yousefali Abedini
Zanjan University, Physics, Faculty Member
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Research Interests:
Research Interests:
we study the free oscillations of a non-rotating earth-like planet in the presence of a force free magnetic field. The model consists of a solid inner core, a liquid outer core and a solid mantle which is spherically symmetric. The... more
we study the free oscillations of a non-rotating earth-like planet in the presence of a force free magnetic field. The model consists of a solid inner core, a liquid outer core and a solid mantle which is spherically symmetric. The lagrangian displacements are decomposed into scaloidal, poloidal and toroidal components using a gauged version of Helmholtz theorem. These components are identified, with p -, g - and t -modes, respectively. The normal modes of the model are determined using a Rayleigh-Ritz variational technique. The consequence of the presence of the solid parts and the magnetic field is the emergence of pure t -oscillations. The magnetic field, in addition to exciting t -modes, couples the everpresent p -and g -modes together. As an application of the model, the real seismic data of the earth is used to calculate eigenvalues and eigenvectors for different modes.
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This work is a study of the Earths free oscillations considering a merge of solid and liquid model. At the turn of 19th century Geophysicists presented the theory of the free oscillations for a self-gravitating, isotropic and compressible... more
This work is a study of the Earths free oscillations considering a merge of solid and liquid model. At the turn of 19th century Geophysicists presented the theory of the free oscillations for a self-gravitating, isotropic and compressible sphere. Assuming a steel structure for an Earth size sphere, they predicted a period of oscillation of about 1 hour. About 50 years later, the free oscillations of stars was studied by Cowling and others. They classified the oscillation modes of the stars into acoustic and gravity modes on the basis of their driving forces. These are pressure and buoyancy forces respectively. The earliest measurements for the period of the free oscillations of the Earth was made by Benyove from a study of Kamchathca earthquake. Since then, the Geophysicists have been trying to provide a theoretical basis for these measurements. Recently, the theory concerning oscillations of celestial fluids is extended by Sobouti to include the possible oscillations of the Earthlike bodies. Using the same technique, we study the free oscillations of a spherically symmetric, non-rotating and elastic model for the Earth. We used the actual data of the Earths interior structure in our numerical calculations. Numerical results show that there exist three distinct oscillation modes namely acoustic, gravity and toroidal modes. These modes are driven by pressure, buoyancy and shear forces respectively. The shear force is due to the elastic properties of the solid part of the Earth. Our numerical results are consistent with the seismic data recorded from earthquake measurements.
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Research Interests:
The site selection for the Iranian National Observatory (INO) was concluded in 2007. As a result of a 7-year campaign, Mount Gargash was identified to host the INO observing facilities. To measure the atmospheric seeing, an Automated... more
The site selection for the Iranian National Observatory (INO) was concluded in 2007. As a result of a 7-year campaign, Mount Gargash was identified to host the INO observing facilities. To measure the atmospheric seeing, an Automated Differential Image Motion Monitoring (automatic DIMM) system has been installed few 100 meters to the mainpeak. Together with a weather station, this automatic DIMM system enabled us to continuously gather data on the main atmospheric features of the site namely seeing, temperature, wind speed and direction, and relative humidity. In this study, we present the analysis of three years of automatic DIMM seeing data of this INO site. The measurements indicate that the site benefits from a low atmospheric seeing with median 0.7 arcsec and 1st and 3rd quartile being equal to 0.4 and 0.8 arcsec, respectively. We study the effect of the target position on the seeing measurements in order to optimize the future target selection criteria. Combining the simultaneous seeing and weather data, we investigate the long-term pattern of the variations in seeing and the meteorological parameters. This helps us understand the nature of variations and how they are influenced by general meteorological conditions. These analyses would improve observation strategies at this site in long and short-term.
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Research Interests:
... C Physica Scripta 2005 Physica Scripta 71 Page 4. 54 Homayoon Eshraghi, Yousefali Abedini and Roman O. Popovych 3. Formulation of the problem ... Physica Scripta 71 Page 6. 56 Homayoon Eshraghi, Yousefali Abedini and Roman O. Popovych... more
... C Physica Scripta 2005 Physica Scripta 71 Page 4. 54 Homayoon Eshraghi, Yousefali Abedini and Roman O. Popovych 3. Formulation of the problem ... Physica Scripta 71 Page 6. 56 Homayoon Eshraghi, Yousefali Abedini and Roman O. Popovych converts to u0 = A √ t∗ ...
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A more detailed study and identification of aerosol types can help to better understand the sources and effects of aerosols. In the present study, a number of optical properties of aerosols have been investigated seasonal for... more
A more detailed study and identification of aerosol types can help to better understand the sources and effects of aerosols. In the present study, a number of optical properties of aerosols have been investigated seasonal for discrimination of aerosol types during 2010-2014 over Zanjan, Iran. Also using AERosol RObotic NETwork (AERONET) data, aerosol was classified by multiple clustering techniques. Both fine and coarse modes particles were seen in seasonal averaged of Aerosol Volume Size Distribution (AVSD). Single Scattering Albedo (SSA) variations indicate the presence of scattering aerosol like dust in the spring, summer and fall, and dominance of absorbing type aerosols in the winter. The maximum value of the phase function was observed in the summer and in small scattering angle which can be due to presence of coarse mode dust particles. The scatter plot of Aerosol Optical Depth (AOD) versus Angstrom Exponent (AE) is one of the most effective methods to find aerosol types. Ext...
