• Imaging Science in Dentistry
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• 제35권4호
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• pp.231-234
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• 2005

Coronoid impingement can cause limitation of mouth opening. In many cases, it appears to be related to the coronoid hyperplasia. We present a case of mouth opening limitation caused by coronoid impingement on the posterior surface of the zygomatic bone without coronoid hyperplasia. The bony changes in coronoid and zygoma including surface irregularity and discontinuity of the cortex and sclerotic change of inner medullary space were noted on computed tomography (CT) scans in different level of axial planes. Through another CT scans in open mouth position could demonstrate that those bony changes were caused by the contact of both surfaces against each other. In case coronoid impingement is suspected of the many possible causes, the open mouth CT scans will be needed to reveal the direct impingement of coronoid on zygoma even without coronoid hyperplasia.

• Journal of The Korean Society of Agricultural Engineers
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• 제59권1호
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• pp.57-70
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• 2017

In this study, we evaluated daily root zone soil moisture dynamics and agricultural drought using a near-surface soil moisture data assimilation scheme with Soil Moisture Active & Passive (SMAP, $3km{\times}3km$) soil moisture footprints under different hydro-climate conditions. Satellite-based LANDSAT and MODIS image footprints were converted to spatially-distributed soil moisture estimates based on the regression model, and the converted soil moisture distributions were used for assessing uncertainties and applicability of SMAP data at fields. In order to overcome drawbacks of the discontinuity of SMAP data at the spatio-temporal scales, the data assimilation was applied to SMAP for estimating daily soil moisture dynamics at the spatial domain. Then, daily soil moisture values were used to estimate weekly agricultural drought based on the Soil Moisture Deficit Index (SMDI). The Yongdam-dam and Soyan river-dam watersheds were selected for validating our proposed approach. As a results, the MODIS/SMAP soil moisture values were relatively overestimated compared to those of the TDR-based measurements and LANDSAT data. When we applied the data assimilation scheme to SMAP, uncertainties were highly reduced compared to the TDR measurements. The estimated daily root zone soil moisture dynamics and agricultural drought from SMAP showed the variability at the sptio-temporal scales indicating that soil moisture values are influenced by not only the precipitation, but also the land surface characteristics. These findings can be useful for establishing efficient water management plans in hydrology and agricultural drought.

• The Journal of the Convergence on Culture Technology
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• 제6권2호
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• pp.467-472
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• 2020

Methods for deriving design input-parameters to ensure the stability of a structure on a common ground are generally well known. Folded metamorphic rocks, such as the study area, are highly foliated and have small faults parallel to the foliation, resulting in special research methods and tests to derive design input parameters, Etc. are required. The metamorphic rock ground with foliation development of several mm intervals has a direct shear test on the foliation surface, the strike/dip mapping of the foliation, the boring investigation to determine the continuity of the foliation, and the rock mass rating of the metamorphic rock. etc. are required. In the case of a large number of small foliation-parallel faults developed along a specific foliation plane, it is essential to analyze the lineament, surface geologic mapping for fault tracing, and direct shear test. Folded ground requires additional geological-structural-domain analysis, discontinuity analysis of stereonet, electrical resistivity exploration along the fold axis, and so on.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.889-901
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• 2014

Very long life fatigue tests were carried out on 16Mn steel base metal and its welded joint by using the ultrasonic fatigue testing technique. Specimen shapes (round and plate) were considered for both the base metal and welded joint. The results show that the specimens present different S-N curve characteristics in the region of $10^5-10^9$ cycles. The round specimens showed continuously decreasing tendency while plate specimens showed a steep decreasing step and an asymptotic horizontal one. The fatigue strength of round specimen was found higher than plate specimen. The fatigue strength of as-welded joint was 45.0% of the base material for butt joint and 40% for cruciform as-welded joint. It was found that fracture can still occur in butt joint beyond $5{\times}10^6$ cycles. The cruciform joint has a fatigue limit in the very long life fatigue regime ($10^7-10^9$ cycles). Fatigue strength of butt as-welded joint was much higher as compared to cruciform as-welded joint. Improvement in fatigue strength of welded joint was found due to UPT. The observation of fracture surface showed crack mainly initiated from welded toe at fusion areas or geometric discontinuity sites at the surface in butt joint and from welded toe in cruciform joint.

