• 한국실내디자인학회논문집
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• 제26권6호
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• pp.97-105
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• 2017

Korea is promoted STEAM education since 2011. Furthermore, in high school education, based on the in-depth elective course's teaching and learning contents of science. The STEAM program can improve students' competence because it encourages to self-directed learning through the vocational project performance. Therefore, in this study, we researched a design education program for the experience of fusion and complex design based on STEAM education concept. We developed an education program to design insulation wall systems using up-cycling concepts to increase energy efficiency. As a result, the characteristics of the fusion education and the theoretical study about the learner-centered education curriculum, the analysis of the high school curriculum, the STEAM elements, The program was revised and supplemented through consultation with STEAM experts. In addition, the developed program was applied to high school students, and each step were analyzed based on the educational method theory. The following results were obtained. First, this study presented a program to cope with the needs of high school intensive education. Second, it provided learning motivation by combining flipped-learning as a way to train STEAM education contents. Third, it is required to develop differentiated and continuous program development and data sharing Fourth, in order to operate and promote the future environment design STEAM school, it is necessary to expand educational programs for high school students in the region through linkage with various universities.

• 복식문화연구
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• 제26권6호
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• pp.899-918
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• 2018

Upcycling is the process of repurposing abandoned resources or useless products into products of better quality or higher environmental value. Upcycling products are evaluated to be sustainable because they demonstrate environmental values. However, domestic upcycling companies are operating on a small scale with a slow growth rate. This study aims to examine the value and risk factors of upcycling products from previous literature and clarify the effect of these ambivalent characteristics on purchase intention. This provides direction regarding factors upcycling companies should focus on. The data were collected via an online experiment with women in their 20s and 30s residing in South Korea, nationwide. The data were statistically analyzed using SPSS 21.0 and AMOS 18.0. Analysis of this data suggests that environmental, design, and self-expression value positively affect purchase intention. This extends previous upcycling literature by identifying design and self-expression value as important antecedents of purchase intention. However, in contrast to previous literature, no significant effect of performance or diversity risk was found. These results indicate that ethical attitude has a moderating effect on the relationship between environmental value and purchase intention. This study confirms that consumers intend to purchase upcycling products when they possess not only environmental value but also design and self-expression value.

• 공업화학
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• 제32권4호
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• pp.467-471
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• 2021

본 연구에서는 가교성 작용기가 기능화된 사다리형 폴리실세스키옥산(LPMA64)을 합성하였고, 이를 액상 전해질의 열 가교 공정에 활용하여 유기-무기 하이브리드 겔 고분자 전해질을 제조하였다. 5 wt%의 낮은 LPMA64 고분자 가교제 함량으로도 전해질 내 네트워크 구조가 잘 발달하여, 우수한 형태 안정성과 높은 이온 전도도를 가지는 전해질의 제조가 가능하였다. 하이브리드 겔 고분자 전해질이 적용된 리튬-황 전지는 안정적인 율속과 장수명 성능 및 높은 쿨롱 효율을 나타냈으며, 이는 완화된 리튬 폴리설파이드 셔틀 현상에 기인했다. 본 연구결과는 제조된 유기-무기 하이브리드 겔 고분자 전해질이 리튬-황 전지 응용에 유망한 전해질임을 보여주었다.

• 한국분말재료학회지
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• 제28권6호
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• pp.470-477
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• 2021

