Investigation of Hydrogen Crossover Phenomena during Operation of Proton Exchange Membrane Fuel Cell Systems

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 8. 김민수.In this study, the crossover phenomenon according to various parameters that have not been covered yet and during operation of proton exchange membrane fuel cell system were investigated to provide practical information and better understanding on thereof. Furthermore, the effect of the pinhole formation and the location of pinhole on hydrogen crossover were analyzed. For successful landing of proton exchange membrane fuel cell system on markets, durability is imperative issue to be improved. Since the crossover phenomenon is strongly related to degradation process of materials, in this sense, conducting the researches for more practical parameters and conditions where the real system operates are needed. However, the most of previous researches were limited because it just had concentrated on the relationship between operating parameters and gas crossover that difficult to know even reflect on system operation. Therefore, in this study, we are focused on the useful parameters and conditions to apply its results on real proton exchange membrane fuel cell system. Firstly, effects of the bipolar plate designs, relative humidity condition difference between anode and cathode and flow direction (co-flow, counter-flow) on hydrogen crossover rate under unloaded condition are experimentally investigated to complements previous researches by dealing with new topics. Through this research, it was found that the bipolar plate design can have an influence both on performance and crossover rate due to the pressure in channel. To identify the effect of the relative humidity condition precisely, not only effect of the relative humidity condition difference between anode and cathode but also the behavior under flooding is analyzed. The relative humidity of air has more effect on hydrogen crossover because the amount of supplied air is higher than that of hydrogen, and higher relative humidity accelerates more crossover rate. However, too much water contributes to blocking the porous of gas diffusion layer and leads to prevent gas crossover. Also, the influence of the flow direction on crossover rate is studied. From the result, even if the performance under the fully humidified condition has little difference between the co and counter-flows, the hydrogen crossover rate greatly differs between both cases due to the gas distribution in the cell. Furthermore, the effect of the clamping pressure, relative humidity condition, flow direction and stoichiometric ratio on hydrogen crossover rate are analyzed under the real system operation condition. The effect of the relative humidity condition, flow direction and stoichiometric ratio with specific condition is totally changed as the current density is increased. Through this research, the importance of measuring crossover rate under loaded condition will give an insight to the further research on crossover phenomenon. Lastly, effect of the pinhole formation on crossover rate is studied. It was found that even if the size of a pinhole is too small to detect its existence by the performance change, it can be confirmed by detecting hydrogen crossover rate under various current densities. In addition, the location of the damage of MEA can be analyzed through the hydrogen crossover rate pattern for loaded and unloaded condition. Greatly scattered hydrogen crossover pattern was measured for blemish at inlet and higher hydrogen crossover rate was detected for pinhole at outlet. Based on this result, it is determined that the membrane of anode inlet and outlet side have an important role in performance and hydrogen crossover. This can suggest the guideline for manufacturing process of MEA that which part should be made carefully and strongly. Furthermore, judgement method for pinhole existence with four different parameters was proposed to provide detecting technique for MEA and stack manufacturers.Chapter 1. Introduction 1 1.1 Background of the study 1 1.2 Literature survey 4 1.3 Objectives and scopes 8 Chapter 2. Measurement of crossover rate under unloaded condition 10 2.1 Introduction 10 2.2 Gas crossover mechanism 11 2.3 Experimental apparatus and test procedure 14 2.3.1 Single cell preparation 14 2.3.2 Experimental apparatus 14 2.3.3 Mass spectrometer 17 2.3.4 Test procedure 17 2.4 Effect of the land/channel width ratio of bipolar plates 19 2.4.1 Bipolar plates 19 2.4.2 The electrochemical performance of PEMFCs 23 2.4.3 Hydrogen crossover rate of PEMFCs 28 2.4.4 Anode inlet pressure of PEMFCs 33 2.5 Effect of the relative humidity condition 34 2.5.1 Hydrogen crossover rate under different relative humidity conditions 34 2.5.2 Effect of the relative humidity condition difference between anode and cathode 37 2.5.3 Analysis on behavior of crossover rate under flooding 42 2.6 Effect of the flow direction 45 2.7 Summary 47 Chapter 3. Analysis on crossover phenomenon for various current densities 49 3.1 Introduction 49 3.2 Effect of the clamping pressure 49 3.3 Effect of the relative humidity condition 54 3.4 Effect of the flow direction 58 3.5 Effect of the stoichiometric ratio 62 3.6 Numerical analysis of crossover phenomenon under various current densities 68 3.7 Summary 69 Chapter 4. Effect of pinhole on the crossover at the membrane 72 4.1 Introduction 72 4.2 Pinhole formation processes 73 4.3 Preparation of materials 74 4.3.1 Preparation of the perforated MEA 74 4.3.2 Test procedure 75 4.4 Effect of formed pinhole on the membrane 75 4.4.1 The electrochemical performance of the perforated MEA 75 4.4.2 Hydrogen crossover rate of the perforated MEA 79 4.5 Effect of the location of pinhole on gas crossover 87 4.5.1 The electrochemical performance according to the location of pinhole 87 4.5.2 Hydrogen crossover rate according to the location of pinhole 92 4.6 Development for judgement method of pinhole existence 95 4.6.1 Open circuit voltage 95 4.6.2 Crossover rate 95 4.6.3 Overshooting under loaded conditions 96 4.6.4 High frequency ratio 96 4.7 Summary 98 Chapter 5. Concluding remarks 99 References 102 Abstract (in Korean) 112Docto

