• The Journal of Engineering Geology
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• v.34 no.3
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• pp.429-445
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• 2024

The Journal of Engineering Geology (JEG), a leading academic journal in the field of engineering geology in South Korea, was first published in 1991 and has since been publishing academic papers and research findings. While several literature reviews have been undertaken on specific research areas in recent decades, comprehensive reviews focusing on JEG have been relatively limited. To address this gap, this study applied the latent Dirichlet allocation (LDA) model to analyze the main research topics and trends, and undertook network analysis to identify relationships between topics over different periods. Results for the LDA indicate seven key research topics categorized into three trends: Classic, Emerging and Stable topics. Classic topics include 'Geophysics' and 'Structural geology', which were major subjects in the early years, with their focus shifting to other areas over time. Emerging topics such as 'Hydrogeology' and 'Geohazards' have gained prominence in recent years. Stable topics including 'Geotechnical structures', 'Geomechanics', and 'Environmental geology' have maintained consistent research interest. Network analysis revealed that Structural geology was the central topic prior to 2008, while Geotechnical structures became the focal point of research after 2008, with a shift in research focus. The results of this study contribute to our understanding of research trends and the development of JEG, providing insights for the setting of future research directions.

• The Journal of Engineering Geology
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• v.34 no.3
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• pp.473-496
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• 2024

This study reviewed image analysis techniques used in non-destructive investigations of solute transport mechanisms in porous media during contaminant transport. Commonly employed image analysis methods include X-ray imaging, light-transmission visualization, and light-reflection visualization using ultraviolet or visible light. These techniques provide precise, high-resolution data on solute concentration distributions, fluid flow dynamics, and multiphase systems. Through continuous monitoring without alteration of the experimental setup, they provide accurate insights into solute transport mechanisms. We outline the principles, applications, advantages, and limitations of each method, and explore their contribution to the understanding and prediction of solute transport. We also examine case studies in which these methods have been effectively applied. This review provides a comprehensive understanding of how image analysis techniques can contribute to addressing environmental issues such as groundwater contamination.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.59-70
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• 1998

Two-dimensional trend-vector model of sediment transport is first tested in the tidal flat of Garolim Bay, mid-western coast of the Korean Peninsula. Three major parameters of surface sediment, i.e., mean grain size, sorting and skewness, are used for defining the best-fitting transport trend-vector on the sand ridge and muddy sand flat. These trend vectors are compared with the real transport directions determined from morphology, field observation and bedforms. The 15 possible cases of trend vectors are calculated from total sediments. In order to find the role of coarse sediments, trend vectors from sediments coarser than < 4.5 ${\phi}$, (sand size) are separately calculated from those of total sediments. As compared with the real directions, the best-fitting transport-vector model is the "case M" of coarse sediments which is the combined trend vectors of two cases: (1) finer, better sorted and more negatively skewed and (2) coarser, better sorted and more positively skewed. This indicates sand-size grains are formed by simpler hydrodynamic processes than total sediments. Transported sediment grains are better sorted than the source sediment grains. This indicates that consistent hydrodynamic energy can make sediment grains better sorted, regardless of complicated mechanisms of sediment transport. Consequently, both transported vector model and real transported direction show that the source of sediments are located outside of bay (offshore Yellow Sea) and in the baymouth. These source sediments are transported through the East Main Tidal Channel adjacent the baymouth. Some are transported from the subtidal zone to the upper tidal flat, but others are transported farther to the south, reaching the south tidal channel in the study area. Also, coarse sediment grains on the sand ridge are originally from the baymouth, and transported through the subtidal zone to the south tidal channel. These coarse sediments are moved to the northeast, but could not pass the small north tidal channel. It is interpreted that the great amount of coarse sediments is returned back to the outside of the bay (Yellow Sea) again through the baymouth during the ebb tide. The distribution of muddy sand in the northeastern part of study area may result from the mixing of two sediment transport mechanisms, i.e., suspension and bedload processes. The landward movement of sand ridge and the formation of the north tidal channel are formed either by the supply of coarse sediments originating from the baymouth and outside of the bay (subaqueous sand ridges including Jang-An-Tae) or by the recent relative sea-level rise.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.164-173
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• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.

