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Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave
Byun, Sun-Joon,Kwak, Dong-Kurl The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.2
Energy is an essential driving force for modern society. In particular, electricity has become the standard source of power for almost every aspect of life. Electric power runs lights, televisions, cell phones, laptops, etc. However, it has become apparent that the current methods of producing this most valuable commodity combustion of fossil fuels are of limited supply and has become detrimental for the Earth's environment. It is also self-evident, given the fact that these resources are non-renewable, that these sources of energy will eventually run out. One of the most promising alternatives to the burning of fossil fuel in the production of electric power is the proton exchange membrane (PEM) fuel cell. The PEM fuel cell is environmentally friendly and achieves much higher efficiencies than a combustion engine. Water management is an important issue of PEM fuel cell operation. Water is the product of the electrochemical reactions inside fuel cell. If liquid water accumulation becomes excessive in a fuel cell, water columns will clog the gas flow channel. This condition is referred to as flooding. A number of researchers have examined the water removal methods in order to improve the performance. In this paper, a new water removal method that investigates the use of vibro-acoustic methods is presented. Piezo-actuators are devices to generate the flexural wave and are attached at end of a cathode bipolar plate. The "flexural wave" is used to impart energy to resting droplets and thus cause movement of the droplets in the direction of the traveling wave.
SMART-ITL 안전주입배관 파단시 노심보충수탱크 주입성능에 관한 실험적 연구
변선준(Sun-Joon Byun),배황(Hwang-Bae),류성욱(Sung-Uk Ryu),전병국(Byong-Guk Jeon),유효봉(Hyo-Bong Ryu),민경호(Kyoung-Ho Min),방윤곤(Yun-Kon Bang),전우진(Woo-Jin Jeon),이성재(Sung-Jae Yi),박현식(Hyun-Sik Park) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
System-integrated modular advanced reactor (SMART) is an integral-type nuclear reactor which received its design certificate in 2012 for the first time in the world. Currently, to improve its safety level, passive safety systems are designed and their performance has been evaluated. In this study, to examine the injection characteristics of a core makeup tank, a small-break loss of coolant accident is simulated using the SMART integral test loop (SMART-ITL). The experimental results provide more understanding on the behaviors of core makeup tanks (CMTs) as well as supporting future licensing process.
A novel synthesis route for Pt-loaded SnO2 nanofibers and their sensing properties.
Byun, Joon-Hyuk,Katoch, Akash,Choi, Sun-Woo,Kim, Jae-Hun,Kim, Sang Sub American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.11
<P>A novel one-pot synthesis method for Pt-loaded SnO2 nanofibers is reported on the basis of the sol-gel and electrospinning-combined process. The ultraviolet illumination was used for in-situ growth of Pt nanoparticles in the electrospinning solution. The sensing capability of pure SnO2 nanofibers was significantly improved by loading Pt nanoparticles. The Pt-loaded SnO2 nanofibers showed a good selectivity to toluene gas. The optimization of Pt amount in SnO2 nanofibers was essential to obtain best sensing performances. The one-pot synthesis method developed in this work may extend the use of oxide nanofibers in chemical gas sensors.</P>
Sun-Joong Yoon,Suk Joon Byun 한국재무학회 2008 한국재무학회 학술대회 Vol.2008 No.05
본 논문은 옵션시장을 통해 유추되는 투자자의 위험회피도가 여러 옵션시장에 대해서 다르 다는 사실을 보이고 이러한 차이가 개인투자자의 기술적분석(technical analysis)에 의한 행태 에 의해 나타날 수 있음을 보인다. 개인투자자의 비율이 개괄적으로 알려진 S&P 500 주가지 수 옵션시장, Nikkei 225 주가지수옵션시장, KOSPI 200 주가지수옵션시장을 본 연구의 대상으 로 선택하여 각 옵션시장의 위험회피도가 개인투자자의 비율과 역의 관계를 가지고 있음을 보였다. 이들 개인투자자는 선행연구들에서 보인 바와 같이 주식의 과거 움직임을 이용한 거래 혹은 방향성 투자(directional trade)를 주로 사용함을 전제로, 이때 이러한 투자행태가 위 험회피도에 영향을 준다는 사실을 시뮬레이션(simulation)을 통해 증명하였다.
