Argonaute 단백질에서의 마이크로RNA 성숙 및 불안정화 조절 메커니즘에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 농생명공학부, 2017. 2. 신찬석.Small RNA silencing is mediated by the effector RNA-induced silencing complex (RISC) that consists of an Argonaute protein (Ago 1–4 in humans). A fundamental step during RISC assembly involves the separation of two strands of a small RNA duplex, whereby only the guide strand is retained to form the mature RISC, a process not well understood. Despite the widely accepted view that slicer-dependent unwinding via passenger-strand cleavage is a prerequisite for the assembly of a highly complementary siRNA into the Ago2-RISC, here I show by careful re-examination that slicer-independent unwinding plays a more significant role in human RISC maturation than previously appreciated, not only for a miRNA duplex, but, unexpectedly, for a highly complementary siRNA as well. I showed that in human cells, the elevated physiological temperature and the functional L1-PAZ domain of the Ago proteins, drive small RNA strand separation, even when slicer-assisted pathway is absent. In contrast to the previous models, I found that slicer-deficient Ago proteins can also be programmed with highly complementary siRNAs at the physiological temperature of humans, which now clearly explains why both miRNA and siRNA are found in all four human Ago proteins. Little is known about the regulation of miRNA stability. Mature miRNAs are stabilized by binding to Ago proteins, the core components of the RISC. Recent studies suggest that interactions between miRNAs and their highly complementary target RNAs promote release of miRNAs from Ago proteins, and this in turn can lead to destabilization of miRNAs. However, the physiological triggers of miRNA destabilization with molecular mechanisms remain largely unknown. Here, using an in vitro system that consists of a minimal human Ago2-RISC in HEK293T cell lysates, I sought to understand how miRNAs are destabilized by their targets. Strikingly, I showed that miRNA destabilization is dramatically enhanced by an interaction with seedless, non-canonical targets. I then showed that this process entails not only unloading of miRNAs from Ago, but also 3ʹ end destabilization of miRNAs occurred within Ago. Furthermore, mutation analysis suggests that conformational changes in the hinge region of the Ago PAZ domain are likely to be the main driving force of the miRNA destabilization. These collective results suggest that non-canonical targets may provide a stability control mechanism in the regulation of miRNAs in humans and also highlight the remarkable flexibility of human Ago proteins that experience dynamic conformational changes during their catalytic cycle. In sum, my findings reflect another layer onto the mutual regulatory circuits between Ago proteins, miRNAs and their targets, which may provide a means to fine-tune, refine and diversify miRNAs in cells.GENERAL INTRODUCTION 1 MicroRNA biogenesis and mechanism of action in mammals 1 Structural features of Argonaute proteins 3 Argonaute as a slicer 6 Experimental validation of miRNA targets 7 The aims and scope of this dissertation 12 Chapter I. Slicer-independent Mechanism Drives Small-RNA Strand Separation during Human RISC Assembly 13 I-1. Introduction 14 I-2. Materials and Methods 17 Cell culture and siRNA transfection 17 Cell lysate preparation 17 General methods for in vitro RNAi 18 Target RNA cleavage assay 18 in vitro RISC assembly assay 18 Passenger-strand cleavage assay 19 Immunopurification of Ago2 complex and unwinding assay 19 in vitro deadenylation assay 19 Native gel mobility-shift assay 20 Northern blotting 20 Western blotting 21 Expression and tandem affinity purification of recombinant human Ago2 21 I-3. Results 23 Small RNA maturation is highly dependent on the ambient temperature both in vitro and in cells 23 Slicer-dependent unwinding increases with Mg2+ concentration and decreases with increasing temperature 29 High temperature drives duplex unwinding largely independently of slicer activity 30 Slicer-deficient Ago proteins are capable of unwinding the siRNA duplex in a temperature-dependent manner 36 Spontaneous unwinding does not occur before duplexes are loaded into the Ago protein 41 Slicer-independent unwinding depends on the thermodynamic stability of the duplex structure 47 Slicer-independent unwinding requires the functional domains of the Ago protein 53 Slicer-independent unwinding is a general mechanism for human RISC maturation 57 Slicer-independent unwinding is a conserved mechanism 60 I-4. Discussion 64 Small RNA sorting and the Mg2+ level in slicer-dependent unwinding 64 Slicer-independent unwinding in human RISCs 66 A thermodynamic perspective of RISC maturation 67 Chapter II. Non-canonical Targets Destabilize MicroRNAs in Human Argonautes 71 II-1. Introduction 72 II-2. Materials and Methods 75 Cell culture and transfection 75 Cell lysate preparation 75 In vitro target RNA-directed miRNA destabilization assay 75 Target-directed miRNA destabilization in cells 76 Northern hybridization 77 Unloading assay 77 Ago2 cleavage assay 78 In vitro RISC assembly assay 79 Antibodies 79 II-3. Results 83 miRNAs are stable in Argonaute but they are destabilized upon non-canonical target binding 83 miRNA seed pairing is important for miRNA stability 91 Non-canonical targets trigger the 3 end destabilization of miRNAs 94 Human Ago2-RISC binds seedless, non-canonical targets with extensive 3 pairing 95 A large fraction of miRNAs is still in Ago2 following target-directed destabilization 100 3ʹ complementarity confers specificity for target-directed destabilization 104 Dynamic conformational changes of the PAZ domain drive 3 end destabilization 112 Non-canonical target and anti-miR possibly employ distinct mechanisms for miRNA destabilization 118 Non-canonical target-directed mechanism is likely to operate in living cells 122 II-4. Discussion 126 CONCLUSION AND PROSPECT 132 REFERENCES 136 ABSTRACT IN KOREAN 148 PUBLICATION 150Docto

