Memory-Based Learning of Latent Structures for Generative Adversarial Networks

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 컴퓨터공학부, 2019. 2. 김건희.본 연구는 Generative Adversarial Network (GAN) 모델의 학습 과정에서 발생하는 두가지 문제점을 해결하는 방안을 제시하였다. 먼저, 일반적인 GAN 모델은 사진과 같은 복잡한 확률변수의 분포를 모델링할 때 잠재변수의 사전확률분포로 표준정규분포를 사용한다. 그러나 이런 연속적인 잠재변수를 사용할 경우 서로 다른 데이터 샘플간의 구조적 불연속성을 반영하기 어렵다. 또 다른 문제점으로, GAN 모델에서 판별자는 학습 과정에서 과거에 생성자 모델이 생성했던 데이터 샘플에 대한 정보를 망각하며, 이로인해 학습 과정이 불안정해진다. 이 두가지 문제점은 생성자가 판별자가 공유하는 memory network를 동시에 학습함으로써 크게 완화할 수 있다. 생성자가 학습 데이터에 내재된 군집의 분포를 학습한다면 이를 통해 구조적 불연속성으로 인한 성능 하락을 피할 수 있으며, 판별자가 주어진 입력 데이터에 대한 판별을 할 때 학습 전 과정에 걸쳐 생성자가 생성했던 데이터 샘플들로부터 학습된 군집 분포를 참조한다면 망각 문제로 인한 영향을 덜 받게 된다. 본 연구에서 제시한 memoryGAN 모델은 비지도학습을 통해 데이터에 내재된 군집의 분포를 학습하여 구조적 불연속성 문제와 망각 문제를 완화하며, 대부분의 GAN 모델에 적용할 수 있다. Fashion-MNIST, CelebA, CIFAR10, 그리고 Chairs 데이터셋에 대한 성능 평가 및 시각화 실험을 통해 memoryGAN이 확률론적으로 해석 가능한 모델이며, 높은 수준의 사진 샘플을 생성한다는 것을 보였다. 특히 memoryGAN은 개선된 최적화 방법이나 Weaker divergence를 도입하지 않고도 CIFAR10 데이터셋에서 Inception Score를 기준으로 비지도학습 방식의 GAN 모델 중 높은 성능을 달성했다.We propose an approach to address two issues that commonly occur during training of unsupervised GANs. First, since GANs use only a continuous latent distribution to embed multiple classes or clusters of data, they often do not correctly handle the structural discontinuity between disparate classes in a latent space. Second, discriminators of GANs easily forget about past generated samples by generators, incurring instability during adversarial training. We argue that these two infamous problems of unsupervised GAN training can be largely alleviated by a learnable memory network to which both generators and discriminators can access. Generators can effectively learn representation of training samples to understand underlying cluster distributions of data, which ease the structure discontinuity problem. At the same time, discriminators can better memorize clusters of previously generated samples, which mitigate the forgetting problem. We propose a novel end-to-end GAN model named memoryGAN, which involves a memory network that is unsupervisedly trainable and integrable to many existing GAN models. With evaluations on multiple datasets such as Fashion-MNIST, CelebA, CIFAR10, and Chairs, we show that our model is probabilistically interpretable, and generates realistic image samples of high visual fidelity. The memoryGAN also achieves the state-of-the-art inception scores over unsupervised GAN models on the CIFAR10 dataset, without any optimization tricks and weaker divergences.Introduction Related Works The MemoryGAN Experiments ConclusionMaste