• The Journal of Engineering Geology
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• 제7권2호
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• pp.101-112
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• 1997

Gravity and electrical resistivity surveys were carried out across the Kwangju fault in the downstream area of the Jangsung Lake, to investigate the location and geometrical feature of the fault. In the resistivity survey, dipole - dipole array method was adopted for 3 survey lines of which length and electrode spacing are 500m and 25m, respectively. Resistivity data are interpreted with aid of computer program "RESIS" which is widely used in resistivity data analysis and two dimensional resistivity profiles are obtained for 3 survey lines. Two large fracture zones relevant to the Kwangju fault are identified in the resistivity profiles. The total of 80 gravity data are observed with the mean spacing of 40 m and the exact leveling is accompanied to obtain more precise gravity anomalies. The subterranean density discontinuities calculated from the inverse method are appeared at the depths of 650rn and 120m. It is considered that the deep discontinuity indicates boundary between Jurassic granites and oveflying Cretaceous tuff formation. while, the shallow discontinuity is interpreted to be a boundary between alluvial deposits and basements. The subsurface geological structure to satisfy the observed Bouguer anomaly is determined from the iterative forward method in which results from existing surface geological informations, the inverse method, and from the resistivity interpretations are employed as an iuitial model. In conclusion, Kwangju fault is appeared to be a high angle normal fault mainly formed in tension stress filed.

• Geophysics and Geophysical Exploration
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• 제13권3호
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• pp.256-267
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• 2010

Earthquakes in the Korean Peninsula occur along the faults formed and boundaries between major geological units ruptured due to violent tectonic activities during the Mesozoic. E-W and/or ENE-SSW compressive stress regime resulting from collisions between the Eurasian plate and neighbouring the Indian plate, the Pacific plate and the Philippine plate trigger Korean earthquakes of thrust faulting with predominant strike-slip components along the mostly NNE-SSW trending active faults. Seismicity of the Korean peninsula has been moderate to low during the past 20 centuries except for the period from the 15th to the 18th centuries of exceptionally high seismicity, showing the typical irregularity of intraplate seismicity. The structure of the Korean peninsula is rather homogeneous without the Conrad discontinuity sharply dividing the upper and lower crust. Lateral heterogeneities exist in the crust. The crust with an average thickness of about 33 km is thicker in the mountainous region than the plain due to the Airy-type isostatic equilibrium maintained in the peninsula. Crustal P-wave velocity with average of about 6.3 km/sec increases gradually from the near surface to the Moho. The upper mantle P-wave (Pn) velocity is about 7.8 km/sec.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 공동학술대회 논문집
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• pp.103-107
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• 2005

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting first arrival times. One-dimensional velocity models derived by joint analyses of teleseismic receiver functions and surface wave dispersion at several stations near the profiles were uesd to build initial models. The raypaths indicate several midcrust interfaces including ones at approximate depths of 2.0 and 14.9 km with refraction velocities of approximately 6.0 and 7.1 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting velocity varies from 7.8 to 8.1 km/s along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at 6-7 km depth under the Okchon fold belt, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin whose thickness is less than 4.2 km.

