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1.
Abstract The analytical applications of the evolved gas analysis (EGA) performed by infrared spectroscopy, for the period extending from 2005 to 2009, are collected in this review. By this technique, the nature of volatile products released by a substance subjected to a controlled temperature program are on-line determined, with the possibility to prove a supposed reaction, either under isothermal or under heating conditions. 相似文献
2.
A. Maignan C. Martin M. Hervieu B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):41-45
The substitution of manganese for cobalt in the perovskite La
0.8
Sr
0.2
CoO
3
has been studied. A significant increase of the magnetoresistance (MR) is obtained, reaching 60% at 5 K under 7 T for . This behavior originates from a spectacular increase of the resistivity correlated to a significant decrease of ferromagnetism
by Mn doping. This enhancement of magnetoresistance can be interpreted by the growth of ferromagnetic clusters in the insulating
matrix, by applying a magnetic field.
Received 7 May 1999 相似文献
3.
R. Calemczuk J. Riera D. Poilblanc J.-P. Boucher G. Chaboussant L. Lévy O. Piovesana 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):171-174
Specific heat (CV) measurements in the spin-1/2 Cu2(C2H12N2)2Cl4 system under a magnetic field up to H
=8.25 T are reported and compared to the results of numerical calculations based on the 2-leg antiferromagnetic Heisenberg ladder.
While the temperature dependences of both the susceptibility and the low-field specific heat are accurately reproduced by
this model, deviations are observed above the critical field HC1 at which the spin gap closes. In this Quantum High Field phase, the contribution of the low-energy quantum fluctuations are
stronger than in the Heisenberg ladder model. We argue that this enhancement can be attributed to dynamical lattice fluctuations.
Finally, we show that such a Heisenberg ladder, for H
>
H
C1, is unstable, when coupled to the 3D lattice, against a lattice distortion. These results provide an alternative explanation
for the observed low temperature ( K-0.8 K) phase (previously interpreted as a 3D magnetic ordering) as a new type of incommensurate gapped state.
Received: 23 July 1998 / Accepted: 24 August 1998 相似文献
4.
The correlation of the local density of states 〈ρɛ(r
1)ρɛ + ω(r
2)〉 in quasi-one-dimensional disordered wires in a magnetic field is calculated under the assumption that |r
1 − r
2| is much smaller than the localization length. This amounts to finding the zero mode of the transfer-matrix Hamiltonian for
the supersymmetric σ model, which is done exactly by mapping to the three-dimensional Coulomb problem. Both the regimes of
level repulsion and level attraction are obtained, depending on |r
1 − r
2|. We demonstrate that the correlations of different eigenfunctions in the quasi-one-dimensional and strictly one-dimensional
cases are dissimilar.
The text was submitted by the authors in English. 相似文献
5.
A. Montorsi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):419-422
We investigate under which circumstances extended Hubbard models, including bond-charge, exchange, and pair-hopping terms,
are invariant under gl
(2,1) superalgebra. This happens for a two-parameter Hamiltonian which includes as particular cases the t
-
J, the EKS and the one-parameter BGLZ Hamiltonians, all integrable in one dimension. We show that the two parameter Hamiltonian
can be recasted as the sum of the BGLZ Hamiltonian plus the graded permutation operator of electronic states on neighbouring
sites. The integrability of the corresponding one-dimensional model is discussed.
Received: 17 February 1998 / Received in final form: 6 March 1998 / Accepted: 17 April 1998 相似文献
6.
Abstract: Periodic publications have been published that address advances in evolved gas analysis techniques, because the correct interpretation for the mechanism of a thermally induced reaction, involving the formation of gaseous species, is strongly dependent on the characterization of the evolved products.When the nature of volatile products released by a substance subjected to a controlled-temperature program are online determined, the results allow one to prove a supposed reaction, either under isothermal or under heating conditions.Very recent analytical applications of evolved gas analysis performed by mass spectrometry, selected among those published in 2012 and 2013, are collected in this review. 相似文献
7.
