共查询到20条相似文献,搜索用时 31 毫秒
1.
The role of aluminum alloying on strength properties and deformation mechanisms (slip, twinning) of 〈123〉 single crystals
of Hadfield steel under tensile loading at T = 300 K is demonstrated. It is found out that aluminum alloying suppresses twinning
deformation in the 〈123〉 single crystals and, during slip, results in a dislocation structure change from a uniform dislocation
distribution to a planar dislocation structure.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 3–7, October, 2007. 相似文献
2.
The manifestations of the existence of free anion excitons, the processes of their self-trapping, and the coexistence of mobile and self-trapped excitons (STEs) in wide-gap alkali halide crystals are reviewed. The radiative channel of decay of anion excitons, yielding luminescence, and a particular type of nonradiative channel with the creation of elementary Frenkel defects (FDs) are considered. We analyzed the criteria for the efficiency of this channel for defect formation, possible mechanisms for the decay of self-trapped excitons with the production of neutral and charged anion Frenkel defects, and the processes of multiplication of electronic excitations in alkali halide crystals. Particular attention is paid to the decay of cation excitons, including from the point of view of the possibility of the low-temperature creation of elementary Frenkel defects in the cation sublattice of alkali halide crystals. 相似文献
3.
Electron emission and luminescence accompanying plastic deformation of alkali halide crystals are studied. It is shown that
the intersection of dislocations can cause electronic excitation. Deformation electron emission and luminescence are produced
by relaxation of these excitations.
Fiz. Tverd. Tela (St. Petersburg) 41, 900–902 (May 1999) 相似文献
4.
B. Kämpfer O.P. Pavlenko S. Zschocke 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):83-87
QCD sum rules predict that the change of the strange quark condensate 〈ˉss〉 in hadron matter at finite baryon density causes a shift of the peak position of the di-electron spectra from φ-meson decays.
Due to the expansion of hadron matter in heavy-ion collisions, the φ peak suffers a smearing governed by the interval of density
in the expanding fireball, which appears as an effective broadening of the di-electron spectrum in the φ region. The emerging
broadening is sensitive to the in-medium change of 〈ˉss〉. This allows to probe directly in-medium modifications of 〈ˉss〉 via di-electron spectra in heavy-ion collisions at SIS energies with HADES.
Received: 22 November 2002 / Accepted: 30 January 2003 / Published online: 29 April 2003 相似文献
5.
Pulsar J0810+37 with a period of 1.2483 s is detected at a frequency of 111 MHz during the pulsar search at the Big Scanning Antenna (BSA) radio telescope of the Lebedev Physical Institute [1]. In this paper, we present the results of the detailed study of radio emission from J0810+37 which exhibits a rare nulling effect of different durations in a very wide time interval with an average nulling fraction in “switch-on” days 〈NF〉 = 38%; considering “switch-off” days, 〈NF〉 = 74%, since radio emission from this source is interrupted on average by 2–3 days, and then it again revives on average for 1–2 days. The “switch-off” periods reach 7 days. 相似文献
6.
The present paper reports the dislocation unpinning model of acoustic emission (AE) from alkali halide crystals. Equations
are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number
of AE pulse emitted. It is found that the AE pulse rate should be maximum for a particular strain of the crystals. The peak
value of the AE pulse rate should depend on the volume and strain rate of the crystals, and also on the pinning time of dislocations.
Since the pinning time of dislocations decreases with increasing strain rate, the AE pulse rate should be weakly dependent
on the strain rate of the crystals. The total number of AE should increase linearly with deformation and then it should attain
a saturation value for the large deformation. By measuring the strain dependence of the AE pulse rate at a fixed strain rate,
the time constantτ
s for surface annihilation of dislocations and the pinning timeτ
p of the dislocations can be determined. A good agreement is found between the theoretical and experimental results related
to the AE from alkali halide crystals. 相似文献
7.
Y. Toh T. Czosnyka M. Oshima T. Hayakawa H. Kusakari M. Sugawara Y. Hatsukawa J. Katakura N. Shinohara M. Matsuda 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):353-356
74Ge beam was Coulomb-excited on a natPb target. Ten E2 matrix elements including diagonal matrix elements for 5 low-lying states have been determined using the least-squares search
code GOSIA. The expectation values of the rotational invariants 〈Q
2〉 and 〈cos3δ〉 show the small and triaxial deformation of the two lowest members of the ground-state band , while the 02
+ and 22
+ states are found to be almost spherical.
Received: 31 August 2000 / Accepted: 4 December 2000 相似文献
8.
In the path-integral formulation of quantum mechanics, the phase factor e
iS(x〈t〉) is associated with every path x〈t〉. Summing this factor over all paths yields Feynman's propagator as a sum-over-paths. In the original formulation, the complex
phase was a mathematical device invoked to extract wave behaviour in a particle framework. In this paper we show that the
continuous phase itself can have a discrete origin in time reversal and that the propagator can be drawn by a single deterministic
path.
