6,764 research outputs found
A computer program to generate equations of motion matrices, L217 (EOM). Volume 1: Engineering and usage
The equations of motion program L217 formulates the matrix coefficients for a set of second order linear differential equations that describe the motion of an airplane relative to its level equilibrium flight condition. Aerodynamic data from FLEXSTAB or Doublet Lattice (L216) programs can be used to derive the equations for quasi-steady or full unsteady aerodynamics. The data manipulation and the matrix coefficient formulation are described
Comparisons of several aerodynamic methods for application to dynamic loads analyses
The results of a study are presented in which the applicability at subsonic speeds of several aerodynamic methods for predicting dynamic gust loads on aircraft, including active control systems, was examined and compared. These aerodynamic methods varied from steady state to an advanced unsteady aerodynamic formulation. Brief descriptions of the structural and aerodynamic representations and of the motion and load equations are presented. Comparisons of numerical results achieved using the various aerodynamic methods are shown in detail. From these results, aerodynamic representations for dynamic gust analyses are identified. It was concluded that several aerodynamic methods are satisfactory for dynamic gust analyses of configurations having either controls fixed or active control systems that primarily affect the low frequency rigid body aircraft response
A computer program to generate equations of motion matrices, L217 (EOM). Volume 2: Supplemental system design and maintenance document
The equations of motion program L217 (EOM) is described. The program formulates the matrix coefficients for a second order linear differential equation which describes the motion of an airplane relative to its level equilibrium flight condition. Aerodynamic data from FLEXSTAB or Doublet Lattice (L216) programs are used to derive the equations for quasi-steady or complete unsteady aerodynamics
Modal interpolation program, L215 (INTERP). Volume 1: Engineering and usage
The usage of the Modal Interpolation Program L215 (INTERP) is described. The program uses modal data to form sets of arrays containing interpolation coefficients. The interpolation arrays can then be used to determine displacements at various aerodynamic surface and surface slopes that are parallel and perpendicular to the freestream direction. Five different interpolation methods are available. A description of the data manipulation and the interpolation methods is presented
Time history solution program, L225 (TEV126). Volume 1: Engineering and usage
Volume 1 of a two volume document is presented. The usage of the convolution program L225 (TEV 126) is described. The program calculates the time response of a linear system by convoluting the impulsive response function with the time-dependent excitation function. The convolution is performed as a multiplication in the frequency domain. Fast Fourier transform techniques are used to transform the product back into the time domain to obtain response time histories. A brief description of the analysis used is presented
Dynamic loads analysis system (DYLOFLEX) summary. Volume 1: Engineering formulation
The DYLOFLEX computer program system expands the aeroelastic cycle from that in the FLEXSTAB computer program system to include dynamic loads analyses involving active controls. Two aerodynamic options exist within DYLOFLEX. The analyst can formulate the problem with unsteady aerodynamics calculated using the doublet lattice method or with quasi-steady aerodynamics formulated from either FLEXSTAB or doublet lattice steady state aerodynamics with unsteady effects approximated by indicial lift growth functions. The equations of motion are formulated assuming straight and level flight and small motions. Loads are calculated using the force summation technique. DYLOFLEX consists of nine standalone programs which can be linked with each other by magnetic files used to transmit the required data between programs
Magnetization of undoped 2-leg S = 1/2 spin ladders in La4Sr10Cu24O41
Magnetization data of single crystalline La4Sr10Cu24O41 are presented. In
this compound, doped spin chains and undoped spin ladders are realized. The
magnetization, at low temperatures, is governed by the chain subsystem with a
finite interchain coupling which leads to short range antiferromagnetic spin
correlations. At higher temperatures, the response of the chains can be
estimated in terms of a Curie-Weiss law. For the ladders, we apply the
low-temperature approximation for a S=1/2 2-leg spin ladder by Troyer et al.Comment: 2 pages, 2 figure
Exclusive Photoproduction of Large Momentum-Transfer K and K* Mesons
The reactions gamma p -> K+ Lambda and gamma p -> K* Lambda are analyzed
within perturbative QCD, allowing for diquarks as quasi-elementary constituents
of baryons. The diquark-model parameters and the quark-diquark distribution
amplitudes of proton and Lambda are taken from previous investigations of
electromagnetic baryon form factors and Compton-scattering off protons.
Unpolarized differential cross sections and polarization observables are
computed for different choices of the K and K* distribution amplitudes. The
asymptotic form of the K distribution amplitude (proportional to x1 x2) is
found to provide a satisfactory description of the K photoproduction data.Comment: 32 pages, 7 figures available as tared, compressed and uuencoded
PS-file
Radiative Corrections to the Muonium Hyperfine Structure. I. The Correction
This is the first of a series of papers on a systematic application of the
NRQED bound state theory of Caswell and Lepage to higher-order radiative
corrections to the hyperfine structure of the muonium ground state. This paper
describes the calculation of the radiative correction. Our
result for the complete correction is 0.424(4) kHz, which
reduces the theoretical uncertainty significantly. The remaining uncertainty is
dominated by that of the numerical evaluation of the nonlogarithmic part of the
term and logarithmic terms of order .Comment: 56 pages, Rev.tex V3.0 and epsf.tex. 12 postscript files are called
in the text. Version accepted by Phys. Rev. D. A new table is adde
Hard exclusive photoproduction of mesons
We calculate the differential cross section and single-polarization
observables for the reaction within perturbative QCD,
treating the proton as a quark-diquark system. The phenomenological couplings
of gauge bosons to (spatially extended) diquarks and the quark-diquark
distribution amplitude of the proton are adopted from previous investigations
of baryon form factors and two-photon processes. Going beyond leading order, we
take into account hadron-mass effects by means of a systematic expansion in the
small parameter (hadron mass/ photon energy). With the -meson
distribution amplitude taken from the literature our predictions for the
differential cross section at | t | \agt 4 \text{GeV}^2 seem to provide a
reasonable extrapolation of the low-t data and are also comparable in magnitude
with the results of a two-gluon exchange model in which the gluons are
considered as a remnant of the pomeron. For momentum transfers of a few GeV
hadron-mass effects appear still to be sizeable.Comment: 37 pages, 7 figures, uses RevTeX styl
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