• Geomechanics and Engineering
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• v.38 no.5
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• pp.507-515
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• 2024

An accurate estimation of the geotechnical parameters in front of tunnel faces is crucial for the safe construction of underground infrastructure using tunnel boring machines (TBMs). This study was aimed at developing a data-driven model for predicting the rock quality designation (RQD) of the ground formation ahead of tunnel faces. The dataset used for the machine learning (ML) model comprises seven geological and mechanical features and 564 RQD values, obtained from an earth pressure balance (EPB) shield TBM tunneling project beneath the Han River in the Republic of Korea. Four ML algorithms were employed in developing the RQD prediction model: k-nearest neighbor (KNN), support vector regression (SVR), random forest (RF), and extreme gradient boosting (XGB). The grid search and five-fold cross-validation techniques were applied to optimize the prediction performance of the developed model by identifying the optimal hyperparameter combinations. The prediction results revealed that the RF algorithm-based model exhibited superior performance, achieving a root mean square error of 7.38% and coefficient of determination of 0.81. In addition, the Shapley additive explanations (SHAP) approach was adopted to determine the most relevant features, thereby enhancing the interpretability and reliability of the developed model with the RF algorithm. It was concluded that the developed model can successfully predict the RQD of the ground formation ahead of tunnel faces, contributing to safe and efficient tunnel excavation.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.2
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• pp.181-194
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• 2015

Spatial-temporal meteorological features of the Ulsan metropolitan region (UMR) were analyzed using observations and high-resolution numerical modeling. Long-term trend analysis (1970~2013) showed a significant increase of $0.033^{\circ}Cyr^{-1}$ in the 5-year moving average temperature, although detailed short-term features varied, whereas wind speed and relative humidity over the same period displayed clear decreases of $-0.007ms^{-1}$ and $-0.29%yr^{-1}$, respectively. These trends indicate the effects of regional climate change and urbanization in the UMR. Seasonal variations averaged for the most recent three years, 2011~2013, showed that temperatures in three different regions (urban/industrial, suburban, coastal areas) of the UMR had similar seasonality, but significant differences among them were observed for a certain season. Urban and industrial complex regions were characterized by relatively higher temperatures with large differences (max.: $3.6^{\circ}C$) from that in the coastal area in summer. For wind speed, strong values in the range from 3.3 to $3.9ms^{-1}$ occurred in the coastal areas, with large differences clearly shown between the three regions in September and October. Diurnal variations of temperature were characterized by pronounced differences during the daytime (in summer) or nighttime (in winter) between the three regions. Results from the WRF modeling performed for four months of 2012 showed large variations in gridaverage temperature and winds in the UMR, which displayed significant changes by season. Especially, a clear temperature rise in the urban center was identified in July ($0.6^{\circ}C$ higher than nearby urban areas), and overall, relatively weak winds were simulated over urban and inland suburban regions in all seasons.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.3
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• pp.103-119
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• 2016

This study aims to assess habitat feature on the large-scale spawning ground of the Boreal Digging Frog Kaloula borealis in Daemyung retarding basin of Daegu, and to analyze the relationships between species abundance and meteorological factors for each habitat. Fifty-seven(57) pitfalls were installed to collect species abundance of 4 survey regions, and high-resolution satellite image, soil sampling equipment, digital topographic map, and GPS were used to develop habitat features such as terrain, soil, vegetation, human disturbance. The analysis shows that the frog is most abundant in sloped region with densely herbaceous cover in southern part of the retarding basin. In the breeding season, lowland regions, where Phragmites communis and P. japonica dominant wetlands and temporary ponds distributed, are heavily concentrated by the species for spawning and foraging. Located in between legally protected Dalsung wetands and lowland regions of the retarding basin, riverine natural levee is ecologically important area as core habitat for Kaloula borealis, and high number of individuals were detected both breeding and non-breeding seasons. Temperate- and pressure-related meteorological elements are selected as statistically significant variables in species abundance of non-breeding season in lowland and highland regions. However, in sloped regions, only a few variables are statistically significant during non-breeding season. Moreover, breeding activities in sloped regions are statistically significant with minimum temperature, grass minimum temperature, dew point temperature, and vapor pressure. Significant meteorological factors with habitat features are effectively applied to establish species conservation strategy of the retarding basin and to construct for avoiding massive road-kills on neighboring roads of the study sites, particularly post-breeding movements from spawning to burrowing areas.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.5
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• pp.135-145
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• 2010

