• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.192-192
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• 2008

As the lifetime of nuclear power plants (NPPs) reaches design life, the probability for fatal accidents increases. Most of accidents are known to be caused by degradation of mechanical components. Pressure tubes are the most important components in CANDU reactor. They are subjected to various aging mechanisms such as delayed hydride cracking (DHC), irradiation and corrosion, etc. Therefore, the integrity of pressure tube is key concern in CANDU reactor. Up to recently, conventional deterministic approaches have been utilized to evaluate the integrity of components. However, there are many uncertainties to prevent a rational evaluation. The objective of this paper is to assess the failure probability of pressure tube in CANDU. To do this, probability fracture mechanics (PFM) analysis based on the Genetic Algorithm (GA) is performed. For the verification of the analysis, a comparison of the PFM analysis using a commercial code and mathematical method is carried out.

• 한국정밀공학회지
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• 제18권10호
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• pp.154-160
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• 2001

For major structural components periodic inspections and integrity assessments are needed for the safety. However, many flaws are undetectable because sampling inspection is carried out during in-service inspection. Probabilistic integrity assessment is applied to take into consideration of uncertainty and variance of input parameters arise due to material properties and undetectable cracks. This paper describes a Probabilistic Fracture Mechanics(PFM) analysis based on the Monte Carlo(MC) algorithms. Taking a number of sampling data of probabilistic variables such as fracture toughness value, crack depth and aspect ratio of an initial surface crack, a MC simulation of failure judgement of samples is performed. for the verification of this analysis, a comparison study of the PFM analysis using a commercial code, mathematical method is carried out and a good agreement was observed between those results.

• 한국항공우주학회지
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• 제39권6호
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• pp.517-525
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• 2011

차분 진동형 가속도계는 입력 가속도에 따른 공진 주파수의 변화를 감지하는 공진형 센서이다. 이 때 가속도계 전기적 동역학의 수학적 모델링 및 구조 특성의 실험적 검증이 정밀한 제어기 및 높은 양질계수를 가지는 구조 설계에 앞서 필요하게 된다. 본 논문에서는 차분 진동형 가속도계의 공진자, 전극 모듈 및 전치증폭기 등의 전기적 모델링을 제시한다. 이러한 모델링 기법은 공진 주파수, 유효 질량, 유효 강성, 양질 계수 등을 측정함으로써 실험적으로 검증된다. 또한 모델링을 통해 예측된 진폭과 측정된 전치증폭기 출력의 직접적인 비교는 본 연구의 유효성을 보여준다.

• 센서학회지
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• 제26권4호
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• pp.274-279
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• 2017

LCD(Liquid Crystal Display) panel cutting problem is a sort of two dimensional cutting stock problem. A cutting stock problem is problem that it minimizes the loss of the stock when a stock is cut into various parts. In the most research of the two dimensional cutting stock problem, it is supposed that the relative angle of a stock and parts is not important. Usually the angle is regarded as horizontal or perpendicular. In the manufacturing of polarizing film of LCD, the relative angle should be maintained at some specific angle because of the physical and/or chemical characteristics of raw material. We propose a mathematical model for solving this problem, a two-dimensional non-Guillotine cutting stock problem that is restricted by an arranged angle. Some example problems are solved by the C++ program using ILOG CPLEX classes. We could get the verification and validation of the suggested model based on the solutions.

• Journal of Power Electronics
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• 제16권6호
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• pp.2221-2230
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• 2016

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

• Advances in nano research
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• 제7권6호
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• pp.419-429
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• 2019

The effect of an increasing percentage of nanofiller (glass cenosphere) with Glass/Epoxy hybrid composite curved panels modeled mathematically using the multiscale concept and subsequent numerical eigenvalues of different geometrical configurations (cylindrical, spherical, elliptical, hyperboloid and flat) predicted in this research article. The numerical model of Glass/Epoxy/Cenosphere is derived using the higher-order polynomial type of kinematic theory in association with isoparametric finite element technique. The multiscale mathematical model utilized for the customized computer code for the evaluation of the frequency data. The numerical model validation and consistency verified with experimental frequency data and convergence test including the experimental elastic properties. The experimental frequencies of the multiscale nano filler-reinforced composite are recorded through the impact hammer frequency test rig including CDAQ-9178 (National Instruments) and LABVIEW virtual programming. Finally, the nano cenosphere filler percentage and different design associated geometrical parameters on the natural frequency data of hybrid composite structural configurations are illustrated through a series of numerical examples.

