• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.847-852
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• 2019

In this study, the effect of additives on the performance of aqueous organic redox flow battery (AORFB) using quinoxaline and ferrocyanide as active materials in alkaline supporting electrolyte is investigated. Quinoxaline shows the lowest redox potential (-0.97 V) in KOH supporting electrolyte, while when quinoxaline and ferrocyanide are used as the target active materials, the cell voltage of this redox combination is 1.3 V. When the single cell tests of AORFBs using 0.1 M active materials in 1 M KCl supporting electrolyte and Nafion 117 membrane are implemented, it does not work properly because of the side reaction of quinoxaline. To reduce or prevent the side reaction of quinoxaline, the two types of additives are considered. They are the potassium sulfate as electrophile additive and potassium iodide as nucleophilie additive. Of them, when the single cell tests of AORFBs using potassium iodide as additive dissolved in quinoxaline solution are performed, the capacity loss rate is reduced to $0.21Ah{\cdot}L^{-1}per\;cycle$ and it is better than that of the single cell test of AORFB operated without additive ($0.29Ah{\cdot}L^{-1}per\;cycle$).

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.10a
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• pp.33-33
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• 2019

너도개미자리(Minuartia laricina (L.) Mattf.)는 석죽과 나도개미자리속 식물로 낭림산 이북부터 백두산까지 분포하며, 7~10월에 백색의 꽃이 아름답게 개화하여 관상 목적으로 이용된다. 본 연구는 너도개미자리를 관상식물로 활용하기 위한 효율적인 육묘 방법을 개발하기 위하여 수행되었다. 실험은 유용식물증식센터에서 분양받은 종자를 2019년 4월 19일에 트레이에 파종하여 6월 14일까지 충북대학교 첨단유리온실에서 8주 동안 육묘하였다. 파종용기에 따른 너도개미자리의 생육을 알아보기 위하여 162, 200, 288구 트레이를 이용하였다. 토양은 단용토로 원예상토를 사용하였으며, 혼용토는 피트모스와 펄라이트를 3:1, 4:1 비율로 혼합하여 진행되었다. 파종립수 실험은 200구 트레이의 셀당 각 1, 2, 4, 6립씩 파종하였으며, 차광 실험은 0, 55, 75%의 차광막이 설치된 육묘배드에서 실시하였다. 추비는 hyponex (6.5-6-19)를 처리별 각 0, 250, 500, $1000mg{\cdot}L^{-1}$의 농도로 출아 후 2, 4, 6주차에 총 3회 살포하였다. 대조구는 200구 트레이에 원예상토를 충진한 다음 셀당 1립씩 파종하여 차광을 하지 않은 온실에 배치하였으며, hyponex $500mg{\cdot}L^{-1}$를 처리하였다. 연구의 결과, 너도개미자리는 셀의 용량이 클수록 모든 생육이 양호한 결과를 보여, 162구 트레이에 육묘하는 것이 가장 효과적이었다. 토양 실험의 결과, 원예상토에서 생육이 양호하였으나, 피트모스와 펄라이트의 혼용토는 생육이 크게 억제되었다. 셀당 파종립수를 달리한 결과, 너도개미자리의 개체별 생육은 파종립수가 적을수록 유리하였으나, 본 연구의 목적인 관상적 가치를 위한 생육과 볼륨을 고려하였을 때 셀당 2립 파종묘가 효과적인 것으로 판단되었다. 추비 실험은 농도가 높을수록 생육이 왕성해지는 경향이었으며, $1000mg{\cdot}L^{-1}$에서 가장 효과적이었다. 차광 실험의 결과, 무차광 조건에서 전반적인 생육이 양호하였으며, 차광율이 높을수록 초장이 길어지는 경향이었다. 결론적으로, 너도개미자리의 육묘는 162구 트레이에 원예상토를 충진하고 셀당 종자를 2립 파종하여 무차광 조건에서 추비를 $1000mg{\cdot}L^{-1}$의 농도로 처리하며 육묘하는 것이 효과적일 것으로 판단된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.253-256
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• 2009