통원수술 환자를 위한 EBP기반 퇴원교육 콘텐츠 개발과 평가

학위논문(박사)--서울대학교 대학원 :간호대학 간호학과,2019. 8. 이인숙.통원수술 환자들은 당일수술 직후 바로 퇴원하며, 가정에서 의료전문가의 도움 없이 자가간호를 통해 수술 후 회복 과정을 거친다. 퇴원 후 환자들은 신체적, 정신적 증상을 겪으며, 일상생활에서 어려운 상황에 직면하기 때문에 자가 관리를 통해 최상의 수술 결과에 도달할 수 있도록 간호사의 효과적인 퇴원교육이 무엇보다 중요하다. 이에 본 연구에서는 퇴원하는 환자에게 적용할 수 있는 퇴원교육 콘텐츠를 EBP를 기반으로 개발하고, 그 효과를 평가하고자 시도되었다. 본 연구의 EBP기반 퇴원교육 콘텐츠(EBP-DECA) 개발을 위해 존스홉킨스 대학의 근거기반실무(JHNEBP)모델의 19단계를 본 연구에 맞게 9단계로 수정하였다. 9단계는 문제의 정의, EBP 질문 개발, 근거 구축, 근거의 질 평가, 근거 요약, 근거의 질 합성, 근거 기반 콘텐츠, 콘텐츠의 적절성 검증, 결과 평가의 단계로 구성되었다. EBP-DECA의 근거를 수집하기 위하여 국내와 국외 DB 검색을 통한 통합적 문헌고찰을 시행하였고, 환자 요구도 조사와 임상전문가 요구도 조사를 실시하였다. 선정된 문헌의 자료 분석 후, 각 문헌에서 통원수술 환자의 퇴원교육 콘텐츠에 적합한 내용을 추출하였으며, 통합적 문헌고찰과 관련 가이드라인의 검색, 전문가와 환자의 요구도 조사를 통합하고 분석하여 EBP-DECA를 신체적 증상 관리, 정신적 증상 관리, 일상생활, 환경-감염 관리의 4가지 범주로 구성하였다. 개발된 EBP-DECA는 전문가 내용 타당도 조사와 AGREE 평가 도구를 통한 질 평가를 거쳤으며, 전문가 내용 타당도는 모든 항목이 80% 이상이었고, AGREE 질 평가에서는 6개 범주 모두에서 70% 이상으로 나타났다. 본 연구는 개발한 EBP-DECA의 평가를 위해 비동등성 대조군 전후 시차설계의 유사실험연구를 실시하였다. 연구대상은 서울 소재 S병원 통원수술실에서 가장 다빈도로 이루어지고 있는 안과 백내장 수술, 산부인과 자궁내시경과 원추절제술, 외과 유방양성종양절제술을 받은 통원수술환자 실험군 30명과 대조군 30명을 대상으로 시행하였으며, 불안, 지식, 만족도, 병원재방문율, 수술부위감염률을 평가하였다. 분석 결과 EBP-DECA를 적용받은 실험군은 이전 퇴원교육을 진행한 대조군에 비해 수술 후 불안이 낮고(t=1.894, p=.030), 만족도 점수는 유의하게 높았으며(t=-10.212, p=.002), 30일간의 병원 재방문율과 수술 부위 감염 발생률은 낮았으나, 자가간호 지식에서는 통계적으로 유의한 차이가 나타나지 않았다. 의료의 효용성과 이용의 편의가 중시되며, 병원의 가동률을 높이기 위해 통원수술은 계속 증가할 것이다. 본 연구에서 개발된 EBP-DECA를 통해 통원수술환자들은 퇴원 후 나타날 수 있는 신체적인 증상 관리, 정신적인 증상 관리, 일상생활, 환경 관리가 이루어질 것이고, 임상 실무 현장과 환자의 자가간호 사이의 격차를 줄여 회복의 질을 향상될 것이다. 최상의 근거를 기반으로 한 퇴원교육 콘텐츠의 개발은 임상 실무와 학계 사이의 연구 활성화에 이바지할 것이며, 향후 통원 환자들이 퇴원 후 이용 가능한 지역사회의 맞춤형 포괄적 간호서비스 제도를 마련하도록 국가적 정책이 필요함을 제언한다.Ambulatory surgery patients are discharged immediately after the operation on that day and recovery occuring at home with little access to professional support. The patients can experience physical, mental symptoms and are confronted with difficult situations in daily life during home recovery. Therefore, discharge education of nurses is most important for self-management to reach the best results of surgery. The purpose of this study is to develop the discharge education contents and to evaluate the effect. In order to develop EBP-based discharge education contents (EBP-DECA) of this study, 19 stages of JHNEBP model were modified to 9 stages according to this study. The stages consisted of the define the problem, development and refine the EBP question, conduct internal and external search for evidence, appraise the level and quality of each piece of evidence, summarize the individual evidence, synthesize overall strength and quality of evidence, develop EBP-DECA for change based on evidence synthesis, determine feasibility of EBP-DECA and evaluate