section of the beam, to the shape of the (possibly) skeletal structure of the manipulator and to the drive functions. The layered cross-section approach and the design element technique are utilized to parameterize the shape of individual elements and the whole structure. A family of implicit time integration methods is adopted for the response and sensitivity analysis. Based on this assumption, the corresponding sensitivity formulas are derived. Two numerical examples illustrate the performance of the proposed element implementation.

  8. Modified impulse method for the measurement of the frequency response of acoustic filters to weakly nonlinear transient excitations

    PubMed

    Payri; Desantes; Broatch

    2000-02-01

    In this paper, a modified impulse method is proposed which allows the determination of the influence of the excitation characteristics on acoustic filter performance. Issues related to nonlinear propagation, namely wave steepening and wave interactions, have been addressed in an approximate way, validated against one-dimensional unsteady nonlinear flow calculations. The results obtained for expansion chambers and extended duct resonators indicate that the amplitude threshold for the onset of nonlinear phenomena is related to the geometry considered.

  9. Three-Dimensional Finite Element Ablative Thermal Response and Thermostructural Design of Thermal Protection Systems

    NASA Technical Reports Server (NTRS)

    Dec, John A.; Braun, Robert D.

    2011-01-01

    A finite element ablation and thermal response program is presented for simulation of three-dimensional transient thermostructural analysis. The three-dimensional governing differential equations and finite element formulation are summarized. A novel probabilistic design methodology for thermal protection systems is presented. The design methodology is an eight step process beginning with a parameter sensitivity study and is followed by a deterministic analysis whereby an optimum design can determined. The design process concludes with a Monte Carlo simulation where the probabilities of exceeding design specifications are estimated. The design methodology is demonstrated by applying the methodology to the carbon phenolic compression pads of the Crew Exploration Vehicle. The maximum allowed values of bondline temperature and tensile stress are used as the design specifications in this study.

  10. Algorithms for accelerated automatic tuning of controllers with estimating the plant model from the plant response to an impulse disturbance and under self-oscillation conditions

    NASA Astrophysics Data System (ADS)

    Kuzishchin, V. F.; Tsarev, V. S.

    2014-04-01

    The problem of automatically tuning controllers in an operating control system is considered. Two methods for quickly determining the model parameters with calculating the plant model and the optimal controller tuning parameters in real time are proposed for the preliminary controller tuning stage: from the experimentally obtained plant response to an impulse disturbance and from two periods of self-oscillations excited in the mode of two-position control. The PID controller tunings are determined using the calculation algorithm of indirect frequency optimality indicators. The results from checking the serviceability of the proposed method in a system fitted with an industry-grade controller are presented.

  11. Effect of randomness on multi-frequency aeroelastic responses resolved by Unsteady Adaptive Stochastic Finite Elements

    SciTech Connect

    Witteveen, Jeroen A.S. Bijl, Hester

    2009-10-01

    The Unsteady Adaptive Stochastic Finite Elements (UASFE) method resolves the effect of randomness in numerical simulations of single-mode aeroelastic responses with a constant accuracy in time for a constant number of samples. In this paper, the UASFE framework is extended to multi-frequency responses and continuous structures by employing a wavelet decomposition pre-processing step to decompose the sampled multi-frequency signals into single-frequency components. The effect of the randomness on the multi-frequency response is then obtained by summing the results of the UASFE interpolation at constant phase for the different frequency components. Results for multi-frequency responses and continuous structures show a three orders of magnitude reduction of computational costs compared to crude Monte Carlo simulations in a harmonically forced oscillator, a flutter panel problem, and the three-dimensional transonic AGARD 445.6 wing aeroelastic benchmark subject to random fields and random parameters with various probability distributions.

  12. Evanescent pressure gradient response in the upper ocean to subinertial wind stress forcing of finite wavelength

    NASA Technical Reports Server (NTRS)

    White, Warren B.; Mcnally, Gerard

    1987-01-01

    A schematic model is used to interpret field observations related to the mixed layer response to wind stress at subinertial frequencies. It is shown that subinertial density and pressure fluctuations can arise locally from the finite wavelength character of the wind stress forcing as a fundamental part of the upper ocean transient, wind-driven response on time scales of 2-10 pendulum days. Evanescent vertical motions arise which alter the density field of the pycnocline, and hence the pressure field over the entire upper ocean. It is thus found that in the real ocean driven by wind stress, a transient geostrophic response exists which can be as large or larger than the transient Eckman response.

  13. Finite-element/progressive-lattice-sampling response surface methodology and application to benchmark probability quantification problems

    SciTech Connect

    Romero, V.J.; Bankston, S.D.

    1998-03-01

    Optimal response surface construction is being investigated as part of Sandia discretionary (LDRD) research into Analytic Nondeterministic Methods. The goal is to achieve an adequate representation of system behavior over the relevant parameter space of a problem with a minimum of computational and user effort. This is important in global optimization and in estimation of system probabilistic response, which are both made more viable by replacing large complex computer models with fast-running accurate and noiseless approximations. A Finite Element/Lattice Sampling (FE/LS) methodology for constructing progressively refined finite element response surfaces that reuse previous generations of samples is described here. Similar finite element implementations can be extended to N-dimensional problems and/or random fields and applied to other types of structured sampling paradigms, such as classical experimental design and Gauss, Lobatto, and Patterson sampling. Here the FE/LS model is applied in a ``decoupled`` Monte Carlo analysis of two sets of probability quantification test problems. The analytic test problems, spanning a large range of probabilities and very demanding failure region geometries, constitute a good testbed for comparing the performance of various nondeterministic analysis methods. In results here, FE/LS decoupled Monte Carlo analysis required orders of magnitude less computer time than direct Monte Carlo analysis, with no appreciable loss of accuracy. Thus, when arriving at probabilities or distributions by Monte Carlo, it appears to be more efficient to expend computer-model function evaluations on building a FE/LS response surface than to expend them in direct Monte Carlo sampling.

  14. Impaired Decisional Impulsivity in Pathological Videogamers

    PubMed Central

    Irvine, Michael A.; Worbe, Yulia; Bolton, Sorcha; Harrison, Neil A.; Bullmore, Edward T.; Voon, Valerie

    2013-01-01

    Background Pathological gaming is an emerging and poorly understood problem. Impulsivity is commonly impaired in disorders of behavioural and substance addiction, hence we sought to systematically investigate the different subtypes of decisional and motor impulsivity in a well-defined pathological gaming cohort. Methods Fifty-two pathological gaming subjects and age-, gender- and IQ-matched healthy volunteers were tested on decisional impulsivity (Information Sampling Task testing reflection impulsivity and delay discounting questionnaire testing impulsive choice), and motor impulsivity (Stop Signal Task testing motor response inhibition, and the premature responding task). We used stringent diagnostic criteria highlighting functional impairment. Results In the Information Sampling Task, pathological gaming participants sampled less evidence prior to making a decision and scored fewer points compared with healthy volunteers. Gaming severity was also negatively correlated with evidence gathered and positively correlated with sampling error and points acquired. In the delay discounting task, pathological gamers made more impulsive choices, preferring smaller immediate over larger delayed rewards. Pathological gamers made more premature responses related to comorbid nicotine use. Greater number of hours played also correlated with a Motivational Index. Greater frequency of role playing games was associated with impaired motor response inhibition and strategy games with faster Go reaction time. Conclusions We show that pathological gaming is associated with impaired decisional impulsivity with negative consequences in task performance. Decisional impulsivity may be a potential target in therapeutic management. PMID:24146789

  15. Lyapunov control of quantum systems with impulsive control fields.

    PubMed

    Yang, Wei; Sun, Jitao

    2013-01-01

    We investigate the Lyapunov control of finite-dimensional quantum systems with impulsive control fields, where the studied quantum systems are governed by the Schrödinger equation. By three different Lyapunov functions and the invariant principle of impulsive systems, we study the convergence of quantum systems with impulsive control fields and propose new results for the mentioned quantum systems in the form of sufficient conditions. Two numerical simulations are presented to illustrate the effectiveness of the proposed control method.

  16. Lyapunov Control of Quantum Systems with Impulsive Control Fields

    PubMed Central

    Yang, Wei; Sun, Jitao

    2013-01-01

    We investigate the Lyapunov control of finite-dimensional quantum systems with impulsive control fields, where the studied quantum systems are governed by the Schrödinger equation. By three different Lyapunov functions and the invariant principle of impulsive systems, we study the convergence of quantum systems with impulsive control fields and propose new results for the mentioned quantum systems in the form of sufficient conditions. Two numerical simulations are presented to illustrate the effectiveness of the proposed control method. PMID:23766712

  17. Low-field diamagnetic response of granular superconductors at finite temperatures

    SciTech Connect

    Auletta, C.; Raiconi, G. ); De Luca, R.; Pace, S. )

    1994-05-01

    We study the low-field diamagnetic response of granular superconductors at finite temperatures by means of a simple two-dimensional Josephson-junction array. The temperature effects are taken into account by inserting white-noise current sources in parallel to the resistively shunted junction circuit models of the Josephson junctions of the network. By this analysis we argue that a simplified one-dimensional description of the equivalent circuit, proposed by the authors for cylindrical granular superconductors, is still valid even in the presence of thermally activated flux jumps. A flux-creep picture for intergranular flux motion follows.

  18. Linear optical response of finite systems using multishift linear system solvers

    SciTech Connect

    Hübener, Hannes; Giustino, Feliciano

    2014-07-28

    We discuss the application of multishift linear system solvers to linear-response time-dependent density functional theory. Using this technique the complete frequency-dependent electronic density response of finite systems to an external perturbation can be calculated at the cost of a single solution of a linear system via conjugate gradients. We show that multishift time-dependent density functional theory yields excitation energies and oscillator strengths in perfect agreement with the standard diagonalization of the response matrix (Casida's method), while being computationally advantageous. We present test calculations for benzene, porphin, and chlorophyll molecules. We argue that multishift solvers may find broad applicability in the context of excited-state calculations within density-functional theory and beyond.

  19. Two-Dimensional Finite Element Ablative Thermal Response Analysis of an Arcjet Stagnation Test

    NASA Technical Reports Server (NTRS)

    Dec, John A.; Laub, Bernard; Braun, Robert D.

    2011-01-01

    The finite element ablation and thermal response (FEAtR, hence forth called FEAR) design and analysis program simulates the one, two, or three-dimensional ablation, internal heat conduction, thermal decomposition, and pyrolysis gas flow of thermal protection system materials. As part of a code validation study, two-dimensional axisymmetric results from FEAR are compared to thermal response data obtained from an arc-jet stagnation test in this paper. The results from FEAR are also compared to the two-dimensional axisymmetric computations from the two-dimensional implicit thermal response and ablation program under the same arcjet conditions. The ablating material being used in this arcjet test is phenolic impregnated carbon ablator with an LI-2200 insulator as backup material. The test is performed at the NASA, Ames Research Center Interaction Heating Facility. Spatially distributed computational fluid dynamics solutions for the flow field around the test article are used for the surface boundary conditions.

  20. Metabolic and transcriptomic response of the wine yeast Saccharomyces cerevisiae strain EC1118 after an oxygen impulse under carbon-sufficient, nitrogen-limited fermentative conditions.

    PubMed

    Orellana, Marcelo; Aceituno, Felipe F; Slater, Alex W; Almonacid, Leonardo I; Melo, Francisco; Agosin, Eduardo

    2014-05-01

    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to continuously changing environmental conditions, such as decreasing sugar and increasing ethanol concentrations. Oxygen, a critical nutrient to avoid stuck and sluggish fermentations, is only discretely available throughout the process after pump-over operation. In this work, we studied the physiological response of the wine yeast S. cerevisiae strain EC1118 to a sudden increase in dissolved oxygen, simulating pump-over operation. With this aim, an impulse of dissolved oxygen was added to carbon-sufficient, nitrogen-limited anaerobic continuous cultures. Results showed that genes related to mitochondrial respiration, ergosterol biosynthesis, and oxidative stress, among other metabolic pathways, were induced after the oxygen impulse. On the other hand, mannoprotein coding genes were repressed. The changes in the expression of these genes are coordinated responses that share common elements at the level of transcriptional regulation. Beneficial and detrimental effects of these physiological processes on wine quality highlight the dual role of oxygen in 'making or breaking wines'. These findings will facilitate the development of oxygen addition strategies to optimize yeast performance in industrial fermentations.

  1. Further evidence of the heterogeneous nature of impulsivity.

    PubMed

    Caswell, Amy J; Bond, Rod; Duka, Theodora; Morgan, Michael J

    2015-04-01

    'Impulsivity' refers to a range of behaviours including preference for immediate reward (temporal-impulsivity) and the tendency to make premature decisions (reflection-impulsivity) and responses (motor-impulsivity). The current study aimed to examine how different behavioural and self-report measurements of impulsivity can be categorised into distinct subtypes. Exploratory factor analysis using full information maximum likelihood was conducted on 10 behavioural and 1 self-report measure of impulsivity. Four factors of impulsivity were indicated, with Factor 1 having a high loading of the Stop Signal Task, which measures motor-impulsivity, factor 2 representing reflection-impulsivity with loadings of the Information Sampling Task and Matching Familiar Figures Task, factor 3 representing the Immediate Memory Task, and finally factor 4 which represents the Delay Discounting Questionnaire and The Monetary Choice Questionnaire, measurements of temporal-impulsivity. These findings indicated that impulsivity is not a unitary construct, and instead represents a series of independent subtypes. There was evidence of a distinct reflection-impulsivity factor, providing the first factor analysis support for this subtype. There was also support for additional factors of motor- and temporal-impulsivity. The present findings indicated that a number of currently accepted tasks cannot be considered as indexing motor- and temporal-impulsivity suggesting that additional characterisations of impulsivity may be required.

  2. Reflected Overpressure Impulse on a Finite Structure

    DTIC Science & Technology

    1983-12-01

    Portsmouth, VA 23709 Commanding Officer Naval Weapons Support Center Crane , IN 47522 No. of Copies Organization Officer In Charge Naval E0D...Engineering Lab ATTN: Code L51, Mr. W.A. Keenan Naval Construction Battalion Center Port Hueneme, CA 93041 Superintendent Naval Postgraduate School

  3. Analysis of the finite deformation response of shape memory polymers: I. Thermomechanical characterization

    NASA Astrophysics Data System (ADS)

    Volk, Brent L.; Lagoudas, Dimitris C.; Chen, Yi-Chao; Whitley, Karen S.

    2010-07-01

    This study presents the analysis of the finite deformation response of a shape memory polymer (SMP). This two-part paper addresses the thermomechanical characterization of SMPs, the derivation of material parameters for a finite deformation phenomenological model, the numerical implementation of such a model, and the predictions from the model with comparisons to experimental data. Part I of this work presents the thermomechanical characterization of the material behavior of a shape memory polymer. In this experimental investigation, the vision image correlation system, a visual-photographic apparatus, was used to measure displacements in the gauge area. A series of tensile tests, which included nominal values of the extension of 10%, 25%, 50%, and 100%, were performed on SMP specimens. The effects on the free recovery behavior of increasing the value of the applied deformation and temperature rate were considered. The stress-extension relationship was observed to be nonlinear for increasing values of the extension, and the shape recovery was observed to occur at higher temperatures upon increasing the temperature rate. The experimental results, aided by the advanced experimental apparatus, present components of the material behavior which are critical for the development and calibration of models to describe the response of SMPs.

  4. A finite element framework for computation of protein normal modes and mechanical response.

    PubMed

    Bathe, Mark

    2008-03-01

    A computational framework based on the Finite Element Method is presented to calculate the normal modes and mechanical response of proteins and their supramolecular assemblies. Motivated by elastic network models, proteins are treated as continuum elastic solids with molecular volume defined by their solvent-excluded surface. The discretized Finite Element representation is obtained using a surface simplification algorithm that facilitates the generation of models of arbitrary prescribed spatial resolution. The procedure is applied to a mutant of T4 phage lysozyme, G-actin, syntenin, cytochrome-c', beta-tubulin, and the supramolecular assembly filamentous actin (F-actin). Equilibrium thermal fluctuations of alpha-carbon atoms and their inter-residue correlations compare favorably with all-atom-based results, the Rotational-Translational Block procedure, and experiment. Additionally, the free vibration and compressive buckling responses of F-actin are in quantitative agreement with experiment. The proposed methodology is applicable to any protein or protein assembly and facilitates the incorporation of specific atomic-level interactions, including aqueous-electrolyte-mediated electrostatic effects and solvent damping. The procedure is equally applicable to proteins with known atomic coordinates as it is to electron density maps of proteins, protein complexes, and supramolecular assemblies of unknown atomic structure.

  5. Electronic chemical response indexes at finite temperature in the canonical ensemble

    SciTech Connect

    Franco-Pérez, Marco E-mail: jlgm@xanum.uam.mx Gázquez, José L. E-mail: jlgm@xanum.uam.mx; Vela, Alberto E-mail: jlgm@xanum.uam.mx

    2015-07-14

    Assuming that the electronic energy is given by a smooth function of the number of electrons and within the extension of density functional theory to finite temperature, the first and second order chemical reactivity response functions of the Helmholtz free energy with respect to the temperature, the number of electrons, and the external potential are derived. It is found that in all cases related to the first or second derivatives with respect to the number of electrons or the external potential, there is a term given by the average of the corresponding derivative of the electronic energy of each state (ground and excited). For the second derivatives, including those related with the temperature, there is a thermal fluctuation contribution that is zero at zero temperature. Thus, all expressions reduce correctly to their corresponding chemical reactivity expressions at zero temperature and show that, at room temperature, the corrections are very small. When the assumption that the electronic energy is given by a smooth function of the number of electrons is replaced by the straight lines behavior connecting integer values, as required by the ensemble theorem, one needs to introduce directional derivatives in most cases, so that the temperature dependent expressions reduce correctly to their zero temperature counterparts. However, the main result holds, namely, at finite temperature the thermal corrections to the chemical reactivity response functions are very small. Consequently, the present work validates the usage of reactivity indexes calculated at zero temperature to infer chemical behavior at room and even higher temperatures.

  6. Electronic chemical response indexes at finite temperature in the canonical ensemble.

    PubMed

    Franco-Pérez, Marco; Gázquez, José L; Vela, Alberto

    2015-07-14

    Assuming that the electronic energy is given by a smooth function of the number of electrons and within the extension of density functional theory to finite temperature, the first and second order chemical reactivity response functions of the Helmholtz free energy with respect to the temperature, the number of electrons, and the external potential are derived. It is found that in all cases related to the first or second derivatives with respect to the number of electrons or the external potential, there is a term given by the average of the corresponding derivative of the electronic energy of each state (ground and excited). For the second derivatives, including those related with the temperature, there is a thermal fluctuation contribution that is zero at zero temperature. Thus, all expressions reduce correctly to their corresponding chemical reactivity expressions at zero temperature and show that, at room temperature, the corrections are very small. When the assumption that the electronic energy is given by a smooth function of the number of electrons is replaced by the straight lines behavior connecting integer values, as required by the ensemble theorem, one needs to introduce directional derivatives in most cases, so that the temperature dependent expressions reduce correctly to their zero temperature counterparts. However, the main result holds, namely, at finite temperature the thermal corrections to the chemical reactivity response functions are very small. Consequently, the present work validates the usage of reactivity indexes calculated at zero temperature to infer chemical behavior at room and even higher temperatures.

  7. Implementing a Finite-State Off-Normal and Fault Response System for Robust Tokamak Operation

    NASA Astrophysics Data System (ADS)

    Eidietis, N. W.; Humphreys, D. A.; Sammuli, B.; Walker, M. L.

    2015-11-01

    The initial implementation and testing of a finite state off-normal & fault response (ONFR) system on the DIII-D and KSTAR tokamaks is presented. Robust ONFR will be critical to the operation of ITER as the physical consequences of unexpected events will be far more extreme than in present devices. ``Off-normal'' refers to unexpected plasma events (e.g. disruptions) and plasma events that are expected but still require asynchronous response (e.g. neoclassical tearing modes). ``Fault'' refers to hardware failure. ONFR priorities are to (1) protect the device from damage, (2) minimize recovery time between shots by avoiding unnecessary initiation of mitigation procedures, and (3) maximize the useful pulse length of a given shot by providing for discharge recovery after deleterious events. The detailed implementation of finite-state ONFR using Matlab/Simulink and Stateflow exported to the DIII-D and KSTAR plasma control systems is described, as are initial tests of multi-stage locked mode handling on both devices. Work supported by the US DOE under DE-FC02-04ER54698.

  8. Dynamics and pattern formation in large systems of spatially-coupled oscillators with finite response times.

    PubMed

    Lee, Wai Shing; Restrepo, Juan G; Ott, Edward; Antonsen, Thomas M

    2011-06-01

    We consider systems of many spatially distributed phase oscillators that interact with their neighbors. Each oscillator is allowed to have a different natural frequency, as well as a different response time to the signals it receives from other oscillators in its neighborhood. Using the ansatz of Ott and Antonsen [Chaos 18, 037113 (2008)] and adopting a strategy similar to that employed in the recent work of Laing [Physica D 238, 1569 (2009)], we reduce the microscopic dynamics of these systems to a macroscopic partial-differential-equation description. Using this macroscopic formulation, we numerically find that finite oscillator response time leads to interesting spatiotemporal dynamical behaviors including propagating fronts, spots, target patterns, chimerae, spiral waves, etc., and we study interactions and evolutionary behaviors of these spatiotemporal patterns.

  9. Blast response of curved carbon/epoxy composite panels: Experimental study and finite-element analysis

    NASA Astrophysics Data System (ADS)

    Phadnis, V. A.; Kumar, P.; Shukla, A.; Roy, A.; Silberschmidt, V. V.

    2013-07-01

    Experimental and numerical studies were conducted to understand the effect of plate curvature on blast response of carbon/epoxy composite panels. A shock-tube system was utilized to impart controlled shock loading to quasi-isotropic composite panels with differing range of radii of curvatures. A 3D Digital Image Correlation (DIC) technique coupled with high-speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. Macroscopic post-mortem analysis was performed to compare yielding and deformation in these panels. A dynamic computational simulation that integrates fluid-structure interaction was conducted to evaluate the panel response in general purpose finite-element software ABAQUS/Explicit. The obtained numerical results were compared to the experimental data and showed a good correlation.

  10. Dynamic response of concrete beams externally reinforced with carbon fiber reinforced plastic (CFRP) subjected to impulsive loads

    SciTech Connect

    Jerome, D.M.; Ross, C.A.

    1996-12-31

    A series of 54 laboratory scale concrete beams 3 x 3 x 30 in. in size were impulsively loaded to failure in a drop weight impact machine. The beams had no internal reinforcement, but instead were externally reinforced on the bottom or tension side of the beams with 1, 2, and 3 ply AS4C/1919 graphite epoxy panels. In addition, several of the beams were also reinforced on the sides with 3 ply CFRP. The beams were simply supported in a drop weight machine and subjected to impact loads with amplitudes up to 10 kips, and durations less than 1 ms, at beam midspan. Measurements made during the loading event included beam total load, midspan displacement, as well as midspan strain at 3 locations in the beam`s cross-section. A high speed framing camera was also used to record the beam`s displacement-time behavior as well as to gain insight into the failure mechanisms. Beam midspan accelerations were determined by double differentiation of the displacement versus time data, and in turn, the beam`s inertial loads were calculated using the beam`s equivalent mass. Beam dynamic bending loads versus time were determined from the difference between the total load versus time and the inertial load versus time data. Bending loads versus displacements were also determined along with fracture energies. Failure to correct the loads for inertia will result in incorrect conclusions being drawn from the data, especially for bending resistance of brittle concrete test specimens. A comparison with quasistatic bending (fracture) energy data showed that the dynamic failure energy absorbed by the beams was always less than the static fracture energy, due to the brittle nature of concrete when impulsively loaded.

  11. An implicit three-dimensional model for describing the inelastic response of solids undergoing finite deformation

    NASA Astrophysics Data System (ADS)

    Rajagopal, K. R.; Srinivasa, A. R.

    2016-08-01

    The aim of this paper is to develop a new unified class of 3D nonlinear anisotropic finite deformation inelasticity model that (1) exhibits rate-independent or dependent hysteretic response (i.e., response wherein reversal of the external stimuli does not cause reversal of the path in state space) with or without yield surfaces. The hysteresis persists with quasistatic loading. (2) Encompasses a wide range of different types of inelasticity models (such as Mullins effect in rubber, rock and soil mechanics, traditional metal plasticity, hysteretic behavior of shape memory materials) into a simple unified framework that is relatively easy to implement in computational schemes and (3) does not require any a priori particular notion of plastic strain or yield function. The core idea behind the approach is the development of an system of implicit rate equations that allow for the continuity of the response but with different rates along different directions. The theory, which is in purely mechanical setting, subsumes and generalizes many commonly used approaches for hypoelasticity and rate-independent plasticity. We illustrate its capability by modeling the Mullins effect which is the inelastic behavior of certain rubbery materials. We are able to simulate the entire cyclic response without the use of additional internal variables, i.e., the entire response is modeled by using an implicit function of stress and strain measures and their rates.

  12. Biodynamic response and spinal load estimation of seated body in vibration using finite element modeling.

    PubMed

    Wang, Wenping; Bazrgari, Babak; Shirazi-Adl, Aboulfazl; Rakheja, Subhash; Boileau, Paul-Émile

    2010-01-01

    Trunk biomechanical models play an indispensable role in predicting muscle forces and spinal loads under whole-body vibration (WBV) exposures. Earlier measurements on the force-motion biodynamic response (impedance, apparent mass) at the body-seat interface and vibration transmissibility (seat to head) have led to the development of different mechanical models. Such models could simulate the overall passive response and serve as an important tool for vehicle seat design. They cannot, however, evaluate physiological parameters of interest under the WBV. On the contrary, anatomical models simulating human's physiological characteristics can predict activities in muscles and their dynamic effects on the spine. In this study, a kinematics-driven nonlinear finite element model of the spine, in which the kinematics data are prescribed, is used to analyse the trunk response in seated WBV. Predictions of the active model (i.e., with varying muscle forces) as compared with the passive model (i.e., with no muscle forces) compared satisfactorily with measurements on vertical apparent mass and seat-to-head transmissibility biodynamic responses. Results demonstrated the crucial role of muscle forces in the dynamic response of the trunk. Muscle forces, while maintaining trunk equilibrium, substantially increased the compression and shear forces on the spine and, hence, the risk of tissue injury.

  13. Dynamic response of laminated composite plates using a three-dimensional hybrid-stress finite-element formulation

    NASA Technical Reports Server (NTRS)

    Liou, W. J.; Sun, C. T.

    1987-01-01

    A method of analysis of dynamic response of laminated composite plates is presented. The analysis is carried by using a hybrid-stress finite element numerical technique. By using this approach, the response of simply supported laminated plates subjected to sinusoidal loading are investigated. For the solution of the finite element equations of motion of free vibrations and dynamic response problems, two effective methods of solution, the space iteration method and the Newmark direct integration method are used. These two methods are discussed here.

  14. Response to selection in finite locus models with non-additive effects.

    PubMed

    Esfandyari, Hadi; Henryon, Mark; Berg, Peer; Thomasen, Jorn Rind; Bijma, Piter; Sørensen, Anders Christian

    2017-01-12

    Under the finite-locus model in the absence of mutation, the additive genetic variation is expected to decrease when directional selection is acting on a population, according to quantitative-genetic theory. However, some theoretical studies of selection suggest that the level of additive variance can be sustained or even increased when non-additive genetic effects are present. We tested the hypothesis that finite-locus models with both additive and non-additive genetic effects maintain more additive genetic variance (V_A) and realize larger medium-to-long term genetic gains than models with only additive effects when the trait under selection is subject to truncation selection. Four genetic models that included additive, dominance, and additive-by-additive epistatic effects were simulated. The simulated genome for individuals consisted of 25 chromosomes, each with a length of 1M. One hundred bi-allelic QTL, four on each chromosome, were considered. In each generation, 100 sires and 100 dams were mated, producing five progeny per mating. The population was selected for a single trait (h(2)=0.1) for 100 discrete generations with selection on phenotype or BLUP-EBV. V_A decreased with directional truncation selection even in presence of non-additive genetic effects. Non-additive effects influenced long-term response to selection and among genetic models additive gene action had highest response to selection. In addition, in all genetic models, BLUP-EBV resulted in a greater fixation of favourable and unfavourable alleles and higher response than phenotypic selection. In conclusion, for the schemes we simulated, the presence of non-additive genetic effects had little effect in changes of additive variance and V_A decreased by directional selection.

  15. Hybrid Finite Element Method for Describing the Electrical Response of Biological Cells to Applied Fields

    PubMed Central

    Ying, Wenjun; Henriquez, Craig S.

    2007-01-01

    A novel hybrid finite element method for modeling the response of passive and active biological membranes to external stimuli is presented. The method is based on the differential equations that describe the conservation of electric flux and membrane currents. By introducing the electric flux through the cell membrane as an additional variable, the algorithm decouples the linear partial differential equation part from the nonlinear ordinary differential equation part that defines the membrane dynamics of interest. This conveniently results in two subproblems: a linear interface problem and a nonlinear initial value problem. The linear interface problem is solved with a hybrid finite element method. The initial value problem is integrated by a standard ordinary differential equation solver such as the Euler and Runge-Kutta methods. During time integration, these two subproblems are solved alternatively. The algorithm can be used to model the interaction of stimuli with multiple cells of almost arbitrary geometries and complex ion-channel gating at the plasma membrane. Numerical experiments are presented demonstrating the uses of the method for modeling field stimulation and action potential propagation. PMID:17405368

  16. Responses of the ocean planktonic ecosystem to finite-amplitude perturbations

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Mu, Mu

    2014-12-01

    The responses of the ocean planktonic ecosystem to finite-amplitude perturbations are investigated using an ocean planktonic ecosystem model. Through changing the higher predation rate on zooplankton, multiple equilibria of the model, namely "high-nutrient" and "low-nutrient" states, are obtained under certain parameter values. Based on these states, the perturbations with maximum nonlinear growth are determined using the conditional nonlinear optimal perturbation (CNOP) method. The linear and nonlinear evolutions of the CNOP perturbation are compared. The results show that the nonlinear evolution of the perturbation leads to predator-prey oscillations with larger amplitude than the linear evolution. Besides, after the perturbation amplitude exceeds a critical value, the nonlinear evolution of the perturbation will induce the linearly stable ecosystem state to lose the stability and become nonlinearly unstable. This implies that nonlinear processes have important impacts on the stability of the ecosystem. Specifically, we identify the nonlinear processes related to zooplankton grazing to impact the stability most for the high-nutrient state, while for the low-nutrient state the main nonlinear process affecting the stability is the uptake process. These results help to improve our understanding of the sensitivity of the oceanic ecosystem model to finite-amplitude perturbations and the underlying nonlinear stability properties.

  17. GABRB1 Single Nucleotide Polymorphism Associated with Altered Brain Responses (but not Performance) during Measures of Impulsivity and Reward Sensitivity in Human Adolescents

    PubMed Central

    Duka, Theodora; Nikolaou, Kyriaki; King, Sarah L.; Banaschewski, Tobias; Bokde, Arun L. W.; Büchel, Christian; Carvalho, Fabiana M.; Conrod, Patricia J.; Flor, Herta; Gallinat, Jürgen; Garavan, Hugh; Heinz, Andreas; Jia, Tianye; Gowland, Penny; Martinot, Jean-Luc; Paus, Tomáš; Rietschel, Marcella; Robbins, Trevor W.; Smolka, Michael; Schumann, Gunter; Stephens, David N.

