• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.51-58
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• 1992

The primary objective of this study is the development of the system reliability analysis of offshore structures against progressive fatigue failure. Two methods based on the second moment reliability methods are used. One is the improved first order reliability method(IFORM) and the other is the modified probabilistic network evaluation technique(MPNET). Using idealized parallel member models, reliability analyses for progressive fatigue failures are carried out for various cases with multiple members composed of multiple connecting joints per member. Numerical results indicate that the effectiveness of the used methods over the conventional ones (i.e. the FORM and the PNET) increases very significantly as the number of failure modes of the system increases.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.496-503
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• 2015

In order to let a wind generator (WG) support the frequency control of a power system, a conventional inertial control algorithm using the rate of change of frequency (ROCOF) and frequency deviation loops was suggested. The ROCOF loop is prevailing at the initial stage of the disturbance, but the contribution becomes smaller as time goes on. Moreover, its contribution becomes negative after the frequency rebound. This paper proposes an inertial control algorithm of a wind power plant (WPP) using the maximum ROCOF and frequency deviation loops. The proposed algorithm replaces the ROCOF loop in the conventional inertial control algorithm with the maximum ROCOF loop to retain the maximum value of the ROCOF and eliminate the negative effect after the frequency rebound. The algorithm releases more kinetic energy both before and after the frequency rebound and increases the frequency nadir more than the conventional ROCOF and frequency loops. The performance of the algorithm was investigated under various wind conditions in a model system, which includes a doubly-fed induction generator-based WPP using an EMTP-RV simulator. The results indicate that the algorithm can improve the frequency drop for a disturbance by releasing more kinetic energy.

• Journal of The Korea Institute of Healthcare Architecture
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• v.12 no.2
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• pp.41-50
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• 2006

Introduction of new longterm care policy for elderly in Korea would change many aspects of elderly care service facilities. Especially elderly home care services like adult daycare centers will expand drastically after beginning of longterm care insurance. The purpose of this study is to estimate demand of adult daycare centers by comparing with the U.S and Japanese cases. Korean government is expecting that adult daycare centers will expand ten times within 4 years. This estimate is exceeding the facility demand estimate of the U.S. and Japan. The results of population study and expecting growth rate of adult daycare centers in Seoul indicate that more than 300 centers, 4 times of the number of existing centers, are in need based on Seoul elderly population in 2004. To supply these numbers of facilities in short period, more in depth study should be followed. Existing adult daycare facilities' in Seoul were analyzed by their building and management types. Interior spaces of adult daycare centers in Korea are similar to the U.S. and Japan in space arrangements but much smaller in size. In depth study of space programming as well as overall demand survey of adult daycare centers is urgently in need for more realistic expansion of adult daycare centers.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.329-337
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• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1261-1268
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• 2013

This study proposes a voltage and reactive coordinative control strategy with distributed generator (DG) in a distribution power system. The aim is to determine the optimum dispatch schedules for an on-load tap changer (OLTC), distributed generator settings and all shunt capacitor switching on the load and DG generation profile in a day. The proposed method minimizes the real power losses and improves the voltage profile using squared deviations of bus voltages. The results indicate that the proposed method reduces the real losses and voltage fluctuations and improve receiving power factor. This paper proposes coordinated voltage and reactive power control methods that adjust optimal control values of capacitor banks, OLTC, and the AVR of DGs by using a voltage sensitivity factor (VSF) and dynamic programming (DP) with branch-and-bound (B&B) method. To avoid the computational burden, we try to limit the possible states to 24 stages by using a flexible searching space at each stage. Finally, we will show the effectiveness of the proposed method by using operational cost of real power losses and voltage deviation factor as evaluation index for a whole day in a power system with distributed generators.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.108-116
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• 2003

