2,546 research outputs found
Coupled rotor-body equations of motion hover flight
A set of linearized equations of motion to predict the linearized dynamic response of a single rotor helicopter in a hover trim condition to cyclic pitch control inputs is described. The equations of motion assume four fuselage degrees of freedom: lateral and longitudinal translation, roll angle, pitch angle: four rotor degrees of freedom: flapping (lateral and longitudinal tilt of the tip path plane), lagging (lateral and longitudinal displacement of the rotor plane center of mass); and dynamic inflow (harmonic components). These ten degrees of freedom correspond to a system with eighteen dynamic states. In addition to examination of the full system dynamics, the computer code supplied with this report permits the examination of various reduced order models. The code is presented in a specific form such that the dynamic response of a helicopter in flight can be investigated. With minor modifications to the code the dynamics of a rotor mounted on a flexible support can also be studied
Molecular collisions. 15 - Classical limit of the generalized phase shift treatment of rotational excitation - Atom-rigid rotor
Generalized phase shift approach to problem of rotationally inelastic molecular collision
Molecular collisions. 16: Comparison of GPS with classical trajectory calculations of rotational inelasticity for the Ar-N2 system
Comparison of generalized phase shift treatment with classical trajectory calculations of rotational inelasticity cross sections of Ar-N2 scatterin
Design and numerical evaluation of full-authority flight control systems for conventional and thruster-augmented helicopters employed in NOE operations
The development and methodology is presented for development of full-authority implicit model-following and explicit model-following optimal controllers for use on helicopters operating in the Nap-of-the Earth (NOE) environment. Pole placement, input-output frequency response, and step input response were used to evaluate handling qualities performance. The pilot was equipped with velocity-command inputs. A mathematical/computational trajectory optimization method was employed to evaluate the ability of each controller to fly NOE maneuvers. The method determines the optimal swashplate and thruster input histories from the helicopter's dynamics and the prescribed geometry and desired flying qualities of the maneuver. Three maneuvers were investigated for both the implicit and explicit controllers with and without auxiliary propulsion installed: pop-up/dash/descent, bob-up at 40 knots, and glideslope. The explicit controller proved to be superior to the implicit controller in performance and ease of design
Unique chromosomal regions associated with virulence of an avian pathogenic Escherichia coli strain.
Optical excitations in organic molecules, clusters and defects studied by first-principles Green's function methods
Spectroscopic and optical properties of nanosystems and point defects are
discussed within the framework of Green's function methods. We use an approach
based on evaluating the self-energy in the so-called GW approximation and
solving the Bethe-Salpeter equation in the space of single-particle
transitions. Plasmon-pole models or numerical energy integration, which have
been used in most of the previous GW calculations, are not used. Fourier
transforms of the dielectric function are also avoided. This approach is
applied to benzene, naphthalene, passivated silicon clusters (containing more
than one hundred atoms), and the F center in LiCl. In the latter, excitonic
effects and the defect line are identified in the energy-resolved
dielectric function. We also compare optical spectra obtained by solving the
Bethe-Salpeter equation and by using time-dependent density functional theory
in the local, adiabatic approximation. From this comparison, we conclude that
both methods give similar predictions for optical excitations in benzene and
naphthalene, but they differ in the spectra of small silicon clusters. As
cluster size increases, both methods predict very low cross section for
photoabsorption in the optical and near ultra-violet ranges. For the larger
clusters, the computed cross section shows a slow increase as function of
photon frequency. Ionization potentials and electron affinities of molecules
and clusters are also calculated.Comment: 9 figures, 5 tables, to appear in Phys. Rev. B, 200
Molecular collisions. 14 - First-order approximation of the generalized phase shift treatment of rotational excitation - Atom-rigid rotor
Applying generalized phase shift approach to rotational excitation problem to atom-rigid rotor case in first order approximatio
Book Reviews
BOOK REVIEWS The Swiss Way of Welfare: Lessons for the Western World. Ralph Segalman. New York: Praeger, 1986, 205 pp., 8.95. - Reviewed by Robert Sheak Shared Responsibility: Families and Social Policy. Robert M. Moroney. Hawthorne, N.Y.: Aldine Publishing Co., 1986, 14.94 paper. - Reviewed by Christina R. Curtiss
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