• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.305-311
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• 2006

We propose a 7-level atom model, which takes into account two-photon coherence effects in saturation absorption spectroscopy. Using this model we explained spectral change with laser intensity and some of crossover resonance lines, which cannot be explained with Nakayama theory. The 7-level model consists of two upper levels and five lower levels, which account for $\pi-\pi$ polarization of both pump and probe beams in Zeeman sub levels. We compared our 7-level model with 4-level Nakayama theory for 5S$_{1/2}$ - 5P$_{1/2}$ transition line in $^{85}$Rb atoms. The results of the 7-level model calculation agree well the saturation absorption spectra data according to laser intensities.

• Korean Journal of Optics and Photonics
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• v.4 no.2
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• pp.188-194
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• 1993

By applying the Nakayama's theory of saturation spectroscopy to 87Rb $D_2$ lines, taking into account the optical pumping process, the relative intensities of the resonance signals were calculated for various polarization combinations of pump and probe beams. The saturated absorption spectra were observed with a linewidth-narrowed semiconductor laser. As the result, it was found that the theoretical calculations were in good agreement with the experimental observations in the case where the geomagnetic field was- shielded.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.2
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• pp.40-46
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• 1989

Recently, the researches on cutting the new material have been done for development of aerospace industrial engineering. Especially, titanium ally is well known as heat resisting, antiwear, anticorrosion and difficult-to-machine materials. Many studies on the analysis of shear angle have been done for improving productivity in cutting these materials. In case of titanium alloy, the saw-toothed type of chip which has wave surface of a triangular form, an eccentric from of a continuous type of chip that is produced in the cutting process, was checked. Nakayama supposed that a maximum shear strewss plane and the shear crack in the free surface made an angle of $45^{\circ}$ .deg. , but it's usually much larger than that. In this paper, the author analyzed the shear conditions of the cutting process in the quick-stopping device with the help SEM-photographs, and measured the hypotenuse angle directly in the photographs of the chips. In conclusion, the author tried to find the shear angle in the cutting process with the saw-toothed chip and compared it with the shear angles which can be calculated from the theories established by others. The results obtained are as follows. 1. In case of the saw-toothed chips, the equivalent cutting ratio can be calculated by using the chip thickness to two-thirds of ramp height. 2. The theory of Ernst-Merchant is not applicable to the titanium and its alloys which does not fractured in accordance with the theory of maximum shear stress. 3. When we cut the titanium alloys which produced the saw-toothed chips, the shear angle can be found with the theories of Rowe-Spick, P.K. Wright and the measurement of hypotenuse angle.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.665-676
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• 1996

Domestic metal mines have contributed to the national industrialization of Japan for over a century through their stable supply of raw materials. However, due to the changes which have taken place in the industries structure, mining industry has been shifted to downstream industries. At present, only three major mines are in production. In recent times, changing economic conditions have made it increasingly difficult to develop new base metal mines. Subsequently, the deposit type targeted has shifted from base metals to epithermal associated gold deposits which, if of sufficient grade and tonnage, can be economical. Accompanying the dramatic rise in the price of gold during the late 1970's, has been an increase in the geological information and our understanding of epithermal gold deposits around the Pacific rim region. In particular, the common acceptance of the plate tectonic theory and the correlation's between modem geothermal systems and fossil epithermal systems were most important developments. In 1988, the Mining Council authorized the domestic exploration of 19 districts, targeting epithermal gold mineralization. Since 1989 the Metal Mining Agency of Japan, semi-government organization, has been conducted gold exploration in such area. With new genetic concepts and new technologies, promising gold mineralization has been discovered. Two such areas which are at an advanced stage of exploration are Seta, in northern Hokkaido, and Noya, in central Kyushu.