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Full-Text Articles in Physical Sciences and Mathematics

An Open Singularity-Free Cosmological Model With Inflation, Koray Karaca, Selçuk Bayin Jan 2003

An Open Singularity-Free Cosmological Model With Inflation, Koray Karaca, Selçuk Bayin

Turkish Journal of Physics

In the light of recent observations which point to an open universe (\Omega _{0} < 1), we reconsider singularity-free models, originally constructed for closed universes. Our model starts from a nonsingular state called prematter, governed by an inflationary equation of state P=( \gamma _{p}-1) \rho , where \gamma _{p} is a small positive parameter representing the initial vacuum dominance of the universe. Unlike the closed models, an open universe cannot be initially static hence, starts with an initial expansion rate represented by the initial value of the Hubble constant H(0). Therefore, our model is a two-parameter universe model (\gamma _{p},H(0)). During the prematter phase, due to the unusual characteristic of the equation of state, the universe heats up even though it expands. When the temperature in the universe reaches the Planck temperature T_{pl}, which is taken as the maximum attainable physical temperature, a first order phase transition carries the universe into the radiation era. Then the universe starts to behave as predicted in the standard model. The model proposed in this work predicts a value between 60 and 80 Km\cdot \sec ^{-1}\cdot Mpc^{-1} for the present value of the Hubble constant H_{0}, and the predicted value of \Omega _{0} lies between 0.3 and 0.6. Comparing the predictions of this model for the present properties of the universe with the recent observational results, we argue that the model constructed in this paper could be used as a realistic universe model.


Inflation In A Flat Universe, Koray Karaca, Selçuk Bayin Jan 2003

Inflation In A Flat Universe, Koray Karaca, Selçuk Bayin

Turkish Journal of Physics

We started the evolution of a flat universe from a nonsingular state called prematter which is governed by an inflationary equation of state P=(\gamma -1)\rho , where \gamma represents the initial vacuum dominance of the universe. The evolution of the universe-except in the prematter era-is affected neither by the initial vacuum dominance nor by the initial expansion rate of the universe. On the other hand, present properties of the universe, such as the Hubble constant, age and density, are sensitive to the value of the temperature at the decoupling ( T_{m}) . Over a range between 3\cdot 10^{4}and 5\cdot 10^{4} …


The Motion Of Cosmic Strings In The Schwarzschild Black Hole Spacetime, Sergey Roshchupkin, Yevgeniy Zinchenko Jan 2003

The Motion Of Cosmic Strings In The Schwarzschild Black Hole Spacetime, Sergey Roshchupkin, Yevgeniy Zinchenko

Turkish Journal of Physics

We study the classical dynamics of a bosonic string in the Schwarzschild spacetime using a perturbative scheme which is based on the assumption of a small value of a rescaled string tension parameter. The proposed approximation selfconsistently describes the string dynamics on the scale of large values for the worldsheet time in a fixed gauge.


Theory Of Antisymmetric Tensor Fields, Valeri Dvoeglazov Jan 2003

Theory Of Antisymmetric Tensor Fields, Valeri Dvoeglazov

Turkish Journal of Physics

It has long been claimed that the antisymmetric tensor field of the second rank is pure longitudinal after quantization. In my opinion, such a situation is quite unacceptable. I repeat the well-known procedure of the derivation of the set of Proca equations. It is shown that it can be written in various forms. Furthermore, on the basis of the Lagrangian formalism I calculate dynamical invariants (including the Pauli-Lubanski vector of relativistic spin for this field). Even on the classical level, the Pauli-Lubanski vector can be equal to zero after applications of well-known constraints. The importance of the normalization is pointed …


Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy Jan 2003

Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy

Turkish Journal of Physics

Selection random number method (Monte Carlo technique) is used to calculate the ion charge state distributions (CSD) and mean ion charge \bar{q} after K-, L_{I}, L_{III}- and M_{I}- shell ionization in neutral atoms and their q-fold ground state ions (q = 0 to 10) from C to Fe elements. Atomic data for radiative and non-radiative transitions and electron shake off process, which is used in the modeling vacancy cascade program, are computed with relativistic wave functions. Use of atomic data is important to accurately model vacancy cascades. To enhance the agreement between calculated and experimental values, the electron shake-off processes …


Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo Jan 2003

Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo

Turkish Journal of Physics

Downward infrared radiation (L) and some easy-to-measure meteorological variables (relative humidity, clearness index and vapour pressure) were collected for a period of two years at Ilorin. Downward infrared radiation data were obtained using a pyrgeometer (Eppley-PIR), while data for relative humidity and vapour pressure for Ilorin were obtained from the Nigerian Meteorological Services, Lagos. Based on these data, using statistical regression analysis, empirical models (seven one-variable and nine two-variable) for predicting daily mean infrared radiation, from both clear and cloudy skies, were tested. Their advantage is that they only make use of easily measured meteorological parameters. The best one-variable model …


Operation Parameters Of The Thermionic Vacuum Arc Discharge, Tamer Akan Jan 2003

Operation Parameters Of The Thermionic Vacuum Arc Discharge, Tamer Akan

Turkish Journal of Physics

The thermionic vacuum arc (TVA) discharge with evaporating anodes employing directly heated thermionic cathodes is investigated. The TVA discharge generates a pure, gas-free metal vapor plasma containing ions with a directed energy. The TVA is strongly controlled by the cathodic electron beam and there is a quite good stability of important operation parameters like the arc voltage and the arc current.


Development Of Double Discharge Pulsed Electron Beam Generator And Its Preliminary Applications In Material Processing, Hi̇lal Göktaş, Gulay Oke, Mircea Udrea Jan 2003

Development Of Double Discharge Pulsed Electron Beam Generator And Its Preliminary Applications In Material Processing, Hi̇lal Göktaş, Gulay Oke, Mircea Udrea

Turkish Journal of Physics

This article presents the construction of a fast, intense electron beam generator, several of its operational properties and its preliminary applications. A fast filamentary discharge produced in a tube filled with Argon gas at pressure of about 0.1 torr. An electron beam is obtained with a current intensity of about 0.6 A for a 25 ns duration. The length of the filamentary discharge and the behavior of the beam in the magnetic field are examined. The interaction of the beam with different targets was investigated by Scanning Electron Microscope. It is also demonstrated that the device can be used to …


Timelike And Spacelike Ricci Collineation Vectors In String Fluid, Hüsnü Baysal, İhsan Yilmaz Jan 2003

Timelike And Spacelike Ricci Collineation Vectors In String Fluid, Hüsnü Baysal, İhsan Yilmaz

Turkish Journal of Physics

We study the consequences of the existence of timelike and spacelike Ricci collineation vectors (RCVs) for string fluid in the context of general relativity. Necessary and sufficient conditions are derived for a space-time with string fluid to admit a timelike RCV, parallel to u^a, and a spacelike RCV, parallel to n^a. In these cases, some results obtained are discussed.


Interaction Integrals Of Extended Bodies And Convolution/Folding Operation, Şule Kehnemi̇, R. Ömür Akyüz Jan 2003

Interaction Integrals Of Extended Bodies And Convolution/Folding Operation, Şule Kehnemi̇, R. Ömür Akyüz

Turkish Journal of Physics

The convolution, or folding, theorem related to Fourier transforms is applied to the evaluation of interaction integrals of certain extended bodies for the specific purpose of nuclear applications The integrals give analytical results for a class of functions when chosen from among uniform sharp and leptodermous spheres, delta-points, Yukawa, and Coulomb shapes. Such shapes are convenient to use as models for source density and point-point interaction.


