Machine learning-based high-frequency neuronal spike reconstruction from low-frequency and low-sampling-rate recordings

Recording neuronal activity using multiple electrodes has been widely used to understand the functional mechanisms of the brain. Increasing the number of electrodes allows us to decode more variety of functionalities. However, handling massive amounts of multichannel electrophysiological data is still challenging due to the limited hardware resources and unavoidable thermal tissue damage. Here, we present machine learning (ML)-based reconstruction of high-frequency neuronal spikes from subsampled low-frequency band signals. Inspired by the equivalence between high-frequency restoration and super-resolution in image processing, we applied a transformer ML model to neuronal data recorded from both in vitro cultures and in vivo male mouse brains. Even with the x8 downsampled datasets, our trained model reasonably estimated high-frequency information of spiking activity, including spike timing, waveform, and network connectivity. With our ML-based data reduction applicable to existing multichannel recording hardware while achieving neuronal signals of broad bandwidths, we expect to enable more comprehensive analysis and control of brain functions. Multichannel neural recording enhances understanding of brain function, but handling large data is challenging. Here, the authors develop machine learning-based high frequency spike reconstruction from subsampled low-frequency neuronal signals.Y

Revealing Two Distinct Formation Pathways of 2D Wurtzite-CdSe Nanocrystals Using In Situ X-Ray Scattering

Understanding the mechanism underlying the formation of quantum-sized semiconductor nanocrystals is crucial for controlling their synthesis for a wide array of applications. However, most studies of 2D CdSe nanocrystals have relied predominantly on ex situ analyses, obscuring key intermediate stages and raising fundamental questions regarding their lateral shapes. Herein, the formation pathways of two distinct quantum-sized 2D wurtzite-CdSe nanocrystals - nanoribbons and nanosheets - by employing a comprehensive approach, combining in situ small-angle X-ray scattering techniques with various ex situ characterization methods is studied. Although both nanostructures share the same thickness of approximate to 1.4 nm, they display contrasting lateral dimensions. The findings reveal the pivotal role of Se precursor reactivity in determining two distinct synthesis pathways. Specifically, highly reactive precursors promote the formation of the nanocluster-lamellar assemblies, leading to the synthesis of 2D nanoribbons with elongated shapes. In contrast, mild precursors produce nanosheets from a tiny seed of 2D nuclei, and the lateral growth is regulated by chloride ions, rather than relying on nanocluster-lamellar assemblies or Cd(halide)2-alkylamine templates, resulting in 2D nanocrystals with relatively shorter lengths. These findings significantly advance the understanding of the growth mechanism governing quantum-sized 2D semiconductor nanocrystals and offer valuable guidelines for their rational synthesis. Two critical pathways of two distinct quantum-sized 2D wurtzite-CdSe nanocrystals are revealed by the combined approach using various characterization techniques. This study provides rational explanations for intermediate stages, the difference in the laterals dimensions, and the origin of different synthesis pathways of quantum-sized 2D semiconductor nanocrystals.imageY

The Korean Academy of Asthma Allergy and Clinical Immunology guidelines for sublingual immunotherapy

Allergen immunotherapy (AIT) has been used for over a century and has been demonstrated to be effective in treating patients with various allergic diseases. AIT allergens can be administered through various routes, including subcutaneous, sublingual, intralymphatic, oral, or epicutaneous routes. Sublingual immunotherapy (SLIT) has recently gained clinical interest, and it is considered an alternative treatment for allergic rhinitis (AR) and asthma. This review provides an overview of the current evidence-based studies that address the use of SLIT for treating AR, including (1) mechanisms of action, (2) appropriate patient selection for SLIT, (3) the current available SLIT products in Korea, and (4) updated information on its efficacy and safety. Finally, this guideline aims to provide the clinician with practical considerations for SLIT.Y

An <i>in-situ</i> hybrid laser-induced integrated sensor system with antioxidative copper

Integration of sensors with engineering thermoplastics allows to track their health and surrounding stimuli. As one of vital backbones to construct sensor systems, copper (Cu) is highly conductive and cost-effective, yet tends to easily oxidize during and after processing. Herein, an in-situ integrated sensor system on engineering thermoplastics via hybrid laser direct writing is proposed, which primarily consists of laser-passivated functional Cu interconnects and laser-induced carbon-based sensors. Through a one-step photothermal treatment, the resulting functional Cu interconnects after reductive sintering and passivation are capable of resisting long-term oxidation failure at high temperatures (up to 170 degrees C) without additional encapsulations. Interfacing with signal processing units, such an all-in-one system is applied for long-term and real-time temperature monitoring. This integrated sensor system with facile laser manufacturing strategies holds potentials for health monitoring and fault diagnosis of advanced equipment such as aircrafts, automobiles, high-speed trains, and medical devices.Y

