Water crossover phenomena in all-vanadium redox flow batteries

Oh, Kyeongmin,Moazzam, Milad,Gwak, Geonhui,Ju, Hyunchul Elsevier 2019 ELECTROCHIMICA ACTA Vol.297 No.-

<P><B>Abstract</B></P> <P>Water crossover through the membrane of a vanadium redox flow battery system is not desirable because it floods one half-cell, diluting the vanadium solution on one side and consequently increasing the concentration of vanadium in the other half-cell. To analyze the effect of water crossover and the resultant electrolyte imbalance issue in the vanadium redox flow battery, herein we newly develop a water transport model and incorporate it into our previously developed 3D vanadium redox flow battery model. The model rigorously accounts for water production/consumption by the redox reaction of VO<SUP>2+</SUP>/VO<SUB>2</SUB> and side reactions as well as various mechanisms of water crossover through the membrane arising from diffusion, electro-osmotic drag (EOD), and vanadium crossover. The numerical model is successfully validated against in situ data collected during experiments in which the electrolyte volumes and cell voltages are measured during charge–discharge cycles carried out under various current densities. The detailed simulation results clearly elucidate water crossover behaviors at different stages of charging and discharging, and further reveal the individual contributions of water crossover mechanisms to the overall electrolyte imbalance between the negative and positive sides of the VRFB system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of water crossover and resultant electrolyte imbalance are considered. </LI> <LI> A water transport model is developed by extending a previous 3D VRFB model. </LI> <LI> The numerical model is validated against in situ experimental data. </LI> <LI> Water crossover flux via EOD was symmetrical between charging and discharging. </LI> <LI> Water diffusion through the membrane was unidirectional, accompanying proton transport. </LI> </UL> </P>

Numerical analysis of effects of gas crossover through membrane pinholes in high-temperature proton exchange membrane fuel cells

Chippar, P.,Oh, K.,Kim, W.G.,Ju, H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.6

Durability is a major issue in the widespread commercialization of proton exchange membrane fuel cells (PEMFCs). Various failure modes have been identified over their long runtime. These mainly originate from membrane and catalyst layer failures. One of the most common failure modes in PEMFCs is due to pinhole formation in the membrane and resultant reactant gas crossover through the membrane. Gas crossover induces several critical problems in PEMFCs, including severe reactant depletion in the downstream regions, mixed potential at the electrodes, and formation of local hot spots by hydrogen/oxygen catalytic reaction, which indicates that the cell performance decreases with increasing gas crossover. In this study, we numerically investigate the effects of gas crossover on the performance of a high-temperature PEMFC based on a phosphoric-acid-doped polybenzimidazole (PBI) membrane. In contrast to previous gas-crossover studies [1,2] in which uniform gas crossover throughout the entire membrane has been simply assumed, our focus is on examining the impacts of localized gas crossover due to membrane pinholes. Numerical simulations are carried out via arbitrarily assuming pinholes in the membrane. The simulation results clearly show that the presence of pinholes in the membrane significantly disrupts the species, current density, and temperature distributions. Our findings may improve the fundamental and detailed understanding of localized gas-crossover phenomena through the membrane pinholes and the influence of these phenomena on high-temperature PEMFC operation.

