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1.
A. Geranios 《Il Nuovo Cimento C》1989,12(5):613-624
Summary The dynamical characteristics of α-particles in the solar wind between 0.3 and 1.0 AU are studied. It has been found that
the connections between alpha temperature and speed, normalized at 1AU, as well as radial temperature exponents significantly
differ from those found for protons. Between α and proton temperature, generally, the α temperature depends stronger on flow
speed. Nevertheless, the flow characteristics of alphas and protons concerning their speeds are similar. For example, the
dependence ofT
α onV
α is stronger also for slow than for fast alpha flows. The alpha radial temperature decreases much slower than proton temperature
away from the Sun, according to the relationT
α/T
0=(r/r
0)−k
withk varying from very low (0.10) to moderate values (0.60).T
α,T
0 are the alpha temperatures at distancesr,r
0(=1 AU), respectively. These findings strongly suggest an additional heating of alphas, for example by Alfven waves or Coulomb
collisions.
To speed up publication, the author of this paper has agreed to not receive the proofs for correction. 相似文献
2.
A. Díaz-Sánchez A. Pérez-Garrido 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):483-486
The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional
Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, f (t) = f
0exp - (t/τ)β
, with the exponent β increasing with the temperature. The relaxation time diverges as an Arrhenius law when T→ 0.
Received 24 May 2001 and Received in final form 12 September 2001 相似文献
3.
When the processive motor protein kinesin walks along the biopolymer microtubule it can occasionally make a backward step.
Recent single molecule experiments on moving kinesin have revealed that the forward-to-backward step ratio decreases exponentially
with the load force. Carter and Cross (Nature 435, 308-312, 2005) found that this ratio tightly followed 802 × exp[−0.95F], where F is the load force in piconewtons. A straightforward analysis of a Brownian step leads to L/(2k
B
T) as the factor in front of the load force, where L is the 8 nm stepsize, k
B
is the Boltzmann constant, and T is the temperature. The factor L/(2k
B
T) does indeed equal 0.95 pN−1. The same analysis shows how the 802 prefactor derives from the power stroke energy G as exp[G/(2k
B
T)]. There are indications that the power stroke derives from the entropically driven coiling of the 30 amino acid neck linker
that connects the two kinesin heads. This idea is examined and consequences are deduced. 相似文献
4.
M. Wołoszyn D. Stauffer K. Kułakowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):331-335
We investigate the network model of community by Watts, Dodds and Newman (D.J. Watts et al., Science 296, 1302 (2002)) as a hierarchy of groups, each of 5 individuals. A homophily parameter
α controls the probability proportional to exp (-αx) of selection of neighbours
against distance x. The network nodes are endowed with spin-like variables si = ± 1,
with Ising interaction J > 0. The Glauber dynamics is used to investigate the
order-disorder transition. The transition temperature Tc is close to 3.8 for
α < 0.0 and it falls down to zero above this value. The result provides a mathematical
illustration of the social ability to a collective action via weak ties, as discussed
by Granovetter in 1973. 相似文献
5.
F. L. Bregolin M. Behar F. Dyment 《Applied Physics A: Materials Science & Processing》2009,95(2):501-505
The diffusion of nitrogen in α-Hf was studied in the temperature range of (823–1123) K using the ion implantation and nuclear resonance techniques. The
measurements show that the diffusion coefficients follow the Arrhenius behavior D(T)=D
0exp (−Q/RT) with D
0=(5.5±2.1)×10−7 m2/s and Q=(228±1) kJ/mol. A comparison of the present results with the previous one is done. 相似文献
6.
Pd80+x
Si20−x
(x = 0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing
and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature
T
g, the initial crystallization temperature T
x and the onset crystallization temperature T
p of Pd-Si binary glassy alloys increase. Moreover, the supercooled liquid region reaches 61 K. It indicates that Pd-Si binary
alloys possess large glass forming ability, which can be greatly improved by fluxing treatment.
Supported by the National Basic Research Program of China (Grant No. 2007CB613905) and the National Natural Science Foundation
of China (Grant Nos. 50671050 and 50431030) 相似文献
7.
