경수로 노심 2차원 출력분포 예측을 위한 합성곱 인공 신경망

학위논문(석사)--서울대학교 대학원 :공과대학 원자핵공학과,2019. 8. 주한규.The purpose of this research is to develop a neural network model that is computationally inexpensive in predicting two-dimensional assembly-wise power distributions along with assembly-wise pin power peaking factors (PPPFs) by taking only a set of beginning of cycle (BOC) macroscopic cross sections. Such a computationally inexpensive and fast prediction model is needed because the conventional prediction model still renders a computational burden in loading pattern(LP) optimization processes. As the first step of the research, the previously developed state-of-the-art power prediction neural network models are evaluated to select the best one. It is then modified using convolutional neural network architectures. 20,000 Korean Standard Nuclear Power Plant (OPR1000) LPs are randomly generated and used for supervised learning. The reference power distributions are generated by using a three-dimensional core analysis code called ASTRA. The averaged and maximum absolute error(AE) in the assembly power predictions obtained by the trained neural network turns out to be 0.19% and 7.34%, respectively, while those for PPPF are 0.31% and 9.13%, respectively. In order to test the model in the region of interest, 3,000 general design bounded LPs which reside outside of the range of the trained data are separately generated. It appears that the maximum AE for assembly-wise power and PPPF are 3% and 5%, respectively. Those errors are within the acceptable range when an approximate model is used in a LP optimization process. The computing time of the neural network model is around 0.2 second, which is about 1000 time faster than ASTRA. The model can greatly reduce the computing time of LP optimization processes. Although it can be a great utility for a nuclear designer as well as in an automatic LP optimization program, it has one limitation. The trained neural network model is only valid within the specified core conditions: a number of total and fresh fuels, initial boron concentration, T/H conditions, and etc. If any of the core condition changes, the model can produce higher than presented errors.이 논문의 주 목표는 2차원 형태의 거시단면적을 이용하여 한국의 대표적인 가압경수로인 OPR1000의 장전모형을 빠르게 분석한 후 집합체 단위의 출력과 최대 핀 출력을 예측하는 인공신경망을 개발하는 것이다. 이와 같은 인공신경망 개발이 필요한 이유는 장전모형 최적화 단계에서 보다 빠른 계산 능력이 필요하기 때문이다. 이번 논문과 비슷한 목표를 가진 선행연구를 바탕으로 다른 형태의 인공신경망을 적용 평가하였다. 최근 이미지 분석을 위해 널리 쓰이고 있는 합성곱 인공신경망을 적용하였으며, 학습을 위한 데이터는 KNF사의 ASTRA 코드를 통해 만들었다. 약 2만개의 랜덤한 장전모형을 생산하였으며, 이를 인공신경망으로 지도학습하였다. 집합체 단위의 출력의 평균 오차와 최대 오차는 각각 0.19%와 7.34%이며, 최대 핀 출력의 평균 오차와 최대 오차는 각각 0.31%와 9.13%이다. 기존의 설계된 최적 장전모형과 비슷한 분포를 가진 약 3천개의 랜덤한 장전모형을 이용하여 검증한 결과 집합체 출력과 최대 핀 출력의 최대 오차는 각각 3%와 5% 수준으로 장전모형 최적화 작업 시 ASTRA 코드 대신 간이 평가 코드로 활용 가능한 수준이다. 계산 시간은 CPU(Intel i7-3770 3.40GHz, DDR3 16GB)기준 ASTRA 코드는 200초 정도 소요되지만, 개발된 인공신경망은 이보다 1000배 빠른 0.2초이다. 개발된 인공신경망은 장전모형 최적화 코드와의 연계를 통해 장전모형 최적화 시간을 크게 단축시킬 수 있을 뿐 아니라 설계자에게도 많은 도움을 줄 수 있다. 지도학습된 인공신경망은 동일한 노심 조건(연료 총 다발 수, 초기 붕소농도, 열수력 조건, 신연료 다발 수 등)에서만 앞선 오차율을 보장하며, 조건이 바뀔 경우 추가로 데이터 생산 후 추가 지도학습이 필요하다.Abstract i Table of Contents iii List of Tables iv List of Figures v 1. Introduction 1 1.1 Background 1 1.2 Purpose and Scope 2 2. Review of previous researches 4 2.1 Optimization Layer by Layer 4 2.2 Improvements 6 3. Method 8 3.1 Deep Learning Models 8 3.2 Convolution Neural Network 9 3.3 Residual Neural Network 10 3.4 Architecture 11 4. Result 24 4.1 Loading Pattern Random Generation 24 4.2 Supervised Learning 27 5. Conclusions 43 Reference 44 초 록 46Maste