On Complex Permittivity Of Dilute Random Binary Dielectric Mixtures In Two-Dimensions, Eni̇s Tuncer, Emre Tuncer Jan 2003

On Complex Permittivity Of Dilute Random Binary Dielectric Mixtures In Two-Dimensions, Eni̇s Tuncer, Emre Tuncer

Turkish Journal of Physics

Influence of the number of particles considered in numerical simulations on the complex dielectric permittivity of binary dilute dielectric mixtures in two-dimensions are reported. In the simulations, dodecagons (polygons with 12-sides) were used to mimic disk-shaped inclusions. Using such an approach we were able to consider 16^2 particles in a unit-square. The effective dielectric permittivity of the mixtures were calculated using the finite element method at two different frequecies which were much higher and lower than the characteristic relaxation rate of the Maxwell-Wagner-Sillars polarization. The results were compared to an analytical solution. It was found that the permittivity values at …


Semi-Infinite Polarized Nuclear Matter With A Seyler-Blanchard Interaction, H. M. M. Mansour, Kh. A. Ramadan Jan 2003

Semi-Infinite Polarized Nuclear Matter With A Seyler-Blanchard Interaction, H. M. M. Mansour, Kh. A. Ramadan

Turkish Journal of Physics

The surface and curvature properties of semi-infinite polarized nuclear matter (SPNM) are calculated using a modified form of the Seyler-Blanchard potential. The level density parameter is extracted from the free energy using T^{2}-approximation. Good agreement is obtained between our calculations for the level density and other parameters which characterize the surface and curvature properties of SPNM and previous theoretical estimates. PACS number(s): 21.65.+f, 21.30.Fe


How Round Is Round? On Accuracy In Complex Dielectric Permittivity Calculations: A Finite-Size Scaling Approach, Eni̇s Tuncer Jan 2003

How Round Is Round? On Accuracy In Complex Dielectric Permittivity Calculations: A Finite-Size Scaling Approach, Eni̇s Tuncer

Turkish Journal of Physics

Accuracy in complex dielectric permittivity calculations in binary dielectric mixtures in two-dimensions are reported by taking into account the shape of the inclusion phase. The dielectric permittivity of the mixtures were calculated using the finite element method, and the permittivities were estimated by two different procedures. The results were compared with those of analytical models based on a mean field approximation and regular arrangement of disks. We have approached the problem emphasizing the finite-size behavior in which regular polygons with n sides were assumed to mimic the disk inclusion phase. It was found that at low concentrations, < 30%, decagon-approximated circles (n = 10) cause an error of < 0.1% in the effective medium quantities compared with results obtained using analytical models.


The Influence Of Ge Content And Annealing Temperature On The D.C And A.C Conductivity Of Ge_{X}Se_{1 - X} Thin Films, Maysoon Faisal Alias, M. N. Makadsi, Z. M. Al-Ajeli Jan 2003

The Influence Of Ge Content And Annealing Temperature On The D.C And A.C Conductivity Of Ge_{X}Se_{1 - X} Thin Films, Maysoon Faisal Alias, M. N. Makadsi, Z. M. Al-Ajeli

Turkish Journal of Physics

Various samples of Ge_{x}Se_{1 - x} system have been prepared for x = 0.05, 0.15& 0.25 in an evacuated quartz tube. Thin films of Ge_{x}Se_{1 - x} film have been prepared via a thermal evaporation method with 350 \pm 5 nm thickness and rate deposition 6 nm/s. The alloy structure and thin films have been examined by X-ray diffraction (XRD). Atomic absorption spectroscopy (AAS) was used to examine the concentration of the composite elements (Ge and Se). The d.c and a.c conductivity of Ge_{x}Se_{1 - x} thin film have been studied as a function of Ge content x and annealing …


Electrical Characteristics Of Si Doped With Sb By Laser Annealing, Raid A. Ismail, Aseel A. Hadi Jan 2003

Electrical Characteristics Of Si Doped With Sb By Laser Annealing, Raid A. Ismail, Aseel A. Hadi

