scholarly journals Inverse Scattering in the Low-Frequency Region by Using Acoustic Point Sources

10.5772/21820 ◽  
2011 ◽  
Author(s):  
Nikolaos L.
Keyword(s):  
Inverse Scattering ◽  
Low Frequency ◽  
Frequency Region ◽  
Point Sources

Incoherent inelastic neutron scattering from polyacetylenes in the low-frequency region

1985 ◽  
Vol 10 (4) ◽  
pp. 293-295 ◽  
Author(s):  
M. Tasumi ◽  
I. Harada ◽  
H. Takeuchi ◽  
H. Shirakawa ◽  
S. Suzuki ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Low Frequency ◽  
Inelastic Neutron ◽  
Frequency Region

Investigations of the Optical Properties of LaNi5 and LaNi4.5Sn0.5

2013 ◽  
Vol 321-324 ◽  
pp. 495-498 ◽  
Author(s):  
Dong Chen ◽  
Chao Xu
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Optical Properties ◽  
Density Functional ◽  
Low Frequency ◽  
Potential Method ◽  
Frequency Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Pseudo Potential

The reflectivity, loss function, refractive index, extinction coefficient and dielectric function of the LaNi5and LaNi4.5Sn0.5intermetallic compounds are investigated through the plane-wave pseudo-potential method based on the density functional theory. The effects of Sn impurity are discussed and some interesting features are found in the low frequency region. Some important optical properties such as static dielectric constant and static refractive index are obtained. The equation [n (0)]2=ε1(0)is satisfied according to our calculation, which indicates that our results are correct and reasonable. Nevertheless, the calculated results need to be testified in the future due to the lack of experimental data.

Anderson-Stuart Model to Analyze AC and DC Conductivity of Lithium Zinc-Silicate Glass / Glass-Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 919-924
Author(s):  
M.S. Jogad ◽  
V.K. Shrikhande ◽  
A.H. Dyama ◽  
L.A. Udachan ◽  
Govind P. Kothiyal
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Low Frequency ◽  
Frequency Region ◽  
Dc Conductivity ◽  
Frequency Range ◽  
High Frequency Region ◽  
Dc Conductivities ◽  
Conductivity Variation ◽  
Different Temperatures

AC and DC conductivities have been measured by using the real (e¢) and imaginary (e¢¢) parts of the dielectric constant data of glass and glass-ceramics (GC) at different temperatures in the rage 297-642K and in the frequency range 100 Hz to 10 MHz. Using Anderson –Stuart model, we have calculated the activation energy, which is observed to be lower than that of the DC conductivity. The analysis for glass/glass-ceramics indicates that the conductivity variation with frequency exhibits an initial linear region followed by nonlinear region with a maximum in the high-frequency region. The observed frequency dependence of ionic conductivity has been analyzed within the extended Anderson–Stuart model considering both the electrostatic and elastic strain terms. In glass/glassceramic the calculations based on the Anderson-Stuart model agree with the experimental observations in the low frequency region but at higher frequencies there is departure from measured data.

Vibronic side bands of Sm2+ in alkali halides

1969 ◽  
Vol 47 (17) ◽  
pp. 1757-1767 ◽  
Author(s):  
M. Buchanan ◽  
E. J. Woll Jr.
Keyword(s):  
Low Frequency ◽  
Alkali Halides ◽  
Frequency Region ◽  
Defects In Crystals ◽  
Side Band

The calculation of vibronic side bands of defects in crystals is discussed. A model for the deformation of the lattice about a Sm2+ defect in alkali halides and side-band calculations on this model for KBr and KCl containing Sm2+ are compared with experimentally observed side bands. Improvements, particularly in the low frequency region, are found over the calculations assuming no deformation.

scholarly journals Subtraction of Bright Point Sources from Synthesis Images of the Epoch of Reionization

2011 ◽  
Vol 28 (1) ◽  
pp. 46-57 ◽  
Author(s):  
B. Pindor ◽  
J. S. B. Wyithe ◽  
D. A. Mitchell ◽  
S. M. Ord ◽  
R. B. Wayth ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Dynamic Range ◽  
Low Frequency ◽  
Neutral Hydrogen ◽  
Galactic Nuclei ◽  
Point Sources ◽  
Field Of View ◽  
Bright Point ◽  
Line Of Sight ◽  
Diffuse Background