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In this paper, we introduce a nanocomposite as a humidity-sensitive sound absorber. The nanocomposites were prepared using hydrogel polymer (HP) as a matrix and graphene oxide (GO) as a filler. Results show that the surface energy of the... more
In this paper, we introduce a nanocomposite as a humidity-sensitive sound absorber. The nanocomposites were prepared using hydrogel polymer (HP) as a matrix and graphene oxide (GO) as a filler. Results show that the surface energy of the nanocomposite is 58.4 mJ m−2, and GO sheets increase the nanocomposite porosity from 2.6716 cm2 g−1 (for HP) up to 3.246 cm2 g−1. In addition, the diameter of nanocomposite pores is 8.5202 nm lower than that of HP (10.274 nm). To study the effect of humidity on the sound absorption, we exposed them to moisture for 30 and 60 min and then measured sound absorption. Results show an absorption peak for the HP at 1022 Hz with an attenuation value of 30%, while the nanocomposite shows two main peaks around 1898 and 3300 Hz. In addition, results show that sound absorption peaks shift to higher frequencies according to humidification time.
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In this paper, we introduce a nanocomposite as a humidity-sensitive sound absorber. The nanocomposites were prepared using hydrogel polymer (HP) as a matrix and graphene oxide (GO) as a filler. Results show that the surface energy of the... more
In this paper, we introduce a nanocomposite as a humidity-sensitive sound absorber. The nanocomposites were prepared using hydrogel polymer (HP) as a matrix and graphene oxide (GO) as a filler. Results show that the surface energy of the nanocomposite is 58.4 mJm-2, and GO sheets increase the nanocomposite porosity from 2.6716 cm2 g-1 (for HP) up to 3.246 cm2 g-1. In addition, the diameter of nanocomposite pores is 8.5202 nm lower than that of HP (10.274 nm). To study the effect of humidity on the sound absorption, we exposed them to moisture for 30 and 60 min and then measured sound absorption. Results show an absorption peak for the HP at 1022 Hz with an attenuation value of 30%, while nanocomposite shows two main peaks around 1898 and 3300 Hz. In addition, results show that sound absorption peaks shift to higher frequency according to humidification time.
Research Interests:
Research Interests:
ABSTRACT We study the non-thermal effects of microwave on the wettability of graphene oxide. It is shown that removal of carboxyl compound by using the non-thermal microwave effects decrease the wettability of graphene oxide. X-ray... more
ABSTRACT We study the non-thermal effects of microwave on the wettability of graphene oxide. It is shown that removal of carboxyl compound by using the non-thermal microwave effects decrease the wettability of graphene oxide. X-ray photoelectron spectroscopy (C1s and O1s peaks) and Fourier transform infrared spectroscopy show that carboxyl compound decreases dramatically due to microwave irradiation while other functional groups were gradually reduced. Consequently, after 20 min microwave irradiation, carboxyl functional groups are removed. Wettability tests of carboxyl-reduced graphene oxide show that water uptake capability decreases to half and contact angle of water droplets increases from ~ 29.7° to ~ 69.9°.
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Solar magnetic tornadoes are known to be one of the mass and energy transport mechanisms from the lower solar atmosphere into the upper layers of the solar corona. A bright spiral structure with two arms is observed using high-cadence EUV... more
Solar magnetic tornadoes are known to be one of the mass and energy transport mechanisms from the lower solar atmosphere into the upper layers of the solar corona. A bright spiral structure with two arms is observed using high-cadence EUV images of 171, 193 and 304 Å channels of Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) on 10th of July 2011 for three hours. The structure studied here looks bright in front of dark background emissions. The rotational energy budget of this tornado is estimated using three different approaches. Results showed the rotational energy ranges between 1.95×10 erg to 3.36×10 erg. After correcting for the solar differential rotation, the oscillatory behaviour of the structure is studied using FFT technique. Results show four different regimes of oscillations: 3-min, 5-6 min, 8-11 min, and 15-17 min. The showed origin of each of these oscillations are discussed.
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Title: Free oscillations of the earth. Authors: Lapwood, ER; Usami, T. Publication: Free oscillations of the earth., by Lapwood, ER; Usami, T.. Cambridge (UK): Cambridge University Press, 12 + 243 p. Publication Date: 00/1981. Origin:... more
Title: Free oscillations of the earth. Authors: Lapwood, ER; Usami, T. Publication: Free oscillations of the earth., by Lapwood, ER; Usami, T.. Cambridge (UK): Cambridge University Press, 12 + 243 p. Publication Date: 00/1981. Origin: ARI. Comment: A&AA ID. AAA030.003.091. ...
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The derivation of a Lagrangian invariant so-called spirality is reviewed through the Lagrangian coordinates. The value of the spirality is fixed up to a gauge transformation. The helicity conservation follows directly from this invariant.... more
The derivation of a Lagrangian invariant so-called spirality is reviewed through the Lagrangian coordinates. The value of the spirality is fixed up to a gauge transformation. The helicity conservation follows directly from this invariant. Among all ideal flows with zero helicity in a domain of ...