Fracture Mechanics of Joints

Almost every engineering design requires that component members be connected. A disadvantage of mechanical connections such as bolts, screws or rivets is that they do not uniformly distribute the load; hence large local stresses result. This problem can often be reduced ~ joining the members adhesively. Major problems with adhesives that have tended to limit their wider us age include: (1) how the strength of an adhesive and the joint in which it is used can reliably be predicted, and (2) what factors tend to limit the strength of an adhesive joint and how they might be eliminated . It is the intent of the authors to show how fracture mechanics might be used to develop a rational philosophy and methodology that will aid in overcoming these problems

A new approximation scheme in quantum mechanics

An approximation method which combines the perturbation theory with the variational calculation is constructed for quantum mechanical problems. Using the anharmonic oscillator and the He atom as examples, we show that the present method provides an efficient scheme in estimating both the ground and the excited states. We also discuss the limitations of the present method.Comment: 14pages, to be published in Eur. J. Phy

Creation of Skyrmions in a Spinor Bose-Einstein Condensate

We propose a scheme for the creation of skyrmions (coreless vortices) in a Bose-Einstein condensate with hyperfine spin F=1. In this scheme, four traveling-wave laser beams, with Gaussian or Laguerre-Gaussian transverse profiles, induce Raman transitions with an anomalous dependence on the laser polarization, thereby generating the optical potential required for producing skyrmions.Comment: 5 pages, 2 figures, RevTe

Escape Behavior of Quantum Two-Particle Systems with Coulomb Interactions

Quantum escapes of two particles with Coulomb interactions from a confined one-dimensional region to a semi-infinite lead are discussed by the probability of particles remaining in the confined region, i.e. the survival probability, in comparison with one or two free particles. For free-particle systems the survival probability decays asymptotically in power as a function of time. On the other hand, for two-particle systems with Coulomb interactions it shows an exponential decay in time. A difference of escape behaviors between Bosons and Fermions is considered as quantum effects of identical two particles such as the Pauli exclusion principle. The exponential decay in the survival probability of interacting two particles is also discussed in a viewpoint of quantum chaos based on a distribution of energy level spacings.Comment: 10 pages, 7 figure

Quantized circular motion of a trapped Bose-Einstein condensate: coherent rotation and vortices

We study the creation of vortex states in a trapped Bose-Einstein condensate by a rotating force. For a harmonic trapping potential the rotating force induces only a circular motion of the whole condensate around the trap center which does not depend on the interatomic interaction. For the creation of a pure vortex state it is necessary to confine the atoms in an anharmonic trapping potential. The efficiency of the creation can be greatly enhanced by a sinusodial variation of the force's angular velocity. We present analytical and numerical calculations for the case of a quartic trapping potential. The physical mechanism behind the requirement of an anharmonic trapping potential for the creation of pure vortex states is explained. [Changes: new numerical and analytical results are added and the representation is improved.]Comment: 13 Pages, 5 Figures, RevTe

Interference scheme to measure light-induced nonlinearities in Bose-Einstein condensates

Light-induced nonlinear terms in the Gross-Pitaevskii equation arise from the stimulated coherent exchange of photons between two atoms. For atoms in an optical dipole trap this effect depends on the spatial profile of the trapping laser beam. Two different laser beams can induce the same trapping potential but very different nonlinearities. We propose a scheme to measure light-induced nonlinearities which is based on this observation.Comment: 2 figure

Research in technology education: Looking back to move forward

This paper attempts to summarize the focus of the research that has recently taken place in Technology Education, and from that basis suggest a trajectory for future research trends. Some research that is considered particularly seminal to the profession is summarised, and the paper is concluded with some reflections about personal research agendas