32,229 research outputs found
Twistable mold for helicopter blades
Design is described of mold for fabrication of blades composed of sets of aerodynamic shells having same airfoil section characteristics but different distributions. Mold consists of opposing stacks of thin templates held together by long bolts. When bolts are loosened, templates can be set at different positions with respect to each other and then locked in place
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Hydrologic verification: A call for action and collaboration
Traditionally, little attention has been focused on the systematic verification of operational hydrologic forecasts. This paper summarizes the results of forecasts verification from 15 river basins in the United States. The verification scores for these forecast locations do not show improvement over the periods of record despite a number of forecast process improvements. In considering a root cause for these results, the authors note that the current paradigm for designing hydrologic forecast process improvements is driven by expert opinion and not by objective verification measures. The authors suggest that this paradigm should be modified and objective verification metrics should become the primary driver for hydrologic forecast process improvements. ©2007 American Meteorological Society
Natural environment support guidelines for space shuttle tests and operations
All space shuttle events from launch through solid rocket booster recovery and orbiter landing are considered in terms of constraints placed on those operations by the natural environment. Thunderstorm activity is discussed as an example of a possible hazard. The activities most likely to require advanced detection and monitoring techniques are identified as those from deorbit decision to Orbiter landing. The inflexible flight plan will require the transmission of real time wind profile information below 24 km and warnings of thunderstorms or turbulence in the Orbiter flight path. Extensive aerial reconnaissance and communication facilities and procedures to permit immediate transmission of aircraft reports to the mission control authority and to the Orbiter will also be required
Renormalisation of gravitational self interaction for wiggly strings
It is shown that for any elastic string model with energy density and
tension , the divergent contribution from gravitational self interaction can
be allowed for by an action renormalisation proportional to . This
formula is applied to the important special case of a bare model of the
transonic type (characterised by a constant value of the product ) that
represents the macroscopically averaged effect of shortwavelength wiggles on an
underlying microscopic model of the Nambu-Goto type (characterised by ).Comment: 11 pages, Latex; original 8 page version extended to include
estimates of relevant orders of magnitude. To be published in Physical
Review,
Recent developments in Vorton Theory
This article provides a concise overview of recent theoretical results
concerning the theory of vortons, which are defined to be (centrifugally
supported) equilibrium configurations of (current carrying) cosmic string
loops. Following a presentation of the results of work on the dynamical
evolution of small circular string loops, whose minimum energy states are the
simplest examples of vortons, recent order of magnitude estimates of the
cosmological density of vortons produced in various kinds of theoretical
scenario are briefly summarised.Comment: 6 pages Latex. Contribution to 1996 Cosmology Meeting, Peyresq,
Franc
Recurrence relation for the 6j-symbol of su_q(2) as a symmetric eigenvalue problem
A well known recurrence relation for the 6j-symbol of the quantum group
su_q(2) is realized as a tridiagonal, symmetric eigenvalue problem. This
formulation can be used to implement an efficient numerical evaluation
algorithm, taking advantage of existing specialized numerical packages. For
convenience, all formulas relevant for such an implementation are collected in
the appendix. This realization is a byproduct of an alternative proof of the
recurrence relation, which generalizes a classical (q=1) result of Schulten and
Gordon and uses the diagrammatic spin network formalism of Temperley-Lieb
recoupling theory to simplify intermediate calculations.Comment: v3: 13 pages, ws-ijgmmp; minor corrections, slight update to
presentation; close to published versio
Reusable Agena study. Volume 2: Technical
The application of the existing Agena vehicle as a reusable upper stage for the space shuttle is discussed. The primary objective of the study is to define those changes to the Agena required for it to function in the reusable mode in the 100 percent capture of the NASA-DOD mission model. This 100 percent capture is achieved without use of kick motors or stages by simply increasing the Agena propellant load by using optional strap-on-tanks. The required shuttle support equipment, launch and flight operations techniques, development program, and cost package are also defined
Symplectic structure for elastic and chiral conducting cosmic string models
This article is based on the covariant canonical formalism and corresponding
symplectic structure on phase space developed by Witten, Zuckerman and others
in the context of field theory. After recalling the basic principles of this
procedure, we construct the conserved bilinear symplectic current for generic
elastic string models. These models describe current carrying cosmic strings
evolving in an arbitrary curved background spacetime. Particular attention is
paid to the special case of the chiral string for which the worldsheet current
is null. Different formulations of the chiral string action are discussed in
detail, and as a result the integrability property of the chiral string is
clarified.Comment: 18 page
Listing of solar radiation measuring equipment and glossary
An attempt is made to list and provide all available information about solar radiation measuring equipment which are being manufactured and are available on the market. The list is in tabular form and includes sensor type, response time, cost data and comments for each model. A cost code is included which shows ranges only
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