• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.1-8
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• 2009

Photobioreactor (PBR) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2, heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

• Journal of Korea Port Economic Association
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• v.20 no.2
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• pp.169-185
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• 2004

It is an urgent problem that Korea logistics enteprises' expansion of advance into China market and the logistics network establishment between Korea and China to back up the former are to be solved. Accordingly, the purpose of this study is to deduce the subjects to establish the logistics network between Korea and China, and to evaluate the priority order. The results of this research are as follows: First, we conducted face-to-face interviews on the advisery group in China and Korean enterprises which advanced into China, and drew out 6 promoting subjects to build the logistics network between the two. Second, the AHP model was adopted, which is a multi-criteria?multi-hierarchical decision making method, to draw out the weight and priority order of the deduced 6 promoting items. Third, the resultant priority order of the promoting subjects is as follows: No.1 - to establish the distribution & logistics support center by region(0.3900); No.2 - to support various taxes in investing the logistics business abroad(0.1980) ; No.3 - to improve the management of CIQ(0.1958); No.4 - to back up the joint-venture of logistics firms(0.1169); No.5 - to enhance trade and foreign policies to deregulate the entry into logistics markets(0.0536); No.6 - to construct the logistics information system of China(Northest Ssia)(0.0458). This paper resulted in finding out Korea logistics enterprises that have not secured their own inland-transport network in China and the actual difficulties of Korean enterprises with using the inferior network that advanced into China. These problems were developed into the analysis adopting the AHP method, and the significancy of this paper is to present the priority order of promoting problems using a sophisticated technique.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.823-832
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• 2007

In this study, the separation of short and long durations for estimation the parameters of IDF curve is suggested by using Multi-Objective Genetic Algorithm (MOGA). Objective functions are to minimize root mean squared error (RMSE) and relative RMSE between observed and computed values. The criteria for separation are two; the first one is to estimate more precisely the parameters of IDF curve and the second is to make a single IDF curve without non-continuous duration point. For this purpose 22 rainfall recording gauges operated by Korea Meteorological Administration are selected and three IDF curves that are used generally in South Korea are tested. The result shows that the IDF curve developed by Heo et al. (1999) would be the best of three tested IDF curves, and the suggested parameter estimation method using MOGA can compute more reliable parameters compared with empirical regression analysis.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.904-910
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• 2014

The D&M(DeLone and McLean) IS(Information System) Success model has been widely studied in various criteria such as e-commerce and education, and many empirical research has been performed enough to execute meta-analysis from original model developed in 1992 to updated model in 2003. However, almost all researches have been validated end-user point of view those could lead IS success factors perceived by users but not applicable to developers because developers could not recognize from those result that how much gap exist between one's perception and users. Therefore, in this research, we apply D&M IS success model to A bank developers and users and compare perceptions by multi-group structural equation model.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.175-184
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• 2008

Uncertainties are unavoidable in engineering applications. In this paper we propose an alpha reliable multi-variable network design problem under demand uncertainty. In order to decide the optimal capacity enhancement, three performance measures based on 3E(Efficiency, Equity, and Environmental) are considered. The objective is to minimize the total budget required to satisfy alpha reliability constraint of total travel time, equity ratio, and total emission, while considering the route choice behavior of network users. The problem is formulated as the chance-constrained model for application of alpha confidence level and solved as a lexicographic optimization problem to consider the multi-variable. A simulation-based genetic algorithm procedure is developed to solve this complex network design problem(NDP). A simple numerical example ispresented to illustrate the features of the proposed NDP model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.357-365
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• 2013

The 4 by 4 series slot sub-array antenna is proposed using substrate integrated waveguide(SIW) technology for 35 GHz of Ka band application. The proposed antenna is realized with multi-layered structure for compact size and easy integration features. 4 by 4 radiating slots are arrayed on top PCB with equal spacing and the feeding SIWs are arranged on middle and bottom PCBs for uniform power distribution. The multi-layered antenna is realized using RT/Duroid 5880 that has dielectric constant of 2.2 and the total antenna size is $750.76mm^2$. The individual parts such as radiators and feeding networks are simulated using full-wave simulator CST MWS. Furthermore, the total sub-array antenna also fabricated and measured the electrical performances such as impedance bandwidth under the criteria of -10 dB(490 MHz), maximum gain(18.02 dBi), sidelobe level(SLL)(-11.0 dB), and cross polarization discrimination (XPD)(-20.16 dB).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.175-185
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• 2011

