5,007 research outputs found
Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays
Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (neff - no) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle
Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment
Measurement of high-power proton beam-halo formation is the ongoing
scientific experiment for the Low Energy Demonstration Accelerator (LEDA)
facility. To attain this measurement goal, a 52-magnet beam line containing
several types of beam diagnostic instrumentation is being installed. The
Experimental Physics and Industrial Control System (EPICS) and commercial
software applications are presently being integrated to provide a real-time,
synchronous data acquisition and control system. This system is comprised of
magnet control, vacuum control, motor control, data acquisition, and data
analysis. Unique requirements led to the development and integration of
customized software and hardware. EPICS real-time databases, Interactive Data
Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation
Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which
interact using the EPICS Channel Access (CA) communication protocol.
Acquisition and control hardware technology ranges from DSP-based diagnostic
instrumentation to the PLC-controlled vacuum system. This paper describes the
control system hardware and software design, and implementation.Comment: LINAC2000 Conference, 4 pg
X-ray Over-Luminous Elliptical Galaxies: A New Class of Mass Concentrations in the Universe?
We detect four isolated, X-ray over-luminous (Lx>2e43 [h/0.5]**-2 erg/s)
elliptical galaxies (OLEGs) in our 160 square degree ROSAT PSPC survey. The
extent of their X-ray emission, total X-ray luminosity, total mass, and mass of
the hot gas in these systems correspond to poor clusters, and the optical
luminosity of the central galaxies (M_R<-22.5 + 5 lg h) is comparable to that
of cluster cDs. However, there are no detectable fainter galaxy concentrations
around the central elliptical. The mass-to-light ratio within the radius of
detectable X-ray emission is in the range 250-450 Msun/Lsun, which is 2-3 times
higher than typically found in clusters or groups. These objects can be the
result of galaxy merging within a group. However, their high M/L values are
difficult to explain in this scenario. OLEGs must have been undisturbed for a
very long time, which makes them the ultimate examples of systmes in
hydrostatic equilibrium. The number density of OLEGs is n=2.4(+3.1-1.2}x10**-7
(h/0.5)**-3 Mpc**-3 at the 90% confidence. They comprise 20% of all clusters
and groups of comparable X-ray luminosity, and nearly all galaxies brighter
than M_R=-22.5. The estimated contirubution of OLEGs to the total mass density
in the Universe is close to that of T>7 keV clusters.Comment: 4 pages, 2 figures, uses emulateapj.sty, submitted to ApJ Letter
Magnetic properties of the complex concentrated alloy system CoFeNi0.5Cr0.5Alx
We study the change in magnetisation with paramagnetic Al addition in the CoFeNi0.5Cr0.5–Alx (x: 0, 0.5, 1, and 1.5) complex concentrated alloy. The compositions were developed utilising the Mulliken electronegativity and d-electron/atom ratio. Spherical FeCr rich nanoprecipitates are observed for X: 1.0 and 1.5 in an AlCoNi-rich matrix. A ~ 5 × increase in magnetisation (from 22 to 96 Am2/kg) coincides with this nanoprecipitate formation—the main magnetic contribution is determined to be from FeCr nanoprecipitates. The magnetisation increase is strange as paramagnetic Al addition dilutes the ferromagnetic Fe/Co/Ni additions. In this paper we discuss the magnetic and structural characterisation of the CoFeNi0.5Cr0.5–Alx composition and attempt to relate it to the interfacial energy
Evolution of the Cluster X-ray Luminosity Function
We report measurements of the cluster X-ray luminosity function out to z=0.8
based on the final sample of 201 galaxy systems from the 160 Square Degree
ROSAT Cluster Survey. There is little evidence for any measurable change in
cluster abundance out to z~0.6 at luminosities less than a few times 10^44
ergs/s (0.5-2.0 keV). However, between 0.6 < z < 0.8 and at luminosities above
10^44 ergs/s, the observed volume densities are significantly lower than those
of the present-day population. We quantify this cluster deficit using
integrated number counts and a maximum-likelihood analysis of the observed
luminosity-redshift distribution fit with a model luminosity function. The
negative evolution signal is >3 sigma regardless of the adopted local
luminosity function or cosmological framework. Our results and those from
several other surveys independently confirm the presence of evolution. Whereas
the bulk of the cluster population does not evolve, the most luminous and
presumably most massive structures evolve appreciably between z=0.8 and the
present. Interpreted in the context of hierarchical structure formation, we are
probing sufficiently large mass aggregations at sufficiently early times in
cosmological history where the Universe has yet to assemble these clusters to
present-day volume densities.Comment: 15 pages, 10 figures, accepted for publication in Ap
The 160 Square Degree ROSAT Survey: the Revised Catalog of 201 Clusters with Spectroscopic Redshifts
We present the revised catalog of galaxy clusters detected as extended X-ray
sources in the 160 Square Degree ROSAT Survey, including spectroscopic
redshifts and X-ray luminosities for 200 of the 201 members. The median
redshift is z~0.25 and the median X-ray luminosity is 4.2e+43 erg/s/h50^2
(0.5-2.0 keV). This is the largest high-redshift sample of X-ray selected
clusters published to date. There are 73 objects at z>0.3 and 22 objects at
z>0.5 drawn from a statistically complete flux-limited survey with a median
object flux of 1.4d-13 erg/cm^2/s. We describe the optical follow-up of these
clusters with an emphasis on our spectroscopy which has yielded 155 cluster
redshifts, 110 of which are presented here for the first time. These
measurements combined with 45 from the literature and other sources provide
near-complete spectroscopic coverage for our survey. We discuss the final
optical identifications for the extended X-ray sources in the survey region and
compare our results to similar X-ray cluster searches.Comment: 17 pages, 7 figs, accepted for publication in ApJ, a version with
full resolution images is available at
http://www.eso.org/~cmullis/papers/160sd-catalog.ps.gz, machine-readable
versions of the catalog are available at
http://www.eso.org/~cmullis/research/160sd-catalog.htm
Applications of infrared thermography in sports. A review
La termografía infrarroja (TI) registra el calor irradiado de un cuerpo, que es emitido en un rango del espectro electromagnético que la visión humana no es capaz de identificar. La respuesta térmica depende de una serie de ajustes fisiológicos específicos como la homeostasis corporal y salud del deportista, lo cual permite establecer interesantes aplicaciones en el deporte. El objetivo de este trabajo ha sido revisar la literatura en torno a las aplicaciones de la TI en el ámbito del deporte, y proponer las características óptimas del registro en relación al evaluado, las condiciones ambientales y la cámara utilizada. Concluimos que la principal contribución de la TI en el ámbito del deporte es ayudar a identificar
signos de lesión antes de que la lesión se produzca, permitiéndonos actuar de manera preventiva durante el proceso de entrenamientoInfrared thermography (IRT) records the radiant heat of a body, which is emitted in the range of the electromagnetic spectrum that human vision is not able to identify. The thermal response depends on a number of specific physiological adjustments as body homeostasis and athlete’s health, which allow us to establishing interesting applications in sport. The aim of this study was to review the literature on IRT applications in sports, and to propose the optimal characteristics of the register in terms of the subject, the environmental conditions and the camera used. We conclude that the main contribution of IRT in the field of sport is to help identify signs of injury before it occurs, allowing us to act proactively along the training proces
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