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1

Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias  

SciTech Connect

Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Macheret, Sergey O. [Lockheed Martin Aeronautics Company, Palmdale, California 93599 (United States)

2008-08-15

2

Experimental Investigation of DBD Plasma Actuators Driven by Repetitive High Voltage Nanosecond Pulses with DC or Low-Frequency Sinusoidal Bias  

Microsoft Academic Search

Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on DC or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations

Dmitry F. Opaits; Gabriele Neretti; Alexandre V. Likhanskii; Sohail Zaidi; Mikhail N. Shneider; Richard B. Miles; Sergey O. Macheret

2007-01-01

3

Sinusoidal voltage controller for uninterruptible power supply by robust control  

Microsoft Academic Search

The output voltage of an uninterruptible power supply (UPS) is distorted by nonlinear loads. To obtain sinusoidal output voltage of a UPS, a new control method of a pulse width modulated (PWM) inverter is proposed applying sliding mode control. The feedback gains of conventional sliding mode control are determined by offline calculation; however this proposed control method calculates the feedback

Tomonobu Senjyu; Katsumi Uezato

1993-01-01

4

A series-parallel compensated uninterruptible power supply with sinusoidal input current and sinusoidal output voltage  

Microsoft Academic Search

In this paper a series-parallel compensated UPS is suggested, which has high input power factor and sinusoidal output voltage regulation capability. Compared to conventional cascaded UPS, the size can be reduced significantly with high quality input and output waveforms. In this paper, analysis and experimental results for a prototype are presented

Seong-Jeub Jeon; Gyu-Hyeong Cho

1997-01-01

5

Harmonics and powers of doubly fed induction generators at balanced sinusoidal voltages  

Microsoft Academic Search

Wind energy converters feeding into the power grid must comply with standards for harmonics. In practice harmonics or subharmonics caused by the generator are difficult to measure, because the grid itself is also distorted. This paper describes test-bench measurements that are performed with an ideal balanced and sinusoidal voltage source instead of a grid. The results show, which significant frequencies

Steffen Schostan; Klaus-Dieter Dettmann; Ilir Purellku; Detlef Schulz

2010-01-01

6

Event synchronous sinusoidal model based on frequency-to-instantaneous frequency mapping  

Microsoft Academic Search

We describe a glottal event synchronous sinusoidal model for speech analysis and synthesis. The sinusoidal components are event synchronously estimated using a mapping from linearly spaced filter center frequencies to the instantaneous frequencies of the filter outputs. Frequency domain fixed points of this mapping correspond to the constituent sinusoidal components of the input signal. A robust technique based on a

Parham Zolfaghari; Hideki Banno; Fumitada Itakura; Hideki Kawahara

2002-01-01

7

Soft-Switched Voltage-Doubler Sinusoidal Rectifier with Balanced Output Capacitor Voltages  

NASA Astrophysics Data System (ADS)

A novel single-phase soft-switched voltage-doubler rectifier is presented. The resonant switch cell for this has a full-bridge DC-DC converter structure built of voltage-bidirectional two-quadrant switch and has a vital function to balance the output capacitor voltages. The switching transitions are mainly governed by a series resonance. The experimental prototype employing four insulated-gate bipolar transistors is implemented to investigate the pulse-width modulated operation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor under the output voltage duplication.

Itoh, Ryozo; Ishizaka, Kouichi

8

A light weight, four quadrant, high switching frequency modular, photovoltaic DC\\/AC inverter, with sinusoidal output and high efficiency  

Microsoft Academic Search

A DC\\/AC power inverter is described for use in stand-alone photovoltaic systems, based on the high-frequency sinusoidal pulse-width modulation principle. The switching frequency is 25 kHz, the nominal battery voltage is 48 V, the output voltage is purely sinusoidal 220 V (RMS) 50 Hz, and the rated power is 1.5 kW. The inverter is modular and has an efficiency of

S. A. Pressas; V. Makios

1988-01-01

9

Sinusoidal frequency tripler using fundamental-rejecting feedback  

Microsoft Academic Search

The author presents a sinusoidal frequency tripling circuit which uses an operational transconductance amplifier (OTA) to distort the input signal and generate odd harmonics. By means of a feedback loop that rejects the fundamental of the distorted signal, the circuit produces an output signal whose frequency is three times the input frequency, and can accommodate input signals of different amplitudes.

Alexandru A. Ciubotaru

1995-01-01

10

A proposal of a pseudo-lock-in light-detection scheme by sinusoidal modulation of bias voltages applied to two dynodes in a photomultiplier tube  

Microsoft Academic Search

We propose a novel lock-in-like light-detection scheme that uses a sinusoidal modulation technique of bias voltages applied to two dynodes in a photomultiplier tube (PMT). By superimposing the sinusoidal modulation signal with a frequency f on the normal bias voltage for one of the dynodes in the PMT, we can obtain a 2f-frequency component from the output of the PMT

Tetsuo Iwata; Hisashi Ochi; Tsutomu Araki

2009-01-01

11

Frequency \\/ duty cycle control of LCC resonant converter supplying high voltage very low frequency test systems  

Microsoft Academic Search

Very low frequency (VLF) high-voltage (HV) sinusoidal test waveforms are suitable for testing characteristics and insulation qualities of long buried power cables. Unlike as with conventional PWM converters, a newly developed LCC resonant inverter combined with a symmetrical three-stage voltage multiplier rectifier is introduced in this paper to generate VLF HV sinusoidal waves. Due to the wide ranges of output

Manli Hu; Norbert Fröhleke; Joachim Böcker

2009-01-01

12

Analysis of conditions of partial discharges inception and development at non-sinusoidal testing voltages  

Microsoft Academic Search

Progress in construction of electrical insulation systems needs new investigations of partial discharges (PD) mechanisms. Working conditions and exploitation stresses, i.e. overvoltages, harmonics and other disturbances have crucial influence on arising of PD in insulation systems. Their influence on partial discharge development is different from normal conditions at nominal sinusoidal voltage. In such a cases interpretation of measurement results (by

Barbara Florkowska; Pawel Zydron

2006-01-01

13

Frequency to Voltage Converter Analog Front-End Prototype  

NASA Technical Reports Server (NTRS)

The frequency to voltage converter analog front end evaluation prototype (F2V AFE) is an evaluation board designed for comparison of different methods of accurately extracting the frequency of a sinusoidal input signal. A configurable input stage is routed to one or several of five separate, configurable filtering circuits, and then to a configurable output stage. Amplifier selection and gain, filter corner frequencies, and comparator hysteresis and voltage reference are all easily configurable through the use of jumpers and potentiometers.

Mata, Carlos; Raines, Matthew

2012-01-01

14

Event synchronous sinusoidal model based on frequency-to-instantaneous frequency mapping  

NASA Astrophysics Data System (ADS)

We describe a glottal event synchronous sinusoidal model for speech analysis and synthesis. The sinusoidal components are event synchronously estimated using a mapping from linearly spaced filter center frequencies to the instantaneous frequencies of the filter outputs. Frequency domain fixed points of this mapping correspond to the constituent sinusoidal components of the input signal. A robust technique based on a wavelet representation of this fixed points model is used for fundamental frequency extraction as used in STRAIGHT [Kawahara et al., IEICE (1999)]. The method for event detection and characterization is based on group delay and similar fixed point analysis. This method enables the detection of precise timing and spread of speech events such as vocal fold closure. A trajectory continuation scheme is also applied to the extracted sinusoidal components. The proposed model is capable of high-quality speech synthesis using the overlap-add synthesis method and is also applicable to other sound sources. System evaluation results using spectral distortion measures and mean opinion scores will be reported. A comparison with the fixed frame-rate sinusoidal models will be given.

Zolfaghari, Parham; Banno, Hideki; Itakura, Fumitada; Kawahara, Hideki

2002-05-01

15

Multilevel-Dc-Bus Inverter For Providing Sinusoidal And Pwm Electrical Machine Voltages  

DOEpatents

A circuit for controlling an ac machine comprises a full bridge network of commutation switches which are connected to supply current for a corresponding voltage phase to the stator windings, a plurality of diodes, each in parallel connection to a respective one of the commutation switches, a plurality of dc source connections providing a multi-level dc bus for the full bridge network of commutation switches to produce sinusoidal voltages or PWM signals, and a controller connected for control of said dc source connections and said full bridge network of commutation switches to output substantially sinusoidal voltages to the stator windings. With the invention, the number of semiconductor switches is reduced to m+3 for a multi-level dc bus having m levels. A method of machine control is also disclosed.

Su, Gui-Jia [Knoxville, TN

2005-11-29

16

Control of the ion flux and ion energy in CCP discharges using non-sinusoidal voltage waveforms  

NASA Astrophysics Data System (ADS)

Using particle-in-cell simulations we perform a characterization of the ion flux and ion energy in a capacitively coupled rf plasma reactor excited with non-sinusoidal voltage waveforms. The waveforms used are positive Gaussian type pulses (with a repetition frequency of 13.56 MHz), and as the pulse width is decreased, three main effects are identified that are not present in typical symmetric sinusoidal discharges: (1) the ion flux (and plasma density) rapidly increases, (2) as the pressure increases a significant asymmetry in the ion fluxes to the powered and grounded electrodes develops and (3) the average ion energy on the grounded electrode cannot be made arbitrarily small, but in fact remains essentially constant (together with the bias voltage) for the pressures investigated (20-500 mTorr). Effects (1) and (3) potentially offer a new form of control in these types of rf discharges, where the ion flux can be increased while keeping the average ion energy on the grounded electrode constant. This is in contrast with the opposite control mechanism recently identified in Donkó et al (2009 J. Phys. D: Appl. Phys. 42 025205), where by changing the phase angle between applied voltage harmonics the ion flux can be kept constant while the ion energy (and bias voltage) varies.

Lafleur, T.; Booth, J. P.

2012-10-01

17

Fast detection of amplitude and frequency of sinusoidal signals using calculus of finite differences  

Microsoft Academic Search

A novel digital method for the fast and simultaneous detection of amplitude and frequency of sinusoidal signals is presented. First and second derivatives of the input signal are evaluated numerically using the calculus of finite differences, from which the desired parameters are measured. The measurement can be accomplished using a few samples of the sinusoidal waveform; and more samples can

AHMAD I. ABU-EL-HAIJA

1986-01-01

18

ML (Maximum Likelihood) Method for Frequency Estimation of Real Sinusoids in Noise.  

National Technical Information Service (NTIS)

The DFT-based maximum likelihood method for frequency estimation of complex sinusoids as proposed in two previous articles is extended to treat the case of real data. Improvements on estimation precision and computation efficiency are obtained by imposing...

M. J. Tsai

1984-01-01

19

Sinusoidal internal model based control of a three-phase voltage source rectifier with buck-boost operation  

Microsoft Academic Search

A rectifier system having a DC voltage step-up and step-down characteristic is treated. The system consists of a PWM voltage source rectifier and a DC-to-DC buck converter connected in cascade. Theoretically, the system can produce a DC output voltage ranging from zero volts to infinity and a sinusoidal AC input current, and the displacement power factor can be kept at

Atsushi Moki; Shoji Fukuda

2003-01-01

20

Homodyne FMCW radar range resolution effects with sinusoidal nonlinearities in the frequency sweep  

Microsoft Academic Search

This paper presents analysis and simulation results describing the effects on the range resolution of linear frequency modulated continuous wave (FMCW) homodyne radar due to sinusoidal nonlinearities in the frequency sweep. Short range applications such as collision avoidance and missile seekers use homodyne FMCW radar. Good range resolution is important to target-to-clutter contrast and to support target discrimination. In FMCW

S. O. Piper

1995-01-01

21

Small-signal model and control design of LCC resonant converter with a capacitive load applied in very low frequency high voltage test system  

Microsoft Academic Search

Very low frequency (VLF) high voltage (HV) sinusoidal waveforms are suitable for testing characteristics and insulation qualities of long buried cables. Such a test generator should provide a sinusoidal voltage from some tens to hundreds of kV. A LCC resonant inverter with a three-stage symmetrical voltage multiplier rectifier is developed for this application. In this context, the contribution deals with

Manli Hu; Norbert Fröhleke; Joachim Böcker

2009-01-01

22

Sinusoidal voltage control of a single phase uninterruptible power supply by a high gain PI circuit  

Microsoft Academic Search

This paper presents analysis and design of a new control method of a single-phase voltage-source uninterruptible power supply (UPS) inverter with a high Q L-C low-pass filter. When a PWM inverter is used to feed the load, a L-C low-pass filter must be employed to eliminate the switching frequency component of output voltage harmonics. But, it may be observed that

Akira Moriyama; I. Ando; I. Takahashi

1998-01-01

23

A generalized weighted linear predictor frequency estimation approach for a complex sinusoid  

Microsoft Academic Search

Based on linear prediction and weighted least squares, three simple iterative algorithms for frequency estima- tion of a complex sinusoid in additive white noise are devised. The proposed approach, which utilizes the first-order as well as higher order linear prediction terms simultaneously but does not require phase unwrapping, can be considered as a generalized version of the weighted linear predictor

Hing-cheung So; Frankie K. W. Chan

2006-01-01

24

The use of sinusoidal frequency modulated pulses for low-Doppler detection  

Microsoft Academic Search

This paper describes in-water testing of the reverberation gain achievable with broadband, Doppler sensitive sinusoidal frequency modulated (SFM) transmissions. Theoretical predictions via the Q-function are compared to experimental results in shallow water using static and moving sonar platforms. The coherence of target echoes is examined through the use of an echo-repeater

S. Ward

2001-01-01

25

Estimation of the frequencies of a complex sinusoidal noisy signal using fourth order statistics  

Microsoft Academic Search

The problem of estimating the frequencies of a complex sinusoidal signal corrupted by a correlated Gaussian noise is dealt with using the fourth order statistics. A definition of the complex fourth order statistics is introduced. A fourth order moments matrix, M4, and a fourth order cumulant matrix, C4, are defined. In the general case of a nonGaussian signal corrupted by

A. Ferrari; G. Alengrin

1991-01-01

26

Statistical analysis of MUSIC and subspace rotation estimates of sinusoidal frequencies  

Microsoft Academic Search

Consideration is given to the analysis of the large-sample second-order properties of multiple signal classification (MUSIC) and subspace rotation (SUR) methods, such as ESPRIT, for sinusoidal frequency estimation. Explicit expressions for the covariance elements of the estimation errors associated with either method are derived. These expressions of covariances are then used to analyze and compare the statistical performances of the

Petre Stoica; Torsten Soderstrom

1991-01-01

27

MODELIZATION AND STABILITY OF AN ASYNCHRONOUS MOTOR DRIVE SUPPLIED AT CONSTANT FREQUENCY AND VOLTAGE  

Microsoft Academic Search

A new variable speed drive system is defined with a three phase cage asynchronous motor fed by normal sinusoidal supply at constant frequency and voltage through line series constant capacitors and parallel thyristor half-bridge. The variable motor voltage is controlled by the SCRs which produce zero sequence component.This very simple drive is of lower cost than inverter ones but the

A. JAMMAL; G. GRELLET

1989-01-01

28

Voltage regulation using dynamic voltage restorer for large frequency variations  

Microsoft Academic Search

The paper discusses the voltage regulation of a critical load bus using a dynamic voltage restorer (DVR) in a distribution system. The critical load cannot tolerate any power quality (PQ) disturbance including large frequency variations occurring in the system. The DVR is operated such that it holds the voltage across the critical load bus terminals constant at system nominal frequency

Amit Kumar Jindal; Arindam Ghosh; Avinash Joshi

2005-01-01

29

Sinusoidal Horns.  

National Technical Information Service (NTIS)

It is shown theoretically that the sinusoid satisfies Salmon's criteria for a good horn shape. It is also shown theoretically that a sinusoidal horn will effect impedance transformation and experimentally that it enhances the directivity of an underwater ...

B. N. Nagarkar R. D. Finch

1969-01-01

30

An amorphous alloy core medium frequency magnetic-link for medium voltage photovoltaic inverters  

NASA Astrophysics Data System (ADS)

The advanced magnetic materials with high saturation flux density and low specific core loss have led to the development of an efficient, compact, and lightweight multiple-input multiple-output medium frequency magnetic-link. It offers a new route to eliminate some critical limitations of recently proposed medium voltage photovoltaic inverters. In this paper, a medium frequency magnetic-link is developed with Metglas amorphous alloy 2605S3A. The common magnetic-link generates isolated and balanced multiple DC supplies for all of the H-bridge inverter cells of the medium voltage inverter. The design and implementation of the prototype, test platform, and the experimental test results are analyzed and discussed. The medium frequency non-sinusoidal excitation electromagnetic characteristics of alloy 2605S3A are also compared with that of alloy 2605SA1. It is expected that the proposed new technology will have great potential for future renewable power generation systems and smart grid applications.

Rabiul Islam, Md.; Guo, Youguang; Wei Lin, Zhi; Zhu, Jianguo

2014-05-01

31

Pseudo-Lock-in Light Detection Method for a Sinusoidally-Gain-Modulated Photomultiplier Tube  

Microsoft Academic Search

In order to detect a weak signal varied in an intensive background light, we propose a novel pseudo-lock-in light detection scheme used for a photomultiplier tube (PMT) whose gain is modulated sinusoidally. Let the signal light incident on the PMT be modulated sinusoidally at a frequency f. In this situation, one of the dynode voltages applied for the PMT is

Tetsuo Iwata; Takafumi Inoue; Tsutomu Araki

2004-01-01

32

Telecom-band single-photon detection with a gigahertz repetition frequency using a sinusoidally gated avalanche photodiode  

NASA Astrophysics Data System (ADS)

Single-photon detection at 1550 nm with a high repetition rate was realized using an InGaAs/InP avalanche photodiode operated with a sinusoidal gating. Removing the AC noise due to the transferred gate signal by use of band elimination filters, it is realized to detect much smaller avalanche signals than that in the conventional gating scheme, which results in the suppression of the afterpulsing. Finally, we achieved the detection efficiency of 11.0%, the dark count probability per gate of 7.7×10-7, and the afterpulsing probability was 3.3% at the repetition frequency of 1.2 GHz and the APD operating temperature of -50 degrees Celsius.

Adachi, S.; Namekata, N.; Inoue, S.

2009-04-01

33

Quartz crystal microbalance based on passive frequency to voltage converter.  

PubMed

In dynamics of evaporation or drying of microdrops from a solid surface, a faster and precise quartz crystal microbalance (QCM) is needed. The fast QCM based on frequency to voltage converter is an attractive and powerful tool in the investigation of the dynamic regime of evaporation to translate the frequency shift in terms of a continuous voltage change. The frequency shift monitoring in fast QCM applications is a real challenge for electronic processing interface. Originally developed as a frequency shift processing interface, this novel passive frequency to voltage converter can produce faster, stable, and accurate results in regard to the QCM sensor behavior. In this article, the concept and circuit of passive frequency to voltage converter will be explained followed by static and dynamic characterization. Experimental results of microdrops evaporation will be given. PMID:22380125

Burda, Ioan; Tunyagi, Arthur

2012-02-01

34

BIOLOGICAL INFLUENCES OF LOW-FREQUENCY SINUSOIDAL ELECTROMAGNETIC SIGNALS ALONE AND SUPERIMPOSED ON RF CARRIER WAVES  

EPA Science Inventory

The report describes in a historical context the experiments that have been performed to examine the biological responses caused by exposure to low frequency electromagnetic radiation directly or as modulation of RF carrier waves. A detailed review is provided of the independentl...

35

Sinusoidal Representation of Acoustic Signals  

NASA Astrophysics Data System (ADS)

Sinusoidal representation of acoustic signals has been an important tool in speech and music processing like signal analysis, synthesis and time scale or pitch modifications. It can be applicable to arbitrary signals, which is an important advantage over other signal representations like physical modeling of acoustic signals. In sinusoidal representation, acoustic signals are composed as sums of sinusoid (sine wave) with different amplitudes, frequencies and phases, which is based on the timedependent short-time Fourier transform (STFT). This article describes the principles of acoustic signal analysis/synthesis based on a sinusoid representation with focus on sine waves with rapidly varying frequency.

Honda, Masaaki

36

A PWM CSI-based vector controlled medium voltage AC drive with sinusoidal input and output waveforms  

Microsoft Academic Search

A vector controlled medium voltage AC motor drive is proposed in this paper which is based on a current source topology consisting of a PWM GTO current source inverter (CSI) as the output connected to the motor and a two-module PWM GTO current source rectifier (CSR) as the front end. The output inverter is operated with selective harmonic elimination (SHE)

Navid Zargari; Yuan Xiao; Bin Wu

1997-01-01

37

High-speed frequency-to-voltage converter  

SciTech Connect

A high-speed frequency-to-voltage converter for use in an automated system to study engines is described. The converter has an input impedance of 10 k omega, an input voltage of 0.1-10 V, and an output voltage of 0-10 V for a load impedance of greater than or equal to 2 k omega. The range of measurable shaft speeds is 0-4095 rpm in steps of 1 rpm, which corresponds to input-pulse frequencies of 0-68.25 Hz. The main normalized error is less than or equal to 0.5%. Speed can be displayed beyond the conversion range. The converter is implemented by integrated circuits of series K155. The supply voltages are +/- 15 and + 5 V.

Gryzov, S.N.; Chistyakov, V.K.; Pesotskii, Yu.S.

1987-08-01

38

Implementation of sinusoidal PWM technique for AC-AC matrix converter using PSIM  

Microsoft Academic Search

Matrix Converter is a single stage AC- AC converter. It can directly convert an ac power supply of fixed voltage into an ac voltage of variable amplitude and frequency. The matrix converters can contribute to the realization of low volume, sinusoidal input current, bidirectional power flow and lack of bulky reactive elements . Due to all these reasons, recently a

Satya Sahitya Sekhar Nuka; R. Saravana Kumar

2011-01-01

39

Evaluation of high-frequency sinusoidal waveform superposed with 3rd harmonic for stable operation of metal halide lamps  

Microsoft Academic Search

In this paper a novel topology to supply MH lamps using sinusoidal waveform with superposed third harmonic is proposed. By employing this technique, the lamp is supplied with an approximated square waveform, but reducing the harmonic content and therefore EMI and RFI. The proposed topology is analyzed and designed for a 35 W MH lamp with ceramic discharge tube. Experimental

J. M. Alonso; J. Ribas; M. Rico-Secades; J. Garcia; J. Cardesin

2002-01-01

40

Capacitively coupled radio-frequency plasmas excited by tailored voltage waveforms  

NASA Astrophysics Data System (ADS)

By applying certain types of ‘tailored’ voltage waveforms (TVWs) to capacitively coupled plasmas, a dc self-bias and an asymmetric plasma response can be produced, even in geometrically symmetric reactors. Furthermore, these arbitrary applied waveforms can produce a number of interesting phenomena that are not present in typical single-frequency sinusoidal discharges. This electrical asymmetry effect presents emerging possibilities for the improved control of the ion energy and ion flux in these systems; parameters of vital importance to both etching and deposition applications for materials processing. With a combined research approach utilizing both experimental measurements, and particle-in-cell simulations, we review and extend recent investigations that study a particular class of TVW. The waveforms used have a pulse-type shape and are composed of a varying number of harmonic frequencies. This allows a strong self-bias to be produced, and causes most of the applied voltage to be dropped across a single sheath. Additionally, decreasing the pulse width (by increasing the number of harmonics), allows the plasma density and ion flux to be increased. Simulation and experimental results both demonstrate that this type of waveform can be used to separately control the ion flux and ion energy, while still producing a uniform plasma over large area (50 cm diameter) rf electrodes.

Lafleur, T.; Delattre, P. A.; Johnson, E. V.; Booth, J. P.

2013-12-01

41

Analytical and computational investigations of airfoils undergoing high-frequency sinusoidal pitch and plunge motions at low Reynolds numbers  

NASA Astrophysics Data System (ADS)

Current interests in Micro Air Vehicle (MAV) technologies call for the development of aerodynamic-design tools that will aid in the design of more efficient platforms that will also have adequate stability and control for flight in gusty environments. Influenced largely by nature MAVs tend to be very small, have low flight speeds, and utilize flapping motions for propulsion. For these reasons the focus is, specifically, on high-frequency motions at low Reynolds numbers. Toward the goal of developing design tools, it is of interest to explore the use of elementary flow solutions for simple motions such as pitch and plunge oscillations to predict aerodynamic performance for more complex motions. In the early part of this research, a validation effort was undertaken. Computations from the current effort were compared with experiments conducted in a parallel, collaborative effort at the Air Force Research Laboratory (AFRL). A set of pure-pitch and pure-plunge sinusoidal oscillations of the SD7003 airfoil were examined. Phase-averaged measurements using particle image velocimetry in a water tunnel were compared with computations using two flow solvers: (i) an incompressible Navier-Stokes Immersed Boundary Method and (ii) an unsteady compressible Reynolds-Averaged Navier-Stokes (RANS) solver. The motions were at a reduced frequency of k = 3.93, and pitch-angle amplitudes were chosen such that a kinematic equivalence in amplitudes of effective angle of attack (from plunge) was obtained. Plunge cases showed good qualitative agreement between computation and experiment, but in the pitch cases, the wake vorticity in the experiment was substantially different from that predicted by both computations. Further, equivalence between the pure-pitch and pure-plunge motions was not attained through matching effective angle of attack. With the failure of pitch/plunge equivalence using equivalent amplitudes of effective angle of attack, the effort shifted to include pitch-rate and wake-effect terms through the use of analytical methods including quasi-steady thin-airfoil theory (QSTAT) and Theodorsen's theory. These theories were used to develop three analytical approaches for determining pitch motions equivalent to plunge motions. A study of variation in plunge height was then examined and followed by a study of the effect of rotation point using the RANS solver. For the range of plunge heights studied, it was observed that kinematic matching between plunge and pitch using QSTAT gave outstanding similarities in flow field, while the matching performed using Theodorsen's theory gave the best equivalence in lift coefficients for all cases. The variation of rotation point revealed that, for the given plunge height, with rotation point in front of the mid-chord location, all three schemes matched flow-field vorticity well, and with rotation point aft of the mid-chord no scheme matched vorticity fields. However, for all rotation points (except for the mid-chord location), CFD prediction of lift coefficients from the Theodorsen matching scheme matched the lift time histories closely to CFD predictions for pure-pitch. Combined pitch and plunge motions were then examined using kinematic parameters obtained from the three schemes. The results showed that QSTAT nearly cancels the vortices emanating from the trailing edge. Theodorsen's matching approach was successful in generating a lift that was close to constant over the entire cycle. Additionally this approach showed the presence of the reverse Karman vortex sheet through the wake. Combined pitch/plunge motions were then analyzed, computationally and experimentally, with a non-zero mean angle of attack. All computational results compared excellently with experiments, capturing vorticity production on the airfoil's surface and through the wake. Lift coefficient through a cycle was shown to tend toward a constant using Theodorsen's parameters, with the constant being dependent on the initial angle of attack. This result points to the possibility of designing an unsteady motion to match a given flig

McGowan, Gregory Z.

42

Studies on the dielectric strength of oil-polymer composite insulation under variable frequency AC voltages  

Microsoft Academic Search

Breakdown characteristics of silicone oil-polyethylene composite insulation under ac voltages at different frequencies were studied using a needle-plane electrode system. Higher breakdown voltages have been observed with LDPE film as a barrier than those with oil alone for frequencies below power frequency. The breakdown voltage decreased with increased frequency with film, whereas, with oil alone, no such frequency effect was

M. Nagao; S. Jayararn; M. Sugio; E. P. Waldi

1999-01-01

43

Time dependent behaviors of ion-ion plasmas exposed to various voltage waveforms in the kilohertz to megahertz frequency range  

SciTech Connect

An ion-ion plasma, situated between two parallel electrodes, is studied with the use of a time dependent one-dimensional particle-in-cell Monte-Carlo collisions model. This plasma consists of only positively and negatively singly charged ions with the same order of mass and temperature (the electron density is zero). The right electrode is grounded, and the left electrode is biased with a voltage waveform varying from sinusoidal to square with the frequency in the kHz to MHz range. The sheath evolution and the particle flux towards the electrodes, as a function of both space and time, are investigated for the various waveforms and frequencies. The sheath evolution has a strong influence on the time averaged ion energy distribution function (IEDF). The IEDF is broad with a low energy tail for low frequency sinusoidal biases (25 kHz) while peaked at low energy for higher frequencies (2 MHz). For square waveforms, the IEDF is mono-energetic with some broadening when the rise time is faster than the typical time to establish the steady state sheath formation (<0.3 {mu}s).

Oudini, N.; Raimbault, J.-L.; Chabert, P.; Aanesland, A. [Laboratoire de Physique des Plasmas, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Garrigues, L. [LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, UPS, INPT Toulouse, 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France); Meige, A. [PRESANS/X-Technologies/Ecole Polytechnique, 91128 Palaiseau Cedex (France)

2012-10-15

44

Instantaneous Symmetrical Component Theory Based Voltage and Frequency Controller for Isolated Small Hydropower Generation  

Microsoft Academic Search

This article deals with the design and implementation of an instantaneous sequence component theory based integrated voltage and frequency controller for an isolated asynchronous generator, which is used in constant power small hydropower generation for feeding three-phase four-wire consumer loads. The proposed integrated voltage and frequency controller is used to control the voltage and frequency of an isolated asynchronous generator

V. Rajagopal; Bhim Singh

2011-01-01

45

Sinusoidal transform coding  

NASA Technical Reports Server (NTRS)

It has been shown that an analysis/synthesis system based on a sinusoidal representation of speech leads to synthetic speech that is essentially perceptually indistinguishable from the original. Strategies for coding the amplitudes, frequencies and phases of the sine waves have been developed that have led to a multirate coder operating at rates from 2400 to 9600 bps. The encoded speech is highly intelligible at all rates with a uniformly improving quality as the data rate is increased. A real-time fixed-point implementation has been developed using two ADSP2100 DSP chips. The methods used for coding and quantizing the sine-wave parameters for operation at the various frame rates are described.

Mcaulay, Robert J.; Quatieri, Thomas F.

1988-01-01

46

Distribution bus voltage control using DVR under the supply frequency variations  

Microsoft Academic Search

This paper discusses a frequency estimation strategy that, when used in conjunction with dynamic voltage restorer (DVR), can hold the magnitude of any distribution bus voltage constant as the supply frequency varies. First the impact of supply frequency variation on the performance of a DVR is illustrated. It has been shown that if a DC battery supplies the DVR, the

Monika Chawla; A. Rajvanshy; A. Ghosh; A. Joshi

2006-01-01

47

Automatic frequency control of voltage-controlled oscillators  

NASA Technical Reports Server (NTRS)

Optical-capacitive coupling is used for isolation of control voltages, such as the high-voltage level of a klystron control electrode that is not referenced to ground, to serve as error voltages referenced to system ground so that the magnitude and sense of correction may be transferred.

Kolbly, R. B.

1969-01-01

48

A new type of the VLF high voltage generator  

Microsoft Academic Search

The purpose of this paper is about a new design and construction of a very low frequency (VLF) high voltage generator. The VLF generates a sinusoidal waveform at 0.1 Hz. It consists of two main parts, a modulation unit and a high voltage switching unit. The modulation unit is compared the 0.1 Hz sinusoidal waveform and the 10 kHz triangular

S. Seesanga; W. Kongnun; A. Sangswang; S. Chotigo

2008-01-01

49

A Voltage-Frequency Island Aware Energy Optimization Framework for Networks-on-Chip  

Microsoft Academic Search

In this paper, we present a partitioning, mapping, routing and interface optimization framework for energy-effi- cient voltage-frequency island (VFI) based networks-on-chip. Unlike the recent work that performs tile partitioning only with voltage-frequency assignment for a given mesh network layout, our framework consists of three key VFI-aware components, i.e., VFI-aware core partitioning with voltage and frequency assignment, VFI-aware mapping, and VFI-aware

Wooyoung Jang; David Z. Pan

2011-01-01

50

Systems and methods for process and user driven dynamic voltage and frequency scaling  

DOEpatents

Certain embodiments of the present invention provide a method for power management including determining at least one of an operating frequency and an operating voltage for a processor and configuring the processor based on the determined at least one of the operating frequency and the operating voltage. The operating frequency is determined based at least in part on direct user input. The operating voltage is determined based at least in part on an individual profile for processor.

Mallik, Arindam (Evanston, IL); Lin, Bin (Hillsboro, OR); Memik, Gokhan (Evanston, IL); Dinda, Peter (Evanston, IL); Dick, Robert (Evanston, IL)

2011-03-22

51

Fringe projection with a sinusoidal phase grating.  

PubMed

Phase-shifting profilometry requires projection of sinusoidal fringes on a 3D object. We analyze the visibility and frequency content of fringes created by a sinusoidal phase grating at coherent illumination. We derive an expression for the intensity of fringes in the Fresnel zone and measure their visibility and frequency content for a grating that has been interferometrically recorded on a holographic plate. Both evaluation of the systematic errors due to the presence of higher harmonics by simulation of a profilometric measurement and measurement of 3D coordinates of test objects confirm the good performance of the sinusoidal phase grating as a projective element. In addition, we prove theoretically that in comparison with a sinusoidal amplitude grating this grating produces better quality of fringes in the near-infrared region. Sinusoidal phase gratings are fabricated easily, and their implementation in fringe projection profilometry facilitates construction of portable, small size, and low-cost devices. PMID:19696868

Stoykova, Elena; Minchev, Georgi; Sainov, Ventseslav

2009-08-20

52

A high voltage-high frequency SOS\\/CMOS pulse generator  

Microsoft Academic Search

A high voltage, high frequency CMOS pulse generator circuit for high voltage driver applications is proposec and its excellent performance is verified experimentally using an integrated circuit on an SOS (Silicon On Sapphire) wafer. The circuit basically consists of a high voltage CMO5 inverter with a \\

T. Suzuki; T. Kuriyama; H. Sakuma

1980-01-01

53

Effect of bias voltage on the frequency response of point contact Josephson radiation detectors  

Microsoft Academic Search

The variation with bias voltage of the video response of superconducting point contacts to high microwave frequencies has been measured by Fourier transform spectroscopy. The signal polarity was observed to reverse at the Josephson frequency, confirming other recent results.

T. G. Blaney

1971-01-01

54

Zero voltage switching approach for flyback converter  

Microsoft Academic Search

A zero voltage switched flyback power converter which realizes soft switching for every semiconductor is proposed. The sinusoidal resonant current flows through the secondary side rectifier diode and zero current switching of the diode is realized. Diode recovery is not generated. The proposed converter can operate with constant frequency pulse width modulation. High frequency switching and low noise are achieved

K. Yoshida; T. Ishii; N. Nagagata

1992-01-01

55

Lower operation voltage in dual-frequency cholesteric liquid crystals based on the thermodielectric effect.  

PubMed

Dual-frequency cholesteric liquid crystal (DFCLC) devices characteristically require high operation voltage, which hinders their further development in thin-film-transistor driving. Here we report on a lower-voltage switching method based on the thermodielectric effect. This technique entails applying a high-frequency voltage to occasion dielectric oscillation heating so to induce the increase in crossover frequency. The subsequent change in dielectric anisotropy of the DFCLC allows the switching, with a lower operation voltage, from the planar state to the focal conic or homeotropic state. The temperature rise incurred by the dielectric heating is described. PMID:24104303

Hsiao, Yu-Cheng; Lee, Wei

2013-10-01

56

Life estimation of water tree deteriorated XLPE cables by VLF (very low frequency) voltage withstand test  

Microsoft Academic Search

The authors investigated a new life estimation method for service-aged, water tree deteriorated 22-77 kV XLPE cables by voltage withstand test. At first, they selected more suitable waveform for testing voltage from damped oscillating wave (OSW) and very low frequency wave (VLF) voltage as the instead of AC and DC. It was found that VLF voltage has high ability to

Katsumi Uchida; Masahiko Nakade; Daisuke Inoue; Hiroyuki Sakakibara; Masashi Yagi

2002-01-01

57

Development of a high frequency and high-voltage pulse transformer for a TWT HVPS  

Microsoft Academic Search

A pulse transformer for a high frequency and high voltage operation had been designed, fabricated, and tested. The high frequency operation of the pulse transformer increases power density. Therefore, it is possible to reduce power supply volume. To produce high voltage output, the transformer should have a high step-up ratio. The step-up ratio is generally limited in pulse transformers due

S. C. KimS; S. H. Nam; H. M. Keon; D. S. Park

2003-01-01

58

Parallel Dynamic Voltage and Frequency Scaling for stream decoding using a multicore embedded system  

Microsoft Academic Search

Parallel structures may be used to increase a system processing speed in case of large amount of data or highly complex calculations. Dynamic Voltage and Frequency Scaling (DVFS) may be used for simpler calculations in order to decrease the system voltage or frequency and achieve lower power consumption. Combining these two mechanisms may lead to higher efficiency and lower power

Ying-Xun Lai; Yueh-Min Huang; Chin-Feng Lai; Ljiljana Trajkovic

2011-01-01

59

Investigation of Frequency\\/AC Voltage Control for Inverter Station of VSC-HVDC  

Microsoft Academic Search

In this paper, the frequency and AC voltage control for the inverter station of a VSC-HVDC is investigated when supplying an industrial system that consists of static loads, synchronous and induction motors. The idea of the proposed control strategy is to exploit the rotating masses kinetic energy by slightly decreasing the frequency of the VSC output voltage to ride through

Cuiqing Du; Evert Agneholm

2006-01-01

60

Adaptive, Transparent Frequency and Voltage Scaling of Communication Phases in MPI Programs  

Microsoft Academic Search

Although users of high-performance computing are most interested in raw performance, both energy and power consumption have become critical concerns. Some microprocessors allow frequency and voltage scaling, which enables a system to reduce CPU performance and power when the CPU is not on the critical path. When properly directed, such dynamic frequency and voltage scaling can produce significant energy savings

Min Yeol Lim; Vincent W. Freeh; David K. Lowenthal

2006-01-01

61

MPI and communication - Adaptive, transparent frequency and voltage scaling of communication phases in MPI programs  

Microsoft Academic Search

Although users of high-performance computing are most interested in raw performance, both energy and power consumption have become critical concerns. Some microprocessors allow frequency and voltage scaling, which enables a system to reduce CPU performance and power when the CPU is not on the critical path. When properly directed, such dynamic frequency and voltage scaling can produce significant energy savings

Min Yeol Lim; Vincent W. Freeh; David K. Lowenthal

2006-01-01

62

Modulation linearization of a frequency-modulated voltage controlled oscillator, part 3  

NASA Technical Reports Server (NTRS)

An analysis is presented for the voltage versus frequency characteristics of a varactor modulated VHF voltage controlled oscillator in which the frequency deviation is linearized by using the nonlinear characteristics of a field effect transistor as a signal amplifier. The equations developed are used to calculate the oscillator output frequency in terms of pertinent circuit parameters. It is shown that the nonlinearity exponent of the FET has a pronounced influence on frequency deviation linearity, whereas the junction exponent of the varactor controls total frequency deviation for a given input signal. A design example for a 250 MHz frequency modulated oscillator is presented.

Honnell, M. A.

1975-01-01

63

Position and Speed Estimation of Maglev Train Based on High-frequency Voltage Signal Injection Method  

Microsoft Academic Search

In this paper high-frequency voltage signal injection method was applied based on the machine-saliencies of linear synchronous motor used by maglev train. Three-phase symmetrical high-frequency voltage signals was added to the system before SVPWM regulator, which produced high-frequency current signals containing positive component and negative component. The negative current component included position and velocity signals of the mover of the

Guirong Wang; Hong Xu; Wei Wei

2007-01-01

64

Dynamic frequency and voltage control for a multiple clock domain microarchitecture  

Microsoft Academic Search

We describe the design, analysis, and performance of an on--line algorithm to dynamically control the frequency\\/voltage of a Multiple Clock Domain (MCD) microarchitecture. The MCD microarchitecture allows the frequency\\/voltage of microprocessor regions to be adjusted independently and dynamically, allowing energy savings when the frequency of some regions can be reduced without significantly impacting performance.Our algorithm achieves on average a 19.0%

Greg Semeraro; David H. Albonesi; Steven G. Dropsho; Grigorios Magklis; Sandhya Dwarkadas; Michael L. Scott

2002-01-01

65

A novel scheme for testing radio frequency voltage controlled oscillators  

Microsoft Academic Search

In this paper, a novel scheme for testing LC-tank CMOS Voltage Controlled Oscillators (VCOs) is presented. The proposed test circuit is capable of detecting soft and hard faults in a percentage that can guarantee safe overall fault coverage. It has been realized that the proposed technique is capable of detecting open and short circuits as well as process variations outside

L. Dermentzoglou; Yiorgos Tsiatouhas; Aggeliki Arapoyanni

2003-01-01

66

Frequency Transition Phenomenon of Self-Oscillated Micro-Cantilever by Changing Driving Voltage  

Microsoft Academic Search

We have found an interesting phenomenon of self-excited oscillation of electrostatic microcantilever; the device was found to be self-oscillated under an applied dc voltage, by repeating charge and discharge between the fixed and the movable electrodes. Oscillation frequency is changed by changing apply dc voltage. The phenomenon can be used to make a MEMS version of voltage-controlled oscillator (VCO) for

Makoto Mita; Manabu Ataka; Tadashi Ishida; Hiroyuki Fujita; H. Toshiyosh

2007-01-01

67

Voltage pulse frequency and duty ratio effects in an electrochemical discharge microdrilling process of Pyrex glass  

Microsoft Academic Search

Electrochemical discharge machining (ECDM) is used to microdrill glass wafers. One of the drawbacks of ECDM is the heat-affected zone (HAZ) left on the microdrilled hole surface. To reduce the HAZ, a series of rectangular voltage pulses, were applied in this study instead of the rectified or full-wave DC voltages. The effect of the frequency and duty ratio of the

Dae-Jin Kim; Yoomin Ahn; Seoung-Hwan Lee; Yong-Kweon Kim

2006-01-01

68

High power density, high frequency, and high voltage pulse transformer  

Microsoft Academic Search

Summary form only given, as follows. In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power

S. C. Kim; S. H. Nam; D. T. Kim

2001-01-01

69

High power density, high frequency, and high voltage pulse transformer  

Microsoft Academic Search

In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power supply. However, a step-up ratio of

S. C. Kim; S. H. Nam; S. H. Kim; D. T. Kim; S. H. Jeong

2001-01-01

70

A voltage-frequency island aware energy optimization framework for networks-on-chip  

Microsoft Academic Search

In this paper, we present a partitioning, mapping, and routing optimization framework for energy-efficient VFI (Voltage-Frequency Island) based Network-on-Chip. Unlike the recent work (10) which only performs partitioning together with voltage-frequency assignment for a given mesh network layout, our framework consists of three key VFI-aware components, i.e., VFI-aware partitioning, VFI-aware mapping, and VFI-aware routing. Thus our technique effectively reduces VFI

Wooyoung Jang; Duo Ding; David Z. Pan

2008-01-01

71

A Voltage-Frequency Island aware energy optimization framework for networks-on-chip  

Microsoft Academic Search

In this paper, we present a partitioning, mapping, and routing optimization framework for energy-efficient VFI (voltage-frequency island) based network-on-chip. Unlike the recent work [10] which only performs partitioning together with voltage-frequency assignment for a given mesh network layout, our framework consists of three key VFI-aware components, i.e., VFI-aware partitioning, VFI-aware mapping, and VFI-aware routing. Thus our technique effectively reduces VFI

Wooyoung Jang; Duo Ding; David Z. Pan

2008-01-01

72

Singleloop vs two-loop voltage and frequency control of isolated SEIG based RECS  

Microsoft Academic Search

Present investigation deals with the comparison of performance of a Generalized Impedance Controller (GIC) based 3-phase self excited induction generator (SEIG) terminal voltage and frequency regulator, having single and two-loop control, in an isolated wind\\/microhydro type renewable energy conversion system (RECS). Where, GIC is a PWM voltage source converter with dc-bus battery, having controlled four-quadrant equivalent impedance. Amplitude and frequency

J. K. Chatterjee; Priyesh J. Chauhan

2011-01-01

73

Frame-based dynamic voltage and frequency scaling for a MPEG decoder  

Microsoft Academic Search

This paper describes a dynamic voltage and frequency scaling (DVFS) technique for MPEG decoding to reduce the energy consumption while maintaining a quality of servic(QoS) constraint. The computational workload for an incoming frame is predicted using a frame-based history so that the processor voltage and frequency can be scaled to provide the exact amount of computing power needed to decode

Kihwan Choi; Karthik Dantu; Wei-Chung Cheng; Massoud Pedram

2002-01-01

74

Low-frequency switching voltage regulators for terrestrial photovoltaic systems  

NASA Technical Reports Server (NTRS)

The photovoltaic technology project and the stand alone applications project are discussed. Two types of low frequency switching type regulators were investigated. The design, operating characteristics and field application of these regulators is described. The regulators are small in size, low in cost, very low in power dissipation, reliable and allow considerable flexibility in system design.

