10,616 research outputs found
Understanding Legislator Experiences of Family-Friendly Working Practices in Political Institutions
This is a post-peer-review, pre-copy edit version of an article published in Politics and Gender. © 2015, Cambridge University Press
Evaluation of a series hybrid thrust bearing at DN values to three million. 2: Fabrication and testing
Results of tests made to determine the experimental performance of a series hybrid bearing are reported. The bearing consists of a 150 mm ball bearing and a centrifugally actuated, conical, fluid film bearing fitting an envelope with an outer radius of 86.4 mm (3.4 in.) and inner radius of 71 mm (2.8 in.). Tests were conducted up to 16,500 rpm, at which speed an axial load of 15,568 N (3500 lb) was safely supported by the hybrid bearing system. Through the employment of the series hybrid bearing principle, it was possible to reduce the effective ball bearing speed to approximately one-half of the shaft speed. A reduction of this magnitude should result in a tenfold increase in the ball bearing fatigue life. A successful simulation of fluid film bearing lubricant supply failure, performed repeatedly at an operating speed of 10,000 rpm, resulted in complete and smooth change over to full scale ball bearing operation when the oil supply to the fluid film bearing was discontinued. Reactivation of the fluid film supply system produced a flawless return to the original mode of hybrid operation
Evaluation of a series hybird thrust bearing at DN values to three million. 1: Analysis and design
The analysis and design are presented of a hybrid bearing consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid film bearing fitting an envelope with an outer radius of 86.4 mm (3.4 in.) and an inner radius of 71 mm (2.8 in.). The bearing analysis, combined with available torque data on ball bearings, indicates that an effective speed split between the ball and fluid-film bearings of 50 percent may be expected during operation at 20,000 rpm and under an axial load of 17,800 newtons (4000 lbs.). This speed split can result in a ten-fold increase in the life of the ball bearing when compared to a simple ball bearing system operating under similar conditions
The Light Curve of the Weakly-Accreting T Tauri Binary KH 15D from 2005-10: Insights into the Nature of its Protoplanetary Disk
Photometry of the unique pre-main sequence binary system KH 15D is presented,
spanning the years 2005-2010. This system has exhibited photometric variations
and eclipses over the last 50 years caused by a precessing circumbinary disk.
Advancement of the occulting edge across the binary orbit has continued and the
photospheres of both stars are now completely obscured at all times. The system
is now visible only by scattered light, and yet it continues to show a periodic
variation on the orbital cycle with an amplitude exceeding two magnitudes. This
variation, which depends only on the binary phase, has likely been present in
the data since at least 1995. It can, by itself, account for shoulders on the
light curve prior to ingress and following egress, obviating the need for
components of extant models such as a scattering halo around star A or forward
scattering from a fuzzy disk edge. A plausible source for the variable
scattering component is reflected light from the far side of a warped occulting
disk. We have detected color changes in V-I of several tenths of a magnitude to
both the blue and red that occur during times of minima. These may indicate the
presence of a third source of light (faint star) within the system, or a change
in the reflectance properties of the disk as the portion being illuminated
varies with the orbital motion of the stars. The data support a picture of the
circumbinary disk as a geometrically thin, optically thick layer of perhaps mm
or cm-sized particles that has been sculpted by the binary stars and possibly
other components into a decidedly nonplanar configuration. A simple (infinitely
sharp) knife-edge model does a good job of accounting for all of the recent
(2005-2010) occultation data.Comment: To appear in The Astronomical Journa
Constructing Cost-Effective and Targetable ICS Honeypots Suited for Production Networks
Honeypots are a technique that can mitigate the risk of cyber threats. Effective honeypots are authentic and targetable, and their design and implementation must accommodate risk tolerance and financial constraints. The proprietary, and often expensive, hardware and software used by Industrial Control System (ICS) devices creates the challenging problem of building a flexible, economical, and scalable honeypot. This research extends Honeyd into Honeyd+, making it possible to use the proxy feature to create multiple high interaction honeypots with a single Programmable Logic Controller (PLC). Honeyd+ is tested with a network of 75 decoy PLCs, and the interactions with the decoys are compared to a physical PLC to test for authenticity. The performance test evaluates the impact of multiple simultaneous connections to the PLC. The functional test is successful in all cases. The performance test demonstrated that the PLC is a limiting factor, and that introducing Honeyd+ has a marginal impact on performance. Notable findings are that the Raspberry Pi is the preferred hosting platform, and more than five simultaneous connections were not optimal
Complex Variability of the H Emission Line Profile of the T Tauri Binary System KH 15D: The Influence of Orbital Phase, Occultation by the Circumbinary Disk, and Accretion Phenomenae
We have obtained 48 high resolution echelle spectra of the pre-main sequence
eclipsing binary system KH~15D (V582 Mon, P = 48.37 d, 0.6, M
= 0.6 M, M = 0.7 M). The eclipses are caused by a
circumbinary disk seen nearly edge on, which at the epoch of these observations
completely obscured the orbit of star B and a large portion of the orbit of
star A. The spectra were obtained over five contiguous observing seasons from
2001/2002 to 2005/2006 while star A was fully visible, fully occulted, and