장르 기반 글쓰기 수업에서 영어를 외국어로 학습하는 세 명의 한국인 고등학생들의 제2 언어 쓰기 발달에 관한 사례 연구

학위논문(박사) -- 서울대학교대학원 : 사범대학 외국어교육과(영어전공), 2022. 8. 김진완.Second language (L2) writing has been neglected in the instruction of Korean English as a foreign language (EFL) context. L2 Writing development in secondary education supports L2 development and provides the foundation of academic literacy for tertiary education. However, L2 writing instruction has been scarcely offered to secondary school students, and writing performance tests required by the Korean national curriculum have raised the issue of validity. In this context, the present case study explored L2 writing development, learner autonomy in L2 writing, and genre awareness of the three novice EFL Korean high school students through genre-based writing instruction based on Systemic Functional Linguistics (SFL). Genre-based writing instruction has facilitated the three participants to develop L2 argument writing based on the expansion of meaning-making resources, gain more control of L2 writing and raise genre awareness. Explicit attention to the rhetorical and linguistic features of argument genre and repetition of writing tasks have assisted them in noticing the gaps and developing repertoires for L2 argument writing. They have shown the expansion of ideational, interpersonal, and textual meaning-making resources in their writing, as shown in the use of expanded noun groups, hypotactic and embedded clauses, interpersonal resources and thematic development, leading to the enhancement of a persuasive argument over time. The instructor’s scaffolding successfully guided the novice writers in noticing the genre-specific features of L2 writing, developing metacognitive genre awareness based on their L1 (Korean) literacy, and taking the initiative in their L2 writing. The three participants have shown diverse developmental trajectories depending on their learning backgrounds. First, SeeEun who has a low level of L2 confidence despite the study-abroad experience has shown development of her autonomy in L2 writing through repeated completion of writing tasks beyond her grammar-and comprehension-oriented L2 study. Secondly, JeeHyung who is a confident L2 speaker from her learning experience in the English-immersion kindergarten in Korea has developed more extended discourse over time, exercising metacognitive strategies such as textual borrowing and conscious attention to the genre-specific features of the genre exemplar. Thirdly, an experienced L1 writer, SooYoung has shown a considerable improvement in her argument writing with expanded metafunctional meaning-making resources and greater autonomy in L2 writing. Her metacognitive genre awareness has affected her L2 academic literacy development and her dialogic style of writing that engages the audience. Although the use of language in the spoken register, the confusion of genre features, and limited use of grammatical metaphor revealed their L2 writing in the early stages of the developmental continuum, explicit attention to genre-specific features through the use of metalanguage encouraged the three novice writers to develop their L2 argument writing, gain more control of their L2 writing, and raise their genre awareness in the Zone of Proximal Development.외국어로 영어를 학습하는 한국인 고등학생의 쓰기 발달은 말하기, 듣기, 읽기의 다른 영역에 비해 등한시되어 왔다. 중등교육과정에서 쓰기 능력의 향상은 영어 능력의 발전을 촉진할 뿐만 아니라, 고등교육의 학문적 글쓰기 능력 향상을 위한 토대 제공을 위해 필수적이다. 그러나 현재 한국의 중등 교육과정에서 영어 쓰기 교육은 거의 제공되지 않고 평가만 이루어지고 있어 그 타당성의 문제 또한 제기되고 있다. 이에 본 연구는 한국인 고등학생들의 영어 쓰기 능력 향상을 돕기 위해 체계 기능 언어학에 기반한 장르 기반 글쓰기 수업을 진행하고, 세 명의 초급 수준의 고등학교 2학년 학생들의 제2 언어 쓰기 발달, 제2 언어 쓰기의 주도성과 장르 인식의 변화를 사례 연구를 통해 심층적으로 탐구하였다. 장르 기반 글쓰기 수업은 세 명의 초급 영어 학습자들이 적절한 언어를 사용하여 논증적 글쓰기 능력을 발전시키고 주도적으로 글을 완성할 수 있도록 촉진하였으며 장르에 대한 인식을 높이는데 기여하였다. 논증적 글쓰기의 장르적 특징에 관한 명시적 교수와 반복적인 글쓰기는 세 명의 학생들이 자신의 부족한 언어적 지식을 인식하고 향상시킬 수 있도록 이끌었다. 학생들은 논증적 글쓰기 장르에 적합한 관념적, 대인관계 및 텍스트의 메타기능에 적절한 언어적 자원을 발전시켜 나가며 글을 완성하였으며, 복합명사구의 사용, 종속 구문과 내포절 사용의 증가, 그리고 주제의 발전적 측면에서 향상을 보였다. 