• Journal of Chest Surgery
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• v.34 no.4
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• pp.329-337
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• 2001

배경: 승포판 전엽이나 교련 또는 여러 판엽에 걸쳐 광범위한 병변으로 인한 승모판 역류의 경우 수술수기에 대한 뚜렷한 정립이 되어 있지 않은 실정이다. 최근 이러한 병변의 승모판 역류의 경우 PTEE(Polytetrafluro-ethylene)을 이용한 신건삭 형성술의 시행이 점차 늘고 있다. 이에 저자들은 PTEE를 이용한 신건삭 형성술이 승모판 성형술에 어떠한 영향을 미치는지 알아보고자 하였다. 대상 및 방법: 1994년 1월부터 1999년 12월까지 승모판막 성형술을 시행 받은 322명의 환자 중에서 신건삭 형성술을 이용하여 승모판 성형술을 시행한 144례(I군)과 신건삭 형성술 이외의 방법으로 승모판 성형술을 시행한 178례(II군)를 대상으로 하였다. 두 군에서 수술 직후ㅘ 수술 후 6개월, 1년 및 1년 단위로 주기적인 심초음파를 시행하였고 이를 통계적 검정하였다. 결과: 같은 기간 승모판 성형술은 승모판막 폐쇄 부전증으로 내원한 환자의 95%(306)에서 추적 관찰이 가능하였다. 두 구난에 수술 전 혈류 역학적인 차이를 보이지 않았고, 수술 전 평균 승모판막 폐쇄 부전의 정도는 I군이 3.8$\pm$0.4, II군이 3.6$\pm$0.3였으나 수술 후 추적 관찰에서 각각 1.3$\pm$0.9와 1.1$\pm$0.7 정도의 양호한 판막 성형술의 결과를 보였고 승모판막 면적의변화나 승모판막에서의 평균 압력차이 등 혈류 역학적인 결과에도 차이를 보이고 있지 않았다. 술 후 3명(0.9%)의 조기 사망과 4명 (1.2%)의 후기 사망이 있었으나 두 군간의 차이는 보이지 않았다. 만기 생존율( 93.7$\pm$3.3 vs 88.0$\pm$1.95) 및 판막살패가 발생하기 않을 확률( 93.7$\pm$3.6 vs 93.3$\pm$3.4%) 과 재수술이 필요치 않을 활률(99.3$\pm$0.7 vs 96.0$\pm$1.9%), 색전증, 감염성 심내막염, 판막과 관련된 합병증 발생률 등에서 두 군간에 의미 있는 차이는 없었다. 전엽과 후엽에서 신건삭 형성술을 시행한 환자에서는 통계학적인 차이가 없었다(p=0.29) 결론: 신건삭 형성술을 이용한 승모판 성형술은 승모판 성형술의 증가(r=0.98, p<0.01)를 가져 왔을 뿐만 아니라 내구성과 안정성에 있어 기존의 안전화된 수술 수기와 견줄만하다. 특히 이러한 신건삭 형성술은 승모판 전엽에 병변이 있는 경우와 교련부 및 여러 엽에 광범위한 병변으로 인하여 재건술이 어려운 경우에도 승모판 재건을 가능하게 하는 우수한 수술 수리가 사료된다.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.4
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• pp.113-122
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• 2013

In this study, the traditional structure of the impact on the stability analysis. Korean traditional landscape architecture column space of stonework stable composition as the foundation of the fence for a long time been known to fall down and not maintained. The destination of research Ohgokmun Damyang Soswaewon fence which is in harmony with nature is one of the traditional structures that affect its shape without being kept so far came true. This includes our ancestral wisdom and that wisdom can guess guesswork. But I let the traditional reproduction incidence structures frequently. This deviation from the traditional method of construction application of shorthand stand. Thus, the subject of this study, the factors that do not fall down fences Ohgokmun solution is to indirectly gain the weak. In addition, epidemiological studies and the methods of calculation of the inferred physical examination, the results of the analysis were derived through the following. First, the internal factors of the fence Ohgokmun constituting the structural member and the coupling of the scheme. 1) based on stable ground. Greater role in the country rock The fact that the settlement will have no symptoms. 2) to minimize the friction caused by hydrological water to remove the two-pronged process through stone work building form and menu sustaining power in hydrology and flooding made against the bypass channel. 3) due to the load bearing capacity and durability to withstand the strength of the material and the construction of structures in the form of a dispersion of power between each individual to maximize the process of getting traction was applied. Second, external factors Ohgokmun fence the results obtained through the calculation of the dynamics of repair, is greatly affected by the wind and the water gate of the fence, but the action of the structural stability of the lack of power that hurt enough conclusion. In this study, the results of the structure of internal and external influence as well through the structure can be viewed as composed consisting. However, over the next follow-up in terms of climate and environmental factors due to the fact that the fall might.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.295-302
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• 2014

