Crack Control and Performance Improvement for Pile to Concrete Pile-cap Connections of Integral Abutment Bridges

최근 늘어나는 교통량과 노후화로 인한 많은 문제를 발생시키고 있는 조인트 교량에 비해, 유지관리 비용이 저렴하고 시공이 간편한 일체형교대교량의 시공 사례가 늘어나고 있다. 북미와 유럽에서는 10,000개 이상의 일체형 교대교량이 사용중에 있으나(Arockiasamy et al. 2004) 국내에서는 시공 사례가 적을 뿐만 아니라, 이에 대한 연구도 미미한 실정이다. 일체형 교대 교량은 조인트를 제외하고 교대와 상부구조물을 일체형으로 시공한 교량을 말한다. 기존의 조인트 교량은 신축이음장치의 차량 충격에 의한 파손과 이를 통한 누수 및 제설제의 침투로 교좌장치의 작동 불능, 잦은 파손으로 인한 교통 장애와 보수비용의 증가, 신축이음장치 및 교좌장치의 설계/시공으로 인한 시설비용의 증가, 상부구조와 하부구조의 연결부에서 지진하중, 풍하중에 대한 횡방향 저항성 취약 등의 문제점을 노출시켜 왔다. 그러나 일체형 교대교량은 신축이음장치의 제거를 통해 이러한 문제점을 개선할 수 있다. 하지만 이러한 일체형 교대 교량은 반복적인 온도하중에 따른 토질과 파일의 상호작용에 의해 파일-교대 연결부에 발생하는 균열이 문제점으로 지적되어 왔다. 미국과 유럽에서는 많은 연구가 진행되어 일체식 교대 교량의 거동 및 설계특성을 파악하고 이를 활용하여 설계를 시도하고 있으나 국내의 도로교설계기준 (2012)에서는 아직 일체식 교대 교량의 설계 지침에 관한 언급이 전무한 실정이며 1980년에 발간된 미국 FHWA Technical Advisory T 5140.13 (1980)의 추천사항에 대한 언급만 되어있다. 따라서 본 논문에서는 일체형 교대교량의 설계와 연구의 진행에 도움이 되고자, 일체형 교대 교량에서 발생 가능한 균열의 형상을 예측하고 균열 발생을 저감하기 위한 철근 상세 또는 연결부 상세를 제안하였다. 또한, 교대-파일 연결부 보강에 효과적인 것으로 확인된 나선 철근 형상의 변수연구를 통해 주요 변수를 확인하였다. 제안된 연결부는 크게 교대 자체의 강성을 높이는 방법과 강성을 줄이고 일정량의 변위를 허용하는 방법을 사용하였으며 강성을 높이는 방법에는 연결부에 나선 철근을 삽입하는 것이 효과적으로 확인되었으며 강성을 줄이고 일정량의 변위를 허용하는 방법에는 지중에 삽입되는 H 파일의 플랜지를 감소시키는 방법과, 변위를 허용하는 연결부가 일체식 교대교량의 균열방지에 효과적인 것으로 나타났다. 또한 제안된 연결부는 교대로부터 전달되는 상부구조물의 반력을 감소시켜 상부구조의 내구성 및 구조건전성도 함께 향상시키는 것으로 확인되었다.TABLES OF CONTENTS List of Tables List of Figures Abstract Chapter 1 Introduction 1.1 Problem Statement 1.2 Objectives 1.3 Research Significance 1.4 Research Methodology Chapter 2 Literature Review 2.1 Research about IA bridges 2.1.1 Research about Structural Performance of Integral Abutment Bridges 2.1.2 Research about Thermal Loads in Integral Abutment Bridges 2.2 Numerical Model 2.3 Summary of Literature Review Chapter 3 Theoretical Background 3.1 Material Model for Concrete 3.2 Material Model for Steel Rebar and H-pile 3.3 Contact Chapter 4 Numerical Analysis 4.1 Numerical Model Development 4.1.1 Description of Numerical Model 4.1.2 Numerical Model Setup 4.1.3 Verification of Numerical Model 4.2 Performance of Various Boundary Conditions 4.2.1 Structural Performance depending on Embedded Length 4.2.2 Behavior of IA Bridges according to Various Boundary Conditions 4.3 Proposed Pile-to-pilecap Connection 4.3.1 Proposed Pile-to-pilecap Increased Stiffness Connection Type 4.3.2 Proposed Pile-to-pilecap Flexible Connection Types 4.3.3 Obtained Results of Increased Stiffness Connection Types 4.3.4 Obtained Results of Flexible Connection Types 4.3.5 Comparison of Load-displacement Curves 4.4 Parametric Study 4.4.1 Parameter of Parametric Study 4.4.2 Results of Parametric Study 4.5 Superstructure Model 4.5.1 Development of Superstructure Model 4.5.2 The Results of Increased Stiffness Superstructure Model 4.5.3 The Results of Flexible Superstructure Model 5. Conclusions and Recommendations 5.1 Conclusions from Proposed Connections 5.2 Conclusions from Parametric Study 5.3 Conclusions from Superstructure Model 5.4 Recommendations for Further Study Acknowledgement Bibliograph