E. A. Kataeva A. D. Bozhko S. V. Demishev 《Bulletin of the Lebedev Physics Institute》2010,37(11):347-351
The conductivity of carbon films grown by polymethylphenylsiloxane vapor decomposition in stimulated dc discharge plasma was
studied. It is found that the Mott hopping conductivity $
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
$
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
is characteristic of the samples under study in the temperature range of 80–400 K in the electric field E to 5 · 104 V/cm. An analysis of the pre-exponential factor σ
0(T) = σ
00(T
0)T
α allowed the conclusion that the hopping transport is most adequately described in the model with the exponential energy dependence
of the density of localized states for which α = −1/2 and the universal relation ln σ
00 −T
01/4 0 is valid, which is satisfied in the range where the parameter σ
00 varies by eight orders of magnitude. 相似文献
8.
M. N. Magomedov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(1):86-91
The temperature dependence of the specific (per atom) entropy and heat capacity of a nanocrystal is studied using a nanocrystal
model in the form of a rectangular parallelepiped with variable surface shape. Accounting for the temperature dependence of
the surface energy showed that the temperature dependence of the surface contribution to specific entropy is described by
the same function that determines the temperature dependence of the isochoric heat capacity of a macrocrystal. Thus, at T → 0 K at T/Θ > 2 the surface contribution to the specific heat is zero. The maximal surface contribution to specific heat is reached
at T/Θ = 0.2026 and is equal to c
st/k
B = 1.0115 (where k
B is the Boltzmann constant, Θ is the characteristic temperature depending both on the size and the shape of the nanocrystal).
The applicability of the Grüneisen rule for a nanocrystal both at low and high temperatures is studied. It has been found
that a case when the surface contribution to specific heat would be negative c(N) < c(∞), i.e. c
st(N) < 0 can occur for nanocrystals with a noncubic habitus. 相似文献
9.
Frank F. Haas Katharina Vollmayr Kurt Binder 《Zeitschrift für Physik B Condensed Matter》1995,99(1):393-400
As a simple model of an anisotropic orientational glass with short range forces, the 3-state Potts model on the simple cubic
lattice with nearest neighbor interactions drawn from a Gaussian distribution is considered. With Monte Carlo methods we study
the response of the system to a uniform “field” which favors one of the states. This is motivated by experiments which apply
stress that favors one molecular orientation of the quadrupolar glass. The responsem to that fieldh=H/k
BT is analyzed in terms of an expansionm= χ1
h+χ1
h
2+χ1
h
3+..., where χ1 is the linear susceptibility, and χ2,χ13 are nonlinear susceptibilities. Unlike the case of spin glasses, where the spin inversion symmetry of the system in the absence
of fields implies χ2≡0,χ2 is nonzero here and diverges to −∞ at the zero temperature transition of the model, while χ3 diverges to +∞ as in spin glasses. At inifinite temperature, however, χ1=1/3, χ2=1/18 and χ3=-1/54, i.e. the nonlinear susceptibilities have a different sign as at low temperature. In contrast, a random field does
not induce a uniform order parameterm but only a glass order parameterq. The temperature dependence of this glass order parameterq(T) shows for intermediate field strength order parameterq(T) shows for intermediate field strength a maximum of the slopedq(T)/dT very similar to corresponding experiments. 相似文献
10.
J. Ke P.-P. Li X.-S. Chen Z. Lin Y. Z. Zheng 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(2):211-215
We propose a growing network model with link
constraint, in which new nodes are continuously introduced into
the system and immediately connected to preexisting nodes, and any
arbitrary node cannot receive new links when it reaches a maximum
number of links km. The connectivity of the network model is
then investigated by means of the rate equation approach. For the
connection kernel A(k)=kγ, the degree distribution nk
takes a power law if γ≥1 and decays stretched
exponentially if 0≤γ< 1. We also consider a network
system with the connection kernel A(k)=kα(km-k)β.
It is found that nk approaches a power law in the α> 1
case and has a stretched exponential decay in the 0≤α<
1 case, while it can take a power law with exponential truncation
in the special α=β=1 case. Moreover, nk may have a
U-type structure if α> β. 相似文献
11.
J. L. Deng K. H. Su X. Wang Q. F. Zeng L. F. Cheng Y. D. Xu L. T. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):21-35
The most stable structures of gaseous Si
m
C
n
(3 ⩽ n+m ⩽ 6) clusters in their ground electronic states are determined with the high level electronic correlation method QCISD(T)/g3large.
