Engineering Physics Commons^™

Magnetic Field Perturbations To A Soft X-Ray-Activated Fe (Ii) Molecular Spin State Transition, Guanhua Hao, Alpha T. N’Diaye, Thilini K. Ekanayaka, Ashley S. Dale, Xuanyuan Jiang, Esha Mishra, Corbyn Mellinger, Saeed Yazdani, John W. Freeland, Jian Zhang, Ruihua Cheng, Xiaoshan Xu, Peter Dowben

Peter Dowben Publications

The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft X-ray activation of the spin crossover transition for [Fe{H₂B(pz)₂ }₂ (bipy)] molecular thin films is reduced in the presence of an applied magnetic field, as measured through X-ray absorption spectroscopy at various temperatures. The influence of a 1.8 T magnetic field is sufficient to cause deviations from the expected exponential spin state transition behavior which is measured in the field free case. We find …

Ultra-Low Frequency Waves At Middle Latitudes During Substorms: Observations And Modeling, Mergen Alimaganbetov

Doctoral Dissertations and Master's Theses

This doctoral dissertation presents the results of investigation of the Ultra-Low Frequency (ULF) waves at middle latitudes during substorms. The dissertation consists of two major parts, observations and simulations. The research in this dissertation proposes that the main role in the generation of ULF waves at middle latitudes during substorm belongs to the plasmapause.

The first part of the dissertation presents results of the data analysis of 84 intense substorm events as well as an overview of space observation programs such as CRRES, Van Allen Probes and DMSP. Data used in this study are from the ACE satellite taken measurements …

High Speed Impact On Graphene Composites, Giovanny A. Espitia

Symposium of Student Scholars

Since the isolation of Graphene occurred in 2004, numerous studies attempting to exploit the properties of this carbon allotrope have been conducted. Graphene exists in a 2-D manner with sp2 bonds, which provides the allotrope with great electrical, conductive, and mechanical properties. In this paper however, we will focus on the latter in order to examine the feasibility of graphene composites for bulletproof material in the military. Pure graphene sheets count with high porosity density that leads to structural defects as well as poor mechanical properties due to physical contact being sole retainer. For this reason, the selected composite is …

Photoluminescence Spectra Of Silicon Doped With Cadmium, N A. Sultanov, E T. Rakhimov, Z Mirzajonov, F T. Yusupov

Scientific-technical journal

Cadmium and zinc, as transition metals, are deep-level impurities (DL) and have a significant effect on the electrical, photoelectric, recombination, and other properties of semiconductor crystals.This paper presents the results of experimental studies of the optical and electrical properties of silicon crystals containing impurity atoms of cadmium and zinc using DLTS and low-temperature photoluminescence (PL).

Infinite Peirce Distribution In The Algebra Of Compact Operators And Description Of Its Local Au-Tomorphisms, Farhodjon N. Arzikulov, Rejabboy Qo’Shaqov

Scientific Bulletin. Physical and Mathematical Research

In the present paper the infinite Peirce decomposition of the algebra 𝐾(𝐻) of com-pact operators on an infinite dimensional separable Gilbert space 𝐻 is constructed, using the norm of the algebra 𝐾(𝐻) and a maximal family of mutually or-thogonal minimal projections, i.e., self-adjoint,idempotent elements. The infinite Peirce decompo-sition on the norm of a 𝐶∗-algebra is also con-structed in 2012 by the first author. But, it turns, the condition, applied then, is not sufficient for the infi-nite Peirce decomposition on the norm constructed in 2012 to be an algebra. Therefore, in the present paper, the infinite Peirce decomposition on the norm …

Computational Modeling Of Black Phosphorus Terahertz Photoconductive Antennas Using Comsol Multiphysics With Experimental Comparison Against A Commercial Lt-Gaas Emitter, Jose Isaac Santos Batista