혈관종 퇴축 과정에서 pigment epithelium-derived factor의 역할에 관한 연구

학위논문 (석사)-- 서울대학교 대학원 : 의과학과, 2014. 8. 조정현.서론: 혈관종은 양성종양으로서 혈관의 비정상적인 성장으로 인해 생겨난다. 가장 대표적인 혈관종은 유아 혈관종이며 주로 태어난 후에 발생하고 발병 원인은 아직 알려져 있지 않다. 다른 종양과 달리 혈관종은 초기 단계에 증식을 하고 후에는 퇴축기를 거치면서 서서히 사라지게 된다. 이러한 혈관종 퇴축 과정은 잘 알려져 있지 않은 상태이며 연구가 진행이 되고 있다. 본 연구의 가설은 혈관종 퇴축기의 원인으로서 특정 요소가 혈관내피세포에 작용할 것으로 예상된다. 연구 목적은 퇴축기의 작용하는 그 특정 요소를 확인하고 혈관종 내피세포의 어떠한 작용을 일으키는지 관측하는 것이다. 방법: 혈관종 환자로부터 혈관종 샘플을 얻고 혈관내피세포를 추출을 한 후, 증식기 및 퇴축기 간의 세포 증식률과 PCR 및 단백질 array를 통해 각종 혈관생성 및 혈관생성억제 요소들의 발현량의 차이를 관측하였다. 추가로 혈관종 조직으로부터 면역조직화학염색을 하였다. 결과: 혈관종 내피세포에서 자신의 증식을 억제하는 자가분비 요소를 발견하였다. 여러 혈관생성 및 혈관생성억제 요소들 중에서 pigment epithelium-derived factor (PEDF)라는 요소가 혈관종 퇴축기에서 상대적으로 많은 발현량을 관측하였다. 이 PEDF는 혈관종 내피세포의 증식을 억제하는 효과를 보였고 PEDF의 knockdown을 통해 억제되었던 세포 증식이 다시 회복하는 현상을 관찰하였다. 또한 혈관종 조직염색을 통해 PEDF가 퇴축기에서 상대적으로 많이 발현하는 것을 재차 확인 하였다. 결론: PEDF는 혈관종 퇴축기에 많은 발현량을 보이며 혈관생성억제 요소로서 혈관내피세포의 증식을 억제한다. 따라서 PEDF는 혈관종 퇴축 과정에서 중요한 역할을 맡고 있으며 추후 혈관종의 원인 또는 치료제 연구에 적합한 연구대상이라고 생각된다.Introduction: Hemangioma is a type of vascular tumor resulting from abnormal growth of blood vessels which the cause is unknown. Compared to other vascular tumors, this benign tumor is commonly found in infancy. Hemangioma is distinctive because of its proliferation during the early stage, however, followed by involution where the tumor undergoes regression. The critical onset which proceeds to involution is not well understood and only minor research are evident regarding the involution process. Therefore, this study is centered on the mechanism of the involution of hemangioma. Through this study, I have identified an anti-angiogenic factor called pigment epithelium-derived factor (PEDF) which was found to be highly expressed during the involution phase. Methods: Endothelial cells were extracted from tissues of hemangioma patients and sorted using CD31 antibodies. Then, I observed the cellular growth rate of the hemangioma-derived endothelial cells (HemECs), and screened for pro- and anti-angiogenic factors using an angiogenesis array. Furthermore, I used hemangioma tissue samples for immunochemical staining. Results: I have identified pigment epithelium-derived factor, (PEDF) an anti-angiogenic factor, to be associated with the growth inhibition of hemangioma-derived endothelial cells (HemECs). Also, I have examined that suppression of PEDF restored cell growth in the involuting phase of HemECs. Furthermore, I have confirmed in vivo by immunochemical staining that PEDF was highly expressed, mainly in the involuting phase of hemangioma tissues. Conclusions: These results suggest that PEDF plays a role in the involution of hemangioma by inhibiting the proliferation of HemEC. The regulatory mechanism of PEDF expression as an anti-angiogenic factor could be a potential therapeutic target to treat hemangiomas.Abstract i Contents iii List of tables and figures iv List of abbreviations v Introduction 1 Material and Methods 4 Results 8 Discussion 23 References 28 Abstract in Korean 32Maste

