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1998

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Articles 1651 - 1680 of 2574

Full-Text Articles in Physical Sciences and Mathematics

\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.

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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.

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Quaternionic Roots Of E 8 Related Coxeter Graphs And Quasicrystals, Mehmet Koca, Nazife Özdeş Koca, Ramazan Koç Jan 1998

Quaternionic Roots Of E 8 Related Coxeter Graphs And Quasicrystals, Mehmet Koca, Nazife Özdeş Koca, Ramazan Koç

Turkish Journal of Physics

The lattice matching of two sets of quaternionic roots of $F_4$ leads to quaternionic roots of $E_8$ which has a decomposition $H_4 + \sigma H_4$ where the Coxeter graph $H_4$ is represented by the 120 quaternionic elements of the binary icosahedral group. The 30 pure imaginary quaternions constitute the roots of $H_3$ which has a natural extension to $H_3 + \sigma H_3$ describing the root system of the Lie algebra $D_6$. It is noted that there exist three lattices in 6-dimensions whose point group $W(D_6)$ admits the icosahedral symmetry $H_3$ as a subgroup, the roots of which describe the mid-points …

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Eect Of Sintering Time On Sb Added Bipbsrcacuo Superconducting Ceramics, K. Kocabaş Jan 1998

Eect Of Sintering Time On Sb Added Bipbsrcacuo Superconducting Ceramics, K. Kocabaş

Turkish Journal of Physics

In this study, superconducting Sb doped BiPbSrCaCuO ceramics with a fixed nominal composition were prepared and sintered at 850^oC for different periods. The structural phases of the sintered ceramics were determined by means of the measurements of the resistivity-temperature behaviour and of the XRD analysis. Sb doping along with Pb doping in the BiSrCaCuO ceramics was observed to increase the volume fraction of the high $T_c$ phase, the onset temperature and the critical temperature $T_c$. The critical temperature for the 100 hour sintered sample was 4K higher than that of the 60 hour sintered sample.

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The Determination Of Thermal Annealing Effect On The Dos Profile Of A-Si:H Film, Tülay Seri̇n Jan 1998

The Determination Of Thermal Annealing Effect On The Dos Profile Of A-Si:H Film, Tülay Seri̇n

Turkish Journal of Physics

In this study the aim was to investigate the effect of thermal annealing on the density of states (DOS) of hydrogenated amorphous silicon (a-Si:H) by means of a Schottky structure. In order to realize that goal the sandwich structured Au/a-Si:H/a-Si:H(n$^+$-type)/Cr Schottky diode was fabricated. The junction capacitance of the samples were measured as a function of the amplitude of alternating voltage in the frequency range of 500 Hz - 100 KHz and in the annealing temperature range of 23 - 175^oC. The density of states profile as a function of both annealing temperature and energy were plotted. The effect of …

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Calculation Of The Reaction Cross-Section For Proton-Nucleus Using Recently Optical Potential, M. M. Osman Jan 1998

Calculation Of The Reaction Cross-Section For Proton-Nucleus Using Recently Optical Potential, M. M. Osman

Turkish Journal of Physics

The eikonal approximation is used to calculate the reaction cross-section for proton scattering from different nuclei. The imaginary proton - nucleus optical potential is derived from relativistic mean field theory approach. We found a fair agreement with experimental data.

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Crystal Data For A_3b_5c_9-Type Ternary Compounds, Hüsnü Özkan, Nizami Gasanly, İbrahim Yilmaz, Ali Çulfaz, Vyaceslav Nagiev Jan 1998

Crystal Data For A_3b_5c_9-Type Ternary Compounds, Hüsnü Özkan, Nizami Gasanly, İbrahim Yilmaz, Ali Çulfaz, Vyaceslav Nagiev

Turkish Journal of Physics

X-ray powder diffraction data were obtained for Cu$_3$Ga$_5$Se$_9$, Cu$_3$In$_5$Se$_9$, Cu$_3$In$_5$Te$_9$, Ag$_3$In$_5$S$_9$, Ag$_3$Ga$_5$S$_9$, Ag$_3$In$_5$Se$_9$, and Ag$_3$Ga$_5$Te$_9$ ternary compounds. The data indicate that these compounds crystallize in orthorhombic, monoclinic, orthorhombic, monoclinic, tetragonal, tetragonal, and orthorhombic systems, respectively.

