(The) Leae-Lag Relationship between Futures and Spot Return of KTB

This study is firstly to examine the lead-lag relationship between spot and futures prices of Korea Treasury Bond (KTB) by using daily return data from 29 September 1998 to 18 August 2000. Five kinds of futures are listed on Korea Futures Exchange (KOFEX) since the launching of April 1999. KTB futures grew as an important futures since the listing on the KOFEX on 28th September 1999 and now the trade volume of KTB futures is the largest among the listed futures. Bank, investment trust, insurance companies and foreigners are major investors of KTB futures. KTB's main financial function is to provide risk management system for mid-term interest rate instrument and to discover its price in the future as well. In particular, this thesis focuses on the function of price discovery of futures over the expected spot price. The price of KTB futures reflects the future interest level which financial institutions or company experts could predict. Therefore, KTB futures could be seen as predicting a proper price for spot goods and plays a role of discovering the future value of KTB. There is time difference between spot and futures prices of KTB. We utilize unit root test, cointegration test, vector error correction models in order to examine the relationship between spot and futures returns. The main finding of this thesis is that the futures price of KTB leads the spot price of KTB. That is, the futures price leads two days prior to the expected spot price. Moreover, two market's lead-lag relationship could be influenced by the trading volume of KTB futures. Then, an empirical analysis of futures prices of June and September 2000 exhibits that the spot price leads the futures price. Therefore, it is argued that there is a feedback relationship between spot and futures of KTB and the infrequent trading has an impact on the relationship between spot and futures prices. Even though the relationship between spot and futures prices are not stable, our finding indicates that the discovery function of futures over the expected spot price is working in the Korea Futures Exchange. Then, the period of our study is too short to investigate in depth of the lead-lag relationship between spot and futures prices. Because of this limitation, we could not examine the difference of two markets's microstructure such as price volatility, trade pattern and so on. Therefore, it is thought that we could not find correct reasons about the lead-lag relationship of two markets. With the passage of KOFEX history, the trading volume and the efficiency of information will be increased with by the growth of participants of this market and then we could explore more on the lead-lag relationship between spot and futures prices of KTB.Ⅰ. 서론 = 1 1. 연구 동기 및 목적 = 1 2. 연구의 방법 및 구？？ = 2 Ⅱ. 국채선물제도의 이해 및 기존 연구에 대한 고찰 = 3 1. 선물거래의 이해 = 3 1) 선물거래의 개념 = 3 2) 선물거래의 경제적 기능 = 3 2. 주요국 거래소의 국채선물의 개요 = 4 3. 호주 국채선물의 상품 개요 = 4 4. 우리 나라의 국채선물 = 6 1) 국채선물의 개요 = 6 2) 가격결정방법 = 6 3) 국채이론가격 = 8 5. 기존 연구에 대한 고찰 = 9 Ⅲ. 연구 모형 및 연구방법 = 11 1. 연구모형 = 11 1) 단위근 검정 = 11 2) Johansen 공적분 검정 = 11 3) 오차수정모형추정 = 11 2. 단위근검정 = 11 3. 공적분의 검정 = 15 4. 오차수정모형 = 17 Ⅳ. 실증분석 = 19 1. 표본자료 = 19 2. 기초통계량 = 20 3. 현물과 선물 수익률의 자기상관관계 = 21 4. 수익률의 선도 지연-관계 분석 = 21 1) 시계열의 정상성에 대한 단위근 검정 = 21 2) 공적분 검정을 통한 장기 균형관계 분석 = 25 3) 오차수정모형의 추정 결과 = 25 Ⅴ. 결론 = 28 참고문헌 = 2

