• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.2
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• pp.69-76
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• 1998

This paper presents a novel algorithm for determining the optimal operation of a cogeneration plant with back-pressure and extraction-condensing turbine/generators. The proposed algorithm determines the optimum load of boilers and turbine/generators, using only one parameter, the steam mass flow rate, which can be obtained directly from on-line measurement during plant operation. The proposed algorithm consists of the non -linear operating cost function, and its correlated constraints. Furthermore, it has been successfully applied to an actual industrial cogeneration plant, with satisfactory results. Comparison of these results with actual operating data has revealed that using the proposed algorithm results in at least 1.2~4.5[%] operating cost saving, depending on the process steam load. Furthermore the proposed algorithm can be easily installed in a process control computer because the required input data can be easily obtained from information available on-line.n-line.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.55-63
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• 2004

빛이 입사각별로 태양투과율이 제어되어지는 첨단 창과 같은 물체를 통과할 때 투과되는 성분은 직달투과와 산란투과성분으로 볼 수 있다. 직달투과는 물체를 통과하면서 일정한 방향으로 굴절되어 투과되는 성질을 말하고, 산란투과는 직달투과를 제외한 나머지 방향의 성분들의 형태를 말한다. 이러한 첨단 창의 냉난방부하에 미치는 에너지성능을 평가하기 위해서는 산란투과에 대한 정보가 필요하고, 이에 대한 물리적 변수는 입사각, 출력각, 양방향 투과율 분산함수인 BTDF로 정의된다. 본 논문에서는 3개의 서로 나른 첨단 창 (1) $42^{\circ}/5^{\circ}$ 프리즘 창 판넬, (2) 레이저 컷 판넬 (3) $45^{\circ}$ 프리즘 3M 필름의 BTDF 데이터 획득을 위한 실험 방안을 소개하고, 실험을 통해 획득한 정보를 이용하여 계산식과 비교 검증을 하였다. 따라서 이 검증된 방안을 이용하여 지역별 냉난방 부하를 최소화 할 수 있는 입사각별로 태양 투과율 제어 판넬을 선정할 수 있게 되었다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.11
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• pp.861-869
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• 1989

The optimization problems, based on Pontryagin's Maximum Principle, for minimizing (damping) Xenon spatial oscillations in Load Following operations of Pressurized Water Reactor (PWR) is presented. The optimization model is formulated as an optimal tracking problem with quadratic objective functional. The oen-group diffusion equations and Xe-I dynamic equations are defined as equality constraints. By applying the maximum principle, the original problem is decomposed into a single time problem with no constraints. The resultant subproblems are optimized by using the conjugate Gradient Method. The computational results show that the Xenon spatial oscillation is minimized, and the reactor follows the load demand of the electrical power systems while maintaining the desired power distribution.

• Journal of the military operations research society of Korea
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• v.35 no.2
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• pp.33-49
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• 2009

The objective of this study is as follows. First, the hazard function on the failure probability density function of the K-1 tracked vehicles can be occurred in the form of the bathtub curve. Second, the failure mode may be different under two different operational situations. The research result shows that the bathtub curve can be fitted in the Weibull distribution, that assumes different shapes according to the specific stage of the system's life cycle. The K-1 tracked vehicle has a relatively high hazard(failure) rate at the time of its first service. The failure rate starts decreasing for a time immediately after it goes into service. After the break-in period, the surviving components have a fairly constant hazard rate. As the K-1 system ages, deterioration of its various parts takes place and the hazard rate starts Increasing. Second, the result shows the failure rate in the harsh operational environment is higher than that in the mild operational environment. In conclusion, the bathtub curve can be logically appropriate in establishing the depot overhaul cycle. Moreover, it is necessary for determining the right time of the depot overhaul to consider not only the age of defense equipment but also the different operational environment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.64-72
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• 1999

The fictitious power theory in time domain is very easy to understand, but power analyzing speed of active power is increased, because power is analyzed using signal tedmiques based on the corre1ation between voltage and current wavefonns. Also, conventional methods in time/frequency domain to evaluate the correlation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundarrental reactive component and distorted component of nonlinear loads current. This trethod has excellent perfonnance, but can not evaluate the characteristics of nonlinear load current whether It is inductive or capacitive. Therefore, To overcorre problems trentioned previously, this paper deals with the simple average power theory and the modified 3-D current coordinates for evaluating the compensation perfonnance of active power filters. To confirm the validity, active power filter simulator is developed using C-language. From the simulation, results are discussed their utility.tility.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.59-68
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• 2009

