A Study on Ice Load Estimation for Icebreaking Cargo Vessels and Ice Transit Model

As the oil price soars and the Russian economy revives, increasing new orders of icebreaking cargo vessels become an important issue in the world's shipbuilding market. One of the areas of the concern which arises during navigation in ice-covered waters is the magnitude of ice impact loads encountered by ships. However, the accurate estimation of ice load still remains as a rather difficult task in the design of icebreaking vessels. This study focuses on the development of a simple ice load prediction formula for the ice-going cargo vessels. For this purpose, various ice load scenarios are discussed concerning possible ship/ice interaction modes. Since the maximum ice loads are expected from unbroken ice sheet, these load are most likely to be concentrated at the bow area. In this study, published ice load data for icebreaking vessels, from the model tests and also from full-scale sea trials, are collected and then several ice load prediction formulas are compared with these data. Finally, based on collected data, a new, semi-empirical, ice load prediction formula is recommended for the design of icebreaking cargo vessels. An ice load estimation software "IceView" is developed by using ice load prediction formulas. In addition, an ice transit model for icebreaking cargo vessels in the Northern Sea Route is studied. The ice transit model can select optimum sea routes with the shortest navigation time and the lowest operation cost. This model, with basic information such as ship capabilities, transit directions and months of transit, can calculate total transit distance and elapsed time, mean speed, operation cost for each vessel. In the ice transit model, environment information such as the site-specific ice conditions, wave and wind states is utilized for four different months (April, June, August, and October) along the Northern Sea Route. The model also defines the necessary periods of an icebreaker escort. Then the optimum sea routes are selected and visually displayed on the digital map using a commercial software ArcGIS. Usefulness of the selected sea routes is discussed.ABSTRACT ⅰ 목 차 ⅲ 그 림 목 차 ⅴ 표 목 차 &#8570Ⅰ. 서 론 1 Ⅱ. 빙하중 시나리오 4 2.1 빙하중과 빙저항 4 2.2 전체 빙하중과 국부 빙압력 6 2.3 빙하중 시나리오 9 Ⅲ. 빙하중 실측자료 분석 및 추정식 고찰 11 3.1 빙하중 실측자료 분석 11 3.1.1 전체 빙하중 실측자료 11 3.1.2 국부 빙압력 실측자료 45 3.1.3 빙하중 실측자료 분석 67 3.2 빙하중 추정 경험식 78 3.2.1 전체 빙하중 추정식 78 3.2.2 국부 빙압력 추정식 90 3.2.3 추정식을 이용한 실선 빙하중 계산 사례 100 Ⅳ. 빙하중 산정 소프트웨어 "IceView" 105 4.1 개요 105 4.2 IceView를 이용한 빙하중 산정 109 4.2.1 전체 빙하중 산정식 109 4.2.2 국부 빙압력 산정식 115 4.2.3 IceView를 이용한 빙하중 산정 예 120 Ⅴ. 빙해역 항행 모델 122 5.1 북극해 항로 항행 모델링 122 5.2 Ice Transit Model 123 5.2.1 빙해역 항행 시뮬레이션 127 5.2.2 ArcGIS를 이용한 최적 운항항로 구현 138 Ⅵ. 결 론 143 참 고 문 헌 14

