• 한국항공우주학회지
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• 제31권10호
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• pp.21-26
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• 2003

본 논문에서는 광섬유 센서를 사용하여 우주환경하에 노출된 그래파이트/에폭시 복합재 적층판의 열팽창계수의 변화를 측정하였다. 열변형률과 온도를 동시에 측정하기 위해서 두개의 FBG 센서를 사용하였다. 또한 열-진공 챔버를 사용하여 고진공, 자외선, 열적 사이클 등의 인자를 가지는 저궤도(LEO) 우주환경을 모사하였다. 예비실험으로써, 본 실험에서 사용되는 온도범위에 대해 FBG 온도센서를 기준온도계로부터 보정하였고 알루미늄 시편에 부착된 FBG 변형률 센서와 변형률 게이지(ESG)의 비교실험을 통해 FBG 변형률 센서의 사용가능성을 검증하였다. 검증된 FBG센서가 삽입된 그래파이트/에폭시 복합재 평판을 모사된 우주환경에 노출하여 일정한 노화간격마다 열팽창계수 변화를 실시간으로 측정하였다. 실험결과 1000 사이클 노화후의 열팽창계수는 노화전에 비해 대체적으로 큰 변화는 없었지만 전 온도구간에서 약간 감소하는 경향을 보였다. 이러한 현상은 가스방출(outgassing), 수분방출, 모재균열 등에 기인한다.

• 한국재료학회지
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• 제23권12호
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• pp.680-686
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• 2013

Tungsten oxide films were prepared by an electrochemical deposition method for use as the anode in rechargeable lithium batteries. Continuous potentiostatic deposition of the film led to numerous cracks of the deposits while pulsed deposition significantly suppressed crack generation and film delamination. In particular, a crack-free dense tungsten oxide film with a thickness of ca. 210 nm was successfully created by pulsed deposition. The thickness of tungsten oxide was linearly proportional to deposition time. Compositional and structural analyses revealed that the as-prepared deposit was amorphous tungsten oxide and the heat treatment transformed it into crystalline triclinic tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium batteries. Typical peaks for the conversion processes of tungsten oxides were observed in cyclic voltammograms, and the reversibility of the heat-treated sample exceeded that of the as-prepared one. Consistently, the cycling stability of the heat-treated sample proved to be much better than that of the as-prepared one in a galvanostatic charge/discharge experiment. These results demonstrate the feasibility of using electrolytic tungsten oxide films as the anode in rechargeable lithium batteries. However, further works are still needed to make a dense film with higher thickness and improved cycling stability for its practical use.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.246-254
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• 2016

Objectives: The aim of this investigation was to give insights into the impact of carbohydrate-electrolyte drinks on the likely capacity of enamel surface dissolution and the influence of human saliva exposure as a biological protective factor. Materials and Methods: The pH, titratable acidity (TA) to pH 7.0, and buffer capacity (${\beta}$) of common beverages ingested by patients under physical activity were analyzed. Then, we randomly distributed 50 specimens of human enamel into 5 groups. Processed and natural coconut water served as controls for testing three carbohydrate-electrolyte drinks. In all specimens, we measured surface microhardness (Knoop hardness numbers) and enamel loss (profilometry, ${\mu}m$) for baseline and after simulated intake cycling exposure model. We also prepared areas of specimens to be exposed to human saliva overnight prior to the simulated intake cycling exposure. The cycles were performed by alternated immersions in beverages and artificial saliva. ANOVA two-way and Tukey HDS tests were used. Results: The range of pH, TA, and ${\beta}$ were 2.85 - 4.81, 8.33 - 46.66 mM/L and 3.48 - $10.25mM/L{\times}pH$, respectively. The highest capacity of enamel surface dissolution was found for commercially available sports drinks for all variables. Single time human saliva exposure failed to significantly promote protective effect for the acidic attack of beverages. Conclusions: In this study, carbohydrate-electrolyte drinks usually consumed during endurance training may have a greater capacity of dissolution of enamel surface depending on their physicochemical proprieties associated with pH and titratable acidity.

