• The Journal of Engineering Geology
• /
• v.33 no.3
• /
• pp.413-426
• /
• 2023

This study presents the geochemical characteristics of cave water to evaluate its origin and flow path. From June 2022 to may 2023, river water was collected at two sites (WE1 and WE2) in the Donggang River around Baengnyongdonggul Cave, and cave water was collected at four sites (WE3 to WE6) inside Baengnyongdonggul Cave. Water samples were analyzed for major dissolved components. Both river and cave waters were classified as Ca-HCO₃ type. All cave water samples were supersaturated in carbonate minerals, suggesting that carbonate minerals would precipitate within the cave. Due to differences in the source of cave water and the degree of water-rock interaction, the geochemical characteristics of water from sites where the flow of cave water is observed (WE3 and WE6) and rimstone pools (WE4 and WE5) could be clearly distinguished. The cave water at WE6 flows in from the Donggang River, then passes through WE3 and flows back out into the Donggang River. The cave water at WE4 and WE5 is supplied from precipitation, but the flow path of cave water at WE4 and WE5 is different.

• Geomechanics and Engineering
• /
• v.32 no.1
• /
• pp.111-123
• /
• 2023

The slope of an open cut tunnel is located above the exit of the Leijia tunnel on the Changgan high-speed railway. During the excavation of the open cut tunnel foundation pit, the slope slipped twice, a large landslide of 92500 m³ formed. The landslide body and unstable slope body not only caused the foundation pit of the open cut tunnel to be buried and the anchor piles to be damaged but also directly threatened the operational safety of the later high-speed railway. Therefore, to study the stability change in the slope of the open cut tunnel under heavy rain and excavation conditions, a 3D numerical calculation model of the slope is carried out by Midas GTS software, the deformation mechanism is analyzed, anti-sliding measures are proposed, and the effectiveness of the anti-sliding measures is analyzed according to the field monitoring results. The results show that when rainfall occurs, rainwater collects in the open cut tunnel area, resulting in a transient saturation zone on the slope on the right side of the open cut tunnel, which reduces the shear strength of the slope soil; the excavation at the slope toe reduces the anti-sliding capacity of the slope toe. Under the combined action of excavation and rainfall, when the soil above the top of the anchor pile is excavated, two potential sliding surfaces are bounded by the top of the excavation area, and the shear outlet is located at the top of the anchor pile. After the excavation of the open cut tunnel, the potential sliding surface is mainly concentrated at the lower part of the downhill area, and the shear outlet moves down to the bottom of the open cut tunnel. Based on the deformation characteristics and the failure mechanism of the landslides, comprehensive control measures, including interim emergency mitigation measures and long-term mitigation measures, are proposed. The field monitoring results further verify the accuracy of the anti-sliding mechanism analysis and the effectiveness of anti-sliding measures.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.2
• /
• pp.43-63
• /
• 2023

With the concentration of the population in the city center and the saturation of the structures on the ground, the development of the underground structures becomes important and the construction of an adjoining tunnel that can reduce the overall problems is respected. In addition, it is necessary to apply the reinforcement construction method for the pillar part of the adjacent tunnel that can secure stability, economy and workability of the site. In this study, the tunnel pillar reinforcement method using prestress and grouting was reviewed. There are various reinforcement methods that can compensate for the problems of the side tunnel, but as the tunnel pillar construction method using prestress and grouting is judged to be excellent in field applicability, stability and economic feasibility, theoretical and numerical analysis of the actual behavior mechanism are conducted. Numerical analysis is divided into PC stranded wire + steel pipe reinforcement grouting + prestress (Case 1), pillar part tie bolt reinforcement (Case 2), pillar part non-reinforcement (Case 3) under the same ground conditions, and the maximum value of the celling displacement, internal displacement, and member force, the stability was confirmed. Through numerical analysis, it was confirmed that Case 1 which reinforced the PC stranded wire, was the best construction method and if it is verified and supplemented through field experiments later, it will be possible to derive superior results in terms of displacement control and member force than the currently applied reinforcement method was judged.

