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1.
Considering the htermal conduction through molecular collisions an expression for the effective thermal conductivityλ
e
of loose and granular two-phase materials at different interstitial air pressure has been derived. The dependence ofλ
e
on pore and particle sizes, characteristic pressure and radiative heat transfer is also discussed. Calculated values ofλ
e
of glass beads and loose building materials are compared with reported results. 相似文献
2.
Thermal conduction through loose and granular two-phase materials at normal pressure 总被引:1,自引:0,他引:1
The integrated theory derived for the lattice-type dispersions is modified and extended to estimate the effective thermal
conductivity of loose and granular two-phase materials at normal pressure assuming an effective continuous media approximation.
A comparison of calculated values ofλ
e
with the reported experimental results over a wide range of loose and granular two-phase materials shows a good agreement. 相似文献
3.
New experimental data on the binding energyB
λλ
ofλλ6He, reported very recently, come up with the valuesB
λλ
= 725 ±0.14 MeV and ΔBλλ = 101 ±0.2 MeV which are substantially lower than the old dataB
λλ
= 109 ±0.8 MeV and ΔBλλ = 4.7±10 MeV in use in literature since 1966. In view of the new data we decided to undertake a re-study of the
λλ
6
He hypernucleus using the same three-body model (α-λ-λ) with a simple coordinate space variational approach which was employed
earlier with the old data onλλ/6He. After fitting different λ-λ potentials to the new data of
λλ
6
He we have applied our method to study some double-λ hypernuclei in light, medium and heavy mass regions and have determined
the structural quantities like Bλλ, the r.m.s. values of core-λ (〈rcore-λ〉〉) and λ-λ (〈rλ-λ〉〉) distances theoretically. The core-λ interaction considered is of Woods-Saxon type. The strength and the range of the core-A
potential have been adjusted to reproduce the λ-binding energy(B
λ)
. These are in good agreement with the relativistic mean field (RMF) results. Our study shows that the λ-λ bonding energy
ΔBλλ decreases with increasing mass number from
λλ
10
Be to
λλ
210
Pb of a double-A hypernucleus 相似文献
4.
Results of spectroscopic investigations into plasma of a pulse-periodic strontium vapor laser operating in the superradiance
mode on the infrared transition at λ = 6.45 μm are presented. The method of determining the electron temperature and concentration
as well as the gas temperature – T
e
, n
e
, and T
g
– based on measuring the absolute intensities of some SrI and SrII and buffer gas (helium or neon) spectral lines is used.
Time dependences of the line intensities during a current pulse (τ = 150 ns) and near afterglow (up to 3 μs) are obtained
under conditions of non-equilibrium plasma ionization and recombination. The optical system collects radiation from the entire
length of the plasma column by means of separating radial volume zones, includingthe central zone and the zone closer to the
walls, with the monochromator slit. The results obtained allow us not only to calculate T
e
, n
e
, and T
g
values, but also to trace the spatiotemporal plasma evolution. 相似文献
5.
The excess 1/f noise in a random lattice with bond resistances r∼exp(−λx), where x is a random variable and λ≪1, is studied theoretically. It is shown that if the correlation function {δr
2}∼r
r
θ+2, then the relative spectral density of the noise in the system is expressed as C
e∼λm exp(−λ(1−p
c)), where p
c is the percolation threshold and m=νd (ν is the critical exponent of the correlation length and d is the dimensionality of the problem). It is hypothesized that the exponent m possesses a dual universality: It is independent of 1) the geometry of the lattice and 2) the θ-mechanism responsible for
the generation of the local noise. Numerical modeling in a three-dimensional lattice gives m=52.3 for θ=1 and θ=0, in agreement with the hypothesis.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 614–618 (25 April 1996) 相似文献
6.