J. M. BESSON 《高压研究》2013,33(1-6):01-11
Abstract Calculations of the properties of condensed matter systems can be crucially tested by comparison with their experimental pressure behavior. When validated by such a comparison theoretical models become reliable computer experiments and can be used to explore properties of the system which are intrinsically unobservable by experiment alone. Three examples are given of such methods: (i) The behavior of wurtzite indium nitride under pressure which is shown to be due to a second-order isostructural phase transition. (ii) The instability of tetrahedrally bonded semiconductors (Ge) under pressure which turns out to be related to a second-order process. (iii) The explanation of the lattice dynamics of a-boron at ambient conditions which can be understood only by comparison of its high pressure behavior with calculations. 相似文献
8.
V. Hankevych F. Wegner 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):333-342
We present a stability analysis of the 2D t
-
t' Hubbard model on a square lattice for various values of the next-nearest-neighbor hopping t' and electron concentration. Using the free energy expression, derived by means of the flow equations method, we have performed
numerical calculation for the various representations under the point group C
4ν
in order to determine at which temperature symmetry broken phases become more favorable than the symmetric phase. A surprisingly
large number of phases has been observed. Some of them have an order parameter with many nodes in -space. Commonly discussed types of order found by us are antiferromagnetism, d
x2 - y2
-wave singlet superconductivity, d-wave Pomeranchuk instability and flux phase. A few instabilities newly observed are a triplet analog of the flux phase, a
particle-hole instability of p-type symmetry in the triplet channel which gives rise to a phase of magnetic currents, an s*-magnetic phase, a g-wave Pomeranchuk instability and the band splitting phase with p-wave character. Other weaker instabilities are found also. A comparison with experiments is made.
Received 25 July 2002 / Received in final form 28 November 2002 Published online 14 February 2003
RID="a"
ID="a"Current address: Département de physique and Centre de recherche sur les propriétés électroniques de matériaux avancés, Université de Sherbrooke,
Sherbrooke, Québec, Canada J1K 2R1 e-mail: vaha@physique.usherb.ca 相似文献
9.
《Journal of Nonlinear Mathematical Physics》2013,20(1):104-116
Abstract The superposition formulas for solutions of integrable vector evolutionary equations on a sphere are constructed by means of auto-Bäcklund transformation. The equations under consideration were obtained earlier by Sokolov and Meshkov in the frame of the symmetry approach. 相似文献
10.
The primitive ideals of the Hopf algebraC
q
[SL(3)] are classified. In particular it is shown that the orbits in PrimC
q
[SL(3)] under the action of the representation groupH C
*×C
* are parameterized naturally byW×W, whereW is the associated Weyl group. It is shown that there is a natural one-to-one correspondence between primitive ideals ofC
q
[SL(3)] and symplectic leaves of the associated Poisson algebraic groupSL(3,C).Partially supported by a grant from the N.S.A. 相似文献
11.
M. Celasco R. Eggenhöffner 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):415-419
A dynamical percolative model explaining the universality of 1/
f
γ
noise is reported. Exponents γ ranging from 0 to 2 are obtained under the hypothesis that noise originates from random switching events between two ON-OFF
states in elemental parts (switchers) of a physical system. The usual noise behaviour with γ very close to 1 in an arbitrarily wide frequency range is obtained assuming a statistical distribution of switcher relaxation
time τ proportional to τ
-1
, as in McWhorter's model. The impact of these results with respect to recent self-organised criticality models is discussed.
Received 6 November 2000 and Received in final form 22 May 2001 相似文献
12.
Abstract An experimental investigation of the secondary ion emission from organic films under heavy ion bombardment at high energies was carried out by using a time-of-flight mass spectrometer coupled to a Tandem heavy ion accelerator. Preliminary results obtained at 3 MeV/A are reported and discussed. 相似文献
13.
