1,132 research outputs found
Study of the influence of temperature on the measurement accuracy of transit-time ultrasonic flowmeters
Purpose: The purpose of this study is to deal largely with the influence of temperature variation on the measurement accuracy of transit-time ultrasonic flowmeter. Design/methodology/approach: The causes of measurement error due to temperature are qualitatively and quantitatively analyzed, and a mathematical model is established. The experimental data are processed and analyzed, and the temperature compensation coefficient of flow measurement is obtained. Findings: The experimental results show that the flow measurement results by temperature compensation are helpful in improving the measurement accuracy of the ultrasonic flowmeter. Practical implications: This study has certain application value, which can provide theoretical support for the design of high-precision ultrasonic flowmeters and design guidance. Originality/value: It is worth emphasizing that there are few research studies on the influence factors of temperature. This paper focuses on the influence of the temperature change on the flowmeter that is modeled, and the high precision flow parameter test system is designed based on the established model
An Event Structure Model for Probabilistic Concurrent Kleene Algebra
We give a new true-concurrent model for probabilistic concurrent Kleene
algebra. The model is based on probabilistic event structures, which combines
ideas from Katoen's work on probabilistic concurrency and Varacca's
probabilistic prime event structures. The event structures are compared with a
true-concurrent version of Segala's probabilistic simulation. Finally, the
algebraic properties of the model are summarised to the extent that they can be
used to derive techniques such as probabilistic rely/guarantee inference rules.Comment: Submitted and accepted for LPAR19 (2013
How model sets can be determined by their two-point and three-point correlations
We show that real model sets with real internal spaces are determined, up to
translation and changes of density zero by their two- and three-point
correlations. We also show that there exist pairs of real (even one
dimensional) aperiodic model sets with internal spaces that are products of
real spaces and finite cyclic groups whose two- and three-point correlations
are identical but which are not related by either translation or inversion of
their windows. All these examples are pure point diffractive.
Placed in the context of ergodic uniformly discrete point processes, the
result is that real point processes of model sets based on real internal
windows are determined by their second and third moments.Comment: 19 page
Control of an atom laser using feedback
A generalised method of using feedback to control Bose-Einstein condensates
is introduced. The condensates are modelled by the Gross-Pitaevskii equation,
so only semiclassical fluctations can be suppressed, and back-action from the
measurement is ignored. We show that for any available control, a feedback
scheme can be found to reduce the energy while the appropriate moment is still
dynamic. We demonstrate these schemes by considering a condensate trapped in a
harmonic potential that can be modulated in strength and position. The
formalism of our feedback scheme also allows the inclusion of certain types of
non-linear controls. If the non-linear interaction between the atoms can be
controlled via a Feshbach resonance, we show that the feedback process can
operate with a much higher efficiency.Comment: 6 pages, 7 figure
Existence and Nonlinear Stability of Rotating Star Solutions of the Compressible Euler-Poisson Equations
We prove existence of rotating star solutions which are steady-state
solutions of the compressible isentropic Euler-Poisson (EP) equations in 3
spatial dimensions, with prescribed angular momentum and total mass. This
problem can be formulated as a variational problem of finding a minimizer of an
energy functional in a broader class of functions having less symmetry than
those functions considered in the classical Auchmuty-Beals paper. We prove the
nonlinear dynamical stability of these solutions with perturbations having the
same total mass and symmetry as the rotating star solution. We also prove local
in time stability of W^{1, \infty}(\RR^3) solutions where the perturbations
are entropy-weak solutions of the EP equations. Finally, we give a uniform (in
time) a-priori estimate for entropy-weak solutions of the EP equations
Nonlinear Dynamical Stability of Newtonian Rotating White Dwarfs and Supermassive Stars
We prove general nonlinear stability and existence theorems for rotating star
solutions which are axi-symmetric steady-state solutions of the compressible
isentropic Euler-Poisson equations in 3 spatial dimensions. We apply our
results to rotating and non-rotating white dwarf, and rotating high density
supermassive (extreme relativistic) stars, stars which are in convective
equilibrium and have uniform chemical composition. This paper is a continuation
of our earlier work ([28])
Photospheric Magnetic Field: Relationship Between North-South Asymmetry and Flux Imbalance
Photospheric magnetic fields were studied using the Kitt Peak synoptic maps
for 1976-2003. Only strong magnetic fields (B>100 G) of the equatorial region
were taken into account. The north-south asymmetry of the magnetic fluxes was
considered as well as the imbalance between positive and negative fluxes. The
north-south asymmetry displays a regular alternation of the dominant hemisphere
during the solar cycle: the northern hemisphere dominated in the ascending
phase, the southern one in the descending phase during Solar Cycles 21-23. The
sign of the imbalance did not change during the 11 years from one polar-field
reversal to the next and always coincided with the sign of the Sun's polar
magnetic field in the northern hemisphere. The dominant sign of leading
sunspots in one of the hemispheres determines the sign of the magnetic-flux
imbalance. The sign of the north-south asymmetry of the magnetic fluxes and the
sign of the imbalance of the positive and the negative fluxes are related to
the quarter of the 22-year magnetic cycle where the magnetic configuration of
the Sun remains constant (from the minimum where the sunspot sign changes
according to Hale's law to the magnetic-field reversal and from the reversal to
the minimum). The sign of the north-south asymmetry for the time interval
considered was determined by the phase of the 11-year cycle (before or after
the reversal); the sign of the imbalance of the positive and the negative
fluxes depends on both the phase of the 11-year cycle and on the parity of the
solar cycle. The results obtained demonstrate the connection of the magnetic
fields in active regions with the Sun's polar magnetic field in the northern
hemisphere.Comment: 24 pages, 12 figures, 2 table
Probing bactericidal mechanisms induced by cold atmospheric plasmas with Escherichia coli mutants
Mechanisms of plasma induced microbial inactivation have commonly been studied with physico-chemical techniques. In this letter, Escherichia coli K-12 and its ∆recA, ∆rpoS and ∆soxS mutants are employed to discriminate effects of UV photons, OH radicals, and reactive oxygen species produced in atmospheric discharges. This microbiological approach exploits the fact that these E. coli mutants are defective in their resistance against various external stresses. By interplaying bacterial inactivation kinetics with optical emission spectroscopy, oxygen atoms are identified as a major contributor in plasma inactivation with minor contribution from UV photons, OH radicals, singlet oxygen metastables, and nitric oxide
Inferring Deleterious-Mutation Parameters in Natural Daphnia Populations
Deng and Lynch (1, 2) proposed to characterize deleterious genomic mutations from changes in the mean and genetic variance of fitness traits upon selfing in outcrossing populations. Such observations can be readily acquired in cyclical parthenogens. Selfing and life-table experiments were performed for two such Daphnia populations. A significant inbreeding depression and an increase of genetic variance for all traits analyzed were observed. Deng and Lynch's (2) procedures were employed to estimate the genomic mutation rate (U), mean dominance coefficient ( [Image: see text] ), mean selection coefficient ( [Image: see text] ), and scaled genomic mutational variance ( [Image: see text] ). On average, [Image: see text] , [Image: see text] , [Image: see text] and [Image: see text] (^ indicates an estimate) are 0.84, 0.30, 0.14 and 4.6E-4 respectively. For the true values, the [Image: see text] and [Image: see text] are lower bounds, and [Image: see text] and [Image: see text] upper bounds
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