• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.185-190
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• 2006

This study carried out an evaluation of an oil tank that was defective in structure. This paper is divided into two sections which are analysis for the working process and suggestion for improving on the structure of the oil tank. As stated above, it has three major factors as to an improvement, such as the life cycle of structure (especially physical life cycle), and the many factors related to the duration years of the oil tank and analysis result. Based on this study, the improvement of oil tank was established. For example, the ground investigation needs before design and construction of oil tank, and constructing the oil tank by retaining wall type tank is good for maintenance. Also, it is important that the system for drainage is related to maintenance.

• Land and Housing Review
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• v.12 no.2
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• pp.99-108
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• 2021

With increasing interest in living in hanoks, there's a growing need for more quantitative data on the thermal comfort performance of modern hanoks. With that in mind, this research project studied a modern hanok located in Jamjeong-Haetsal Village in Hwasun, Jeollanam Province as a case study to evaluate the Predicted Mean Vote (PMV) of modernized hanoks. Based on environmental data collected at the hanok and computer simulation both Life-Cycle PMV (L.C.PMV) and Normal PMV (N.PMV) were calculated for the hanok. Study results showed that during the summer and winter seasons the PMV and heat index at major heat and major cold weather points significantly deviated from the comfort zone. The rate of change in PMV was also greater in the winter than in the summer. The study found that the modern hanok lacks proper thermal insulation for maintaining thermal comfort.

• Computers and Concrete
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• v.30 no.4
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• pp.277-287
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• 2022

Due to the scarcity of extortionate experimental data, fatigue failure of the reinforced concrete (RC) element might be achieved economically adopting nonlinear finite element (FE) analysis as an alternative approach. However, conventional implicit dynamic analysis is expensive, quasi-static method overlooks interaction effects and inertia, direct cyclic analysis computes stabilized responses. Apart from this, explicit dynamic analysis may provide a numerical operating system for factual long-term responses. The study explores the fatigue behavior based on a simplified explicit dynamic solution employing nonlinear time domain analysis. Among fourteen RC beams, one beam is selected to validate under static loading, one under fatigue with the experimental study and other twelve to check the detail fatigue behavior. The SWOT (Strength, Weakness, Opportunities, Threats) analysis has been carried out to pinpoint the detail scenario in the adoption of numerical approach as an alternative to the experimental study. Excellent agreement of FE and experimental results is seen. The 3D nonlinear RC beam model at service fatigue limits is truthful to be used as an expedient contrivance to envisage the precise fatigue behavior. The simplified analysis approach for RC beam under fatigue offers savings in computation to predict responses providing acceptable accuracy rather than the complicated laboratory investigation. At higher frequency, the flexural failure occurs a bit earlier gradually compared to the repeated loading case of lower frequency. The deflection increases by 6%-10% at the end of first cycle for beams with increasing frequency of cyclic loading. However, at the end of fatigue loading, greater deflection occur earlier for higher load range because of more rapid stiffness degradation. For higher frequency, a slight boost in concrete compressive strains at an initial stage of loading has been seen indicating somewhat stepper increment. Stiffness degradation in larger loading cycle at same duration escalates the upsurge of the rate of strain in case of higher frequency.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.24-32
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• 2021

Personal Air Vehicle (PAV), Cargo UAS (Cargo UAS), and existing manned and unmanned aircraft are key vehicles for urban air mobility (UAM), and should demonstrate compatibility for the design of aircraft systems. The safety assessment required by for certification to ensure safety and reliability should be systematically performed throughout the entire cycle from the beginning of the aircraft development process. However, with the increasing complexity of safety critical aviation systems and the application of state-of-the-art systems, conventional experience-based and procedural-based safety evaluation methods make ir difficult to objectively assess safety requirements and system safety. Therefore, Model-Based Safety Assessment (MBSA) using modeling and simulation techniques is actively being studied at domestic and foreign countries to address these problems. In this paper, we propose a Model-Based Safety Evaluation framework utilizing modeling and simulation-based integrated flight simulators. Our case studies on the Traffic Collision Availability System (TCAS) and Wheel Brake System (WBS) confirmed that they are practical for future safety assessments.

• Journal of The Korean Association of Information Education
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• v.19 no.3
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• pp.345-360
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• 2015

This study was designed to implement Activity-Orientated Career Education for college students, using the web-based interface. A draft web interface was designed by Rapid Prototyping and was thereafter taken to experts to review and determine the designs, in order to achieve the purpose of the study. Firstly, the sequence of activities of career education was run in accordance with the systematic order of Action Learning, in order to understand the overall design direction. Secondly, the design of the study may result in virtuous cycle-to-cycle. According to two major design directions, on the learning environment platform, the interface consisted of, knowing who I am; knowing who others think I am, knowing the job world; career decisions; career action plans; action planning; individual and co-evaluation; reflection; etc. These steps were designed to be implemented in accordance with strong interactivity of Wiki and Web 2.0 designs. This study was able to implement career education experiences centered around the activities of students at university, as well as experts, in order to increase the accessibility of Career Based Education on the web.

