GPU 상에서의 빠르고 가벼운 Path Guiding 알고리즘

학위논문(석사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2022.2. 김영민.We propose a simple, yet practical path guiding algorithm that runs on GPU. Path guiding renders photo-realistic images by simulating the iterative bounces of rays, which are sampled from the radiance distribution. The radiance distribution is often learned by serially updating the hierarchical data structure to represent complex scene geometry, which is not easily implemented with GPU. In contrast, we employ a regular data structure and allow fast updates by processing a significant number of rays with GPU. We further increase the efficiency of radiance learning by employing SARSA used in reinforcement learning. SARSA does not include aggregation of incident radiance from all directions nor storing all of the previous paths. The learned distribution is then importance-sampled with an optimized rejection sampling, which adapts the current surface normal to reflect finer geometry than the grid resolution. All of the algorithms have been implemented on GPU using megakernal architecture with NVIDIA OptiX. Through numerous experiments on complex scenes, we demonstrate that our proposed path guiding algorithm works efficiently on GPU, drastically reducing the number of wasted paths.본 연구는 GPU 상에서 작동하는 간단하지만 효과적인 path guiding 알고리즘을 제안한다. Path guiding은 path tracing의 노이즈를 줄이기 위해 제안된 기법으로 샘플링 과정에서 복사 휘도(radiance)를 배우고 이를 이용해 중요도 샘플링(importance sampling)을 수행한다. 복사 휘도의 복잡한 분포를 배우기 위해 이전의 논문들에서는 복잡한 재귀적 데이터 구조를 제안하고 이를 순차적으로 업데이트 하였지만 이는 CPU상에서의 path tracing만을 가정한 것으로 GPU상에서는 쉽게 구현하기 어려우며 효과적으로 작동하지 않는다. 본 논문에서는 GPU 친화적인 간단한 그리드 형태의 데이터를 사용해 path guiding 알고리즘을 진행하였다. 또한 path guiding의 두 가지 목표-(1) 복사 휘도 학습과 (2) 학습된 복사 휘도 분포를 이용한 중요도 샘플링-를 GPU 상에서 효과적으로 구현하기 위해 다음과 같은 방법을 제시한다. 우선 복사 휘도 학습의 경우, 강화학습과 복사 휘도 학습의 구조적 유사성을 밝힌 이전 연구를 확장하여 가볍고 빠른 SARSA를 이용한 학습 방법을 제안하였다. 학습된 복사 휘도는 공간-방향을 그리드 형태로 분할한 GPU상의 데이터 구조에 저장된다. 학습된 복사 휘도를 사용한 중요도 샘플링의 경우 법선 벡터 방향에 유효하지 않은 샘플들은 제외한 뒤, 리젝션 샘플링(rejection sampling)을 이용해 중요도 샘플링(importance sampling)을 수행하였다. 모든 알고리즘은 NVIDIA OptiX를 사용해 GPU상에서 megakernel 구조로 구현되었다. 복잡한 구조의 씬 데이터에 대해 여러 번 실험을 수행하였으며 본 연구에서 제안한 방법의 우수성을 확인하였다.Abstract i Chapter 1 Introduction 1 Chapter 2 Background and Related Works 4 2.1 Ray Tracing on GPU 4 2.2 Path Guiding 5 2.3 Reinforcement Learning and Light Transport 6 Chapter 3 Problem Setting and Overview 7 Chapter 4 Fast and Lightweight Radiance Learning 10 4.1 Analogy between the Rendering Equation and Reinforcement Learning 10 4.2 Fast and Lightweight Radiance Learning with SARSA 12 Chapter 5 Efficient Importance Sampling from Learned Radiance 16 5.1 Importance Sampling on Hemispherical Domain 16 5.2 Fast and Efficient Importance Sampling with Optimized Rejection Sampling 18 5.3 Normalizing Term Calculation with Memoization 20 Chapter 6 Experiments and Results 22 6.1 GPU-based Path Guiding with a Regular Grid 23 6.2 Comparison for Radiance Learning Methods 25 6.3 Comparison for Radiance Sampling Methods 27 Chapter 7 Conclusion 35 Appendix A Additional Experimental Results 36 A.1 Comparison for Spatial Directional Resolution 36 A.2 Equal SPP Comparison 36 Appendix B Pseudocode for the Algorithm 39 초록 46 Acknowledgements 47석

