Hisao Taira

Flux-free conductance modulation in a helical Aharonov--Bohm interferometer.

A novel conductance oscillation in a twisted quantum ring composed of a helical atomic configuration is theoretically predicted. The internal torsion of the ring is found to cause a quantum phase shift in the wavefunction that describes the electrons motion along the ring. The resulting conductance oscillation is free from magnetic flux penetrating inside the ring, which is in complete contrast with the case for the ordinary Aharonov-Bohm effect observed in untwisted quantum rings.

Curvature effects on surface electron states in ballistic nanostructures

The curvature effect on the electronic states of a deformed cylindrical conducting surface of variable diameter is theoretically investigated. The quantum confinement of electrons normal to the curved surface results in an effective potential energy that affects the electronic structures of the system at low-energies. This suggests the possibility that ballistic transport of electrons in low-dimensional nanostructures can be controlled by inducing a local geometric deformation.

Electronic States in Cylindrical Surfaces with Local Deformation

Effects of the surface curvature on the electronic states of a cylindrical conducting surface with a variable diameter are theoretically investigated. The quantum confinement of electrons normal to the curved surface results in an effective potential energy that affects the electronic structures of the system at low energies. This suggests the possibility of controlling the electric conductivity of low-dimensional nanostructures by inducing a local geometric deformation.

Embedding effect on the mechanical stability of pressurised carbon nanotubes

We elaborate on the cross-sectional deformation of carbon nanotubes embedded into a self-contracting host medium. The continuum elastic approach is used to formulate the mechanical energy of both the embedded nanotubes and the self-contracting outer medium with finite thickness. Our formula allows us to evaluate the critical radial pressure applied on the interface between the embedded nanotube and the outer contracting medium as well as the deformation mode that arises immediately above the critical pressure. An interesting mechanical implication of the embedding effect, that is, the power-law dependence of the critical pressure on the elastic modulus of the medium, is deduced by the theoretical approach established.

Spin transfer of light waves in twisted optical waveguides

We investigate the propagation of light waves in quasi-one-dimensional twisted photonic lattices of optical waveguides. The helical structure of the waveguides leads to a phase shift in light waves. This torsion-induced phase shift serves as spin transfer when the orbital angular momentum is nonzero. This result is different from rotation of a linearly polarized plane caused by a helicity-induced phase shift. We discuss the similarities and differences between torsion-induced phase shift and the helicity-induced one, and show that both of them are inherently caused by Berrys phase.

Cavitation bubble dynamics based on Keller equation in human joint

The present study numerically clarifies the mechanism of generation and propagation of cracking sound by the manipulation of human joint such as the finger, neck, under the assumption of formation of cavitation bubble. We recognize a sound generation by bending a human joint. This sound is called a cracking sound. Some researchers study the reason why a cracking sound is generated, and advocate that formation of cavitation bubble in the synovial fluid of these joints when a cracking sound is produced. A number of bubbles are produced in the synovial fluid of a human joint when the cracking sound is generated. However, in our analysis, we analyze dynamics of one bubble since this study is the first step to clarify the mechanism of generation of cracking sound. In this study, we numerically solve the Rayleigh–Plesset and Keller equations as classical ordinary differential equations in the field of bubble dynamics, which are utilized to determine the nonlinear oscillations of bubbles generating sound in the human joint. By solving these equations numerically, we discuss the mechanism and reason of generation of cracking sound.The present study numerically clarifies the mechanism of generation and propagation of cracking sound by the manipulation of human joint such as the finger, neck, under the assumption of formation of cavitation bubble. We recognize a sound generation by bending a human joint. This sound is called a cracking sound. Some researchers study the reason why a cracking sound is generated, and advocate that formation of cavitation bubble in the synovial fluid of these joints when a cracking sound is produced. A number of bubbles are produced in the synovial fluid of a human joint when the cracking sound is generated. However, in our analysis, we analyze dynamics of one bubble since this study is the first step to clarify the mechanism of generation of cracking sound. In this study, we numerically solve the Rayleigh–Plesset and Keller equations as classical ordinary differential equations in the field of bubble dynamics, which are utilized to determine the nonlinear oscillations of bubbles generating sound in the ...