Delombard, R.

1984-01-01

75

Sinusoidal Current-Tracking Control for Utility Interactive Inverter with an LCL Filter  

NASA Astrophysics Data System (ADS)

A voltage source inverter with an LCL filter is often used for a utility interface to control its output current to a grid side because of its harmonic reduction advantages. The integral compensator is often used to reduce the steady-state errors. However, there is always a control delay due to sinusoidal variations. This paper proposes a digital sinusoidal compensator which is based on the internal model principle to realize a fast sinusoidal response with no delay. It is based on the internal model principle to realize a response with no deviation for a periodic sinusoidal reference input. It has a simple numerator and a denominator z2-2zcos?T +1 of a transfer function which is equal to the z function of a sinusoidal waveform of the angular frequency ? and the sample time T. Compensator and feedback gains of the inverter are determined by the dead-beat or the optimal control principle. The proposed method is investigated for performances and it is validated through simulation and experimental results by a DSP control system.

Kato, Toshiji; Inoue, Kaoru; Donomoto, Yoshihisa

76

Dead Beat Microprocessor Control of PWM Inverter for Sinusoidal Output Waveform Synthesis  

Microsoft Academic Search

A new control technique based on dead beat control theory to obtain a nearly sinusoidal PWM inverter output voltage is described. The closed-loop digital feedback system measures the output and controls the inverter switches to generate the required pulsewidth-modulated (PWM) pattern to produce low total harmonic distortion (THD) sinusoidal output voltage. This scheme inherently provides very good voltage regulation, phase

Kalyan P. Gokhale; Atsuo Kawamura; Richard G. Hoft

1987-01-01

77

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment  

NASA Astrophysics Data System (ADS)

We have developed a senior undergraduate experiment that illustrates frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique is commonly applied to stabilize lasers at optical frequencies. By using only radio-frequency equipment, it is possible to systematically study aspects of the technique more thoroughly, inexpensively, and free from eye hazards. Students also learn about modular radio-frequency electronics and basic feedback control loops. By varying the temperature of the resonator, students can determine the thermal expansion coefficients of copper, aluminum, and super invar.

Liekhus-Schmaltz, C. E.; Martin, J. D. D.

2012-03-01

78

Microchip design for a low-frequency Josephson-array voltage standard  

Microsoft Academic Search

The complexity of the Josephson array voltage standard can be reduced by using lower-frequency microwaves to excite the junction array. For operation at reduced frequencies, the design of the array must take the large size of the junctions, and the perturbing effect of the junction reactance on the distribution of microwave power into account. Such issues are especially important when

W. F. Avrin; M. B. Simmonds; C. A. Hamilton

1991-01-01

79

Improvement in ozone generation with low voltage high frequency power converters  

Microsoft Academic Search

This paper proposes a low voltage, high frequency power converters to produce ozone gas in atmospheric pressure. The ozone chamber is made of a dielectric barrier discharge (DBD) chamber using perforated electrodes sheet and insulation material which has lower dielectric breakdown. The power converter is an isolated high frequency inverter with resonance at the secondary of the transformer. This converter

Mochammad Facta; Zainal Salam; Awang Jusoh; Zolkafle Bin Buntat

2008-01-01

80

Frequency stabilization of a GaAIAs semiconductor laser by voltage control.  

PubMed

A single-mode GaAlAs laser is frequency stabilized by keeping the injection current and the voltage across the laser constant. A long-term frequency stability of 7 x 10(-8) and a reproducibility of 3 x 10(-7) were obtained. PMID:20725295

Ludvigsen, H; Holmilund, C; Ikonen, E; Junttila, M L

1992-06-20

81

Variable speed constant frequency constant voltage alternator. Annual report  

SciTech Connect

A test alternator is operated with digital control of its output frequency for variable shaft speed. The machine is a two-pole alternator with power removed through slip rings. The output frequency of the alternator is controlled by rotating the field by stepping through sixteen coils around the rotor. Usually four coils are active at one time. The rotating field in the stationary coils of the stator is controlled by microcircuits. The control circuits are constructed with available low-cost, low-power integrated circuits (ICs). The test results from the first test alternator indicate the feasibility of using this type of alternator to convert available wind power directly to usable 60 hertz power.

Grannemann, W.W.; Yang, C.E.; Seo, P.H.

1980-07-01

82

Sinusoids: Applications and Modeling  

NSDL National Science Digital Library

This demo actively involves students via the software simulations so that the determination of the sinusoidal model has a geometric flavor that complements the algebraic tools stressed in texts. This approach also introduces a modeling aspect since in some situations we may only be able to obtain a "close" approximation to the actual curve or data. Animations and Excel routines are included.

Roberts, Lila F.; Hill, David R.

2004-07-21

83

Development of Low-Frequency AC Voltage Measurement System Using Single-Junction Thermal Converter  

NASA Astrophysics Data System (ADS)

Accurate measurement of low-frequency AC voltage using a digital multimeter at frequencies of 4-200Hz is a challenge in the mechanical engineering industry. At the National Metrology Institute of Japan, we developed a low-frequency AC voltage measurement system for calibrating digital multimeters operating at frequencies down to 1 Hz. The system uses a single-junction thermal converter and employs a theoretical model and a three-parameter sine wave fitting algorithm based on the least-square (LS) method. We calibrated the AC voltage down to 1Hz using our measurement system and reduced the measurement time compared with that using thin-film thermal converters. Our measurement results are verified by comparison with those of a digital sampling method using a high-resolution analog-to-digital converter; our data are in agreement to within a few parts in 105. Our proposed method enables us to measure AC voltage with an uncertainty of 25 ?V/V (k = 1) at frequencies down to 4 Hz and a voltage of 10 V.

Amagai, Yasutaka; Nakamura, Yasuhiro

84

Frequency and voltage dependence of glow and pseudoglow discharges in helium under atmospheric pressure  

Microsoft Academic Search

The pseudoglow and glow discharge behavior of a 0.5-mm metallic-dielectric electrode gap in helium under atmospheric pressure was examined as a function of ac voltage between 0.3 and 32 kHz. The number of discharge current pulses per half-cycle within the pseudoglow was found to diminish with rising frequency, as opposed to the increase observed with rising voltage. The reduction in

Ion Radu; Ray Bartnikas; Michael R. Wertheimer

2003-01-01

85

A UPS With 110-V\\/220-V Input Voltage and High-Frequency Transformer Isolation  

Microsoft Academic Search

This paper proposes an isolated double-conversion uninterruptible power system with power factor correction using a high-frequency transformer and with input voltages equal to 110 V\\/220 V. The arrangement is suitable to rack-type structures because it has a small size and a reduced weight. For both input voltages, the proposed converter has almost the same efficiency processing the same output power.

RenÉ P. Torrico-Bascope; Carlos G. C. Branco; Fernando L. M. Antunes

2008-01-01

86

Improved high-voltage, high-frequency square-wave generator  

NASA Technical Reports Server (NTRS)

This paper describes the design and operation of a prototype high-voltage full-floating high-frequency square-wave generator which is an improved version of the generator developed by Bernius and Chutjian (1989). The present design overcomes possible momentary simultaneous ON states in the MOSFET configuration and is less susceptible to deleterious effects caused by the component aging and replacements with nonidentical parts. The circuit performs well over a wide voltage and frequency range, until a limit is imposed by the operating characteristics of the active MOSFET elements. Circuit diagrams are presented.

Bernius, Mark T.; Chutjian, Ara

1990-01-01

87

Nonholonomic motion planning: steering using sinusoids  

Microsoft Academic Search

Methods for steering systems with nonholonomic c·onstraints between arbitrary configurations are investigated. Suboptimal trajectories are derived for systems that are not in canonical form. Systems in which it takes more than one level of bracketing to achieve controllability are considered. The trajectories use sinusoids at integrally related frequencies to achieve motion at a given bracketing level. A class of systems

Richard M. Murray; S. Shankar Sastry

1993-01-01

88

Frequency dependence of the onset voltage of electroconvection in the nematic liquid crystal N4  

NASA Astrophysics Data System (ADS)

Onset voltages Vc of electroconvection in a nematic liquid crystal (NLC) cell were measured as a function of the drive frequency ?/ 2 ?. The cell (from E.H.C Co, Ltd Japan) had a nominal spacing of 25 ?m and planar alignment. It was filled with the NLC Merck phase IV (N4). The NLC was doped with 0.1% by weight of tetra butylammonium bromide(TBAB) and the conductivity was near 1.0 × 10-6 (? m)-1 at 30^oC. At low frequencies (15 to 80Hz) the onset voltage dropped as the frequency increased. This is contrary to the usual interpretation of the standard model which yields Vc (1+?^2 ?^2)/[?^2-(1+?^2 ?^2)] (? is related to NLC material properities), with the charge relaxation time ?=?/ ( 4? ?) assumed to be independent of ?. Measurements at higher frequencies agreed reasonably with the standard model prediction. Further measurements using an AC bridge revealed that the dielectric constant ? is strongly frequency dependent at low frequencies, whereas the conductivity ? was roughly constant. Taking into account the frequency dependence of ? (and thus of ?), the onset-voltage measurements agreed fairly well with the standard-model prediction.

Xu, Xiaochao; Bowers, Steve; Bajaj, Kapil; Ahlers, Guenter

2003-03-01

89

High-frequency high-voltage high-power DC-to-DC converters  

NASA Technical Reports Server (NTRS)

The current and voltage waveshapes associated with the power transitor and the power diode in an example current-or-voltage step-up (buck-boost) converter were analyzed to highlight the problems and possible tradeoffs involved in the design of high voltage high power converters operating at switching frequencies in the range of 100 Khz. Although the fast switching speeds of currently available power diodes and transistors permit converter operation at high switching frequencies, the resulting time rates of changes of current coupled with parasitic inductances in series with the semiconductor switches, produce large repetitive voltage transients across the semiconductor switches, potentially far in excess of the device voltage ratings. The need is established for semiconductor switch protection circuitry to control the peak voltages appearing across the semiconductor switches, as well as to provide the waveshaping action require for a given semiconductor device. The possible tradeoffs, as well as the factors affecting the tradeoffs that must be considered in order to maximize the efficiency of the converters are enumerated.

Wilson, T. G.; Owen, H. A., Jr.; Wilson, P. M.

1981-01-01

90

Positive feedback frequency compensation for low-voltage low-power three-stage amplifier  

Microsoft Academic Search

The use of a new frequency compensation scheme for a three-stage operational amplifier is presented. The use of a positive feedback compensation (PFC) is employed to improve frequency response when compared to nested Miller compensation. A set of design equations is derived to give insight into the sizing of the amplifier. In addition, some characteristics relevant to the low-voltage low-power

Joao Ramos; Michiel S. J. Steyaert

2004-01-01

91

A Low-Voltage Mobility-Based Frequency Reference for Crystal-Less ULP Radios  

Microsoft Academic Search

The design of a 100 kHz frequency reference based on the electron mobility in a MOS transistor is presented. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for application in wireless sensor networks (WSN). After a single-point calibration, the spread of its output frequency is less than 1.1% (3sigma) over the temperature range from -22degC to

Fabio Sebastiano; Lucien J. Breems; Kofi A. A. Makinwa; Salvatore Dargo; Domine M. W. Leenaerts; Bram Nauta

2009-01-01

92

Frequency Coupling Matrix of a Voltage-Source Converter Derived From Piecewise Linear Differential Equations  

Microsoft Academic Search

When a power-electronic converter is introduced into a linear network, voltage and current harmonics of differing orders become coupled (through the modulation effect of the converter). The interharmonic coupling introduced by the modulation effect of a converter may be mathematically represented through a frequency coupling matrix (FCM). Given that the source of the coupling is a modulation process, researchers have,

P. W. Lehn; K. L. Lian

2007-01-01

93

Design of High Voltage, High Power and High Frequency Transformer in LCC Resonant Converter  

Microsoft Academic Search

The design of a high voltage, high power and high frequency transformer is introduced considering its operation in the LCC resonant converter. The leakage inductance and winding capacitance of the transformer are used as the resonant elements. An additional series resonant capacitor is added to form the LCC topology. The discontinuous current mode (DCM) is adopted to achieve the ZCS

Jun Liu; Licheng Sheng; Jianjiang Shi; Zhongchao Zhang; Xiangning He

2009-01-01

94

A new measurement technique for tracking voltage phasors, local system frequency, and rate of change of frequency  

SciTech Connect

With the advent of Substation Computer Systems dedicated to protection, control and data logging functions in a Substation, it becomes possible to develop new applications which can utilize the processing power available within the substation. The microcomputer based Symmetrical Component Distance Relay (SCDR) described in the references cited at the end of this paper possesses certain characteristics which facilitate real-time monitoring of positive sequence voltage phasor at the local power system bus. With a regression analysis the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle. This paper describes the theoretical basis of these computations and describes results of experiments performed in the AEP power system simulation laboratory. Plans for future field tests on the AEP system are also outlined.

Phadke, A.G.; Adamiak, M.G.; Thorp, J.S.

1983-05-01

95

Sensorless optimal sinusoidal brushless direct current for hard disk drives  

NASA Astrophysics Data System (ADS)

Initiated by the availability of digital signal processors and emergence of new applications, market demands for permanent magnet synchronous motors have been surging. As its back-emf is sinusoidal, the drive current should also be sinusoidal for reducing the torque ripple. However, in applications like hard disk drives, brushless direct current (BLDC) drive is adopted instead of sinusoidal drive for simplification. The adoption, however, comes at the expense of increased harmonics, losses, torque pulsations, and acoustics. In this paper, we propose a sensorless optimal sinusoidal BLDC drive. First and foremost, the derivation for an optimal sinusoidal drive is presented, and a power angle control scheme is proposed to achieve an optimal sinusoidal BLDC. The scheme maintains linear relationship between the motor speed and drive voltage. In an attempt to execute the sensorless drive, an innovative power angle measurement scheme is devised, which takes advantage of the freewheeling diodes and measures the power angle through the detection of diode voltage drops. The objectives as laid out will be presented and discussed in this paper, supported by derivations, simulations, and experimental results. The proposed scheme is straightforward, brings about the benefits of sensorless sinusoidal drive, negates the need for current sensors by utilizing the freewheeling diodes, and does not incur additional cost.

Soh, C. S.; Bi, C.

2009-04-01

96

A conceit of unipolar N-multiple frequency SPWM and the main circuit topology  

Microsoft Academic Search

The sinusoidal pulse width modulation (SPWM) has been widely used because of its simple implementation. The number of output voltage pulses and the frequency of the lowest harmonic voltage in unipolar SPWM are twice that of bipolar SPWM with the same switching frequency, so the unipolar SPWM facilitates the choice of filter and has better output waveforms. For the medium

Xiumei Yue; Xuejun Ma; Hongliang Wang

2009-01-01

97

Stability of voltage and frequency control in distributed generation based on parallel-connected converters feeding constant power loads  

Microsoft Academic Search

In this paper stability and dynamic properties of voltage and frequency droop control of power electronic converters are investigated for a distributed generation system. Droop control is utilized to share active and reactive power among the source converters. The voltage and frequency controllers are designed so that stand-alone converter operation feeding constant power loads performs satisfactory. These controllers are adapted

P. Karlsson; J. Bjornstedt; M. Strom

2005-01-01

98

Pathology of the liver sinusoids.  

PubMed

The hepatic sinusoids comprise a complex of vascular conduits to transport blood from the porta hepatis to the inferior vena cava through the liver. Under normal conditions, portal venous and hepatic artery pressures are equalized within the sinusoids, oxygen and nutrients from the systemic circulation are delivered to the parenchymal cells and differentially distributed throughout the liver acini, and proteins of liver derivation are carried into the cardiac/systemic circulation. Liver sinusoid structures are lined by endothelial cells unique to their location, and Kupffer cells. Multifunctional hepatic stellate cells and various immune active cells are localized within the space of Disse between the sinusoid and the adjacent hepatocytes. Flow within the sinusoids can be compromised by physical or pressure blockage in their lumina as well as obstructive processes within the space of Disse. The intimate relationship of the liver sinusoids to neighbouring hepatocytes is a significant factor affecting the health of hepatocytes, or transmission of the effects of injury within the sinusoidal space. Pathologists should recognize several patterns of injury involving the sinusoids and surrounding hepatocytes. In this review, injury, alterations and accumulations within the liver sinusoids are illustrated and discussed. PMID:24393125

Brunt, Elizabeth M; Gouw, Annette S H; Hubscher, Stefan G; Tiniakos, Dina G; Bedossa, Pierre; Burt, Alastair D; Callea, Francesco; Clouston, Andrew D; Dienes, Hans P; Goodman, Zachary D; Roberts, Eve A; Roskams, Tania; Terracciano, Luigi; Torbenson, Michael S; Wanless, Ian R

2014-06-01

99

Breakdown voltages for discharges initiated from plasma pulses produced by high-frequency excimer lasers  

SciTech Connect

The triggering ability under the different electric field was investigated using a KrF excimer laser with a high repetition rate of kilohertz order. Measurements were made of the magnitude of impulse voltages that were required to initiate a discharge from plasmas produced by a high-frequency excimer laser. Breakdown voltages were found to be reduced by 50% through the production of plasmas in the discharge gap by a high-frequency excimer laser. However, under direct-current electric field, triggering ability decreased drastically due to low plasma density. It is considered that such laser operation applied for laser-triggered lightning due to the produced location of plasma channel is formed under the impulse electric field since an electric field of the location drastically reduces temporary when the downward leader from thunderclouds propagates to the plasma channel.

Yamaura, Michiteru [Department of Electrical and Electronic Engineering, Faculty of Science and Engineering, Saga University, 1 Honjo-machi, Saga 840-8502 (Japan)

2006-06-19

100

Voltage and frequency island optimizations for many-core\\/networks-on-chip designs  

Microsoft Academic Search

Many-core chips interconnected by networks-on-chip (NoC) are increasingly challenged by the tight power consumption constraints. The concept of voltage and frequency island (VFI) which has been recently introduced for achieving fine-grain core-level power management fits well with an NoC design style. This paper will discuss some recent advancement of VFI optimizations for many-core\\/NoC designs. We will also discuss other research

Wooyoung Jang; Duo Ding; David Z. Pan

2010-01-01

101

Zero-Voltage-Switching Bi-Frequency Push-Pull Driver for Liquid Crystal Displays  

NASA Astrophysics Data System (ADS)

In this paper, a bi-frequency control based zero-voltage-switching push-pull driver with a wide dimming range is proposed for the cold cathode fluorescent lamp (CCFL) based back lighting of the liquid crystal display (LCD). As a result, not only the design of the driver transformer can be simplified but also the efficiency of CCFL can be improved. Finally, a prototype is constructed for verifying the effectiveness of the proposed LCD driver.

Chern, Gwo-Tarng; Shieh, Jenn-Jong

102

Improved Reversed Nested Miller Frequency Compensation Technique With Voltage Buffer and Resistor  

Microsoft Academic Search

This brief introduces and develops a novel frequency compensation technique for three-stage operational transconductance amplifiers. The new compensation topology exploits a voltage buffer and a nulling resistor to achieve a double pole-zero cancellation, occurring beyond the gain-bandwidth product. To verify the effectiveness of the compensation scheme, an amplifier has been fabricated in a standard 0.5-mum CMOS process. Experimental measurements are

Alfio Dario Grasso; Davide Marano; Gaetano Palumbo; Salvatore Pennisi

2007-01-01

103

An improved frequency compensation techinique for low power, low voltage CMOS amplifiers [techinique read technique  

Microsoft Academic Search

This paper presents an improved frequency compensation technique for low power and low voltage CMOS operational amplifier. The op amp designed for a high speed high resolution pipeline ADC is a two-stage with folded-cascode as the first stage and uses this improved compensation technique to achieve closed loop bandwidth of 350 MHz while driving a 2K resistor load and a

Preetam Tadeparthy

2004-01-01

104

Widely linear adaptive frequency estimation in three-phase power systems under unbalanced voltage sag conditions  

Microsoft Academic Search

A new framework for the estimation of the instan- taneous frequency in a three-phase power system is proposed. It is first illustrated that the complex-valued signal, obtained by the ?? transformation of three-phase power signals under unbalanced voltage sag conditions, is second order noncircular, for which standard complex adaptive estimators are suboptimal. To cater for second order noncircularity, an adaptive

Yili Xia; Scott C. Douglas; Danilo P. Mandic

2011-01-01

105

Recent Advances in High-Voltage, High-Frequency Silicon-Carbide Power Devices  

Microsoft Academic Search

The emergence of high-voltage, high-frequency (HV-HF) silicon-carbide (SiC) power devices is expected to revolutionize commercial and military power distribution and conversion systems. The DARPA wide bandgap semiconductor technology (WEST) high power electronics (HPE) program is spearheading the development of HV-HF SiC power semiconductor technology. In this paper, some of the recent advances in development of HV-HF devices by the HPE

Allen Hefner; Sei-Hyung Ryu; Brett Hull; David Berning; Colleen Hood; Jose M. Ortiz-Rodriguez; Angel Rivera-Lopez; Tam Duong; Adwoa Akuffo; Madelaine Hernandez-Mora

2006-01-01

106

Voltage and frequency dependent dielectric properties of BST-0.5 thin films on alumina substrates  

Microsoft Academic Search

Dielectric properties of Ba0.5Sr0.5TiO3 (BST-0.5) polycrystalline thin films, deposited on alumina substrates by means of reactive pulsed laser deposition (PLD), were measured at GHz frequencies using an interdigital capacitor (IDC). By applying a voltage up to 40 V between the two groups of fingers at room temperature, a high tunability of ?27% was achieved at 5 GHz. A relative dielectric

Sébastien Delprat; Mossaab Ouaddari; François Vidal; Mohamed Chaker; Ke Wu

2003-01-01

107

Plasma characteristics in non-sinusoidally excited CCP discharges  

NASA Astrophysics Data System (ADS)

Using particle-in-cell (PIC) simulations we perform a characterization of the plasma response to positive pulse-type voltage excitations (with a repetition frequency of 13.56 MHz) in a geometrically symmetric CCP reactor (with a gap length of 2 cm) operated with argon (for pressures between 20-500 mTorr). Use of these non-sinusoidal waveforms generates an electrical asymmetry effect in the system, which necessitates the formation of a DC bias. This DC bias, together with the shape of the voltage waveforms used, produces a number of new phenomena that are not present in typical sinusoidal discharges: (1) the plasma density and ion flux can be increased as the pulse width is reduced, (2) a significant asymmetry in the ion fluxes to the powered and grounded electrodes develops as the pressure increases, (3) the average ion energy striking the grounded electrode remains low and approximately constant as the pulse width decreases, and (4) the sheath at the grounded electrode never fully collapses; electrons are no longer lost in sharp pulses, but escape essentially throughout the rf cycle. Effects (1) and (3) above offer the possibility for a new form of control in these types of discharges, where the ion flux can be increased while the ion energy on the grounded electrode can be kept small and essentially constant. This effect has recently been exploited to control the crystallinity of silicon thin films [1], where the low ion bombarding energy was found to improve the quality of films grown. [4pt] [1] Johnson E V, Pouliquen S, Delattre P A, and Booth J P, J. Non-Cryst. Solids 2012, in press.

Lafleur, Trevor; Booth, Jean-Paul

2012-10-01

108

Effects of voltage errors caused by gap-voltage and automatic-frequency tuning in an alternating-phase-focused linac  

NASA Astrophysics Data System (ADS)

A compact injector for a heavy-ion medical-accelerator complex was developed. It consists of an electron-cyclotron-resonance ion-source (ECRIS) and two linacs, which are a radio-frequency-quadrupole (RFQ) linac and an Interdigital H-mode drift-tube-linac (IH-DTL). Beam acceleration tests of the compact injector were performed, and the designed beam quality was verified by the measured results, as reported earlier. Because the method of alternating-phase-focusing (APF) was used for beam focusing of the IH-DTL, the motion of beam ions would be sensitive to gap-voltage errors, caused during tuning of the gap-voltage distribution and by automatic-frequency tuning in actual operation. To study the effects of voltage errors to beam quality, further measurements were performed during acceleration tests. In this report, the effects of voltage errors for the APF IH-DTL are discussed.

Iwata, Y.; Yamada, S.; Murakami, T.; Fujimoto, T.; Fujisawa, T.; Ogawa, H.; Miyahara, N.; Yamamoto, K.; Hojo, S.; Sakamoto, Y.; Muramatsu, M.; Takeuchi, T.; Mitsumoto, T.; Tsutsui, H.; Watanabe, T.; Ueda, T.

2008-05-01

109

Sinusoidal Potential and Cosmology  

NASA Astrophysics Data System (ADS)

The nature of dark matter (and dark energy) remains a mystery. An alternative is being explored by several scientists: changing Einstein's field equations. With the exception of cosmologists, astronomers generally have been content to test the older alternative, MOdified Newtonian Dynamics (Milgrom 1984) that challenges Newton but leaves relativistic gravity as an issue for the future. At recent meetings of the AAS, I have presented evidence for a new, non-Newtonian, potential, the sinusoidal potential, ? = (GM/r) cos(ko r), where 2 ? / ko = 425 pc is a proposed universal constant. Instead of Poisson's equation, this potential satisfies an equation similar to Helmholtz equation, ? 2?m +ko2?m = 4? G ? m. At AAS 200, I showed that a similar equation for electricity, the Proca equation, ? 2?e - ko 2?e = -4? rhoe (with the same ko as for gravity) could remove the need for dark matter to bind the Coma cluster. Conventional electrodynamics can readily be extended to include ko (Goldhaber & Nieto 1971). Recently I have found how to include ko in relativistic gravity. I will show how this inclusion affects the interpretation of the Cosmic Microwave Background and the expansion of the universe.

Bartlett, D. F.

2004-05-01

110

Monitoring voltage-sensitive membrane impedance change using radio frequency interrogation.  

PubMed

Here we present a new technique to monitor dynamic conformational changes in voltage-sensitive membrane-bound proteins using radio frequency (RF) impedance measurements. Xenopus oocytes were transfected to express ShakerB-IR K(+) ion channels, and step changes in membrane potential were applied using two-electrode voltage clamp (TEVC). Simultaneously, bipolar extracellular electrodes were used to measure the RF electrical impedance across the cell (300 kHz - 1 MHz). RF current will either pass through the media, around the cell, or displace charge across the cell membrane. The change in displacement current in the cell membrane during voltage clamp resulted in measurable RF impedance change. RF impedance change during DC membrane depolarization was significantly greater in ShakerB-IR expressing oocytes than in endogenous controls at 300 kHz, 500 kHz and, to a lesser extent, 1 MHz. Since the RF were too high to modulate ShakerB-IR protein conformational state (e.g. open channel probability), impedance changes are interpreted as reflections of voltage-dependent protein conformation and associated biophysics such as ion-channel dipole interactions, fluctuations in bound water, or charged lipid head-group rotations. PMID:21097203

Dharia, Sameera; Rabbitt, Richard D

2010-01-01

111

High voltage-power frequency electrical heating in-situ conversion technology of oil shale  

NASA Astrophysics Data System (ADS)

With the depletion of conventional energy sources,oil shale has got much attention as a new type of energy resource,which is rich and widespread in the world.The conventional utilization of oil shale is mainly focused on resorting to produce shale oil and fuel gas with low extraction efficiency about one in a million due to many shortcomings and limitations.And the in-situ conversion of oil shale,more environmentally friendly,is still in the experimental stage.High voltage-power frequency electrical heating in-situ conversion of oil shale is a new type of in-situ pyrolysis technology.The main equipment includes a high voltage-power frequency generator and interior reactor. The high voltage-power frequency generator can provide a voltage between 220-8000 V which can be adjusted in real time according to the actual situation.Firstly,high voltage is used to breakdown the oil shale to form a dendritic crack between two electrodes providing a conductive channel inside the oil shale rock.And then the power frequency(220V) is used to generate the electric current for heating the internal surface of conductive channel,so that the energy can be transmitted to the surrounding oil shale.When the temperature reaches 350 degree,the oil shale begins to pyrolysis.In addition,the temperature in the conductive channel can be extremely high with high voltage,which makes the internal surface of conductive channel graphitization and improves its heat conduction performance.This technology can successfully make the oil shale pyrolysis, based on a lot of lab experiments,and also produce the combustible shale oil and fuel gas.Compared to other in-situ conversion technology,this method has the following advantages: high speed of heating oil shale,the equipment underground is simple,and easy to operate;it can proceed without the limitation of shale thickness, and can be used especially in the thin oil shale reservoir;the heating channel is parallel to the oil shale layers,which has more effective area for heating and heat transmitting;it has very good adaptability to the formation,the location and depth of the electrodes which can be adjusted according to the specific stratigraphic depth case;A positive(negative) electrode can be connected to multiple negative(positive) electrodes,and the arrangement of the positive and negative electrodes can be evaluated for improving the extraction efficiency.High voltage-power frequency electrical heating in-situ conversion technology is a very promising in-situ pyrolysis method,which could provide a new way of mining oil shale resources.

Sun, Youhong; Yang, Yang; Lopatin, Vladimir; Guo, Wei; Liu, Baochang; Yu, Ping; Gao, Ke; Ma, Yinlong

2014-05-01

112

Microcontroller modulation for VLF high voltage generator rate 3 kV peak using DSPIC-30F2010  

Microsoft Academic Search

This paper describes a microcontroller modulation at 0.1 Hz for very low frequency (VLF) high voltage generator. This is used for testing field aged cable. This paper shows a simple type of the modulation circuit for VLF high voltage generator by microcontroller modulation with a sinusoidal signal at frequency 0.1 Hz and carrier signal at frequency 10 kHz. The unipolar

S. Seesanga; W. Kongnun; S. Chotigo

2008-01-01

113

Steering car-like systems with trailers using sinusoids  

Microsoft Academic Search

Methods for steering car-like robots with trailers are investigated. A connection is demonstrated between Murray and Sastry's (1990, 1991) work of steering with integrally related sinusoids and Sussmann and Liu's (1991) recent work on asymptotic behavior of systems with high-frequency sinusoids as inputs. The merits of coordinate transformations, relative to the convergence properties, are discussed. Simulation results for a car-like

D. Tilbury; J.-P. Laumond; R. Murray; S. Sastry; G. Walsh

1992-01-01

114

Flow reversal at low voltage and low frequency in a microfabricated ac electrokinetic pump  

NASA Astrophysics Data System (ADS)

Microfluidic chips have been fabricated in Pyrex glass to study electrokinetic pumping generated by a low-voltage ac bias applied to an in-channel asymmetric metallic electrode array. A measurement procedure has been established and followed carefully resulting in a high degree of reproducibility of the measurements over several days. A large coverage fraction of the electrode array in the microfluidic channels has led to an increased sensitivity allowing for pumping measurements at low bias voltages. Depending on the ionic concentration a hitherto unobserved reversal of the pumping direction has been measured in a regime, where both the applied voltage and the frequency are low, Vrms<1.5V and f<20kHz , compared to previously investigated parameter ranges. The impedance spectrum has been thoroughly measured and analyzed in terms of an equivalent circuit diagram to rule out trivial circuit explanations of our findings. Our observations agree qualitatively, but not quantitatively, with theoretical electrokinetic models published in the literature.

Gregersen, Misha Marie; Olesen, Laurits Højgaard; Brask, Anders; Hansen, Mikkel Fougt; Bruus, Henrik

2007-11-01

115

Effect of screening on the variation of transmittance with voltage and frequency for a twisted nematic liquid crystal cell  

NASA Astrophysics Data System (ADS)

The transmittance (T) versus voltage (V) curve for a 90° twisted nematic liquid crystal cell with positive dielectric anisotropic liquid crystal sample is revisited to elucidate the ion charge effect or screening effect. It is shown explicitly why the application of ac voltage is more suitable to enhance the performance of the liquid crystal devices as compared to the dc voltage. The observed variation of transmittance with frequency shows an interesting ``U'' shaped behavior between 10Hz-300 kHz for a fixed ac voltage of 2.5 V (rms value).

Sinha, Subhojyoti; Chatterjee, Sanat Kumar; Meikap, Ajit Kumar

2012-06-01

116

A new control strategy to achieve sinusoidal line current in a cascade buck-boost converter  

Microsoft Academic Search

This work presents a detailed theoretical analysis and experimental results of a novel means of obtaining sinusoidal input current and unity power factor (UPF) via a cascade buck-boost power converter. Using the new configuration, sinusoidal line current in phase with the bus voltage is achieved, thanks to a new and simple to implement control strategy. Comparison between the input and

Mohamed C. Ghanem; Kamal Al-Haddad; Gilles Roy

1996-01-01

117

All-Polymer modulator for high frequency low drive voltage applications  

NASA Astrophysics Data System (ADS)

Organic electro-optic material based optical modulators have been fervently pursued over the past two decades. The material properties of organic materials over crystalline electro-optic materials such as LiNbO3 have yielded devices with record low drive voltages and significant promise for high frequency operation that are ideal for implementation in many developing telecommunication technologies. This paper will discuss a TM electro-optic phase modulator based on a recently developed material IKD-1-50. A simple fabrication process that is compatible with wafer scale manufacturability using commercially available cladding materials, spin processing, standard photolithography, and dry etching will be presented. Non-centrosymmetric order is induced in the core material via a thermally enabled poling process that was developed based on work in simple slab waveguide material characterization devices, and optimized for polymer stack waveguide architectures. Basic phase modulators are characterized for half wave voltage and optical loss. In device r33 values are estimated from a combination of measured and simulated values. Additional work will be discussed including amplitude modulation and high frequency applications. The design for a Mach-Zehnder interferometer amplitude modulator that implements a multi mode interference cavity splitter will be presented along with plans for a microstrip transmission line traveling wave modulator.

Eng, David L. K.; Kozacik, Stephen; Shi, Shouyuan; Olbricht, Benjamin C.; Prather, Dennis W.

2014-03-01

118

Signal Analysis Algorithms for Optimized Fitting of Nonresonant Laser Induced Thermal Acoustics Damped Sinusoids.  

National Technical Information Service (NTIS)

This study seeks a numerical algorithm which optimizes frequency precision for the damped sinusoids generated by the nonresonant LITA technique. It compares computed frequencies, frequency errors, and fit errors obtained using five primary signal analysis...

C. A. Miller, R. J. Balla

2008-01-01

119

Analysis of transistor and snubber turn-off dynamics in high-frequency high-voltage high-power converters  

NASA Technical Reports Server (NTRS)

Dc to dc converters which operate reliably and efficiently at switching frequencies high enough to effect substantial reductions in the size and weight of converter energy storage elements are studied. A two winding current or voltage stepup (buck boost) dc-to-dc converter power stage submodule designed to operate in the 2.5-kW range, with an input voltage range of 110 to 180 V dc, and an output voltage of 250 V dc is emphasized. In order to assess the limitations of present day component and circuit technologies, a design goal switching frequency of 10 kHz was maintained. The converter design requirements represent a unique combination of high frequency, high voltage, and high power operation. The turn off dynamics of the primary circuit power switching transistor and its associated turn off snubber circuitry are investigated.

Wilson, P. M.; Wilson, T. G.; Owen, H. A., Jr.

1982-01-01

120

Frequency analysis of the voltage oscillation of an ac- and dc-current-biased resistively shunted Josephson-junction analogue  

Microsoft Academic Search

We have frequency analyzed the voltage osicllation of a current-biased resistively lshunted Josephson-junction (RSJ) model. In particular we have been interested in the situation where there is an ac (microwave) -induced step in the I-V characteristic. Conversion of the Josephson oscillation into other frequency modes is studied under various bias conditions.

E. Hendricks; P. E. Lindelof

1976-01-01

121

A high frequency active voltage doubler in standard CMOS using offset-controlled comparators for inductive power transmission.  

PubMed

In this paper, we present a fully integrated active voltage doubler in CMOS technology using offset-controlled high speed comparators for extending the range of inductive power transmission to implantable microelectronic devices (IMD) and radio-frequency identification (RFID) tags. This active voltage doubler provides considerably higher power conversion efficiency (PCE) and lower dropout voltage compared to its passive counterpart and requires lower input voltage than active rectifiers, leading to reliable and efficient operation with weakly coupled inductive links. The offset-controlled functions in the comparators compensate for turn-on and turn-off delays to not only maximize the forward charging current to the load but also minimize the back current, optimizing PCE in the high frequency (HF) band. We fabricated the active voltage doubler in a 0.5-?m 3M2P std . CMOS process, occupying 0.144 mm(2) of chip area. With 1.46 V peak AC input at 13.56 MHz, the active voltage doubler provides 2.4 V DC output across a 1 k? load, achieving the highest PCE = 79% ever reported at this frequency. In addition, the built-in start-up circuit ensures a reliable operation at lower voltages. PMID:23853321

Lee, Hyung-Min; Ghovanloo, Maysam

2013-06-01

122

A High Frequency Active Voltage Doubler in Standard CMOS Using Offset-Controlled Comparators for Inductive Power Transmission  

PubMed Central

In this paper, we present a fully integrated active voltage doubler in CMOS technology using offset-controlled high speed comparators for extending the range of inductive power transmission to implantable microelectronic devices (IMD) and radio-frequency identification (RFID) tags. This active voltage doubler provides considerably higher power conversion efficiency (PCE) and lower dropout voltage compared to its passive counterpart and requires lower input voltage than active rectifiers, leading to reliable and efficient operation with weakly coupled inductive links. The offset-controlled functions in the comparators compensate for turn-on and turn-off delays to not only maximize the forward charging current to the load but also minimize the back current, optimizing PCE in the high frequency (HF) band. We fabricated the active voltage doubler in a 0.5-?m 3M2P std. CMOS process, occupying 0.144 mm2 of chip area. With 1.46 V peak AC input at 13.56 MHz, the active voltage doubler provides 2.4 V DC output across a 1 k? load, achieving the highest PCE = 79% ever reported at this frequency. In addition, the built-in start-up circuit ensures a reliable operation at lower voltages.

Lee, Hyung-Min; Ghovanloo, Maysam

2014-01-01

123

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements.  

PubMed

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level. PMID:24784633

Scandurra, Graziella; Giusi, Gino; Ciofi, Carmine

2014-04-01

124

A single phase uninterruptible power supply system using a bidirectional sinusoidal PWM inverter  

Microsoft Academic Search

This paper presents an uninterruptible power supply system using a bidirectional sinusoidal PWM inverter. This system offers a smooth transition during grid failure, load voltage stabilisation under varying input grid voltage and lower line current harmonic distortion. The inverter maintains the load voltage and the power flow from the grid by controlling its magnitude and phase angle with respect to

C. V. Nayar; M. Ashari; W. W. L. Keerthipala

1998-01-01

125

Reciprocity-transposition-based sinusoidal pulsewidth modulation for diode-clamped multilevel converters  

Microsoft Academic Search

Modulation strategies for multilevel inverters have typically focused on synthesizing a desired set of three phase sinusoidal voltage waveforms using a fixed number of DC voltage levels. This results in the average current injection and hence the net power drawn from the multiple DC bus terminals to be unmatched and time varying. Subsequently, the DC-bus voltages are unregulated, requiring corrective

Giri Venkataramanan; Ashish Bendre

2002-01-01

126

Sinusoidal phase modulating interferometry system for 3D profile measurement  

NASA Astrophysics Data System (ADS)

We describe a fiber-optic sinusoidal phase modulating (SPM) interferometer for three-dimensional (3D) profilometry, which is insensitive to external disturbances such as mechanical vibration and temperature fluctuation. Sinusoidal phase modulation is created by modulating the drive voltage of the piezoelectric transducer (PZT) with a sinusoidal wave. The external disturbances that cause phase drift in the interference signal and decrease measuring accuracy are effectively eliminated by building a closed-loop feedback system. The phase stability can be measured with a precision of 2.75 mrad, and the external disturbances can be reduced to 53.43 mrad for the phase of fringe patterns. By measuring the dynamic deformation of the rubber membrane, the RMSE is about 0.018 mm, and a single measurement takes less than 250 ms. The feasibility for real-time application has been verified.

En, Bo; Fa-jie, Duan; Chang-rong, Lv; Fu-kai, Zhang; Fan, Feng

2014-07-01

127

The selection of the frequency range for high-voltage on-site testing of extruded insulation cable systems  

Microsoft Academic Search

High-voltage on-site tests of extruded insulation cables are necessary to check the quality of the installation of the system. The test voltage should simulate the stress under service conditions, and generate the same failure mechanism. With respect to an optimum design of test systems, a frequency range of 20 to 300 Hz, proposed in the latest IEC Draft for on-site

E. Gockenbach; W. Hauschild

2000-01-01

128

Voltage and Frequency Controller for a Three-Phase Four-Wire Autonomous Wind Energy Conversion System  

Microsoft Academic Search

This paper deals with control of voltage and frequency of an autonomous wind energy conversion system (AWECS) based on capacitor-excited asynchronous generator and feeding three-phase four-wire loads. The proposed controller consists of three single-phase insulated gate bipolar junction transistor (IGBT)-based voltage source converters (VSCs) and a battery at dc link. These three single-phase VSCs are connected to each phase of

Bhim Singh; Gaurav Kumar Kasal

2008-01-01

129

The design of high-frequency switching power supply for field test of high-voltage circuit breaker  

Microsoft Academic Search

Based on the working conditions and development trend of operating mechanism of high-voltage circuit breaker, this paper presented a high-load adjustment rate of portable high-frequency switching power supply designed for high-voltage circuit breakers test. The main circuit topological structure is analysed in detail, which uses the fullbridge circuit and IGBTs (insulated gate bipolar transistor) as switches. The focus is on

Yi Sun; Xiaodong Zhang; Lingling Wang

2008-01-01

130

Frequency-Domain Model for Calculation of Voltage Distribution Through Random Wound Coils and Its Interaction With Stray Capacitances  

Microsoft Academic Search

Modern pulsewidth-modulation (PWM) low-voltage drives are recognized as one of the most demanding applications for a motor. Pulses facing motor terminals are responsible for turn-to-turn high electrical stresses that lead to unexpected failures in stator windings. In this paper, an accurate new model for frequency-domain voltage distribution calculation through random wound coils is presented. In addition to checking its applicability

Juan M. MartÍnez-Tarifa; Hortensia AmarÍs-Duarte; Javier Sanz-Feito

2008-01-01

131

Regenerator performance with sinusoidal flow  

NASA Technical Reports Server (NTRS)

The ineffectiveness of regenerators with sinusoidal laminar flow through parallel plate, screen, and packed sphere matrices is evaluated in the limit of infinite matrix heat capacity. Increases in ineffectiveness of up to 23 percent over the constant flow values result for parallel plate regenerators.

Daney, D. E.

1991-01-01

132

Performance comparison of a new current regulator for 3-level NPC inverter for sinusoidal and non-sinusoidal current tracking applications  

Microsoft Academic Search

In this paper, a new current regulator is applied for a 3-level NPC inverter to achieve both current regulation and neutral-point voltage balance. The performance of the proposed current regulator is validated for both sinusoidal current tracking, such as for a 3-level NPC inverter based motor drive application, and also for non-sinusoidal current tracking, such as for active filter application.

Jun Li; Subhashish Bhattacharya; Alex Huang

2008-01-01

133

An optimized low voltage and High Frequency CCII based multifunction Filters  

Microsoft Academic Search

In this paper, a low voltage current conveyor (CCII) based multifunction filter is presented. Firstly, thanks to an optimizing heuristic, an optimal sizing of a low voltage low power CMOS current conveyor (CCII) was done. Hence, we improve static and dynamic performances of this configuration. The optimized CCII configuration has a current bandwidth of 1.103 GHz and a voltage bandwidth

Samir Ben Salem; Dorra Sellami Masmoudi; Ashwek Ben Saïd; Mourad Loulou

2006-01-01

134

Overvoltages in inverter fed induction machines using high frequency power electronic components  

Microsoft Academic Search

Inverter supplied induction motors have become common. One of the tendencies that can be observed over the years, is that the switching frequencies of the power electronic components increase. This allows the manufacturers to build more compact inverters with an improved sinusoidal wave shape of the output voltage and\\/or current. The increase in the switching frequency is made possible by

P. Van Poucke; R. Belmans; W. Geysen; E. Ternier

1994-01-01

135

Running DFT-Based PLL Algorithm for Frequency, Phase, and Amplitude Tracking in Aircraft Electrical Systems  

Microsoft Academic Search

Phase-locked loop (PLL) algorithms are commonly used to track sinusoidal components in currents and voltage sig- nals in three-phase power systems. Despite the simplicity of those algorithms, problems arise when signals have variable frequency or amplitude, or are polluted with harmonic content and measure- ment noise, as can be found in aircraft ac power systems where the fundamental frequency can

Francesco Cupertino; Elisabetta Lavopa; Pericle Zanchetta; Mark Sumner; Luigi Salvatore

2011-01-01

136

Complex heterodyne for undersampled chirped sinusoidal signals  

NASA Astrophysics Data System (ADS)

We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 109) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers).