단체복합체에서 조화 공간의 이론과 응용

학위논문(박사)--서울대학교 대학원 :자연과학대학 수리과학부,2020. 2. 국웅.A harmonic cycle λ, also called a discrete harmonic form, is a solution of the Laplace's equation with the combinatorial Laplace operator obtained from the boundary operators of a simplicial chain complex. By combinatorial Hodge theory, harmonic spaces are isomorphic to homology groups with real coefficients. In particular, if a cell complex has a reduced homology with Betti number β_i = 1 of a specific dimension i, it has a unique harmonic cycle up to scalar multiplication, which we call the standard harmonic cycle. We will present a formula for the standard harmonic cycle λ of a cell complex based on a high-dimensional generalization of cycletrees. Moreover, by using duality, we will define the standard harmonic cocycle λ* and show intriguing combinatorial properties of λ and λ* in relation to (dual) spanning trees, (dual) cycletrees, winding numbers w( · ) and cutting numbers c( · ) in high dimensions. Finally, we will also suggest two application methods; an analysis to detect oscillations by using winding number, and cutting number, and a network embedding method, called harmonic mirroring.조화 사이클 λ는 이산 조화 형식으로도 부르며 라플라시안 방정식의 해이다. 이 라플라시안 방정식은 단체 연쇄복합체의 경계 작용소로부터 만든 조합론적 라플라시안 작용소가 0일 때 생기는 수식이다. 조합론적 호지 이론에 의하여 조화 공간은 실수를 계수로 갖는 호몰로지군과 동형이다. 특히 연쇠복합체의 특정 차원 i에서 축소 호몰리지군의 베티수 β_i가 1이라면, 스칼라곱을 제외하고 불변하는 고유한 조화 사이클을 얻을 수 있고, 이를 표준 조화 사이클이라 부른다. 우리는 표준 조화 사이클 λ을 표현하는 공식을 고차원으로 일반화된 사이클 트리를 바탕으로 나타내었다. 더욱이, 쌍대성을 이용하여 표준 조화 쌍대사이클 λ*를 정의하였고, λ와 λ*의 흥미롭고 조합론적인 성질들을 고차원 상태에서 보였다. 이는 (쌍대) 생성나무와 (쌍대) 사이클 트리, 회전수 w( · ), 자름수 c( · )와의 관계를 갖는다. 마지막으로 우리는 응용을 위한 두 가지 방법론을 제시한다. 회전수와 자름수를 이용한 진동 측정법과 조화 미러링으로 불리는 네트워크 매장 방법이다.1 Introduction 1 2 Preliminaries 3 2.1 Review of nite chain complex and (co)homology 3 2.2 High dimensional spanning trees 4 2.3 Harmonic space and combinatorial Hodge theory 5 3 Cycletree and its minimal cycle 7 3.1 Cycletree 7 3.2 Minimal cycle 9 4 Winding number 14 5 Standard harmonic cycle 17 6 Duality and dual spanning tree 20 7 Dual cycletree and cutting number 25 7.1 Dual cycletree and its minimal cocycle 25 7.2 Cutting number 27 8 Standard harmonic cocycle and relationship 31 9 Application 35 9.1 Oscillation Detection 35 9.2 Harmonic Mirroring 38 Abstract (in Korean) 41 Acknowledgement (in Korean) 42Docto

Mechanism-based Drug Therapy of Inflammatory Bowel Disease With Special Reference to Rheumatic Disease

nflammatory bowel disease (IBD), comprised of Crohn’s disease and ulcerative colitis, is a chronic, relapsing, and remitting disease of the gastrointestinal tract whose incidence is rising worldwide, especially in East Asian countries. The etiopatho genesis of IBD remains poorly understood. It is currently considered that a combination of genetic and environmental factors triggers an aberrant immune response against the commensal intestinal flora in IBD patients. Over the past decades, advances in the knowledge of the inflammatory cascade involved in IBD pathogenesis have expanded the pharmacological armamenta rium in IBD. Actually, the introduction of specific biological therapies, including anti- tumor necrosis factor, anti-inter leukin-12/23, and anti-integrin, has revolutionized the treatment of IBD. Moreover, small molecule agents such as Janus kinase inhibitors also now under clinical use. In IBD, a substantial number of patient accompanies various articular manifestations and, rheumatic involvement is one of the most common extra-intestinal symptoms. Many of the mechanisms based drugs described above have already been used in rheumatic diseases. In addition, some of those drugs can be used to treat both IBD itself and accompanied rheumatic involvement, however there are differences in drug usage between these two indications. This review aims to briefly review the mechanism-based drug therapies of IBD with particular reference to rheumatic diseaseope

