• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.553-562
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• 2017

In these days, agricultural reservoirs are considered as a useful resource for recreational purposes, tour and cultural amenity for vicinity communities as well as irrigation water supply. However, many of the agricultural reservoirs are showing a eutrophic or hyper-eutrophic state and high level of organic contamination. In particular, about 44.7% of the aged agricultural reservoirs that constructed before 1945 exceed the water quality criteria for irrigational water use. In addition to external loading, internal nutrient loading from bottom sediment may play an important role in the nutrient budget of the aged reservoirs. The objectives of this study were to characterize variations of thermal structure of a shallow M reservoir (mean depth 1.7 m) and examine the potential of internal nutrient loading by continuous monitoring of vertical water temperature and dissolved oxygen (DO) concentration profiles in 2015 and 2016. The effect of internal loading on the total loading of the reservoir was evaluated by mass balance analysis. Results showed that a weak thermal stratification and a strong DO stratification were developed in the shallow M Reservoir. And, dynamic temporal variation in DO was observed at the bottom of the reservoir. Persistent hypoxic conditions (DO concentrations less than 2 mg/L) were established for 87 days and 98 days in 2015 and 2016, respectively, during the no-rainy summer periods. The DO concentrations intermittently increased during several events of atmospheric temperature drop and rainfall. According to the mass balance analysis, the amount of internal $PO_4-P$ loading from sediment to the overlying water were 37.9% and 39.7% of total loading during no-rainy season in 2015 and 2016, respectively on August when algae growth is enhanced with increasing water temperature. Consequently, supply of DO to the lower layer of the reservoir could be effective countermeasure to reduce nutrient release under the condition of persistent DO depletion in the bottom of the reservoir.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.143-156
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• 2015

In order to understand the dynamic characteristics of water column environments in the Western Pacific seamount area (approximately $150.2^{\circ}E$, $20^{\circ}N$), we investigated the water mass and the behavior of water column parameters such as dissolved oxygen, inorganic nutrients (N, P), and chlorophyll-a. Physico-chemical properties of water column were obtained by CTD system at the nine stations which were selected along the east-west and south-north direction around the seamount (OSM14-2) in October 2014. From the temperature-salinity diagram, the main water masses were separated into North Pacific Tropical Water and Thermocline Water in the surface layer, North Pacific Intermediate Water in the intermediate layer, and North Pacific Deep Water in the bottom layer, respectively. Oxygen minimum zone (OMZ, mean $O_2$ $73.26{\mu}M$), known as dysoxic condition ($O_2<90{\mu}M$), was distributed in the depth range of 700~1,200 m throughout the study area. Inorganic nutrients typified by nitrite + nitrate and phosphate showed the lowest concentration in the surface mixed layer and then gradually increased downward with representing the maximum concentration in the OMZ, with lower N:P ratio (13.7), indicating that the nitrogen is regarded as limiting factor for primary production. Vertical distribution of water column parameters along the east-west and south-north station line around the seamount showed the effect of bottom water inflowing at around 500 m deep in the western and southern region, and concentrations of water column parameters in the bottom layer (below 2,500 m deep) of the western and southern region were differently distributed comparing to those of the other side regions (eastern and northern). The value of Excess N calculated from Redfield ratio (N:P=16:1) represented the negative value throughout the study area, which indicated the nitrogen sink dominant environments, and relative higher value of Excess N observed in the bottom layer of western and southern region. These observations suggest that the topographic features of a seamount influence the circulation of bottom current and its effects play a significant role in determining the behavior of water column environmental parameters.

• Korean Business Review
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• v.17 no.2
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• pp.63-87
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• 2004

