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131.
J. Agostinho Moreira A. Almeida M.R. Chaves J.M. Machado da Silva S.M.F. Vilela 《Solid State Communications》2011,151(5):368-371
This work reports an experimental investigation of the ferroelectric character of magnetic phases of the orthorhombic Eu1−xY xMnO3 system at low temperatures. The temperature dependence of the polarization curves clearly reveals the existence of a re-entrant improper ferroelectric phase for x=0.2, 0.3 and 0.5. A ferroelectric phase is also stable for x=0.4, and we have no experimental evidence for its vanishing down to 7 K. From these and early results obtained using other experimental techniques, the corresponding (x,T) phase diagram was traced, yielding significant differences with regard to the ones previously reported. 相似文献
132.
L. de Arcangelis H. J. Herrmann M. Kolb René Thomas C. Amitrano L. Peliti M. Saber G. Weisbuch Sara A. Solla F. Bagnoli A. Francescato R. Livi S. Ruffo Pablo Tamayo Michel Droz Peter Jörg Plath S. Romano Yves Pomeau Stéphane Zaleski D. Stauffer Luciano R. da Silva Alex Hansen Stéphane Roux Antonio Coniglio B. Derrida Henrik Flyvbjerg Naeem Jan Dietrich Stauffer Peter Grassberger A. Zippelius K. E. Kurten Werner Krauth Jean -Pierre Nadal Marc Mézard Per Bak Chao Tang Itzhak Webman M. L. Martins H. F. V. Resende C. Tsallis A. C. N. Magalhaes 《Journal of statistical physics》1989,55(5-6):1333-1359
133.
A. F. G. Monte M. A. G. Soler S. W. da Silva B. B. D. Rodrigues P. C. Morais A. A. Quivy J. R. Leite 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):466
We have investigated the influence of vicinal GaAs substrates on the optical and electronic properties of InGaAs/GaAs quantum wells (QWs). A single In0.10Ga0.90As QW was grown by molecular-beam epitaxy on a vicinal GaAs(0 0 1) substrate with a miscut angle of 0° (nominal), 2°, 4° and 6° towards [1 1 0]. The carrier diffusion was obtained by a micro-photoluminescence scan technique that permits to observe the effective diffusion length characterized by the lateral spread of carriers in the QW followed by radiative recombination. The carrier diffusion length was obtained parallel (L||) and perpendicular (L) to the atomic steps. The diffusion length decreases as the temperature increases up to 100 K. Above this temperature we found different behaviours that depend on the sample miscut angle. 相似文献
134.
Poisson Voronoi diagrams are useful for modeling and describing various natural patterns and for generating random lattices. Although this particular space tessellation is intensively studied by mathematicians, in two- and three-dimensional (3D) spaces there is no exact result known for the size distribution of Voronoi cells. Motivated by the simple form of the distribution function in the 1D case, a simple and compact analytical formula is proposed for approximating the Voronoi cell's size-distribution function in the practically important 2D and 3D cases as well. Denoting the dimensionality of the space by d (d=1,2,3) the compact form is suggested for the normalized cell-size distribution function. By using large-scale computer simulations the viability of the proposed distribution function is studied and critically discussed. 相似文献
135.
This paper introduces a relative structural complexity measure for the characterization of disordered surfaces. Numerical solutions of 2d+1 KPZ equation and scanning force microscopy (SFM) patterns of porous silicon samples are analyzed using this methodology. The results and phenomenological interpretation indicate that the proposed measure is efficient for quantitatively characterize the structural complexity of disordered surfaces (and interfaces) observed and/or simulated in nano, micro and ordinary scales. 相似文献
136.
Lie symmetries and solitons in nonlinear systems with spatially inhomogeneous nonlinearities 总被引:1,自引:0,他引:1
Belmonte-Beitia J Pérez-García VM Vekslerchik V Torres PJ 《Physical review letters》2007,98(6):064102
Using Lie group theory and canonical transformations, we construct explicit solutions of nonlinear Schr?dinger equations with spatially inhomogeneous nonlinearities. We present the general theory, use it to show that localized nonlinearities can support bound states with an arbitrary number solitons, and discuss other applications of interest to the field of nonlinear matter waves. 相似文献
137.
傅里叶变换近红外光谱信息资源共享的基础研究 总被引:1,自引:0,他引:1
为了实现农产品傅里叶变换近红外光谱库信息资源的共享 ,使光谱库的信息资源达到充分利用 ,首先研究了仪器间光谱信息的准确表达 ,即仪器到仪器光谱信息间的映射 ;并以映射光谱研究了用于不同仪器上进行定量分析的无标样建模方法。对于 2 2个小麦样品蛋白质含量 ,无标样建模模型预测值与凯氏定氮结果的相关系数r =0 94 1,平均相对误差为 3 2 8% ;为了考察无标样建模模型定量分析的使用性 ,同时亦对 2 2个小麦样品的蛋白质含量采用有标样建模定量分析 ,模型预测值与凯氏定氮结果的相关系数r =0 96 3,平均相对误差为 2 4 %。有标样建模与无标样建模的模型分析结果的比较 ,为不同仪器间光谱信息的可共享性提供了依据。由此根据不同仪器建立的光谱信息库的库信息即可转化为另一仪器的映射光谱信息 ,保证了光谱库信息资源在不同仪器上的共享利用 相似文献
138.
D. Bazeia O. J. P. Éboli G. C. Marques A. J. da Silva 《Zeitschrift fur Physik C Particles and Fields》1990,46(3):457-463
We compute, within the one loop approximation, the temperature dependent surface tension for a model involving a scalar field coupled to a fermionic field. The fermionic and bosonic contributions have been computed in this approximation by evaluating explicitly the determinants in the presence of a domain wall. 相似文献
139.
Spontaneous-search method and short-time dynamics: applications to the
Domany-Kinzel cellular automaton 总被引:1,自引:0,他引:1
S. D. da Cunha U. L. Fulco L. R. da Silva F. D. Nobre 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):93-100
The one-dimensional Domany-Kinzel cellular automaton is investigated by two
numerical approaches: (i) the spontaneous-search method, which is a method
appropriated for a search of criticality; (ii) short-time dynamics. Both
critical frontiers of the system are investigated, namely, the one
separating the frozen and active phases, as well as the critical line
determined by damage spreading between two cellular automata, that splits
the active phase into the nonchaotic and chaotic phases.
The efficiency of the spontaneous-search method is established herein
through a precise estimate of both critical frontiers, and in addition to
that, it is shown that this method may also be used in the determination
of the critical exponent ν⊥. Using the critical frontiers
obtained, other exponents are estimated through short-time dynamics. It is
verified that the critical exponents of both critical frontiers fall in the
universality class of directed percolation. 相似文献
140.
Fábio Dahia Carlos Romero Lúcio F. P. da Silva Reza Tavakol 《General Relativity and Gravitation》2008,40(6):1341-1351
We study the classical geodesic motions of nonzero rest mass test particles and photons in (3 + 1 + n)- dimensional warped product spaces. An important feature of these spaces is that they allow a natural decoupling between
the motions in the (3 + 1)-dimensional spacetime and those in the extra n dimensions. Using this decoupling and employing phase space analysis we investigate the conditions for confinement of particles
and photons to the (3 + 1)- spacetime submanifold. In addition to providing information regarding the motion of photons, we
also show that these motions are not constrained by the value of the extrinsic curvature. We obtain the general conditions
for the confinement of geodesics in the case of pseudo-Riemannian manifolds as well as establishing the conditions for the
stability of such confinement. These results also generalise a recent result of the authors concerning the embeddings of hypersurfaces
with codimension one. 相似文献