Synthesis and High-Frequency Absorption Property of Flower-Like Nickel-Ferrite Composites

2017 ◽  
Vol 898 ◽  
pp. 1625-1630 ◽  
Author(s):  
Guang Qiang Zhang ◽  
Hang Rong Dong ◽  
Zong Zhen Li ◽  
Shao Xiong Zhou ◽  
Yu Wang ◽  
...  
Keyword(s):  
High Frequency ◽  
Nickel Ferrite ◽  
Wave Attenuation ◽  
Magnetic Loss ◽  
Synergetic Effect ◽  
Three Dimensional ◽  
Nickel Ion ◽  
Frequency Wave ◽  
Nickel Iron ◽  
Ferrite Composites

Three-dimensional flower-like nickel-ferrite composites were successfully synthesized via decomposition of the nickel-iron alkoxide precursors by varying the ratio of iron and nickel ion in the solution. The overall morphology and size of the particles had no obvious change compared with the precursors. The high-frequency absorption properties of the composites were investigated in a frequency range of 2-18 GHz. The reflection loss and bandwidth varied with the nickel ratio and thicknesses of the compositions, showing valuable prospect in high-frequency wave attenuation. The wave absorbing mechanism was also discussed, which could be attributed to the dielectric loss, magnetic loss, and the synergetic effect.

Relating P‐wave attenuation to permeability

Geophysics ◽  
1993 ◽  
Vol 58 (1) ◽  
pp. 20-29 ◽  
Author(s):  
Nabil Akbar ◽  
Jack Dvorkin ◽  
Amos Nur
Keyword(s):  
Pore Radius ◽  
Wave Attenuation ◽  
Three Dimensional ◽  
Low Frequency ◽  
P Wave ◽  
Frequency Wave ◽  
Cylindrical Pore ◽  
Isotropic Elastic Medium ◽  
Plane P Wave ◽  
Attenuation Values

To relate P‐wave attenuation to permeability, we examine a three‐dimensional (3-D) theoretical model of a cylindrical pore filled with viscous fluid and embedded in an infinite isotropic elastic medium. We calculate both attenuation and permeability as functions of the direction of wave propagation. Attenuation estimates are based on the squirt flow mechanism; permeability is calculated using the Kozeny‐Carman relation. We find that in the case when a plane P‐wave propagates perpendicular to the pore orientation [Formula: see text], attenuation is always higher than when a wave propagates parallel to this orientation [Formula: see text]. The ratio of these two attenuation values [Formula: see text] increases with an increasing pore radius and decreasing frequency and saturation. By changing permeability, varying the radius of the pore, we find that the permeability‐attenuation relation is characterized by a peak that shifts toward lower permeabilities as frequency decreases. Therefore, the attenuation of a low‐frequency wave decreases with increasing permeability. We observe a similar trend on relations between attenuation and permeability experimentally obtained on sandstone samples.

Near-surface scattering effects observed with a high-frequency phased array at Pinyon Flats, California

1998 ◽  
Vol 88 (6) ◽  
pp. 1548-1560
Author(s):  
Frank L. Vernon ◽  
Gary L. Pavlis ◽  
Tom J. Owens ◽  
Dan E. McNamara ◽  
Paul N. Anderson
Keyword(s):  
Surface Wave ◽  
Wave Field ◽  
Particle Motion ◽  
High Frequency ◽  
Body Wave ◽  
Three Dimensional ◽  
Wave Guide ◽  
Surface Scattering ◽  
Near Surface ◽  
Frequency Wave

