• Journal of Korean Society for Quality Management
• /
• v.16 no.2
• /
• pp.1-9
• /
• 1988

This paper considers a machine maintenance problem. The machine's condition is partially known by observing the machine's output products. This problem is formulated as an infinite horizon partially observable Markov decison process to find an optimal maintenance policy. However, even though the optimal policy of the model exists, finding the optimal policy is very time consuming. Thus, the intends of this study is to find ${\varepsilon}-optimal$ stationary policy minimizing the expected discounted total cost of the system, ${\varepsilon}-optimal$ policy is found by using a modified version of the well-known policy iteration algorithm. A numerical example is also shown.

• Proceedings of the KIEE Conference
• /
• 1997.07c
• /
• pp.781-783
• /
• 1997

Genetic Algorithm is a kind of an evolution programming based on natural evolution principle. It applied to probabilistic searching, machine learning and optimization, and many good results were reported. Generator maintenance scheduling is an optimization Problem with constraints. This paper applied a genetic algorithm to generator maintenance scheduling problem and tested on sample systems. The results are compared with heuristic method and branch-and-bound method.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.63-64
• /
• 2022

Inter-floor noise in an apartment building is a serious problem that causes conflicts between tenants. Accordingly, there are various attempts to solve this problem, but it is not easy to find a clear solution. Therefore, in this study, a soundproofing material between floors was developed that can improve the sagging that occurs after construction. And as a result of testing the developed interlayer soundproofing material, both light weight and weight were grade 1. And it was analyzed that maintenance performance could be improved with integrated structural characteristics.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.1 s.256
• /
• pp.26-35
• /
• 2007

The vehicle of urban transit is a complex system that consists of various electric, electronic, and mechanical equipments, and the maintenance cost of this complex and large-scale system generally occupies sixty percent of the LCC (Life Cycle Cost). For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. The concept of system reliability has been introduced and optimized as the key of reasonable maintenance strategies. For optimization, three preceding studies were accomplished; standardizing a maintenance classification, constructing RBD (Reliability Block Diagram) of VVVF (Variable Voltage Variable Frequency) urban transit, and developing a web based reliability evaluation system. Historical maintenance data in terms of reliability index can be derived from the web based reliability evaluation system. In this paper, we propose applying inverse problem analysis method and hybrid neuro-genetic algorithm to system reliability optimization for using historical maintenance data in database of web based system. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between several component reliability (input) and system reliability (output) of structural system. The inverse problem can be formulated by using neural network. One of the neural network training algorithms, the back propagation algorithm, can attain stable and quick convergence during training process. Genetic algorithm is used to find the minimum square error.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.12 no.3
• /
• pp.1-12
• /
• 2009

This study aims to analyze the existing problem of geo-spatial information maintenance and then, show maintenance strategies suitable for new integrated environments. We look for AS-IS which is provider-centered, top-down, and also drive implications from analyzing oversea best practice. For analyzing of geo-spatial maintenance pattern, we polled about 20 local governments and private enterprise to find out AS-IS of geo-spatial information and result in maintenance pattern and component. From this, we suggest 4 kinds of strategies. This study shows the strategy not only which decide the question about the problem of existing geo-spatial maintenance but which find a way of combining and utilizing all geo-spatial information which is 8 criteria basic geographical information. This is a win-win program of all organization which produce, construct, make full use of national geo-spatial information.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.2A
• /
• pp.223-231
• /
• 2008

This research presents a new maintenance planning method for deteriorating bridges considering simultaneously the minimization of the maintenance cost and maximization of the bridge performance. Optimal maintenance planning is formulated as a multi-objective optimization problem that treats the maintenance cost as well as the bridge performance such as the condition grade of the bridge deck, girder and pier. To effectively address the multi-objective optimization problem and decision making process for the obtained solution set, we apply a genetic algorithm as a numerical searching technique and adopt a preference-based optimization method. A numerical example for a typical 5-span prestressed concrete girder bridge shows that the maintenance cost and the performance of the bridge can be balanced reasonably without severe trade-offs between each objectives.

• IE interfaces
• /
• v.16 no.2
• /
• pp.229-239
• /
• 2003

The On-Line Analytical Processing (OLAP) tools access data from the data warehouse for complex data analysis, such as multidimensional data analysis, and decision support activities. Current research has lead to new developments in all aspects of data warehousing, however, there are still a number of problems that need to be solved for making data warehousing effective. View maintenance, one of them, is to maintain view in response to updates in source data. Keeping the view consistent with updates to the base relations, however, can be expensive, since it may involve querying external sources where the base relations reside. In order to reduce maintenance costs, it is possible to maintain the views using information that is strictly local to the data warehouse. This process is usually referred to as "self-maintenance of views". A number of algorithm have been proposed for self maintenance of views where they keep some additional information in data warehouse in the form of auxiliary views. But those algorithms did not consider a consistency of materialized views using view self-maintenance. The purpose of this paper is to research consistency problem when self-maintenance of views is implemented. The proposed "conveyor algorithm" will resolved a complete consistency of materialized view using self-maintenance with considering network delay. The rationale for conveyor algorithm and performance characteristics are described in detail.

• Journal of Applied Reliability
• /
• v.11 no.2
• /
• pp.141-149
• /
• 2011

Environment Conversion Factors, which are stipulated in System Reliability Toolkit, have a lot of advantages once applied in a reliability data handbook such as NPRD-95, during the process of reliability prediction. However, the factors have a restriction in their applications because they don't deal with a few environments, e.g., Missile Launch (ML). In this study, environment factors of various components from MIL-HDBK-217F were analyzed to address this problem. Statistical computations showed that converting from Airborne Rotary Wing (ARW) to Missile Launch (ML) was the most coherent by comparing coefficient of determination. In addition, conversion factors from System Reliability Toolkit and those from the statistical calculations were evaluated in terms of their similarities.

• Journal of the Korean Society for Railway
• /
• v.9 no.5 s.36
• /
• pp.555-560
• /
• 2006

This study finds out and suggests success factors for the application of RIMS project through the case study of Seoul Metro and literature survey. The successful application of RIMS needs expert knowledge and concept of BOM, standardization of maintenance planning, check lists of heavy maintenance inspection, organization structure of rolling stock maintenance offices, material management system of warehousing and the process of parts repairing between offices, connection of material ordering system, problem solving of circular spare parts administration among inspection, maintenance, and material organizational units, systemic serial number management of parts with RFID, daily closing diary connected with work process chart, and sufficient period of RIMS's test run. RIMS contributes to real time management of rolling stock maintenance, transparency of management, reliability of train operation, customer satisfaction, and management innovation.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.2 no.2
• /
• pp.1-4
• /
• 1979

In order to cope with the violent environment of surrounding enterprises, development of new products, advance to other industry field, unification or abolition of factories and rationlization of labor are needed. But production process being made quality and using process after shipment are the things that we have to think about, first of all and to practice always. Insurance problem of reliability, that is, the positive quality maintenance that has being presented many debate issues recently, will be studied. The accident of nuclear power-plant in America, in connection with reliability maintenance and human engineering, will be analyzed. But as its accident details is not announced, in this study, it is a sort of method of methodology to be studied this paper rather than studying the fact of the accident. Therefore this study will be done as follows, For reliability study. 1. Investigation of problems. 2. Quality maintenance activity and reliability maintenance activity 3. Reliability acquisition in production process, 4. Reliability maintenance after shipment. 5. Conclusion. In addition to stating above, it is sure that liberalization of trade, interchange between nations and strengthening of international competition ability, etc. need high quality. But possibility that quality maintenance or reliability aquisition needs understanding and cooperation of consumer, will be stated.