• Steel and Composite Structures
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• v.4 no.1
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• pp.9-21
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• 2004

The present study aims at the reliability analysis of steel towers against the limit state of deflection. For this purpose tip deflection of the tower has been obtained after carrying out the dynamic analysis of the tower using modal method. This tip deflection is employed for subsequent reliability analysis. A limit state function based on serviceability criterion of deflection is derived in terms of random variables. A complete procedure of reliability computation is then presented. To study the influence of various random variables on tower reliability, sensitivity analysis has been carried out. Design points, important for probabilistic design of towers, are also located on the failure surface. Some parametric studies have also been included to obtain the results of academic and field interest.

• Structural Engineering and Mechanics
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• v.55 no.5
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• pp.1055-1086
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• 2015

The dynamic response of two-dimensional unbounded domain on the rigid bedrock in the time domain is numerically obtained. It is realized by the modified scaled boundary finite element method (SBFEM) in which the original scaling center is replaced by a scaling line. The formulation bases on expanding dynamic stiffness by using the continued fraction approach. The solution converges rapidly over the whole time range along with the order of the continued fraction increases. In addition, the method is suitable for large scale systems. The numerical method is employed which is a combination of the time domain SBFEM for far field and the finite element method used for near field. By using the continued fraction solution and introducing auxiliary variables, the equation of motion of unbounded domain is built. Applying the spectral shifting technique, the virtual modes of motion equation are eliminated. Standard procedure in structural dynamic is directly applicable for time domain problem. Since the coefficient matrixes of equation are banded and symmetric, the equation can be solved efficiently by using the direct time domain integration method. Numerical examples demonstrate the increased robustness, accuracy and superiority of the proposed method. The suitability of proposed method for time domain simulations of complex systems is also demonstrated.

• Journal of Information Technology Services
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• v.11 no.2
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• pp.147-167
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• 2012

In this paper, we attempted to theorize the multi-faceted impacts of smart work on economic activities. In this vein, we adopted socio-economic perspective which includes individual, firm, and social support aspects, and explored the variables related to the quality of life among them. First, smart work patterns are categorized as telework, mobile office, teleconferencing, and social collaboration. And relevant variables are extracted with reference to industrial cases and relevant literatures which investigated economic impacts of digital convergence. Next, with the data collected from experts, following delphi method, validation of variables and explorations of significant factors affecting quality of life were conducted by adopting stepwise regression method. The distinguishing traits of this research are two-folds. The one is the investigation of social support and quality of life aspects of smart work, which has been relatively limited in the digital convergence research field. The other is the comparative analysis of smart work advantages by distinguishing individual and firm aspects separately. The result offers useful insights for socio-economic perspective researches on digital convergence application area.

• Journal of Engineering Education Research
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• v.23 no.2
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• pp.31-42
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• 2020

This study aims to analyze the research trends of female engineering students focused on domestic research and to suggest implications for future researches. For this purpose, 67 domestic researches (academic articles & graduate theses) which were published since 1996 were collected using the academic research information service and the National Assembly Library search service. All of these 67 researches have been reviewed and classified according to analytical criteria such as publication year, research method, journal's research field and research subjects. Our findings show that firstly, related research on female engineering students has been growing since 1996. Secondly, there were more researches of both academic journals and graduate theses, using quantitative method compared to those with the other research methods. Thirdly, the research themes could be classified as follows: gender-awareness, female engineering students'(hereafter, FES) psychological variables, customized education for FES, career related variables, FES's properties and counselling for them. Fourth, regarding the result of analysis on the research topic, 41.79% of the researches were related to FES's 'career' related factors as well as diverse correlates. Based on these findings, it is necessary to continue studying on FES using various research methods as well as adopting different research perspectives. Also, practical and educational treatments for FES are required with particular attention to their individual variables.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10c
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• pp.103-122
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• 2001

