23,723 research outputs found
Opaque Service Virtualisation: A Practical Tool for Emulating Endpoint Systems
Large enterprise software systems make many complex interactions with other
services in their environment. Developing and testing for production-like
conditions is therefore a very challenging task. Current approaches include
emulation of dependent services using either explicit modelling or
record-and-replay approaches. Models require deep knowledge of the target
services while record-and-replay is limited in accuracy. Both face
developmental and scaling issues. We present a new technique that improves the
accuracy of record-and-replay approaches, without requiring prior knowledge of
the service protocols. The approach uses Multiple Sequence Alignment to derive
message prototypes from recorded system interactions and a scheme to match
incoming request messages against prototypes to generate response messages. We
use a modified Needleman-Wunsch algorithm for distance calculation during
message matching. Our approach has shown greater than 99% accuracy for four
evaluated enterprise system messaging protocols. The approach has been
successfully integrated into the CA Service Virtualization commercial product
to complement its existing techniques.Comment: In Proceedings of the 38th International Conference on Software
Engineering Companion (pp. 202-211). arXiv admin note: text overlap with
arXiv:1510.0142
The X-ray transient XTE J1118+480: Multiwavelength observations of a low-state mini-outburst
We present multiwavelength observations of the newly discovered X-ray
transient XTE J1118+480 obtained in the rising phase of the 2000 April
outburst. This source is located at unusually high Galactic latitude and in a
very low absorption line of sight. This made the first EUVE spectroscopy of an
X-ray transient outburst possible. Together with our HST, RXTE, and UKIRT data
this gives unprecedented spectral coverage. We find the source in the low hard
state. The flat IR-UV spectrum appears to be a combination of optically thick
disk emission and flat spectrum emission, possibly synchrotron, while at higher
energies, including EUV, a typical low hard state power-law is seen. EUVE
observations reveal no periodic modulation, suggesting an inclination low
enough that no obscuration by the disk rim occurs. We discuss the nature of the
source and this outburst and conclude that it may be more akin to
mini-outbursts seen in GRO J0422+32 than to a normal X-ray transient outburst.Comment: 4 pages, 3 figures, replaced with accepted version. Uses
emulateapj5.st
Characterizing time series : when Granger causality triggers complex networks
In this paper, we propose a new approach to characterize time series with noise perturbations in both the time and frequency domains by combining Granger causality and complex networks. We construct directed and weighted complex networks from time series and use representative network measures to describe their physical and topological properties. Through analyzing the typical dynamical behaviors of some physical models and the MIT-BIH* human electrocardiogram data sets, we show that the proposed approach is able to capture and characterize various dynamics and has much potential for analyzing real-world time series of rather short length
Determination of the Sign of g factors for Conduction Electrons Using Time-resolved Kerr Rotation
The knowledge of electron g factor is essential for spin manipulation in the
field of spintronics and quantum computing. While there exist technical
difficulties in determining the sign of g factor in semiconductors by the
established magneto-optical spectroscopic methods. We develop a time resolved
Kerr rotation technique to precisely measure the sign and the amplitude of
electron g factor in semiconductors
Atom-molecule conversion with particle losses
Based on the mean-field approximation and the phase space analysis, we study
the dynamics of an atom-molecule conversion system subject to particle loss.
Starting from the many-body dynamics described by a master equation, an
effective nonlinear Schr\"odinger equation is introduced. The classical phase
space is then specified and classified by fixed points. The boundary, which
separate different dynamical regimes have been calculated and discussed. The
effect of particle loss on the conversion efficiency and the self-trapping is
explored.Comment: 6 pages, 5 figure
Carrier Sense Random Packet CDMA Protocol in Dual-Channel Networks
Code resource wastage is caused by the reason that many hopping frequency (FH) sequences are unused, which occurs under the condition that the number of the actual subnets needed for the tactical network is far smaller than the networking capacity of code division net¬working. Dual-channel network (DCN), consisting of one single control channel and multiple data channels, can solve the code resource wastage effectively. To improve the anti-jamming capability of the control channel of DCN, code division multiple access (CDMA) technology was introduced, and a carrier sense random packet (CSRP) CDMA protocol based on random packet CDMA (RP-CDMA) was proposed. In CSRP-CDMA, we provide a carrier sensing random packet mechanism and a packet-segment acknowledgement policy. Furthermore, an analytical model was developed to evaluate the performance of CSRP-CDMA networks. In this model, the impacts of multi-access interference from both inter-clusters and intra-clusters were analyzed, and the mathematical expressions of packet transmission success probability, normalized network throughput and signal interference to noise ratio, were also derived. Analytical and simulation results demonstrate that the normalized network throughput of CSRP-CDMA outperforms traditional RP-CDMA by 10%, which can guarantee the resource utilization efficiency of the control channel in DCNs
An automated method for comparing motion artifacts in cine four-dimensional computed tomography images.
The aim of this study is to develop an automated method to objectively compare motion artifacts in two four-dimensional computed tomography (4D CT) image sets, and identify the one that would appear to human observers with fewer or smaller artifacts. Our proposed method is based on the difference of the normalized correlation coefficients between edge slices at couch transitions, which we hypothesize may be a suitable metric to identify motion artifacts. We evaluated our method using ten pairs of 4D CT image sets that showed subtle differences in artifacts between images in a pair, which were identifiable by human observers. One set of 4D CT images was sorted using breathing traces in which our clinically implemented 4D CT sorting software miscalculated the respiratory phase, which expectedly led to artifacts in the images. The other set of images consisted of the same images; however, these were sorted using the same breathing traces but with corrected phases. Next we calculated the normalized correlation coefficients between edge slices at all couch transitions for all respiratory phases in both image sets to evaluate for motion artifacts. For nine image set pairs, our method identified the 4D CT sets sorted using the breathing traces with the corrected respiratory phase to result in images with fewer or smaller artifacts, whereas for one image pair, no difference was noted. Two observers independently assessed the accuracy of our method. Both observers identified 9 image sets that were sorted using the breathing traces with corrected respiratory phase as having fewer or smaller artifacts. In summary, using the 4D CT data of ten pairs of 4D CT image sets, we have demonstrated proof of principle that our method is able to replicate the results of two human observers in identifying the image set with fewer or smaller artifacts
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