14,239 research outputs found
Swashplate control system
A mechanical system to control the position of a rotating swashplate is developed. This system provides independent lateral cyclic, longitudinal cyclic and collective pitch control of a helicopter rotor attached to the swashplate, without use of a mixer box. The system also provide direct, linear readout of cyclic and collective swashplate positions
Oil
With only two lecture periods devoted to the subject of Oil this year, my presentation this morning will be limited to a quick survey of some of the fundamentals of our petroleum situation, and to preparing you for Admiral Biggs\u27 more detailed discussion of some of the military problems which we may face
Micrasema kluane, a probable stepping stone to the Arctic (Trichoptera, Brachycentridae)
The arctic fauna has tactily been considered as a collection of offshoots arising from elements of the boreal deciduous forest, its neighboring biome to the south. Two circumstances make this conjecture plausible. First, the Arctic has a relatively small fauna compared to biomes south of it, and second, the animal species found in the Arctic usually show phylogenetic affinities to groups found in more southern regions. In order to test the validity of the boreal-to-arctic evolutionary pathway, it is necessary to discover circumstances in which the arctic species are derived entities that evolved from more ancestral southern relatives
Resonance modes in a 1D medium with two purely resistive boundaries: calculation methods, orthogonality and completeness
Studying the problem of wave propagation in media with resistive boundaries
can be made by searching for "resonance modes" or free oscillations regimes. In
the present article, a simple case is investigated, which allows one to
enlighten the respective interest of different, classical methods, some of them
being rather delicate. This case is the 1D propagation in a homogeneous medium
having two purely resistive terminations, the calculation of the Green function
being done without any approximation using three methods. The first one is the
straightforward use of the closed-form solution in the frequency domain and the
residue calculus. Then the method of separation of variables (space and time)
leads to a solution depending on the initial conditions. The question of the
orthogonality and completeness of the complex-valued resonance modes is
investigated, leading to the expression of a particular scalar product. The
last method is the expansion in biorthogonal modes in the frequency domain, the
modes having eigenfrequencies depending on the frequency. Results of the three
methods generalize or/and correct some results already existing in the
literature, and exhibit the particular difficulty of the treatment of the
constant mode
An interacting quark-diquark model of baryons
A simple quark-diquark model of baryons with direct and exchange interactions
is constructed. Spectrum and form factors are calculated and compared with
experimental data. Advantages and disadvantages of the model are discussed.Comment: 13 pages, 3 eps-figures, accepted by Phys.Rev. C Rapid Communication
Uniqueness of a Negative Mode About a Bounce Solution
We consider the uniqueness problem of a negative eigenvalue in the spectrum
of small fluctuations about a bounce solution in a multidimensional case. Our
approach is based on the concept of conjugate points from Morse theory and is a
natural generalization of the nodal theorem approach usually used in one
dimensional case. We show that bounce solution has exactly one conjugate point
at with multiplicity one.Comment: 4 pages,LaTe
Capillary-gravity waves: The effect of viscosity on the wave resistance
The effect of viscosity on the wave resistance experienced by a 2d
perturbation moving at uniform velocity over the free surface of a fluid is
investigated. The analysis is based on Rayleigh's linearized theory of
capillary-gravity waves. It is shown in particular that the wave resistance
remains bounded as the velocity of the perturbation approches the minimun phase
speed, unlike what is predicted by the inviscid theory.Comment: Europhysics Letters, in pres
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