학습자들은 교사의 비계 제공을 통해 장르적 특징에 주목하고 제1 언어(한국어)의 메타인지적 장르 인식을 활용하여 교사의 도움에 대한 의존을 낮추고 주도적으로 자신의 글쓰기를 완성하는 능력의 향상을 보였다. 세 명의 학습자들은 개인적 특성에 따라 다양한 발달 궤적을 드러냈다. 외국에서의 영어 학습 경험에도 불구하고 낮은 읽기 성적으로 영어에 대한 자신감이 낮은 시은이는 문법과 이해 중심의 학습에서 나아가 반복적인 글쓰기 학습을 통해 자신의 생각을 언어로 표현하고 이에 대한 피드백을 받음으로써 주도적으로 글을 작성하는 능력이 향상되었다. 국내에서 유아기에 영어 몰입 교육을 받은 지형이는 영어 말하기에 자신감을 가진 내적 동기가 높은 학생으로서, 메타인지 전략을 활용하여 읽기 지문의 장르적 요소에 주목하고 교사와 함께 구성한 텍스트의 구문을 활용하여 보다 확장된 글을 작성하는 능력의 향상을 보였다. 유창한 한국어 글쓰기 능력을 가진 수영이는 자신의 글쓰기 경험을 바탕으로 영어 글쓰기 활동에 적극적으로 참여하여, 논증적 글쓰기 장르에 적합한 언어적 자원을 활용하여 설득력 있는 글을 주도적으로 완성해나가는 측면에서 큰 향상을 보였다. 그녀의 메타인지적 장르 인식은 논증 장르의 읽기 문해력과 독자의 참여를 유도하는 글쓰기적 특징에 영향을 주었다. 비록 구어체의 사용, 장르적 특징의 혼용, 그리고 제한적인 문법적 은유의 사용은 학생들의 영어 쓰기가 초기 수준의 발달 단계에 있음을 드러냈으나, 교사의 메타언어 사용을 통한 명시적 장르 지도는 학습자들의 메타기능적 언어사용력 증가를 통한 논증적 글쓰기의 향상과 글쓰기의 주도성 및 장르 인식의 향상에 기여하여 잠재적 발달 수준에 이를 수 있도록 이끌어냈다는 측면에서 교육학적 함의를 지닌다.CHAPTER 1. INTRODUCTION 1 1.1. Background of the Study 1 1.2. Purpose of the Study 11 1.3. Organization of the Dissertation 13 CHAPTER 2. LITERATURE REVIEW 15 2.1. Theoretical Framework 15 2.1.1. Systemic Functional Linguistics 15 2.1.1.1. Grammatical Metaphor 19 2.1.2. Sociocultural Theory 20 2.1.2.1. Learner Autonomy 24 2.1.3. Genre Pedagogy 26 2.1.3.1. SFL-informed Genre Pedagogy 27 2.1.3.2. Genre in Systemic Functional Linguistics 32 2.1.3.3. Rhetorical and Linguistic Features of Argument Genre 34 2.2. L2 Writing Development in SFL-informed Genre-based Instruction 37 2.2.1. SFL-informed Genre-based Curriculum 37 2.2.2. L2 Writing Development in Genre-based Instruction 43 2.2.2.1. L2 Development in Genre-Specific Text Production 43 2.2.2.2. L2 Development in Academic Language and Literacy 47 2.2.2.3. Development in Genre Awareness and Critical Language Awareness 57 2.3. Limitations of Previous Studies 61 CHAPTER 3. METHODOLOGY 67 3.1. Context of the Study 67 3.1.1. Setting 67 3.1.2. Participants 68 3.2. Genre-based Writing Instruction 69 3.2.1. Procedures 69 3.2.2. Curriculum of Genre-based Writing Instruction 73 3.2.3. Teaching Materials 76 3.2.4. The Use of Metalanguage in Genre-based Writing Instruction 85 3.3. Data Collection & Analysis 90 3.3.1. Data Collection 90 3.3.2. Data Analysis 91 3.3.2.1. L2 Writing Development in SFL Meaning-making Resources 92 3.3.2.2. Development of Learner Autonomy in L2 Writing 97 3.3.2.3. Changes in Genre Awareness Through Genre-based Writing Instruction 100 CHAPTER 4. TOWARDS A MORE INDEPENDENT WRITER: THE CASE OF SEEEUN 102 4.1. SeeEun's Background: A Diligent Learner of English Comprehension with Study-abroad Experience 102 4.2. L2 Writing Development of SeeEun in SFL Meaning-making Resources 105 4.3. Development of SeeEun's Autonomy in L2 Writing 125 4.4. Changes in SeeEun's Genre Awareness Through Genre-based Writing Instruction 130 CHAPTER 5. TOWARDS A MORE FLUENT WRITER: THE CASE OF JEEHYUNG 135 5.1. JeeHyung's Background: A Confident English Speaker with a High Level of Intrinsic Motivation 135 5.2. L2 Writing Development of JeeHyung in SFL Meaning-making Resources 138 5.3. Development of JeeHyung's Autonomy in L2 Writing 153 5.4. Changes in JeeHyung 's Genre Awareness Through Genre-based Writing Instruction 163 CHAPTER 6. TOWARDS AN AUTONOMOUS WRITER: THE CASE OF SOOYOUNG 168 6.1. SooYoung's Background: An Earnest Writer and Learner of English within the Korean Curriculum 168 6.2. L2 Writing Development of SooYoung in SFL Meaning-making Resources 171 6.3. Development of SooYoung's Autonomy in L2 Writing 187 6.4. Changes in SooYoung 's Genre Awareness Through Genre-based Writing Instruction 194 CHAPTER 7. DISCUSSION & CONCLUSION 200 7.1. L2 Writing Development, Autonomy in L2 Writing, and Genre Awareness of the Three Participants 200 7.2. The Developmental Trajectories of the Three Participants 208 7.2.1. The Developmental Trajectory of SeeEun 209 7.2.2. The Developmental Trajectory of JeeHyung 212 7.2.3. The Developmental Trajectory of SooYoung 216 7.3. Pedagogical Implications and Suggestions for Further Research 219 REFERENCES 225 APPENDICES 249 ABSTRACT IN KOREAN 258박