This study demonstrates a double-path CDI as an alternative of advanced wastewater treatment process. While the CDI typically consists of many pairs of electrodes connected in parallel, the new double-path CDI is designed to have series flow path by dividing the module into two stages. The CFD model showed that the double-path had uniform flow distribution with higher velocity and less dead zone compared with the single-path. However, the double-path was predicted to have higher pressure drop(0.7 bar) compared the single-path (0.4 bar). From the unit cell test, the highest TDS removal efficiencies of single- and double-path were up to 88% and 91%, respectively. The rate of increase in pressure drop with an increase of flow rate was higher in double-path than single-path. At 70 mL/min of flow rate, the pressure drop of double-path was 1.67 bar, which was two times higher than single-path. When the electrode spacing was increased from 100 to $200{\mu}m$, the pressure drop of double-path decreased from 1.67 to 0.87 bar, while there was little difference in TDS removal. When proto type double-path CDI was operated using sewage water, TDS, $NH_4{^+}$-N, $NO_3{^-}$-N and $PO_4{^{3-}}$-P removal efficiencies were up to 78%, 50%, 93% and 50%, respectively.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.355-363
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• 2015

The present work quantified the growth of young biofilm in a model distribution system that was fed with chlorinated drinking water at a hydraulic retention time of 2 h. Bacterial biofilms grew on the surface of polyvinyl chloride (PVC) slides at a specific growth rate of $0.14{\pm}0.09day^{-1}$ for total bacteria and $0.16{\pm}0.08day^{-1}$ for heterotrophic bacteria, reaching $3.1{\times}10^4cells/cm^2$ and $6.6{\times}10^3CFU/cm^2$ after 10 days, respectively. The specific growth rates of biofilm-forming bacteria were found to be much higher than those of bulk-phase bacteria, suggesting that biofilm bacteria account for a major part of the bacterial production in this model system. Biofilm isolates exhibited characteristic kinetic properties, as determined by ${\mu}_{max}$ and $K_S$ values using the Monod model, in a defined growth medium containing various amounts of acetate. The lowest ${\mu}_{max}$ value was observed in bacterial species belonging to the genus Methylobacterium, and their slow growth seemed to confer high resistance to chlorine treatment (0.5 mg/L for 10 min). $K_S$ values (inversely related to substrate affinity) of Sphingomonas were two orders of magnitude lower for acetate carbon than those of other isolates. The Sphingomonas isolates may have obligate-oligotrophic characteristics, since the lower $K_S$ values allow them to thrive under nutrient-deficient conditions. These results provide a better understanding and control of multi-species bacterial biofilms that develop within days in a drinking water distribution system.

• Journal of Korean Association for Spatial Structures
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• v.4 no.2 s.12
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• pp.89-97
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• 2004

The objective of this study is the development of a scheme and discrete optimum design algorithm, which is based on the genetic algorithm. The algorithm can perform both scheme and size optimum designs of plane trusses. The developed Scheme genetic algorithm was implemented in a computer program. For the optimum design, the objective function is the weight of structures and the constraints are limits on loads and serviceability. The basic search method for the optimum design is the genetic algorithm. The algorithm is known to be very efficient for the discrete optimization. However, its application to the complicated structures has been limited because of the extreme time need for a number of structural analyses. This study solves the problem by introducing the size & scheme genetic algorithm operators into the genetic algorithm. The genetic process virtually takes no time. However, the evolutionary process requires a tremendous amount of time for a number of structural analyses. Therefore, the application of the genetic algorithm to the complicated structures is extremely difficult, if not impossible. The scheme genetic algorithm operators was introduced to overcome the problem and to complement the evolutionary process. It is very efficient in the approximate analyses and scheme and size optimization of plane trusses structures and considerably reduces structural analysis time. Scheme and size discrete optimum combined into the genetic algorithm is what makes the practical discrete optimum design of plane fusses structures possible. The efficiency and validity of the developed discrete optimum design algorithm was verified by applying the algorithm to various optimum design examples: plane pratt, howe and warren truss.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.81-94
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• 1997

In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It has been accepted that no priority exists in the selection of concentration mode in the study of solute transport. It would be questionable, however, to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the horizontally-positioned TDR probes. Two different solute transport models namely, convection-dispersion equation (CDE) and convective lognormal transfer function (CLT) models, were fitted to the observed breakthrough data in order to quantify the difference between two concentration modes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. Accordingly, the estimated parameters of flux mode differed greatly from those of resident mode and the difference was more pronounced in CDE than CLT model. Especially in CDE model, the parameters of flux mode were much higher than those of resident mode. This was mainly due to the bypassing of solute through soil macropores and failure of the equilibrium CDE model to adequate description of solute transport in studied soils. In the domain of the relationship between the ratio of hydrodynamic dispersion to molecular diffusion and the peclet number, both concentrations fall on a zone of predominant mechanical dispersion. However, it appears that more molecular diffusion contributes to the solute spreading in the matrix region than the macropore region due to the nonliearity present in the pore water velocity and dispersion coefficient relationship.