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Sample records for aerodynamic impulse responses

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Optimal impulsive manoeuvres and aerodynamic braking

    NASA Technical Reports Server (NTRS)

    Jezewski, D. J.

    1985-01-01

    A method developed for obtaining solutions to the aerodynamic braking problem, using impulses in the exoatmospheric phases is discussed. The solution combines primer vector theory and the results of a suboptimal atmospheric guidance program. For a specified initial and final orbit, the solution determines: (1) the minimum impulsive cost using a maximum of four impulses, (2) the optimal atmospheric entry and exit-state vectors subject to equality and inequality constraints, and (3) the optimal coast times. Numerical solutions which illustrate the characteristics of the solution are presented.

  7. 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.

  8. 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…

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Extension of a nonlinear systems theory to general-frequency unsteady transonic aerodynamic responses

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1993-01-01

    A methodology for modeling nonlinear unsteady aerodynamic responses, for subsequent use in aeroservoelastic analysis and design, using the Volterra-Wiener theory of nonlinear systems is presented. The methodology is extended to predict nonlinear unsteady aerodynamic responses of arbitrary frequency. The Volterra-Wiener theory uses multidimensional convolution integrals to predict the response of nonlinear systems to arbitrary inputs. The CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code is used to generate linear and nonlinear unit impulse responses that correspond to each of the integrals for a rectangular wing with a NACA 0012 section with pitch and plunge degrees of freedom. The computed kernels then are used to predict linear and nonlinear unsteady aerodynamic responses via convolution and compared to responses obtained using the CAP-TSD code directly. The results indicate that the approach can be used to predict linear unsteady aerodynamic responses exactly for any input amplitude or frequency at a significant cost savings. Convolution of the nonlinear terms results in nonlinear unsteady aerodynamic responses that compare reasonably well with those computed using the CAP-TSD code directly but at significant computational cost savings.

  15. Cascade flutter analysis with transient response aerodynamics

    NASA Technical Reports Server (NTRS)

    Bakhle, Milind A.; Mahajan, Aparajit J.; Keith, Theo G., Jr.; Stefko, George L.

    1991-01-01

    Two methods for calculating linear frequency domain aerodynamic coefficients from a time marching Full Potential cascade solver are developed and verified. In the first method, the Influence Coefficient, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier Transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers.

  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. 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.

  20. Response inhibition and its relation to multidimensional impulsivity.

    PubMed

    Wilbertz, Tilmann; Deserno, Lorenz; Horstmann, Annette; Neumann, Jane; Villringer, Arno; Heinze, Hans-Jochen; Boehler, Carsten N; Schlagenhauf, Florian

    2014-12-01

    Impulsivity is a multidimensional construct that has been suggested as a vulnerability factor for several psychiatric disorders, especially addiction disorders. Poor response inhibition may constitute one facet of impulsivity. Trait impulsivity can be assessed by self-report questionnaires such as the widely used Barratt Impulsiveness Scale (BIS-11). However, regarding the multidimensionality of impulsivity different concepts have been proposed, in particular the UPPS self-report questionnaire ('Urgency', 'Lack of Premeditation', 'Lack of Perseverance', 'Sensation Seeking') that is based on a factor analytic approach. The question as to which aspects of trait impulsivity map on individual differences of the behavioral and neural correlates of response inhibition so far remains unclear. In the present study, we investigated 52 healthy individuals that scored either very high or low on the BIS-11 and underwent a reward-modulated Stop-signal task during fMRI. Neither behavioral nor neural differences were observed with respect to high- and low-BIS groups. In contrast, UPPS subdomain Urgency best explained inter-individual variability in SSRT scores and was further negatively correlated to right IFG/aI activation in 'Stop>Go' trials - a key region for response inhibition. Successful response inhibition in rewarded compared to nonrewarded stop trials yielded ventral striatal (VS) activation which might represent a feedback signal. Interestingly, only participants with low Urgency scores were able to use this VS feedback signal for better response inhibition. Our findings indicate that the relationship of impulsivity and response inhibition has to be treated carefully. We propose Urgency as an important subdomain that might be linked to response inhibition as well as to the use of reward-based neural signals. Based on the present results, further studies examining the influence of impulsivity on psychiatric disorders should take into account Urgency as an important

  1. Forced response analysis of an aerodynamically detuned supersonic turbomachine rotor

    NASA Technical Reports Server (NTRS)

    Hoyniak, D.; Fleeter, S.

    1985-01-01

    High performance aircraft-engine fan and compressor blades are vulnerable to aerodynamically forced vibrations generated by inlet flow distortions due to wakes from upstream blade and vane rows, atmospheric gusts, and maldistributions in inlet ducts. In this report, an analysis is developed to predict the flow-induced forced response of an aerodynamically detuned rotor operating in a supersonic flow with a subsonic axial component. The aerodynamic detuning is achieved by alternating the circumferential spacing of adjacent rotor blades. The total unsteady aerodynamic loading acting on the blading, as a result of the convection of the transverse gust past the airfoil cascade and the resulting motion of the cascade, is developed in terms of influence coefficients. This analysis is used to investigate the effect of aerodynamic detuning on the forced response of a 12-blade rotor, with Verdon's Cascade B flow geometry as a uniformly spaced baseline configuration. The results of this study indicate that, for forward traveling wave gust excitations, aerodynamic detuning is very beneficial, resulting in significantly decreased maximum-amplitude blade responses for many interblade phase angles.

  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. 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.

  4. 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)

  5. 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…

  6. 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.

  7. 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.

  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.

  9. Satellite Aerodynamics and Density Determination from Satellite Dynamic Response

    NASA Technical Reports Server (NTRS)

    Karr, G. R.

    1972-01-01

    The aerodynamic drag and lift properties of a satellite are first expressed as a function of two parameters associated with gas-surface interaction at the satellite surface. The dynamic response of the satellite as it passes through the atmosphere is then expressed as a function of the two gas-surface interaction parameters, the atmospheric density, the satellite velocity, and the satellite orientation to the high speed flow. By proper correlation of the observed dynamic response with the changing angle of attack of the satellite, it is found that the two unknown gas-surface interaction parameters can be determined. Once the gas-surface interaction parameters are known, the aerodynamic properties of the satellite at all angles of attack are also determined.

  10. Unsteady aerodynamics and gust response in compressors and turbines

    SciTech Connect

    Manwaring, S.R.; Wisler, D.C. . GE Aircraft Engines)

    1993-10-01

    A comprehensive series of experiments and analyses was performed on compressor and turbine blading to evaluate the ability of current, practical, engineering/analysis models to predict unsteady aerodynamic loading of modern gas turbine blading. This is part of an ongoing effort to improve methods for preventing blading failure. The experiments were conducted in low-speed research facilities capable of simulating the relevant aerodynamic features of turbomachinery. Unsteady loading on compressor and turbine blading was generated by upstream wakes and, additionally for compressors, by a rotating inlet distortion. Fast-response hot-wire anemometry and pressure transducers embedded in the airfoil surfaces were used to determine the aerodynamic gusts and resulting unsteady pressure responses acting on the airfoils. This is the first time that gust response measurements for turbines have been reported in the literature. Several different analyses were used to predict the unsteady component of the blade loading: (1) a classical flat-plate analysis, (2) a two-dimensional linearized flow analysis with a frozen gust model, (3) a two-dimensional linearized flow analysis with a distorted gust model, (4) a two-dimensional linearized Euler analysis, and (5) a two-dimensional nonlinear Euler analysis. Also for the first time, a detailed comparison of these analyses methods is made and the importance of properly accounting for both vortical and potential disturbances is demonstrated. The predictions are compared with experiment and their abilities assessed to help guide designers in using these prediction schemes.

  11. 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

  12. Ground/Flight Correlation of Aerodynamic Loads with Structural Response

    NASA Technical Reports Server (NTRS)

    Mangalam, Arun S.; Davis, Mark C.

    2009-01-01

    Ground and flight tests provide a basis and methodology for in-flight characterization of the aerodynamic and structural performance through the monitoring of the fluid-structure interaction. The NF-15B flight tests of the Intelligent Flight Control System program provided a unique opportunity to test the correlation of aerodynamic loads with points of flow attaching and detaching from the surface, which are also known as flow bifurcation points, as observed in a previous wind tunnel test performed at the U.S. Air Force Academy (Colorado Springs, Colorado). Moreover, flight tests, along with the subsequent unsteady aerodynamic tests in the NASA Transonic Dynamics Tunnel (TDT), provide a basis using surface flow sensors as means of assessing the aeroelastic performance of flight vehicles. For the flight tests, the NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. This data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in a structural response, which were then compared with the hot-film sensor signals. The hot-film sensor signals near the stagnation region were found to be highly correlated with the root-bending strains. For the TDT tests, a flexible wing section developed under the U.S. Air Force Research Lab SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at two span stations. The TDT tests confirmed the correlation between flow bifurcation points and the wing structural response to tunnel-generated gusts. Furthermore, as the wings structural modes were excited by the gusts, a gradual phase change between the flow bifurcation point and the structural mode occurred during a resonant condition.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Aerodynamic configuration design using response surface methodology analysis

    NASA Astrophysics Data System (ADS)

    Engelund, Walter C.; Stanley, Douglas O.; Lepsch, Roger A.; McMillin, Mark M.; Unal, Resit

    1993-08-01

    An investigation has been conducted to determine a set of optimal design parameters for a single-stage-to-orbit reentry vehicle. Several configuration geometry parameters which had a large impact on the entry vehicle flying characteristics were selected as design variables: the fuselage fineness ratio, the nose to body length ratio, the nose camber value, the wing planform area scale factor, and the wing location. The optimal geometry parameter values were chosen using a response surface methodology (RSM) technique which allowed for a minimum dry weight configuration design that met a set of aerodynamic performance constraints on the landing speed, and on the subsonic, supersonic, and hypersonic trim and stability levels. The RSM technique utilized, specifically the central composite design method, is presented, along with the general vehicle conceptual design process. Results are presented for an optimized configuration along with several design trade cases.

  2. Aerodynamic configuration design using response surface methodology analysis

    NASA Technical Reports Server (NTRS)

    Engelund, Walter C.; Stanley, Douglas O.; Lepsch, Roger A.; Mcmillin, Mark M.; Unal, Resit

    1993-01-01

    An investigation has been conducted to determine a set of optimal design parameters for a single-stage-to-orbit reentry vehicle. Several configuration geometry parameters which had a large impact on the entry vehicle flying characteristics were selected as design variables: the fuselage fineness ratio, the nose to body length ratio, the nose camber value, the wing planform area scale factor, and the wing location. The optimal geometry parameter values were chosen using a response surface methodology (RSM) technique which allowed for a minimum dry weight configuration design that met a set of aerodynamic performance constraints on the landing speed, and on the subsonic, supersonic, and hypersonic trim and stability levels. The RSM technique utilized, specifically the central composite design method, is presented, along with the general vehicle conceptual design process. Results are presented for an optimized configuration along with several design trade cases.

  3. 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.

  4. 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.

  5. 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…

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Flights to asteroids from the orbit of an artificial earth satellite with a perturbational-aerodynamical impulse maneuver near Mars

    NASA Astrophysics Data System (ADS)

    Livanov, L. B.

    1992-06-01

    A spacecraft leaves the low orbit of an artificial earth satellite and, approaching Mars, descends, making the first half of a perturbational maneuver. Then the spacecraft slows down somewhat while flying in the Martian atmosphere at a constant altitude with a constant L/D(sc) less than 2.4. On some spacecraft launch dates in the time span from 1970 to 2020 a velocity impulse to about 2 km/s may be required upon exit from the atmosphere in the case of an optimal choice of dates for earth-Mars and Mars-asteroids flights. Then the spacecraft ascends over Mars, completing the second half of the perturbational maneuver. On the spacecrafts approach to the target asteroid, impulse equalization of the velocities of the spacecraft and the asteroid occurs. The sum of the three impulses - at the earth, Mars, and the asteroid - is usually 2 to 3 km/s less than the sum of the impulses required with direct optimal-trajectory earth-asteroid flights on the best dates in the same launch time span.

  11. 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.

  12. Flutter and forced response of turbomachinery with frequency mistuning and aerodynamic asymmetry

    NASA Astrophysics Data System (ADS)

    Miyakozawa, Tomokazu

    This dissertation provides numerical studies to improve bladed disk assembly design for preventing blade high cycle fatigue failures. The analyses are divided into two major subjects. For the first subject presented in Chapter 2, the mechanisms of transonic fan flutter for tuned systems are studied to improve the shortcoming of traditional method for modern fans using a 3D time-linearized Navier-Stokes solver. Steady and unsteady flow parameters including local work on the blade surfaces are investigated. It was found that global local work monotonically became more unstable on the pressure side due to the flow rollback effect. The local work on the suction side significantly varied due to nodal diameter and flow rollback effect. Thus, the total local work for the least stable mode is dominant by the suction side. Local work on the pressure side appears to be affected by the shock on the suction side. For the second subject presented in Chapter 3, sensitivity studies are conducted on flutter and forced response due to frequency mistuning and aerodynamic asymmetry using the single family of modes approach by assuming manufacturing tolerance. The unsteady aerodynamic forces are computed using CFD methods assuming aerodynamic symmetry. The aerodynamic asymmetry is applied by perturbing the influence coefficient matrix. These aerodynamic perturbations influence both stiffness and damping while traditional frequency mistuning analysis only perturbs the stiffness. Flutter results from random aerodynamic perturbations of all blades showed that manufacturing variations that effect blade unsteady aerodynamics may cause a stable, perfectly symmetric engine to flutter. For forced response, maximum blade amplitudes are significantly influenced by the aerodynamic perturbation of the imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to blade frequency mistuning where the stiffness perturbation dominates.

  13. 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.

  14. 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.

  15. Force balance in the take-off of a pierid butterfly: relative importance and timing of leg impulsion and aerodynamic forces.

    PubMed

    Bimbard, Gaëlle; Kolomenskiy, Dmitry; Bouteleux, Olivier; Casas, Jérôme; Godoy-Diana, Ramiro

    2013-09-15

    Up to now, the take-off stage has remained an elusive phase of insect flight that was relatively poorly explored compared with other maneuvers. An overall assessment of the different mechanisms involved in force production during take-off has never been explored. Focusing on the first downstroke, we have addressed this problem from a force balance perspective in butterflies taking off from the ground. In order to determine whether the sole aerodynamic wing force could explain the observed motion of the insect, we have firstly compared a simple analytical model of the wing force with the acceleration of the insect's center of mass estimated from video tracking of the wing and body motions. Secondly, wing kinematics were also used for numerical simulations of the aerodynamic flow field. Similar wing aerodynamic forces were obtained by the two methods. However, neither are sufficient, nor is the inclusion of the ground effect, to predict faithfully the body acceleration. We have to resort to the leg forces to obtain a model that best fits the data. We show that the median and hind legs display an active extension responsible for the initiation of the upward motion of the insect's body, occurring before the onset of the wing downstroke. We estimate that legs generate, at various times, an upward force that can be much larger than all other forces applied to the insect's body. The relative timing of leg and wing forces explains the large variability of trajectories observed during the maneuvers.

  16. 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.

  17. 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

  18. 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.

  19. Nonlinear Response of Composite Panels Under Combined Acoustic Excitation and Aerodynamic Pressure

    NASA Technical Reports Server (NTRS)

    Abdel-Motagaly, K.; Duan, B.; Mei, C.

    1999-01-01

    A finite element formulation is presented for the analysis of large deflection response of composite panels subjected to aerodynamic pressure- at supersonic flow and high acoustic excitation. The first-order shear deformation theory is considered for laminated composite plates, and the von Karman nonlinear strain-displacement relations are employed for the analysis of large deflection panel response. The first-order piston theory aerodynamics and the simulated Gaussian white noise are employed for the aerodynamic and acoustic loads, respectively. The nonlinear equations of motion for an arbitrarily laminated composite panel subjected to a combined aerodynamic and acoustic pressures are formulated first in structure node degrees-of-freedom. The system equations are then transformed and reduced to a set of coupled nonlinear equations in modal coordinates. Modal participation is defined and the in-vacuo modes to be retained in the analysis are based on the modal participation values. Numerical results include root mean square values of maximum deflections, deflection and strain response time histories, probability distributions, and power spectrum densities. Results showed that combined acoustic and aerodynamic loads have to be considered for panel analysis and design at high dynamic pressure values.

  20. Ground/Flight Correlation of Aerodynamic Loads with Structural Response

    NASA Technical Reports Server (NTRS)

    Mangalam, Arun S.; Davis, Mark C.

    2009-01-01

    United States Air Force Research Laboratory (AFRL) ground tests at the NASA Transonic Dynamics Tunnel (TDT) and NASA flight tests provide a basis and methodology for in-flight characterization of the aeroelastic performance through the monitoring of the fluid-structure interaction using surface flow sensors. NASA NF-15B flight tests provided a unique opportunity to test the correlation of aerodynamic loads with sectional flow attachment/detachment points, also known as flow bifurcation points (FBPs), as observed in previous wind tunnel tests. The NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. These data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in root-bending strains and hot-film sensor signals near the stagnation region that were highly correlated. For the TDT tests, a flexible wing section developed under the AFRL SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at multiple span stations. The TDT tests provided data showing a gradual phase change between the FBP and the structural mode occurred during a resonant condition as the wings structural modes were excited by the tunnel-generated gusts.

  1. Aeroelastic stability consideration of supersonic flight vehicle using nonlinear aerodynamic response surfaces

    NASA Astrophysics Data System (ADS)

    Fathi Jegarkandi, M.; Nobari, A. S.; Sabzehparvar, M.; Haddadpour, H.

    2009-08-01

    Aeroelastic stability of a flexible supersonic flight vehicle is considered using nonlinear dynamics, nonlinear aerodynamics, and a linear structural model. Response surfaces including global multivariate orthogonal modeling functions are invoked to derive applied nonlinear aerodynamic coefficients. A modified Gram-Schmidt method is utilized to orthogonalize the produced polynomial multivariate functions, selected and ranked by predicted squared error metric. Local variation of angle-of-attack and side-slip angle is applied to the analytical model. Identification of nonlinear aerodynamic coefficients of the flight vehicle is conducted employing a CFD code and the required analytical model for simulation purposes is constructed. The method is used to determine the aeroelastic instability and response of a selected flight vehicle.

  2. 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

  3. Unsteady Cascade Aerodynamic Response Using a Multiphysics Simulation Code

    NASA Technical Reports Server (NTRS)

    Lawrence, C.; Reddy, T. S. R.; Spyropoulos, E.

    2000-01-01

    The multiphysics code Spectrum(TM) is applied to calculate the unsteady aerodynamic pressures of oscillating cascade of airfoils representing a blade row of a turbomachinery component. Multiphysics simulation is based on a single computational framework for the modeling of multiple interacting physical phenomena, in the present case being between fluids and structures. Interaction constraints are enforced in a fully coupled manner using the augmented-Lagrangian method. The arbitrary Lagrangian-Eulerian method is utilized to account for deformable fluid domains resulting from blade motions. Unsteady pressures are calculated for a cascade designated as the tenth standard, and undergoing plunging and pitching oscillations. The predicted unsteady pressures are compared with those obtained from an unsteady Euler co-de refer-red in the literature. The Spectrum(TM) code predictions showed good correlation for the cases considered.

  4. 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…

  5. 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.

  6. Estimation of Supersonic Stage Separation Aerodynamics of Winged-Body Launch Vehicles Using Response Surface Methods

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.; Deloach, Richard

    2008-01-01

    A collection of statistical and mathematical techniques referred to as response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration using data obtained on small-scale models at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. The simulated Mach 3 staging was dominated by multiple shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. This motivated a partitioning of the overall inference space into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using cuboidal and spherical central composite designs capable of fitting full second-order response functions. The primary goal was to approximate the underlying overall aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle using relatively simple, lower-order polynomial functions that were piecewise-continuous across the full independent variable ranges of interest. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. The potential benefits of augmenting the central composite designs to full third order using computer-generated D-optimality criteria were also evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting low-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed.

  7. Estimation of Supersonic Stage Separation Aerodynamics of Winged-Body Launch Vehicles Using Response Surface Methods

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.

    2010-01-01

    Response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration at supersonic speeds in the NASA LaRC Unitary Plan Wind Tunnel. The Mach 3 staging was dominated by shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. The inference space was partitioned into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using central composite designs capable of fitting full second-order response functions. The underlying aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle were estimated using piecewise-continuous lower-order polynomial functions. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. Augmenting the central composite designs to full third-order using computer-generated D-optimality criteria was evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting lower-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed.

  8. 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

  9. Response of a Rotating Propeller to Aerodynamic Excitation

    NASA Technical Reports Server (NTRS)

    Arnoldi, Walter E.

    1949-01-01

    The flexural vibration of a rotating propeller blade with clamped shank is analyzed with the object of presenting, in matrix form, equations for the elastic bending moments in forced vibration resulting from aerodynamic forces applied at a fixed multiple of rotational speed. Matrix equations are also derived which define the critical speeds end mode shapes for any excitation order and the relation between critical speed and blade angle. Reference is given to standard works on the numerical solution of matrix equations of the forms derived. The use of a segmented blade as an approximation to a continuous blade provides a simple means for obtaining the matrix solution from the integral equation of equilibrium, so that, in the numerical application of the method presented, the several matrix arrays of the basic physical characteristics of the propeller blade are of simple form, end their simplicity is preserved until, with the solution in sight, numerical manipulations well-known in matrix algebra yield the desired critical speeds and mode shapes frame which the vibration at any operating condition may be synthesized. A close correspondence between the familiar Stodola method and the matrix method is pointed out, indicating that any features of novelty are characteristic not of the analytical procedure but only of the abbreviation, condensation, and efficient organization of the numerical procedure made possible by the use of classical matrix theory.

  10. 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.

  11. 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.

  12. Forcing function effects on unsteady aerodynamic gust response. II - Low solidity airfoil row response

    NASA Technical Reports Server (NTRS)

    Henderson, Gregory H.; Fleeter, Sanford

    1992-01-01

    The paper investigates the fundamental gust modeling assumption on the basis of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady period flow field is generated by rotating flows of perforated plates and airfoil cascades, with the resulting unsteady periodic chordwise pressure response of a downstream low solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the forcing function exhibited the characteristics of a linear-theory gust, the resulting response on the downstream stator airfoils was in excellent agreement with the linear-theory models. When the forcing function did not exhibit linear-theory gust characteristics, the resulting unsteady aerodynamic response of the downstream stators was much more complex and correlated poorly with the linear-theory gust predictions. It is shown that the forcing function generator significantly affects the resulting gust response, with the complexity of the response characteristics increasing from the perforated-plate to the airfoil-cascade forcing functions.

  13. Forcing function effects on unsteady aerodynamic gust response: Part 2--Low solidity airfoil row response

    SciTech Connect

    Henderson, G.H.; Fleeter, S. . School of Mechanical Engineering)

    1993-10-01

    The fundamental gust modeling assumption is investigated by means of series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades, with the resulting unsteady periodic chord wise pressure response of a downstream low-solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the forcing function exhibited the characteristic of a linear-theory vortical gust, as was the case for the perforated-plate wake generators, the resulting response on the downstream stator airfoils was in excellent agreement with the linear-theory models. In contrast, when the forcing function did not exhibit linear-theory vortical gust characteristics, i.e., for the airfoil wake generators, the resulting unsteady aerodynamic responses of the downstream stators were much more complex and correlated poorly with the linear-theory gust predictions. Thus, this investigation has quantitatively shown that the forcing function generator significantly affects the resulting gust response, with the complexity of the response characteristics increasing from the perforated-plate to the airfoil-cascade forcing functions.

  14. 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.

  15. 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

  16. Development of a system for aerodynamic fast-response probe measurements

    NASA Astrophysics Data System (ADS)

    Gossweiler, C.; Humm, H.; Kupferschmied, P.

    This paper describes the development of a fast-response probe measurement system. Small pressure probes have been equipped with up to 4 miniature pressure sensors. The high frequency response of such sensors allied to minimized cavities between the flow and the sensing diaphragm enables the probe system to take measurements up to 40 kHz bandwidth (typical blade passing frequency: 2-10 kHz). First results of investigations on the aerodynamic of high frequency response measurement probes are presented including experiments in a water towing channel with unsteady flows around different probe geometries. The packaging of the sensor chip into the probe, the properties of the sensors and the measurement errors are examined. Probe calibration methods and aerodynamic evaluation procedures are discussed, followed by a presentation of the data acquisition system and of the data evaluation software. Measurements in a radial compressor test rig and in a fully developed pipe flow are shown as applications.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Linearized Unsteady Aerodynamic Analysis of the Acoustic Response to Wake/Blade-Row Interaction

    NASA Technical Reports Server (NTRS)

    Verdon, Joseph M.; Huff, Dennis L. (Technical Monitor)

    2001-01-01

    The three-dimensional, linearized Euler analysis, LINFLUX, is being developed to provide a comprehensive and efficient unsteady aerodynamic scheme for predicting the aeroacoustic and aeroelastic responses of axial-flow turbomachinery blading. LINFLUX couples a near-field, implicit, wave-split, finite-volume solution to far-field acoustic eigensolutions, to predict the aerodynamic responses of a blade row to prescribed structural and aerodynamic excitations. It is applied herein to predict the acoustic responses of a fan exit guide vane (FEGV) to rotor wake excitations. The intent is to demonstrate and assess the LINFLUX analysis via application to realistic wake/blade-row interactions. Numerical results are given for the unsteady pressure responses of the FEGV, including the modal pressure responses at inlet and exit. In addition, predictions for the modal and total acoustic power levels at the FEGV exit are compared with measurements. The present results indicate that the LINFLUX analysis should be useful in the aeroacoustic design process, and for understanding the three-dimensional flow physics relevant to blade-row noise generation and propagation.

  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. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  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. 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

  11. 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.

  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. 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.

  14. Development of Unsteady Aerodynamic State-Space Models from CFD-Based Pulse Responses

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.; Raveh, Daniella E.

    2001-01-01

    A method for computing discrete-time state-space models of linearized unsteady aerodynamic behavior directly from aeroelastic CFD codes is presented. The method involves the treatment of CFD-based pulse responses as Markov parameters for use in a system identification /realization algorithm. Results are presented for the AGARD 445.6 Aeroelastic Wing with four aeroelastic modes at a Mach number of 0.96 using the EZNSS Euler/Navier-Stokes flow solver with aeroelastic capability. The System/Observer/Controller Identification Toolbox (SOCIT) algorithm, based on the Ho-Kalman realization algorithm, is used to generate 15th- and 32nd-order discrete-time state-space models of the unsteady aerodynamic response of the wing over the entire frequency range of interest.

  15. 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.

  16. Development of a linearized unsteady aerodynamic analysis for cascade gust response predictions

    NASA Technical Reports Server (NTRS)

    Verdon, Joseph M.; Hall, Kenneth C.

    1990-01-01

    A method for predicting the unsteady aerodynamic response of a cascade of airfoils to entropic, vortical, and acoustic gust excitations is being developed. Here, the unsteady flow is regarded as a small perturbation of a nonuniform isentropic and irrotational steady background flow. A splitting technique is used to decompose the linearized unsteady velocity into rotational and irrotational parts leading to equations for the complex amplitudes of the linearized unsteady entropy, rotational velocity, and velocity potential that are coupled only sequentially. The entropic and rotational velocity fluctuations are described by transport equations for which closed-form solutions in terms of the mean-flow drift and stream functions can be determined. The potential fluctuation is described by an inhomogeneous convected wave equation in which the source term depends on the rotational velocity field, and is determined using finite-difference procedures. The analytical and numerical techniques used to determine the linearized unsteady flow are outlined. Results are presented to indicate the status of the solution procedure and to demonstrate the impact of blade geometry and mean blade loading on the aerodynamic response of cascades to vortical gust excitations. The analysis described herein leads to very efficient predictions of cascade unsteady aerodynamic response phenomena making it useful for turbomachinery aeroelastic and aeroacoustic design applications.

  17. 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.

  18. Assessment of CFD-based Response Surface Model for Ares I Supersonic Ascent Aerodynamics

    NASA Technical Reports Server (NTRS)

    Hanke, Jeremy L.

    2011-01-01

    The Ascent Force and Moment Aerodynamic (AFMA) Databases (DBs) for the Ares I Crew Launch Vehicle (CLV) were typically based on wind tunnel (WT) data, with increments provided by computational fluid dynamics (CFD) simulations for aspects of the vehicle that could not be tested in the WT tests. During the Design Analysis Cycle 3 analysis for the outer mold line (OML) geometry designated A106, a major tunnel mishap delayed the WT test for supersonic Mach numbers (M) greater than 1.6 in the Unitary Plan Wind Tunnel at NASA Langley Research Center, and the test delay pushed the final delivery of the A106 AFMA DB back by several months. The aero team developed an interim database based entirely on the already completed CFD simulations to mitigate the impact of the delay. This CFD-based database used a response surface methodology based on radial basis functions to predict the aerodynamic coefficients for M > 1.6 based on only the CFD data from both WT and flight Reynolds number conditions. The aero team used extensive knowledge of the previous AFMA DB for the A103 OML to guide the development of the CFD-based A106 AFMA DB. This report details the development of the CFD-based A106 Supersonic AFMA DB, constructs a prediction of the database uncertainty using data available at the time of development, and assesses the overall quality of the CFD-based DB both qualitatively and quantitatively. This assessment confirms that a reasonable aerodynamic database can be constructed for launch vehicles at supersonic conditions using only CFD data if sufficient knowledge of the physics and expected behavior is available. This report also demonstrates the applicability of non-parametric response surface modeling using radial basis functions for development of aerodynamic databases that exhibit both linear and non-linear behavior throughout a large data space.

  19. 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.

  20. Advanced Response Surface Modeling of Ares I Roll Control Jet Aerodynamic Interactions

    NASA Technical Reports Server (NTRS)

    Favaregh, Noah M.

    2010-01-01

    The Ares I rocket uses roll control jets. These jets have aerodynamic implications as they impinge on the surface and protuberances of the vehicle. The jet interaction on the body can cause an amplification or a reduction of the rolling moment produced by the jet itself, either increasing the jet effectiveness or creating an adverse effect. A design of experiments test was planned and carried out using computation fluid dynamics, and a subsequent response surface analysis ensued on the available data to characterize the jet interaction across the ascent portion of the Ares I flight envelope. Four response surface schemes were compared including a single response surface covering the entire design space, separate sector responses that did not overlap, continuously overlapping surfaces, and recursive weighted response surfaces. These surfaces were evaluated on traditional statistical metrics as well as visual inspection. Validation of the recursive weighted response surface was performed using additionally available data at off-design point locations.

  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. Investigation on the forced response of a radial turbine under aerodynamic excitations

    NASA Astrophysics Data System (ADS)

    Ma, Chaochen; Huang, Zhi; Qi, Mingxu

    2016-04-01

    Rotor blades in a radial turbine with nozzle guide vanes typically experience harmonic aerodynamic excitations due to the rotor stator interaction. Dynamic stresses induced by the harmonic excitations can result in high cycle fatigue (HCF) of the blades. A reliable prediction method for forced response issue is essential to avoid the HCF problem. In this work, the forced response mechanisms were investigated based on a fluid structure interaction (FSI) method. Aerodynamic excitations were obtained by three-dimensional unsteady computational fluid dynamics (CFD) simulation with phase shifted periodic boundary conditions. The first two harmonic pressures were determined as the primary components of the excitation and applied to finite element (FE) model to conduct the computational structural dynamics (CSD) simulation. The computed results from the harmonic forced response analysis show good agreement with the predictions of Singh's advanced frequency evaluation (SAFE) diagram. Moreover, the mode superposition method used in FE simulation offers an efficient way to provide quantitative assessments of mode response levels and resonant strength.