An Artwork Study on the Representation of Insubstantiality of Desire Consumption

사람들은 생활에 필수적인 요소를 채우는 ‘필요소비’뿐만 아니라 결핍과 쾌락을 채우는 ‘욕망소비’를 한다. 사물의 생산자는 기능 이상의 이미지를 광고하고, 소비자는 기능 이상의 기대감을 가지며 사물에 매개하는 욕망을 과장한다. 사람들은 사물을 기본적인 필요를 충족해주는 대상을 넘어 욕망을 매개하는 대상으로 여기며 사물에 지나친 욕망을 투영하지만, 이를 인지하지 못한 채 사물을 소비하는 경우가 많다. 또한, 사물을 소유하는 것은 즉각적인 결과를 내어 손쉬운 성취가 가능하기 때문에, 사람들은 욕망의 근원과 실체를 정확히 파악하지 못한 채 사물을 소비하는 경향이 있다. 그러나 사물을 통한 욕망 실현은 허구일 수 있다. 왜냐하면 사물은 욕망이 투사된 매개물일 뿐 욕망 그 자체가 아니기 때문이며, 사물의 이미지가 허구적 욕망을 생성하기도 하기 때문이다. 게다가 허구적 욕망은 소비를 조장하고, 이미지가 실체를 대신하는 전복 현상을 발생시키기도 한다. 또한, 이러한 현상 속에서 허영이 만들어지며, 사람들은 이로 인해 결핍감을 느끼기도 한다. 본 연구는 사물을 통한 욕망 성취의 허구성을 시각화하는 조형 방법을 연구하는 데 목적이 있다. 본인은 개인적인 경험과 사회 현상을 통해 특정 사물이 매개하는 욕망을 분석하며 사물의 허구적 아우라를 탐구하였다. 사물의 허상은 작품으로 물질화되어 노출되는데, 이는 크게 세 가지 표현 방법으로 분류된다. 첫째는 사물의 껍질을 해체하거나 변형하여 표상성을 제거하는 것이고, 둘째는 사물의 재질을 바꾸어 인식의 혼란을 가해 표상성을 교란하는 것이며, 셋째는 사물의 이미지와 대비되는 재료를 사용하여 표상성을 전환하는 것이다. 본인은 허구성을 뒤집어 쓴 사물을 위와 같은 조형 방법으로 풀어내어 사람들이 사물에 투영하고 있는 허구성을 드러내고, 이를 통해 허구적 욕망을 완화하고자 한다. 작품에서 표상성이 제거/교란/전환된 사물은 이미지가 전환되어 기존의 매개하던 욕망을 상실한다. 본인의 작업은 사물의 외형을 변화 시켜 사물을 기호가 아닌 물질로서 인식하게 함으로써 욕망소비의 허구성으로부터 자유롭게 하고자 하는 시도이다.People engage not only in ‘necessary consumption’ to satisfy essential elements of life, but also in ‘desire consumption’ to feel pleasure and contentment. The producers advertise an image that transcends the object’s function and designated purpose, and, naturally, consumers accept this exaggerated expectation, which amplifies the desire they project onto the objects. People consider objects not just as a means to satisfy basic needs but as something more, a medium of desire, and project excessive desires on them. However, they often consume objects without realizing this. In addition, since purchasing and owning objects produces immediate results that can easily be achieved, people tend to consume objects without accurately grasping the source and reality of their desires. Nevertheless, fulfilling desire through acquisition of objects may lead to false satisfaction. This is because objects are only the medium through which desire is projected, not the end goal itself, and the image, or visual representation, of objects often creates illusory desire. Furthermore, fabricated desire encourages compulsive consumption and can cause an overturning phenomenon in which images of an object replace the object itself. Also, in this phenomenon, vanity is created, and this leads people to feel a sense of deficiency. The purpose of this study is to study the sculpting methods to visualize the inefficacy of fulfilling desire through acquisition of objects. Based on personal experiences and social phenomena, I explored the fictitious aura of objects by analyzing the desires mediated by specific objects. The fictitious image of an object is materialized and exposed as a piece of work, which can be largely classified into three methods. The first is to remove the representation by dismantling or transforming the surface skin of the object, the second is to disrupt the representation by changing the consisting material of the object, and the third is to convert the representation by using the material that contrasts with the image of the object. By unraveling the objects covered in fictitious and fabricated imagery using the methods mentioned above, I intend to reveal the vanity that people are projecting onto the object, thereby alleviating the misguided desire. Objects whose representation has been removed/disrupted/converted through artistic endeavor lose their exaggerated illusory images and the desire forged by those images. My work is an attempt to free us, the consumers, from the insubstantiality of desire consumption by altering the appearance of objects and allowing us to recognize objects as mere materials rather than symbols of our desires.들어가며 1 허상성의 도출과 허구성 표현 5 1. 해체 및 분해를 통한 표상성의 제거 5 2. 재질감의 대조를 통한 표상성의 교란 14 3. 재료의 변화를 통한 표상성의 전환 34 마치며 47 작품 목록 50 참고 문헌 51 Abstract 52석

