• 전기학회논문지
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• 제60권4호
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• pp.717-725
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• 2011

In the power system with an electric storage system that can increase utilization rate of the source of such new renewable energy, this paper introduces the approach on the daily unit commitment scheduling that determines simultaneously optimum operational condition and output of thermal generators and electric storage device. The unit commitment is one of the most important issues in economic operation and security of short-term operational plan of the power system. It is to determine on/off status of generator to minimize operational cost during the given period. The committed generator should satisfy various operational limitation such as estimated demand by system, spinning reserve condition within minimum operational cost. In order to determine on/off or charge/discharge/idle condition and output level of units and electric storage system, the MILP(Mixed Integer Linear Programming) is suggested. The proposed approach is the mixed method between LP(Linear Programming) and IP(integer programming) which seeks the value of real number and integer that maximize or minimize function objective within given condition. The daily unit commitment problem with the electric storage system is applied to MILP algorithm through linearization and formulation process. The proposed approach is applied to the test system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권8호
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• pp.2399-2416
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• 2024

The current automotive industry is transitioning from Internal Combustion Engine (ICE) vehicles to Electric Vehicles (EVs), adopting a mixed assembly production approach to respond to fluctuating demand. While mixed assembly production offers the advantages of lower investment costs and flexibility in responding to changing demands, the supply of EV components requires more extensive provisioning compared to ICE vehicle components, potentially leading to unexpected issues such as congestion of transport vehicles. This study proposes a digital twin system architecture that uses Discrete Event Simulation (DES) and Business Intelligence (BI) tools to specifically address logistics challenges. The proposed architecture facilitates real-time, data-driven decision making across three layers; Data source, Simulation, and BI. It was implemented in factories engaged in the mixed assembly production of ICE and EV vehicles. The simulation challenges involve a tier 1 vendor supplying parts to Korean automobile manufacturers that produce both ICE and EV parts. A total of 240 scenarios were created to run the simulations. The deployment of the proposed architecture demonstrates its capability to quickly respond to diverse experimental situations and promptly identify potential issues.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권3호
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• pp.171-177
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• 2002

The metabolic flux pattern for L-histidine production was analyzed when glucose and/or acetate were used as carbon sources. Total L-histidine production was enhanced when mixed substrate (glucose and acetate) was used, compared wish that when either glucose or acetate was used as the sole carbon source. Theoretical maximum carbon fluxes through the main pathways for L-histldine production, cell growth, and ATP consumption for cell maintenance were obtained by the linear programming (LP) method. By comparison of the theoretical maximum carbon fluxes tilth actual ones, it was found that a large amount of glucose was actually used for maintenance of cell viability. On the other hand, acetate was used for cell growth. After depletion of acetate in the mixed substrate culture, the flux for glucose to L-histldine synthesis was markedly enhanced. A strategy for effective L-histidine production using both carbon sources was proposed.

• 전기전자학회논문지
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• 제13권1호
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• pp.71-76
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• 2009

As one of the most important requirements for wireless sensor networks, prolonging network lifetime can be realized by minimizing energy consumption in cluster heads as well as sensor nodes. While most of the previous researches have focused on the energy of sensor nodes, we devote our attention to cluster heads because they are most dominant source of power consumption in the cluster-based sensor networks. Therefore, we seek to minimize energy consumption by minimizing the maximum(MINMAX) energy dissipation at each cluster heads. This work requires energy-efficient clustering of the sensor nodes while satisfying given energy constraints. In this paper, we present a constraint satisfaction modeling of cluster-based routing in a heterogeneous sensor networks because mixed integer programming cannot provide solutions to this MINMAX problem. Computational experiments show that substantial energy savings can be obtained with the MINMAX algorithm in comparison with a minimum total energy(MTE) strategy.

• 에너지공학
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• 제9권2호
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• pp.83-88
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• 2000

In this study, the performance and pollutant emission of CNG engine using diesel oil as a source of ignition, so called CNG dual fuel diesel engine is considered by experiment. One of the unsolved problems of the natural gas dual fuel engine is that there is too much exhaust of total hydrocarbon (THC) at a low equivalent mixture ratio. To fix it, a natural gas mixed with hydrogen was applied to engine test. The results showed that the higher the mixture ratio of hydrogen to natural gas, the higher the combustion efficiency. and when the amount of the intake air is reached to 90% of WOT, the combustion efficiency was promoted. But, like a case making the injection timing earlier, the equivalent mixture ratio for the knocking limit decrease and the produce of NOx increases.

