Effect of input compression and input frequency response on music perception in cochlear implant users.

PubMed

Halliwell, Emily R; Jones, Linor L; Fraser, Matthew; Lockley, Morag; Hill-Feltham, Penelope; McKay, Colette M

2015-06-01

A study was conducted to determine whether modifications to input compression and input frequency response characteristics can improve music-listening satisfaction in cochlear implant users. Experiment 1 compared three pre-processed versions of music and speech stimuli in a laboratory setting: original, compressed, and flattened frequency response. Music excerpts comprised three music genres (classical, country, and jazz), and a running speech excerpt was compared. Experiment 2 implemented a flattened input frequency response in the speech processor program. In a take-home trial, participants compared unaltered and flattened frequency responses. Ten and twelve adult Nucleus Freedom cochlear implant users participated in Experiments 1 and 2, respectively. Experiment 1 revealed a significant preference for music stimuli with a flattened frequency response compared to both original and compressed stimuli, whereas there was a significant preference for the original (rising) frequency response for speech stimuli. Experiment 2 revealed no significant mean preference for the flattened frequency response, with 9 of 11 subjects preferring the rising frequency response. Input compression did not alter music enjoyment. Comparison of the two experiments indicated that individual frequency response preferences may depend on the genre or familiarity, and particularly whether the music contained lyrics.

78 FR 21121 - Information Collection(s) Being Reviewed by the Federal Communications Commission, Comments...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-09

... the carrier frequency, output power, and modulation of each transmitter authorized to operate with... per Response: .033 hours. Frequency of Response: Recordkeeping requirement. Obligation to Respond... which would likely affect the modulation characteristics. Such measurements, which help ensure proper...

Feedback and feedforward control of frequency tuning to naturalistic stimuli.

PubMed

Chacron, Maurice J; Maler, Leonard; Bastian, Joseph

2005-06-08

Sensory neurons must respond to a wide variety of natural stimuli that can have very different spatiotemporal characteristics. Optimal responsiveness to subsets of these stimuli can be achieved by devoting specialized neural circuitry to different stimulus categories, or, alternatively, this circuitry can be modulated or tuned to optimize responsiveness to current stimulus conditions. This study explores the mechanisms that enable neurons within the initial processing station of the electrosensory system of weakly electric fish to shift their tuning properties based on the spatial extent of the stimulus. These neurons are tuned to low frequencies when the stimulus is restricted to a small region within the receptive field center but are tuned to higher frequencies when the stimulus impinges on large regions of the sensory epithelium. Through a combination of modeling and in vivo electrophysiology, we reveal the respective contributions of the filtering characteristics of extended dendritic structures and feedback circuitry to this shift in tuning. Our results show that low-frequency tuning can result from the cable properties of an extended dendrite that conveys receptor-afferent information to the cell body. The shift from low- to high-frequency tuning, seen in response to spatially extensive stimuli, results from increased wide-band input attributable to activation of larger populations of receptor afferents, as well as the activation of parallel fiber feedback from the cerebellum. This feedback provides a cancellation signal with low-pass characteristics that selectively attenuates low-frequency responsiveness. Thus, with spatially extensive stimuli, these cells preferentially respond to the higher-frequency components of the receptor-afferent input.

Modeling of Millimeter-Wave Modulation Characteristics of Semiconductor Lasers under Strong Optical Feedback

PubMed Central

Bakry, Ahmed

2014-01-01

This paper presents modeling and simulation on the characteristics of semiconductor laser modulated within a strong optical feedback (OFB-)induced photon-photon resonance over a passband of millimeter (mm) frequencies. Continuous wave (CW) operation of the laser under strong OFB is required to achieve the photon-photon resonance in the mm-wave band. The simulated time-domain characteristics of modulation include the waveforms of the intensity and frequency chirp as well as the associated distortions of the modulated mm-wave signal. The frequency domain characteristics include the intensity modulation (IM) and frequency modulation (FM) responses in addition to the associated relative intensity noise (RIN). The signal characteristics under modulations with both single and two mm-frequencies are considered. The harmonic distortion and the third order intermodulation distortion (IMD3) are examined and the spurious free dynamic range (SFDR) is calculated. PMID:25383381

Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Longfang; Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH; López-García, Martin

2014-11-10

The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that couplingmore » between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.« less

Design of piezoelectric probe for measurement of longitudinal and shear components of elastic wave

NASA Astrophysics Data System (ADS)

Aoyanagi, Masafumi; Wakatsuki, Naoto; Mizutani, Koichi; Ebihara, Tadashi

2017-07-01

We focus on ultrasonic probes for nondestructive tests and evaluation. Transient characteristics of probes are important for nondestructive tests such as the pulse echo method. We previously reported the principle of measurement using a piezoelectric probe with triaxial sensitivities. In the results, it was calculated that the probe could transmit and receive particle displacement which contains normal and tangential components. It was confirmed that the probe had sensitivities in triaxial directions. However, its performance in terms of frequency and transient characteristics has not been evaluated. The purpose of this study is to design a probe by changing its shape to obtain better performance. The transient characteristics of probes in longitudinal and shear driving were evaluated by the inverse Fourier transformation of frequency responses of longitudinal and shear components, using the two-dimensional finite element method. As a result, the sensitivities at the dips of frequency characteristics increased when using our probe compared with those measured using conventional probes in longitudinal and shear driving. Hence, the performance in terms of the frequency response was improved by more than 3 dB under the conditions in this simulation. Also, the pulse width of impulse response was decreased by half compared with that of probes with conventional shapes.

Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

NASA Astrophysics Data System (ADS)

Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

2017-11-01

A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

Tuning the Stiffness Balance Using Characteristic Frequencies as a Criterion for a Superconducting Gravity Gradiometer

PubMed Central

Liu, Xikai; Ma, Dong; Chen, Liang; Liu, Xiangdong

2018-01-01

Tuning the stiffness balance is crucial to full-band common-mode rejection for a superconducting gravity gradiometer (SGG). A reliable method to do so has been proposed and experimentally tested. In the tuning scheme, the frequency response functions of the displacement of individual test mass upon common-mode accelerations were measured and thus determined a characteristic frequency for each test mass. A reduced difference in characteristic frequencies between the two test masses was utilized as the criterion for an effective tuning. Since the measurement of the characteristic frequencies does not depend on the scale factors of displacement detection, stiffness tuning can be done independently. We have tested this new method on a single-component SGG and obtained a reduction of two orders of magnitude in stiffness mismatch. PMID:29419796

Study on DFIG wind turbines control strategy for improving frequency response characteristics

NASA Astrophysics Data System (ADS)

Zhao, Dongmei; Wu, Di; Liu, Yanhua; Zhou, Zhiyu

2012-01-01

The active and reactive power decoupling control for the double-fed induction generator wind turbines(DFIG) does not play a positive role to the frequency response ability of power grid because it performs as the hidden inertia for the power grid. If we want to improve the transient frequency stability of the wind turbine when it is integrated with the system, we must ameliorate its frequency response characteristics. The inability of frequency control due to DFIG decoupling control could be overcome through releasing (or absorbing) a part of the kinetic energy stored in the rotor, so as to increase (or decrease) active power injected to the power system when the deviation of power system frequency appears. This paper discusses the mathematical model of the variable speed DFIG, including the aerodynamic model, pitch control system model, shaft model, generator model and inverter control model, and other key components, focusing on the mathematical model of the converters in rotor side and grid side. Based on the existing model of wind generator, the paper attaches the frequency control model on the platform of the simulation software DIgSILENT/PowerFactory. The simulation results show that the proposed control strategy can response quickly to transient frequency deviation and prove that wind farms can participate in the system frequency regulation to a certain extent. Finally, the result verifies the accuracy and plausibility of the inverter control model which attaches the frequency control module.

Study on DFIG wind turbines control strategy for improving frequency response characteristics

NASA Astrophysics Data System (ADS)

Zhao, Dongmei; Wu, Di; Liu, Yanhua; Zhou, Zhiyu

2011-12-01

The active and reactive power decoupling control for the double-fed induction generator wind turbines(DFIG) does not play a positive role to the frequency response ability of power grid because it performs as the hidden inertia for the power grid. If we want to improve the transient frequency stability of the wind turbine when it is integrated with the system, we must ameliorate its frequency response characteristics. The inability of frequency control due to DFIG decoupling control could be overcome through releasing (or absorbing) a part of the kinetic energy stored in the rotor, so as to increase (or decrease) active power injected to the power system when the deviation of power system frequency appears. This paper discusses the mathematical model of the variable speed DFIG, including the aerodynamic model, pitch control system model, shaft model, generator model and inverter control model, and other key components, focusing on the mathematical model of the converters in rotor side and grid side. Based on the existing model of wind generator, the paper attaches the frequency control model on the platform of the simulation software DIgSILENT/PowerFactory. The simulation results show that the proposed control strategy can response quickly to transient frequency deviation and prove that wind farms can participate in the system frequency regulation to a certain extent. Finally, the result verifies the accuracy and plausibility of the inverter control model which attaches the frequency control module.

Evaluation of space shuttle main engine fluid dynamic frequency response characteristics

NASA Technical Reports Server (NTRS)

Gardner, T. G.

1980-01-01

In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.

Design of helicopter rotor blades for optimum dynamic characteristics

NASA Technical Reports Server (NTRS)

Peters, D. A.; Ko, T.; Korn, A.; Rossow, M. P.

1984-01-01

The optimal design of helicopter rotor blades is addressed. The forced response of an initial (i.e., non-optimized) blade to those of a final (optimized) blade are compared. Response of starting design and optimal designs for varying forcing frequencies, blade response to harmonics of rotor speed, and derivation of mass and stiffness matrices or functions of natural frequencies are discussed.

Experimental and Predicted Longitudinal and Lateral-Directional Response Characteristics of a Large Flexible 35 Degree Swept-Wing Airplane at an Altitude of 35,000 Feet

NASA Technical Reports Server (NTRS)

Cole, Henry A , Jr; Brown, Stuart C; Holleman, Euclid C

1957-01-01

Measured and predicted dynamic response characteristics of a large flexible swept-wing airplane to control surface inputs are presented for flight conditions of 0.6 to 0.85 Mach number at an altitude of 35,000 feet. The report is divided into two parts. The first part deals with the response of the airplane to elevator control inputs with principal responses contained in a band of frequencies including the longitudinal short-period mode and several symmetrical structural modes. The second part deals with the response of the airplane to aileron and rudder control inputs with principal responses contained in a band of frequencies including the dutch roll mode, the rolling mode, and three antisymmetrical structural modes.

Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles

NASA Technical Reports Server (NTRS)

Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, M.; Jordan, Robert; Schwartz, Jeffrey L.

2003-01-01

The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.

Dynamic characterization of frequency response of shock mitigation of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam

DOE PAGES

Song, Bo; Nelson, Kevin

2015-09-01

Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent themore » characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.« less

Dynamic characterization of frequency response of shock mitigation of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Nelson, Kevin

Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent themore » characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.« less

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

PubMed Central

Hsu, Hung-Yao

2016-01-01

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

Vertical Vibration Characteristics of a High-Temperature Superconducting Maglev Vehicle System

NASA Astrophysics Data System (ADS)

Jiang, Jing; Li, Ke Cai; Zhao, Li Feng; Ma, Jia Qing; Zhang, Yong; Zhao, Yong

2013-06-01

The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0-100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

Closed Loop Real-Time Evaluation of Missile Guidance and Control Components: Simulator Hardware/Software Characteristics and Use

DTIC Science & Technology

1974-08-01

Node Control Logic 2-27 2.16 Pitch Channel Frequence Response 2-36 2.17 Yaw Channel Frequency Response 2-37 K 4 2.18 Analog Computer Mechanlzation of...8217S 0 121 £l1:c IL-I. TABLE I Elements of the Slgma 5 Digital Computer System Xerox Model- Performance MIOP Channel Description Number Characteristics...transfer control signals to or from the CPU. The MIOP can handle up to 32 I/0 channels each operating simultaneously, provided the overall data

Tires

DTIC Science & Technology

2015-12-15

during shipment, protect the threads of the valve stem, and shield the folded tube against abrasion by the threads . A metal valve cap contains a...Test types include force and moment, rolling resistance , steer frequency response, load-deflection curves, characteristics, endurance, and...several on-vehicle tests. 15. SUBJECT TERMS tire test rig force and moment rolling resistance steer frequency response

Sound characteristics of Terapon jorbua as a response to temperature changes

NASA Astrophysics Data System (ADS)

Amron; Jaya, I.; Hestirianoto, T.; Juterzenka, K. v.

2017-10-01

The change of water temperature has potential impact on the behavior of aquatic animal including fish which generated by their sound productivity and characteristics. This research aimed to study the response of sound productivity and characteristics of Terapon jorbua to temperature change. As a response to temperature increase, T. jorbua to have decreased the number of sound productivity. Two characteristic parameters of fish sound, i.e. intensity and frequency as were quadratic increased during the water temperature rises. In contrast, pulse duration was quadratic decreased.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. III. Responses To translation

NASA Technical Reports Server (NTRS)

Angelaki, D. E.

1998-01-01

The three-dimensional (3-D) properties of the translational vestibulo-ocular reflexes (translational VORs) during lateral and fore-aft oscillations in complete darkness were studied in rhesus monkeys at frequencies between 0.16 and 25 Hz. In addition, constant velocity off-vertical axis rotations extended the frequency range to 0.02 Hz. During lateral motion, horizontal responses were in phase with linear velocity in the frequency range of 2-10 Hz. At both lower and higher frequencies, phase lags were introduced. Torsional response phase changed more than 180 degrees in the tested frequency range such that torsional eye movements, which could be regarded as compensatory to "an apparent roll tilt" at the lowest frequencies, became anticompensatory at all frequencies above approximately 1 Hz. These results suggest two functionally different frequency bandwidths for the translational VORs. In the low-frequency spectrum (<<0.5 Hz), horizontal responses compensatory to translation are small and high-pass-filtered whereas torsional response sensitivity is relatively frequency independent. At higher frequencies however, both horizontal and torsional response sensitivity and phase exhibit a similar frequency dependence, suggesting a common role during head translation. During up-down motion, vertical responses were in phase with translational velocity at 3-5 Hz but phase leads progressively increased for lower frequencies (>90 degrees at frequencies <0.2 Hz). No consistent dependence on static head orientation was observed for the vertical response components during up-down motion and the horizontal and torsional response components during lateral translation. The frequency response characteristics of the translational VORs were fitted by "periphery/brain stem" functions that related the linear acceleration input, transduced by primary otolith afferents, to the velocity signals providing the input to the velocity-to-position neural integrator and the oculomotor plant. The lowest-order, best-fit periphery/brain stem model that approximated the frequency dependence of the data consisted of a second order transfer function with two alternating poles (at 0.4 and 7.2 Hz) and zeros (at 0.035 and 3.4 Hz). In addition to clearly differentiator dynamics at low frequencies (less than approximately 0.5 Hz), there was no frequency bandwidth where the periphery/brain stem function could be approximated by an integrator, as previously suggested. In this scheme, the oculomotor plant dynamics are assumed to perform the necessary high-frequency integration as required by the reflex. The detailed frequency dependence of the data could only be precisely described by higher order functions with nonminimum phase characteristics that preclude simple filtering of afferent inputs and might be suggestive of distributed spatiotemporal processing of otolith signals in the translational VORs.

Low-Loss Coupler For Microwave Laser-Diode Modulation

NASA Technical Reports Server (NTRS)

Toda, Minoru

1991-01-01

Elimination of series resistor reduces loss of radio-frequency power. Quarter-wavelength matching section connected to transmission line eliminates need for resistor near laser diode and extends frequency response of system. Concept significantly extends relatively flat frequency response of laser diode or similar component, while simplifying design of its package, increasing amplitude of output signal, and reducing dissipation of heat by eliminating resistance. Phase characteristics approximately linear and any digital information transmitted not significantly altered.

Neural coding of high-frequency tones

NASA Technical Reports Server (NTRS)

Howes, W. L.

1976-01-01

Available evidence was presented indicating that neural discharges in the auditory nerve display characteristic periodicities in response to any tonal stimulus including high-frequency stimuli, and that this periodicity corresponds to the subjective pitch.

Comparative Research on Characteristics of the Isolation Systems with Dry Friction Damping and with Vicious Damping under Base Excitation

NASA Astrophysics Data System (ADS)

Hou, Junfang; jing, Min; Zhang, Weihua; Lu, Yahui; He, Haiwen

2017-12-01

As for the isolation problem of electronic equipments on vehicle, the vibration response characteristics of dry friction damping isolation system under base displacement excitation was analyzed in theory by harmonic balance method, and the displacement response was compared between the isolation systems with dry friction damping and vicious damping separately. The results show that the isolation system with small dry friction damping can’t meet the demands of displacement reduction close to the natural frequency, and it can realize full-frequency vibration isolation by improving dry friction damping when the lock frequency passes beyond the resonance frequency band. The results imply that the damping mechanism of dry friction isolator can’t be described only by dry friction damping, and the composite damping with dry friction and vicious damping is more appropriate.

Systems for low frequency seismic and infrasound detection of geo-pressure transition zones

DOEpatents

Shook, G. Michael; LeRoy, Samuel D.; Benzing, William M.

2007-10-16

Methods for determining the existence and characteristics of a gradational pressurized zone within a subterranean formation are disclosed. One embodiment involves employing an attenuation relationship between a seismic response signal and increasing wavelet wavelength, which relationship may be used to detect a gradational pressurized zone and/or determine characteristics thereof. In another embodiment, a method for analyzing data contained within a response signal for signal characteristics that may change in relation to the distance between an input signal source and the gradational pressurized zone is disclosed. In a further embodiment, the relationship between response signal wavelet frequency and comparative amplitude may be used to estimate an optimal wavelet wavelength or range of wavelengths used for data processing or input signal selection. Systems for seismic exploration and data analysis for practicing the above-mentioned method embodiments are also disclosed.

Comparison of the frequency response characteristics of catheter-mounted piezoelectric and micromanometric phonotransducers.

PubMed

Garcia, J C; Layton, S A; Rubal, B J

1989-05-01

This study compares the frequency response characteristics of catheter-mounted piezoelectric sound transducers with micromanometric transducers. The tip of a 8F catheter with two piezoelectric transducers and two micromanometers was inserted into a water-filled chamber that had a speaker fixed at one end. The speaker was driven by a power amplifier and sine wave generator. The outputs of the transducers were connected to a low-level amplifier. The piezoelectric transducer behaved as a tunable high-pass filter that could be modified by altering the input impedance of the low level amplifier; the frequency response characteristics were examined at five input impedances ranging from 0.96 to 11.8 megohms. The peak-to-peak outputs of the piezoelectric and pressure transducers were recorded at frequency ranges from DC to 1 kHz with a wide-band oscilloscope. The ratio of the outputs from the piezotransducer and micromanometer (Vph/Vpr) was plotted vs. frequency for each input impedance and analyzed to determine the piezotransducer's output resistance and equivalent capacitance; roll-off frequencies were then calculated. The equivalent capacitance of the piezo-element was determined to be 500-700 picofarads. Series capacitance acted with network resistance to produce a predictable frequency-dependent change in signal amplitude and phase angle. The inherent noise of the pressure transducer was found to be approximately 0.2 mm Hg, while the noise of the piezoelectric transducer was immeasurably low. The piezoelectric phonotransducers were superior to micromanometer transducers in their higher gain and lower noise, suggesting that these transducers may prove useful to physiologic and clinical studies for measuring intravascular sound.

Continuously varying skin potentials elicited by sinusoidally varying electric shock potentials

NASA Technical Reports Server (NTRS)

Senders, J. W.; Senders, V. L.; Tursky, B.

1973-01-01

An investigation was carried out to determine whether a form of quasi-linear systems analysis can be applied to electrodormal responses to yield new insights into the nature of the response mechanisms and their interrelationships. The response investigated was the electrodermal response (galvanic skin potential, GSP) as elicited by an electric shock stimulus applied to the skin. The response subsequent to this stimulation was examined and its characteristics measured. A series of experimental runs on three Ss was accomplished, using sinusoidal modulation envelopes of frequencies. Results showed that it was possible to drive the GSP and to achieve relatively high coherence between the driving frequency and the response itself. The analysis was limited to Fourier analysis of the response in order to determine the relative energies at the driving frequency and at successive harmonics of that driving frequency, and correlational analysis in order to determine the degree of linear relationship between the driving frequency and the driven response.

Spatiotemporal frequency tuning of BOLD and gamma band MEG responses compared in primary visual cortex.

PubMed

Muthukumaraswamy, Suresh D; Singh, Krish D

2008-05-01

In this study, the spatial and temporal frequency tuning characteristics of the MEG gamma (40-60 Hz) rhythm and the BOLD response in primary visual cortex were measured and compared. In an identical MEG/fMRI paradigm, 10 participants viewed reversing square wave gratings at 2 spatial frequencies [0.5 and 3 cycles per degree (cpd)] reversing at 5 temporal frequencies (0, 1 6, 10, 15 Hz). Three-dimensional images of MEG source power were generated with synthetic aperture magnetometry (SAM) and showed a high degree of spatial correspondence with BOLD responses in primary visual cortex with a mean spatial separation of 6.5 mm, but the two modalities showed different tuning characteristics. The gamma rhythm showed a clear increase in induced power for the high spatial frequency stimulus while BOLD showed no difference in activity for the two spatial frequencies used. Both imaging modalities showed a general increase of activity with temporal frequency, however, BOLD plateaued around 6-10 Hz while the MEG generally increased with a dip exhibited at 6 Hz. These results demonstrate that the two modalities may show activation in similar spatial locations but that the functional pattern of these activations may differ in a complex manner, suggesting that they may be tuned to different aspects of neuronal activity.

Microwave response of an HEMT photoconductor

NASA Technical Reports Server (NTRS)

Claspy, P. C.; Bhasin, K. B.

1988-01-01

Interdigitated photodetectors of various geometries have been fabricated on GaAlAs/GaAs heterostructure material. Optical response characteristics of these devices have been examined at both dc and microwave frequencies. The microwave response, at frequencies to 8 GHz, was studied by illuminating the devices with the output of an internally modulated GaAlAs diode laser. Results of these measurements are presented and compared with that of GaAs photoconductors.

Impact of the time scale of model sensitivity response on coupled model parameter estimation

NASA Astrophysics Data System (ADS)

Liu, Chang; Zhang, Shaoqing; Li, Shan; Liu, Zhengyu

2017-11-01

That a model has sensitivity responses to parameter uncertainties is a key concept in implementing model parameter estimation using filtering theory and methodology. Depending on the nature of associated physics and characteristic variability of the fluid in a coupled system, the response time scales of a model to parameters can be different, from hourly to decadal. Unlike state estimation, where the update frequency is usually linked with observational frequency, the update frequency for parameter estimation must be associated with the time scale of the model sensitivity response to the parameter being estimated. Here, with a simple coupled model, the impact of model sensitivity response time scales on coupled model parameter estimation is studied. The model includes characteristic synoptic to decadal scales by coupling a long-term varying deep ocean with a slow-varying upper ocean forced by a chaotic atmosphere. Results show that, using the update frequency determined by the model sensitivity response time scale, both the reliability and quality of parameter estimation can be improved significantly, and thus the estimated parameters make the model more consistent with the observation. These simple model results provide a guideline for when real observations are used to optimize the parameters in a coupled general circulation model for improving climate analysis and prediction initialization.

role of altruistic behavior, empathetic concern, and social responsibility motivation in blood donation behavior.

PubMed

Steele, Whitney Randolph; Schreiber, George B; Guiltinan, Anne; Nass, Catharie; Glynn, Simone A; Wright, David J; Kessler, Debra; Schlumpf, Karen S; Tu, Yongling; Smith, James W; Garratty, George

2008-01-01

Blood donation can be described as a prosocial behavior, and donors often cite prosocial reasons such as altruism, empathy, or social responsibility for their willingness to donate. Previous studies have not quantitatively evaluated these characteristics in donors or examined how they relate to donation frequency. As part of a donor motivation study, 12,064 current and lapsed donors answered questions used to create an altruistic behavior, empathetic concern, and social responsibility motivation score for each donor. Analysis of variance was used to compare mean scores by demographics and donor status and to determine the influence of each variable on the mean number of donations in the past 5 years. The mean score for each prosocial characteristic appeared high, with lower scores in male and younger donors. Higher altruistic behavior and social responsibility motivation scores were associated with increased past donation frequency, but the effects were minor. Empathetic concern was not associated with prior donation. The largest differences in prior donations were by age and donor status, with older and current donors having given more frequently. Most blood donors appear to have high levels of the primary prosocial characteristics (altruism, empathy, and social responsibility) commonly thought to be the main motivators for donation, but these factors do not appear to be the ones most strongly related to donation frequency. Traditional donor appeals based on these characteristics may need to be supplemented by approaches that address practical concerns like convenience, community safety, or personal benefit.

Before and after retrofit - response of a building during ambient and strong motions

USGS Publications Warehouse

Celebi, M.; Liu, Huaibao P.; ,

1998-01-01

This paper presents results obtained from ambient vibration and strong-motion responses of a thirteen-story, moment-resisting steel framed Santa Clara County Office Building (SCCOB) before being retrofitted by visco-elastic dampers and from ambient vibration response following the retrofit. Understanding the cumulative structural and site characteristics that affect the response of SCCOB before and after the retrofit is important in assessing earthquake hazards to other similar buildings and decision making in retrofitting them. The results emphasize the need to better evaluate structural and site characteristics in developing earthquake resisting designs that avoid resonating effects. Various studies of the strong-motion response records from the SCCOB during the 24 April 1984 (MHE) Morgan Hill (MS = 6.1), the 31 March 1986 (MLE) Mt. Lewis (MS = 6.1) and the 17 October 1989 (LPE) Loma Prieta (MS = 7.1) earthquakes show that the dynamic characteristics of the building are such that it (a) resonated (b) responded with a beating effect due to close-coupling of its translational and torsional frequencies, and (c) had a long-duration response due to low-damping. During each of these earthquakes, there was considerable contents damage and the occupants felt the rigorous vibration of the building. Ambient tests of SCCOB performed following LPE showed that both translational and torsional periods of the building are smaller than those derived from strong motions. Ambient tests performed following the retrofit of the building with visco-elastic dampers show that the structural fundamental mode frequency of the building has increased. The increased frequency implies a stiffer structure. Strong-motion response of the building during future earthquakes will ultimately validate the effectiveness of the retrofit method.This paper presents results obtained from ambient vibration and strong-motion responses of a thirteen-story, moment-resisting steel framed Santa Clara County Office Building (SCCOB) before being retrofitted by visco-elastic dampers and from ambient vibration response following the retrofit. Understanding the cumulative structural and site characteristics that affect the response of SCCOB before and after the retrofit is important in assessing earthquake hazards to other similar buildings and decision making in retrofitting them. The results emphasize the need to better evaluate structural and site characteristics in developing earthquake resisting designs that avoid resonating effects. Various studies of the strong-motion response records from the SCCOB during the 24 April 1984 (MHE) Morgan Hill (Ms = 6.1), the 31 March 1986 (MLE) Mt. Lewis (Ms = 6.1) and the 17 October 1989(LPE) Loma Prieta (Ms = 7.1) earthquakes show that the dynamic characteristics of the building are such that it (a) resonated (b) responded with a beating effect due to close-coupling of its translational and torsional frequencies, and (c) had a long-duration response due to low-damping. During each of these earthquakes, there was considerable contents damage and the occupants felt the rigorous vibration of the building. Ambient tests of SCCOB performed following LPE showed that both translational and torsional periods of the building are smaller than those derived from strong motions. Ambient tests performed following the retrofit of the building with visco-elastic dampers show that the structural fundamental mode frequency of the building has increased. The increased frequency implies a stiffer structure. Strong-motion response of the building during future earthquakes will ultimately validate the effectiveness of the retrofit method.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganguly, Jayanta; Ghosh, Manas, E-mail: pcmg77@rediffmail.com

We investigate the profiles of diagonal components of frequency-dependent first nonlinear (β{sub xxx} and β{sub yyy}) optical response of repulsive impurity doped quantum dots. We have assumed a Gaussian function to represent the dopant impurity potential. This study primarily addresses the role of noise on the polarizability components. We have invoked Gaussian white noise consisting of additive and multiplicative characteristics (in Stratonovich sense). The doped system has been subjected to an oscillating electric field of given intensity, and the frequency-dependent first nonlinear polarizabilities are computed. The noise characteristics are manifested in an interesting way in the nonlinear polarizability components. Inmore » case of additive noise, the noise strength remains practically ineffective in influencing the optical responses. The situation completely changes with the replacement of additive noise by its multiplicative analog. The replacement enhances the nonlinear optical response dramatically and also causes their maximization at some typical value of noise strength that depends on oscillation frequency.« less

Characterization of noncontact piezoelectric transducer with conically shaped piezoelement

NASA Technical Reports Server (NTRS)

Williams, James H., Jr.; Ochi, Simeon C. U.

1988-01-01

The characterization of a dynamic surface displacement transducer (IQI Model 501) by a noncontact method is presented. The transducer is designed for ultrasonic as well as acoustic emission measurements and, according to the manufacturer, its characteristic features include a flat frequency response range which is from 50 to 1000 kHz and a quality factor Q of less than unity. The characterization is based on the behavior of the transducer as a receiver and involves exciting the transducer directly by transient pulse input stress signals of quasi-electrostatic origin and observing its response in a digital storage oscilloscope. Theoretical models for studying the response of the transducer to pulse input stress signals and for generating pulse stress signals are presented. The characteristic features of the transducer which include the central frequency f sub o, quality factor Q, and flat frequency response range are obtained by this noncontact characterization technique and they compare favorably with those obtained by a tone burst method which are also presented.

Simultaneous EEG/fMRI analysis of the resonance phenomena in steady-state visual evoked responses.

PubMed

Bayram, Ali; Bayraktaroglu, Zubeyir; Karahan, Esin; Erdogan, Basri; Bilgic, Basar; Ozker, Muge; Kasikci, Itir; Duru, Adil D; Ademoglu, Ahmet; Oztürk, Cengizhan; Arikan, Kemal; Tarhan, Nevzat; Demiralp, Tamer

2011-04-01

The stability of the steady-state visual evoked potentials (SSVEPs) across trials and subjects makes them a suitable tool for the investigation of the visual system. The reproducible pattern of the frequency characteristics of SSVEPs shows a global amplitude maximum around 10 Hz and additional local maxima around 20 and 40 Hz, which have been argued to represent resonant behavior of damped neuronal oscillators. Simultaneous electroencephalogram/functional magnetic resonance imaging (EEG/fMRI) measurement allows testing of the resonance hypothesis about the frequency-selective increases in SSVEP amplitudes in human subjects, because the total synaptic activity that is represented in the fMRI-Blood Oxygen Level Dependent (fMRI-BOLD) response would not increase but get synchronized at the resonance frequency. For this purpose, 40 healthy volunteers were visually stimulated with flickering light at systematically varying frequencies between 6 and 46 Hz, and the correlations between SSVEP amplitudes and the BOLD responses were computed. The SSVEP frequency characteristics of all subjects showed 3 frequency ranges with an amplitude maximum in each of them, which roughly correspond to alpha, beta and gamma bands of the EEG. The correlation maps between BOLD responses and SSVEP amplitude changes across the different stimulation frequencies within each frequency band showed no significant correlation in the alpha range, while significant correlations were obtained in the primary visual area for the beta and gamma bands. This non-linear relationship between the surface recorded SSVEP amplitudes and the BOLD responses of the visual cortex at stimulation frequencies around the alpha band supports the view that a resonance at the tuning frequency of the thalamo-cortical alpha oscillator in the visual system is responsible for the global amplitude maximum of the SSVEP around 10 Hz. Information gained from the SSVEP/fMRI analyses in the present study might be extrapolated to the EEG/fMRI analysis of the transient event-related potentials (ERPs) in terms of expecting more reliable and consistent correlations between EEG and fMRI responses, when the analyses are carried out on evoked or induced oscillations (spectral perturbations) in separate frequency bands instead of the time-domain ERP peaks.

Research on Harmonic Characteristic of Electronic Current Transformer Based on the Rogowski Coil

NASA Astrophysics Data System (ADS)

Shen, Diqiu; Hu, Bei; Wang, Xufeng; Zhu, Mingdong; Wang, Liang; Lu, Wenxing

2017-05-01

The nonlinear load present in the power system will cause the distortion of AC sine wave and generate the harmonic, which havea severe impact on the accuracy of energy metering and reliability of relay protection. Tosatisfy the requirements of energy metering and relay protection for the new generation of intelligent substation, based on the working principle of Rogowski coil current transformer, mathematical model and transfer characteristics of Rogowski coil sensors were studied in this paper, and frequency response characteristics of Rogowski coil current transformer system were analysed. Finally, the frequency response characteristics of the Rogowski coil current transformer at 2 to 13 harmonics was simulated and experimented. Simulation and experiments show that Rogowski coil current transformer couldmeet 0.2 accuracy requirements of harmonic power measurement of power system, and measure the harmonic components of the grid reliably.

Esophageal sensation in premature human neonates: temporal relationships and implications of aerodigestive reflexes and electrocortical arousals

PubMed Central

Parks, Vanessa N.; Peng, Juan; Dzodzomenyo, Samuel; Fernandez, Soledad; Shaker, Reza; Splaingard, Mark

2012-01-01

Electrocortical arousal (ECA) as an effect of visceral provocation or of its temporal relationships with aerodigestive reflexes in premature neonates is not known. We tested the hypothesis that esophageal provocation results in both esophageal reflex responses and ECAs during sleep and that ECAs are dependent on the frequency characteristics of esophageal neuromotor responses. We defined the spatiotemporal relationship of ECAs in relation to 1) spontaneous pharyngoesophageal swallow sequences and gastroesophageal reflux (GER) events and 2) sensory-motor characteristics of esophageal reflexes. Sixteen healthy premature neonates born at 27.9 ± 3.4 wk were tested at 36.8 ± 1.9 wk postmenstrual age. Ninety-five midesophageal and 31 sham stimuli were given in sleep during concurrent manometry and videopolysomnography. With stimulus onset as reference point, we scored the response latency, frequency occurrence and duration of arousals, peristaltic reflex, and upper esophageal sphincter contractile reflex (UESCR). Changes in polysomnography-respiratory patterns and esophageal sensory-motor parameters were scored by blinded observers. Significantly (for each characteristic listed, P < 0.05), swallow sequences were associated with arousals and sleep state changes, and arousals were associated with incomplete peristalsis, response delays to lower esophageal sphincter relaxation, and prolonged esophageal clearance. GER events (73.5%) provoked arousals, and arousals were associated with response delays to peristaltic reflexes or clearance, sleep state modification, and prolonged respiratory arousal. Midesophageal stimuli (54%) provoked arousals and were associated with increased frequency, prolonged latency, prolonged response duration of peristaltic reflexes and UESCR, and increased frequency of sleep state changes and respiratory arousals. In human neonates, ECAs are provoked upon esophageal stimulation; the sensory-motor characteristics of esophageal reflexes are distinct when accompanied by arousals. Aerodigestive homeostasis is defended by multiple tiers of aerodigestive safety mechanisms, and when esophageal reflexes are delayed, cortical hypervigilance (ECAs) occurs. PMID:21852361

Application of several methods for determining transfer functions and frequency response of aircraft from flight data

NASA Technical Reports Server (NTRS)

Eggleston, John M; Mathews, Charles W

1954-01-01

In the process of analyzing the longitudinal frequency-response characteristics of aircraft, information on some of the methods of analysis has been obtained by the Langley Aeronautical Laboratory of the National Advisory Committee for Aeronautics. In the investigation of these methods, the practical applications and limitations were stressed. In general, the methods considered may be classed as: (1) analysis of sinusoidal response, (2) analysis of transient response as to harmonic content through determination of the Fourier integral by manual or machine methods, and (3) analysis of the transient through the use of least-squares solutions of the coefficients of an assumed equation for either the transient time response or frequency response (sometimes referred to as curve-fitting methods). (author)

Methods and systems for low frequency seismic and infrasound detection of geo-pressure transition zones

DOEpatents

Shook, G. Michael; LeRoy, Samuel D.; Benzing, William M.

2006-07-18

Methods for determining the existence and characteristics of a gradational pressurized zone within a subterranean formation are disclosed. One embodiment involves employing an attenuation relationship between a seismic response signal and increasing wavelet wavelength, which relationship may be used to detect a gradational pressurized zone and/or determine characteristics thereof. In another embodiment, a method for analyzing data contained within a response signal for signal characteristics that may change in relation to the distance between an input signal source and the gradational pressurized zone is disclosed. In a further embodiment, the relationship between response signal wavelet frequency and comparative amplitude may be used to estimate an optimal wavelet wavelength or range of wavelengths used for data processing or input signal selection. Systems for seismic exploration and data analysis for practicing the above-mentioned method embodiments are also disclosed.

Eigenspace Design of Helicopter Flight Control Systems

DTIC Science & Technology

1990-11-01

Attitude Changes ......... 44 2.6 Yaw Cross Coupling Criteria . ............................................... 45 I 4. i Definition of the Rigid Body...laws. The methodology detailed in this report allows the designer to synthesize control laws which result in desirable response types such as attitude ...it is simple to relate the desired frequency response characteristics to the natural frequencies and damping factors or the time constants of the

User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics

NASA Technical Reports Server (NTRS)

Yasue, M.

1974-01-01

A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.

Optical feedback technique extends frequency response of photoconductors

NASA Technical Reports Server (NTRS)

Katzberg, S. J.

1975-01-01

Feedback circuit consists of high-gain light-to-voltage converter with frequency-limited nonlinear photoconductor inside feedback loop. Feedback element is visible light-emitting diode with light-out versus current-in characteristic that is linear over several decades.

Frequency dispersion of nonlinear response of thin superconducting films in the Berezinskii-Kosterlitz-Thouless state

DOE PAGES

Dietrich, Scott; Mayer, William; Byrnes, Sean; ...

2015-02-20

The effects of microwave radiation on transport properties of atomically thin La 2-xSr xCuO₄ films were studied in the 0.1-20 GHz frequency range. Resistance changes induced by microwaves were investigated at different temperatures (8–15 K) near the superconducting transition. A strong decrease of the nonlinear response is observed within a few GHz of a cutoff frequency ν cut ≈ 2GHz. The expected frequency dependence vastly underestimates the sharpness of this drop. Numerical simulations that assume ac response to follow dc V-I characteristics of the films reproduce well the low frequency behavior, but fail above ν cut. Thus, high-frequency radiation ismore » much less effective in inducing vortex-antivortex dissociation in the oscillating superconducting condensate.« less

Metabolic gene regulation in a dynamically changing environment.

PubMed

Bennett, Matthew R; Pang, Wyming Lee; Ostroff, Natalie A; Baumgartner, Bridget L; Nayak, Sujata; Tsimring, Lev S; Hasty, Jeff

2008-08-28

Natural selection dictates that cells constantly adapt to dynamically changing environments in a context-dependent manner. Gene-regulatory networks often mediate the cellular response to perturbation, and an understanding of cellular adaptation will require experimental approaches aimed at subjecting cells to a dynamic environment that mimics their natural habitat. Here we monitor the response of Saccharomyces cerevisiae metabolic gene regulation to periodic changes in the external carbon source by using a microfluidic platform that allows precise, dynamic control over environmental conditions. We show that the metabolic system acts as a low-pass filter that reliably responds to a slowly changing environment, while effectively ignoring fast fluctuations. The sensitive low-frequency response was significantly faster than in predictions arising from our computational modelling, and this discrepancy was resolved by the discovery that two key galactose transcripts possess half-lives that depend on the carbon source. Finally, to explore how induction characteristics affect frequency response, we compare two S. cerevisiae strains and show that they have the same frequency response despite having markedly different induction properties. This suggests that although certain characteristics of the complex networks may differ when probed in a static environment, the system has been optimized for a robust response to a dynamically changing environment.

Toward an ecological analysis of Bayesian inferences: how task characteristics influence responses

PubMed Central

Hafenbrädl, Sebastian; Hoffrage, Ulrich

2015-01-01

In research on Bayesian inferences, the specific tasks, with their narratives and characteristics, are typically seen as exchangeable vehicles that merely transport the structure of the problem to research participants. In the present paper, we explore whether, and possibly how, task characteristics that are usually ignored influence participants’ responses in these tasks. We focus on both quantitative dimensions of the tasks, such as their base rates, hit rates, and false-alarm rates, as well as qualitative characteristics, such as whether the task involves a norm violation or not, whether the stakes are high or low, and whether the focus is on the individual case or on the numbers. Using a data set of 19 different tasks presented to 500 different participants who provided a total of 1,773 responses, we analyze these responses in two ways: first, on the level of the numerical estimates themselves, and second, on the level of various response strategies, Bayesian and non-Bayesian, that might have produced the estimates. We identified various contingencies, and most of the task characteristics had an influence on participants’ responses. Typically, this influence has been stronger when the numerical information in the tasks was presented in terms of probabilities or percentages, compared to natural frequencies – and this effect cannot be fully explained by a higher proportion of Bayesian responses when natural frequencies were used. One characteristic that did not seem to influence participants’ response strategy was the numerical value of the Bayesian solution itself. Our exploratory study is a first step toward an ecological analysis of Bayesian inferences, and highlights new avenues for future research. PMID:26300791

Frequency Response Calculations of Input Characteristics of Cavity-Backed Aperture Antennas Using AWE with Hybrid FEM/MoM Technique

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.

1997-01-01

Application of Asymptotic Waveform Evaluation (AWE) is presented in conjunction with a hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique to calculate the input characteristics of cavity-backed aperture antennas over a frequency range. The hybrid FEM/MoM technique is used to form an integro-partial-differential equation to compute the electric field distribution of the cavity-backed aperture antenna. The electric field, thus obtained, is expanded in a Taylor series around the frequency of interest. The coefficients of 'Taylor series (called 'moments') are obtained using the frequency derivatives of the integro-partial-differential Equation formed by the hybrid FEM/MoM technique. Using the moments, the electric field in the cavity is obtained over a frequency range. Using the electric field at different frequencies, the input characteristics of the antenna are obtained over a wide frequency band. Numerical results for an open coaxial line, probe fed cavity, and cavity-backed microstrip patch antennas are presented. Good agreement between AWE and the exact solution over the frequency range is observed.

System and method for non-destructive evaluation of surface characteristics of a magnetic material

DOEpatents

Jiles, David C.; Sipahi, Levent B.

1994-05-17

A system and a related method for non-destructive evaluation of the surface characteristics of a magnetic material. The sample is excited by an alternating magnetic field. The field frequency, amplitude and offset are controlled according to a predetermined protocol. The Barkhausen response of the sample is detected for the various fields and offsets and is analyzed. The system produces information relating to the frequency content, the amplitude content, the average or RMS energy content, as well as count rate information, for each of the Barkhausen responses at each of the excitation levels applied during the protocol. That information provides a contiguous body of data, heretofore unavailable, which can be analyzed to deduce information about the surface characteristics of the material at various depths below the surface.

High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple

NASA Astrophysics Data System (ADS)

Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei

2017-07-01

With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.

A Noise Level Prediction Method Based on Electro-Mechanical Frequency Response Function for Capacitors

PubMed Central

Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

2013-01-01

The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective. PMID:24349105

A noise level prediction method based on electro-mechanical frequency response function for capacitors.

PubMed

Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

2013-01-01

The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

Quantitative analysis of neuronal response properties in primary and higher-order auditory cortical fields of awake house mice (Mus musculus)

PubMed Central

Joachimsthaler, Bettina; Uhlmann, Michaela; Miller, Frank; Ehret, Günter; Kurt, Simone

2014-01-01

Because of its great genetic potential, the mouse (Mus musculus) has become a popular model species for studies on hearing and sound processing along the auditory pathways. Here, we present the first comparative study on the representation of neuronal response parameters to tones in primary and higher-order auditory cortical fields of awake mice. We quantified 12 neuronal properties of tone processing in order to estimate similarities and differences of function between the fields, and to discuss how far auditory cortex (AC) function in the mouse is comparable to that in awake monkeys and cats. Extracellular recordings were made from 1400 small clusters of neurons from cortical layers III/IV in the primary fields AI (primary auditory field) and AAF (anterior auditory field), and the higher-order fields AII (second auditory field) and DP (dorsoposterior field). Field specificity was shown with regard to spontaneous activity, correlation between spontaneous and evoked activity, tone response latency, sharpness of frequency tuning, temporal response patterns (occurrence of phasic responses, phasic-tonic responses, tonic responses, and off-responses), and degree of variation between the characteristic frequency (CF) and the best frequency (BF) (CF–BF relationship). Field similarities were noted as significant correlations between CFs and BFs, V-shaped frequency tuning curves, similar minimum response thresholds and non-monotonic rate-level functions in approximately two-thirds of the neurons. Comparative and quantitative analyses showed that the measured response characteristics were, to various degrees, susceptible to influences of anesthetics. Therefore, studies of neuronal responses in the awake AC are important in order to establish adequate relationships between neuronal data and auditory perception and acoustic response behavior. PMID:24506843

Electrical Stimulation Frequency and Skeletal Muscle Characteristics: Effects on Force and Fatigue.

PubMed

Vromans, Maria; Faghri, Pouran

2017-12-05

This investigation aimed to determine the force and muscle surface electromyography (EMG) responses to different frequencies of electrical stimulation (ES) in two groups of muscles with different size and fiber composition (fast- and slow-twitch fiber proportions) during a fatigue-inducing protocol. Progression towards fatigue was evaluated in the abductor pollicis brevis (APB) and vastus lateralis (VL) when activated by ES at three frequencies (10, 35, and 50Hz). Ten healthy adults (mean age: 23.2 ± 3.0 years) were recruited; participants signed an IRB approved consent form prior to participation. Protocols were developed to 1) identify initial ES current intensity required to generate the 25% maximal voluntary contraction (MVC) at each ES frequency and 2) evaluate changes in force and EMG activity during ES-induced contraction at each frequency while progressing towards fatigue. For both muscles, stimulation at 10Hz required higher current intensity of ES to generate the initial force. There was a significant decline in force in response to ES-induced fatigue for all frequencies and for both muscles (p<0.05). However, the EMG response was not consistent between muscles. During the progression towards fatigue, the APB displayed an initial drop in force followed by an increase in EMG activity and the VL displayed a decrease in EMG activity for all frequencies. Overall, it appeared that there were some significant interactions between muscle size and fiber composition during progression towards fatigue for different ES frequencies. It could be postulated that muscle characteristics (size and fiber composition) should be considered when evaluating progression towards fatigue as EMG and force responses are not consistent between muscles.

A time-frequency analysis method to obtain stable estimates of magnetotelluric response function based on Hilbert-Huang transform

NASA Astrophysics Data System (ADS)

Cai, Jianhua

2017-05-01

The time-frequency analysis method represents signal as a function of time and frequency, and it is considered a powerful tool for handling arbitrary non-stationary time series by using instantaneous frequency and instantaneous amplitude. It also provides a possible alternative to the analysis of the non-stationary magnetotelluric (MT) signal. Based on the Hilbert-Huang transform (HHT), a time-frequency analysis method is proposed to obtain stable estimates of the magnetotelluric response function. In contrast to conventional methods, the response function estimation is performed in the time-frequency domain using instantaneous spectra rather than in the frequency domain, which allows for imaging the response parameter content as a function of time and frequency. The theory of the method is presented and the mathematical model and calculation procedure, which are used to estimate response function based on HHT time-frequency spectrum, are discussed. To evaluate the results, response function estimates are compared with estimates from a standard MT data processing method based on the Fourier transform. All results show that apparent resistivities and phases, which are calculated from the HHT time-frequency method, are generally more stable and reliable than those determined from the simple Fourier analysis. The proposed method overcomes the drawbacks of the traditional Fourier methods, and the resulting parameter minimises the estimation bias caused by the non-stationary characteristics of the MT data.

Punch stretching process monitoring using acoustic emission signal analysis. II - Application of frequency domain deconvolution

NASA Technical Reports Server (NTRS)

Liang, Steven Y.; Dornfeld, David A.; Nickerson, Jackson A.

1987-01-01

The coloring effect on the acoustic emission signal due to the frequency response of the data acquisition/processing instrumentation may bias the interpretation of AE signal characteristics. In this paper, a frequency domain deconvolution technique, which involves the identification of the instrumentation transfer functions and multiplication of the AE signal spectrum by the inverse of these system functions, has been carried out. In this way, the change in AE signal characteristics can be better interpreted as the result of the change in only the states of the process. Punch stretching process was used as an example to demonstrate the application of the technique. Results showed that, through the deconvolution, the frequency characteristics of AE signals generated during the stretching became more distinctive and can be more effectively used as tools for process monitoring.

Guidelines for Selecting Microphones for Human Voice Production Research

ERIC Educational Resources Information Center

Svec, Jan G.; Granqvist, Svante

2010-01-01

Purpose: This tutorial addresses fundamental characteristics of microphones (frequency response, frequency range, dynamic range, and directionality), which are important for accurate measurements of voice and speech. Method: Technical and voice literature was reviewed and analyzed. The following recommendations on desirable microphone…

Investigation of Critical Burning of Fuel Droplets. [of liquid rocket propellant

NASA Technical Reports Server (NTRS)

Chanin, S. P.; Shearer, A. J.; Faeth, G. M.

1976-01-01

An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point.

Primary Frequency Response with Aggregated DERs: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guggilam, Swaroop S.; Dhople, Sairaj V.; Zhao, Changhong

2017-03-03

Power networks have to withstand a variety of disturbances that affect system frequency, and the problem is compounded with the increasing integration of intermittent renewable generation. Following a large-signal generation or load disturbance, system frequency is arrested leveraging primary frequency control provided by governor action in synchronous generators. In this work, we propose a framework for distributed energy resources (DERs) deployed in distribution networks to provide (supplemental) primary frequency response. Particularly, we demonstrate how power-frequency droop slopes for individual DERs can be designed so that the distribution feeder presents a guaranteed frequency-regulation characteristic at the feeder head. Furthermore, the droopmore » slopes are engineered such that injections of individual DERs conform to a well-defined fairness objective that does not penalize them for their location on the distribution feeder. Time-domain simulations for an illustrative network composed of a combined transmission network and distribution network with frequency-responsive DERs are provided to validate the approach.« less

Characterizing Oscillatory Bursts in Single-Trial EEG Data

NASA Technical Reports Server (NTRS)

Knuth, K. H.; Shah, A. S.; Lakatos, P.; Schroeder, C. E.

2004-01-01

Oscillatory bursts in numerous bands ranging from low (theta) to high frequencies (e.g., gamma) undoubtedly play an important role in cortical dynamics. Largely because of the inadequacy of existing analytic techniques. however, oscillatory bursts and their role in cortical processing remains poorly understood. To study oscillatory bursts effectively one must be able to isolate them and characterize them in the single trial. We describe a series of straightforward analysis techniques that produce useful indices of burst characteristics. First, stimulus-evoked responses are estimated using Differentially Variable Component Analysis (dVCA), and are subtracted from the single-trial. The single-trial characteristics of the evoked responses are stored to identify possible correlations with burst activity. Time-frequency (T-F), or wavelet, analyses are then applied to the single trial residuals. While T-F plots have been used in recent studies to identify and isolate bursts, we go further by fitting each burst in the T-F plot with a two-dimensional Gaussian. This provides a set of burst characteristics, such as, center time. burst duration, center frequency. frequency dispersion. and amplitude, all of which contribute to the accurate characterization of the individual burst. The burst phase can also be estimated. Burst characteristics can be quantified with several standard techniques (e.g.. histogramming and clustering), as well as Bayesian techniques (e.g., blocking) to allow a more parametric description analysis of the characteristics of oscillatory bursts, and the relationships of specific parameters to cortical excitability and stimulus integration.

Application of Model Based Parameter Estimation for Fast Frequency Response Calculations of Input Characteristics of Cavity-Backed Aperture Antennas Using Hybrid FEM/MoM Technique

NASA Technical Reports Server (NTRS)

Reddy C. J.

1998-01-01

Model Based Parameter Estimation (MBPE) is presented in conjunction with the hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique for fast computation of the input characteristics of cavity-backed aperture antennas over a frequency range. The hybrid FENI/MoM technique is used to form an integro-partial- differential equation to compute the electric field distribution of a cavity-backed aperture antenna. In MBPE, the electric field is expanded in a rational function of two polynomials. The coefficients of the rational function are obtained using the frequency derivatives of the integro-partial-differential equation formed by the hybrid FEM/ MoM technique. Using the rational function approximation, the electric field is obtained over a frequency range. Using the electric field at different frequencies, the input characteristics of the antenna are obtained over a wide frequency range. Numerical results for an open coaxial line, probe-fed coaxial cavity and cavity-backed microstrip patch antennas are presented. Good agreement between MBPE and the solutions over individual frequencies is observed.

Is impaired control of reactive stepping related to falls during inpatient stroke rehabilitation?

PubMed

Mansfield, Avril; Inness, Elizabeth L; Wong, Jennifer S; Fraser, Julia E; McIlroy, William E

2013-01-01

Individuals with stroke fall more often than age-matched controls. Although many focus on the multifactorial nature of falls, the fundamental problem is likely the ability for an individual to generate reactions to recover from a loss of balance. Stepping reactions to recover balance are particularly important to balance recovery, and individuals with stroke have difficulty executing these responses to prevent a fall following a loss of balance. The purpose of this study is to determine if characteristics of balance recovery steps are related to falls during inpatient stroke rehabilitation. We conducted a retrospective review of individuals with stroke attending inpatient rehabilitation (n = 136). Details of falls experienced during inpatient rehabilitation were obtained from incident reports, nursing notes, and patient interviews. Stepping reactions were evoked using a "release-from-lean" postural perturbation. Poisson regression was used to determine characteristics of stepping reactions that were related to increased fall frequency relative to length of stay. In all, 20 individuals experienced 29 falls during inpatient rehabilitation. The characteristics of stepping reactions significantly related to increased fall rates were increased frequency of external assistance to prevent a fall to the floor, increased frequency of no-step responses, increased frequency of step responses with inadequate foot clearance, and delayed time to initiate stepping responses. Impaired control of balance recovery steps is related to increased fall rates during inpatient stroke rehabilitation. This study informs the specific features of stepping reactions that can be targeted with physiotherapy intervention during inpatient rehabilitation to improve dynamic stability control and potentially prevent falls.

Event terms in the response spectra prediction equation and their deviation due to stress drop variations

NASA Astrophysics Data System (ADS)

Kawase, H.; Nakano, K.

2015-12-01

We investigated the characteristics of strong ground motions separated from acceleration Fourier spectra and acceleration response spectra of 5% damping calculated from weak and moderate ground motions observed by K-NET, KiK-net, and the JMA Shindokei Network in Japan using the generalized spectral inversion method. The separation method used the outcrop motions at YMGH01 as reference where we extracted site responses due to shallow weathered layers. We include events with JMA magnitude equal to or larger than 4.5 observed from 1996 to 2011. We find that our frequency-dependent Q values are comparable to those of previous studies. From the corner frequencies of Fourier source spectra, we calculate Brune's stress parameters and found a clear magnitude dependence, in which smaller events tend to spread over a wider range while maintaining the same maximum value. We confirm that this is exactly the case for several mainshock-aftershock sequences. The average stress parameters for crustal earthquakes are much smaller than those of subduction zone, which can be explained by their depth dependence. We then compared the strong motion characteristics based on the acceleration response spectra and found that the separated characteristics of strong ground motions are different, especially in the lower frequency range less than 1Hz. These differences comes from the difference between Fourier spectra and response spectra found in the observed data; that is, predominant components in high frequency range of Fourier spectra contribute to increase the response in lower frequency range with small Fourier amplitude because strong high frequency component acts as an impulse to a Single-Degree-of-Freedom system. After the separation of the source terms for 5% damping response spectra we can obtain regression coefficients with respect to the magnitude, which lead to a new GMPE as shown in Fig.1 on the left. Although stress drops for inland earthquakes are 1/7 of the subduction-zone earthquakes, we can see linear regression works quite well. After this linear regression we correlate residuals as a function of Brune's stress parameters of corresponding events as shown in Fig.1 on the right for the case of 1Hz. We found quite good linear correlation, which makes aleatoric uncertainty 40 to 60 % smaller than the original.

Flight testing and frequency domain analysis for rotorcraft handling qualities characteristics

NASA Technical Reports Server (NTRS)

Ham, Johnnie A.; Gardner, Charles K.; Tischler, Mark B.

1993-01-01

A demonstration of frequency domain flight testing techniques and analyses was performed on a U.S. Army OH-58D helicopter in support of the OH-58D Airworthiness and Flight Characteristics Evaluation and the Army's development and ongoing review of Aeronautical Design Standard 33C, Handling Qualities Requirements for Military Rotorcraft. Hover and forward flight (60 knots) tests were conducted in 1 flight hour by Army experimental test pilots. Further processing of the hover data generated a complete database of velocity, angular rate, and acceleration frequency responses to control inputs. A joint effort was then undertaken by the Airworthiness Qualification Test Directorate (AQTD) and the U.S. Army Aeroflightdynamics Directorate (AFDD) to derive handling qualities information from the frequency response database. A significant amount of information could be extracted from the frequency domain database using a variety of approaches. This report documents numerous results that have been obtained from the simple frequency domain tests; in many areas, these results provide more insight into the aircraft dynamics that affect handling qualities than to traditional flight tests. The handling qualities results include ADS-33C bandwidth and phase delay calculations, vibration spectral determinations, transfer function models to examine single axis results, and a six degree of freedom fully coupled state space model. The ability of this model to accurately predict aircraft responses was verified using data from pulse inputs. This report also documents the frequency-sweep flight test technique and data analysis used to support the tests.

Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane

PubMed Central

Zhou, Qiuzhan; Wang, Chunhui; Chen, Yongzhi; Chen, Shuozhang; Lin, Jun

2016-01-01

The Molecular Electric Transducer (MET), widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner. PMID:27171086

A wide-frequency-range air-jet shaker

NASA Technical Reports Server (NTRS)

Herr, Robert W

1957-01-01

This paper presents a description of a simple air-jet shaker. Its force can be calibrated statically and appears to be constant with frequency. It is relatively easy to use, and it has essentially massless characteristics. This shaker is applied to define the unstable branch of a frequency-response curve obtained for a nonlinear spring with a single degree of freedom.

Ultrasonic Resonance Spectroscopy of Composite Rims for Flywheel Rotors

NASA Technical Reports Server (NTRS)

Harmon, Laura M.; Baaklini, George Y.

2002-01-01

Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The ultrasonic system employs a continuous swept-sine waveform and performs a fast Fourier transform (FFT) on the frequency response spectrum. In addition, the system is capable of equalizing the amount of energy at each frequency. Equalization of the frequency spectrum, along with interpretation of the second FFT, aids in the evaluation of the fundamental frequency. The frequency responses from multilayered material samples, with and without known defects, were analyzed to assess the capabilities and limitations of this nondestructive evaluation technique for material characterization and defect detection. Amplitude and frequency changes were studied from ultrasonic responses of thick composite rings and a multiring composite rim. A composite ring varying in thickness was evaluated to investigate the full thickness resonance. The frequency response characteristics from naturally occurring voids in a composite ring were investigated. Ultrasonic responses were compared from regions with and without machined voids in a composite ring and a multiring composite rim. Finally, ultrasonic responses from the multiring composite rim were compared before and after proof spin testing to 63,000 rpm.

Measurement of deformation and frequency response characteristic of PZT tube in tunable fiber laser with short period based on coherent laser beam

NASA Astrophysics Data System (ADS)

Lai, Zhi; Zeng, Xiaodong; Fan, Zhaojin; Xu, Zhichen

2016-09-01

The parameters of light source in synthetic aperture ladar (SAL) is very important to both the design of system and the signal processing algorithm. As the light source in the SAL, the fiber laser use PZT (piezoelectric ceramics) tube stretching the fiber Bragg grating in order to tune the laser frequency. So it is necessary to obtain the deformation and frequency response of PZT tube driven by saw-tooth voltage of different periods. Accordingly, the homodyne detection is used to measure the girth variation of PZT tube. Meanwhile, the frequency response of PZT tube can be viewed with the homodyne signal. The results from measuring a PZT tube show that the method can work well.

LOGARITHMIC AMPLIFIER

DOEpatents

De Shong, J.A. Jr.

1957-12-31

A logarithmic current amplifier circuit having a high sensitivity and fast response is described. The inventor discovered the time constant of the input circuit of a system utilizing a feedback amplifier, ionization chamber, and a diode, is inversely proportional to the input current, and that the amplifier becomes unstable in amplifying signals in the upper frequency range when the amplifier's forward gain time constant equals the input circuit time constant. The described device incorporates impedance networks having low frequency response characteristic at various points in the circuit to change the forward gain of the amplifler at a rate of 0.7 of the gain magnitude for every two times increased in frequency. As a result of this improvement, the time constant of the input circuit is greatly reduced at high frequencies, and the amplifier response is increased.

[Recording of ventricular pressure by conventional catheter manometer systems. Efficiency of several combinations of conventional catheters, modern transducers and catheter-flush systems (author's transl)].

PubMed

Hellige, G

1976-01-01

The experimentally in vitro determined dynamic response characteristics of 38 catheter manometer systems were uniform in the worst case to 5 c.p.s. and optimally to 26 c.p.s. Accordingly, some systems are only satisfactory for ordinary pressure recording in cardiac rest, while better systems record dp/dt correct up to moderate inotropic stimulation of the heart. In the frequency range of uniform response (amplitude error less +/- 5%) the phase distortion is also negligible. In clinical application the investigator is often restricted to special type of cardiac catheter. In this case a low compliant transducer yields superior results. In all examined systems the combination with MSD 10 transducers is best, whereas the combination with P 23 Db transducers leads to minimal results. An inadequate system for recording ventricular pressure pulses leads in most cases to overestimations of dp/dtmax. The use of low frequency pass filters to attenuate higher frequency artefacts is, under clinical conditions, not suitable for extending the range of uniform frequency response. The dynamic response of 14 catheter manometer systems with two types of continuous self flush units was determined. The use of the P 37 flush unit in combination with small internal diameter catheters leads to serious error in ordinary pressure recording, due to amplitude distortion of the lower harmonics. The frequency response characteristics of the combination of an Intraflow flush system and MSD 10 transducer was similar to the non-flushing P 23 Db transducer feature.

Stereo Sound Field Controller Design Using Partial Model Matching on the Frequency Domain

NASA Astrophysics Data System (ADS)

Kumon, Makoto; Miike, Katsuhiro; Eguchi, Kazuki; Mizumoto, Ikuro; Iwai, Zenta

The objective of sound field control is to make the acoustic characteristics of a listening room close to those of the desired system. Conventional methods apply feedforward controllers, such as digital filters, to achieve this objective. However, feedback controllers are also necessary in order to attenuate noise or to compensate the uncertainty of the acoustic characteristics of the listening room. Since acoustic characteristics are well modeled on the frequency domain, it is efficient to design controllers with respect to frequency responses, but it is difficult to design a multi input multi output (MIMO) control system on a wide frequency domain. In the present study, a partial model matching method on the frequency domain was adopted because this method requires only sampled data, rather than complex mathematical models of the plant, in order to design controllers for MIMO systems. The partial model matching method was applied to design two-degree-of-freedom controllers for acoustic equalization and noise reduction. Experiments demonstrated effectiveness of the proposed method.

Development of the Mathematics of Learning Curve Models for Evaluating Small Modular Reactor Economics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, Thomas J.

2014-03-01

This report documents the efforts to perform dynamic model validation on the Eastern Interconnection (EI) by modeling governor deadband. An on-peak EI dynamic model is modified to represent governor deadband characteristics. Simulation results are compared with synchrophasor measurements collected by the Frequency Monitoring Network (FNET/GridEye). The comparison shows that by modeling governor deadband the simulated frequency response can closely align with the actual system response.

Sloshing response of a reactor tank with internals

NASA Astrophysics Data System (ADS)

Ma, D. C.; Gvildys, J.; Chang, Y. W.

The sloshing response of a large reactor tank with in tank components is presented. It is indicated that the presence of the internal components can significantly change the dynamic characteristics of the sloshing motion. The sloshing frequency of a tank with internals is considerably higher than that of a tank without internal. The higher sloshing frequency reduces the sloshing wave height on the free surface but increases the dynamic pressure in the fluid.

Electric vehicle power train instrumentation: Some constraints and considerations

NASA Technical Reports Server (NTRS)

Triner, J. E.; Hansen, I. G.

1977-01-01

The application of pulse modulation control (choppers) to dc motors creates unique instrumentation problems. In particular, the high harmonic components contained in the current waveforms require frequency response accommodations not normally considered in dc instrumentation. In addition to current sensing, accurate power measurement requires not only adequate frequency response but must also address phase errors caused by the finite bandwidths and component characteristics involved. The implications of these problems are assessed.

Steady-state MEG responses elicited by a sequence of amplitude-modulated short tones of different carrier frequencies.

PubMed

Kuriki, Shinya; Kobayashi, Yusuke; Kobayashi, Takanari; Tanaka, Keita; Uchikawa, Yoshinori

2013-02-01

The auditory steady-state response (ASSR) is a weak potential or magnetic response elicited by periodic acoustic stimuli with a maximum response at about a 40-Hz periodicity. In most previous studies using amplitude-modulated (AM) tones of stimulus sound, long lasting tones of more than 10 s in length were used. However, characteristics of the ASSR elicited by short AM tones have remained unclear. In this study, we examined magnetoencephalographic (MEG) ASSR using a sequence of sinusoidal AM tones of 0.78 s in length with various tone frequencies of 440-990 Hz in about one octave variation. It was found that the amplitude of the ASSR was invariant with tone frequencies when the level of sound pressure was adjusted along an equal-loudness curve. The amplitude also did not depend on the existence of preceding tone or difference in frequency of the preceding tone. When the sound level of AM tones was changed with tone frequencies in the same range of 440-990 Hz, the amplitude of ASSR varied in a proportional manner to the sound level. These characteristics are favorable for the use of ASSR in studying temporal processing of auditory information in the auditory cortex. The lack of adaptation in the ASSR elicited by a sequence of short tones may be ascribed to the neural activity of widely accepted generator of magnetic ASSR in the primary auditory cortex. Copyright © 2012 Elsevier B.V. All rights reserved.