The Road to My Car: The Development and Limitation of Koreans Desire for Car Ownership

화석에너지를 토대로 만들어진 현대문명은 기후위기와 생태계 파괴 등으로 파생되는 각종 문제가 일어나고 지구 생태계와 인류 사회가 위협받게 되면서 그 존립 기반이 흔들리고 있다. 자동차는 화석에너지 체제와 대량생산‧대량소비 사회의 상징으로서, 현대문명의 위기 문제를 성찰하는 데 적절한 대상이 된다. 이러한 문제의식에서 한국에서의 자동차 소유 욕망을 비판적으로 살펴보았다. 먼저 한국에서 다수가 자가용을 갖게 되는 마이카 시대의 기점을 살펴보았다. 자동차 등록 대수와 마이카 담론 추이를 볼 때, 3저 호황과 더불어 1인당 GDP가 급상승하고 자동차의 대량생산체제가 확립되는 1980년대 후반에 비로소 마이카 시대에 접어들었다. 1970년대 이후 한국 사회에서의 자동차 소유 욕구가 시간이 갈수록 더욱 확산했고, 1980년대 들어서면 자동차에 대한 경쟁적이고 과시적인 소비 현상이 나타났다. 다음으로 자동차 소유 욕망이 함께한 자동차 보급은 사회 전반의 이동성(mobility)을 증대시키며 자동차 여행의 확장, 외식과 쇼핑문화의 확대로 이어졌고, 자동차 연관 산업의 발달을 촉진했다. 이러한 사회문화적, 산업적 변화는 자동차 중심 교통체계의 형성과 함께했다. 한국의 교통예산은 자동차 운행을 위한 도로 중심으로 편성되었다. 육교와 지하도 등 교통시설은 자동차 운행을 이동의 중심에 놓고 교통약자의 보행권을 배제한 것이었다. 한편, 자동차 소유 욕망의 실현과 자동차 중심 교통체계는 사회생태적 비용을 증가시켰다. 교통 정체와 교통사고 등 외부비용의 증가와 생태계 파괴, 대기오염 및 온실가스 배출은 현재까지 계속되고 있다. 끝으로 대량생산-유통-소비-폐기의 물질대사에 따른 인간의 다른 인간과 자연에 대한 착취와 기후위기를 일으키는 자동차 사회로부터 벗어나기 위한 로드맵을 제시하고자 하였다. Modern civilization, which was built on fossil energy, is shaken by various problems such as climate crisis and ecological destruction. As a symbol of the fossil energy system, mass production and mass consumption society, the automobile is an appropriate object to reflect on the crisis of modern civilization. With this in mind, I critically examined the desire for car ownership in Korea. First, I considered the beginning of the My Car Era, when the majority of Korea began to have their cars. Based on the number of car registrations and the trend of my car discourse, the my car era was finally entered in the late 1980s, when GDP per capita rose rapidly along with the three-low boom and the mass production system of cars was established. Since the 1970s, Korean societys desire for car ownership has become more widespread over time, and the competitive and ostentatious consumption of automobiles became prominent in the 1980s. Next, the proliferation of automobiles, coupled with the desire for car ownership, increased mobility across society, leading to the expansion of automobile travel, the expansion of dining and shopping culture, and the development of automobile-related industries. These socio-cultural and industrial changes have been accompanied by the formation of an automobile-centered transportation system. South Korea's transportation budget was organized around roads for automobile transportation. Transportation facilities such as overpasses and underpasses put automobiles at the center of movement and excluded the right to walk for the transportation disadvantaged. Meanwhile, the realization of the desire to own a car and the car-centred transportation system increased the socio-ecological costs. The increase in transportation external costs such as traffic congestion and traffic accidents, ecosystem destruction, air pollution, and greenhouse gas emissions continue to this day. Finally, this paper attempted to present a roadmap to escape from the car society that causes climate crisis and human exploitation of humans and nature through the material metabolism of mass production, distribution, consumption, and disposal.N

