A cystic artery arising from the middle hepatic artery detected during laparoscopic cholecystectomy: a case report

We herein report a case in which a cystic artery arising from the middle hepatic artery (MHA) was encountered during cholecystectomy. A 42-year-old man visited the outpatient department complaining of chronic epigastric pain and a laparoscopic cholecystectomy was decided upon. During the preoperative evaluation, an interesting finding was observed on computed tomography. The patient had a cystic artery arising from the MHA. An MHA derived from the hilum of the proper hepatic artery runs along the medial border of the gallbladder and enters segment IV. In the operative field, the MHA that entered segment IV was observed. Dissecting downward along the MHA, a cystic artery was observed around the cystic duct. The cystic artery and duct were isolated and each was separately ligated and cut. Rare anatomical variations of the cystic artery, as in this case, can be a pitfall inducing complications during cholecystectomy.ope

RC 벽체의 성능기반 내진설계 및 평가를 위한 전단 강도와 강도저하 예측모델

학위논문(박사) -- 서울대학교대학원 : 공과대학 건축학과, 2021.8. 박홍근.In the performance based seismic design/evaluation, the behavior of structure by earthquakes is evaluated by the nonlinear analysis. In the slender walls of high-rise residential buildings, because the large shear force is applied by a dynamic mode effect, the high-strength reinforcement is required for economic design. Therefore, in this dissertation, experimental studies were conducted to provide the evidence of validity of RC walls with 700 MPa high-strength reinforcement. In the case of walls in the existing buildings, because the deformation capacity is limited by not applying the seismic design, it is necessary to evaluate the shear strength and inelastic deformation of the walls accurately. Therefore, the present dissertation investigated the major design parameters affecting the shear strength of wall, and developed the shear strength and strength degradation model based on the shear failure mechanism. The large demand force is applied by the gravity loads and earthquake loads at the walls in the high-rise residential buildings. Thus, the validity of 700 MPa reinforcement should be verified for the walls with high shear reinforcement ratio and high axial force. Even the demand force is small, the current design code requires the minimum reinforcement ratio for serviceability and safety. Thus, it is required to investigate the effects of the low reinforcement ratio on the strength and deformation capacity of the walls. For these purpose, the cyclic loading tests were conducted for the 700 MPa RC walls with various test parameters. The test results showed that the shear strength of walls with 700 MPa reinforcement was greater than the design strength, regardless of the test parameters. 700 MPa shear reinforcement was yielded at the peak shear strength. However, because of the greater yield strain and less reinforcement ratio, the walls with 700 MPa rebars showed the less strength margin, the greater crack width, the less energy dissipation and the less drift ductility ratio. Based on the test results, the effects of design parameters on the shear strength were investigated. The major design parameters were the yield strength of shear reinforcement, the vertical web reinforcement ratio, the axial load ratio, and the shape of the cross section. Since such parameters