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1998

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Articles 451 - 480 of 502

Full-Text Articles in Physics

Remote Sensing And Synchronous Land Surface Measurements Of Soil Moisture And Soil Temperature In The Field, N.V. Kolev, K.P. Penev, Y.M. Kirkova, B.S. Krustanov, T.G. Nazarsky, G.K. Dimitrov, C.P. Levchev, H.I. Prodanov, L.H. Kraleva Jan 1998

Remote Sensing And Synchronous Land Surface Measurements Of Soil Moisture And Soil Temperature In The Field, N.V. Kolev, K.P. Penev, Y.M. Kirkova, B.S. Krustanov, T.G. Nazarsky, G.K. Dimitrov, C.P. Levchev, H.I. Prodanov, L.H. Kraleva

Turkish Journal of Physics

The paper presents the results of remote sensing and synchronous land surface measurements for estimation of soil (surface and profile) water content and soil temperature for different soil types in Bulgaria. The relationship between radiometric temperature and soil surface water content is shown. The research is illustrated by some results from aircraft and land surface measurements carried out over three test areas near Pleven, Sofia and Plovdiv, respectively, during the period 1988-1990.


Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Cheettu Ammal, P. Venuvanalingam Jan 1998

Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Cheettu Ammal, P. Venuvanalingam

Faculty Publications

Ab initio calculations at the Hartree–Fock and correlated levels and density functional theory calculations have been performed with 6-31++G(d,p) and 6-311++G(d,p)basis sets on LiF and HF complexes of benzene, ethylene, and acetylene. Complex binding energies have been corrected for basis set superposition error, and zero point energy corrections have been done on Hartree–Fock binding energies. Computed results indicate that the complexes exist in different conformations and among them those with π-lithium and π-hydrogen bonds are the most stable. π-lithium bonds are stronger than π-hydrogen bonds. The computed binding energies and geometry of HF complexes correlate well with the available experimental …


Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam Jan 1998

Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam

Faculty Publications

Ab initio and DFT computations have been carried out on LiF and HF complexes of a set of n-donors viz. trimethylamine, dimethyl ether and dimethyl sulfide with a 6-31++G(d,p) basis set. The effect of correlation has been included with MP2, MP4 and DFT calculations. NBO analyses of the wavefunctions have been performed to examine the intermolecular interaction at the orbital level. Calculations reveal that these donors form strong n→σ* complexes and computed binding energies of the (CH3)2O···HF complex agree very well with the experimental binding energies from IR spectroscopy. LiF forms stronger complexes than HF, …


Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz Jan 1998

Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz

Physics & Astronomy Faculty Publications

We investigate the computational requirements for all-sky, all-frequency searches for gravitational waves from spinning neutron stars, using archived data from interferometric gravitational wave detectors such as LIGO. These sources are expected to be weak, so the optimal strategy involves coherent accumulaton of signal-to-noise using Fourier transforms of long stretches of data (months to years). Earth-motion-induced Doppler shifts, and intrinsic pulsar spindown, will reduce the narrow-band signal-to-noise by spreading power across many frequency bins; therefore, it is necessary to correct for these effects before performing the Fourier transform. The corrections can be implemented by a parametrized model, in which one does …


Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich Jan 1998

Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich

Physics & Astronomy Faculty Publications

Long-ranged correlations in a fluid close to its critical point Tc cause distinct forces between immersed colloidal particles and the container walls. We calculate such a force and its temperature dependence for the generic case of a spherical particle located at a distance D from a planar wall and find that the force attains a maximum at a temperature Tmax(D) above Tc, which facilitates quantitative experimental tests. The corresponding effective pair interaction between the colloidal particles themselves, potentially leading to aggregation, is also discussed.


Biomineralization Of Magnetic Iron Minerals In Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Dirk Schϋler Jan 1998

Biomineralization Of Magnetic Iron Minerals In Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Dirk Schϋler

Physics

Magnetotactic bacteria orient and migrate along magnetic field lines. This ability is based on a submicron assembly of single-magnetic domain iron mineral particles that elegantly solves the problem of how to construct a magnetic dipole that is large enough to be oriented in the geomagnetic field at ambient temperature, yet fit inside a micron-sized cell. The solution is based on the ability of the bacteria to accumulate high concentrations of iron, and control the deposition, size and orientation of a specific iron mineral at specific locations in the cell.


