28,631 research outputs found
Offshore Space Center (offshore launch site)
Any activity requiring the development of the HLLV can benefit by operations from an offshore space center (OSC) since operating near the equator provides a twenty percent increase in payload in an ecliptic plan orbit. Some OSC concepts considered include a moored floating (semisubmersible) design, a stationary design supported by fixed piles, and a combination of these two. The facility supports: a 15,000 foot long, 300 foot wide runway, designed to accommodate a two staged winged launch vehicle, with a one million pound payload capacity to low earth orbit; an industrial area for HLLV maintenance; an airport terminal, control and operation center, and observation tower; liquid hydrogen and liquid oxygen production and storage, and fuel storage platforms; a power generation station, docks with an unloading area; two separate launch sites; and living accommodations for 10,000 people. Potential sites include the Paramount Seamount in the Pacific Ocean off the north coast of South America. Cost estimates are considered
Flexible drive allows blind machining and welding in hard-to-reach areas
Flexible power and control unit performs welding and machining operations in confined areas. A machine/weld head is connected to the unit by a flexible transmission shaft, and a locking- indexing collar is incorporated onto the head to allow it to be placed and held in position
Transverse spreading of electrons in high-intensity laser fields
We show that for collisions of electrons with a high-intensity laser,
discrete photon emissions introduce a transverse beam spread which is distinct
from that due to classical (or beam shape) effects. Via numerical simulations,
we show that this quantum induced transverse momentum gain of the electron is
manifest in collisions with a realistic laser pulse of intensity within reach
of current technology, and we propose it as a measurable signature of
strong-field quantum electrodynamics.Comment: 5 pages, 3 figures. Accepted for publication in Physical Review
Letter
SIMLA: Simulating laser-particle interactions via classical and quantum electrodynamics
We present the Fortran code SIMLA, which is designed for the study of charged
particle dynamics in laser and other background fields. This can be done
classically via the Landau-Lifshitz equation, or alternatively, via the
simulation of photon emission events determined by strong-field
quantum-electrodynamics amplitudes and implemented using Monte-Carlo type
routines. Multiple laser fields can be included in the simulation and the
propagation direction, beam shape (plane wave, focussed paraxial, constant
crossed, or constant magnetic), and time envelope of each can be independently
specified.Comment: Submitted to Comp. Phys. Comm. The associated computer program and
corresponding manual will be made available on the CPC librar
EFFECTS OF ENERGY DEVELOPMENT ON AGRICULTURAL LAND VALUES
This paper uses multiple regression analysis to examine the effects of energy resource development on sale prices of agricultural land in western North Dakota. The findings suggest that energy resources development has exerted only modest upward pressure on agricultural land values in the northern Great Plains. The land market in this region remains dominated by active farmers who are purchasing farmland as a long-term investment, and energy development has not had a major impact on the structure of that market.Land Economics/Use, Resource /Energy Economics and Policy,
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Geographies of Production II: Political Economic Geographies: A pluralist direction?
Within economic geography, it has been argued that political economy approaches have diminished in both prevalence and influence to the detriment of both the sub-discipline and to human geography as a whole. This report challenges such a perspective, arguing that political economic geographies remains very much vibrant and engaging in contemporary economic geography and in the way in which economic geographers engages with the nature of the contemporary global economy. It argues that the perceived retreat of political economy approaches corresponds more to a diversification of the ways in which political economic thinking is integrated into more recent economic geography, acknowledging that this does reduce the apparent coherence around a singular articulation or approach to geographical political economy. However, it also seeks to demonstrate through reviewing recent pluralist theoretical work that political economic geography has broadened its theoretical framework and thus made significant contributions to ongoing debates around the geographies of production within the sub-discipline that had not previously been the object of political economic analysis
Focusing a fountain of neutral cesium atoms with an electrostatic lens triplet
An electrostatic lens with three focusing elements in an alternating-gradient
configuration is used to focus a fountain of cesium atoms in their ground
(strong-field-seeking) state. The lens electrodes are shaped to produce only
sextupole plus dipole equipotentials which avoids adding the unnecessary
nonlinear forces present in cylindrical lenses. Defocusing between lenses is
greatly reduced by having all of the main electric fields point in the same
direction and be of nearly equal magnitude. The addition of the third lens gave
us better control of the focusing strength in the two transverse planes and
allowed focusing of the beam to half the image size in both planes. The beam
envelope was calculated for lens voltages selected to produced specific
focusing properties. The calculations, starting from first principles, were
compared with measured beam sizes and found to be in good agreement.
Application to fountain experiments, atomic clocks, and focusing polar
molecules in strong-field-seeking states is discussed.Comment: 8 pages 10 figure
Elements of Design for Containers and Solutions in the LinBox Library
We describe in this paper new design techniques used in the \cpp exact linear
algebra library \linbox, intended to make the library safer and easier to use,
while keeping it generic and efficient. First, we review the new simplified
structure for containers, based on our \emph{founding scope allocation} model.
We explain design choices and their impact on coding: unification of our matrix
classes, clearer model for matrices and submatrices, \etc Then we present a
variation of the \emph{strategy} design pattern that is comprised of a
controller--plugin system: the controller (solution) chooses among plug-ins
(algorithms) that always call back the controllers for subtasks. We give
examples using the solution \mul. Finally we present a benchmark architecture
that serves two purposes: Providing the user with easier ways to produce
graphs; Creating a framework for automatically tuning the library and
supporting regression testing.Comment: 8 pages, 4th International Congress on Mathematical Software, Seoul :
Korea, Republic Of (2014
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