• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.32-37
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• 2009

An energy loss through the window system occupies about 10 to 30 percent on energy consumption of the whole building. That is the reason, several elements for a building composition of window system are the weakest from the heat. Insulation performance increases for the reducing heat loss. Heat transfer through the window system that is reducing heat transfer through conduction, convection and radiation. Insulation performance reinforcement methods classify improving heat specific quality of window system and improving efficiency of whole window system. The most application method among each methods is reducing emission ratio of the window system(Low-E glass), increasing a number of glazing(multiple window) and a method of vacuuming between glazing and glazing. Therefore this study is investigated a sort of glazing and specific character, U-value calculation with changing glazing thickness and calculation of temperature distribution and U-value with a glazing charging gas kind from double glazing. For a conclusion, an aspect of U-value figure at the smallest value case of vacuum glazing with Low-E coating. That means insulation efficiency is the best advantage during a building plan selecting vacuum glazing with Low-E coating for a energy saving aspect. In this way, U-value become different the number of glazing, coating whether or not and selecting injection gas. Therefore selecting of glazing is very important after due consideration by a characteristic and use of building and consideration of strong point and weak point.

• 한국병원경영학회지
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• 제25권4호
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• pp.38-47
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• 2020

Purposes: The problem in the recent immigration policy and social policy changes for foreigners is that the preliminary analysis or research on the actual impact of the influx of foreigners has not been done enough in Korea yet.. This study is to examine the impact of the Korean health insurance finances on the influx of foreigners. Approach: This study analyzed the health insurance statistics for foreigners and overseas Koreans of the Health Insurance Corporation from 2013 to 2017. The data is the "Status of Health Insurance Premiums for Nationals, Foreigners, and Overseas Koreans from 2013 to 2017" submitted by the National Health Insurance Service to the Health and Welfare Committee during the 2018 National Audit Period. Findings: To summarize the analysis, first, the proportion of foreigners was only 1% of all subscribers (1.7% at work, 1.9% in regions) until 2017. Second, employees at work have a lower pay-to-pay ratio, and local subscribers have a higher pay-to-pay rate, regardless of nationality. Third, as immigrants are mostly concentrated in younger ages, they are healthy and use of hospitals is relatively low. Fourth, in terms of gender distribution, there are many women of childbearing age due to marriage immigration among foreign local subscribers, and more men use hospitals than workers who have a high proportion of males due to childbirth. In conclusion, the impact of immigration on health insurance finances is not large, and has a positive effect on finances. Practical Implications: If we simply consider the financial aspect, encouraging foreigners to subscribe to health insurance has a positive effect on finances. In particular, the more foreign workers are enrolled, the greater the financial gain. In particular, increasing the employment of foreign women through language education, vocational training, and employment support will help finance health insurance. One of the reasons foreign subscribers have a positive impact on health insurance finance is the low medical utilization rate. It can be said that young and healthy foreigners use fewer hospitals and clinics, but another aspect means that foreigners have difficulty using health insurance for various reasons. Therefore, various supports must be accompanied so that foreign subscribers can use medical services when necessary.

• 자원리싸이클링
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• 제29권2호
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• pp.28-36
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• 2020

폐유리병을 순환 잔골재로 활용하여 재활용률을 향상시키기 위해 다양한 파분쇄 산물의 입도, 입형, 에너지 분석을 통해서 재활용 공정에 적용할 수 있는 최적의 장비 선정을 위한 파분쇄 특성 연구를 수행하였다. 파분쇄시 발생하는 힘의 종류인 충격, 압축, 마모가 특징적으로 나타는 장비인 해머크러셔, 슈레더 및 롤크러셔, 볼밀 총 4가지 장비를 선정하여 실험을 진행하였다. 각 장비의 파분쇄 산물의 입도분석을 수행한 결과 슈레더에서 발생한 산물만이 콘크리트용, 아크팔트용 순환 잔골재의 품질 기준을 만족시키는 것으로 확인되었다. 화상소프트웨어(Image J, National institute of health)를 이용한 입형 분석 결과 대부분 입자의 입형이 1.6 이하의 값을 가지고 있어 순환 잔골재로 재활용하기에 위험성이 적고 편장석 비율 규정 조건 또한 충족하는 것으로 판단되었다. 또한 각 장비에서 소모되는 에너지를 측정해본 결과 에너지 대비 입자의 감소 비율이 슈레더의 산물이 가장 높은 것으로 확인되었다. 따라서 10mm 이하의 일정 입도구간에서 폐유리병 파분쇄시 적용될 수 있는 최적의 장비는 슈레더임을 판단할 수 있었다. 본 연구를 통해서 폐유리병 파분쇄 공정의 에너지 효율 및 제품의 경쟁력 향상에 큰 기여를 할 수 있을 것이라고 사료된다.