This paper describes a core generator (FFT_Core_Gen) which generates Verilog HDL models of 8 different FFT/IFFT cores with $N=64{\times}2^k$($0{\leq}k{\leq}7$ for OFDM-based communication systems. The generated FFT/IFFT cores are based on in-place single memory architecture, and use a hybrid structure of radix-4 and radix-2 DIF algorithm to accommodate various FFT lengths. To achieve both memory reduction and the improved SQNR, a conditional scaling technique is adopted, which conditionally scales the intermediate results of each computational stage, and the internal data and twiddle factor has 14 bits. The generated FFT/IFFT cores have the SQNR of 58-dB for N=8,192 and 63-dB for N=64. The cores synthesized with a $0.35-{\mu}m$ CMOS standard cell library can operate with 75-MHz@3.3-V, and a 8,192-point FFT can be computed in $762.7-{\mu}s$, thus the cores satisfy the specifications of wireless LAN, DMB, and DVB systems.

• Journal of the Korea Society of Computer and Information
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• v.25 no.6
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• pp.155-164
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• 2020

In this paper, we proposed the dimensional system and pattern of middle-aged women's rashguard swimwear for breast cancer patients. First, a survey of 37 breast cancer patients was conducted to determine the preferred swimsuit design for breast cancer patients. According to a survey of breast cancer patients, a rashguard swimwear with a low-exposure chest was designed. It has a pocket shape in which the cap is easy to insert and the cap is fixed. Second, we developed a dimensional system for swimsuits for breast cancer patients. Using direct measurement data from Size Korea for 1,625 women aged 30 to 69, 17-sizes for breast cancer patient's swimsuits were set through cross-analysis of major dimensions, with a coverage rate of 74.3%. It also extracted a standard size of bust circ. 90cm, hip circ. 95cm, and trunk circ. 150cm. Third, we developed a pattern for the central size of the swimsuit for breast cancer patients. For this purpose, we first produced the first central size pattern, and then completed the pattern after modifying it through the second and third wearing experiments. Experimental suits were produced at each pattern-making stage to evaluate wearing fit and motion suitability. Finally, the reduction rate of each dimension item for optimal pattern production was obtained, and the lashguard swimwear pattern for breast cancer patients was developed.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.461-468
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• 2006

Optical characteristics in polymer films of MEH-PPV/DFPP blends were for the first time investigated. DFPP (N, N'-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide) used here was a novel n-type polymer, which had good stability in air and solubility in common solvents. For a 1:9 DFPP:MEH-PPV blend, highly efficient quenching of photoluminescence (PL) was observed. In addition, the photocurrent responses of these MEH-PPV/DFPP photovoltaic cells were measured. When the light intensity was $50mW/cm^2$, short-circuit photocurrent densities were two times higher than those of single layer MEH-PPV devices.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.768-773
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• 2019

The Fenton reaction, which evaluates the electrochemical durability of polymer membranes of polymer electrolyte fuel cells (PEMFC), and the degradation of polymer membranes by OCV holding method are compared. The Fenton reaction is a method that can evaluate the chemical durability of the polymer membrane at outside the cell in a shorter time than the OCV Holding method. The Fenton reaction was carried out at 30% hydrogen peroxide, 10 ppm iron, and $80^{\circ}C$ for 24 hours. OCV Holding was driven at $90^{\circ}C$, 30% relative humidity and OCV for 168 hours. The Fenton reaction caused a lot of degradation inside the polymer membrane. On the other hand, in OCV Holding, the membrane thickness was thinned by the entire surface and internal degradation. The fluorine emission rate was more than 10 times higher than that of OCV Holding due to the Fenton reaction. The hydrogen permeation rate increased about 30% at 24 hours of Fenton reaction. At OCV Holding, hydrogen permeability decreased after 24 hours and then increased. As a whole, there was a difference in a membranes deteriorated by Fenton reaction and OCV Holding.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.642-649
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• 2021