Graduate Theses and Dissertations

This thesis presents computational models of terahertz (THz) photoconductive antenna (PCA) emitter using COMSOL Multiphysics commercial package. A comparison of the computer simulated radiated THz signal against that of an experimentally measured signal of commercial reference LT-GaAs emitter is presented. The two-dimensional model (2D) aimed at calculating the photoconductivity of a black phosphorus (BP) PCA at two laser wavelengths of 780 nm and 1560 nm. The 2D model was applied to the BP PCA emitter and the LT-GaAs devices to compare their simulated performance in terms of the photocurrent and radiated THz signal pulse. The results showed better performance of …

Structural And Electronic Properties Of Few-Layer Monochalcogenides, Brandon Joel Miller

Graduate Theses and Dissertations

This work discusses a new class of materials with novel properties that have only recently begun being studied. These materials are two-dimensional group IV-VI monochalcogenides, so named because they are formed from group IV (carbon group) and group VI (chalcogens) elements. These materials display several interesting physical properties such as ferroelasticity and ferroelectricity, and the contents within Chapters Two, Three, and Four concern a collaborative effort between theory and experiment between our group at the University of Arkansas and Dr. Kai Chang at the Max Planck Institute of Microstructure Physics in Halle, Germany in studying these properties. This thesis is …

Effect Of Excess Tellurium And Lead On Defor-Mation - Characteristics Of Polycrystalline Pbte Films, Yu.Yu. Vaitkus, Otajonov Salimjon

Scientific Bulletin. Physical and Mathematical Research

In this work, we studied the ef-fect of excess tellurium and lead on the defor-mation characteristics of polycrystalline PbTe films obtained on different substrates. It was found that the resistance of the films first increases and reach-es a maximum, and with a further increase in the level of deformation, it decreases and the sign of the tensile resistance begins to change, which are associated with the presence of internal stresses in the films. It was also shown that with an increase in the amount of lead in the composition of the PbTe film, the electrical conductivity increases in com-parison with …

Structure And Electrophysical Properties Of A Solid Solution (Gaas1-Δbiδ)1-X-Y(Ge2)X(Znse)Y, S.Z. Zainabidinov, I.N. Karimov, Hotamjon Mansurov, Akramjon Boboev, Dilkhayotjon Pulatjon Ugli Abdurakhimov

Scientific Bulletin. Physical and Mathematical Research

This paper shows the possibility of growing a single-crystal solid solution of substitution (GaAs1-δBiδ)1-x-y(Ge2)x(ZnSe)y on GaAs substrates by liquid-phase epitaxy from a bismuthcontaining solution-melt. The grown films had a ptype of conductivity with a current carrier concentration of 1,86·1017 сm-3, a mobility of р = 300 cm2/V·s, and a resistivity of 0,13 Ohms·cm. Structural studies have shown that the epitaxial films have a sphalerite structure of the ZnS type and are monocrystalline with an orientation of (100). The crystal lattice parameter of the film was af = 0,56697 nm. Studies of current-voltage characteris-tics of n-GaAs – p-(GaAs1-δBiδ)1-x-y(Ge2)x(ZnSe)y heterostructures at different …

Simulation Of Self-Heating Effect In Mosfet Based On 2d Mos2, Atabek E. Atamuratov, Xushnudbek Sh. Saparov, A Yusupov, Frank Schwierz

Scientific Bulletin. Physical and Mathematical Research

One of the main trends of today's electronics is the decreasing the sizes of MOSFET up to nanometer scale. In this connection there are two main views to the perspective of scaling. According to one of them limit of scaling is reached at sizes 10 nm order, however according to second view, still there are opportunity to decrease transistor to more lower sizes. In accordance with second approach it is suggested to continue the size scaling by modification the transistor structure or by using the new materials, particularly one or two dimensional materials. One of such suggestions is the designing …

Method Of Characteristics For Solving The Problem Of Gas Outflow From An Elementary Sec-Tion Of A Gas Pipeline, Madaminjon K. Mahkamov, S.S. Akhmadjonov, I.K. Khujaev

