• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.67-71
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• 2017

Debris disks are circumstellar dust disks around main-sequence stars. They are important observational clues to understanding the planetary system formation. The zodiacal light is the thermal emission from the dust disk in our Solar system. For a comprehensive understanding of the nature and the evolution of dust disks around main-sequence stars, we try a comparative study of debris disks and the zodiacal light. We search for debris disks using the AKARI mid-infrared all-sky point source catalog. By applying accurate flux estimate of the photospheric emission based on the follow-up near-infrared observations with IRSF, we have improved the detection rate of debris disks. For a detailed study of the structure and grain properties in the zodiacal dust cloud, as an example of dust disks around main-sequence stars, we analyze the AKARI mid-infrared all-sky diffuse maps. As a result of the debris disks search, we found old (>1 Gyr) debris disks which have large excess emission compared to their age, which cannot be explained simply by the conventional steady-state evolution model. From the zodiacal light analysis, we find the possibility that the dust grains trapped in the Earth's resonance orbits have increased by a factor of ~3 in the past ~20 years. Combining these results, we discuss the non-steady processes in debris disks and the zodiacal light.

• Journal of the Korean Geotechnical Society
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• v.30 no.10
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• pp.55-65
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• 2014

Recent researches on debris flow is focused on understanding its movement mechanism and building a numerical simulator to predict its behavior. However, previous simulators emulating fluid-like debris flow have limitations in numerical stability, geometric modeling and application of various boundary conditions. In this study, depth integration is applied to continuity equation and force equilibrium for debris flow. Thickness of sediment, and average velocities in x and y flow direction are chosen for main variables in the analysis, which improve numerical stability in the area with zero thickness. Petrov-Galerkin formulation uses a discontinuous test function of the weighted matrix from DG scheme. Presented mechanical constitutive model combines fluid and granular behaviors for debris flow. Effects on slope angle, inducing debris height, and bottom friction resistance are investigated for a simple slope. Numerical results also show the effect of embankment at the bottom of the slope. Developed numerical simulator can assess various risk factors for the expected area of debris flow, and facilitate embankment design in order to minimize damage.

• Spatial Information Research
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• v.17 no.3
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• pp.389-395
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• 2009

In spite of many numerical analysis of debris flow, a little information has been found out. In this paper the watershed is divided to apply rainfall runoff and to estimate debris flow integrating flow and soil article. We use the contour data to extract spatially distributed topographical information like stream channels and networks of sub-basins. A Quasi Digital Elevation Model (Q-DEM) is developed, integrated, and adopted to estimate runoff based on marked one. As a results, it has been found out that the debris flow was close to observed flow hydrograph. Because debris flow is finished in 30 second, it is important that we have to prepare its prior countermeasure to minimize the damage of debris flow. The GIS-linked model will provide effective information to plan river works for debris flow.

• Restorative Dentistry and Endodontics
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• v.45 no.3
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• pp.33.1-33.10
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• 2020

Objectives: This study was conducted to evaluate the effects of traditional and contracted endodontic cavity (TEC and CEC) preparation with the use of Reciproc Blue (RPC B) and One Curve (OC) single-file systems on the amount of apical debris extrusion in mandibular first molar root canals. Materials and Methods: Eighty extracted mandibular first molar teeth were randomly assigned to 4 groups (n = 20) according to the endodontic access cavity shape and the single file system used for root canal preparation (reciprocating motion with the RCP B and rotary motion with the OC): TEC-RPC B, TEC-OC, CEC-RPC B, and CEC-OC. The apically extruded debris during preparation was collected in Eppendorf tubes. The amount of extruded debris was quantified by subtracting the weight of the empty tubes from the weight of the Eppendorf tubes containing the debris. Data were analyzed using 1-way analysis of variance with the Tukey post hoc test. The level of significance was set at p < 0.05. Results: The CEC-RPC B group showed more apical debris extrusion than the TEC-OC and CEC-OC groups (p < 0.05). There were no statistically significant differences in the amount of apical debris extrusion among the TEC-OC, CEC-OC, and TEC-RPC B groups. Conclusions: RPC B caused more apical debris extrusion in the CEC groups than did the OC single-file system. Therefore, it is suggested that the RPC B file should be used carefully in teeth with a CEC.