To create and maintain comparative supremacy as a strategic tool of business, many organizations have introduced informational technology and system. By using this system, Some companies got a beneficial value for achieving organizational goals but others could not obtain their effectiveness and efficiency. In particular, a lot of organizations that tried to make strategic supremacy with e-commercial trade are under hard condition because of poor profit. It implies that it is essential to identify and analyse the consumer who uses e-commercial trade. This paper, therefore, focusing on internet shopping malls between business and consumer as one of areas of e-commercial trades, shows the difference between consumer expectation and performance. The results of this study are as follows: First, as for the significant difference of influencing factors to consumer satisfactions according to the types of internet shopping malls, there is a meaningful difference in consumer anxiety and internet usefulness, but not in consumer service. Prior to verify the differences in detail on consumer's anxiety and internet usefulness, we examined that there is any difference between expectation and performance. T-test was used for the variants of consumer anxiety and internet usefulness, and its meaningful probability was 0.000, which means that both showed statistically significant difference. Based on the results, we also found that regardless of the types of internet shopping malls, consumer expectation was greater than performance. although the difference between expectation and performance was not equal according to the internet shopping malls. Second, a regression analysis was performed to understand the relation between consumer service, internet usefulness, consumer anxiety, and consumer satisfaction, it was found that consumer service, internet usefulness, consumer anxiety had significantly effected on consumer satisfaction. Third, To verify the relation between consumer satisfaction and repurchase-intentions, intentions to spread out, Pearson correlation analysis was used. it was found that consumer satisfaction had positive effect on both intentions. This study has some limitations because of the shorts of money and time. since the sample of this study was consumers who have ever bought one or more products via internet shopping mall, this sample was appropriate. but the major parts of sample were college students, and the sample size was so small. therefore this results should carefully be generalized. For further study, it is required to select more precise samples and to include more variables.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.279-299
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• 2019

Recently occurred earthquake Gyeongju and Pohang served as a momentum to remind that Korean peninsular is not a safety zone from earthquake anymore. The importance of seismic design, therefore, have been realized and researches regarding design response spectrum have been actively carried out by many researchers and engineers. Current tunnel seismic design method is conducted to check safety of tunnel structure by dynamic numerical analysis with condition of completed lining installation, so, it is impossible to consider safety of tunnel behavior under construction. In this study, therefore, dynamic numerical analysis considering seismic wave propagations has been performed after back analysis using results from field monitoring of tunnel under construction in fractured zone and 1st reinforcement (shotcrete, rockbolt) behaviour are analyzed. Waves are classified by period characteristic (short and long). As a result, the difference depending on period characteristic is minor, and increasements of displacement are obtained at crown displacement due to seismic wave is 28~31%, 14~16% at left side of tunnel in the fractured zone, 13~27% at right side of tunnel in the bed rock, respectively. In case of shotcrete axial force is increased 113~115% at tunnel crown, 102% at left side, 106~110% at right side, respectively. Displacement and axial force of rockbolts which are selected by type of anchored grounds (only fractured zone, fractured zone and bed rock, only bedrock) are analyzed, as a result, rockbolt which is anchored to fractured zone and bed rock at the same time are weaker than any other case.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.3 s.10
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• pp.151-163
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• 2003

In this study, the algorithm of groundwater flow process was established for koreanized groundwater program development dealing with the geographic and geologic conditions of the aquifer have dynamic behaviour in groundwater flow system. All the input data settings of the 3-DFM model which is developed in this study are organized in Korean, and the model contains help function for each input data. Thus, it is designed to get detailed information about each input parameter when the mouse pointer is placed on the corresponding input parameter. This model also is designed to easily specify the geologic boundary condition for each stratum or initial head data in the work sheet. In addition, this model is designed to display boxes for input parameter writing for each analysis condition so that the setting for each parameter is not so complicated as existing MODFLOW is when steady and unsteady flow analysis are performed as well as the analysis for the characteristics of each stratum. Descriptions for input data are displayed on the right side of the window while the analysis results are displayed on the left side as well as the TXT file for this results is available to see. The model developed in this study is a numerical model using finite differential method, and the applicability of the model was examined by comparing and analyzing observed and simulated groundwater heads computed by the application of real recharge amount and the estimation of parameters. The 3-DFM model is applied in this study to Sehwa-ri, and Songdang-ri area, Jeju, Korea for analysis of groundwater flow system according to pumping, and obtained the results that the observed and computed groundwater head were almost in accordance with each other showing the range of 0.03 - 0.07 error percent. It is analyzed that the groundwater flow distributed evenly from Nopen-orum and Munseogi-orum to Wolang-bong, Yongnuni-orum, and Songja-bong through the computation of equipotentials and velocity vector using the analysis result of simulation which was performed before the pumping started in the study area. These analysis results show the accordance with MODFLOW's.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.185-195
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• 2012

