• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.95-102
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• 2020

For the purpose of developing a PE fiber-reinforced highly ductile cementitious composite having high tensile strain capacity more than 2% under the condition of containing aggregates with large particle size, this study investigated the tensile behavior of composites according to the particle size and distribution of aggregates in the composite. Compared with the mixture containing silica sand of which particle size is less than 0.6 mm, mixtures containing river sand and/or gravel with the maximum particle size of 2.36 mm, 4.75 mm, 5.6 mm, 6.7 mm were considered in the experimental design. The particle size distributions of aggregates were adjusted for the optimized distribution curves obtained from modified A&A model by blending different sizes of aggregates. All the mixtures presented clear strain-hardening behavior in the direct tensile tests. The mixtures with the blended aggregates to meet the optimum curves of aggregate size distributions showed higher tensile strain capacity than the mixture with silica sand. It was also found that the tensile strain capacity was improved as the maximum size of aggregate increased which resulted in wider particle size distribution. The mixtures with the maximum size of 5.6 mm and 6.7 mm presented very high tensile strain capacities of 4.83% and 5.89%, respectively. This study demonstrated that it was possible to use coarse aggregates in manufacturing highly ductile fiber-reinforced cementitous composite by adjusting the particle size distribution.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.227-234
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• 2022

In this study, the rheological properties of cement paste composites applied with carbon-based nano-materials were experimental analyzed. Flow table and rheological properties, compressive strength were measured in the cement paste using graphene oxide asqueous solution and carbon nanotube aqueous solution. When carbon nano-materials was mixed in an aqueous solution, flow decreased and plastic viscosity and shear stress were increased. In particular, graphene oxide rapidly increased the plastic viscosity and shear stress. In the case of carbon nanotube aqueous solution, when less than 0.2 % was mixed, the increase rate was low compared to graphene oxide. This is because the specific surface area of graphene, which is in the form of a plate, is large. The compressive strength showed a small amount in strength increase when graphene mix, and CNT had a strength about 112 % of OPC. Carbon-based nanomaterials, is considered that CNT are suitable more to be used construction materials. However, extra studies on the surfactant to be used for mixing proportion and dispersion will be needed.

• Journal of the Korean Wood Science and Technology
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• v.30 no.1
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• pp.25-33
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• 2002

Improvement of density profile and sound absorption capability of particleboard was attempted. Three types of hot pressing methods examined ; flat-platen pressing method (A-type pressing), hot pressing in forming box (B-type pressing), and hot pressing set up jagged caul in forming box (C-type pressing). The raw materials were larch(Larix leptolepis (S, et. Z.) Gorden) shavings, phenol formaldehyde resin, and the particleboard perforated with stair type. The physical and mechanical properties such as specific gravity, bending strength (MOR), internal bonding strength (IB) and sound absorption coefficients were examined. The results are summarized as follows : 1) The MOR and internal bonding strength of the board pressed in forming box were higher than those of flat-platen pressed board. 2) The minimum density to average density ratio in thickness direction which pressed in forming box showed about 923%, in the case of 35 mm commercial particleboard and 50 mm flat-platen pressed board, its values showed about 66.4% and 865% respectively. 3) Sound absorption coefficients of the particleboard perforated with stair type were higher than those of flat-plated pressed board and commercial particleboard.

• Journal of Korea Water Resources Association
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• v.56 no.4
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• pp.245-259
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• 2023

The agricultural reservoir is a critical water supply system in South Korea, providing approximately 60% of the agricultural water demand. However, the reservoir faces several issues that jeopardize its efficient operation and management. To address this issues, we propose a novel deep-learning-based water level recognition model that uses CCTV image data to accurately estimate water levels in agricultural reservoirs. The model consists of three main parts: (1) dataset construction, (2) image segmentation using the U-Net algorithm, and (3) CCTV-based water level recognition using either CNN or ResNet. The model has been applied to two reservoirs G-reservoir and M-reservoir with observed CCTV image and water level time series data. The results show that the performance of the image segmentation model is superior, while the performance of the water level recognition model varies from 50 to 80% depending on water level classification criteria (i.e., classification guideline) and complexity of image data (i.e., variability of the image pixels). The performance of the model can be improved if more numbers of data can be collected.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.3
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• pp.185-192
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• 2023

