• Journal of ILASS-Korea
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• v.25 no.3
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• pp.119-125
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• 2020

In this paper, we used Helmholtz solver based on 3D finite element method to quantitatively analyze the effects of change of gain, time delay and time delay spread, which are the main variables of flame transfer function, on combustion instability in gas turbine combustor. The effects of the variable of flame transfer function on the frequency and growth rate, which are the main results of combustion instability, were analyzed by applying the conventional heat release fluctuation model and modified one considering the time spread. The analysis results showed that the change of gain and time delay in the same resonance mode affected the frequency of the given resonance modes as well as growth rate of the feedback instability, however, the effect of time delay spread was not relatively remarkable, compared with the dominant effect of time delay.

• Korean Journal of Child Studies
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• v.30 no.2
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• pp.43-55
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• 2009

This study investigated trajectories of change in the career maturity of elementary school students and of attachment to parents and academic achievement as predictors of change. The 2844 participants were 1524 boys and 1320 girls in the Korea Youth Panel Survey. They were fourth graders in 2004 and became seventh graders in 2007. Latent growth curve modeling indicated that : (1) Trajectories of change in career maturity from fourth grade to seventh grade modeled quadratic growth. (2) Variance of career maturity in initial levels, linear slope and quadratic slope indicated individual differences intrajectories of change in career maturity. (3) Attachment to parents influenced initial levels of career maturity academic achievement influenced both initial levels and linear slope of career maturity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.120-126
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• 2003

Finite element analysis model is suggested for analysis of milli-forming process, which forms milli-size products. Since the size of workpiece in a milli-forming process ranges from a few hundred micrometers to a few millimeters, microstructural changes such as the growth of micro-voids and the development of preferred orientation in a grain become crucial factors for the success of milli-forming. This analysis model incorporates anisotropy from deformation torture and deterioration of mechanical properties due to the growth of micro-voids. Applications of the proposed modeling to milli-forming are given and the results are carefully examined to understand the deformation characteristics such as texture development and damage evolution during extrusion/drawing of a milli-bar.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1337-1343
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• 2004

Shape optimization was performed to obtain a precise shape of cutouts including the internal shape of cutouts in a laminated composite plate by three dimensional modeling using solid element. Volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. It makes Tsai-Hill failure index at each element uniform in laminated composites under the predetermined volume a designer requires. Shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study; (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure indices of the optimal shapes were remarkably reduced comparing with those of the initial shapes.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.529-547
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• 2011

This paper presents the global-local finite cover method (GL-FCM) that is capable of analyzing structures involving local heterogeneities and propagating cracks. The suggested method is composed of two techniques. One of them is the FCM, which is one of the PU-based generalized finite element methods, for the analysis of local cohesive crack growth. The mechanical behavior evaluated in local heterogeneous structures by the FCM is transferred to the overall (global) structure by the so-called mortar method. The other is a method of mesh superposition for hierarchical modeling, which enables us to evaluate the average stiffness by the analysis of local heterogeneous structures not subjected to crack propagation. Several numerical experiments are conducted to validate the accuracy of the proposed method. The capability and applicability of the proposed method is demonstrated in an illustrative numerical example, in which we predict the mechanical deterioration of a reinforced concrete (RC) structure, whose local regions are subjected to propagating cracks induced by reinforcement corrosion.

• Knowledge Management Research
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• v.12 no.5
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• pp.71-87
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• 2011

This study focuses on influencing factors of TAM on personality, subjective norm and then examines the relationship between influencing factors such as KMS usage and system performance. The survey was collected from KMS users by e-mail and on-line questionnaire. Finally, 206 questionnaires were chosen for the analysis of data. It was analyzed by SPSS and AMOS for the frequency analysis, reliability analysis, CFA(Confirmatory Factor Analysis) and SEM(Structural Equation Modeling). The results were as follows. First, subjective norm is found to be especially important to KMS usage. Second, Extraversion positively moderated the relationship between subjective norm and perceived usefulness. Third, KMS usage is significant to personal performance such as knowledge growth, decision making and the ability of problem solving. This study proposed that the usage of Knowledge Management System positively contributes to the improvement of personal performance.

• Microbiology and Biotechnology Letters
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• v.17 no.6
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• pp.619-623
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• 1989

The effects of temperature on yeast growth and ethanol production were investigated in batch cultures. The maximum specific growth rate of yeast was obtained at 36$^{\circ}C$ and the maximum specific production rate of ethanol was obtained at 33$^{\circ}C$. A mathematical model was employed to describe the temperature effects in ethanol fermentation and the parameters in the model were expressed as a function of temperature. Optimum temperature control strategy, from the simulation result, consists of starting the fermentation at high temperature and lowering the temperature as the fermentation proceeds.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.53-64
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• 2005

Rapid growth of digitalization in telecommunication and broadcasting and remarkable enhancement in broadband and high speed transmission capability of media raised a problem of integrating communication and broadcasting. In order to implement this, the government has selected construction of Broadband Convergence Network (BcN) as a main new growth engine of the country. The BcN will be realized based on FTTH and Broadband Home Network (BHN) will be implemented through this solution. Transfer rate and bandwidth required for the BcN to be constructed aiming at integration of communication and broadcasting will be specified and the performance of basic transmission media, the plastic optical fiber, will be discussed in order to present its appropriateness.

• Computers and Concrete
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• v.8 no.3
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• pp.327-341
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• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.581-584
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• 2003

Most modeling about dynamic behavior of Antiferroelectric Liquid Crystal (AFLC) is limited to the hysteric characteristics of AFLC cells or thresholdless switching of frustrated AFLC cells. In this paper, domain growth of AFLC cells is modeled with extended bilayer model. When driving pulses that consist of a selection voltage, a bias voltage, and a reset voltage are applied to the AFLC cell, its dynamic behavior is simulated.