• The Journal of Engineering Geology
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• v.26 no.1
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• pp.15-22
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• 2016

Hydraulic falling head and slug tests were carried out in an alluvium aquifer using a borehole stability device. The hydraulic testing had proved difficult in alluvial formations of sands and gravels due to borehole collapse and unstable borehole walls within the test section. This study aims to improve the hydraulic test results by using a borehole stability device. The device can minimize the collapse of borehole walls, and the use of a filter with a constant opening ratio improves the calculations per unit area of the test section. Permeability obtained from the falling head test without a borehole stability device was 8.82 × 10⁻⁵m/sec. When the borehole stability device was installed in the same test section the measured permeability increased to 4.00 × 10⁻⁴m/sec, which is 4.5 times that obtained without the borehole device. The relatively low permeability obtained using the conventional test method is attributed to the presence of a fine-grained slime generated during drilling and a reduction of the test area in the test interval due to a gradual collapse of the borehole walls. This study considers how the use of a borehole stability device to prevent borehole collapse can influence the results of hydraulic tests in alluvial formations. It is expected that the results can be used as a basis for improving the reliability and applicability of hydraulic tests performed in alluvial aquifers.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.291-298
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• 2015

For hydrogeological studies, it is of importance to observe hydraulic head in order to interpret groundwater flow, characterize aquifers, and calibrate groundwater flow model. This study analyzed the zonal variation of hydraulic heads at the eight monitoring wells (GM-1~GM-8) installed with multi-packers in a coastal area and verified vertical and lateral trends of the hydraulic gradients. Hydraulic heads were expressed as the depth of water because the monitoring wells have different depths. The hydraulic gradient at the nearest well (GM-5) shows 0.0142 with increasing trend of hydraulic gradient along depth. This fact indicates typical phenomenon of the discharge area. On the other hand, GM-1 and GM-2 wells in coastal area demonstrate constant hydraulic gradient down to the depth of 100 meters while at the zone of deeper than 100 m the hydraulic gradients illustrate 0.0196 and 0.0735, respectively. This indicates that horizontal flow is dominant at shallower zone than 100 m whereas upward flow is dominant at the zone deeper than 100 m. GM-3 well located farther than the other wells from the coast shows a small hydraulic gradient of 0.0046 that evidences a prevalent horizontal flow between the recharge area and the discharge area.

• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.20-30
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• 2006

Hydrogeochemistry of deep geothermal water (temperature: $42.2-47.9^{\circ}C$) at Heunghae, Pohang was evaluated using core logging, temperature and electrical conductivity (EC) logging before and after pumping tests, chemical analysis of geothermal water with depth, and observation of water quality variations during pumping tests. The geology of the area is composed of highly fractured marine sedimentary rocks. The hydrogeochemistry of geothermal water varies with drilling depth, distance from the coast, and pumping duration. According to the temperature and EC variations during 4 times of pumping tests, main aquifer of the area is considered as the fractured zones (540 to 900 m) developed in rhyolitic rocks. The high content of Na and $HCO_3$ in geothermal water can be explained by the inflow of deep groundwater from inland regulated by dissolution of silicates and carbonates. High TDS, Na and Cl concentrations indicate that the geothermal water was also strongly affected by seawater. The molar ratios of Na:Cl ($0.88{\sim}2.14$) and Br:Cl ($21.0{\sim}24.9{\times}10^{-4}$) deviate from those of seawater (0.84 and $34.7{\times}10^{-4}$, respectively), suggesting that water-rock interaction also plays an important role in the formation of water quality.