The Effect Of Temperature Dependent Frequency Factor On The Evaluated Trapping Parameters Of Tsl Glow Curves, A. N. Yazici, Z. Öztürk Jan 1998

The Effect Of Temperature Dependent Frequency Factor On The Evaluated Trapping Parameters Of Tsl Glow Curves, A. N. Yazici, Z. Öztürk

Turkish Journal of Physics

The effect of temperature dependency on frequency factor and its relationship to trapping parameters is discussed by using the peak shape method. The coefficients appearing in the peak shape formula for the calculation of the activation energy have been determined and tabulated for the symmetry factor $\mu_g(X)$ for $x=0.50$ and 0.75 of the peak intensity. It is found that significant errors occur in the value of the trapping parameters if the temperature dependecy of the frequency factor is not consider.


Fine Structure Analysis Of 4702 ^Oa Band Of The Molecule, M.B. Sureshkumar, S.R. Srikant Jan 1998

Fine Structure Analysis Of 4702 ^Oa Band Of The Molecule, M.B. Sureshkumar, S.R. Srikant

Turkish Journal of Physics

The emission spectrum of the cobalt monochloride molecule has been excited in a high frequency discharge tube source and the (0,0) band of H-system at 4702 \AA was photo-graphed at an inverse dispersion of 0.973 \AA/mm in the 5th order of a two meter plane grating spectrograph (Carl-Zeiss). The fine structure analysis of the band has been carried out and the molecular constants are reported for the first time. Rotational isotopic shift due to $^{37}$Cl support the analysis. The electronic transition involved is of the type $0^-$----- $0^-$ of case (c) which is equivalent of $^{3}\sum^{+}$-----$^{3}\sum^+$ or $^5\sum^+$-----$^5\sum^+$.


A Study On The Effect Of Ni Dopping On Bi-Pb-Sr-Ca-Cu-O System, M. Tepe, D. Abukay Jan 1998

A Study On The Effect Of Ni Dopping On Bi-Pb-Sr-Ca-Cu-O System, M. Tepe, D. Abukay

Turkish Journal of Physics

The effect of $Ni$ doping on superconductivity properties of the $Bi_{1.7}Pb_{0.3}Sr_2Ca_2(Cu_{1-x}Ni_x)_3O_y$ system has been investigated by means of $x$-ray diffraction, ac electrical resistance, ac magnetic susceptibility and critical current measurements. The volume fraction of the 2223 phase decreases with increasing $Ni$ concentration. The zero-resistance temperature and the critical current density are suppressed with $Ni$ substitution.


Microscopic Calculations Of The Nucleus-Nucleus Optical Potential, M. M. Osman Jan 1998

Microscopic Calculations Of The Nucleus-Nucleus Optical Potential, M. M. Osman

Turkish Journal of Physics

In present work, a density dependent nucleon-nucleon interactions based on the $G$-matrix elements of the Paris nucleon-nucleon potential have been used to calculate the real part of the nucleus-nucleus optical potential. We have compared our results with those deduced from experiment. We found that our results, obtained using a suitable approximation of the kinetic energy density, agree satisfactory with those extracted from experiment at the strong absorption radius. Moreover, the higher values of the compressibility, $K$, agree better with experiment than the lower values.