are closely related to the compression zone depth, the shear strength and shear strength degradation of walls are explained based on the effective compressive stress of concrete and effective area of concrete in compression. Based on the consideration, the present study developed the shear strength and strength degradation model. The major failure mechanisms of diagonal tension cracking and web crushing were addressed. The diagonal tension strength was defined by the compression zone depth and the normal stress of concrete in the compression zone. As the inelastic deformation increased, concrete crushing occurred in the compression zone. Thus, the effective compression zone gradually decreased, and diagonal tension strength degraded. The web crushing strength was defined by effective compressive stress of diagonal strut. By the compression softening effect, the effective concrete stress decreased as the crack width increased. Therefore, the web crushing strength degraded as the lateral deformation increased. Based on these shear failure mechanisms, simplified shear strength and strength degradation models were developed. Compared to existing design method, the proposed model agreed with the existing test results. To implement the proposed model into the practical design, design tables and guideline were suggested. The proposed model was applied in the Perform 3D, and the analysis results were compared with the test results. The Perform 3D analysis results showed that the strength degradation occurred after flexural yielding, and the deformation capacity was limited by the strength degradation.성능기반 내진설계 및 평가 기법에서는 비선형 해석을 통해 지진에 의한 건축물의 거동을 평가한다. 성능설계 시, 고층 공동주택의 세장한 벽체는 구조적 동적 특성으로 인해 지진하중에 의해 큰 전단력이 벽체에 작용하므로 경제적인 설계를 위해 고강도 철근의 사용이 요구된다. 이를 위하여 본 연구에서는 실험적 연구를 바탕으로 700 MPa 철근을 사용한 벽체의 유효성에 대하여 입증 자료를 제공하였다. 한편, 기존 건물의 벽체는 내진설계가 미비하여 연성능력이 부족하고 전단파괴에 취약하기 때문에, 성능 평가 시 벽체의 전단강도와 변형능력을 정확히 평가하는 것이 중요하다. 따라서, 벽체의 전단거동에 영향을 미치는 주요 요인을 조사하고, 벽체의 전단 거동 메커니즘을 기반으로 전단 강도와 변형능력을 평가하는 설계모델을 개발하였다. 고층 공동주택의 벽체에는 중력하중과 지진하중에 의하여 큰 요구하중이 작용한다. 따라서 높은 축력비가 작용하고 철근비가 높은 벽체에 대하여 700 MPa 철근의 유효성이 검증되어야 한다. 한편 요구강도가 크지 않더라도 현행 설계 기준은 벽체의 사용성 및 안전성을 확보하기 위하여 최소 철근비를 규정하고 있다. 따라서 낮은 철근비가 벽체의 강도와 변형능력에 미치는 영향이 평가되어야 한다. 이를 위하여 700 MPa 철근을 사용한 벽체에 대하여 반복 주기 횡 하중 실험이 수행되었다. 실험 결과, 700 MPa 철근을 사용한 벽체는 파괴모드 및 설계변수와 관계없이 설계 강도 이상의 전단 강도를 나타냈다. 700 MPa 전단철근은 최대강도에서 항복하였다. 그러나 700 MPa 철근은 항복 변형률이 크고 철근비가 감소하기 때문에 일반강도 (400 MPa) 철근을 사용한 벽체와 비교하여 강도 여유치는 감소하였고, 균열폭 증가, 에너지 소산량 감소, 연성능력 감소가 나타났다. 실험 연구 결과를 바탕으로 벽체 전단 강도에 영향을 미치는 설계 변수를 분석하였다. 주요한 설계변수는 전단철근 강도, 복부 수직철근비, 축력비, 단면 형상 등이었다. 이러한 설계변수들은 압축대 깊이와 밀접한 관련이 있으므로 콘크리트의 압축 응력을 기반으로 전단강도와 강도저하를 설명할 수 있다. 이러한 고찰을 바탕으로 본 연구에서는 전단강도와 강도저하 예측모델을 개발하였다. 대표적인 전단파괴 메커니즘인 대각 인장 균열 파괴와 복부 압괴 파괴를 고려하였다. 대각인장 균열 강도는 콘크리트 압축대의 깊이와 압축대에 작용하는 평균 응력으로부터 산정하였다. 비탄성 변형이 증가하면 콘크리트 압괴가 압축대에서 발생한다. 유효 압축대 깊이가 감소함에 따라 대각 인장 균열 강도는 저하된다. 복부 압괴 강도는 대각 압축 스트럿의 유효 응력을 사용하여 정의하였다. 콘크리트의 압축강도 연화 작용에 의하여 유효 콘크리트 응력은 균열폭이 증가함에 따라 감소한다. 따라서 횡 변형이 증가할수록 복부 압괴 강도는 저하된다. 이러한 전단거동 메커니즘을 바탕으로 단순 모델을 개발하였다. 기존 설계 기준과 비교하여 제안 모델은 실험 결과를 비교적 잘 예측하였다. 