• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.411-418
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• 2000

By calculating the location and size of the relative eddy formed in the rotating impellers with the logarithmic spiral vanes, a new simple but accurate slip factor is analytically derived. The proposed slip factor depends on only one parameter that is a function of the number of vanes and the vane exit angle. Predicted slip factor for various cases are compared with those estimated by a number of previous slip factors as well as a recent theoretical calculation by Visser et al. ( JFM, Vol. 268, pp. 107-141, 1994). It is found that the present slip factor yields almost similar results to Wiesner's which has been empirically formulated based on the theoretical calculation of Busemann.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.433-438
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• 1998

Design lateral strength calculated by current seismic design code is prescribed to be much lower than the force level required for a structure to respond elastically during design level earthquake ground motion. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factor known as "response modification factor, R". This factor accounts for the inherent ductility, overstrength, redundancy, and damping of a structural system. This study considers ductility and overstrength of the wall-type structure for investigating R factor. This means that R factor is determined from the product of "ductility-based R factor($R_$\mu$$) and overstrength factor($R_s$). $R_$\mu$$ factor is calibrated to attain the targer ductility ratio (system ductility capacity) and produced in the from of $R_$\mu$$ spectra considering the influence of target ductility, natural period, and hysteretic model. On the other hand, $R_s$ is more difficult to quantify, since it depends on both material and system-dependent uncertain parameters. In this study Rs factor was determined from the result of push-over analysis.-over analysis.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1507-1513
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• 1999

This paper describes simulation and experimental results to analyze the dynamic characteristics of STATCOM, which is connected to the ac system for compensation the power factor and improving the voltage stability. The simulation and experimental results confirm that the scaled model for STATCOM can properly compesate the power factor of the load and regulate the bus voltage at the common connection point.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.619-621
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• 1996

This paper presents the study on the development of the power factor correction convener with ZVT Boost converter, which is better than the conventional PWM Boost converter to increase the switching frequency for high density and lower stress of switch. A simple DC and small signal model for the power factor correction converter with constant switching frequency is derived. The guide line for design of controller is summarized.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.229-235
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• 1993

Thermal history and thermal stress of alumina specimen, which occured from thermal shock process, were calculated by finite difference method. Stress intensity factor and crack growth in cyclic thermal fatigue were calculated from single thermal shock temperature history and thermal stress. Cyclic thermal life were estimated by bending strength after cyclic thermal shock under critical thermal shock temperature. Calculated stress intensity factor was compared with real experimental thermal fatigue life of specimen. Fatigue life until critical stress intensity factor and real experimental result were comparable.

• Communications for Statistical Applications and Methods
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• v.23 no.6
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• pp.587-592
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• 2016

It is a long-standing issue to correctly determine the number of long-run relationships among time series processes. We revisit nonparametric test for cointegration rank and propose bootstrap refinements. Consistent with model-free nature of the tests, we make use of Cholesky factor bootstrap methods, which require weak conditions for data generating processes. Simulation studies show that the original Breitung's test have difficulty in obtaining the correct size due to dependence in cointegrated errors. Our proposed bootstrapped tests considerably mitigate size distortions and represent a complementary approach to other bootstrap refinements, including sieve methods.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.231-238
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• 2003

The overstrength factor and the ductility factor are the two important factors that determines response modification factors used in current seismic codes. The objective of this paper is to obtain the overstrength and ductility factors of special concentric braced frames. For this purpose pushover analysis is performed with model structures until the maximum inter-story drift reaches 2.5% of story height. According to the analysis results, the overstrength factors increase as the height of structures decreases and the span length increases. Ductility factors for mid-story structures turns out to be higher than the other structures and span length does not contribute much to ductility factors.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.67-74
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• 1999

Self-Boring Pressuremeter Test(SBPT) is known to be the most effective in-situ test method which can reliably determine consolidation characteristics as well as deformation modules and untrained shear strength. In order to derive the coefficient of consolidation using SBPT results it is necessary to obtain the dissipation behavior from the pore pressure change with time during constant radial strain(generally 10%) and to derive the reliable time factor(Τ) from the analytical method which considers the real in-situ conditions. As previous studies on time factor are based on the assumptions of plane strain condition that the membrane of SBP is infinite, of untrained condition during the expansion of the probe and of elastic soil behavior during consolidation, these analyses can't consider the real boundary conditions and the real soil behaviour. In this study, consolidation analysis similar to real in-situ conditions including test procedure is conducted using finite element program which employs MCC model and Biot theory. Time factor considering the effects of finite membrane length, the total pressure change during consolidation and partial drainage is proposed and compared with previous results.

• Culinary science and hospitality research
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• v.8 no.3
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• pp.39-56
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• 2002

This is the study to stir up importance in bakery and to present evaluation of menu goods in barkery of tourist hotels. In order to achieve the purpose of this paper, it is gone ahead of the literature review including the previous research on the manu goods evaluation of tourist hotels. The major field research is to build a frame of the paper and present the model to release my humble theory. The limitation of the study was to make much of literature basis due to insufficient previous research on the issue. This is an unprecedented study on bakery department in tourist hotels in Korea thus no research model was unavailable for cross reference or comparative research. The evaluation of bakery menu good is directly related to the satisfaction of tourist hotels bakery consumers and we need a substantial managerial development method of bakery menu goods. This study has two goals in line with the purpose of investigation, that is to say, by understanding vital statistics of consumer and influence factor were created, and finally the factors and consumers and professional worker identified. The study would be framed into 5 parts like introduction, literature review, inquiry a plan and analysis method, consequence and discussion & conclusion. After the exploitative research, the study was approached to make findings through the questionnaires designed to find the relationship factor between consumer's evaluation and professional worker's evaluation of bakery menu goods in tourist hotels.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.1032-1041
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• 2005

This study is performed to investigate the heat transfer characteristics of heat exchanger according to the arrangement of fins as well as fin configuration by using the four times enlarged model. Friction factor, Colburn j factor and goodness factors are compared to each other to estimate performance of each case for 4 different kinds of fins, which are plain, single side slit, double side slit and louver fin. Results show that heat transfer would be altered by fin arrangement and that friction loss is more affected by fin configurations than by the fin arrangements. In particular, heat transfer depends more on the shape of front row than that of rear row. The heat transfer rate of combined fin arrangement increases a lot more under the same pressure drop than that of conventional fin arrangement. This indicates that the heat exchanger of higher efficiency would be designed by the proper combination of fins, of different shapes.