짝지어 영작문 쓰기 과업에서 한국 고등학생들의 협력적 대화

학위논문 (석사)-- 서울대학교 대학원 : 외국어교육과(영어전공), 2015. 6. 김진완.This study explores how four Korean high school learners of English interact with each other in L2 pair writing and how collaborative dialogues affect their pair writing and L2 learning. For this purpose, the general patterns of interaction of the Korean EFL learners, and the functions and dynamics of collaborative dialogues in their L2 pair writing were investigated in detail. Four female Korean students in the 10th grade volunteered to a four-week collaborative pair writing program as an extracurricular class (dyad A and B). Self-selected pairs formed a heterogeneous group, and they participated in the collaborative process writing of planning, drafting and revising. Peer interaction was video- taped and analyzed microgenetically, and individual interviews were conducted at the end of the program. The analysis of the data revealed the followings as to the research questions addressed. First, dyad A displayed a collaborative interaction pattern consistently in EFL pair writing, while dyad B showed a transition in the interaction pattern: from dominant/passive to collaborative interaction. Though dyad B engaged in a dominant/passive interaction at the beginning due to a relatively large L2 proficiency difference, their interaction pattern changed over time, as the lower-level participant as well as the higher-level partner actively engaged in the writing process and negotiated mediation. Collaborative peer interaction facilitated the learners to complete the L2 composition task and gain a sense of confidence in L2 writing. Second, the L1 collaborative dialogue functioned as a crucial cognitive and social tool for L2 learning and writing of the EFL students. L1 collaborative dialogues promoted the learners to maintain focus on the task, provide affective support with one another and deepen their understanding of the target language. Mutual scaffolding and private speech in L1 collaborative dialogues helped the learners to regulate their cognitive process of strategic L2 writing and L2 reflection. In addition, L1 collaborative dialogues served social functions of mediating communication and establishing intersubjectivity. Third, collaborative dialogues in the Language-Related Episodes demonstrated that a high level of mutual scaffolding and mutual engagement facilitated the learners to consciously reflect on the L2 and co-construct L2 composition beyond their individual language competence. Both higher-level and lower-level participants actively initiated the discussion over linguistic problems and the peer interlocutors provided appropriate assistance attuned to the needs of their partner. The students mostly provided explicit forms of assistance, and negotiated the mediation offered by their peer interlocutors. Lastly, lack of the learners L2 linguistic knowledge and limited engagement of the pairs affected unsuccessfully resolved LREs. Proper use of other resources, the teacher and the dictionary, helped the students to resolve linguistic challenges outside their ZPDs during collaborative writing. In conclusion, L1 collaborative dialogues of the Korean students in L2 pair writing created a cognitive and social space where the peer interlocutors mutually provided scaffolding with one another and actively engaged in writing process and L2 learning. This study suggests that collaborative dialogues in the shared L1 function as an integral mediating tool in the Korean learners L2 pair writing. Thus, L2 pair writing tasks can be an effective complement to the English writing courses in Korean high schools, when teachers unfasten the restrictions on the exclusive L2 use and create a collaborative learning environment while providing proper resources.ABSTRACT i TABLE OF CONTENTS v LIST OF TABLES viii CHAPTER 1 INTRODUCTION 1 1.1 The Purpose of the Study 1 1.2 Research Questions 5 1.3 Organization of the Thesis 6 CHAPTER 2 LITERATURE REVIEW 7 2.1 Pair Writing in Second/Foreign Language Learning 7 2.1.1 Definitions of Pair Writing 7 2.1.2 Effects of Pair Writing on Second/Foreign Language Learning 8 2.1.3 Variables in Pair Writing: Proficiency Difference and Patterns of Pair Interaction 11 2.2 Collaborative Dialogue in Second/Foreign Language Learning 13 2.2.1 Definitions of Collaborative Dialogue 13 2.2.2 Functions of Collaborative Dialogue in Second/Foreign Language Learning 15 2.2.3 Effects of Collaborative Dialogue on Second/Foreign Language Learning 18 2.2.4 Dynamics of Collaborative Dialogue in Second/Foreign Language Learning 19 CHAPTER 3 METHODOLOGY 23 3.1 Participants 23 3.2 Procedures 25 3.3 Data Analysis 28 3.3.1 Data Analysis for Research Question 1: Dyadic Interaction Patterns 28 3.3.2 Data Analysis for Research Question 2: Functions of Collaborative Dialogue 31 3.3.3 Data Analysis for Research Question 3: Dynamics of Peer Interaction in Pair Writing in Terms of Language-Related Episodes 32 CHAPTER 4 RESULTS AND DISCUSSION 36 4.1 Dyadic Interaction Patterns in Pair Writing 36 4.1.1 General Interaction Pattern: Focusing on Dyad A 37 4.1.2 Transition in Interaction Pattern: Focusing on Dyad B 44 4.2 Functions of Collaborative Dialogue in Pair Writing 55 4.2.1 Maintaining Focus on the Task 55 4.2.2 Providing Affective Support to the Peer Interlocutor 60 4.2.3 Promoting Self-regulation 65 4.2.4 Discussion on Functions of Collaborative Dialogue 70 4.3 Dynamics of Peer Interaction in Pair Writing in Terms of Language-Related Episodes 72 4.3.1 Successfully Resolved Language-Related Episodes: Dynamics of Collaborative Dialogues 73 4.3.1.1 Requested Assistance 73 4.3.1.2 Unrequested Assistance: Corrective Feedback 80 4.3.2 Unsuccessfully Resolved Language-Related Episodes 84 4.3.2.1 What Brings about the Unsuccssfully Resolved LREs 85 4.3.2.2 How the Learners Resolve the Unsuccssfully Resolved LREs: Turning to Other Available Resources 90 CHAPTER 5 CONCLUSION 96 5.1 Summary of the Major Findings 96 5.2 Pedagogical Implications 100 5.3 Limitations of the Present Study and Suggestions for Future Research 102 REFERENCES 106 APPENDICES 118 ABSTRACT IN KOREAN 127Maste