    2017-01-01

    Variations in genes encoding several GABAA receptors have been associated with human drug and alcohol abuse. Among these, a number of human studies have suggested an association between GABRB1, the gene encoding GABAA receptor β1 subunits, with Alcohol dependence (AD), both on its own and comorbid with other substance dependence and psychiatric illnesses. In the present study, we hypothesized that the GABRB1 genetically-associated increased risk for developing alcoholism may be associated with impaired behavioral control and altered sensitivity to reward, as a consequence of altered brain function. Exploiting the IMAGEN database (Schumann et al., 2010), we explored in a human adolescent population whether possession of the minor (T) variant of the single nucleotide polymorphism (SNP) rs2044081 is associated with performance of tasks measuring aspects of impulsivity, and reward sensitivity that are implicated in drug and alcohol abuse. Allelic variation did not associate with altered performance in either a stop-signal task (SST), measuring one aspect of impulsivity, or a monetary incentive delay (MID) task assessing reward anticipation. However, increased functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) response in the right hemisphere inferior frontal gyrus (IFG), left hemisphere caudate/insula and left hemisphere inferior temporal gyrus (ITG) during MID performance was higher in the minor (T) allelic group. In contrast, during SST performance, the BOLD response found in the right hemisphere supramarginal gyrus, right hemisphere lingual and left hemisphere inferior parietal gyrus indicated reduced responses in the minor genotype. We suggest that β1-containing GABAA receptors may play a role in excitability of brain regions important in controlling reward-related behavior, which may contribute to susceptibility to addictive behavior. PMID:28261068

  18. GABRB1 Single Nucleotide Polymorphism Associated with Altered Brain Responses (but not Performance) during Measures of Impulsivity and Reward Sensitivity in Human Adolescents.

    PubMed

    Duka, Theodora; Nikolaou, Kyriaki; King, Sarah L; Banaschewski, Tobias; Bokde, Arun L W; Büchel, Christian; Carvalho, Fabiana M; Conrod, Patricia J; Flor, Herta; Gallinat, Jürgen; Garavan, Hugh; Heinz, Andreas; Jia, Tianye; Gowland, Penny; Martinot, Jean-Luc; Paus, Tomáš; Rietschel, Marcella; Robbins, Trevor W; Smolka, Michael; Schumann, Gunter; Stephens, David N

    2017-01-01

    Variations in genes encoding several GABAA receptors have been associated with human drug and alcohol abuse. Among these, a number of human studies have suggested an association between GABRB1, the gene encoding GABAA receptor β1 subunits, with Alcohol dependence (AD), both on its own and comorbid with other substance dependence and psychiatric illnesses. In the present study, we hypothesized that the GABRB1 genetically-associated increased risk for developing alcoholism may be associated with impaired behavioral control and altered sensitivity to reward, as a consequence of altered brain function. Exploiting the IMAGEN database (Schumann et al., 2010), we explored in a human adolescent population whether possession of the minor (T) variant of the single nucleotide polymorphism (SNP) rs2044081 is associated with performance of tasks measuring aspects of impulsivity, and reward sensitivity that are implicated in drug and alcohol abuse. Allelic variation did not associate with altered performance in either a stop-signal task (SST), measuring one aspect of impulsivity, or a monetary incentive delay (MID) task assessing reward anticipation. However, increased functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) response in the right hemisphere inferior frontal gyrus (IFG), left hemisphere caudate/insula and left hemisphere inferior temporal gyrus (ITG) during MID performance was higher in the minor (T) allelic group. In contrast, during SST performance, the BOLD response found in the right hemisphere supramarginal gyrus, right hemisphere lingual and left hemisphere inferior parietal gyrus indicated reduced responses in the minor genotype. We suggest that β1-containing GABAA receptors may play a role in excitability of brain regions important in controlling reward-related behavior, which may contribute to susceptibility to addictive behavior.

  19. Campground marketing - the impulse camper

    Treesearch

    Wilbur F. LaPage; Dale P. Ragain

    1972-01-01

    Impulse or unplanned campground visits may account for one-fourth to one-half of all camping activity. The concepts of impulse travel and impulse camping appear to be potentially useful extensions of the broader concept of impulse purchasing, which has become an important influence in retail marketing. Impulse campers may also be impulse buyers; they were found to...

  20. Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study

    PubMed Central

    Hsu, Hung-Yao

    2016-01-01

    Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies. PMID:28074178

  1. A finite element random response analysis of a complex panel with fluid-conveying pipes

    NASA Technical Reports Server (NTRS)

    Chiang, C. K.

    1991-01-01

    A finite element approach is developed for a complex panel with fluid-conveying pipes undergoing large deflections subjected to random loadings. The influence of fluid velocity on the random response is investigated. The root-mean-square (rms) deflections and frequencies for different sound spectrum level value are studied. All four edges of the panel are considered to have the same conditions and restrictions. Either simply supported of clamped boundary condition with respect to the transverse deflection of the panel is considered. The prediction of fatigue life is then based on obtained rms stress. This analytical investigation will help to broaden the basic understanding of the role of fluid flow within structures subjected to acoustic loading.

  2. Finite strain response of crimped fibers under uniaxial traction: An analytical approach applied to collagen

    NASA Astrophysics Data System (ADS)

    Marino, Michele; Wriggers, Peter

    2017-01-01

    Composite materials reinforced by crimped fibers intervene in a number of advanced structural applications. Accordingly, constitutive equations describing their anisotropic behavior and explicitly accounting for fiber properties are needed for modeling and design purposes. To this aim, the finite strain response of crimped beams under uniaxial traction is herein addressed by obtaining analytical relationships based on the Principle of Virtual Works. The model is applied to collagen fibers in soft biological tissues, coupling geometric nonlinearities related to fiber crimp with material nonlinearities due to nanoscale mechanisms. Several numerical applications are presented, addressing the influence of geometric and material features. Available experimental data for tendons are reproduced, integrating the proposed approach within an optimization procedure for data fitting. The obtained results highlight the effectiveness of the proposed approach in correlating fibers structure with composite material mechanics.

  3. [Affective disorders and impulsivity].

    PubMed

    Belzeaux, R; Correard, N; Mazzola-Pomietto, P; Adida, M; Cermolacce, M; Azorin, J-M

    2014-12-01

    Impulsivity is a complex and important phenomenon in mood disorders. Impulse control disorders, as defined in DSM, are more frequent in mood disorders especially in Bipolar Disorder type I, and are associated with a more severe course of illness. Dimensional studies demonstrate that impulsivity is a core manifestation of bipolar disorder both as state- and trait-dependent markers in patients. Comorbid substance use disorders are often associated with a higher level of impulsivity whereas the relation between suicidal behaviors and higher impulsivity remains uncertain. Moreover, neuropsychological tests were used to study correlation between clinical impulsivity and laboratory measurements of impulsivity. Level of correlation remains weak and several explanations are proposed in the literature. Copyright © 2014 L’Encéphale. Published by Elsevier Masson SAS.. All rights reserved.

  4. Genetics of impulsive behaviour.

    PubMed

    Bevilacqua, Laura; Goldman, David

    2013-01-01

    Impulsivity, defined as the tendency to act without foresight, comprises a multitude of constructs and is associated with a variety of psychiatric disorders. Dissecting different aspects of impulsive behaviour and relating these to specific neurobiological circuits would improve our understanding of the etiology of complex behaviours for which impulsivity is key, and advance genetic studies in this behavioural domain. In this review, we will discuss the heritability of some impulsivity constructs and their possible use as endophenotypes (heritable, disease-associated intermediate phenotypes). Several functional genetic variants associated with impulsive behaviour have been identified by the candidate gene approach and re-sequencing, and whole genome strategies can be implemented for discovery of novel rare and common alleles influencing impulsivity. Via deep sequencing an uncommon HTR2B stop codon, common in one population, was discovered, with implications for understanding impulsive behaviour in both humans and rodents and for future gene discovery.

  5. Genetics of impulsive behaviour

    PubMed Central

    Bevilacqua, Laura; Goldman, David

    2013-01-01

    Impulsivity, defined as the tendency to act without foresight, comprises a multitude of constructs and is associated with a variety of psychiatric disorders. Dissecting different aspects of impulsive behaviour and relating these to specific neurobiological circuits would improve our understanding of the etiology of complex behaviours for which impulsivity is key, and advance genetic studies in this behavioural domain. In this review, we will discuss the heritability of some impulsivity constructs and their possible use as endophenotypes (heritable, disease-associated intermediate phenotypes). Several functional genetic variants associated with impulsive behaviour have been identified by the candidate gene approach and re-sequencing, and whole genome strategies can be implemented for discovery of novel rare and common alleles influencing impulsivity. Via deep sequencing an uncommon HTR2B stop codon, common in one population, was discovered, with implications for understanding impulsive behaviour in both humans and rodents and for future gene discovery. PMID:23440466

  6. Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force

    NASA Astrophysics Data System (ADS)

    Nightingale, Kathryn R.; Palmeri, Mark L.; Congdon, Amy N.; Frinkely, Kristin D.; Trahey, Gregg E.

    2004-05-01

    Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.

  7. Combining sudomotor nerve impulse estimation with fMRI to investigate the central sympathetic response to nausea.

    PubMed

    Sclocco, Roberta; Citi, Luca; Garcia, Ronald G; Cerutti, Sergio; Bianchi, Anna M; Kuo, Braden; Napadow, Vitaly; Barbieri, Riccardo

    2015-01-01

    The skin conductance (SC) signal is one of the most important non-invasive indirect measures of autonomic outflow. Several mathematical models have been proposed in the literature to characterize specific SC features. In this work, we present a method for the estimation of central control of sudomotor nerve impulse (SMI) function using SC. The method is based on a differential formulation decomposed into two first order differential equations. We validate our estimation framework by applying it on an experimental protocol where eleven motion sickness-prone subjects were exposed to a nauseogenic visual stimulus while SC and fMRI signals were recorded. Our results show an expected significant increase in the mean amplitude of SMI peaks during the highest reported nausea, as well as a decreasing trend during recovery, which was not evident for skin conductance level. Importantly, SMI/fMRI analysis found a negative association between SMI and fMRI signal in orbitofrontal, dorsolateral prefrontal, and posterior insula cortices, consistent with previous studies correlating brain fMRI and microneurographic signals.

  8. Unruh-DeWitt detector response across a Rindler firewall is finite

    NASA Astrophysics Data System (ADS)

    Louko, Jorma

    2014-09-01

    We investigate a two-level Unruh-DeWitt detector coupled to a massless scalar field or its proper time derivative in (1 + 1)-dimensional Minkowski spacetime, in a quantum state whose correlation structure across the Rindler horizon mimics the stationary aspects of a firewall that Almheiri et al. have argued to ensue in an evaporating black hole spacetime. Within first-order perturbation theory, we show that the detector's response on falling through the horizon is sudden but finite. The difference from the Minkowski vacuum response is proportional to ω -2 ln(| ω|) for the non-derivative detector and to ln(| ω|) for the derivative-coupling detector, both in the limit of a large energy gap ω and in the limit of adiabatic switching. Adding to the quantum state high Rindler temperature excitations behind the horizon increases the detector's response proportionally to the temperature; this situation has been suggested to model the energetic curtain proposal of Braunstein et al. We speculate that the (1 + 1)-dimensional derivative-coupling detector may be a good model for a non-derivative detector that crosses a firewall in 3 + 1 dimensions.

  9. NIKE3D: an implicit, finite-deformation, finite element code for analyzing the static and dynamic response of three-dimensional solids

    SciTech Connect

    Hallquist, J.O.

    1981-01-01

    A user's manual is provided for NIKE3D, a fully implicit three-dimensional finite element code for analyzing the large deformation static and dynamic response of inelastic solids. A contact-impact algorithm permits gaps and sliding along material interfaces. By a specialization of this algorithm, such interfaces can be rigidly tied to admit variable zoning without the need of transition regions. Spatial discretization is achieved by the use of 8-node constant pressure solid elements. Bandwidth minimization is optional. Post-processors for NIKE3D include GRAPE for plotting deformed shapes and stress contours and DYNAP for plotting time histories.

  10. Impulsive action: emotional impulses and their control

    PubMed Central

    Frijda, Nico H.; Ridderinkhof, K. Richard; Rietveld, Erik

    2014-01-01

    This paper presents a novel theoretical view on impulsive action, integrating thus far separate perspectives on non-reflective action, motivation, emotion regulation, and impulse control. We frame impulsive action in terms of directedness of the individual organism toward, away, or against other givens – toward future states and away from one’s present state. First, appraisal of a perceived or thought-of event or object on occasion, rapidly and without premonition or conscious deliberation, triggers a motive to modify one’s relation to that event or object. Situational specifics of the event as perceived and appraised motivate and guide selection of readiness for a particular kind of purposive action. Second, perception of complex situations can give rise to multiple appraisals, multiple motives, and multiple simultaneous changes in action readiness. Multiple states of action readiness may interact in generating action, by reinforcing or attenuating each other, thereby yielding impulse control. We show how emotion control can itself result from a motive state or state of action readiness. Our view links impulsive action mechanistically to states of action readiness, which is the central feature of what distinguishes one kind of emotion from another. It thus provides a novel theoretical perspective to the somewhat fragmented literature on impulsive action. PMID:24917835

  11. Prefrontal Cortex and Impulsive Decision Making

    PubMed Central

    Kim, Soyoun; Lee, Daeyeol

    2010-01-01

    Impulsivity refers to a set of heterogeneous behaviors that are tuned suboptimally along certain temporal dimensions. Impulsive inter-temporal choice refers to the tendency to forego a large but delayed reward and to seek an inferior but more immediate reward, whereas impulsive motor responses also result when the subjects fail to suppress inappropriate automatic behaviors. In addition, impulsive actions can be produced when too much emphasis is placed on speed rather than accuracy in a wide range of behaviors, including perceptual decision making. Despite this heterogeneous nature, the prefrontal cortex and its connected areas, such as the basal ganglia, play an important role in gating impulsive actions in a variety of behavioral tasks. Here, we describe key features of computations necessary for optimal decision making, and how their failures can lead to impulsive behaviors. We also review the recent findings from neuroimaging and single-neuron recording studies on the neural mechanisms related to impulsive behaviors. Converging approaches in economics, psychology, and neuroscience provide a unique vista for better understanding the nature of behavioral impairments associated with impulsivity. PMID:20728878

  12. Parametric Comparisons of Intracranial Mechanical Responses from Three Validated Finite Element Models of the Human Head

    PubMed Central

    Ji, Songbai; Ghadyani, Hamidreza; Bolander, Richard P.; Beckwith, Jonathan G.; Ford, James C.; Mcallister, Thomas W.; Flashman, Laura A.; Paulsen, Keith D.; Ernstrom, Karin; Jain, Sonia; Raman, Rema; Zhang, Liying; Greenwald, Richard M.

    2015-01-01

    A number of human head finite element (FE) models have been developed from different research groups over the years to study the mechanisms of traumatic brain injury. These models can vary substantially in model features and parameters, making it important to evaluate whether simulation results from one model are readily comparable with another, and whether response-based injury thresholds established from a specific model can be generalized when a different model is employed. The purpose of this study is to parametrically compare regional brain mechanical responses from three validated head FE models to test the hypothesis that regional brain responses are dependent on the specific head model employed as well as the region of interest (ROI). The Dartmouth Scaled and Normalized Model (DSNM), the Simulated Injury Monitor (SIMon), and the Wayne State University Head Injury Model (WSUHIM) were selected for comparisons. For model input, 144 unique kinematic conditions were created to represent the range of head impacts sustained by male collegiate hockey players during play. These impacts encompass the 50th, 95th, and 99th percentile peak linear and rotational accelerations at 16 impact locations around the head. Five mechanical variables (strain, strain rate, strain × strain rate, stress, and pressure) in seven ROIs reported from the FE models were compared using Generalized Estimating Equation statistical models. Highly significant differences existed among FE models for nearly all output variables and ROIs. The WSUHIM produced substantially higher peak values for almost all output variables regardless of the ROI compared to the DSNM and SIMon models (p < 0.05). DSNM also produced significantly different stress and pressure compared with SIMon for all ROIs (p < 0.05), but such differences were not consistent across ROIs for other variables. Regardless of FE model, most output variables were highly correlated with linear and rotational peak accelerations. The

  13. Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound.

    PubMed

    Maftoon, Nima; Funnell, W Robert J; Daniel, Sam J; Decraemer, Willem F

    2015-10-01

    We present a finite-element model of the gerbil middle ear that, using a set of baseline parameters based primarily on a priori estimates from the literature, generates responses that are comparable with responses we measured in vivo using multi-point vibrometry and with those measured by other groups. We investigated the similarity of numerous features (umbo, pars-flaccida and pars-tensa displacement magnitudes, the resonance frequency and break-up frequency, etc.) in the experimental responses with corresponding ones in the model responses, as opposed to simply computing frequency-by-frequency differences between experimental and model responses. The umbo response of the model is within the range of variability seen in the experimental data in terms of the low-frequency (i.e., well below the middle-ear resonance) magnitude and phase, the main resonance frequency and magnitude, and the roll-off slope and irregularities in the response above the resonance frequency, but is somewhat high for frequencies above the resonance frequency. At low frequencies, the ossicular axis of rotation of the model appears to correspond to the anatomical axis but the behaviour is more complex at high frequencies (i.e., above the pars-tensa break-up). The behaviour of the pars tensa in the model is similar to what is observed experimentally in terms of magnitudes, phases, the break-up frequency of the spatial vibration pattern, and the bandwidths of the high-frequency response features. A sensitivity analysis showed that the parameters that have the strongest effects on the model results are the Young's modulus, thickness and density of the pars tensa; the Young's modulus of the stapedial annular ligament; and the Young's modulus and density of the malleus. Displacements of the tympanic membrane and manubrium and the low-frequency displacement of the stapes did not show large changes when the material properties of the incus, stapes, incudomallear joint, incudostapedial joint, and

  14. Forensic GPR: finite-difference simulations of responses from buried human remains

    NASA Astrophysics Data System (ADS)

    Hammon, William S.; McMechan, George A.; Zeng, Xiaoxian

    2000-10-01

    Time domain 2.5-D finite-difference simulations of ground-penetrating radar (GPR) responses from models of buried human remains suggest the potential of GPR for detailed non-destructive forensic site investigation. Extraction of information beyond simple detection of cadavers in forensic investigations should be possible with current GPR technology. GPR responses are simulated for various body cross-sections with different depths of burial, soil types, soil moisture contents, survey frequencies and antenna separations. Biological tissues have high electrical conductivity so diagnostic features for the imaging of human bodies are restricted to the soil/skin interface and shallow tissue interfaces. A low amplitude reflection shadow zone occurs beneath a body because of high GPR attenuation within the body. Resolution of diagnostic features of a human target requires a survey frequency of 900 MHz or greater and an increment between recording stations of 10 cm or less. Depth migration focuses field GPR data into an image that reveals accurate information on the number, dimensions, locations and orientations of body elements. The main limitation on image quality is attenuation in the surrounding soil and within the body. 3-D imaging is also feasible.

  15. Finite element modeling of human brain response to football helmet impacts.

    PubMed

    Darling, T; Muthuswamy, J; Rajan, S D

    2016-10-01

    The football helmet is used to help mitigate the occurrence of impact-related traumatic (TBI) and minor traumatic brain injuries (mTBI) in the game of American football. While the current helmet design methodology may be adequate for reducing linear acceleration of the head and minimizing TBI, it however has had less effect in minimizing mTBI. The objectives of this study are (a) to develop and validate a coupled finite element (FE) model of a football helmet and the human body, and (b) to assess responses of different regions of the brain to two different impact conditions - frontal oblique and crown impact conditions. The FE helmet model was validated using experimental results of drop tests. Subsequently, the integrated helmet-human body FE model was used to assess the responses of different regions of the brain to impact loads. Strain-rate, strain, and stress measures in the corpus callosum, midbrain, and brain stem were assessed. Results show that maximum strain-rates of 27 and 19 s(-1) are observed in the brain-stem and mid-brain, respectively. This could potentially lead to axonal injuries and neuronal cell death during crown impact conditions. The developed experimental-numerical framework can be used in the study of other helmet-related impact conditions.

  16. Stochastic finite element model calibration based on frequency responses and bootstrap sampling

    NASA Astrophysics Data System (ADS)

    Vakilzadeh, Majid K.; Yaghoubi, Vahid; Johansson, Anders T.; Abrahamsson, Thomas J. S.

    2017-05-01

    A new stochastic finite element model calibration framework for estimation of the uncertainty in model parameters and predictions from the measured frequency responses is proposed in this paper. It combines the principles of bootstrapping with the technique of FE model calibration with damping equalization. The challenge for the calibration problem is to find an initial estimate of the parameters that is reasonably close to the global minimum of the deviation between model predictions and measurement data. The idea of model calibration with damping equalization is to formulate the calibration metric as the deviation between the logarithm of the frequency responses of FE model and a test data model found from measurement where the same level of modal damping is imposed on all modes. This formulation gives a smooth metric with a large radius of convergence to the global minimum. In this study, practical suggestions are made to improve the performance of this calibration procedure in dealing with noisy measurements. A dedicated frequency sampling strategy is suggested for measurement of frequency responses in order to improve the estimate of a test data model. The deviation metric at each frequency line is weighted using the signal-to-noise ratio of the measured frequency responses. The solution to the improved calibration procedure with damping equalization is viewed as a starting value for the optimization procedure used for uncertainty quantification. The experimental data is then resampled using the bootstrapping approach and the FE model calibration problem, initiating from the estimated starting value, is solved on each individual resampled dataset to produce uncertainty bounds on the model parameters and predictions. The proposed stochastic model calibration framework is demonstrated on a six degree-of-freedom spring-mass system prior to being applied to a general purpose satellite structure.

  17. Controlling your impulses: electrical stimulation of the human supplementary motor complex prevents impulsive errors.

    PubMed

    Spieser, Laure; van den Wildenberg, Wery; Hasbroucq, Thierry; Ridderinkhof, K Richard; Burle, Borís

    2015-02-18

    To err is human. However, an inappropriate urge does not always result in error. Impulsive errors thus entail both a motor system capture by an urge to act and a failed inhibition of that impulse. Here we show that neuromodulatory electrical stimulation of the supplementary motor complex in healthy humans leaves action urges unchanged but prevents them from turning into overt errors. Subjects performed a choice reaction-time task known to trigger impulsive responses, leading to fast errors that can be revealed by analyzing accuracy as a function of poststimulus time. Yet, such fast errors are only the tip of the iceberg: electromyography (EMG) revealed fast subthreshold muscle activation in the incorrect response hand in an even larger proportion of overtly correct trials, revealing covert response impulses not discernible in overt behavior. Analyzing both overt and covert response tendencies enables to gauge the ability to prevent these incorrect impulses from turning into overt action errors. Hyperpolarizing the supplementary motor complex using transcranial direct current stimulation (tDCS) preserves action impulses but prevents their behavioral expression. This new combination of detailed behavioral, EMG, and tDCS techniques clarifies the neurophysiology of impulse control, and may point to avenues for improving impulse control deficits in various neurologic and psychiatric disorders.

  18. Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers

    NASA Astrophysics Data System (ADS)

    Davis, Allen; Kennedy, James

    1998-03-01

    Alkali-aggregate reaction (AAR) has affected the concrete in drilled shafts (cast in place piles) beneath electricity transmission towers along a 42-mile (67 km) section of transmission line in Southern California. In order to prioritize the maintenance program for these shafts, a nondestructive test methodology was sought to quantify the severity of the AAR with depth in each shaft. Shaft diameters of 19, 30, 36, 42, and 54 inches (475, 760, 910, 1067 and 1660 mm) were present, with shaft lengths between 10 and 30 feet (3 and 6 m). Over the last thirty years, impulse-response (I-R) testing has been successfully used to evaluate the integrity of drilled shafts, and computer simulation programs have also been developed for matching I-R test responses with theoretical shaft shapes and concrete quality. A program to test as many shafts as could be accessed in the difficult, mountainous terrain along this transmission line included mobilization of equipment and testing personnel by helicopter. Two hundred ten shafts were tested along the line in five days. Matching of test response mobility-frequency plots in computer simulation was achieved by varying the simulated concrete modulus and density, as well as the shaft cross section area. Up to three grades of concrete quality were identified in each shaft, representing the decreasing degree of AAR with depth. The tested shafts were then rated for increasing AAR severity, in order to select shafts for repair or replacement.

  19. Nerve Impulses in Plants

    ERIC Educational Resources Information Center

    Blatt, F. J.

    1974-01-01

    Summarizes research done on the resting and action potential of nerve impulses, electrical excitation of nerve cells, electrical properties of Nitella, and temperature effects on action potential. (GS)

  20. Nerve Impulses in Plants

    ERIC Educational Resources Information Center

    Blatt, F. J.

    1974-01-01

    Summarizes research done on the resting and action potential of nerve impulses, electrical excitation of nerve cells, electrical properties of Nitella, and temperature effects on action potential. (GS)

  1. Using cross correlations of turbulent flow-induced ambient vibrations to estimate the structural impulse response. Application to structural health monitoring.

    PubMed

    Sabra, Karim G; Winkel, Eric S; Bourgoyne, Dwayne A; Elbing, Brian R; Ceccio, Steve L; Perlin, Marc; Dowling, David R

    2007-04-01

    It has been demonstrated theoretically and experimentally that an estimate of the impulse response (or Green's function) between two receivers can be obtained from the cross correlation of diffuse wave fields at these two receivers in various environments and frequency ranges: ultrasonics, civil engineering, underwater acoustics, and seismology. This result provides a means for structural monitoring using ambient structure-borne noise only, without the use of active sources. This paper presents experimental results obtained from flow-induced random vibration data recorded by pairs of accelerometers mounted within a flat plate or hydrofoil in the test section of the U.S. Navy's William B. Morgan Large Cavitation Channel. The experiments were conducted at high Reynolds number (Re > 50 million) with the primary excitation source being turbulent boundary layer pressure fluctuations on the upper and lower surfaces of the plate or foil. Identical deterministic time signatures emerge from the noise cross-correlation function computed via robust and simple processing of noise measured on different days by a pair of passive sensors. These time signatures are used to determine and/or monitor the structural response of the test models from a few hundred to a few thousand Hertz.

  2. Modifying the biomechanical response of mouthguards with hard inserts: A finite element study.

    PubMed

    Verissimo, Crisnicaw; Santos-Filho, Paulo César Freitas; Tantbirojn, Daranee; Versluis, Antheunis; Soares, Carlos José

    2015-04-01

    To investigate the influence of a high elastic modulus material insert on the stress, shock absorption and displacement of mouthguards. Finite element models of a human maxillary central incisor with and without mouthguard were created based on cross-sectional CT-tomography. The mouthguard models had four designs: without insert, and middle, external, or palatal hard insert. The hard inserts had a relatively high elastic modulus when compared to the elastic modulus of ethylene vinyl acetate (EVA): 15 GPa versus 18 MPa. A non-linear dynamic impact analysis was performed in which a heavy rigid object hit the model at 1 m/s. Strain and stress (von Mises and critical modified von Mises) distributions and shock absorption during impact were calculated as well as the mouthguard displacement. The model without mouthguard had the highest stress values at the enamel and dentin structures in the tooth crown during the impact. It was concluded that the use of a mouthguard promoted lower stress and strain values in the teeth during impact. Hard insertion in the middle and palatal side of the mouthguard improved biomechanical response by lowering stress and strain on the teeth and lowering mouthguard displacement.

  3. Finite element prediction of seismic response modification of monumental structures utilizing base isolation

    NASA Astrophysics Data System (ADS)

    Spanos, Konstantinos; Anifantis, Nikolaos; Kakavas, Panayiotis

    2015-05-01

    The analysis of the mechanical behavior of ancient structures is an essential engineering task concerning the preservation of architectural heritage. As many monuments of classical antiquity are located in regions of earthquake activity, the safety assessment of these structures, as well as the selection of possible restoration interventions, requires numerical models capable of correctly representing their seismic response. The work presented herein was part of a research project in which a better understanding of the dynamics of classical column-architrave structures was sought by means of numerical techniques. In this paper, the seismic behavior of ancient monumental structures with multi-drum classical columns is investigated. In particular, the column-architrave classical structure under strong ground excitations was represented by a finite element method. This approach simulates the individual rock blocks as distinct rigid blocks interconnected with slidelines and incorporates seismic isolation dampers under the basement of the structure. Sliding and rocking motions of individual stone blocks and drums are modeled utilizing non-linear frictional contact conditions. The seismic isolation is modeled through the application of pad bearings under the basement of the structure. These pads are interpreted by appropriate rubber and steel layers. Time domain analyses were performed, considering the geometric and material non-linear behavior at the joints and the characteristics of pad bearings. The deformation and failure modes of drum columns subject to seismic excitations of various types and intensities were analyzed. The adverse influence of drum imperfections on structural safety was also examined.

  4. Sensitivity of lumbar spine response to follower load and flexion moment: finite element study.

    PubMed

    Naserkhaki, Sadegh; El-Rich, Marwan

    2017-04-01

    The follower load (FL) combined with moments is commonly used to approximate flexed/extended posture of the lumbar spine in absence of muscles in biomechanical studies. There is a lack of consensus as to what magnitudes simulate better the physiological conditions. Considering the in-vivo measured values of the intradiscal pressure (IDP), intervertebral rotations (IVRs) and the disc loads, sensitivity of these spinal responses to different FL and flexion moment magnitudes was investigated using a 3D nonlinear finite element (FE) model of ligamentous lumbosacral spine. Optimal magnitudes of FL and moment that minimize deviation of the model predictions from in-vivo data were determined. Results revealed that the spinal parameters i.e. the IVRs, disc moment, and the increase in disc force and moment from neutral to flexed posture were more sensitive to moment magnitude than FL magnitude in case of flexion. The disc force and IDP were more sensitive to the FL magnitude than moment magnitude. The optimal ranges of FL and flexion moment magnitudes were 900-1100 N and 9.9-11.2 Nm, respectively. The FL magnitude had reverse effect on the IDP and disc force. Thus, magnitude for FL or flexion that minimizes the deviation of all the spinal parameters together from the in-vivo data can vary. To obtain reasonable compromise between the IDP and disc force, our findings recommend that FL of low magnitude must be combined with flexion moment of high intensity and vice versa.

  5. Forced responses of solid axially polarized piezoelectric ceramic finite cylinders with internal losses.

    PubMed

    Ebenezer, D D; Ravichandran, K; Ramesh, R; Padmanabhan, Chandramouli

    2005-06-01

    A method is presented to determine the forced responses of piezoelectric cylinders using weighted sums of only certain exact solutions to the equations of motion and the Gauss electrostatic conditions. One infinite set of solutions is chosen such that each field variable is expressed in terms of Bessel functions that form a complete set in the radial direction. Another infinite set of solutions is chosen such that each field variable is expressed in terms of trigonometric functions that form a complete set in the axial direction. Another solution is used to account for the electric field that can exist even when there is no vibration. The weights are determined by using the orthogonal properties of the functions and are used to satisfy specified, arbitrary, axisymmetric boundary conditions on all the surfaces. Special cases including simultaneous mechanical and electrical excitation of cylinders are presented. All numerical results are in excellent agreement with those obtained using the finite element software ATILA. For example, the five lowest frequencies at which the conductance and susceptance of a stress-free cylinder, of length 10 mm and radius 5 mm, reach a local maximum or minimum differ by less than 0.01% from those computed using ATILA.

