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The investigation of thermoluminescence properties ofdental ceramics
Dental ceramics taken from humans who are potentially exposed to radiation, are commonly used as retrospective dosimetry for quick and reliable dose estimations due to nuclear power plants that are close to settlement of people. Nowadays most people have a dental restoration for the compulsory health problem and aesthetic beauty. Moreover dental restorations are usually applied to the front teeth, it can be considered that the radiation directly interact with the material. Therefore, dental ceramics could be potentially used for retrospective dosimetry purposes since allows a quick and reliable dose assessment in case of nuclear accident or bad use of a nuclear attack. Therefore, dental ceramics that used in restoration of human teeth as an accident dosimetry by thermally stimulated luminescence method have been investigated in this study. Glass ceramic, lithium disilicate glass ceramic and feldspathic dental ceramic which used in this study were obtained from Vivadent ivoclar, Sweden and Turkey, respectively. The aim of the study is to investigate the thermoluminescence dose response, the effects of heating rates on the thermoluminescence characteristics, the stability of the dental ceramics with respect to the cycle of measurement and also fading properties of dental ceramics. Finally we compared the samples with respect to their TL characteristic properties to choose the most suitable dosimetric ceramic.
Tactile, embedded, audible sensation system for blind people
ABSTRACT TACTILE, EMBEDDED, AUDIBLE SENSATION SYSTEM FOR BLIND PEOPLE KARAOĞLAN, Kemal M.Sc. in Physical Engineering Supervisor: Prof. Dr. Zihni ÖZTÜRK April 2019 59 pages It is not possible for visually impaired individuals to move around without getting support from another person when they go out of their houses and perceive their surroundings. He gets help to get to where he is going in the city and in all settlements, he does not know which street, street, building or institution he is when he comes to a door or entrance, when he comes to a street. For this reason, the visually impaired individual is guiding another person, which limits the individual life opportunities of the visually impaired individual. For this purpose, dots called the sensitive line, which are developed for this purpose, are not sufficient but only allow the visually impaired person to follow a line and realize that the end of the line is at the end of the line. You can not find out where you are walking, where you will be at the end of your walk, where you end up, and where the junction is. For this reason, he needs a support or knowledge again.This thesis study examines a system that allows the visually impaired individuals to use and perceive the place to go. It consists of a cane, wireless glasses and earphone, a movable cane carried by the user, and an informative unit which can be placed on the surface, buried in the pavement walkway and used indoors and outdoors Key Words: Audible eye, Sensitive lines, Voice relief lines, Voice access, Visual impairment orientation
A study on the computerized tomographic x-Ray radiation on duration and Ramsay scale of sedation
the effect of CT
Structure, composition and corrosion studies of Zn, Cu, Sn and their alloys electrodeposited from a deep eutectic solvent
In this thesis, platinum and steel were coated with metals (Cu, Zn and Sn), binary alloys (Cu-Zn, Cu-Sn and Zn-Sn) and a triple alloy (Cu-Zn-Sn) by electrochemical method. The corrosion behaviour of these films were investigated in 3.5% NaCl solution. Chlorine chloride-ethylene glycol based ionic liquid was used for electrodeposition of metals and alloys. The plating process was carried out on platinum and steel by a three electrode system by applying constant potential. As metals/alloys were electrodeposited potentiostatically, chronoamperometric graphs of deposition were obtained. The resulting coated samples were analyzed by SEM, XRD/EDAX and optical microscope. Potentiodynamic polarization (Tafel Plot) was applied to understand the corrosion mechanism of uncoated and coated samples in 3.5% NaCl. Corrosion current of Zn is lower than the other two metals and among these three metals zinc has passivation behaviour. Corrosion behaviours of binary alloys (Cu-Zn, Cu-Sn and Zn-Sn) and ternary Cu-Zn-Sn were examined. Generally, corrosion resistivity of binary alloys on Pt is higher than that of metals on Pt. It could be said that Zn dominates corrosion current of alloys deposited from a deep eutectic solvent. Corrosion resistivity of binary alloys on steel is close to each other. Corrosion current density of binary alloys on Pt is approximately 10 times more resistive than bare steel. The polarisation curve of the ternary alloy of Corrosion resistivity of ternary alloy (Cu-Zn-Sn) on Pt is eight times greater than bare steel. Alloys could be electrodeposited on steel to prevent corrosion.
Investigation of the effects of beta rays on phosphorescent materials
The aim of this thesis is to investigate the effects of beta radiation on phosphorescent materials. Nowadays phosphorescent materials are used to get the production of more efficient beta voltaic nuclear batteries. They convert the kinetic energy of particles to fluorescence by using phosphor material and then to convert electricity via photovoltaic cell. We have researched the effects of beta particles by analyzing the parameters such as range and generation rate for different type of phosphorescent materials that are used in nuclear batteries. These parameters effectively improve the output performance and energy conversion efficiency in nuclear batteries.
Design and production of a portable solar test device to test, the characteristic values and the classification of solar panels
The electric output performance of crystalline silicon and thin film PV modules are generally measured under standard test conditions (STC), ensuring a relatively independent comparison and output evaluation of different solar PV modules. STC is an industry-wide standard to indicate the performance of PV modules and specifies a cell temperature of 25°C and an irradiance of 1000 watt/m2 with an air mass 1.5 (AM 1.5). These correspond to the irradiance and spectrum of sunlight incident on a clear day upon a sun-facing 37 degrees tilted surface with the sun at an angle of 41.81 degrees above the horizon. This condition approximately represents solar noon near the spring and autumn equinoxes in the continental United States with surface of the cell aimed directly at the sun. However, these conditions are rarely encountered in the real-world. In this study, DC voltmeter and DC ammeter has been used which has RS485 communication protocol. Open circuit voltage (Voc) , short circuit current (Isc), maximum voltage under load (Vmp) and maximum current under load (Imp) of different power solar panels have been measured after that compared with label values. Additionally, Open circuit voltage (Voc) , short circuit current (Isc), maximum voltage under load (Vmp) and maximum current under load (Imp) values have been transferred to touchable Liquid crystal display (LCD) with the aid of RS485 protocol for user benefit. With aid of this portable test device also can measure personal solar panel power as small scale project and detect defect modules of in photovoltaic farm as large project. Key Words: PV Modules, Testing Measurement and Classification System for the PV Panels
Investigation of factors influencing the efficiency of nuclear batteries
In this thesis, the conversion of the kinetic energy of beta particles emitted from a radioactive isotope to electricity is investigated by using the direct and indirect conversion methods. In the experimental part, analysis of the effects of low-activity radiation from Pm147 and Sr90 beta sources, two different phosphors and graphene on Si photovoltaic cell is performed. Phosphor layers with different mass thicknesses are prepared from ZnS:CuCl and SrAl2O4:Eu2+,Dy3+ phosphor powders. The electrical performances of direct and indirect nuclear battery models are analyzed by measuring short-circuit current and open-circuit voltage. Furthermore, the time-dependent variation of the short-circuit current during the beta irradiation is researched. The most efficient battery model is determined as Pm147/SrAl2O4:Eu2+,Dy3+/PV cell. In the theoretical part, betavoltaic battery designs are modeled using the p-n homojunctions, p-n heterojunctions, and Ni63, Pm147 beta sources by considering the parameters affecting the efficiency. A theoretical investigation of the electrical performances has been carried out on Si, GaP, GaN, GaP-Si, and GaN-Si betavoltaic batteries. In addition, the effects of doping concentration and junction depth on the maximum power are examined. The heterojunction photovoltaic cells are preferred to increase the collection efficiency and the power in the betavoltaic battery according to our calculations. By optimizing the doping concentration and junction depth, high-efficient heterojunction betavoltaic batteries are achieved.