• Journal of Service Research and Studies
• /
• v.12 no.4
• /
• pp.94-105
• /
• 2022

Urban Air Transportation (UAM) is a three-dimensional transport within the city using eVTOL as an alternative to the saturation of land transportation due to overcrowding in major cities around the world. Design has played its roles in various fields in the development of transport, but research on the design application of UAM, which will be commercialized soon, is insufficient. Accordingly, there is a growing need for prior research on the forecasting the future environment and the design application through phenomenon analysis. The purpose of this study is to derive mega trends through STEP analysis for UAM and present ways to apply design in the UAM field based on this. The research method was conducted in the following order. First, the theoretical background of UAM was established by analyzing prior art documents on UAM. Second, five trends in the future environment centered on UAM were derived through STEP analysis. Finally, in order to derive a design application, five experts in each design area (product, visual, video, environment, service) discussed the design application focusing on the results of STEP analysis and derived a design application plan for each design area in the UAM field. Through this study, it was found that the most frequent design area in the STEEP analysis is product design and service design, and therefore related design development is important. After analyzing UAM's information provision plan, display method, and usage process suggested in this study, it is expected that it will lead to various prior design studies related to UAM, such as customized service design, to establish an infrastructure environment for commercialization of UAM.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.12
• /
• pp.103-111
• /
• 2008

Soils naturally contain grains of different minerals which may be dissolved under chemical or physical processes. The dissolution leads changes in microstructure of particulate media, such as an increase in local void or permeability, which affects the strength and deformation of soils. This study focuses on the small strain stiffness characteristics of vanishing mixtures, which consist of sand and salt particles at different volume fractions. Experiments are carried out in a conventional oedometer cell (Ko-loading) integrated with bender elements for the measurement of shear waves. Dissolutions of particles are implemented by saturating the mixtures at various confining stresses. Axial deformation and shear waves are recorded after each loading stage and during dissolution process. Experimental results show that after dissolution, the vertical strain and the void ratio increase, while the shear wave velocity and small strain shear modulus decrease. The decrease of the velocity results from the void ratio increase and particle contact decrease. The process monitoring during dissolution of the particles shows that the vertical strain dramatically increases at the beginning of the saturation process and converges after vanishing process finishes, and that the shear wave velocity decreases at the beginning and increases due to the particle reorientation. Specimens prepared by sand and salt particles are proved to be able to provide a valuable insight in macro structural behaviors of the vanishings mixtures.

• Korean Journal of Environmental Biology
• /
• v.40 no.3
• /
• pp.352-362
• /
• 2022

Photosynthesis and respiration of seagrasses are mainly controlled by water temperature. In this study, the photosynthetic physiology and respiratory changes of the Asian surfgrass Phyllospadix japonicus, which is mainly distributed on the eastern and southern coasts of Korea, were investigated in response to changing water temperature (5, 10, 15, 20, 25, and 30℃) by conducting mesocosm experiments. Photosynthetic parameters (maximum photosynthetic rate, P_max; compensation irradiance, I_c; and saturation irradiance, I_k) and respiration rate of surfgrass increased with rising water temperature, whereas photosynthetic efficiency (α) was fairly constant among the water temperature conditions. The P_max and I_k dramatically decreased under the highest water temperature condition (30℃), whereas the I_c and respiration rate increased continuously with the increasing water temperature. Ratios of maximum photosynthetic rates to respiration rates (P_max : R) were highest at 5℃ and declined markedly at higher temperatures with the lowest ratio at 30℃. The minimum requirement of H_sat (the daily period of irradiance-saturated photosynthesis) of P. japonicus was 2.5 hours at 5℃ and 10.6 hours at 30℃ for the positive carbon balance. Because longer H_sat was required for the positive carbon balance of P. japonicus under the increased water temperature, the rising water temperature should have negatively affected the growth, distribution, and survival of P. japonicus on the coast of Korea. Since the temperature in the temperate coastal waters is rising gradually due to global warming, the results of this study could provide insights into surfgrass responses to future severe sea warming and light attenuation.

