• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.121-129
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• 2017

There have been a number of water and sewer pipe breakdown reports followed by ground subsidence. Also, the excavating works for construction due to overcrowding of city have been common. Particularly, in urban areas ground becomes unstable because of the lowered lifeline sinkage followed excavation and backfilling. In order to solve the problem, some reinforcement works for ground by rod tamping or grouting have been applied. However, it is hard to predict when the buried utilities in underground will be damaged. Also, there is a limit for the underground exploration and investigation methods. Therefore, in this study, the estimated about the water soluble polymer pouch including poor mixed admixture which is designed to eliminate the dangerous factors. The reinforcement strength of this method was confirmed by verifying three points: meltiness in a certain period, water solubility in the ground water level, and characteristics of the pouch, which can be stored in daily conditions. It is also proved that this method allows to keep the ground from getting weakened in the installation of water and sewer pipe along with back filling materials.

• (The)Study of the Eastern Classic
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• no.69
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• pp.419-450
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• 2017

This study aims to discover the clue of the current modern postal system development by looking at the delivery patterns of Korean letters during the Joseon Dynasty. A letter is a text medium that the sender sends to a recipient by sending a message of news. The form and contents of the letter are influenced by the various surrounding factors and are adapted to circumstances. The study aims to clear up the method of delivery and the nature of the transmitter among the environmental factors which affects the format and contents of Korean letters. Depending on the public or private matters, the delivery method is divided into a public agency and a private messenger, or divided into one-phase delivery and the multi-phase delivery depending on whether or not a phase is divided into stages. It is also divided into a one-way and a round-transmission depending on whether or not it is round-switched. The transmitter is divided into a verbal communication, the letter and verbal communication, and the letter communication according to whether or not it is by verbal, and divided into the relational and the non-relational person according to the relationship with the sender. Also depending on whether the transmitter is exclusive or not, it is divided into the exclusive messenger and the messenger who deliver a letter incidentally while come and go. In the aspect of the delivery method, We can see the possibility of developing to a modern mail system through the public method, the multi-phase delivery, one-way delivery and in the aspect of the transmitter, we can see the possibility through the letter delivery, non-related transmitter, and the exclusive messenger.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.346-355
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• 2019

When evaluating pillar stability in very closely spaced tunnels, a local safety factor (strength/stress ratio) at the minimum width has been widely used. Tension bolts have been frequently applied as reinforcement for the cases where safety factors are less than 1.0 from FEM stress analysis. However, the local safety factor shows a constant value irrespective of the change in pillar width/tunnel diameter (PW/D) and the safety factor of the pillar is underestimated because the variation of deviation stress is relatively small even when the pre-stressing is applied to the tension bolt. In addition, the average safety factor proposed by Hoek and Brown(1980) was reviewed, but the pillar safety factor was relatively overestimated when the width of the pillar was increased. As an alternative, the SRM safety factor using shear strength reduction method shows the effect of changing the safety factor in the case of no reinforcement and tension bolt reinforcement as the pillar width/tunnel diameter(PW/D) changes. The failure shape is also similar to the previous limit theory result. In this study, the safety factor was evaluated without considering rock bolt and shotcrete to distinguish reinforcing effect of tension bolt.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1215-1222
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• 2021

In this study, a study on how to use a fire hydrant as a heat wave reduction facility through hydraulic analysis of the water supply pipe network was conducted. Assuming that the fire hydrant installation point is open for heat wave reduction, the water pressure at each point was derived. And the reduction rate of the temperature according to the hydrant watering was compared with the watering area according to the operation of the watering truck. The watering area according to the opening of the fire hydrant was calculated by deriving the pressure value at the node where the fire hydrant was installed through hydraulic analysis of the water pipe network, and then using the watering radius relational expression according to the pressure value. As a result of applying the proposed methodology to two real city areas, the temperature reduction effect of the watering method by a fire hydrant can be derived lower than the watering method by a watering truck according to the difference in the absolute watering area. However, unlike a watering truck, a fire hydrant does not have a relative restriction on the amount of water supply and is expected to allows continuous divided spraying of the same area.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.413-418
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• 2020

It is necessary to manage the prediction accuracy of the machine learning model to prevent the decrease in the performance of the grid network condition prediction model due to overfitting of the initial training data and to continuously utilize the prediction model in the field by maintaining the prediction accuracy. In this paper, we propose an automation technique for maintaining the performance of the model, which increases the accuracy and reliability of the prediction model by considering the characteristics of the power grid state data that constantly changes due to various factors, and enables quality maintenance at a level applicable to the field. The proposed technique modeled a series of tasks for maintaining the performance of the power grid condition prediction model through the application of the workflow management technology in the form of a workflow, and then automated it to make the work more efficient. In addition, the reliability of the performance result is secured by evaluating the performance of the prediction model taking into account both the degree of change in the statistical characteristics of the data and the level of generalization of the prediction, which has not been attempted in the existing technology. Through this, the accuracy of the prediction model is maintained at a certain level, and further new development of predictive models with excellent performance is possible. As a result, the proposed technique not only solves the problem of performance degradation of the predictive model, but also improves the field utilization of the condition prediction model in a complex power grid system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.203-210
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• 2019