Abstract Analysis of data collected by a high-frequency array experiment conducted at Pinyon Flat in southern California provides strong evidence that the high-frequency wave field from local earthquakes at this hard-rock site are strongly distorted by near-surface scattering. The seismic array we deployed consisted of 60, 2-Hz natural frequency, three-component sensors deployed in a three-dimensional array. Two of the sensors were located in boreholes at 150 and 275 m depth. The other 58 sensors were deployed in an areal array above these boreholes. Thirty-six of these were deployed in a 6-by-6 element grid array with a nominal spacing of 7 m centered over the borehole sensors. The remaining 22 seismometers were laid out in two 11-element linear arrays radiating outward from the grid. Coherence calculations reveal a rapid loss of coherence at frequencies over 15 Hz at all but the shortest length scales of this array. Three-dimensional visualization techniques were used to closely examine the spatial stability of particle motions of P and S waves. This reveals systematic variations of particle motion across the array in which the particle motion tracks tilt drastically away from the backazimuth expected for an isotropic medium. These variations, however, are frequency dependent. Below around 8 Hz, the particle motions become virtually identical for all stations. At progressively higher frequencies, the wave-field particle motion becomes increasingly chaotic. Frequency-wave-number analysis of these data provide quantitative measures of the same phenomena. We find that direct wave f-k spectra are bathed in a background of signal-generated noise that varies from 10 to 30 dB down from the direct arrival signal. This signal-generated noise appears to be nearly white in wavenumber indicating the wavelength of this “noise” on the scale of tens of meters and less. Refraction measurements we made on two lines crisscrossing the array reveal that the weathered layer velocities are highly variable and define a very strong wave guide. Measured surface P-wave velocities varied from 400 to 1300 m/sec, and velocities at depth of approximately 15 m varied from 1600 to 2700 m/sec. Previous measurements in the boreholes showed that the intact granite below about 65 m depth has a velocity of approximately 5400 m/sec. These results demonstrate the extreme velocity contrast and degree of velocity heterogeneity of the near surface at this site. We conclude that all the observations we made can be explained by strong scattering of incident body-wave signals into a complex mishmash of body-wave and surface-wave modes in this heterogeneous near-surface wave guide.

scholarly journals Three-dimensional tellurium and nitrogen Co-doped mesoporous carbons for high performance supercapacitors

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8628-8635
Author(s):  
Chang Ki Kim ◽  
Jung-Min Ji ◽  
M. Aftabuzzaman ◽  
Hwan Kyu Kim
Keyword(s):  
High Performance ◽  
Carbon Materials ◽  
Synergetic Effect ◽  
Three Dimensional ◽  
Mesoporous Carbons ◽  
Capacitive Performance ◽  
Nitrogen Doped ◽  
Carbon Based Nanomaterials ◽  
Nitrogen Doped Carbon ◽  
Co Doped

The incorporation of the Te element into nitrogen-doped carbon-based nanomaterials is a good strategy to improve the capacitive performance of carbon materials and the incorporation of two types of atoms improves the overall capacitive performance of the materials due to a synergetic effect.

scholarly journals Research of the process of vegetable oil extracting under the influence of a high frequency wave field

2020 ◽  
Vol 941 ◽  
pp. 012052
Author(s):  
V Yu Ovsyannikov ◽  
A A Berestovoy ◽  
N N Lobacheva ◽  
V V Toroptsev ◽  
S A Trunov
Keyword(s):  
Wave Field ◽  
Vegetable Oil ◽  
High Frequency ◽  
Frequency Wave ◽  
High Frequency Wave

scholarly journals Novel Polyimide/Copper-Nickel Ferrite Composites with Tunable Magnetic and Dielectric Properties

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1646
Author(s):  
Corneliu Hamciuc ◽  
Mihai Asandulesa ◽  
Elena Hamciuc ◽  
Tiberiu Roman ◽  
Marius Andrei Olariu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Nickel Ferrite ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Broadband Dielectric Spectroscopy ◽  
Copper Nickel ◽  
Low Dielectric ◽  
Magnetic Remanence ◽  
Polyimide Matrix ◽  
Ferrite Composites

Heat-resistant magnetic polymer composites were prepared by incorporating cerium-doped copper-nickel ferrite particles, having the general formula Ni1-xCuxFe1.92Ce0.08O4 (x: 0.0, 0.3, 0.6, 1.0), into a polyimide matrix. The effects of particle type and concentration on the thermal, magnetic, and electrical properties of the resulting composites were investigated. The samples were characterized by FTIR, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, differential scanning calorimetry, vibrating sample magnetometer, and broadband dielectric spectroscopy. The composites exhibited high thermal stability, having initial decomposition temperatures between 495 and 509 °C. Saturation magnetization (Ms), magnetic remanence (Mr), and coercivity (Hc) were found in range of 2.37–10.90 emu g−1, 0.45–2.84 emu g−1, and 32–244 Oe, respectively. The study of dielectric properties revealed dielectric constant values of 3.0–4.3 and low dielectric losses of 0.016–0.197 at room temperature and a frequency of 1 Hz.

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