Semi-Quantitative Scoring of Late Gadolinium Enhancement of the Left Ventricle in Patients with Ischemic Cardiomyopathy: Consensus Statement from the Asian Society of Cardiovascular Imaging-Practical Tutorial (ASCI-PT) 2020

The Asian Society of Cardiovascular Imaging-Practical Tutorial (ASCI-PT) is an educational program of the ASCI School, which was founded in 2019. In 2020, ASCI-PT was held from November 23rd to 25th for the purpose of creating a consensus statement on semi-quantitative scoring for late gadolinium enhancement (LGE) in patients with ischemic cardiomyopathy. Eighteen panelists from five countries meticulously reviewed the existing guidelines and addressed seven issues to improve the communication of LGE interpretation and reduce inter-observer variability. All panels participated in online or offline sessions to build a consensus on LGE scoring. This summarizes the ASCI-PT 2020 proceedings and provides a consensus statement for conducting semi-quantitative LGE scoring.ope

Phosphorus-based High Capacity Negative Electrode Materials for Sodium-ion Batteries

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부(에너지환경화학융합기술 전공), 2016. 2. 오승모.In recent years, the demand for large scale energy storage devices has increased with the development of electric vehicles (EVs) and energy storage system (ESS), and Li-ion batteries are considered promising candidates because of their high energy density. However, there is growing concern that lithium resources are insufficient to meet the demands of large scale applications due to the limited reserve and too geographically constrained. Actually, the recent price of lithium raw materials has shown sharp increases. Cosquently, Na-ion batteries are an alternative to Li-ion batteries because sodium resources are much more abundant and inexpensive than lithium. However, there is a critical obstacle to their development. The energy density of Na-ion batteries is slightly lower than that of Li-ion batteries because the reversible capacity and operating voltage of currently reported electrode materials in Na-ion batteries are lower in comparison. This implies that it is not easy to replace Li-ion batteries with Na-ion batteries because the cost per energy stored ($/Wh) of Na-ion batteries does not provide much advantage. Therefore, new negative electrode materials having higher reversible capacities are necessary if one is to increase the energy density of Na-ion batteries. In this study, firstly, exploring the possibility and investigating electrochemical reaction mechanism of red phosphorus as negative electrode materials for sodium-ion battery are performed based on thermodynamic information. In order to improve electrical conductivity, carbon coating via ball-milling is carried out. This carbon coating is enhanced electrochemical reactivity including the highest specific capacity among any reported negative electrode materials. The understanding is that during the sodiation process amorphous red phosphorus undergoes a phase change to crystalline sodium phosphide (Na3P) by electrochemical reaction and structure analysis. The corresponding to Na3P peaks in dQ/dV plots are shown at the ca. 0.2 and 0.55 V vs. Na/Na+ during sodiation and desodiation, respectively. However, poor cycle performance is observed due to volume change during charge/discharge. Secondly, the study on failure mechanism and enhanced cycle performance of phosphorus electrode materials are carried out. The failure mechanism of this material comes from volume change. The large volume change of electrode materials is attributed to be the main reason for their rapid capacity loss. It increases internal resistance by contact loss between phosphorus and conducting agent. The instability of solid electrolyte interphase (SEI) at the electrode surface via repetitive volume expansion is also considered to failure mechanism. In order to improve cell performance, tried to change the phosphorus to carbon ratio and add electrolyte additive such as fluoroethylene carbonate (FEC). In case of increasing active materials, it is shown alleviating volume expansion. In addition, excellent cycle performance is observed for 100 cycles with FEC additives in electrolytes. It is attributed that NaF-like SEI film is mechanically strong and EC decomposition is minimized. Finally, the volumetric capacity is improved by Sn4P3 electrode materials. Phosphorus has poor electrical conductivity. Accordingly, a large amount of carbon has to be used in order to enhance their electrical conductivity, leading to decreases their gravimetric and volumetric capacity. The volumetric capacity in a cell is one of the most key factors that determine its feasibility as a post battery. Therefore, it is important to develop new negative electrode materials delivering high volumetric capacity for sodium-ion batteries. Sn4P3 is one of the candidates for high volumetric capacity electrode materials. Sn4P3 showed excellent electrochemical performance for Na-ion batteries. Sn4P3 delivered a high volumetric capacity and exhibited very stable cycle performance with a negligible capacity fading over 100 cycles. The redox potential of Sn4P3 is lower than that of phosphorus, indicating that the energy density of full cells with Sn4P3 can be higher than those of cells with phosphorus when the same reversible capacity is utilized.1. Introduction 1 2. Background 6 2.1. Sodium-ion batteries 6 2.2. Negative electrode materials 10 2.2.1. Carboneous materials 10 2.2.2. Alloy-based materials 12 2.2.3 Conversion reaction 15 3. Experimental 17 3.1. Simulation method 17 3.2. Synthesis of active materials 18 3.2.1. Phosphorus and graphite composites 18 3.2.2 Tin phosphide 18 3.3. Electrochemical characterization 18 3.4. Spectroscopic analysis 19 3.4.1. Surface analysis 19 3.4.2. Structural analysis 20 3.4.3 Morphology analysis 20 4. Results and discussion 21 4.1. The red phosphorus and carbon composites as high capacity negative electrode materials for sodium-ion battery and its electrochemical reaction mechanism 21 4.2. Failure mechanism and improved cycle performance of Phosphorus/carbon composites 43 4.3. Tin phosphide as High volumetric capacity negative electrode for Sodium-ion battery 65 5. Conclusions 89 References 92 요약 (국문초록) 101Docto