Measurement of the inclusive production of the d*0 (2007) meson in hadronic z decays with the aleph detector at the lep collider
A measurement of the inclusive production rate of the charmed D*0 (2007) meson in hadronic Z decays is performed using data from the ALEPH detector at the LEP collider. A total of 3,239,746 hadronic events are selected from data recorded by ALEPH from the 1991 to 1995 running periods. Decays of D*0 D0pi0 are reconstructed for x_E >= 0.3 where x_E = E_D*0 / Ebeam. The average D*0 multiplicity per hadronic event is evaluated to be: =0.289 +- 0.031 +- 0.067 +- 0.009 where the first error is statistical and the second is systematic. The third error is from the extrapolation to x_E = 0. The rates and differential cross-sections are compared with Monte Carlo model predictions. The signal significance is improved explicitly by applying machine learning algorithms based on Multi Variate classification methods of artificial intelligence applications.
The investigation of the effects of velocity dependent potential in the solution of wave equation
ABSTRACT THE INVESTIGATION OF THE EFFECTS OF VELOCITY DEPENDENT POTENTIAL IN THE SOLUTION OF WAVE EQUATION BERK ATEŞ, Yıldız Ph.D in Engineering Physics Supervisor: Prof. Dr. Eser OLĞAR February 2020 88 pages In this thesis, the effect of the velocity-dependent potential is taken into consideration in order to obtain the solution of Schrödinger equation (SE) for different physical potentials. By choosing form factors as three different cases such as ε(r)=γρ_0,ε(r)=γr and ε(r)=γr^2, the velocity-dependent potential is determined and the energy eigenvalues and eigenfunction are obtained for any quantum numbers n and l. During all calculations, the well-known method Nikiforov-Uvarov (NU) method is used. It is seen that by taking γ=0, the obtained results are reduced to results of velocity-independent potential case which are in good agreement with those of in literature. The variations of energy eigenvalues are tabulated and graphed with respect to quantum numbers n and l. Key Words: Velocity-Dependent Potentials, Analytical Solution, Numerical Solution, Nikiforov-Uvarov Method.
Investigation of spectral radiance responsivity for optical systems
The aim of this thesis is establishment and determination of radiance responsivity to be used in calibrations of polychromatic radiation sources. In realizing the radiance, Ar-Ion (457, 477,488 and 514 nm), He-Ne (543, 594, 604, 612 and 632.8 nm) and Nd:YAG (532 nm,1064 nm) lasers and an integrating sphere with 15 cm diameter are used to get radiation sources having Lambertian distributions. Then silicon photodiode based trap detector which is treaceble to the liquid helium cooled laser based cryogenic radiometer is used to measure the photocurrent corresponding to each wavelength and thereby to obtain radiance. The measurement system used to have spectral current response of this laser based radiance is a double grating monochromator with 2 x 300 mm focal length and triple gratings in its each turrets. The gratings used for these measurements have 2400 g/mm and 1200 g/mm grove densities and blazed to 250 nm and 500 nm respectively. The laser beams emerged from the integrating sphere after the radiance evaluation directed on monochromator and from its exit slit the photocurrent responses record at each laser wavelengths. From the radiance realized at laser wavelengths and the photocurrent, values recorded at the exit slit of monochromator, transfer function (radiance responsivity) of the optical system is obtained. This radiance responsivity together with monochromator system is used to derive the spectral radiance of polychromatic radiation sources with low uncertainty. Moreover, in this work the uncertainty scale is determined using both classical and Monte Carlo methods.
Numerical and algebraic treatment of dynamical systems equation and soluable potentials
ABSTRACT NUMERICAL AND ALGEBRAIC TREATMENT OF DYNAMICAL SYSTEMS EQUATION AND SOLVABLE POTENTIALS EserKÖRCÜK M.Sc, Engineering Physics Department Supervisor: Assists. Prof. Dr. Ramazan KOÇ January, 2001, In this thesis, the solution of the dynamic system equations of physics have been studied by using algebraic and numerical methods. In recent times Lie algebraic techniques have been used to construct complex quasi exactly solvable potentials with real spectrum. In our study, we find the solution of the several different Schrödinger equations using the method of Lie algebra and show how the use of Lie algebra helps in simplifying the eigenvalue problem. In the present study, we begin with a specific differential realization of the SU(l,l)«SO(2,l) algebra which can be used to derive the second order differential equation. Then apply variable and similarity transformations to the group generators in order to recover the Schrödinger equations for various potentials. We also demonstrated that non-Hermition PT symmetric Hamiltonians have real eigenvalues. In addition, the two well-known non linear equations, the Heat and Lorenz equations are solved by numerical Runge Kutta 4 method and via Mathematica in physics. The effects of parameters and the initial conditions are examined. Finally, we review the topological analysis of data generated by a dynamical system operating a chaotic regime. UlKey Words: Lie Algebra, Realization of SO(2,l), PT Symmetric Hamiltonians and Dynamical System. IV
Mappings between potentials
ABSTRACT MAPPINGS BETWEEN POTENTIALS KOÇAK Mehmet M. Sc. in Engineering Physics Supervisor: Assoc. Prof. Dr. Bülent GÖNÜL September 2002, 65 pages In this work we scrutinize applications of the point canonical transformations (PCT), which have received a tot of attention in the literature recently. The method has been applied to exactly solvable central and non-central potentials together with quasi-exactly solvable potentials. The PCT technique has led to new insights in the studies of physical problems posed in this thesis. The applications allow something of a systematic approach enabling one to recognize the equivalence of superficially unrelated quantum mechanical problems. Keywords: Point Canonical Transformation, quasi-exactly solvable potentials, exactly solvable central and non-central potentials. m
Investigation of thermally stimulated luminescence characteristics of synthetic and natural quartz
Quartz is one of the most important synthetic and natural crystals used in thermally stimulated luminescence studies, shortly named thermoluminescence (TL), and TL age estimation of historical samples which include the quartz minerals. Natural quartz minerals are highly found in the crust of the earth, the historical vestiges and meteors. It exhibits a number of TL peaks when quartz is heated from room temperature to 500oC. In this work, thermally stimulated luminescence characteristics of synthetic quartz which is purchased from Aldrich Company and natural quartz extracted from ceramics of Kubad Abad palace, Beyşehir, Konya, Turkey were carried out for different aims. The first aim was to see the stabilities of TL peak intensities and kinetic parameters of synthetic and natural quartz at different annealing temperatures. The second aim was to investigate the effects of thermal treatments on the TL intensity and kinetic parameters of natural quartz. The thermoluminescence dose responses of synthetic and natural quartz after different annealing protocols and the effects of heating rates on the thermoluminescence characteristics of synthetic and natural quartz constitute the third and fourth aim of this thesis, respectively.