centrobin의 미세소관 안정화 기능 조절기전 연구

학위논문 (박사)-- 서울대학교 대학원 : 생명과학부, 2013. 2. 이건수.세포골격의 주요구성 성분 중 하나인 미세소관은 튜불린 이합체가 붙었다가 떨어짐을 반복하며 역동적으로 변화하는 구조로 되어있다. 미세소관의 역동성은 다양한 미세소관 결합 단백질들에 의해 조절되는데, 그것들은 대부분 미세소관을 안정화 또는 불안정화하는데 관여한다. centrobin은 새로 생긴 중심립에 존재하며 중심립 복제에 필요한 단백질로 동정되었지만 미세소관 안정화에 관여한다는 일련의 증거들이 보고되었다. 또한, centrobin은 서로 다른 두 인산화효소, NEK2와 PLK1의 기질임이 보고되었다. PLK1에 의한 centrobin의 인산화가 정상적인 방추사의 형성에 중요하다고 알려졌으나, NEK2에 의한 centrobin의 인산화의 기능이 무엇인지에 대해서는 아직 명확히 밝혀지지 않았다. 따라서, 본 연구를 통해 NEK2에 의해 조절되는 centrobin의 기능을 밝히고자 했고, 몇 가지 중요한 생물학적 현상들을 발견하였다. 첫 번째, centrobin이 세포질 내에서 작은 과립형태로 존재하며 간기세포의 미세소관 그물구조와 결합하고 있음을 발견하였다. 나아가 때때로 그것들이 안정화된 미세소관을 따라 크고 길쭉한 형태의 입자를 형성함을 관찰하였다. 이러한 결과는 centrobin이 미세소관의 안정화에 관여함을 뒷받침한다. 두 번째, centrobin이 결여된 세포들은 심각하게 손상된 미세소관을 가지고 있으며, 세포가 바닥에 퍼지거나 이동 또는 증식하는 능력이 감소하게 된다. 반대로, centrobin의 인산화효소로 알려진 NEK2의 경우, 세포 내에서 발현을 감소시켰을 때, 세포의 퍼짐 현상과 이동 또는 증식 능력이 현저히 증가한다. 나아가, centrobin의 발현이 감소되었을 때 간기세포의 미세소관 안정화가 감소하는 반면 NEK2의 발현을 감속시켰을 때는 증가하는 것을 관찰하였다. 이러한 결과는 centrobin이 미세소관 안정화를 통해 세포내의 다양한 활동들에 영향을 미치며 NEK2가 이 과정을 조절할 것 임을 시사한다. 세 번째, 세포 내 또는 세포 외에서의 인산화 반응을 통해 36번째 세린을 포함한 centrobin의 4개의 아미노산 서열이 NEK2에 의한 인산화에 중요함을 확인하였다. NEK2에 의해 인산화가 되지 않는 centrobin을 세포 내에서 안정적으로 발현시켰을 때, 미세소관의 안정화와 세포의 퍼짐 현상과 이동능력이 증가함을 관찰하였다. 그러나 PLK1에 의한 인산화는 이러한 현상에 영향을 미치지 않음을 관찰하였다. 이는 NEK2가 인산화를 통해 간기세포에서의 centrobin의 기능을 특이적으로 조절함을 의미한다. 종합적으로, 이러한 결과들은 NEK2가 centrobin 인산화를 통해 미세소관의 안정화를 조절하며 이것이 세포의 퍼짐이나 이동, 증식 등의 활동에 영향을 미침을 의미한다. 따라서, 본 연구는 centrobin이 새로운 형태의 미세소관 결합 단백질이며 NEK2에 의한 centrobin의 인산화가 간기세포의 미세소관 안정화를 조절하는 중요 경로임을 시사한다.ABSTRACT..................................................................i CONTENTS................................................................iv LIST OF FIGURES.......................................................vii BACKGROUND..............................................................1 1. Microtubules.............................................................1 1.1. Structure and dynamics...........................................1 1.2. Functions...............................................................2 1.3. Modification and stabilization....................................4 2. Microtubule-related proteins........................................5 2.1. Structural MAPs......................................................5 2.2. Plus-end tracking proteins........................................6 2.3. Motor proteins.........................................................6 3. Cell spreading, migration............................................7 3.1. Cell spreading.........................................................8 3.2. Cell migration..........................................................9 4. Centrosome..............................................................9 4.1. Structure and functions...........................................10 4.2. Cycle...................................................................11 5. NEK (NIMA-related kinase) family proteins.................11 5.1. NEK2....................................................................12 6. Centrobin.................................................................13 PURPOSE...................................................................26 