Scientific Bulletin. Physical and Mathematical Research

Numerous problems based on equations of hyperbolic type are solved by the method of characteristics when boundary conditions of the first, second and third kinds are set on the boundary. These include, in particular, the problems of pipeline transportation of various media. The quasi-one-dimensional equations of conservation of mass and momentum are linearized and separate equations are drawn up for a specific indicator (flow rate, gas pressure) of the process. This approach is associated with the tradition of forming boundary conditions and solving problems only with respect to a specific indicator, in particu-lar, with respect to pressure, velocity, and flow …

Electrophysical Properties Of Supercapacitor On The Basis Of New Gel Polymer Electrolyte, J.A. Shodmanov, Azamat Boymirzaev

Scientific Bulletin. Physical and Mathematical Research

The results showed a slight increase in internal resistance under the influence of bending and confirmed that the equivalent circuit model of electrons did not change under bending conditions as indicated in graphically illustrated the results by cyclic voltamperometry (TsV) at a scanning speed of 10 mV / s under the above bending angles of the SK prepared on the basis of PG 10 GPE. From ex-periments we found that the shapes are almost rec-tangular, with no redox peaks observed. We can see that the area of the TsV curves changes slightly as the bending angle increases, but this does …

Influence Of A Strong Magnetic Field On Fermi Energy Oscillations In Two-Dimensional Semiconductor Materials, Gafur Gulyamov, Ulugbek Inayatillyevich Erkaboev, Rustam Gulomzhonovich Rakhimov, Nozimjon Sayidov Sayidov, Jasurbek Mirzaev

Scientific Bulletin. Physical and Mathematical Research

This article discusses the effect of a quantizing magnetic field and temperature on Fermi energy oscillations in nanoscale semiconductor materials. A generalized mathematical expression is obtained for calculating the dependence of the Fermi energy oscillations on the magnetic field, temperature, and thickness of the quantum well. It is shown that the Fermi energy in nanoscale semiconductor materials under a quantizing magnetic field is quantized. The proposed theory explains the experimental results in two-dimensional semiconductor structures with a parabolic dispersion law.

Determination Of The Specific Thermo Emf Of Granulated Silicon Doped With Alkaline Metals., B.M. Abdurakhmanov, Zarnigor Sohibova, M.M. Adilov

Scientific Bulletin. Physical and Mathematical Research

The value of the specific thermo EMF is one of the most important thermoelectric parameters of a material and in practice is estimat-ed mainly by two well-known methods - integral and differential. To measure the thermo EMF of granular silicon, we used a differential method. In this work, the thermoelectric properties of granular silicon containing alkali metal atoms have been studied, the presence of which, for example, in single-crystal structures makes it possible to improve the characteristics of a number of devices, and in polycrystalline ones, the effect of grain boundaries on the electrical properties, in particular, to reduce the …

The State Of Solar Energy In Uzbekistan In The Framework Of The Devel-Opment Of Renewable Energy Sources, E.Z. Imamov, Ramizulla Abdullaevich Muminov, Temur Asfandiyarovich Djalalov, I.Sh. Abdullaeva

Scientific Bulletin. Physical and Mathematical Research

The paper analyzes the possibilities of renewable energy sources to become the main sources of ener-gy that can in the future replace traditional technologies for the production of thermal and electrical energy based on the use of fossil fuels and nuclear energy.

Technological approaches are considered that make it possible to significantly increase the efficiency of solar energy, and it is also shown that such a possibility can be realized by using weakly crystalline and cheap modifications of silicon, which have previously passed the corresponding nanotechnological effect.

