• International Journal of Reliability and Applications
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• 제14권2호
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• pp.107-114
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• 2013

Modelling of failures is an important element of reliability modelling. Empirical modelling approach suitable for complex item is explored in this paper. First step of the empirical modelling approach is to plot hazard function, density function, Weibull probability plot as well as cumulative intensity function to see which model fits best for the given data. Next step of the empirical modelling approach is select appropriate model for the data and fit the parametric model accordingly and estimate the parameters.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.179-184
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• 2005

Empirical findings on interet rate dynamics imply that short rates show some long memories and non-Markovin. It is well-known that fractional Brownian motion(fBm) is a proper candidate for modelling this empirical phenomena. fBm, however, is not a semimartingale process. For this reason, it is very hard to apply such processes for asset price modelling. With some modifications, this paper investigate the fBm interest rate theory, and obtain a pure discount bond price and Greeks.

• Membrane and Water Treatment
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• 제2권4호
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• pp.225-237
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• 2011

In this study, response of reversibility of membrane flux during chemically enhanced backwash (CEB) to changes in filtration time, filtration flux and coagulant concentration dosing during ultrafiltration (UF) process was investigated using a regression model. The model was developed via empirical modelling approach using response surface methodology. In developing the model, statistically designed UF experiments were conducted and the results compared with the model output. The results showed that the performance of CEB, evaluated in terms of the reversibility of the membrane flux, depends strongly on the changes in coagulant concentration dosage and the filtration flux. Also the response of the reversibility of membrane flux during CEB is independent of the filtration time. The variance ratio, VR << $F_{value}$ and $R^2$ = 0.98 obtained from the cross-validation experiments indicate perfect agreement of the model output with experimental results and also testify to the validity and suitability of the model to predict reversibility of the membrane flux during CEB in UF operation.

• Asia pacific journal of information systems
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• 제10권4호
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• pp.37-56
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• 2000

This study proposes the concept and measurement of object-oriented systems modelling activity based on the previous research in the area of systems engineering, object-oriented modelling, and information systems. The modelling activity is related to information systems development success for exploring the correlation of each other. The object-oriented modeling activity is found to be related to user satisfaction with developed information systems, But the modeling activity does not have relation to the other successes, such as cost, development schedule, and maintenance. This study contributes to systems development modeling research, systems success, and object-oriented systems modelling research. Practically, the results support the usefulness of object-oriented modelling effort in the field in terms of user satisfaction.

• Steel and Composite Structures
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• 제23권5호
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• pp.501-516
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• 2017

Numerical simulations are prevalently used to evaluate the seismic behaviour of structures. The accuracy of the simulation results depends directly on the accuracy of the modelling techniques employed to simulate the behaviour of individual structural members. An empirical modelling technique is employed in this paper to simulate the behaviour of column members under cyclic and seismic loading. Despite the common modelling techniques, this technique is capable of simulating two important aspects of the cyclic and seismic behaviour of columns simultaneously. The proposed fiber-based modelling technique captures explicitly the interaction between the bending moment and the axial force in columns, and the cyclic deterioration of the hysteretic behaviour of these members is implicitly taken into account. The fiber-based model is calibrated based on the cyclic behaviour of square hollow steel sections. The behaviour of several column archetypes is investigated under a dual cyclic loading protocol to develop a benchmark database before the calibration procedure. The dual loading protocol used in this study consists of both axial and lateral loading cycles with varying amplitudes. After the calibration procedure, a regression analysis is conducted to derive an equation for predicting a varying calibrated modelling parameter. Finally, several nonlinear time-history analyses are conducted on a 6-story steel special moment frame in order to investigate how the results of numerical simulations can be affected by employing the intended modelling technique for columns instead of other common modelling techniques.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.1-10
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• 2009