Strategic Pricing Behavior of Channel Members Before and After the Horizontal Merger Between Manufacturers

학위논문 (석사)-- 서울대학교 대학원 : 경영학과, 2012. 8. 송인성.In this research, I study the interactions between several manufacturers and one common retailer, focusing on their pricing behavior. Particularly, I try to uncover the nature of the retailer-manufacturer interaction before and after a horizontal merger between two manufacturers in the toilet tissue market. I take a new empirical industrial organization approach, specifying consumer and firm behaviors and using the notion of equilibrium. For the demand side, I apply the random coefficient logit model. The estimation strategy uses simulation and contraction mapping suggested by Berry, Levinsohn, and Pakes (1995). While they estimated demand and cost equations simultaneously, I follow a two-step approach suggested by Chintagunta, Bonfrer, and Song (2002). For the supply side, using the estimate results obtained from the demand equation, I recover price-cost margins and estimate cost parameters under three different games―vertical Nash, manufacturer Stackelberg, and retailer Stackelberg―to determine which game fits the data best. Additionally, I introduce a conduct parameter in the model in case the three discrete games are not sufficient to capture a wide enough range of possible interactions. As a result of the nonnested hypothesis test, the conduct parameter model fits the data best. By examining the change in the value of conduct parameters, I find that the merging firm became tougher in its pricing. This implies that the manufacturer priced more competitively trying to increase its price-cost margin. Conversely, the manufacturer whose market share was the lowest behaved in a more accommodating manner toward the retailer resulting in the manufacturer's lower price-cost margin than before the merger. The results suggest that the retailer-manufacturer interaction is heterogeneous across manufacturers. This research shows that channel members are interacting with one another and they devise different strategies depending on the market structure they are confronting.1. introduction 2. Literature Review 3. The Model 4. Estimation Procedure 5. Data 6. Results 7. ConclusionsMaste

Fundamental research for introducing the probabilistic flood forecasting to Korea

학위논문 (석사)-- 서울대학교 대학원 : 건설환경공학부, 2011.2. 김영오.Maste

Real-time control of neoclassical tearing mode in time-dependent simulations on tokamak plasmas

학위논문 (석사)-- 서울대학교 대학원 : 에너지시스템공학부, 2011.8. 나용수.Maste

Beliefs about gifted education and classroom practice of the science teachers at science academy in Korea

학위논문(박사)--서울대학교 대학원 :과학교육과 지구과학전공,2005.Docto

LNG 플랜트의 Fractionation 공정의 모델링 및 시뮬레이션

학위논문 (석사)-- 서울대학교 대학원 : 화학생물공학부, 2011.8. 한종훈.Maste

Development of 3-D elastic-plastic finite element program for analysis of large deformation in metal forming

Maste

Plasma Current and Pressure Profile Effects on Tearing Mode Onset in Steady-state Hybrid Scenarios on DIII-D Tokamak