  6. [Response of a finite element model of the pelvis to different side impact loads].

    PubMed

    Ruan, Shijie; Zheng, Huijing; Li, Haiyan; Zhao, Wei

    2013-08-01

    The pelvis is one of the most likely affected areas of the human body in case of side impact, especially while people suffer from motor vehicle crashes. With the investigation of pelvis injury on side impact, the injury biomechanical behavior of pelvis can be found, and the data can help design the vehicle security devices to keep the safety of the occupants. In this study, a finite element (FE) model of an isolated human pelvis was used to study the pelvic dynamic response under different side impact conditions. Fracture threshold was established by applying lateral loads of 1000, 2000, 3000, 4000 and 5000 N, respectively, to the articular surface of the right acetabulum. It was observed that the smaller the lateral loads were, the smaller the von Mises stress and the displacement in the direction of impact were. It was also found that the failure threshold load was near 3000 N, based on the fact that the peak stress would not exceed the average compressive strength of the cortical bone. It could well be concluded that with better design of car-door and hip-pad so that the side impact force was brought down to 3000 N or lower, the pelvis would not be injured.

  7. Hybrid finite element method for describing the electrical response of biological cells to applied fields.

    PubMed

    Ying, Wenjun; Henriquez, Craig S

    2007-04-01

    A novel hybrid finite element method (FEM) for modeling the response of passive and active biological membranes to external stimuli is presented. The method is based on the differential equations that describe the conservation of electric flux and membrane currents. By introducing the electric flux through the cell membrane as an additional variable, the algorithm decouples the linear partial differential equation part from the nonlinear ordinary differential equation part that defines the membrane dynamics of interest. This conveniently results in two subproblems: a linear interface problem and a nonlinear initial value problem. The linear interface problem is solved with a hybrid FEM. The initial value problem is integrated by a standard ordinary differential equation solver such as the Euler and Runge-Kutta methods. During time integration, these two subproblems are solved alternatively. The algorithm can be used to model the interaction of stimuli with multiple cells of almost arbitrary geometries and complex ion-channel gating at the plasma membrane. Numerical experiments are presented demonstrating the uses of the method for modeling field stimulation and action potential propagation.

  8. A Finite Element Study of the Dynamic Response of Brain Based on Two Parasagittal Slice Models.

    PubMed

    Song, Xuewei; Wang, Cong; Hu, Hao; Huang, Tianlun; Jin, Jingxu

    2015-01-01

    The objective of this study is to investigate the influence of gyri and sulci on the response of human head under transient loading. To this end, two detailed parasagittal slice models with and without gyri and sulci have been developed. The models comprised not only cerebrum and skull but also cerebellum, brain stem, CSF, and corpus callosum. In addition, white and gray matters were separated. The material properties were adopted from the literature and assigned to different parts of the models. Nahum's and Trosseille's experiments reported in relevant literature were simulated and the simulation results were compared with the test data. The results show that there is no evident difference in terms of intracranial pressure between the models with and without gyri and sulci under simulated conditions. The equivalent stress below gyri and sulci in the model with gyri and sulci is slightly higher than that in the counterpart model without gyri and sulci. The maximum principle strain in brain tissue is lower in the model with gyri and sulci. The stress and strain distributions are changed due to the existence of gyri and sulci. These findings highlight the necessity to include gyri and sulci in the finite element head modeling.

  9. Rats with different profiles of impulsive choice behavior exhibit differences in responses to caffeine and d-amphetamine and in medial prefrontal cortex 5-HT utilization.

    PubMed

    Barbelivien, Alexandra; Billy, Erwan; Lazarus, Christine; Kelche, Christian; Majchrzak, Monique

    2008-03-05

    This study investigated if sub-populations of rats characterized by their basal level of impulsivity (BLI) in a delayed-reinforcement task, displayed differences in the functioning of neurotransmitter systems modulating impulsive choice behavior. For this, the effects of various doses of caffeine and d-amphetamine were investigated in three sub-populations of rats displaying pronounced differences in their impulsive choice behavior and their post-mortem serotonergic and dopaminergic functions were assessed. Caffeine and d-amphetamine reduce impulsive choice behavior only in the Medium BLI sub-population. Dopamine utilization was similar in the three sub-populations, but serotonin utilization was lower in the prefrontal cortex of the Medium and Very high BLI sub-populations as compared to the low BLI one. These results suggest that anti-impulsive effects of caffeine and d-amphetamine are dependent on the BLI of rats and that a low serotonergic function in the prefrontal cortex may be a trait marker of impulsivity evaluated by impulsive choice behavior.

  10. Advantage of impulse oscillometry over spirometry to diagnose chronic obstructive pulmonary disease and monitor pulmonary responses to bronchodilators: An observational study

    PubMed Central

    Saadeh, Charles; Cross, Blake; Gaylor, Michael; Griffith, Melissa

    2015-01-01

    Objectives: This retrospective study was a comparative analysis of sensitivity of impulse oscillometry and spirometry techniques for use in a mixed chronic obstructive pulmonary disease group for assessing disease severity and inhalation therapy. Methods: A total of 30 patients with mild-to-moderate chronic obstructive pulmonary disease were monitored by impulse oscillometry, followed by spirometry. Lung function was measured at baseline after bronchodilation and at follow-up (3–18 months). The impulse oscillometry parameters were resistance in the small and large airways at 5 Hz (R5), resistance in the large airways at 15 Hz (R15), and lung reactance (area under the curve X; AX). Results: After the bronchodilator therapy, forced expiratory volume in 1 second (FEV1) readings evaluated by spirometry were unaffected at baseline and at follow-up, while impulse oscillometry detected an immediate improvement in lung function, in terms of AX (p = 0.043). All impulse oscillometry parameters significantly improved at follow-up, with a decrease in AX by 37% (p = 0.0008), R5 by 20% (p = 0.0011), and R15 by 12% (p = 0.0097). Discussion: Impulse oscillometry parameters demonstrated greater sensitivity compared with spirometry for monitoring reversibility of airway obstruction and the effect of maintenance therapy. Impulse oscillometry may facilitate early treatment dose optimization and personalized medicine for chronic obstructive pulmonary disease patients. PMID:26770777

  11. Nonlinear random response of large-scale sparse finite element plate bending problems

    NASA Astrophysics Data System (ADS)

    Chokshi, Swati

    Acoustic fatigue is one of the major design considerations for skin panels exposed to high levels of random pressure at subsonic/supersonic/hypersonic speeds. The nonlinear large deflection random response of the single-bay panels aerospace structures subjected to random excitations at various sound pressure levels (SPLs) is investigated. The nonlinear responses of plate analyses are limited to determine the root-mean-square displacement under uniformly distributed pressure random loads. Efficient computational technologies like sparse storage schemes and parallel computation are proposed and incorporated to solve large-scale, nonlinear large deflection random vibration problems for both types of loading cases: (1) synchronized in time and (2) unsynchronized and statistically uncorrelated in time. For the first time, large scale plate bending problems subjected to unsynchronized load are solved using parallel computing capabilities to account for computational burden due to the simulation of the unsynchronized random pressure fluctuations. The main focus of the research work is placed upon computational issues involved in the nonlinear modal methodologies. A nonlinear FEM method in time domain is incorporated with the Monte Carlo simulation and sparse computational technologies, including the efficient sparse Subspace Eigen-solutions are presented and applied to accurately determine the random response with a refined, large finite element mesh for the first time. Sparse equation solver and sparse matrix operations embedded inside the subspace Eigen-solution algorithms are also exploited. The approach uses the von-Karman nonlinear strain-displacement relations and the classical plate theory. In the proposed methodologies, the solution for a small number (say less than 100) of lowest linear, sparse Eigen-pairs need to be solved for only once, in order to transform nonlinear large displacements from the conventional structural degree-of-freedom (dof) into the modal

  12. Finite Element Analysis of the Random Response Suppression of Composite Panels at Elevated Temperatures using Shape Memory Alloy Fibers

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Zhong, Z. W.; Mei, Chuh

    1994-01-01

    A feasibility study on the use of shape memory alloys (SMA) for suppression of the random response of composite panels due to acoustic loads at elevated temperatures is presented. The constitutive relations for a composite lamina with embedded SMA fibers are developed. The finite element governing equations and the solution procedures for a composite plate subjected to combined acoustic and thermal loads are presented. Solutions include: 1) Critical buckling temperature; 2) Flat panel random response; 3) Thermal postbuckling deflection; 4) Random response of a thermally buckled panel. The preliminary results demonstrate that the SMA fibers can completely eliminate the thermal postbuckling deflection and significantly reduce the random response at elevated temperatures.

  13. Impulsivity and Academic Cheating

    ERIC Educational Resources Information Center

    Anderman, Eric M.; Cupp, Pamela K.; Lane, Derek

    2009-01-01

    The authors examined the relations between academic cheating and impulsivity in a large sample of adolescents enrolled in high school health education classes. Results indicated that impulsivity predicts academic cheating for students who report extensive involvement in cheating. However, students who engage in extensive cheating are less likely…

  14. Rethinking Impulsivity in Suicide

    ERIC Educational Resources Information Center

    Klonsky, E. David; May, Alexis

    2010-01-01

    Elevated impulsivity is thought to facilitate the transition from suicidal thoughts to suicidal behavior. Therefore, impulsivity should distinguish those who have attempted suicide (attempters) from those who have only considered suicide (ideators-only). This hypothesis was examined in three large nonclinical samples: (1) 2,011 military recruits,…

  15. Rethinking Impulsivity in Suicide

    ERIC Educational Resources Information Center

    Klonsky, E. David; May, Alexis

    2010-01-01

    Elevated impulsivity is thought to facilitate the transition from suicidal thoughts to suicidal behavior. Therefore, impulsivity should distinguish those who have attempted suicide (attempters) from those who have only considered suicide (ideators-only). This hypothesis was examined in three large nonclinical samples: (1) 2,011 military recruits,…

  16. Dealing with Impulsivity.

    ERIC Educational Resources Information Center

    Neidhardt, Janet

    1987-01-01

    A mother recounts her neurologically impaired son's struggles and progress in combating impulsivity in his work and social habits. Now 23 years old, employed full-time, and off medication, the son is still impulsive, has problems with social skills, but has improved his self-image through a photography hobby. (CB)

  17. Number-Right, Item-Response, and Finite-State Scoring: Robustness with Respect to Lack of Equally Classifiable Options and Item Option Dependence.

    ERIC Educational Resources Information Center

    Rogers, W. Todd; Ndalichako, Joyce

    2000-01-01

    Determined the robustness of several types of scoring (number-right; one-, two-, and three-parameter item response; finite-state, and partial-credit) with respect to the violation of the equally classifiable options and option independence made in finite-state scoring using analysis of test responses of 1,232 high school seniors. (SLD)

  18. The non-linear response of a muscle in transverse compression: assessment of geometry influence using a finite element model.

    PubMed

    Gras, Laure-Lise; Mitton, David; Crevier-Denoix, Nathalie; Laporte, Sébastien

    2012-01-01

    Most recent finite element models that represent muscles are generic or subject-specific models that use complex, constitutive laws. Identification of the parameters of such complex, constitutive laws could be an important limit for subject-specific approaches. The aim of this study was to assess the possibility of modelling muscle behaviour in compression with a parametric model and a simple, constitutive law. A quasi-static compression test was performed on the muscles of dogs. A parametric finite element model was designed using a linear, elastic, constitutive law. A multi-variate analysis was performed to assess the effects of geometry on muscle response. An inverse method was used to define Young's modulus. The non-linear response of the muscles was obtained using a subject-specific geometry and a linear elastic law. Thus, a simple muscle model can be used to have a bio-faithful, biomechanical response.

  19. Barratt Impulsivity and Neural Regulation of Physiological Arousal

    PubMed Central

    Zhang, Sheng; Hu, Sien; Hu, Jianping; Wu, Po-Lun; Chao, Herta H.; Li, Chiang-shan R.

    2015-01-01

    Background Theories of personality have posited an increased arousal response to external stimulation in impulsive individuals. However, there is a dearth of studies addressing the neural basis of this association. Methods We recorded skin conductance in 26 individuals who were assessed with Barratt Impulsivity Scale (BIS-11) and performed a stop signal task during functional magnetic resonance imaging. Imaging data were processed and modeled with Statistical Parametric Mapping. We used linear regressions to examine correlations between impulsivity and skin conductance response (SCR) to salient events, identify the neural substrates of arousal regulation, and examine the relationship between the regulatory mechanism and impulsivity. Results Across subjects, higher impulsivity is associated with greater SCR to stop trials. Activity of the ventromedial prefrontal cortex (vmPFC) negatively correlated to and Granger caused skin conductance time course. Furthermore, higher impulsivity is associated with a lesser strength of Granger causality of vmPFC activity on skin conductance, consistent with diminished control of physiological arousal to external stimulation. When men (n = 14) and women (n = 12) were examined separately, however, there was evidence suggesting association between impulsivity and vmPFC regulation of arousal only in women. Conclusions Together, these findings confirmed the link between Barratt impulsivity and heightened arousal to salient stimuli in both genders and suggested the neural bases of altered regulation of arousal in impulsive women. More research is needed to explore the neural processes of arousal regulation in impulsive individuals and in clinical conditions that implicate poor impulse control. PMID:26079873

  20. Specific Impulse and Mass Flow Rate Error

    NASA Technical Reports Server (NTRS)

    Gregory, Don A.

    2005-01-01

    Specific impulse is defined in words in many ways. Very early in any text on rocket propulsion a phrase similar to .specific impulse is the thrust force per unit propellant weight flow per second. will be found.(2) It is only after seeing the mathematics written down does the definition mean something physically to scientists and engineers responsible for either measuring it or using someone.s value for it.

  1. Finite element comparison of human and Hybrid III responses in a frontal impact.

    PubMed

    Danelson, Kerry A; Golman, Adam J; Kemper, Andrew R; Gayzik, F Scott; Clay Gabler, H; Duma, Stefan M; Stitzel, Joel D

    2015-12-01

    The improvement of finite element (FE) Human Body Models (HBMs) has made them valuable tools for investigating restraint interactions compared to anthropomorphic test devices (ATDs). The objective of this study was to evaluate the effect of various combinations of safety restraint systems on the sensitivity of thoracic injury criteria using matched ATD and Human Body Model (HBM) simulations at two crash severities. A total of seven (7) variables were investigated: 3-point belt with two (2) load limits, frontal airbag, knee bolster airbag, a buckle pretensioner, and two (2) delta-v's - 40kph and 50kph. Twenty four (24) simulations were conducted for the Hybrid III ATD FE model and repeated with a validated HBM for 48 total simulations. Metrics tested in these conditions included sternum deflection, chest acceleration, chest excursion, Viscous Criteria (V*C) criteria, pelvis acceleration, pelvis excursion, and femur forces. Additionally, chest band deflection and rib strain distribution were measured in the HBM for additional restraint condition discrimination. The addition of a frontal airbag had the largest effect on the occupant chest metrics with an increase in chest compression and acceleration but a decrease in excursion. While the THUMS and Hybrid III occupants demonstrated the same trend in the chest compression measurements, there were conflicting results in the V*C, acceleration, and displacement metrics. Similarly, the knee bolster airbag had the largest effect on the pelvis with a decrease in acceleration and excursion. With a knee bolster airbag the simulated occupants gave conflicting results, the THUMS had a decrease in femur force and the ATD had an increase. Preferential use of dummies or HBM's is not debated; however, this study highlights the ability of HBM metrics to capture additional chest response metrics.

  2. The role of retardation in the structure and linear response of finite nuclei

    SciTech Connect

    Crecca, M.A.

    1989-01-01

    Conventional random phase approximation (RPA) and Tamm-Dancoff approximation (TDA) calculations of nuclear structure and the linear response employ interactions between nucleons that are instantaneous. However, N-N interactions derived from the exchange of mesons between nucleons must depend on the space-time separation of the nucleons since the mesons travel at finite speeds. Furthermore, a quantum field theory that contains interacting meson and nucleon degrees of freedom employ the Feynman propagator, i{Delta}{sub F}(x - x{prime}), to connect the nucleon-meson vertices of Feynman diagrams. This raises the question of whether calculations done with space-time dependent interactions differ significantly from the conventional calculations that employ instantaneous forces, and what are the qualitative features of the difference. The inquiry into this question begins by generalizing the traditional RPA and TDA equations into the domain of retarded (space-time dependant) interactions. This entails establishing an integral equation (the Bethe-Salpeter equation) for the polarization propagator with the appropriate RPA or TDA kernel such that the integral equation reduces to the usual RPA or TDA matrix equation for the polarization propagator as the interaction becomes instantaneous. After establishing this generalization of the RPA and TDA, a TDA calculation is performed for an interaction arising from the exchange of a scalar meson. The results are compared with those obtained from the conventional instantaneous reduction of the scalar meson exchange interaction, the Yukawa potential. Upon comparing these results one finds that in general the nuclear structure obtained from scalar meson exchange differ little less than 10%.

  3. Response analysis of the lumbar spine during regular daily activities--a finite element analysis.

    PubMed

    Schmidt, Hendrik; Shirazi-Adl, Aboulfazl; Galbusera, Fabio; Wilke, Hans-Joachim

    2010-07-20

    A non-linear poroelastic finite element model of the lumbar spine was developed to investigate spinal response during daily dynamic physiological activities. Swelling was simulated by imposing a boundary pore pressure of 0.25 MPa at all external surfaces. Partial saturation of the disc was introduced to circumvent the negative pressures otherwise computed upon unloading. The loading conditions represented a pre-conditioning full day followed by another day of loading: 8h rest under a constant compressive load of 350 N, followed by 16 h loading phase under constant or cyclic compressive load varying in between 1000 and 1600 N. In addition, the effect of one or two short resting periods in the latter loading phase was studied. The model yielded fairly good agreement with in-vivo and in-vitro measurements. Taking the partial saturation of the disc into account, no negative pore pressures were generated during unloading and recovery phase. Recovery phase was faster than the loading period with equilibrium reached in only approximately 3h. With time and during the day, the axial displacement, fluid loss, axial stress and disc radial strain increased whereas the pore pressure and disc collagen fiber strains decreased. The fluid pressurization and collagen fiber stiffening were noticeable early in the morning, which gave way to greater compression stresses and radial strains in the annulus bulk as time went by. The rest periods dampened foregoing differences between the early morning and late in the afternoon periods. The forgoing diurnal variations have profound effects on lumbar spine biomechanics and risk of injury.

  4. Dimensions and disorder specificity of impulsivity in pathological gambling.

    PubMed

    Kräplin, Anja; Bühringer, Gerhard; Oosterlaan, Jaap; van den Brink, Wim; Goschke, Thomas; Goudriaan, Anna E

    2014-11-01

    Impulsivity is a core characteristic of pathological gambling (PG), even though the underlying structure and disorder specificity is unclear. This study aimed to explore different dimensions of impulsivity in a clinical sample including PG. Furthermore, we aimed to test which alterations of the impulsivity-related dimensions are disorder specific for PG. Participants were individuals diagnosed with PG (n=51) and two groups also characterized by various impulsive behaviors: an alcohol dependence (AD; n=45) and a Gilles de la Tourette syndrome (GTS; n=49) group. A healthy control (HC; n=53) group was recruited as comparison group. A comprehensive assessment was used including impulsivity-related and antipodal parameters of the Stop Signal Task, Stroop Task, Tower of London Task, Card Playing Task, Iowa Gambling Task and the Barratt Impulsiveness Scale-11. Principal axis factor analysis revealed four impulsivity-related dimensions that were labeled 'self-reported impulsivity', 'prepotent response impulsivity', 'choice impulsivity' and 'motor impulsivity'. The PG group scored significantly higher on all four dimensions compared to the HC group. In contrast, the PG group did not differ on any of the dimensions from the AD or the GTS group, except for 'choice impulsivity' where the PG group exhibited higher factor scores compared to the GTS group. Altogether, PG is associated with generally heightened impulsivity profiles compared to a HC group, which may be further used for intervention strategies. However, heightened scores in the impulsivity dimensions are not disorder specific for PG. Further research on shared or different underlying mechanisms of these overlapping impulsivity impairments is necessary. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Time-fixed rendezvous by impulse factoring with an intermediate timing constraint. [for transfer orbits

    NASA Technical Reports Server (NTRS)

    Green, R. N.; Kibler, J. F.; Young, G. R.

    1974-01-01

    A method is presented for factoring a two-impulse orbital transfer into a three- or four-impulse transfer which solves the rendezvous problem and satisfies an intermediate timing constraint. Both the time of rendezvous and the intermediate time of a alinement are formulated as any element of a finite sequence of times. These times are integer multiples of a constant plus an additive constant. The rendezvous condition is an equality constraint, whereas the intermediate alinement is an inequality constraint. The two timing constraints are satisfied by factoring the impulses into collinear parts that vectorially sum to the original impulse and by varying the resultant period differences and the number of revolutions in each orbit. Five different types of solutions arise by considering factoring either or both of the two impulses into two or three parts with a limit for four total impulses. The impulse-factoring technique may be applied to any two-impulse transfer which has distinct orbital periods.

  6. Linear and nonlinear optical response of one-dimensional semiconductors: finite-size and Franz–Keldysh effects

    NASA Astrophysics Data System (ADS)

    Bonabi, Farzad; Pedersen, Thomas G.

    2017-04-01

    The dipole moment formalism for the optical response of finite electronic structures breaks down in infinite ones, for which a momentum-based method is better suited. Focusing on simple chain structures, we compare the linear and nonlinear optical response of finite and infinite one-dimensional semiconductors. This comparison is then extended to cases including strong electro-static fields breaking translational invariance. For large electro-static fields, highly non-perturbative Franz–Keldysh (FK) features are observed in both linear and nonlinear spectra. It is demonstrated that dipole and momentum formalisms agree in the limit of large structures provided the intraband momentum contributions are carefully treated. This convergence is established even in the presence of non-perturbative electro-static fields.

  7. Short Time Impulse Response Function (STIRF) for automatic evaluation of the variation of the dynamic parameters of reinforced concrete framed structures during strong earthquakes.

    NASA Astrophysics Data System (ADS)

    Carlo Ponzo, Felice; Ditommaso, Rocco

    2015-04-01

    This study presents an innovative strategy for automatic evaluation of the variable fundamental frequency and related damping factor of nonlinear structures during strong motion phases. Most of methods for damage detection are based on the assessment of the variations of the dynamic parameters characterizing the monitored structure. A crucial aspect of these methods is the automatic and accurate estimation of both structural eigen-frequencies and related damping factors also during the nonlinear behaviour. A new method, named STIRF (Short-Time Impulse Response Function - STIRF), based on the nonlinear interferometric analysis combined with the Fourier Transform (FT) here is proposed in order to allow scientists and engineers to characterize frequencies and damping variations of a monitored structure. The STIRF approach helps to overcome some limitation derived from the use of techniques based on simple Fourier Transform. These latter techniques provide good results when the response of the monitored system is stationary, but fails when the system exhibits a non-stationary, time-varying behaviour: even non-stationary input, soil-foundation and/or adjacent structures interaction phenomena can show the inadequacy of classic techniques to analysing the nonlinear and/or non-stationary behaviour of structures. In fact, using this kind of approach it is possible to improve some of the existing methods for the automatic damage detection providing stable results also during the strong motion phase. Results are consistent with those expected if compared with other techniques. The main advantage derived from the use of the proposed approach (STIRF) for Structural Health Monitoring is based on the simplicity of the interpretation of the nonlinear variations of the fundamental frequency and the related equivalent viscous damping factor. The proposed methodology has been tested on both numerical and experimental models also using data retrieved from shaking table tests. Based on

  8. Different subtypes of impulsivity differentiate uncontrolled eating and dietary restraint.

    PubMed

    Leitch, Margaret A; Morgan, Michael J; Yeomans, Martin R

    2013-10-01

    The current study explored the relationship between three subtypes of impulsivity (Reflection Impulsivity, Impulsive Choice, and Impulsive Action) and measures of uncontrolled eating (TFEQ-D) and restraint (TFEQ-R). Eighty women classified as scoring higher or lower on TFEQ-D and TFEQ-R completed the Matching Familiar Figures Test (MFFT20), Delay Discounting Task (DDT), a Go No Go task, Balloon Analogue Risk Task (BART), and the Barrett Impulsivity Scale-11 (BIS-11). To test whether these relationships were affected by enforced controls overeating, half of the participants fasted the night before and ate breakfast in the laboratory before testing and half had no such control. Women scoring higher on the TFEQ-D were significantly more impulsive on the MFFT20 and BIS-11 overall but not on DDT, Go No Go or BART. Women scoring higher on TFEQ-R were significantly less impulsive on the Go No Go task but did not differ on other measures. The eating manipulation modulated responses on the BART and BIS-11 non-planning scale depending on TFEQ-D classification. These results confirm recent data that high scores on TFEQ-D are related to impulsivity, but imply this relates more to Reflection Impulsivity rather than Impulsive Choice or Action. In contrast restrained eating was associated with better inhibitory control. Taken together, these results suggest that subtypes of impulsivity further differentiate uncontrolled eating and restraint, and suggest that a poor ability to reflect on decisions may underlie some aspects of overeating.

  9. Extended two-temperature model for ultrafast thermal response of band gap materials upon impulsive optical excitation

    SciTech Connect

    Shin, Taeho; Teitelbaum, Samuel W.; Wolfson, Johanna; Nelson, Keith A.; Kandyla, Maria

    2015-11-21

    Thermal modeling and numerical simulations have been performed to describe the ultrafast thermal response of band gap materials upon optical excitation. A model was established by extending the conventional two-temperature model that is adequate for metals, but not for semiconductors. It considers the time- and space-dependent density of electrons photoexcited to the conduction band and accordingly allows a more accurate description of the transient thermal equilibration between the hot electrons and lattice. Ultrafast thermal behaviors of bismuth, as a model system, were demonstrated using the extended two-temperature model with a view to elucidating the thermal effects of excitation laser pulse fluence, electron diffusivity, electron-hole recombination kinetics, and electron-phonon interactions, focusing on high-density excitation.

  10. Arterial stiffness measurements with acoustic radiation force impulse imaging

    NASA Astrophysics Data System (ADS)

    Trahey, Gregg E.; Dahl, Jeremy J.; McAleavey, Stephen A.; Gallippi, Caterina M.; Nightingale, Kathryn R.

    2003-05-01

    We have developed a new method of imaging the mechanical properties of tissues based on very brief (<1msec) and localized applications of acoustic radiation force and the ultrasonic measurement of local tissues' responses to that force. Initial results with this technique demonstrate its ability to image mechanical properties of the medial and adventitial layers within ex vivo and in vivo arteries, and to distinguish hard and soft atherosclerotic plaques from normal vessel wall. We have labeled this method Acoustic Radiation Force Impulse (ARFI) imaging. We describe studies to utilize this technique in the characterization of diffuse and focal atherosclerosis. We describe phantom trials and finite element simulations which explore the fundamental resolution and contrast achievable with this method. We describe in vivo and ex vivo trials in the popliteal, femoral and brachial arteries to assess the relationship between the mechanical properties of healthy and diseased arteries provided by this method and those obtained by alternative methods.

  11. Maternal overreactive sympathetic nervous system responses to repeated infant crying predicts risk for impulsive harsh discipline of infants.

    PubMed

    Joosen, Katharina J; Mesman, Judi; Bakermans-Kranenburg, Marian J; van Ijzendoorn, Marinus H

    2013-11-01

    Physiological reactivity to repeated infant crying was examined as a predictor of risk for harsh discipline use with 12-month-olds in a longitudinal study with 48 low-income mother-infant dyads. Physiological reactivity was measured while mothers listened to three blocks of infant cry sounds in a standard cry paradigm when their infants were 3 months old. Signs of harsh discipline use were observed during two tasks during a home visit when the infants were 12 months old. Mothers showing signs of harsh discipline (n = 10) with their 12-month-olds were compared to mothers who did not (n = 38) on their sympathetic (skin conductance levels [SCL]) and parasympathetic (respiratory sinus arrhythmia) reactivity to the cry sounds. Results showed a significant interaction effect for sympathetic reactivity only. Mean SCL of harsh-risk mothers showed a significant different response pattern from baseline to crying and onward into the recovery, suggesting that mean SCL of mothers who showed signs of harsh discipline continued to rise across the repeated bouts of cry sounds while, after an initial increase, mean SCL level of the other mothers showed a steady decline. We suggest that harsh parenting is reflected in physiological overreactivity to negative infant signals and discuss our findings from a polyvagal perspective.

  12. Impulsivity and methamphetamine use.

    PubMed

    Semple, Shirley J; Zians, Jim; Grant, Igor; Patterson, Thomas L

    2005-09-01

    The purpose of this study was to explore the relationship between methamphetamine (meth) use and impulsivity in a sample of 385 HIV-negative heterosexually identified meth users. Participants who scored highest on a self-report measure of impulsivity were compared with those who scored lower in terms of background characteristics, meth use patterns, use of alcohol and other illicit drugs, sexual risk behavior, and psychiatric health variables. Methamphetamine users in the high impulsivity group were younger, less educated, used larger quantities of meth, were more likely to be binge users, had a larger number of sexual partners, engaged in more unprotected vaginal and oral sex, and scored higher on the Beck Depression Inventory as compared with those in the low impulsivity group. In a logistic regression analysis, Beck depression was the factor that best distinguished between meth users who scored high and those who scored low on impulsivity. Neurophysiological pathways that may underlie the relationship between impulsivity and meth use are discussed.

  13. Finite-time Lyapunov exponents and metabolic control coefficients for threshold detection of stimulus-response curves.

    PubMed

    Duc, Luu Hoang; Chávez, Joseph Páez; Son, Doan Thai; Siegmund, Stefan

    2016-01-01

    In biochemical networks transient dynamics plays a fundamental role, since the activation of signalling pathways is determined by thresholds encountered during the transition from an initial state (e.g. an initial concentration of a certain protein) to a steady-state. These thresholds can be defined in terms of the inflection points of the stimulus-response curves associated to the activation processes in the biochemical network. In the present work, we present a rigorous discussion as to the suitability of finite-time Lyapunov exponents and metabolic control coefficients for the detection of inflection points of stimulus-response curves with sigmoidal shape.

  14. Finite-difference time-domain simulation of ultrashort pulse propagation incorporating quantum-mechanical response functions

    NASA Astrophysics Data System (ADS)

    Gruetzmacher, Julie A.; Scherer, Norbert F.

    2003-04-01

    A semiclassical implementation of the finite-difference time-domain method is used to simulate coherent linear propagation of ultrashort mid-infrared pulses through optically dense samples of isotropically diluted liquid water. Bloch equations for the density matrix are used as a simple model of the O-H oscillator relaxation, and the algorithm is extended to other response functions. Sensitivity of the field to the form of the response function is demonstrated, and the results are compared with experimentally determined electric fields in the same media [Rev. Sci. Instrum. 73, 2227 (2002)].

