280 research outputs found
Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. An all-sky survey of
We measure the smoothness of the infrared sky using the COBE DIRBE maps, and
obtain interesting limits on the production of the diffuse cosmic infrared
background (CIB) light by matter clustered like galaxies. The predicted
fluctuations of the CIB with the DIRBE beam size of 0.7\deg\ are of the order
of 10\%, and the maps are smooth at the level of a few
\nwm2sr rms from 2.2 to 100 \um. The lowest numbers are achieved at mid- to
far-IR where the foreground is bright but smooth; they are
\nwm2sr at 10-100 \um. If the CIB comes
from clustered matter evolving according to typical scenarios, then the
smoothness of the maps implies CIB levels less than \nwm2sr
over this wavelength range.Comment: 15 pages (LATEX) with 2 figures and 1 plate; Ap. J. Letters, in pres
Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. I. and limits on the near-IR background
This paper is devoted to studying the CIB through its correlation properties.
We studied the limits on CIB anisotropy in the near IR (1.25, 2.2, and 3.5 \um,
or ) bands at a scale of 0.7\deg\ using the COBE\footnote{ The
National Aeronautics and Space Administration/Goddard Space Flight Center
(NASA/GSFC) is responsible for the design, development, and operation of the
{\it COBE}. Scientific guidance is provided by the {\it COBE} Science Working
Group. GSFC is also responsible for the development of the analysis software
and for the production of the mission data sets.} Diffuse Infrared Background
Experiment (DIRBE) data. In single bands we obtain the upper limits on the
zero-lag correlation signal \w2m4sr2 for the
bands respectively. The DIRBE data exhibit a clear color between the
various bands with a small dispersion. On the other hand most of the CIB is
expected to come from redshifted galaxies and thus should have different color
properties. We use this observation to develop a `color subtraction' method of
linear combinations of maps at two different bands. This method is expected to
suppress the dominant fluctuations from foreground stars and nearby galaxies,
while not reducing (or perhaps even amplifying) the extragalactic contribution
to . Applying this technique gives significantly lower and more isotropic
limits.Comment: 44 pages postcript; includes 5 tables, 14 figures. Astrophysical
Journal, in pres
Clustering of DIRBE Light and IR Background
We outline a new method for estimating the cosmic infrared background using
the spatial and spectral correlation properties of infrared maps. The cosmic
infrared background from galaxies should have a minimum fluctuation of the
order of 10\% on angular scales of the order of 1\deg. We show that a linear
combination of maps at different wavelengths can greatly reduce the
fluctuations produced by foreground stars, while not eliminating the
fluctuations of the background from high redshift galaxies. The method is
potentially very powerful, especially at wavelengths where the foreground is
bright but smooth.Comment: 7 pages postcript, talk at "Unveiling the cosmic infrared background"
workshop, College Park, M
Application-specific design of sports equipment from anisotropic fiber-reinforced plastics with stiffness related coupling effect
AbstractFloating sports equipment such as snowboards experience extreme loads during riding it. A common style in riding a freestyle snowboard is to use a handrail to slide sideways on it. During this maneuver the steel edge of a snowboard could easily hook into the handrail, researches worked out. This will lead to an abrupt interruption in the athletes motion. This problematic aspect is eliminated by using an all new anisotropic layer design (ALD)snowboard which was developed and tested by the Professorship of Lightweight Structures and Polymer Technology (SLK) in cooperation with the Competence Center for Structural Lightweight (SLB e. V.)
DISCREPANCIES BETWEEN MECHANICAL AND BIOMECHANICAL MEASUREMENTS OF SOCCER SHOE TRACTION ON ARTIFICIAL TURF
This study analyzed mechanical and biomechanical traction properties of four different stud configurations on artificial soccer turf. Mechanical traction parameters showed statistical differences between the shoe conditions for the friction coefficient during acceleration and force rates during cutting and turning. Biomechanical force ratios statistically discriminated between the four stud configurations for cutting. It is concluded that stud configurations featuring more studs are better suited for playing on artificial turf compared to more aggressive stud configurations with only a small number of studs. It was shown that a combined approach of mechanical and biomechanical testing procedures is needed for traction testing as results differ. In contrast to mechanical testing biomechanical testing can detect movement adaptation of players
Low-Velocity Impacts on a Polymeric Foam for the Passive Safety Improvement of Sports Fields: Meshless Approach and Experimental Validation
Over the past few years, foam materials have been increasingly used in the passive safety of sport fields, to mitigate the risk of crash injury. Currently, the passive safety certification process of these materials represents an expensive and time-consuming task, since a considerable number of impact tests on material samples have to be carried out by an ad hoc testing apparatus. To overcome this difficulty and speed up the design process of new protective devices, a virtual model for the low-velocity impact behaviour of foam protective mats is needed. In this study a modelling approach based on the mesh-free Element Galerkin method was developed to investigate the impact behaviour of ethylene-vinyl acetate (EVA) foam protective mats. The main advantage of this novel technique is that the difficulties related to the computational mesh distortion and caused by the large deformation of the foam material are avoided and a good accuracy is achieved at a relatively low computational cost. The numerical model was validated statistically by comparing numerical and experimental acceleration data acquired during a series of impact events on EVA foam mats of various thicknesses. The findings of this study are useful for the design and improvement of foam protective devices and allow for optimizing sports fields’ facilities by reducing head injury risk by a reliable computational method
Far and mid infrared observations of two ultracompact H II regions and one compact CO clump
Two ultracompact H II regions (IRAS 19181+1349 and 20178+4046) and one
compact molecular clump (20286+4105) have been observed at far infrared
wavelengths using the TIFR 1 m balloon-borne telescope and at mid infrared
wavelengths using ISO. Far infrared observations have been made simultaneously
in two bands with effective wavelengths of ~ 150 and ~ 210 micron, using liquid
3He cooled bolometer arrays. ISO observations have been made in seven spectral
bands using the ISOCAM instrument; four of these bands cover the emission from
Polycyclic Aromatic Hydrocarbon (PAH) molecules. In addition, IRAS survey data
for these sources in the four IRAS bands have been processed using the HIRES
routine. In the high resolution mid infrared maps as well as far infrared maps
multiple embedded energy sources have been resolved. There are structural
similarities between the images in the mid infrared and the large scale maps in
the far infrared bands, despite very different angular resolutions of the two.
Dust temperature and optical depth (tau_150 um) maps have also been generated
using the data from balloon-borne observations. Spectral energy distributions
(SEDs) for these sources have been constructed by combining the data from all
these observations. Radiation transfer calculations have been made to
understand these SEDs. Parameters for the dust envelopes in these sources have
been derived by fitting the observed SEDs. In particular, it has been found
that radial density distribution for three sources is diffrent. Whereas in the
case of IRAS 20178+4046, a steep distribution of the form r^-2 is favoured, for
IRAS 20286+4105 it is r^-1 and for IRAS 19181+1349 it the uniform distribution
(r^0). Line ratios for PAH bands have generally been found to be similar to
those for other compact H II regions but different from general H II regions.Comment: To appear in Astronomy & Astrophysics; (19 pages including 14 Figures
and 6 Tables
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