19,998 research outputs found
Heat exchanger with oscillating flow
Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators, or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit
Implementation of the barotropic vorticity equation on the MPP
A finite difference version of the equations governing two-dimensional, non-divergent flow on a sphere is implemented and integrated on the Massively Parallel Processor (MPP). The MPP's performance is then compared with the Cyber's. The feasibility of using a massively parallel architecture to solve the hydrodynamic equations as they are used in numerical weather prediction (NWP) are described
Omniscopes: Large Area Telescope Arrays with only N log N Computational Cost
We show that the class of antenna layouts for telescope arrays allowing cheap
analysis hardware (with correlator cost scaling as N log N rather than N^2 with
the number of antennas N) is encouragingly large, including not only previously
discussed rectangular grids but also arbitrary hierarchies of such grids, with
arbitrary rotations and shears at each level. We show that all correlations for
such a 2D array with an n-level hierarchy can be efficiently computed via a
Fast Fourier Transform in not 2 but 2n dimensions. This can allow major
correlator cost reductions for science applications requiring exquisite
sensitivity at widely separated angular scales, for example 21cm tomography
(where short baselines are needed to probe the cosmological signal and long
baselines are needed for point source removal), helping enable future 21cm
experiments with thousands or millions of cheap dipole-like antennas. Such
hierarchical grids combine the angular resolution advantage of traditional
array layouts with the cost advantage of a rectangular Fast Fourier Transform
Telescope. We also describe an algorithm for how a subclass of hierarchical
arrays can efficiently use rotation synthesis to produce global sky maps with
minimal noise and a well-characterized synthesized beam.Comment: Replaced to match accepted PRD version. 10 pages, 9 fig
Multi-Lattice Kinetic Monte Carlo Simulations from First-Principles: Reduction of the Pd(100) Surface Oxide by CO
We present a multi-lattice kinetic Monte Carlo (kMC) approach that
efficiently describes the atomistic dynamics of morphological transitions
between commensurate structures at crystal surfaces. As an example we study the
reduction of a PdO(101) overlayer on
Pd(100) in a CO atmosphere. Extensive density-functional theory calculations
are used to establish an atomistic pathway for the oxide reduction process.
First-principles multi-lattice kMC simulations on the basis of this pathway
fully reproduce the experimental temperature dependence of the reduction rate
[Fernandes et al., Surf. Sci. 2014, 621, 31-39] and highlight the crucial role
of elementary processes special to the boundary between oxide and metal
domains.Comment: 19 pages, 10 figure
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