A case of Seoul, South Korea

학위논문(석사) -- 서울대학교대학원 : 농업생명과학대학 생태조경·지역시스템공학부(생태조경학), 2024. 2. 윤희연.Globally, urban areas have faced the challenge of significant levels of population density. This leads to environmental pollution, scarcity of outdoor spaces, and the disease outbreaks. In reaction to such condition, urban parks have attracted attention in urban planning. Urban parks satisfy the demand for outdoor spaces and offer venues for physical activity and community engagement to increase physical and mental health status. Most relevant studies have indicated that physical activities within urban parks contribute to improving the health status of citizens. These studies often use indicators that simply reflect the existence of urban parks. However, understanding the actual usage patterns of urban parks is crucial to accurately gauge their impact. In light of this, our study examines the effect of urban parks on the health status of citizens, using K-means clustering and a three level logistic regression model, with park visits as variables. The study focuses on urban parks located in Seoul, South Korea, and spans from January 1, 2019, to December 31, 2019. We propose that urban parks, particularly those close to residential areas and of medium to small size, have a positive effect on the BMI, stress levels, depression, and fatigue of citizens. These parks are utilized throughout the day or predominantly at night, suggesting usage post-work hours. Given the increasing recognition of urban parks from a wellness perspective, we anticipate that empirical studies on the health impacts of urban parks could bolster local government policies concerning the management and development of these spaces.전 세계적으로 도시 지역은 높은 수준의 인구 밀집 문제에 직면해있다. 고밀화된 도시 환경은 환경 오염, 외부 공간 부족, 질병 심화 등의 문제를 야기한다. 이러한 상황에 대응하기 위해 도시공원이 주목을 받고 있다. 도시공원은 도시민의 옥외 공간에 대한 수요를 충족하고, 신체활동과 사회적 활동을 위한 장소를 제공하여 신체적, 정신적 건강 수준을 향상시킨다. 도시공원이 도시민의 건강에 미치는 영향을 분석한 대부분의 선행 연구들은 도시공원에서의 신체활동이 시민의 건강 수준을 개선하는데 기여한다고 주장한다. 이러한 연구들은 도시공원의 면적, 주거지역으로부터의 거리 등을 주요 지표로 사용하였으나, 이는 단순히 도시공원의 존재 유무만을 나타낸다. 그러나, 도시공원의 효과를 보다 정확하게 추정하기 위해서는 시민들이 도시공원을 어떠한 방식으로 이용하는지에 대한 고려가 필요하다. 이에 따라 본 연구에서는 도시공원 방문자 수를 이용하여, K-means clustering 과 three level logistic regression model을 이용하여 도시공원이 시민의 건강상태에 미치는 영향을 추정하였다. 연구 대상지는 대한민국 서울이며, 연구 기간은 2019년 1월 1일부터 2019년 12월 31일까지이다. 분석 결과, 하루 동안 꾸준히 이용 되거나, 퇴근 시간 이후에 이용률이 높은 도시공원의 면적이 증가하면, 시민들의 체질량지수, 스트레스, 우울, 피로 수준에 긍정적인 효과를 미치는 것으로 나타났다. 해당 군집에 포함된 도시공원은 주로 주거지역과 근접해 있으며, 중소형 규모인 것으로 나타났다. 삶의 질에 대한 시민들의 인식이 증가하고, 도시공원의 중요도가 증가하고 있는 상황에서, 도시공원이 건강에 미치는 영향에 대한 실증적 연구는 도시 공간의 관리 및 개발에 관한 정책에 도움을 줄 수 있을 것으로 기대된다.Chapter 1. Introduction 1 Chapter 2. Background 4 Chapter 3. Analytical design 5 3.1. Study site 5 3.2. Data and samples 6 3.3. Analytical method 8 Chapter 4. Results 12 4.1. Cluster analysis 12 4.2. Statistical analysis 18 Chapter 5. Conclusion and discussion 24 Bibliography 26 Abstract in Korean 30석

