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Articles 31021 - 31050 of 36659

Full-Text Articles in Physical Sciences and Mathematics

Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka Jan 1998

Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka

Electrical and Computer Engineering Faculty Publications

In many practical situations, it is important to determine and measure the attitude of a particular vehicle, such as a ship, an airplane, a piece of mechanical equipment such as a, crane lifter, or a spacecraft. For this reason, many attitude sensors have been developed with advanced computer and semiconductor technologies. This section first introduces the various attitude sensors with an explanation of their operating principles and then presents several methodologies for attitude measurement and determination, including ships and crane lifters, aircraft, and spacecraft applications.

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Physical Dependence Of The Sensitivity And Room-Temperature Stability Of Auxge1-X Thin Film Resistive Thermometers On Annealing Conditions, Nathanael A. Fortune, Michael J. Graf, Keizo Murata Jan 1998

Physical Dependence Of The Sensitivity And Room-Temperature Stability Of Auxge1-X Thin Film Resistive Thermometers On Annealing Conditions, Nathanael A. Fortune, Michael J. Graf, Keizo Murata

Physics: Faculty Publications

The reported nearly constant temperature sensitivity of appropriately annealed polycrystalline AuxGe1-x thin films at cryogenic temperatures would appear to make them promising materials for low mass, rapid thermal response resistive thermometers, but their adoption has been limited by difficulties in fabrication and uncertainties in annealing. In this work, we present a method of fabrication and annealing which allows control of the two most important parameters for these films: the room-temperature resistivity ρRT and the temperature sensitivity η(T), where η ≡ -d In R/d In T. We find that the dependence of ρRT on total anneal duration t for x≈0.18 is …

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Letter To The Editor, John C. Wheeler Jan 1998

Letter To The Editor, John C. Wheeler

Journal of the Minnesota Academy of Science

No abstract provided.

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Cusp Energetic Particle Events: Implications For A Major Acceleration Region Of The Magnetosphere, J. Chen, T. A. Fritz, R. B. Sheldon, Harlan E. Spence, W. N. Spjeldvik, J. F. Fennell, S. Livi, C. T. Russell, J. S. Pickett, D. A. Gurnett Jan 1998

Cusp Energetic Particle Events: Implications For A Major Acceleration Region Of The Magnetosphere, J. Chen, T. A. Fritz, R. B. Sheldon, Harlan E. Spence, W. N. Spjeldvik, J. F. Fennell, S. Livi, C. T. Russell, J. S. Pickett, D. A. Gurnett

Physics & Astronomy

The Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) on board the Polar spacecraft observed 75 energetic particle events in 1996 while the satellite was at apogee. All of these events were associated with a decrease in the magnitude of the local magnetic field measured by the Magnetic Field Experiment (MFE) on Polar. These new events showed several unusual features: (1) They were detected in the dayside polar cusp near the apogee of Polar with about 79% of the total events in the afternoonside and 21% in the morningside; (2) an individual event could last for hours; (3) the measured …

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Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt Jan 1998

Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A Mach-Zehnder based variable resolution fringe projection system has been built for 3-D video moini machine vision. This system uses the three main advantages of the Mach-Zehnder - 1) There is no optical feedback to the laser source, 2) The interfemmeter can accept two different laser wavelengths simultaneously, and 3) The interferometer produces two orthngonal output beams. The lack of optical feedback makes the Mach-Zehnder especially attractive for use with high power laser diode sources which are sensitive to optical feedback. When the two input ports axe used with two different wavelength lasers, the target can be illuminated by simultaneous …

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Solar Cycle Variability Of Hot Oxygen Atoms At Mars, Jhoon Kim, Andrew F. Nagy, Jane L. Fox, Thomas E. Cravens Jan 1998

Solar Cycle Variability Of Hot Oxygen Atoms At Mars, Jhoon Kim, Andrew F. Nagy, Jane L. Fox, Thomas E. Cravens

