Abstract: Einstein's field equations predict the existence of four-dimensional black holes. The first uncharged and charged four-dimensional black hole solutions are known as Schwarzschild and Riesenordstrom black holes, respectively. The first three-dimensional black hole solution known as BTZ (Banados-Teitelboim-Zanelli) black holes was obtained in 1992 by solving the field equations in the presence of the negative cosmological constant. In the first part of this thesis, we obtained three-dimensional black hole solutions, with spherical symmetry, in Einstein's gravity, and after calculating thermodynamic quantities, we show that the first law of thermodynamics is true for these black holes. Then, using the canonical ensemble method, we check the thermodynamic stability of these black holes. In the second part, we extend the above idea to dilaton black holes (in Einstein-dilaton gravity). For this purpose, we obtain the black hole solutions of the field equations in the presence of a scalar field and considering the Lagrangian of the electromagnetic field as a material field and examine their geometric properties. Then we calculate the thermodynamic parameters of these black holes (mass, electric charge, temperature, entropy and electric potential) in appropriate ways. We show that the obtained quantities apply to the first law of thermodynamics of black holes and at the end we analyze the thermodynamic stability of dilatonic black holes using the canonical ensemble method. Keywords: 3D black holes, linear electrodynamics, Einstein-dilaton gravity, dilaton black holes, coupled gravity.

Abstract The presence of electromagnetic pollution not only poses a threat to human health but also disrupts the proper functioning of large-scale machinery. In light of this,a novel method involving sol-gel technique   was utilized to synthesize PVA/Mn Ferrite/(MoS2)x nanocomposites, which exhibit remarkable electromagnetic wave absorption roperties. By intelligently combining MoS2 with PVA/Mn Ferrite, the composite's electromagnetic parameters were optimized, leading to enhanced impedance matching. A   a   result,   the PVA/Mn Ferrite/(MoS2)x nanocomposites showcased an exceptional minimum reflection loss of -15.971dB at a thickness of 1 mm.The remarkable capability of absorbing substances can primarily be attributed to the outstanding synergistic interaction between PVA/Mn Ferrite and MoS2. Additionally, MoS2 also plays a significant role in generating dielectric loss and achieving ideal impedance matching. As a result, the potential applications of PVA/Mn Ferrite/(MoS2)x nanocomposites extend to serving as both absorption materials and light dependent resistance (LDR) sensors. These nanocomposites exhibit not only high efficiency but also possess the added advantages of flexibility and lightweight properties, further enhancing their desirability. Keywords: Absorbing material, Electrical and magnetic properties, Impedance matching, LDR sensor   

in 1916 , einstein expressed his theory of gravity as a second - order symmetric tensor , which is based on the theory of gravity as the curvature of spacetime .one of the ويژگيهاي of this theory is known as the بيني of the black hole as the field equation , the most simple جوابها in the four - dimensional case is called شوارتزشيلد and رايزنر - نوردستروم solution .the search for جوابهاي سياهچالهاي in space - the three - dimensional space in 1992 ended .بانادوس and his colleagues ( Banados - Teitelboim - Zanelli ) demonstrated that the field equations in the presence of the negative cosmological constant have also a non - stationary response ( if einstein used the cosmological constant to say that the universe is static , but it is later used to show the universe that is expanding ) [ 2 , 1 ] … this is called سياهچالههاي سياهچالههاي .later , سياهچالههاي BTZ were also obtained from solving the gravitational field equations coupled with maxwell 's electrodynamics [ 3 ] .next , the three - dimensional سياهچالههاي was introduced as the جوابهاي of the field equations in the presence of maxwell 's electrodynamics and in einstein - ديلاتون theory [ 5 , 4 ] .recently , a model of maxwell 's modified electrodynamics is introduced in the name of euler - heisenberg electrodynamics , which is used to study the scalar tensor of maxwell in scalar - tensor theory [ 6 ] .in ref . [ 7 ] , einstein 's field equations are solved in the presence of euler - heisenberg and cosmological constant .­­­­­­­­ at the end of the thesis we can develop a novel method based on the einstein - ديلاتون gravitational theory .for this purpose , euler - heisenberg electrodynamics is used as a model of nonlinear electrodynamics which is called maxwell 's modified model .first , by using the three - dimensional theory of euler - heisenberg 's lagrangian theorem , the coupled equations of tensor , vector , and scalar field equations are obtained in einstein 's theory and then by introducing a three - dimensional symmetric metric , the equations are obtained which are a second - order coupled system .in order to solve this problem , we use different حدسي مدلهاي to solve this problem by calculating the number of equations obtained for حلمعادلات and finding unknown unknowns .finally , we obtain the potential field of ديلاتوني , faraday 's law tensor , and the black solution of nonlinear charged چاله .by calculating the thermodynamic and thermodynamic properties of the black holes , the first law of ترموديناميكرابررسي is ميكنيم .the transition phase transition of the black hole is determined by using the canonical ensemble method and by calculating the black thermal capacity of the holes , the transition points of the first type and transition horizon of the second type and also the radius of the black event horizon are determined which are in the thermodynamic equilibrium state .

