• The Journal of Korean Academy of Prosthodontics
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• v.59 no.3
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• pp.291-298
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• 2021

Purpose. The purpose of this study is to compare five interdental cleansing products' effectiveness on removing artificial dental plaque on the interdental space of zirconia crowns. Materials and methods. A model with abutments on the right mandibular second premolar and first molar were prepared. 10 zirconia crowns for each abutment were fabricated. After applying artificial dental plaque between the zirconia crowns, a single clinician attempted to remove the plaque with five products: interdental toothbrush, end-tuft toothbrush, dental floss, Easypick, Water pik. They were conducted 10 times per group. The aspect and area of removed surfaces were analyzed using images taken with a digital camera. One factor analysis of variance was performed as a statistical analysis, and a post-hoc test was performed using the Scheffé method (P < .05). Results. There were differences in the area and the pattern according to the characteristics of the products. The largest area, including the marginal portion, was removed in the dental floss group. Interdental toothbrush group was the most effective in removing the dental plaque at the marginal portion. Easypick was less effective than the interdental toothbrush. The end-tuft toothbrush showed better results than other products in cleansing mesiobuccal and distobuccal area, but could not cleanse the area directly below the contact point. In Water pik group, artificial dental plaque was scarcely removed. The removal rate of artificial dental plaque was in the order of floss (69.47%), end-tuft toothbrush (49.36%), interdental toothbrush (44.20%), Easy pick (13.04%), and Water pik (0.59%). Conclusion. Dental floss showed the highest removal rate in the interdental space restored with zirconia crowns, while interdental toothbrush was the most effective in removing the dental plaque at the marginal portion.

• Korea Science and Art Forum
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• v.37 no.4
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• pp.205-216
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• 2019

Today, there have been more museums with architectural freeform structure. From an academic perspective, that caused a change in the paradigm of the genealogy of architectural forms. Accordingly, it has been required to find whether the freeform architecture influences an exhibition space. Therefore, in order to analyze the correlation between freeform architecture and exhibition space, this study looks into the tendency of actual freeform architecture through case analysis after 2000. An exhibition space of museum serves as a socially, culturally, and locally symbolic icon and has the function of delivering information to viewers through the aesthetic presentation of articles on exhibition. This study is meaningful in the point that it drew the conclusion of the correlation between freeform architecture and exhibition space in order to infer that a freeform exhibition space is more effective at viewers' spatial experience. The method and results of this study are presented as follows: Firstly, literature survey on the concept of the freerform architecture of museum and the classification of architectural forms was conducted and previous studies were analyzed in order to establish criteria. Secondly, a case study was conducted through visits to Singapore, Germany, and the Netherlands in order to look into the current state and characteristics of freeform architecture and exhibition space. In this case, Karel Vollers' architectural freeform criteria were used for analysis. Thirdly, to prove the correlation between freeform architecture and exhibition space, each case was cross-checked on the basis of Karel Vollers' architectural freeform criteria and freeform exhibition classification, and then results were drawn. The study results are presented as follows: Firstly, EX(angle, ortho) of freeform architecture had a significant correlation with the diagonal form of exhibition space. That was proved 92.3% accurately more in the Netherlands and Germany than in Singapore. However, the curve form of exhibition space had a unclear correlation. In Singapore case, the curve form correlation was made through RO, FR, and TW. Secondly, freeform architecture had complex-typed combination with the diagonal and curve forms of exhibition space. In particular, N-02 and G-02 had a combination form, basically EX, and partially various forms so as to induce the complexity of free form. As such, architectural freeform makes it possible to achieve infinite transformation in various combinations. For responses, combinational approaches are required in multilateral ways. Based on this study, it will be planned to analyze the correlation between freeform architecture of museum and exhibition presentation.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1657-1667
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• 2021

