• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.203-213
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• 2024

This study delves into the mechanical properties of fiber-reinforced cement composites(FRCC) concerning the dispersion method of multi-walled carbon nanotubes(MWCNTs). MWCNTs find utility in industrial applications, particularly in magnetic sensing and crack detection, owing to their diverse properties including heat resistance and chemical stability. However, current research endeavors are increasingly directed towards leveraging the electrical properties of MWCNTs for self-sensing and smart sensor development. Notably, achieving uniform dispersion of MWCNTs poses a challenge due to variations in researchers' skills and equipment, with excessive dispersion potentially leading to deterioration in mechanical performance. To address these challenges, this study employs ultrasonic dispersion for a defined duration along with PCE surfactant, known for its efficacy in dispersion. Test specimens of FRCC are prepared and subjected to strength, drawing, and direct tensile tests to evaluate their mechanical properties. Additionally, the influence of MWCNT dispersion efficiency on the enhancement of FRCC mechanical performance is scrutinized across different dispersion methods.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.3
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• pp.33-45
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• 2024

The government is promoting the reorganization of the construction indusrty under the theme of reorganizing the production system. However, it has been pointed out that this is contrary to the increasingly specialized and technical skills of the landscaping field. Therefore, it is urgent to respond to the construction industry integration policy and improve an appropriate work system and the content of the landscape field. Therefore, this study investigated the intention of the industry to reorganize the production system and the production structure of the landscape field, so that it can be used as a reference for future changes. As a result of the survey, 1) the perception of the reorganization policy is a highly requesting step-by-step promotion that reflects the industry's will, 2) the system is divided into generalization and specialization and is highly opposed to integration, 3) appropriate design and construction costs are the most important directions for improving landscape construction projects, and 4) reestablishing the relationship with related civil engineering works is important for improving detailed construction types. Overall, it was pointed out that the current specialized landscape construction does not sufficiently reflect the changing landscape business and is only appropriate for subcontractors in other industries. Therefore, it is necessary to promote policies that reflect this. In the long run, it is urgent to establish the status of landscape construction as an independent object, and it is necessary to supplement the legal system and change the industry accordingly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.427-432
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• 2024

The polymer crystallization process, promoting the formation of ferroelectric β-phase, is essential for developing polyvinylidene fluoride (PVDF)-based high-performance piezoelectric energy harvesters. However, traditional high-temperature annealing is unsuitable for the manufacture of flexible piezoelectric devices due to the thermal damage to plastic components that occurs during the long processing times. In this study, we investigated the feasibility of introducing a flash lamp annealing that can rapidly induce the β-phase in the PVDF layer while avoiding device damage through selective heating. The flash light-irradiated PVDF films achieved a maximum β-phase content of 76.52% under an applied voltage of 300 V and an on-time of 1.5 ms, a higher fraction than that obtained through thermal annealing. The PVDF-based piezoelectric energy harvester with the optimized irradiation condition generates a stable output voltage of 0.23 V and a current of 102 nA under repeated bendings. These results demonstrate that flash lamp annealing can be an effective process for realizing the mass production of PVDF-based flexible electronics.

• Korean Journal of Environment and Ecology
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• v.38 no.3
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• pp.310-323
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• 2024

The purpose of this study was to understand the vegetation structure and ecological characteristic of Bulgapsan(Mt.) Provincial Park by setting up and surveying 64 plots(100m²). The analysis using the TWINSPAN and DCA techniques found seven community groups: Pinus densiflora-Quercus variabilis community, P. densiflora-P. rigida-Q. serrata community, Q. variabilis-Carpinus tschonoskii community, Q. aliena-Q. variabilis-Cornus controversa community, Q. aliena-Platycarya strobilacea community, Broad-leaved miced community and Q. variabilis community. The result of vegetation community structure analysis showed that P. densiflora community and deciduous Quercus spp. community were in competition, and succession to Quercus spp. community was expected. In the case of other broad-leaved forests, the current status is expected to be maintained. But continuous monitoring is required in areas where Neolitsea sericea and Cephalotaxus appear, which grow naturally in warm temperate forest and southern temperate vegetation zone. Species diversity by communities are confirmed to be highest at 2.6654 in the actively competitive P. densiflora-P. rigida-Q. serrata community, and the lowest in the Deciduous broad-leaved forests community at 1.2548. The results of the tree rings and annual growth analysis showed that dominant trees had an average age of more than 37~87 years. Among them, N. sericea designated as a natural monument was 48~56 years old.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.4
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• pp.56-68
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• 2024