  4. Summary of methods for calculating dynamic lateral stability and response and for estimating aerodynamic stability derivatives

    NASA Technical Reports Server (NTRS)

    Campbell, John P; Mckinney, Marion O

    1952-01-01

    A summary of methods for making dynamic lateral stability and response calculations and for estimating the aerodynamic stability derivatives required for use in these calculations is presented. The processes of performing calculations of the time histories of lateral motions, of the period and damping of these motions, and of the lateral stability boundaries are presented as a series of simple straightforward steps. Existing methods for estimating the stability derivatives are summarized and, in some cases, simple new empirical formulas are presented. Detailed estimation methods are presented for low-subsonic-speed conditions but only a brief discussion and a list of references are given for transonic and supersonic speed conditions.

  5. 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

  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. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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).

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Handling properties of diverse automobiles and correlation with full scale response data. [driver/vehicle response to aerodynamic disturbances

    NASA Technical Reports Server (NTRS)

    Hoh, R. H.; Weir, D. H.

    1973-01-01

    Driver/vehicle response and performance of a variety of vehicles in the presence of aerodynamic disturbances are discussed. Steering control is emphasized. The vehicles include full size station wagon, sedan, compact sedan, van, pickup truck/camper, and wagon towing trailer. Driver/vehicle analyses are used to estimate response and performance. These estimates are correlated with full scale data with test drivers and the results are used to refine the driver/vehicle models, control structure, and loop closure criteria. The analyses and data indicate that the driver adjusts his steering control properties (when he can) to achieve roughly the same level of performance despite vehicle variations. For the more disturbance susceptible vehicles, such as the van, the driver tightens up his control. Other vehicles have handling dynamics which cause him to loosen his control response, even though performance degrades.

  18. 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…

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. A simulator investigation of the influence of engine response characteristics on the approach and landing for an externally blown flap aircraft. Part 2: Aerodynamic model

    NASA Technical Reports Server (NTRS)

    Ciffone, D. L.; Robinson, G. H.

    1973-01-01

    An analysis of the influence of engine response characteristics on the approach and landing of an externally blown flap aircraft was conducted using flight simulator facilities. The configuration of the aerodynamic model is described. The aerodynamic characteristics as a function of angle of attack, thrust coefficient, and flap deflection are presented in tabular form and as graphs.

  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. 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

  10. 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.

  11. Application of two-dimensional unsteady aerodynamic to a free-tip rotor response analysis

    NASA Technical Reports Server (NTRS)

    Yates, L.; Kumagai, H.

    1985-01-01

    The free-tip rotor utilizes a rotor blade tip which is structurally decoupled from the blade inboard section. The tip is free to pitch about its own pitch axis to respond to the local flow angularity changes. The tip also experiences the heaving motion due to the flapping of the rotor blade. For an airfoil in any pitching and heaving motion which can be expanded into a Fourier series, the lift and moment calculated by Theodoren's theory is simply the linear combination of the lift and moment calculated for each harmonic. These lift and moment are then used to determine the response of the free-tip rotor. A parametric study is performed to determine the effect of mechanical damping, mechanical spring, sweep, friction, and a constant control moment on the free-tip rotor response characteristics and the resulting azimuthal lift distributions. The results showed that the free-tip has the capability to suppress the oscillatory lift distribution around the azimuth and to eliminate a significant negative life peak on the advancing tip. This result agrees with the result of the previous analysis based on the steady aerodynamics.

  12. 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.

  13. 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.

  14. Forcing function effects on unsteady aerodynamic gust response: Part 1--Forcing functions

    SciTech Connect

    Henderson, G.H.; Fleeter, S. . School of Mechanical Engineering)

    1993-10-01

    The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades. In this paper, the measured unsteady flow fields are compared to linear-theory vortical gust requirements, with the resulting unsteady gust response of a downstream stator cascade correlated with linear theory predictions in an accompanying paper. The perforated-plate forcing functions closely resemble linear-theory forcing functions, with the static pressure fluctuations small and the periodic velocity vectors parallel to the downstream mean-relative flow angle over the entire periodic cycle. In contrast, the airfoil forcing functions exhibit characteristics far from linear-theory vortical gusts, with the alignment of the velocity vectors and the static pressure fluctuation amplitudes dependent on the rotor-loading conditions, rotor solidity, and the inlet mean-relative flow angle. Thus, these unique data clearly show that airfoil wakes, both compressor and turbine, are not able to be modeled with the boundary conditions of current state-of-the-art linear unsteady aerodynamic theory.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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)

  20. 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.

  1. 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.

  2. 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

  3. Unsteady Aerodynamic Response of Oscillating Contra-Rotating Annular Cascades Part II: Numerical Study

    NASA Astrophysics Data System (ADS)

    Nishino, Ryohei; Namba, Masanobu

    The unsteady aerodynamic force and work for contra-rotating annular cascades of oscillating blades are numerically investigated. A comparison among frequency components of unsteady blade loadings on oscillating blades and stationary blades in relative rotational motion is conducted. It is proved that the state of generated acoustic duct mode of the lowest order is a key factor governing the aeroacoustic interaction between the blade rows. The effect of the neighboring blade row on the aerodynamic force and work is never small and will make substantial modifications to the flutter boundaries of an isolated blade row.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. The influence of vehicle aerodynamic and control response characteristics on driver-vehicle performance

    NASA Technical Reports Server (NTRS)

    Alexandridis, A. A.; Repa, B. S.; Wierwille, W. W.

    1978-01-01

    The effects of changes in understeer, control sensitivity, and location of the lateral aerodynamic center of pressure (c.p.) of a typical passenger car on the driver's opinion and on the performance of the driver-vehicle system were studied in a moving-base driving simulator. Twelve subjects with no prior experience on the simulator and no special driving skills performed regulation tasks in the presence of both random and step wind gusts.

  10. 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.

  11. 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

  12. 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).

  13. Flight investigation of XB-70 structural response to oscillatory aerodynamic shaker excitation and correlation with analytical results

    NASA Technical Reports Server (NTRS)

    Mckay, J. M.; Kordes, E. E.; Wykes, J. H.

    1973-01-01

    The low frequency symmetric structural response and damping characteristics of the XB-70 airplane were measured at four flight conditions: heavyweight at a Mach number of 0.87 at an altitude of 7620 meters (25,000 feet); lightweight at a Mach number of 0.86 at an altitude of 7620 meters (25,000 feet); a Mach number of 1.59 at an altitude of 11,918 meters (39.100 feet); and a Mach number of 2.38 and an altitude of 18,898 meters (62,000 feet). The flight data are compared with the response calculated by using early XB-70 design data and with the response calculated with mass, structural, and aerodynamic data updated to reflect as closely as possible the airplane characteristics at three of the flight conditions actually flown.

  14. 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

  15. 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.

  16. Analysis of aerodynamic coefficients using gradient data: Spanwise turbulence effects on airplane response

    NASA Technical Reports Server (NTRS)

    Ringnes, E. A.; Frost, W.

    1986-01-01

    The influence of spanwise turbulence on airplane dynamic behavior is determined. Calculations are based on data collected from test flights with the NASA B-57 research aircraft. The approach is to first compute aerodynamic forces and moments due to a spanwise distribution of angle of attack and airspeed. Secondly, these quantities are incorporated into the equations of motion. Simulation of flights done with the effects of spanwise turbulence included are compared to simulations without any spanwise turbulence. The findings of the study are that the moments developed by turbulence along the span are significant and that more realistic flight simulation can be achieved by including the spanwise turbulence terms.

  17. The effect of the nonlinear velocity and history dependencies of the aerodynamic force on the dynamic response of a rotating wind turbine blade

    NASA Astrophysics Data System (ADS)

    van der Male, Pim; van Dalen, Karel N.; Metrikine, Andrei V.

    2016-11-01

    Existing models for the analysis of offshore wind turbines account for the aerodynamic action on the turbine rotor in detail, requiring a high computational price. When considering the foundation of an offshore wind turbine, however, a reduced rotor model may be sufficient. To define such a model, the significance of the nonlinear velocity and history dependency of the aerodynamic force on a rotating blade should be known. Aerodynamic interaction renders the dynamics of a rotating blade in an ambient wind field nonlinear in terms of the dependency on the wind velocity relative to the structural motion. Moreover, the development in time of the aerodynamic force does not follow the flow velocity instantaneously, implying a history dependency. In addition, both the non-uniform blade geometry and the aerodynamic interaction couple the blade motions in and out of the rotational plane. Therefore, this study presents the Euler-Bernoulli formulation of a twisted rotating blade connected to a rigid hub, excited by either instantaneous or history-dependent aerodynamic forces. On this basis, the importance of the history dependency is determined. Moreover, to assess the nonlinear contributions, both models are linearized. The structural response is computed for a stand-still and a rotating blade, based on the NREL 5-MW turbine. To this end, the model is reduced on the basis of its first three free-vibration mode shapes. Blade tip response predictions, computed from turbulent excitation, correctly account for both modal and directional couplings, and the added damping resulting from the dependency of the aerodynamic force on the structural motion. Considering the deflection of the blade tip, the history-dependent and the instantaneous force models perform equally well, providing a basis for the potential use of the instantaneous model for the rotor reduction. The linearized instantaneous model provides similar results for the rotating blade, indicating its potential

  18. 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.

  19. 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.

  20. 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.

  1. Forcing function effects on unsteady aerodynamic gust response. I - Forcing functions

    NASA Technical Reports Server (NTRS)

    Henderson, Gregory H.; Fleeter, Sanford

    1992-01-01

    The paper investigates the fundamental gust modeling assumption on the basis of a series of experiments performed in the Purdue Annular Cascade Research Facility. The measured unsteady flow fields are compared to linear-theory gust requirements. The perforated plate forcing functions closely resemble linear-theory forcing functions, with the static pressure fluctuations small and the periodic velocity vectors parallel to the downstream mean-relative flow angle over the entire periodic cycle. The airfoil forcing functions exhibit characteristics far from linear-theory gusts, with the alignment of the velocity vectors and the static pressure fluctuation amplitudes dependent on the rotor-loading condition, rotor solidity, and the inlet mean-relative flow angle. It is shown that airfoil wakes, both compressor and turbine, cannot be modeled with the boundary conditions of current state-of-the-art linear unsteady aerodynamic theory.

  2. Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

    NASA Astrophysics Data System (ADS)

    Panther, Chad C.

    Vertical Axis Wind Turbines (VAWTs) have experienced a renewed interest in development for urban, remote, and offshore applications. Past research has shown that VAWTs cannot compete with Horizontals Axis Wind Turbines (HAWTs) in terms of energy capture efficiency. VAWT performance is plagued by dynamic stall (DS) effects at low tip-speed ratios (lambda), where each blade pitches beyond static stall multiple times per revolution. Furthermore, for lambda<2, blades operate outside of stall during over 70% of rotation. However, VAWTs offer many advantages such as omnidirectional operation, ground proximity of generator, lower sound emission, and non-cantilevered blades with longer life. Thus, mitigating dynamic stall and improving VAWT blade aerodynamics for competitive power efficiency has been a popular research topic in recent years and the directive of this study. Past research at WVU focused on the addition of circulation control (CC) technology to improve VAWT aerodynamics and expand the operational envelope. A novel blade design was generated from the augmentation of a NACA0018 airfoil to include CC capabilities. Static wind tunnel data was collected for a range of steady jet momentum coefficients (0.01≤ Cmu≤0.10) for analytical vortex model performance projections. Control strategies were developed to optimize CC jet conditions throughout rotation, resulting in improved power output for 2≤lambda≤5. However, the pumping power required to produce steady CC jets reduced net power gains of the augmented turbine by approximately 15%. The goal of this work was to investigate pulsed CC jet actuation to match steady jet performance with reduced mass flow requirements. To date, no experimental studies have been completed to analyze pulsed CC performance on a pitching airfoil. The research described herein details the first study on the impact of steady and pulsed jet CC on pitching VAWT blade aerodynamics. Both numerical and experimental studies were

  3. Unsteady Aerodynamic Response of Oscillating Contra-Rotating Annular Cascades Part I: Description of Model and Mathematical Formulations

    NASA Astrophysics Data System (ADS)

    Namba, Masanobu; Nishino, Ryohei

    The purpose of this paper is to study the effect of neighboring blade rows on the unsteady aerodynamic response of oscillating cascade blades on the basis of a genuine three-dimensional model. To this end, mathematical formulations based on the lifting surface theory are developed for a pair of contra-rotating annular cascades of oscillating blades. The mechanism of frequency scattering of blade loadings and mode scattering of acoustic waves resulting from interaction between the blade rows in relative rotational motions is mathematically explained. Simultaneous integral equations for all frequency components of blade loadings are derived from the flow tangency condition on the blade surfaces of both blade rows. The validity of the computation codes is verified.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. Aerodynamics and vortical structures in hovering fruitflies

    NASA Astrophysics Data System (ADS)

    Meng, Xue Guang; Sun, Mao

    2015-03-01

    We measure the wing kinematics and morphological parameters of seven freely hovering fruitflies and numerically compute the flows of the flapping wings. The computed mean lift approximately equals to the measured weight and the mean horizontal force is approximately zero, validating the computational model. Because of the very small relative velocity of the wing, the mean lift coefficient required to support the weight is rather large, around 1.8, and the Reynolds number of the wing is low, around 100. How such a large lift is produced at such a low Reynolds number is explained by combining the wing motion data, the computed vortical structures, and the theory of vorticity dynamics. It has been shown that two unsteady mechanisms are responsible for the high lift. One is referred as to "fast pitching-up rotation": at the start of an up- or downstroke when the wing has very small speed, it fast pitches down to a small angle of attack, and then, when its speed is higher, it fast pitches up to the angle it normally uses. When the wing pitches up while moving forward, large vorticity is produced and sheds at the trailing edge, and vorticity of opposite sign is produced near the leading edge and on the upper surface, resulting in a large time rate of change of the first moment of vorticity (or fluid impulse), hence a large aerodynamic force. The other is the well known "delayed stall" mechanism: in the mid-portion of the up- or downstroke the wing moves at large angle of attack (about 45 deg) and the leading-edge-vortex (LEV) moves with the wing; thus, the vortex ring, formed by the LEV, the tip vortices, and the starting vortex, expands in size continuously, producing a large time rate of change of fluid impulse or a large aerodynamic force.

  9. 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

  10. Unsteady aerodynamics of blade rows

    NASA Technical Reports Server (NTRS)

    Verdon, Joseph M.

    1989-01-01

    The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic or aeroacoustic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The major emphasis is placed on the description of a linearized inviscid theory which fully accounts for the affects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this linearization was developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to prescribed blade motions. The motivation for this linearized unsteady aerodynamic theory is focused on, its physical and mathematical formulation is outlined and examples are presented to illustrate the status of numerical solution procedures and several effects of mean flow nonuniformity on unsteady aerodynamic response.

  11. 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…

  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. User's Guide for MSAP2D: A Program for Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Multistage Compressors and Turbines. 1.0

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Srivastava, R.

    1996-01-01

    This guide describes the input data required for using MSAP2D (Multi Stage Aeroelastic analysis Program - Two Dimensional) computer code. MSAP2D can be used for steady, unsteady aerodynamic, and aeroelastic (flutter and forced response) analysis of bladed disks arranged in multiple blade rows such as those found in compressors, turbines, counter rotating propellers or propfans. The code can also be run for single blade row. MSAP2D code is an extension of the original NPHASE code for multiblade row aerodynamic and aeroelastic analysis. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The aeroelastic equations are solved in time domain. For single blade row analysis, frequency domain analysis is also provided to obtain unsteady aerodynamic coefficients required in an eigen analysis for flutter. In this manual, sample input and output are provided for a single blade row example, two blade row example with equal and unequal number of blades in the blade rows.

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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

  19. Chaff Aerodynamics

    DTIC Science & Technology

    1975-11-01

    further improve the contrast all of the interior surfaces of the test chamber are painted flat black and the bac!-,ground walls in view of the cameras...to be adequate to eliminate wall effects on the chaff aerodynamics. Secondly, the chamber air mass had to be sufficiently small that it would damp out...independently- supported special rotating-shutter system to "strobe" the dipole images. The integral shutter in each lens assembly is also retained for

  20. 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.

  1. 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

  2. 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.

  3. PREFACE: Aerodynamic sound Aerodynamic sound

    NASA Astrophysics Data System (ADS)

    Akishita, Sadao

    2010-02-01

    The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied to newly emerged public nuisances. This issue of Fluid Dynamics Research (FDR) reflects problems of environmental sound in present Japanese technology. The Japanese community studying aerodynamic sound has held an annual symposium since 29 years ago when the late Professor S Kotake and Professor S Kaji of Teikyo University organized the symposium. Most of the Japanese authors in this issue are members of the annual symposium. I should note the contribution of the two professors cited above in establishing the Japanese community of aerodynamic sound research. It is my pleasure to present the publication in this issue of ten papers discussed at the annual symposium. I would like to express many thanks to the Editorial Board of FDR for giving us the chance to contribute these papers. We have a review paper by T Suzuki on the study of jet noise, which continues to be important nowadays, and is expected to reform the theoretical model of generating mechanisms. Professor M S Howe and R S McGowan contribute an analytical paper, a valuable study in today's fluid dynamics research. They apply hydrodynamics to solve the compressible flow generated in the vocal cords of the human body. Experimental study continues to be the main methodology in aerodynamic sound, and it is expected to explore new horizons. H Fujita's study on the Aeolian tone provides a new viewpoint on major, longstanding sound problems. The paper by M Nishimura and T Goto on textile fabrics describes new technology for the effective reduction of bluff-body noise. The paper by T Sueki et al also reports new technology for the

  4. 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

  5. A methodology for using nonlinear aerodynamics in aeroservoelastic analysis and design

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1991-01-01

    A methodology is presented for using the Volterra-Wiener theory of nonlinear systems in aeroservoelastic (ASE) analyses and design. The theory is applied to the development of nonlinear aerodynamic response models that can be defined in state-space form and are, therefore, appropriate for use in modern control theory. The theory relies on the identification of nonlinear kernels that can be used to predict the response of a nonlinear system due to an arbitrary input. A numerical kernel identification technique, based on unit impulse responses, is presented and applied to a simple bilinear, single-input single-output (SISO) system. The linear kernel (unit impulse response) and the nonlinear second-order kernel of the system are numerically-identified and compared with the exact, analytically-defined and linear and second-order kernels. This kernel identification technique is then applied to the CAP-TSD (Computational Aeroelasticity Program-Transonic Small Disturbance) code for identification of the linear and second-order kernels of a NACA64A010 rectangular wing undergoing pitch at M = 0.5, M = 8.5 (transonic), and M = 0.93 (transonic). Results presented demonstrate the feasibility of this approach for use with nonlinear, unsteady aerodynamic responses.

  6. A methodology for using nonlinear aerodynamics in aeroservoelastic analysis and design

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1991-01-01

    A methodology is presented for using the Volterra-Wiener theory of nonlinear systems in aeroservoelastic (ASE) analyses and design. The theory is applied to the development of nonlinear aerodynamic response models that can be defined in state-space form and are, therefore, appropriate for use in modern control theory. The theory relies on the identification of nonlinear kernels that can be used to predict the response of a nonlinear system due to an arbitrary input. A numerical kernel identification technique, based on unit impulse responses, is presented and applied to a simple bilinear, single-input-single-output system. The linear kernel (unit impulse response) and the nonlinear second-order kernel of the system are numerically-identified and compared with the exact, analytically-defined linear and second-order kernels. This kernel identification technique is then applied to the CAP-TSD code for identification of the linear and second-order kernels of a NACA64A010 rectangular wing undergoing pitch at M = 0.5, M = 0.85 (transonic), and M = 0.93 (transonic). Results presented demonstrate the feasibility of this approach for use with nonlinear, unsteady aerodynamic responses.

  7. 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

    2017-02-07

    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.

  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. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Configuration Aerodynamics: Past - Present - Future

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.; Agrawal, Shreekant; Bencze, Daniel P.; Kulfan, Robert M.; Wilson, Douglas L.

    1999-01-01

    The Configuration Aerodynamics (CA) element of the High Speed Research (HSR) program is managed by a joint NASA and Industry team, referred to as the Technology Integration Development (ITD) team. This team is responsible for the development of a broad range of technologies for improved aerodynamic performance and stability and control characteristics at subsonic to supersonic flight conditions. These objectives are pursued through the aggressive use of advanced experimental test techniques and state of the art computational methods. As the HSR program matures and transitions into the next phase the objectives of the Configuration Aerodynamics ITD are being refined to address the drag reduction needs and stability and control requirements of High Speed Civil Transport (HSCT) aircraft. In addition, the experimental and computational tools are being refined and improved to meet these challenges. The presentation will review the work performed within the Configuration Aerodynamics element in 1994 and 1995 and then discuss the plans for the 1996-1998 time period. The final portion of the presentation will review several observations of the HSR program and the design activity within Configuration Aerodynamics.

  17. Classical Aerodynamic Theory

    NASA Technical Reports Server (NTRS)

    Jones, R. T. (Compiler)

    1979-01-01

    A collection of papers on modern theoretical aerodynamics is presented. Included are theories of incompressible potential flow and research on the aerodynamic forces on wing and wing sections of aircraft and on airship hulls.

  18. Aerodynamics at NASA JSC

    NASA Technical Reports Server (NTRS)

    Vicker, Darby

    2006-01-01

    A viewgraph presentation describing aerodynamics at NASA Johnson Space Center is shown. The topics include: 1) Personal Background; 2) Aerodynamic Tools; 3) The Overset Computational Fluid Dynamics (CFD) Process; and 4) Recent Applicatoins.

  19. NASA aerodynamics program

    NASA Technical Reports Server (NTRS)

    Williams, Louis J.; Hessenius, Kristin A.; Corsiglia, Victor R.; Hicks, Gary; Richardson, Pamela F.; Unger, George; Neumann, Benjamin; Moss, Jim

    1992-01-01

    The annual accomplishments is reviewed for the Aerodynamics Division during FY 1991. The program includes both fundamental and applied research directed at the full spectrum of aerospace vehicles, from rotorcraft to planetary entry probes. A comprehensive review is presented of the following aerodynamics elements: computational methods and applications; CFD validation; transition and turbulence physics; numerical aerodynamic simulation; test techniques and instrumentation; configuration aerodynamics; aeroacoustics; aerothermodynamics; hypersonics; subsonics; fighter/attack aircraft and rotorcraft.

  20. NASA aerodynamics program

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.; Schairer, Edward; Hicks, Gary; Wander, Stephen; Blankson, Isiaiah; Rose, Raymond; Olson, Lawrence; Unger, George

    1990-01-01

    Presented here is a comprehensive review of the following aerodynamics elements: computational methods and applications, computational fluid dynamics (CFD) validation, transition and turbulence physics, numerical aerodynamic simulation, drag reduction, test techniques and instrumentation, configuration aerodynamics, aeroacoustics, aerothermodynamics, hypersonics, subsonic transport/commuter aviation, fighter/attack aircraft and rotorcraft.

  1. 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.

  2. 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.

  3. 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

  4. An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. Volume 2: Data report. Part 1: Text and mode 1 data

    NASA Technical Reports Server (NTRS)

    Carta, F. O.

    1981-01-01

    Tests were conducted a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blade along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge. The tests were conducted for all 96 combinations 2 mean camberline incidence angles 2 pitching amplitudes 3 reduced frequencies and 8 interblade phase angles. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and particularly, the aerodynamic damping coefficient. Data obtained during the test program, reproduced from the printout of the data reduction program are complied. A further description of the contents of this report is found in the text that follows.

  5. 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

  6. Investigation of helicopter rotor blade/wake interactive impulsive noise

    NASA Technical Reports Server (NTRS)

    Miley, S. J.; Hall, G. F.; Vonlavante, E.

    1987-01-01

    An analysis of the Tip Aerodynamic/Aeroacoustic Test (TAAT) data was performed to identify possible aerodynamic sources of blade/vortex interaction (BVI) impulsive noise. The identification is based on correlation of measured blade pressure time histories with predicted blade/vortex intersections for the flight condition(s) where impulsive noise was detected. Due to the location of the recording microphones, only noise signatures associated with the advancing blade were available, and the analysis was accordingly restricted to the first and second azimuthal quadrants. The results show that the blade tip region is operating transonically in the azimuthal range where previous BVI experiments indicated the impulsive noise to be. No individual blade/vortex encounter is identifiable in the pressure data; however, there is indication of multiple intersections in the roll-up region which could be the origin of the noise. Discrete blade/vortex encounters are indicated in the second quadrant; however, if impulsive noise were produced here, the directivity pattern would be such that it was not recorded by the microphones. It is demonstrated that the TAAT data base is a valuable resource in the investigation of rotor aerodynamic/aeroacoustic behavior.

  7. 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.

  8. 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)

  9. 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.

  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. Fourier functional analysis for unsteady aerodynamic modeling

    NASA Technical Reports Server (NTRS)

    Lan, C. Edward; Chin, Suei

    1991-01-01

    A method based on Fourier analysis is developed to analyze the force and moment data obtained in large amplitude forced oscillation tests at high angles of attack. The aerodynamic models for normal force, lift, drag, and pitching moment coefficients are built up from a set of aerodynamic responses to harmonic motions at different frequencies. Based on the aerodynamic models of harmonic data, the indicial responses are formed. The final expressions for the models involve time integrals of the indicial type advocated by Tobak and Schiff. Results from linear two- and three-dimensional unsteady aerodynamic theories as well as test data for a 70-degree delta wing are used to verify the models. It is shown that the present modeling method is accurate in producing the aerodynamic responses to harmonic motions and the ramp type motions. The model also produces correct trend for a 70-degree delta wing in harmonic motion with different mean angles-of-attack. However, the current model cannot be used to extrapolate data to higher angles-of-attack than that of the harmonic motions which form the aerodynamic model. For linear ramp motions, a special method is used to calculate the corresponding frequency and phase angle at a given time. The calculated results from modeling show a higher lift peak for linear ramp motion than for harmonic ramp motion. The current model also shows reasonably good results for the lift responses at different angles of attack.

  12. 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)

  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. 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

  16. Feasibility investigation of general time-domain unsteady aerodynamics of rotors

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    1990-01-01

    The feasibility of a general theory for the time-domain unsteady aerodynamics of helicopter rotors is investigated. The wake theory gives a linearized relation between the downwash and the wing bound circulation, in terms of the impulse response obtained directly in the time domain. This approach makes it possible to treat general wake configurations, including discrete wake vorticity with rolled-up and distorted geometry. The investigation establishes the approach for model order reduction; determines when a constrained identification method is needed; verifies the formulation of the theory for rolled-up, distorted trim wake geometry; and verifies the formulation of the theory for wake geometry perturbations. The basic soundness of the approach is demonstrated by the results presented. A research program to complete the development of the method is outlined. The result of this activity will be an approach for analyzing the aeroelastic stability and response of helicopter rotors, while retaining the important influence of the complicated rotor wake configuration.

  17. NASA Iced Aerodynamics and Controls Current Research

    NASA Technical Reports Server (NTRS)

    Addy, Gene

    2009-01-01

    This slide presentation reviews the state of current research in the area of aerodynamics and aircraft control with ice conditions by the Aviation Safety Program, part of the Integrated Resilient Aircraft Controls Project (IRAC). Included in the presentation is a overview of the modeling efforts. The objective of the modeling is to develop experimental and computational methods to model and predict aircraft response during adverse flight conditions, including icing. The Aircraft icing modeling efforts includes the Ice-Contaminated Aerodynamics Modeling, which examines the effects of ice contamination on aircraft aerodynamics, and CFD modeling of ice-contaminated aircraft aerodynamics, and Advanced Ice Accretion Process Modeling which examines the physics of ice accretion, and works on computational modeling of ice accretions. The IRAC testbed, a Generic Transport Model (GTM) and its use in the investigation of the effects of icing on its aerodynamics is also reviewed. This has led to a more thorough understanding and models, both theoretical and empirical of icing physics and ice accretion for airframes, advanced 3D ice accretion prediction codes, CFD methods for iced aerodynamics and better understanding of aircraft iced aerodynamics and its effects on control surface effectiveness.

  18. 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.

  19. PROP3D: A Program for 3D Euler Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Propellers. Version 1.0

    NASA Technical Reports Server (NTRS)

    Srivastava, R.; Reddy, T. S. R.

    1996-01-01

    This guide describes the input data required, for steady or unsteady aerodynamic and aeroelastic analysis of propellers and the output files generated, in using PROP3D. The aerodynamic forces are obtained by solving three dimensional unsteady, compressible Euler equations. A normal mode structural analysis is used to obtain the aeroelastic equations, which are solved using either time domain or frequency domain solution method. Sample input and output files are included in this guide for steady aerodynamic analysis of single and counter-rotation propellers, and aeroelastic analysis of single-rotation propeller.

  20. Sequential-Impulse Generator Uses Fiber-Optics

    NASA Technical Reports Server (NTRS)

    Yang, L. C.

    1982-01-01

    Light pulse from a ruby or neodymium-glass laser enters miniature optics of repetitive-detonation apparatus. Traveling along a bundle of optical fibers, light strikes laser-sensitive microdetonator and charge explodes. Apparatus then advances next charge in train into position. Possible applications of sequential-impulse generator are in creating shock waves for aerodynamics research and in generating electrical power by magnetohydrodynamics.

  1. Unsteady transonic aerodynamics

    SciTech Connect

    Nixon, D.

    1989-01-01

    Various papers on unsteady transonic aerodynamics are presented. The topics addressed include: physical phenomena associated with unsteady transonic flows, basic equations for unsteady transonic flow, practical problems concerning aircraft, basic numerical methods, computational methods for unsteady transonic flows, application of transonic flow analysis to helicopter rotor problems, unsteady aerodynamics for turbomachinery aeroelastic applications, alternative methods for modeling unsteady transonic flows.

  2. Uncertainty in Computational Aerodynamics

    NASA Technical Reports Server (NTRS)

    Luckring, J. M.; Hemsch, M. J.; Morrison, J. H.

    2003-01-01

    An approach is presented to treat computational aerodynamics as a process, subject to the fundamental quality assurance principles of process control and process improvement. We consider several aspects affecting uncertainty for the computational aerodynamic process and present a set of stages to determine the level of management required to meet risk assumptions desired by the customer of the predictions.

  3. 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

  4. 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.

  5. Iced-airfoil aerodynamics

    NASA Astrophysics Data System (ADS)

    Bragg, M. B.; Broeren, A. P.; Blumenthal, L. A.

    2005-07-01

    Past research on airfoil aerodynamics in icing are reviewed. This review emphasizes the time period after the 1978 NASA Lewis workshop that initiated the modern icing research program at NASA and the current period after the 1994 ATR accident where aerodynamics research has been more aircraft safety focused. Research pre-1978 is also briefly reviewed. Following this review, our current knowledge of iced airfoil aerodynamics is presented from a flowfield-physics perspective. This article identifies four classes of ice accretions: roughness, horn ice, streamwise ice, and spanwise-ridge ice. For each class, the key flowfield features such as flowfield separation and reattachment are discussed and how these contribute to the known aerodynamic effects of these ice shapes. Finally Reynolds number and Mach number effects on iced-airfoil aerodynamics are summarized.

  6. Aerodynamic Characterization of a Modern Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Hall, Robert M.; Holland, Scott D.; Blevins, John A.