A control method for congested traffic in the coupled map car-following model 总被引:1,自引:0,他引:1
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Based on the pioneer work of Konishi et al, a new control
method is presented to suppress the traffic congestion in the
coupled map (CM) car-following model under an open boundary.
A control signal concluding the velocity differences of the two
vehicles in front is put forward. The condition under which the
traffic jam can be contained is analyzed. The results are
compared with that presented by Konishi et al [Phys.
Rev. 1999 E 60 4000--4007]. The simulation results show that
the temporal behavior obtained by our method is better than that by
the Konishi's et al. method, although both the methods could
suppress the traffic jam. The simulation results are consistent
with the theoretical analysis. 相似文献
14.
《Journal of Nonlinear Mathematical Physics》2013,20(3-4):364-376
Abstract The variational bicomplex of forms invariant under the symmetry algebra of the potential Kadomtsev-Petviashvili equation is described and the cohomology of the associated Euler-Lagrange complex is computed. The results are applied to a characterization problem of the Kadomtsev-Petviashvili equation by its symmetry algebra originally posed by David, Levi, and Winternitz. 相似文献
15.
A new form of empirical spectral distribution of a Wigner matrix W
n
with weights specified by the eigenvectors is defined and it is then shown to converge with probability one to the semicircular
law. Moreover, central limit theorem for linear spectral statistics defined by the eigenvectors and eigenvalues is also established
under some moment conditions, which suggests that the eigenvector matrix of W
n
is close to being Haar distributed. 相似文献
16.
Ricardo Gallego Torrome 《General Relativity and Gravitation》2007,39(11):1833-1845
Caianiello’s derivation of Quantum Geometry through an isometric embedding of the spacetime (M, g̃) in the pseudo-Riemannian structure (T*M, g*
AB
) is reconsidered. In the new derivation, using a non-linear connection and the bundle formalism, we obtain a Lorentzian-type
structure in the 4-dimensional manifold M that is covariant under arbitrary local coordinate transformations in M. We obtain that if models with maximal acceleration are non-trivial, gravity should be supplied with other interactions in
a unification framework. 相似文献
17.
Abstract New mechanism of reduction of the scattering rate by charged impurities is investigated under hydrostatic pressure by means of classical and quantum transport. Also the critical pressures for the stuctural phase transitions in HgFeSe are determined. 相似文献
18.
Jan Paseka 《International Journal of Theoretical Physics》2008,47(1):291-296
Following B. Banaschewski’s work on so-called K-flat projective frames, we treat their non-commutative generalization, i.e. K-flat projective quantales. Besides a categorical definition of a K-flat projective quantale we also give an elementary characterization in terms of a binary relation on the quantale, and we
prove that K-flat projective quantales are precisely the coalgebras for a certain comonad on the category of quantales. Finally we define
and study a natural notion of K-coherentness for quantales.
Financial Support of the Ministry of Education of the Czech Republic under the project MSM0021622409 is gratefully acknowledged. 相似文献
19.
Abstract We report here an electrical resistivity study on La1+xCu3Oy system under high pressure up to 80 kbar. The three different oxides, %ained from the main system by varying the values of x, are prepared by solid state reactions. Bridgman opposed anvil device is used. The normalised resistivity as a function of pressure for the oxides yields interesting results. 相似文献
20.
A protocol for the synthesis of N-substituted 2-hydro-4-amino-pyrido[2,3-d]pyrimidin-7(8H)-ones (11) is described. Thus, the formylation of a 2-aminopyridone 12 in 85% formic acid/Ac2O, proceeding via in situ cyclization to the intermediate formamide 13, affords the corresponding 2-hydro-4-oxo-pyridopyrimidine 14, which is converted to a 4-chloro-pyridopyrimidine 15 upon treatment with POCl3. The subsequent transformation to the title compounds is carried by treatment with the corresponding amine in MeOH under
microwave irradiation conditions. 相似文献