  15. Finite Mixture Dynamic Regression Modeling of Panel Data with Implications for Dynamic Response Analysis

    ERIC Educational Resources Information Center

    Kaplan, David

    2005-01-01

    This article considers the problem of estimating dynamic linear regression models when the data are generated from finite mixture probability density function where the mixture components are characterized by different dynamic regression model parameters. Specifically, conventional linear models assume that the data are generated by a single…

  16. Dynamic and thermal response finite element models of multi-body space structural configurations

    NASA Technical Reports Server (NTRS)

    Edighoffer, Harold H.

    1987-01-01

    Presented is structural dynamics modeling of two multibody space structural configurations. The first configuration is a generic space station model of a cylindrical habitation module, two solar array panels, radiator panel, and central connecting tube. The second is a 15-m hoop-column antenna. Discussed is the special joint elimination sequence used for these large finite element models, so that eigenvalues could be extracted. The generic space station model aided test configuration design and analysis/test data correlation. The model consisted of six finite element models, one of each substructure and one of all substructures as a system. Static analysis and tests at the substructure level fine-tuned the finite element models. The 15-m hoop-column antenna is a truss column and structural ring interconnected with tension stabilizing cables. To the cables, pretensioned mesh membrane elements were attached to form four parabolic shaped antennae, one per quadrant. Imposing thermal preloads in the cables and mesh elements produced pretension in the finite element model. Thermal preload variation in the 96 control cables was adjusted to maintain antenna shape within the required tolerance and to give pointing accuracy.

  17. Acoustic response from a bubble pulsating near a fluid layer of finite density and thickness.

    PubMed

    Doinikov, Alexander A; Aired, Leila; Bouakaz, Ayache

    2011-02-01

    A theory is developed that allows one to consider the dynamics of an acoustically induced bubble near a fluid layer of finite density and thickness. The theory reveals that, as far as the scattered field of a bubble in the far-field zone is concerned, the layer thickness is a very important factor because the behavior of the scattered field in the cases of infinite and finite layers is qualitatively different even if both layers are of the same density. The amplitude of the scattered pressure from a bubble pulsating in the vicinity of an infinite layer is larger than that for the same bubble in an unbounded fluid, while in the case of a finite layer, on the contrary, the amplitude of the scattered pressure for a bubble near the layer is smaller than that in an unbounded fluid. It is also shown that the higher the layer density, the greater the difference between the scattered pressure amplitudes for infinite and finite layers.

  18. A sum-over-paths algorithm for third-order impulse-response moment extraction within RC IC-interconnect networks

    NASA Astrophysics Data System (ADS)

    Wojcik, E. A.; Ni, D.; Lam, T. M.; Le Coz, Y. L.

    2015-07-01

    We have created the first stochastic SoP (Sum-over-Paths) algorithm to extract third-order impulse-response (IR) moment within RC IC interconnects. It employs a newly discovered Feynman SoP Postulate. Importantly, our algorithm maintains computational efficiency and full parallelism. Our approach begins with generation of s-domain nodal-voltage equations. We then perform a Taylor-series expansion of the circuit transfer function. These expansions yield transition diagrams involving mathematical coupling constants, or weight factors, in integral powers of complex frequency s. Our SoP Postulate enables stochastic evaluation of path sums within the circuit transition diagram to order s3-corresponding to the order of IR moment (m3) we seek here. We furnish, for the first time, an informal algebraic proof independently validating our SoP Postulate and algorithm. We list, as well, detailed procedural steps, suitable for coding, that define an efficient stochastic algorithm for m3 IR extraction. Origins of the algorithm's statistical "capacitor-number cubed" correction and "double-counting" weight factors are explained, for completeness. Our algorithm was coded and successfully tested against exact analytical solutions for 3-, 5-, and 10-stage RC lines. We achieved better than 0.65% 1-σ error convergence, after only 10K statistical samples, in less than 1 s of 2-GHz Pentium® execution time. These results continue to suggest that stochastic SoP algorithms may find useful application in circuit analysis of massively coupled networks, such as those encountered in high-end digital IC-interconnect CAD.

  19. Low-Velocity Impact Response and Finite Element Analysis of Four-Step 3-D Braided Composites

    NASA Astrophysics Data System (ADS)

    Sun, Baozhong; Zhang, Yan; Gu, Bohong

    2013-08-01

    The low-velocity impact characters of 3-D braided carbon/epoxy composites were investigated from experimental and finite element simulation approaches. The quasi-static tests were carried out at a constant velocity of 2 mm/min on MTS 810.23 material tester system to obtain the indentation load-displacement curves and indentation damages. The low-velocity tests were conducted at the velocities from 1 m/s to 6 m/s (corresponding to the impact energy from 3.22 J to 116 J) on Instron Dynatup 9250 impact tester. The peak force, energy for peak force, time to peak force, and total energy absorption were obtained to determine the impact responses of 3-D braided composites. A unit cell model was established according to the microstructure of 3-D braided composites to derive the constitutive equation. Based on the model, a user-defined material subroutine (VUMAT) has been compiled by FORTRAN and connected with commercial finite element code ABAQUS/Explicit to calculate the impact damage. The unit cell model successfully predicted the impact response of 3-D braided composites. Furthermore, the stress wave propagation and failure mechanisms have been revealed from the finite element simulation results and ultimate damage morphologies of specimens.

  20. Impulsivity across the course of bipolar disorder.

    PubMed

    Strakowski, Stephen M; Fleck, David E; DelBello, Melissa P; Adler, Caleb M; Shear, Paula K; Kotwal, Renu; Arndt, Stephan

    2010-05-01

    To determine whether abnormalities of impulse control persist across the course of bipolar disorder, thereby representing potential state markers and endophenotypes. Impulse control of 108 bipolar I manic or mixed patients was measured on three tasks designed to study response inhibition, ability to delay gratification, and attention; namely, a stop signal task, a delayed reward task, and a continuous performance task, respectively. Barrett Impulsivity Scale (BIS-11) scores were also obtained. Patients were then followed for up to one year and reassessed with the same measures if they developed depression or euthymia. Healthy comparison subjects were also assessed with the same instruments on two occasions to assess measurement stability. At baseline, bipolar subjects demonstrated significant deficits on all three tasks as compared to healthy subjects, consistent with more impulsive responding in the bipolar manic/mixed group. In general, performance on the three behavioral tasks normalized upon switching to depression or developing euthymia. In contrast, BIS-11 scores were elevated during mania and remained elevated as bipolar subjects developed depression or achieved euthymia. Bipolar I disorder patients demonstrate deficits on laboratory tests of various aspects of impulsivity when manic, as compared to healthy subjects, that largely normalize with recovery and switching into depression. However, elevated BIS-11 scores persist across phases of illness. These findings suggest that impulsivity has both affective-state dependent and trait components in bipolar disorder.

  1. Impulse noise generator--design and operation.

    PubMed

    Brinkmann, H

    1991-01-01

    In the seventies PFANDER (Pfander, 1975) proposed a screening test with an impulse noise simulator to check the particular responsivity of soldiers on vulnerability of the inner ear concerning the impulse noise-induced hearing loss. According to a system developed at the University of Oldenburg (Germany) (Klug & Radek, 1987), we have constructed an impulse noise generator designed for our specific requirements that will be presented. The simulator consists of an electrical ignited impulse noise spark gap which is supplied by a 3.5 kV high voltage source. At a distance of 1.10 m from the center of the impulse noise spark gap a peak pressure level of 155 dB with a C-Duration (Pfander, 1975) of .2 msec and with the main energy in the frequency range from 1 kHz to 2 kHz was good reproducible. It would be preferable to shift the impulse noise spectrum to lower frequencies but experimental effort has failed so far.

  2. Impulsivity, self-control, and hypnotic suggestibility.

    PubMed

    Ludwig, V U; Stelzel, C; Krutiak, H; Prunkl, C E; Steimke, R; Paschke, L M; Kathmann, N; Walter, H

    2013-06-01

    Hypnotic responding might be due to attenuated frontal lobe functioning after the hypnotic induction. Little is known about whether personality traits linked with frontal functioning are associated with responsiveness to hypnotic suggestions. We assessed whether hypnotic suggestibility is related to the traits of self-control and impulsivity in 154 participants who completed the Brief Self-Control Scale, the Self-Regulation Scale, the Barratt Impulsiveness Scale (BIS-11), and the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:A). BIS-11 non-planning impulsivity correlated positively with HGSHS:A (Bonferroni-corrected). Furthermore, in the best model emerging from a stepwise multiple regression, both non-planning impulsivity and self-control positively predicted hypnotic suggestibility, and there was an interaction of BIS-11 motor impulsivity with gender. For men only, motor impulsivity tended to predict hypnotic suggestibility. Hypnotic suggestibility is associated with personality traits linked with frontal functioning, and hypnotic responding in men and women might differ. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Impulsivity across the course of bipolar disorder

    PubMed Central

    Strakowski, Stephen M.; Fleck, David E.; DelBello, Melissa P.; Adler, Caleb M.; Shear, Paula K.; Kotwal, Renu; Arndt, Stephan

    2010-01-01

    Objective To determine whether abnormalities of impulse control persist across the course of bipolar disorder, thereby representing potential state markers and endophenotypes. Methods Impulse control of 108 bipolar I manic or mixed patients was measured on three tasks designed to study response inhibition, ability to delay gratification, and attention; namely a stop signal task, a delayed reward task, and a continuous performance task, respectively. Barrett Impulsivity Scale (BIS-11) scores were also obtained. Patients were then followed for up to one year and re-assessed with the same measures if they developed depression or euthymia. Healthy comparison subjects were also assessed with the same instruments on two occasions to assess measurement stability. Results At baseline, bipolar subjects demonstrated significant deficits on all three tasks as compared to healthy subjects, consistent with more impulsive responding in the bipolar manic/mixed group. In general, performance on the three behavioral tasks normalized upon switching to depression or developing euthymia. In contrast, BIS-11 scores were elevated during mania and remained elevated as bipolar subjects developed depression or achieved euthymia. Conclusions Bipolar I disorder patients demonstrate deficits on laboratory tests of various aspects of impulsivity when manic, as compared to healthy subjects, that largely normalize with recovery and switching into depression. However, elevated BIS scores persist across phases of illness. These findings suggest that impulsivity has both affective-state dependent and trait components in bipolar disorder. PMID:20565435

  4. SANTOS - a two-dimensional finite element program for the quasistatic, large deformation, inelastic response of solids

    SciTech Connect

    Stone, C.M.

    1997-07-01

    SANTOS is a finite element program designed to compute the quasistatic, large deformation, inelastic response of two-dimensional planar or axisymmetric solids. The code is derived from the transient dynamic code PRONTO 2D. The solution strategy used to compute the equilibrium states is based on a self-adaptive dynamic relaxation solution scheme, which is based on explicit central difference pseudo-time integration and artificial mass proportional damping. The element used in SANTOS is a uniform strain 4-node quadrilateral element with an hourglass control scheme to control the spurious deformation modes. Finite strain constitutive models for many common engineering materials are included. A robust master-slave contact algorithm for modeling sliding contact is implemented. An interface for coupling to an external code is also provided. 43 refs., 22 figs.

  5. Experimental Validation of Two-dimensional Finite Element Method for Simulating Constitutive Response of Polycrystals During High Temperature Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Agarwal, Sumit; Briant, Clyde L.; Krajewski, Paul E.; Bower, Allan F.; Taleff, Eric M.

    2007-04-01

    A finite element method was recently designed to model the mechanisms that cause superplastic deformation (A.F. Bower and E. Wininger, A Two-Dimensional Finite Element Method for Simulating the Constitutive Response and Microstructure of Polycrystals during High-Temperature Plastic Deformation, J. Mech. Phys. Solids, 2004, 52, p 1289-1317). The computations idealize the solid as a collection of two-dimensional grains, separated by sharp grain boundaries. The grains may deform plastically by thermally activated dislocation motion, which is modeled using a conventional crystal plasticity law. The solid may also deform by sliding on the grain boundaries, or by stress-driven diffusion of atoms along grain boundaries. The governing equations are solved using a finite element method, which includes a front-tracking procedure to monitor the evolution of the grain boundaries and surfaces in the solid. The goal of this article is to validate these computations by systematically comparing numerical predictions to experimental measurements of the elevated-temperature response of aluminum alloy AA5083 (M.-A. Kulas, W.P. Green, E.M. Taleff, P.E. Krajewski, and T.R. McNelley, Deformation Mechanisms in Superplastic AA5083 materials. Metall. Mater. Trans. A, 2005, 36(5), p 1249-1261). The experimental work revealed that a transition occurs from grain-boundary sliding to dislocation (solute-drag) creep at approximately 0.001/s for temperatures between 425 and 500 °C. In addition, increasing the grain size from 7 to 10 μm decreased the transition to significantly lower strain rates. Predictions from the finite element method accurately predict the effect of grain size on the transition in deformation mechanisms.

  6. Genetic association of impulsivity in young adults: a multivariate study

    PubMed Central

    Khadka, S; Narayanan, B; Meda, S A; Gelernter, J; Han, S; Sawyer, B; Aslanzadeh, F; Stevens, M C; Hawkins, K A; Anticevic, A; Potenza, M N; Pearlson, G D

    2014-01-01

    Impulsivity is a heritable, multifaceted construct with clinically relevant links to multiple psychopathologies. We assessed impulsivity in young adult (N~2100) participants in a longitudinal study, using self-report questionnaires and computer-based behavioral tasks. Analysis was restricted to the subset (N=426) who underwent genotyping. Multivariate association between impulsivity measures and single-nucleotide polymorphism data was implemented using parallel independent component analysis (Para-ICA). Pathways associated with multiple genes in components that correlated significantly with impulsivity phenotypes were then identified using a pathway enrichment analysis. Para-ICA revealed two significantly correlated genotype–phenotype component pairs. One impulsivity component included the reward responsiveness subscale and behavioral inhibition scale of the Behavioral-Inhibition System/Behavioral-Activation System scale, and the second impulsivity component included the non-planning subscale of the Barratt Impulsiveness Scale and the Experiential Discounting Task. Pathway analysis identified processes related to neurogenesis, nervous system signal generation/amplification, neurotransmission and immune response. We identified various genes and gene regulatory pathways associated with empirically derived impulsivity components. Our study suggests that gene networks implicated previously in brain development, neurotransmission and immune response are related to impulsive tendencies and behaviors. PMID:25268255

  7. Benchmark solution of the dynamic response of a spherical shell at finite strain

    SciTech Connect

    Versino, Daniele; Brock, Jerry S.

    2016-09-28

    Our paper describes the development of high fidelity solutions for the study of homogeneous (elastic and inelastic) spherical shells subject to dynamic loading and undergoing finite deformations. The goal of the activity is to provide high accuracy results that can be used as benchmark solutions for the verification of computational physics codes. Furthermore, the equilibrium equations for the geometrically non-linear problem are solved through mode expansion of the displacement field and the boundary conditions are enforced in a strong form. Time integration is performed through high-order implicit Runge–Kutta schemes. Finally, we evaluate accuracy and convergence of the proposed method by means of numerical examples with finite deformations and material non-linearities and inelasticity.

  8. Benchmark solution of the dynamic response of a spherical shell at finite strain

    DOE PAGES

    Versino, Daniele; Brock, Jerry S.

    2016-09-28

    Our paper describes the development of high fidelity solutions for the study of homogeneous (elastic and inelastic) spherical shells subject to dynamic loading and undergoing finite deformations. The goal of the activity is to provide high accuracy results that can be used as benchmark solutions for the verification of computational physics codes. Furthermore, the equilibrium equations for the geometrically non-linear problem are solved through mode expansion of the displacement field and the boundary conditions are enforced in a strong form. Time integration is performed through high-order implicit Runge–Kutta schemes. Finally, we evaluate accuracy and convergence of the proposed method bymore » means of numerical examples with finite deformations and material non-linearities and inelasticity.« less

  9. Benchmark solution of the dynamic response of a spherical shell at finite strain

    SciTech Connect

    Versino, Daniele; Brock, Jerry S.

    2016-09-28

    Our paper describes the development of high fidelity solutions for the study of homogeneous (elastic and inelastic) spherical shells subject to dynamic loading and undergoing finite deformations. The goal of the activity is to provide high accuracy results that can be used as benchmark solutions for the verification of computational physics codes. Furthermore, the equilibrium equations for the geometrically non-linear problem are solved through mode expansion of the displacement field and the boundary conditions are enforced in a strong form. Time integration is performed through high-order implicit Runge–Kutta schemes. Finally, we evaluate accuracy and convergence of the proposed method by means of numerical examples with finite deformations and material non-linearities and inelasticity.

  10. Fractionating impulsivity: contrasting effects of central 5-HT depletion on different measures of impulsive behavior.

    PubMed

    Winstanley, Catharine A; Dalley, Jeffrey W; Theobald, David E H; Robbins, Trevor W

    2004-07-01

    Reducing levels of 5-HT in the central nervous system has been associated with increases in impulsive behavior. However, the impulsivity construct describes a wide range of behaviors, including the inability to withhold a response, intolerance to delay of reward and perseveration of a nonrewarded response. Although these behaviors are generally studied using instrumental paradigms, impulsivity may also be reflected in simple Pavlovian tasks such as autoshaping and conditioned activity. This experiment aimed to characterize further the effects of central 5-HT depletion and to investigate whether different behavioral measures of impulsivity are inter-related, thus validating the construct. Rats received intracerebroventricular (ICV) infusions of vehicle (n=10) or the serotonergic neurotoxin 5,7-dihydroxytryptamine (n=12) which depleted forebrain 5-HT levels by about 90%. Lesioned animals showed significant increases in the speed and number of responses made in autoshaping, increased premature responding on a simple visual attentional task, enhanced expression of locomotor activity conditioned to food presentation, yet no change in impulsive choice was observed, as measured by a delay-discounting paradigm. Significant positive correlations were found between responses made in autoshaping and the level of conditioned activity, indicating a possible common basis for these behaviors, yet no correlations were found between other behavioral measures. These data strengthen and extend the hypothesis that 5-HT depletion increases certain types of impulsive responding. However, not all measures of impulsivity appear to be uniformly affected by 5-HT depletion, or correlate with each other, supporting the suggestion that impulsivity is not a unitary construct.

  11. Food intake in response to food-cue exposure. Examining the influence of duration of the cue exposure and trait impulsivity.

    PubMed

    Larsen, Junilla K; Hermans, Roel C J; Engels, Rutger C M E

    2012-06-01

    The present study experimentally tested whether the effect of olfactory food-cue exposure on young women's food intake was moderated by the duration of the cue exposure and trait impulsivity. The study employed a 2 (food-cue exposure: smell of baked cookies present vs. no-smell present) by 2 (duration of cue exposure: short-term vs. long-term) between-participants design. Participants were 109 normal-weight young women (mean age=21.6 years) whose food intake was examined during a bogus taste-test. Additional saliva measures were taken during food-cue exposure. Results showed that the duration of the cue exposure did not affect intake. Impulsivity moderated intake, but not saliva flow. Low impulsive females consumed more food when confronted with an olfactory food-cue, whereas high-impulsive females did not eat more after food-cue exposure. Our findings may be explained by the fact that we did not instruct our participants to pay attention to the olfactory food-cue. Results indicate that even people who are normally well controlled are susceptible to the effects of less explicit olfactory food-cues. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Eyes wide shopped: shopping situations trigger arousal in impulsive buyers.

    PubMed

    Serfas, Benjamin G; Büttner, Oliver B; Florack, Arnd

    2014-01-01

    The present study proposes arousal as an important mechanism driving buying impulsiveness. We examined the effect of buying impulsiveness on arousal in non-shopping and shopping contexts. In an eye-tracking experiment, we measured pupil dilation while participants viewed and rated pictures of shopping scenes and non-shopping scenes. The results demonstrated that buying impulsiveness is closely associated with arousal as response to viewing pictures of shopping scenes. This pertained for hedonic shopping situations as well as for utilitarian shopping situations. Importantly, the effect did not emerge for non-shopping scenes. Furthermore, we demonstrated that arousal of impulsive buyers is independent from cognitive evaluation of scenes in the pictures.

  13. Impulsive action and motivation.

    PubMed

    Frijda, Nico H

    2010-07-01

    This paper explores the way in which emotions are causal determinants of action. It argues that emotional events, as appraised by the individual, elicit changes in motive states (called states of action readiness), which in turn may (or may not) cause action. Actions can be elicited automatically, without prior intention (called impulsive actions), or intentionally. Impulsive actions reflect the simplest and biologically most general form in which emotions can cause action, since they require no reflection, no foresight, and no planning. Impulsive actions are determined conjointly by the nature of action readiness, the affordances perceived in the eliciting event as appraised, and the individual's action repertoire. Those actions from one's repertoire are performed that both match the perceived affordances and the aim of the state of action readiness. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. Ballistic impulse gauge

    DOEpatents

    Ault, S.K.

    1993-12-21

    A gauge for detecting the impulse generated in sample materials by X-rays or other impulse producing mechanisms utilizes a pair of flat annular springs to support a plunger relative to a housing which may itself be supported by a pair of flat annular springs in a second housing. The plunger has a mounting plate mounted on one end and at the other, a position or velocity transducer is mounted. The annular springs consist of an outer ring and an inner ring with at least three arcuate members connecting the outer ring with the inner ring. 4 figures.

  15. Endeavour Impulse Tests

    NASA Image and Video Library

    2003-10-27

    In the Orbiter Processing Facility, Eric Madaras, NASA-Langley Research Center, conducts impulse tests on the right wing leading edge (WLE) of Space Shuttle Endeavour. The tests monitor how sound impulses propagate through the WLE area. The data collected will be analyzed to explore the possibility of adding new instrumentation to the wing that could automatically detect debris or micrometeroid impacts on the Shuttle while in flight. The study is part of the initiative ongoing at KSC and around the agency to return the orbiter fleet to flight status.

  16. Ballistic impulse gauge

    DOEpatents

    Ault, Stanley K.

    1993-01-01

    A gauge for detecting the impulse generated in sample materials by X-rays or other impulse producing mechanisms utilizes a pair of flat annular springs to support a plunger relative to a housing which may itself be supported by a pair of flat annular springs in a second housing. The plunger has a mounting plate mounted on one end and at the other, a position or velocity transducer is mounted. The annular springs consist of an outer ring and an inner ring with at least three arcuate members connecting the outer ring with the inner ring.

  17. Sensitivity Analysis of Flutter Response of a Wing Incorporating Finite-Span Corrections

    NASA Technical Reports Server (NTRS)

    Issac, Jason Cherian; Kapania, Rakesh K.; Barthelemy, Jean-Francois M.

    1994-01-01

    Flutter analysis of a wing is performed in compressible flow using state-space representation of the unsteady aerodynamic behavior. Three different expressions are used to incorporate corrections due to the finite-span effects of the wing in estimating the lift-curve slope. The structural formulation is based on a Rayleigh-Pitz technique with Chebyshev polynomials used for the wing deflections. The aeroelastic equations are solved as an eigen-value problem to determine the flutter speed of the wing. The flutter speeds are found to be higher in these cases, when compared to that obtained without accounting for the finite-span effects. The derivatives of the flutter speed with respect to the shape parameters, namely: aspect ratio, area, taper ratio and sweep angle, are calculated analytically. The shape sensitivity derivatives give a linear approximation to the flutter speed curves over a range of values of the shape parameter which is perturbed. Flutter and sensitivity calculations are performed on a wing using a lifting-surface unsteady aerodynamic theory using modules from a system of programs called FAST.

  18. Coronary stent strut size dependent stress-strain response investigated using micromechanical finite element models.

    PubMed

    Savage, P; O'Donnell, B P; McHugh, P E; Murphy, B P; Quinn, D F

    2004-02-01

    Cardiovascular stents are metal scaffolds that are used in the treatment of atherosclerosis. These devices are typically composed of very thin struts (< or = 100 microm thickness, for coronary applications). At this size-scale the question arises as to the suitability of using bulk material properties in stent design. This paper investigates the use of finite element analysis to predict the mechanical failure of stent struts, typical of the strut size used in coronary stents. 316 L stainless steel in uniaxial loading was considered. To accurately represent the constitutive behavior of the material at this size-scale, a computational micromechanics approach was taken involving an explicit representation of the grain structure in the steel struts, and the use of crystal plasticity theory to represent the constitutive behavior of the individual grains. The development of the finite element models is discussed and results are presented for the predictions of tensile mechanical behavior as a function of strut thickness. The results showed that using this modelling approach, a size effect, already seen experimentally, is produced. This has significant implications for stent design, especially in the context of the desire to produce smaller stents for small bore neurovascular and peripheral artery applications.

  19. A modified impulse-response representation of the global near-surface air temperature and atmospheric concentration response to carbon dioxide emissions

    NASA Astrophysics Data System (ADS)

    Millar, Richard J.; Nicholls, Zebedee R.; Friedlingstein, Pierre; Allen, Myles R.

    2017-06-01

    Projections of the response to anthropogenic emission scenarios, evaluation of some greenhouse gas metrics, and estimates of the social cost of carbon often require a simple model that links emissions of carbon dioxide (CO2) to atmospheric concentrations and global temperature changes. An essential requirement of such a model is to reproduce typical global surface temperature and atmospheric CO2 responses displayed by more complex Earth system models (ESMs) under a range of emission scenarios, as well as an ability to sample the range of ESM response in a transparent, accessible and reproducible form. Here we adapt the simple model of the Intergovernmental Panel on Climate Change 5th Assessment Report (IPCC AR5) to explicitly represent the state dependence of the CO2 airborne fraction. Our adapted model (FAIR) reproduces the range of behaviour shown in full and intermediate complexity ESMs under several idealised carbon pulse and exponential concentration increase experiments. We find that the inclusion of a linear increase in 100-year integrated airborne fraction with cumulative carbon uptake and global temperature change substantially improves the representation of the response of the climate system to CO2 on a range of timescales and under a range of experimental designs.

  20. Impulsivity, frontal lobes and risk for addiction.

    PubMed

    Crews, Fulton Timm; Boettiger, Charlotte Ann

    2009-09-01

    Alcohol and substance abuse disorders involve continued use of substances despite negative consequences, i.e. loss of behavioral control of drug use. The frontal-cortical areas of the brain oversee behavioral control through executive functions. Executive functions include abstract thinking, motivation, planning, attention to tasks and inhibition of impulsive responses. Impulsiveness generally refers to premature, unduly risky, poorly conceived actions. Dysfunctional impulsivity includes deficits in attention, lack of reflection and/or insensitivity to consequences, all of which occur in addiction [Evenden JL. Varieties of impulsivity. Psychopharmacology (Berl) 1999;146:348-361.; de Wit H. Impulsivity as a determinant and consequence of drug use: a review of underlying processes. Addict Biol 2009;14:22-31]. Binge drinking models indicate chronic alcohol damages in the corticolimbic brain regions [Crews FT, Braun CJ, Hoplight B, Switzer III RC, Knapp DJ. Binge ethanol consumption causes differential brain damage in young adolescent rats compared with adult rats. Alcohol Clin Exp Res 2000;24:1712-1723] causing reversal learning deficits indicative of loss of executive function [Obernier JA, White AM, Swartzwelder HS, Crews FT. Cognitive deficits and CNS damage after a 4-day binge ethanol exposure in rats. Pharmacol Biochem Behav 2002b;72:521-532]. Genetics and adolescent age are risk factors for alcoholism that coincide with sensitivity to alcohol-induced neurotoxicity. Cortical degeneration from alcohol abuse may increase impulsivity contributing to the development, persistence and severity of alcohol use disorders. Interestingly, abstinence results in bursts of neurogenesis and brain regrowth [Crews FT, Nixon K. Mechanisms of neurodegeneration and regeneration in alcoholism. Alcohol Alcohol 2009;44:115-127]. Treatments for alcoholism, including naltrexone pharmacotherapy and psychotherapy may work through improving executive functions. This review will examine the

  1. Relativistic impulse dynamics.

    PubMed

    Swanson, Stanley M

    2011-08-01

    Classical electrodynamics has some annoying rough edges. The self-energy of charges is infinite without a cutoff. The calculation of relativistic trajectories is difficult because of retardation and an average radiation reaction term. By reconceptuallizing electrodynamics in terms of exchanges of impulses rather than describing it by forces and potentials, we eliminate these problems. A fully relativistic theory using photonlike null impulses is developed. Numerical calculations for a two-body, one-impulse-in-transit model are discussed. A simple relationship between center-of-mass scattering angle and angular momentum was found. It reproduces the Rutherford cross section at low velocities and agrees with the leading term of relativistic distinguishable-particle quantum cross sections (Møller, Mott) when the distance of closest approach is larger than the Compton wavelength of the particle. Magnetism emerges as a consequence of viewing retarded and advanced interactions from the vantage point of an instantaneous radius vector. Radiation reaction becomes the local conservation of energy-momentum between the radiating particle and the emitted impulse. A net action is defined that could be used in developing quantum dynamics without potentials. A reinterpretation of Newton's laws extends them to relativistic motion.

  2. Impulse radar studfinder

    DOEpatents

    McEwan, T.E.

    1995-10-10

    An impulse radar studfinder propagates electromagnetic pulses and detects reflected pulses from a fixed range. Unmodulated pulses, about 200 ps wide, are emitted. A large number of reflected pulses are sampled and averaged. Background reflections are subtracted. Reflections from wall studs or other hidden objects are detected and displayed using light emitting diodes. 9 figs.

  3. Impulse radar studfinder

    DOEpatents

    McEwan, Thomas E.

    1995-01-01

    An impulse radar studfinder propagates electromagnetic pulses and detects reflected pulses from a fixed range. Unmodulated pulses, about 200 ps wide, are emitted. A large number of reflected pulses are sampled and averaged. Background reflections are subtracted. Reflections from wall studs or other hidden objects are detected and displayed using light emitting diodes.

  4. Non-linear finite element analysis for prediction of seismic response of buildings considering soil-structure interaction

    NASA Astrophysics Data System (ADS)

    Çelebi, E.; Göktepe, F.; Karahan, N.

    2012-11-01

    The objective of this paper focuses primarily on the numerical approach based on two-dimensional (2-D) finite element method for analysis of the seismic response of infinite soil-structure interaction (SSI) system. This study is performed by a series of different scenarios that involved comprehensive parametric analyses including the effects of realistic material properties of the underlying soil on the structural response quantities. Viscous artificial boundaries, simulating the process of wave transmission along the truncated interface of the semi-infinite space, are adopted in the non-linear finite element formulation in the time domain along with Newmark's integration. The slenderness ratio of the superstructure and the local soil conditions as well as the characteristics of input excitations are important parameters for the numerical simulation in this research. The mechanical behavior of the underlying soil medium considered in this prediction model is simulated by an undrained elasto-plastic Mohr-Coulomb model under plane-strain conditions. To emphasize the important findings of this type of problems to civil engineers, systematic calculations with different controlling parameters are accomplished to evaluate directly the structural response of the vibrating soil-structure system. When the underlying soil becomes stiffer, the frequency content of the seismic motion has a major role in altering the seismic response. The sudden increase of the dynamic response is more pronounced for resonance case, when the frequency content of the seismic ground motion is close to that of the SSI system. The SSI effects under different seismic inputs are different for all considered soil conditions and structural types.

