Cost-Based Directed Scheduling : Part Ⅱ, An Inter-Job Cost Propagation Algorithm

Min Soo Suh(서민수),Jae Kyeong Kim(김재경) 한국지능정보시스템학회 2008 지능정보연구 Vol.14 No.1

The cost-based scheduling work has been done in both the Operations Research (OR) and Artificial Intelligence (AI) literature. To deal with more realistic problems, AI-based heuristic scheduling approach with non-regular performance measures has been studied. However, there has been little research effort to develop a full inter-job cost propagation algorithm (CPA) for different jobs having multiple downstream and upstream activities. Without such a CPA, decision-making in scheduling heuristics relies upon local, incomplete cost information, resulting in poor schedule performance from the overall cost minimizing objective. For such a purpose, we need two types of CPAs : intra-job CPA and inter-job CPA. Whenever there is a change in cost information of an activity in a job in the process of scheduling, the intra-job CPA updates cost curves of other activities connected through temporal constraints within the same job. The inter-job CPA extends cost propagation into other jobs connected through precedence relationships. By utilizing the cost information provided by CPAs, we propose cost-based scheduling heuristics that attempt to minimize the total schedule cost. This paper develops inter-job CPAs that create and update cost curves of each activity in each search state, and propagate cost information throughout a whole network of temporal constraints. Also we propose various cost-based scheduling heuristics that attempt to minimize the total schedule cost by utilizing the cost propagation algorithm.

알칼리금속이온 열-전기 변환 신뢰성 평가

서민수(Min-Soo SUH),박세국(Se-Kook PARK),김기주(Kee Joo Kim) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.7

SIC섬유강화 복합재료의 트라이볼로지컬 연구경향과 전망

서민수(Min-Soo Suh) 한국트라이볼로지학회 2011 한국트라이볼로지학회 학술대회 Vol.2011 No.4

알칼리금속 열전기변환장치의 장기운전실험

서민수(Min-Soo Suh),이욱현(Wook Hyun Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.4

Carbon Neutral Vessel Propulsion Technology for Implementing Net-zero Reliability

Min-Soo Suh(서민수),Kee Joo Kim(김기주) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

Inception of cutting surlphur oxide emission, the new limit was made compulsory following an amendment to Annex VI of the international convention for the prevention of pollution from ships. The International Maritime Organization (IMO), a significant reduction from the previous limit of 3.5% known as IMO 2020, the rule limits the sulphur in the fuel oil used on board ships operating outside designated emission control areas to 0.50% m/m (mass by mass). Within specific designated emission control areas the limits were already stricter (0.10%). Sulphur oxide (SOx) emissions from ships, the resulting reduction, is having major environmental benefits for the world, particularly for health of populations living close to ports and coasts. SOX can lead to acid rain, once released in the atmosphere, which impacts crops, forests and aquatic species and contributes to the acidification of the oceans. It is also harmful to human health, causing respiratory, cardiovascular and lung disease. Alkali-metal based energy transforming technology, the working principle is ionization of element and vibration of phonons, is clean and high efficiency with zero emission. According to SERI report, AMTEC is known as the highest efficiency among most of other thermally regenerative electrochemical cells (TRES). Electrochemical cells are core component where the dominant reaction occurred in and working substance are produced for fuel cell, battery, galvanic cell, electromotive force cell and thermocell. Under the principle of electrochemistry, thermal-to-electric is the dominant process in the sense of an energy conversion and the electrical-to-chemical is dominant in the sense of an energy storage. AMTEC is a thermodynamically closed system that converts thermal energy into electric energy. It is an electrochemical heat engine that is Carnot cycle limited in efficiency, and a great part of output involve in electricity. Transforming energy in TRES involves energy transport, energy conversion and energy storage. This study is to report the effort to develop ecofriendly vessel propulsion as dual fuel direct conversion (DFDC) utilizing AMTEC technology for vessel propulsion in order to contribute net-zero carbon-neutrality.

R&D Insight of Convergence Technology Aiming for Carbon-Neutrality

Min-Soo SUH(서민수),Kotaro TANAKA(田中耕太朗) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.06

Electrical Power and Material Characterization under High Grade Temperature for Na-AMTEC(Natrium Alkali-Metal Thermal-to-Electric Convertor)

Min-Soo SUH(서민수),Dae Hun CHUNG(정대헌) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.06

