• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.49-49
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• 2009

Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

• 반도체디스플레이기술학회지
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• 제23권1호
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• pp.12-18
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• 2024

The accelerated pace of climate crisis due to continuous industrialization and greenhouse gas emissions necessitates sustainable solutions that simultaneously address mitigation and adaptation to climate change. Naturebased Solutions (NbS) have gained prominence as viable approaches, with Green Infrastructure being a representative NbS. Green Infrastructure involves securing green spaces within urban areas, providing diverse climate adaptation functions such as removal of various air pollutants, carbon sequestration, and isolation. The proliferation of Green Infrastructure is influenced by the quantification of improvement effects related to various projects. To support decision-making by assessing the climate vulnerability of Green Infrastructure, the U.S. Department of Agriculture (USDA) has developed i-Tree Tools. This study proposes a comprehensive evaluation approach for climate change adaptation types by quantifying the climate adaptation performance of urban Green Infrastructure. Using i-Tree Canopy, the analysis focuses on five urban green spaces covering more than 30 hectares, considering the tree ratio relative to the total area. The evaluation encompasses aspects of thermal environment, aquatic environment, and atmospheric environment to assess the overall eco-friendliness in terms of climate change adaptation. The results indicate that an increase in the tree ratio correlates with improved eco-friendliness in terms of thermal, aquatic, and atmospheric environments. In particular, it is necessary to prioritize consideration of the water environment sector in order to realize climate change adaptive green infrastructure, such as increasing green space in urban areas, as it has been confirmed that four out of five target sites are specialized in improving the water environment.

• Nuclear Engineering and Technology
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• 제37권1호
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• pp.91-100
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• 2005

Kyung-hee Thorium Fuel (KTF), a heterogeneous thorium-based seed and blanket design concept for pressurized light water reactors, is being studied as an alternative to enhance proliferation resistance and fuel cycle economics of PWRs. The proliferation resistance characteristics of the KTF assembly design were evaluated through parametric studies using neutronic performance indices such as Bare Critical Mass (BCM), Spontaneous Neutron Source rate (SNS), Thermal Generation rate (TG), and Radio-Toxicity. Also, Fissile Economic Index (FEI), a new index for gauging fuel cycle economy, was suggested and applied to optimize the KTF design. A core loaded with optimized KTF assemblies with a seed-to-blanket ratio of 1: 1 was tested at the Korea Next Generation Reactor (KNGR), ARP-1400. Core design characteristics for cycle length, power distribution, and power peaking were evaluated by HELIOS and MASTER code systems for nine reload cycles. The core calculation results show that the KTF assembly design has nearly the same neutronic performance as those of a conventional $UO_2$ fuel assembly. However, the power peaking factor is relatively higher than that of conventional PWRs as the maximum Fq is 2.69 at the M$9^{th}$ equilibrium cycle while the design limit is 2.58. In order to assess the economic potential of a heterogeneous thorium fuel core, the front-end fuel cycle costs as well as the spent fuel disposal costs were compared with those of a reference PWR fueled with $UO_2$. In the case of comprising back-end fuel cycle cost, the fuel cycle cost of APR-1400 with a KTF assembly is 4.99 mills/KWe-yr, which is lower than that (5.23 mills/KWe-yr) of a conventional PWR. Proliferation resistance potential, BCM, SNS, and TG of a heterogeneous thorium-fueled core are much higher than those of the $UO_2$ core. The once-through fuel cycle application of heterogeneous thorium fuel assemblies demonstrated good competitiveness relative to $UO_2$ in terms of economics.

• 설비공학논문집
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• 제17권1호
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• pp.56-61
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• 2005

Indoor air quality becomes of a concern recently in view of human health. This study investigates the air diffusion performance and the air change efficiency of a classroom, when outdoor air is introduced in addition to the heating/cooling operation of a ceiling-mounted heat pump. A CFD analysis has been performed to investigate the effect of the discharge angle of the air jets from the heat pump for both parallel and series types of outdoor air system. It is observed that the series type creates more uniform indoor environment compared to the parallel type in general. It can be concluded the discharge angle should not be larger than 40o for the parallel type, in order not to generate thermal stratification in the room.

