17,455 research outputs found
Computer integration of hydrodynamics equations for heat pipes
Program has five operational modes that provide user flexibility in answering crucial heat-pipe design questions. User specifies heat input and rejection distribution
Journal Staff
Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape
Lifetimes and Gj factors in excited states of chromium. Hyperfine structure of Cr53
Electronic and nuclear properties of excited chromium isotopes using level crossing and double resonance spectroscopy technique
Singlet levels of the NV centre in diamond
The characteristic transition of the NV- centre at 637 nm is between
and triplet states. There are also
intermediate and singlet states, and the
infrared transition at 1042 nm between these singlets is studied here using
uniaxial stress. The stress shift and splitting parameters are determined, and
the physical interaction giving rise to the parameters is considered within the
accepted electronic model of the centre. It is established that this
interaction for the infrared transition is due to a modification of
electron-electron Coulomb repulsion interaction. This is in contrast to the
visible 637 nm transition where shifts and splittings arise from modification
to the one-electron Coulomb interaction. It is also established that a dynamic
Jahn-Teller interaction is associated with the singlet state,
which gives rise to a vibronic level 115 above the
electronic state. Arguments associated with this level are
used to provide experimental confirmation that the is the
upper singlet level and is the lower singlet level.Comment: 19 pages, 6 figure
Modeling Disordered Quantum Systems with Dynamical Networks
It is the purpose of the present article to show that so-called network
models, originally designed to describe static properties of disordered
electronic systems, can be easily generalized to quantum-{\em dynamical}
models, which then allow for an investigation of dynamical and spectral
aspects. This concept is exemplified by the Chalker-Coddington model for the
Quantum Hall effect and a three-dimensional generalization of it. We simulate
phase coherent diffusion of wave packets and consider spatial and spectral
correlations of network eigenstates as well as the distribution of
(quasi-)energy levels. Apart from that it is demonstrated how network models
can be used to determine two-point conductances. Our numerical calculations for
the three-dimensional model at the Metal-Insulator transition point delivers
among others an anomalous diffusion exponent of .
The methods presented here in detail have been used partially in earlier work.Comment: 16 pages, Rev-TeX. to appear in Int. J. Mod. Phys.
Variable Conductance Heat Pipe Technology
A research and development program in variable conductance heat pipe technology is reported. The project involved: (1) theoretical and/or experimental studies in hydrostatics, (2) hydrodynamics, (3) heat transfer into and out of the pipe, (4) fluid selection, and (5) materials compatibility. The development, fabrication, and test of the space hardware resulted in a successful flight of the heat pipe experiment on the OAO-3 satellite. A summary of the program is provided and a guide to the location of publications on the project is included
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