Turkish Journal of Physics

Laser induced diffusion of antimony in silicon was obtained using a Nd:YAG pulsed laser. The irradiation of antimony-coated silicon by laser beam allowed melting and diffusion of antimony inside the silicon. Diodes were fabricated. Laser beam energy and substrate temperature played a major role in electrical sheet conductivity I-V, and C-V characteristics of the fabricated diodes. High laser energy reduced the electrical sheet conductivity and dominated the recombination current due to the generation-recombination process and trapping centers. On the other hand, the diffusion current dominated for diodes fabricated under heating conditions of the sample during laser irradiation. The C-V measurements …


Microwave Signal Attenuation In Harmattan Weather Along Calabar-Akampkpa Line-Of-Sight Link, O. E. Eyo, A. I. Menkiti, Sunday O. Udo Jan 2003

Microwave Signal Attenuation In Harmattan Weather Along Calabar-Akampkpa Line-Of-Sight Link, O. E. Eyo, A. I. Menkiti, Sunday O. Udo

Turkish Journal of Physics

Line-of-sight (LOS) attenuation at 6.44GHz was measured at Calabar (4° 58' N, 8° 17' E) for ten months (Aug '93-May '94) using the Nigerian Telecommunications radio signal. The measurement was made with the intent of highlighting microwave signal attenuation in Harmattan weather conditions. The results are presented in terms of mean signal level and fog attenuation, fade rate distribution, fade depth distribution and scintillation index. The observed attenuation values due to Harmattan (fog) and the calculated (using Altshuler's model) are in fairly good agreement. Also, the statistics of fade distribution show fast fading of longer duration of the order of …


Relationship Between Global Solar Radiation And Sunshine Duration For Onne, Nigeria, Louis E. Akpabio, Sunday E. Etuk Jan 2003

Relationship Between Global Solar Radiation And Sunshine Duration For Onne, Nigeria, Louis E. Akpabio, Sunday E. Etuk

Turkish Journal of Physics

Measurements of global solar radiation and sunshine duration data during the period from 1984 to 1999 at Onne (within the rainforest climatic zone of southern Nigeria) were used to establish an Angstrom-type correlation equation. Five other commonly used correlations between global solar radiation and sunshine duration were also used to estimate global solar irradiation for Onne and their results are compared with our model. A good agreement (greater than 90% in most cases) was observed between the measured and the predicted values of our model.


Initial Electron Beam Polarization Measurement In E-\Gamma Collisions, Gökhan Ünel Jan 2003

Initial Electron Beam Polarization Measurement In E-\Gamma Collisions, Gökhan Ünel

Turkish Journal of Physics

The future high energy e e colliders, together with the complementary \gamma \gamma option, will offer possibilities for both discovery and precision physics. The uncertainty on the initial beam polarizations contributes to the systematic errors in each case. Therefore, it is crucial to obtain the precise beam polarizations by independent measurements. The e \gamma \rightarrow \nu W process in the e \gamma mode can be used to experimentally determine the polarization of the initial e beam. This note addresses the feasibility of making such a measurement with a relative statistical error of one percent. Generator and detector level MC tools …


Fourth Sm Family Manifestations At Clic, R. Çi̇ftçi̇, A. K. Çi̇ftçi̇, Erdal Recepoğlu, Saleh Sultansoy Jan 2003

Fourth Sm Family Manifestations At Clic, R. Çi̇ftçi̇, A. K. Çi̇ftçi̇, Erdal Recepoğlu, Saleh Sultansoy

Turkish Journal of Physics

The latest electroweak precision data allow the existence of additional chiral generations in the standard model. We study prospects of search for the fourth standard model family fermions and quarkonia at e^{+}e^{-} and \gamma \gamma options of CLIC. It is shown that CLIC will be powerfull machine for discovery and investigation of both fourth family leptons and quarkonia. Moreover, the formation of the fourth family quarkonia will give a new opportunity to investigate Higgs boson properties.


