共查询到20条相似文献,搜索用时 15 毫秒
1.
The wave-vector dependence of the liquid-vapor interfacial tension of Ga, gamma(q), has been determined from diffuse x-ray scattering measurements. The ratio gamma(q)/gamma(0)=1 for q<0.05 A(-1) decreases to 0.5 near q=0.22 A(-1), and increases strongly for larger q. The observed form for gamma(q)/gamma(0) is consistent with the prediction from the Mecke-Dietrich theory when the known stratified liquid-vapor interfacial density profile of Ga and a pseudopotential based pair interaction with appropriate asymptotic (r--> infinity ) behavior are used. The detailed behavior of gamma(q)/gamma(0) depends on the particular forms of both the interfacial density profile and the asymptotic falloff of the atomic pair interaction. 相似文献
2.
3.
The mosaic structure in a Ni-based single-crystal superalloy is simulated by
molecular dynamics using a potential employed in a modified analytic embedded atom
method. From the calculated results we find that a closed three-dimensional misfit
dislocation network, with index of $\langle 011\rangle${\{}100{\}} and the side
length of the mesh 89.6\,{\AA}, is formed around a cuboidal $\gamma '$ precipitate.
Comparing the simulation results of the different mosaic models, we find that the
side length of the mesh only depends on the lattice parameters of the $\gamma $ and
$\gamma '$ phases as well as the $\gamma $/$\gamma '$ interface direction, but is
independent of the size and number of the cuboidal $\gamma '$ precipitate. The
density of dislocations is inversely proportional to the size of the cuboidal
$\gamma '$ precipitate, i.e.~the amount of the dislocation is proportional to the
total area of the $\gamma $/$\gamma '$ interface, which may be used to explain the
relation between the amount of the fine $\gamma '$ particles and the creep rupture
life of the superalloy. In addition, the closed three-dimensional networks assembled
with the misfit dislocations can play a significant role in improving the mechanical
properties of superalloys. 相似文献
4.
Z. Grabowski J. E. Thun M. S. El-Nesr W. D. Hamilton 《Zeitschrift für Physik A Hadrons and Nuclei》1962,167(1):111-122
The study of nuclear structure effects in internal conversion has been extended to the Tm169 nucleus. Gamma-gamma, electron-gamma and gamma-electron directional correlations of the 177 keV-131 keV and the 198 keV-110 keV cascades have been measured. The following results were obtained:
$$\begin{array}{l} A_2 (177\gamma - 131\gamma ) = + 0 \cdot 275 \pm 0 \cdot 007,A_4 (177\gamma - 131\gamma ) = - 0 \cdot 005 \pm 0 \cdot 016, \\ A_2 (177\gamma - 131\gamma ) = + 0 \cdot 002 \pm 0 \cdot 007, \\ A_2 (177\gamma - 131K) = + 0 \cdot 497 \pm 0 \cdot 010, \\ A_2 (198\gamma - 110\gamma ) = + 0 \cdot 295 \pm 0 \cdot 007,A_4 (198\gamma - 110\gamma ) = - 0 \cdot 013 \pm 0 \cdot 017, \\ A_2 (198K - 110\gamma ) = + 0 \cdot 001 \pm 0 \cdot 008, \\ A_2 (198\gamma - 110K) = - 0 \cdot 005 \pm 0 \cdot 006. \\ \end{array}$$ 相似文献
5.
瞬发伽马活化成像中,样品内部的中子自屏蔽和伽马自吸收效应会使测量结果产生不均匀分布。针对成像单元响应不一致的问题,研究了样品内部中子场不均匀分布和伽马自吸收效应的影响,并进行了理论推导,建立了用于修正成像单元响应和图像重建的数学模型,利用数学模型对Fe,H元素瞬发伽马活化成像的蒙特卡罗模拟进行了元素图像重建。结果显示,样品内中子场和γ自吸收对成像的影响得到明显改善,Fe和H元素的含量分布使用此模型可以被精确重建,验证了数学模型的有效性。 相似文献
6.