학위논문 (박사)-- 서울대학교 대학원 : 에너지시스템공학부, 2017. 2. 나용수.Tearing mode (TM) instability is a kind of resistive magnetohydrodynamic instability that limits the performance of the tokamak plasma. A correct understanding of this phenomenon is essential for high performance steady-state operation, especially the onset of TMs. Based on the steady-state hybrid experiments performed on the DIII-D device, the occurrence of TM is identified and analyzed, and the effect of the plasma current and the pressure profiles on the tearing stability is investigated in terms of the tearing stability index ∆". The characteristics of the mode is mainly investigated using the system of magnetic pick-up Mirnov probes. The FFT analysis and the phase-fitting method are applied to identify the mode onset, the mode amplitude, and the mode number in the experiments. The mode onset was defined for this thesis that the phasefolding disappears in the phase-fitting results of poloidal probe array. Since the tearing stability is sensitive to the equilibrium current and pressure profiles, the more accurate and tightly constrained equilibrium is reconstructed using the well-measured plasma profiles using various diagnostics for the discharges in the database. The characteristics of plasma current and pressure profiles at tearing mode onset in the database of DIII-D steady-state hybrid discharges seems to be more sensitive to the global feature of plasma profile through li and fp, and the effect of plasma resistivity at the mode surface through '( than the local feature of plasma profile through Lq and Lp. From the result of the best fit equation in the dimensionless form using rs and 'TA the global feature of profiles and the current profile can affect more than the local feature of profiles and the pressure profile, respectively. The tearing stability index ∆" is calculated with the experimental equilibria in two ways, by MHD codes (PEST-III and resistive DCON) and by MRE. They are verified and validated in reasonable agreement. It is noteworthy that the determined ∆′ can be positive regardless of the mode onset, so the conventional wisdom of ∆" > 0 for tearing destabilization may not be the sufficient condition, rather a positive value greater than a certain threshold could replace this under the toroidal geometry. The analytical formula of the tearing stability threshold ∆1 " is reviewed for the semi-collisional regime and the collisionless banana regime. By comparing the analytical ∆1 " with the ∆" calculated from PEST-III code near the TM onset, it is found that the condition of ∆" > ∆1 " is required for the mode onset in the experiment. A preliminary study on the ∆1 " estimation from the normalized mode growth rate is performed by NIMROD code. The ∆2 " can be fitted for negative or marginal growth rate using the relation between the normalized mode growth rate 3'- from NIMROD and the ∆" from PEST-III. Finally, a stability diagram of n = 1 tearing mode onset is suggested with local and global features of plasma profiles. Onset condition of n = 1 TM is analyzed by the difference between ∆" and ∆1 " , and its stability diagram is derived in terms of the local (▽/II and ▽p) and global (BN) variations for steady-state hybrid scenarios. To calculate ∆" − ∆1 " for the stability diagram, a novel modeling package has been developed by integrating IPS/FASTRAN for equilibrium reconstruction, PEST-III/DCON for linear stability ∆" calculation, and the ∆1 " solver for analytical ∆1 " calculation. The stability boundary at the mode onset, ∆" = ∆1 " , is mapped on Lp-Lq diagram. Characteristics of this stability boundary show that the TM unstable area expands, then the stability boundary moves as BN increases. This stability diagram can be used to design and control experiments to avoid n = 1 TM.Chapter 1. Research background and objectives 1 1.1. Thermonuclear fusion in tokamak 2 1.2. Advanced operation scenarios for fusion reactor 7 1.3. Tearing instability in the steady-state hybrid scenarios 11 1.4. Physics of tearing mode 14 1.5. Objective and outline of this dissertation 18 Chapter 2. Experimental observations of tearing mode in DIII-D steady-state hybrid discharges 19 2.1. Identification of the tearing mode and its onset 23 2.2. Equilibrium reconstruction with kinetic measurements constraints – Kinetic EFIT 27 2.3. Characteristics of plasma current and pressure profiles at tearing mode onset 33 Chapter 3. Determination of tearing mode stability in terms of ∆′39 3.1. Numerical evaluation of tearing mode stability ∆′ from the MHD codes 41 3.2. Experimental estimation of tearing mode stability ∆′ from the modified Rutherford equation 45 3.3. Validation and verification of determined ∆′ 47 Chapter 4. Determination of the onset condition for tearing mode in terms of ∆2" 51 4.1. Analysis of tearing instability threshold ∆> " 53 4.2. Comparison of ∆′ with ∆> " for stable and unstable discharges of tearing mode 55 4.3. Estimation of ∆> " from the extended MHD simulation 59 Chapter 5. Development of tearing mode onset model 65 5.1. Descriptions of tearing mode onset model 66 5.2. Construction of modeled equilibrium with the parametric variations 68 5.3. Stability boundary for tearing mode onset on Lp-Lq diagram 71 Chapter 6. Conclusions 79 6.1. Summary and concluding remarks 80 6.2. Recommendations for future work 82 Bibliography 84 Abstract in Korean 90Docto

(An) approach to Extension of Unified Modeling Language for Business Process Modeling

Maste