넓은 입력 전력 범위를 갖는 에너지 하베스팅 시스템에 관한 연구

학위논문(박사)--서울대학교 대학원 :공과대학 전기·컴퓨터공학부,2019. 8. 김재하.Energy harvesting integrated circuit is a power converter that transfers the energy generated from ambient energy sources, such as a photovoltaic cell or a thermoelectric generator, to charge the battery of a mobile system, including Internet-of-Things (IoT) sensor nodes. As the power level of the microprocessors decrease, the energy harvester that operates in a nanowatt input and output power scale has been studied. However, the resulting low-power energy harvesters have limited its operation speed, that it cannot properly handle the generated power when the input power level rises. To enhance the input power range so that a single energy harvesting system can be applicable to battery-powered mobile systems with different input power condition, this paper presents a design methodology for designing a boost converter energy harvesting system, which operates in discontinuous conduction mode (DCM). The methodology suggests that the input voltage monitor should be properly designed, so that the performance and the power consumption of the monitor is adapted to the current input power condition. Specifically, the power consumption of the input voltage monitor should maintain the power consumption below the conduction loss and the static loss of the harvester, while maximizing its operating frequency. As an example of such input voltage monitor, the frequency-sweeping oscillator is proposed, which consists of a clocked comparator and an oscillator of which frequency is set to the maximum and exponentially dropped for each clock for each energy conversion. Using the frequency-sweeping input voltage monitor, a prototype energy harvesting IC is designed and fabricated in 250nm CMOS technology, which shows the maximum input power range of 10 nW to 60 mW with the peak efficiency of 97%, achieving the dynamic range of 6 × 106. The proposed design methodology is also applicable for the voltage regulators using DCM inductive converter topology with a wide the dynamic range.에너지 하베스팅 집적회로는 광전 소자와 같은 에너지 수집 소자로부터 에너지를 수집하여 배터리를 충전하는 회로로, 사물인터넷 (IoT; Internet-of-Things) 센서와 같은 어플리케이션에 적합하며, 특히 입력 전력과 센서 노드가 소모하는 전력이 모두 작은 경우에 적합하게 이용될 수 있다. 하지만 작은 입력 전력을 활용할 수 있는 에너지 하베스팅 집적회로를 설하게 되면 전력이 크게 들어올 때 빠르게 반응하지 못하여, 최대 입력 번위가 줄어들게 되어 범용적으로 사용하기가 힘들어지는 문제가 발생한다. 본 논문은 이러한 배경에서, 특히 입력 범위를 최대화하는 에너지 하베스팅 집적회로의 설계 방법론을 제안한다. 제안하는 방법은 에너지 하베스터에서 입력 전압을 모니터링하는 회로에서 소모하는 전력량을 입력 전력에 비례하여 적절하게 변경하되, 에너지를 전달할 때 마다 소모되는 전력, 그리고 입력과 관계 없이 지속적으로 소모되는 전력보다 작은 값으로 디자인하는 방법으로, 이를 통해 에너지 하베스터에서 최대의 입력 전력 범위를 얻을 수 있게 됨을 보인다. 이러한 성질을 가지는 입력 전압 모니터의 하나로 주파수 변경 방식 입력 전력 모니터 회로를 제시하였으며, 이는 매 에너지 전달 마다 최대 주파수로 동작시키고 이후 지수함수적으로 주파수를 줄이는 방법으로 동작한다. 제시한 주파수 변경 방식 입력 전압 모니터 회로를 활용하여 에너지 하베스터 프로토타입을 250 나노 CMOS 공정으로 제작하였으며, 10 nW 부터 60 mW 까지의 입력 전력을 받아서 배터리에 저장할 수 있음을 보였으며, 최고 97%의 에너지 수집 효율을 보였다. 본 논문에서 제시하는 설계 방법론은 에너지 하베스터 뿐만 아니라 불연속 전류 모드에서 동작하는 인덕터를 활용하는 전압 레귤레이터 디자인 등에서도 사용될 수 있다.CHAPTER 1. INTRODUCTION 1 1.1. MOTIVATION . 1 1.2. THESIS CONTRIBUTION AND ORGANIZATION 4 CHAPTER 2. DESIGN PRINCIPLES OF DISCONTINUOUS CONDUCTION MODE INDUCTIVE ENERGY HARVESTERS 6 2.1. BACKGROUNDS 6 2.1.1. ENERGY HARVESTING BATTERY CHARGER . 6 2.1.2. COMPARISON OF POWER STAGE TOPOLOGIES . 9 2.2. OPERATION PRINCIPLE OF A BOOST CONVERTER-BASED ENERGY HARVESTER 11 2.3. DEFINITION OF INPUT POWER RANGE . 12 2.4. AVERAGE POWER LOSS ANALYSIS 13 2.4.1. CALCULATION OF THE CONVERSION LOSS . 15 2.5. REQUIREMENT ON OPERATING FREQUENCY OF THE INPUT VOLTAGE MONITOR 21 2.6. DESIGN GUIDELINE FOR A BOOST CONVERTER-BASED ENERGY HARVESTER 25 2.6.1. VISUALIZATION OF THE INPUT POWER RANGE 25 2.6.2. PROPOSED DESIGN GUIDELINE . 29 2.6.3. MAXIMUM INPUT POWER LIMIT OF THE BOOST CONVERTER IN DCM 31 CHAPTER 3. DESIGN OF A FREQUENCY-SWEEPING INPUT VOLTAGE MONITOR 33 3.1. PREVIOUS DESIGN FOR THE INPUT VOLTAGE MONITOR . 33 3.2. PROPOSED FREQUENCY-SWEEPING INPUT VOLTAGE MONITOR . 37 3.3. ANALYSIS OF THE PROPOSED FREQUENCY-SWEEPING INPUT VOLTAGE MONITORS 39 3.3.1. POWER CONSUMPTION . 40 3.3.2. VOLTAGE RIPPLE 42 3.3.3. INPUT TRANSIENT RESPONSE TIME 44 CHAPTER 4. CIRCUIT IMPLEMENTATIONS 45 4.1. TOP ARCHITECTURE 45 4.2. DESIGN FLOW 51 4.3. POWER STAGE SWITCHES 52 4.4. PULSE GENERATORS 54 4.4.1. PULSE WIDTH OPTIMIZATION . 55 4.4.2. ON-PULSE GENERATOR 57 4.4.3. ZERO-CURRENT-SWITCHING PULSE GENERATOR 61 4.5. ALWAYS-ON CIRCUITS 63 4.6. FREQUENCY-SWEEPING INPUT VOLTAGE MONITOR . 64 4.6.1. CIRCUIT IMPLEMENTATION 64 4.7. PARAMETER OPTIMIZATION 69 CHAPTER 5. MEASUREMENT RESULTS 72 5.1. MEASUREMENT SETUPS 72 5.2. ON-TIME AND ZERO-CURRENT-SWITCHING MEASUREMENTS . 73 5.3. CLOCK FREQUENCY . 75 5.4. TRANSIENT ANALYSIS . 76 5.5. STEADY-STATE VOLTAGE RIPPLE . 79 5.6. EFFICIENCY OF THE SYSTEM . 82 CHAPTER 6. CONCLUSION 89 BIBLIOGRAPHY 91 초 록 94Docto

