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Tensile Properties of Hybrid Fiber Reinforced Cement Composite according to the Hooked & Smooth Steel Fiber Blending Ratio and Strain Rate (후크형 및 스무스형 강섬유의 혼합 비율과 변형속도에 따른 하이브리드 섬유보강 시멘트복합체의 인장특성)

  • Son, Min-Jae;Kim, Gyu-Yong;Lee, Sang-Kyu;Kim, Hong-Seop;Nam, Jeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.3
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    • pp.31-39
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    • 2021
  • In this study, the fiber blending ratio and strain rate effect on the tensile properties synergy effect of hybrid fiber reinforced cement composite was evaluated. Hooked steel fiber(HSF) and smooth steel fiber(SSF) were used for reinforcing fiber. The fiber blending ratio of HSF+SSF were 1.5+0.5, 1.0+1.0 and 0.5+1.5vol.%. As a results, in the cement composite(HSF2.0) reinforced with HSF, as the strain rate increases, the tensile stress sharply decreased after the peak stress because of the decrease in the number of straightened pull-out fibers by increase of micro cracks in the matrix around HSF. When 0.5 vol.% of SSF was mixed, the micro cracks was effectively controlled at the static rate, but it was not effective in controlling micro cracks and improving the pull-out resistance of HSF at the high rate. On the other hand, the specimen(HSF1.0SSF1.0) in which 1.0vol.% HSF and 1.0vol.% SSF were mixed, each fibers controls against micro and macro cracks, and SSF improves the pull-out resistance of HSF effectively. Thus, the fiber blending effect of the strain capacity and energy absorption capacity was significantly increased at the high rate, and it showed the highest dynamic increase factor of the tensile strength, strain capacity and peak toughness. On the other hand, the incorporation of 1.5 vol.% SSF increases the number of fibers in the matrix and improves the pull-out resistance of HSF, resulting in the highest fiber blending effect of tensile strength and softening toughness. But as a low volume fraction of HSF which controlling macro crack, it was not effective for synergy of strain capacity and peak toughness.

Development of tracer concentration analysis method using drone-based spatio-temporal hyperspectral image and RGB image (드론기반 시공간 초분광영상 및 RGB영상을 활용한 추적자 농도분석 기법 개발)

  • Gwon, Yeonghwa;Kim, Dongsu;You, Hojun;Han, Eunjin;Kwon, Siyoon;Kim, Youngdo
    • Journal of Korea Water Resources Association
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    • v.55 no.8
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    • pp.623-634
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    • 2022
  • Due to river maintenance projects such as the creation of hydrophilic areas around rivers and the Four Rivers Project, the flow characteristics of rivers are continuously changing, and the risk of water quality accidents due to the inflow of various pollutants is increasing. In the event of a water quality accident, it is necessary to minimize the effect on the downstream side by predicting the concentration and arrival time of pollutants in consideration of the flow characteristics of the river. In order to track the behavior of these pollutants, it is necessary to calculate the diffusion coefficient and dispersion coefficient for each section of the river. Among them, the dispersion coefficient is used to analyze the diffusion range of soluble pollutants. Existing experimental research cases for tracking the behavior of pollutants require a lot of manpower and cost, and it is difficult to obtain spatially high-resolution data due to limited equipment operation. Recently, research on tracking contaminants using RGB drones has been conducted, but RGB images also have a limitation in that spectral information is limitedly collected. In this study, to supplement the limitations of existing studies, a hyperspectral sensor was mounted on a remote sensing platform using a drone to collect temporally and spatially higher-resolution data than conventional contact measurement. Using the collected spatio-temporal hyperspectral images, the tracer concentration was calculated and the transverse dispersion coefficient was derived. It is expected that by overcoming the limitations of the drone platform through future research and upgrading the dispersion coefficient calculation technology, it will be possible to detect various pollutants leaking into the water system, and to detect changes in various water quality items and river factors.