• Structural Engineering and Mechanics
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• 제71권5호
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• pp.553-562
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• 2019

This paper presents the results of a study into the dynamic behaviour of a support structure of a mobile elevating work platform. The vibrations of the mechanical system of the observed structure are examined analytically, numerically, and experimentally. Within the analytical examination, a simple mathematical model is developed to describe free and forced vibrations. The dynamic analysis of the mechanical system is conducted using a discrete dynamic model with a reduced number of vibrational degrees of freedom. On the basis of the expression for the system energy, and by applying Lagrange's equations of the second kind, differential equations are derived for system vibrations, frequencies are determined, and the laws of forced platform vibration are established. At the same time, a nonlinear FEM model is developed and the laws of free and forced vibration are determined. The experimental and numerical part of the study deal with the examination of the real structure in extreme conditions, taking into account: the lowest eigenfrequency, forced actions that could endanger the general stability, the maximal amplitudes, and the acceleration of the work platform. The obtained analytical and numerical results are compared with the experiments. The experimental verification points to the adverse behaviour of the platform in excitation cases - swaying. In such a situation, even a relatively small physical force can lead to unacceptably high amplitudes of displacement and acceleration - exceeding the usual work values.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.657-666
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• 2020

A reliable and cost-effective technique for the development of corrosion damage model is introduced to predict nonlinear time-dependent corrosion wastage of steel structures. A detailed explanation on how to propose a generalised mathematical formulation of the corrosion model is investigated in this paper (Part I), and verification and application of the developed method are covered in the following paper (Part II) by adopting corrosion data of a ship's ballast tank structure. In this study, probabilistic approaches including statistical analysis were applied to select the best fit probability density function (PDF) for the measured corrosion data. The sub-parameters of selected PDF, e.g., the largest extreme value distribution consisting of scale, and shape parameters, can be formulated as a function of time using curve fitting method. The proposed technique to formulate the refined time-dependent corrosion wastage model (TDCWM) will be useful for engineers as it provides an easy and accurate prediction of the 1) starting time of corrosion, 2) remaining life of the structure, and 3) nonlinear corrosion damage amount over time. In addition, the obtained outcome can be utilised for the development of simplified engineering software shown in Appendix B.

• Advances in concrete construction
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• 제11권1호
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• pp.1-9
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• 2021

This article discusses the issue of optimizing controller design issues, in which the artificial intelligence (AI) evolutionary bat (EB) optimization algorithm is combined with the fuzzy controller in the practical application of the building. The controller of the system design includes different sub-parts such as system initial condition parameters, EB optimal algorithm, fuzzy controller, stability analysis and sensor actuator. The advantage of the design is that for continuous systems with polytypic uncertainties, the integrated H2/H∞ robust output strategy with modified criterion is derived by asymptotically adjusting design parameters. Numerical verification of the time domain and the frequency domain shows that the novel system design provides precise prediction and control of the structural displacement response, which is necessary for the active control structure in the fuzzy model. Due to genetic algorithm (GA), we use a hierarchical conditions of the Hurwitz matrix test technique and the limits of average performance, Hierarchical Fitness Function Structure (HFFS). The dynamic fuzzy controller proposed in this paper is used to find the optimal control force required for active nonlinear control of building structures. This method has achieved successful results in closed system design from the example.

• 대한토목학회논문집
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• 제26권6C호
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• pp.421-429
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• 2006

본 연구에서는 국내 연약지반의 신뢰성 있는 강성지수 추정을 위하여 인공신경망기법을 적용하였다. 실내시험을 통한 물성치결과들을 통하여 인공신경망을 위한 입력자료를 확보한 뒤 이를 이용하여 모델을 학습시킨 후 모델검증을 실시하였다. 개발된 모델의 검증결과 측정값과 예측값의 상관관계가 매우 높게 나타났으며 이를 통하여 수학적 모델 수립이 곤란한 국내 연약지반의 신뢰성 있는 강성지수 추정의 전반적인 고찰의 기초를 확립하였다.