Deformation Methods For Investigation Of The Deep Level Parameters In Semiconductors, S. Z. Zainabidinov, A. Abduraimov, O. O. Mamatkarimov, I.G. Tursunov, R.Kh. Khamidov Jan 1998

Deformation Methods For Investigation Of The Deep Level Parameters In Semiconductors, S. Z. Zainabidinov, A. Abduraimov, O. O. Mamatkarimov, I.G. Tursunov, R.Kh. Khamidov

Turkish Journal of Physics

In this paper deformation methods are offered to investigate deep level parameters in semiconductors. It is based on strain parameters measurements of compensated and overcompensated semiconductors. The dynamic changes of current flow in compensated and overcompensated samples of $p$-type $Si: Ni$ and $n$-type $Si: Mn$ under uniform pulse hydrostatic compression (UHC) was investigated. It was observed that in $p$-type $Si: Ni$ samples ionization energy levels $Ni$ at UHC increases, on the contrary in samples $n$-type $Si: Mn$ it decreases. The ionization energy and baric coefficient of the shift of $Ni$ and $Mn$ levels were bounded.


Interrelation Of Magnetic Properties With The Crystal Structures Of Mefese (Me = Ti; V; Cr; Fe; Co; Ni) Compounds, R. Sadikhov, A. Namazov, J. Guseinov Jan 1998

Interrelation Of Magnetic Properties With The Crystal Structures Of Mefese (Me = Ti; V; Cr; Fe; Co; Ni) Compounds, R. Sadikhov, A. Namazov, J. Guseinov

Turkish Journal of Physics

Magnetization of MeFe$_2$Se$_4$ (Me = Ti; V; Cr; Fe; Co; Ni) compounds at low temperatures has been investigated. It is shown that these compounds are ferrimagnetics with low values of specific magnetization. It is established that along the crystal axis $c$ of a given compound, there have been carried out two types of exchange interactions; cation-cation and cation-anion-cation with different dependence of their quantity on interatomic distance.


Anomalous Electrical Characteristics Of Ion Implanted P^+-N Juntions, N. Siddiqui Jan 1998

Anomalous Electrical Characteristics Of Ion Implanted P^+-N Juntions, N. Siddiqui

Turkish Journal of Physics

Electrical characteristics of three $P^+ - n$ diodes fabricated on high resistivity silicon by ion implantation technique are studied by making capacitance-voltage (C-V), reverse current-voltage (I-V) and dielectric spectroscopy of semiconductor (DSS) measurements. The C-V characteristics show abrupt fall in capacitance, while I-V characteristics show abrupt rise in current at the same voltages as in the C-V characteristics. These abrupt discontinuities are ascribed to the formation of defect clusters in the lightly doped base regions where charge transfer might be taking place by thermally assisted tunneling. Low activation energies obtained in the DSS measurements also point toward the same mechanism.


Elastic Scattering Of 344.5 Mev ^{12}C Ions From ^{11}B Nucleus, S.A.E. Khallaf, M.A. Abdel-Rahman, S.K. Abdel-Rahman, S.W.Z. Mahmoud Jan 1998

Elastic Scattering Of 344.5 Mev ^{12}C Ions From ^{11}B Nucleus, S.A.E. Khallaf, M.A. Abdel-Rahman, S.K. Abdel-Rahman, S.W.Z. Mahmoud

Turkish Journal of Physics

The angular distribution of the elastic scattering differential cross section of 344.5 MeV $^{12}$C ions from $^{11}$B nucleus is calculated and compared with the experimental data as well as the previously published calculations. The real part of the central optical potential is derived using the double-folding and single-folding procedures assuming Gaussian forms of the nucleon-nucleon and alpha-nucleon interactions, respectively. A nuclear matter density distribution function of $^{11}$B consisting of a spherical part plus a quadrupole term is used. The inclusion of the quadrupole term is found necessary to obtain good fits to the experimental data.


Reorientation Of Magnetization In Thin Films, Bengü Kaplan Jan 1998

Reorientation Of Magnetization In Thin Films, Bengü Kaplan

Turkish Journal of Physics

The spin wave energy is determined by the competition between uniaxial and cubic anisotropy. We discuss the reorientation temperature $ T_{R} $ of magnetization in two-dimension and calculate its dependence on the exchange, $J$, and the uniaxial anisotropy, $G$, parameters within random phase approximation. We find that $ T_{R} $ varies as $ \sqrt{JG} $ in the planar regime.