코딩 기법과 학습방법을 이용한 오류정정부호네트워크의 성능강화

학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2024. 2. 노종선.This dissertation encompasses three main research areas: i) the design methodol- ogy of codebooks for error correcting output code (ECOC) networks using low-density parity-check (LDPC) codes, ii) mitigation of class unfairness issues in ECOC net- works, and iii) parameter optimization in the design of binary neural networks (BNN) using Fourier series representation. Firstly, a method for designing LDPC codes for ECOC networks through perfor- mance analysis using EXIT is proposed. Replacing the conventional use of Hadamard codes in ECOC networks, the LDPC-based ECOC networks allows for a scalable de- sign over various numbers of binary classifiers and classes. LDPC-based ECOC net- works have fast decoding performance and near-maximum likelihood decoding accu- racy. For the cases of large number of class, this dissertation presents the optimization of LDPC codes for use in ECOC networks, utilizing extrinsic information transfer analysis and various version of the differential evolution method. Secondly, the issue of unfairness in adversarial classification within ECOC net- works is addressed. The dissertation identifies class classification unfairness issues arising in ECOC networks and introduces cost-sensitive learning for fairness to allevi- ate performance disparities across classes. Thirdly, the dissertation designs a network using Fourier series representations for binary neural networks and optimizes the parameters used in the Fourier series rep- resentations. Optimizing parameters enhances the performance of the BNN networks utilizing Fourier series representations. keywords: Error correcting codes, low-density parity-check (LDPC) codes, error correcting output codes (ECOC) network, protograph extrinsic information transfer (EXIT) analysis, differential evolution algorithm, fairness problem, binary neural network, Hadamard code student number: 2018-22615이 학위 논문에서는 다음 세 가지의 연구가 이루어졌다: i) low-density parity-check (LDPC)를 사용한 Error Correcting Output Code (ECOC) 네트워크의 부호책 설계방법. ii) ECOC에서의 클래스 불공정 문제 약화 iii) 푸리에 급수를 이용한 이진인공신경망 (BNN) 설계에서의 파라미터 최적화. 첫 번재로, ECOC 네트워크에서 EXIT를 통한 성능 분석으로 LDPC 부호책을 설계하는 방법이 제안되었다. 기존의 하다마드를 부호책으로 사용한 ECOC 네트워크를 대신하여, LDPC를 사용한 ECOC 네트워크는 다양한 이진분류기 갯수와 클래스에 대해서 자유로운 설계가 가능하고, 신뢰전파 복호방식을 이용해 최대가능도 복호방식에 가까운 성능을 보이면서도 빠르게 복호 할 수 있다. 본 학위논문에서는 ECOC 네트워크에 쓰일 LDPC 부호책을 설계 할 때, EXIT 분석과 differential evolution 방법을 이용해 부호책을 최적화 했다. 두 번째로, ECOC 네트워크에서 발생하는 불공정 문제를 제시했다. ECOC 네트워크에서 발생하는 클래스 분류 불공정 문제를 확인하고 이를 완화하기 위해 공정성을 위한 비용민감 학습을 도입하고 클래스별 성능 차이를 완화했다. 세 번째로, 이진 인공신경망에서 푸리에 변환을 이용한 네트워크를 설계하고, 푸리에 변환에 쓰이는 변수들을 최적화 했다. 이를 통해 푸리에 변환을 이용한 BNN 네트워크의 성능을 증진시켰다.Abstract i Contents ii List of Tables iv List of Figures v 1 INTRODUCTION 1 1.1 Background . 1 1.1.1 Brief History of Error Correcting Output Code Networks 1 1.1.2 Brief History of Channel Coding Theory 3 1.2 Overview of Dissertation 6 2 Overview of ECOC Networks and LDPC Codes 8 2.1 ECOC Networks . 8 2.1.1 Training of ECOC Networks 8 2.1.2 Decoding of Error Correcting Output Codes Network 11 2.2 LDPC Codes 11 2.2.1 Progressive Edge Growth Algorithm 16 2.2.2 Belief Propagation Decoding of LDPC Codes 16 2.2.3 Density Evolution 18 2.2.4 Extrinsic Information Transfer Chart 19 ii 3 Scalable ECOC Networks Using LDPC Codes 21 3.1 Conventional Codebook Design for ECOC Networks 21 3.2 LDPC Codes Design For ECOC Networks 22 3.3 LDPC-Based ECOC Networks Simulation Results . 24 3.3.1 ML and BP Decoding Performance 25 3.3.2 Flexibility and Scalability . 32 3.3.3 Performance Comparison with Regular LDPC codes 33 3.3.4 Test Environment 33 3.4 Conclusion . 38 4 Adversarial Fairness Problem in ECOC Networks 40 4.1 Adversarial Fairness Problem . 40 4.2 Fair Learning 41 4.3 Simulation Results 44 4.4 Conclusion . 45 5 Fourier Series BNN 48 5.1 Binarized Neural Networks 49 5.2 Straight Through Estimator 50 5.3 Fourier Series BNN 51 5.4 Results and Discussion . 53 5.4.1 Evaluation Result 53 5.4.2 Effect of the Period and Number of Terms in the FSR 54 5.5 Conclusion . 55 6 Conclusion 59 Abstract (In Korean) 70 iii박