Anthropogenic activities and natural processes have been causes of land subsidence which is sudden sinking or gradual settlement of the earth's solid surface. Mexico City, the capital of Mexico, is one of the most severe land subsidence areas which are resulted from excessive groundwater extraction. Because groundwater is the primary water resource occupies almost 70% of total water usage in the city. Traditional terrestrial observations like the Global Navigation Satellite System (GNSS) or leveling survey have been preferred to measure land subsidence accurately. Although the GNSS observations have highly accurate information of the surfaces' displacement with a very high temporal resolution, it has often been limited due to its sparse spatial resolution and highly time-consuming and high cost. However, space-based synthetic aperture radar (SAR) interferometry has been widely used as a powerful tool to monitor surfaces' displacement with high spatial resolution and high accuracy from mm to cm-scale, regardless of day-or-night and weather conditions. In this paper, advanced interferometric approaches have been applied to get a time-series of land subsidence of Mexico City using four-year-long twenty ALOS PALSAR L-band observations acquired from Feb-11, 2007 to Feb-22, 2011. We utilized persistent scatterer interferometry (PSI) and small baseline subset (SBAS) techniques to suppress atmospheric artifacts and topography errors. The results show that the maximum subsidence rates of the PSI and SBAS method were -29.5 cm/year and -27.0 cm/year, respectively. In addition, we discuss the different subsidence rates where the study area is discriminated into three districts according to distinctive geotechnical characteristics. The significant subsidence rate occurred in the lacustrine sediments with higher compressibility than harder bedrock.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.337-357
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• 2021

Because the growth of paddy rice is affected by meteorological factors, the selection of appropriate meteorological variables is essential to build a rice yield prediction model. This paper examines the suitability of multiple meteorological datasets for the rice yield modeling in South Korea, 1996-2019, and a hindcast experiment for rice yield using a machine learning method by considering the nonlinear relationships between meteorological variables and the rice yield. In addition to the ASOS in-situ observations, we used CRU-JRA ver. 2.1 and ERA5 reanalysis. From the multiple meteorological datasets, we extracted the four common variables (air temperature, relative humidity, solar radiation, and precipitation) and analyzed the characteristics of each data and the associations with rice yields. CRU-JRA ver. 2.1 showed an overall agreement with the other datasets. While relative humidity had a rare relationship with rice yields, solar radiation showed a somewhat high correlation with rice yields. Using the air temperature, solar radiation, and precipitation of July, August, and September, we built a random forest model for the hindcast experiments of rice yields. The model with CRU-JRA ver. 2.1 showed the best performance with a correlation coefficient of 0.772. The solar radiation in the prediction model had the most significant importance among the variables, which is in accordance with the generic agricultural knowledge. This paper has an implication for selecting from multiple meteorological datasets for rice yield modeling.

• Journal of Korea Water Resources Association
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• v.54 no.7
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• pp.535-544
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• 2021

Agricultural water occupies 48% of water demand, and management of agricultural reservoirs is essential for water resources management within agricultural basins. For more efficient use of agricultural water, monitoring the distribution of water resources in agricultural reservoirs and agricultural basins is required. Therefore, in this study, three threshold determination methods (i.e., fixed threshold, Otsu threshold, Kittler-Illingworth (KI) threshold) were compared to detect terrestrial water bodies using Sentinel-1 images for 3 years from 2018 to 2020. The purpose of this study was to evaluate methods for determining threshold values to more accurately estimate the reservoir area. In addition, by analyzing the relationship between the water surface and water storage at the Edong, Gosam, and Giheung reservoirs, water storage based on the SAR image was estimated and validated with observations. The thresholding method for detecting a waterbody was found to be the most accurate in the case of the KI threshold, and the water storage estimated by the KI threshold indicated a very high agreement (r = 0.9235, KGE' = 0.8691). Although the seasonal error characteristics were not observed, the problem of underestimation at high water levels may occur; the relationship between the water surface and the water storage could change rapidly. Therefore, it is necessary to understand the relationship between the water surface area and water storage through ground observation data for a more accurate estimation of water storage. If the use of SAR data through water resources satellites becomes possible in the future, based on the results of this study, it is judged that it will be beneficial for monitoring water storage and managing drought.