국내 푸드메틱(Foodmetic) 패키지디자인 트렌드에 관한 연구

강용원 한국일러스아트학회 2021 조형미디어학 Vol.24 No.3

The domestic cosmetics market is also paying attention to the domestic cosmetics market under the name K-Beauty. Foodmetics has become a genre in the cosmetics industry. However, while research and development of cosmetics are actively carried out, research on foodmetics is insufficient. Therefore, in this study, we are going to analyze the trend of package design of foodmetics in Korea. In addition, the company wants to know the current status of cosmetics items of Foodmetic. The scope of the study was limited to six brands with experience in selling out foodmetics in Korea. In the process, we would like to divide it into two categories: food exterior design crossover and food brand crossover. Food exterior design crossover includes Tonymoly fruit-shaped hand cream, It's Skin Macaron Lip Balm, and Labiotte wine tint, while crossover with food brands includes Round Around X Binggrae Banana Milk Body Care, Korea Yakult Haru Vegetable Mask Pack and The Saem X Choco Pie Hand Cream. According to the analysis with the crossover trend map, Tony Moly's fruit-shaped hand cream among crossover designs and The Saem X Choco Pie hand cream among crossover brands are located on the same line on the crossover trend map. These results can be analyzed that Tony Moly's fruit-type hand cream, the beginning of Foodmetic, and The Saem X Choco Pie hand cream, which revolutionized crossover with food brands, continued the same trend in that they created new values in the cosmetics market. As a result, Foodmetic's package design has the advantage of creating creative value and bringing familiarity with existing food brands. Foodmetic, which has become a genre of cosmetics, is presented as a way to move toward a differentiated strategy of cosmetics package design in the future and is expected to be used as basic data. 국내 화장품 시장은 K-Beauty 라는 명칭으로 해외에서도 국내 화장품 시장을 주목하고 있다. 이러한 화장품 산업에서 하나의 장르처럼 푸드메틱(Foodmetic)이 자리잡게 되었다. 하지만 화장품에 대한 연구와 개발은 활발히 이루어지지만 푸드메틱(Foodmetic)이라는 분야는 연구가 미흡한 실정이다. 따라서 본 연구에서는 국내 푸드메틱(Foodmetic)의 패키지디자인의 트렌드에 대해서 분석하고자한다. 더불어 푸드메틱(Foodmetic)의 화장품 품목에 대한 현황도 파악하고자 한다. 연구의 범위는 국내 푸드메틱(Foodmetic)의 완판된 경험이 있는 브랜드 6가지로 한정하여 진행하였다. 그 과정에서 푸드 외관 디자인의 크로스오버, 푸드 브랜드와의 크로스오버로 두 분야로 분류해서 진행하고자 한다. 푸드 외관 디자인의 크로스오버에는 토니모리 과일 형태 핸드크림, 잇츠스킨 마카롱 립밤, 라비오뜨 와인 틴트가 있으며, 푸드 브랜드와의 크로스오버에는 라운드어라운드 X 빙그레 바나나우유 바디케어, 한국야쿠르트 하루야채 마스크팩, 더샘 X 초코파이 핸드크림이 있다. 크로스오버 트렌드 맵으로 분석한 결과 푸드 외관 디자인의 크로스오버 중 토니모리 과일형태 핸드크림과 푸드 브랜드와의 크로스오버 중 더샘 X 초코파이 핸드크림은 크로스오버 트렌드 맵에서 동일한 선상에 위치하고 있다. 이러한 결과는 푸드메틱(Foodmetic)의 시초라고 할 수 있는 토니모리 과일형태 핸드크림과 푸드 브랜드와의 크로스오버의 혁신을 일으켰던 더샘 X 초코파이 핸드크림은 화장품 시장에서 새로운 가치를 창출했다는 점에서 동일한 트렌드를 이어 나갔다라고 분석할 수 있다. 결과적으로 푸드메틱(Foodmetic)의 패키지디자인은 창조적 가치를 창출 할 수 있으면서, 기존의 푸드 브랜드의 친근감을 가지고 올 수 있는 장점을 지니고 있다. 화장품의 하나의 장르로 자리잡은 푸드메틱(Foodmetic)으로 향후 화장품 패키지디자인의 차별화된 전략으로 나아가기 위한 방안으로 제시하고 기초자료로 활용되기를 기대해본다.

Crossover of emotions among dual-earner couples and the quality of their marital relationship

김여진 연세대학교 사회복지연구소 2009 한국사회복지조사연구 Vol.20 No.-

The link between work life and family life is an essential subject matter in understanding the lives of dual-earner couples. Concepts of crossover explains the link between work and family. The present study examines both the positive and negative sides in these processes. Moreover, this study looks at the extent to which the quality of marital relationships play moderating roles in the processes of crossover. The data come from the Sloan Working Families Study conducted by the Alfred P. Sloan Center on Parents, Children, and Work and NORC at the University of Chicago. The Experience Sampling Method employed explores directly the daily life experiences of the participants. The data were analyzed using t-test. Crossover were found in the lives of dual-earner couples in this study. Men appear responsive to the positive and negative emotional experiences their spouse brings home, especially if highly satisfied with their marriage. But, women were found to be responsive to their spouses’ negative emotional experiences at work, but not to their spouses’ positive emotional experiences. By looking closely into the emotions experienced by working parents in their daily lives, this study adds contextual understanding concerning the link between work and family life. The findings on husbands who are highly satisfied with their marriage invite social work practitioners and researchers to further investigate the phenomena of crossover processes in greater detail, taking into account of contextual aspect of family life such as gender role attitudes of the couples, and the children at home. The link between work life and family life is an essential subject matter in understanding the lives of dual-earner couples. Concepts of crossover explains the link between work and family. The present study examines both the positive and negative sides in these processes. Moreover, this study looks at the extent to which the quality of marital relationships play moderating roles in the processes of crossover. The data come from the Sloan Working Families Study conducted by the Alfred P. Sloan Center on Parents, Children, and Work and NORC at the University of Chicago. The Experience Sampling Method employed explores directly the daily life experiences of the participants. The data were analyzed using t-test. Crossover were found in the lives of dual-earner couples in this study. Men appear responsive to the positive and negative emotional experiences their spouse brings home, especially if highly satisfied with their marriage. But, women were found to be responsive to their spouses’ negative emotional experiences at work, but not to their spouses’ positive emotional experiences. By looking closely into the emotions experienced by working parents in their daily lives, this study adds contextual understanding concerning the link between work and family life. The findings on husbands who are highly satisfied with their marriage invite social work practitioners and researchers to further investigate the phenomena of crossover processes in greater detail, taking into account of contextual aspect of family life such as gender role attitudes of the couples, and the children at home.

