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1.
A differential thermal analysis ΔT
y
(T) in vacuum has been performed, and the temperature gradient ΔT
x
(T) along the Ag2Se sample during the transition α → β has been studied. It has been shown that the transitions α → α′ and β′ → β are displacive
transitions and that the transition α′ → β′ is a reconstructive transition. It has been found that the temperature gradient
along the sample during the transition α′ → β′ passes through a deep minimum due to a strong increase in the specific heat
capacity. 相似文献
2.
M. Modarres M. M. Yazdanpanah F. Zolfagharpour 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):327-333
The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α
p(E
0+) = + 3.2, α
n(E
0+) = + 4.1, the t-channel α
t
p, n = - β
t
p, n = + 7.6 and the resonant β
p, n(P
33(1232)) = + 8.3 contributions (in units of 10-4fm^3). The remaining deviations from the experimental data Δα
p = 1.2±0.6, Δβ
p = 1.2±0.6, Δα
n = 0.8±1.7 and Δβ
n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions.
This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms
of two-photon coupling to the σ-meson having the predicted mass m
σ
= 666MeV and two-photon width Γ
γγ
= 2.6keV. 相似文献
3.
G A V Ramanamurthy K Ramachandra Rao Y Rama Krishna P Venkateswarlu K Bhaskara Rao P V Ramana Rao S Venkata Ratnam V Seshagiri Rao G J Nagaraju S Bhuloka Reddy 《Pramana》2001,56(5):697-703
The Measurement of K
β
K
/α
intensity ratios are measured in some 3d shell elements by using a 2 MeV proton beam along with a high resolution Si(Li) detector. The present Measurement of K
β
K
/α
intensity ratios are in good agreement with Scofield modified theoretical values, thus supporting the basic assumptions in
that theory. From the present Measurement of K
β
K
/α
intensity ratios, it is evident that due to chemical effects, the experimental Measurement of K
β
K
/α
intensity ratios will be increased while they will be decreased due to the presence of simultaneous M-shell vacancies which are produced due to proton excitation. 相似文献
4.
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
5.
S. Firmino?Mendes C. M. Costa V. Sencadas J. Serrado?Nunes P. Costa R. Gregorio J. L. Gomez Ribelles S. Lanceros-Méndez 《Applied Physics A: Materials Science & Processing》2009,96(4):1037-908
In this work, poly(vinilidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1−x
/[PZT]
x
) composites of volumetric fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powder of crystallite size of 0.84, 1.68, and 2.35
μm in different amounts of PZT (10, 20, 30, and 40%) was mixed with the polymeric matrix. The crystalline phase of the polymeric
matrix was the nonpolar α-phase and the polar β-phase.
Dielectric and dynamic mechanical (DMA) measurements were performed to these composites in order to evaluate the influence
of particle size and the amount of PZT filler with respect to the PVDF matrix. The inclusion of ceramic particles in the PVDF
polymer matrix increases the complex dielectric constant and dynamical mechanical response of the composites. A similar behavior
is observed for the α- or β-phase of the polymeric matrix indicating that the PVDF polymer matrix is not particularly relevant for the composite behavior.
On the other hand, ceramic size and especially content play the major role in the increase of the dielectric response and
the room temperature storage modulus. In particular, the storage modulus increases with increasing PZT concentration, but
this increase is more pronounced, in terms of maximum value, for the sample with 2.35 μm particle size; DMA reveals two main
relaxations in the analyzed samples. A low-temperature process maximum at ca. −40°C, usually labeled by β or α
a
associated to the T
g
of the polymer and the α-relaxation at temperatures above 30°C. The β-relaxation is also observed in the dielectric measurements.
The models used to asses the dielectric behavior of the samples with increasing PZT concentration indicate that the particle–matrix
interaction plays a relevant role, as well as the particle asymmetry and relative orientation, being the Yamada model the
most appropriate to describe the composite behavior.
An erratum to this article can be found at 相似文献
6.