  5. A Generalized Finite Element Formulation for 3D Microscale Simulation of the Response of Heterogeneous Materials to Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Robbins, Joshua; Voth, Thomas

    2009-06-01

    Most engineering materials exhibit significant heterogeneity at the microscale due to polycrystalline and/or multi-phase structure, inclusions, voids, and micro-cracks. Much of the complex, nonlinear response observed in these materials originates at this length scale. The Generalized Finite Element Method (GFEM) greatly simplifies explicit treatment of material microstructure [1] by allowing for non-conformal discretization without loss of accuracy. We present our application of the GFEM to examine the dynamic response of polycrystalline materials at the microscale. The microstructure is approximated with a Voronoi tessellation, and the material basis of each resulting grain is selected randomly. An anisotropic single crystal constitutive model is applied in the local basis. The method has been implemented for massively parallel computation using a geometric decomposition and the Message Passing Interface (MPI) standard. [1] Simone A., Duarte C.A., Van der Giessen E., 2006, ``A generalized finite element method for polycrystals with discontinuous grain boundaries,'' Int. J. Numer. Methods Eng., 67, pp. 1122-1145. (Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.)

  6. Energetics of impulsive solar flares: Correlating BATSE hard x-ray bursts and the solar atmosphere's soft x-ray response

    NASA Technical Reports Server (NTRS)

    Newton, Elizabeth

    1996-01-01

    This investigation has involved the correlation of BATSE-observed solar hard X-ray emission with the characteristics of soft X-ray emitting plasma observed by the Yohkoh Bragg Crystal Spectrometers. The goal was to test the hypothesis that localized electron beam heating is the dominant energy transport mechanism in impulsive flares, as formulated in the thick-target electron-heated model of Brown.

  7. Impulse response of nonlinear Schrödinger equation and its implications for pre-dispersed fiber-optic communication systems.

    PubMed

    Kumar, Shiva; Shao, Jing; Liang, Xiaojun

    2014-12-29

    In the presence of pre-dispersion, an exact solution of nonlinear Schrödinger equation (NLSE) is derived for impulse input. The phase factor of the exact solution is obtained in a closed form using the exponential integral. The nonlinear interaction among periodically placed impulses launched at the input is investigated, and the condition under which these pulses do not exchange energy is examined. It is found that if the complex weights of the impulses at the input have a secant-hyperbolic envelope and a proper chirp factor, they will propagate over long distances without exchanging energy. To describe their interaction, a discrete version of NLSE is derived. The derived equation is a form of discrete self-trapping (DST) equation, which is found to admit fundamental and higher order soliton solutions in the presence of high pre-dispersion. Nonlinear eigenmodes derived here may be useful for description of signal propagation and nonlinear interaction in highly pre-dispersion fiber-optic systems.

  8. Finite Element Simulation of the Response of No-Tension Materials

    NASA Astrophysics Data System (ADS)

    Alipour, Alieh; Scarpas, Tom

    Unbound granular materials that are used at base layer of flexible pavement cannot resist tensile forces. These materials are called no-tension materials. In this paper, a modified strain-energy function was used to describe the constitutive behavior of granular materials to simulate flexible pavement within the finite element framework CAPA3D .The constitutive model was defined such that the positive stresses in principal directions were zero. Comparisons between the no-tension materials and linear elastic materials for different boundary conditions and geometries were presented in this paper. The results of FE analysis show that effect of using no-tension model for base layer on pavement performance is significant. The deformation at top and horizontal strain at the bottom of asphalt concrete layer are higher when the no-tension model is used.

  9. Finite-size effects on the magnetoelectric response of field-driven ferroelectric/ferromagnetic chains

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Sukhov, Alexander; Horley, Paul P.; Berakdar, Jamal

    2011-07-01

    We study theoretically the coupled multiferroic dynamics of a finite one-dimensional ferroelectric/ferromagnet chain driven by harmonic magnetic and electric fields as a function of the chain length. We consider the case of a linear magnetoelectric coupling that results from the spin-polarized screening charge at the interface. We performed Monte-Carlo simulations and calculations based on the coupled Landau-Lifshitz-Gilbert and Landau-Khalatnikov equations showing that the net magnetization and the total polarization of thin heterostructures, i.e. with up to ten ferroelectric and ferromagnetic sites counted from the interface, can be completely reversed by external electric and magnetic fields, respectively. However, for larger systems merely a limited magnetoelectrical control is achievable.

  10. EARTHQUAKE RESPONSE ANALYSIS OF STEEL PORTAL FRAMES BY PSEUDODYNAMIC SIMULATION TECHNIQUE USING A GENERAL-PURPOSE FINITE ELEMENT ANALYSIS PROGRAM

    NASA Astrophysics Data System (ADS)

    Miki, Toshihiro; Mizusawa, Tomisaku; Yamada, Osamu; Toda, Tomoki

    This paper studies the earthquake response of steel portal frames when the shear collapse occurs at the centre of the beam. The pseudodynamic simulation technique for the earthquake response analysis of the frames is developed in correspondence to the pseudodynamic substructure testing method. For the thin-walled box element under shear force in the middle of beam, the numerical process is utilized by a general-purpose finite element analysis program. The numerical results show the shear collapse behaviour in stiffened box beams and corresponding restoring force - displacement relationship of frames. The advantages of shear collapse of beams for the use in frames during earthquakes are discussed from the point of view of the hysteretic energy dissipated by the column base.

  11. A finite element model technique to determine the mechanical response of a lumbar spine segment under complex loads.

    PubMed

    Tsouknidas, Alexander; Michailidis, Nikoalos; Savvakis, Savvas; Anagnostidis, Kleovoulos; Bouzakis, Konstantinos-Dionysios; Kapetanos, Georgios

    2012-08-01

    This study presents a CT-based finite element model of the lumbar spine taking into account all function-related boundary conditions, such as anisotropy of mechanical properties, ligaments, contact elements, mesh size, etc. Through advanced mesh generation and employment of compound elements, the developed model is capable of assessing the mechanical response of the examined spine segment for complex loading conditions, thus providing valuable insight on stress development within the model and allowing the prediction of critical loading scenarios. The model was validated through a comparison of the calculated force-induced inclination/deformation and a correlation of these data to experimental values. The mechanical response of the examined functional spine segment was evaluated, and the effect of the loading scenario determined for both vertebral bodies as well as the connecting intervertebral disc.

  12. Mechanical responses of the periodontal ligament based on an exponential hyperelastic model: a combined experimental and finite element method.

    PubMed

    Huang, Huixiang; Tang, Wencheng; Yan, Bin; Wu, Bin; Cao, Dan

    2016-01-01

    The V-W exponential hyperelastic model is adopted to describe the instantaneous elastic response of the periodontal ligament (PDL). The general theoretical framework of constitutive modeling is described based on nonlinear continuum mechanics, and the elasticity tensor used to develop UMAT subroutine is formulated. Nanoindentation experiment is performed to characterize mechanical properties of an adult pig PDL specimen. Then the experiment is simulated by using the finite element (FE) analysis. Meanwhile, the optimized material parameters are identified by the inverse FE method. The good agreement between the simulated results and experimental data demonstrates that the V-W model is capable of describing the mechanical behavior of the PDL. Therefore, the model and its implementation into FE code are validated. By using the model, we simulate the tooth movement under orthodontic loading to predict the mechanical responses of the PDL. The results show that local concentrations of stress and strain in the PDL are found.

  13. The application of finite element analysis to investigate the vibrational response of a turbine blade under thermosonic excitation

    NASA Astrophysics Data System (ADS)

    Bolu, Gabriel; Gachagan, Anthony; Pierce, Gareth; Barden, Tim

    2013-01-01

    This paper presents a methodology, using a combination of experimental vibration measurements and finite element analysis (FEA), to model the vibrational energy within a turbine blade corresponding to a typical thermosonic inspection scenario. Laser vibrometry measurements were used to determine the steady-state vibration response at several locations on a blade and used to identify the prominent spectral components. These were then used to generate an excitation function for the FEA approach. After validation of the FEA model, the vibration response across the whole blade was simulated. Finally, the predicted displacement field was used to determine the vibrational energy at every point on the blade which was mapped onto a CAD representation of the blade, thereby highlighting areas on the blade that may be below the defect detection threshold.

  14. CONV--convolution for responses to a finite diameter photon beam incident on multi-layered tissues.

    PubMed

    Wang, L; Jacques, S L; Zheng, L

    1997-11-01

    A convolution program (CONV) solving responses to a collimated finite diameter photon beam perpendicularly incident on a multi-layered tissue has been coded in ANSI Standard C, hence, the program can be executed on various computers. The program, employing an extended trapezoidal rule for integration, convolves the responses to an infinitely narrow photon beam computed by a companion program (MCML). Dynamic data allocation is used for CONV as well as MCML, therefore, the number of tissue layers and grid elements of the grid system can be varied at run time. The potential error due to not scoring the first photon-tissue interactions separately is illustrated. The program, including the source code, has been in the public domain since 1992 and can be downloaded from the web site at http:(/)/biomed.tamu.edu/-lw.

  15. Does impulse noise induce vestibular disturbances?

    PubMed

    Pyykkö, I; Aalto, H; Ylikoski, J

    1989-01-01

    The effect of impulse noise on postural stability was evaluated in 54 subjects from the Finnish army, who were suffering from acute hearing loss caused by exposure to firearms noise. For referents we used 20 non-exposed army recruits and 39 civilian volunteers. The effects of vision, pressoreceptor function and proprioception were stepwise excluded or altered, leaving mainly the vestibular guidance of postural control intact. Since the postural perturbation was fairly smooth during these instances we assume that the condition evaluates mainly the function of the otolith organs in guiding stance. We found no difference in any of the test conditions used, between normal controls, army controls and impulse noise exposed subjects. Furthermore, there was no dose response with body sway and severity of hearing loss. The results indicate that impulse noise may not be the cause of significant functional changes in the vestibular system that can account for noise-induced postural instability.

  16. Annoyance of helicopter impulsive noise

    NASA Technical Reports Server (NTRS)

    Dambra, F.; Damongeot, A.

    1978-01-01

    Psychoacoustic studies of helicopter impulsive noise were conducted in order to qualify additional annoyance due to this feature and to develop physical impulsiveness descriptors to develop impulsivity correction methods. The currently proposed descriptors and methods of impulsiveness correction are compared using a multilinear regression analysis technique. It is shown that the presently recommended descriptor and correction method provides the best correlation with the subjective evaluations of real helicopter impulsive noises. The equipment necessary for data processing in order to apply the correction method is discussed.

  17. Childhood Symptoms of ADHD and Impulsivity in Abstinent Heroin Users.

    PubMed

    Segalà, Laura; Vasilev, Georgi; Raynov, Ivaylo; Gonzalez, Raul; Vassileva, Jasmin

    2015-01-01

    Heroin dependence is associated with deficits in impulsivity, which is also a core feature of attention deficit hyperactivity disorder (ADHD). This study aimed to explore the association between childhood ADHD symptoms and cognitive and motor impulsivity among abstinent individuals with a history of heroin dependence. Thirty-two abstinent Bulgarian males with a history of heroin dependence participated in the study. Self-rated childhood ADHD symptoms were obtained using the Wender-Utah Rating Scale. Cognitive impulsivity was measured using the Iowa Gambling Task (IGT), an index of impulsive decision making, and the Delayed Reward Discounting Task (DRDT), a measure of intertemporal choice. Motor impulsivity was indexed with the Stop Signal Task (SST), a measure of response inhibition. Participants, whose average age was 27.66 years (SD = 2.7), had an average ADHD symptom score of 36.6 (SD = 18.6), had roughly 7 years (SD = 2.9) of heroin use, and had been abstinent for just over a year (M = 402.5 days, SD = 223.8). Linear regression analyses revealed that self-reported ADHD symptoms predicted impulsive decision making (IGT), but not delayed discounting (DRDT) or response inhibition (SST). Self-reported childhood ADHD symptoms do not uniformly predict impulsivity among abstinent individuals with heroin dependence. Results suggest the IGT may be more sensitive to externalizing psychopathology among individuals with heroin dependence than other measures of impulsivity.

  18. Steep front short duration low voltage impulse performance of distribution transformers

    SciTech Connect

    Burrage, L.M.; Veverka, E.F.; McConnell, B.W.

    1987-01-01

    An extensive literature search of steep front short duration (SFSD) impulse sources, their characteristics and effect on power system equipment has led to the specification of a test program to evaluate key apparatus and insulations. Distribution transformers, although not overly susceptible to impulse damage, have been selected as one of the candidate apparatus for low and high voltage SFSD impulse tests. This paper covers the low voltage SFSD impulse response of conventional oil insulated shell form and core form distribution transformers.

  19. A Coupled Experiment-finite Element Modeling Methodology for Assessing High Strain Rate Mechanical Response of Soft Biomaterials

    PubMed Central

    Prabhu, Rajkumar; Whittington, Wilburn R.; Patnaik, Sourav S.; Mao, Yuxiong; Begonia, Mark T.; Williams, Lakiesha N.; Liao, Jun; Horstemeyer, M. F.

    2015-01-01

    This study offers a combined experimental and finite element (FE) simulation approach for examining the mechanical behavior of soft biomaterials (e.g. brain, liver, tendon, fat, etc.) when exposed to high strain rates. This study utilized a Split-Hopkinson Pressure Bar (SHPB) to generate strain rates of 100-1,500 sec-1. The SHPB employed a striker bar consisting of a viscoelastic material (polycarbonate). A sample of the biomaterial was obtained shortly postmortem and prepared for SHPB testing. The specimen was interposed between the incident and transmitted bars, and the pneumatic components of the SHPB were activated to drive the striker bar toward the incident bar. The resulting impact generated a compressive stress wave (i.e. incident wave) that traveled through the incident bar. When the compressive stress wave reached the end of the incident bar, a portion continued forward through the sample and transmitted bar (i.e. transmitted wave) while another portion reversed through the incident bar as a tensile wave (i.e. reflected wave). These waves were measured using strain gages mounted on the incident and transmitted bars. The true stress-strain behavior of the sample was determined from equations based on wave propagation and dynamic force equilibrium. The experimental stress-strain response was three dimensional in nature because the specimen bulged. As such, the hydrostatic stress (first invariant) was used to generate the stress-strain response. In order to extract the uniaxial (one-dimensional) mechanical response of the tissue, an iterative coupled optimization was performed using experimental results and Finite Element Analysis (FEA), which contained an Internal State Variable (ISV) material model used for the tissue. The ISV material model used in the FE simulations of the experimental setup was iteratively calibrated (i.e. optimized) to the experimental data such that the experiment and FEA strain gage values and first invariant of stresses were in good

  20. Active control of the forced and transient response of a finite beam. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Post, John T.

    1990-01-01

    Structural vibrations from a point force are modelled on a finite beam. This research explores the theoretical limit on controlling beam vibrations utilizing another point source as an active controller. Three different types of excitation are considered, harmonic, random, and transient. For harmonic excitation, control over the entire beam length is possible only when the excitation frequency is near a resonant frequency of the beam. Control over a subregion may be obtained even between resonant frequencies at the cost of increasing the vibration outside of the control region. For random excitation, integrating the expected value of the displacement squared over the required interval, is shown to yield the identical cost function as obtained by integrating the cost function for harmonic excitation over all excitation frequencies. As a result, it is always possible to reduce the cost function for random excitation whether controlling the entire beam or just a subregion, without ever increasing the vibration outside the region in which control is desired. The last type of excitation considered is a single, transient pulse. The form of the controller is specified as either one or two delayed pulses, thus constraining the controller to be casual. The best possible control is examined while varying the region of control and the controller location. It is found that control is always possible using either one or two control pulses.

  1. Micropower impulse radar imaging

    SciTech Connect

    Hall, M.S.

    1995-11-01

    From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

  2. Some inconsistencies of the finite element method as applied to inelastic response

    NASA Technical Reports Server (NTRS)

    Kamat, M. P.; Killian, D. E.

    1976-01-01

    The inadequacy of a two noded beam-column element with a linear axial and a cubic transverse displacement field for inelastic analysis is demonstrated. For complete equilibrium satisfaction in the linear elastic range a three noded beam-column element is shown to be consistent. Next, the sensitivity of the inelastic response to numerical solutions of the inelastic response of a cantilever beam resulting from approximate integration of strain energy are brought out and finally, consequences of this on the nonlinear transient response of structures are considered.

  3. Pre-attentive information processing and impulsivity in bipolar disorder.

    PubMed

    Swann, Alan C; Lijffijt, Marijn; Lane, Scott D; Steinberg, Joel L; Acas, Michelle D; Cox, Blake; Moeller, F Gerard

    2013-12-01

    Early responses to stimuli can be measured by sensory evoked potentials (EP) using repeated identical stimuli, S1 and S2. Response to S1 may represent efficient stimulus detection, while suppression of response to S2 may represent inhibition. Early responses to stimuli may be related to impulsivity. We compared EP reflecting stimulus detection and inhibition in bipolar disorder and healthy controls, and investigated relationships to impulsivity. Subjects were 48 healthy controls without family histories of mood disorder and 48 with bipolar disorder. EP were measured as latencies and amplitudes for auditory P50 (pre-attentional), N100 (initial direction of attention) and P200 (initial conscious awareness), using a paired-click paradigm, with identical stimuli 0.5 s apart. Impulsivity was measured by questionnaire and by laboratory tests for inability to suppress responses to stimuli or to delay response for a reward. Analyses used general linear models. S1 amplitudes for P50, N100, and P200, and gating of N100 and P200, were lower in bipolar disorder than in controls. P50 S1 amplitude correlated with accurate laboratory-task responding, and S2 amplitude correlated with impulsive task performance and fast reaction times, in bipolar disorder. N100 and P200 EP did not correlate with impulsivity. These findings were independent of symptoms, treatment, or substance-use history. EPs were not related to questionnaire-measured or reward-based impulsivity. Bipolar I disorder is characterized by reduced pre-attentional and early attentional stimulus registration relative to controls. Within bipolar disorder, rapid-response impulsivity correlates with impaired pre-attentional response suppression. These results imply specific relationships between ERP-measured response inhibition and rapid-response impulsivity.

  4. Nonlinear viscoelastic response of highly filled elastomers under multiaxial finite deformation

    NASA Technical Reports Server (NTRS)

    Peng, Steven T. J.; Landel, Robert F.

    1990-01-01

    A biaxial tester was used to obtain precise biaxial stress responses of highly filled, high strain capability elastomers. Stress-relaxation experiments show that the time-dependent part of the relaxation response can be reasonably approximated by a function which is strain and biaxiality independent. Thus, isochronal data from the stress-relaxation curves can be used to determine the stored energy density function. The complex behavior of the elastomers under biaxial deformation may be caused by dewetting.

  5. Waiting Impulsivity: The Influence of Acute Methylphenidate and Feedback

    PubMed Central

    Chang-Webb, Yee Chien; Morris, Laurel S.; Cooper, Ella; Sethi, Arjun; Baek, Kwangyeol; Grant, Jon; Robbins, Trevor W.; Harrison, Neil A

    2016-01-01

    Background: The ability to wait and to weigh evidence is critical to behavioral regulation. These behaviors are known as waiting and reflection impulsivity. In Study 1, we examined the effects of methylphenidate, a dopamine and norepinephrine reuptake inhibitor, on waiting and reflection impulsivity in healthy young individuals. In study 2, we assessed the role of learning from feedback in disorders of addiction. Methods: We used the recently developed 4-Choice Serial Reaction Time task and the Beads task. Twenty-eight healthy volunteers were tested twice in a randomized, double-blind, placebo-controlled cross-over trial with 20mg methylphenidate. In the second study, we analyzed premature responses as a function of prior feedback in disorders of addiction. Results: Study 1: Methylphenidate was associated with greater waiting impulsivity to a cue predicting reward along with faster responding to target onset without a generalized effect on reaction time or attention. Methylphenidate influenced reflection impulsivity based on baseline impulsivity. Study 2: More premature responses occurred after premature responses in stimulant-dependent subjects. Conclusions: We show that methylphenidate has dissociable effects on waiting and reflection impulsivity. Chronic stimulant exposure impairs learning from prior premature responses, suggesting a failure to learn that premature responding is suboptimal. These findings provide a greater mechanistic understanding of waiting impulsivity. PMID:26136351

  6. Local and linear chemical reactivity response functions at finite temperature in density functional theory

    SciTech Connect

    Franco-Pérez, Marco E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Ayers, Paul W. E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Gázquez, José L. E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx; Vela, Alberto E-mail: ayers@mcmaster.ca E-mail: avela@cinvestav.mx

    2015-12-28

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.

  7. Local and linear chemical reactivity response functions at finite temperature in density functional theory.

    PubMed

    Franco-Pérez, Marco; Ayers, Paul W; Gázquez, José L; Vela, Alberto

    2015-12-28

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.

  8. Heroin and amphetamine users display opposite relationships between trait and neurobehavioral dimensions of impulsivity

    PubMed Central

    Vassileva, Jasmin; Paxton, Jessica; Moeller, F. Gerard; Wilson, Michael; Bozgunov, Kiril; Martin, Eileen; Gonzalez, Raul; Vasilev, Georgi

    2014-01-01

    The multidimensional construct of impulsivity is implicated in all phases of the addiction cycle. Substance dependent individuals (SDIs) demonstrate elevated impulsivity on both trait and laboratory tests of neurobehavioral impulsivity; however our understanding of the relationship between these different aspects of impulsivity in users of different classes of drugs remains rudimentary. The goal of this study was to assess for commonalities and differences in the relationships between trait and neurobehavioral impulsivity in heroin and amphetamine addicts. Participants included 58 amphetamine dependent (ADI) and 74 heroin dependent individuals (HDI) in protracted abstinence. We conducted principal components analyses (PCA) on two self-report trait and six neurobehavioral measures of impulsivity, which resulted in two trait impulsivity (action, planning) and four neurobehavioral impulsivity composites (discriminability, response inhibition efficiency, decision-making efficiency, quality of decision-making). Multiple regression analyses were used to determine whether neurobehavioral impulsivity is predicted by trait impulsivity and drug type. The analyses revealed a significant interaction between drug type and trait action impulsivity on response inhibition efficiency, which showed opposite relationships for ADIs and HDIs. Specifically, increased trait action impulsivity was associated with worse response inhibition efficiency in ADIs, but with better efficiency in HDIs. These results challenge the unitary account of drug addiction and contribute to a growing body of literature that reveals important behavioral, cognitive, and neurobiological differences between users of different classes of drugs. PMID:24342174

  9. Heroin and amphetamine users display opposite relationships between trait and neurobehavioral dimensions of impulsivity.

    PubMed

    Vassileva, Jasmin; Paxton, Jessica; Moeller, F Gerard; Wilson, Michael J; Bozgunov, Kiril; Martin, Eileen M; Gonzalez, Raul; Vasilev, Georgi

    2014-03-01

    The multidimensional construct of impulsivity is implicated in all phases of the addiction cycle. Substance dependent individuals (SDIs) demonstrate elevated impulsivity on both trait and laboratory tests of neurobehavioral impulsivity; however our understanding of the relationship between these different aspects of impulsivity in users of different classes of drugs remains rudimentary. The goal of this study was to assess for commonalities and differences in the relationships between trait and neurobehavioral impulsivity in heroin and amphetamine addicts. Participants included 58 amphetamine dependent (ADIs) and 74 heroin dependent individuals (HDIs) in protracted abstinence. We conducted Principal Component Analyses (PCA) on two self-report trait and six neurobehavioral measures of impulsivity, which resulted in two trait impulsivity (action, planning) and four neurobehavioral impulsivity composites (discriminability, response inhibition efficiency, decision-making efficiency, quality of decision-making). Multiple regression analyses were used to determine whether neurobehavioral impulsivity is predicted by trait impulsivity and drug type. The analyses revealed a significant interaction between drug type and trait action impulsivity on response inhibition efficiency, which showed opposite relationships for ADIs and HDIs. Specifically, increased trait action impulsivity was associated with worse response inhibition efficiency in ADIs, but with better efficiency in HDIs. These results challenge the unitary account of drug addiction and contribute to a growing body of literature that reveals important behavioral, cognitive, and neurobiological differences between users of different classes of drugs.

  10. On the use of waveform images to describe the initial response of finite-length waveguides

    NASA Astrophysics Data System (ADS)

    Ginsberg, Jerry H.

    2005-09-01

    The d'Alembert solution of the wave equation can be adapted to describe reflection from planar boundaries. One technique for doing so images the incident wave on the opposite side of the boundary. This concept has been introduced in a few texts, most extensively by Morse and Ingard [Theoretical Acoustics, McGraw-Hill, New York (1964), pp. 106-115], but only for nondissipative ends (infinite or zero impedance.) This paper formalizes the procedure for the case where the boundary has a resistive impedance that is independent of frequency, and then extends it to treat waveguides of finite length. It is shown that the field that results from arbitrary initial conditions can be represented by an infinite number of images. This leads to a representation of the acoustic field as oppositely propagating wave in an unbounded waveguide, with only a limited number of images overlapping at any instant. Both mathematical and graphical descriptions of these waves are derived. In addition to assisting the student to understand the evolution of the field, mathematical analysis of the image construction leads to a number of physical and mathematical insights to fundamental acoustic phenomena. These include the fact that the field in the dissipationless case can be represented as a modal series with associated natural frequencies, and a quantitative understanding of the manner in which the field decays when either end is dissipative. A corollary of the latter analysis is an expression for reverberation time that is remarkably similar to the Norris-Eyring formula. From an instructional viewpoint, the fact that all results are derived without recourse to solving differential equations makes the image waveform concept especially useful as a way of introducing new students to fundamental acoustic phenomena.

  11. Development of a Finite Element Model of the Human Shoulder to Investigate the Mechanical Responses and Injuries in Side Impact

    NASA Astrophysics Data System (ADS)

    Iwamoto, Masami; Miki, Kazuo; Yang, King H.

    Previous studies in both fields of automotive safety and orthopedic surgery have hypothesized that immobilization of the shoulder caused by the shoulder injury could be related to multiple rib fractures, which are frequently life threatening. Therefore, for more effective occupant protection, it is important to understand the relationship between shoulder injury and multiple rib fractures in side impact. The purpose of this study is to develop a finite element model of the human shoulder in order to understand this relationship. The shoulder model included three bones (the humerus, scapula and clavicle) and major ligaments and muscles around the shoulder. The model also included approaches to represent bone fractures and joint dislocations. The relationships between shoulder injury and immobilization of the shoulder are discussed using model responses for lateral shoulder impact. It is also discussed how the injury can be related to multiple rib fractures.

  12. Targeting the finite-deformation response of wavy biological tissues with bio-inspired material architectures.

    PubMed

    Tu, Wenqiong; Pindera, Marek-Jerzy

    2013-12-01

    The Particle Swarm Optimization algorithm driven by a homogenized-based model is employed to target the response of three types of heart-valve chordae tendineae with different stiffening characteristics due to different degrees of waviness of collagen fibril/fiber bundles. First, geometric and material parameters are identified through an extensive parametric study that produce excellent agreement of the simulated response based on simplified unit cell architectures with the actual response of the complex biological tissue. These include amplitude and wavelength of the crimped chordae microstructure, elastic moduli of the constituent phases, and degree of microstructural refinement of the stiff phase at fixed volume fraction whose role in the stiffening response is elucidated. The study also reveals potential non-uniqueness of bio-inspired wavy microstructures in attaining the targeted response of certain chordae tendineae crimp configurations. The homogenization-based Particle Swarm Optimization algorithm, whose predictions are validated through the parametric study, is then shown to be an excellent tool in identifying optimal unit cell architectures in the design space that exhibits very steep gradients. Finally, defect criticality of optimal unit cell architectures is investigated in order to assess their feasibility in replacing actual biological tendons with stiffening characteristics.

  13. Impulse Testing of Corporate-Fed Patch Array Antennas

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil F.

    2011-01-01

    This paper discusses a novel method for detecting faults in antenna arrays. The method, termed Impulse Testing, was developed for corporate-fed patch arrays where the element is fed by a probe and is shorted at its center. Impulse Testing was devised to supplement conventional microwave measurements in order to quickly verify antenna integrity. The technique relies on exciting each antenna element in turn with a fast pulse (or impulse) that propagates through the feed network to the output port of the antenna. The resulting impulse response is characteristic of the path through the feed network. Using an oscilloscope, a simple amplitude measurement can be made to detect faults. A circuit model of the antenna elements and feed network was constructed to assess various fault scenarios and determine fault-detection thresholds. The experimental setup and impulse measurements for two patch array antennas are presented. Advantages and limitations of the technique are discussed along with applications to other antenna array topologies

  14. Functional impulsivity and reinforcement sensitivity theory.

    PubMed

    Smillie, Luke D; Jackson, Chris J

    2006-02-01

    In this article, we attempt to integrate Dickman's (1990) descriptive concept of Functional Impulsivity (FI) with Gray's (1970, 1991) Reinforcement Sensitivity Theory (RST). Specifically, we consider that FI bears great conceptual similarity to Gray's concept of reward-reactivity, which is thought to be caused by the combined effects of a Behavioral Activation System (BAS) and Behavioral Inhibition System (BIS). In our first study, we examine the construct validity and structural correlates of FI. Results indicate that FI is related positively to measures of BAS and Extraversion, negatively to measures of BIS and Neuroticism, and is separate from Psychoticism and typical trait Impulsivity, which Dickman calls Dysfunctional Impulsivity (DI). In our second study, we use a go/no-go discrimination task to examine the relationship between FI and response bias under conditions of rewarding and punishing feedback. Results indicate that FI, along with two measures of BAS, predicted the development of a response bias for the rewarded alternative. In comparison, high DI appeared to reflect indifference toward either reward or punishment. We consider how these findings might reconcile the perspectives of Gray and Dickman and help clarify the broader understanding of Impulsivity.

