308 research outputs found
Dynamic characteristics of flow meters for fuel consumption measurement in ships
The dynamic characteristics of various flow meters for fuel
consumption measurement aboard shipswere evaluated. The
flow rate was measured using the Korea Research Institute of
Standards and Science (KRISS) oil flow standard system using
K-oil(density : 0.804 g/cm3, viscosity : 3.679 cSt), which has
similar fluid properties as diesel oil. The flow meters were tested
in a test bed that simulated the vibration conditions in ships. The
vibration conditions were established in accordance to vibration
standard IEC 60068-2-6 as follows: a±0.7g acceleration and 30
Hz frequency. The K-factors (mL/pulse) of various flow meters
(PD meter, turbine flow meter, Coriolis flow meter, and
ultrasonic flow meter) were obtained for various flow rates (60
L/h ~ 300 L/h). The PD meter, Coriolis flow meter, and
ultrasonic flow meter were found to have almost constant Kfactors
according to the flow rates. However, the K-factor of the
turbine flow meter was reduced at a low flow rate owing to
bearing friction in the turbine blade. The flow rate errors of the
PD meter, Coriolis flow meter, and ultrasonic flow meter were
found to be under ±0.5 % with and without vibration. However,
the flow rate error of the turbine flow meter was approximately
-4.3 % at a low flow rate (60 L/h) owing to the friction effect.
The Coriolis flow meter had the lowest flow rate error (< 0.1%)
according to the flow rate. The vibration influenced the flow rate
error of the Coriolis flow meter at high flow rates owing to its
measuring principle. However, the difference in flow rate errors
was a negligible value (0.05 %) with and without vibration.
Therefore, we confirmed that the PD meter, turbine meter,
Coriolis flow meter and ultrasonic flow meter could be used for
measuring flow rates in ships with a ±0.5 % flow rate error.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers
Magnetoresistance of Two-Dimensional Fermions in a Random Magnetic Field
We perform a semiclassical calculation of the magnetoresistance of spinless
two-dimensional fermions in a long-range correlated random magnetic field. In
the regime relevant for the problem of the half filled Landau level the
perturbative Born approximation fails and we develop a new method of solving
the Boltzmann equation beyond the relaxation time approximation. In absence of
interactions, electron density modulations, in-plane fields, and Fermi surface
anisotropy we obtain a quadratic negative magnetoresistance in the weak field
limit.Comment: 12 pages, Latex, no figures, Nordita repor
Quantum corrections to the conductivity of fermion - gauge field models: Application to half filled Landau level and high- superconductors
We calculate the Altshuler-Aronov type quantum correction to the conductivity
of charge carriers in a random potential (or random magnetic field)
coupled to a transverse gauge field. The gauge fields considered simulate the
effect of the Coulomb interaction for the fractional quantum Hall state at half
filling and for the model of high- superconducting compounds. We
find an unusually large quantum correction varying linearly or quadratically
with the logarithm of temperature, in different temperature regimes.Comment: 12 pages REVTEX, 1 figure. The figure is added and minor misprints
are correcte
Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts
It is only now, with low-frequency radio telescopes, long exposures with
high-resolution X-ray satellites and gamma-ray telescopes, that we are
beginning to learn about the physics in the periphery of galaxy clusters. In
the coming years, Sunyaev-Zeldovich telescopes are going to deliver further
great insights into the plasma physics of these special regions in the
Universe. The last years have already shown tremendous progress with detections
of shocks, estimates of magnetic field strengths and constraints on the
particle acceleration efficiency. X-ray observations have revealed shock fronts
in cluster outskirts which have allowed inferences about the microphysical
structure of shocks fronts in such extreme environments. The best indications
for magnetic fields and relativistic particles in cluster outskirts come from
observations of so-called radio relics, which are megaparsec-sized regions of
radio emission from the edges of galaxy clusters. As these are difficult to
detect due to their low surface brightness, only few of these objects are
known. But they have provided unprecedented evidence for the acceleration of
relativistic particles at shock fronts and the existence of muG strength fields
as far out as the virial radius of clusters. In this review we summarise the
observational and theoretical state of our knowledge of magnetic fields,
relativistic particles and shocks in cluster outskirts.Comment: 34 pages, to be published in Space Science Review
Lowest-Landau-level theory of the quantum Hall effect: the Fermi-liquid-like state
A theory for a Fermi-liquid-like state in a system of charged bosons at
filling factor one is developed, working in the lowest Landau level. The
approach is based on a representation of the problem as fermions with a system
of constraints, introduced by Pasquier and Haldane (unpublished). This makes
the system a gauge theory with gauge algebra W_infty. The low-energy theory is
analyzed based on Hartree-Fock and a corresponding conserving approximation.