In this study, fluctuating wind velocity for time history analysis is simulated by a single variate, single-dimensional random process using the KBC2022 spectrum about across-wind direction. This study analyzed and obtained the inelastic dynamic response for structures modeled as a single-degree-of-freedom system. It is assumed that the wind response is excellent in the primary mode, the change in vibration owing to plasticization is minor, along-wind vibration and across-wind vibration are independent, and the effect of torsional vibration is small. The numerical results, obtained by the Newmark-𝛽 method, shows the time-history responses and trends of maximum displacements. As a result of analyzing the inelastic dynamic response of the structure with the second stiffness ratio(𝛼) and yield displacement ratio (𝛽) as variables, it is identified that as the yield displacement ratio (𝛽) increases when the second stiffness ratio is constant, the maximum displacement ratio decreases, then reaches a minimum value, and then increases. When the stiffness ratio is greater than 0.5, there is a yield point ratio at which the maximum displacement ratio is less than 1, indicating that the maximum deformation is reduced compared to the elastically designed building even if the inelastic behavior is permitted in the inelastic wind design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.839-848
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• 2006

Korea has become the 5th country to own and operate the high speed railroad in 2004. However, there were many difficulties until Koreans enjoy the first bullet train service with the average hourly speed of 300km. The high speed railroad requires elevated quality standards differently from the traditional railways. In addition to the technical difficulties, the construction project itself was an unpleasant case with huge delays and cost overruns mainly due to the lack of experiences, deficiency of owner$^{\circ}{\O}$s role, and increase of public resistances triggered by environmental concerns. This paper analyzes the reasons for delays on this mega-project. With respect to the characteristics of the whole project level, it is very complicated/linear project, whose total length is around 412 km with the composition of various sections in the route of the railway which have basically different conditions. For that reason, the analysis is performed in both macro and micro level. First, macroscopic analysis is performed to find critical subdivisions in the railway route that induces the significant delay in the opening due date. Then, microscopic analysis is followed to quantify the causes and effects of delays focused on these critical subdivisions in more detailed way. Finally, this paper provides lessons learned from this project to avoid the decisive delays in performing the similar large-scaled projects.

• Journal of agricultural medicine and community health
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• v.25 no.2
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• pp.427-440
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• 2000

A comparative study was made about health resources, medical care service statistics and public health service statistics by health subcenters at Jangdong and Jangpyung townships, Jangheung County, Chollanamdo before and after the unification of two health subcenter to improve their function. 1. While two general physicians, one dentist, 4 nurse aids arid one oral hygienist were working at two health subcenters with simple facility with examination room and public health office in 1997 prior to the unification, in 1999 after the unification of two health subcenters 14 staff including a specialist physician, a general physician, a dentist, a herb hygienist, a radiology technician and a physical therapist were working in the new health subcenters equipped with appropriate facilities in two storey building. 2. In 1997 before the unification the yearly total income of two health subcenters was 78,815 thousand won(about 14,000 won per capita) and the amount was 140,376 thousand won(about 25,000 won per capita) in 1999 after the unification. And the income was used for operation of health subcenters excluding personnel expense. 3. While 90.5% of visitors to the health subcenters came for general medical care, and 91.6% came for the revisit before the unification, after the unification 71.2% came for general medical care, 10.8% for dental care, 16.5% for oriental physician's care, 29.7% for the first visit and 70.3% for revisit. Most common problem cared for was musculoskeletal disorder like arthralgia. Average treatment cost per person per month was 9,363 won before the unification and 8,309 won after the unification. 4. Through the comparison of execution rate of public health services before and after the unification. the practice rate of most health service among target population including visiting service for chronic illness, maternal and child health service and immunization service increased after the unification. The practice rate of tuberculosis control service, hypertension control and diabetes management was a little decreased. In conclusion, continuous effort to satisfy all persons in two townships and evaluation are necessary to coincide with the spirit of unification of two health subcenters.

• Journal of Korean Society of Archives and Records Management
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• v.3 no.1
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• pp.159-184
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• 2003

In this research the issues of record management of national archives in Korea are classified into four categories: 1) improving the status of the Central Archives of Korea, 2) constructing a new national archives, 3) revising the law on the record management, 4) creating qualifications for a professional administrator for Archivist. 1) In order to strengthen the function of the Central Archives of Korea, it is very urgent to create a systematic mechanism in which the Central Archives oversees and administers public archives(documents) collected from all the public institutions not only under the Administration but also the legislature and the judicial authorities. 2) This paper suggests that a new National Archives should be a symbolic building representing Korea as archives. Considering the fact that Presidents archives will be a part of this new National Archives, it also suggests that artistic and decorative pieces which embody Korea's representative archives or people should be included in the building. The budget for these should be supplied by the government. 3) This paper looks at the matter of revising the law on Record Management in two respects: (1)strengthening the function of the Central Archives of Korea, (2)making it obligatory to produce archives not open to the public, or making a protection clause for secret archives. This paper proposes that the Central Archives of Korea will be able to collect all the public archives from all the public institutions, and to oversee and administer them by revising the 5th and 6th clauses of the current law on the record management. It also proposes that some laws which make it obligatory to produce archives for documents not open to the public, and which protect those secrecy. 4) Regarding the qualifications for a professional administrator for the record management, this paper suggests lowering the qualification a little to the bachelor's degree of the record management. Also it suggests taking into consideration the persons in charge of the record management in public institutions and acknowledging their qualifications after a certain period of training at the Central Archives of Korea or something like that. In addition, it classifies the ranks of the professional administrators according to their qualifications.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.38 no.2
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• pp.60-76
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• 2020