A Study on the Characterization of Carbon Nanotubes by Terahertz Spectroscopy

We have measured the absorption and dispersion of single- walled carbon nanotubes (SWCNTs) films using an optoelectronic THz beam system for THz time-domain spectroscopy (THz- TDS). The angle-dependent conductivities of anisotropically aligned nanotube films, which were prepared by a mechanical squeezing with a bar coater, were also characterized. Samples were prepared raw SWCNT and purified SWCNT, respectively. As the frequency increases, the power absorption coefficient of SWCNT increases. Also, the power absorption shows maximum at parallel orientation of the film to the THz beam polarization and minimum at perpendicular orientation, which was explained by a 'wire grid' model indicating that SWCNTs were aligned. The refractive indices decrease with increasing frequency. This trend is similar to that yielded by lightly doped semiconductors. The real conductivities increase with increasing frequency in the low frequency ranges. This is not congruent with the simple Drude theory.목차 Abstract 제1장 서론 = 1 1.1 연구 목적 및 배경 = 1 1.2 연구 내용 및 방법 = 3 제2장 테라헤르츠 시간영역 분광법 시스템 = 4 2.1 테라헤르츠 시스템 구성 = 4 2.2 송신부 및 수신부 = 8 2.3 설치 및 조정 = 11 2.4 데이터 수집 = 14 2.5 교류전압을 이용한 테라헤르츠 이진신호 = 16 제3장 측정 = 21 3.1 수분에 의한 테라헤르츠 전자기 펄스 = 21 3.2 Thin 필름 측정 = 22 제4장 탄소 나노튜브 = 25 4.1 탄소 나노튜브 = 25 4.2 탄소 나노튜브의 성장 및 배열 = 27 4.3 탄소 나노튜브의 측정 결과 = 30 제5장 결론 = 42 참고 문헌 = 4

A Study on Design and Implementation of Wideband High Power Amplifier for Digital TV Repeater

In this dissertation, a high power amplifier has been implemented and performed evaluation, which is operating at UHF band (470 ~ 806 MHz) for Digital TV repeater. The theoretical consideration of 100 Watt power amplifier at UHF band used in Digital TV repeater is studied. After extracting target specification of each part, amplifier is designed and fabricated. When the driving amplifier stage is flown by bias voltage of 28 V DC and current of 900 mA, it has the gain of more than 53.5 dB, the gain flatness of ±0.5 dB and return loss of less than -12 dB in 470 ~ 806 MHz. Also, when two signals at 2 MHz frequency interval are input port into the driving amplifier stage with 1 Watt output, it resulted in excellent characteristics to design specification with showing intermodulation distortion characteristics of more than 48 dBc. The middle amplifier stage using 85 Watt device is fabricated by RO-4003 electric substrate which is 3.38 in dielectric constant and 32 mil-thickness. When the driving amplifier stage and the middle amplifier stage were flown by bias voltage of 28 V DC and current of 4 A, they revealed the gain of more than 66 dB, the gain flatness of ±0.2 dB and return loss of less than -16 dB. Also, when two signals at 2 MHz frequency interval in using frequency band is input port into the driving amplifier stage with 40 dBm of output power, it showed intermodulation distortion characteristics of more than 38.50 dBc. The 100 Watt unit power amplifier using temperature independent biasing for Digital TV repeater application is designed and fabricated. The DC operation point of this unit power amplifier at temperature variation from 20 ℃ to 100 ℃ is fixed by active bias circuit. The variation of current consumption in the 100 Watt unit power amplifier has an excellent characteristics of less than 0.6 A. The implemented unit power amplifier has the gain over 12 dB, the gain flatness of less than ±0.5 dB and return loss of less than 15 dB over the DTV repeater frequency range. This unit power amplifier yields intermodulation distortion of more than 32 dBc at 2 MHz offset, which satisfies the IMD at output power of 100 Watt (50 dBm). The broadband high power 3-way combiner was designed and fabricated for the digital TV repeater. To achieve increase of bandwidth and high power capability, Wilkinson type power divider was adopted in our research. First of all, Wilkinson type power divider of equal-split and unequal-split were combined, the characteristics variation of the same phase four port power combiner was simulated according to the various thicknesses of dielectric substrates. As the results of simulation, the power combiner fabricated by using dielectric substrate of 120 mil-thickness has the characteristics as follows: insertion loss of less than -6 dB, return loss of less than -13 dB, isolation among the output ports of less than -15 dB, and phase difference among the output ports of smaller than 13°. Therefore, this power combiner was possible to improve the limit of microstrip line width due to high impedance, the problems of power loss due to interaction between strip lines in high power combiner and narrow bandwidth simultaneously. Furthermore, since the fabricated 3-way combiner has good characteristics of insertion loss, the return loss, separation between ports and phase difference, making broadband and high power could be achieved. By using 3-way power divider and power combiner, 100 Watt unit power amplifier stage was designed and fabricated as a type of 3-stage balanced amplifier and to detect the final signal output power with using of 40 dB parallel coupled-line directional coupler. The fabricated 40 dB parallel couled-line directional coupler detects the signal power emitting to the antenna, and then supplies its voltage to the attenuator. In addition, this sets to be changed with a basic attenuation 8 dB, according to the changing of the power amplifier's temperature and 8-VSB modulator's input signal. Besides, in order to measure the fabricated 100 Watt power amplifier, the estimation technique function which makes equivalent mask by Tektronix RFA-300A was used. As a result of the measurement, the existence of pilot signal is confirmed and the signal transmitted at the rated output power 100 Watt is brought out the flat feature through 6 MHz bandwidth. And it resulted that its value was less than -47 dB at the edge of radiation channel and less than -110 dB at more than 6 MHz position from channel edge. Finally a positive results on the equivalent mask has been complied with related regulations.목차 Abbreviations Abstract 제1장 서론 = 12 1.1 연구 배경 = 12 1.2 연구 목적 = 14 제2장 디지털 TV 방송 시스템 = 16 2.1 통신 시스템의 형태 = 16 2.2 DTV 시스템 설계 파라미터 = 17 2.3 지상파 DTV 중계기 시스템 = 25 2.4 지상파 DTV HPA 서브 시스템 = 27 제3장 전력증폭기의 설계 및 구현 = 31 3.1 구동증폭단의 설계 및 구현 = 31 3.2 중간증폭단의 설계 및 구현 = 50 3.3 100 Watt 단위 전력증폭기의 설계 및 구현 = 62 3.4 결과 분석 = 75 제4장 100 Watt 전력증폭기의 구성 및 평가 = 77 4.1 3-Way 동위상 고출력 전력결합기 = 77 4.2 전력검출기 및 감쇠기 = 97 4.3 100 Watt 전력증폭기의 구성 및 특성 평가 = 103 4.4 결과 분석 = 115 제5장 결론 = 116 참고문헌 = 11

