• Smart Structures and Systems
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• 제3권4호
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• pp.423-437
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• 2007

The empirical mode decomposition (EMD) method is well-known for its ability to decompose a multi-component signal into a set of intrinsic mode functions (IMFs). The method uses a sifting process in which local extrema of a signal are identified and followed by a spline fitting approximation for decomposition. This method provides an effective and robust approach for decomposing nonlinear and non-stationary signals. On the other hand, the IMF components do not automatically guarantee a well-defined physical meaning hence it is necessary to validate the IMF components carefully prior to any further processing and interpretation. In this paper, an attempt to use the EMD method to identify properties of nonlinear elastic multi-degree-of-freedom structures is explored. It is first shown that the IMF components of the displacement and velocity responses of a nonlinear elastic structure are numerically close to the nonlinear normal mode (NNM) responses obtained from two-dimensional invariant manifolds. The IMF components can then be used in the context of the NNM method to estimate the properties of the nonlinear elastic structure. A two-degree-of-freedom shear-beam building model is used as an example to illustrate the proposed technique. Numerical results show that combining the EMD and the NNM method provides a possible means for obtaining nonlinear properties in a structure.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1043-1046
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• 2013

Prediction of physicochemical properties of organic molecules is an important process in chemistry and chemical engineering. The MSEP approach developed in our lab calculates the molecular surface electrostatic potential (ESP) on van der Waals (vdW) surfaces of molecules. This approach includes geometry optimization and frequency calculation using hybrid density functional theory, B3LYP, at the 6-31G(d) basis set to find minima on the potential energy surface, and is known to give satisfactory QSPR results for various properties of organic molecules. However, this MSEP method is not applicable to screen large database because geometry optimization and frequency calculation require considerable computing time. To develop a fast but yet reliable approach, we have re-examined our previous work on organic molecules using two semi-empirical methods, AM1 and PM3. This new approach can be an efficient protocol in designing new molecules with improved properties.

• 한국지능시스템학회논문지
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• 제6권2호
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• pp.52-56
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• 1996

신경망을 학습하는데 있어서, 망의 학습속도는 학습율에 의해 크게 좌우된다. 그러나 대부분의 정적인 학습율 선택 방법들은 몇몇 결정적인 방법들을 제외하곤 경험적인 방식에 의존해 왔다. 경험적인 방식을 사용하여 좋은 학습율을 찾아내는 것은 배우 지류하고 어려운 일이다. 또한 결정적인 방법들은 학습율의 질을 보장하지는 못한다. 본 논문에서 우리는 새로운 학습율 선택 방법을 제안한다. 우리의 방법은 진화 프로그래밍기법을 사용하여 통계적인 방식으로 접근함으로써 좋은 학습율을 찾을 수 있다. 모의 실험을 통하여 우리의 방식이 경험적인 방식들이나 결정적인 방식보다 우수함을 보였다.

• 대한안전경영과학회지
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• 제19권1호
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• pp.219-226
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• 2017

This study investigates application cases of facility management system model for enhancing facility productivity of industry filed around medium and small facility processing companies and finds the inefficiency of the existing management model. Following items are researched to seek out methods and measures to maximize facility productivity through empirical analysis by exploring and establishing a new management model. First, the empirical analysis, it is found that the overall equipment efficiency index used for facility productivity management in the companies has a difficulty being used as the index for it in actual medium-small processing companies. Second, a new facility management system model applying standard cycle time is suggested among facility management index system to measure facility productivity. Third, the empirical analysis is used to verify that developed facility management system model is a useful method to manage the facility productivity by applying the model to actual medium-small processing companies. Finally, it is necessary to implement comparison analysis on whether actual productivity enhancement induces a distinctly different result by using a new facility management index system model to be inhibited in this study.

• Steel and Composite Structures
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• 제42권2호
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• pp.221-241
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• 2022

Perfobond rib connectors are widely used in composite structures to achieve the composite action between the steel and the concrete, and empirical expressions for their strength and secant stiffness have been obtained by numerical simulations or push-out tests. Since perfobond connections are generally in an elastic state in the service process and the structural analysis are always based on the elastic properties of the members, the secant stiffness is not applicable for the normal structural analysis. However, the tangent stiffness of perfobond connections has not been introduced in previous studies. Moreover, the perfobond connections are bearing tension and shear force simultaneously when the composite beams subjected to torque or local loads, but the current studies fail to arrive at the elastic stiffness considering the combined effects. To resolve these discrepancies, this paper investigates the initial elastic stiffness of perfobond connections under combined forces. The calculation method for the elastic stiffness of perfobond connections is analyzed, and the contributions of the perfobond rib, the perforating rebar and the concrete dowel are investigated. A finite element method was verified with a high value of correlation for the test results. Afterwards, parametric studies are carried out using the reliable finite element analysis to explore the trends of several factors. Empirical equations for predicting the initial elastic stiffness of perfobond connections are proposed by the numerical regression of the data extracted by parametric studies. The equations agree well with finite element analysis and test results, which indicates that the proposed empirical equations reflect a high accuracy for predicting the initial elastic stiffness of perfobond connections.