INTRODUCTION...........................................................28 MATERIALS AND METHODS.........................................31 Antibodies, transfection and RNA interference..................31 Cell culture and stable cell lines....................................31 Immunoblot and immunoprecipitation.............................32 Immunocytochemistry and image processing.................32 Nocodazole-resistance assay.......................................33 Phosphorylation assays...............................................33 Cell migration and cell spreading...................................34 RESULTS....................................................................36 Centrobin is associated with cytoplasmic microtubules....36 The NEK2- and centrobin-depleted cells reveal opposite outcomes in cell morphology, proliferation and migration..37 The microtubule network is stabilized in NEK2-depleted cells but destabilized in centrobin-depleted cells.............38 Determination of specific NEK2 phosphorylation sites of centrobin....................................................................40 The phospho-resistant centrobin against NEK2 stabilizes microtubules...............................................................41 NEK2 phosphorylation of centrobin does not affect centriole duplication..................................................................44 NEK2 phosphorylation of centrobin regulates subcellular distribution of centrobin................................................45 DISCUSSION..............................................................101 REFERENCES............................................................105 ABSTRACT IN KOREAN..............................................122Docto

MicroRNA-directed cleavage of a pseudogene in C. elegans

학위논문 (석사)-- 서울대학교 대학원 : 농생명공학부, 2012. 2. 신찬석.MicroRNAs (miRNA), discovered in C. elegans, are short non-coding RNAs that bind and regulate the expression of target mRNAs in plants and animals. C. elegans miRNAs bind to partially complementary sequences in the 3' untranslated region (3'UTRs) of the target mRNA, which results in translational repression through mRNA destabilization. The high-throughput sequencing of RNA cleavage fragments was performed to directly detect cleaved miRNA targets in C. elegans. Based on this analysis, mir-249 was identified as a potential miRNA that regulates a pseudogene (zk637.6) that is paralogous to asna-1(zk637.5) by cleavage mechanism with extensive, evolutionary conserved complementarity. Additionally, I validated mir-249 directed cleavage of the zk637.6 by a gene-specific 5 rapid amplification of cDNA ends (RACE) and observed notable difference in expression of zk637.6 in wild-type versus mir-249 mutant C. elegans by quantitative real-time PCR (qRT-PCR). Furthermore, the expression of zk637.6 was strongly dependent on the expression of mir-249, that is, the higher expression of mir-249 in early stage result in stronger repression of zk637.6 expression. These findings may lead to a better understanding of the biological roles of miRNAs for pseudogenes in C. elegans.Maste