Niebauer, T. M.; Schiel, A.; van Westrum, D.

2006-11-01

137

Complex heterodyne for undersampled chirped sinusoidal signals.  

PubMed

We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 10(9)) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers). PMID:17068577

Niebauer, T M; Schiel, A; van Westrum, D

2006-11-10

138

Distributed Voltage and Frequency Control of Offshore Wind Farms Connected With a Diode-Based HVdc Link  

Microsoft Academic Search

This paper introduces a new technique for the distributed voltage and frequency control of the local ac-grid in offshore wind farms based on synchronous generators. The proposed control technique allows the connection of the offshore wind farm using a diode based HVdc rectifier. The use of microgrid control techniques allowed the system comprising the wind farm and the diode HVdc

Ramon Blasco-Gimenez; S. Año?-Villalba; J. Rodri?guez-D'Derle?e; F. Morant; S. Bernal-Perez

2010-01-01

139

Cell property determination from the acoustic microscope generated voltage versus frequency curves.  

PubMed

Among the methods for the determination of mechanical properties of living cells acoustic microscopy provides some extraordinary advantages. It is relatively fast, of excellent spatial resolution and of minimal invasiveness. Sound velocity is a measure of the stiffness or Young's modulus of the cell. Attenuation of cytoplasm is a measure of supramolecular interactions. These parameters are of crucial interest for studies of cell motility, volume regulations and to establish the functional role of the various elements of the cytoskeleton. Using a phase and amplitude sensitive modulation of a scanning acoustic microscope (Hillman et al., 1994, J. Alloys Compounds. 211/212:625-627) longitudinal wave speed, attenuation and thickness profile of a biological cell are obtained from the voltage versus frequency or V(f) curves. A series of pictures, for instance in the frequency range 980-1100 MHz with an increment of 20 MHz, allows the experimental generation of V(f) curves for each pixel while keeping the lens-specimen distance unchanged. Both amplitude and phase values of the V(f) curves are used for obtaining the cell properties and the cell thickness profile. The theoretical analysis shows that the thin liquid layer, between the cell and the substrate, has a strong influence on the reflection coefficient and should not be ignored during the analysis. Cell properties, cell profile and the thickness of the thin liquid layer are obtained from the V(f) curves by the simplex inversion algorithm. The main advantages of this new method are that imaging can be done near the focal plane, therefore an optimal signal to noise ratio is achieved, no interference with Rayleigh waves occurs, and the method requires only an approximate estimate of the material properties of the solid substratum where the cells are growing on. PMID:10777725

Kundu, T; Bereiter-Hahn, J; Karl, I

2000-05-01

140

Cell property determination from the acoustic microscope generated voltage versus frequency curves.  

PubMed Central

Among the methods for the determination of mechanical properties of living cells acoustic microscopy provides some extraordinary advantages. It is relatively fast, of excellent spatial resolution and of minimal invasiveness. Sound velocity is a measure of the stiffness or Young's modulus of the cell. Attenuation of cytoplasm is a measure of supramolecular interactions. These parameters are of crucial interest for studies of cell motility, volume regulations and to establish the functional role of the various elements of the cytoskeleton. Using a phase and amplitude sensitive modulation of a scanning acoustic microscope (Hillman et al., 1994, J. Alloys Compounds. 211/212:625-627) longitudinal wave speed, attenuation and thickness profile of a biological cell are obtained from the voltage versus frequency or V(f) curves. A series of pictures, for instance in the frequency range 980-1100 MHz with an increment of 20 MHz, allows the experimental generation of V(f) curves for each pixel while keeping the lens-specimen distance unchanged. Both amplitude and phase values of the V(f) curves are used for obtaining the cell properties and the cell thickness profile. The theoretical analysis shows that the thin liquid layer, between the cell and the substrate, has a strong influence on the reflection coefficient and should not be ignored during the analysis. Cell properties, cell profile and the thickness of the thin liquid layer are obtained from the V(f) curves by the simplex inversion algorithm. The main advantages of this new method are that imaging can be done near the focal plane, therefore an optimal signal to noise ratio is achieved, no interference with Rayleigh waves occurs, and the method requires only an approximate estimate of the material properties of the solid substratum where the cells are growing on.

Kundu, T; Bereiter-Hahn, J; Karl, I

2000-01-01

141

Dust charge and ion drag forces in a high-voltage, capacitive radio frequency sheath  

SciTech Connect

The charge of an isolated dust grain and ion drag forces on the grain in a collisionless, high-voltage, capacitive rf sheath are studied theoretically. The studies are carried out assuming that the positive ions are monoenergetic, as well as in more realistic approximation, assuming that the time-averaged energy distribution of ions impinging on the dust grain has a double-peaked hollow profile. For the nonmonoenergetic case, an analytical expression for the ion flux to the dust grain is obtained. It is studied how the dust charge and ion drag forces depend on the rf frequency, electron density at plasma-sheath boundary, electron temperature and ratio of the effective oscillation amplitude of rf current to the electron Debye length. It is shown that the dust charge and ion drag forces obtained in the monoenergetic ion approximation may differ from those calculated assuming that the ions are nonmonoenergetic. The difference increases with increasing the width of the ion energy spread in the ion distribution.

Denysenko, I.; Azarenkov, N. A. [School of Physics and Technology, V. N. Karazin Kharkiv National University, 4 Svobody sq., 61077 Kharkiv (Ukraine); Ostrikov, K. [CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia) and Plasma Nanoscience, School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia)

2009-11-15

142

Stable sinusoidal driver circuit for tuning fork choppers  

Microsoft Academic Search

A circuit is presented which can drive tuning fork choppers, such as the Bulova L40 and L2 series. The advantages of this circuit over the factory-supplied 5A-type driver are better drive-amplitude stability, freedom from drift due to line-voltage variations, and a cleaner, transient-free sinusoidal reference signal. Test results indicate an improvement in long-term stability by as much as a factor

James Podolske

1979-01-01

143

DNA fragmentation induced by Intense Burst Sinusoidal Electric Fields  

Microsoft Academic Search

It is a well known fact that intense electric fields with frequencies exceeding MHz ranges cause intracellular effect to mammalian cells. We have used the Intense Burst Sinusoidal Electric Field (IBSEF) which is narrow band spectra, to put the electrical energy into biological cells efficiently. We have experimentally demonstrated here the presence of intense electric fields inside the cell membrane,

N. Nomura; Y. Yamamoto; R. Hayashi; K. Uto; S. Katsuki; H. Akiyama; I. Uchida; S. I. Abe; H. Takano

2007-01-01

144

A polarimetric glucose sensor using a liquid-crystal polarization modulator driven by a sinusoidal signal  

Microsoft Academic Search

Rather than using a conventional Faraday modulator, this study adopts a liquid-crystal based rotator to modulate the azimuth of the linear polarized light in a sinusoidal signal for the measurement of glucose concentrations. The tilt angle of the LC director would vary as a sinusoidal-like function; however the modulating frequency in the sensing system is the double of the driving

Yu-Lung Lo; Tsung-Chih Yu

2006-01-01

145

Performance Study of Algorithms for Detecting Pulsed Sinusoidal Interference in Microwave Radiometry  

Microsoft Academic Search

The performance of four algorithms for detecting the presence of pulsed sinusoidal interference in microwave radiometry is compared. The pulsed sinusoidal interference sources considered have unknown frequency, initial phase, amplitude, arrival time, and duration. The statistical properties of three of the algorithms are determined analytically, although numerical integrations are required in some cases in order to compute the obtained probabilities

Joel T. Johnson; Lee C. Potter

2009-01-01

146

Estimating the parameters of exponentially damped sinusoids and pole-zero modeling in noise  

Microsoft Academic Search

We have presented techniques [1] - [6] based on linear prediction (LP) and singular value decomposition (SVD) for accurate estimation of closely spaced frequencies of sinusoidal signals in noise. In this note we extend these techniques to estimate the parameters of exponentially damped sinusoidal signals in noise. The estimation procedure presented here makes use of \\

RAMDAS KUMARESAN; DONALD W. TUFTS

1982-01-01

147

Firing pattern of bursting neurons under sinusoidal drive in mean-field modeling.  

PubMed

Bursting has been observed in many sensory neurons, and is thought to be important in neural signaling, sleep, and some disorders of the brain. Bursting neurons have been studied via various types of conductance-based models at the single-neuron level. Important features of bursting have been reproduced by this type of model, but it is not certain how well the behavior of populations of bursting neurons can be represented solely by that of individual neurons. To study bursting neurons at the population level, a conductance-based model is incorporated into a mean-field model to yield a mean-field bursting model. The responses of the model to sinusoidal inputs are studied, showing that neurons with various different initial states are capable of phase-locked or intermittent firing, depending on their baseline voltage. Furthermore, depending on this voltage, the bursting frequency either slaves to the original unperturbed bursting frequency or approaches a steady value when the external driving frequency increases. Finally, use of white noise perturbations shows that the bursting frequency of the neurons remains the same even under a more general external stimulus. PMID:19336235

Wu, H; Kim, J W; Robinson, P A; Drysdale, P M

2009-07-01

148

High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC  

NASA Technical Reports Server (NTRS)

Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

1990-01-01

149

Frequency Spectrum of the Generated Voltage of Claw Pole Automotive Alternators on No Load  

Microsoft Academic Search

The harmonic spectrum of generated voltage in claw pole automotive alternators has to be examined since the load components in future automobiles have to be rated for over-voltages and transients. The present work gives a new 3D finite element modeling and simulation along with a conventional analysis supplemented by experimental work on a 12 pole claw pole alternator. Further work

K. P. P. Pillai; M. K. Idiculla; A. S. Nair

2005-01-01

150

Radio-frequency powered glow discharge device and method with high voltage interface  

SciTech Connect

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components.

Duckworth, Douglas C. (Knoxville, TN); Marcus, R. Kenneth (Clemson, SC); Donohue, David L. (Vienna, AT); Lewis, Trousdale A. (Oak Ridge, TN)

1994-01-01

151

Radio-frequency powered glow discharge device and method with high voltage interface  

DOEpatents

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components. 11 figures.

Duckworth, D.C.; Marcus, R.K.; Donohue, D.L.; Lewis, T.A.

1994-06-28

152

The effect of high voltage, high frequency pulsed electric field on slain ovine cortical bone.  

PubMed

High power, high frequency pulsed electric fields known as pulsed power (PP) has been applied recently in biology and medicine. However, little attention has been paid to investigate the application of pulse power in musculoskeletal system and its possible effect on functional behavior and biomechanical properties of bone tissue. This paper presents the first research investigating whether or not PP can be applied safely on bone tissue as a stimuli and what will be the possible effect of these signals on the characteristics of cortical bone by comparing the mechanical properties of this type of bone pre and post expose to PP and in comparison with the control samples. A positive buck-boost converter was applied to generate adjustable high voltage, high frequency pulses (up to 500 V and 10 kHz). The functional behavior of bone in response to pulse power excitation was elucidated by applying compressive loading until failure. The stiffness, failure stress (strength) and the total fracture energy (bone toughness) were determined as a measure of the main bone characteristics. Furthermore, an ultrasonic technique was applied to determine and comprise bone elasticity before and after pulse power stimulation. The elastic property of cortical bone samples appeared to remain unchanged following exposure to pulse power excitation for all three orthogonal directions obtained from ultrasonic technique and similarly from the compression test. Nevertheless, the compressive strength and toughness of bone samples were increased when they were exposed to 66 h of high power pulsed electromagnetic field compared to the control samples. As the toughness and the strength of the cortical bone tissue are directly associated with the quality and integrity of the collagen matrix whereas its stiffness is primarily related to bone mineral content these overall results may address that although, the pulse power stimulation can influence the arrangement or the quality of the collagen network causing the bone strength and toughness augmentation, it apparently did not affect the mineral phase of the cortical bone material. The results also confirmed that the indirect application of high power pulsed electric field at 500 V and 10 kHz through capacitive coupling method was safe and did not destroy the bone tissue construction. PMID:24761375

Asgarifar, Hajarossadat; Oloyede, Adekunle; Zare, Firuz

2014-04-01

153

The Effect of High Voltage, High Frequency Pulsed Electric Field on Slain Ovine Cortical Bone  

PubMed Central

High power, high frequency pulsed electric fields known as pulsed power (PP) has been applied recently in biology and medicine. However, little attention has been paid to investigate the application of pulse power in musculoskeletal system and its possible effect on functional behavior and biomechanical properties of bone tissue. This paper presents the first research investigating whether or not PP can be applied safely on bone tissue as a stimuli and what will be the possible effect of these signals on the characteristics of cortical bone by comparing the mechanical properties of this type of bone pre and post expose to PP and in comparison with the control samples. A positive buck-boost converter was applied to generate adjustable high voltage, high frequency pulses (up to 500 V and 10 kHz). The functional behavior of bone in response to pulse power excitation was elucidated by applying compressive loading until failure. The stiffness, failure stress (strength) and the total fracture energy (bone toughness) were determined as a measure of the main bone characteristics. Furthermore, an ultrasonic technique was applied to determine and comprise bone elasticity before and after pulse power stimulation. The elastic property of cortical bone samples appeared to remain unchanged following exposure to pulse power excitation for all three orthogonal directions obtained from ultrasonic technique and similarly from the compression test. Nevertheless, the compressive strength and toughness of bone samples were increased when they were exposed to 66 h of high power pulsed electromagnetic field compared to the control samples. As the toughness and the strength of the cortical bone tissue are directly associated with the quality and integrity of the collagen matrix whereas its stiffness is primarily related to bone mineral content these overall results may address that although, the pulse power stimulation can influence the arrangement or the quality of the collagen network causing the bone strength and toughness augmentation, it apparently did not affect the mineral phase of the cortical bone material. The results also confirmed that the indirect application of high power pulsed electric field at 500 V and 10 kHz through capacitive coupling method was safe and did not destroy the bone tissue construction.

Asgarifar, Hajarossadat; Oloyede, Adekunle; Zare, Firuz

2014-01-01

154

Dual frame control scheme with a plug-in frequency domain based repetitive controller for three phase PWM boost rectifier under distorted and unbalanced supply voltages  

Microsoft Academic Search

This paper presents a dual frame control scheme with a digital plug-in frequency domain based repetitive controller (FDRC) for minimizing the even order harmonics at the output dc link voltage and odd order harmonics in the line currents under the distorted and unbalanced supply voltage conditions. The proposed current controller consists of a conventional PI controller and a frequency domain

Xinhui Wu; Sanjib K. Panda; Jianxin Xu

2008-01-01

155

Energy conversion and performance of switched-voltage control based on negative capacitance with arbitrary switching frequency  

NASA Astrophysics Data System (ADS)

In semi-active synchronized switch damping (SSD) approaches for structural vibration control, the damping effect is achieved by properly switching the voltage on the piezoelectric actuators. In this study, the energy conversion of a synchronized switch damping system based on negative capacitance (SSDNC) with an arbitrary switching frequency is investigated theoretically and validated numerically. First, the model of a general SSDNC system with an arbitrary switching frequency is presented. The general expression of the switched voltage on the piezoelectric actuator is derived. Next, the average converted energy per vibration cycle was derived for arbitrary switching frequency. The results show that the efficiency of energy conversion is reduced by about one half even if the switching frequency deviates slightly from the optimal frequency, which is similar to the SSDI control system. However, the control performance of SSDNC is better than that of SSDI for most non-optimal switching frequencies. Finally, the general expression of control performance of a SSDNC control system for a specific mode is derived and a numerical example is given to support the theoretical results.

Ji, Hongli; Qiu, Jinhao; Xia, Pinqi; Nie, Hong

2012-12-01

156

The Digital Simulation of Synchronous Motors Fed by Voltage-Source Inverters Over Wide Speed and Frequency Ranges  

NASA Astrophysics Data System (ADS)

Both voltage-source and current-source inverters are widely used for supplying three-phase power to induction motor drives, each having their advantages and disadvantages. For high power drives and applications requiring accurate speed and tracking coordination, the synchronous motors are the optimum choice. For constant speed applications of synchronous motor drives, current-source inverters tend to be favored as the motor can usually be operated in the overexcited leading power factor region, thus providing the inverter with sufficient electro-motive force to allow natural commutation. Generally speaking low speed operation of synchronous motors is not satisfactory from naturally commutated current-source inverters. To provide a dynamic range of speed and frequency would require expensive control circuitry and complicates the performance of the drive. The advantage of the voltage-source inverter for the wide range of speed and frequency control herein envisaged is that forced commutation is employed throughout the range and the commutating circuits have been well developed and established. On balance, voltage-source inverters represent a viable compromise for variable-speed three -phase synchronous motor drives including start-up. To investigate the transient response of the voltage -source fed-synchronous motor drives, a digital computer program is developed. The program is based on two models --machine model and inverter model. The machine is represented by a detailed two-axis model which includes the effects due to saliency, damper windings, and machine resistances. The inverter model represents a forced-commutated voltage-source inverter assuming ideal switching devices (thyristors and diodes). To cope with the wide variations of power factor during start-up, a thyristor with a reverse connected parallel diode are integrated as a bidirectional switch. The digital program provides the machine variables of interest (phase currents, field current, damper winding currents, and electromagnetic torque). Two start-up techniques are investigated: fixed-frequency fixed-voltage start-up and variable-frequency start-up with constant voltage per Hertz ratio (v/f) control. The second technique has valuable consequences because it relieves the stresses imposed on the inverter and the motor due to inrush currents encountered when the first technique is employed. Simulation results are obtained for both start-up techniques. To check the validity of the inverter model, the results are compared with those obtained when the motor is started from a conventional three-phase supply. (Abstract shortened with permission of author.).

Rowihal, Said Soliman

157

Adaptive fuzzy control of a single-phase sinusoidal rectifier with step-up\\/down characteristics  

Microsoft Academic Search

This paper proposes an adaptive fuzzy logic controller for feedback output voltage control of a single-phase sinusoidal rectifier with step-up\\/down characteristics. These rectifiers, with a sliding mode current controller, ensure a near unity power factor operation and an input current with low harmonic content. The reference of the current controller is a sinusoidal waveform whose amplitude is modulated by the

Tito G. Amaral; V. F. Pires; M. Crisostomo; J. F. Silva

2000-01-01

158

Series resonant high-voltage PFM DC-DC converter with voltage multiplier based a two-step frequency switching control for medical-use X ray power generator  

Microsoft Academic Search

In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady-state performances can not be achieved under wide load variations for a medical-use high voltage X ray generator ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250

Junming Sun; Hitoshi Konishi; Yoshio Ogino; Enhui Chu; M. Nakaoka

2000-01-01

159

Photonic high-frequency capacitance-voltage characterization of interface states in metal-oxide-semiconductor capacitors  

Microsoft Academic Search

A new characterization method based on the photonic high-frequency capacitance-voltage (HF C-V) response of metal-oxide semiconductor (MOS) capacitors is reported for the analysis of interface states in MOS systems. An optical source with a photon energy less than the silicon band-gap (h? = 0.799 eV < Eg = 1.11 eV) is employed for the photonic characterization of interface states (Bit)

D. M. Kim; H. C. Kim

2002-01-01

160

Distributed voltage and frequency control of off-shore wind farms connected with a diode based HVDC link  

Microsoft Academic Search

This paper introduces a new technique for the distributed voltage and frequency control of the local ac-grid in off-shore wind farms based on synchronous generators. The proposed control technique allows the connection of the off-shore wind farm using a diode based HVDC rectifier. The system comprising the wind farm and the diode HVDC rectifier can be operated in current or

R. Blasco-Gimenez; S. An?o?-Villalba; J. Rodri?guez-D?Derle?e; F. Morant; S. Bernal

2010-01-01

161

High frequency capacitance-voltage technique for the extraction of interface trap density of the heterojunction capacitor: Terman's method revised  

Microsoft Academic Search

In a multi-layer heterojunction system, the interface responsible for trap charging is spatially displaced from the two-dimensional charge gas, in contrast to the typical SiO2\\/Si capacitor. This displacement causes the effective trap capacitance to occur in a different configuration than that of the SiO2\\/Si system that Terman originally considered. The adaptation of Terman's high frequency capacitance-voltage method for interface trap

David A. Deen; James G. Champlain

2011-01-01

162

A PFC pre-regulator with 110 V\\/220 V input voltage and high frequency isolation for UPS applications  

Microsoft Academic Search

This work deals with the development of a PFC pre-regulator circuit with possibility of 110 V\\/220 V AC main input voltages, while maintaining the same efficiency for a wide load range. Other relevant features of this circuit topology are high frequency transformer isolation, soft commutation of the controlled switches, simple control strategy that can be implemented with well-known integrated circuits

René P. Torrico-Bascopé; Demercil S. Oliveira Jr; Carlos G. C. Branco; Fernando L. M. Antunes

2005-01-01

163

LCC Resonant Converter Operating under Discontinuous Resonant Current Mode in High Voltage, High Power and High Frequency Applications  

Microsoft Academic Search

The full-bridge series-parallel resonant converters (also known as LCC resonant converters) with capacitive output filter is evaluated in high output voltage (>50 kV), high power (>50 kW) and high frequency (20 kHz) ESP (Electrostatic Precipitator) power supply applications. By using the leakage inductance and the winding capacitance of the transformer as the resonant elements only an additional series resonant capacitor

Jun Liu; Licheng Sheng; Jianjiang Shi; Zhongchao Zhang; Xiangning He

2009-01-01

164

DSP-based closed-loop control of bi-directional voltage mode high frequency link inverter with active clamp  

Microsoft Academic Search

This paper presents a novel modulation and digital controller based on a bi-directional voltage mode high frequency link inverter with active clamp to achieve fast dynamic response and high static performance. The inverter consists of a full-bridge converter, a bi-directional active rectifier, an active clamp branch and a pulse width modulation (SPWM) inverter bridge. A novel modulation strategy is applied

Zhao Qinglin; Xu Yunhua; Jin Xiaoyi; Wu Weiyang; Cao Lingling

2005-01-01

165

A medium frequency transformer with multiple secondary windings for medium voltage converter based wind turbine power generating systems  

NASA Astrophysics Data System (ADS)

Recent advances in magnetic materials have led to the development of compact and light weight, medium and high frequency transformers, which would be a possible solution to reducing the size and weight of wind turbine power generating systems. This paper presents the overall design and analysis of a Metglas amorphous alloy 2605SA1 based medium frequency transformer to generate the isolated balanced multiple DC supplies for medium voltage converter systems. A comprehensive electromagnetic analysis is conducted on the proposed design based on experimental results. The test stand, data analysis, and test results are discussed.

Islam, Md Rabiul; Guo, Youguang; Zhu, Jianguo

2013-05-01

166

Simple and precise chromatic dispersion measurement using sinusoidally phase-modulated CW light  

Microsoft Academic Search

A novel chromatic dispersion measurement technique using a sinusoidally phase-modulated CW light is described. We utilize the fact that the phase to intensity modulation conversion induced by the dispersion disappears at specific phase modulation frequencies.

Takashi Yamamoto; Kenji Kurokawa; Katsusuke Tajima; Toshio Kurashima

2009-01-01

167

Improved Transient and Steady-State Performances of Series Resonant ZCS High-Frequency Inverter-Coupled Voltage Multiplier Converter with Dual Mode PFM Control Scheme  

NASA Astrophysics Data System (ADS)

The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

Chu, Enhui; Gamage, Laknath; Ishitobi, Manabu; Hiraki, Eiji; Nakaoka, Mutsuo

168

Induction generator produces constant-frequency voltage from variable-speed drive  

NASA Technical Reports Server (NTRS)

Two-stage polyphase generator is usable as induction motor operable over range of speeds while powered from constant frequency source. It requires neither slip rings nor special adjustable-frequency power supplies or external reactive sources.

Riaz, M.

1970-01-01

169

High frequency capacitor-diode voltage multiplier dc-dc converter development  

NASA Technical Reports Server (NTRS)

A power conditioner was developed which used a capacitor diode voltage multiplier to provide a high voltage without the use of a step-up transformer. The power conditioner delivered 1200 Vdc at 100 watts and was operated from a 120 Vdc line. The efficiency was in excess of 90 percent. The component weight was 197 grams. A modified boost-add circuit was used for the regulation. A short circuit protection circuit was used which turns off the drive circuit upon a fault condition, and recovers within 5 ms after removal of the short. High energy density polysulfone capacitors and high speed diodes were used in the multiplier circuit.

Kisch, J. J.; Martinelli, R. M.

1977-01-01

170

Spontaneous periodic pulsation of contact line in oil/water system--frequency control with divalent cations and applied voltage.  

PubMed

Periodic oscillatory change of hydrophilicity (or hydrophobicity) of a glass surface was studied. A glass capillary was immersed normally at an oil/water interface. The water phase contained the cationic surfactant trimethyloctadecylammoniumchloride, and the oil phase contained bis(2ethylhexyl) phosphate. Adsorption of the surfactant molecules and their desorption via anionic chemicals dissolved in the oil generated a gradual wetting by the water, followed by a rapid wetting by oil. The three phase contact line exhibited a pulse-like motion that continued, at least for a few minutes. The frequency depended on the cation species dissolved in water and the applied voltage across the oil/water interface. Four kinds of cations, Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were used. While the frequency order was Ba(2+)>Sr(2+)>Mg(2+), the Ca(2+)-containing interface did not show any motion irrespective of the applied voltage. There was a threshold voltage and concentration of anionic chemical that was necessary for the onset of this motion. The pulsation mechanism and its ion selectivity are also discussed. This interfacial motion was a typical nonlinear oscillation with an ion-selective nature. In this regard, this interfacial motion had biomimetic characteristics. PMID:21784428

Oomiya, Katsuhito; Mori, Daishi; Ban, Takahiko; Shioi, Akihisa

2011-10-15

171

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components  

NASA Astrophysics Data System (ADS)

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.

Subramanyam, Guru; Cole, M. W.; Sun, Nian X.; Kalkur, Thottam S.; Sbrockey, Nick M.; Tompa, Gary S.; Guo, Xiaomei; Chen, Chonglin; Alpay, S. P.; Rossetti, G. A.; Dayal, Kaushik; Chen, Long-Qing; Schlom, Darrell G.

2013-11-01

172

Monitoring voltage and frequency in smart distribution grids. A case study on data compression and accessibility  

Microsoft Academic Search

Synchronized measurements became recently an affordable tool ready to be implemented not only at transmission system level but also at distribution level, mostly in conjunction with the applicability of the smart grid approach. As a preliminary step of introducing PMUs on a larger scale, extensive measurements campaigns, primarily dedicated to power quality purposes, were conducted within medium and low voltage

Mihaela M. Albu; Ralf Neurohr; Dan Apetrei; Ioan Silvas; Dumitru Federenciuc

2010-01-01

173

A Low Voltage Programmable Gain Amplifier for DC to medium frequency applications with small die size  

Microsoft Academic Search

This paper describes a new programmable gain amplifier (PGA) for data acquisition systems. Its small size, low voltage capability and versatility make it ideally suited for high volume integration. A new DC-offset technique is introduced to achieve 0V compliant operation without the need of switched capacitor techniques. Offset cancellation is achieved on a system level in the digital domain, greatly

A. D. Gunther; K. Mahooti

2006-01-01

174

Power quality issues with adjustable frequency drives -- Coping with power loss and voltage transient occurrences  

SciTech Connect

The power quality issue is not new to consumers of electrical power. From individual home owners to large industrial complexes, power quality problems can cause eyebrows to raise or bring industrial giants to their knees. Power quality comes in many forms. It can appear in the form of a voltage source which decreases to a small fraction of its normal strength or as a voltage transient, briefly far exceeding its normal value, ready to break down electrical insulation. It can appear as an oscillating voltage or a traveling voltage wave beating against barriers designed as added protection. Defining a single set of rules to control the characteristics of power quality is difficult, since its impact on electrical equipment changes as the characteristics of equipment change. A key to understanding how to cope with power quality issues begins with understanding the nature of electrical products. The nature of any product is defined by how its components are selected and how the designers apply those components. Reviewing design criteria, component selection and product characteristics can provide this basis of understanding.

Murphy, H.G. (Allen-Bradley Co., Mequon, WI (United States))

1993-07-01

175

A Sixty-Cycle Bridge for the Study of Radio-Frequency Power Amplifiers  

Microsoft Academic Search

A selective bridge, consisting of three resistive arms and a fourth arm comprising a sinusoidal sixty-cycle voltage, has been devised and applied to the study of radio-frequency power amplifiers. In Part I the measuring circuits are described, and in Part II some typical data on a type 10 tube are presented. The observed linearity of contours of constant plate loss

1935-01-01

176

Transient visually evoked potentials to sinusoidal gratings in optic neuritis.  

PubMed Central

Transient visually evoked potentials (VEPs) to sinusoidal gratings over a range of spatial frequencies have been recorded in cases of optic neuritis. The use of the response to pattern onset in addition to the response to pattern reversal extended the range to higher spatial frequencies by up to two octaves. There was an increase in VEP delay and a greater degree of discrimination from a control group at higher spatial frequencies. This finding is discussed in the light of previous reports of luminance and checkerboard VEPs in demyelinating optic nerve disease. An attempt is made to relate amplitude changes in various VEP components to contrast sensitivity measurements in this group of patients.

Plant, G T

1983-01-01

177

Characterization of carbon nanotube nanoswitches with gigahertz resonance frequency and low pull-in voltages using electrostatic force microscopy  

NASA Astrophysics Data System (ADS)

An electrostatic force microscope (EFM) was used to characterize single-walled carbon nanotube (SWNT)-based nanoswitches in this paper. A conductive atomic force microscopy (AFM) tip acted as a mechanical probe as well as a positioning electrode in the experiment. The resonance frequency of the SWNT beams was computed from the measured SWNTs' dimension and spring constant. The pull-in voltages and the corresponding gaps were extracted simultaneously from a set of force curves at different EFM probe bias voltages. The adhesive force between the AFM tip and the SWNT beam was measured through the analysis of retract force curves. The relationship between the pull-in voltage and the SWNT nanoswitch gap was in agreement with the electrostatic pull-in theory. Long-range forces such as meniscus force or electrostatic force from surface charges engaged the SWNT beam when the gap was below 6 nm in atmosphere. The SWNT beam with a resonance frequency of 1.1 GHz was actuated by a voltage of 2 V for a gap of 6.5 nm. The average adhesive force between an SWNT beam and a platinum/iridium (PtIr5)-coated tip was found to be about 50 nN. Considering the stiffness of the 1.1 GHz SWNT beam, the elastic restoring force at 6.5 nm exceeds 53 nN, which will overcome the adhesive force and release the 1.1 GHz SWNT beam. Finally, some possible approaches to further improve the behavior of SWNT nanoswitches are discussed.

Lu, Miao; Lu, Xuekun; Jang, Min-Woo; Campbell, Stephen A.; Cui, Tianhong

2010-10-01

178

Control of plasma process by use of harmonic frequency components of voltage and current  

DOEpatents

The present invention provides for a technique for taking advantage of the intrinsic electrical non-linearity of processing plasmas to add additional control variables that affect process performance. The technique provides for the adjustment of the electrical coupling circuitry, as well as the electrical excitation level, in response to measurements of the reactor voltage and current and to use that capability to modify the plasma characteristics to obtain the desired performance.

Miller, Paul A. (Albuquerque, NM); Kamon, Mattan (Cambridge, MA)

1994-01-01

179

Issues on the design and implementation of radio frequency CMOS LC tank voltage-controlled oscillators  

Microsoft Academic Search

This paper is a general tutorial on the design and implementation of integrated submicron CMOS voltage-controlled oscillators\\u000a based on LC resonator tanks. Although special reference to phase noise reduction is made, the discussion also includes issues\\u000a such as power consumption, oscillator reliability and adaptivity together with tuning range. Important guidelines on oscillator\\u000a and LC tank design are discussed, with emphasis

Owen Casha; Ivan Grech; Joseph Micallef

2009-01-01

180

DC Link Voltage and Supply-Side Current HarmonicsMinimization of Three Phase PWM BoostRectifiers Using Frequency Domain BasedRepetitive Current Controllers  

Microsoft Academic Search

This paper presents a digital plug-in frequency domain based repetitive control scheme for minimizing the odd order harmonics in the supply line side currents of the three phase pulsewidth modulation (PWM) boost rectifier under the distorted and unbalanced supply voltage conditions. Based on the mathematical model of the three-phase PWM boost rectifier under the generalized supply voltage conditions, the control

X. H. Wu; S. K. Panda; J. X. Xu

2008-01-01

181

Verification of voltage/frequency requirement for emergency diesel generator in nuclear power plant using dynamic modeling  

NASA Astrophysics Data System (ADS)

One major cause of the plant shutdown is the loss of electrical power. The study is to comprehend the coping action against station blackout including emergency diesel generator, sequential loading of safety system and to ensure that the emergency diesel generator should meet requirements, especially voltage and frequency criteria using modeling tool. This paper also considered the change of the sequencing time and load capacity only for finding electrical design margin. However, the revision of load list must be verified with safety analysis. From this study, it is discovered that new load calculation is a key factor in EDG localization and in-house capability increase.

Hur, Jin-Suk; Roh, Myung-Sub

2014-02-01

182

A filamentary method for calculating induced voltages within resistive structures in either the frequency or time domain  

NASA Astrophysics Data System (ADS)

A program was developed to predict current distributions resulting from a direct lightning strike to a structure of constant cross section consisting of both metallic and composite conductors. The structure is represented by a set of filaments which are assigned values of both resistance and self inductance. The current can be calculated in either the frequency or time domain; this current distribution then allows either the transfer impedance of wires located within the structure or the induced voltage on these wires as a function of time to be calculated.

Hardwick, C. J.; Haigh, S. J.; Burrows, B. J. C.

1988-04-01

183

A novel non-fragile single-loop voltage and frequency controller for induction generator based isolated renewable energy conversion system  

Microsoft Academic Search

Poor voltage and frequency regulation under source and load perturbations limit the use of self excited induction generator (SEIG) in isolated and dispersed generation, which can exploit wind\\/microhydro type renewable energy sources. In the present work, a Generalized Impedance Controller (GIC), which is a pulse-width-modulated voltage-source-inverter with a dc-link battery, is used to regulate both, amplitude and frequency of the

J. K. Chatterjee; Priyesh J. Chauhan

2010-01-01

184

Innovative electromagnetic induction eddy current-based dual packs heater using voltage-fed high-frequency PWM resonant inverter for continuous fluid processing in pipeline  

Microsoft Academic Search

This paper presents an innovative electromagnetic induction-heated fluid heating appliance using voltage-fed quasi-resonant zero voltage soft switching (ZVS)-PWM high frequency inverter, which operates under the variable power constant frequency (VPCF) regulation strategy. This appliance includes various features as compared with conventional gas contribution type and sheathed heater type fluid heating; rapid heating, clean heating, high efficiency and so on. This

M. Kaneda; S. Hishikawa; T. Tamaka; B. Guo; M. Nakaoka

1999-01-01

185

A Space Vector PWM Scheme for Multifrequency Output Voltage Generation With Multiphase Voltage-Source Inverters  

Microsoft Academic Search

Multiphase variable-speed drives, supplied from two-level voltage-source inverters (VSIs), are nowadays considered for various industrial applications. Depending on the drive structure and\\/or the motor design, the VSI is required to generate either sinusoidal voltages or voltages that contain a certain number of sinusoidal components (ldquomultifrequency output voltagesrdquo). The existing space vector pulsewidth-modulation (SVPWM) schemes are based on selection of (n-1)

Drazen Dujic; Gabriele Grandi; Martin Jones; Emil Levi

2008-01-01

186

Frequency-dependent reduction of voltage-gated sodium current modulates retinal ganglion cell response rate to electrical stimulation  

NASA Astrophysics Data System (ADS)

The ability to elicit visual percepts through electrical stimulation of the retina has prompted numerous investigations examining the feasibility of restoring sight to the blind with retinal implants. The therapeutic efficacy of these devices will be strongly influenced by their ability to elicit neural responses that approximate those of normal vision. Retinal ganglion cells (RGCs) can fire spikes at frequencies greater than 200 Hz when driven by light. However, several studies using isolated retinas have found a decline in RGC spiking response rate when these cells were stimulated at greater than 50 Hz. It is possible that the mechanism responsible for this decline also contributes to the frequency-dependent 'fading' of electrically evoked percepts recently reported in human patients. Using whole-cell patch clamp recordings of rabbit RGCs, we investigated the causes for the spiking response depression during direct subretinal stimulation of these cells at 50-200 Hz. The response depression was not caused by inhibition arising from the retinal network but, instead, by a stimulus-frequency-dependent decline of RGC voltage-gated sodium current. Under identical experimental conditions, however, RGCs were able to spike at high frequency when driven by light stimuli and intracellular depolarization. Based on these observations, we demonstrated a technique to prevent the spiking response depression.

Tsai, David; Morley, John W.; Suaning, Gregg J.; Lovell, Nigel H.

2011-10-01

187

Kinetic Analyses of Colloidal Crystallization in a Sinusoidal Electric Field as Studied by Reflection Spectroscopy.  

PubMed

The effect of a sinusoidal electric field on crystal growth rates in the colloidal crystallization of silica spheres (110 nm in diameter) in exhaustively deionized aqueous suspensions has been studied by reflection spectroscopy. Sphere concentration is 0.0016 in volume fraction. Nucleation time is shorter than 1 s. The crystal growth rates, v, of the body-centered cubic lattices have been determined from the increase in the cube root of the intensity in the sharpened reflection peaks. The v value is 20 µm/s in the absence of an electric field. v decreases from 20 to 8 µm/s as the voltage applied increases from 0 to 10 V at 1 Hz. v decreases from 30 to 15 µm/s when frequency increases from 0.01 to 10 Hz at E = 6 V, and remains constant irrespective of frequencies higher than 10 Hz up to 10 kHz. Interestingly, the crystallization of bcc lattices is enhanced at low frequencies between 0.01 and 0.5 Hz. The main causes for the retardation of crystallization at high frequencies and voltages are (a) the additional translational fluctuation of the spheres and the surrounding electrical double layers by the electric field, and (b) the partial melting of the crystals by the shearing forces in an electric field. The importance of electrostatic intersphere repulsion resulting from overlap of the electrical double layers and cooperative and synchronized fluctuation of colloidal spheres in crystallization processes is strongly supported. Copyright 1999 Academic Press. PMID:9929447

Okubo; Ishiki

1999-03-01

188

Voltage-Sensitive Dye Imaging of Neocortical Spatiotemporal Dynamics to Afferent Activation Frequency  

Microsoft Academic Search

The spatial and temporal patterns of neocortex activation are determined not only by the dynamic character of the input but also by the intrinsic dynamics of the cortical circuitry. To study the role of afferent input frequency on cortical activation dy- namics, the electrical activity of in vitro neocortex slices was imaged during white-matter electrical stimulation. High-speed optical imaging was

Diego Contreras; Rodolfo Llinas

2001-01-01

189

Low-voltage operation of a CMOS image sensor based on pulse frequency modulation  

Microsoft Academic Search

Inspired by biological information scheme, pulse frequency modulation (PFM) technique is robust for noise sources due to its digital encode of analog signals. In a viewpoint of image sensors, PFM is also useful for a wide dynamic range and has already been demonstrated over 60 dB. We have designed a pixel circuit of a CMOS image sensor using PFM for

Jun Ohta; Hirohiko Sakata; Takashi Tokuda; Masahiro Nunoshita

2001-01-01

190

I Found Sinusoids in My Gas Bill.  

ERIC Educational Resources Information Center

Uses the average-monthly-temperature function as an application of the sine wave. Argues that the attractive aspect of gas bill graphs is that they clearly illustrate that sinusoidal curves are useful and meaningful in an everyday context. (ASK)

Schloemer, Cathy G.

2000-01-01

191

Deconvolution of sinusoidal rapid EPR scans.  

PubMed

In rapid scan EPR the magnetic field is scanned through the signal in a time that is short relative to electron spin relaxation times. Previously it was shown that the slow-scan lineshape could be recovered from triangular rapid scans by Fourier deconvolution. In this paper a general Fourier deconvolution method is described and demonstrated to recover the slow-scan lineshape from sinusoidal rapid scans. Since an analytical expression for the Fourier transform of the driving function for a sinusoidal scan was not readily apparent, a numerical method was developed to do the deconvolution. The slow scan EPR lineshapes recovered from rapid triangular and sinusoidal scans are in excellent agreement for lithium phthalocyanine, a trityl radical, and the nitroxyl radical, tempone. The availability of a method to deconvolute sinusoidal rapid scans makes it possible to scan faster than is feasible for triangular scans because of hardware limitations on triangular scans. PMID:21163677

Tseitlin, Mark; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

2011-02-01

192

Deconvolution of Sinusoidal Rapid EPR Scans  

PubMed Central

In rapid scan EPR the magnetic field is scanned through the signal in a time that is short relative to electron spin relaxation times. Previously it was shown that the slow scan lineshape could be recovered from triangular rapid scans by Fourier deconvolution. In this paper a general Fourier deconvolution method is described and demonstrated to recover the slow scan lineshape from sinusoidal rapid scans. Since an analytical expression for the Fourier transform of the driving function for a sinusoidal scan was not readily apparent, a numerical method was developed to do the deconvolution. The slow scan EPR lineshapes recovered from rapid triangular and sinusoidal scans are in excellent agreement for lithium phthalocyanine, a trityl radical, and the nitroxyl radical, tempone. The availability of a method to deconvolute sinusoidal rapid scans makes it possible to scan faster than is feasible for triangular scans because of hardware limitations on triangular scans.

Tseitlin, Mark; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

2011-01-01

193

Sinusoidal pumping of groundwater near cylindrical inhomogeneities  

Microsoft Academic Search

A new analytic-element solution is presented for a well with a sinusoidal discharge pumping near cylindrical inhomogeneities.\\u000a Both the transmissivity and the storage coefficient may be different inside each cylinder. The solution consists of separate\\u000a series solutions inside and outside each cylinder; asymptotic expansions are presented for cases where the sinusoidal period\\u000a is small and the radius and transmissivity of

Mark Bakker

2009-01-01

194

Three-phase PWM sinusoidal current rectifier with power conditioning capability  

Microsoft Academic Search

This paper presents a PWM three-phase rectifier controlled to demand a sinusoidal source current in phase with the positive-sequence fundamental source voltage, providing unity displacement power factor. The operation of the rectifier is controlled so that in case of a nonlinear load connected to the grid, the power converter also operates as an active power filter, improving the global power

M. I. Milanés Montero; E. Romero Cadaval; V. M. Miñambres Marcos; M. A. G. Martinez

2009-01-01

195

Readily implemented enhanced sinusoid detection in noise  

SciTech Connect

Significant efforts have been devoted, spanning many years, to the problem of sinusoid detection in noise. Many of these efforts have produced superb, yet complex, algorithms which may be difficult to use for a wide segment of the Digital Signal Processing (DSP) community. This paper presents a simple, easily implemented and high effective method which solves this problem. This method severely degrades non-sinusoidal noise while leaving the embedded sinusoid(s) relatively undisturbed. The algorithm, simply put, exploits the difference between the net effect of integration and differentiation of sinusoids versus the effect of these operations on random noise and other signal sequences. The cross-correlation of sine wave with its differentiated (and/or integrated) self is quite high. Conversely, the cross-reduction of a noise sequence with its differentiated (and/or integrated) self is much lower. Therefore, it is reasonable to assume that for sequences consisting of a sinusoid in noise, significant signal-to-noise-ratios (SNRs) in the correlation results are achievable using a combination of differentiation (and/or integration) and cross-correlation operations on such sequences. This technique has been applied to actual Doppler radar data, as well as to synthesized data, with excellent improvement in signal detection capability. 4 refs.

Lindsay, K.V.