    2011-01-01

    A modern launch vehicle is by necessity an extremely integrated design. The accurate characterization of its aerodynamic characteristics is essential to determine design loads, to design flight control laws, and to establish performance. The NASA Ares Aerodynamics Panel has been responsible for technical planning, execution, and vetting of the aerodynamic characterization of the Ares I vehicle. An aerodynamics team supporting the Panel consists of wind tunnel engineers, computational engineers, database engineers, and other analysts that address topics such as uncertainty quantification. The team resides at three NASA centers: Langley Research Center, Marshall Space Flight Center, and Ames Research Center. The Panel has developed strategies to synergistically combine both the wind tunnel efforts and the computational efforts with the goal of validating the computations. Selected examples highlight key flow physics and, where possible, the fidelity of the comparisons between wind tunnel results and the computations. Lessons learned summarize what has been gleaned during the project and can be useful for other vehicle development projects.

  7. Mathematical modeling of the aerodynamic characteristics in flight dynamics

    NASA Technical Reports Server (NTRS)

    Tobak, M.; Chapman, G. T.; Schiff, L. B.

    1984-01-01

    Basic concepts involved in the mathematical modeling of the aerodynamic response of an aircraft to arbitrary maneuvers are reviewed. The original formulation of an aerodynamic response in terms of nonlinear functionals is shown to be compatible with a derivation based on the use of nonlinear functional expansions. Extensions of the analysis through its natural connection with ideas from bifurcation theory are indicated.

  8. An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. 1: Experimental and theoretical results. [turbine blades

    NASA Technical Reports Server (NTRS)

    Carta, F. O.

    1982-01-01

    Tests were conducted on a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blades along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and, particularly, the aerodynamic damping coefficient. Results from the unsteady Verdon/Caspar theory for cascaded blades with nonzero thickness and camber were compared with the experimental measurements. The three primary results are: (1) from the leading edge plane blade data, the cascade was judged to be periodic in unsteady flow over the range of parameters tested; (2) the interblade phase angle was found to be the single most important parameter affecting the stability of the oscillating cascade blades; and (3) the real blade theory and the experiment were in excellent agreement for the several cases chosen for comparison.

  9. 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.

  10. Unsteady Newton-Busemann flow theory. III - Frequency dependence and indicial response

    NASA Technical Reports Server (NTRS)

    Hui, W. H.

    1982-01-01

    Hui and Tobak applied the complete unsteady Newton-Busemann flow theory to the study of dynamic stability of oscillating aerofoils and bodies in revolution. The present article extends the results to general frequencies that may be applicable to flutter analysis. The results are likewise applied to the indicial response fluctuations in unsteady flow at very high Mach numbers. The study shows that for a group of body shapes in Newtonian flow (including the cone and wedge), the aerodynamic response to a step change in angle of attack or pitching velocity contains an initial-instant impulse followed by a rapid adjustment to the new steady-flow conditions. The impulse component is in effect an apparent mass term analogous to that which occurs initially in the aerodynamic indicial response at the zero Mach number limit.

  11. Comparison of aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks

    NASA Astrophysics Data System (ADS)

    Haque, Md. Naimul; Katsuchi, Hiroshi; Yamada, Hitoshi; Nishio, Mayuko

    2016-07-01

    Aerodynamics of the long-span bridge deck should be well understood for an efficient design of the bridge system. For practical bridges various deck shapes are being recommended and adopted, yet not all of their aerodynamic behaviors are well interpreted. In the present study, a numerical investigation was carried out to explore the aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks. A relative comparison of steady state aerodynamic responses was made and the flow field was critically analyzed for better understanding the aerodynamic responses. It was found that the hexagonal shaped bridge deck has better aerodynamic characteristics as compared to the pentagonal shaped bridge deck.

  12. 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.

  13. 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

  14. Aerodynamic Design Using Neural Networks

    NASA Technical Reports Server (NTRS)

    Rai, Man Mohan; Madavan, Nateri K.

    2003-01-01

    The design of aerodynamic components of aircraft, such as wings or engines, involves a process of obtaining the most optimal component shape that can deliver the desired level of component performance, subject to various constraints, e.g., total weight or cost, that the component must satisfy. Aerodynamic design can thus be formulated as an optimization problem that involves the minimization of an objective function subject to constraints. A new aerodynamic design optimization procedure based on neural networks and response surface methodology (RSM) incorporates the advantages of both traditional RSM and neural networks. The procedure uses a strategy, denoted parameter-based partitioning of the design space, to construct a sequence of response surfaces based on both neural networks and polynomial fits to traverse the design space in search of the optimal solution. Some desirable characteristics of the new design optimization procedure include the ability to handle a variety of design objectives, easily impose constraints, and incorporate design guidelines and rules of thumb. It provides an infrastructure for variable fidelity analysis and reduces the cost of computation by using less-expensive, lower fidelity simulations in the early stages of the design evolution. The initial or starting design can be far from optimal. The procedure is easy and economical to use in large-dimensional design space and can be used to perform design tradeoff studies rapidly. Designs involving multiple disciplines can also be optimized. Some practical applications of the design procedure that have demonstrated some of its capabilities include the inverse design of an optimal turbine airfoil starting from a generic shape and the redesign of transonic turbines to improve their unsteady aerodynamic characteristics.

  15. Effects of Acoustic Impulses on the Middle Ear

    DTIC Science & Technology

    2015-10-01

    impulsive noises (impacts and impulses). Keywords: Noise exposure; hearing loss, noise-induced; impulsive noise; reflex ; conditioned response...stated in the approved SOW are: 1. Determine the prevalence of acoustic reflexes to among young people with H-1 hearing status as per Army...Regulation 40-501, Table 7-1. 2. Determine whether reflexive MEMC are pervasive for multiple acoustic and non-acoustic stimuli. 3. Determine whether

  16. 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

  17. Quasi-steady state aerodynamics of the cheetah tail.

    PubMed

    Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-08-15

    During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.

  18. Quasi-steady state aerodynamics of the cheetah tail

    PubMed Central

    Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-01-01

    ABSTRACT During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267

  19. Aerodynamic Lifting Force.

    ERIC Educational Resources Information Center

    Weltner, Klaus

    1990-01-01

    Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)

  20. Aerodynamic Shutoff Valve

    NASA Technical Reports Server (NTRS)

    Horstman, Raymond H.

    1992-01-01

    Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Unsteady Aerodynamic Force Sensing from Measured Strain

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi

    2016-01-01

    A simple approach for computing unsteady aerodynamic forces from simulated measured strain data is proposed in this study. First, the deflection and slope of the structure are computed from the unsteady strain using the two-step approach. Velocities and accelerations of the structure are computed using the autoregressive moving average model, on-line parameter estimator, low-pass filter, and a least-squares curve fitting method together with analytical derivatives with respect to time. Finally, aerodynamic forces over the wing are computed using modal aerodynamic influence coefficient matrices, a rational function approximation, and a time-marching algorithm. A cantilevered rectangular wing built and tested at the NASA Langley Research Center (Hampton, Virginia, USA) in 1959 is used to validate the simple approach. Unsteady aerodynamic forces as well as wing deflections, velocities, accelerations, and strains are computed using the CFL3D computational fluid dynamics (CFD) code and an MSC/NASTRAN code (MSC Software Corporation, Newport Beach, California, USA), and these CFL3D-based results are assumed as measured quantities. Based on the measured strains, wing deflections, velocities, accelerations, and aerodynamic forces are computed using the proposed approach. These computed deflections, velocities, accelerations, and unsteady aerodynamic forces are compared with the CFL3D/NASTRAN-based results. In general, computed aerodynamic forces based on the lifting surface theory in subsonic speeds are in good agreement with the target aerodynamic forces generated using CFL3D code with the Euler equation. Excellent aeroelastic responses are obtained even with unsteady strain data under the signal to noise ratio of -9.8dB. The deflections, velocities, and accelerations at each sensor location are independent of structural and aerodynamic models. Therefore, the distributed strain data together with the current proposed approaches can be used as distributed deflection

  6. 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

  7. 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.

  8. Powered-Lift Aerodynamics and Acoustics. [conferences

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Powered lift technology is reviewed. Topics covered include: (1) high lift aerodynamics; (2) high speed and cruise aerodynamics; (3) acoustics; (4) propulsion aerodynamics and acoustics; (5) aerodynamic and acoustic loads; and (6) full-scale and flight research.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Applied computational aerodynamics

    SciTech Connect

    Henne, P.A.

    1990-01-01

    The present volume discusses the original development of the panel method, the mapping solutions and singularity distributions of linear potential schemes, the capabilities of full-potential, Euler, and Navier-Stokes schemes, the use of the grid-generation methodology in applied aerodynamics, subsonic airfoil design, inverse airfoil design for transonic applications, the divergent trailing-edge airfoil innovation in CFD, Euler and potential computational results for selected aerodynamic configurations, and the application of CFD to wing high-lift systems. Also discussed are high-lift wing modifications for an advanced-capability EA-6B aircraft, Navier-Stokes methods for internal and integrated propulsion system flow predictions, the use of zonal techniques for analysis of rotor-stator interaction, CFD applications to complex configurations, CFD applications in component aerodynamic design of the V-22, Navier-Stokes computations of a complete F-16, CFD at supersonic/hypersonic speeds, and future CFD developments.

  14. 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.

  15. Identification of aerodynamic models for maneuvering aircraft

    NASA Technical Reports Server (NTRS)

    Lan, C. Edward; Hu, C. C.

    1992-01-01

    A Fourier analysis method was developed to analyze harmonic forced-oscillation data at high angles of attack as functions of the angle of attack and its time rate of change. The resulting aerodynamic responses at different frequencies are used to build up the aerodynamic models involving time integrals of the indicial type. An efficient numerical method was also developed to evaluate these time integrals for arbitrary motions based on a concept of equivalent harmonic motion. The method was verified by first using results from two-dimensional and three-dimensional linear theories. The developed models for C sub L, C sub D, and C sub M based on high-alpha data for a 70 deg delta wing in harmonic motions showed accurate results in reproducing hysteresis. The aerodynamic models are further verified by comparing with test data using ramp-type motions.

  16. Computational aerodynamics and design

    NASA Technical Reports Server (NTRS)

    Ballhaus, W. F., Jr.

    1982-01-01

    The role of computational aerodynamics in design is reviewed with attention given to the design process; the proper role of computations; the importance of calibration, interpretation, and verification; the usefulness of a given computational capability; and the marketing of new codes. Examples of computational aerodynamics in design are given with particular emphasis on the Highly Maneuverable Aircraft Technology. Finally, future prospects are noted, with consideration given to the role of advanced computers, advances in numerical solution techniques, turbulence models, complex geometries, and computational design procedures. Previously announced in STAR as N82-33348

  17. Nonlinear aerodynamic wing design

    NASA Technical Reports Server (NTRS)

    Bonner, Ellwood

    1985-01-01

    The applicability of new nonlinear theoretical techniques is demonstrated for supersonic wing design. The new technology was utilized to define outboard panels for an existing advanced tactical fighter model. Mach 1.6 maneuver point design and multi-operating point compromise surfaces were developed and tested. High aerodynamic efficiency was achieved at the design conditions. A corollary result was that only modest supersonic penalties were incurred to meet multiple aerodynamic requirements. The nonlinear potential analysis of a practical configuration arrangement correlated well with experimental data.

  18. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.

    PubMed

    Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers

    2015-03-06

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.

  19. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds

    PubMed Central

    Lentink, David; Haselsteiner, Andreas F.; Ingersoll, Rivers

    2015-01-01

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier–Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing. PMID:25589565

  20. Computer graphics in aerodynamic analysis

    NASA Technical Reports Server (NTRS)

    Cozzolongo, J. V.

    1984-01-01

    The use of computer graphics and its application to aerodynamic analyses on a routine basis is outlined. The mathematical modelling of the aircraft geometries and the shading technique implemented are discussed. Examples of computer graphics used to display aerodynamic flow field data and aircraft geometries are shown. A future need in computer graphics for aerodynamic analyses is addressed.

  1. 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.

  2. 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.

  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. 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.

  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. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Rarefied-flow aerodynamics

    NASA Technical Reports Server (NTRS)

    Potter, J. Leith

    1992-01-01

    Means for relatively simple and quick procedures are examined for estimating aerodynamic coefficients of lifting reentry vehicles. The methods developed allow aerospace designers not only to evaluate the aerodynamics of specific shapes but also to optimize shapes under given constraints. The analysis was also studied of the effect of thermomolecular flow on pressures measured by an orifice near the nose of a Space Shuttle Orbiter at altitudes above 75 km. It was shown that pressures corrected for thermomolecular flow effect are in good agreement with values predicted by independent theoretical methods. An incidental product was the insight gained about the free molecular thermal accommodation coefficient applicable under 'real' conditions of high speed flow in the Earth's atmosphere. The results are presented as abstracts of referenced papers. One reference paper is presented in its entirety.

  12. HYSHOT-2 Aerodynamics

    NASA Astrophysics Data System (ADS)

    Cain, T.; Owen, R.; Walton, C.

    2005-02-01

    The scramjet flight test Hyshot-2, flew on the 30 July 2002. The programme, led by the University of Queensland, had the primary objective of obtaining supersonic combustion data in flight for comparison with measurements made in shock tunnels. QinetiQ was one of the sponsors, and also provided aerodynamic data and trajectory predictions for the ballistic re-entry of the spinning sounding rocket. The unconventional missile geometry created by the nose-mounted asymmetric-scramjet in conjunction with the high angle of attack during re-entry makes the problem interesting. This paper presents the wind tunnel measurements and aerodynamic calculations used as input for the trajectory prediction. Indirect comparison is made with data obtained in the Hyshot-2 flight using a 6 degree-of-freedom trajectory simulation.

  13. Advanced Aerodynamic Control Effectors

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.; Bauer, Steven X. S.

    1999-01-01

    A 1990 research program that focused on the development of advanced aerodynamic control effectors (AACE) for military aircraft has been reviewed and summarized. Data are presented for advanced planform, flow control, and surface contouring technologies. The data show significant increases in lift, reductions in drag, and increased control power, compared to typical aerodynamic designs. The results presented also highlighted the importance of planform selection in the design of a control effector suite. Planform data showed that dramatic increases in lift (greater than 25%) can be achieved with multiple wings and a sawtooth forebody. Passive porosity and micro drag generator control effector data showed control power levels exceeding that available from typical effectors (moving surfaces). Application of an advanced planform to a tailless concept showed benefits of similar magnitude as those observed in the generic studies.

  14. Aerodynamic Leidenfrost effect

    NASA Astrophysics Data System (ADS)

    Gauthier, Anaïs; Bird, James C.; Clanet, Christophe; Quéré, David

    2016-12-01

    When deposited on a plate moving quickly enough, any liquid can levitate as it does when it is volatile on a very hot solid (Leidenfrost effect). In the aerodynamic Leidenfrost situation, air gets inserted between the liquid and the moving solid, a situation that we analyze. We observe two types of entrainment. (i) The thickness of the air gap is found to increase with the plate speed, which is interpreted in the Landau-Levich-Derjaguin frame: Air is dynamically dragged along the surface and its thickness results from a balance between capillary and viscous effects. (ii) Air set in motion by the plate exerts a force on the levitating liquid. We discuss the magnitude of this aerodynamic force and show that it can be exploited to control the liquid and even to drive it against gravity.

  15. 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.

  16. Aerodynamics: The Wright Way

    NASA Technical Reports Server (NTRS)

    Cole, Jennifer Hansen

    2010-01-01

    This slide presentation reviews some of the basic principles of aerodynamics. Included in the presentation are: a few demonstrations of the principles, an explanation of the concepts of lift, drag, thrust and weight, a description of Bernoulli's principle, the concept of the airfoil (i.e., the shape of the wing) and how that effects lift, and the method of controlling an aircraft by manipulating the four forces using control surfaces.

  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. Efficient Global Aerodynamic Modeling from Flight Data

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    2012-01-01

    A method for identifying global aerodynamic models from flight data in an efficient manner is explained and demonstrated. A novel experiment design technique was used to obtain dynamic flight data over a range of flight conditions with a single flight maneuver. Multivariate polynomials and polynomial splines were used with orthogonalization techniques and statistical modeling metrics to synthesize global nonlinear aerodynamic models directly and completely from flight data alone. Simulation data and flight data from a subscale twin-engine jet transport aircraft were used to demonstrate the techniques. Results showed that global multivariate nonlinear aerodynamic dependencies could be accurately identified using flight data from a single maneuver. Flight-derived global aerodynamic model structures, model parameter estimates, and associated uncertainties were provided for all six nondimensional force and moment coefficients for the test aircraft. These models were combined with a propulsion model identified from engine ground test data to produce a high-fidelity nonlinear flight simulation very efficiently. Prediction testing using a multi-axis maneuver showed that the identified global model accurately predicted aircraft responses.

  19. Identification of aerodynamic models for maneuvering aircraft

    NASA Technical Reports Server (NTRS)

    Chin, Suei; Lan, C. Edward

    1990-01-01

    Due to the requirement of increased performance and maneuverability, the flight envelope of a modern fighter is frequently extended to the high angle-of-attack regime. Vehicles maneuvering in this regime are subjected to nonlinear aerodynamic loads. The nonlinearities are due mainly to three-dimensional separated flow and concentrated vortex flow that occur at large angles of attack. Accurate prediction of these nonlinear airloads is of great importance in the analysis of a vehicle's flight motion and in the design of its flight control system. A satisfactory evaluation of the performance envelope of the aircraft may require a large number of coupled computations, one for each change in initial conditions. To avoid the disadvantage of solving the coupled flow-field equations and aircraft's motion equations, an alternate approach is to use a mathematical modeling to describe the steady and unsteady aerodynamics for the aircraft equations of motion. Aerodynamic forces and moments acting on a rapidly maneuvering aircraft are, in general, nonlinear functions of motion variables, their time rate of change, and the history of maneuvering. A numerical method was developed to analyze the nonlinear and time-dependent aerodynamic response to establish the generalized indicial function in terms of motion variables and their time rates of change.

  20. On aerodynamic noise generation from vortex shedding in rotating blades

    NASA Astrophysics Data System (ADS)

    Martin, B. T.; Bies, D. A.

    1992-06-01

    The interaction of the shed wakes of plates in a cascade with each following plate is investigated in a water tunnel and shown to provide an explanation for an observed very powerful aerodynamic noise source. In particular, the noise generation of an idling circular saw may be explained as due to the interaction of the wake shed by an upstream tooth with the leading edge of the following downstream tooth. When a vortex travelling downstream in the gullet between teeth encounters the leading edge of the downstream tooth it is deflected out of the gullet into the main stream. The associated impulses which the teeth encounter give rise to the radiated noise.

  1. 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.

  2. Comparisons of several aerodynamic methods for application to dynamic loads analyses

    NASA Technical Reports Server (NTRS)

    Kroll, R. I.; Miller, R. D.

    1976-01-01

    The results of a study are presented in which the applicability at subsonic speeds of several aerodynamic methods for predicting dynamic gust loads on aircraft, including active control systems, was examined and compared. These aerodynamic methods varied from steady state to an advanced unsteady aerodynamic formulation. Brief descriptions of the structural and aerodynamic representations and of the motion and load equations are presented. Comparisons of numerical results achieved using the various aerodynamic methods are shown in detail. From these results, aerodynamic representations for dynamic gust analyses are identified. It was concluded that several aerodynamic methods are satisfactory for dynamic gust analyses of configurations having either controls fixed or active control systems that primarily affect the low frequency rigid body aircraft response.

  3. The impulse resistance welding: A new technique for joining advanced thermoplastic composite parts

    SciTech Connect

    Arias, M.; Ziegmann, G.

    1996-12-31

    Welding is a joining technique suitable for thermoplastic composites. This paper presents the development of a new, fast joining technique, which is based on the common resistance welding process. Heat is introduced by using electrical power pulses into the heating area and therefore this technique was called the Impulse Resistance Welding (IRW). The new technique will be described and discussed and the application of this technique by joining ribs to the skin of an aerodynamic spoiler part is demonstrated. The potential of an automation of the Impulse resistance welding process will be shown. Carbon fibre /PEEK (APC-2/AS4) has been selected as the material both for the skin and the rib.

  4. Aerodynamics of wing-assisted incline running in birds.

    PubMed

    Tobalske, Bret W; Dial, Kenneth P

    2007-05-01

    Wing-assisted incline running (WAIR) is a form of locomotion in which a bird flaps its wings to aid its hindlimbs in climbing a slope. WAIR is used for escape in ground birds, and the ontogeny of this behavior in precocial birds has been suggested to represent a model analogous to transitional adaptive states during the evolution of powered avian flight. To begin to reveal the aerodynamics of flap-running, we used digital particle image velocimetry (DPIV) and measured air velocity, vorticity, circulation and added mass in the wake of chukar partridge Alectoris chukar as they engaged in WAIR (incline 65-85 degrees; N=7 birds) and ascending flight (85 degrees, N=2). To estimate lift and impulse, we coupled our DPIV data with three-dimensional wing kinematics from a companion study. The ontogeny of lift production was evaluated using three age classes: baby birds incapable of flight [6-8 days post hatching (d.p.h.)] and volant juveniles (25-28 days) and adults (45+ days). All three age classes of birds, including baby birds with partially emerged, symmetrical wing feathers, generated circulation with their wings and exhibited a wake structure that consisted of discrete vortex rings shed once per downstroke. Impulse of the vortex rings during WAIR was directed 45+/-5 degrees relative to horizontal and 21+/-4 degrees relative to the substrate. Absolute values of circulation in vortex cores and induced velocity increased with increasing age. Normalized circulation was similar among all ages in WAIR but 67% greater in adults during flight compared with flap-running. Estimated lift during WAIR was 6.6% of body weight in babies and between 63 and 86% of body weight in juveniles and adults. During flight, average lift was 110% of body weight. Our results reveal for the first time that lift from the wings, rather than wing inertia or profile drag, is primarily responsible for accelerating the body toward the substrate during WAIR, and that partially developed wings, not yet

  5. 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.

  6. 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…

  7. Freight Wing Trailer Aerodynamics

    SciTech Connect

    Graham, Sean; Bigatel, Patrick

    2004-10-17

    Freight Wing Incorporated utilized the opportunity presented by this DOE category one Inventions and Innovations grant to successfully research, develop, test, patent, market, and sell innovative fuel and emissions saving aerodynamic attachments for the trucking industry. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck's fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Market research early in this project revealed the demands of truck fleet operators regarding aerodynamic attachments. Products must not only save fuel, but cannot interfere with the operation of the truck, require significant maintenance, add significant weight, and must be extremely durable. Furthermore, SAE/TMC J1321 tests performed by a respected independent laboratory are necessary for large fleets to even consider purchase. Freight Wing used this information to create a system of three practical aerodynamic attachments for the front, rear and undercarriage of standard semi trailers. SAE/TMC J1321 Type II tests preformed by the Transportation Research Center (TRC) demonstrated a 7% improvement to fuel economy with all three products. If Freight Wing is successful in its continued efforts to gain market penetration, the energy and environmental savings would be considerable. Each truck outfitted saves approximately 1,100 gallons of fuel every 100,000 miles, which prevents over 12 tons of CO2 from entering the atmosphere. If all applicable trailers used the technology, the country could save approximately 1.8 billion gallons of diesel fuel, 18 million tons of emissions and 3.6 billion dollars annually.

  8. TAD- THEORETICAL AERODYNAMICS PROGRAM

    NASA Technical Reports Server (NTRS)

    Barrowman, J.

    1994-01-01

    This theoretical aerodynamics program, TAD, was developed to predict the aerodynamic characteristics of vehicles with sounding rocket configurations. These slender, axisymmetric finned vehicle configurations have a wide range of aeronautical applications from rockets to high speed armament. Over a given range of Mach numbers, TAD will compute the normal force coefficient derivative, the center-of-pressure, the roll forcing moment coefficient derivative, the roll damping moment coefficient derivative, and the pitch damping moment coefficient derivative of a sounding rocket configured vehicle. The vehicle may consist of a sharp pointed nose of cone or tangent ogive shape, up to nine other body divisions of conical shoulder, conical boattail, or circular cylinder shape, and fins of trapezoid planform shape with constant cross section and either three or four fins per fin set. The characteristics computed by TAD have been shown to be accurate to within ten percent of experimental data in the supersonic region. The TAD program calculates the characteristics of separate portions of the vehicle, calculates the interference between separate portions of the vehicle, and then combines the results to form a total vehicle solution. Also, TAD can be used to calculate the characteristics of the body or fins separately as an aid in the design process. Input to the TAD program consists of simple descriptions of the body and fin geometries and the Mach range of interest. Output includes the aerodynamic characteristics of the total vehicle, or user-selected portions, at specified points over the mach range. The TAD program is written in FORTRAN IV for batch execution and has been implemented on an IBM 360 computer with a central memory requirement of approximately 123K of 8 bit bytes. The TAD program was originally developed in 1967 and last updated in 1972.

  9. Impulsivity and rapid decision-making for reward.

    PubMed

    Burnett Heyes, Stephanie; Adam, Robert J; Urner, Maren; van der Leer, Leslie; Bahrami, Bahador; Bays, Paul M; Husain, Masud

    2012-01-01

    Impulsivity is a feature of many brain disorders. Although often defined as the predisposition to act with an inadequate degree of deliberation, forethought, or control, it has proven difficult to measure. This may in part be due to the fact that it is a multifaceted construct, with impulsive decisions potentially arising as a result of a number of underlying mechanisms. Indeed, a "functional" degree of impulsivity may even promote effective behavior in healthy participants in a way that can be advantageous under certain circumstances. Although many tasks have been developed to study impulsivity, few examine decisions made rapidly, for time-sensitive rewards. In the current study we examine behavior in 59 adults on a manual "Traffic Light" task which requires participants to take risks under time pressure, if they are to maximize reward. We show that behavioral variables that index rapid anticipatory responding in this paradigm are correlated with one, specific self-report measure of impulsivity: "lack of premeditation" on the UPPS Impulsive Behavior Scale. Participants who scored more highly on this subscale performed better on the task. Moreover, anticipatory behavior reduced significantly with age (18-79 years), an effect that continued to be upheld after correction for potential age differences in the ability to judge the timing of responses. Based on these findings, we argue that the Traffic Light task provides a parametric method to study one aspect of impulsivity in health and disease: namely, rapid decision-making in pursuit of risky, time-sensitive rewards.

  10. 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.

  11. 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.

  12. Prediction of Aerodynamic Loading

    DTIC Science & Technology

    1977-02-01

    predictable even with knowledge of the motion and the quasi- steady aerodynamic coefficients . It sems likely that the unsteady boundary-layer...build up, which are explainable 41 terams of the stability coefficients . More research is needed on the former type of undemanded manoeuvre. In some...drag 81, 82... B5 body sections I. kg lift St strdke 1M kg m pitching moment N kg normal force T kg axial force a 0 angle of attack Coefficie its: CD, cD

  13. 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.

  14. On Wings: Aerodynamics of Eagles.

    ERIC Educational Resources Information Center

    Millson, David

    2000-01-01

    The Aerodynamics Wing Curriculum is a high school program that combines basic physics, aerodynamics, pre-engineering, 3D visualization, computer-assisted drafting, computer-assisted manufacturing, production, reengineering, and success in a 15-hour, 3-week classroom module. (JOW)

  15. Aerodynamics of a Party Balloon

    ERIC Educational Resources Information Center

    Cross, Rod

    2007-01-01

    It is well-known that a party balloon can be made to fly erratically across a room, but it can also be used for quantitative measurements of other aspects of aerodynamics. Since a balloon is light and has a large surface area, even relatively weak aerodynamic forces can be readily demonstrated or measured in the classroom. Accurate measurements…

  16. Aerodynamics of sports balls

    NASA Astrophysics Data System (ADS)

    Mehta, R. D.

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  17. The Aerodynamic Plane Table

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1924-01-01

    This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.

  18. Aerodynamic challenges of ALT

    NASA Technical Reports Server (NTRS)

    Hooks, I.; Homan, D.; Romere, P. O.

    1985-01-01

    The approach and landing test (ALT) of the Space Shuttle Orbiter presented a number of unique challenges in the area of aerodynamics. The purpose of the ALT program was both to confirm the use of the Boeing 747 as a transport vehicle for ferrying the Orbiter across the country and to demonstrate the flight characteristics of the Orbiter in its approach and landing phase. Concerns for structural fatigue and performance dictated a tailcone be attached to the Orbiter for ferry and for the initial landing tests. The Orbiter with a tailcone attached presented additional challenges to the normal aft sting concept of wind tunnel testing. The landing tests required that the Orbiter be separated from the 747 at approximately 20,000 feet using aerodynamic forces to fly the vehicles apart. The concept required a complex test program to determine the relative effects of the two vehicles on each other. Also of concern, and tested, was the vortex wake created by the 747 and the means for the Orbiter to avoid it following separation.

  19. Aerodynamics of sports balls

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1985-01-01

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  20. 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

  1. Rotor-generated unsteady aerodynamic interactions in a 1½ stage compressor

    NASA Astrophysics Data System (ADS)

    Papalia, John J.

    Because High Cycle Fatigue (HCF) remains the predominant surprise failure mode in gas turbine engines, HCF avoidance design systems are utilized to identify possible failures early in the engine development process. A key requirement of these analyses is accurate determination of the aerodynamic forcing function and corresponding airfoil unsteady response. The current study expands the limited experimental database of blade row interactions necessary for calibration of predictive HCF analyses, with transonic axial-flow compressors of particular interest due to the presence of rotor leading edge shocks. The majority of HCF failures in aircraft engines occur at off-design operating conditions. Therefore, experiments focused on rotor-IGV interactions at off-design are conducted in the Purdue Transonic Research Compressor. The rotor-generated IGV unsteady aerodynamics are quantified when the IGV reset angle causes the vane trailing edge to be nearly aligned with the rotor leading edge shocks. A significant vane response to the impulsive static pressure perturbation associated with a shock is evident in the point measurements at 90% span, with details of this complex interaction revealed in the corresponding time-variant vane-to-vane flow field data. Industry wide implementation of Controlled Diffusion Airfoils (CDA) in modern compressors motivated an investigation of upstream propagating CDA rotor-generated forcing functions. Whole field velocity measurements in the reconfigured Purdue Transonic Research Compressor along the design speedline reveal steady loading had a considerable effect on the rotor shock structure. A detached rotor leading edge shock exists at low loading, with an attached leading edge and mid-chord suction surface normal shock present at nominal loading. These CDA forcing functions are 3--4 times smaller than those generated by the baseline NACA 65 rotor at their respective operating points. However, the IGV unsteady aerodynamic response to the CDA

  2. Flight Test Maneuvers for Efficient Aerodynamic Modeling

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.

    2011-01-01

    Novel flight test maneuvers for efficient aerodynamic modeling were developed and demonstrated in flight. Orthogonal optimized multi-sine inputs were applied to aircraft control surfaces to excite aircraft dynamic response in all six degrees of freedom simultaneously while keeping the aircraft close to chosen reference flight conditions. Each maneuver was designed for a specific modeling task that cannot be adequately or efficiently accomplished using conventional flight test maneuvers. All of the new maneuvers were first described and explained, then demonstrated on a subscale jet transport aircraft in flight. Real-time and post-flight modeling results obtained using equation-error parameter estimation in the frequency domain were used to show the effectiveness and efficiency of the new maneuvers, as well as the quality of the aerodynamic models that can be identified from the resultant flight data.

  3. Unsteady aerodynamic modeling for arbitrary motions

    NASA Technical Reports Server (NTRS)

    Edwards, J. W.; Ashley, H.; Breakwell, J. V.

    1977-01-01

    A study is presented on the unsteady aerodynamic loads due to arbitrary motions of a thin wing and their adaptation for the calculation of response and true stability of aeroelastic modes. In an Appendix, the use of Laplace transform techniques and the generalized Theodorsen function for two-dimensional incompressible flow is reviewed. New applications of the same approach are shown also to yield airloads valid for quite general small motions. Numerical results are given for the two-dimensional supersonic case. Previously proposed approximate methods, starting from simple harmonic unsteady theory, are evaluated by comparison with exact results obtained by the present approach. The Laplace inversion integral is employed to separate the loads into 'rational' and 'nonrational' parts, of which only the former are involved in aeroelastic stability of the wing. Among other suggestions for further work, it is explained how existing aerodynamic computer programs may be adapted in a fairly straightforward fashion to deal with arbitrary transients.

