10,534 research outputs found
The determination of measures of software reliability
Measurement of software reliability was carried out during the development of data base software for a multi-sensor tracking system. The failure ratio and failure rate were found to be consistent measures. Trend lines could be established from these measurements that provide good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the individual run submission rather than with the code proper. Possible application of these findings for line management, project managers, functional management, and regulatory agencies is discussed. Steps for simplifying the measurement process and for use of these data in predicting operational software reliability are outlined
Inconsistencies in the MIT bag model of hadrons
It is shown that what is commonly referred to as the MIT `bag' model of
hadrons is thermodynamically wrong: The adiabatic conditions between pressure
and temperature, and between pressure and volume imply the third, an adiabatic
relation between temperature and volume. Consequently, the bag model is
destitute of any predictive power since it reduces to a single adiabatic state.
The virial theorems proposed by the MIT group are shown to be the result of the
normal power density of states of a non-degenerate gas and not the exponential
density of states of the Hagedorn mass spectrum. A number of other elementary
misconceptions and inaccuracies are also pointed out.Comment: 9 page
Effective Medium Theory of Filamentous Triangular Lattice
We present an effective medium theory that includes bending as well as
stretching forces, and we use it to calculate mechanical response of a diluted
filamentous triangular lattice. In this lattice, bonds are central-force
springs, and there are bending forces between neighboring bonds on the same
filament. We investigate the diluted lattice in which each bond is present with
a probability . We find a rigidity threshold which has the same value
for all positive bending rigidity and a crossover characterizing bending-,
stretching-, and bend-stretch coupled elastic regimes controlled by the
central-force rigidity percolation point at of the
lattice when fiber bending rigidity vanishes.Comment: 15 pages, 9 figure
Generalized Jarzynski Equality under Nonequilibrium Feedback Control
The Jarzynski equality is generalized to situations in which nonequilibrium
systems are subject to a feedback control. The new terms that arise as a
consequence of the feedback describe the mutual information content obtained by
measurement and the efficacy of the feedback control. Our results lead to a
generalized fluctuation-dissipation theorem that reflects the readout
information, and can be experimentally tested using small thermodynamic
systems. We illustrate our general results by an introducing "information
ratchet," which can transport a Brownian particle in one direction and extract
a positive work from the particle
Exactly solvable models of adaptive networks
A satisfiability (SAT-UNSAT) transition takes place for many optimization
problems when the number of constraints, graphically represented by links
between variables nodes, is brought above some threshold. If the network of
constraints is allowed to adapt by redistributing its links, the SAT-UNSAT
transition may be delayed and preceded by an intermediate phase where the
structure self-organizes to satisfy the constraints. We present an analytic
approach, based on the recently introduced cavity method for large deviations,
which exactly describes the two phase transitions delimiting this adaptive
intermediate phase. We give explicit results for random bond models subject to
the connectivity or rigidity percolation transitions, and compare them with
numerical simulations.Comment: 4 pages, 4 figure
Modeling Maxwell's demon with a microcanonical Szilard engine
Following recent work by Marathe and Parrondo [PRL, 104, 245704 (2010)], we
construct a classical Hamiltonian system whose energy is reduced during the
adiabatic cycling of external parameters, when initial conditions are sampled
microcanonically. Combining our system with a device that measures its energy,
we propose a cyclic procedure during which energy is extracted from a heat bath
and converted to work, in apparent violation of the second law of
thermodynamics. This paradox is resolved by deriving an explicit relationship
between the average work delivered during one cycle of operation, and the
average information gained when measuring the system's energy
On the dependence of the avalanche angle on the granular layer thickness
A layer of sand of thickness h flows down a rough surface if the inclination
is larger than some threshold value theta which decreases with h. A tentative
microscopic model for the dependence of theta with h is proposed for rigid
frictional grains, based on the following hypothesis: (i) a horizontal layer of
sand has some coordination z larger than a critical value z_c where mechanical
stability is lost (ii) as the tilt angle is increased, the configurations
visited present a growing proportion $_s of sliding contacts. Instability with
respect to flow occurs when z-z_s=z_c. This criterion leads to a prediction for
theta(h) in good agreement with empirical observations.Comment: 6 pages, 2 figure
Energy Requirement of Control: Comments on Szilard's Engine and Maxwell's Demon
In mathematical physical analyses of Szilard's engine and Maxwell's demon, a
general assumption (explicit or implicit) is that one can neglect the energy
needed for relocating the piston in Szilard's engine and for driving the trap
door in Maxwell's demon. If this basic assumption is wrong, then the
conclusions of a vast literature on the implications of the Second Law of
Thermodynamics and of Landauer's erasure theorem are incorrect too. Our
analyses of the fundamental information physical aspects of various type of
control within Szilard's engine and Maxwell's demon indicate that the entropy
production due to the necessary generation of information yield much greater
energy dissipation than the energy Szilard's engine is able to produce even if
all sources of dissipation in the rest of these demons (due to measurement,
decision, memory, etc) are neglected.Comment: New, simpler and more fundamental approach utilizing the physical
meaning of control-information and the related entropy production. Criticism
of recent experiments adde
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