Browsing by Author "Tsai, KH"

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Local structural effects on low-frequency vibrational spectrum of liquid water: The instantaneous-normal-mode analysis
(2006-01-10)
Tsai, KH
;
Wu, TM
;
物理研究所
;
Institute of Physics
Currently, the designations for the low-frequency vibrational spectrum of liquid water are still diversified. In this Letter. using the instantaneous normal mode (INM) formalism for subensembles, we have examined the effects of local structure on the low-frequency INM spectrum of liquid water. The classified subensembles of water molecules are characterized by either the geometry of Voronoi polyhedron or the H-bond configuration. With these subensembles, the translational contribution to the INM spectrum is investigated. Providing insights into the local structural dependence of the vibrations between H-bonded water molecules. our results are consistent with the conventional designations for the Raman spectrum of liquid water. (c) 2005 Elsevier B.V. All rights reserved.
Lower bounds for wide-sense nonblocking Clos network
(2001-06-28)
Tsai, KH
;
Wang, DW
;
Hwang, F
;
應用數學系
;
Department of Applied Mathematics
The 3-stage Clos network is generally considered the most basic multistage interconnecting network (MIN). The nonblocking property of such network has been extensively studied in the past. However, there are only a few lower bound results regarding wide-sense nonblocking. We show that in the classical circuit switching environment, to guarantee wide-sense nonblocking for large r, 2n - 1 center switches are necessary, where I is the number of input switches and n is the number of inlets of each input switch. For the multirate environment, we show that for large r, any 3-stage Clos network needs atleast 3n - 2 center switches to guarantee wide-sense nonblocking. Our proof works even for the two-rate environment. (C) 2001 Elsevier Science B.V. All rights reserved.
Mechanism for singular behavior in vibrational spectra of topologically disordered systems: Short-range attractions
(2005-05-22)
Wu, TM
;
Chang, SL
;
Tsai, KH
;
物理研究所
;
Institute of Physics
At low-enough fluid densities, we have found some naive singular behavior, like the van Hove singularities in the phonon spectra of lattices, appearing in the instantaneous normal mode spectra of the Lennard-Jones (LJ) 2n-n fluids, which serve as a prototype of topologically disordered systems. The singular behavior cannot be predicted by the mean-field theory, but interpreted by the perturbed binary modes of some special pairs, called the mutual nearest neighbor pairs, at separations corresponding to the extreme binary frequencies, which are solely determined by the attractive part of the LJ 2n-n pair potential. By reducing the range of attraction in the pair potential under the conditions of the same particle diameter and well depth, the tendency for the appearance of the singular behavior shifts to higher fluid densities. From this study, we conclude that pair potential with a short-range attraction can be a mechanism to produce a counterpart of the van Hove singularity in the vibrational spectra of disordered systems without a reference lattice. 2005 American Institute of Physics.