  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. 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.

  7. Vortex flow aerodynamics

    NASA Technical Reports Server (NTRS)

    Smith, J. H. B.; Campbell, J. F.; Young, A. D. (Editor)

    1992-01-01

    The principal emphasis of the meeting was to be on the understanding and prediction of separation-induced vortex flows and their effects on vehicle performance, stability, control, and structural design loads. This report shows that a substantial amount of the papers covering this area were received from a wide range of countries, together with an attendance that was even more diverse. In itself, this testifies to the current interest in the subject and to the appropriateness of the Panel's choice of topic and approach. An attempt is made to summarize each paper delivered, and to relate the contributions made in the papers and in the discussions to some of the important aspects of vortex flow aerodynamics. This reveals significant progress and important clarifications, but also brings out remaining weaknesses in predictive capability and gaps in understanding. Where possible, conclusions are drawn and areas of continuing concern are identified.

  8. 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.

  9. Influence of unsteady aerodynamics on driving dynamics of passenger cars

    NASA Astrophysics Data System (ADS)

    Huemer, Jakob; Stickel, Thomas; Sagan, Erich; Schwarz, Martin; Wall, Wolfgang A.

    2014-11-01

    Recent approaches towards numerical investigations with computational fluid dynamics methods on unsteady aerodynamic loads of passenger cars identified major differences compared with steady-state aerodynamic excitations. Furthermore, innovative vehicle concepts such as electric-vehicles or hybrid drives further challenge the basic layout of passenger cars. Therefore, the relevance of unsteady aerodynamic loads on cross-wind stability of changing basic vehicle architectures should be analysed. In order to assure and improve handling and ride characteristics at high velocity of the actual range of vehicle layouts, the influence of unsteady excitations on the vehicle response was investigated. For this purpose, a simulation of the vehicle dynamics through multi-body simulation was used. The impact of certain unsteady aerodynamic load characteristics on the vehicle response was quantified and key factors were identified. Through a series of driving simulator tests, the identified differences in the vehicle response were evaluated regarding their significance on the subjective driver perception of cross-wind stability. Relevant criteria for the subjective driver assessment of the vehicle response were identified. As a consequence, a design method for the basic layout of passenger cars and chassis towards unsteady aerodynamic excitations was defined.

  10. Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach.

    PubMed

    Nakata, Toshiyuki; Liu, Hao

    2012-02-22

    Insect wings are deformable structures that change shape passively and dynamically owing to inertial and aerodynamic forces during flight. It is still unclear how the three-dimensional and passive change of wing kinematics owing to inherent wing flexibility contributes to unsteady aerodynamics and energetics in insect flapping flight. Here, we perform a systematic fluid-structure interaction based analysis on the aerodynamic performance of a hovering hawkmoth, Manduca, with an integrated computational model of a hovering insect with rigid and flexible wings. Aerodynamic performance of flapping wings with passive deformation or prescribed deformation is evaluated in terms of aerodynamic force, power and efficiency. Our results reveal that wing flexibility can increase downwash in wake and hence aerodynamic force: first, a dynamic wing bending is observed, which delays the breakdown of leading edge vortex near the wing tip, responsible for augmenting the aerodynamic force-production; second, a combination of the dynamic change of wing bending and twist favourably modifies the wing kinematics in the distal area, which leads to the aerodynamic force enhancement immediately before stroke reversal. Moreover, an increase in hovering efficiency of the flexible wing is achieved as a result of the wing twist. An extensive study of wing stiffness effect on aerodynamic performance is further conducted through a tuning of Young's modulus and thickness, indicating that insect wing structures may be optimized not only in terms of aerodynamic performance but also dependent on many factors, such as the wing strength, the circulation capability of wing veins and the control of wing movements.

  11. 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.

  12. 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.

  13. 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

  14. Payload vehicle aerodynamic reentry analysis

    NASA Astrophysics Data System (ADS)

    Tong, Donald

    An approach for analyzing the dynamic behavior of a cone-cylinder payload vehicle during reentry to insure proper deployment of the parachute system and recovery of the payload is presented. This analysis includes the study of an aerodynamic device that is useful in extending vehicle axial rotation through the maximum dynamic pressure region. Attention is given to vehicle configuration and reentry trajectory, the derivation of pitch static aerodynamics, the derivation of the pitch damping coefficient, pitching moment modeling, aerodynamic roll device modeling, and payload vehicle reentry dynamics. It is shown that the vehicle dynamics at parachute deployment are well within the design limit of the recovery system, thus ensuring successful payload recovery.

  15. 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.

  16. Spacecraft Re-Entry Impact Point Targeting Using Aerodynamic Drag

    NASA Technical Reports Server (NTRS)

    Omar, Sanny R.; Bevilacqua, Riccardo

    2017-01-01

    The ability to re-enter the atmosphere at a desired location is important for spacecraft containing components that may survive re-entry. While impact point targeting has traditionally been initiated through impulsive burns with chemical thrusters on large vehicles such as the Space Shuttle, and the Soyuz and Apollo capsules, many small spacecraft do not host thrusters and require an alternative means of impact point targeting to ensure that falling debris do not cause harm to persons or property. This paper discusses the use of solely aerodynamic drag force to perform this targeting. It is shown that by deploying and retracting a drag device to vary the ballistic coefficient of the spacecraft, any desired longitude and latitude on the ground can be targeted provided that the maneuvering begins early enough and the latitude is less than the inclination of the orbit. An analytical solution based on perturbations from a numerically propagated trajectory is developed to map the initial state and ballistic coefficient profile of a spacecraft to its impact point. This allows the ballistic coefficient profile necessary to reach a given target point to be rapidly calculated, making it feasible to generate the guidance for the decay trajectory onboard the spacecraft. The ability to target an impact point using aerodynamic drag will enhance the capabilities of small spacecraft and will enable larger space vehicles containing thrusters to save fuel by more effectively leveraging the available aerodynamic drag.

  17. Improved Aerodynamic Analysis for Hybrid Wing Body Conceptual Design Optimization

    NASA Technical Reports Server (NTRS)

    Gern, Frank H.

    2012-01-01

    This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Modeling Aerodynamically Generated Sound of Helicopter Rotors

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.; Farassat, F.

    2002-01-01

    A great deal of progress has been made in the modeling of aerodynamically generated sound of rotors over the past decade. Although the modeling effort has focused on helicopter main rotors, the theory is generally valid for a wide range of rotor configurations. The Ffowcs Williams Hawkings (FW-H) equation has been the foundation for much of the development. The monopole and dipole source terms of the FW-H equation account for the thickness and loading noise, respectively. Bladevortex-interaction noise and broadband noise are important types of loading noise, hence much research has been directed toward the accurate modeling of these noise mechanisms. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H equation has also been utilized on permeable surfaces surrounding all physical noise sources. Comparisons of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems. Finally, significant progress has been made incorporating the rotor noise models into full vehicle noise prediction tools.

  5. Computational aerodynamics and artificial intelligence

    NASA Technical Reports Server (NTRS)

    Mehta, U. B.; Kutler, P.

    1984-01-01

    The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

  6. Dynamic soaring: aerodynamics for albatrosses

    NASA Astrophysics Data System (ADS)

    Denny, Mark

    2009-01-01

    Albatrosses have evolved to soar and glide efficiently. By maximizing their lift-to-drag ratio L/D, albatrosses can gain energy from the wind and can travel long distances with little effort. We simplify the difficult aerodynamic equations of motion by assuming that albatrosses maintain a constant L/D. Analytic solutions to the simplified equations provide an instructive and appealing example of fixed-wing aerodynamics suitable for undergraduate demonstration.

  7. Supersonic aerodynamics of delta wings

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.

    1988-01-01

    Through the empirical correlation of experimental data and theoretical analysis, a set of graphs has been developed which summarize the inviscid aerodynamics of delta wings at supersonic speeds. The various graphs which detail the aerodynamic performance of delta wings at both zero-lift and lifting conditions were then employed to define a preliminary wing design approach in which both the low-lift and high-lift design criteria were combined to define a feasible design space.

  8. 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.

  9. 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

  10. Introduction. Computational aerodynamics.

    PubMed

    Tucker, Paul G

    2007-10-15

    The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.

  11. Aerodynamics of bird flight

    NASA Astrophysics Data System (ADS)

    Dvořák, Rudolf

    2016-03-01

    Unlike airplanes birds must have either flapping or oscillating wings (the hummingbird). Only such wings can produce both lift and thrust - two sine qua non attributes of flying.The bird wings have several possibilities how to obtain the same functions as airplane wings. All are realized by the system of flight feathers. Birds have also the capabilities of adjusting the shape of the wing according to what the immediate flight situation demands, as well as of responding almost immediately to conditions the flow environment dictates, such as wind gusts, object avoidance, target tracking, etc. In bird aerodynamics also the tail plays an important role. To fly, wings impart downward momentum to the surrounding air and obtain lift by reaction. How this is achieved under various flight situations (cruise flight, hovering, landing, etc.), and what the role is of the wing-generated vortices in producing lift and thrust is discussed.The issue of studying bird flight experimentally from in vivo or in vitro experiments is also briefly discussed.

  12. 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.

  13. 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.

  14. A versatile low-dimensional vortex model for investigating unsteady aerodynamics

    NASA Astrophysics Data System (ADS)

    Darakananda, Darwin; Eldredge, Jeff D.

    2016-11-01

    In previous work, we demonstrated a hybrid vortex sheet/point vortex model that captures the non-linear aerodynamics of a plate translating at a high angle of attack. We used vortex sheets to model the shear layers emerging from the plate, and point vortices to capture the effect of the coherent vortex structures. In this work, we introduce modifications that allow the model to work for a larger range of plate kinematics over longer periods of time. First, following the example of Ramesh et al., we relax the Kutta condition at the leading edge and determine vorticity flux based on a suction parameter instead. To prevent the vortex sheet from becoming unstable near the resulting singular edge, we explicitly filter out short-wave disturbances along the sheet while redistributing the sheet's control points. Second, by looking for intersections between the vortex sheets and any repelling Lagrangian coherent structures, the model can detect the formation of new coherent vortices. Trailing portions of the sheets that become dynamically distinct from the shear layers are rolled up into point vortices. We test these modifications on a variety of problems, including pitch-up, impulsive translation at low angles of attack, as well as flow response to pulse actuation near the leading edge. This work has been supported by AFOSR, under award FA9550-14-1-0328.

  15. Do different facets of impulsivity predict different types of aggression?

    PubMed

    Derefinko, Karen; DeWall, C Nathan; Metze, Amanda V; Walsh, Erin C; Lynam, Donald R

    2011-01-01

    This 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.

  16. 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

  17. Is impulsivity a link between childhood abuse and suicide?

    PubMed

    Braquehais, M Dolores; Oquendo, Maria A; Baca-García, Enrique; Sher, Leo

    2010-01-01

    Childhood abuse and neglect are known to affect psychological states through behavioral, emotional, and cognitive pathways. They increase the risk of having psychiatric diseases in adulthood and have been considered risk factors for suicidal behavior in all diagnostic categories. Early, prolonged, and severe trauma is also known to increase impulsivity, diminishing the capacity of the brain to inhibit negative actions and to control and modulate emotions. Many neurobiological studies hold that childhood maltreatment may lead to a persistent failure of the inhibitory processes ruled mainly by the frontal cortex over a fear-motivated hyperresponsive limbic system. Multiple neurotransmitters and hormones are involved in the stress response, but, to our knowledge, the two major biological consequences of the chronic exposure to trauma are the hypofunction of the serotonergic system and changes in the hypothalamic-pituitary-adrenal axis function. Some of these findings overlap with the neurobiological features of impulsivity and of suicidal behavior. Impulsivity has also been said to be both a consequence of trauma and a risk factor for the development of a pathological response to trauma. Thus, we suggest that impulsivity could be one of the links between childhood trauma and suicidal behavior. Prevention of childhood abuse could significantly reduce suicidal behavior in adolescents and adults, in part, through a decrease in the frequency of impulsive behaviors in the future.

  18. Trait impulsivity and increased pre-attentional sensitivity to intense stimuli in bipolar disorder and controls.

    PubMed

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

    2015-01-01

    Impulsivity and sensation seeking are stimulus-oriented traits. Because they differ in degree of intention and planning, they may have distinct neurophysiological mechanisms. Impulsivity is prominent in bipolar disorder, and may be related to pre-attentional information filtering and stimulus-orientation. We investigated specificity of relationships between impulsivity and sensitivity to stimulus intensity in bipolar disorder and controls, using intensity-sensitivity of auditory evoked potentials. Seventy-six subjects (37 healthy controls, 39 with bipolar disorder) were administered an intensity-sensitivity paradigm. Additional measures included Barratt Impulsiveness Scale (BIS-11) and Eysenck Impulsivity and Venturesomeness scores. State-dependent rapid-response impulsivity was measured using the Immediate Memory Task. Intensity-sensitivities of the auditory evoked P1N1, N1P2, P1, N1, and P2 potentials were assessed as the slope of amplitude relative to loudness. Analyses used general linear models (GLM) with impulsivity-related measures as dependent variables and age, gender, education, and diagnosis as dependent variables. BIS-11 total, motor, and attentional impulsivity scores correlated positively with pre-attentional N1 and P1N1 intensity-sensitivity slopes in bipolar disorder, but not in controls. BIS-11 nonplanning and Eysenck Venturesomeness scores did not correlate with intensity-sensitivity. Intensity-sensitivity slopes did not correlate with rapid-response impulsivity. Correlations between N1 or P1N1 slopes and BIS-11 scores in bipolar disorder were not affected by age, education, WAIS, treatment, symptoms, or gender. Trait impulsivity in bipolar disorder may be related to poorly modulated stimulus-driven late pre-attentional responses to stimuli, potentially resulting in exaggerated responses to intense stimuli even before conscious awareness. Components of trait impulsivity are physiologically heterogenous relative to intensity-sensitivity.

  19. Aerodynamic prediction techniques for hypersonic configuration design

    NASA Technical Reports Server (NTRS)

    1981-01-01

    An investigation of approximate theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at moderate hypersonic speeds was performed. Emphasis was placed on approaches that would be responsive to preliminary configuration design level of effort. Potential theory was examined in detail to meet this objective. Numerical pilot codes were developed for relatively simple three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the computations indicate good agreement with higher order solutions and experimental results for a variety of wing, body, and wing-body shapes for values of the hypersonic similarity parameter M delta approaching one.

  20. Aerodynamics Via Acoustics: Application of Acoustic Formulas for Aerodynamic Calculations

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Myers, M. K.

    1986-01-01

    Prediction of aerodynamic loads on bodies in arbitrary motion is considered from an acoustic point of view, i.e., in a frame of reference fixed in the undisturbed medium. An inhomogeneous wave equation which governs the disturbance pressure is constructed and solved formally using generalized function theory. When the observer is located on the moving body surface there results a singular linear integral equation for surface pressure. Two different methods for obtaining such equations are discussed. Both steady and unsteady aerodynamic calculations are considered. Two examples are presented, the more important being an application to propeller aerodynamics. Of particular interest for numerical applications is the analytical behavior of the kernel functions in the various integral equations.

  1. Aerodynamic Design Study of Advanced Multistage Axial Compressor

    NASA Technical Reports Server (NTRS)

    Larosiliere, Louis M.; Wood, Jerry R.; Hathaway, Michael D.; Medd, Adam J.; Dang, Thong Q.

    2002-01-01

    As a direct response to the need for further performance gains from current multistage axial compressors, an investigation of advanced aerodynamic design concepts that will lead to compact, high-efficiency, and wide-operability configurations is being pursued. Part I of this report describes the projected level of technical advancement relative to the state of the art and quantifies it in terms of basic aerodynamic technology elements of current design systems. A rational enhancement of these elements is shown to lead to a substantial expansion of the design and operability space. Aerodynamic design considerations for a four-stage core compressor intended to serve as a vehicle to develop, integrate, and demonstrate aerotechnology advancements are discussed. This design is biased toward high efficiency at high loading. Three-dimensional blading and spanwise tailoring of vector diagrams guided by computational fluid dynamics (CFD) are used to manage the aerodynamics of the high-loaded endwall regions. Certain deleterious flow features, such as leakage-vortex-dominated endwall flow and strong shock-boundary-layer interactions, were identified and targeted for improvement. However, the preliminary results were encouraging and the front two stages were extracted for further aerodynamic trimming using a three-dimensional inverse design method described in part II of this report. The benefits of the inverse design method are illustrated by developing an appropriate pressure-loading strategy for transonic blading and applying it to reblade the rotors in the front two stages of the four-stage configuration. Multistage CFD simulations based on the average passage formulation indicated an overall efficiency potential far exceeding current practice for the front two stages. Results of the CFD simulation at the aerodynamic design point are interrogated to identify areas requiring additional development. In spite of the significantly higher aerodynamic loadings, advanced CFD

  2. Dopaminergic influences on executive function and impulsive behaviour in impulse control disorders in Parkinson's disease.

    PubMed

    Leroi, Iracema; Barraclough, Michelle; McKie, Shane; Hinvest, Neal; Evans, Jonathan; Elliott, Rebecca; McDonald, Kathryn

    2013-09-01

    The development of impulse control disorders (ICDs) in Parkinson's disease (PD) may arise from an interaction among cognitive impairment, impulsive responding and dopaminergic state. Dopaminergic state may be influenced by pharmacologic or genotypic (catechol-O-methyltransferase; COMT) factors. We sought to investigate this interaction further by comparing those with (n = 35) and without (n = 55) ICDs on delay-discounting in different pharmacologic conditions (ON or OFF dopaminergic medication) and on response inhibition as well as aspects of executive functioning in the ON state. We then undertook an exploratory sub-group analysis of these same tasks when the overall PD group was divided into different allelic variants of COMT (val/val vs. met/met). A healthy control group (HC; n = 20) was also included. We found that in those with PD and ICDs, 'cognitive flexibility' (set shifting, verbal fluency, and attention) in the ON medication state was not impaired compared with those without ICDs. In contrast, our working memory, or 'cognitive focus', task was impaired in both PD groups compared with the HC group when ON. During the delay-discounting task, the PD with ICDs group expressed greater impulsive choice compared with the PD group without ICDs, when in the ON, but not the OFF, medication state. However, no group difference on the response inhibition task was seen when ON. Finally, the met homozygous group performed differently on tests of executive function compared with the val homozygous group. We concluded that the disparity in levels of impairment among different domains of executive function and impulsive decision-making distinguishes those with ICD in PD from those without ICD, and may in part be affected by dopaminergic status. Both pharmacologic and genotypic influences on dopaminergic state may be important in ICD.

  3. Differential associations between obesity and behavioral measures of impulsivity.

    PubMed

    Lawyer, Steven R; Boomhower, Steven R; Rasmussen, Erin B

    2015-12-01

    A growing literature indicates that impulsivity is a fundamental behavioral process that underlies obesity. However, impulsivity is a multidimensional construct, which comprises independent patterns of decision-making that could be uniquely associated with obesity. No research to date has clarified whether obesity is differentially associated with specific behavioral aspects of impulsivity. This study examined whether obesity was differentially associated with patterns of decision-making associated with impulsivity-delay discounting, probability discounting, and response inhibition. Young adults (n = 296; 44.3% male) age 18-30 were recruited from the community with media advertisements. Participants completed a series of standard self-report measures of health outcomes and behavioral measures of delay discounting, probability discounting, and response inhibition individually in a laboratory. Associations between body mass index (BMI) and behavioral outcomes in the whole sample indicated that BMI was associated with age, delay discounting, and probability discounting, but not response inhibition. A logistic regression that included age, sex, and substance use as covariates found that delay discounting, but neither probability discounting nor response inhibition, was associated with obesity status. Sensitivity to delay, rather than response inhibition and sensitivity to uncertainty, may be the best correlate of obesity status in adults. These findings are relevant to our understanding of the fundamental behavioral processes associated with obesity.

  4. Aerodynamic drag on intermodal railcars

    NASA Astrophysics Data System (ADS)

    Kinghorn, Philip; Maynes, Daniel

    2014-11-01

    The aerodynamic drag associated with transport of commodities by rail is becoming increasingly important as the cost of diesel fuel increases. This study aims to increase the efficiency of intermodal cargo trains by reducing the aerodynamic drag on the load carrying cars. For intermodal railcars a significant amount of aerodynamic drag is a result of the large distance between loads that often occurs and the resulting pressure drag resulting from the separated flow. In the present study aerodynamic drag data have been obtained through wind tunnel testing on 1/29 scale models to understand the savings that may be realized by judicious modification to the size of the intermodal containers. The experiments were performed in the BYU low speed wind tunnel and the test track utilizes two leading locomotives followed by a set of five articulated well cars with double stacked containers. The drag on a representative mid-train car is measured using an isolated load cell balance and the wind tunnel speed is varied from 20 to 100 mph. We characterize the effect that the gap distance between the containers and the container size has on the aerodynamic drag of this representative rail car and investigate methods to reduce the gap distance.

  5. Choice-impulsivity in children and adolescents with attention-deficit/hyperactivity disorder (ADHD): A meta-analytic review.

    PubMed

    Patros, Connor H G; Alderson, R Matt; Kasper, Lisa J; Tarle, Stephanie J; Lea, Sarah E; Hudec, Kristen L

    2016-02-01

    Impulsive behavior is a core DSM-5 diagnostic feature of attention-deficit/hyperactivity disorder (ADHD) that is associated with several pejorative outcomes. Impulsivity is multidimensional, consisting of two sub-constructs: rapid-response impulsivity and reward-delay impulsivity (i.e., choice-impulsivity). While previous research has extensively examined the presence and implications of rapid-response impulsivity in children with ADHD, reviews of choice-impulsive behavior have been both sparse and relatively circumscribed. This review used meta-analytic methods to comprehensively examine between-group differences in choice-impulsivity among children and adolescents with and without ADHD. Twenty-eight tasks (from 26 studies), consisting of 4320 total children (ADHD=2360, TD=1,960), provided sufficient information to compute an overall between-group effect size for choice-impulsivity performance. Results revealed a medium-magnitude between-group effect size (g=.47), suggesting that children and adolescents with ADHD exhibited moderately increased impulsive decision-making compared to TD children and adolescents. Further, relative to the TD group, children and adolescents with ADHD exhibited similar patterns of impulsive decision-making across delay discounting and delay of gratification tasks. However, the use of single-informant diagnostic procedures relative to multiple informants yielded larger between-group effects, and a similar pattern was observed across samples that excluded females relative to samples that included females.

  6. Trait Impulsivity and Newlyweds' Marital Trajectories.

    PubMed

    Lavner, Justin A; Lamkin, Joanna; Miller, Joshua D

    2017-02-01

    Despite the relationship of impulsivity with interpersonal dysfunction, including romantic relationship dysfunction, surprisingly little research has examined the degree to which impulsivity predicts how marriages unfold over time. The current study used data from 172 newlywed couples to examine spouses' impulsivity in relation to their 4-year trajectories of marital satisfaction, marital problems, relationship commitment, and verbal aggression, as well as their 10-year divorce rates. Hierarchical linear modeling indicated that husbands' and wives' impulsivity predicted their own intercepts of marital satisfaction and marital problems, reflecting lower levels of satisfaction and higher levels of problems. Wives' impulsivity also predicted their relationship commitment and their verbal aggression intercepts. No cross-spouse effects or effects on slopes were found, and impulsivity did not predict 10-year divorce rates. These findings indicate that the relationship distress associated with impulsivity begins early in marriage, and they suggest a need for further research on the processes by which impulsivity undermines marital quality.

  7. An experimental investigation of gapwise periodicity and unsteady aerodynamic response in an oscillating cascade. Volume 2: Data report. Part 2: Mode 2 data

    NASA Technical Reports Server (NTRS)

    Carta, F. O.

    1981-01-01

    Computer data are provided for tests conducted on a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blades along the leading edge plane of the cascade, over the chord of the center blade, and on the sidewall in the plane of the leading edge.

  8. Children's Help Seeking and Impulsivity

    ERIC Educational Resources Information Center

    Puustinen, Minna; Kokkonen, Marja; Tolvanen, Asko; Pulkkinen, Lea

    2004-01-01

    The aim of the present study was to analyze the relationship between students' (100 children aged 8 to 12) help-seeking behavior and impulsivity. Help-seeking behavior was evaluated using a naturalistic experimental paradigm in which children were placed in a problem-solving situation and had the opportunity to seek help from the experimenter, if…

  9. Demonstrating Sound Impulses in Pipes.

    ERIC Educational Resources Information Center

    Raymer, M. G.; Micklavzina, Stan

    1995-01-01

    Describes a simple, direct method to demonstrate the effects of the boundary conditions on sound impulse reflections in pipes. A graphical display of the results can be made using a pipe, cork, small hammer, microphone, and fast recording electronics. Explains the principles involved. (LZ)

  10. Commentary on Hyperkinetic Impulse Disorder

    ERIC Educational Resources Information Center

    Barkley, Russell A.

    2011-01-01

    Dr. Goldstein continues the laudable practice of reprinting articles of historical significance in the history of ADHD with this selective reprinting of material from the original article by Maurice Laufer, Eric Denhoff, and Gerald Solomons on hyperkinetic impulsive disorder (HID) in children. This article on HID is among the first articles to…

  11. Trait impulsivity and impaired prefrontal impulse inhibition function in adolescents with internet gaming addiction revealed by a Go/No-Go fMRI study

    PubMed Central

    2014-01-01

    Background Recent studies suggest that Internet gaming addiction (IGA) is an impulse disorder, or is at least related to impulse control disorders. In the present study, we hypothesized that different facets of trait impulsivity may be specifically linked to the brain regions with impaired impulse inhibition function in IGA adolescents. Methods Seventeen adolescents with IGA and seventeen healthy controls were scanned during performance of a response-inhibition Go/No-Go task using a 3.0 T MRI scanner. The Barratt Impulsiveness Scale (BIS)-11 was used to assess impulsivity. Results There were no differences in the behavioral performance on the Go/No-Go task between the groups. However, the IGA group was significantly hyperactive during No-Go trials in the left superior medial frontal gyrus, right anterior cingulate cortex, right superior/middle frontal gyrus, left inferior parietal lobule, left precentral gyrus, and left precuneus and cuneus. Further, the bilateral middle temporal gyrus, bilateral inferior temporal gyrus, and right superior parietal lobule were significantly hypoactive during No-Go trials. Activation of the left superior medial frontal gyrus was positively associated with BIS-11 and Chen Internet Addiction Scale (CIAS) total score across IGA participants. Conclusions Our data suggest that the prefrontal cortex may be involved in the circuit modulating impulsivity, while its impaired function may relate to high impulsivity in adolescents with IGA, which may contribute directly to the Internet addiction process. PMID:24885073

  12. Overweight in adolescent, psychiatric inpatients: A problem of general or food-specific impulsivity?

    PubMed

    Deux, Natalie; Schlarb, Angelika A; Martin, Franziska; Holtmann, Martin; Hebebrand, Johannes; Legenbauer, Tanja

    2017-05-01

    Adolescent psychiatric patients are vulnerable to weight problems and show an overrepresentation of overweight compared to the healthy population. One potential factor that can contribute to the etiology of overweight is higher impulsivity. As of yet, it is unclear whether it is a general impulse control deficit or weight-related aspects such as lower impulse control in response to food that have an impact on body weight. As this may have therapeutic implications, the current study investigated differences between overweight and non-overweight adolescent psychiatric inpatients (N = 98; aged 12-20) in relation to trait impulsivity and behavioral inhibition performance. The Barratt Impulsiveness Scale and two go/no-go paradigms with neutral and food-related stimulus materials were applied. Results indicated no significant differences concerning trait impulsivity, but revealed that overweight inpatients had significantly more difficulties in inhibition performance (i.e. they reacted more impulsively) in response to both food and neutral stimuli compared to non-overweight inpatients. Furthermore, no specific inhibition deficit for high-caloric vs. low-caloric food cues emerged in overweight inpatients, whereas non-overweight participants showed significantly lower inhibition skills in response to high-caloric than low-caloric food stimuli. The results highlight a rather general, non-food-specific reduced inhibition performance in an overweight adolescent psychiatric population. Further research is necessary to enhance the understanding of the role of impulsivity in terms of body weight status in this high-risk group of adolescent inpatients.

  13. Aerodynamic preliminary analysis system 2. Part 2: User's manuals

    NASA Technical Reports Server (NTRS)

    Divan, P.

    1981-01-01

    An aerodynamic analysis system based on potential theory at subsonic/supersonic speeds and impact type finite element solutions at hypersonic conditions is described. Three dimensional configurations having multiple nonplanar surfaces of arbitrary planform and bodies of noncircular contour may be analyzed. Static, rotary, and control longitudinal and lateral directional chracteristics may be generated. The analysis has been implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis problem. Typical simulation indicates that program provides an efficient analysis for systematically performing various aerodynamic configuration tradeoff and evaluation studies.

  14. Aerodynamic preliminary analysis system 2. Part 1: Theory

    NASA Technical Reports Server (NTRS)

    Bonner, E.; Clever, W.; Dunn, K.

    1991-01-01

    An aerodynamic analysis system based on potential theory at subsonic and/or supersonic speeds and impact type finite element solutions at hypersonic conditions is described. Three dimensional configurations having multiple nonplanar surfaces of arbitrary planform and bodies of noncircular contour may be analyzed. Static, rotary, and control longitudinal and lateral directional characteristics may be generated. The analysis was implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis problem. The program provides an efficient analysis for systematically performing various aerodynamic configuration tradeoff and evaluation studies.

  15. Baseline impulsive choice predicts the effects of nicotine and nicotine withdrawal on impulsivity in rats.

    PubMed

    Kayir, Hakan; Semenova, Svetlana; Markou, Athina

    2014-01-03

    Impulsive choice, a form of impulsivity, is associated with tobacco smoking in humans. Trait impulsivity may be a vulnerability factor for smoking, or smoking may lead to impulsive behaviors. We investigated the effects of 14-day nicotine exposure (6.32mg/kg/day base, subcutaneous minipumps) and spontaneous nicotine withdrawal on impulsive choice in low impulsive (LI) and high impulsive (HI) rats. Impulsive choice was measured in the delayed reward task in which rats choose between a small immediate reward and a large delayed reward. HI and LI rats were selected from the highest and lowest quartiles of the group before exposure to nicotine. In non-selected rats, nicotine or nicotine withdrawal had no effect on impulsive choice. In LI rats, chronic nicotine exposure decreased preference for the large reward with larger effects at longer delays, indicating increased impulsive choice. Impulsive choices for the smaller immediate rewards continued to increase during nicotine withdrawal in LI rats. In HI rats, nicotine exposure and nicotine withdrawal had no effect on impulsive choice, although there was a tendency for decreased preference for the large reward at short delays. These results indicate that nicotine- and nicotine withdrawal-induced increases in impulsive choice depend on trait impulsivity with more pronounced increases in impulsive choice in LI compared to HI subjects. Increased impulsivity during nicotine exposure may strengthen the addictive properties of nicotine and contribute to compulsive nicotine use.