Drutskoy A Abe K Abe K Abe T Aihara H Akatsu M Asano Y Aulchenko V Aushev T Bakich AM Ban Y Bay A Bedny I Behera PK Bizjak I Bondar A Bozek A Bracko M Browder TE Casey BC Chao Y Cheon BG Chistov R Choi Y Chuvikov A Danilov M Dash M Dong LY Eidelman S Eiges V Gabyshev N Garmash A Gershon T Golob B Haba J Hagner C Handa F Hastings NC Hayashii H Hazumi M Hinz L Hokuue T Hoshi Y Hou WS Huang HC Igarashi Y Iijima T Inami K Ishikawa A Itoh R Iwasaki H Iwasaki M Iwasaki Y Jang HK Kang JH Kang JS 《Physical review letters》2004,92(5):051801
The radiative decay B-->phi K gamma is observed for the first time. The branching fraction for the charged B--->phi K- gamma decay mode is measured to be B(B--->phi K- gamma)=(3.4+/-0.9+/-0.4)x10(-6). The photon energy distribution for the B--->phi K- gamma decay is presented. The signal for the neutral B(0)-->phi K(0)gamma decay mode is not statistically significant and an upper limit, B(B(0)-->phi K(0)gamma)<8.3x10(-6) at 90% C.L., is set. The analysis is based on a data set of 90 fb(-1) collected by the Belle experiment at the e(+)e(-) asymmetric collider KEKB. 相似文献
7.
利用基于Geant4建立起来的针孔成像模型获得了不同偏移量下γ与中子的好事例、能量沉积的比值,并模拟分析了强γ背景对中子针孔成像点扩展函数的影响。研究结果表明:在偏移量小于1 cm时,γ与中子的好事例之比、γ与中子的能量沉积峰值之比以及γ与中子的能量沉积总和之比分别在0.40~0.42,0.63~0.65以及0.46~0.49之间;偏移量大于1 cm时,比值下降明显,γ对中子的影响减小。在同一偏移量下,γ射线的点扩展函数的分布范围要比中子的小,两者叠加后所获得的点扩展函数的分布范围介于两者之间。在一定入射偏移范围内的成像质量优于在针孔中心位置入射时的成像质量。 相似文献
8.
The theory of spatiotemporal dynamics of gamma radiation in a resonant medium upon excitation of two-frequency gamma magnetic resonance in magnetic materials is considered. The radiation absorption at the fundamental frequency and the harmonic generation are investigated under conditions when the frequency of gamma radiation is shifted by the half-sum or half-difference of the frequencies of radio-frequency magnetic fields. It is shown that the propagation of gamma radiation through an absorber is characterized by a steady-state gamma intensity (resonant transparency). A consistent radio-frequency spectral analysis demonstrates that the intensities of harmonics drastically change at the transparency region boundaries due to nonlinear interference. The theory of quantum and dynamical beats of synchrotron radiation under conditions of induced resonant transparency is proposed. 相似文献
9.
使用自行开发出的基于Web的gamma估计程序,分别通过Internet对CRT和LCD显示器在暗、微暗和办公环境三种观察环境下,进行了视觉估计显示器gamma精确度研究实验.实验得出:不同实验者估计偏差范围,对CRT和LCD显示器分别是0.13和0.20|估计与测量结果的平均误差范围,对CRT和LCD显示器分别是0.07和0.17|gamma估计基本与观察环境无关|观察视角对LCD显示器gamma值影响很大|显示器的“亮度”和“对比度”设置,不影响视觉估计结果. 相似文献
10.
The production rate of light photinos in radiative pion decay \(\pi ^0 \to \gamma \tilde \gamma \tilde \gamma\) is calculated. Experimental constraints on masses and mass splittings of scalar quarks imply the following upper bound on the decay rate \(BR(\pi ^0 \to \gamma \tilde \gamma \tilde \gamma ) \lesssim 10^{ - 16}\) . 相似文献
11.