Thermodynamic properties on heat capacity (C
p,m
Θ), entropy (S
m
Θ), Gibbs energy function (−[G
Θ −H
Θ(T
r
)]/T) and enthalpy function (H
Θ−H
Θ(T
r
)) are predicted with standard statistical thermodynamics using the structure parameters and vibrational frequencies obtained
with B3PW91/6-31G(d) method combined with the electronic excitation energies determined with time dependent density functional (TD DFT) method
at B3PW91/6-31G(d) level. The electronic energies are calculated with the accurate model chemistry method at G3(QCI) level of theory and the
Δ
f
H
m
Θ (0 K), Δ
f
H
m
Θ (298.15 K) and Δ
f
G
m
Θ (298.15 K) values are predicted. The heat capacities C
p,m
Θ(T) as a function of temperature within 298.15-2000 K are fitted into analytical equations. The thermodynamic functions at higher
temperatures are determined classically by using these equations. Most of the results obtained in this work are consistent
with the available experiments. 相似文献
12.
M. Bryushinin V. Golubev Y. Kumzerov D. Kurdyukov I. Sokolov 《Applied physics. B, Lasers and optics》2009,95(3):489-495
We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous
glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created
by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal
amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10−10 Ω−1 cm−1 (λ=442 nm, I
0=0.045–0.19 W/cm2, T=293 K) and σ=(3.5–4.6)×10−10 Ω−1 cm−1 (λ=532 nm, I
0=2.3 W/cm2, T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L
D=0.18 μm. 相似文献
13.
It is well known that the superconducting transition temperature of high-T
c
cuprates depends on the number of CuO2 planes in the unit cell. The multilayer structure implies the possibility of interlayer hopping. Under the assumption that
the interlayer hopping can be specified by the parameter t
⊥(k) = t
⊥(cos(k
x
) − cos(k
y
))2, the quasiparticle excitation spectrum for the bilayer cuprate in the superconducting state has been determined in the framework
of the t − t′ − t″ − t
⊥ − J* model using the generalized mean-field approximation. It turns out that the interlayer hoppings does not create any additional
mechanism of the Cooper paring and does not lead to an increase in T
c
. The splitting of the upper Hubbard quasiparticle band attributed to the interlayer hoppings is manifested as two peaks in
the doping dependence of the superconducting transition temperature at temperatures below the maximum T
c
value for a single-layer cuprate. It has been found that antiferromagnetic interlayer correlations suppress the interlayer
splitting. This probably leads to the common doping dependence of T
c
for both single-layer and bilayer cuprates. 相似文献
14.
The luminescence response of xylene-based liquid scintillator (scintillation grade), xylene + 1 g/l PPO + 0.1 g/l BBOT, has
been studied as a function of temperature in the range 200 to 242 K. It has been observed that under gamma-ray excitation
the light output increases with the decrease of temperature. The data are well described by the Arrhenius relation,I
low−I=I
0 exp(−E/kT), whereI is the count rate at temperatureT.I
low is a constant equal to 5600 counts per min, theI
0 factor is 3.3 × 106 counts/min,k is the Boltzmann constant. The activation energyE was found to be equal to 0.20 eV. It is typical for thermally activated diffusion controlled process. 相似文献
15.
Summary Crystallization kinetics is studied in glassy Ge22Se78−x
Bi
x
(0≤x≤10) using isothermal annealing at various temperatures between the glass transition and melting. D.c. conductivity is taken
as a parameter to estimate the extent of crystallization (α). The activation energy of crystallization (ΔE) and the order parameter (n) are calculated by fitting the values of α in Avrami’s equations of isothermal transformation. The results indicate that
ΔE is highly composition dependent and decreases as the Bi concentration increases. 相似文献
16.
Bound states and critical behavior of the Yukawa potential 总被引:1,自引:0,他引:1
We investigate the bound states of the Yukawa potential V (r)=−λexp(−αr)/r, using different algorithms: solving the Schr?dinger equation numerically and our Monte Carlo Hamiltonian approach. There
is a critical α = αC, above which no bound state exists. We study the relation between αC and λ for various angular momentum quantum number l, and find in atomic units, αC(l) = λ[A
1 exp(−l/B
1) + A
2 exp(−l/B
2)], with A
1 = 1.020(18), B
1 = 0.443(14), A
2 = 0.170(17), and B
2 = 2.490(180). 相似文献
17.