Re-examining the Concept of 'Seeking Out the Original Root (原始返本)' as an Example of Religious Language (종교언어로서의 '원시반본(原始返本)' 개념 재검토)

  • Cha, Seon-keun
    • Journal of the Daesoon Academy of Sciences
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    • v.29
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    • pp.171-207
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    • 2017
  • The research regarding religious concepts used in Daesoon Jinrihoe are still incomplete. This study is a suggestion to critically review the existing research on 'seeking out the original root (原始返本)', one of the religious terms of Daesoon Jinrihoe. In addition, this concept will be seen from a new perspective. 'Seeking out the original root' plays a major role in Daesoon theology due to the cosmology established by Daesoon Jinrihoe. However, the existing research on this topic are prone to the perspective of 'returning' and assuming a 'cyclical view on the order of history'. Therefore, the cosmology that has been built by the religious language misleads readers to assume a retrospective process or that the process itself is realized on its own in accordance with the cosmic order. These kinds of studies do not specifically manifest the world view of Daesoon Jinrihoe. They fail to do so because Sangje's reordering works and its fruit, the earthly paradise of the Later World, have never existed before. The concept of 'seeking out the original root' should break away from the frame of a cyclical view of history and exert the uniqueness of Daesoon Jinrihoe. In this regard, this study can be summarized as follows: 'Seeking out the original root', one of the principles needed to achieve the re-creation of the Later World, endeavors to find a way to account for the origin of all things such as civilizations, cultures, and dharmas. If such a way is found, the facts between the root and the beginning should be acknowledged, as the root itself is what has been sustained, succeeded, used, resolved, revised, and rectified. The origin is usually dealt with from the position of rewarding. This was all achieved in Sangje's decisions and his reordering works. Its outcome will be utilized as a basis to establish an earthly paradise in the Later World. This concept, as defined above, excludes a cyclical view of history and implies that the concept of 'seeking out the original root' is a flexible frame within the context of dynamic structuralism. Given the style of this approach, this study provides a view which can be easily differentiated from existing research.

A Study on Dosu Theory in Daesoon Thought (대순사상의 도수론(度數論) 연구)

  • Park, In-gyu
    • Journal of the Daesoon Academy of Sciences
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    • v.28
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    • pp.207-241
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    • 2017
  • In the scripture of Daesoon Jinrihoe, the expression 'Dosu (度數)' is frequently used and Jeungsan, Jeongsan, and Wudang also left behind many teachings related to Dosu. In this paper, the concept of Dosu is analyzed in detail and the achievement of an in-depth understanding of the concept of Dosu is attempted. The term Dosu is often used in traditional literature. In the classics, Dosu was used to mean institutions, standards, rules, law, figures, and the laws of heavenly bodies. In other words, Dosu is used to mean the laws of astronomy and the norms of human society. This meaning is expanded and used as the principle of the universe and nature. This concept of Dosu is related to the mathematical cosmological understanding of numbers as the principle of the universe. This type of mathematical cosmology was systematized by Shao Yong (邵雍). In the Joseon Dynasty, Seo Gyungduk (徐敬德) accepted it positively, and it thereby became an influential trend in Korean thought. In the world view of Daesoon thought, there exists the view that numbers as a principle of the universe, and of course this world view is connected to mathematical cosmology. In Daesoon thought, the concept of Dosu is based on the concept of traditional Dosu and adds an additional meaning which connects it to the Reordering of the Universe (Cheonjigongsa). Also, Dosu is used to mean the process of changing the principles and laws of cosmos through Jeungsan's Reordering of the Universe. It is especially the case that discourse about Dosu is widely used when describing the Reordering of the Universe. Jeungsan corrected, reorganized, and adjusted Dosu, as well as establishing new Dosu. Jeongsan, who succeeded Jeungsan, followed the Reordering of the Universe by Jeungsan, and also realized Dosu. In other words, Jeongsan acted and practiced according to the Dosu that had been enacted by Jeungsan. Also, Dosu means the process of the transformation of principle according to the Reordering of the Universe, and Wudang used the concept of Dosu to describe the historical process of Daesoon Jinrihoe. This means that the foundation of Mugeukdo, the change to Taegukdo, the establishment of Daesoon Jinrihoe, and the contruction of Yeoju headquarters are episodes in a divine history carried out through Dosu. Through this discourse, Daesoon Jinrihoe asserts a legitimacy that distinguishes itself from other sects, and believers can be inspired by the sacred meaning that they are participating in the Dosu of heaven and earth. This empowers their devotion and sincerity.