고객유형에 따른 서비스품질과 고객만족 간의 관계에 대한 연구 : 한전KPS를 중심으로

학위논문 (석사)-- 서울대학교 행정대학원 : 공기업정책학과, 2012. 8. 엄석진.최근의 대규모 정전사태와 관련해 주목받고 있는 전력설비에 대한 정비서비스 시장은 고품질의 정비서비스를 원하는 고객의 목소리가 점점 커지고 있고 경쟁의 확대로 정비서비스 회사 간 경쟁이 심화되는 어려움에 처해 있다. 따라서 정비서비스 회사는 고객이 무엇을 원하는지를 파악하여 정비서비스품질을 개선․보완함으로써 이러한 어려움을 헤쳐 나갈 필요성이 있겠다. 이에 본 연구는 전력설비 정비서비스품질이 고객만족에 어떠한 영향이 있는지와 전력설비 정비서비스품질과 고객만족 간의 관계에 있어 고객 유형이 어떠한 조절작용을 하는지를 분석하였다. 이를 위하여 선행연구의 이론적 배경을 바탕으로 서비스품질을 성과로 측정하는 SERVPERF 모형을 기반으로 연구모형을 도출하고 연구가설을 설정하였으며 이를 검정하기 위해 한전KPS의 고객을 대상으로 설문지를 통하여 수집된 자료를 이용하여 요인분석, 신뢰성 분석, 다중회귀분석, 조절효과 분석을 실시하였다. 연구결과를 요약하면 다음과 같다. 첫째, 전력설비 정비서비스품질을 독립변수로 설정하고 고객만족을 종속변수로 설정한 가설에서 정비서비스품질의 5개 하위차원 중 신뢰성, 대응성, 확신성 및 공감성은 고객만족에 통계적으로 유의미한 정(+)의 영향을 주는 것으로 확인되었으나 유형성은 통계적으로 유의미한 영향이 없는 것으로 확인되었다. 정비서비스품질의 고객만족에의 영향력의 크기는 확신성, 신뢰성, 공감성, 대응성의 순으로 나타났다. 둘째, 전력설비 정비서비스품질을 독립변수로, 고객유형을 조절변수로, 그리고 고객만족을 종속변수로 설정한 가설에서 고객 유형은 유형성과 신뢰성에서는 조절작용을 수행하지 않으나 대응성, 확신성, 공감성에서는 조절작용을 하는 것으로 나타났다. 고객 유형별로 조절효과의 크기를 보면 송변전 고객은 대응성과 고객만족 간의 관계에서 원자력․화력․수력 고객에 비해 큰 조절작용을 하는 것으로 확인된 반면 원자력 고객은 확신성 및 공감성과 고객만족 간의 관계에서 화력․수력․송변전 고객에 비해 작은 조절작용을 하는 것으로 나타났다. 이상의 연구결과를 토대로 전력설비 정비서비스품질은 고객만족에 부분적으로 정(+)의 영향을 미치고 있으며 고객 유형은 정비서비스품질과 고객만족 간의 관계에서 부분적으로 조절작용을 하는 것으로 결론을 지을 수 있다.제 1 장 서론 1 제 1 절 연구의 배경 및 목적 1 제 2 절 연구의 범위 및 방법 2 제 2 장 이론적 논의와 선행연구 검토 4 제 1 절 이론적 논의 4 1. 고객만족 4 2. 서비스품질 8 3. 전력설비 정비서비스의 특성 14 제 2 절 선행연구 검토 19 1. 서비스품질과 고객만족 간의 관계 19 2. 전력설비 정비서비스에 대한 선행연구 20 3. 비판적 검토 21 제 3 장 연구의 설계 23 제 1 절 연구방법 23 1. 연구모형 23 2. 연구가설 24 제 2 절 조사설계 26 1. 변수의 조작적 정의 26 2. 설문지의 구성과 측정 30 3. 자료의 수집 31 4. 분석방법 32 제 4 장 실증분석 및 연구결과 33 제 1 절 기초분석 33 1. 자료의 구성 33 2. 타당성 분석 35 3. 신뢰성 분석 37 4. 상관관계 분석 40 제 2 절 가설의 검정 41 1. 전력설비 정비서비스품질의 고객만족에의 영향 41 2. 고객 유형의 조절효과 분석 44 3. 가설검정 결과 및 해석 58 제 5 장 결론 62 제 1 절 연구결과의 요약 및 시사점 62 1. 연구결과의 요약 62 2. 시사점 63 제 2 절 연구의 한계점 65 참고문헌 66 부록[설문지] 71 Abstract 74Maste

Development of Entrustable Professional Activity, Core Competencies, and Guidelines in 2021 Radiology Competency Education Project

To provide high-quality training to residents in a rapidly changing medical environment, it is very important to improve the annual training curriculum centered on competency and ensure that training hospitals maintain an environment suitable for training. The Korean Society of Radiology (KSR) has been steadily improving the training system and has suggested the improvement of the training system by strengthening the competency-based evaluation and faculty development. Currently, KSR was selected for the second annual training curriculum systematization construction project in July 2021, and developed entrustable professional activities, core competencies, and assessment guidelines required by the construction project. Therefore, the development process and assessment guidelines will be introduced to residents and the faculty.ope

The impact of cardiovascular risk factors on cardiac structure and function: Insights from the UK Biobank imaging enhancement study

