Showing papers by "Aoyama Gakuin University published in 1978"

A cosmic-ray nuclear event of abnormally high multiplicity and large transverse momenta

Abstract: We give a description of a nuclear event of new character observed in an emulsion chamber exposed on Mt. Chacaltaya. The interaction has its vertex within the chamber and contains 40 γ-rays, whose energies sum up to ∼42 TeV. The most remarkable feature of the event are: 1) Abnormally large transverse momenta. The average transverse momentum of the γ-rays is ∼0.5 GeV/c. 2) Abnormally high transverse-momentum density. That of the γ-rays is (70÷90) GeV/c per unit log tgϑ interval. 3) Multijetlike angular structure. At least three structures are observed. 4) Noncoplanarity. The γ-ray momentum distribution deviates appreciably from a coplanar one. If a fireball picture is adopted, the event can be interpreted as a production of a giant fireball, out of whose rest energy an energy of (60÷80) GeV is liberated in the form of γ-rays, and which decays into hadrons through smaller fireballs. The highest-energy γ-ray pair starts in an empty space within the chamber, suggesting that they come from a parent particle with a lifetime of the order of 10−13 s.

Exchange enhancement of the electron-phonon coupling in metals

Abstract: It is well known that ferromagnetic tendency is destructive to superconductivity through the spin-fluctuation coupling effect. Experimentally, however, the relation between superconductivity and magnetism is not that simple. Recently, we pointed out that by softening phonons the exchange interaction between electrons enhances the electron-phonon coupling constant ${\ensuremath{\lambda}}_{p}$, and, accordingly, superconductivity. If the effect of the exchange enhancement of ${\ensuremath{\lambda}}_{p}$ overrides the destructive effect of the spin-fluctuation coupling, resultantly, superconductivity can be helped by magnetism. In order to substantiate the above idea, in the present paper we carry out a quantitative estimation of ${\ensuremath{\lambda}}_{p}$ for a model in which deviations from the jellium model are conveniently included by a parameter $\ensuremath{\xi}$. The size of the exchange enhancement of ${\ensuremath{\lambda}}_{p}$ is found to depend very sensitively on $\ensuremath{\xi}$. Thus, assuming different values for $\ensuremath{\xi}$, we can explain why in Pd the exchange enhancement of ${\ensuremath{\lambda}}_{p}$ is small, resulting in the absence of superconductivity, whereas it is large in ${\mathrm{V}}_{3}$Si, producing high superconducting transition temperature.

Magnetic Transition of Orthoferrites with Compositions YFe 1-x Mn x O 3

Abstract: The spin configuration was studied by means of magnetic torque measurements on single crystals of manganese substituted orthoferrites, YFe 1- x Mn x O 3 where 0≤ x ≤055, at temperatures between 77 K and 450 K Spin reorientations were observed in the samples containing more than x =01 It was concluded that the antiferromagnetic spin axis should be along the a -axis of the orthorhombic crystal axes and the weak ferromagnetic moment is along the c -axis above the reorientation temperature, and that the spin axis should be along the b-axis below the reorientation temperature

Representation of a diffracted wave field by the band-limited angular spectrum

Abstract: A spherical wave field is exactly represented by the angular spectrum of the plane waves with the limited bandwidth. It is given by superposing the minimum amount of plane waves which really contribute to the wave field. This representation is reduced to the circular plane-wave (CPW) expansion with a good approximation, if a distance from the source to an observation point is larger than a few wavelengths. The band-limited angular spectrum representation of the diffracted wave field is also obtained from the Fresnel-Kirchhoff diffraction formula by applying the CPW expansion of the spherical wave. The bandwidth is W = 2(r0λ)−1/2 + ρmaxcos(k,n)/r0λ[(r0λ)1/2 > ρmax] or W = 2(r0λ)−1/2 [(r0λ) ≫ ρmax], where r0 is the distance from the center of the aperture to the observation point, and ρmax is half of the maximum of the linear dimension of the aperture.

A Low-Pass Filter Type of Delta Modulation

Abstract: A new method is presented for the analysis and design of a lowpass filter type of delta modulation. This system has a nonideal integrator acting as a low-pass filter in the signal band and is suited for dc transmission. Analyses are made of overload performances and signal-to-noise ratio (SNR) for sinusoidal inputs and of periodic noises for dc inputs. Point transformations, defined in the phase plane, permit us to describe algebraically the dc response of the modulator and to analyze its dc characteristics. In the results section, it is shown that asymmetric quantization contributes to improving SNR at low signal levels. A simple design method, specified with equivalent bandwidth, desired SNR, and dynamic range, is proposed and verified with experimental results obtained for a design example.

Recognition of shape from the frequency spectrum of the e.m.g.

Abstract: Visual processing is one of the important aspects of research into an intelligent robot and upper extremity prostheses. The study has shown the relationship between the recognition of shape and the electromyogram generated in the human on the surface of the extensor carpi radialis muscle. To observe the corresponding electric signals, the subject was placed inside a shielded room with Ag−AgCl electrodes located at two points on his skin. The two electrodes were spaced 50 mm apart, but variation of the separation in the range 5–10 mm had no effect on the e.m.g. Three spectral peaks (100, 160 and 250 Hz) for the response are obtained for each shape. The frequencies corresponding with the peak values in the spectra are the same, and are independent of the shapes. Shape recognition can therefore be quantified as an e.m.g. spectral variation.