대칭 순회 판매원문제를 위한 Subtour 보존 교차 연산자

석상문(Sang-Moon Soak),이홍걸(Hong-Girl Lee),변성철(Sung-Cheal Byun) 대한산업공학회 2007 대한산업공학회지 Vol.33 No.2

Genetic algorithms (GAs) are very useful methods for global search and have been applied to various optimization problems. They have two kinds of important search mechanisms, crossover and mutation. Because the performance of GAs depends on these operators, a large number of operators have been developed for improving the performance of GAs. Especially, many researchers have been more interested in a crossover operator than a mutation operator. The reason is that a crossover operator is a main search operator in GAs and it has a more effect on the search performance. So, we also focus on a crossover operator. In this paper we first investigate the drawback of various crossovers, especially subtour-based crossovers and then introduce a new crossover operator to avoid such drawback and to increase efficiency. Also we compare it with several crossover operators for symmetric traveling salesman problem (STSP) for showing the performance of the proposed crossover. Finally, we introduce an efficient simple hybrid genetic algorithm using the proposed operator and then the quality and efficiency of the obtained results are discussed.

효모 감수분열과정에서의 유전자 재조합 기전 특이적 DNA 중간체의 구조 변화

성영진,윤상욱,김근필,Sung, Young Jin,Yoon, Sang Wook,Kim, Keun Pil 한국미생물학회 2013 미생물학회지 Vol.49 No.1

유전자 재조합체는 상동염색체간의 예정된 DNA 가닥 전이와 교환이 이루어지는 상동염색체 재조합 과정에 의하여 생성된다. 이 재조합 경로는 DNA 이중 가닥 절단(double-strand breaks, DSBs)에 의해서 개시되며, 전이 과정의 중간단계에서 DNA의 구조적 변이 중간체인 단일 가닥 침투(single-end invasions, SEIs)와 이중 홀리데이 접합(double-Holliday junctions, dHJs)이 형성되어 교차성(crossover, CO) 혹은 비교차성(non-crossover, NCO) 결과물이 만들어진다. 본 연구는 이중 가닥 절단, 단일 가닥 침투, 이중 홀리데이 접합과 같은 재조합 중간체와 재조합 결과물의 구조분석에 초점을 두고, 이를 출아효모에서 인위적으로 이중 가닥 절단을 발생시킬 수 있는 HIS4LEU2 "hot spot" 을 이용한 물리적 분석방법으로 감수분열 재조합 중간체를 규명하였다. 물리적 분석을 위하여 동조화 된 세포에 감수분열을 유도한 후 hot spot 자리를 인식하는 제한효소를 처리하면, 재조합 중간체를 형성하고 있는 DNA 단편들을 Southern 분석법을 통해 탐지 및 정량 할 수 있다. 본 연구는 이 시스템으로 감수분열에서 이중가닥 절단으로부터 기인하는 단일 가닥 침투, 이중 홀리데이 접합 그리고 교차성/비교차성 재조합체로 전이되는 DNA의 구조 다형을 분석할 수 있음을 제시한다. During meiosis, genetic recombinants are formed by homologous recombination accompanying with the programmed double-strand breaks (DSBs) and strand exchanges between homologous chromosomes. The mechanism is generated by recombination intermediates such as single-end invasions (SEIs) and double-Holliday junctions (dHJs), and followed by crossover (CO) or non-crossover (NCO) products. Our study was focused on the analysis of meiotic recombination intermediates (DSBs, SEIs, and dHJs) and final recombination products (CO and NCO). We identified these meiotic recombination intermediates using DNA physical analysis under HIS4LEU2 "hot spot" system in budding yeast, Saccharomyces cerevisiae. For DNA physical analysis, when the hot spot locus is recognized by restriction enzyme from synchronous meiotic cells, the fragmented DNA that are forming recombination intermediates can be detected and quantified through Southern hybridization analysis. Our study suggests that this system can analyze the structural change of recombination intermediates during DSB-SEI transition, double-Holiday junctions and crossover/non-crossover products in meiosis.

Simulation and Validation of Methanol Crossover in DMFCs

고요한(Ko, Johan),주현철(Ju, Hyunchul) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

In direct methanol fuel cells(DMFCs), it is well known that methanol crossover severely reduces the cell performance and the cell efficiency. There are a number of design and operating parameters that influence the methanol crossover. This indicates that a DMFC demands a high degree of optimization. For the successful design and operation of a DMFC system, a better understanding of methanol crossover phenomena is essential. The main objective of this study is to examine methanol-crossover phenomena in DMFCs. In this study, 1D DMFC model previously developed by Ko et al. is used. The simulation results were compared with methanol-crossover data that were measured by Eccarius et al. The numerical predictions agree well with the methanol crossover data and the model successfully captures key experimental trends.