IoT 프로토콜에서의 상황 인식 기반 자원 관리 기법에 대한 연구

학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·컴퓨터공학부, 2022.2. 권태경.수많은 기기가 서로 연결되는 초연결 사회를 현실화하기 위해 다양한 사물인터넷(IoT) 프로토콜이 등장했다. 특히 LoRa/LoRaWAN, Wi-Fi, 그리고 Bluetooth와 같은 비면허 대역 프로토콜은 저렴한 비용으로 공공 및 사설 네트워크의 구축을 용이하게 하여, 도시 규모에서 근거리에 이르기까지 광범위한 서비스에 널리 적용되었다. 그러나 이기종 IoT 프로토콜에서는 통신 기기들의 안정적인 연결을 보장하는 동시에, 에너지, 연산 및 무선 자원을 효율적으로 관리토록 하는 연구 과제를 제시한다. 해당 과제를 수행함에 있어, 구성 가능한 다양한 무선 매개변수 조합, 그로 인한 링크 성능상의 복잡한 절충 관계, 그리고 끊임없이 변화하는 무선 환경이 주요 장애물로 작용한다. 이러한 특성 때문에 일반적으로 효과적인 자원 관리 전략을 고안하기 위해 자칫 불규칙적으로 보이는 무선 속성을 정확하게 진단할 수 있는 네트워크 전문 지식이 필요로 된다. 이 논문에서는 1) LoRa/LoRaWAN의 전송 매개변수 제어, 2) 저전력 라디오를 통한 Wi-Fi 스캔 오프로딩, 3) Wi-Fi 및 Bluetooth의 협동적 공존 세 가지 연구 주제를 다루며, 이 과정에서 우리는 무선 신호에서 추출한 유용한 상황 정보를 활용하여 기기들의 자원을 효율적으로 관리한다. 첫째, 비면허 대역에서 작동하는 가장 유망한 LPWA 프로토콜 중 하나인 LoRa는 무선 자원 및 링크 성능을 관리하기 위해 적절하게 제어해야 하는 전송 매개변수 집합을 제시한다. 이 연구에서 우리는 프레임 전달율과 에너지 소비 간의 균형을 최적화하기 위해 CR (Coding Rate)을 적응적으로 활용하는 향상된 ADR (Adaptive Data Rate) 메커니즘인 EARN을 제안한다. EARN은 먼저 이론적으로 LoRaWAN의 링크 성능을 모델링하여 최상의 매개변수 집합을 찾고, 캡처 효과를 이용하여 충돌하는 신호의 생존율을 높인다. 우리는 실제 실험에서 적응적 CR 설정의 타당성을 검증하고, 대규모 시뮬레이션을 통해 EARN이 기존 방식을 능가하는 것을 보인다. 둘째, 스마트 기기에서 고품질의 무선 연결을 위한 기본 기능인 Wi-Fi 스캐닝은 액세스 포인트(AP)가 존재하지 않는 채널에 대해 불필요한 검색을 수행하여 자원 및 성능상의 낭비를 초래한다. 우리는 함께 배치된 저전력 무선 인터페이스를 활용하여 이러한 Wi-Fi 스캐닝 오버헤드를 상쇄하는 C-SCAN 방법을 제안한다. C-SCAN은 Bluetooth 라디오로 2.4 GHz 공유 스펙트럼을 검사하고 실제 Wi-Fi 스캔 전에 사용 중인 Wi-Fi 채널을 식별한다. 비어 있는 것으로 판단된 채널을 검색 대상에서 제외함으로써 Wi-Fi 스캐닝의 대기 시간과 에너지를 절약할 수 있다. 실험 결과는 우리가 구현한 C-SCAN의 프로토타입이 밀집된 Wi-Fi 환경에서도 사용 중인 Wi-Fi 채널을 정확히 탐지하는 것을 보인다. 마지막으로, 최신 스마트 기기에 함께 배치된 Wi-Fi와 Bluetooth는 단일 안테나와 스펙트럼을 공유하기 때문에 내외부적으로 기술 간 간섭(CTI)을 겪는다. 우리는 이 연구에서 새로운 협동적 공존 메커니즘인 D-SCAN을 제안한다. D-SCAN은 Bluetooth 라디오로 주변 Wi-Fi에 대한 포괄적인 정보를 효율적으로 추론하여 주요 Wi-Fi 기능의 오버헤드를 상쇄하고 나아가 Wi-Fi와 Bluetooth 간의 충돌을 방지한다. 이를 위해 D-SCAN은 Bluetooth의 스펙트럼 측정 결과에 심층 신경망을 활용하여 Wi-Fi 신호의 고유한 시간 및 스펙트럼 특성을 캡처하는 데이터 기반 접근 방식을 채택한다. 실제 실험에서 D-SCAN 프로토타입은 기존 Wi-Fi 스캐닝의 대기 시간과 에너지 소비를 줄이고 Bluetooth의 간섭 회피를 촉진한다.To bring a hyper-connected society, where a large number of devices are connected to each other, into reality, various Internet of Things (IoT) protocols have emerged. In particular, unlicensed band protocols such as LoRa/LoRaWAN, Wi-Fi, and Bluetooth are widespread from city-scale to local area services, as they enable impromptu establishment of public and private networks at low cost. However, the devices that communicate with heterogeneous IoT protocols presents research tasks of efficiently managing energy, computation, and radio resources while ensuring reliable connectivity. The various possible combinations of radio parameters, thereby induced complex trade-offs in link performance, and constantly changing wireless environments are the major factors making such tasks challenging. It often requires expert knowledge on wireless networks to accurately diagnose seemingly random radio properties and devise effective resource management strategies. In this dissertation, we cover three topics, i.e., 1) transmission