개방경제국가의 통화정책 및 재정정책 효과에 관한 논문

학위논문(박사) -- 서울대학교대학원 : 사회과학대학 경제학부, 2024. 2. 박웅용.This dissertation consists of three independent studies focusing on the economic policies, particularly monetary and fiscal policy of open economies. The first chapter explores the changes in the effectiveness of monetary policy in Korea and major ASEAN countries (such as Malaysia, Indonesia, and the Philippines) since the 2000s. Through analysis using the TVP-VAR methodology, the impact of monetary policy generally weakens or shows a similar trend in the short term but tends to strengthen in the mid to long term. However, when considering the peak point and the size of the policy effect, patterns vary by country. In Malaysia and the Philippines, the peak point remains stable, and the size of the effect increases, indicating that the overall effectiveness of monetary policy is growing. However, in Korea and Indonesia, the size of the effect increases, while the point of peak effect is significantly delayed. This suggests that in the cases of Korea and Indonesia, the uncertainty surrounding the implementation of monetary policy is significant, diminishing its effectiveness. Furthermore, severe side effects may occur if monetary policy is not implemented at the appropriate time. In the second chapter, the objective is to examine whether there are variations in the effects of government spending shocks on macroeconomic variables such as GDP across groups and states of household debt. Specifically, we focus on 26 OECD countries, categorizing them into two groups: (i) countries using international currency and (ii) those not using it. Using the state-dependent local projection model for analysis, the results indicate that expansionary government spending increases GDP and consumption. This effect is more pronounced when household debt is low. Upon examining each group, it is evident that the international currency group experiences a rise in GDP and consumption as a result of expansionary government spending, with mild discernible differences based on household debt levels. However, the non-international currency group exhibits significant variation in the effects of expansionary government spending on GDP and consumption based on household debt levels. In other words, the effect of expansionary government spending is relatively significant when household debt is low, whereas the effect is considerably constrained when household debt is high. Therefore, this chapter suggests that non-international currency countries should pay more attention to preventing excessive increases in household debt to ensure policy effectiveness. The third chapter examines whether the impact of monetary policy on asset prices is state dependent depending on economic and financial fluctuations in small open economy countries. As a result of the analysis of small open economy countries and a relatively large open economy countries, the effect of monetary policy on asset prices appears to be state dependent depending on the country group and asset type. In the case of small open economies, the effect of monetary policy appears to be state-dependent on stock prices. In particular, it significantly reduces stock prices during expansionary state, but shows an insignificant response during recessionary state. Meanwhile, the effect of monetary policy on real property prices and real effective exchange rates is not clear. For relatively large open economies, the impact of monetary policy on stock and property markets is unclear. However, in the case of the real effective exchange rate, it can be confirmed that there is a state dependent effect, such as a tendency for an immediate appreciation during the recession, while a significantly delayed appreciation occurs during the expansion. Keyword : Monetary Policy, Fiscal Policy, Household debt, Asset price, VAR, Local Projection Student Number : 2019-21070본 논문은 개방경제국가들의 경제 정책 즉 통화정책과 재정정책을 주제로 한 3장의 독립적인 연구로 구성되어 있다. 