본 연구의 제안 모델을 실무설계에 적용하기 위하여 설계 테이블과 가이드라인이 제시되었다. Perform 3D 해석 프로그램을 기반으로 제안 모델을 적용하고 실험결과와 비교하였다. Perform 3D를 사용한 해석 결과는 항복 이후 강도 저하를 모사할 수 있었으며, 벽체의 변형능력이 강도저하에 의하여 제한되었다.Chapter 1. Introduction 1 1.1 General 1 1.2 Scope and objectives 9 1.3 Outline of dissertation 11 Chapter 2. Literature Review 14 2.1 Current design codes 14 2.1.1 ACI 318-19 (ACI Committee 318, 2019) 14 2.1.2 Eurocode 2 and 8 (British Standards Institution, 2004) 16 2.1.3 KDS 14 20 22 (Korean Concrete Institute, 2020) 18 2.1.4 ASCE/SEI 41-17 (American Society of Civil Engineers, 2017) 21 2.1.5 Design guideline for performance based design of RC structure (Architectural Institute of Korea, 2020) 23 2.2 Existing model for shear strength and deformation capacity of RC shear walls 25 2.2.1 Cardenas et al. (1973) 25 2.2.2 Barda et al. (1977) 27 2.2.3 Duffey et al. (1994) 28 2.2.4 Hidalgo and Jordan (1996) 29 2.2.5 Carrillo and Alcocer (2012) 31 2.2.6 Sanchez (2013) 34 2.2.7 Carlos (2016) 37 2.2.8 Epackachi et al. (2019) 39 2.2.9 Gulec and Whittaker (2011) 40 2.2.10 Zeynep and Cagri (2021) 41 2.3 Shear wall failure mechanism models 42 2.3.1 Compression zone failure mechanism model (Choi et al., 2007) 44 2.3.2 Truss mechanism model (Eom and Park, 2010) 51 Chapter 3. Shear Strength of RC Walls with Various Design Parameters 59 3.1 Overview 59 3.2 Backgrounds 60 3.3 Test program 64 3.3.1 Test parameters and specimens details 64 3.3.2 Test setup and instrumentation 78 3.4 Test results 80 3.4.1 Failure modes 80 3.4.2 Lateral load- displacement relationships 90 3.4.3 Strains of reinforcing bars 98 3.4.4 Contributions of displacement components 105 3.4.5 Average crack width 109 3.4.6 Energy dissipation and drift ductility ratio 112 3.5 Shear strength predictions of existing methods 116 3.5.1 Predictions of existing methods 116 3.5.2 Strength and deformation predictions by compression zone failure mechanism model 118 3.6 Summary 122 Chapter 4. Effects of Design Parameters on Wall Shear Strength and Deformation 124 4.1 Overview 124 4.2 Shear reinforcement 125 4.3 Wall aspect ratio and axial load ratio 130 4.4 Vertical web reinforcement ratio 136 4.5 Shape of wall section 140 4.6 Summary 144 Chapter 5. Simplified Wall Shear Strength Model 146 5.1 Overview 146 5.2 Background 147 5.3 Shear strength of walls controlled by diagonal tension failure 149 5.3.1 Diagonal tension cracking mechanism model 149 5.3.2 Simplified diagonal tension strength 152 5.4 Shear strength of walls controlled by web crushing failure 163 5.5 Verification of proposed shear strength model 168 5.6 Summary 176 Chapter 6. Simplified Wall Shear Strength Degradation Model 177 6.1 Overview 177 6.2 Background 178 6.3 Shear strength degradation controlled by tension failure 183 6.3.1 Compression zone failure mechanism model 183 6.3.2 Deformation model 190 6.3.3 Simplified strength degradation model controlled by diagonal tension failure 199 6.4 Shear strength degradation controlled by web crushing failure 205 6.4.1 Truss mechanism model 205 6.4.2 Simplified strength degradation model controlled by web crushing failure 207 6.5 Verification of proposed shear strength degradation model 210 6.6 Summary 224 Chapter 7. Application of Proposed Models 225 7.1 Overview 225 7.2 Review on Perform 3D wall element 226 7.3 Envelope curve model for the plastic hinge region 227 7.3.1 Envelope curve model 227 7.3.2 Design table 235 7.4 Perform 3D modeling procedure 238 7.4.1 Overview 238 7.4.2 Example walls 239 7.4.3 Geometries of model 241 7.4.4 Materials 243 7.4.5 Cyclic properties 251 7.4.6 Loading conditions 253 7.4.7 Boundary conditions 254 7.4.8 Analysis results 255 7.5 Limitations 258 7.6 Summary 260 Chapter 8. Conclusions 261 References 265 Appendix: Verification of Simplified Strength Degrdation Models 273 초 록 298박

