271,829 research outputs found
The Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses
We introduce a new class of nondiffracting optical pulses possessing orbital
angular momentum. By generalizing the X-waves solution of the Maxwell equation,
we discover the coupling between angular momentum and the temporal degrees of
freedom of ultra-short pulses. The spatial twist of propagation invariant light
pulse turns out to be directly related to the number of optical cycles. Our
results may trigger the development on novel multi-level classical and quantum
transmission channels free of dispersion and diffraction, may also find
application in the manipulation of nano-structured objects by ultra-short
pulses, and for novel approaches to the spatio-temporal measurements in
ultrafast photonics
An Intelligent QoS Identification for Untrustworthy Web Services Via Two-phase Neural Networks
QoS identification for untrustworthy Web services is critical in QoS
management in the service computing since the performance of untrustworthy Web
services may result in QoS downgrade. The key issue is to intelligently learn
the characteristics of trustworthy Web services from different QoS levels, then
to identify the untrustworthy ones according to the characteristics of QoS
metrics. As one of the intelligent identification approaches, deep neural
network has emerged as a powerful technique in recent years. In this paper, we
propose a novel two-phase neural network model to identify the untrustworthy
Web services. In the first phase, Web services are collected from the published
QoS dataset. Then, we design a feedforward neural network model to build the
classifier for Web services with different QoS levels. In the second phase, we
employ a probabilistic neural network (PNN) model to identify the untrustworthy
Web services from each classification. The experimental results show the
proposed approach has 90.5% identification ratio far higher than other
competing approaches.Comment: 8 pages, 5 figure
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