• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.45.3-46
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• 2015

Space weathering agents such as micrometeoroids and solar wind particles continuously age the uppermost regolith of the lunar surface by comminuting as well as darkening and reddening. Among several maturity indices, we investigate median grain size () and optical maturity (OMAT) of the crater rim walls. Crater rim wall is the most immature place among the impact crater features because the vertical mixing process by mass-movement can enhance the gardening of regolith and the supply of immature materials in the deeper layer to the surface. More than 140 simple and complex craters were considered. Both and OMAT values of the inner rim wall initially increase as the crater size increases until ~10-20 km, then decrease. This transition crater size happens to correspond to the transition diameter from simple to complex craters. For larger craters, i.e., complex craters, it is clear that the inner rim wall of the craters formed in recent eras tend to remain fresh and become mature along with time. For the simple crater case, smaller craters are more mature, which is opposite to the case of complex craters. This is thought to be because smaller craters become flattened more quickly, thus have smaller vertical mixing in the regolith due to mass-movement. We will also discuss on the maturity indices of the crater rim walls at high latitudes as a function of the position angle to see the latitude dependence of the space weathering process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.248-254
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• 2009

The worn crater wear geometry of coated tools after machining has been configured by using Confocal Laser Scanning Microscopy(CLSM) and the Wavelet-based filtering technique. The CLSM can be well suited to construct the three-dimensional crater wear on the rake surfaces of coated tips. However, The raw heightness data of HEI(height encoded image) acquired by CLSM must be filtered due to the electronic and imaging noise occurring in constructing the crater image. So the Wavelet-based filtering algorithm is necessary to denoise the shape features in a micro scales so as to realize accurate crater wear topography analysis. The crater wear patterns filtered enable us to predict the crater wear shape in order to study the tool wear evolution. The study shows that the technique by combining the CLSM and Wavelet-based filtering is an excellent one to obtain the geometries of worn tool rake surfaces over a wide range of surface resolution in a micro scale.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.564-571
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• 1995

This paper deals with the arc discharge characteristics of kerosene oil as a basic study on electrical discharge machine. Using needle electrode the discharge voltage, discharge current, discharge energy and the shape of discharge crater are measured. In consequence, it becomes clear that the discharge crater(depth, height, diameter) is depending on the discharge energy. Rapid increase in depth, height and diameter of discharge crater was observed during initial discharge, where discharge energy is large. However, rather slow decrease of those values was found when discharge energy is low or N is more than 3. As the ratio of $I_p$$T_on$ increase, the shape of discharge crater gets near circle. The protuberances of the discharge crater were not formed by the melted needle electrode but by the that of work piece.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.84-95
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• 1991

This paper deals with crater wear when the SUS304 steel which forms the saw- toothed chip was cut by carbide tools. When the saw-toothed chip was formed, and optical creater wear measuring technique was used which provides complete information, both qualitatively and quantitatively, on the crater development. In this optical contour mapping technique an profile projector was used, making it possible to draw the depth contours of the crater directly. 98 contour maps of crater wear representing twelve different cutting conditions were presented. Also, the rake angles changed to have ${\alpha}$ =$6^{\circ}$, ${\alpha}$ =$-6^{\circ}$

• The Journal of the Petrological Society of Korea
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• v.25 no.3
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• pp.283-298
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• 2016

Sangumburi crater, designated as Natural Monument No. 63, recognized as a maar, but precise geological mapping and geological characteristics in the field indicate that Sangumburi crater is a pit crater. Two stages of volcanic activities created Sangumburi pit crater. Lava flow (aphanitic pyroxene basalt I) and associated pyroclastic deposit (pyroclast I), composed of ash and lapilli, were formed at the stage 1. In the stage 2, lava flow (feldspar olivine basalt) was overlain by lava flow (aphanitic pyroxene basalt II) and associated pyroclastic deposit (pyroclast II), composed of agglomerate. Sangumburi pit crater formed at $0.073{\pm}0.036Ma$, determined by Ar-Ar age dating for the feldspar olivine basalt at the stage 2. It is not clear the preferred migration direction of subsurface magma after Sangumburi pit crater formed.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.182-188
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• 2004