Design of High Power Balanced Amplifier Using Branch Line Coupler in Reduced Type

The hybrid coupler plays an important role in microwave circuits such as balanced mixers, image-rejection mixers, and balanced amplifier. Among them, the balanced amplifier is used for the mismatched power amplifier. However, the balanced amplifier may still be mismatched at both path of two equal amplifier because the power TR has low input-output impedance. Besides of it the standard balanced amplifier configuration has the disadvantage requiring a large space owing to the coupler's size. The method of applying arbitrary lumped-distributed impedance transforming couplers to balanced amplifiers significantly reduces the size of over the conventional balanced amplifier with 50 Ω input/output couplers. then, the size of arbitrary lumped-distributed impedance transforming couplers tend to be restricted by the characteristic impedance. In order to solve the above problem, in this thesis, design graphs were drawn for the reduced size coupler, which was terminated by arbitrary impedances and shorted coupled-line pair. The coupler size was 90 percent smaller than the conventional coupler. A balanced amplifier was designed using the coupler with shorted coupled-line pair and lumped capacitor. The measured gain is 6 ± 0.2 dB, the input and output VSWR are lower than 1.40.목차 Abstract = i Nomenclature = ii 제1장 서론 = 1 제2장 브랜치 라인 결합기의 설계 이론 = 3 2.1 임피던스 변환 결합기 = 3 2.2 소형 임피던스 변환 결합기 = 8 2.3 각 포트에서 임의의 종단 임피던스를 갖는 결합기 = 15 2.4 결합 선로를 이용한 초소형 λ/4 전송선로 = 19 제3장 전력 증폭기의 설계 = 25 3.1 전력 이득 = 24 3.2 안정성(Stability) = 29 3.3 고주파 전력 증폭소자의 특성 = 30 3.4 고주파 전력 증폭소자의 선택 = 32 3.5 평형증폭기 = 34 제4장 평형증폭기의 제작 및 측정 = 36 4.1 실험에 사용된 전력 증폭기의 특성 = 36 4.2 제작 및 실험 = 37 제5장 결론 = 41 참고문