• Economic and Environmental Geology
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• v.6 no.4
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• pp.231-233
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• 1973

1. 칠레의 중앙(中央)에 위치(位置)한 리오-아콘카우와 계곡(溪谷)은 600m 심도(深度)의 충적층(沖積層)으로 형성(形成)되어 있음. 2. 계곡(溪谷)의 물관리구역(管理區域)은 4 개구역중(個區域中) 3 개구역(個區域)에 걸쳐 있음. 3. 주요농업관개지역(主要農業灌漑地域)으로서 차카부퀴토에서 태평양연안(太平洋沿岸)까지의 거리(距離)는 113km가 됨. 4. 관개(灌漑)는 9 월(月)부터 5 월(月)사이에 도수로(導水路)와 관정(管井)에 의(依)하나 용수불족(用水不足)으로 저수지(貯水池)와 지하수개발(地下水開發)이 구상(構想)되었음. 5. 디지탈 모델 시험(試驗)은 제(第) 3 관리구역내(管理區域內) 약(約)7km의 거리(距離)의 히주에라스구간(區間)에서 이루어졌었음. 6. 시험결과(試驗結果) 가. 하천(河川)과 대수층(帶水層)과의 관련성(關聯性) 나. 다각도(多角度) 관개용수(灌漑用水)로 인(因)한 하천(河川)과 지하수(地下水) 저류(貯溜)의 효율성(效率性)의 확인(確認). 다. 지하수(地下水) 양수(揚水)에 의(依)한 지하수(地下水) 저류량(貯留量)의 감소(減少)와 라. 하천(河川)에의 재유입수량(再流入水量)이 관개(灌漑) 종료시(終了時)나 직후(直後)에 최대치(最大値)였음. 마. 리오 아콘카우와 계곡(溪谷)에 대(對)한 모델시험(試驗)을 제안(提案)하여 a) 장차(將次) 지하수개발(地下水開發)의 효과(效果)를 분석(分析)하고 b) 제안(提案)된 저수지(貯水池)의 효율(效率)과 c) 수자원(水資源)의 적절(適切)한 이용계획(利用計劃)을 수립(樹立)토록 하였음.

• Journal for History of Mathematics
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• v.22 no.4
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• pp.41-52
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• 2009

This study investigates a mathematical subject, 'triangles' in mathematics books of Chosun Dynasty, in special Muk Sa Jib San Bub(默思集算法), Gu Il Jib(九一集), San Hak Ib Mun(算學入門), Ju Hae Su Yong(籌解需用), and San Sul Gwan Gyun(算術管見). It is likely that they apt to avoid manipulating general triangles except the right triangles and the isosceles triangles etc. Our investigation says that the progress of triangle-related contents in Chosun mathematics can fall into three stages: measurement of the triangle-shaped fields, transition from the object of measurement to the object of geometrical study, and examination of definition, properties and validation influenced by western mathematics.

• Microbiology and Biotechnology Letters
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• v.15 no.5
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• pp.356-360
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• 1987

Effects of temperature on sisomicin fermentation were investigated. From the specific growth rates for logarithmic phase estimated at various temperatures, 8.2 kcal/g-mol was obtained as an activation energy for cell growth. It suggests that cell growth rate was limited by the internal diffusion layers for nutrients or oxygen caused by aggregated cells. Final antibiotic titer was decreased with in-creasing temperature, and it depended highly on the temperature to which cells were exposed during the logarithmic phase of growth. Temperature shifts during fermentation brought about an increase in antibiotic productivity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1384-1390
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• 2001

This paper deals with the forward kinematics of the 6-6 Stewart platform of planar base and moving platform using one extra linear sensor. Based on algebraic elimination method, it first derives an 8th-degree univariate equation and then finds tentative solution sets out of which the actual solution is to be selected. In order to provide more exact solution despite the error between measured sensor value and the theoretic alone, a correction method is also used in this paper. The overall procedure requires so little computation time that it can be efficiently used for real-time applications. In addition, unlike the iterative scheme e.g. Newton-Raphson, the algorithm does not require initial estimates of solution and is free of the problems that it does not converge to actual solution within limited time. The presented method has been implemented in C language and a numerical example is given to confirm the effectiveness and accuracy of the developed algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.2
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• pp.1-6
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• 2001

