Published Articles Archive

Abstract
The Lie symmetry group of the Zabolotskaya-Khokhlov equation has been seriously studied, earlier than this. Eventually, it has been endowed with a general model by N.J.C. Ndogmo, in 2008. This research is devoted to introducing the algebra, the group, and the reductions of a new symmetry which is an exception of that model.

Abstract
In 2015, after the discovery of Kepler-186f, the fifth exoplanet in orbit of its star, Kepler-186, we investigated for three new undetected planets in the Kepler-186 system [1]. Of the planets which are owned by the Kepler-186, the first Earth-like planet and far from its star is Kepler-186f. Considering the order of these five discovered planets, there is a strong possibility for the existence of three new and undetected planets. Theoretically, we have recognized these three new planets locating before and after Kepler-186f. The first two new planets, orbit in the gap between Kepler-186e and Kepler-186f, and are called Kepler-186e(X1) and Kepler-186e(X2) respectively. The third planet also orbits in the exterior region of Kepler-186f is called Kepler-186f(X1). Now, after 6 years, we have reinvestigated these findings using the new information and data available.

Abstract
One of the most important geotechnical issues is the stabilization and deep excavation of the city, which many research has been done about it., especially in recent decades. One thing that adds to the complexity and challenge of such projects is the existence of cavities and empty spaces in the vicinity of the excavation. Therefore, careful study and in-depth analysis play a crucial role in such projects. In this research, we try to examine this issue from different aspects and its practical result use in future projects. Due to the fact that the two methods of anchorage and nailing are the most widely used methods in strengthening and stabilizing the excavations, these two methods were selected also interaction of excavation-underground cavities were investigated. parameters such as the cavity depth, the distance of the cavity from the excavation, the diameter of the cavity, and the thickness of the cavity cover, have been investigated in this research. In this research, for analysis and modeling, PLAXIS 2D finite element software has been used with the assumption of plain strain and hardening soil model which is suitable for drilling. The results of the analysis showed that the horizontal displacement of the excavation increases due to the presence of cavities and the sensitivity of the cavities stabilized with the anchorage method is greater than the nailing method. The greatest effect of the cavity on the behavior of excavation, on the one hand, is special critical distances and depths. Studies have also shown that the field of soil deformation changes despite the cavity, but it will not have a significant effect on the forces created in consolidating elements. On the other hand, drilling operations near cavities can lead to changes in the internal stresses of the cavity covering elements that must be considered in the design.

Abstract
There are many aspects that have direct effects on total hip replacement performance (THR), such as material properties, applied loads, surgical approach, femur size and quality, prosthesis design, bone-implant interface etc. One of the purposes to study different structures in THR is reducing the stress shielding. For the current study, an innovative hollow spherical structure is developed for femoral hip stems. The aim is to extract volume in the spherical shape from the stainless-steel hip implant stems, in order to focus solely on correlating with titanium behavior. Internal geometry for the femoral stem is optimized in order to transfer more stress onto the bone. Moreover, the approach involves extracting volume in the spherical shape from the internal structure to reduce stress shielding. A new novel implant is proposed that demonstrated a reduction in stress shielding. The sphered models have a smaller young’s modulus and strength than the solid stainless-steel sample. The spheres in hollowed structures reduce the stress shielding and they transfer more stress onto the bone when compared to the solid stainless-steel models. This approach also involves restructuring a hard material, such as stainless steel, to enhance osseointegration. The reduction of the young’s modulus and stress directly depends on the volume of the hollow spheres in the models; however, there is a certain volume that can be extracted from solid

Abstract
Rapid plasma formation and evolution during microwave gas discharge device produce a macroscopic plasma shield to the microwave transmission, which can severely limit the performance of the device. In this paper, the electromagnetic (TE)- plasma interaction and the chlorine Discharge Global modeled in a standard rectangular waveguide WR 284 (72.14 mm× 32.04 mm) by COMSOL multiphysics provide to be a very good compromise between flexibility and work efficiency.

Abstract
In the IR-T1 Tokamak the effect of a resonance helical magnetic field (RHF) on plasma confienment are presented using Hilbert-Huang Transform method.Mirnov coil data analyzed by Hilbert-Huang Transform (HHT) and decomposed to the main intrinsic mode functions(imfs) and their instantanous frequencies (IFs). We find that, HHT method can extract MHD activities with different amplitudes in the different times. Then, the IFs of these modes can be calculated by Hilbert Transform (HT). As a comparison of WT and HHT analysis the Hilbert spectrum has much better frequency definition. Amplitude modulation of Mironov oscillations in IR-T1 tokamak plasma generate intra-wave frequency modulation, In the Hilbert spectrum analysis this effect is small compared to the STFT and WT spectrums. In our study, Magnetic islands with frequency around 40 kHz can be seen in wavlet Transform(WT) and HHT results in ohmic and RHF discharges. The HHT results after application of l=2/n=1 resonant field show that, the amplitude of m=2 poloidal MHD mode are amplified and then suppressed for a few milliseconds after amplification. Similarly, the amplitude of the m=3 MHD mode are amplified and then strongly suppressed by the start of the l=3/n=1 resonant field.

Abstract
Schwarzschild's external solution of Einstein’s gravitational field equations in the general theory of relativity for a static star has been generalized by Vaidya [1], taking into account the radiation of the star. Here, we generalize Vaidya’s metric to a star that is rotating and radiating. Although, there is a famous Kerr solution [2] for a rotating star, but here is a simple solution for a rotating star which may be termed as a zero approximate version of the Kerr solution. Results are discussed.