De Novo Augmentation approach in NLP

학위논문(석사) -- 서울대학교대학원 : 데이터사이언스대학원 데이터사이언스학과, 2023. 2. 이상학.With a deluge of text-based data available, the ability to automatically extract important information from the text data is crucial, especially extracting events from factual text data like news articles. Finding causal relations in texts has been a challenge since it requires methods ranging from defining event ontologies to developing proper algorithmic approaches. In this paper, I developed a framework which classifies whether a given sentence contains a causal event. As my approach, I exploited an external corpus that has causal labels to overcome the small size of the original corpus (Causal News Corpus) provided by task organizers. Further, I employed a data augmentation technique utilizing PartOf-Speech (POS) based on my observation that some parts of speech are more (or less) relevant to causality. My approach especially improved the recall of detecting causal events in sentences.1. Introduction 1 1.1 Study Background 1 1.2 Purpose of Research 2 2. Task and Dataset 2 3. Methodology 3 3.1 Causal Graph of the task 4 3.2 Data Augmentation via POS tagging 4 3.3 Model, pages 5 3.4 Experiment Setup 7 4. Result and Discussion 8 4.1 Result 8 4.2 Discussion 11 5. Future work and Conclusion 12 5.1 Future work 12 5.2 Conclusion 13 Bibliography 14석

부조직 적합항원 H60특이적CD8 T세포 반응 발달에서의 PD-1 결핍에 의한 영향 연구

학위논문 (석사)-- 서울대학교 대학원 : 의과학과, 2014. 8. 최은영.Activated CD8 T cells go through robust expansion and then a certain portion of the expanded CD8 T cells remain as memory cells after antigen is cleared. It has been well known that help from concomittantly activated CD4 T cells is essential for generation of memory CD8 T cells and the CD8 T cells activated in the absence of CD4 help show defect in memory expansion when re-exposured to the same antigen. PD-1 (programmed cell death-1CD279), which is an inhibitory receptor up-regulated on activated T cells, has been suggested to be implicated in the memory generation of CD8 T cells. In this study, using a minor histocompatibility antigen H60 as a model antigen, for which specific primary and memory CD8 T cell expansion is heavily dependent on CD4 help, the impact of the presence and absence of PD-1-expression on the development of antigen-specific CD8 T cell response was investigated. In the absence of PD-1 expression, the H60-specific CD8 T cells underwent higher degree of proliferation and showed enhanced functionality including cytotoxicity for antigen clearance, compared to those with PD-1 expression, even under help-deficient condition. However, PD-1-deficiency did not restore central memory cell generation of CD8 T cells under help-deficient condition. These results suggest that role of PD-1 is not directly related to programming of memory CD8 T cell generation, but rather to enhancing effector function of activated CD8 T cells. The results from this study will provide insight into development of CD8 T cell response and memory generation.CONTENTS Abstract i Contents iv List of figures v Introduction 3 Material and Methods 8 Results 11 Induction of tolerance of H60-specific CD8 T cell response by lack of CD4 help 11 Increased PD-1-positive population in the CD8 T cells primed under CD4 help-deficient condition 15 Impaired memory response under the help-deficient condition was restored in the absence of PD-1 expression 18 PD-1-deficient CD8 T cells proliferated and migrated to inflamed sites in fast kinetics 22 Enhanced IFN-γ production from Ag-specific CD8 T cells in the absence of PD-1 signaling 27 Skewing toward memory precursor effector cells in the absence of PD-1 signaling 29 Help-deficient CD8 T cells did not convert to central memory CD8 T cells in the absence of PD-1 signaling 33 Discussion 38 References 42 Abstract in Korean 49Maste