• 대한설비공학회지:설비저널
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• 제15권1호
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• pp.87-96
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• 1986

An experiment on the devices that enchance the stratification of storage tanks in a solar heat ins system has been carried out. The benefits of thermal stratification in sensible heat storage are to increase the system performance such as the collector efficiency or the fraction of the total load supplied by solar energy. Using the diffuser and the distributor as the stratification enchancement device, the expeliments were perfomed in the different condition of diameter and material of the distributor. As a result of experiments, there exists the diameter of distributor in which the stratification is made maximum under certain design and operation condition. Also it was identified that the kind of distributor material influenced the degree of stratification. Comparing the experimental result to the computational results calculated under the same conditions, the node number N(stratification index) was determined. The results of computer simulation that was performed about the actual solar heating system in Seoul for 24 hours show the relative advantage of stratified over well-mixed storage and the significant improvements in system performance.

• 폴리머
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• 제39권2호
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• pp.346-352
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• 2015

폴리알파올레핀(PAO)은 유동점, 점도지수, 열/산화 안정성이 광유 기반의 윤활유보다 우수한 합성 윤활유이다. 본 연구에서는 1-펜텐, 1-헥센, 1-옥텐, 및 1-도데센을 단량체로 사용하고 세가지 종류의 알루미늄계 루이스 산촉매로 양이온 중합을 수행하여 다양한 PAO를 합성하였다. PAO 중합 성능과 제조된 PAO의 분자량, 동점도, 유동점과 점도지수를 다양한 중합 조건에서 조절할 수 있었다. 알킬 알루미늄 할라이드계 촉매가 기존의 $AlCl_3$계 촉매에 비하여 촉매 성능이 우수하였다. PAO의 미세구조를 비행-시간형 질량분석기(TOF-MS) 해석을 통하여 PAO의 미세구조와 윤활유로의 성능(점도지수, 유동점)과의 상관관계를 규명하였다. 특히, PAO의 점도지수는 알파 올레핀의 탄소수 증가에 따라 상승하여, PAO의 분지길이가 점도지수와 밀접한 상관관계가 있음을 확인하였다.

• 한국표면공학회지
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• 제51권4호
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• pp.207-213
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• 2018

Not only efficiency of chlorine evolution reaction (CER) but also durability namely service life is very important property in dimensional stable anode for Ballast Water Management System (BWMS) for marine ships. Many researchers have been focused on improving efficiency of CER by controlling composition, phase and surface area for a long time, but the efforts to increase durability was relatively small. In this study, we have investigated the effect of $TiO_2$ protective interlayers on efficiency and durability of DSA electrodes. $TiO_2$ protective interlayers were prepared by thermal oxidation at 500, 600 and $700^{\circ}C$ on Ti substrate. And then the DSA electrodes consisting of $Ti/RuO_2-PdO-TiO_2$ were prepared by thermal decomposition method on $TiO_2$ interlayers. The efficiencies of CER of DSA electrodes without $TiO_2$ interlayer and with $TiO_2$ interlayer grown at 500, 600 and $700^{\circ}C$ were 94.19, 94.45, 84.60 and 76.75% respectively. On the otherhand, durabilities were 30, 55, 90 and 65 hours respectively. In terms of industrial aspect, the performance of DSA is considered high efficiency and durability which can correspond to total production of chlorine. If we considered the performance index of DSA as the product of efficiency and durability, performance indices could be recalculated as 28.26, 50.85, 76.14 and 49.89 respectively. As the thermal oxidation temperature increasing, life time were increased remarkerbly, while efficiency of CER was decreased slightly. As a result, DSA electrode with $TiO_2$ interlayer grown at $600^{\circ}C$ has shown about 2.7 times performace of original DSA electrode without $TiO_2$ interlayer.