This is shown to be equivalent to introducing a gauge field, which at long
wavelengths gives an infinite-coupling U(1) gauge theory, without a
Chern-Simons term. The system is compressible, and the Fermi-liquid properties
are similar, but not identical, to those in the previous U(1) Chern-Simons
fermion theory. The fermions in the theory are effectively neutral but carry a
dipole moment. The density-density response, longitudinal conductivity, and the
current density are considered explicitly.Comment: 32 pages, revtex multicol
Apolipoprotein J is a hepatokine regulating muscle glucose metabolism and insulin sensitivity
Crosstalk between liver and skeletal muscle is vital for glucose homeostasis. Hepatokines, liver-derived proteins that play an important role in regulating muscle metabolism, are important to this communication. Here we identify apolipoprotein J (ApoJ) as a novel hepatokine targeting muscle glucose metabolism and insulin sensitivity through a low-density lipoprotein receptor-related protein-2 (LRP2)-dependent mechanism, coupled with the insulin receptor (IR) signaling cascade. In muscle, LRP2 is necessary for insulin-dependent IR internalization, an initial trigger for insulin signaling, that is crucial in regulating downstream signaling and glucose uptake. Of physiologic significance, deletion of hepatic ApoJ or muscle LRP2 causes insulin resistance and glucose intolerance. In patients with polycystic ovary syndrome and insulin resistance, pioglitazone-induced improvement of insulin action is associated with an increase in muscle ApoJ and LRP2 expression. Thus, the ApoJ-LRP2 axis is a novel endocrine circuit that is central to the maintenance of normal glucose homeostasis and insulin sensitivity
The Physics of Cluster Mergers
Clusters of galaxies generally form by the gravitational merger of smaller
clusters and groups. Major cluster mergers are the most energetic events in the
Universe since the Big Bang. Some of the basic physical properties of mergers
will be discussed, with an emphasis on simple analytic arguments rather than
numerical simulations. Semi-analytic estimates of merger rates are reviewed,
and a simple treatment of the kinematics of binary mergers is given. Mergers
drive shocks into the intracluster medium, and these shocks heat the gas and
should also accelerate nonthermal relativistic particles. X-ray observations of
shocks can be used to determine the geometry and kinematics of the merger. Many
clusters contain cooling flow cores; the hydrodynamical interactions of these
cores with the hotter, less dense gas during mergers are discussed. As a result
of particle acceleration in shocks, clusters of galaxies should contain very
large populations of relativistic electrons and ions. Electrons with Lorentz
factors gamma~300 (energies E = gamma m_e c^2 ~ 150 MeV) are expected to be
particularly common. Observations and models for the radio, extreme
ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles
accelerated in these mergers are described.Comment: 38 pages with 9 embedded Postscript figures. To appear in Merging
Processes in Clusters of Galaxies, edited by L. Feretti, I. M. Gioia, and G.
Giovannini (Dordrecht: Kluwer), in press (2001
Simulation techniques for cosmological simulations
Modern cosmological observations allow us to study in great detail the
evolution and history of the large scale structure hierarchy. The fundamental
problem of accurate constraints on the cosmological parameters, within a given
cosmological model, requires precise modelling of the observed structure. In
this paper we briefly review the current most effective techniques of large
scale structure simulations, emphasising both their advantages and
shortcomings. Starting with basics of the direct N-body simulations appropriate
to modelling cold dark matter evolution, we then discuss the direct-sum
technique GRAPE, particle-mesh (PM) and hybrid methods, combining the PM and
the tree algorithms. Simulations of baryonic matter in the Universe often use
hydrodynamic codes based on both particle methods that discretise mass, and
grid-based methods. We briefly describe Eulerian grid methods, and also some
variants of Lagrangian smoothed particle hydrodynamics (SPH) methods.Comment: 42 pages, 16 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 12; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Observation of the Decays B0->K+pi-pi0 and B0->rho-K+
We report the observation of B^0 decays to the K^+pi^-pi^0 final state using
a data sample of 78 fb^-1 collected by the Belle detector at the KEKB e^+e^-
collider. With no assumptions about intermediate states in the decay, the
branching fraction is measured to be (36.6^{+4.2}_{-4.3}+- 3.0)*10^-6.We also
search for B decays to intermediate two-body states with the same K^+pi^-pi^0
final state. Significant B signals are observed in the rho(770)^- K^+ and
K^*(892)^+pi^- channels, with branching fractions of
(15.1^{+3.4+1.4+2.0}_{-3.3-1.5-2.1})* 10^-6 and
(14.8^{+4.6+1.5+2.4}_{-4.4-1.0-0.9})* 10^-6, respectively. The first error is
statistical, the second is systematic and the third is due to the largest
possible interference. Contributions from other possible two-body states will
be discussed. No CP asymmetry is found in the inclusive K^+pi^-pi^0 or rho^-K^+
modes, and we set 90% confidence level bounds on the asymmetry of
-0.12<A_{CP}<0.26 and -0.18<A_{CP}<0.64, respectively.Comment: 18 pages, 7 figure
Measurements of exclusive B_s^0 decays at the Y(5S) resonance
Several exclusive decays are studied using a 1.86 fb-1 data sample
collected at the Y(5S) resonance with the Belle detector at the KEKB asymmetric
energy e^+ e^- collider. In the decay mode we find 10
candidates and measure the corresponding branching fraction. Combining
the B_s^0 -> D_s^{(*)-} \pi^+, B_s^0 -> D_s^{(*)-} \rho^+, B_s^0 -> J/\psi \phi
and B_s^0 -> J/\psi \eta decay modes, a significant signal is observed.
The ratio \sigma (e^+ e^- -> B_s^* \bar{B}_s^*) / \sigma (e^+ e^- -> B_s^{(*)}
\bar{B}_s^{(*)}) = (93^{+7}_{-9} \pm 1)% is obtained at the Y(5S) energy,
indicating that meson production proceeds predominantly through the
creation of pairs. The and meson masses are
measured to be M(B_s^0)=(5370 \pm 1 \pm 3)MeV/c^2 and M(B_s^*)=(5418 \pm 1 \pm
3)MeV/c^2. Upper limits on the B_s^0 -> \gamma \gamma, B_s^0 -> \phi \gamma,
B_s^0 -> K^+ K^- and B_s^0 -> D_s^{(*)+} D_s^{(*)-} branching fractions are
also reported.Comment: 9 pages, 5 figures, published in Phys. Rev. D76, 012002 (2007
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