  16. Comparison of impulsivity in non-problem, at-risk and problem gamblers

    PubMed Central

    Yan, Wan-Sen; Zhang, Ran-Ran; Lan, Yan; Li, Yong-Hui; Sui, Nan

    2016-01-01

    As a non-substance addiction, gambling disorder represents the model for studying the neurobiology of addiction without toxic consequences of chronic drug use. From a neuropsychological perspective, impulsivity is deemed as a potential construct responsible in the onset and development of drug addiction. The objective of this study was to investigate the associations between impulsivity and gambling status in young adults with varying severity of gambling. A sample of 1120 college students, equally divided into non-problem, at-risk and problem gamblers, were administered multiple measures of impulsivity including the UPPSP Impulsive Behaviors Scale (UPPSP), the Barratt Impulsiveness Scale-11 (BIS-11), and the Delay-discounting Test (DDT). Compared with non-problem gamblers, both at-risk gamblers and problem gamblers displayed elevated scores on Negative Urgency, Positive Urgency, Motor Impulsiveness, and Attentional Impulsiveness. Problem gamblers showed higher scores than at-risk gamblers on Positive Urgency. Logistic regression models revealed that only Negative Urgency positively predicted both at-risk gambling and problem gambling compared to non-problem gambling. These results suggest that dimensions of impulsivity may be differentially linked to gambling behavior in young adults, with Negative Urgency putatively identified as an important impulsivity-related marker for the development of gambling disorder, which may provide a better understanding of the pathogenesis. PMID:27976705

  17. Psychedelic symptoms of cannabis and cocaine use as a function of trait impulsivity.

    PubMed

    van Wel, J H P; Spronk, D B; Kuypers, K P C; Theunissen, E L; Toennes, S W; Verkes, R J; Ramaekers, J G

    2015-03-01

    Trait impulsivity has been linked to addiction in humans. It has been suggested that drug users with high trait impulsivity levels are more sensitive to subjective drug intoxication. This study assessed whether subjective response to drugs differs between drug users with normal or high levels of trait impulsivity. Regular drug users (N = 122) received doses of cocaine HCl, cannabis, and placebo in a three-way crossover study. Their mood, dissociative state, and psychedelic symptoms were measured with subjective rating scales (CADDS, Bowdle, POMS). Trait impulsivity was assessed with the Barratt Impulsiveness Scale. Cannabis increased dissociation and psychedelic state, as well as fatigue, confusion, depression and anxiety, and decreased arousal, positive mood, vigor, friendliness, and elation. Cocaine increased dissociation, psychedelic state, vigor, friendliness, elation, positive mood, anxiety and arousal, while decreasing fatigue. Only a few subjective items revealed a drug × trait impulsivity interaction, suggesting that psychedelic symptoms were most intense in high impulsivity subjects. Trait impulsiveness ratings were negatively correlated with ratings of vigor (r = -.197) and positively correlated with ratings of loss of thought control (r = .237) during cannabis intoxication. It is concluded that a broad association between trait impulsivity and psychedelic subjective drug experience appears to be absent.

  18. High Level Impulse Sounds and Human Hearing: Standards, Physiology, Quantification

    DTIC Science & Technology

    2012-05-01

    1976; Dancer , 2004). 3.1.2.2 Warned and Unwarned Response of the Ear The role of the AR in protecting hearing against impulse sounds has been...1974; Dancer , 2004). Price (2007a) refers to human reaction to unexpected and expected sounds as the unwarned response and warned response. The...Henderson et al., 2001; Maison and Liberman, 2000). This system has been referred to by Dancer (2004) as the inner ear acoustic reflex. Although

  19. Impulsive control for angular momentum management of tumbling spacecraft

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Shoji; Yamada, Katsuhiko

    2007-05-01

    We discuss an angular momentum control of a tumbling spacecraft. The proposed control method is to apply an impulse by a space robot arm, to measure and control the relative position and attitude between the target spacecraft, and then to apply another impulse until the rotational motion of the target spacecraft is well damped. A discrete controller is designed using the simplified equations of rotational motion through appropriate coordinate transformation. The stationary response under contact model uncertainty is investigated and stability condition is analytically derived. Numerical simulations are given to validate the proposed approach.

  20. On-Orbit Propellant Motion Resulting from an Impulsive Acceleration

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.; Aydelott, John C.; Mjolsness, Raymond C.; Torrey, Martin D.

    1994-01-01

    In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undesirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low-gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle cargo bay. Although the shuttle/Centaur development activity has been suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.

  1. The interference aerodynamics caused by the wing elasticity during store separation

    NASA Astrophysics Data System (ADS)

    Lei, Yang; Zheng-yin, Ye

    2016-04-01

    Air-launch-to-orbit is the technology that has stores carried aloft and launched the store from the plane to the orbit. The separation between the aircraft and store is one of the most important and difficult phases in air-launch-to-orbit technology. There exists strong aerodynamic interference between the aircraft and the store in store separation. When the aspect ratio of the aircraft is large, the elastic deformations of the wing must be considered. The main purpose of this article is to study the influence of the interference aerodynamics caused by the elastic deformations of the wing to the unsteady aerodynamics of the store. By solving the coupled functions of unsteady Navier-Stokes equations, six degrees of freedom dynamic equations and structural dynamic equations simultaneously, the store separation with the elastic deformation of the aircraft considered is simulated numerically. And the interactive aerodynamic forces are analyzed. The study shows that the interference aerodynamics is obvious at earlier time during the separation, and the dominant frequency of the elastic wing determines the aerodynamic forces frequencies of the store. Because of the effect of the interference aerodynamics, the roll angle response and pitch angle response increase. When the store is mounted under the wingtip, the additional aerodynamics caused by the wingtip vortex is obvious, which accelerate the divergence of the lateral force and the lateral-directional attitude angle of the store. This study supports some beneficial conclusions to the engineering application of the air-launch-to-orbit.

  2. Characteristics of Impulsive Suicide Attempts and Attempters.

    ERIC Educational Resources Information Center

    Simon, Thomas R.; Swann, Alan C.; Powell, Kenneth E.; Potter, Lloyd B.; Kresnow, Marcie-jo; O'Carroll, Patrick W.

    2002-01-01

    Examined impulsive suicide attempts within a population-based, case-control study of nearly lethal suicide attempts among adolescents and young adults. Impulsive attempts were more likely among those who had been in a physical fight and less likely among those who were depressed. Findings suggest inadequate control of aggressive impulses as a…

  3. Measurements of Aerodynamic Damping in the MIT Transonic Rotor

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1981-01-01

    A method was developed and demonstrated for the direct measurement of aerodynamic forcing and aerodynamic damping of a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade disk system in order to determine the forces acting on the system. The disturbing and damping forces acting on a given blade are determined if the equations of motion are expressed in individual blade coordinates. If the structural dynamic equations are transformed to multiblade coordinates, the damping can be measured for blade disk modes, and related to a reduced frequency and interblade phase angle. In order to measure the aerodynamic damping in this way, the free response to a known excitation is studied.

  4. Why obese children cannot resist food: the role of impulsivity.

    PubMed

    Nederkoorn, Chantal; Braet, Caroline; Van Eijs, Yvonne; Tanghe, Ann; Jansen, Anita

    2006-11-01

    Facing the undesirable health consequences of being obese, an important question is why some people are not able to resist eating to excess. It is theorized that increased impulsivity at least partly underlies the inability to control eating behaviour; being more impulsive is supposed to make it more difficult to resist food intake. Thirty-three obese children in a residential setting and 31 lean control children are tested. Impulsivity is measured with two behavioural measures (inhibitory control and sensitivity to reward) and questionnaires. Results show that the obese children in treatment were more sensitive to reward and showed less inhibitory control than normal weight children. In addition, the obese children with eating binges were more impulsive than the obese children without eating binges. Most interesting finding was that the children that were the least effective in inhibiting responses, lost less weight in the residential treatment program. To conclude: impulsivity is a personality characteristic that potentially has crucial consequences for the development and maintenance, as well as treatment of obesity.

  5. Special opportunities in helicopter aerodynamics

    NASA Technical Reports Server (NTRS)

    Mccroskey, W. J.

    1983-01-01

    Aerodynamic research relating to modern helicopters includes the study of three dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomenon that hamper the development of satisfactory engineering prediction techniques, but which provides a rich source of research opportunities: flow separations, compressibility effects, complex vortical wakes, and aerodynamic interference between components. Several examples of work in progress are given, including dynamic stall alleviation, the development of computational methods for transonic flow, rotor-wake predictions, and blade-vortex interactions.

  6. Aerodynamics Research Revolutionizes Truck Design

    NASA Technical Reports Server (NTRS)

    2008-01-01

    During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.

  7. Relations between trait impulsivity, behavioral impulsivity, physiological arousal, and risky sexual behavior among young men.

    PubMed

    Derefinko, Karen J; Peters, Jessica R; Eisenlohr-Moul, Tory A; Walsh, Erin C; Adams, Zachary W; Lynam, Donald R

    2014-08-01

    The current study examined how impulsivity-related traits (negative urgency, sensation seeking, and positive urgency), behavioral measures of risk taking and reward seeking, and physiological reactivity related to three different risky sexual behaviors in sexually active undergraduate men (N = 135). Regression analyses indicated that sensation seeking and behavioral risk-taking predicted unique variance in number of sexual partners. These findings suggest that, for young men, acquisition of new partners is associated with need for excitement and reward and willingness to take risks to meet those needs. Sensation seeking, behavioral risk-taking, and skin conductance reactivity to arousing stimuli was related to ever having engaged in sex with a stranger, indicating that, for men, willingness to have sex with a stranger is related not only to the need for excitement and risk-taking but also with innate responsiveness to arousing environmental triggers. In contrast, regression analyses indicated that young men who were impulsive in the context of negative emotions were less likely to use condoms, suggesting that emotion-based impulsivity may be an important factor in negligent prophylactic use. This study adds to the current understanding of the divergence between the correlates of risky sexual behaviors and may lend utility to the development of individualized HIV prevention programming.

  8. Relations Between Trait Impulsivity, Behavioral Impulsivity, Physiological Arousal, and Risky Sexual Behavior among Young Men

    PubMed Central

    Derefinko, Karen J.; Peters, Jessica R.; Eisenlohr-Moul, Tory A.; Walsh, Erin C.; Adams, Zachary W.; Lynam, Donald R.

    2014-01-01

    The current study examined how impulsivity-related traits (negative urgency, sensation seeking, and positive urgency), behavioral measures of risk taking and reward seeking, and physiological reactivity related to three different risky sexual behaviors in sexually active undergraduate men (N = 135). Regression analyses indicated that sensation seeking and behavioral risk-taking predicted unique variance in number of sexual partners. These findings suggest that, for young men, acquisition of new partners is associated with need for excitement and reward and willingness to take risks to meet those needs. Sensation seeking, behavioral risk-taking, and skin conductance reactivity to arousing stimuli was related to ever having engaged in sex with a stranger, indicating that, for men, willingness to have sex with a stranger is related not only to the need for excitement and risk-taking but also with innate responsiveness to arousing environmental triggers. In contrast, regression analyses indicated that young men who were impulsive in the context of negative emotions were less likely to use condoms, suggesting that emotion-based impulsivity may be an important factor in negligent prophylactic use. This study adds to the current understanding of the divergence between the correlates of risky sexual behaviors and may lend utility to the development of individualized HIV prevention programming. PMID:24958252

  9. Three-dimensional, Impulsive Magnetic Reconnection in a Laboratory Plasma

    SciTech Connect

    S Dorfman, et al

    2013-05-03

    Impulsive, local, 3-D reconnection is identified for the first time in a laboratory current sheet. The events observed in the Magnetic Reconnection Experiment (MRX) are characterized by large local gradients in the third direction and cannot be explained by 2-D models. Detailed measurements show that the ejection of flux rope structures from the current sheet plays a key role in these events. By contrast, even though electromagnetic fluctuations in the lower hybrid frequency range are also observed concurrently with the impulsive behavior, they are not the key physics responsible. A qualitative, 3-D, two-fluid model is proposed to explain the observations. The experimental results may be particularly applicable to space and astrophysical plasmas where impulsive reconnection occurs.

  10. THz impulse radar for biomedical sensing: nonlinear system behavior

    NASA Astrophysics Data System (ADS)

    Brown, E. R.; Sung, Shijun; Grundfest, W. S.; Taylor, Z. D.

    2014-03-01

    The THz impulse radar is an "RF-inspired" sensor system that has performed remarkably well since its initial development nearly six years ago. It was developed for ex vivo skin-burn imaging, and has since shown great promise in the sensitive detection of hydration levels in soft tissues of several types, such as in vivo corneal and burn samples. An intriguing aspect of the impulse radar is its hybrid architecture which combines the high-peak-power of photoconductive switches with the high-responsivity and -bandwidth (RF and video) of Schottky-diode rectifiers. The result is a very sensitive sensor system in which the post-detection signal-to-noise ratio depends super-linearly on average signal power up to a point where the diode is "turned on" in the forward direction, and then behaves quasi-linearly beyond that point. This paper reports the first nonlinear systems analysis done on the impulse radar using MATLAB.

  11. Modelling Aerodynamically Generated Sound: Recent Advances in Rotor Noise Prediction

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.

    2000-01-01

    A great deal of progress has been made in the modeling of aerodynamically generated sound for rotors over the past decade. The Ffowcs Williams-Hawkings (FW-H ) equation has been the foundation for much of the development. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H has also been utilized on permeable surfaces surrounding all physical noise sources. Comparison of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems.

  12. Langley Symposium on Aerodynamics, volume 1

    NASA Technical Reports Server (NTRS)

    Stack, Sharon H. (Compiler)

    1986-01-01

    The purpose of this work was to present current work and results of the Langley Aeronautics Directorate covering the areas of computational fluid dynamics, viscous flows, airfoil aerodynamics, propulsion integration, test techniques, and low-speed, high-speed, and transonic aerodynamics. The following sessions are included in this volume: theoretical aerodynamics, test techniques, fluid physics, and viscous drag reduction.

  13. Exposure to Ketamine Anesthesia Affects Rat Impulsive Behavior.

    PubMed

    Melo, António; Leite-Almeida, Hugo; Ferreira, Clara; Sousa, Nuno; Pêgo, José M

    2016-01-01

    Introduction: Ketamine is a general anesthetic (GA) that activates several neurotransmitter pathways in various part of the brain. The acute effects as GA are the most well-known and sought-after: to induce loss of responsiveness and to produce immobility during invasive procedures. However, there is a concern that repeated exposure might induce behavioral changes that could outlast their acute effect. Most research in this field describes how GA affects cognition and memory. Our work is to access if general anesthesia with ketamine can disrupt the motivational behavior trait, more specifically measuring impulsive behavior. Methods: Aiming to evaluate the effects of exposure to repeat anesthetic procedures with ketamine in motivational behavior, we tested animals in a paradigm of impulsive behavior, the variable delay-to-signal (VDS). In addition, accumbal and striatal medium spiny neurons morphology was assessed. Results: Our results demonstrated that previous exposure to ketamine deep-anesthesia affects inhibitory control (impulsive behavior). Specifically, ketamine exposed animals maintain a subnormal impulsive rate in the initial periods of the delays. However, in longer delays while control animals progressively refrain their premature unrewarded actions, ketamine-exposed animals show a different profile of response with higher premature unrewarded actions in the last seconds. Animals exposed to multiple ketamine anesthesia also failed to show an increase in premature unrewarded actions between the initial and final periods of 3 s delays. These behavioral alterations are paralleled by an increase in dendritic length of medium spiny neurons of the nucleus accumbens (NAc). Conclusions: This demonstrates that ketamine anesthesia acutely affects impulsive behavior. Interestingly, it also opens up the prospect of using ketamine as an agent with the ability to modulate impulsivity trait.

  14. Exposure to Ketamine Anesthesia Affects Rat Impulsive Behavior

    PubMed Central

    Melo, António; Leite-Almeida, Hugo; Ferreira, Clara; Sousa, Nuno; Pêgo, José M.

    2016-01-01

    Introduction: Ketamine is a general anesthetic (GA) that activates several neurotransmitter pathways in various part of the brain. The acute effects as GA are the most well-known and sought-after: to induce loss of responsiveness and to produce immobility during invasive procedures. However, there is a concern that repeated exposure might induce behavioral changes that could outlast their acute effect. Most research in this field describes how GA affects cognition and memory. Our work is to access if general anesthesia with ketamine can disrupt the motivational behavior trait, more specifically measuring impulsive behavior. Methods: Aiming to evaluate the effects of exposure to repeat anesthetic procedures with ketamine in motivational behavior, we tested animals in a paradigm of impulsive behavior, the variable delay-to-signal (VDS). In addition, accumbal and striatal medium spiny neurons morphology was assessed. Results: Our results demonstrated that previous exposure to ketamine deep-anesthesia affects inhibitory control (impulsive behavior). Specifically, ketamine exposed animals maintain a subnormal impulsive rate in the initial periods of the delays. However, in longer delays while control animals progressively refrain their premature unrewarded actions, ketamine-exposed animals show a different profile of response with higher premature unrewarded actions in the last seconds. Animals exposed to multiple ketamine anesthesia also failed to show an increase in premature unrewarded actions between the initial and final periods of 3 s delays. These behavioral alterations are paralleled by an increase in dendritic length of medium spiny neurons of the nucleus accumbens (NAc). Conclusions: This demonstrates that ketamine anesthesia acutely affects impulsive behavior. Interestingly, it also opens up the prospect of using ketamine as an agent with the ability to modulate impulsivity trait. PMID:27932959

  15. Food reinforcement and impulsivity in overweight children and their parents.

    PubMed

    Epstein, Leonard H; Dearing, Kelly K; Temple, Jennifer L; Cavanaugh, Meghan D

    2008-08-01

    Pediatric obesity involves choices among healthy and less healthy alternatives, as well as choices whose consequences vary over time, such as engaging in unhealthy behaviors now at the expense of future health. The purpose of this study was to examine the relative reinforcing value of food and behavioral impulsivity under different experimental conditions in a sample of 50 families screened for participation in a pediatric obesity treatment program. Relative reinforcing value for food versus money was studied under conditions in which increased response requirements were placed on either access to food or money, and the amount of money, the alternative reinforcer, was varied. Impulsivity for small immediate versus larger delayed monetary rewards was studied under conditions in which the value of the immediate reward and the duration of the delay were varied. Results showed that response requirements affected the choice of food for both parents and children (p<0.001), and there was a significant correlation between the number of food reinforcers chosen by parents and children (r=0.57, p<0.001). The value of the immediate reward differentially influenced choice of the immediate reward for parents and children (p<0.05), with children (p<0.001) but not parents (p=0.36) more impulsive as value of the immediate reward increased. The length of the delay influenced both parent (p=0.004) and child (p<0.01) choice of the immediate reward. Parent and child impulsivity were not correlated (r=0.15, p=0.29). This study suggests that food reinforcement may be more similar between parents and children than behavioral impulsivity, though additional research using other measures of relative reinforcing value and impulsivity is warranted.

  16. Progesterone attenuates impulsive action in a Go/No-Go task for sucrose pellets in female and male rats.

    PubMed

    Swalve, Natashia; Smethells, John R; Carroll, Marilyn E

    2016-09-01

    Impulsivity, or a tendency to act without anticipation of future consequences, is associated with drug abuse. Impulsivity is typically separated into two main measures, impulsive action and impulsive choice. Given the association of impulsivity and drug abuse, treatments that reduce impulsivity have been proposed as an effective method for countering drug addiction. Progesterone has emerged as a promising treatment, as it is associated with decreased addiction-related behaviors and impulsive action. The goal of the present study was to determine the effects of progesterone (PRO) on impulsive action for food: a Go/No-Go task. Female and male rats responded for sucrose pellets during a Go component when lever pressing was reinforced on a variable-interval 30-s schedule. During the alternate No-Go component, withholding a lever press was reinforced on a differential reinforcement of other (DRO) behavior 30-s schedule, where a lever press reset the DRO timer. Impulsive action was operationally defined as the inability to withhold a response during the No-Go component (i.e. the number of DRO resets). Once Go/No-Go behavior was stable, responding between rats treated with PRO (0.5mg/kg) or vehicle was examined. Progesterone significantly decreased the total number of DRO resets in both males and females, but it did not affect VI responding for sucrose pellets. This suggests that PRO decreases motor impulsivity for sucrose pellets without affecting motivation for food. Thus, PRO may reduce motor impulsivity, a behavior underlying drug addiction.

  17. POEMS in Newton's Aerodynamic Frustum

    ERIC Educational Resources Information Center

    Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

    2010-01-01

    The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

  18. Aerodynamic laboratory at Cuatro Vientos

    NASA Technical Reports Server (NTRS)

    JUBERA

    1922-01-01

    This report presents a listing of the many experiments in aerodynamics taking place at Cuatro Vientos. Some of the studies include: testing spheres, in order to determine coefficients; mechanical and chemical tests of materials; and various tests of propeller strength and flexibility.

  19. Aerodynamic design via control theory

    NASA Technical Reports Server (NTRS)

    Jameson, Antony

    1988-01-01

    The question of how to modify aerodynamic design in order to improve performance is addressed. Representative examples are given to demonstrate the computational feasibility of using control theory for such a purpose. An introduction and historical survey of the subject is included.

  20. Dynamic Soaring: Aerodynamics for Albatrosses

    ERIC Educational Resources Information Center

    Denny, Mark

    2009-01-01

    Albatrosses have evolved to soar and glide efficiently. By maximizing their lift-to-drag ratio "L/D", albatrosses can gain energy from the wind and can travel long distances with little effort. We simplify the difficult aerodynamic equations of motion by assuming that albatrosses maintain a constant "L/D". Analytic solutions to the simplified…

  1. Feedback Control for Aerodynamics (Preprint)

    DTIC Science & Technology

    2006-09-01

    AFRL-VA-WP-TP-2006-348 FEEDBACK CONTROL FOR AERODYNAMICS (PREPRINT) R. Chris Camphouse, Seddik M. Djouadi, and James H. Myatt...CONSTRUCTION FOR THE DESIGN OF BOUNDARY FEEDBACK CONTROLS FROM REDUCED ORDER MODELS (PREPRINT) 5c. PROGRAM ELEMENT NUMBER 0601102F 5d. PROJECT NUMBER...

  2. Emotion Regulation and Impulsivity in Young Adults

    PubMed Central

    Schreiber, Liana R.N.; Grant, Jon E.; Odlaug, Brian L.

    2012-01-01

    Past research has linked both emotion regulation and impulsivity with the development and maintenance of addictions. However, no research has investigated the relationship between emotion regulation and impulsivity within young adults. In the present study, we analyzed 194 young adults (27.8% female; 21.3 ± 3.32 years old; 91.8% single; 85.1% Caucasian), grouping them as low, average, or high emotionally dysregulated, and compared self-reported impulsivity, impulsive behaviors (such as alcohol and substance use and gambling) and cognitive impulsivity. We hypothesized that those with high levels of emotion dysregulation would score higher on self-reported and cognitive impulsivity, and report more impulsive behaviors. Analysis indicated that compared to low, the high emotion dysregulation group scored significantly higher on two self-report measures of impulsivity, harm avoidance, and cognitive reasoning. No significant differences were found between groups in impulsive behaviors and cognitive impulsivity. Overall, this study highlights the relationship between emotion dysregulation and impulsivity, suggesting that emotion regulation may be an important factor to consider when assessing individuals at a higher risk for developing an addiction. PMID:22385661

  3. Measurement of Aerodynamic Shear Stress Using Side Chain Liquid Crystal Polymers

    DTIC Science & Technology

    1992-01-01

    A novel concept was proposed exploiting the optical property response of liquid crystalline materials to various external effects. This study determined the feasibility of using side chain liquid crystal polymers as aerodynamic shear sensors. A method was developed to

  4. A Neurogenetic Approach to Impulsivity

    PubMed Central

    Congdon, Eliza; Canli, Turhan

    2008-01-01

    Impulsivity is a complex and multidimensional trait that is of interest to both personality psychologists and to clinicians. For investigators seeking the biological basis of personality traits, the use of neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) revolutionized personality psychology in less than a decade. Now, another revolution is under way, and it originates from molecular biology. Specifically, new findings in molecular genetics, the detailed mapping and the study of the function of genes, have shown that individual differences in personality traits can be related to individual differences within specific genes. In this article, we will review the current state of the field with respect to the neural and genetic basis of trait impulsivity. PMID:19012655

  5. Impulse Response Operators for Structural Complexes

    DTIC Science & Technology

    1990-05-12

    systems of the complex. The statistical energy analysis (SEA) is one such a device [ 13, 14]. The rendering of SEA from equation (21) and/or (25) lies...Propagation.] 13. L. Cremer, M. Heckl, and E.E. Ungar 1973 Structure-Borne Sound (Springer Verlag). 14. R. H. Lyon 1975 Statistical Energy Analysis of

  6. Double trouble. Trait food craving and impulsivity interactively predict food-cue affected behavioral inhibition.

    PubMed

    Meule, Adrian; Kübler, Andrea

    2014-08-01

    Impulsivity and food craving have both been implicated in overeating. Recent results suggest that both processes may interactively predict increased food intake. In the present study, female participants performed a Go/No-go task with pictures of high- and low-calorie foods. They were instructed to press a button in response to the respective target category, but withhold responses to the other category. Target category was switched after every other block, thereby creating blocks in which stimulus-response mapping was the same as in the previous block (nonshift blocks) and blocks in which it was reversed (shift blocks). The Food Cravings Questionnaires and the Barratt Impulsiveness Scale were used to assess trait and state food craving and attentional, motor, and nonplanning impulsivity. Participants had slower reaction times and more omission errors (OE) in high-calorie than in low-calorie blocks. Number of commission errors (CE) and OE was higher in shift blocks than in nonshift blocks. Trait impulsivity was positively correlated with CE in shift blocks while trait food craving was positively correlated with CE in high-calorie blocks. Importantly, CE in high-calorie-shift blocks were predicted by an interaction of food craving × impulsivity such that the relationship between food craving and CE was particularly strong at high levels of impulsivity, but vanished at low levels of impulsivity. Thus, impulsive reactions to high-calorie food-cues are particularly pronounced when both trait impulsivity and food craving is high, but low levels of impulsivity can compensate for high levels of trait food craving. Results support models of self-regulation which assume that interactive effects of low top-down control and strong reward sensitive, bottom-up mechanisms may determine eating-related disinhibition, ultimately leading to increased food intake.

  7. A Quasi-Steady Flexible Launch Vehicle Stability Analysis Using Steady CFD with Unsteady Aerodynamic Enhancement

    NASA Technical Reports Server (NTRS)

    Bartels, Robert E.

    2011-01-01

    Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin is caused by an undamping of the aerodynamics in one of the lower frequency flexible or rigid body modes. Analysis of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic lineloads derived from steady rigid computational fluid dynamics (CFD). However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers where experiment or unsteady computational aeroelastic (CAE) analysis show a reduced or even negative aerodynamic damping. This paper will present a method of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics. The enhanced formulation uses unsteady CFD to compute the response of selected lower frequency modes. The response is contained in a time history of the vehicle lineloads. A proper orthogonal decomposition of the unsteady aerodynamic lineload response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping and mass matrices. The results of the enhanced quasi-static aeroelastic stability analysis are compared with the damping and frequency computed from unsteady CAE analysis and from a quasi-steady analysis. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic stability analysis into close agreement with the unsteady CAE analysis.

  8. Computerized aerodynamic design of a transonically 'quiet' blade

    NASA Technical Reports Server (NTRS)

    Tauber, M. E.

    1984-01-01

    The high noise levels produced by helicopters are major sources of concern. There are many sources of the noise, but during high-speed forward flight, impulsive noise dominates the noise spectrum. The cause of the high-speed impulsive noise is the propagation into the far field of shock waves that form on the advancing blade. This mechanism has been labeled 'delocalization'. It has been shown, however, that by judicious design of the blade-tip planform, delocalization can be prevented. The objective of the present study is to illustrate how blade-tip configurations (both planform and airfoil shape) can be systematically varied to identify shapes that avoid delocalization and simultaneously improve aerodynamic performance. This has been done using the latest version of the ROT22 transonic, full-potential, quasi-steady, rotor flow-field code. A hypothetical modern rotor blade was postulated, and tip modifications consisting of taper, sweep, and airfoil section alterations were investigated. Planform modifications were found to be most effective in eliminating delocalization.

  9. Cricket Ball Aerodynamics: Myth Versus Science

    NASA Technical Reports Server (NTRS)

    Mehta, Rabindra D.; Koga, Demmis J. (Technical Monitor)

    2000-01-01

    Aerodynamics plays a prominent role in the flight of a cricket ball released by a bowler. The main interest is in the fact that the ball can follow a curved flight path that is not always under the control of the bowler. ne basic aerodynamic principles responsible for the nonlinear flight or "swing" of a cricket ball were identified several years ago and many papers have been published on the subject. In the last 20 years or so, several experimental investigations have been conducted on cricket ball swing, which revealed the amount of attainable swing, and the parameters that affect it. A general overview of these findings is presented with emphasis on the concept of late swing and the effects of meteorological conditions on swing. In addition, the relatively new concept of "reverse" swing, how it can be achieved in practice and the role in it of ball "tampering", are discussed in detail. A discussion of the "white" cricket ball used in last year's World Cup, which supposedly possesses different swing properties compared to a conventional red ball, is also presented.

  10. Aerodynamic Interference During Sabot Discard

    DTIC Science & Technology

    1977-09-01

    J. Mik.WNe, - -desirc4 trajoctory. For the rouns tested , the impulse due to aerodynsmic interaction during sabot discard is of the sae magnitude as...TABLE OF CONiENTS Page LIST OFILLUSTRATIONS . . . . . . . . . . . . . . . . . . . 5 1, INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . II...Figure Page 1. Test Projectile (60mm, AAAC). . . . . . ... . 19 2. Schematic of Test Set-Up . . . . . . . . . . . . . . . 20 3. Sample X-ray Exposure

  11. Multidimensional assessment of impulsivity in relation to obesity and food addiction.

    PubMed

    VanderBroek-Stice, Lauren; Stojek, Monika K; Beach, Steven R H; vanDellen, Michelle R; MacKillop, James

    2017-05-01

    Based on similarities between overconsumption of food and addictive drugs, there is increasing interest in "food addiction," a compulsive eating pattern defined using symptoms parallel to substance use disorders. Impulsivity, a multidimensional construct robustly linked to drug addiction, has been increasingly examined as an obesity determinant, but with mixed findings. This study sought to clarify relations between three major domains of impulsivity (i.e., impulsive personality traits, discounting of delayed rewards, and behavioral inhibition) in both obesity and food addiction. Based on the association between impulsivity and compulsive drug use, the general hypothesis was that the impulsivity-food addiction relation would be stronger than and responsible for the impulsivity-obesity relation. Using a cross-sectional dimensional design, participants (N = 181; 32% obese) completed a biometric assessment, the Yale Food Addiction Scale (YFAS), the UPPS-P Impulsive Behavior Scales, a Go/NoGo task, and measures of monetary delay discounting. Results revealed significantly higher prevalence of food addiction among obese participants and stronger zero-order associations between impulsivity indices and YFAS compared to obesity. Two aspects of impulsivity were independently significantly associated with food addiction: (a) a composite of Positive and Negative Urgency, reflecting proneness to act impulsively during intense mood states, and (b) steep discounting of delayed rewards. Furthermore, the results supported food addiction as a mediator connecting both urgency and delay discounting with obesity. These findings provide further evidence linking impulsivity to food addiction and obesity, and suggest that food addiction may be a candidate etiological pathway to obesity for individuals exhibiting elevations in these domains.

  12. Periodic components of hand acceleration/deceleration impulses during telemanipulation

    SciTech Connect

    Draper, J.V.; Handel, S.