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Progess In Photon Colliders, Valery Telnov Jan 1998

Progess In Photon Colliders, Valery Telnov

Turkish Journal of Physics

Last two years were very important in history of a photon colliders. This option is included now in conceptual design reports of the NLC, JLC and TESLA/SBLC projects. All the designs foresee two interaction regions: one for e^+e^- and the second for \gamma\gamma, \gamma e and e^-e^- collisions. This paper is focused on three aspects: 1) arguments for photon colliders; 2) parameters of current projects; 3) ultimate luminosities and energies, new ideas. Recent studies have shown that the main collision effect - coherent pair creation - is suppressed at photon colliders with the energy (2E $

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High Luminosity Muon Collider Studies In The U.S.A., Muzaffer Ataç Jan 1998

High Luminosity Muon Collider Studies In The U.S.A., Muzaffer Ataç

Turkish Journal of Physics

Muon colliders as a future collider project in the U.S.A., have attracted many physicists from many institutions in recent years. Workshops and conferences have been held on the subject in the last few years. The studies show that high luminosity circular muon colliders can be built at high luminosities and at high center-of-mass energies. Some aspects of the muon colliders, physics possibilities, background and detector issues will be discussed. Some comparisons between the muon and hadron colliders, and electron-positron colliders, will be made.

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Possibility To Measure Polarized Gluon Distribution Via Real Gamma Beam, A. Çeli̇kel Jan 1998

Possibility To Measure Polarized Gluon Distribution Via Real Gamma Beam, A. Çeli̇kel

Turkish Journal of Physics

We propose an experiment to measure the polarized gluon and quark distributions in scattering of polarized real $\gamma$ beam on polarized nuclear target.

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Four Ways To Tev Scale, S. Sultansoy Jan 1998

Four Ways To Tev Scale, S. Sultansoy

Turkish Journal of Physics

Four known types of colliders, which may give an opportunity to achieve TeV center of mass energies in the near future (10-15 years), are discussed. Parameters of the linac-ring type $ep$ and $\gamma p$ machines are roughly estimated. Some speculations on TeV scale physics are given. The physics goals of the TeV energy $ep$ and $\gamma p$ colliders are considered.

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Interaction Region And Luminosity Limitations For Thetesla/Hera E/P Collider, R. Brinkmann Jan 1998

Interaction Region And Luminosity Limitations For Thetesla/Hera E/P Collider, R. Brinkmann

Turkish Journal of Physics

No abstract provided.

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Tune Shift Limitations For Linac-Ring Type Colliders, Ö. Yavaş Jan 1998

Tune Shift Limitations For Linac-Ring Type Colliders, Ö. Yavaş

Turkish Journal of Physics

Limitations on incoherent and beam-beam tune shift values are calculated by using gaussian beam distribution for linac-ring type $ep$ colliders. The advantage of this machine is achievement of multi TeV center of mass energies in lepton-hadron interactions at sufficiently high luminosities. Tune shift puts a limit on the number of electrons per effective area for the stability of proton beam and, therefore, gives an upper bound for the luminosity.

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Main Parameters Of \Gammap Colliders, A.K. Çi̇ftçi̇ Jan 1998

Main Parameters Of \Gammap Colliders, A.K. Çi̇ftçi̇

Turkish Journal of Physics

Main parameters of TeV energy $\gamma $p colliders have been investigated for HERA+ SBLC, HERA+TESLA, HERA+e-linac, LHC+TESLA, LHC+CLIC and LHC+$e$ -linac proposals. Luminosity of $\gamma p$ collisions for these colliders are studied in terms of a distance between the conversion region and the collision point.

