35,402 research outputs found
Evolutionary multi-objective workflow scheduling in Cloud
Cloud computing provides promising platforms for executing large applications with enormous computational resources to offer on demand. In a Cloud model, users are charged based on their usage of resources and the required quality of service (QoS) specifications. Although there are many existing workflow scheduling algorithms in traditional distributed or heterogeneous computing environments, they have difficulties in being directly applied to the Cloud environments since Cloud differs from traditional heterogeneous environments by its service-based resource managing method and pay-per-use pricing strategies. In this paper, we highlight such difficulties, and model the workflow scheduling problem which optimizes both makespan and cost as a Multi-objective Optimization Problem (MOP) for the Cloud environments. We propose an evolutionary multi-objective optimization (EMO)-based algorithm to solve this workflow scheduling problem on an infrastructure as a service (IaaS) platform. Novel schemes for problem-specific encoding and population initialization, fitness evaluation and genetic operators are proposed in this algorithm. Extensive experiments on real world workflows and randomly generated workflows show that the schedules produced by our evolutionary algorithm present more stability on most of the workflows with the instance-based IaaS computing and pricing models. The results also show that our algorithm can achieve significantly better solutions than existing state-of-the-art QoS optimization scheduling algorithms in most cases. The conducted experiments are based on the on-demand instance types of Amazon EC2; however, the proposed algorithm are easy to be extended to the resources and pricing models of other IaaS services.This work is supported by the National Science Foundation of China under Grand no. 61272420 and the Provincial Science Foundation of Jiangsu Grand no. BK2011022
Double Resonance Nanolaser based on Coupled Slit-hole Resonator Structures
This work investigates a kind of metallic magnetic cavity based on slit-hole
resonators (SHRs). Two orthogonal hybrid magnetic resonance modes of the cavity
with a large spatial overlap are predesigned at the wavelengths of 980 nm and
1550 nm. The Yb-Er co-doped material serving as a gain medium is set in the
cavity; this enables the resonator to have high optical activity. The numerical
result shows that the strong lasing at 1550 nm may be achieved when the cavity
array is pumped at 980 nm. This double resonance nanolaser array has potential
applications in future optical devices and quantum information techniques.Comment: 11 pages, 3 figures, http://www.dsl.nju.edu/mp
High-sensing properties of magnetic plasmon resonances in double- and triple-rod structures
We numerically investigated the magnetic plasmon resonances in double-rod and
triple-rod structures (DRSs and TRSs, respectively) for sensing applications.
According to the equivalent circuit model, one magnetic plasmon mode was
induced in the DRS. Due to the hybridization effect, two magnetic plasmon modes
were obtained in the TRS. Compared with the electric plasmon resonance in a
single-rod structure (SRS), the electromagnetic fields near the DRS and TRS
were much more localized in the dielectric surrounding the structures at the
resonance wavelengths. This caused the magnetic plasmon resonance wavelengths
to become very sensitive to refractive index changes in the environment medium.
As a result, a large figure of merit that is much larger than the electric
plasmon modes of SRS could be obtained in the magnetic plasmon modes of DRS and
TRS. These magnetic plasmon mode properties enable the use of DRSs and TRSs as
sensing elements with remarkable performance
Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers
We have experimentally studied the pump-probe Kerr rotation dynamics in
WSe monolayers. This yields a direct measurement of the exciton valley
depolarization time . At T=4K, we find ps, a fast
relaxation time resulting from the strong electron-hole Coulomb exchange
interaction in bright excitons. The exciton valley depolarization time
decreases significantly when the lattice temperature increases with
being as short as 1.5ps at 125K. The temperature dependence is well explained
by the developed theory taking into account the exchange interaction and a fast
exciton scattering time on short-range potentials.Comment: 5 pages, 3 figure
The dispersive contribution of decays and X(1576)
We study whether the broad enhancement X(1576) arises from the final state
interaction (FSI) of decays. We
consider both the absorptive and dispersive contribution of the above
amplitudes since the intermediate states are very close to .
The same mechanism leads to a similar enhancement around 1580 MeV in the
spectrum in the channel, which
can be used to test whether X(1576) can be ascribed to the FSI effect of
.Comment: 4 pages, 4 figure
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