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1.
The magnetic structure of UAs0.97Se0.03 has been studied by neutron diffraction from a single crystal in zero applied magnetic field. It is found to be antiferromagnetic, of type-IA (++--) below To = 75.6 K and of type-I (+-+-) above To. The type-I persists till TIC = 113.5 K, while above it and up to TN = 122 K an incommensurate phase appears, thereby modifying the magnetic structure in pure UAs. The k-value of the wavevector (along cubic axes) is changing from 0.642 at TN to 0.652 at TIC. The transitions at To and TIC are first-order while the transition at TN is second-order. The ordered magnetic moment is 2.15 μB at T = 4.2 K, it varies smoothly to 1.95 μB at T = 75.4 K and drops drastically to 1.47 μB at T = 76 K. 相似文献
2.
《Solid State Communications》1989,70(6):687-691
Temperature dependence of dark and photoconductivity is studied in amorphous films of Se80Te20−xCdx in the temperature range (300 K to 380 K) with a view to see the effect of Cd impurity on a-Se80Te20 binary alloy. It is observed that, at low concentration of Cd (x = 0.5), the dark and photoconductivity increase at all temperatures. However, at higher concentration of Cd (x = 10), an appreciable reduction in these parameters occurs in the same temperature range. The photosensitivity (σph/σd) remains unchanged at x = 0.5 but decreases quite significantly at x = 10. The results are explained in terms of impurity doping at x = 0.5 and alloying effect at x = 10. 相似文献
3.
M. Banner J.L. Hamel J.P. Pansart A.V. Stirling J. Teiger H. Zaccone J. Zsembery G. Bassompierre M. Croissiaux J. Greeser R. Morand M. Riedinger M. Schneegans 《Physics letters. [Part B]》1973,44(6):537-540
Total charged particle fluxes above 1.2 GeV/c transverse momentum at 90° have been measured at the CERN Intersecting Storage Rings for c.m. energies between 23.2 and 52.7 GeV. In addition, charged pion spectra above 3 GeV/c have been obtained at 44.4 and 52.7 GeV, as well as gamma-ray spectra at the same energies. The upper limit to produce a single electron above 3 GeV/c at 90° is less than 1.2 × 10?33cm2/sr at 90% confidence level. 相似文献
4.
Helmut Friedrich 《Communications in Mathematical Physics》2013,321(2):419-482
In the Cauchy problem for asymptotically flat vacuum data the solution-jets along the cylinder at space-like infinity develop in general logarithmic singularities at the critical sets at which the cylinder touches future/past null infinity. The tendency of these singularities to spread along the null generators of null infinity obstructs the development of a smooth conformal structure at null infinity. For the solution-jets arising from time reflection symmetric data to extend smoothly to the critical sets it is necessary that the Cotton tensor of the initial three-metric h satisfies a certain conformally invariant condition (*) at space-like infinity, it is sufficient that h be asymptotically static at space-like infinity. The purpose of this article is to characterize the gap between these conditions. We show that with the class of metrics which satisfy condition (*) on the Cotton tensor and a certain non-degeneracy requirement is associated a one-form κ with conformally invariant differential dκ. We provide two criteria. If h is real analytic, κ is closed, and one of its integrals satisfies a certain equation then h is conformal to static data near space-like infinity. If h is smooth, κ is asymptotically closed, and one of its integrals satisfies a certain equation asymptotically then h is asymptotically conformal to static data at space-like infinity. 相似文献
5.
E. H. Brandt G. P. Mikitik E. Zeldov 《Journal of Experimental and Theoretical Physics》2013,117(3):439-448
Vortex penetration into a thin superconducting strip of a rectangular cross section is considered at an increasing applied magnetic field H a , taking an interplay between the Bean-Livingston and the geometric barriers in the sample into account. We calculate the magnetic field H p at which the penetration begins and show that two regimes of vortex penetration are possible. In the first regime, vortices appearing at the corners of the strip at H a = H p immediately move to its center, where a vortex dome starts to develop. In the second regime, the penetration occurs in two stages. In the first stage, at H a < H p , tilted vortices penetrate into the edge regions of the strip, where novel domes are shown to be formed at the top, bottom, and lateral surfaces. In the second stage, at H a = H p , the vortex propagation to the center becomes possible. The difference between the regimes manifests itself in slightly different dependences of the magnetic moment of the strip on H a . 相似文献
6.
