7,258 research outputs found
Robust Dynamic Selection of Tested Modules in Software Testing for Maximizing Delivered Reliability
Software testing is aimed to improve the delivered reliability of the users.
Delivered reliability is the reliability of using the software after it is
delivered to the users. Usually the software consists of many modules. Thus,
the delivered reliability is dependent on the operational profile which
specifies how the users will use these modules as well as the defect number
remaining in each module. Therefore, a good testing policy should take the
operational profile into account and dynamically select tested modules
according to the current state of the software during the testing process. This
paper discusses how to dynamically select tested modules in order to maximize
delivered reliability by formulating the selection problem as a dynamic
programming problem. As the testing process is performed only once, risk must
be considered during the testing process, which is described by the tester's
utility function in this paper. Besides, since usually the tester has no
accurate estimate of the operational profile, by employing robust optimization
technique, we analysis the selection problem in the worst case, given the
uncertainty set of operational profile. By numerical examples, we show the
necessity of maximizing delivered reliability directly and using robust
optimization technique when the tester has no clear idea of the operational
profile. Moreover, it is shown that the risk averse behavior of the tester has
a major influence on the delivered reliability.Comment: 19 pages, 4 figure
Switching and Rectification of a Single Light-sensitive Diarylethene Molecule Sandwiched between Graphene Nanoribbons
The 'open' and 'closed' isomers of the diarylethene molecule that can be
converted between each other upon photo-excitation are found to have
drastically different current-voltage characteristics when sandwiched between
two graphene nanoribbons (GNRs). More importantly, when one GNR is metallic and
another one is semiconducting, strong rectification behavior of the 'closed'
diarylethene isomer with the rectification ratio >10^3 is observed. The
surprisingly high rectification ratio originates from the band gap of GNR and
the bias-dependent variation of the lowest unoccupied molecular orbital (LUMO)
of the diarylethene molecule, the combination of which completely shuts off the
current at positive biases. Results presented in this paper may form the basis
for a new class of molecular electronic devices.Comment: The Journal of Chemical Physics 135 (2011
Radiative Leptonic Decays of Meson
To the leading order, the radiative leptonic decays () are studied carefully. In the study, a non-relativistic
constituent quark model and the effective Lagrangian for the heavy flavour
decays are used. As a result, the branching ratios turn out to be of the orders
of for or for . Based on this study, we point out the decays being accessible
experimentally at the future LHC, and the possibility to determine the decay
constant through the radiative decays.Comment: 9 pages Latex, including 2 figure
Dielectric properties and lattice dynamics of alpha-PbO2-type TiO2: The role of soft phonon modes in pressure-induced phase transition to baddeleyite-type TiO2
Dielectric tensor and lattice dynamics of alpha-PbO2-type TiO2 have been
investigated using the density functional perturbation theory, with a focus on
responses of the vibrational frequencies to pressure. The calculated Raman
spectra under different pressures are in good agreement with available
experimental results and the symmetry assignments of the Raman peaks of
alpha-PbO2-type TiO2 are given for the first time. In addition, we identified
two anomalously IR-active soft phonon modes, B1u and B3u, respectively, around
200 cm-1 which have not been observed in high pressure experiments. Comparison
of the phonon dispersions at 0 and 10 GPa reveals that softening of phonon
modes also occurs for the zone-boundary modes. The B1u and B3u modes play an
important role in transformation from the alpha-PbO2-type phase to baddeleyite
phase. The significant relaxations of the oxygen atoms from the Ti4 plane in
the Ti2O2Ti2 complex of the baddeleyite phase are directly correlated to the
oxygen displacements along the directions given by the eigenvectors of the soft
B1u and B3u modes in the alpha-PbO2-type phase.Comment: 8 pages, 9 figure
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