1992-03-05

196

A Novel Switching Sequence Design for Five-Level NPC\\/H-Bridge Inverters with Improved Output Voltage Spectrum and Minimized Device Switching Frequency  

Microsoft Academic Search

This paper presents a novel flexible 3-segment switching sequence for the space vector modulation (SVM) of high-power multilevel converters. The switching sequence is optimized for the improvement of harmonic spectrum and the minimization of device switching frequency. Compared to other commonly used switching sequences, the output voltage spectrum of the proposed scheme shows higher inverter equivalent switching frequencies and lower

Zhongyuan Cheng; Bin Wu

2006-01-01

197

Performance evaluation of half-bridge cascaded multilevel converters operated with multicarrier sinusoidal PWM techniques  

Microsoft Academic Search

High-power high-voltage power electronics systems with fully-controlled semiconductors can benefit from the development of modular solutions based on voltage-sourced building blocks. This paper offers a performance comparison of various multicarrier sinusoidal pulse width modulation (PWM) techniques for the control of the modular multilevel converter (MMC) based on the half-bridge capacitor cell. It is found that the PWM method can significantly

Georgios S. Konstantinou; Vassilios G. Agelidis

2009-01-01

198

One-dimensional plasma photonic crystals with sinusoidal densities  

NASA Astrophysics Data System (ADS)

Properties of electromagnetic waves with normal and oblique incidence have been studied for one-dimensional plasma layers with sinusoidal densities. Wave transmittance as a function of wave frequency exhibits photonic band gaps characteristic of photonic crystals. For periodic structures, increasing collision frequency is demonstrated to lead to greater absorption, increasing the modulation factor enlarges the gap width, and increasing incidence angle can change the gap locations of the two polarizations. If a defect layer is introduced by inserting a new plasma layer in the center, a defect mode may appear within the gap. Periodic number, collision frequency, and modulation factor can affect magnitude of the defect mode. The incidence angle enables the frequency to be tuned. Defect layer thickness affects both frequency and number of defect modes. These results may provide theoretical guidance in designing tunable narrow-band filters.

Qi, L.; Shang, L.; Zhang, S.

2014-01-01

199

Frequency and temperature dependences of capacitance-voltage characteristics of InGaN/GaN light-emitting structures with multiple quantum wells  

SciTech Connect

A frequency dependence of capacitance-voltage (C-V) characteristics in multiple quantum well InGaN/GaN heterostructures in the range of 60 Hz-5 MHz is investigated at temperatures from 77 to 300 K. It is found that temperature lowering and test frequency increase lead to the similar changes in obtained apparent carrier distributions. It is shown that commonly used conditions for capacitance-voltage profiling of InGaN/GaN LEDs correspond to an intermediate case between low- and high-frequency capacitance approximations. At all temperatures investigated, the edge low-frequency capacitance-voltage profiles are experimentally reached and found to be identical. The process of attainment of equilibrium of the charges in the active region is most likely determined by tunneling of the carriers through the barriers.

Soltanovich, O. A. [Russian Academy of Sciences, Institute of Microelectronic Technology and High-Purity Materials (Russian Federation); Shmidt, N. M. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Yakimov, E. B., E-mail: yakimov@iptm.ru [Russian Academy of Sciences, Institute of Microelectronic Technology and High-Purity Materials (Russian Federation)

2011-02-15

200

Incomplete Inactivation and Rapid Recovery of Voltage-Dependent Sodium Channels During High-Frequency Firing in Cerebellar Purkinje Neurons  

PubMed Central

Purkinje neurons can spike very rapidly for sustained periods. We examined the cycle of sodium channel gating during high-frequency firing of Purkinje neurons, focusing on the kinetics of sodium channel inactivation and recovery during and after spikes. To analyze sodium channel availability during spiking, we recorded the firing patterns of acutely dissociated Purkinje neurons in current clamp and used these records as command voltages in voltage-clamp experiments in the same cell, adding step depolarizations at various points to assay availability. Sodium channel availability decreased abruptly during the spike, as expected, but never reached zero. During spontaneous firing (?40 Hz at 37°C), availability decreased from nearly 90% before the spike to about 10–20% after the spike. With fast steady firing stimulated by current injection (?300 Hz at 37°C), the availability decreased from about 60% between spikes to roughly 15–20% after the spike. Thus even at the fastest firing rates, sodium channel inactivation is incomplete after a spike, leaving a substantial fraction of sodium channels immediately available for activation. Also, inactivation recovered quickly during the early interspike interval (time constant ?1 ms at 37°C), but developed slowly during the depolarization of the late interspike interval, ensuring high availability until spike threshold. These features of sodium channel gating, especially the availability remaining after the spike, reduce the refractory period and facilitate rapid repetitive firing.

Carter, Brett C.

2011-01-01

201

Digitally synthesized high purity, high-voltage radio frequency drive electronics for mass spectrometry  

NASA Astrophysics Data System (ADS)

Reported herein is development of a quadrupole mass spectrometer controller (MSC) with integrated radio frequency (rf) power supply and mass spectrometer drive electronics. Advances have been made in terms of the physical size and power consumption of the MSC, while simultaneously making improvements in frequency stability, total harmonic distortion, and spectral purity. The rf power supply portion of the MSC is based on a series-resonant LC tank, where the capacitive load is the mass spectrometer itself, and the inductor is a solenoid or toroid, with various core materials. The MSC drive electronics is based on a field programmable gate array (FPGA), with serial peripheral interface for analog-to-digital and digital-to-analog converter support, and RS232/RS422 communications interfaces. The MSC offers spectral quality comparable to, or exceeding, that of conventional rf power supplies used in commercially available mass spectrometers; and as well an inherent flexibility, via the FPGA implementation, for a variety of tasks that includes proportional-integral derivative closed-loop feedback and control of rf, rf amplitude, and mass spectrometer sensitivity. Also provided are dc offsets and resonant dipole excitation for mass selective accumulation in applications involving quadrupole ion traps; rf phase locking and phase shifting for external loading of a quadrupole ion trap; and multichannel scaling of acquired mass spectra. The functionality of the MSC is task specific, and is easily modified by simply loading FPGA registers or reprogramming FPGA firmware.

Schaefer, R. T.; Macaskill, J. A.; Mojarradi, M.; Chutjian, A.; Darrach, M. R.; Madzunkov, S. M.; Shortt, B. J.

2008-09-01

202

Digitally synthesized high purity, high-voltage radio frequency drive electronics for mass spectrometry.  

PubMed

Reported herein is development of a quadrupole mass spectrometer controller (MSC) with integrated radio frequency (rf) power supply and mass spectrometer drive electronics. Advances have been made in terms of the physical size and power consumption of the MSC, while simultaneously making improvements in frequency stability, total harmonic distortion, and spectral purity. The rf power supply portion of the MSC is based on a series-resonant LC tank, where the capacitive load is the mass spectrometer itself, and the inductor is a solenoid or toroid, with various core materials. The MSC drive electronics is based on a field programmable gate array (FPGA), with serial peripheral interface for analog-to-digital and digital-to-analog converter support, and RS232/RS422 communications interfaces. The MSC offers spectral quality comparable to, or exceeding, that of conventional rf power supplies used in commercially available mass spectrometers; and as well an inherent flexibility, via the FPGA implementation, for a variety of tasks that includes proportional-integral derivative closed-loop feedback and control of rf, rf amplitude, and mass spectrometer sensitivity. Also provided are dc offsets and resonant dipole excitation for mass selective accumulation in applications involving quadrupole ion traps; rf phase locking and phase shifting for external loading of a quadrupole ion trap; and multichannel scaling of acquired mass spectra. The functionality of the MSC is task specific, and is easily modified by simply loading FPGA registers or reprogramming FPGA firmware. PMID:19044454

Schaefer, R T; MacAskill, J A; Mojarradi, M; Chutjian, A; Darrach, M R; Madzunkov, S M; Shortt, B J

2008-09-01

203

Digitally synthesized high purity, high-voltage radio frequency drive electronics for mass spectrometry  

SciTech Connect

Reported herein is development of a quadrupole mass spectrometer controller (MSC) with integrated radio frequency (rf) power supply and mass spectrometer drive electronics. Advances have been made in terms of the physical size and power consumption of the MSC, while simultaneously making improvements in frequency stability, total harmonic distortion, and spectral purity. The rf power supply portion of the MSC is based on a series-resonant LC tank, where the capacitive load is the mass spectrometer itself, and the inductor is a solenoid or toroid, with various core materials. The MSC drive electronics is based on a field programmable gate array (FPGA), with serial peripheral interface for analog-to-digital and digital-to-analog converter support, and RS232/RS422 communications interfaces. The MSC offers spectral quality comparable to, or exceeding, that of conventional rf power supplies used in commercially available mass spectrometers; and as well an inherent flexibility, via the FPGA implementation, for a variety of tasks that includes proportional-integral derivative closed-loop feedback and control of rf, rf amplitude, and mass spectrometer sensitivity. Also provided are dc offsets and resonant dipole excitation for mass selective accumulation in applications involving quadrupole ion traps; rf phase locking and phase shifting for external loading of a quadrupole ion trap; and multichannel scaling of acquired mass spectra. The functionality of the MSC is task specific, and is easily modified by simply loading FPGA registers or reprogramming FPGA firmware.

Schaefer, R. T.; Mojarradi, M. [Advanced Computer Systems and Technologies Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); MacAskill, J. A.; Chutjian, A.; Darrach, M. R.; Madzunkov, S. M. [Atomic and Molecular Physics Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Shortt, B. J. [Astrium Satellites Ltd., Gunnels Wood Road, Stevenage, Hertfordshire SG1 2AS (United Kingdom)

2008-09-15

204

Influence of High-Frequency Charge–Discharge Cycling Induced by Cell Voltage Equalizers on the Life Performance of Lithium-Ion Cells  

Microsoft Academic Search

Various types of cell voltage equalizers that exchange charges among cells have been proposed for series-connected lithium-ion cells. During equalization, cells are possibly cycled not only over a conventional period that ranges from seconds to hours but at a high frequency that is equal to the operating frequency of the equalizers as well. This paper investigates how the high-frequency cycling

Masatoshi Uno; Koji Tanaka

2011-01-01

205

A New Initial-Rotor-Position Estimation Method for SPM Synchronous Motors Using Spatially Rotating High-Frequency Voltage  

NASA Astrophysics Data System (ADS)

First of all, this paper proposes a new dynamic mathematical model of surface-mounted permanent magnet synchronous motors (SPMSMs) with flux saturation phenomena, in stationary reference frame. Secondly, based on the dynamic model, this paper establishes new dynamic simulators taking flux saturation phenomena into account, which act as very powerful tools for developing initial-rotor-position estimation methods for SPMSMs. Thirdly, this paper proposes a new initial-rotor-position estimation method for SPMSMs. The proposed method is so simple that it inputs a spatially rotating high-frequency voltage to SPMSMs, measures current output and can estimate directly rotor position of N-pole through norm evaluation of the current. The method exploits flux saturation phenomena inherent to SPMSMs and is insensitive to all motor parameters. According to experiments, the maximum estimation error is about ±0.035(rad) (±2(degree)) in mechanical sense, which is comparable to sensor mounting error and is sufficient small for initial drive of SPMSMs.

Shinnaka, Shinji; Kumakura, Takeshi

206

Frequency-dependent reliability of spike propagation is function of axonal voltage-gated sodium channels in cerebellar Purkinje cells.  

PubMed

The spike propagation on nerve axons, like synaptic transmission, is essential to ensure neuronal communication. The secure propagation of sequential spikes toward axonal terminals has been challenged in the neurons with a high firing rate, such as cerebellar Purkinje cells. The shortfall of spike propagation makes some digital spikes disappearing at axonal terminals, such that the elucidation of the mechanisms underlying spike propagation reliability is crucial to find the strategy of preventing loss of neuronal codes. As the spike propagation failure is influenced by the membrane potentials, this process is likely caused by altering the functional status of voltage-gated sodium channels (VGSC). We examined this hypothesis in Purkinje cells by using pair-recordings at their somata and axonal blebs in cerebellar slices. The reliability of spike propagation was deteriorated by elevating spike frequency. The frequency-dependent reliability of spike propagation was attenuated by inactivating VGSCs and improved by removing their inactivation. Thus, the functional status of axonal VGSCs influences the reliability of spike propagation. PMID:23775547

Yang, Zhilai; Wang, Jin-Hui

2013-12-01

207

Single chip controller for a high-switching frequency DC\\/AC power inverter  

Microsoft Academic Search

The design and implementation of a new controller for a DC\\/AC power inverter is described. The controller uses the high switching frequency sinusoidal PWM technique and achieves excellent output voltage regulation, frequency stability and dynamic response in a noiseless, light-weight and cost-effective construction. The inverter performance is analysed using experimental results as well as the harmonic analysis based on the

T. ANTONAKOPOULOS; S. PRESSAS; V. MAKIOS

1992-01-01

208

Drag prediction over steep sinusoidal wavy surfaces  

NASA Astrophysics Data System (ADS)

A parametrization of the form drag due to airflow over sinusoidal wavy surfaces in the presence of significant flow separation is investigated; it is based on a bluff-body analogy. To this aim, the results of large-eddy simulations carried out for various Reynolds numbers and wave slopes are used, together with the data from experiments and other simulations available in the literature. It is shown that, as a first approximation, the drag coefficient may be considered independent of the wave slope and Reynolds number. The value obtained here for rigid sinusoidal waves is close to that computed for wind-ruffled breaking paddle waves.

Salvetti, M. V.; Damiani, R.; Beux, F.

2001-09-01

209

Measuring adaptation with a sinusoidal perturbation function.  

PubMed

We examine the possibility that sensory and motor adaptation may be induced via a sinusoidally incremented perturbation. This sinewave adaptation method provides superior data for fitting a parametric model than when using the standard step-function method of perturbation, due to the relative difficulty of fitting a decaying exponential vs. a sinusoid. Using both experimental data and simulations, we demonstrate the difficulty of detecting the presence of motor adaptation using a step-function perturbation, compared to detecting motor adaptation using our sinewave perturbation method. PMID:22565135

Hudson, Todd E; Landy, Michael S

2012-06-30

210

Rem2-targeted shRNAs reduce frequency of miniature excitatory postsynaptic currents without altering voltage-gated Ca²? currents.  

PubMed

Ca²? influx through voltage-gated Ca²? channels (VGCCs) plays important roles in neuronal cell development and function. Rem2 is a member of the RGK (Rad, Rem, Rem2, Gem/Kir) subfamily of small GTPases that confers potent inhibition upon VGCCs. The physiologic roles of RGK proteins, particularly in the brain, are poorly understood. Rem2 was implicated in synaptogenesis through an RNAi screen and proposed to regulate Ca²? homeostasis in neurons. To test this hypothesis and uncover physiological roles for Rem2 in the brain, we investigated the molecular mechanisms by which Rem2 knockdown affected synaptogenesis and Ca²? homeostasis in cultured rat hippocampal neurons. Expression of a cocktail of shRNAs targeting rat Rem2 (rRem2) reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs) measured 10 d after transfection (14 d in vitro), but did not affect mEPSC amplitude. VGCC current amplitude after rRem2-targeted knockdown was not different from that in control cells, however, at either 4 or 10 d post transfection. Co-expression of a human Rem2 that was insensitive to the shRNAs targeting rRem2 was unable to prevent the reduction in mEPSC frequency after rRem2-targeted knockdown. Over-expression of rRem2 resulted in 50% reduction in VGCC current, but neither the mEPSC frequency nor amplitude was affected. Taken together, the observed effects upon synaptogenesis after shRNA treatment are more likely due to mechanisms other than modulation of VGCCs and Ca²? homeostasis, and may be independent of Rem2. In addition, our results reveal a surprising lack of contribution of VGCCs to synaptogenesis during early development in cultured hippocampal neurons. PMID:21980534

Wang, Hong-Gang; Wang, Chuan; Pitt, Geoffrey S

2011-01-01

211

Riding the Ferris Wheel: A Sinusoidal Model  

ERIC Educational Resources Information Center

When thinking of models for sinusoidal waves, examples such as tides of the ocean, daily temperatures for one year in your town, light and sound waves, and certain types of motion are used. Many textbooks [1, p. 222] also present a "Ferris wheel description problem" for students to work. This activity takes the Ferris wheel problem out of the…

Mittag, Kathleen Cage; Taylor, Sharon E.

2011-01-01

212

Adaptive line enhancement and sinusoidal burst detection  

SciTech Connect

This paper concerns an adaptive short-term correlator (ASC) algorithm. Three possible applications are discussed. Two of these are line enhancement and sinusoidal-burst detection, as indicated in the title. Some results related to a third application, source detection, are also included.

Ahmed, N.; Vijayendra, S.; Fogler, R.J.; Elliott, G.R.

1982-12-01

213

Adaptive line enhancement and sinusoidal burst detection  

SciTech Connect

This paper concerns an adaptive short-term correlator (ASC) algorithm. Three possible applications are presented. Two of these are line enhancement and sinusoidal burst detection, as indicated in the title. Some results related to a third application are also included.

Ahmed, N.; Vijayendra, S.; Fogler, R.J.; Elliott, G.R.

1982-01-01

214

Study on Corona Discharge Test under the Power Frequency Voltage of the Severe Non-uniform Electric Field Based on the UV-light Imaging Technology  

Microsoft Academic Search

The study on corona discharge test under the power frequency voltage of the severe non-uniform electric field based on the UV-light imaging technology is conducted. The results illuminate that the corresponding relationship between the characterizing parameter of quantifying the intensity of corona discharge and the comparing parameter is accordant; the characterizing parameter can reflect the basic physical process of gas

Ma Bin; Zhou Wenjun; Wang Tao; Ding Yigong

2006-01-01

215

A control approach for voltage and frequency regulation of a Wind-Diesel-battery based hybrid remote area power supply system  

Microsoft Academic Search

A novel Remote Area Power Supply (RAPS) system consisting of a Doubly Fed Induction Generator (DFIG) wind turbine generator, synchronous diesel generator system, battery storage system and a dump load is considered in this paper. A control coordination strategy is formulated with a view to regulate the system voltage and frequency within acceptable limits while extracting the maximum power available

Nishad Mendis; Kashem M. Muttaqi; S. Sayeef; S. Perera

2010-01-01

216

Northeast Corridor Improvement Project Task 204: Electric Multiple-Unit Car and Locomotive Conversion for Dual-Voltage, Dual-Frequency Operation.  

National Technical Information Service (NTIS)

The report covers engineering requirements of converting electric MU cars and locomotives operating on the Northeast Corridor for dual-voltage, dual-frequency operation during and after rehabilitation of the electrification system for 25 kV, 60 Hz power. ...

1977-01-01

217

Partial discharge endurence test on several kinds of nano-filled enameled wires under high-frequency AC voltage simulating inverter surge voltage  

Microsoft Academic Search

Partial discharge (PD) endurance test was performed on twisted pair specimens of enameled wires consisting of polyamide-imide resin with nanometer-size fillers. Specimens were prepared with containing nanometer-scale silica or titania fillers, as well as specimens without fillers. In the PD endurance test, so-called V-t characteristics of the twisted pair specimen were measured by applying a constant ac voltage 1-2 kVrms

Masayuki Hikita; Kouhei Yamaguchi; Masato Fujimoto; Masahiro Kozako; Shinya Ohtsuka; Makoto Ohya; Keiichi Tomizawa; Noriyoshi Fushimi

2009-01-01

218

Frequency- and voltage-dependent dielectric properties and electrical conductivity of Au/PVA (Bi-doped)/n-Si Schottky barrier diodes at room temperature  

NASA Astrophysics Data System (ADS)

In this study, frequency and voltage dependence of dielectric constant ( ?'), dielectric loss ( ??), loss tangent (tan ?), the real and imaginary parts of electric modulus ( M' and M?) and ac electrical conductivity ( ? ac) of an Au/PVA (Bi-doped)/n-Si Schottky barrier diode have been investigated in detail by using experimental C- V and G- V measurements in the wide frequency range of 5 kHz-10 MHz and the voltage range of ±2 V at room temperature. Experimental results indicate that the values of ?', ??, tan ? and ? ac are strongly frequency and voltage dependent. It has found that the values of ?', ?? and tan ? decrease while the values of ? ac, M' and M? increase. It is clear that the values of M? show a distinctive peak with a U-shape and its position shifts towards the positive-bias region with increasing frequency. Such behavior of the peak can be attributed to the particular distribution of interface states located at the Si/PVA interface and interfacial polarization. It can be concluded that the interfacial polarization and the charge at the interface can easily follow the ac signal at low frequencies.

Demirezen, Selçuk

2013-09-01

219

Rectification of confined diffusion driven by a sinusoidal force.  

PubMed

A particle diffusing in an asymmetric periodic channel, driven by a sinusoidal force F(t)=F0cos?t (the rocking ratchet) is considered. The asymptotic solution of the generalized Fick-Jacobs equation describing the system is studied in the nonadiabatic regime. The leading term of the rectified current, appearing in the order ?F02, is derived. The method presented enables us to solve the problem analytically for a sawtooth channel and also to look for approximative formulas applicable in a wide range of frequencies ?. Even the simplest approximation qualitatively reproduces the current reversal at higher frequencies as the result of growing phase lag of the rocking density behind the driving force. PMID:24827209

Kalinay, Pavol

2014-04-01

220

Rectification of confined diffusion driven by a sinusoidal force  

NASA Astrophysics Data System (ADS)

A particle diffusing in an asymmetric periodic channel, driven by a sinusoidal force F(t )=F0cos?t (the rocking ratchet) is considered. The asymptotic solution of the generalized Fick-Jacobs equation describing the system is studied in the nonadiabatic regime. The leading term of the rectified current, appearing in the order ˜F02, is derived. The method presented enables us to solve the problem analytically for a sawtooth channel and also to look for approximative formulas applicable in a wide range of frequencies ?. Even the simplest approximation qualitatively reproduces the current reversal at higher frequencies as the result of growing phase lag of the rocking density behind the driving force.

Kalinay, Pavol

2014-04-01

221

Sufficiency of Sinusoidal Motions in Seismic Ground Motion Studies.  

National Technical Information Service (NTIS)

This study evaluates the effectiveness of using sinusoidal input motions in seismic ground motion studies. The computer program SHAKE-88 is used to compute the peak surface accelerations in three different soil profiles subjected to sinusoidal and earthqu...

B. W. Boyce

1994-01-01

222

Sinusoidal portal hypertension in hepatic amyloidosis.  

PubMed Central

Hepatic venous catheterisation and transvenous liver biopsy were performed in five patients with hepatic amyloidosis. In three patients, hepatic venous pressures were normal and histological examination of the liver biopsy specimen showed discrete and sparse perisinusoidal amyloid deposits. In the other two, however, the gradient between wedged and free hepatic venous pressures was increased (12 and 16 mmHg; normal 1-4 mmHg) and amyloid deposits were abundant and diffuse in the Disse's space. This study shows that portal hypertension in patients with hepatic amyloidosis is of the sinusoidal type and is related to the reduction of vascular space of hepatic sinusoids by massive perisinusoidal amyloid deposits. Furthermore, portal hypertension is associated with a poor prognosis in patients with hepatic amyloidosis. Images Figure 1 Figure 2

Bion, E; Brenard, R; Pariente, E A; Lebrec, D; Degott, C; Maitre, F; Benhamou, J P

1991-01-01

223

Human comfort in relation to sinusoidal vibration  

NASA Technical Reports Server (NTRS)

An investigation was made to assess the overall subjective comfort levels to sinusoidal excitations over the range 1 to 19 Hz using a two axis electrohydraulic vibration simulator. Exposure durations of 16 minutes, 25 minutes, 1 hour, and 2.5 hours have been considered. Subjects were not exposed over such durations, but were instructed to estimate the overall comfort levels preferred had they been constantly subjected to vibration over such durations.

Jones, B.; Rao, B. K. N.

1975-01-01

224

Sinusoidal shaking in event-driven simulations  

NASA Astrophysics Data System (ADS)

Event-driven algorithms are a powerful and efficient simulation method that can be used to numerically study the behavior of particulate systems, such as granular materials or powders. Its superior efficiency originates from only considering analytically calculable points in time, where physically relevant events occur. This, however, is only possible for pairs of trajectories whose relative distance can be expressed as a polynomial of order less than or equal to four. For more complex trajectories, like a sinusoidal motion of a wall, the collision times have to be calculated numerically, which dramatically reduces the efficiency. In this paper we present a tabulation method implemented in an event-driven algorithm, which is able to efficiently handle the one-dimensional motion of a periodically moving wall. By demonstrating this for a sinusoidally moving wall, we enhance the comparability of simulations with (usually sinusoidally driven) experiments. Because granular materials or powders are systems which are easily accessible through both experiments and simulations, our work enhances the growing field of statistical physics far from equilibrium.

Roeller, K.; Herminghaus, S.; Hager-Fingerle, A.

2012-02-01

225

Corrections for sinusoidal background and non-orthogonality of signal channels in sinusoidal rapid magnetic field scans  

PubMed Central

The rapidly-changing magnetic field of sinusoidal rapid scans creates background signals that are dominated by oscillations at the scan frequency. The background oscillations can be removed without acquiring off-resonance data. For data acquired in quadrature, up-field and down-field scan signals can be separated in the frequency domain. For each scan direction, the background oscillation can be calculated by fitting to the half cycle that does not contain the EPR signal. The extrapolated fit function is then subtracted from the half cycle that contains the EPR signal. By zeroing the array for the half cycles that do not contain the EPR signal, the signal-to-noise is improved and the data are corrected for non-orthogonality of the quadrature channels.

Tseitlin, Mark; Mitchell, Deborah G.; Eaton, Sandra S.; Eaton, Gareth R.

2012-01-01

226

A New Method of Dynamic Electric Birefringence Measurement Using a Sinusoidal Digital Lock-In System  

NASA Astrophysics Data System (ADS)

A new apparatus for measuring the birefringence of a polymer solution under a continuous a.c. electric field has been developed. The birefringence signal is modulated by sinusoidal amplitude modulation (AM) and frequency modulation (FM) of the applied electric field in the frequency range from 0.1 Hz to 100 kHz. The birefringence response is detected with a digital lock-in system with a sinusoidal reference wave. Digital data processing ensures a high accuracy even at ultra-low frequencies. The data for nitrobenzene indicate that a birefringence as low as 10-13 can be accurately measured for an optical path of 1 cm. Illustrative results for poly(?-benzyl-L-glutamate) in m-cresol and DNA in aqueous NaCl are presented. The FM technique yields the frequency derivative of the AM curve and gives the relaxational frequency of these solutions clearly.

Ookubo, Norio; Mori, Yasushi; Hayakawa, Reinosuke; Wada, Yasaku

1980-11-01

227

Estimation of the Parameters of Sinusoidal Signals inNon-Gaussian Noise  

Microsoft Academic Search

Accurate estimation of the amplitude and frequency parameters of sinusoidal signals from noisy observations is an important problem in many signal processing applications. In this paper, the problem is investigated under the assumption of non-Gaussian noise in general and Laplace noise in particular. It is proven mathematically that the maximum likelihood estimator derived under the condition of Laplace white noise

Ta-hsin Li; Kai-sheng Song

2009-01-01

228

VALIDATION OF A MODEL FOR RAILWAY ROLLING NOISE USING FIELD MEASUREMENT WITH SINUSOIDALLY PROFILED WHEELS  

Microsoft Academic Search

Field measurements have been carried out using a series of railway wheels with specially machined running surfaces. These were given a sinusoidal profile around their circumference. This allows accurate measurements of noise and vibration to be made for single frequency excitation. A series of wheels with different wavelengths has been used in combination with a range of running speeds to

D. J. Thompson; N. Vincent; P. E. Gautier

1999-01-01

229

Matrix pencil method for estimating parameters of exponentially damped\\/undamped sinusoids in noise  

Microsoft Academic Search

A study of a matrix pencil method for estimating frequencies and damping factors of exponentially damped and\\/or undamped sinusoids in noise is presented. Comparison of this method to a polynomial method (SVD-Prony method) shows that the matrix pencil method and the polynomial method are two special cases of a matrix prediction approach and that the pencil method is more efficient

Y. Hua; T. K. Sarkar

1990-01-01

230

Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature  

NASA Astrophysics Data System (ADS)

In order to investigate of cobalt-doped interfacial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, Al/p-Si Schottky barrier diodes (SBDs) are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carried out in the frequency and voltage ranges of 30 kHz–300 kHz and ?5 V–6 V, respectively. C–V or ?'–V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance (Rs), and interfacial layer. Both the real and imaginary parts of dielectric constant (?' and ??) and electric modulus (M' and M?), loss tangent (tan ?), and AC electrical conductivity (?ac) are investigated, each as a function of frequency and applied bias voltage. Each of the M' versus V and M? versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance (C) and conductance (G/w) values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of Al/Co-doped PVA/p-Si (MPS) type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low–high frequency capacitance (CLF?CHF) method.

Ibrahim, Yüceda?; Ahmet, Kaya; ?emsettin, Alt?ndal; Ibrahim, Uslu

2014-04-01

231

High voltage power supply  

NASA Technical Reports Server (NTRS)

A high voltage power supply is formed by three discrete circuits energized by a battery to provide a plurality of concurrent output signals floating at a high output voltage on the order of several tens of kilovolts. In the first two circuits, the regulator stages are pulse width modulated and include adjustable ressistances for varying the duty cycles of pulse trains provided to corresponding oscillator stages while the third regulator stage includes an adjustable resistance for varying the amplitude of a steady signal provided to a third oscillator stage. In the first circuit, the oscillator, formed by a constant current drive network and a tuned resonant network included a step up transformer, is coupled to a second step up transformer which, in turn, supplies an amplified sinusoidal signal to a parallel pair of complementary poled rectifying, voltage multiplier stages to generate the high output voltage.

Ruitberg, A. P.; Young, K. M. (inventors)

1985-01-01

232

Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (< 1 kV) and series connected step-up (1:10) transformers.  

PubMed

This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed. PMID:17411205

Redondo, L M; Fernando Silva, J; Margato, E

2007-03-01

233

Connecting Renewables Directly to the Grid: Resilient Multi-Terminal HVDC Networks with High-Voltage High-Frequency Electronics  

SciTech Connect

GENI Project: GE is developing electricity transmission hardware that could connect distributed renewable energy sources, like wind farms, directly to the grid—eliminating the need to feed the energy generated through intermediate power conversion stations before they enter the grid. GE is using the advanced semiconductor material silicon carbide (SiC) to conduct electricity through its transmission hardware because SiC can operate at higher voltage levels than semiconductors made out of other materials. This high-voltage capability is important because electricity must be converted to high-voltage levels before it can be sent along the grid’s network of transmission lines. Power companies do this because less electricity is lost along the lines when the voltage is high.

None

2012-01-23

234

Effects of voltage errors caused by gap-voltage and automatic-frequency tuning in an alternating-phase-focused linac  

Microsoft Academic Search

A compact injector for a heavy-ion medical-accelerator complex was developed. It consists of an electron-cyclotron-resonance ion-source (ECRIS) and two linacs, which are a radio-frequency-quadrupole (RFQ) linac and an Interdigital H-mode drift-tube-linac (IH-DTL). Beam acceleration tests of the compact injector were performed, and the designed beam quality was verified by the measured results, as reported earlier. Because the method of alternating-phase-focusing

Y. Iwata; S. Yamada; T. Murakami; T. Fujimoto; T. Fujisawa; H. Ogawa; N. Miyahara; K. Yamamoto; S. Hojo; Y. Sakamoto; M. Muramatsu; T. Takeuchi; T. Mitsumoto; H. Tsutsui; T. Watanabe; T. Ueda

2008-01-01

235

Comparison between piezoelectric material properties obtained by using low-voltage magnitude frequency sweeping and high-level short impulse signals.  

PubMed

Determination of electromechanical piezoceramic material parameters is usually done by fitting the measured input electrical impedance of the piezoceramic sample to the theoretical modelling equation for the input electrical impedance of the unloaded free piezoceramic resonator. The input electrical impedance of the sample is usually measured by using low voltage or current magnitude frequency sweeping signals. In this work, the complex material parameters of piezoceramic samples are determined in the real operating conditions by using the high voltage short impulse excitation signals. The input electrical impedance determined in the impulse mode around thickness extensional vibration mode (TE) and calculated piezoceramic parameters (clamped dielectric permittivity, electromechanical coupling factor, elastic stiffness and piezoelectric constant) are compared to the results obtained by using the low voltage magnitude frequency sweeping signals. When impulse excitation is used, the series resonance frequency is decreased and the input electrical impedance magnitude at series resonance is increased, which means that overall losses included in the piezoceramic parameters are increased. The complex material parameters obtained from the input electrical impedances determined by using the low voltage magnitude sweeping signal and high level short impulse signals are included in the KLM theoretical model describing the piezoceramic sample behaviour around TE mode. Better agreement between measured and theoretically determined current magnitude response around TE mode has been obtained, in the KLM model, when piezoceramic parameters determined by using the impulse signal excitations are included in the modelling. The physical reason for increase of the losses in piezoceramic material could lie in the fact that the ferroelectric domains in the piezoceramic respond harder on very short impulse excitation signals than on continuous frequency sweeping signals which are usually used in determination of piezoelectric material parameters. PMID:23562492

Petoši?, Antonio; Budimir, Marko; Pavlovi?, Nikola

2013-08-01

236

The frequency behavior of InGaAs-AlInAs metal-semiconductor-metal photodetectors at low bias voltages for data communication applications  

Microsoft Academic Search

The authors have fabricated lattice matched InGaAs\\/AlInAs metal-semiconductor-metal photodetectors on InP. The detectors have very low dark currents, low capacitance, and good responsivity, corresponding to at least 95% internal collection efficiency. It is demonstrated that multigigahertz bandwidths, as measured in the frequency domain, are achievable at typical logic-level bias voltages, and that therefore these detectors are viable candidates for long-wavelength

J. H. Burroughes; M. S. Milshtein; G. D. Pettit; N. Pakdaman; H. Heinrich; J. M. Woodall

1992-01-01

237

High-voltage high-frequency transformer design for a 7.2kV to 120V\\/240V 20kVA solid state transformer  

Microsoft Academic Search

Solid state transformer (SST) exhibits good features such as high power density, small volume and weight, controlled power factor, voltage sag ride through, etc. compared with traditional line frequency transformer. The 7.2 kV AC to 120V\\/240V AC 20 kVA solid state transformer is a key component of the future renewable electric energy delivery and management (FREEDM) systems as the interface

Yu Du; Seunghun Baek; Subhashish Bhattacharya; Alex Q. Huang

2010-01-01

238

High frequency capacitance-voltage technique for the extraction of interface trap density of the heterojunction capacitor: Terman’s method revised  

Microsoft Academic Search

In a multi-layer heterojunction system, the interface responsible for trap charging is spatially displaced from the two-dimensional charge gas, in contrast to the typical SiO2\\/Si capacitor. This displacement causes the effective trap capacitance to occur in a different configuration than that of the SiO2\\/Si system that Terman originally considered. The adaptation of Terman’s high frequency capacitance-voltage method for interface trap

David A. Deen; James G. Champlain

2011-01-01

239

Simultaneous Reactive-Power and Frequency Estimations Using Simple Recursive WLS Algorithm and Adaptive Filtering  

Microsoft Academic Search

A new simple approach to the design of digital algo- rithm for simultaneous reactive-power and frequency estimations of local system is presented. The algorithm is derived using the weighted-least-square method. During the algorithm derivation, a pure sinusoidal voltage model was assumed. Cascade finite- impulse-response (FIR) comb digital filters are used to minimize the noise effect and to eliminate the presence

Miodrag D. Kušljevi? Kusljevic; Predrag D. Poljak

2011-01-01

240

High-Frequency Loss Calculation in a Smooth Rotor Induction Motor Using FEM  

Microsoft Academic Search

In this paper, a new approach for the calculation of high-frequency losses in induction motors is presented. The input to the motors is assumed to be supplied from a sinusoidal voltage source. The method is based on the two-dimensional (2-D) field solutions of the magnetic circuit, obtained by using a nonlinear ldquoharmonicrdquo solution. Hence, the solution time is very short.

H. BÜlent Ertan; K. Leblebicioglu; B. Avenoglu; Murat Pirgaip

2007-01-01

241

Voltage harmonic control of Z-source inverter for UPS applications  

Microsoft Academic Search

This paper presents a control method for obtaining sinusoidal output voltage regardless of the nonlinear and unbalanced loads. Control of the DC boost stage and capacitor voltage is presented. The resonant regulators are used for selective harmonic cancellation of the output AC voltage. The Z-source inverter is able to provide higher AC voltage related to the DC link voltage than

Arkadiusz Kulka; Tore Undeland

2008-01-01

242

Spur-reduced digital sinusoid synthesis  

NASA Technical Reports Server (NTRS)

This article presents and analyzes a technique for reducing the spurious signal content in digital sinusoid synthesis. Spurious-harmonic (spur) reduction is accomplished through dithering both amplitude and phase values prior to word-length reduction. The analytical approach developed for analog quantization is used to produce new bounds on spur performance in these dithered systems. Amplitude dithering allows output word-length reduction without introducing additional spurs. Effects of periodic dither similar to those produced by a pseudonoise (PN) generator are analyzed. This phase-dithering method provides a spur reduction of 6(M plus one) dB per phase bit when the dither consists of M uniform variates. While the spur reduction is at the expense of an increase in system noise, the noise power can be made white, making the power spectral density small. This technique permits the use of a smaller number of phase bits addressing sinusoid lookup tables, resulting in an exponential decrease in system complexity. Amplitude dithering allows the use of less complicated multipliers and narrower data paths in purely digital applications, as well as the use of coarse resolution, highly linear digital to analog converters (DAC's) to obtain spur performance limited by the DAC linearity rather than its resolution.

Flanagan, M. J.; Zimmerman, G. A.

1993-01-01

243

Effect of the voltage waveform on induced flow of a dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

Flow control technique using surface plasma is attracting a lot of attention because of its ability to be the innovative technology for the wide range application. In this paper, we have conducted experiments to inspect relationship of velocity of the induced flow, frequency and voltage of power source. First, when sinusoidal voltage was applied between the electrodes, the result showed the induced flow was the faster, the greater the power was, regardless of the frequency and voltage. Then, the waveform was changed to bipolar pulse with shorter ON period than that of sine wave with a frequency of 3 kHz, almost the same induced velocity was observed at the same power, regardless of the voltage waveform. By the same experiment with a frequency of 10 kHz, the relationship of induced velocity and the power was affected by the waveform unlike the case of frequency at 3 kHz. The highest induced velocity was observed in case of sine wave. Induced velocity was able to be expressed as a function of the full width half maximum of voltage waveform, under constant power. From these facts, it is believed that it is required for external electric field to be applied for more than certain period of time in order for ions to be accelerated by electric field even in a case that almost same amount of ions were generated under an almost same condition of discharge power.

Shimura, Naohiko; Tanaka, Motofumi; Yasui, Hiroyuki

2012-10-01

244

Calibrator for alternating voltage, current, and power  

Microsoft Academic Search

A computer-controlled calibrator capable of delivering ac sinusoidal and distorted waveform voltage, current, and power with an accuracy of several parts per million is described. The reference ac voltage is obtained using digital-to-analog conversion and the reference ac current by applying the reference voltage to a reference ac resistor. The phase relation is obtained digitally. A combination of feedback and

P. N. Miljanic

1989-01-01

245

Outer Solar System and the Sinusoidal Potential  

NASA Astrophysics Data System (ADS)

At recent meetings of the AAS I have presented posters defending a new, sinusoidal gravitational potential. Here the customary numerator in Newton's law is replaced by GM cos(2? r/? o) where ? o is a universal constant, 425 pc. Because there are 20 oscillations of the potential between the sun and the center of the Milky Way, galactic tidal forces should be about 120 times as strong as normally believed. Such a large tidal force is needed if the global galactic potential is to explain the surprisingly large modulation in the galactic longitude of the perihelia of comets teased from the Oort cloud. (A modulation with prominent peaks at longitudes of 45,135, Å degrees was first observed by Matese and Whitmire (1996). They now feel that an impactor is the culprit, but it could instead be the sinusoidal potential (Bartlett, AAS-199)). Here I discuss how the same large tidal force might be responsible for two more observations in our solar system. Recently, Shaviv and Veizer (2003) have found a periodicity of about 140 Myrs in the observed isotopic fraction of heavy oxygen (O-18) in terrestrial calcite. They ascribe the period to variations in the cosmic ray rate caused by the revolution of the solar system through 4 rotating spiral arms. I find it rather to be the effect of variations in the strength of the galactic tidal force as the sun rotates in the nearly stationary quadrupole field of the central bar. There is increasing evidence that the Kuiper belt really ends at about 50 AU. (Donnes 1997; Allen, Bernstein, and Molhotra 2001). The cause for this cut-off is unknown, but galactic tidal forces are dismissed. I will show how the new, stronger forces can be effective.

Bartlett, D. F.

2003-12-01

246

Interplay between low threshold voltage-gated K+ channels and synaptic inhibition in neurons of the chicken nucleus laminaris along its frequency axis  

PubMed Central

Central auditory neurons that localize sound in horizontal space have specialized intrinsic and synaptic cellular mechanisms to tightly control the threshold and timing for action potential generation. However, the critical interplay between intrinsic voltage-gated conductances and extrinsic synaptic conductances in determining neuronal output are not well understood. In chicken, neurons in the nucleus laminaris (NL) encode sound location using interaural time difference (ITD) as a cue. Along the tonotopic axis of NL, there exist robust differences among low, middle, and high frequency (LF, MF, and HF, respectively) neurons in a variety of neuronal properties such as low threshold voltage-gated K+ (LTK) channels and depolarizing inhibition. This establishes NL as an ideal model to examine the interactions between LTK currents and synaptic inhibition across the tonotopic axis. Using whole-cell patch clamp recordings prepared from chicken embryos (E17–E18), we found that LTK currents were larger in MF and HF neurons than in LF neurons. Kinetic analysis revealed that LTK currents in MF neurons activated at lower voltages than in LF and HF neurons, whereas the inactivation of the currents was similar across the tonotopic axis. Surprisingly, blockade of LTK currents using dendrotoxin-I (DTX) tended to broaden the duration and increase the amplitude of the depolarizing inhibitory postsynaptic potentials (IPSPs) in NL neurons without dependence on coding frequency regions. Analyses of the effects of DTX on inhibitory postsynaptic currents led us to interpret this unexpected observation as a result of primarily postsynaptic effects of LTK currents on MF and HF neurons, and combined presynaptic and postsynaptic effects in LF neurons. Furthermore, DTX transferred subthreshold IPSPs to spikes. Taken together, the results suggest a critical role for LTK currents in regulating inhibitory synaptic strength in ITD-coding neurons at various frequencies.

Hamlet, William R.; Liu, Yu-Wei; Tang, Zheng-Quan; Lu, Yong

2014-01-01

247

Entwicklung von Methoden Zur Analyse der Frequenz- und Spannungsstakik Elektrischer Verbraucher und Netze (Development of Methods for the Analysis of the Frequency and Voltage Statics of Electricity Users and Electrical Networks).  

National Technical Information Service (NTIS)

Two methods that allow predictions concerning the effect of varying frequency and/or voltage on the real power requirements of partial networks, are presented. Measuring and data processing techniques were developed. The first method determines the respec...

J. Dollinger

1985-01-01

248

Pseudolinear Circuit Theory for Sinusoidal Oscillator Performance Maximization  

NASA Astrophysics Data System (ADS)

This paper introduces a theory for fast optimization of the circuit topology and parameters in sinusoidal oscillators. The theory starts from a system model composed of standard active and passive elements. We then include even the output load in the circuit, so that there is no longer any interaction with the outside of the system through the port. This model is thus called no-input-no-output (NINO) oscillator. The circuit is cut at an arbitrary branch, and is characterized in terms of the scalar impedance from the cut point. This is called active impedance because it is a function of not only the stimulating frequency but also the active device gain. The oscillation frequency and necessary device gain are estimated by solving impedance-domain Barkhausen equilibrium equations. This estimation works for the adjustment of circuit elements to meet the specified oscillation frequency. The estimation of necessary device gain enables us to maximize the oscillation amplitude, thanks to the inherent negative-slope nonlinearity of active devices. The active impedance is also used to derive the oscillation Q (quality) factor, which serves as a key criterion for sideband noise minimization i.e. frequency spectrum purification. As an alternative measure to active impedance, we also introduce branch admittance matrix determinant. This has the same numerical effect as the scalar impedance but can be used to formulate oscillator characteristics in a more elegant fashion, and provides a lucent picture of the physical behavior of each element in the circuit. Based on the proposed theory, we provide the tabled formulas of oscillation frequency, necessary device gain, active Q factor for a variety of typical Colpitts, Hartley, and cross-coupled twin-FET (field-effect transistor) oscillators.

