38,958 research outputs found
High repetition rate sealed CO2 TEA lasers using heterogeneous catalysts
The significant operational advantages offered by CO2 lasers, operating in the 10.6 micron region of the spectrum, over current solid state lasers, emitting in the near IR region, have prompted increased interest in the development of compact, reliable, rugged CO2 laser sources. Perhaps the most critical aspect associated with achieving a laser compatible with military use is the development of lasers which require no gas replenishment. Sealed, single shot, CO2 TEA lasers have been available for a number of years. Stark et al were first to demonstrate reliable sealed operation in single shot CO2 TEA lasers in 1975 using gas catalysis. GEC Avionics reported the compact, environmentally qualified, MKIII CO2 TEA laser with a pulse life of greater than 10 to the 6th power pulses in 1980. A sealed laser lifetime of greater than 10 to the 6th power pulses is acceptable for single shot cases, such as direct detection rangefinders for tank laser sights. However, in many other applications, such as tracking of fast moving targets, it is essential that a repetition rate of typically 30Hz to 100Hz is employed. In such cases, a pulse lifetime of 10 to the 6th power pulses is no longer sufficient and a minimum pulse lifetime 10 to the 7th power pulses is essential to ensure a useful service life. In 1983 Stark el al described a sealed, 100Hz CO2 TEA laser, with a life of greater than 2.6 x 10 to the 6th power, which employed heterogeneous catalysis. Following this pioneering work, GEC Avionics has been engaged in the development of sealed high repetition rate lasers with a pulse lifetime of 20 million pulses
Decoherence induced CPT violation and entangled neutral mesons
We discuss two classes of semi-microscopic theoretical models of stochastic
space-time foam in quantum gravity and the associated effects on entangled
states of neutral mesons, signalling an intrinsic breakdown of CPT invariance.
One class of models deals with a specific model of foam, initially constructed
in the context of non-critical (Liouville) string theory, but viewed here in
the more general context of effective quantum-gravity models. The relevant
Hamiltonian perturbation, describing the interaction of the meson with the foam
medium, consists of off-diagonal stochastic metric fluctuations, connecting
distinct mass eigenstates (or the appropriate generalisation thereof in the
case of K-mesons), and it is proportional to the relevant momentum transfer
(along the direction of motion of the meson pair). There are two kinds of
CPT-violating effects in this case, which can be experimentally disentangled:
one (termed ``omega-effect'') is associated with the failure of the
indistinguishability between the neutral meson and its antiparticle, and
affects certain symmetry properties of the initial state of the two-meson
system; the second effect is generated by the time evolution of the system in
the medium of the space-time foam, and can result in time-dependent
contributions of the $omega-effect type in the time profile of the two meson
state. Estimates of both effects are given, which show that, at least in
certain models, such effects are not far from the sensitivity of experimental
facilities available currently or in the near future. The other class of
quantum gravity models involves a medium of gravitational fluctuations which
behaves like a ``thermal bath''. In this model both of the above-mentioned
intrinsic CPT violation effects are not valid.Comment: 16 pages revtex, no figure
Device and method for frictionally testing materials for ignitability
Test apparatus for determining ignition characteristics of various metal in oxidizer environments simulating operating conditions for materials is invented. The test apparatus has a chamber through which the oxidizing agent flows, and means for mounting a stationary test sample therein, a powered, rotating shaft in the chamber rigidly mounts a second test sample. The shaft is axially movable to bring the samples into frictional engagement and heated to the ignition point. Instrumentation connected to the apparatus provides for observation of temperatures, pressures, loads on and speeds of the rotating shaft, and torques whereby components of stressed oxygen systems can be selected which will avoid accidental fires under working conditions
Optical enhancement of sensitivity in laser Doppler velocity systems
Utilization of optical enhancement techniques prevents loss of light by reflections at the photocathode of a photomultiplier and increases signal detection sensitivity
The Value of the Cosmological Constant
We make the cosmological constant, {\Lambda}, into a field and restrict the
variations of the action with respect to it by causality. This creates an
additional Einstein constraint equation. It restricts the solutions of the
standard Einstein equations and is the requirement that the cosmological wave
function possess a classical limit. When applied to the Friedmann metric it
requires that the cosmological constant measured today, t_{U}, be {\Lambda} ~
t_{U}^(-2) ~ 10^(-122), as observed. This is the classical value of {\Lambda}
that dominates the wave function of the universe. Our new field equation
determines {\Lambda} in terms of other astronomically measurable quantities.
Specifically, it predicts that the spatial curvature parameter of the universe
is {\Omega}_{k0} \equiv -k/a_(0)^(2)H^2= -0.0055, which will be tested by
Planck Satellite data. Our theory also creates a new picture of self-consistent
quantum cosmological history.Comment: 6 pages. This article received Third Prize in the 2011 Gravity
Research Foundation Awards for Essays on Gravitatio
Liver rejection and its differentiation from other causes of graft dysfunction.
Numerous causes can lead to hepatic dysfunction following orthotopic liver transplantation. The most common cause is rejection, which is usually nonpreventable. The clinical presentation, time of onset, and even treatment are variable. Other causes, such as perioperative ischemic injury, vascular thrombosis, and complications of bile duct reconstruction may be preventable with good surgical technique. Infections can also be minimized by careful adjustment of immunotherapy, avoidance overimmunosuppression, and the judicious use of antibiotics. Hepatic dysfunction following orthotopic liver transplantation requires rapid assessment and proper treatment in order to prevent serious and possibly fatal complications
An In Depth Study into Using EMI Signatures for Appliance Identification
Energy conservation is a key factor towards long term energy sustainability.
Real-time end user energy feedback, using disaggregated electric load
composition, can play a pivotal role in motivating consumers towards energy
conservation. Recent works have explored using high frequency conducted
electromagnetic interference (EMI) on power lines as a single point sensing
parameter for monitoring common home appliances. However, key questions
regarding the reliability and feasibility of using EMI signatures for
non-intrusive load monitoring over multiple appliances across different sensing
paradigms remain unanswered. This work presents some of the key challenges
towards using EMI as a unique and time invariant feature for load
disaggregation. In-depth empirical evaluations of a large number of appliances
in different sensing configurations are carried out, in both laboratory and
real world settings. Insights into the effects of external parameters such as
line impedance, background noise and appliance coupling on the EMI behavior of
an appliance are realized through simulations and measurements. A generic
approach for simulating the EMI behavior of an appliance that can then be used
to do a detailed analysis of real world phenomenology is presented. The
simulation approach is validated with EMI data from a router. Our EMI dataset -
High Frequency EMI Dataset (HFED) is also released
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