1On leave from Department of Mathematics, Ryerson University, Toronto,
Ontario Canada. 相似文献
9.
A. Michels J. Weissmüller R. Birringer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):533-540
Based on a micromagnetics model, we develop a method through which quantitative information on the volume-averaged mean-square
magnetostatic stray field 〈|H
b
d|2〉
v due to non-zero divergences of the magnetization M within the bulk of a ferromagnetic body can be obtained by analysis of magnetic-field-dependent small-angle neutron scattering
data. In the limit of high applied magnetic field H
a, when the direction of M deviates only sligthly from H
a, we have estimated a lower bound for 〈|H
b
d|2〉
v as a function of the external field, and we have applied the method to bulk samples of nanocrystalline electrodeposited Ni
and Co and coarse-grained polycrystalline cold-worked Ni. The root-mean-square magnetostatic stray field, which is inherent
to a particular magnetic microstructure, shows a pronounced field dependence, with values ranging from about 5 to 50mT. Even
at applied fields as large as 1.7T, the quantity μ〈|H
b
d|2〉1/2
v of nanocrystalline Co is still 24mT, which suggests that contributions to the total magnetostatic field originating from
the bulk are significant in nanocrystalline ferromagnets; therefore, 〈|H
b
d|2〉
v cannot be ignored in the interpretation of e.g. measurements of magnetization or spin-wave resonance. A comparison of 〈|H
b
d|2〉
v with the volume-averaged mean-square anisotropy field reveals that both quantities are of comparable magnitude.
Received 25 April 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: anmi@nano.uni.saarland.de 相似文献
10.
Abstract Molecular statics method is used to determine the energy and configuration peculiarities of vacancy-bivacancy interaction in alkali halide crystals. It is shown that high level of local vacancy supersaturation defines the possibility of cluster formation. The study of carrier traps by luminescence methods is used to reveal vacancy clusters. 相似文献
11.
The elastico-mechanoluminescence (EML) intensity of X or γ-irradiated alkali halide crystals can be used in radiation dosimetry. The EML intensity of X or γ-irradiated alkali halide crystals increases linearly with the strain of the crystals, and when the crosshead of the testing machine deforming an X or γ-irradiated crystal is stopped, then the EML intensity decreases with time. The semilog plot of the EML intensity versus (t − tc) (where tc is the time where the crosshead of the testing machine is stopped) indicates that, in the post-deformation region, the EML intensity initially decreases exponentially at a fast rate and later on it decreases exponentially at a slow rate. The EML intensity increases linearly with the density of the F-centres in the crystals. This fact indicates that elastico-ML can suitably be used for the radiation dosimetry. The EML spectra of X or γ-irradiated alkali halide crystals are similar to their thermoluminescence spectra. Based on the detrapping of electrons during the mechanical interaction between the dislocation segments and F-centres, an expression is derived, which indicates that the EML intensity should increase linearly with the density of F-centres in the crystals. The expression derived for the decay of EML indicates that the decay time for the fast decrease of EML should gives the pinning time of dislocation segments (lifetime of interacting F-centres), and the decay time for the slow decrease of EML intensity should gives the lifetime of electrons in the shallow traps. As the elastic deformation is non-destructive phenomenon and the EML intensity depends on the radiation dosage given to the alkali halide crystals, similar to the thermoluminescence and photo-stimulated luminescence, the EML of alkali halide crystals and other crystals may be used for the radiation dosimetry. In EML dosimetry, the same crystal can be used number of times because the elastic deformation does not cause permanent deformation in the crystals, and moreover, comparatively the devices needed for the EML measurements are of low cost and very simple. In recent years, a large number of elastico mechanoluminescent materials have been investigated, and the study of their suitability for the radiation dosimetry may be interesting. 相似文献
12.
Correlation between deformation bleaching and mechanoluminescence in coloured alkali halide crystals
The present paper reports the correlation between deformation bleaching of coloration and mechanoluminescence (ML) in coloured
alkali halide crystals. When the F-centre electrons captured by moving dislocations are picked up by holes, deep traps and other compatible traps, then deformation
bleaching occurs. At the same time, radiative recombination of dislocation captured electrons with the holes gives rise to
the mechanoluminescence. Expressions are derived for the strain dependence of the density of colour centres in deformed crystals
and also for the number of colour centres bleached. So far as strain, temperature, density of colour centres, E
a and volume dependence are concerned, there exists a correlation between the deformation bleaching and ML in coloured alkali
halide crystals. From the strain dependence of the density of colour centres in deformed crystals, the value of coefficient
of deformation bleaching D is determined and it is found to be 1.93 and 2.00 for KCl and KBr crystals, respectively. The value of (D+χ) is determined from the strain dependence of the ML intensity and it is found to be 2.6 and 3.7 for KCl and KBr crystals,
respectively. This gives the value of coefficient of deformation generated compatible traps χ to be 0.67 and 1.7 for KCl and KBr crystals, respectively. 相似文献
13.
