44,280 research outputs found
Explorer 12 observations of charged particles in the inner radiation zone
Explorer XII satellite observations of charged particles in inner radiation zon
Correlated satellite measurements of low-energy electron precipitation and ground based observations of a visible auroral arc
Comparison of Injun 5 satellite measurements of low energy electron precipitation and ground based observations of visible auroral ar
Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-Row Radial Aircraft Engine
The NACA injection impeller was developed to improve the mixture distribution of aircraft engines by discharging the fuel from a centrifugal supercharger impeller, thus promoting a thorough mixing of fuel and charge air. Tests with a double-row radial aircraft engine indicated that for the normal range of engine power the NACA injection impeller provided marked improvement in mixture distribution over the standard spray-bar injection system used in the same engine. The mixture distribution at cruising conditions was excellent; at 1200, 15OO, and 1700 brake horsepower, the differences between the fuel-air ratios of the richest and the leanest cylinders were reduced to approximately one-third their former values. The maximum cylinder temperatures were reduced about 30 [degrees] F and the temperature distribution was improved by approximately the
degree expected from the improvement in mixture distribution. Because the mixture distribution of the engine tested improves slightly at engine powers exceeding 1500 brake horsepower and because the effectiveness of the particular impeller diminished slightly at high rates of fuel flow, the improvement in mixture distribution at
rated power and rich mixtures was less than that for other conditions.
The difference between the fuel-air ratios of the richest and the leanest cylinders of the engine using the standard spray bar was so great that the fuel-air ratios of several cylinders were well below the chemically correct mixture, whereas other cylinders were operating at rich mixtures. Consequently, enrichment to improve engine cooling actually increascd some of the critical temperatures. The uniform mixture distribution providod by the injection impeller restored the normal response of cylinder temperatures to mixture enrichnent
The Enigmatic HH 255
To gain insight into the nature of the peculiar Herbig-Haro object HH 255
(also called Burnham's nebula), we use previously published observations to
derive information about the emission line fluxes as a function of position
within HH 255 and compare them with the well-studied, and relatively
well-behaved bow shock HH 1. There are some qualitative similarities in the
H and [O III] 5007 lines in both objects. However, in contrast to the
expectation of the standard bow shock model, the fluxes of the [O I] 6300, [S
II] 6731, and [N II] 6583 lines are essentially constant along the axis of the
flow, while the electron density decreases, over a large distance within HH
255.
We also explore the possibility that HH 255 represents the emission behind a
standing or quasi-stationary shock. The shock faces upwind, and we suggest,
using theoretical arguments, that it may be associated with the collimation of
the southern outflow from T Tauri. Using a simplified magnetohydrodynamic
simulation to illustrate the basic concept, we demonstrate that the existence
of such a shock at the north edge of HH 255 could indeed explain its unusual
kinematic and ionization properties. Whether or not such a shock can explain
the detailed emission line stratification remains an open question.Comment: Accepted by PASP, 12 pages including 8 figure
Electron precipitation in the post midnight sector of the auroral zones
Comprehensive measurements of the angular distributions and energy spectra of electron intensities with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported. These are for the post-midnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for energetic electrons with E greater than 45 keV were examined. No evidences of maxima in the differential energy spectra or of strongly field-aligned currents which are indicative of quasi-static electric fields aligned parallel to the geomagnetic field were found. Precipitation of low-energy electron intensities fluctuated on time scales greater than 2 seconds as viewed at the satellite position. This precipitation was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone
Trapped radiation experiment
Trapped radiation detector on Mariner IV space probe measurement of outer Van Allen belt - feasibility of detecting trapped radiation at Mar
Resummation Improved Rapidity Spectrum for Gluon Fusion Higgs Production
Gluon-induced processes such as Higgs production typically exhibit large
perturbative corrections. These partially arise from large virtual corrections
to the gluon form factor, which at timelike momentum transfer contains Sudakov
logarithms evaluated at negative arguments . It has been
observed that resumming these terms in the timelike form factor leads to a much
improved perturbative convergence for the total cross section. We discuss how
to consistently incorporate the resummed form factor into the perturbative
predictions for generic cross sections differential in the Born kinematics,
including in particular the Higgs rapidity spectrum. We verify that this indeed
improves the perturbative convergence, leading to smaller and more reliable
perturbative uncertainties, and that this is not affected by cancellations
between resummed and unresummed contributions. Combining both fixed-order and
resummation uncertainties, the perturbative uncertainty for the total cross
section at NLONLL is about a factor of two smaller
than at NLO. The perturbative uncertainty of the rapidity spectrum at
NNLONNLL is similarly reduced compared to NNLO. We also
study the analogous resummation for quark-induced processes, namely Higgs
production through bottom quark annihilation and the Drell-Yan rapidity
spectrum. For the former the resummation leads to a small improvement, while
for the latter it confirms the already small uncertainties of the fixed-order
predictions.Comment: 30 pages + 17 pages in Appendices, 10 figures; v2: journal version;
references added, discussed individual partonic channels for Drell-Ya
Generation and detection of NOON states in superconducting circuits
NOON states, states between two modes of light of the form
allow for super-resolution interformetry. We
show how NOON states can be efficiently produced in circuit quntum
electrodynamics using superconducting phase qubits and resonators. We propose a
protocol where only one interaction between the two modes is required, creating
all the necessary entanglement at the start of the procedure. This protocol
makes active use of the first three states of the phase qubits. Additionally,
we show how to efficiently verify the success of such an experiment, even for
large NOON states, using randomly sampled measurements and semidefinite
programming techniques.Comment: 15 pages and 3 figure
Studying the Variation of the Fine Structure Constant Using Emission Line Multiplets
As an extension of the method by Bahcall et al. (2004) to investigate the
time dependence of the fine structure constant, we describe an approach based
on new observations of forbidden line multiplets from different ionic species.
We obtain optical spectra of fine structure transitions in [Ne III], [Ne V], [O
III], [OI], and [SII] multiplets from a sample of 14 Seyfert 1.5 galaxies in
the low-z range 0.035 < z < 0.281. Each source and each multiplet is
independently analyzed to ascertain possible errors. Averaging over our sample,
we obtain a conservative value alpha^2(t)/\alpha^2(0) = 1.0030+-0.0014.
However, our sample is limited in size and our fitting technique simplistic as
we primarily intend to illustrate the scope and strengths of emission line
studies of the time variation of the fine structure constant. The approach can
be further extended and generalized to a "many-multiplet emission line method"
analogous in principle to the corresponding method using absorption lines. With
that aim, we note that the theoretical limits on emission line ratios of
selected ions are precisely known, and provide well constrained selection
criteria. We also discuss several other forbidden and allowed lines that may
constitute the basis for a more rigorous study using high-resolution
instruments on the next generation of 8 m class telescopes.Comment: 20 pages, 4 figures, sumbitted to A
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