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961.
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964.
M. D. Martín L. Via J. K. Son R. Ruf E. E. Mendez 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We have used time-resolved photoluminescence spectroscopy to study the light emission dynamics in a semiconductor microcavity as a function of excitation density and exciton-cavity detuning. We paid special attention to polariton spin relaxation by using circularly polarized excitation. We have found a striking behavior of the photoluminescence degree of polarization, which reaches its maximum value at a finite time. As the excitation density is increased and the system enters the stimulated emission regime, this maximum is followed by a negative dip, whose depth strongly depends on exciton-cavity detuning. 相似文献
965.
聚乙烯吡咯烷酮中纳米邻苯二甲酸铽络合物的不寻常荧光特性 总被引:3,自引:0,他引:3
本文以聚乙烯吡咯烷酮为基质制得了纳米邻苯二甲酸铽络合物并对其荧光光谱进行了研究 ,结果表明聚乙烯吡咯烷酮中纳米邻苯二甲酸铽络合物主要荧光发射峰的相对强度及峰的半高宽有明显变化 ,并且主峰附近分化出两个峰。 相似文献
966.
This study proposes and construct a primitive quantum arithmetic logic unit (qALU) based on the quantum Fourier transform (QFT). The qALU is capable of performing arithmetic ADD (addition) and logic NAND gate operations. It designs a scalable quantum circuit and presents the circuits for driving ADD and NAND operations on two-input and four-input quantum channels, respectively. By comparing the required number of quantum gates for serial and parallel architectures in executing arithmetic addition, it evaluates the performance. It also execute the proposed quantum Fourier transform-based qALU design on real quantum processor hardware provided by IBM. The results demonstrate that the proposed circuit can perform arithmetic and logic operations with a high success rate. Furthermore, it discusses in detail the potential implementations of the qALU circuit in the field of computer science, highlighting the possibility of constructing a soft-core processor on a quantum processing unit. 相似文献
967.
This is a general and exact study of multiple Hamiltonian walks (HAW) filling the two-dimensional (2D) Manhattan lattice. We generalize the original exact solution for a single HAW by Kasteleyn to a system ofmultiple closed walks, aimed at modeling a polymer melt. In 2D, two basic nonequivalent topological situations are distinguished. (1) the Hamiltonian loops are allrooted andcontractible to a point:adjacent one to another, and, on a torus,homotopic to zero. (2) the loops can encircle one another and, on a torus, canwind around it. Forcase 1, the grand canonical partition function and multiple correlation functions are calculated exactly as those of multiple rooted spanningtrees or of a massive 2Dfree field, critical at zero mass (zero fugacity). The conformally invariant continuum limit on a Manhattantorus is studied in detail. The melt entropy is calculated exactly. We also consider the relevant effect of free boundary conditions. The number of single HAWs on Manhattan lattices with other perimeter shapes (rectangular, Kagomé, triangular, and arbitrary) is studied and related to the spectral theory of the Dirichlet Laplacian. This allows the calculation of exact shape-dependent configuration exponents y. An exact surface critical exponent is obtained. Forcase 2, nested and winding Hamiltonian circuits are allowed. An exact equivalence to thecritical Q-state Potts model exists, whereQ
1/2 is the walk fugacity. The Hamiltonian system is then always critical (forQ<-4). The exact critical exponents, in infinite numbers, are universal and identical to those of theO(n=Q
1/2) model in its low-temperature phase, i.e. are those of dense polymers. The exact critical partition functions on the torus are given from conformai invariance theory. These models 1 and 2 yield the two first exactly solved models of polymer melts. 相似文献
968.
The purpose of this paper is to provide a new, unified and complete study for uniform dichotomy and exponential dichotomy
on the half-line. First we deduce conditions for the existence of uniform dichotomy, using classes of function spaces over
_+{\mathbb {R}_+} which are invariant under translations. After that, we obtain a classification of the main classes of function spaces over
\mathbb R+{\mathbb {R}_+}, in order to deduce necessary and sufficient conditions for the existence of exponential dichotomy, emphasizing on the main
technical qualitative properties of the underlying spaces. We motivate our approach by illustrative examples and show that
the main hypotheses cannot be dropped. We provide optimal methods regarding the input space in the study of dichotomy and
deduce as particular cases some interesting situations as well as several dichotomy results published in the past few years. 相似文献
969.
A multiwave approximate Riemann solver for ideal MHD based on relaxation II: numerical implementation with 3 and 5 waves 总被引:1,自引:0,他引:1
In the first part of this work Bouchut et al. (J Comput Phys 108:7–41, 2007) we introduced an approximate Riemann solver for
one-dimensional ideal MHD derived from a relaxation system. We gave sufficient conditions for the solver to satisfy discrete
entropy inequalities, and to preserve positivity of density and internal energy. In this paper we consider the practical implementation,
and derive explicit wave speed estimates satisfying the stability conditions of Bouchut et al. (J Comput Phys 108:7–41, 2007).
We present a 3-wave solver that well resolves fast waves and material contacts, and a 5-wave solver that accurately resolves
the cases when two eigenvalues coincide. A full 7-wave solver, which is highly accurate on all types of waves, will be described
in a follow-up paper. We test the solvers on one-dimensional shock tube data and smooth shear waves. 相似文献
970.
For k, d?2, a Bethe tree is a rooted tree with k levels which the root vertex has degree d, the vertices from level 2 to k-1 have degree d+1 and the vertices at the level k are pendent vertices. So et al, using a theorem by Ky Fan have obtained both upper and lower bounds for the Laplacian energy of bipartite graphs. We shall employ the above mentioned theorem to obtain new and improved bounds for the Laplacian energy in the case of Bethe trees. 相似文献