첫번째 장은 한국과 주요 아세안국가(말레이시아, 인도네시아 및 필리핀)을 대상으로 2000년대 이후 통화정책의 효과가 어떻게 변화해 왔는지를 분석한다. TVP-VAR 방법론을 사용하여 분석한 결과, 공통적으로 통화정책의 효과가 단기적으로는 다소 약화되거나 유사한 흐름을 보이나, 중장기적으로는 강화되는 경향을 보인다. 그러나, 통화정책이 가장 큰 효과를 보이는 시점과 해당 시점의 정책 효과의 크기를 보면, 국가별로 다른 양상을 보인다. 말레이시아와 필리핀은 통화정책이 가장 큰 효과를 보이는 시점이 안정적으로 유지되면서 효과의 크기도 커지고 있어 통화정책의 유용성이 증가하는 것으로 나타난다. 그러나, 한국과 인도네시아는 효과의 크기는 커지면서도 가장 큰 효과를 보이는 시점이 상당히 지연되고 있음이 드러났다. 이는 한국과 인도네시아의 경우 통화정책 시행의 불확실성이 커 오히려 유용성이 감소하고, 적절한 시점에 통화정책을 수행하지 못할 경우 부작용이 커질 수 있음을 시사한다. 두번째 장에서는 가계부채의 높고 낮음에 따라 정부 지출 충격의 효과가 달라지는 지 여부를 살펴본다. 특히 OECD 26개 국가를 대상으로 (i) 국제통화를 사용하는 국가 그룹과 (ii) 그렇지 않은 그룹으로 나누어, 정부 지출 충격이 GDP 등 거시 경제 변수에 미치는 영향이 그룹간 및 상태별로(state) 차이가 있는지를 살펴보고자 한다. State-dependent Local Projection 모형을 사용하여 분석한 결과, 확장적 정부지출은 GDP와 소비를 증가시키며 특히, 가계부채가 적을 때에 효과가 더 커지는 것으로 나타났다. 한편, 그룹별로 살펴보면, 국제통화 그룹의 경우 확장적 정부 지출 충격은 전반적으로 GDP와 소비 등을 늘리지만 가계부채 수준에 따른 차이는 크지 않았다. 그러나, 비국제통화 그룹은 확장적정부 지출 충격이 GDP와 소비 등을 늘리는 한편 그 효과는 가계 부채수준에 따라 상당한 차이가 있음을 보였다. 즉, 가계 부채가 적을 때에는 확장적 정부 지출 충격의 경기 부양 효과가 상대적으로 큰 반편, 가계 부채가 많은 때에는 그 효과가 상당히 제약되는 것으로 나타났다. 따라서 본 연구는 비국제통화 국가들의 경우, 정책 유효성을 담보하기 위하여 가계 부채가 과도하게 높아지지 않도록 주의를 기울일 필요가 있음을 시사한다. 세번째 장에서는 소규모 개방경제 국가들을 대상으로, 통화정책이 자산가격에 미치는 영향이 경기 변동 및 금융 변동에 따라 상태 의존적(state-dependent)인지 여부를 살펴본다. 소규모 개방경제국가 그룹과 상대적으로 큰 규모의 개방경제국가 그룹을 대상으로 분석한 결과 통화정책이 자산 가격에 미치는 효과는 국가 그룹 및 자산 종류에 따라 상태 의존적인 효과가 있는 것으로 나타났다. 소규모 개방경제국가의 경우, 통화정책의 효과는 주식가격에 대해 상태 의존적인 것으로 나타났다. 특히 경기 호황시에 유의하게 주식가격을 하락시키는 반면 불황시에는 유의하지 않은 반응이 나타났다. 한편, 부동산 가격과 실질 실효 환율에 대한 통화정책 효과는 명확하지 않았다. 상대적으로 큰 규모의 개방경제국가의 경우, 통화정책이 주식 및 부동산 시장에 미치는 영향은 명확하지 않은 것으로 나타났다. 다만, 실질 실효 환율의 경우 불황시에 다소 즉각적인 평가절상 경향을 보이는 한편, 호황시에는 상당히 지연된 평가 절상이 나타나는 등 상태 의존적인 효과가 있는 것으로 나타났다.Abstract iii Table of Contents vi Chapter 1. The Time-Varying Effects of Monetary Policy on the Real Economy: An Analysis of Korea and Major ASEAN Countries . １ 1.1. Introduction １ 1.2. Model structure and specification . ６ 1.2.1 TVC-VAR model ６ 1.2.2 Model specification ８ 1.3. Empirical Analysis １０ 1.3.1 Korea . １０ 1.3.2 Malaysia １３ 1.3.3 Indonesia . １５ 1.3.4 The Philippines １６ 1.4. Conclusion １８ Appendix A. Figures ２１ Appendix B. Data .２７ Reference ２８ Chapter 2. Effects of Government Spending Shocks by Household Indebtedness: An OECD Panel Analysis ３０ 2.1. Introduction ３０ 2.2. Data and Empirical Procedure ３８ 2.2.1 Data ３８ 2.2.2 State specification ３９ 2.2.3. Local projection methodology ４１ 2.2.4. Construction of Government Spending Shocks ４３ 2.3. Empirical Results ４５ 2.4. Extended Analyses ４９ 2.4.1. Robustness ４９ 2.4.2. Alternative Grouping Strategies ５０ 2.4.2.1. Alternative Grouping 1 : Household Debt to GDP ratio ５１ 2.4.2.2. Alternative Grouping 2 : Long-term interest rate ５３ 2.5. Conclusion . ５５ Appendix A. Data. ５７ Appendix B. Tables ５８ Appendix C. Figures ６２ Reference ６７ Chapter 3. The State-dependent Effects of Monetary Policy on Asset Prices in Small Open Economies ７０ 3.1 Introduction and Literature Review . ７０ 3.1.1 Introduction ７０ 3.1.2 Literature Review . ７４ 3.2 Methodology and Data ７８ 3.2.1 First step: Sequence of Monetary Policy Shocks ７８ 3.2.2 Second step : Local projection ８１ 3.2.3 Identification of state ８４ 3.2.4 Data ８５ 3.3 Empirical Results ８７ 3.3.1 Small Open Economy Group Analysis ８７ 3.3.1 Relatively Large Open Economy Group Analysis ９２ 3.4 Conclusion . ９５ Appendix A. Figures ９９ Appendix B. DATA １０３ Reference １０５ Abstract in Korean １１０ Acknowledgements １１２박

