13,974 research outputs found
MobiPADS: a reflective middleware for context-aware mobile computing
distributed computing services that essentially abstract the underlying network services to a monolithic “black box. ” In a mobile operating environment, the fundamental assumption of middleware abstracting a unified distributed service for all types of applications operating over a static network infrastructure is no longer valid. In particular, mobile applications are not able to leverage the benefits of adaptive computing to optimize its computation based on current contextual situations. In this paper, we introduce the Mobile Platform for Actively Deployable Service (MobiPADS) system. MobiPADS is designed to support context-aware processing by providing an executing platform to enable active service deployment and reconfiguration of the service composition in response to environments of varying contexts. Unlike most mobile middleware, MobiPADS supports dynamic adaptation at both the middleware and application layers to provide flexible configuration of resources to optimize the operations of mobile applications. Within the MobiPADS system, services (known as mobilets) are configured as chained service objects to provide augmented services to the underlying mobile applications so as to alleviate the adverse conditions of a wireless environment. Index Terms—Middleware, mobile applications, mobile computing support services, mobile environments.
Spinodal nanodecomposition in magnetically doped semiconductors
This review presents the recent progress in computational materials design,
experimental realization, and control methods of spinodal nanodecomposition
under three- and two-dimensional crystal-growth conditions in spintronic
materials, such as magnetically doped semiconductors. The computational
description of nanodecomposition, performed by combining first-principles
calculations with kinetic Monte Carlo simulations, is discussed together with
extensive electron microscopy, synchrotron radiation, scanning probe, and ion
beam methods that have been employed to visualize binodal and spinodal
nanodecomposition (chemical phase separation) as well as nanoprecipitation
(crystallographic phase separation) in a range of semiconductor compounds with
a concentration of transition metal (TM) impurities beyond the solubility
limit. The role of growth conditions, co-doping by shallow impurities, kinetic
barriers, and surface reactions in controlling the aggregation of magnetic
cations is highlighted. According to theoretical simulations and experimental
results the TM-rich regions appear either in the form of nanodots (the {\em
dairiseki} phase) or nanocolumns (the {\em konbu} phase) buried in the host
semiconductor. Particular attention is paid to Mn-doped group III arsenides and
antimonides, TM-doped group III nitrides, Mn- and Fe-doped Ge, and Cr-doped
group II chalcogenides, in which ferromagnetic features persisting up to above
room temperature correlate with the presence of nanodecomposition and account
for the application-relevant magneto-optical and magnetotransport properties of
these compounds. Finally, it is pointed out that spinodal nanodecomposition can
be viewed as a new class of bottom-up approach to nanofabrication.Comment: 72 pages, 79 figure
Kaluza-Klein towers for real vector fields in flat space
We consider a free real vector field propagating in a five dimensional flat
space with its fifth dimension compactified either on a strip or on a circle
and perform a Kalaza Klein reduction which breaks SO(4,1) invariance while
reserving SO(3,1) invariance. Taking into account the Lorenz gauge condition,
we obtain from the most general hermiticity conditions for the relevant
operators all the allowed boundary conditions which have to be imposed on the
fields in the extra-dimension. The physical Kaluza-Klein mass towers, which
result in a four-dimensional brane, are determined in the different distinct
allowed cases. They depend on the bulk mass, on the parameters of the boundary
conditions and on the extra parameter present in the Lagrangian. In general,
they involve vector states together with accompanying scalar states.Comment: 28 pages, 4 independent table
Formation of an Icosahedral Structure during the Freezing of Gold Nanoclusters: Surface-Induced Mechanism
The freezing behavior of gold nanoclusters was studied by employing molecular
dynamics simulations based on a semi-empirical embedded-atom method.
Investigations of the gold nanoclusters revealed that, just after freezing,
ordered nano-surfaces with a fivefold symmetry were formed with interior atoms
remaining in the disordered state. Further lowering of temperatures induced
nano-crystallization of the interior atoms that proceeded from the surface
towards the core region, finally leading to an icosahedral structure. These
dynamic processes explain why the icosahedral cluster structure is dominantly
formed in spite of its energetic metastability.Comment: 9 pages, 4 figures(including 14 eps-files
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