Ohira, Takashi; Wuren, Tuya

249

Frequency-Controlled Voltage Regulator: Converting input ac to a higher frequency reduces size and weight and makes possible a unique kind of regulation.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A proposed power supply would be smaller and lighter than conventional supplies because it converts its ac line input to a much higher frequency before regulating it...

1982-01-01

250

A digital frequency synthesizer  

Microsoft Academic Search

A digital frequency synthesizer has been designed and constructed based on generating digital samples ofexp [j(2^{pi}nk\\/N)]at timenT. The real and imaginary parts of this exponential form samples of quadrature sinusoids where the frequency indexkis allowed to vary(-N\\/4) leq K < (N\\/4). The digital samples drive digital to analog converters followed by low-pass interpolating filters to produce analog sinusoids. The method

JOSEPH TIERNEY; CHARLES M. RADER; B. Gold

1971-01-01

251

Potential damage to DC superconducting magnets due to the high frequency electromagnetic waves  

NASA Technical Reports Server (NTRS)

Experimental data are presented in support of the hypothesis that a dc superconducting magnet coil does not behave strictly as an inductor, but as a complicated electrodynamic device capable of supporting electromagnetic waves. Travel times of nanosecond pulses and evidence of sinusoidal standing waves were observed on a prototype four-layer solenoidal coil at room temperature. Ringing observed during switching transients appears as a sequence of multiple reflected square pulses whose durations are related to the layer lengths. With sinusoidal excitation of the coil, the voltage amplitude between a pair of points on the coil exhibits maxima at those frequencies such that the distance between these points is an odd multiple of half wavelength in free space. Evidence indicates that any disturbance, such as that resulting from switching or sudden fault, initiates multiple reflections between layers, thus raising the possibility for sufficiently high voltages to cause breakdown.

Gabriel, G. J.

1977-01-01

252

Improved temporal coding of sinusoids in electric stimulation of the auditory nerve using desynchronizing pulse trainsa)  

PubMed Central

Rubinstein et al. [Hearing Res. 127, 108–118 (1999)] suggested that the representation of electric stimulus waveforms in the temporal discharge patterns of auditory-nerve fiber (ANF) might be improved by introducing an ongoing, high-rate, desynchronizing pulse train (DPT). To test this hypothesis, activity of ANFs was studied in acutely deafened, anesthetized cats in response to 10-min-long, 5-kpps electric pulse trains that were sinusoidally modulated for 400 ms every second. Two classes of responses to sinusoidal modulations of the DPT were observed. Fibers that only responded transiently to the unmodulated DPT showed hyper synchronization and narrow dynamic ranges to sinusoidal modulators, much as responses to electric sinusoids presented without a DPT. In contrast, fibers that exhibited sustained responses to the DPT were sensitive to modulation depths as low as 0.25% for a modulation frequency of 417 Hz. Over a 20-dB range of modulation depths, responses of these fibers resembled responses to tones in a healthy ear in both discharge rate and synchronization index. This range is much wider than the dynamic range typically found with electrical stimulation without a DPT, and comparable to the dynamic range for acoustic stimulation. These results suggest that a stimulation strategy that uses small signals superimposed upon a large DPT to encode sounds may evoke temporal discharge patterns in some ANFs that resemble responses to sound in a healthy ear.

Litvak, Leonid M.; Delgutte, Bertrand; Eddington, Donald K.

2008-01-01

253

Nonlinear dynamics in VCSELs driven by a sinusoidally modulated current and Rössler oscillator  

NASA Astrophysics Data System (ADS)

We firstly investigate the dynamics of vertical-cavity surface-emitting lasers (VCSELs) subject to sinusoidally modulated current using numerical simulations. For a few-hundred MHz frequency of injection current, the VCSELs emit a single pulse or a package of pulses when the injection current fluctuates around the threshold current. By varying the amplitude of the modulation, we show that the width of the bistability hysteresis loop can be suppressed and replaced by smooth single or multiple switching. For a few GHz frequency of injection current, the polarization modes of VCSELs exhibit a period-doubling transition to chaotic behavior. Then by modulating the VCSELs pump current by one of the outputs of a Rössler oscillator, we generate dynamical behaviors found in VCSELs subject to a sinusoidally modulated current. This new way of modulation of semiconductor lasers would bring a general benefit in the physical equipment, and reduce their cost.

Kingni, S. T.; Talla Mbé, J. H.; Woafo, P.

2012-05-01

254

Analysis and design of a multiple feedback loop control strategy for single-phase voltage-source UPS inverters  

SciTech Connect

This paper presents the analysis and design of a multiple feedback loop control scheme for single-phase voltage-source uninterruptible power supply (UPS) inverters with an L-C filter. The control scheme is based on sensing the current in the capacitor of the load filter and using it in an inner feedback loop. An outer voltage feedback loop is also incorporated to ensure that the load voltage is sinusoidal and well regulated. A general state-space averaged model of the UPS system is first derived and used to establish the steady-steady quiescent point. A linearized small signal dynamic model is then developed from the system general model using perturbation and small-signal approximation. The linearized system model is employed to examine the incremental dynamics of the power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS system. Experimental verification of a laboratory model of the UPS system under the proposed closed-loop operation is provided for both linear and nonlinear loads. It is shown that the control scheme offers improved performance measures over existing schemes. It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of filter parameters. Furthermore, the scheme has excellent dynamic response and high voltage utilization of the dc source.

Abdel-Rahim, N.M.; Quaicoe, J.E. [Memorial Univ. of Newfoundland, St. Johns, Newfoundland (Canada). Faculty of Engineering and Applied Science] [Memorial Univ. of Newfoundland, St. Johns, Newfoundland (Canada). Faculty of Engineering and Applied Science

1996-07-01

255

Sinusoidal wavy channels with Taylor-Goertler vortices  

Microsoft Academic Search

In the concave part of sinusoidal wavy ducts, a flow instability can be observed, leading to longitudinal vortices comparable to the Goertler instability at concave walls or the Dean instability in tube flows. Near-wall flow phenomena are visualized by the visualization of the local mass transfer. The pressure losses are evaluated in a sinusoidal wavy duct with constant wavelength ?\\/a,

P. Gschwind; A. Regele; V. Kottke

1995-01-01

256

Skin profiles during sinusoidal vibration of the fingerpad  

Microsoft Academic Search

Skin on the fingertips of humans and monkeys was stimulated by a probe vibrating with a sinusoidal displacement. The probe and the skin were illuminated stroboscopically and were viewed through a dissecting microscope. The stroboscope was triggered by the sinusoidal generator via a digital delay, so that the position of both the probe and the skin could be measured at

A. W. Goodwin; K. T. John; I. Darian-Smith

1989-01-01

257

Surface discharge plasma actuator driven by a pulsed 13.56 MHz-5 kHz voltage waveform  

NASA Astrophysics Data System (ADS)

The effect of incorporating pulses of radio-frequency (rf: 13.56 MHz) voltage into the driving waveform of a surface discharge plasma actuator is investigated. Rf voltage is applied to the actuator to increase the production of ions and thereby increase the thrust that is generated by the discharge. This waveform is coupled to the powered electrode in 5 µs pulses and combined with a relatively low-frequency (LF) 5 kHz sinusoid to form a pulsed 13.56 MHz-5 kHz (rf-LF) driving voltage. Measurements of the applied voltage, rf and LF currents, effective power, and velocity field of the surrounding air are undertaken at atmospheric pressure. The thrust that is generated using the rf-LF waveform is estimated from the velocity fields using a momentum balance and is found to increase for increasing rf voltage when the LF voltage remains constant. Maximum thrust is achieved when the rf pulses are positioned at the LF voltage minima and this suggests the importance of negative ions. The efficacy of rf-LF actuation is investigated by comparing the thrust that is generated per unit increase in peak voltage with that obtained using an LF-driven discharge.

Dedrick, J.; Im, S.; Cappelli, M. A.; Boswell, R. W.; Charles, C.

2013-10-01

258

Field oriented control of an induction machine in a high frequency link power system  

NASA Technical Reports Server (NTRS)

A field-oriented controlled induction machine drive operating with a high-frequency single-phase sinusoidal voltage link is presented. System performance is investigated by computer simulation and is verified by a test on a prototype system. A novel control loop to minimize the link voltage fluctuation is proposed. The capability of rapid demagnetization of the induction machine by current regulation is investigated. A current-modulation technique termed mode control is proposed, and its performance is compared with that of the conventional delta-modulation technique.

Sul, Seung K.; Lipo, Thomas A.

1988-01-01

259

Digital control of high frequency pulse-width modulated inverters  

NASA Astrophysics Data System (ADS)

The effect of word length on the hormonic content of pulse width modulated (PWM) waveform generators, and voltage control in high carrier frequency PWM waveform generators were studied. Eight and four bit microprocessor-based PWM waveform generators operating silently with a 20 kHz carrier were developed. The PWM output of each generator is determined by voltage, modulating frequency, and carrier frequency. Eight bit systems are capable of generating virtually pure sinusoids from 0 to greater than 2 kHz and can form general purpose, PWM waveform generators suitable for driving a variety of inverter power switches. An inverter power stage with a selection of MOSFET gate drive circuits, depending upon the switching characteristics required of the power devices, was constructed.

Stevens, Michael John

1985-08-01

260

Observation of peripheral charge induced low frequency capacitance-voltage behaviour in metal-oxide-semiconductor capacitors on Si and GaAs substrates  

NASA Astrophysics Data System (ADS)

We report on experimental observations of room temperature low frequency capacitance-voltage (CV) behaviour in metal oxide semiconductor (MOS) capacitors incorporating high dielectric constant (high-k) gate oxides, measured at ac signal frequencies (2 kHz to 1 MHz), where a low frequency response is not typically expected for Si or GaAs MOS devices. An analysis of the inversion regions of the CV characteristics as a function of area and ac signal frequency for both n and p doped Si and GaAs substrates indicates that the source of the low frequency CV response is an inversion of the semiconductor/high-k interface in the peripheral regions outside the area defined by the metal gate electrode, which is caused by charge in the high-k oxide and/or residual charge on the high-k oxide surface. This effect is reported for MOS capacitors incorporating either MgO or GdSiOx as the high-k layers on Si and also for Al2O3 layers on GaAs(111B). In the case of NiSi/MgO/Si structures, a low frequency CV response is observed on the p-type devices, but is absent in the n-type devices, consistent with positive charge (>8 × 1010 cm-2) on the MgO oxide surface. In the case of the TiN/GdSiOx/Si structures, the peripheral inversion effect is observed for n-type devices, in this case confirmed by the absence of such effects on the p-type devices. Finally, for the case of Au/Ni/Al2O3/GaAs(111B) structures, a low-frequency CV response is observed for n-type devices only, indicating that negative charge (>3 × 1012 cm-2) on the surface or in the bulk of the oxide is responsible for the peripheral inversion effect.

O'Connor, É.; Cherkaoui, K.; Monaghan, S.; O'Connell, D.; Povey, I.; Casey, P.; Newcomb, S. B.; Gomeniuk, Y. Y.; Provenzano, G.; Crupi, F.; Hughes, G.; Hurley, P. K.

2012-06-01

261

The Sinusoidal Potential and Spiral Galaxies  

NASA Astrophysics Data System (ADS)

In the sinusoidal potential (Bartlett, 2001) the numerator of Newton's law is replaced by GM cos(ko r) where ko = 2? /? o and the'wavelength' ? o is 425 pc. When this potential is used with an extended mass distribution, the distant potential from any multipole moment diminishes simply as 1/r. Suppose the mass distribution to be azimuthally symmetric and symmetric about the galactic equator. Then the distant potential factors into radial and angular parts, ? (r,b)= [cos (ko r)/r] [? a2n P2n(sin b)], where the a2n are coefficients determined by the mass distribution and the P2n are the Legendre polynomials. The summation stops at about n=6 for the Milky Way. We will show that the potential depends critically on whether or not odd n's as well as even contribute to the sum. In the latter case the galaxy is likely to have a substantial bulge and to have strong distant potentials near the poles as well as on the equator. This is the case for the Milky Way, where we relate the strong polar potential to the break-up of the Sagittarius Dwarf Spheroidal. Alternatively, a disk-only galaxy, such as M33, has contributions from both odd and even terms and no strong distant potential away from the equator. If any galaxy has just an exponential disk, the predicted dependence of the rotation velocity on the luminosity and the decay length of the disk is particularly simple.

Wilson, G. R.; Bartlett, D. F.

2004-05-01

262

Analysis of the sinusoidal nanopatterning grating structure  

NASA Astrophysics Data System (ADS)

To accurately utilize the sinusoidal nanopatterning grating structure for greatly improving the light extraction efficiency of light-emitting diodes, the transmittance characteristics of these nanostructures as a function of the normalized period and the normalized depth are investigated quantitatively. It is found that when the normalized period of nanostructure is less than 0.46; in other words, only zeroth order transmission light is propagating, the light extraction efficiency can be enhanced immensely due to the higher transmittance of surface structure. When the period scale of nanostructure is more than the emitted wavelength, the transmittances decrease as the structure height increase. However, as the period dimension is less than the emitted wavelength, the transmittance of surface profile is increased as the depth increases. Besides, in order to easily analyze and effectively design the transmittance characteristics of these nanopatterning structures integrated in LEDs, we propose that the developed scalar method and the effective medium theory can be used accurately. The accuracy of both uncomplicated methods is quantitatively evaluated by the comparison of diffraction efficiencies predicted by the scalar theory and effective medium method, to exact results calculated by the rigorous coupled wave analysis method.

Jing, Xufeng; Jin, Shangzhong; Tian, Ying; Liang, Pei; Dong, Qianmin; Wang, Le

2013-06-01

263

Nystagmus generated by sinusoidal pitch while rotating.  

PubMed

Sinusoidal pitch while rotating about a vertical axis in darkness causes continuous horizontal compensatory nystagmus in the monkey which persists for the duration of stimulation. The steady-state velocity sums with post-rotatory nystagmus to reduce or cancel it, suggesting involvement of the velocity storage mechanism. Analysis of the labyrinthine excitation during pitch while rotating suggests that the vertical canals play a predominant role in generating the response. Effects of selective labyrinthine lesions are in agreement with this hypothesis. Plugging the lateral canals, leaving the vertical canals intact, blocked the initial rapid response at the onset of rotation, but did not interrupt the continuous nystagmus induced by pitch while rotating. On the other hand, plugging the vertical canals abolished the response. If the lateral canal nerves were cut so that the velocity storage mechanism was inactivated, the continuous response to pitch while rotating also disappeared. The dominant labyrinth activation responsible for the nystagmus during pitching while rotating appears to arise in the vertical semicircular canals and to couple to the oculomotor system through the velocity storage mechanism. PMID:6626995

Raphan, T; Cohen, B; Suzuki, J; Henn, V

1983-10-01

264

Response of the seated human body to whole-body vertical vibration: biodynamic responses to sinusoidal and random vibration.  

PubMed

The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1-1.6 ms(-2) r.m.s.) and with random vibration (1-16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation. PMID:24730687

Zhou, Zhen; Griffin, Michael J

2014-01-01

265

A Practical Guide to Harmonic Frequency Interference Affecting High-Voltage Power-Line Carrier Coupling Systems  

Microsoft Academic Search

Power-line carrier (PLC) systems have proven to be susceptible to interference caused by harmonics produced by loads, such as HVDC converters, DC electric arc furnaces, static var compensators, and motor speed controllers. Previous work in this area has provided information regarding the nature and origin of harmonic frequency interference affecting PLC systems as well as discussion of problem mitigation. However,

Gregory A. Franklin

2009-01-01

266

Effect of voltage dips on frequency relays: Case study of Power Quality improvements in a petrochemical plant  

Microsoft Academic Search

Industrial process interruption is one of the major power quality issues. Load-shedding schemes based on sub-frequency monitoring are normally employed to disconnect loads so that the balance between the system generation and loading is restored. This procedure should be very reliable and well adjusted. In this paper, a case study is presented, wherein an industrial process of a petrochemical plant

H. S. Bronzeado; S. L. Zimath; J. Coser

2008-01-01

267

Suppression of axonal conduction by sinusoidal stimulation in rat hippocampus in vitro  

NASA Astrophysics Data System (ADS)

Deep brain stimulation (DBS), also known as high frequency stimulation (HFS), is a well-established therapy for Parkinson's disease and essential tremor, and shows promise for the therapeutic control of epilepsy. However, the direct effect of DBS on neural elements close to the stimulating electrode remains an important unanswered question. Computational studies have suggested that HFS has a dual effect on neural elements inhibiting cell bodies, while exciting axons. Prior experiments have shown that sinusoidal HFS (50 Hz) can suppress synaptic and non-synaptic cellular activity in several in vitro epilepsy models, in all layers of the hippocampus. However, the effects of HFS on axons near the electrode are still unclear. In the present study, we tested the hypothesis that HFS suppresses axonal conduction in vitro. Sinusoidal HFS was applied to the alvear axon field of transverse rat hippocampal slices. The results show that HFS suppresses the alvear compound action potential (CAP) as well as the CA1 antidromic evoked potential (AEP). Complete suppression was observed as a 100% reduction in the amplitude of the evoked field potential for the duration of the stimulus. Evoked potential width and latency were not significantly affected by sinusoidal HFS. Suppression was dependent on HFS amplitude and frequency, but independent of stimulus duration and synaptic transmission. The frequency dependence of sinusoidal HFS is similar to that observed in clinical DBS, with maximal suppression between 50 and 200 Hz. HFS produced not only suppression of axonal conduction but also a correlated rise in extracellular potassium. These data provide new insights into the effects of HFS on neuronal elements, and show that HFS can block axonal activity through non-synaptic mechanisms.

Jensen, A. L.; Durand, D. M.

2007-06-01

268

Analysis-by-Synthesis Sinusoidal Model without an Overlapping Scheme  

NASA Astrophysics Data System (ADS)

A new sinusoidal modeling approach for the analysis-by-synthesis (AbS) of parameters that characterize a linear combination of damped sinusoids is proposed. In addition to the typical sinusoidal parameters, two different damping factors, which represent the time-varying nature of speech, were used to efficiently reduce the modeling error. Even though the proposed model does not employ the overlap-adding synthesis or smoothly interpolative synthesis scheme, it shows substantially better modeling performance in the synthesis of voiced and transient segments.

Kim, Jong-Hark; Jeong, Gyu-Hyeok; Lee, In-Sung

269

Computer Program for Thin Wire Antenna over a Perfectly Conducting Ground Plane. [using Galerkins method and sinusoidal bases  

NASA Technical Reports Server (NTRS)

A computer program is presented for a thin-wire antenna over a perfect ground plane. The analysis is performed in the frequency domain, and the exterior medium is free space. The antenna may have finite conductivity and lumped loads. The output data includes the current distribution, impedance, radiation efficiency, and gain. The program uses sinusoidal bases and Galerkin's method.

Richmond, J. H.

1974-01-01

270

High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys  

NASA Technical Reports Server (NTRS)

Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

1990-01-01

271

High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys  

NASA Technical Reports Server (NTRS)

Limited experimental data exists for the specific core loss and dynamic B-H loop for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

1990-01-01

272

Design and Digital Implementation of Constant Frequency Hysteresis Current Controller for Three-Phase Voltage Source Inverter Using TMS320F2812  

NASA Astrophysics Data System (ADS)

A constant frequency hysteresis current control technique for a three-phase voltage source inverter (VSI) has been developed for AC drives, power quality and renewable energy applications. This paper presents a digital implementation of a constant frequency hysteresis current control technique for a three-phase VSI feeding an inductive load, using digital signal controller TMS320F2812. The limitations of variable frequency hysteresis control have been discussed and overcoming these limitations by means of digital implementation has been proposed. The complete design procedure of the proposed technique has been presented with an illustrative example. The three-phase VSI feeding an inductive load has also been simulated by using MATLAB and the simulation results have been presented. The hardware results of hysteresis current controlled three-phase VSI feeding an inductive load have been presented. Also the performance analysis of the hysteresis current controller has been presented. Operation of this controller has also been explained with a help of phase plane trajectory of hysteresis controller.

Kalyanraj, D.; Lenin Prakash, S.

2014-01-01

273

A variable step-size gradient adaptive lattice algorithm for multiple sinusoidal interference cancelation  

NASA Astrophysics Data System (ADS)

In passive sonar, adaptive algorithms can be used to cancel strong sinusoidal self-interferences. In order to correctly recover low-power target signals during the early stages of processing, these adaptive algorithms must provide fast convergence and, at the same time, narrow notches at the frequencies of the sinusoids. In this respect, the gradient adaptive lattice (GAL) algorithm is a very attractive choice. However, the GAL algorithm with a constant step-size parameter has to compromise between the convergence rate and notch bandwidths. Therefore, in this article, we propose a variable step-size scheme for the GAL algorithm that can achieve both a fast convergence rate and narrow notches. Simulation results demonstrate the efficiency of the proposed algorithm compared to both the conventional GAL algorithm and transversal adaptive filter combined with the variable step-size scheme.

Kim, Seong-woo; Park, Young-cheol; Youn, Dae Hee

2013-12-01

274

Sinusoidal reference strategy for adaptive feedforward vibration control: numerical simulation and experimental study  

NASA Astrophysics Data System (ADS)

A new control approach named Sinusoidal Reference Strategy is developed for adaptive feedforward structural control. In this approach, the recursive-least-squares algorithm is used and a higher frequency sinusoidal signal is utilized as the reference signal. The present approach is able to overcome some of the shortcomings of the conventional adaptive feedforward control. Numerical simulations are then conducted on reducing wind-induced vibrations of the JIN MAO Building in Shanghai, China, with a height of 420 m. A multiple-degree-of-freedom (m.d.o.f.) aeroelastic model of a general super-tall building and an active mass damper (AMD) actuator are designed and manufactured. Wind tunnel tests are carried out to investigate further the control efficiency and robustness of the present approach. Both the simulation and experimental results show that the approach can reduce vibration of super-tall buildings remarkably, and can adapt to dynamic uncertainties and modelling errors of the buildings.

Peng, F. J.; Gu, M.; Niemann, H.-J.

2003-08-01

275

Speech reconstruction from mel frequency cepstral coefficients and pitch frequency  

Microsoft Academic Search

This paper presents a novel low complexity, frequency domain algorithm for reconstruction of speech from the mel-frequency cepstral coefficients (MFCC), commonly used by speech recognition systems, and the pitch frequency values. The reconstruction technique is based on the sinusoidal speech representation. A set of sine-wave frequencies is derived using the pitch frequency and voicing decisions, and synthetic phases are then

Dan Chazan; Ron Hoory; Gilad Cohen; Meir Zibulski

2000-01-01

276

Magnetostrictive vibrations model of a three-phase transformer core and the contribution of the fifth harmonic in the grid voltage  

NASA Astrophysics Data System (ADS)

The effect of the fifth harmonic in the grid voltage (with fundamental frequency of 50 Hz) on the vibrations of a three-phase transformer core is computed, since such harmonic has the largest contribution in the European grid voltage. The computational method is a two-dimensional (2D) finite element technique. The modal vibrations under various magnetisations (viz with different fifth harmonic components) are compared with those obtained under a purely sinusoidal magnetisation and showed that the variations for the 100 Hz harmonic of the vibrations are small. However, the 200 Hz harmonic showed a significant increase when a fifth harmonic was present on the applied voltage. In fact, the presence of a fundamental component with 50 Hz frequency and a fifth harmonic on the magnetisation signal generates a 200 Hz harmonic on the magnetostriction strains (and the magnetic forces), and thus this harmonic increases significantly.

Gorji Ghalamestani, Setareh; Vandevelde, Lieven; Dirckx, Joris J. J.; Melkebeek, Jan A. A.

2014-05-01

277

Nonequilibrium atmospheric pressure plasma jet using a combination of 50 kHz/2 MHz dual-frequency power sources  

SciTech Connect

An atmospheric pressure plasma jet is generated by dual sinusoidal wave (50 kHz and 2 MHz). The dual-frequency plasma jet exhibits the advantages of both low frequency and radio frequency plasmas, namely, the long plasma plume and the high electron density. The radio frequency ignition voltage can be reduced significantly by using dual-frequency excitation compared to the conventional radio frequency without the aid of the low frequency excitation source. A larger operating range of ? mode discharge can be obtained using dual-frequency excitation which is important to obtain homogeneous and low-temperature plasma. A larger controllable range of the gas temperature of atmospheric pressure plasma could also be obtained using dual-frequency excitation.

Zhou, Yong-Jie; Yuan, Qiang-Hua; Li, Fei; Wang, Xiao-Min; Yin, Gui-Qin; Dong, Chen-Zhong [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)] [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

2013-11-15

278

Fluid Modeling of a Nitrogen Atmospheric-Pressure Planar Dielectric Barrier Discharge Driven by a Realistic Distorted Sinusoidal Alternating Current Power Source  

NASA Astrophysics Data System (ADS)

One-dimensional self-consistent simulations of a parallel-plate atmospheric-pressure nitrogen dielectric barrier discharge (DBD) are presented. The DBD was driven by a realistic distorted-sinusoidal voltage power source with a frequency of 60 kHz. The simulated discharge currents are in quantitative agreement with experimental measurements. N4+ ions gain more of the input electric power than electrons, which is unlike most glow discharges. The densities of all charged and neutral species increase exponentially with increasing applied peak voltage in the range of 6.2--8.6 kV. The higher the permittivity of the dielectric material, the larger the discharge current and the longer the period of gas breakdown. In addition, the quantity of accumulated charges at each electrode increases with increasing permittivity of the dielectric material. Finally, the increase in dielectric thickness from 1.0 to 2.0 mm greatly reduces the densities of all species and also the plasma absorbed by the power.

Cheng, Kai-Wen; Hung, Chieh-Tsan; Lin, Kun-Mo; Chiu, Yuan-Ming; Wu, Jong-Shinn; Yu, Jen-Perng

2012-11-01

279

Sinusoidal B-M method based spectral domain optical coherence tomography for the elimination of complex-conjugate artifact.  

PubMed

A high speed spectral domain optical coherence tomography based on the spatial sinusoidal phase modulation for the elimination of complex-conjugate artifact is presented, where sinusoidal phase modulation of reference arm (M scan) and transverse scanning of sample arm (B scan) are performed simultaneously (sinusoidal B-M method). Herein, the linear phase modulation of the reference arm in conventional linear B-M method is modified to sinusoidal phase modulation. The proposed sinusoidal B-M method relaxes the requirements on the phase-shifting mechanical system and avoids sensitivity fall-off along the transverse direction in contrast to the linear B-M method. A criterion for the relation between transverse over-sampling factor and modulation frequency for optimal complex conjugate rejection is deduced and verified by experiments. Under this criterion, the complex spectral interferogram is reconstructed by harmonic analysis and digital synchronous demodulation. Double imaging depth range on fresh shrimp at A-scan rate of 10 kHz with complex conjugate rejection ratio up to 45 dB is achieved. PMID:19770899

Wang, Kai; Ding, Zhihua; Zeng, Yan; Meng, Jie; Chen, Minghui

2009-09-14

280

Signal Analysis Algorithms for Optimized Fitting of Nonresonant Laser Induced Thermal Acoustics Damped Sinusoids  

NASA Technical Reports Server (NTRS)

This study seeks a numerical algorithm which optimizes frequency precision for the damped sinusoids generated by the nonresonant LITA technique. It compares computed frequencies, frequency errors, and fit errors obtained using five primary signal analysis methods. Using variations on different algorithms within each primary method, results from 73 fits are presented. Best results are obtained using an AutoRegressive method. Compared to previous results using Prony s method, single shot waveform frequencies are reduced approx.0.4% and frequency errors are reduced by a factor of approx.20 at 303K to approx. 0.1%. We explore the advantages of high waveform sample rates and potential for measurements in low density gases.

Balla, R. Jeffrey; Miller, Corey A.

2008-01-01

281

The voltage—current relationship and equivalent circuit implementation of parallel flux-controlled memristive circuits  

NASA Astrophysics Data System (ADS)

A flux-controlled memristor characterized by smooth cubic nonlinearity is taken as an example, upon which the voltage—current relationships (VCRs) between two parallel memristive circuits — a parallel memristor and capacitor circuit (the parallel MC circuit), and a parallel memristor and inductor circuit (the parallel ML circuit) — are investigated. The results indicate that the VCR between these two parallel memristive circuits is closely related to the circuit parameters, and the frequency and amplitude of the sinusoidal voltage stimulus. An equivalent circuit model of the memristor is built, upon which the circuit simulations and experimental measurements of both the parallel MC circuit and the parallel ML circuit are performed, and the results verify the theoretical analysis results.

Bao, Bo-Cheng; Feng, Fei; Dong, Wei; Pan, Sai-Hu

2013-06-01

282

Evaluation of medium voltage enameled wire exposed to fast repetitive voltage pulses  

Microsoft Academic Search

The paper describes the investigation of the failure mechanisms of medium voltage inter-turn insulation, as a consequence of pulse aging. To study the performance and failure behaviour of enameled wires, models of inter-turn insulation are prepared with enameled wires having polyimide and nano-filled coatings. The aging of such bar samples is attained by sinusoidal (60Hz), fast repetitive unipolar voltage pulses,

Saeed Ul Haq; Shesha H. Jayaram; Edward A. Cherney

2007-01-01

283

System analysis of Phycomyces light-growth response with sum-of-sinusoids test stimuli.  

PubMed Central

The light-growth response of Phycomyces has been studied with the sum-of-sinusoids method of nonlinear system identification (Victor, J.D., and R.M. Shapley, 1980, Biophys. J., 29:459). This transient response of the sporangiophore has been treated as a black-box system with one input (logarithm of the light intensity, I) and one output (elongation rate). The light intensity was modulated so that log I, as a function of time, was a sum of sinusoids. The log-mean intensity was 10(-4) W m-2 and the wavelength was 477 nm. The first- and second-order frequency kernels, which represent the linear and nonlinear behavior of the system, were obtained from the Fourier transform of the response at the appropriate component and combination frequencies. Although the first-order kernel accounts for most of the response, there remains a significant nonlinearity beyond the logarithmic transducer presumed to occur at the input of the sensory transduction chain. From the analysis of the frequency kernels, we have derived a dynamic nonlinear model of the light-growth response system. The model consists of a nonlinear subsystem followed by a linear subsystem. The model parameters were estimated from a combined nonlinear least-squares fit to the first- and second-order frequency kernels.

Pratap, P; Palit, A; Lipson, E D

1986-01-01

284

Thresholds for the perception of whole-body linear sinusoidal motion in the horizontal plane  

NASA Technical Reports Server (NTRS)

An improved linear sled has been developed to provide precise motion stimuli without generating perceptible extraneous motion cues (a noiseless environment). A modified adaptive forced-choice method was employed to determine perceptual thresholds to whole-body linear sinusoidal motion in 25 subjects. Thresholds for the detection of movement in the horizontal plane were found to be lower than those reported previously. At frequencies of 0.2 to 0.5 Hz, thresholds were shown to be independent of frequency, while at frequencies of 1.0 to 3.0 Hz, thresholds showed a decreasing sensitivity with increasing frequency, indicating that the perceptual process is not sensitive to the rate change of acceleration of the motion stimulus. The results suggest that the perception of motion behaves as an integrating accelerometer with a bandwidth of at least 3 Hz.

Mah, Robert W.; Young, Laurence R.; Steele, Charles R.; Schubert, Earl D.

1989-01-01

285

SLM-based sinusoidal fringe projection under coherent illumination  

NASA Astrophysics Data System (ADS)

The paper is dedicated to SLM implementation of a sinusoidal phase grating for fringe projection profilometry with sinusoidal fringes. A low-contrast sinusoidal phase grating is capable of projecting focused sinusoidal fringes with satisfactory visibility in a large spatial region under coherent divergent illumination. The paper presents analysis of distortions in the projected fringes due to phase quantization when the phase grating is generated by a phase-only 8-bit SLM. We showed by simulation of propagation in the free space that the spread of intensity fluctuations of the projected fringes comprises 4-5 gray levels if an SLM with a 2? phase span is used and is much lower for an SLM with ?/2 phase span. In addition, we proved that distortion due to the phase encoding of the grating complex amplitude can be modeled as gamma distortion with an invariable behavior in time at small values of the modulation parameter and removed by a proper correction of fringes after polyspectral analysis. The experiments we made with an 8-bit SLM of ?/2 phase span confirmed the ability of this optical element to project sinusoidal fringes with a high spectral purity.

Berberova, Natalia; Stoykova, Elena; Kang, Hoonjong; Park, Joo Sup; Ivanov, Branimir

2013-09-01

286

Transformerless Hybrid Topology for Medium-Voltage Reactive-Power Compensation  

Microsoft Academic Search

In this paper, natural sinusoidal hybrid converter is presented for medium-voltage reactive-power control applications. Main high-voltage inverter that produces fundamental reactive current is a square-wave inverter. Several single-phase full-bridge converters are connected in series with this square inverter to elim- inate harmonic voltages from the net output voltage of this hybrid converter. DC bus voltages of these cells are naturally

Malaya Kumar Sahu; Gautam Poddar

2011-01-01

287

Phase and amplitude retrieval of objects embedded in a sinusoidal background from its diffraction pattern  

SciTech Connect

Efforts of phase and amplitude retrieval from diffraction patterns have almost exclusively been applied for nonperiodic objects. We investigated the quality of retrieval of nonperiodic objects embedded in a sinusoidal background, using the approach of iterative hybrid input-output with oversampling. Two strategies were employed; one by filtering in the frequency domain prior to phase retrieval, and the other by filtering the phase or amplitude image after retrieval. Results obtained indicate better outcomes with the latter approach provided detector noise is not excessive.

Wu, Chu; Ng, Tuck Wah; Neild, Adrian

2010-04-01

288

A surface profile reconstruction system using sinusoidal phase-modulating interferometry and fiber-optic fringe projection  

NASA Astrophysics Data System (ADS)

A fiber-optic sinusoidal phase modulating (SPM) interferometer for surface profile reconstruction is presented. Sinusoidal phase modulation is created by modulating the drive voltage of the piezoelectric transducer. The surface profile is constructed basing on fringe projection. Fringe patterns are vulnerable to external disturbances such as temperature fluctuation and mechanical vibration, which cause phase drift and decrease measuring accuracy. We build a closed-loop feedback phase compensation system, the bias value of external disturbances superimposed on fringe patterns can be reduced to about 50 mrad, and the phase stability for interference fringes is less than 5.76 mrad. By measuring the surface profile of a paper plate for two times, the repeatability is estimated to be about 11 nm, and is equivalent to be about ?/69. For a plane with 100 × 100 points, a single measurement takes less than 140 ms, and the feasibility for real-time profile measurement with high accuracy has been verified.

En, Bo; Fa-jie, Duan; Chang-rong, Lv; Fan, Feng; Xiao, Fu

2014-06-01

289

An automated system for measuring parameters of nematode sinusoidal movement  

PubMed Central

Background Nematode sinusoidal movement has been used as a phenotype in many studies of C. elegans development, behavior and physiology. A thorough understanding of the ways in which genes control these aspects of biology depends, in part, on the accuracy of phenotypic analysis. While worms that move poorly are relatively easy to describe, description of hyperactive movement and movement modulation presents more of a challenge. An enhanced capability to analyze all the complexities of nematode movement will thus help our understanding of how genes control behavior. Results We have developed a user-friendly system to analyze nematode movement in an automated and quantitative manner. In this system nematodes are automatically recognized and a computer-controlled microscope stage ensures that the nematode is kept within the camera field of view while video images from the camera are stored on videotape. In a second step, the images from the videotapes are processed to recognize the worm and to extract its changing position and posture over time. From this information, a variety of movement parameters are calculated. These parameters include the velocity of the worm's centroid, the velocity of the worm along its track, the extent and frequency of body bending, the amplitude and wavelength of the sinusoidal movement, and the propagation of the contraction wave along the body. The length of the worm is also determined and used to normalize the amplitude and wavelength measurements. To demonstrate the utility of this system, we report here a comparison of movement parameters for a small set of mutants affecting the Go/Gq mediated signaling network that controls acetylcholine release at the neuromuscular junction. The system allows comparison of distinct genotypes that affect movement similarly (activation of Gq-alpha versus loss of Go-alpha function), as well as of different mutant alleles at a single locus (null and dominant negative alleles of the goa-1 gene, which encodes Go-alpha). We also demonstrate the use of this system for analyzing the effects of toxic agents. Concentration-response curves for the toxicants arsenite and aldicarb, both of which affect motility, were determined for wild-type and several mutant strains, identifying P-glycoprotein mutants as not significantly more sensitive to either compound, while cat-4 mutants are more sensitive to arsenite but not aldicarb. Conclusions Automated analysis of nematode movement facilitates a broad spectrum of experiments. Detailed genetic analysis of multiple alleles and of distinct genes in a regulatory network is now possible. These studies will facilitate quantitative modeling of C. elegans movement, as well as a comparison of gene function. Concentration-response curves will allow rigorous analysis of toxic agents as well as of pharmacological agents. This type of system thus represents a powerful analytical tool that can be readily coupled with the molecular genetics of nematodes.

Cronin, Christopher J; Mendel, Jane E; Mukhtar, Saleem; Kim, Young-Mee; Stirbl, Robert C; Bruck, Jehoshua; Sternberg, Paul W

2005-01-01

290

Half-Tone Video Images Of Drifting Sinusoidal Gratings  

NASA Technical Reports Server (NTRS)

Digital technique for generation of slowly moving video image of sinusoidal grating avoids difficulty of transferring full image data from disk storage to image memory at conventional frame rates. Depends partly on trigonometric identity by which moving sinusoidal grating decomposed into two stationary patterns spatially and temporally modulated in quadrature. Makes motion appear smooth, even at speeds much less than one-tenth picture element per frame period. Applicable to digital video system in which image memory consists of at least 2 bits per picture element, and final brightness of picture element determined by contents of "lookup-table" memory programmed anew each frame period and indexed by coordinates of each picture element.

Mulligan, Jeffrey B.; Stone, Leland S.

1991-01-01

291

Measurement of diffusion parameters using a sinusoidal iontophoretic source in rat cortex.  

PubMed

A new method was developed to extract diffusion parameters in brain tissue using a sinusoidal iontophoretic point source of tetramethylammonium operated at different frequencies. The resulting steady state oscillating extracellular concentration of this probe molecule was continuously monitored using an ion-selective microelectrode located about 100 microm from the source. Because the probe molecules must diffuse through the extracellular space (ECS), the oscillating concentration at the recording location will develop a phase lag and an amplitude attenuation relative to the sinusoidal source. These two components of the signal can be analyzed to determine the tortuosity factor lambda and the ECS volume fraction alpha. The method also measures the nonspecific clearance rate constant kappa. In brain slices this reflects washout of diffusing molecules. Values of alpha (0.18+/-0.05) and lambda (1.67+/-0.08) obtained from this frequency method in rat cortical slices were similar to those obtained by the real-time iontophoretic method employing a square pulse source. The relative merits of the frequency method compared to the pulse method are discussed. PMID:12535769

Chen, Kevin C; Nicholson, Charles

2002-12-31

292

High-Voltage, Asymmetric-Waveform Generator  

NASA Technical Reports Server (NTRS)

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

2008-01-01

293

Improvement of a large-amplitude sinusoidal pressure generator for dynamic calibration of pressure transducers  

NASA Technical Reports Server (NTRS)

Results of research on the improvement of a sinusoidal pressure generator are presented. The generator is an inlet-area-modulated, gas-flow-through device (siren type) which was developed to dynamically calibrate pressure transducers and pressure probes. Tests were performed over a frequency range of 100 Hz to 20 kHz at average chamber pressures (bias pressure) between 30 and 50 psia (21 and 35 N/sq cm abs) and between 150 and 300 psia (104 and 207 N/sq cm abs). Significant improvements in oscillation pressure waveform were obtained but with reduction in available generator oscillation pressure amplitude range. Oscillation pressure amplitude, waveform, and waveform spectral content are given as functions of frequency for the two bias pressure conditions. The generator and instrumentation for frequency, amplitude, and spectrum measurements are described.

Robinson, R. E.

1972-01-01

294

Sinusoidal Regge Oscillations from Short Lived Resonances  

NASA Astrophysics Data System (ADS)

It is well known that a resonance with a large angular life can produce sharp Breit-Wigner peaks in the energy dependence of integral cross sections [1,2]. Here we show that a short-lived resonance whose angular life is of order of one full rotation may produce a different kind of contribution to the integral cross section. This contribution has a sinousoidal form and its frequency is determined by the rotational constant of the complex. As one of the examples, we analyze the Regge oscillations observed in numerical simulations of the F+H2(v=0,j=0,?=0) ->FH(v'=2,j'=0,?'=0) + H reaction. In particular, we show that these oscillations are produced by two overlapping resonances located near the transition state and the van der Waals well, respectively [3]. [1] J. H. Macek, et al., Phys. Rev. Lett., 93, 183202, (2004). [2] Z. Felfli et al., J. Phys. B 39, L353 (2006) [3] D. Sokolovski, D. De Fazio, S. Cavalli and V. Aquilanti, J. Chem. Phys. (2007) (submitted).

Sokolovski, D.; Felfli, Z.; Msezane, A. Z.

2007-06-01

295

Visual Evoked Cortical Potential (VECP) Elicited by Sinusoidal Gratings Controlled by Pseudo-Random Stimulation  

PubMed Central

The contributions of contrast detection mechanisms to the visual cortical evoked potential (VECP) have been investigated studying the contrast-response and spatial frequency-response functions. Previously, the use of m-sequences for stimulus control has been almost restricted to multifocal electrophysiology stimulation and, in some aspects, it substantially differs from conventional VECPs. Single stimulation with spatial contrast temporally controlled by m-sequences has not been extensively tested or compared to multifocal techniques. Our purpose was to evaluate the influence of spatial frequency and contrast of sinusoidal gratings on the VECP elicited by pseudo-random stimulation. Nine normal subjects were stimulated by achromatic sinusoidal gratings driven by pseudo random binary m-sequence at seven spatial frequencies (0.4–10 cpd) and three stimulus sizes (4°, 8°, and 16° of visual angle). At 8° subtence, six contrast levels were used (3.12–99%). The first order kernel (K1) did not provide a consistent measurable signal across spatial frequencies and contrasts that were tested–signal was very small or absent–while the second order kernel first (K2.1) and second (K2.2) slices exhibited reliable responses for the stimulus range. The main differences between results obtained with the K2.1 and K2.2 were in the contrast gain as measured in the amplitude versus contrast and amplitude versus spatial frequency functions. The results indicated that K2.1 was dominated by M-pathway, but for some stimulus condition some P-pathway contribution could be found, while the second slice reflected the P-pathway contribution. The present work extended previous findings of the visual pathways contribution to VECP elicited by pseudorandom stimulation for a wider range of spatial frequencies.

Araujo, Carolina S.; Souza, Givago S.; Gomes, Bruno D.; Silveira, Luiz Carlos L.

2013-01-01

296

Sinusoidal galvanic vestibular stimulation (sGVS) induces a vasovagal response in the rat  

PubMed Central

Blood pressure (BP) and heart rate (HR) were studied in isoflurane-anesthetized Long-Evans rats during sinusoidal galvanic vestibular stimulation (sGVS) and sinusoidal oscillation in pitch to characterize vestibular influences on autonomic control of BP and HR. sGVS was delivered binaurally via Ag/AgCl needle electrodes inserted over the mastoids at stimulus frequencies 0.008–0.4 Hz. Two processes affecting BP and HR were induced by sGVS: 1) a transient drop in BP (?15–20 mmHg) and HR (?3 beat*s?1), followed by a slow recovery over 1–6 min; and 2) inhibitory modulations in BP (?4.5 mmHg/g) and HR (?0.15 beats*s?1/g) twice in each stimulus cycle. The BP and HR modulations were approximately in-phase with each other and were best evoked by low stimulus frequencies. A wavelet analysis indicated significant energies in BP and HR at scales related to twice and four times the stimulus frequency bands. BP and HR were also modulated by oscillation in pitch at frequencies 0.025–0.5 Hz. Sensitivities at 0.025 Hz were ?4.5 mmHg/g (BP) and ?0.17 beat*s?1/g (HR) for pitches of 20–90°. The tilt-induced BP and HR modulations were out-of-phase, but the frequencies at which responses were elicited by tilt and sGVS were the same. The results show that the sGVS-induced responses, which likely originate in the otolith organs, can exert a powerful inhibitory effect on both BP and HR at low frequencies. These responses have a striking resemblance to human vasovagal responses. Thus, sGVS-activated rats can potentially serve as a useful experimental model of the vasovagal response in humans.

Martinelli, Giorgio P.; Ogorodnikov, Dmitri; Xiang, Yongqing; Raphan, Theodore; Holstein, Gay R.; Yakushin, Sergei B.

