High frequency and precision 3-phase sine/PWM controller with near-zero frequency of MPU intervention

2002 ◽  
Author(s):  
J. Chang
Keyword(s):  
High Frequency ◽  
Zero Frequency

Frequency of Pairs of Items and Associative Probability in Learning

1971 ◽  
Vol 29 (1) ◽  
pp. 127-133
Author(s):  
Charles S. Berdiansky
Keyword(s):  
Associative Learning ◽  
Word Pair ◽  
High Frequency ◽  
Paired Associate ◽  
Low Frequency ◽  
Similar Rate ◽  
Frequency Of Occurrence ◽  
Control Pair ◽  
Zero Frequency

The study was designed to compare Underwood and Schulz's associative probability hypothesis and the paired frequency of two words in performance on a paired-associate task. After being presented a list, 16 Ss matched responses with their stimuli. Each list contained a word pair or item, of (a) high frequency of occurrence, (b) low frequency, (c) zero frequency plus a mediator, and (d) zero frequency (the control pair). While the high-frequency items were learned more rapidly than the low-frequency items, the mediator did not affect the zero-frequency items which were learned at a similar rate to that for the control. This result was interpreted as showing the superiority of paired frequency in associative learning.

scholarly journals High-frequency homogenization of zero-frequency stop band photonic and phononic crystals

2013 ◽  
Vol 15 (10) ◽  
pp. 103014 ◽  
Author(s):  
T Antonakakis ◽  
R V Craster ◽  
S Guenneau
Keyword(s):  
High Frequency ◽  
Stop Band ◽  
Phononic Crystals ◽  
Zero Frequency

Suppression of runaway of electrons in a Lorentz plasma.: I. Harmonically time varying electric field

1970 ◽  
Vol 4 (2) ◽  
pp. 387-402 ◽  
Author(s):  
Barbara Abraham-Shrauner
Keyword(s):  
Electric Field ◽  
High Frequency ◽  
Particle Distribution ◽  
Collision Frequency ◽  
Uniform Electric Field ◽  
Perturbation Scheme ◽  
Time Varying ◽  
Runaway Electrons ◽  
Two Component ◽  
Zero Frequency

The suppression of runaway electrons in a Lorentz plasma is demonstrated for a two-component, fully ionized plasma in the presence of a high frequency, weak, uniform electric field. The time for runaway to occur for electric field frequencies high compared to the collision frequency is longer than the runaway time for low electric field frequencies or zero frequency, by the ratio of the frequency of the electric field to the collision frequency squared. Both the resolvant method developed by Prigogine and co-workers and the double perturbation scheme of the Poincaré—Lighthill method are employed to derive the diffusion equation for the modified one-particle distribution function in the collision-dominated region of velocity space.

scholarly journals Frequency Spectra Fluctuations in the Radio Interferometry of Polarized Radiation

2002 ◽  
Vol 199 ◽  
pp. 402-403
Author(s):  
M.R. Olyak
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Longitudinal Magnetic Field ◽  
Magnetoactive Plasma ◽  
Frequency Spectra ◽  
Random Magnetic Field ◽  
Linearly Polarized ◽  
Electron Density Irregularities ◽  
Zero Frequency ◽  
Polarized Radiation

The presence of a longitudinal magnetic field is shown to lead to the appearance of an additional component of the frequency spectrum of the linearly polarized emission. This component is proportional to the spectrum of normal waves phase difference fluctuations. The fluctuations spectra baseline dependence of a linear polarized radiation is periodical near zero frequency, one is absent in the high frequency ranges and such dependence has different character in magnetoactive plasma with electron density irregularities and in plasma with a random magnetic field.

scholarly journals High-frequency asymptotics for microstructured thin elastic plates and platonics

2012 ◽  
Vol 468 (2141) ◽  
pp. 1408-1427 ◽  
Author(s):  
T. Antonakakis ◽  
R. V. Craster
Keyword(s):  
High Frequency ◽  
Continuum Model ◽  
Two Dimensional ◽  
Elastic Plates ◽  
Dimensional Model ◽  
Defect Modes ◽  
High Frequencies ◽  
Two Dimensional Model ◽  
Thin Elastic Plates ◽  
Zero Frequency

We consider microstructured thin elastic plates that have an underlying periodic structure, and develop an asymptotic continuum model that captures the essential microstructural behaviour entirely in a macroscale setting. The asymptotics are based upon a two-scale approach and are valid even at high frequencies when the wavelength and microscale length are of the same order. The general theory is illustrated via one- and two-dimensional model problems that have zero-frequency stop bands that preclude conventional averaging and homogenization theories. Localized defect modes created by material variations are also modelled using the theory and compared with numerical simulations.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

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