58 research outputs found
Corée et Journée des doctorants de l'UMR 8173 Chine, Corée, Japon
No full text18 juin 2013 9h30 – 17h30, EHESS, Salle 638-640, 190 – 198 avenue de France 75013 Paris Comité scientifique : G. Carré, I. Deron, V. Gelézeau, F. Gipouloux, F. Obringer, Comité d’organisation : L. Daeye, M. Seo 10h : Au croisement d’une esthétique orientale et occidentale : le concept de «Cinéma ouvert » chez Jang Sun-woo / Kyoung-Hee Cho (Université Paris 3) 10h 35 : Les espaces marchands dans les villes sud coréennes : formes, dynamiques et pratiques / HunHee Cho (Université Paris 8, EHES..
Compte rendu : « Quand les dieux ont le bras long... Les divinités du bouddhisme ésotérique dans la culture chinoise prémoderne »
No full textCompte rendu de la présentation de Vincent Durand-Dastès (INaLCO) « Quand les dieux ont le bras long... Les divinités du bouddhisme ésotérique dans la culture chinoise prémoderne », 20 novembre 2014 Colloque international « Pluralité religieuse et culturelle en Asie de l'Est (Chine, Corée, Japon) », organisé par l'équipe ASIEs de l’INaLCO et le Réseau des Études sur la Corée (INaLCO-Paris-Diderot-EHESS), 20-21 novembre 2014 Compte rendu réalisé par Hunhee Cho, Lucie Daeye, Hugo Desmettre..
Automatic data processing system for integrated cost and schedule control of excavation works in NATM tunnels
Get PDFA type-based system is widely used for cost and schedule control in the NATM (New Austrian Tunnelling Method) tunnel. This study raises several limitations of the type-based system: a broad level of control, a distributed approach to cost and schedule data, ad hoc management, and difficulty in deriving meaningful data. Integrated cost and schedule control promises a myriad of benefits on both information flow and construction management. Nevertheless, the integrated approach still seems to be a long way from common use in the construction industry because it requires considerable overhead effort to acquire, track, and analyze the integrated data. The objective of this study is to propose a new method to automate the required processes for implementing cost and schedule integration. We propose an operational-level automatic data processing system for cost and schedule integration. The proposed system consists of a real-time location system for detecting equipment locations, a wireless mesh network for transmitting the location signals to a field office, and a prototype model for transforming the signals to cost and schedule data. Technical feasibility is analyzed through a pilot project. The study offers a new approach to facilitating sensor technologies for cost and schedule integration
A DEFECT FORECASTING STUDY BY THE ELAPSE OF THE YEAR RAISED IN KOREAN APARTMENT HOUSING : A study on the model of forecasting defect occurrences by the elapse of a year in Korean apartment housing (Part 2)
No full textDynamic Lifecycle Assessment in Building Construction Projects: Focusing on Embodied Emissions
No full textUnderstanding the structure and behavior of emissions in building systems is the first step toward improving the reliability of the environmental impact assessment of buildings. The shortcomings of current building lifecycle assessment (LCA) research is the lack of understanding of embodied emissions and static analysis. This study presents a methodology for the dynamic LCA of buildings, combined with the system dynamics technique. Dynamic factors related to recurrent embodied emissions are explored through a literature review. Applying the dynamic factors based on the review, a causal map and stock-flow diagram are invented. Collecting the field data and establishing the assumptions based on the literature, a case study is performed for the proposed model. As a result, through dynamic analysis, it was found that recurrent embodied emissions have a considerably different behavior from static ones during their whole life. Additionally, it was found that the environmental impacts changed by more than 10%, according to the variation of the users’ required performance level in sensitivity analysis. This result thoroughly addressed the necessity and appropriateness of dynamic LCA. The dynamic LCA model developed in this study can contribute to the long-term behavioral understanding of the embodied environmental impacts of building LCA
Simulation model incorporating genetic algorithms for optimal temporary hoist planning in high-rise building construction
No full text
Economic Analysis of USN-Based Data Acquisition Systems in Tall Building Construction
