• Journal of the military operations research society of Korea
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• v.35 no.3
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• pp.17-30
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• 2009

In this study, we propose the operational availability computation model that can be used on the weapon system's requirement planning phase. The proposed model consists of the time parameters of Ao(Operational Availability) for a system and each time parameter's estimation method. The time parameters for Ao computation are TT(Total Time) and TDT(Total Down Time). The time parameters are defined by considering OMS/MP(Operational Mode Summary/Mission Profile) elements. TT is a calendar time as a specific mission time at wartime or one year at peacetime. TDT consists of TPM(Total Preventive Maintenance time), TCM (Total Corrective maintenance time), TALDT(Total Administrative and Logistics Down Time). Then the estimation method for these time parameters are presented by the weapon systems types.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.521-528
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• 2009

One of reliability measurements of vehicle is estimated by driving mileage but the reliability of component, such as an hydraulic clutch system, is defined from the number of successful operational cycle. Relationship between these reliability measurement variables(mileage and cycle) should be examined first of all in the reliability estimation of components. Relationship between mileage and cycles is commonly known as linear function. However, the gradient depends on the operational environmental condition. Therefore, estimation of mission profile variable should be done with correlation analysis at the same time. In this paper, we derive mission profile variable of an hydraulic clutch system by field vehicle test and suggest the determination process of durability test parameters of CMC(Clutch Master Cylinder) with mission profile variable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.26-32
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• 2010

This paper proposes a new effective installed reserve rate in order to evaluate reliability of power system considering renewable generators, which include uncertainty of resource supply. It is called EIRR(effective installed reserve rate) in this paper. It is developed with considering capacity credit based on ELCC by using LOLE reliability criterion. While the conventional installed reserve rate index yields over-evaluation reliability of renewable generators, the proposed EIRR describes actual effective installed reserve rate. However, it is not the probabilistic reliability index as like as LOLE or EENS but another deterministic effective reliability index. The proposed EIRR is able to evaluate the realistic contribution to the reliability level for power system considering wind turbine generators and solar cell generators with high uncertainty in resource supply. The case study in model system as like as Jeju power system size presents a possibility that the proposed EIRR can be used practically as a new deterministic reliability index for generation expansion planning or operational planning in future.

• Journal of the Korean Society of Safety
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• v.23 no.2
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• pp.37-44
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• 2008

The safety assessment for facility industry is now being periodically performed. For the purpose of scientific safety management, QRA(Quantitative Risk Assessment) is also being performed, and reliability data of the facilities is essential to perform the assessment. Generally, the existing safety assessment is performed by using the values announced in other industry processes, which result in the drop of reliability. In order to solve this problem, there is an urgent need to establish reliability database for the facilities. The most appropriate method is to perform a direct reliability analysis towards the facilities undergoing safety assessment. In this study, in compliance with the assessment method and procedure of OREDA-2002 handbook, the facility reliability data are collected, which include the calendar time and operational time in terms of different facility items, the number of failures in terms of different failure mode, the mean, standard deviation, lower limit and upper limit of failure rate, and the failure rate. And the data process method for this special occasion is also proposed when the number of failure is 0.

• Journal of Applied Reliability
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• v.16 no.3
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• pp.224-230
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• 2016

Purpose: Military maintenance involves corrective and preventive actions carried out to keep a system in or restore it to a predetermined condition. This research develops an optimal maintenance cycle for aviation oil testing equipment with acceptable reliability level and minimum maintenance cost. Methods: The optimal maintenance policy in this research aims to satisfy the desired reliability level at the lowest cost. We assume that the failure process of equipment follows the power law non-homogeneous Poisson process model and the maintenance system is a minimal repair policy. Estimation and other statistical procedures (trend test and goodness of fit test) are given for this model. Results: With time varying failure rate, we developed reliability-based maintenance cost optimization model. This model will reduce the ownership cost through adopting a proactive reliability focused maintenance system. Conclusion: Based on the analysis, it is recommended to increase the current maintenance cycle by three times which is 0.5 year to 1.5 years. Because of the system's built-in self-checking features, it is not expected to have any problems of preventative maintenance cycle.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.6
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• pp.77-82
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• 2008