parameter tuning in LoRa/LoRaWAN, 2) Wi-Fi scan offloading via a collocated low-power radio, and 3) collaborative Wi-Fi and Bluetooth coexistence, where we efficiently manage device resources by exploiting useful information extracted from radio signals. First, LoRa, which is one of the most promising low-power wide-area protocols operating in unlicensed bands, presents a set of transmission parameters that have to be properly regulated to manage radio resources and link performance. In this work, we present EARN, an enhanced Adaptive Data Rate (ADR) mechanism with Coding Rate (CR) adaptation, to optimize the trade-off between delivery ratio and energy consumption. In EARN design, we theoretically model the link performance of LoRaWAN to find the best parameter set and leverage the capture effect to increase the survival rate of colliding signals. We validate the feasibility of the CR adaptation with an empirical study, and large-scale simulations reveal that EARN outperforms the conventional schemes. Secondly, Wi-Fi scanning, which is a fundamental feature to provide high-quality and seamless wireless connectivity in modern smart devices, induces performance overheads while unnecessarily probing on channels where no access points (APs) exist. We present C-SCAN, which exploits a collocated low-power wireless interface to offload the Wi-Fi scanning overheads. C-SCAN inspects the shared spectrum with a Bluetooth radio and identifies which Wi-Fi channels are in use prior to the actual Wi-Fi scanning. By excluding the channels determined to be empty, the Wi-Fi can perform scanning only on available Wi-Fi channels. We implement a prototype of C-SCAN using a Bluetooth-compliant wireless transceiver and demonstrate its efficiency. Experimental results show that C-SCAN achieves high detection accuracy with low latency and energy even in dense Wi-Fi environments. Lastly, Wi-Fi and Bluetooth are collocated in modern smart devices and suffer from cross-technology interference (CTI) internally and externally, as they share a single antenna and spectrum. In this work, we present D-SCAN, a novel collaborative coexistence mechanism. D-SCAN infers nearby Wi-Fi information efficiently with a Bluetooth radio, thereby offsetting the overhead of key Wi-Fi functions and preventing collisions between Wi-Fi and Bluetooth. To this end, D-SCAN adopts a data-driven approach that captures the unique temporal and spectral features of Wi-Fi signals from Bluetooth spectrum measurements by leveraging deep neural networks. D-SCAN prototype in real-world experiments reduces the latency and energy consumption of legacy Wi-Fi scanning, and it also promotes the agile interference avoidance of Bluetooth. In summary, from Chapters 2 to 4, the aforementioned three research tasks, i.e., EARN for LoRa parameter distribution, C-SCAN for Wi-Fi scan offloading, and D-SCAN for Wi-Fi and Bluetooth coexistence, will be presented, respectively.I. Introduction 1 1.1 Limited Resources of IoT