21,914 research outputs found
Accurate thickness measurement of easily compressed materials
Sheet of material is placed between two thin, uniform, and flat sheets of glass of known thickness; light pressure is applied by means of weights. Micrometer aids thickness measurement of sandwich. Thickness of two sheets of glass is then subtracted
Improved insulating materials effective at extremely high temperatures
Wrapped molybdenum foil with silica fabric insulation and wrapped tantalum foil with carbon fabric insulation are usable to 1367 K and up to 2478 K, respectively, both offer marked space saving and efficiency in high temperature operations. Graph displays temperature profiles at end of firing period
Selective tube roughening increases heat transfer capability
Selectively roughening inside surfaces of tubes increases the heat transfer capabilities, but minimizes the pressure drop. This technique is used to construct roughened test sections for hydrogen heat transfer studies
A New Nearctic Triclistus (Hymenoptera: Ichneumonidae)
[excerpt] When Townes and Townes (1959) revised the genus Triclistus along with the rest of the Nearctic Metopiinae, they decided not to describe what was thought likely to be an additional new species, because only one male specimen was known. More recently, additional specimens, both males and females, were collected. From the females, which are even more distinctive than the males, it was easily seen that the species described below is indeed a new one
A modification to linearized theory for prediction of pressure loadings on lifting surfaces at high supersonic Mach numbers and large angles of attack
A new linearized-theory pressure-coefficient formulation was studied. The new formulation is intended to provide more accurate estimates of detailed pressure loadings for improved stability analysis and for analysis of critical structural design conditions. The approach is based on the use of oblique-shock and Prandtl-Meyer expansion relationships for accurate representation of the variation of pressures with surface slopes in two-dimensional flow and linearized-theory perturbation velocities for evaluation of local three-dimensional aerodynamic interference effects. The applicability and limitations of the modification to linearized theory are illustrated through comparisons with experimental pressure distributions for delta wings covering a Mach number range from 1.45 to 4.60 and angles of attack from 0 to 25 degrees
Application of an aerodynamic analysis method including attainable thrust estimates to low speed leading-edge flap design for supersonic cruise vehicles
A study of low speed leading-edge flap design for supersonic cruise vehicle was conducted. Wings with flaps were analyzed with the aid of a newly developed subsonic wing program which provides estimates of attainable leading-edge thrust. Results indicate that the thrust actually attainable can have a significant influence on the design and that the resultant flaps can be smaller and simpler than those resulting from more conventional approaches
The design and analysis of simple low speed flap systems with the aid of linearized theory computer programs
The purpose here is to show how two linearized theory computer programs in combination may be used for the design of low speed wing flap systems capable of high levels of aerodynamic efficiency. A fundamental premise of the study is that high levels of aerodynamic performance for flap systems can be achieved only if the flow about the wing remains predominantly attached. Based on this premise, a wing design program is used to provide idealized attached flow camber surfaces from which candidate flap systems may be derived, and, in a following step, a wing evaluation program is used to provide estimates of the aerodynamic performance of the candidate systems. Design strategies and techniques that may be employed are illustrated through a series of examples. Applicability of the numerical methods to the analysis of a representative flap system (although not a system designed by the process described here) is demonstrated in a comparison with experimental data
Infinitesimal Variations of Hodge Structure at Infinity
By analyzing the local and infinitesimal behavior of degenerating polarized
variations of Hodge structure the notion of infinitesimal variation of Hodge
structure at infinity is introduced. It is shown that all such structures can
be integrated to polarized variations of Hodge structure and that, conversely,
all are limits of infinitesimal variations of Hodge structure (IVHS) at finite
points. As an illustration of the rich information encoded in this new
structure, some instances of the maximal dimension problem for this type of
infinitesimal variation are presented and contrasted with the "classical" case
of IVHS at finite points
Band structure of Charge Ordered Doped Antiferromagnets
We study the distribution of electronic spectral weight in a doped
antiferromagnet with various types of charge order and compare to angle
resolved photoemission experiments on lightly doped LaSrCuO
(LSCO) and electron doped NdCeCuO. Calculations on
in-phase stripe and bubble phases for the electron doped system are both in
good agreement with experiment including in particular the existence of in-gap
spectral weight. In addition we find that for in-phase stripes, in contrast to
anti-phase stripes, the chemical potential is likely to move with doping. For
the hole doped system we find that ``staircase'' stripes which are globally
diagonal but locally vertical or horizontal can reproduce the photoemission
data whereas pure diagonal stripes cannot. We also calculate the magnetic
structure factors of such staircase stripes and find that as the stripe
separation is decreased with increased doping these evolve from diagonal to
vertical separated by a coexistence region. The results suggest that the
transition from horizontal to diagonal stripes seen in neutron scattering on
underdoped LSCO may be a crossover between a regime where the typical length of
straight stripe segments is longer than the inter-stripe spacing to one where
it is shorter and that locally the stripes are always aligned with the Cu-O
bonds.Comment: 13 pages, 16 figure
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