네마틱 액정을 이용한 이진 위상 회절 격자에 관한 연구

학위논문(석사)--서울대학교 대학원 :전기·컴퓨터공학부,2003.Maste

Dielectric Breakdown of Cu Interconnect under Cycling Eelctric Field and Temperature

As integrated circuits scale down in size, their interconnects are placed under harsher conditions such as high electric fields, high current density, and high temperature. These conditions can cause a significant reliability issue in a Cu interconnect. Cu is well-known to migrate into the dielectric. This migration is accelerated under a high electric field and high temperature. A time-dependent dielectric breakdown (TDDB) is one of the most significant reliability issues in a Cu interconnect. A conventional TDDB test is conducted under a constant electric field and temperature. However, under real operating conditions, both the polarity of the electric field and the temperature is alternated. Therefore, this thesis concentrates on a time-dependent dielectric breakdown in a Cu interconnect under alternating polarity bias and after thermal cycle stress. First, the bias polarity effect of a Cu-migration-induced failure was revealed using a simple metal-insulator-semiconductor (MIS) structure. A Cu migrating system (Cu/SiO2) and non-migrating system (Al/SiO2) were compared. In the Cu/SiO2, the leakage current increased and decreased as the polarity of the applied electric field alternated during forward and reverse pre-BTS (bias temperature stress), whereas the current in the Al/SiO2 did not change. The leakage current increase in the Cu/SiO2 was due to the increase in the number of PF traps from the Cu migration under forward bias. The leakage current decrease under reverse bias was due to a recovery from backward migration, which was revealed through a voltage ramp test. The polarity effect of Cu migration was confirmed. The dielectric contamination due to Cu migration can be recovered through the polarity effect. Next, this study considered the real device operational conditions of a real device. The mechanism of Cu-ion migration was investigated in damascene Cu/SiO2 interconnects. The lifetime was investigated as the most useful factor for estimating reliability. The polarity effect differed from the MIS structure, because a damascene structure has both sides of a Cu electrode. Cu ions were injected at opposite sides of the electrode while reverse bias was applied. Backward migration and recovery cannot achive the during remove the application of reverse bias. Backward Cu-ion migration was investigated using TDDB tests under an alternating polarity. When alternating-polarity bias stress was applied, the Cu-ion migration could not be completely recovered because the diffusional and drift fluxes were in opposite directions. Therefore, the TDDB lifetime increases under the alternating-polarity bias stress than under DC. Longer TTFs were obtained with an increase in frequency. Finally, the stress effect was considered. In this chapter, a time-dependent dielectric breakdown after a thermal cycle is investigated. Although the samples suffered thermal stress, the TDDB reliability was enhanced. An increase in lifetime and decrease in leakage current were observed in both wafer-level and package-level TDDB tests. There are two possible explanations for this reliability enhancement, the annihilation of reactant residue in the inter-metal-dielectric (IMD), and thermo-mechanical considerations. The reliability enhancement mechanism originates from the thermo-mechanical effect rather than the annihilation of reactant residue. This was confirmed through an application of heat. Because the TC condition used in this study is a tensile-to-tensile stress cycle, the Cu interconnect tends to shrink. Therefore, the Cu interconnect pull down the capping layer, which enhances the interface between this layer and the IMD. It is expected that low temperature aging can enhance the TDDB reliabilityDocto