Mixed neuroendocrine-non-neuroendocrine carcinoma (MiNEN) in gallbladder with liver metastasis of neuroendocrine carcinoma component: a case report

Mixed neuroendocrine-non-neuroendocrine neoplasms of the gallbladder are rare with a lack of established standardized therapeutic strategies. We report a case of gallbladder mixed neuroendocrine-non-neuroendocrine neoplasm with liver metastasis of neuroendocrine carcinoma. A patient who underwent radical cholecystectomy for gallbladder adenocarcinoma was detected with increasing liver mass, and hepatectomy was performed. Pathological report revealed neuroendocrine carcinoma. To find primary origin, pathological review of the old specimen from previous cholecystectomy with a slightly different perspective was conducted, where the neuroendocrine component was positively dyed. In conclusion, though it might be impossible to review every pathological result in cases with ambiguous findings, reviewing the previous specimen can be a useful option in diagnosis. Published by Oxford University Press and JSCR Publishing Ltd. © The Author(s) 2023.ope

Inguinal hernia repair with or without mesh in late adolescent males

Purpose: Inguinal hernia repair is one of the most common treatments worldwide, but there are few studies about the use of mesh in late adolescent patients because hernias are rare in this group. This study aimed to evaluate the postoperative outcomes of hernia repair with and without mesh in late adolescent patients. Methods: We retrospectively reviewed the data of 243 male patients aged between 18 and 21 years who underwent inguinal hernia repair at a single institution from January 2013 to December 2017. We distinguished 2 groups depending on the repair method; mesh (n = 121) and no-mesh (n = 122) groups. We compared the baseline characteristics, immediate postoperative outcomes, and recurrence and chronic pain rates between the 2 groups. Results: There were no significant differences between the mesh and no-mesh groups on immediate postoperative outcomes (length of stay: 18.5 ± 8.9 days vs. 17.0 ± 6.0 days, P = 0.139; postoperative complications: 8.2% vs. 6.6%, P = 0.821) and 2-year recurrence rate (0.8% vs. 2.6%, P = 0.194). There was a significant difference in the chronic pain rate (9.0% vs. 1.7%, P = 0.023). Conclusion: Using mesh for inguinal hernia repair in late adolescent male patients increases chronic postoperative inguinal pain.ope