A Study on Constructive Total Loss on Ship

1) The value of the wreck must not be added. 2) No deduction is to be allowed in respect of general average contributions to the vessel's repairs payable by other parties (e.g. G/A contribution of cargo to the refloating damage of the vessel or a probable recovery from the other vessel in case of a collision) 3) The ship's proportion of future salvage and general average should be added. The 'future', I think, should be construed as after the casualty, no the notice of abandonment, which is normally applied in practice. However, it is required to amend ITC-Hulls Clauses or International Hull Clauses to clarify to cover the cost after the casualty. 4) No deduction is to be made of one-third new for old. 5) Cost of several distinct casualties may not be aggregated. Only cost relating to a single accident or sequence of damages arising from the same accident shall be taken into account. Finally, considering clause 21 of International Hull Clauses which the figure to be taken into account in assessing whether the vessel is a CTL is now 80% of the insured value rather than 100%, I suppose that the using a compromised total loss settlement shall be made, in practice, in place of carrying out uneconomical repairs, not being a CTL. However, there is no provision in the MIA, nor in the policy for this type of settlement and controversy could rise. Therefore, the insured value of vessel shall be closed to the cost of market value and it is a necessary to appoint a fair and reasonable average adjuster to settle such a controversial claim as soon as possible.1) where an actual total loss appears to be unavoidable 2) where the assured is deprived of the ship and is unlikely to recover it 3) where the estimated cost of recovering/repairing the ship would exceed the value of the ship when repaired. Most CTL cases fall within category 3) above. As to how the value of the ship when repaired is to be arrived at, the MIA givers little guidance. However, for a long time it has been customary for hull underwriters to take the insured value as the repaired value in ascertaining whether the ship is a CTL, which is evidenced by clause 19 of ITC-Hulls(1/10/83) and 21 of International Hull Clauses. 3. The estimated cost of repair should cover all expenses which would have been necessary had the vessel been repaired, including salvage charge, temporary repairs, class survey fee & etc. In calculating the probable cost of recovering/repairing the vessel which has to be compared with the insured value, the followings should be taken into account1. Under the MIA, a total loss of the a ship may be either an actual total loss or a constructive total loss. In practice, there is another form of total loss named compromised total loss. But it is actually partial loss because it is used in the circumstance of not being a total loss and it pays less than the sum-insured. 