Endoscopic Selective Neck Dissection via Retroauricular Approach

Lymph node metastasis is the single, most powerful prognostic factor in head and neck squamous cell cancer, which means that cervical lymph node management should be considered even in treatment of a clinically node-negative neck. More conservative and selective techniques of neck dissection have been developed ever since radical neck dissection was first introduced. Despite that selective neck dissection provides less functional damage, disfiguring scar after neck dissection still remains inevitable. Recently, surgical endoscopy and robotic system was introduced and many clinical trials for aesthetic approach for neck dissection using endoscopy have shown their feasibility and safety. Hereby, we describe the preparation and surgical procedure for endoscopic selective neck dissection (level I, II, and III) via retroauricular approach for 41-year-old male patient with clinically node-negative oral tongue cancer.ope

Effect of human acellular dermal matrix (Megaderm™) on infra-auricular depressed deformities, Frey's syndrome, and first bite syndrome following parotidectomy: a multi-center prospective study

Background: Parotidectomy is the primary treatment for parotid gland tumors. However, complications may include a prominent facial scar or infra-auricular depressed deformity, Frey's syndrome, first bite syndrome, or other facial pain, numbness, and paralysis. Acellular dermal matrix (ADM) has been widely used to prevent these complications in parotid surgery, but there have been no prospective, multi-center trials documenting its efficacy. This study evaluates the effectiveness of ADM implantation in preventing infra-auricular depressed deformity, Frey's syndrome and first bite syndrome after parotidectomy. Methods: We analyzed 51 cases of standard parotidectomy and 58 cases of parotidectomy with implantation of Megaderm™ ADM through prospective multicenter trial. Acute complications including infection, seroma, hematoma, skin necrosis, and acute parotid area pain were evaluated 1 week postoperatively. Clinician grading of Frey's syndrome and blinded clinician evaluation of infra-auricular depressed deformities were conducted at 3, 6, and 12 months. Patients evaluated subjective satisfaction with neck appearance, Frey's syndrome quality, and acute parotid area pain at 3, 6, and 12 months. Results: There was a higher incidence of seroma in the Megaderm™ group than in the control group at week 1. The incidence and total clinician-evaluated Frey's syndrome scores were significantly lower in the Megaderm™ group than in the control group at 3, 6, and 12 months. Both the objective and subjective evaluations of the facial contour showed a better outcome in the Megaderm™ group compared to the control group at 3, 6, and 12 months. There were no significant differences between the groups in the patient-reported Frey's syndrome quality scores at 3, 6, and 12 months, but the Megaderm™ group reported significantly less acute pain than the control group. Conclusions: ADM implantation can effectively reduce the occurrence of Frey's syndrome, infra-auricular depressed deformity, and first bite syndrome after parotidectomy. ADM may be especially advantageous in complex parotidectomy cases when significant complications are expected.ope

Characteristic facial expressions in chronic facial paralysis suggest an incidental finding of an intratemporal mass

Background : The objective of this study was to analyze the characteristics of facial expressions by their pathogenesis in subjects with chronic facial paralysis and to describe the partial defect of facial function in elucidating the etiology of facial paralysis. Materials and Methods : The etiology of chronic facial paralysis could be categorized into 3 groups: Group I, total resection without any reanimation surgery; Group II, acute facial nerve injury such as Bell’s palsy, and Group III, facial nerve resection and anastomosis. There was a total number of 104 subjects included in this study. Each subject with chronic facial paralysis and were investigated based on the severity of synkinesis, regression of muscular volume, latency and amplitude in electromyography, and facial movement by House-Brackmann grade system. Results : Subjects from the Group I had no synkinesis with profound regression of muscular volume, H-B grade 5.7 ± 0.34. Subjects from the Group II had moderate to severe synkinesis with moderate to severe regression of muscular volume, H-B grade 3.4 ± 0.96. In this group, thirteen subjects with atypical facial expression also had an incidental finding of a hidden mass in the intratemporal area. Lastly, subjects from the Group III had severe synkinesis without regression of muscular volume, H-B grade 3.7 ± 0.76. Conclusions : With careful examination of facial expression, a crucial point for elucidating the pathogenesis of facial paralysis may be provided. Severe facial palsy without muscular regression may indicate an incidental finding of a hidden mass in the intratemporal area.ope