As determined from ? vs T measurements, the TN vs Al content curve for CrAl alloys exhibits three distinct regions. The first region extends from 0 to about 2 at.% Al. Here the Néel temperature decreases linearly in two stages, with an abrupt change in slope occurring at about 1.2 at.% Al. From 2 to 4 at.% Al no TN value could be defined from the resistivity measurements. Finally, at concentrations higher than 4 at.% Al, TN was observed to increase with increasing Al content. The variation of dTN/dp with Al concentration was found to be similar to the TN curve in the first region. Exceptionally high values of dTN/dp were found. 相似文献
7.
This paper is a continuation of a previous investigation of oxygen adsorption on tungsten at high temperature using Auger electron spectroscopy. In this paper the adsorption isotherms of oxygen on (100), (110) and (111) faces of tungsten are reported. It is shown that these isotherms can be described by an equation of the form pO2 = AF(θ) exp [?q(θ)/ kT]. The coverage depended functions F(θ) and q(θ) evaluated from the isotherms are different for all three investigated faces. The isosteric adsorption energy q has following initial values at very low oxygen coverage: q100 = 6.1 eV, q110 = 6.8 eV and q111 = 6.5 eV. Increasing the oxygen coverage has only small influence on q111; it changes from the initial value to q111 ≈ 6.0 eV at θ ≈ 0.3 and remains constant at this value up to θ ≈ 1. q110 shows the strongest dependence on oxygen coverage. It decreases rapidly at low coverages, slowly at moderate coverages and reaches the value q110 = 5.0 atθ ≈ 1. The variation of q110 with increasing oxygen coverage is monotonie from the initial value to q111 = 4.9 eV at θ ≈ 1. Assuming that the atomic oxygen is the dominant species leaving the tungsten surface at high temperatures the functions F(θ) are used to calculate the oxygen equilibration probability ζO2 (high temperature sticking probability) as a function of oxygen coverage θ. The main characteristic of ζO2(θ) for all three faces is that it shows a maximum for (100) and (111) faces at θ = 0.3 and for (110) face at θ = 0.55. 相似文献
8.
S. Kuroita K. Sagara T. Kudoh T. Sueta T. Sugimoto H. Shimoda Y. Yamada T. Wakasa T. Noro Y. Tameshige Y. Shimizu T. Ishida J. Kamiya Y. Sakemi A. Tamii K. Hatanaka 《Few-Body Systems》2008,44(1-4):53-56
Inclusive measurements of the D(p, p)pn reaction were made at incident proton energies of 248?MeV and 13?MeV, to investigate the global feature of the pd breakup reaction at intermediate and low energies. At 248?MeV, the cross section and analyzing power A y were measured at four angles from 7° to 20°. The data largely disagree with Faddeev calculations even if 2π-exchange three-nucleon force (2π3NF) or Δ-isobar is included, and the disagreement increases at forward angles. At 13?MeV, the cross section was measured at eight angles from 10° to 70°. The data are well reproduced by a recent pd Faddeev calculation, and the effects of Δ-isobar at 13?MeV are very small. 相似文献
9.
《Applied Surface Science》1987,28(4):331-344
Etch rate-potential curves of p-InP in HBrandBr2/HBr solutions in the dark and under illumination were correlated with current-potential curves. It was found that InP is etched via a “chemical” mechanism both by HBrandBr2. In aqueous HBr solutions InP is only etched at a significant rate at concentrations higher than 5 mol/ℓ. The Br2 etchants contained 4.5M HBr; in this case HBr only serves to complex Br2toBr-3. The etch rate in Br2/HBr solutions is mass-transport controlled at InP(001) and kinetically controlled at InP with the (111) In orientation. The macroscopically obtained results are consistent with the profiles etched at resist edges in InP. The electrochemistry of Br2 at p-InP under illumination reveals some interesting aspects with regard to the agreement between the etch rate and the Br2 reduction. 相似文献
10.
K. Sagara T. Sugimoto S. Kuroita Y. Maeda T. Sueta H. Shimoda 《Few-Body Systems》2008,44(1-4):203-205
Systematic measurement of the D(p, pp)n cross section at E p = 13 MeV at star configurations at various inclined angle α is in progress at Kyushu University tandem accelerator laboratory (KUTL). The measured cross section at space star (α = 90°) is about 12% below the recent pd calculation. The next measurement is being made at 0° < α < 90° to see if the large anomaly of about 25% found by the Köln group (2006) at backward α exists also at forward α. 相似文献
11.
