Recent developmental status and prospects of hydrogen refueling stations

( Wang Lai Yoon ),( Dong Joo Seo ) 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1

Hydrogen refueling infrastructure to support the introduction of fuel cell and other hydrogen(and hydrogen mixture)-fueled vehicles is seen as one of the key factors for the transition to the hydrogen economy. Basically, hydrogen station can be configured by any combination of six modules : hydrogen generator, purifier, compression, storage, dispenser and power generator. And there can be several ways in hydrogen delivery for use at refueling stations. In the early demonstration phase, the use of distributed hydrogen refueling system(cryogenic liquid hydrogen, compressed hydrogen, reforming of hydrocarbonfeedstocks such as natural, gas, LPG and naphtha, electrolysis of water) may be a intermediate pathways to infrastructure development with future development of hydrogen pipeline delivery. The understanding of the implications of each system as well as comparisons between the choices of generation methods for use is essential in developing the refueling infrastructure. In this session, we present the recent developmental status and prospects of hydrogen refueling stations in advanced countries such as America, Japan, and Europe. Especially, national demonstration programs to promote early introduction of hydrogen fueled vehicles are reviewed.

수소 인프라 구축을 위한 스테이션 기술개발 동향 및 전망

윤왕래(Wang Lai Yoon),서동주(Dong Joo Seo) 대한설비공학회 2004 대한설비공학회 학술발표대회논문집 Vol.2004 No.-

고순도 수소생산 스키드 유닛 국산화 및 스케일-업 설계

윤왕래(Wang Lai Yoon),서동주(Dong Joo Seo),박상호(Sang Ho Park),김우현(Woohyun Kim),김두욱(Doo-Wook Kim),하동수(Dong Su Ha),김영지(Young Ji Kim) 한국에너지기후변화학회 2022 한국에너지기후변화학회 학술대회 Vol.2022 No.10

5㎾급 고분자연료전지용 천연가스 개질기 시스템 운전 특성 연구

윤왕래,박종원,이영우,한명완,정진혁,박종수,정헌,이호태,김창수 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.3

가정용 고분자 연료전지 스택운전에 필요한 수소공급기술로서 천연가스 수증기 개질법에 기초한 5k급 열 및 시스템 통합형 연료개질기 시작품을 설계 및 제작하였다. 수증기 개질에 필요한 흡열 반응열은 복사 전열 방식의 metal fiber burner를 이용하여 공급하였다. 시스템 성능은 각 반응기의 일정한 공간속도 및 상압조건 하에서 개질기 반응온도 600-800℃에서 운전결과를 토대로 평가하였다. 최종시작품인 β+ 형에 있어서 개질가스 총유량은 6.5N㎥/h(H_2 농도: 74%, 건식 기준)이었으며 이때의 수증기 개질 반응기에 있어서 반응온도 및 GHSV는 각기 800℃, 1,950 h^-1이었다. 그리고 개질기 출구(혹은 스택 입구) 제한조건인 CO 농도를 맞추기 위하여 2단 직렬 선택적 산화 반응기(1단 : P_t, 2단 : Ru)를 구성하였으며, 1단과 2단 반응기 사이에 공냉식 핀(fin) 형 열교환기를 설치하여 1단 반응기에서 배출되는 개질가스의 온도를 저온(120℃)으로 제어 유지시킨 후 2단 PrOx 반응기로 공급함으로써 최종 개질가스 중의 일산화탄소의 농도를 10ppm 이하로 낮출 수 있었다. 연료 개질 효율(개질된 수소의 고발열량/리포머 및 버너에 공급된 천연가스의 고위발열량×100%)은 약 52% 정도로서 약간 낮은 편이며 이는 리포머 열공급을 위한 버너 연소열이 시스템 외부로 과도하게 배출되는 것에 기인하였다. Prototype 5 kW-class fuel processor based on steam reforming of natural gas with heat and system integration has been designed and fabricated for use in proton exchange membrane(PEM) fuel cell with residential applications. Endothermic heat for steam reforming has been supplied by radiation type metal fiber burner. The performance of the integrated system has been experimentally evaluated for the reformer temperature of 600-800℃ at constant GHSV of each reactor and atmospheric system pressure. The final product(β^= type) can produce the total gas flow of 6.5 6.5N㎥/h(H_2 conc.: 74%, dry basis) under reformer temperature and space velocities of 800℃, 1,950 h^-1, respectively and also remove CO concentration under 10 ppm by two series fin type packed beds employing Pt[λ2O_2/CO)=2.1] and Ru[λ(2O_2/CO)=3.5] catalysts with interstage cooling. The overall fuel processing efficiency of about 52% calculated by the total H_2 output after PrOx to total methane flow into the reformer and the burner based upon higher heating values is somewhat lower. This was mainly attributed from the fact that heat loss from the exhaust gas after supplying heat necessary for raising the reformer temperature by combustion of natural gas was excessively high.