This study aimed to derive the concept and types of school outdoor spaces in Seoul. The research results showed that the concept of school outdoor space can be viewed as an outdoor activity space in schools that secures the value of integrated public life and communal life, including "behavioral rights, walking rights, living rights, urban rights, landscape rights (viewing rights), and nature experience rights." It can also be defined as a basic educational space that reflects the value of education, which is the basic function of schools and the characteristics of the community. As a result of the analysis based on the general types of outdoor spaces, it was found that the outdoor spaces of Seoul schools can be divided into three major categories: walking space (movement function), educational space (educational activities), and rest and other spaces (other services). Based on this, outdoor spaces were categorized and subcategorized to serve as the basis for policy implementation. These classifications are characterized by 1) simplifying the classification of spaces by function into three (movement functions, educational activities, and other services) to enable the use of outdoor spaces for integrated purposes; 2) reflecting the complex use of spaces by subdividing educational spaces focusing on major activities, and in particular, discovering complex spaces due to the three-dimensionalization of buildings; and 3) enabling spatial-level planning and facility element-level access according to school characteristics. It is characterized by applying the recent trends and systems of general outdoor space projects to the current situation of schools.

• Journal of dental hygiene science
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• v.12 no.1
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• pp.63-70
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• 2012

The purpose of this study was to research sociodemographic characteristic, work-concerned characteristic, health behavior, life stress, psychosocial stress, job stress and self-esteem of dental hygienists and to find their effects on cortisol level in saliva. The target of this study is 219 dental hygienists registered in Daegu and Gyeongbuk Dental Hygienists Association as of February 2010. For life stress, there was significant difference depending on working years of current job(p<0.05), self health status and regular meal(p<0.01). For psychosocial stress, there was significant difference depending on age(p<0.05), daily working hours(p<0.01), self health status, sleeping hours, regular meal and hobby and leisure activity(p<0.01). For job stress, there was significant difference depending on academic background (p<0.05), job experience, position, man power appropriateness in department and working years of current job(p<0.05). For cortisol level in saliva, extra working days(p<0.05) and self health status(p<0.05) showed significant difference and job stress and cortisol level in saliva showed the negative correlation(p<0.01). Health behavior gave a significant effect to life stress by path coefficient -36.807(p<0.05) and that to psychosocial stress by path coefficient -5.209(p<0.001). And health behavior also gave a significant effect to self-esteem by path coefficient 0.561(p<0.05). Life stress gave a significant effect to psychosocial stress by 0.012(p<0.05) with self-esteem to psychosocial stress by -2.437(p<0.001) and psychosocial stress to job stress by 0.523(p<0.001). Job stress gave a significant effect to cortisol level in saliva by -0.060 (p<0.05). It was found that the most significant factor that affects cortisol level in saliva was job stress, but showed negative correlation. It can be assumed that chromic job stress cause shortage in cortisol excretion, and caused lower cortisol level in saliva.

• Journal of Korea Water Resources Association
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• v.50 no.7
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• pp.455-465
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• 2017

Understanding of the two-dimensional velocity field is crucial in terms of analyzing various hydrodynamic and fluvial processes in the riverine environments. Until recently, many numerical models have played major roles of providing such velocity field instead of in-situ flow measurements, because there were limitations in instruments and methodologies suitable for efficiently measuring in the broad range of river reaches. In the last decades, however, the advent of modernized instrumentations started to revolutionize the flow measurements. Among others, acoustic Doppler current profilers (ADCPs) became very promising especially for accurately assessing streamflow discharge, and they are also able to provide the detailed velocity field very efficiently. Thus it became possible to capture the velocity field only with field observations. Since most of ADCPs measurements have been mostly conducted in the cross-sectional lines despite their capabilities, it is still required to apply appropriate interpolation methods to obtain dense velocity field as likely as results from numerical simulations. However, anisotropic nature of the meandering river channel could have brought in the difficulties for applying simple spatial interpolation methods for handling dynamic flow velocity vector, since the flow direction continuously changes over the curvature of the channel shape. Without considering anisotropic characteristics in terms of the meandering, therefore, conventional interpolation methods such as IDW and Kriging possibly lead to erroneous results, when they dealt with velocity vectors in the meandering channel. Based on the consecutive ADCP cross-sectional measurements in the meandering river channel. For this purpose, the geographic coordinate with the measured ADCP velocity was converted from the conventional Cartesian coordinate (x, y) to a curvilinear coordinate (s, n). The results from application of A-VIM showed significant improvement in accuracy as much as 41.5% in RMSE.

