1,479 research outputs found
Laser assisted proton collision on light nuclei at moderate energies
We present analytic angular differential cross section model for laser
assisted proton nucleon scattering on a Woods-Saxon optical potential where the
nth-order photon absorption is taken into account simultaneously. As a physical
example we calculate cross sections for proton - C collision at 49 MeV
in the laboratory frame where the laser intensity is in the range of W/cm at optical frequencies. The upper intensity limit is slightly
below the relativistic regime.Comment: 6 pages, 4 figures, will be submitted to Phys. Rev.
Proton scattering on carbon nuclei in bichromatic laser field at moderate energies
We present the general theory for proton nuclei scattering in a bichromatic
laser field. As a physical example we consider proton collision on carbon
twelve at 49 MeV/amu moderate energies in the field of a titan sapphire laser
with its second harmonic.Comment: 6 pages 5 figures, submitted to NIMB. arXiv admin note: text overlap
with arXiv:1406.631
Vibration analysis of rotor blades with an attached concentrated mass
The effect of an attached concentrated mass on the dynamics of helicopter rotor blades is determined. The point transmission matrix method was used to define, through three completely automated computer programs, the natural vibrational characteristics (natural frequencies and mode shapes) of rotor blades. The problems of coupled flapwise bending, chordwise bending, and torsional vibration of a twisted nonuniform blade and its special subcase pure torsional vibration are discussed. The orthogonality relations that exist between the natural modes of rotor blades with an attached concentrated mass are derived. The effect of pitch, rotation, and point mass parameters on the collective, cyclic, scissor, and pure torsional modes of a seesaw rotor blade is determined
Experimental studies on the aerodynamic performance and dynamic response of flow direction sensing vanes
Systematic investigations were performed on a variety of aerodynamic surfaces to obtain their potential for possible application to wind vanes. Among the surfaces tested were: (1) single vanes consisting of flat plates of various planforms having aspect ratios between 0.5 and 5; (2) bi-vanes with aspect ratio 2.5; (3) various cone and box vanes; and (4) various cruciform configurations. The models were subjected to windtunnel tests. In addition to lift and drag force measurements, damping and frequency test were performed under a variety of flow conditions
Experiential Learning in School Counselor Preparation: Supporting Professional Skill Development
Professional standards require school counselor educators to prepare students to competently perform the many necessary skills of a school counselor. Integration of experiential learning activities into existing pre-fieldwork school counseling courses supports both skill development and standard compliance. A framework for planning, implementing, and evaluating this classroom pedagogy is detailed
Effect of Collector Configuration on Test Section Turbulence Levels in an Open-Jet Wind Tunnel
Flow quality studies in the Langley 14- by 22-Foot Subsonic Tunnel indicated periodic flow pulsation at discrete frequencies in the test section when the tunnel operated in an open-jet configuration. To alleviate this problem, experiments were conducted in a 1/24-scale model of the full-scale tunnel to evaluate the turbulence reduction potential of six collector configurations. As a result of these studies, the original bell-mouth collector of the 14- by 22-Foot Subsonic Tunnel was replaced by a collector with straight walls, and a slot was incorporated between the trailing edge of the collector and the entrance of the diffuser
Sensor for measuring instantaneous angle of attack of helicopter blades
Systematic investigations were performed on a variety of probes to determine their potential for possible application as sensors attached to helicopter blades to measure both the instantaneous angle of attack as well as the dynamic head during actual flight operations. After some preliminary considerations a sensor of essentially spherical shape, about 30 mm in diameter, was designed. The sensor was provided with three pressure ports, and it housed two pressure transducers required for sensing the prevailing pressures acting outside on the surface. The sensors were subsequently tested in the laboratory under a variety of flow conditions to determine their aerodynamic characteristics. Two series of tests were performed: in the first series the sensor was fixed in space while exposed to steady uniform flow, while in the second series the sensor was made to oscillate, thus simulating the cyclic pitch change of the helicopter blades. While the cyclic pitch frequencies were of about the same magnitude as encountered in flight, the flow velocities during tests fell well below those experienced in a rotating blade. The tests showed that the sensors performed satisfactorily under low subsonic flow conditions with frequencies not exceeding five Hz
Experimental studies on the effects of a sting support on the pressure distribution around a spherical object
Experiments were conducted on a spherical object, 2.5 inches in diameter, to obtain the pressure distribution around its meridan plane. In most of the tests the sphere was provided with a tail consisting of a circular cylinder that was attached directly to the rear with its axis in alignment with the center of the sphere. In some tests the tail was removed and the sphere alone was tested for comparison purposes. The main object of the tests was to obtain information on tail interference with the pressure distribution. The results of the tests show that the pressure distribution was affected by the presence of the tail to a minor extent only, while major differences occurred with the variation of the Reynolds number. The experiments were performed both in an open as well as inside a closed wind tunnel under steady flow conditions at Reynolds numbers ranging from 0.91 to 2.6 x 100000
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