금융통합, 무역과 성장

학위논문 (석사)-- 서울대학교 대학원 : 경제학부 경제학전공, 2015. 8. 김소영.This study adds to vast literature on financial integration and its impact on growth by suggesting that trade level should be more carefully considered to assess the effect of reduction of capital restriction. The study argues that the impact of financial openness on growth varies among countries with different level of trade openness. Some previous studies using rule-based index of capital restriction argue that financial liberalization promotes growth, but this argument does not hold for countries with low trade openness. However, the degree of impact of financial liberalization on growth monotonically increases as countries level of trade openness increases. For low-level countries, insufficient commercial opening not preceded by financial market liberalization are exposed to greater external risk when capital restriction is reduced. Hence, capital restriction is indeed important to mitigate current account reversals. Countries with highly integrated trade sector are positively affected by opening financial sector possibly as they are relatively safe to sudden-stop and current account reversal risk. Sufficient degree of commercial opening seems to be a prerequisite for countries to reap benefit from financial liberalization. Thus one should be cautious that there is no one-size-fits-all policy of financial liberalization.Contents 1. Introduction 1 2. Literature Review 2 3. Empirical Model and Data 8 4. Robustness Check 12 5. Conclusion 14 Appendix 15 References 16 국문초록 18Maste

Selective Catalytic Reduction of Nitrogen oxides by Hydrocarbon over dealuminated zeolitecatalysts