Due to the high reduction and sorption capacity as well as the large specific surface area, nanosized mackinawite (FeS) is useful in reductively transforming chlorinated organic pollutants and sequestering toxic metals and metalloids. Due to the dynamic nature in its colloid stability, however, nanosized FeS may be washed out with the groundwater flow or result in aquifer clogging via particle aggregation. Thus, these nanoparticles should be modified such as to be built into permeable reactive barriers. This study employed coating methods in efforts to facilitate the installation of permeable reactive barriers of nanosized mackinawite. In applying the methods, nanosized mackinawite was coated on non-treated silica sand (NTS) and chemically treated silica sand (CTS). For both silica sands, the maximum coating of mackinawite occurred around pH 5.4, the condition of which was governed by (1) the solubility of mackinawite and (2) the surface charge of both silica and mackinawite. Under this pH condition, the maximum coating by NTS and CTS were found to be 0.101 mmol FeS/g and 0.043 mmol FeS/g respectively, with such elevated coatings by NTS likely linked with impurities (e.g., iron oxides) on its surface. Arsenite sorption experiments were performed under anoxic conditions using uncoated silica sands and those coated with mackinawite at the optimal pH to compare their reactivity. At pH 7, the relative sorption efficiency between uncoated NTS and coated NTS changed with the initial concentration of arsenite. At the lower initial concentration, uncoated NTS showed the higher sorption efficiency, whereas at the higher concentration, coated NTS exhibited the higher sorption efficiency. This could be attributed to different sorption mechanisms as a function of arsenite concentration: the surface complexation of arsenite with the iron oxide impurity on silica sand at the low concentration and the precipitation as arsenic sulfides by reaction with mackinawite coating at the high concentration. Compared to coated NTS, coated CTS showed the lower arsenite removal at pH 7 due to its relatively lower mackinawite coating. Taken together, our results indicate that NTS is a more effective material than CTS for the coating of nanosized mackinawite.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.4
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• pp.218-227
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• 2015

A prerequisite for precise quantification of nanomaterials contained in environmental samples is to prepare suitable preservation conditions of samples. This study was initiated to suggest preservation conditions of aqueous samples for analyses of metal nanomaterials. Variation in the size of silver nanomaterial (cit-AgNP) was observed according to change in various conditions, such as pH, electrolyte concentration, temperature, nanomaterial concentration, and time. Aggregation of AgNP was characterized for each environmental condition, and finally proper preservation conditions of samples were proposed based on experimental results on AgNP aggregation. In addition, the preservation period of sample was computed by the doublet time of AgNP. The results indicate that the aggregation rate of cit-AgNP was close to 0 at the conditions of pH of ${\geq}7$, electrolyte ($Ca(NO_3)_2$) concentration of ${\leq}3mM$, temperature of $4^{\circ}C$, and cit-AgNP concentration of ${\leq}2mg/L$. Furthermore, the experimental results on doublet time of cit-AgNP suggest that maximum preservation period was evaluated to be 15.79~17.53 days when the concentration of 100 nm cit-AgNP is assumed to be $1{\mu}g/L$ which is considered as an environmentally-relevant concentration of engineered nanomaterials. Our results suggest that samples should be preserved at $4^{\circ}C$ and analyzed within 2 weeks.

• Journal of Wetlands Research
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• v.16 no.1
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• pp.41-50
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• 2014

The purpose of this study is to evaluate the High Rate Spiral Clarifier(HRSC) availability for the improvement of polluted retention pond water quality. A lab scale and a pilot scale test was performed for this. The fluid flow patterns in a HRSC were studied using Fluent which is one of the computational fluid dynamic(CFD) programs, with inlet velocity and inlet diameter, length of body($L_B$) and length of lower cone(Lc), angle and gap between the inverted sloping cone, the lower exit hole installed or not installed. A pilot scale experimental apparatus was made on the basis of the results from the fluid flow analysis and lab scale test, then a field test was executed for the retention pond. In the study of inside fluid flow for the experimental apparatus, we found out that the inlet velocity had a greater effect on forming spiral flow than inlet flow rate and inlet diameter. There was no observable effect on forming spiral flow LB in the range of 1.2 to $1.6D_B$(body diameter) and Lc in the range of 0.35 to $0.5L_B$, but decreased the spiral flow with a high ratio of $L_B/D_B$ 2.0, $Lc/L_B$ 0.75. As increased the angle of the inverted sloping cone, velocity gradually dropped and evenly distributed in the inverted sloping cone. The better condition was a 10cm distance of the inverted sloping cone compared to 20cm to prevent turbulent flow. The condition that excludes the lower exit hole was better to prevent channeling and to distribute effluent flow rate evenly. From the pilot scale field test it was confirmed that particulate matters were effectively removed, therefore, this apparatus could be used for one of the plans to improve water quality for a large water body such as retention ponds.