• 한국화재소방학회논문지
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• 제33권1호
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• pp.69-75
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• 2019

본 연구에서는 5종의 섬유강화플라스틱(Fiber Reinforced Plastic, FRP), 폴리스티렌(Polystylene, PS), 폴리카보네이트(Polycarbonate, PC), 폴리프로필렌(Polypropylene, PP), 폴리염화비닐(Polyvinyl chloride, PVC) 판을 콘칼로리미터(Cone calorimeter, ISO 5660)를 이용하여 연소성을 시험하였다. 그 결과 PVC판은 최대열방출률($HRR_{peak}$)이 $44.65kW/m^2$, 최대평균열방사율(MARHE)이 $30.97kW/m^2$로 가장 낮게 나타났고, PS판은 $HRR_{peak}$은 $773.44kW/m^2$, MARHE는 $399.14kW/m^2$으로 가장 높게 나타났다. 일산화탄소의 평균($CO_{mean}$) 발생량은 PC판과 PS판이 최대 3.88배로 가장 많이 발생하였고, 반대로 이산화탄소($CO_{2mean}$)의 평균 발생량은 PS판과 PP판이 최대 4.88배로 가장 많이 발생하였다. 또 PS판은 다른 플라스틱보다 연기성능지수(SPI)가 74.81%~95.99% 감소하였고, 연기성장지수(SGI)는 76%~300%, 연기강도(SI)는 917.73%~9607.57% 증가하여 연기위험성이 높다는 것을 알 수 있었다. 따라서 PS판은 열적 측면에서나 연기 측면 모두 연기로 인한 인명피해의 위험성이 가장 높았음을 알았다.

• The Korean Journal of Pain
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• 제34권3호
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• pp.250-261
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• 2021

Background: Complex regional pain syndrome type I (CRPS-I) consists of disorders caused by spontaneous pain or induced by some stimulus. The objective was to verify the effects of photobiomodulation (PBM) using 830 nm wavelength light at the affected paw and involved spinal cord segments during the warm or acute phase. Methods: Fifty-six mice were randomized into seven groups. Group (G) 1 was the placebo group; G2 and G3 were treated with PBM on the paw in the warm and acute phase, respectively; G4 and G5 treated with PBM on involved spinal cord segments in the warm and acute phase, respectively; G6 and G7 treated with PBM on paw and involved spinal cord segments in the warm and acute phase, respectively. Edema degree, thermal and mechanical hyperalgesia, skin temperature, and functional quality of gait (Sciatic Static Index [SSI] and Sciatic Functional Index [SFI]) were evaluated. Results: Edema was lower in G3 and G7, and these were the only groups to return to baseline values at the end of treatment. For thermal hyperalgesia only G3 and G5 returned to baseline values. Regarding mechanical hyperalgesia, the groups did not show significant differences. Thermography showed increased temperature in all groups on the seventh day. In SSI and SFI assessment, G3 and G7 showed lower values when compared to G1, respectively. Conclusions: PBM irradiation in the acute phase and in the affected paw showed better results in reducing edema, thermal and mechanical hyperalgesia, and in improving gait quality, demonstrating efficacy in treatment of CRPS-I symptoms.

• 반도체디스플레이기술학회지
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• 제21권1호
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• pp.79-84
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• 2022

As various flexible display products are released, the demand for high-performance colorless and transparent polyimide (CPI) film is continuously increasing. The primary purpose of this study is to establish a systematic procedure for optimizing the optical performance of CPI films by applying the response surface method. After selecting three key factors (monomer type, stirring time for varnish synthesis, and maximum temperature of vacuum furnace for film production) affecting optical performance based on experiences and references, CPI films were manufactured according to the experimental sequence designed by the central composite design, and then the yellowness index (YI) and optical transmittance (Tr) of the films were measured. When producing a CPI film by pouring varnish into a petri dish, the change in optical properties according to thickness should be considered, and there was a meaningful linear relationship between YI and Tr. The species of monomer and the maximum temperature were the critical factors that had an influence on YI and Tr, respectively. It is expected that the procedure proposed in this study can serve as a starting point for CPI film optimization studies considering the other factors that were not considered and responses such as thermal properties.