• Korea Science and Art Forum
• /
• v.31
• /
• pp.171-180
• /
• 2017

The purpose of this study is to analyze the characteristics of color image for establishing the color environment contributing to the promotion of public health in the public health facilities and to utilize it as data of public health color plan and index development. For this purpose, the results of the previous precedent studies were integrated and public health facilities were classified into medical facilities (general hospitals), health facilities (public health centers), and sub - healing facilities (elderly care facilities). We visited 18 public health facilities in total, measured the environmental color of with a spectroscopic, compared the results and the precedent studies results, and identified color image characteristics and future supplement points. The results are as follows. First, the previous studies related to the environment color image vocabulary of the public health facilities, it prefer comfortable, bright and positive image. Second, as a result of direct measurement the environmental color of the public health facilities, it is found that most of them use the high brightness and low saturation color of Y series. Third, as a result of analyzing vocabulary of environmental color image of public health facilities, 'natural' image showed the highest frequency, and other images such as 'gentle' and 'decent' appeared. It was difficult to understand the characteristics of the color image vocabularies of public health facilities. This study is a convergence study of color science and environmental design, and it extends the scope of multidisciplinary research related to design and it will be helpful in environmental planning on user's emotion.

• The Journal of Engineering Geology
• /
• v.33 no.2
• /
• pp.335-353
• /
• 2023

Site selection processes for high-level radioactive waste disposal facilities in different countries differ in terms of local geology and degree of public engagement. There seem to be three alternative processes for site selection: (1) selection with community consent after government choice; (2) selection with continuous community engagement after exclusion of unsuitable areas based on existing survey data; or (3) site selection where communities have expressed a willingness to participate. The Yucca Mountain site in Nevada, USA, was selected as the final disposal site by process (1) through six stages, but its development was suspended owing to opposition from the local governor and environmental groups. In Sweden, Switzerland, and Germany, process (2) is used and sites are selected through three stages. Sweden and Switzerland have completed site selection, and Germany is currently engaged in the process. The UK adopted process (3) with six stages, although the process has been suspended owing to poor community participation. In Korea, temporary storage facilities for spent nuclear fuel will reach saturation from 2030, so site selection must be promoted through various laws and systems, with continuous communication with local communities based on transparent and scientifically undertaken procedures.

• Korean Journal of Remote Sensing
• /
• v.39 no.2
• /
• pp.157-168
• /
• 2023

Image segmentation and supervised classification techniques are widely used to monitor the ground surface using high-resolution remote sensing images. In order to classify various objects, a process of defining a class corresponding to each object and selecting samples belonging to each class is required. Existing methods for extracting class samples should select a sufficient number of samples having similar intensity characteristics for each class. This process depends on the user's visual identification and takes a lot of time. Representative samples of the class extracted are likely to vary depending on the user, and as a result, the classification performance is greatly affected by the class sample extraction result. In this study, we propose an image classification technique that minimizes user intervention when extracting class samples by applying the histogram back-projection technique and has consistent intensity characteristics of samples belonging to classes. The proposed classification technique using histogram back-projection showed improved classification accuracy in both the experiment using hue subchannels of the hue saturation value transformed image from Compact Advanced Satellite 500-1 imagery and the experiment using the original image compared to the technique that did not use histogram back-projection.

• Korean Journal of Health Psychology
• /
• v.16 no.3
• /
• pp.557-575
• /
• 2011

This study tried to examine the characteristics of attention deficits in patients with Obstructive Sleep Apenea(OSA) with different age levels, and to examine which indices of polysomnograms might be related to the indices of attention deficits in OSAs. Two age-level groups and a normal control group were subjected to two computerized attention tests, including a continuous performance test(CPT) and a change blindness task(CBT). In addition, the three groups were subjected to a Polysomnography to extract several sub-indicators of polysomnogram, and an Epworth Sleepiness Scale which measures subjective sleepiness. As results, the OSAs showed significantly more omission and commission errors in CPT, and they showed lower accuracy in CBT compared to the normal group. The results of a correlational analysis showed that attention deficits in OSA are significantly correlated with arterial oxygen saturation among sub-indicators of polysomnograms. In conclusion, OSAs seems to be less attentive, having difficulties in response inhibition, and having deficiencies in noticing important environmental changes. Age seems to make these deficiencies even worse. Especially, the relationship between attention deficiency and hypoxia which could cause irreversible cerebrum damage has an implication in cognitive impairment prevention through early treatment.