A variational approach is developed for bound state calculations in three- and four-electron atomic systems. This approach
can be applied to determine, in principle, an arbitrary bound state in three- and four-electron ions and atoms. Our variational
wave functions are constructed from four- and five-body Gaussoids that respectively depend on six (r
12, r
13, r
14, r
23, r
24, r
34) and ten (r
12, r
13, r
14, r
15, r
23, r
24, r
25, r
34, r
35 and r
45) relative coordinates. The approach allows operating with the more than one electron spin functions. In particular, the trial
wave functions for the 1
S states in four-electron atomic systems include the two independent spin functions χ1 = αβαβ + βαβα − βααβ − αββα and χ2 = 2ααββ + 2ββαα − βααβ − αββα − βαβα − αβαβ. We also discuss the construction of variational wave functions for the excited
23
S states in four- electron atomic systems. 相似文献
7.
The focal switch of cosine-Gaussian (CsG) beams passing through a system with the aperture and lens separated is studied analytically
and numerically. It is shown that the focal switch of CsG beams can appear not only for the apertured case, but also for the
unapertured case. The necessary condition for the focal switch is that truncation parameter α > αc and the beam parameter β > βc, αc, βc being the corresponding critical values. There exists a maximum of the relative transition height Δz
sw as α varies, and Δz
sw increases with increasing β and decreasing N
w. The normalized axial intensity minimum I
min / I
max decreases with an increase of α and β, and I
min / I
max remains unchanged as N
w varies. 相似文献
8.
A differential thermal analysis in vacuum and studies of the coefficients of electrical conductivity and thermal conductivity,
and of the thermal emf are made in Ag2Te in the neighborhood of the structural phase transition. It is shown that these data can be used to calculate the switching
factor L(T), determine the region in which the phases coexist within the transition, and calculate the thermodynamic parameters. Prior
to and after the main phase transition, additional displacement transitions are observed. It is found that the phase transition
takes place roughly according to the scheme α
385 K→α′405 K→β′420 K→β
440 K. The specific heat C
p, changes in entropy ΔS and transition enthalpy ΔH, as well as the minimum phase fluctuation volume V, and the heat Q of the phase transition are determined. It is shown that excesses of Te and Ag have almost no effect on the transition temperatures
T
0, but have a substantial effect on the thermodynamic parameters.
Fiz. Tverd. Tela (St. Petersburg) 40, 1693–1697 (September 1998) 相似文献
9.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
10.
Hartmann L Gorbatschow W Hauwede J Kremer F 《The European physical journal. E, Soft matter》2002,8(2):145-154
The molecular dynamics in thin films (18 nm-137 nm) of isotactic poly(methyl methacrylate) (i-PMMA) of two molecular weights
embedded between aluminium electrodes are measured by means of dielectric spectroscopy in the frequency range from 50 mHz
to 10 MHz at temperatures between 273 K and 392 K. The observed dynamics is characterized by two relaxation processes: the
dynamic glass transition (α-relaxation) and a (local) secondary β-relaxation. While the latter does not depend on the dimensions
of the sample, the dynamic glass transition becomes faster (≤2 decades) with decreasing film thickness. This results in a
shift of the glass transition temperature T
g to lower values compared to the bulk. With decreasing film thickness a broadening of the relaxation time distribution and
a decrease of the dielectric strength is observed for the α-relaxation. This enables to deduce a model based on immobilized
boundary layers and on a region displaying a dynamics faster than in the bulk. Additionally, T
g was determined by temperature-dependent ellipsometric measurements of the thickness of films prepared on silica. These measurements
yield a gradual increase of T
g with decreasing film thickness. The findings concerning the different thickness dependences of T
g are explained by changes of the interaction between the polymer and the substrates. A quantitative analysis of the T
g shifts incorporates recently developed models to describe the glass transition in thin polymer films.
Received 12 August 2001 and Received in final form 16 November 2001 相似文献
11.