Space Charge Limited Current In Films Obtained In Glow Discharge Plasma, M.M. Akhmedov, M.K. Kerimov, B.A. Suleimanov, S.A. Mansimov Jan 1998

Space Charge Limited Current In Films Obtained In Glow Discharge Plasma, M.M. Akhmedov, M.K. Kerimov, B.A. Suleimanov, S.A. Mansimov

Turkish Journal of Physics

The electrical current in thin films obtained by the polymerization of acetonitrile in glow discharge on a heated substrate were investigated in order to determine the mechanism of electrical conduction. The results of the field dependence, sample thickness dependence of the dark conductivity, supported by the results of photocurrent measurements, suggest an exponential energy distribution of traps inside the band gap of the polymer.


Shallow Donors In A Quantum Well Wire; Electric Field And Geometrical Effects, M. Ulaş, H. Akbaş, M. Tomak Jan 1998

Shallow Donors In A Quantum Well Wire; Electric Field And Geometrical Effects, M. Ulaş, H. Akbaş, M. Tomak

Turkish Journal of Physics

Subband and shallow donor binding energies are calculated. The emphasis is given on the electric field effects for wires of different shapes. It is shown that the donor binding energy is sensitive to the interplay of the electric field and geometrical effects.


The Eect Of Exposure Time To Clean Room Air On Characteristic Parameters Of Au /Epilayer N-Si Schottky Diodes, M. Sağlam, Ç. Nuhoğlu, E. Ayyildiz, A. Türüt, H.A. Çeti̇nkara Jan 1998

The Eect Of Exposure Time To Clean Room Air On Characteristic Parameters Of Au /Epilayer N-Si Schottky Diodes, M. Sağlam, Ç. Nuhoğlu, E. Ayyildiz, A. Türüt, H.A. Çeti̇nkara

Turkish Journal of Physics

A study has been made on determination and comparison of current-voltage (I-V) and capacitance-voltage (C-V) characteristics parameters of $Au/n-Si$ Schottky barrier diodes (SBDs) with and without thin native oxide layer fabricated on $n$-type $Si$ grown by LPE (Liquid-phase Epitaxy) technique. The native oxide layer with different thicknesses on chemically cleaned on $Si$ surface were obtained by exposing the surfaces to clean room air before evaporating metal. The native oxide thicknesses of samples D2, D3, D4 and D5 are in the form $D2 < D3 < D4 \leq D5$, depending on the exposing time. It has been seen that the values of barrier height $\Phi_b$ of samples D2(0.64 eV), D3(0.66 eV), D4(0.69 eV) and D5(0.69 eV) with the interfacial layer increased with increasing the exposure time and tended to that of the initial sample D1 (nonoxidezed sample, 0.74 eV), and thus also their I-V and C-V curves. The reverse current of sample D1 showed slight nonsaturating behavior. This ''soft'' behavior has been ascribed to the spatial inhomogeneity in the barrier heights at the MS interface. In particular, reverse bias curves of samples D2, D3, D4 and D5 have shown excellent saturation which may be attributed to the passivation of the semiconductor surface states by the native oxide layer which reduces the penetration of the wave functions of electron in the metal into the semiconductor. Especially, the I-V characteristics and experimental parameters of our devices are in agreement with recently reported results revealed by the pulsed surface photovoltage technique for the electronic properties of the HF-treated Si surface during initial oxidation in air.


\Tau->\Rho\Nu Decay And Leptonic Decay Constants Of Vector Mesons, Kh. Ablakulov, B.N. Kuranov, T.Z. Nasyrov Jan 1998

\Tau->\Rho\Nu Decay And Leptonic Decay Constants Of Vector Mesons, Kh. Ablakulov, B.N. Kuranov, T.Z. Nasyrov

Turkish Journal of Physics

The new Salpeter equation for vector mesons is proposed and the representation for their leptonic decay constants is obtained.


Resonance Production Of New Resonances At Ep And \Gamma P Colliders, A. Çeli̇kel And M. Kantar Jan 1998

Resonance Production Of New Resonances At Ep And \Gamma P Colliders, A. Çeli̇kel And M. Kantar

Turkish Journal of Physics

We study the resonance production of new particles predicted by preonic models at Linac-Ring type $ep$ and $\gamma p$ colliders. It is shown that these machines will allow to investigate the new particles with masses up to few TeV scale.


