Free oscillation of the Earth
Y. Abedini
author
text
article
2019
per
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.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
141
150
http://ijpr.iut.ac.ir/article_495_e0100c1ecfdce1cff2ea40bb85f486e8.pdf
Application of neutron activation analysis in discovering plastic explosive
S. H.
M.
author
R.
K.
author
M. H.
H.
author
text
article
2019
per
In this work, the ability of neuron probes to detect to plastic bombs in airway luggage or postal parcels has been investigated. As explosives are rich in nitrogen, 10.83 MeV gamma radiations may be employed to detect this nitrogen. First, the method is studied theoretically by using the Monte-Carlo simulation method and the MCNP code. The optimum distance, the positions of the detector and the sample, and the optimum moderator thickness are determined by considering the important pile-up effect. Second, by using the model obtained from the data, the Am-Be neuron source is deployed experimentally. In practice, given the role of the source and the pile up effect, the optimum conditions found by calculations are changed and the primary plan is revised, according to experimental results. Finally, the potential of this method is tested by analyzing the results which are obtained for the two kinds of moderators, paraffin and graphite. The data are then reviewed from different perspectives, and different effect on the response of the detectors.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
151
161
http://ijpr.iut.ac.ir/article_496_ed41111518f3726be76f589c69af3390.pdf
Quakonium spectroscopy by Klein-Gordon equation
M. Haghighat B Mirza
author
A. Dadkhah
author
علی دادخواه
author
text
article
2019
per
A model is proposed to obtain the qq spectra by using a generalized Klein-Gordon equation for a two-body system. A variety of different potentials are coupled to the mass term of the generalized equation. The eigenvalues and the corresponding mass spectra are evaluated by using numerical and analytical methods. The resulting spectra match dosely with the experimental data. The obtained values are also compared with those of models such as quasipotential equation (QPE).
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
163
175
http://ijpr.iut.ac.ir/article_497_78a44053cbd4a1cc7bd9a87ca2256741.pdf
Experimental investigation of optically dense fluid and pump energy on the photothermal lensing signal
M. Soltanolkotabi
author
text
article
2019
per
Photothermal lensing signal was experimentally investigated by using Second Harmonic Generation (SHG) of Nd:YAG laser with energies of E0 = 7, 10, and 15 mJ. The medium used in this experiment was N2 at atmospheric pressure, seeded with NO2 to make the medium more absorbing. The experiment was carried out for optically thin medium (1025 PPM NO2) as well as for an optically thick medium (5125 PPM NO2). The results show that the signal shape highly depends on the thickness of the medium as well as the pump energy.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
177
187
http://ijpr.iut.ac.ir/article_498_a53d0a5e58a2a95b16b7d8f63e09d108.pdf
Design and construct of a tunable semiconductor laser
J. Sabbaghzadeh
author
S. Dadras
author
Z. Haghi
author
text
article
2019
per
In this paper we explain in detail the design of a semiconductor laser coupled with the reflected beams from a grating. Since the beams reflected are diffracted at different angles, only one component of them can be resonated in the cavity. This technique reduces the output frequency of the laser and increases its stability. Since this system has various applications in the spectroscopy, gas concentrations, air pollution measurements, investigation of atomic and molecular structure, and so on, system is believed to be simple and accurate. This design is made for the first time in Iran and its reliability has been tested by the measurement of the rubidium atom, and the result is given.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
189
195
http://ijpr.iut.ac.ir/article_499_56c7b767a1bf44d6783f052cc5a61afa.pdf
Thermal instability in the interstellar medium
J. Ghanbari
author
M. Shadmehri
author
text
article
2019
per
This study demonstrates how thermal structures in the interstellar medium can emerge as a result of thermal instability. For a two-dimensional case, the steady state thermal structures was investigeted and it was shown that a large class of solutions exist. For a one –dimensional case the conductivity was found to be negligible. The effects of to cal cooling on the thermal instability were explored in some depth. In this case analytical results for time-dependent cooling function were presented, too. We studied nonlinear wave phenomena in thermal fluid systems, with a particular emphasis on presenting analytical results. When conductivity is proportional to temperature, the beliavior of thermal waves is soliton like. For slow thermal waves, approximate analytical results were presented. Extensions of this work are discussed briefly, together with possible astrophysical applications.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
2
v.
3
no.
2019
197
197
http://ijpr.iut.ac.ir/article_500_8bea7ce145059e1ec12d8764c20842ea.pdf