K. Azizi 《The European Physical Journal C - Particles and Fields》2009,61(2):311-319
Due to the very short life time of the Δ baryons, a direct measurement on the electromagnetic moments of these systems is almost impossible in the experiment and
can only be done indirectly. Although only for the magnetic dipole moments of Δ
++ and Δ
+ systems there are some experimental data, the theoretical, phenomenological and lattice calculations could play crucial role.
In the present work, the magnetic dipole (μ
Δ
), electric quadrupole (Q
Δ
) and magnetic octupole (O
Δ
) moments of these baryons are computed within the light cone QCD sum rules. The results are compared with the predictions
of the other phenomenological approaches, lattice QCD and existing experimental data. 相似文献
12.
The relaxation processes (α, β, and γ) in UHMW PE fibres drawn to different draw ratios λ have been studied by dynamic-mechanical and nuclear magnetic resonance methods. The temperature dependences of tensile loss
moduli E″ and spin-lattice relaxation times T
1 have been analyzed assuming distribution of correlation times τ according to the Davidson—Cole function. The activation energies E
a and parameters ε characterizing widths of distribution, and asymptotic value τ
0 for correlation times have been determined from experimental data for low-temperature γ-process and for high-temperature α-process. A weak β-process has been found by dynamic-mechanical method and quantitative analysis was made only for fibres with λ = 9. The temperature dependences of second moment M
2 of the broad-line NMR spectra have been analyzed according to the Gutowsky—Pake formula, which includes only a single correlation
time τ
c without distribution. In this case the activation energies E
a and values of τ
0 have been determined. 相似文献
13.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Kouji Satou 《Applied Physics A: Materials Science & Processing》2009,94(1):57-64
The resultant local Seebeck coefficient α
R (=α
S−α
T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric
efficiency, where α
S is the local Seebeck coefficient and α
T is the one caused by the Thomson effect. It is shown in this paper that α
S, α
T, and α
R of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of
the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position
from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of α
S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite,
respectively, while those of α
T are less than 8% of α
S all over the composite and are so small that the relation α
R≈α
S can be held. We thus succeeded in measuring α
R at the interfaces of the composite. 相似文献
14.
K.R. Rao Y.R. Krishna P. Venkateswarlu K.B. Rao V.S. Rao G.J.N. Raju S.B. Reddy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):283-286
A method is suggested to effect the self absorption correction in a different way to estimate the K X-ray intensity ratios
particularly when heavy ions are used as projectiles. Employing this method, the Kβ/Kα intensity ratios are measured in some 3d shell elements by using Carbon and Nitrogen ions as exciting agents. The Kβ/Kα intensity ratios thus obtained in the present work are compared with the intensity ratios due to some previous authors and
also with Scofield theoretical values.
Received 14 August 2000 and Received in final form 3 January 2001 相似文献
15.
Current and upcoming experiments should improve the sensitivity to e
α
→e
β
γ decays by an order of magnitude. This paper assumes that one of the τ→e
β
γ decays is observed, and explores the structure and consequences of the required new flavoured couplings. In simple models
(a low-scale seesaw, leptoquarks) it is shown that the dipole vertex function is proportional to a product of flavoured matrices
from the Lagrangian (a “Jarlskog-like” invariant), provided that the loop particles are weakly coupled to the Higgs. Secondly,
if the dipole vertex function has a hierarchical structure, this might imply that only some of the τ→e
β
γ modes can be observed, due to the “approximate zero” implied by the bound on μ→eγ. The assumptions underlying this potential test of a hierarchical structure are discussed. 相似文献
16.
A. V. Guskov 《Physics of Particles and Nuclei Letters》2010,7(3):192-200
The electromagnetic structure of charged pions can be described by the electric (απ) and magnetic (βπ) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. It is shown that the
values of απ and βπ can be precisely measured via the Primakoff reaction π− + (A, Z) → π− + (A, Z) + γ in the COMPASS experiment at CERN. 相似文献
17.
