جستجوی مقالات مرتبط با کلیدواژه « comsol » در نشریات گروه « فیزیک »

Jiles-Atherton model equations was used in many ways to describe the hysteresis loops of ferromagnetic, ferroelectric and piezoelectric materials. The main advantage of this model is establishing a connection between the hysteresis loop and the physical parameters of magnetic materials. In this study, the magnetic hysteresis curve was presented by using the finite element method and the COMSOL code. The Jiles-Atherton model equations was used to simulate the hysteresis loop, magnetic flux density and magnetic field components in the software. The purpose of this study, while examining the Jiles-Atherton model equations, is to know the effect of changes in the physical parameters of the magnetic material on the magnetic hysteresis curve. The obtained results indicate the changes in the area of the hysteresis loop, the characteristic values of this loop, the changes in the magnetic flux density and the components of the magnetic field by increasing or decreasing the parameters of the Jiles-Atherton model. The decrease in the area of the hysteresis loop and the decrease in the characteristic values of this loop is a reason for changing the behavior of the ferromagnetic material towards soft magnetization and reducing the interaction of the magnetic domains of the ferromagnetic material and vice versa.

In a polywell reactor, it is critical to have a stable and energetic virtual cathode that is necessary to accelerate ions and create fusion interactions. Increasing the confinement time of virtual cathode electrons is of critical importance in the performance of polywell reactors. In this paper, COMSOL Multiphysics software was used to perform a three-dimensional numerical simulation in order to investigate the impacts of effective variables of a polywell on the virtual cathode. The findings indicated that the confinement time depends on the distance between the coils, coil radius, coil current, and the kinetic energy of the injected electrons. In addition, by using the simulation results, the dependence of the mentioned parameters on the confinement time is obtained, and then a mathematical model was developed.

Performance of a micropattern gaseous detector of parallel plate type, a Micromega detector, was assessed for X-ray astronomical studies in this research. For this purpose, COMSOL Multiphysics software which solves differential equations based on Finite Element Method was used. Thus, by solving Poisson equation in the detector geometry, electric field in each point was obtained. Gain of the detector was estimated by using the obtained electric field and solving continuity equation. Results show that simulated detector gain was 100 at voltage of 400 V. Obtained results corresponds well with the results of simulation of the detector with Garfield code which verifies the performed simulation. This detector is a proper tool for X-ray polarimetry with respect to its good characteristics such as high resolution, large area and good performance at high flux.

An electric dipole magnet quite similar to that of the IRANCYC10 cyclotron was designed and constructed to conduct the initial tests on the internal Penning ion source to be installed in the cyclotron. This magnet which was designed and constructed in the department of physics, University of Tehran, is capable of producing a magnetic field of 7000 G in the location of the source, a region in the center of the magnet with the radial extent of 15 mm, with no need for cooling. Magnetic fields as high as 1.1 T are also accessible for a few minutes. The ion source in IRANCYC10 is expected to be exposed by a magnetic field of 1100 G. The measurements show that the magnetic field in the location of the source is homogeneous with the maximum deviation value of 1.1% with respect to the magnetic field strength at the center. The magnet is H type with 100 mm pole diameter and 60 mm gap size. Comsol, Ansys Maxwell and SolidWorks codes were employed in the design and construction of the electric dipole magnet.

The purpose of this study is to reduce the temperature of the attic of the building of department of physics in university of Tehran. To achieve this goal, eighteen natural ventilators with the area of 0.25 m2 each were installed on the roof. The natural ventilators alone did not decrease the temperature significantly. To help natural ventilation, a laminar flow of air from the floors to the attic was provided. This led to a temperature decrease around 1.5 to 2o C. In addition, a powered ventilation was resulted 3 to 8o C temperature decrease. Since the volume (4533 m3) and area (1416 m2) of the attic are too large, further tests were conducted on two small models (47×33×51 cm3) of the attic, build from the same material as the main attic. The models were used to investigate the effect of covering the roof with aluminum foil and painting the roof with a withe color as a reflector, and installation of polystyrene panels under the roof as an insulator. Covering with aluminum foil, painting in withe, and installation of polystyrene resulted in 3-5, 2-3.5, and 1-2 degrees decrease in temperature, respectively. Reason of these changes was explained by reflection spectrum of UV-Vis-NIR spectrophotometry. Finally, the attic was simulated by the COMSOL Multiphysics software. It showed that a temperature reduction of 10 degrees could be accomplished by installation of six fans as inlet in the gables, three in each gable. Each fan has to generate 4 m/sec air flow velocity.

