34,166 research outputs found
Charged particle concepts for fog dispersion
Charged particle techniques hold promise for dispersing warm fog in the terminal area of commercial airports. This report focuses on features of the charged particle technique which require further study. The basic physical principles of the technique and the major verification experiments carried out in the past are described. The fundamentals of the nozzle operation are given. The nozzle characteristics and the theory of particle charging in the nozzle are discussed, including information from extensive literature on electrostatic precipitation relative to environmental pollution control and a description of some preliminary reported analyses on the jet characteristics and interaction with neighboring jets. The equation governing the transfer of water substances and of electrical charge is given together with a brief description of several semi-empirical, mathematical expressions necessary for the governing equations. The necessary ingredients of a field experiment to verify the system once a prototype is built are described
Measurements in the turbulent boundary layer at constant pressure in subsonic and supersonic flow. Part 1: Mean flow
Experiments were carried out to test the accuracy of laser Doppler instrumentation for measurement of Reynolds stresses in turbulent boundary layers in supersonic flow. Two facilities were used to study flow at constant pressure. In one facility, data were obtained on a flat plate at M sub e = 0.1, with Re theta up to 8,000. In the other, data were obtained on an adiabatic nozzle wall at M sub e = 0.6, 0.8, 1.0, 1.3, and 2.2, with Re theta = 23,000 and 40,000. The mean flow as observed using Pitot tube, Preston tube, and floating element instrumentation is described. Emphasis is on the use of similarity laws with Van Driest scaling and on the inference of the shearing stress profile and the normal velocity component from the equations of mean motion. The experimental data are tabulated
Monte Carlo calculations of energy depositions and radiation transport. Volume 1 - Validation of COHORT codes
Monte Carlo codes for IBM 7090 digital computer to calculate radiation heating in propellant tanks, and radiation environment about nuclear rocket stag
X-ray photoelectron spectroscopy investigation of the mixed anion GaSb/InAs heterointerface
X-ray photoelectron spectroscopy has been used to measure levels of anion cross-incorporation and to study interface formation for the mixed anion GaSb/lnAs heterojunction. Anion
cross-incorporation was measured in 20 Å thick GaSb layers grown on lnAs, and 20 Å thick InAs layers grown on GaSb for cracked and uncracked sources. It was found that significantly
less anion cross-incorporation occurs in structures grown with cracked sources. Interface formation was investigated by studying Sb soaks of InAs surfaces and As soaks of GaSb surfaces
as a function of cracker power and soak time. Exchange of the group V surface atoms was found to be an increasing function of both cracker power and soak time. We find that further
optimization of current growth parameters may be possible by modifying the soak time used at interfaces
Programmable networks for quantum algorithms
The implementation of a quantum computer requires the realization of a large
number of N-qubit unitary operations which represent the possible oracles or
which are part of the quantum algorithm. Until now there are no standard ways
to uniformly generate whole classes of N-qubit gates. We have developed a
method to generate arbitrary controlled phase shift operations with a single
network of one-qubit and two-qubit operations. This kind of network can be
adapted to various physical implementations of quantum computing and is
suitable to realize the Deutsch-Jozsa algorithm as well as Grover's search
algorithm.Comment: 4 pages. Accepted version; Journal-ref. adde
Role of climate feedback on methane and ozone studied with a coupled ocean-atmosphere-chemistry model.
Study of interface asymmetry in InAs–GaSb heterojunctions
We present reflection high energy electron diffraction, secondary ion mass spectroscopy, scanning tunneling microscopy and x‐ray photoelectron spectroscopy studies of the abruptness of InAs–GaSb interfaces. We find that the interface abruptness depends on growth order: InAs grown on GaSb is extended, while GaSb grown on InAs is more abrupt. We first present observations of the interfacial asymmetry, including measurements of band alignments as a function of growth order. We then examine more detailed studies of the InAs–GaSb interface to determine the mechanisms causing the extended interface. Our results show that Sb incorporation into the InAs overlayer and As exchange for Sb in the GaSb underlayer are the most likely causes of the interfacial asymmetry
Seed Yield Prediction Models of Four Common Moist-Soil Plant Species in Texas
Seed production by moist-soil plant species often varies within and among managed wetlands and on larger landscapes. Quantifying seed production of moist-soil plants can be used to evaluate wetland management strategies and estimate wetland energetic carrying capacity, specifically for waterfowl. In the past, direct estimation techniques were used, but due to excessive personnel and time costs, other indirect methods have been developed. Because indirect seed yield models do not exist for moist-soil plant species in east-central or coastal Texas, we developed direct and indirect methods to model seed production on regional managed wetlands. In September 2004 and 2005, we collected Echinochloa crusgalli (barnyard grass), E. walterii (wild millet), E. colona (jungle rice), and Oryza sativa (cultivated rice) for phytomorphological measurements and seed yield modeling. Initial simple linear and point of origin regression analyses demonstrate strong relationships (P \u3c 0.001) among phytomorphological and dot grid methods in predicting seed production for all four species. These models should help regional wetland managers evaluate moist-soil management success and create models for seed production for other moist-soil plants in this region
Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model
The impact of convection on tropospheric O<sub>3</sub> and its precursors has been examined in a coupled chemistry-climate model. There are two ways that convection affects O<sub>3</sub>. First, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> itself. Convection lifts lower tropospheric air to regions where the O<sub>3</sub> lifetime is longer, whilst mass-balance subsidence mixes O<sub>3</sub>-rich upper tropospheric (UT) air downwards to regions where the O<sub>3</sub> lifetime is shorter. This tends to decrease UT O<sub>3</sub> and the overall tropospheric column of O<sub>3</sub>. Secondly, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> precursors. This affects O<sub>3</sub> chemical production and destruction. Convection transports isoprene and its degradation products to the UT where they interact with lightning NO<sub>x</sub> to produce PAN, at the expense of NO<sub>x</sub>. In our model, we find that convection reduces UT NO<sub>x</sub> through this mechanism; convective down-mixing also flattens our imposed profile of lightning emissions, further reducing UT NO<sub>x</sub>. Over tropical land, which has large lightning NO<sub>x</sub> emissions in the UT, we find convective lofting of NO<sub>x</sub> from surface sources appears relatively unimportant. Despite UT NO<sub>x</sub> decreases, UT O<sub>3</sub> production increases as a result of UT HO<sub>x</sub> increases driven by isoprene oxidation chemistry. However, UT O<sub>3</sub> tends to decrease, as the effect of convective overturning of O<sub>3</sub> itself dominates over changes in O<sub>3</sub> chemistry. Convective transport also reduces UT O<sub>3</sub> in the mid-latitudes resulting in a 13% decrease in the global tropospheric O<sub>3</sub> burden. These results contrast with an earlier study that uses a model of similar chemical complexity. Differences in convection schemes as well as chemistry schemes – in particular isoprene-driven changes are the most likely causes of such discrepancies. Further modelling studies are needed to constrain this uncertainty range
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