In this work a numerical investigation has been carried out to study the effect of g-jitter on zero-gravity (0ge) opposed flow spreading flame over thin solid fuels. For comparison simulations have also been carried out for normal gravity (1ge) downward spreading flames. G-jitter is emulated by gravity modulation of sinusoidal (Age sin(2πt/Tge)) gravity perturbation (g-perturbation) of a particular time-period (Tge) and amplitude (Age) over a selected base gravity level (0ge or 1ge). The response of flames at 0ge base gravity and at 1ge base gravity was different to the imposed g-perturbation. While at 0ge the mean and the amplitude of the oscillatory flame spread rate (FSR) magnified with increase in the time period of g-perturbation, interestingly for the 1ge flame a maximum mean FSR and oscillation amplitude occurs at certain perturbation time period. Further, at very small perturbation time-periods (Tge) the FSR at 1ge was lower than the steady state FSR. The amplitude of oscillatory FSR increased with increase in perturbation amplitude (Age). However, the 0ge flame which is little affected (compared to 1ge flame) at small perturbation amplitude (Age) is affected severely at large perturbation amplitude (Age). Both the gas phase and fuel pyrolysis (or fuel response) follow perturbation signal with a lag but fuel pyrolysis is more sluggish and lags behind gas phase. The phase lag between fuel pyrolysis and gas increases at smaller time-periods (Tge) and tends to enhance the effect of external perturbation whereas at larger time-periods (Tge) this lag inhibits the effect of external perturbation. 相似文献
12.
《Infrared physics》1989,29(2-4):371-380
Spectroscopic investigations have been carried out on IR emission (and induced absorption) of bulky InSb subjected to a magnetic field H across a current density J passing through it at 80–300 K. Significant contribution of deep-level acceptors, such as Cu− and Cu−−, to the radiative recombination has been observed at low excitations by J × H force at 80 and 300 K. While at high excitations the emission due to band-to-band recombination dominates even at low temperatures, and at further high excitations notable line narrowing in the spectral line has been disclosed at 80 K, demonstrating occurrence of lasing mostly in a form of multi-mode oscillations but occasionally with single-mode oscillation. 相似文献
13.
J.J. Jarmer J.C. Martin G.G. Ohlsen G.C. Salzman J.E. Simmons 《Physics letters. [Part B]》1974,48(3):215-217
The longitudinal polarization of neutrons has been measured for the reaction with the incident proton beam longitudinally polarized. Measurements were performed at 0° for proton energies from 4 to 15 MeV and an angular distribution was measured at 10 MeV. The data determine the polarization transfer coefficient Kzz′, which is equivalent to the Wolfenstein A′ parameter for nucleon-nucleon scattering. The quantity Kzz′ at 0° increases from about 0.3 at 3 MeV incident energy to 0.9 at 9 MeV, and then decreases to 0.5 at 15 MeV. The data are computed with R-matrix calculations which reproduce the qualitative shape of the data at 0° and the angular distribution at 10 MeV. 相似文献
14.
Jesús Villa María AraizaDaniel Alaniz Rumen IvanovMarvin Ortiz 《Optics and Lasers in Engineering》2012,50(2):256-261
In this work we present a phase to (x,y,z)-coordinates transformation method for the calibration of a fringe projection profilometer. Our technique is divided in two parts: (1) phase to z transformation (for axial calibration) based on the typical polynomial fitting which uses a flat plane placed at several z positions to measure the phase of the projected fringes. (2) Phase to x and y transformation (for transverse calibration) based on the use of a crossed gratings pattern and a Fourier phase measurement method to determine x and y coordinates at several z positions. As will be shown the use of the crossed gratings pattern and the Fourier phase measurement method for transverse calibration is advantageous in several aspects: an unique image can give us x and y information at once. It provides x and y coordinates at each pixel in the image avoiding the use of interpolation methods. We present some experimental results and explain the viability of the proposed technique. 相似文献
15.
The effects of finite grid resolution on the statistics of small scales in direct numerical simulations of turbulent mixing of passive scalars are addressed in this paper. Simulations at up to 20483 grid points with grid spacing Δx varied from about 2 to 1/2 Batchelor scales (ηB) show that most conclusions on Schmidt number (Sc) dependence from prior work at less stringent resolution remain qualitatively correct, although simulations at resolution Δx≈ηB are preferred and will give adequate results for many important quantities including the scalar dissipation intermittency exponent and structure functions at moderately high orders. For Sc≥1, since ηB=ηSc−1/2 (where η is the Kolmogorov scale), the requirement Δx≈ηB is more stringent than the corresponding criterion Δx≈η for the velocity field, which is thus well resolved in simulations aimed at high Schmidt number mixing. A simple argument is given to help interpret the effects of Schmidt and Reynolds numbers on trends towards local isotropy and saturation of intermittency at high Schmidt number. The present results also provide evidence for a trend to isotropy at high Reynolds number with fixed Sc=1.0. This is a new observation apparently not detected in less well resolved simulations in the past, and will require further investigation in the future. 相似文献
16.
