3,482 research outputs found
Hybrid redundancy system for improving reliability - A concept
System combines two concepts - triple modular redundancy (TMR) and spares (replacement system) redundancy. System has triplicated active unit core with associated bank of specifically arranged standby spare units. Curves plotted from characteristic equation show hybrid system is more reliable than conventional TMR systems
Reliability modeling and analysis of a dynamic TMR system using standby spares
Reliability modeling and analysis of dynamic TMR using standby spare
Reliability estimation procedures and CARE: The Computer-Aided Reliability Estimation Program
Ultrareliable fault-tolerant onboard digital systems for spacecraft intended for long mission life exploration of the outer planets are under development. The design of systems involving self-repair and fault-tolerance leads to the companion problem of quantifying and evaluating the survival probability of the system for the mission under consideration and the constraints imposed upon the system. Methods have been developed to (1) model self-repair and fault-tolerant organizations; (2) compute survival probability, mean life, and many other reliability predictive functions with respect to various systems and mission parameters; (3) perform sensitivity analysis of the system with respect to mission parameters; and (4) quantitatively compare competitive fault-tolerant systems. Various measures of comparison are offered. To automate the procedures of reliability mathematical modeling and evaluation, the CARE (computer-aided reliability estimation) program was developed. CARE is an interactive program residing on the UNIVAC 1108 system, which makes the above calculations and facilitates report preparation by providing output in tabular form, graphical 2-dimensional plots, and 3-dimensional projections. The reliability estimation of fault-tolerant organization by means of the CARE program is described
A survey of an introduction to fault diagnosis algorithms
This report surveys the field of diagnosis and introduces some of the key algorithms and heuristics currently in use. Fault diagnosis is an important and a rapidly growing discipline. This is important in the design of self-repairable computers because the present diagnosis resolution of its fault-tolerant computer is limited to a functional unit or processor. Better resolution is necessary before failed units can become partially reuseable. The approach that holds the greatest promise is that of resident microdiagnostics; however, that presupposes a microprogrammable architecture for the computer being self-diagnosed. The presentation is tutorial and contains examples. An extensive bibliography of some 220 entries is included
Black Ring Deconstruction
We present a sample microstate for a black ring in four and five dimensional
language. The microstate consists of a black string microstate with an
additional D6-brane. We show that with an appropriate choice of parameters the
piece involving the black string microstate falls down a long AdS throat, whose
M-theory lift is AdS_3 X S^2. We wrap a spinning dipole M2-brane on the S^2 in
the probe approximation. In IIA, this corresponds to a dielectric D2-brane
carrying only D0-charge. We conjecture this is the first approximation to a
cloud of D0-branes blowing up due to their non-abelian degrees of freedom and
the Myers effect.Comment: 10 pages, 2 figure
Superconductivity on the threshold of magnetism in CePd2Si2 and CeIn3
The magnetic ordering temperature of some rare earth based heavy fermion
compounds is strongly pressure-dependent and can be completely suppressed at a
critical pressure, p, making way for novel correlated electron states close
to this quantum critical point. We have studied the clean heavy fermion
antiferromagnets CePdSi and CeIn in a series of resistivity
measurements at high pressures up to 3.2 GPa and down to temperatures in the mK
region. In both materials, superconductivity appears in a small window of a few
tenths of a GPa on either side of p. We present detailed measurements of
the superconducting and magnetic temperature-pressure phase diagram, which
indicate that superconductivity in these materials is enhanced, rather than
suppressed, by the closeness to magnetic order.Comment: 11 pages, including 9 figure
Temperature dependent orbital degree of freedom in a bilayer manganite by magnetic Compton scattering
We have measured temperature-dependent magnetic Compton profiles (MCPs) from
a single crystal of LaSrMnO. The MCPs, which involved
the scattering of circularly polarized x-rays, are in general related to the
momentum density of all the unpaired spins in the system. Nevertheless, we show
that when the x-ray scattering vector lies along the [110] direction, the
number of magnetic electrons of a specific symmetry, i.e. -electrons of
symmetry, yield a distinct signature in the MCP, allowing us to
monitor substantial changes in the occupancy of the states over
the investigated temperature range of 5-200K. This study indicates that
magnetic Compton scattering can provide a powerful window on the properties of
specific magnetic electrons in complex materials.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let
Modular differential equations for characters of RCFT
We discuss methods, based on the theory of vector-valued modular forms, to
determine all modular differential equations satisfied by the conformal
characters of RCFT; these modular equations are related to the null vector
relations of the operator algebra. Besides describing effective algorithmic
procedures, we illustrate our methods on an explicit example.Comment: 13 page
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