Determination Of Temperature Dependent Frequency Factor Constant From Tl Glow Curves, A. Necmeddin Yazici Jan 1998

Determination Of Temperature Dependent Frequency Factor Constant From Tl Glow Curves, A. Necmeddin Yazici

Turkish Journal of Physics

A new method solely based on the theoretical and experimental analysis of thermoluminescence glow curves is proposed for the determination of the temperature dependent frequency factor constant.


Eects Of Post Deposition Treatments On Vacuum Evaporated Cdte Thin Films And Cds=Cdte Heterojunction Devices, Habibe Bayhan, Çiğdem Erçelebi̇ Jan 1998

Eects Of Post Deposition Treatments On Vacuum Evaporated Cdte Thin Films And Cds=Cdte Heterojunction Devices, Habibe Bayhan, Çiğdem Erçelebi̇

Turkish Journal of Physics

$CdTe, CdS$ thin films and $n-CdS/p-CdTe$ heterostructures have been prepared by conventional vacuum evaporation technique. Some post deposition treatments to optimize the device efficiency have been analyzed and the effects of the individual process steps on the material and device properties were investigated. Annealing in air with and without $CdCl_2$-treatment decreased the $CdTe$ resistivity. The $CdCl_2$-dip followed by annealing in air at $300^{\circ}C$ for 5 min improved the grain size and polycrystalline nature of $CdTe$ thin films. Solar efficiency improvements were achieved when heterojunctions were prepared on successively treated (i.e. etched, air annealed, $CdCl_2$-processed) $CdTe$ surfaces. Etching of the $CdTe$ …


Studies Of Structure Of Ceramic Materials Containing Molibdenum Particles Within The Framework Of Theory Of Non-Homogeneous Systems, Sh. Kami̇lov, M. Karabaeva, U. Abdurahmanov Jan 1998

Studies Of Structure Of Ceramic Materials Containing Molibdenum Particles Within The Framework Of Theory Of Non-Homogeneous Systems, Sh. Kami̇lov, M. Karabaeva, U. Abdurahmanov

Turkish Journal of Physics

The structure of ceramic materials containing molibdenum powder is considered within the framework of leakage theory. Determined are the density of the endless cluster, volumetric parts of the skeleton and dead ends, as well as their dependence on the component concentration. Volumetric part of the skeleton near the threshold of leakage makes a negligible part of the full volume.


Measurement Of The Compton And Coherent Scattering Differential Cross-Sections, Yakup Kurucu, Salih Erzeneoğlu, Rıdvan Durak, Yusuf Şahi̇n Jan 1998

Measurement Of The Compton And Coherent Scattering Differential Cross-Sections, Yakup Kurucu, Salih Erzeneoğlu, Rıdvan Durak, Yusuf Şahi̇n

Turkish Journal of Physics

The total atomic Compton and coherent scattering differential cross section of Al, Sn and Ta for 59.5 keV gamma rays of Am-241 point source have been measured for scattering angles $\theta=81^{\circ}$, $85.5^{\circ}$, $90^{\circ}$ and $94.5^{\circ}$ by a direct method with an energy dispersive x-ray spectrometer. The background correction and detection efficiency are also included the study. The experimental results are comparatively given with some available theoretical data obtained with some approximation methods.


The Relation Between Dislocation Density And Crystal Crosscut In \Beta-Sn Grown By Modified Bridgman Method, Bahattin Düzgün, İbrahim Karaman, Nazım Uçar Jan 1998

The Relation Between Dislocation Density And Crystal Crosscut In \Beta-Sn Grown By Modified Bridgman Method, Bahattin Düzgün, İbrahim Karaman, Nazım Uçar

Turkish Journal of Physics

Crystals $\beta$-Sn are grown from ingots of 99.99\% purity by modified Bridgman method under $10^{-3}$ torr pressure and oriented by Laue back reflection method. The relation between crystal crosscut and dislocation density calculated using etch hillock technique is investigated. It is found that the dislocation density increases with increasing crystal crosscut.