Paper : Stitching Effect on Flexural and Interlaminar Properties of MWK Textile Composites
( Joon Hyung Byun ),( Yi Qi Wang ),( Moon Kwang Um ),( Sang Kwan Lee ),( Jung Il Song ),( Byung Sun Kim ) 한국복합재료학회 2015 Composites research Vol.28 No.3
The stitching process has been widely utilized for the improvement of through-thickness property of the conventional laminated composites. This paper reports the effects of stitching on the flexural and interlaminar shear properties of multi-axial warp knitted (MWK) composites in order to identify the mechanical property improvements. In order to minimize the geometric uncertainties associated with the stacking pattern of fabrics, the regular lay-up was considered in the examination of the stitching effect. The key parameters are as follows: the stitch spacings, the stitching types, the stitching location, and the location of compression fixture nose. These parameters have little effect on the flexural and interlaminar shear properties, except for the case of stitching location. However, the geometry variations caused by the stitching resulted in minor changes to the mechanical properties consistently. Stitching on the 0o fibers showed the lowest flexural strength and modulus (12% reduction for both properties). The stitch spacing of 5 mm resulted in 8% reduction for the case of interlaminar strength compared with that of 10 mm spacing.
변태준,이오영,양선영,박성현,현일식,이항락,한동수,전용철,윤병철,최호순,함준수,이흥우,박문향,임현철 한양대학교 의과대학 2002 한양의대 학술지 Vol.22 No.2
Type I neurofibromatosis (NF-1), first clearly described by von Recklinghausen in 1881, is a dominantly inherited neuroectodermal dysplagia occurring in one of 3,000 births. It is fundamentally characterized by the existence of multiple neurofibromas, 'cafe au lait' spots and Lisch nodules (pigmented hamartomas of the iris). NF-1 may affect the gastrointestinal tract in about 25% of cases. Most NF-1 are located in the jejunum or stomach. In up to 40% of patients, there may be acute or recurrent gastrointestinal bleeding. We report the case of a 36-year-old patient diagnosed as having NF-1 in the stool occult blood test accidentally that was located in ascending colon with a review of literature.
The Role of the Variance Premium in GARCH Option Pricing Models
Suk Joon Byun,Byoung-Hyun Jeon,Byungsun Min,Sun-Joong Yoon 한국재무학회 2014 한국재무학회 학술대회 Vol.2014 No.05
We develop a discrete-time option pricing model using a variance-dependent pricing kernel of Christoffersen, Heston and Jacobs (2013) under an economic framework allowing for dynamic volatility and dynamic jump intensity. Using this model, we examine the role of the variance premium and jump risk premium in explaining S&P 500 index option returns. Our results stress the importance of the variance premium in explaining the stylized characteristics of index option returns, including short-term option returns, which are insufficiently explained by extant option pricing models. In particular, the variance premium can explain both 1-month holding period returns of 2-month maturity straddles, which are significantly negative, and call returns, which decrease according to moneyness. Even though the jump risk premium emphasized in the previous literature is able to well fit the option prices, it does not improve the explanatory power for the above two stylized option returns. The outperformance of the variance premium stems from its ability to capture the wedge between physical and risk-neutral volatilities.
Analysis of reasons for extracting permanent teeth among Korean adults with oral diseases
( Jae-joon Byun ),( Eun-sun Jang ),( Dae-ryong Kong ),( Gyeong-je Lee ) 조선대학교 치의학연구원(구 조선대학교 구강생물학연구소) 2021 Oral Biology Research (Oral Biol Res) Vol.45 No.1
This study aimed to analyze the main reasons for the extraction of permanent teeth among Koreans with oral diseases. The electronic medical record data for past 10 years was used in a target population comprising of 26,795 adults diagnosed with oral disease and scheduled to undergo permanent tooth extraction. The oral diseases were classified into periodontal disease, dental caries, impacted teeth, prosthodontic treatment, orthodontic treatment, tooth fracture, trauma, and others. The relationship between these diseases and permanent tooth extraction was analyzed. Permanent teeth were extracted due to periodontal disease (34.5%), dental caries (26.6%), and tooth impactions (22.3%). Permanent teeth were extracted as the cause of dental caries (28.6%) and periodontal disease (45.9%) from patients in 26-35 and 46-55 years of age respectively. The mandibular first molars (17.2%), mandibular second molars (16.0%), maxillary first molars (14.7%), and maxillary second molars (14.3%) were extracted due to dental caries. The incidence of periodontal disease was highest in the mandibular central incisor (72.6%; p<0.05). These findings indicated that periodontal disease was the chief cause of extraction of permanent teeth among Korean adults.