Maste

쇄빙패턴과 빙-선체 접촉조건을 고려한 빙저항 추정기법 연구

A ship’s resistance in level ice is a fairly significant concern from a design point of view, and thus many types of related research are underway, including studies of ice and hull interaction, icebreaking patterns, and pressure-area effects. Meanwhile, various semi-empirical or analytical methods and numerical models are being developed to predict a ship’s resistance in ice. This study investigates ice-hull interaction phenomena and develops a numerical model that can determine ice resistance based on icebreaking patterns and ice-hull contact conditions. The characteristics of icebreaking patterns for the hull form, ship speed, and ice properties are analyzed, and two ice-hull contact cases are considered: one for triangular and one for quadrilateral crushing during the ice-hull interaction. In addition, normal crushing displacement is calculated based on the relationship between indentation energy and kinetic energy. To calculate normal contact force, the pressure-area effect is applied and parameters used in the pressure-area equation are selected based on the full-scale ice load measurement results of the Korean icebreaker Araon, which operated in the Beaufort Sea in 2010. To determine the failure criteria of ice, an ice sheet is assumed to be a semi-infinite plate on an elastic foundation. The maximum load at which the ice fails is then determined. In the numerical model, a numerical integration method is used to analyze the ship’s motions and the ice resistance characteristics. The predicted results from this model are compared with the model test results, showing relatively good correlation regarding the prediction of ship resistance in level ice. The presented method should be useful for future studies of ship performance in ice and ice resistance prediction at the design stage of a vessel. In addition, the developed numerical model can contribute to the Korea Research Institute of Ships and Ocean Engineering (KRISO) ice tank, by helping to predict the preliminary ice resistance of vessels, given various ice conditions and hull forms.평탄빙에서 선박의 저항은 설계 관점에서 매우 중요한 관심 사항이다. 따라서 빙-선체 상호작용과 쇄빙패턴, 압력-면적 효과를 포함하는 다양한 연구들이 수행되고 있으며, 선박에 작용하는 빙저항을 추정하기 위해 다양한 준 경험적 또는 해석적 방법들과 수치모델들이 개발되고 있다. 본 연구에서는 빙-선체 상호작용 현상에 관한 연구와 함께 쇄빙패턴과 빙-선체 접촉조건을 고려한 빙저항 추정용 수치모델을 개발하였다. 선형과 선속, 빙특성을 고려한 쇄빙패턴 특성이 분석되었고 빙-선체 충돌 시 삼각형 충돌과 다각형 충돌 같은 두 가지 빙-선체 접촉조건이 고려되었다. 또한 충돌에 따른 수직 관입변위는 관입에너지와 운동에너지와의 관계를 통해 계산되었다. 수직한 방향의 접촉력을 계산하기 위해 압력-면적 효과가 적용되었고 압력-면적 효과식에 사용되는 변수들은 2010년 북극 보퍼트해에서 쇄빙연구선 아라온호의 실선 빙하중 계측자료를 바탕으로 도출되었다. 빙판의 파괴기준을 정의하기 위해 빙판은 탄성기초 위 반무한평판으로 고려되었고 빙판의 파괴를 위한 최대하중이 정의되었다. 또한 수치모델에서는 선박의 운동과 빙저항 특성을 해석하기 위해 수치적분법이 적용되었다. 특히 개발된 모델을 통해 추정된 빙저항 결과는 모형시험 결과와 비교 시 비교적 우수한 상관성을 나타내었다. 본 연구에서 도출된 기법은 선박의 설계단계에서 선박의 빙성능과 빙저항 추정을 위한 연구에 활용이 가능하며, 개발된 수치모델은 선박해양플랜트연구소 빙해수조에서 다양한 빙상환경에 따른 선형을 고려한 선박의 초기 빙저항 추정 연구에 기여할 수 있을 것으로 판단된다.1. Introduction 1 1.1 Objectives 1 1.2 Approaches and Methodology 4 1.3 Organization of Thesis 5 2. Reviews on Ice Resistance Prediction 6 2.1 Empirical and Analytical Approaches 6 2.2 Numerical Approaches 9 3. Development of Ice Resistance Prediction Model 14 3.1 Ship Resistance in Ice 14 3.1.1 Icebreaking Pattern in Level Ice 18 3.1.2 Definition of Ice and Hull Contact Conditions 32 3.2 Calculation of Ship Resistance in Ice 40 3.2.1 Contact Force and Pressure-Area Effect 40 3.2.2 Failure Criterion of Ice 46 3.2.3 Resistance Components in Ice 49 3.3 Motion Analysis by Numerical Integration 53 4. Comparison of Ice Resistance between Predictions 58 4.1. Experimental Test in Ice Tank 58 4.1.1 Overview of Test Facility 58 4.1.2 Preparation of Model Ice and Material Properties Measurement 61 4.1.3 Description of Model Ships and Test Conditions 70 4.1.4 Analysis Procedures of Model Tests 74 4.1.4.1 Correction of Deviations in Ice Thickness and Strength 77 4.1.4.2 Correction of Scale Effect 78 4.2. Discussions 79 4.2.1 Analysis of Icebreaking Patterns 80 4.2.2 Effect of Number of Ice Cusps 84 4.2.3 Open-water and Ice Resistance Characteristics 87 4.2.4 Comparison of Ice Resistance between Predictions and Test Results 106 5. Conclusions and Recommendations 115 5.1. Conclusions 115 5.2. Recommendations 118 References Appendix A. Photographs of Icebreaking Patterns for Icebreaking Model Ships Appendix B. Difference between KRISO Method and HSVA Method in Correctio