Tunnel lighting in Korea has the problems of unsatisfactory illuminance uniformity which obstructs driver's vision, a flicker phenomenon on wall of tunnel, a heavy glare, low efficiency of luminaires, low utilization factor, and high energy consumption. We developed a high efficiency luminaire reflector for tunnel lighting which removes these problems. Developed luminaire saves energy and improves lighting environment by increasing 10% of luminaire efficiency. It can reduce installation cost by decreasing the number of luminaires, while average illuminance of 200[lx], overall uniformity of 0.4, longitudinal uniformity of 0.7, and electric power consumptions per unit area of 3.7[W/m$^2$] are accomplished.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.367-368
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• 2020

최근 SocailNetworkService(SNS) 플랫폼은 중독을 유발하는 알고리즘을 통해서 시장점유율을 높이는 전략을 사용하고 있다. 이에 따른 부작용으로 일상생활에 무리가 갈 정도의 사용자가 나타나고 있다. SNS 중독 사용자는 스스로가 문제를 인지하고 있으나 자제를 못하고 있어 SNS 중독 완화를 돕는 어플리케이션이 개발되고 있다. 이러한 어플리케이션은 일정 부분 중독 완화에 도움은 주고 있으나 다음과 같은 문제점을 갖는다. 첫째 일반적으로 SNS 사용자는 여러 SNS를 동시에 사용하기 때문에 이를 통합하여 볼 수 있는 기능이 필요하다. 기존 어플리케이션에서는 특정 SNS만을 대상으로 하는 문제가 있다. 둘째 SNS의 사용량을 표현하는 방식이 단순이 그래프 형태로만 지원되어 다양한 정보 제공에 한계가 있다. 마지막으로 SNS의 과도한 사용에 대한 경각심을 새겨줄 수 있는 요소가 부족하다. 이 논문에서는 여러 SNS 사용량을 통합하여 제공하는 대시보드 기능, 게이미피케이션 요소를 접목하여 사용량을 다양한 가치로 보여주는 기능, 그리고 SNS 중독 정도에 따라 다양한 공포소구 메시지를 지원하는 기능을 통해 SNS 사용자의 중독 완화를 지원하는 어플리케이션을 제안한다.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.137-142
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• 1997

At the tailings dam of the disused Brukunga pyrite mine in South Australia, reaction of groundwater with the tailings causes the formation and discharge of sulphuric acid. There is a need to improve remediation efforts by decreasing groundwater flow through the tailings dam. Geophysical methods have been investigated to determine whether they can be used to characterise variations in depth to watertable and map preferred groundwater flow paths. Three methods were used: transient electromagnetic (TEM) soundings, direct current (DC) soundings and profiling, and self potential (SP) profiling. The profiling methods were used to map the areal extent of a given response, while soundings was used to determine the variation in response with depth. The results of the geophysical surveys show that the voltages measured with SP profiling are small and it is hard to determine any preferred channels of groundwater flow from SP data alone. Results obtained from TEM and DC soundings, show that the DC method is useful for determining layer boundaries at shallow depths (less than about 10 m), while the TEM method can resolve deeper structures. Joint use of TEM and DC data gives a more complete and accurate geoelectric section. The TEM and DC measurements have enabled accurate determination of depth to groundwater. For soundings centred at piezometers, this depth is consistent with the measured watertable level in the corresponding piezometer. A map of the watertable level produced from all the TEM and DC soundings at the site shows that the shallowest level is at a depth of about 1 m, and occurs at the southeast of the site, while the deepest watertable level (about 17 m) occurs at the northwest part of the site. The results indicate that a possible source of groundwater occurs at the southeast area of the dam, and the aquifer thickness varies between 6 and 13 m. A map of the variation of resistivity of the aquifer has also been produced from the TEM and DC data. This map shows that the least resistive (i.e., most conductive) section of the aquifer occurs in the northeast of the site, while the most resistive part of the aquifer occurs in the southeast. These results are interpreted to indicate a source of fresh (resistive) groundwater in the southeast of the site, with a possible further source of conductive groundwater in the northeast.