• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.9
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• pp.392-398
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• 2006

Maintenance scheduling of generating units (MSU) has strategic dimension in an oligopolistic market. Strategic MSU of gencos can affect a market power through capacity withdrawal which is related to bidding strategy in an generation wholesale market. This paper presents a combined framework that models the interrelation between competitive bidding and strategic MSU. The combined game model is represented as some sub-optimization problems of a market operator (MO) and gencos, that should be solved through bi-level optimization scheme. The gradient method with dual variables is also adopted to calculate a Nash Equilibrium (NE) by an iterative update technique in this paper. Illustrative numerical example shows that NE of a supply function equilibrium is obtained properly by using proposed solution technique. The MSU made by MO is compared with that by each genco and that under perfect competition market.

• The Journal of Korea Robotics Society
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• v.5 no.2
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• pp.120-126
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• 2010

This paper presents to study the path tracking method of AGV(autonomous guided vehicle) which has a laser guidance system. An existing automatic guided vehicles(AGVs) which were able to drive on wired line only had a automatic guidance system. However, the automatic guidance systems that those used had the high cost of installation and maintenance, and the difficulty of system change according to variation of working environment. To solve such problems, we make the laser guidance system which is consisted of a laser navigation and gyro, encoder. That is robust against noise, and flexible according to working environment through sensor fusion. The laser guidance system can do a perfect autonomous driving. However, the commercialization of perfect autonomous driving system is difficult, because the perfect autonomous driving system must recognize the whole environment of working space. Hence, this paper studied the path tracking of AGV using laser guidance system without wired line. The path tracking method is consisted of virtual path generation method and driving control method. To experiment, we use the fork-type AGV which is made by ourselves, and do a path tracking experiments repeatedly on same experimental environment. In result, we verified that proposed system is efficient and stable for actual fork-type AGV.

• Journal of Communications and Networks
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• v.17 no.2
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• pp.172-183
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• 2015

To provide an efficient link maintenance approach, we propose a cross layer medium access control (LM-MAC) protocol for multichannel cognitive radio ad hoc networks. Link establishment and reliable transmission are two key problems for a perfect link maintenance mechanism. Since the cognitive user (CU) pairs have to reestablish their links each frame, in the proposed MAC protocol, three different access modes are designed to guarantee transmission efficiency in continuous frames. To enhance the transmission reliability, each CU will create a father spectrum list (FSL) after joining in the network. FSL is divided into three groups of sub-channels with different functions to compensate the packet loss caused by the primary users' appearance and the deep fading. Meanwhile, since the transmitter and the receiver will share the same FSL, periodical cooperative sensing is adopted to further optimize the former problem. Finally, compared with the existing opportunistic multichannel (OMC)-MAC protocol, the proposed LM-MAC protocol achieves better system performance in terms of saturation throughput, continuity and access delay.

• ETRI Journal
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• v.34 no.5
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• pp.775-778
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• 2012

We propose integrating random network coding with the Enhanced On-Demand Multicast Routing Protocol (E-ODMRP). With the Network Coded E-ODMRP (NCE-ODMRP), we present a framework that enables a seamless integration of random linear network coding with conventional ad hoc multicast protocols for enhanced reliability. Simulation results show that the NCE-ODMRP achieves a nearly perfect packet delivery ratio while keeping the route maintenance overhead low to a degree similar to that of the E-ODMRP.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.51-54
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• 2005

The concrete structure hasn't perfect waterproofing performance but if it doesn't have a joint part that could isolate a permeability. Concrete structure(communication tunnel and underground structure) has an expansion joint and construction joint. There are a lot of joint type after construction or expansion, shrinkage, vibration, over load, performance of decline etc.. they offer a water of way by variety change. In this reason, It carries in effect a waterproofing work for the concrete structure of waterproofing. but the structure has a behavior that cause a problem by waterproofing layer of damage, heaving phenomenon, temperature of shrinkage. In this study, we will estimate a field of application for Sealer of injection type for leakage maintenance of construction standard on the waterproofing performance.

• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.284-289
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• 2007

We analyze the real-field operational results of the RIMS. Four aspects are considered; 1) economical, 2) managerial, 3) safety and reliability and 4) RIMS user evaluation. In economical aspect we investigate the fields where some economical gains are anticipated. In managerial aspect the efficiency and effectiveness of management through RIMS are investigated. The improvement of safety and reliability are qualitatively discussed. And RIMS user evaluation is performed through survey. We also suggest several conditions for the successful settlement of RIMS and future study area for RIMS to be more reliable and perfect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.789-796
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• 2019

If the development of Integrated Logistics Support (ILS) for maintenance of the end step is conducted systematically and efficiently, the weapon system lifecycle can be postponed and the availability can be improved. DEFense CONdition (DEFCON) is maintained as perfect. Nevertheless, like its importance, the guide for maintaining the depot performance is applied differently for each weapon system. The errors that can result cause additional cost, etc. ILS development at depot level maintenance is different from full scale development. Therefore, this study distinguishes the management and deployment section for the development concept. An additional way to perform an efficient development of depot maintenance element when determining the depot maintenance period were presented. This study examined how the Reliability, Availability, Maintainability (RAM), Logistics Support Analysis (LSA), and ILS 11 elements intersect at the depot maintenance sources. An analytical study of concrete adoptable plans was performed. The systematic adoption of a development procedure can make it possible to calculate the adoptable development cost. In addition, it can be helpful for improving the quality level and practical use of work products.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.191-201
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• 2016

A stochastic process has been used to develop a condition-based model for preventive maintenance of armor units of rubble-mound breakwaters that can make a decision the optimal interval at which some repair actions should be performed under the perfect maintenance. The proposed cost model in this paper based on renewal reward process can take account of the interest rate, also consider the unplanned maintenance cost which has been treated like a constant in the previous studies to be a time-dependent random variable. A function for the unplanned maintenance cost has been mathematically proposed so that the cumulative damage, serviceability limit and importance of structure can be taken into account, by which a age-based maintenance can be extended to a condition-based maintenance straightforwardly. The coefficients involved in the function can also be properly estimated using a method expressed in this paper. Two stochastic processes, Wiener process and gamma process have been applied to armor stones of rubble-mound breakwaters. By evaluating the expected total cost rate as a function of time for various serviceability limits, interest rates and importances of structure, the optimal period of preventive maintenance can easily determined through the minimization of the expected total cost rate. For a fixed serviceability limit, it shows that the optimal period has been delayed while the interest rate increases, so that the expected total cost rate has become lower. In addition, the gamma process tends to estimate the optimal period more conservatively than the Wiener process. Finally, it is found that the more crucial the level of importance of structure becomes, the more often preventive maintenances should be carried out.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.191-198
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• 2003

The pavement stiffness is scarcely used in structural analysis to design the superstructure of bridge. It is reasonable not to consider it in the case of asphalt concrete pavement over concrete deck because the pavement stiffness compared with the concrete deck plate can be ignored. However, sometimes, the pavement materials have a similar amount of elastic modulus to concrete and are applied to the orthotropic steel deck plate which has relatively less stiffness compared with the concrete deck plate. In this paper, the steel plate deck of a real bridge project was analyzed by considering the pavement stiffness by linear elastic FEM. It was assumed that a perfect bond between the steel plate deck and the pavement exited. The results indicated that the structural behavior of the orthotropic steel deck plate can be estimated enough to affect the evaluation result of structural capacity in some cases. Therefore, the investigations by experimental tests and more advanced numerical model are indispensible in figuring the design formula for considering the effects of pavement stiffness in the structural analysis of an orthotropic bridge.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.233-244
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• 2001

Stress-strain behaviour of soil varies based on stress path and stress history. There has been few study on the characteristics of yielding curve which has anisotropic compression stress history in decomposed granite soil. During this study, various stress path tests in previous anisotropic compression stress history are performed on compacted decomposed granite soil sampled at Iksan, Chonbuk. Yielding points are determined from various stress-strain curves (${\eta}-{\varepsilon}$, ${\eta}$-v, and ${\eta}$-k, ${\eta}$-W curves). Stress-strain curve is certified which shows yielding point very clearly. The shape and characteristics of anisotropic compression yielding curves are examined. The main results are summarized as follows : 1) p' constant and compressive direction in stress paths, which has experienced previous anisotropic compression stress history, shows relatively dear yielding points. 2) Yielding curves defined from ${\eta}$-k and ${\eta}$-W curve show almost perfect ellipse. 3) Directions of plastic strain incremental vector($dv^p/d{\varepsilon}^p$) are not perpendicular to yielding curve.