Discourse on Awaiting an Immortal in Honam Daoism and the Birth of Kang Jeungsan (호남 도교의 진인대망론(眞人待望論)과 강증산의 탄강(誕降))

  • Jung Jae-seo
    • Journal of the Daesoon Academy of Sciences
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    • v.41
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    • pp.1-25
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    • 2022
  • This paper examines whether the dynamic and practical nature of Daoism has a significant relationship with the messianic figure Kang Jeungsan (姜甑山) via Honam (湖南) Daoism's Jinindaemangron (眞人待望論, discourse on awaiting an immortal). To this end, the historical implementation of Daoism's social transformation of consciousness in China and Korea is explored, and then the circumstances of Honam Daoism, in particular, are considered. Following that, analysis turns to the 'Jinindaemangron' in the late Joseon Dynasty that developed in Honam. As a result of the discussion, Daoism's social transformation of consciousness was expressed in China through the anti-establishment activities of the early Daoist groups such as Wudoumidao (五斗米道) and Taipingdao (太平道), movements that sought to build utopias. Throughout this process, the term, zhenren (眞人, 'jinin' in Korean), that originally meant 'master,' was transformed into the idea of a future savior. In the case of Korea, the dynamic and practical nature of Daoism can be found in the preface of Nanrang tombstone (鸞郎碑序) written by Choi Chi-won (崔致遠) which was later inherited by the Danhak sect (丹學派) practitioners who struggled against Buddhist monastics. Additionally, examined is the Docham theory of geomancy (圖讖說) that rose after Goryeo, the prophecy of 'Mokjadeuksul (木子得國說 a Lee clansman shall attain the kingdom)' that appeared thereafter, and the Prophecies of Jeong Gam (鄭鑑錄)'s 'Jinindaemangron' in the Joseon Dynasty. Next, the circumstances of Honam Daoism can be considered with regards ti Choi Chi-won and Doseon (道詵) in ancient times, and it can be confirmed that Nam Gung-du (南宮斗) and Kwon Geuk-jung (權克中) were entangled behind Kang Jeungsan. The close relationship among the Daoist Jeong family of Onyang (溫陽鄭氏), the Koh family of Jangheung (長興 高氏), and Kwon Geuk-jung was also confirmed in this study. Finally, in dealing with the 'Jinindaemangron' of Honam in the late Joseon Dynasty and the birth of Kang Jeungsan, Honam Daoism's intense consciousness of social transformation receives first focus, and this is expressed through Prophecies of Jeong Gam, and the religious ideologies of Donghak (東學) and Namhak (南學). These expressions are analyzed through Song of Gungeul (弓乙歌), composed by Jeongryeom (鄭磏), and through Daesoon Jinrihoe's The Canonical Scripture (典經). As a result, it can be confirmed that the messianic significance of the Kang Jeungsan's advent lay on the basis of the people's desire for an ideal future, which is a notion that had been ripening for several centuries.

Chemical and Physical Influence Factors on Performance of Bentonite Grouts for Backfilling Ground Heat Exchanger (지중 열교환기용 멘토나이트 뒤채움재의 화학적, 물리적 영향 요소에 관한 연구)

  • Lee, Chul-Ho;Wi, Ji-Hae;Park, Moon-Seo;Choi, Hang-Seok;Shon, Byong-Hu
    • Journal of the Korean Geotechnical Society
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    • v.26 no.12
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    • pp.19-30
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    • 2010
  • Bentonite-based grout has been widely used to seal a borehole constructed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because of its high swelling potential and low hydraulic conductivity. Three types of bentonites were compared one another in terms of viscosity and thermal conductivity in this paper. The viscosity and thermal conductivity of the grouts with bentonite contents of 5%, 10%, 15%, 20% and 25% by weight were examined to take into account a variable water content of bentonite grout depending on field conditions. To evaluate the effect of salinity (i.e., concentration of NaCl : 0.1M, 0.25M, and 0.5M) on swelling potential of the bentonite-based grouts, a series of volume reduction tests were performed. In addition, if the viscosity of bentonite-water mixture is relatively low, particle segregation can occur. To examine the segregation phenomenon, the degree of segregation has been evaluated for the bentonite grouts especially in case of relatively low viscosity. From the experimental results, it is found that (1) the viscosity of the bentonite mixture increased with time and/or with increasing the mixing ratio. However, the thermal conductivity of the bentonite mixture did not increase with time but increased with increasing the mixing ratio; (2) If bentonite grout has a relatively high swelling index, the volume reduction ratio in the saline condition will be low; (3) The additive, such as a silica sand, can settle down on the bottom of the borehole if the bentonite has a very low viscosity. Consequently, the thermal conductivity of the upper portion of the ground heat exchanger will be much smaller than that of the lower portion.