Energy storage systems should address issues such as power fluctuations and rapid charge-discharge; to meet this requirement, CoFe₂O₄ (CFO) spinel nanoparticles with a suitable electrical conductivity and various redox states are synthesized and used as electrode materials for supercapacitors. In particular, CFO electrodes combined with carbon nanofibers (CNFs) can provide long-term cycling stability by fabricating binder-free three-dimensional electrodes. In this study, CFO-decorated CNFs are prepared by electrospinning and a low-cost hydrothermal method. The effects of heat treatment, such as the activation of CNFs (ACNFs) and calcination of CFO-decorated CNFs (C-CFO/ACNFs), are investigated. The C-CFO/ACNF electrode exhibits a high specific capacitance of 142.9 F/g at a scan rate of 5 mV/s and superior rate capability of 77.6% capacitance retention at a high scan rate of 500 mV/s. This electrode also achieves the lowest charge transfer resistance of 0.0063 Ω and excellent cycling stability (93.5% retention after 5,000 cycles) because of the improved ion conductivity by pathway formation and structural stability. The results of our work are expected to open a new route for manufacturing hybrid capacitor electrodes containing the C-CFO/ACNF electrode that can be easily prepared with a low-cost and simple process with enhanced electrochemical performance.

• 청정기술
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• 제28권2호
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• pp.97-102
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• 2022

Lithium sulfur (Li-S) batteries have attracted considerable attention as a promising candidate for next-generation power sources due to their high theoretical energy density, low cost, and eco-friendliness. However, the poor electrical conductivity of sulfur and its insoluble discharging products (Li₂S₂/Li₂S), large volume changes, severe self-discharge, and dissolution of lithium polysulfide intermediates result in rapid capacity fading, low Coulombic efficiency, and safety risks, hindering Li-S battery commercial development. In this study, a three-dimensionally (3D) connected hierarchical porous carbon framework (HPCF) derived from waste sunflower seed shells was synthesized as a sulfur host for Li-S batteries via a chemical activation method. The natural 3D connected structure of the HPCF, originating from the raw material, can effectively enhance the conductivity and accessibility of the electrolyte, accelerating the Li⁺/electron transfer. Additionally, the generated micropores of the HPCF, originated from the chemical activation process, can prevent polysulfide dissolution due to the limited space, thereby improving the electrochemical performance and cycling stability. The HPCF/S cell shows a superior capacity retention of 540 mA h g^-1 after 70 cycles at 0.1 C, and an excellent cycling stability at 2 C for 700 cycles. This study provides a potential biomass-derived material for low-cost long-life Li-S batteries.

• Steel and Composite Structures
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• 제48권3호
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• pp.305-320
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• 2023

The mechanical properties of polymeric composites are degraded under elevated temperatures due to the effect of temperature on the mechanical behavior of the resin and resin fiber interfaces. In this study, the effect of temperature on the impact response of the carbon fiber reinforced plastics (CFRP) was investigated at low-velocity impact (LVI) using a drop-weight impact tester machine. All the composite plates were fabricated using a vacuum infusion process with a stacking sequence of [45/0_2/-45/90_2]s, and a thickness of 2.9 mm. A group of the specimens was exposed to an environment with a temperature cycling at the range of -30 ℃ to 65 ℃. In addition, three other groups of the specimens were aged at ambient (28 ℃), -30 ℃, and 65 ℃ for ten days. Then all the conditioned specimens were subjected to LVI at three energy levels of 10, 15, and 20 J. To assess the behavior of the damaged composite plates, the force-time, force-displacement, and energy-time diagrams were analyzed at all temperatures. Finally, radiography, optical microscopy, and scanning electron microscopy (SEM) were used to evaluate the effect of the temperature and damages at various impact levels. Based on the results, different energy levels have a similar effect on the LVI behavior of the samples at various temperatures. Delamination, matrix cracking, and fiber failure were the main damage modes. Compared to the samples tested at room temperature, the reduction of temperature to -30 ℃ enhanced the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. The temperature increasing to 65 ℃ increased the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. Applying 200 thermal cycles at the range of -30 ℃ to 65 ℃ led to the formation of fine cracks in the matrix while decreasing the absorbed energy. The maximum contact force is recorded under cyclic temperature as 5.95, 6.51 and 7.14 kN, under impact energy of 10, 15 and 20 J, respectively. As well as, the minimum contact force belongs to the room temperature condition and is reported as 3.93, 4.94 and 5.71 kN, under impact energy of 10, 15 and 20 J, respectively.