Frequency domain kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics

NASA Astrophysics Data System (ADS)

Fl'unt, Orest; Klym, Halyna; Ingram, Adam

2018-03-01

In this work, the kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics sintered at different temperatures (1100, 1200 and 1400 °C) has been calculated and analyzed in a frequency domain. The spectra of real (in-phase) and imaginary (quadrature) components of positron-electron annihilation kinetic have been obtained numerically from usual temporal characteristics using integral Fourier transform. The numerical calculations were carried out using cubic spline interpolation of the pulse characteristics of MgO-Al2O3 ceramics in time domain with following analytical calculations of integrals. The obtained spectra as real so imaginary part of MgO-Al2O3 ceramics in frequency domain almost good obey a Debye law denying correlation between elementary positron annihilation processes. Complex diagrams of frequency domain responses of as-prepared samples have a shape of semicircles with close characteristic frequencies. Some deviation on low-frequency side of the semicircles is observed confirming an availability of longer time kinetic processes. Sintering temperature dependencies of the relaxation times and characteristic frequencies of positron-electron annihilation processes have been obtained. It is shown that position of large maxima on the frequency dependencies of imaginary part corresponds to fast average relaxation lifetime representing the most intensive interaction process of positrons with small cavity traps in solids.

A window on perception: Response times of odontocete cetaceans in audiometric tests

NASA Astrophysics Data System (ADS)

Blackwood, Diane J.; Ridgway, Sam H.; Evans, William E.

2002-05-01

A standard psychometric measurement is response time, the interval elapsing between a stimulus and a response. While studies of response time have been published for humans and other terrestrial mammals, this study marks the first report of response times for odontocete cetaceans at threshold in an audiometric task. Two white whales (Delphinapterus leucas) and four Atlantic bottlenose dolphins (Tursiops truncatus) were given audiometric tests to determine masked hearing thresholds. Animals were tested at 26 frequencies over a range from 200 Hz to 100 kHz using pure tones. The test tone amplitudes covered a range of 20 dB re 1 microPascal including the hearing threshold of the animal at that frequency. Hearing thresholds varied from 87.5 dB to 125.5 dB depending on frequency, masking noise intensity and individual animal. Data was analyzed to determine characteristic relationships between response time and amplitude of test tone for each frequency and animal. The two whales responded significantly slower (640 ms, 0.001) than the four dolphins (430 ms). As in terrestrial animals, reaction time became shorter as stimulus strength increased. At threshold, median response time across frequencies within each animal varied about 150 ms.

Auditory brainstem responses predict auditory nerve fiber thresholds and frequency selectivity in hearing impaired chinchillas

PubMed Central

Henry, Kenneth S.; Kale, Sushrut; Scheidt, Ryan E.; Heinz, Michael G.

2011-01-01

Non-invasive auditory brainstem responses (ABRs) are commonly used to assess cochlear pathology in both clinical and research environments. In the current study, we evaluated the relationship between ABR characteristics and more direct measures of cochlear function. We recorded ABRs and auditory nerve (AN) single-unit responses in seven chinchillas with noise induced hearing loss. ABRs were recorded for 1–8 kHz tone burst stimuli both before and several weeks after four hours of exposure to a 115 dB SPL, 50 Hz band of noise with a center frequency of 2 kHz. Shifts in ABR characteristics (threshold, wave I amplitude, and wave I latency) following hearing loss were compared to AN-fiber tuning curve properties (threshold and frequency selectivity) in the same animals. As expected, noise exposure generally resulted in an increase in ABR threshold and decrease in wave I amplitude at equal SPL. Wave I amplitude at equal sensation level (SL), however, was similar before and after noise exposure. In addition, noise exposure resulted in decreases in ABR wave I latency at equal SL and, to a lesser extent, at equal SPL. The shifts in ABR characteristics were significantly related to AN-fiber tuning curve properties in the same animal at the same frequency. Larger shifts in ABR thresholds and ABR wave I amplitude at equal SPL were associated with greater AN threshold elevation. Larger reductions in ABR wave I latency at equal SL, on the other hand, were associated with greater loss of AN frequency selectivity. This result is consistent with linear systems theory, which predicts shorter time delays for broader peripheral frequency tuning. Taken together with other studies, our results affirm that ABR thresholds and wave I amplitude provide useful estimates of cochlear sensitivity. Furthermore, comparisons of ABR wave I latency to normative data at the same SL may prove useful for detecting and characterizing loss of cochlear frequency selectivity. PMID:21699970

A study on thermal characteristics analysis model of high frequency switching transformer

NASA Astrophysics Data System (ADS)

Yoo, Jin-Hyung; Jung, Tae-Uk

2015-05-01

Recently, interest has been shown in research on the module-integrated converter (MIC) in small-scale photovoltaic (PV) generation. In an MIC, the voltage boosting high frequency transformer should be designed to be compact in size and have high efficiency. In response to the need to satisfy these requirements, this paper presents a coupled electromagnetic analysis model of a transformer connected with a high frequency switching DC-DC converter circuit while considering thermal characteristics due to the copper and core losses. A design optimization procedure for high efficiency is also presented using this design analysis method, and it is verified by the experimental result.

Vibration characteristics of walls and a plate glass window representative of those of a wood-frame house

NASA Technical Reports Server (NTRS)

Carden, H. D.

1979-01-01

Mechanical excitation was used, and measurements of acceleration response, natural frequencies, and nodal patterns were performed. Results indicate that the wall sections and the complete wall did not act as a unit in responding to sinusoidal vibration inputs. Calculated frequencies of the components that account for this independent behavior of the studs and face sheets agreed resonably well with experimental frequencies. Experimental vibrations of the plate glass window agreed with the calculated behavior, and responses of the window exposed to airplane flyover noise were readily correlated with the test results.

Convergent properties of vestibular-related brain stem neurons in the gerbil

NASA Technical Reports Server (NTRS)

Kaufman, G. D.; Shinder, M. E.; Perachio, A. A.

2000-01-01

Three classes of vestibular-related neurons were found in and near the prepositus and medial vestibular nuclei of alert or decerebrate gerbils, those responding to: horizontal translational motion, horizontal head rotation, or both. Their distribution ratios were 1:2:2, respectively. Many cells responsive to translational motion exhibited spatiotemporal characteristics with both response gain and phase varying as a function of the stimulus vector angle. Rotationally sensitive neurons were distributed as Type I, II, or III responses (sensitive to ipsilateral, contralateral, or both directions, respectively) in the ratios of 4:6:1. Four tested factors shaped the response dynamics of the sampled neurons: canal-otolith convergence, oculomotor-related activity, rotational Type (I or II), and the phase of the maximum response. Type I nonconvergent cells displayed increasing gains with increasing rotational stimulus frequency (0.1-2.0 Hz, 60 degrees /s), whereas Type II neurons with convergent inputs had response gains that markedly decreased with increasing translational stimulus frequency (0.25-2.0 Hz, +/-0.1 g). Type I convergent and Type II nonconvergent neurons exhibited essentially flat gains across the stimulus frequency range. Oculomotor-related activity was noted in 30% of the cells across all functional types, appearing as burst/pause discharge patterns related to the fast phase of nystagmus during head rotation. Oculomotor-related activity was correlated with enhanced dynamic range compared with the same category that had no oculomotor-related response. Finally, responses that were in-phase with head velocity during rotation exhibited greater gains with stimulus frequency increments than neurons with out-of-phase responses. In contrast, for translational motion, neurons out of phase with head acceleration exhibited low-pass characteristics, whereas in-phase neurons did not. Data from decerebrate preparations revealed that although similar response types could be detected, the sampled cells generally had lower background discharge rates, on average one-third lower response gains, and convergent properties that differed from those found in the alert animals. On the basis of the dynamic response of identified cell types, we propose a pair of models in which inhibitory input from vestibular-related neurons converges on oculomotor neurons with excitatory inputs from the vestibular nuclei. Simple signal convergence and combinations of different types of vestibular labyrinth information can enrich the dynamic characteristics of the rotational and translational vestibuloocular responses.

Estimation of automobile-driver describing function from highway tests using the double steering wheel

NASA Technical Reports Server (NTRS)

Delp, P.; Crossman, E. R. F. W.; Szostak, H.

1972-01-01

The automobile-driver describing function for lateral position control was estimated for three subjects from frequency response analysis of straight road test results. The measurement procedure employed an instrumented full size sedan with known steering response characteristics, and equipped with a lateral lane position measuring device based on video detection of white stripe lane markings. Forcing functions were inserted through a servo driven double steering wheel coupling the driver to the steering system proper. Random appearing, Gaussian, and transient time functions were used. The quasi-linear models fitted to the random appearing input frequency response characterized the driver as compensating for lateral position error in a proportional, derivative, and integral manner. Similar parameters were fitted to the Gabor transformed frequency response of the driver to transient functions. A fourth term corresponding to response to lateral acceleration was determined by matching the time response histories of the model to the experimental results. The time histories show evidence of pulse-like nonlinear behavior during extended response to step transients which appear as high frequency remnant power.

Order reduction of z-transfer functions via multipoint Jordan continued-fraction expansion

NASA Technical Reports Server (NTRS)

Lee, Ying-Chin; Hwang, Chyi; Shieh, Leang S.

1992-01-01

The order reduction problem of z-transfer functions is solved by using the multipoint Jordan continued-fraction expansion (MJCFE) technique. An efficient algorithm that does not require the use of complex algebra is presented for obtaining an MJCFE from a stable z-transfer function with expansion points selected from the unit circle and/or the positive real axis of the z-plane. The reduced-order models are exactly the multipoint Pade approximants of the original system and, therefore, they match the (weighted) time-moments of the impulse response and preserve the frequency responses of the system at some characteristic frequencies, such as gain crossover frequency, phase crossover frequency, bandwidth, etc.

Temporal-frequency tuning of cross-orientation suppression in the cat striate cortex.

PubMed

Allison, J D; Smith, K R; Bonds, A B

2001-01-01

A sinusoidal mask grating oriented orthogonally to and superimposed onto an optimally oriented base grating reduces a cortical neuron's response amplitude. The spatial selectivity of cross-orientation suppression (XOR) has been described, so for this paper we investigated the temporal properties of XOR. We recorded from single striate cortical neurons (n = 72) in anesthetized and paralyzed cats. After quantifying the spatial and temporal characteristics of each cell's excitatory response to a base grating, we measured the temporal-frequency tuning of XOR by systematically varying the temporal frequency of a mask grating placed at a null orientation outside of the cell's excitatory orientation domain. The average preferred temporal frequency of the excitatory response of the neurons in our sample was 3.8 (+/- 1.5 S.D.) Hz. The average cutoff frequency for the sample was 16.3 (+/- 1.7) Hz. The average preferred temporal frequency (7.0 +/- 2.6 Hz) and cutoff frequency (20.4 +/- 6.9 Hz) of the XOR were significantly higher. The differences averaged 1.1 (+/- 0.6) octaves for the peaks and 0.3 (+/- 0.4) octaves for the cutoffs. The XOR mechanism's preference for high temporal frequencies suggests a possible extrastriate origin for the effect and could help explain the low-pass temporal-frequency response profile displayed by most striate cortical neurons.

Spike Phase Locking in CA1 Pyramidal Neurons depends on Background Conductance and Firing Rate

PubMed Central

Broiche, Tilman; Malerba, Paola; Dorval, Alan D.; Borisyuk, Alla; Fernandez, Fernando R.; White, John A.

2012-01-01

Oscillatory activity in neuronal networks correlates with different behavioral states throughout the nervous system, and the frequency-response characteristics of individual neurons are believed to be critical for network oscillations. Recent in vivo studies suggest that neurons experience periods of high membrane conductance, and that action potentials are often driven by membrane-potential fluctuations in the living animal. To investigate the frequency-response characteristics of CA1 pyramidal neurons in the presence of high conductance and voltage fluctuations, we performed dynamic-clamp experiments in rat hippocampal brain slices. We drove neurons with noisy stimuli that included a sinusoidal component ranging, in different trials, from 0.1 to 500 Hz. In subsequent data analysis, we determined action potential phase-locking profiles with respect to background conductance, average firing rate, and frequency of the sinusoidal component. We found that background conductance and firing rate qualitatively change the phase-locking profiles of CA1 pyramidal neurons vs. frequency. In particular, higher average spiking rates promoted band-pass profiles, and the high-conductance state promoted phase-locking at frequencies well above what would be predicted from changes in the membrane time constant. Mechanistically, spike-rate adaptation and frequency resonance in the spike-generating mechanism are implicated in shaping the different phase-locking profiles. Our results demonstrate that CA1 pyramidal cells can actively change their synchronization properties in response to global changes in activity associated with different behavioral states. PMID:23055508

A voltage to frequency converter for astronomical photometry

NASA Technical Reports Server (NTRS)

Dunham, E.; Elliot, J. L.

1978-01-01

A voltage to frequency converter (VFC) for general use with photomultipliers is described. For high light levels, when the dead-time corrections for a photon counter would be excessive, the VFC maintains a linear response and allows the recording of data at high time resolution. Results of laboratory tests are given for the signal-to-noise characteristics, linearity, stability, and transient response of the VFC when used in conjunction with EMI 9658 and RCA C31034 photomultipliers.

Influence of impeller shroud forces on turbopump rotor dynamics

NASA Technical Reports Server (NTRS)

Williams, J. P.; Childs, Dara W.

1993-01-01

The shrouded-impeller leakage path forces calculated by Childs have been analyzed to answer two questions. First, because of certain characteristics or the results of Childs, the forces could not be modeled with traditional approaches. Therefore, an approach has been devised to include the forces in conventional rotordynamic analyses. The forces were found to be well-modeled with this approach. Finally, the effect these forces had on a simple rotor-bearing system was analyzed, and, therefore, they, in addition to seal forces, were applied to a Jeffcott rotor. The traditional methods of dynamic system analysis were modified to incorporate the impeller forces and yielded results for the eigenproblem, frequency response, critical speed, transient response, and an iterative technique for finding the frequency of free vibration as well as system stability. All results lead to the conclusion that the forces have little influence on natural frequency but can have appreciable effects on system stability. Specifically, at higher values of fluid swirl at the leakage path entrance, relative stability is reduced. The only unexpected response characteristics that occurred are attributed to the nonlinearity of the model.

ProteinAC: a frequency domain technique for analyzing protein dynamics

NASA Astrophysics Data System (ADS)

Bozkurt Varolgunes, Yasemin; Demir, Alper

2018-03-01

It is widely believed that the interactions of proteins with ligands and other proteins are determined by their dynamic characteristics as opposed to only static, time-invariant processes. We propose a novel computational technique, called ProteinAC (PAC), that can be used to analyze small scale functional protein motions as well as interactions with ligands directly in the frequency domain. PAC was inspired by a frequency domain analysis technique that is widely used in electronic circuit design, and can be applied to both coarse-grained and all-atom models. It can be considered as a generalization of previously proposed static perturbation-response methods, where the frequency of the perturbation becomes the key. We discuss the precise relationship of PAC to static perturbation-response schemes. We show that the frequency of the perturbation may be an important factor in protein dynamics. Perturbations at different frequencies may result in completely different response behavior while magnitude and direction are kept constant. Furthermore, we introduce several novel frequency dependent metrics that can be computed via PAC in order to characterize response behavior. We present results for the ferric binding protein that demonstrate the potential utility of the proposed techniques.

The application of the Wigner Distribution to wave type identification in finite length beams

NASA Technical Reports Server (NTRS)

Wahl, T. J.; Bolton, J. Stuart

1994-01-01

The object of the research described in this paper was to develop a means of identifying the wave-types propagating between two points in a finite length beam. It is known that different structural wave-types possess different dispersion relations: i.e., that their group speeds and the frequency dependence of their group speeds differ. As a result of those distinct dispersion relationships, different wave-types may be associated with characteristic features when structural responses are examined in the time frequency domain. Previously, the time-frequency character of analytically generated structural responses of both single element and multi-element structures were examined by using the Wigner Distribution (WD) along with filtering techniques that were designed to detect the wave-types present in the responses. In the work to be described here, the measure time-frequency response of finite length beam is examined using the WD and filtering procedures. This paper is organized as follows. First the concept of time-frequency analysis of structural responses is explained. The WD is then introduced along with a description of the implementation of a discrete version. The time-frequency filtering techniques are then presented and explained. The results of applying the WD and the filtering techniques to the analysis of a transient response is then presented.

Effects of word frequency and phonological neighborhood characteristics on confrontation naming in children who stutter and normally fluent peers.

PubMed

Ratner, Nan Bernstein; Newman, Rochelle; Strekas, Amy

2009-12-01

In a prior study (Newman & Bernstein Ratner, 2007), we examined the effects of word frequency and phonological neighborhood characteristics on confrontation naming latency, accuracy and fluency in adults who stutter and typically fluent speakers. A small difference in accuracy favoring fluent adults was noted, but no other patterns differentiated fluent speaker responses from those obtained from the adults who stutter. Because lexical organization or retrieval differences might be more easily observed in less mature language users, we replicated the experiment using 15 children who stutter (ages 4;10 16;2) and age- and gender-matched peers. Results replicated the earlier study: the two groups of participants showed strikingly similar patterns of responses based on word frequency and neighborhood characteristics. There were also no differences in naming accuracy overall between the two groups. Given our results and those of other researchers who have explored the impact of neighborhood variables on lexical retrieval in people who stutter, we suggest that differences between language production in PWS and fluent speakers are not likely to involve atypical phonological organization of lexical neighborhoods. After reading this article, the reader will be able to: (1) define and illustrate words that have differing frequency and phonological neighborhood characteristics; (2) evaluate whether or not children who stutter appear to organize their mental lexicons differently than those of children who are typically fluent; (3) suggest future areas of research into language processing in people who stutter.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dall-Anese, Emiliano; Zhao, Changhong; Guggilam, Swaroop

Power networks have to withstand a variety of disturbances that affect system frequency, and the problem is compounded with the increasing integration of intermittent renewable generation. Following a large-signal generation or load disturbance, system frequency is arrested leveraging primary frequency control provided by governor action in synchronous generators. In this work, we propose a framework for distributed energy resources (DERs) deployed in distribution networks to provide (supplemental) primary frequency response. Particularly, we demonstrate how power-frequency droop slopes for individual DERs can be designed so that the distribution feeder presents a guaranteed frequency-regulation characteristic at the feeder head. Furthermore, the droopmore » slopes are engineered such that injections of individual DERs conform to a well-defined fairness objective that does not penalize them for their location on the distribution feeder. Time-domain simulations for an illustrative network composed of a combined transmission network and distribution network with frequency-responsive DERs are provided to validate the approach.« less

The experimental research on response characteristics of coal samples under the uniaxial loading process

NASA Astrophysics Data System (ADS)

Jia, Bing; Wei, Jian-Ping; Wen, Zhi-Hui; Wang, Yun-Gang; Jia, Lin-Xing

2017-11-01

In order to study the response characteristics of infrasound in coal samples under the uniaxial loading process, coal samples were collected from GengCun mine. Coal rock stress loading device, acoustic emission tested system and infrasound tested system were used to test the infrasonic signal and acoustic emission signal under uniaxial loading process. The tested results were analyzed by the methods of wavelet filter, threshold denoise, time-frequency analysis and so on. The results showed that in the loading process, the change of the infrasonic wave displayed the characteristics of stage, and it could be divided into three stages: initial stage with a certain amount infrasound events, middle stage with few infrasound events, and late stage gradual decrease. It had a good consistency with changing characteristics of acoustic emission. At the same time, the frequency of infrasound was very low. It can propagate over a very long distance with little attenuation, and the characteristics of the infrasound before the destruction of the coal samples were obvious. A method of using the infrasound characteristics to predict the destruction of coal samples was proposed. This is of great significance to guide the prediction of geological hazards in coal mines.

Effects of temperature on tuning of the auditory pathway in the cicada Tettigetta josei (Hemiptera, Tibicinidae).

PubMed

Fonseca, P J; Correia, T

2007-05-01

The effects of temperature on hearing in the cicada Tettigetta josei were studied. The activity of the auditory nerve and the responses of auditory interneurons to stimuli of different frequencies and intensities were recorded at different temperatures ranging from 16 degrees C to 29 degrees C. Firstly, in order to investigate the temperature dependence of hearing processes, we analyzed its effects on auditory tuning, sensitivity, latency and Q(10dB). Increasing temperature led to an upward shift of the characteristic hearing frequency, to an increase in sensitivity and to a decrease in the latency of the auditory response both in the auditory nerve recordings (periphery) and in some interneurons at the metathoracic-abdominal ganglionic complex (MAC). Characteristic frequency shifts were only observed at low frequency (3-8 kHz). No changes were seen in Q(10dB). Different tuning mechanisms underlying frequency selectivity may explain the results observed. Secondly, we investigated the role of the mechanical sensory structures that participate in the transduction process. Laser vibrometry measurements revealed that the vibrations of the tympanum and tympanal apodeme are temperature independent in the biologically relevant range (18-35 degrees C). Since the above mentioned effects of temperature are present in the auditory nerve recordings, the observed shifts in frequency tuning must be performed by mechanisms intrinsic to the receptor cells. Finally, the role of potassium channels in the response of the auditory system was investigated using a specific inhibitor of these channels, tetraethylammonium (TEA). TEA caused shifts on tuning and sensitivity of the summed response of the receptors similar to the effects of temperature. Thus, potassium channels are implicated in the tuning of the receptor cells.

Damage detection in sandwich composite materials using laser vibrometry in conjunction with nonlinear system identification

NASA Astrophysics Data System (ADS)

Underwood, Sara; Koester, David; Adams, Douglas E.

2009-03-01

Fiberglass sandwich panels are tested to study a vibration-based method for locating damage in composite materials. This method does not rely on a direct comparison of the natural frequencies, mode shapes, or residues in the forced vibration response data. Specifically, a nonlinear system identification based method for damage detection is sought that reduces the sensitivity of damage detection results to changes in vibration measurements due to variations in boundary conditions, environmental conditions, and material properties of the panel. Damage mechanisms considered include a disbond between the core and face sheet and a crack within the core. A panel is excited by a skewed piezoelectric actuator over a broad frequency range while a three-dimensional scanning laser vibrometer measures the surface velocity of the panel along three orthogonal axes. The forced frequency response data measured using the scanning laser vibrometer at multiple excitation amplitudes is processed to identify areas of the panel that exhibit significant nonlinear response characteristics. It is demonstrated that these localized nonlinearities in the panel coincide with the damaged areas of the composite material. Because changes in the measured frequency response functions due to nonlinear distortions associated with the damage can be identified without comparing the vibration data to a reference (baseline) signature of the undamaged material, this vibration technique for damage detection in composite materials exhibits less sensitivity to variations in the underlying linear characteristics than traditional methods. It is also demonstrated that the damage at a given location can be classified as either due to a disbond or core crack because these two types of damage produce difference signatures when comparing the multi-amplitude frequency response functions.

Vibrational characteristics of FRP-bonded concrete interfacial defects in a low frequency regime

NASA Astrophysics Data System (ADS)

Cheng, Tin Kei; Lau, Denvid

2014-04-01

As externally bonded fiber-reinforced polymer (FRP) is a critical load-bearing component of strengthened or retrofitted civil infrastructures, the betterment of structural health monitoring (SHM) methodology for such composites is imperative. Henceforth the vibrational characteristics of near surface interfacial defects involving delamination and trapped air pockets at the FRP-concrete interface are investigated in this study using a finite element approach. Intuitively, due to its lower interfacial stiffness compared with an intact interface, a damaged region is expected to have a set of resonance frequencies different from an intact region when excited by acoustic waves. It has been observed that, when excited acoustically, both the vibrational amplitudes and frequency peaks in the response spectrum of the defects demonstrate a significant deviation from an intact FRP-bonded region. For a thin sheet of FRP bonded to concrete with sizable interfacial defects, the fundamental mode under free vibration is shown to be relatively low, in the order of kHz. Due to the low resonance frequencies of the defects, the use of low-cost equipment for interfacial defect detection via response spectrum analysis is highly feasible.

Electronic stethoscope with frequency shaping and infrasonic recording capabilities.

PubMed

Gordon, E S; Lagerwerff, J M

1976-03-01

A small electronic stethoscope with variable frequency response characteristics has been developed for aerospace and research applications. The system includes a specially designed piezoelectric pickup and amplifier with an overall frequency response from 0.7 to 5,000 HZ (-3 dB points) and selective bass and treble boost or cut of up to 15 dB. A steep slope, high pass filter can be switched in for ordinary clinical auscultation without overload distortion from strong infrasonic signal inputs. A commercial stethoscope-type headset, selected for best overall response, is used which can adequately handle up to 100 mW of audio power delivered from the amplifier. The active components of the amplifier consist of only four opamp-type integrated circuits.

High-Frequency Response of the Atmospheric Electric Potential Gradient Under Strong and Dry Boundary-Layer Convection

NASA Astrophysics Data System (ADS)

Conceição, Ricardo; Silva, Hugo Gonçalves; Bennett, Alec; Salgado, Rui; Bortoli, Daniele; Costa, Maria João; Collares Pereira, Manuel

2018-01-01

The spectral response of atmospheric electric potential gradient gives important information about phenomena affecting this gradient at characteristic time scales ranging from years (e.g., solar modulation) to fractions of a second (e.g., turbulence). While long-term time scales have been exhaustively explored, short-term scales have received less attention. At such frequencies, space-charge transport inside the planetary boundary layer becomes a sizeable contribution to the potential gradient variability. For the first time, co-located (Évora, Portugal) measurements of boundary-layer backscatter profiles and the 100-Hz potential gradient are reported. Five campaign days are analyzed, providing evidence for a relation between high-frequency response of the potential gradient and strong dry convection.

Dynamic Deformation of Vortex Lattice in the Hollow Superconducting YBaCuO Cylinder

NASA Astrophysics Data System (ADS)

Babayan, V. H.; Ayvazyan, M. T.; Kteyan, A. A.; Vardanyan, R. A.

The elastic and viscous properties of vortex lattice in ceramic YBaCuO are studied by the measurements of ac response U in the cavity of the hollow cylinder placed in the magnetic field H aligned along the cylinder's axis. It is observed that the U(H) dependence is reaching saturation with increase of magnetic field. We interpret this effect by nonlocality of the vortex lattice elastic constants. Based on the analysis of the response dependence on excitation frequency, we conclude that vortex lattice deformation vector decreases at higher frequencies. The amplitude-frequency characteristics of the response indicate that vortices perform overdamped oscillations. The estimated damping coefficient value exceeds the evaluation by Bardeen-Stephen theory.

Magnetoelastic sensors in combination with nanometer-scale honeycombed thin film ceramic TiO2 for remote query measurement of humidity

NASA Technical Reports Server (NTRS)

Grimes, C. A.; Kouzoudis, D.; Dickey, E. C.; Qian, D.; Anderson, M. A.; Shahidain, R.; Lindsey, M.; Green, L.

2000-01-01

Ribbonlike magnetoelastic sensors can be considered the magnetic analog of an acoustic bell; in response to an externally applied magnetic field impulse the sensors emit magnetic flux with a characteristic resonant frequency. The magnetic flux can be detected external to the test area using a pick-up coil, enabling query remote monitoring of the sensor. The characteristic resonant frequency of a magnetoelastic sensor changes in response to mass loads. [L.D. Landau and E. M. Lifshitz, Theory of Elasticity, 3rd ed. (Pergamon, New York, 1986). p. 100].Therefore, remote query chemical sensors can be fabricated by combining the magnetoelastic sensors with a mass changing, chemically responsive layer. In this work magnetoelastic sensors are coated with humidity-sensitive thin films of ceramic, nanodimensionally porous TiO2 to make remote query humidity sensors. c2000 American Institute of Physics.

Response of a Bell–Bloom Magnetometer to a Magnetic Field of Arbitrary Direction

PubMed Central

Ding, Zhichao; Yuan, Jie; Long, Xingwu

2018-01-01

The Bell–Bloom magnetometer in response to a magnetic field of arbitrary direction is observed theoretically and experimentally. A theoretical model is built from a macroscopic view to simulate the magnetometer frequency response to an external magnetic field of arbitrary direction. Based on the simulation results, the magnetometer characteristics, including the signal phase and amplitude at resonance, the linewidth, and the magnetometer sensitivity, are analyzed, and the dependencies of these characteristics on the external magnetic field direction are obtained, which are verified by the experiment. PMID:29724059

Corrective jitter motion shows similar individual frequencies for the arm and the finger.

PubMed

Noy, Lior; Alon, Uri; Friedman, Jason

2015-04-01

A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes.

Input-output characterization of an ultrasonic testing system by digital signal analysis

NASA Technical Reports Server (NTRS)

Williams, J. H., Jr.; Lee, S. S.; Karagulle, H.

1986-01-01

Ultrasonic test system input-output characteristics were investigated by directly coupling the transmitting and receiving transducers face to face without a test specimen. Some of the fundamentals of digital signal processing were summarized. Input and output signals were digitized by using a digital oscilloscope, and the digitized data were processed in a microcomputer by using digital signal-processing techniques. The continuous-time test system was modeled as a discrete-time, linear, shift-invariant system. In estimating the unit-sample response and frequency response of the discrete-time system, it was necessary to use digital filtering to remove low-amplitude noise, which interfered with deconvolution calculations. A digital bandpass filter constructed with the assistance of a Blackman window and a rectangular time window were used. Approximations of the impulse response and the frequency response of the continuous-time test system were obtained by linearly interpolating the defining points of the unit-sample response and the frequency response of the discrete-time system. The test system behaved as a linear-phase bandpass filter in the frequency range 0.6 to 2.3 MHz. These frequencies were selected in accordance with the criterion that they were 6 dB below the maximum peak of the amplitude of the frequency response. The output of the system to various inputs was predicted and the results were compared with the corresponding measurements on the system.

Response Properties of Neighboring Neurons in the Auditory Midbrain for Pure-Tone Stimulation: A Tetrode Study

PubMed Central

Seshagiri, Chandran V.; Delgutte, Bertrand

2007-01-01

The complex anatomical structure of the central nucleus of the inferior colliculus (ICC), the principal auditory nucleus in the midbrain, may provide the basis for functional organization of auditory information. To investigate this organization, we used tetrodes to record from neighboring neurons in the ICC of anesthetized cats and studied the similarity and difference among the responses of these neurons to pure-tone stimuli using widely used physiological characterizations. Consistent with the tonotopic arrangement of neurons in the ICC and reports of a threshold map, we found a high degree of correlation in the best frequencies (BFs) of neighboring neurons, which were mostly <3 kHz in our sample, and the pure-tone thresholds among neighboring neurons. However, width of frequency tuning, shapes of the frequency response areas, and temporal discharge patterns showed little or no correlation among neighboring neurons. Because the BF and threshold are measured at levels near the threshold and the characteristic frequency (CF), neighboring neurons may receive similar primary inputs tuned to their CF; however, at higher levels, additional inputs from other frequency channels may be recruited, introducing greater variability in the responses. There was also no correlation among neighboring neurons' sensitivity to interaural time differences (ITD) measured with binaural beats. However, the characteristic phases (CPs) of neighboring neurons revealed a significant correlation. Because the CP is related to the neural mechanisms generating the ITD sensitivity, this result is consistent with segregation of inputs to the ICC from the lateral and medial superior olives. PMID:17671101

Response properties of neighboring neurons in the auditory midbrain for pure-tone stimulation: a tetrode study.

PubMed

Seshagiri, Chandran V; Delgutte, Bertrand

2007-10-01

The complex anatomical structure of the central nucleus of the inferior colliculus (ICC), the principal auditory nucleus in the midbrain, may provide the basis for functional organization of auditory information. To investigate this organization, we used tetrodes to record from neighboring neurons in the ICC of anesthetized cats and studied the similarity and difference among the responses of these neurons to pure-tone stimuli using widely used physiological characterizations. Consistent with the tonotopic arrangement of neurons in the ICC and reports of a threshold map, we found a high degree of correlation in the best frequencies (BFs) of neighboring neurons, which were mostly <3 kHz in our sample, and the pure-tone thresholds among neighboring neurons. However, width of frequency tuning, shapes of the frequency response areas, and temporal discharge patterns showed little or no correlation among neighboring neurons. Because the BF and threshold are measured at levels near the threshold and the characteristic frequency (CF), neighboring neurons may receive similar primary inputs tuned to their CF; however, at higher levels, additional inputs from other frequency channels may be recruited, introducing greater variability in the responses. There was also no correlation among neighboring neurons' sensitivity to interaural time differences (ITD) measured with binaural beats. However, the characteristic phases (CPs) of neighboring neurons revealed a significant correlation. Because the CP is related to the neural mechanisms generating the ITD sensitivity, this result is consistent with segregation of inputs to the ICC from the lateral and medial superior olives.

Induction motor control

NASA Technical Reports Server (NTRS)

Hansen, Irving G.

1990-01-01

Electromechanical actuators developed to date have commonly utilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilizes induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Induction motor control

NASA Technical Reports Server (NTRS)

Hansen, Irving G.

1990-01-01

Electromechanical actuators developed to date have commonly ultilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilized induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high-frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high-frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Compensation based on linearized analysis for a six degree of freedom motion simulator

NASA Technical Reports Server (NTRS)

Parrish, R. V.; Dieudonne, J. E.; Martin, D. J., Jr.; Copeland, J. L.

1973-01-01

The inertial response characteristics of a synergistic, six-degree-of-freedom motion base are presented in terms of amplitude ratio and phase lag as functions of frequency data for the frequency range of interest (0 to 2 Hz) in real time, digital, flight simulators. The notch filters which smooth the digital-drive signals to continuous drive signals are presented, and appropriate compensation, based on the inertial response data, is suggested. The existence of an inverse transformation that converts actuator extensions into inertial positions makes it possible to gather the response data in the inertial axis system.

Experimental modal analysis of the fuselage panels of an Aero Commander aircraft

NASA Technical Reports Server (NTRS)

Geisler, D.

1981-01-01

The reduction of interior noise in light aircraft was investigated with emphasis the thin fuselage sidewall. The approach used is theoretical and involves modeling of the sidewall panels and stiffeners. Experimental data obtained from tests investigating the effects of mass and stiffness treatments to the sidewalls are presented. The dynamic characteristics of treated panels are contrasted with the untreated sidewall panels using experimental modal analysis techniques. The results include the natural frequencies, modal dampling, and mode shapes of selected panels. Frequency response functions, data relating to the global fuselage response, and acoustic response are also presented.

Frequency-response identification of XV-15 tilt-rotor aircraft dynamics

NASA Technical Reports Server (NTRS)

Tischler, Mark B.

1987-01-01

The timely design and development of the next generation of tilt-rotor aircraft (JVX) depend heavily on the in-depth understanding of existing XV-15 dynamics and the availability of fully validated simulation models. Previous studies have considered aircraft and simulation trim characteristics, but analyses of basic flight vehicle dynamics were limited to qualitative pilot evaluation. The present study has the following objectives: documentation and evaluation of XV-15 bare-airframe dynamics; comparison of aircraft and simulation responses; and development of a validated transfer-function description of the XV-15 needed for future studies. A nonparametric frequency-response approach is used which does not depend on assumed model order or structure. Transfer-function representations are subsequently derived which fit the frequency responses in the bandwidth of greatest concern for piloted handling-qualities and control-system applications.

Cochlear microphonic responses to acoustic clicks in guinea pig and their relation with microphonic responses to pure tones.

PubMed

Echeverría, E L; Robles, L W

1983-02-01

Cochlear microphonic (CM) responses to acoustic transient stimuli were studied at the three more basal turns of the cochlea in the guinea pig. The responses to rarefaction and condensation pressure pulses of less than 100-mus duration were recorded using the differential electrode technique. In some animals the CM response to pure tones was recorded at the same position at which the transient response was obtained. The transient responses recorded at the three turns of the cochlea displayed a damped oscillation at a frequency consistent with the values of cutoff frequency already known for the electrode positions. Some of the responses were significantly less damped than click responses previously reported. There was a good correlation between the cutoff frequency in the frequency response curve and the frequency of oscillation in the transient response for recordings obtained at the same position in the cochlea. A nonlinear effect was observed for changes in stimulus intensity. There was a less than proportional decrease in amplitude of the initial part of the damped oscillation for a decrease of the stimulus intensity, while the late part of the response behaved almost linearly. This nonlinearity observed in the CM transient response could not be explained by a nonlinear characteristic of the sort reported in the basilar membrane of the squirrel monkey by Robles et al. [J. Acoust. Soc. Am. 59, 926-939 (1976)]; rather it seems to be a saturation nonlinearity similar to the one known for sinusoidal stimulation.

High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapaev, V. V., E-mail: kapaev@sci.lebedev.ru; Kopaev, Yu. V.; Savinov, S. A.

2013-03-15

The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schroedinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In{sub 0.53}Ga{sub 0.47}As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V{sub dc} in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in suchmore » structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.« less

Generalized characteristic ratios assignment for commensurate fractional order systems with one zero.

PubMed

Tabatabaei, Mohammad

2017-07-01

In this paper, a new method for determination of the desired characteristic equation and zero location of commensurate fractional order systems is presented. The concept of the characteristic ratio is extended for zero-including commensurate fractional order systems. The generalized version of characteristic ratios is defined such that the time-scaling property of characteristic ratios is also preserved. The monotonicity of the magnitude frequency response is employed to assign the generalized characteristic ratios for commensurate fractional order transfer functions with one zero. A simple pattern for characteristic ratios is proposed to reach a non-overshooting step response. Then, the proposed pattern is revisited to reach a low overshoot (say for example 2%) step response. Finally, zero-including controllers such as fractional order PI or lag (lead) controllers are designed using generalized characteristic ratios assignment method. Numerical simulations are provided to show the efficiency of the so designed controllers. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Analysis of heating, ventilation, and air conditioning ducts as a radio frequency communication channel

NASA Astrophysics Data System (ADS)

Nikitin, Pavel Viktorovich

2002-01-01

A typical HVAC duct system is a network of interconnected hollow metal pipes which can serve as waveguides and carry electromagnetic waves. This work presents an analysis of this system as a radio frequency communication channel. Two main parts of the analysis include channel modelling and antenna design. The propagation modelling approach used here is based on the waveguide mode theory and employs the transfer matrix method to describe propagation through various cascaded HVAC elements. This allows one to model the channel response in the frequency domain. Impulse response characteristics of the ducts are also analyzed in this work. The approximate transfer matrices of cylindrical straight sections, bends, and tapers are derived analytically. The transforming properties of cylindrical T-junctions are analyzed experimentally. Antenna designs in waveguides and free-space are different. In waveguides, mode excitation characteristics are important as well as the impedance match. The criteria for antenna design in waveguides are presented here. Antennas analyzed in this work are monopole antennas, dipole antennas, and antenna arrays. The developed model can predict both channel response and antenna characteristics for a given geometry and dimensions of the duct system and the antennas. The model is computationally efficient and can potentially be applied to duct systems of multiple story buildings. The accuracy of the model has been validated with extensive experimental measurements on real HVAC ducts.

Dipole source encoding and tracking by the goldfish auditory system.

PubMed

Coombs, Sheryl; Fay, Richard R; Elepfandt, Andreas

2010-10-15

In goldfish and other otophysans, the Weberian ossicles mechanically link the saccule of the inner ear to the anterior swimbladder chamber (ASB). These structures are correlated with enhanced sound-pressure sensitivity and greater sensitivity at high frequencies (600-2000 Hz). However, surprisingly little is known about the potential impact of the ASB on other otolithic organs and about how auditory responses are modulated by discrete sources that change their location or orientation with respect to the ASB. In this study, saccular and lagenar nerve fiber responses and conditioned behaviors of goldfish were measured to a small, low-frequency (50 Hz) vibrating sphere (dipole) source as a function of its location along the body and its orientation with respect to the ASB. Conditioned behaviors and saccular nerve fiber activity exhibited response characteristics nearly identical to those measured from a hydrophone in the same relative position as the ASB. By contrast, response patterns from lagena fibers could not be predicted by pressure inputs to the ASB. Deflation of the ASB abolished the characteristic spatial response pattern of saccular but not lagena fibers. These results show that: (1) the lagena is not driven by ASB-mediated pressure inputs to the ear; (2) the ASB-saccule pathway dominates behavioral responsiveness, operating effectively at frequencies as low as 50 Hz; and (3) behavioral and neural (saccular) responses are strongly modulated by the position and orientation of the dipole with respect to the ASB.

What Kinds of Skills Are Necessary for Physicians Involved in International Disaster Response?

PubMed

Noguchi, Norihito; Inoue, Satoshi; Shimanoe, Chisato; Shibayama, Kaoru; Matsunaga, Hitomi; Tanaka, Sae; Ishibashi, Akina; Shinchi, Koichi

2016-08-01

Introduction Physicians are key disaster responders in foreign medical teams (FMTs) that provide medical relief to affected people. However, few studies have examined the skills required for physicians in real, international, disaster-response situations. Problem The objectives of this study were to survey the primary skills required for physicians from a Japanese FMT and to examine whether there were differences in the frequencies of performed skills according to demographic characteristics, previous experience, and dispatch situations to guide future training and certification programs. This cross-sectional survey used a self-administered questionnaire given to 64 physicians with international disaster-response site experience. The questionnaire assessed demographic characteristics (sex, age, years of experience as a physician, affiliation, and specialty), previous experience (domestic disaster-relief experience, international disaster-relief experience, or disaster medicine training experience), and dispatch situation (length of dispatch, post-disaster phase, disaster type, and place of dispatch). In addition, the frequencies of 42 performed skills were assessed via a five-point Likert scale. Descriptive statistics were used to assess the participants' characteristics and total scores as the frequencies of performed skills. Mean scores for surgical skills, health care-related skills, public health skills, and management and coordination skills were compared according to the demographic characteristics, previous experience, and dispatch situations. Fifty-two valid questionnaires (81.3% response rate) were collected. There was a trend toward higher skill scores among those who had more previous international disaster-relief experience (P=.03). The more disaster medicine training experience the participants had, the higher their skill score was (P<.001). Physicians reported involvement in 23 disaster-relief response skills, nine of which were performed frequently. There was a trend toward higher scores for surgical skills, health care-related skills, and management and coordination skills related to more disaster medicine training experience. This study's findings can be used as evidence to boost the frequency of physicians' performed skills by promoting previous experience with international disaster relief and disaster medicine training. Additionally, these results may contribute to enhancing the quality of medical practice in the international disaster relief and disaster training curricula. Noguchi N , Inoue S , Shimanoe C , Shibayama K , Matsunaga H , Tanaka S , Ishibashi A , Shinchi K . What kinds of skills are necessary for physicians involved in international disaster response? Prehosp Disaster Med. 2016;31(4):397-406.

Identification of characteristic frequencies of damaged railway tracks using field hammer test measurements

NASA Astrophysics Data System (ADS)

Oregui, M.; Li, Z.; Dollevoet, R.

2015-03-01

In this paper, the feasibility of the Frequency Response Function (FRF)-based statistical method to identify the characteristic frequencies of railway track defects is studied. The method compares a damaged track state to a healthy state based on non-destructive field hammer test measurements. First, a study is carried out to investigate the repeatability of hammer tests in railway tracks. By changing the excitation and measurement locations it is shown that the variability introduced by the test process is negligible. Second, following the concepts of control charts employed in process monitoring, a method to define an approximate healthy state is introduced by using hammer test measurements at locations without visual damage. Then, the feasibility study includes an investigation into squats (i.e. a major type of rail surface defect) of varying severity. The identified frequency ranges related to squats agree with those found in an extensively validated vehicle-borne detection system. Therefore, the FRF-based statistical method in combination with the non-destructive hammer test measurements has the potential to be employed to identify the characteristic frequencies of damaged conditions in railway tracks in the frequency range of 300-3000 Hz.

Effect of eddy current damping on phononic band gaps generated by locally resonant periodic structures

NASA Astrophysics Data System (ADS)

Ozkaya, Efe; Yilmaz, Cetin

2017-02-01

The effect of eddy current damping on a novel locally resonant periodic structure is investigated. The frequency response characteristics are obtained by using a lumped parameter and a finite element model. In order to obtain wide band gaps at low frequencies, the periodic structure is optimized according to certain constraints, such as mass distribution in the unit cell, lower limit of the band gap, stiffness between the components in the unit cell, the size of magnets used for eddy current damping, and the number of unit cells in the periodic structure. Then, the locally resonant periodic structure with eddy current damping is manufactured and its experimental frequency response is obtained. The frequency response results obtained analytically, numerically and experimentally match quite well. The inclusion of eddy current damping to the periodic structure decreases amplitudes of resonance peaks without disturbing stop band width.

Differences between mechanical and neural tuning at the apex of the intact guinea pig cochlea

NASA Astrophysics Data System (ADS)

Recio-Spinoso, Alberto; Oghalai, John S.

2018-05-01

While most of human speech information is contained within frequencies < 3-4 kHz, only a few mechanical measurements have been made in cochlear regions responsive to such low frequencies. Furthermore, the data that do exist are difficult to interpret given the technical difficulties in performing the experiments and/or the artifacts that result from opening the otic capsule bone to visualize the organ of Corti. Here, we overcame historical technical limitations and non-invasively measured sound-induced vibrations within the apex of the guinea pig cochlea using volumetric optical coherence tomography vibrometry (VOCTV). We found that vibrations within apical cochlear regions, with neural tuning below 2 kHz, demonstrate low-pass filter characteristics. There was evidence of a low-level of broad-band cochlear amplification that did not sharpen frequency selectivity. We compared the vibratory responses we measured to previously-measured single-unit auditory nerve tuning curves in the same frequency range, and found that mechanical responses do not match neural responses. These data suggest that, for low frequency cochlear regions, inner hair cells not only transduce vibrations of the organ of Corti but also sharpen frequency tuning.

A Spatial and Temporal Frequency Based Figure-Ground Processor

NASA Astrophysics Data System (ADS)

Weisstein, Namoi; Wong, Eva

1990-03-01

Recent findings in visual psychophysics have shown that figure-ground perception can be specified by the spatial and temporal response characteristics of the visual system. Higher spatial frequency regions of the visual field are perceived as figure and lower spatial frequency regions are perceived as background/ (Klymenko and Weisstein, 1986, Wong and Weisstein, 1989). Higher temporal frequency regions are seen as background and lower temporal frequency regions are seen as figure (Wong and Weisstein, 1987, Klymenko, Weisstein, Topolski, and Hsieh, 1988). Thus, high spatial and low temporal frequencies appear to be associated with figure and low spatial and high temporal frequencies appear to be associated with background.

Vibration characteristics of bone conducted sound in vitro.

PubMed

Stenfelt, S; Håkansson, B; Tjellström, A

2000-01-01

A dry skull added with damping material was used to investigate the vibratory pattern of bone conducted sound. Three orthogonal vibration responses of the cochleae were measured, by means of miniature accelerometers, in the frequency range 0.1-10 kHz. The exciter was attached to the temporal, parietal, and frontal bones, one at the time. In the transmission response to the ipsilateral cochlea, a profound low frequency antiresonance (attenuation) was found, verified psycho-acoustically, and shown to yield a distinct lateralization effect. It was also shown that, for the ipsilateral side, the direction of excitation coincides with that of maximum response. At the contralateral cochlea, no such dominating response direction was found for frequencies above the first skull resonance. An overall higher response level was achieved, for the total energy transmission in general and specifically for the direction of excitation, at the ipsilateral cochlea when the transducer was attached to the excitation point closest to the cochlea. The transranial attenuation was found to be frequency dependent, with values from -5 to 10 dB for the energy transmission and -30 to 40 dB for measurements in a single direction, with a tendency toward higher attenuation at the higher frequencies.

Simulated sensitivity of African terrestrial ecosystem photosynthesis to rainfall frequency, intensity, and rainy season length

NASA Astrophysics Data System (ADS)

Guan, Kaiyu; Good, Stephen P.; Caylor, Kelly K.; Medvigy, David; Pan, Ming; Wood, Eric F.; Sato, Hisashi; Biasutti, Michela; Chen, Min; Ahlström, Anders; Xu, Xiangtao

2018-02-01

There is growing evidence of ongoing changes in the statistics of intra-seasonal rainfall variability over large parts of the world. Changes in annual total rainfall may arise from shifts, either singly or in a combination, of distinctive intra-seasonal characteristics -i.e. rainfall frequency, rainfall intensity, and rainfall seasonality. Understanding how various ecosystems respond to the changes in intra-seasonal rainfall characteristics is critical for predictions of future biome shifts and ecosystem services under climate change, especially for arid and semi-arid ecosystems. Here, we use an advanced dynamic vegetation model (SEIB-DGVM) coupled with a stochastic rainfall/weather simulator to answer the following question: how does the productivity of ecosystems respond to a given percentage change in the total seasonal rainfall that is realized by varying only one of the three rainfall characteristics (rainfall frequency, intensity, and rainy season length)? We conducted ensemble simulations for continental Africa for a realistic range of changes (-20% ~ +20%) in total rainfall amount. We find that the simulated ecosystem productivity (measured by gross primary production, GPP) shows distinctive responses to the intra-seasonal rainfall characteristics. Specifically, increase in rainfall frequency can lead to 28% more GPP increase than the same percentage increase in rainfall intensity; in tropical woodlands, GPP sensitivity to changes in rainy season length is ~4 times larger than to the same percentage changes in rainfall frequency or intensity. In contrast, shifts in the simulated biome distribution are much less sensitive to intra-seasonal rainfall characteristics than they are to total rainfall amount. Our results reveal three major distinctive productivity responses to seasonal rainfall variability—‘chronic water stress’, ‘acute water stress’ and ‘minimum water stress’ - which are respectively associated with three broad spatial patterns of African ecosystem physiognomy, i.e. savannas, woodlands, and tropical forests.

Photoacoustic signal and noise analysis for Si thin plate: signal correction in frequency domain.

PubMed

Markushev, D D; Rabasović, M D; Todorović, D M; Galović, S; Bialkowski, S E

2015-03-01

Methods for photoacoustic signal measurement, rectification, and analysis for 85 μm thin Si samples in the 20-20 000 Hz modulation frequency range are presented. Methods for frequency-dependent amplitude and phase signal rectification in the presence of coherent and incoherent noise as well as distortion due to microphone characteristics are presented. Signal correction is accomplished using inverse system response functions deduced by comparing real to ideal signals for a sample with well-known bulk parameters and dimensions. The system response is a piece-wise construction, each component being due to a particular effect of the measurement system. Heat transfer and elastic effects are modeled using standard Rosencweig-Gersho and elastic-bending theories. Thermal diffusion, thermoelastic, and plasmaelastic signal components are calculated and compared to measurements. The differences between theory and experiment are used to detect and correct signal distortion and to determine detector and sound-card characteristics. Corrected signal analysis is found to faithfully reflect known sample parameters.

Response dynamics of bluff-body stabilized conical premixed turbulent flames with spatial mixture gradients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhuri, Swetaprovo; Cetegen, Baki M.

2009-03-15

Response of bluff-body stabilized conical turbulent premixed flames was experimentally studied for a range of excitation frequencies (10-400 Hz), mean flow velocities (5, 10 and 15 m/s) and three different spatial mixture distributions (uniform, inner and outer enrichment). Upstream excitation was provided by a loudspeaker producing velocity oscillation amplitudes of about 8% of the mean flow velocity. Flame response was detected by a photomultiplier observing the CH{sup *} emission from the flame. The studied turbulent flames exhibited transfer function characteristics of a low-pass filter with a cutoff Strouhal number between 0.08 and 0.12. The amplification factors at low frequencies rangedmore » from 2 to 20 and generally increased for mean flow velocities from 5 to 15 m/s. The highest levels of amplification were found for the outer mixture enrichment followed in decreasing order by uniform and inner mixture gradient cases. The high levels of flame response for the outer enrichment case were attributed to the enhanced flame-vortex interaction in outer jet shear layer. At high excitation levels (u{sup '}/U{sub m}{approx}0.3) for U{sub m}=5 m/ s where non-linear flame response is expected, the flame exhibited a reduced amplitude response in the frequency range between 40 and 100 Hz for the uniform and outer equivalence ratio gradient cases and no discernible effect for the inner equivalence ratio gradient. In all cases, transfer function phase was found to vary linearly with excitation frequency. Finally, a relationship between the amplitude characteristics of the bluff-body wake transfer function and flame blowoff equivalence ratio was presented. (author)« less

Frequency-Selective Attention in Auditory Scenes Recruits Frequency Representations Throughout Human Superior Temporal Cortex.

PubMed

Riecke, Lars; Peters, Judith C; Valente, Giancarlo; Kemper, Valentin G; Formisano, Elia; Sorger, Bettina

2017-05-01

A sound of interest may be tracked amid other salient sounds by focusing attention on its characteristic features including its frequency. Functional magnetic resonance imaging findings have indicated that frequency representations in human primary auditory cortex (AC) contribute to this feat. However, attentional modulations were examined at relatively low spatial and spectral resolutions, and frequency-selective contributions outside the primary AC could not be established. To address these issues, we compared blood oxygenation level-dependent (BOLD) responses in the superior temporal cortex of human listeners while they identified single frequencies versus listened selectively for various frequencies within a multifrequency scene. Using best-frequency mapping, we observed that the detailed spatial layout of attention-induced BOLD response enhancements in primary AC follows the tonotopy of stimulus-driven frequency representations-analogous to the "spotlight" of attention enhancing visuospatial representations in retinotopic visual cortex. Moreover, using an algorithm trained to discriminate stimulus-driven frequency representations, we could successfully decode the focus of frequency-selective attention from listeners' BOLD response patterns in nonprimary AC. Our results indicate that the human brain facilitates selective listening to a frequency of interest in a scene by reinforcing the fine-grained activity pattern throughout the entire superior temporal cortex that would be evoked if that frequency was present alone. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Characteristics of genomic instability in clones of TK6 human lymphoblasts surviving exposure to 56Fe ions

NASA Technical Reports Server (NTRS)

Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, Mireya; Jordan, Robert; Schwartz, Jeffrey L.

2002-01-01

Genomic instability in the human lymphoblast cell line TK6 was studied in clones surviving 36 generations after exposure to accelerated 56Fe ions. Clones were assayed for 20 characteristics, including chromosome aberrations, plating efficiency, apoptosis, cell cycle distribution, response to a second irradiation, and mutant frequency at two loci. The primary effect of the 56Fe-ion exposure on the surviving clones was a significant increase in the frequency of unstable chromosome aberrations compared to the very low spontaneous frequency, along with an increase in the phenotypic complexity of the unstable clones. The radiation-induced increase in the frequency of unstable chromosome aberrations was much greater than that observed previously in clones of the related cell line, WTK1, which in comparison to the TK6 cell line expresses an increased radiation resistance, a mutant TP53 protein, and an increased frequency of spontaneous unstable chromosome aberrations. The characteristics of the unstable clones of the two cell lines also differed. Most of the TK6 clones surviving exposure to 56Fe ions showed unstable cytogenetic abnormalities, while the phenotype of the WTK1 clones was more diverse. The results underscore the importance of genotype in the characteristics of instability after radiation exposure.

Electrical stimulation of the midbrain excites the auditory cortex asymmetrically.

PubMed

Quass, Gunnar Lennart; Kurt, Simone; Hildebrandt, Jannis; Kral, Andrej

2018-05-17

Auditory midbrain implant users cannot achieve open speech perception and have limited frequency resolution. It remains unclear whether the spread of excitation contributes to this issue and how much it can be compensated by current-focusing, which is an effective approach in cochlear implants. The present study examined the spread of excitation in the cortex elicited by electric midbrain stimulation. We further tested whether current-focusing via bipolar and tripolar stimulation is effective with electric midbrain stimulation and whether these modes hold any advantage over monopolar stimulation also in conditions when the stimulation electrodes are in direct contact with the target tissue. Using penetrating multielectrode arrays, we recorded cortical population responses to single pulse electric midbrain stimulation in 10 ketamine/xylazine anesthetized mice. We compared monopolar, bipolar, and tripolar stimulation configurations with regard to the spread of excitation and the characteristic frequency difference between the stimulation/recording electrodes. The cortical responses were distributed asymmetrically around the characteristic frequency of the stimulated midbrain region with a strong activation in regions tuned up to one octave higher. We found no significant differences between monopolar, bipolar, and tripolar stimulation in threshold, evoked firing rate, or dynamic range. The cortical responses to electric midbrain stimulation are biased towards higher tonotopic frequencies. Current-focusing is not effective in direct contact electrical stimulation. Electrode maps should account for the asymmetrical spread of excitation when fitting auditory midbrain implants by shifting the frequency-bands downward and stimulating as dorsally as possible. Copyright © 2018 Elsevier Inc. All rights reserved.

Early Changes in QRS Frequency Following Cardiac Resynchronization Predict Hemodynamic Response in Left Bundle Branch Block Patients.

PubMed

Niebauer, Mark J; Rickard, John; Tchou, Patrick J; Varma, Niraj

2016-05-01

QRS characteristics are the cornerstone of patient selection in cardiac resynchronization therapy (CRT) and the presence of left bundle branch block (LBBB) and baseline QRS ≥150 milliseconds portends a good outcome. We previously showed that baseline QRS frequency analysis adds predictive value to LBBB alone and have hypothesized that a change in frequency characteristics following CRT may produce additional predictive value. We examined the QRS frequency characteristics of 182 LBBB patients before and soon after CRT. Patients were assigned to responder and nonresponder groups. Responders were defined by a decrease in left ventricular end-systolic volume (LVESV) ≥15% following CRT. We analyzed the QRS in ECG leads I, AVF, and V3 before and soon after CRT using the discrete Fourier transform algorithm. The percentage of total QRS power within discrete frequency intervals before and after CRT was calculated. The reduction in lead V3 power <10 Hz was the best indicator of response. Baseline QRS width was similar between the responders and nonresponders (162.2 ± 17.2 milliseconds vs. 158 ± 22.1 milliseconds, respectively; P = 0.180). Responders exhibited a greater reduction in QRS power <10 Hz (-17.0 ± 11.9% vs. -6.6 ± 12.5%; P < 0.001) and a significant AUC (0.743; P < 0.001). A ≥8% decline in QRS power <10 Hz produced the best predictive values (PPV = 84%, NPV = 59%). Importantly, when patients with baseline QRS <150 milliseconds were compared, the AUC improved (0.892, P < 0.001). Successful CRT produces a significant reduction in QRS power below 10 Hz, particularly when baseline QRS <150 milliseconds. These results indicate that QRS frequency changes after CRT provide additional predictive value to QRS alone. © 2016 Wiley Periodicals, Inc.

Experimental Investigations on Effect of Damage on Vibration Characteristics of a Reinforced Concrete Beam

NASA Astrophysics Data System (ADS)

Srinivas, V.; Jeyasehar, C. Antony; Ramanjaneyulu, K.; Sasmal, Saptarshi

2012-02-01

Need for developing efficient non-destructive damage assessment procedures for civil engineering structures is growing rapidly towards structural health assessment and management of existing structures. Damage assessment of structures by monitoring changes in the dynamic properties or response of the structure has received considerable attention in recent years. In the present study, damage assessment studies have been carried out on a reinforced concrete beam by evaluating the changes in vibration characteristics with the changes in damage levels. Structural damage is introduced by static load applied through a hydraulic jack. After each stage of damage, vibration testing is performed and system parameters were evaluated from the measured acceleration and displacement responses. Reduction in fundamental frequencies in first three modes is observed for different levels of damage. It is found that a consistent decrease in fundamental frequency with increase in damage magnitude is noted. The beam is numerically simulated and found that the vibration characteristics obtained from the measured data are in close agreement with the numerical data.

Analysis of the time-varying energy of brain responses to an oddball paradigm using short-term smoothed Wigner-Ville distribution.

PubMed

Tağluk, M E; Cakmak, E D; Karakaş, S

2005-04-30

Cognitive brain responses to external stimuli, as measured by event related potentials (ERPs), have been analyzed from a variety of perspectives to investigate brain dynamics. Here, the brain responses of healthy subjects to auditory oddball paradigms, standard and deviant stimuli, recorded on an Fz electrode site were studied using a short-term version of the smoothed Wigner-Ville distribution (STSW) method. A smoothing kernel was designed to preserve the auto energy of the signal with maximum time and frequency resolutions. Analysis was conducted mainly on the time-frequency distributions (TFDs) of sweeps recorded during successive trials including the TFD of averaged single sweeps as the evoked time-frequency (ETF) brain response and the average of TFDs of single sweeps as the time-frequency (TF) brain response. Also the power entropy and the phase angles of the signal at frequency f and time t locked to the stimulus onset were studied across single trials as the TF power-locked and the TF phase-locked brain responses, respectively. TFDs represented in this way demonstrated the ERP spectro-temporal characteristics from multiple perspectives. The time-varying energy of the individual components manifested interesting TF structures in the form of amplitude modulated (AM) and frequency modulated (FM) energy bursts. The TF power-locked and phase-locked brain responses provoked ERP energies in a manner modulated by cognitive functions, an observation requiring further investigation. These results may lead to a better understanding of integrative brain dynamics.

Coordinated control of wind generation and energy storage for power system frequency regulation

NASA Astrophysics Data System (ADS)

Baone, Chaitanya Ashok

Large-scale centralized synchronous generators have long been the primary actors in exercising active power and frequency control, and much of the existing grid control framework is predicated upon their dynamic terminal characteristics. Important among these characteristics is the inertia of such generators. These play key roles in determining the electromechanical stability of the electric power grid. Modern wind generator systems are partially or fully connected to the grid through power electronic interfaces, and hence do not present the same level of inertial coupling. The absence of inertial frequency response from modern wind generator systems is a topic of growing concern in power engineering practice, as the penetration of wind generation is expected to grow dramatically in the next few years. Solutions proposed in the literature have sought to address this problem by seeking to mimic the inherent inertial response characteristics of traditional synchronous generators via control loops added to wind generators. Recent literature has raised concerns regarding this approach, and the work here will further examine its shortcomings, motivating approaches that seek to optimally design for the characteristics of the equipment exercising the control, rather than forcing new technologies to mimic the characteristics of synchronous machines. In particular, this work will develop a new approach to power system frequency regulation, with features suited to distributed energy storage devices such as grid-scale batteries and wind turbine speed and blade pitch control. The dynamic characteristics of these new technologies are treated along with existing mechanisms, such as synchronous machine governor control, to develop a comprehensive multi-input control design approach. To make the method practically feasible for geographically distributed power systems, an observer-based distributed control design utilizing phasor measurement unit (PMU) signals along with local measurements is developed. In addition to the system-wide objective of frequency regulation, a local objective of reducing the wind turbine drivetrain stress is considered. Also, an algorithm is proposed to characterize the modal degrees of controllability and observability on a subspace of critical modes of the system, so that the most effective sensor and actuator locations to be used in the control design can be found.

Techniques for analyzing frequency selective surfaces - A review

NASA Technical Reports Server (NTRS)

Mittra, Raj; Chan, Chi H.; Cwik, Tom

1988-01-01

A number of representative techniques for analyzing frequency-selective surfaces (FSSs), which comprise periodic arrays of patches or apertures in a conducting screen and find important applications as filters in microwaves and optics, are discussed. The basic properties of the FSSs are reviewed and several different approaches to predicting their frequency-response characteristics are described. Some recent developments in the treatment of truncated, curved, and doubly periodic screens are mentioned and representative experimental results are included.

Simulative research on generating UWB signals by all-optical BPF

NASA Astrophysics Data System (ADS)

Yang, Chunyong; Hou, Rui; Chen, Shaoping

2007-11-01

The simulating technique is used to investigate generating and distributing Ultra-Wide-Band signals depend on fiber transmission. Numerical result for the system about the frequency response shows that the characteristics of band-pass filter is presented, and the shorter the wavelength is, the bandwidth of lower frequency is wider. Transmission performance simulation for 12.5Gb/s psudo-random sequence also shows that Gaussian pulse signal after transported in fiber is similar to UWB wave pattern mask of FCC in time domain and frequency spectrum specification of FCC in frequency domain .

Non-tip auditory-nerve responses that are suppressed by low-frequency bias tones originate from reticular lamina motion.

PubMed

Nam, Hui; Guinan, John J

2017-12-14

Recent cochlear mechanical measurements show that active processes increase the motion response of the reticular lamina (RL) at frequencies more than an octave below the local characteristic frequency (CF) for CFs above 5 kHz. A possible correlate is that in high-CF (>5 kHz) auditory-nerve (AN) fibers, responses to frequencies 1-3 octaves below CF ("tail" frequencies) can be inhibited by medial olivocochlear (MOC) efferents. These results indicate that active processes enhance the sensitivity of tail-frequency RL and AN responses. Perhaps related is that some apical low-CF AN fibers have tuning-curve (TC) "side-lobe" response areas at frequencies above and below the TC-tip that are MOC inhibited. We hypothesized that the tail and side-lobe responses are enhanced by the same active mechanisms as CF cochlear amplification. If responses to CF, tail-frequency, and TC-side-lobe tones are all enhanced by prestin motility controlled by outer-hair-cell (OHC) transmembrane voltage, then they should depend on OHC stereocilia position in the same way. To test this, we cyclically changed the OHC-stereocilia mechano-electric-transduction (MET) operating point with low-frequency "bias" tones (BTs) and increased the BT level until the BT caused quasi-static OHC MET saturation that reduced or "suppressed" the gain of OHC active processes. While measuring cat AN-fiber responses, 50 Hz BT level series, 70-120 dB SPL, were run alone and with CF tones, or 2.5 kHz tail-frequency tones, or side-lobe tones. BT-tone-alone responses were used to exclude BT sound levels that produced AN responses that might obscure BT suppression. Data were analyzed to show the BT phase that suppressed the tone responses at the lowest sound level. We found that AN responses to CF, tail-frequency, and side-lobe tones were suppressed at the same BT phase in almost all cases. The data are consistent with the enhancement of responses to CF, tail-frequency, and side-lobe tones all being due to the same OHC-stereocilia MET-dependent active process. Thus, OHC active processes enhance AN responses at frequencies outside of the cochlear-amplified TC-tip region in both high- and low-frequency cochlear regions. The data are consistent with the AN response enhancements being due to enhanced RL motion that drives IHC-stereocilia deflection by traditional RL-TM shear and/or by changing the RL-TM gap. Since tail-frequency basilar membrane (BM) motion is not actively enhanced, the tail-frequency IHC drive is from a vibrational mode little present on the BM, not a "second filter" of BM motion. Copyright © 2017 Elsevier B.V. All rights reserved.