Physics Faculty Publications

The population of hot oxygen atoms in the Martian exosphere is reexamined using newly calculated hot O production rates for both low and high solar cycle conditions. The hot oxygen production rates are assumed to result from the dissociative recombination of O2+ ions. These calculations take into account the calculated vibrational distribution of O2+ and the new measured branching ratios. Furthermore, these calculations also consider the variation of the dissociative recombination cross section with the relative speed of the participating ions and electrons, the rotational energy of the O2+ ions, and the spread of …

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A Longitudinal Study Of Engineering Student Performance And Retention. V. Comparisons With Traditionally-Taught Students, Richard M. Felder, Gary Felder, E. Jacquelin Dietz Jan 1998

A Longitudinal Study Of Engineering Student Performance And Retention. V. Comparisons With Traditionally-Taught Students, Richard M. Felder, Gary Felder, E. Jacquelin Dietz

Physics: Faculty Publications

In a longitudinal study at North Carolina State University, a cohort of students took five chemical engineering courses taught by the same instructor in five consecutive semesters. The courses made extensive use of active and cooperative learning and a variety of other techniques designed to address a broad spectrum of learning styles. Previous reports on the study summarized the instructional methods used in the experimental course sequence, described the performance of the cohort in the introductory chemical engineering course, and examined performance and attitude differences between students from rural and urban backgrounds and between male and female students.1–4 This paper …

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Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek Jan 1998

Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek

Christian Binek Publications

The previous kinetics of the two-dimensional diluted Ising antiferromagnet Rb2Co0.85Mg0.15F4 is studied via the temporal relaxation of the field-induced magnetization after field cooling (FC) and zero-field cooling (ZFC), respectively, to T < TN = 75.2K. After FC different non-exponential decay laws indicate a crossover from domain reorientation to wall rearrangement at decreasing T. After ZFC rapidly saturating magnetization of naturally grown domain walls precedes the slow random-field-controlled disordering process.

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Effect Of High-Temperature Annealing On Electrical And Optical Properties Of Undoped Semi-Insulating Gaas, Z-Q. Fang, D. C. Reynolds, David C. Look, N. G. Paraskevopoulos, T. E. Anderson, R. L. Jones Jan 1998

Effect Of High-Temperature Annealing On Electrical And Optical Properties Of Undoped Semi-Insulating Gaas, Z-Q. Fang, D. C. Reynolds, David C. Look, N. G. Paraskevopoulos, T. E. Anderson, R. L. Jones

Physics Faculty Publications

A comprehensive characterization, including room temperature Hall effect, near infrared absorption, temperature dependent dark current and photocurrent (using 1.13 eV light), normalized thermally stimulated current (NTSC), photoluminescence at 4.2 K in both near band edge and deep level regions, and selective pair photoluminescence (SPL) at 2 K, has been carried out on undoped semi-insulating GaAs samples, cut from four wafers which were grown by the low pressure liquid encapsulated Czochralski technique and annealed by three different schedules: a 1100 °C anneal with either fast or slow cooling, or a 1000 °C standard anneal. The 1100 °C anneal clearly introduces higher …

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Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms, Alejandro Garcia, F. Alexander, B. Alder Jan 1998

Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms, Alejandro Garcia, F. Alexander, B. Alder

Alejandro Garcia

Using the Green–Kubo theory, the dependence of the viscosity and thermal conductivity on cell size is obtained explicitly for stochastic particle methods such as direct simulation Monte Carlo (DSMC) and its generalization, the consistent Boltzmann algorithm (CBA). These analytical results confirm empirical observations that significant errors occur when the cell dimensions are larger than a mean free path.

