광촉매 물분해 수소생산을 위한 효율적인 구리 기반의 감광제에 대한 연구

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2017. 2. 박수영.현재 인구의 증가과 산업화에 따라 에너지의 수요가 급증하고 있다. 주 에너지원으로 쓰이는 화석연료는 고갈자원이고, 원자력 에너지 등은 그 자체의 위험성에 대한 논란이 아직도 많다. 그리하여 안전하고 친환경적이면서 부족한 자원을 대체할 수 있는 에너지에 대한 인류의 관심이 높아지고 있다. 다양한 대체 에너지 후보 중 수소 에너지는 부산물이 오직 물이라는 점에서 친환경적이고 가볍기 때문에 에너지 밀도가 상당히 높다는 장점이 있다. 이러한 수소를 생산하기 위해 다양한 항법이 있다. 그 중에서 화석연료를 개질하는 것이 현재 대부분이고 물을 전기분해하는 방법도 있다. 하지만 그들은 여전히 환경오염에 대한 문제와 추가의 에너지를 필요로 한다는 단점이 있다. 그리하여 무한한 자원인 태양에너지와 물을 이용한 인공 광합성이 최근 활발히 연구되고 있다. 본 논문에서는 수소를 생산하기 위하여 광촉매 물분해 시스템을 활용하기로 하였다. 광촉매 작용을 일으키기 위해서는 빛을 흡수하여 화학 에너지로 전환해주는 감광제가 필요하다. 감광제로 많이 쓰이는 물질은 루테늄 혹은 이리듐과 같은 귀금속을 이용한 금속착물들이 있다. 이러한 금속 착물들은 가시광선을 흡수할 수 있고 효율적이고 안정하다는 장점이 있지만 실용적인 관점에서 보았을 때 적합하지 않다는 단점이 있다. 그러므로 이러한 귀금속 기반의 금속착물을 값싼 금속을 이용한 착물로 대체하는 것이 필요하다. 그리하여 본 2단원에서는 값싼 금속인 구리를 이용한 효율적인 감광제를 디자인하고 합성하여 그들의 광물리적 특성을 관찰하였고, 실제로 수소생산에 적용한 연구를 보고하였다. 구리 감광제의 수소 생산에 대한 성능이 리간드의 작용기에 의해 어떻게 바뀌는지 알아보기 위하여 다양한 작용기의 구분을 크기와 전자적 성질로 나누어 착물의 성질을 미세 조정하였다. 그 중에서 부피가 크고 전자 주개의 성질을 갖는 triphenylamine 작용기가 붙은 구리 기반 감광제(Cu(TPA))는 리간드 내에 전자 주개가 있어서 금속-리간드 전하이동(MLCT) 뿐 아니라 리간드 내 전하이동(ILCT)가 함께 일어나 가시광선 영역의 빛을 많이 흡수 할 수 있었다. 그 뿐 아니라 감광제로서 필요로 하는 긴 들뜬상태의 수명, 낮은 비발광 소멸을 갖기 때문에 높은 수소 생산 효율을 가질 수 있었다. 그리고 triphenylamine의 큰 부피 때문에 빛에 대하여 가장 안정한 구조를 유지하였다. 그 결과, 4일 동안 turnover number를 18974를 기록하여 가장 효율적인 수소 생산을 보여주었다. Cu(TPA)는 높은 빛의 흡수와 전자 전달 자유 에너지에 비례하여 수소 생산의 빠른 turnover frequency를 보여주었다.Recently the energy demand is surging as the polulation increases and the industrialization is accelerated. Fossil fuel which is the primary energy source is depletable and nuclear energy have a highly controversial topic about intrinsic dangers. Therefore, there is a rising interest in safe and eco-friendly energy which can replace scarce resources. Among the various alternative energies, hydrogen have the benefits of environment-friendly resource because the combustion by-product is only water. In addition, the specific energy of 120 to 142 MJ/kg is very high. There are many ways to produce hydrogen. Reforming fossil fuels, which is the major way, causes environmental pollution. Electrolysis of water requires additional electric energy. To replace them, many researchers have been actively studying artificial photosynthesis that utilize