   In today's world, the need for flexible, light, small and at the same time energy storage devices with high energy storage density for use in the manufacture and design of electronic devices is very much felt. Preparing capacitors in the shortest possible time with high energy storage capacity based on cheap and environmentally friendly materials is one of the challenges of today's human progress in using energy storage tools. Therefore, in this thesis, the design and construction of flexible microsupercapacitor based on the active materials of graphene nanocomposites was put on the agenda. In this research, by emphasizing the use of environmentally friendly materials and in the shortest possible time, a tool is designed and built to store as much energy as possible in small and portable dimensions. The morphology of the surface and the crystal structure of the manufactured electrodes are evaluated by different analyses. Also, the capacity and energy density of the prepared microsupercapacitor is investigated by electrochemical analysis. In this research, by making two different electrodes, RGO and RGO/CuO, and examining the electrochemical characteristics of each, we achieved a compatible and useful material for increasing energy density and power density. By performing cyclic voltammetry on these two electrode materials, we obtained a capacity of 2.73 mF.cm-2 and 9.02 mF.cm-2 at a scan rate of 10 mV.s-1 for RGO and RGO/CuO electrodes. The capacity of the composite supercapacitor after 1000 cycles has been maintained at 87%, which is an acceptable number compared to valid articles.   

In this work, we investigate the optical response of a molecule in an active layer in core-shell and multilayer metallic nanoparticles by calculating its scattering cross section. The molecule in the active layer as a point electric dipole is considered. We also study the effect of an external point charge placed next to the nanoshell on the far-field Raman scattering or fluoresce emission of molecules residing inside the particle. It shown that the presence of an electric charge near plasmonic nanoshells can increase the far-field enhancement. The effect of physical and geometrical parameters on the far-field scattering cross section of the Raman active layer is investigated.

Over the past several years, attention has been focused on Alternating crystal structures of various materials in physics and photonics. In this study, first the Alternating crystal structures (or photonic crystal) is introduced and the laws that is controlling the transmission of electromagnetic waves through the photonic crystal and the transfer matrix method are studied. Then the relationship of the transfer coefficient of the electromagnetic wave through the crystal layers is estimated and different structures of the dielectric layer alternation is studied. In order to improve the transfer coefficient of wave through the photon crystal and reduce the band gap energy, a metal nanoparticles composite and graphene layer is introduced and added to the structure and the results are studied. The results of the theoretical calculations that was performed in this study represente that the addition of a metal nanoparticles composite and the use of graphene monolayers in one-dimensional photonic crystal structure causes the destroy of band gap energy in the transmitted spectrum of the structure. This result can be used in the manufacture of photonic devices over a wide frequency range.

 elasticity and conductivity of graphene affected by zn and si and sn adatoms

Abstract    A nanostructure is defined as a structure with 1-100 nanometer size. These materials have different properties with respect to those bulk forms.Zinc oxid in bulk form is a semiconductor with 3.37ev gap energy, and therefor it has interesting properties and applications in optoelectronic device.The energies of arousal of 60 Mev signify the emission of radiation. To calculate structure and electronic properties of different forms ZnO. We have performed self-consistent calculations using the FP-LAPW approach based on density functional theory. We have used WIEN2K code for our calculations. The exchange correlation potential was calculated in the generalized gradient approximation (GGA).

In this project due to the importance of Ti6AL4VO2 thin films in turbine blades, disks, electronic junctions, floaters and medical implants; we investigate their crystallographic and optical properties. Thin films of Ti6Al4VO2 were deposited on glass substrates using sputtering method. The deposition process were performed in constant 200W RF magnetron sputtering for 20, 30 and 40 min. The as sputtered films were characterized and analyzed by XRD method, UV-Vis spectrometer, Atomic force microscope (AFM) and SEM. XRD patterns showed that amorphous Ti6Al4VO2 thin films were coated on glass substrates. The films are highly tra  arent about 90%. Using transmittance and absorption spectra and by Kramers-Kronig method, refractive index and extinction coefficient spectra variations vs. wavelength were obtained. It is observed that by increasing deposition time these optical parameters were decreased. Surface morphology indicates that with increasing deposition time the sizes of the nanoparticles and surface roughness were decreased. But increasing time of deposition increases the optical band gap of the films from 3.03 to 3.15 eV.

       In recent years , tra  arent conductive structures have been studied extensively. Dielectric/Metal/Dielectric (DMD) structures are suitable alternatives for tra  arent conductive structures . In DMD structures , dielectric layers suppress the reflection of the metal layer.These structures can be used in various applications such as flat panel displays , energy – efficient windows , thin film transistors , gas sensors , organic solar cells , organic light emitting diodes , and photovoltaic applications.In this project , DMD thin films are deposited on the glass substrate , whose dielectric layers are Titanium dioxide (TiO2) and Zinc Sulfide (ZnS) , as well as Au and Ag   metal layers . The ZnS layer and Ag layer are maked by thermal evaporation and Au layer deposited by sputtering method and the TiO2 layer is deposited by dip coating method. The purpose of this work is to produce DMD structures with different metal layers and to compare structural properties , morohology , optical transition , and band gap energy of these structures. In other words, the purpose of this study is   to investigate   the effect of metal layer change on optical and structural properties.