고분자 연료전지에서 산소 크로스오버 특성에 관한 연구

백경돈(Kyung Don Baik),김성일(Sung Il Kim),공임모(Im Mo Kong),김민수(Min Soo Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Gas crossover through the membrane is well known phenomena in PEM fuel cells. Characterization of oxygen crossover which represents the permeation was investigated in this study. Oxygen crossover from the cathode side to the anode side causes the carbon corrosion which affects the fuel cell durability. Thus it is important to analyze the characterization of oxygen crossover in PEM fuel cells at various conditions such as different cell temperature and relative humidity of supplying gases. In this study, mass spectrometer has been applied at anode exit stream to measure the amount of oxygen crossover at OCV condition. Instead of supplying hydrogen gas, helium gas was supplied at anode side because helium gas does not react with oxygen gas at anode side. Results show that temperature and relative humidity affect the oxygen crossover. As temperature increases, anode exit concentration of oxygen decreases due to the change of oxygen concentration at cathode side.

교차주문을 갖는 리드타임 분포의 분석

김기태(Gitae Kim) 한국산업경영시스템학회 2021 한국산업경영시스템학회지 Vol.44 No.4

In supply chain, there are a variety of different uncertainties including demand, service time, lead time, and so forth. The uncertainty of demand has been commonly studied by researchers or practitioners in the field of supply chain. However, the uncertainty of upstream supply chain has also increased. A problem of uncertainty in the upstream supply chain is the fluctuation of the lead time. The stochastic lead time sometimes causes to happen so called the order crossover which is not the same sequences of the order placed and the order arrived. When the order crossover happens, ordinary inventory policies have difficult to find the optimal inventory solutions. In this research, we investigate the lead time distribution in case of the order crossover and explore the resolutions of the inventory solution with the order crossover.

철-크롬 산화환원흐름전지에서 Nafion막의 철-크롬 Crossover

김영숙,오소형,김은비,김다영,김성지,추천호,박권필,Kim, Young-Sook,Oh, So-Hyeong,Kim, Eunbi,Kim, Dayoung,Kim, Seongji,Chu, Cheun-Ho,Park, Kwonpil 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.1

산화환원흐름전지(Redox Flow Battery, RFB)는 대용량 에너지 저장장치로 바나듐 산화환원흐름전지가 대표적인 RFB인데, VRFB는 고가인 점이 문제다. 철-크롬RFB는 저가의 활물질을 사용해 경제적인 점이 장점인데, 성능이 낮은 점이 해결해야할 과제다. 낮은 성능의 한 원인이 활물질의 크로스오버인데, 본 연구에서 철과 크롬 이온의 Nafion 막 크로스오버 및 Nafion 막의 안정성에 대해 실험하였다. 철과 크롬이온의 Nafion 막 투과도는 각각 $5.5{\times}10^{-5}$, $6.0{\times}10^{-5}cm^2/min$ 이었다. Nafion 막에서 바나듐 이온의 투과도 $2.9{\times}10^{-6}cm^2/min$ 보다 18.9~20.7배 높아 철과 크롬 이온의 Nafion 막 크로스오버가 성능 저하의 한 원인임을 보였다. 온도 증가에 따라 크로스오버가 급증(활성화 에너지 38.8 kJ/mol)하므로 낮은 온도에서 구동하는 것이 크로스오버에 의한 성능감소를 저하시키는 방법임을 나타냈다. Nafion막은 3M HCl용액에서 비교적 안정적이었다. The redox flow battery (RFB) is a large-capacity energy storage equipment, and the vanadium redox flow cell is a typical RFB, but VRFB is expensive. Iron-chrome RFBs are economical because they use low-cost active materials, but their low performance is a urgent problem. In this study, the crossover of iron and chromium ion through Nafion membrane and the stability of Nafion membrane in HCl solution were investigated. The permeability of iron and chrome ion through Nafion were $5.5{\times}10^{-5}$ and $6.0{\times}10^{-5}cm^2/min$, respectively, which was 18.9~20.7 times higher than that of vanadium ion ($2.9{\times}10^{-6}cm^2/min$). The crossover of iron and chromium ions were shown to be a cause of performance decrease in Iron-chrome RFB. As the temperature increases, the crossover increases rapidly (activation energy 38.8 kJ/ mol), indicating that operation at low temperature is a methode to reduce the performance loss due to crossover. Nafion membranes were relatively stable in 3 M HCl solution.