Aims: The UK Biobank is a large-scale population-based study utilising cardiovascular magnetic resonance (CMR) to generate measurements of atrial and ventricular structure and function. This study aimed to quantify the association between modifiable cardiovascular risk factors and cardiac morphology and function in individuals without known cardiovascular disease. Methods: Age, sex, ethnicity (non-modifiable) and systolic blood pressure, diastolic blood pressure, smoking status, exercise, body mass index (BMI), high cholesterol, diabetes, alcohol intake (modifiable) were considered important cardiovascular risk factors. Multivariable regression models were built to ascertain the association of risk factors on left ventricular (LV), right ventricular (RV), left atrial (LA) and right atrial (RA) CMR parameters. Results: 4,651 participants were included in the analysis. All modifiable risk factors had significant effects on differing atrial and ventricular parameters. BMI was the modifiable risk factor most consistently associated with subclinical changes to CMR parameters, particularly in relation to higher LV mass (+8.3% per SD [4.3 kg/m2], 95% CI: 7.6 to 8.9%), LV (EDV: +4.8% per SD, 95% CI: 4.2 to 5.4%); ESV: +4.4% per SD, 95% CI: 3.5 to 5.3%), RV (EDV: +5.3% per SD, 95% CI: 4.7 to 5.9%; ESV: +5.4% per SD, 95% CI: 4.5 to 6.4%) and LA maximal (+8.6% per SD, 95% CI: 7.4 to 9.7%) volumes. Increases in SBP were associated with higher LV mass (+6.8% per SD, 95% CI: 5.9 to 7.7%), LV (EDV: +4.5% per SD, 95% CI: 3.6 to 5.4%; ESV: +2.0% per SD, 95% CI: 0.8 to 3.3%) volumes. The presence of diabetes or high cholesterol resulted in smaller volumes and lower ejection fractions. Conclusions: Modifiable risk factors are associated with subclinical alterations in structure and function in all four cardiac chambers. BMI and systolic blood pressure are the most important modifiable risk factors affecting CMR parameters known to be linked to adverse outcomes.ope