Carbon-Neutral Energy Transforming Platform for Heat-to-Power Network

Min-Soo SUH(서민수) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

Transforming of energy, in general, is essential for most of advance energy system. Energy transform is one way to transform a source of energy into required form of energy. Three major categories can be derived from the energy transformation: energy conversion, energy transportation and energy storage. Energy conversion of Na-AMTEC can be classified as a thermal energy input into an electrical energy and thermal energy output. Alkali-metal based carbon-neutral energy transforming platform utilize alkali-metal for energy transportation as heat transfer fluid (HTF) due to the high thermal conductivity of 60 W/m·K. Energy conversion of solar-to-thermal, atomic-to-thermal, and thermal-to-electric. Energy storage utilize phase change material to enlarge the amount of stored heat, Q. Especially for the energy conversion, the Na-AMTEC directly convert thermal energy into electrical energy. The principle of Na-AMTEC is electrochemical heat engine as known as thermo-cell. This study is to report efforts of reliability evaluation of heat-to-power energy transforming platform to connect between heat network and electricity network on-demand. (refer to the formula in the text)

Electrical Resistance Evaluation Reliability under High Grade Temperature for Na-AMTEC(Natrium Alkali-Metal Thermal-to-Electric Convertor)

Min-Soo SUH(서민수) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

In general, an electrical circuit, electrical resistance is a measure of the opposition to current flow. Resistance is a measured in ohms, symbolized by the Greek letter omega(Ω). In practical, specialized on Na-AMTEC(Natrium Alkali-Metal Thermal-to-Electric Convertor), the input energy is directly converted to electrical energy. In microscopic view, the energy transforming of one source to another useful forms classified as storage, transportation and conversion is simultaneous taken place in one small circuit. In macroscopic view, thermal energy directly converted into electrical energy, in other words it is energy transforming primarily solar-to-thermal and thermal-to-electric. In case of metallic substances, free electrons are moving randomly in the crystal structure of it. Due mainly to the electric field across the resistance, free electrons drift from lower potential point to higher potential when voltage is applied. Free electron continually collides with atoms of the substance during drifting motion, this phenomenon prevents the free motion of electrons. The resistance is known to be caused by the collision of free electron with atoms of the substance. Physicist George Simon Ohm suggest the law ohm that electric resistance is equal to voltage per ampere on pure metal. Hence, resistance is defined as the ratio of the applied voltage to the current through the substance. Most of metallic substance with rising temperatures the inter atomic vibrations increase and consequently offer more resistance to the movement of electrons causing the current. Thus, with increasing temperature the resistance of metallic substances increases. Refractory metals are a class of metals that are extraordinarily resistant to heat. The well-known Na-AMTEC is working between 800 K to 1300 K. Most of materials does not meet the criteria of aforementioned working condition in sense of thermo-condition except the five elements two of fifth period (niobium and molybdenum) and three of the sixth period (tantalum, tungsten and rhenium). They all share some properties, including a melting point above 2,200 K and high hardness at room temperature, except ductile transition character of niobium. Pure niobium has a Mohs hardness rating similar to that of pure titanium. Hence, the selection of candidate materials for Na-AMTEC as electrical electrode, current collector and lead is narrowed down to the minimum requirement of temperature resistance and electrical conductivity. In case of electrical resistance of Na-AMTEC is derived as following that the total resistance, R_T of Na-AMTEC is sum of the following resistances R_B (Resistance of Beta-Alumina Solid Electrolyte, BASE) + R_S (sheet resistance) + R_C (contact resistance) + R_L (lead resistance). Mostly, the sum of the rest of resistances is larger than the resistance of BASE. ● Correlation of Voltage, Ampere and Resistance: V ∝ I , V = RI , R= V/I ● Total electrical resistance of Na-AMTEC: R_T = R_B + R_S + R_C + R_L, R_B < R_S + R_C + R_L ● Correlation of resistances of Na-AMTEC: R_T ∝ 2 R_B Nonetheless, there is a reliability issue when measuring the electrical resistance which is intricate compared to the concept of electrical conductivity measurement on room temperature by virtue of the continuous temperature deviation during the Na-AMTEC cell test under elevated temperature. This study is to report the effort to develop the methodology of measurement reliability of the electrical resistance under high temperature state.

구조용 세라믹의 Tribo-Fatigue 마멸 특성

서민수(Suh Min-soo),신동우(Shin Dong-woo),김석삼(Kim Seock-Sam) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

Currently, the study on structural ceramics helps to suggest the precise data related to friction and wear in accordance with the various operational conditions. Also, the study predicts effective operating conditions by monitoring the occurrence of wear transition. However, the past studies were mainly concentrated on ball on disk, pin-on disk, four ball types. In view of serious operation conditions, experimental data related to real operation condition is necessary. In this study, tribo-fatigue tester was designed and manufactured for evaluation of wear characteristics of structural ceramics, Al₂O₃, Si₃N₄, SiC. It was found from the analysis of worn surface by using the EPMA that the oxidative film on the worn surface of Alumina contributes to wear volume. When oxidative film is formed on the worn surface that wear volume is decreased but oxidative film is disjoined on the worn surface that wear volume is increased. Because wear mechanism changes oxidative wear to adhesive wear. The main factor of wear caused by the amount of oxidation on the worn surface was observed.