A Study on Proper Location of Welding Defect in Three Point Bend Testing with MDPE Pipe

Lai, Huan Sheng,Yoon, Kee Bong,Kil, Seong Hee The Korean Society for Energy 2015 에너지공학 Vol.24 No.1

Welding defects affect the performance of welded pipe joints. In this study, a three point bend test of welded steel and medium density polyethylene (MDPE) pipe joints with defects of various defect locations and defect materials was studied using the finite element method. The defect was assumed to be located at 12 o'clock, 3 o'clock or 6 o'clock direction. The results showed that pipes failed more easily on the compression side due to stress or local buckling. The air defect was more dangerous than the steel defect if the defect was located in the compression side; otherwise, the defect material effect on the integrity of pipes was ignorable. It is argued that the integrity of pipes with defects in the compression side is weaker than that in other regions, and the defect should be located in the compression side or the 12 o'clock position in the three point bend test to maximize the effect of defect existence on the pipe structural integrity.

Imaging and Clinicopathologic Characteristics of Breast Cancers in Younger Group Compared to in Old Group

Yoon Jung Choi,Shin-Ho Kook,Hyon Joo Kwag,Yong Lai Park 한국유방암학회 2009 Journal of breast cancer Vol.12 No.2

Purpose: We wanted to evaluate the difference of the images and the clinicopathological characteristics of young-age female breast cancer patients as compared to older Korean women with breast cancer. Methods: A total of 351 breast cancers cases during the previous 3 years were evaluated. A cut-off level of 40 years was used to divide the patients into the young (≤40 years, 86 cases, 24.5%) and older groups (>40 years, 265 cases, 75.5%). We reviewed the BI-RADS results, the sensitivity of mammography (MMG) and sonography (US), the presenting symptoms, the histopathological type, the post-operative stage and the receptor status. These factors were compared between the young age group and the older age group. Chi-squared tests were used for statistical analysis. Results: BI-RADS category 1 disease on the MMG (12.8% vs 6.4%, respectively) and BI-RADS category 3 disease on the US (3.5% vs 1.1%) were more common for the younger group as compared to the older group. The sensitivity of MMG and US was lower for the younger group than for the older group (69.2% and 82.3% vs 84.5% and 93.3%, respectively). Clinical symptom, histopathology, final stage, and the size of tumor or receptor status did not show statistical significant differences. Conclusion: Imaging young women breast cancers were less sensitive, more frequently assessed as normal on MMG and as more probably benign on US, and no clinicopathological differences were shown.

Study on the estimation of high temperature fracture parameter for mismatched weld creep cracks

Lai, H.S.,Yoon, K.B. Pergamon Press 2016 Engineering fracture mechanics Vol.163 No.-

<P>Evaluation of the creep crack growth is very important for predicting the life of high temperature structures. Since C-t can uniquely characterize creep crack growth from the small scale creep stage to the extensive steady state creep stage, an engineering estimation method of C-t was proposed for a crack located in the weld with mismatched material properties between the base material and the weld material based on the simulation results of compact tension specimens. For the crack located in the center of welding seam, C-t was estimated by the proposed method under the small scale creep stage and by the reference stress method under the extensive steady state creep stage; in this way, C-t was estimated under the whole creep stage. The estimated results agreed well with the simulation results if the width of welding seam of h was no smaller than the size of the stress intensity factor dominance zone. (C) 2016 Elsevier Ltd. All rights reserved.</P>

The synaptotagmin 1 linker may function as an electrostatic zipper that opens for docking but closes for fusion pore opening.