Powder Temperature Effect on Heat Transfer Property for Nano Powder Synthesis Using Thermal Plasma

학위논문 (석사)-- 서울대학교 대학원 : 에너지시스템공학부, 2012. 8. 김곤호.열플라즈마 내 입사한 분말과 열플라즈마 간의 상호작용에 대한 연구는 1980년대에 간단한 전도 및 전하에 의한 구체의 가열에서부터 현재 난류 유동에 이르는 복잡한 현상까지 연구되어 왔다. 본 연구에서는 열플라즈마 내 입사한 분말과 열플라즈마 사이의 열전달 과정을 해석하는데 있어 전하에 의한 가열이 중요시 되는 높은 누센 (Knudsen) 수의 조건에서 분말 표면의 전자 균형에 따른 열플라즈마 – 분말 간 에너지 전달 과정에 대한 연구를 수행하였다. 본 연구에서는 선행 연구에서 주로 연구되었던 저압 스프레이 용사 공정이 아닌 나노 분말 합성 공정에서 분말 표면에서의 열전자 방출에 의한 분말 표면의 부유 전위 변화 및 열플라즈마와 에너지 전달 현상에 대해 연구하였다. 이를 위해 본 연구에서는 비이송식 열플라즈마 반응기를 이용해 나노 분말 합성 장치를 구성하였으며 합성 장치의 조건에 대해 선행 연구를 기반으로 열플라즈마 내 입사한 분말의 열적 특성 모사 코드를 작성하였다. 전산 모사 코드를 통해 운전 조건에 따라 모사된 분말의 온도 및 주변 열플라즈마 특성을 통해 분말의 열플라즈마 내 체류시간에 따른 분말 표면의 부유 전위 변화를 예측하였다. 운전 조건에 따른 분말 표면의 부유 전위 변화에서 선행 연구에서 고려되지 않았던 분말 표면에서의 열전자 방출이 열플라즈마 – 분말 간 에너지 전달에 미치는 영향을 확인하였다. 전산 모사를 통해 공정 조건에 따라 분말 표면의 열전자 방출 효과를 고려하지 않을 경우 열플라즈마 – 분말 간 에너지 전달을 과대해석 할 개연성이 있음을 확인하였고 이를 검증하기 위해 나노 분말 합성 장치를 통해 열플라즈마 내 테스트 분말 주입 환경을 모사하였다. 실험에서 얻어진 결과와 전산 모사 결과의 비교 검증을 통해 작성된 전산 모사 코드의 신뢰성을 평가하였고 열플라즈마 – 분말 간 에너지 전달에 열전자 방출이 미치는 영향을 검증하였다. 본 연구를 통해 얻은 플라즈마 내 입사 분말의 체류 시간 내 부유 전위 변화와 이에 따른 열전달 해석은 열플라즈마 내 공정 중 분말 가열 효과 예측 및 저압 공정에서 생성된 더스트 거동 및 에너지 전달 연구에 기여할 것으로 예상된다.Researches an interaction between thermal plasma and immersed powder has been studied from the early 1980s. In the early 1980s, they dealt with simple heat conduction model on spherical conductor inside hot gases, but in current state, they dealt with complex physical phenomena like turbulence effect on thermal plasma – powder interaction. For the study of thermal plasma – immersed powder energy transfer mechanism in high Knudsen number condition, in which is the effect of charged particle heating on immersed powder is the dominant case, the evaluation of charge balance on powder surface is essential. The researches on high Knudsen number condition has been intensively studied in low pressure plasma spray process, however this dissertation studied nano powder synthesis process and consider thermionic emission on the powder surface to evaluate the charge balance model and energy transfer properties on powder surface during the powder inflight time, which was not considered in previous researches. DC plasma torch and immersed powder simulation code was equipped to evaluate the effect of thermionic emission on the powder surface to powder surface charge balance model and energy transfer properties. Use of the immersed powder simulation code regarding thermionic powder emissions confirmed the possibility of overestimating the thermal plasma – powder energy transfer To confirm simulation results, modified test particle experiment condition was used on nano powder synthesis system. Comparative studies of experimental results and simulation results support the reliability of simulation code and confirm the thermionic electron emission effect on thermal plasma – powder energy transfer properties Results of this dissertation about thermal plasma – immersed powder energy transfer during the inflight time will contribute toward to evaluation powder heat transfer in thermal plasma process and predict the dust behavior in low pressure process제 1 장 서 론 6 제 1 절 연구의 배경 6 제 2 장 8 제 1 절 열플라즈마 – 분말 간 에너지 전달의 선행 연구 8 제 2 절 전하에 의한 열플라즈마 내 입사 분말 가열 메커니즘 12 제 3 절 분말 표면 전하 균형 및 분말 표면 전위 형성 메커니즘 16 제 3 장 20 제 1 절 실험 장치 구성 20 제 2 절 열플라즈마 내 입사 분말 열적 특성 모사 코드 23 제 4 장 31 제 1 절 열플라즈마 내 체류 분말의 온도, 속도 분포 특성 31 제 2 절 분말 표면에서의 열전자 방출에 따른 열플라즈마 내 체류 분말의 부유 전위특성 변화 37 제 3 절 분말 표면에서의 열전자 방출이 열플라즈마 – 분말 간 에너지 전달에 미치는 영향 41 제 4 절 분산된 크기의 분말에서 열플라즈마 – 분말 간 에너지 전달 특성 49 제 5 장 55 제 1 절 나노 분말 합성 시스템을 이용한 실리콘 나노 분말 합성 및 전산 모사를 이용한 분말 크기 분산 분석 55 제 6 장 64 제 1 절 결 론 64 참고문헌 66 Abstract 67Maste