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A Possibility To Control The Polarization Of High-Energy Photons By Means Of A Laser Beam, G.L. Kotkin, V.G. Serbo Jan 1998

A Possibility To Control The Polarization Of High-Energy Photons By Means Of A Laser Beam, G.L. Kotkin, V.G. Serbo

Turkish Journal of Physics

The elastic light-light scattering below the threshold of the $e^+e^-$ pair production leads to a variation in polarization of hard $\gamma$-quanta traversing without loss a region where the laser light is focused. This effect can be used to control the $\gamma$-quantum polarization. Equations are obtained which determine the variation of Stokes parameters of $\gamma$-quanta in this case, and their solutions are given. It is pointed out that this effect can be observed in the experiment E-144 at SLAC. It should be taken into account and, perhaps, it can be used in experiments at future $\gamma \gamma$ colliders.

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Ordinary And Coherent Bremsstrahlung At Linac-Ring Ep Colliders, V.G. Serbo, D.V. Serebryakova Jan 1998

Ordinary And Coherent Bremsstrahlung At Linac-Ring Ep Colliders, V.G. Serbo, D.V. Serebryakova

Turkish Journal of Physics

The ordinary bremsstrahlung $ep \rightarrow ep\gamma$ can be used at the linac-ring $ep$ colliders for luminosity measurement. It is known that at high energies this process has a large correction due to beam-size effect. We have calculated this effect for $ep$ colliders of the linac-ring type. For the LHC+CLIC collider the correction exceeds 10\% for $E_{\gamma} < 0.95\;E_e$. As a rule, the bremsstrahlung of protons in the $ep$ scattering is not considered due to its small cross section. However, if the photon energy $E_{\gamma}$ becomes small enough, the number of produced photons become large because in this case the radiation is determined by the interaction of a proton with the collective electromagnetic field of the electron bunch. It is coherent bremsstrahlung (CBS). We present the main characteristics of CBS calculated for linac-ring $ep$ colliders. At the LHC+CLIC collider it should be about $1700 \; dE_\gamma /E_\gamma$ photons for a single collision of bunches at $E_\gamma \stackrel{

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Electroweak Gauge Boson Production At \Gamma\Gamma Collider, G. Jikia Jan 1998

Electroweak Gauge Boson Production At \Gamma\Gamma Collider, G. Jikia

Turkish Journal of Physics

No abstract provided.

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Hard Diffractive Photoproduction With Rapidity Gap, Ilya F. Ginzburg Jan 1998

Hard Diffractive Photoproduction With Rapidity Gap, Ilya F. Ginzburg

Turkish Journal of Physics

Hard diffractive photoproduction with rapidity gap is the best place for study of perturbative Pomeron. Some predictions of pQCD and the range of their applicability are described.

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The Heavy Higgs Effects In The Framework Of Sm, V. Borodulin, G. Jikia Jan 1998

The Heavy Higgs Effects In The Framework Of Sm, V. Borodulin, G. Jikia

Turkish Journal of Physics

No abstract provided.

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Structural And Optical Characterisation Of Vacuum Deposited Cdte Thin Films, Murat Bayhan Jan 1998

Structural And Optical Characterisation Of Vacuum Deposited Cdte Thin Films, Murat Bayhan

Turkish Journal of Physics

The structural and optical properties of vacuum deposited CdTe thin films on glass substrates were investigated. The effect of the heat treatment in air over the former properties of the layers was also examined. Grain sizes of air heated layers estimated by net broading in the XRD spectra were found to be larger than as-grown layers, confirming that grain growth had occurred during the heat treatment. RHEED patterns of the layers grown at substrate temperatures between 150°C and 170°C had a distinct \{111\} preferred orientation. As-grown CdTe layers were slightly p-type, but highly resistive. Air heat treated layers were p-type …

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9. Alteration Of Uppermost Lavas And Volcaniclastics Recovered During Leg 152 To The East Greenland Margin, Mary Anne Holmes Jan 1998

9. Alteration Of Uppermost Lavas And Volcaniclastics Recovered During Leg 152 To The East Greenland Margin, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