In view of the circular geometry of the Serra da Cangalha impact crater, we have carried out a 3D forward modeling computation for twenty-five MT data in order to obtain the 3D resistivity forward model for the crater region. The 3D resistivity forward model revealed a five-layer model, showing a significant reduction in the basement resistivity. We suggest that this, perhaps, could be due to the structural disturbances that have been caused by the meteorite impact on the crater about 220 million years ago resulting in brecciation, fracturing, alteration and shocked zone filled with fluids. Also, the sensitivity analysis of the 3D model chosen indicates that 3D models having a crater diameter greater than 151 are inconsistent with our data because the 3D model responses are very sensitive to changes in the diameter beyond 15 km. This analysis also reveals that, the depth limits (for the 3D body) causing the anisotropic effects seen on some of our apparent resistivity curves maximally does not extend beyond 1.2 km depth.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.1
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• pp.82-95
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• 1992

There is the high interest for sensing of tool wear with the aim of controlling machine tools productivity from the point of view of qualitity. Difficulties in this measurement are also known. This study is on the development of measurement setup for crater wear by CCD image inturning. In this study, the crater wear measurement system consists of the He-Ne gas laser, diffraction grating. CCD camera, noise filter, slit, microcomputer, diverging lens, converging lens and so on. He-Ne laser beam passes through a diverging lens and a diffraction grating is positioned properly. A converging lens focuses so that the interference fringes can be obtained on the crater wear. Performance test revealed that the developed image technique provides precise, absolute tool-wear quantification and reduces human measurement errors. The results obtained are as follows 1. The digitizing of one image requires less than 2ses. 2. It can give detailed information on crater wear with limited times and errors 3. All parameters required by specification are easily obtained for several points of the cutting edge.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.333-336
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• 2007

SELENE, a Japanese lunar mission, has been launched this year. There are large volumes of images that were already archived and will be archived by missions such as SELENE. Automatic image analysis systems, which extract useful information from large amounts of data, are now required. The authors propose Lunar Surface GIS, which archives lunar surface information collected by lunar orbiting spacecraft and conducts geological analysis automatically. This system includes automatic crater detection, automatic age determination, and lava thickness estimation methods. In this paper, methods for automatically determining the age and estimating the lava thickness of lunar mare are described. The lunar surface age was determined by analyzing data of detected crater size and number using a crater chronology method. Lava thickness was estimated by the extent of the overlying material around the crater as well as the composition of underlying terrain units. In this result, the age map at Mare Crisium suggests the mare had been formed 3.0-3.7 b.y. ago. The lava thickness result suggests the thickest part of the mare is distributed around the center of the mare. The Lunar Surface GIS can produce a geological map, age map, and mare lava thickness map, for example.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.329-344
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• 2015

Cratering tests in rock are generally carried out to identify its fragmentation characteristics. The test results can be used to estimate the minimum amount of explosives required for the target volume of rock fragmentation. However, it is not easy to perform this type of test due to its high cost and difficulty in securing the test site with the same ground conditions as the site where blasting is to be performed. Consequently, this study investigates the characteristics of rock fragmentation by using the hydrocode in the platform of AUTODYN. The effectiveness of the numerical models adopted are validated against several cratering test results available in the literature, and the effects of rock mass classification and ground formation on crater size are examined. The numerical analysis shows that the dimension of a crater is increased with a decrease in rock quality, and the formation of a crater is highly dependent on a rock of lowest quality in the case of mixed ground. It is expected that the results of the present study can also be applied to the estimation of the level and extent of the damage induced by blasting in concrete structures.

• 한국기계연구소 소보
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• s.19
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• pp.69-79
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• 1989

Cutting tool life monitoring is a critical element needed for designing unmanned machining systems. This paper describes a tool wear measurement system using computer vision which repeatedly measures flank and crater wear of a single point cutting tool. This direct tool wear measurement method is based on an interactive procedure utilizing a image processor and multi-vision sensors. A measurement software calcultes 7 parameters to characterize flank and crater wear. Performance test revealed that the computer vision technique provides precise, absolute tool-wear quantification and reduces human maesurement errors.