3,199 research outputs found
Mass entrainment rate of an ideal momentum turbulent round jet
We propose a two-phase-fluid model for a full-cone turbulent round jet that
describes its dynamics in a simple but comprehensive manner with only the apex
angle of the cone being a disposable parameter. The basic assumptions are that
(i) the jet is statistically stationary and that (ii) it can be approximated by
a mixture of two fluids with their phases in dynamic equilibrium. To derive the
model, we impose conservation of the initial volume and total momentum fluxes.
Our model equations admit analytical solutions for the composite density and
velocity of the two-phase fluid, both as functions of the distance from the
nozzle, from which the dynamic pressure and the mass entrainment rate are
calculated. Assuming a far-field approximation, we theoretically derive a
constant entrainment rate coefficient solely in terms of the cone angle.
Moreover, we carry out experiments for a single-phase turbulent air jet and
show that the predictions of our model compare well with this and other
experimental data of atomizing liquid jets.Comment: 17 pages, 10 figure
Microwave Spectroscopy
Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E
Magnetic Susceptibility for
We examine experimental magnetic susceptibility for
CaVO by fitting with fitting function .
The function is a power series of 1/T and the lowest order
term is fixed as , where is the Curie constant as determined by the
experimental -value (g=1.96). Fitting parameters are , and
expansion coefficients except for the first one in .
We determine and as 0.73 and 0 for an
experimental sample. We interpret as the volume fraction of
CaVO in the sample and as the susceptibility for the
pure CaVO. The result of means that the sample includes
nonmagnetic components. This interpretation consists with the result of a
perturbation theory and a neutron scattering experiment.Comment: 4pages, 4figure
Two-Triplet-Dimer Excitation Spectra in the Shastry-Sutherland Model for SrCu_2(BO_3)_2
By using the perturbation expansion up to the fifth order, we study the
two-triplet-dimer excitation spectra in the Shastry-Sutherland model, where the
localized nature of a triplet-dimer, the propagation of a triplet-dimer pair by
the correlated hopping and the long-range interactions between triplet-dimers
play an essential role. It is found that the dispersion relations for
first-neighbor triplet-dimer pair excitations with S=1 and p-type symmetry
qualitatively explain the second-lowest branch observed in the neutron
inelastic scattering experiment. It is also predicted that the second-lowest
branch consists of two components, p_x- and p_y-states, with slightly different
excitation energies. The origin of the singlet mode at 3.7meV observed in the
Raman scattering experiment is also discussed.Comment: 5 pages, 3 figure
Effect of Forest Grazing in Summer on Grazing Behaviour, Heart Beat and Heat Production of Beef Cows
In Japan summer is very hot and humid, particularly in daytime, therefore the supply of shade to animals is important. At the same time, a lot of forest and partial forest area is under-utilised in most of the mountain areas. Introduction of animals to forest areas might result in not only less labour demanding animal management, but also in the efficient weeding in the forest (Sugimoto et al., 1999). We compared the grazing behaviour, heart beat and heat production of beef cows in partial forest with those in the normal grazing place outside the forest
Investigation of over-horizon VHF radio signals associated with earthquakes
International audienceThis paper presents the preliminary results on the possible reception of over-horizon VHF radio signals from a FM (frequency modulation) transmitter during abnormal situations (probably in close association with earthquakes). The transmitter is FM Sendai (frequency = 77.1 MHz) and the receiving station is our university (UEC) at Chofu, Tokyo, with the transmitter-receiver distance being about 310 km. We first show a typical example of the reception of over-horizon VHF signals in which we present the amplitude behavior, azimuthal and incident angle estimation, etc. Then, we study the correlation between a signal anomaly and an earthquake and it seems that the over-horizon VHF signals observed are probably associated with earthquakes, observed about 7 to 0 days before an earthquake. The direction finding measurements have indicated that such signals are due to favorable tropospheric (but not ionospheric) conditions attributed to the effects of earthquakes
Competing Spin-Gap Phases in a Frustrated Quantum Spin System in Two Dimensions
We investigate quantum phase transitions among the spin-gap phases and the
magnetically ordered phases in a two-dimensional frustrated antiferromagnetic
spin system, which interpolates several important models such as the
orthogonal-dimer model as well as the model on the 1/5-depleted square lattice.
By computing the ground state energy, the staggered susceptibility and the spin
gap by means of the series expansion method, we determine the ground-state
phase diagram and discuss the role of geometrical frustration. In particular,
it is found that a RVB-type spin-gap phase proposed recently for the
orthogonal-dimer system is adiabatically connected to the plaquette phase known
for the 1/5-depleted square-lattice model.Comment: 6 pages, to appear in JPSJ 70 (2001
Magnetization Plateaus in the Shastry-Sutherland Model for SrCu_2(BO_3)_2: Results of Fourth-Order Perturbation Expansion with a Low-Density Approximation
Magnetization plateaus in the Shastry-Sutherland model for are studied by the perturbation expansion method. The
fourth-order effective Hamiltonian which describes the dynamics of triplet
dimers (TD's) with in the singlet sea is derived and then
partially diagonalized for the space that consists of the TD configurations
with the lowest second-order energy. The fourth-order terms are treated within
a low-density approximation. Our procedure makes clear how TD interactions are
responsible for the formation of magnetization plateaus. Particularly, the
1/4-plateau is obtained by the fourth-neighbor TD repulsion in the fourth-order
perturbation, and a diagonal stripe arrangement of TD's appears at this
plateau.Comment: 8 pages, 12 figure
Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies
We present the results of a variety of simulations concerning the evolution
of multiphase (inhomogeneous) hot interstellar medium (ISM) in elliptical
galaxies. We assume the gases ejected from stars do not mix globally with the
circumferential gas. The ejected gas components evolve separately according to
their birth time, position, and origin. We consider cases where supernova
remnants (SNRs) mix with local ISM. The components with high metal abundance
and/or high density cool and drop out of the hot ISM gas faster than the other
components because of their high metal abundance and/or density. This makes the
average metal abundance of the hot ISM low. Furthermore, since the metal
abundance of mass-loss gas decreases with radius, gas inflow from outer region
makes the average metal abundance of the hot ISM smaller than that of mass-loss
gas in the inner region. As gas ejection rate of stellar system decreases, mass
fraction of mass-loss gas ejected at outer region increases in a galaxy. If the
mixing of SNRs is ineffective, our model predicts that observed [Si/Fe] and
[Mg/Fe] should decrease towards the galactic center because of strong iron
emission by SNRs. In the outer region, where the cooling of time of the ISM is
long, the selective cooling is ineffective and most of gas components remain
hot. Thus, the metal abundance of the ISM in this region directly reflects that
of the gas ejected from stars. Our model shows that supernovae are not
effective heating sources in the inner region of elliptical galaxies, because
most of the energy released by them radiates. Therefore, cooling flow is
established even if the supernova rate is high. Mixing of SNRs with ambient ISM
makes the energy transfer between supernova explosion and ambient ISM more
effective.Comment: 21 pages (AASTeX), 14 figures, accepted for publication in The
Astrophysical Journa
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