M R M Witwit 《Pramana》1994,42(2):159-165
Eigenenergies are calculated for the potentialsV
1(r)=−(a/r)[1+(1+br)e−2br
] andV
2(r)=−(v/r)[1 −λr(1−Z
−1)(1+λr)−1], using renormalized series technique. Accurate results produced here for various eigenstates agree with those available
in the literature. 相似文献
7.
For operators with a discrete spectrum, {λ
j
2}, the counting function of λ
j
's, N (λ), trivially satisfies N ( λ+δ ) −N ( λ−δ ) =∑
j
δλ
j
((λ−δ,λ+δ]). In scattering situations the natural analogue of the discrete spectrum is given by resonances, λ
j
∈ℂ+, and of N (λ), by the scattering phase, s(λ). The relation between the two is now non-trivial and we prove that
where ωℂ+ is the harmonic measure of the upper of half plane and δ can be taken dependent on λ. This provides a precise high energy
version of the Breit–Wigner approximation, and relates the properties of s (λ) to the distribution of resonances close to the real axis.
Received: 16 October 1998 / Accepted: 28 January 1999 相似文献
8.
A phenomenological theory of the magnetic-field penetration-depth (λ
iα
) anisotropy in high-temperature superconductors is constructed taking account of the magnetic susceptibility (χ
ik
) anisotropy of the surface layer. The factor of 1.9 change in the anisotropy λ
c
/λ
ab
with 4% substitution of Co for Cu ions in YBa2Cu3O7 is virtually completely due to the increase in the magnetic susceptibility anisotropy. For Cu-Zn substitutions the change
in λ
c
/λ
ab
is characterized primarily by a change in the anisotropy of the tensor of the reciprocal effective masses of the charge carriers
(pairs).
Fiz. Tverd. Tela (St. Petersburg) 41, 1552–1555 (September 1999) 相似文献
9.
10.
B. Forghan 《International Journal of Theoretical Physics》2012,51(5):1503-1508
We calculate the four-point function in λϕ
4 theory by using Krein regularization and compare our result, which is finite, with the usual result in λϕ
4 theory. The effective coupling constant (λ
μ
) is also calculated in this method. 相似文献
11.
V. R. Bom J. N. Bradbury J. D. Davies A. M. Demin D. L. Demin C. W. E. van Eijk V. V. Filchenkov A. N. Golubkov N. N. Grafov V. G. Grebinnik S. K. Grishechkin K. I. Gritsaj V. G. Klevtsov A. D. Konin A. A. Kukolkin S. V. Medved' V. A. Nazarov V. V. Perevozchikov A. N. Ponomarev V. Ya. Rozhkov A. I. Rudenko S. M. Sadetsky Yu. V. Smirenin N. I. Voropaev A. A. Yukhimchuk S. A. Yukhimchuk V. G. Zinov S. V. Zlatoustovskii 《Hyperfine Interactions》2001,138(1-4):213-223
Experiments on the study of the muon catalyzed fusion (μCF) process in a double D/T mixture of hydrogen isotopes in the temperature
range 300–800 K at densities 0.3–0.5 LHD are performed at the JINR phasotron. The values of the effective μCF parameters (cycling
rate λ
c
, neutron yield Y
n
, muon losses w) are obtained. Tentative dtμ-molecule formation rates on D2 and DT molecules (λ
dtμ−d
and λ
dtμ−t
) are obtained for different mixture temperatures and densities. The results obtained show that λ
dtμ−t
increases with temperature, but its value is smaller than theoretical predictions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
The effective muon losses w measured in the last experiment of the JINR group with D/T mixture are analyzed. They are considered as a function of the
tritium concentration C
t
taken for different temperatures. The obtained results indicate different muon transfer rates from deuterium and tritium
to impurities with Z>1 (λ
dZ
and λ
tZ
) and show that the ratio λ
tZ
/λ
dZ
increases with temperature.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
P. Politi A. Torcini 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(3):401-404
We consider a class of unstable surface growth models,
?t z = -?x J\partial_t z = -\partial_x {\cal J}
,
developing a mound structure of size λ and displaying a
perpetual coarsening process, i.e. an endless increase in time of λ.
