• Journal of Korean Society of Environmental Engineers
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• v.35 no.3
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• pp.192-199
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• 2013

The Tandong-cheon stream is a 7.4 km long small urban stream that passes through Daeduk Science Town in Daejeon Korea. Despite the stream has great potential as an educational and recreational site due to its central location in the science town and science museums nearby, environmental aspect especially for water quality has not been evaluated properly. Through field survey, major pollution sources of the stream were identified and effect of water quality improvement alternatives were evaluated using a QUAL2K water quality model for the stream. The study indicated that controlling major pollution sources of the stream alone may not be sufficient for reaching the water quality target. Therefore, additional pollution control methods are necessary. We applied the developed model to evaluate the effects of a constructed wetland on the terrace land, and analyzed whether the water quality target can be met at the outlet of the stream. It is expected that this study would provide a good reference for environmentally sound management of small urban streams in Korea.

• Geophysics and Geophysical Exploration
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• v.16 no.2
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• pp.79-90
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• 2013

Geophysical investigation in non-destructive testing is economically less expensive than boring testing and providing geotechnical information over wide-area. But, it provides only limited geotechnical information, which is hardly used to the design. Accordingly, we performed electrical resistivity experiments on large scale of soil model to analyze the correlation between electrical resistivity response and soil water contents. The soils used in the experiments were the Jumunjin standard sand and weathered granite soil. Each soil particle size distribution and coefficient of uniformity of experimental material obtained in the experiments were maintained in a state of the homogeneous. The specifications of the model used in this study is $160{\times}100{\times}50$(cm) of acrylic, and each soil was maintained at the height 30 cm. The water content were measured using the 5TE sensors (water contents sensors) which is installed 7 ~ 8 cm apart vertically by plugging to floor. The results of the resistivity behavior pattern for Jumunjin standard sand was found to be sensitive to the water content, while the weathered granite soil was showing lower resistivity over the time, and there was no significant change in behavior pattern observed. So, it results that the Jumunjin standard sand's particle current conduction was better than the weathered granite soil's particle through contact with the distilled water. This lab test was also compared with the result of a test bed site composed of similar weathered soil. It was confirmed that these experiments were underlying research of non-destructive investigation techniques to improve the accuracy to estimate the geotechnical parameter.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.2
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• pp.101-113
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• 2013

The concern on environmental quality makes the landscape analysis more important than before ever. For the landscape analysis, selection of viewpoint is one of most important stage. Because of its subjectiveness, the conventional viewpoint selection method often missed some viewpoints of importance. The purpose of this study is to develop a viewpoint selection method for landscape analysis using GIS data and techniques. During the viewpoint selection process, spatial and attribute data from several GIS systems were hired. Query and overlay methods were mainly adapted for analysis to find out meaningful viewpoints. The 3D simulation analysis on DEM(Digital Elevation Model) was used for every selected viewpoint to examine wether the view target is screened out or not. Application study at a sample site showed some omissions of good viewpoints without any screening. It also exhibited the possibility to reduce time and cost for the viewpoint selection process of landscape analysis. For the progress of applicability, GIS data analysis process have to be improved and more modules such as automatic screening analysis system on selected viewpoint have to be developed.

• Journal of Environmental Science International
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• v.16 no.10
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• pp.1179-1187
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• 2007

This paper represents the statistical characteristics of sources and receptors for road traffic noise in apartment complex. Also we suggested that the site-specific characteristics of vertical and horizontal distributions in the complex apartment have been derived using a different analysis for evaluating levels of Leq1h by the apartment floor at a given distance from a road in terms of the flow rate, the mean speed of the traffic, and the percentage of the type vehicles in the day and night periods. As a result, the contribution orders of traffic quantity by the type of vehicles showed as followed: light vehicle>medium vehicle>heavy vehicle>motorcycle. Especially, the mixing ratio of entering the road on the heavy vehicle in the daytime was two times higher than that of in the night. The speed in all types of vehicle is in the range of 41 and 81 km/hr and noise level was not significantly different in day and night-time. The sources of road traffic noise had different variations and uncertainties using a random variable and probability distribution. The sound distribution to receptors by the apartment floor showed S curve between 1st floor and $15^{th}$ floor With the normality test, the normal distributions using Anderson-Darling Test followed $1^{st},\;3^{th},\;13^{th}$ and $15^{th}$, floor in the daytime and all floors except $7^{th}$ floor in the night (p>0.05). And also, the value of the pearson correlation coefficient (r) obtained in this study have significantly different at the range of floor. In conclusion, the results suggested that the distribution characteristics of levels of $Leq_{1h}$ on the sources and receptors of road traffic noise in apartment complex must be improved and developed on the guideline of regulation of road traffic noise.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.31-37
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• 2014

In situ investigations and laboratory tests using elastic wave have become popular in geotechnical and geoenvironmental engineering. Propagation velocity of elastic wave is the key index to evaluate the ground characteristics. To evaluate this, various methods were used in both time domain and frequency domain. In time domain, the travel time can be found from the two points that have the same phase such as peaks or first rises. Cross-correlation can also be used in time domain by evaluating the time shift amount that makes the product of signals of input and received waveforms maximum. In frequency domain, wave propagation velocity can be evaluated by computing the phase differences between the source and received waves. In this study, wave propagation velocity evaluated by the methods listed above were compared. Bender element tests were conducted on the specimens cut from the undisturbed hand-cut block samples obtained from Block 37 excavation site in Chicago, IL, US. The evaluation methods in time domain provides relatively wide range of wave propagation velocities due to the noise in signals and the sampling frequency of data logger. Frequency domain approach provides relatively accurate wave propagation velocities and is irrelevant to the sampling frequency of data logger.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.443-454
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• 2013

Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically $V^{5+}$, $Co^{2+}$, and $Ni^{2+}$-incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated.