    1994-01-01

    Responsiveness is the ability of a telemanipulator to recreate user trajectories and impedance in time and space. For trajectory production, a key determinant of responsiveness is the ability of the system to accept user inputs, which are forces on the master handle generated by user hand acceleration/deceleration (a/d) impulses, and translate them into slave arm acceleration/deceleration. This paper presents observations of master controller a/d impulses during completion of a simple target acquisition task. Power spectral density functions (PSDF`s) calculated from hand controller a/d impulses were used to assess impulse waveform. The relative contributions of frequency intervals ranging up to 25 Hz for three spatially different versions of the task were used to determine which frequencies were most important. The highest relative power was observed in frequencies between 1 Hz and 6 Hz. The key frequencies related to task difficulty were in the range from 2 Hz to 8 Hz. the results provide clues to the source of the performance inhibition.

  13. Dimensions of impulsive behavior and treatment outcomes for adolescent smokers.

    PubMed

    Harris, Millie; Penfold, Robert B; Hawkins, Ariane; Maccombs, Jared; Wallace, Bryan; Reynolds, Brady

    2014-02-01

    Adolescent cigarette smoking rates remain a significant public health concern, and as a result there is a continued need to understand factors that contribute to an adolescent's ability to reduce or quit smoking. Previous research suggests that impulsive behavior may be associated with treatment outcomes for smoking. The current research (N = 81) explored 3 dimensions of impulsive behavior as predictors of treatment response from a social-cognitive type program for adolescent smokers (i.e., Not On Tobacco; N-O-T). Measures included laboratory assessments of delay discounting, sustained attention, and behavioral disinhibition. A self-report measure of impulsivity was also included. Adolescent smokers who had better sustained attention were more likely to reduce or quit smoking by the end of treatment. No other measures of impulsivity were significantly associated with treatment response. From these findings, an adolescent smoker's ability to sustain attention appears to be an important behavioral attribute to consider when implementing smoking cessation programs such as N-O-T.

  14. Cued to Act on Impulse: More Impulsive Choice and Risky Decision Making by Women Susceptible to Overeating after Exposure to Food Stimuli

    PubMed Central

    Yeomans, Martin R.; Brace, Aaron

    2015-01-01

    There is increasing evidence that individual differences in tendency to overeat relate to impulsivity, possibly by increasing reactivity to food-related cues in the environment. This study tested whether acute exposure to food cues enhanced impulsive and risky responses in women classified on tendency to overeat, indexed by scores on the three factor eating questionnaire disinhibition (TFEQ-D), restraint (TFEQ-R) and hunger scales. Ninety six healthy women completed two measures of impulsive responding (delayed discounting, DDT and a Go No-Go, GNG, task) and a measure of risky decision making (the balloon analogue risk task, BART) as well as questionnaire measures of impulsive behaviour either after looking at a series of pictures of food or visually matched controls. Impulsivity (DDT) and risk-taking (BART) were both positively associated with TFEQ-D scores, but in both cases this effect was exacerbated by prior exposure to food cues. No effects of restraint were found. TFEQ-D scores were also related to more commission errors on the GNG, while restrained women were slower on the GNG, but neither effect was modified by cue exposure. Overall these data suggest that exposure to food cues act to enhance general impulsive responding in women at risk of overeating and tentatively suggest an important interaction between tendency for impulsive decision making and food cues that may help explain a key underlying risk factor for overeating. PMID:26378459

  15. An Abbreviated Impulsiveness Scale (ABIS) Constructed through Confirmatory Factor Analysis of the BIS-11

    PubMed Central

    Coutlee, Christopher G.; Politzer, Cary S.; Hoyle, Rick H.; Huettel, Scott A.

    2015-01-01

    Impulsiveness is a personality trait that reflects an urge to act spontaneously, without thinking or planning ahead for the consequences of your actions. High impulsiveness is characteristic of a variety of problematic behaviors including attention deficit disorder, hyperactivity, excessive gambling, risk-taking, drug use, and alcoholism. Researchers studying attention and self-control often assess impulsiveness using personality questionnaires, notably the common Barratt Impulsiveness Scale version 11 (BIS-11; last revised in 1995). Advances in techniques for producing personality questionnaires over the last 20 years prompted us to revise and improve the BIS-11. We sought to make the revised scale shorter – so that it would be quicker to administer – and better matched to current behaviors. We analyzed responses from 1549 adults who took the BIS-11 questionnaire. Using a statistical technique called factor analysis, we eliminated 17 questions that did a poor job of measuring the three major types of impulsiveness identified by the scale: inattention, spontaneous action, and lack of planning. We constructed our ABbreviated Impulsiveness Scale (ABIS) using the remaining 13 questions. We showed that the ABIS performed well when administered to additional groups of 657 and 285 adults. Finally, we showed expected relationships between the ABIS and other personality measurements related to impulsiveness, and showed that the ABIS can help predict alcohol consumption. We present the ABIS as a useful and efficient tool for researchers interested in measuring impulsive personality. PMID:26258000

  16. Skin impulse excitation of spinal sensory neurons in developing Xenopus laevis (Daudin) tadpoles.

    PubMed

    James, Lisa J; Soffe, Stephen R

    2011-10-15

    Responses to gentle touch in young Xenopus tadpoles are mediated by spinal cord sensory Rohon-Beard neurons. Tadpoles also respond to noxious stimuli that elicit 'skin impulses', which propagate between epithelial cells over the whole body surface, somehow entering the CNS to generate a response. After hatching (~48 h post-fertilization), skin impulse signals enter the CNS only via cranial nerves, but previous evidence suggested the possibility of direct entry to the spinal cord before this (~24 h). We have used behavioural and electrophysiological methods to explore the developmental pattern of skin impulse entry into the spinal cord and the involvement of Rohon-Beard neurons. Lesioning confirmed that skin impulse signals can directly enter the spinal cord in young embryos, but access decreases over ~12 h and disappears soon after hatching. Electrical recordings from central Rohon-Beard axons in young embryos showed firing in response to skin impulses. However, unit recordings from Rohon-Beard somata showed that individuals that responded to touch within a characteristic, localised receptive field did not fire to skin impulses, whereas others from similar locations responded reliably. Developmental loss of skin impulse access to the spinal cord mirrored the known spread of sensitivity to gentle touch as the peripheral mechanosensory endings of Rohon-Beard neurons mature. Together, these results suggest that Rohon-Beard neurons respond to skin impulses only while immature, providing a transitory route for skin impulses to excite the CNS. In this way, Rohon-Beard neurons would mediate responses first to noxious and then to localised, gentle touch stimuli as the neurons developed.

  17. Three-dimensional whole-brain perfusion quantification using pseudo-continuous arterial spin labeling MRI at multiple post-labeling delays: accounting for both arterial transit time and impulse response function.

    PubMed

    Qin, Qin; Huang, Alan J; Hua, Jun; Desmond, John E; Stevens, Robert D; van Zijl, Peter C M

    2014-02-01

    Measurement of the cerebral blood flow (CBF) with whole-brain coverage is challenging in terms of both acquisition and quantitative analysis. In order to fit arterial spin labeling-based perfusion kinetic curves, an empirical three-parameter model which characterizes the effective impulse response function (IRF) is introduced, which allows the determination of CBF, the arterial transit time (ATT) and T(1,eff). The accuracy and precision of the proposed model were compared with those of more complicated models with four or five parameters through Monte Carlo simulations. Pseudo-continuous arterial spin labeling images were acquired on a clinical 3-T scanner in 10 normal volunteers using a three-dimensional multi-shot gradient and spin echo scheme at multiple post-labeling delays to sample the kinetic curves. Voxel-wise fitting was performed using the three-parameter model and other models that contain two, four or five unknown parameters. For the two-parameter model, T(1,eff) values close to tissue and blood were assumed separately. Standard statistical analysis was conducted to compare these fitting models in various brain regions. The fitted results indicated that: (i) the estimated CBF values using the two-parameter model show appreciable dependence on the assumed T(1,eff) values; (ii) the proposed three-parameter model achieves the optimal balance between the goodness of fit and model complexity when compared among the models with explicit IRF fitting; (iii) both the two-parameter model using fixed blood T1 values for T(1,eff) and the three-parameter model provide reasonable fitting results. Using the proposed three-parameter model, the estimated CBF (46 ± 14 mL/100 g/min) and ATT (1.4 ± 0.3 s) values averaged from different brain regions are close to the literature reports; the estimated T(1,eff) values (1.9 ± 0.4 s) are higher than the tissue T1 values, possibly reflecting a contribution from the microvascular arterial blood compartment.

  18. Control of helicopter rotorblade aerodynamics

    NASA Technical Reports Server (NTRS)

    Fabunmi, James A.

    1991-01-01

    The results of a feasibility study of a method for controlling the aerodynamics of helicopter rotorblades using stacks of piezoelectric ceramic plates are presented. A resonant mechanism is proposed for the amplification of the displacements produced by the stack. This motion is then converted into linear displacement for the actuation of the servoflap of the blades. A design which emulates the actuation of the servoflap on the Kaman SH-2F is used to demonstrate the fact that such a system can be designed to produce the necessary forces and velocities needed to control the aerodynamics of the rotorblades of such a helicopter. Estimates of the electrical power requirements are also presented. A Small Business Innovation Research (SBIR) Phase 2 Program is suggested, whereby a bench-top prototype of the device can be built and tested. A collaborative effort between AEDAR Corporation and Kaman Aerospace Corporation is anticipated for future effort on this project.

  19. Impulsive behavior and nicotinic acetylcholine receptors.

    PubMed

    Ohmura, Yu; Tsutsui-Kimura, Iku; Yoshioka, Mitsuhiro

    2012-01-01

    Higher impulsivity is thought to be a risk factor for drug addiction, criminal involvement, and suicide. Excessive levels of impulsivity are often observed in several psychiatric disorders including attention-deficit/hyperactivity disorder and schizophrenia. Previous studies have demonstrated that nicotinic acetylcholine receptors (nAChRs) are involved in impulsive behavior. Here, we introduce recent advances in this field and describe the role of the following nAChR-related brain mechanisms in modulating impulsive behavior: dopamine release in the ventral striatum; α4β2 nAChRs in the infralimbic cortex, which is a ventral part of the medial prefrontal cortex (mPFC); and dopamine release in the mPFC. We also suggest several potential therapeutic drugs to address these mechanisms in impulsivity-related disorders and explore future directions to further elucidate the roles of central nAChRs in impulsive behavior.

  20. Impulsivity and sexual assault in college men.

    PubMed

    Mouilso, Emily R; Calhoun, Karen S; Rosenbloom, Thomas G

    2013-01-01

    Although impulsivity has been consistently linked to perpetration of sexual aggression, results lack clarity because they do not account for the substantial heterogeneity associated with the construct. The UPPS-P model (Lynam, Smith, Whiteside, & Cyders, 2006), which was proposed to clarify the multidimensional nature of impulsivity, has yet to be applied to sexual aggression. We measured UPPS-P Impulsivity in a sample of male college students who also self-reported on perpetration of sexual aggression. As predicted, impulsivity distinguished perpetrators from nonperpetrators. Perpetrators scored higher than non-perpetrators on Negative Urgency, Positive Urgency, and lack of Premeditation. Results suggest that the impulsivity traits most relevant to sexual aggression are the tendency to act impulsively when experiencing intense emotions (Positive and Negative Urgency) and lack of forethought and planning (lack of Premeditation).

  1. Simulating Magneto-Aerodynamic Actuator

    DTIC Science & Technology

    2007-12-20

    2005. 19. Boeuf, J.P., Lagmich, Y., Callegari, Th., and Pitchford , L.C., Electro- hydrodynamic Force and Acceleration in Surface Discharge, AIAA 2006...Plasmadynamics and Laser Award, 2004 AFRL Point of Contact Dr. Donald B. Paul , AFRL/VA WPAFB, OH 937-255-7329, met weekly. Dr. Alan Garscadden, AFRL/PR...validating database for numerical simulation of magneto-aerodynamic actuator for hypersonic flow control. Points of contact at the AFRL/VA are Dr. D. Paul

  2. Nonaxisymmetric Body Supersonic, Aerodynamic Prediction

    DTIC Science & Technology

    1987-08-01

    wing - tail configuration are compared in Figure 27. CN comparisons are good. C. is a sensitive computation for xcp close to x’. 7.2...Analytical and Experimental Supersonic Aerodynamic Characteristics of a Forward Control Missile , AIAA Paper No. 81-0398, AIAA 19th Aerospace Sciences...body diameter. The next computational example is for a body- wing - tail configuration from Reference 32 A body-alone comparison has been made earlier in

  3. Aerodynamics of Supersonic Lifting Bodies

    DTIC Science & Technology

    1981-02-01

    verso of front cover. 19 Y WOROS (Continue on rt.’,;erso side i recessary and identily by block number) Theoretical Aerodynamics Lifting Bodies Wind ...waverider solution, developed from the supersonic wedge flow solution, is then i Fused to fashion vertLcal stabilizer-likh control surfaces. Wind ...served as Project Engineers ror thE wind tunnel work. Important contributions were also made bv: Mr. iis±ung Miin; Lee, -M. Beom-Soo Kim, Mtr. Martin Weeks

  4. Unsteady Aerodynamic Phenomena in Turbomachines

    DTIC Science & Technology

    1990-02-01

    The first part of a systematic variation of important parameters shows their influence on the aerodynamic forces and moments coefficients . 2-2...real physical phenomena. Besides, for reasons of stability it in necessary to introduce an additional damping coefficient , which depends on the... coefficients for the "Fourth Standard Configu- ration No. 4" /10/, using a mesh with 51 x 17 points (Fig. I). This grid represents a typical section of

  5. Teens impulsively react rather than retreat from threat.

    PubMed

    Dreyfuss, Michael; Caudle, Kristina; Drysdale, Andrew T; Johnston, Natalie E; Cohen, Alexandra O; Somerville, Leah H; Galván, Adriana; Tottenham, Nim; Hare, Todd A; Casey, B J

    2014-01-01

    There is a significant inflection in risk taking and criminal behavior during adolescence, but the basis for this increase remains largely unknown. An increased sensitivity to rewards has been suggested to explain these behaviors, yet juvenile offences often occur in emotionally charged situations of negative valence. How behavior is altered by changes in negative emotional processes during adolescence has received less attention than changes in positive emotional processes. The current study uses a measure of impulsivity in combination with cues that signal threat or safety to assess developmental changes in emotional responses to threat cues. We show that adolescents, especially males, impulsively react to threat cues relative to neutral ones more than adults or children, even when instructed not to respond. This adolescent-specific behavioral pattern is paralleled by enhanced activity in limbic cortical regions implicated in the detection and assignment of emotional value to inputs and in the subsequent regulation of responses to them when successfully suppressing impulsive responses to threat cues. In contrast, prefrontal control regions implicated in detecting and resolving competing responses show an adolescent-emergent pattern (i.e. greater activity in adolescents and adults relative to children) during successful suppression of a response regardless of emotion. Our findings suggest that adolescence is a period of heightened sensitivity to social and emotional cues that results in diminished regulation of behavior in their presence.

  6. X-34 Vehicle Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Brauckmann, Gregory J.

    1998-01-01

    The X-34, being designed and built by the Orbital Sciences Corporation, is an unmanned sub-orbital vehicle designed to be used as a flying test bed to demonstrate key vehicle and operational technologies applicable to future reusable launch vehicles. The X-34 will be air-launched from an L-1011 carrier aircraft at approximately Mach 0.7 and 38,000 feet altitude, where an onboard engine will accelerate the vehicle to speeds above Mach 7 and altitudes to 250,000 feet. An unpowered entry will follow, including an autonomous landing. The X-34 will demonstrate the ability to fly through inclement weather, land horizontally at a designated site, and have a rapid turn-around capability. A series of wind tunnel tests on scaled models was conducted in four facilities at the NASA Langley Research Center to determine the aerodynamic characteristics of the X-34. Analysis of these test results revealed that longitudinal trim could be achieved throughout the design trajectory. The maximum elevon deflection required to trim was only half of that available, leaving a margin for gust alleviation and aerodynamic coefficient uncertainty. Directional control can be achieved aerodynamically except at combined high Mach numbers and high angles of attack, where reaction control jets must be used. The X-34 landing speed, between 184 and 206 knots, is within the capabilities of the gear and tires, and the vehicle has sufficient rudder authority to control the required 30-knot crosswind.

  7. Applied aerodynamics: Challenges and expectations

    NASA Technical Reports Server (NTRS)

    Peterson, Victor L.; Smith, Charles A.

    1993-01-01

    Aerospace is the leading positive contributor to this country's balance of trade, derived largely from the sale of U.S. commercial aircraft around the world. This powerfully favorable economic situation is being threatened in two ways: (1) the U.S. portion of the commercial transport market is decreasing, even though the worldwide market is projected to increase substantially; and (2) expenditures are decreasing for military aircraft, which often serve as proving grounds for advanced aircraft technology. To retain a major share of the world market for commercial aircraft and continue to provide military aircraft with unsurpassed performance, the U.S. aerospace industry faces many technological challenges. The field of applied aerodynamics is necessarily a major contributor to efforts aimed at meeting these technological challenges. A number of emerging research results that will provide new opportunities for applied aerodynamicists are discussed. Some of these have great potential for maintaining the high value of contributions from applied aerodynamics in the relatively near future. Over time, however, the value of these contributions will diminish greatly unless substantial investments continue to be made in basic and applied research efforts. The focus: to increase understanding of fluid dynamic phenomena, identify new aerodynamic concepts, and provide validated advanced technology for future aircraft.

  8. Transitory Control of the Aerodynamic Loads on an Airfoil in Dynamic Pitch and Plunge

    NASA Astrophysics Data System (ADS)

    Tan, Yuehan; Crittenden, Thomas; Glezer, Ari

    2016-11-01

    Transitory control and regulation of trapped vorticity concentrations are exploited in wind tunnel experiments for control of the aerodynamic loads on an airfoil moving in time-periodic 2-DOF (pitch and plunge) beyond the dynamic stall margin. Actuation is effected using a spanwise array of integrated miniature chemical (combustion based) high-impulse actuators that are triggered intermittently relative to the airfoil's motion. Each actuation pulse has sufficient control authority to alter the global aerodynamic performance throughout the motion cycle on a characteristic time scale that is an order of magnitude shorter than the airfoil's convective time scale. The effects of the actuation on the aerodynamic characteristics of the airfoil are assessed using time-dependent measurements of the lift force and pitching moment coupled with time-resolved particle image velocimetry that is acquired phased-locked to the motion of the airfoil. It is shown that the aerodynamic loads can be significantly altered using actuation programs based on multiple actuation pulses during the time-periodic pitch/plunge cycle. Superposition of such actuation programs leads to enhancement of cycle lift and pitch stability, and reduced cycle hysteresis and peak pitching moment. Supported by GT-VLRCOE.

  9. In vivo measurement of aerodynamic weight support in freely flying birds

    NASA Astrophysics Data System (ADS)

    Lentink, David; Haselsteiner, Andreas; Ingersoll, Rivers

    2014-11-01

    Birds dynamically change the shape of their wing during the stroke to support their body weight aerodynamically. The wing is partially folded during the upstroke, which suggests that the upstroke of birds might not actively contribute to aerodynamic force production. This hypothesis is supported by the significant mass difference between the large pectoralis muscle that powers the down-stroke and the much smaller supracoracoideus that drives the upstroke. Previous works used indirect or incomplete techniques to measure the total force generated by bird wings ranging from muscle force, airflow, wing surface pressure, to detailed kinematics measurements coupled with bird mass-distribution models to derive net force through second derivatives. We have validated a new method that measures aerodynamic force in vivo time-resolved directly in freely flying birds which can resolve this question. The validation of the method, using independent force measurements on a quadcopter with pulsating thrust, show the aerodynamic force and impulse are measured within 2% accuracy and time-resolved. We demonstrate results for quad-copters and birds of similar weight and size. The method is scalable and can be applied to both engineered and natural flyers across taxa. The first author invented the method, the second and third authors validated the method and present results for quadcopters and birds.

  10. Aerodynamic Indicial Functions and Their Use in Aeroelastic Formulation of Lifting Surfaces

    NASA Technical Reports Server (NTRS)

    Marzocca, Piergiovanni; Librescu, Liviu; Silva, Walter A.

    2000-01-01

    An investigation related to the use of linear indicial functions in the time and frequency domains, enabling one to derive the proper aerodynamic loads as to study the subcritical response and flutter of swept lifting surfaces, respectively, of the open/closed loop aeroelastic system is presented. The expressions of the lift and aerodynamic moment in the frequency domain are given in terms of the Theodorsen's function, while, in the time domain, these are obtained directly with the help of the Wagner's function. Closed form solutions of aerodynamic derivatives are obtained, graphical representations are supplied and conclusions and prospects for further developments are outlined.

  11. Impulsively started incompressible turbulent jet

    SciTech Connect

    Witze, P O

    1980-10-01

    Hot-film anemometer measurements are presented for the centerline velocity of a suddenly started jet of air. The tip penetration of the jet is shown to be proportional to the square-root of time. A theoretical model is developed that assumes the transient jet can be characterized as a spherical vortex interacting with a steady-state jet. The model demonstrates that the ratio of nozzle radius to jet velocity defines a time constant that uniquely characterizes the behavior and similarity of impulsively started incompressible turbulent jets.

  12. Modeling of impulsive propellant reorientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.; Patag, Alfredo E.; Chato, David J.

    1988-01-01

    The impulsive propellant reorientation process is modeled using the (Energy Calculations for Liquid Propellants in a Space Environment (ECLIPSE) code. A brief description of the process and the computational model is presented. Code validation is documented via comparison to experimentally derived data for small scale tanks. Predictions of reorientation performance are presented for two tanks designed for use in flight experiments and for a proposed full scale OTV tank. A new dimensionless parameter is developed to correlate reorientation performance in geometrically similar tanks. Its success is demonstrated.

  13. The annoyance of impulsive helicopter noise

    NASA Technical Reports Server (NTRS)

    Karamcheti, K.

    1981-01-01

    A total of 96 impulsive and non-impulsive sounds were rated for annoyance by 10 subjects. The signals had the same amplitude spectrum with a maximum frequency of 4.75 kHz. By changing the phase of the spectral components different levels of impulsivity were obtained. The signals had coefficients of impulsivity of 10,8, 7,9, and -0.2 respectively. Further, signals had intensity levels 89 and 95 dBA, pulse repetition rates 10 and 20 Hz, and half the signals had pink noise added at a level 12 dBA lower than the level of the sound. The significant results were: The four females and six male subjects rated the impulsive sounds respectively 3.7 dB less annoying and 2.6 dB more annoying than the non-impulsive sounds. Overall, impulsivity had no effect. The hish pulse repetition rate increased annoyance by 2.2 dB. Addition of pink noise increased annoyance of the non-impulsive sounds 1.2 dB, but decreased the annoyance of the impulsive sounds 0.5 dB.

  14. Impulsiveness without discounting: the ecological rationality hypothesis.

    PubMed Central

    Stephens, David W.; Kerr, Benjamin; Fernández-Juricic, Esteban

    2004-01-01

    Observed animal impulsiveness challenges ideas from foraging theory about the fitness value of food rewards, and may play a role in important behavioural phenomena such as cooperation and addiction. Behavioural ecologists usually invoke temporal discounting to explain the evolution of animal impulsiveness. According to the discounting hypothesis, delay reduces the fitness value of the delayed food. We develop an alternative model for the evolution of impulsiveness that does not require discounting. We show that impulsive or short-sighted rules can maximize long-term rates of food intake. The advantages of impulsive rules come from two sources. First, naturally occurring choices have a foreground-background structure that reduces the long-term cost of impulsiveness. Second, impulsive rules have a discrimination advantage because they tend to compare smaller quantities. Discounting contributes little to this result. Although we find that impulsive rules are optimal in a simple foreground-background choice situation in the absence of discounting, in contrast we do not find comparable impulsiveness in binary choice situations even when there is strong discounting. PMID:15590596

  15. Aerodynamic and Aerothermal TPS Instrumentation Reference Guide

    NASA Technical Reports Server (NTRS)

    Woollard, Bryce A.; Braun, Robert D.; Bose, Deepack

    2016-01-01

    The hypersonic regime of planetary entry combines the most severe environments that an entry vehicle will encounter with the greatest amount of uncertainty as to the events unfolding during that time period. This combination generally leads to conservatism in the design of an entry vehicle, specifically that of the thermal protection system (TPS). Each planetary entry provides a valuable aerodynamic and aerothermal testing opportunity; the utilization of this opportunity is paramount in better understanding how a specific entry vehicle responds to the demands of the hypersonic entry environment. Previous efforts have been made to instrument entry vehicles in order to collect data during the entry period and reconstruct the corresponding vehicle response. The purpose of this paper is to cumulatively document past TPS instrumentation designs for applicable planetary missions, as well as to list pertinent results and any explainable shortcomings.

  16. Nacelle aerodynamic performance

    NASA Technical Reports Server (NTRS)

    Obara, Clifford J.; Dodbele, S. S.

    1987-01-01

    The boundary layer transition location was measured on a nacelle shape using the sublimating chemical flow visualization technique. This technique involves coating the surface with a thin film of volatile chemical solid, which, during exposure to a free stream airflow, rapidly sublimates in the turbulent boundary layer as a result of high shear stress and high mass transfer near the surface. Transition is indicated because the chemical coating remains relatively unaffected in the laminar region due to lower shear and low mass transfer. The slow response time of the chemical in a laminar boundary allowed for two test conditions during the same flight. The aircraft was first flown at the desired airspeed and altitude with the noise source off. Once a pattern had developed, the noise source was turned on to the desired setting and a new chemical pattern was sought. In this fashion a direct comparison of the effect of the noise could be determined.

  17. Passive flow control by membrane wings for aerodynamic benefit

    NASA Astrophysics Data System (ADS)

    Timpe, Amory; Zhang, Zheng; Hubner, James; Ukeiley, Lawrence

    2013-03-01

    The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.

  18. Booster aerodynamic heating: Test support

    NASA Technical Reports Server (NTRS)

    Engel, C. D.; Reardon, J. E.; Fuller, C. E.

    1974-01-01

    Several technical areas were encompassed in providing support for booster thermal environment test work. These areas included: (1) cavity flow heating, (2) rarefied flow heating, and (3) impulse operated model research and testing. Cavity flow heating problems were studied with respect to the proposed altitude control motors for the space shuttle. Available literature on this subject was reviewed and analytical predictive methods were summarized for use in planning testing work. Rarefied flow heating data was reviewed and correlated. The study showed the importance of considering rarefied flow conditions in launch thermal environment prediction. Impulse operated model research and testing was conducted to provide a basis for understanding and designing such models for booster thermal environment testing.

  19. Impulsivity moderates the association between racial discrimination and alcohol problems.

    PubMed

    Latzman, Robert D; Chan, Wing Yi; Shishido, Yuri

    2013-12-01

    Alcohol use among university students is a serious public health concern, particularly among minority students who may use alcohol to cope with experiences of racial discrimination. Although the impact of racial discrimination on alcohol use has been well-established, individual differences in factors that may act to either attenuate or exacerbate the negative effects of racial discrimination are largely unknown. One potentially fruitful individual differences trait that has repeatedly been found to predict alcohol problems is the multidimensional personality trait of impulsivity. Nonetheless, the ways in which various aspects of impulsivity interact with racial discrimination is yet unknown. The current study, therefore, examined the joint and interactive contribution of racial discrimination and impulsivity in the prediction of alcohol consumption among racial minority university students. Participants included 336 Black/African-American and Asian/Asian-American university students. Results revealed both racial discrimination and impulsivity to be significantly associated with alcohol problems. Further, individuals' responses to racial discrimination were not uniform. Specifically, the association between racial discrimination and alcohol problems was moderated by lack of Premeditation; racial discrimination was most strongly predictive of alcohol problems for those who reported low level of premeditation. Findings from the present study highlight the importance of investigating risk factors for alcohol problems across multiple levels of the ecology as individual personality traits appear to relate to how one might respond to the experience of racial discrimination.

  20. Brain structure correlates of emotion-based rash impulsivity

    PubMed Central

    Muhlert, N.; Lawrence, A.D.

    2015-01-01

    Negative urgency (the tendency to engage in rash, ill-considered action in response to intense negative emotions), is a personality trait that has been linked to problematic involvement in several risky and impulsive behaviours, and to various forms of disinhibitory psychopathology, but its neurobiological correlates are poorly understood. Here, we explored whether inter-individual variation in levels of trait negative urgency was associated with inter-individual variation in regional grey matter volumes. Using voxel-based morphometry (VBM) in a sample (n = 152) of healthy participants, we found that smaller volumes of the dorsomedial prefrontal cortex and right temporal pole, regions previously linked to emotion appraisal, emotion regulation and emotion-based decision-making, were associated with higher levels of trait negative urgency. When controlling for other impulsivity linked personality traits (sensation seeking, lack of planning/perseverance) and negative emotionality per se (neuroticism), these associations remained, and an additional relationship was found between higher levels of trait negative urgency and smaller volumes of the left ventral striatum. This latter finding mirrors recent VBM findings in an animal model of impulsivity. Our findings offer novel insight into the brain structure correlates of one key source of inter-individual differences in impulsivity. PMID:25957991

  1. Effects of mood state on impulsivity in pathological buying.

    PubMed

    Nicolai, Jennifer; Darancó, Stefaniá; Moshagen, Morten

    2016-10-30

    Pathological buying is characterized by irrepressible buying behaviour and its negative consequences. A possible mechanism contributing to its development and maintenance is that buying episodes act as a maladaptive strategy to cope with negative emotions. Accordingly, pathological buying has been repeatedly associated with impulsivity, in particular with the tendency to experience strong reactions under negative affect. Relying on an experimental mood induction procedure, the present study tested in a sample of 100 individuals (a) whether individuals with pathological buying symptoms respond more impulsively in the Go/No-Go Task (as a measure of the behavioural inhibition aspect of impulsivity) and (b) whether this association is more pronounced in a negative mood. While controlling for comorbidities, the results show that pathological buying is associated with faster responses and a larger number of commission errors. Moreover, a significant interaction indicated that the association between pathological buying and performance the Go/No-Go Task was stronger in the negative mood condition. The present study thus shows that pathological buying is associated with deficits in the behavioural inhibition component of impulsivity. These deficits are most pronounced when mood is negative; in turn, this provides an explanation for the occurrence of excessive buying episodes following negative affect.

  2. The video head impulse test during post-rotatory nystagmus: physiology and clinical implications.

    PubMed

    Mantokoudis, Georgios; Tehrani, Ali S Saber; Xie, Li; Eibenberger, Karin; Eibenberger, Bernhard; Roberts, Dale; Newman-Toker, David E; Zee, David S

    2016-01-01

    The aim of this study was to test the effects of a sustained nystagmus on the head impulse response of the vestibulo-ocular reflex (VOR) in healthy subjects. VOR gain (slow-phase eye velocity/head velocity) was measured using video head impulse test goggles. Acting as a surrogate for a spontaneous nystagmus (SN), a post-rotatory nystagmus (PRN) was elicited after a sustained, constant-velocity rotation, and then head impulses were applied. 'Raw' VOR gain, uncorrected for PRN, in healthy subjects in response to head impulses with peak velocities in the range of 150°/s-250°/s was significantly increased (as reflected in an increase in the slope of the gain versus head velocity relationship) after inducing PRN with slow phases of nystagmus of high intensity (>30°/s) in the same but not in the opposite direction as the slow-phase response induced by the head impulses. The values of VOR gain themselves, however, remained in the normal range with slow-phase velocities of PRN < 30°/s. Finally, quick phases of PRN were suppressed during the first 20-160 ms of a head impulse; the time frame of suppression depended on the direction of PRN but not on the duration of the head impulse. Our results in normal subjects suggest that VOR gains measured using head impulses may have to be corrected for any superimposed SN when the slow-phase velocity of nystagmus is relatively high and the peak velocity of the head movements is relatively low. The suppression of quick phases during head impulses may help to improve steady fixation during rapid head movements.