outcomes. We followed integrated review of literature searched for studies all databases based on PICO and conducted a survey of patient needs and a survey of clinical expert needs for evidence. After analyzing and synthesizing data, we were extracted the appropriate contents from each literature for discharge education contents of hospital patients. The EBP-DECA was divided into 4 categories: physical symptoms management, mental symptoms management, daily life management and environment-infection control. The EBP-DECA was evaluated expert verification and the AGREE evaluation tool. The results was over 80% for all items in expert contents validity and over 70% in the AGREE quality evaluation. This study was designed as a nonequivalent control group quasi-experimental study to evaluate the EBP-DECA. The purpose of this study was to evaluate the effects of discharge contents on postoperative anxiety, knowledge, satisfaction, hospital return visits and surgical site infection. We were collected the participants who underwent cataract surgery, hysteroscopy and conization and breast excision surgery in the 'S' hospital ambulatory surgery center in Seoul. The experimental group (n=30) was given EBP-DECA and the control group (n=30) was given current education. There were significant differences in postoperative anxiety (t=1.894, p=.030), satisfaction (t=-10.212, p=.002), hospital return visits and surgical site infection. But this finding was not statistically significant in knowledge. The volume and diversity of day surgery will continue to increase in order to healthcare cost and patient preference for minimal stay. The EBP-DECA will provide information about physical and mental symptoms management, daily life and environmental management that can occur after discharge from the hospital. The gap between clinical professional and patient self-care in the quality of the recovery will reduce. This can be used as a reference for developing the evidence-based patient education for other similar areas in the future and will contribute to the activation of research between the clinical practice and academia. In addition, the results suggest to prepare the comprehensive national policy nursing service system on the community for discharge patients following surgery.제 1 장 서 론 1 제 1 절 연구의 필요성 1 제 2 절 연구 목적 4 제 3 절 용어의 정의 4 제 2 장 문헌고찰 7 제 1 절 통원수술 환자 간호 7 제 2 절 통원수술 환자의 퇴원교육 16 제 3 절 근거기반실무 (Evidence-based Practice) 18 제 3 장 이론적 기틀 23 제 1 절 연구의 개념틀 23 제 2 절 연구의 가설 26 제 4 장 연구방법 27 제 1 절 EBP-DECA 개발 27 제 2 절 EBP-DECA 효과 평가 37 제 5 장 연구결과 41 제 1 절 EBP-DECA 개발 결과 41 제 2 절 EBP-DECA 효과 평가 결과 56 제 6 장 논의 62 제 1 절 논의 62 제 2 절 연구의 제한점 72 제 3 절 간호학적 의의 73 제 7 장 결론 및 제언 74 참고문헌 76 부록 95 Abstract 157Docto