during several ingress and egress events. The H line profile shows
dramatic changes in these time series data over timescales ranging from days to
years. A fraction of the variations are due to "edge effects" and depend only
on the height of star A above or below the razor sharp edge of the occulting
disk. Other observed variations depend on the orbital phase: the H
emission line profile changes from an inverse P Cygni type profile during
ingress to an enhanced double-peaked profile, with both a blue and red emission
component, during egress. Each of these interpreted variations are complicated
by the fact that there is also a chaotic, irregular component present in these
profiles. We find that the complex data set can be largely understood in the
context of accretion onto the stars from a circumbinary disk with gas flows as
predicted by the models of eccentric T Tauri binaries put forward by Artymowicz
& Lubow, G\"{u}nther & Kley, and de Val-Borro et al. In particular, our data
provide strong support for the pulsed accretion phenomenon, in which enhanced
accretion occurs during and after perihelion passage.Comment: accepted to Ap
Design and evaluation of a 3 million DN series-hybrid thrust bearing
The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation
Line-profile tomography of exoplanet transits I: The Doppler shadow of HD 189733b
We present a direct method for isolating the component of the starlight
blocked by a planet as it transits its host star, and apply it to spectra of
the bright transiting planet HD 189733b. We model the global shape of the
stellar cross-correlation function as the convolution of a limb-darkened
rotation profile and a gaussian representing the Doppler core of the average
photospheric line profile. The light blocked by the planet during the transit
is a gaussian of the same intrinsic width, whose trajectory across the line
profile yields a precise measure of the misalignment angle and an independent
measure of v sin I. We show that even when v sin I is less than the width of
the intrinsic line profile, the travelling Doppler "shadow" cast by the planet
creates an identifiable distortion in the line profiles which is amenable to
direct modelling. Direct measurement of the trajectory of the missing starlight
yields self-consistent measures of the projected stellar rotation rate, the
intrinsic width of the mean local photospheric line profile, the projected
spin-orbit misalignment angle, and the system's centre-of-mass velocity.
Combined with the photometric rotation period, the results give a geometrical
measure of the stellar radius which agrees closely with values obtained from
high-precision transit photometry if a small amount of differential rotation is
present in the stellar photosphere.Comment: 8 pages, 5 figures, 2 tables; accepted by MNRA
Bipolar jets produced by a spectroscopic binary
We present evidence that the spectroscopically identified bipolar jets of the
pre-main sequence binary KH 15D are a common product of the whole binary
system, rather than being launched from either star individually. They may be
launched from the innermost part of the circumbinary disk (CBD) or may result
from the merging of two outflows driven by the individual stars. This evidence
is based on high-resolution H-alpha and [OI] 6300A line profiles obtained
during eclipse phases of this nearly edge-on system. The occultation of star A
(the only currently visible star) by the disk strongly suppresses the stellar
H-alpha and continuum emission and allows one to study the faint redshifted and
blueshifted emission components of the bipolar jets. The strongest evidence for
jet production by the whole binary system comes from the observed radial
velocity symmetry of the two jet components relative to the systemic velocity
of the binary, in combination with current accretion models from the CBD onto a
binary system.Comment: ApJ Letters, in press [6 pages
The association of shift work and coronary heart disease risk factors among male factory workers in Kota Bharu, Kelantan
Shift work is one of the work hour systems in which a relay of employees extends the period of production beyond the conventional 8-hour working day. It has been found to be associated with various health problems and there is concern that shift workers are at higher risk to develop risk factors for coronary heart disease (CHD). The study was undertaken to examine relationships between shift work and CHD risk factors, namely hypertension, dyslipidaemia (either hypercholesterolaemia, hyper-low density lipoprotein-cholesterolaemia, hypo-high density lipoprotein-cholesterolaemia or hypertriglyceridaemia), high body mass index (BMI), hyperglycemia and physical inactivity among male factory workers in a factory in Kota Bharu, Kelantan. METHODS: This study was a contrived cross-sectional study of 76 shift and 72 day workers from one ofthe factories in Kota Bharu, Kelantan. Data was collected through a questionnaire on psychosocial and life-style factors, anthropometric and blood pressure measurement, fasting blood sugar and fasting lipid proJiles analyses. RESULTS: The prevalence of hypertension, hypercholesterolaemia, hypertriglyceridaemia and high body mass index (BMO were significantly higher among shift workers compared to day workers. There was no difference in the prevalence of hyperg[ycemia, hypo-high-density lipoprotein-cholesterolaemia, hyper-high-density lipoprotein-cholesterolaemia and physical inactivity. When the shiji workers were compared with the day workers, the aajusted odds ratio (OR) for hypertension, high BMI andphysical inactivity were 9.1 (95% CI 1.4-56.8), 2.9 (95% CI 1.3-6.1) and 7.7 (95% CI 2.1-27.5) respectively. There was neither association of shift work with dyslipidaemia, nor with hyperglycemia. CONCLUSIONS: There were positive association between shiji work and hypertension, high BMI andphysical inactivity which denotes a higher risk of CHD risk factors among shift workers compared to day workers
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