2. Under section 60 of MIA, a constructive total loss of a ship may be claimed in any of the circumstances belowand on the notice and acceptance of abandonment for a long time. Total loss caused by the insured peril is basically covered by a hull policy which has minimum coverage such as TLO(Total Loss Only). In marine insurance, a loss amy be either total loss or partial loss but total loss casualties of ships continue to cover steadily in spite of the developments in shipbuilding technology, navigation equipment and communication method in recent years. The Institute Time Clauses-Hulls, which are mostly used in hull insurance all over the world, were amended in 1970 and 1983 so several controversial points on total losses are clarified. However, there remain some points to be clarified. In recently, The Joint Hull Committee's(JHC) ambitious project to product a new set of hull insurance clauses which accurately reflect the needs and requirements of today's shipowners and insurers has been completed on time. The new clauses, which have been drafted following extensive consultation with shiponwer and other interested parties, will be available for use form 1st November, 2002 and wll be known as the International Hull Clauses. The purpose of this thesis is to examine closely rule of interpretation when a ship damaged on the sea consider as constructive total loss according to M.I.A. and concrete specially the extent of indemnity when policy included the content that insurer shall recover total loss addition to the costs. The findings of this study are briefly summarized as followsThere has been much controversy between the insurer and the assured in ascertaining whether there is a total loss or not목차 第1章 序論 = 1 第1節 硏究의 目的 = 1 第2節 硏究方法 및 範圍 = 3 第2章 船舶推定全損의 意義 = 5 第1節 船舶推定全損의 槪念 = 5 第2節 船舶推定全損 關聯 條項 = 7 I. 英國海上保險法(1906)上 推定全損條項 = 7 II. 船舶保險約款上의 推定全損條項 = 8 1. 協會期間船舶保險約款(1/10/83) = 8 2. 國際船舶保險約款(1/11/02) = 9 第3節 다른 槪念과의 差異 = 9 I. 現實全損과의 差異 = 9 II. 分損과의 差異 = 12 III. 妥協全損과의 差異 = 13 第3章 船舶推定全損의 要件 = 16 第1節 保險目的物의 物理的 修繕不能 = 16 I. 現實全損이 不可避한 것으로 보일 때 = 16 II. 船舶의 占有를 喪失하여 回復의 可能性이 없는 경우 = 18 1. 現實的으로 占有를 喪失할 것 = 18 2. '相當한 期間'의 意味 = 22 3. 現實全損에서의 '回復할 수 없는'과의 差異 = 25 第2節 保險目的物의 經濟的 修繕不能 = 25 I. 經濟的 修繕不能의 意味 = 25 II. 修繕後 船舶의 價額 = 26 1. 未評價保險(unvalued policy)의 境遇 = 26 2. 旣評價保險(valued policy)의 境遇 = 29 3. 修繕後 船舶의 價額과 協定保險價額 = 30 III. 船舶의 修繕費用 = 33 1. 修繕費의 意味 = 33 2. 修繕의 程度 = 34 3. 修繕費의 決定場所와 時期 = 35 4. 具體的인 修繕費의 內容 = 37 5. 愼重한 無保險船主 理論과 例外 = 39 第4章 船舶推定全損과 保險委付 = 47 第1節 保險委付의 意義 = 47 第2節 保險委付의 法的性質 = 48 第3節 保險委付의 成立要件 = 50 I. 委付通知의 時期 = 51 II. 委付通知方法 및 無條件的인 委付通知 = 51 III. 委付通知의 承認 = 52 IV. 委付通知가 必要없는 境遇 = 53 第4節 有效한 保險委付의 效果 = 54 I. 被保險者의 保險金請求權 = 55 II. 保險目的物上의 權利移轉 = 55 III. 運賃請求權 = 59 第5節 船舶推定全損과 保險委付의 關係 = 60 第5章 船舶推定全損 成立의 諸問題 = 63 第1節 "連續損害"(Successive Partial Losses) = 64 I. 問題의 提起 = 64 II. 約款의 改正 = 65 1. 多數說의 立場 = 65 2. 判例의 立場 = 66 3. 船舶保險約款의 改正 = 67 第2節 "將來"의 救助費 = 68 I. 問題의 提起 = 68 II. "將來"의 解釋對立 = 69 1. 保險者의 立場 - "委付通知 以後" = 69 2. 被保險者의 立場 - "事故發生 以後" = 70 III. 美國의 경우 = 72 IV. "將來"의 意味는 "事故日子 以後" = 74 V. "將來의 救助費"의 保險補償 = 75 1. 損害防止費用으로 補償의 原則 = 76 2. 救助失敗時 損害防止費用의 補償基準 = 80 3. 推定全損과 損害防止費用과의 關係 = 83 第6章 結論 = 85 參考文獻 = 88 ABSTRACT = 8