Perioperative risk factors for in-hospital mortality after emergency gastrointestinal surgery

Few studies have evaluated the risk factors for in-hospital mortality in critically ill surgical patients who have undergone emergency gastrointestinal (GI) surgery. The aim of this study was to identify the risk factors associated with in-hospital mortality in critically ill surgical patients after emergency GI surgery.The medical records of 362 critically ill surgical patients who underwent emergency GI surgery, admitted to intensive care unit between January 2007 and December 2011, were reviewed retrospectively. Perioperative biochemical and clinical parameters of survivors and nonsurvivors were compared. Logistic regression multivariate analysis was performed to identify the independent risk factors of mortality.The in-hospital mortality rate was 15.2% (55 patients). Multivariate analyses revealed cancer-related perforation (odds ratio [OR] 16.671, 95% confidence interval [CI] 2.629-105.721, P?=?0.003), preoperative anemia (hemoglobin <10?g/dL; OR 6.976, 95% CI 1.376-35.360, P?=?0.019), and preoperative hypoalbuminemia (albumin <2.7?g/dL; OR 9.954, 95% CI 1.603-61.811, P?=?0.014) were independent risk factors of in-hospital mortality after emergency GI surgery.The findings of this study suggest that in critically ill patients undergoing emergency GI surgery, cancer-related peritonitis, preoperative anemia, and preoperative hypoalbuminemia are associated with in-hospital mortality. Recognizing risk factors at an early stage could aid risk stratification and the provision of optimal perioperative care.ope

MUC1 selectively targets human pancreatic cancer in orthotopic nude mouse models

The goal of this study was to determine whether MUC1 antibody conjugated with a fluorophore could be used to visualize pancreatic cancer. Anti-MUC1 (CT2) antibody was conjugated with 550 nm or 650 nm fluorophores. Nude mouse were used to make subcutaneous and orthotopic models of pancreatic cancer. Western blot and flow cytometric analysis confirmed the expression of MUC1 in human pancreatic cancer cell lines including BxPC-3 and Panc-1. Immunocytochemistry with fluorophore conjugated anti-MUC1 antibody demonstrated fluorescent areas on the membrane of Panc-1 cancer cells. After injecting the conjugated anti-MUC1 antibodies via the tail vein, subcutaneously transplanted Panc-1 and BxPC-3 tumors emitted strong fluorescent signals. In the subcutaneous tumor models, the fluorescent signal from the conjugated anti-MUC1 antibody was noted around the margin of the tumor and space between the cells. The conjugated anti-MUC1 antibody bound the tumor in orthotopically-transplanted Panc-1 and BxPC-3 models enabling the tumors to be imaged. This study showed that fluorophore conjugated anti-MUC1 antibodies could visualize pancreatic tumors in vitro and in vivo and may help to improve the diagnosis and treatment of pancreatic cancer.ope