The purpose of this study was to examine the spatial and visual arrangement characteristics of Imsil Yi Ung-jae's old house's spatial and visual aspects in order to discover the value of landscape and traditional house garden. The results of this study are as follows. Dongchon-village in Dundeok-ri, where old house is located, is a typical form of with "Back to the mountain and facing the water(背山臨水)", and is located in the north of the three streams of water, forming a Jeonchaghugwan(前窄後寬). Dongchon Village, which has a traditional scenic spot between Danguidae(丹丘臺) and Samgyeseokmun(三溪石門), is understood to be the main street of Nojeokbong Peak and Gyegwanbong Peak, which is Ansan(案山), where the "A centipede flying in the sky(飛天蜈蚣形)". Yi Ung-jae's old house is the oldest existing high-priced house in the North Jeolla region and the closing price of a royal family of the Joseon Dynasty, which was arranged by Chunseongjeong(春城正), Yi Dam-son(李聃孫) in the mid-16C. The Japanese Invasion of Korea in 1592 and Japanese colonial era, the loyalty of the gate quarters, the filial piety of the gate quarters, and the faithfulness of the tablet(扁額) and Juryeons(柱聯) are enough to contribute to the rise of the value of a physical house. The men's quarters(Sarangchae), which are placed on a high-pocket or a layout without going against the sloping terrain, have the effect of making the distance as far as possible, enhancing its dignity and hierarchy as a royal building. In addition, the entrance to the main quarters(Anchae) through the four pillar gates(四柱門), the extensive support and the appropriation of the Chaewon(vegetable garden), and the official base for the Anchae are very unique compared to the general nobility. However, in the context of the postwar relationship, the shrine seeks to realize Confucian ideals while harmonizing with nature by arranging wide sponsorships around it. On the other hand, it is confirmed that there was a pond in the form of a circle in a square(方池圓島型) with a relatively large area, which is now disturbed and damaged. Written by the high priced planting species are sponsored pine trees, hackberry, persimmon trees, Japanese apricot flower, Ohmomiji, and plum tree in the side garden, as well as cotyledon trees in the outside garden. However, although flower bed(花階), which is built on the stone axis, is a place that clearly shows the expensive garden, it seems to have lost the texture of the plant due to the extremely high variety of species and the splendor that does not match the plant landscape of the flower world. Yi Ung-jae's old house is highly valuable as it is a portrait house of a prince of the blood in the mid-Joseon Dynasty. Based on these findings, this study proposed a plan to improve the management of high prices that could be met.

• Korean Journal of Heritage: History & Science
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• v.51 no.3
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• pp.88-103
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• 2018

The purpose of this study was to excavate the items of the comprehensive maintenance plan for scenic sites considering sustainability and analyze the needs of them. In this sense, based on 35 reports of the comprehensive maintenance plan established between 2006, when scenic sites started to be designated, and 2017, the items used in 'investigation field' and 'planning field' were examined, and then a survey regarding the needs of the items was conducted using a "5-point Likert Scale", targeting officials at 60 local governments in the whole country. Of 60 local governments, opinions from 48 officials at 45 local governments were analyzed. In order to verify the consistency of their opinions, "Reliability Analysis" was conducted, and Cronbach's alpha coefficient was 0.968 and 0.970 for 'investigation field' and 'planning field', respectively, showing high reliability. As a result of the survey, most opinions generally expressed the needs of 6 items of 'investigation field' of the comprehensive maintenance plan. Especially, the needs to investigate 'historical environment', 'natural environment', 'humanistic environment', and 'landscape' turned out to be high. In addition, as for 'general environment' and 'users', the needs of specific items such as 'distribution of main cultural properties and historic sites' (4.04) and 'acceptance of opinions from local residents and interested parties' (4.15) were found to be high. Besides, the items of 'planning field' also turned out to be needed in general (4.0). Particularly, the needs of 'enhancement of designated value and status' (4.26) and 'the comprehensive maintenance plan for designated areas of cultural properties and historic and cultural environment preservation areas' (4.25) in 'historical environment', 'maintenance of historic buildings at scenic sites' (4.28) in 'humanistic environment', and 'landscape trail planning' (4.28) in 'landscape' were found to be high. In conclusion, the practical items related to investigation and planning of the comprehensive maintenance plan for scenic sites are expected to contribute to effective conservation and management of scenic sites in the future.