One of the non-invasive methods of cancer treatment is photothermal laser therapy. Adding metal nanospheres and nanorods to tissue improves the healing process. On the other hand, temperature control is also essential to maintain healthy tissue. This article investigates the process of cancer treatment using laser and cobalt oxide nanoparticles as well as iron and copper metals. For this, we consider cobalt oxide nanospheres in a spherical cancer cell; Then, a number of cylindrical cobalt oxide nanorods are regarded in an aqueous hemisphere (as a cancer cell) and simulated with the help of COMSOL finite element approximation software. Appropriate boundary conditions are important for heat transfer on internal and external surfaces and temperature distribution should be obtained in different parts of the cell and nanoparticles. In addition, we investigated the magnetic and non-magnetic effects of iron and copper metals with the same laser intensity and similar boundary conditions. The calculation results show that the average temperature of the cell water volume during the first 0.8 microseconds of irradiation in the presence of cobalt oxide nanospheres is 43 degrees Celsius; also, in the presence of cobalt oxide nanorods, it reaches a temperature of 53 degrees Celsius. The average temperature of the water volume of the cell reaches 100 degrees Celsius in the presence of iron nanospheres and 100 degrees Celsius in the presence of copper nanorods with a steeper slope.

Quadrupole mass filter device is a key component in mass spectrometers which analysis ion particles based on their mass to charge ratio; this mean by applying a specific potential on the instrument, crossing most of ions diverge and lost and just some are survived through crossing mass filter. Using multi-physics simulation, one may obtain deep knowledge on performance of the filter and investigate the effect of different variable parameters on operation of the instrument. In this paper by implementing COMSOL multi-physics software the impact of operating line slope stability, ion beam position displacement, and oscillation of potential field on ions filtering is investigated.

In this paper, a one-dimensional simulation for discus plate dielectric barrier discharge (DBD) is done by COMSOL Multiphysics software. The effects of different parameters such as voltage, frequency, dielectric thickness, dielectric constant and electrode’s material on the temperature and density of electrons are investigated, it is found that secondary electron emission coefficient of the electrode, dielectric constant and the thickness of dielectric have a direct impact on the density of electron. The voltage increment from 5 to 50 kV, causes electron density growing from 4×1017</sup>m-3 </sup>to 3.2×1018</sup>m-3</sup>. Based on this study, electron density could reach up to the orders of 1018</sup>m-3</sup> by optimizing material and dimensions of dielectric and electrodes without applying high voltage and frequency which results a significant lower production cost.

In this article, the use of magnetic nanoparticles as transport agents in various biological programs is investigated and a magnetic process is analyzed in which magnetic carrier particles are guided to an object by an external magnetic field for drug delivery to the target. In addition, the paths of magnetic nanoparticles are simulated using the COMSOL software. In order to accumulate the drug at tumor sites and to prevent its undesirable side effects on healthy cells, the drug needs to be targeted merely to lesion sites. Therefore, nanoparticles are used for targeted drug delivery to the tumor cells. Among these, several factors influence the movement of nanoparticles. The direction of particles is affected by strength of the magnetic field, the shape of the magnet, the size and the magnetic properties of the nanoparticles. The external magnetic field can be generated in several ways, which in this research we have simulated a magnetic field generated by two special magnets.

Side-coupled standing wave tubes in AWT IMAGE mode are widely used in the low-energy electron linear accelerator, due to high accelerating gradient and low sensitivity to construction tolerances. The use of various simulation software for designing these kinds of tubes is very common nowadays. In this paper, SUPERFISH code and COMSOL are used for designing the accelerating and coupling cavities for a 6 MeV electron linear accelerator. Finite difference method in SUPERFISH code and Finite element method in COMSOL are used to solve the equations. Besides, dimension of accelerating and coupling cavities and also coupling iris dimension are optimized to achieve resonance frequency of 2.9985 MHz and coupling constant of 0.0112. Considering the results of this study and designing of the RF energy injection port subsequently, the construction of 6 MeV electron tube will be provided