infinite solar energy and water. In this thesis, as a part of the artificial photosynthesis, I narrowed scope of study for photocatalytic water splitting to produce hydrogen. For the photocatalytic reaction, development of an efficient photosensitizer is important. The photosensitizer is required to absorb visible light. The absorbed solar energy is converted into chemical energy. The most common photosensitizer materials are noble metal complexes such as Ru(bpy)32+ or Ir(ppy)2(bpy)+. They are efficient, robust and able to absorb visible light. But the noble metals are inappropriate in point of practical view. For real application, they should be replaced to earth abundant metal complexes. In chapter 2, I reported the design, synthesis, photophysical properties and hydrogen evolution application of efficient photosensitizers made from copper. To know how hydrogen evolution efficiencies vary according to functional group of ligand, I fine-tuned the properties of copper complex by changing size and electronic properties of ligands. Among them, a copper photosensitizer with bulky and electron donating triphenylamine moiety (Cu(TPA)) could absorb visible light largely because it can utilize ILCT (intralignad charge transfer) as well as MLCT (metal to ligand charge transfer). In addition, outstanding photophysical properties of Cu(TPA) such as high PLQY, long excited state lifetime and low non-radiative rate constant of Cu(TPA) were observed. Furthermore the bulky moiety of TPA enhanced the photostability. As a result, Cu(TPA) showed the highest efficiency for hydrogen evolution and the turnover number (TON) was 18974 for four days. The turnover frequency (TOF) of Cu(TPA) also increased in proportion to both of visible light absorption and free energy for electron transfer.Chapter 1 Introduction 1 1.1 Articial photosynthesis 1 1.2 Photocatalytic hydrogen evolution 3 1.3 Metal complex as photosensitizer 6 1.4 Copper(I) complex 10 1.5 References 15 Chapter 2 Efficient photocatalytic hydrogen evolution from water using robust copper(I) photosensitizer containing bulky substituents 18 2.1 Introduction 18 2.2 Experimental section 22 2.3 Result and discussion 38 2.4 Conclusions 81 2.5 References 82 2.6 Appendix 85 Abstract in Korean 96Maste