  15. Structural Responses and Finite Element Modeling of Hakka Tulou Rammed Earth Structures

    NASA Astrophysics Data System (ADS)

    Sranislawski, Daniel

    Hakka Tulous are rammed earth structures that have survived the effects of aging and natural elements upwards of even over a thousand years. These structures have housed the Hakka people of the Fujian Province, China in natural yet modern housing that has provided benefits over newer building materials. The key building material, rammed earth, which is used for the walls of the Hakka Tulou structures, has provided structural stability along with thermal comfort to the respective inhabitants of the Hakka Tulous. Through material testing and analysis this study has examined how the Tulou structures have maintained their structural stability while also providing thermal comfort. Reports of self healing cracks in the rammed earth walls were also analyzed for their validity in this study. The study has found that although the story of the self healing crack cannot be validated, there is reason to believe that with the existence of lime, some type of autogenous healing could occur on a small scale. The study has also found, through the use of nondestructive testing, that both the internal wooden systems (flooring, roof, and column support) and the rammed earth walls, are still structurally sound. Also, rammed earth's high thermal mass along with the use of sufficient shading has allowed for a delay release of heat energy from the walls of the Tulous, thus providing thermal comfort that can be felt during both night and day temperatures. The Hakka Tulou structures have been found to resist destruction from natural disasters such as strong earthquakes even when more modern construction has not. Through finite element modeling, this study has shown that the high volume of rammed earth used in the construction of the Hakka Tulous helps dissipate lateral force energy into much lower stresses for the rammed earth wall. This absorption of lateral force energy allows the rammed earth structures to survive even the strongest of earthquakes experienced in the region. The Hakka

  16. Active Control of the Forced and Transient Response of a Finite Beam. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Post, John Theodore

    1989-01-01

    When studying structural vibrations resulting from a concentrated source, many structures may be modelled as a finite beam excited by a point source. The theoretical limit on cancelling the resulting beam vibrations by utilizing another point source as an active controller is explored. Three different types of excitation are considered, harmonic, random, and transient. In each case, a cost function is defined and minimized for numerous parameter variations. For the case of harmonic excitation, the cost function is obtained by integrating the mean squared displacement over a region of the beam in which control is desired. A controller is then found to minimize this cost function in the control interval. The control interval and controller location are continuously varied for several frequencies of excitation. The results show that control over the entire beam length is possible only when the excitation frequency is near a resonant frequency of the beam, but control over a subregion may be obtained even between resonant frequencies at the cost of increasing the vibration outside of the control region. For random excitation, the cost function is realized by integrating the expected value of the displacement squared over the interval of the beam in which control is desired. This is shown to yield the identical cost function as obtained by integrating the cost function for harmonic excitation over all excitation frequencies. As a result, it is always possible to reduce the cost function for random excitation whether controlling the entire beam or just a subregion, without ever increasing the vibration outside the region in which control is desired. The last type of excitation considered is a single, transient pulse. A cost function representative of the beam vibration is obtained by integrating the transient displacement squared over a region of the beam and over all time. The form of the controller is chosen a priori as either one or two delayed pulses. Delays

  17. The effect of precrash velocity reduction on occupant response using a human body finite element model.

    PubMed

    Guleyupoglu, B; Schap, J; Kusano, K D; Gayzik, F S

    2017-07-04

    The objective of this study is to use a validated finite element model of the human body and a certified model of an anthropomorphic test dummy (ATD) to evaluate the effect of simulated precrash braking on driver kinematics, restraint loads, body loads, and computed injury criteria in 4 commonly injured body regions. The Global Human Body Models Consortium (GHBMC) 50th percentile male occupant (M50-O) and the Humanetics Hybrid III 50th percentile models were gravity settled in the driver position of a generic interior equipped with an advanced 3-point belt and driver airbag. Fifteen simulations per model (30 total) were conducted, including 4 scenarios at 3 severity levels: median, severe, and the U.S. New Car Assessment Program (U.S.-NCAP) and 3 extra per model with high-intensity braking. The 4 scenarios were no precollision system (no PCS), forward collision warning (FCW), FCW with prebraking assist (FCW+PBA), and FCW and PBA with autonomous precrash braking (FCW + PBA + PB). The baseline ΔV was 17, 34, and 56.4 kph for median, severe, and U.S.-NCAP scenarios, respectively, and were based on crash reconstructions from NASS/CDS. Pulses were then developed based on the assumed precrash systems equipped. Restraint properties and the generic pulse used were based on literature. In median crash severity cases, little to no risk (<10% risk for Abbreviated injury Scale [AIS] 3+) was found for all injury measures for both models. In the severe set of cases, little to no risk for AIS 3+ injury was also found for all injury measures. In NCAP cases, highest risk was typically found with No PCS and lowest with FCW + PBA + PB. In the higher intensity braking cases (1.0-1.4 g), head injury criterion (HIC), brain injury criterion (BrIC), and chest deflection injury measures increased with increased braking intensity. All other measures for these cases tended to decrease. The ATD also predicted and trended similar to the human body models predictions for both the median

  18. Skin-stringer panel normal mode response experimental data and finite element computer program documentation

    NASA Technical Reports Server (NTRS)

    Rudder, F. F., Jr.

    1971-01-01

    Detailed information is presented for the analytical and the experimental programs described in the report on Effects of Design Details on Structural Response to Acoustic Excitation, NASA CR-1959. This is a supplement to the basic report and detailed experimental data from all the specimens described in that report are discussed and presented in tabular form.

  19. Finite Element Nonlinear Random Response of Composite Panels of Arbitrary Shape to Acoustic and Thermal Loads

    DTIC Science & Technology

    1997-10-31

    and Monte Cristo , off the Italian western coast." It was Monday, when people went to work, they read this news very sadly. The jet airliner was the...domain monte carlo for nonlinear response and sonic fatigue". 13th AIAA Aeroacoustics Conference, Paper 90-3938, Tallahassee, FL, October 1990. 89

  20. Elaboration of a finite element model of pancreatic islet dielectric response to gap junction expression and insulin release.

    PubMed

    Heileman, Khalil Leon; Daoud, Jamal; Tabrizian, Maryam

    2016-12-01

    Dielectric spectroscopy could potentially be a powerful tool to monitor isolated human pancreatic islets for applications in diabetes therapy and research. Isolated intact human islets provide the most relevant means to understand the cellular and molecular mechanisms associated with diabetes. The advantages of dielectric spectroscopy for continuous islet monitoring are that it is a non-invasive, inexpensive and real-time technique. We have previously assessed the dielectric response of human islet samples during stimulation and differentiation. Because of the complex geometry of islets, analytical solutions are not sufficiently representative to provide a pertinent model of islet dielectric response. Here, we present a finite element dielectric model of a single intact islet that takes into account the tight packing of islet cells and intercellular junctions. The simulation yielded dielectric spectra characteristic of cell aggregates, similar to those produced with islets. In addition, the simulation showed that both exocytosis, such as what occurs during insulin secretion, and differential gap junction expression have significant effects on islet dielectric response. Since the progression of diabetes has some connections with dysfunctional islet gap junctions and insulin secretion, the ability to monitor these islet features with dielectric spectroscopy would benefit diabetes research. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Convergence of Galerkin truncation for dynamic response of finite beams on nonlinear foundations under a moving load

    NASA Astrophysics Data System (ADS)

    Ding, Hu; Chen, Li-Qun; Yang, Shao-Pu

    2012-05-01

    The present paper investigates the convergence of the Galerkin method for the dynamic response of an elastic beam resting on a nonlinear foundation with viscous damping subjected to a moving concentrated load. It also studies the effect of different boundary conditions and span length on the convergence and dynamic response. A train-track or vehicle-pavement system is modeled as a force moving along a finite length Euler-Bernoulli beam on a nonlinear foundation. Nonlinear foundation is assumed to be cubic. The Galerkin method is utilized in order to discretize the nonlinear partial differential governing equation of the forced vibration. The dynamic response of the beam is obtained via the fourth-order Runge-Kutta method. Three types of the conventional boundary conditions are investigated. The railway tracks on stiff soil foundation running the train and the asphalt pavement on soft soil foundation moving the vehicle are treated as examples. The dependence of the convergence of the Galerkin method on boundary conditions, span length and other system parameters are studied.

  2. Validation of Shoulder Response of Human Body Finite-Element Model (GHBMC) Under Whole Body Lateral Impact Condition.

    PubMed

    Park, Gwansik; Kim, Taewung; Panzer, Matthew B; Crandall, Jeff R

    2016-08-01

    In previous shoulder impact studies, the 50th-percentile male GHBMC human body finite-element model was shown to have good biofidelity regarding impact force, but under-predicted shoulder deflection by 80% compared to those observed in the experiment. The goal of this study was to validate the response of the GHBMC M50 model by focusing on three-dimensional shoulder kinematics under a whole-body lateral impact condition. Five modifications, focused on material properties and modeling techniques, were introduced into the model and a supplementary sensitivity analysis was done to determine the influence of each modification to the biomechanical response of the body. The modified model predicted substantially improved shoulder response and peak shoulder deflection within 10% of the observed experimental data, and showed good correlation in the scapula kinematics on sagittal and transverse planes. The improvement in the biofidelity of the shoulder region was mainly due to the modifications of material properties of muscle, the acromioclavicular joint, and the attachment region between the pectoralis major and ribs. Predictions of rib fracture and chest deflection were also improved because of these modifications.

  3. Impulse pumping modelling and simulation

    NASA Astrophysics Data System (ADS)

    Pierre, B.; Gudmundsson, J. S.

    2010-08-01

    Impulse pumping is a new pumping method based on propagation of pressure waves. Of particular interest is the application of impulse pumping to artificial lift situations, where fluid is transported from wellbore to wellhead using pressure waves generated at wellhead. The motor driven element of an impulse pumping apparatus is therefore located at wellhead and can be separated from the flowline. Thus operation and maintenance of an impulse pump are facilitated. The paper describes the different elements of an impulse pumping apparatus, reviews the physical principles and details the modelling of the novel pumping method. Results from numerical simulations of propagation of pressure waves in water-filled pipelines are then presented for illustrating impulse pumping physical principles, and validating the described modelling with experimental data.

  4. Prediction of the structural response of the femoral shaft under dynamic loading using subject-specific finite element models.

    PubMed

    Park, Gwansik; Kim, Taewung; Forman, Jason; Panzer, Matthew B; Crandall, Jeff R

    2017-08-01

    The goal of this study was to predict the structural response of the femoral shaft under dynamic loading conditions using subject-specific finite element (SS-FE) models and to evaluate the prediction accuracy of the models in relation to the model complexity. In total, SS-FE models of 31 femur specimens were developed. Using those models, dynamic three-point bending and combined loading tests (bending with four different levels of axial compression) of bare femurs were simulated, and the prediction capabilities of five different levels of model complexity were evaluated based on the impact force time histories: baseline, mass-based scaled, structure-based scaled, geometric SS-FE, and heterogenized SS-FE models. Among the five levels of model complexity, the geometric SS-FE and the heterogenized SS-FE models showed statistically significant improvement on response prediction capability compared to the other model formulations whereas the difference between two SS-FE models was negligible. This result indicated the geometric SS-FE models, containing detailed geometric information from CT images with homogeneous linear isotropic elastic material properties, would be an optimal model complexity for prediction of structural response of the femoral shafts under the dynamic loading conditions. The average and the standard deviation of the RMS errors of the geometric SS-FE models for all the 31 cases was 0.46 kN and 0.66 kN, respectively. This study highlights the contribution of geometric variability on the structural response variation of the femoral shafts subjected to dynamic loading condition and the potential of geometric SS-FE models to capture the structural response variation of the femoral shafts.

  5. Impulsive action and impulsive choice across substance and behavioral addictions: cause or consequence?

    PubMed

    Grant, Jon E; Chamberlain, Samuel R

    2014-11-01

    Substance use disorders are prevalent and debilitating. Certain behavioral syndromes ('behavioral addictions') characterized by repetitive habits, such as gambling disorder, stealing, shopping, and compulsive internet use, may share clinical, co-morbid, and neurobiological parallels with substance addictions. This review considers overlap between substance and behavioral addictions with a particular focus on impulsive action (inability to inhibit motor responses), and impulsive choice (preference for immediate smaller rewards to the detriment of long-term outcomes). We find that acute consumption of drugs with abuse potential is capable of modulating impulsive choice and action, although magnitude and direction of effect appear contingent on baseline function. Many lines of evidence, including findings from meta-analyses, show an association between chronic drug use and elevated impulsive choice and action. In some instances, elevated impulsive choice and action have been found to predate the development of substance use disorders, perhaps signifying their candidacy as objective vulnerability markers. Research in behavioral addictions is preliminary, and has mostly focused on impulsive action, finding this to be elevated versus controls, similar to that seen in chronic substance use disorders. Only a handful of imaging studies has explored the neural correlates of impulsive action and choice across these disorders. Key areas for future research are highlighted along with potential implications in terms of neurobiological models and treatment. In particular, future work should further explore whether the cognitive deficits identified are state or trait in nature: i.e. are evident before addiction perhaps signaling risk; or are a consequence of repetitive engagement in habitual behavior; and effects of novel agents known to modulate these cognitive abilities on various addictive disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Micropower impulse radar

    SciTech Connect

    Azevedo, S.; McEwan, T.E.

    1996-01-01

    Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s Laser Directorate stem from Nova`s transient digitizer. The MIR`s extraordinary range of applications include security, search and rescue, life support, nondestructive evaluation, and transportation.

  7. Ventral–striatal responsiveness during reward anticipation in ADHD and its relation to trait impulsivity in the healthy population: A meta-analytic review of the fMRI literature

    PubMed Central

    Plichta, Michael M.; Scheres, Anouk

    2013-01-01

    A review of the existing functional magnetic resonance imaging (fMRI) studies on reward anticipation in patients with attention-deficit/hyperactivity disorder (ADHD) is provided. Meta-analysis showed a significant medium effect size (Cohen’s d = 0.48–0.58) in terms of ventral–striatal (VS)-hyporesponsiveness in ADHD. Studies on VS-responsiveness and trait impulsivity in the healthy population demonstrate the opposite relationship, i.e. impulsivity-scores positively correlated with VS activation during reward processing. Against the background that ADHD may represent an extreme on a continuum of normal variability, the question arises as to how these contrasting findings can be integrated. We discuss three theoretical approaches, each of which integrates the opposing findings: (1) an inverted-u-shape model; (2) a (genetic) moderator model; and (3) the “unrelated model”. We conclude that at the present stage the number of existing studies in the healthy population as well as in ADHD groups is too small for a final answer. Therefore, our presented integrative approaches should be understood as an attempt to frame future research directions by generating testable hypotheses and giving practical suggestions for future studies. PMID:23928090

  8. Ventral-striatal responsiveness during reward anticipation in ADHD and its relation to trait impulsivity in the healthy population: a meta-analytic review of the fMRI literature.

    PubMed

    Plichta, Michael M; Scheres, Anouk

    2014-01-01

    A review of the existing functional magnetic resonance imaging (fMRI) studies on reward anticipation in patients with attention-deficit/hyperactivity disorder (ADHD) is provided. Meta-analysis showed a significant medium effect size (Cohen's d=0.48-0.58) in terms of ventral-striatal (VS)-hyporesponsiveness in ADHD. Studies on VS-responsiveness and trait impulsivity in the healthy population demonstrate the opposite relationship, i.e. impulsivity-scores positively correlated with VS activation during reward processing. Against the background that ADHD may represent an extreme on a continuum of normal variability, the question arises as to how these contrasting findings can be integrated. We discuss three theoretical approaches, each of which integrates the opposing findings: (1) an inverted-u-shape model; (2) a (genetic) moderator model; and (3) the "unrelated model". We conclude that at the present stage the number of existing studies in the healthy population as well as in ADHD groups is too small for a final answer. Therefore, our presented integrative approaches should be understood as an attempt to frame future research directions by generating testable hypotheses and giving practical suggestions for future studies. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. The Contribution of Pre-impact Posture on Restrained Occupant Finite Element Model Response in Frontal Impact.

    PubMed

    Poulard, David; Subit, Damien; Nie, Bingbing; Donlon, John-Paul; Kent, Richard W

    2015-01-01

    The objective of this study was to discuss the influence of the pre-impact posture to the response of a finite element human body model (HBM) in frontal impacts. This study uses previously published cadaveric tests (PMHS), which measured six realistic pre-impact postures. Seven postured models were created from the THUMS occupant model (v4.0): one matching the standard UMTRI driving posture as it was the target posture in the experiments, and six matching the measured pre-impact postures. The same measurements as those obtained during the cadaveric tests were calculated from the simulations, and biofidelity metrics based on signals correlation (CORA) were established to compare the response of the seven models to the experiments. The HBM responses showed good agreement with the PMHS responses for the reaction forces (CORA = 0.80 ± 0.05) and the kinematics of the lower part of the torso but only fair correlation was found with the head, the upper spine, rib strains (CORA= 0.50 ± 0.05) and chest deflections (CORA = 0.67 ± 0.08). All models sustained rib fractures, sternal fracture and clavicle fracture. The average number of rib fractures for all the models was 5.3 ± 1.0, lower than in the experiments (10.8 ± 9.0). Variation in pre-impact posture greatly altered the time histories of the reaction forces, deflections and the rib strains, mainly in terms of time delay, but no definite improvement in HBM response or injury prediction was observed. By modifying only the posture of the HBM, the variability in the impact response was found to be equivalent to that observed in the experiments. The postured HBM sustained from 4 to 8 rib fractures, confirming that the pre-impact posture influenced the injury outcome predicted by the simulation. This study tries to answer an important question: what is the effect of occupant posture on kinematics and kinetics. Significant differences in kinematics observed between HBM and PMHS suggesting more coupling between the pelvis

  10. Impulsivity in disorders of food and drug misuse

    PubMed Central

    Mole, Tom B.; Irvine, Michael A.; Worbe, Yulia; Collins, Phoebe; Mitchell, Simon P.; Bolton, Sorcha; Harrison, Neil A.; Robbins, Trevor W.; Voon, Valerie

    2016-01-01

    Background Evidence suggests some overlap between the pathological use of food and drugs, yet how impulsivity compares across these different clinical disorders remains unclear. Substance use disorders are commonly characterized by elevated impulsivity, and impulsivity subtypes may show commonalities and differences in various conditions. We hypothesized that obese subjects with binge eating disorder (BED) and abstinent alcohol-dependent cohorts would have relatively more impulsive profiles compared to obese subjects without BED. We also predicted decision impulsivity impairment in obesity with and without BED. Methods Thirty obese subjects with BED, 30 without BED and 30 abstinent alcohol-dependent subjects and age- and gender-matched controls were tested on delay discounting (preference for a smaller immediate reward over a larger delayed reward), reflection impulsivity (rapid decision making prior to evidence accumulation) and motor response inhibition (action cancellation of a prepotent response). Results All three groups had greater delay discounting relative to healthy volunteers. Both Obese subjects without BED and alcohol dependent subjects had impaired motor response inhibition. Only Obese subjects without BED had impaired integration of available information to optimize outcomes over later trials with a cost condition. Conclusions Delay discounting appears to be a common core impairment across disorders of food and drug intake. Unexpectedly, obese subjects without BED showed greater impulsivity than obese subjects with BED. We highlight the dissociability and heterogeneity of impulsivity subtypes and add to the understanding of neurocognitive profiles across disorders involving food and drugs. Our results have therapeutic implications suggesting that disorder-specific patterns of impulsivity could be targeted. PMID:25118940

  11. Wave spectral response to sudden changes in wind direction in finite-depth waters

    NASA Astrophysics Data System (ADS)

    Aijaz, Saima; Rogers, W. Erick; Babanin, Alexander V.

    2016-07-01

    The response of a wind-sea spectrum to sudden changes in wind directions of 180° and 90° is investigated. Numerical simulations using the third-generation wave spectral model SWAN have been undertaken at micro timescales of 30 s and fine spatial resolution of less than 10 m. The results have been validated against the wave data collected during the field campaign at Lake George, Australia. The newly implemented 'ST6' physics in the SWAN model has been evaluated using a selection of bottom-friction terms and the two available functions for the nonlinear energy transfer: (1) exact solution of the nonlinear term (XNL), and (2) discrete interactions approximation (DIA) that parameterizes the nonlinear term. Good agreement of the modelled data is demonstrated directly with the field data and through the known experimental growth curves obtained from the extensive Lake George data set. The modelling results show that of the various combinations of models tested, the ST6/XNL model provides the most reliable computations of integral and spectral wave parameters. When the winds and waves are opposing (180° wind turn), the XNL is nearly twice as fast in the aligning the young wind-sea with the new wind direction than the DIA. In this case, the young wind-sea gradually decouples from the old waves and forms a new secondary peak. Unlike the 180° wind turn, there is no decoupling in the 90° wind turn and the entire spectrum rotates smoothly in the new direction. In both cases, the young wind-sea starts developing in the new wind direction within 10 min of the wind turn for the ST6 while the directional response of the default physics lags behind with a response time that is nearly double of ST6. The modelling results highlight the differences in source term balance among the different models in SWAN. During high wind speeds, the default settings provide a larger contribution from the bottom-friction dissipation than the whitecapping. In contrast, the whitecapping

  12. Finite element modeling of the dynamic response of a composite reinforced concrete bridge for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Zanjani Zadeh, V.; Patnaik, A.

    2014-06-01

    This paper describes three-dimensional (3D) finite element (FE) modeling of a composite steel stinger supported reinforced concrete (RC) deck highway bridge subjected to moving truck loads. FE models were validated using test data that were generated elsewhere for structural health monitoring. The FE models were established using a commercial FE analysis package called ABAQUS/standard. The case study bridge was discretized to a combination of shell and solid elements which represent the deck and piers, respectively. Numerous constrain interactions were defined to make the model suitable to obtain accurate results. Moving loads induced by two standard AASHTO trucks were developed through a specific load-time history, applied on 35 nodes on the superstructure. To study the dynamic behavior of the bridge under a moving load, a modal analysis followed by an implicit dynamic analysis was carried out. Acceptable agreement was found between the field measurements and FE simulation. Most concerned dynamic response was strains at different locations in bridge girders and columns, because it is the only critical parameter that can be measured with confidence during SHM at site. The range of strains determined in analysis was reasonably close to the measured strains at the site of the study bridge. Several parameters including damping, truck weight and speed, and material properties were studied. Truck speed had the highest effect on strain response of both girders and columns.

  13. A cell-centered Lagrangian finite volume approach for computing elasto-plastic response of solids in cylindrical axisymmetric geometries

    NASA Astrophysics Data System (ADS)

    Sambasivan, Shiv Kumar; Shashkov, Mikhail J.; Burton, Donald E.

    2013-03-01

    A finite volume cell-centered Lagrangian formulation is presented for solving large deformation problems in cylindrical axisymmetric geometries. Since solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum and energy conservation laws. The total strain-rate realized in the material is split into an elastic and plastic response. The elastic and plastic components in turn are modeled using hypo-elastic theory. In accordance with the hypo-elastic model, a predictor-corrector algorithm is employed for evolving the deviatoric component of the stress tensor. A trial elastic deviatoric stress state is obtained by integrating a rate equation, cast in the form of an objective (Jaumann) derivative, based on Hooke's law. The dilatational response of the material is modeled using an equation of state of the Mie-Grüneisen form. The plastic deformation is accounted for via an iterative radial return algorithm constructed from the J2 von Mises yield condition. Several benchmark example problems with non-linear strain hardening and thermal softening yield models are presented. Extensive comparisons with representative Eulerian and Lagrangian hydrocodes in addition to analytical and experimental results are made to validate the current approach.

  14. Calculating room acoustic parameters from pseudo-impulsive acoustic sources

    NASA Astrophysics Data System (ADS)

    San Martin, Maria L.; Vela, Antonio; San Martin, Ricardo; Arana, Miguel A.

    2002-11-01

    The impulse response function provides complete information to predict the acoustic response of a room to an acoustic input of arbitrary characteristics. At this job study, small explosions of firecrackers are proposed to be used as pseudo-impulsive acoustics sources to determine some acoustic parameters of a room such as reverberation time, definition, and clarity, comparing these results to those obtained with other techniques. A previous characterization of these sources allows us to state that they can be used for this purpose because they are, in practice, omnidirectional, their temporary pattern is highly repetitive and their spectral power is, as well, repetitive and with enough power in octave bands from 125 Hz to 8 kHz. If the linear time-invariant system impulse response h(t) is known, output signal s(t) regarding any arbitrary signal s(t) can be obtained. For our pseudo-impulsive sources, the output signal s(t) has been taken as impulse response h(t). Using the integrated impulse response method suggested by Schroeder, it has been stated that both the mean values and standard deviations for some parameters are practically identical to results obtained with other usual techniques. (To be presented in Spanish.)

  15. Emergence of nanoscale inhomogeneity and finite frequency superfluid response in disordered superconductors

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, Pratap

    2015-03-01

    The notion of spontaneous formation of an inhomogeneous superconducting state is at the heart of most theories attempting to understand the superconducting state in the presence of strong disorder. Using a combination of low-temperature scanning tunneling spectroscopy and high resolution scanning transmission electron microscopy, we experimentally demonstrate that under the competing effects of strong homogeneous disorder and superconducting correlations, the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains. Tracking the superconducting state as a function of temperature we show that these superconducting domains persist across the bulk superconducting transition, Tc, and disappear close to the pseudogap temperature, T*, where signatures of superconducting correlations disappear from the tunneling spectrum and the superfluid response of the system. These results along with complementary measurements of the superfluid stiffness at microwave frequencies underpins the importance of phase fluctuations in strongly disordered s-wave superconductors.

  16. Impulsive phase transport

    NASA Technical Reports Server (NTRS)

    Canfield, Richard C.; Bely-Dubau, Francoise; Brown, John C.; Dulk, George A.; Emslie, A. Gordon; Enome, Shinzo; Gabriel, Alan H.; Kundu, Mukul R.; Melrose, Donald; Neidig, Donald F.

    1986-01-01

    The transport of nonthermal electrons is explored. The thick-target electron beam model, in which electrons are presumed to be accelerated in the corona and typically thermalized primarily in the chromosphere and photosphere, is supported by observations throughout the electromagnetic spectrum. At the highest energies, the anisotropy of gamma-ray emission above 10 MeV clearly indicates that these photons are emitted by anisotropically-directed particles. The timing of this high-energy gamma-radiation with respect to lower-energy hard X-radiation implies that the energetic particles have short life-times. For collisional energy loss, this means that they are stopped in the chromosphere or below. Stereoscopic (two-spacecraft) observations at hard X-ray energies (up to 350 keV) imply that these lower-energy (but certainly nonthermal) electrons are also stopped deep in the chromosphere. Hard X-ray images show that, in spatially resolved flares whose radiation consists of impulsive bursts, the impulsive phase starts with X-radiation that comes mostly from the foot-points of coronal loops whose coronal component is outlined by microwaves.

  17. Propagation of Impulse-Like Waveforms Through the Ionosphere Modeled by Cold Plasma

    NASA Astrophysics Data System (ADS)

    Giri, D. V.; Dvorak, S. L.

    In this chapter, we have studied the propagation of short, impulse-like pulses propagating through the ionosphere. The ionosphere is modeled by simple, cold plasma. The impulse response of such a plasma model is known to consist of two terms. The first term is the impulse itself and the second term contains a Bessel function of first order. This means that the impulse propagates as an impulse followed by a long, oscillatory tail. The numerical example studied here is that of the prototype impulse radiating antenna (IRA). Closed-form expressions are developed for the prototype IRA waveform propagation through the cold-plasma model of the ionosphere. The results are cross-checked with numerical evaluation via a convolution process that uses the known impulse response.

  18. Deformation and fracture of impulsively loaded sandwich panels

    NASA Astrophysics Data System (ADS)

    Wadley, H. N. G.; Børvik, T.; Olovsson, L.; Wetzel, J. J.; Dharmasena, K. P.; Hopperstad, O. S.; Deshpande, V. S.; Hutchinson, J. W.

    2013-02-01

    Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying

  19. A path model of different forms of impulsivity with externalizing and internalizing psychopathology: Towards greater specificity.

    PubMed

    Johnson, Sheri L; Tharp, Jordan A; Peckham, Andrew D; Carver, Charles S; Haase, Claudia M

    2017-09-01

    A growing empirical literature indicates that emotion-related impulsivity (compared to impulsivity that is unrelated to emotion) is particularly relevant for understanding a broad range of psychopathologies. Recent work, however, has differentiated two forms of emotion-related impulsivity: A factor termed Pervasive Influence of Feelings captures tendencies for emotions (mostly negative emotions) to quickly shape thoughts, and a factor termed Feelings Trigger Action captures tendencies for positive and negative emotions to quickly and reflexively shape behaviour and speech. This study used path modelling to consider links from emotion-related and non-emotion-related impulsivity to a broad range of psychopathologies. Undergraduates completed self-report measures of impulsivity, depression, anxiety, aggression, and substance use symptoms. A path model (N = 261) indicated specificity of these forms of impulsivity. Pervasive Influence of Feelings was related to anxiety and depression, whereas Feelings Trigger Action and non-emotion-related impulsivity were related to aggression and substance use. The findings of this study suggest that emotion-relevant impulsivity could be a potentially important treatment target for a set of psychopathologies. Recent work has differentiated two forms of emotion-related impulsivity. This study tests a multivariate path model linking emotion-related and non-emotion-related impulsivity with multiple forms of psychopathology. Impulsive thoughts in response to negative emotions were related to anxiety and depression. Impulsive actions in response to emotions were related to aggression and substance use, as did non-emotion-related impulsivity. The study was limited by the reliance on self-report measures of impulsivity and psychopathology. There is a need for longitudinal work on how these forms of impulsivity predict the onset and course of psychopathology. © 2017 The British Psychological Society.

  20. IMPULSIVITY PARAMETER FOR SOLAR FLARES

    SciTech Connect

    Fajardo-Mendieta, W. G.; Alvarado-Gómez, J. D.; Calvo-Mozo, B.; Martinez-Oliveros, J. C. E-mail: bcalvom@unal.edu.co E-mail: jalvarad@eso.org

    2016-02-10

    Three phases are typically observed during solar flares: the preflare, impulsive, and decay phases. During the impulsive phase, it is believed that the electrons and other particles are accelerated after the stored energy in the magnetic field is released by reconnection. The impulsivity of a solar flare is a quantifiable property that shows how quickly this initial energy release occurs. It is measured via the impulsivity parameter, which we define as the inverse of the overall duration of the impulsive phase. We take the latter as the raw width of the most prominent nonthermal emission of the flare. We computed this observable over a work sample of 48 M-class events that occurred during the current Solar Cycle 24 by using three different methods. The first method takes into account all of the nonthermal flare emission and gives very accurate results, while the other two just cover fixed energy intervals (30–40 keV and 25–50 keV) and are useful for fast calculations. We propose an alternative way to classify solar flares according to their impulsivity parameter values, defining three different types of impulsivity, namely, high, medium, and low. This system of classification is independent of the manner used to calculated the impulsivity parameter. Lastly, we show the relevance of this tool as a discriminator of different HXR generation processes.

  1. Teaching about Impulse and Momentum

    ERIC Educational Resources Information Center

    Franklin, Bill

    2004-01-01

    This American Association of Physics Teachers/Physics Teaching Resource Agents (APPT/PTRA) spiral-bound manual features labs and demos physics teachers can use to give students hands-on opportunities to learn about impulse and momentum. "Make-and-take activities" include AAPT Apparatus Contest winners "An Air Impulse Rocket," "A Fan Driven…

  2. Teaching about Impulse and Momentum

    ERIC Educational Resources Information Center

    Franklin, Bill

    2004-01-01

    This American Association of Physics Teachers/Physics Teaching Resource Agents (APPT/PTRA) spiral-bound manual features labs and demos physics teachers can use to give students hands-on opportunities to learn about impulse and momentum. "Make-and-take activities" include AAPT Apparatus Contest winners "An Air Impulse Rocket," "A Fan Driven…

  3. Expansion and improvement of the FORMA system for response and load analysis. Volume 2C: Listings, finite element FORMA subroutines

    NASA Technical Reports Server (NTRS)

    Wohlen, R. L.

    1976-01-01

    A listing of the source deck of each finite element FORMA subroutine is given to remove the 'black-box' aura of the subroutines so that the analyst may better understand the detailed operations of each subroutine. The FORTRAN 4 programming language is used in all finite element FORMA subroutines.