We examine via molecular simulation the dependence of the crystal-melt interfacial free energy gamma on molecular interaction and crystal structure (fcc vs bcc) for systems interacting with inverse-power repulsive potentials, u(r)=epsilon(sigma/r)(n), 6< or =n< or =100. Both the magnitude and anisotropy of gamma are found to increase as the range of the potential increases. Also we find that gamma(bcc)相似文献
12.
In digital fringe projection profilometry, the gamma effect of the used electronic devices seriously affects the accuracy of three-dimensional (3D) topography measurements. Previous gamma correction methods do not take full advantage of the Fourier spectrum of the captured spatial-carrier phase-shifting fringe patterns. Hence, dozens of phase-shifting fringe patterns are required to carry out gamma pre-calibration. In this paper, a fast and accurate gamma correction technique based on a Fourier spectrum analysis is proposed. Only two spatial-carrier fringe patterns with different pre-encoded gamma values are needed and the number of fringe patterns required for gamma pre-calibration is significantly reduced without loss of accuracy. The proposed method is validated by experiments. 相似文献
13.
F. M. Sayed Ahmed 《Annalen der Physik》1988,500(6):443-451
In the present work the radial distribution of total gamma doses arising from the interaction of reactor neutrons and gamma radiations inside ilmenite heavy concrete shield are measured. The ilmenite concrete is pierced with neutral beam injector ducts having different diameters and lengths. The results obtained show a relative increase in radial gamma doses at a distance of 10 cm from the neutral beam end. An empirical formula was obtained, fitting the measured gamma doses at the peak position in good agreement within a factor of 1.27. Moreover the variation of the total gamma radiation was measured along straight filled ducted with different diameters and length. The experimental data obtained show a reasonable agreement with calculated ones. The scattered as well as unscattered components of the gamma radiation transmitted through a straight duct were investigated. An empirical formula describing this behaviour was obtained. 相似文献
14.
We investigate the origin of Paris' law, which states that the velocity of a crack at subcritical load grows like a power law, da/dt ~ (DeltaK)(m), where DeltaK is the stress-intensity-factor amplitude. Starting from a damage-accumulation function proportional to (Deltasigma)(gamma), Deltasigma being the stress amplitude, we show analytically that the asymptotic exponent m can be expressed as a piecewise-linear function of the exponent gamma, namely, m=6-2gamma for gamma or =gamma(c), reflecting the existence of a critical value gamma(c)=2. We perform numerical simulations to confirm this result for finite sizes. Finally, we introduce bounded disorder in the breaking thresholds and find that below gamma(c) disorder is relevant, i.e., the exponent m is changed, while above gamma(c) disorder is irrelevant. 相似文献
15.
Lopez A Mehrabyan S Mendez H Ramirez J Ge JY Miller DH Sanghi B Shipsey IP Xin B Adams GS Anderson M Cummings JP Danko I Hu D Moziak B Napolitano J He Q Insler J Muramatsu H Park CS Thorndike EH Yang F Artuso M Blusk S Khalil S Li J Menaa N Mountain R Nisar S Randrianarivony K Sia R Skwarnicki T Stone S Wang JC Bonvicini G Cinabro D Dubrovin M Lincoln A Asner DM Edwards KW Naik P Briere RA Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP Cassel DG Duboscq JE Ehrlich R 《Physical review letters》2007,99(12):122001
The decay psi(2S) --> etaJ/psi is used to measure, for the first time, all prominent eta-meson branching fractions with the same experiment in the same dataset, thereby providing a consistent treatment of systematics across branching fractions. We present results for eta decays to gamma gamma, pi(+)pi(-)pi(0), 3pi(0), pi(+)pi(-)gamma and e(+)e(-)gamma, accounting for 99.9% of all eta decays. The precision of several of the branching fractions and their ratios is improved. Two channels, pi(+)pi(-)gamma and e(+)e(-)gamma, show results that differ at the level of three standard deviations from those previously determined. 相似文献
16.