• Journal of the Korea Society of Computer and Information
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• v.17 no.1
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• pp.203-209
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• 2012

Recently, k-nearest neighbors query methods based on wireless broadcasting environment are actively studied. The advantage of wireless broadcasting environment is the scalability that enables collective query processing for unspecified users connected to the server. However, in case existing k-NN query is applied in wireless broadcasting environment, there can be a disadvantage that backtracking may occur and consequently the query processing time is increasing. In this paper proposes a hierarchical bitmap-based spatial index in order to efficiently process the k-NN queries in wireless broadcasting environment. HBI reduces the bitmap size using such bitmap information and tree structure. As a result, reducing the broadcast cycle can reduce the client's tuning time and query processing time. In addition, since the locations of all the objects can be detected using bitmap information, it is possible to tune to necessary data selectively. For this paper, a test was conducted implementing HBI to k-NN query and the proposed technique was proved to be excellent by a performance evaluation.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.115-127
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• 2007

Developed countries, especially in road construction and management fields, introduce new road porjects such as National Scenic Byways Program(NSBP program) in USA and the Eco-road project in Japan. This study develops a conceptual model for deploying new road projects in Korea. The four step approach is suggested to create new road projects, including foundation of an act based on the existing Road Act, creation of new road project ideas, development of evaluation process and guidelines, and enhancement of an administrative scheme. To create new road projects, three different ways are devised; (1) designation of national roads having uniqueness in overall spectrum, (2) designation of roads having intrinsic values in a different aspect, (3) designation of single structures of engineering outcomes such as bridges, tunnels, new design techniques, considerable Value Engineering output, and well analyzed Life Cycle Cost Analysis practices. For the evaluation process, NSBP program of USA and/or Sustainable City Award program of Korea would be recommended. An administrative scheme and integrated funding process for the new road projects are also suggested based on evaluation of tasks of each team or division of Korea Ministry of Construction and Transportation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.3
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• pp.231-237
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• 2017

The present study researched and analyzed decontamination technology for decommissioning a nuclear power plant. The decision-making technique (EXPERT-CHOICE) was used to evaluate and select the optimal decontamination technology. In principle, this evaluation method is generally performed by a group of experts in the relevant field. The results of the weights were calculated by multiplying the weights with regard to each criterion and evaluation score. The evaluation scores were categorized into 3 ranges (high, medium, and low), and each range was weighted for differentiation. The level of the technology analysis was improved by additionally quantifying the weights with regard to each criterion and subdividing criteria into subcriteria. The basic assumption of the evaluation was that the weight values would decided on in an expert survey and assigned to each criterion. The evaluation criteria followed high weight for the 'High' range. Accordingly, H, M, and L were assigned weights of 10:5:1, respectively. This was based on the EXPERT-CHOICE optimal analysis. The minimum and maximum values were excluded, and the average value was used as the evaluation value for each scenario.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.100-109
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• 2019

Maintainability indicates the extent to which maintenance can be done easily and quickly. The consideration of maintainability is crucial to reduce the operation and support costs of weapon systems, but if the maintainability is evaluated after the prototype production is done and necessitates design changes, it may increase the cost and delay the schedule. The evaluation should verify whether maintenance work can be performed, and support the designers in developing a design to improve maintainability. In previous studies, the maintainability index was calculated using the graph theory at the early design phase, but evaluation accuracy appeared to be limited. Analyzing the methods of evaluating the maintainability using fuzzy logic and 3D modeling indicate that the design of a system with good maintainability should be done in an integrated manner during the whole system life cycle. This paper proposes a method to evaluate maintainability using SysML-based modeling and simulation technique and fuzzy logic. The physical design structure with maintainability attributes was modeled using SysML 'bdd' diagram, and the maintainability was represented by an AHP matrix for maintainability attributes. We then calculated the maintainability using AHP-based weighting calculation and fuzzy logic through the use of SysML 'par' diagram that incorporated MATLAB. The proposed maintainability model can be managed efficiently and consistently, and the state of system design and maintainability can be analyzed quantitatively, thereby improving design by early identifying the items with low maintainability.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.7-18
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• 2005

Over the past twenty years, the maintenance system has been developed and its importance has been increased. For the effective maintenance of the urban transit, we have developed the maintenance system based on the concept of RCM(Reliability Centered Maintenance). RCM analysis is a systematic approach to developing a cost-effective maintenance strategy based on the various components's reliability of the system in question. It is performed according to process that includes the following steps; definition of function and functional failures of the systems, construction of RB D(Reliability Block Diagram), performance of FMEA(Failure Modes & Effects Analysis) and calculation of the reliability index. The final process of RCM is to determine appropriate failure maintenance strategies. This paper aims to define the procedure of maintenace based on the concept of RCM for urban transit. The key for a successful maintenance system is an automated scheduling to the maximum extent possible and timely executions. The developed system issues maintenance plan and repair request based on analyzed data and maintenance experience.