고층주거용건물의 성능설계 과정에서 세장한 벽체와 필로티가 있는 벽체의 설계

학위논문 (석사)-- 서울대학교 대학원 : 건축학과, 2017. 2. 박홍근.As the risk of earthquake in Korea increases, interest in seismic design increases and application of related design standard is strengthened. It is difficult to predict seismic load accurately by seismic design method based on conventional elastic analysis. Therefore, capacity design method can be used for seismic design of high-rise residential building to evaluate seismic load more accurately and obtain optimal design result. However, in order to apply the capacity design method in design of Korean high-rise residential buildings, some precautions due to characteristics of structural system should be considered. Therefore, in this study, among the considerations for capacity design of high-rise residential building, the shear demand distribution for the slender shear wall system and the design of transfer zone in the pilotis-wall system were studied. First, the problem that occurred in the capacity design of slender shear wall system was that shear demand of actual case is considerably amplified compared to that of design case. If the amplified shear demand is not considered in design, structural members can be under-designed, resulting structural unsafety of the building. Therefore, amplification effect of shear demand was investigated and some design factors reflecting it in the capacity design process were proposed. By using Perform 3D, a nonlinear analysis program, nonlinear analysis modeling for each parameter were established and nonlinear dynamic analysis was carried out. Based on the analysis results, the factors affecting the shear demand amplification effect were analyzed and the base shear amplification factor for predicting the nonlinear shear demand was proposed. The proposed base shear amplification factor was determined by base over-strength factor and it can predict the nonlinear shear demand within the error range of 20%. Also, the story shear distribution model for nonlinear shear demand was suggested on the basis of average shear distribution of analysis results. The proposed story shear distribution model can predict the story shear demand more economically than conventional model which is suggested in Eurocode 8. The proposed base shear amplification factor and story shear distribution model can predict nonlinear shear demand of the wall more reasonably and secure the structural safety by preventing under-design. Next, the design consideration of the capacity design of the pilotis-wall system was an economical design method for the transfer zone in which the pilotis and wall are connected. A system in which the transfer girder was eliminated was proposed and a reasonable capacity design method for this system is proposed. To evaluate the structural performance of proposed system and verify the design method, cyclic loading tests and compression test were carried out. Based on principle of capacity design, the proposed pilotis-wall system without transfer girder was designed to prevent premature brittle failure in the transfer zone and pilotis and to induce ductile failure in the upper wall. Test results show that, in all the specimens, the premature brittle failure of the transfer zone and pilotis did not occurred, but in the upper wall, re-bars were yielded in the tensile side and concrete crushing occurred in the compressive side. The internal and external damage of the transfer zone and the pilotis were relatively limited. Through these results, it was confirmed that the preliminary design of the pilotis-wall system can be improved more economically without applying the special earthquake load and the presence of transfer girder.Chapter 1. Introduction 1 1.1 General 1 1.2 Scope and Objectives 7 1.3 Outline of the masters thesis 8 Chapter 2. Literature Review 9 2.1 Capacity design 9 2.2 Shear amplification and the story shear distribution 11 2.2.1 Blakeley et al 11 2.2.2 Eibl and keintzel et al 13 2.2.3 Rutenberg and Nsieri 13 2.3 Pilotis-wall system 16 2.3.1 Jung, Yoon, Hong and Kim 16 2.3.2 Jang, Kim and Hong 20 Chapter 3. Capacity Design of Slender Shear Wall 25 3.1 Introduction 25 3.2 Analysis model 26 3.2.1 Modeling concept 26 3.2.2 Modeling procedure 30 3.3 Analysis parameters 41 3.3.1 Parameter 1 : Axial force ratio 41 3.3.2 Parameter 2 : Response modification factor (R factor) 42 3.3.3 Parameter 3 : The number of stories designed identically 45 3.3.4 Parameter 4 : Characteristics of selected ground motions 46 3.3.5 Parameter 5 : Detail of connection beam 47 3.4 Analysis results 50 3.4.1 Parameter 1 : Axial force ratio 50 3.4.2 Parameter 2 : Response modification factor (R factor) 52 3.4.3 Parameter 3 : The number of stories designed identically 53 3.4.4 Parameter 4 : Characteristics of selected ground motions 56 3.4.5 Parameter 5 : Detail of connection beam 58 3.5 Design of slender shear wall 59 3.5.1 Base shear amplification factor 59 3.5.2 Story shear distribution model 64 Chapter 4. Capacity Design of Pilotis-Wall System without Transfer Girder 67 4.1 Introduction 67 4.2 Test program 69 4.2.1 Design concept 69 4.2.2 Design procedure 70 4.2.3 Test parameters 73 4.2.4 Test specimens 73 4.2.5 Test setups 82 4.3 Test results 88 4.3.1 Cyclic loading tests 88 4.3.2 Compression Test 102 Chapter 5. Conclusion 108 References 112 초 록 114Maste

The improving accuracy of classifying an image \\ using interpretable machine learning (IML)