The coarsening exponents n,
defined by the growth law of the mound size λ with time,
λ∼tn, were previously found by numerical integration of the
growth equations [A. Torcini, P. Politi, Eur. Phys. J. B 25, 519 (2002)].
Recent analytical work
now allows to interpret such findings as finite time effective
exponents. The asymptotic exponents are shown to appear at so large
time that cannot be reached by direct integration of
the growth equations. The reason for the appearance of effective exponents
is clearly identified. 相似文献
14.
Claudio Dappiaggi Valter Moretti Nicola Pinamonti 《Communications in Mathematical Physics》2009,285(3):1129-1163
As a starting point, we state some relevant geometrical properties enjoyed by the cosmological horizon of a certain class
of Friedmann-Robertson-Walker backgrounds. Those properties are generalised to a larger class of expanding spacetimes M admitting a geodesically complete cosmological horizon common to all co-moving observers. This structure is later exploited in order to recast, in a cosmological background, some
recent results for a linear scalar quantum field theory in spacetimes asymptotically flat at null infinity. Under suitable
hypotheses on M, encompassing both the cosmological de Sitter background and a large class of other FRW spacetimes, the algebra of observables
for a Klein-Gordon field is mapped into a subalgebra of the algebra of observables constructed on the cosmological horizon. There is exactly one pure quasifree state λ on which fulfills a suitable energy-positivity condition with respect to a generator related with the cosmological time displacements.
Furthermore λ induces a preferred physically meaningful quantum state λ
M
for the quantum theory in the bulk. If M admits a timelike Killing generator preserving , then the associated self-adjoint generator in the GNS representation of λ
M
has positive spectrum (i.e., energy). Moreover λ
M
turns out to be invariant under every symmetry of the bulk metric which preserves the cosmological horizon. In the case of
an expanding de Sitter spacetime, λ
M
coincides with the Euclidean (Bunch-Davies) vacuum state, hence being Hadamard in this case. Remarks on the validity of the
Hadamard property for λ
M
in more general spacetimes are presented.
Dedicated to Professor Klaus Fredenhagen on the occasion of his 60th birthday. 相似文献
15.
Shahn Majid 《Letters in Mathematical Physics》2011,98(2):167-191
We provide a new unified construction of the two-parameter Podleś two-spheres as characterised by a projector e with trace
q
(e) = 1 + λ. In our formulation the limit in which q → 1 with λ fixed is the fuzzy sphere, while the limit λ → 0 with q fixed is the standard q-deformed sphere. We show further that the non-standard Podleś spheres arise geometrically as ‘constant time slices’ of the
unit hyperboloid in q-Minkowski space viewed as the braided group B
q
[SU
2]. Their localisations are then isomorphic to quotients of U
q
(su
2) at fixed values of the q-Casimir precisely q-deforming the fuzzy case. We also use transmutation and twisting theory to introduce a
Cq[G\mathbb C]{C_q[G_\mathbb {C}]} -covariant differential calculus on general B
q
[G] and U
q
(g), with Ω(B
q
[SU
2]) and Ω(U
q
(su
2) given in detail. To complete the picture, we show how the covariant calculus on the 3D bicrossproduct spacetime arises from
Ω(C
q
[SU
2]) prior to twisting. 相似文献
16.
A self consistent formulation of the Jeans instability of a dusty plasma with proper inclusion of charge dynamics is described.
