Hideo Akabane

Asymmetrical Property of 1/f Resistance Fluctuation for Time Inversion

The 1/f resistance fluctuations of carbon fiber are observed under four different nonequilibrium conditions controlled by the heat diffusion from the fiber to the external environment. A higher-order correlation function of an observed 1/f time series is analyzed and compared with those of three different types of computer-generated 1/f time series. It is found that the higher-order correlation function related to the time-inversion asymmetry of the 1/f resistance fluctuation shows the same statistical property as that of a one-dimensional diffusion system. Further more, the higher-order correlation function of the 1/f resistance fluctuations with the same 1/f spectra is shown to be affected by the heat diffusion from the carbon fiber.

1/f fluctuations in the dielectric response of triglycine sulfate

1/f fluctuations have been observed in the imaginary part of the complex dielectric constant of ferroelectric triglycine sulfate crystals near the Curie temperature Tc. The observed 1/f power spectral density Sei (f) of the imaginary dielectric constant, when normalized to the square of the real part of the dielectric constant er, is given by Sei (f)/er2=3.2×10-15/f(ΔT) where ΔT=T-47.73(°C) in the paraelectric phase and ΔT=47.82-T(°C) in the ferroelectric phase.

Correlation between mode fluctuations in a semiconductor laser

The correlation between fluctuations of different modes of a single mode semiconductor laser has been measured at several temperatures. The lasing mode is found to have a strong coupling with its adjacent nonlasing modes, but the coupling is exceptionally weak if the adjacent mode does not become a lasing mode when the temperature is changed.

1/f Resistance Fluctuation of a Carbon Fiber

1/f resistance fluctuations of carbon fiber are measured under the condition that tension of the carbon fiber is changed. The deformation of the fiber extends from an elastic region to a plastic one. It is found that the intensity of 1/f resistance fluctuations increases significantly as the applied tension increases, while the change of the mean value of the resistance is very small. The increase of the 1/f intensity is considered to originate from the change of the nonlinear potential caused by the applied tension.

Fluctuation in the Scattering Probability of an Electron in a One-Dimensional Nonlinear Lattice System

In this research, we study the fluctuation in the scattering probability of an electron in a nonlinear one-dimensional lattice system. A simulation of atomic vibration is performed and the fluctuation in the electron scattering probability by acoustic phonons is investigated. It is found that the fluctuation in the electron scattering probability of the equilibrium phonon mode state shows a 1/ f α spectrum in the low-frequency range, provided that the temperature of the system is sufficiently high. Furthermore, the dependence of the number of atoms constituting the system is investigated. The 1/ f α spectrum is more easily observed in a larger system than in a smaller one.

Fractal Characters of 1/2-order Integration of White Noise and 1/f Resistance Fluctuation

Four different types of 1/f time series are generated by computer simulations and the analyses of their fractal characteristics are carried out. The numerical evaluation shows that the differences in the generation mechanism results in a 1/f time series having different fractal structures. The 1/f resistance fluctuation of a carbon fiber is observed and its fractal property is analyzed in comparison with that of computer-generated 1/f fluctuations. It is found that the fractal property of the resistance fluctuation is the same as that of the fluctuation generated by 1/2-order integration of white noise.

Compression Pressure Dependence of 1/f Resistance Fluctuation in Single-Walled Carbon Nanotubes

Resistance and its fluctuation in single-walled carbon nanotubes (SWNTs) is measured using pressured powder samples. It is found that the 1/f resistance fluctuation increases exponentially with increasing compression pressure but the mean resistance is scarcely affected. Compression pressure changes the nonlinearity and phonon mode interaction in atomic vibration. These results proved that the origin of the 1/f resistance fluctuation in SWNTs is mainly the mobility fluctuation.

1/f Resistance Fluctuation In Carbon Nanotubes

The resistance fluctuation of carbon nanotubes(CNTs) in low temperature was measured and the results were compared to that of a simulation of lattice vibration. Further, the influence of laser irradiation except the contact parts of the electrodes was studied. As the result, it was thought that the main causes of 1/f resistance fluctuation of CNTs derived from mobility fluctuation.

1= f Fluctuation in a Discrete One-Dimensional Diffusion System

A one-dimensional diffusion system is considered to be a convenient tool to generate 1/f fluctuations by a computer, since its frequency response to the driving force concentrated at one point is proportional to 1/√f. However, the frequency response of a discrete diffusion system depends not only on the spatial increment and time step but also on the type of finite difference used to approximate the derivative. In the present paper, we specify the conditions under which a discrete diffusion system has a frequency response strictly proportional to 1/√f.

Time-Reversible Property of 1/f Fluctuation Using Higher-Order Correlation Function

1/f fluctuation is usually generated in a complex system composed of many dissipative or nondissipative partial systems. Based on a postulate that the 1/f fluctuation is related to higher-order non-Gaussian processes, we investigate the time-reversible property of the computer-generated 1/f fluctuation using a higher-order correlation function. It is shown that several types of 1/f fluctuations exist although they have the same 1/f spectrum.