• Korean Journal of Construction Engineering and Management
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• v.7 no.5
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• pp.138-148
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• 2006

In constructing projects, there exist various kinds of work interferences, which cause a delay of the outset and completion of planned schedule because of some attributions, such as variability, uncertainty and complexity, and so schedule delay has been treated as a natural phenomenon. To reduce or prevent the schedule delay, a constant confirmation of schedule delay and a preparation of counter plans for finding out the cause structure of schedule delay should have been done. However, all this time the research has been mostly done on the calculation method or claim cases of schedule delay, and the range of analysis method of the cause structure of schedule delay has been multifarious from industrial views to views of specific work. Moreover, the classifying system and analysis method did not consider the trait, which cause the schedule delay, in constructing projects. For this reason, it is difficult to compare the cause of delay factors of the projects and to understand the effect of schedule delay by each factor. This paper restricts the range of the cause analysis of schedule delay to the field of site management in the projects and divides the cause structure of schedule delay into the cause objects and cause attributes of schedule delay according to the input elements. The system of classifying causes of schedule delay is examined by interviews with experts and questionnaire. Additionally, this paper analyzes the attributes of cause attributes and cause subjects and presents the analysis method and procedure of schedule delay with the application of VSM.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.97-111
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• 2013

It is very important to understand the condition of the surround rock for the successful construction of underground space. Representative methods of estimating the rock mass condition are RMR method and Q-system, and they are applied on design, construction, and maintenance. However, many problems with the accuracy of the measurement method and the subjective viewpoint are questioned continuously, so many researchers have been studied for estimating rock condition from various methods. Most of them show only the local relation and a tendency between site investigation data and rock conditions. In this paper, the relationship between RMR method and electrical resistivity is deducted using the analytical equation derived theoretically from electric field analysis on jointed rock mass. And also, probabilistic relationship between RMR method and electrical resistivity is deducted for the increase of accuracy. If a suggested method is applied with the conventional method for estimating the rock condition, it will be helpful to estimate RMR values on the field.

• Geophysics and Geophysical Exploration
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• v.19 no.3
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• pp.111-120
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• 2016

In order to enhance the connectivity of fracture network as fluid path in enhanced/engineered geothermal system (EGS), the exact locating of hydraulic fractured zone is very important. Hydraulic fractures can be tracked by locating of microseismic events which are occurred during hydraulic fracture stimulation at each stage. However, since the subsurface velocity is changed due to hydraulic fracturing at each stage, in order to find out the exact location of microseismic events, we have to consider the velocity change due to hydraulic fracturing at previous stage when we perform the mapping of microseimic events at the next stage. In this study, we have modified 3D locating algorithm of microseismic data which was developed by Kim et al. (2015) and have developed 3D velocity update algorithm using occurred microseismic data. Eikonal equation which can efficiently calculate traveltime for complex velocity model at anywhere without shadow zone is used as forward engine in our inversion. Computational cost is dramatically reduced by using Fresnel volume approach to construct Jacobian matrix in velocity inversion. Through the numerical test which simulates the geothermal survey geometry, we demonstrated that the initial velocity model was updated by using microseismic data. In addition, we confirmed that relocation results of microseismic events by using updated velocity model became closer to true locations.

• Korean Journal of Environment and Ecology
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• v.23 no.4
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• pp.285-293
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• 2009

This research had been executed to find out the structure of Magnolia obovata community, a dispersal range and characteristics of scatter investigation, and to prepare management measure of it. In the result of this study, Magnolia obovata was distributed in a native plant community from planting trees of UNESCO Peace Center. The maximum numbers of Magnolia obovata were found in $20{\sim}100m$ from trees of mother. Seed of Magnolia obovata has a characteristics of gravity dispersal. But some individuals was found in 420m from its tree of mother. Seeds of Magnolia obovata has a characteristics of animal dispersal, too. Major species of animal dispersal are Garrulus glandarius, Ciurus vulgaris coreae, and Tamias sibiricus asiaticus in the study site. The importance value between native plants and Magnolia obovata had a negative relation. Because Magnolia obovata is more shade tolerant than other trees. Also, the growth of Magnolia obovata is faster than other trees. And so if the influence of Magnolia obovata reduce, it is necessary to expand native plant community, and to cut Magnolia obovata over 10m of the height and over 10cm of the DBH, for preventing influence of Magnolia obovata.