Lai, Ying,Lou, Xiaochu,Jho, Yongseok,Yoon, Tae-Young,Shin, Yeon-Kyun Biochemical Society 2013 The Biochemical journal Vol.456 No.1

<P>Syt1 (synaptotagmin 1), a major Ca2+ sensor for fast neurotransmitter release, contains tandem Ca2+-binding C2 domains (C2AB), a single transmembrane α-helix and a highly charged 60-residue-long linker in between. Using single-vesicle-docking and content-mixing assays we found that the linker region of Syt1 is essential for its two signature functions: Ca2+-independent vesicle docking and Ca2+-dependent fusion pore opening. The linker contains the basic-amino-acid-rich N-terminal region and the acidic-amino-acid-rich C-terminal region. When the charge segregation was disrupted, fusion pore opening was slowed, whereas docking was unchanged. Intramolecular disulfide cross-linking between N- and C-terminal regions of the linker or deletion of 40 residues from the linker reduced docking while enhancing pore opening, although the changes were subtle. EPR analysis showed Ca2+-induced line broadening reflecting a conformational change in the linker region. Thus the results of the present study suggest that the electrostatically bipartite linker region may extend for docking and fold to facilitate pore opening.</P>

Phase IIb multicentred randomised trial of besifovir (LB80380) versus entecavir in Asian patients with chronic hepatitis B

Lai, Ching-Lung,Ahn, Sang Hoon,Lee, Kwan Sik,Um, Soon Ho,Cho, Mong,Yoon, Seung Kew,Lee, Jin-Woo,Park, Neung Hwa,Kweon, Young-Oh,Sohn, Joo Hyun,Lee, Jiyoon,Kim, Jeong-Ae,Han, Kwang-Hyub,Yuen, Man-Fung BMJ Publishing Group Ltd 2014 Gut Vol.63 No.6

<P><B>Background</B></P><P>Besifovir (LB80380) is an acyclic nucleotide phosphonate effective in hepatitis B virus (HBV) DNA suppression for both treatment-naive and lamivudine-resistant chronic hepatitis B (CHB) patients in preliminary studies.</P><P><B>Design</B></P><P>We aimed to compare the safety and antiviral activity of two doses of besifovir (90 mg and 150 mg daily) with entecavir 0.5 mg daily in CHB patients. 114 patients were randomised to receive besifovir 90 mg daily (n=36), besifovir 150 mg daily (n=39) or entecavir 0.5 mg daily (n=39). HBV DNA and liver biochemistry, including serum L-carnitine levels, were monitored.</P><P><B>Results</B></P><P>At week 48, in the intention-to-treat population, the proportion of patients achieving undetectable HBV DNA (<20 IU/mL) were 63.6%, 62.9% and 58.3%, respectively (p>0.05). The serum mean log<SUB>10</SUB> HBV DNA changes from baseline for the HBeAg-positive patients were −5.84, −5.91 and −6.18, respectively; and for the HBeAg-negative patients were −4.65, −4.55 and −4.67, respectively (p>0.05). There were no differences in the proportions of patients achieving normalisation of alanine aminotransferase (91.7%, 76.9%, 89.7%, respectively) and HBeAg seroconversion (11.11%, 15%, 9.52%, respectively) among all three groups. None of the patients had resistant mutations or increase in serum creatinine of >0.5 mg/dL from baseline. 64 (94.1%) patients on besifovir had lowering of serum L-carnitine (not tested in entecavir patients). L-carnitine levels returned to normal with carnitine supplement.</P><P><B>Conclusions</B></P><P>At 48 weeks, 90 mg and 150 mg daily of besifovir were non-inferior to entecavir 0.5 mg daily in treatment-naive CHB patients. The only significant side effect of besifovir was L-carnitine depletion, requiring carnitine supplementation.</P>

Estimation of <i>C</i>(<i>t</i>) and the creep crack tip stress field of functionally graded materials and verification via finite element analysis

Lai, Huan Sheng,Yoon, Kee Bong Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.153 No.-

<P><B>Abstract</B></P> <P>Functionally graded materials (FGMs) are increasingly being used in high-temperature structural components. The time-dependent <I>C</I>-integral, <I>C</I>(<I>t</I>), is a significant parameter in characterizing the crack tip stress field from the small-scale to the extensive steady-state creep stages. In this paper, the creep crack behavior of FGMs with a crack parallel to the material property gradients was studied by using the finite element method. It was proven that <I>C</I>(<I>t</I>) remained valid for FGMs. An engineering method was proposed to estimate <I>C</I>(<I>t</I>) in the small scale and transition creep stages and estimate the crack tip stress field. Finite element results verified that the method could estimate <I>C</I>(<I>t</I>) in the small scale and transition creep stages and estimate the crack tip stress field. For cases with creep properties that increased in the crack growth direction, the effect of constraint on the estimated crack tip stress field had to be considered. The constraint parameter of <I>Q</I> was significantly affected by the creep property gradients. The method was independent of the gradient variation law of material properties.</P>