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1.
The reflection of monochromatic and quasi-monochromatic pulsed light incident on a moving inhomogeneity in the optical characteristics
of a medium having plasma-type dispersion has been analyzed. The velocity V of the inhomogeneity, induced in the medium by an intense laser pulse, has been changed by varying its carrier frequency.
It has been shown that the usual back-reflection mode, when the reflected radiation pulse moves in the direction opposite
the direction of incident radiation, is implemented only if the velocity V is less than the critical value V
min, which depends on the carrier frequency of the incident radiation pulse. It has been found that reflected radiation moves
in the same direction as the incident radiation in a certain range of the velocity V
min < V < V
max (forward reflection). In this case, the reflected radiation pulse begins to lag behind a fast-moving inhomogeneity. When
V
max < V < c, where c is the speed of light in vacuum, the group velocity of the incident radiation pulse is less than the speed of inhomogeneity,
and there is no reflection. Analytical treatment is supported by numerical simulation. 相似文献
2.
The effect of post- and pre-high doses of γ–radiation in CR-39 plastic detectors has been studied in the dose range of 3×10 1?10 6 Gy. Some properties like bulk-etch rate ( V B), track-etch rate ( V T), sensitivity ( V T/ V B) and efficiency have been found out for different gamma doses from a 60Co source in CR-39. It is found that V B and V T remain almost invariant up to gamma doses of 10 4 Gy. Then they start increasing slowly till 10 5 Gy. Between 10 5 Gy and 10 6 Gy there is a sharp increase of V B and V T values for pre- and post-gamma exposed samples. The present data are compared with the previous literature. 相似文献
3.
Five-dimensional classical unified field theories may be described in terms of the geometry of a five-dimensional Lorentz space V
5.This space may be considered as a principal bundle over spacetime V
4with metric g
ij
and gauge group U(1). It has been shown that when V
4is asymptotically flat, the total energy momentum vector of V
5is nonspacelike, and that the gravitational mass of V
4has a lower bound. These results obtain when V
5is replaced by a Lorentzian space V
N
,a principal bundle over an asymptotically flat V
4with an Abelian group G as its gauge group. 相似文献
4.
A relationship between the torsional frequency ( v
10) and the potential barrier ( V
n) has been determined for AB
n type molecular system having n-fold symmetry axis. It is found that v
10 varies prominently as V
n
1/2
, V
n and V
n
2
in certain ranges. The V
n value computed from v
10 and I*
r
has been compared with that obtained from other experimental data for some AB
n units in different molecular-crystalline systems. Although there is in general a good agreement, in some cases the values
differ significantly, perhaps due to the erroneous assignment of torsional mode and/or the large errors in the V
n value obtained from other experimental data. 相似文献
5.
Effect of DC bias on the spatio‐temporal distribution of the electron density for L = 25 mm, V pp = 150 V at p = 10 Pa with V DC = 0 V. The color scales are given in units of 10 9 cm –3. (Figure 2b of the paper by N.Kh. Bastykova et al.) 相似文献
6.
A computer program has been used to determine the effects of 10-fold potential energy ( V10) and kinetic energy ( B10) terms on the pseudorotational energy levels of cyclopentane. The magnitudes of the calculated perturbations on the spectra have been evaluated, and the values of V10 and B10 are shown to be less than 20 and 0.2 cm −1, respectively. 相似文献
7.
Field-effect transistor structures based on whiskers of layered quasi-one-dimensional semiconductor TiS3 have been fabricated. The dependences of the conductivity σ on the gate voltage Vg, as well as the current-voltage characteristics of whiskers (“source-drain”) at different Vg values, have been measured in the temperature range of 4.2-300 K. As the temperature decreases, the sensitivity of the conductivity to the gate voltage, α ≡ 1/σdσ/dVg, increases in the range from 300 to 80 K and decreases sharply below 80 K, where the nonlinear conductivity begins to depend on Vg. The results can be explained by the formation of an electronic crystal at low temperatures. 相似文献
8.
Abstract Initial rates of hydrolysis of maltose and maltotriose over an immobilized glucoamylase have been measured up to 127 MPa at 25±0.1°C. The observed rates have been analyzed showing the reaction pathways of both hydrolyses to be E+S?ES*?ES7ast;E+P, where E, S, P, ES*, and ES denote the enzyme, the substrate, the product, a substrate-subsite complex, and a substrate-active site complex, respectively. The apparent maximum rate r mand the apparent Michaelis constant K m as well as their respective pressure dependences in terms of the apparent activation volume Δ V app # and the apparent volume of reaction Δ V app have been evaluated. Small absolute values of Δ V app num; and Δ V app for both reactions have been discussed on the basis of the reaction mechanism. 相似文献
9.
