Internal resonance of an L-shaped beam with a limit stop .1. Free vibration

Real-life structures often possess piecewise stiffness because of clearances or interference between subassemblies. Such an aspect can alter a system's fundamental free vibration response and leads to complex mode interaction. The free vibration behaviour of an L-shaped beam with a limit stop is analyzed by using the frequency response function and the incremental harmonic balance method. The presence of multiple internal resonances, which involve interactions among the first five modes and are extremely complex, have been discovered by including higher harmonics in the analysis. The results show that mode interaction may occur if the higher harmonics of a vibration mode are close to the natural frequency of a higher mode. The conditions for the existence of internal resonance are explored, and it is shown that a prerequisite is the presence of bifurcation points in the form of intersecting backbone curves. A method to compute such intersections by using only one harmonic in the free vibration solution is proposed. (C) 1996 Academic Press Limited

Internal resonance of an L-shaped beam with a limit stop .2. Forced vibration

A limit stop is placed at the elbow of an L-shaped beam whose linear natural frequencies are nearly commensurable. As a result of this hardening device the non-linear system exhibits multiple internal resonances, which involve various degree of coupling between the first five modes of the beam in free vibration. A point load is so placed as to excite several modes and the resulting forced vibration is examined. In the undamped case, three in-phase and two out-of-phase solution branches have been found. The resonance curve is extremely complicated, with multiple branches and interactions between the first four modes. The amplitudes of the higher harmonics are highly influenced by damping, the presence of which can effectively attenuate internal resonances. Consequently parts of the resonance curve may be eliminated, with the resulting response comprising different distinctive branches. (C) 1996 Academic Press Limited

The effect of variable currents on internal solitary waves

The effect of variable currents on internal solitary waves is described within the context of a variable coefficient Korteweg-de Vries (KdV) equation, and the approximate slowly varying, solitary-wave solution of this equation. The general theory which leads to the variable coefficient KdV equation is described; a derivation for the special case when the solitary wave and the current are aligned in the same direction is given in the Appendix. Using further simplifications and approximations, a number of analytical expressions are obtained for the variation in the solitary wave amplitude resulting from variable shear in the basic current or from when the basic current is a depth-independent flow which is a simple representation of a geostrophic current, tidal flow or inertial wave.

Visualization of turbulence and internal waves in a stratified fluid

A new method for measuring the density, temperature and velocity of N2 gas flow by laser induced biacetyl phosphorescence is proposed. The characteristics of the laser induced phosphorescence of biacetyl mixed with N2 are investigated both in static gas and in one-dimensional flow along a pipe with constant cross section. The theoretical and experimental investigations show that the temperature and density of N2 gas flow could be measured by observing the phosphorescence lifetime and initial intensity of biacetyl triplet (3Au) respectively. The velocity could be measured by observing the time-of-flight of the phosphorescent gas after pulsed laser excitation. The prospect of this method is also discussed.

Moral Hazard and the Internal Organization of Joint Research

Revised 2006-06

Estudio empírico del endeudamiento, coste de la deuda y rentabilidades de la industria de calzado de La Rioja. Comparación por tamaño y sector

[ES] El presente trabajo tiene por objeto el estudio del nivel de endeudamiento, el coste de la deuda y las rentabilidades de la industria del calzado de la Comunidad Autónoma de La Rioja por sectores y tamaños. De acuerdo con la Economía Industrial, que considera el sector de actividad como el principal determinante de los resultados de las organizaciones, se analiza si las variables estudiadas son distintas en función de su pertenencia al sector del calzado en comparación con el de la industria agroalimentaria, por ser éste el más importante de la economía de la región. Por otro lado, de acuerdo con la Teoría de los Recursos y Capacidades, que considera que son los factores internos los que explican las diferentes rentabilidades, estudiaremos un recurso interno como es el tamaño, viendo su influencia sobre las variables comentadas. Por último, los resultados del estudio conjunto de la pertenencia a un sector de actividad por tamaños homogéneos nos permiten afirmar que el coste de la deuda de las pequeñas empresas es significativamente distinto en función de dicho sector de pertenencia.