Female harbor seal (Phoca vitulina) behavioral response to playbacks of underwater male acoustic advertisement displays

PubMed Central

Blades, Brittany; Parks, Susan E.

2018-01-01

During the breeding season, male harbor seals (Phoca vitulina) make underwater acoustic displays using vocalizations known as roars. These roars have been shown to function in territory establishment in some breeding areas and have been hypothesized to be important for female choice, but the function of these sounds remains unresolved. This study consisted of a series of playback experiments in which captive female harbor seals were exposed to recordings of male roars to determine if females respond to recordings of male vocalizations and whether or not they respond differently to roars from categories with different acoustic characteristics. The categories included roars with characteristics of dominant males (longest duration, lowest frequency), subordinate males (shortest duration, highest frequency), combinations of call parameters from dominant and subordinate males (long duration, high frequency and short duration, low frequency), and control playbacks of water noise and water noise with tonal signals in the same frequency range as male signals. Results indicate that overall females have a significantly higher level of response to playbacks that imitate male vocalizations when compared to control playbacks of water noise. Specifically, there was a higher level of response to playbacks representing dominant male vocalization when compared to the control playbacks. For most individuals, there was a greater response to playbacks representing dominant male vocalizations compared to playbacks representing subordinate male vocalizations; however, there was no statistical difference between those two playback types. Additionally, there was no difference between the playbacks of call parameter combinations and the controls. Investigating female preference for male harbor seal vocalizations is a critical step in understanding the harbor seal mating system and further studies expanding on this captive study will help shed light on this important issue. PMID:29607261

Female harbor seal (Phoca vitulina) behavioral response to playbacks of underwater male acoustic advertisement displays.

PubMed

Matthews, Leanna P; Blades, Brittany; Parks, Susan E

2018-01-01

During the breeding season, male harbor seals ( Phoca vitulina ) make underwater acoustic displays using vocalizations known as roars. These roars have been shown to function in territory establishment in some breeding areas and have been hypothesized to be important for female choice, but the function of these sounds remains unresolved. This study consisted of a series of playback experiments in which captive female harbor seals were exposed to recordings of male roars to determine if females respond to recordings of male vocalizations and whether or not they respond differently to roars from categories with different acoustic characteristics. The categories included roars with characteristics of dominant males (longest duration, lowest frequency), subordinate males (shortest duration, highest frequency), combinations of call parameters from dominant and subordinate males (long duration, high frequency and short duration, low frequency), and control playbacks of water noise and water noise with tonal signals in the same frequency range as male signals. Results indicate that overall females have a significantly higher level of response to playbacks that imitate male vocalizations when compared to control playbacks of water noise. Specifically, there was a higher level of response to playbacks representing dominant male vocalization when compared to the control playbacks. For most individuals, there was a greater response to playbacks representing dominant male vocalizations compared to playbacks representing subordinate male vocalizations; however, there was no statistical difference between those two playback types. Additionally, there was no difference between the playbacks of call parameter combinations and the controls. Investigating female preference for male harbor seal vocalizations is a critical step in understanding the harbor seal mating system and further studies expanding on this captive study will help shed light on this important issue.

The ultrasonic characteristics of high frequency modulated arc and its application in material processing.

PubMed

He, Longbiao; Yang, Ping; Li, Luming; Wu, Minsheng

2014-12-01

To solve the difficulty of introducing traditional ultrasonic transducers to welding molten pool, high frequency current is used to modulate plasma arc and ultrasonic wave is excited successfully. The characteristics of the excited ultrasonic field are studied. The results show that the amplitude-frequency response of the ultrasonic emission is flat. The modulating current is the main factor influencing the ultrasonic power and the sound pressure depends on the variation of arc plasma stream force. Experimental study of the welding structure indicates grain refinement by the ultrasonic emission of the modulated arc and the test results showed there should be an energy region for the arc ultrasonic to get best welding joints. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental hingeless rotor characteristics at low advance ratio with thrust. [wind tunnel tests of rotary wing operating at moderate to high lift

NASA Technical Reports Server (NTRS)

London, R. J.; Watts, G. A.; Sissingh, G. J.

1973-01-01

An experimental investigation to determine the dynamic characteristics of a hingeless rotor operating at moderate to high lift was conducted on a small scale, 7.5-foot diameter, four-bladed hingeless rotor model in a 7 x 10-foot wind tunnel. The primary objective of this research program was the empirical determination of the rotor steady-state and frequency responses to swashplate and body excitations. Collective pitch was set from 0 to 20 degrees, with the setting at a particular advance ratio limited by the cyclic pitch available for hub moment trim. Advance ratio varied from 0.00 to 0.36 for blades with nondimensional first-flap frequencies at 1.15, 1.28 and 1.33 times the rotor rotation frequency. Several conditions were run with the rotor operating in the transition regime. Rotor response at high lift is shown to be generally nonlinear in this region. As a secondary objective an experimental investigation of the rotor response to 4/revolution swashplate excitations at advance ratios of 0.2 to 0.85 and at a nondimensional, first-flap modal frequency of 1.34 was also conducted, using the 7 x 10-foot wind tunnel. It is shown that 4/revolution swashplate inputs are a method for substantially reducing rotor-induced, shafttransmitted vibratory forces.

Pattern reversal responses in man and cat: a comparison.

PubMed

Schuurmans, R P; Berninger, T

1984-01-01

In 42 enucleated and arterially perfused cat eyes, graded potentials were recorded from the retina (ERG) and from the optic nerve ( ONR ) in response to checker-board stimuli, reversing at a low temporal frequency in a square wave mode. The ERG and ONR responses show an almost perfect duplication of the response to each reversal of the pattern and exhibit, in contrast to luminance responses, striking similarities in response characteristics such as amplitude, wave shape and time course. Furthermore, the amplitude versus check size plots coincide in both responses. In cat, pattern reversal responses can be recorded from 74 to 9 min of arc, correlating to the cat's visual resolution. In man, almost identical responses can be recorded for the pattern ERG. However, in accordance with the difference in visual resolution in man and cat, a parallel shift for the human pattern reversal ERG response to higher spatial frequencies is observed.

The Frequency Versus Length Response for a Deformed SLIFER Cable.

DTIC Science & Technology

1980-02-01

lux- 0 Vph where o M the frequency of the oscillator when the length of the shorted cable is zero (it depends only on the internal inductance of the...form of Eq. (2) that takes into account the characteristic impedance of the cable. x = harctan Y j- x tan . (12) WX cWxW( Vph ) For a co-axial cable, the

Parametric traveling wave amplifier with a low pump frequency

NASA Astrophysics Data System (ADS)

Marchenko, V. F.; Streltsov, A. M.; Zhmurov, S. E.

1983-01-01

Consideration is given to the model of a parametric traveling wave amplifier with a cubic nonlinearity in the form of an LF filter with MOS varactors. The operation of the amplifier is analyzed with allowance for wave damping and nonlinearity saturation, and the nonlinear mode of operation is examined. Experimental results are discussed, with emphasis on the amplitude-frequency response characteristics.

Response of a hypersonic boundary layer to freestream pulse acoustic disturbance.

PubMed

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter.

Response of a Hypersonic Boundary Layer to Freestream Pulse Acoustic Disturbance

PubMed Central

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter. PMID:24737993

Multiscale energy reallocation during low-frequency steady-state brain response.

PubMed

Wang, Yifeng; Chen, Wang; Ye, Liangkai; Biswal, Bharat B; Yang, Xuezhi; Zou, Qijun; Yang, Pu; Yang, Qi; Wang, Xinqi; Cui, Qian; Duan, Xujun; Liao, Wei; Chen, Huafu

2018-05-01

Traditional task-evoked brain activations are based on detection and estimation of signal change from the mean signal. By contrast, the low-frequency steady-state brain response (lfSSBR) reflects frequency-tagging activity at the fundamental frequency of the task presentation and its harmonics. Compared to the activity at these resonant frequencies, brain responses at nonresonant frequencies are largely unknown. Additionally, because the lfSSBR is defined by power change, we hypothesize using Parseval's theorem that the power change reflects brain signal variability rather than the change of mean signal. Using a face recognition task, we observed power increase at the fundamental frequency (0.05 Hz) and two harmonics (0.1 and 0.15 Hz) and power decrease within the infra-slow frequency band (<0.1 Hz), suggesting a multifrequency energy reallocation. The consistency of power and variability was demonstrated by the high correlation (r > .955) of their spatial distribution and brain-behavior relationship at all frequency bands. Additionally, the reallocation of finite energy was observed across various brain regions and frequency bands, forming a particular spatiotemporal pattern. Overall, results from this study strongly suggest that frequency-specific power and variability may measure the same underlying brain activity and that these results may shed light on different mechanisms between lfSSBR and brain activation, and spatiotemporal characteristics of energy reallocation induced by cognitive tasks. © 2018 Wiley Periodicals, Inc.

Neuro-muscular transmission in blood vessels: phasic and tonic components. An in-vitro study of mesenteric arteries of the rat.

PubMed

Sjöblom-Widfeldt, N

1990-01-01

For many years noradrenaline was considered to be the exclusive transmitter released from sympathetic nerves. However, during recent years both ATP and NPY have been suggested to be co-transmitters to noradrenaline in these nerves. The present study aimed to investigate the functional relationship between these suggested transmitters during nerve stimulation with different frequencies and in different extracellular calcium concentrations. Also the importance of the pattern of nerve stimulation and the potentiation of the neurogenic response after a period of high-frequency nerve stimulation were investigated. Contractions caused by nerve stimulation and applied agonists were investigated in segments of small mesenteric arteries from rat. The biophysical, electrophysiological, and pharmacological properties of these vessels are well characterized in previous studies. The rapid contraction caused by a single nerve stimulus, the "single twitch", and the initial, phasic contraction caused by high-frequency nerve stimulation were only slightly affected by alpha-adrenoceptor blockade with prazosin, whereas the tonic response to high-frequency stimulation was markedly reduced. The phasic responses and those to low-frequency nerve stimulation thus appear to be due mainly to a non-adrenergic transmitter. After inhibiting the response to exogenous ATP by alpha beta-methylene ATP, the response to single impulses and to low-frequency nerve stimulation were markedly reduced, while those to high-frequency stimulation were unaffected. This suggests that ATP acts as a true transmitter in sympathetic nerves, being responsible mainly for rapid responses to low-frequency stimulation, and for the initial part of responses to high-frequency stimulation. When alpha beta-methylene ATP and prazosin were given in combination, no contraction was obtained during nerve stimulation at any frequency. However, if in this situation a contraction was induced by e.g. exogenous vasopressin, field stimulation caused a further, slow contraction. This additional response was undoubtedly neurogenic, but required high-frequency nerve stimulation. The response to nerve stimulation was found to be calcium-dependent, the calcium-dependency being more pronounced at low than at high stimulation frequencies. A continuous, high-frequency (8-16 Hz) nerve stimulation could greatly (5-15 fold) enhance the response to subsequent low-frequency nerve stimulation. This potentiation increased with the frequency of the conditioning stimulation and, within limits, with the number of impulses delivered. Also the extracellular calcium concentration during the conditioning stimulation determined the magnitude of the potentiation. This post-tetanic potentiation has many characteristics in common with the post-tetanic potentiation studied in the central and somatomotor nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)

Response of a 14-story Anchorage, Alaska, building in 2002 to two close earthquakes and two distant Denali fault earthquakes

USGS Publications Warehouse

Celebi, M.

2004-01-01

The recorded responses of an Anchorage, Alaska, building during four significant earthquakes that occurred in 2002 are studied. Two earthquakes, including the 3 November 2002 M7.9 Denali fault earthquake, with epicenters approximately 275 km from the building, generated long trains of long-period (>1 s) surface waves. The other two smaller earthquakes occurred at subcrustal depths practically beneath Anchorage and produced higher frequency motions. These two pairs of earthquakes have different impacts on the response of the building. Higher modes are more pronounced in the building response during the smaller nearby events. The building responses indicate that the close-coupling of translational and torsional modes causes a significant beating effect. It is also possible that there is some resonance occurring due to the site frequency being close to the structural frequency. Identification of dynamic characteristics and behavior of buildings can provide important lessons for future earthquake-resistant designs and retrofit of existing buildings. ?? 2004, Earthquake Engineering Research Institute.

Adaptive changes in echolocation sounds by Pipistrellus abramus in response to artificial jamming sounds.

PubMed

Takahashi, Eri; Hyomoto, Kiri; Riquimaroux, Hiroshi; Watanabe, Yoshiaki; Ohta, Tetsuo; Hiryu, Shizuko

2014-08-15

The echolocation behavior of Pipistrellus abramus during exposure to artificial jamming sounds during flight was investigated. Echolocation pulses emitted by the bats were recorded using a telemetry microphone mounted on the bats' backs, and their adaptation based on acoustic characteristics of emitted pulses was assessed in terms of jamming-avoidance responses (JARs). In experiment 1, frequency-modulated jamming sounds (3 ms duration) mimicking echolocation pulses of P. abramus were prepared. All bats showed significant increases in the terminal frequency of the frequency-modulated pulse by an average of 2.1-4.5 kHz when the terminal frequency of the jamming sounds was lower than the bats' own pulses. This frequency shift was not observed using jamming frequencies that overlapped with or were higher than the bats' own pulses. These findings suggest that JARs in P. abramus are sensitive to the terminal frequency of jamming pulses and that the bats' response pattern was dependent on the slight difference in stimulus frequency. In experiment 2, when bats were repeatedly exposed to a band-limited noise of 70 ms duration, the bats in flight more frequently emitted pulses during silent periods between jamming sounds, suggesting that the bats could actively change the timing of pulse emissions, even during flight, to avoid temporal overlap with jamming sounds. Our findings demonstrate that bats could adjust their vocalized frequency and emission timing during flight in response to acoustic jamming stimuli. © 2014. Published by The Company of Biologists Ltd.

Frequency-tuning characteristics of cervical and ocular vestibular evoked myogenic potentials induced by air-conducted tone bursts.

PubMed

Park, Hong Ju; Lee, In-Sik; Shin, Jung Eun; Lee, Yeo Jin; Park, Mun Su

2010-01-01

To better characterize both ocular and cervical vestibular evoked myogenic potentials (VEMP) responses at different frequencies of sound in 20 normal subjects. Cervical and ocular VEMPs were recorded. The intensities of sound stimulation decreased from the maximal intensity, until no responses were evoked. Thresholds, amplitudes, latencies and interaural amplitude difference ratio (IADR) at the maximal stimulation were calculated. Both tests showed the similar frequency tuning, with the lowest threshold and highest amplitude for 500-Hz tone-burst stimuli. Sound stimulation at 500Hz showed the response rates of 100% in both tests. Cervical VEMPs showed higher incidence than ocular VEMPs. Ocular VEMP thresholds were significantly higher than those of cervical VEMP. Cervical VEMP amplitudes were significantly higher than ocular VEMP amplitudes. IADRs of ocular and cervical VEMPs did not differ significantly. Ocular VEMP showed the similar frequency tuning to cervical VEMP. Cervical VEMP responses showed higher incidence, lower thresholds and larger amplitudes than ocular VEMP. Cervical VEMP is a more reliable measure than ocular VEMP, though the results of both tests will be complementary. Five hundred Hertz is the optimal frequency to use. Copyright 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

47 CFR 73.128 - AM stereophonic broadcasting.

Code of Federal Regulations, 2013 CFR

2013-10-01

... negative peaks of 100%. (ii) Stereophonic (L−R) modulated with audio tones of the same amplitude at the... characteristics: (1) The audio response of the main (L+R) channel shall conform to the requirements of the ANSI... (NRSC-1). (2) The left and right channel audio signals shall conform to frequency response limitations...

76 FR 28246 - Information Collection Requests Under OMB Review

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-16

... collection request to the Office of Management and Budget (OMB) for approval of an existing collection in use... characteristics and skills to serve as a Peace Corps Response Volunteer. OMB Control Number: 0420-pending. Title... of reference forms received: 1,000. e. Frequency of response: One time. f. Estimated average time to...

Linearized blade row compression component model. Stability and frequency response analysis of a J85-3 compressor

NASA Technical Reports Server (NTRS)

Tesch, W. A.; Moszee, R. H.; Steenken, W. G.

1976-01-01

NASA developed stability and frequency response analysis techniques were applied to a dynamic blade row compression component stability model to provide a more economic approach to surge line and frequency response determination than that provided by time-dependent methods. This blade row model was linearized and the Jacobian matrix was formed. The clean-inlet-flow stability characteristics of the compressors of two J85-13 engines were predicted by applying the alternate Routh-Hurwitz stability criterion to the Jacobian matrix. The predicted surge line agreed with the clean-inlet-flow surge line predicted by the time-dependent method to a high degree except for one engine at 94% corrected speed. No satisfactory explanation of this discrepancy was found. The frequency response of the linearized system was determined by evaluating its Laplace transfer function. The results of the linearized-frequency-response analysis agree with the time-dependent results when the time-dependent inlet total-pressure and exit-flow function amplitude boundary conditions are less than 1 percent and 3 percent, respectively. The stability analysis technique was extended to a two-sector parallel compressor model with and without interstage crossflow and predictions were carried out for total-pressure distortion extents of 180 deg, 90 deg, 60 deg, and 30 deg.

A review of responsive MRI contrast agents: 2005–2014

PubMed Central

Hingorani, Dina V.; Bernstein, Adam S.; Pagel, Mark D.

2014-01-01

This review focuses on MRI contrast agents that are responsive to a change in a physiological biomarker. The response mechanisms are dependent on six physicochemical characteristics, including the accessibility of water to the agent, tumbling time, proton exchange rate, electron spin state, MR frequency, or superparamagnetism of the agent. These characteristics can be affected by changes in concentrations or activities of enzymes, proteins, nucleic acids, metabolites, or metal ions, or changes in redox state, pH, temperature, or light. A total of 117 examples are presented, including examples that employ nuclei other than 1H, which attests to the creativity of multidisciplinary research efforts to develop responsive MRI contrast agents. PMID:25355685

Analysis of Nonlinear Dynamics in Linear Compressors Driven by Linear Motors

NASA Astrophysics Data System (ADS)

Chen, Liangyuan

2018-03-01

The analysis of dynamic characteristics of the mechatronics system is of great significance for the linear motor design and control. Steady-state nonlinear response characteristics of a linear compressor are investigated theoretically based on the linearized and nonlinear models. First, the influence factors considering the nonlinear gas force load were analyzed. Then, a simple linearized model was set up to analyze the influence on the stroke and resonance frequency. Finally, the nonlinear model was set up to analyze the effects of piston mass, spring stiffness, driving force as an example of design parameter variation. The simulating results show that the stroke can be obtained by adjusting the excitation amplitude, frequency and other adjustments, the equilibrium position can be adjusted by adjusting the DC input, and to make the more efficient operation, the operating frequency must always equal to the resonance frequency.

Criteria for Handling Qualities of Military Aircraft.

DTIC Science & Technology

1982-06-01

loop precognitive manner. The pilot is able to apply discrete, step-like inputs which more or less exactly produce the desired aircraft response. Some...While closed loop operation depends upon the frequency domain response characteristics, successful precognitive control requires the time domain...represents the other extreme of the pilot task from the precognitive time response situation. Mich work was done in attempting to predict pilot opinion from

Dynamic response analysis of surrounding rock under the continuous blasting seismic wave

NASA Astrophysics Data System (ADS)

Gao, P. F.; Zong, Q.; Xu, Y.; Fu, J.

2017-10-01

The blasting vibration that is caused by blasting excavation will generate a certain degree of negative effect on the stability of surrounding rock in underground engineering. A dynamic response analysis of surrounding rock under the continuous blasting seismic wave is carried out to optimize blasting parameters and guide underground engineering construction. Based on the theory of wavelet analysis, the reconstructed signals of each layer of different frequency bands are obtained by db8 wavelet decomposition. The difference of dynamic response of the continuous blasting seismic wave at a certain point caused by different blasting sources is discussed. The signal in the frequency band of natural frequency of the surrounding rock shows a certain degree of amplification effect deduced from the dynamic response characteristics of the surrounding rock under the influence of continuous blasting seismic wave. Continuous blasting operations in a fixed space will lead to the change of internal structure of the surrounding rock. It may result in the decline of natural frequency of the whole surrounding rock and it is also harmful for the stability of the surrounding rock.

The relationship of gender balance at work, family responsibilities and workplace characteristics to drinking among male and female attorneys.

PubMed

Shore, E R

1997-05-01

The purpose of this study was to investigate the relationship of gender balance at work, family and home responsibilities and workplace factors to the drinking behaviors of attorneys. Using a stratified random sampling procedure, attorneys were selected from the bar associations of two large Midwestern cities. Telephone interviews were completed with 300 men and 257 women (37.3% of those originally selected), who were asked about characteristics of their work, the numbers of female attorneys they had contact with in four types of working relationships, overall and work-related drinking, and family and home responsibilities. Multiple regression and discriminant analyses were used to study the influence of these variables on drinking. Gender balance variables entered several of the analyses. For both men and women the frequency of work-related drinking positively correlated with the number of female attorneys in the organization, but was negatively related to the number of women who were peers. Family and home responsibilities entered predictive equations, both positively and negatively, for both men and women. Size of firm was positively correlated with frequency of business-related drinking and, for men, with frequency of social drinking related to work. The influence of the gender composition of the workplace on drinking behaviors may vary, for both men and women, by the type of contact involved, with closer or more active involvement with female colleagues associated with decreased frequency of drinking. Work-related drinking may also be related to home and family demands and the size of the firm, again for both genders.

Clinical usefulness and feasibility of time-frequency analysis of chemosensory event-related potentials.

PubMed

Huart, C; Rombaux, Ph; Hummel, T; Mouraux, A

2013-09-01

The clinical usefulness of olfactory event-related brain potentials (OERPs) to assess olfactory function is limited by the relatively low signal-to-noise ratio of the responses identified using conventional time-domain averaging. Recently, it was shown that time-frequency analysis of the obtained EEG signals can markedly improve the signal-to-noise ratio of OERPs in healthy controls, because it enhances both phase-locked and non phase-locked EEG responses. The aim of the present study was to investigate the clinical usefulness of this approach and evaluate its feasibility in a clinical setting. We retrospectively analysed EEG recordings obtained from 45 patients (15 anosmic, 15 hyposmic and 15 normos- mic). The responses to olfactory stimulation were analysed using conventional time-domain analysis and joint time-frequency analysis. The ability of the two methods to discriminate between anosmic, hyposmic and normosmic patients was assessed using a Receiver Operating Characteristic analysis. The discrimination performance of OERPs identified using conventional time-domain averaging was poor. In contrast, the discrimination performance of the EEG response identified in the time-frequency domain was relatively high. Furthermore, we found a significant correlation between the magnitude of this response and the psychophysical olfactory score. Time-frequency analysis of the EEG responses to olfactory stimulation could be used as an effective and reliable diagnostic tool for the objective clinical evaluation of olfactory function in patients.

Contrasting responses of leaf stomatal characteristics to climate change: a considerable challenge to predict carbon and water cycles.

PubMed

Yan, Weiming; Zhong, Yangquanwei; Shangguan, Zhouping

2017-09-01

Stomata control the cycling of water and carbon between plants and the atmosphere; however, no consistent conclusions have been drawn regarding the response of stomatal frequency to climate change. Here, we conducted a meta-analysis of 1854 globally obtained data series to determine the response of stomatal frequency to climate change, which including four plant life forms (over 900 species), at altitudes ranging from 0 to 4500 m and over a time span of more than one hundred thousand years. Stomatal frequency decreased with increasing CO 2 concentration and increased with elevated temperature and drought stress; it was also dependent on the species and experimental conditions. The response of stomatal frequency to climate change showed a trade-off between stomatal control strategies and environmental factors, such as the CO 2 concentration, temperature, and soil water availability. Moreover, threshold effects of elevated CO 2 and temperature on stomatal frequency were detected, indicating that the response of stomatal density to increasing CO 2 concentration will decrease over the next few years. The results also suggested that the stomatal index may be more reliable than stomatal density for determination of the historic CO 2 concentration. Our findings indicate that the contrasting responses of stomata to climate change bring a considerable challenge in predicting future water and carbon cycles. © 2017 John Wiley & Sons Ltd.

Frequency Bandwidth Optimization of Left-Handed Metamaterial

NASA Technical Reports Server (NTRS)

Chevalier, Christine T.; Wilson, Jeffrey D.

2004-01-01

Recently, left-handed metamaterials (LHM s) have been demonstrated with an effective negative index of refraction and with antiparallel group and phase velocities for microwave radiation over a narrow frequency bandwidth. In order to take advantage of these characteristics for practical applications, it will be beneficial to develop LHM s with increased frequency bandwidth response and lower losses. In this paper a commercial three-dimensional electromagnetic simulation code is used to explore the effects of geometry parameter variations on the frequency bandwidth of a LHM at microwave frequencies. Utilizing an optimizing routine in the code, a geometry was generated with a bandwidth more than twice as large as the original geometry.

Changes in Infants' Vocalizations as a Function of Differential Acoustic Stimulation

ERIC Educational Resources Information Center

Webster, R. L.; And Others

1972-01-01

Results of this study indicated that the frequency of an auditory stimulus is a dimension to which infants differentially respond in terms of response rate and acoustic characteristics of their vocalizations. (Authors)

Analysis of multidimensional difference-of-Gaussians filters in terms of directly observable parameters.

PubMed

Cope, Davis; Blakeslee, Barbara; McCourt, Mark E

2013-05-01

The difference-of-Gaussians (DOG) filter is a widely used model for the receptive field of neurons in the retina and lateral geniculate nucleus (LGN) and is a potential model in general for responses modulated by an excitatory center with an inhibitory surrounding region. A DOG filter is defined by three standard parameters: the center and surround sigmas (which define the variance of the radially symmetric Gaussians) and the balance (which defines the linear combination of the two Gaussians). These parameters are not directly observable and are typically determined by nonlinear parameter estimation methods applied to the frequency response function. DOG filters show both low-pass (optimal response at zero frequency) and bandpass (optimal response at a nonzero frequency) behavior. This paper reformulates the DOG filter in terms of a directly observable parameter, the zero-crossing radius, and two new (but not directly observable) parameters. In the two-dimensional parameter space, the exact region corresponding to bandpass behavior is determined. A detailed description of the frequency response characteristics of the DOG filter is obtained. It is also found that the directly observable optimal frequency and optimal gain (the ratio of the response at optimal frequency to the response at zero frequency) provide an alternate coordinate system for the bandpass region. Altogether, the DOG filter and its three standard implicit parameters can be determined by three directly observable values. The two-dimensional bandpass region is a potential tool for the analysis of populations of DOG filters (for example, populations of neurons in the retina or LGN), because the clustering of points in this parameter space may indicate an underlying organizational principle. This paper concentrates on circular Gaussians, but the results generalize to multidimensional radially symmetric Gaussians and are given as an appendix.

Dimensionless figure of merit and its efficiency estimation for transient response of thermoelectric module based on impedance spectroscopy

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Hasegawa, Yasuhiro; Arisaka, Taichi; Shinozaki, Ryo; Morita, Hiroyuki

2017-11-01

The dimensionless figure of merit and its efficiency for the transient response of a Π-shaped thermoelectric module are estimated according to the theory of impedance spectroscopy. The effective dimensionless figure of merit is described as a function of the product of the characteristic time to reduce the temperature and the representative angular frequency of the module, which is expressed by the thermal diffusivity and the length of the elements used. The characteristic time required for achieving a higher dimensionless figure of merit and efficiency is derived quantitatively for the transient response using the properties of a commercial thermoelectric module.

Extended frequency turbofan model

NASA Technical Reports Server (NTRS)

Mason, J. R.; Park, J. W.; Jaekel, R. F.

1980-01-01

The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine.

Efferent control of temporal response properties of the Limulus lateral eye

PubMed Central

1990-01-01

The sensitivity of the Limulus lateral eye exhibits a pronounced circadian rhythm. At night a circadian oscillator in the brain activates efferent fibers in the optic nerve, inducing multiple changes in the physiological and anatomical characteristics of retinal cells. These changes increase the sensitivity of the retina by about five orders of magnitude. We investigated whether this increase in retinal sensitivity is accompanied by changes in the ability of the retina to process temporal information. We measured the frequency transfer characteristic (FTC) of single receptors (ommatidia) by recording the response of their optic nerve fibers to sinusoidally modulated light. We first measured the FTC in the less sensitive daytime state and then after converting the retina to the more sensitive nighttime state by electrical stimulation of the efferent fibers. The activation of these fibers shifted the peak of the FTC to lower frequencies and reduced the slope of the low-frequency limb. These changes reduce the eye's ability to detect rapid changes in light intensity but enhance its ability to detect dim flashes of light. Apparently Limulus sacrifices temporal resolution for increased visual sensitivity at night. PMID:2307958

Interference of Overlapping Insect Vibratory Communication Signals: An Eushistus heros Model

PubMed Central

Čokl, Andrej; Laumann, Raul Alberto; Žunič Kosi, Alenka; Blassioli-Moraes, Maria Carolina; Virant-Doberlet, Meta; Borges, Miguel

2015-01-01

Plants limit the range of insect substrate-borne vibratory communication by their architecture and mechanical properties that change transmitted signal time, amplitude and frequency characteristics. Stinkbugs gain higher signal-to-noise ratio and increase communication distance by emitting narrowband low frequency vibratory signals that are tuned with transmission properties of plants. The objective of the present study was to investigate hitherto overlooked consequences of duetting with mutually overlapped narrowband vibratory signals. The overlapped vibrations of the model stinkbug species Eushistus heros, produced naturally or induced artificially on different plants, have been analysed. They represent female and male strategies to preserve information within a complex masked signal. The brown stinkbugs E. heros communicate with species and gender specific vibratory signals that constitute characteristic duets in the calling, courtship and rivalry phases of mating behaviour. The calling female pulse overlaps the male vibratory response when the latency of the latter is shorter than the duration of the female triggering signal or when the male response does not inhibit the following female pulse. Overlapping of signals induces interference that changes their amplitude pattern to a sequence of regularly repeated pulses in which their duration and the difference between frequencies of overlapped vibrations are related inversely. Interference does not occur in overlapped narrow band female calling pulses and broadband male courtship pulse trains. In a duet with overlapped signals females and males change time parameters and increase the frequency difference between signals by changing the frequency level and frequency modulation pattern of their calls. PMID:26098637

Effect of temperature oscillation on thermal characteristics of an aluminum thin film

NASA Astrophysics Data System (ADS)

Ali, H.; Yilbas, B. S.

2014-12-01

Energy transport in aluminum thin film is examined due to temperature disturbance at the film edge. Thermal separation of electron and lattice systems is considered in the analysis, and temperature variation in each sub-system is formulated. The transient analysis of frequency-dependent and frequency-independent phonon radiative transport incorporating electron-phonon coupling is carried out in the thin film. The dispersion relations of aluminum are used in the frequency-dependent analysis. Temperature at one edge of the film is oscillated at various frequencies, and temporal response of phonon intensity distribution in the film is predicted numerically using the discrete ordinate method. To assess the phonon transport characteristics, equivalent equilibrium temperature is introduced. It is found that equivalent equilibrium temperature in the electron and lattice sub-systems oscillates due to temperature oscillation at the film edge. The amplitude of temperature oscillation reduces as the distance along the film thickness increases toward the low-temperature edge of the film. Equivalent equilibrium temperature attains lower values for the frequency-dependent solution of the phonon transport equation than that corresponding to frequency-independent solution.

Improving Drive Files for Vehicle Road Simulations

NASA Astrophysics Data System (ADS)

Cherng, John G.; Goktan, Ali; French, Mark; Gu, Yi; Jacob, Anil

2001-09-01

Shaker tables are commonly used in laboratories for automotive vehicle component testing to study durability and acoustics performance. An example is development testing of car seats. However, it is difficult to repeat the measured road data perfectly with the response of a shaker table as there are basic differences in dynamic characteristics between a flexible vehicle and substantially rigid shaker table. In addition, there are performance limits in the shaker table drive systems that can limit correlation. In practice, an optimal drive signal for the actuators is created iteratively. During each iteration, the error between the road data and the response data is minimised by an optimising algorithm which is generally a part of the feed back loop of the shake table controller. This study presents a systematic investigation to the errors in time and frequency domains as well as joint time-frequency domain and an evaluation of different digital signal processing techniques that have been used in previous work. In addition, we present an innovative approach that integrates the dynamic characteristics of car seats and the human body into the error-minimising iteration process. We found that the iteration process can be shortened and the error reduced by using a weighting function created by normalising the frequency response function of the car seat. Two road data test sets were used in the study.

Biomechanics and Biotensegrity: Study Method and Frequency Response of the Simplex and 3-bar-SVD Tensegrity Configurations

NASA Astrophysics Data System (ADS)

Castro Arenas, C.; Ghersi, I.; Miralles, M. T.

2016-04-01

The purpose of this work is to study the frequency response of 3D tensegrity structures. These are structures that have been used, since the 80’s, to model biological systems of different scales. This fact led to the origin of the field of biotensegrity, which includes biomechanics as a natural field of application. In this work: a) A simple method for the analysis of frequency response of different nodes in 3D tensegrity structures was set up and tuned. This method is based on a video-analysis algorithm, which was applied to the structures, as they were vibrated along their axis of symmetry, at frequencies from 1 Hz to 60 Hz. b) Frequency-response analyses were performed, for the simplest 3D structure, the Simplex module, as well as for two towers, formed by stacking two and three Simplex modules, respectively. Resonant frequencies were detected for the Simplex module at (19.2±0.1) Hz and (50.2±0.1) Hz (the latter being an average of frequencies between homologous nodes). For the towers with two and three modules, each selected node presented a characteristic frequency response, modulated by their spatial placement in each model. Resonances for the two-stage tower were found at: (12±0.1) Hz; (16.2±0.1) Hz; (29.4±0.1) Hz and (37.2±0.1) Hz. For the tower with three Simplex modules, the main resonant frequencies were found at (12.0±0.1) Hz and (21.0±0.1) Hz. Results show that the proposed method is adequate for the study (2D) of any 3D tensegrity structure, with the potential of being generalized to the study of oscillations in three dimensions. A growing complexity and variability in the frequency response of the nodes was observed, as modules were added to the structures. These findings were compared to those found in the available literature.

Direct system parameter identification of mechanical structures with application to modal analysis

NASA Technical Reports Server (NTRS)

Leuridan, J. M.; Brown, D. L.; Allemang, R. J.

1982-01-01

In this paper a method is described to estimate mechanical structure characteristics in terms of mass, stiffness and damping matrices using measured force input and response data. The estimated matrices can be used to calculate a consistent set of damped natural frequencies and damping values, mode shapes and modal scale factors for the structure. The proposed technique is attractive as an experimental modal analysis method since the estimation of the matrices does not require previous estimation of frequency responses and since the method can be used, without any additional complications, for multiple force input structure testing.

47 CFR 2.1047 - Measurements required: Modulation characteristics.

Code of Federal Regulations, 2013 CFR

2013-10-01

... equipment. A curve or equivalent data showing the frequency response of the audio modulating circuit over a range of 100 to 5000 Hz shall be submitted. For equipment required to have an audio low-pass filter, a...

47 CFR 2.1047 - Measurements required: Modulation characteristics.

Code of Federal Regulations, 2014 CFR

2014-10-01

... equipment. A curve or equivalent data showing the frequency response of the audio modulating circuit over a range of 100 to 5000 Hz shall be submitted. For equipment required to have an audio low-pass filter, a...

Dynamic characteristics of heart rate control by the autonomic nervous system in rats.

PubMed

Mizuno, Masaki; Kawada, Toru; Kamiya, Atsunori; Miyamoto, Tadayoshi; Shimizu, Shuji; Shishido, Toshiaki; Smith, Scott A; Sugimachi, Masaru

2010-09-01

We estimated the transfer function of autonomic heart rate (HR) control by using random binary sympathetic or vagal nerve stimulation in anaesthetized rats. The transfer function from sympathetic stimulation to HR response approximated a second-order, low-pass filter with a lag time (gain, 4.29 +/- 1.55 beats min(1) Hz(1); natural frequency, 0.07 +/- 0.03 Hz; damping coefficient, 1.96 +/- 0.64; and lag time, 0.73 +/- 0.12 s). The transfer function from vagal stimulation to HR response approximated a first-order, low-pass filter with a lag time (gain, 8.84 +/- 4.51 beats min(1) Hz(1); corner frequency, 0.12 +/- 0.06 Hz; and lag time, 0.12 +/- 0.08 s). These results suggest that the dynamic characteristics of HR control by the autonomic nervous system in rats are similar to those of larger mammals.

New lumped-mass-stick model based on modal characteristics of structures: development and application to a nuclear containment building

NASA Astrophysics Data System (ADS)

Roh, Hwasung; Lee, Huseok; Lee, Jong Seh

2013-06-01

In this study, a new lumped-mass-stick model (LMSM) is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the "frequency adaptive lumped-massstick model," hasonly a small number of stick elements and nodes to provide the same natural frequencies of the structure and is applied to a nuclear containment building. To investigate the numerical performance of the LMSM, a time history analysis is carried out on both the LMSM and the finite element model (FEM) for a nuclear containment building. A comparison of the results shows that the dynamic responses of the LMSM in terms of displacement and acceleration are almost identical to those of the FEM. In addition, the results in terms of fl oor response spectra at certain elevations are also in good agreement.

Characteristic analysis of a photoexcited metamaterial perfect absorber at terahertz frequencies

NASA Astrophysics Data System (ADS)

Bing, Pibin; Huang, Shichao; Li, Zhongyang; Yu, Zhou; Lu, Ying; Yao, Jianquan

2017-06-01

The absorption characteristics of a photoexcited metamaterial absorber at terahertz frequencies were analyzed in this study. Filling photosensitive semiconductor silicon into the gap between the resonator arms leads to modulation of its electromagnetic response through a pump beam which changes conductivity of silicon. Comparisons of terahertz absorbing properties which were caused by different thicknesses and dielectric constants of polyimide, cell sizes and widths of SRRs, and lengths and conductivities of the photosensitive silicon, were studied by using Finite Difference Time Domain (FDTD) from 0.4 THz to 1.6 THz. The results of this study will facilitate the design and preparation of terahertz modulator, filters and absorbers.

Dynamic response characteristics of dual flow-path integrally bladed rotors

NASA Astrophysics Data System (ADS)

Beck, Joseph A.; Brown, Jeffrey M.; Scott-Emuakpor, Onome E.; Cross, Charles J.; Slater, Joseph C.

2015-02-01

New turbine engine designs requiring secondary flow compression often look to dual flow-path integrally bladed rotors (DFIBRs) since these stages have the ability to perform work on the secondary, or bypassed, flow-field. While analogous to traditional integrally bladed rotor stages, DFIBR designs have many differences that result in unique dynamic response characteristics that must be understood to avoid fatigue. This work investigates these characteristics using reduced-order models (ROMs) that incorporate mistuning through perturbations to blade frequencies. This work provides an alternative to computationally intensive geometric-mistuning approaches for DFIBRs by utilizing tuned blade mode reductions and substructure coupling in cyclic coordinates. Free and forced response results are compared to full finite element model (FEM) solutions to determine if any errors are related to the reduced-order model formulation reduction methods. It is shown that DFIBRs have many more frequency veering regions than their single flow-path integrally blade rotor (IBR) counterparts. Modal families are shown to transition between system, inner-blade, and outer-blade motion. Furthermore, findings illustrate that while mode localization of traditional IBRs is limited to a single or small subset of blades, DFIBRs can have modal energy localized to either an inner- or outer-blade set resulting in many blades responding above tuned levels. Lastly, ROM forced response predictions compare well to full FEM predictions for the two test cases shown.

Characteristics of Physical Training Activities of West Coast U.S. Navy Sea-Air-Land Personnel (SEALS)

DTIC Science & Technology

1992-11-01

REPETITIONS, OR LOADS VARY. USE TIHE AVERAGE FOR YOUR RESPONSE TO THIESE QUESTIONS Body Weight: _ pounds I Repetition Average Exercise Maximum Sets...Sea, Air, Land (SEAL) personnel undergoing advanced training. Responses to this questionnaire provided information on the types, frequencies, and...their responses were used to characterize training activity according to the American College of Sports Medicine guidelines for maintenance of aerobic

Control of a flexible link by shaping the closed loop frequency response function through optimised feedback filters

NASA Astrophysics Data System (ADS)

Del Vescovo, D.; D'Ambrogio, W.

1995-01-01

A frequency domain method is presented to design a closed-loop control for vibration reduction flexible mechanisms. The procedure is developed on a single-link flexible arm, driven by one rotary degree of freedom servomotor, although the same technique may be applied to similar systems such as supports for aerospace antennae or solar panels. The method uses the structural frequency response functions (FRFs), thus avoiding system identification, that produces modeling uncertainties. Two closed-loops are implemented: the inner loop uses acceleration feedback with the aim of making the FRF similar to that of an equivalent rigid link; the outer loop feeds back displacements to achieve a fast positioning response and null steady state error. In both cases, the controller type is established a priori, while actual characteristics are defined by an optimisation procedure in which the relevant FRF is constrained into prescribed bounds and stability is taken into account.

Dynamic Characteristics of Simple Cylindrical Hydraulic Engine Mount Utilizing Air Compressibility

NASA Astrophysics Data System (ADS)

Nakahara, Kazunari; Nakagawa, Noritoshi; Ohta, Katsutoshi

A cylindrical hydraulic engine mount with simple construction has been developed. This engine mount has a sub chamber formed by utilizing air compressibility without a diaphragm. A mathematical model of the mount is presented to predict non-linear dynamic characteristics in consideration of the effect of the excitation amplitude on the storage stiffness and loss factor. The mathematical model predicts experimental results well for the frequency responses of the storage stiffness and loss factor over the frequency range of 5 Hz to 60Hz. The effect of air volume and internal pressure on the dynamic characteristics is clarified by the analysis and dynamic characterization testing. The effectiveness of the cylindrical hydraulic engine mount on the reduction of engine shake is demonstrated for riding comfort through on-vehicle testing with a chassis dynamometer.

Input-output characterization of an ultrasonic testing system by digital signal analysis

NASA Technical Reports Server (NTRS)

Karaguelle, H.; Lee, S. S.; Williams, J., Jr.

1984-01-01

The input/output characteristics of an ultrasonic testing system used for stress wave factor measurements were studied. The fundamentals of digital signal processing are summarized. The inputs and outputs are digitized and processed in a microcomputer using digital signal processing techniques. The entire ultrasonic test system, including transducers and all electronic components, is modeled as a discrete-time linear shift-invariant system. Then the impulse response and frequency response of the continuous time ultrasonic test system are estimated by interpolating the defining points in the unit sample response and frequency response of the discrete time system. It is found that the ultrasonic test system behaves as a linear phase bandpass filter. Good results were obtained for rectangular pulse inputs of various amplitudes and durations and for tone burst inputs whose center frequencies are within the passband of the test system and for single cycle inputs of various amplitudes. The input/output limits on the linearity of the system are determined.

Rate and timing cues associated with the cochlear amplifier: level discrimination based on monaural cross-frequency coincidence detection.

PubMed

Heinz, M G; Colburn, H S; Carney, L H

2001-10-01

The perceptual significance of the cochlear amplifier was evaluated by predicting level-discrimination performance based on stochastic auditory-nerve (AN) activity. Performance was calculated for three models of processing: the optimal all-information processor (based on discharge times), the optimal rate-place processor (based on discharge counts), and a monaural coincidence-based processor that uses a non-optimal combination of rate and temporal information. An analytical AN model included compressive magnitude and level-dependent-phase responses associated with the cochlear amplifier, and high-, medium-, and low-spontaneous-rate (SR) fibers with characteristic frequencies (CFs) spanning the AN population. The relative contributions of nonlinear magnitude and nonlinear phase responses to level encoding were compared by using four versions of the model, which included and excluded the nonlinear gain and phase responses in all possible combinations. Nonlinear basilar-membrane (BM) phase responses are robustly encoded in near-CF AN fibers at low frequencies. Strongly compressive BM responses at high frequencies near CF interact with the high thresholds of low-SR AN fibers to produce large dynamic ranges. Coincidence performance based on a narrow range of AN CFs was robust across a wide dynamic range at both low and high frequencies, and matched human performance levels. Coincidence performance based on all CFs demonstrated the "near-miss" to Weber's law at low frequencies and the high-frequency "mid-level bump." Monaural coincidence detection is a physiologically realistic mechanism that is extremely general in that it can utilize AN information (average-rate, synchrony, and nonlinear-phase cues) from all SR groups.

Comparison of air-charged and water-filled urodynamic pressure measurement catheters.

PubMed

Cooper, M A; Fletter, P C; Zaszczurynski, P J; Damaser, M S

2011-03-01

Catheter systems are utilized to measure pressure for diagnosis of voiding dysfunction. In a clinical setting, patient movement and urodynamic pumps introduce hydrostatic and motion artifacts into measurements. Therefore, complete characterization of a catheter system includes its response to artifacts as well its frequency response. The objective of this study was to compare the response of two disposable clinical catheter systems: water-filled and air-charged, to controlled pressure signals to assess their similarities and differences in pressure transduction. We characterized frequency response using a transient step test, which exposed the catheters to a sudden change in pressure; and a sinusoidal frequency sweep test, which exposed the catheters to a sinusoidal pressure wave from 1 to 30 Hz. The response of the catheters to motion artifacts was tested using a vortex and the response to hydrostatic pressure changes was tested by moving the catheter tips to calibrated heights. Water-filled catheters acted as an underdamped system, resonating at 10.13 ± 1.03 Hz and attenuating signals at frequencies higher than 19 Hz. They demonstrated significant motion and hydrostatic artifacts. Air-charged catheters acted as an overdamped system and attenuated signals at frequencies higher than 3.02 ± 0.13 Hz. They demonstrated significantly less motion and hydrostatic artifacts than water-filled catheters. The transient step and frequency sweep tests gave comparable results. Air-charged and water-filled catheters respond to pressure changes in dramatically different ways. Knowledge of the characteristics of the pressure-measuring system is essential to finding the best match for a specific application. Copyright © 2011 Wiley-Liss, Inc.

Modeling and performance analysis of an all-optical photonic microwave filter in the frequency range of 0.01-15 GHz

NASA Astrophysics Data System (ADS)

Aguayo-Rodríguez, Gustavo; Zaldívar-Huerta, Ignacio E.; Rodríguez-Asomoza, Jorge; García-Juárez, Alejandro; Alonso-Rubio, Paul

2010-01-01

The generation, distribution and processing of microwave signals in the optical domain is a topic of research due to many advantages such as low loss, light weight, broadband width, and immunity to electromagnetic interference. In this sense, a novel all-optical microwave photonic filter scheme is proposed and experimentally demonstrated in the frequency range of 0.01-15.0 GHz. A microwave signal generated by optical mixing drives the microwave photonic filter. Basically, photonic filter is composed by a multimode laser diode, an integrated Mach- Zehnder intensity modulator, and 28.3-Km of single-mode standard fiber. Frequency response of the microwave photonic filter depends of the emission spectral characteristics of the multimode laser diode, the physical length of the single-mode standard fiber, and the chromatic dispersion factor associated to this type of fiber. Frequency response of the photonic filter is composed of a low-pass band centered at zero frequency, and several band-pass lobes located periodically on the microwave frequency range. Experimental results are compared by means of numerical simulations in Matlab exhibiting a small deviation in the frequency range of 0.01-5.0 GHz. However, this deviation is more evident when higher frequencies are reached. In this paper, we evaluate the causes of this deviation in the range of 5.0-15.0 GHz analyzing the parameters involved in the frequency response. This analysis permits to improve the performance of the photonic microwave filter to higher frequencies.

Electro-optical effects in porous PET films filled with liquid crystal: new possibilities for fiber optics and THZ applications.

PubMed

Chopik, A; Pasechnik, S; Semerenko, D; Shmeliova, D; Dubtsov, A; Srivastava, A K; Chigrinov, V

2014-03-15

The results of investigation of electro-optical properties of porous polyethylene terephthalate films filled with a nematic liquid crystal (5 CB) are presented. It is established that the optical response of the samples on the applied voltage drastically depends on the frequency range. At low frequencies of applied electrical field (ffc) electric field induces an overall change in the light intensity, which is typical for an electro-optical response of a liquid crystal (LC) layer in a conventional "sandwich"-like cell. The dependences of critical frequency fc, threshold voltages, and characteristic times on a pore diameter d were established. The peculiarities of electro-optical effects can be explained in the framework of the approach which connects the variations of light intensity with the corresponding changes of the effective refractive index n(eff) of a composite LC media. The unusual behavior of the electro-optical response at low frequencies is assigned to the orienting action of the specific shear flow typical for electrokinetic phenomena in polar liquids.

[Clinical characteristics and disease course in patients treated with efalizumab following suspension of marketing authorization by the European medicines agency: a multicenter observational study].

PubMed

Morell, L; Carrascosa, J M; Ferrándiz, C; García-Bustinduy, M; Fonseca, E; Carretero, G; Daudén, E; Marrón, S E; López-Estebaranz, J L; Ferrán, M; Sánchez-Regaña, M; Muñoz-Santos, C; Belinchón, I; Puig, Luis

2011-06-01

The withdrawal of marketing authorization for efalizumab by the European Medicines Agency in February, 2009 provided a unique opportunity to assess the course of disease in patients who were not subject to the selection criteria and biases that were common in the pivotal trials. The aim of this study was to evaluate the course of psoriasis following forced suspension of efalizumab in a group of patients treated in normal clinical practice. As secondary objectives, we sought to assess the relationships between clinical characteristics, treatment response, and disease course during efalizumab treatment and 12 and 24 weeks after suspension. Information on the epidemiological profile and disease course during treatment and following suspension of the drug was collected from a group of patients treated with efalizumab. Statistical analyses were performed to identify predictive factors. One hundred forty-seven patients from 12 Spanish hospitals were included in the study. During treatment, 4% of patients were diagnosed with generalized inflammatory flares. Most patients could be classified as having a good (55%) or moderate (18%) response to treatment. Rebound following withdrawal of efalizumab was observed in 30% of patients. The likelihood of rebound was independent of clinical characteristics, treatment response, or therapeutic approach used by the dermatologist following suspension. There was a high frequency of rebound following suspension of efalizumab, exceeding the rate reported in pivotal trials. This is particularly noteworthy given the large proportion of patients with a good response to treatment and therefore believed to have a better prognosis. Other significant findings were the higher frequency of positive treatment response than observed in previous studies (possibly influenced by the mean treatment duration) and the high frequency of generalized inflammatory flares. 2010 Elsevier España, S.L. y AEDV. All rights reserved.

Aurally-adequate time-frequency analysis for scattered sound in auditoria

NASA Astrophysics Data System (ADS)

Norris, Molly K.; Xiang, Ning; Kleiner, Mendel

2005-04-01

The goal of this work was to apply an aurally-adequate time-frequency analysis technique to the analysis of sound scattering effects in auditoria. Time-frequency representations were developed as a motivated effort that takes into account binaural hearing, with a specific implementation of interaural cross-correlation process. A model of the human auditory system was implemented in the MATLAB platform based on two previous models [A. Härmä and K. Palomäki, HUTear, Espoo, Finland; and M. A. Akeroyd, A. Binaural Cross-correlogram Toolbox for MATLAB (2001), University of Sussex, Brighton]. These stages include proper frequency selectivity, the conversion of the mechanical motion of the basilar membrane to neural impulses, and binaural hearing effects. The model was then used in the analysis of room impulse responses with varying scattering characteristics. This paper discusses the analysis results using simulated and measured room impulse responses. [Work supported by the Frank H. and Eva B. Buck Foundation.

Engineering Inertial and Primary-Frequency Response for Distributed Energy Resources: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dall-Anese, Emiliano; Zhao, Changhong; Guggilam, Swaroop

We propose a framework to engineer synthetic-inertia and droop-control parameters for distributed energy resources (DERs) so that the system frequency in a network composed of DERs and synchronous generators conforms to prescribed transient and steady-state performance specifications. Our approach is grounded in a second-order lumped-parameter model that captures the dynamics of synchronous generators and frequency-responsive DERs endowed with inertial and droop control. A key feature of this reduced-order model is that its parameters can be related to those of the originating higher-order dynamical model. This allows one to systematically design the DER inertial and droop-control coefficients leveraging classical frequency-domain responsemore » characteristics of second-order systems. Time-domain simulations validate the accuracy of the model-reduction method and demonstrate how DER controllers can be designed to meet steady-state-regulation and transient-performance specifications.« less

Engineering Inertial and Primary-Frequency Response for Distributed Energy Resources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dall-Anese, Emiliano; Zhao, Changhong; Guggilam, Swaroop

We propose a framework to engineer synthetic-inertia and droop-control parameters for distributed energy resources (DERs) so that the system frequency in a network composed of DERs and synchronous generators conforms to prescribed transient and steady-state performance specifications. Our approach is grounded in a second-order lumped-parameter model that captures the dynamics of synchronous generators and frequency-responsive DERs endowed with inertial and droop control. A key feature of this reduced-order model is that its parameters can be related to those of the originating higherorder dynamical model. This allows one to systematically design the DER inertial and droop-control coefficients leveraging classical frequency-domain responsemore » characteristics of second-order systems. Time-domain simulations validate the accuracy of the model-reduction method and demonstrate how DER controllers can be designed to meet steady-state-regulation and transient-performance specifications.« less

Field camera measurements of gradient and shim impulse responses using frequency sweeps.

PubMed

Vannesjo, S Johanna; Dietrich, Benjamin E; Pavan, Matteo; Brunner, David O; Wilm, Bertram J; Barmet, Christoph; Pruessmann, Klaas P

2014-08-01

Applications of dynamic shimming require high field fidelity, and characterizing the shim field dynamics is therefore necessary. Modeling the system as linear and time-invariant, the purpose of this work was to measure the impulse response function with optimal sensitivity. Frequency-swept pulses as inputs are analyzed theoretically, showing that the sweep speed is a key factor for the measurement sensitivity. By adjusting the sweep speed it is possible to achieve any prescribed noise profile in the measured system response. Impulse response functions were obtained for the third-order shim system of a 7 Tesla whole-body MR scanner. Measurements of the shim fields were done with a dynamic field camera, yielding also cross-term responses. The measured shim impulse response functions revealed system characteristics such as response bandwidth, eddy currents and specific resonances, possibly of mechanical origin. Field predictions based on the shim characterization were shown to agree well with directly measured fields, also in the cross-terms. Frequency sweeps provide a flexible tool for shim or gradient system characterization. This may prove useful for applications involving dynamic shimming by yielding accurate estimates of the shim fields and a basis for setting shim pre-emphasis. Copyright © 2013 Wiley Periodicals, Inc.

The Association Between Fall Frequency, Injury Risk, and Characteristics of Falls in Older Residents of Long-Term Care: Do Recurrent Fallers Fall More Safely?

PubMed

van Schooten, Kimberley S; Yang, Yijian; Feldman, Fabio; Leung, Ming; McKay, Heather; Sims-Gould, Joanie; Robinovitch, Stephen N

2018-05-09

Although a fall is a necessary prerequisite to a fall-related injury, previous studies suggest that frequent fallers are at lower injury risk for a given fall. We tested the hypotheses that differences in protective responses or the circumstances of falls underlie differences in injury risk with fall frequency. We analyzed video footage of 897 falls experienced by 220 long-term care residents (mean age 82 ± 9 years) to identify the cause of imbalance, activity leading to falling, direction of fall initiation, balance recovery and fall protective responses, and occurrence of impact to the head or hip. We further obtained injury information from the facilities' fall registration. We used generalized estimating equation models to examine the association between quartiles of fall frequency, injury risk, and fall characteristics. Residents with the highest fall frequency group (Q4; ≥5.6 falls/year) were less likely to sustain an injury per fall. They were less likely to fall during walking and more likely to fall during stand-to-sit transfers. Residents in the lowest fall frequency group (Q1; <1.15 falls/year) were more likely to fall during walking, and walking was associated with an increased risk for injury. When compared to less frequent fallers, more frequent fallers had a lower risk for injury per fall. This appeared to be explained by differences in the circumstances of falls, and not by protective responses. Injury prevention strategies in long-term care should target both frequent and infrequent fallers, as the latter are more mobile and apt to sustain injury.

Comparison of self-reported and audiometrically-measured hearing loss in the Australian Defence Force.

PubMed

Kirk, Katherine M; McGuire, Annabel; Nasveld, Peter E; Treloar, Susan A

2012-04-01

To investigate the relationship between self-reported and audiometrically-measured hearing loss in a sample of Australian Defence Force personnel. Responses to a question regarding hearing problems were compared with contemporaneous audiometric data. 3335 members of the Australian Defence Force for whom anonymised medical records were available. The sensitivity of self-report data to identify higher-frequency hearing loss was lower than sensitivity at other frequencies, and positive predictive values were moderate to poor at all frequencies. Performance characteristics of self-report compared with audiometric data also varied with age, sex, and rank. While self-report hearing loss data have good performance characteristics for estimating prevalence of hearing loss as defined by audiometric criteria, this study indicates that the usefulness of self-report data in identifying individuals with hearing loss may be limited in this population.

Synchronized oscillations and acoustic fluidization in confined granular materials

NASA Astrophysics Data System (ADS)

Giacco, F.; de Arcangelis, L.; Ciamarra, M. Pica; Lippiello, E.

2018-01-01

According to the acoustic fluidization hypothesis, elastic waves at a characteristic frequency form inside seismic faults even in the absence of an external perturbation. These waves are able to generate a normal stress which contrasts the confining pressure and promotes failure. Here, we study the mechanisms responsible for this wave activation via numerical simulations of a granular fault model. We observe the particles belonging to the percolating backbone, which sustains the stress, to perform synchronized oscillations over ellipticlike trajectories in the fault plane. These oscillations occur at the characteristic frequency of acoustic fluidization. As the applied shear stress increases, these oscillations become perpendicular to the fault plane just before the system fails, opposing the confining pressure, consistently with the acoustic fluidization scenario. The same change of orientation can be induced by external perturbations at the acoustic fluidization frequency.

Basic characteristics of high-frequency Stark-effect modulation of CO2 lasers.

NASA Technical Reports Server (NTRS)

Claspy, P. C.; Pao, Y. H.

1971-01-01

The molecular Stark effect and its application to the modulation of infrared laser radiation have been investigated both theoretically and experimentally. Using a density matrix approach, a quantum mechanical description of the effect of a time-varying electric field on the absorption coefficient and refractive index of a molecular gas near an absorption line has been formulated. For modulation applications a quantity known as the ?modulation depth' is of prime importance. Theoretical expressions for the frequency dependence of the modulation depth show that the response to the frequency of a time-varying Stark field is separated into a nondispersive and a dispersive region, depending on whether the modulating frequency is less than or greater than the homogeneous absorption linewidth. Experimental results showing nondispersive modulation at frequencies to 30 MHz are presented. In addition it is shown that the response of modulation depth to Stark field amplitude is separated into linear and nonlinear regions, the field at which nonlinearities begin being determined by the absorption spectrum of the molecule being used.

Monaural and binaural response properties of neurons in the inferior colliculus of the rabbit: effects of sodium pentobarbital.

PubMed

Kuwada, S; Batra, R; Stanford, T R

1989-02-01

1. We studied the effects of sodium pentobarbital on 22 neurons in the inferior colliculus (IC) of the rabbit. We recorded changes in the sensitivity of these neurons to monaural stimulation and to ongoing interaural time differences (ITDs). Monaural stimuli were tone bursts at or near the neuron's best frequency. The ITD was varied by delivering tones that differed by 1 Hz to the two ears, resulting in a 1-Hz binaural beat. 2. We assessed a neuron's ITD sensitivity by calculating three measures from the responses to binaural beats: composite delay, characteristic delay (CD), and characteristic phase (CP). To obtain the composite delay, we first derived period histograms by averaging, showing the response at each stimulating frequency over one period of the beat frequency. Second, the period histograms were replotted as a function of their equivalent interaural delay and then averaged together to yield the composite delay curve. Last, we calculated the composite peak or trough delay by fitting a parabola to the peak or trough of this composite curve. The composite delay curve represents the average response to all frequencies within the neuron's responsive range, and the peak reflects the interaural delay that produces the maximum response. The CD and CP were estimated from a weighted fit of a regression line to the plot of the mean interaural phase of the response versus the stimulating frequency. The slope and phase intercept of this regression line yielded estimates of CD and CP, respectively. These two quantities are thought to reflect the mechanism of ITD sensitivity, which involves the convergence of phase-locked inputs on a binaural cell. The CD estimates the difference in the time required for the two inputs to travel from either ear to this cell, whereas the CP reflects the interaural phase difference of the inputs at this cell. 3. Injections of sodium pentobarbital at subsurgical dosages (less than 25 mg/kg) almost invariably altered the neuron's response rate, response latency, response pattern, and spontaneous activity. Most of these changes were predictable and consistent with an enhancement of inhibitory influences. For example, if the earliest response was inhibitory, later excitation was usually reduced and latency increased. If the earliest response was excitatory, the level of this excitation was unaltered or slightly enhanced, and changes in latency were minimal. 4. The neuron's response pattern also changed in a predictable way. For example, a response with an inhibitory pause could either change to a response with a longer pause or to a response with an onset only.(ABSTRACT TRUNCATED AT 400 WORDS)

Microwave characteristics of GaAs MMIC integratable optical detectors

NASA Technical Reports Server (NTRS)

Claspy, Paul C.; Hill, Scott M.; Bhasin, Kul B.

1989-01-01

Interdigitated photoconductive detectors were fabricated on microwave device structures, making them easily integratable with Monolithic Microwave Integrated Circuits (MMIC). Detector responsivity as high as 2.5 A/W and an external quantum efficiency of 3.81 were measured. Response speed was nearly independent of electrode geometry, and all detectors had usable response at frequencies to 6 GHz. A small signal model of the detectors based on microwave measurements was also developed.

Narrow sound pressure level tuning in the auditory cortex of the bats Molossus molossus and Macrotus waterhousii.

PubMed

Macías, Silvio; Hechavarría, Julio C; Cobo, Ariadna; Mora, Emanuel C

2014-03-01

In the auditory system, tuning to sound level appears in the form of non-monotonic response-level functions that depict the response of a neuron to changing sound levels. Neurons with non-monotonic response-level functions respond best to a particular sound pressure level (defined as "best level" or level evoking the maximum response). We performed a comparative study on the location and basic functional organization of the auditory cortex in the gleaning bat, Macrotus waterhousii, and the aerial-hawking bat, Molossus molossus. Here, we describe the response-level function of cortical units in these two species. In the auditory cortices of M. waterhousii and M. molossus, the characteristic frequency of the units increased from caudal to rostral. In M. waterhousii, there was an even distribution of characteristic frequencies while in M. molossus there was an overrepresentation of frequencies present within echolocation pulses. In both species, most of the units showed best levels in a narrow range, without an evident topography in the amplitopic organization, as described in other species. During flight, bats decrease the intensity of their emitted pulses when they approach a prey item or an obstacle resulting in maintenance of perceived echo intensity. Narrow level tuning likely contributes to the extraction of echo amplitudes facilitating echo-intensity compensation. For aerial-hawking bats, like M. molossus, receiving echoes within the optimal sensitivity range can help the bats to sustain consistent analysis of successive echoes without distortions of perception caused by changes in amplitude. Copyright © 2013 Elsevier B.V. All rights reserved.

Elastic Dispersion and Attenuation in Fully Saturated Sandstones: Role of Mineral Content, Porosity, and Pressures

NASA Astrophysics Data System (ADS)

Pimienta, Lucas; Borgomano, Jan V. M.; Fortin, Jérôme; Guéguen, Yves

2017-12-01

Because measuring the frequency dependence of elastic properties in the laboratory is a technical challenge, not enough experimental data exist to test the existing theories. We report measurements of three fluid-saturated sandstones over a broad frequency band: Wilkenson, Berea, and Bentheim sandstones. Those sandstones samples, chosen for their variable porosities and mineral content, are saturated by fluids of varying viscosities. The samples elastic response (Young's modulus and Poisson's ratio) and hydraulic response (fluid flow out of the sample) are measured as a function of frequency. Large dispersion and attenuation phenomena are observed over the investigated frequency range. For all samples, the variation at lowest frequency relates to a large fluid flow directly measured out of the rock samples. These are the cause (i.e., fluid flow) and consequence (i.e., dispersion/attenuation) of the transition between drained and undrained regimes. Consistently, the characteristic frequency correlates with permeability for each sandstone. Beyond this frequency, a second variation is observed for all samples, but the rocks behave differently. For Berea sandstone, an onset of dispersion/attenuation is expected from both Young's modulus and Poisson's ratio at highest frequency. For Bentheim and Wilkenson sandstones, however, only Young's modulus shows dispersion/attenuation phenomena. For Wilkenson sandstone, the viscoelastic-like dispersion/attenuation response is interpreted as squirt flow. For Bentheim sandstone, the second effect does not fully follow such response, which could be due to a lower accuracy in the measured attenuation or to the occurence of another physical effect in this rock sample.