Delay Time Fluctuations Of The Tunnel Josephson Junction In The Case Of Linearly Growing Current, Iman Novruzoglu Askerzade Jan 1998

Delay Time Fluctuations Of The Tunnel Josephson Junction In The Case Of Linearly Growing Current, Iman Novruzoglu Askerzade

Turkish Journal of Physics

Delay time thermal fluctuations intensity of the tunnel Josephson junction for the case of high current rate is calculated.


A New Probe Head Design For The Weak Field Double Resonance Spectrometer, A. Oral Salman, M. Maral Sünnetçi̇oğlu, Rıza Sungur, Gökçe Bi̇ngöl Jan 1998

A New Probe Head Design For The Weak Field Double Resonance Spectrometer, A. Oral Salman, M. Maral Sünnetçi̇oğlu, Rıza Sungur, Gökçe Bi̇ngöl

Turkish Journal of Physics

In order to observe low field $\sigma$ EPR spectra of free radicals a new probe head was designed to work at 1.53 mT. As a double resonance spectrometer, at 1.53 mT the probe head includes both NMR and EPR rf coils. To induce the $\sigma$ transitions EPR rf coil must produce an rf field parallel to the main static field. Various coil designs were examined for this aim and the best results was obtained with a solenoid NMR coil and saddle shaped single turn EPR coil design combination.


Characterization Of Spray Deposited Bismuth Oxide Thin Films From Non-Aqueous Medium, V.V. Killedar, C.H. Bhosale, C.D. Lokhande Jan 1998

Characterization Of Spray Deposited Bismuth Oxide Thin Films From Non-Aqueous Medium, V.V. Killedar, C.H. Bhosale, C.D. Lokhande

Turkish Journal of Physics

Bismuth oxide thin films have been prepared on amorphous glass substrates from non-aqueous medium using spray pyrolysis method. Characterization of the films was carried out with XRD, optical absorption, dark resistivity and thermoelectric power (TEP) measurements. These studies reveal that films as deposited are polycrystalline; having an optical band gap of 2.6 eV; electrical resistivity is of the order of $10^6$ ohm-cm; and electron carrier concentration and mobility are of the order of $3.8 \times 10^{19}$cm$^3$ and $1.5 \times 10^{-4}$cm$^2$ V$^{-1}$s$^{-1}$, respectively.


A Study Of Events From Si 28 With Emulsion At 4.5 A Gev/C Without Target Fragmentation, A.A. El-Daiem Jan 1998

A Study Of Events From Si 28 With Emulsion At 4.5 A Gev/C Without Target Fragmentation, A.A. El-Daiem

Turkish Journal of Physics

Atotal sample of 1000 inelastic interactions of Si$^{28}$ in emulsion at 4.5 A GeV/c has been used characteristics of projectile fragments. This paper is therefore to devoted to the study of projectile fragments, with special attention to the class of events $n_h$=0, in which the traget nucleus is unwounded. This paper include the multiplicity distributinon and angular distributions of projectile fragments.


Transfer Of Photometric Quantities At Arbitrary Distribution Temperatures, İzmir Mamedbeyli̇, Zafer Ürey, A. Kamuran Türkoğlu Jan 1998

Transfer Of Photometric Quantities At Arbitrary Distribution Temperatures, İzmir Mamedbeyli̇, Zafer Ürey, A. Kamuran Türkoğlu

Turkish Journal of Physics

Characteristics of a photometric setup used for the measurement of photometric quantities at the National Institute of Metrology (UME) in Turkey are reported. A high accuracy method is developed to adjust the filaments of incandescent lamps with respect to the optical axis. The method also provides the basis for low uncertainty distance measurements between lamp filaments and photometers. Transfer of photometric quantities at arbitrary distribution temperatures is examined both theoretically and experimentally, and the results are compared to the calibration values of the Bureau International Des Poids Et Measures (BIPM), Paris, France.