2,798 research outputs found
An experimental evaluation of software redundancy as a strategy for improving reliability
The strategy of using multiple versions of independently developed software as a means to tolerate residual software design faults is suggested by the success of hardware redundancy for tolerating hardware failures. Although, as generally accepted, the independence of hardware failures resulting from physical wearout can lead to substantial increases in reliability for redundant hardware structures, a similar conclusion is not immediate for software. The degree to which design faults are manifested as independent failures determines the effectiveness of redundancy as a method for improving software reliability. Interest in multi-version software centers on whether it provides an adequate measure of increased reliability to warrant its use in critical applications. The effectiveness of multi-version software is studied by comparing estimates of the failure probabilities of these systems with the failure probabilities of single versions. The estimates are obtained under a model of dependent failures and compared with estimates obtained when failures are assumed to be independent. The experimental results are based on twenty versions of an aerospace application developed and certified by sixty programmers from four universities. Descriptions of the application, development and certification processes, and operational evaluation are given together with an analysis of the twenty versions
Effect of kinetic resonances on the stability of Resistive Wall Mode in Reversed Field Pinch
The kinetic effects, due to the mode resonance with thermal particle drift
motions in the reversed field pinch (RFP) plasmas, are numerically investigated
for the stability of the resistive wall mode, using a non-perturbative
MHD-kinetic hybrid formulation. The kinetic effects are generally found too
weak to substantially change the mode growth rate, or the stability margin,
re-enforcing the fact that the ideal MHD model is rather adequate for
describing the RWM physics in RFP experiments.Comment: Submitted to: Plasma Phys. Control. Fusio
The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-Time Observations, First-Light Time, Distance to NGC 4666, and Progenitor Constraints
On 2014 Dec. 9.61, the All-Sky Automated Survey for SuperNovae (ASAS-SN or
"Assassin") discovered ASASSN-14lp just days after first light using a
global array of 14-cm diameter telescopes. ASASSN-14lp went on to become a
bright supernova ( mag), second only to SN 2014J for the year. We
present prediscovery photometry (with a detection less than a day after first
light) and ultraviolet through near-infrared photometric and spectroscopic data
covering the rise and fall of ASASSN-14lp for more than 100 days. We find that
ASASSN-14lp had a broad light curve (), a
-band maximum at , a rise time of days, and moderate host--galaxy extinction (). Using ASASSN-14lp we derive a distance modulus for NGC 4666 of
corresponding to a distance of Mpc.
However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae
still requires an independent distance to the host galaxy. Finally, using our
early-time photometric and spectroscopic observations, we rule out red giant
secondaries and, assuming a favorable viewing angle and explosion time, any
non-degenerate companion larger than .Comment: 12 pages, 9 figures, 4 tables. Accepted to ApJ. Photometric data
presented in this submission are included as an ancillary file. For a brief
video explaining this paper, see https://www.youtube.com/watch?v=1bOV-Cqs-a
Observation of confined current ribbon in JET plasmas
we report the identification of a localised current structure inside the JET
plasma. It is a field aligned closed helical ribbon, carrying current in the
same direction as the background current profile (co-current), rotating
toroidally with the ion velocity (co-rotating). It appears to be located at a
flat spot in the plasma pressure profile, at the top of the pedestal. The
structure appears spontaneously in low density, high rotation plasmas, and can
last up to 1.4 s, a time comparable to a local resistive time. It considerably
delays the appearance of the first ELM.Comment: 10 pages, 6 figure
Who I Am: The Meaning of Early Adolescents’ Most Valued Activities and Relationships, and Implications for Self-Concept Research
Self-concept research in early adolescence typically measures young people’s self-perceptions of competence in specific, adult-defined domains. However, studies have rarely explored young people’s own views of valued self-concept factors and their meanings. For two major self domains, the active and the social self, this mixed-methods study identified factors valued most by 526 young people from socioeconomically diverse backgrounds in Ireland (10-12 years), and explored the meanings associated with these in a stratified subsample (n = 99). Findings indicate that self-concept scales for early adolescence omit active and social self factors and meanings valued by young people, raising questions about content validity of scales in these domains. Findings also suggest scales may under-represent girls’ active and social selves; focus too much on some school-based competencies; and, in omitting intrinsically salient self domains and meanings, may focus more on contingent (extrinsic) rather than true (intrinsic) self-esteem
Homozygous knockout of the piezo1 gene in the zebrafish is not associated with anemia
We have now examined the erythroid phenotype in this zebrafish strain carrying a ZFN genomic knockout of piezo1. Genotyping was performed as previously described. In contrast to the anemic phenotype observed in zebrafish subjected to morpholino knockdown of piezo, the genomic ZFN knockout of piezo1 did not segregate either with anemia in the 3-dpf embryo or with dysmorphic erythrocyte morphology in the adult fish
Thermal phenomenology of hadrons from 200 AGeV S+S collisions
We develop a complete and consistent description for the hadron spectra from
heavy ion collisions in terms of a few collective variables, in particular
temperature, longitudinal and transverse flow. To achieve a meaningful
comparison with presently available data, we also include the resonance decays
into our picture. To disentangle the influences of transverse flow and
resonance decays in the -spectra, we analyse in detail the shape of the
-spectra.Comment: 31 pages, 13 figs in seperate uuencoded file, for LaTeX, epsf.sty and
dvips, TPR-93-16 and BNL-(no number yet
Studies of the dose-effect relation
Dose-effect relations and, specifically, cell survival curves are surveyed with emphasis on the interplay of the random factors — biological variability, stochastic reaction of the cell, and the statistics of energy deposition —that co-determine their shape. The global parameters mean inactivation dose, , and coefficient of variance, V, represent this interplay better than conventional parameters. Mechanisms such as lesion interaction, misrepair, repair overload, or repair depletion have been invoked to explain sigmoid dose dependencies, but these notions are partly synonymous and are largely undistinguishable on the basis of observed dose dependencies. All dose dependencies reflect, to varying degree, the microdosimetric fluctuations of energy deposition, and these have certain implications, e.g. the linearity of the dose dependence at small doses, that apply regardless of unresolved molecular mechanisms of cellular radiation action
- …