Energy saving standard for buildings are strengthened, the application of exterior insulation finishing system and thickness of insulation materials are increasing. Most buildings with exterior insulation finishing system is applied organic insulating material. Organic insulating material have workability, economic feasibility, reduction in construction cost, and excellent thermal insulation performance. However, Organic insulating material is very vulnerable to heat, so when a fire occurs, rapid fire spread and toxic gas are generated, causing many casualties. Inorganic insulating material can be non-combustible performance, but it is heavy and has low thermal insulation performance. Mineral wool has higher thermal insulation performance than other types of inorganic insulating material, but mineral wool is disadvantageous to workability and vulnerable to moisture. Glass bubble are highly resistant to water and chemically stable substances. In addition, the density of the glass bubble is very low and the particles are spherical, fluidity is improved by the ball bearing effect. Glass bubbles can be used with cement-based ino rganic insulating material to impro ve the weight and thermal insulatio n perfo rmance o f cement-based inorganic insulation. This study produced a inorganic insulating materials were manufactured using cement-based materials and glass bubble. In order to evaluate the insulation performance and flame retardant performance of cement-based super light-weight inorganic insulating materials using with glass bubble, insulation performance or flame retardant and non-combustible performance were evaluated after manufacturing insulating materials using micro cement and two types of glass bubbles. From the test result, Increasing the mixing ratio of glass bubbles improved the insulation performance of cement-based super light-weight inorganic insulating materials, and when the mixing ratio of glass bubbles was 10%, it sho wed sufficient flame retardant and no n-co mbustible perfo rmance.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.98-105
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• 2021

This study presented the results of the static load tests conducted to verify the structural robustness of the composite oxidant tank for a space launch vehicle. First, we introduced the test equipment used in the static load test of the composite oxidant tank, and then described the test requirements that the composite oxidant tank must satisfy. In addition, we presented a test set-up diagram consisting of the static load test fixture, hydraulic pressure, control equipment, and data acquisition equipment, and the load profile of the static load test of the composite oxidant tank consisting of shear, equivalent compression, bending, and combination tests. As a result of load control, we verified the reliability of this test by showing the errors between the input load and the feedback load in each channel according to the increase of the test load, and the feedback error between the channel A and channel B of load cell in each load actuator. As a result of the static load test, the load of the actuator was properly controlled within the allowable error range in each test, and we found that the test specimen did not cause damage or buckling that causes significant structural defects in the required load.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.3
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• pp.17-24
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• 2021

Perovskite solar cells (PSCs) can be fabricated through solution process economically with variable bandgap that is controlled by composition of precursor solution. Tandem cells in which PSCs combined with silicon solar cells have potential to reach high power conversion efficiency over 30%, however, lack of long-term stability of PSCs is an obstacle to commercialization. Degradation of PSCs is mainly attributed to the mass transport of halide and metal electrode materials. In order to ensure the long-term stability, the mass transport should be inhibited. In this study, we confirmed degradation behaviors due to the mass transport in PSCs and designed buffer layers with LiF and/or SnO₂ to improve the long-term stability by suppressing the mass transport. Under high-temperature storage test at 85℃, PSCs without the buffer layers were degraded by forming PbI₂, AgI, and the delta phase of the perovskite material, while PSCs with the buffer layers showed improved stability with keeping the original phase of the perovskite. When the LiF buffer and encapsulation were applied to PSCs, superior long-term stability on 85℃-85% RH dump heat test was achieved; efficiency drop was not observed after 200 h. It was also confirmed that 90.6% of the initial efficiency was maintained after 200 hours of maximum power tracking test under AM 1.5G-1SUN illumination. Here, we have demonstrated that the buffer layer is essential to achieve long-term stability of PSCs.

• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.5-12
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• 2019

On November 15, 2017, a unpredictable liquefaction damage was occurred at the $M_L=5.4$ Pohang earthquake and after, many researches have been conducted in Korea. In Korea, where there were no cases of earthquake damage, it has been extremely neglectable in preparing earthquake risk maps and building earthquake systems that corresponded to prevention and preparation. Since it is almost impossible to observe signs and symptoms of drought, floods, and typhoons in advance, it is very effective to predict the impacts and magnitudes of seismic events. In this study, 14,040 borehole data were collected in the metropolitan area and liquefaction evaluation was performed using the amplification factor. Based on this data, liquefaction hazard maps were prepared for ground accelerations of 0.06 g, 0.14 g, 0.22 g, and 0.30 g, including 200years return period to 4,800years return period. Also, the correlation analysis between the earthquake acceleration and LPI was carried out to draw a real-time predictable liquefaction hazard map. As a result, 707 correlation equations in every cells in GIS map were proposed. Finally, the simulation for liquefaction risk mapping against artificial earthquake was performed in the metropolitan area using the proposed correlation equations.