Sound wave resonances in micro-electro-mechanical systems devices vibrating at high frequencies according to the kinetic theory of gases

NASA Astrophysics Data System (ADS)

Desvillettes, Laurent; Lorenzani, Silvia

2012-09-01

The mechanism leading to gas damping in micro-electro-mechanical systems (MEMS) devices vibrating at high frequencies is investigated by using the linearized Boltzmann equation based on simplified kinetic models and diffuse reflection boundary conditions. Above a certain frequency of oscillation, the sound waves propagating through the gas are trapped in the gaps between the moving elements and the fixed boundaries of the microdevice. In particular, we found a scaling law, valid for all Knudsen numbers Kn (defined as the ratio between the gas mean free path and a characteristic length of the gas flow), that predicts a resonant response of the system. This response enables a minimization of the damping force exerted by the gas on the oscillating wall of the microdevice.

Seated Occupant Apparent Mass Characteristics Under Automotive Postures and Vertical Vibration

NASA Astrophysics Data System (ADS)

RAKHEJA, S.; HARU, I.; BOILEAU, P.-É.

2002-05-01

The biodynamic apparent mass response characteristics of 24 human subjects (12 males and 12 females) seated under representative automotive postures with hands-in-lap (passengers) and hands-on-steering wheel (drivers) are reported. The measurements were carried out under white noise vertical excitations of 0·25, 0·5 and 1·0m/s2r.m.s. acceleration magnitudes in the 0·5-40Hz frequency range and a track measured input (1·07m/s2). The measured data have been analyzed to study the effects of hands position, body mass, magnitude and type of vibration excitation, and feet position, on the biodynamic response expressed in terms of apparent mass. A comparison of the measured response of subjects assuming typical automotive postures involving inclined cushion, inclined backrest and full use of backrest support with data determined under different postural conditions and excitation levels revealed considerable differences. The biodynamic response of automobile occupants seated with hands in lap, peaks in the 6·5-8·6Hz frequency range, which is considerably higher than the reported range of fundamental frequencies (4·5-5Hz) in most other studies involving different experimental conditions. The peak magnitude tends to decrease considerably for the driving posture with hands-on-steering wheel, while a second peak in the 8-12 Hz range becomes more apparent for this posture. The results suggest that biodynamic response of occupants seated in automotive seats and subject to vertical vibration need to be characterized, as a minimum, by two distinct functions for passenger and driving postures. A higher body mass, in general, yields higher peak magnitude response and lower corresponding frequency for both postures. The strong dependence of the response on the body mass is further demonstrated by grouping the measured data into four different mass ranges: less than 60 kg, between 60·5 and 70 kg, between 70·5 and 80 kg, and above 80 kg. From the results, it is concluded that hands position and body mass have the most significant influence on the apparent mass response under automotive posture and vibration.

Voluntary control of arm movement in athetotic patients

PubMed Central

Neilson, Peter D.

1974-01-01

Visual tracking tests have been employed to provide a quantitative description of voluntary control of arm movement in a group of patients suffering from athetoid cerebral palsy. Voluntary control was impaired in all patients in a characteristic manner. Maximum velocity and acceleration of arm movement were reduced to about 30-50% of their values in normal subjects and the time lag of the response to a visual stimulus was two or three times greater than in normals. Tracking transmission characteristics indicated a degree of underdamping which was not presnet in normal or spastic patients. This underdamping could be responsible for a low frequency (0·3-0·6 Hz) transient oscillation in elbow-angle movements associated with sudden voluntary movement. The maximum frequency at which patients could produce a coherent tracking response was only 50% of that in normal subjects and the relationship between the electromyogram and muscle contraction indicated that the mechanical load on the biceps muscle was abnormal, possibly due to increased stiffness of joint movement caused by involuntary activity in agonist and antagonist muscles acting across the joint. Images PMID:4362243

Performance Dependences of Multiplication Layer Thickness for InP/InGaAs Avalanche Photodiodes Based on Time Domain Modeling

NASA Technical Reports Server (NTRS)

Xiao, Yegao; Bhat, Ishwara; Abedin, M. Nurul

2005-01-01

InP/InGaAs avalanche photodiodes (APDs) are being widely utilized in optical receivers for modern long haul and high bit-rate optical fiber communication systems. The separate absorption, grading, charge, and multiplication (SAGCM) structure is an important design consideration for APDs with high performance characteristics. Time domain modeling techniques have been previously developed to provide better understanding and optimize design issues by saving time and cost for the APD research and development. In this work, performance dependences on multiplication layer thickness have been investigated by time domain modeling. These performance characteristics include breakdown field and breakdown voltage, multiplication gain, excess noise factor, frequency response and bandwidth etc. The simulations are performed versus various multiplication layer thicknesses with certain fixed values for the areal charge sheet density whereas the values for the other structure and material parameters are kept unchanged. The frequency response is obtained from the impulse response by fast Fourier transformation. The modeling results are presented and discussed, and design considerations, especially for high speed operation at 10 Gbit/s, are further analyzed.

Wireless System and Method for Collecting Motion and Non-Motion Related Data of a Rotating System

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2011-01-01

A wireless system for collecting data indicative of a tire's characteristics uses at least one open-circuit electrical conductor in a tire. The conductor is shaped such that it can store electrical and magnetic energy. In the presence of a time-varying magnetic field, the conductor resonates to generate a harmonic response having a frequency, amplitude and bandwidth. A magnetic field response recorder is used to (i) wirelessly transmit the time-varying magnetic field to the conductor, and (ii) wirelessly detect the harmonic response and the frequency, amplitude and bandwidth, associated therewith. The recorder is adapted to be positioned in a location that is fixed with respect to the tire as the tire rotates.

High frequency characteristic of a monolithic 500 °C OpAmp-RC integrator in SiC bipolar IC technology

NASA Astrophysics Data System (ADS)

Tian, Ye; Zetterling, Carl-Mikael

2017-09-01

This paper presents a comprehensive investigation of the frequency response of a monolithic OpAmp-RC integrator implemented in a 4H-SiC bipolar IC technology. The circuits and devices have been measured and characterized from 27 to 500 °C. The devices have been modelled to identify that the substrate capacitance is a dominant factor affecting the OpAmp's high-frequency response. Large Miller compensation capacitors of more than 540 pF are required to ensure stability of the internal OpAmp. The measured unit-gain-bandwidth product of the OpAmp is ∼1.1 MHz at 27 °C, and decreases to ∼0.5 MHz at 500 °C mainly due to the reduction of the transistor's current gain. On the other hand, it is not necessary to compensate the integrator in a relatively wide bandwidth ∼0.7 MHz over the investigated temperature range. At higher frequencies, the integrator's frequency response has been identified to be significantly affected by that of the OpAmp and load impedance. This work demonstrates the potential of this technology for high temperature applications requiring bandwidths of several megahertz.

A method of investigating the phase response characteristic of the ionospheric scattering communications channel

NASA Technical Reports Server (NTRS)

Yakovets, A. F.

1972-01-01

A method is proposed for measuring the phase difference fluctuations between vibrations at different frequencies that result from scattering properties of the medium. The measurement equipment is described, along with an ideal communication channel.

Inflight dynamics testing of the Apollo spacecraft

NASA Technical Reports Server (NTRS)

Peters, W. H.; Marchantel, B.

1972-01-01

Response of the Apollo command module, service and lunar module airframe while in a docked configuration in the flight environment was measured in a frequency band encompassing the first two bending modes. Transfer characteristics from thrust-application point to control-system sensor were examined. The frequency and the stability margins of the first two predominant structural resonances were verified by the test. This report describes the flight test that was performed and the postflight data analysis.

Microfluctuations in accommodation: an update on their characteristics and possible role.

PubMed

Charman, W Neil; Heron, Gordon

2015-09-01

Following the recognition, some 80 years ago, that the accommodation of the eye is not stable but fluctuates over a range of about ±0.5 D, mainly at frequencies of up to a few Hz, there has been a continuing interest in the characteristics of these microfluctuations (MFs) and their possible role in the control of accommodation. This paper reviews relevant work carried out since 1988, when we previously reviewed the same topic (Charman WN, Heron G. Fluctuations in accommodation: a review. Ophthalmic Physiol Opt 1988; 8: 153-164). Studies relating to the effects on the MFs of stimulus form, luminance and vergence are described, together with those of pupil diameter, age and ametropia. Important advances in the understanding of the links between the characteristics of the MFs and those of the cardiopulmonary system, higher-order aberrations and ocular depth-of-focus are outlined. Only limited progress has been made in understanding the role of MFs in accommodation control. While the dependence of the characteristics of the MFs in relation to observing conditions is now reasonably well understood, their involvement in accommodation control still needs clarification. The current consensus appears to be that any role is more likely to be concerned with maintaining an appropriate response, rather than in initiating responses to abrupt changes in stimulus vergence. Fluctuations at lower temporal frequencies (<0.6 Hz) are probably important to the control process, which may make use of the associated changes in the contrast and spatial frequency spectrum of the retinal image. © 2015 The Authors Ophthalmic & Physiological Optics © 2015 The College of Optometrists.

A multilevel path analysis of contact frequency between social network members

NASA Astrophysics Data System (ADS)

van den Berg, Pauline; Arentze, Theo; Timmermans, Harry

2012-04-01

Recently, there has been an increasing interest in the role of social networks in spatial-choice and travel behavior. It has been acknowledged that social activities and the travel for these activities can emerge from individuals' social networks and that social activities are responsible for an important portion of travel demand. The influence of information and communication technologies (ICT's) is also important in this respect. The purpose of the paper is to examine the effects of characteristics of egos and ego-alter relationships on the frequency of social interaction by different communication modes, using multilevel path analysis. The analyses are based on social network data collected in 2008 in the Eindhoven region in the Netherlands among 116 respondents. The results indicate a complementary relationship between contact frequencies by different modes. The contact frequencies of the different modes, especially face-to-face and telephone, can also be largely explained by the ego's personal characteristics and the type of relationship and the distance between ego and alter.

Microwave energy harvesting based on metamaterial absorbers with multi-layered square split rings for wireless communications

NASA Astrophysics Data System (ADS)

Karaaslan, Muharrem; Bağmancı, Mehmet; Ünal, Emin; Akgol, Oguzhan; Sabah, Cumali

2017-06-01

We propose the design of a multiband absorber based on multi-layered square split ring (MSSR) structure. The multi-layered metamaterial structure is designed to be used in the frequency bands such as WIMAX, WLAN and satellite communication region. The absorption levels of the proposed structure are higher than 90% for all resonance frequencies. In addition, the incident angle and polarization dependence of the multi-layered metamaterial absorber and harvester is also investigated and it is observed that the structure has polarization angle independent frequency response with good absorption characteristics in the entire working frequency band. The energy harvesting ratios of the structure is investigated especially for the resonance frequencies at which the maximum absorption occurs. The energy harvesting potential of the proposed MSSRs is as good as those of the structures given in the literature. Therefore, the suggested design having good absorption, polarization and angle independent characteristics with a wide bandwidth is a potential candidate for future energy harvesting applications in commonly used wireless communication bands, namely WIMAX, WLAN and satellite communication bands.

Wireless Strain Measurement with a Micromachined Magnetoelastic Resonator Using Ringdown Frequency Locking

PubMed Central

Green, Scott R.; Gianchandani, Yogesh B.

2017-01-01

Resonant magnetoelastic devices are widely used as anti-theft tags and are also being investigated for a range of sensing applications. The vast majority of magnetoelastic devices are operated at resonance, and rely upon an external interface to wirelessly detect the resonant frequency, and other characteristics. For micromachined devices, this detection method must accommodate diminished signal strength and elevated resonant frequencies. Feedthrough of the interrogating stimulus to the detector also presents a significant challenge. This paper describes a method of interrogating wireless magnetoelastic strain sensors using a new frequency-lock approach. Following a brief excitation pulse, the sensor ring-down is analyzed and a feedback loop is used to match the excitation frequency and the resonant frequency. Data acquisition hardware is used in conjunction with custom software to implement the frequency-lock loop. Advantages of the method include temporal isolation of interrogating stimulus from the sensor response and near real-time tracking of resonant frequencies. The method was investigated using a family of wireless strain sensors with resonant frequencies ranging from 120 to 240 kHz. Strain levels extending to 3.5 mstrain and sensitivities up to 14300 ppm/mstrain were measured with response times faster than 0.5 s. The standard deviation of the locked frequency did not exceed 0.1%. PMID:28713873

Responses to pure tones and linear FM components of the CF-FM biosonar signal by single units in the inferior colliculus of the mustached bat.

PubMed

O'Neill, W E

1985-12-01

The responses of 682 single-units in the inferior colliculus (IC) of 13 mustached bats (Pteronotus parnellii parnellii) were measured using pure tones (CF), frequency modulations (FM) and pairs of CF-FM signals mimicking the species' biosonar signal, which are stimuli known to be essential to the responses of CF/CF and FM-FM facilitation neurons in auditory cortex. Units were arbitrarily classified into 'reference frequency' (RF), 'FM2' and 'Non-echolocation' (NE) categories according to the relationship of their best frequencies (BF) to the biosonar signal frequencies. RF units have high Q10dB values and are tuned to the reference frequency of each bat, which ranged between 60.73 and 62.73 kHz. FM2 units had BF's between 50 and 60 kHz, while NE units had BF's outside the ranges of the RF and FM2 classes. PST histograms of the responses revealed discharge patterns such as 'onset', 'onset-bursting' (most common), 'on-off', 'tonic-on','pauser', and 'chopper'. Changes in discharge patterns usually resulted from changes in the frequency and/or intensity of the stimuli, most often involving a change from onset-bursting to on-off. Different patterns were also elicited by CF and FM stimuli. Frequency characteristics and thresholds to CF and FM stimuli were measured. RF neurons were very sharply tuned with Q10dB's ranging from 50-360. Most (92%) also responded to FM2 stimuli, but 78% were significantly more sensitive (greater than 5 dB) to CF stimuli, and only 3% had significantly lower thresholds to FM2. The best initial frequency for FM2 sweeps in RF units was 65.35 +/- 2.138 kHz (n = 118), well above the natural frequency of the 2nd harmonic. FM2 and NE units were indistinguishable from each other, but were quite different from RF units: 41% of these two classes had lower thresholds to CF, 49% were about equally sensitive, and 10% had lower thresholds to FM. For FM2 units, mean best initial frequency for FM was 60.94 kHz +/- 3.162 kHz (n = 114), which is closely matched to the 2nd harmonic in the biosonar signal. Very few units (5) responded only to FM signals, i.e., were FM-specialized. The characteristics of spike-count functions were determined in 587 units. The vast majority (79%) of RF units (n = 228) were nonmonotonic, and about 22% had upper-thresholds.(ABSTRACT TRUNCATED AT 400 WORDS)

Three-dimensional micro electromechanical system piezoelectric ultrasound transducer

NASA Astrophysics Data System (ADS)

Hajati, Arman; Latev, Dimitre; Gardner, Deane; Hajati, Azadeh; Imai, Darren; Torrey, Marc; Schoeppler, Martin

2012-12-01

Here we present the design and experimental acoustic test data for an ultrasound transducer technology based on a combination of micromachined dome-shaped piezoelectric resonators arranged in a flexible architecture. Our high performance niobium-doped lead zirconate titanate film is implemented in three-dimensional dome-shaped structures, which form the basic resonating cells. Adjustable frequency response is realized by mixing these basic cells and modifying their dimensions by lithography. Improved characteristics such as high sensitivity, adjustable wide-bandwidth frequency response, low transmit voltage compatible with ordinary integrated circuitry, low electrical impedance well matched to coaxial cabling, and intrinsic acoustic impedance match to water are demonstrated.

Research pressure instrumentation for NASA Space Shuttle main engine, modification no. 5

NASA Technical Reports Server (NTRS)

Anderson, P. J.; Nussbaum, P.; Gustafson, G.

1984-01-01

The objective of the research project described is to define and demonstrate methods to advance the state of the art of pressure sensors for the space shuttle main engine (SSME). Silicon piezoresistive technology was utilized in completing tasks: generation and testing of three transducer design concepts for solid state applications; silicon resistor characterization at cryogenic temperatures; experimental chip mounting characterization; frequency response optimization and prototype design and fabrication. Excellent silicon sensor performance was demonstrated at liquid nitrogen temperature. A silicon resistor ion implant dose was customized for SSME temperature requirements. A basic acoustic modeling software program was developed as a design tool to evaluate frequency response characteristics.

Dynamic characteristic of electromechanical coupling effects in motor-gear system

NASA Astrophysics Data System (ADS)

Bai, Wenyu; Qin, Datong; Wang, Yawen; Lim, Teik C.

2018-06-01

Dynamic characteristics of an electromechanical model which combines a nonlinear permeance network model (PNM) of a squirrel-cage induction motor and a coupled lateral-torsional dynamic model of a planetary geared rotor system is analyzed in this study. The simulations reveal the effects of internal excitations or parameters like machine slotting, magnetic saturation, time-varying mesh stiffness and shaft stiffness on the system dynamics. The responses of the electromechanical system with PNM motor model are compared with those responses of the system with dynamic motor model. The electromechanical coupling due to the interactions between the motor and gear system are studied. Furthermore, the frequency analysis of the electromechanical system dynamic characteristics predicts an efficient way to detect work condition of unsymmetrical voltage sag.

Experimental research on crack detection in pipes based on Fiber Bragg grating

NASA Astrophysics Data System (ADS)

Cai, Lin; Wei, Qin; Yu, Zhaoxiang; Lu, Ming; Li, Xiaowei

2017-11-01

Crack is one of the primary faults in pipes, and its detection is a significant measure to ensure the safety of pipes. The feasibility of circumferential crack detection in pipes on the basis of fiber Bragg grating (FBG) detection technology is discussed through experimental research. Crack is formed on the surface of a metal pipe, the circumferential length of crack is one index of the damage degree. In the experiments, both electronic vibration sensor and FBG strain sensors are used to collect response signals of impulse excitation in different damage degrees. Furthermore, the characteristics of damage detection are analysed in both frequency domain and time domain. First, the natural frequencies are compared between practical and simulated results in different damage degrees of pipes; second, the multi-fractal detrended fluctuation analysis (MFDFA) is applied to acquire the singular values α as the characteristic parameter. The experimental results indicate that FBG strain sensors can perceive the impulse response of the pipe and change in different damage degrees effectively, like the vibration sensor. And both the natural frequency and the singular value are sensitive to increasing length of crack, they are able to distinguish different degrees of crack on the pipe.

Study of Site Response in the Seattle and Tacoma Basins, Washington, Using Spectral Ratio Methods

NASA Astrophysics Data System (ADS)

Keshvardoost, R.; Wolf, L. W.

2014-12-01

Sedimentary basins are known to have a pronounced influence on earthquake-generated ground motions, affecting both predominant frequencies and wave amplification. These site characteristics are important elements in estimating ground shaking and seismic hazard. In this study, we use three-component broadband and strong motion seismic data from three recent earthquakes to determine site response characteristics in the Seattle and Tacoma basins, Washington. Resonant frequencies and relative amplification of ground motions were determined using Fourier spectral ratios of velocity and acceleration records from the 2012 Mw 6.1 Vancouver Island earthquake, the 2012 Mw 7.8 Queen Charlotte Island earthquake, and the 2014 Mw 6.6 Vancouver Island earthquake. Recordings from sites within and adjacent to the Seattle and Tacoma basins were selected for the study based on their signal to noise ratios. Both the Standard Spectral Ratio (SSR) and the Horizontal-to-Vertical Spectral Ratio (HVSR) methods were used in the analysis, and results from each were compared to examine their agreement and their relation to local geology. Although 57% of the sites (27 out of 48) exhibited consistent results between the two methods, other sites varied considerably. In addition, we use data from the Seattle Liquefaction Array (SLA) to evaluate the site response at 4 different depths. Results indicate that resonant frequencies remain the same at different depths but amplification decreases significantly over the top 50 m.

Dynamic response of active twist rotor blades

NASA Astrophysics Data System (ADS)

Cesnik, Carlos E. S.; Shin, Sang Joon; Wilbur, Matthew L.

2001-02-01

Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An ATR prototype blade was designed and manufactured to experimentally study the vibration reduction capabilities of such systems. Several bench and hover tests were conducted and those results are presented and discussed here. Selected results on sensitivity of the ATR system to collective setting (i.e. blade loading), blade rpm (i.e. centrifugal force and blade station velocity), and media density (i.e. altitude) are presented. They indicated that the twist actuation authority of the ATR blade is independent of the collective setting up to approximately 10P, and dependent on rotational speed and altitude near the torsional resonance frequency due to its dependency on the aerodynamic damping. The proposed model captures very well the physics and sensitivities to selected test parameters of the ATR system. The numerical result of the blade torsional loads show an average error of 20% in magnitude and virtually no difference in phase for the blade frequency response. Overall, the active blade model is in very good agreement with the experiments and can be used to analyze and design future active helicopter blade systems.

Eye movements during the Rorschach test in schizophrenia.

PubMed

Hori, Yasuko; Fukuzako, Hiroshi; Sugimoto, Yoko; Takigawa, Morikuni

2002-08-01

In order to understand relationships between scanning behaviors, characteristics of visual stimuli and the clinical symptoms in schizophrenia, eye movements of 37 schizophrenic patients and 36 controls were recorded using an eye-mark recorder during a free-response period in a Rorschach test. Four cards (I, II, V and VIII) were used. Data were analyzed during 15 s from the presentation of each card. For all cards, the number of eye fixations and the number of eye fixation areas were fewer, and total scanning length and mean scanning length were shorter for schizophrenic patients than for controls. For card II, in the non-popular response group, eye fixation frequency upon area 5 + 6 (red) was higher for schizophrenic patients. For card VIII, in the popular response group, eye fixation frequency upon area 5 + 6 (pink) was lower for schizophrenic patients. For cards II and VIII, the number of eye fixations was inversely correlated with negative symptoms. For card II, total scanning length tended to be inversely correlated with negative symptoms, and mean eye fixation time was correlated with negative symptoms. The number of eye fixation areas was inversely correlated with positive symptoms. For card VIII, eye fixation frequency in a stimulative area tended to be correlated with positive symptoms. Scanning behaviors in schizophrenic patients are affected by characteristics of visual stimuli, and partially by clinical symptoms.

Comparison of lung sound transducers using a bioacoustic transducer testing system.

PubMed

Kraman, Steve S; Wodicka, George R; Pressler, Gary A; Pasterkamp, Hans

2006-08-01

Sensors used for lung sound research are generally designed by the investigators or adapted from devices used in related fields. Their relative characteristics have never been defined. We employed an artificial chest wall with a viscoelastic surface and a white noise signal generator as a stable source of sound to compare the frequency response and pulse waveform reproduction of a selection of devices used for lung sound research. We used spectral estimation techniques to determine frequency response and cross-correlation of pulses to determine pulse shape fidelity. The sensors evaluated were the Siemens EMT 25 C accelerometer (Siemens); PPG 201 accelerometer (PPG); Sony ECM-T150 electret condenser microphone with air coupler (air coupler; with cylindrical air chambers of 5-, 10-, and 15-mm diameter and conical air chamber of 10-mm diameter); Littman classic stethoscope head (Littman) connected to an electret condenser microphone; and the Andries Tek (Andries) electronic stethoscope. We found that the size and shape of the air coupler chamber to have no important effect on the detected sound. The Siemens, air coupler, and Littman performed similarly with relatively flat frequency responses from 200 to 1,200 Hz. The PPG had the broadest frequency response, with useful sensitivity extending to 4,000 Hz. The Andries' frequency response was the poorest above 1,000 Hz. Accuracy in reproducing pulses roughly corresponded with the high-frequency sensitivity of the sensors. We conclude that there are important differences among commonly used lung sound sensors that have to be defined to allow the comparison of data from different laboratories.

Intracellular responses of onset chopper neurons in the ventral cochlear nucleus to tones: evidence for dual-component processing.

PubMed

Paolini, A G; Clark, G M

1999-05-01

Intracellular responses of onset chopper neurons in the ventral cochlear nucleus to tones: evidence for dual-component processing. The ventral cochlear nucleus (VCN) contains a heterogeneous collection of cell types reflecting the multiple processing tasks undertaken by this nucleus. This in vivo study in the rat used intracellular recordings and dye filling to examine membrane potential changes and firing characteristics of onset chopper (OC) neurons to acoustic stimulation (50 ms pure tones, 5 ms r/f time). Stable impalements were made from 15 OC neurons, 7 identified as multipolar cells. Neurons responded to characteristic frequency (CF) tones with sustained depolarization below spike threshold. With increasing stimulus intensity, the depolarization during the initial 10 ms of the response became peaked, and with further increases in intensity the peak became narrower. Onset spikes were generated during this initial depolarization. Tones presented below CF resulted in a broadening of this initial depolarizing component with high stimulus intensities required to initiate onset spikes. This initial component was followed by a sustained depolarizing component lasting until stimulus cessation. The amplitude of the sustained depolarizing component was greatest when frequencies were presented at high intensities below CF resulting in increased action potential firing during this period when compared with comparable high intensities at CF. During the presentation of tones at or above the high-frequency edge of a cell's response area, hyperpolarization was evident during the sustained component. The presence of hyperpolarization and the differences seen in the level of sustained depolarization during CF and off CF tones suggests that changes in membrane responsiveness between the initial and sustained components may be attributed to polysynaptic inhibitory mechanisms. The dual-component processing resulting from convergent auditory nerve excitation and polysynaptic inhibition enables OC neurons to respond in a unique fashion to intensity and frequency features contained within an acoustic stimulus.

Signal Processing Methods for Liquid Rocket Engine Combustion Stability Assessments

NASA Technical Reports Server (NTRS)

Kenny, R. Jeremy; Lee, Erik; Hulka, James R.; Casiano, Matthew

2011-01-01

The J2X Gas Generator engine design specifications include dynamic, spontaneous, and broadband combustion stability requirements. These requirements are verified empirically based high frequency chamber pressure measurements and analyses. Dynamic stability is determined with the dynamic pressure response due to an artificial perturbation of the combustion chamber pressure (bomb testing), and spontaneous and broadband stability are determined from the dynamic pressure responses during steady operation starting at specified power levels. J2X Workhorse Gas Generator testing included bomb tests with multiple hardware configurations and operating conditions, including a configuration used explicitly for engine verification test series. This work covers signal processing techniques developed at Marshall Space Flight Center (MSFC) to help assess engine design stability requirements. Dynamic stability assessments were performed following both the CPIA 655 guidelines and a MSFC in-house developed statistical-based approach. The statistical approach was developed to better verify when the dynamic pressure amplitudes corresponding to a particular frequency returned back to pre-bomb characteristics. This was accomplished by first determining the statistical characteristics of the pre-bomb dynamic levels. The pre-bomb statistical characterization provided 95% coverage bounds; these bounds were used as a quantitative measure to determine when the post-bomb signal returned to pre-bomb conditions. The time for post-bomb levels to acceptably return to pre-bomb levels was compared to the dominant frequency-dependent time recommended by CPIA 655. Results for multiple test configurations, including stable and unstable configurations, were reviewed. Spontaneous stability was assessed using two processes: 1) characterization of the ratio of the peak response amplitudes to the excited chamber acoustic mode amplitudes and 2) characterization of the variability of the peak response's frequency over the test duration. This characterization process assists in evaluating the discreteness of a signal as well as the stability of the chamber response. Broadband stability was assessed using a running root-mean-square evaluation. These techniques were also employed, in a comparative analysis, on available Fastrac data, and these results are presented here.

Frequency Responses of Rat Retinal Ganglion Cells

PubMed Central

Cloherty, Shaun L.; Hung, Yu-Shan; Kameneva, Tatiana; Ibbotson, Michael R.

2016-01-01

There are 15–20 different types of retinal ganglion cells (RGC) in the mammalian retina, each encoding different aspects of the visual scene. The mechanism by which post-synaptic signals from the retinal network generate spikes is determined by each cell’s intrinsic electrical properties. Here we investigate the frequency responses of morphologically identified rat RGCs using intracellular injection of sinusoidal current waveforms, to assess their intrinsic capabilities with minimal contributions from the retinal network. Recorded cells were classified according to their morphological characteristics (A, B, C or D-type) and their stratification (inner (i), outer (o) or bistratified) in the inner plexiform layer (IPL). Most cell types had low- or band-pass frequency responses. A2, C1 and C4o cells were band-pass with peaks of 15–30 Hz and low-pass cutoffs above 56 Hz (A2 cells) and ~42 Hz (C1 and C4o cells). A1 and C2i/o cells were low-pass with peaks of 10–15 Hz (cutoffs 19–25 Hz). Bistratified D1 and D2 cells were also low-pass with peaks of 5–10 Hz (cutoffs ~16 Hz). The least responsive cells were the B2 and C3 types (peaks: 2–5 Hz, cutoffs: 8–11 Hz). We found no difference between cells stratifying in the inner and outer IPL (i.e., ON and OFF cells) or between cells with large and small somas or dendritic fields. Intrinsic physiological properties (input resistance, spike width and sag) had little impact on frequency response at low frequencies, but account for 30–40% of response variability at frequencies >30 Hz. PMID:27341669

Response characteristic of high-speed on/off valve with double voltage driving circuit

NASA Astrophysics Data System (ADS)

Li, P. X.; Su, M.; Zhang, D. B.

2017-07-01

High-speed on/off valve, an important part of turbocharging system, its quick response has a direct impact on the turbocharger pressure cycle. The methods of improving the response characteristic of high speed on/off valve include increasing the magnetic force of armature and the voltage, decreasing the mass and current of coil. The less coil number of turns, the solenoid force is smaller. The special armature structure and the magnetic material will raise cost. In this paper a new scheme of double voltage driving circuit is investigated, in which the original driving circuit of high-speed on/off valve is replaced by double voltage driving circuit. The detailed theoretical analysis and simulations were carried out on the double voltage driving circuit, it showed that the switching time and delay time of the valve respectively are 3.3ms, 5.3ms, 1.9ms and 1.8ms. When it is driven by the double voltage driving circuit, the switching time and delay time of this valve are reduced, optimizing its response characteristic. By the comparison related factors (such as duty cycle or working frequency) about influences on response characteristic, the superior of double voltage driving circuit has been further confirmed.

Influence of sampling rate on the calculated fidelity of an aircraft simulation

NASA Technical Reports Server (NTRS)

Howard, J. C.

1983-01-01

One of the factors that influences the fidelity of an aircraft digital simulation is the sampling rate. As the sampling rate is increased, the calculated response of the discrete representation tends to coincide with the response of the corresponding continuous system. Because of computer limitations, however, the sampling rate cannot be increased indefinitely. Moreover, real-time simulation requirements demand that a finite sampling rate be adopted. In view of these restrictions, a study was undertaken to determine the influence of sampling rate on the response characteristics of a simulated aircraft describing short-period oscillations. Changes in the calculated response characteristics of the simulated aircraft degrade the fidelity of the simulation. In the present context, fidelity degradation is defined as the percentage change in those characteristics that have the greatest influence on pilot opinion: short period frequency omega, short period damping ratio zeta, and the product omega zeta. To determine the influence of the sampling period on these characteristics, the equations describing the response of a DC-8 aircraft to elevator control inputs were used. The results indicate that if the sampling period is too large, the fidelity of the simulation can be degraded.

The influence of cochlear spectral processing on the timing and amplitude of the speech-evoked auditory brain stem response

PubMed Central

Nuttall, Helen E.; Moore, David R.; Barry, Johanna G.; Krumbholz, Katrin

2015-01-01

The speech-evoked auditory brain stem response (speech ABR) is widely considered to provide an index of the quality of neural temporal encoding in the central auditory pathway. The aim of the present study was to evaluate the extent to which the speech ABR is shaped by spectral processing in the cochlea. High-pass noise masking was used to record speech ABRs from delimited octave-wide frequency bands between 0.5 and 8 kHz in normal-hearing young adults. The latency of the frequency-delimited responses decreased from the lowest to the highest frequency band by up to 3.6 ms. The observed frequency-latency function was compatible with model predictions based on wave V of the click ABR. The frequency-delimited speech ABR amplitude was largest in the 2- to 4-kHz frequency band and decreased toward both higher and lower frequency bands despite the predominance of low-frequency energy in the speech stimulus. We argue that the frequency dependence of speech ABR latency and amplitude results from the decrease in cochlear filter width with decreasing frequency. The results suggest that the amplitude and latency of the speech ABR may reflect interindividual differences in cochlear, as well as central, processing. The high-pass noise-masking technique provides a useful tool for differentiating between peripheral and central effects on the speech ABR. It can be used for further elucidating the neural basis of the perceptual speech deficits that have been associated with individual differences in speech ABR characteristics. PMID:25787954

Analysis of axial compressive loaded beam under random support excitations

NASA Astrophysics Data System (ADS)

Xiao, Wensheng; Wang, Fengde; Liu, Jian

2017-12-01

An analytical procedure to investigate the response spectrum of a uniform Bernoulli-Euler beam with axial compressive load subjected to random support excitations is implemented based on the Mindlin-Goodman method and the mode superposition method in the frequency domain. The random response spectrum of the simply supported beam subjected to white noise excitation and to Pierson-Moskowitz spectrum excitation is investigated, and the characteristics of the response spectrum are further explored. Moreover, the effect of axial compressive load is studied and a method to determine the axial load is proposed. The research results show that the response spectrum mainly consists of the beam's additional displacement response spectrum when the excitation is white noise; however, the quasi-static displacement response spectrum is the main component when the excitation is the Pierson-Moskowitz spectrum. Under white noise excitation, the amplitude of the power spectral density function decreased as the axial compressive load increased, while the frequency band of the vibration response spectrum increased with the increase of axial compressive load.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. II. Inertial detection of angular velocity

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Hess, B. J.

1996-01-01

1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For horizontal VOR, the amplitude of the steady-state slow-phase velocity during constant velocity rotation and the reduction of phase leads during sinusoidal oscillation were relatively independent of tilt angle (for angles larger than approximately 10 degrees). For vertical and torsional VOR, the amplitude of steady-state slow-phase eye velocity during constant velocity rotation increased, and the phase leads during sinusoidal oscillation decreased with increasing tilt angle. The largest steady-state response amplitudes and smallest phase leads were observed during vertical/torsional VOR about an earth-horizontal axis. 5. The dynamic range of otolith-borne head angular velocity information in the VOR was limited to velocities up to approximately 110 degrees/s. Higher head velocities resulted in saturation and a decrease in the amplitude of the steady-state response components during constant velocity rotation and in increased phase leads during sinusoidal oscillations. 6. The response characteristics of otolith-borne angular VORs were also studied in animals after selective semicircular canal inactivation. Otolith angular VORs exhibited clear low-pass filtered properties with a corner frequency of approximately 0.05-0.1 Hz. Vectorial summation of canal VOR alone (elicited during earth-vertical axis rotations) and otolith VOR alone (elicited during off-vertical axis oscillations after semicircular canal inactivation) could not predict VOR gain and phase during off-vertical axis rotations in intact animals. This suggests a more complex interaction of semicircular canal and otolith signals. 7. The results of this study show that the primate low-frequency enhancement of VOR dynamics during off-vertical axis rotation is independent of a simultaneous activation of the vertical and torsional "tilt" otolith-ocular reflexes that have been characterized in the preceding paper. (ABSTRACT TRUNCATED).

The calcium–frequency response in the rat ventricular myocyte: an experimental and modelling study

PubMed Central

Gattoni, Sara; Røe, Åsmund Treu; Frisk, Michael; Louch, William E.; Niederer, Steven A.

2016-01-01

Key points In the majority of species, including humans, increased heart rate increases cardiac contractility. This change is known as the force–frequency response (FFR). The majority of mammals have a positive force–frequency relationship (FFR). In rat the FFR is controversial.We derive a species‐ and temperature‐specific data‐driven model of the rat ventricular myocyte.As a measure of the FFR, we test the effects of changes in frequency and extracellular calcium on the calcium–frequency response (CFR) in our model and three altered models.The results show a biphasic peak calcium–frequency response, due to biphasic behaviour of the ryanodine receptor and the combined effect of the rapid calmodulin buffer and the frequency‐dependent increase in diastolic calcium.Alterations to the model reveal that inclusion of Ca2+/calmodulin‐dependent protein kinase II (CAMKII)‐mediated L‐type channel and transient outward K+ current activity enhances the positive magnitude calcium–frequency response, and the absence of CAMKII‐mediated increase in activity of the sarco/endoplasmic reticulum Ca2+‐ATPase induces a negative magnitude calcium–frequency response. Abstract An increase in heart rate affects the strength of cardiac contraction by altering the Ca2+ transient as a response to physiological demands. This is described by the force–frequency response (FFR), a change in developed force with pacing frequency. The majority of mammals, including humans, have a positive FFR, and cardiac contraction strength increases with heart rate. However, the rat and mouse are exceptions, with the majority of studies reporting a negative FFR, while others report either a biphasic or a positive FFR. Understanding the differences in the FFR between humans and rats is fundamental to interpreting rat‐based experimental findings in the context of human physiology. We have developed a novel model of rat ventricular electrophysiology and calcium dynamics, derived predominantly from experimental data recorded under physiological conditions. As a measure of FFR, we tested the effects of changes in stimulation frequency and extracellular calcium concentration on the simulated Ca2+ transient characteristics and showed a biphasic peak calcium–frequency relationship, consistent with recent observations of a shift from negative to positive FFR when approaching the rat physiological frequency range. We tested the hypotheses that (1) inhibition of Ca2+/calmodulin‐dependent protein kinase II (CAMKII)‐mediated increase in sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) activity, (2) CAMKII modulation of SERCA, L‐type channel and transient outward K+ current activity and (3) Na+/K+ pump dynamics play a significant role in the rat FFR. The results reveal a major role for CAMKII modulation of SERCA in the peak Ca2+–frequency response, driven most significantly by the cytosolic calcium buffering system and changes in diastolic Ca2+. PMID:26916026

Small-amplitude oscillations of electrostatically levitated drops

NASA Astrophysics Data System (ADS)

Feng, J. Q.; Beard, K. V.

1990-07-01

The nature of axisymmetric oscillations of electrostatically levitated drops is examined using an analytical method of multiple-parameter perturbations. The solution for the quiescent equilibrium shape exhibits both stretching of the drop surface along the direction of the externally applied electric field and asymmetry about the drop's equatorial plane. In the presence of electric and gravitational fields, small-amplitude oscillations of charged drops differ from the linear modes first analyzed by Rayleigh. The oscillatory response at each frequency consists of several Legendre polynomials rather than just one, and the characteristic frequency for each axisymmetric mode decreases from that calculated by Rayleigh as the electric field strength increases. This lowering of the characteristic frequencies is enhanced by the net electric charge required for levitation against gravity. Since the contributions of the various forces appear explicitly in the analytic solutions, physical insight is readily gained into their causative role in drop behavior.

Induction heating apparatus and methods of operation thereof

DOEpatents

Richardson, John G.

2006-08-01

Methods of operation of an induction melter include providing material within a cooled crucible proximate an inductor. A desired electromagnetic flux skin depth for heating the material within the crucible may be selected, and a frequency of an alternating current for energizing the inductor and for producing the desired skin depth may be selected. The alternating current frequency may be adjusted after energizing the inductor to maintain the desired electromagnetic flux skin depth. The desired skin depth may be substantially maintained as the temperature of the material varies. An induction heating apparatus includes a sensor configured to detect changes in at least one physical characteristic of a material to be heated in a crucible, and a controller configured for selectively varying a frequency of an alternating current for energizing an inductor at least partially in response to changes in the physical characteristic to be detected by the sensor.

Real-ear acoustical characteristics of impulse sound generated by golf drivers and the estimated risk to hearing: a cross-sectional study.

PubMed

Zhao, Fei; Bardsley, Barry

2014-01-21

This study investigated real-ear acoustical characteristics in terms of the sound pressure levels (SPLs) and frequency responses in situ generated from golf club drivers at impact with a golf ball. The risk of hearing loss caused by hitting a basket of golf balls using various drivers was then estimated. Cross-sectional study. The three driver clubs were chosen on the basis of reflection of the commonality and modern technology of the clubs. The participants were asked to choose the clubs in a random order and hit six two-piece range golf balls with each club. The experiment was carried out at a golf driving range in South Wales, UK. 19 male amateur golfers volunteered to take part in the study, with an age range of 19-54 years. The frequency responses and peak SPLs in situ of the transient sound generated from the club at impact were recorded bilaterally and simultaneously using the GN Otometric Freefit wireless real-ear measurement system. A swing speed radar system was also used to investigate the relationship between noise level and swing speed. Different clubs generated significantly different real-ear acoustical characteristics in terms of SPL and frequency responses. However, they did not differ significantly between the ears. No significant correlation was found between the swing speed and noise intensity. On the basis of the SPLs measured in the present study, the percentage of daily noise exposure for hitting a basket of golf balls using the drivers described above was less than 2%. The immediate danger of noise-induced hearing loss for amateur golfers is quite unlikely. However, it may be dangerous to hearing if the noise level generated by the golf clubs exceeded 116 dBA.

TECHNICAL NOTE: Direct finite-element analysis of the frequency response of a Y-Z lithium niobate SAW filter

NASA Astrophysics Data System (ADS)

Xu, Guanshui

2000-12-01

A direct finite-element model is developed for the full-scale analysis of the electromechanical phenomena involved in surface acoustic wave (SAW) devices. The equations of wave propagation in piezoelectric materials are discretized using the Galerkin method, in which an implicit algorithm of the Newmark family with unconditional stability is implemented. The Rayleigh damping coefficients are included in the elements near the boundary to reduce the influence of the reflection of waves. The performance of the model is demonstrated by the analysis of the frequency response of a Y-Z lithium niobate filter with two uniform ports, with emphasis on the influence of the number of electrodes. The frequency response of the filter is obtained through the Fourier transform of the impulse response, which is solved directly from the finite-element simulation. It shows that the finite-element results are in good agreement with the characteristic frequency response of the filter predicted by the simple phase-matching argument. The ability of the method to evaluate the influence of the bulk waves at the high-frequency end of the filter passband and the influence of the number of electrodes on insertion loss is noteworthy. We conclude that the direct finite-element analysis of SAW devices can be used as an effective tool for the design of high-performance SAW devices. Some practical computational challenges of finite-element modeling of SAW devices are discussed.

Estimation of HF artificial ionospheric turbulence characteristics using comparison of calculated plasma wave decay rates with the measured decay rates of the stimulated electromagnetic emission

NASA Astrophysics Data System (ADS)

Bareev, D. D.; Gavrilenko, V. G.; Grach, S. M.; Sergeev, E. N.

2016-02-01

It is shown experimentally that the relaxation time of the stimulated electromagnetic emission (SEE) after the pump wave turn off decreases when frequency of the electromagnetic wave, responsible for the SEE generation (pump wave f0 or diagnostic wave fdw) approaches 4th harmonic of the electron cyclotron frequency fce . Since the SEE relaxation is determined by the damping rate of plasma waves with the same frequency, responsible for the SEE generation, we calculated damping rates of plasma waves with ω ∼ωuh (ω is the plasma wave frequency, ωuh is the upper hybrid frequency) for frequencies close to and distant from the double resonance where ωuh ∼ 4ωce (ωce = 2 πfce). The calculations were performed numerically on the base of linear plasma wave dispersion relation at arbitrary ratio between | Δ | = ω - 4ωce and |k‖ |VTe (VTe is the electron thermal speed and k‖ is the projection of the wave vector onto the magnetic field direction. A comparison of calculation and experimental results has shown that obtained frequency dependence of the SEE decay rate is similar to the damping rate frequency dependence for plasma waves with wave vectors directed at the angles 60-70° to the magnetic field, and gives a strong hint that oblique upper hybrid plasma waves should be responsible for the SEE generation.

A heuristic method for identifying chaos from frequency content.

PubMed

Wiebe, R; Virgin, L N

2012-03-01

The sign of the largest Lyapunov exponent is the fundamental indicator of chaos in a dynamical system. However, although the extraction of Lyapunov exponents can be accomplished with (necessarily noisy) the experimental data, this is still a relatively data-intensive and sensitive endeavor. This paper presents an alternative pragmatic approach to identifying chaos using response frequency characteristics and extending the concept of the spectrogram. The method is shown to work well on both experimental and simulated time series.

Power conversion distribution system using a resonant high-frequency AC link

NASA Technical Reports Server (NTRS)

Sood, P. K.; Lipo, T. A.

1986-01-01

Static power conversion systems based on a resonant high frequency (HF) link offers a significant reduction in the size and weight of the equipment over that achieved with conventional approaches, especially when multiple sources and loads are to be integrated. A faster system response and absence of audible noise are the other principal characteristics of such systems. A conversion configuration based on a HF link which is suitable for applications requiring distributed power is proposed.

Validation of simulated earthquake ground motions based on evolution of intensity and frequency content

USGS Publications Warehouse

Rezaeian, Sanaz; Zhong, Peng; Hartzell, Stephen; Zareian, Farzin

2015-01-01

Simulated earthquake ground motions can be used in many recent engineering applications that require time series as input excitations. However, applicability and validation of simulations are subjects of debate in the seismological and engineering communities. We propose a validation methodology at the waveform level and directly based on characteristics that are expected to influence most structural and geotechnical response parameters. In particular, three time-dependent validation metrics are used to evaluate the evolving intensity, frequency, and bandwidth of a waveform. These validation metrics capture nonstationarities in intensity and frequency content of waveforms, making them ideal to address nonlinear response of structural systems. A two-component error vector is proposed to quantify the average and shape differences between these validation metrics for a simulated and recorded ground-motion pair. Because these metrics are directly related to the waveform characteristics, they provide easily interpretable feedback to seismologists for modifying their ground-motion simulation models. To further simplify the use and interpretation of these metrics for engineers, it is shown how six scalar key parameters, including duration, intensity, and predominant frequency, can be extracted from the validation metrics. The proposed validation methodology is a step forward in paving the road for utilization of simulated ground motions in engineering practice and is demonstrated using examples of recorded and simulated ground motions from the 1994 Northridge, California, earthquake.

Frequency locking in auditory hair cells: Distinguishing between additive and parametric forcing

NASA Astrophysics Data System (ADS)

Edri, Yuval; Bozovic, Dolores; Yochelis, Arik

2016-10-01

The auditory system displays remarkable sensitivity and frequency discrimination, attributes shown to rely on an amplification process that involves a mechanical as well as a biochemical response. Models that display proximity to an oscillatory onset (also known as Hopf bifurcation) exhibit a resonant response to distinct frequencies of incoming sound, and can explain many features of the amplification phenomenology. To understand the dynamics of this resonance, frequency locking is examined in a system near the Hopf bifurcation and subject to two types of driving forces: additive and parametric. Derivation of a universal amplitude equation that contains both forcing terms enables a study of their relative impact on the hair cell response. In the parametric case, although the resonant solutions are 1 : 1 frequency locked, they show the coexistence of solutions obeying a phase shift of π, a feature typical of the 2 : 1 resonance. Different characteristics are predicted for the transition from unlocked to locked solutions, leading to smooth or abrupt dynamics in response to different types of forcing. The theoretical framework provides a more realistic model of the auditory system, which incorporates a direct modulation of the internal control parameter by an applied drive. The results presented here can be generalized to many other media, including Faraday waves, chemical reactions, and elastically driven cardiomyocytes, which are known to exhibit resonant behavior.

Characterisation of the human-seat coupling in response to vibration.

PubMed

Kim, Eunyeong; Fard, Mohammad; Kato, Kazuhito

2017-08-01

Characterising the coupling between the occupant and vehicle seat is necessary to understand the transmission of vehicle seat vibration to the human body. In this study, the vibration characteristics of the human body coupled with a vehicle seat were identified in frequencies up to 100 Hz. Transmissibilities of three volunteers seated on two different vehicle seats were measured under multi-axial random vibration excitation. The results revealed that the human-seat system vibration was dominated by the human body and foam below 10 Hz. Major coupling between the human body and the vehicle seat-structure was observed in the frequency range of 10-60 Hz. There was local coupling of the system dominated by local resonances of seat frame and seat surface above 60 Hz. Moreover, the transmissibility measured on the seat surface between the human and seat foam is suggested to be a good method of capturing human-seat system resonances rather than that measured on the human body in high frequencies above 10 Hz.Practitioner Summary: The coupling characteristics of the combined human body and vehicle seat system has not yet been fully understood in frequencies of 0.5-100 Hz. This study shows the human-seat system has distinctive dynamic coupling characteristics in three different frequency regions: below 10 Hz, 10-60 Hz, and above 60 Hz.

Frequency range selection method of trans-impedance amplifier for high sensitivity lock-in amplifier used in the optical sensors

NASA Astrophysics Data System (ADS)

Park, Chang-In; Jeon, Su-Jin; Hong, Nam-Pyo; Choi, Young-Wan

2016-03-01

Lock-in amplifier (LIA) has been proposed as a detection technique for optical sensors because it can measure low signal in high noise level. LIA uses synchronous method, so the input signal frequency is locked to a reference frequency that is used to carry out the measurements. Generally, input signal frequency of LIA used in optical sensors is determined by modulation frequency of optical signal. It is important to understand the noise characteristics of the trans-impedance amplifier (TIA) to determine the modulation frequency. The TIA has a frequency range in which noise is minimized by the capacitance of photo diode (PD) and the passive component of TIA feedback network. When the modulation frequency is determined in this range, it is possible to design a robust system to noise. In this paper, we propose a method for the determination of optical signal modulation frequency selection by using the noise characteristics of TIA. Frequency response of noise in TIA is measured by spectrum analyzer and minimum noise region is confirmed. The LIA and TIA circuit have been designed as a hybrid circuit. The optical sensor is modeled by the laser diode (LD) and photo diode (PD) and the modulation frequency was used as the input to the signal generator. The experiments were performed to compare the signal to noise ratio (SNR) of the minimum noise region and the others. The results clearly show that the SNR is enhanced in the minimum noise region of TIA.

Vibration Measurement Method of a String in Transversal Motion by Using a PSD.

PubMed

Yang, Che-Hua; Wu, Tai-Chieh

2017-07-17

A position sensitive detector (PSD) is frequently used for the measurement of a one-dimensional position along a line or a two-dimensional position on a plane, but is more often used for measuring static or quasi-static positions. Along with its quick response when measuring short time-spans in the micro-second realm, a PSD is also capable of detecting the dynamic positions of moving objects. In this paper, theoretical modeling and experiments are conducted to explore the frequency characteristics of a vibrating string while moving transversely across a one-dimensional PSD. The theoretical predictions are supported by the experiments. When the string vibrates at its natural frequency while moving transversely, the PSD will detect two frequencies near this natural frequency; one frequency is higher than the natural frequency and the other is lower. Deviations in these two frequencies, which differ from the string's natural frequency, increase while the speed of motion increases.

An ultrasensitive quartz crystal microbalance-micropillars based sensor for humidity detection

NASA Astrophysics Data System (ADS)

Wang, Pengtao; Su, Junwei; Su, Che-Fu; Dai, Wen; Cernigliaro, George; Sun, Hongwei

2014-06-01

A unique sensing device, which couples microscale pillars with quartz crystal microbalance (QCM) substrate to form a resonant system, is developed to achieve several orders of magnitude enhancement in sensitivity compared to conventional QCM sensors. In this research, Polymethyl Methacrylate (PMMA) micropillars are fabricated on a QCM substrate using nanoimprinting lithography. The effects of pillar geometry and physical properties, tuned by molecular weight (MW) of PMMA, on the resonant characteristics of QCM-micropillars device are systematically investigated. It is found that the resonant frequency shift increases with increasing MW. The coupled QCM-micropillars device displays nonlinear frequency response, which is opposite to the linear response of conventional QCM devices. In addition, a positive resonant frequency shift is captured near the resonant point of the coupled QCM-micropillars system. Humidity detection experiments show that compared to current nanoscale feature based QCM sensors, QCM-micropillars devices offer higher sensitivity and moderate response time. This research points to a novel way of improving sensitivity of acoustic wave sensors without the need for fabricating surface nanostructures.

Fast-response free-running frequency-stabilized dc-to-dc converter employing a state plane-trajectory control law

NASA Technical Reports Server (NTRS)

Huffman, S. D.; Burns, W. W., III; Wilson, T. G.; Owen, H. A., Jr.

1976-01-01

Implementations of a state-plane-trajectory control law for energy storage dc-to-dc converters are presented. Performance characteristics of experimental voltage step-up converter systems employing these implementations are reported and compared to theoretical predictions.

Dynamic and energetic characteristics of a bistable piezoelectric vibration energy harvester with an elastic magnifier

NASA Astrophysics Data System (ADS)

Wang, Guangqing; Liao, Wei-Hsin; Yang, Binqiang; Wang, Xuebao; Xu, Wentan; Li, Xiuling

2018-05-01

Bistable piezoelectric energy harvesters are being increasingly seen as an alternative to batteries in low-power devices. However, their energy harvesting characteristics are limited. To enhance these, we use a configuration including an elastic magnifier to amplify base excitation and provide sufficient kinetic energy to overcome potential well barriers, thus leading to large-amplitude bistable motion. We derive the distributed parameter mathematical model of this configuration by using Hamilton's principle. We then investigate the nonlinear dynamic behaviors and energetic characteristics and analyze the bifurcation for the equilibrium solution of the model. The simulations and experiments show high electromechanical responses and energy generation characteristics of the proposed system over a broad frequency band. The results suggest that, compared with a typical bistable piezoelectric energy harvester, the proposed energy harvester system with an elastic magnifier can provide higher output over a broader frequency band at lower excitation levels by adjusting the system's mass and stiffness ratios.

Flying qualities and control system characteristics for superaugmented aircraft

NASA Technical Reports Server (NTRS)

Myers, T. T.; Mcruer, D. T.; Johnston, D. E.

1984-01-01

Aircraft-alone dynamics and superaugmented control system fundamental regulatory properties including stability and regulatory responses of the basic closed-loop systems; fundamental high and low frequency margins and governing factors; and sensitivity to aircraft and controller parameters are addressed. Alternative FCS mechanizations, and mechanizational side effects are also discussed. An overview of flying qualities considerations encompasses general pilot operations as a controller in unattended, intermittent and trim, and full-attention regulatory or command control; effective vehicle primary and secondary response properties to pilot inputs and disturbances; pilot control architectural possibilities; and comparison of superaugmented and conventional aircraft path responses for different forms of pilot control. Results of a simple experimental investigation into pilot dynamic behavior in attitude control of superaugmented aircraft configurations with high frequency time laps and time delays are presented.

Improved near-field characteristics of phased arrays for assessing concrete and cementitious materials

NASA Astrophysics Data System (ADS)

Wooh, Shi-Chang; Azar, Lawrence

1999-01-01

The degradation of civil infrastructure has placed a focus on effective nondestructive evaluation techniques to correctly assess the condition of existing concrete structures. Conventional high frequency ultrasonic response are severely affected by scattering and material attenuation, resulting in weak and confusing signal returns. Therefore, low frequency ultrasonic transducers, which avoid this problem of wave attenuation, are commonly used for concrete with limited capabilities. The focus of this research is to ascertain some benefits and limitations of a low frequency ultrasonic phased array transducer. In this paper, we investigate a novel low-frequency ultrasonic phased array and the results of experimental feasibility test for practical condition assessment of concrete structures are reported.

Granular metamaterials for vibration mitigation

NASA Astrophysics Data System (ADS)

Gantzounis, G.; Serra-Garcia, M.; Homma, K.; Mendoza, J. M.; Daraio, C.

2013-09-01

Acoustic metamaterials that allow low-frequency band gaps are interesting for many practical engineering applications, where vibration control and sound insulation are necessary. In most prior studies, the mechanical response of these structures has been described using linear continuum approximations. In this work, we experimentally and theoretically address the formation of low-frequency band gaps in locally resonant granular crystals, where the dynamics of the system is governed by discrete equations. We investigate the quasi-linear behavior of such structures. The analysis shows that a stopband can be introduced at about one octave lower frequency than in materials without local resonances. Broadband and multi-frequency stopband characteristics can also be achieved by strategically tailoring the non-uniform local resonance parameters.

Dynamic response characteristics of the high-temperature superconducting maglev system under lateral eccentric distance

NASA Astrophysics Data System (ADS)

Wang, Bo; Zheng, Jun; Si, Shuaishuai; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang

2016-07-01

Off-centre operation of high-temperature superconducting (HTS) maglev systems caused by inevitable conditions such as the misregistration of vehicle, crosswind and curve negotiation, may change the distribution of the trapped flux in the HTS bulks and the magnetic interaction between HTS bulks and the PMG. It impacts on the performance of HTS maglev, and more seriously makes the maglev vehicle overturned. Therefore, understanding the performance of the HTS maglev in off-center operation is very important. In this paper, the dynamic response characteristics of a cryostat with twenty-four onboard YBaCuO superconductor bulks were experimentally investigated at different eccentric distances under loads before the initial FC process. Parameters such as vibration accelerations, displacement, natural frequency and dynamic stiffness were acquired and analyzed via the B&K vibration analyzer and laser displacement sensors. Results suggest that the natural frequency and dynamic stiffness of the maglev vehicle would be obviously reduced with the eccentric distance, posing negative effects on the stability of HTS maglev.

Flow and thermal characteristics of high Reynolds number (2800-17,000) dye cell: simulation and experiment.

PubMed

Mishra, G K; Kumar, Abhay; Prakash, O; Biswal, R; Dixit, S K; Nakhe, S V

2015-04-10

This paper presents computational and experimental studies on wavelength/frequency fluctuation characteristics of a high pulse repetition rate (18 kHz) dye laser pumped by a frequency-doubled Nd:YAG laser (532 nm). The temperature gradient in the dye solution is found to be responsible for wavelength fluctuations of the dye laser at low flow rates (2800

Design and Operation of a Vibration-Acoustic-Thermal Apparatus for Identifying Variations in Free and Forced Response of Sandwich Panels Due to Combined Loading

NASA Astrophysics Data System (ADS)

Ellmer, Claudia; Adams, Douglas E.; White, Jonathan R.; Jata, Kumar

2008-02-01

Combined vibration, thermal, and acoustic environments cause significant changes in the free and forced response characteristics of spacecraft metallic, ceramic, and carbon thermal protection systems, exhaust wash structures in fixed wing aircraft, and ground vehicle components exposed to blast loading. When structural components become damaged, the effects of combined loads are even more apparent on the structural response. A new combined vibration-acoustic-thermal apparatus designed to simultaneously expose specimens up to 4' by 4' with 10 g vibration up to either 100 Hz or 1 inch displacement vibrations, 140 dB acoustic pressures, and >400 °F temperatures will first be described in this paper. Then observations from experiments conducted on a sandwich metallic panel exposed to thermal loads will be described. Modal impact and active sensor data will be utilized to extract frequency response function models that change as a function of the loading. These frequency response models indicate significant changes in the free response properties of the panel. For example, it will be shown that temperature changes cause the resonant frequencies of the panel to decrease resulting in higher response amplitudes. Likewise, acoustic pressure loads distributed across the panel will be shown to change as a function of temperature.

Interferometric sensor based on the polarization-maintaining fibers

NASA Astrophysics Data System (ADS)

Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Vašinek, Vladimir; Liner, Andrej; Papes, Martin

2012-01-01

The interferometers composed of optical fibers are due to its high sensitivity capable of to measure various influences affecting the fiber. These influences may be bending or different sorts of fiber deformations, vibration, temperature, etc. In this case the vibration is the measured quantity, which is evaluated by analyzing the interference fringes representing changes in the fiber. Was used a Mach-Zehnder interferometer composed of the polarization maintaining elements. The polarization maintaining elements were used because of high sensitivity to polarization state inside the interferometer. The light was splitted into the two optical paths, where the first one is the reference fiber and it is separated from the actual phenomenon, and the second one is measuring fiber, which is directly exposed to vibration transmission from the underlying surface. The light source was narrowband DFB laser serating at a wavelength of 1550nm and as a detector an InGaAs PIN photodiode were used in this measurement. The electrical signal from the photodiode was amplified and fed into the measuring card. On the incoming signal the FFT was applied, which performs the transformation into the frequency domain and the results were further evaluated by software. We were evaluating the characteristic frequencies and their amplitude ratios. The frequency responses are unique for a given phenomenon, thus it is possible to identify recurring events by the characteristic frequencies and their amplitude ratios. The frequency range was limited by the properties of the used speaker, by the frequency characteristics of the filter in the amplifier and used resonant element. For the experiment evaluation the repeated impact of the various spherical objects on the surface board was performed and measured. The stability of amplitude and frequency and also the frequency range was verified in this measurement.

Attributions of Blame in a Hypothetical Child Sexual Abuse Case: Roles of Behavior Problems and Frequency of Abuse.

PubMed

Theimer, Kate; Hansen, David J

2017-06-01

Youth who are blamed for their sexual abuse may experience increased negative outcomes, such as amplified self-blame. Similarly, blaming nonoffending parents can impede their ability to support their child following disclosure. Understanding the factors that influence how people perceive victim, caregiver, and perpetrator responsibility is imperative for the protection and treatment of families who have experienced sexual abuse. Little research has explored victim and abuse characteristics that influence the perception of sexual abuse. As such, the purpose of this study was to examine the roles of behavior problems and frequency of abuse in the attribution of blame in a hypothetical sexual abuse case. In addition, the relationship between several respondent characteristics and assignment of responsibility were explored as secondary aims. The study used a two (behavior problems: three suspensions in one school semester vs. no mention of behavior problems) by two (one abuse occurrence vs. five abuse occurrences) between-subjects design. Seven hundred forty-two participants read one of the four child sexual abuse (CSA) vignettes and completed measures related to responsibility. ANOVAs revealed those who read a vignette where the youth experienced multiple abuse incidents rated the victim as more responsible regardless of whether or not the youth was described as having behavior problems. Results indicate that respondents may have attributed more blame to the victim due to the belief that she could have done something to stop the abuse after the first incident. The abuse frequency manipulation when combined with the behavior manipulation appeared to relate to how respondents perceived the victim's parents. Males and younger respondents attributed more blame to the victim; however, sexual abuse or assault history did not associate with victim responsibility ratings. Clinical and research implications were discussed.

Transitioning hearing aid users with severe and profound loss to a new gain/frequency response: benefit, perception, and acceptance.

PubMed

Convery, Elizabeth; Keidser, Gitte

2011-03-01

Adults with severe and profound hearing loss tend to be long-term, full-time users of amplification who are highly reliant on their hearing aids. As a result of these characteristics, they are often reluctant to update their hearing aids when new features or signal-processing algorithms become available. Due to the electroacoustic constraints of older devices, many severely and profoundly hearing-impaired adults continue to wear hearing aids that provide more low- and mid-frequency gain and less high-frequency gain than would be prescribed by the National Acoustic Laboratories' revised formula with profound correction factor (NAL-RP). To investigate the effect of a gradual change in gain/frequency response on experienced hearing-aid wearers with moderately severe to profound hearing loss. Double-blind, randomized controlled trial. Twenty-three experienced adult hearing-aid users with severe and profound hearing loss participated in the study. Participants were selected for inclusion in the study if the gain/frequency response of their own hearing aids differed significantly from their NAL-RP prescription. Participants were assigned either to a control or to an experimental group balanced for aided ear three-frequency pure-tone average (PTA) and age. Participants were fitted with Siemens Artis 2 SP behind-the-ear (BTE) hearing aids that were matched to the gain/frequency response of their own hearing aids for a 65 dB SPL input level. The experimental group progressed incrementally to their NAL-RP targets over the course of 15 wk, while the control group maintained their initial settings throughout the study. Aided speech discrimination testing, loudness scaling, and structured questionnaires were completed at 3, 6, 9, 12, and 15 wk postfitting. A paired comparison between the old and new gain/frequency responses was completed at 1 and 15 wk postfitting. Statistical analysis was conducted to examine differences between the experimental and control groups and changes in objective performance and subjective perception over time. The results of the study showed that participants in the experimental group were subjectively accepting of the changes to their amplification characteristics, as evidenced by nonsignificant changes in the ratings of device performance over time. Perception of loudness, sound quality, speech intelligibility, and own voice volume did not change significantly throughout the study. Objectively, participants in the experimental group demonstrated poorer speech discrimination performance as the study progressed, although there was no change in objective loudness perception. According to the paired comparison, there was an overall subjective preference for the original gain/frequency response among all participants, although participants in the experimental group did show an increase in preference for the NAL-RP response by the end of the study. Based on the findings of this study, we suggest that undertaking a gradual change to a new gain/frequency response with severely and profoundly hearing-impaired adults is a feasible procedure. However, we recommend that clinicians select transition candidates carefully and initiate the procedure only if there is a clinical reason for doing so. A validated prescriptive formula should be used as a transition target, and speech discrimination performance should be monitored throughout the transition. American Academy of Audiology.

Pilot-model analysis and simulation study of effect of control task desired control response

NASA Technical Reports Server (NTRS)

Adams, J. J.; Gera, J.; Jaudon, J. B.

1978-01-01

A pilot model analysis was performed that relates pilot control compensation, pilot aircraft system response, and aircraft response characteristics for longitudinal control. The results show that a higher aircraft short period frequency is required to achieve superior pilot aircraft system response in an altitude control task than is required in an attitude control task. These results were confirmed by a simulation study of target tracking. It was concluded that the pilot model analysis provides a theoretical basis for determining the effect of control task on pilot opinions.