• Agricultural and Biosystems Engineering
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• 제4권2호
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• pp.58-65
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• 2003

An understanding of the cooling requirements of horticultural commodities begins with adequate knowledge of their biological responses. All fresh horticultural products are living organisms, carrying on the many biological processes that are essential to the maintenance of life. The pre-cooling is essential technique for the construction of cold chain system, which is necessary to maintain marketing quality of fresh produces during the transportation and distribution. The purpose of this study is to develop the pressure cooling tunnel using conveyer for the reduction of labor and improvement of pre-cooling efficiency. Performance of developed facility was tested for the strawberries, tomatoes and Chinese cabbages. Cooling ratio as a result of pre-cooling efficiency was 1.57, 1.56 and 1.32 for strawberries, tomatoes, and Chinese cabbages respectively. Cooling ratio decreased with increasing the distance of heat conduction from surface to center. The cooling ratio of Chinese cabbages was lower than that of fruit because of its head and leaf. In aspect of cooling uniformity, there was no significant difference of final temperature among inlet, outlet and middle layers of cold air in fresh produces. After pre-cooling treatment, quality changes were measured for the weight loss, Vit. C content, and titratable acidity. The quality of pre-cooling treatment was better than that of non-treatment and was kept on well during long-term storage.

• 한국산학기술학회논문지
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• 제20권4호
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• pp.619-625
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• 2019

저심도 터널에서는 온도차에 의한 부력을 이용한 자연배기시스템이 많이 사용되고 있지만 이는 연기배출을 인위적으로 조절할 수 없다. 그러므로 자연배기시스템에서는 수직환기구에서 연기 배출량이 설계된 연기 배출량보다 적어지는 Plug-holing 현상을 고려한 설계가 필수적이다. Plug-holing 현상은 터널과 수직환기구의 형상 위치, 화원의 위치와 발열량 등에 영향을 받는다. 본 연구에서는 터널과 자연 환기구의 단면적 비와 화원의 열방출률이 자연배기시스템에서 발생하는 Plug-holing 현상에 미치는 영향에 대하여 실험적으로 분석하였다. 1/20 크기로 축소시킨 실험모델에서 터널과 수직환기구의 종횡비는 고정시키고 터널과 수직환기구의 단면적 비를 달리하여 Plug-holing 현상에 미치는 영향을 확인하였다. 화원의 열방출율은 0.55 kW, 0.98 kW, 1.67 kW로 고정시켰다. 실험결과, 연기 경계층온도와 수직환기구 내의 온도와의 비교를 통한 Plug-holing 발생을 판단하였고, 터널과 수직환기구의 단면적 비가 증가함에 따라서 수직환기구 하부의 유동과 온도분포 특성이 변함을 확인하였다. 터널 화재 시 Plug-holing 현상은 터널과 수직환기구의 단면적 비에 영향을 받으며 단면적 비가 클수록 Plug-holing 발생 가능성이 증가하였다.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.537-550
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• 2018

본 스마트시티의 개발초점은 점차 물리적 개발측면에서 공간적 개발측면으로 변화하고 있다. 공간적 개발의 주요적용 기술로는 환경기술(ET), 정보기술(ET), 그리고 환경기술과 정보기술이 융합된 환경 정보기술(ET+IT)이 있다. 그러나 스마트시티에 공간융합이 3가지의 기술들에 의해 변화 한다는 것은 아직까지 불투명하다. 따라서 본 연구는 스마트시티 공간(지구, 가로, 건물, 시설)의 융합 변화를 3가지 기술들을 통해 구체적으로 분석하는데 목적을 두고 있다. 주요연구 내용은 스마트시티에 융합된 환경기술, 정보기술, 환경 정보기술과 4개의 공간 사이의 융합 분포비율을 시기별(시기 1 : 1972~1999, 시기 2 : 2000~2009, 시기 3 : 2010~2017)로 파악하는 것이다. 그에 따라 연구결과는 다음과 같다. 첫째, 스마트시티 1기의 공간 적용개수와 융합 분포비율 합계는 지구(53개/43.0%)-건물(36개/29.1%)-가로(22개/17.9%)-시설(12개/10.0%) 순으로 높았다. 둘째, 스마트시티 2기의 공간 적용개수와 융합 분포비율 합계는 지구(223개/32.4%)-건물(197개/28.6%)-가로(195개/28.3%)-시설(74개/14.8%) 순으로 높았다. 셋째, 3기에는 4개의 공간 위계 중, 지구(467개/33%)가 가장 높았다. 그러나 1기, 2기와 다른 점은 가로(384개/27.4%)가 건물(361개/25.8%)보다 높았으며, 그 뒤로 시설(188개/13.4%)의 융합되고 있다. 넷째, 스마트시티는 1기와 2기 모두 적용개수와 융합비율에서 지구-건물-가로-시설 순으로 높은 결과 값이 나왔으나, 개수평균에서는 건물-가로-지구-시설 순으로 높았다. 3기에는 적용개수와 융합비율이 지구-가로-건물-시설 순으로 높았으며, 개수평균은 1,2기와 동일하였다. 결과적으로 스마트시티 공간(지구, 가로, 건물, 시설)은 초창기에 도시의 거시적 공간(항만, 공원, 녹지, 유원지, 공공공지, 수도전기, 열 공급시설, 하천, 궤도, 운하)의 개발을 통해 변화 되었다. 이후 지구 공간중심 개발과 스마트시티를 구축하는 중요한 건물(내부, 외부, 사이)공간에 다양한 디바이스/기술이 융합되어 시민유입을 목표로 변화하게 되었다. 건물공간은 계속해서 진화하고 있으며, 향후 스마트시티 공간은 완료된 건물과 건물을 연결하는 가로 공간으로 활성화 될 것이라 예상된다.

