34,870 research outputs found
Outer raceway fault detection and localization for deep groove ball bearings by using thermal imaging
This paper discusses outer raceway fault detection and localization for rolling element bearings by means of thermal imaging. In particular, deep groove ball bearings have been monitored. Whereas bearings in industrial applications are usually fully covered, the used test setup allows to monitor the uncovered bearings to understand their heat increase and propagation. The main contribution of this paper is the methodology to process and analyse the thermal data of the bearings. The presented methodology is applied on both a healthy bearing and a bearing with outer raceway fault. By revealing significantly higher temperatures for the faulty bearing than for the healthy bearing, thermal imaging enables fault detection. Additionally, the stationary characteristic of the outer ring allows to locate the outer raceway fault by means of its thermal impact
The IceCube Neutrino Observatory: Instrumentation and Online Systems
The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy
neutrino detector built into the ice at the South Pole. Construction of
IceCube, the largest neutrino detector built to date, was completed in 2011 and
enabled the discovery of high-energy astrophysical neutrinos. We describe here
the design, production, and calibration of the IceCube digital optical module
(DOM), the cable systems, computing hardware, and our methodology for drilling
and deployment. We also describe the online triggering and data filtering
systems that select candidate neutrino and cosmic ray events for analysis. Due
to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are
operating and collecting data. IceCube routinely achieves a detector uptime of
99% by emphasizing software stability and monitoring. Detector operations have
been stable since construction was completed, and the detector is expected to
operate at least until the end of the next decade.Comment: 83 pages, 50 figures; updated with minor changes from journal review
and proofin
Experimental Study of Various Techniques to Protect Ice-Rich Cut Slopes
INE/AUTC 15.08 and INE/AUTC 13.07 (2013) Construction Repor
INTEGRAL: science highlights and future prospects
ESA's hard X-ray and soft gamma-ray observatory INTEGRAL is covering the 3
keV to 10 MeV energy band, with excellent sensitivity during long and
uninterrupted observations of a large field of view (~100 square degrees), with
ms time resolution and keV energy resolution. It links the energy band of
pointed soft X-ray missions such as XMM-Newton with that of high-energy
gamma-ray space missions such as Fermi and ground based TeV observatories. Key
results obtained so far include the first sky map in the light of the 511 keV
annihilation emission, the discovery of a new class of high mass X-ray binaries
and detection of polarization in cosmic high energy radiation. For the
foreseeable future, INTEGRAL will remain the only observatory allowing the
study of nucleosynthesis in our Galaxy, including the long overdue next nearby
supernova, through high-resolution gamma-ray line spectroscopy. Science results
to date and expected for the coming mission years span a wide range of
high-energy astrophysics, including studies of the distribution of positrons in
the Galaxy; reflection of gamma-rays off clouds in the interstellar medium near
the Galactic Centre; studies of black holes and neutron stars particularly in
high- mass systems; gamma-ray polarization measurements for X-ray binaries and
gamma-ray bursts, and sensitive detection capabilities for obscured active
galaxies with more than 1000 expected to be found until 2014. This paper
summarizes scientific highlights obtained since INTEGRAL's launch in 2002, and
outlines prospects for the INTEGRAL mission.Comment: 39 pages, accepted, 24 October 2011, Space Science Review
Seoul National University Camera II (SNUCAM-II): The New SED Camera for the Lee Sang Gak Telescope (LSGT)
We present the characteristics and the performance of the new CCD camera
system, SNUCAM-II (Seoul National University CAMera system II) that was
installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory
in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength
from 0.3 {\mu}m to 1.1 {\mu}m with high sensitivity (QE at > 80% over 0.4 to
0.9 {\mu}m). It is equipped with the SDSS ugriz filters and 13 medium band
width (50 nm) filters, enabling us to study spectral energy distributions
(SEDs) of diverse objects from extragalactic sources to solar system objects.
On LSGT, SNUCAM-II offers 15.7 {\times} 15.7 arcmin field-of-view (FOV) at a
pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag and
z=18.20 AB mag at 5{\sigma} with 180 sec exposure time for point source
detection.Comment: 8 pages, 9 figures, 4 tables, published in 2017 June issue of JKA
Laser interferometric measurement of ion electrode shape and charge exchange erosion
A projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thrustor. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3-D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid, nondestructive, digital data acquisition coupled with automated computer data processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes
High Precision Astrometry with MICADO at the European Extremely Large Telescope
In this article we identify and discuss various statistical and systematic
effects influencing the astrometric accuracy achievable with MICADO, the
near-infrared imaging camera proposed for the 42-metre European Extremely Large
Telescope (E-ELT). These effects are instrumental (e.g. geometric distortion),
atmospheric (e.g. chromatic differential refraction), and astronomical
(reference source selection). We find that there are several phenomena having
impact on ~100 micro-arcsec scales, meaning they can be substantially larger
than the theoretical statistical astrometric accuracy of an optical/NIR
42m-telescope. Depending on type, these effects need to be controlled via
dedicated instrumental design properties or via dedicated calibration
procedures. We conclude that if this is done properly, astrometric accuracies
of 40 micro-arcsec or better - with 40 micro-arcsec/year in proper motions
corresponding to ~20 km/s at 100 kpc distance - can be achieved in one epoch of
actual observationsComment: 15 pages, 9 figures, 3 tables. Accepted by MNRA
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