루테늄, 구리 나노입자 및 로듐 균일화 촉매를 이용한 촉매반응

학위논문 (박사)-- 서울대학교 대학원 : 화학부 무기화학전공, 2017. 2. 정영근.Transition metal-catalyzed catalytic reaction is one of the most fundamental processes to construct the chemical structure. Depending on the type of transition metal catalysts, the catalytic reactivity is quite different. In the field of heterogeneous catalysts, nanoparticle catalysts have been attracted due to their unique reactivity and relatively simple process for reuse. Homogeneous catalysts have many advantages such as high reaction rate and selectivity to achieve catalytic reaction of fine chemicals. Thus, developing a unique catalytic reaction with transition metal catalysts is essential to expand the field of synthetic methods. This dissertation describes the development of catalytic reaction of transition metal nanoparticles and rhodium compounds. We discovered that ruthenium nanoparticle on non-activated charcoal is quite effective for constructing azobenzen derivatives which are useful materials of dyes and pigments. Furthermore, instead of hydrogen gas, ethanol is used as a hydrogen source. Three different products derived from nitroarene derivatives were obtained by changing the amount of ethanol. Copper is abundant and inexpensive metal than ruthenium metal. Using commercially available copper nanoparticles as a catalyst, cross-coupling reactions between alkyl halides with Grignard reagents were studied. The cross-coupling reaction did not require any phosphine or amine ligands and proceeded smoothly at room temperature. In particular, quaternary carbon center, being difficult to synthesize, was established in the presence of copper nanoparticle and tertiary alkyl Grignard reagents. Alcohol is one of the most common organic compounds in our lives. It is often used as a polar solvent in chemical reactions. As mentioned above, alcohol can be employed as a hydrogen source. In addition, the role of alcohol can be extended to a carbon monoxide surrogate, a hydride-donor, and a nucleophile in the presence of rhodium catalysts. In the synthesis of esters from aryl iodides and alcohols in the presence of a rhodium catalyst and a base, an alcohol acted as carbon monoxide and nucleophile. Alcohol acted as a hydride source to form a rhodium hydride intermediate and a carbon monoxide surrogate in intermolecular carbonylative cycloaddition reactions with alkyne.Chapter 1. Introduction 1 1.1. Research Background 1 1.2. References 7 Part I. Ruthenium and Copper Nanoparticle Catalyzed Various Bond Forming Reactions 12 Chapter 2. Ruthenium Nanoparticle-Catalyzed Chemoselective Hydrogenation of Nitroarenes Using Ethanol as a Hydrogen Source 13 2.1. Introduction 13 2.2. Results and Discussion 15 2.2.1. Characterization of Catalyst and Optimization of reaction conditions 15 2.2.2. Substrate Scope 19 2.2.3. Reusability and Mechanistic Investigation 25 2.3. Conclusion 27 2.4. Experimental Section 28 2.5. Supporting Information 36 2.6. References 40 Chapter 3. Copper Nanoparticle-Catalyzed Cross-Coupling of Alkyl Halides with Grignard Reagents 42 3.1. Introduction 42 3.2. Results and Discussion 44 3.2.1. Optimization of reaction conditions and Substrate Scope 44 3.2.2. Reusability and Mechanistic Investigation 51 3.3. Conclusion 55 3.4. Experimental Section 56 3.5. References 61 Chapter 4. Copper Nanoparticle-Catalyzed Borylation of Alkyl Bromides with Organodiboron Compound 63 4.1. Introduction 63 4.2. Results and Discussion 65 4.2.1. Optimization of reaction conditions 65 4.2.2. Substrate Scope and Mechanistic Experiment 67 4.3. Conclusion 70 4.4. Experimental Section 71 4.5. References 76 Part II. Rhodium-Catalyzed Carbonylation Reaction Using Alcohol as the Carbon Monoxide Source 78 Chapter 5. Rhodium-Catalyzed Synthesis of Esters from Aryl Iodides and Alcohols: Use of Alcohols with/without the Assistance of Aldehydes as Carbon Monoxide and Nucleophile Sources 79 5.1. Introduction 79 5.2. Results and Discussion 81 5.2.1. Optimization of reaction conditions 81 5.2.2. Substrate Scope 90 5.3. Conclusion 95 5.4. Experimental Section 96 5.5. Supporting Information 106 5.6. References 108 Chapter 6. Rhodium-Catalyzed Intermolecular Carbonylative [2+2+1] Cycloaddition of Alkynes Using Alcohol as the Carbon Monoxide Source for the Formation of Cyclopentenones 110 6.1. Introduction 110 6.2. Results and Discussion 113 6.2.1. Optimization of the reaction conditions 113 6.2.2. Substrate Scope and Mechanistic Investigation 121 6.3. Conclusion 128 6.4. Experimental Section 129 6.5. Supporting Information 138 6.6. References 141 국문초록 144Docto