During the last stages of the eruption of syn-rift basalts along the East Greenland Margin, debris flows and/or pyroclastic deposits were emplaced at Ocean Drilling Program Sites 915 and 916. The deposits and the tops of the lava flows at Site 918 were altered by subaerial weathering processes as indicated by downhole changes in mineral and chemical composition, and by the mineral paragenesis. Kaolinite and goethite, which form in acidic waters, are abundant at the tops of the weathering profiles and decrease in abundance downward. They are replaced by a smectite-hematite-opal assemblage at the bases of the weathered profiles. Gibbsite …

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High-Resolution Pliocene–Pleistocene Biostratigraphy Of Site 959, Eastern Equatorial Atlantic Ocean, Im Chul Shin, Samir Shafik, David K. Watkins Jan 1998

High-Resolution Pliocene–Pleistocene Biostratigraphy Of Site 959, Eastern Equatorial Atlantic Ocean, Im Chul Shin, Samir Shafik, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

High-resolution calcareous nannofossil biostratigraphy was examined from Cores 159-959C-1H through 8H in 20-cm intervals for the Ocean Drilling Program in the eastern equatorial Atlantic Ocean. Well-preserved marker species occur continuously and are relatively abundant in Hole 959C. Six zones (CN10 through CN15) are identified. All calcareous nannofossils are well preserved. Late Neogene (Pliocene–Pleistocene) sediment is dominated by Florisphaera profunda, Gephyrocapsa caribbeanica, G. oceanica, Gephyrocapsa spp., Reticulofenestra pseudoumbilica, R. minutula, and small Reticulofenestra. The sedimentation rate varies from 0.4 cm/k.y. to 13.5 cm/k.y. This strong variations are related to disconformities. The lowest sedimentation rate occurs in the early late …

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Evolution Of The Aeluroid Carnivora: Diversity Of The Earliest Aeluroids From Eurasia (Quercy, Hsanda-Gol) And The Origin Of Felids, Robert M. Hunt Jr. Jan 1998

Evolution Of The Aeluroid Carnivora: Diversity Of The Earliest Aeluroids From Eurasia (Quercy, Hsanda-Gol) And The Origin Of Felids, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

The oldest known fossil aeluroids are from Lower Oligocene sediments in France (Quercy) and Upper Eocene-Lower Oligocene sediments in Mongolia. These small (< 5 kg) carnivorans are primarily represented by mandibles, with hypercarnivorous dentitions in almost all lineages. The six aeluroid genera from France and those from Mongolia share a common dental pattern despite their geographic separation near the extremes of the Eurasian landmass. This similarity is not surprising, however, because faunal exchange across Eurasia at this time is documented not only by populations of small aeluroids but also by small arctoid carnivorans. Basicrania of Oligocene aeluroids are preserved only in the Quercy deposits. The auditory regions of two genera from Quercy (Palaeoprionodon, Stenoplesictis), and of two additional aeluroid genera (Stenogale, Proailurus) known only from mandibles at Quercy (but matched with congeneric mandibles with associated basicrania from early Miocene sediments at St.-Gerand), reveal a common basicranial morphotype. The living African palm civet Nandinia binotata retains a basicranial and auditory anatomy closely approaching the ancestral aeluroid morphotype. European paleontologists working with the Quercy faunas have regarded several of these aeluroids as early members of the Viverridae and …

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Dissociation Constants Of Oxalic Acid In Aqueous Sodium Chloride And Sodium Trifluoromethanesulfonate Media To 175 °C, Richard Kettler, David J. Wesolowski, Donald A. Palmer Jan 1998

Dissociation Constants Of Oxalic Acid In Aqueous Sodium Chloride And Sodium Trifluoromethanesulfonate Media To 175 °C, Richard Kettler, David J. Wesolowski, Donald A. Palmer

Department of Earth and Atmospheric Sciences: Faculty Publications

The first and second molal dissociation constants of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. Measurements were made at six temperatures ranging from 5 °C to 125 °C at four ionic strengths ranging from 0.1 mol•kg-1 to 1.0 mol•kg-1 (NaCl and NaCF3-SO3). The second molal dissociation constant was measured in NaCF3SO3 media only. The data obtained in this study were combined with the corresponding literature values, including a number of recalculated Harned cell and concentration cell measurements and previous results from this laboratory. Data for …

