• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.3
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• pp.248-256
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• 1995

The numerical study on the surface buoyant jets has remained of requiring more intensive investigation for problems due to the treatments of free surface, Reynolds stress/flux terms in turbulent flow and especially buoyancy effects on the turbulent fluctuation. etc. The verification of predicted results from the numerical study continues in the qualitative study. because of the lack of experimental data, which seems to be due to the difficulties in measuring the turbulent fluctuations in concentration or temperature fields. In this study, the computer program of Algebraic Stress Model has been developed to investigate the behaviours of two-dimensional surface buoyant jets with free surface boundary condition. The computational results are compared with published experimental data. By comparing these results with experimental data. it is found that this model can predict fairly well the flow characteristics of two-dimensional surface buoyant jets in the momentum-dominant region and buovancy-dominant region. Especially, it is proved that this model can predict the flow characteristics reasonably in buoyancy-dominant region stably stratified due to buoyancy effect.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.396-397
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• 2006

현재 우리나라의 전력 산업은 과거 공급자위주의 전력시장에서 점차적으로 수요자 선택권이 확대되고 다양한 형태의 새로운 부가서비스가 개발되는 시장으로 변화하고 있다. 이는 신기술 도입과 융합을 통하여 기존의 전력서비스에 통신기술이 융합된 전력정보기술의 도입으로 가능해진 것이다. 이러한 시장과 기술의 변화를 반영하여 우리나라에서도 광범위한 영역에서 전력 부가서비스에 대한 연구가 시작되고 있다. 다양한 방향으로 진화 가능한 전력부가서비스를 효율적으로 개발하기 위해서는 서비스 제공 대상을 명확하게 하고 소비자의 needs를 파악하는 과정이 필수적이다. 이러한 과정을 통하여 전력부가서비스 사업 초기에 집중적으로 개발, 보급하여야 할 부가서비스를 취사선택할 수 있을 것이다. 본 연구는 대수용가를 대상으로 하는 전력부가서비스의 형태를 파악하고 현재 진행 중인 선행연구를 분석하여 대수용가 전력부가서비스의 개발 방향을 제시하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.113-116
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• 2001

본 연구에서는 상보적인 빔형성에 기반한 대수적 마이크로폰 배열을 이용한 음성개선 시스템을 제안한다. 사람들이 많이 모여있는 회의실이나 사무실 환경에서는 백색잡음 보다 음성잡음, 즉, 다른 화자의 음성신호가 더 큰 영향력을 가질 수 있다. 따라서 대수적인 마이크로폰 배열을 사용함으로써 기존의 빔형성 기법에 비하여 저주파 영역에서의 성능을 향상시키고자 하였다. 모의실험 결과, 백색 가우시안 잡음에 대해서는 별다른 성능저하 없이 저주파 성분이 강한 음성잡음에 대해서는 우수한 성능을 가짐을 알 수 있었다.

• Communications of Mathematical Education
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• v.31 no.2
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• pp.103-121
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• 2017

Taxicab geometry was a typical non-Euclid geometry for mathematically gifted. Most educational material related quadratic curves on taxicab geometry for mathematically gifted served them to inquire the graph of the curves defined by focis and constant. In this study, we provide a shape of quadratic curves on taxicab geometry by applying three definitions(geometric algebraic definition, eccentricity definition, conic section definition).

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.1-11
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• 2004

Foam reduces the mobility of gas phase in porous media to overcome gravity override and to divert acid into desired layers in the petroleum industry and to enhance the efficiency of environmental remediation. Recent experimental studies on foam show that foam exhibits a remarkably different flow rheology depending on the flow regime. This study, for the first time, focuses on the issues of foam diversion process under the conditions relevant to groundwater remediation, combining results from laboratory linear-flow experiments and a simple numerical model with permeability contrasts. Linear flow tests performed at two different permeabilities (k = 9.1 and 30.4 darcy) confirmed that two flow regimes of steady-state strong foams were also observed within the permeability range of shallow geological formations. Foam exhibited a shear-thinning behavior in a low-quality regime and near Newtonian rheology in a high-quality regime. Data taken from linear flow tests were incorporated into a simple numerical model to evaluate the efficiency of foam diversion process in the presence of permeability contrasts. The simple model illustrated that foam in the high-quality regime exhibited a successful diversion but foam in the low-quality regime resulted in anti-diversion, implying that only foam in the high-quality regime would be applicable to the diversion process. Sensitivity study proved that the success of diversion process using foam in the high-quality regime was primarily controlled by the limiting capillary pressures (${P_c}{^*}$) of the two layers of interest. Limitations and implications are also discussed and included.