Protocols at ISM Bands 1 1.2 Overview of Existing Approaches 4 1.2.1 Coding Rate Adaptation in LoRa/LoRaWAN 4 1.2.2 Wi-Fi Scan Offloading via Bluetooth Radio 4 1.2.3 Better Coexistence Between Wi-Fi and Bluetooth 5 1.3 Main Contributions 6 1.3.1 EARN: Enhanced ADR with Coding Rate Adaptation in LoRaWAN 6 1.3.2 C-SCAN: Wi-Fi Scan Offloading via Collocated Low-Power Radios 7 1.3.3 D-SCAN: Toward Collaborative Multi-Radio Coexistence in Mobile Devices via Deep Learning 7 1.4 Organization of the Dissertation 8 II. EARN: Enhanced ADR with Coding Rate Adaptation in LoRaWAN 10 2.1 Introduction 10 2.2 Preliminaries 13 2.2.1 LoRa/LoRaWAN 13 2.2.2 Transmission Parameters 14 2.2.3 Adaptive Data Rate 15 2.2.4 Capture Effect 16 2.2.5 Related Works 16 2.3 Link Performance Modeling 18 2.3.1 Collision Probability 19 2.3.2 BER and FER 21 2.3.3 Link Performance 22 2.3.4 Pilot Experiment on the Impact of CR 24 2.4 EARN: Proposed Algorithm 28 2.5 Evaluations 31 2.5.1 Simulation Setup 32 2.5.2 Parameter Distribution 32 2.5.3 Noise Level 39 2.5.4 Cell Radius 41 2.5.5 Traffic Load 43 2.5.6 Fairness 45 2.6 Summary 49 III. C-SCAN: Wi-Fi Scan Offloading via Collocated Low-Power Radios 50 3.1 Introduction 50 3.2 Related Work 55 3.2.1 Wi-Fi Channel Discovery 56 3.2.2 Multi-Radio Cooperation Technology 57 3.3 C-SCAN Overview 59 3.3.1 Problem Statement and Overview 59 3.3.2 Background and Notations 60 3.3.3 Channel Identification Using Bluetooth Radio 62 3.4 C-SCAN Design 64 3.4.1 Scanning Scheduler 64 3.4.2 RSSI Sampler 65 3.4.3 Binary Converter 67 3.4.4 Channel Inspector 68 3.4.5 Experiments 69 3.4.6 Discussion 70 3.5 Enhanced C-SCAN 72 3.5.1 Minimization of Scanning Points 72 3.5.2 Sample Normalization and Similarity Analysis 74 3.5.3 Results 78 3.6 Implementation of C-SCAN in Android 78 3.7 Performance Evaluation 81 3.7.1 Experimental Setups and Parameters 82 3.7.2 Detection Accuracy 82 3.7.3 Detection Latency 85 3.7.4 Energy Consumption 88 3.7.5 Throughput 90 3.8 Summary 91 IV. D-SCAN: Toward Collaborative Multi-Radio Coexistence in Mobile Devices via Deep Learning 92 4.1 Introduction 92 4.2 Preliminaries 96 4.2.1 Wi-Fi Characteristics 96 4.2.2 Wi-Fi and Bluetooth Coexistence in a Combo-Module 98 4.3 D-SCAN 99 4.3.1 Overview 99 4.3.2 Divide-and-Conquer Approach 100 4.3.3 Temporal and Spectral Features of Wi-Fi Signals 102 4.3.4 Sweeping the Entire 2.4 GHz Band 103 4.3.5 Deep Learning Models 105 4.4 D-SCAN Use Cases 111 4.4.1 Wi-Fi Scanning 112 4.4.2 Wi-Fi Handover 113 4.4.3 Synergy for Wi-Fi and Bluetooth Coexistence 114 4.5 Performance Evaluations 115 4.5.1 Training and Testing Data Collection 116 4.5.2 Signal Strength and Channel Utilization 116 4.5.3 Wi-Fi Scanning 118 4.5.4 Wi-Fi Handover 125 4.5.5 Synergy for Wi-Fi and Bluetooth Coexistence 127 4.6 Discussion 129 4.6.1 Sub-1 GHz and 5 GHz Wi-Fi 129 4.6.2 Bonded Wi-Fi Channels 130 4.6.3 Differentiation of APs and Clients 130 4.7 Summary 131 V. Conclusion 132 5.1 Research Contributions 132 5.2 Future Research Directions 133박