2011-01-01

297

Using Antenna Arrays to Motivate the Study of Sinusoids  

ERIC Educational Resources Information Center

Educational activities involving antenna arrays to motivate the study of sinusoids are described. Specifically, using fundamental concepts related to phase and simple geometric arguments, students are asked to predict the location of interference nulls in the radiation pattern of two-element phased array antennas. The location of the radiation…

Becker, J. P.

2010-01-01

298

Sound waves in two-dimensional ducts with sinusoidal walls  

NASA Technical Reports Server (NTRS)

The method of multiple scales is used to analyze the wave propagation in two-dimensional hard-walled ducts with sinusoidal walls. For traveling waves, resonance occurs whenever the wall wavenumber is equal to the difference of the wavenumbers of any two duct acoustic modes. The results show that neither of these resonating modes could occur without strongly generating the other.

Nayfeh, A. H.

1974-01-01

299

High frequency pressure oscillator for microcryocoolers  

NASA Astrophysics Data System (ADS)

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

Vanapalli, S.; Ter Brake, H. J. M.; Jansen, H. V.; Zhao, Y.; Holland, H. J.; Burger, J. F.; Elwenspoek, M. C.

2008-04-01

300

Cell shape-dependent rectification of surface receptor transport in a sinusoidal electric field.  

PubMed Central

In the presence of an extracellular electric field, transport dynamics of cell surface receptors represent a balance between electromigration and mutual diffusion. Because mutual diffusion is highly dependent on surface geometry, certain asymmetrical cell shapes effectively create an anisotropic resistance to receptor electromigration. If the resistance to receptor transport along a single axis is anisotropic, then an applied sinusoidal electric field will drive a net time-average receptor displacement, effectively rectifying receptor transport. To quantify the importance of this effect, a finite difference mathematical model was formulated and used to describe charged receptor transport in the plane of a plasma membrane. Representative values for receptor electromigration mobility and diffusivity were used. Model responses were examined for low frequency (10(-4)-10 Hz) 10-V/cm fields and compared with experimental measurements of receptor back-diffusion in human fibroblasts. It was found that receptor transport rectification behaved as a low-pass filter; at the tapered ends of cells, sinusoidal electric fields in the 10(-3) Hz frequency range caused a time-averaged accumulation of receptors as great as 2.5 times the initial uniform concentration. The extent of effective rectification of receptor transport was dependent on the rate of geometrical taper. Model studies also demonstrated that receptor crowding could alter transmembrane potential by an order of magnitude more than the transmembrane potential directly induced by the field. These studies suggest that cell shape is important in governing interactions between alternating current (ac) electric fields and cell surface receptors.

Lee, R C; Gowrishankar, T R; Basch, R M; Patel, P K; Golan, D E

1993-01-01

301

What is new in the liver sinusoids? meeting report, 16th International Symposium on Cells of the Hepatic Sinusoid (ISCHS)  

PubMed Central

The 16th International Symposium on Cells of the Hepatic Sinusoid (ISCHS) took place in Florence, Italy on 22-24 September 2011. This symposium is a multidisciplinary meeting where new and important findings on the biology of liver cells are presented and discussed.

2011-01-01

302

Spectral and temporal properties of optical signals with multiple sinusoidal phase modulations.  

PubMed

Optical signals generated by multiple sinusoidal temporal phase modulations (multi-FMs) applied to a monochromatic field are studied from the viewpoint of their optical spectrum and temporal modulations arising from spectral impairments. Statistical analysis based on the central limit theorem shows that the signals' optical spectrum converges to a normal distribution as the number of modulations increases, allowing one to predict the frequency range containing a given fraction of the total energy with the associated cumulative density function. The conversion of frequency modulation to amplitude modulation is analyzed and simulated for arbitrary multi-FM signals. These developments are of theoretical and practical importance for high-energy laser systems, where optical pulses are phase modulated in the front end to smooth out the on-target beam profile and prevent potentially catastrophic damage to optical components. PMID:24663283

Dorrer, C

2014-02-10

303

Validation of a Model for Railway Rolling Noise Using Field Measurement with Sinusoidally Profiled Wheels  

NASA Astrophysics Data System (ADS)

Field measurements have been carried out using a series of railway wheels with specially machined running surfaces. These were given a sinusoidal profile around their circumference. This allows accurate measurements of noise and vibration to be made for single frequency excitation. A series of wheels with different wavelengths has been used in combination with a range of running speeds to allow a wide frequency range to be scanned. Results are compared with predictions using a theoretical model in order to investigate a number of detailed aspects of the model. The predicted behaviour has been confirmed in terms of the magnitude of the response of the track and the wheel and the apparent damping of the wheel during rolling. An experimental estimate of the filtering introduced by the finite contact patch length is also possible.

Thompson, D. J.; Vincent, N.; Gautier, P. E.

1999-06-01

304

Interactive Tools for Sound Signal Analysis/Synthesis Based on a Sinusoidal Representation.  

National Technical Information Service (NTIS)

This thesis develops a series of programs that implement the sinusoidal representation model for speech and sound waveform analysis and synthesis. This sinusoidal representation model can also be used for a variety of sound signal transformations such as ...

M. F. Chuang

1997-01-01

305

Frequency response of polypyrrole trilayer actuator displacement  

NASA Astrophysics Data System (ADS)

Conducting polymer trilayers are attractive for use in functional devices, given low actuation voltages, operation in air and potentially useful stresses and strains; however, their dynamic behavior must be understood from an engineering perspective before they can be effectively incorporated into a design. As a step towards the identification of the actuator dynamics, frequency response analysis has been performed to identify the magnitude and phase shift of displacement in response to a sinusoidal voltage input. The low damping of the trilayer operating in air and the use of a laser displacement sensor has allowed the frequency response to be continuously identified up to 100Hz, demonstrating a resonant peak at 80Hz for a 10mm long actuator. Two linear transfer function models have been fitted to the frequency response of the trilayer displacement (i) a 3rd order model to represent the dynamics below 20Hz and (ii) a higher complexity 6th order model to also include the resonant peak. In response to a random input signal, the 3rd order model coarsely follows the experimental identified displacement, while the 6th order model is able to fully simulate the real trilayer movement. Step responses have also been obtained for the 3rd and 6th order transfer functions, with both models capable of following the first 4 seconds of experimental displacement. The application of empirical transfer function models will facilitate accurate simulation and analysis of trilayer displacement, and will lead to the design of accurate positional control systems.

John, Stephen; Alici, Gursel; Cook, Christopher

2008-05-01

306

Frequency modulation television analysis: Threshold impulse analysis. [with computer program  

NASA Technical Reports Server (NTRS)

A computer program is developed to calculate the FM threshold impulse rates as a function of the carrier-to-noise ratio for a specified FM system. The system parameters and a vector of 1024 integers, representing the probability density of the modulating voltage, are required as input parameters. The computer program is utilized to calculate threshold impulse rates for twenty-four sets of measured probability data supplied by NASA and for sinusoidal and Gaussian modulating waveforms. As a result of the analysis several conclusions are drawn: (1) The use of preemphasis in an FM television system improves the threshold by reducing the impulse rate. (2) Sinusoidal modulation produces a total impulse rate which is a practical upper bound for the impulse rates of TV signals providing the same peak deviations. (3) As the moment of the FM spectrum about the center frequency of the predetection filter increases, the impulse rate tends to increase. (4) A spectrum having an expected frequency above (below) the center frequency of the predetection filter produces a higher negative (positive) than positive (negative) impulse rate.

Hodge, W. H.

1973-01-01

307

Investigation of Calibrating Force Transducer Using Sinusoidal Force  

SciTech Connect

Sinusoidal force calibration method was studied several years before at Physikalisch-Technische Bundesanstalt (PTB). A similar dynamic force calibration system is developed at Changcheng Institute of Metrology and Measurement (CIMM). It uses electro-dynamic shakers to generate dynamic force in the range from 1 N to 20 kN, and heterodyne laser interferometers are used for acceleration measurement. The force transducer to be calibrated is mounted on the shaker, and a mass block is screwed on the top of force transducer, the sinusoidal forces realized by accelerated load masses are traceable to acceleration and mass according to the force definition. The methods of determining Spatial-dependent acceleration on mass block and measuring the end mass of force transducer in dynamic force calibration are discussed in this paper.

Zhang Li [School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing (China); Key Laboratory for Metrology, Changcheng Institute of Metrology and Measurement (CIMM), Beijing 100095 (China); Wang Yu; Zhang Lizhe [Key Laboratory for Metrology, Changcheng Institute of Metrology and Measurement (CIMM), Beijing 100095 (China)

2010-05-28

308

Sinusoidal modulation control method in a chaotic neural network  

NASA Astrophysics Data System (ADS)

Chaotic neural networks (CNNs) have chaotic dynamic associative memory properties: The memory states appear non-periodically, and cannot be converged to a stored pattern. Thus, it is necessary to control chaos in a CNN in order to recognize associative memory. In this paper, a novel control method, the sinusoidal modulation control method, has been proposed to control chaos in a CNN. In this method, a sinusoidal wave simplified from brain waves is used as a control signal to modulate a parameter of the CNN. The simulation results demonstrate the effectiveness of this control method. The controlled CNN can be applied to information processing. Moreover, the method provides a way to associate brain waves by controlling CNNs.

Zhang, Qihanyue; Xie, Xiaoping; Zhu, Ping; Chen, Hongping; He, Guoguang

2014-08-01

309

Sinusoidal input describing function for hysteresis followed by elementary backlash  

NASA Technical Reports Server (NTRS)

The author proposes a new sinusoidal input describing function which accounts for the serial combination of hysteresis followed by elementary backlash in a single nonlinear element. The output of the hysteresis element drives the elementary backlash element. Various analytical forms of the describing function are given, depending on the a/A ratio, where a is the half width of the hysteresis band or backlash gap, and A is the amplitude of the assumed input sinusoid, and on the value of the parameter representing the fraction of a attributed to the backlash characteristic. The negative inverse describing function is plotted on a gain-phase plot, and it is seen that a relatively small amount of backlash leads to domination of the backlash character in the describing function. The extent of the region of the gain-phase plane covered by the describing function is such as to guarantee some form of limit cycle behavior in most closed-loop systems.

Ringland, R. F.

1976-01-01

310

Improved sinusoidal phase plate to extend depth of field in incoherent hybrid imaging systems.  

PubMed

An improved sinusoidal phase plate is proposed by adding a new parameter to the conventional sinusoidal phase plate. A series of performance comparisons are made among various phase plates, including sinusoidal, cubic phase, and the modified logarithmic phase. The results demonstrate that the improved sinusoidal phase plate can further extend the depth of field in incoherent hybrid imaging systems, with lower surface relief phase structures fabricated in photoresist (AR-N 4340, ALL Resist, Germany). PMID:23114354

Wang, Jingang; Bu, Jing; Wang, Mingwei; Yang, Yong; Yuan, X-C

2012-11-01

311

Voltage Sensor  

NASA Technical Reports Server (NTRS)

Under a Lewis Research Center Small Business Innovation Research contract, SRICO, Inc. developed a fiber optic voltage sensor to measure voltage in electronic systems in spacecraft. The sensor uses glass and light to sense and transmit electricity, and is relatively safe and accurate. SRICO then commercialized the sensor for measurement of electric field and voltage in applications such as electric power systems and hazardous environments, lightning detection, and fiber optic communication systems.

1996-01-01

312

Reduced Circular Sinusoidal Cone-beam CT for Industrial Applications  

PubMed Central

Cone-beam computed tomography (CBCT) plays an important role in industrial, nondestructive testing applications not to mention in medical applications. Circular scanning configuration is widely used for its mechanical simplicity and for readily available and efficient reconstruction algorithms based on the Feldkamp algorithm. However, due to the lack of data sufficiency, circular CBCT does not guarantee image accuracy, and is not free from image artifacts related to the cone-angle and axial variation of the object anatomy. Therefore, non-circular scanning geometries such as helix or circular sinusoid, which provide sufficient data for exact image reconstruction within the scanned volume, are favorable when accurate images free of cone-angle artifacts are desired. Analytic algorithms have been developed for image reconstruction from cone-beam data acquired with a full-scan (or, equivalently, a closed) circular sinusoidal trajectory. In many applications such as industrial inspection of a product where a high throughput is important, it is desirable to have a short scan time. In this work, we propose an innovative imaging approach in which a reduced-scan (or, equivalently, an open) circular sinusoidal trajectory is used for acquiring data sufficient for exact 3D image reconstruction. A filtered backprojection (FBP) algorithm based on Pack-Noo's reconstruction formula is applied for image reconstruction in reduced-scan circular sinusoidal scans. We have conducted numerical studies to demonstrate the reduced-scan approach and to validate the FBP reconstruction algorithm in the proposed approach. The proposed scanning method can contribute to increasing the throughput of a scanner, while improving the image quality compared to a conventional circular scan.

Xia, Dan; Cho, Seungryong; Pan, Xiaochuan

2010-01-01

313

Mini-Scale Power Distribution Network Feeding Trapezoidal-Wave Voltages to Power Electronic Loads with Diode Rectifiers  

Microsoft Academic Search

This paper proposes a novel three-phase power distribution system feeding trapezoidal voltages to various power electronic loads with diode rectifier front-ends. The network distributes trapezoidal voltages generated by synchronous superposition of wave-shaping voltages onto sinusoidal voltages available from a utility power grid. The power distribution by the trapezoidal voltages allows reducing harmonics of the line currents without electronic switching devices

Toshihiko Noguchi; Masaru Imoto; Yoshikazu Sato

2004-01-01

314

A Compact Design for High Voltage Direct Current Circuit Breaker  

Microsoft Academic Search

The absence of current-zero points in the direct current (DC) waveform of high voltage DC (HVDC) circuit breakers makes the interruption process more severe than the case of conventional AC networks with sinusoidal currents. In this way, in the current HVDC networks, a parallel precharged capacitor is inserted to inject the reverse current into the interruption chamber of the vacuum

Jouya Jadidian

2009-01-01

315

The sinusoidal probe: a new approach to improve electrode longevity  

PubMed Central

Micromotion between the brain and implanted electrodes is a major contributor to the failure of invasive brain–machine interfaces. Movements of the electrode tip cause recording instabilities while spike amplitudes decline over the weeks/months post-implantation due to glial cell activation caused by sustained mechanical trauma. We have designed a sinusoidal probe in order to reduce movement of the recording tip relative to the surrounding neural tissue. The probe was microfabricated from flexible materials and incorporated a sinusoidal shaft to minimize tethering forces and a 3D spheroid tip to anchor the recording site within the brain. Compared to standard microwire electrodes, the signal-to-noise ratio and local field potential power of sinusoidal probe recordings from rabbits was more stable across recording periods up to 678 days. Histological quantification of microglia and astrocytes showed reduced neuronal tissue damage especially for the tip region between 6 and 24 months post-implantation. We suggest that the micromotion-reducing measures incorporated into our design, at least partially, decreased the magnitude of gliosis, resulting in enhanced longevity of recording.

Sohal, Harbaljit S.; Jackson, Andrew; Jackson, Richard; Clowry, Gavin J.; Vassilevski, Konstantin; O'Neill, Anthony; Baker, Stuart N.

2014-01-01

316

A new eigenstructure method for sinusoidal signal retrieval in white noise: estimation and pattern recognition  

Microsoft Academic Search

A new approach, in a framework of an eigenstructure method using a Hankel matrix, is developed for sinusoidal signal retrieval in white noise. A closed-form solution for the singular pairs of the matrix is defined in terms of the associated sinusoidal signals and noise. The estimated sinusoidal singular vectors are applied to form the noise-free Hankel matrix. A pattern recognition

Baogang Hu; Raymond G. Gosine

1997-01-01

317

Phase-locking of auditory-nerve discharges to sinusoidal electric stimulation of the cochlea.  

PubMed

The activity of auditory-nerve fibers was recorded in anesthetized cats in response to sinusoidal electric stimuli applied through a bipolar electrode pair inserted about 5 mm into the cochlea through the round window. The synchronization index was calculated from period histograms for frequencies ranging from 0.2 to over 10 kHz. The stimulus artifact was largely eliminated through the use of differential micropipettes and an adaptive digital filter. Measured synchronization indices were many times larger than the indices that could be attributed to the residual stimulus artifact. Synchronization indices at each stimulus frequency varied considerably from fiber to fiber, even in the same animal. The dependence of synchrony on stimulus frequency was also variable, decreasing monotonically in some fibers and nonmonotonically in others. The average electric synchronization index for all fibers did not fall as steeply with frequency as does the average synchrony for acoustic stimuli. The finding of significant phase locking to electric stimuli well above 1 kHz suggests that the poor frequency discrimination of cochlear-implant recipients for single-channel stimulation above this frequency may be due to the inability of the central processor to make effective use of the available phase-locking information for monaural stimulation. PMID:1559909

Dynes, S B; Delgutte, B

1992-02-01

318

Motor cortical activity during drawing movements: single-unit activity during sinusoid tracing.  

PubMed

1. This study examines the neuronal activity of motor cortical cells associated with the production of arm trajectories during drawing movements. Three monkeys were trained to perform two tasks. The first task ("center----out" task) required the animal to move its arm in different directions from a center start position to one of eight targets spaced at equal angular intervals and equal distances from the origin. Movements to each target were in a constant direction, and the average rate of neuronal discharge with movements to different targets varied in a characteristic pattern. A cosine tuning function was used to map each cell's discharge rate to the direction of arm movement. This function spanned all movement directions, with a peak firing rate in the cell's preferred direction. 2. The second task ("tracing" task) required the animal to trace curved figures consisting of sine waves of different spatial frequencies and amplitudes. Both the speed and direction changed continuously throughout these movements. The cosine tuning function derived from the center----out task was used to model the activity of the cell during the tracing of sinusoids in the second task. Sinusoidal data were divided into 20-ms bins; instantaneous direction, speed, and discharge rate were analyzed bin by bin. This provided a way to compare directly the tuning parameters during a task with constant direction to a task where the direction varied continuously. 3. Movement direction as it changed during the tracing task was an important factor in the discharge pattern of cells that had discharge patterns that could be represented by the cosine tuning function. 4. The modulation of discharge rate during figure tracing depended on both the cell's preferred direction and the orientation of the figure. The activity of cells with preferred directions perpendicular to the axis of the sinusoidal figure was most modulated, whereas the activity of those cells with preferred directions aligned to the figure's axis was least modulated. 5. The cells with modulated activity tended to have firing rates that differed from the predicted cosine tuning function during the sinusoidal movements for those portions of the trajectory where the movement direction was in the cell's preferred direction. 6. Finger speed during figure tracing varied inversely with path curvature with the same relation that has been found during human drawing. To assess the relation of instantaneous speed to discharge rate, the component of the discharge pattern related to direction was subtracted from the total discharge.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1527573

Schwartz, A B

1992-08-01

319

Optical characterization of a dual-frequency hybrid aligned nematic liquid crystal cell  

NASA Astrophysics Data System (ADS)

The dielectric anisotropy of a highly dispersive dual-frequency nematic liquid crystal (MDA-00-3969 (Merck KGa)) has been determined using the optical fully-leaky guided-mode technique. A 4Vrms sinusoidal voltage was applied across a 5µm hybrid aligned nematic (HAN) cell at various frequencies in both the positive and negative dielectric anisotropy regime. Optical data was collected at each frequency enabling the director profile in each case to be determined using a multi-layer optics model in combination with a liquid crystal free-energy minimization routine. The thresholdless response of the HAN cell combined with the extreme sensitivity of the optical characterization technique has allowed subtle changes in dielectric permittivity with frequency to be observed. The resulting measured dispersion shows excellent agreement with a single Debye-type relaxation model.

Jewell, S. A.; Sambles, J. R.

2005-04-01

320

Constant-amplitude, frequency- independent phase shifter  

NASA Technical Reports Server (NTRS)

Electronic circuit using operational amplifiers provides output with constant phase shift amplitude, with respect to sinusoidal input, over wide range of frequencies. New circuit includes field effect transistor, Q, operational amplifiers, A1 and A2, and phase detector.

Deboo, G. J.

1971-01-01

321

Existence of partial discharges in low-voltage induction machines supplied by PWM drives  

Microsoft Academic Search

When standard low voltage induction motors are supplied by pulse-width modulated (PWM) adjustable speed drives, some of the traditional sinusoidal system concepts cannot be applied. This paper reports the results of an investigation of the effect of PWM drives on the insulation of the stator winding. The characteristics of the employed dielectric material and the magnitude of the applied voltages

A. Mbaye; F. Grigorescu; T. Lebey; Bui Ai

1996-01-01

322

Effect of Substrate Bias Voltage on the Physical Properties of Zirconium Nitride (ZrN) Films Deposited by Mid Frequency Reactive Magnetron Sputtering  

NASA Astrophysics Data System (ADS)

Present work involves the preparation of Zirconium Nitride thin films on stainless steel (SS) (304L grade) substrate by reactive cylindrical magnetron sputtering method. The X-ray diffraction (XRD) profile of the ZrN thin films prepared with different bias voltage conforms face centered cubic structure with preferred orientation along the (111) plane at lower bias voltage (100 V) and at higher bias voltage (300 V) the preferred orientation shifted to (220) plane. The influences of bias voltage on the thickness and microhardness ZrN thin films have been studied. ZrN thin film sputtered with 300 V bias voltage shows the maximum reflectance of 90% at a wavelength of 1000 nm. The coated substrates have been found to exhibit improved corrosion resistance compared to the SS plate. The root mean square surface roughness and surface morphology were investigated from 3D atomic force microscope (AFM) images and scanning electron microscope (SEM), which indicate smooth and uniform surface pattern without any pin holes.

Kavitha, A.; Kannan, R.; Loganathan, S.

2014-05-01

323

Voltage Amplification using Plasma  

SciTech Connect

The purpose of this work is to present experimental results about voltage amplification using plasma produced by a simple neon lamp, series connected with a signal generator and discrete circuit elements. The main advantage of employing plasma as an amplifier is due to its ability to drive larger power and potentially to operate in a larger frequency range compared with traditional amplifiers. Our results show that both, the voltage gain and the frequency range where the gain is bigger than one, are related to the plasma density which may be adjusted by a proper control of electrical discharge conditions. The plasma produced into the neon lamp exhibits a diode characteristic that is the principal responsible by the nonlinear plasma response. The amplification occurs when the plasma shows a negative conductance. In this regime the lamp works as an active amplifier and voltage gain higher than 18 was obtained.

Farias, E. E.; Cavalcanti, G. H.; Santiago, M. A. M. [Av. Gal Milton Tavares de Souza - 24310 240 - Instituto de Fisica - Universidade Federal Fluminense (Brazil)

2006-12-04

324

Response Linearity of Alert Monkey Non-Eye Movement Vestibular Nucleus Neurons During Sinusoidal Yaw Rotation  

PubMed Central

Vestibular afferents display linear responses over a range of amplitudes and frequencies, but comparable data for central vestibular neurons are lacking. To examine the effect of stimulus frequency and magnitude on the response sensitivity and linearity of non-eye movement central vestibular neurons, we recorded from the vestibular nuclei in awake rhesus macaques during sinusoidal yaw rotation at frequencies between 0.1 and 2 Hz and between 7.5 and 210°/s peak velocity. The dynamics of the neurons' responses across frequencies, while holding peak velocity constant, was consistent with previous studies. However, as the peak velocity was varied, while holding the frequency constant, neurons demonstrated lower sensitivities with increasing peak velocity, even at the lowest peak velocities tested. With increasing peak velocity, the proportion of neurons that silenced during a portion of the response increased. However, the decrease in sensitivity of these neurons with higher peak velocities of rotation was not due to increased silencing during the inhibitory portion of the cycle. Rather the neurons displayed peak firing rates that did not increase in proportion to head velocity as the peak velocity of rotation increased. These data suggest that, unlike vestibular afferents, the central vestibular neurons without eye movement sensitivity examined in this study do not follow linear systems principles even at low velocities.

Newlands, Shawn D.; Lin, Nan; Wei, Min

2009-01-01

325

Frequency of subthreshold oscillations at different membrane potential voltages in neurons at different anatomical positions on the dorsoventral axis in the rat medial entorhinal cortex.  

PubMed

Neurons from layer II of the medial entorhinal cortex show subthreshold membrane potential oscillations (SMPOs) which could contribute to theta-rhythm generation in the entorhinal cortex and to generation of grid cell firing patterns. However, it is unclear whether single neurons have a fixed unique oscillation frequency or whether their frequency varies depending on the mean membrane potential in a cell. We therefore examined the frequency of SMPOs at different membrane potentials in layer II stellate-like cells of the rat medial entorhinal cortex in vitro. Using whole-cell patch recordings, we found that the fluctuations in membrane potential show a broad band of low power frequencies near resting potential that transition to more narrowband oscillation frequencies with depolarization. The transition from broadband to narrowband frequencies depends on the location of the neuron along the dorsoventral axis in the entorhinal cortex, with dorsal neurons transitioning to higher-frequency oscillations relative to ventral neurons transitioning to lower-frequency oscillations. Once SMPOs showed a narrowband frequency, systematic frequency changes were not observed with further depolarization. Using a Hodgkin-Huxley-style model of membrane currents, we show that differences in the influence of depolarization on the frequency of SMPOs at different dorsal to ventral positions could arise from differences in the properties of the h current. The properties of frequency changes in this data are important for evaluating models of the generation of grid cell firing fields with different spacings along the dorsal-to-ventral axis of medial entorhinal cortex. PMID:21880929

Yoshida, Motoharu; Giocomo, Lisa M; Boardman, Ian; Hasselmo, Michael E

2011-08-31

326

A Novel Switching Sequence Design for Five-Level NPC\\/H-Bridge Inverters With Improved Output Voltage Spectrum and Minimized Device Switching Frequency  

Microsoft Academic Search

This paper presents a novel switching sequence design for the space-vector modulation of high-power multilevel converters. The switching sequences are optimized for the improvement of harmonic spectrum and the minimization of device switching frequency. Compared to other commonly used switching sequences, the output spectrum of the proposed design shows higher inverter equivalent switching frequency. Meanwhile, the device switching frequency is

Zhongyuan Cheng; Bin Wu

2007-01-01

327

Received Voltage Versus Antenna Height  

Microsoft Academic Search

Relative received voltage versus antenna height above ground is a function of field intensity height gain and the height dependent antenna effective length and impedance. The results of an empirical investigation of relative received voltage versus antenna height using typical EMI antennas in the frequency range 2.5 MHz to 1 GHz are presented. In a theoretical analysis field and antenna

ALBERT A. SMITH

1969-01-01

328

Accurate modeling of voltage and current waveforms with saturation and power losses in a ferrite core via two-dimensional finite elements and a circuit simulator  

NASA Astrophysics Data System (ADS)

This paper presents a new dynamic model of equivalent circuit to simulate in the time-domain the effects of saturation and power losses in a nonlinear magnetic component. The parameters of the model are a nonlinear inductance and a nonlinear loss resistance that are computed via two-dimensional finite elements. The effectiveness of the model is analyzed in the case of a soft ferrite inductor excited by a sinusoidal voltage source at frequencies of 500 Hz and 40 kHz. The resulting voltage and current waveforms of the inductor taken in the laboratory are then compared with those computed via the PSIM circuit simulator. PSIM is a simulation software designed for power electronics, motor control, and dynamic system simulation.

Salas, R. A.; Pleite, J.

2010-05-01

329

Measurement of magnetic losses by thermal method applied to power ferrites at high level of induction and frequency.  

PubMed

Classically, low frequency losses in soft magnetic materials and ferrites in particular are measured by flux metric method under sinusoidal waveform excitation voltage. However, in typical application of modern power electronics, the frequency currently exceeds 100 kHz. This feature is at the origin of a difficulty: the phase shift between current and voltage can be disturbed by current probe delay. Thus, the results can be affected by large errors. As a consequence, it becomes more and more important to develop alternative methods to measure losses in magnetic materials. It is proposed to use calorimetric method which is by principle free of the above mentioned problems. The experimental device is described in details and the results are reported for experiments conducted on a commercial Mn-Zn ferrite under sinusoidal waveform regime for frequencies varying from 10 to 200 kHz. Comparisons with flux metric measurement show that significant differences appear typically for Bf products above 5000 V/m(2) (50 kHzx100 mT). PMID:19256669

Loyau, V; Lo Bue, M; Mazaleyrat, F

2009-02-01

330

[Regeneration of liver parenchyma and sinusoidal cells following partial hepatectomy].  

PubMed

Partial hepatectomy (30 percent of the liver weight) was performed in 225 female Wistar rats, ages 6 weeks, 6 and 9 months. The animals were sacrificed in intervals between 4 hours and 21 d after the operation. The automated microscopic image analysis after Simon et al. (1984) and histoautoradiography were utilized for evaluation of liver cell regeneration. Despite measurement of more than 1,000 cells per animal we were not able to confirm enlargement of hepatocytes as the first reaction to partial hepatectomy The number of liver cells per unit area increased whereas sinusoidal size remained rather constant, corresponding to a decrease in average cell size and in the standard deviation of cell area. The importance of binucleated hepatocytes in the process is emphasized. Measurement of the nucleoli and of the mean extinction values of liver cell nuclei as a measure of the DNA content did not provide any essentially new perspectives. The investigation did however emphasize the importance of the extent of the hepatic resection and the age of the experimental animals on the intensity and subsequent course of liver cell regeneration. Proliferation of the sinusoidal cells themselves after partial hepatectomy could not definitively be demonstrated to be age-dependent. PMID:3984545

Simon, H; Wenzelides, K; Guski, H; Kranz, D

1985-01-01

331

Liver Sinusoidal Endothelial Cells Link Hyperinsulinemia to Hepatic Insulin Resistance  

PubMed Central

Insulin signaling in vascular endothelial cells (ECs) is critical to maintain endothelial function but also to mediate insulin action on peripheral glucose disposal. However, gene knockout studies have reached disparate conclusions. Thus, insulin receptor inactivation in ECs does not impair insulin action, whereas inactivation of Irs2 does. Previously, we have shown that endothelial ablation of the three Foxo genes protects mice from atherosclerosis. Interestingly, here we show that mice lacking FoxO isoforms in ECs develop hepatic insulin resistance through excessive generation of nitric oxide (NO) that impairs insulin action in hepatocytes via tyrosine nitration of insulin receptors. Coculture experiments demonstrate that NO produced in liver sinusoidal ECs impairs insulin’s ability to suppress glucose production in hepatocytes. The effects of liver sinusoidal ECs can be mimicked by NO donors and can be reversed by NO inhibitors in vivo and ex vivo. The findings are consistent with a model in which excessive, rather than reduced, insulin signaling in ECs predisposes to systemic insulin resistance, prompting a reevaluation of current approaches to insulin sensitization.

Tsuchiya, Kyoichiro; Accili, Domenico

2013-01-01

332

The forces generated at the human elbow joint in response to imposed sinusoidal movements of the forearm  

PubMed Central

1. The mechanical resistance of the human forearm has been measured during imposed sinusoidal flexion-extension movements of the elbow joint. 2. The force required to move the limb can be divided into components required to move the mass, and components required to overcome the resistance offered by elastic and frictional properties of the muscles and other soft tissues. 3. When during a vigorous flexing effort the limb was subjected to a small amplitude sinusoidal movement each extension was followed by a considerable reflex contraction of the flexor muscles. At low frequencies of movement this reflex provided an added resistance to extension, but at 8-12 Hz the delay in the reflex pathway was such that the reflex response to extension occurred after the extension phase of the movement was over and during the subsequent flexion movement. The reflex activity then assisted the movement whereas at other frequencies it impeded it. 4. The reflex response to movement increased as the subject exerted a greater flexing force. 5. Small movements generated a relatively larger reflex response than big ones. 6. Even with large amplitudes of movement when the reflex activity was relatively small, the limb resisted extension with a high level of stiffness; this was comparable with the short range stiffness of muscles in experimental animals. 7. The fact that at some frequencies the reflex response assisted the movement implies that with appropriate loading the limb could undergo a self-sustaining oscillation at those frequencies.

Joyce, G. C.; Rack, Peter M. H.; Ross, H. F.

1974-01-01

333

Ballast structure for central high frequency dimming apparatus  

SciTech Connect

An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 hz mains. Several ballasts are disclosed, which consist principally of circuits using passive linear components. Some of the ballasts disclosed are conjugate ballasts which are those made of complex conjugate impedances which resonate with or near the input power frequency. Some ballasts disclosed are non-linear when the lamp is out in order to limit the open circuit voltage. The ballasts disclosed all have the following characteristics: (A) good power factor (Above 0.8) and include at least one capacitor and one inductor; (B) are dimmable by at least 50% by a variable amplitude input having a substantially continuous wave form; (C) use only two input wires; (D) operate at a relatively high frequency (at least an order of magnitude above line frequency); and (E) a good current crest factor.

Capewell, D.; Luchaco, D.G.; Spira, J.S.

1980-06-10

334

Transient voltage oscillations in coils  

SciTech Connect

Magnet coils may be excited into internal voltage oscillations by transient voltages. Such oscillations may electrically stress the magnet's dielectric components to many times its normal stress. This may precipitate a dielectric failure, and the attendant prolonged loss of service and costly repair work. Therefore, it is important to know the natural frequencies of oscillations of a magnet during the design stage, and to determine whether the expected switching transient voltages can excite the magnet into high-voltage internal oscillations. The series capacitance of a winding significantly affects its natural frequencies. However, the series capacitance is difficult to calculate, because it may comprise complex capacitance network, consisting of intra- and inter-coil turn-to-turn capacitances of the coil sections. A method of calculating the series capacitance of a winding is proposed. This method is rigorous but simple to execute. The time-varying transient voltages along the winding are also calculated.

Chowdhuri, P.

1985-01-01

335

The Use of Harmonic Distortion to Increase the Output Voltage of a Three-Phase PWM Inverter  

Microsoft Academic Search

By adding a measure of third harmonic to the output of each phase of a three-phase inverter, it is possible to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed. The line-to-line voltage is undistorted. The method permits the inverter to deliver an output voltage approximately equal to the voltage

John A. Houldsworth; Duncan A. Grant

1984-01-01

336

An automatic voltage sag detector using a discrete wavelet transform and a CFAR detector  

Microsoft Academic Search

The authors present a novel algorithm for a voltage sag detector on transmission and distribution lines. A wavelet transform is utilized to extract voltage sag disturbances from a fundamental 60 Hz sinusoidal wave, and a SG-CA CFAR (stop-and-go cell average constant false alarm rate) detector detects the starting and ending time of the voltage sag. Based on this result, they

Jaehak Chung; Edward J. Powers; W. Mack Grady; Siddharth C. Bhatt

2001-01-01

337

Mode oscillation and harmonic distortions associated with sinusoidal modulation of semiconductor lasers  

NASA Astrophysics Data System (ADS)

This paper investigates mode dynamics, operation characteristics and signal distortions associated with sinusoidal modulation of semiconductor lasers. The study is based on intensive integrations of the multimode rate equation model of semiconductor lasers over wide ranges of the modulation frequency and depth. The rate equations take into account both spectral symmetric and asymmetric suppressions of modal gain. The higher harmonic distortions as well as the half harmonic distortion associated with the period doubling effect are investigated. The study is applied to both cases of single-mode and multimode oscillations of the non-modulated laser. The obtained results showed that the modulated signal has six distinct waveforms depending on the modulation conditions; three types have continuous periodic waveforms and the others have periodic pulsing waveforms. The modulated laser is found to oscillate in a single mode under weak modulation where the modulated signal is continuous, whereas the pulsing signals are associated with multimode oscillation. The higher harmonic distortions of single-mode laser are lower than those of two-mode lasers, and become serious at modulation frequencies around the relaxation oscillation frequency. These distortions are highest when the laser output is pulsating and the pulses are superposed by relaxation oscillations.

Ahmed, M.; Yamada, M.

2012-09-01

338

LASERS AND LASER AMPLIFIERS: Synchronous pumping of jet organic dye lasers with sinusoidally modulated argon laser radiation  

NASA Astrophysics Data System (ADS)

A simple and convenient method of synchronous pumping of jet organic dye lasers is described. In this method a cw argon laser with sinusoidally modulated radiation is used as the pump source. The argon laser is modulated by a standing-wave acoustooptic modulator operating at the frequency of intermode beats of the dye laser. The results are given of an experimental investigation of the width of the mode locking range under synchronous pumping conditions and of the time and energy characteristics of the output radiation. The duration of the output pulses of the dye laser was ~ 350 ps under synchronous pumping conditions.

Ra?, G. I.; Ustinov, B. P.; Sharonov, G. V.

1988-09-01

339

Stream Segregation in the Perception of Sinusoidally Amplitude-Modulated Tones  

PubMed Central

Amplitude modulation can serve as a cue for segregating streams of sounds from different sources. Here we evaluate stream segregation in humans using ABA- sequences of sinusoidally amplitude modulated (SAM) tones. A and B represent SAM tones with the same carrier frequency (1000, 4000 Hz) and modulation depth (30, 100%). The modulation frequency of the A signals (fmodA) was 30, 100 or 300 Hz, respectively. The modulation frequency of the B signals was up to four octaves higher (?fmod). Three different ABA- tone patterns varying in tone duration and stimulus onset asynchrony were presented to evaluate the effect of forward suppression. Subjects indicated their 1- or 2-stream percept on a touch screen at the end of each ABA- sequence (presentation time 5 or 15 s). Tone pattern, fmodA, ?fmod, carrier frequency, modulation depth and presentation time significantly affected the percentage of a 2-stream percept. The human psychophysical results are compared to responses of avian forebrain neurons evoked by different ABA- SAM tone conditions [1] that were broadly overlapping those of the present study. The neurons also showed significant effects of tone pattern and ?fmod that were comparable to effects observed in the present psychophysical study. Depending on the carrier frequency, modulation frequency, modulation depth and the width of the auditory filters, SAM tones may provide mainly temporal cues (sidebands fall within the range of the filter), spectral cues (sidebands fall outside the range of the filter) or possibly both. A computational model based on excitation pattern differences was used to predict the 50% threshold of 2-stream responses. In conditions for which the model predicts a considerably larger 50% threshold of 2-stream responses (i.e., larger ?fmod at threshold) than was observed, it is unlikely that spectral cues can provide an explanation of stream segregation by SAM.

Dollezal, Lena-Vanessa; Beutelmann, Rainer; Klump, Georg M.

2012-01-01

340

Measurement of n-type Dry Thermally Oxidized 6H-SiC Metal-oxide Semiconductor Diodes by Quasistatic and High-Frequency Capacitance Versus Voltage and Capacitance Transient Techniques  

NASA Technical Reports Server (NTRS)

Dry-oxidized n-type 6H-SiC metal-oxide-semiconductor capacitors are investigated using quasistatic capacitance versus voltage (C-V), high-frequency C-V, and pulsed high-frequency capacitance transient (C-t) analysis over the temperature range from 297 to 573 K. The quasistatic C - V characteristics presented are the first reported for 6H-SiC MOS capacitors, and exhibit startling nonidealities due to nonequilibrium conditions that arise from the fact that the recombination/generation process in 6H-SiC is extraordinarily slow even at the highest measurement temperature employed. The high-frequency dark C-V characteristics all showed deep depletion with no observable hysteresis. The recovery of the high-frequency capacitance from deep depletion to inversion was used to characterize the minority-carrier generation process as a function of temperature. Zerbst analysis conducted on the resulting C-t transients, which were longer than 1000 s at 573 K, showed a generation lifetime thermal activation energy of 0.49 eV.

Neudeck, P.; Kang, S.; Petit, J.; Tabib-Azar, M.

1994-01-01

341

Comparison of high frequency, high temperature core loss and B-H loop characteristics of an 80 Ni-Fe crystalline alloy and two iron-based amorphous alloys  

NASA Technical Reports Server (NTRS)

Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H characteristics of a nickel-iron crystalline magnetic alloy (Supermalloy) and two iron-based amorphous magnetic materials (Metglas 2605S-3A and Metglas 2605SC) over the frequency range of 1-50 kHz and temperature range of 23-300 C under sinusoidal voltage excitation. The effects of maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined. The Supermalloy and Metglass 2605S-3A and 2605SC data are used to compare the core loss of transformers with identical kVA and voltage ratings.

Wieserman, William R.; Schwarze, Gene E.; Niedra, Janis M.

1991-01-01

342

Voltage-dependent capacitance of human embryonic kidney cells.  

PubMed

We determine membrane capacitance, C as a function of dc voltage for the human embryonic kidney (HEK) cell. C was calculated from the admittance, Y, obtained during a voltage ramp when the HEK cell was held in whole-cell patch-clamp configuration. Y was determined at frequencies of 390.625 and from the measured current, i obtained with a dual-sinusoidal stimulus. We find that the fractional increase in the capacitance, C is small ( < 1%) and grows with the square of the voltage, Psi. C can be described by: C=C(0)(1+alpha(Psi+psi(s))2)[where C(0): Capacitance at 0 volts, psi(s): Difference in surface potential between cytoplasmic and extracellular leaflets and alpha: Proportionality constant]. We find that alpha and psi(s) are 0.120 (+/- 0.01) V(-2) and -0.073 (+/-0.017 V in solutions that contain ion channel blockers and 0.108 (+/- 0.29) V(-2) and -0.023 (+/- 0.009) V when 10 mM sodium salicylate was added to the extracellular solution. This suggests that salicylate does not affect the rate at which C grows with Psi, but reduces the charge asymmetry of the membrane. We also observe an additional linear differential capacitance of about (-46 fFV(-1)) in about 60% of the cells, this additional component acts simultaneously with the quadratic component and was not observed when salicylate was added to the solution. We suggest that the voltage dependent capacitance originates from electromechanical coupling either by electrostriction and/or Maxwell stress effects and estimate that a small electromechanical force (approximately equal to 1 pN) acts at physiological potentials. These results are relevant to understand the electromechanical coupling in outer hair cells (OHCs) of the mammalian cochlea, where an asymmetric bell-shaped C versus Psi relationship is observed upon application of a similar field. Prestin, a membrane protein expressed in OHCs is required to observe this function. When we compare the total charge contributions from HEK cell membrane (7 x 10(4) electrons, 10 pF cell) with that determined for prestin transfected cells (up to 5 x 10(6) electrons) we conclude that the charge contributions from the collective motion of membrane proteins and lipids in the field is dwarfed relative to that when prestin is present. We suggest that the capacitance-voltage relationships should be similar to that observed for HEK cells for OHCs that do not express prestin in their membranes. PMID:16711859

Farrell, Brenda; Do Shope, Cythnia; Brownell, William E

2006-04-01

343

The Impact of Voltage Generation on Harmonic Spectra of Current and Flux Density in the Welding Transformer for a Middle Frequency Resistance Spot Welding System  

Microsoft Academic Search

This paper deals with a middle frequency direct current (MFDC) resistance spot welding system (RSWS). It consists of a semiconductor input converter, a single-phase welding transformer with one primary coil and two secondary coils, and a full-wave output rectifier connected to the transformer's secondary coils. The unwanted current spikes in the input converter, caused by interaction among the asymmetrical design

G. Stumberger; K. Dezelak; B. Polajzer; D. Dolinar; B. Klopcic

2008-01-01

344

Experimental studies for determining human discomfort response to vertical sinusoidal vibration  

NASA Technical Reports Server (NTRS)

A study was conducted to investigate several problems related to methodology and design of experiments to obtain human comfort response to vertical sinusoidal vibration. Specifically, the studies were directed to the determination of (1) the adequacy of frequency averaging of vibration data to obtain discomfort predictors, (2) the effect of practice on subject ratings, (3) the effect of the demographic factors of age, sex, and weight, and (4) the relative importance of seat and floor vibrations in the determination of measurement and criteria specification location. Results indicate that accurate prediction of discomfort requires knowledge of both the acceleration level and frequency content of the vibration stimuli. More importantly, the prediction of discomfort was shown to be equally good based upon either floor accelerations or seat accelerations. Furthermore, it was demonstrated that the discomfort levels in different seats resulting from similar vibratory imputs were equal. Therefore, it was recommended that criteria specifications and acceleration measurements be made at the floor location. The results also indicated that practice did not systematically influence discomfort responses nor did the demographic factors of age, weight, and sex contribute to the discomfort response variation.

Dempsey, T. K.; Leatherwood, J. D.

1975-01-01

345

Long latency reflex force of human finger muscles in response to imposed sinusoidal movements.  