It is shown that charge fluctuations significantly affect the Jeans as well as the Buneman mode. For plasma particles (electrons
and ions) in local thermal equilibrium, the Jeans lengthλ
J is given byλ
J≈λ
g
F(R, ε, β/η), whereλ
g is the Debye length of the charged grains,R is the square of the ratio of the Jeans to the plasma frequency of the grains,ε is the square of the ratio of the Debye length of the grains and the plasma particles andβ/η is the ratio of the attachment to the decay frequency of the electronic charges to the grain surface. The functional form
ofF is given in the text. Numerical investigation of the Jeans-Buneman mode for a two and three component plasma shows that the
Jeans mode dominates atkλ
D≪1 (wherek is the wave number andλ
D is the Debye length of plasma particles), whereas atkλ
D≫1 only the Buneman mode operates. Charge fluctuations reduce the area of overlap of the two modes. Furthermore, in the absence
of gravity, there exists a new, charge fluctuation induced unstable mode in a streaming dusty plasma. Astrophysical applications
of the results are discussed. 相似文献
17.
The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at
the frequencies ω
r < Ωe, propagating downward in the direction of the Earth’s magnetic field, has been analysed in the auroral region at ω
e/Ωe < 1 where ω
e is the plasma frequency and Ωe is the gyrofrequency. The FEBs with low to high energy (E
b) but with low temperature (T
‖b) have no effect on these waves. The FEBs with E
b < 1 keV and T
‖b (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the T
‖b which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher
frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in T
‖b. The FEBs with less E
b (giving drift velocity) reduce growth rate more than the beams with larger E
b. The inhibition of growth rate increases with the increase in the ratio ω
e/Ωe indicating that the beams are more effective at higher altitudes.
相似文献
18.
Gerald Rosen 《International Journal of Theoretical Physics》1995,34(9):1899-1905
Lepton-quark mass may reflect a correspondence in spacetime structure described by a modular conformal scaling group. Stemming
in part from a spacetime line element correspondenceds → (expλ
n)ds in which the eight quantitiesλ
0,λ
1, ...,λ
7 constitute a closed set under a modular addition, the associated formula for lepton-quark mass (yielding values at the 1
GeV scale for the leptons and lighter quarks and at the physical pole for the top) is conjectured to bem=m
fQ2(exp −λ
n), wherem
f=10.245 TeV is the progenitor fermion mass,Q is the charge number of the lepton or quark, and the modular group parameterλ
n is indexed by a fermion principal quantum numbern that depends on three mutually independent projection operators. 相似文献
19.
E. I. Salamatov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(11):1442-1447
Peculiarities of the kinetics of weakly nonequilibrium thermal phonons (λph = 10−50 nm) in nanodispersed ceramics are investigated. The features of the phonon spectrum in the wavelength range λph ∼ R
g (where R
g is the average size of a ceramic grain) are studied. The conditions yielding the formation of a gap in the phonon spectrum
of nanodispersed materials are analyzed. It is shown that the presence of inclusions with characteristic sizes smaller than
the grain size of the parent ceramic material (pores, inclusions of other phases) shifts the gap toward the high-frequency
range of the phonon spectrum. Peculiarities of the transport of nonequilibrium phonons during the transition from nano- to
microdispersed sizes of the ceramic structure are analyzed. 相似文献
20.
Rottereau M Gimel JC Nicolai T Durand D 《The European physical journal. E, Soft matter》2003,11(1):61-64
We present off-lattice Monte Carlo simulations of site-bond percolation of semi-penetrable spheres or, equivalently, of hard
spheres with a finite bond range. We will show that the crucial parameter is the effective volume fraction ( φe), i.e. the volume that is occupied or within the bond range of at least one particle. For the equivalent system of semi-penetrable
spheres 1 - φe is the porosity. The bond percolation threshold (p
b) can be described in terms of φe by a simple analytical expression: log(φe)/log(φec) + log(p
b)/log(p
bc) = 1, with p
bc = 0.12 independent of the bond range and φec a constant that decreases with increasing bond range.
Received: 10 March 2003 / Accepted: 23 April 2003 / Published online: 21 May 2003
RID="a"
ID="a"e-mail: jean-christophe.gimel@univ-lemans.fr 相似文献