• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.218-221
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• 2006

High reliability and minimization of operating cost are important problems for both engine-manufacturer and user in operation of gas-turbine engine, for which various performance diagnostics including a fault identification have been a major issue nowadays. Performance estimation in the off-design conditions, however, encounters problems of large errors and of poor convergence because of much required data to be evaluated. In this study, a diagnostics code of engine performance has been developed by using GPA(Gas Path Analysis). Quantitative performance deterioration of the turbo-shaft engine for SUAV has been estimated with altitude variation and is compared with that obtained by GSP code.

• Journal of Construction Engineering and Project Management
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• v.2 no.2
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• pp.1-17
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• 2012

The automated construction machines have been recently developed to help solve the construction industry problems that significantly affect labour, productivity, quality, and profit. Despite the importance of performance analysis to commercialize the automated construction machines, previous studies have mainly concentrated on developing hardware and software of automated construction machines. This research now focuses on two objectives: (1) to propose an analysis model which can measure productivity, quality, and safety improvement rate of automated construction machines based on research and development (R&D); and (2) to develop a performance analysis system which will aid the evaluator in analysing the performance of automated construction machines. Finally, it is anticipated that the effective use of the performance analysis model and computerized system will ably develop the high-performance, automated construction machines and establish the marketing strategy to increase not only the commercial value but also the upkeep and development of construction machines.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.750-769
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• 2015

The geometry of engineering systems affects their performances. For this reason, the shape of engineering systems needs to be optimized in the initial design stage. However, engineering system design problems consist of multi-objective optimization and the performance analysis using commercial code or numerical analysis is generally time-consuming. To solve these problems, many engineers perform the optimization using the approximation model (response surface). The Response Surface Method (RSM) is generally used to predict the system performance in engineering research field, but RSM presents some prediction errors for highly nonlinear systems. The major objective of this research is to establish an optimal design method for multi-objective problems and confirm its applicability. The proposed process is composed of three parts: definition of geometry, generation of response surface, and optimization process. To reduce the time for performance analysis and minimize the prediction errors, the approximation model is generated using the Backpropagation Artificial Neural Network (BPANN) which is considered as Neuro-Response Surface Method (NRSM). The optimization is done for the generated response surface by non-dominated sorting genetic algorithm-II (NSGA-II). Through case studies of marine system and ship structure (substructure of floating offshore wind turbine considering hydrodynamics performances and bulk carrier bottom stiffened panels considering structure performance), we have confirmed the applicability of the proposed method for multi-objective side constraint optimization problems.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.1-8
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• 1994

An automated procedure which allows adaptation of spatial and time discretization simultaneously in finite element analysis of linear elastodynamic problems is presented. For dynamic problems having responses dominated by high frequency modes, such as those with impact, explosive, traveling and earthquake loads high gradient stress regions change their locations from time to time. And the time step size may need to vary in order to deal with whole process ranging from transient phase to steady state phase. As the sizes of elements in space vary in different regions, the procedure also permits different time stepping. In such a way, the best performance attainable by the finite element method can be achieved. In this study, we estimate both of the kinetic energy error and stran energy error induced by spatial and time discretization in a consistent manner. Numerical examples are used to demonstrate the performance of the procedure.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.109-114
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• 2002

This paper analysis the transient performance of the modified excitation system using 4-quadrant chopper for a synchronous machine connected to HVDC system. Conventionally, capacitors are used to supply reactive power requirement at a strong converter bus. And the installation of a synchronous machine is essential in an isolated weak network to re-start after a shutdown of HVDC and to increase the system strength. However, a conventional static excitation system has some problems which are harmonic instability and the system stress due to overvoltage. To reduce these problems, the new excitation system, which has 4-quadrant chopper, is proposed. As the proposed system provides the capability to allow reverse current and isolate between AC network and excitation power, problems of overvoltage and harmonic instability can be solved. The investigation is performed and confirmed by the time domain digital simulation using PSCAD/EMTDC program.

• Knowledge Management Research
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• v.10 no.1
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• pp.71-100
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• 2009

Recently, many of organizations build up their performance measurement system (PMS) to measure their knowledge management performance. However, the system that doesn't well reflect the organization's strategies as well as surroundings could obstruct their performance improvement, instead. Therefore, It is really important to establish the PMS to reflect organization's surroundings and strategies. The purpose of this study is to make a diagnosis of a performance measurement practice of a domestic university's knowledge management. To serve this research purpose, we examine the uptight performance index and PMS from existing references. And we diagnose the specific practices and maturity rates of measuring performances, and the recognition of the performance index at "D" university recently adopting balanced scorecard to performance evaluation through the survey on academic affairs committee members, performance evaluation committee members, and administration members. The method analyzing data from the survey is a gap analysis which includes alignment analysis, congruence analysis, consensus analysis, and confusion analysis. We make a diagnosis of performance measurement practices at "D" university, raise several points of this performance measurement system, and present the improvement plans from these problems.

• Structural Engineering and Mechanics
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• v.3 no.4
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• pp.391-410
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• 1995

The application of adaptive finite element method to dynamic problems is investigated. Both the kinetic and strain energy errors induced by space and time discretization were estimated in a consistent manner and controlled by the simultaneous use of the adaptive mesh generation and the automatic time stepping. Also an optimal ratio of spatial discretization error to temporal discretization error was discussed. In this study it was found that the best performance can be obtained when the specified spatial and temporal discretization errors have the same value. Numerical examples are carried out to verify the performance of the procedure.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1081-1087
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• 2009

An automatic construction system in Korea is now at the stage of the full automation like in Japan, and an actual pilot project is going to be built in 2009. However, in developing a new construction system that has never been implemented before, there is a need to assess the performance and to consider the uncertainty of the system. The program evaluation and review technique (PERT) allows dealing with this uncertainty. Thus, this paper implements an analysis of the process of steel fabrication and makes suggestions for time-related problems arising from the analysis. The time required for steel erection by the automatic system was compared with that in the traditional method. In the result, finding out another construction process and improving robot performance were proposed to resolve the problems. The results will contribute to promoting the development of an efficient system for the new automatic construction system.

• KIISE Transactions on Computing Practices
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• v.22 no.8
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• pp.351-356
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• 2016

In recent years, as smartphones with Android platforms expand, the number of Android applications increases. Android applications implement Java and XML to compose the user interface, among other things. Between Java and XML, various problems may occur. Nonetheless, static analysis research and tools are not sufficient. In this paper we will list the problems which may occur between Java and XML. Subsequently, we will propose a detection method for them. Using the proposed technique, we found 172 Android-specific problems and 35 performance drop issues in 150 Android applications in the Google Play Store. We would like to contribute to research into static analysis and software quality improvement.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.69-74
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• 2015

We propose a rigorous and practical methodology to evaluate the performance of symbolic manipulation program such as Mathematica, Maple, and Maxima. First, we demonstrate an inverse method to construct the benchmark problems of an initial value problems. The benchmark problems associated with the discrete version of the Chebyshev polynomials provide a rigorous and objective measure to evaluate the performance of symbolic manipulation programs. We compare three symbolic manipulation programs, which are Mathematica, Maple and Maxima, using this methodology. The computation time, the used memory and the perturbation terms are chosen for comparison parameters.