A recent earthquake on the Korean Peninsula caused much damage to masonry buildings, and research on performance evaluation has been underway. A masonry building is generally constructed using wet construction and is affected by temperature, which reduces the efficiency of the construction. In this study, we propose a dry construction technique for assembling concrete blocks without using mortar and evaluated its performance through experimental and analytical research. To evaluate the performance, experiments were carried out for the prismatic compressive strength, direct terminal strength, and diagonal tensile strength of the dry construction wall. The adequacy of the cross section shape was also reviewed through FEM analysis. The results show that the compressive strength and diagonal tensile strength could exert a certain intensity or higher. Furthermore, the H-type module of a key block acted as a shear key for the entire concrete block, which resulted in excellent shear strength performance. In addition, the shape and thickness of the main block have a major effect on the strength performance of each block. Therefore, an optimal shape and the proposed dry construction method could be applied to replace the wet method by studying the construction or seismic performance of the proposed method.

• Korean Journal of Construction Engineering and Management
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• v.22 no.2
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• pp.21-30
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• 2021

The existing construction industry is classified into industries with low productivity compared to other industries. In order to solve the decline in productivity in the construction industry, the world is focusing on off-site construction (OSC), which is about 40% more productive than existing construction methods. This high productivity is possible because the three stages of production, transport to the site, and site assembly are consistently maintained in a continuous flow. This study conducted a functional survey through literature review, preliminary field survey, questionnaire, and expert interview. The surveyed function were classified into five categories: convenience, flexibility, manageability, communication, and safety, and the functional characteristics of flexibility, manageability, and communication were high. Because of the change according to the construction progress, the production schedule of the factory, and the variety of transportation time required. Finally, A functional block diagram was developed based on the 15 functions corresponding with an average score of 4 or more in the surveyed function score result. If the OSC transport system is established through this study, It can contribute to a successful construction OSC project and increase productivity.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1049-1057
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• 2020

This study aimed to develop a flow measurement method using drone in flood season. Measuring flow in all branches is difficult to conduct annually due to budget and labor limitation, safety and river works. Especially when heavy rain like storm comes, changes in stage-discharge relationship should be reviewed; however, it is usually impeded by the aforementioned issues. To solve the problem, it developed a simple measuring method with a minimum of labor and time. A numeric map and numeric orthophoto coordinate of South Korea are mostly based on Transverse Mercator Projection (TM) in accordance with rectangular coordinate system and use World Geodetic Reference System 1980 (GRS80) oval figure for conversion. Applying a concept of aerial photogrammetry, it located four visible Ground Control Points (GCP) near the river at Uijeongbu-si (Singok Bridge) and Yeongdong-gun (Youngdong 2nd Bridge) station and measured the coordinates using VRS DGPS. Hovering at a same level, drones took orthophoto of water surface at an interval of 3 seconds. It defined the pictures with GRS80 TM coordinate system, a rectangular coordinate system and then conducted an orthometric correction using GCP coordinates. According to X and Y coordinate analysis, it estimated the distance between the floating positions at 3 seconds-intervals and calculated the flow through the flow area according to the flow path. This study attested applicability of the flow measurement method using drone in flood season by applying the rectangular coordinate system based on the concept of aerial photogrammetry.

• Land and Housing Review
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• v.13 no.1
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• pp.11-22
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• 2022

This paper estimates the demand of newly married couples for public rental housing in Chungnam. This research attempts to overcome data limitations by linking survey data with administrative data for analysis. First, the results of a binary logit model that analyzes newly married couples' intention to move into public rental housing, based on the Chungnam Social Survey 2019, reveal that residential location, educational level, housing type, and tenure type have a statistically significant effect. By combining the estimated coefficients with another dataset, the statistics of newly married couples for administration purposes acquired from Statistics Korea, this research estimates the demand for public rental housing among the newly married couples in Chungnam. The estimation results show that the total demand for public rental housing in Chungnam is 11,424 units among 43,705 newly married couples. The total demand of 21,685 newly married couples who occupy rental housing is estimated to be 9,436 units. The policy for providing public rental housing to newly married couples in Chungnam aims to increase their fertility rates. Hence, further research should be followed up to evaluate the effect of the supply of public rental housing on fertility rates. Also, a research method should be developed to control for possible endogeneity between the demand for public rental housing and childbirths.

• Land and Housing Review
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• v.13 no.2
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• pp.65-79
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• 2022

To suggest implications of future housing problems, this study investigates which characteristics affect the housing satisfaction of young single households. Using the survey data, we perform the multiple regression and decision tree models based on the SPSS Statistics 25.0. Our empirical results show several key features. First, housing characteristics and intention to continue single households had a positive (+) effect on housing satisfaction, in the order of natural, housing, physical characteristics, and intention to continue single households. Second, housing characteristics and intention to marry in the future had a positive (+) effect on housing satisfaction in the order of natural, housing, and physical characteristics. Third, housing characteristics and intention to increase household members in the future had a positive (+) effect on housing satisfaction, in the order of natural, housing, and physical characteristics satisfaction. Finally, the results of the decision tree model show that the natural characteristics were over 3.4, and housing satisfaction was the highest in the case of Jeonse. The results of this study provide three implications for policymakers. First, improving the residential environment of young single households is important. Second, providing customized housing for young single households could enhance the housing satisfaction of young people. Finally, housing provision needs to be carried out with suitable space for the lifestyle of young single households.