Nuclear Matrix Elements Of Double Beta Decay In Deformed Nuclei, C. Selam, Atalay Küçükbursa, H. Bi̇rcan, H. A. Aygör, T. Babacan, İ. Maraş, A. Kökçe Jan 2003

Nuclear Matrix Elements Of Double Beta Decay In Deformed Nuclei, C. Selam, Atalay Küçükbursa, H. Bi̇rcan, H. A. Aygör, T. Babacan, İ. Maraş, A. Kökçe

Turkish Journal of Physics

Nuclear matrix elements (M_{GT}) for two-neutrino double beta transitions of selected nuclei were calculated via a QRPA approach by considering the charge-exchange spin-spin interactions in the particle-hole channel among nucleons. Calculations were performed for both spherical and deformed cases of nuclei. As a result of these calculations, it has been seen that, although the value of the nuclear matrix elements in deformation case are 2-4 times smaller when compared with that of the spherical case, it is still 2-8 times greater than the experimental values.


High-Pressure Phase Transition In Some Alkali Halides Using Interatomic Potential Model, Harun Reşi̇t Yazar Jan 2003

High-Pressure Phase Transition In Some Alkali Halides Using Interatomic Potential Model, Harun Reşi̇t Yazar

Turkish Journal of Physics

We have predicted the phase transition pressure in some alkali halides NaCl and KCl using an interatomic potential approach based on a rigid ion model. We have obtained phase transition pressures 28.69 and 2.4 GPa, respectively, and are in close agreement with their corresponding experimental transition pressures 29.0 and 2.0 GPa. This approach is promising with respect to the prediction of the phase transition pressures of other alkali halides.


Clebsch-Gordan Equalities That Imply The Vanishing Of Particular 6j Symbols, Harry A. Mavromatis Jan 2003

Clebsch-Gordan Equalities That Imply The Vanishing Of Particular 6j Symbols, Harry A. Mavromatis

Turkish Journal of Physics

Three Clebsch-Gordan equalities and three individual Clebsh-Gordan relations are obtained by studying the non-accidental vanishing of certain 6j symbols.


Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden Jan 2003

Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden

Turkish Journal of Physics

The electron transport mechanism in GaN/AlGaN HEMT (High Electron Mobility Transistors) structures grown with MBE on sapphire substrate was investigated by using the temperature dependence of the Hall coefficient, resistivity, carrier density and Hall mobility. Hall measurements were carried out using Van der Pauw geometry. From the LO-phonon-scattering-limited component of the mobility, we obtain LO phonon energy \hbar \omega \approx 90 meV and the momentum relaxation time of \tau_{m} \approx 4 fs. Also, from the temperature dependence of the 2D carrier density, we obtain the donor activation energy E_{a} \approx 29 meV.


Characterization Of In_{4}Te_{3} Single Crystals, M. Dongol, M. M. Nassary, M. K. Gerges, M. A. Sebag Jan 2003

Characterization Of In_{4}Te_{3} Single Crystals, M. Dongol, M. M. Nassary, M. K. Gerges, M. A. Sebag

Turkish Journal of Physics

Single crystals of In_{4}Te_{3} grown by modified Bridgman technique were characterized by measurement of the Hall coefficient, electrical conductivity and Seebeck coefficient, in the temperature range 200-500 K. The investigated sample was found to be of P-type conductivity.R_{H} at room temperature was 3.1 \times 10^{14} cm^{3}/coul and the carrier concentration was evaluated as 2.007 \times 10^{14} cm^{3}. Energy gap \Delta E_{g} and ionization energy \Delta E_{a} were estimated as 0.28 eV and 0.12 eV, respectively, and the diffusion coefficient, the diffusion length, the mean free time between collision and the effective mass of carriers were evaluated. The variation of the …


Variation In Thickness Of Copper Films Deposited At Various Distances And Angles Using The Thermionic Vacuum Arc, Tamer Akan, Naci̇ Ekem Jan 2003

Variation In Thickness Of Copper Films Deposited At Various Distances And Angles Using The Thermionic Vacuum Arc, Tamer Akan, Naci̇ Ekem

Turkish Journal of Physics

The thermionic vacuum arc (TVA) is a new technique for the deposition of thin metallic films. Copper depositions were made on glass substrates placed at various distances and angles with respect to the TVA source. By measuring the thickness of the film on each substrate, the variation in the thickness as a function of the distance and angle with respect to the TVA source is investigated.


