13,897 research outputs found
Edge coating of flat wires
An apparatus and technique is described for the coating of the edge surfaces of flat ribbon conductors with an adherent coating of a dielectric insulating material. Means for passing the ribbon conductors between a pair of generally axially aligned rollers is provided. The edge surfaces of the conductor are disposed adjacent to and generally tangentially to the confronting surfaces of the roller so as to form a fillet of dielectric material along the edge surface of the conductor
Advection-Dominated Accretion with Infall and Outflows
We present self-similar solutions for advection-dominated accretion flows
with radial viscous force in the presence of outflows from the accretion flow
or infall. The axisymmetric flow is treated in variables integrated over polar
sections and the effects of infall and outflows on the accretion flow are
parametrised for possible configurations compatible with the self-similar
solution. We investigate the resulting accretion flows for three different
viscosity laws and derive upper limits on the viscosity parameter alpha. In
addition, we find a natural connection to non-rotating and spherical accretion
with turbulent viscosity, which is assumed to persist even without differential
rotation. Positive Bernoulli numbers for advection-dominated accretion allow a
fraction of the gas to be expelled in an outflow and the upper limit on the
viscosity predicts that outflows are inevitable for equations of state close to
an ideal gas.Comment: 17 pages, 9 figures, accepted for publication in the Astrophysical
Journa
Aerothermal modeling program, phase 1
Aerothermal submodels used in analytical combustor models are analyzed. The models described include turbulence and scalar transport, gaseous full combustion, spray evaporation/combustion, soot formation and oxidation, and radiation. The computational scheme is discussed in relation to boundary conditions and convergence criteria. Also presented is the data base for benchmark quality test cases and an analysis of simple flows
Truncated Levy Random Walks and Generalized Cauchy Processes
A continuous Markovian model for truncated Levy random walks is proposed. It
generalizes the approach developed previously by Lubashevsky et al. Phys. Rev.
E 79, 011110 (2009); 80, 031148 (2009), Eur. Phys. J. B 78, 207 (2010) allowing
for nonlinear friction in wondering particle motion and saturation of the noise
intensity depending on the particle velocity. Both the effects have own reason
to be considered and individually give rise to truncated Levy random walks as
shown in the paper. The nonlinear Langevin equation governing the particle
motion was solved numerically using an order 1.5 strong stochastic Runge-Kutta
method and the obtained numerical data were employed to calculate the geometric
mean of the particle displacement during a certain time interval and to
construct its distribution function. It is demonstrated that the time
dependence of the geometric mean comprises three fragments following one
another as the time scale increases that can be categorized as the ballistic
regime, the Levy type regime (superballistic, quasiballistic, or superdiffusive
one), and the standard motion of Brownian particles. For the intermediate Levy
type part the distribution of the particle displacement is found to be of the
generalized Cauchy form with cutoff. Besides, the properties of the random
walks at hand are shown to be determined mainly by a certain ratio of the
friction coefficient and the noise intensity rather then their characteristics
individually.Comment: 7 pages, 3 figure
Jet power extracted from ADAF and the applications to X-ray binaries and radio galaxy FR dichotomy
We calculate the jet power of the classical Blandford-Znajek(BZ) model and
hybrid model developed by Meier based on the global solutions of advection
dominated accretion flows (ADAFs) surrounding Kerr black holes. We find that
the jet power of the hybrid model is larger than that of the pure BZ model. The
jet power will dominate over the accretion power, and the objects will enter
into "jet-power-dominated advective systems", when the accretion rate is less
than a critical value mdot_c=Mdot_c/Mdot_Edd, where 3*10^-4 < mdot_c < 5*10^-3
is a function of black hole spin parameter. The accretion power will be
dominant when mdot<mdot_c and the objects will enter into
"accretion-power-dominated advective systems." This is roughly consistent with
that constrained from the low/hard-state black hole X-ray binaries (e.g.,
Fender et al.). We calculate the maximal jet power as a function of black hole
mass with the hybrid jet formation model, and find it can roughly reproduce the
dividing line of the Ledlow-Owen relation for FR I/FR II dichotomy in the jet