(A) Study on the Optimization of Berth Planning Problem

A Study on the Optimization of Berth Planning Problem This paper treats the berth planning problem which is encountered at public container terminals. The main issue of the berth planning problem is to decide how to allocate the berths to scheduled calling containers of which the ETA's are given beforehand. The author, at first, made a literature survey concerning the subject and summarized it to make clear the scope of the problem. Then, the optimization models for tackling the berth planning problem are proposed in the formulation of set problems. Some heuristic algorithms for generating the decision variables of the models are also devised by using the concept of the ship's waiting time and the modified berth occupancy rate. Computational experiments based on the data arisings from the real public container terminal(BCTOC) are also carried out and the results are reported to show that the proposed optimization models and the heuristic for generating the decision variables are applicable and useful for the berth planning problem at public container terminals

(A) Study on Sea Water Freezing Behavior in a Flow Field with Bubbly Flow

One of the most essential things to maintain our lives is water. Water consumption is rapidly increasing due to the exclusive overpopulation, industrial development and improvement of people's living standards. However, only 1% of water source is available for human being, so the ever-increasing scarcity of water is getting serious as time goes by. Korea also will be no exception of this tendency and many researches have often proven how urgent Korea is water deficiency problem. In order to reduce this problem, we try to make the most water through building multi-functional dams, rainmaking and developing desalination system. Among those, desalination system is expected to be the most effective method because of its availability of seawater. It'll enable us to get water steady and readily. When we select particular kind of desalination system devices, that decision is mostly influenced by fresh water produce cost. In order words, its efficiency depends on whether we can achieve possible energy source easily or not. As environmentally friendly means, many people are encouraged to use LNG (Liquefied Natural Gas) in Korea and many countries of the world. Amount of LNG consumption is currently heading higher. In general, LNG which is stored below -162℃ in super-liquid tank requires certain energy to gasify because it changed into the gaseous state with high pressure wasted cold energy when it is sent to each part in need. LNG loses lots of cold energy (850kJ/kg) during this process of absorbing heat. To take advantage of this wasted cold energy, we are developing the systems such as producing the frozen food processing, dry ice, liquefied hydrogen, liquefied nitrogen and seawater freezing desalination. Therefore we'll mainly focus on the development of a seawater freezing desalination system and design technique using wasted cold energy necessary to freezing behavior of seawater. This study is intended to achieve qualitative and quantitative fundamental data with respect to it. The device mainly consists of test section(transparent acryl rectangular duct), a brine loopvisualizing the flow in freezing part, etc. After considering mean concentration of seawater measuring water and refined salt with digital balance and salinity meter, the operating fluid can function as 3.5wt% NaCl aqueous solution. We operate brine loop using ethylene glycol 40% aqueous solution within the temperature of -21.12℃(eutectic point of seawater). Visualizing section using nylon12 tracer measures PIV with Argon-ion laser. After injecting -0.5℃ air into the test-section accompanied by flow field, investigated the flow appearance in around cooled parts by using the PIV system. The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled part temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. And the flow patterns around cooled parts were visualized using the PIV to analyze the relationship between the flow structure and the freezing characteristics. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layermaintaining the temperature of cooled parts, PIV(Particle Image Velocimetry) systemAbstract = ⅲ 사용기호 = ⅵ 제 1 장 서론 = 1 1.1 연구의 배경 = 1 1.2 종래의 연구 = 11 제 2 장 실험방법 및 실험범위 = 15 2.1 실험방법 및 실험범위 = 15 2.2 PIV = 20 2.3 해수의 동결거동 = 22 제 3 장 냉각원관에서의 해수동결 = 24 3.1 실험장치 = 24 3.2 냉각원관의 열전달해석 = 28 3.3 냉각원관 주위의 해수동결거동 = 33 3.4 유속의 영향 = 38 3.5 공기 분사량의 영향 = 48 3.6 냉각면 온도의 영향 = 58 3.7 동결량의 무차원정리 = 68 3.8 결론 = 70 제 4 장 수？邰嗔？ 냉각평판에서의 해수동결 = 71 4.1 실험장치 = 71 4.2 수직평행 냉각평판의 열전달해석 = 75 4.3 수직평행 냉각평판 주위의 해수동결거동 = 79 4.4 유속의 영향 = 83 4.5 공기 분사량의 영향 = 93 4.6 냉각면 온도의 영향 = 103 4.7 동결량의 무차원정리 = 113 4.8 결론 = 115 제 5 장 총결론 = 116 참고문헌 = 118 맺음말 = 12

(A) Study on Dynamic and Static Recrystallization Behaviors and Microstructure Evolution Prediction of Die Steels