本文研究了90nm CMOS工艺下栅氧化层厚度为1.4 nm沟道长度为100 nm的轻掺杂漏(LDD)nMOSFET栅电压 VG对栅致漏极泄漏 (GIDL)电流 Id的影响,发现不同 VG下ln ( Id/( VDG-1.2))-1/( VDG-1.2)曲线相比大尺寸厚栅器件时发生了分裂现象. 通过比较 VG变化下ln( Id/( VDG-1.2))的差值,得出 VG与这种分裂现象之间的作用机理,分裂现象的产生归因于 VG的改变影响了GIDL电流横向空穴隧穿部分所致. 随着| VG|的变小,ln( Id/( VDG-1.2))曲线的斜率的绝对值变小.进一步发现不同 VG对应的ln ( Id/( VDG-1.2))曲线的斜率 c及截距 d与 VG呈线性关系, c,d曲线的斜率分别为3.09和-0.77. c与 d定量的体现了超薄栅超短沟器件中 VG对GIDL电流的影响,基于此,提出了一个引入 VG 影响的新GIDL电流关系式. 相似文献
10.
We present ab initio calculation within the framework of the density‐functional theory (DFT) on band structure and vibrational properties of bulk V 2O 5. The structure of V 2O 5 comes from optimization of the experimental data with lattice parameters fixed. The band structure of the optimized structure has been calculated, and the result fits the experimental data very well and also gives similar results as those calculated by other methods. The phonon eigenwavenumbers of the Γ‐ point of V 2O 5 bulk have been calculated ab initio in density‐functional perturbation theory (DFPT). The calculated vibrational wavenumbers are in good agreement with observed infrared and Raman wavenumbers, and the predictive full phonon dispersion of bulk V 2O 5 has also been obtained. Further we calculated the Raman spectrum of vanadium pentoxide (V 2O 5) powder sample using the obtained Raman susceptibility. Calculated and measured intensities show overall good agreement. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
11.
CuV2O6 and Cu2V2O7 compounds have been produced from initial components CuO and V2O5 by solid-phase synthesis. The high-temperature heat capacity of the oxide compounds has been measured using differential scanning calorimetry. The thermodynamic properties (the enthalpy change, the entropy change, and the reduced Gibbs energy) have been calculated using experimental dependences C
P
= f(T). It is found that there is a correlation between the specific heat capacity and the composition of oxides of the CuO–V2O5 system. 相似文献
12.
Recently, a formally exact integral equation for the exchange potential V x( r) has been presented by the authors. In the admittedly simplistic limit in which Slater–Kohn–Sham and Hartree–Fock determinants become equal, this integral equation reduces to that given by Della Sala and Görling. Here, a proposal is made to relate, but now approximately, the formally exact equation for V x( r) to HOMO–LUMO properties. The addition of a correlation contribution V c( r) to V x( r), the sum being the exchange-correlation potential V xc( r), is finally considered, some exact properties and especially sum rules for the force ?? V xc/? r being the focus. 相似文献
13.
Measurements of the dependence of track etch rate on the energy-loss of different ions have been presented. In this method,
18
40
Ar,
10
22
Ne,
8
16
O and
6
12
C-ions of different energies are used as energetic heavy ions for track formation in the detectors. The bulk etch rate and
track etch rate are measured for different temperatures and hence the activation energies are determined. The variation of V = V
t
/ V
b
along the trajectory of the track has been shown for different temperatures. The maximum etched track length is compared
with the theoretical range as well as with the range reported earlier. The experimental results indicate the absence of a
well-defined threshold in the plastics studied. 相似文献
14.