  3. A multifactorial and integrative approach to impulsivity in neuropsychology: insights from the UPPS model of impulsivity.

    PubMed

    Rochat, Lucien; Billieux, Joël; Gagnon, Jean; Van der Linden, Martial

    2017-04-11

    Risky and excessive behaviors, such as aggressive and compulsive behaviors, are frequently described in patients with brain damage and have dramatic psychosocial consequences. Although there is strong evidence that impulsivity constitutes a key factor at play in these behaviors, the literature about impulsivity in neuropsychology is to date scarce. In addition, examining and understanding these problematic behaviors requires the assumption that impulsivity is a multidimensional construct. Consequently, this article aims at shedding light on frequent risky and excessive behaviors in patients with brain damage by focusing on a unified, comprehensive, and well-validated model, namely, the UPPS model of impulsivity. This model considers impulsivity as a multidimensional construct that includes four facets: urgency, (lack of) premeditation, (lack of) perseverance, and sensation seeking. Furthermore, we discuss the psychological mechanisms underlying the dimensions of impulsivity, as well as the laboratory tasks designed to assess each mechanism and their neural bases. We then present a scale specifically designed to assess these four dimensions of impulsivity in patients with brain damage and examine the data regarding this multidimensional approach to impulsivity in neuropsychology. This review supports the need to adopt a multifactorial and integrative approach toward impulsive behaviors, and the model presented provides a valuable rationale to disentangle the nature of brain systems and mechanisms underlying impulsive behaviors in patients with brain damage. It may also foster further relevant research in the field of impulsivity and improve assessment and rehabilitation of impulsive behaviors in clinical settings.

  4. Impulsivity and the Sexes: Measurement and Structural Invariance of the UPPS-P Impulsive Behavior Scale

    ERIC Educational Resources Information Center

    Cyders, Melissa A.

    2013-01-01

    Before it is possible to test whether men and women differ in impulsivity, it is necessary to evaluate whether impulsivity measures are invariant across sex. The UPPS-P Impulsive Behavior Scale (negative urgency, lack of premeditation, lack of perseverance, and sensation seeking, with added subscale of positive urgency) is one measure of five…

  5. Fast-Running Aeroelastic Code Based on Unsteady Linearized Aerodynamic Solver Developed

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Bakhle, Milind A.; Keith, T., Jr.

    2003-01-01

    The NASA Glenn Research Center has been developing aeroelastic analyses for turbomachines for use by NASA and industry. An aeroelastic analysis consists of a structural dynamic model, an unsteady aerodynamic model, and a procedure to couple the two models. The structural models are well developed. Hence, most of the development for the aeroelastic analysis of turbomachines has involved adapting and using unsteady aerodynamic models. Two methods are used in developing unsteady aerodynamic analysis procedures for the flutter and forced response of turbomachines: (1) the time domain method and (2) the frequency domain method. Codes based on time domain methods require considerable computational time and, hence, cannot be used during the design process. Frequency domain methods eliminate the time dependence by assuming harmonic motion and, hence, require less computational time. Early frequency domain analyses methods neglected the important physics of steady loading on the analyses for simplicity. A fast-running unsteady aerodynamic code, LINFLUX, which includes steady loading and is based on the frequency domain method, has been modified for flutter and response calculations. LINFLUX, solves unsteady linearized Euler equations for calculating the unsteady aerodynamic forces on the blades, starting from a steady nonlinear aerodynamic solution. First, we obtained a steady aerodynamic solution for a given flow condition using the nonlinear unsteady aerodynamic code TURBO. A blade vibration analysis was done to determine the frequencies and mode shapes of the vibrating blades, and an interface code was used to convert the steady aerodynamic solution to a form required by LINFLUX. A preprocessor was used to interpolate the mode shapes from the structural dynamic mesh onto the computational dynamics mesh. Then, we used LINFLUX to calculate the unsteady aerodynamic forces for a given mode, frequency, and phase angle. A postprocessor read these unsteady pressures and

  6. Impulsive model for reactive collisions

    NASA Technical Reports Server (NTRS)

    Marron, M. T.; Bernstein, R. B.

    1972-01-01

    A simple classical mechanical model of the reactive scattering of a structureless atom A and a quasi-diatomic BC is developed which takes full advantage of energy, linear and angular momentum conservation relations but introduces a minimum of further assumptions. These are as follows: (1) the vibrational degree of freedom of the reactant (BC) and product (AB) molecules is suppressed, so the change in vibrational energy is simply a parameter; (2) straight-line trajectories are assumed outside of a reaction shell; (3) within this zone, momentum transfer occurs impulsively (essentially instantaneously) following mass transfer; (4) the impulse, which may be either positive or negative, is directed along the BC axis, which may, however, assume all orientations with respect to the incident relative velocity. The model yields differential and total cross sections and product rotational energy distributions for a given collision exoergicity Q, or for any known distribution over Q. Numerical results are presented for several prototype reactions whose dynamics have been well-studied.

  7. HIAD-2 (Hypersonic Inflatable Aerodynamic Decelerator)

    NASA Video Gallery

    The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project is a disruptive technology that will accommodate the atmospheric entry of heavy payloads to planetary bodies such as Mars. HIAD over...

  8. Aerodynamic lift effect on satellite orbits

    NASA Technical Reports Server (NTRS)

    Karr, G. R.; Cleland, J. G.; Devries, L. L.

    1975-01-01

    Numerical quadrature is employed to obtain orbit perturbation results from the general perturbation equations. Both aerodynamic lift and drag forces are included in the analysis of the satellite orbit. An exponential atmosphere with and without atmospheric rotation is used. A comparison is made of the perturbations which are caused by atmospheric rotation with those caused by satellite aerodynamic effects. Results indicate that aerodynamic lift effects on the semi-major axis and orbit inclination can be of the same order as the effects of atmosphere rotation depending upon the orientation of the lift vector. The results reveal the importance of including aerodynamic lift effects in orbit perturbation analysis.

  9. Impulse gage development for the 100-200 ktap range

    SciTech Connect

    Rose, P.C.; Naumann, W.J. . Advanced Technologies Div.)

    1990-07-31

    Special effects underground test (UGT) material response and source diagnostics data require impulse gages that can be used in the 50--150 ktap range and have equilibrated from electrical and mechanical noise sources within 0.001 s. Such gages were designed, analyzed, and tested under this program. One- and two-dimensional stress propagation calculations were performed and predictions were developed for deformation of the gage specimen cup. These predictions were conservative when compared to gas gun test results. The response of the gage will equilibrate within 5% to its final value within 300 {mu}sec. The impulse delivered to the gages for these tests exceeded 250 ktap. The code and experimental results provides a basis for confidence in the operability of the gage in an actual UGT environment.

  10. Reliability and Validity of Measures of Impulsive Choice and Impulsive Action in Smokers Trying to Quit

    PubMed Central

    McCarthy, Danielle E.; Bold, Krysten W.; Minami, Haruka; Yeh, Vivian M.; Rutten, Emily; Nadkarni, Shruti G.; Chapman, Gretchen B.

    2016-01-01

    Cross-sectional research suggests that smokers are more impulsive than are non-smokers, but few studies have examined relations between impulsiveness and later success in quitting smoking. The purpose of this study was to investigate the reliability and predictive validity of facets of impulsiveness in adult smokers trying to quit. Baseline behavioral measures of impulsive choice (assessed with a delay discounting task) and impulsive action (assessed with a measure of behavioral disinhibition) were used as predictors of smoking cessation success over 12 weeks. The sample included 116 adult (18 years old or older) daily smokers from central New Jersey. Impulsive choice, impulsive action, and self-reported impulsiveness were not significantly related to one another at baseline. Impulsive choice had high test-retest reliability from pre- to post-quit, whereas impulsive action was less stable. Test-retest reliability from pre-quit to three weeks post-quit was moderated by achievement of seven-day abstinence. Baseline impulsive action was significantly negatively related to quitting for at least one day in the first two weeks of a quit attempt and of prolonged abstinence (no relapse over the next 10 weeks). Baseline impulsive choice was robustly associated with biochemically verified seven-day point-prevalence abstinence 12 weeks post-quit, such that those with lower delay discounting were more likely to achieve abstinence. Facets of impulsiveness appear to function largely independently in adult smokers, as indicated by their lack of inter-correlation, differential stability, and differential relations with abstinence. Impulsive action may impede initial quitting, whereas impulsive choice may be an obstacle to maintaining lasting abstinence. PMID:26751623

  11. Modal forced vibration analysis of aerodynamically excited turbosystems

    NASA Technical Reports Server (NTRS)

    Elchuri, V.

    1985-01-01

    Theoretical aspects of a new capability to determine the vibratory response of turbosystems subjected to aerodynamic excitation are presented. Turbosystems such as advanced turbopropellers with highly swept blades, and axial-flow compressors and turbines can be analyzed using this capability. The capability has been developed and implemented in the April 1984 release of the general purpose finite element program NASTRAN. The dynamic response problem is addressed in terms of the normal modal coordinates of these tuned rotating cyclic structures. Both rigid and flexible hubs/disks are considered. Coriolis and centripetal accelerations, as well as differential stiffness effects are included. Generally non-uniform steady inflow fields and uniform flow fields arbitrarily inclined at small angles with respect to the axis of rotation of the turbosystem are considered sources of aerodynamic excitation. The spatial non-uniformities are considered to be small deviations from a principally uniform inflow. Subsonic and supersonic relative inflows are addressed, with provision for linearly interpolating transonic airloads.

  12. Reflection-Impulsivity and Wholist-Analytic: Two Fledglings...or is R-I a cuckoo?

    ERIC Educational Resources Information Center

    Jones, Anne Elizabeth

    1997-01-01

    Considers the theoretical validity of two approaches to cognitive style. Wholist-Analytic maintains that cognitive processes depend on the interaction of two opposing forces, destructive and constructive. Reflection-Impulsivity characterizes learners according to their reflective or impulsive responses to solution hypotheses. Evaluates these…

  13. An experimental technique to study impulse-wave propagation in materials

    NASA Astrophysics Data System (ADS)

    Yazdani-Ardakani, S.; Kesavan, S. K.; Chu, M. L.

    1986-01-01

    The dynamic characteristics of materials are studied with a technique which uses a mechanical shaker to subject vertically mounted specimens to impulsive forces. The mounting of the specimens over the mechanical shaker with a suspension system is examined. The components of the coupling assembly are described. The electric circuitries for the adjustment of shaker-platform height and suspending-wire tension, and for the acceleration-response measurement of impacted specimens are diagramatically presented. The procedures for studying impulse-wave propagation in materials are discussed; accelerometer response is utilized to determine the velocity of the impulse-wave propagation in the test specimens. The design and function of the suspension and coupling system are evaluated. The data reveal that the technique is applicable for analyzing the impulse-wave propagation in cylindrical specimens, biomechanical measurements, and modal analysis.

  14. Impulsive events in the evolution of a forced nonlinear system

    SciTech Connect

    Longcope, D.W.; Sudan, R.N. )

    1992-03-16

    Long-time numerical solutions of a low-dimensional model of the reduced MHD equations show that, when this system is driven quasistatically, the response is punctuated by impulsive events. The statistics of these events indicate a Poisson process; the frequency of these events scales as {Delta}{ital E}{sub {ital M}}{sup {minus}1}, where {Delta}{ital E}{sub {ital M}} is the energy released in one event.

  15. Hyperkinetic Impulse Disorder in Children's Behavior Problems

    ERIC Educational Resources Information Center

    Laufer, Maurice W.; Denhoff, Eric; Solomons, Gerald

    2011-01-01

    A very common cause of children's behavior disorder disturbance is an entity described as the hyperkinetic impulse disorder. This is characterized by hyperactivity, short attention span and poor powers of concentration, irritability, impulsiveness, variability, and poor schoolwork. The existence of this complexity may lead to many psychological…

  16. Assessing impulsivity changes in Alzheimer disease.

    PubMed

    Rochat, Lucien; Delbeuck, Xavier; Billieux, Joël; d'Acremont, Mathieu; Van der Linden, Anne-Claude Juillerat; Van der Linden, Martial

    2008-01-01

    Impulsive behaviors are common in brain-damaged patients including those with neurodegenerative diseases such as Alzheimer disease (AD). The objective of this study was to develop and validate a short version of the UPPS Impulsive Behavior Scale assessing changes on 4 different dimensions of impulsivity, namely urgency, (lack of) premeditation, (lack of) perseverance, and sensation seeking, arising in the course of a neurodegenerative disease. To this end, caregivers of 83 probable AD patients completed a short questionnaire adapted from the UPPS Impulsive Behavior Scale. Exploratory and confirmatory factor analyses of the data were performed and revealed that a model with 4 distinct but related latent variables corresponding to 4 different dimensions of impulsivity fit the data best. Furthermore, the results showed that lack of perseverance, followed by lack of premeditation and urgency, increased after the onset of the disease, whereas sensation seeking decreased. Overall, the multifaceted nature of impulsivity was confirmed in a sample of AD patients, whose caregivers reported significant changes regarding each facet of impulsivity. Consequently, the short version of the UPPS Impulsive Behavior Scale opens up interesting prospects for a better comprehension of behavioral symptoms of dementia.

  17. Impulsive Vaccination for an Epidemiology Model

    NASA Astrophysics Data System (ADS)

    De la Sen, M.; Garrido, A. J.

    2017-03-01

    This paper investigates sufficient conditions of almost periodic sand periodic solutions of an integral model under impulsive controls. Since the model is of generic epidemiological interest, such impulsive controls are either vaccination actions or abrupt variations of the infected population due to infected immigration or lost of infective numbers due to either vaccination or lost of infected population by out-migration.

  18. Impulsivity, School Context, and School Misconduct

    ERIC Educational Resources Information Center

    Vogel, Matt; Barton, Michael S.

    2013-01-01

    Impulsivity holds a central place in the explanations of adolescent delinquency. Recent research suggests that neighborhood characteristics, particularly SES (socioeconomic status), perceived supervision, and collective efficacy, moderate the association between impulsivity and delinquency. However, findings to date have been equivocal, and the…

  19. Solar Impulse's Solar-Powered Plane

    ScienceCinema

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2016-07-12

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  20. Solar Impulse's Solar-Powered Plane

    SciTech Connect

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2013-07-08

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  1. Influence of satellite aerodynamics on atmospheric density determination.

    NASA Technical Reports Server (NTRS)

    Karr, G. R.; Smith, R. E.

    1972-01-01

    Discussion of aerodynamic factors which influence the interpretation of satellite dynamic response. These factors include: (1) the influence of satellite orientation and shape on the drag coefficient; (2) the effect of changes in the gas flow properties with altitude; and (3) the influence of upper atmospheric winds on the interpretation of data. These factors represent the greatest source of error in current data reduction. For this reason, an estimate is made of a possible correction to present density models.

  2. Multidimensionality in Impulsivity and Alcohol Use: A Meta-Analysis using the UPPS Model of Impulsivity

    PubMed Central

    Coskunpinar, Ayca; Dir, Allyson L.; Cyders, Melissa A.

    2013-01-01

    Background Although there is considerable support for the relationship between impulsivity and alcohol use, the use of multidimensional conceptualizations of impulsivity and alcohol use has lead to varying relationship sizes across studies. The aims of the current meta-analysis are to (1) examine variability in the magnitude of the bivariate relationship between impulsivity and alcohol use across studies, and (2) describe the pattern of effects between specific impulsivity traits and alcohol use variables, using the UPPS Model of Impulsivity. Methods Ninety-six studies were meta-analyzed using a random effects model to examine the relationship between general impulsivity and alcohol use, as well as the relationships among separate impulsivity traits based in the UPPS model of impulsivity and specific alcohol use outcomes. Results Results indicate that, in general, impulsivity and alcohol use are related (r = .28); however, this effect size varied significantly across studies (from −.05 to 1.02). Drinking quantity was most strongly predicted by lack of perseverance (r = .32), whereas all traits equally predicted drinking frequency. Drinking problems were most highly related to negative (r = .35) and positive (r = .34) urgency, and alcohol dependence was most highly related to negative urgency (r = .38) and lack of planning (r = .37). Conclusion Effect sizes between impulsivity and alcohol use vary significantly by UPPS trait used in each study; thus, findings suggest and further reinforce the view in the literature that specific impulsivity-related constructs differentially relate to specific alcohol use outcomes. PMID:23578176

  3. Aerodynamic performance of centrifugal compressors

    SciTech Connect

    Sayyed, S.

    1981-12-01

    Saving money with an efficient pipeline system design depends on accurately predicting compressor performance and ensuring that it meets the manufacturer's guaranteed levels. When shop testing with the actual gas is impractical, an aerodynamic test can ascertain compressor efficiency, but the accuracy and consistency of data acquisition in such tests is critical. Low test-pressure levels necessitate accounting for the effects of Reynolds number and heat transfer. Moreover, the compressor user and manufacturer must agree on the magnitude of the corrections to be applied to the test data.

  4. Multi-Disciplinary Computational Aerodynamics

    DTIC Science & Technology

    2016-01-01

    However, as the DSV is shed and propagates along the wing it induces sudden and difficult to predict variations in aerodynamic forces and pitching ...circulation build- up around the airfoil. The pitching moment is also shifted to a lower value due to rotation- induced camber effects. Beyond a critical...on vortex breakdown,” AIAA J., Vol. 12, No. 5, 1974, pp. 602–607. 66Visbal, M. R., “Onset of vortex breakdown about a pitching delta wing ,” AIAA J

  5. Simulation of iced wing aerodynamics

    NASA Technical Reports Server (NTRS)

    Potapczuk, M. G.; Bragg, M. B.; Kwon, O. J.; Sankar, L. N.

    1991-01-01

    The sectional and total aerodynamic load characteristics of moderate aspect ratio wings with and without simulated glaze leading edge ice were studied both computationally, using a three dimensional, compressible Navier-Stokes solver, and experimentally. The wing has an untwisted, untapered planform shape with NACA 0012 airfoil section. The wing has an unswept and swept configuration with aspect ratios of 4.06 and 5.0. Comparisons of computed surface pressures and sectional loads with experimental data for identical configurations are given. The abrupt decrease in stall angle of attack for the wing, as a result of the leading edge ice formation, was demonstrated numerically and experimentally.

  6. Impulse position control algorithms for nonlinear systems

    NASA Astrophysics Data System (ADS)

    Sesekin, A. N.; Nepp, A. N.

    2015-11-01

    The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of such regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.

  7. Impulse position control algorithms for nonlinear systems

    SciTech Connect

    Sesekin, A. N.; Nepp, A. N.

    2015-11-30

    The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of such regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.

  8. Modified impulsive synchronization of hyperchaotic systems

    NASA Astrophysics Data System (ADS)

    Haeri, Mohammad; Dehghani, Mahsa

    2010-03-01

    In an original impulsive synchronization only instantaneous errors are used to determine the impulsive inputs. To improve the synchronization performance, addition of an integral term of the errors is proposed here. In comparison with the original form, the proposed modification increases the impulse distances which leads to reduction in the control cost as the most important characteristic of the impulsive synchronization technique. It can also decrease the error magnitude in the presence of noise. Sufficient conditions are presented through four theorems for different situations (nominal, uncertain, noisy, and noisy uncertain cases) under which stability of the error dynamics is guaranteed. Results from computer based simulations are provided to illustrate feasibility and effectiveness of the modified impulsive synchronization method applied on Rossler hyperchaotic systems.

  9. Helicopter impulsive noise: Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1983-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  10. The horizontal computerized rotational impulse test.

    PubMed

    Furman, Joseph M; Shirey, Ian; Roxberg, Jillyn; Kiderman, Alexander

    2016-01-01

    Whole-body impulsive rotations were used to overcome several limitations associated with manual head impulse testing. A computer-controlled rotational chair delivered brief, whole-body, earth-vertical axis yaw impulsive rotations while eye movements were measured using video-oculography. Results from an unselected group of 20 patients with dizziness and a group of 22 control subjects indicated that the horizontal computerized rotational head impulse test (crHIT) is well-tolerated and provides an estimate of unidirectional vestibulo-ocular reflex gain comparable to results from caloric testing. This study demonstrates that the horizontal crHIT is a new assessment tool that overcomes many of the limitations of manual head impulse testing and provides a reliable laboratory-based measure of unilateral horizontal semicircular canal function.

  11. Successful restrained eating and trait impulsiveness.

    PubMed

    van Koningsbruggen, Guido M; Stroebe, Wolfgang; Aarts, Henk

    2013-01-01

    Restrained eaters with high scores on the Perceived Self-Regulatory Success in Dieting Scale (PSRS) are more successful than low scorers in regulating their food intake. According to the theory of temptation-elicited goal activation (Fishbach, Friedman, & Kruglanski, 2003), they have become successful because, due to earlier repeated instances of successful self-control, they formed an associative link between temptations and thoughts of dieting. It is unclear, however, why they should have been more successful in earlier attempts at self-control than their unsuccessful counterparts. We examined whether trait impulsiveness plays a role by investigating the associations between dietary restraint, trait impulsiveness, and PSRS. Results showed that the interaction between dietary restraint and impulsiveness predicted dieting success: A lower level of impulsiveness was associated with greater dieting success among restrained eaters. These results suggest that restrained eaters who are less impulsive are more likely to become successful restrained eaters as identified with the PSRS.

  12. Conversion of Impulse Voltage Generator Into Steep Wave Impulse Test-Equipment

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed Zaid; Tanwar, Surender Singh; Dayama, Ravindra; Choudhary, Rahul Raj; Mangal, Ravindra

    This paper demonstrates the alternative measures to generate the Steep wave impulse by using Impulse Voltage Generator (IVG) for high voltage testing of porcelain insulators. The modification of IVG by incorporating compensation of resistor, inductor, and capacitor has been achieved and further performance of the modified system has been analyzed by applying the generated lightning impulse and analyzing the electrical characteristics of impulse waves under standard lightning and fast rise multiple lightning waveform to determine the effect to improve rise time. The advantageous results have been received and being reported such as increase in overshoot compensation, increase in capacitive and inductive load ranges. Such further reduces the duration of oscillations of standard impulse voltages. The reduction in oscillation duration of steep front impulse voltages may be utilized in up gradation of Impulse Voltage Generator System. Stray capacitance could further be added in order to get the minimized difference of measurement between simulation and the field establishment.

  13. A method for characterizing aerodynamic sound sources in turbomachines

    NASA Astrophysics Data System (ADS)

    Mongeau, L.; Thompson, D. E.; Mclaughlin, D. K.

    1995-03-01

    A method based on Weidemann's acoustic similarity laws [1] was used to investigate the aerodynamic sound generated by a partially ducted centrifugal pump rotor. The primary objective of the method was to determine the spectral characteristics of the sound source by isolating the effects of acoustic phenomena such as duct resonances or sound reflections. Pump-radiated sound pressure spectra were measured for different impeller rotational speeds, keeping the operating condition constant. The spectra, assumed to be expressed as the product of a source spectral distribution function and an acoustic frequency response function, were then decomposed into a product form following a computer-implemented algorithm. The method was successful in accurately determining the spectral distribution of the broadband aerodynamic noise generating mechanisms involved and that of the acoustic frequency response of the system. The absolute levels of the source function and the acoustic function were established by assuming that, over a limited low frequency range, the average gain of the frequency response function is unity so that comparisons between different pump operating conditions could be made. The source spectral distribution was found to be independent of the microphone location and the acoustic loading. When applicable, this method therefore allows the characterization of aerodynamic sound sources by measuring ordinary sound pressure spectra, at any one point around the source, without having to isolate the source from the system. The source characterization method was instrumental in the study of sound generation by rotating stall presented in a previous publication [2].

  14. Identification of an unsteady aerodynamic model up to high angle of attack regime

    NASA Astrophysics Data System (ADS)

    Fan, Yigang

    1997-12-01

    The harmonic oscillatory tests for a fighter aircraft configuration using the Dynamic Plunge-Pitch-Roll (DyPPiR) model mount at Virginia Tech Stability Wind Tunnel are described and analyzed. The corresponding data reduction methods are developed on the basis of multirate digital signal processing techniques. Since the model is sting-mounted to the support system of DyPPiR, the Discrete Fourier Transform (DFT) is first used to identify the frequencies of the elastic modes of sting. Then the sampling rate conversion systems are built up in digital domain to resample the data at a lower rate without introducing distortions to the signals of interest. Finally linear-phase Finite Impulse Response (FIR) filters are designed by Remez exchange algorithm to extract the aerodynamic characteristics responses to the programmed motions from the resampled measurements. These data reduction procedures are also illustrated through examples. The results obtained from the harmonic oscillatory tests are then illustrated and the associated flow mechanisms are discussed. Since no significant hysteresis loops are observed for the lift and the drag coefficients for the current angle of attack range and the tested reduced frequencies, the dynamic lags of separated and vortex flow effects are small in the current oscillatory tests. However, large hysteresis loops are observed for pitch moment coefficient in the current tests. This observation suggests that at current flow conditions, pitch moment has large pitch rate dotalpha dependencies. Then the nondimensional maximum pitch rate \\ qsb{max} is introduced to characterize these harmonic oscillatory motions. It is found that at current flow conditions, all the hysteresis loops of pitch moment coefficient with same \\ qsb{max} are tangential to one another at both top and bottom of the loops, implying approximately same maximum offset of these loops from static values. Several cases are also illustrated. Based on the results obtained and

  15. Tourette-like behaviors in the normal population are associated with hyperactive/impulsive ADHD-like behaviors but do not relate to deficits in conditioned inhibition or response inhibition

    PubMed Central

    Heym, Nadja; Kantini, Ebrahim; Checkley, Hannah L. R.; Cassaday, Helen J.

    2014-01-01

    Attention-Deficit Hyperactivity Disorder (ADHD) and Tourette Syndrome (TS) present as distinct conditions clinically; however, comorbidity and inhibitory control deficits have been proposed for both. Whilst such deficits have been studied widely within clinical populations, findings are mixed—partly due to comorbidity and/or medication effects—and studies have rarely distinguished between subtypes of the disorders. Studies in the general population are sparse. Using a continuity approach, the present study examined (i) the relationships between inattentive and hyperactive/impulsive aspects of ADHD and TS-like behaviors in the general population, and (ii) their unique associations with automatic and executive inhibitory control, as well as (iii) yawning (a proposed behavioral model of TS). One hundred and thirty-eight participants completed self-report measures for ADHD and TS-like behaviors as well as yawning, and a conditioned inhibition task to assess automatic inhibition. A sub-sample of fifty-four participants completed three executive inhibition tasks. An exploratory factor analysis of the TS behavior checklist supported a distinction between phonic and motor like pure TS behaviors. Whilst hyperactive/impulsive aspects of ADHD were associated with increased pure and compulsive TS-like behaviors, inattention in isolation was related to reduced obsessive-compulsive TS-like behaviors. TS-like behaviors were associated with yawning during situations of inactivity, and specifically motor TS was related to yawning during stress. Phonic TS and inattention aspects of ADHD were associated with yawning during concentration/activity. Whilst executive interference control deficits were linked to hyperactive/impulsive ADHD-like behaviors, this was not the case for inattentive ADHD or TS-like behaviors, which instead related to increased performance on some measures. No associations were observed for automatic conditioned inhibition. PMID:25228890

  16. The aerodynamics of small Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Schmitz, F. W.

    1980-01-01

    Aerodynamic characteristics of wing model gliders and bird wings in particular are discussed. Wind tunnel measurements and aerodynamics of small Reynolds numbers are enumerated. Airfoil behavior in the critical transition from laminar to turbulent boundary layer, which is more important to bird wing models than to large airplanes, was observed. Experimental results are provided, and an artificial bird wing is described.

  17. A new technique for aerodynamic noise calculation

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.; Pope, D. S.

    1992-01-01

    A novel method for the numerical analysis of aerodynamic noise generation is presented. The method involves first solving for the time-dependent incompressible flow for the given geometry. This fully nonlinear method that is tailored to extract the relevant acoustic fluctuations seems to be an efficient approach to the numerical analysis of aerodynamic noise generation.

  18. Future Computer Requirements for Computational Aerodynamics

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Recent advances in computational aerodynamics are discussed as well as motivations for and potential benefits of a National Aerodynamic Simulation Facility having the capability to solve fluid dynamic equations at speeds two to three orders of magnitude faster than presently possible with general computers. Two contracted efforts to define processor architectures for such a facility are summarized.

  19. Aerodynamics of Sounding-Rocket Geometries

    NASA Technical Reports Server (NTRS)

    Barrowman, J.

    1982-01-01

    Theoretical aerodynamics program TAD predicts aerodynamic characteristics of vehicles with sounding-rocket configurations. These slender, Axisymmetric finned vehicles have a wide range of aeronautical applications from rockets to high-speed armament. TAD calculates characteristics of separate portions of vehicle, calculates interference between portions, and combines results to form total vehicle solution.

  20. Aerodynamic seal assemblies for turbo-machinery

    DOEpatents

    Bidkar, Rahul Anil; Wolfe, Christopher; Fang, Biao

    2015-09-29

    The present application provides an aerodynamic seal assembly for use with a turbo-machine. The aerodynamic seal assembly may include a number of springs, a shoe connected to the springs, and a secondary seal positioned about the springs and the shoe.

  1. Behavioral assessment of impulsivity in pathological gamblers with and without substance use disorder histories versus healthy controls.

    PubMed

    Ledgerwood, David M; Alessi, Sheila M; Phoenix, Natalie; Petry, Nancy M

    2009-11-01

    Pathological gamblers (PGs) may have high levels of impulsivity, and a correlation between substance use disorders (SUDs) and impulsivity is well established. However, only a handful of studies have attempted to assess impulsivity and other impulse-spectrum traits (e.g., sensation seeking) using a variety of behavioral and self-report measures in PGs and few examined the independent impact of SUDs. We compared 30 PGs without SUD histories, 31 PGs with SUD histories and 40 control participants on self-reported impulsivity, delayed discounting, attention/memory, response inhibition, risk taking, sensation seeking and distress tolerance measures. PGs, regardless of SUD history, discounted delayed rewards at greater rates than controls. PGs also reported acting on the spur of the moment, experienced trouble planning and thinking carefully, and noted greater attention difficulties than controls. PGs with SUD took greater risks on a risk-taking task than did PGs without SUD histories, but the two groups did not differ on any other measures of impulsivity. We conclude that PGs are more impulsive than non-problem gamblers in fairly specific ways, but PGs with and without SUD histories differ on few measures. More research should focus on specific ways in which PGs exhibit impulsivity to better address impulsive behaviors in treatment.

  2. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will design, build, and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604BOO02G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate the aerodynamic flight database for the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. Al these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  3. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database i n the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  4. Orion Crew Module Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Bibb, Karen L.; Brauckmann, Gregory J.; Rhode, Matthew N.; Owens, Bruce; Chan, David T.; Walker, Eric L.; Bell, James H.; Wilson, Thomas M.

    2011-01-01

    The Apollo-derived Orion Crew Exploration Vehicle (CEV), part of NASA s now-cancelled Constellation Program, has become the reference design for the new Multi-Purpose Crew Vehicle (MPCV). The MPCV will serve as the exploration vehicle for all near-term human space missions. A strategic wind-tunnel test program has been executed at numerous facilities throughout the country to support several phases of aerodynamic database development for the Orion spacecraft. This paper presents a summary of the experimental static aerodynamic data collected to-date for the Orion Crew Module (CM) capsule. The test program described herein involved personnel and resources from NASA Langley Research Center, NASA Ames Research Center, NASA Johnson Space Flight Center, Arnold Engineering and Development Center, Lockheed Martin Space Sciences, and Orbital Sciences. Data has been compiled from eight different wind tunnel tests in the CEV Aerosciences Program. Comparisons are made as appropriate to highlight effects of angle of attack, Mach number, Reynolds number, and model support system effects.