• 한국해양학회지:바다
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• 제18권1호
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• pp.47-52
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• 2013

생태계 질소 순환 연구에서 동위원소 추적자를 이용한 실험은 그 유용성에도 불구하고, 무기 질소의 안정동위원소 측정이 어려워 자료의 생산이 활발하지 못한 형편이다. Gardner et al. (1996)은 HPLC (high performance liquid chromatography)를 이용하여 비교적 간편하고 정밀하게 암모늄의 동위원소 비를 측정하는 방법을 개발해 질소순환 연구에 활발하게 활용하였다. 그러나 일반적이지 않은 syringe 펌프가 필요해 다른 실험실에 이 시스템이 도입되지는 못하였다. 본 연구에서는 최신 HPLC 펌프 기술을 활용하여 Dr. Gardner 그룹 이후 최초로 암모늄 동위원소비 측정 시스템을 구축하였다. 표준시료 측정 결과 RTS (retention time shift)는 안정동위원소 비와 좋은 상관관계를 보였다. 이 시스템은 측정 자료를 디지털 형태로 변환하는 장치까지 갖추어 컴퓨터 프로그램을 이용한 다양한 자료처리가 가능하다. 특히 Matlab$^{(R)}$ 이용하여 retention time 계산에 peak 면적을 이용함으로써 측정의 정확성을 높이고, 직선성을 향상할 수 있었다. 영산강 하구 해수를 가지고 실시한 $^{15}N$-암모늄 첨가 실험에서 $^{15}N/^{14}N$ 비율 변화를 HPLC-RTS법을 통해 측정하였으며, 식물성 플랑크톤에 의한 암모늄 섭취와 재광물화 과정을 각각 독립적으로 측정하는 것이 가능했다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3446-3451
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• 2007

The thermal behavior of a building in response to heat input from an active solar space heating system is analysed to determine the effect of the variable storage tank temperature on the cycling rate, on and off temperature of a heating cycle and on the comfort characteristics of room air temperature. A computer simulation of the system behavior has been performed and verified by comparisons with various parameters. Especially, this study is focused on the effect of the system's performance when subjected to dynamic cooling loads. The heat input to the absorption system is provided by an array of solar collectors that coupled to a thermal storage tank.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.48.1-48.1
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• 2011

In this presentation, We monitored weather data, such as global irradiance, ambient temperature, temperature of PV module, relative humidity and windspeed for 2 years, for determining accelerated test condition. then, we determined the temperature limit of accelerated test through weather data and FEM analysis. Detailed procedures will be summarized in this work. After analysing outdoor stress such as thermal stress, we decided main failure modes and mechanisms of PV module, especially solder joint of ribbon wire. we carried out the measurement of material properties such as thermal expansion coefficient for planning of accelerated test. we designed accelerated test based on FEM analysis results. we carried out thermal cycling test with 1 cell mini module for 3 months. We monitored the change of electrical performance every 1 week such as Voc, Isc, Pmax, etc. and then, we analized the ribbon wire/electrode intefaces. Detailed results will be summarized in this work.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1393-1405
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• 2017

It is well known that duty-cycling control by dynamically adjusting the polling interval according to the traffic loads can effectively achieve power saving in wireless sensor networks. Thus, there has been a significant research effort in developing polling interval adaptation schemes. Especially, Dynamic Low Power Listening (DLPL) scheme is one of the most widely adopted open-looping polling interval adaptation techniques in wireless sensor networks. In DLPL scheme, if consecutive idle (busy) samplings reach a given fixed threshold, the polling interval is increased (decreased). However, due to the trial-and-error based approach, it may significantly deteriorate the system performance depending on given threshold parameters. In this paper, we propose a novel DLPL scheme, called SDL (Sequential hypothesis testing based Dynamic LPL), which employs sequential hypothesis testing to decide whether to change the polling interval conforming to various traffic conditions. Simulation results show that SDL achieves substantial power saving over state-of-the-art DLPL schemes.