Surface effects and reflection refractometry of optical fibres

Refractive index profiles of several types of silica-based low-loss optical fibres have been measured by the surface reflection technique. When polished samples are used inaccurate data are obtained. For germanium- and phosphorus-doped samples good results are obtained using samples prepared by fracturing the end of the fibre. For borosilicate fibres rapid changes due to atmospheric exposure result in inaccurate data.     

The Secondary Bifurcation of an Aeroelastic Airfoil Motion: Effect of High Harmonics

The nonlinear dynamical response of a two-degree-of-freedom aeroelastic airfoil motion with cubic restoring forces is investigated. A secondary bifurcation after the primary Hopf (flutter) bifurcation is detected for a cubic hard spring in the pitch degree-of-freedom. Furthermore, there is a hysteresis in the secondary bifurcation: starting from different initial conditions the motion may jump from one limit cycle to another at different fluid flow velocities. A high-order harmonic balance method is employed to investigate the possible bifurcation branches. Furthermore, a numerical time simulation procedure is used to confirm the stable and unstable bifurcation branches.     

A novel harmonic balance analysis for the Van Der Pol oscillator

This study focuses on a novel harmonic balance formulation, the high-dimensional harmonic balance method. To investigate a non-linearity in the damping term, the system chosen for study is the Van der Pol's oscillator. Both unforced and forced oscillators are analyzed. The results from the analysis are compared with those obtained from the classical harmonic balance and the time marching (Runge-Kutta) methods.     

The infrared spectrum of californium-249

The Cf-249 spectrum between 3700 and 12,000 cm^?1 has been recorded. The strongest 90 lines are listed.     

Chromatic uniqueness and equivalence of K4 homeomorphs

We derive a new formula for the chromatic polynomial of any K₄ homeomorph. We obtain a large family of chromatically unique K₄ homeomorphs. We obtain seven infinite pairs of chromatically equivalent nonisomorphic K₄ homeomorphs.