Study of Dynamic Characteristics of Aeroelastic Systems Utilizing Randomdec Signatures

NASA Technical Reports Server (NTRS)

Chang, C. S.

1975-01-01

The feasibility of utilizing the random decrement method in conjunction with a signature analysis procedure to determine the dynamic characteristics of an aeroelastic system for the purpose of on-line prediction of potential on-set of flutter was examined. Digital computer programs were developed to simulate sampled response signals of a two-mode aeroelastic system. Simulated response data were used to test the random decrement method. A special curve-fit approach was developed for analyzing the resulting signatures. A number of numerical 'experiments' were conducted on the combined processes. The method is capable of determining frequency and damping values accurately from randomdec signatures of carefully selected lengths.

Enhanced response of non-Hermitian photonic systems near exceptional points

NASA Astrophysics Data System (ADS)

Sunada, Satoshi

2018-04-01

This paper theoretically and numerically studies the response characteristics of non-Hermitian resonant photonic systems operating near an exceptional point (EP), where two resonant eigenmodes coalesce. It is shown that a system near an EP can exhibit a non-Lorentzian frequency response, whose line shape and intensity strongly depend on the modal decay rate and coupling parameters for the input waves, unlike a normal Lorentzian response around a single resonance. In particular, it is shown that the peak intensity of the frequency response is inversely proportional to the fourth power of the modal decay rate and can be significantly enhanced with the aid of optical gain. The theoretical results are numerically verified by a full wave simulation of a microring cavity with gain. In addition, the effects of the nonlinear gain saturation and spontaneous emission are discussed. The response enhancement and its parametric dependence may be useful for designing and controlling the excitation of eigenmodes by external fields.

Convergent input from brainstem coincidence detectors onto delay-sensitive neurons in the inferior colliculus.

PubMed

McAlpine, D; Jiang, D; Shackleton, T M; Palmer, A R

1998-08-01

Responses of low-frequency neurons in the inferior colliculus (IC) of anesthetized guinea pigs were studied with binaural beats to assess their mean best interaural phase (BP) to a range of stimulating frequencies. Phase plots (stimulating frequency vs BP) were produced, from which measures of characteristic delay (CD) and characteristic phase (CP) for each neuron were obtained. The CD provides an estimate of the difference in travel time from each ear to coincidence-detector neurons in the brainstem. The CP indicates the mechanism underpinning the coincidence detector responses. A linear phase plot indicates a single, constant delay between the coincidence-detector inputs from the two ears. In more than half (54 of 90) of the neurons, the phase plot was not linear. We hypothesized that neurons with nonlinear phase plots received convergent input from brainstem coincidence detectors with different CDs. Presentation of a second tone with a fixed, unfavorable delay suppressed the response of one input, linearizing the phase plot and revealing other inputs to be relatively simple coincidence detectors. For some neurons with highly complex phase plots, the suppressor tone altered BP values, but did not resolve the nature of the inputs. For neurons with linear phase plots, the suppressor tone either completely abolished their responses or reduced their discharge rate with no change in BP. By selectively suppressing inputs with a second tone, we are able to reveal the nature of underlying binaural inputs to IC neurons, confirming the hypothesis that the complex phase plots of many IC neurons are a result of convergence from simple brainstem coincidence detectors.

AC electroosmosis in microchannels packed with a porous medium

NASA Astrophysics Data System (ADS)

Kang, Yuejun; Yang, Chun; Huang, Xiaoyang

2004-08-01

This paper presents a theoretical study on ac-driven electroosmotic flow in both open-end and closed-end microchannels packed with uniform charged spherical microparticles. The time-periodic oscillating electroosmotic flow in an open-end capillary in response to the application of an alternating (ac) electric field is obtained using the Green function approach. The analysis is based on the Carman-Kozeny theory. The backpressure associated with the counter-flow in a closed-end capillary is obtained by analytically solving the modified Brinkman momentum equation. It is demonstrated that in a microchannel with its two ends connected to reservoirs and subject to ambient pressure, the oscillating Darcy velocity profile depends on both the pore size and the excitation frequency; such effects are coupled through an important aspect ratio of the tubule radius to the Stokes penetration depth. For a fixed pore size, the magnitude of the ac electroosmotic flow decreases with increasing frequency. With increasing pore size, however, the magnitude of the maximum velocity shows two different trends with respect to the excitation frequency: it gets higher in the low frequency domain, and gets lower in the high frequency domain. In a microchannel with closed ends, for a fixed excitation frequency, use of smaller packing particles can generate higher backpressure. For a fixed pore size, the backpressure magnitude shows two different trends changing with the excitation frequency. When the excitation frequency is lower than the system characteristic frequency, the backpressure decreases with increasing excitation frequency. When the excitation frequency is higher than the system characteristic frequency, the backpressure increases with increasing excitation frequency.

Centaur engine gimbal friction characteristics under simulated thrust load

NASA Technical Reports Server (NTRS)

Askew, J. W.

1986-01-01

An investigation was performed to determine the friction characteristics of the engine gimbal system of the Centaur upper stage rocket. Because the Centaur requires low-gain autopilots in order to meet all stability requirements for some configurations, control performance (response to transients and limit-cycle amplitudes) depends highly on these friction characteristics. Forces required to rotate the Centaur engine gimbal system were measured under a simulated thrust load of 66,723 N (15,000 lb) and in an altitude/thermal environment. A series of tests was performed at three test conditions; ambient temperature and pressure, ambient temperature and vacuum, and cryogenic temperature and vacuum. Gimbal rotation was controlled, and tests were performed in which rotation amplitude and frequency were varied by using triangular and sinusoidal waveforms. Test data revealed an elastic characteristic of the gimbal, independent of the input signal, which was evident prior to true gimbal sliding. The torque required to initiate gimbal sliding was found to decrease when both pressure and temperature decreased. Results from the low amplitude and low frequency data are currently being used in mathematically modeling the gimbal friction characteristics for Centaur autopilot performance studies.

Centaur engine gimbal friction characteristics under simulated thrust load

NASA Astrophysics Data System (ADS)

Askew, J. W.

1986-09-01

An investigation was performed to determine the friction characteristics of the engine gimbal system of the Centaur upper stage rocket. Because the Centaur requires low-gain autopilots in order to meet all stability requirements for some configurations, control performance (response to transients and limit-cycle amplitudes) depends highly on these friction characteristics. Forces required to rotate the Centaur engine gimbal system were measured under a simulated thrust load of 66,723 N (15,000 lb) and in an altitude/thermal environment. A series of tests was performed at three test conditions; ambient temperature and pressure, ambient temperature and vacuum, and cryogenic temperature and vacuum. Gimbal rotation was controlled, and tests were performed in which rotation amplitude and frequency were varied by using triangular and sinusoidal waveforms. Test data revealed an elastic characteristic of the gimbal, independent of the input signal, which was evident prior to true gimbal sliding. The torque required to initiate gimbal sliding was found to decrease when both pressure and temperature decreased. Results from the low amplitude and low frequency data are currently being used in mathematically modeling the gimbal friction characteristics for Centaur autopilot performance studies.

Cardiovascular regulation in humans in response to oscillatory lower body negative pressure

NASA Technical Reports Server (NTRS)

Levenhagen, D. K.; Evans, J. M.; Wang, M.; Knapp, C. F.

1994-01-01

The frequency response characteristics of human cardiovascular regulation during hypotensive stress have not been determined. We therefore exposed 10 male volunteers to seven frequencies (0.004-0.1 Hz) of oscillatory lower body negative pressure (OLBNP; 0-50 mmHg). Fourier spectra of arterial pressure (AP), central venous pressure (CVP), stroke volume (SV), cardiac output (CO), heart rate (HR), and total peripheral resistance (TPR) were determined and first harmonic mean, amplitude, and phase angles with respect to OLBNP are presented. AP was relatively well regulated as demonstrated by small oscillations in half amplitude (3.5 mmHg) that were independent of OLBNP frequency and similar to unstressed control spectra. Due to the biomechanics of the system, the magnitudes of oscillations in calf circumference (CC) and CVP decreased with increasing frequency; therefore, we normalized responses by these indexes of the fluid volume shifted. The ratios of oscillations in AP to oscillations in CC increased by an order of magnitude, whereas oscillations in CVP to oscillations in CC and oscillations in AP to oscillations in CVP both tripled between 0.004 and 0.1 Hz. Therefore, even though the amount of fluid shifted by OLBNP decreased with increasing frequency, the magnitude of both CVP and AP oscillations per volume of fluid shifted increased (peaking at 0.08 Hz). The phase relationships between variables, particularly the increasing lags in SV and TPR, but not CVP, indicated that efferent responses with lags of 5-6 s could account for the observed responses. We conclude that, at frequencies below 0.02 Hz, the neural system of humans functioned optimally in regulating AP; OLBNP-induced decreases in SV (by as much as 50%) were counteracted by appropriate oscillations in HR and TPR responses. As OLBNP frequency increased, SV, TPR, and HR oscillations increasingly lagged the input and became less optimally timed for AP regulation.

Human Pulse Wave Measurement by MEMS Electret Condenser Microphone

NASA Astrophysics Data System (ADS)

Nomura, Shusaku; Hanasaka, Yasushi; Ishiguro, Tadashi; Ogawa, Hiroshi

A micro Electret Condenser Microphone (ECM) fabricated by Micro Electro Mechanical System (MEMS) technology was employed as a novel apparatus for human pulse wave measurement. Since ECM frequency response characteristic, i.e. sensitivity, logically maintains a constant level at lower than the resonance frequency (stiffness control), the slightest pressure difference at around 1.0Hz generated by human pulse wave is expected to detect by MEMS-ECM. As a result of the verification of frequency response of MEMS-ECM, it was found that -20dB/dec of reduction in the sensitivity around 1.0Hz was engendered by a high input-impedance amplifier, i.e. the field effect transistor (FET), mounted near MEMS chip for amplifying tiny ECM signal. Therefore, MEMS-ECM is assumed to be equivalent with a differentiation circuit at around human pulse frequency. Introducing compensation circuit, human pulse wave was successfully obtained. In addition, the radial and ulnar artery tracing, and pulse wave velocity measurement at forearm were demonstrated; as illustrating a possible application of this micro device.

Flicker-Driven Responses in Visual Cortex Change during Matched-Frequency Transcranial Alternating Current Stimulation

PubMed Central

Ruhnau, Philipp; Keitel, Christian; Lithari, Chrysa; Weisz, Nathan; Neuling, Toralf

2016-01-01

We tested a novel combination of two neuro-stimulation techniques, transcranial alternating current stimulation (tACS) and frequency tagging, that promises powerful paradigms to study the causal role of rhythmic brain activity in perception and cognition. Participants viewed a stimulus flickering at 7 or 11 Hz that elicited periodic brain activity, termed steady-state responses (SSRs), at the same temporal frequency and its higher order harmonics. Further, they received simultaneous tACS at 7 or 11 Hz that either matched or differed from the flicker frequency. Sham tACS served as a control condition. Recent advances in reconstructing cortical sources of oscillatory activity allowed us to measure SSRs during concurrent tACS, which is known to impose strong artifacts in magnetoencephalographic (MEG) recordings. For the first time, we were thus able to demonstrate immediate effects of tACS on SSR-indexed early visual processing. Our data suggest that tACS effects are largely frequency-specific and reveal a characteristic pattern of differential influences on the harmonic constituents of SSRs. PMID:27199707

Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

PubMed

Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

2016-01-01

Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (<1 Hz). However, it is difficult to determine the frequency characteristics of brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities. © 2015 Wiley Periodicals, Inc.

Numerical analysis for the stick-slip vibration of a transversely moving beam in contact with a frictional wall

NASA Astrophysics Data System (ADS)

Won, Hong-In; Chung, Jintai

2018-04-01

This paper presents a numerical analysis for the stick-slip vibration of a transversely moving beam, considering both stick-slip transition and friction force discontinuity. The dynamic state of the beam was separated into the stick state and the slip state, and boundary conditions were defined for both. By applying the finite element method, two matrix-vector equations were derived: one for stick state and the other for slip state. However, the equations have different degrees of freedom depending on whether the end of a beam sticks or slips, so we encountered difficulties in time integration. To overcome the difficulties, we proposed a new numerical technique to alternatively use the matrix-vector equations with different matrix sizes. In addition, to eliminate spurious high-frequency responses, we applied the generalized-α time integration method with appropriate value of high-frequency numerical dissipation. Finally, the dynamic responses of stick-slip vibration were analyzed in time and frequency domains: the dynamic behavior of the beam was explained to facilitate understanding of the stick-slip motion, and frequency characteristics of the stick-slip vibration were investigated in relation to the natural frequencies of the beam. The effects of the axial load and the moving speed upon the dynamic response were also examined.

Dynamic memory of a single voltage-gated potassium ion channel: A stochastic nonequilibrium thermodynamic analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Kinshuk, E-mail: kbpchem@gmail.com

2015-05-14

In this work, we have studied the stochastic response of a single voltage-gated potassium ion channel to a periodic external voltage that keeps the system out-of-equilibrium. The system exhibits memory, resulting from time-dependent driving, that is reflected in terms of dynamic hysteresis in the current-voltage characteristics. The hysteresis loop area has a maximum at some intermediate voltage frequency and disappears in the limits of low and high frequencies. However, the (average) dissipation at long-time limit increases and finally goes to saturation with rising frequency. This raises the question: how diminishing hysteresis can be associated with growing dissipation? To answer this,more » we have studied the nonequilibrium thermodynamics of the system and analyzed different thermodynamic functions which also exhibit hysteresis. Interestingly, by applying a temporal symmetry analysis in the high-frequency limit, we have analytically shown that hysteresis in some of the periodic responses of the system does not vanish. On the contrary, the rates of free energy and internal energy change of the system as well as the rate of dissipative work done on the system show growing hysteresis with frequency. Hence, although the current-voltage hysteresis disappears in the high-frequency limit, the memory of the ion channel is manifested through its specific nonequilibrium thermodynamic responses.« less

Design and numerical simulation of novel giant magnetostrictive ultrasonic transducer

NASA Astrophysics Data System (ADS)

Li, Pengyang; Liu, Qiang; Li, Shujuan; Wang, Quandai; Zhang, Dongya; Li, Yan

This paper provides a design method of a novel giant magnetostrictive ultrasonic transducer utilized in incremental sheet metal forming. The frequency equations of the ultrasonic vibrator were deduced and the corresponding correctness verified by the modal and harmonic response characteristic through the finite element method (FEM) and ANSYS software. In addition, the magnetic field of the vibrator system was designed and verified by the ANSYS. Finally, the frequency tests based on the impedance response analysis and the amplitude measurements based on the laser displacement sensor were performed on the prototype. The results confirmed the appropriate design of this transducer, setting the foundation for a low mechanical quality factor and satisfying amplitude.

Two-dimensional fourier transform spectrometer

DOEpatents

DeFlores, Lauren; Tokmakoff, Andrei

2016-10-25

The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

Two-dimensional fourier transform spectrometer

DOEpatents

DeFlores, Lauren; Tokmakoff, Andrei

2013-09-03

The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

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.

Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves

NASA Astrophysics Data System (ADS)

Grach, S. M.; Sergeev, E. N.; Mishin, E. V.; Shindin, A. V.

2016-11-01

A review is given of the current state-of-the-art of experimental studies and the theoretical understanding of nonlinear phenomena that occur in the ionospheric F-layer irradiated by high-power high-frequency ground-based transmitters. The main focus is on the dynamic features of high-frequency turbulence (plasma waves) and low-frequency turbulence (density irregularities of various scales) that have been studied in experiments at the Sura and HAARP heating facilities operated in temporal and frequency regimes specially designed with consideration of the characteristic properties of nonlinear processes in the perturbed ionosphere using modern radio receivers and optical instruments. Experimental results are compared with theoretical turbulence models for a magnetized collisional plasma in a high-frequency electromagnetic field, allowing the identification of the processes responsible for the observed features of artificial ionospheric turbulence.

Frequency-agile electromagnetically induced transparency analogue in terahertz metamaterials.

PubMed

Xu, Quan; Su, Xiaoqiang; Ouyang, Chunmei; Xu, Ningning; Cao, Wei; Zhang, Yuping; Li, Quan; Hu, Cong; Gu, Jianqiang; Tian, Zhen; Azad, Abul K; Han, Jiaguang; Zhang, Weili

2016-10-01

Recently reported active metamaterial analogues of electromagnetically induced transparency (EIT) are promising in developing novel optical components, such as active slow light devices. However, most of the previous works have focused on manipulating the EIT resonance strength at a fixed characteristic frequency and, therefore, realized on-to-off switching responses. To further extend the functionalities of the EIT effect, here we present a frequency tunable EIT analogue in the terahertz regime by integrating photoactive silicon into the metamaterial unit cell. A tuning range from 0.82 to 0.74 THz for the EIT resonance frequency is experimentally observed by optical pump-terahertz probe measurements, allowing a frequency tunable group delay of the terahertz pulses. This straightforward approach delivers frequency agility of the EIT resonance and may enable novel ultrafast tunable devices for integrated plasmonic circuits.

The calcium-frequency response in the rat ventricular myocyte: an experimental and modelling study.

PubMed

Gattoni, Sara; Røe, Åsmund Treu; Frisk, Michael; Louch, William E; Niederer, Steven A; Smith, Nicolas P

2016-08-01

In the majority of species, including humans, increased heart rate increases cardiac contractility. This change is known as the force-frequency response (FFR). The majority of mammals have a positive force-frequency relationship (FFR). In rat the FFR is controversial. We derive a species- and temperature-specific data-driven model of the rat ventricular myocyte. As a measure of the FFR, we test the effects of changes in frequency and extracellular calcium on the calcium-frequency response (CFR) in our model and three altered models. The results show a biphasic peak calcium-frequency response, due to biphasic behaviour of the ryanodine receptor and the combined effect of the rapid calmodulin buffer and the frequency-dependent increase in diastolic calcium. Alterations to the model reveal that inclusion of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated L-type channel and transient outward K(+) current activity enhances the positive magnitude calcium-frequency response, and the absence of CAMKII-mediated increase in activity of the sarco/endoplasmic reticulum Ca(2+) -ATPase induces a negative magnitude calcium-frequency response. An increase in heart rate affects the strength of cardiac contraction by altering the Ca(2+) transient as a response to physiological demands. This is described by the force-frequency response (FFR), a change in developed force with pacing frequency. The majority of mammals, including humans, have a positive FFR, and cardiac contraction strength increases with heart rate. However, the rat and mouse are exceptions, with the majority of studies reporting a negative FFR, while others report either a biphasic or a positive FFR. Understanding the differences in the FFR between humans and rats is fundamental to interpreting rat-based experimental findings in the context of human physiology. We have developed a novel model of rat ventricular electrophysiology and calcium dynamics, derived predominantly from experimental data recorded under physiological conditions. As a measure of FFR, we tested the effects of changes in stimulation frequency and extracellular calcium concentration on the simulated Ca(2+) transient characteristics and showed a biphasic peak calcium-frequency relationship, consistent with recent observations of a shift from negative to positive FFR when approaching the rat physiological frequency range. We tested the hypotheses that (1) inhibition of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated increase in sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) activity, (2) CAMKII modulation of SERCA, L-type channel and transient outward K(+) current activity and (3) Na(+) /K(+) pump dynamics play a significant role in the rat FFR. The results reveal a major role for CAMKII modulation of SERCA in the peak Ca(2+) -frequency response, driven most significantly by the cytosolic calcium buffering system and changes in diastolic Ca(2+) . © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Fourier Transformation Theory for Averaged Functions, with Application to Very Long Baseline Radio Interferometry.

DTIC Science & Technology

1981-02-01

primary parameters affecting the SNR. For an earth-based interferometer, the physical aperture may usually be constructed adequately large to keep the...bandwidth Av cent--.c. on vo0 by an interferometer with frequency characteristic F(v) and primary power pattern G(s-s ) (defined as the product of the...infinitely narrow beam for the primary power pattern, G(g- 0 ) = (;-S )] we have where we have assumed a flat frequency response and included as a

Comparison of the Frequency Response and Voltage Tuning Characteristics of a FFP and a MEMS Fiber Optic Tunable Filter

DTIC Science & Technology

2004-05-12

Structural Engineering, La Jolla, CA 92093 14. ABSTRACT Tunable optical filters based on a Fabry - Perot element are a critical component in many...wavelength based fiber optic sensor systems. This report compares the performance of two fiber-pigtailed tunable optical filters, the fiber Fabry - Perot (FFP...both filters suggests that they can operate at frequencies up to 20 kHz and possibly as high as 100 kHz. 15. SUBJECT TERMS Tunable Fabry - Perot filters

Extending a Lippmann style seismometer's dynamic range by using a non-linear feedback circuit

NASA Astrophysics Data System (ADS)

Romeo, Giovanni; Spinelli, Giuseppe

2013-04-01

A Lippmann style seismometer uses a single-coil velocity-feedback method in order to extend toward lower frequencies a geophone's frequency response. Strong seismic signals may saturate the electronics, sometimes producing a characteristic whale-shaped recording. Adding a non linear feedback in the electronic circuit may avoid saturation, allowing the strong-motion use of the seismometer without affecting the usual performance. We show results from both simulations and experiments, using a Teledyne Geotech s13 as a mechanical part.

The firing characteristics of foot sole cutaneous mechanoreceptor afferents in response to vibration stimuli.

PubMed

Strzalkowski, Nicholas D J; Ali, R Ayesha; Bent, Leah R

2017-10-01

Single unit microneurography was used to record the firing characteristics of the four classes of foot sole cutaneous afferents [fast and slowly adapting type I and II (FAI, FAII, SAI, and SAII)] in response to sinusoidal vibratory stimuli. Frequency (3-250 Hz) and amplitude (0.001-2 mm) combinations were applied to afferent receptive fields through a 6-mm diameter probe. The impulses per cycle, defined as the number of action potentials evoked per vibration sine wave, were measured over 1 s of vibration at each frequency-amplitude combination tested. Afferent entrainment threshold (lowest amplitude at which an afferent could entrain 1:1 to the vibration frequency) and afferent firing threshold (minimum amplitude for which impulses per cycle was greater than zero) were then obtained for each frequency. Increases in vibration frequency are generally associated with decreases in expected impulses per cycle ( P < 0.001), but each foot sole afferent class appears uniquely tuned to vibration stimuli. FAII afferents tended to have the lowest entrainment and firing thresholds ( P < 0.001 for both); however, these afferents seem to be sensitive across frequency. In contrast to FAII afferents, SAI and SAII afferents tended to demonstrate optimal entrainment to frequencies below 20 Hz and FAI afferents faithfully encoded frequencies between 8 and 60 Hz. Contrary to the selective activation of distinct afferent classes in the hand, application of class-specific frequencies in the foot sole is confounded due to the high sensitivity of FAII afferents. These findings may aid in the development of sensorimotor control models or the design of balance enhancement interventions. NEW & NOTEWORTHY Our work provides a mechanistic look at the capacity of foot sole cutaneous afferents to respond to vibration of varying frequency and amplitude. We found that foot sole afferent classes are uniquely tuned to vibration stimuli; however, unlike in the hand, they cannot be independently activated by class-specific frequencies. Viewing the foot sole as a sensory structure, the present findings may aid in the refinement of sensorimotor control models and design of balance enhancement interventions. Copyright © 2017 the American Physiological Society.

Methods and apparatuses using filter banks for multi-carrier spread-spectrum signals

DOEpatents

Moradi, Hussein; Farhang, Behrouz; Kutsche, Carl A

2014-10-14

A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.

Methods and apparatuses using filter banks for multi-carrier spread-spectrum signals

DOEpatents

Moradi, Hussein; Farhang, Behrouz; Kutsche, Carl A

2014-05-20

A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.

Image Quality Characteristics of Handheld Display Devices for Medical Imaging

PubMed Central

Yamazaki, Asumi; Liu, Peter; Cheng, Wei-Chung; Badano, Aldo

2013-01-01

Handheld devices such as mobile phones and tablet computers have become widespread with thousands of available software applications. Recently, handhelds are being proposed as part of medical imaging solutions, especially in emergency medicine, where immediate consultation is required. However, handheld devices differ significantly from medical workstation displays in terms of display characteristics. Moreover, the characteristics vary significantly among device types. We investigate the image quality characteristics of various handheld devices with respect to luminance response, spatial resolution, spatial noise, and reflectance. We show that the luminance characteristics of the handheld displays are different from those of workstation displays complying with grayscale standard target response suggesting that luminance calibration might be needed. Our results also demonstrate that the spatial characteristics of handhelds can surpass those of medical workstation displays particularly for recent generation devices. While a 5 mega-pixel monochrome workstation display has horizontal and vertical modulation transfer factors of 0.52 and 0.47 at the Nyquist frequency, the handheld displays released after 2011 can have values higher than 0.63 at the respective Nyquist frequencies. The noise power spectra for workstation displays are higher than 1.2×10−5 mm2 at 1 mm−1, while handheld displays have values lower than 3.7×10−6 mm2. Reflectance measurements on some of the handheld displays are consistent with measurements for workstation displays with, in some cases, low specular and diffuse reflectance coefficients. The variability of the characterization results among devices due to the different technological features indicates that image quality varies greatly among handheld display devices. PMID:24236113

Identifying the dynamic characteristics of a dual core-wall and frame building in Chile using aftershocks of the 27 February 2010 (Mw=8.8) Maule, Chile, earthquake

USGS Publications Warehouse

Çelebi, Mehmet; Sereci, Mark; Boroschek, Ruben; Carreño, Rodrigo; Bonelli, Patricio

2013-01-01

Following the 27 February 2010 (Mw = 8.8) Offshore Maule, Chile earthquake, a temporary, 16-channel, real-time data streaming array was installed in a recently constructed building in Viña del Mar to capture its responses to aftershocks. The cast-in-place, reinforced concrete building is 16 stories high, with 3 additional basement levels, and has dual system comprising multiple structural walls and perimeter frames. This building was not damaged during the main-shock, but other buildings of similar design in Viña del Mar and other parts of Chile were damaged, although none collapsed. Dynamic characteristics of the building identified from the low-amplitude (PGA of about 2 Gal) response recordings of aftershocks are found to compare well with those determined from modal analyses using a design level FEM model. Distinct “major-axes” translational and torsional fundamental frequencies, as well as frequencies of secondary modes, are identified. Evidence of beating is consistently observed in the response data for each earthquake. Results do not match well with U.S. code formulas.

Sensitivity to Regional Earthquake Triggering and Magnitude-Frequency Characteristics of Microseismicity Detected via Matched-Filter Analysis, Central Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Boese, C. M.; Townend, J.; Chamberlain, C. J.; Warren-Smith, E.

2016-12-01

Microseismicity recorded since 2008 by the Southern Alps Microseismicity Borehole Array (SAMBA) and other predominantly short-period seismic networks deployed in the central Southern Alps, New Zealand, reveals distinctive patterns of triggering in response to regional seismicity (magnitudes larger than 5, epicentral distances of 100-500 km). Using matched-filter detection methods implemented in the EQcorrscan package (Chamberlain et al., in prep.), we analyze microseismicity occurring in several geographically distinct swarms in order to examine the responses of specific microearthquake sources to earthquakes of different sizes occurring at different distances and azimuths. The swarms exhibit complex responses to regional seismicity which reveal that microearthquake triggering in these cases involves a combination of extrinsic factors (related to the dynamic stresses produced by the regional earthquake) and intrinsic factors (controlled by the local state of stress and possibly by hydrogeological processes). We find also that the microearthquakes detected by individual templates have Gutenberg-Richter magnitude-frequency characteristics. Since the detected events, by design, have very similar hypocentres and focal mechanisms, the observed scaling pertains to a restricted set of fault planes.

Life characteristics assessment of the communications technology satellite transmitter experiment package

NASA Technical Reports Server (NTRS)

Smetana, J.; Curren, A. N.

1979-01-01

The performance characteristics of the transmitter experiment package (TEP) aboard the Communications Technology Satellite (CTS) measured during its first 2 years in orbit are presented. The TEP consists of a nominal 200 watt output stage tube (OST), a supporting power processing system (PPS), and a variable conductance heat pipe system (VCHPS). The OST, a traveling wave tube augmented with a 10 stage depressed collector has an overall saturated average efficiency of 51.5 percent and an average saturated radio frequency (rf) output power at center band frequency of 240 watts. The PPS operated with a measured efficiency of 86.5 to 88.5 percent. The VCHPS, using three pipes to conduct heat from the PPS and the OST to a 52 by 124 centimeter radiator fin, maintained the PPS baseplate temperature below 50 C for all operating conditions. The TEP performance characteristics presented include frequency response, rf output power, thermal performance, and efficiency. Communications characteristics were evaluated by using both video and audio modulated signals. On four occasions, the TEP experienced temporary thermal control system malfunctions. The anomalies were terminated safely, and the problem was investigated because of the potential for TEP damage due to the signficant temperature increases. Safe TEP operating procedures were established.

Low-Frequency Dielectric Responses of Barium Strontium Titanate Thin Films with Conducting Perovskite LaNiO3 Electrode

NASA Astrophysics Data System (ADS)

Lee, Su-Jae; Moon, Seung-Eon; Ryu, Han-Cheol; Kwak, Min-Hwan; Kim, Young-Tae

2002-07-01

Highly (h00)-oriented (Ba,Sr)TiO3 [BST] thin films were deposited by pulsed laser depositi on on the perovskite LaNiO3 metallic oxide layer as a bottom electrode. The LaNiO3 films were deposited on SiO2/Si substrates by the rf-magnetron sputtering method. The crystal line phases of the BST film were characterized by X-ray θ-2θ, ω-rocking curve and Φ-scan diffraction measurements. The surface microstructure observed by scanning electron mi croscopy was very dense and smooth. The low-frequency dielectric responses of the BST films grown at various substrate temperatures were measured as a function of frequency in the frequency range from 0.1 Hz to 10 MHz. The BST films have the dielectric constant of 265 at 1 kHz and showed multiple dielectric relaxations in the measured frequency region. The origins of these low-frequency dielectric relaxations are attributed to ionized space charge carriers such as the oxygen vacancies and defects in the BST film, the interfacial polarization in the grain boundary region and the electrode polarization. We also studied the capacitance-voltage characteristics of BST films.

Experimental measurements on transverse vibration characteristics of piezoceramic rectangular plates by optical methods

NASA Astrophysics Data System (ADS)

Ma, Chien-Ching; Lin, Hsien-Yang

2005-09-01

This study provides two non-contact optical techniques to investigate the transverse vibration characteristics of piezoceramic rectangular plates in resonance. These methods, including the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are full-field measurement for AF-ESPI and point-wise displacement measurement for LDV, respectively. The edges of these piezoceramic rectangular plates may either be fixed or free. Both resonant frequencies and mode shapes of vibrating piezoceramic plates can be obtained simultaneously by AF-ESPI. Excellent quality of the interferometric fringe patterns for the mode shapes is obtained. In the LDV system, a built-in dynamic signal analyzer (DSA) composed of DSA software and a plug-in waveform generator board can provide the piezoceramic plates with the swept-sine excitation signal, whose gain at corresponding frequencies is analyzed by the DSA software. The peaks appeared in the frequency response curve are resonant frequencies. In addition to these optical methods, the numerical computation based on the finite element analysis is used to verify the experimental results. Good agreements of the mode shapes and resonant frequencies are obtained for experimental and numerical results.

Temporal and Spatial Evolution Characteristics of Disturbance Wave in a Hypersonic Boundary Layer due to Single-Frequency Entropy Disturbance

PubMed Central

Lv, Hongqing; Shi, Jianqiang

2014-01-01

By using a high-order accurate finite difference scheme, direct numerical simulation of hypersonic flow over an 8° half-wedge-angle blunt wedge under freestream single-frequency entropy disturbance is conducted; the generation and the temporal and spatial nonlinear evolution of boundary layer disturbance waves are investigated. Results show that, under the freestream single-frequency entropy disturbance, the entropy state of boundary layer is changed sharply and the disturbance waves within a certain frequency range are induced in the boundary layer. Furthermore, the amplitudes of disturbance waves in the period phase are larger than that in the response phase and ablation phase and the frequency range in the boundary layer in the period phase is narrower than that in these two phases. In addition, the mode competition, dominant mode transformation, and disturbance energy transfer exist among different modes both in temporal and in spatial evolution. The mode competition changes the characteristics of nonlinear evolution of the unstable waves in the boundary layer. The development of the most unstable mode along streamwise relies more on the motivation of disturbance waves in the upstream than that of other modes on this motivation. PMID:25143983

Temporal and spatial evolution characteristics of disturbance wave in a hypersonic boundary layer due to single-frequency entropy disturbance.

PubMed

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing; Shi, Jianqiang

2014-01-01

By using a high-order accurate finite difference scheme, direct numerical simulation of hypersonic flow over an 8° half-wedge-angle blunt wedge under freestream single-frequency entropy disturbance is conducted; the generation and the temporal and spatial nonlinear evolution of boundary layer disturbance waves are investigated. Results show that, under the freestream single-frequency entropy disturbance, the entropy state of boundary layer is changed sharply and the disturbance waves within a certain frequency range are induced in the boundary layer. Furthermore, the amplitudes of disturbance waves in the period phase are larger than that in the response phase and ablation phase and the frequency range in the boundary layer in the period phase is narrower than that in these two phases. In addition, the mode competition, dominant mode transformation, and disturbance energy transfer exist among different modes both in temporal and in spatial evolution. The mode competition changes the characteristics of nonlinear evolution of the unstable waves in the boundary layer. The development of the most unstable mode along streamwise relies more on the motivation of disturbance waves in the upstream than that of other modes on this motivation.

Dielectric investigation of the sliding charge-density wave in Tl0.3MoO3

NASA Astrophysics Data System (ADS)

Ramanujachary, K. V.; Collins, B. T.; Greenblatt, M.; Gerhardt, R.; Rietman, E. A.

1988-10-01

We have investigated the low-frequency complex conductivity of the charge-density-wave condensate in Tl0.3MoO3, in the temperature range 40-90 K, by the measurement of admittance sampled in the frequency interval 5 Hz-13 MHz. The observed response can be characterized in terms of a simple Debye relaxation model with a distribution of relaxation times by analogy with the reported behavior of its isostructural analog K0.3MoO3. Despite qualitative similarities with the general trends observed in K0.3MoO3, the relaxational response in Tl0.3MoO3 differed significantly in detail. Both the mean relaxation times (τ0) and static dielectric constants (ɛ0) are shown to have Arrhenius temperature dependence with activation energies of 743 and 152 K, respectively. For applied dc biases above the threshold field (ET) for nonlinear conduction, the response shows structure at frequencies that resemble ``washboard'' characteristics of a moving charge condensate. From the values of the high-frequency real and imaginary parts of the dielectric constants, the existence of yet another relaxation process is proposed.

Understanding the effect of hammering process on the vibration characteristics of cymbals

NASA Astrophysics Data System (ADS)

Kuratani, F.; Yoshida, T.; Koide, T.; Mizuta, T.; Osamura, K.

2016-09-01

Cymbals are thin domed plates used as percussion instruments. When cymbals are struck, they vibrate and radiate sound. Cymbals are made through spin forming, hammering, and lathing. The spin forming creates the basic shape of the cymbal, which determines its basic vibration characteristics. The hammering and lathing produce specific sound adjustments by changing the cymbal's vibration characteristics. In this study, we study how hammering cymbals affects their vibration characteristics. The hammering produces plastic deformation (small, shallow dents) on the cymbal's surface, generating residual stresses throughout it. These residual stresses change the vibration characteristics. We perform finite element analysis of a cymbal to obtain its stress distribution and the resulting change in vibration characteristics. To reproduce the stress distribution, we use thermal stress analysis, and then with this stress distribution we perform vibration analysis. These results show that each of the cymbal's modes has a different sensitivity to the thermal load (i.e., hammering). This difference causes changes in the frequency response and the deflection shape that significantly improves the sound radiation efficiency. In addition, we explain the changes in natural frequencies by the stress and modal strain energy distributions.

A Characteristic Mode Analysis of Conductive Nanowires and Microwires Above a Lossy Dielectric Half-Space

NASA Astrophysics Data System (ADS)

Kiddle, Daniel S.

Nanowires possess extraordinary mechanical, thermoelectric and electromagnetic properties which led to their incorporation in a wide variety of applications. The purpose of this study is to investigate the effect of material on the electromagnetic response of these nanowires. We used the Method of Moments (MOM) for Arbitrarily Thin Wire (ATW) formulation as an efficient computational technique for calculating the electromagnetic response of nanowires. To explain the calculated electromagnetic response, we evoked the Characteristic Mode Analysis (CMA) which decomposes the current on the wire into a superposition of fundamental current modes. These modes are weighted by two coefficients: (i) the relative importance of each mode at a certain frequency, termed Modal Significance, and (ii) the level of coupling between the incident field and the mode termed the Modal Excitation Coefficient. In this, work we study how the wire's material affect the Modal Significance and the Modal Excitation Coefficient of nanowires. Our results show that the material of the nanowire has a strong effect on the resonance frequency, the bandwidth, and the overlap of the modes showing that the material of the nanowire can be used as a tuning factor to develop sensors with desired radiation characteristics. Nanowires are commonly grown vertically on a substrate and, therefore, we also study the effect of the presence of a lossy dielectric half-space on their electromagnetic response. To efficiently account for this interface, we utilize a modified Green's function using the rigorous Sommerfeld integrals. Our results show that the relative permittivity of the substrate decreases the resonance frequencies of the nanowires and significantly alters their radiation patterns. Most importantly, we find that, if the nanowire is near the interface, its evanescent field's couple to the dielectric half space leading to the majority of the scattered power radiated into the substrate with high directivity. The results of this thesis has the potential to quantify the electromagnetic response of vertical nanowires in their realistic environment as well as facilitate the incorporation of nanowires in novel sensing applications.

A bio-inspired auditory perception model for amplitude-frequency clustering (keynote Paper)

NASA Astrophysics Data System (ADS)

Arena, Paolo; Fortuna, Luigi; Frasca, Mattia; Ganci, Gaetana; Patane, Luca

2005-06-01

In this paper a model for auditory perception is introduced. This model is based on a network of integrate-and-fire and resonate-and-fire neurons and is aimed to control the phonotaxis behavior of a roving robot. The starting point is the model of phonotaxis in Gryllus Bimaculatus: the model consists of four integrate-and-fire neurons and is able of discriminating the calling song of male cricket and orienting the robot towards the sound source. This paper aims to extend the model to include an amplitude-frequency clustering. The proposed spiking network shows different behaviors associated with different characteristics of the input signals (amplitude and frequency). The behavior implemented on the robot is similar to the cricket behavior, where some frequencies are associated with the calling song of male crickets, while other ones indicate the presence of predators. Therefore, the whole model for auditory perception is devoted to control different responses (attractive or repulsive) depending on the input characteristics. The performance of the control system has been evaluated with several experiments carried out on a roving robot.

Upgrade of the Mirnov probe arrays on the J-TEXT tokamak.

PubMed

Guo, Daojing; Hu, Qiming; Li, Da; Shen, Chengshuo; Wang, Nengchao; Huang, Zhuo; Huang, Mingxiang; Ding, Yonghua; Xu, Guo; Yu, Qingquan; Tang, Yuejin; Zhuang, Ge

2017-12-01

The magnetic diagnostic of Mirnov probe arrays has been upgraded on the J-TEXT tokamak to measure the magnetohydrodynamic instabilities with higher spatial resolution and better amplitude-frequency characteristics. The upgraded Mirnov probe array contains one poloidal array with 48 probe modules and two toroidal arrays with 25 probe modules. Each probe module contains two probes which measure both the poloidal and the radial magnetic fields (B p and B r ). To ensure that the Mirnov probe possess better amplitude-frequency characteristics, a novel kind of Mirnov probe made of low temperature co-fired ceramics is utilized. The parameters and frequency response of the probe are measured and can meet the experiment requirement. The new Mirnov arrays have been normally applied for a round of experiments, including the observation of tearing modes and their coupling as well as high frequency magnetic perturbation due to the Alfvén eigenmode. In order to extract useful information from raw signals, visualization processing methods based on singular value decomposition and cross-power spectrum are applied to decompose the coupled modes and to determine the mode number.

Upgrade of the Mirnov probe arrays on the J-TEXT tokamak

NASA Astrophysics Data System (ADS)

Guo, Daojing; Hu, Qiming; Li, Da; Shen, Chengshuo; Wang, Nengchao; Huang, Zhuo; Huang, Mingxiang; Ding, Yonghua; Xu, Guo; Yu, Qingquan; Tang, Yuejin; Zhuang, Ge

2017-12-01

The magnetic diagnostic of Mirnov probe arrays has been upgraded on the J-TEXT tokamak to measure the magnetohydrodynamic instabilities with higher spatial resolution and better amplitude-frequency characteristics. The upgraded Mirnov probe array contains one poloidal array with 48 probe modules and two toroidal arrays with 25 probe modules. Each probe module contains two probes which measure both the poloidal and the radial magnetic fields (Bp and Br). To ensure that the Mirnov probe possess better amplitude-frequency characteristics, a novel kind of Mirnov probe made of low temperature co-fired ceramics is utilized. The parameters and frequency response of the probe are measured and can meet the experiment requirement. The new Mirnov arrays have been normally applied for a round of experiments, including the observation of tearing modes and their coupling as well as high frequency magnetic perturbation due to the Alfvén eigenmode. In order to extract useful information from raw signals, visualization processing methods based on singular value decomposition and cross-power spectrum are applied to decompose the coupled modes and to determine the mode number.

Local defect resonance (LDR): A route to highly efficient thermosonic and nonlinear ultrasonic NDT

NASA Astrophysics Data System (ADS)

Solodov, Igor

2014-02-01

The concept of LDR is based on the fact that inclusion of a defect leads to a local drop of rigidity for a certain mass of the material that should manifest in a particular characteristic frequency of the defect. A frequency match between the driving ultrasonic wave and this characteristic frequency provides an efficient energy pumping from the wave directly into the defect. For simulated and realistic defects in various materials the LDR-induced local resonance increase in the vibration amplitude averages up to ˜ (20-40 dB). Due to a strong resonance amplification of the local vibrations, the LDR-driven defects manifest a profound nonlinearity even at moderate ultrasonic excitation level. The nonlinearity combined with resonance results in efficient generation of the higher harmonics and is also used as a filter/amplifier in the frequency mixing mode of nonlinear NDT. The LDR high-Q thermal response enables to realize a frequency-selective imaging with an opportunity to distinguish between different defects by changing the driving frequency. The LDR-thermosonics requires much lower acoustic power to activate defects that makes it possible to avoid high-power ultrasonic instrumentation and proceed to a noncontact ultrasonic thermography by using air-coupled ultrasonic excitation.

Mechanics of the Mammalian Cochlea

PubMed Central

Robles, Luis; Ruggero, Mario A.

2013-01-01

In mammals, environmental sounds stimulate the auditory receptor, the cochlea, via vibrations of the stapes, the innermost of the middle ear ossicles. These vibrations produce displacement waves that travel on the elongated and spirally wound basilar membrane (BM). As they travel, waves grow in amplitude, reaching a maximum and then dying out. The location of maximum BM motion is a function of stimulus frequency, with high-frequency waves being localized to the “base” of the cochlea (near the stapes) and low-frequency waves approaching the “apex” of the cochlea. Thus each cochlear site has a characteristic frequency (CF), to which it responds maximally. BM vibrations produce motion of hair cell stereocilia, which gates stereociliar transduction channels leading to the generation of hair cell receptor potentials and the excitation of afferent auditory nerve fibers. At the base of the cochlea, BM motion exhibits a CF-specific and level-dependent compressive nonlinearity such that responses to low-level, near-CF stimuli are sensitive and sharply frequency-tuned and responses to intense stimuli are insensitive and poorly tuned. The high sensitivity and sharp-frequency tuning, as well as compression and other nonlinearities (two-tone suppression and intermodulation distortion), are highly labile, indicating the presence in normal cochleae of a positive feedback from the organ of Corti, the “cochlear amplifier.” This mechanism involves forces generated by the outer hair cells and controlled, directly or indirectly, by their transduction currents. At the apex of the cochlea, nonlinearities appear to be less prominent than at the base, perhaps implying that the cochlear amplifier plays a lesser role in determining apical mechanical responses to sound. Whether at the base or the apex, the properties of BM vibration adequately account for most frequency-specific properties of the responses to sound of auditory nerve fibers. PMID:11427697

The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe.

PubMed

Guan, Yaoyi; Berntsen, Carl R; Bilka, Michael J; Morris, Scott C

2016-12-03

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a "T" junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.

Inferior colliculus contributions to phase encoding of stop consonants in an animal model

PubMed Central

Warrier, Catherine M; Abrams, Daniel A; Nicol, Trent G; Kraus, Nina

2011-01-01

The human auditory brainstem is known to be exquisitely sensitive to fine-grained spectro-temporal differences between speech sound contrasts, and the ability of the brainstem to discriminate between these contrasts is important for speech perception. Recent work has described a novel method for translating brainstem timing differences in response to speech contrasts into frequency-specific phase differentials. Results from this method have shown that the human brainstem response is surprisingly sensitive to phase-differences inherent to the stimuli across a wide extent of the spectrum. Here we use an animal model of the auditory brainstem to examine whether the stimulus-specific phase signatures measured in human brainstem responses represent an epiphenomenon associated with far field (i.e., scalp-recorded) measurement of neural activity, or alternatively whether these specific activity patterns are also evident in auditory nuclei that contribute to the scalp-recorded response, thereby representing a more fundamental temporal processing phenomenon. Responses in anaesthetized guinea pigs to three minimally-contrasting consonant-vowel stimuli were collected simultaneously from the cortical surface vertex and directly from central nucleus of the inferior colliculus (ICc), measuring volume conducted neural activity and multiunit, near-field activity, respectively. Guinea pig surface responses were similar to human scalp-recorded responses to identical stimuli in gross morphology as well as phase characteristics. Moreover, surface recorded potentials shared many phase characteristics with near-field ICc activity. Response phase differences were prominent during formant transition periods, reflecting spectro-temporal differences between syllables, and showed more subtle differences during the identical steady-state periods. ICc encoded stimulus distinctions over a broader frequency range, with differences apparent in the highest frequency ranges analyzed, up to 3000 Hz. Based on the similarity of phase encoding across sites, and the consistency and sensitivity of response phase measured within ICc, results suggest that a general property of the auditory system is a high degree of sensitivity to fine-grained phase information inherent to complex acoustical stimuli. Furthermore, results suggest that temporal encoding in ICc contributes to temporal features measured in speech-evoked scalp-recorded responses. PMID:21945200

Respiration in neonate sea turtles.

PubMed

Price, Edwin R; Paladino, Frank V; Strohl, Kingman P; Santidrián T, Pilar; Klann, Kenneth; Spotila, James R

2007-03-01

The pattern and control of respiration is virtually unknown in hatchling sea turtles. Using incubator-raised turtles, we measured oxygen consumption, frequency, tidal volume, and minute volume for leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) turtle hatchlings for the first six days after pipping. In addition, we tested the hatchlings' response to hypercapnic, hyperoxic, and hypoxic challenges over this time period. Hatchling sea turtles generally showed resting ventilation characteristics that are similar to those of adults: a single breath followed by a long respiratory pause, slow frequency, and high metabolic rate. With hypercapnic challenge, both species responded primarily by elevating respiratory frequency via a decrease in the non-ventilatory period. Leatherback resting tidal volume increased with age but otherwise, neither species' resting respiratory pattern nor response to gas challenge changed significantly over the first few days after hatching. At the time of nest emergence, sea turtles have achieved a respiratory pattern that is similar to that of actively diving adults.

Shock loading predictions from application of indicial theory to shock-turbulence interactions

NASA Technical Reports Server (NTRS)

Keefe, Laurence R.; Nixon, David

1991-01-01

A sequence of steps that permits prediction of some of the characteristics of the pressure field beneath a fluctuating shock wave from knowledge of the oncoming turbulent boundary layer is presented. The theory first predicts the power spectrum and pdf of the position and velocity of the shock wave, which are then used to obtain the shock frequency distribution, and the pdf of the pressure field, as a function of position within the interaction region. To test the validity of the crucial assumption of linearity, the indicial response of a normal shock is calculated from numerical simulation. This indicial response, after being fit by a simple relaxation model, is used to predict the shock position and velocity spectra, along with the shock passage frequency distribution. The low frequency portion of the shock spectra, where most of the energy is concentrated, is satisfactorily predicted by this method.

The Academic Ethics of Graduate Business Students: A Survey.

ERIC Educational Resources Information Center

Brown, Bob S.

1995-01-01

Survey responses from 207 of 313 graduate business students revealed that 80% had engaged in at least 1 of 15 unethical practices. No relationship appeared between ethical behavior/attitudes and student characteristics. Despite their self-perception as more ethical than undergraduates, graduate students had similar frequency of unethical behavior…

Effect of initial strain and material nonlinearity on the nonlinear static and dynamic response of graphene sheets

NASA Astrophysics Data System (ADS)

Singh, Sandeep; Patel, B. P.

2018-06-01

Computationally efficient multiscale modelling based on Cauchy-Born rule in conjunction with finite element method is employed to study static and dynamic characteristics of graphene sheets, with/without considering initial strain, involving Green-Lagrange geometric and material nonlinearities. The strain energy density function at continuum level is established by coupling the deformation at continuum level to that at atomic level through Cauchy-Born rule. The atomic interactions between carbon atoms are modelled through Tersoff-Brenner potential. The governing equation of motion obtained using Hamilton's principle is solved through standard Newton-Raphson method for nonlinear static response and Newmark's time integration technique to obtain nonlinear transient response characteristics. Effect of initial strain on the linear free vibration frequencies, nonlinear static and dynamic response characteristics is investigated in detail. The present multiscale modelling based results are found to be in good agreement with those obtained through molecular mechanics simulation. Two different types of boundary constraints generally used in MM simulation are explored in detail and few interesting findings are brought out. The effect of initial strain is found to be greater in linear response when compared to that in nonlinear response.

A fresh look at the predictors of naming accuracy and errors in Alzheimer's disease.

PubMed

Cuetos, Fernando; Rodríguez-Ferreiro, Javier; Sage, Karen; Ellis, Andrew W

2012-09-01

In recent years, a considerable number of studies have tried to establish which characteristics of objects and their names predict the responses of patients with Alzheimer's disease (AD) in the picture-naming task. The frequency of use of words and their age of acquisition (AoA) have been implicated as two of the most influential variables, with naming being best preserved for objects with high-frequency, early-acquired names. The present study takes a fresh look at the predictors of naming success in Spanish and English AD patients using a range of measures of word frequency and AoA along with visual complexity, imageability, and word length as predictors. Analyses using generalized linear mixed modelling found that naming accuracy was better predicted by AoA ratings taken from older adults than conventional ratings from young adults. Older frequency measures based on written language samples predicted accuracy better than more modern measures based on the frequencies of words in film subtitles. Replacing adult frequency with an estimate of cumulative (lifespan) frequency did not reduce the impact of AoA. Semantic error rates were predicted by both written word frequency and senior AoA while null response errors were only predicted by frequency. Visual complexity, imageability, and word length did not predict naming accuracy or errors. ©2012 The British Psychological Society.

Hybrid Evidence Theory-based Finite Element/Statistical Energy Analysis method for mid-frequency analysis of built-up systems with epistemic uncertainties

NASA Astrophysics Data System (ADS)

Yin, Shengwen; Yu, Dejie; Yin, Hui; Lü, Hui; Xia, Baizhan

2017-09-01

Considering the epistemic uncertainties within the hybrid Finite Element/Statistical Energy Analysis (FE/SEA) model when it is used for the response analysis of built-up systems in the mid-frequency range, the hybrid Evidence Theory-based Finite Element/Statistical Energy Analysis (ETFE/SEA) model is established by introducing the evidence theory. Based on the hybrid ETFE/SEA model and the sub-interval perturbation technique, the hybrid Sub-interval Perturbation and Evidence Theory-based Finite Element/Statistical Energy Analysis (SIP-ETFE/SEA) approach is proposed. In the hybrid ETFE/SEA model, the uncertainty in the SEA subsystem is modeled by a non-parametric ensemble, while the uncertainty in the FE subsystem is described by the focal element and basic probability assignment (BPA), and dealt with evidence theory. Within the hybrid SIP-ETFE/SEA approach, the mid-frequency response of interest, such as the ensemble average of the energy response and the cross-spectrum response, is calculated analytically by using the conventional hybrid FE/SEA method. Inspired by the probability theory, the intervals of the mean value, variance and cumulative distribution are used to describe the distribution characteristics of mid-frequency responses of built-up systems with epistemic uncertainties. In order to alleviate the computational burdens for the extreme value analysis, the sub-interval perturbation technique based on the first-order Taylor series expansion is used in ETFE/SEA model to acquire the lower and upper bounds of the mid-frequency responses over each focal element. Three numerical examples are given to illustrate the feasibility and effectiveness of the proposed method.

Evaluation of simulation motion fidelity criteria in the vertical and directional axes

NASA Technical Reports Server (NTRS)

Schroeder, Jeffery A.

1993-01-01

An evaluation of existing motion fidelity criteria was conducted on the NASA Ames Vertical Motion Simulator. Experienced test pilots flew single-axis repositioning tasks in both the vertical and the directional axes. Using a first-order approximation of a hovering helicopter, tasks were flown with variations only in the filters that attenuate the commands to the simulator motion system. These filters had second-order high-pass characteristics, and the variations were made in the filter gain and natural frequency. The variations spanned motion response characteristics from nearly full math-model motion to fixed-base. Between configurations, pilots recalibrated their motion response perception by flying the task with full motion. Pilots subjectively rated the motion fidelity of subsequent configurations relative to this full motion case, which was considered the standard for comparison. The results suggested that the existing vertical-axis criterion was accurate for combinations of gain and natural frequency changes. However, if only the gain or the natural frequency was changed, the rated motion fidelity was better than the criterion predicted. In the vertical axis, the objective and subjective results indicated that a larger gain reduction was tolerated than the existing criterion allowed. The limited data collected in the yaw axis revealed that pilots had difficulty in distinguishing among the variations in the pure yaw motion cues.

Characterizing Observed Limit Cycles in the Cassini Main Engine Guidance Control System

NASA Technical Reports Server (NTRS)

Rizvi, Farheen; Weitl, Raquel M.

2011-01-01

The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur due to the interaction between the unmodeled nonlinear elements and linear ME guidance controller.

Dual-Phase Lock-In Amplifier Based on FPGA for Low-Frequencies Experiments

PubMed Central

Macias-Bobadilla, Gonzalo; Rodríguez-Reséndiz, Juvenal; Mota-Valtierra, Georgina; Soto-Zarazúa, Genaro; Méndez-Loyola, Maurino; Garduño-Aparicio, Mariano

2016-01-01

Photothermal techniques allow the detection of characteristics of material without invading it. Researchers have developed hardware for some specific Phase and Amplitude detection (Lock-In Function) applications, eliminating space and unnecessary electronic functions, among others. This work shows the development of a Digital Lock-In Amplifier based on a Field Programmable Gate Array (FPGA) for low-frequency applications. This system allows selecting and generating the appropriated frequency depending on the kind of experiment or material studied. The results show good frequency stability in the order of 1.0 × 10−9 Hz, which is considered good linearity and repeatability response for the most common Laboratory Amplitude and Phase Shift detection devices, with a low error and standard deviation. PMID:26999138

Dual-Phase Lock-In Amplifier Based on FPGA for Low-Frequencies Experiments.

PubMed

Macias-Bobadilla, Gonzalo; Rodríguez-Reséndiz, Juvenal; Mota-Valtierra, Georgina; Soto-Zarazúa, Genaro; Méndez-Loyola, Maurino; Garduño-Aparicio, Mariano

2016-03-16

Photothermal techniques allow the detection of characteristics of material without invading it. Researchers have developed hardware for some specific Phase and Amplitude detection (Lock-In Function) applications, eliminating space and unnecessary electronic functions, among others. This work shows the development of a Digital Lock-In Amplifier based on a Field Programmable Gate Array (FPGA) for low-frequency applications. This system allows selecting and generating the appropriated frequency depending on the kind of experiment or material studied. The results show good frequency stability in the order of 1.0 × 10(-9) Hz, which is considered good linearity and repeatability response for the most common Laboratory Amplitude and Phase Shift detection devices, with a low error and standard deviation.

Signal coding in cockroach photoreceptors is tuned to dim environments.

PubMed

Heimonen, K; Immonen, E-V; Frolov, R V; Salmela, I; Juusola, M; Vähäsöyrinki, M; Weckström, M

2012-11-01

In dim light, scarcity of photons typically leads to poor vision. Nonetheless, many animals show visually guided behavior with dim environments. We investigated the signaling properties of photoreceptors of the dark active cockroach (Periplaneta americana) using intracellular and whole-cell patch-clamp recordings to determine whether they show selective functional adaptations to dark. Expectedly, dark-adapted photoreceptors generated large and slow responses to single photons. However, when light adapted, responses of both phototransduction and the nontransductive membrane to white noise (WN)-modulated stimuli remained slow with corner frequencies ~20 Hz. This promotes temporal integration of light inputs and maintains high sensitivity of vision. Adaptive changes in dynamics were limited to dim conditions. Characteristically, both step and frequency responses stayed effectively unchanged for intensities >1,000 photons/s/photoreceptor. A signal-to-noise ratio (SNR) of the light responses was transiently higher at frequencies <5 Hz for ~5 s after light onset but deteriorated to a lower value upon longer stimulation. Naturalistic light stimuli, as opposed to WN, evoked markedly larger responses with higher SNRs at low frequencies. This allowed realistic estimates of information transfer rates, which saturated at ~100 bits/s at low-light intensities. We found, therefore, selective adaptations beneficial for vision in dim environments in cockroach photoreceptors: large amplitude of single-photon responses, constant high level of temporal integration of light inputs, saturation of response properties at low intensities, and only transiently efficient encoding of light contrasts. The results also suggest that the sources of the large functional variability among different photoreceptors reside mostly in phototransduction processes and not in the properties of the nontransductive membrane.

Manipulating neuronal activity with low frequency transcranial ultrasound

NASA Astrophysics Data System (ADS)

Moore, Michele Elizabeth

Stimulation of the rodent cerebral cortex is used to investigate the underlying biological basis for the restorative effects of slow wave sleep. Neuronal activation by optogenetic and ultrasound stimulation elicits changes in action potentials across the cerebral cortex that are recorded as electroencephalograms. Optogenetic stimulation requires an invasive implantation procedure limiting its application in human studies. We sought to determine whether ultrasound stimulation could be as effective as optogenetic techniques currently used, in an effort to further understand the physiological and metabolic requirements of sleep. We successfully recorded electroencephalograms in response to transcranial ultrasound stimulation of the barrel cortex at 1 and 7 Hz frequencies, comparing them to those recorded in response to optogenetic stimuli applied at the same frequencies. Our results showed application of a 473 nm blue LED positioned 6 cm above the skull and ultrasound stimulation at an output voltage of 1000 mVpp produced electroencephalograms with physiological responses of similar amplitude. We concluded that there exists an intensity-proportionate response in the optogenetic stimulation, but not with ultrasound stimulation at the frequencies we surveyed. Activation of neuronal cells in response to optogenetic stimulation in a Thy1-ChR2 transgenic mouse line is specifically targeted to pyramidal cells in the cerebral cortex. ChR2 responses to optogenetic stimulation are mediated by a focal activation of neuronal ion channels. We measured electrophysiological responses to ultrasound stimulation, comparing them to those recorded from optogenetic stimuli. Our results show striking similarities between ultrasound-induced responses and optogenetically-induced responses, which may indicate that transcranial ultrasound stimulation is also mediated by ion channel dependent processes in cerebral cortical neurons. The biophysical substrates for electrical excitability of neurons impose temporal constraints on their response to stimulation. If ultrasound-mediated responses are, in fact, ion channel mediated responses, ultrasound-induced responses should exhibit time-dependence characteristics similar to those of optogenetically-triggered responses. Minimal stimulus duration thresholds and the temporal limits of paired pulse facilitation for ultrasound stimulation were identical to those of optogenetic stimulation. Collectively, these experiments demonstrate an electrophysiological basis for low-frequency transcranial ultrasound stimulation of cerebral cortical neuronal activity.

Biodynamic response at the palm of the human hand subjected to a random vibration.

PubMed

Dong, Ren G; McDowell, Thomas W; Welcome, Daniel E

2005-01-01

This study investigated the biodynamic response (BR) distributed at the palm of the hand subjected to a random vibration. Twelve male subjects were used in the experiment. Each subject applied three coupling actions (grip-only, push-only, and combined grip and push) on a simulated tool handle at three different levels (50, 75, and 100 N) of palm force. This study found that the hand-arm system resonated mostly in the frequency range of 20 to 50 Hz, depending on the specific test treatment and individual characteristics. The maximum vibration power transmission through the palm occurred at the resonant frequency. Increasing the effective palm force generally increased the BR magnitude and resonant frequency. The apparent stiffness measured at the middle frequencies (80-100 Hz) is correlated to the BR in almost the entire frequency range (20-1,000 Hz). Under the same palm force, the push-only action corresponded to the highest BR values while the grip-only action generally produced the lowest values. Since the resonant frequency range matches the dominant vibration frequency range of many percussive tools, it is anticipated that the palm BR and vibration power transmission may have an association with vibration-induced injuries or disorders in the wrist-arm system among the workers using these tools.

Sugar-sweetened beverages and dental caries in adults: a 4-year prospective study.

PubMed

Bernabé, Eduardo; Vehkalahti, Miira M; Sheiham, Aubrey; Aromaa, Arpo; Suominen, Anna L

2014-08-01

To explore the association between frequency of consumption of sugar-sweetened beverages (SSB) and caries increment over 4 years in adults. A second objective was to explore whether the association between frequency of SSB consumption and caries increment varied by socio-demographic characteristics and use of fluoride toothpaste. Data from 939 dentate adults who participated in both the Health 2000 Survey and the Follow-Up Study of Finnish Adults' Oral Health were analysed. At baseline, participants provided information on demographic characteristics, education and dental behaviours, including two questions on frequency of SSB consumption. The 4-year net DMFT increment was calculated using data from baseline and follow-up clinical oral examinations. The association was tested in negative binomial regression models and the moderating role of sex, age, education and use of fluoride toothpaste was examined by adding their two-way interaction with SSB consumption to the main effects model. A positive association was found between frequency of SBS consumption and 4-year net DMFT increment, regardless of participants' socio-demographic and behavioural characteristics. Adults drinking 1-2 and 3+ SSB daily had, respectively, 31% (Incidence Rate Ratio: 1.31; 95%CI: 1.02-1.67) and 33% (IRR: 1.33; 95%CI; 1.03-1.72) greater net DMFT increments than those not drinking any SSB. None of the four two-way interaction terms was significant (all p>0.05). There seems to be a dose-response relationship between frequency of SSB consumption and caries increment in adults. That association was consistent across socio-demographic characteristics, and more importantly, use of fluoride toothpaste. Drinking sugar-sweetened beverages on a daily basis is related to greater caries risk in adults. Copyright © 2014 Elsevier Ltd. All rights reserved.

Vibration mode and vibration shape under excitation of a three phase model transformer core

NASA Astrophysics Data System (ADS)

Okabe, Seiji; Ishigaki, Yusuke; Omura, Takeshi

2018-04-01

Structural vibration characteristics and vibration shapes under three-phase excitation of a archetype transformer core were investigated to consider their influences on transformer noise. Acoustic noise and vibration behavior were measured in a three-limb model transformer core. Experimental modal analysis by impact test was performed. The vibration shapes were measured by a laser scanning vibrometer at different exciting frequencies. Vibration amplitude of the core in out-of-plane direction were relatively larger than those in other two in-plane directions. It was consistent with the result that the frequency response function of the core in out-of-plane direction was larger by about 20 dB or more than those in in-plane directions. There were many vibration modes having bending deformation of limbs in out-of-plane direction. The vibration shapes of the core when excited at 50 Hz and 60 Hz were almost the same because the fundamental frequencies of the vibration were not close to the resonance frequencies. When excitation frequency was 69 Hz which was half of one of the resonance frequencies, the vibration shape changed to the one similar to the resonance vibration mode. Existence of many vibration modes in out-of-plane direction of the core was presumed to be a reason why frequency characteristics of magnetostriction and transformer noise do not coincide.

Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Hess, B. J.; Arai, Y.; Suzuki, J.

1996-01-01

1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4-0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1-0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this torsional component resembled those of the adapted horizontal slow-phase responses: gain decreased and large phase leads were introduced at frequencies below approximately 0.05-0.1 Hz. Torsional responses elicited by roll oscillations in supine position, on the other hand, were indistinguishable in their dynamics from intact animals. No consistent vertical nystagmus was elicited during yaw rotation. 6. Our results show that there is a slow, frequency-specific recovery of horizontal VOR after selective inactivation of the lateral semicircular canals. Both the spatial organization and the dynamic properties of the adapted VOR responses are distinctly different from responses in intact animals, suggesting complex changes in the underlying vestibuloocular circuitry.

The dynamic-response characteristics of a 35 degree swept-wing airplane as determined from flight measurements

NASA Technical Reports Server (NTRS)

Triplett, William C; Brown, Stuart C; Smith, G Allan

1955-01-01

The longitudinal and lateral-directional dynamic-response characteristics of a 35 degree swept-wing fighter-type airplane determined from flight measurements are presented and compared with predictions based on theoretical studies and wind-tunnel data. Flights were made at an altitude of 35,000 feet covering the Mach number range of 0.50 to 1.04. A limited amount of lateral-directional data were also obtained at 10,000 feet. The flight consisted essentially of recording transient responses to pilot-applied pulsed motions of each of the three primary control surfaces. These transient data were converted into frequency-response form by means of the Fourier transformation and compared with predicted responses calculated from the basic equations. Experimentally determined transfer functions were used for the evaluation of the stability derivatives that have the greatest effect on the dynamic response of the airplane. The values of these derivatives, in most cases, agreed favorably with predictions over the Mach number range of the test.