NS5A S2204I 변이의 치환이 C형 간염 바이러스의 복제에 미치는 영향

Dept. of Medical Science/석사Background & Aims: The nonstructural protein 5A (NS5A) of hepatitis C virus is a phosphoprotein that is required for both RNA replication and virion assembly. Differential phosphorylation has been proposed as a molecular switch that modulates the two functions of NS5A protein. Efficient replication of H77 (genotype 1a) in Huh7.5 cells requires five cell culture-adaptive mutations, including K2040R andS2204I in NS5A protein. However, replication of JFH1 (genotype 2a) in cell culture system does not require any cell culture-adaptive mutations. Therefore in this study, we tested whether the reversion of K2040R and S2204I cell culture-adaptive mutations of H77S NS5A to wild-type sequence have any effect on viral RNA replication in diverse genotypic backgrounds.Method: We generated various JFH1-based H77 NS5A chimeras, including both K2040R and S2204I cell culture-adaptive mutations (JFH1/H5A), single amino acid substitution mutations (JFH1/H5A/RK andJFH1/H5A/IS), and a wild-type sequence (JFH1/H5A/RKIS). Huh-7.5 cells were transfected with in-vitro transcribed viral RNA from the respective recombinant plasmid DNA and viral replication was evaluated by Gaussia luciferase reporter assay.Results: The efficiency of viral replication was severely impaired in cells transfected with JFH1/H5A. The reversion of S2204I to a wild-type sequence (JFH/H5A/IS) restored viral RNA replication capacity. Similar levels of replication efficiency was observed for the constructs bearing both R2040K and I2204S substitution mutations (JFH1/H5A/RKIS). However, R2040K substitution alone (JFH1/H5A/RK) did not affect the viral replication rate. Focus-forming assay showed that no infectious virus particles were released from cells transfected with the JFH1/H5A and JFH1/H5A/RK. In contrast, infectious virus particles were efficiently released by cells transfected with the JFH1/H5A/IS and JFH1/H5A/RKIS, the titer of which was comparable to that of wild-type JFH1. Consistent with these results, immunoblot analysis demonstrated no significant differences in the expression levels of NS5A protein in cells transfected with JFH1/H5A/IS, JFH1/H5A/RKIS.Conclusion: S2204I cell culture-adaptive mutation, conferring high viral replication in H77 strains, had negative effect in the context of JFH1. This result suggests that phosphorylation of serine residue at position 2204 in NS5A protein is important for efficient replication of JFH1 RNAope

Effects of the Provision of Information on Anxiety in Patients during Outpatient Surgery: A Systematic Review

Purpose: The purpose of this study was to investigate the research methods, contents, and effects of providing information to alleviate patients anxiety during outpatient surgery. Methods: The PICOTS-SD (Participants, Interventions, Comparisons, Outcomes, Time, Setting, Study design) was used and 11 randomized controlled trials studies that met the inclusion and exclusion criteria were selected. For assessing the quality of the studies, the Cochrane Risk of Bias tool was used. Results: In the 11 selected studies, intervention methods included verbal, written paper, video, and websites, and the outcome variable was anxiety. Regarding the effectiveness of providing information on anxiety, the result of the present study was ambivalent. Conclusion: This study showed the current trends in providing information as an intervention. However, randomized controlled trials are further needed in Korea, to verify the effects of such an intervention on patients anxiety

Pre-S mutations of hepatitis B virus affect genome replication and expression of surface antigens

BACKGROUNDS AND AIMS: In chronic hepatitis B virus (HBV) infection, quantitative HBV surface antigen (qHBsAg) is useful for monitoring viral replication and treatment responses. We aimed to determine whether pre-S mutations have any effect on circulating qHBsAg. METHODS: Plasmids expressing 1–8 amino acid deletion in pre-S1 ("pre-S1Δ1-8") and 3-25 amino acid deletion in pre-S2 ("pre-S2Δ3-25") were constructed. At 72 h posttransfection into Huh7 cells, qHBsAg were measured using electrochemiluminescence immunoassay analyzer. To mimic milieus of quasispecies, we co-transfected either pre-S1Δ1-8 or pre-S2Δ3-25 with wild type (WT). RESULTS: Pre-S mutations affected transcription and replication ability of HBV because of altered overlapping polymerase. Compared with WT, extracellular qHBsAg in pre-S1Δ1-8 and pre-S2Δ3-25 were on average 3.87-fold higher and 0.92-fold lower, respectively, whereas intracellular qHBsAg in pre-S1Δ1-8 and pre-S2Δ3-25 were 0.57-fold lower and 1.60-fold higher, respectively. Immunofluorescence staining of cellular HBsAg showed that pre-S1Δ1-8 had less staining and that pre-S2Δ3-25 had denser staining. As ratios of either pre-S1Δ1-8 or pre-S2Δ3-25:WT increased from 0:10 to 10:0 gradually, relative extracellular qHBsAg increased from 1.0 to 3.85 in pre-S1Δ1-8 co-transfection, whereas those decreased from 1.0 to 0.88 in pre-S2Δ3-25 co-transfection. CONCLUSION: Pre-S mutations exhibit different phenotypes of genome replication and HBsAg expression according to their locations. Thus, qHBsAg level for diagnosis and prognostification in chronic HBV infection should be used more cautiously, considering emergences of pre-S deletion mutants.ope