학위논문 (석사) -- 서울대학교 대학원 : 공학전문대학원 응용공학과, 2021. 2. 윤성로.인공 지능은 데이터에 편향이 없다면, 인과 관계가 아닌 데이터 내의 패턴에 있어서 가장 높은 확률을 보여준다. 왜냐하면 대부분의 기계 학습 알고리즘은 데이터에 의존하고 있기 때문이다. 이 논문은 복잡성과 신뢰성 사이의 균형을 기반으로 인간의 해석 가능성을 다루는 것을 목표로 한다. 그러기 위해서, IML 또는 XAI 기술들 중에서 몇 가지 이론적 관점을 소개하고, 그 접근 방식의 이해를 바탕으로 실제 데이터 샘플을 사용하여 모델을 구현하고, 그 시각화 결과는 기계 학습 모델의 해석에서 일반화 오류에 대한 더 나은 이해를 제공함을 확인했다. 결과적으로 모델의 해석은 데이터에 잘못된 답이나 질문이 있는지 분석가의 편견을 명확히 하고, 전이 학습에 기반한 미세 조정의 근거를 제시한다.Artificial Intelligence illustrate not the causality, but the highest probability of the pattern in data unless the data has a bias because many algorithms depend on the data. This paper aims to tackle human interpretability based on the trade-off between complexity and reliability. This study first emphasized several theoretical perspectives among IML methods taxonomy. Based on the comprehension of IML approaches, it highlighted the implementation of modeling using real data sample. The research results give better understanding of generalization error in the interpretation of Machine Learning. Consequently, the interpretation of a model is to clarify the bias of the analysts whether data has a wrong answer or question.I. 서론 1 1.1 연구동기 1 1.2 연구범위 2 1.3 논문의구성 3 II. 관련연구 4 2.1 해석가능한인공지능 (IML) 4 2.1.1 IML 기술분류 (Taxonomy) 6 2.2 데이터주변의희소선형결합해석 8 2.3 CNN 모델의특징추출시각화 11 2.3.1 클래스활성화맵 (CAM) 12 2.3.2 Gradient-weighted CAM 12 2.3.3 CAM vs. Grad-CAM 14 2.4 합성곱신경망 (CNN) 15 2.5 전이학습 (Transfer Learning) 19 2.6 미세조정 (Fine Tuning) 21 2.7 최적화 (Optimization) 24 III. 연구방법 28 3.1 이미지분류모델링개발 28 3.2 성능개선문제의해결방안 29 3.3 성능평가지표 31 IV. 실험및결과 33 4.1 실험개요 33 4.2 실험환경 35 4.3 비정형데이터의결함패턴분류모델링 36 4.3.1 스크래치 37 4.3.2 전이학습 39 4.4 수퍼픽셀로표현한모델링결과분석 40 4.5 특징시각화를활용한모델링결과분석 41 4.5.1 CAM 41 4.5.2 Grad-CAM 42 4.6 미세조정에따른모델링결과 43 4.7 성능평가 44 4.8 결과분석 45 V. 결론 49 5.1 고찰 49 5.2 연구제한 50 5.3 향후계획 51 참고문헌 52 Abstract 59Maste

웃고 있는 조선화 : 북한 회화에 담긴 웃음의 정치

인류학과 "북한의 인류학" 수업 수강생들이 제작한 미니

Dynamics of Business Cycles in Korea: The Role of External Shocks

Using a multi-sector dynamic stochastic general equilibrium model, we investigate the dynamic effects of a variety of shocks to a small open economy. In particular, we calibrate the model to match the main characteristics of business cycles in Korea and aI. Introduction 　　II. Properties of Business Cycles in Korea 　　III. Model 　　IV. calibration 　　V. Comparing the Second Moments 　　VI. Impulse Responses 　　VII. Conclusion 　　Reference 　　Appendix. Data Sources and Definitio