Research on relation between bending stress and characteristic frequency of H-shaped beam by free vibration deflection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshida, Tsutomu; Watanabe, Takeshi

2014-05-27

In order to investigate a relation between a bending stress and a characteristic frequency of a beam, 4-point loading which had constant moment region was conducted to a beam with H shape configuration experimentally and numerically. H-shaped beam has many characteristic deformation modes. Axial tensile stress in the beam made its characteristic frequency higher, and compressive stress lower. In the experiment, some characteristic frequencies got higher by a bending stress, and the others stayed in a small frequency fluctuation. The distinction is anticipated as a capability to measure a bending stress of a beam by its characteristic frequencies.

Neoclassical quasilinear theory in the superbanana plateau regime and banana kinetics in tokamaks

NASA Astrophysics Data System (ADS)

Shaing, K. C.

2017-12-01

Neoclassical quasilinear transport theory, which is part of a more general theory that unifies neoclassical and quasilinear theories, is extended to the superbanana plateau regime for low frequency (of the order of the drift frequency) electrostatic fluctuations. The physics mechanism that is responsible for the transport losses in this regime is the superbanana plateau resonance. Besides the usual magnetic drifts, Doppler shifted mode frequency also contributes to the resonance condition. Because the characteristic frequency involved in the resonance is of the order of the drift frequency, which is lower than either the bounce or the transit frequency of the particles, the transport losses are higher than the losses calculated in the conventional quasilinear theory. The important effects of the finite banana width, i.e., banana kinetics, are included and are found to reduce the transport losses for short wavelength modes. The implications on the energetic alpha particle energy loss are discussed.

Analytical approach for modeling and performance analysis of microring resonators as optical filters with multiple output bus waveguides

NASA Astrophysics Data System (ADS)

Lakra, Suchita; Mandal, Sanjoy

2017-06-01

A quadruple micro-optical ring resonator (QMORR) with multiple output bus waveguides is mathematically modeled and analyzed by making use of the delay-line signal processing approach in Z-domain and Mason's gain formula. The performances of QMORR with two output bus waveguides with vertical coupling are analyzed. This proposed structure is capable of providing wider free spectral response from both the output buses with appreciable cross talk. Thus, this configuration could provide increased capacity to insert a large number of communication channels. The simulated frequency response characteristic and its dispersion and group delay characteristics are graphically presented using the MATLAB environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorogush, E S; Afonenko, A A

The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

Multi-objective optimization of hole characteristics during pulsed Nd:YAG laser microdrilling of gamma-titanium aluminide alloy sheet

NASA Astrophysics Data System (ADS)

Biswas, R.; Kuar, A. S.; Mitra, S.

2014-09-01

Nd:YAG laser microdrilled holes on gamma-titanium aluminide, a newly developed alloy having wide applications in turbine blades, engine valves, cases, metal cutting tools, missile components, nuclear fuel and biomedical engineering, are important from the dimensional accuracy and quality of hole point of view. Keeping this in mind, a central composite design (CCD) based on response surface methodology (RSM) is employed for multi-objective optimization of pulsed Nd:YAG laser microdrilling operation on gamma-titanium aluminide alloy sheet to achieve optimum hole characteristics within existing resources. The three characteristics such as hole diameter at entry, hole diameter at exit and hole taper have been considered for simultaneous optimization. The individual optimization of all three responses has also been carried out. The input parameters considered are lamp current, pulse frequency, assist air pressure and thickness of the job. The responses at predicted optimum parameter level are in good agreement with the results of confirmation experiments conducted for verification tests.

Holographic Floquet states I: a strongly coupled Weyl semimetal

NASA Astrophysics Data System (ADS)

Hashimoto, Koji; Kinoshita, Shunichiro; Murata, Keiju; Oka, Takashi

2017-05-01

Floquet states can be realized in quantum systems driven by continuous time-periodic perturbations. It is known that a state known as the Floquet Weyl semimetal can be realized when free Dirac fermions are placed in a rotating electric field. What will happen if strong interaction is introduced to this system? Will the interaction wash out the characteristic features of Weyl semimetals such as the Hall response? Is there a steady state and what is its thermodynamic behavior? We answer these questions using AdS/CFT correspondence in the N = 2 supersymmetric massless QCD in a rotating electric field in the large N c limit realizing the first example of a "holographic Floquet state". In this limit, gluons not only mediate interaction, but also act as an energy reservoir and stabilize the nonequilibrium steady state (NESS). We obtain the electric current induced by a rotating electric field: in the high frequency region, the Ohm's law is satisfied, while we recover the DC nonlinear conductivity at low frequency, which was obtained holographically in a previous work. The thermodynamic properties of the NESS, e.g., fluctuation-dissipation relation, is characterized by the effective Hawking temperature that is defined from the effective horizon giving a holographic meaning to the "periodic thermodynamic" concept. In addition to the strong (pump) rotating electric field, we apply an additional weak (probe) electric field in the spirit of the pump-probe experiments done in condensed matter experiments. Weak DC and AC probe analysis in the background rotating electric field shows Hall currents as a linear response, therefore the Hall response of Floquet Weyl semimetals survives at the strong coupling limit. We also find frequency mixed response currents, i.e., a heterodyning effect, characteristic to periodically driven Floquet systems.

Vibration Measurement Method of a String in Transversal Motion by Using a PSD

PubMed Central

Yang, Che-Hua; Wu, Tai-Chieh

2017-01-01

A position sensitive detector (PSD) is frequently used for the measurement of a one-dimensional position along a line or a two-dimensional position on a plane, but is more often used for measuring static or quasi-static positions. Along with its quick response when measuring short time-spans in the micro-second realm, a PSD is also capable of detecting the dynamic positions of moving objects. In this paper, theoretical modeling and experiments are conducted to explore the frequency characteristics of a vibrating string while moving transversely across a one-dimensional PSD. The theoretical predictions are supported by the experiments. When the string vibrates at its natural frequency while moving transversely, the PSD will detect two frequencies near this natural frequency; one frequency is higher than the natural frequency and the other is lower. Deviations in these two frequencies, which differ from the string’s natural frequency, increase while the speed of motion increases. PMID:28714915

In vivo electrochemical characterization and inflammatory response of multiwalled carbon nanotube-based electrodes in rat hippocampus

NASA Astrophysics Data System (ADS)

Minnikanti, Saugandhika; Pereira, Marilia G. A. G.; Jaraiedi, Sanaz; Jackson, Kassandra; Costa-Neto, Claudio M.; Li, Qiliang; Peixoto, Nathalia

2010-02-01

Stimulating neural electrodes are required to deliver charge to an environment that presents itself as hostile. The electrodes need to maintain their electrical characteristics (charge and impedance) in vivo for a proper functioning of neural prostheses. Here we design implantable multi-walled carbon nanotubes coating for stainless steel substrate electrodes, targeted at wide frequency stimulation of deep brain structures. In well-controlled, low-frequency stimulation acute experiments, we show that multi-walled carbon nanotube electrodes maintain their charge storage capacity (CSC) and impedance in vivo. The difference in average CSCs (n = 4) between the in vivo (1.111 mC cm-2) and in vitro (1.008 mC cm-2) model was statistically insignificant (p > 0.05 or P-value = 0.715, two tailed). We also report on the transcription levels of the pro-inflammatory cytokine IL-1β and TLR2 receptor as an immediate response to low-frequency stimulation using RT-PCR. We show here that the IL-1β is part of the inflammatory response to low-frequency stimulation, but TLR2 is not significantly increased in stimulated tissue when compared to controls. The early stages of neuroinflammation due to mechanical and electrical trauma induced by implants can be better understood by detection of pro-inflammatory molecules rather than by histological studies. Tracking of such quantitative response profits from better analysis methods over several temporal and spatial scales. Our results concerning the evaluation of such inflammatory molecules revealed that transcripts for the cytokine IL-1β are upregulated in response to low-frequency stimulation, whereas no modulation was observed for TLR2. This result indicates that the early response of the brain to mechanical trauma and low-frequency stimulation activates the IL-1β signaling cascade but not that of TLR2.

On the additive effects of stimulus quality and word frequency in lexical decision: evidence for opposing interactive influences revealed by RT distributional analyses.

PubMed

Yap, Melvin J; Balota, David A; Tse, Chi-Shing; Besner, Derek

2008-05-01

The joint effects of stimulus quality and word frequency in lexical decision were examined in 4 experiments as a function of nonword type (legal nonwords, e.g., BRONE, vs. pseudohomophones, e.g., BRANE). When familiarity was a viable dimension for word-nonword discrimination, as when legal nonwords were used, additive effects of stimulus quality and word frequency were observed in both means and distributional characteristics of the response-time distributions. In contrast, when the utility of familiarity was undermined by using pseudohomophones, additivity was observed in the means but not in distributional characteristics. Specifically, opposing interactive effects in the underlying distribution were observed, producing apparent additivity in means. These findings are consistent with the suggestion that, when familiarity is deemphasized in lexical decision, cascaded processing between letter and word levels is in play, whereas, when familiarity is a viable dimension for word-nonword discrimination, processing is discrete.

High sensitivity pressure transducer based on the phase characteristics of GMI magnetic sensors

NASA Astrophysics Data System (ADS)

Benavides, L. S.; Costa Silva, E.; Costa Monteiro, E.; Hall Barbosa, C. R.

2018-03-01

This paper presents a new configuration for a GMI pressure transducer based on the reading of the phase characteristics of GMI sensor, intended for biomedical applications. The development process of this new class of magnetic field transducers is discussed, beginning with the definition of the ideal conditioning of the GMI sensor elements (dc level and frequency of the excitation current and sample length) and continuing with computational simulations of the full electronic circuit performed using the experimental data obtained from measured GMI curves, and have shown that the improvement in the sensitivity of GMI magnetometers is larger when phase-based transducers are used instead of magnitude-based transducers. Parameters of interest of the developed prototype are thoroughly analyzed, such as: sensitivity, linearity and frequency response. Also, the spectral noise density of the developed pressure transducer is evaluated and its resolution in the passband is estimated. A low-cost GMI pressure transducer was developed, presenting high resolution, high sensitivity and a frequency bandwidth compatible to the desired biomedical applications.

Magnetic sensor technology based on giant magneto-impedance effect in amorphous wires

NASA Astrophysics Data System (ADS)

Wang, X.; Teng, Y.; Wang, C.; Li, Q.

2012-12-01

This project focuses on giant magneto-impedance (GMI) effect that found in the soft magnetic amorphous wires in recent years, when AC current through the amorphous wire, induced voltage in the wires would change sensitively with a small external magnetic field along the wire vertical imposed changes. GMI magnetic sensor could compensate for the shortcomings of the traditional magnetic sensors and detect weak magnetic field, meanwhile the characteristics of high stability, high sensitivity, high resolution, fast response and low power consumption, which makes it becoming the focus of extensive research at home and abroad and being new mode of the next age of the physical geography observation. The emphasis of the project is the research on the high sensitivity amorphous wire detector and the low noise capability circuit design. In this paper, it is analyzed the theory of the Amorphous Wire Giant-Magneto-Impedance (AWGMI) effect and its influence factors in details, and expatiated the sensor principle based on AWGMI. On the basis of AWGMI, the experimental system of the micro-magnetic sensor is designed, which is composed of the detecting signals, processing and collecting data, display and transmitting data circuit and corresponding functional software etc. The properties of this kind of micro-magnetic sensor are studied by experiments, such as its linearity, sensitivity, frequency response, noise, stability and temperature properties and so on, especially analyzed the relation of the drive signals with all kinds of characteristics. The results show that there is no direct relationship between the frequency of the drive signals and linear property of the sensor. But with the increase of its frequency, some fluctuation appears on the characteristic curves; the direct relation is found between the frequency of the drive signal and sensitivity, with the increase of the frequency, AWGMI effect increases monotonously. It leads to the amplitude of the output voltage increase with the change of the outer magnetic field and results in the increase of the sensor sensitivity; it can be enhanced the corresponding rate of the sensor to the low frequency magnetic field by increasing the drive signal frequency. By experiments, the best sensitivity and noise valves is 0.5225 mV/nT, 1.566nT respectively.

Frequency coded sensors incorporating tapers

NASA Technical Reports Server (NTRS)

Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor)

2010-01-01

A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.

Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence

USGS Publications Warehouse

Rajaure, S.; Asimaki, Domniki; Thompson, Eric M.; Hough, Susan E.; Martin, Stacey; Ampuero, J.P.; Dhital, M.R.; Inbal, A; Takai, N; Shigefuji, M.; Bijukchhen, S; Ichiyanagi, M; Sasatani, T; Paudel, L

2017-01-01

We analyze strong motion records and high-rate GPS measurements of the M 7.8 Gorkha mainshock, M 7.3 Dolakha, and two moderate aftershock events recorded at four stations on the Kathmandu basin sediments, and one on rock-outcrop. Recordings on soil from all four events show systematic amplification relative to the rock site at multiple frequencies in the 0.1–2.5 Hz frequency range, and de-amplification of higher frequencies ( >2.5–10 Hz). The soil-to-rock amplification ratios for the M 7.8 and M 7.3 events have lower amplitude and frequency peaks relative to the ratios of the two moderate events, effects that could be suggestive of nonlinear site response. Further, comparisons to ground motion prediction equations show that 1) both soil and rock mainshock recordings were severely depleted of high frequencies, and 2) the depletion at high frequencies is not present in the aftershocks. These observations indicate that the high frequency deamplification is additionally related to characteristics of the source that are not captured by simplified ground motion prediction equations, and allude to seismic hazard analysis models being revised – possibly by treating isolated high frequency radiation sources separately from long period components to capture large magnitude near-source events such as the 2015 Gorkha mainshock.

Robust Frequency Invariant Beamforming with Low Sidelobe for Speech Enhancement

NASA Astrophysics Data System (ADS)

Zhu, Yiting; Pan, Xiang

2018-01-01

Frequency invariant beamformers (FIBs) are widely used in speech enhancement and source localization. There are two traditional optimization methods for FIB design. The first one is convex optimization, which is simple but the frequency invariant characteristic of the beam pattern is poor with respect to frequency band of five octaves. The least squares (LS) approach using spatial response variation (SRV) constraint is another optimization method. Although, it can provide good frequency invariant property, it usually couldn’t be used in speech enhancement for its lack of weight norm constraint which is related to the robustness of a beamformer. In this paper, a robust wideband beamforming method with a constant beamwidth is proposed. The frequency invariant beam pattern is achieved by resolving an optimization problem of the SRV constraint to cover speech frequency band. With the control of sidelobe level, it is available for the frequency invariant beamformer (FIB) to prevent distortion of interference from the undesirable direction. The approach is completed in time-domain by placing tapped delay lines(TDL) and finite impulse response (FIR) filter at the output of each sensor which is more convenient than the Frost processor. By invoking the weight norm constraint, the robustness of the beamformer is further improved against random errors. Experiment results show that the proposed method has a constant beamwidth and almost the same white noise gain as traditional delay-and-sum (DAS) beamformer.

Influence des conditions climatiques saisonnières sur quelques paramètres physiologiques dès boucs Créoles alimentés avec de l'ensilage de banane

NASA Astrophysics Data System (ADS)

Fauconneau, B.; Xande, A.

1986-06-01

Response of three groups of 12 male creole goats (weighing about 10 kg) to environmental variations was tested in Guadeloupe (French West Indies) respectively at three times in the year: end of humid season (October November), dry season (February March) and beginning of humid season (July August). Voluntary free intake of banana silage (silage of mixed green banana, bagassa, wheat bran and urea complemented with molasse) was not significantly affected by climatic variations. Three physiological parameters: rectal temperature, respiratory frequency and cardiac frequency were measured. These parameters were correlated with heat production dependent factors such as metabolic body weight, body weight gain and voluntary free intake. Rectal temperature increased all through the day until sunset and then decreased during the night. Both minimal rectal temperature and daily increase of rectal temperature were correlated with ambient temperature. Cardiac frequency increased during feeding. Generally cardiac frequency seemed to be correlated with activity of animals and so with behavioural response to environmental variations. Respiratory frequency was the most sensitive index of goat response to climate. The daily increase of respiratory frequency was important at the end of the humid season but was not observed in dry season. This increase was dependent on ambient temperature increase but also on air humidity characteristics and air velocity. These points are discussed according to integration of those physiological parameters in thermoregulation.

Input-Specific Gain Modulation by Local Sensory Context Shapes Cortical and Thalamic Responses to Complex Sounds.

PubMed

Williamson, Ross S; Ahrens, Misha B; Linden, Jennifer F; Sahani, Maneesh

2016-07-20

Sensory neurons are customarily characterized by one or more linearly weighted receptive fields describing sensitivity in sensory space and time. We show that in auditory cortical and thalamic neurons, the weight of each receptive field element depends on the pattern of sound falling within a local neighborhood surrounding it in time and frequency. Accounting for this change in effective receptive field with spectrotemporal context improves predictions of both cortical and thalamic responses to stationary complex sounds. Although context dependence varies among neurons and across brain areas, there are strong shared qualitative characteristics. In a spectrotemporally rich soundscape, sound elements modulate neuronal responsiveness more effectively when they coincide with sounds at other frequencies, and less effectively when they are preceded by sounds at similar frequencies. This local-context-driven lability in the representation of complex sounds-a modulation of "input-specific gain" rather than "output gain"-may be a widespread motif in sensory processing. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

A Phase-Locked Loop Model of the Response of the Postural Control System to Periodic Platform Motion

PubMed Central

Schilling, Robert J.; Robinson, Charles J.

2010-01-01

A phase-locked loop (PLL) model of the response of the postural control system to periodic platform motion is proposed. The PLL model is based on the hypothesis that quiet standing (QS) postural sway can be characterized as a weak sinusoidal oscillation corrupted with noise. Because the signal to noise ratio is quite low, the characteristics of the QS oscillator are not measured directly from the QS sway, instead they are inferred from the response of the oscillator to periodic motion of the platform. When a sinusoidal stimulus is applied, the QS oscillator changes speed as needed until its frequency matches that of the platform, thus achieving phase lock in a manner consistent with a PLL control mechanism. The PLL model is highly effective in representing the frequency, amplitude, and phase shift of the sinusoidal component of the phase-locked response over a range of platform frequencies and amplitudes. Qualitative analysis of the PLL control mechanism indicates that there is a finite range of frequencies over which phase lock is possible, and that the size of this capture range decreases with decreasing platform amplitude. The PLL model was tested experimentally using nine healthy subjects and the results reveal good agreement with a mean phase shift error of 13.7° and a mean amplitude error of 0.8 mm. PMID:20378479

Applying transfer matrix method to the estimation of the modal characteristics of the NASA Mini-Mass Truss

NASA Technical Reports Server (NTRS)

Shen, Ji-Yao; Taylor, Lawrence W., Jr.

1994-01-01

It is beneficial to use a distributed parameter model for large space structures because the approach minimizes the number of model parameters. Holzer's transfer matrix method provides a useful means to simplify and standardize the procedure for solving the system of partial differential equations. Any large space structures can be broken down into sub-structures with simple elastic and dynamical properties. For each single element, such as beam, tether, or rigid body, we can derive the corresponding transfer matrix. Combining these elements' matrices enables the solution of the global system equations. The characteristics equation can then be formed by satisfying the appropriate boundary conditions. Then natural frequencies and mode shapes can be determined by searching the roots of the characteristic equation at frequencies within the range of interest. This paper applies this methodology, and the maximum likelihood estimation method, to refine the modal characteristics of the NASA Mini-Mast Truss by successively matching the theoretical response to the test data of the truss. The method is being applied to more complex configurations.

The Ketogenic Diet Improves Recently Worsened Focal Epilepsy

ERIC Educational Resources Information Center

Villeneuve, Nathalie; Pinton, Florence; Bahi-Buisson, Nadia; Dulac, Olivier; Chiron, Catherine; Nabbout, Rima

2009-01-01

Aim: We observed a dramatic response to the ketogenic diet in several patients with highly refractory epilepsy whose seizure frequency had recently worsened. This study aimed to identify whether this characteristic was a useful indication for the ketogenic diet. Method: From the 70 patients who received the ketogenic diet during a 3-year period at…

Vibration, performance, flutter and forced response characteristics of a large-scale propfan and its aeroelastic model

NASA Technical Reports Server (NTRS)

August, Richard; Kaza, Krishna Rao V.

1988-01-01

An investigation of the vibration, performance, flutter, and forced response of the large-scale propfan, SR7L, and its aeroelastic model, SR7A, has been performed by applying available structural and aeroelastic analytical codes and then correlating measured and calculated results. Finite element models of the blades were used to obtain modal frequencies, displacements, stresses and strains. These values were then used in conjunction with a 3-D, unsteady, lifting surface aerodynamic theory for the subsequent aeroelastic analyses of the blades. The agreement between measured and calculated frequencies and mode shapes for both models is very good. Calculated power coefficients correlate well with those measured for low advance ratios. Flutter results show that both propfans are stable at their respective design points. There is also good agreement between calculated and measured blade vibratory strains due to excitation resulting from yawed flow for the SR7A propfan. The similarity of structural and aeroelastic results show that the SR7A propfan simulates the SR7L characteristics.

Dynamic response characteristics of high temperature superconducting maglev systems: Comparison between Halbach-type and normal permanent magnet guideways

NASA Astrophysics Data System (ADS)

Wang, B.; Zheng, J.; Che, T.; Zheng, B. T.; Si, S. S.; Deng, Z. G.

2015-12-01

The permanent magnet guideway (PMG) is very important for the performance of the high temperature superconducting (HTS) system in terms of electromagnetic force and operational stability. The dynamic response characteristics of a HTS maglev model levitating on two types of PMG, which are the normal PMG with iron flux concentration and Halbach-type PMG, were investigated by experiments. The dynamic signals for different field-cooling heights (FCHs) and loading/unloading processes were acquired and analyzed by a vibration analyzer and laser displacement sensors. The resonant frequency, stiffness and levitation height of the model were discussed. It was found that the maglev model on the Halbach-type PMG has higher resonant frequency and higher vertical stiffness compared with the normal PMG. However, the low lateral stiffness of the model on the Halbach-type PMG indicates poor lateral stability. Besides, the Halbach-type PMG has better loading capacity than the normal PMG. These results are helpful to design a suitable PMG for the HTS system in practical applications.

Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon

NASA Technical Reports Server (NTRS)

Zhang, D.; Cowin, S. C.; Weinbaum, S.

1997-01-01

A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

Surface Currents and Winds at the Delaware Bay Mouth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muscarella, P A; Barton, N P; Lipphardt, B L

2011-04-06

Knowledge of the circulation of estuaries and adjacent shelf waters has relied on hydrographic measurements, moorings, and local wind observations usually removed from the region of interest. Although these observations are certainly sufficient to identify major characteristics, they lack both spatial resolution and temporal coverage. High resolution synoptic observations are required to identify important coastal processes at smaller scales. Long observation periods are needed to properly sample low-frequency processes that may also be important. The introduction of high-frequency (HF) radar measurements and regional wind models for coastal studies is changing this situation. Here we analyze synoptic, high-resolution surface winds andmore » currents in the Delaware Bay mouth over an eight-month period (October 2007 through May 2008). The surface currents were measured by two high-frequency radars while the surface winds were extracted from a data-assimilating regional wind model. To illustrate the utility of these monitoring tools we focus on two 45-day periods which previously were shown to present contrasting pictures of the circulation. One, the low-outflow period is from 1 October through 14 November 2007; the other is the high-outflow period from 3 March through 16 April 2008. The large-scale characteristics noted by previous workers are clearly corroborated. Specifically the M2 tide dominates the surface currents, and the Delaware Bay outflow plume is clearly evident in the low frequency currents. Several new aspects of the surface circulation were also identified. These include a map of the spatial variability of the M2 tide (validating an earlier model study), persistent low-frequency cross-mouth flow, and a rapid response of the surface currents to a changing wind field. However, strong wind episodes did not persist long enough to set up a sustained Ekman response.« less

Characteristics of the NASA Lewis bumpy torus plasma generated with high positive or negative applied potentials

NASA Technical Reports Server (NTRS)

Roth, J. R.; Gerdin, G. A.

1976-01-01

The toroidal ring of plasma contained in the NASA Lewis bumpy-torus superconducting magnet facility may be biased to positive or negative potentials approaching 50 kilovolts by applying direct-current voltages of the respective polarity to 12 or fewer of the midplane electrode rings. The electric fields which are responsible for heating the ions by E/B drift then point radially outward or inward. The low-frequency fluctuations below the ion cyclotron frequency appeared to be dominated by rotating spokes.

Measures of Progress: 1995 Project Follow-Up, Los Rios Community College District (American River College, Cosumnes River College, Sacramento City College). Results of a Survey of 1993-94 Graduates and Non-Returning Students. Volume I of II--Frequencies and Percents by District, College and Academic Program.

ERIC Educational Resources Information Center

Beachler, Judith A.; Pagtalunan, Jose

In 1995, the three colleges in California's Los Rios Community College District (LRCCD) surveyed 6,151 former students from 1993-94 to gather information on student outcomes and characteristics. This report presents districtwide findings related to the frequencies and percents of responses by academic program. Following an executive summary and…

High Q-factor metasurfaces based on miniaturized asymmetric single split resonators

NASA Astrophysics Data System (ADS)

Al-Naib, Ibraheem A. I.; Jansen, Christian; Koch, Martin

2009-04-01

We introduce asymmetric single split rectangular resonators as bandstop metasurfaces, which exhibit very high Q-factors in combination with low passband losses and a small electrical footprint. The effect of the degree of asymmetry on the frequency response is thoroughly studied. Furthermore, complementary structures, which feature a bandpass behavior, were derived by applying Babinet's principle and investigated with regards to their transmission characteristics. In future, asymmetric single split rectangular resonators could provide efficient unit cells for frequency selective surface devices, such as thin-film sensors or high performance filters.

Investigating strength and frequency effects in recognition memory using type-2 signal detection theory.

PubMed

Higham, Philip A; Perfect, Timothy J; Bruno, Davide

2009-01-01

Criterion- versus distribution-shift accounts of frequency and strength effects in recognition memory were investigated with Type-2 signal detection receiver operating characteristic (ROC) analysis, which provides a measure of metacognitive monitoring. Experiment 1 demonstrated a frequency-based mirror effect, with a higher hit rate and lower false alarm rate, for low frequency words compared with high frequency words. In Experiment 2, the authors manipulated item strength with repetition, which showed an increased hit rate but no effect on the false alarm rate. Whereas Type-1 indices were ambiguous as to whether these effects were based on a criterion- or distribution-shift model, the two models predict opposite effects on Type-2 distractor monitoring under some assumptions. Hence, Type-2 ROC analysis discriminated between potential models of recognition that could not be discriminated using Type-1 indices alone. In Experiment 3, the authors manipulated Type-1 response bias by varying the number of old versus new response categories to confirm the assumptions made in Experiments 1 and 2. The authors conclude that Type-2 analyses are a useful tool for investigating recognition memory when used in conjunction with more traditional Type-1 analyses.

Visually induced adaptation in three-dimensional organization of primate vestibuloocular reflex

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Hess, B. J.

1998-01-01

The adaptive plasticity of the spatial organization of the vestibuloocular reflex (VOR) has been investigated in intact and canal-plugged primates using 2-h exposure to conflicting visual (optokinetic, OKN) and vestibular rotational stimuli about mutually orthogonal axes (generating torsional VOR + vertical OKN, torsional VOR + horizontal OKN, vertical VOR + horizontal OKN, and horizontal VOR + vertical OKN). Adaptation protocols with 0.5-Hz (+/-18 degrees ) head movements about either an earth-vertical or an earth-horizontal axis induced orthogonal response components as high as 40-70% of those required for ideal adaptation. Orthogonal response gains were highest at the adapting frequency with phase leads present at lower and phase lags present at higher frequencies. Furthermore, the time course of adaptation, as well as orthogonal response dynamics were similar and relatively independent of the particular visual/vestibular stimulus combination. Low-frequency (0. 05 Hz, vestibular stimulus: +/-60 degrees ; optokinetic stimulus: +/-180 degrees ) adaptation protocols with head movements about an earth-vertical axis induced smaller orthogonal response components that did not exceed 20-40% of the head velocity stimulus (i.e., approximately 10% of that required for ideal adaptation). At the same frequency, adaptation with head movements about an earth-horizontal axis generated large orthogonal responses that reached values as high as 100-120% of head velocity after 2 h of adaptation (i.e., approximately 40% of ideal adaptation gains). The particular spatial and temporal response characteristics after low-frequency, earth-horizontal axis adaptation in both intact and canal-plugged animals strongly suggests that the orienting (and perhaps translational) but not inertial (velocity storage) components of the primate otolith-ocular system exhibit spatial adaptability. Due to the particular nested arrangement of the visual and vestibular stimuli, the optic flow pattern exhibited a significant component about the third spatial axis (i.e., orthogonal to the axes of rotation of the head and visual surround) at twice the oscillation frequency. Accordingly, the adapted VOR was characterized consistently by a third response component (orthogonal to both the axes of head and optokinetic drum rotation) at twice the oscillation frequency after earth-horizontal but not after earth-vertical axis 0.05-Hz adaptation. This suggests that the otolith-ocular (but not the semicircular canal-ocular) system can adaptively change its spatial organization at frequencies different from those of the head movement.

Fabrication and characterization of non-resonant magneto-mechanical low-frequency vibration energy harvester

NASA Astrophysics Data System (ADS)

Nammari, Abdullah; Caskey, Logan; Negrete, Johnny; Bardaweel, Hamzeh

2018-03-01

This article presents a non-resonant magneto-mechanical vibration energy harvester. When externally excited, the energy harvester converts vibrations into electric charge using a guided levitated magnet oscillating inside a multi-turn coil that is fixed around the exterior of the energy harvester. The levitated magnet is guided using four oblique mechanical springs. A prototype of the energy harvester is fabricated using additive manufacturing. Both experiment and model are used to characterize the static and dynamic behavior of the energy harvester. Measured restoring forces show that the fabricated energy harvester retains a mono-stable potential energy well with desired stiffness nonlinearities. Results show that magnetic spring results in hardening effect which increases the resonant frequency of the energy harvester. Additionally, oblique mechanical springs introduce geometric, negative, nonlinear stiffness which improves the harvester's response towards lower frequency spectrum. The unique design can produce a tunable energy harvester with multi-well potential energy characteristics. A finite element model is developed to estimate the average radial flux density experienced by the multi-turn coil. Also, a lumped parameter model of the energy harvester is developed and validated against measured data. Both upward and downward frequency sweeps are performed to determine the frequency response of the harvester. Results show that at higher excitation levels hardening effects become more apparent, and the system dynamic response turns into non-resonant. Frequency response curves exhibit frequency jump phenomena as a result of coexistence of multiple energy states at the frequency branch. The fabricated energy harvester is hand-held and measures approximately 100.5 [cm3] total volume. For a base excitation of 1.0 g [m/s2], the prototype generates a peak voltage and normalized power density of approximately 3.5 [V] and 0.133 [mW/cm3 g2], respectively, at 15.5 [Hz].

Intralaminar stimulation of the inferior colliculus facilitates frequency-specific activation in the auditory cortex

NASA Astrophysics Data System (ADS)

Allitt, B. J.; Benjaminsen, C.; Morgan, S. J.; Paolini, A. G.

2013-08-01

Objective. Auditory midbrain implants (AMI) provide inadequate frequency discrimination for open set speech perception. AMIs that can take advantage of the tonotopic laminar of the midbrain may be able to better deliver frequency specific perception and lead to enhanced performance. Stimulation strategies that best elicit frequency specific activity need to be identified. This research examined the characteristic frequency (CF) relationship between regions of the auditory cortex (AC), in response to stimulated regions of the inferior colliculus (IC), comparing monopolar, and intralaminar bipolar electrical stimulation. Approach. Electrical stimulation using multi-channel micro-electrode arrays in the IC was used to elicit AC responses in anaesthetized male hooded Wistar rats. The rate of activity in AC regions with CFs within 3 kHz (CF-aligned) and unaligned CFs was used to assess the frequency specificity of responses. Main results. Both monopolar and bipolar IC stimulation led to CF-aligned neural activity in the AC. Altering the distance between the stimulation and reference electrodes in the IC led to changes in both threshold and dynamic range, with bipolar stimulation with 400 µm spacing evoking the lowest AC threshold and widest dynamic range. At saturation, bipolar stimulation elicited a significantly higher mean spike count in the AC at CF-aligned areas than at CF-unaligned areas when electrode spacing was 400 µm or less. Bipolar stimulation using electrode spacing of 400 µm or less also elicited a higher rate of elicited activity in the AC in both CF-aligned and CF-unaligned regions than monopolar stimulation. When electrodes were spaced 600 µm apart no benefit over monopolar stimulation was observed. Furthermore, monopolar stimulation of the external cortex of the IC resulted in more localized frequency responses than bipolar stimulation when stimulation and reference sites were 200 µm apart. Significance. These findings have implications for the future development of AMI, as a bipolar stimulation strategy may improve the ability of implant users to discriminate between frequencies.

Biomechanics of fundamental frequency regulation: Constitutive modeling of the vocal fold lamina propria.

PubMed

Chan, Roger W; Siegmund, Thomas; Zhang, Kai

2009-12-01

Accurate characterization of biomechanical characteristics of the vocal fold is critical for understanding the regulation of vocal fundamental frequency (F(0)), which depends on the active control of the intrinsic laryngeal muscles as well as the passive biomechanical response of the vocal fold lamina propria. Specifically, the tissue stress-strain response and viscoelastic properties under cyclic tensile deformation are relevant, when the vocal folds are subjected to length and tension changes due to posturing. This paper describes a constitutive modeling approach quantifying the relationship between vocal fold stress and strain (or stretch), and establishes predictions of F(0) with the string model of phonation based on the constitutive parameters. Results indicated that transient and time-dependent changes in F(0), including global declinations in declarative sentences, as well as local F(0) overshoots and undershoots, can be partially attributed to the time-dependent viscoplastic response of the vocal fold cover.

A closed-loop phase-locked interferometer for wide bandwidth position sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, Andrew J., E-mail: Andrew.Fleming@Newcastle.edu.au; Routley, Ben S., E-mail: Ben.Routley@Newcastle.edu.au

This article describes a position sensitive interferometer with closed-loop control of the reference mirror. A calibrated nanopositioner is used to lock the interferometer phase to the most sensitive point in the interferogram. In this configuration, large low-frequency movements of the sensor mirror can be detected from the control signal applied to the nanopositioner and high-frequency short-range signals can be measured directly from the photodiode. It is demonstrated that these two signals are complementary and can be summed to find the total displacement. The resulting interferometer has a number of desirable characteristics: it is optically simple, does not require polarization ormore » modulation to detect the direction of motion, does not require fringe-counting or interpolation electronics, and has a bandwidth equal to that of the photodiode. Experimental results demonstrate the frequency response analysis of a high-speed positioning stage. The proposed instrument is ideal for measuring the frequency response of nanopositioners, electro-optical components, MEMs devices, ultrasonic devices, and sensors such as surface acoustic wave detectors.« less

A self-mixing based ring-type fiber-optic acoustic sensor

NASA Astrophysics Data System (ADS)

Wang, Lutang; Wu, Chunxu; Fang, Nian

2014-07-01

A novel, simple fiber-optic acoustic sensor consisting of a self-mixing effect based laser source and a ring-type interferometer is presented. With weak external optical feedbacks, the acoustic wave signals can be detected by measuring the changes of oscillating frequency of the laser diode, induced by the disturbances of sensing fiber, with the ring-type interferometer. The operation principles of the sensor system are explored in-depth and the experimental researches are carried out. The acoustic wave signals produced by various actions, such as by pencil broken, mental pin free falling and PZT are detected for evaluating the sensing performances of the experimental system. The investigation items include the sensitivity as well as frequency responses of the sensor system. An experiment for the detection of corona discharges is carried out, which occur in a high-voltage environment between two parallel copper electrodes, under different humidity levels. The satisfied experimental results are obtained. These experimental results well prove that our proposed sensing system has very high sensitivity and excellent high frequency responses characteristics in the detections of weak, high-frequency acoustic wave signals.

Amplification of Reynolds number dependent processes by wave distortion. [acoustic instability of liquid propellant rocket engines

NASA Technical Reports Server (NTRS)

Ventrice, M. B.; Fang, J. C.; Purdy, K. R.

1975-01-01

A system using a hot-wire transducer as an analog of a liquid droplet of propellant was employed to investigate the ingredients of the acoustic instability of liquid-propellant rocket engines. It was assumed that the combustion process was vaporization-limited and that the combustion chamber was acoustically similar to a closed-closed right-circular cylinder. Before studying the hot-wire closed-loop system (the analog system), a microphone closed-loop system, which used the response of a microphone as the source of a linear feedback exciting signal, was investigated to establish the characteristics of self-sustenance of acoustic fields. Self-sustained acoustic fields were found to occur only at resonant frequencies of the chamber. In the hot-wire closed-loop system, the response of hot-wire anemometer was used as the source of the feedback exciting signal. The self-sustained acoustic fields which developed in the system were always found to be harmonically distorted and to have as their fundamental frquency a resonant frequency for which there also existed a second resonant frequency which was approximately twice the fundamental frequency.

Forced responses on a radial turbine with nozzle guide vanes

NASA Astrophysics Data System (ADS)

Liu, Yixiong; Yang, Ce; Ma, Chaochen; Lao, DaZhong

2014-04-01

Radial turbines with nozzle guide vanes are widely used in various size turbochargers. However, due to the interferences with guide vanes, the blades of impellers are exposed to intense unsteady aerodynamic excitations, which cause blade vibrations and lead to high cycle failures (HCF). Moreover, the harmonic resonance in some frequency regions are unavoidable due to the wide operation conditions. Aiming to achieve a detail insight into vibration characteristics of radial flow turbine, a numerical method based on fluid structure interaction (FSI) is presented. Firstly, the unsteady aerodynamic loads are determined by computational fluid dynamics (CFD). And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform (FFT). Then, the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element (FE) method. Meanwhile, harmonic analyses, applying the pressure fluctuation from CFD, are conducted to investigate the impeller vibration behavior and blade forced response in frequency domain. The prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.

Damage assessment of RC buildings subjected to the different strong motion duration

NASA Astrophysics Data System (ADS)

Mortezaei, Alireza; mohajer Tabrizi, Mohsen

2015-07-01

An earthquake has three important characteristics; namely, amplitude, frequency content and duration. Amplitude and frequency content have a direct impact but not necessarily the sole cause of structural damage. Regarding the duration, some researchers show a high correlation between strong motion duration and structural damage whereas some others find no relation. This paper focuses on the ground motion durations characterized by Arias Intensity (AI). High duration may increase the damage state of structure for the damage accumulation. This paper investigates the response time histories (acceleration, velocity and displacement) of RC buildings under the different strong motion durations. Generally, eight earthquake records were selected from different soil type, and these records were grouped according to their PGA and frequency ranges. Maximum plastic rotation and drift response was chosen as damage indicator. In general, there was a positive correlation between strong motion duration and damage; however, in some PGA and frequency ranges input motions with shorter durations might cause more damage than the input motions with longer durations. In soft soils, input motions with longer durations caused more damage than the input motions with shorter durations.

High-order synchronization of hair cell bundles

NASA Astrophysics Data System (ADS)

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-Wook; Cheon, Jinwoo; Bozovic, Dolores

2016-12-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells.

An image based vibration sensor for soft tissue modal analysis in a Digital Image Elasto Tomography (DIET) system.

PubMed

Feng, Sheng; Lotz, Thomas; Chase, J Geoffrey; Hann, Christopher E

2010-01-01

Digital Image Elasto Tomography (DIET) is a non-invasive elastographic breast cancer screening technology, based on image-based measurement of surface vibrations induced on a breast by mechanical actuation. Knowledge of frequency response characteristics of a breast prior to imaging is critical to maximize the imaging signal and diagnostic capability of the system. A feasibility analysis for a non-invasive image based modal analysis system is presented that is able to robustly and rapidly identify resonant frequencies in soft tissue. Three images per oscillation cycle are enough to capture the behavior at a given frequency. Thus, a sweep over critical frequency ranges can be performed prior to imaging to determine critical imaging settings of the DIET system to optimize its tumor detection performance.

High-order synchronization of hair cell bundles

PubMed Central

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-wook; Cheon, Jinwoo; Bozovic, Dolores

2016-01-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells. PMID:27974743

Effect of Propellant Feed System Coupling and Hydraulic Parameters on Analysis of Chugging

NASA Technical Reports Server (NTRS)

Wood, Don J.; Dorsch, Robert G.

1967-01-01

A digital distributed parameter model was used to study the effects of propellant-feed- system coupling and various hydraulic parameters on the analytical prediction of chugging instabilities. Coupling between the combustion chamber and feed system was controlled by varying the compliance of the injector-dome region. The coupling with the feed system above the pump was varied by changing the amount of cavitation compliance at the pump inlet. The stability limits and chugging frequencies proved to be strongly dependent on the degree of feed-system coupling. The maximum stability condition occurred with intermediate coupling. Under conditions of a high degree of feed-system-combustor coupling, the stability limits and chugging frequencies were primarily dependent on the feed-system characteristics; the responses were characterized by beating patterns. For the system analyzed, the pump suction line had little effect on the stability limits or chugging frequencies. Beating, present under the condition of near zero injector -dome compliance, was eliminated when the suction line was decoupled by employing a sufficiently high value of pump-inlet compliance. Under conditions of maximum feed-system coupling, the magnitude and distribution of line losses in the discharge line had a significant effect on the stability limits but had negligible effect on the chugging frequency and beating characteristics. Also, the length of the discharge line greatly affected the stability limits, chugging frequency, and beating characteristics. The length of the suction line, however, had little effect on the stability limits and chugging frequency but did influence the beating pattern. A resistive-shunt device attached to the pump discharge line to suppress chugging was investigated. The analysis showed that the device was effective under conditions of high feed-system coupling.

Alternating current conduction studies on polypyrrole-iron nanocomposite at room temperature

NASA Astrophysics Data System (ADS)

Kumar, T. G. Naveen; Megha, R.; Revanasiddappa, M.; Ravikiran, Y. T.; Kumari, S. C. Vijaya

2018-05-01

In the present work, Polypyrrole (PPy) and Polypyrrole-Iron (PPy-Fe) nanocomposite were synthesized separately by chemical polymerisation method and then they were structurally characterised by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM) techniques. The alternate current (AC) response characteristics at room temperature of PPy and the composite were comparatively studied in the frequency range 100Hz-1MHz. The real part of conductivities of both PPy and the composite were interpreted as power law of frequency and the frequency exponent s was found to lie in the range 0< s<1 in both the cases. The nanocomposite has shown significant improvement in conductivity as compared to PPy.

Real-ear acoustical characteristics of impulse sound generated by golf drivers and the estimated risk to hearing: a cross-sectional study

PubMed Central

Zhao, Fei; Bardsley, Barry

2014-01-01

Objectives This study investigated real-ear acoustical characteristics in terms of the sound pressure levels (SPLs) and frequency responses in situ generated from golf club drivers at impact with a golf ball. The risk of hearing loss caused by hitting a basket of golf balls using various drivers was then estimated. Design Cross-sectional study. Setting The three driver clubs were chosen on the basis of reflection of the commonality and modern technology of the clubs. The participants were asked to choose the clubs in a random order and hit six two-piece range golf balls with each club. The experiment was carried out at a golf driving range in South Wales, UK. Participants 19 male amateur golfers volunteered to take part in the study, with an age range of 19–54 years. Outcome measures The frequency responses and peak SPLs in situ of the transient sound generated from the club at impact were recorded bilaterally and simultaneously using the GN Otometric Freefit wireless real-ear measurement system. A swing speed radar system was also used to investigate the relationship between noise level and swing speed. Results Different clubs generated significantly different real-ear acoustical characteristics in terms of SPL and frequency responses. However, they did not differ significantly between the ears. No significant correlation was found between the swing speed and noise intensity. On the basis of the SPLs measured in the present study, the percentage of daily noise exposure for hitting a basket of golf balls using the drivers described above was less than 2%. Conclusions The immediate danger of noise-induced hearing loss for amateur golfers is quite unlikely. However, it may be dangerous to hearing if the noise level generated by the golf clubs exceeded 116 dBA. PMID:24448845

On-line, adaptive state estimator for active noise control

NASA Technical Reports Server (NTRS)

Lim, Tae W.

1994-01-01

Dynamic characteristics of airframe structures are expected to vary as aircraft flight conditions change. Accurate knowledge of the changing dynamic characteristics is crucial to enhancing the performance of the active noise control system using feedback control. This research investigates the development of an adaptive, on-line state estimator using a neural network concept to conduct active noise control. In this research, an algorithm has been developed that can be used to estimate displacement and velocity responses at any locations on the structure from a limited number of acceleration measurements and input force information. The algorithm employs band-pass filters to extract from the measurement signal the frequency contents corresponding to a desired mode. The filtered signal is then used to train a neural network which consists of a linear neuron with three weights. The structure of the neural network is designed as simple as possible to increase the sampling frequency as much as possible. The weights obtained through neural network training are then used to construct the transfer function of a mode in z-domain and to identify modal properties of each mode. By using the identified transfer function and interpolating the mode shape obtained at sensor locations, the displacement and velocity responses are estimated with reasonable accuracy at any locations on the structure. The accuracy of the response estimates depends on the number of modes incorporated in the estimates and the number of sensors employed to conduct mode shape interpolation. Computer simulation demonstrates that the algorithm is capable of adapting to the varying dynamic characteristics of structural properties. Experimental implementation of the algorithm on a DSP (digital signal processing) board for a plate structure is underway. The algorithm is expected to reach the sampling frequency range of about 10 kHz to 20 kHz which needs to be maintained for a typical active noise control application.

Hypothesis on interactions of macromolecules based on molecular vibration patterns in cells and tissues.

PubMed

Jaross, Werner

2018-01-01

The molecular vibration patterns of structure-forming macromolecules in the living cell create very specific electromagnetic frequency patterns which might be used for information on spatial position in the three-dimensional structure as well as the chemical characteristics. Chemical change of a molecule results in a change of the vibration pattern and thus in a change of the emitted electromagnetic frequency pattern. These patterns have to be received by proteins responsible for the necessary interactions and functions. Proteins can function as resonators for frequencies in the range of 1013-1015 Hz. The individual frequency pattern is defined by the amino acid sequence and the polarity of every amino acid caused by their functional groups. If the arriving electromagnetic signal pattern and the emitted pattern of the absorbing protein are matched in relevant parts and in opposite phase, photon energy in the characteristic frequencies can be transferred resulting in a conformational change of that molecule and respectively in an increase of its specific activity. The electromagnetic radiation is very weak. The possibilities to overcome intracellular distances are shown. The motor-driven directed transport of macromolecules starts in the Golgi apparatus. The relevance of molecular interactions based on this signaling for the induction and navigation in the intracellular transport is discussed.

Perceived neighborhood characteristics predict severity and emotional response to daily stressors.

PubMed

Scott, Stacey B; Munoz, Elizabeth; Mogle, Jacqueline A; Gamaldo, Alyssa A; Smyth, Joshua M; Almeida, David M; Sliwinski, Martin J

2018-03-01

Neighborhood characteristics may influence health and well-being outcomes through stressors in daily life. This study tested whether a varied set of perceived characteristics of neighborhood (i.e., social cohesion, safety, aesthetic quality, violence) predicted stressor frequency and severity as well as negative emotional responses to stressors. We predicted greater reported cohesion and safety and less violence would be associated with less frequent stressor exposure and severity and less intense negative affect following stressors; we conducted subsequent tests of neighborhood aesthetic quality as a predictor. Participants (n = 233, age 25-65 years) were residents in a socio-economically, racially, and ethnically diverse zip code in Bronx, New York, most who participated in the Effects of Stress on Cognitive Aging, Physiology and Emotion study between 2012 and 2013. They provided demographic information and neighborhood ratings, then participated in the EMA protocol in which they completed brief smartphone surveys of current negative affect and stressor exposure, severity, and recency, five times daily for 14 days. No coded neighborhood characteristic was related to the frequency of stressors. Individuals who reported greater neighborhood violence, however, rated their stressors as more severe. Individuals rating their neighborhood lower in safety or aesthetic quality, or higher in violence, had greater negative affect following stressors. Even among people living within the same zip code, individual differences in perceptions of neighborhood predict how stressful they appraised stressors in daily life to be and how much negative affect they reported following stressors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Osteocyte calcium signals encode strain magnitude and loading frequency in vivo.

PubMed

Lewis, Karl J; Frikha-Benayed, Dorra; Louie, Joyce; Stephen, Samuel; Spray, David C; Thi, Mia M; Seref-Ferlengez, Zeynep; Majeska, Robert J; Weinbaum, Sheldon; Schaffler, Mitchell B

2017-10-31

Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical loading remains poorly understood. Intracellular calcium (Ca 2+ ) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca 2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca 2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000 [Formula: see text] and frequencies from 0.5 to 2 Hz, which are characteristic of physiological conditions reported for bone. At all loading frequencies examined, the number of responding osteocytes increased strongly with applied strain magnitude. However, Ca 2+ intensity within responding osteocytes did not change significantly with physiological loading magnitudes. Our studies offer a glimpse into how these critical bone cells respond to mechanical load in vivo, as well as provide a technique to determine how the cells encode magnitude and frequency of loading. Published under the PNAS license.

The effects of pressure sensor acoustics on airdata derived from a High-angle-of-attack Flush Airdata Sensing (HI-FADS) system

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A.; Moes, Timothy R.

1991-01-01

The accuracy of a nonintrusive high angle-of-attack flush airdata sensing (HI-FADS) system was verified for quasi-steady flight conditions up to 55 deg angle of attack during the F-18 High Alpha Research Vehicle (HARV) Program. The system is a matrix of nine pressure ports arranged in annular rings on the aircraft nose. The complete airdata set is estimated using nonlinear regression. Satisfactory frequency response was verified to the system Nyquist frequency (12.5 Hz). The effects of acoustical distortions within the individual pressure sensors of the nonintrusive pressure matrix on overall system performance are addressed. To quantify these effects, a frequency-response model describing the dynamics of acoustical distortion is developed and simple design criteria are derived. The model adjusts measured HI-FADS pressure data for the acoustical distortion and quantifies the effects of internal sensor geometries on system performance. Analysis results indicate that sensor frequency response characteristics very greatly with altitude, thus it is difficult to select satisfactory sensor geometry for all altitudes. The solution used presample filtering to eliminate resonance effects, and short pneumatic tubing sections to reduce lag effects. Without presample signal conditioning the system designer must use the pneumatic transmission line to attenuate the resonances and accept the resulting altitude variability.

Distributed Bandpass Filtering and Signal Demodulation in Cortical Network Models

NASA Astrophysics Data System (ADS)

McDonnell, Mark D.

Experimental recordings of cortical activity often exhibit narrowband oscillations, at various center frequencies ranging in the order of 1-200 Hz. Many neuronal mechanisms are known to give rise to oscillations, but here we focus on a population effect known as sparsely synchronised oscillations. In this effect, individual neurons in a cortical network fire irregularly at slow average spike rates (1-10 Hz), but the population spike rate oscillates at gamma frequencies (greater than 40 Hz) in response to spike bombardment from the thalamus. These cortical networks form recurrent (feedback) synapses. Here we describe a model of sparsely synchronized population oscillations using the language of feedback control engineering, where we treat spiking as noisy feedback. We show, using a biologically realistic model of synaptic current that includes a delayed response to inputs, that the collective behavior of the neurons in the network is like a distributed bandpass filter acting on the network inputs. Consequently, the population response has the character of narrowband random noise, and therefore has an envelope and instantaneous frequency with lowpass characteristics. Given that there exist biologically plausible neuronal mechanisms for demodulating the envelope and instantaneous frequency, we suggest there is potential for similar effects to be exploited in nanoscale electronics implementations of engineered communications receivers.

Building the analytical response in frequency domain of AC biased bolometers. Application to Planck/HFI

NASA Astrophysics Data System (ADS)

Sauvé, Alexandre; Montier, Ludovic

2016-12-01

Context: Bolometers are high sensitivity detector commonly used in Infrared astronomy. The HFI instrument of the Planck satellite makes extensive use of them, but after the satellite launch two electronic related problems revealed critical. First an unexpected excess response of detectors at low optical excitation frequency for ν < 1 Hz, and secondly the Analog To digital Converter (ADC) component had been insufficiently characterized on-ground. These two problems require an exquisite knowledge of detector response. However bolometers have highly nonlinear characteristics, coming from their electrical and thermal coupling making them very difficult to model. Goal: We present a method to build the analytical transfer function in frequency domain which describe the voltage response of an Alternative Current (AC) biased bolometer to optical excitation, based on the standard bolometer model. This model is built using the setup of the Planck/HFI instrument and offers the major improvement of being based on a physical model rather than the currently in use had-hoc model based on Direct Current (DC) bolometer theory. Method: The analytical transfer function expression will be presented in matrix form. For this purpose, we build linearized versions of the bolometer electro thermal equilibrium. A custom description of signals in frequency is used to solve the problem with linear algebra. The model performances is validated using time domain simulations. Results: The provided expression is suitable for calibration and data processing. It can also be used to provide constraints for fitting optical transfer function using real data from steady state electronic response and optical response. The accurate description of electronic response can also be used to improve the ADC nonlinearity correction for quickly varying optical signals.

Spectral analysis techniques for characterizing cadmium zinc telluride polarization modulators

NASA Astrophysics Data System (ADS)

FitzGerald, William R.; Taherion, Saeid; Kumar, F. Joseph; Giles, David; Hore, Dennis K.

2018-04-01

The low frequency electro-optic characteristics of cadmium zinc telluride are demonstrated in the mid-infrared, in the spectral range 2.5-11 μm. Conventional methods for characterizing the dynamic response by monitoring the amplitude of the time-varying light intensity do not account for spatial variation in material properties. In such cases, a more revealing method involves monitoring two distinct frequency components in order to characterize the dynamic and static contributions to the optical retardation. We demonstrate that, while this method works well for a ZnSe photo-elastic modulator, it does not fully capture the response of a cadmium zinc telluride electro-optic modulator. Ultimately, we show that acquiring the full waveform of the optical response enables a model to be created that accounts for inhomogeneity in the material that results in an asymmetric response with respect to the polarity of the driving voltage. This technique is applicable to broadband and fixed-wavelength applications in a variety of spectral ranges.

Modulation characteristics of a high-power semiconductor Master Oscillator Power Amplifier (MOPA)

NASA Technical Reports Server (NTRS)

Cornwell, Donald Mitchell, Jr.

1992-01-01

A semiconductor master oscillator-power amplifier was demonstrated using an anti-reflection (AR) coated broad area laser as the amplifier. Under CW operation, diffraction-limited single-longitudinal-mode powers up to 340 mW were demonstrated. The characteristics of the far-field pattern were measured and compared to a two-dimensional reflective Fabry-Perot amplifier model of the device. The MOPA configuration was modulated by the master oscillator. Prior to injection into the amplifier, the amplitude and frequency modulation properties of the master oscillator were characterized. The frequency response of the MOPA configuration was characterized for an AM/FM modulated injection beam, and was found to be a function of the frequency detuning between the master oscillator and the resonant amplifier. A shift in the phase was also observed as a function of frequency detuning; this phase shift is attributed to the optical phase shift imparted to a wave reflected from a Fabry-Perot cavity. Square-wave optical pulses were generated at 10 MHz and 250 MHz with diffraction-limited peak powers of 200 mW and 250 mW. The peak power for a given modulation frequency is found to be limited by the injected power and the FM modulation at that frequency. The modulation results make the MOPA attractive for use as a transmitter source in applications such as free-space communications and ranging/altimetry.

A study of amplitude information-frequency characteristics for underwater active electrolocation system.

PubMed

Peng, Jiegang

2015-11-04

Weakly electric fish sense their surroundings in complete darkness by their active electrolocation system. For biologists, the active electrolocation system has been investigated for near 60 years. And for engineers, bio-inspired active electrolocation sensor has been investigated for about 20 years. But how the amplitude information response will be affected by frequencies of detecting electric fields in the active electrolocation system was rarely investigated. In this paper, an electrolocation experiment system has been built. The amplitude information-frequency characteristics (AIFC) of the electrolocation system for sinusoidal electric fields of varying frequencies have been investigated. We find that AIFC of the electrolocation system have relevance to the material properties and geometric features of the probed object and conductivity of surrounding water. Detect frequency dead zone (DFDZ) and frequency inflection point (FIP) of AIFC for the electrolocation system were found. The analysis model of the electrolocation system has been investigated for many years, but DFDZ and FIP of AIFC can be difficult to explain by those models. In order to explain those AIFC phenomena for the electrolocation system, a simple relaxation model based on Cole-Cole model which is not only a mathematical explanation but it is a physical one for the electrolocation system was advanced. We also advance a hypothesis for physical mechanism of weakly electrical fish electrolocation system. It may have reference value for physical mechanism of weakly electrical fish active electrolocation system.

Seizures in juvenile Huntington's disease: frequency and characterization in a multicenter cohort.

PubMed

Cloud, Leslie J; Rosenblatt, Adam; Margolis, Russel L; Ross, Christopher A; Pillai, Jagan A; Corey-Bloom, Jody; Tully, Hannah M; Bird, Thomas; Panegyres, Peter K; Nichter, Charles A; Higgins, Donald S; Helmers, Sandra L; Factor, Stewart A; Jones, Randi; Testa, Claudia M

2012-12-01

Little is known about the epilepsy that often occurs in the juvenile form of Huntington's disease (HD), but is absent from the adult-onset form. The primary aim of this study was to characterize the seizures in juvenile HD (JHD) subjects with regard to frequency, semiology, defining EEG characteristics, and response to antiepileptic agents. A multicenter, retrospective cohort was identified by database query and/or chart review. Data on age of HD onset, primary HD manifestations, number of CAG repeats, the presence or absence of seizures, seizure type(s), antiepileptic drugs used, subjects' response to antiepileptic drugs (AEDs), and EEG results were assembled, where available. Ninety subjects with genetically confirmed JHD were included. Seizures were present in 38% of subjects and were more likely to occur with younger ages of HD onset. Generalized tonic-clonic seizures were the most common seizure type, followed by tonic, myoclonic, and staring spells. Multiple seizure types commonly occurred within the same individual. Data on EEG findings and AED usage are presented. Seizure risk in JHD increases with younger age of HD onset. Our ability to draw firm conclusions about defining EEG characteristics and response to AEDs was limited by the retrospective nature of the study. Future prospective studies are required. Copyright © 2012 Movement Disorder Society.

FIR signature verification system characterizing dynamics of handwriting features

NASA Astrophysics Data System (ADS)

Thumwarin, Pitak; Pernwong, Jitawat; Matsuura, Takenobu

2013-12-01

This paper proposes an online signature verification method based on the finite impulse response (FIR) system characterizing time-frequency characteristics of dynamic handwriting features. First, the barycenter determined from both the center point of signature and two adjacent pen-point positions in the signing process, instead of one pen-point position, is used to reduce the fluctuation of handwriting motion. In this paper, among the available dynamic handwriting features, motion pressure and area pressure are employed to investigate handwriting behavior. Thus, the stable dynamic handwriting features can be described by the relation of the time-frequency characteristics of the dynamic handwriting features. In this study, the aforesaid relation can be represented by the FIR system with the wavelet coefficients of the dynamic handwriting features as both input and output of the system. The impulse response of the FIR system is used as the individual feature for a particular signature. In short, the signature can be verified by evaluating the difference between the impulse responses of the FIR systems for a reference signature and the signature to be verified. The signature verification experiments in this paper were conducted using the SUBCORPUS MCYT-100 signature database consisting of 5,000 signatures from 100 signers. The proposed method yielded equal error rate (EER) of 3.21% on skilled forgeries.

Impact of the rail-pad multi-discrete model upon the prediction of the rail response

NASA Astrophysics Data System (ADS)

Mazilu, T.; Leu, M.

2017-08-01

Wheel/rail vibration has many technical effects such as wear of the rolling surfaces, rolling noise, settlement of the ballast and subgrade etc. This vibration is depending on the rail pad characteristic and subsequently, it is important to have an accurate overview on the relation between the rail pad characteristic and the level of the wheel/rail vibration. To this end, much theoretical and experimental research has been developed in the past, and for the theoretical approach the track model, in general, and, particularly, the rail pad model is of crucial importance. Usually, the rail pad model is discrete model one, neglecting the length of the rail pad. This fact is questionable because the sleepers span is only 4 times the rail pad length. Using the rail pad discrete model, the rail response is overestimated when the frequency of the excitation equals the pinned-pinned resonance frequency. In this paper, a multi-discrete model for the rail pad, consisting in many Kelvin-Voigt parallel systems, is inserted into an analytical model of the track. The track model is reduced to a rail taken as infinite Timoshenko beam, discretely supported via rail pad, sleeper and ballast. The influence of the number of Kelvin-Voigt systems of the rail pad model on the rail response is analysed.

Methods and apparatuses using filter banks for multi-carrier spread spectrum signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moradi, Hussein; Farhang, Behrouz; Kutsche, Carl A

2017-01-31

A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to themore » synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.« less

Methods and apparatuses using filter banks for multi-carrier spread spectrum signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moradi, Hussein; Farhang, Behrouz; Kutsche, Carl A.

2016-06-14

A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to themore » synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.« less

Rod Electroretinograms Elicited by Silent Substitution Stimuli from the Light-Adapted Human Eye

PubMed Central

Maguire, John; Parry, Neil R. A.; Kremers, Jan; Kommanapalli, Deepika; Murray, Ian J.; McKeefry, Declan J.

2016-01-01

Purpose To demonstrate that silent substitution stimuli can be used to generate electroretinograms (ERGs) that effectively isolate rod photoreceptor function in humans without the need for dark adaptation, and that this approach constitutes a viable alternative to current clinical standard testing protocols. Methods Rod-isolating and non-isolating sinusoidal flicker stimuli were generated on a 4 primary light-emitting diode (LED) Ganzfeld stimulator to elicit ERGs from participants with normal and compromised rod function who had not undergone dark-adaptation. Responses were subjected to Fourier analysis, and the amplitude and phase of the fundamental were used to examine temporal frequency and retinal illuminance response characteristics. Results Electroretinograms elicited by rod-isolating silent substitution stimuli exhibit low-pass temporal frequency response characteristics with an upper response limit of 30 Hz. Responses are optimal between 5 and 8 Hz and between 10 and 100 photopic trolands (Td). There is a significant correlation between the response amplitudes obtained with the silent substitution method and current standard clinical protocols. Analysis of signal-to-noise ratios reveals significant differences between subjects with normal and compromised rod function. Conclusions Silent substitution provides an effective method for the isolation of human rod photoreceptor function in subjects with normal as well as compromised rod function when stimuli are used within appropriate parameter ranges. Translational Relevance This method of generating rod-mediated ERGs can be achieved without time-consuming periods of dark adaptation, provides improved isolation of rod- from cone-based activity, and will lead to the development of faster clinical electrophysiologic testing protocols with improved selectivity. PMID:27617180

Frequency domain system identification of helicopter rotor dynamics incorporating models with time periodic coefficients

NASA Astrophysics Data System (ADS)

Hwang, Sunghwan

1997-08-01

One of the most prominent features of helicopter rotor dynamics in forward flight is the periodic coefficients in the equations of motion introduced by the rotor rotation. The frequency response characteristics of such a linear time periodic system exhibits sideband behavior, which is not the case for linear time invariant systems. Therefore, a frequency domain identification methodology for linear systems with time periodic coefficients was developed, because the linear time invariant theory cannot account for sideband behavior. The modulated complex Fourier series was introduced to eliminate the smearing effect of Fourier series expansions of exponentially modulated periodic signals. A system identification theory was then developed using modulated complex Fourier series expansion. Correlation and spectral density functions were derived using the modulated complex Fourier series expansion for linear time periodic systems. Expressions of the identified harmonic transfer function were then formulated using the spectral density functions both with and without additive noise processes at input and/or output. A procedure was developed to identify parameters of a model to match the frequency response characteristics between measured and estimated harmonic transfer functions by minimizing an objective function defined in terms of the trace of the squared frequency response error matrix. Feasibility was demonstrated by the identification of the harmonic transfer function and parameters for helicopter rigid blade flapping dynamics in forward flight. This technique is envisioned to satisfy the needs of system identification in the rotating frame, especially in the context of individual blade control. The technique was applied to the coupled flap-lag-inflow dynamics of a rigid blade excited by an active pitch link. The linear time periodic technique results were compared with the linear time invariant technique results. Also, the effect of noise processes and initial parameter guess on the identification procedure were investigated. To study the effect of elastic modes, a rigid blade with a trailing edge flap excited by a smart actuator was selected and system parameters were successfully identified, but with some expense of computational storage and time. Conclusively, the linear time periodic technique substantially improved the identified parameter accuracy compared to the linear time invariant technique. Also, the linear time periodic technique was robust to noises and initial guess of parameters. However, an elastic mode of higher frequency relative to the system pumping frequency tends to increase the computer storage requirement and computing time.

Binaural Interaction Effects of 30-50 Hz Auditory Steady State Responses.