• Steel and Composite Structures
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• 제44권4호
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• pp.545-555
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• 2022

Empirical relationships that capture the nonlinear behavior of headed steel shear stud anchors have been derived from standard push out tests, where the specimens are comprised of large wide flanged steel sections attached to flat concrete slabs via the anchors. However, many composite systems used in practice utilize much smaller steel members and/or steel decking as part of the slab system. Composite open web steel joist systems generally include both of these elements and consequently the nonlinear performance ofthe anchor is not accurately represented by existing models. In this paper, a new empirical relation is presented for open web steel joist systems based on experimental results from a modified push out test that more realistically represent a composite open web steel joist system. The methodology for obtaining the proposed nonlinear function where the response of the system is characterized by two parameters(α and β) is presented. The two-step process for obtaining the two parameters is described and the empirical relation is calibrated with the experimental data. In comparison with existing expressions, the new proposal herein more accurately predicts the high initialstiffness of the system and overall nonlinear system performance.

• The Journal of Asian Finance, Economics and Business
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• 제8권4호
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• pp.777-786
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• 2021

The main purposes of this study are (1) to investigate the extent and level of corporate social responsibility (CSR) practices of the hotel in Thailand, (2) to test the different level of CSR practices of the hotel between CSR-in-process and CSR-after-process, and (3) to examine the effect of CSR practices on hotel's performance measured by balanced scorecard (BSC). This study employs survey data collected from 402 owners and executives of hotels in Thailand. Descriptive analysis, paired sample t-test, correlation matrix, and multiple regression were used to analyze the data from the mailed questionnaire. The results show that both CSR-in-process and CSR-after-process practices of hotels were at a high level. However, the level of CSR-in-process practice of hotels was significantly higher than CSR-after-process practice. Moreover, the study found the positive effect of both CSR-in-process and CSR-after-process practices on hotel performance measured by BSC. The results of sensitivity analysis also show the positive effect of CSR-in-process and CSR-after-process practices on each of all six perspectives of BSC. The findings of this study can point to the reasonable reason why hotels should implement CSR practices into their business strategies. In addition, the study demonstrates that stakeholder theory can explain the effect of CSR practices on corporate performance.

• 복식
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• 제52권4호
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• pp.141-154
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• 2002

The purpose of this study was to define 'sponsorship' as a kind of advertising tool, and to describe its effects on consumer brand attitude and actual purchase behavior. From previous research results, clothing sponsorship was defined as 'indirect advertisement', which has common ad traits as well as the uncommon ad traits, such as indirectness, emotional affinity, and symbolism. Results from empirical research using 1,227 data collected in Seoul and Kyounggi Areas were as follows ; (1) Television drama clothing sponsorship was proved to have effects on brand image, emotional & rational brand attitudes, decision making process, and actual purchase behavior. (2) Each of drama clothing sponsorship factors, such as 'drama', 'role', and 'actress', had different effects on brand memory and attitudes. (3) Consumer decision making process initiated by drama clothing sponsorship followed two different processes, which were called 'rational' and 'heuristic'. The rational process followed every steps of EKB model, which explained consumer's rational shopping, but heuristic model was closer to emotional and impulsive shopping.

• 한국정밀공학회지
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• 제19권11호
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• pp.83-88
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• 2002

In order to predict the moldability of a injection molded part, a simulation of filling is needed. Short shot is one of the most frequent troubles encountered during injection molding process. The adjustment of process conditions is the most economic way to troubleshoot the problematic short shot in cost and time since the mold doesn't need to be modified at all. But it is difficult to adjust the process conditions appropriately in no times since it requires an empirical knowledge of injection molding. In this paper, the intelligent CAE system synergistically combines fuzzy-neural network (FNN) for heuristic knowledge with CAE programs for analytical knowledge. To evaluate the intelligent algorithms, a cellular phone flip has been chosen as a finite element model and filling analyses have been performed with a commercial CAE software. As the results, the intelligent CAE system drastically reduces the troubleshooting time of short shot in comparison with the experts' conventional methodology which is similar to the golden section search algorithm.

• 산업공학
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• 제12권3호
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• pp.406-413
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• 1999

In this study, we analyzed the innovation pattern of product and process between Korean, Japanese and German chemical firms. To do this study, a mail survey was chosen as the data collection method. For the empirical study, 36 Korean, 35 Japanese and 50 German chemical firms were analyzed. The major results are indicated as follows: (1) The Korean and Japanese firms have focused more on the process innovation, while the German firm have focused more on the product innovation. (2) The Korean and Japanese firms have oriented more to cost saving, while the German firms have oriented more market share. Based on these findings, the Korean firms have no purse simultaneously product and process innovation for strengthening of international. competitiveness, but the direction of the innovation patterns depends on the situations of the nation, industry and company.