Arrayas M Kaufman IK Luchinsky DG McClintock PV Soskin SM 《Physical review letters》2000,84(12):2556-2559
Fluctuational escape from a multiwell potential is shown to display new features, as compared to the conventional single-well case. The flux J may depend on friction gamma exponentially strongly, over an exponentially long period; for small enough temperatures, J(gamma) undergoes marked oscillations in the range of small gamma, and the time evolution of J changes drastically as gamma exceeds a critical value. 相似文献
17.
Trokiner A Bellot PV Zhdanov Y Yakubovskii A 《Solid state nuclear magnetic resonance》2000,16(3):171-175
The experimental determination of the Sternheimer antishielding factor gamma(infinity) for Ca2+ in a sold material is reported for the first time. The gamma(infinity) value was obtained by comparing the quadrupole frequency measured by 43Ca NMR with the electric field gradient calculated in a frame of the point charge approximation in the high-Tc superconducting compound, Tl0.5Pb0.5Sr2CaCu2O7. The deduced value (gamma(infinity)= -6.1+/-.9) is about one-third of that obtained from the quantum mechanical calculations, whereas in the same sample, the gamma(infinity)value for O2- deduced by the same procedure (gamma(infinity)= -13.7+/-2.0) is very close to the calculated one. 相似文献
18.
Uehara S Abe K Abe K Adachi I Aihara H Arinstein K Asano Y Aulchenko V Aushev T Bakich AM Balagura V Barberio E Bedny I Belous K Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Browder TE Chang MC Chen A Chen WT Cheon BG Chistov R Choi SK Choi Y Choi YK Chuvikov A Dalseno J Danilov M Dash M Dragic J Eidelman S Epifanov D Fratina S Gabyshev N Garmash A Gershon T Gokhroo G Gorisek A Ha HC Hayasaka K Hayashii H Hazumi M Hinz L Hoshi Y Hou S Iijima T Inami K Ishikawa A Itoh R Iwasaki M 《Physical review letters》2006,96(8):082003
We report on a search for new resonant states in the process gamma gamma --> DD. A candidate C-even charmonium state is observed in the vicinity of 3.93 GeV/c2. The production rate and the angular distribution in the gamma gamma center-of-mass frame suggest that this state is the previously unobserved chi(c2)', the 2(3)P2 charmonium state. 相似文献
19.
Measurements are reported on the differential cross section for secondary gamma ray production on hydrogen and nuclear targets at 90° in the laboratory through the interactions of primary gamma rays in the energy range 270–375 MeV. A difference method using bremsstrahlung beams at different end point energies was employed. The gamma ray detector was a high resolution Nal(Tl) spectrometer and time of flight discrimination was used to reject neutrons. For incident gamma rays in the range 270–375 MeV the first pion nucleon resonance is strongly excited and the observed gamma ray yields are consistent with those expected due to an admixture of coherent and incoherent π0 photoproduction in the resonance region. The experiment marks the first successful use of a large Nal(Tl) crystals as a gamma ray spectrometer at a high energy electron linear accelerator, despite the low duty cycle and its accompanying difficulties for such detectors. 相似文献
20.
Alexander-Katz A Schneider MF Schneider SW Wixforth A Netz RR 《Physical review letters》2006,97(13):138101
The behavior of a single collapsed polymer under shear flow is examined using hydrodynamic simulations and scaling arguments. Below a threshold shear rate gamma[.]{*}, the chain remains collapsed and only deforms slightly, while above gamma[.]{*} the globule exhibits unfolding/refolding cycles. Hydrodynamics are crucial: In the free draining case, gamma[.]{*} scales with the globule radius R as gamma[.]{*} approximately R{-1}, while in the presence of hydrodynamic interactions gamma[.]{*} approximately R. Experiments on the globular von Willebrand protein confirm the presence of an unfolding transition at a well-defined critical shear rate. 相似文献