A Study on Decision Making on Ship Acquisition in the Liner Shipping Industry

The volume of container movements has increased more than 10% every year since 2000 and it has made liner carriers need additional fleet. To meet those explosive demands, the liner carriers have made investment to expand their fleet rapidly by ordering newly-built ships, making time charter contracts and attempting M&A. For liner carriers, the advantages of economies of scale, such as cost saving, expansion of service range and provision the customers with high quality services, encourage them to expand fleet size continuously, thus carriers' operating fleet capacity has become more important factor to make their own competitiveness to the others. When it comes to fleet expansion, among purchasing own ship, time charter, and bareboat charter, it is not easy to decide which method of ship acquisition is most efficient way to their given management environments. This paper is to demonstrate the level of importance in 4 major factors: economical efficiency, efficiency operation, safety management and financial liquidity, by using AHP analysis when liner carriers decide ship acquisition by those three ways above. In detail, the 4 major factors are divided into 14 sub-factors and the level of importance in each factor can be used to find out the best way of fleet expansion with consideration of each carrier's different management conditions. Traditionally, liner carriers had operated their fleets with their own ships, but explosive fleet expansion and developing new financial scheme, for example, K/S fund of Norway and K/G fund of German, have made time charter more common in ship acquisition. Analyzing the fleet structures of world 30 top liners, it can be found that the proportion of time charter has been increasing slightly since the year of 2004 and the rate marked around 51% as of April 2008. Another precedent study regarding this subject illustrates that, from the point of financial and operating costs, the decision of ship acquisition is different from ship sizesand time charter is preferred in smaller sized ones. In order to approve logically the importance grade of each factors, Analytic Hierarchy Program is used in this study. The data of this study are collected from three expert groups in liner industry: planning/purchase group, operating group and maintenance/repair group and the results are extracted as follows: First, the entire investment cost and initial investment cost are found to be the most important among the factors. It means the total cost and beginning cost for the ship acquisition should be considered as a first priority item because the cost competition is getting more seriously considered under same economy circumstances. Second, accident ratio takes the next stand. The shipping industry is always exposed to unexpected accidents such as, the potential risk on the sea, marine pollution and collision. According to past records, a serious maritime accident can change carrier's future status. Third, utilization of ship space and the rate of ship operation are selected as the next ranking. Space utilization and maximizing the rate of ship operation depends on the method of ship acquisition because above two factors can be changed by on board crew who are controlled under direction of owners or charterers as per method of ship acquisition. Finally, own ship purchasing is selected as first priority in the important level among the three types of ship acquisition, followed by bareboat charter and time charter. This result can be explained by the answer to the question, who is in charge of ship management between owners and charters.owned ship is preferred in bigger sized vesselsAbstract i 제1장 서 론 1 제1절 연구의 목적 1 제2절 연구의 범위 및 방법 2 제2장 정기선사의 선박확보 유형에 관한 이론적 고찰 5 제1절 선박확보 유형 5 1. 사선확보 유형 5 2. 기간용선 10 3. 나용선 13 4. 선박확보 유형별 해운비용 비교 15 제2절 선사별 선박확보 현황 17 1. 선사별 선박확보 현황 17 2. 선박 크기별 선박확보 현황 19 제3절 선행연구 고찰 20 1. 선박확보 의사결정 20 2. 선박금융제도 24 제3장 AHP 분석방법 및 선행연구 고찰 29 제1절 계층분석적의사결정법(AHP)의 고찰 29 1. AHP 정의 29 2. AHP 특징 31 제2절 계층분석적의사결정법의 평가절차 31 1. 의사결정문제의 계층화 32 2. 평가기준의 쌍대비교(pairwise comparison) 33 3. 가중치의 추정 36 4. 일관성 측정 39 5. 가중치의 종합 40 제3절 AHP에 관한 선행 연구 42 제4장 정기선사의 선박확보유형 의사결정 모형 구축 46 제1절 세부평가 속성의 도출 46 1. 세부 평가 속성 도출 방법 46 2. 세부평가속성의 분류 및 평가 항목 도출 48 제2절 평가 대안 설정 및 계층분석 구조 52 1. 평가 대안 설정 52 제3절 설문조사 대상자의 선정과 응답 결과 53 제5장 AHP 분석 결과 55 제1절 계층별 중요도 평가 55 1. 평가 항목의 중요도 55 2. 세부평가속성의 중요도 56 3. 최종 평가 대안 속성의 중요도 61 제2절 종합 중요도 평가 65 제3절 분석 결과의 시사점 69 제6장 결론 71 제1절 연구의 요약 71 제2절 연구의 한계 및 향후 연구 방향 72 74 1. 국내 문헌 74 2. 외국 문헌 77 기초 설문지 78 본 설문지 8

Efficiency Enhancement of CFDS Code

The numerical analyses of the complicated flows are widely attempted in these days. Because of the enormous demanding memory and calculation time, parallel processing is used for these problems. In order to obtain calculation efficiency, it is important to choose proper domain decomposition technique and numerical algorithm. In this research we enhanced the efficiency of the CFDS code developed by ADD, using parallel computation and newly developed numerical algorithms. For the huge amount of data transfer between blocks non-blocking method is used, and newly developed data transfer algorithm is used for non-aligned block interface. Recently developed RoeM scheme is adpoted as a spatial difference method, and AF-ADI and LU-SGS methods are used as a time integration method to enhance the convergence of the code. Analyses of the flows around the ONERA M6 wing and the high angle of attack missile configuration are performed to show the efficiency improvement.OAIID:oai:osos.snu.ac.kr:snu2005-01/104/0000004648/22SEQ:22PERF_CD:SNU2005-01EVAL_ITEM_CD:104USER_ID:0000004648ADJUST_YN:NEMP_ID:A001138DEPT_CD:446CITE_RATE:0FILENAME:CFDS_코드의_효율성_개선.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