Development of new sensitive thermoluminescent materials for radiation dosimetry
In this work, the thermoluminescent properties of undoped, and rare earth and metallic elements doped some alkaline earth borates were studied. The following materials BaB4O7, LiB3O5, Li2B4O7, MgB4O7 and CaB4O7 were synthesized by solid state and melting methods in air condition. The X-ray diffractometer method was firstly used to characterize and identify the products and then the various metals and rare earth elements were doped to enhance the thermoluminescence (TL) sensitivity of developed materials. Some of the TL properties of developed phosphors were studied in detail. Comparative TL studies of these compounds were shown that the Ce-doped BaB4O7 and Al-doped LiB3O5 compounds have higher TL sensitivity than the others. In addition, after the investigation of TL properties of Ce-doped BaB4O7 and Al-doped LiB3O5 samples, they seem as a good promising TL detector for different dosimetric applications owing to its simple glow curve structures with high sensitivity, the absence of thermal fading even at elevated temperatures, reduced light sensitivity, re-usability with excellent reproducibility and chemical stability. Therefore, it was assumed that the obtained Ce-doped BaB4O7 and Al-doped LiB3O5 crystal are quite suitable for use in high dose measurements in medical or industrial areas. The trap parameters namely the order of kinetics (b), activation energy (E) and frequency factor (s) associated with the glow peaks of some TL samples were also obtained by computer glow curve deconvolution (CGCD) method.Keywords: Thermoluminescence, Dosimetry, Alkaline earth borates
Investigations on compositional, structural and optical properties of In2S3 films produced by spray pyrolysis method at different substrate temperatures
In this study, In2S3 films were prepared by spray pyrolysis technique and their compositional, structural, and optical properties were investigated by using different methods. The In2S3 films were obtained on glass substrates at various substrate temperatures in the range of 250-350 ºC. The compositional analysis of the chemicals was made by EDX method. The EDX results taken from an area on the film indicated that the film is composed of O, Na, and Si in small amounts, and also provided the ratio of the In (indium) to S (sulphur) on the film. The optical properties of In2S3 films were examined from optical absorption coefficient data using double beam visible spectrophotometer. The band gap energy of the In2S3 films was found to be between 2.61 eV and 2.71 eV. The crystal structure of the In2S3 film samples were studied by SEM and X-ray diffraction peaks. In addition, In2S3 films at different annealing temperature in O2 flow were transformed into In2O3 films by thermal oxidation.
SR1 atlas TRT development and test facility
The Transition Radiation Tracker (TRT) is particle tracking detector of the ATLAS Inner Detector which is designed as a robust and powerful gaseous detector that provides tracking through individual drift-tubes (straws) as well as particle identification via Transition Radiation (TR) detection. The TRT consists of 370000 straw proportional tubes of 4 mm diameter with a 30 micron anode wire, which operates with a Xe/CO2/O2 gas mixture at a high voltage of approximately 1.5 kV. This detector enters a new area that requires it to operate at unprecedented high rates and integrated particle fluxes. Full functionality of the detector over the lifetime (10 years) of the experiment is demanded.This MSc. thesis presents development, testing process and cosmic data analysis of a replica has been built in an above-ground laboratory environment in SR1 at CERN.
Properties of electrodeposited metalic systems(Schottky diodes) on semiconductor substrates
In this study, by using n-type Si substrate with (100) orientation, 150 nm thickness and 10-20 ?m resistivity and chromium doped, thin film Schottky diode system (Cr/n-Si SBHs which is electrochemically formed on n-type Si) is constructed and characterized.In the electrical characterization of this diodes, the current ?voltoge (I-V) and the capacitance ? voltage (C-V) measurements are done.The basic diode parameters such as ideality factor (n) and barrier height (?b) were consequently extracted from electrical measurements. It has been shown that the ideality factors increased and barrier heights decreased with the decreasing temperatures, on the basis of the thermionic emission (TE) theory.The homogeneity or the uniformity of the Schottky BH is an issue with important implications on the theory of Schottky barrier formation and important ramifications for the operation of Schottky barrier diodes and contacts. Thus, provided semiconductor substrate is well characterized, the homogeneous Schottky BH may be obtained even from the I-V characteristics of one contact. For this purpose ,Cr/n-type Si SBHs with a doping density of about 1.25x1015 cm-3 is prepared and the linear region with large BHs is used. The electrical characterisitics of Cr/n-type structures were investigated in the wide temperature range (80-320 K) by steps of 20 K.Key words: Silicon, Schottky barrier diodes, Electrodeposition Method.
Differential thermal analysis instrument design
In this work, thermal analysis methods are introduced and differential thermal analysis (DTA) is briefly investigated, designed and constructed. The instrument then checked with native sulphates which are CaSO^.^O, MgSO^.TE^O, MgSC^.I^O, CuSO^.Sf^O, FeSO^.Tl^O, NiSO^.TI^O and ZnSO^O. Analysis have been carried out to the temperature range of (room temperature - 350 C) and the exponential heating rate is used. The obtained DTA curves are compared with literature. As seen that, the resultant curves which are obtained as same as the available documents. The minimum detectable sample is found as 20 mg.Keywords: Thermal analysis, DTA,
Developing a computer programme for simulating the reflectance and the transmittance of N-Layered systems
This study Is the computer simulation of the method developed by F. Abeles to represent the optical multilayers as 2X2 matrices to calculate the overall reflection and transmission characteristics of an n-layered optical system for a selected wavelength region. It Is assumed that all layers are made of non-absorbing, plane-parallel sided dielectrics. The number of layers are unlimited. The programme Is developed in Fortran 77 language and performed on an IBM compatible PC. The results are represented In graphical form showing the variation of reflectance with wavelength.Key Words: Optical Coatings, Reflectance, Transmittance, Computer Programme
The Determination sensitizing centers and band gap of the photoconductive materials
ÖZET FOTOILETKEN MALZEMELERİN HASSASLAŞTIRMA MERKEZLERİNİN VE BAND ARALIKLARININ HESAPLANMASI YAZICI Ahmet Necmeddin Yüksek Lisans Tezi, Fizik Mühendisliği Bölümü Tez Yöneticisi: Doç. Dr. Ata SELÇUK Şubat 1993, 96 sayfa Bu çalışmada, yüksek vakuum ve yüksek sxcaklik koşullarında Selenyum (Se) tozları Klor (Cl) tozları ile karıştırılıp Selenyum fotoiletkeni geliştirildi. Aynı şartlar altında Çinkosülfür (ZnS) ve Çinkoklörür (ZnCİ) tozları karıştırılıp Çinkosülfür fotoiletkeni yapıldı. Geliştirilen fotoiletkenler İşığa karşı oldukça hassastırlar. Bu fotoiletkenlerdeki hassaslaştirma merkezlerinin yoğunluğu Kapasitör-Voltaj (C-V) ve sinırlandırılmiş boşluk yükleri methodları kullanılarak bulundu. Se ve ZnS'nin yasak bölgesindeki hassaslaştirma merkezlerinin enerji seviyeleri dalgaboyu ile f otoiletkenlik uyarımının değişmesi methodu kullanılarak elde edildi. Hassaslaştirma merkezlerinin yoğunluğu ışık yoğunluğu ile düzgün değiştiği görüldü; Se ve ZnS fotoiletkenlerinin band enerji değerlerinin teorik değerleri ile çok iyi uyum içinde olduğu bulundu. Anahtar Kelimeler: Birleşme merkezleri II, Hassaslaştirma merkezleri, Fotohassaslık, Se, ZnS iv
Design and fabrication of mos solar cells
ABSTRACT DESIGN AND FABRICATION OF MOS SOLAR CELLS TÜTÜNCÜLER, Hayriye M. S in Physics Engineering Supervisor: Assoc. Prof.Dr. M. Sadettin ÖZYAZICI February 1994, 81 pages In this thesis, effects of insulating (oxide) layer on Schottky barrier (metal -semiconductor contact) has been investigated. To make this investigation more specific minority carrier metal -oxide-semiconductor (MOS) solar cells were designed and fabricated in the form of Al-oxide-p-type silicon crystal. Resistivity of samples were measured before fabricating MOS solar cells. Aluminum coating was made by Vacuum Coater System with Diffusion Pumping System. To maximize the efficiency of the MOS solar cell, the open circuit photovoltage, short circuit photocurrent and the fill factor must be as high as possible when the total incident light energy is kept constant. But these factors depend on the same parameters and related to each other. When one parameter is increasing as a function of certain parameter, the others may be decreasing. Therefore, straightforward maximization of efficiency is not possible. To see the effects of insulating layer thickness on the short circuit current, different oxidation techniques were used. After device fabrication was completed I-V and C-V iiicharacteristics of solar cells have been measured. Open circuit voltage(VQC) and short circuit current (Iscj which affect the conversion efficiency have been determined. Experimental results showed that presence of positive charges in oxide layer enhance the Voc as indicated by the increase in barrier height. High barrier height decreases the dark current altering the I-V characteristics in the dark. Efficiencies of MOS solar cells were calculated as 7.3 %. This value is low as compared to published results. The reasons of getting low conversion efficiencies have been also discussed. Key words: MIS/MOS solar cells, photocurrent, photovoltage, efficiency. IV