The safe and reliable performance of fusion and fission plants depends on the choice of suitable materials and an assessment of long-term materials degradation. These materials are degraded by their exposure to extreme conditions; it is necessary, therefore, to address the issue of long-term damage evolution of materials under service exposure in advanced plants. The empirical approach to the study of structural materials and fuels is reaching its limit when used to define and extrapolate new materials, new environments, or new operating conditions due to a lack of knowledge of the basic principles and mechanisms present. Materials designed for future Gen IV systems require significant innovation for the new environments that the materials will be exposed to. Thus, it is a challenge to understand the materials more precisely and to go far beyond the current empirical design methodology. Breakthrough technology is being achieved with the incorporation in design codes of a fundamental understanding of the properties of materials. This paper discusses the multi-scale, multi-code computations and multi-dimensional modelling undertaken to understand the mechanical properties of these materials. Such an approach is envisaged to probe beyond currently possible approaches to become a predictive tool in estimating the mechanical properties and lifetimes of materials.

• 한국항만경제학회지
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• 제22권1호
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• pp.151-173
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• 2006

This paper aims to explore the strategic roles of information and strategic planning capabilities for firms' performance, and to examine the direct and indirect relationships between information capability, strategic planning capability, logistics performance and competitive advantage. The present research adopts resource based theory (RBT) to explore the relationships between a firm's specific capability and its performance and employs structural equation modelling (SEM) in order to test the validation of the measurement models and examine the relationships between construct variables. The current empirical test was conducted using the data collected from logistics managers of 101 Korean electronics companies. The empirical research presents positive influential relationships between (1) information/planning formality capability and strategic planning capability; (2) strategic planning capability and logistics performance; (3) logistics performance and competitive advantage; and (4) competitive advantage and competitive position in the market.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2827-2830
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• 2003

Tele manipulator is distingushed from industrial robot by iterating same specified work. Manipulator operator is included in control loop for controlling the telemanipulator because he decide directly during the work and order controllabily reducing the modelling error of telemanipulator which depend on the PID controller. But position-force control method of bidirectional control impose unsafety of vibiration and Analytic Hierachy Method can stabilize for reducing nonlinear modelling error by expert operator because of transformation empirical control rule to linear model.

• 한국항해항만학회지
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• 제27권2호
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• pp.239-246
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• 2003

해양에 기름이 유출되면 방제작업의 초기단계에서 기름의 이동 및 확산을 차단하기 위하여 오일 붐을 사용하는 것이 일반적이다. 그러나 오일 붐은 유속, 기름의 밀도와 점성, 수심, 기름의 양, 그리고 붐 흘수의 길이 등과 같은 여러 인자들에 의해 그 포획능력이 영향을 받는다. 본 연구에서는 이들 누유인자가 오일 붐의 포획과정에 어떠한 영향을 미치는지를 체계적으로 파악하기 위하여 컴퓨터 모델링을 수행하였다. 모델링을 위하여 CFD(computational fluid dynamics) 프로그램 중에서 가장 널리 알려진 Fluent를 이용하였으며 기존의 실험자료와 비교함으로써 모델링 결과를 검증하였다. 본 연구의 결과는 방제작업 책임자와 오일 붐 설계자에게 유용한 참고자료가 될 것으로 기대된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.19-24
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• 2000

The objective of this study is to develope a computer simulation model and estimate theoretically the transient performance characteristics of heat exchangers in an automotive air-conditioning system. To do that, the mathematical modelling of heat exchangers, such as evaporator and condenser, is presented first of all. For detail calculation, evaporator and condenser are divided into many sub-sections. Each sub-section is an elemental volume for transient modelling. The elemental volume is assumed to consist of three components, refrigerant, tube with fin, and air, and various properties including temperatures of three components are determined step along sub-sections. The properties of refrigerant R134a and air are calculated directly in the program. The heat transfer coefficients and pressure drop in single or two phase are also calculated by suitable empirical correlations. The overall tendencies of the simulation results were agreed well with those of actual situation.