Evaluation of microstructural changes during open die forging of heavy ingots is important for process control. The objective of the control of forging parameters, such as shape of the dies, reduction, temperature and sequence of passes, is to maximize the forging effects and to minimize inhomogeneities of mechanical properties. A numerical analysis was performed to predict flow curves and dynamic and static recrystallization behaviors of die steel(0.36%C, 1.1%Mn and 1.21%Cr) from hot compression test results. The hot compression tests were carried out in the ranges of temperature 950∼1150℃ and strain rate 0.01∼1.0sec-1. The modeling equation for flow curves was a function of strain, strain rate and temperature. Models for predicting the evolution of microstructure in die steel during thermomechanical processing was developed in terms of dynamic, static recrystallization and grain growth phenomena. The microstructure model was combined with rigid visco-plastic finite element modeling to predict microstructure development. Predicted microstructure is consistent with results obtained in multiple compression tests. For the grain growth evolution, hot compression test carried out the temperature of 950 and 1150℃, and the strain rate of 0.01 and 1.0sec-1. The specimens were compressed 10%, 20% and 30% in height, unloaded and held for holding times at isothermal condition resulting in static and metadynamic recrystallization in specimens. The softening occurred during the holding time between the first and the second compression was calculated from the experimental result. Predicted grain size and load are consistent with experiment results from double compression test with constant velocity. Thereforce, the usefulness of the program is verified.Abstract = ⅰ 기호설명 = ⅲ List of Table and Photographs = ⅳ List of Figures = ⅵ 1. 서론 = 1 1.1 연구 배경 = 1 1.2 연구 동향 = 2 1.3 연구 목적 = 3 2. 이론적 배경 = 4 2.1 열간 가공시 재료의 미세 조직 변화 = 4 2.1.1 동적 재결정 = 4 2.1.2 정적 및 준동적 재결정 = 6 2.1.3 입자 성장 = 7 2.2 강소성 유한요소법 = 8 3. 실험과 시뮬레이션 = 12 3.1 기초 실험 = 12 3.1.1 동적 재결정 실험 = 12 3.1.2 입자 성장 실험 = 13 3.1.3 정적 및 준동적 연화 실험 = 14 3.2 등속 압축 실험 = 15 3.3 시뮬레이션 = 15 4. 결과 및 고찰 = 18 4.1 유동 곡선 모델링 = 18 4.1.1 구성식 정량화 = 18 4.1.2 유동 응력 곡선 모델링 = 23 4.1.3 재결정 및 입자 성장 모델링 = 27 4.2 기초 실험 결과 및 고찰 = 29 4.2.1 동적 재결정 실험 고찰 = 29 4.2.2 입자 성장 실험 고찰 = 36 4.2.3 정적 및 준동적 연화 실험 고찰 = 41 4.3 시뮬레이션 결과 및 고찰 = 55 5. 결론 = 66 참고문헌 = 6

Combustion Characteristics and Durability of Diesel Engine Utilizing Emulsified Fuel

This study is carried out to investigate the combustion characteristics and durability of a diesel engine utilizing emulsified fuel. Recently, air pollution from the vehicle is one of the most serious problem . NOx, PM and sfc reduction is further required in diesel engines. In this study, for the reduction of harmful emissions, W/O(water in oil) type emulsified fuels with 13%, 15%, 17% water are used. Piezo-electric pressure sensor is used to get combustion pressure in cylinder and exhaust gas analyzer is used to measure exhaust emissions. Specific fuel consumption, sound level, and maximum torque are also measured. It was ascertained that the results show the 15% water emulsified fuel is good for NOx and PM reduction simultaneously and does not have much effect on a fuel consumption and a durability.목차 List of Tables = iii List of figures = iv ABSTRACT = viii I. 序論 1.1 연구배경 = 1 1.2 선행연구 = 2 1.3 연구목표 = 5 II. 理論的 考察 2.1 에멀션연료(Emulsified fuel) = 6 2.1.1 에멀션연료의 연소특성 = 8 2.1.2 에멀션연료의 미세폭발(Micro-explosion) = 10 2.1.3 해외 에멀션연료 개발현황 = 10 III. 實驗裝置 및 方法 3.1 D-13 모드 기관내구실험 및 배기가스 측정 = 12 3.1.1 실험장치 = 12 3.1.2 실험방법 = 16 3.2 연소실 압력측정 = 18 3.2.1 실험장치 = 18 3.2.2 실험방법 = 20 3.3 노즐 연료 분사량 = 20 3.3.1 실험장치 = 20 3.3.2 실험방법 = 23 3.4 에멀션연료의 제조 = 23 IV. 實驗結果 및 考察 4.1 D-13 모드 기관내구실험 = 26 4.2 D-13 모드 기관 배기가스 = 37 4.3 연소압력 측정 = 46 4.4 연료노즐 연료분사량 측정 및 기관소음측정 = 62 V. 結論 = 64 參考文獻 = 6