Formulation and Applications

학위논문(박사) -- 서울대학교대학원 : 공과대학 건설환경공학부, 2024. 2. 이청원.This study proposes a new segment-level traffic state monitoring method and freeway traffic management strategies by investigating the elliptic bivariate relationship between vehicle accumulation and travel time. The validity of the proposed monitoring method is demonstrated through comparison with conventional traffic flow models (e.g. input-output diagram, flow-density bivariate relationship), and the proposed method can describe not only the evolution of congestion but also its irreversible recovery. Two parameters of the elliptic bivariate relationship that characterize the traffic state are derived by applying complex eigenvalue analysis, a useful method that leverages the properties of an ellipse. The meaning of these parameters with regard to traffic flow is investigated with a mathematical approach and an empirical analysis. This reveals parameterλto indicate congestion severity, while parameter ϕ describes whether the congestion is evolving or in recovery, and its difference Δϕ refers to how rapidly the traffic state changes. Using those parameters of the elliptic bivariate relationship as control parameters, Variable Speed Limit (VSL) control, Ramp Metering (RM) control and an integrated control are developed.and ϕ determine the triggering and actuating values (e.g. speed limit value, metering rate), and also used for integrating VSL and RM control by applying reinforcement learning framework that has two agents, one for each control. The effectiveness of the proposed strategies is evaluated using microsimulation, VISSIM. The algorithm of the proposed strategy is implemented on a calibrated real-world network. The results show that the proposed VSL and RM control are proactively triggered prior to the congestion by identifying the segment-level traffic state and properly adjust the speed limit values and metering rates. Moreover, integrating the variable speed limit and ramp metering controls by contemplating their respective characteristics is significantly more effective than operating them independently. The findings of this study demonstrate the possible promise in leveragingand ϕ for not only individual traffic management strategies but also integrating the proposed strategies.본 연구는 차량 누적과 통행 시간 간의 타원형 이변량 관계에 기반하여 지점 검지자료로부터 구간 교통상태를 모니터링 하는 새로운 방법을 제안하고, 이를 적용한 고속도로 교통관리 전략을 개발한다. 제안된 모니터링 방법은 전통적인 교통류 모니터링 방법들과의 비교를 통해 그 타당성이 입증되었으며, 자유류 상태에서 정체발생에 이르는 과정은 물론, 정체 이후 교통상태가 비가역적으로 회복되는 과정도 설명할 수 있다. 타원형 이변량 관계를 교통관리전략에 적용하기 위해, 타원이 가지는 수학적 특성을 응용하여 실시간으로 구간교통상태를 진단할 수 있는 방법을 제안하였다. 타원형 이변량 관계에 복소 고유값 해석(Complex eigenvalue analysis)를 적용하여 교통상태를 특정하는 두 가지 매개변수를 도출하고, 연속류 혼잡 측면에서 두 매개변수들이 가지는 의미를 해석하였다. 첫째, 매개변수는 수학적으로 특정 상태가 얼마나 큰 타원 궤적을 따라 움직이는지를 나타내며, 연속류 혼잡 측면에서는 정체의 강도를 의미한다. 둘째, 매개변수 ϕ는 현재상태가 특정 기준상태로부터 얼마나 회전하였는지를 나타내며, 연속류 혼잡 측면에서는 현재 교통상태가 정체가 심화되고 있는 상태인지, 혹은 정체로부터 회복되고 있는 상태인지 여부를 의미한다. 그리고 각 시간대별 매개변수 ϕ의 차이인 Δϕ는 교통상태가 얼마나 빠르게 변화하고 있는지를 의미할 수 있다. 본 연구는 연속류 혼잡을 설명할 수 있을 뿐만 아니라 실시간으로 계산 가능한 매개변수들을 제어변수로써 활용하는 가변속도제어(VSL)와 램프미터링(RM) 전략을 개발하였다. 제안된 전략 알고리즘에서 매개변수와 ϕ는 전략의 개시여부, 그리고 VSL의 속도제한 값 및 RM의 미터링율을 결정한다. 또한, 본 연구는 강화학습을 이용한 VSL-RM 통합제어전략 역시 개발하였으며, 효율적인 전략 통합을 위해 타원형 이변량 관계의 두 매개변수를 상태-보상 함수에 적용하였다. 제안된 전략의 효과는 실제 고속도로 자료를 이용하여 정산된 네트워크가 구축된 마이크로시뮬레이션을 이용하여 분석하였다. 시뮬레이션 결과, 본 연구의 구간교통상태 모니터링 방법을 통해 정체발생을 선제적으로 파악하여 정체가 발생하기 전에 VSL 및 램프미터링 제어전략이 개시되었다. 또한, 구간교통상태에 적절히 대응하여 과도하거나 부족하지 않은 속도제한 값 및 미터링율을 조정함으로써, 통행시간과 지연은 물론 정체지속시간이나 통행시간 신뢰도 등 다양한 효과지표들을 상당히 개선하였다. 그리고 통합전략에 대한 효과분석 결과, VSL과 RM 제어의 각각의 특성을 고려하여 통합한 전략이 개별 전략을 독립적으로 운영하는 것보다 더 효과적임을 확인하였다. 또한, 타원형 이변량 관계의 두 매개변수를 이용하여 상태-보상 함수가 일관성이 있도록 설계된 본 연구 통합전략이 일반적인 교통류 변수를 사용한 전략대비 더 효율적인 학습을 달성하는 것으로 나타났다.Chapter 1. Introduction 1 1.1. Research Backgrounds 1 1.2. Research Objectives and Framework 5 Chapter 2. Literature Review 7 2.1. Variable Speed Limit 7 2.2. Ramp Metering 9 2.3. Integrated Control 12 Chapter 3. Modeling 16 3.1. Constructing Elliptic Bivariate Relationship 16 3.2. Comparing the Elliptic Bivariate Relationship 20 3.3. Deriving Parameters of the Proposed Model. 24 3.3.1. Estimating the Boundary Condition of Recurrent Congestion 24 3.3.2. Applying Complex Eigenvalue Analysis 31 3.4. Investigating the Meaning of Derived Parameters 33 3.4.1. Analytical Relationship Between Parameters and Travel Time 33 3.4.2. Mathematical Relationship Between Parameters and Travel Time 34 Chapter 4. Applications 37 4.1. Variable Speed Limit Control 37 4.1.1. VSL Triggering Algorithm 37 4.1.2. Determining Speed Limit Value 39 4.2. Ramp Metering Control 42 4.2.1. Formulating a Feedback Controller 42 4.2.2. Constructing Flowchart of the Proposed Strategy 44 4.3. Integrated Control 45 4.4. Experimental Setup 48 4.4.1. Simulation Tools 48 4.4.2. Study Site and Data Description 48 4.4.3. Calibration 49 Chapter 5. Results and Discussions 51 5.1. Results on VSL Control 51 5.1.1. Simulation Scenarios for VSL Control 51 5.1.2. Speed Limit History of the Proposed VSL Control 52 5.1.3. Simulation Results for VSL Control 54 5.2. Results on RM Control 59 5.2.1. Simulation Scenarios for RM Control 59 5.2.2. Metering Rate History of the Proposed RM Control 59 5.2.3. Simulation Results for RM Control 62 5.3. Results on Integrated Control 64 5.3.1. Simulation Scenarios for Integrated Control 64 5.3.2. Simulation Results for Integrated Control 67 5.3.3. Discussion of Simulation Results 71 Chapter 6. Conclusions 74 References 77박