Methods for solution of Schrödinger equation with position dependent mass (PDM)
In this study, construction of PDM Schrödinger equation has been examined starting from the kinetic energy operator approximations. In addition to this, the role and improvement of the Schrödinger type equations? solutions have been discussed.Some of the most common methods used in order to solve Schrödinger type equations have been explained by using important articles. The potentials and the mass functions used have been emphasized. Also, the opportunity of comparing the studies have been given.To solve PDM Schrödinger equation which has been transformed in the form of the constant mass Schrödinger equation by changing coordinate and wave function is discussed for physical acceptability. Although it was expected to have different results from both of the experiments, the same eigenvalues have been found. This situation caused the improvement of a new method without transformation. The method improved by modifying Taylor Expansion Method is called Asymptotic Taylor Expansion Method.PDM Schrödinger equation has been solved by using Asymptotic Taylor Expansion Method for harmonic oscillator potentials. Asymptotic analyze has been done for four different Hamitonians and highly accurate energy eigenvalues and wavefunctions have been obtained. As a result of this, Asymptotic Taylor Expansion Method has been proved very useful to determine energy eigenvalues and wavefunctions in Schrödinger type equations.
Determination of trapping parameters from thermoluminescence glow curves by computer glow curve deconvolution method
In the given study, the synthetic glow curves were numerically obtained by directly solving the differential equations of thermoluminescence (TL) process without the use of approximating functions that have no physical meaning after different heating rates. The synthetic glow curves include a single TL glow peak. All of the simulated glow curves were analyzed by a glow curve deconvolution (fitting) program. The results of curve fitting program were compared with the input values to obtaining whether it reflects correct values of them or not. It was observed that the agreements between input parameters and results of curve fitting program are very good when the input parameters were chosen as very close to the first-order (An<
Phase-equivalent supersymmetric deep and shallow potentials
ABSTRACT PHASE-EQUIVALENT SUPERSYMMETRIC DEEP AND SHALLOW POTENTIALS ÖZER Okan M. Sc. in Physics Engineering Supervisor: Assoc. Prof. Dr Bülent GÖNÜL July 1999, 80 pages In this work we review theoretical formulation of the Supersymmetric Quantum Mechanics, which has received a lot of attention in the literature recently, and apply it to the determination of a shallow potential which is phase-equivalent to a deep potential, whose bound spectrum is identical except for the ground state which is suppressed. With this method, the non-physical Pauli forbidden bound states encountered in the spectrum of any potential can be eliminated, preserving the phase shift. The present approach is exact and provides differential relations between the wavefunctions of the two types of potentials. The method is applied to the a+a scattering, the deuteron and 11Be systems. We show that the deep potentials involving unphysical bound states and its supersymmetric, shallow, phase-equivalent partner excluding Pauli forbidden states give very similar physical quantities, although the corresponding eigenstates differ iiiin the node-number. This lends support to two nearly equivalent treatments of the Pauli principle. The supersymmetry aspect of nuclear interactions in the light of the calculation results obtained is discussed. Keywords : Supersymmetric Quantum Mechanics, Phase-Equivalent Potentials. IV
Effects of growth orientation on the properties of strained semiconductor quantum well lasers
ABSTRACT \ EFFECTS OF GROWTH ORIENTATION ON THE PROPERTIES OF STRAINED SEMICONDUCTOR QUANTUM WELL LASERS ODUNCUOGLU Murat M. Sc in Physics Engineering Supervisor: Assoc. Prof. Dr Beşire GÖNÜL January 2000, 77 Pages The work described in this thesis investigates how strain and crystal orientation affect the band structure of quantum well lasers. The study provides a better understanding of the dependence of effective mass, strain-induced band-edge shift, change in the band-gaps and emission wavelengths on the substrate orientation. A detailed calculation of the confined states considering the effects of well width, substrate orientation, piezoelectric field, band-offsets, transition strengths of allowed and forbidden transitions was carried out. The lack of inversion symmetry in polar, zinc-blende crystals when grown on axes other than (001) leads to the formation of internal piezoelectric fields when such structures are strained. The built-in electric field modifies the electronic uistructure and optical properties of the crystal. Recently, it has been suggested that piezoelectric quantum well lasers operated under forward bias could be used in an integrated laser. Design of such devices requires a knowledge of the behaviour of the quantum well structure as a function of carrier and current densities. It has been shown previously that maximum gain reduces with increasing piezoelectric field. We explain the reductions of maximum gain in the presence of internal piezoelectric fields considering the overlaps between envelope functions of the confined states. Keywords: Quantum wells, growth orientation, strain, critical thickness, optical gain IV
Investigation of electronic structure and vibrational spectrum of C60 and its various compounds
ABSTRACT INVESTIGATION OF THE ELECTRONIC STRUCTURE AND VIBRATIONAL SPECTRUM OF C60 AND ITS VARIOUS COMPOUNDS TÜTÜNCÜLER, Hayriye Ph.D. in E.P., University of Gaziantep Supervisor: Asst. Prof. Dr. Ramazan Koç August 2000, 113 Pages In this thesis three main properties of Coo molecule are investigated. These are electronic energy levels, normal modes of vibrations, and Jahn-Teller (JT) effect due to electron-vibron interaction for the ionised Coo molecule. The electronic energy levels have been computed by using Hiickel method as a function of bond strength between the atoms in the molecule. The effect of bond strength is investigated and it is seen that the result is satisfactory for all icosahedral complexes. In order to simplify Hiickel matrices, the projection operators and molecular orbitals of icosahedral structure are constructed Vibrational modes of Coo molecule were found by using the force constant model. This model includes bending force constants in addition to the bond stretching force constants and the interaction between the nearest ten neighbour atoms is taken into consideration to get accurate results. The H®(2h©g) Jahn-Teller problem is investigated analytically by developing a new method. It is checked that the method is applicable to all JT problems. The JT problem is then solved by breaking symmetries of icosahedral group into its mmaximal little groups. It is seen that the energy surfaces are located trigonal (D3) or pentagonal (D5) symmetry depending on the coupling strength constant. Several computer programs are developed to calculate electronic energy levels and to solve JT problems. Keywords: Fullerenes, C60, normal modes, Hiickel method, electronic energy level, symmetry breaking, JT effect. IV
Particle identification with the ATLAS TRT
This study compares three methods for the analysis electron-pion separation using the Transition Radiation Tracker in the ATLASIn this study, the dalitz decay channel of neutral pion is selected using electron identification based on a simplified simulation of the TRT response to electrons and pions. A study of alternative treatments of high threshold information is performed to determine the most optimal approach to particle ID using the TRT detector. A chi approach is found to give the best signal significance in this decay channel.Key Words: transition radiation, transition radiation tracker, particle identification, e/? separation, the high-threshold, the low-threshold, LHC, ATLAS.