• 한국식품영양과학회지
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• 제13권1호
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• pp.117-126
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• 1984

Aflatoxins are toxic and carcinogenic secondary metabolites which are produced by trains of A. flavus and A. parasiticus during their growth on foods and feedstuffs. Aflatoxins are a group of closely related heterocyclic compounds of which $B_1$, $B_2$, and $G_2$ are the major members. Aflatoxins are synthesized via a polyketide pathway in which the general steps are acetate, an-thraquinones, xanthone and aflatoxins. Aflatoxin formation is favored by high moisture or high $a_w$(0.95${\sim}$0.99). The limiting $a_w$ for aflatoxin production on agricultural commodities is 0.83. Optimum temperature for aflatoxin production by the molds is $25{\sim}30^{\circ}C$ and the incubation time for the maximum production of the toxin is 7${\sim}$15 days. The limiting temperatures for aflatoxin production are ${\leq}7.5^{\circ}C\;and\;\geq40^{\circ}C$. Cycling temperatures may or may not stimulate aflatoxin production depending on the amplitude of cycling, substrate and strains of molds. Aflatoxin pro-ducing molds are aerobic organisms and thus have a requirement for oxygen. A decreasing $O_2$ concentration and/or increasing concentrations of $CO_2$ or $N_2$ depress the mold growth and aflatoxin formation. A. flavus grows competitively or associatively in the presence of other microorganisms and occasionally loses the competition with other microorganisms. Some lactic acid bacteria have been shown to reduce growth and aflatoxin production by A. parasiticus. Carbon source is the most important nutritional factors affecting aflatoxin formation by the molds. Sucrose, fructose and glucose are the most favorable carbon sources. Food substrates of plant derived products which have high carbohydrate content such as agricultural commodities and their products are most vulnerable to contamination by aflatoxins.

• 한국시뮬레이션학회논문지
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• 제28권3호
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• pp.25-40
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• 2019

오늘날 컨테이너 터미널은 증가하는 물동량을 유치하기 위하여 치열한 경쟁을 펼치고 있다. 이에 본 연구는 컨테이너 터미널의 생산성 향상을 위한 노력의 일환으로 두 가지 야드 트럭 우선순위 규칙(Dispatching rule)을 제안하였다. 첫 번째 Multi-attribute Dispatching은 컨테이너 터미널 생산성에 영향을 미치는 복수 요인들의 가중합으로 구성된 할당 방법이며, 선박의 체류시간을 감소시키기 위하여 안벽 크레인의 작업량을 고려하였다. 두 번째 Cycling Dispatching은 터미널 생산성 개선에 가장 큰 영향을 미치는 Double cycle횟수를 증가시키기 위한 할당 방법이다. 또한 본 연구는 풀링(Pooling)과 우선순위 규칙(Dispatching rule)이 터미널 생산성에 미치는 영향을 파악하기 위하여 풀링과 우선순위 규칙을 조합한 8가지 시나리오를 구성하였다. 실험은 실제 컨테이너 터미널의 데이터를 이용하여 시뮬레이션을 구현하였다. 실험 결과, 풀링과 우선순위 규칙 그리고 둘의 교호작용이 생산성에 영향을 미치는 것으로 나타났으며, 8가지 시나리오 중에서는 터미널 기준 풀링과 Multi-attribute Dispatching의 조합이 GCR, 선박 출항지연시간 등 KPI 지표에서 우수한 결과를 보임을 확인하였다.

• 패션비즈니스
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• 제28권2호
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• pp.125-138
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• 2024

The purpose of this study is to develop and implement a step-by-step upcycling fashion education program that can be utilized within the local community. This program aims to provide basic data by analyzing the current state of community-based upcycling projects and upcycling center programs. To achieve this, the study first examined the meaning and value of upcycling in fashion through literature research and explored upcycling projects and programs in connection with local communities. Subsequently, an upcycling fashion education program platform was developed and applied using the design thinking process. The program involved students from nine high schools in Gwangju Metropolitan City. Depending on the school's circumstances, the time and difficulty level of the upcycling education program were adjusted accordingly. A unique eco-bag making kit, using jeans developed in this study, was employed. Following the completion of the program, a satisfaction survey was conducted among 167 participating students from the high school community class. The findings indicated that the majority of students experienced an increased appreciation, attraction, and interest in upcycling products. They also demonstrated an understanding of the environmental impact of upcycling products and the distinction between upcycling and recycling. It is believed that the educational program developed in this study can promote ethical fashion and foster a sense of value-based consumption. This program can be customized and flexibly adapted to different educational levels and institutional characteristics, making it accessible to a wide range of learners.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.179-180
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• 2010