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Generalized Multiphoton-Ionization Cross Sections Of The Rare Gases For 500-Fs, 248.6-Nm Pulses, Cornelis J. Uiterwaal, D. Xenakis, D. Charalambidis, P. Maragakis, H. Schröder, P. Lambropoulus Jan 1998

Generalized Multiphoton-Ionization Cross Sections Of The Rare Gases For 500-Fs, 248.6-Nm Pulses, Cornelis J. Uiterwaal, D. Xenakis, D. Charalambidis, P. Maragakis, H. Schröder, P. Lambropoulus

C.J.G.J. Uiterwaal Publications

Absolute values for the generalized multiphoton-ionization cross sections and saturation intensities of rare gases are reported for 500-fs, 248.6-nm pulses. For He, Ar, and Kr these values are experimentally determined from the intensity dependence of the ponderomotive shift for intensities comparable to and above the saturation intensity. The measured experimental cross sections [σ(5)He=(0.9+9-o.4)×10-152 cm10 s4, σ(4)Ar=(1.3+1-0.5)×10-116 cm8 s3, σ(5)Kr=(1.2+1.7-0.6)×10-82 cm6 s2, σ(3)Xe=(50-45+350)×10-82 cm …

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Dimensionality And Energy Levels Of Quantum Mechanical Systems, Harry A. Mavromatis Jan 1998

Dimensionality And Energy Levels Of Quantum Mechanical Systems, Harry A. Mavromatis

Turkish Journal of Physics

The $N$-dimensional Schrödinger equation involving a general, central potential $V_N(r)$, is decomposed into a 3-dimensional component plus a term that may be treated as a dimension-dependent perturbation. This allows discussion of the general $N$-dimensional system from a 3-dimensional perspective.

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Structural Defects And Electrical Properties Of Extruded Samples Of Bi_{85}Sb_{15} Solid Solutions, Farkhad Samedov, Mail Tagiev Jan 1998

Structural Defects And Electrical Properties Of Extruded Samples Of Bi_{85}Sb_{15} Solid Solutions, Farkhad Samedov, Mail Tagiev

Turkish Journal of Physics

The effect of 5 hours annealing in vacuum $\sim 10^{-3} Pa$ at $503 K$ on the electroconductivity $(\sigma)$, the coefficient of thermoelectric power $(\alpha)$ and the Hall coefficient $(R_x)$ for extruded samples of $Bi_{85}Sb_{15}$ has been investigated in the temperature range from $\sim 77 K$ up to $\sim 300 K$. The samples were taken with a different concentration of $Pb$ (lead) up to $\sim 0.1 a.w \%$. The anisotropy of electrical properties of these samples was also studied in the temperature range between $77 K$ and $300 K$ and in the presence of magnetic field up to $\sim 74 \times …

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Theoretical Analysis Of The Crystallography For Do_3 --> M18r Martensitic Transformation, Seyfettin Çakmak, Ekrem Artunç Jan 1998

Theoretical Analysis Of The Crystallography For Do_3 --> M18r Martensitic Transformation, Seyfettin Çakmak, Ekrem Artunç

Turkish Journal of Physics

A mathematical approach of the phenomenological theory has been applied to the martensitic transformation of DO$_3 \rightarrow$ M18R close-packed structure. The crystallography of DO$_3 \rightarrow$ M18R martensitic transformation in Fe-25.8 wt\%Mn-7.4wt\%Al-0.11wt\%C alloy was studied using single crystals. Martensitic crystallographic parameters such as habit plane, magnitude of lattice invariant shear, shape deformation direction and orientation relationships are calculated with new mathematical approach. Phenomenological theoretical calculations were compared with predictions of the phenomenological crystallographic CRAB theory and with experimental observations.

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Effect Of Neutron Irradiation On Carriers Removel Rates In N-Si, M.S. Yunusov, M. Karimov, B.L. Oksengendler, M.A. Zhalelov Jan 1998

Effect Of Neutron Irradiation On Carriers Removel Rates In N-Si, M.S. Yunusov, M. Karimov, B.L. Oksengendler, M.A. Zhalelov

Turkish Journal of Physics

Carrier removal rate in $n-Si \langle P, Rh \rangle$ with different doping rhodium concentrations were investigated under fast neutrons irradiation. It is shown that the rate of carrier removal increases with phosphorus atom concentration but decreases with rhodium atom concentration. Theoretical analysis on the base of kinetic equations has shown that standard scheme of quasichemical reactions taking into account the interaction between rhodium atoms, vacancies and self interstitial atoms could not explain the results of experiment. Therefore a new model based on the use of radiation to increase the barrier between regions of fluctuating impurity concentration has been proposed.