F. Le Blanc L. Cabaret J.E. Crawford S. Essabaa V. Fedoseyev W. Geithner J. Genevey M. Girod R. Horn G. Huber S. Kappertz J. Lassen J.K.P. Lee G. Le Scornet V. Mishin R. Neugart J. Obert J. Oms A. Ouchrif S. Peru J. Pinard H. Ravn B. Roussière J. Sauvage D. Verney 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):49-51
Laser spectroscopy measurements have been carried out on the very neutron-rich tin isotopes with the COMPLIS experimental
setup. Using the 5s
25p
23
P
0 → 5s
25p6s
3
P
1 optical transition, hyperfine spectra of 126-132Sn and 125m, 127m, 129m-131mSn where recorded for the first time. The variation of the mean-square charge radius ( δ〈r
2〉) between these nuclei and nuclear moments of the isomers and the odd isotopes were thus measured. An odd-even staggering
which inverts at A = 130 is clearly observed. This indicates a small appearance of a plateau on the δ〈r
2〉 which has to be confirmed by measuring the isotope shift beyond A = 132.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: leblanc@ipno.in2p3.fr 相似文献
14.
K. Shunkeev E. Sarmukhanov A. Barmina L. Myasnikova Sh. Sagimbaeva S. Shunkeev 《Physics of the Solid State》2008,50(10):1799-1802
The activation energy of temperature quenching of luminescence of self-trapped excitons in alkali halide crystals subjected to low-temperature uniaxial deformation is evaluated experimentally. It is found that an increase in the activation energy is observed in the following series of crystals: KBr → NaCl → KI → NaBr → CsBr → RbI. The effect of enhancement of intrinsic luminescence of alkali halide crystals due to the lowering of the symmetry of the crystal lattice under low-temperature uniaxial deformation is interpreted by analyzing the observed increase in the activation energy that characterizes the height of the potential barrier separating channels of radiative and nonradiative decay (with the formation of radiation defects) of self-trapped excitons. 相似文献
15.
Stefan Großkinsky Gunter M. Schütz Richard D. Willmann 《Journal of statistical physics》2007,128(3):587-606
We study spontaneous symmetry breaking in a one-dimensional driven two-species stochastic cellular automaton with parallel
sublattice update and open boundaries. The dynamics are symmetric with respect to interchange of particles. Starting from
an empty initial lattice, the system enters a symmetry broken state after some time T
1 through an amplification loop of initial fluctuations. It remains in the symmetry broken state for a time T
2 through a traffic jam effect. Applying a simple martingale argument, we obtain rigorous asymptotic estimates for the expected
times 〈 T
1〉 ∝ Lln L and ln 〈 T
2〉 ∝ L, where L is the system size. The actual value of T
1 depends strongly on the initial fluctuation in the amplification loop. Numerical simulations suggest that T
2 is exponentially distributed with a mean that grows exponentially in system size. For the phase transition line we argue
and confirm by simulations that the flipping time between sign changes of the difference of particle numbers approaches an
algebraic distribution as the system size tends to infinity. 相似文献
16.
I. N. Ogorodnikov N. E. Poryvai I. N. Sedunova A. V. Tolmachev R. P. Yavetskiy 《Optics and Spectroscopy》2011,110(2):266-276
The luminescence and thermally stimulated recombination processes in lithium borate crystals Li6Gd(BO3)3 and Li6Gd(BO3)3:Ce have been studied. The steady-state luminescence spectra under X-ray excitation (X-ray luminescence), temperature dependences
of the intensity of steady-state X-ray luminescence (XL), and thermally stimulated luminescence (TSL) spectra of these compounds
have been investigated in the temperature range of 90–500 K. The intrinsic-luminescence 312-nm band, which is due to the 6
P
J
→ 8
S
7/2 transitions in Gd3+ matrix ions, dominates in the X-ray luminescence spectra of these crystals; in addition, there is a wide complex band at
400–420 nm, which is due to the d → f transitions in Ce3+ impurity ions. It is found that the steady-state XL intensity in these bands increases several times upon heating from 100
to 400 K. The possible mechanisms of the observed temperature dependence of the steady-state XL intensity and their correlation
with the features of electronic-excitation energy transfer in these crystals are discussed. The main complex TSL peak at 110–160
K and a number of minor peaks, whose composition and structure depend on the crystal type, have been found in all crystals
studied. The nature of the shallow traps that are responsible for TSL at temperatures below room temperature and their relation
with defects in the lithium cation sublattice are discussed. 相似文献
17.