희귀변이의 임퓨테이션 정확도 향상을 위한 분석 전략 및 방법 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 생물정보학전공, 2015. 8. 박태성.Rare variants have gathered much attention as an alternative source of missing heritability. Rapid development in high throughput sequencing technology has enabled us to discover a large number of rare variants. Although next-generation sequencing technology is becoming a powerful tool in genomics, it is not yet feasible to perform a large-scale population based genome study due to its high cost and required high computing power. Alternatively, two approaches, imputation and customized chips such as exome array and Metabochip, have been widely used in large scale genome studies. Imputation is a cost-effective approach that imputes rare variants into existing genotype data. Generally imputation analysis requires two panels as input: reference panel is the template for predicting untyped markers and genotype panel is the target for imputation analysis. After imputation analysis, the information of genotype panel contains previously experimentally genotyped information and predicted genotypes based on reference panel information. However, imputing rare variants is very challenging due to low accuracy of imputed rare variants. Moreover, low accuracy of imputed rare variants would mislead the results of region-based association tests. Customized chips are designed to contain rare variants yet those chips are designed only for the specific targets. Therefore, new analysis strategy and method for obtaining rare variants are urgently in need. In this study, we developed two novel rare variant imputation approaches, combined approach and pre-collapsing imputation approach. We also applied two approaches to real data analysis. Imputation based association study was performed on liver enzyme traits. First, we proposed combined approach that imputes genotype panel consists of combined data of GWAS chip and exome array. The effectiveness and performance of combined approach were demonstrated using reference panel comprising exome sequencing, exome array, and GWAS chip of 848 identical samples and 5,349 samples of genotype panel consisting of exome array and GWAS chip. As a result, the combined approach increased about 11% in imputation accuracy and enhanced about two times of genomic coverage for rare variants (MAF < 1%) compared to imputation results of genotype panel with GWAS chip alone. Regardless of samples size of reference panel, combined approach showed better imputation performance. Also combined approach outperformed previously reported two-step imputation approach. Second, we developed new method, pre-collapsing based imputation approach (PreCimp), to increase imputation accuracy in forms of collapsed variables. Unlike with previously introduced imputation approaches, PreCimp only requires computational cost. PreCimp consists of two steps. In the first step, collapsed variables are generated using rare variants in the reference panel and new reference panel is constructed by inserting pre-collapsed variables (PCVs) into the reference panel. Next, typical imputation analysis with the new reference provides the imputed genotypes of collapsed variables. We demonstrated the performance of PreCimp on 5,349 genotyped samples using a Korean population specific reference panel including 848 samples of exome sequencing, Affymetrix 5.0, and exome chip. PreCimp outperformed a traditional post-collapsing method that collapses imputed variants after single rare variant imputation analysis. Although PreCimp poorly performed for genes sized larger than 200kb (about 3% of all genes), PreCimp approach by split large-sized genes into small sub-regions could control the poor performance issues. PreCimp