• Journal of architectural history
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• v.1 no.1 s.1
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• pp.68-87
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• 1992

This study is the conditions of location according to formed the times in the clan village. The results of this study are as follows ; 1. in the 15th century, the characterestics of the village established residencial place where mountain stream flowed surrounded by the mountain and deep in the mountains with superior quality land. That's because Sa-dae-bu put equal importance on beautiful scenery and practical benefit for living. Stream House provided economical foundation for Sa-dae-bu to be able to keep confucial manners by putting limit their economic status to small medium sized land owner. Topographical condition such as valley or hollow separated from the exterior maintained unification of consanguineous village in self sufficient farming society and held on to independent territory against external to be able to stay away from turbulent days so that they formed residential area of Sa-dae-bu clan. And the valley where flowed clean water was considered as the connection of continuous place where distinctiveness of form in each curve and and factor of calm and dynamic scenery of the clean stream. Scholars in the middle of Chosun Dynasty located in the utopia as place for confucious retirement to study, a place for refinement by combination with the nature or as a way of spacial practice based on Confucious view of nature. 2. in the 16th-l7th century, Most of existing consanguineous villages adopt deep in the mountains for refuge. at that place, upward rank was established by settlement of the ancestor who entered in the village first, the principal was placed in the center of the village and since descendants became numerous, it was serialized as the space of descendants. So, it was arranged in the order of social rank. Most of the villages showed development step by step started from precaution by apperance of the mountain to the lower part. It's because the topography of valley around the village worked as the natural hedge against external force and genealogy of the clan, regularity of social status, order of entrance into the village were reflected into residencial destribution. Also, order of the rank coincided with the one of aspects on geomancy. Genealogical rank within the village represented spacial rank. Houses of descendants and branch families were placed lower than the principal which showed worship to the principal. 3. In 18th century after, as the village was settled nearby cultivated land considering economical loss caused by long distance between residencial area and cultivated land, direction of sect followed by development of village expanded from the front part of the village to the rear part. The principal that was poped out to the front presented frontage over exterior. Therefore, residencial area of branch families expanded to the rear starting from the principal. This represented a slice of social structure at that time. after 18th century, spirit was percieved superior over material, After then, development of cultivation and expantion of land created difference of economic strength within one village. In order to maintain and show off the status of Yang-ban, economic power of indigenous land owner became fundamental, so, sense to worship and to keep the principal became weak eventually. Taking advantage of that situation, residencial area of branch family expanded to the rear part of the principal which showed dual disposition conflicted with each other. However, these clan rules were destroyed and new rules were created after 18th century because of the situation and consciousness at that time.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.116-122
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• 2010

A $Cu_3Si$ film electrode is obtained by Si deposition on a Cu foil using DC magnetron sputtering, which is followed by annealing at $800^{\circ}C$ for 10 h. The Si component in $Cu_3Si$ is inactive for lithiation at ambient temperature. The linear sweep thermammetry (LSTA) and galvano-static charge/discharge cycling, however, consistently illustrate that $Cu_3Si$ becomes active for the conversion-type lithiation reaction at elevated temperatures (> $85^{\circ}C$). The $Cu_3Si$ electrode that is short-circuited with Li metal for one week is converted to a mixture of $Li_{21}Si_5$ and metallic Cu, implying that the Li-Si alloy phase generated at 0.0 V (vs. Li/$Li^+$) at the quasi-equilibrium condition is the most Li-rich $Li_{21}Si_5$. However, the lithiation is not extended to this phase in the constant-current charging (transient or dynamic condition). Upon de-lithiation, the metallic Cu and Si react to be restored back to $Cu_3Si$. The $Cu_3Si$ electrode shows a better cycle performance than an amorphous Si electrode at $120^{\circ}C$, which can be ascribed to the favorable roles provided by the Cu component in $Cu_3Si$. The inactive element (Cu) plays as a buffer against the volume change of Si component, which can minimize the electrode failure by suppressing the detachment of Si from the Cu substrate.