• Journal of The Geomorphological Association of Korea
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• v.24 no.1
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• pp.77-91
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• 2017

Many debris landforms in the mountains of Korea have formed in the periglacial environment during the last glacial stage when the generation of sediments was active. Because these landforms are generally located on steep slopes and mostly covered by vegetation, however, it is difficult to observe and access them through field investigation. A scientific method is required to reduce the survey range before performing field investigation and to save time and cost. For this purpose, the use of remote sensing and GIS technologies is essential. This study has extracted the potential area of debris landform formation using a fuzzy set model as a mathematical data integration method. The first step was to obtain information about the location of debris landforms and their related factors. This information was verified through field observation and then used to build a database. In the second step, we conducted the fuzzy set modeling to generate a map, which classified the study area based on the possibility of debris formation. We then applied a cross-validation technique in order to evaluate the map. For a quantitative analysis, the calculated potential rate of debris formation was evaluated by plotting SRC(Success Rate Curve) and calculating AUC(Area Under the Curve). The prediction accuracy of the model was found to be 83.1%. We posit that the model is accurate and reliable enough to contribute to efficient field investigation and debris landform management.

• Journal of Korean Society of Disaster and Security
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• v.15 no.4
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• pp.71-78
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• 2022

Recently, mountain disasters such as landslides and debris flows have flowed along mountain streams and hit residential areas and roads, increasing damage. In this study, in order to reduce damage and analyze causes of mountain disasters, field surveys and Terrestrial LiDAR terrain analysis were conducted targeting debris flow areas, and debris flow flow processes were simulated using FLO-2D and RAMM models, which are numerical models of debris flows. In addition, the debris flow deposition area was calculated and compared and analyzed with the actual occurrence section. The sedimentation area of the debris flow generation section of the LiDAR scan data was estimated to be approximately 21,336 ㎡, and was analyzed to be 20,425 ㎡ in the FLO-2D simulation and 19,275 ㎡ in the case of the RAMMS model. The constructed topographical data can be used as basic data to secure the safety of disaster risk areas.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1300-1309
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• 2023

Simulated debris was synthesized using UO₂, Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO₂, whereas a (U, Zr)O₂ solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U₃O₈ and (Fe, Cr)UO₄ phases formed at 1473 K, whereas a (U, Zr)O_2+x solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous solution for immersion. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.369-376
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• 2009

Field investigation was performed right after the occurrence of debris flow at Jinbu area. Geomorphic and geotechnical characteristics were investigated and rain fall data were collected. Based on these data, seepage and slope stability analysis was performed to verify the behavior of ground water and factor of safety of the slope according to the rainfall intensity and time. As a results, the minimum value of factor of safety achieved in long time after the moment of maximum precipitation rate. And it is confirmed that the factor of safety is susceptible to ground water level rather than rainfall intensity.

• Tribology and Lubricants
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• v.13 no.2
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• pp.82-88
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• 1997

This paper describes an empirical equation which can be used to predict the engine condition of supersonic aircraft. The equation, which is derived from the trend analysis of JOAP data, represents the concentration of Fe particles in the engine oil. The result of the trend analysis shows that the concentration of Fe particles is a function of running time of engine oil. Meanwhile the slope of Fe concentration is a function of running time of engine. Threfore, the empirical equation was derived as $w=a(t_e).t_o+b$. However, the equation could not enough to diagnose the damaged part of engine quantitatively. To make up for the weak points of the equation, qualitative analysis was carried out. For that purpose wear debris were collected from the abnormal engine and analyzed by EDS to detect the damaged parts of engine.

• Elastomers and Composites
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• v.48 no.3
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• pp.225-231
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• 2013

In this study, we observed the effect of carboxylated SBR latex and zinc oxide on styrene-butadiene-styrene( SBS) composites for improving abrasion and debris. SBS composite, which added only silica, showed poor mechanical properties, NBS abrasion, and debris, caused by strong filler-filler interaction of silica. In case of adding carboxylated SBR latex, mechanical properties, NBS abrasion and debris of SBS composite were improved. Because of carboxyl group of carboxylated SBR latex interacted with silanol group of silica. Both carboxylated SBR latex and zinc oxide were added, SBS composite showed highest mechanical properties, NBS abrasion, and debris by forming ion cluster between carboxylated SBR latex and zinc oxide. By FT-IR analysis, ion clusters were confirmed that observed zinc carboxylated group stretch peak at $1550{\sim}1650cm^{-1}$ range. SBS composite, SC-4, showed excellent mechanical properties ; tensile strength $156kgf/cm^2$, elongation 936%, tear strength 59.4kgf/cm ; and excellent abrasion characteristics ; NBS abrasion 338%. Also, debris of SC-4 was minimized and showed wave-shape in fracture surface.