approach was shown to increase imputation accuracy about 3.4 ~ 6.3% (dosage r2 0.6 ~ 0.8), 10.9 ~ 16.1% (dosage r2 0.4 ~ 0.6), and 21.4 ~ 129.4% (dosage r2 below 0.4) compared with the results of post-collapsing method. Two imputation approaches were applied to real data analysis. We performed imputation based association analysis on liver enzymes. Using whole-exome reference panel, imputation analysis was performed on 8,529 samples of combined data consisting of GWAS chip and exome chip. Subsequent association analysis on about half million imputed and genotyped variants revealed 20 associated loci responsible for the variation of liver enzymes (P < 5x10-6). Among them, 7 novel loci including two missense variants were discovered. Taken together, two novel rare variant imputation approach were developed and applied to real data analysis. Imputation based association analysis on liver enzyme discovered several novel findings. This study proposed efficient analysis approaches for enhancing imputation accuracy of rare variants. Additionally, in application to real data analysis, discovered variants will be valuable resource for understanding rare variants and its association to various phenotypes.Abstract i List of Tables viii List of Figures ix Chapter 1 Introduction 1 1.1 Background and Motivation 1 1.1.1 Geome-wide association study 1 1.1.2 Genotype imputation 4 1.1.3 Missing heritability 9 1.1.4 Rare variant imputation 9 1.2 Objective of the research 10 Chapter 2 Imputation approach using combined data 12 2.1 Introduction 12 2.2 Materials and Methods 14 2.2.1 Overview of combined approach 14 2.2.2 Exome sequencing 18 2.2.3 GWAS and exome chip genotyping 18 2.2.4 Building reference panel 19 2.2.5 Building genotype panel 21 2.2.6 Two-step imputation approach 21 2.2.7 Statistical analysis 22 2.3 Results 22 2.3.1 Selecting MAF threshold for non-imputable variants 22 2.3.2 Comparison of imputation accuracy among genotype panels 25 2.3.3 Comparison of genomic coverage among genotype panels 28 2.3.4 Sample size effect of reference panel and comparison analysis 30 2.4 Discussion 35 Chapter 3 Pre-collapsing Imputation approach 38 3.1 Introduction 38 3.2 Materials and Methods 46 3.2.1 Subjects 46 3.2.2 Exome sequencing 46 3.2.3 GWAS and exome chip genotyping 47 3.2.4 Building the population specific exome reference panel 48 3.2.5 Pre-collapsing and post-collapsing based imputation 48 3.2.6 Comparison of imputation performance 50 3.2.7 Statistical analysis 50 3.3 Results 51 3.3.1 PostC vs. PreCimp methods 51 3.3.2 PreCimp with additional information 60 3.3.3 Effect of PCV position on imputation performance 64 3.3.4 Example of PreCimp and PostC in association study 66 3.4 Discussion 70 Chapter 4 Imputation based association analysis on liver enzyme traits 73 4.1 Introduction 73 4.2 Materials and Methods 74 4.2.1 Subjects 74 4.2.2 GWAS and exome chip genotyping 75 4.2.3 Building the population specific exome reference panel 76 4.2.4 Statistical analysis 76 4.3 Results 77 4.4 Discussion 92 Chapter 5 Summary and Conclusion 93 References 96 Abstract (Korean) 109Docto

High field strength magnetic resonance imaging of cardiovascular diseases

Given the continuous advances in the hardware and software of magnetic resonance imaging (MRI), cardiac MRI has come to be a routine imaging modality in clinical settings for evaluating both cardiac function and anatomy in various cardiovascular diseases. Recently, 3 tesla (T) MRI has become available and has demonstrated advantages over 1.5T in a broad range of clinical applications although some technical challenges still remain. This review will focus on the potential advantages and limitations of 3T cardiac MRI and its current clinical applicationsope