• Proceedings of the KWS Conference
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• 2003.05a
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• pp.193-195
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• 2003

Micro-structure and shear properties with reflow conditions, reflow temperature and time, for In-48Sn solder on BGA package were examined at the temperature between 140 and 170$^{\circ}C$ for 10 to 3600sec. With increasing reflow temperature and time, the thickness of intermetallic compound formed between solder and pad increased. Shear test indicated shear force increased in the range to a critical value of reflow time, and decreased over a critical reflow time. With increasing reflow temperature and time, the crater occurred on fracture surface because of a increase of crater by voids and IMC particles precipitated in solder.

• Laser Solutions
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• v.3 no.3
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• pp.39-45
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• 2000

The volume and depth of the craters produced on silicon samples during high power laser ablation show a strong nonlinear change as the laser irradiance increases across a threshold value, approximately 2.2$\times$10$\^$10/ W/㎠. Time-resolved shadowgraph images of the ablation plume reveal the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 ㎱. The numerically estimated thickness of the superheated liquid layer, considering the transformation of liquid metal into liquid dielectric near the critical state, agrees with the measured agrees with crater depths. It is suggested that a phase explosion of the deep superheated liquid layer near the critical state is responsible for the measured sudden increase of crater volume and the ejection of large particulates.

• YAKHAK HOEJI
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• v.4 no.1
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• pp.21-34
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• 1959

(1) Plants in the crater of Halla-San (Mt. Halla), a conical volcano that originated in the Tertiary period, were studied on three different occasions; July 1937, July 1955, and August 1957, and noted 52 familites, 149 species. In the latest study undergone in 1957, the authors collected 108 species. Notable species among them are Geranium Shikokianum Matsum which has not been reported in Korea, Clematis Chiisanensis Nakai, Lactuca Chelidonifolia Makino, and Platanthera Maximowiczana Schelchter which have not been reported in Jeu-Do(Island) so far. (2) Plants in To-Do(Island), territorial island of Jeju-do, were also studied. The authors noted Canavalia lineata D.C.non-reported Species in Korea, usually distributed along Southern Honshu, Shikoku, and Kyushu of Japna, Ryukyu and Taiwan. The overfall flora of the island is composed of 30 families, 44 Species; 5 Species of wood plants and 39 species of herbs, and is mostly of littoral plants.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.2
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• pp.83-92
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• 2019

This study set out to analyze James Turrell's Skyspace works by applying the object relations theory, compare them with several modern architectural works with a sky window based on the analysis results, and check common and differentiating features between them. The findings were as follows: first, Turrell's Skyspace works shed new light on the images of the sky by projecting inner light to the outside; second, sky windows in architecture make the self-representation of inner space clear through the introjection of light; third, 'Hill of the Buddha' reflects the most general aspect of the object relations theory as the nature of projection found in Turrell's Skyspace is added to it; and finally, Turrell installed event-like spaces and steps in 'Roden Crater' to apply the introjection of others that was deficient in Skyspace.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.86-97
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• 1994

An experimental investigation is reported on the wear mechanism of CBN cutting tools. The cutting experiments were conducted on a lathe equipped with a tool dynamometer for cutting force measurement. The investigation of wear mechanism was executed by observing the worn tools using tool microscope and scanning electron microscope. Results indicate that the flank wear occurs dominantly by abrasive wear mode and the crater wear by adhesive wear mode. The results also indicate that the width of flank wear is closely related with the passive component of cutting force.

• Ocean and Polar Research
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• v.24 no.4
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• pp.491-500
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• 2002

Magnetic anomalies in the Dokdo and it's surroundings were investigated with respect to structure and origin of the Dokdo and surrounding seamounts. After normal and diurnal correction of measured magnetic data, crossover correction was applied to reduce errors between sets of magnetic anomalies. The errors from crossover operation result in decrease of about 51%, from 62.2 nT to 30.1 nT in standard deviation. Reduction-to-the-pole, second vertical derivative and analytic signal processing were applied to explore magnetic anomaly signatures in detail. Magnetic anomalies are most complicated in the 1st-Dok seamount, show SWW-NEE linear pattern in the 2nd-Dok seamount and lower to the 3rd-Dok seamount. Different magnetic anomaly patterns in three seamounts imply that three volcanic seamounts were formed at different times and are composed of rocks that were produced in different conditions. It seems that the 3rd-Dok seamount was first to form and followed by the 1st-Dok seamount. The complicated magnetic and second vertical derivative anomaly patterns in the 1st-Dok seamount may be due to subsidiary cones around crater or the presence of intruded magma bodies below sea surface and the Dokdo is probably a marginal subsidiary part of crater.