Prevalences of Incidental Findings in Trauma Patients by Abdominal and Pelvic Computed Tomography

Purpose: Abdominal and pelvic computed tomography (APCT) is frequently used as a diagnostic tool in trauma patients. However, trauma unrelated, incidental findings are frequently encountered. The aim of this study was to determine the prevalences of incidental findings on APCT scans in trauma patients. Methods: The archived records of 801 trauma patients treated from January 2013 to December 2015 were reviewed retrospectively. Six hundred and forty of these patients underwent contrast enhanced APCT in an emergency department and were included in this study, and 205 (32.1%) of these patients had incidental findings. These findings were divided into two categories: category I, meaning a radiological benign finding not requiring further evaluation or follow-up, and category II, requiring further evaluation and follow-up. Results: One hundred and sixty (24.8%) patients were allocated to category I and 45 (7.2%) to category II. The most frequent incidental findings were discovered in kidneys (34.6%), followed by liver (28.8%), and gallbladder (15.6%). The most frequent finding in category I was a benign cyst (60.1%), followed by a simple stone (15.6%), and hemangioma (11.9%). Adenomyomatosis of the gallbladder (17.8%) was the most common lesion in category II, followed by atypical mass (15.6%), complicated stone (15.6%) and cystic neoplasm (15.6%). Conclusion: The prevalence of an incidental finding on APCT scans was 32.1%. Although category II lesions were not common in trauma patients, these findings should be communicated to patients, and when necessary referred to a primary care physician. Systems are required for producing appropriate discharge summaries and informing patients about the implications of incidental findings.ope

Severe persistent hypocholesterolemia after emergency gastrointestinal surgery predicts in-hospital mortality in critically ill patients with diffuse peritonitis

BACKGROUND: Plasma cholesterol acts as a negative acute phase reactant. Total cholesterol decreases after surgery and in various pathological conditions, including trauma, sepsis, burns, and liver dysfunction. This study aimed to determine whether hypocholesterolemia after emergency gastrointestinal (GI) surgery is associated with in-hospital mortality in patients with diffuse peritonitis. METHODS: The medical records of 926 critically ill patients who had undergone emergency GI surgery for diffuse peritonitis, between January 2007 and December 2015, were retrospectively analyzed. The integrated areas under the curve (iAUCs) were calculated to compare the predictive accuracy of total cholesterol values from postoperative days (PODs) 0, 1, 3, and 7. Cox proportional hazard regression modeling was performed for all possible predictors identified in the univariate and multivariable analyses. RESULTS: The total cholesterol level measured on POD 7 had the highest iAUC (0.7292; 95% confidence interval, 0.6696-0.7891) and was significantly better at predicting in-hospital mortality than measurements on other days. The optimal total cholesterol cut-off value for predicting in-hospital mortality was 61 mg/dL and was determined on POD 7. A Cox proportional hazard regression analysis revealed that a POD 7 total cholesterol level < 61 mg/dL was an independent predictor of in-hospital mortality after emergency GI surgery (hazard ratio, 3.961; 95% confidence interval, 1.786-8.784). CONCLUSION: Severe persistent hypocholesterolemia (<61 mg/dL) on POD 7 independently predicted in-hospital mortality, after emergency GI surgery, in critically ill patients with diffuse peritonitis.ope

A lexicon for hepatocellular carcinoma surveillance ultrasonography: benign versus malignant lesions

BACKGROUND/AIMS: To suggest a lexicon for liver ultrasonography and to identify radiologic features indicative of benign or malignant lesions on surveillance ultrasonography. METHODS: This retrospective study included 188 nodules (benign, 101; malignant, 87) from 175 at-risk patients identified during surveillance ultrasonography for hepatocellular carcinoma. We created a lexicon for liver ultrasonography by reviewing relevant literature regarding the ultrasonographic features of hepatic lesions. Using this lexicon, two abdominal radiologists determined the presence or absence of each ultrasonographic feature for the included hepatic lesions. Independent factors associated with malignancy and interobserver agreement were determined by logistic regression analysis and kappa statistics, respectively. RESULTS: Larger tumor size (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.06-1.183; P<0.001), multinodular confluent morphology (OR, 7.712; 95% CI, 1.053-56.465; P=0.044), thick hypoechoic rim (OR, 5.878; 95% CI, 2.681-12.888; P<0.001), and posterior acoustic enhancement (OR, 3.077; 95% CI, 1.237-7.655; P=0.016) were independently associated with malignant lesions. In a subgroup analysis of lesions <2 cm, none of the ultrasonographic features were significantly associated with malignancy or benignity. Interobserver agreement for morphology was fair (κ=0.36), while those for rim (κ=0.427), echogenicity (κ=0.549), and posterior acoustic enhancement (κ=0.543) were moderate. CONCLUSIONS: For hepatic lesions larger than 2 cm, some ultrasonography (US) features might be suggestive of malignancy. We propose a lexicon that may be useful for surveillance US.ope