This study was carried out to investigate the current urban forest network and future plan of forest framework using nearest features program where stepping stones within 5km from the core forest were selected in the program. We found several conclusions as follows: First, we found that cities in inland area including Daegu, Dajeon and Gwangju have quite different types of forest network with comparing to the cities nearby coastline including Busan, Incheon and Ulsan. The cities in inland area have large mountain patch around each city. However they have small and lower number of island forests within their urban area. Otherwise, cities nearby coastline have more forest patches than in the cities in inland area, and Busan and Incheon especially have strong forest network using various size of forest patches. Second, Daegu and Daejeon have much smaller forest patches distributed in each urban area. So additional forest patches should be added to have highly strong forest network within urban area. Third, Ulsan and Gwangju have most stepping-stone forests close to the large mountain patches in suburban area, which are not able to connect to the forest patches in the central area of each city So additional forest patches are needed to be added in the central area of each city for reinforcing the effect of stepping stone in the central area. Though there should be an addition approach except for forest size and its isolation to construct the ecological network in an urban area, this indices can be a good method to check an environmental and ecological status in an urban area.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.4
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• pp.61-68
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• 2019

As high schools implement credit completion system these days, concerns about the dissolution of classes, which are the original stable groups of studying and living, and the instability of the basal space, is growing due to the extended operation of moving optional classes. The purpose of this research is to understand the effect that environmental features of the basal space within the school and the operation method have on the students' space use and formation of attachment place within the school. For this, the main activity places, attachment places, school life satisfaction and others were investigated at 2 Japanese credit-based comprehensive high schools, which are different in the physical environmental features of school buildings. Based on this, a quantitative analysis about the distribution of activity places and attachment places was implemented. The space use features for each student attribute were compared, and the school life satisfaction for each type of attachment place formation was analyzed. As a result, the change of the territorial consciousness about the class space according to the implementation of moving optional classes could be understood. And it was confirmed that the students' space using behavior and place evaluation change according to the physical environmental feature of the class space and common space, and that this is affecting the life satisfaction of students.

• Journal of Broadcast Engineering
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• v.25 no.6
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• pp.845-853
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• 2020

In this paper, we propose a method for classifying environmental sound for selective noise cancellation in industrial sites. Noise in industrial sites causes hearing loss in workers, and researches on noise cancellation have been widely conducted. However, the conventional methods have a problem of blocking all sounds and cannot provide the optimal operation per noise type because of common cancellation method for all types of noise. In order to perform selective noise cancellation, therefore, we propose a method for environmental sound classification based on deep learning. The proposed method uses new sets of acoustic features consisting of temporal and statistical properties of Mel-spectrogram, which can overcome the limitation of Mel-spectrogram features, and uses convolutional neural network as a classifier. We apply the proposed method to five-class sound classification with three noise classes and two non-noise classes. We confirm that the proposed method provides improved classification accuracy by 6.6% point, compared with that using conventional Mel-spectrogram features.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.6
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• pp.1-13
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• 2008