PubMed

Gransier, Robin; van Wieringen, Astrid; Wouters, Jan

Auditory stimuli modulated by modulation frequencies within the 30 to 50 Hz region evoke auditory steady state responses (ASSRs) with high signal to noise ratios in adults, and can be used to determine the frequency-specific hearing thresholds of adults who are unable to give behavioral feedback reliably. To measure ASSRs as efficiently as possible a multiple stimulus paradigm can be used, stimulating both ears simultaneously. The response strength of 30 to 50Hz ASSRs is, however, affected when both ears are stimulated simultaneously. The aim of the present study is to gain insight in the measurement efficiency of 30 to 50 Hz ASSRs evoked with a 2-ear stimulation paradigm, by systematically investigating the binaural interaction effects of 30 to 50 Hz ASSRs in normal-hearing adults. ASSRs were obtained with a 64-channel EEG system in 23 normal-hearing adults. All participants participated in one diotic, multiple dichotic, and multiple monaural conditions. Stimuli consisted of a modulated one-octave noise band, centered at 1 kHz, and presented at 70 dB SPL. The diotic condition contained 40 Hz modulated stimuli presented to both ears. In the dichotic conditions, the modulation frequency of the left ear stimulus was kept constant at 40 Hz, while the stimulus at the right ear was either the unmodulated or modulated carrier. In case of the modulated carrier, the modulation frequency varied between 30 and 50 Hz in steps of 2 Hz across conditions. The monaural conditions consisted of all stimuli included in the diotic and dichotic conditions. Modulation frequencies ≥36 Hz resulted in prominent ASSRs in all participants for the monaural conditions. A significant enhancement effect was observed (average: ~3 dB) in the diotic condition, whereas a significant reduction effect was observed in the dichotic conditions. There was no distinct effect of the temporal characteristics of the stimuli on the amount of reduction. The attenuation was in 33% of the cases >3 dB for ASSRs evoked with modulation frequencies ≥40 Hz and 50% for ASSRs evoked with modulation frequencies ≤36 Hz. Binaural interaction effects as observed in the diotic condition are similar to the binaural interaction effects of middle latency responses as reported in the literature, suggesting that these responses share a same underlying mechanism. Our data also indicated that 30 to 50 Hz ASSRs are attenuated when presented dichotically and that this attenuation is independent of the stimulus characteristics as used in the present study. These findings are important as they give insight in how binaural interaction affects the measurement efficiency. The 2-ear stimulation paradigm of the present study was, for the most optimal modulation frequencies (i.e., ≥40 Hz), more efficient than a 1-ear sequential stimulation paradigm in 66% of the cases.

Modeling and parameter identification of impulse response matrix of mechanical systems

NASA Astrophysics Data System (ADS)

Bordatchev, Evgueni V.

1998-12-01

A method for studying the problem of modeling, identification and analysis of mechanical system dynamic characteristic in view of the impulse response matrix for the purpose of adaptive control is developed here. Two types of the impulse response matrices are considered: (i) on displacement, which describes the space-coupled relationship between vectors of the force and simulated displacement, which describes the space-coupled relationship between vectors of the force and simulated displacement and (ii) on acceleration, which also describes the space-coupled relationship between the vectors of the force and measured acceleration. The idea of identification consists of: (a) the practical obtaining of the impulse response matrix on acceleration by 'impact-response' technique; (b) the modeling and parameter estimation of the each impulse response function on acceleration through the fundamental representation of the impulse response function on displacement as a sum of the damped sine curves applying linear and non-linear least square methods; (c) simulating the impulse provides the additional possibility to calculate masses, damper and spring constants. The damped natural frequencies are used as a priori information and are found through the standard FFT analysis. The problem of double numerical integration is avoided by taking two derivations of the fundamental dynamic model of a mechanical system as linear combination of the mass-damper-spring subsystems. The identified impulse response matrix on displacement represents the dynamic properties of the mechanical system. From the engineering point of view, this matrix can be also understood as a 'dynamic passport' of the mechanical system and can be used for dynamic certification and analysis of the dynamic quality. In addition, the suggested approach mathematically reproduces amplitude-frequency response matrix in a low-frequency band and on zero frequency. This allows the possibility of determining the matrix of the static stiffness due to dynamic testing over the time of 10- 15 minutes. As a practical example, the dynamic properties in view of the impulse and frequency response matrices of the lathe spindle are obtained, identified and investigated. The developed approach for modeling and parameter identification appears promising for a wide range o industrial applications; for example, rotary systems.

Softwall acoustical characteristics and measurement capabilities of the NASA Lewis 9x15 foot low speed wind tunnel

NASA Technical Reports Server (NTRS)

Rentz, P. E.

1976-01-01

Acoustical characteristics and source directionality measurement capabilities of the wind tunnel in the softwall configuration were evaluated, using aerodynamically clean microphone supports. The radius of measurement was limited by the size of the test section, instead of the 3.0 foot (1 m) limitation of the hardwall test section. The wind-on noise level in the test section was reduced 10 dB. Reflections from the microphone support boom, after absorptive covering, induced measurement errors in the lower frequency bands. Reflections from the diffuser back wall were shown to be significant. Tunnel noise coming up the diffuser was postulated as being responsible, at least partially, for the wind-on noise in the test section and settling chamber. The near field characteristics of finite-sized sources and the theoretical response of a porous strip sensor in the presence of wind are presented.

An equivalent frequency approach for determining non-linear effects on pre-tensioned-cable cross-braced structures

NASA Astrophysics Data System (ADS)

Giaccu, Gian Felice

2018-05-01

Pre-tensioned cable braces are widely used as bracing systems in various structural typologies. This technology is fundamentally utilized for stiffening purposes in the case of steel and timber structures. The pre-stressing force imparted to the braces provides to the system a remarkable increment of stiffness. On the other hand, the pre-tensioning force in the braces must be properly calibrated in order to satisfactorily meet both serviceability and ultimate limit states. Dynamic properties of these systems are however affected by non-linear behavior due to potential slackening of the pre-tensioned brace. In the recent years the author has been working on a similar problem regarding the non-linear response of cables in cable-stayed bridges and braced structures. In the present paper a displacement-based approach is used to examine the non-linear behavior of a building system. The methodology operates through linearization and allows obtaining an equivalent linearized frequency to approximately characterize, mode by mode, the dynamic behavior of the system. The equivalent frequency depends on both the mechanical characteristics of the system, the pre-tensioning level assigned to the braces and a characteristic vibration amplitude. The proposed approach can be used as a simplified technique, capable of linearizing the response of structural systems, characterized by non-linearity induced by the slackening of pre-tensioned braces.

Annoyance due to simulated blade-slap noise

NASA Technical Reports Server (NTRS)

Powell, C. A.

1978-01-01

The effects of several characteristics of blade slap noise on annoyance response were studied. These characteristics or parameters were the sound pressure level of the continuous noise used to simulate helicopter broadband noise, the ratio of impulse peak to broadband noise or crest factor, the number of pressure excursions comprising an impulse event, the rise and fall time of the individual impulses, and the repetition frequency of the impulses. Analyses were conducted to determine the correlation between subjective response and various physical measures for the range of parameters studied. A small but significant improvement in the predictive ability of PNL was provided by an A-weighted crest factor correlation. No significant improvement in predictive ability was provided by a rate correction.

The use of linear programming techniques to design optimal digital filters for pulse shaping and channel equalization

NASA Technical Reports Server (NTRS)

Houts, R. C.; Burlage, D. W.

1972-01-01

A time domain technique is developed to design finite-duration impulse response digital filters using linear programming. Two related applications of this technique in data transmission systems are considered. The first is the design of pulse shaping digital filters to generate or detect signaling waveforms transmitted over bandlimited channels that are assumed to have ideal low pass or bandpass characteristics. The second is the design of digital filters to be used as preset equalizers in cascade with channels that have known impulse response characteristics. Example designs are presented which illustrate that excellent waveforms can be generated with frequency-sampling filters and the ease with which digital transversal filters can be designed for preset equalization.

Microwave properties of sea ice in the marginal ice zone

NASA Technical Reports Server (NTRS)

Onstott, R. G.; Larson, R. W.

1986-01-01

Active microwave properties of summer sea ice were measured. Backscatter data were acquired at frequencies from 1 to 17 GHz, at angles from 0 to 70 deg from vertical, and with like and cross antenna polarizations. Results show that melt-water, snow thickness, snowpack morphology, snow surface roughness, ice surface roughness, and deformation characteristics are the fundamental scene parameters which govern the summer sea ice backscatter response. A thick, wet snow cover dominates the backscatter response and masks any ice sheet features below. However, snow and melt-water are not distributed uniformly and the stage of melt may also be quite variable. These nonuniformities related to ice type are not necessarily well understood and produce unique microwave signature characteristics.

Effect of acoustic resonance phenomenon on fluid flow with light dust

NASA Astrophysics Data System (ADS)

Hamakawa, Hiromitsu; Arshad, Azim B. M.; Ohta, Mitsuo

2011-10-01

In the present paper, the attention is focused on the characteristics of lightweight materials collection in the duct using acoustic resonance phenomena. The acoustic resonance was excited by using a controlled speaker at the middle of a test duct. We measured the sound pressure level, frequency response characteristics, acoustic damping ratio, mode shape, and lightweight materials response to acoustic resonance excited by a speaker. As a result, the acoustic damping ratio decreased as the mode number of acoustic resonance increased. The tissue strips and the lightweight materials were collected at the node of acoustic pressure when the acoustic resonance was excited. It was made clear that it is possible to control lightweight materials using acoustic resonance excited by a speaker.

Simulation of pyroshock environments using a tunable resonant fixture

DOEpatents

Davie, N.T.

1996-10-15

Disclosed are a method and apparatus for simulating pyrotechnic shock for the purpose of qualifying electronic components for use in weapons, satellite, and aerospace applications. According to the invention, a single resonant bar fixture has an adjustable resonant frequency in order to exhibit a desired shock response spectrum upon mechanical impact. The invention eliminates the need for availability of a large number of different fixtures, capable of exhibiting a range of shock response characteristics, in favor of a single tunable system. 32 figs.

Simulation of pyroshock environments using a tunable resonant fixture

DOEpatents

Davie, Neil T.

1996-01-01

Disclosed are a method and apparatus for simulating pyrotechnic shock for the purpose of qualifying electronic components for use in weapons, satellite, and aerospace applications. According to the invention, a single resonant bar fixture has an adjustable resonant frequency in order to exhibit a desired shock response spectrum upon mechanical impact. The invention eliminates the need for availability of a large number of different fixtures, capable of exhibiting a range of shock response characteristics, in favor of a single tunable system.

Excess noise in Pb(1-x)Sn(x)Se semiconductor lasers

NASA Technical Reports Server (NTRS)

Harward, C. N.; Sidney, B. D.

1980-01-01

The noise characteristics of the TDL were studied for frequencies less than 20 kHz. For heterodyne applications, the high frequency ( 1 MHz) characteristics are also important. Therefore, the high frequency noise characteristics of the TDL were studied as a part of a full TDL characterization program which has been implemented for the improvement of the TDL as a local oscillator in the LHS system. It was observed that all the devices showed similar high frequency noise characteristics even though they were all constructed using different techniques. These common high frequency noise characteristics are reported.

Effects of variations of stage and flux at different frequencies on the estimates using river stage tomography

NASA Astrophysics Data System (ADS)

Wang, Y. L.; Yeh, T. C. J.; Wen, J. C.

2017-12-01

This study is to investigate the ability of river stage tomography to estimate the spatial distribution of hydraulic transmissivity (T), storage coefficient (S), and diffusivity (D) in groundwater basins using information of groundwater level variations induced by periodic variations of stream stage, and infiltrated flux from the stream boundary. In order to accomplish this objective, the sensitivity and correlation of groundwater heads with respect to the hydraulic properties is first conducted to investigate the spatial characteristics of groundwater level in response to the stream variations at different frequencies. Results of the analysis show that the spatial distributions of the sensitivity of heads at an observation well in response to periodic river stage variations are highly correlated despite different frequencies. On the other hand, the spatial patterns of the sensitivity of the observed head to river flux boundaries at different frequencies are different. Specifically, the observed head is highly correlated with T at the region between the stream and observation well when the high-frequency periodic flux is considered. On the other hand, it is highly correlated with T at the region between monitoring well and the boundary opposite to the stream when the low-frequency periodic flux is prescribed to the stream. We also find that the spatial distributions of the sensitivity of observed head to S variation are highly correlated with all frequencies in spite of heads or fluxes stream boundary. Subsequently, the differences of the spatial correlations of the observed heads to the hydraulic properties under the head and flux boundary conditions are further investigated by an inverse model (i.e., successive stochastic linear estimator). This investigation uses noise-free groundwater and stream data of a synthetic aquifer, where aquifer heterogeneity is known exactly. The ability of river stage tomography is then tested with these synthetic data sets to estimate T, S, and D distribution. The results reveal that boundary flux variations with different frequencies contain different information about the aquifer characteristics while the head boundary does not.

Differences between vocalization evoked by social stimuli in feral cats and house cats.

PubMed

Yeon, Seong C; Kim, Young K; Park, Se J; Lee, Scott S; Lee, Seung Y; Suh, Euy H; Houpt, Katherine A; Chang, Hong H; Lee, Hee C; Yang, Byung G; Lee, Hyo J

2011-06-01

To investigate how socialization can affect the types and characteristics of vocalization produced by cats, feral cats (n=25) and house cats (n=13) were used as subjects, allowing a comparison between cats socialized to people and non-socialized cats. To record vocalization and assess the cats' responses to behavioural stimuli, five test situations were used: approach by a familiar caretaker, by a threatening stranger, by a large doll, by a stranger with a dog and by a stranger with a cat. Feral cats showed extremely aggressive and defensive behaviour in most test situations, and produced higher call rates than those of house cats in the test situations, which could be attributed to less socialization to other animals and to more sensitivity to fearful situations. Differences were observed in the acoustic parameters of feral cats in comparison to those of house cats. The feral cat produced significantly higher frequency in fundamental frequency, peak frequency, 1st quartile frequency, 3rd quartile frequency of growls and hisses in agonistic test situations. In contrast to the growls and hisses, in meow, all acoustic parameters like fundamental frequency, first formant, peak frequency, 1st quartile frequency, and 3rd quartile frequency of house cats were of significantly higher frequency than those of feral cats. Also, house cats produced calls of significantly shorter in duration than feral cats in agonistic test situations. These results support the conclusion that a lack of socialization may affect usage of types of vocalizations, and the vocal characteristics, so that the proper socialization of cat may be essential to be a suitable companion house cat. Copyright © 2011 Elsevier B.V. All rights reserved.

Ambient response of a unique performance-based design building with dynamic response modification features

USGS Publications Warehouse

Çelebi, Mehmet; Huang, Moh; Shakal, Antony; Hooper, John; Klemencic, Ron

2012-01-01

A 64-story, performance-based design building with reinforced concrete core shear-walls and unique dynamic response modification features (tuned liquid sloshing dampers and buckling-restrained braces) has been instrumented with a monitoring array of 72 channels of accelerometers. Ambient vibration data recorded are analyzed to identify modes and associated frequencies and damping. The low-amplitude dynamic characteristics are considerably different than those computed from design analyses, but serve as a baseline against which to compare with future strong shaking responses. Such studies help to improve our understanding of the effectiveness of the added features to the building and help improve designs in the future.

Vibration of a hydrostatic gas bearing due to supply pressure oscillations

NASA Technical Reports Server (NTRS)

Branch, H. D.; Watkins, C. B.; Eronini, I. E.

1984-01-01

The vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating supply pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and the sleeve is solved numerically together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The results presented include Bode plots of bearing oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency. The results are compared with the results of an earlier study involving the response of a similar bearing to oscillating exhaust pressure.

Speech Spectrum's Correlation with Speakers' Eysenck Personality Traits

PubMed Central

Hu, Chao; Wang, Qiandong; Short, Lindsey A.; Fu, Genyue

2012-01-01

The current study explored the correlation between speakers' Eysenck personality traits and speech spectrum parameters. Forty-six subjects completed the Eysenck Personality Questionnaire. They were instructed to verbally answer the questions shown on a computer screen and their responses were recorded by the computer. Spectrum parameters of /sh/ and /i/ were analyzed by Praat voice software. Formant frequencies of the consonant /sh/ in lying responses were significantly lower than that in truthful responses, whereas no difference existed on the vowel /i/ speech spectrum. The second formant bandwidth of the consonant /sh/ speech spectrum was significantly correlated with the personality traits of Psychoticism, Extraversion, and Neuroticism, and the correlation differed between truthful and lying responses, whereas the first formant frequency of the vowel /i/ speech spectrum was negatively correlated with Neuroticism in both response types. The results suggest that personality characteristics may be conveyed through the human voice, although the extent to which these effects are due to physiological differences in the organs associated with speech or to a general Pygmalion effect is yet unknown. PMID:22439014

Rotorcraft Blade Mode Damping Identification from Random Responses Using a Recursive Maximum Likelihood Algorithm

NASA Technical Reports Server (NTRS)

Molusis, J. A.

1982-01-01

An on line technique is presented for the identification of rotor blade modal damping and frequency from rotorcraft random response test data. The identification technique is based upon a recursive maximum likelihood (RML) algorithm, which is demonstrated to have excellent convergence characteristics in the presence of random measurement noise and random excitation. The RML technique requires virtually no user interaction, provides accurate confidence bands on the parameter estimates, and can be used for continuous monitoring of modal damping during wind tunnel or flight testing. Results are presented from simulation random response data which quantify the identified parameter convergence behavior for various levels of random excitation. The data length required for acceptable parameter accuracy is shown to depend upon the amplitude of random response and the modal damping level. Random response amplitudes of 1.25 degrees to .05 degrees are investigated. The RML technique is applied to hingeless rotor test data. The inplane lag regressing mode is identified at different rotor speeds. The identification from the test data is compared with the simulation results and with other available estimates of frequency and damping.

Modeling and characterization of an electromagnetic system for the estimation of Frequency Response Function of spindle

NASA Astrophysics Data System (ADS)

Tlalolini, David; Ritou, Mathieu; Rabréau, Clément; Le Loch, Sébastien; Furet, Benoit

2018-05-01

The paper presents an electromagnetic system that has been developed to measure the quasi-static and dynamic behavior of machine-tool spindle, at different spindle speeds. This system consists in four Pulse Width Modulation amplifiers and four electromagnets to produce magnetic forces of ± 190 N for the static mode and ± 80 N for the dynamic mode up to 5 kHz. In order to measure the Frequency Response Function (FRF) of spindle, the applied force is required, which is a key issue. A dynamic force model is proposed in order to obtain the load from the measured current in the amplifiers. The model depends on the exciting frequency and on the magnetic characteristics of the system. The predicted force at high speed is validated with a specific experiment and the performance limits of the experimental device are investigated. The FRF obtained with the electromagnetic system is compared to a classical tap test measurement.

Electrokinetically induced alterations in dynamic response of viscoelastic fluids in narrow confinements.

PubMed

Bandopadhyay, Aditya; Chakraborty, Suman

2012-05-01

We investigate a dynamical interplay between interfacial electrokinetics and a combined dissipative and elastic behavior of flow through narrow confinements, in analogy with spatiotemporal hydrodynamics of porous media. In particular, we investigate the effects of streaming potential on the pertinent dynamic responses, by choosing a Maxwell fluid model for representing the consequent electro-hydrodynamic characteristics. We transform the pertinent governing equation to the frequency domain, so that a dynamic generalization of Darcy's law in the presence of streaming potential effects can be effectively realized. We show that the frequencies corresponding to local maxima in the dynamic permeability also correspond to local maxima in the induced streaming potential. We also bring out the effects of Stern layer conductivity on the dynamic permeability. Our analytical estimates do reveal that serious overestimations in the commonly portrayed notion of massive amplifications of dynamic permeability at resonating frequencies may be possible, if interactions between spontaneous electrochemical interfacial phenomena and pulsating pressure-gradient-driven viscoelastic transport are trivially ignored.

[Study on the Spectral Characteristics of the Narrow-Band Filter in SHS].

PubMed

Luo, Hai-yan; Shi, Hai-liang; Li, Zhi-wei; Li, Shuang; Xiong, Wei; Hong, Jin

2015-04-01

The spectral response of spatial heterodyne spectroscopy (SHS) is determined by the spectrum property of narrow-band filter. As discussed in previous studies, the symmetric heterodyned interferogram of high frequency waves modulated by SHS and lack of sample lead to spectral confusion, which is associated with the true and ghost spectra. Because of the deviation from theoretical index of narrow-band filter in the process of coating, the boarded spectral response and middle wave shift are presented, and conditions in the theoretical Littrow wavelength made the effective wavelength range of SHS reduced. According to the measured curve of filter, a new wavenumber of zero spatial frequency can be reset by tunable laser, and it is easy for SHS to improve the spectral aliasing distortion. The results show that it is utilized to the maximum extent of the effective bandwidth by adjusting the grating angle of rotation to change the Littrow wavelength of the basic frequency, and the spectral region increased to 14.9 nm from original 12.9 nm.

Inductive sensor performance in partial discharges and noise separation by means of spectral power ratios.

PubMed

Ardila-Rey, Jorge Alfredo; Rojas-Moreno, Mónica Victoria; Martínez-Tarifa, Juan Manuel; Robles, Guillermo

2014-02-19

Partial discharge (PD) detection is a standardized technique to qualify electrical insulation in machines and power cables. Several techniques that analyze the waveform of the pulses have been proposed to discriminate noise from PD activity. Among them, spectral power ratio representation shows great flexibility in the separation of the sources of PD. Mapping spectral power ratios in two-dimensional plots leads to clusters of points which group pulses with similar characteristics. The position in the map depends on the nature of the partial discharge, the setup and the frequency response of the sensors. If these clusters are clearly separated, the subsequent task of identifying the source of the discharge is straightforward so the distance between clusters can be a figure of merit to suggest the best option for PD recognition. In this paper, two inductive sensors with different frequency responses to pulsed signals, a high frequency current transformer and an inductive loop sensor, are analyzed to test their performance in detecting and separating the sources of partial discharges.

Effect of planecta and ROSE™ on the frequency characteristics of blood pressure-transducer kits.

PubMed

Fujiwara, Shigeki; Kawakubo, Yoshifumi; Mori, Satoshi; Tachihara, Keiichi; Toyoguchi, Izumi; Yokoyama, Takeshi

2015-12-01

Pressure-transducer kits have frequency characteristics such as natural frequency and damping coefficient, which affect the monitoring accuracy. The aim of the present study was to investigate the effect of planecta ports and a damping device (ROSE™, Argon Medical Devices, TX, USA) on the frequency characteristics of pressure-transducer kits. The FloTrac sensor kit (Edwards Lifesciences, CA, USA) and the DTXplus transducer kit (Argon Medical Devices) were prepared with planecta ports, and their frequency characteristics were tested with or without ROSE™. The natural frequency and damping coefficient of each kit were obtained using frequency characteristics analysis software and evaluated by plotting them on the Gardner's chart. By inserting a planecta port, the natural frequency markedly decreased in both the FloTrac sensor kit (from 40 to 22 Hz) and the DTXplus transducer kit (from 35 to 22 Hz). In both kits with one planecta port, the damping coefficient markedly increased by insertion of ROSE™ from 0.2 to 0.5, optimising frequency characteristics. In both kits with two planecta ports, however, the natural frequency decreased from 22 to 12 Hz. The damping coefficient increased from 0.2 to 0.8 by insertion of ROSE™; however, optimisation was not achieved even by ROSE™ insertion. Planecta ports decrease the natural frequency of the kit. ROSE™ is useful to optimise the frequency characteristics in the kits without or with one planecta port. However, optimisation is difficult with two or more planecta ports, even with the ROSE™ device.

Novel characterization method for fibrous materials using non-contact acoustics: material properties revealed by ultrasonic perturbations.

PubMed

Periyaswamy, Thamizhisai; Balasubramanian, Karthikeyan; Pastore, Christopher

2015-02-01

Fibrous materials are unique hierarchical complex structures exhibiting a range of mechanical, thermal, optical and electrical properties. The inherent discontinuity at micro and macro levels, heterogeneity and multi-scale porosity differentiates fibrous materials from other engineering materials that are typically continuum in nature. These structural complexities greatly influence the techniques and modalities that can be applied to characterize fibrous materials. Typically, the material response to an applied external force is measured and used as a characteristic number of the specimen. In general, a range of equipment is in use to obtain these numbers to signify the material properties. Nevertheless, obtaining these numbers for materials like fiber ensembles is often time consuming, destructive, and requires multiple modalities. It is hypothesized that the material response to an applied acoustic frequency would provide a robust alternative characterization mode for rapid and non-destructive material analysis. This research proposes applying air-coupled ultrasonic acoustics to characterize fibrous materials. Ultrasonic frequency waves transmitted through fibrous assemblies were feature extracted to understand the correlation between the applied frequency and the material properties. Mechanical and thermal characteristics were analyzed using ultrasonic features such as time of flight, signal velocity, power and the rate of attenuation of signal amplitude. Subsequently, these temporal and spectral characteristics were mapped with the standard low-stress mechanical and thermal properties via an empirical artificial intelligence engine. A high correlation of >0.92 (S.D. 0.06) was observed between the ultrasonic features and the standard measurements. The proposed ultrasonic technique can be used toward rapid characterization of dynamic behavior of flexible fibrous assemblies. Copyright © 2014 Elsevier B.V. All rights reserved.

The characteristics and effects of motivational music in exercise settings: the possible influence of gender, age, frequency of attendance, and time of attendance.

PubMed

Priest, D L; Karageorghis, C I; Sharp, N C C

2004-03-01

The purpose of the present study was to investigate the characteristics and effects of motivational music in British gymnasia. The secondary purpose was to determine whether the characteristics and effects of motivational music were invariant in relation to gender, age, frequency of gymnasium attendance, and the time of day at which exercise participants attended gymnasia. Participants (n=532) from 29 David Lloyd Leisure exercise facilities across Britain responded to a questionnaire that was designed to assess music preferences during exercise via 2 open-ended questions and 1 scaled-response item. A content analysis of the questionnaire data yielded 45 analytic properties that were grouped into the following categories: specific music factors, general music factors, music programme factors, delivery factors, televisual factors, personal factors, contextual factors, and psychophysical response factors. The relative incidence of these analytic properties across gender groups (male/female), age groups (16-26 y, 27-34 y, 35-45 y, 46+ y), frequency of attendance groups (low, medium, high), and time of attendance groups (morning, afternoon, evening) was tested by use of chi(2) analyses. Of the personal variables tested, age exerted the greatest influence on musical preference during exercise; older participants expressed a preference for quieter, slower, and generally less overtly stimulative music. Music programmes that are prescribed to accompany exercise should be varied in terms of musical idiom and date of release. Such programmes will account for the preferences of different groups of exercise participants that attend gymnasia at different times of the day. Further, the music chosen should be characterised by a strong rhythmical component.

BK potassium channels facilitate high-frequency firing and cause early spike frequency adaptation in rat CA1 hippocampal pyramidal cells

PubMed Central

Gu, Ning; Vervaeke, Koen; Storm, Johan F

2007-01-01

Neuronal potassium (K+) channels are usually regarded as largely inhibitory, i.e. reducing excitability. Here we show that BK-type calcium-activated K+ channels enhance high-frequency firing and cause early spike frequency adaptation in neurons. By combining slice electrophysiology and computational modelling, we investigated functions of BK channels in regulation of high-frequency firing in rat CA1 pyramidal cells. Blockade of BK channels by iberiotoxin (IbTX) selectively reduced the initial discharge frequency in response to strong depolarizing current injections, thus reducing the early spike frequency adaptation. IbTX also blocked the fast afterhyperpolarization (fAHP), slowed spike rise and decay, and elevated the spike threshold. Simulations with a computational model of a CA1 pyramidal cell confirmed that the BK channel-mediated rapid spike repolarization and fAHP limits activation of slower K+ channels (in particular the delayed rectifier potassium current (IDR)) and Na+ channel inactivation, whereas M-, sAHP- or SK-channels seem not to be important for the early facilitating effect. Since the BK current rapidly inactivates, its facilitating effect diminishes during the initial discharge, thus producing early spike frequency adaptation by an unconventional mechanism. This mechanism is highly frequency dependent. Thus, IbTX had virtually no effect at spike frequencies < 40 Hz. Furthermore, extracellular field recordings demonstrated (and model simulations supported) that BK channels contribute importantly to high-frequency burst firing in response to excitatory synaptic input to distal dendrites. These results strongly support the idea that BK channels play an important role for early high-frequency, rapidly adapting firing in hippocampal pyramidal neurons, thus promoting the type of bursting that is characteristic of these cells in vivo, during behaviour. PMID:17303637

Non-linearity of visual evoked potentials in cerveau isolé and midpontine pretrigeminal cats.

PubMed

Shibagaki, M; Kiyono, S; Kawashima, T; Watanabe, S

1985-01-01

Characteristics of the visual evoked responses to the flickering flash stimulation were studied in the cerveau isolé and midpontine pretrigeminal cats. The flash stimulation frequency was changed stepwise between 1 and 30 Hz in increasing and decreasing order. In all cases of both preparations, with drawing of fixed sweep speed of 200 msec in whole length, P1 and N1 latencies in the successive response slightly prolonged progressively 1 to about 20 Hz and thereafter shortened about 20-30 Hz stimulus frequencies in the course of the increasing phase, and vice versa in the course of the decreasing phase. Moreover, no difference in each latency (P1, N1, P2, N2) was found at the same stimulus frequency during increasing and decreasing phases. In the amplitude taken from the P1-N1 component, the peak was found in 5-9 Hz frequency bands. This peak was higher during the decreasing phase than during the increasing phase, which indicated a hysteresis phenomenon. A peak of power for the 1st harmonics was found at 3-6 Hz driving frequency bands, and that of the 2nd harmonics at 6-10 Hz. In the state without flash stimulus, no peaks or valleys in the power spectrum were found in specific frequencies, for example 3-10 Hz. The peak in the amplitude and that in the power spectrum at 3-10 Hz stimulus frequency bands suggested an entrainment phenomenon induced by forced oscillation. The phenomena of entrainment and hysteresis suggest the existence of a non-linear structure in the oscillation generating systems of visual evoked response.

Dependence of the Startle Response on Temporal and Spectral Characteristics of Acoustic Modulatory Influences in Rats and Gerbils

PubMed Central

Steube, Natalie; Nowotny, Manuela; Pilz, Peter K. D.; Gaese, Bernhard H.

2016-01-01

The acoustic startle response (ASR) and its modulation by non-startling prepulses, presented shortly before the startle-eliciting stimulus, is a broadly applied test paradigm to determine changes in neural processing related to auditory or psychiatric disorders. Modulation by a gap in background noise as a prepulse is especially used for tinnitus assessment. However, the timing and frequency-related aspects of prepulses are not fully understood. The present study aims to investigate temporal and spectral characteristics of acoustic stimuli that modulate the ASR in rats and gerbils. For noise-burst prepulses, inhibition was frequency-independent in gerbils in the test range between 4 and 18 kHz. Prepulse inhibition (PPI) by noise-bursts in rats was constant in a comparable range (8–22 kHz), but lower outside this range. Purely temporal aspects of prepulse–startle-interactions were investigated for gap-prepulses focusing mainly on gap duration. While very short gaps had no (rats) or slightly facilitatory (gerbils) influence on the ASR, longer gaps always had a strong inhibitory effect. Inhibition increased with durations up to 75 ms and remained at a high level of inhibition for durations up to 1000 ms for both, rats and gerbils. Determining spectral influences on gap-prepulse inhibition (gap-PPI) revealed that gerbils were unaffected in the limited frequency range tested (4–18 kHz). The more detailed analysis in rats revealed a variety of frequency-dependent effects. Gaps in pure-tone background elicited constant and high inhibition (around 75%) over a broad frequency range (4–32 kHz). For gaps in noise-bands, on the other hand, a clear frequency-dependency was found: inhibition was around 50% at lower frequencies (6–14 kHz) and around 70% at high frequencies (16–20 kHz). This pattern of frequency-dependency in rats was specifically resulting from the inhibitory effect by the gaps, as revealed by detailed analysis of the underlying startle amplitudes. An interaction of temporal and spectral influences, finally, resulted in higher inhibition for 500 ms gaps than for 75 ms gaps at all frequencies tested. Improved prepulse paradigms based on these results are well suited to quantify the consequences of central processing disorders. PMID:27445728

Communicating risk information: the influence of graphical display format on quantitative information perception-Accuracy, comprehension and preferences.

PubMed

Price, Melanie; Cameron, Rachel; Butow, Phyllis

2007-12-01

Statistical health risk information has proved notoriously confusing and difficult to understand. While past research indicates that presenting risk information in a frequency format is superior to relative risk and probability formats, the optimal characteristics of frequency formats are still unclear. The aim of this study is to determine the features of 1000 person frequency diagrams (pictographs) which result in the greatest speed and accuracy of graphical perception. Participants estimated the difference in chance of survival when taking or not taking Drug A, on a pictograph format, varying by mode (one-graph/two-graph), direction (vertical/horizontal), and shading (shaded/unshaded), and their preferences for the different formats. Their understanding of different components of the 1000 person diagram was assessed. Responses were timed and scored for accuracy. Horizontal pictographs were perceived faster and more accurately than vertical formats. Two-graph pictographs were perceived faster than one-graph formats. Shading reduced response time in two-graph formats, but increased response times in one-graph formats. Shaded and one-graph pictographs were preferred. As shading and one-graph formats were preferred, further clarification as to why shading negatively impacts on response times in the one-graph format is warranted. Horizontal pictographs are optimal.

Role of angiotensin II in dynamic renal blood flow autoregulation of the conscious dog

PubMed Central

Just, Armin; Ehmke, Heimo; Wittmann, Uwe; Kirchheim, Hartmut R

2002-01-01

The influence of angiotensin II (ANGII) on the dynamic characteristics of renal blood flow (RBF) was studied in conscious dogs by testing the response to a step increase in renal artery pressure (RAP) after a 60 s period of pressure reduction (to 50 mmHg) and by calculating the transfer function between physiological fluctuations in RAP and RBF. During the RAP reduction, renal vascular resistance (RVR) decreased and upon rapid restoration of RAP, RVR returned to baseline with a characteristic time course: within the first 10 s, RVR rose rapidly by 40 % of the initial change (first response, myogenic response). A second rise began after 20–30 s and reached baseline after an overshoot at 40 s (second response, tubuloglomerular feedback (TGF)). Between both responses, RVR rose very slowly (plateau). The transfer function had a low gain below 0.01 Hz (high autoregulatory efficiency) and two corner frequencies at 0.026 Hz (TGF) and at 0.12 Hz (myogenic response). Inhibition of angiotensin converting enzyme (ACE) lowered baseline RVR, but not the minimum RVR at the end of the RAP reduction (autoregulation-independent RVR). Both the first and second response were reduced, but the normalised level of the plateau (balance between myogenic response, TGF and possible slower mechanisms) and the transfer gain below 0.01 Hz were not affected. Infusion of ANGII after ramipril raised baseline RVR above the control condition. The first and second response and the transfer gain at both corner frequencies were slightly augmented, but the normalised level of the plateau was not affected. It is concluded that alterations of plasma ANGII within a physiological range do not modulate the relative contribution of the myogenic response to the overall short-term autoregulation of RBF. Consequently, it appears that ANGII augments not only TGF, but also the myogenic response. PMID:11773325

Rock friction under variable normal stress

USGS Publications Warehouse

Kilgore, Brian D.; Beeler, Nicholas M.; Lozos, Julian C.; Oglesby, David

2017-01-01

This study is to determine the detailed response of shear strength and other fault properties to changes in normal stress at room temperature using dry initially bare rock surfaces of granite at normal stresses between 5 and 7 MPa. Rapid normal stress changes result in gradual, approximately exponential changes in shear resistance with fault slip. The characteristic length of the exponential change is similar for both increases and decreases in normal stress. In contrast, changes in fault normal displacement and the amplitude of small high-frequency elastic waves transmitted across the surface follow a two stage response consisting of a large immediate and a smaller gradual response with slip. The characteristic slip distance of the small gradual response is significantly smaller than that of shear resistance. The stability of sliding in response to large step decreases in normal stress is well predicted using the shear resistance slip length observed in step increases. Analysis of the shear resistance and slip-time histories suggest nearly immediate changes in strength occur in response to rapid changes in normal stress; these are manifested as an immediate change in slip speed. These changes in slip speed can be qualitatively accounted for using a rate-independent strength model. Collectively, the observations and model show that acceleration or deceleration in response to normal stress change depends on the size of the change, the frictional characteristics of the fault surface, and the elastic properties of the loading system.

Temporal evolution of near-surface chlorophyll over cyclonic eddy lifecycles in the southeastern Pacific

NASA Astrophysics Data System (ADS)

Huang, Jie; Xu, Fanghua; Zhou, Kuanbo; Xiu, Peng; Lin, Yanluan

2017-08-01

Temporal evolution of near-surface chlorophyll (CHL) associated with mesoscale eddies over entire eddy lifespan is complicated. Based on satellite measurements and a reanalysis data set, we identify and quantify major temporal and spatial CHL responses in cyclonic eddies in the southeastern Pacific, and explore the associated mechanisms. Only few temporal CHL variations can be directly linked to the four primary mechanisms: "eddy pumping," "eddy trapping," "eddy stirring," and "eddy-induced Ekman pumping." About 80% of the temporal CHL variations are too complex to be explained by a single mechanism. Five characteristic CHL responses, including classic dipoles (CD), positive-dominant dipoles (PD), negative-dominant dipoles (ND), positive monopoles (PM), and negative monopoles (NM) are identified using the self-organizing map (SOM). CD, a dominant response induced primarily by "eddy stirring," has a continued increasing of frequency of occurrence with time, although its contribution to the total CHL variability remains low. As the secondary prominent response, NM has two peaks of frequency of occurrence at eddy formation and maturation stages, mainly accounted by "eddy trapping" after eddy breakup and "eddy-induced Ekman pumping," respectively. The sum of frequency of occurrence of PD and PM are comparable to that of NM. The initial positive CHL at eddy formation stage is associated with "eddy trapping." The significant positive CHL increase from the eddy intensification to early decay stage is mainly attributed to "eddy pumping." Although the frequency of occurrence of ND is the smallest, its contribution to negative CHL anomalies is unnegligible.

Vibroacoustic study of a point-constrained plate mounted in a duct

NASA Astrophysics Data System (ADS)

Sapkale, Swapnil L.; Sucheendran, Mahesh M.; Gupta, Shakti S.; Kanade, Shantanu V.

2018-04-01

The vibroacoustic study of the interaction of sound with a point-constrained, simply-supported square plate is considered in this paper. The plate is mounted flush on one of the walls of an infinite duct of rectangular cross section and is backed by a cavity. The plate response and the acoustic field is predicted by solving the coupled governing equations using modal expansion with the relevant eigenmodes of the plate dynamics and acoustic fields in the duct and cavity. By varying the location of the point constraint, the frequency characteristics of the transmission loss in the duct can be tuned. The point constraint can also alter the amplitude and spectral characteristics of the plate's response. Interestingly, some new peaks are observed in the response because of the excitation of unsymmetric modes which are otherwise dormant. Mode-localization phenomenon, which is the localization of vibration in specific regions of the plate, is observed for selected constrained points.

Factors Associated With Pediatrician Responses to Alternative Immunization Schedule Requests.

PubMed

Mohanty, Salini; Feemster, Kristen A; Buttenheim, Alison; Moser, Charlotte A; Field, Robert I; Mayer, Whitney; Carroll-Scott, Amy

2018-02-01

We conducted a cross-sectional online survey among 4 chapters of the American Academy of Pediatrics from July through October 2014 to describe characteristics of pediatricians and practices associated with practice-level responses to alternative immunization schedule requests. Among 374 pediatricians, 58% reported frequent alternative immunization schedule requests and 24% reported feeling comfortable using them. Pediatricians who work in practices that accommodate alternative immunization schedule requests have increased odds of having a high frequency of alternative immunization schedule requests, and beliefs that relationships with families would be negatively affected if they refused requests. Practices that discontinue care to families who request alternative immunization schedules have increased odds of being a private group practice and having a formal office vaccine policy. Pediatricians are frequently asked to use alternative immunization schedules and many are not comfortable using them. Practice-level responses to alternative immunization schedules are associated with characteristics of pediatricians and practices.

Health Monitoring System for Composite Structures

NASA Technical Reports Server (NTRS)

Tang, S. S.; Riccardella, P. C.; Andrews, R. J.; Grady, J. E.; Mucciaradi, A. N.

1996-01-01

An automated system was developed to monitor the health status of composites. It uses the vibration characteristics of composites to identify a component's damage condition. The vibration responses are characterized by a set of signal features defined in the time, frequency and spatial domains. The identification of these changes in the vibration characteristics corresponding to different health conditions was performed using pattern recognition principles. This allows efficient data reduction and interpretation of vast amounts of information. Test components were manufactured from isogrid panels to evaluate performance of the monitoring system. The components were damaged by impact to simulate different health conditions. Free vibration response was induced by a tap test on the test components. The monitoring system was trained using these free vibration responses to identify three different health conditions. They are undamaged vs. damaged, damage location and damage zone size. High reliability in identifying the correct component health condition was achieved by the monitoring system.

Post-fire Water Quality Response and Associated Physical Drivers

NASA Astrophysics Data System (ADS)

Rust, A.; Saxe, S.; Hogue, T. S.; McCray, J. E.; Rhoades, C.

2017-12-01

The frequency and severity of forest fires is increasing across the western US. Wildfires are known to impact water quality in receiving waters; many of which are important sources of water supply. Studies on individual forest fires have shown an increase in total suspended solids, nutrient and metal concentrations and loading in receiving streams. The current research looks at a large number of fires across a broad region (Western United States) to identify typical water quality changes after fire and the physical characteristics that drive those responses. This presentation will overview recent development of an extensive database on post-fire water quality. Across 172 fires, we found that water quality changed significantly in one out of three fires up to five years after the event compared to pre-burn conditions. For basins with higher frequency data, it was evident that water quality changes were significant in the first three years following fire. In both the initial years following fire and five years after fire, concentrations and loading rates of dissolved nutrients such as nitrite, nitrate and orthophosphate and particulate forms of nutrients, total organic nitrogen, total nitrogen, total phosphate, and total phosphorus increase thirty percent of the time. Concentrations of some major dissolved ions and metals decrease, with increased post-fire flows, while total particulate concentrations increased; the flux of both dissolved and particulate forms increase in thirty percent of the fires over five years. Water quality change is not uniform across the studied watersheds. A second goal of this study is to identify physical characteristics of a watershed that drive water quality response. Specifically, we investigate the physical, geochemical, and climatological characteristics of watersheds that control the type, direction, and magnitude of water quality change. Initial results reveal vegetation recovery is a key driver in post-fire water quality response. Ultimately, improved understanding of post-fire response and related drivers will advance potential mitigation and treatment strategies as well as aid in the parametrization of post-fire models of water quality.

Data Mining of NASA Boeing 737 Flight Data: Frequency Analysis of In-Flight Recorded Data

NASA Technical Reports Server (NTRS)

Butterfield, Ansel J.

2001-01-01

Data recorded during flights of the NASA Trailblazer Boeing 737 have been analyzed to ascertain the presence of aircraft structural responses from various excitations such as the engine, aerodynamic effects, wind gusts, and control system operations. The NASA Trailblazer Boeing 737 was chosen as a focus of the study because of a large quantity of its flight data records. The goal of this study was to determine if any aircraft structural characteristics could be identified from flight data collected for measuring non-structural phenomena. A number of such data were examined for spatial and frequency correlation as a means of discovering hidden knowledge of the dynamic behavior of the aircraft. Data recorded from on-board dynamic sensors over a range of flight conditions showed consistently appearing frequencies. Those frequencies were attributed to aircraft structural vibrations.

Charge-state dynamics in electrostatic force spectroscopy

NASA Astrophysics Data System (ADS)

Ondráček, Martin; Hapala, Prokop; Jelínek, Pavel

2016-07-01

We present a numerical model that allows us to study the response of an oscillating probe in electrostatic force spectroscopy to charge switching in quantum dots at various time scales. The model provides more insight into the behavior of frequency shift and dissipated energy under different scanning conditions when measuring a temporarily charged quantum dot on a surface. Namely, we analyze the dependence of the frequency shift, the dissipated energy, and their fluctuations on the resonance frequency of the tip and on the electron tunneling rates across the tip-quantum dot and quantum dot-sample junctions. We discuss two complementary approaches to simulating the charge dynamics, a stochastic and a deterministic one. In addition, we derive analytic formulas valid for small amplitudes, describing relations between the frequency shift, dissipated energy, and the characteristic rates driving the charging and discharging processes.

Electromagnetic reflection from multi-layered snow models

NASA Technical Reports Server (NTRS)

Linlor, W. I.; Jiracek, G. R.

1975-01-01

The remote sensing of snow-pack characteristics with surface installations or an airborne system could have important applications in water-resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayered snow models is analyzed in this paper. Normally incident plane waves at frequencies ranging from 1 MHz to 10 GHz are assumed, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice layers. Layers are defined by thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the variations of reflection coefficient as a function of frequency.

Dew Point Calibration System Using a Quartz Crystal Sensor with a Differential Frequency Method.

PubMed

Lin, Ningning; Meng, Xiaofeng; Nie, Jing

2016-11-18

In this paper, the influence of temperature on quartz crystal microbalance (QCM) sensor response during dew point calibration is investigated. The aim is to present a compensation method to eliminate temperature impact on frequency acquisition. A new sensitive structure is proposed with double QCMs. One is kept in contact with the environment, whereas the other is not exposed to the atmosphere. There is a thermal conductivity silicone pad between each crystal and a refrigeration device to keep a uniform temperature condition. A differential frequency method is described in detail and is applied to calibrate the frequency characteristics of QCM at the dew point of -3.75 °C. It is worth noting that frequency changes of two QCMs were approximately opposite when temperature conditions were changed simultaneously. The results from continuous experiments show that the frequencies of two QCMs as the dew point moment was reached have strong consistency and high repeatability, leading to the conclusion that the sensitive structure can calibrate dew points with high reliability.

Effects of Mechanical Loading on the Dynamics of Hair-Cell Stereociliary Bundles

NASA Astrophysics Data System (ADS)

Fredrickson, Lea

Hearing is remarkably sensitive and still not entirely understood. Hair cells of the inner ear are the mechano-electrical transducers of sound and understanding how they function is essential to the understanding of hearing in general. Spontaneous oscillations exhibited by stereociliary bundles of the bullfrog sacculus provide a useful probe for the study of the hair cells' internal dynamic state. In this work we study the effects of mechanical loading on these hair-cell bundles in order to study their dynamics. When applying stiffness loads, we find that the spontaneous oscillation profile changes from multimode to single mode with light loading, and decreases in amplitude and increases in frequency with stiffer loads. We also find that tuning decreases with increasing load such that at loads comparable to in vivo conditions the tuning is flat. We further explore loading via deflections to hair cell bundles, both in the form of steady-state offsets and slow ramps. We find that steady state offsets lead to significant modulation of the characteristic frequency of response, decreasing the frequency in the channels closed direction (negative) and increasing it in the channels open direction (positive). Attachment to the overlying membrane was found, in vitro, to affect bundle offset position in hair cells of the bullfrog sacculus. Application of similar offsets on free-standing, spontaneously oscillating hair bundles shows modulation of their dynamic state, i.e. oscillation profile, characteristic frequency, and response to stimulus. Large offsets are found to arrest spontaneous oscillations, which recover upon reversal of the stimulus. The dynamical state of the hair bundle is dependent on both the history and direction of the offset stimulus. Oscillation suppression occurs much more readily in the negative direction and the bundle behavior approaching quiescence is distinct from that in the positive direction. With the change in spontaneous oscillation frequency and profile comes a change in the phase-locked response amplitude, dependent on bundle offset, winch extends the range of detection frequencies of the hair cell. We explore the broadband phase-locked response of spontaneously oscillating saccular hair cell bundles subject to time-dependent mechanical deflections. The experimental phase-locked amplitude shows an Arnold Tongue, consistent with theoretically predicted dynamical behavior. An offset that steadily increases in time, imposed on the position of the bundle to explore its dynamics at the zero frequency limit, is observed to progressively suppress spontaneous oscillations in a transition that displays strong frequency modulation, with the frequency vanishing at the critical point. When deflected at a faster rate and when allowed to recover to the oscillatory regime, the bundles also displayed a modulation in the amplitude of oscillation. We propose the dynamics of this transition to be dominated by a multi-critical region such that slight variations of a control parameter can produce either an infinite-period, supercritical Hopf, or Bogdanov-Takens bifurcation.

Modeling and design of a high-performance hybrid actuator

NASA Astrophysics Data System (ADS)

Aloufi, Badr; Behdinan, Kamran; Zu, Jean

2016-12-01

This paper presents the model and design of a novel hybrid piezoelectric actuator which provides high active and passive performances for smart structural systems. The actuator is composed of a pair of curved pre-stressed piezoelectric actuators, so-called commercially THUNDER actuators, installed opposite each other using two clamping mechanisms constructed of in-plane fixable hinges, grippers and solid links. A fully mathematical model is developed to describe the active and passive dynamics of the actuator and investigate the effects of its geometrical parameters on the dynamic stiffness, free displacement and blocked force properties. Among the literature that deals with piezoelectric actuators in which THUNDER elements are used as a source of electromechanical power, the proposed study is unique in that it presents a mathematical model that has the ability to predict the actuator characteristics and achieve other phenomena, such as resonances, mode shapes, phase shifts, dips, etc. For model validation, the measurements of the free dynamic response per unit voltage and passive acceleration transmissibility of a particular actuator design are used to check the accuracy of the results predicted by the model. The results reveal that there is a good agreement between the model and experiment. Another experiment is performed to teste the linearity of the actuator system by examining the variation of the output dynamic responses with varying forces and voltages at different frequencies. From the results, it can be concluded that the actuator acts approximately as a linear system at frequencies up to 1000 Hz. A parametric study is achieved here by applying the developed model to analyze the influence of the geometrical parameters of the fixable hinges on the active and passive actuator properties. The model predictions in the frequency range of 0-1000 Hz show that the hinge thickness, radius, and opening angle parameters have great effects on the frequency dynamic responses, passive isolation characteristics and the locations of their peaks and dips. Furthermore, the output actuating force can be improved by increasing the hinge hardness, which is controlled by its dimensions, although increasing the hinge hardness may cause a decrease in the free displacement and passive insulation performance, particularly at low frequencies.

Frequency characteristics of human muscle and cortical responses evoked by noisy Achilles tendon vibration.

PubMed

Mildren, Robyn L; Peters, Ryan M; Hill, Aimee J; Blouin, Jean-Sébastien; Carpenter, Mark G; Inglis, J Timothy

2017-05-01

Noisy stimuli, along with linear systems analysis, have proven to be effective for mapping functional neural connections. We explored the use of noisy (10-115 Hz) Achilles tendon vibration to examine somatosensory reflexes in the triceps surae muscles in standing healthy young adults ( n = 8). We also examined the association between noisy vibration and electrical activity recorded over the sensorimotor cortex using electroencephalography. We applied 2 min of vibration and recorded ongoing muscle activity of the soleus and gastrocnemii using surface electromyography (EMG). Vibration amplitude was varied to characterize reflex scaling and to examine how different stimulus levels affected postural sway. Muscle activity from the soleus and gastrocnemii was significantly correlated with the tendon vibration across a broad frequency range (~10-80 Hz), with a peak located at ~40 Hz. Vibration-EMG coherence positively scaled with stimulus amplitude in all three muscles, with soleus displaying the strongest coupling and steepest scaling. EMG responses lagged the vibration by ~38 ms, a delay that paralleled observed response latencies to tendon taps. Vibration-evoked cortical oscillations were observed at frequencies ~40-70 Hz (peak ~54 Hz) in most subjects, a finding in line with previous reports of sensory-evoked γ-band oscillations. Further examination of the method revealed 1 ) accurate reflex estimates could be obtained with <60 s of low-level (root mean square = 10 m/s 2 ) vibration; 2 ) responses did not habituate over 2 min of exposure; and importantly, 3 ) noisy vibration had a minimal influence on standing balance. Our findings suggest noisy tendon vibration is an effective novel approach to characterize somatosensory reflexes during standing. NEW & NOTEWORTHY We applied noisy (10-115 Hz) vibration to the Achilles tendon to examine the frequency characteristics of lower limb somatosensory reflexes during standing. Ongoing muscle activity was coherent with the noisy vibration (peak coherence ~40 Hz), and coherence positively scaled with increases in stimulus amplitude. Our findings suggest that noisy tendon vibration, along with linear systems analysis, is an effective novel approach to study somatosensory reflex actions in active muscles. Copyright © 2017 the American Physiological Society.

Ultrasonic fatigue of SiC particle reinforced aluminum in the VHCF-regime

NASA Astrophysics Data System (ADS)

Wolf, M.; Wagner, G.; Eifler, D.

At the WKK ultrasonic testing facilities (UTF) are used to perform fatigue experiments in the VHCF regime with a frequency of 20 kHz. These systems allow an on-line characterization of the actual fatigue state by changes of different process parameters such as generator power, displacement, temperature or frequency-response characteristic. Moreover the experiments can be interrupted at user defined events in order to investigate variations of the surface microstructure or changes in the electrical resistance of the specimens. The fatigue tests were realized as load increase tests as well as constant amplitude tests.

Two dimensional eye tracking: Sampling rate of forcing function

NASA Technical Reports Server (NTRS)

Hornseth, J. P.; Monk, D. L.; Porterfield, J. L.; Mcmurry, R. L.

1978-01-01

A study was conducted to determine the minimum update rate of a forcing function display required for the operator to approximate the tracking performance obtained on a continuous display. In this study, frequency analysis was used to determine whether there was an associated change in the transfer function characteristics of the operator. It was expected that as the forcing function display update rate was reduced, from 120 to 15 samples per second, the operator's response to the high frequency components of the forcing function would show a decrease in gain, an increase in phase lag, and a decrease in coherence.

Spatial Variations of Poloidal and Toroidal Mode Field Line Resonances Observed by MMS

NASA Astrophysics Data System (ADS)

Le, G.; Chi, P. J.; Strangeway, R. J.; Russell, C. T.; Slavin, J. A.; Anderson, B. J.; Kepko, L.; Nakamura, R.; Plaschke, F.; Torbert, R. B.

2017-12-01

Field line resonances (FLRs) are magnetosphere's responses to solar wind forcing and internal instabilities generated by solar wind-magnetospheric interactions. They are standing waves along the Earth's magnetic field lines oscillating in either poloidal or toroidal modes. The two types of waves have their unique frequency characteristics. The eigenfrequency of FLRs is determined by the length of the field line and the plasma density, and thus gradually changes with L. For toroidal mode oscillations with magnetic field perturbations in the azimuthal direction, ideal MHD predicts that each field line oscillates independently with its own eigenfrequency. For poloidal mode waves with field lines oscillating radially, their frequency cannot change with L easily as L shells need to oscillate in sync to avoid efficient damping due to phase mixing. Observations, mainly during quiet times, indeed show that poloidal mode waves often exhibit nearly constant frequency across L shells. Our recent observations, on the other hand, reveal a clear L-dependent frequency trend for a long lasting storm-time poloidal wave event, indicating the wave can maintain its power with changing frequencies for an extended period [Le et al., 2017]. The spatial variation of the frequency shows discrete spatial structures. The frequency remains constant within each discrete structure that spans about 1 REalong L, and changes discretely. We present a follow-up study to investigate spatial variations of wave frequencies using the Wigner-Ville distribution. We examine both poloidal and toroidal waves under different geomagnetic conditions using multipoint observations from MMS, and compare their frequency and occurrence characteristics for insights into their generation mechanisms. Reference: Le, G., et al. (2017), Global observations of magnetospheric high-m poloidal waves during the 22 June 2015 magnetic storm, Geophys. Res. Lett., 44, 3456-3464, doi:10.1002/2017GL073048.

Simultaneous acquisition of EEG and NIRS during cognitive tasks for an open access dataset.

PubMed

Shin, Jaeyoung; von Lühmann, Alexander; Kim, Do-Won; Mehnert, Jan; Hwang, Han-Jeong; Müller, Klaus-Robert

2018-02-13

We provide an open access multimodal brain-imaging dataset of simultaneous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) recordings. Twenty-six healthy participants performed three cognitive tasks: 1) n-back (0-, 2- and 3-back), 2) discrimination/selection response task (DSR) and 3) word generation (WG) tasks. The data provided includes: 1) measured data, 2) demographic data, and 3) basic analysis results. For n-back (dataset A) and DSR tasks (dataset B), event-related potential (ERP) analysis was performed, and spatiotemporal characteristics and classification results for 'target' versus 'non-target' (dataset A) and symbol 'O' versus symbol 'X' (dataset B) are provided. Time-frequency analysis was performed to show the EEG spectral power to differentiate the task-relevant activations. Spatiotemporal characteristics of hemodynamic responses are also shown. For the WG task (dataset C), the EEG spectral power and spatiotemporal characteristics of hemodynamic responses are analyzed, and the potential merit of hybrid EEG-NIRS BCIs was validated with respect to classification accuracy. We expect that the dataset provided will facilitate performance evaluation and comparison of many neuroimaging analysis techniques.

Simultaneous acquisition of EEG and NIRS during cognitive tasks for an open access dataset

PubMed Central

Shin, Jaeyoung; von Lühmann, Alexander; Kim, Do-Won; Mehnert, Jan; Hwang, Han-Jeong; Müller, Klaus-Robert

2018-01-01

We provide an open access multimodal brain-imaging dataset of simultaneous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) recordings. Twenty-six healthy participants performed three cognitive tasks: 1) n-back (0-, 2- and 3-back), 2) discrimination/selection response task (DSR) and 3) word generation (WG) tasks. The data provided includes: 1) measured data, 2) demographic data, and 3) basic analysis results. For n-back (dataset A) and DSR tasks (dataset B), event-related potential (ERP) analysis was performed, and spatiotemporal characteristics and classification results for ‘target’ versus ‘non-target’ (dataset A) and symbol ‘O’ versus symbol ‘X’ (dataset B) are provided. Time-frequency analysis was performed to show the EEG spectral power to differentiate the task-relevant activations. Spatiotemporal characteristics of hemodynamic responses are also shown. For the WG task (dataset C), the EEG spectral power and spatiotemporal characteristics of hemodynamic responses are analyzed, and the potential merit of hybrid EEG-NIRS BCIs was validated with respect to classification accuracy. We expect that the dataset provided will facilitate performance evaluation and comparison of many neuroimaging analysis techniques. PMID:29437166

Acoustoelectric Effect on the Responses of SAW Sensors Coated with Electrospun ZnO Nanostructured Thin Film

PubMed Central

Tasaltin, Cihat; Ebeoglu, Mehmet Ali; Ozturk, Zafer Ziya

2012-01-01

In this study, zinc oxide (ZnO) was a very good candidate for improving the sensitivity of gas sensor technology. The preparation of an electrospun ZnO nanostructured thin film on a 433 MHz Rayleigh wave based Surface Acoustic Wave (SAW) sensor and the investigation of the acoustoelectric effect on the responses of the SAW sensor are reported. We prepared an electrospun ZnO nanostructured thin film on the SAW devices by using an electrospray technique. To investigate the dependency of the sensor response on the structure and the number of the ZnO nanoparticles, SAW sensors were prepared with different coating loads. The coating frequency shifts were adjusted to fall between 100 kHz and 2.4 MHz. The sensor measurements were performed against VOCs such as acetone, trichloroethylene, chloroform, ethanol, n-propanol and methanol vapor. The sensor responses of n-propanol have opposite characteristics to the other VOCs, and we attributed these characteristics to the elastic effect/acoustoelectric effect.

Characteristics of Paraspinal Muscle Spindle Response to Mechanically Assisted Spinal Manipulation: A Preliminary Report.

PubMed

Reed, William R; Pickar, Joel G; Sozio, Randall S; Liebschner, Michael A K; Little, Joshua W; Gudavalli, Maruti R

The purpose of this preliminary study is to determine muscle spindle response characteristics related to the use of 2 solenoid powered clinical mechanically assisted manipulation (MAM) devices. L6 muscle spindle afferents with receptive fields in paraspinal muscles were isolated in 6 cats. Neural recordings were made during L7 MAM thrusts using the Activator V (Activator Methods Int. Ltd., Phoenix, AZ) and/or Pulstar (Sense Technology Inc., Pittsburgh, PA) devices at their 3 lowest force settings. Mechanically assisted manipulation response measures included (a) the time required post-thrust until the first action potential, (b) differences in mean frequency (MF) and mean instantaneous frequency (MIF) 2 seconds before and after MAM, and (c) the time required for muscle spindle discharge (MF and MIF) to return to 95% of baseline after MAM. Depending on device setting, between 44% to 80% (Pulstar) and 11% to 63% (Activator V) of spindle afferents required >6 seconds to return to within 95% of baseline MF values; whereas 66% to 89% (Pulstar) and 75% to 100% (Activator V) of spindle responses returned to within 95% of baseline MIF in <6 seconds after MAM. Nonparametric comparisons between the 22 N and 44 N settings of the Pulstar yielded significant differences for the time required to return to baseline MF and MIF. Short duration (<10 ms) MAM thrusts decrease muscle spindle discharge with a majority of afferents requiring prolonged periods (>6 seconds) to return to baseline MF activity. Physiological consequences and clinical relevance of described MAM mechanoreceptor responses will require additional investigation. Copyright © 2017. Published by Elsevier Inc.

Field Measurement-Based System Identification and Dynamic Response Prediction of a Unique MIT Building.

PubMed

Cha, Young-Jin; Trocha, Peter; Büyüköztürk, Oral

2016-07-01

Tall buildings are ubiquitous in major cities and house the homes and workplaces of many individuals. However, relatively few studies have been carried out to study the dynamic characteristics of tall buildings based on field measurements. In this paper, the dynamic behavior of the Green Building, a unique 21-story tall structure located on the campus of the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA), was characterized and modeled as a simplified lumped-mass beam model (SLMM), using data from a network of accelerometers. The accelerometer network was used to record structural responses due to ambient vibrations, blast loading, and the October 16th 2012 earthquake near Hollis Center (ME, USA). Spectral and signal coherence analysis of the collected data was used to identify natural frequencies, modes, foundation rocking behavior, and structural asymmetries. A relation between foundation rocking and structural natural frequencies was also found. Natural frequencies and structural acceleration from the field measurements were compared with those predicted by the SLMM which was updated by inverse solving based on advanced multiobjective optimization methods using the measured structural responses and found to have good agreement.

Field Measurement-Based System Identification and Dynamic Response Prediction of a Unique MIT Building

PubMed Central

Cha, Young-Jin; Trocha, Peter; Büyüköztürk, Oral

2016-01-01

Tall buildings are ubiquitous in major cities and house the homes and workplaces of many individuals. However, relatively few studies have been carried out to study the dynamic characteristics of tall buildings based on field measurements. In this paper, the dynamic behavior of the Green Building, a unique 21-story tall structure located on the campus of the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA), was characterized and modeled as a simplified lumped-mass beam model (SLMM), using data from a network of accelerometers. The accelerometer network was used to record structural responses due to ambient vibrations, blast loading, and the October 16th 2012 earthquake near Hollis Center (ME, USA). Spectral and signal coherence analysis of the collected data was used to identify natural frequencies, modes, foundation rocking behavior, and structural asymmetries. A relation between foundation rocking and structural natural frequencies was also found. Natural frequencies and structural acceleration from the field measurements were compared with those predicted by the SLMM which was updated by inverse solving based on advanced multiobjective optimization methods using the measured structural responses and found to have good agreement. PMID:27376303

Resonant frequencies in an elevated spherical container partially filled with water: FEM and measurement

NASA Astrophysics Data System (ADS)

Curadelli, O.; Ambrosini, D.; Mirasso, A.; Amani, M.

2010-01-01

In this paper, a numerical-experimental study of the overall dynamical response of elevated spherical tanks subjected to horizontal base motion is presented. The main objective is to gain insight in the physical response of this particular structural typology widely used in the petrochemical industry as liquefied petroleum gas (LPG) containers. In order to identify the natural frequencies of the modes that mainly contribute to the response, experimental free vibration tests on an elevated spherical tank model for different liquid levels were carried out. Next, a numerical model that takes into account the coupling between fluid and structure was developed and validated against the experimental results. A very good agreement between experimental and numerical results was obtained. The results obtained show the influence of liquid levels on natural frequencies and indicate that the sloshing has a significant effect on the dynamical characteristics of the analyzed system. In order to obtain a good representation of the overall dynamical behaviour of the system by means of a simplified lumped mass model, a minimum of three masses is suggested. Finally, appropriate names of these three masses are proposed in the present paper.

Reflex effects on components of synchronized renal sympathetic nerve activity.

PubMed

DiBona, G F; Jones, S Y

1998-09-01

The effects of peripheral thermal receptor stimulation (tail in hot water, n = 8, anesthetized) and cardiac baroreceptor stimulation (volume loading, n = 8, conscious) on components of synchronized renal sympathetic nerve activity (RSNA) were examined in rats. The peak height and peak frequency of synchronized RSNA were determined. The renal sympathoexcitatory response to peripheral thermal receptor stimulation was associated with an increase in the peak height. The renal sympathoinhibitory response to cardiac baroreceptor stimulation was associated with a decrease in the peak height. Although heart rate was significantly increased with peripheral thermal receptor stimulation and significantly decreased with cardiac baroreceptor stimulation, peak frequency was unchanged. As peak height reflects the number of active fibers, reflex increases and decreases in synchronized RSNA are mediated by parallel increases and decreases in the number of active renal nerve fibers rather than changes in the centrally based rhythm or peak frequency. The increase in the number of active renal nerve fibers produced by peripheral thermal receptor stimulation reflects the engagement of a unique group of silent renal sympathetic nerve fibers with a characteristic response pattern to stimulation of arterial baroreceptors, peripheral and central chemoreceptors, and peripheral thermal receptors.

Enhanced two dimensional electron gas transport characteristics in Al2O3/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

NASA Astrophysics Data System (ADS)

Freedsman, J. J.; Watanabe, A.; Urayama, Y.; Egawa, T.