An Algebraic approach to the band structure of periodic potentials
ABSTRACT AN ALGEBRAIC APPROACH TO THE BAND STRUCTURE OF PERIODIC POTENTIALS OL?AR, Eser M.Sc, Engineering Physics Department Supervisor: Assists. Prof. Dr. Ramazan KOÇ January 2002, 63 pages A general method based on Lie algebra with three generators is proposed in order to successfully produce physically significant periodic potentials. Some potentials in one dimension are solved in algebraic framework using the Lie algebra. A novel Kronig-Penney model is developed to obtain energy band structure of Kronig-Penney type and Hyperbolic periodic potentials. Our approach can be applied to the other periodic systems with some modifications. In addition, generalized Kronig-Penney model is formulated in one dimension for contact interactions. Here, eigenvalue equations are obtained by using transfer matrix formalism. It has been shown that the method given in this thesis is useful to generate periodic quasi-exactly solvable potentials and to clarify their band structure. The algebraic method presented here leads to a number of physical potentials given in the literature. TC YÛKSEKÖÖRTTIM KDB0UT DOKÜMANTASYON Key words: Periodic potentials, Kronig-Penney model, contact interaction, Lie algebra. m
Theoretical investigation of strain-compensated laser structures
ABSTRACT THEORETICAL INVESTIGATION OF STRAIN- COMPENSATED LASER STRUCTURES TOKTAMŞ, Hüseyin M.Sc, Engineering Physics Department Supervisor: Assoc. Prof Dr. Beşire GÖNÜL September 2002, 79 Pages The work described in this thesis is a theoretical investigation of the effect of strain compensation optical confinement factor, conduction- and valence- band offsets, allowed energy levels, transparency and threshold carrier density, peak gain and band line-ups. Different concepts for achieving strain-compensated quantum well structures emitting around 1.3 urn have been investigated. The study provides a better understanding of strain-compensated structures. The modeling of strain-compensated laser structures require a knowledge of the behavior of this novel structure in terms of gain characteristics. The work carried out in this thesis indicate that strain compensated compression active layers show better device performance compared to the strain compensated tension active layers. Key words: strain-compensated structures, compression, tension, optical confinement factor, optical gain. m
Band-offset ratio calculations of nitrogen containing III-V quantum wells
2fc^, ABSTRACT BAND-OFFSET RATIO CALCULATIONS OF NITROGEN CONTAINING III-V QUANTUM WELLS KOÇAK, Fatma M. Sc, Engineering Physics Department Supervisor: Assoc. Prof. Dr. Beşire GÖNÜL September 2003, 58 Pages A comparative study of the band-offset ratio of the three competing laser materials, namely InGaAsP-InP, AlGalnAs-InP, and GalnNAs-GaAs has been undertaken. Our theoretical study shows that model solid theory can be used to calculate the band offset ratios of the GalnNAs-GaAs for small nitrogen concentration including the effect of strain and modifications in conduction band but neglecting the direct effect of nitrogen. We have calculated that the alternative AlGalnAs and GalnNAs laser systems have substantially better band alignment than the commonly used InGaAsP. Strain compensation brings further benefits to that of the three competing laser systems. Therefore, high temperature operation has been anticipated in these alternative material systems with strain compensated barriers due to better electron and hole confinement as a result of the increased band offset and a more favourable band offset ratio. Our theoretical calculations indicate a significant increase in conduction band offset ratio and a decrease in valence band offset ratio with the introduction of nitrogen to InGaAs. This result highlights the intrinsic superiority of the N-based laser system. Keywords: III-V Semiconductors, Nitrides, Quantum Well Lasers, Band-offset ratios, Band alignments. iii
Supersymmetric quantum mechanics and its applications in physics
Ill ABSTRACT SUPERSYMMETRIC QUANTUM MECHANICS AND ITS APPLICATIONS IN PHYSICS ÖZER, Okan Ph. D in Engineering Physics Supervisor: Prof. Dr Bülent GÖNÜL June 2003, 95 pages Theoretical formulation of the supersymmetric quantum mechanics is re viewed and its applications to some physical problems are studied. The super- symmetric quantum mechanics (SUSYQM) is based on the factorization of the Schrödinger equation, leading to generalized operators and partner potentials. The Hamiltonian hierarchy and the factorization in the method are briefly dis cussed. It is also combined with the perturbation theory which is used for the systems that are not exactly solvable. The method is applied to the Hulthen po tential and an expression for the energy levels which gives satisfactory values for the non-zero angular momentum states of the potential is obtained. It is shown that a very general connection can be established between a class of singular potentials in iV-dimensional space through the application of a suitable transfor mation by SUSYQM. Using this way, a connection between screened Coulomb and anharmonic oscillator potentials is obtained. A general mapping procedure is described for the transformation of a differential equation with a position- dependent mass to the Shrödinger equation with a constant mass under canoni cal transformations. In the frame of SUSYQM, it is shown that the Schrödinger equation in its new form may have solutions if the original potential is solvable and shape-invariant one. Finally, It is demonstrated how the SUSYQM method can also be employed for the construction of n-parameter family of potentials which possess localized positive energy state(s) in the continuum. Key words: Supersymmetric Quantum Mechanics, Shape invariant potentials, Hamiltonian hierarchy, Supersymmetric perturbation theory, Hulthen potential, iV-dimensional space, Position-dependent mass, Bound states in continuum.
Construction of Klein-Gordon equation (KG) with position dependent mass and application to the physical systems
In this study, Klein-Gordon equation with position dependent mass is formulated via Einstein?s theory of relativity. The relation between scalar and vector potentials is defined as S(x)=(ß-1)V(x) in order to be solved in the bound state solutions. Asymptotic iteration method, one of the most common methods to solve Klein-Gordon type equations, is chosen and explained.The solutions of the equations are analyzed for both position-dependent and constant mass situations and their eigenvalues and eigenfunctions are derived. Before the solution of Klein-Gordon equations with position-dependent mass, the validity of asymptotic iteration method for Klein-Gordon equation with constant mass is examined. The spectrums are obtained by applying the method to Morse potential, Harmonic oscillator potential and Kratzer potential for the Klein-Gordon equation with constant mass, and applied to Kratzer potential and exponential potentials for Klein-Gordon equation with position-dependent mass.Key Words: Position dependent mass Klein-Gordon equation, eigenvalue, eigenfunction, asymptotic iteration method, scalar potential, vector potential.