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An Analysis Of The Variation In Calculated Confined-State Energies Using Different Envelope-Function Models, Beşire Gönül Jan 1998

An Analysis Of The Variation In Calculated Confined-State Energies Using Different Envelope-Function Models, Beşire Gönül

Turkish Journal of Physics

We investigate different formulations of the envelope-function method and show that the accuracy of the calculated zone-centre confinement energies can be calculated by means of bulk band structure. We show how coupling to the conduction and spin-split-off bands can decrease the light-hole zone-centre confinement energies and lead to significant differences in the calculated subband dispersion.

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Fibonaccization And Multiparameter Q-Oscillator, M. Arik, T. Rador, G. Ünel Jan 1998

Fibonaccization And Multiparameter Q-Oscillator, M. Arik, T. Rador, G. Ünel

Turkish Journal of Physics

Starting from Coon-Baker-Yu (CBY) q-oscillator, a two parameter, multidimensional q-oscillator is formulated. It is shown that this procedure, called Fibonaccization, can be extended to any number of parameters. The relation between CBY states and Fibonacci CBY states are also investigated.

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Comparison Of Metallicities Adopted For The Synthetic Ubv Photometry With Those Evaluated By Means Of Rgu Photometry, S. Karaali̇, S. Güngör, Y. Karataş Jan 1998

Comparison Of Metallicities Adopted For The Synthetic Ubv Photometry With Those Evaluated By Means Of Rgu Photometry, S. Karaali̇, S. Güngör, Y. Karataş

Turkish Journal of Physics

Comparison of metallicities adopted for synthetic UBV photometry with those evaluated by means of RGU photometry for 92 stars is presented. The agreement is only for zero metallicity. The discrepancy increases to low metallicities which cover Intermediate Population II and Population II main-sequence stars. U-G and G-R colour indices are transformed from UBV synthetic data and do not include any observational error. Therefore, the disagreement may originate from a systematic error in the metallicity calibration of relatively metal-poor stars in RGU photometry. Keywords: photometry - stars : abundances - metal-poor.

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Magnetic Diffuse Scattering In The Frustrated Square Lattice, Ali Bayri, Funda Ersoy Atalay, Hüseyin Gencer Jan 1998

Magnetic Diffuse Scattering In The Frustrated Square Lattice, Ali Bayri, Funda Ersoy Atalay, Hüseyin Gencer

Turkish Journal of Physics

Some of the first transition metal alloys show first order antiferromagnetic phase transition as a function of alloy concentration [1-5]. The antiferromagnetism of materials can be classified into three different class: type I, type II and type III. Although the neutron diffraction studies give information about the type of magnetism, they do not show the fluctuations of magnetic moment from the original direction. So in order to have some information about this fluctuations one must perform the magnetic diffuse scattering. Recently, we proposed that the square lattice may have a double-Q structure as well as single-Q [6]. We showed that …

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Solution Of Optic Reconstructive Problem Considering Registered Signal Velocity, A.A. Aliverdiev, M.G. Karimov Jan 1998

Solution Of Optic Reconstructive Problem Considering Registered Signal Velocity, A.A. Aliverdiev, M.G. Karimov

Turkish Journal of Physics

A solution to the tomographic problem of dynamic reconstruction of a processes, the rate of which is comparable with the velocity of the registered signal is presented. The obtained data can be used both for theoretical and applied tomography.

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Resonans Reflectionless Absorption Ofelectromagnetic Waves In Solutions, E. Salaev, E. Gasimov, S. Azizov, J. Qajar Jan 1998

Resonans Reflectionless Absorption Ofelectromagnetic Waves In Solutions, E. Salaev, E. Gasimov, S. Azizov, J. Qajar

Turkish Journal of Physics

No abstract provided.

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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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