• The Journal of Engineering Geology
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• v.8 no.1
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• pp.51-73
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• 1998

Hydrogeological systems in a metrnpolitan area can be understood by analyzing the groundwater disturbing factors such as constructions and land applications, the groundwater usage for domestic and industrial purposes, and the groundwater pumpage to lower the groundwater level for the structural safety of subway and underground facilities. This study is part of the study performed to understand the groundwater system in the Seoul area and it is focusing on the hydraulic properties. Groundwater well inventory, barometric efficiency measurements, pumping and slug tests, and long-term groundwater monitoring have been perfonrmed during the last 2 years. The relations between Han River and the groundwater around the river also have been observed. These observations and test data, together with the information on soil distribution, geology, and logging data are used to construct a database and GIS(Geographic Information System) presentation system using ARC/INFO. Barometric efficiencies appeared to have no special trends associated with well depths, which maeans that the degree of confinement of the crystaline rock aquifer of the Seoul area is distributed locally depending on the developrnent of fractures. Hydraulic conductivities exponentialiy decrease with well depth. The stage of Han River fluctuates according to the tidal movement of nearby seawater but the tidal effects attenuate due to the underwater dams. Groundwater levels in the Seoul area seem to have declined for the last two years,but it is not certain that the declination represents the long-term trend.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.381-390
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• 2005

S City depends on the T River as source water for water supply. Arsenic and boron from the hot-spring waste-water discharged from the hot-spring spa resort and emerging from the fractures of bedrock of the river have been prevalent contaminant of the T River water. This research was conducted to propose the simple and quick surrogate parameter for water quality management easily. And through making hexa-diagram of principal ions in the water samples, existing state of the water and influence of the human activity or geological origin can be figured out. As a results of characteristics of the T River water quality using principal component analysis, the contributory percentages of the 1st, 2nd and 3rd principal components were $40.80\%,\;21.40\%\;and\;11.31\%$, respectively. Therefore it was clarified that the quality of the T River water could be explained by these three principal components. Concentration of the chloride ion, which is one of the characteristics of the hot-spring water, was well correlated to both arsenic and boron concentrations. Hence concentrations of the arsenic and boron in the raw water of the water reatment plant can be predicted by the measurement of concentration of the chloride ion.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.171-178
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• 1998

Silicon piezoresistive absolute pressure sensor for gas leakage alarm system was developed. This sensor must operate normally in the range of $0{\sim}600\;mmH_{2}O$ pressure, and $0{\sim}100^{\circ}C$ temperature. To make the most of this sensor for gas leakage alarm system, gas must not leak from the sensor itself when the diaphragm of the sensor fractures. Thus, the sealed diaphragm cavity was anodically bonded to pyrex 7740 glass under the condition of $10^{-4}$ torr, at $400^{\circ}C$. The sensitivity of developed sensor was $4.06{\mu}V/VmmH_{2}O$ for $600\;mmH_{2}O$ full-scale pressure range. And temperature compensation method of this sensor is to change bridge-in put-voltage linearly in proportion to the temperature variation by using diode(PXIN4001) or Al thin film resistor. By these methods the temperature effect in the range of $0{\sim}100^{\circ}C$ was compensated over 80 % for offset drift, 95 % for sensitivity.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.291-316
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• 1993

Restorative procedures can lead to tooth fracture due to the relatively small amount of the remaining tooth structure. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations. Among the several parameters in cavity designs, profound understanding of isthmus width factor would facilitate selection of the appropriate cavity preparation for a specific clinical situation. In this study, MO amalgam cavity were prepared on maxillary first premolar and filled with amalgam. Three dimensional, model with 1365 8-node brick elements was made by serial photographic method. In this model, isthmus was varied in width at 1/4, 1/3, 1/2 and 2/3 of intercuspal width and material properties were given for three element groups, i.e., enamel, dentin and amalgam. A load of 500 N was applied vertically on amalgam and enamel. In case of enamel loading, 2 model (with and without amalgam) was compared to consider the possibility of play at the interface between tooth material and amalgam. These models were analyzed with three dimensional finite element method. The results were as follows: 1. The stress was concentrated on the facio-pulpal line angle and distal marginal ridge of the cavity. 2. With the increase of the isthmus width, the stress spread around the facio-pulpal line angle and the area of stress concentration moved toward the proximal box. 3. In case of narrow isthmus width, the initiation point of crack would be in the area of isthmus corner of the cavity, and with the increase of the isthmus width, it would move toward the proximal box and at the same time the possibility of crack increase at the distal marginal ridge. 4. The direction of crack progressed outward and downward from the facio-pulpal line angle, and with the increase of the isthmus width, it approximated vertical direction. At the marginal ridge, it occurred in vertical direction. 5. It would be favorable to make the isthmus width narrower than a third of the intercuspal width, and to cover the cusp if isthmus width were wider than half of the intercuspal width. 6. It is necessary to apply the possibility of play to the finite element analysis.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.428-446
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• 1997