Electrical resistivity (ρ) of the amorphous (a-)Fe100−c
Zr
c
(c=8.5, 9.5 and 10) alloys has been measured in the temperature range 77 to 300 K, which embraces the second-order magnetic
phase transition at the Curie temperature point T
c. Analysis of the resistivity data particularly in the critical region reveals that these systems have a much wider range
of critical region compared to other crystalline ferromagnetic materials. The value of T
c and specific heat critical exponent, α has the same values as those determined from our earlier magnetic measurements. The value of α for all the present investigated alloys are in close agreement with the values predicted for three-dimensional (3D) Heisenberg
ferromagnet systems, which gives contradiction to the earlier results on similar alloys. It is observed from the analysis
that the presence of quenched disorder does not have any influence on critical behavior. 相似文献
18.
C. Monthus T. Garel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):39-45
The directed polymer in a 1+3 dimensional
random medium is known to present a disorder-induced phase
transition. For a polymer of length L, the high temperature
phase is characterized by a diffusive behavior for the end-point
displacement R2 ∼L and by free-energy fluctuations of order
ΔF(L) ∼O(1). The low-temperature phase is characterized by
an anomalous wandering exponent R2/L ∼Lω and
by free-energy fluctuations of order ΔF(L) ∼Lω
where ω∼0.18. In this paper, we first study the scaling
behavior of various properties to localize the critical temperature
Tc. Our results concerning R2/L and ΔF(L) point towards
0.76 < Tc ≤T2=0.79, so our conclusion is that Tc is equal
or very close to the upper bound T2 derived by Derrida and
coworkers (T2 corresponds to the temperature above which the ratio
remains finite as L ↦
∞). We then present histograms for the free-energy, energy and
entropy over disorder samples. For T ≫Tc, the free-energy
distribution is found to be Gaussian. For T ≪Tc, the free-energy
distribution coincides with the ground state energy distribution, in
agreement with the zero-temperature fixed point picture. Moreover the
entropy fluctuations are of order ΔS ∼L1/2 and follow a
Gaussian distribution, in agreement with the droplet predictions,
where the free-energy term ΔF ∼Lω is a near
cancellation of energy and entropy contributions of order L1/2. 相似文献
19.
K. Lal S. K. Chattopadhyay A. K. Meikap S. K. Chatterjee M. Ghosh 《Czechoslovak Journal of Physics》2001,51(9):897-908
A detailed study on the weak localization phenomenon vis-a-vis electron-electron interaction effects in magnetic metallic
glasses has been carried out. We measured the electrical conductivity and magnetoconductivity within the temperature range
1.8≤T≤300K. A maximum on the conductivity versus temperature curve exists atT=T
m. The conductivity was observed to follow aT
1/2 law forT<T
m andT
2 law forT>T
m. Magnetoconductivity data of these alloys indicate the prominence of electron-electron interaction at low temperatures. The
authors have determined the inelastic scattering field and spin-orbit scattering field from the magnetoconductivity data.
The inelastic scattering field obeys aT
p law (p=2) at low temperatures. 相似文献
20.
X. G. Tang Q. X. Liu J. Wang H. L. W. Chan 《Applied Physics A: Materials Science & Processing》2009,96(4):945-952
The effect of a dc bias field on the diffuse phase transition and nonlinear dielectric properties of sol-gel derived Ba(Zr0.2Ti0.8)O3 (BZT) ceramics are investigated. Diffuse phase transitions were observed in BZT ceramics and the Curie–Weiss exponent (CWE)
was γ∼2.0. The dielectric constant versus temperature characteristics and the γ in the modified Curie–Weiss law, ε
−1=ε
m
−1[1+(T−T
m
)
γ
/C1](1≤γ≤2), as a function of the dc bias field was obtained for BZT ceramics. The results indicated that γ is a function of dc bias field, and the γ value decreased from 2.04 to 1.73 with dc bias field increasing from 0 to 20 kV/cm. The dielectric constant decreases with
increasing dc bias field, indicating a field-induced phase transition. The dc bias field has a strong effect on the position
of the dielectric peak and affects the magnitude of the dielectric properties over a rather wide temperature range. The peak
temperature of the dielectric loss does not coincide with the dielectric peak and an obvious minimum value for the dielectric
loss at the temperature of the dielectric peaks is observed. At room temperature, 300 K, the high tunability (K=80%), the low loss tangent (≈0.01) and the large FOM (74), clearly imply that these ceramics are promising materials for tunable capacitor-device applications. 相似文献