GaInNAs/GaAs uzun dalgaboylu kuantum kuyu lazerlerin teorik olarak incelemmesi
İİİ Abstract A THEORETICAL ANALYSIS OF GalnNAs/GaAs QUANTUM WELLS FOR LONG WAVELENGTH EMISSION ODUNCUO?LU, Murat Ph. D in Engineering Physics Supervisor: Assoc. Prof. Dr Beşire GÖNÜL July 2004, 136 pages III-N-V alloys of Gaı-xInxNyAsı-y display unusual physical properties compared to that of the conventional III-V semiconductors. While conventional semiconductors have a tendency of increasing bandgap energy with decreasing lattice constant, III-N-V exhibit quite different behaviour, an increase of N con centration causes a monotonic decrease of the bandgap, instead of an increase, towards that of cubic GaN. The work carried out in this thesis reveals that doping and pressure can cause the III-N-V systems having additional unusual properties compared to that of the III-V systems. The theoretical calculations have shown that the effective mass of the elec tron increases with nitrogen concentration. This behaviour is opposite to the conventional semiconductors. We have seen that the addition of nitrogen into InGaAs leads the GalnNAs system having a band alignment of that of the ideal case (deep conduction wells and shallow valence wells). Therefore, the use of GalnNAs as an active layer causes better carrier confinement and hence reduces the carrier leakage at high temperatures. We have presented model calculations to analyze the pressure dependence of band structure, effective mass, optical confinement factor, peak gain and the differential gain. These calculations have shown that although transparency car rier density increases with pressure, the threshold carrier density, can decrease due to the increased optical confinement factor. The loss mechanism in a semi conductor laser are strongly wavelength dependent and pressure can vary the bandgap. Therefore, we have used the pressure dependence of the above laser parameters to investigate the loss mechanism for a typical three competing laserIV devices emitting in the neighborhood of 1.3 /J,m. The variation of pressure de pendence of laser parameters indicates that aluminium and nitride based laser systems are superior to that of the phosphide based laser system and offers the Al- and N-based laser systems as ideal candidates for low threshold and high speed applications, respectively. We have found that the estimated variation of phonon-assisted Auger rates with pressure in N-based system has a slower de crease than that of the other two laser systems. The threshold carrier density nth in N-based system increases with pressure whereas it decreases in Al- and P-based laser systems. This opposite variation change the overall behaviour of the threshold current in these three competing laser systems. Our theoretical calculations indicate- a significant increase of the radiative to non-radiative re combination current in N-based laser system. This result highlights the intrinsic superiority of the N-based laser system. We have presented calculations which shows that doping has a reverse ef fect on gain characteristic of GalnNAs/GaAs laser system than that of the N-free corresponding laser system. So we have concluded, for the first time, that this is another unusual physical property of nitrogen containing alloys due to the nitrogen-induced modified conduction band. We have also shown that the gain characteristics of GalnNAs/GaAs laser system can be significantly improved by means of doping following the route of the high indium and low nitrogen con centration. We have seen that the optimal route of 1.3 fj,m wavelength GalnNAs would be the choice of the higher indium instead of the higher nitrogen due to the better matching of the effective masses, favorable band alignment, smaller trans parency carrier density, higher peak and differential gain and lower spontaneous emission factor. An accurate material gain calculation is a necessary ingredient for a full characterization of III-V and III-N-V laser systems. Material gain calculations, generally ignores the Coulomb interaction between electrons and holes. We have determined that the neglect of the Coulombic attraction between electrons and holes is an overestimation, since the linear gain is enhanced at least three orders of the magnitude when these interactions are taken into account. The optimization of III-N-V quantum well active layer for improved de vice performance requires a clear understanding of exciton behavior in quantum wells. An enhancement of the ground state heavy hole exciton have been calcu lated in Gaı-xInxNyAsı-.y / GaAs compared to that of the InxGai-xAs/GaAs. Moreover, we have seen that the binding energy of the exciton increases with increasing nitrogen concentration. The close examination of the In/N ratio de pendence of the band offsets and reduced exciton mass revealed the fact that low In / high N route must be chosen to get higher exciton binding energies in 1.3 /im laser systems. We have also compared the P-based laser seems as an ideal laser system due to the enhanced exciton binding energies. N-based lasers have intermediate binding energy values and Al- based lasers seem the worst one. Key words: GalnNAs/GaAs, nitrides, band anti-crossing model, pressure, bandgap renormalization, band offsets, exciton binding energy, gain, doping.
Sentetik kuvars ve CaSO4:Dy (TLD-900) kristallerinin dozimetrik ve termoluminesans özelliklerinin incelenmesi
ABSTRACT INVESTIGATION OF DOSIMETRIC AND THERMOLUMINESCENCE PROPERTIES OF CaS04:Dy (TLD-900) AND SYNTHETIC QUARTZ CRYSTALS KAFADAR Emir Vural M. SC, in P.E. University of Gaziantep Supervisor: Assoc.Prof. Dr. Zihni ÖZTÜRK July 2004, 53 pages The additive dose (AD), Tm(E^-Tstop, repeated initial rise (RIR), variable heating rate (VHR) and computerized glow curve deconvolution (CGCD) methods were used to determine the number of peaks and kinetic parameters (kinetic orders b, activation energy E& and attempt-to-escape frequency s) associated with the TL glow peaks in unannealed acid purified synthetic quartz (APSQ) produced by the Fluka company after beta-irradiation between the dose level 0.02 Gy and 2.5 kGy. The Ea- Tstop and CGCD methods were indicated that the glow curve of this material is the superposition of at least seven first-order components, which were referred to as Pl- P7, in the temperature range between room temperature and 500 °C. The results have indicated that kinetic parameters vary fairly from method to method. The dose responses and fading process, which are very useful in radiation dosimetry and archeological dating, of individual TL peaks of this material were also examined. The dose responses of all peaks have similar pattern, first they follow strong linearity and then saturate at different dose levels. The peaks 1 and 2 were completely mdisappeared after one month storage in the dark room at room temperature. On the other hand, the intensity of peak 3 was reduced to 27% of its original value whereas the other peaks (P4-P7) were not sufficiently affected during this period. Additionaly, the glow curve structure of CaSC>4 was studied by AD method and it was observed that its glow curve is the superposition of six firs order glow peaks. Keywords: thermoluminescence, thermoluminescent dosimetry, TLD, kinetic parameters, trapping parameters, CaSO^Dy, APSQ, TLD- 900. IV
Algebraic solution of the hamiltonians of the two level quantum optical systems
In this thesis an algebraic method is developed for solution of two-levelquantum optical problems based on su(2) and su(1; 1) Lie algebras. The methodprovides a general framework within which many related problems can similarlybe solved. We concentrate our attention to the solution of the Jaynes-CummingsHamiltonian, as well as other quantum optical Hamiltonians. It is shown thatthe solution of quantum optical problems can be reduced to a homogenousordinary di¤erential equation. Our systematic approach reproduces a numberof earlier results and also leads to some novelties. Most of the quantum opticalHamiltonians possess hidden group structure based on su(2) or su(1; 1) algebraand they can be treated in the framework of the quasi-exactly solvable problems.Furthermore construction of the quantum optical Hamiltonians using â¦nite-group invariance is discussed. Generalization of the method to the variousquantum physics problems is indicated.Key words: Exactly solvable systems, Lie algebraic methods, Quantumoptical systems1
Magnetoresistance effect CuAgCo allo films