The purpose of this study is to examine residents' perceptions of the outdoor spaces of environmentally-friendly apartment complexes focused on quality of life. On-site intercept surveys were performed to collect data and samples were selected from the residents who are currently living in two different environmentally-friendly certified apartment complexes. This study has examined importance and satisfaction of outdoor spaces of the study sites as they relate to quality of life, as well as they correlation between the New Environmental Paradigm(NEP), and satisfaction and loyalty, respectively. Data were analyzed using several statistical methods including descriptive statistics, Importance-Satisfaction Analysis(ISA), t-test, and correlation. The results suggest that outdoor spaces of the apartment complexes are perceived as an important place to improve residents' quality of life. Residents showed a high satisfaction rate to the natural environmental features(e.g. natural areas present, amenity of space) while they showed a lower satisfaction rate to the social environmental features(e.g. access to public transportation). Although most residents tend to have the New Environmental Paradigm based on the study results, NEP did not influence the level of satisfaction in environmentally-friendly apartment complexes. In contrast, there was a significant relationship between NEP and loyalty. In addition, a strong correlation emerged between satisfaction of outdoor spaces and loyalty to the housing estates. Given these results, various recommendations were given to promote better use of outdoor spaces of dwellings to improve residents' quality of life.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.217-227
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• 2023

Crystalline calcium carbonate (CaCO₃) occurs in various geological and aqueous environments as calcite, aragonite, and vaterite. These minerals also have practical applications in engineered settings. Synthetic methods of calcium carbonate have been developed for scientific research and technical applications. For example, these methods have become widely adopted for studying the formation of CaCO₃ minerals and (geo-)chemical processes involving these minerals in natural and engineered systems. Furthermore, these methods have the potential to be applied in various technical and biomedical fields. Water-based synthesis is particularly important for simulating the formation of calcium carbonate minerals in natural aqueous environments. This review paper describes the procedures and experimental conditions for water-based synthetic methods of each calcium carbonate polymorph, compares the morphological and structural features of the resulting crystals, and analyzes the crystallization mechanisms.

• Journal of the Korean Wood Science and Technology
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• v.38 no.4
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• pp.292-297
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• 2010

Sound absorption capability and anatomical features of kagikazura (Uncaria rhynchophylla) and larch (lalix kaemferi) wood were estimated. Sound absorption coefficients had been measured by the two microphone transfer function method and anatomical features of kagikazura wood examined by SEM observation. The sound absorption coefficients of Uncaria rhynchophylla was higher than lalix kaemferi. Especially, in the frequency range of 1 to 4KHz, sound absorption coefficients of kagikazura was about 2~3 times higher than those of lalix kaemferi. Abundant and big vessel observed on the cross sectional surface of kagikazura wood and simple perforation plate observed on the longitudinal surface. It was surmised that the abundant big vessel element and simple perforation plate behaved as a sound absorbing pore.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.4
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• pp.1-8
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• 1999

Forest devastation in Korea was caused by several factors such as internal factors from geological features and external factors from artificial forest damages including fuel wood collection from forests, forest fires, shifting cultivations and so on. According to the reports of 1935, lots of forest devastation in Kyungpook province area occurred around the main and branch stream of Nakdong river. Main factors of occurring forest devastation in 1935 were investigated by the methods of forest devastation rate and the population density at the basin of Nakdong river. But based on our study, forest devastation mainly occurred in rock zones of granite and granite gneiss, next to Nakdong formation but scarcely occurred in Hayang formation. Clay of the weathered soils of granite and granite gneiss was lost by rainfall, but remaining coarse-sandy soils(or grits) have poored conditions in vegetation's growth, which are due to high level of water permeability, lack of water-holding capacity and dried conditions. Generally, pine forests are mainly growing up in these regions. It is supposed that forest devastation was accelerated due to long periods of natural regeneration and no ability of natural regeneration by sprout after frequent collections of fuel wood and cuttings from pine forest on those grit areas. These results indicated that the high rate of forest devastation occurred around the basin with the high resident population density, which was partly due to forest damages by fuel collection. Moreover, both geological features and number of residents had much influence on forest devastation. Forest devastation was positively correlated with those variables(r=+0.73).