• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.261-265
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• 2004

This paper proposes a fuzzy dual method for analyzing long-term transmission system expansion planning problem considering ambiguities of the power system using fuzzy lineal programming. Transmission expansion planning problem can be formulated integer programming or linear programming with minimization total cost subject to reliability (load balance). A long-term expansion planning problem of a grid is very complex, which have uncertainties fur budget, reliability criteria and construction time. Too much computation time is asked for actual system. Fuzzy set theory can be used efficiently in order to consider ambiguity of the investment budget (economics) for constructing the new transmission lines and the delivery marginal rate (reliability criteria) of the system in this paper. This paper presents formulation of fuzzy dual method as first step for developing a fuzzy Ford-Fulkerson algorithm in future and demonstrates sample study. In application study, firstly, a case study using fuzzy integer programming with branch and bound method is presented for practical system. Secondly, the other case study with crisp Ford Fulkerson is presented.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.297-300
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• 2004

This paper proposes a method for choosing the best composite power system expansion plan considering probabilistic reliability criterion. The proposed method was modeled as the minimization of the investment budget (economics) for constructing new transmission lines subject to not only deterministic(demand constraint) but also probabilistic reliability criterion(LOLE) with considering the uncertainties of the system elements. This is achieved by modeling the power system expansion problem as an integer programming one. The method solves for the optimal strategy using a probabilistic theory based branch and bound method that utilizes a network flow approach and the maximum flow-minimum cut set theorem. Although the proposed method is applied to a simple sample study, the test results demonstrate a fact that the proposed method is suitable for solving the power system expansion planning problem subject to practical uncertainties for future.

• KIEE International Transactions on Power Engineering
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• v.4A no.4
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• pp.254-261
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• 2004

Traditionally, electrical power systems had formed the vertically integrated industry structures based on the economics of scale. However, power systems have been recently reformed to increase their energy efficiency. According to these trends, the Korean power industry underwent partial reorganization and competition in the generation market was initiated in 2001. In competitive electric markets, accurate load data is one of the most important issues to maintaining flexibility in the electric markets as well as reliability in the power systems. In practice, the measuring load data can be uncertain because of mechanical trouble, communication jamming, and other issues. To obtain reliable load data, an efficient evaluation technique to adjust the missing load data is required. This paper analyzes the load pattern of historical real data and then the tuned ARIMA (Autoregressive Integrated Moving Average), PCHIP (Piecewise Cubic Interpolation) and Branch & Bound method are applied to seek the missing parameters. The proposed method is tested under a variety of conditions and also tested against historical measured data from the Korea Energy Management Corporation (KEMCO).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1571-1579
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• 2009

This paper proposes a P2P(Peer-to-Peer) streaming protocol which allows various QoS(Qualify of Service) requirements of video streaming to be supported for various personal IPTV applications in ubiquitous Internet environments. The proposed P2P streaming protocol takes fairly short startup delay, guarantees end-to-end delay bound and bandwidth requirements, and supports reliability level of video streaming for an IPTV application. The QoS-based P2P streaming protocol can properly use not only the advantages of scalability, availability, and ubiquity of P2P streaming but also complement its disadvantages of performance and reliability so that various types of personal IPTV applications can be properly implemented in the existing broadband Internet environments.

• Computational Structural Engineering
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• v.1 no.2
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• pp.101-109
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• 1988

The evaluation of the system reliability is generally quite difficult and costly as the structure becomes large and complex, especially when it is subjected to multiple time varying loads, and for redundant structures which have many possible modes of failur, e.g., system collapse through the formation of plastic hinge mechanisms. In reality most loadings acting on the structures are random in intensity as well as in occurrence time and duration. To include the load variability in time, the loads are described in terms of stochastic processes. Based on a tri-modal upper bound, a point estimate for the system reliability has been developed for more accuracy without extensive computational effort. This tri-modal point estimate also ensures the continuity of the system reliability function, which is a necessary condition in many nonlinear programming techniques. In addition, the Load Coincidence method, by which the combined effect of time varying loads are taken into account, has been modified to suitable for cases with an always-on load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.79-88
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• 1987

This study is intended to propose a system reliability analysis model for R.C. bridge superstructures based on the systems reliability theory. Approximately assuming that the ultimate capacity of the superstructures is reached, when two adjacent girders fail subsequently, a practical system reliability model is proposed, which is based on a point estimate for Level II parallel-series system modelling. The sensitivity analysis of system reliabilities for the variation of the coefficients of correlations between the failure modes is performed by applying the proposed model for R.C. T beam bridges. It is observed that the point estimate method for the proposed model corresponds to the average value of the Ditlevsen's bound, and the system reliability index, ${\beta}_s$, varies quite sensitively according to the variation of the cofficients of correlations. Systems reliabilities of a few existing T beam bridges are analyzed by applying the proposed practical system reliability method of this study, and, in addition, the preferable direction of the development of the reliability-based code calibration using the system target reliability index concept are suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.689-697
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• 2005

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, $B_{10}$ life and its lower bound with $90\%$ confidence at worst case use condition are estimated by analyzing the accelerated life test data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.711-718
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• 2019

BDD is a well-known alternative to the conventional Boolean logic method in fault tree analysis. As the size of fault tree increases, the calculation time and computer resources for BDD dramatically increase. A new failure path search and path restructure method is proposed for efficient calculation of CS and MCS from BDD. Failure path grouping and bottom-up path search is proved to be efficient in failure path search in BDD and path restructure is also proved to be used in order to reduce the number of CS comparisons for MCS extraction. With these newly proposed methods, the top event probability can be calculated using the probability by ASDMP(Approximate Sum of Disjoint MCS Products), which is shown to be equivalent to the result by the conventional MCUB(Minimal Cut Upper Bound) probability.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.29-34
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• 2016

A controller area network (CAN) controller is an integral part of an electronic control unit, particularly in an advanced driver assistance system application, and its characteristics should always be advantageous in all aspects of functionality especially in real time application. The cost should be low, while maintaining the functionality and reliability of the technology. However, a CAN protocol implementing serial operation results in slow throughput, especially in a cyclical redundancy checking (CRC) unit. In this paper, digital signal processing (DSP) algorithms are implemented, namely pipelining, unfolding, and retiming the CAN controller in the CRC unit, particularly for the encoder and decoder sections. It must attain a feasible iteration bound, a critical path that is appropriate for a CAN system, and must obtain a superior design of a high-speed parallel circuit for the CRC unit in order to have a faster transmission rate. The source code for the encoder and decoder was formulated in the Verilog hardware description language.

• International Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.9-18
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• 2018

The longitudinal flight parameters of a light airplane are estimated from flight test data by use of the output error method. The reliability of the flight test measurement is examined in engineering judgment, scatter and Cramer-Rao bound, which turns out to be satisfactory with minor defects. Estimated parameter values are validated by comparing the simulated responses with the ones from actual flight tests. The FTD(Flight Training Device) of a light airplane turns out to satisfy the qualification of FAA Level 5 FTD in longitudinal motion. All the necessary practices for generation of high-fidelity data in longitudinal motion of a light aircraft are successfully performed in this study.