The electrodeposition technique was employed to grow magnetic CuAgCosystems. The deposition was performed on Al substrate using a computer controlledpotensiostat/galvanostat. Three types of CuAgCo films were grown by varying i) Cocontent in bath, ii) the bath pH and iii) the deposition current density. Compositionalanalyses indicate that all our films are mainly composed of Cu and Co elements. Theamount of silver component in each system was at most 1%. The amount of Agcomponent in any film did not increase even when Co and Cu contents in bath werevaried, and the magnitude of Ag component persisted around 1% in all the filmsgrown in this study. SEM studies show that the CuAgCo films have granular nature.The magnitude of the MR value in our films varied between 0.3% and 1% forthe films of the Co variation from 25g/l to 50g/l, between 0.5% and 0.9% for thefilms of the pH variation of 5.2 to 6 and between 0.3% and 0.8% for the films of thecurrent variation between 2.5 and 4.5 mA/cm2. In the longitudinal and transverse MRmeasurements generally an isotropic behavior was detected. Although the isotropicbehavior mainly indicates the GMR presence, a small anisotropic magnetoresistance(AMR) component was also detected in some of the films. The presence of AMRmay be attributed to the coalescence of Co grains under the certain preparationconditions: Above certain threshold limits of the amount of Co component in bath,the pH value and the deposition current density, the connection of the magneticgrains may be formed. Above the 32% Co content in the film and above the bath pHvalue of 5.6, a decrease in MR effect and the presence of anisotropic MR effect werevidetected while below these values of the Co content and pH, the CuAgCo films showisotropic and increasing MR effect with increasing Co content and pH. An irregularvariation of the MR effect was seen in the current variation films. From the MRcurves it may therefore be deduced that below the 32% Co content and below the pHvalue of 5.6, the magnetic Co entities in our films form superparamagnetic grainswhereas the Co grains may be connected to each other to form ferromagneticallycoupled grains in these films with the Co content higher than 32% and in the filmswith the pH value higher than 5.6 which results in the creation of AMR.In the analysis of our superparamagnetic CuAgCo films which have Co contentless than 32% or were prepared with a pH value less than 5.6, the assumption of thesuperparamagnetic behavior of small magnetic Co grains was employed. From thisanalysis, the average magnitude of Co grain was obtained to be between 9 Ã and10Ã . Any correlation between the surface to volume ratio of Co grains and thehighest MR at 10kOe was not detected but a linear increase in the MR value at10kOe with the increasing Co grain concentration was found in the CuAgCo films ofCo and pH variations.Keywords: Giant magnetoresistance, Electrodeposition, CuAgCo Thin Filmsvii
Photovoltaic power generation for polycrystalline solar cells and turning sunlight into electricity
This thesis is an overview of photovoltaic (PV) power generation in order toprovide the reader with a general understanding of photovoltaic power generation and howPV technology can be practically applied. We provide a review of the history, the presentstatus and possible future developments of photovoltaic materials for terrestrialapplications. We were investigated the analysis of the system performance, evaluation ofthe system efficiency and power output, taking into account the weather conditions. Fromour work , we can conclude that a photovoltaic system should be applied, not just forgenerating electricity, but also for improving general aspects including the use of thermalenergy behind the panel during the summer, daylight provision inside the room, shadeprovision for the interior of the building during the winter, and aesthetical contribution tothe interior view and exterior of the building.Keywords: solar cell, photovoltaic, solar panel3
Investigation of variations in collection efficiency of photovoltaic panels
This thesis reviews recent progress in solar cell research and development.Moreover it also explains the concepts and engineering related with solar electricalgenerators or the photovoltaics cells and panels. And also it is investigated that theperformance of a photovoltaic (PV) panel is affected by its orientation and its tiltangle. This is because both of these parameters change the amount of solar energyreceived by the surface of the PV panel. A mathematical model was used to estimatethe total solar radiation on the tilted PV surface, and to determine optimum tilt anglesfor PV panels installed in Gaziantep, Adiyaman, Diyarbakir, Mardin, Siirt andSanliurfa. This study determined that the monthly optimum tilt angle for a PV panelchanges throughout the year with its minimum value as 120 in June and maximumvalue as 600 in December.iii
Comprehensive treatments for Schrödinger equations involving constant and non-constant masses
The concept of the elegant work introduced by Lévai in Ref. [21] is extended for the solutions of the Schrödinger equation with more realistic other potentials used in different disciplines of physics within the constant mass consideration. The connection between the present model and the other alternative algebraic technique [32] in the literature is discussed in detail. Extending the point canonical transformation approach introduced in this thesis in a manner distinct from the previous ones, we also propose a unified approach of generating potentials of all classes having non-constant masses.
Investigation of dosimetric properties and kinetic parameters of cu and pr doped Sr2P2O7
In this study; the TL dosimetric properties and kinetic parameters of Cu and Pr-doped Sr2P2O7 were investigated. The investigations on pure Sr2P2O7 were indicated that it has one glow peak around 100 0C. On the other hand, it was observed that the Cu and Pr doped Sr2P2O7 has two glow peaks around 100 0C and 200 0C. The detail dosimetric studies of glow peak around 200 0C were shown that this material can be one of the promising TLD material for dosimetric applications, i.e., personal dosimeter. The kinetic parameters of Sr2P2O7:Cu,Pr were analyzed by different methods such as additive dose (AD), TM -TS, repeteated initial rise (RIR), peak shape(PS) and computer glow curve deconvolution (CGCD). The additive dose technique was indicated that the kinetic orders of glow peaks of this sample were described with first-order kinetics. But the other methods were indicated that they have general-order kinetics. The results were shown that there is no good agreement and consensus between the kinetic parameters by various techniques due the variation in the emission spectrum of this sample with temperature, self-absorption and thermal quenching.
A comparison of multi-variate probability density estimate methods in neutral pion discrimination
A number of multi-variate PDE (Probability Density Estimator)methodsare compared for the discrimination of signal from background in the selection ofneutral pion candidates reconstructed at the ALEPH experiment at CERN. Inthis case-study, the question ?which method is the best choice?? reveals that theanswer depends strongly on the size of the data set used to train and optimisethe method, and the required simplicity of the algorithm.
Differential realizations of the various Lie superalgebra and their applications to the physical problems
Lie algebras have been studied for many years and their roles in solving quantumechanical problems are well known. In particular, exactly and quasi-exactly solvable quantumechanical problems are classifed according to their Lie algebraic properties. They provide thelgebraic basis for a unified language for physics and mathematics which offers many advantagesover current techniques. In this thesis, the solutions of the quantum optical problems in theframework of the Lie algebraic technique have been mainly studied and this work consists ofthree parts.One of the principle aims of this thesis is the development of a number of new algebraictechniques which serve to broaden the field of applicability of Lie (super) algebra. The spectra ofthe many quantum optical Hamiltonians have been obtained by introducing a novel similaritytransformation technique which transforms the multi-boson systems in the form of the singleboson systems. This transformation leads to the determination of the solvability of the associatedHamiltonian.The other contention of this thesis is that systems of the spin ½ particles can be solved byreformulating the Hamiltonians. To support this contention a diagonalization method isdeveloped. In the solution of a general Hamiltonian for spin ½ particles, it is argued that thediagonalization method is easily applicable to solve a wide range of quantum mechanicalproblems and it provides many new insights.Both methods have been applied to the solution of the quantum optical Hamiltonians aswell as the solution of the Dirac equation. In this context second harmonic generation problem,interacting electrons in a quantum dot, Jaynes-Cumings model, quantum dot including spin-orbitcoupling and Dirac equation have been solved. It has been shown that these physical systemsassociated with the algebras of the groups SU(2), SU(1,1), OSP(2,1) and OSP(2,2).This thesis also includes the solution of Eckart potential in the s-wave Klein-Gordonequation by using super-symmetric quantum mechanical method.The ultimate goal of the methods developed in this thesis is that they can be extended tosolve the other physical Hamiltonians which include multi-boson or multi-fermion-bosonsystems.Key words: Lie (super)algebra, (Quasi)exactly solvable potentials, Dirac equation, Klein-GordonEquation
Neural networks in pi_o discrimination
In this study the basics of artiï¬cial neural networks are investigated and aneural network is employed in the discrimination of signal from background forpion candidates from the ALEPH experiment. The performance of the neuralnetwork is found to compare well with that of a standard and a PDE method.