H295R과 MVLN 세포주를 이용한 인체접촉 생분해 플라스틱의 성 호르몬 교란 영향 연구

학위논문(석사) -- 서울대학교대학원 : 보건대학원 환경보건학과, 2024. 2. 최경호.Endocrine disruption potentials of several biodegradable plastics of human use : Effects on sex hormones in H295R and MVLN cell lines Eun Hye Kim Department of Environmental Health Sciences Graduate School of Public Health Seoul National University Biodegradable plastics are generally recognized as a safer and more sustainable alternative to petroleum-based plastics. While some studies have reported the presence of endocrine-disrupting chemicals in biodegradable plastic products, current knowledge on the endocrine disruption effects and mechanisms of biodegradable plastics remains limited. In the present study, we utilized human adrenocortical carcinoma (H295R) cells and human breast carcinoma (MVLN) cells to evaluate the sex hormone disruption potential of major biodegradable plastics manufactured for direct human contact. Biodegradable plastics tested in this study, intended for human use, included a sanitary bag (n=1), disposable gloves (n=2), a plastic cup (n=1), a straw (n=1), and a plate (n=1). These products were made from plastics such as polybutylene adipate terephthalate (PBAT), polylactic acid (PLA), and a PBAT+PLA polymer. Products made from high-density polyethylene (HDPE) were included for comparison. The products were shredded into small pieces and extracted using acetone. After exposure to the extracts of these samples to H295R cells, sex hormone and key gene expression levels involved in sex hormone synthesis were measured. Moreover, binding affinity with estrogen receptors was observed using MVLN cells. In H295R cell experiments, exposure to eight plastic extracts generally led to increased 17β-estradiol (E2) levels. However, statistical significance was not always observed. Particularly, the PLA plastic cup (sample 7) extract exhibited a significant 1.46-fold increase at the highest concentration (5 mg/mL) compared to the solvent control. For testosterone (T) levels, a significant decrease was observed in HDPE sanitary bag (sample 2) and PBAT disposable gloves (sample 3) extracts. For most products, up- regulation of the cyp19a1 gene and down-regulation of the 17βhsd1 were observed in H295R cells. In MVLN cell experiments, only the PLA plastic cup (sample 7) showed affinity for estrogen receptors. The results of this study demonstrate that biodegradable plastics may influence sex hormone homeostasis, potentially through alteration of aromatase activity. Effects toward anti-androgenicity observed in the biodegradable plastics were similar to those reported for some phthalates, typical components of PVC plastics. Further investigations are warranted on the environmental health implications of this in vitro observation. Keywords: Biodegradable plastics; Endocrine disruption; Sex steroid hormones; H295R cell line; MVLN cell line Student Number: 2022-205001. Introduction 1 2. Materials and Methods 1-6 3. Results 6-10 4. Conclusions 11 5. Discussions 12석