Jiro Chiba

Radio Communication in Tunnels

The attenuation constant of radio waves in tunnels was obtained experimentally and theoretically. According to this study, the tunnel is a transmission channel of high-pass type. It is found that the higher the frequency, the smaller the attenuation constant. The experimental values of attenuation constants are similar to the theoretical values of the the TE/sub 01/ and EH/sub 11/ and modes when the tunnel is regarded as a circular waveguide with the same cross-sectional area as the tunnel. Radio communication using the tunnel was proven to be fully possible in spite of the standing wave effects due to the interference of the propagation modes.

Propagation of electromagnetic waves of crossroads with a reflector inside a tunnel

We analyzed the wave propagation characteristics of the crossroad inside a tunnel, using the boundary‐element method. To simplify, the tunnel structure is assumed to be two‐dimensional and the side walls to be lossy dielectrics. We could improve the radio communication characteristics between two cross tunnels by a tetragonal reflector placed at the center of the crossroad. The diagonal length of the proper reflector is about 10%–20% of the tunnel width.

Scanning tunneling microscopy investigation of single electron tunneling in Co–Al–O and Cu–Al–O granular films

We have investigated single electron tunneling in Co–Al–O and Cu–Al–O granular films using scanning tunneling microscopy (STM). Topographic images show well-defined granular structures where nanometer-sized metal granules are embedded in insulating matrix. The Coulomb staircases in the current–voltage (I–V) curves are clearly observed even at room temperature in both films. For the Co–Al–O film, furthermore, negative differential conductance appears in the Coulomb staircase.

Improved theory for E-plane symmetrical tee junctions

L. Lewins theory (1975), which describes an E-plane symmetrical tee junction by an equivalent circuit with only three parameters, is examined. It is shown that although the theory is formally correct, its circuit parameters depend on the amplitudes of reflected waves. An improved theory corrects this fault. >

A new geometrical gravitational theory

A geometrical gravitational theory based on the connection Γβγα={βγα} + δβα∂γ lnϕ + δγα∂β lnϕ −gβγ∂α ln ψ is developed. The field equations for the new theory are uniquely determined apart from one unknown dimensionless parameter Ω2. The geometry on which our theory is based is an extension of the Weyl geometry, and by the extension the gravitational coupling constant and the gravitational mass are made to be dynamical and geometrical. The fundamental geometrical objects in the theory are a metricgμν and two gauge scalarsϕ andψ. Physically the gravitational potential corresponds togμν in the same way as in general relativity, the gravitational coupling constant toψ−2, and the gravitational mass tou(ϕ, ψ), which is a coscalar of power −1 algebraically made ofϕ andψ. The theory satisfies the weak equivalence principle, but breaks the strong one generally. We shall find outu(ϕ, ψ)=ϕ on the assumption that the strong one keeps holding good at least for bosons of low spins. Thus we have the simple correspondence between the geometrical objects and the gravitational objects. Since the theory satisfies the weak one, the inertial mass is also dynamical and geometrical in the same way as is the gravitational mass. Moreover, the cosmological term in the theory is a coscalar of power −4 algebraically made ofψ andu(ϕ, ψ), so it is dynamical, too. Finally we give spherically symmetric exact solutions. The permissible range of the unknown parameter Ω2 is experimentally determined by applying the solutions to the solar system.

Gravitational field sensor for prediction of big seismic waves

The authors outline the gravitational field sensor for prediction of large seismic waves. They studied the turbulence of a Newtonian gravitational field due to large seismic waves and the detection of the turbulent field by an interferometric gravitational wave antenna. The cause of the turbulent field is the variation of the mass density in the ground by the waves. The warning system using the antenna is superior to that of a seismograph. When the seismograph and the antenna are set at the same place, for instance, 100 km away from the epicenter of a strong earthquake of M/sub S/ approximately 7, the seismograph does not respond until the arrival of the P-wave, but the antenna will respond to the gravitational field with about a 20-dB sensitivity 7 s before the arrival.<<ETX>>

Variational principle for gravitational equations of the Bianchi identity type

It is shown that a square invariant of the Weyl conformal curvature tensor can lead to a Lagrangian in a variational principle for a gravitational equation in vacuum of the Bianchi identity type which is compatible with the Einstein equation. Moreover we show that such a Lagrangian implicitly includes a conformally invariant theory characterized by two gauge fields and the metric tensor.

A viewpoint of Kaluza–Klein type in elasticity theory

An N‐dimensional anisotropic elastic body without the interior gravity is, under some conditions concerning the Nth dimension, equivalent to an (N−1)‐dimensional isotropic elastic body under the influence of the interior gravity. According to this theorem, our method of solving the equation of free motion of anisotropic elastic bodies includes Bromwich’s method of solving the equation of motion of incompressible isotropic elastic bodies under the influence of the interior gravity.

Hydrodynamics in theO4 gravity

We develop hydrodynamics in a new geometrical gravitational theory, calledO4 gravity, which we recently proposed. According to this formulation, matter is not necessarily conserved. The nonconservation of matter might have been considerable in an early era of cosmological evolution.

Studies in electromagnetic fields and phase constants of a concentric line having a helical inner conductor

This paper describes a wire helix which has a coaxial shielding cylinder since in practice a wire helix is often used with a shielding cylinder. Analyses are done by wire theory. The electromagnetic field, phase constant, characteristic impedance, and attenuation constant of the shielded wire helix are necessary in the engineering field, and the first two of them are dealt with in this paper. As for the phase constant, we present the concrete results of calculations using the numerical solution by a computer.