3,140 research outputs found
Phase-conjugate reflection by degenerate four-wave mixing in a nematic liquid crystal in the isotropic phase
We report the generation of conjugate wave fronts by degenerate four-wave mixing in the isotropic phase of the nematic substance p-methoxy-benzylidene p-n-butylaniline. The temporal and spatial properties of the conjugate wave fronts are verified. The dependence of the nonlinear reflectivity on the pump-wave power and the temperature of the medium is discussed
Calculation of hyperfine splitting in mesons using configuration interaction approach
The spin - spin mass splitting of light, heavy and mixed mesons are described
within a good accuracy in the potential model with screened potential. We
conclude that the long - distance part of the potential cannot be pure scalar
and that a vector - scalar mixture is favoured. With the same parameters which
gives correct average mass spectrum excellent spin - spin splittings of heavy
quarkonia is obtained. The results are obtained by going beyond usually used
perturbation method, namely using configuration interaction approach.Comment: 8 pages, LaTe
Shortest path discovery of complex networks
In this paper we present an analytic study of sampled networks in the case of
some important shortest-path sampling models. We present analytic formulas for
the probability of edge discovery in the case of an evolving and a static
network model. We also show that the number of discovered edges in a finite
network scales much slower than predicted by earlier mean field models.
Finally, we calculate the degree distribution of sampled networks, and we
demonstrate that they are analogous to a destructed network obtained by
randomly removing edges from the original network.Comment: 10 pages, 4 figure
AlGaAs lasers with micro-cleaved mirrors suitable for monolithic integration
A technique has been developed for cleaving the mirrors of AlGaAs lasers without cleaving the
substrate. Micro-cleaving involves cleaving a suspended heterostructure cantilever by ultrasonic
vibrations. Lasers with microcleaved mirrors have threshold currents and quantum efficiencies
identical to those of similar devices with conventionally cleaved mirrors
Extreme-Point-based Heuristics for the Three-Dimensional Bin Packing problem
One of the main issues in addressing three-dimensional packing problems is finding an efficient and accurate definition of the points at which to place the items inside the bins, because the performance of exact and heuristic solution methods is actually strongly influenced by the choice of a placement rule. We introduce the extreme point concept and present a new extreme point-based rule for packing items inside a three-dimensional container. The extreme point rule is independent from the particular packing problem addressed and can handle additional constraints, such as fixing the position of the items. The new extreme point rule is also used to derive new constructive heuristics for the three-dimensional bin-packing problem. Extensive computational results show the effectiveness of the new heuristics compared to state-of-the-art results. Moreover, the same heuristics, when applied to the two-dimensional bin-packing problem, outperform those specifically designed for the proble
Spin-dependent Scattering by a Potential Barrier on a Nanotube
The electron spin effects on the surface of a nanotube have been considered
through the spin-orbit interaction (SOI), arising from the electron confinement
on the surface of the nanotube. This is of the same nature as the
Rashba-Bychkov SOI at a semiconductor heterojunction. We estimate the effect of
disorder within a potential barrier on the transmission probability. Using a
continuum model, we obtained analytic expressions for the spin-split energy
bands for electrons on the surface of nanotubes in the presence of SOI. First
we calculate analytically the scattering amplitudes from a potential barrier
located around the axis of the nanotube into spin-dependent states. The effect
of disorder on the scattering process is included phenomenologically and
induces a reduction in the transition probability. We analyzed the relative
role of SOI and disorder on the transmission probability which depends on the
angular and linear momentum of the incoming particle, and its spin orientation.
We demonstrated that in the presence of disorder perfect transmission may not
be achieved for finite barrier heights.Comment: 16 pages, 15 figure
Reallocation Problems in Scheduling
In traditional on-line problems, such as scheduling, requests arrive over
time, demanding available resources. As each request arrives, some resources
may have to be irrevocably committed to servicing that request. In many
situations, however, it may be possible or even necessary to reallocate
previously allocated resources in order to satisfy a new request. This
reallocation has a cost. This paper shows how to service the requests while
minimizing the reallocation cost. We focus on the classic problem of scheduling
jobs on a multiprocessor system. Each unit-size job has a time window in which
it can be executed. Jobs are dynamically added and removed from the system. We
provide an algorithm that maintains a valid schedule, as long as a sufficiently
feasible schedule exists. The algorithm reschedules only a total number of
O(min{log^* n, log^* Delta}) jobs for each job that is inserted or deleted from
the system, where n is the number of active jobs and Delta is the size of the
largest window.Comment: 9 oages, 1 table; extended abstract version to appear in SPAA 201
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