For prediction of ground movement per the excavation step, observational results of ground movement during the construction was very different with prediction during the analysis of design. step because of the uncertainty of the numerical analysis modelling, the soil parameter, and the condition of a construction field, etc. however accuratly numerical analysis method was applied. Therefore, the management system through the construction field measurement should be achieved for grasping the situation during the excavation. Until present, the measurement system restricted by ‘Absolute Value Management system’only analyzing the stability of present step was executed. So, it was difficult situation to expect the prediction of ground movement for the next excavation step. In this situation, it was developed that ‘The Management system TOMAS-EXCAV’ consisted of ‘Absolute value management system’ analyzing the stability of present step and ‘Prediction management system’ expecting the ground movement of next excavation step and analyzing the stability of next excavation step by‘Back Analysis’. TOMAS-EXCAV could be applied to all uncertainty of earth retaining structures analysis by connecting ‘Forward analysis program’ and ‘Back analysis program’ and optimizing the main design variables using SQP-MMFD optimization method through measurement results. The application of TOMAS-EXCAV was confirmed that verifed the three earth retaing construction field by back analysis.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1804-1806
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• 1996

For the rather complicated and time-consuming three-dimensional electric field calculation in the vicinity of substations, this paper proposes a numerical calculation method based on charge simulation method(CSM). In order to represent non-uniform charge distribution on an electrode better, it is subdivided into small segments with linear charge density. Non-uniform arrangement of subdivided segments makes it possible to obtain high accuracy with a small number of variables. As for the arrangement of subdivided segments, effective formulars were derived from multiple regression analysis of many simulations. These formulars make the arrangement of segments fast and effective. The proposed method is applied to the electric field calculation around the 345kV Sinmasan Substation busbars and the distribution of calculated electric fields is compared with that of the measured electric fields.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.127-127
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• 2010

This study describes the optimal design of shield to improve the insulation performance of vacuum interrupter(VI). Axi-symmetric finite element routine including floating boundary condition for shields was applied to analyze electric potential and field distribution in VI. A ($\mu-\lambda$) Evolution Strategy(ES) is employed as optimization method. Three design variables of shield are selected for minimizing the maximum electric field strength in VI. Finally, optimal solution for shield is obtained and compared with the result of the prototype.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.826-834
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• 1994

The purpose of this study is to identify torque characteristics in capacitor type electric motors and to illustrate the effects of several design parameters on the fluctuating components of the motor torque. To do this, two revolving field theory and stationary reference frame theory were applied to derive governing equations for the torque generated by motor. For simulation studies, parameters of the motor components were measured under the conditions of no loading and locking. Based on these, effects of several design variables on the torque characteristics were analyzed and compared with the actual measurements, which were estimated indirectly by measuring the stator voltage and current. Then, some illustrative improvements in design are suggested by taking Taguchi method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.939-944
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• 2004

The numerical methods including the performance analysis and the noise prediction of the centrifugal compressor impeller are coupled with the optimization design skill, which consists of response surface method, statistical approach, and genetic algorithm. The flow-field Inside of a centrifugal compressor is obtained numerically by solving Wavier-Stokes equations. and then the propagating noise is estimated from the distributed surface pressure by using Ffowcs Williams-Hawkings formulation. The quadratic response surface model with D-optimal 3-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor. The statistical analysis shows that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with high performance and low far-field noise level. The influences of selected design variables, objective functions, and constraints on the impeller performance and the impeller noise are also examined as a result of the optimization process.

• International Journal of Reliability and Applications
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• v.4 no.2
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• pp.79-95
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• 2003

Manufacturers collect and analyze field reliability data to enhance the quality and reliability of their products and to improve customer satisfaction. To reduce the data collecting and maintenance costs, the amount of data maintained for evaluating product quality and reliability should be minimized. With this in mind, some industrial companies assemble warranty databases by gathering data from different sources for a particular time period. This “marginal count failure data” does not provide (i) the number of failures by when the product entered service, (ii) the number of failures by product age, or (iii) information about the effects of the operating season or environment. This article describes a method for estimating age-based claim rates from marginal count failure data. It uses covariates to identify variations in claims relative to variables such as manufacturing characteristics, time of manufacture, operating season or environment. A Poisson model is presented, and the method is illustrated using warranty claims data for two electrical products.