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Accelerational Implications of Hummingbird Display Dives
Integrative Biolog
Citizen Soldiers: The North Carolina Volunteers and the War on Poverty
During the summers of 1964 and 1965, more than 300 college students fanned out across the state of North Carolina in a bold campaign to defeat poverty and, as they saw it, to uplift the poor. Korstad and Leloudis trace the history of the North Carolina Fund\u27s Volunteers program, provide an analysis of the contribution that those students made to fighting poverty in the state, and evaluate the impact of that experience on the lives of the Volunteers themselves
Catalytic ignition of hydrogen and oxygen propellants
An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalyst are presented
Income growth shows Houston's economic strength and maturity
Metropolitan areas ; Economics ; Wages ; Natural gas
Catalytic ignition of hydrogen/oxygen
An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen. Shell 405 granular catalyst and a unique monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant inlet temperature, and back pressure were varied parametrically in testing to determine the operational limits of a catalytic igniter. The test results showed that the gaseous hydrogen/oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. The results of the experimental program and the established operational limits for a catalytic igniter using both the granular and monolithic catalysts are presented. The capabilities of a facility constructed to conduct the igniter testing and the advantages of a catalytic igniter over other ignition systems for gaseous hydrogen and oxygen are also discussed
An evaluation of metallized propellants based on vehicle performance
An analytical study was conducted to determine the improvements in vehicle performance possible by burning metals with conventional liquid bipropellants. These metallized propellants theoretically offer higher specific impulse, increased propellant density and improved vehicle performance compared with conventional liquid bipropellants. Metals considered were beryllium, lithium, aluminum and iron. Liquid bipropellants were H2/O2, N2H4/N2O4, RP-1/O2 and H2/F2. A mission with a delta V = 4267.2 m/sec (14,000 ft/sec) and vehicle with propellant volume fixed at 56.63 cu m (2000 cu ft) and dry mass fixed at 2761.6 kg (6000 lb) was used, roughly representing the transfer of a chemically propelled upper-stage vehicle from a low-Earth orbit to a geosynchronous orbit. The results of thermochemical calculations and mission analysis calculations for bipropellants metallized with beryllium, lithium, aluminum and iron are presented. Technology issues pertinent to metallized propellants are discussed
Amplitude death criteria for coupled complex Ginzburg-Landau systems
Amplitude death, which occurs in a system when one or more macroscopic
wavefunctions collapse to zero, has been observed in mutually coupled
solid-state lasers, analog circuits, and thermoacoustic oscillators, to name a
few applications. While studies have considered amplitude death on oscillator
systems and in externally forced complex Ginzburg-Landau systems, a route to
amplitude death has not been studied in autonomous continuum systems. We derive
simple analytic conditions for the onset of amplitude death of one macroscopic
wavefunction in a system of two coupled complex Ginzburg-Landau equations with
general nonlinear self- and cross-interaction terms. Our results give a more
general theoretical underpinning for recent amplitude death results reported in
the literature, and suggest an approach for tuning parameters in such systems
so that they either permit or prohibit amplitude death of a wavefunction
(depending on the application). Numerical simulation of the coupled complex
Ginzburg-Landau equations, for examples including cubic, cubic-quintic, and
saturable nonlinearities, is used to illustrate the analytical results.Comment: 7 pages, 4 figure
Metals Production Requirements for Rapid Photovoltaics Deployment
If global photovoltaics (PV) deployment grows rapidly, the required input
materials need to be supplied at an increasing rate. In this paper, we quantify
the effect of PV deployment levels on the scale of metals production. For
example, we find that if cadmium telluride {copper indium gallium diselenide}
PV accounts for more than 3% {10%} of electricity generation by 2030, the
required growth rates for the production of indium and tellurium would exceed
historically-observed production growth rates for a large set of metals. In
contrast, even if crystalline silicon PV supplies all electricity in 2030, the
required silicon production growth rate would fall within the historical range.
More generally, this paper highlights possible constraints to the rate of
scaling up metals production for some PV technologies, and outlines an approach
to assessing projected metals growth requirements against an ensemble of past
growth rates from across the metals production sector. The framework developed
in this paper may be useful for evaluating the scalability of a wide range of
materials and devices, to inform technology development in the laboratory, as
well as public and private research investment
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