Properties And Applications Of Metal-Oxide Thin Films In Converters Of En-Ergy (Review), Shakhriyor Kh. Yulchiev, Akramjon Boboev, Xushruybek Mahmudov

Scientific Bulletin. Physical and Mathematical Research

Metal-oxide semiconductors (SnO2, ZnO, TiO2, etc.) have a wide band gap (~3 eV) and are trans-parent in the visible range of the optical spectrum. Therefore, transparent semiconductor devices (diodes, transistors, integrated circuits, etc.) can be made based on them. There are two peaks in the emission spectrum of the LED. One of the peaks (3.3 eV), apparently, is as-sociated with exciton recombination, and the other peak is associated with recombination through a deep impuri-ty level. The emission spectrum of the LED was ob-served at a direct current of 40 mA. The electrolumines-cence spectrum obtained on the heterostructure at room temperature …

Development And Implementation Of A Photovoltaic Power Plant With A Capacity Of 3-6 Kw With “Smart Greed” Elements In The Conditions Of The Fergana Valley, Райимжон Алиев, Жамшидбек Каххоров, Авазбек Мирзаалимов, Наврузбек Мирзаалимов, Бобур Рашидов

Scientific Bulletin. Physical and Mathematical Research

Today, solar cells are manufactured at the industrial level mainly from polycrystalline and monocrystalline silicon. Solar elements made of silicon make up more than 90% of the solar elements that are produced worldwide. Depending on the seasons of the year in the Ferghana Valley, the movement of the Sun, geographical location, air humidity, temperature changes, the intensity of light falling on the surface of solar panels and other parameters, the characteristic (I-V) of solar panels was studied. The installation of solar panels installed at Andijan State University consists of the installation, commissioning and analysis of the results obtained on sunny, …

A Cauchy-Goursat Problem For A Second Kind Degenerated Equation Of Hyperbolic Type, Doniyor Usmonov

Scientific Bulletin. Physical and Mathematical Research

In the work a Cauchy-Goursta problem has been formulated and investigated for a second kind degenerated equation of hyperbolic type. During the investigation, it was used properties of Gauss’s hyper geometric function and symbol of Pochhammer, the considered problem equivalently reduced to an integral equation with respect to trace of unknown function. Properties of Riemann-Liuvill integral-differential and generalized integral-differential operators have found solution of the taken integral equation. To find solution of the problem it was used general solution of the equation. A class of generalized solutions was introduced for the correctness of the problem. It was found necessary conditions …

Evolution Of Quantum Systems Consisting Of Mul-Tiple Various Particles Interacting With General-Ized Yukasha Potential, N.N. Bogolyubov, Rasulova Mukhayo, U.O. Avazov

Scientific Bulletin. Physical and Mathematical Research

In this paper, multi-variety densely packed par-ticle dynamic systems with the ability to interact with the shielded Yukawa potential were studied. Also, in order to study more widely the dynamics of systems containing particles interacting via shielded potential, the theoretical foundations of the dynam-ics of systems consisting of an arbitrary number of bounded - sorted multi-particles are analyzed. The dynamics of an arbitrary number of interacting par-ticle systems on a screening potential was studied using the Bogolyubov-Born-Green-Kirkwood-Yvon (BBGKY) chain of quantum kinetic equations. The BBGKY chain of quantum kinetic equations has solutions for the case that characterizes the evo-lution of …

Measurement Of Geometric Fractals On The Basis Of Hausdorf-Bezikovich And Minkovsky-Buligan Measurements, Anorova Amanbaevna Shaxzoda, Jabborov Sindorovich Jamoliddin, Meliyev Fattoevich Farxod

Scientific Bulletin. Physical and Mathematical Research

This article is devoted to the study of the future position of fractal measurements. Different methods of computer modeling of a wide range of classes of fractal geometric objects are described in detail, as well as the main methods of mathematical analysis of fractal size of virtual and real fractals are described. The article explains the differences between the concept of fractals, their properties, B. Mandelbrot's tariff, Hausdorf-Bezikovich scale, Minkowski-Buligan scale, topological measurement, the concept of fractal measurement and measurement in Euclidean geometry. This article provides basic information about fractals. A detailed description of the various methods of computer modeling …