단어 임베딩을 활용한 텍스트 임베딩 모델 연구

학위논문 (석사)-- 서울대학교 대학원 : 융합과학기술대학원 융합과학부(디지털정보융합전공), 2018. 8. 서봉원.가변 길이의 텍스트를 텍스트의 맥락 정보를 반영한 벡터로 변환하는 방법인 문장 혹은 문단 임베딩은 다양한 기계학습 시스템에서 감성 분석 등의 텍스트 분류 문제, 텍스트의 유사도 측정, 클러스터링, 시각화 등 고정된 차원의 벡터를 입력으로 요구하는 각종 과제를 수행하기 위한 기본적인 특징 추출 방법으로 사용되고 있다. 기존의 텍스트의 벡터 표현을 위해 널리 사용되고 있었던 단어 자루(Bag-of-Words) 모형은 단순하고 효과적이지만 차원의 크기가 단어의 숫자에 비례해서 증가하며 레이블 없는 텍스트 데이터를 활용하기 어렵다는 단점이 있다. 이러한 한계를 극복하기 위해 제안된 문단 벡터(Paragraph Vector)는 새로운 데이터에 대한 벡터 표현을 학습하고 생성하는데 적용하기 위해서는 기존 모델을 새로운 데이터에 대해 추가적으로 학습시키는 추정 과정을 필요로 한다는 한계가 있다. 시퀀스 투 시퀀스(Sequence to Sequence) 모형을 기반으로 선후 문장과의 문장 간 관계를 활용해 문장의 벡터 표현을 생성하는 인코더를 학습하는 생각 생략 벡터(Skip-Thought Vectors) 모형은 학습을 위해 문장 간 선후 관계를 활용하기에 여러 문장이 포함되며 선후 관계를 설정하기 어려운 문단 수준에는 바로 적용되기 어려우며 텍스트 임베딩의 생성에 많은 연산 자원을 필요로 한다는 단점을 갖고 있다. 본 연구에서는 전이 학습의 문제와 임베딩 생성에 필요한 연산량 및 가변 길이 텍스트 처리의 용이성의 문제 등을 고려하여 단어 임베딩의 합을 통해 텍스트 임베딩을 생성하는 모형을 제안한다. 기존의 단어 임베딩이 유니그램(Unigram)을 사용하는 것과는 달리 본 연구의 모형에서는 바이그램(Bigram) 및 트라이그램(Trigram) 등의 n-그램(n-gram)을 활용해 텍스트 임베딩을 개선하였다. 또한 이를 컨볼루션 신경망을 사용한 모형과 비교하여 컨볼루션 신경망과 같은 추가적인 구조의 도입 없이도 좋은 성능적 특성을 보일 수 있음을 검토하였다. 본 연구는 문장 혹은 문단의 벡터 표현을 생성하기 위한 단순한 방법을 제시하는 동시에 부수적으로 학습한 n-그램 단어 임베딩의 특성을 분석하였다. 단어 임베딩의 특성에 대한 분석과 단어 임베딩의 단순한 결합이 보여주는 효과성을 통해 자연어 처리 과제에 요구되는 텍스트의 특성을 포착하기 위해 필요한 조건을 이해하는 것과 함께 텍스트의 고속 처리가 필요한 실용적인 상황에서 사용할 수 있는 도구로서 기여할 수 있을 것으로 기대한다.제 1 장 서 론 6 제 1 절 연구의 배경 6 제 2 절 연구의 목표 9 제 2 장 선행 연구 11 제 1 절 문장 및 문단 임베딩 11 1.1 Word2vec 12 1.2 문단 벡터(Paragraph Vector) 14 1.3 생각생략 벡터(Skip-Thought Vectors) 16 제 2 절 텍스트 처리를 위한 신경망 구조 19 2.1 문장 분류를 위한 컨볼루션 신경망(Convolutional Neural Networks for Sentence Classification) 19 2.2 구조적 자기 주의 문장 임베딩(A Structured Self-Attentive Sentence Embedding) 20 제 3 장 연구 방법 및 설계 23 제 1 절 시스템 구조 23 제 2 절 데이터셋과 전처리 및 학습 절차 31 2.1 데이터셋 31 2.1 학습 절차 및 모형 상세 34 제 4 장 실험 결과 38 제 1 절 데이터셋에 대한 전이 학습 결과 38 제 2 절 모형의 변형에 따른 성능 변화 41 제 2 절 학습된 모형의 특성 분석 44 제 5 장 논의 52 제 6 장 결론 및 향후 연구를 위한 제언 59 참고문헌 62Maste

Dynamic Welfare Effects of Tax Reform: Case of Korea

This paper analyzes welfare effects of revenue neutral tax reform using a small open economy dynamic general equilibrium model. We apply this model to the Korean data and examine welfare effects of various tax reformsremoval of capital income tax and/orⅠ. Introduction Ⅱ. Model 　1. Consumer 　2. Firms 　3. Government Ⅲ. Solution Method Ⅳ. Calibration Ⅴ. The Effects of Tax Reforms 　1. Comparison of welfare effects 　2. Dynamics of welfare gains 　3. Sensitivity Analysi