• Journal of Korea Technology Innovation Society
• /
• v.4 no.2
• /
• pp.157-171
• /
• 2001

This paper discusses the economics of local loop architecture focusing on existing technologies, ADSL, HFC, and new one, PLC, and suggests a new modeling approach of access network system and the numerical equations. To modelize access network system and drive the numerical equations, we consider the double star and the tree & branch architecture and made block diagram of each access system. In addition, we introduce the density of subscriber as a variable and the equation of seeking the optimal number of cell in a service area. The economics of local loop architecture is analyzed in two ways, i.e. with and without consideration of the cost of cable and infrastructure. From the numerical analysis, we find that in case of not including the cost of cable and infrastructure, there is no much difference in the cost per one subscriber, while, in case of including it, there is remarkable difference among technologies. Therefore we conclude that the economics of local loop architecture is depend on the density of subscriber and existing network infrastructures.

• Structural Engineering and Mechanics
• /
• v.61 no.6
• /
• pp.807-816
• /
• 2017

In this paper, we introduce an efficient new model reduction method, named the automated static condensation method, which is developed for the local analysis of large finite element models. The algebraic multilevel substructuring procedure is modified appropriately, and then applied to the original static condensation method. The retained substructure, which is the local finite element model to be analyzed, is defined, and then the remaining part of the global model is automatically partitioned into many omitted substructures in an algebraic perspective. For an efficient condensation procedure, a substructural tree diagram and substructural sets are established. Using these, the omitted substructures are sequentially condensed into the retained substructure to construct the reduced model. Using several large practical engineering problems, the performance of the proposed method is demonstrated in terms of its solution accuracy and computational efficiency, compared to the original static condensation method and the superelement technique.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.4
• /
• pp.23-30
• /
• 2013

Reliability Centered Maintenance(RCM) is one of most widely used methods in the modern power system to schedule a maintenance cycle and determine the priority of inspection. A precedence study for the new structure of rearranged system should be performed due to introduction of additional installation. This paper proposes a new method to evaluate the priority of maintenance and inspection of the power system facilities. In order to calculate that risk index, it is required that the reliability block diagram should be analyzed for the power system. Additionally, a fault cause analysis is also performed through the event-tree analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.936-941
• /
• 2001

This paper deals with the design of oil-tree motor-driven two-stage centrifugal compressor supported by air-lubricated multi-leaf foil bearings. The design of this compressor is performed, based upon prediction of critical speeds, load capacity, and stability. It is demonstrated in this paper that multi-leaf foil bearings can be adopted to satisfactorily support this centrifugal compressor.

• Journal of Applied Reliability
• /
• v.17 no.1
• /
• pp.28-37
• /
• 2017

Purpose: This paper proposes a procedure that may infer and identify interaction failures in a module. Methods: In design FMEA, we defined an interaction model between components and proposed a method for selecting a single component by using the standard specification classification table and four methods for choosing the related components. We also introduced the function tree for function and requirement characteristic analysis and proposed utilization of standard stress lists and 1st and 2nd stress analysis tables to determine the effect the stress analysis has on interactions. Finally, the interaction mechanism diagram was proposed and used to infer the failure mechanism. Process FMEA also established procedures in a similar way. Results: We established a procedure for predicting the failure mode due to interaction between components based on Company A's multi-step FMEA procedure. Conclusion: By applying the proposed interaction FMEA procedure to the development model, we were able to confirm the effect of the new derivation on the failure mode of interaction, which was not predicted by the existing FMEA.

• The Mathematical Education
• /
• v.42 no.2
• /
• pp.111-119
• /
• 2003

This research discussed a general concept on the qualitative research methods in mathematics education. It provided a classification of research methods in mathematics education. It also described research trends in mathematics education. It addressed how research design facilitates formulating a research problem, selecting a research design, choosing who and what to study, deciding how to approach Participants, selecting means to collect data choosing how to analyzing data, and interpreting data and applying the analysis. This study addressed the issues involved in choosing relevant populations and in selecting and sampling qualitative data. It described how populations are conceptualized and distinguished between probability sampling and criterion based selection. It discussed not only data arrangement such as, cross-sectional and categorical indexing, non-cross- sectional data organization, but also diagram flow chart matrix, cognitive map, family tree to facilitate analyzing data.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2009.11a
• /
• pp.253-256
• /
• 2009

To the success of the megaproject including various and complex facilities, it is needed to establish a database system. Developments in data collection, storage and extracting technology have enabled iPMIS to manage various and complex information about cost and time. Especially, when we consider that both the go and no go decision in feasibility, Cost is an important and clear criteria in megaproject. Thus, Cost data modeling is the basis of the system and is necessary process. This research is focus on the structure and definition about CBS data which is collected from sites. We used four tools which are Function Analysis in VE, Casual loop Diagram in System Dynamics, Decision Tree in Data-mining, and Normalization in SQL to identify its cause and effect relationship on CBS data. Cost data modeling provide iPMIS with helpful guideline.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 1995.11a
• /
• pp.55-66
• /
• 1995

Earlier studies indicated clearly that information obtained from conventional statistics cannot provide guidance on detailed casualty analysis. Much more is needed if casualty statistics are to play a proficient and vigorous role in encouraging safety. Specific difficulties originate from making the causal relationships clear. Fault tree analysis and symbolic modeling of functional block diagram are an efficient aid in safety analysis so that these methods are generally used in other industries. This paper describes the application of these tools in shipping casualties and how to evaluate the relationships between different causes of ship casualties. Thesee methods are proved to be an efficient and useful tools to indicate the relationships between individual physical factors. In addition these models permit easy understanding and recognition of the factors leading to individual casualty

• Proceedings of the Korea Information Processing Society Conference
• /
• 2003.11c
• /
• pp.1685-1688
• /
• 2003

객체지향 환경에서 복잡한 소프트웨어 시스템을 개발하기 위해서는, 그것의 복잡성과 대규모성 때문에 추상화에 의한 다계층적인 use case model 의 사용이 불가피하다. 이러한 경우 모델의 consistency 유지가 매우 주요하고 어려운 이슈가 된다. 본 논문에서는 각 추상화 단계에 따른 use case model 들 사이에서 자동적으로 형식적인 consistency 를 체킹할 수 있는 방법을 제안한다. 이 접근 방법은 rule 을 기반으로 하여 actor tree, use cose composition diagram를 use case description을 활용한다. 본 접근법을 검증하기 위하여, ITS 아키텍처 (Intelligent Transportation System architecture)의 한 파트를 예로 들어 적용하였다.

• Korean System Dynamics Review
• /
• v.12 no.4
• /
• pp.63-92
• /
• 2011

The purpose of this paper is to investigate a possibility of applying multimethodological approach for solving a dilemma. The motivation of this attempt is that the two different approaches, the system dynamics and the theory of constraints, resemble each other in having mental models for describing the target system and using graphic tools for representing those mental models. After a brief discussion on the comparison of the two approaches, a combined method applying to the problem of dilemma is suggested. For an experimental example, the proposed approach is applied to the sales and finance conflict on an inventory issue. The study shows that the suggested approach is able to complement each other's drawbacks. Especially constructing a stock-and-flow model and implementing a computer simulation would be very useful for quantifying the system's behavior which is hardly tracked down when applying the theory of constraints alone.