• Journal of the Korean Geophysical Society
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• 제9권1호
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• pp.47-62
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• 2006

More than 70% of Korean Peninsula is consisted of mountains, so that lots of roads, rail-roads and tunnel,which play a pivotal role in the industry activity, are existed along the rock-slope and in the rock-mass. Thus,it is urgent that tegration of management system through the optimum survey and design of rock-slope excavation, proper stabilization method and database of rock-slope. However, conventional methods have shortcoming with the economy of survey time and human resources, and the overcome of difficulties of approach to the in-situ rock-slope. To overcome the limitation of conventional method, this paper proposed the development of remote measurement system using Terrestrial Laser Scanning System. The method using Terrestrial 3D Laser Scanning System, which can get 3D spatial information on the rock-slope and2)Dept. Geosystem Engineering, Kangwon National University, Korea tunnel, has an advantage of reduction of measurement time and the overcome of difficulties of approach to the in-situ rock-slope/dam/tunnel. In the case of rock-slope, through the analysis of 3D modeling of point-cloud by Terrestrial Laser Scanning System, orientation of discontinuity, roughness of joint surface, failure shape and volume were successively achieved. in the case of tunnel face, through reverse-engineering, monitoring of displacement was possible.

• Geophysics and Geophysical Exploration
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• 제20권3호
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• pp.185-192
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• 2017

A sequence of earthquakes with the main shock $M_L$ 5.8 occurred on September 12 2016 in the Gyeongju area. The main shock was the largest earthquakes in the southern part of the Korean peninsula since the instrumental seismic observation began in the peninsula in 1905 and clearly demonstrated that the Yangsan fault is seismically active. The mean focal depth of the foreshock, main shock, and aftershock of the Gyeongju earthquakes estimated by the crustal model of single layer of the Korean peninsula without the Conrad discontinuity turns out to be 12.9 km, which is 2.8 km lower than that estimated based on the IASP91 reference model with the Conrad discontinuity. The distribution of the historical and instrumental earthquakes in the Gyeongju area indicates that the Yangsan fault system comprising the main Yangsan fault and its subsidiary faults is a large fracture zone. The epicenters of the Gyeongju earthquakes show that a few faults of the Yangsan fault system are involved in the release of the strain energy accumulated in the area. That the major earthquakes of Gyeongju earthquakes occurred not on the surface but below 10 km depth suggests the necessity of the study of the distribution of deep active faults of the Yangsan fault system. The magnitude of maximum earthquake of the Gyeongju area estimated based on the earthquake data of the area turns out to be 7.3. The recurrence intervals of the earthquakes over magnitudes 5.0, 6.0 and 7.0 based on the earthquake data since 1978, which is the most complete data in the peninsula, are estimated as 80, 670, and 5,900 years, respectively. The September 2016 Gyeongju earthquakes are basically intraplate earthquakes not related to the Great East Japan earthquake of March 11 2011 which is interplate earthquake.

• 한국문화재보존과학회:학술대회논문집
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• 한국문화재보존과학회 2004년도 제20회 발표논문집
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• pp.81-91
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• 2004

The host rock of standing sculptured Buddha in the Yongamsa temple was macular biotite granite, which has gone through mechanical and chemical weathering. The principal rock-forming minerals are quartz, plagioclase, alkali feldspar, and biotite, the last two of which have been transformed into clay minerals and chlorite due to weathering processes. The bed rock around the Buddha statue is busily scattered with steep inclinations that are almost vertical and discontinuous planes with the strikes of $N8^{\circ}E$. The major joints have the strikes of N4 to $52^{\circ}W$ and N6 to $88^{\circ}E$ and the dips of 42 to $89^{\circ}$. Especially thee development of the joints that cross the major joints causes tile structural instability of the rock. The host rock of the Buddha image is separated into many different rock masses because of the also many different discontinuity, which group accounts for about $12{\%}$ of the rock. Thus it's estimated that the bed rock has not only plane and toppling failure but also wedge failure in all the sides. Since the earth pressure and the inclination pressure are imposed on the body of the Buddha in the basement rock, it's urgent to give a treatment of geotechnical engineering for the sake of its structural stability. The parts where serious fractures are seen should receive the hardening process using the fillers for stones. It's also necessary to introduce a landfill liner system in order to reduce the ground humidity. The rock surface of the Buddha statue are partly contaminated by lichens and bryophyte. The joints have turned into earth, which promotes the growth of weeds and plant roots. Thus biochemical treatments should also be considered to get rid of the vegetation along the discontinuous planes and prevent further biological damages.