• Korean Journal of Environment and Ecology
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• v.33 no.1
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• pp.28-51
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• 2019

The purpose of this study was to analyze forest vegetation structure in Marugeum (the ridge line) area between Dakmokryeong and Daetjae in Baekdudaegan through vegetation classification, importance value, species diversity, and CCA using the data that were collected from 245 quadrates through Braun-Blanquet vegetation survey method from May to September in 2017. The results of the forest vegetation classification identified 8 vegetation units with Quercus mongolica community group at the highest level. Q. mongolica community group was classified into the Cornus controversa community, Buxus koreana community, Sasa borealis community, Abies nephrolepis community, and Q. mongolica typical community. C. controversa community was further classified into Quercus dentata group, Filipendula glaberrima group, Larix kaempferi group, and C. controversa typical group. The result of the important value analysis showed that Q. dentata had the highest importance value at 19.1% in vegetation unit 1 while Q. mongolica had the highest importance value at 22.7%, 38.3%, 25.6%, 41.3%, 27.9%, and 41.6% in vegetation unit 2, 4, 5, 6, 7, and 8, respectively, and L. kaempferi had the highest importance value at 27.6% in vegetation unit 3. As such, Q. mongolica species generally represented the communities of Marugeum (the ridge line) area of Dakmokryeong to Daetjae in Baekdudaegan. The results of species diversity showed that vegetation unit 1 and 2 were 3.305 and 3.236, respectively, which were relatively higher than other vegetation units. It was considered that this result was due to the influence of high emergence of present species. The results of the CCA analysis of the correlations between biotic environmental factors and vegetation types showed that vegetation unit 1 was mainly correlated with the megaphanerophyte ratio and vine plant ratio. In the correlations between abiotic environmental factors and vegetation types, vegetation unit 7 was significantly correlated with altitude. From the perspective of ecological management, vegetation unit 5 represented by B. koreana community was inhabited by a variety of plants due to the species composition and location environment due to the geological characteristics that are typical of limestone area. Vegetation unit 7 represented by A. nephrolepis community was typified as subalpine vegetation widely distributed by relict species and endemic species. We concluded that it is necessary to manage these vegetation units with an ecologically differentiated approach.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.363-369
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• 2018

One of the recent environmental problems is climate change due to the increase of atmospheric $CO_2$, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce $CO_2$ in the world in order to solve various environmental problems caused by increase of $CO_2$. The $CO_2$ reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the $CO_2$ fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to $CO_2$ concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of $CO_2$ concentration and biomass and chlorophyll-a increased faster flow rate at the same $CO_2$ concentration. Also, the quantity of $CO_2$ fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for $CO_2$ fixation of microalgae in rivers and the quantification of the quantity of $CO_2$ fixation from microalgae in rivers can be used as basic data for future policy of $CO_2$ reduction.

• Korean Journal of Heritage: History & Science
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• v.47 no.1
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• pp.32-45
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• 2014

In this study, the characteristics of Mongsimjae in Namwon-si, Jeollabuk-do have been researched focusing on the writings engraved in huge stones and rocks of pavilion standing beside a lotus pond and its formative languages in the garden has been interpreted as follows. Name of pavilion(堂號) Mongsimjae(夢心齋) includes a classical scholar's spirit, refusing to serve two kings and homecoming after resignation from a government office(歸去來) of Songam(松菴) Park Moonsu(朴門壽), an ancestor who has brought to the Juksan(竹山) Park's family again. A pavilion standing beside a lotus pond(蓮塘) built in the reception garden is a gardening facility symbolizing 'Yeondang(蓮堂)' Park Dongsik(朴東式) who built Mongsimjae. The bamboo hill connected to the backyard seems to be relevant to 'Juksan', the family clan of Mongsimjae's owner and this kinds of intention can be found in the bamboos in the outer garden naturally led to inside the garden through the flower beds. The purpose for the western arrangement of the main building and gate contrary to the 'chukjwamihyaug'(丑坐未向; a direction toward to the south-southwest) of the prospect of Sarangchae(guesthouse) is interpreted to naturally attract people's eyes to the pavilion standing beside a lotus pond and to mitigate the sense of closure resulting from the huge stones located in the reception garden. Also the writing engraved in the three huge stones, 'Jonsimdae(存心臺)', implies that it is a place where was selected with heart by Juksan Park family who settled down in Homsil, Namwon after 'Haengchon(杏村) Park Jaryang(朴子良)' in Yiphyangjo(入鄕祖), Namwon and 'Jeongwa(靖窩)' is interpreted as a signature representing that it is the most comfortable house where Jeongwa Park Haechang(朴海昌: 1876~1933), the third owner of Mongsimjae, has lived. The pavilion standing beside a lotus pond of the 'Bangjibangdo(方池方島; square pond and square island)' type has no lotus for now and waterside cornerstones roughly piled with broken stones naturally mitigate the slope. There are two water inflows gathering rainwater in the reception garden other than the water inflow of valley and the upper-side water inflow was built using a high waterfall method. The middle island cut into a square was designed to use in two ways, as 'island' or 'steppingstone', according to the water level and the old name of the pavilion standing beside a lotus pond was revealed as 'Cheonundam(天雲潭)' from the engraved writing located in the side of the middle island. In addition, 'Imni(臨履)', engraved writing in the finishing stone of waterside by citing a line of 'Sigyeong(詩經)', implies 'Be a upright classical scholar who pays close attention to one's own behaviors' and 'Jeongchuk(渟?)' is interpreted as a message that desires the eternal staying of the Juksan Park family's wealth. Ultimately, the writings engraved in the huge stones and rocks of the pavilion standing beside a lotus pond are interpreted as a symbol language that wishes the heaven protects and maintains the wealth of the Juksan Park family who is the owner of Mongsimjae.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.249-258
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• 2019