In this paper, the experimental results of condensation heat transfer were reported for the plate and shell heat exchangers(P&SHE) using R-l34a. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-l34a in a vertical P&SHE. Two vertical counter flow channels were formed in the P&SHE by three plates of geometry with a corrugated trapezoid shape of a chevron angle of 45$^{\circ}$. Downflow of the condensing R-l34a in one channel releases heat to the cold up flow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-l34a on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficients are significantly higher. Condensation heat transfer coefficients were increased when the refrigerant mass flux was increased. A rise in the average heat flux causes an slight increase in the hr. Finally, at a higher system pressure the hr is found to be lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.58-67
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• 2000

Electron gun heaters are used to heat a cathode in video(TV) monitors. Major defects of the electron gun heaters include dimensional inaccuracy and pollution with dirty materials. In this paper, to save the labor and time being taken to inspect the heaters, a machine vision system is considered. For the system, a new algorithm is developed to measure the 9 different dimensions of each heater and to detect polluted defects. The algorithm consists of three stages. In the first stage, the center of the heater image is obtained and then its boundary detection is performed. For the efficient boundary detection, a mask called the sum mask is used. In the second stage of the algorithm, a set of fiducial points are determined on the boundary image. Finally, using the fiducial points specified dimensions are measured and the amount of polluted area is computed in the third stage. The performance of the algorithm is evaluated for a set of real specimens. The results indicate that measurements obtained by the algorithm satisfy the tolerance limits fur most of the dimensions and the algorithm detects the polluted defects successfully.

• Toxicological Research
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• v.22 no.2
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• pp.145-151
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• 2006

We have investigated the genotoxicity of STB-HO-BM using in vitro and in vivo system such as Ames reverse mutation test, chromosomal aberration test and micronucleus test. in Ames reverse mutation test, STB-HO-BM treatment at the dose range up to 5,000 ug/plate did not induce mutagenicity in Salmonella typhimurium TA98, TA100, TA102, TA1535, TA 1537 and in Escherichia coli WP2 uvrA with and without metabolic activation. Any significant aberration wasn't observed in chinese hamster lung (CHL) fibroblast cells treated with STB-HO-BM at the concentration of 12.5, 2.5, 5 mg/ml both in the absense and presence of metabolic activation system. In mouse micrnucleus test, no significant increase in the occurrence of micronucleated polychromatic erythrocytes was observed in ICR male mice orally administered with STB-HO-BM at the doses of 0.5, 1.0, 2.0 g/kg. These results indicate that STB-HO-BM has no mutagenic potential under the condition in this study.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1229-1239
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• 2005

Human immunodeficiency virus-like particles (HIVVLPs) with native conformations similar to that of the wild-type virion could be valid candidates for vaccine development. To this end, we used a Semliki Forest Virus (SFV) expression system to produce HIV- VLPs containing high quantities of native envelope proteins. Here, we described a single SFV replicon containing the HIV gagpol and env genes under the control of separate subgenomic promoters. Mature VLPs incorporating the Gag and Env proteins were detected in the supernatant of replicon-expressing cells by Western blot analysis. The HIV-VLPs showed the expected molecular density (1.14-1.18 g/ml) on a $20-60\%$ sucrose gradient; the particles were 100-120 nm in diameter and Env proteins were observed on their surfaces by immunogold electron microscopy. RT-PCR analysis of VLP-associated RNAs in mature HIV-VLPs revealed two SF V-derived RNA species (full-length and subgenomic). Immunization studies in Balb/c mice showed that these HIV-VLPs were capable of inducing both HIV-specific antibodies and cell-mediated immune responses. Taken together, our results indicate that the SFV replicon system is useful for the production of HIV-VLPs, which may be valuable candidates for an HIV vaccine.

• Journal of the Korean Society for information Management
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• v.24 no.1 s.63
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• pp.55-74
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• 2007

The purposes of this study are to examine the influences of appraisal and reward on the activities of knowledge management and to search the strategies for effective appraisal and reward system to activate the knowledge management. The results of covariance structural analyses indicate that appraisal has a significant direct effect on reward and knowledge creation as well as a significant indirect effect on knowledge sharing via reward and knowledge creation. Reward has a significant direct influence on knowledge sharing. Knowledge creation also significantly affects knowledge sharing. Based on the results, the potential implications of effective appraisal and reward system to activate the knowledge management are discussed.