5,254 research outputs found
Synthesizing Short-Circuiting Validation of Data Structure Invariants
This paper presents incremental verification-validation, a novel approach for
checking rich data structure invariants expressed as separation logic
assertions. Incremental verification-validation combines static verification of
separation properties with efficient, short-circuiting dynamic validation of
arbitrarily rich data constraints. A data structure invariant checker is an
inductive predicate in separation logic with an executable interpretation; a
short-circuiting checker is an invariant checker that stops checking whenever
it detects at run time that an assertion for some sub-structure has been fully
proven statically. At a high level, our approach does two things: it statically
proves the separation properties of data structure invariants using a static
shape analysis in a standard way but then leverages this proof in a novel
manner to synthesize short-circuiting dynamic validation of the data
properties. As a consequence, we enable dynamic validation to make up for
imprecision in sound static analysis while simultaneously leveraging the static
verification to make the remaining dynamic validation efficient. We show
empirically that short-circuiting can yield asymptotic improvements in dynamic
validation, with low overhead over no validation, even in cases where static
verification is incomplete
An Intelligent Auxiliary Vacuum Brake System
The purpose of this paper focuses on designing an intelligent, compact, reliable, and robust auxiliary vacuum brake system (VBS) with Kalman filter and self-diagnosis scheme. All of the circuit elements in the designed system are integrated into one programmable system-on-chip (PSoC) with entire computational algorithms implemented by software. In this system, three main goals are achieved: (a) Kalman filter and hysteresis controller algorithms are employed within PSoC chip by software to surpass the noises and disturbances from hostile surrounding in a vehicle. (b) Self-diagnosis scheme is employed to identify any breakdown element of the auxiliary vacuum brake system. (c) Power MOSFET is utilized to implement PWM pump control and compared with relay control. More accurate vacuum pressure control has been accomplished as well as power energy saving. In the end, a prototype has been built and tested to confirm all of the performances claimed above
Very Old Isolated Compact Objects as Dark Matter Probes
Very old isolated neutron stars and white dwarfs have been suggested to be
probes of dark matter. To play such a role, two requests should be fulfilled,
i.e., the annihilation luminosity of the captured dark matter particles is
above the thermal emission of the cooling compact objects (request-I) and also
dominate over the energy output due to the accretion of normal matter onto the
compact objects (request-II). Request-I calls for very dense dark matter medium
and the critical density sensitively depends on the residual surface
temperature of the very old compact objects. The accretion of
interstellar/intracluster medium onto the compact objects is governed by the
physical properties of the medium and by the magnetization and rotation of the
stars and may outshine the signal of dark matter annihilation. Only in a few
specific scenarios both requests are satisfied and the compact objects are dark
matter burners. The observational challenges are discussed and a possible way
to identify the dark matter burners is outlined.Comment: 9 pages including 1 Figure, to appear in Phys. Rev.
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