  5. Aerodynamics of the hovering hummingbird.

    PubMed

    Warrick, Douglas R; Tobalske, Bret W; Powers, Donald R

    2005-06-23

    Despite profound musculoskeletal differences, hummingbirds (Trochilidae) are widely thought to employ aerodynamic mechanisms similar to those used by insects. The kinematic symmetry of the hummingbird upstroke and downstroke has led to the assumption that these halves of the wingbeat cycle contribute equally to weight support during hovering, as exhibited by insects of similar size. This assumption has been applied, either explicitly or implicitly, in widely used aerodynamic models and in a variety of empirical tests. Here we provide measurements of the wake of hovering rufous hummingbirds (Selasphorus rufus) obtained with digital particle image velocimetry that show force asymmetry: hummingbirds produce 75% of their weight support during the downstroke and only 25% during the upstroke. Some of this asymmetry is probably due to inversion of their cambered wings during upstroke. The wake of hummingbird wings also reveals evidence of leading-edge vortices created during the downstroke, indicating that they may operate at Reynolds numbers sufficiently low to exploit a key mechanism typical of insect hovering. Hummingbird hovering approaches that of insects, yet remains distinct because of effects resulting from an inherently dissimilar-avian-body plan.

  6. Perching aerodynamics and trajectory optimization

    NASA Astrophysics Data System (ADS)

    Wickenheiser, Adam; Garcia, Ephrahim

    2007-04-01

    Advances in smart materials, actuators, and control architecture have enabled new flight capabilities for aircraft. Perching is one such capability, described as a vertical landing maneuver using in-flight shape reconfiguration in lieu of high thrust generation. A morphing, perching aircraft design is presented that is capable of post stall flight and very slow landing on a vertical platform. A comprehensive model of the aircraft's aerodynamics, with special regard to nonlinear affects such as flow separation and dynamic stall, is discussed. Trajectory optimization using nonlinear programming techniques is employed to show the effects that morphing and nonlinear aerodynamics have on the maneuver. These effects are shown to decrease the initial height and distance required to initiate the maneuver, reduce the bounds on the trajectory, and decrease the required thrust for the maneuver. Perching trajectories comparing morphing versus fixed-configuration and stalled versus un-stalled aircraft are presented. It is demonstrated that a vertical landing is possible in the absence of high thrust if post-stall flight capabilities and vehicle reconfiguration are utilized.

  7. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database in the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  8. X-33 Hypersonic Aerodynamic Characteristics

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Nowak, Robert J.; Thompson, Richard A.; Hollis, Brian R.; Prabhu, Ramadas K.

    1999-01-01

    Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database in the hypersonic regime, The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown to be small relative to X-33 control authority.

  9. The Video Head Impulse Test in a Case of Suspected Bilateral Loss of Vestibular Function

    PubMed Central

    Albernaz, Pedro L. Mangabeira; Cusin, Flavia Salvaterra

    2014-01-01

    Introduction A patient who had no symptoms suggestive of bilateral loss of vestibular function presented no responses in rotational and caloric tests. Objectives To demonstrate the importance of the video head impulse test in neuro-otologic diagnosis. Resumed Report This patient had a neuro-otologic evaluation and presented no responses in torsion swing tests, caloric tests, and rotational tests in a Bárány chair. The video head impulse test elicited responses in four of the six semicircular canals. Conclusion Absent responses in caloric and rotatory tests alone are not sufficient to diagnose bilateral loss of vestibular function. PMID:26722351

  10. The Video Head Impulse Test in a Case of Suspected Bilateral Loss of Vestibular Function.

    PubMed

    Albernaz, Pedro L Mangabeira; Cusin, Flavia Salvaterra

    2016-01-01

    Introduction A patient who had no symptoms suggestive of bilateral loss of vestibular function presented no responses in rotational and caloric tests. Objectives To demonstrate the importance of the video head impulse test in neuro-otologic diagnosis. Resumed Report This patient had a neuro-otologic evaluation and presented no responses in torsion swing tests, caloric tests, and rotational tests in a Bárány chair. The video head impulse test elicited responses in four of the six semicircular canals. Conclusion Absent responses in caloric and rotatory tests alone are not sufficient to diagnose bilateral loss of vestibular function.

  11. Mathematical modeling of the aerodynamics of high-angle-of-attack maneuvers

    NASA Technical Reports Server (NTRS)

    Schiff, L. B.; Tobak, M.; Malcolm, G. N.

    1980-01-01

    This paper is a review of the current state of aerodynamic mathematical modeling for aircraft motions at high angles of attack. The mathematical model serves to define a set of characteristic motions from whose known aerodynamic responses the aerodynamic response to an arbitrary high angle-of-attack flight maneuver can be predicted. Means are explored of obtaining stability parameter information in terms of the characteristic motions, whether by wind-tunnel experiments, computational methods, or by parameter-identification methods applied to flight-test data. A rationale is presented for selecting and verifying the aerodynamic mathematical model at the lowest necessary level of complexity. Experimental results describing the wing-rock phenomenon are shown to be accommodated within the most recent mathematical model by admitting the existence of aerodynamic hysteresis in the steady-state variation of the rolling moment with roll angle. Interpretation of the experimental results in terms of bifurcation theory reveals the general conditions under which aerodynamic hysteresis must exist.

  12. Aerodynamic effects of flexibility in flapping wings.

    PubMed

    Zhao, Liang; Huang, Qingfeng; Deng, Xinyan; Sane, Sanjay P

    2010-03-06

    Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re approximately 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small

  13. XB-70 aerodynamic, geometric, mass, and symmetric structural mode data

    NASA Technical Reports Server (NTRS)

    Wykes, J. H.; Mori, A. S.

    1970-01-01

    XB-70-1 mass, structural, and aerodynamic data were updated to reflect as closely as possible the characteristics of the airplane at three specific flight conditions which were actually flown; a nominal Mach number of 0.90 at an altitude of 25,000 feet (two cases) and a nominal Mach number of 1.6 at an altitude of 40,000 feet (one case). In-flight response characteristics at a number of points on the vehicle were obtained by exciting a pair of shaker vanes on the nose of the airplane. Data were recorded with the basic stability augmentation system (SAS) operating both alone and together with the identical location of accelerometer and force (ILAF) structural mode control system. Detailed total vehicle weight, mass characteristics, structural frequencies, generalized masses, all aerodynamic data used in the present analyses, and a description of the actual mode shapes are tabulated and presented.

  14. Formulation of aerodynamic prediction techniques for hypersonic configuration design

    NASA Technical Reports Server (NTRS)

    1979-01-01

    An investigation of approximate theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at moderate hypersonic speeds was performed. Emphasis was placed on approaches that would be responsive to preliminary configuration design level of effort. Supersonic second order potential theory was examined in detail to meet this objective. Shock layer integral techniques were considered as an alternative means of predicting gross aerodynamic characteristics. Several numerical pilot codes were developed for simple three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the second order computations indicated good agreement with higher order solutions and experimental results for a variety of wing like shapes and values of the hypersonic similarity parameter M delta approaching one.

  15. Fluid-thermal-structural study of aerodynamically heated leading edges

    NASA Technical Reports Server (NTRS)

    Deuchamphai, Pramote; Thornton, Earl A.; Wieting, Allan R.

    1988-01-01

    A finite element approach for integrated fluid-thermal-structural analysis of aerodynamically heated leading edges is presented. The Navier-Stokes equations for high speed compressible flow, the energy equation, and the quasi-static equilibrium equations for the leading edge are solved using a single finite element approach in one integrated, vectorized computer program called LIFTS. The fluid-thermal-structural coupling is studied for Mach 6.47 flow over a 3-in diam cylinder for which the flow behavior and the aerothermal loads are calibrated by experimental data. Issues of the thermal-structural response are studied for hydrogen-cooled, super thermal conducting leading edges subjected to intense aerodynamic heating.

  16. Aerodynamic preliminary analysis system. Part 1: Theory. [linearized potential theory

    NASA Technical Reports Server (NTRS)

    Bonner, E.; Clever, W.; Dunn, K.

    1978-01-01

    A comprehensive aerodynamic analysis program based on linearized potential theory is described. The solution treats thickness and attitude problems at subsonic and supersonic speeds. Three dimensional configurations with or without jet flaps having multiple non-planar surfaces of arbitrary planform and open or closed slender bodies of non-circular contour may be analyzed. Longitudinal and lateral-directional static and rotary derivative solutions may be generated. The analysis was implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis problem. Nominal case computation time of 45 CPU seconds on the CDC 175 for a 200 panel simulation indicates the program provides an efficient analysis for systematically performing various aerodynamic configuration tradeoff and evaluation studies.

  17. Integrated aerodynamic-structural design of a transport wing

    NASA Technical Reports Server (NTRS)

    Grossman, B.; Haftka, R. T.; Kao, P.-J.; Polen, D. M.; Rais-Rohani, M.; Sobieszczanski-Sobieski, J.

    1989-01-01

    The integrated aerodynamic-structural design of a subsonic transport wing for minimum weight subject to required range is formulated and solved. The problem requires large computational resources, and two methods are used to alleviate the computational burden. First, a modular sensitivity method that permits the usage of black-box disciplinary software packages, is used to reduce the cost of sensitivity derivatives. In particular, it is shown that derivatives of the aeroelastic response and divergence speed can be calculated without the costly computation of derivatives of aerodynamic influence coefficient and structural stiffness matrices. A sequential approximate optimization is used to further reduce computational cost. The optimization procedure is shown to require a relatively small number of analysis and sensitivity calculations.

  18. Passive control of rotorcraft high-speed impulsive noise

    NASA Astrophysics Data System (ADS)

    Szulc, O.; Doerffer, P.; Tejero, F.

    2016-10-01

    A strong, normal shock wave, terminating a local supersonic area located at the tip of a helicopter blade, not only limits the aerodynamic performance, but also constitutes an origin of the High-Speed Impulsive (HSI) noise. The application of a passive control device (a shallow cavity covered by a perforated plate) just beneath the interaction region weakens the compression level, thus reducing the main source of the HSI noise. The numerical investigation based on the URANS approach and Bohning/Doerffer (BD) transpiration law (SPARC code) confirms a large potential of the new method. Two exemplary implementations, adapted to model helicopter rotors tested at NASA Ames facility in transonic conditions: Caradonna-Tung (lifting, transonic hover) and Caradonna-Laub-Tung (non-lifting, high-speed forward flight), demonstrate the possible gains in terms of the reduction of acoustic pressure fluctuations in the near-field of the blade tip. The CFD results are validated against the experimental data obtained for the reference configurations (no control), while the analysis of the passive control arrangement is based on a purely numerical research. The normal shock wave is effectively eliminated by the wall ventilation exerting a positive impact on the generated level of the HSI noise.

  19. [Serotonin and impulsivity (experiments on animals)].

    PubMed

    Grigor'ian, G A

    2011-01-01

    In the current paper a role of the serotinergic system in organization of impulsive behaviour in animals was considered. The results of influence of antagonists and agonists of the different types and subtypes of 5-HT receptors (1A, B; 2A, B, C; 7) and the effects of the dorsal raphe nuclei lesions on characteristics of impulsivity related with a motor control, mechanisms of attention, reinforcement and decision making were summarized. The data on knock-out animals and the experiments with microdialysis have been also considered. There was emphasized the important role of interaction of 5-HT-, dopamine- and glutamatergic systems in mediation of impulsive behaviour.

  20. Two-impulse reorientation of asymmetric spacecraft

    NASA Technical Reports Server (NTRS)

    Martz, C. W.

    1979-01-01

    An investigation conducted to determine minimum maneuver costs for attitude reorientation of spacecraft of all possible inertial distribution over a wide range of maneuver angles by use of a two impulse coning method of reorientation is reported. Maneuver cost, proportional to the product of fuel consumed (total impulse) and time expended during a maneuver is discussed. Assumptions included external impulsive control torques, rigid body spacecraft rest-to-rest maneuvers, and no disturbance torques. Results are presented in terms of average cost and standard deviation for various maneuver ranges. Costs of individual reorientations are calculated with the computer program included.

  1. Suicidality in Bipolar Disorder: The Role of Emotion-Triggered Impulsivity.

    PubMed

    Johnson, Sheri L; Carver, Charles S; Tharp, Jordan A

    2017-04-01

    A growing body of research suggests that impulsive responses to emotion more robustly predict suicidality than do other forms of impulsivity. This issue has not yet been examined within bipolar disorder, however. Participants diagnosed with bipolar I disorder (n = 133) and control participants (n = 110) diagnosed with no mood or psychotic disorder completed self-report measures of emotion-triggered impulsivity (Negative and Positive Urgency Scales) and interviews concerning lifetime suicidality. Analyses examined the effects of emotion-triggered impulsivity alone and in combination with gender, age of onset, depression severity, comorbid anxiety, comorbid substance use, and medication. A history of suicide ideation and attempts, as well as self-harm, were significantly more common in the bipolar disorder group compared with the control group. Impulsive responses to positive emotions related to suicide ideation, attempts, and self-harm within the bipolar group. Findings extend research on the importance of emotion-triggered impulsivity to a broad range of key outcomes within bipolar disorder. The discussion focuses on limitations and potential clinical implications.

  2. Associations between regional brain physiology and trait impulsivity, motor inhibition, and impaired control over drinking

    PubMed Central

    Weafer, Jessica; Dzemidzic, Mario; Eiler, William; Oberlin, Brandon G.; Wang, Yang; Kareken, David A.

    2015-01-01

    Trait impulsivity and poor inhibitory control are well-established risk factors for alcohol misuse, yet little is known about the associated neurobiological endophenotypes. Here we examined correlations among brain physiology and self-reported trait impulsive behavior, impaired control over drinking, and a behavioral measure of response inhibition. A sample of healthy drinkers (n=117) completed a pulsed arterial spin labeling (PASL) scan to quantify resting regional cerebral blood flow (rCBF), and measures of self-reported impulsivity (Eysenck I7 Impulsivity scale) and impaired control over drinking. A subset of subjects (n=40) performed a stop signal task during blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging to assess brain regions involved in response inhibition. Eysenck I7 scores were inversely related to blood flow in the right precentral gyrus. Significant BOLD activation during response inhibition occurred in an overlapping right frontal motor/premotor region. Moreover, impaired control over drinking was associated with reduced BOLD response in the same region. These findings suggest that impulsive personality and impaired control over drinking are associated with brain physiology in areas implicated in response inhibition. This is consistent with the idea that difficulty controlling behavior is due in part to impairment in motor restraint systems. PMID:26065376

  3. Transient vibration analytical modeling and suppressing for vibration absorber system under impulse excitation

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Yang, Bintang; Yu, Hu; Gao, Yulong

    2017-04-01

    The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.

  4. Impulsivity Characterization in the Roman High- and Low-Avoidance Rat Strains: Behavioral and Neurochemical Differences

    PubMed Central

    Moreno, Margarita; Cardona, Diana; Gómez, Maria José; Sánchez-Santed, Fernando; Tobeña, Adolf; Fernández-Teruel, Alberto; Campa, Leticia; Suñol, Cristina; Escarabajal, Maria Dolores; Torres, Carmen; Flores, Pilar

    2010-01-01

    The selective breeding of Roman high- (RHA) and low-avoidance (RLA) rats for rapid vs extremely poor acquisition of active avoidance behavior in a shuttle-box has generated two phenotypes with different emotional and motivational profiles. The phenotypic traits of the Roman rat lines/strains (outbred or inbred, respectively) include differences in sensation/novelty seeking, anxiety/fearfulness, stress responsivity, and susceptibility to addictive substances. We designed this study to characterize differences between the inbred RHA-I and RLA-I strains in the impulsivity trait by evaluating different aspects of the multifaceted nature of impulsive behaviors using two different models of impulsivity, the delay-discounting task and five-choice serial reaction time (5-CSRT) task. Previously, rats were evaluated on a schedule-induced polydipsia (SIP) task that has been suggested as a model of obsessive-compulsive disorder. RHA-I rats showed an increased acquisition of the SIP task, higher choice impulsivity in the delay-discounting task, and poor inhibitory control as shown by increased premature responses in the 5-CSRT task. Therefore, RHA-I rats manifested an increased impulsivity phenotype compared with RLA-I rats. Moreover, these differences in impulsivity were associated with basal neurochemical differences in striatum and nucleus accumbens monoamines found between the two strains. These findings characterize the Roman rat strains as a valid model for studying the different aspects of impulsive behavior and for analyzing the mechanisms involved in individual predisposition to impulsivity and its related psychopathologies. PMID:20090672

  5. Effects of tryptophan depletion and a simulated alcohol binge on impulsivity

    PubMed Central

    Dougherty, Donald M.; Mullen, Jillian; Hill-Kapturczak, Nathalie; Liang, Yuanyuan; Karns, Tara E.; Lake, Sarah L.; Mathias, Charles W.; Roache, John D.

    2015-01-01

    Background Researchers have suggested that binge drinkers experience disproportionate increases in impulsivity during the initial period of drinking, leading to a loss of control over further drinking, and that serotonergic mechanisms may underlie such effects. Methods We examined the effects of a simulated-alcohol binge and tryptophan depletion on three types of impulsivity: response initiation (IMT task), response inhibition (GoStop task), and delay discounting (SKIP task), and tested whether observed effects were related to “real world” binge drinking. 179 adults with diverse drinking histories completed a within-subject crossover design over 4 experimental days. Each day, participants underwent one of four test conditions: tryptophan depletion/alcohol, tryptophan depletion/placebo, tryptophan balanced control/alcohol, or tryptophan balanced control/placebo. The simulated binge involved consuming 0.3 g/kg of alcohol at 5, 6, and 7 hours after consuming the tryptophan depletion/balanced mixture. Impulsivity was measured before and after each drink. Results Relative to the placebo beverage condition, when alcohol was consumed, impulsive responding was increased at moderate and high levels of intoxication on the IMT and GoStop, but only at high levels of intoxication on the SKIP. Tryptophan depletion had no effect on impulsivity measured under either placebo or alcohol beverage conditions. Effects of alcohol and tryptophan manipulations on impulsivity were unrelated to patterns of binge drinking outside the laboratory. Conclusion The effects of alcohol consumption on impulsivity depend on the component of impulsivity being measured and the dose of alcohol consumed. Such effects do not appear to be a result of reduced serotonin synthesis. Additionally, “real world” binge drinking behaviors were unrelated to behavioral changes observed in the laboratory. PMID:25730415

  6. Imaging Impulsivity in Parkinson's Disease and the Contribution of the Subthalamic Nucleus

    PubMed Central

    Ray, Nicola; Antonelli, Francesca; Strafella, Antonio P.

    2011-01-01

    Taking risks is a natural human response, but, in some, risk taking is compulsive and may be detrimental. The subthalamic nucleus (STN) is thought to play a large role in our ability to inhibit responses. Differences between individuals' ability to inhibit inappropriate responses may underlie both the normal variation in trait impulsivity in the healthy population, as well as the pathological compulsions experienced by those with impulse control disorders (ICDs). Thus, we review the role of the STN in response inhibition, with a particular focus on studies employing imaging methodology. We also review the latest evidence that disruption of the function of the STN by deep brain stimulation in patients with Parkinson's disease can increase impulsivity. PMID:21765999

  7. On Cup Anemometer Rotor Aerodynamics

    PubMed Central

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup. PMID:22778638

  8. On cup anemometer rotor aerodynamics.

    PubMed

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

  9. System for determining aerodynamic imbalance

    NASA Technical Reports Server (NTRS)

    Churchill, Gary B. (Inventor); Cheung, Benny K. (Inventor)

    1994-01-01

    A system is provided for determining tracking error in a propeller or rotor driven aircraft by determining differences in the aerodynamic loading on the propeller or rotor blades of the aircraft. The system includes a microphone disposed relative to the blades during the rotation thereof so as to receive separate pressure pulses produced by each of the blades during the passage thereof by the microphone. A low pass filter filters the output signal produced by the microphone, the low pass filter having an upper cut-off frequency set below the frequency at which the blades pass by the microphone. A sensor produces an output signal after each complete revolution of the blades, and a recording display device displays the outputs of the low pass filter and sensor so as to enable evaluation of the relative magnitudes of the pressure pulses produced by passage of the blades by the microphone during each complete revolution of the blades.

  10. Rarefaction Effects in Hypersonic Aerodynamics

    NASA Astrophysics Data System (ADS)

    Riabov, Vladimir V.

    2011-05-01

    The Direct Simulation Monte-Carlo (DSMC) technique is used for numerical analysis of rarefied-gas hypersonic flows near a blunt plate, wedge, two side-by-side plates, disk, torus, and rotating cylinder. The role of various similarity parameters (Knudsen and Mach numbers, geometrical and temperature factors, specific heat ratios, and others) in aerodynamics of the probes is studied. Important kinetic effects that are specific for the transition flow regime have been found: non-monotonic lift and drag of plates, strong repulsive force between side-by-side plates and cylinders, dependence of drag on torus radii ratio, and the reverse Magnus effect on the lift of a rotating cylinder. The numerical results are in a good agreement with experimental data, which were obtained in a vacuum chamber at low and moderate Knudsen numbers from 0.01 to 10.

  11. Aerodynamic seals for rotary machine

    DOEpatents

    Bidkar, Rahul Anil; Cirri, Massimiliano; Thatte, Azam Mihir; Williams, John Robert

    2016-02-09

    An aerodynamic seal assembly for a rotary machine includes multiple sealing device segments disposed circumferentially intermediate to a stationary housing and a rotor. Each of the segments includes a shoe plate with a forward-shoe section and an aft-shoe section having multiple labyrinth teeth therebetween facing the rotor. The sealing device segment also includes multiple flexures connected to the shoe plate and to a top interface element, wherein the multiple flexures are configured to allow the high pressure fluid to occupy a forward cavity and the low pressure fluid to occupy an aft cavity. Further, the sealing device segments include a secondary seal attached to the top interface element at one first end and positioned about the flexures and the shoe plate at one second end.

  12. Impulsively generated fast coronal pulsations

    NASA Technical Reports Server (NTRS)

    Edwin, P. M.; Roberts, B.

    1986-01-01

    Rapid oscillations in the corona are discussed from a theoretical standpoint, developing some previous work on ducted, fast magnetoacoustic waves in an inhomogeneous medium. In the theory, impulsively (e.g., flare) generated mhd (magnetohydrodynamic) waves are ducted by regions of low Alfven speed (high density) such as coronal loops. Wave propagation in such ducts is strongly dispersive and closely akin to the behavior of Love waves in seismology, Pekeris waves in oceanography and guided waves in fiber optics. Such flare-generated magnetoacoustic waves possess distinctive temporal signatures consisting of periodic, quasi-periodic and decay phases. The quasi-periodic phase possesses the strongest amplitudes and the shortest time scales. Time scales are typically of the order of a second for inhomogeneities (coronal loop width) of 1000 km and Alfven speeds of 1000/kms, and pulse duration times are of tens of seconds. Quasi-periodic signatures have been observed in radio wavelengths for over a decade and more recently by SMM. It is hoped that the theoretical ideas outlined may be successfully related to these observations and thus aid the interpretation of oscillatory signatures recorded by SMM. Such signatures may also provide a diagnostic of coronal conditions. New aspects of the ducted mhd waves, for example their behavior in smoothly varying as opposed to tube-like inhomogeneities, are currently under investigation. The theory is not restricted to loops but applied equally to open field regions.

  13. Individual Differences in Impulsive Action Reflect Variation in the Cortical Serotonin 5-HT2A Receptor System

    PubMed Central

    Fink, Latham HL; Anastasio, Noelle C; Fox, Robert G; Rice, Kenner C; Moeller, F Gerard; Cunningham, Kathryn A

    2015-01-01

    Impulsivity is an important feature of multiple neuropsychiatric disorders, and individual variation in the degree of inherent impulsivity could play a role in the generation or exacerbation of problematic behaviors. Serotonin (5-HT) actions at the 5-HT2AR receptor (5-HT2AR) promote and 5-HT2AR antagonists suppress impulsive action (the inability to withhold premature responses; motor impulsivity) upon systemic administration or microinfusion directly into the medial prefrontal cortex (mPFC), a node in the corticostriatal circuit that is thought to play a role in the regulation of impulsive action. We hypothesized that the functional capacity of the 5-HT2AR, which is governed by its expression, localization, and protein/protein interactions (eg, postsynaptic density 95 (PSD95)), may drive the predisposition to inherent impulsive action. Stable high-impulsive (HI) and low-impulsive (LI) phenotypes were identified from an outbred rodent population with the 1-choice serial reaction time (1-CSRT) task. HI rats exhibited a greater head-twitch response following administration of the preferential 5-HT2AR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and were more sensitive to the effects of the selective 5-HT2AR antagonist M100907 to suppress impulsive action relative to LI rats. A positive correlation was observed between levels of premature responses and 5-HT2AR binding density in frontal cortex ([3H]-ketanserin radioligand binding). Elevated mPFC 5-HT2AR protein expression concomitant with augmented association of the 5-HT2AR with PSD95 differentiated HI from LI rats. The observed differential sensitivity of HI and LI rats to 5-HT2AR ligands and associated distinct 5-HT2AR protein profiles provide evidence that spontaneously occurring individual differences in impulsive action reflect variation in the cortical 5-HT2AR system. PMID:25666313

  14. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  15. Impulsive behaviour in interpersonal encounters: associations with quarrelsomeness and agreeableness.

    PubMed

    aan Het Rot, Marije; Moskowitz, D S; Young, Simon N

    2015-02-01

    Associations between impulsivity and interpersonal behaviours have rarely been examined, even though impulsivity may disrupt the flow of social interactions. For example, it is unknown to what extent the commonly used Barratt Impulsiveness Scale (BIS-11) predicts impulsive behaviour in social situations, and how behaving impulsively during interpersonal encounters might influence levels of quarrelsomeness and agreeableness. In this study, 48 healthy working individuals completed the BIS-11 and recorded their behaviour in social situations using event-contingent recording. Record forms included items representing quarrelsome, agreeable, and impulsive behaviours. BIS-11 motor impulsiveness scores predicted impulsive behaviour in social situations. Impulsive behaviour was associated, in different interactions, with both agreeableness and quarrelsomeness. Behaving impulsively in specific interactions was negatively associated with agreeableness in participants with higher BIS-11 motor impulsiveness and positively associated with agreeableness in participants with lower BIS-11 motor impulsiveness. Impulsive quarrelsome behaviour may cause interpersonal problems. Impulsive agreeable behaviour may have positive effects in individuals with low trait impulsivity. The idea that there are between-person differences in the effects of state impulsivity on the flow of social interaction deserves further study.

  16. Aperture Engineering for Impulse Radiating Antennas

    NASA Astrophysics Data System (ADS)

    Tyo, J. S.

    The past several years have seen the development of an improved understanding of the role of aperture design for impulse radiating antennas (IRAs). The understanding began with the emergence of the concept of prompt aperture efficiency for ultra-wideband (UWB) antennas. This emergence allowed us to concentrate on ways to shape the aperture and control the field distribution within the aperture in order to maximize the prompt response from IRAs. In many high voltage UWB applications it is impossible to increase the radiated fields by increasing the source power. This is because in such instances the sources are already at the limits of linear electromagnetics. In these cases, we would like to come up with methods to improve the radiated field without altering the input impedance of the IRA. In this paper we will explore several such methods including the position of the feed arms to maximize field uniformity, the shaping of the aperture to increase radiated fields by reducing the aperture size, the relative sizing of the reflector (or lens) and the feed horn, and actually reorienting the currents on the reflector by controlling the direction of current flow. One common thread appears in all of these studies, that is the influence of Dr. Carl Baum on the direction and development of the work.

  17. Transpiration Control Of Aerodynamics Via Porous Surfaces

    NASA Technical Reports Server (NTRS)

    Banks, Daniel W.; Wood, Richard M.; Bauer, Steven X. S.

    1993-01-01

    Quasi-active porous surface used to control pressure loading on aerodynamic surface of aircraft or other vehicle, according to proposal. In transpiration control, one makes small additions of pressure and/or mass to cavity beneath surface of porous skin on aerodynamic surface, thereby affecting rate of transpiration through porous surface. Porous skin located on forebody or any other suitable aerodynamic surface, with cavity just below surface. Device based on concept extremely lightweight, mechanically simple, occupies little volume in vehicle, and extremely adaptable.

  18. Active Control of Aerodynamic Noise Sources

    NASA Technical Reports Server (NTRS)

    Reynolds, Gregory A.

    2001-01-01

    Aerodynamic noise sources become important when propulsion noise is relatively low, as during aircraft landing. Under these conditions, aerodynamic noise from high-lift systems can be significant. The research program and accomplishments described here are directed toward reduction of this aerodynamic noise. Progress toward this objective include correction of flow quality in the Low Turbulence Water Channel flow facility, development of a test model and traversing mechanism, and improvement of the data acquisition and flow visualization capabilities in the Aero. & Fluid Dynamics Laboratory. These developments are described in this report.

  19. Multi-impulsivity of Japanese patients with eating disorders: primary and secondary impulsivity.

    PubMed

    Nagata, T; Kawarada, Y; Kiriike, N; Iketani, T

    2000-07-17

    Several studies have noted that multi-impulsive bulimia nervosa tends to be refractory to treatment. However, it is not known whether these impulsivities are an expression of more fundamental psychopathology or simply the consequence of chaotic eating behaviors. Studies of the temporal relationship between the onset of eating disorder and the occurrence of impulsive behaviors will facilitate a better understanding of these issues. Subjects consisted of 60 patients with anorexia nervosa restricting type (AN-R), 62 patients with anorexia nervosa binge-eating/purging type (AN-BP), 114 patients with bulimia nervosa purging type (BN) and 66 control subjects. Impulsive behaviors and childhood traumatic experiences were assessed by self-report questionnaire. Multi-impulsivity (defined by at least three of the following: heavy regular alcohol drinking; suicide attempt; self-mutilation; repeated shoplifting of items other than food; sexual relationships with persons not well known to the subject) was found in 2% of AN-R, 11% of AN-BP, 18% of BN and 2% of control subjects. Eighty percent of BN patients with multi-impulsivity had a history of suicide attempts or self-mutilation history prior to the onset of bulimia nervosa. In BN patients, there tended to be a relationship between childhood parental loss or borderline personality disorder and multi-impulsivity. In conclusion, primary impulsivity (chronological prior occurrence of impulsive behaviors) does exist even in a very different culture, although the number of patients of this type is very limited.

  20. Impulsive Social Influence Increases Impulsive Choices on a Temporal Discounting Task in Young Adults

    PubMed Central

    Gilman, Jodi M.; Curran, Max T.; Calderon, Vanessa; Stoeckel, Luke E.; Evins, A. Eden

    2014-01-01

    Adolescents and young adults who affiliate with friends who engage in impulsive behavior are more likely to engage in impulsive behaviors themselves, and those who associate with prosocial (i.e. more prudent, future oriented) peers are more likely to engage in prosocial behavior. However, it is difficult to disentangle the contribution of peer influence vs. peer selection (i.e., whether individuals choose friends with similar traits) when interpreting social behaviors. In this study, we combined a novel social manipulation with a well-validated delay discounting task assessing impulsive behavior to create a social influence delay discounting task, in which participants were exposed to both impulsive (smaller, sooner or SS payment) and non-impulsive (larger, later or LL payment) choices from their peers. Young adults in this sample, n = 51, aged 18–25 had a higher rate of SS choices after exposure to impulsive peer influence than after exposure to non-impulsive peer influence. Interestingly, in highly susceptible individuals, the rate of non-impulsive choices did not increase after exposure to non-impulsive influence. There was a positive correlation between self-reported suggestibility and degree of peer influence on SS choices. These results suggest that, in young adults, SS choices appear to be influenced by the choices of same-aged peers, especially for individuals who are highly susceptible to influence. PMID:24988440