Performance Improvement of a Fuzzy PID Controller and Its Application to the Position Control of Nonlinear Hydraulic Cylinders

In order to derive a new fuzzy controller, a fixed design-parameter fuzzy PID controller was surveyed in view of deriving a control law based on the design procedure of general fuzzy logic controllers. The controller is known to be very useful to control unknown nonlinear systems because it has nonlinear time-varying PID controller gains. While it has advantages that the resultant form of the controller is an analytical mathematical form and fuzzy rules are so simple, it also has a disadvantage that the PID control action is not applied at all or cannot be accurately applied when operating inputs are greater than or smaller than the reference input used to decide design-parameters in initial controller design procedure. In this paper, in order to improve the disadvantage of the fixed design-parameter fuzzy PID controller, a new fuzzy PID controller named a variable design-parameter fuzzy PID controller was suggested. The main characteristic of the controller is to adjust design-parameters of the controller by comparing magnitudes between fuzzy controller inputs at each sampling time when controller inputs are measured. As a result, all fuzzy input partitions converge within a time-varying normalization parameter and the resultant PID control action can always be applied precisely regardless of operating input magnitudes. In order to verify the effectiveness of the suggested controller, several computer simulations were executed for example mathematical systems such as a linear system and a nonlinear system. And another simulations were executed for a hydraulic position control system which is one of the typical nonlinear systems in the real field. The output of the suggested control system was compared with the outputs of linear PID and the fixed design-parameter fuzzy PID control system for several reference inputs. In the conclusion, the variable design-parameter fuzzy PID controller was assured to be a very effective and useful method to control unknown nonlinear systems from the simulation results.목차 Abstract 제 1 장 서론 = 1 제 2 장 고정 설계파라미터 비선형 퍼지 PID 제어기 = 3 2..1 개요 = 3 2.2 고정 설계파라미터 비선형 퍼지 PID 제어기의 구성 = 4 2.2.1 제어기의 기본구조 = 4 2.2.2 퍼지화 알고리즘 = 6 2.2.3 피지 제어규칙 = 8 2.2.4 비퍼지화 알고리즘 = 11 2.2.5 제어기의 특징 및 설계절차 = 14 제 3 장 가변 설계파라미터 비선형 퍼지 PID 제어기의 제안 = 18 3.1 고정 설계파라미터 퍼지 PID 제어기의 단점 = 19 3.1.1 작동범위에 따른 퍼지 PID 제어동작의 효능저하 = 19 3.1.2 설계시 퍼지 P, I, D 제어동작 사이의 불균형성 = 19 3.1.3 고정 설계파라미터 비선형 퍼지 PID 제어기의 성능개선 방법 = 20 3.2 가변 설계파라미터 비선형 퍼지 PID 제어기 = 22 3.2.1 작동범위에 무관한 퍼지 PID 제어동작의 적용성 입증 = 22 3.2.2 가변 설계파라미터 비선형 퍼지 PID 제어기의 구조 및 설계절차 = 24 제 4 장 컴퓨터 시뮬레이션 및 결과 고찰 = 29 4.1 선형 시스템에 대한 적용 = 29 4.2 비선형 시스템에 대한 적용 = 34 제 5 장 비선형 유압시스템의 위치제어 문제에 적용 = 40 5.1 개요 = 40 5.2 유압시스템의 구성 = 41 5.3 유압시스템의 비선형 수학모델 = 43 5.3.1 전자비례제어밸브 = 44 5.3.2 편로드 실린더 = 44 5.3.3 부하구동부 = 52 5.3.4 밸브-실린더-부하시스템의 동적 방정식 = 53 5.4 시뮬레이션 및 결과 고찰 = 55 제 6 장 결론 = 62 참고 문