This paper presents a Reliability-Based Topology Optimization(RBTO) using the Evolutionary Structural Optimization(ESO). An actual design involves some uncertain conditions such as material property, operational load and dimensional variation. The Deterministic Topology Optimization(DTO) is obtained without considering the uncertainties related to the uncertainty parameters. However, the RBTO can consider the uncertainty variables because it has the probabilistic constraints. In order to determine whether the probabilistic constraints are satisfied or not, simulation techniques and approximation methods are developed. In this paper, the reliability index approach(RIA) is adopted to evaluate the probabilistic constraints. In order to apply the ESO method to the RBTO, sensitivity number is defined as the change in the reliability index due to the removal of the ith element. Numerical examples are presented to compare the DTO with the RBTO.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.3
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• pp.173-179
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• 2012

The purpose of this paper is to examine the effects on reliability of equipment or product which spends a great deal of its time in the dormant condition. Many systems experienced periods of dormancy throughout their life cycle, such as periods of operational storage where the system waits, ready for use. The design of such systems must account for how these period of dormant effects system performance. The methodology for predict and analysis was developed to support the evaluation of dormant modes of operation of systems and subsystems. For proper handling of the dormant environment, issues relating to dormant failures need to be taken into consideration from design stage of the lifecycle. Furthermore, the relevant environmental concerns that need to be taken into consideration depend on the environmental factors associated with each different target environment. This paper will look at dormant reliability, the possible dormant reliability models and the methodology on life cycle reliability which has different dormant phase.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.60-67
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• 2003

For risk or reliability assessment of ship structures against particular hazardous situations such as total loss or sinking due to hull girder collapse, the short-term based response analysis rather than the long-term response analysis is required to determine wave-induced bending moments when the ship encounters a storm of specific duration and with a specified small encounter probability. In the present study, the effects of operational condition and sea states on wave-induced bending moments of large merchant vessels are investigated. A series of the short-term response analyses for a hypothetical VLCC and a Capesize bulk carrier (CSBC) are carried out with varying operational condition and sea states which include ship speed, significant wave height and wave persistence time, using the linear-strip theory based program ABS/SHIPMOTION and the MIT sea-keeping tables. The computed results are also compared with the IACS design formula predictions. The results and insights developed from the present study are summarized.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.34-39
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• 2014

Airworthiness authorities specify the technical standards of airworthiness that propose minimum requirement of the commercial transport category and apply the rules in the certification process to ensure the safety of the aircraft. The Federal Aviation Administration and other national airworthiness authorities define the fatal accident risk levels for the safety assessment of the aircraft system and establish standard procedures to apply both qualitative and quantitative analysis techniques. However, an accident or incident may occur by the combination of various factors, although the aircraft is designed in accordance with the strict standards and approval by the Airworthiness Authorities. There are some key factors, such as human error, unpredictable complex system failures, degradation of the components reliability, improper maintenance task and intervals. Risk can be reduced by reflecting aircraft operational experience with similar types of aircraft in the process of aircraft development and safety assessment. Result of the root cause analysis for the Airbus A300-600 incident in which the aircraft engine reverser was deployed in the air have been introduced to reflect the design of system and related components. Also, this paper suggests to create a big-database in order to provide a feed-back to the FAR Part 25 transport category design and safety assessment of the operational experience.

• Journal of Astronomy and Space Sciences
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• v.39 no.4
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• pp.181-194
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• 2022

Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, was successfully launched on 4 Aug. from Cape Canaveral Space Force Station using a Space-X Falcon-9 rocket. Flight dynamics (FD) operational readiness was one of the critical parts to be checked before the flight. To demonstrate FD software's readiness and enhance the operator's contingency response capabilities, KPLO FD specialists planned, organized, and conducted four simulations and two rehearsals before the KPLO launch. For the efficiency and integrity of FD simulation and rehearsal, different sets of blind test data were prepared, including the simulated tracking measurements that incorporated dynamical model errors, maneuver execution errors, and other errors associated with a tracking system. This paper presents the simulation and rehearsal results with lessons learned for the KPLO FD operational readiness checkout. As a result, every functionality of FD operation systems is firmly secured based on the operation procedure with an enhancement of contingency operational response capability. After conducting several simulations and rehearsals, KPLO FD specialists were much more confident in the flight teams' ability to overcome the challenges in a realistic flight and FD software's reliability in flying the KPLO. Moreover, the results of this work will provide numerous insights to the FD experts willing to prepare deep space flight operations.