• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.843-851
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• 2009

Much work has already been done to control and regulate the worldwide problems caused by climate change, particularly the issues on greenhouse gas (GHG) emissions. Carbon dioxide ($CO_2$), having the highest form of concentration among GHGs composed around 1.0 billion tons of emission, and comprises about 98% of the total emissions from the shipping industry. Korean trade mainly rely on the sea transportation. Korean ship tonnages that was brought about by shipbuilders all over the country, continues to grow annually due to the prevailing demands on goods or material supplies and depicting only a small part of the global maritime activity. Nowadays, new build ships coming from the Korean Shipbuilders are being optimized by hull, structure and appendages design, The operational capability of the propulsion and auxiliary machineries in its maximum capacity to achieve the highest possible efficiencies for energy and onboard power use to mitigate $CO_2$ emissions are continually being done through the help of research and development. In this paper, the energy efficiency design index and anboard power capacity of Korean new build ships have been analyzed with response to data collected by ship types, and its respective fuel consumption in relation to $CO_2$ emission results. In response to climate change convention outcome proposals, the best way for the new build ships to become energy efficient is by lowering its operational speed thru adopting the state of the art diesel propulsion engines, patronizing the best sailing practice to lower the transportation cost on the different sea trade routes also helps in $CO_2$ mitigation.

• 한국수소및신에너지학회논문집
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• 제27권3호
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• pp.283-289
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• 2016

In this study, electrochemical characterizations of PdCu/C catalysts that are synthesized by modified polyol method are investigated. Most of all, amount of ethylene glycol (EG) that is used as main component for catalyst synthesis is mainly modulated to optimize synthetic condition of the PdCu/C catalyst, For evaluations about catalytic activity and performance of direct formic acid fuel cell (DFAFC), half cell and full cell tests are implemented. As a result, when amount of EG is 4M, catalytic activities of the PdCu/C catalyst such as peak current of formic acid oxidation and active surface area are best, while maximum power density of DFAFC using the optimized PdCu/C catalyst is better than that using commercial Pd/C (30 wt%) by 6%. Based on that, PdCu/C catalyst synthesized by modified polyol method plays a critical role in improving (i) catalytic activity for formic acid oxidation and (ii) DFAFC performance by employing as anodic catalyst.

• 한국연소학회지
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• 제20권2호
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• pp.40-45
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• 2015

This study is aimed to study combustion characteristics of low $NO_X$ burner using petroleum cokes as fuel. The petroleum coke, which is produced through the oil refining process, is an attractive fuel in terms of its high heating value and relatively low price. But petroleum coke is a challenging fuel because of its low volatile content, high sulfur and nitrogen content, which give rise to undesirable emission characteristics and low ignitability. The petroleum cokes burner is operated at fuel rich condition, and overfire air are supplied to achieve fuel lean condition. The low $NO_X$ burner is designed to control fuel and air mixing to achieve air staged combustion, in addition secondary and tertiary air are supplied through swirler. Air distribution ratio of triple staged air are optimized experimentally. The result showed that $NO_X$ concentration is lowest when overfire air is used, and the burner function at a fuel rich condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.209-218
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• 2009

In a wireless sensor network(WSN) each sensor node deals with numerous sensing data elements. For the sake of energy efficiency and network lifetime, sensing data must be handled effectively. A technique used for this is data aggregation. Sending/receiving data involves numerous steps such as MAC layer control packet handshakes and route path setup, and these steps consume energy. Because these steps are involved in all data communication, the total cost increases are related to the counts of data sent/received. Therefore, many studies have proposed sending combined data, which is known as data aggregation. Very effective methods to aggregate sensing data have been suggested, but there is no means of deciding how long the sensor node should wait for aggregation. This is a very important issue, because the wait time affects the total communication cost and data reliability. There are two types of data aggregation; the data counting method and the time waiting method. However, each has weaknesses in terms of the delay. A hybrid method can be adopted to alleviate these problems. But, it cannot provide an optimal point of aggregation. In this paper, we suggest a stochastic-based data aggregation scheme, which provides the cost(in terms of communication and delay) optimal aggregation point. We present numerical analysis and results.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.22-30
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• 2011

In recently, inductor and transformer is the common device using widely in the photovoltaic system and power electronics. Therefore, each inductor and transformer has different core loss and iron loss depending on the size and kinds of core materials, it is important to analyze loss characteristics for better transformer efficiency. This paper offers an efficiency calculation method for PCS inductor and transformer loss, and different kinds of core materials are analyzed for optimized PCS design.