  4. Quasi-elastic Coulomb response function for finite systems and elimination of the Landau ghost in the relativistic σ-ω model

    NASA Astrophysics Data System (ADS)

    Kazuhiro, Tanaka; Wolfgang, Bentz; Akito, Arima

    1990-11-01

    The quasi-elastic Coulomb response function of finite nuclei including vacuum polarization effects is investigated in the relativistic σ-ω model. For the consistent elimination of the Landau ghost in meson propagators, the description of the ground state and the response function of the system is formulated utilizing the effective action method, and the effects of the ghost elimination on the nuclear matter response function are discussed. Finite system calculations are performed for 12C (|q|= 300, 400, 550 MeV) and 40Ca (|q|= 410, 500, 550 MeV) , in which particle-hole continuum states are fully taken into account by the method of continuum RPA, while the vacuum polarization effects are included by the local density approximation. The effects of the particle-hole effective interaction and the medium modified single-nucleon form factor on the response function are also discussed.

  5. Recent Insights into the Neurobiology of Impulsivity

    PubMed Central

    Mitchell, Marci R.; Potenza, Marc N.

    2014-01-01

    Impulsivity is associated with various psychopathologies, and elevated impulsivity is typically disadvantageous. This manuscript reviews recent investigations into the neurobiology of impulsivity using human imaging techniques and animal models. Both human imaging and preclinical pharmacological manipulations have yielded important insights into the neurobiological underpinnings of impulsivity. A more thorough understanding of the complex neurobiology underlying aspects of impulsivity may provide insight into new treatment options that target elevated impulsivity and psychopathologies such as addictions. PMID:25431750

  6. [Kleptomania: an irresistible impulse].

    PubMed

    Hatzigeorgiou, K

    2011-01-01

    This review presents the historical-epidemiological and clinical aspects of Kleptomania. The diagnostic criteria, on the basis of which it is categorized in the group of Impulse Control Disorders, are defined precisely. All the aspects of its causative pathogenesis are deeply analyzed, as they are projected through its phenomenological, psychoanalytical and psycho-biological approach. Particular emphasis is given on its differential diagnosis from other psycho-pathological conditions and especially from the co-morbidities that often accompany it. The frame of treatment is established and its course and the final outcome are analyzed. Finally, it is determined what should be the objectives of future research, which will contribute decisively to the ascertainment of the exact incidence of Kleptomania in the general population, to the clarification of its causative pathogenesis and especially to the most effective treatment of this serious mental disorder.

  7. Nonsputtering impulse magnetron discharge

    SciTech Connect

    Khodachenko, G. V.; Mozgrin, D. V.; Fetisov, I. K.; Stepanova, T. V.

    2012-01-15

    Experiments with quasi-steady high-current discharges in crossed E Multiplication-Sign B fields in various gases (Ar, N{sub 2}, H{sub 2}, and SF{sub 6}) and gas mixtures (Ar/SF{sub 6} and Ar/O{sub 2}) at pressures from 10{sup -3} to 5 Torr in discharge systems with different configurations of electric and magnetic fields revealed a specific type of stable low-voltage discharge that does not transform into an arc. This type of discharge came to be known as a high-current diffuse discharge and, later, a nonsputtering impulse magnetron discharge. This paper presents results from experimental studies of the plasma parameters (the electron temperature, the plasma density, and the temperature of ions and atoms of the plasma-forming gas) of a high-current low-pressure diffuse discharge in crossed E Multiplication-Sign B fields.

  8. Probing the Elastic-Plastic, Time-Dependant Response of Test Fasteners using Finite Element Analysis (FEA)

    SciTech Connect

    ML Renauld; H Lien

    2004-12-13

    The evolution of global and local stress/strain conditions in test fasteners under test conditions is investigated using elastic-plastic, time-dependent finite element analyses (FEA). For elastic-plastic response, tensile data from multiple specimens, material heats and test temperatures are integrated into a single, normalized flow curve from which temperature dependency is extracted. A primary creep model is calibrated with specimen- and fastener-based thermal relaxation data generated under a range of times, temperatures, stress levels and environments. These material inputs are used in analytical simulations of experimental test conditions for several types of fasteners. These fastener models are constructed with automated routines and contact conditions prescribed at all potentially mating surfaces. Thermal or mechanical room temperature pre-loading, as appropriate for a given fastener, is followed by a temperature ramp and a dwell time at constant temperature. While the amount of thermal stress relaxation is limited for the conditions modeled, local stress states are highly dependent upon geometry (thread root radius, for example), pre-loading history and thermal expansion differences between the test fastener and test fixture. Benefits of this FE approach over an elastic methodology for stress calculation will be illustrated with correlations of Stress Corrosion Cracking (SCC) initiation time and crack orientations in stress concentrations.

  9. FINITE ELEMENT SIMULATION FOR STRUCTURAL RESPONSE OF U7MO DISPERSION FUEL PLATES VIA FLUID-THERMAL-STRUCTURAL INTERACTION

    SciTech Connect

    Hakan Ozaltun; Herman Shen; Pavel Madvedev

    2010-11-01

    This article presents numerical simulation of dispersion fuel mini plates via fluid–thermal–structural interaction performed by commercial finite element solver COMSOL Multiphysics to identify initial mechanical response under actual operating conditions. Since fuel particles are dispersed in Aluminum matrix, and temperatures during the fabrication process reach to the melting temperature of the Aluminum matrix, stress/strain characteristics of the domain cannot be reproduced by using simplified models and assumptions. Therefore, fabrication induced stresses were considered and simulated via image based modeling techniques with the consideration of the high temperature material data. In order to identify the residuals over the U7Mo particles and the Aluminum matrix, a representative SEM image was employed to construct a microstructure based thermo-elasto-plastic FE model. Once residuals and plastic strains were identified in micro-scale, solution was used as initial condition for subsequent multiphysics simulations at the continuum level. Furthermore, since solid, thermal and fluid properties are temperature dependent and temperature field is a function of the velocity field of the coolant, coupled multiphysics simulations were considered. First, velocity and pressure fields of the coolant were computed via fluidstructural interaction. Computed solution for velocity fields were used to identify the temperature distribution on the coolant and on the fuel plate via fluid-thermal interaction. Finally, temperature fields and residual stresses were used to obtain the stress field of the plates via fluid-thermal-structural interaction.

  10. Utilizing a general purpose finite element approach for assessing the rotordynamic response of a flexible disk/shaft system

    NASA Astrophysics Data System (ADS)

    Wroblewski, Adam C.; Gyekenyesi, Andrew L.

    2014-04-01

    With continual improvement in computing power and software codes that simulate multiple physical effects, complex analyses can be performed that allow for more accurate modeling of real world systems. Here, a general purpose finite element (FE) code was utilized to conduct a rotordynamic assessment of a rotor system containing a flexible disk. Typically, specialized rotordynamic software packages make numerous assumptions to simplify the various types of rotor response calculations. Disks, for example, are commonly assumed rigid and are represented by lumped masses or discrete beam elements. Such idealizations may cause inaccuracies when calculating critical speeds for rotor systems that involve a relatively flexible disk. By utilizing a general purpose FE approach, where multiple rotational effects are considered, a more accurate model can be developed that includes the dynamic contributions of a flexible disk. This paper illustrates the rotordynamic analysis of a generic, yet realistic, compressor with a shrouded impeller model, without extensive geometric simplification. Furthermore, through the utilization of the fully featured geometry, several dynamic effects are demonstrated to have a significant influence on the rotor system's Campbell diagram. The dynamic effects investigated include disk flexibility, stress stiffening, and spin softening. It is shown that neglecting any of these may cause significant errors regarding the rotordynamic analysis predictions.

  11. Modelling the optical response of human retinal photoreceptors to plane wave illumination with the finite integration technique

    NASA Astrophysics Data System (ADS)

    Akhlagh Moayed, Alireza; Dang, Shannon; Ramahi, Omar M.; Bizheva, Kostadinka K.

    2009-02-01

    The early stages of ocular diseases such as Diabetic Retinopathy are manifested by morphological changes in retinal tissue occurring on cellular level. Therefore, a number of ophthalmic diseases can be diagnosed at an early stage by detecting spatial and temporal variations in the scattering profile of retinal tissue. It was recently demonstrated that, OCT can be used to probe the functional response of retinal photoreceptors to external light stimulation [1]-[3]. fUHROCT measures localized differential changes in the retina reflectivity over time resulting from external light stimulation of the retina. Currently the origins of the observed reflectivity changes are not well understood. However, due to the complex nature of retinal physiology using purely experimental approaches in this case is problematic. For example fUHROCT is sensitive to small changes in the refractive index of biological tissue which as demonstrated previously, can result from a number of processes such as membrane hyperpolarization, osmotic swelling, metabolic changes, etc. In this paper, we present a computational model of interaction between photoreceptor cells and optical plane wave based on the Finite Integration Technique (FIT).

  12. Negative emotion-driven impulsivity predicts substance dependence problems.

    PubMed

    Verdejo-García, Antonio; Bechara, Antoine; Recknor, Emily C; Pérez-García, Miguel

    2007-12-01

    Impulsivity is predominant among users of several drugs of abuse including alcohol, cocaine, and amphetamines, and it is considered a risk factor for later development of alcohol and substance abuse and dependence. However, there is little consensus on how impulsivity should be defined and measured, and there are few studies on the relationship between separate dimensions of impulsivity and substance dependence. We used a multidimensional measure of impulsivity (the UPPS scale) to examine differences between 36 individuals with substance dependence (ISD) and 36 drug-free controls on the dimensions of urgency, lack of premeditation, lack of perseverance, and sensation seeking. In addition, we examined which dimensions of impulsivity better predicted addiction-related problems as measured with the addiction severity index. Results revealed that ISD show high scores on dimensions of urgency, lack of perseverance, and lack of premeditation (effect sizes ranging from 1.10 to 1.96), but not on sensation seeking. Among the different impulsivity dimensions, urgency was the best predictor of severity of medical, employment, alcohol, drug, family/social, legal and psychiatric problems in ISD, explaining 13-48% of the total variance of these indices. Furthermore, urgency scores alone correctly classified 83% of the participants in the ISD group. Urgency is characterized by a tendency to act impulsively in response to negative emotional states. Thus, our results could have important implications for novel treatment approaches for substance dependence focused on emotional regulation.

  13. Links between self-reported and laboratory behavioral impulsivity.

    PubMed

    Havik, Merle; Jakobson, Ainika; Tamm, Maria; Paaver, Marika; Konstabel, Kenn; Uusberg, Andero; Allik, Jüri; Oöpik, Vahur; Kreegipuu, Kairi

    2012-06-01

    A major problem in the research considering impulsivity is the lack of mutual understanding on how to measure and define impulsivity. Our study examined the relationship between self-reported impulsivity, behavioral excitatory and inhibitory processes and time perception. Impulsivity--fast, premature, thoughtless or disinhibited behavior--was assessed in 58 normal, healthy participants (30 men, mean age 21.9 years). Self-reported impulsivity as measured by Adaptive and Maladaptive Impulsivity Scale (AMIS) and behavioral excitatory and inhibitory processes as measured by Stop Signal Task were not directly related. Time perception, measured by the retrospective Time Estimation Task, was related to both. The length of the perceived time interval was positively correlated to AMIS Disinhibition subscale and negatively to several Stop Signal Task parameters. The longer subjects perceived the duration to last, the higher was their score on Disinhibition scale and the faster were their reactive responses in the Stop Signal Task. In summary our findings support the idea of cognitive tempo as a possible mechanism underlying impulsive behavior. © 2012 The Authors. Scandinavian Journal of Psychology © 2012 The Scandinavian Psychological Associations.

  14. Finite element simulations of the head-brain responses to the top impacts of a construction helmet: Effects of the neck and body mass.

    PubMed

    Wu, John Z; Pan, Christopher S; Wimer, Bryan M; Rosen, Charles L

    2017-01-01

    Traumatic brain injuries are among the most common severely disabling injuries in the United States. Construction helmets are considered essential personal protective equipment for reducing traumatic brain injury risks at work sites. In this study, we proposed a practical finite element modeling approach that would be suitable for engineers to optimize construction helmet design. The finite element model includes all essential anatomical structures of a human head (i.e. skin, scalp, skull, cerebrospinal fluid, brain, medulla, spinal cord, cervical vertebrae, and discs) and all major engineering components of a construction helmet (i.e. shell and suspension system). The head finite element model has been calibrated using the experimental data in the literature. It is technically difficult to precisely account for the effects of the neck and body mass on the dynamic responses, because the finite element model does not include the entire human body. An approximation approach has been developed to account for the effects of the neck and body mass on the dynamic responses of the head-brain. Using the proposed model, we have calculated the responses of the head-brain during a top impact when wearing a construction helmet. The proposed modeling approach would provide a tool to improve the helmet design on a biomechanical basis.

  15. Finite element simulations of the head–brain responses to the top impacts of a construction helmet: Effects of the neck and body mass

    PubMed Central

    Wu, John Z; Pan, Christopher S; Wimer, Bryan M; Rosen, Charles L

    2017-01-01

    Traumatic brain injuries are among the most common severely disabling injuries in the United States. Construction helmets are considered essential personal protective equipment for reducing traumatic brain injury risks at work sites. In this study, we proposed a practical finite element modeling approach that would be suitable for engineers to optimize construction helmet design. The finite element model includes all essential anatomical structures of a human head (i.e. skin, scalp, skull, cerebrospinal fluid, brain, medulla, spinal cord, cervical vertebrae, and discs) and all major engineering components of a construction helmet (i.e. shell and suspension system). The head finite element model has been calibrated using the experimental data in the literature. It is technically difficult to precisely account for the effects of the neck and body mass on the dynamic responses, because the finite element model does not include the entire human body. An approximation approach has been developed to account for the effects of the neck and body mass on the dynamic responses of the head–brain. Using the proposed model, we have calculated the responses of the head–brain during a top impact when wearing a construction helmet. The proposed modeling approach would provide a tool to improve the helmet design on a biomechanical basis. PMID:28097935

  16. An overview of measuring impulsive behavior in mice.

    PubMed

    Dent, Claire L; Isles, Anthony R

    2014-06-16

    Impulsive behavior is a key constituent of many psychiatric illnesses, with maladaptive response control being a feature of disorders such as ADHD, schizophrenia, mania, and addiction. In order to understand the neurological underpinnings of impulsivity, a number of behavioral tasks have been developed for use with animal models. Data from studies with rats and other animals have led to the idea of the existence of dissociable components of impulsivity, which in turn informs studies of human disorders and potentially the development of specific therapies. Increasingly, mouse models are being used to investigate the known genetic contribution to psychiatric disorders in which abnormal response control leads to altered impulsive behaviors. In order to maximize the potential of these mouse models, it is important that researchers take into account the non-unitary nature of response control and impulsivity. In this article, we briefly review the tasks available to behavioral neuroscientists and how these can be used in order to tease apart the contribution of a specific genetic lesion into the discrete aspects of impulsive behavior.

  17. Neuropsychological profiling of impulsivity and compulsivity in cocaine dependent individuals.

    PubMed

    Fernández-Serrano, María José; Perales, José César; Moreno-López, Laura; Pérez-García, Miguel; Verdejo-García, Antonio

    2012-01-01

    Research on the relative impact of trait impulsivity vs. drug exposure on neuropsychological probes of response inhibition vs. response perseveration has been posited as a valid pathway to explore the transition between impulsivity and compulsivity on psychostimulant dependence. The objectives of this study are to examine performance differences between cocaine-dependent individuals (CDI) and healthy comparison individuals (HCI) on neuropsychological probes of inhibition and perseveration and to examine the predictive impact of trait impulsivity-a proxy of premorbid vulnerability, and severity of cocaine use-a proxy of drug exposure, on CDI's performance. Forty-two CDI and 65 HCI were assessed using the UPPS-P Scale (trait impulsivity), the Stroop and go/no-go (inhibition) and revised-strategy application and probabilistic reversal tests (perseveration). CDI, compared to HCI, have elevated scores on trait impulsivity and perform significantly poorer on inhibition and perseveration, with specific detrimental effects of duration of cocaine use on perseveration. CDI have both inhibition and perseveration deficits; both patterns were broadly indicative of orbitofrontal dysfunction in the context of reinforcement learning. Impulsive personality and cocaine exposure jointly contribute to deficits in response perseveration or compulsivity.

  18. Finite Element Modeling of the Magnetotelluric Phase Tensor Response to Evaluate Sensitivity to Lateral and Vertical Resistivity Contrasts

    NASA Astrophysics Data System (ADS)

    Hawkes, S.; McClain, J. S.

    2015-12-01

    Phase tensor analysis of magnetotelluric data is a relatively new technique introduced by Caldwell et. al. (2004) and requires substantial research efforts to evaluate the capabilities of the method. We have conducted finite element (FE) modeling using the AC/DC module of Comsol Multiphysics to determine the effect of resistivity structure on the phase tensor response. Measurements are made at eleven frequencies from 10-104 Hz at points on a 5x5 grid above various simple model geometries. Phase tensor plotting methods are adapted from Booker (2013) and involve displaying data graphically as stacks of colored ellipses. This allows for interpretation across the frequency spectrum vertically as well as laterally between stations. Two types of plot are presented for each model, a "ϕmin plot" where the ellipses are colored according to the minimum principle phase and a "delta plot" where the ellipses are colored according to the difference between the principle phases (ϕmax - ϕmin), which provides a quantification of the phase anisotropy. Results suggest that the principle phases ϕmin and ϕmax are sensitive to vertical resistivity contrasts but not lateral resistivity contrasts. Conversely, delta plots reveal sensitivity to lateral resistivity contrasts but not vertical resistivity contrasts. A clear distance relationship is observed with proximity to the boundary controlling the frequency range that senses a lateral resistivity contrast. Rotation of the phase tensor ellipses and increased skew values occur in the presence of resistivity contrasts that strike nonparallel to the source field, with the effect increasing towards lower frequencies. The total phase tensor response is confirmed to be sensitive to both vertical and lateral resistivity contrasts and can be used effectively to interpret subsurface resistivity structure.

  19. Hydro-mechanical pressure response to fluid injection into finite aquifers highlights the non-local behavior of storage

    NASA Astrophysics Data System (ADS)

    De Simone, Silvia; Carrera, Jesus

    2017-04-01

    Specific storage reflects the volumetric deformation capacity of permeable media. Classical groundwater hydrology equals elastic storage to medium compressibility, which is a constant-in-time and locally-defined parameter. This allows simplifying the flow equation into a linear diffusion equation that is relatively easy to solve. However, the hydraulic gradients, generated by fluid injection or pumping, act as forces that push the medium in the direction of flow causing it to deform, even in regions where pressure has not changed. Actual deformation depends on the elastic properties of the medium, but also on aquifer geometry and on surrounding strata, which act like constraints to displacements. Therefore the storage results to be non-local (i.e., the volume of water released at a point depends on the poroelastic response over the whole aquifer) and the proper evaluation of transient pressure requires acknowledging the hydro-mechanical (HM) coupling, which is generally disregarded by conventional hydrogeology. Here we discuss whether HM coupling effects are relevant, which is of special interest for the activities of enhanced geothermics, waste disposal, CO2 storage or shale gas extraction. We propose analytic solutions to the HM problem of fluid injection (or extraction) into finite aquifers with one-dimensional or cylindrical geometries. We find that the deviation respect to traditional purely hydraulic solutions is significant when the aquifer has limited capacity to deform. The most relevant implications are that the response time is faster and the pressure variation greater than expected, which may be relevant for aquifer characterization and for the evaluation of pressure build-up due to fluid injection.

  20. Brain Response to Primary Blast Wave Using Validated Finite Element Models of Human Head and Advanced Combat Helmet

    PubMed Central

    Zhang, Liying; Makwana, Rahul; Sharma, Sumit

    2013-01-01

    Blast-induced traumatic brain injury has emerged as a “signature injury” in combat casualty care. Present combat helmets are designed primarily to protect against ballistic and blunt impacts, but the current issue with helmets is protection concerning blasts. In order to delineate the blast wave attenuating capability of the Advanced Combat Helmet (ACH), a finite element (FE) study was undertaken to evaluate the head response against blast loadings with and without helmet using a partially validated FE model of the human head and ACH. Four levels of overpressures (0.27–0.66 MPa) from the Bowen’s lung iso-damage threshold curves were used to simulate blast insults. Effectiveness of the helmet with respect to head orientation was also investigated. The resulting biomechanical responses of the brain to blast threats were compared for human head with and without the helmet. For all Bowen’s cases, the peak intracranial pressures (ICP) in the head ranged from 0.68 to 1.8 MPa in the coup cortical region. ACH was found to mitigate ICP in the head by 10–35%. Helmeted head resulted in 30% lower average peak brain strains and product of strain and strain rate. Among three blast loading directions with ACH, highest reduction in peak ICP (44%) was due to backward blasts whereas the lowest reduction in peak ICP and brain strains was due to forward blast (27%). The biomechanical responses of a human head to primary blast insult exhibited directional sensitivity owing to the different geometry contours and coverage of the helmet construction and asymmetric anatomy of the head. Thus, direction-specific tolerances are needed in helmet design in order to offer omni-directional protection for the human head. The blasts of varying peak overpressures and durations that are believed to produce the same level of lung injury produce different levels of mechanical responses in the brain, and hence “iso-damage” curves for brain injury are likely different than the Bowen

  1. Serotonergic modulation of ‘waiting impulsivity' is mediated by the impulsivity phenotype in humans

    PubMed Central

    Neufang, S; Akhrif, A; Herrmann, C G; Drepper, C; Homola, G A; Nowak, J; Waider, J; Schmitt, A G; Lesch, K-P; Romanos, M

    2016-01-01

    In rodents, the five-choice serial reaction time task (5-CSRTT) has been established as a reliable measure of waiting impulsivity being defined as the ability to regulate a response in anticipation of reinforcement. Key brain structures are the nucleus accumbens (NAcc) and prefrontal regions (for example, pre- and infralimbic cortex), which are, together with other transmitters, modulated by serotonin. In this functional magnetic resonance imaging study, we examined 103 healthy males while performing the 5-CSRTT measuring brain activation in humans by means of a paradigm that has been widely applied in rodents. Subjects were genotyped for the tryptophan hydroxylase-2 (TPH2; G-703T; rs4570625) variant, an enzyme specific for brain serotonin synthesis. We addressed neural activation patterns of waiting impulsivity and the interaction between the NAcc and the ventromedial prefrontal cortex (vmPFC) using dynamic causal modeling. Genetic influence was examined via interaction analyses between the TPH2 genotype (GG homozygotes vs T allele carriers) and the degree of impulsivity as measured by the 5-CSRTT. We found that the driving input of the vmPFC was reduced in highly impulsive T allele carriers (reflecting a reduced top-down control) in combination with an enhanced response in the NAcc after correct target processing (reflecting an augmented response to monetary reward). Taken together, we found a high overlap of our findings with reports from animal studies in regard to the underlying cognitive processes, the brain regions associated with waiting impulsivity and the neural interplay between the NAcc and vmPFC. Therefore, we conclude that the 5-CSRTT is a promising tool for translational studies. PMID:27824354

  2. Eyes Wide Shopped: Shopping Situations Trigger Arousal in Impulsive Buyers

    PubMed Central

    Serfas, Benjamin G.; Büttner, Oliver B.; Florack, Arnd

    2014-01-01

    The present study proposes arousal as an important mechanism driving buying impulsiveness. We examined the effect of buying impulsiveness on arousal in non-shopping and shopping contexts. In an eye-tracking experiment, we measured pupil dilation while participants viewed and rated pictures of shopping scenes and non-shopping scenes. The results demonstrated that buying impulsiveness is closely associated with arousal as response to viewing pictures of shopping scenes. This pertained for hedonic shopping situations as well as for utilitarian shopping situations. Importantly, the effect did not emerge for non-shopping scenes. Furthermore, we demonstrated that arousal of impulsive buyers is independent from cognitive evaluation of scenes in the pictures. PMID:25489955

  3. Impulse encoding across the dendritic morphologies of retinal ganglion cells.

    PubMed

    Sheasby, B W; Fohlmeister, J F

    1999-04-01

    Nerve impulse entrainment and other excitation and passive phenomena are analyzed for a morphologically diverse and exhaustive data set (n = 57) of realistic (3-dimensional computer traced) soma-dendritic tree structures of ganglion cells in the tiger salamander (Ambystoma tigrinum) retina. The neurons, including axon and an anatomically specialized thin axonal segment that is observed in every ganglion cell, were supplied with five voltage- or ligand-gated ion channels (plus leakage), which were distributed in accordance with those found in a recent study that employed an equivalent dendritic cylinder. A wide variety of impulse-entrainment responses was observed, including regular low-frequency firing, impulse doublets, and more complex patterns involving impulse propagation failures (or aborted spikes) within the encoder region, all of which have been observed experimentally. The impulse-frequency response curves of the cells fell into three groups called FAST, MEDIUM, and SLOW in approximate proportion as seen experimentally. In addition to these, a new group was found among the traced cells that exhibited an impulse-frequency response twice that of the FAST category. The total amount of soma-dendritic surface area exhibited by a given cell is decisive in determining its electrophysiological classification. On the other hand, we found only a weak correlation between the electrophysiological group and the morphological classification of a given cell, which is based on the complexity of dendritic branching and the physical reach or "receptive field" area of the cell. Dendritic morphology determines discharge patterns to dendritic (synaptic) stimulation. Orthodromic impulses can be initiated on the axon hillock, the thin axonal segment, the soma, or even the proximal axon beyond the thin segment, depending on stimulus magnitude, soma-dendritic membrane area, channel distribution, and state within the repetitive impulse cycle. Although a sufficiently high dendritic

  4. Executive (Dys)Functioning and Impulsivity as Possible Vulnerability Factors for Aggression in Forensic Patients.

    PubMed

    Tonnaer, Franca; Cima, Maaike; Arntz, Arnoud

    2016-04-01

    This study investigated whether executive dysfunction and impulsivity are both predictors of reactive aggression and is the first to use behavioral assessment of aggression in response to provocation by means of a personalized boxing body opponent bag giving harassing feedback. Aggressive behavior, self-reported aggression, executive functioning (ie, working memory, flexibility, and divided attention), and impulsivity dimensions (i.e., Sensation Seeking, Impulsive Decision Making, and [inadequate] Response Inhibition) were measured in 44 incarcerated psychiatric patients. Results show that both executive functioning (working memory) and impulsivity (Impulsive Decision Making) predicted self-reported reactive aggression, whereas Response Inhibition was the only predictor for reactive aggressive behavioral responses. The study suggests that Response Inhibition is a stronger predictor of reactive aggressive behavior than executive capacities of working memory, flexibility, and divided attention. Therefore, future research should investigate whether (inadequate) Response Inhibition could also be a valuable predictor for violent recidivism.

  5. Impulsive choice and environmental enrichment: effects of d-amphetamine and methylphenidate.

    PubMed

    Perry, Jennifer L; Stairs, Dustin J; Bardo, Michael T

    2008-11-03

    Individual differences in impulsive choice and rearing in differential environments are factors that predict vulnerability to drug abuse. The present study determined if rearing influences impulsive choice, and if d-amphetamine or methylphenidate alters impulsive choice in differentially reared rats. Male Sprague-Dawley rats were raised from 21 days of age in either an enriched condition (EC) or an isolated condition (IC) and were tested as young adults on an adjusting delay task. In this task, two levers were available and a response on one lever yielded one 45mg food pellet immediately, whereas a response on the other yielded three pellets after an adjusting delay. The delay was initially set at 6s, and it decreased or increased by 1s following responses on the immediate or delayed levers, respectively. A mean adjusted delay (MAD) was calculated upon completion of each daily session, and it served as the quantitative measure of impulsivity. Once MADs stabilized, rats were injected with saline, d-amphetamine (0.5, 1.0, or 2.0mg/kg, s.c.), or methylphenidate (2.5, 5.0, or 10.0mg/kg, s.c.) 15min prior to adjusting delay sessions. EC rats had higher baseline MADs (were less impulsive) than IC rats. Additionally, administration of d-amphetamine, but not methylphenidate, dose-dependently increased impulsive choice (decreased MADs) in EC rats. In IC rats, d-amphetamine and methylphenidate dose-dependently decreased impulsivity (increased MADs). These results indicate that rearing environment influences impulsive choice and moderates the effect of psychostimulants on impulsive choice. Specifically, psychostimulants may decrease environment-dependent impulsive choice in individuals with high levels of impulsivity (e.g., those with ADHD), whereas they may increase impulsive choice in individuals with low levels of impulsivity.

  6. Impulsive control for fast nanopositioning.

    PubMed

    Tuma, Tomas; Sebastian, Abu; Häberle, Walter; Lygeros, John; Pantazi, Angeliki

    2011-04-01

    In this paper we present a non-linear control scheme for high-speed nanopositioning based on impulsive control. Unlike in the case of a linear feedback controller, the controller states are altered in a discontinuous manner at specific instances in time. Using this technique, it is possible to simultaneously achieve good tracking performance, disturbance rejection and tolerance to measurement noise. Impulsive control is demonstrated experimentally on an atomic force microscope. A significant improvement in tracking performance is demonstrated.

  7. Interacting Mechanisms of Impulsivity in Bipolar Disorder and Antisocial Personality Disorder

    PubMed Central

    Swann, Alan C.; Lijffijt, Marijn; Lane, Scott D.; Steinberg, Joel L.; Moeller, F. Gerard

    2011-01-01

    Background Bipolar disorder and antisocial personality disorder (ASPD) overlap in clinical characteristics and behavioral consequences. Impulsivity is prominent in both, but there is little information on how specific mechanisms of impulsivity differentiate, bridge, or underlie the disorders. Methods Subjects, all males, were controls (n=46), bipolar disorder without cluster B personality disorder (n=21), ASPD without bipolar disorder (n=50), and bipolar disorder with ASPD (n=16). Impulsivity measures were the Immediate Memory Task (IMT), a continuous performance test of response inhibition measuring ability to evaluate a stimulus before responding, and the Two Choice Impulsivity Paradigm (TCIP), a choice between smaller-sooner and larger-later reward. Data were analyzed using general linear models analysis. Results Subjects with bipolar disorder had fewer IMT correct detections and slower reaction times than controls. Reaction times were faster with combined diagnoses than in bipolar disorder alone. TCIP responding in either diagnosis alone resembled controls, but was more impulsive in combined disorders. These differences persisted after correction for age and education, which had significant independent effects. In combined ASPD and bipolar disorder, increased reaction speed, impulsive response bias, and reward-delay impulsivity occurred independent of substance-use disorder history. Conclusions Impulsivity was increased in the combined disorders over either disorder alone. Results were consistent with at least partially distinct mechanisms of impulsivity in ASPD and bipolar disorder. Compensatory mechanisms for impulsivity in uncomplicated ASPD or bipolar disorder appear to be compromised or lost when the disorders are combined. PMID:21719028

  8. Impulsivity and overeating in children in the absence and presence of hunger.

    PubMed

    Nederkoorn, Chantal; Dassen, Fania C M; Franken, Loes; Resch, Christine; Houben, Katrijn

    2015-10-01

    Overweight children appear to be more responsive to environmental, hedonic cues and easily overeat in the current obesogenic environment. They are also found to overeat in the absence of hunger, and this overeating seems related to impulsivity: impulsive participants are more prone to external eating. However, some studies showed that impulsive adults are also more prone to hunger cues: impulsive participants overate especially when feeling hungry. This would mean impulsive people are more reactive to both external and internal cues. The overeating was limited to palatable high energy-dense foods: hunger made them fancy a snack. In the current study, we wanted to test the interaction between impulsivity, hunger and consumption of food type in children. Impulsivity was measured in 88 children between the ages of 7 and 9. Next, half of the participants performed a taste test before their own regular lunch and half of the participants immediately after their lunch. During the taste test, low, medium and high energy-dense food items were presented. Results showed that impulsive children ate more high energy-dense foods than low impulsive children, both before and after their lunch. No differences were found on low or medium energy-dense foods. Impulsive children therefore showed normal sensitivity for internal hunger and satiety cues, but abnormal response to high energy-dense foods. This might render them vulnerable to tasty temptation in the environment and to weight gain in their future.

