19,483 research outputs found
Latest developments in cryogenic safety
The Cryogenic Safety Manual, sponsored by the British Cryogenics Council, was published over 10 years ago. A new updated version is now available. Some general aspects of cryogenic safety are highlighted, and attention is drawn to some of the more unusual hazardous situations. An awareness of the physical properties of the cryogenic fluids being dealt with is important in directing attention to hazardous situations which may arise. Because of this, the more important properties of the cryogenic fluids are given, such as molecular weight, boiling point and freezing point. From these properties, hazardous situations can be deduced. There are hidden dangers that are not always easy to spot. Some of the unexpected hazards, most of which have led to deaths, are: asphyxiation (anoxia), frost bites and hypothermia, explosions, and combustion. The aim of this publication is to help bring about increased safety in the production and use of cryogenic products through a deeper appreciation of the scientific, technological and administrative steps which must be made if accidents, some fatal, are to be voided in the future
Possible safety hazards associated with the operation of the 0.3-m transonic cryogenic tunnel at the NASA Langley Research Center
The 0.3 m Transonic Cryogenic Tunnel (TCT) at the NASA Langley Research Center was built in 1973 as a facility intended to be used for no more than 60 hours in order to verify the validity of the cryogenic wind tunnel concept at transonic speeds. The role of the 0.3 m TCT has gradually changed until now, after over 3000 hours of operation, it is classified as a major NASA research facility and, under the administration of the Experimental Techniques Branch, it is used extensively for the testing of airfoils at high Reynolds numbers and for the development of various technologies related to the efficient operation and use of cryogenic wind tunnels. The purpose of this report is to document the results of a recent safety analysis of the 0.3 m TCT facility. This analysis was made as part of an on going program with the Experimental Techniques Branch designed to ensure that the existing equipment and current operating procedures of the 0.3 m TCT facility are acceptable in terms of today's standards of safety for cryogenic systems
Eliminating flutter for clamped von Karman plates immersed in subsonic flows
We address the long-time behavior of a non-rotational von Karman plate in an
inviscid potential flow. The model arises in aeroelasticity and models the
interaction between a thin, nonlinear panel and a flow of gas in which it is
immersed [6, 21, 23]. Recent results in [16, 18] show that the plate component
of the dynamics (in the presence of a physical plate nonlinearity) converge to
a global compact attracting set of finite dimension; these results were
obtained in the absence of mechanical damping of any type. Here we show that,
by incorporating mechanical damping the full flow-plate system, full
trajectories---both plate and flow---converge strongly to (the set of)
stationary states. Weak convergence results require "minimal" interior damping,
and strong convergence of the dynamics are shown with sufficiently large
damping. We require the existence of a "good" energy balance equation, which is
only available when the flows are subsonic. Our proof is based on first showing
the convergence properties for regular solutions, which in turn requires
propagation of initial regularity on the infinite horizon. Then, we utilize the
exponential decay of the difference of two plate trajectories to show that full
flow-plate trajectories are uniform-in-time Hadamard continuous. This allows us
to pass convergence properties of smooth initial data to finite energy type
initial data. Physically, our results imply that flutter (a non-static end
behavior) does not occur in subsonic dynamics. While such results were known
for rotational (compact/regular) plate dynamics [14] (and references therein),
the result presented herein is the first such result obtained for
non-regularized---the most physically relevant---models
Improved calorimeter provides accurate thermal measurements of space batteries
Isothermal continuous flow calorimeter measures the thermal characteristics of space batteries undergoing typical orbital cycling. This is 28 times as sensitive as calorimeters previously used
Flow-plate interactions: Well-posedness and long-time behavior
We consider flow-structure interactions modeled by a modified wave equation
coupled at an interface with equations of nonlinear elasticity. Both subsonic
and supersonic flow velocities are treated with Neumann type flow conditions,
and a novel treatment of the so called Kutta-Joukowsky flow conditions are
given in the subsonic case. The goal of the paper is threefold: (i) to provide
an accurate review of recent results on existence, uniqueness, and stability of
weak solutions, (ii) to present a construction of finite dimensional,
attracting sets corresponding to the structural dynamics and discuss
convergence of trajectories, and (iii) to state several open questions
associated with the topic. This second task is based on a decoupling technique
which reduces the analysis of the full flow-structure system to a PDE system
with delay.Comment: 1 figure. arXiv admin note: text overlap with arXiv:1208.5245,
arXiv:1311.124
Heater improves cold-temperature capacity of silver-cadmium batteries
Eight heaters are included in 14-cell package to provide 14-Vdc. Each heater is 11-ohm self-adhesive strip placed across broad face of each pair of cells. They are installed before cells are wired. Heaters are in series and are connected through pair of redundant thermostats
Research into fundamental phenomena associated with spacecraft electrochemical devices - calorimetry of nickel-cadmium cells Progress report, 1 Oct. 1966 - 31 Dec. 1966
Cycling, charge efficiency, and transducer studies with nickel-cadmium cell for spacecraft power supply system
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