Applications of a new approach to bound-states
Recently developed approach for the treatment of Schrödinger equations isapplied to anharmonic oscillator and Yukawa type potentials to have reliableexpressions for their bound state energies and eigenfunctions. In addition, weshow that the present novel formalism is entirely equivalent to a well knownalternative model in the literature.Keywords: Anharmonic Oscillator, Yukawa Potential, Perturbation, Exactlysolvable potentials
Exploration of quasi exactly solvable matrix models for Jahn Teller systems
Lie algebras play important role for solving the quantum mechanical problems. Exactly and quasi exactly solvable (QES) systems can be classified using algebraic approachs in which the Hamiltonians are expressed in terms of the generators of the Lie algebra. In this thesis, quasi exact solvability of some Jahn Teller (JT) Hamiltonians and quantum mechanical potentials have been discussed in the framework of the Lie algebra. This work includes two main parts. In the first part, QES quantum mechanical potentials whose eigenstates and eigenfunctions have been obtained in terms of the orthogonal polynomials and these potentials have been obtained from each other by a proper transformation. The second part covers the solutions of the E ⊗ ² and T ⊗ t JT Hamiltonians. It is well known that JT effect (electron vibron coupling) is important phenomenon in high symmetry systems for understanding the structure and dynamics of molecules and solids. The quasi exact solution of the E ⊗ ² JT Hamiltonian has been obtained in the context of the osp(2,2) Lie super algebra.This Hamiltonian has been reduced in the form of one variable differential equations by introducing a similarity transformation technique. The T ⊗t JT Hamiltonian has been solved using the rotating wave approximation method which is based on Lie type transformation and simplifies the mathematical complexity of the JT problems. Its eigenvalues and associated eigenfunctions have been obtained in a closed form when the coupling constant is smaller than the natural frequency of the oscillator. The applicability of this method is firstly demostrated for a simple system known as Jaynes Cumming (JC) Hamiltonian in the literature. These methods can also be extended to solve the other JT Hamiltonians which includes multi boson or multi boson-fermion systems. Key words: Jahn Teller Effect, Lie (super)algebra, Quasi-exact solvability
Investigation of the band alignment of long wavelength InGa(N)As(Sb) quantum wells on GaAs and InP substrates
The aim of this thesis work is to investigate the band alignment configuration of InGa(N)As(Sb) and its related alloys on common substrates of GaAs and InP. We employed the Model Solid theory to obtain the band offsets. This work also aims to compare our calculated results with those of the conventional laser structures. By means of using different barriers we try to find the ideal band alignment configuration for InGa(N)As(Sb) quantum well lasers and offer the best material system suitable for long wavelength emission.
Z0 Bozonu'nun hadronik bozunumunda ?±(770) mezonu ölçümü
The inclusive production rate of the charged vector meson ±(770) in hadronic Z decays is measured with the ALEPH detector at the LEP collider. A total of 3,239,746 hadronic events are selected from data recorded by ALEPH from the 1991 to 1995 running periods. Decays of ± 0 + ± are reconstructed for xE > 0.05 and xp > 0.05 where xE = E/Ebeam and xp = p/pbeam. The ± multiplicity per hadronic event is evaluated to be: = 2.59 ± 0.03 ± 0.15 ± 0.04 where the first error is statistical and the second systematic. The third error is from the extrapolation to the xp = xE =0. The rates and differential cross-section are compared with Monte Carlo model predictions and OPAL measurements. Key words: ± meson production, ALEPH, LEP, hadronic Z decays
Identification of irradiated food by thermoluminescence method
The purpose of this study is to give general and technical information about food irradiation and the detection of irradiated food by thermoluminescence technique (TL). Two types of dried legumes were used to identify the irradiated and unirradiated foods by TL technique. These spices are corn and chickpea which were packed in polyethylene bags and irradiated using a 60Co source with dose of 1, 4, 8, 10 kGy, respectively, with a dose rate of ?1kGy/h. The TL method requires that the inorganic components be separated from the samples. Separation of the organic and inorganic phases was made by using a chemical method. Then, the samples were dried and stored at room temperature in dark region. TL measurement was carried out using a TL reader at a heating rate 1 0C/sec between room temperature and 4000C. The light emission was recorded in a temperature-dependent mode as a glow curve and was measured in units of nano coulombs (nC). It was observed that the extracted samples from both legumes exhibit good TL Intensity and the TL intensity of glow curves of them increased proportionally to irradiation doses. Maximum TL temperatures of all irradiated samples are found to be between the 250-280 oC temperature intervals, it was also found that unirradiated samples did not exhibit any glow peaks. Key Words: Food irradiation, thermoluminescence, TL measurement, glow curve.
Applications of a novel approach to relativistic and non-relativistic problems in physics
We have developed an algebraic approach for the treatment of time-independent Schrödinger equation with constant/non-constant masses within the frame of non-relativistic quantum theory. The model developed then has been successfully applied in various fields of physics involving exactly/approximately solvable potentials. The first part of the thesis work is devoted to the presentation of these applications, such as the application results for noncentral potentials, applicability of the scheme for scattering theory and careful analysis of the application results for quantum systems with position-dependent masses in arbitrary dimensions After gaining confidence from the successful applications of this novel formalism to non-relativistic systems, we have extended our investigations by studying the applicability of the model also for the relativistic considerations in the light of Klein-Gordon and Dirac equations involving only bound quantum states. These considerations require naturally the split of the relativistic equations into two parts, unlike the other models in the literature, which provide a clear visualization of the relativistic contributions, in an explicit manner, to the solution in the non-relativistic limit. Key words: Schrödinger Equation, Dirac Equation, Klein-Gordon Equation, Exactly-solvable Systems, Non-central Potentials, Position-dependent Mass.
Manyetik alan ve çeşitli potansiyeller içeren dirac denkleminin tam ve yaklaşık çözüm
Dirac equation has been studied for many years and its role in modeling physical problems is well known. In particular, Dirac equation is useful to describe properties of the spin 1/2 particles. Therefore the study of the Dirac equation has considerable impact on physics. On the other hand the study of position dependent mass Schr¨odinger equation has recently attracted some interest arising from the study of the electronic properties of the semiconductors, quantum dots etc. In this thesis, the solution of the Dirac equation and transmission probabilities of the scattering problem with a position dependent mass are studied. Thus this work consists of two parts. In the first part, exact solvability of the position dependent mass Schr¨odinger equation including a constant potential has been discussed and calculations of the transmission coefficients for various spatially varying effective masses have been represented. The second part covers the construction and solution of the Dirac equation including various potentials in the presence of the magnetic field. The ultimate goal of the models developed in this thesis is that the solution of the effective mass Dirac equation with constant potential. Key words: Dirac equation, (Quasi) exactly solvable potentials