Fuel cell generators as the distributed generation system with a few hundred watt$\sim$a few hundred kilowatt capacity, can supply the high quality electric power to user as compared with conventional large scale power plants. In this paper, PEMFC(polymer electrolyte membrane fuel cell) generator as micro-source is modelled by using PSIM simulation software and DSP based fuel cell hardware simulator based on the PSIM simulation model is implemented. The relation of fuel cell voltage and current(V-I curve) is linearized by first order function on the ohmic area in voltage-current curve of fuel cell. The implemented system is composed of a PEMFC hardware simulator, an isolated full bridge dc boost converter, and a 60[Hz] voltage source PWM inverter. The voltage-current-power(V-I-P) characteristics of the implemented fuel cell hardware simulator are verified in load variation and transient state and the 60[Hz] output voltage sinusoidal waveform of the PWM inverter is investigated under the resistance load and nonlinear diode load.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.584-591
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• 2000

Power Quality Compensator(PQC) has been installed to protect the sensitive loads against the voltage disturbances, such as voltage sag and interruption. In general, static switch is used for the purpose of link between utility and PQC. So transfer operation of the static switch play a important part in the PQC. Many studies on the structure and control of PQC have been progressed in active, but these researches have been rarely mentioned about any voltage-disturbances-detection method to start the PQC operation. In this paper, a new voltage-disturbances-detection algorithm for computer application loads using the CBEMA/ITIC curve is proposed for transfer operation of the static switch. The proposed detection algorithm is implemented to get fast detecting time through the comparison of instantaneous 3-phase voltage values transferred to DC values in the synchronous reference frame with the operating reference values. To get the robust characteristics against the noise, a first order digital filter is designed. The magnitude falling and phase delay caused by the filter are compensated through the error normalizing and numerical analysis using transfer function, respectively. Finally, the validity of the proposed algorithm is proved by ACSL simulation and experimental results.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.6
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• pp.296-305
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• 2005

TCP/IP, the most popular communication protocol, is processed on a host CPU in traditional computer systems and this imposes enormous loads on the host CPU. Recently TCP/IP Offload Engine (TOE) technology, which processes TCP/IP on a network adapter instead of the host CPU, becomes an important way to solve the problem. In this paper we analysed the structure of a TCP/IP protocol stack in the Linux operating system and important factors, which cause a lot of loads on the host CPU, by measuring the time spent on processing each function in the protocol stack. Based on these analyses, we propose a Hybrid TOE architecture, in which functions imposing much loads on the host CPU are implemented using hardware and other functions are implemented using software.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.8
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• pp.445-455
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• 2002

In this paper, we present a new task scheduling scheme ior the efficient execution of the tasks of compound nodes of hierarchical task graph(HTG) on shared memory system. The proposed scheme for exploitation functional parallelism is autoscheduling that performs the role of scheduling by processor itself without any dedicated global scheduler. To adapt the proposed scheduling scheme for various platforms, Including a uni-processor systems, Java threads were used for implementation, and the performance is analyzed in comparison with a conventional bit vector method. The experimental results showed that the proposed method was found to be more efficient in its execution time and exhibited good load-balancing when using the experimental parameter values. Furthermore, the memory size could be reduced when using the proposed algorithm compared with a conventional scheme.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.2
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• pp.9-15
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• 2017

When applying geothermal systems in cities such as seoul where high density development prevails, the selection of geothermal system capable of obtaining a large capacity in the limited grounds is necessary. In this study, an easy-to-use design tool is developed in the form of spreadsheet by applying the calculation theory of existing closed-loop vertical ground heat exchanger that can be used in the early design stage of the open-loop ground heat exchanger. By only using the maximum cooling and heating load, it is possible to calculate optimal design open-loop ground heat exchanger. Further research is needed, we are plan to improve the program considering the heat loss of groundwater flowing in the inner casing, G-Function for Open-Loop, and verification by applying actual projects.