• Journal of the Korean Institute of Gas
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• v.7 no.4 s.21
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• pp.20-23
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• 2003

The analysis of reliabilities of process facilities often uses models based on the Weibull distribution. The parameters in these models are functions of operating conditions, and determined by experiments. Using these values, we calculate the reliability, mean time to failure, and standard deviation. The conventional method assumes that the operating condition is constant, and thus treats the model parameters as constants. In this paper, a reliability function is proposed which is applicable when the scale parameter is a function of time, and an analysis method based on this is also presented. A case study on a cooling fan resulted in a big difference from the conventional method to which the average operating conditions were applied. The proposed method is also applicable to other process facilities, and expected to effectively take into account the effects of changes in the operating conditions on the reliabilities of the facilities.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1336-1342
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• 2022

Risk-informed safety classification of structures, systems and components (SSCs) is very important for ensuring the safety and economic efficiency of nuclear power plants (NPPs). However, previous methods for safety classification of SSCs do not take the plant operating modes or the operational process of SSCs into consideration, thus cannot concentrate on the safety and economic efficiency accurately. In this contribution, a new method for safety classification of SSCs based on the categorization of plant operating modes is proposed, which considers the NPPs operating history to improve the economic efficiencies while maintaining the safety. According to the time duration of plant configurations in plant operating modes, average importances of SSCs are accessed for an NPP considering the operational process, and then safety classification of SSCs is performed for plant operating modes. The correctness and effectiveness of the proposed method is demonstrated by application in an NPP's safety classification of SSCs.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.10
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• pp.1280-1285
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• 1995

In this paper the optimized overlap driving scheme for improving the reduction problem of the operating voltage range occured by the overlap driving scheme proposed precedently and increasing the contrast ratio of screen image in the simple matrix LCDs is proposed. The characteristic estimation of the proposed method was performed in a condition that the number of scan electrodes was 120 and the threshold voltage of LC pixel was 2V and the overlap rate of scan signal was varied from 0% to 40% . As a result of estimation compared with the overlap driving scheme proposed precedently, this new method was certified as a method which it could increase the operating voltage range of the LC pixel by 16% in 20% overlap condition and it's operating voltage range was also increased very much with the increase of the overlap rate. Consequently this newly proposed method was certified as a method which it could maintain the improvement effect of the operating characteristics obtained by the overlap driving scheme proposed precedently with the big improvement in the contrast ratio of screen image.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.1
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• pp.22-31
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• 2008

The operating window method is a novel approach in quality improvement. But it has not received deserved attention in academic research. If a critical factor for competing failure modes can be identified, the probability of failure can be reduced by widening the operating window of this factor. Traditional SN ratio for the operating window advocated by Taguchi has a critical shortcoming, which has been derived under the assumption that failure rates are determined by the operating window factor only. A new metric for robustness is given for the operating window method, which has relaxed the restrictive assumption of Taguchi's SN ratio. And procedures for determining optimal conditions based on the new metric is presented. The effectiveness of the proposed approach over the traditional practice is tested with the aid of a wave soldering process.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.313-319
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• 2002

Since the oil crisis in 1970, a great deal of effort has been made to develop automatic electric load sharing systems as a part of the efforts to save energy. A large scale electric generating system composes more than two generators whose characteristics may be different. When such a system is operated individually or in parallel, the lagrange multiplier's method has difficulty in achieving optimal load distribution because generators usually have the limitations of the operating range with inequality constraints. Therefore, a suitable operating mode of generators has to be decided according to the selection of the generators to meet electric power requirements at the minimum cost. In this study, a method which solves the optimal electric load distribution problem using the dynamic programming technique is proposed. This study also shows that the dynamic programming method has an advantage in dealing with the optimal load distribution problem under the limitations of the operating range with inequality constraints including generator operation mode. In this study, generator operating cost curve of second order equation by shop trial test results of diesel generators are used. The results indicate that the proposed method can be applied to the ship's electric generating system.

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.372-377
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• 2012

In this paper, we propose an implementation of a real-time operating system for the two-wheel mobile robot. With this implementation, we have the ability to control the complex embedded systems of the two-wheel mobile robot. The advantage of the real-time operating system is increasing the reliability and stability of the two-wheel mobile robot when they work in critical environments such as military and industrial applications. The real-time operating system which was ported to this implementation is open systems and the corresponding interfaces for automotive electronics (OSEK/VDX). It is known as the set of specifications on automotive operating systems, published by a consortium founded by the automotive industry. The mechanical design and kinematics of the two-wheel mobile robot are described in this paper. The contributions of this paper suggest a method for adapting and porting OSEK/VDX real-time operating system to the two-wheel mobile robot with the differential drive method, and we are also able to apply the real-time operating system to any complex embedded system easily.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.4
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• pp.209-217
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• 2003

The term “energy saving is economical” is appropriate for the national view point and for design and assessment of one system, but not appropriate when choosing the system by comparing alternative systems in the early design step. Sometimes, non-energy saving system is more economical than energy saving system because of the price of electricity, gas or oil, which are used for operating the air conditioning system. Therefore, when designing a system, we should consider the efficient alternatives through economic assessment of energy saving method. However, research on non-operating number control of the system is not sufficient because it is more common to use operating number control of the system for most economic assessment of air conditioning systems. For this reason, this research can provide the economic operating number control method as basic design data. The data obtained through analysis of life cycle cost based on amount of yearly energy use, are produced by system simulation of HASP/ACLD/8501 and HASP/ACSS/8502 for six alternative heating$.$cooling systems based on seasonal air conditioning system, which is widely used for medium and large size office buildings in Busan.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1142-1152
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• 2019

This paper presents a control method for reducing the current distortion in an indirect matrix converter (IMC) operating in boost mode under unbalanced input conditions. IMCs operating in boost mode are useful in distributed generation (DG) systems. They are connected with renewable energy systems (RESs) and the grid to transmit the power generated by the RES. However, under unbalanced voltage conditions of the RES, which is connected with the input stage of the IMC operating in boost mode, the input-output currents are distorted. In particular, the output current distortions cause a ripple of the power, which is transferred to the grid. This aggravates the reliability and stability of the DG system. Therefore, in this paper, a control method using positive/negative sequence voltages and currents is proposed for reducing the current distortion of both side in IMCs operating in boost mode. Simulation and experimental results have been presented to validate effectiveness of the proposed control method.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2100-2104
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• 2004

Amount of Electricity which product generator decide control valve at Turbine. Operating method of Control valve have two mode. First operating method is Partial Arc Admission, and second operating method is Full Arc Admission. Failure of Control Valve have on serious damage electricity lineage. In this Paper, We have investigated resonance that Control Valve spring casing.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.824-829
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• 2011

In Fischer-Tropsch Synthesis, because of few reactants ($H_2$, CO), scarce operating parameters affected on efficiency especially the selectivity of products. In this research, effect of operating parameters on the selectivity of Co-Mn-$TiO_2$ Fischer-Tropsch synthesis catalyst were studied by design of experimental procedure and Taguchi method. According to this research, interactions between operating factors have a crucial effect on light products selectivity. Among these interactions, (temperature${\times}$feed ratio) has the main influence on light hydrocarbons selectivity. It was concluded that temperature and feed ratio ($H_2$/CO) were the most integral operating parameters for much greater selectivity of light hydrocarbons.