First‐principles LDA + U calculations have been performed to study the effects of oxygen vacancies (V O) on the electronic structure and magnetism in undoped rutile TiO 2–x . Instead of treated as an adjustive parameter, the value of U was determined by constrained‐density‐functional calculations. The calculated electronic structure reveals that the valence electrons released by V O would occupy mainly the neighboring Ti:3d orbital which then becomes spin‐polarized due to intra‐atomic exchange interaction, thereby giving rise to the half‐metallic ferromagnetism. The magnetization induced by V O in rutile TiO 2–x is almost proportional to the V O concentration ( x) for x > 0.0625, and becomes 0 for x ≤ 0.0417. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Two-Dimensional Angular Correlation of positron Annihilation Radiation (2D-ACAR) experiments have been performed on n-type GaAs. By combining these results with those from positron lifetime experiments, the momentum distribution of the arsenic vacancy in its neutral ( V
aAs
0
) and negative ( V
As
–
) charge states have been extracted. These distributions were all normalized to the respective positron lifetime that characterizes them. The first thing to be noticed is that the momentum distributions of the vacancies, as seen by the positron, are fairly isotropic and structureless. The distribution for V
As
0
is more peaked than that of V
As
–
while the latter is more intense in the large momentum regions of the spectra. From this, it can be inferred that VA. has a smaller open volume than V
As
0
A closer look at the momentum distribution of the vacancies reveals that they are not entirely isotropic, but, in fact, have a bulk-like component. Finally, the experimental results for bulk GaAs and V
As
–
compare well in a qualitative manner with the momentum distributions that result from an ab-initio molecular dynamics calculation. 相似文献
16.
Vanadates Cd2V2O7 and CdV2O6 have been prepared from CdO и V2O5 by three-phase synthesis with subsequent burning at 823–1073 K and 823–853 K, respectively. The molar heat capacity of these oxide compounds has been measured by differential scanning calorimetry. The enthalpy change, the entropy change, and the reduced Gibbs energy are calculated using the experimental dependences C
p
= f(T). It is shown that there is a correlation between the specific heat capacity and the composition of CdO–V2O5 oxide system. 相似文献
17.
The chiral constituent quark model with configuration mixing ( c \chi
CQM
config , which is successful in explaining the weak vector and axial-vector form factors for the strangeness-changing as well as
strangeness-nonchanging hyperon semileptonic decays at Q
2 = 0 , has been extended to determine the CKM matrix element V
us for the strangeness-changing decays. The implications of the effect of the SU(3) symmetry breaking, Q 2-dependence and radiative corrections on the form factors and V
us have also been investigated. It is found that the results with SU(3) symmetry breaking show considerable improvement over the SU(3) symmetric results when compared with the existing experimental data. The inclusion of the Q 2-dependence and radiative corrections in form factors have only a small effect on the prediction of V
us as is expected from the theory. 相似文献
18.
基于密度泛函理论,利用局域密度近似的第一性原理平面波赝势方法,对掺K以及含有氢填隙(H i)、氧空位( VO)、锌填隙(Zn i)和锌空位( VZn)的K:ZnO电子结构分别进行了研究.结果表明,1) 单独掺K可引入浅受主,但系统总能增高;2) K与H共掺可降低系统总能,提升稳定性;3) VO在K+H:ZnO中的形成比Zn i困难得多,二者都是
关键词:
氧化锌
p型
第一性原理
电子结构 相似文献
19.
Fritzsch like mass matrices with non-zero 22-elements both in U sector and D sector have been investigated in the context
of latest data regarding m
t
phys
, | V
ub|, | V
cb|, | V
td| and | V
ts|. Unlike several other phenomenological models, the present model not only accommodates the value of m
t
phys
in the range 150–240 GeV, encompassing the CDF and D0 values, but is also able to reproduce | V
cb| ≊0.040 and | V
ub/V cb| = 0.08±0.02 and | V
td| is predicted to lie in the range 0.005–0.014. Further, the angles of the unitarity triangle, related to the CP-violating
asymmetries, are calculated to be in the ranges −1.0⩽sin2α⩽−0.1, 0.6 ⩽sin2α⩽1.0 and 0.48⩽sin2β⩽0.56, which are in agreement
with other recent calculations. 相似文献
20.
对不同场板尺寸的AlGaN/GaN 场板结构高电子迁移率晶体管进行了研究,建立简化模型分析场板长度对沟道电场分布的影响.结果表明,调整钝化层厚度和场板长度都可以调制沟道电场的分布形状,当场板长度较小时,随着长度的增大器件击穿电压随之增加,而当长度增大到一定程度后器件击穿电压不再增加.通过优化场板长度,器件击穿电压提高了64%,且实验结果与模拟结果相符.
关键词:
AlGaN/GaN
击穿电压
场板长度 相似文献
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