Characterization of a delayed leaf senescence mutation and a senescence-induced gene of arabidopsis

Maste

Conditional BERT를 이용한 패션 아웃핏 데이터 증강 연구

MasterArtificial intelligence (AI) models have been recently used for fashion outfit recommendation tasks. However, an AI-based recommendation system tends to be influenced by imbalanced training data. The bias due to data can cause the system to recommend only outfits with specific attributes or generate incompatible outfits for infrequent clothes in the data. Therefore, a vast amount of clothing data with various items is essential for AI-based recommendations. However, obtaining fashion outfits from experts is expensive and time-consuming. Thus, we use augmentation to obtain new outfits. We propose a fashion outfit data augmentation model consisting of an outfit compatibility model using a bidirectional encoder representation from transformer (BERT) and conditional constraints. The conditional constraints are used in the form of embedding layer architecture used for Conditional BERT. We compared the proposed model with sequence models used for the outfit compatibility model for evaluation. The result shows that the proposed model outperforms these models in maintaining target attributes and diversity. Furthermore, we evaluated the effect of retraining with augmentation outfits. Using our model to balance training data is better than using oversampling. Additionally, retraining with augmented outfits can change the recommendation tendency for the target attribute.최근 패션 아웃핏 추천 연구에서 AI 기반 모델을 사용하는 경우가 많다. AI 기반 추천 시스템에서는 학습 데이터의 불균형으로 인해, 추천 결과의 편향이 발생할 수 있다. 특히, 패션 아웃핏 추천에서는 지속적으로 변화하는 환경에 대해 새로운 추천이 가능해야 하므로 기존 아웃핏에 대한 편향을 해결하는 것이 중요하다. 편향이 조정된 학습 데이터로 모델을 재학습하여 문제를 해결할 수 있으나, 이를 위해 새로운 아웃핏 데이터를 수집하는 것은 어려운 문제이다. 본 연구에서는 이러한 문제의 해결을 위해, 패션 아웃핏 증강 모델을 제안한다. 증강 모델을 통해 소수 데이터를 증강하여 학습 데이터를 조정할 수 있다. 본 연구에서는 패션 아웃핏 어울림 모델과 조건부 제약 모델을 결합하여 패션 아웃핏 증강 모델 구조를 새롭게 제시하였다. 본 연구에서는 실험을 통해, 이 모델을 통해 증강된 아웃핏이 비교 모델로 증강된 아웃핏에 비해 목표 속성을 유지하고, 다양성을 갖추는데 있어서 유리함을 확인하였다. 또한 이렇게 증강된 아웃핏을 패션 아웃핏 추천 모델에 학습시킴으로써, 추천 결과의 편향을 줄이고, 추천 경향성을 변경할 수 있음도 확인하였다

Incentive regulation in duopoly markets

학위논문(석사) - 한국과학기술원 : 경영정책학과, 1995.2, [ iii, 61 p. ]한국과학기술원 : 경영정책학과

노드에 용량이 있는 그래프에서의 용량 할당 방법 및 상계에 관한 연구

학위논문(석사) - 한국과학기술원 : 전기 및 전자공학과, 2010.2, [ vi, 31 p. ]In this thesis, we study node capacity allocation schemes and multicasting schemes to achieve single multicast capacity in node-capacitated graphs. Node-capacitated graphs are closely connected P2P overlay networks, and has potential to capture configurable nature of wireless relay networks. Although techniques for solving optimization problems can be used for node-capacitated graphs, it does not give any connection between graph parameters such as topology or node capacity setting and optimal strategies to achieve capacity. Accordingly, rather than just solving optimization problems for arbitrary graphs, we consider some structured node-capacitated graphs, and try to find an optimal node capacity allocation scheme and multicasting scheme for them without applying numerical methods to solve optimization problems. In addition, an upper bound called multi-region cut set bound is proposed, The key is that, rather than considering only 2 regions for a cut, it considers cuts separating a graph into multiple regions each of which corresponds to a source or a receiver. We study layered node-capacitated graphs with node upload capacity, and derive explicit characterization of single multicast capacity of maximally connected, layered graphs. For such graphs, it is shown that ratio-based node capacity allocation and routing achieve multicast capacity. In addition, some examples of other layered graphs are examined.한국과학기술원 : 전기 및 전자공학과

Analysis of Arabidopsis Mutant That Confer Delayed Senescence Sympotoms or Prolonged Longevity

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