Purpose: The purpose of this study is to attain the correlation analysis and thereby to deduce the uniaxial compressive strength of rock specimens through the elastic wave velocity and the elastic modulus among the physical characteristics measured from the rock specimens collected during drilling investigations in Seoul and Gyeonggi region. Method: Experiments were conducted in the laboratory with 119 granite specimens in order to derive the correlation between the compressive strength of the rocks and elastic wave velocity and elastic modulus. Results: In the case of granite, the results of the analysis of the interaction between the compressive strength of a rock and the elastic wave velocity and elastic modulus were found to be less reliable in the relation equation as a whole. And it is believed that the estimation of the compressive strength by the elastic wave velocity and elastic modulus is less used because of the composition of non-homogeneous particles of granite. Conclusion: In this study, the analysis of correlation between the compressive strength of a rock and the elastic wave velocity and elastic modulus was performed with simple regression analysis and multiple regression analysis. The coefficient determination ($R^2$) of simple regression analysis was shown between 0.61 and 0.67. Multiple regression analysis was 0.71. Thus, using multiple regression analysis when estimating compressive strength can increase the reliability of the correlation. Also, in the future, a variety of statistical analysis techniques such as recovery analysis, and artificial neural network analysis, and big data analysis can lead to more reliable results when estimating the compressive sterength of a rock based on the elastic wave velocity and elastic modulus.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.102-113
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• 2019

Slack-tide sampling was carried out at 6 stations at high and low tide for a tidal cycle during spring tide of the early summer (June) and summer (July, August) of 2016 to determine the difference of water quality according to tide in Masan Bay, Korea. The mixing regime of all the water quality components investigated was well explained through the correlation with SAL. In the early summer and summer, TURB, DSi and NNN which mainly flow into the bay from the streams and SS, COD, AMN and $H_2S$ which mainly indicate the internal sink and source materials have a property of conservative mixing and non-conservative mixing, respectively. The conservative mixing showed a good linear relationship of the water quality between high and low tide, and the non-conservative mixing showed a variation of different pattern each other. Factor analysis performed on the concentration difference data sets between high and low tide helped in identifying the principal latent variables for them. In early summer, multiple effects (tidal action, natural influx and internal sinks and sources etc.) acted in combination for the differences to be distributed evenly in four factors (VF1~4), since there were few allochthonous inputs as a low-water season. On the contrary, in summer, the parameters showing large concentration difference at ST-1 affected by stream water were concentrated in one factor (VF1) and clearly distinguished from the parameters affected by the internal sinks and sources. In fact, there is no estuary (bay) that always maintains steady state flow conditions. The mixing regime of an estuary might be changed at any time due to the change of flushing time, and furthermore the change of end-member conditions due to the internal sinks and sources makes the occurrence of concentration difference inevitable. Therefore, when investigating the water quality of the estuary, it is necessary to take a sampling method considering the tide to obtain average water quality data.