• 전력전자학회논문지
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• 제18권4호
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• pp.349-358
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• 2013

In this paper, the sensorless MPPT algorithm is proposed where the performance of varied duty ratio change has been improved using multi-layer neuro-fuzzy that aligns with neuro-fuzzy based optimized membership function. Since the change of duty ratio of sensorless MPPT is varied by using the neuro-fuzzy, the MPPT response speed is faster than the convectional method and is able to reduce the steady-state ripple. The neuro fuzzy controller has the response characteristics which is superior to the existing fuzzy controller, because of the usage of the optimal width of the fuzzy membership function. The effectiveness of the proposed method has been verified by simulations and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.92-94
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• 1988

One of the recurring problems facing energy control center dispatchers each day is how to operate the system during the periods of high load pick up and fluctuation. This method reduces the problem to a forward - revised by backward - sequence of dispatch problem, with the generator Limits being carefully adjusted between each time interval in the total intervals to be optimized. It is applied to system of 31 units. It is observed that the method presented here achieves that generation fellows the load changes without any mismatch.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1170-1178
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• 2007

Repeated hardware tests and tuning, investing cost and time, are usually required to assure a satisfactory performance of the suspension seat. In this study, an EILS(ECU-in-the-loop) method was proposed to develop a controller for a semi-active suspension seat with a MR(magneto-rheological) damper. EILS system was developed using a real-time seat dynamics model communicating with ECU hardwares under a closed loop environment utilizing Matlab/Simulink and xPC $TargetBox^{TM}$. A sky-hook based control algorithm with optimized damping coefficients was verified to reduce the energy consumption and to improve the vibration response performance.

• 한국세라믹학회지
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• 제52권2호
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• pp.92-102
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• 2015

Current plans for legacy nuclear wastes stored in underground tanks at the U.S. Department of Energy's Hanford Site in Washington are that they will be separated into high-level waste and low-activity waste fractions that will be vitrified separately. Formulating optimized glass compositions that maximize the waste loading in glass is critical for successful and economical treatment and immobilization of these nuclear wastes. Glass property-composition models have been developed and applied to formulate glass compositions for various objectives for the past several decades. Property models with associated uncertainties combined with composition and property constraints have been used to develop preliminary glass formulation algorithms designed for vitrification process control and waste-form qualification at the planned waste vitrification plant. This paper provides an overview of the current status of glass property-composition models, constraints applicable to Hanford waste vitrification, and glass formulation approaches that have been developed for vitrification of hazardous and highly radioactive wastes stored at the Hanford Site.

• 대한임베디드공학회논문지
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• 제16권3호
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• pp.113-117
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• 2021

The data gathering delay and the network lifetime are important indicators to measure the service quality of wireless sensor and actuator networks (WSANs). This study proposes a dynamically cluster head (CH) selection strategy and automatic scheduling scheme of collectors for prolonging the network lifetime and shorting data gathering delay in WSAN. First the monitoring region is equally divided into several subregions and each subregion dynamically selects a sensor node as CH. These can balance the energy consumption of sensor node thereby prolonging the network lifetime. Then a task allocation method based on genetic algorithm is proposed to uniformly assign tasks to actuators. Finally the trajectory of each actuator is optimized by ant colony optimization algorithm. Simulations are conducted to evaluate the effectiveness of the proposed method and the results show that the method performs better to extend network lifetime while also reducing data delay.