Study Of The Structure And Some Physical Properties Of Sodium-Boro-Phosphate Glasses Containing Antimony And Iron Oxides, Karam Abdel-Aati̇ Ali, Ahmet Gamal El-Din Mostafa Jan 2003

Study Of The Structure And Some Physical Properties Of Sodium-Boro-Phosphate Glasses Containing Antimony And Iron Oxides, Karam Abdel-Aati̇ Ali, Ahmet Gamal El-Din Mostafa

Turkish Journal of Physics

Boro-phosphate glasses containing transition metal oxides are of special interest. Hence, some sodium-Boro-phosphate glasses containing iron and antimony oxides were prepared and investigated. The structural investigation indicated the presence of different borate groups as well as tetragonal phosphate units. Most of the iron cations were found to occupy the low spin Fe^{3 +} in the tetrahedral coordination state. It was observed that some antimony act as network former cations and some others act as bridges between any two adjacent polyhedra. At high antimony oxide content, the formation of some Sb-Fe bonds was also detected. The magnetic susceptibility measurements showed a …


Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak Jan 2003

Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak

Turkish Journal of Physics

We discriminated between the extragalactic objects (galaxies and quasars) and stars for Basle star fields, Plaut I, SA 54, and SA 82 by comparing Basle fields and APS POSS I finder charts. Their numbers are 187, 70, and 93 for Plaut I, SA 54, and SA 82, respectively. Most of these objects are apparently faint in V, and they cause an overestimated local luminosity function for absolutely faint magnitudes, M(V) > 5. This effect is more conspicious for the field Plaut I.


A Study Of Direct Two-Proton Transfer Reactions Using Optical Potential Model, A. K. A. R. Al-Farra Jan 2003

A Study Of Direct Two-Proton Transfer Reactions Using Optical Potential Model, A. K. A. R. Al-Farra

Turkish Journal of Physics

^{12}C, ^{26}Mg(^3He,n) reactions have been studied at high bombardment energy with evaluation of the differential cross sections to the ground and the first excited states evaluated in the framework of the exact finite-range Born approximation (DWBA) calculations using the optical model. With the constraint that bound-state interactions have a Thomas-Fermi spin orbit form, different formations of the bound-state wave functions are explored. The calculated angular distributions are found to be in a good agreement with the experimental data. The present DWBA predictions are normalized to give the best overall fits to the data. The extracted spectroscopic factors are reasonable.


Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts Jan 2003

Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts

Turkish Journal of Physics

Some rotational components have been measured in the ground, the \nu _9 = 1 and the \nu _{10} = 2 vibrational states for ^{13}CH_3CCH isotopic species in the frequency range 16--50 GHz. A set of rotational constants has been determined, which gives the best fit between the observed and the calculated frequencies, for each vibrational state. A Fermi resonance was found between these two states.


Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya Jan 2003

Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya

Turkish Journal of Physics

A lithium-borate-glass system containing iron and copper cations has been thoroughly investigated, in order to obtain information about the structural role of both the iron and copper in such glass hosts. The amorphous phase of the prepared glass samples was confirmed from their X-ray diffraction. From the infrared spectra it was concluded that the glass networks are highly deformed and boron appeared in both tri- and tetra-hedral coordination states as well as in some ring structure. As copper was introduced, replacing lithium, it acts as a network modifier only while the iron acts as network former (FeO_4). The molar magnetic …