AbstractBright point sources associated with extragalactic active galactic nuclei and radio galaxies are an important foreground for low-frequency radio experiments aimed at detecting the redshifted 21-cm emission from neutral hydrogen during the epoch of reionization. The frequency dependence of the synthesized beam implies that the sidelobes of these sources will move across the field of view as a function of observing frequency, hence frustrating line-of-sight foreground subtraction techniques. We describe a method for subtracting these point sources from dirty maps produced by an instrument such as the MWA. This technique combines matched filters with an iterative centroiding scheme to locate and characterize point sources in the presence of a diffuse background. Simulations show that this technique can improve the dynamic range of epoch-of-reionization maps by 2—3 orders of magnitude.

scholarly journals The active dynamic vibration damper in non-stationary operation of a vibroactive unit

2021 ◽  
pp. 13-17
Author(s):  
D. V. Sitnikov ◽  
◽  
A. A. Burian ◽  
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Resonance Region ◽  
Frequency Region ◽  
Vibration Damper ◽  
Passive System ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Dynamic Vibration ◽  
Impulse Characteristics

The paper considers a vibration isolation system, in which a force is applied to the moving mass of the active dynamic vibration damper by an actuator in proportion to the measured value of the base response. The amplitude-frequency and impulse characteristics are plotted depending on the parameters of the system, assuming the actuator without distortion generates the force proportional to the base response. It is shown that the considered vibration isolation system is quite effective in the low-frequency region, including in the resonance region of the passive system, both in stationary and nonstationary modes of vibroactive forces

scholarly journals Magnetic Field due to the Radiation of High Altitude Lightning

2020 ◽  
Vol 8 (2S12) ◽  
pp. 49-50
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Radiation ◽  
High Altitude ◽  
Low Frequency ◽  
Frequency Region ◽  
Middle Region ◽  
Very Low Frequency ◽  
Lightning Discharges ◽  
Cloud To Ground Lightning ◽  
Frequency Radiation

High altitude optical discharges generated by extreme cloud-to-ground lightning strokes, which occur in the middle region of the atmosphere known as sprites. Streamer formation in sprites has been well stated to be existing by several previous workers. These streamers are not only responsible for the initiation of sprites but also they are composed of these streamers. It causes the production of electromagnetic radiation upto or below the ELF (very low frequency) region which have been reported earlier through various research theories. Thus, we are reporting out for the formulation of the model by using an earlier model used to estimate higher frequency radiation from cloud and ground lightning discharges through these positive corona streamers. Taking it into account, other terms like radiation magnetic field has been evaluated with the studied observations.

Dimensional tailoring of nitrogen-doped graphene for high performance supercapacitors

RSC Advances ◽  
2016 ◽  
Vol 6 (60) ◽  
pp. 55577-55583 ◽  
Author(s):  
Seung Yong Lee ◽  
Chang Hyuck Choi ◽  
Min Wook Chung ◽  
Jae Hoon Chung ◽  
Seong Ihl Woo
Keyword(s):  
High Performance ◽  
Low Frequency ◽  
Frequency Region ◽  
Transfer Resistance ◽  
One Dimensional ◽  
Nitrogen Doped ◽  
Efficient Charge ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
Low Mass

In supercapacitors, one dimensional graphene ribbons which form net-like porous structure demonstrate low mass transfer resistance at low frequency region and a consequent efficient charge transferability.

Measurement of the angular motion parameters of the mirror of the scanning device

2021 ◽  
pp. 3-7
Author(s):  
Petr A. Pavlov ◽  
Elena M. Ivashchenko
Keyword(s):  
Angular Velocity ◽  
Angular Position ◽  
Low Frequency ◽  
Frequency Region ◽  
Angular Motion ◽  
Main Attention ◽  
Scanning Angle ◽  
Scanning Device ◽  
Environmental Monitoring System

A scanning device for a space-based environmental monitoring system has been investigated. The main attention is paid to the study of the parameters of the angular motion of the mirror of the scanning device, the uniformity of rotation of which largely determines the quality of the image of the Earth's surface. The principle and results of measuring the parameters of the mirror rotation carried out in a wide angular range are considered. The measurements were performed using a dynamic goniometer-autocollimator, which has been calibrated at the State Standard of Plane Angle Unit GET 22-2014. The repeatability of the average angular velocity of the scanning device mirror and the repeatability of the initial scanning angle are calculated. Nonstationarity in mathematical expectation and variance in random deviations of the angular motion of the mirror from the linear law of scanning is noted. The use of wavelet analysis revealed the frequency of excitation of oscillations in the low-frequency region of the spectrum. The possibility of using the a dynamic goniometer-autocollimator for measuring not only the angular position of the scanning device mirror, but also the angular velocity is shown.

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