• Proceedings of the Korean DIstribution Association Conference
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• 2001.11b
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• pp.125-141
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• 2001

In this paper, the current problems of logistics industry in Korea and their possible solutions were discussed. With Korea Telecoms KT-Logis, the supplier and demander of logistics service would not have to invest large sum of money into their computer system. All they need is just a computer with internet connected. What KT-Logis influence on the logistics industry are the following; 1. Many logistics service supplier and demander can do the business on the web with one computer system. 2. This web based computer system does not only work on the office but also apply on the field worker such as delivery personnel or even the forwarder with mobile phone. 3. KT-Logis is an integrated system which cover the broad arrange of logistics management from truck management to customer relations management. 4. Finally, KT-Logis is web based systems which suits for current e-business and mobile environment. In future, more studies should be done to develop more progressive integrated logistics information systems with enterprise resource planning(ERP) and supply chain management(SCM).

• 대한공업교육학회지
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• v.38 no.1
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• pp.125-143
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• 2013

The purpose of this study was to investigate the current Status and practical use of technology laboratory at the junior high school in Chungbuk Province in order to give some suggestions on hands-on activities for technology education. First, concerning present actual conditions of technology laboratory, There was a large disparity between the urban and rural schools in the possession of a technology laboratory, as the rate of the schools equipped with the rooms respectively stood at 69.84 percent and 33.38 percent in the urban and rural regions. By the type of foundation, every national school, 86.24 percent of the public schools and 37.50 percent of the private schools were equipped with the technology laboratory. By school size, 35.59 of the schools with fewer than 10 classes, 62.11 percent of the schools with 10 to fewer than 30 classes and 85.71 percent of the schools with 31 classes or more were in possession of the laboratory. Thus, the type of foundation and school size made differences to that. As a result of asking the schools without the laboratory about the reason, as many as 88.52 percent had been equipped with the laboratory in the past but converted them into spaces for another purpose. When the schools that had no such laboratory were asked a question whether they had any plans to install a technology laboratory, just five schools(8.19%) had that plan. Second, as for the practical use of the technology laboratory, for what the rooms were actually used was asked, and most of the schools made use of them as Comprehensive General laboratory. As to the size of the rooms, each of the rooms was as large as a classroom($66m^2$) in 62.12 percent of the schools, and their region, type of foundation and student gender made little significant differences to that. Regarding the time for utilizing the laboratory, the majority of the schools used the laboratory approximately once or twice a year, and their region, type of foundation, student gender and school size made few distinctive differences to that. In terms of budget for practice in the rooms, the largest number of the schools that accounted for 36.36 percent earmarked three thousand won to less than five thousand won per student.

• Journal of Animal Science and Technology
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• v.45 no.4
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• pp.585-592
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• 2003

The current study was conducted to determine the relationships of vitamin A on meat quality of Hanwoo as a basic study to manipulate vitamin A contents in feeds to produce high quality beef. Concentrations of vitamin A in serum and liver of Hanwoo steers(n=328) were analyzed and correlation coefficients with carcass properties were evaluated. Mean vitamin A concentration in the serum of Hanwoo steers in the early fattening period was 212.0$\pm$32.7 IU/dl, and that in the late fattening period was 117.56$\pm$43.15 IU/dl. Mean vitamin A concentration in the liver of Hanwoo steers in the late fattening period was 143.62$\pm$110 IU/g expressing large variations might be depended on animals, feeds and farms. There were negative correlations between serum vitamin A concentration and marbling degree(r=-0.24, P<0.01), fat contents in M. Logissimus dorsi (r=-0.21, P<0.01), and beef quality grade(r=-0.20, P<0.01). Vitamin A-palmitate in liver also expressed negative correlations with fat contents in M. Logissimus dorsi (r=-0.18, P<0.01) and beef quality grade(r=-0.16, P<0.05). From the results obtained in the current study, we concluded that it might be possible to produce high quality beef in Hanwoo by manipulating vitamin A contents in the feeds. Further detailed studies, however, are necessary to determine vitamin A contents in feeds, feeding levels, and feeding periods.