PubMed

Reflex stiffness of the flexing human index finger was studied using sinusoidal movements at 3-16 Hz. The Nyquist stiffness diagram indicates the presence of a 'presonance' at around 4 Hz, its 'C' shape after correction for the mechanical properties of the relaxed finger is consistent with the involvement of a stretch reflex in its generation. This contention was supported by the presence of negative friction around 4 Hz and the disappearance of the modulation of the stiffness curve after afferent ischaemic block. Correction for the mechanical properties of active muscle, measured after afferent block, permitted the isolation of the reflex component of stiffness. The circular form of the Nyquist diagram indicates a relatively flat frequency response for the reflex over the range tested, and its radius gives a measure of reflex gain. The low value of the frequency at which the frictional force is minimal, suggests the involvement of a reflex of longer than spinal latency. This is discussed in relation to mechanisms of tremor genesis and the interaction of spinal and long latency reflexes in distal hand muscles. PMID:6745369

Noth, J; Matthews, H R; Friedemann, H H

1984-01-01

346

Actin filaments around endothelial fenestrae in rat hepatic sinusoidal endothelial cells  

Microsoft Academic Search

The presence of microfilaments in the vicinity of sinusoidal endothelial fenestrae (SEF) suggests that the cytoskeleton of liver sinusoidal endothelial cells (LSEC) plays an important role in the modulation of SEF. In this study, we investigated actin filaments around SEF in LSECs. Monolayers of LSEC culture were established by infusing a rat liver with collagenase for 30?min and then culturing

Toshihiro Nagai; Hiroaki Yokomori; Kazunori Yoshimura; Kayo Fujimaki; Masahiko Nomura; Toshifumi Hibi; Masaya Oda

2004-01-01

347

Electromagnetic induction over a two-layer earth with a sinusoidal overburden  

Microsoft Academic Search

Summary An attempt is made to estimate the effect of a sinusoidal variation of the depth of the interface for a two-layer earth model. The source is a line current that varies harmonically with time. A perturbation theory is employed that is valid when the deviation of the sinusoidal interface from a plane is reasonably small compared with a skin

W. J. Hughes; J. R. Wait

1975-01-01

348

Electromagnetic induction over a two-layer earth with a sinusoidal overburden  

Microsoft Academic Search

An attempt is made to estimate the effect of a sinusoidal variation of the depth of the interface for a two-layer earth model. The source is a line current that varies harmonically with time. A perturbation theory is employed that is valid when the deviation of the sinusoidal interface from a plane is reasonably small compared with a skin depth

W. J. Hughes; J. R. Wait

1975-01-01

349

Stability of a cantilever beam with tip mass subject to axial sinusoidal excitations  

Microsoft Academic Search

The equation of motion of a cantilever beam with a tip mass subject to axial sinusoidal excitations at the clamped end is derived based on Hamilton’s principle and the assumed mode method. The effects of axial sinusoidal excitation of the axial displacement, velocity or acceleration at the clamped end on the stability of the beam are then examined by using

H. P. Lee

1995-01-01

350

The impedance of a thin wire transmission line-dipole system with sinusoidal surface currents  

Microsoft Academic Search

Thin wire transmission lines and dipoles with diameters 2a which are much less than the operating wavelength ? carry essentially sinusoidally distributed surface currents. The Poynting vector method was used on a thin ?-gap fed dipole while retaining the sinusoidal surface current distribution. This present paper extends this work to the much more realistic case of the actual transmission line-dipole

R. H. MacPhie; K. Hui

1996-01-01

351

Design of two-winding voltage step-up\\/current step-up constant-frequency DC-to-DC converters  

Microsoft Academic Search

This paper presents procedures for designing the transformer for a two-winding energy-storage dc-to-dc power converter in which the power transistor is pulsewidth modulated by means of a constant-frequency type of controller. The presence of the second winding provides an additional degree of freedom in the design procedures beyond those for single-winding converters and leads to a number of design options

De Chen; H. Owen; T. Wilson

1973-01-01

352

Development of nanocrystalline Mn-Zn ferrites for high frequency transformer applications  

NASA Astrophysics Data System (ADS)

Microwave-Hydrothermal (M-H) method has been successfully used for the synthesis of nanocrystalline Mn-Zn ferrites which are used for high-frequency applications. As synthesized powders were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanopowders were annealed at 600 °C/20 min using the microwave sintering method. The frequency dependence of dielectric constant ( ?') was measured in the range of 10 Hz-1.3 GHz and initial permeability ( ?i) was measured in the range of 10 Hz-1 MHz. The total power loss ( Pt) was measured on the annealed samples at 100 kHz and 200 mT condition. Conductor-embedded-ferrite transformers were fabricated and output power ( Po), efficiency ( ?) and temperature rise (? T) were measured at sinusoidal voltage of 25 V at 1 MHz. The transformer efficiency ( ?) was found to be high and surface rise of temperature (? T) is very low.

Praveena, K.; Sadhana, K.; Bharadwaj, S.; Murthy, S. R.

2009-08-01

353

Low-frequency noise in serial arrays of MgO-based magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

We have studied the low-frequency noise in MgO-based magnetic tunnel junctions (MTJs) in serial configurations. Two types of junctions were compared: MTJ Wheatstone bridges and MTJ discrete resistors closely packed on a wafer die. We have characterized each individual junction to ensure that they have uniform parameters such as linear field sensitivity and noise level. In the array of bridges, the low-frequency noise decreases with an increasing number (N) of bridges, but does not scale with 1/N, as expected from noise theory. The deviation is likely due to the statistical dispersions in MTJ bridge resistance and normalized voltage noise. The total noise of the discrete resistor series does not scale with 1/N either, but rather exhibits a sinusoidal-like variation with N. We attribute it to the possible enhancement of noise from magnetic coupling among the tightly spaced MTJ elements.

Zhang, Wenzhe; Hao, Qiang; Xiao, Gang

2011-09-01

354

A globally convergent frequency estimator  

Microsoft Academic Search

Online estimation of the frequency of a sinusoidal signal is a classical problem in systems theory that has many practical applications. In this paper the authors provide a solution to the problem of ensuring a globally convergent estimation. More specifically, they propose a new adaptive notch filter whose dynamic equations exhibit the following remarkable features: 1) all signals are globally

Liu Hsu; Romeo Ortega; G. Damm

1999-01-01

355

Sinusoidal crossflow microfiltration device--experimental and computational flowfield analysis.  

PubMed

We present an analysis of the flowfield inside a novel crossflow microfiltration device. The filter performance relies on shear focusing by means of a corrugated channel. The flow and shear stress characteristics inside the filter are studied by means of both micro Particle Image Velocimetry (micro-PIV) measurements and Computational Fluid Dynamics (CFD) analysis. We show that an increase of the shear rate by 55-85% as compared to a straight channel geometry is achieved for crossflow velocities ranging from 0.05 m s(-1)-0.8 m s(-1)(Re 5-70). This substantial increase in the local wall shear may improve filter performance in terms of reduced clogging and cell cake formation as compared to conventional crossflow filtration devices. Our current investigation, along with the fact that the filter employs no complex, three dimensional geometrical patterns, advanced pumping schemes, nor has a need for costly assembly and sealing procedures, indicates that the sinusoidal crossflow microfiltration module may serve as a technically and economically feasible solution for integrated lab-on-a-chip devices. Furthermore, the presented approach of shear-focusing may be beneficial in other bio-chemical contexts, such as cell lysis and surface chemistry. PMID:16027942

Mielnik, Michal M; Ekatpure, Rahul P; Saetran, Lars R; Schönfeld, Friedhelm

2005-08-01

356

Interaction of a Shock with a Sinusoidally Perturbed Flame  

NASA Astrophysics Data System (ADS)

The interaction of a shock wave and a sinusoidally perturbed premixed flame was studied using reactive 2D and 3D Navier-Stokes simulations resolved down to the viscous microscale. The chemical model reproduced the combustion properties of a mixture of stoichiometric acetylene-air. The range of Mach numbers considered (1.25 - 3.0) is too low to cause direct detonation initiation. The basic interaction is a Richtmyer-Meshkov instability that creates vorticity, increases the surface area of the flame, and increases the energy-release rate. Vortices present long after the shock wave has passed through the flame maintain a high level of energy release. 3D perturbations (of given amplitude and wavelength) grow a factor of ~= 2 faster than comparable 2D perturbations, and the maximum energy-release rate is a factor of ~= 2 larger in 3D. The vorticity generated is too weak to stretch and extinguish the flame locally. The maximum increase in the energy generation rate due the interaction is at most a factor of 20 to 30. To greatly increase the burning rate, multiple shock-flame interactions are required.

Oran, Elaine; Khokhlov, Alexei

1997-11-01

357

In Hepatic Fibrosis, Liver Sinusoidal Endothelial Cells Acquire Enhanced Immunogenicity  

PubMed Central

The normal liver is characterized by immunologic tolerance. Primary mediators of hepatic immune tolerance are liver sinusoidal endothelial cells (LSECs). LSECs block adaptive immunogenic responses to Ag and induce the generation of T regulatory cells. Hepatic fibrosis is characterized by both intense intrahepatic inflammation and altered hepatic immunity. We postulated that, in liver fibrosis, a reversal of LSEC function from tolerogenic to proinflammatory and immunogenic may contribute to both the heightened inflammatory milieu and altered intrahepatic immunity. We found that, after fibrotic liver injury from hepatotoxins, LSECs become highly proinflammatory and secrete an array of cytokines and chemokines. In addition, LSECs gain enhanced capacity to capture Ag and induce T cell proliferation. Similarly, unlike LSECs in normal livers, in fibrosis, LSECs do not veto dendritic cell priming of T cells. Furthermore, whereas in normal livers, LSECs are active in the generation of T regulatory cells, in hepatic fibrosis LSECs induce an immunogenic T cell phenotype capable of enhancing endogenous CTLs and generating potent de novo CTL responses. Moreover, depletion of LSECs from fibrotic liver cultures mitigates the proinflammatory milieu characteristic of hepatic fibrosis. Our findings offer a critical understanding of the role of LSECs in modulating intrahepatic immunity and inflammation in fibro-inflammatory liver disease.

Connolly, Michael K.; Bedrosian, Andrea S.; Malhotra, Ashim; Henning, Justin R.; Ibrahim, Junaid; Vera, Valery; Cieza-Rubio, Napoleon E.; Hassan, Burhan U.; Pachter, H. Leon; Cohen, Steven; Frey, Alan B.; Miller, George

2011-01-01

358

In hepatic fibrosis, liver sinusoidal endothelial cells acquire enhanced immunogenicity.  

PubMed

The normal liver is characterized by immunologic tolerance. Primary mediators of hepatic immune tolerance are liver sinusoidal endothelial cells (LSECs). LSECs block adaptive immunogenic responses to Ag and induce the generation of T regulatory cells. Hepatic fibrosis is characterized by both intense intrahepatic inflammation and altered hepatic immunity. We postulated that, in liver fibrosis, a reversal of LSEC function from tolerogenic to proinflammatory and immunogenic may contribute to both the heightened inflammatory milieu and altered intrahepatic immunity. We found that, after fibrotic liver injury from hepatotoxins, LSECs become highly proinflammatory and secrete an array of cytokines and chemokines. In addition, LSECs gain enhanced capacity to capture Ag and induce T cell proliferation. Similarly, unlike LSECs in normal livers, in fibrosis, LSECs do not veto dendritic cell priming of T cells. Furthermore, whereas in normal livers, LSECs are active in the generation of T regulatory cells, in hepatic fibrosis LSECs induce an immunogenic T cell phenotype capable of enhancing endogenous CTLs and generating potent de novo CTL responses. Moreover, depletion of LSECs from fibrotic liver cultures mitigates the proinflammatory milieu characteristic of hepatic fibrosis. Our findings offer a critical understanding of the role of LSECs in modulating intrahepatic immunity and inflammation in fibro-inflammatory liver disease. PMID:20639479

Connolly, Michael K; Bedrosian, Andrea S; Malhotra, Ashim; Henning, Justin R; Ibrahim, Junaid; Vera, Valery; Cieza-Rubio, Napoleon E; Hassan, Burhan U; Pachter, H Leon; Cohen, Steven; Frey, Alan B; Miller, George

2010-08-15

359

Frequency-domain SQUID multiplexing of transition-edge sensors  

Microsoft Academic Search

We describe our frequency-domain readout multiplexer for transition-edge sensor (TES) bolometers and present measurements of an eight-channel multiplexer. Each sensor is biased with a sinusoidal bias at a distinct frequency. As the sensor absorbs power, it amplitude-modulates its sinusoidal bias. Sensor currents are summed and measured with a single superconducting quantum interference device (SQUID) array. The SQUID array consists of

T. M. Lanting; Hsiao-Mei Cho; J. Clarke; M. A. Dobbs; W. L. Holzapfel; A. T. Lee; M. Lueker; P. L. Richards; A. D. Smith; H. G. Spieler

2005-01-01

360

Method of barrier voltages in cyclic accelerators  

NASA Astrophysics Data System (ADS)

Principle of operation of barrier RF voltage systems that are used for stacking and acceleration of charged particles in proton synchrotrons and storage rings is presented. The description is based on two sample models of such systems: with rectangular and quasi-sinusoidal barriers. Two different methods are used for description of particle dynamics in synchrotrons with barrier RF voltage. The first method is "stepwise" analysis of particle motion in the "momentum-phase" space. This method allows to give a clear and simple description of physical principles of the method and to obtain its main properties in analytical form. However, this method is not always efficient. Therefore, a method of analysis of phase motion of particles in barrier systems based on solution of differential equations of phase motion is presented in the paper and is widely used in practice. This method allows both analytical calculations and numeric simulation, which is illustrated with the aid of supplied examples.

Meshkov, I. N.

2014-03-01

361

Structural and functional differentiation of sinusoidal endothelial cells during liver organogenesis in humans.  

PubMed

During fetal life, human liver sinusoids, which differentiate between 4 and 12 weeks of gestation from capillaries of the septum transversum, must support an important hematopoietic function and acquire the structural and functional characteristics of adult sinusoids. To gain insight into their differentiation process, we studied the expression of (1) markers of continuous endothelia, absent from adult sinusoidal endothelial cells (PECAM-1, CD34, and 1F10); (2) functional markers of adult sinusoidal endothelial calls (CD4, 1CAM-1, CD32, and CD14); and (3) extracellular matrix components (laminin, tenascin, fibronectin, and thrombospondin) in 37 fetuses of different gestational ages. We identified two successive differentiation events. (1) An early structural differentiation, occurring from 5 to 12 weeks of gestation, was characterized by the loss of continuous endothelial cell markers and a reduction in the perisinusoidal amount of laminin and in the deposition of tenascin, fibronectin, and thrombospondin; at the end of this process, fetal liver sinusoids present structural characteristics comparable to those of the sinuses in adult hematopoietic bone marrow. (2) A later functional differentiation was characterized by the acquisition of the markers of adult sinusoidal endothelial cells, initiating at 10 weeks of gestation and completed by 20 weeks of gestation; this process likely contributes to adapt liver sinusoids to the specific functions of the adult hepatic tissue. PMID:8639825

Couvelard, A; Scoazec, J Y; Dauge, M C; Bringuier, A F; Potet, F; Feldmann, G

1996-06-01

362

Organization of flux line system and voltage oscillations in superconducting MgB2  

NASA Astrophysics Data System (ADS)

The influence of bidirectional square wave (BSW) current on the evolution of the V-t curves was studied in a polycrystalline sample of MgB2. Regular sinusoidal-like voltage oscillations were observed at well-defined values of the amplitude (IBSW) and period (PI) of the BSW current, temperature, and external magnetic field. The voltage oscillations were interpreted mainly in terms of short- and long-range spatial correlations in a flux line system, relaxation effects, and the dynamic competition between pinning and depinning. The oscillating mode was also discussed in terms of sliding charge density waves associated with density fluctuations. Alternatively, the coupling between conventional thermally activated flux creep theory and annealing of the disordered states was considered as another possible mechanism in describing the voltage oscillations. Due to the complex interplay of pinning and driving forces, the oscillating mode is correlated to the drifting of flux lines, which are in motion, and it is assumed that the majority of flux lines try to traverse the sample, but do not leave it entirely. The symmetry in voltage oscillations was attributed to the equality between flux exit and entry along the sample edges. In this process, the majority of flux lines leave the sample and the direction of motion of flux lines reverses. During the oscillatory motion, we suggest that the interaction between flux lines and pinning centers may be elastic coupling in nature, because of rigidity of the flux line lattice in MgB2. Non-oscillatory behavior of V-t curves measured for BSW drive with low PI was attributed pre-dominantly to the effect of pinning on the distribution of the flux lines. The vortex capacitor model could be applied to explain the voltage decays in these V-t curves. However, the voltage decays associated with switching of IBSW to dc current (Idc) were correlated to current-induced quenched disorder and to the glassy state relaxation. Further, angular dependence of voltage oscillations reveals that the anisotropic effects are nearly negligible on the evolution of V-t curves. It was shown that the voltage oscillations can be described well by an empirical expression V(t) ~ sin(wt + J), where w is the frequency and J is the phase angle. Finally, at well-defined values of IBSW and PI of BSW current, H, and T, it was argued that the MgB2 sample behaves like a double-integrator.

Kiliç, A.; Oluta?, M.; Kiliç, K.; Altinkok, A.

2011-12-01

363

Hedgehog signaling regulates liver sinusoidal endothelial cell capillarisation  

PubMed Central

Objective Vascular remodeling during liver damage involves loss of healthy liver sinusoidal endothelial cell (LSEC) phenotype via capillarisation. Hedgehog (Hh) signaling regulates vascular development and increases during liver injury. Therefore, we examined its role in capillarisation. Design Primary LSEC were cultured for 5 days to induce capillarisation. Pharmacologic, antibody-mediated, and genetic approaches were used to manipulate Hh signaling. Effects on mRNA and protein expression of Hh-regulated genes and capillarisation markers were evaluated by qRT-PCR and immunoblot. Changes in LSEC function were assessed by migration and tube forming assay, and gain/loss of fenestrae was examined by electron microscopy. Mice with acute or chronic liver injury were treated with Hh inhibitors; effects on capillarisation were assessed by immunohistochemistry. Results Freshly isolated LSEC expressed Hh ligands, Hh receptors, and Hh ligand antagonist Hhip. Capillarisation was accompanied by repression of Hhip and increased expression of Hh-regulated genes. Treatment with Hh agonist further induced expression of Hh ligands and Hh-regulated genes, and up-regulated capillarisation-associated genes; whereas Hh signaling antagonist or Hh ligand neutralizing antibody each repressed expression of Hh target genes and capillarisation markers. LSEC isolated from SmoloxP/loxP transgenic mice that had been infected with adenovirus expressing Cre-recombinase to delete Smoothened showed over 75% knockdown of Smoothened. During culture, Smoothened-deficient LSEC had inhibited Hh signaling, less induction of capillarisation-associated genes, and retention of fenestrae. In mice with injured livers, inhibiting Hh signaling prevented capillarisation. Conclusions LSEC produce and respond to Hh ligands, and use Hh signaling to regulate complex phenotypic changes that occur during capillarisation.

Xie, Guanhua; Choi, Steve S.; Syn, Wing-Kin; Michelotti, Gregory A.; Swiderska-Syn, Marzena; Karaca, Gamze; Chan, Isaac S.; Chen, Yuping; Diehl, Anna Mae

2013-01-01

364

The effect of sinusoidal rolling ground motion on lifting biomechanics.  

PubMed

The objective of this study was to quantify the effects of ground surface motion on the biomechanical responses of a person performing a lifting task. A boat motion simulator (BMS) was built to provide a sinusoidal ground motion (simultaneous vertical linear translation and a roll angular displacement) that simulates the deck motion on a small fishing boat. Sixteen participants performed lifting, lowering and static holding tasks under conditions of two levels of mass (5 and 10 kg) and five ground moving conditions. Each ground moving condition was specified by its ground angular displacement and instantaneous vertical acceleration: A): +6°, -0.54 m/s(2); B): +3°, -0.27 m/s(2); C): 0°, 0m/s(2); D): -3°, 0.27 m/s(2); and E): -6°, 0.54 m/s(2). As they performed these tasks, trunk kinematics were captured using the lumbar motion monitor and trunk muscle activities were evaluated through surface electromyography. The results showed that peak sagittal plane angular acceleration was significantly higher in Condition A than in Conditions C, D and E (698°/s(2) vs. 612-617°/s(2)) while peak sagittal plane angular deceleration during lowering was significantly higher in moving conditions (conditions A and E) than in the stationary condition C (538-542°/s(2) vs. 487°/s(2)). The EMG results indicate that the boat motions tend to amplify the effects of the slant of the lifting surface and the external oblique musculature plays an important role in stabilizing the torso during these dynamic lifting tasks. PMID:20591409

Ning, Xiaopeng; Mirka, Gary A

2010-12-01

365

A phase detection method for harmonics and unbalanced voltage  

Microsoft Academic Search

This paper proposes a phase detection method for harmonics and unbalanced voltage conditions. The proposed method uses harmonics and unbalanced voltage compensation circuit in addition to basic PLL (Phase Locked Loop) circuit. In the harmonic compensation circuit, the harmonic voltage components are eliminated from the input voltages using specific harmonic detection method. Besides, frequency information of power system used in

Tomonobu Senjyu; Yuri Yonaha; Norihiro Nakasone; Atsushi Yona; Chul-Hwan Kim

2008-01-01

366

Differential Sampling For Fast Acquisition Of Frequency  

NASA Technical Reports Server (NTRS)

Algorithm rapidly estimates frequency of sinusoidal signal corrupted by zero-mean, additive, white Gaussian noise. Incorporates differential mathematical model of signal, cyclic sampling of signal, and least-squares best-estimate criterion. Adapts to changing signal frequency. Amount of computation required to obtain estimate increases only linearly with number of successive measurements processed.

Kumar, Rajendra

1990-01-01

367

Analysis, modeling, and simulation of phase noise in monolithic voltage-controlled oscillators  

Microsoft Academic Search

In this paper, the phase noise of monolithic voltage-controlled oscillators is formulated with the aid of a linearized model. A new definition of Q is introduced and three mechanisms leading to phase noise are identified. A simulation technique using sinusoidal noise components is also described

Behzad Razavi

1995-01-01

368

Direct frequency convertor with sinusoidal line currents for speed-variable AC motors  

Microsoft Academic Search

A novel concept for a static three-phase to three-phase power converter for an AC drive with a unity power factor and reduced harmonics on the line side is presented. The power circuit comprises two back-to-back connected six-pulse bridges having no energy storage elements in the DC link. This permits pulse-width modulation (PWM) control in both bridges while requiring active turn-off

J. Holtz; U. Boelkens

1989-01-01

369

Clean speech reconstruction from noisy mel-frequency cepstral coefficients using a sinusoidal model  

Microsoft Academic Search

This paper extends the technique of speech reconstruction from MFCC by considering the effect of noisy speech. To reconstruct a clean speech signal from noise contaminated MFCC an estimate of the clean mel-filterbank vector is required together with a robust estimate of the pitch. This work applies spectral subtraction to the mel-filterbank vector (derived from noisy MFCC) to provide a

Xu Shao; Ben Milner

2003-01-01

370

Spatial Frequency Discrimination in Schizophrenia  

PubMed Central

Pathways within the visual system can be distinguished on the basis of selectivity for low or high spatial frequencies. Spatial frequency discrimination was evaluated in 17 medicated male patients with schizophrenia and 19 male control subjects. Subjects were required to discriminate whether pairs of high contrast, sinusoidally modulated gratings were the same or different in spatial frequency. Accuracy performance was compared at high, medium, and low spatial frequencies on tasks matched for control performance. Patients showed a greater performance decrement of 12% on low as compared with 4% on high spatial frequencies. These findings suggest a disturbance of right hemisphere mechanisms involved in spatial perception and attention in schizophrenia.

O'Donnell, Brian F.; Potts, Geoffrey F.; Nestor, Paul G.; Stylianopoulos, Kiriaki C.; Shenton, Martha E.; McCarley, Robert W.

2010-01-01

371

A Control Scheme for PWM Voltage-Source Distributed-Generation Inverters for Fast Load-Voltage Regulation and Effective Mitigation of Unbalanced Voltage Disturbances  

Microsoft Academic Search

This paper presents a control scheme for grid-connected pulsewidth-modulated voltage-source inverters (VSIs) featuring fast load-voltage regulation and effective mitigation of unbalanced voltage disturbances. To ensure perfect regulation of the voltage at the point of common coupling (PCC) and provide means for rejecting fast and dynamic voltage disturbances, the frequency modes of the disturbances to be eliminated should be included in

Yasser Abdel-Rady Ibrahim Mohamed; Ehab F. El-Saadany

2008-01-01

372

Extended modular multilevel converters suitable for medium-voltage and large-current STATCOM applications  

Microsoft Academic Search

This paper discusses a new transformerless shunt static compensator (STATCOM) based on the extended modular multilevel converter (EMMC), to achieve higher performance in a medium-voltage large-current network. It introduces an appropriate control algorithm based on a phase-shifted carrier modulation strategy, to ensure the source-end three-phase currents are sinusoidal and balanced, balancing the voltages of the dc-link capacitors of the modules

H. Mohammadi Pirouz; M. Tavakoli Bina

2010-01-01

373

The generalized discontinuous PWM scheme for three-phase voltage source inverters  

Microsoft Academic Search

This paper presents analytical techniques for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse-width modulation schemes for two-level, three-phase voltage source inverters. The proposed modulation schemes are applicable to inverters generating balanced or unbalanced phase voltages. Some results presented in this paper analytically generalize the several expressions for the modulation

Olorunfemi Ojo

2004-01-01

374

Single-Phase Voltage-Quadrupler Rectifier Using Only One Dual-Switch Power Module  

NASA Astrophysics Data System (ADS)

A single-phase voltage-quadrupler rectifier using only one dual-switch power module is presented. This is based on the half-bridge converter and the higher output voltage can easily be obtained by introducing the pumping action. The prototype, employing a power module with two insulated-gate bipolar transistors, is implemented. The experimental results under the current-mode control confirm that the input current can be wave-shaped sinusoidally with a near-unity power factor.

Itoh, Ryozo; Ishizaka, Kouichi; Neba, Yasuhiko; Matsumoto, Hirokazu; Haraguchi, Takahiro

375

Spontaneous voltage oscillations and response dynamics of a Hodgkin-Huxley type model of sensory hair cells  

PubMed Central

We employ a Hodgkin-Huxley-type model of basolateral ionic currents in bullfrog saccular hair cells for studying the genesis of spontaneous voltage oscillations and their role in shaping the response of the hair cell to external mechanical stimuli. Consistent with recent experimental reports, we find that the spontaneous dynamics of the model can be categorized using conductance parameters of calcium-activated potassium, inward rectifier potassium, and mechano-electrical transduction (MET) ionic currents. The model is demonstrated for exhibiting a broad spectrum of autonomous rhythmic activity, including periodic and quasi-periodic oscillations with two independent frequencies as well as various regular and chaotic bursting patterns. Complex patterns of spontaneous oscillations in the model emerge at small values of the conductance of Ca2+-activated potassium currents. These patterns are significantly affected by thermal fluctuations of the MET current. We show that self-sustained regular voltage oscillations lead to enhanced and sharply tuned sensitivity of the hair cell to weak mechanical periodic stimuli. While regimes of chaotic oscillations are argued to result in poor tuning to sinusoidal driving, chaotically oscillating cells do provide a high sensitivity to low-frequency variations of external stimuli.

2011-01-01

376

Procedure for Deconvolution of Time-Dependent Signals with Sinusoidal Shape  

SciTech Connect

The present paper deals with development of the deconvolution procedure of two time-dependent signals with sinusoidal shape in order to extract the genuine optogalvanic signal from the registered one in hollow cathode glow discharge.

Todorov, M. D. [Faculty of Applied Mathematics and Informatics, Technical University of Sofia, 1000 Sofia (Bulgaria); Djulgerova, R.; Mihailov, V. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Koperski, J. [Institute of Physics, Jagellonian University, 30-059 Krakow (Poland)

2008-10-30

377

Improved approach to power losses in magnetic laminations under non-sinusoidal induction wave form.  

National Technical Information Service (NTIS)

This paper shows how it is possible to accurately predict power losses in ferromagnetic laminations (in transformer and rotating machine cores) under non-sinusoidal magnetic flux by specifically considering the dependence of hysteresis, classical, and exc...

F. Fiorillo A. Novikov

1990-01-01

378

Binary Chirped Grating Diffractive Element for Sinusoidal to Linear Scanning Conversion: The Beam Propagation Design (Preprint).  

National Technical Information Service (NTIS)

We fabricated and tested our previously designed optical correction element with zoom capability to convert nonlinear sinusoidal scans into linear scans. The design methodology is based on derivating a graded index of refraction device as a reference desi...

B. Haji-saeed C. L. Woods J. Khoury J. Kierstead W. Bailey

2008-01-01

379

Comparative Study of the Rayleigh Hypothesis and Analytic Continuation Methods as Applied to Sinusoidal Gratings.  

National Technical Information Service (NTIS)

Two methods are investigated for solving the problem of plane-wave diffraction by gratings with sinusoidal profiles. The first is based on an extension of the Rayleigh hypothesis, and the second employs an analytic continuation technique for computing the...

R. Mittra T. Itoh V. Jamnejad-Dailami

1971-01-01

380

Coupling Enhances Stochastic Resonance in Nonlinear Dynamic Elements Driven by a Sinusoid Plus Noise.  

National Technical Information Service (NTIS)

We consider the response signal to noise ratio of a network of N globally and nonlinearly coupled overdamped nonlinear dynamic elements driven by a weak sinusoidal signal embedded in Gaussian white noise. In the stochastic resonance operating regime, the ...

M. E. Inchiosa A. R. Bulsara

1995-01-01

381

Fabrication and Metrology of Micro-Scale Sinusoidal Surfaces in Polymer Workpiece Materials  

SciTech Connect

This study investigates the fabrication of precision, micro-scale sinusoidal surfaces in polymer workpiece materials and discusses methods to quantitatively characterize these surfaces. These precision sinusoidal surfaces are an important feature in a mesoscale assembly that will be used as part of a physics experiment. The experiment will study the formation of Rayleigh Taylor instabilities and requires a sinusoidal surface with an amplitude of 2.5 {micro}m and a wavelength of 70.7 {micro}m in both the x- and y-directions. The sinusoids must have sub-{micro}m form accuracy with a surface finish on the order of 100 nm, and they must be produced in a workpiece consisting of adjacent pieces of polyimide and iodine-doped polystyrene, a portion of which is illustrated in Figure 1.

Bono, M J; Hibbard, R L

2004-08-02

382

The effect of surface geometry on fracture permeability: A case study using a sinusoidal fracture  

NASA Astrophysics Data System (ADS)

Measurements of water flow through a sinusoidal fracture were undertaken to compare sinusoidal flow with parallel plate flow. Flow rates were measured through a fracture with an amplitude of 1.02 mm and a wavelength of 5.08 mm, with vertical separation ranging from 0.21 mm to 0.71 mm, and for Reynolds numbers (Re) ranging from 0.05 to 58. In addition, a series of lattice gas automata flow simulations of water flow through a sinusoidal fracture with the same dimensions were performed. Results from both the experiments and the numerical simulations reflect that, compared to a parallel plate channel, a sinusoidal channel has a significantly lower ability to transmit fluid. This is proposed to be due to the variation in the aperture measured normal to the flow path, the tortuosity of the flow path, and potential instabilities within the flow field.

Waite, Miles E.; Ge, Shemin; Spetzler, Hartmut; Bahr, David B.

383

The Propagation of Sinusoidal Small-Amplitude Waves in a Deformed Viscoelastic Solid I.  

National Technical Information Service (NTIS)

An isotropic viscoelastic solid is first subjected to a static pure homogeneous deformation. A plane sinusoidal wave is propagated in it. The amplitude of this wave is sufficiently small so that terms of second degree in the displacement gradients associa...

M. A. Hayes R. S. Rivlin

1968-01-01

384

Design of error-compensating algorithms for sinusoidal phase shifting interferometry  

SciTech Connect

An improved approach to interferometry using sinusoidal phase shifting balances several harmonic components in the interference signal against each other. The resulting computationally efficient phase-estimation algorithms have low sensitivity to errors such as spurious intensity noise, vibration, and errors in the phase shift pattern. Specific example algorithms employing 8 and 12 camera frames illustrate design principles that are extendable to algorithms of any length for applications that would benefit from a simplified, sinusoidal phase shift.

Groot, Peter de

2009-12-10

385

Flow pattern and pressure drop of vertical upward gas-liquid flow in sinusoidal wavy channels  

Microsoft Academic Search

Flow patterns and pressure drop of upward liquid single-phase flow and air-water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20mm, an amplitude of 5.76mm. Different phase shifts between the side walls of the wavy channel of 0{sup o}, 90{sup

Kitti Nilpueng; Somchai Wongwises

2006-01-01

386

Flow pattern and pressure drop of vertical upward gas–liquid flow in sinusoidal wavy channels  

Microsoft Academic Search

Flow patterns and pressure drop of upward liquid single-phase flow and air–water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20mm, an amplitude of 5.76mm. Different phase shifts between the side walls of the wavy channel of 0°, 90° and

Kitti Nilpueng; Somchai Wongwises

2006-01-01

387

Persisting myocardial sinusoids of both ventricles as an isolated anomaly: Echocardiographic, angiographic, and pathologic anatomical findings  

Microsoft Academic Search

The persistence of myocardial sinusoids in both ventricles as an isolated anomaly is described. A 21-year-old patient had\\u000a progressive heart failure considered as cardiomyopathy of obscure etiology. Two-dimensional echocardiography demonstrated\\u000a channel-like structures in the thickened myocardium of both hypokinetic ventricles. Angiography showed a honeycomblike inner\\u000a contour in both ventricles. Autopsy proved the diagnosis of persistent sinusoids in a thickened myocardium.

Rolf Jenni; Norbert Goebel; Roberto Tartini; Jakob Schneider; Urs Arbenz; Oswald Oelz I

1986-01-01

388

Compact multi-element antennas of sinusoidal printed monopoles for sensors and portable devices  

Microsoft Academic Search

We present small printed sinusoidal monopoles as enhanced meander-line antennas shaped after smooth curves, capable of forming compact multi-element antennas. The antennas were designed at 2-3 GHz according to the size and bandwidth constraints of multimedia sensor networks. Their performance was characterized in terms of electrical size, bandwidth, and broadband radiation efficiency. Results show that the sinusoidal monopole achieves 68%

Constantine G. Kakoyiannis; Penelope Gika; Philip Constantinou

2009-01-01

389

Multilevel cascade voltage source inverter with separate DC sources  

DOEpatents

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

Peng, F.Z.; Lai, J.S.

1997-06-24

390

Multilevel cascade voltage source inverter with seperate DC sources  

DOEpatents

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Peng, Fang Zheng (Oak Ridge, TN); Lai, Jih-Sheng (Knoxville, TN)

1997-01-01

391

Multilevel cascade voltage source inverter with seperate DC sources  

DOEpatents

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Peng, Fang Zheng (Knoxville, TN); Lai, Jih-Sheng (Blacksburg, VA)

2002-01-01

392

Comparison of high temperature, high frequency core loss and dynamic B-H loops of a 2V-49Fe-49Co and a grain oriented 3Si-Fe alloy  

NASA Technical Reports Server (NTRS)

The design of power magnetic components such as transformers, inductors, motors, and generators, requires specific knowledge about the magnetic and electrical characteristics of the magnetic materials used in these components. Limited experimental data exists that characterizes the performance of soft magnetic materials for the combined conditions of high temperature and high frequency over a wide flux density range. An experimental investigation of a 2V-49-Fe-49Co (Supermendur) and a grain oriented 3 Si-Fe (Magnesil) alloy was conducted over the temperature range of 23 to 300 C and frequency range of 0.1 to 10 kHz. The effects of temperature, frequency, and maximum flux density on the core loss and dynamic B-H loops for sinusoidal voltage excitation conditions are examined for each of these materials. A comparison of the core loss of these two materials is also made over the temperature and frequency range investigated.

Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

1992-01-01

393

Possible link between right ventricular coronary sinusoids and noncompaction sinusoids in pulmonary atresia with intact ventricular septum patients that later develop left ventricular noncompaction.  

PubMed

Patients who have pulmonary atresia with intact ventricular septum have been shown to have a number of various myocardium anomalies like ischemia, fibrosis, infarction, rupture, disarray, spongious myocardium and ventricular endocardial fibroelastosis. Multiple connections have been found between right ventricular myocardial sinusoids and small branches of intramural coronary arteries. Noncompation of ventricular myocardium has been shown to be the result of myocardial ischemia or excessive pressure preventing the reduction of embryonic sinusoids. The persistence of intertrabecular recesses that are connected to both the ventricular cavity and coronary circulation is the result of this process. In this text, we describe a PA-IVS patient who underwent patent ductus arteriosus stenting and pulmonary valve perforation to create antegrade flow and later developed left ventricular noncompaction. We posit that there is a connection between right ventricular coronary sinusoids and noncompaction sinusoids. As our patient's RV outflow tract stenosis and RV pressure increased, the coronary circulation connected to coronary sinuses became sufficient and LV function improved, which further supports our hypothesis. PMID:24767937

Ozyilmaz, Isa; Ergul, Yakup; Guzeltas, Alper; Odemis, Ender

2014-07-01

394

Electro-Optical High-Voltage Sensors  

NASA Technical Reports Server (NTRS)

Electro-optical sensors for measuring high voltages developed for use in automatically controlled power-distribution systems. Sensors connected to optoelectronic interrogating equipment by optical fibers. Because sensitive material and optical fibers are all dielectric, no problem in electrically isolating interrogating circuitry from high voltage, and no need for voltage dividers. Sensor signals transmitted along fibers immune to electromagnetic noise at radio and lower frequencies.

Gottsche, Allan; Johnston, Alan R.

1992-01-01

395

Fully on-chip temperature, process, and voltage sensors  

Microsoft Academic Search

A process, voltage, and temperature (PVT) sensor without a voltage\\/current analog-to-digital converter (ADC) or bandgap reference is proposed for high accuracy, low power, and wide voltage range portable applications. Conventional temperature sensors rely on voltage\\/current ADC for digital output code conversion. The proposed temperature sensor generates a clock frequency proportional to the measured temperature, and converts the frequency into a

Shi-Wen Chen; Ming-Hung Chang; Wei-Chih Hsieh; Wei Hwang

2010-01-01

396

Measurement of a cross-sectional profile of a thread gauge using a sinusoidally vibrating interference pattern  

SciTech Connect

A sinusoidally vibrating interference pattern (SVIP) is used as an exact spatial scale in order to measure a cross-sectional profile of a thread gauge. The SVIP is projected on the thread gauge surface, and lights diffracted and reflected from the end points of the thread gauge surface are extracted by spatial frequency filtering in an imaging system to make an image of the end points whose positions are decided by the peak positions of amplitude distributions in the image. The coordinates of the end points or the cross-sectional profile of the thread gauge is obtained from the phases measured at the positions of the end points, phase distribution of the SVIP on a CCD image sensor, and the pixel positions of the CCD image sensor.

Li Jinhuan; Sasaki, Osami

2011-07-10

397

Spectral-threshold characteristics of a distributed-feedback laser with the sinusoidal modulation of coupling coefficient  

SciTech Connect

The spectral-threshold characteristics of a distributed-feedback (DFB) laser with the sinusoidal modulation of the complex coupling coefficient are studied within the framework of the linear theory of coupled modes. The analysis is performed in a broad range of amplitudes of the coupling coefficient for phase, amplitude, and amplitude - phase gratings providing distributed feedback in the active medium of the laser. It is shown that the eigenmode spectrum of the DFB laser on a phase grating with a large-scale modulation of the coupling coefficient is similar to the eigenmode spectrum of the DFB laser on an amplitude grating with a constant coupling coefficient. The DFB laser under study is promising for obtaining stable single-frequency lasing and can find applications in devices in integrated optics. (lasers)

Afanas'ev, Anatolii A; Mikhnevich, Svetlana Yu [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

2004-04-30

398

High Voltage Lines: Hazard at a Distance.  

ERIC Educational Resources Information Center

It appears that a variety of biological organisms, including man, are sensitive to both long and short-term exposure to the extra low frequency electric and magnetic fields produced by high voltage lines. (BB)

Marino, Andrew A.; Becker, Robert O.

1978-01-01

399

Digital-PLL Assisted Frequency Estimation with Improved Error Variance  

Microsoft Academic Search

In this paper we present a novel frequency estimation technique, assisted by an imperfect second order arctan based Digital Phase-Locked Loop (D-PLL), for complex single sinusoidal signals in additive white Gaussian noise. The imperfect loop contains the frequency information in its phase error process, at steady state, which is then used to estimate the frequency after the signal has been

Kandeepan Sithamparanathan

2008-01-01

400

High frequency excitation waveform for efficient operation of a xenon excimer dielectric barrier discharge lamp  

NASA Astrophysics Data System (ADS)

The application of a high frequency (~2.5 MHz) burst (amplitude-modulated sinusoidal) excitation voltage waveform is investigated for driving a fluorescent dielectric barrier discharge (DBD) light source. The excitation waveform presents a novel method for generating spatially stable homogeneous Xe DBD possessing a high conversion efficiency from electrical energy to VUV Xe_{2}^{\\ast} excimer radiation (~172 nm), even at a significantly higher electrical energy deposition than realized by pulsed excitation. Simulation and experimental results predict discharge efficiencies around 60%. Lamp efficacy above 74 lm W-1 has been achieved. VUV emission and loss mechanisms are investigated extensively and the performance of burst and pulsed waveforms is compared both theoretically and experimentally.

Beleznai, Sz; Mihajlik, G.; Maros, I.; Balázs, L.; Richter, P.

2010-01-01

401

Localization of four phosphatases in rat liver sinusoidal cells. An enzyme cytochemical study.  

PubMed

In the present study we have localized neutral phosphatase, acid phosphatase, alkaline phosphatase and 5' nucleotidase in the sinusoidal cells of rat liver using enzyme cytochemistry at light and electron microscopical level. Neutral phosphatase was present in the endoplasmic reticulum and nuclear envelope of parenchymal cells and of sinusoidal endothelial, Kupffer and fat-storing cells. The intensity of the neutral phosphatase reaction was stronger in sinusoidal than in parenchymal cells. Sinusoidal cells were devoid of cytochemically demonstrable alkaline phosphatase. Abundant acid phosphatase was present in the many lysosomes of endothelial and Kupffer cells. Substantially less acid phosphatase-positive lysosomes were found in fat-storing cells. 5' nucleotidase was present on the cell membrane of fat-storing cells, on 90% of all Kupffer cells and on the microvilli of parenchymal cells. We have further shown that combined staining for 5' nucleotidase and for endogenous peroxidase, offers a histochemical tool to discriminate between the three main sinusoidal cell types in normal rat liver. PMID:2842279

De Valck, V; Geerts, A; Schellinck, P; Wisse, E

1988-01-01

402

Investigation of voltage swell mitigation using STATCOM  

NASA Astrophysics Data System (ADS)

STATCOM is one of the best applications of a self commutated FACTS device to control power quality problems in the distribution system. This project proposed a STATCOM model with voltage control mechanism. DQ transformation was implemented in the controller system to achieve better estimation. Then, the model was used to investigate and analyse voltage swell problem in distribution system. The simulation results show that voltage swell could contaminate distribution network with unwanted harmonic frequencies. Negative sequence frequencies give harmful effects to the network. System connected with proposed STATCOM model illustrates that it could mitigate this problems efficiently.

Razak, N. A. Abdul; >S Jaafar, I. S.

2013-06-01

403

The Integrity bare-metal stent made by continuous sinusoid technology.  

PubMed

The Integrity Coronary Stent System (Medtronic Vascular, CA, USA) is a low-profile, open-cell, cobalt-chromium-alloy advanced bare-metal iteration of the well-known Driver/Micro-Driver Coronary Stent System (Medtronic Vascular). The Integrity stent is made with a process called continuous sinusoid technology. This process allows stent construction via wrapping a single thin strand of wire around a mandrel in a sinusoid configuration, with laser fusion of adjacent crowns. The wire-forming process and fusion pattern provide the stent with a continuous preferential bending plane, intended to allow easier access to, and smoother tracking within, distal and tortuous vessels while radial strength is maintained. Continuous sinusoid technology represents innovation in the design of stent platforms and will provide a future stent platform for newer technology, including drug-eluting stent platforms, drug-filled stents and core wire stents. PMID:21542702

Turco, Mark A

2011-05-01

404

Characteristics of probe current harmonics based on various applied voltage waveforms in low temperature plasmas  

SciTech Connect

The characteristics of probe currents induced by applying various probe voltage waveforms, such as sinusoidal, sawtooth, square, and triangular, were investigated at a floating potential. It was found that the measured probe currents have many harmonics depending on the voltage waveforms. This was mainly due to the nonlinearity of the sheath in the plasma and was analyzed using the fast Fourier transform and a circuit model. By applying a triangular voltage waveform to a probe, plasma parameters such as electron temperature and plasma density could be obtained and compared to those of a single Langmuir probe and a floating harmonic method.