No full textThe successful construction of tall buildings requires effective construction management based on various quantitative data. The recent development of ubiquitous sensor networks (USNs) enables massive amounts of data to be collected in real-time. However, the application of USN-based data acquisition systems to repetitive tasks on typical floors of tall buildings can be inefficient, because this may involve the repetitive reinstallation of sensors and the repositioning of data loggers and routers to enable continuous data transfer. To minimize this cumbersome work, a modified data acquisition method using reusable sensor nodes and mobile devices can be a useful solution. This study analyzes the economic aspects of the USN-based systems for concrete temperature monitoring by using the activity-based costing technique. The case study shows that the modified system can reduce the process cost by about 19%. It can also reduce the resource input time of management by about 55%, freeing up time for other management activities. Moreover, the cost benefits should scale up as projects increasingly require more measurement and monitoring. This study should facilitate the application of USN-based information management systems, particularly for tall building construction
4H-SiC Homoepitaxial Growth on Various SiC Substrates for Power Device Application
Get PDF학위논문 (박사)-- 서울대학교 대학원 : 재료공학부, 2015. 8. 김형준.Silicon carbide (SiC) has been considered as a promising wide bandgap material for high power, high frequency, and high temperature devices owing to its high breakdown field (~3×106 V/cm), high thermal conductivity, high saturated electron drift velocity (~2×107 cm/s), and chemical stability. The commercialization of its large single-crystal wafer and excellent epitaxial growth technique provide a better candidate for application in high-power and high-frequency electronic devices compared with other wide-bandgap materials such as GaN, ZnO, and diamond. Among the many SiC polytypes, most of the recent work has focused on 4H-SiC, owing to its high saturated electron drift velocity and commercial availability. For growth of high quality SiC epitaxial layers, many techniques were tried such methods as molecular-beam epitaxy (MBE), liquid-phase epitaxy (LPE), and vapor-phase epitaxy (VPE), there are some remaining problems. To solve this problem, the author focuses on the homoepitaxial growth of a 4H-SiC epilayer by MOCVD using bis-trimethylsilylmethane (BTMSM, C7H20Si2). BTMSM is an organo-silicon source which has a non-toxic and non-flammable nature, thus giving it certain advantages in comparison with the normal process using silane (SiH4). Moreover, because BTMSM has a Si-C bonding structure, low temperature epitaxial growth is also possible.
Homoepitaxial growth of SiC epitaxial layers on various substrates including 4H-SiC 4°, 8° off-axis, on-axis Si-face substrates, and C-faces substrates was carried out at temperature ranging from 1240 to 1550 °C and carrier gas flow rates of 5-20 sccm for the BTMSM source.
In the case of homoepitaxial growth on various off-angle substrates, it was found that the structure perfection of SiC epilayers is improved with higher temperature and lower flow rate of BTMSM. This growth behavior can be explained by the step-controlled epitaxy model. At the nominally on-axis surface spiral growth occurs via micro-steps provided by screw dislocations intersecting the surface. When growth temperature became 1480 °C on the nominally on-axis, we conducted island growth, which possesses a number of blocks, but hexagonal shapes were sparsely appeared. In addition, epilayer began to have smooth surface in macroscopic view as well as a shape of continuous chain of hexagonal-shape, when the temperature reached 1550 °C. When epilayer grows at 1480 °C, 4H-SiC was grown to a hexagonal shape, and nearby blocks were composed of 3C-SiC. This means the application of BTMSM source enabled growth of 4H-SiC at a relatively lower temperature of 1480 °C, which is the same as the polytype of substrate. Moreover, we could identify that 4H-SiC could grow at 1550 °C, satisfying stability of 4H-SiC polytype for 100%. The whole area was grown to 4H-SiC epilayer, revealing two types of surface regions which are hexagonal chain-shape and smooth surface. The smooth surface could be obtained due to high dislocation density of the area when compared to the hexagonal chain region. Increasing the growth temperature helps to enhance the mobility of the adatoms on the surface, lowering the probability for a two dimensional nucleation of 3C.