• Journal of Advanced Marine Engineering and Technology
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• 제37권7호
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• pp.729-736
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• 2013

The turbulent properties in a mixed statistically stationary flow were investigated experimentally by a pseudo stereoscopic PIV. In order to validate the experimental results, the profiles of the turbulent kinetic energy were evaluated with the flow features. A mechanical agitator having 6 blades was installed at the bottom of the mixing tank (D=60cm, H=60cm). The agitator was rotated with 80rpm clockwise and counter-clockwise. For the measurements, three cameras were used and all were synchronized. The images captured by one of the three cameras was used for the measurement of rotational speed, and the images captured by the other two cameras were used to measure three dimensional components of velocity vectors. All vectors captured at the same rotational angle were phase averaged to construct three-dimensional vector fields to reconstruct the spatial distribution of the flow properties. It was seen that the jet scrolling along the tank was the main source of mixing.

• 한국환경보건학회지
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• 제27권4호
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• pp.79-83
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• 2001

The sludge wastes fermentation process reactors were operated to produce the VFAs(volatile fatty acids) as supplemental carbon sources and to determine the optimum operating conditions. The experiment was carried out by varied mixture ration of 400:0 350:30 300:100 200:200 and operating temperature 2$0^{\circ}C$ 3$0^{\circ}C$ and 4$0^{\circ}C$ The results were as follows: Higher VFAs production rate observed at higher mixed ratio of primary sludge. When the mixed ratio of primary sludge and return sludge were 400:0 350:50 300:100 200:200 respectively. VFAs production are were 829.6mg/l 944.2 mg/l 597.9mg/ml an d441.6 mg/l , respectively. the yield of VFAs increased with temperature, but decreased with initial TSS concentration Because fermented sludge has relatively low nitrogen and phosphorus and relatively high VFAs it can be used as a substitute for external carbon in biological nutrient removal process.

• 전기학회논문지
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• 제57권5호
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• pp.881-888
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• 2008

We present a novel fault diagnosis methodology using acoustic sensor systems and neural independent component analysis for large-scaled power machines. Acoustic sensors are carried out to measure sounds generated from power machines whose signal is used to determine whether fault is occurred or not. Acoustic measurements are independently mixed and deteriorated from original source signals. We propose a demixing algorithm against such mixed signals by means of independent component analysis which is achieved based on information theory and higher-order statistics to derive learning mechanism.

• 한국컴퓨터산업학회논문지
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• 제5권2호
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• pp.269-274
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• 2004

기존 음성 인식의 실세계 적용에서 큰 문제점은 잡음이다. 본 논문에서는 잡음이 섞인 음성 신호로부터 잡음 성분을 분리해 내는 방법을 제안한다. 이 방법은 잡음이 섞인 음성 신호에 독립성분분석(ICA:Independent Component Analysis)을 사용한 암묵신호 분리(blind source separation)를 적용하여 잡음 성분을 제거하게 된다. 잡음이 혼합된 음성 신호에 독립성분분석을 전처리(preprocessing) 과정에 이용함으로써 인식성능을 향상시킬 수 있다. 깨끗한 음성 신호에 음악과 거리잡음을 섞었을 경우 인식률이 잡음 없는 음성의 인식률보다 각각 최대 14.98%, 13.78%까지 저하되었다. 그러나 독립성분분석으로 복원된 음성의 경우 잡음 없는 음성의 인식률 수준(각각 97.39%, 96.49%)으로 나타났으며, 독립성분분석을 이용한 음성의 잡음 제거가 인식률 향상에 좋은 결과를 가져옴을 확인 할 수 있다.

• Journal of Magnetics
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• 제21권1호
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• pp.153-158
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• 2016

This paper aims to discuss the Non Darcy boundary layer flow of non-conducting viscous fluid with magnetic ferroparticles over a permeable linearly stretching surface with ohmic dissipation and mixed convective heat transfer. A magnetic dipole is applied "a" distance below the surface of stretching sheet. The governing equations are modeled. Similarity transformation is used to convert the system of partial differential equations to a system of non-linear but ordinary differential equations. The ODEs are solved numerically. The effects of sundry parameters on the flow properties like velocity, pressure, skin-friction coefficient and Nusselt number are presented. It is deduced the frictional resistance of Lorentz force decreases with stronger electric field and the trend reverses for temperature. Skin friction coefficient increase with increase in ferromagnetic interaction parameter. Whereas, Nusselt number decrease.