가상모의수술기법을 활용한 비골을 이용한 3차원 하악재건술

Fibular vascularized osteocutaneous free flap is the gold standard for mandibular reconstruction. The traditional method is very difficult and challenging work. This technique has so far been performed solely depending on the experience of the surgeons. Recently, several software programs that can make accurate preoperative surgical plans in a three dimensional (3D)-virtual system have been developed and used to solve this problem. The aim of this study is to describe our experience and to share several tips and pitfalls of mandibular reconstruction with virtual surgical planning (VSP).ope

Clinical Characteristics and Management of Saccular Cysts: A Single Institute Experience

Objectives: A saccular cyst is defined as a dilated saccule of the larynx, filled with mucus, and is located between the false vocal cords and the thyroid cartilage. Although this uncommon laryngeal condition is benign in nature, it could lead to dyspnea, stridor, and airway obstruction, depending on its size and location. Furthermore, some saccular cysts have been associated with laryngeal carcinoma. This study aimed to characterize this rather uncommon laryngeal condition to aid in determining the proper management of this pathology. Methods: Medical records were retrospectively reviewed of all patients with saccular cysts diagnosed and treated between 2006 and 2017 at a tertiary otolaryngologic care center. Results: Seven patients with saccular cysts were identified (male:female=2:5; mean age, 34.1 years); two were pediatric patients. Surgical intervention was performed in all patients by laryngo-microsurgery using CO2 laser. There was no recurrence after the initial surgical treatment. Conclusion: Saccular cysts can be managed endoscopically using CO2 laser, without requiring an external approach. Therefore, an endoscopic approach should be actively considered for an optimal treatment outcome.ope

Guideline for the Surgical Management of Locally Invasive Differentiated Thyroid Cancer From the Korean Society of Head and Neck Surgery

The aim of this study was to develop evidence-based recommendations for determining the surgical extent in patients with locally invasive differentiated thyroid cancer (DTC). Locally invasive DTC with gross extrathyroidal extension invading surrounding anatomical structures may lead to several functional deficits and poor oncological outcomes. At present, the optimal extent of surgery in locally invasive DTC remains a matter of debate, and there are no adequate guidelines. On October 8, 2021, four experts searched the PubMed, Embase, and Cochrane Library databases; the identified papers were reviewed by 39 experts in thyroid and head and neck surgery.The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess the quality of evidence, and to develop and report recommenda-tions. The strength of a recommendation reflects the confidence of a guideline panel that the desirable effects of an inter-vention outweigh any undesirable effects, across all patients for whom the recommendation is applicable. After completing the draft guidelines, Delphi questionnaires were completed by members of the Korean Society of Head and Neck Surgery. Twenty-seven evidence-based recommendations were made for several factors, including the preoperative workup; surgical extent of thyroidectomy; surgery for cancer invading the strap muscles, recurrent laryngeal nerve, laryngeal framework, trachea, or esophagus; and surgery for patients with central and lateral cervical lymph node involvement. Evidence-based guidelines were devised to help clinicians make safer and more efficient clinical decisions for the optimal surgical treatment of patients with locally invasive DTC. © 2023 by Korean Society of Otorhinolaryngology-Head and Neck Surgery.ope