• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.24-27
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• 2008

For high voltage DC-DC converters, the parallel operation of several high voltage source modules is necessary to reduce the material cost. In the conventional parallel operation with HDC module control unit, it is difficult to repair the HDC system for the failure of control unit. To overcome these problems, new parallel operating algorithm for high voltage DC-DC converter is presented. The proposed algorithm has no main control unit and each module can be selected as the master according to the operating conditions. Therefore, one of modules can be replaced as the master immediately when the previous master module is failed. In addition, the extension of extra modules can be simple.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1446-1448
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• 2004

Communication line used in the rail-road have different use from subscriber line in the public telecommunication. But, when an existing communication equipment is replaced, by applying new high-speed transfer technology, we can anticipate the increase of transmission rate and decrease of waiting time according to high-speed of communication line. cost reduction of infrastructure construction and maintenance/repair according to centralization of communication line and transmission equipment. In this study, the transmission scheme of several xDSL(Digital Subscriber Line) modems were compared and analyzed. The way of applying xDSL modem to the metal cable which is used in the JR(Japan Railroad) is analyzed. In addition, the result tested in railroad communication line was reviewed.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.48
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• pp.15-23
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• 1998

This paper concerns the problem of determining the spare inventory level for multi-echelon repairable-item inventory system with finite number of operating items. We consider the system which has several bases and a central depot. When an item fails, it is dispatched to a repair facility and, a spare, if available, is plugged in immediately. When the failed item is repaired, it is sent to the base and either is used to fill a backorder or is stored at a spare inventory point. Using queueing network, we develop an algorithm to find the spare inventory level which minimizes the total expected cost and, simultaneously, satisfies a specified minimum fill rate. The results of the algorithm clearly indicate that the algorithm successfully generate output with optimal solution.

• Journal of the military operations research society of Korea
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• v.10 no.2
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• pp.61-73
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• 1984

A block replacement policy using items with different reliability is discussed. We divide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0, $T-{\delta}$), failure item A is replaced by new item A. If mode-2 failure of item A happens in ($T-{\delta}$, T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval $T^{*}$ and the interval ${\delta}^{*}$ of item B replacement which minimize the cost rate per unit time.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.253-258
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• 2000

Recently, the area of design optimization, especially structural optimization, has been and to be a continuous active area of research. And the design optimizations of port facilities have been achieved by many other civil engineers. But the design optimization of port facilities were limited to the design optimization of the breasting dolphin. This paper invested the design optimization of mooring pier and the foundations of mooring pier was suggested considering the convenience of repair and reinforcement work. The mooring pier devised with prestressed precast concrete panel and rigid frame welded wide flange beam to steel pipe pile. To accomplish the design optimization of mooring pier, the Augmented Lagrangian Multiplier Method(ALM) of ADS(Garret N. Vanderplaats) optimization routine, BFGS method as optimizer and Golden Section Method as one dimensional search were utilized. As a result, thirty percent of material cost for construction was reduced by design optimization. The tensile stress of concrete panel and bottom flage was critical constraints under service load. So, using high strength concrete and steel will be economical. And lots of initial values must be invested to accomplish the design optimization in design procedures.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.637-640
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• 2006

Corrosion from various causes of reinforcing steel in concrete structures not only shortened the life of structures but also it is necessary a great repair cost to return and protect to the health condition. Using Nitrite inhibitors is a typical protection method. But there is no materials for the study about corrosion protection using nitrite. Therefore it is important to evaluate the additional rate and influence on congealment using the nitrite inhibitors in cement paste which is originally the basic material and crucial factors consisting concrete. The purpose of this study is finding influence of the type of nitrite inhibitors and mixing ratio on congealment of cement paste, and finding best corrosion inhibitors and ratio in cement paste.

• Journal of the Korea Institute of Building Construction
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• v.13 no.6
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• pp.549-556
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• 2013

This study analyzed the actual use of defect deposits for financing long-term expenses (that is, expenses incurred within 4-10 years of building completion) and for financing short-term expenses (that is, expenses incurred within 3 years of building completion). Therefore, 36 cost data on the expenses financed out of defect deposits for apartment complexes were collected from construction companies and analyzed using statistical methods. The findings revealed that 62.6 percent of defect deposits were spent to resolve actual defects, and 37.4 percent were spent resolving resident complaints. Furthermore, these results are valid regardless of the location of the complexes. As such, these results could be of significance when establishing or revising regulations regarding the repair of the long-term defects of apartment complexes.

• ETRI Journal
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• v.6 no.3
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• pp.17-20
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• 1984

A block replacement policy using items with different reliability is discussed. We devide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0,T- $\delta$). failure item A is replaced by new item A. If mode-2 failure of item A happens in(T-$\delta$,T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval T and the interval $\delta$ of item B replacement which minimize the cost rate per unit time.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.59
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• pp.53-67
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• 2000

In this paper we consider the CSP requirements determination problem of new equipment(machine) system. For the newly procured equipment systems, mathematical analyses are made for the system which is constructed with the consumable parts and the repairable parts to derive the associated CSP requirement determination model in mathematical expression. Based on these analyses, a mathematical model Is derived for making an optimal CSP requirement determination subject to the constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process and the repair time has an exponential distribution. Firstly, the operational availability concept in CSP is defined and the relation between the general system availability and the operational availability is established. Secondly, the problem is formulated as the cost minimization problem that should satisfy the operational availability limitation, and then, using the generalized Lagrange multipliers method, the optimal solution procedure Is derived.

• Journal of Korean Society for Quality Management
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• v.24 no.3
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• pp.31-36
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• 1996

A Markovian stochastic model for a system subject to random shocks is considered. Each shock arriving according to a Poisson process decreases the state of the system by a random amount. A repairman arrives at the system periodically for inspection and repairs the system only if the state is below a threshold. Costs are assigned to each inspection of the repairman, to each repair, and to the system being in bad states below the threshold. The expected long run average cost is obtained and compared with that of the random inspection introduced by Lee and Lee(1994).