Z.J. Li H.J. Li X.L. Chen A.L. Meng K.Z. Li Y.P. Xu L. Dai 《Applied Physics A: Materials Science & Processing》2003,76(4):637-640
Large quantities of high-purity crystalline β-SiC nanowires have been synthesized at relatively low temperature via a new
simple method, the chemical-vapor-reaction approach, in a home-made graphite reaction cell. A mixture of milled Si and SiC
powders and C3H6 were employed as the starting materials. The results show that the nanowires with diameters of about 10–35 nm are single
crystalline β-SiCwithout any wrapping of amorphous material, and the nanowire axes lie along the 〈111〉 direction. Some unique
properties are found in the Raman scattering from the β-SiC nanowires, which are different from previous observations of β-SiC
materials. A possible growth mechanism for the β-SiC nanowires is proposed.
Received: 27 August 2002 / Accepted: 28 August 2002 / Published online: 4 December 2002
RID="*"
ID="*"Corresponding author. Fax: +86-29/8491-000, E-mail: zjli-sohu@sohu.com 相似文献
18.
V. Yu. Ivanov V. A. Pustovarov A. V. Kruzhalov D. S. Tausenev E. I. Zinin 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):671-674
The results of comparative luminescence investigation of natural and synthetic BeO crystals are presented. Time-resolved luminescence
(2.5–8 eV) and luminescence excitation spectra, and the kinetics of glow decay were measured using ultraviolet-vacuum-ultraviolet
(VUV) synchrotron radiation (5–22 eV) or x-radiation (50–620 eV or 3–62 keV) ranges. X-ray and thermostimulated luminescence
of natural BeO crystals were compared to the glow of additively colored synthetic crystals. The characteristic luminescence
of F and F
+ centers was found in natural crystals. In synthetic crystals similar luminescence is observed only after additive or radiation
coloration by virtue of the creation of F
− and F
+ centers on anion vacancies. The defects found in the crystal lattice of a natural BeO crystal testify to the degree of mineral
metamictization of the given deposit. 相似文献
19.
The features of the intraband luminescence spectrum of wide-gap insulators (KI, KBr, CsCl, etc.) and semiconductors (GaP,
CdS, α-SiC, and ZnS) are studied in the temperature interval 80–760 K. The spectra of the intraband luminescence are compared with
the spectra of the pre-breakdown electroluminescence of GaP and α-SiC surface-barrier diode structures and of a ZnS thin-film electroluminescence indicator. In alkali halide crystals the
short-wavelength boundary hν
m of the intraband luminescence is less than the band gap E
g and is governed by complex excitonic processes. In semiconductors with indirect transitions hν
m>E
g. The differences in the spectra of the intraband luminescence and the intraband pre-breakdown electroluminescence can be
explained by differences in the distributions of the hot charge carriers over levels of the allowed bands and in the maximum
energies of the carriers involved in the formation of the spectra.
Fiz. Tverd. Tela (St. Petersburg) 39, 613–617 (April 1997) 相似文献
20.
A. A. Turban S. L. Bondarev V. N. Knyukshto A. P. Stupak 《Journal of Applied Spectroscopy》2006,73(5):678-685
We used fluorescence spectroscopy and nanosecond flash photolysis to study the photophysical properties of the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylamino)styryl-4H-pyran
(DCM) and its two fluoro derivatives: (E)-2-〈2-[2-(4-dimethylaminophenyl)ethenyl]-6-trifluoromethyl-4H-4-pyranylidene〉malononitrile
(DCMF3) and (E)-2-〈2-[2-(4-dimethylaminophenyl)ethenyl]-6-n-heptafluoro-propyl-4H-4-pyranylidene〉 malononitrile (DCMF7), in
nonpolar n-hexane, mixtures of low-polarity toluene and polar dimethylsulfoxide (DMSO), n-propanol at room temperature and
at 77 K. The fluorescence quantum yield Φfl of the laser dye DCM increases linearly as the polarity of the binary solvent mixture (toluene+DMSO) increases, from 0.08
in toluene to 0.80 in DMSO. The dependence of Φfl on the polarity of the mixture toluene+DMSO for DCMF3 and DCMF7 reaches a maximum for a small amount (∼2 vol.%) of added
polar DMSO; and with further increase in the DMSO concentration (≥50 vol.%), the fluorescence of the fluoro derivatives of
DCM is practically completely quenched. The quantum yield for intersystem crossing ΦST for DCM, DCMF3, and DCMF7 is no greater than 0.01 in solutions of different polarities. We discuss the mechanisms for nonradiative
deactivation of the electronic excitation energy for the fluoro derivatives compared with DCM.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 606–612, September–October, 2006. 相似文献