  9. Impulsivity, risk taking, and timing.

    PubMed

    Baumann, Ana A; Odum, Amy L

    2012-07-01

    This study examined the relations among measures of impulsivity and timing. Impulsivity was assessed using delay and probability discounting, and self-report impulsivity (as measured by the Barratt Impulsiveness Scale; BIS-11). Timing was assessed using temporal perception as measured on a temporal bisection task and time perspective (as measured by the Zimbardo Time Perspective Inventory). One hundred and forty three college students completed these measures in a computer laboratory. The degree of delay discounting was positively correlated with the mean and range of the temporal bisection procedure. The degree of delay and probability discounting were also positively correlated. Self-reported motor impulsiveness on the BIS-11 was positively correlated with present hedonism and negatively correlated with future orientation on the ZTPI. Self-reported non-planning on the BIS-11 was positively correlated with fatalism on the ZTPI. These results show that people who overestimate the passage of time (perceive time as passing more quickly) hold less value in delayed rewards. They also confirm previous results regarding the relation between delay and probability discounting, as well as highlight similarities in self-report measures of impulsivity and time perspective.

  10. Impulsivity, Risk Taking, and Timing

    PubMed Central

    Baumann, Ana A.; Odum, Amy. L.

    2012-01-01

    This study examined the relations among measures of impulsivity and timing. Impulsivity was assessed using delay and probability discounting, and self-report impulsivity (as measured by the Barratt Impulsiveness Scale; BIS-11). Timing was assessed using temporal perception as measured on a temporal bisection task and time perspective (as measured by the Zimbardo Time Perspective Inventory). One hundred and forty three college students completed these measures in a computer laboratory. The degree of delay discounting was positively correlated with the mean and range of the temporal bisection procedure. The degree of delay and probability discounting were also positively correlated. Self-reported Motor impulsiveness on the BIS-11 was positively correlated with Present Hedonism and negatively correlated with Future orientation on the ZTPI. Self-reported Non-Planning on the BIS-11 was positively correlated with Fatalism on the ZTPI. These results show that people who overestimate the passage of time (perceive time as passing more quickly) hold less value in delayed rewards. They also confirm previous results regarding the relation between delay and probability discounting, as well as highlight similarities in self-report measures of impulsivity and time perspective. PMID:22542458

  11. The nonlinear elastic response of suspensions of rigid inclusions in rubber: II—A simple explicit approximation for finite-concentration suspensions

    NASA Astrophysics Data System (ADS)

    Lopez-Pamies, Oscar; Goudarzi, Taha; Danas, Kostas

    2013-01-01

    In Part I, an exact solution was determined for the problem of the overall nonlinear elastic response of Gaussian (or Neo-Hookean) rubber reinforced by a dilute isotropic distribution of rigid particles. Here, this fundamental result is utilized to construct an approximate solution for non-Gaussian rubber reinforced by an isotropic distribution of rigid particles at finite concentration. This is accomplished by means of two different techniques in two successive steps. First, the dilute solution is utilized together with a differential scheme in finite elasticity to generate a solution for Neo-Hookean rubber filled with an isotropic distribution of rigid particles of polydisperse sizes and finite concentration. This non-dilute result is then employed within the context of a new comparison medium method — derived as an extension of Talbot-Willis (1985) variational framework to the non-convex realm of finite elasticity — to generate in turn a corresponding solution for filled non-Gaussian rubber wherein the underlying elastomeric matrix is characterized by any I1-based stored-energy function Ψ(I1) of choice. The solution is fully explicit and remarkably simple. Its key theoretical and practical merits are discussed in detail. Additionally, the constructed analytical solution is confronted to 3D finite-element simulations of the large-deformation response of Neo-Hookean and non-Gaussian rubber reinforced by isotropic distributions of rigid spherical particles with the same size, as well as with different sizes. Good agreement is found among all three sets of results. The implications of this agreement are discussed.

  12. (Dis)similarity in Impulsivity and Marital Satisfaction: A Comparison of Volatility, Compatibility, and Incompatibility Hypotheses

    PubMed Central

    Derrick, Jaye L.; Houston, Rebecca J.; Quigley, Brian M.; Testa, Maria; Kubiak, Audrey; Levitt, Ash; Homish, Gregory G.; Leonard, Kenneth E.

    2016-01-01

    Impulsivity is negatively associated with relationship satisfaction, but whether relationship functioning is harmed or helped when both partners are high in impulsivity is unclear. The influence of impulsivity might be exacerbated (the Volatility Hypothesis) or reversed (the Compatibility Hypothesis). Alternatively, discrepancies in impulsivity might be particularly problematic (the Incompatibility Hypothesis). Behavioral and self-report measures of impulsivity were collected from a community sample of couples. Mixed effect polynomial regressions with response surface analysis provide evidence in favor of both the Compatibility Hypothesis and the Incompatibility Hypothesis, but not the Volatility Hypothesis. Mediation analyses suggest results for satisfaction are driven by perceptions of the partner's negative behavior and responsiveness. Implications for the study of both impulsivity and relationship functioning are discussed. PMID:26949275

  13. Braking and propulsive impulses increase with speed during accelerated and decelerated walking.

    PubMed

    Peterson, Carrie L; Kautz, Steven A; Neptune, Richard R

    2011-04-01

    The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior-posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from 10 healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0-1.8 m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects' preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Braking and Propulsive Impulses Increase with Speed during Accelerated and Decelerated Walking

    PubMed Central

    Peterson, Carrie L.; Kautz, Steven A.; Neptune, Richard R.

    2011-01-01

    The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior-posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from ten healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0 to 1.8 m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects’ preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking. PMID:21356590

  15. Cigarette Cravings, Impulsivity, and the Brain

    PubMed Central

    Potvin, Stéphane; Tikàsz, Andràs; Dinh-Williams, Laurence Lê-Anh; Bourque, Josiane; Mendrek, Adrianna

    2015-01-01

    Craving is a core feature of tobacco use disorder as well as a significant predictor of smoking relapse. Studies have shown that appetitive smoking-related stimuli (e.g., someone smoking) trigger significant cravings in smokers impede their self-control capacities and promote drug seeking behavior. In this review, we begin by an overview of functional magnetic resonance imaging (fMRI) studies investigating the neural correlates of smokers to appetitive smoking cues. The literature reveals a complex and vastly distributed neuronal network underlying smokers’ craving response that recruits regions involved in self-referential processing, planning/regulatory processes, emotional responding, attentional biases, and automatic conducts. We then selectively review important factors contributing to the heterogeneity of results that significantly limit the implications of these findings, namely between- (abstinence, smoking expectancies, and self-regulation) and within-studies factors (severity of smoking dependence, sex-differences, motivation to quit, and genetic factors). Remarkably, we found that little to no attention has been devoted to examine the influence of personality traits on the neural correlates of cigarette cravings in fMRI studies. Impulsivity has been linked with craving and relapse in substance and tobacco use, which prompted our research team to examine the influence of impulsivity on cigarette cravings in an fMRI study. We found that the influence of impulsivity on cigarette cravings was mediated by fronto-cingulate mechanisms. Given the high prevalence of cigarette smoking in several psychiatric disorders that are characterized by significant levels of impulsivity, we conclude by identifying psychiatric patients as a target population whose tobacco-smoking habits deserve further behavioral and neuro-imaging investigation. PMID:26441686

  16. An Impulse Based Substructuring approach for impact analysis and load case simulations

    NASA Astrophysics Data System (ADS)

    Rixen, Daniel J.; van der Valk, Paul L. C.

    2013-12-01

    In the present paper we outline the basic theory of assembling substructures for which the dynamics are described as Impulse Response Functions. The assembly procedure computes the time response of a system by evaluating per substructure the convolution product between the Impulse Response Functions and the applied forces, including the interface forces that are computed to satisfy the interface compatibility. We call this approach the Impulse Based Substructuring method since it transposes to the time domain the Frequency Based Substructuring approach. In the Impulse Based Substructuring technique the Impulse Response Functions of the substructures can be gathered either from experimental tests using a hammer impact or from time-integration of numerical submodels. In this paper the implementation of the method is outlined for the case when the impulse responses of the substructures are computed numerically. A simple bar example is shown in order to illustrate the concept. The Impulse Based Substructuring allows fast evaluation of impact response of a structure when the impulse response of its components is known. It can thus be used to efficiently optimize designs of consumer products by including impact behavior at the early stage of the design, but also for performing substructured simulations of complex structures such as offshore wind turbines.

  17. Use of instant messaging predicts self-report but not performance measures of inattention, impulsiveness, and distractibility.

    PubMed

    Levine, Laura E; Waite, Bradley M; Bowman, Laura L

    2013-12-01

    We examined how young adults' use of instant messaging, text messaging, and traditional reading related to their self-reported experience of distractibility and impulsiveness and to their performance on computerized tasks designed to assess inattention and impulsive responses to visual stimuli. Participants reported their media use and completed self-report measures of impulsiveness (i.e., the Barratt Impulsiveness Scale) and distractibility for academic reading. They also completed performance based measures of inattention and impulsiveness using the Tests of Variables of Attention (T.O.V.A.(®)). Results demonstrated that instant message use was significantly related to higher levels of attentional impulsiveness and distractibility on the self-report measures, while traditional reading consistently predicted lower levels of impulsiveness and distractibility. However, media use was not significantly related to the performance measures of inattention and behavioral impulsiveness.

  18. The Video Head Impulse Test

    PubMed Central

    Halmagyi, G. M.; Chen, Luke; MacDougall, Hamish G.; Weber, Konrad P.; McGarvie, Leigh A.; Curthoys, Ian S.

    2017-01-01

    In 1988, we introduced impulsive testing of semicircular canal (SCC) function measured with scleral search coils and showed that it could accurately and reliably detect impaired function even of a single lateral canal. Later we showed that it was also possible to test individual vertical canal function in peripheral and also in central vestibular disorders and proposed a physiological mechanism for why this might be so. For the next 20 years, between 1988 and 2008, impulsive testing of individual SCC function could only be accurately done by a few aficionados with the time and money to support scleral search-coil systems—an expensive, complicated and cumbersome, semi-invasive technique that never made the transition from the research lab to the dizzy clinic. Then, in 2009 and 2013, we introduced a video method of testing function of each of the six canals individually. Since 2009, the method has been taken up by most dizzy clinics around the world, with now close to 100 refereed articles in PubMed. In many dizzy clinics around the world, video Head Impulse Testing has supplanted caloric testing as the initial and in some cases the final test of choice in patients with suspected vestibular disorders. Here, we consider seven current, interesting, and controversial aspects of video Head Impulse Testing: (1) introduction to the test; (2) the progress from the head impulse protocol (HIMPs) to the new variant—suppression head impulse protocol (SHIMPs); (3) the physiological basis for head impulse testing; (4) practical aspects and potential pitfalls of video head impulse testing; (5) problems of vestibulo-ocular reflex gain calculations; (6) head impulse testing in central vestibular disorders; and (7) to stay right up-to-date—new clinical disease patterns emerging from video head impulse testing. With thanks and appreciation we dedicate this article to our friend, colleague, and mentor, Dr Bernard Cohen of Mount Sinai Medical School, New York, who since his

  19. Dopamine-agonists and impulsivity in Parkinson's disease: impulsive choices vs. impulsive actions.

    PubMed

    Antonelli, Francesca; Ko, Ji Hyun; Miyasaki, Janis; Lang, Anthony E; Houle, Sylvain; Valzania, Franco; Ray, Nicola J; Strafella, Antonio P

    2014-06-01

    The control of impulse behavior is a multidimensional concept subdivided into separate subcomponents, which are thought to represent different underlying mechanisms due to either disinhibitory processes or poor decision-making. In patients with Parkinson's disease (PD), dopamine-agonist (DA) therapy has been associated with increased impulsive behavior. However, the relationship among these different components in the disease and the role of DA is not well understood. In this imaging study, we investigated in PD patients the effects of DA medication on patterns of brain activation during tasks testing impulsive choices and actions. Following overnight withdrawal of antiparkinsonian medication, PD patients were studied with a H2 ((15)) O PET before and after administration of DA (1 mg of pramipexole), while they were performing the delay discounting task (DDT) and the GoNoGo Task (GNG). We observed that pramipexole augmented impulsivity during DDT, depending on reward magnitude and activated the medial prefrontal cortex and posterior cingulate cortex and deactivated ventral striatum. In contrast, the effect of pramipexole during the GNG task was not significant on behavioral performance and involved different areas (i.e., lateral prefrontal cortex). A voxel-based correlation analysis revealed a significant negative correlation between the discounting value (k) and the activation of medial prefrontal cortex and posterior cingulate suggesting that more impulsive patients had less activation in those cortical areas. Here we report how these different subcomponents of inhibition/impulsivity are differentially sensitive to DA treatment with pramipexole influencing mainly the neural network underlying impulsive choices but not impulsive action.

  20. Impulsivity, Working Memory, and Impaired Control over Alcohol: A Latent Variable Analysis

    PubMed Central

    Wardell, Jeffrey D.; Quilty, Lena C.; Hendershot, Christian S.

    2017-01-01

    Impaired control over alcohol is an important risk factor for heavy drinking among young adults and may mediate, in part, the association between personality risk and alcohol problems. Research suggests that trait impulsivity is associated with impaired control over alcohol; however, few studies of this association have included a range of impulsivity facets. The purpose of this study was to examine specific pathways from higher-order impulsivity factors to alcohol problems mediated via impaired control over alcohol. We also examined the moderating role of working memory in these associations. Young heavy drinkers (N=300) completed two multidimensional impulsivity measures (UPPS-P and BIS-11) along with self-report measures of impaired control over alcohol, alcohol use, and alcohol problems. Working memory was assessed using a computerized digit span task. Results showed that the impulsivity facets loaded onto two higher-order factors that were labeled response and reflection impulsivity. Response impulsivity predicted unique variance in self-reported impaired control and alcohol problems, whereas reflection impulsivity predicted unique variance in heavy drinking frequency only. Further, significant indirect associations were observed from response and reflection impulsivity to alcohol problems mediated via impaired control and heavy drinking frequency, respectively. Working memory and sensation seeking were not uniquely associated with the alcohol variables, and no support was found for the moderating role of working memory. The results help to clarify associations among impulsivity, impaired control, and alcohol problems, suggesting that impaired control may play a specific role in the pathway to alcohol problems from response impulsivity but not from reflection impulsivity. PMID:27269291

  1. Determination of acoustical transfer functions using an impulse method

    NASA Astrophysics Data System (ADS)

    MacPherson, J.

    1985-02-01

    The Transfer Function of a system may be defined as the relationship of the output response to the input of a system. Whilst recent advances in digital processing systems have enabled Impulse Transfer Functions to be determined by computation of the Fast Fourier Transform, there has been little work done in applying these techniques to room acoustics. Acoustical Transfer Functions have been determined for auditoria, using an impulse method. The technique is based on the computation of the Fast Fourier Transform (FFT) of a non-ideal impulsive source, both at the source and at the receiver point. The Impulse Transfer Function (ITF) is obtained by dividing the FFT at the receiver position by the FFT of the source. This quantity is presented both as linear frequency scale plots and also as synthesized one-third octave band data. The technique enables a considerable quantity of data to be obtained from a small number of impulsive signals recorded in the field, thereby minimizing the time and effort required on site. As the characteristics of the source are taken into account in the calculation, the choice of impulsive source is non-critical. The digital analysis equipment required for the analysis is readily available commercially.

  2. Effects of finite laser pulse width on two-dimensional electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Leng, Xuan; Yue, Shuai; Weng, Yu-Xiang; Song, Kai; Shi, Qiang

    2017-01-01

    We combine the hierarchical equations of motion method and the equation-of-motion phase-matching approach to calculate two-dimensional electronic spectra of model systems. When the laser pulse is short enough, the current method reproduces the results based on third-order response function calculations in the impulsive limit. Finite laser pulse width is found to affect both the peak positions and shapes, as well as the time evolution of diagonal and cross peaks. Simulations of the two-color two-dimensional electronic spectra also show that, to observe quantum beats in the diagonal and cross peaks, it is necessary to excite the related excitonic states simultaneously.

  3. The influence of laser ablation plume at different laser incidence angle on the impulse coupling coefficient with metal target

    NASA Astrophysics Data System (ADS)

    Zhao, Xiong-Tao; Tang, Feng; Han, Bing; Ni, Xiao-Wu

    2016-12-01

    A calibrated pendulum measuring device and a dimensionless analysis method were used to measure the impulse coupling coefficient at different laser intensities with aluminum, steel, and iron targets. The experiment was performed with a pulsed laser with the wavelength of 1.06 μm and the pulse duration of 7 ns. The experimental measurements of the variation of the impulse coupling coefficient versus the laser energy density agree with the theoretical prediction, and the optimum laser energy density correlated with the maximum impulse coupling coefficient corresponding to the theoretical predictions. The impulse coupling coefficients with laser incidence angles of 0 ° and 45 ° are compared for understanding of the effects of the ablation plume on the impulse coupling effect, and the experimental result shows that the impulse coupling effect grows as the incidence angle changes from 0 ° to 45 ° . Furthermore, the transmittance of the incident laser through the ablation plume in front of the target is deduced from the impulse measurements, and the effect of the ablation plume on the impulse coupling at high laser intensity is discussed. In order to investigate the weak impulse coupling effect, which is difficult to obtain from the experiments, the impulse coupling coefficient at low laser energy density was calculated by the finite element simulation.

  4. Dopamine agonists and the suppression of impulsive motor actions in Parkinson disease.

    PubMed

    Wylie, Scott A; Claassen, Daniel O; Huizenga, Hilde M; Schewel, Kerilyn D; Ridderinkhof, K Richard; Bashore, Theodore R; van den Wildenberg, Wery P M

    2012-08-01

    The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-BG circuitry. BG dysfunction caused by Parkinson disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD but can also provoke impulsive-compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in 38 PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared with an off-agonist state, patients on their agonists were no more susceptible to reacting impulsively but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off-agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less-proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication.

  5. Impulsivity is associated with the disinhibition but not restraint factor from the Three Factor Eating Questionnaire.

    PubMed

    Yeomans, Martin R; Leitch, Margaret; Mobini, Sirous

    2008-01-01

    Recent data implicate impulsivity as a personality trait associated with obesity, binge eating and restrained eating. However, impulsivity is recognised as having multiple dimensions, and it remains unclear which aspects of impulsive behaviour best predict disordered eating. To try and elucidate further the relationship between impulsivity and eating behaviour, 147 women completed a behavioural measure and two self-report measures of impulsivity along with the Three Factor Eating Questionnaire (TFEQ). Overall scores on the Barratt Impulsiveness Scale (BIS-II), along with scores on the Non-planning and Motor Subscales of the BIS-II, were higher in women scoring high on the TFEQ disinhibition (TFEQ-D) scale. Likewise, women scoring high on the TFEQ-D showed more impulsive choice when discounting hypothetical monetary awards. However, responses to measures of functional relative to dysfunctional impulsivity did not differ depending on TFEQ-D score. No measure of impulsivity was related to scores on the TFEQ restraint scale. These data suggest that a tendency to act impulsively is associated with a tendency to overeat, and may be a factor which predicts the likelihood of the development of binge eating and the breakdown of dieting.

  6. Minimum impulse trajectories for Mars round trip missions

    NASA Technical Reports Server (NTRS)

    Horvat, Glen M.; Alexander, Stephen W.

    1992-01-01

    Data are presented for minimum-impulse earth-Mars round-trip trajectories for the 2010 to 2027 Mars launch opportunities. Round-trip mission times from 120 to 600 days, including a 30-day rendezvous at Mars, for direct trajectories and trajectories utilizing a Venus gravitational assist are considered. Optimal planetary launch and arrival dates and total impulse requirements are based on all maneuvers being performed propulsively with no finite burn or other losses. Direct trajectories have the lowest impulse requirements for shorter mission times and Venus gravitational assist trajectories have the lowest impulse requirements for longer mission times. It is shown that one can depart on trajectories to Mars, beginning with lower energy trajectories to the moon. The fuel savings varies, depending on the final energy level required and on the swingby procedure used. Procedures discussed include single lunar swingbys, double-powered or unpowered lunar swingbys, third lunar flybys a year later, and gravity assists by Venus and earth after the final lunar swingby.

  7. Impulse control disorders and depression.

    PubMed

    Lejoyeux, Michel; Arbaretaz, Marie; McLoughlin, Mary; Adès, Jean

    2002-05-01

    This study assessed the frequency of impulse control disorders (ICDs) and their association with bulimia, compulsive buying, and suicide attempts in a population of depressed inpatients. We investigated ICDs using the Minnesota Impulsive Disorders Interview. Patients answered the Zuckerman Sensation-Seeking Scale and the Barratt Impulsivity Rating Scale. Among the 31 depressed patients who met criteria for ICD (ICD+ group), we found 18 cases of intermittent explosive disorder, three cases of pathological gambling, four cases of kleptomania, three cases of pyromania, and three cases of trichotillomania. Patients with co-occurring ICDs were significantly younger (mean age = 37.7 versus 42.8 years). Patients with kleptomania had a higher number of previous depressive episodes (5.7 versus 1.3), and patients with pyromania had a higher number of previous depressions (3.3 versus 1.3, p =.01). Bipolar disorders were more frequent in the ICD+ group than in the ICD- group (19% versus 1.3%, p =.002), whereas antisocial personality was not (3% versus 1%, p = ns). Bulimia (42% versus 10.5%, p =.005) and compulsive buying (51% versus 22%, p =.006) were significantly more frequent in the ICD+ group. Patients from the ICD+ group had higher scores of motor impulsivity assessed with the Barratt Impulsivity rating scale (p =.01).

  8. Neurocognitive and psychiatric dimensions of “hot” impulsivity, but not “cool” impulsivity, predict HIV sexual risk behaviors among drug users in protracted abstinence

    PubMed Central

    Wilson, Michael J.; Vassileva, Jasmin

    2016-01-01

    Background Impulsivity is an important risk factor for HIV risky drug and sexual behaviors. Research identifies “hot” (i.e., affectively-mediated, reward-based) and “cool” (motoric, attentional, independent of context) neurocognitive and psychiatric dimensions of impulsivity, though the impact of specific drugs of abuse on these varieties of impulsivity remains an open question. Objectives The present study examined the associations of neurocognitive and psychiatric varieties of “hot” and “cool” impulsivity with measures of lifetime and recent sexual risk behaviors among users of different classes of drugs. Methods The study sample was comprised drug users in protracted (>1yr) abstinence: heroin monodependent (n=61), amphetamine monodependent (n=44), and polysubstance dependent (n= 73). “Hot” impulsivity was operationalized via neurocognitive tasks of reward-based decision-making and symptoms of psychopathy. “Cool” impulsivity was operationalized via neurocognitive tasks of response inhibition and symptoms of ADHD. Results “Hot” impulsivity was associated with sexual risk behaviors among heroin and amphetamine users in protracted abstinence, whereas “cool” impulsivity was not associated with sexual risk behaviors among any drug-using group. Neurocognitive “hot” impulsivity was associated with recent (past 30-day) sexual risk behaviors, whereas psychopathy was associated with sexual risk behaviors during more remote time-periods (past 6 month and lifetime) and mediated the association between heroin dependence and past 6-month sexual risk behaviors. Conclusion Assessments and interventions aimed at reducing sexual risk behaviors among drug users should focus on “hot” neurocognitive and psychiatric dimensions of impulsivity, such as decision-making and psychopathy. “Cool” dimensions of impulsivity such as response inhibition and ADHD were not related to sexual risk behaviors among drug users in protracted abstinence. PMID

  9. On the Spur of the Moment: Intrinsic Predictors of Impulse Sports Betting.

    PubMed

    Hing, Nerilee; Li, En; Vitartas, Peter; Russell, Alex M T

    2017-09-27

    Betting on impulse, without thoughtful consideration, research or informed decision-making, may cause financial and other harms and lead to the development of gambling problems. Impulse betting undermines responsible consumption of gambling because it reflects self-regulatory failure, impaired control, unreflective decision-making and betting more than planned. In this paper we define impulse gambling and report on a study that aimed to understand more about the intrinsic characteristics of sports bettors who have a greater tendency to bet on impulse. Specifically, the study aimed to identify behavioural, psychological and socio-demographic predictors of impulse sports betting. A sample of 1816 Australian sports bettors completed an online survey that measured the proportion of their bets placed on impulse both before and during sporting events, as well as bets that were researched and planned in advance. Impulse betting was common, accounting for nearly one-half of all past-year sports bets by respondents. Over three-quarters of respondents had placed one or more impulse bets in the last year and one in seven respondents had made all of their sports bets on impulse. More impulsive sports bettors were characterised as having higher trait impulsiveness, higher problem gambling severity, more frequent sports betting and a shorter history of sports betting. They favoured betting on in-match contingencies instead of overall match outcomes. While health promotion strategies are needed to discourage impulse betting, research into contextual factors that arouse urges to bet would also provide direction for harm minimisation measures that help consumers to resist impulsive betting decisions.

  10. Output feedback model matching in linear impulsive systems with control feedthrough: a structural approach

    NASA Astrophysics Data System (ADS)

    Zattoni, Elena

    2017-01-01

    This paper investigates the problem of structural model matching by output feedback in linear impulsive systems with control feedthrough. Namely, given a linear impulsive plant, possibly featuring an algebraic link from the control input to the output, and given a linear impulsive model, the problem consists in finding a linear impulsive regulator that achieves exact matching between the respective forced responses of the linear impulsive plant and of the linear impulsive model, for all the admissible input functions and all the admissible sequences of jump times, by means of a dynamic feedback of the plant output. The problem solvability is characterized by a necessary and sufficient condition. The regulator synthesis is outlined through the proof of sufficiency, which is constructive.

  11. Reduced punishment sensitivity in neural systems of behavior monitoring in impulsive individuals.

    PubMed

    Potts, Geoffrey F; George, Mary Reeni M; Martin, Laura E; Barratt, Ernest S

    This study measured the response-locked event-related potential during a flanker task with performance-based monetarily rewarding and punishing trials in 37 undergraduate students separated into high- and low-impulsive groups based on a median split on self-reported Barrett Impulsiveness Scale. The high-impulsive group had a smaller medial frontal error-related negativity (ERN) on punishment trials than the low-impulsive group. The medial prefrontal neural system of behavior monitoring, indexed by the ERN, appears less sensitive to punishment signals in normal impulsivity. This reduced punishment sensitivity in impulsivity, a personality variation associated with several mental and personality disorders including ADHD and substance abuse may be related to the tendency to select short-term rewards despite potential long-term negative consequences in these individuals.

  12. Finite Earth

    NASA Astrophysics Data System (ADS)

    2015-10-01

    The world has agreed on 17 Sustainable Development Goals, to be adopted this week. This is great progress towards acknowledging that the planet's finite resources need to be managed carefully in the face of humanity's unlimited aspirations.

  13. Do Different Facets of Impulsivity Predict Different Types of Aggression?

    PubMed Central

    Derefinko, Karen; DeWall, C. Nathan; Metze, Amanda V.; Walsh, Erin C.; Lynam, Donald R.

    2011-01-01

    The current study examined the relations between impulsivity-related traits (as assessed by the UPPS-P Impulsive Behavior Scale) and aggressive behaviors. Results indicated that UPPS-P Lack of Premeditation and Sensation Seeking were important in predicting general violence. In contrast, UPPS-P Urgency was most useful in predicting intimate partner violence. To further explore relations between intimate partner violence and Urgency, a measure of autonomic response to pleasant and aversive stimuli and facets of Neuroticism from the NEO PI-R were used as control variables. Autonomic responsivity was correlated with intimate partner violence at the zero-order level, and predicted significant variance in intimate partner violence in regression equations. However, UPPS-P Urgency was able to account for unique variance in intimate partner violence above and beyond measures of Neuroticism and arousal. Implications regarding the use of a multifaceted conceptualization of impulsivity in the prediction of different types of violent behavior are discussed. PMID:21259270

  14. Impulsivity, "advergames," and food intake.

    PubMed

    Folkvord, Frans; Anschütz, Doeschka J; Nederkoorn, Chantal; Westerik, Henk; Buijzen, Moniek

    2014-06-01

    Previous studies have focused on the effect of food advertisements on the caloric intake of children. However, the role of individual susceptibility in this effect is unclear. The aim of this study was to examine the role of impulsivity in the effect of advergames that promote energy-dense snacks on children's snack intake. First, impulsivity scores were assessed with a computer task. Then a randomized between-subject design was conducted with 261 children aged 7 to 10 years who played an advergame promoting either energy-dense snacks or nonfood products. As an extra manipulation, half of the children in each condition were rewarded for refraining from eating, the other half were not. Children could eat freely while playing the game. Food intake was measured. The children then completed questionnaire measures, and were weighed and measured. Overall, playing an advergame containing food cues increased general caloric intake. Furthermore, rewarding children to refrain from eating decreased their caloric intake. Finally, rewarding impulsive children to refrain from eating had no influence when they were playing an advergame promoting energy-dense snacks, whereas it did lead to reduced intake among low impulsive children and children who played nonfood advergames. Playing an advergame promoting energy-dense snacks contributes to increased caloric intake in children. The advergame promoting energy-dense snacks overruled the inhibition task to refrain from eating among impulsive children, making it more difficult for them to refrain from eating. The findings suggest that impulsivity plays an important role in susceptibility to food advertisements. Copyright © 2014 by the American Academy of Pediatrics.

  15. Depression and Impulsivity as Pathways to Violence: Implications for Antiaggressive Treatment

    PubMed Central

    Krakowski, Menahem I.; Czobor, Pal

    2014-01-01

    Background: Difficulties with affect regulation and impulse control have a strong influence on violence. The objective of this study was to determine whether baseline depression and impulsivity predict aggression and whether they predict differential response to antiaggressive treatment. This is important, as we lack knowledge as to the selection of antipsychotics for the treatment of aggression. Methods: Physically aggressive inpatients with schizophrenia who received an evaluation of depression and impulsivity at baseline were randomly assigned in a double-blind, parallel group, 12-week trial to clozapine, olanzapine, or haloperidol. Trait impulsivity was measured by the Barratt Impulsiveness Scale; depression by the Positive and Negative Syndrome Scale Depression factor. The number and severity of aggressive events, as measured by the Modified Overt Aggression Scale (MOAS), were the outcome measures. Results: Baseline depression and impulsivity predicted higher levels of aggression, as measured by the MOAS total score, over the 12-week treatment period across all 3 medication groups. In addition, there was a strong interaction effect between baseline depression/impulsivity and medication grouping in predicting MOAS score. In particular, when higher depression and impulsivity were present at baseline, patients on haloperidol presented with more aggression than patients on the other 3 medications. Conclusions: Depression and impulsivity are important predictors of aggression and of differential response to antiaggressive treatment. This is most likely due to the medications’ dissimilar neurotransmitter profiles. By identifying patients who will respond b