power-black hole(BH) mass plane (Q_jet-M_BH) if the dimensionless accretion
rate mdot~0.01 and BH spin parameter j~0.9-0.99 are adopted. This accretion
rate mdot~0.01 is consistent with that of the critical accretion rate for the
accretion mode transition of a standard disk to an ADAF constrained from the
state transition of X-ray binaries. Our results imply that most FR I galaxies
may be in the ADAF accretion mode similar to the low/hard-state XRBs.Comment: 6 pages, 3 color figures, ApJ in press, edited with ApJ style and
English is improved as suggested by Edito
On The Reddening in X-ray Absorbed Seyfert 1 Galaxies
There are several Seyfert galaxies for which there is a discrepancy between
the small column of neutral hydrogen deduced from X-ray observations and the
much greater column derived from the reddening of the optical/UV emission lines
and continuum. The standard paradigm has the dust within the highly ionized gas
which produces O~VII and O~VIII absorption edges (i.e., a ``dusty warm
absorber''). We present an alternative model in which the dust exists in a
component of gas in which hydrogen has been stripped, but which is at too low
an ionization state to possess significant columns of O~VII and O~VIII (i.e, a
``lukewarm absorber''). The lukewarm absorber is at sufficient radial distance
to encompass much of the narrow emission-line region, and thus accounts for the
narrow-line reddening, unlike the dusty warm absorber. We test the model by
using a combination of photoionization models and absorption edge fits to
analyze the combined ROSAT/ASCA dataset for the Seyfert 1.5 galaxy, NGC 3227.
We show that the data are well fit by a combination of the lukewarm absorber
and a more highly ionized component similar to that suggested in earlier
studies. We predict that the lukewarm absorber will produce strong UV
absorption lines of N V, C IV, Si IV and Mg II. Finally, these results
illustrate that singly ionized helium is an important, and often overlooked,
source of opacity in the soft X-ray band (100 - 500 eV).Comment: 17 pages, Latex, includes 1 figure (encapsulated postscript), one
additional table in Latex (landscape format), to appear in the Astrophysical
Journa
Atomic Deuterium Adsorbed on the Surface of Liquid Helium
We investigate deuterium atoms adsorbed on the surface of liquid helium in
equilibrium with a vapor of atoms of the same species. These atoms are studied
by a sensitive optical method based on spectroscopy at a wavelength of 122 nm,
exciting the 1S-2P transition. We present a direct measurement of the
adsorption energy of deuterium atoms on helium and show evidence for the
existence of resonantly enhanced recombination of atoms residing on the surface
to molecules.Comment: 6 pages 4 figure
Response Function of the Fractional Quantized Hall State on a Sphere II: Exact Diagonalization
We study the excitation spectra and the dynamical structure factor of quantum
Hall states in a finite size system through exact diagonalization. Comparison
is made between the numerical results so obtained and the analytic results
obtained from a modified RPA in the preceding companion paper. We find good
agreement between the results at low energies.Comment: 22 pages (REVTeX 3.0). 10 figures available on request. Complete
postscript file (including figures) for this paper are available on the World
Wide Web at http://cmtw.harvard.edu/~simon/ ; Preprint number HU-CMT-94S0
An Investigation of Single- and Dual-Rotation Propellers at Positive and Negative Thrust, and in Combination with an NACA 1-series D-Type Cowling at Mach Numbers up to 0.84
An investigation has been made to determine the aerodynamic characteristics of the NACA 4-(5)(05)-041 four-blade, single-relation propeller and the NACA 4-(5)(05)-037 six- and eight-blade, dual-rotation propellers in combination with various spinners and NACA d-type spinner-cowling combinations at Mach numbers up to 0.84. Propeller force characteristics, local velocity distributions in the propeller planes, inlet pressure recoveries, and static-pressure distributions on the cowling surfaces were measured for a wide range of blade angles, advance ratios, and inlet-velocity ratios. Included are data showing: (a) the effect of extended cylindrical spinners on the characteristics of the single-rotation propeller, (b) the effect of variation of the difference in blade angle setting between the front and rear components of the dual-rotation propellers, (c) the negative- and static-thrust characteristics of the propellers with 1 series spinners, and (d) the effects of ideal- and platform-type propeller-spinner junctures on the pressure-recovery characteristics of the single-rotation propeller-spinner-cowling combination
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