E. A. Gastilovich V. G. Klimenko N. V. Korol’kova R. N. Nurmukhametov 《Optics and Spectroscopy》2010,108(3):486-494
The dipole moments (P
s
) of the T
1
S
→ S
0 transition from the triplet sublevels s = z, y, x, which are determined by the spin-orbit (SO) coupling, are studied for a series of mono- and dichloro derivatives of naphthalene.
Based on the model calculations, the effects of different factors (SO coupling in individual chlorine atoms occupying the
α and β positions in the molecule, SO coupling in the carbon backbone of the molecule, and the compensation effect caused
by the interference of SO interactions in individual structural elements of the molecule) on P
s
are differentiated and discussed. 相似文献
18.
High pressure Raman spectroscopic studies on Gd2(MoO4)3(GMO) have been carried out at ambient temperature in the diamond cell to 10 GPa hydrostatic pressure. These experiments have
revealed pressure-induced phase transitions in GMO near 2 GPa and 6.0 GPa. The first transition is from Pba2(β′) phase to another undetermined crystalline phase, designated as phase II, and the second transition is to an amorphized
state. On releasing pressure there is a partial reversion to the crystalline state. The Raman data indicate that the amorphization
is due to disordering of the MoO4 tetrahedral units. Further, it is inferred from the nature of the Raman bands in the amorphized material that the Mo-O bond
lengths and bond angles have a range of values, instead of a few set values. The results of the present study as well as previous
high pressure-high temperature quenching experiments strongly support that pressure-induced amorphization in GMO is a consequence
of the kinetically impededβ toα phase transition. The system in frustration becomes disordered. The rare earth trimolybdates crystallizing in theβ′ structure are all expected to undergo similar pressure-induced amorphization. 相似文献
19.
I. Savatinova I. Savova C.C. Ziling V. Atuchin 《Applied Physics A: Materials Science & Processing》2000,70(5):555-559
Refractive index change and Raman scattering of Z-cut proton-exchanged LiTaO3 optical waveguides with different composition have been studied. Probing of the waveguide depth was carried out by using
micro-Raman spectroscopy in order to distinguish layers with different phase states. Varying the proton-exchange and post-exchange
annealing regimes, two phases –α and β– in addition to the pure LiTaO3, were clearly observed. The behaviour of the A
1 vibrations of the TaO6 groups was found to be very sensitive to the phase changes. Using data from waveguide Raman spectra, normal and oblique E(TO,
LO) phonons were sorted and their properties were followed in the α and β phases. The OH-stretchings are considered to correspond
to dipoles turned out of the oxygen planes.
Received: 9 July 1999 / Accepted: 11 October 1999 / Published online: 24 March 2000 相似文献
20.
S. Moreno R.G. Rubio G. Luengo F. Ortega M.G. Prolongo 《The European physical journal. E, Soft matter》2001,4(2):173-182
The complex dielectric permittivity has been measured for three poly(ethylenglycol)-b-poly(propylenglycol)-b-poly(ethylenglycol)
copolymers with different content of poly(ethylenglycol) (15%, 33% and 80%), and increasing degree of crystallinity (0%, 10%
and 20%, respectively). Only the non-crystalline sample shows the normal mode relaxation together with the segmental (α-relaxation)
and the Johari-Goldstein (β-relaxation) modes. The crystalline samples show also polarization contributions due to the existence
of interfaces between the crystallites and the amorphous phase. The relaxation times of the (α and normal modes can be described
by a VFT equation with the same value of T0. There is a slowing-down of the segmental mode due to the presence of crystallites. The temperature dependence of the α and
β relaxations in the copolymers is very similar to that found in pure PPG, while there are significant differences in the
case of the normal mode of the non-crystalline sample. The size of the cooperatively rearranging regions CRR, and the width
of the glass transition region increase slightly with the degree of crystallinity. The temperature dependence of the size
of CRRs is compatible with the prediction of fluctuation theory. No systematic effect of the degree of crystallinity on the
β-relaxation has been found. Near T
g the β-relaxation time is close to the primitive time of the coupling model.
Received: 31 May 2000 相似文献