Many researchers have attempted epitaxial growth using 4H-SiC Si-face substrates, but there are few studies that have investigated the epitaxial growth on the C-face. Therefore, it is essential to determine the dependence of the quality of epitaxial layers on substrate polarity. This study has its significance in that an organosilicon source material of BTMSM was used and the epitaxial growth on C-face 4H-SiC substrates was analyzed in detail, which has not been previously attempted by other groups. In situ H2 etching and homoepitaxial growth of 4H-SiC have been carried out on 4° off-axis Si-face and C-face 4H-SiC substrates by low-pressure CVD. H2 etching characteristics and epitaxial growth behaviors on two different polarities using a BTMSM were systematically analyzed and discussed. When the temperature of in situ H2 etching was 1500 °C, the Si-face and C-face showed macro step-bunching and some clusters, respectively, whereas both faces showed fairly good quality when treated at 1450 °C for 10 min. High-quality 4H-SiC epitaxial layers with less crystallographic defects and free of step-bunching were demonstrated on both Si-face and C-face substrates. The optimal growth temperature on the Si-face substrate was 1320-1440 °C with a BTMSM source flow rate of 5-10 sccm, while the growth temperature should be increased to 1500 °C on the C-face substrate with a lower source flow rate of 5 sccm. A mechanism for the observed generation of step-bunching and surface morphological defect on both substrates depending on the growth temperature and source flow rate was also proposed.Abstract………………………………………………………………...i
Contents………………...…………...………..………………………iv
List of Tables…………………………………………………………vii
List of Figures………………………………………………………..viii
1. Introduction……………………………….…………….……….1
1.1. Overview ……………………..…..……………………………....1
1.2. Dissertation Outline………………………………..……………..2
2. Literature Review……..………...……………....………….…..3
2.1. Properties of SiC….…………………………………...……..…...3
2.1.1. Phase Equilibrium and Polytypism……....……………..…...3
2.1.2. Physical properties of SiC and Its Potential Applications.…..8
2.1.2.1. Mechanical Properties……….............................…............8
2.1.2.2. Thermal Properties…………………….……………...…..8
2.1.2.3. Optical Properties........…….…………………………….12
2.1.2.4. Electrical Properties…………..…………………...….….12
2.1.2.5. Potential Applications of SiC…………………………….15
2.2. SiC Epitaxial Growth ………………………………………...…19
2.2.1. Chemical Vapor Deposition (CVD)........……………….….19
2.2.1.1. Principle of CVD process……….……...…………….….21
2.2.1.2. Heteroepitaxial Growth of 3C-SiC….…………….….….24
2.2.1.3. Homoepitaxial Growth of 3C-SiC.....……….…………...25
2.2.1.4. Homoepitaxial Growth of α-SiC…………......…………..26
2.2.1.5. Structural Properties of α-SiC……..……………………..33
2.2.1.6. Growth Equipment and Precursor Materials for CVD.......36
2.3. SiC Doping……………………………………………..……….38
2.3.1. Site-competition Epitaxy………………..……………….38
2.3.2. Diffusion of Impurities in SiC……………………………..39
2.3.3. Ion Implantation…………………………………………...40
2.4. Step Kinetics on Vicinal Surface…………...…………………...43
2.5. SiC Power Device Application..………………….……………..49
Bibliography……………..…………………………...……………...53
3. Experimental Procedure……….…………………………….60
3.1. CVD System…….........................…………...……………….…60
3.2. Procedure for the Growth of 4H-SiC Epitaxial Layer………….62
3.3. Characterization Method…………………..………….………...63
3.3.1. Thickness Evaluation………………..………......................63
3.3.2. Surface Morphology……………………...…………..……63
3.3.3. Structure and Defect Analysis …………..…………………63
3.3.4. Electrical Properties……………………………..…………64
3.4. Precursor for Homoepitxial Growth of 4H-SiC……..…............66
3.4.1. Estimation of BTMSM vapor pressure and actual flow rate..67
Bibliography……………..…………………………...……………...69
4. Results and Discussions………….……..…………………….70
4.1. Comparative Study of 4H-SiC Epitaxial Layers Grown on 4° off-axis Si- and C-face Substrates using BTMSM……………………70
4.1.1. Intoduction……………..…………………………………...70
4.1.2. In-situ Surface Preparation …………..……...………...........73
4.1.3. 4H-SiC Epitaxial Layers Grown on Si-face Substrates .…..76
4.1.4. 4H-SiC Epitaxial Layers Grown on C-face Substrates……84
4.1.5. Background doping concentration and the growth rate of two polar face substrates ……………………………………………..97
4.2. 4H-SiC Epitaxial Growth on SiC substrates with Various Off- angles using BTMSM……………..……………………………98
4.2.1. Introduction ………………………….…………..………...98
4.2.2. 4H-SiC Epitaxial Layers Grown on 8° off-axis Substrates..100
4.2.2.1. Morphological Characteristics…………………………..100
4.2.2.2. Structural Characteristics………………..……..………..105
4.2.3. 4H-SiC Epitaxial Layers Grown on 4° off-axis Substrates...111
4.2.3.1. Morphological Characteristics…………………………..111
4.2.3.2. Structural Characteristics………………..……..………..116
4.2.4. 4H-SiC Epitaxial Layers Grown on On-axis Substrates …..122
4.2.4.1. In-situ surface preparation………….…………........……...122
4.2.4.2. 4H-SiC Epitaxial Growth on On-axis Substrates..……....126
4.2.4.3 Growth Rate…………………..…………………….……140
Bibliography……………..…………………………...…………….142
5. Conclusions...………………………………….………………146
List of Publications……………………….……………………..149
Abstract (in Korean)……………………….…………………...156Docto
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