Development of disaster severity classification model using machine learning technique (머신러닝 기법을 이용한 재해강도 분류모형 개발)

  • Lee, Seungmin;Baek, Seonuk;Lee, Junhak;Kim, Kyungtak;Kim, Soojun;Kim, Hung Soo
    • Journal of Korea Water Resources Association
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    • v.56 no.4
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    • pp.261-272
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    • 2023
  • In recent years, natural disasters such as heavy rainfall and typhoons have occurred more frequently, and their severity has increased due to climate change. The Korea Meteorological Administration (KMA) currently uses the same criteria for all regions in Korea for watch and warning based on the maximum cumulative rainfall with durations of 3-hour and 12-hour to reduce damage. However, KMA's criteria do not consider the regional characteristics of damages caused by heavy rainfall and typhoon events. In this regard, it is necessary to develop new criteria considering regional characteristics of damage and cumulative rainfalls in durations, establishing four stages: blue, yellow, orange, and red. A classification model, called DSCM (Disaster Severity Classification Model), for the four-stage disaster severity was developed using four machine learning models (Decision Tree, Support Vector Machine, Random Forest, and XGBoost). This study applied DSCM to local governments of Seoul, Incheon, and Gyeonggi Province province. To develop DSCM, we used data on rainfall, cumulative rainfall, maximum rainfalls for durations of 3-hour and 12-hour, and antecedent rainfall as independent variables, and a 4-class damage scale for heavy rain damage and typhoon damage for each local government as dependent variables. As a result, the Decision Tree model had the highest accuracy with an F1-Score of 0.56. We believe that this developed DSCM can help identify disaster risk at each stage and contribute to reducing damage through efficient disaster management for local governments based on specific events.

Vegetation classification based on remote sensing data for river management (하천 관리를 위한 원격탐사 자료 기반 식생 분류 기법)

  • Lee, Chanjoo;Rogers, Christine;Geerling, Gertjan;Pennin, Ellis
    • Proceedings of the Korea Water Resources Association Conference
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    • 2021.06a
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    • pp.6-7
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    • 2021
  • Vegetation development in rivers is one of the important issues not only in academic fields such as geomorphology, ecology, hydraulics, etc., but also in river management practices. The problem of river vegetation is directly connected to the harmony of conflicting values of flood management and ecosystem conservation. In Korea, since the 2000s, the issue of river vegetation and land formation has been continuously raised under various conditions, such as the regulating rivers downstream of the dams, the small eutrophicated tributary rivers, and the floodplain sites for the four major river projects. In this background, this study proposes a method for classifying the distribution of vegetation in rivers based on remote sensing data, and presents the results of applying this to the Naeseong Stream. The Naeseong Stream is a representative example of the river landscape that has changed due to vegetation development from 2014 to the latest. The remote sensing data used in the study are images of Sentinel 1 and 2 satellites, which is operated by the European Aerospace Administration (ESA), and provided by Google Earth Engine. For the ground truth, manually classified dataset on the surface of the Naeseong Stream in 2016 were used, where the area is divided into eight types including water, sand and herbaceous and woody vegetation. The classification method used a random forest classification technique, one of the machine learning algorithms. 1,000 samples were extracted from 10 pre-selected polygon regions, each half of them were used as training and verification data. The accuracy based on the verification data was found to be 82~85%. The model established through training was also applied to images from 2016 to 2020, and the process of changes in vegetation zones according to the year was presented. The technical limitations and improvement measures of this paper were considered. By providing quantitative information of the vegetation distribution, this technique is expected to be useful in practical management of vegetation such as thinning and rejuvenation of river vegetation as well as technical fields such as flood level calculation and flow-vegetation coupled modeling in rivers.

