• Korean Journal of Materials Research
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• v.23 no.5
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• pp.281-285
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• 2013

In the present work, ZnO nanofibers were applied to electrode materials for the detection of cholesterol. ZnO nanofibers were synthesized using the electrospinning technique with zinc acetate as a precursor. Electrospinning-synthesized ZnO nanofibers were uniformly distributed by properly controlling the electrospinning parameters. After the calcination treatment, nanofibers of pure ZnO phase were synthesized. Then, these fibers were successfully placed on Au-coated glass substrates by dispersion of ZnO nanofibers in ethanol, dropping, and drying, in sequence. Cholesterol oxidase was then immobilized onto the surface of the ZnO nanofibers. To enhance the immobilization, Nafion was additionally applied. The sensing performances of the fabricated ZnO nanofibers-based sensors were analyzed by cyclic voltammetry in terms of cholesterol concentration ranging from 100 to 400 mg/dl. In the I-V curves, measured by cyclic voltammetry, the ZnO nanofiber-based sensor showed a proportional current behavior with cholesterol concentrations in phosphate buffered saline solution. The sensitivity was measured and found to be $30.7nA/mM{\cdot}cm^2$, which is comparable to the values reported in the literature. After not only optimizing the shape of the ZnO nanofibers but also improving the adhesion nature between the ZnO nanofibers and the Au conducting layer, these fibers can be a good candidate for electrode materials in devices used to detect low concentrations of cholesterol in blood.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.393-405
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• 2000

Monthly runoff was estimated using TOPMODEL which simulates ground water movement as well as surface runoff in the area of catchment. SAYUN dam which is being operated by Korea Water Resources Corporation was selected for the study, and the topographic factors of the watershed were analyzed using 1/5,000 digital map and GIS software(Arc/Info). The comparison shows good agreement between observed monthly runoff and the computation results simulated by using TOPMODEL. The catchment area of SAYUN dam was modeled by using various grid sizes in order to check the sensitivity of grid size, and the grid size of 180m was found most proper among 6 different sizes. TOPMODEL was also found superior to the existing monthly runoff models such as Kajiyama, KRIHS and Tank. Because the model requires limited number of parameters and considers topographic aspects, it is reckoned to be very useful for practical use.

• Korean Journal of Medicinal Crop Science
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• v.22 no.1
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• pp.38-45
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• 2014

This study was performed to investigate the physiological responses of Oplopanax elatus by water condition. Drought stress was induced by withholding water for 26 days. The results show that $P_{N\;max}$, SPAD, gs, E and Ci were significantly decreased with decreasing of soil moisture contents. However, AQY and WUE were decreased slightly only at 26 day. This implies that photosynthetic rate is reduced due to an inability to regulate water and $CO_2$ exchange through the stomatal. According to JIP analysis, ${\Phi}_{PO}$, ${\Psi}_O$, ${\Phi}_{EO}$ and $PI_{ABS}$ were dramatically decreased at 21 day and 26 day, which reflects the relative reduction state of the photosystem II. On the other hand, the relative activities per reaction center such as ABS/RC, TRo/RC were significantly increased at 26 day. Particularly, Dio/RC and DIo/CS increased substantially under drought stress, indicating that excessive energy was consumed by heat dissipation. These results of chlorophyll a fluorescence show that the sensitivity changes photosystem II activity. Thus, according to the results, O. elatus was exhibited a strong reduction of photosynthetic activity to approximately 10% soil moisture contents, and JIP parameters could be useful indicator to monitor the physiological states of O. elatus under drought stress.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.154-165
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• 2006

In the present study, a numerical model using Boussinesq equation is set up to predict the interacted equilibrium between waves and their induced currents in the occurrence of breaking waves over an underwater shoal, and the numerical results are compared with results of existing hydraulic experiments. A sensitivity analysis has been done to find out appropriate values of breaking wave parameters with the result (regular wave case) of Vincent and Briggs (1989)’ experiment. Then the numerical model is applied to the irregular wave cases of the experiment and the hydraulic model test of Ieodo which is a natural undersea shoal. The results show that a strong current forms in the wave direction at the downstream side of the shoals, causing the attenuation of wave heights there. The calculated wave heights generally show a similar pattern with the measured data.

• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.225-232
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• 1998

Results of Monte Carlo simulations on amorphous silicon based x-ray imaging arrays are described. In order to investigate the characteristics of amorphous silicon x-ray imaging devices and to provide the optimum design parameter, Monte Carlo simulations were performed. Monte Carlo simulation codes for our purpose were developed and various combinations of x-ray peak voltages, aluminum filter thicknesses, CsI(TI) thicknesses, and amorphous silicon photodiode pixel sizes were tested in connection with detection efficiency and spatial resolution of the amorphous silicon based x-ray imager. With usual Csl(TI) thickness of 300${\mu}{\textrm}{m}$-500${\mu}{\textrm}{m}$, detection efficiency was in the range of 70%-95% and energy absorption efficiency was in the range of 40%-70% for 60kVp-120kVp x-ray. From the simulations it was found that amorphous silicon pixel size and Csl(TI) thickness were the most important parameters which determine the resolution of the imager. By use of our simulation results we could provide proper combinations of Csl(TI) thicknesses and pixels sizes for optimum sensitivity and resolution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.3
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• pp.126-136
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• 1991

This study is concerned with the nonlinear dynamic behaviors of guyed towers for wave loadings. In order to analyze the nonlinear responses of guyed towers efficiently, the main tower is modeled as an equivalent stick, the guyline system is idealized as a spring with nonlinear stiffness in the horizontal direction. and the pile foundation system is represented as a linear spring in the rotational direction. The wave forces on the main tower are evaluated by using Morison's equation. In order to consider adequately the nonlinearities of the guying system and drag forces due to fluid viscosity. the analyses are performed in the time domain. The mode superposition method is adopted for solving the nonlinear equation of motion efficiently. which is based on the Newmark integration scheme. Numerical analyses are carried out to investigate the sensitivity of two major design parameters for guyed towers. i.e., the clump weight conditions and the base renditions of the tower.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.4
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• pp.287-294
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• 2012

Sedimentary environment in coastal zone has been changing due to a large number of coastal structures and continuous coastal development. As a result, the environment has been changing. In particular, the economic and environmental damage can occur due to cohesive sediment transport closely related with the fate of pollutants. Due to large sea wall construction the ebb dominance in the Mokpo coastal waters has been clearer. Cohesive sediment transport was simulated by the EFDC model. The simulated SS showed good agreements with the observed SS. From the sensitivity analysis of sediment parameters, we found out that the erosion rate, the critical shear stresses for erosion and deposition, and the settling velocity are important factors in cohesive sediment transport modeling.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.95-104
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• 2002

In this study, a reliability-based design (RBD) procedure for determining design values fur anchored sheet pile wall is proposed considering overturning about the anchor point as the major failure mode. In this design procedure, the depth of embedment of the sheet pile wall is logically chosen in accordance with degrees of uncertainties of design input parameters using approximate probabilistic computation methods. These methods have been successfully used in the geotechnical engineering requiring neither understandings of complex probabilistic theories nor efforts to prepare more data. It was investigated that the design results by the proposed method were compatible with those by commonly used deterministic design methods. Additionally, in an effort to investigate the effects of changes in the degree of uncertainties of major design variables on the design results of the sheet pile wall, a sensitivity analysis was peformed.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.113-125
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• 2002

Although there are several empirical and semi-empirical formulae available for predicting ground surface settlement, most of them do not simultaneously take into consideration all the relevant factors, resulting in inaccurate predictions. In this study, an artificial neural network (ANN) is incorporated with 113 of monitored field results to predict surface settlement for a tunnel site with prescribed conditions. To achieve this, a format for a database of monitored field data is first proposed and then used for sorting out a variety of monitored data sets available in Korea Institute of Construction Technology. An optimal neural network model is suggested through preliminary parametric studies and introduces a concept of RSE (Yang and Zhang, 1997) in sensitivity analysis for various major factors affecting the surface settlement in tunnelling. It is seen in some examples that the RSE rationally enables to recognize the most significant factors of all the contributing factors. Two verification examples are undertaken with the trained ANN using the database created in this study. It is shown from the examples that the ANN has adequately recognized the characteristics of the monitored data sets retaining a generality fur further prediction.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.164-173
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• 2015

This study aims to design energy supply systems from various energy sources for transportation sectors and comparatively analyze the life cycle cost of different scenario-based systems. For components of the proposed energy supply system, we consider a typical oil refinery, byproduct hydrogen system, renewable energy source (RES)-based electric generation system and existing electricity grid. We also include three types of vehicles in transportation sector such as internal combustion engine vehicle (ICEV), electric vehicle (EV), fuel cell vehicle (FCV). We then develop various energy supply scenarios which consist of such components and evaluate the economic performance of different systems from the viewpoint of life cycle cost. Finally we illustrate the applicability of the proposed framework by conducting the design problem of energy supply systems of Jeju, Korea. As the results of life cycle cost analysis, EV fueled by electricity from grid is the most economically feasible. In addition, we identify key parameters to contribute the total life cycle cost such as fuel cost, vehicle cost, infra cost and maintenance cost using sensitivity analysis.