60,230 research outputs found
ROSAT Observations of the Flare Star CC Eri
The flare/spotted spectroscopic binary star CC Eri was observed with the
Position Sensitive Proportional Counter (PSPC) on the X-ray satellite ROSAT on
1990 July 9-11 and 1992 January 26-27. During the observations, the source was
variable on time scales from a few minutes to several hours, with the X-ray
(0.2-2 keV) luminosity in the range . An
X-ray flare-like event, which has a one hour characteristic rise time and a two
hour decay time, was observed from CC Eri on 1990 July 10 16:14-21:34 (UT). The
X-ray spectrum of the source can be described by current thermal plasma codes
with two temperature components or with a continuous temperature distribution.
The spectral results show that plasma at K exists in the corona
of CC Eri. The variations in the observed source flux and spectra can be
reproduced by a flare, adopting a magnetic reconnection model. Comparisons with
an unheated model, late in the flare, suggest that the area and volume of the
flare are substantially larger than in a solar two ribbon flare, while the
electron pressure is similar. The emission measure and temperature of the
non-flaring emission, interpreted as the average corona, lead to an electron
pressure similar to that in a well-developed solar active region. Rotational
modulation of a spot related active region requires an unphysically large X-ray
flux in a concentrated area.Comment: 14 pages, compressed and uuencoded postscript file, to be published
in MNRA
Squeeze-film gas bearing technology
Squeeze-film bearing is studied to develop a low-friction suspension for the output-axis gimbal of a single-degree-of-freedom gyroscope. Included are a review of pertinent literature, the theory of squeeze-film lubrication, and design elements
On asymptotic analysis of gaseous squeeze-film bearings
Asymptotic analysis for obtaining steady state solution of time dependent gas lubrication equation, of diffusion type, for gaseous squeeze film bearing
Compact and Broadband Microstrip-Line-Fed Modified Rhombus Slot Antenna
The printed microstrip-line-fed broadband rhombus slot antenna is investigated in this paper. With the use of the offset microstrip feed line and the corner-truncated protruded ground plane, the bandwidth enhancement and the slot size reduction for the proposed slot antenna can be obtained. The experimental results demonstrate that the impedance bandwidth for 10 dB return loss reaches 5210 MHz (108.2%, 2210-7420 MHz), which is about 2.67 times of a conventional microstrip-line-fed rhombus slot antenna. This bandwidth can provide with the wireless communication services operating in wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) bands. Under the use of the protruded ground plane, the slot size can be reduced by about 52%. Details of simulated and measured results are presented and discussed
Rotational correlation and dynamic heterogeneity in a kinetically constrained lattice gas
We study dynamical heterogeneity and glassy dynamics in a kinetically
constrained lattice gas model which has both translational and rotational
degrees of freedom. We find that the rotational diffusion constant tracks the
structural relaxation time as density is increased whereas the translational
diffusion constant exhibits a strong decoupling. We investigate distributions
of exchange and persistence times for both the rotational and translational
degrees of freedom and compare our results on the distributions of rotational
exchange times to recent single molecule studies.Comment: 7 pages, 5 figure
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