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Simulation and Feasibility Analysis of Aging Urban Park Refurbishment Project through the Application of Japan's Park-PFI System (일본 공모설치관리제도(Park-PFI)의 적용을 통한 노후 도시공원 정비사업 시뮬레이션 및 타당성 분석)

  • Kim, Yong-Gook;Kim, Young-Hyeon;Kim, Min-Seo
    • Journal of the Korean Institute of Landscape Architecture
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    • v.51 no.5
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    • pp.13-29
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    • 2023
  • Urban parks are social infrastructure supporting citizens' health, quality of life, and community formation. As the proportion of urban parks that have been established for more than 20 years is increasing, the need for refurbishment to improve the physical space environment and enhance the functions of aging urban parks is increasing. Since the government's refurbishment of aging urban parks has limitations in securing financial resources and promoting attractiveness, they must be promoted through public-private partnerships. Japan, which suffered from the problem of aging urban parks, has successfully promoted several park refurbishment projects by introducing the Park-PFI through the revision of the 「Urban Park Act」 in 2017. This study examines and analyzes the characteristics of the Japan Park-PFI as an alternative to improving the quality of aging domestic urban park services through public-private partnerships and the validity of the aging urban park refurbishment projects through Park-PFI. The main findings are as follows. First, it is necessary to start discussions on introducing Japan's Park-PFI according to the domestic conditions as a means of public-private partnership to improve the service quality and diversify the functions of aging urban parks. In order to introduce Park-PFI social discussions and follow-up studies on the deterioration of urban parks. Must be conducted. The installation of private capital and profit facilities and improvements of related regulations, such as the 「Parks and Green Spaces Act」 and the 「Public Property Act」, is required. Second, it is judged that the Park-PFI project is a policy alternative that can enhance the benefits to citizens, local governments, and private operators under the premise that the need to refurbish aging urban parks is high and the location is suitable for promoting the project. As a result of a pilot application of the Park-PFI project to Seyeong Park, an aging urban park located in Bupyeong-gu, Incheon, it was analyzed to be profitable in terms of the profitability index (PI), net present value (FNPV), and internal rate of return (FIRR). It is considered possible to participate in the business sector. At the local government level, private capital is used to improve the physical space environment of aging urban parks, as well as the refurbishment of the urban parks by utilizing financial resources generated by returning a portion of the facility usage fees and profits (0.5% of annual sales) of private operators. It was found that management budgets could be secured.

GOCI-II Based Low Sea Surface Salinity and Hourly Variation by Typhoon Hinnamnor (GOCI-II 기반 저염분수 산출과 태풍 힌남노에 의한 시간별 염분 변화)

  • So-Hyun Kim;Dae-Won Kim;Young-Heon Jo
    • Korean Journal of Remote Sensing
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    • v.39 no.6_2
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    • pp.1605-1613
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    • 2023
  • The physical properties of the ocean interior are determined by temperature and salinity. To observe them, we rely on satellite observations for broad regions of oceans. However, the satellite for salinity measurement, Soil Moisture Active Passive (SMAP), has low temporal and spatial resolutions; thus, more is needed to resolve the fast-changing coastal environment. To overcome these limitations, the algorithm to use the Geostationary Ocean Color Imager-II (GOCI-II) of the Geo-Kompsat-2B (GK-2B) was developed as the inputs for a Multi-layer Perceptron Neural Network (MPNN). The result shows that coefficient of determination (R2), root mean square error (RMSE), and relative root mean square error (RRMSE) between GOCI-II based sea surface salinity (SSS) (GOCI-II SSS) and SMAP was 0.94, 0.58 psu, and 1.87%, respectively. Furthermore, the spatial variation of GOCI-II SSS was also very uniform, with over 0.8 of R2 and less than 1 psu of RMSE. In addition, GOCI-II SSS was also compared with SSS of Ieodo Ocean Research Station (I-ORS), suggesting that the result was slightly low, which was further analyzed for the following reasons. We further illustrated the valuable information of high spatial and temporal variation of GOCI-II SSS to analyze SSS variation by the 11th typhoon, Hinnamnor, in 2022. We used the mean and standard deviation (STD) of one day of GOCI-II SSS, revealing the high spatial and temporal changes. Thus, this study will shed light on the research for monitoring the highly changing marine environment.