Electron paramagnetic resonance measurements in single crystals of NiSiF6. 6D2O were made at K, Ku and Ka bands at 4.2 K and between 77 K and 300 K. The measured g values were in the range 2.23–2.26, while the zero-field splitting parameter D varied from ?(0.185 ± 0.005) cm?1 at 4.2 K to ?(0.53 ± 0.01) cm?1 at 298 K. The parameters of the trimolecular hexagonal unit cell were determined to be approximately a = 9.28 Å, c = 9.58 Å from powder X-ray diffraction measurements at room temperature. 相似文献
17.
The current-voltage (I-V) characteristics of Al/Rhodamine-101/p-Si/Al contacts have been measured at temperatures ranging from 280 to 400 K at 20 K intervals. A barrier height (BH) value of 0.817 eV for the Al/Rh101/p-Si/Al contact was obtained at the room temperature that is significantly larger than the value of 0.58 eV of the conventional Al/p-Si Schottky diode. While the barrier height Φb0 decreases the ideality factors (n) become larger with lowering temperature. The high values of n depending on the sample temperature may be ascribed to decrease of the exponentially increase rate in current due to space-charge injection into Rh101 thin film at higher voltage. Therefore, at all temperatures, it has been seen that the I-V characteristics show three different regions, the ohmic behavior at low voltages, and the space charge limited current with an exponential distribution of traps at high voltages. 相似文献
18.
《Nuclear Physics A》1987,469(4):726-748
Two high statistics measurements of antiproton-proton small-angle elastic scattering, at p = 233 MeV/c and p = 272 MeV/c, are presented. The measurements were carried out at the LEAR facility at CERN. By the Coulomb-nuclear interference method, values are obtained for the real-to-imaginary ratio ρ of the p̄p forward nuclear scattering amplitude and for its exponential slope b: ρ = + 0.041 ± 0.026 and b = 71.5 ± 4.5 (GeV/c)−2 at 233 MeV/c and ρ = −0.014 ± 0.027 and b = 47.7 ± 2.7 (GeV/c)−2 at 272 MeV/c. The method to derive these values is discussed in detail and so are the uncertainties contributing to their systematic error. The results are compared with predictions from forward dispersion relation calculations and with predictions from p̄p potential models. 相似文献
19.
W. Lang C. Fussenegger S. Proyer E. Stangl D. Bäuerle 《Zeitschrift für Physik B Condensed Matter》1996,100(1):13-18
Abstract. We report on investigations of the current-dependent ac impedance Z at 17 Hz of a YBa2Cu3O7 thinfilm microbridge in magnetic fields from 1 to 8 T. A phasesensitive lock-in technique was applied and supplemented by a pulsed method for high current densities. Above the vortex-glass transition temperature T g a constant Z(j) is observed with low current densities j, and a power-law behavior at high currents. Below T g, the curvature of the Re Z vs. j curve is negative in a log-log plot. The Re Z(j) isotherms can be collapsed onto two universal scaling functions according to the predictions of the vortex-glass model. Close to and below T g, a phase lag between current and voltage appears, which saturates to finite values at low j and to zero at high j. The phase lag within the constant-Z(j) region remains below the critical value, predicted theoretically by Dorsey, if T > T g and approaches 90° at T < T g indicating the freezing of the vortices into the dissipation-free vortex-glass state. 相似文献
20.
Measurements of the EPR linewidth ΔH of EuO at 9 GHz are reported in the temperature range of 66–300° K, with particular attention to the region near Tc (69.6° K). Comparison with the earlier data of Eastman at 25 GHz in the critical region shows considerable suppression of ΔH at 25 GHz. The temperature-dependent behavior of ΔH in EuO at 9 GHz is similar to the observations in CrBr3 and it is in qualitative agreement with the zero-field predictions of Huber and Maleev. The quantitative discrepancies are believed to be due to the effect of the resonance magnetic field on EPR spin dynamics near Tc and an inadequate decoupling of the four-spin correlation functions used in the theories. 相似文献