• Economic and Environmental Geology
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• v.53 no.5
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• pp.543-552
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• 2020

In this study, we measured groundwater fluxes with a passive flux meter and a borehole dilution test in the Upper Floridan Aquifer. In addition, the feasibility of the passive flux meter is also evaluated within matrix and non-matrix zones. The results of the PFM (5.96 ± 1.75 cm/day) showed good agreement with those of the BHD (4.68 ± 2.99 cm/day) in matrix zones, whereas the results of the PFM (9.94 ± 0.90 cm/day) showed poor agreement with those of the BHD (1817.37 ± 1795.50 cm/day) in non-matrix zones. We assumed that the groundwater passes through the sorbent material inside the PFM. However, it could not pass through the sorbent when the groundwater flux is faster than 11 cm/day. The flow might bypass between monitoring well and the PFM. The PFM used in this study might be suitable for measuring the groundwater fluxes under 11 cm/day. Therefore, more extensive research is needed in the future to measure fast groundwater fluxes (> 11 cm/day).

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.24-31
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• 2005

This study presents a contaminant transport model suitable for a 2-dimensional heterogeneous aquifer with multiple contaminant sources. It uses a streamline simulation, which transforms a multi-dimensional problem into multiple 1dimensional problems. It runs flow simulation, streamline tracking, and calculation of contaminant concentrations by turns. The model is verificated with a Visual MODFLOW by comparing contaminant concentration distributions and breakthrough curves at an observation well. Due to its fast simulation, it can be applied to time consuming simulations such as in a fine-grided aquifer, an inverse modeling and other applications.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.131-145
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• 2015

Thermodynamic prediction of weathering products from primary aquifer minerals around underground disposal sites was investigated. The distribution of solubility quotients for kaolinite-smectite reactions showed the trend of reaching at equilibrium with Ca-, Mg-, and Na-smectite for deep groundwaters in granitic aquifers. The values of $10^{-14.56}$, $10^{-15.73}$, and $10^{-7.76}$ were proposed as equilibrium constants between kaolinite and Ca-, Mg-, and Na-smectite end members, respectively. On stability diagrams, most of deep groundwaters were located at equilibrium boundaries between stability fields of kaolinite and smectites or on stability fields of smectites and illite. Shallow groundwaters in basic rock aquifer were plotted at the same stability areas of deep granitic groundwaters on stability diagrams. The results indicated that the primiary mineralogical composition may be important to predict weathering products in deep aquifers.

• Journal of the Korean School Mathematics Society
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• v.8 no.3
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• pp.367-382
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• 2005

In this paper, we deal with various contents relating to the group concept in school mathematics and teaching of algebraic structures indirectly by combining these contents. First, we consider structure of knowledge based on Bruner, and apply these discussions to the teaching of algebraic structure in school algebra. As a result of these analysis, we can verify that the essence of algebraic structure is group concept. So we investigate the previous researches about group concept: Piaget, Freudenthal, Dubinsky. In our school, the contents relating to the group concept have been taught from elementary level indirectly. Tn elementary school, the commutative law and associative law is implicitly taught in the number contexts. And in middle school, various linear equations are taught by the properties of equality which include group concept. But these algebraic contents is not related to the high school. Though we deal with identity and inverse in the binary operations in high school mathematics, we don't relate this algebraic topics with the previous learned contents. In this paper, we discussed algebraic structure focusing to the group concept to obtain a connectivity among school algebra. In conclusion, the group concept can take role in relating these algebraic contents and teaching the algebraic structures in school algebra.

• Journal of Soil and Groundwater Environment
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• v.9 no.4
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• pp.32-41
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• 2004

Analysis of water-level fluctuation due to goundwater-surface water interaction in coastal aquifers is carried out by numerical modeling. The conceptual model used in this study has a stream boundary and a tidal boundary that forms a right angle and the stream partially penetrates the aquifer. We analyzed the effect of each boundary and the simultaneous effect of the two boundary conditions. The area of influence caused by the stream boundary increased during the simulation, while the influence zone of the coastal boundary was relatively constant. The groundwater level near the zone where two boundaries meet may rise by the action of combined effect of the two boundaries or may not change by cancelling the effect of each boundary. Thereafter, care must be taken when hydraulic parameters are estimated using sinusoidal oscillations of hydraulic head in coastal aquifers. Sensitivity analysis is employed to develop insight into the controls on groundwater level fluctuations. In this study our analyses focused on the effect of conductance and the stream width to the aquifer nearby.