본 연구에서는 염분 혼입량을 6단계로 나누어 시험을 실시하였다. 이때 코팅재와 염분 혼입량 외의 영향인자에 대한 영향을 줄이기 위해서 모르타르의 구성 성분은 동일하게 하여 시편을 제작하였으며 부식 결과를 빠른 시간내에 도출하기 위하여 부식 촉진법을 사용하여 20주간 시험을 실시하였다. 20주 동안 Galvanic과 Half-cell을 통하여 부식 개시시기에 대한 모델링을 하였으며, 싸이클 완료 후 Linear polarization을 이용하여 부식 전류를 측정하였으며, 철근을 모르타르와 동일한 방법으로 코팅하여 콘크리트에 적용 부식개시 시기를 알아보았다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 춘계학술발표대회
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• pp.216-217
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• 2015

Duty-cycling could efficiently prolong the life time of Wireless Sensor Networks (WSNs) by let nodes be in dormant state most of the time, and only wake up (for sending or receiving) for a very short period. Flooding is one critical operation of WSNs. Many studies have been studied to improve the delay and/or energy efficiency of flooding. In this paper, we propose a novel time slot design, and the switching decision that reduce energy consumption for the schedule-based flooding tree. Each node, if failed to receive from its parent, will look for other candidate, among its siblings to overhear the flooding packet. By accurately collect information from other siblings, each node can make the best as possible switching decision; therefore the energy efficiency of the network is improved.

• 한국컴퓨터정보학회논문지
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• 제11권3호
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• pp.161-166
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• 2006

본 논문은 시간 제약 조건하에서의 모듈 선택 재사용을 이용한 CPLD 저전력 기술 매핑을 제안한다. 일반적인 상위 수준 합성에서의 스케줄링은 실제적인 라이브러리의 복잡한 재사용을 허용하지 않는다. 반면 제안한 알고리즘은 주어진 사용자 정의 모듈을 실제적인 RT 라이브러리 모듈 재사용과 공유된 자원에서의 스위치 활동의 자원 공유하여 스케줄링을 수행한다. 스케줄링은 체이닝과 멀티사이클링을 이용해 다양한 상위 레벨 벤치마크의 환경에서 최적의 스케줄링의 결과를 얻는다. 스케쥴링의 결과 재사용된 자원은 CPLD 저전력 기술 매핑 알고리즘을 이용하여 저전력으로 회로를 구현한다.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3617-3627
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• 2023

This study presents a method to solidify spent ion-exchange resin (IER) in a metakaolin-based geopolymer and shows results of mechanical strength, immersion, leaching, irradiation, and thermal cycling tests for waste acceptance criteria (WAC) to repository. The geopolymer waste form with 20 wt% of simulated spent IER met the WAC in South Korea (ROK), and the leaching tests of various sized-waste forms up to 15.0 × 30.0 cm and waste loadings up to 20 wt% for 1-5 d and 1-90 d achieved a leachability index, L_i > 6. In a leaching test for 5 d, the cumulative fraction leached (CFL) for Cs, which leached the most, was linearly correlated with the square root of leaching time for all waste forms, and L_i increased as the size of the waste form increased. The CFL was also correlated with elapsed time in the 90 d leaching test. The correlations among CFL, time, and volume-to-surface area ratio of waste forms used to estimate the L_i of Cs of a 200-L sized geopolymer with 15 wt% IER showed the L_i values as 14.73 (5 d) and 17.71 (90 d), respectively, indicating that the large-sized geopolymer waste form met the WAC.