• The Journal of the Petrological Society of Korea
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• v.12 no.4
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• pp.184-195
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• 2003

Hawaii Island makes up of five volcanos of Kohala, Mauna Kea, Hualalai, Mauna Loa, and Kilauea. They are big shield volcanoes rising above the Pacific ocean floor and final two volcanoes provide a natural laboratory for the study of active volcanoes. Mauna Loa is the largest single volcano on earth. At the submmit is an oval-shaped Mokuaweoweo caldera, from which two rift zones extend to the southwest and northeast, and in the medial part are the longest lava tube systems in the world. Kilauea has been formed largely by eruption along southwest and eastern rift zones extending from Kilauea caldera at the submmit. On the eastern rift zone, spectacularly, the 1989-1974 eruption of Kilauea at Mauna Ulu crater formed the Mauna Ulu lava flow field. The 1983-1986 eruption of aa flows at Puu Oo crater, and the activities of pahoehoe flows during 1986-1990 at Kupaianaha crater and during 1991-recent at the Puu Oo has produced the Puu Oo and Kupaianaha lava flow field.

• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.377-385
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• 2012

In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fiber, PP and PVA, and these were mixed in at 0.1, 0.5 and 1.0 vol.%, respectively. Impact resistance is evaluated with an apparatus for testing impact resistance performance by high-speed projectile crash by gas-pressure. For the experimental conditions, Specimen size was $100{\times}100{\times}20$, 30mm ($width{\times}height{\times}thickness$). Projectile diameter was 7 and 10 mm and impact speed is 350m/s. After impact test, destruction grade, penetration depth, spalling thickness and crater area were evaluated. Through this evaluation, it was found that as compressive strength is increased, penetration is suppressed. In addition, as the mixing ratio of fiber is increased, the spalling thickness and crater area are suppressed. Organic fibers have lower density than the steel fiber, and population number per unit area is bigger. As a result, the improvement of impact resistance is more significant thanks to dispersion and degraded attachment performance.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.72-78
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• 2009

For the electro-discharge machining of an electro-conductive anisotropic composite, an unsteady state formulation was established and solved by Galerkin's finite element method. The distribution of temperature on work piece, the shape of the crater and the material removal rate were obtained in terms of the process parameters. The $12{\times}12$ irregular mesh that was chosen as the optimum in the previous analysis was used for computational accuracy and efficiency. A material having the physical properties of alumina/titanium carbide composite was selected and an electricity with power of 51.4 V and current of 7 A was applied, assuming the removal efficiency of 10 % and the thermal anisotropic factors of 2 and 3. As the spark was initiated the workpiece immediately started to melt and the heat affected zone was formed. The moving boundary of the crater was also identified with time. When the radial and axial conductivities were increased separately, the temperature distribution and the shape of the crater were shifted in the radial and axial directions, respectively. The material removal rate was found to be higher when the conductivity was increased in the radial direction rather than in the axial direction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.37-45
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• 2013

In this study, the resistance of various reinforced concrete (RC) slabs subjected to contact detonation was assessed. In order to enhance the blast resistance, fibers and external FRP sheets were reinforced to RC slabs. In the experiment, the $2,000{\times}1,000{\times}100mm$ sized RC slabs were fabricated using normal concrete (NC), steel fiber reinforced concrete (SFRC), polyvinyl alcohol fiber reinforced cementitious composite (PVA FRCC), and ultra-high performance cementitious composites (UHPCC). The damage levels of RC slabs subjected to contact detonation were evaluated by measuring the diameter and depth of crater, spall and breach. The experimental results were compared to the analyzed data using LS-DYNA program and three different prediction equations. The diameter and depth of crater, spall and breach were able to be predicted using LS-DYNA program approximately. The damage process of RC slabs under blast load was also well expressed. Three prediction equations suggested by other researchers had limitations to apply in terms of empirical approaches, therefore it needs further research to set more analytical considerations.