CIP 방법을 이용한 이상유동해석

학위논문(석사)--서울대학교 대학원 :기계항공공학부,2003.Maste

A Study on the Effects of Logistics Capabilities of Ship Management Business on their Business Performance

Since 1990s, the international shipping has experienced a number of changes such as explosive fleet expansion, economies of scale, and the advent of the specialized shipping. Combined with ever-increasing international trade flows, these changes have raised concerns about maritime traffic accidents. To come up with the dynamic changes, international shipping governing bodies have introduced a set of new regulations, for instant, the ISM code, the ISPS, and the MLC convention, which require specialties and strict quality controls in ship management. As the shipping industry becomes more sophisticated and specialized, the ship management business is not any longer regarded as an in-house function, but as one of the major sub-sectors of the whole shipping industry and it is playing a pivotal role in establishing international logistics networks. Domestic ship management business, however, is far behind the international developments and losing competitive edges in terms of size and specialty. This thesis aims to investigate the current logistics capabilities of domestic ship management companies and to suggest which logistic capabilities need improving for enhanced operational or financial performance. Especially, in this study, the ship management companies are categorized into three groups: the integrated units, the intermediate players and the independent players. In the literature review, this study presents previous studies on ship management, logistics capabilities and business performance. Then, the empirical analysis is carried out to demonstrate the relationships between variables such as company-specific factors and logistics capabilities, logistics capabilities and business performance, etc. The data is collected from the questionnaire circulated to ship management practitioners and analyzed in the regression and the variance model. The result demonstrates that logistics capabilities are significantly dependent on the company type, customers’ nationality, the contract type, the number of staff and the number of ships, but there is no relevance with the coverage of ship management service. This is attributed to the low recognition of commercial management and the relatively small portion of crew manning in the domestic ship management business. In regard to the relationship between logistics capabilities and business performance, intangible factors, such as business experience, management ability and corporate image, have a significant impact on business performancewhile tangible factors do not. In conclusion, each ship management entity needs to gain its logistics competitive edge according to its company type and customers’ nationality. Especially, gaining more outsourcing contracts and company expansion are the major factors to logistics capabilities enhancement. In addition, the ship management business should focus on increasing the value of intangible assets combined with staff education and electronic business process renovation for better business performance.외 선박관리업 현황 17 제2절 물류역량 32 1. 물류역량의 개념 32 2. 물류역량에 관한 선행연구 37 3. 선박관리업의 물류역량 44 제3절 경영성과 48 1. 경영성과의 개념 48 2. 경영성과의 구성요인 50 3. 선박관리업의 경영성과 52 제3장 연구모형과 가설의 설정 56 제1절 연구모형의 설계 56 1. 연구문제 56 2. 변수의 조작적 정의와 측정 57 3. 표본설계 및 설문지의 구성 59 제2절 연구가설의 설정 61 1. 기업특성과 물류역량과의 관계 61 2. 물류역량과 경영성과와의 관계 61 제4장 실증분석 63 제1절 연구의 설계 63 1. 자료의 수집 및 분석방법 63 2. 표본의 특성 64 제2절 측정항목의 평가 70 1. 물류역량 요인의 신뢰성 및 타당성 검정 71 2. 경영성과 요인의 신뢰성 및 타당성 검정 72 제3절 연구가설의 검정 74 1. 가설의 검정 74 2. 가설검정 결과의 해석 86 제5장 결 론 89 제1절 연구결과의 요약 및 시사점 89 제2절 연구의 한계점과 과제 91 참고 문헌 93 93 95 [부 록] 설문지 99제1장 서 론 1 제1절 연구의 배경과 목적 1 제2절 연구의 방법 및 구성 4 제2장 이론적 고찰 6 제1절 선박관리업의 의의 6 1. 선박관리업의 개념 6 2. 선박관리업의 유형 및 특징 8 3. 국내&#822