Restorative procedures can lead to weakening tooth due to reduction and alteration of tooth structure. It is essential to prevent fractures to conserve tooth. The resistance to fracture of the restored tooth may be influenced by many factors, among these are the cavity dimension and the physical properties of the restorative material. The placement of direct composite resin restorations has generally been found to have a strengthening effect on the prepared teeth. It is the purpose of this investigation to study the relationship between the cavity isthmus and the fracture resistance of a tooth in composite resin restorations. In this study, MO cavity was prepared on maxillary first premolar. Three dimensional finite element models were made by serial photographic method and isthmus(1/4, 1/3, 1/2 of intercuspal distance) were varied. Two types of model(B and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall and R model was left unfilled. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows : 1. Displacement of buccal cusp in R model occurred and increased as widening of the cavity, and displacement in B model was little and not influenced by cavity width. 2. There was a significant decrease of stress resulting in increase of fracture resistance in B model when compared with R model. 3. With the increase of the isthmus width, B model showed no change in the stress and strain. In R model, the stress and strain increased both in the area of buccal-pulpal line angle and the buccal side of marginal ridge, therefore the possibility of crack increased. 4. The stress and strain were distributed evenly on the tooth in B model, but in R model, were concentrated on the buccal side of the distal marginal ridge and buccal-pulpal line angle, therefore the possibility of fracture increased.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.141-151
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• 2013

This study examines the mineralogy of sepiolites occurred within the carbonaceous rocks of Songak schist and Pyeongtaek migmatitic gneiss of Precambrian Seosan group, in the western part of Chungnam. Host rocks of the sepiolite were dolomitic rocks and have experienced hydrothermal alteration and metamorphism. Mesozoic granite is assumed as a main source of hydrothermal alteration for the dolomitic rocks. Some of the tremolite asbestos coexist with the sepiolites. Representative sepiolite and tremolite samples were collected from the layers cracks or fractures of the dolomitic rocks and/or examined with microscope with microscope, XRD, SEM and TEM. Sepiolites are mainly recognized along the cracks assumed as pathways of hydrothermal solution. Tremolites are mainly found at layers or cracks of the dolomitic rocks and occur as asbestos as well as non-asbestos forms. It was confirmed that some of the tremolite asbestos were coexisted with the sepiolites. Overall results suggest that the occurrences of sepiolites within the dolomitic rocks mainly result in the hydrothermal alteration and the fluid from the acidic rocks, possibly granites. It also suggests that coexisting tremolite asbestos were formed by similar geological environment.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.105-121
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• 2013

This study introduces integrated approach on detection of a leakage in a sea wall based on remote sensing, electric resistivity survey, electromagnetic survey, and borehole survey for the Seosan A-Region sea wall. The satellite temperature distribution from Landsat ETM+ data identifies water leakage distribution and period by analyzing temperature mixing patterns between sea water and fresh water. Electric resistivity survey provides both horizontal and vertical anomaly distributions over the sea wall showing below average electric resistivity. Electromagnetic survey(electrical conductivity survey) reveals the potential possible leakage areas with minimal background impact by comparing electrical conductivity values between high and low tides. Borehole image processing system confirmed the locations of anomalies identified from the other survey methods and distributions of vertical fracture zones. The integrated approach identified 41.7% of the sea wall being the most probable area vulnerable to water leakage and effectively approximated both horizontal and vertical distribution of water leakage. The integrated analysis of remote sensing, electric resistivity survey, electromagnetic survey and borehole survey is considered to be an optimal method in identifying water leakage distribution, period, and extent of fractures knowledged from the boreholes.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.199-206
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• 2013