• 한국주조공학회지
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• 제11권4호
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• pp.293-302
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• 1991

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by a combined technique of rheo-compocasting and hot extrusion. Distribution of fibers in the composites fabricated by rheo-compocasting was relatively uniform. A good degree of uniaxial fiber alignment has been achieved by hot extrusion, but a lot of fibers fractured during extrusion. The tendency of fiber fracturing increases as the aspect ratio and the amount of fibers increase. Relatively good bonding between fiber and matrix was obtained by the formation of $MgAl_2O_4$ and Mg(Al, Fe)$_2O_4$ at the interface between fiber and matrix. In extruded composites, fiber-strengthening effect was relatively small since a lot of fibers fractured during hot extrusion. On the other hand, dispersion strengthening effect may increase. In order to improve the fiber strengthening effect, it is important to optimize the extrusion condition with consideration of metal flow in extrusion die.

• Journal of the Korean Wood Science and Technology
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• 제40권2호
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• pp.71-77
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• 2012

Cellulose nanowhisker (CNW) isolated from hardwood bleached kraft pulp (HW-BKP) using sulfuric acid hydrolysis was suspended in polyvinyl alcohol (PVA) and electrospun into composites nanofibers. Transmission electron microscopy (TEM) revealed the CNW to be rod-like, approximately of $16.1{\pm}4.6$ nm wide and $194{\pm}61$ nm long, providing an aspect ratio of about 12, with a particle size distribution range of $662.2{\pm}301.2$ nm. Uniform and high quality CNW/PVA composite nanofibers were successfully manufactured by the electrospinning method. As the CNW loading increases, the viscosity of CNW/PVA solutions shows a minimum at 1% CNW level which subsequently results in the smallest diameter (193 nm) of electrospun nanofibers. The average diameter of the nanofibers increased up to 284 nm with increasing CNW loading. These results suggest that the electrospinning method provides a great potential of manufacturing consistent and reliable nanofibers from CNW/PVA solution for the formation of scaffolds with potentials in future application.

• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.141-164
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• 2018

In this paper, the thermal effect on buckling and free vibration characteristics of functionally graded (FG) size-dependent Timoshenko nanobeams subjected to an in-plane thermal loading are investigated by presenting a Navier type solution for the first time. Material properties of FG nanobeam are supposed to vary continuously along the thickness according to the power-law form and the material properties are assumed to be temperature-dependent. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on Timoshenko beam theory through Hamilton's principle and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared to some cases in the literature. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as thermal effect, material distribution profile, small scale effects, aspect ratio and mode number on the critical buckling temperature and normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the thermal buckling and vibration behaviour of a FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

• Steel and Composite Structures
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• 제23권5호
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• pp.529-541
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• 2017

In the present study, vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) plate moving in two directions is investigated. Various types of shear deformation theories are utilized to obtain more accurate and simplest theory. Single-walled carbon nanotubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Moreover, different kinds of distributions of CNTs are considered. Based on extended rule of mixture, the structural properties of composite face sheets are considered. Motion equations are obtained by Hamilton's principle and solved analytically. Influences of various parameters such as moving speed in x and y directions, volume fraction and distribution of CNTs, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of composite plate on the vibration characteristics of moving system are discussed in details. The results indicated that thenatural frequency or stability of FGCNTRC plate is strongly dependent on axially moving speed. Moreover, a better configuration of the nanotube embedded in plate can be used to increase the critical speed, as a result, the stability is improved. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.