• 산업공학
• /
• 제3권1호
• /
• pp.1-11
• /
• 1990

The purpose of this study is to develop the decision support model for the investment in the operation and maintenance in telecommunication networks. First, we analyze the relation between the cost of quality and the quality of service, and then establish and analysis tool of the investment alternatives for the improvement of the quality of service. This study will offer a decision tool to enhance an efficiency of the operation and maintenance for telecommunication facilities, and will contribute to shaping a policy of network performance management.

• Structural Monitoring and Maintenance
• /
• 제10권3호
• /
• pp.191-205
• /
• 2023

In this paper, through operational modal analysis and ambient vibration tests, the dynamic characteristics of a multi-span simply-supported reinforced concrete highway bridge deck was determined and the results were used to assess the quality of construction of the individual spans. Supporting finite element (FE) models were created and analyzed according to the design drawings. After carrying out the dynamic tests and extracting the modal properties of the deck, the quality of construction was relatively assessed by comparing the results obtained from all the tests from the individual spans and the FE results. A comparison of the test results among the different spans showed a maximum difference value of around 9.3 percent between the superstructure's natural frequencies. These minor differences besides the obtained values of modal damping ratios, in which the differences were not more than 5 percent, can be resulted from suitable performance, health, and acceptable construction quality of the bridge.

• 산업경영시스템학회지
• /
• 제42권4호
• /
• pp.145-152
• /
• 2019

All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

• 품질경영학회지
• /
• 제18권2호
• /
• pp.33-42
• /
• 1990

This paper proposes the maintenance model of multi-component system when the failure characteristics and types of components are considered. In this model, it is assumed that a system is composed of a critical component, a major component and a minor component. Also, failure types is classified into major failure and minor failure. If major failure occurs to critical component before system age replacement time, the system is renewed. If major failure does not occur until its age replacement time, preventive maintenance is performed at age replacement time T. Minimal repairs are carried out after each minor failure. Major component is minimal-repaired if any failure is discovered during operation. Minor component should be replaced as soon as any failure is found. This paper determines the optimal replacement time of the system which minimizes total maintenance cost. Numerical example illustrates these results.

• 경영과학
• /
• 제9권1호
• /
• pp.41-52
• /
• 1992

The QOS(Quality of Service) recognized by the customer will become the most important thing under the competitive telecommunications market. Korea Telecom is going to develop many system to manage the telecommunication network, to improve the level of QOS, and to increase the revenue. Operation and Maintenance Adiministration System is one of the systems developed to meet those purposes efficiently. This system gathers qualities data from telephone offices or operation centers and analyze the results of QOS improvement activities and evaluate overall QOS. And also system makes it possible to improve the cost/effectiveness of operation and maintenance of telecommunication network. Operation and Maintenance Administration System has four functional modules, i.e., the user interface module, the database management module, the QOS management module, and the database conversion module. The purpose of this study is to develop the QOS management program, one of the four functional modules of the system,using FOCUS 4GL/DBMS. Since Operation and Maintenance Administration System is developed using FOCUS 4GL, every user can handle and maintain the system very easily and reduce system backlogs.

• 경영과학
• /
• 제24권1호
• /
• pp.77-90
• /
• 2007

Taguchi assumed that a product characteristic has the uniform distribution in its preventive maintenance limit when deriving the expected loss generated by the quality deviation. But it is reasonable to assume that a product characteristic has the normal distribution than the uniform distribution. On this paper, we first find the optimum inspection interval and the optimum preventive maintenance limit under the truncated triangular distribution. Secondly we use the beta-general distribution and compare with the truncated triangular distribution. By using the numerical examples, we find the optimum inspection interval and the optimum preventive maintenance limit under their distributions. As a result, we find that the beta-general distribution gives the best solution and easy calculation.

• International Journal of Railway
• /
• 제1권4호
• /
• pp.134-142
• /
• 2008

Serving as a strategic crossing point for major corridors in Central Europe, Railnet Austria's Infrastructure Network incurs continual increases in international traffic flows and is therefore subject to accumulating traffic congestion with potential restrictions to infrastructure access. This imposes challenges towards preserving open access to Railnet Austria's existing railway network and hinders quality infrastructure service during maintenance, repair, and upgrading. Through Railnet Austria's experiences, the economic viability of a railway network can be sustained through maintaining open access with good quality service of planned trainpaths, thus representing new challenges for future infrastructure maintenance and capacity planning. Railnet Austria's Capacity Management Department has proven that these challenges can be accommodated more effectively through recent technological developments in data warehousing and software development.

• 소프트웨어공학소사이어티 논문지
• /
• 제26권1호
• /
• pp.17-29
• /
• 2013

소프트웨어 시스템 진화는 소프트웨어 시스템의 유지보수의 일종으로 계획적이고 체계적인 유지보수 프로세스이다. 소프트웨어 진화 연구는 기존 시스템의 비용편익 분석을 통해 시스템의 유지가치에 대한 판단 근거를 제공하며, 아키텍처를 기반으로 하는 진화는 반복적인 진화 작업의 자동화를 가능케 하여 유지보수 비용 감소를 가능하게 해주는 연구이다. 본 논문에서는 아키텍처 변환패턴을 이용한 소프트웨어 시스템 진화 프레임워크를 제안한다.

• 국제학술발표논문집
• /
• The 3th International Conference on Construction Engineering and Project Management
• /
• pp.1216-1222
• /
• 2009

Ecological Engineering (EE) refers to all sustainable engineering that can reduce damage to ecosystems and that adopts ecology as a base and safety as an orientation in order to implement conservation of biodiversity and sustainable development. In short, EE attempts to safeguard the ecological environment while any essential construction projects proceed. EE encompasses many fields, including construction skills, ecosystem preservation, landscape, and even related cultures and so on. Such variety results in greater complexity of construction, and, consequently, indirectly increases the difficulty of construction quality control. The objective of our research is to explore a promising model for EE via an extensive literature survey. This model includes three principal stages: plan-design, construction, and maintenance, along with individual accompanying phases concerned with quality control and vital management. In this article, a river restoration example is adopted to describe in detail the critical points of quality control in the three stages (plan-design, construction, and maintenance) of the construction life cycle. This study proposes an integrated structure for quality management of EE to guarantee its quality and to enhance its core applications in order to achieve long-lasting preservation of the environment.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제15권1호
• /
• pp.6-11
• /
• 2015

Maintenance plays an important role in keeping product availability, reliability and quality at an appropriate level. In this paper, two-types of maintenance policies are studied following the expiration of two-dimensional (2D) free replacement warranty. Both the fixed-maintenance-period policy and the variable-maintenance-period policy are based on a specified region of the warranty defined in terms of age and usage where all failures are minimally repaired. An accelerating failure time (AFT) model is used to allow for the effect of usage rate on product degradation. The maintenance model that arises following the expiration of 2D warranty is discussed. The expected cost rates per unit time from the user's point of view are formulated and the optimal maintenance policies are determined to minimize the expected cost rate to the user. Finally numerical examples are given to illustrate the optimal maintenance polices.