2015-09-01

The authors report on Al2O3/Al0.85In0.15N/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistor (MOS-HEMT) on Si fabricated by using atomic layer deposited Al2O3 as gate insulator and passivation layer. The MOS-HEMT with the gate length of 2 μm exhibits excellent direct-current (dc) characteristics with a drain current maximum of 1270 mA/mm at a gate bias of 3 V and an off-state breakdown voltage of 180 V for a gate-drain spacing of 4 μm. Also, the 1 μm-gate MOS-HEMT shows good radio-frequency (rf) response such as current gain and maximum oscillation cut-off frequencies of 10 and 34 GHz, respectively. The capacitance-voltage characteristics at 1 MHz revealed significant increase in two-dimensional electron gas (2DEG) density for the MOS-HEMT compared to conventional Schottky barrier HEMTs. Analyses using drain-source conductivity measurements showed improvements in 2DEG transport characteristics for the MOS-HEMT. The enhancements in dc and rf performances of the Al2O3/Al0.85In0.15N/GaN MOS-HEMT are attributed to the improvements in 2DEG characteristics.

Salicylate-induced cochlear impairments, cortical hyperactivity and re-tuning, and tinnitus.

PubMed

Chen, Guang-Di; Stolzberg, Daniel; Lobarinas, Edward; Sun, Wei; Ding, Dalian; Salvi, Richard

2013-01-01

High doses of sodium salicylate (SS) have long been known to induce temporary hearing loss and tinnitus, effects attributed to cochlear dysfunction. However, our recent publications reviewed here show that SS can induce profound, permanent, and unexpected changes in the cochlea and central nervous system. Prolonged treatment with SS permanently decreased the cochlear compound action potential (CAP) amplitude in vivo. In vitro, high dose SS resulted in a permanent loss of spiral ganglion neurons and nerve fibers, but did not damage hair cells. Acute treatment with high-dose SS produced a frequency-dependent decrease in the amplitude of distortion product otoacoustic emissions and CAP. Losses were greatest at low and high frequencies, but least at the mid-frequencies (10-20 kHz), the mid-frequency band that corresponds to the tinnitus pitch measured behaviorally. In the auditory cortex, medial geniculate body and amygdala, high-dose SS enhanced sound-evoked neural responses at high stimulus levels, but it suppressed activity at low intensities and elevated response threshold. When SS was applied directly to the auditory cortex or amygdala, it only enhanced sound evoked activity, but did not elevate response threshold. Current source density analysis revealed enhanced current flow into the supragranular layer of auditory cortex following systemic SS treatment. Systemic SS treatment also altered tuning in auditory cortex and amygdala; low frequency and high frequency multiunit clusters up-shifted or down-shifted their characteristic frequency into the 10-20 kHz range thereby altering auditory cortex tonotopy and enhancing neural activity at mid-frequencies corresponding to the tinnitus pitch. These results suggest that SS-induced hyperactivity in auditory cortex originates in the central nervous system, that the amygdala potentiates these effects and that the SS-induced tonotopic shifts in auditory cortex, the putative neural correlate of tinnitus, arises from the interaction between the frequency-dependent losses in the cochlea and hyperactivity in the central nervous system. Copyright © 2012 Elsevier B.V. All rights reserved.

Dynamic adjustment of echolocation pulse structure of big-footed myotis (Myotis macrodactylus) in response to different habitats.

PubMed

Wang, Lei; Luo, Jinhong; Wang, Hongna; Ou, Wei; Jiang, Tinglei; Liu, Ying; Lyle, Dennis; Feng, Jiang

2014-02-01

Studying relationships between characteristics of sonar pulses and habitat clutter level is important for the understanding of signal design in bat echolocation. However, most studies have focused on overall spectral and temporal parameters of such vocalizations, with focus less on potential variation in frequency modulation rates (MRs) occurring within each pulse. In the current study, frequency modulation (FM) characteristics were examined in echolocation pulses recorded from big-footed myotis (Myotis macrodactylus) bats as these animals searched for prey in five habitats differing in relative clutter level. Pulses were analyzed using ten parameters, including four structure-related characters which were derived by dividing each pulse into three elements based on two knees in the FM sweep. Results showed that overall frequency, pulse duration, and MR all varied across habitat. The strongest effects were found for MR in the body of the pulse, implying that this particular component plays a major role as M. macrodactylus, and potentially other bat species, adjust to varying clutter levels in their foraging habitats.

Development of in-series piezoelectric bimorph bending beam actuators for active flow control applications

NASA Astrophysics Data System (ADS)

Chan, Wilfred K.; Clingman, Dan J.; Amitay, Michael

2016-04-01

Piezoelectric materials have long been used for active flow control purposes in aerospace applications to increase the effectiveness of aerodynamic surfaces on aircraft, wind turbines, and more. Piezoelectric actuators are an appropriate choice due to their low mass, small dimensions, simplistic design, and frequency response. This investigation involves the development of piezoceramic-based actuators with two bimorphs placed in series. Here, the main desired characteristic was the achievable displacement amplitude at specific driving voltages and frequencies. A parametric study was performed, in which actuators with varying dimensions were fabricated and tested. These devices were actuated with a sinusoidal waveform, resulting in an oscillating platform on which to mount active flow control devices, such as dynamic vortex generators. The main quantification method consisted of driving these devices with different voltages and frequencies to determine their free displacement, blocking force, and frequency response. It was found that resonance frequency increased with shorter and thicker actuators, while free displacement increased with longer and thinner actuators. Integration of the devices into active flow control test modules is noted. In addition to physical testing, a quasi-static analytical model was developed and compared with experimental data, which showed close correlation for both free displacement and blocking force.

Effects of high fire frequency in creosote bush scrub vegetation of the Mojave Desert

USGS Publications Warehouse

Brooks, M.L.

2012-01-01

Plant invasions can increase fire frequency in desert ecosystems where fires were historically infrequent. Although there are many resource management concerns associated with high frequency fire in deserts, fundamental effects on plant community characteristics remain largely unstudied. Here I describe the effects of fire frequency on creosote bush scrub vegetation in the Mojave Desert, USA. Biomass of the invasive annual grass Bromus rubens L. increased following fire, but did not increase further with additional fires. In contrast, density, cover and species richness of native perennial plants each decreased following fire and continued to decrease with subsequent fires, although not as dramatically as after the initial fire. Responses were similar 5 and 14 years post-fire, except that cover of Hymenoclea salsola Torr. & A. Gray and Achnatherum speciosa Trin. & Rupr. both increased in areas burnt once. These results suggest that control of B. rubens may be equally warranted after one, two or three fires, but revegetation of native perennial plants is most warranted following multiple fires. These results are valid within the scope of this study, which is defined as relatively short term vegetation responses (???14 years) to short fire return intervals (6.3 and 7.3 years for the two and three fire frequency levels) within creosote bush scrub of the Mojave Desert. ?? 2012 IAWF.

Inertial mass sensing with low Q-factor vibrating microcantilevers

NASA Astrophysics Data System (ADS)

Adhikari, S.

2017-10-01

Mass sensing using micromechanical cantilever oscillators has been established as a promising approach. The scientific principle underpinning this technique is the shift in the resonance frequency caused by the additional mass in the dynamic system. This approach relies on the fact that the Q-factor of the underlying oscillator is high enough so that it does not significantly affect the resonance frequencies. We consider the case when the Q-factor is low to the extent that the effect of damping is prominent. It is shown that the mass sensing can be achieved using a shift in the damping factor. We prove that the shift in the damping factor is of the same order as that of the resonance frequency. Based on this crucial observation, three new approaches have been proposed, namely, (a) mass sensing using frequency shifts in the complex plane, (b) mass sensing from damped free vibration response in the time domain, and (c) mass sensing from the steady-state response in the frequency domain. Explicit closed-form expressions relating absorbed mass with changes in the measured dynamic properties have been derived. The rationale behind each new method has been explained using non-dimensional graphical illustrations. The new mass sensing approaches using damped dynamic characteristics can expand the current horizon of micromechanical sensing by incorporating a wide range of additional measurements.

Flight-testing and frequency-domain analysis for rotorcraft handling qualities

NASA Technical Reports Server (NTRS)

Ham, Johnnie A.; Gardner, Charles K.; Tischler, Mark B.

1995-01-01

A demonstration of frequency-domain flight-testing techniques and analysis was performed on a U.S. Army OH-58D helicopter in support of the OH-58D Airworthiness and Flight Characteristics Evaluation and of the Army's development and ongoing review of Aeronautical Design Standard 33C, Handling Qualities Requirements for Military Rotorcraft. Hover and forward flight (60 kn) tests were conducted in 1 flight hour by Army experimental test pilots. Further processing of the hover data generated a complete database of velocity, angular-rate, and acceleration-frequency responses to control inputs. A joint effort was then undertaken by the Airworthiness Qualification Test Dirtectorate and the U.S. Army Aeroflightdynamics Directorate to derive handling-quality information from the frequency-domain database using a variety of approaches. This report documents numerous results that have been obtained from the simple frequency-domain tests; in many areas, these results provide more insight into the aircraft dynmamics that affect handling qualities than do traditional flight tests. The handling-quality results include ADS-33C bandwidth and phase-delay calculations, vibration spectral determinations, transfer-function models to examine single-axis results, and a six-degree-of-freedom fully coupled state-space model. The ability of this model to accurately predict responses was verified using data from pulse inputs. This report also documents the frequency-sweep flight-test technique and data analysis used to support the tests.

High frequency oscillations evoked by peripheral magnetic stimulation.

PubMed

Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

2011-01-01

The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

Ares I-X Flight Test Validation of Control Design Tools in the Frequency-Domain

NASA Technical Reports Server (NTRS)

Johnson, Matthew; Hannan, Mike; Brandon, Jay; Derry, Stephen

2011-01-01

A major motivation of the Ares I-X flight test program was to Design for Data, in order to maximize the usefulness of the data recorded in support of Ares I modeling and validation of design and analysis tools. The Design for Data effort was intended to enable good post-flight characterizations of the flight control system, the vehicle structural dynamics, and also the aerodynamic characteristics of the vehicle. To extract the necessary data from the system during flight, a set of small predetermined Programmed Test Inputs (PTIs) was injected directly into the TVC signal. These PTIs were designed to excite the necessary vehicle dynamics while exhibiting a minimal impact on loads. The method is similar to common approaches in aircraft flight test programs, but with unique launch vehicle challenges due to rapidly changing states, short duration of flight, a tight flight envelope, and an inability to repeat any test. This paper documents the validation effort of the stability analysis tools to the flight data which was performed by comparing the post-flight calculated frequency response of the vehicle to the frequency response calculated by the stability analysis tools used to design and analyze the preflight models during the control design effort. The comparison between flight day frequency response and stability tool analysis for flight of the simulated vehicle shows good agreement and provides a high level of confidence in the stability analysis tools for use in any future program. This is true for both a nominal model as well as for dispersed analysis, which shows that the flight day frequency response is enveloped by the vehicle s preflight uncertainty models.

Based on optical fiber Michelson interferometer for acoustic emission detection experimental research

NASA Astrophysics Data System (ADS)

Liang, Yijun; Qu, Dandan; Deng, Hu

2013-08-01

A type of Michelson interferometer with two optical fiber loop reflectors acoustic emission sensor is proposed in the article to detect the vibrations produced by ultrasonic waves propagating in a solid body. Two optical fiber loop reflectors are equivalent to the sensing arm and the reference arm instead of traditional Michelson interferometer end reflecter Theoretical analyses indicate that the sensitivity of the system has been remarkably increased because of the decrease of the losses of light energy. The best operating point of optical fiber sensor is fixed by theoretical derivation and simulation of computer, and the signal frequency which is detected by the sensor is the frequency of input signal. PZT (Piezoelectric Ceramic) is powered by signal generator as known ultrasonic source, The Polarization controller is used to make the reflected light interference，The fiber length is changed by adjusting the DC voltage on the PZT with the fiber loop to make the sensor system response that ΔΦ is closed to π/2. the signal basis frequency detected by the sensor is the frequency of the input signal. Then impacts the surface of the marble slab with home-made mechanical acoustic emission source. And detect it. and then the frequency characteristic of acoustic emission signal is obtained by Fourier technique. The experimental results indicate that the system can identify the frequency characteristic of acoustic emission signal, and it can be also used to detect the surface feeble vibration which is generated by ultrasonic waves propagating in material structure.

Dynamic characteristics of a hydrostatic gas bearing driven by oscillating exhaust pressure

NASA Technical Reports Server (NTRS)

Watkins, C. B.; Eronini, I. E.; Branch, H. D.

1984-01-01

Vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating exhaust pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and sleeve is solved together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The numerical solutions of the perturbation equations are obtained by discretizing the pressure field using finite-difference aproximations with a discrete, nonuniform line-source model which excludes effects due to feeding hole volume. An iterative scheme is used to simultaneously satisfy the equations of motion for the journal. The results presented include Bode plots of bearing-oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency.

What aspects of future rainfall changes matter for crop yields in West Africa?

NASA Astrophysics Data System (ADS)

Guan, Kaiyu; Sultan, Benjamin; Biasutti, Michela; Baron, Christian; Lobell, David B.

2015-10-01

How rainfall arrives, in terms of its frequency, intensity, the timing and duration of rainy season, may have a large influence on rainfed agriculture. However, a thorough assessment of these effects is largely missing. This study combines a new synthetic rainfall model and two independently validated crop models (APSIM and SARRA-H) to assess sorghum yield response to possible shifts in seasonal rainfall characteristics in West Africa. We find that shifts in total rainfall amount primarily drive the rainfall-related crop yield change, with less relevance to intraseasonal rainfall features. However, dry regions (total annual rainfall below 500 mm/yr) have a high sensitivity to rainfall frequency and intensity, and more intense rainfall events have greater benefits for crop yield than more frequent rainfall. Delayed monsoon onset may negatively impact yields. Our study implies that future changes in seasonal rainfall characteristics should be considered in designing specific crop adaptations in West Africa.

Effect of Longitudinal Magnetic Field on Vibration Characteristics of Single-Walled Carbon Nanotubes in a Viscoelastic Medium

NASA Astrophysics Data System (ADS)

Zhang, D. P.; Lei, Y.; Shen, Z. B.

2017-12-01

The effect of longitudinal magnetic field on vibration response of a sing-walled carbon nanotube (SWCNT) embedded in viscoelastic medium is investigated. Based on nonlocal Euler-Bernoulli beam theory, Maxwell's relations, and Kelvin viscoelastic foundation model, the governing equations of motion for vibration analysis are established. The complex natural frequencies and corresponding mode shapes in closed form for the embedded SWCNT with arbitrary boundary conditions are obtained using transfer function method (TFM). The new analytical expressions for the complex natural frequencies are also derived for certain typical boundary conditions and Kelvin-Voigt model. Numerical results from the model are presented to show the effects of nonlocal parameter, viscoelastic parameter, boundary conditions, aspect ratio, and strength of the magnetic field on vibration characteristics for the embedded SWCNT in longitudinal magnetic field. The results demonstrate the efficiency of the proposed methods for vibration analysis of embedded SWCNTs under magnetic field.

Test and Analysis of an Inflatable Parabolic Dish Antenna

NASA Technical Reports Server (NTRS)

Gaspar, james L.; Sreekantamurthy, Tham; Mann, Troy; Behun, Vaughn; Romanofsky, Robert; Lambert, Kevin; Pearson, James

2006-01-01

NASA is developing ultra-lightweight structures technology for large communication antennas for application to space missions. With these goals in mind, SRS Technologies has been funded by NASA Glenn Research Center (GRC) to undertake the development of a subscale ultra-thin membrane inflatable antenna for deep-space applications. One of the research goals is to develop approaches for prediction of the radio frequency and structural characteristics of inflatable and rigidizable membrane antenna structures. GRC has teamed with NASA Langley Research Center (LaRC) to evaluate inflatable and rigidizable antenna concepts for potential space missions. GRC has completed tests to evaluate RF performance, while LaRC completed structural tests and analysis to evaluate the static shape and structural dynamic responses of a laboratory model of a 0.3 meter antenna. This paper presents the details of the tests and analysis completed to evaluate the radio frequency and structural characteristics of the antenna.

Distributed parameter modelling of flexible spacecraft: Where's the beef?

NASA Technical Reports Server (NTRS)

Hyland, D. C.

1994-01-01

This presentation discusses various misgivings concerning the directions and productivity of Distributed Parameter System (DPS) theory as applied to spacecraft vibration control. We try to show the need for greater cross-fertilization between DPS theorists and spacecraft control designers. We recommend a shift in research directions toward exploration of asymptotic frequency response characteristics of critical importance to control designers.

Chamber-core structures for fairing acoustic mitigation

NASA Astrophysics Data System (ADS)

Ardelean, Emil; Williams, Andrew; Korshin, Nicholas; Henderson, Kyle; Lane, Steven; Richard, Robert

2005-05-01

Extreme noise and vibration levels at lift-off and during ascent can damage sensitive payload components. Recently, the Air Force Research Laboratory, Space Vehicles Directorate has investigated a composite structure fabrication approach, called chamber-core, for building payload fairings. Chamber-core offers a strong, lightweight structure with inherent noise attenuation characteristics. It uses one-inch square axial tubes that are sandwiched between inner and outer face-sheets to form a cylindrical fairing structure. These hollow tubes can be used as acoustic dampers to attenuate the amplitude response of low frequency acoustic resonances within the fairing"s volume. A cylindrical, graphite-epoxy chamber-core structure was built to study noise transmission characteristics and to quantify the achievable performance improvement. The cylinder was tested in a semi-reverberant acoustics laboratory using bandlimited random noise at sound pressure levels up to 110 dB. The performance was measured using external and internal microphones. The noise reduction was computed as the ratio of the spatially averaged external response to the spatially averaged interior response. The noise reduction provided by the chamber-core cylinder was measured over three bandwidths, 20 Hz to 500 Hz, 20 Hz to 2000 Hz, and 20 Hz to 5000 Hz. For the bare cylinder with no acoustic resonators, the structure provided approximately 13 dB of attenuation over the 20 Hz to 500 Hz bandwidth. With the axial tubes acting as acoustic resonators at various frequencies over the bandwidth, the noise reduction provided by the cylinder increased to 18.2 dB, an overall increase of 4.8 dB over the bandwidth. Narrow-band reductions greater than 10 dB were observed at specific low frequency acoustic resonances. This was accomplished with virtually no added mass to the composite cylinder.

Preformed Frequencies of Cytomegalovirus (CMV)–Specific Memory T and B Cells Identify Protected CMV-Sensitized Individuals Among Seronegative Kidney Transplant Recipients

PubMed Central

Lúcia, Marc; Crespo, Elena; Melilli, Edoardo; Cruzado, Josep M.; Luque, Sergi; Llaudó, Inés; Niubó, Jordi; Torras, Joan; Fernandez, Núria; Grinyó, Josep M.; Bestard, Oriol

2014-01-01

Background. Cytomegalovirus (CMV) infection remains a major complication after kidney transplantation. Baseline CMV risk is typically determined by the serological presence of preformed CMV-specific immunoglobulin (Ig) G antibodies, even though T-cell responses to major viral antigens are crucial when controlling viral replication. Some IgG-seronegative patients who receive an IgG-seropositive allograft do not develop CMV infection despite not receiving prophylaxis. We hypothesized that a more precise evaluation of pretransplant CMV-specific immune-sensitization using the B and T-cell enzyme-linked immunospot assays may identify CMV-sensitized individuals more accurately, regardless of serological evidence of CMV-specific IgG titers. Methods. We compared the presence of preformed CMV-specific memory B and T cells in kidney transplant recipients between 43 CMV IgG–seronegative (sR−) and 86 CMV IgG–seropositive (sR+) patients. Clinical outcome was evaluated in both groups. Results. All sR+ patients showed a wide range of CMV-specific memory T- and B-cell responses. High memory T- and B-cell frequencies were also clearly detected in 30% of sR− patients, and those with high CMV-specific T-cell frequencies had a significantly lower incidence of late CMV infection after prophylactic therapy. Receiver operating characteristic curve analysis for predicting CMV viremia and disease showed a high area under the receiver operating characteristic curve (>0.8), which translated into a high sensitivity and negative predictive value of the test. Conclusions. Assessment of CMV-specific memory T- and B-cell responses before kidney transplantation among sR− recipients may help identify immunized individuals more precisely, being ultimately at lower risk for CMV infection. PMID:25048845

Psychosocial and Health-Related Characteristics of Adolescent Television Viewers.

ERIC Educational Resources Information Center

Page, Randy M.; And Others

1996-01-01

Examined relationship between television viewing frequency and adolescents' health-related and psychosocial characteristics. Found that shyness and exercise frequency predicted television viewing frequency. Among females, exercise frequency, shyness, loneliness, and perceived attractiveness predicted viewing frequency. Light viewers exercised more…

Identifying indicators of harmful and problem gambling in a Canadian sample through receiver operating characteristic analysis.

PubMed

Quilty, Lena C; Avila Murati, Daniela; Bagby, R Michael

2014-03-01

Many gamblers would prefer to reduce gambling on their own rather than to adopt an abstinence approach within the context of a gambling treatment program. Yet responsible gambling guidelines lack quantifiable markers to guide gamblers in wagering safely. To address these issues, the current investigation implemented receiver operating characteristic (ROC) analysis to identify behavioral indicators of harmful and problem gambling. Gambling involvement was assessed in 503 participants (275 psychiatric outpatients and 228 community gamblers) with the Canadian Problem Gambling Index. Overall gambling frequency, duration, and expenditure were able to distinguish harmful and problematic gambling at a moderate level. Indicators of harmful gambling were generated for engagement in specific gambling activities: frequency of tickets and casino; duration of bingo, casino, and investments; and expenditures on bingo, casino, sports betting, games of skill, and investments. Indicators of problem gambling were similarly produced for frequency of tickets and casino, and expenditures on bingo, casino, games of skill, and investments. Logistic regression analyses revealed that overall gambling frequency uniquely predicted the presence of harmful and problem gambling. Furthermore, frequency indicators for tickets and casino uniquely predicted the presence of both harmful and problem gambling. Together, these findings contribute to the development of an empirically based method enabling the minimization of harmful or problem gambling through self-control rather than abstinence.

Conceptualizing and Measuring Weekend versus Weekday Alcohol Use: Item Response Theory and Confirmatory Factor Analysis

PubMed Central

Handren, Lindsay; Crano, William D.

2018-01-01

Culturally, people tend to abstain from alcohol intake during the weekdays and wait to consume in greater frequency and quantity during the weekends. The current research sought to empirically justify the days representing weekday versus weekend alcohol consumption. In study 1 (N = 419), item response theory was applied to a two-parameter (difficulty and discrimination) model that evaluated the days of drinking (frequency) during the typical 7-day week. Item characteristic curves were most similar for Monday, Tuesday, and Wednesday (prototypical weekday) and for Friday and Saturday (prototypical weekend). Thursday and Sunday, however, exhibited item characteristics that bordered the properties of weekday and weekend consumption. In study 2 (N = 403), confirmatory factor analysis was applied to test six hypothesized measurement structures representing drinks per day (quantity) during the typical week. The measurement model producing the strongest fit indices was a correlated two-factor structure involving separate weekday and weekend factors that permitted Thursday and Sunday to double load on both dimensions. The proper conceptualization and accurate measurement of the days demarcating the normative boundaries of “dry” weekdays and “wet” weekends are imperative to inform research and prevention efforts targeting temporal alcohol intake patterns. PMID:27488456

Effects of Morphology Constraint on Electrophysiological Properties of Cortical Neurons

NASA Astrophysics Data System (ADS)

Zhu, Geng; Du, Liping; Jin, Lei; Offenhäusser, Andreas

2016-04-01

There is growing interest in engineering nerve cells in vitro to control architecture and connectivity of cultured neuronal networks or to build neuronal networks with predictable computational function. Pattern technologies, such as micro-contact printing, have been developed to design ordered neuronal networks. However, electrophysiological characteristics of the single patterned neuron haven’t been reported. Here, micro-contact printing, using polyolefine polymer (POP) stamps with high resolution, was employed to grow cortical neurons in a designed structure. The results demonstrated that the morphology of patterned neurons was well constrained, and the number of dendrites was decreased to be about 2. Our electrophysiological results showed that alterations of dendritic morphology affected firing patterns of neurons and neural excitability. When stimulated by current, though both patterned and un-patterned neurons presented regular spiking, the dynamics and strength of the response were different. The un-patterned neurons exhibited a monotonically increasing firing frequency in response to injected current, while the patterned neurons first exhibited frequency increase and then a slow decrease. Our findings indicate that the decrease in dendritic complexity of cortical neurons will influence their electrophysiological characteristics and alter their information processing activity, which could be considered when designing neuronal circuitries.

Conceptualizing and Measuring Weekend versus Weekday Alcohol Use: Item Response Theory and Confirmatory Factor Analysis.

PubMed

Lac, Andrew; Handren, Lindsay; Crano, William D

2016-10-01

Culturally, people tend to abstain from alcohol intake during the weekdays and wait to consume in greater frequency and quantity during the weekends. The current research sought to empirically justify the days representing weekday versus weekend alcohol consumption. In study 1 (N = 419), item response theory was applied to a two-parameter (difficulty and discrimination) model that evaluated the days of drinking (frequency) during the typical 7-day week. Item characteristic curves were most similar for Monday, Tuesday, and Wednesday (prototypical weekday) and for Friday and Saturday (prototypical weekend). Thursday and Sunday, however, exhibited item characteristics that bordered the properties of weekday and weekend consumption. In study 2 (N = 403), confirmatory factor analysis was applied to test six hypothesized measurement structures representing drinks per day (quantity) during the typical week. The measurement model producing the strongest fit indices was a correlated two-factor structure involving separate weekday and weekend factors that permitted Thursday and Sunday to double load on both dimensions. The proper conceptualization and accurate measurement of the days demarcating the normative boundaries of "dry" weekdays and "wet" weekends are imperative to inform research and prevention efforts targeting temporal alcohol intake patterns.

Critical speeds and forced response solutions for active magnetic bearing turbomachinery, part 2

NASA Technical Reports Server (NTRS)

Rawal, D.; Keesee, J.; Kirk, R. Gordon

1991-01-01

The need for better performance of turbomachinery with active magnetic bearings has necessitated a study of such systems for accurate prediction of their vibrational characteristics. A modification of existing transfer matrix methods for rotor analysis is presented to predict the response of rotor systems with active magnetic bearings. The position of the magnetic bearing sensors is taken into account and the effect of changing sensor position on the vibrational characteristics of the rotor system is studied. The modified algorithm is validated using a simpler Jeffcott model described previously. The effect of changing from a rotating unbalance excitation to a constant excitation in a single plane is also studied. A typical eight stage centrifugal compressor rotor is analyzed using the modified transfer matrix code. The results for a two mass Jeffcott model were presented previously. The results obtained by running this model with the transfer matrix method were compared with the results of the Jeffcott analysis for the purposes of verification. Also included are plots of amplitude versus frequency for the eight stage centrifugal compressor rotor. These plots demonstrate the significant influence that sensor location has on the amplitude and critical frequencies of the rotor system.

Achilles tendinopathy modulates force frequency characteristics of eccentric exercise.

PubMed

Grigg, Nicole L; Wearing, Scott C; O'Toole, John M; Smeathers, James E

2013-03-01

Previous research has demonstrated that ground reaction force (GRF) recorded during eccentric ankle exercise is characterized by greater power in the 8- to 12-Hz bandwidth when compared with that recorded during concentric ankle exercise. Subsequently, it was suggested that vibrations in this bandwidth may underpin the beneficial effect of eccentric loading in tendon repair. However, this observation has been made only in individuals without Achilles tendinopathy. This research compared the force frequency characteristics of eccentric and concentric exercises in individuals with and without Achilles tendinopathy. Eleven male adults with unilateral midportion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Kinematics and GRF were recorded while the participants performed a common eccentric rehabilitation exercise protocol and a concentric equivalent. Ankle joint kinematics and the frequency power spectrum of the resultant GRF were calculated. Eccentric exercise was characterized by a significantly greater proportion of spectral power between 4.5 and 11.5 Hz when compared with concentric exercise. There were no significant differences between limbs in the force frequency characteristics of concentric exercise. Eccentric exercise, in contrast, was defined by a shift in the power spectrum of the symptomatic limb, resulting in a second spectral peak at 9 Hz, rather than 10 Hz in the control limb. Compared with healthy tendon, Achilles tendinopathy was characterized by lower frequency vibrations during eccentric rehabilitation exercises. This finding may be associated with changes in neuromuscular activation and tendon stiffness that have been shown to occur with tendinopathy and provides a possible rationale for the previous observation of a different biochemical response to eccentric exercise in healthy and injured Achilles tendons.

Response-only method for damage detection of beam-like structures using high accuracy frequencies with auxiliary mass spatial probing

NASA Astrophysics Data System (ADS)

Zhong, Shuncong; Oyadiji, S. Olutunde; Ding, Kang

2008-04-01

This paper proposes a new approach based on auxiliary mass spatial probing using spectral centre correction method (SCCM), to provide a simple solution for damage detection by just using the response time history of beam-like structures. The natural frequencies of a damaged beam with a traversing auxiliary mass change due to change in the inertia of the beam as the auxiliary mass is traversed along the beam, as well as the point-to-point variations in the flexibility of the beam. Therefore the auxiliary mass can enhance the effects of the crack on the dynamics of the beam and, therefore, facilitate the identification and location of damage in the beam. That is, the auxiliary mass can be used to probe the dynamic characteristic of the beam by traversing the mass from one end of the beam to the other. However, it is impossible to obtain accurate modal frequencies by the direct operation of the fast Fourier transform (FFT) of the response data of the structure because the frequency spectrum can be only calculated from limited sampled time data which results in the well-known leakage effect. SCCM is identical to the energy centrobaric correction method (ECCM) which is a practical and effective method used in rotating mechanical fault diagnosis and which resolves the shortcoming of FFT and can provide high accuracy estimate of frequency, amplitude and phase. In the present work, the modal responses of damaged simply supported beams with auxiliary mass are computed using the finite element method (FEM). The graphical plots of the natural frequencies calculated by SCCM versus axial location of auxiliary mass are obtained. However, it is difficult to locate the crack directly from the curve of natural frequencies. A simple and fast method, the derivatives of natural frequency curve, is proposed in the paper which can provide crack information for damage detection of beam-like structures. The efficiency and practicability of the proposed method is illustrated via numerical simulation. For real cases, experimental noise is expected to corrupt the response data and, ultimately, the natural frequencies of beam-like structures. Therefore, the response data with a normally distributed random noise is also studied. Also, the effects of crack depth, auxiliary mass and damping ratios on the proposed method are investigated. From the simulated results, the efficiency and robustness of the proposed method is demonstrated. The results show that the proposed method has low computational cost and high precision.

Reward Expectation Modulates Feedback-Related Negativity and EEG Spectra

PubMed Central

Cohen, Michael X; Elger, Christian E.; Ranganath, Charan

2007-01-01

The ability to evaluate outcomes of previous decisions is critical to adaptive decision-making. The feedback-related negativity (FRN) is an event-related potential (ERP) modulation that distinguishes losses from wins, but little is known about the effects of outcome probability on these ERP responses. Further, little is known about the frequency characteristics of feedback processing, for example, event-related oscillations and phase synchronizations. Here, we report an EEG experiment designed to address these issues. Subjects engaged in a probabilistic reinforcement learning task in which we manipulated, across blocks, the probability of winning and losing to each of two possible decision options. Behaviorally, all subjects quickly adapted their decision-making to maximize rewards. ERP analyses revealed that the probability of reward modulated neural responses to wins, but not to losses. This was seen both across blocks as well as within blocks, as learning progressed. Frequency decomposition via complex wavelets revealed that EEG responses to losses, compared to wins, were associated with enhanced power and phase coherence in the theta frequency band. As in the ERP analyses, power and phase coherence values following wins but not losses were modulated by reward probability. Some findings between ERP and frequency analyses diverged, suggesting that these analytic approaches provide complementary insights into neural processing. These findings suggest that the neural mechanisms of feedback processing may differ between wins and losses. PMID:17257860

Fashion advertisements: a comparison of viewers' perceptual and affective responses to illustrated and photographed stimuli.

PubMed

Kimle, P A; Fiore, A M

1992-12-01

The perceptual and affective responses of 44 women to actual illustrated and photographed fashion advertisements during focused interviews were explored. Content analysis methods identified categories of response; frequency of response categories for the two media were compared using Fisher's z tests. Significant differences in perceptual responses included greater visual interest created by the use of color in photographs, greater interest in layout and design features of the illustrations, and interest in characteristics of the models in the photographs. Affective response differences included greater preference for photographic advertisements and the garments in them. Contrary to suggestions from professionals in fashion advertising, no significant differences were found in viewers' perceptions of information about the products in the advertisements or perceptions of meaning and aesthetic response.

Optimal apparent damping as a function of the bandwidth of an array of vibration absorbers.

PubMed

Vignola, Joseph; Glean, Aldo; Judge, John; Ryan, Teresa

2013-08-01

The transient response of a resonant structure can be altered by the attachment of one or more substantially smaller resonators. Considered here is a coupled array of damped harmonic oscillators whose resonant frequencies are distributed across a frequency band that encompasses the natural frequency of the primary structure. Vibration energy introduced to the primary structure, which has little to no intrinsic damping, is transferred into and trapped by the attached array. It is shown that, when the properties of the array are optimized to reduce the settling time of the primary structure's transient response, the apparent damping is approximately proportional to the bandwidth of the array (the span of resonant frequencies of the attached oscillators). Numerical simulations were conducted using an unconstrained nonlinear minimization algorithm to find system parameters that result in the fastest settling time. This minimization was conducted for a range of system characteristics including the overall bandwidth of the array, the ratio of the total array mass to that of the primary structure, and the distributions of mass, stiffness, and damping among the array elements. This paper reports optimal values of these parameters and demonstrates that the resulting minimum settling time decreases with increasing bandwidth.

Vestibular evoked myogenic potential (VEMP) testing: normative threshold response curves and effects of age.

PubMed

Janky, Kristen L; Shepard, Neil

2009-09-01

Vestibular evoked myogenic potential (VEMP) testing has gained increased interest in the diagnosis of a variety of vestibular etiologies. P13/N23 latency, amplitude and threshold response curves have been used to compare pathologic groups to normal controls. Appropriate characterization of these etiologies requires normative data across the frequency spectrum and age range. The objective of the current study was to test the hypothesis that significant changes in VEMP responses occur as a function of increased age across all test stimuli as well as characterize the VEMP threshold response curve across age. This project incorporated a prospective study design using a sample of convenience. Openly recruited subjects were assigned to groups according to age. Forty-six normal controls ranging between 20 and 76 years of age participated in the study. Participants were separated by decade into five age categories from 20 to 60 plus years. Normal participants were characterized by having normal hearing sensitivity, no history of neurologic or balance/dizziness involvement, and negative results on a direct office vestibular examination. VEMP responses were measured at threshold to click and 250, 500, 750, and 1000 Hz tone burst stimuli and at a suprathreshold level to 500 Hz toneburst stimuli at123 dB SPL. A mixed group factorial ANOVA (analysis of variance) and linear regression were performed to examine the effects of VEMP characteristics on age. There were no significant differences between ears for any of the test parameters. There were no significant differences between age groups for n23 latency or amplitude in response to any of the stimuli. Significant mean differences did exist between age groups for p13 latency (250, 750, and 1000 Hz) and threshold (500 and 750 Hz). Age was significantly correlated with VEMP parameters. VEMP threshold was positively correlated (250, 500, 750, 1000 Hz); and amplitude was negatively correlated (500 Hz maximum). The threshold response curves revealed best frequency tuning at 500 Hz with the highest thresholds in response to click stimuli. However, this best frequency tuning dissipated with increased age. VEMP response rates also decreased with increased age. We have demonstrated that minor differences in VEMP responses occur with age. Given the reduced response rates and flattened frequency tuning curve for individuals over the age of 60, frequency tuning curves may not be a good diagnostic indicator for this age group.

Evaluation of the British Columbia AIDS Information Line.

PubMed

Parsons, D C; Bell, M A; Gilchrist, L D

1991-01-01

We evaluated implementation of the British Columbia AIDS Information Line during its initial 15 weeks of operation. Data collected during daily operation of the line included call frequency, caller characteristics, response patterns, caller concerns and community referrals. Information on activities and resources required to implement the AIDS Line was also assembled. The study concluded that the advertising campaign sponsored by the provincial government and other AIDS-related media events had a strong impact on the frequency of calls made to the AIDS Line. However, the effect of both advertising and media events was of relatively short duration, suggesting that utilization of an AIDS information line is dependent on continuing promotional activities. The evaluation results demonstrate the importance of continuous collection of data online utilization, to track public awareness of and response to AIDS-related issues, and to facilitate planning of public education.

Time and frequency domain analysis of sampled data controllers via mixed operation equations

NASA Technical Reports Server (NTRS)

Frisch, H. P.

1981-01-01

Specification of the mathematical equations required to define the dynamic response of a linear continuous plant, subject to sampled data control, is complicated by the fact that the digital components of the control system cannot be modeled via linear ordinary differential equations. This complication can be overcome by introducing two new mathematical operations; namely, the operation of zero order hold and digial delay. It is shown that by direct utilization of these operations, a set of linear mixed operation equations can be written and used to define the dynamic response characteristics of the controlled system. It also is shown how these linear mixed operation equations lead, in an automatable manner, directly to a set of finite difference equations which are in a format compatible with follow on time and frequency domain analysis methods.

Optical frequency locked loop for long-term stabilization of broad-line DFB laser frequency difference

NASA Astrophysics Data System (ADS)

Lipka, Michał; Parniak, Michał; Wasilewski, Wojciech

2017-09-01

We present an experimental realization of the optical frequency locked loop applied to long-term frequency difference stabilization of broad-line DFB lasers along with a new independent method to characterize relative phase fluctuations of two lasers. The presented design is based on a fast photodiode matched with an integrated phase-frequency detector chip. The locking setup is digitally tunable in real time, insensitive to environmental perturbations and compatible with commercially available laser current control modules. We present a simple model and a quick method to optimize the loop for a given hardware relying exclusively on simple measurements in time domain. Step response of the system as well as phase characteristics closely agree with the theoretical model. Finally, frequency stabilization for offsets within 4-15 GHz working range achieving <0.1 Hz long-term stability of the beat note frequency for 500 s averaging time period is demonstrated. For these measurements we employ an I/Q mixer that allows us to precisely and independently measure the full phase trace of the beat note signal.

Early performance of the 12-GHz, 200-watt transmitter experiment package in the communications technology satellite

NASA Technical Reports Server (NTRS)

1977-01-01

Measured performance characteristics of the transmitter experiment package (TEP) aboard the Communications Technology Satellite for the first 90 operating days in orbit are presented. The TEP consists of a nominal 200-watt output stage tube (OST), a supporting power processing system (PPS), and a variable-conductance heat pipe system (VCHPS). The OST, a traveling-wave tube augmented with a 10-stage depressed collector, has an overall saturated average efficiency of 51.5 percent and an average saturated radiofrequency (RF) output power at center-band frequency of 240 watts. The PPS operated with a measured efficiency of 86.5 percent to 88.5 percent. The VCHPS, using three pipes to conduct heat from the PPS and the body of the OST to a 52-centimeter by 124-centimeter (20.5-in. by 48.75-in.) radiator fin, maintained by the PPS baseplate temperature below 50 C for all operating conditions. The TEP performance characteristics presented include frequency response, RF output power, efficiency, and distortions. Communications characteristics were evaluated by using both video and audio modulated signals.

Characterization of linear viscoelastic anti-vibration rubber mounts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lodhia, B.B.; Esat, I.I.

1996-11-01

The aim of this paper is to identify the dynamic characteristics that are evident in linear viscoelastic rubber mountings. The characteristics under consideration included the static and dynamic stiffnesses with the variation of amplitude and frequency of the sinusoidal excitation. Test samples of various rubber mix were tested and compared to reflect magnitude of dependency on composition. In the light of the results, the validity and effectiveness of a mathematical model was investigated and a suitable technique based on the Tschoegl and Emri Algorithm, was utilized to fit the model to the experimental data. The model which was chosen, wasmore » an extension of the basic Maxwell model, which is based on linear spring and dashpot elements in series and parallel called the Wiechert model. It was found that the extent to which the filler and vulcanisate was present in the rubber sample, did have a great effect on the static stiffness characteristics, and the storage and loss moduli. The Tschoegl and Emri Algorithm was successfully utilized in modelling the frequency response of the samples.« less

Acoustic emission characteristics of copper alloys under low-cycle fatigue conditions

NASA Technical Reports Server (NTRS)

Krampfner, Y.; Kawamoto, A.; Ono, K.; Green, A.

1975-01-01

The acoustic emission (AE) characteristics of pure copper, zirconium-copper, and several copper alloys were determined to develop nondestructive evaluation schemes of thrust chambers through AE techniques. The AE counts rms voltages, frequency spectrum, and amplitude distribution analysis evaluated AE behavior under fatigue loading conditions. The results were interpreted with the evaluation of wave forms, crack propagation characteristics, as well as scanning electron fractographs of fatigue-tested samples. AE signals at the beginning of a fatigue test were produced by a sample of annealed alloys. A sample of zirconium-containing alloys annealed repeatedly after each fatigue loading cycle showed numerous surface cracks during the subsequent fatigue cycle, emitting strong-burst AE signals. Amplitude distribution analysis exhibits responses that are characteristic of certain types of AE signals.

System and method for controlling remote devices

DOEpatents

Carrender, Curtis Lee [Richland, WA; Gilbert, Ronald W [Benton City, WA; Scott, Jeff W [Pasco, WA; Clark, David A [Kennewick, WA

2006-02-07

A system and method for controlling remote devices utilizing a radio frequency identification (RFID) tag device having a control circuit adapted to render the tag device, and associated objects, permanently inoperable in response to radio-frequency control signals. The control circuit is configured to receive the control signals that can include an enable signal, and in response thereto enable an associated object, such as a weapon; and in response to a disable signal, to disable the tag itself, or, if desired, to disable the associated weapon or both the device and the weapon. Permanent disabling of the tag can be accomplished by several methods, including, but not limited to, fusing a fusable link, breaking an electrically conductive path, permanently altering the modulation or backscattering characteristics of the antenna circuit, and permanently erasing an associated memory. In this manner, tags in the possession of unauthorized employees can be remotely disabled, and weapons lost on a battlefield can be easily tracked and enabled or disabled automatically or at will.

Tremor frequency characteristics in Parkinson's disease under resting-state and stress-state conditions.

PubMed

Lee, Hong Ji; Lee, Woong Woo; Kim, Sang Kyong; Park, Hyeyoung; Jeon, Hyo Seon; Kim, Han Byul; Jeon, Beom S; Park, Kwang Suk

2016-03-15

Tremor characteristics-amplitude and frequency components-are primary quantitative clinical factors for diagnosis and monitoring of tremors. Few studies have investigated how different patient's conditions affect tremor frequency characteristics in Parkinson's disease (PD). Here, we analyzed tremor characteristics under resting-state and stress-state conditions. Tremor was recorded using an accelerometer on the finger, under resting-state and stress-state (calculation task) conditions, during rest tremor and postural tremor. The changes of peak power, peak frequency, mean frequency, and distribution of power spectral density (PSD) of tremor were evaluated across conditions. Patients whose tremors were considered more than "mild" were selected, for both rest (n=67) and postural (n=25) tremor. Stress resulted in both greater peak powers and higher peak frequencies for rest tremor (p<0.001), but not for postural tremor. Notably, peak frequencies were concentrated around 5 Hz under stress-state condition. The distributions of PSD of tremor were symmetrical, regardless of conditions. Tremor is more evident and typical tremor characteristics, namely a lower frequency as amplitude increases, are different in stressful condition. Patient's conditions directly affect neural oscillations related to tremor frequencies. Therefore, tremor characteristics in PD should be systematically standardized across patient's conditions such as attention and stress levels. Copyright © 2016. Published by Elsevier B.V.

A Wide Band Absorbing Material Design Using Band-Pass Frequency Selective Surface

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Xu, Qiang; Liu, Ting; Zheng, Dianliang; Zhou, Li

2018-03-01

Based on the high frequency advantage characteristics of the Fe based absorbing coating, a method for designing the structure of broadband absorbing structure by using frequency selective surface (FSS) is proposed. According to the transmission and reflection characteristic of the different size FSS structure, the frequency variation characteristic was simulated. Secondly, the genetic algorithm was used to optimize the high frequency broadband absorbing materials, including the single and double magnetic layer material. Finally, the absorbing characteristics in iron layer were analyzed as the band pass FSS structure was embedded, the results showed that the band-pass FSS had the influence on widening the absorbing frequency. As the FSS was set as the bottom layer, it was effective to achieve the good absorbing property in low frequency and the high frequency absorbing performance was not weakened, because the band-pass FSS led the low frequency absorption and the high frequency shielding effect. The results of this paper are of guiding significance for designing and manufacturing the broadband absorbing materials.

A scaling procedure for the response of an isolated system with high modal overlap factor

NASA Astrophysics Data System (ADS)

De Rosa, S.; Franco, F.

2008-10-01

The paper deals with a numerical approach that reduces some physical sizes of the solution domain to compute the dynamic response of an isolated system: it has been named Asymptotical Scaled Modal Analysis (ASMA). The proposed numerical procedure alters the input data needed to obtain the classic modal responses to increase the frequency band of validity of the discrete or continuous coordinates model through the definition of a proper scaling coefficient. It is demonstrated that the computational cost remains acceptable while the frequency range of analysis increases. Moreover, with reference to the flexural vibrations of a rectangular plate, the paper discusses the ASMA vs. the statistical energy analysis and the energy distribution approach. Some insights are also given about the limits of the scaling coefficient. Finally it is shown that the linear dynamic response, predicted with the scaling procedure, has the same quality and characteristics of the statistical energy analysis, but it can be useful when the system cannot be solved appropriately by the standard Statistical Energy Analysis (SEA).

Investigations into the triggered lightning response of the F106B thunderstorm research aircraft

NASA Technical Reports Server (NTRS)

Rudolph, Terence H.; Perala, Rodney A.; Mckenna, Paul M.; Parker, Steven L.

1985-01-01

An investigation has been conducted into the lightning characteristics of the NASA F106B thunderstorm research aircraft. The investigation includes analysis of measured data from the aircraft in the time and frequency domains. Linear and nonlinear computer modelling has also been performed. In addition, new computer tools have been developed, including a new enhanced nonlinear air breakdown model, and a subgrid model useful for analyzing fine details of the aircraft's geometry. Comparison of measured and calculated electromagnetic responses of the aircraft to a triggered lightning environment are presented.

Generalized fluid impulse functions for oscillating marine structures

NASA Astrophysics Data System (ADS)

Janardhanan, K.; Price, W. G.; Wu, Y.

1992-03-01

A selection of generalized impulse response functions is presented for a variety of rigid and flexible marine structures (i.e. mono-hull, SWATH, floating drydock and twin dock, fixed flexible pile). These functions are determined from calculated and experimental frequency-dependent hydrodynamic data, and the characteristics of these data depend on the type of structure considered. This information is reflected in the shape and duration of the generalized impulse response functions which are pre-requisites for a generalized integro-differential mathematical model describing the dynamic behaviour of the structures to seaway excitation.

Assessment of autonomic response by broad-band respiration

NASA Technical Reports Server (NTRS)

Berger, R. D.; Saul, J. P.; Cohen, R. J.

1989-01-01

We present a technique for introducing broad-band respiratory perturbations so that the response characteristics of the autonomic nervous system can be determined noninvasively over a wide range of physiologically relevant frequencies. A subject's respiratory bandwidth was broadened by breathing on cue to a sequence of audible tones spaced by Poisson intervals. The transfer function between the respiratory input and the resulting instantaneous heart rate was then computed using spectral analysis techniques. Results using this method are comparable to those found using traditional techniques, but are obtained with an economy of data collection.

Bandpass x-ray diode and x-ray multiplier detector

DOEpatents

Wang, C.L.

1982-09-27

An absorption-edge of an x-ray absorption filter and a quantum jump of a photocathode determine the bandpass characteristics of an x-ray diode detector. An anode, which collects the photoelectrons emitted by the photocathode, has enhanced amplification provided by photoelectron-multiplying means which include dynodes or a microchannel-plate electron-multiplier. Suppression of undesired high frequency response for a bandpass x-ray diode is provided by subtracting a signal representative of energies above the passband from a signal representative of the overall response of the bandpass diode.

Dynamic Characteristics of Micro-Beams Considering the Effect of Flexible Supports

PubMed Central

Zhong, Zuo-Yang; Zhang, Wen-Ming; Meng, Guang

2013-01-01

Normally, the boundaries are assumed to allow small deflections and moments for MEMS beams with flexible supports. The non-ideal boundary conditions have a significant effect on the qualitative dynamical behavior. In this paper, by employing the principle of energy equivalence, rigorous theoretical solutions of the tangential and rotational equivalent stiffness are derived based on the Boussinesq's and Cerruti's displacement equations. The non-dimensional differential partial equation of the motion, as well as coupled boundary conditions, are solved analytically using the method of multiple time scales. The closed-form solution provides a direct insight into the relationship between the boundary conditions and vibration characteristics of the dynamic system, in which resonance frequencies increase with the nonlinear mechanical spring effect but decrease with the effect of flexible supports. The obtained results of frequencies and mode shapes are compared with the cases of ideal boundary conditions, and the differences between them are contrasted on frequency response curves. The influences of the support material property on the equivalent stiffness and resonance frequency shift are also discussed. It is demonstrated that the proposed model with the flexible supports boundary conditions has significant effect on the rigorous quantitative dynamical analysis of the MEMS beams. Moreover, the proposed analytical solutions are in good agreement with those obtained from finite element analyses.

Comparisons of spectral characteristics of wind noise between omnidirectional and directional microphones.

PubMed

Chung, King

2012-06-01

Wind noise reduction is a topic of ongoing research and development for hearing aids and cochlear implants. The purposes of this study were to examine spectral characteristics of wind noise generated by directional (DIR) and omnidirectional (OMNI) microphones on different styles of hearing aids and to derive wind noise reduction strategies. Three digital hearing aids (BTE, ITE, and ITC) were fitted to Knowles Electronic Manikin for Acoustic Research. They were programmed to have linear amplification and matching frequency responses between the DIR and OMNI modes. Flow noise recordings were made from 0° to 360° azimuths at flow velocities of 4.5, 9.0, and 13.5 m/s in a quiet wind tunnel. Noise levels were analyzed in one-third octave bands from 100 to 8000 Hz. Comparison of wind noise revealed that DIR generally produced higher noise levels than OMNI for all hearing aids, but it could result in lower levels than OMNI at some frequencies and head angles. Wind noise reduction algorithms can be designed to detect noise levels of DIR and OMNI outputs in each frequency channel, remove the constraint to switch to OMNI in low-frequency channel(s) only, and adopt the microphone mode with lower noise levels to take advantage of the microphone differences.

Human body modeling method to simulate the biodynamic characteristics of spine in vivo with different sitting postures.

PubMed

Dong, Rui-Chun; Guo, Li-Xin

2017-11-01

The aim of this study is to model the computational model of seated whole human body including skeleton, muscle, viscera, ligament, intervertebral disc, and skin to predict effect of the factors (sitting postures, muscle and skin, buttocks, viscera, arms, gravity, and boundary conditions) on the biodynamic characteristics of spine. Two finite element models of seated whole body and a large number of finite element models of different ligamentous motion segments were developed and validated. Static, modal, and transient dynamic analyses were performed. The predicted vertical resonant frequency of seated body model was in the range of vertical natural frequency of 4 to 7 Hz. Muscle, buttocks, viscera, and the boundary conditions of buttocks have influence on the vertical resonant frequency of spine. Muscle played a very important role in biodynamic response of spine. Compared with the vertical posture, the posture of lean forward or backward led to an increase in stress on anterior or lateral posterior of lumbar intervertebral discs. This indicated that keeping correct posture could reduce the injury of vibration on lumbar intervertebral disc under whole-body vibration. The driving posture not only reduced the load of spine but also increased the resonant frequency of spine. Copyright © 2017 John Wiley & Sons, Ltd.

The use of a digital computer for calculation of acoustic fields of complex vibrating structures by the reciprocity principle

NASA Technical Reports Server (NTRS)

Rimskiy-Korsakov, A. V.; Belousov, Y. I.

1973-01-01

A program was compiled for calculating acoustical pressure levels, which might be created by vibrations of complex structures (an assembly of shells and rods), under the influence of a given force, for cases when these fields cannot be measured directly. The acoustical field is determined according to transition frequency and pulse characteristics of the structure in the projection mode. Projection characteristics are equal to the reception characteristics, for vibrating systems in which the reciprocity principle holds true. Characteristics in the receiving mode are calculated on the basis of experimental data on a point pulse space velocity source (input signal) and vibration response of the structure (output signal). The space velocity of a pulse source, set at a point in space r, where it is necessary to calculate the sound field of the structure p(r,t), is determined by measurements of acoustic pressure, created by a point source at a distance R. The vibration response is measured at the point where the forces F and f exciting the system should act.

High-frequency output characteristics of AlGaAs/GaAs heterojunction bipolar transistors for large-signal applications

NASA Astrophysics Data System (ADS)

Chen, J.; Gao, G. B.; Ünlü, M. S.; Morkoç, H.

1991-11-01

High-frequency ic- vce output characteristics of bipolar transistors, derived from calculated device cutoff frequencies, are reported. The generation of high-frequency output characteristics from device design specifications represents a novel bridge between microwave circuit design and device design: the microwave performance of simulated device structures can be analyzed, or tailored transistor device structures can be designed to fit specific circuit applications. The details of our compact transistor model are presented, highlighting the high-current base-widening (Kirk) effect. The derivation of the output characteristics from the modeled cutoff frequencies are then presented, and the computed characteristics of an AlGaAs/GaAs heterojunction bipolar transistor operating at 10 GHz are analyzed. Applying the derived output characteristics to microwave circuit design, we examine large-signal class A and class B amplification.

Somatic cell mutations at the glycophorin A locus in erythrocytes of atomic bomb survivors: Implications for radiation carcinogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyoizumi, Seishi; Akiyama, Mitoshi; Tanabe, Kazumi

To clarify the relationship between somatic cell mutations and radiation exposure, the frequency of hemizygous mutant erythrocytes at the glycophorin A (GPA) locus was measured by flow cytometry for 1,226 heterozygous atomic bomb (A-bomb) survivors in HIroshima and Nagasaki. For statistical analysis, both GPA mutant frequency and radiation dose were log-transformed to normalize skewed distributions of these variables. The GPA mutant frequency increased slightly but significantly with age at testing and with the number of cigarettes smoked. Also, mutant frequency was significantly higher in males than in females even with adjustment for smoking and was higher to Hiroshima than inmore » Nagasaki. These characteristics of background GPA mutant frequency are qualitatively similar to those of background solid cancer incidence or mortality obtained from previous epidemiological studies of survivors. An analysis of the mutant frequency dose response using a descriptive model showed that the doubling dose is about 1.20 Sv [95% confidence interval (CI): 0.95-1.56], whereas the minimum dose for detecting a significant increase in mutant frequency is about 0.24 Sv (95% CI: 0.041-0.51). No significant effects of sex, city or age at the time of exposure on the dose response were detected. Interestingly, the doubling dose of the GPA mutant frequency was similar to that of solid cancer incidence in A-bomb survivors. This observation is in line with the hypothesis that radiation-induced somatic cell mutations are the major cause of excess cancer risk after radiation. 49 refs., 6 figs., 2 tabs.« less

Kinship as a frequency dependent strategy

PubMed Central

Ji, Ting; Zheng, Xiu-Deng; He, Qiao-Qiao; Wu, Jia-Jia; Tao, Yi

2016-01-01

Humans divide themselves up into separate cultures, which is a unique and ubiquitous characteristic of our species. Kinship norms are one of the defining features of such societies. Here we show how norms of marital residence can evolve as a frequency-dependent strategy, using real-world cases from southwestern China and an evolutionary game model. The process of kinship change has occurred in the past and is also occurring now in southwestern China. Our data and models show how transitions between residence types can occur both as response to changing costs and benefits of co-residence with kin, and also due to the initial frequency of the strategies adopted by others in the population: patrilocal societies can become matrilocal, and neolocal societies can become duolocal. This illustrates how frequency-dependent selection plays a role both in the maintenance of group-level cultural diversity and in cultural extinction. PMID:26998333

Multilayered models for electromagnetic reflection amplitudes

NASA Technical Reports Server (NTRS)

Linlor, W. I.

1976-01-01

The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.

Tunable meta-atom using liquid metal embedded in stretchable polymer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Peng; Yang, Siming; Wang, Qiugu

2015-07-07

Reconfigurable metamaterials have great potential to alleviate complications involved in using passive metamaterials to realize emerging electromagnetic functions, such as dynamical filtering, sensing, and cloaking. This paper presents a new type of tunable meta-atoms in the X-band frequency range (8–12 GHz) toward reconfigurable metamaterials. The meta-atom is made of all flexible materials compliant to the surface of an interaction object. It uses a liquid metal-based split-ring resonator as its core constituent embedded in a highly flexible elastomer. We demonstrate that simple mechanical stretching of the meta-atom can lead to the great flexibility in reconfiguring its resonance frequency continuously over moremore » than 70% of the X-band frequency range. The presented meta-atom technique provides a simple approach to dynamically tune response characteristics of metamaterials over a broad frequency range.« less

Human comfort response to random motions with a dominant pitching motion

NASA Technical Reports Server (NTRS)

Stone, R. W., Jr.

1980-01-01

The effects of random pitching velocities on passenger ride comfort response were examined on the NASA Langley Visual Motion Simulator. The effects of power spectral density shape and frequency ranges from 0 to 2 Hz were studied. The subjective rating data and the physical motion data obtained are presented. No attempt at interpretation or detailed analysis of the data is made. Motions in all degrees of freedom existed as well as the intended pitching motion, because of the characteristics of the simulator. These unwanted motions may have introduced some interactive effects on passenger responses which should be considered in any analysis of the data.

Targeting dopa-sensitive and dopa-resistant gait dysfunction in Parkinson's disease: selective responses to internal and external cues.

PubMed

Rochester, Lynn; Baker, Katherine; Nieuwboer, Alice; Burn, David

2011-02-15

Independence of certain gait characteristics from dopamine replacement therapies highlights its complex pathophysiology in Parkinson's disease (PD). We explored the effect of two different cue strategies on gait characteristics in relation to their response to dopaminergic medications. Fifty people with PD (age 69.22 ± 6.6 years) were studied. Participants walked with and without cues presented in a randomized order. Cue strategies were: (1) internal cue (attention to increase step length) and (2) external cue (auditory cue with instruction to take large step to the beat). Testing was carried out two times at home (on and off medication). Gait was measured using a Stride Analyzer (B&L Engineering). Gait outcomes were walking speed, stride length, step frequency, and coefficient of variation (CV) of stride time and double limb support duration (DLS). Walking speed, stride length, and stride time CV improved on dopaminergic medications, whereas step frequency and DLS CV did not. Internal and external cues increased stride time and walking speed (on and off dopaminergic medications). Only the external cue significantly improved stride time CV and DLS CV, whereas the internal cue had no effect (on and off dopaminergic medications). Internal and external cues selectively modify gait characteristics in relation to the type of gait disturbance and its dopa-responsiveness. Although internal (attention) and external cues target dopaminergic gait dysfunction (stride length), only external cues target stride to stride fluctuations in gait. Despite an overlap with dopaminergic pathways, external cues may effectively address nondopaminergic gait dysfunction and potentially increase mobility and reduce gait instability and falls. Copyright © 2010 Movement Disorder Society.

Effects of sensorineural hearing loss on temporal coding of narrowband and broadband signals in the auditory periphery

PubMed Central

Henry, Kenneth S.; Heinz, Michael G.

2013-01-01

People with sensorineural hearing loss have substantial difficulty understanding speech under degraded listening conditions. Behavioral studies suggest that this difficulty may be caused by changes in auditory processing of the rapidly-varying temporal fine structure (TFS) of acoustic signals. In this paper, we review the presently known effects of sensorineural hearing loss on processing of TFS and slower envelope modulations in the peripheral auditory system of mammals. Cochlear damage has relatively subtle effects on phase locking by auditory-nerve fibers to the temporal structure of narrowband signals under quiet conditions. In background noise, however, sensorineural loss does substantially reduce phase locking to the TFS of pure-tone stimuli. For auditory processing of broadband stimuli, sensorineural hearing loss has been shown to severely alter the neural representation of temporal information along the tonotopic axis of the cochlea. Notably, auditory-nerve fibers innervating the high-frequency part of the cochlea grow increasingly responsive to low-frequency TFS information and less responsive to temporal information near their characteristic frequency (CF). Cochlear damage also increases the correlation of the response to TFS across fibers of varying CF, decreases the traveling-wave delay between TFS responses of fibers with different CFs, and can increase the range of temporal modulation frequencies encoded in the periphery for broadband sounds. Weaker neural coding of temporal structure in background noise and degraded coding of broadband signals along the tonotopic axis of the cochlea are expected to contribute considerably to speech perception problems in people with sensorineural hearing loss. PMID:23376018

Contrast computation methods for interferometric measurement of sensor modulation transfer function

NASA Astrophysics Data System (ADS)

Battula, Tharun; Georgiev, Todor; Gille, Jennifer; Goma, Sergio

2018-01-01

Accurate measurement of image-sensor frequency response over a wide range of spatial frequencies is very important for analyzing pixel array characteristics, such as modulation transfer function (MTF), crosstalk, and active pixel shape. Such analysis is especially significant in computational photography for the purposes of deconvolution, multi-image superresolution, and improved light-field capture. We use a lensless interferometric setup that produces high-quality fringes for measuring MTF over a wide range of frequencies (here, 37 to 434 line pairs per mm). We discuss the theoretical framework, involving Michelson and Fourier contrast measurement of the MTF, addressing phase alignment problems using a moiré pattern. We solidify the definition of Fourier contrast mathematically and compare it to Michelson contrast. Our interferometric measurement method shows high detail in the MTF, especially at high frequencies (above Nyquist frequency). We are able to estimate active pixel size and pixel pitch from measurements. We compare both simulation and experimental MTF results to a lens-free slanted-edge implementation using commercial software.

Effect of using a Planecta™ port with a three-way stopcock on the natural frequency of blood pressure transducer kits.

PubMed

Fujiwara, Shigeki; Tachihara, Keiichi; Mori, Satoshi; Ouchi, Kentaro; Yokoe, Chizuko; Imaizumi, Uno; Morimoto, Yoshinari; Miki, Yoichiro; Toyoguchi, Izumi; Yoshida, Kazu-Ichi; Yokoyama, Takeshi

2016-12-01

Blood pressure transducer kits are equipped with two types of Planecta™ ports-the flat-type Planecta™ port (FTP) and the Planecta™ port with a three-way stopcock (PTS). We reported that FTP application decreased the natural frequency of the kits. However, Planecta™ is an invaluable tool as it prevents infection, ensures technical simplicity, and excludes air. Hence, an ideal Planecta™ port that does not decrease the frequency characteristics is required. As a first step in this direction, we aimed to assess the influence of PTSs on the natural frequency of blood transducer kits. A DTXplus transducer kit (DT4812J; Argon Medical Devices, TX, USA) was used along with ≥1 PTSs (JMS, Hiroshima, Japan), and the frequency characteristics were assessed. The natural frequency and damping coefficient of each kit were obtained by using frequency characteristics analysis software, and these parameters were evaluated by plotting them on Gardner's chart. Regardless of whether one or two PTSs were inserted, the natural frequency of the kits only slightly decreased (from 42.5 to 41.1 Hz, when 2 PTSs were used). Thus, the frequency characteristics of the kits with PTSs were adequate for pressure monitoring. The insertion of ≥2 FTPs in pressure transducer kits should be avoided, as they markedly decrease the natural frequency and lead to underdamping. However, the effect of PTS insertion in pressure transducer kits on the frequency characteristics is minimal. Thus, we found that the use of PTS markedly improved the frequency characteristics as compared to the use of FTP.

The viscoelastic standard nonlinear solid model: predicting the response of the lumbar intervertebral disk to low-frequency vibrations.

PubMed

Groth, Kevin M; Granata, Kevin P

2008-06-01

Due to the mathematical complexity of current musculoskeletal spine models, there is a need for computationally efficient models of the intervertebral disk (IVD). The aim of this study is to develop a mathematical model that will adequately describe the motion of the IVD under axial cyclic loading as well as maintain computational efficiency for use in future musculoskeletal spine models. Several studies have successfully modeled the creep characteristics of the IVD using the three-parameter viscoelastic standard linear solid (SLS) model. However, when the SLS model is subjected to cyclic loading, it underestimates the load relaxation, the cyclic modulus, and the hysteresis of the human lumbar IVD. A viscoelastic standard nonlinear solid (SNS) model was used to predict the response of the human lumbar IVD subjected to low-frequency vibration. Nonlinear behavior of the SNS model was simulated by a strain-dependent elastic modulus on the SLS model. Parameters of the SNS model were estimated from experimental load deformation and stress-relaxation curves obtained from the literature. The SNS model was able to predict the cyclic modulus of the IVD at frequencies of 0.01 Hz, 0.1 Hz, and 1 Hz. Furthermore, the SNS model was able to quantitatively predict the load relaxation at a frequency of 0.01 Hz. However, model performance was unsatisfactory when predicting load relaxation and hysteresis at higher frequencies (0.1 Hz and 1 Hz). The SLS model of the lumbar IVD may require strain-dependent elastic and viscous behavior to represent the dynamic response to compressive strain.