This study investigates tsunami force acting on a group of onshore structures numerically by using three-dimensional one-field model for immiscible multi-phase flows, which is based on Navier-Stokes solver. In particular, we studied on the characteristics of tsunami with respect to the arrangement of onshore structures and the distance from seawall trough numerical experiments. For validation of the numerical method used in this study to calculate tsunami force, numerical results for tsunami force on the structures in coastal area are compared with available experimental data. Furthermore, a detail study on the efficiency of the numerical method is performed for the estimation of tsunami force based on the hydrostatic and hydrodynamic methods in which the numerical results are used. The obtained results are compared to the previous experimental one and design criteria. Considering both experimental results and numerical analysis results, semi-empirical formula by regression analysis is proposed. As a result, it was confirmed that the numerical analysis is effective to estimate on tsunami force acting on onshore structures.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.7
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• pp.4005-4013
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• 2013

Background: Although breast cancer is a major public health worry among Asian women, adherence to screening for the disease remains an obstacle to its prevention. A variety of psycho-social and cultural factors predispose women to delay or avoidance of screening for breast cancer symptoms at the early stages when cure is most likely to be successful. Yet few interventions implemented to date to address this condition in this region have drawn on health behavior theory. Materials and Methods: This paper reviews the existing literature on several cognitive theories and models associated with breast cancer screening, with an emphasis on the work that has been done in relation to Asian women. To conduct this review, a number of electronic databases were searched with context-appropriate inclusion criteria. Results: Little empirical work was found that specifically addressed the applicability of health theories in promoting adherence to the current breast cancer prevention programs Among Asian women. However, a few studies were found that addressed individual cognitive factors that are likely to encourage women's motivation to protect themselves against breast cancer in this region of the world. The findings suggest that multi-level, socio-cultural interventions that focus on cognitive factors have much promise with this issue. Conclusions: Interventions are needed that effectively and efficiently target the personal motivation of at-risk Asian women to seek out and engage in breast cancer prevention. Concerning implications, personal motivation to seek out and engage in individual preventive actions for breast cancer prevention among Asian women is a timely, high priority target with practical implications for community development and health promotion. Further studies using qualitative, anthropologic approaches shaped for implementation in multi-ethnic Asian settings are needed to inform and guide these interventions.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.695-703
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• 2015

Acceptance criteria for chemical admixtures of cement concrete were investigated in domestic and international specifications. The reliability was verified for solid content test method of chemical admixture examined statistical analysis by round robin test. The applicability of FT-IR spectroscopy for qualitative measurement of multi-compound chemical admixtures verified. From solid content experimental results, outlier analysed using Cochran, Grubbs and Dickson's Q test. Repeatability and reproducibility standard deviation for solid content results showed 0.25 and 0.098% respectively according to KS A ISO 5725-2 procedure, it can be confirmed reliability of test methods. FT-IR spectrum of liquefied or oven-dried chemical admixtures condition showed big differences. It is needed that the FT-IR analysis is performed on dry material. However there's no difference with the applicability of FT-IR spectroscopy for multi-compound chemical admixtures. So the utility of method analysis could not identify.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.311-320
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• 2014

Rotor blades are important devices that affect the power performance, efficiency of energy conversion, and loading and dynamic stability of wind turbines. Therefore, considering the characteristics of a wind turbine system is important for achieving optimal blade design. When a design is complete, a design evaluation should be performed to verify the structural integrity of the proposed blade in accordance with international standards or guidelines. This paper presents a detailed exposition of the evaluation items and acceptance criteria required for the design certification of wind turbine blades. It also presents design evaluation results for a 2-MW blade (KR40.1b). Analyses of ultimate strength, buckling stability, and tip displacement were performed using FEM, and Miner's rule was applied to evaluate the fatigue life of the blade. The structural integrity of the KR40.1b blade was found to satisfy the design standards.