Kim, Young-Do; Kim, Yu-Sin; Lee, Hyo-Chang; Bang, Jin-Young; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Heangdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2011-03-15

405

Response of sinusoidal mouse liver cells to choline-deficient ethionine-supplemented diet  

PubMed Central

Background Proliferation of oval cells, the bipotent precursor cells of the liver, requires impeded proliferation and loss of hepatocytes as well as a specific micro-environment, provided by adjacent sinusoidal cells of liver. Despite their immense importance for triggering the oval cell response, cells of hepatic sinusoids are rarely investigated. To elucidate the response of sinusoidal liver cells we have employed a choline-deficient, ethionine-supplemented (CDE) diet, a common method for inducing an oval cell response in rodent liver. We have utilised selected expression markers commonly used in the past for phenotypic discrimination of oval cells and sinusoidal cells: cytokeratin, E-cadherin and M2-pyruvate kinase for oval cells; and glial fibrillary acidic protein (GFAP) was used for hepatic stellate cells (HSCs). Results CDE diet leads to an activation of all cells of the hepatic sinusoid in the mouse liver. Beside oval cells, also HSCs and Kupffer cells proliferate. The entire fraction of proliferating cells in mouse liver as well as endothelial cells and cholangiocytes express M2-pyruvate kinase. Concomitantly, GFAP, long considered a unique marker of quiescent HSCs was upregulated in activated HSCs and expressed also in cholangiocytes and oval cells. Conclusions Our results point to an important role of all types of sinusoidal cells in regeneration from CDE induced liver damage and call for utmost caution in using traditional marker for identifying specific cell types. Thus, M2-pyruvate kinase should no longer be used for estimating the oval cell response in mouse liver. CDE diet leads to activation of GFAP positive HSCs in the pericentral zone of liver lobulus. In the periportal zone the detection of GFAP in biliary cells and oval cells, calls other cell types as progenitors of hepatocytes into question under CDE diet conditions.

2010-01-01

406

Beam induced rf cavity transient voltage  

SciTech Connect

The authors calculate the transient voltage induced in a radio frequency cavity by the injection of a relativistic bunched beam into a circular accelerator. A simplified model of the beam induced voltage, using a single tone current signal, is generated and compared with the voltage induced by a more realistic model of a point-like bunched beam. The high Q limit of the bunched beam model is shown to be related simply to the simplified model. Both models are shown to induce voltages at the resonant frequency {omega}{sub r} of the cavity and at an integer multiple of the bunch revolution frequency (i.e. the accelerating frequency for powered cavity operation) h{omega}{sub {omicron}}. The presence of two nearby frequencies in the cavity leads to a modulation of the carrier wave exp(h{omega}{sub {omicron}}t). A special emphasis is placed in this paper on studying the modulation function. These models prove useful for computing the transient voltage induced in superconducting rf cavities, which was the motivation behind this research. The modulation of the transient cavity voltage discussed in this paper is the physical basis of the recently observed and explained new kinds of longitudinal rigid dipole mode which differs from the conventional Robinson mode.

Kramer, S.L.; Wang, J.M. [Brookhaven National Lab., Upton, NY (United States)

1998-10-01

407

BEAM INDUCED RF CAVITY TRANSIENT VOLTAGE  

SciTech Connect

The authors calculate the transient voltage induced in a radio frequency cavity by the injection of a relativistic bunched beam into a circular accelerator. A simplified model of the beam induced voltage, using a single tone current signal, is generated and compared with the voltage induced by a more realistic model of a point-like bunched beam. The high Q limit of the bunched beam model is shown to be related simply to the simplified model. Both models are shown to induce voltages at the resonant frequency w{sub r} of the cavity and at an integer multiple of the bunch revolution frequency (i.e. the accelerating frequency for powered cavity operation) hw{sub o}. The presence of two near-by frequencies in the cavity leads to a modulation of the carrier wave exp(jhw{sub o}t). A special emphasis is placed in this paper on studying the modulation function. These models prove useful for computing the transient voltage induced in superconducting rf cavities, which was the motivation behind this research. The modulation of the transient cavity voltage discussed in this paper is the physical basis of the recently observed and explained new kind of longitudinal rigid dipole mode which differs from the conventional Robinson mode.

KRAMER,S.L.; WANG,J.M.

1998-11-01

408

Effects of low-temperature ozone annealing on current-voltage and low-frequency noise characteristics of [100]-tilt YBa2Cu3O7-X grain-boundary Josephson junctions  

NASA Astrophysics Data System (ADS)

The dc and noise characteristics of YBa2Cu3O7-X [100]-tilt bicrystal Josephson junctions have been studied before and after annealing in ozone. Junctions with a misorientation angle 2×14° have been characterized in the temperature range from 7 K to 75 K, and their IcRn-product values were equal up to 5.4 mV at 7 K. Ozone annealing of the junctions at 140°C results in a two-fold decrease of the normal-state resistances Rn. The values of the IcRn-product have been increased not more than 7% after annealing. The spectral densities SV(f) of the voltage fluctuations measured at various currents were of 1/f? -type with ? = 0.8-1.0. The normalized spectral densities Sr(f) = Sr(f)/Rn2 and Si(f) = SIc(f)/Ic2 of normal-state resistance fluctuations ?Rn and critical current fluctuations ?Ic, respectively, plus a coefficient k of the correlation between ?Rn and ?Ic fluctuations have been derived from the measured spectra SV(f) before and after annealing. The modification of transport and noise characteristics were consistent with a junction model of the [100]-tilt junction, where the supercurrent and quasiparticle current flow through the same junction area, the annealing in ozone results in a decrease of the barrier thickness and the barrier is free from localized states. We suggest that the low-frequency noise arises at the interface between superconductor and the barrier.

Liatti, M. V.; Divin, Y. Y.; Poppe, U.; Gubankov, V. N.; Urban, K.

2006-06-01

409

F-TF.A, F-BF.A.3 Exploring Sinusoidal Functions  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: In this task we will explore the effect that changing the parameters in a sinusoidal function has on the graph of the function. A general sinusoidal fu...

410

Frequency Analysis of Vestibular Influence on Extensor Motoneurons. I. Response to Tilt in Forelimb Extensors.  

National Technical Information Service (NTIS)

The experiments were conducted with the aim of obtaining a quantitative description of the dynamic relationships between motor unit activity in forelimb extensor muscles and vestibular inputs. A frequency analysis of the EMG response to sinusoidal angular...

A. Berthoz J. H. Anderson

1971-01-01

411

VHF frequency multiplier  

NASA Technical Reports Server (NTRS)

Low-power step-recovery-diode frequency multiplier generates 361-MHz signal. Diode conducts when ac waveform is positive at its upper terminal. When voltage is negative, diode continues to conduct stored charge in its junction.

Cusack, J. A.

1979-01-01

412

Experimental validation of a high voltage pulse measurement method.  

SciTech Connect

This report describes X-cut lithium niobate's (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps - 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensor's U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.

2013-09-01

413

A modified dichotomous search frequency estimator  

Microsoft Academic Search

The estimation of the frequency of a sinusoidal signal has been dealt with extensively in the literature. In this letter, we examine the dichotomous search of the periodogram peak algorithm. We provide an insight into the need to pad the data with zeros in order to achieve a performance that is comparable to the Cramer-Rao lower bound (CRB). We also

Elias Aboutanios

2004-01-01

414

Dynamic optical frequency domain reflectometry.  

PubMed

We describe a dynamic Optical Frequency Domain Reflectometry (OFDR) system which enables real time, long range, acoustic sensing at high sampling rate. The system is based on a fast scanning laser and coherent detection scheme. Distributed sensing is obtained by probing the Rayleigh backscattered light. The system was tested by interrogation of a 10km communication type single mode fiber and successfully detected localized impulse and sinusoidal excitations. PMID:24787772

Arbel, Dror; Eyal, Avishay

2014-04-21

415

Dc-bus voltage control of three-phase ac\\/dc converter using load predictive method  

Microsoft Academic Search

A three-phase AC\\/DC converter should extract the pure sinusoidal current from the AC source, and maintain the DC-bus voltage at a demand level when the dc load varies. In this paper, a novel control method is presented to match these requirements. At the AC side, a real-time voltage and current predictive methods are used to reduce the influence of control

Zitao Wang; Liuchen Chang

2009-01-01

416

Analytical calculation of the RMS current stress on the DC-link capacitor of voltage-PWM converter systems  

Microsoft Academic Search

A simple analytical expression for the current stress on the DC-link capacitor caused by the load-side inverter of a voltage DC-link-converter system is derived. The DC-link capacitor- current RMS value is determined from the modulation depth and by the amplitude and the phase angle of the inverter output current assuming a sinusoidal inverter output current and a constant DC-link voltage.

J. W. Kolar; S. D. Round

2006-01-01

417

A DSP based multi-frequency 3D electrical impedance tomography system.  

PubMed

This paper describes the design of a multi-frequency Electrical impedance tomography (EIT) system, which provides a flexible mechanism for addressing up to 48 electrodes for imaging conductivity and permittivity distributions. A waveform generator based on a digital signal processor is used to produce sinusoidal waveforms with the ability to select frequencies in the range of 0.1-125 kHz. A software based phase-sensitive demodulation technique is used to extract amplitudes and phases from the raw measurements. Signal averaging and automatic gain control are also implemented in voltage and phase measurements. System performance was validated using a Cardiff-Cole Phantom and a saline filled cylindrical tank. The signal-to-noise ratio (SNR) using saline tank was greater than 60 dB and the maximum reciprocity error less than 4% for most frequencies. The common-mode rejection ratio (CMRR) was nearly 60 dB at 50 kHz. Image reconstruction performance was assessed using data acquired through a range of frequencies. This EIT system offers image reconstruction of both conductivity and permittivity distributions in three dimensions. The imaging results are presented in time difference and frequency difference imaging. PMID:18629646

Goharian, Mehran; Soleimani, Manuchehr; Jegatheesan, Aravinthan; Chin, Kenrick; Moran, Gerald R

2008-09-01

418

Reduction of common mode voltage and current in voltage source inverters by passive methods  

Microsoft Academic Search

High frequency common mode voltage (CMV) in voltage source inverter driven AC motors results in parasitic common mode current (CMC) in the motor. In this paper, the cause and the undesired effects of the CMV\\/CMC are reviewed, the improvements of the passive suppression techniques, the common mode inductor (CMI) and the pure sine filter (PSF), are progressively studied and their

N. Onur Çetin; Ahmet M. Hava

2010-01-01

419

Transient Voltage Recorder  

NASA Technical Reports Server (NTRS)

A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

2002-01-01

420

Booster synchrotron frequency below transition  

SciTech Connect

The dipole mode synchrotron frequency is a basic beam parameter; it and a few similarly basic quantities measured at small time intervals serve to characterize the longitudinal beam dynamics throughout the acceleration cycle. The effective accelerating voltage, in conjunction with the amount of rf voltage required for the acceleration, is important for the estimate of the beam energy loss per turn. The dipole mode frequency can be used to obtain the effective accelerating rf voltage, providing that it can be measured precisely. The synchrotron frequency measured from the synchrotron phase detector signal (SPD) generally agrees well with calculation, and it can be applied for such purposes as inferring the effective rf voltage.

Xi Yang et al.

2004-04-21

421

INTERACTION OF ELECTROMAGNETIC WAVE AND PLASMA SLAB WITH PARTIALLY LINEAR AND SINUSOIDAL ELECTRON DENSITY PROFILE  

Microsoft Academic Search

Interaction of an electromagnetic wave and an inhomoge- neous plasma slab with electron distribution in the form of partially linear and sinusoidal proflles is analysed to determine new re?ection, absorbtion and transmission characteristics. Broadband and tunable absorbtion performance of the plasma layer accompanied with narrow- band re?ection characteristic is presented as the function of electron density proflle parameters and external

S. Gurel; Emrah Oncu

2009-01-01

422

Regular Orbits Exhibiting Multiple Impact Characteristics from a Cracked Beam Under Sinusoidal Excitation  

Microsoft Academic Search

Previous work by the authors and co-workers has predicted the occurrence of multiple impacts when a cracked beam was subject to sinusoidal excitation. A limited amount of experimental evidence, indicating complex periodic trajectories, was observed in an earlier study but limitations in the instrumentation made positive identification of impulsive events impossible. The paper presents observations of regular orbits which clearly

J. A Brandon; A. E Stephens; E. M. O Lopes; A. S. K Kwan

1998-01-01

423

The sinusoidal air-gap magnetic field design of axial flux permanent magnet synchronous motors  

Microsoft Academic Search

The axial flux permanent magnet synchronous motors have features of short axial length, high energy density and great torque. They have found applications in computer peripherals, electric vehicles in-wheel drive and flywheel energy storage devices. The paper research analytically three methods for forming sinusoidal air-gap magnetic field, and put forward that the method with magnets of uniform magnetization, equal thickness

C. S. Zhang; Y. Fan; G. G. Li; H. Y. Chu

2005-01-01

424

Design of CCI-based tuneable active filters and sinusoidal oscillator  

Microsoft Academic Search

A CMOS compatible current-controlled first generation current conveyor (CCCI), is presented. The parasitic resistance (Rx) of the CCCI is controlled by varying the bias current (Iref). Further, the CCCI is used to test two filtering applications: a Band-pass (BPF) and High- pass (HPF) filters, and also a sinusoidal oscillator. For the filtering applications, Rx is varied to tune the center

D. Moro-Frias; E. Tlelo-Cuautle; M. Fakhfakh

2008-01-01

425

Universal instantaneous power theory for DC, single-phase AC sinusoidal and nonsinusoidal circuits  

Microsoft Academic Search

A novel power component theory based on instantaneous power concept for single-phase AC circuits is proposed in this paper. Every kind of power component advanced here is concerned directly with the instantaneous power process in circuits and possesses clear physical meaning. This new power component definition theory is immediately suited to DC, single-phase AC sinusoidal and nonsinusoidal circuits at the

Dairun Zhang; Nianci Huang

2000-01-01

426

Extraction of Peak-to-Peak and RMS Sinusoidal Jitter Using an Analytic Signal Method  

Microsoft Academic Search

This paper proposes a new method based on analytic signal theory for extracting both instantaneous and RMS sinusoidal jitter from PLL output signals. The method relies on the extension of a real signal into an analytic signal by utilizing the Hilbert transform. Both the theoretical basis and fundamental concepts of the proposed method are explained. A review of conventional testing

Takahiro J. Yamaguchi; Masahiro Ishida; Mani Soma; Toshifumi Watanabe; Tadahiro Ohmi

2000-01-01

427

Sinusoidal oscillation of the ankle as a means of evaluating the spastic patient  

Microsoft Academic Search

Sinusoidally modulated torque was applied to rotate the ankle joint of normal subjects and clinically spastic patients. Measurements were made of the effective joint compliance and of the evoked EMG activity. These procedures provide a well-quantified and reliable measure of muscle tone and hyperreflexia which is well correlated with the patient's clinical status.

G L Gottlieb; G C Agarwal; R Penn

1978-01-01

428

Wind tunnel generation of sinusoidal lateral and longitudinal gusts by circulation of twin parallel airfoils  

Microsoft Academic Search

A gust generator capable of producing sinusoidal lateral and longitudinal gusts was developed for the purpose of studying the gust response of a model rotor-propeller in a wind tunnel. The gust generator utilized harmonic circulation control of twin parallel airfoils to achieve the harmonic lift variation required for gust generation. The gust generator design, construction, and testing is described. Typical

N. D. Ham; P. H. Bauer; T. L. Lawrence

1974-01-01

429

EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM  

EPA Science Inventory

A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

430

Intensity Distribution from a Sinusoidal Grating and Application to Diffusion Measurements.  

National Technical Information Service (NTIS)

The general vector analysis of Stroke has been applied to the calculation of the intensity distribution among the real diffraction order of a sinusoidal grating at normal incidence. The results are presented for gratings of period 10 and 20 microns and fo...

J. M. Blakely D. L. Olson

1967-01-01

431

Hydrogen sulfide modulates sinusoidal constriction and contributes to hepatic microcirculatory dysfunction during endotoxemia.  

PubMed

Hydrogen sulfide (H?S) affects vascular resistance; however, its effect on the hepatic microcirculation has not been investigated. Hepatic sinusoidal perfusion is dysregulated during sepsis, contributing to liver injury. Therefore, the present study determined the effect of H?S on the hepatic microcirculation and the contribution of endogenous H?S to hepatic microcirculatory dysfunction in an endotoxin model of sepsis. Portal infusion of H?S increased portal pressure in vivo (6.8 ± 0.2 mmHg before H?S vs. 8.6 ± 0.8 mmHg peak during H?S infusion, P < 0.05). Using intravital microscopy, we observed decreased sinusoidal diameter (6.2 ± 0.27 ?m before H?S vs. 5.7 ± 0.3 ?m after H?S, P < 0.05) and increased sinusoidal heterogeneity during H?S infusion (P < 0.05) and net constriction. Since hepatic H?S levels are elevated during sepsis, we used the cystathionine ? lyase inhibitor DL-propargylglycine (PAG) to determine the contribution of H?S to the hypersensitization of the sinusoid to the vasoconstrictor effect of endothelin-1 (ET-1). PAG treatment significantly attenuated the sinusoidal sensitization to ET-1 in endotoxin-treated animals. ET-1 infusion increased portal pressure to 175% of baseline in endotoxemic animals, which was reduced to 143% following PAG treatment (P < 0.05). PAG abrogated the increase in sinusoidal constriction after ET-1 infusion in LPS-treated rats (30.9% reduction in LPS rats vs. 11.6% in PAG/LPS rats, P < 0.05). Moreover, PAG treatment significantly attenuated the increase in NADH fluorescence following ET-1 exposure during endotoxemia (61 grayscale units LPS vs. 21 units in PAG/LPS, P < 0.05), suggesting an improvement in hepatic oxygen availability. This study is the first to demonstrate a vasoconstrictor action of H?S on the hepatic sinusoid and provides a possible mechanism for the protective effect of PAG treatment during sepsis. PMID:23518685

Norris, Eric J; Feilen, Nicole; Nguyen, Nhat H; Culberson, Cathy R; Shin, Min C; Fish, Madeleine; Clemens, Mark G

2013-06-15

432

Liver sinusoidal endothelial cell lectin inhibits CTL-dependent virus clearance in mouse models of viral hepatitis.  

PubMed

Liver sinusoidal endothelial cell lectin (LSECtin) was recently reported to suppress intrahepatic T cell immunity and to limit immune-mediated liver injury. However, its role in the outcome and pathogenesis of viral infection has not yet been elucidated. Using a mouse model infected with a hepatotropic adenovirus, we found that the absence of LSECtin led to a higher frequency of intrahepatic effector CTLs. These cells produced higher levels of antiviral cytokines and cytotoxic factors and exhibited an increased expression of the transcription factors T-bet and Runx3. This phenotype observed in the LSECtin-knockout cells mediated a more efficient virus-specific cytotoxicity compared with that of wild-type cells. As a consequence, LSECtin deficiency significantly accelerated liver adenovirus clearance. In contrast, LSECtin upregulation in the liver delayed viral clearance; this delayed clearance was accompanied by the downregulation of the antiviral activity of CTLs. We further constructed an immunocompetent mouse model of acute hepatitis B viral infection to demonstrate that LSECtin significantly delayed the clearance of hepatitis B virus from blood and infected hepatocytes by limiting the frequency of hepatitis B virus-specific IFN-?-producing cells. Consistent with this function, LSECtin was upregulated in the liver of mouse models of viral hepatitis. Taken together, our results suggest that LSECtin may facilitate the reduction of liver inflammation at the cost of delaying virus clearance and that this effect might be hijacked by the virus as an escape mechanism. PMID:23487419

Liu, Biao; Wang, Min; Wang, Xiaowen; Zhao, Dianyuan; Liu, Di; Liu, Jing; Chen, Pei-Jer; Yang, Dongliang; He, Fuchu; Tang, Li

2013-04-15

433

Performance improvement of plasma actuators using asymmetric high voltage waveforms  

NASA Astrophysics Data System (ADS)

An experimental study is conducted on high voltage waveforms used to power plasma actuators. Shapes that present an asymmetry between the two half cycles are investigated by means of induced thrust and velocity measurements. A parametric study is performed based on thrust measurements in order to find the optimum shape within the tested range. An asymmetric waveform which is made as a combination of sinusoidal and square shapes is found to increase produced thrust by almost 30% compared with the conventional sinusoidal waveform. The asymmetric waveform is further analysed using time-resolved particle image velocimetry in order to reveal the forcing mechanism governed by the shape differences. It is shown that the shape of the waveform has a significant effect on the performance of the actuator. Push and pull events occur within the actuation period and their respective strength and duration closely correlates with the shape of the waveform. It is found that the pull event is significantly weakened for the case of the optimized asymmetric waveform in comparison with the sinusoidal shape. This effectively increases the net momentum transfer and an improvement of approximately 40% in maximum induced velocity is achieved compared with sine waveform. Power consumption due to the asymmetric waveform is marginally increased which provides a significant increase in the actuator's relative efficiency.

Kotsonis, M.; Ghaemi, S.

2012-02-01

434

Low distortion automatic phase control circuit. [voltage controlled phase shifter  

NASA Technical Reports Server (NTRS)

A voltage controlled phase shifter is rendered substantially harmonic distortion free over a large dynamic input range by employing two oppositely poled, equally biased varactor diodes as the voltage controlled elements which adjust the phase shift. Control voltages which affect the bias of both diodes equally are used to adjust the phase shift without increasing distortion. A feedback stabilized phase shifter is rendered substantially frequency independent by employing a phase detector to control the phase shift of the voltage controlled phase shifter.

Hauge, G.; Pederson, C. W. (inventors)

1974-01-01

435

Interleaved-Boost Converter With High Voltage Gain  

Microsoft Academic Search

This paper presents an interleaved-boost converter, magnetically coupled to a voltage-doubler circuit, which provides a voltage gain far higher than that of the conventional boost topology. Besides, this converter has low-voltage stress across the switches, natural-voltage balancing between output capacitors, low-input current ripple, and magnetic components operating with the double of switching frequency. These features make this converter suitable to

Gustavo A. L. Henn; R. N. A. L. Silva; Paulo P. Praca; Luiz H. S. C. Barreto

2010-01-01

436

A closed-loop system for frequency tracking of piezoresistive cantilever sensors  

NASA Astrophysics Data System (ADS)

A closed loop circuit capable of tracking resonant frequencies for MEMS-based piezoresistive cantilever resonators is developed in this work. The proposed closed-loop system is mainly based on a phase locked loop (PLL) circuit. In order to lock onto the resonant frequency of the resonator, an actuation signal generated from a voltage-controlled oscillator (VCO) is locked to the phase of the input reference signal of the cantilever sensor. In addition to the PLL component, an instrumentation amplifier and an active low pass filter (LPF) are connected to the system for gaining the amplitude and reducing the noise of the cantilever output signals. The LPF can transform a rectangular signal into a sinusoidal signal with voltage amplitudes ranging from 5 to 10 V which are sufficient for a piezoactuator input (i.e., maintaining a large output signal of the cantilever sensor). To demonstrate the functionality of the system, a self-sensing silicon cantilever resonator with a built-in piezoresistive Wheatstone bridge is fabricated and integrated with the circuit. A piezoactuator is utilized for actuating the cantilever into resonance. Implementation of this closed loop system is used to track the resonant frequency of a silicon cantilever-based sensor resonating at 9.4 kHz under a cross-sensitivity test of ambient temperature. The changes of the resonant frequency are interpreted using a frequency counter connected to the system. From the experimental results, the temperature sensitivity and coefficient of the employed sensor are 0.3 Hz/°C and 32.8 ppm/°C, respectively. The frequency stability of the system can reach up to 0.08 Hz. The development of this system will enable real-time nanoparticle monitoring systems and provide a miniaturization of the instrumentation modules for cantilever-based nanoparticle detectors.

Wasisto, Hutomo Suryo; Zhang, Qing; Merzsch, Stephan; Waag, Andreas; Peiner, Erwin

2013-05-01

437

Age and Individual Differences in Controlled Force Exertion Measured by a Computer-Generated Sinusoidal and Quasi-Random Display  

ERIC Educational Resources Information Center

This study examined age group and individual differences in controlled force exertion by emulating sinusoidal and quasi-random waveforms in 222 right-handed female adults aged 20 to 86 years. The subjects matched their submaximal grip strength by the dominant hand to changing demand values displayed as either a sinusoidal or a quasi-random…

Nagasawa, Yoshinori; Demura, Shinichi

2010-01-01

438

Multi-frequency EIT and TAS Hardware Development  

Microsoft Academic Search

We present the development of a multi-frequency EIT (electrical impedance tomography) and TAS (trans- admittance scanner) system. Both systems share a common main platform based on a DSP and wireless serial RF connection to a PC. A digital waveform generator is used in both EIT and TAS producing sinusoidal waveforms with a chosen set of frequencies in the range of

J. K. Seo

439

Optical voltage reference.  

National Technical Information Service (NTIS)

An optical voltage reference for providing an alternative to a battery source. The optical reference apparatus provides a temperature stable, high precision, isolated voltage reference through the use of optical isolation techniques to eliminate current a...

R. Rankin D. Kotter

1992-01-01

440

Automatic voltage imbalance detector  

DOEpatents

A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

Bobbett, Ronald E. (Los Alamos, NM); McCormick, J. Byron (Los Alamos, NM); Kerwin, William J. (Tucson, AZ)

1984-01-01

441

Mixed voltage VLSI design  

NASA Technical Reports Server (NTRS)

A technique for minimizing the power dissipated in a Very Large Scale Integration (VLSI) chip by lowering the operating voltage without any significant penalty in the chip throughput even though low voltage operation results in slower circuits. Since the overall throughput of a VLSI chip depends on the speed of the critical path(s) in the chip, it may be possible to sustain the throughput rates attained at higher voltages by operating the circuits in the critical path(s) with a high voltage while operating the other circuits with a lower voltage to minimize the power dissipation. The interface between the gates which operate at different voltages is crucial for low power dissipation since the interface may possibly have high static current dissipation thus negating the gains of the low voltage operation. The design of a voltage level translator which does the interface between the low voltage and high voltage circuits without any significant static dissipation is presented. Then, the results of the mixed voltage design using a greedy algorithm on three chips for various operating voltages are presented.

Panwar, Ramesh; Rennels, David; Alkalaj, Leon

1993-01-01

442

Vehicle mounted voltage regulator  

SciTech Connect

In a roadway vehicle having a storage battery and an engine-driven alternator, the battery voltage is controlled by a voltage regulator which has a first voltage detector for detecting when the battery voltage reduces below a higher reference level at which the battery voltage is normally controlled, and a second voltage detector for detecting when the battery voltage reduces below a lower reference level. A third voltage detector detects when the alternator voltage rises above a predetermined level. A logic gate circuit responds to outputs from the second and third voltage detectors by generating a warning signal. A semiconductor switching element is coupled in series with the field coil of the alternator to supply thereto the alternator voltage in response to a switching control which is generated in response to an output signal from the first voltage detector to cause the switching element to operate the alternator in a high output state and in response to the logic gate circuit to operate the alternator in a low output state.

Akita, Y.; Maruyama, T.; Teshima, T.; Torii, K.

1984-05-29

443

Interception of frequency hopped spread spectrum signals  

Microsoft Academic Search

A frequency-hopped, spread-spectrum signal is modeled as a sinusoid that has one of N random, discrete frequencies. Based on this model, the Neyman-Pearson detection theory is used to derive optimum coherent and noncoherent receiver structures. It is shown that the probability of detection, PD, approaches, the probability of false alarm, PF, as N gets large. For large N, simple formulas

N. C. Beaulieu; P. J. McLane; W. L. Hopkins

1990-01-01

444

Frequency Estimation Techniques For High Dynamic Trajectories  

NASA Technical Reports Server (NTRS)

Report presents comparative study of four techniques for estimating frequency of sinusoidal signal received in presence of noise when transmitter and/or receiver experiencing very high dynamics. Four techniques involve approximate-maximum-likelihood estimator, extended Kalman filter, cross-product automatic frequency control loop, and digital phase locked loop, respectively. In numerical simulations, each technique applied to signal from transmitter maneuvering along common trajectory; performance of each examined to determine its useful operating range, and performances compared.

Vilnrotter, V. A.; Hinedi, S. M.; Kumar, R.

1989-01-01

445

CZT-Based High Performance Frequency Estimation  

Microsoft Academic Search

Accurate and high-performance frequency estimation of a noisy sampled sinusoid sequence with short time length and adjacent overlapping has been attracting top focus in the field of signal processing. Based on the CZT of a single-tone sequence, this paper presents a novel improved Rife CZT-interpolated frequency estimator, which develops an improved Rife algorithm on the symmetry of CZT Linear Spectrum

Huang Yuchun; Huang Zailu; Huang Benxiong; Xu Shuhua

2007-01-01

446

Stable voltage source for Penning trap experiments  

SciTech Connect

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10{sup 8} over all time scales shorter than 10{sup 4} s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry.

Pinegar, David B.; Blaum, Klaus [Division of Stored and Cooled Ions, Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, 69029 Heidelberg (Germany); Biesiadzinski, Tomasz P.; Zafonte, Steven L.; Van Dyck, Robert S. Jr. [Department of Physics, University of Washington, PAB 351560, Seattle, Washington 98195 (United States)

2009-06-15

447

Stable voltage source for Penning trap experiments.  

PubMed

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10(8) over all time scales shorter than 10(4) s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry. PMID:19566217

Pinegar, David B; Blaum, Klaus; Biesiadzinski, Tomasz P; Zafonte, Steven L; Van Dyck, Robert S

2009-06-01

448

Large endolymphatic potentials from low-frequency and infrasonic tones in the guinea pig.  

PubMed

Responses of the ear to low-frequency and infrasonic sounds have not been extensively studied. Understanding how the ear responds to low frequencies is increasingly important as environmental infrasounds are becoming more pervasive from sources such as wind turbines. This study shows endolymphatic potentials in the third cochlear turn from acoustic infrasound (5?Hz) are larger than from tones in the audible range (e.g., 50 and 500?Hz), in some cases with peak-to-peak amplitude greater than 20?mV. These large potentials were suppressed by higher-frequency tones and were rapidly abolished by perilymphatic injection of KCl at the cochlear apex, demonstrating their third-turn origins. Endolymphatic iso-potentials from 5 to 500?Hz were enhanced relative to perilymphatic potentials as frequency was lowered. Probe and infrasonic bias tones were used to study the origin of the enhanced potentials. Potentials were best explained as a saturating response summed with a sinusoidal voltage (Vo), that was phase delayed by an average of 60° relative to the biasing effects of the infrasound. Vo is thought to arise indirectly from hair cell activity, such as from strial potential changes caused by sustained current changes through the hair cells in each half cycle of the infrasound. PMID:23464026

Salt, Alec N; Lichtenhan, Jeffery T; Gill, Ruth M; Hartsock, Jared J

2013-03-01

449

Nonlinear electrokinetics at large voltages  

NASA Astrophysics Data System (ADS)

The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, kBT/e=25 mV. In nonlinear 'induced-charge' electrokinetic phenomena, such as ac electro-osmosis, several volts ?100kBT/e are applied to the double layer, and the theory breaks down and cannot explain many observed features. We argue that, under such a large voltage, counterions 'condense' near the surface, even for dilute bulk solutions. Based on simple models, we predict that the double-layer capacitance decreases and the electro-osmotic mobility saturates at large voltages, due to steric repulsion and increased viscosity of the condensed layer, respectively. The former suffices to explain observed high-frequency flow reversal in ac electro-osmosis; the latter leads to a salt concentration dependence of induced-charge flows comparable to experiments, although a complete theory is still lacking.

Bazant, Martin Z.; Sabri Kilic, Mustafa; Storey, Brian D.; Ajdari, Armand

2009-07-01

450

Voltage monitoring system  

NASA Technical Reports Server (NTRS)

A description is given of a system for monitoring the voltage at a remote location and determining when the voltage exceeds upper and lower levels. The system includes transmission lines for transmitting the voltage back to a central station and applying such to an amplifier having a pair of outputs. One of the outputs of the amplifier is applied to an oscillograph. The other output is fed through an isolation transformer, a full wave rectifier, to a pair of unijunctional transistor circuits for producing pulses when the voltage exceeds or drops below a predetermined level. These pulses, in turn, energize a relay which turns on the oscillograph for recording the voltages being monitored.

Canicatti, C. L. (inventor)

1975-01-01

451

Control Strategy of a Parallel System Using Both Matrix Converter and Voltage Type Inverter  

NASA Astrophysics Data System (ADS)

This paper proposes a control strategy for a matrix converter and voltage type inverter in a parallel system that does not require of interconnection reactors. The proposed control strategy is to divide the operation time between a matrix converter and a voltage type inverter. The operation time of each converter is divided in every carrier cycle. As a result, interconnection reactors are not required and the sinusoidal input current waveform of a matrix converter can be obtained. The total output voltage of the proposed system and the output power division ratio for a matrix converter and a voltage type inverter are controlled by the time division ratio of each converter. Furthermore, the voltage error resulting from the operation of time division control was analyzed and compensated. The availability of the proposed system and the validity of the proposed control method are confirmed by experimental results.

Itoh, Jun-Ichi; Tamura, Hiroshi

452

Research on submodule capacitance voltage balancing of MMC based on carrier phase shifted SPWM technique  

Microsoft Academic Search

Modular multilevel converter (MMC) is a new multilevel converter suitable for VSC-HVDC. The principle of the submodules and converter topology are introduced in this paper. A novel carried phase shifted sinusoidal pulse width modulation (CPS-SPWM) scheme suitable for MMC in VSC-HVDC is presented. Voltage balancing among the submodules is a crucial problem of MMC. Based on the energy equipartition and

Xin Zhao; Guangkai Li; Chengyong Zhao

2010-01-01

453

Microwave integrated circuit for Josephson voltage standards  

NASA Technical Reports Server (NTRS)

A microwave integrated circuit comprised of one or more Josephson junctions and short sections of microstrip or stripline transmission line is fabricated from thin layers of superconducting metal on a dielectric substrate. The short sections of transmission are combined to form the elements of the circuit and particularly, two microwave resonators. The Josephson junctions are located between the resonators and the impedance of the Josephson junctions forms part of the circuitry that couples the two resonators. The microwave integrated circuit has an application in Josephson voltage standards. In this application, the device is asymmetrically driven at a selected frequency (approximately equal to the resonance frequency of the resonators), and a d.c. bias is applied to the junction. By observing the current voltage characteristic of the junction, a precise voltage, proportional to the frequency of the microwave drive signal, is obtained.

Holdeman, L. B.; Toots, J.; Chang, C. C. (inventors)

1980-01-01

454

Selective and localized radiofrequency heating of skin and fat by controlling surface distributions of the applied voltage: analytical study  

NASA Astrophysics Data System (ADS)

At low frequencies (hundreds of kHz to a few MHz), local energy absorption is proportional to the conductivity of tissue and the intensity of the internal electric field. At 1 MHz, the electric conductivity ratio between skin and fat is approximately 10; hence, skin would heat more provided the intensity of the electric field is similar in both tissues. It follows that selective and localized heat deposition is only feasible by varying electric fields locally. In this study, we vary local intensities of the internal electric field in skin, fat and muscle by altering its direction through modifying surface distributions of the applied voltage. In addition, we assess the long-term effects of these variations on tissue thermal transport. To this end, analytical solutions of the electric and bioheat equations were obtained using a regular perturbation method. For voltage distributions given by second- and eight-degree functions, the power absorption in fat is much greater than in skin by the electrode center while the opposite is true by the electrode edge. For a sinusoidal function, the absorption in fat varies laterally from greater to lower than in skin, and then this trend repeats from the center to the edge of the electrode. Consequently, zones of thermal confinement selectively develop in the fat layer. Generalizing these functions by parametrization, it is shown that radiofrequency (RF) heating of layered tissues can be selective and precisely localized by controlling the spatial decay, extent and repetition of the surface distribution of the applied voltage. The clinical relevance of our study is to provide a simple, non-invasive method to spatially control the heat deposition in layered tissues. By knowing and controlling the internal electric field, different therapeutic strategies can be developed and implemented.

Jiménez-Lozano, Joel; Vacas-Jacques, Paulino; Anderson, R. Rox; Franco, Walfre

2012-11-01

455

Selective and localized radiofrequency heating of skin and fat by controlling surface distributions of the applied voltage: analytical study.  

PubMed

At low frequencies (hundreds of kHz to a few MHz), local energy absorption is proportional to the conductivity of tissue and the intensity of the internal electric field. At 1 MHz, the electric conductivity ratio between skin and fat is approximately 10; hence, skin would heat more provided the intensity of the electric field is similar in both tissues. It follows that selective and localized heat deposition is only feasible by varying electric fields locally. In this study, we vary local intensities of the internal electric field in skin, fat and muscle by altering its direction through modifying surface distributions of the applied voltage. In addition, we assess the long-term effects of these variations on tissue thermal transport. To this end, analytical solutions of the electric and bioheat equations were obtained using a regular perturbation method. For voltage distributions given by second- and eight-degree functions, the power absorption in fat is much greater than in skin by the electrode center while the opposite is true by the electrode edge. For a sinusoidal function, the absorption in fat varies laterally from greater to lower than in skin, and then this trend repeats from the center to the edge of the electrode. Consequently, zones of thermal confinement selectively develop in the fat layer. Generalizing these functions by parametrization, it is shown that radiofrequency (RF) heating of layered tissues can be selective and precisely localized by controlling the spatial decay, extent and repetition of the surface distribution of the applied voltage. The clinical relevance of our study is to provide a simple, non-invasive method to spatially control the heat deposition in layered tissues. By knowing and controlling the internal electric field, different therapeutic strategies can be developed and implemented. PMID:23104083

Jiménez-Lozano, Joel; Vacas-Jacques, Paulino; Anderson, R Rox; Franco, Walfre

2012-11-21

456

Semaphorin 3E Secreted by Damaged Hepatocytes Regulates the Sinusoidal Regeneration and Liver Fibrosis during Liver Regeneration.  

PubMed

The liver has a remarkable capacity to regenerate after injury. Although the regulatory mechanisms of hepatocytic regeneration have been a subject of intense study, the dynamism of the sinusoids, specialized blood vessels in the liver, remains largely unknown. Transient activation of hepatic stellate cells and hepatic sinusoidal endothelial cells, which constitute the sinusoids, contributes to liver regeneration during acute injury, whereas their sustained activation causes liver fibrosis during chronic injury. We focused on understanding the association between damaged hepatocytes and sinusoidal regeneration or liver fibrogenesis using a carbon tetrachloride-induced liver injury mouse model. Damaged hepatocytes rapidly expressed semaphorin 3E (Sema3e), which induced contraction of sinusoidal endothelial cells and thereby contributed to activating hepatic stellate cells for wound healing. In addition, ectopic and consecutive expression of Sema3e in hepatocytes by the hydrodynamic tail-vein injection method resulted in disorganized regeneration of sinusoids and sustained activation of hepatic stellate cells. In contrast, liver fibrosis ameliorated in Sema3e-knockout mice compared with wild-type mice in a chronic liver injury model. Our results indicate that Sema3e, secreted by damaged hepatocytes, affects sinusoidal regeneration in a paracrine manner during liver regeneration, suggesting that Sema3e is a novel therapeutic target in liver fibrogenesis. PMID:24930441

Yagai, Tomoki; Miyajima, Atsushi; Tanaka, Minoru

2014-08-01

457

Actin filaments around endothelial fenestrae in rat hepatic sinusoidal endothelial cells.  

PubMed

The presence of microfilaments in the vicinity of sinusoidal endothelial fenestrae (SEF) suggests that the cytoskeleton of liver sinusoidal endothelial cells (LSEC) plays an important role in the modulation of SEF. In this study, we investigated actin filaments around SEF in LSECs. Monolayers of LSEC culture were established by infusing a rat liver with collagenase for 30 min and then culturing in RMPI medium for 24 h. Cells were reacted with 0.1% Triton X for 5 s and 15% glycerinated PHEM buffer (60 mM PIPES, 25 mM HEPES, 10 mM EGTA, 2 mM MgCl, pH 6.9) containing heavy meromyosin for 10 min and observed under a transmission electron microscope. By electron microscopy with the modified heavy meromyosin decorated reaction, actin filaments were clearly demonstrated around SEF in LSEC. PMID:15614450

Nagai, Toshihiro; Yokomori, Hiroaki; Yoshimura, Kazunori; Fujimaki, Kayo; Nomura, Masahiko; Hibi, Toshifumi; Oda, Masaya

2004-12-01

458

Bone marrow long label-retaining cells reside in the sinusoidal hypoxic niche  

SciTech Connect

In response to changing signals, quiescent hematopoietic stem cells (HSCs) can be induced to an activated cycling state and provide multi-lineage hematopoietic cells to the whole body via blood vessels. However, the precise localization of quiescent HSCs in bone marrow microenvironment is not fully characterized. Here, we performed whole-mount immunostaining of bone marrow and found that BrdU label-retaining cells (LRCs) definitively reside in the sinusoidal hypoxic zone distant from the 'vascular niche'. Although LRCs expressed very low level of a well-known HSC marker, c-kit in normal circumstances, myeloablation by 5-FU treatment caused LRCs to abundantly express c-kit and proliferate actively. These results demonstrate that bone marrow LRCs reside in the sinusoidal hypoxic niche, and function as a regenerative cell pool of HSCs.

Kubota, Yoshiaki; Takubo, Keiyo [Department of Cell Differentiation, Sakaguchi Laboratory, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582 (Japan); Suda, Toshio [Department of Cell Differentiation, The Sakaguchi Laboratory, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582 (Japan)], E-mail: sudato@sc.itc.keio.ac.jp

2008-02-08

459

Differential influence of sinusoidal and noisy inputs on synaptic connections in a network with STDP  

NASA Astrophysics Data System (ADS)

We hypothesize that the type of cortical network activation influences synaptic connectivity in the network, eventually expressed in an altered responsiveness to external stimuli. Our predictions are based on a time discrete canonical model of spike-time-dependent plasticity. The results show that, at a given synaptic connection strength in the network, sinusoidal input to the network can decrease synaptic potentiation whereas uncorrelated noise increases synaptic potentiation, implying that these opposing effects manifest themselves in respective decreases and increases of the network response to an external stimulus. These predictions are in qualitative agreement with visually evoked responses obtained in humans after 9 hour periods of visual deprivation (used to increase sinusoidal EEG alpha-activity in cortical networks) or normal daytime vision (as an approximate of noise input).

Mayer, J.; Schuster, H. G.; Ngo, H.-V. V.; Mölle, M.; Born, J.

2012-05-01

460

Effects of extremely low-frequency magnetic fields on the response of a conductance-based neuron model.  

PubMed

To provide insights into the modulation of neuronal activity by extremely low-frequency (ELF) magnetic field (MF), we present a conductance-based neuron model and introduce ELF sinusoidal MF as an additive voltage input. By analyzing spike times and spiking frequency, it is observed that neuron with distinct spiking patterns exhibits different response properties in the presence of MF exposure. For tonic spiking neuron, the perturbations of MF exposure on spike times is maximized at the harmonics of neuronal intrinsic spiking frequency, while it is maximized at the harmonics of bursting frequency for burst spiking neuron. As MF intensity increases, the perturbations also increase. Compared with tonic spiking, bursting dynamics are less sensitive to the perturbations of ELF MF exposure. Further, ELF MF exposure is more prone to perturb neuronal spike times relative to spiking frequency. Our finding suggests that the resonance may be one of the neural mechanisms underlying the modulatory effects of the low-intensity ELF MFs on neuronal activities. The results highlight the impacts of ELF MFs exposure on neuronal activity from the single cell level, and demonstrate various factors including ELF MF properties and neuronal spiking characteristics could determine the outcome of exposure. These insights into the mechanism of MF exposure may be relevant for the design of multi-intensity magnetic stimulus protocols, and may even contribute to the interpretation of MF effects on the central nervous systems. PMID:24344694

Yi, Guosheng; Wang, Jiang; Wei, Xile; Deng, Bin; Tsang, Kai-Ming; Chan, Wai-Lok; Han, Chunxiao

2014-02-01