The Daehyun gold-silver deposit consists of two hydrothermal quartz veins that fill NE-trending fractures in the Cambro-Ordovician calcitic marble. I have sampled wallrock, hydrothermaly-altered rock and gold-silver ore vein to study the element dispersion and element gain/loss during wallrock alteration. The hydrothermal alteration doesn't remarkably recognized at this deposit and consists of mainly calcite, dolomite, quartz and minor epidote. The ore minerals composed of arsenopyrite, pyrrhotite, pyrite, sphalerite, stannite, chalcopyrite, galena, electrum, native bismuth and silver-bearing mineral. Based on analyzed data, the chemical composition of wallrock consists of mainly $SiO_2$, CaO, $CO_2$ with amounts of $Al_2O_3$, $Fe_2O_3(T)$ and MgO. The contents of $SiO_2$, $Fe_2O_3(T)$, MgO, CaO and $CO_2$ vary significantly with distance from ore vein. The element dispersion doesn't remarkably recognized during wallrock alteration and only occurs near the ore vein margin because of physical and chemical properties of wallrock. Remarkable gain elements during wallrock alteration are $Fe_2O_3(T)$, total S, Ag, As, Bi, Cd, Cu, Ni, Pb, Sb, Sn, W and Zn. Remarkable loss elements are $SiO_2$, MnO, MgO, CaO. $CO_2$ and Sr. Therefore, Our result may be used when geochemical exploration carry out at deposits hosted calcitic marble in the Hwanggangri metallogenic district.

• The Journal of Engineering Geology
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• v.22 no.4
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• pp.459-466
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• 2012

A difficulty encountered in engineering seismic mapping is that reflection events from shallow discontinuities are commonly overlapped with coherent noise such as air wave, direct waves, head waves, and high-amplitude surface waves. Here, the radial trace transform, a simple geometric re-mapping of a trace gather (x-t domain) to another trace gather (v-t domain), is applied to investigate the rejection effect of coherent linear noises. Two different types of data sets were selected as a representative database: good-quality data for intermediate sounding (hundreds of meters) in a sedimentary basin and very noisy data for shallow (${\leq}50m$) mapping of the weathered zone and bedrock surface. Results obtained with cascaded application of the radial transform and low-cut filtering proved to be as good as, or better than, those produced using f-k filtering, and were especially effective for air wave and direct wave. This simple transform enables better understanding of the characteristics of various types of noise in the RT domain, and can be generally applied to overcoming diffractions and back-scatterings caused by joints, fractures, and faults commonly that are encountered in geotechnical problems.

• Clinics in Shoulder and Elbow
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• v.2 no.2
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• pp.178-186
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• 1999

Twenty-three patients with chronic shoulder pain beyond 6 months after the fracture of the greater tuberosity underwent arthroscopic treatment and were retrospectively assessed after an average of 29 months(range, 22 to 40 months). There were 18 men and 5 women with the average age of 39 years(range, 24 to 61 years). Fourteen were isolated fractures and nine were related to acute anterior instability episode. The average displacement of the fracture was 2.3mm(range, 0 to 4mm) on the anteroposterior view of the plane radiographs. At the time of arthroscopy, all patients had partial thickness rotator cuff tears in the articular surface. The cuff tears were located on the tuberosity fracture area and were an Ellman's grade I to n in depth. With the arthroscopic debridement or repair of the tear depending on the condition of the tear itself, as well as the subacromial decompression, the UCLA score revealed good to excellent results in 20 and fair in 3 patients. Nineteen of the patients had returned to the previous level of activities. The patient with a higher activity demand revealed a lower level of activity return(p=0.034). The partial thickness rotator cuff tear should be considered in patients with chronic shoulder pain after the minimally displaced fracture of the greater tuberosity, and arthroscopic debridement or repair is an appropriate procedure.