116,447 research outputs found
Interface refactoring in performance-constrained web services
This paper presents the development of REF-WS an approach to enable a Web Service provider to reliably evolve their service through the application of refactoring transformations. REF-WS is intended to aid service providers, particularly in a reliability and performance constrained domain as it permits upgraded ’non-backwards compatible’ services to be deployed into a performance constrained network where existing consumers depend on an older version of the service interface. In order for this to be successful, the refactoring and message mediation needs to occur without affecting functional compatibility with the services’ consumers, and must operate within the performance overhead expected of the original service, introducing as little latency as possible. Furthermore, compared to a manually programmed solution, the presented approach enables the service developer to apply and parameterize refactorings with a level of confidence that they will not produce an invalid or ’corrupt’ transformation of messages. This is achieved through the use of preconditions for the defined refactorings
Size dependence of second-order hyperpolarizability of finite periodic chain under Su-Schrieffer-Heeger model
The second hyperpolarizability of
double-bond finite chain of trans-polyactylene is analyzed using the
Su-Schrieffer-Heeger model to explain qualitative features of the
size-dependence behavior of . Our study shows that is
{\it nonmonotonic} with and that the nonmonotonicity is caused by the
dominant contribution of the intraband transition to in polyenes.
Several important physical effects are discussed to reduce quantitative
discrepancies between experimental and our resultsComment: 3 figures, 1 tabl
Decomposition of Triebel-Lizorkin and Besov spaces in the context of Laguerre expansions
A pair of dual frames with almost exponentially localized elements (needlets)
are constructed on \RR_+^d based on Laguerre functions. It is shown that the
Triebel-Lizorkin and Besov spaces induced by Laguerre expansions can be
characterized in terms of respective sequence spaces that involve the needlet
coefficients.Comment: 42 page
An efficient hybrid model and dynamic performance analysis for multihop wireless networks
Multihop wireless networks can be subjected to nonstationary phenomena due to a dynamic network topology and time varying traffic. However, the simulation techniques used to study multihop wireless networks focus on the steady-state performance even though transient or nonstationary periods will often occur. Moreover, the majority of the simulators suffer from poor scalability. In this paper, we develop an efficient performance modeling technique for analyzing the time varying queueing behavior of multihop wireless networks. The one-hop packet transmission (service) time is assumed to be deterministic, which could be achieved by contention-free transmission, or approximated in sparse or lightly loaded multihop wireless networks. Our model is a hybrid of time varying adjacency matrix and fluid flow based differential equations, which represent dynamic topology changes and nonstationary network queues, respectively. Numerical experiments show that the hybrid fluid based model can provide reasonably accurate results much more efficiently than standard simulators. Also an example application of the modeling technique is given showing the nonstationary network performance as a function of node mobility, traffic load and wireless link quality. © 2013 IEEE
Spin-3/2 physics of semiconductor hole nanowires: Valence-band mixing and tunable interplay between bulk-material and orbital bound-state spin splittings
We present a detailed theoretical study of the electronic spectrum and Zeeman
splitting in hole quantum wires. The spin-3/2 character of the topmost
bulk-valence-band states results in a strong variation of subband-edge g
factors between different subbands. We elucidate the interplay between quantum
confinement and heavy-hole - light-hole mixing and identify a certain
robustness displayed by low-lying hole-wire subband edges with respect to
changes in the shape or strength of the wire potential. The ability to address
individual subband edges in, e.g., transport or optical experiments enables the
study of holes states with nonstandard spin polarization, which do not exist in
spin-1/2 systems. Changing the aspect ratio of hole wires with rectangular
cross-section turns out to strongly affect the g factor of subband edges,
providing an opportunity for versatile in-situ tuning of hole-spin properties
with possible application in spintronics. The relative importance of cubic
crystal symmetry is discussed, as well as the spin splitting away from
zone-center subband edges.Comment: 16 pages, 12 figures, RevTe
Carrier Dynamics in Submonolayer InGaAs/GaAs Quantum Dots
Carrier dynamics of submonolayer (SML) InGaAs/GaAs quantum dots (QDs) were
studied by micro-photoluminecence (MPL), selectively excited photoluminescence
(SEPL), and time-resolved photoluminescence (TRPL). MPL and SEPL show the
coexistence of localized and delocalized states, and different local phonon
modes. TRPL reveal shorter recombination lifetimes and longer capture times for
the QDs with higher emission energy. This suggests that the smallest SML QDs
are formed by perfectly vertically correlated 2D InAs islands, having the
highest In content and the lowest emission energy, while a slight deviation
from the perfectly vertical correlation produces larger QDs with lower In
content and higher emission energy.Comment: 12 pages, 5 figure
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