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Tcp/Ip Implementation With Endsystem Qos, Sherlia Y. Shi, Gurudatta M. Parulkar, R. Gopalakrishnan Jan 1998

Tcp/Ip Implementation With Endsystem Qos, Sherlia Y. Shi, Gurudatta M. Parulkar, R. Gopalakrishnan

All Computer Science and Engineering Research

This paper presents a Real-time Upcall (RTU) [1] based TCP/IP implementation that guarantees throughput for continuous media applications and ensures low latency bounds for interactive applications. RTU is an endsystem rate-based scheduling mechanism that provides quality of service (QoS) in terms of CPU cycles, to applications. We restructured the existing NetBSD TCP/IP implementation to exploit the RTU concurrency model and to provide predictable performance. Our experimental results show that on two 200 MHz NetBSD PCs connected by a 155Mbps ATM link, the RTU based kernel TCP/IP implementation provides excellent throughput guarantees for periodic connections regardless the system or network load. …

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Integrating A Constraint Mechanism With The Javabeans Model, William M. Shapiro Jan 1998

Integrating A Constraint Mechanism With The Javabeans Model, William M. Shapiro

All Computer Science and Engineering Research

The JavaBeans component model allows users to plug together software components to create Java applications by specifying simple relationships between component events and properties. This paper describes work on augmenting the simple JavaBeans model with a multi-way constraint mechanism that allows users to graphically specify more complex multi-way contraints, resolve cyclical constraints between bean properties and graphically layout bean components. We also discuss weaknesses in the JavaBeans model and Java Abstract Windowing Toolkit (AWT) that were discovered while integrating a constraint mechanism with JavaBeans.

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Congestion Control In Multicast Transport Protocols, Rajib Ghosh, George Varghese Jan 1998

Congestion Control In Multicast Transport Protocols, Rajib Ghosh, George Varghese

All Computer Science and Engineering Research

We discuss congestion control mechanisms in multicast transport protocols and we propose TCP-M - a TCP-friendly Multicast transport protocol. TCP-M uses IP multicast to deliver data packets and acknowledgements to provide reliability. Ack implosion at the source is prevented by fusing acknowledgements at some intermediate routers. TCP-M reacts to network congestion exactly like TCP by having the sender emulate a TCP sender.

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Terabit Burst Switching Progress Report (6/98-9/98), Jonathan S. Turner Jan 1998

Terabit Burst Switching Progress Report (6/98-9/98), Jonathan S. Turner

All Computer Science and Engineering Research

This report summarizes progress on the Terabit Burst Switching Project at Washington University for the period from June 15, 1998 through September 15, 1998.

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Terabit Burst Switching Progress Report (12/97-2/98), Jonathan S. Turner Jan 1998

Terabit Burst Switching Progress Report (12/97-2/98), Jonathan S. Turner

All Computer Science and Engineering Research

This report summarizes progress on the Terabit Burst Switching Project at Washington University for the period from December 15, 1997 through March 15, 1998. Efforts during this period have concentrated on working out details of the burst switch architecture, evaluating a variety of implementation alternatives and developing the physical design of the 160 Gb/s ATM switch to allow demonstration of the burst switch within a realistic network context.

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Diagnostic Screening Of Digital Mammograms Using Wavelets And Neural Networks To Extract Structure, Barry L. Kalman, Stan C. Kwasny, William R. Reinus Jan 1998

Diagnostic Screening Of Digital Mammograms Using Wavelets And Neural Networks To Extract Structure, Barry L. Kalman, Stan C. Kwasny, William R. Reinus

All Computer Science and Engineering Research

As the primary tool for detecting breast carcinoma, mammography provides visual images from which a trained radiologist can identify suspicious areas that suggest the presence of cancer. We describe an approach to image processing that reduces an image to a small number of values based on its structural characteristics using wavelets and neural networks. To illustrate its utility, we apply this methodology to the automatic screening of mammograms for mass lesions. Our results approach performance levels of trained human mammographers.

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