• Journal of the Korean Society of Food Science and Nutrition
• /
• v.24 no.1
• /
• pp.67-73
• /
• 1995

Effects of tocopherols and $\beta$-carotene on the oxidation of the solid model system of a free fatty acid mixture (64.5% of linolic acid ; 26.4% of oleic acid ; 5.0% of palmitic acid) with tocopherols and $\beta$-carotene were studied. $\alpha$-tocopherol revealed an antioxidant activity at the concentration below 0.05%, however, it showed a prooxidant activity when the concentration was higher than 0.05%. The antioxidant activity of ${\gamma}$ -tocopherol was not affected by the concentrations in the range of 0.01~0.10% in the model and ${\gamma}$-tocopherol showed higher antioxidant activity than that of $\alpha$-tocopherol. It seemed that $\alpha$-tocopherol was unstable compared to ${\gamma}$-tocopherol during oxidation. $\beta$-carotene showed a weak antioxidative activity at the initial stage of this system while $\beta$-carotene showed a prooxidant activity in the presence of tocopherol. $\beta$ -carotene was highly susceptible to autoxidative degradation during oxidation.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.6
• /
• pp.42-53
• /
• 2015

In this study, the influence of Al particle size, as an additive for solid propellant, on the mechanical erosion of the carbon-composite nozzle was evaluated. A new model which can predict the size and distribution of the agglomerated reaction product($Al(l)/Al_2O_3(l)$) was established, and the size of agglomerate were calculated according to the various initial size of Al in the solid propellant. With predicted results of the model, subsequently, the characteristics of mechanical erosion on the carbon-composite nozzle was estimated using a commercial CFD software, STAR CCM+. The result shows that the smaller the initial Al particles are, in the solid propellant, the lower is the mechanical erosion rate of the composite nozzle wall, especially for the nano-size Al particle.

• Journal of Hydrogen and New Energy
• /
• v.27 no.1
• /
• pp.49-62
• /
• 2016

In this study, a solid oxide fuel cell (SOFC) system model including balance of plant (BOP) for building electric power generation is developed to study the effect of operating conditions on the system efficiency and power output. SOFC system modeled in this study consists of three heat-exchangers, an external reformer, burner, and two blowers. A detailed computational cell model including internal reforming reaction is developed for a planer SOFC stack which is operated at intermediate temperature (IT). The BOP models including an external reformer, heat-exchangers, a burner, blowers, pipes are developed to predict the gas temperature, pressure drops and flow rate at every component in the system. The SOFC stack model and BOP models are integrate to estimate the effect of operating parameters on the performance of the system. In this study, the design of experiment (DOE) is used to compare the effects of fuel flow rate, air flow rate, air temperature, current density, and recycle ratio of anode off gas on the system efficiency and power output.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.569-577
• /
• 2020

Based on laboratory experiments and numerical simulations, the scale effect of Internal Solitary Wave (ISW) loads on spar platforms is investigated. First, the waveforms, loads, and torques on the spar model at a laboratory obtained by the experiments and simulations agree well with each other. Then, a prototype spar platform is simulated numerically to elucidate the scale effect. The scale effect for the horizontal forces is significant owing to the viscosity effect, whereas it is insignificant and can be neglected for the vertical forces. From the similarity point of view, the Froude number was the same for the scaled model and its prototype, while the Reynolds number increased significantly. The results show that the Morison equation with the same set of drag and inertia coefficients is not applicable to estimate the ISW loads for both the prototype and laboratory scale model. The coefficients should be modified to account for the scale effect. In conclusion, the dimensionless vertical forces on experimental models can be applied to the prototype, but the dimensionless horizontal forces of the experimental model are larger than those of the prototype, which will lead to overestimation of the horizontal force of the prototype if direct conversion is implemented.

• Coupled systems mechanics
• /
• v.7 no.2
• /
• pp.141-162
• /
• 2018

This work presents a novel model for analysis of the loading rate influence onto structure response. The model is based on the principles of nonlinear system dynamics, i.e., consists of a system of nonlinear differential equations. In contrast to classical linearized models, this one comprises mass and loading as integral parts of the model. Application of the Kelvin and the Maxwell material models relates the novel formulation to the existing material formulations. All the analysis is performed on a proprietary computer program based on Wolfram Mathematica. This work can be considered as an extended proof of concept for the application of the nonlinear solid model in material response to dynamic loading.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.2
• /
• pp.383-388
• /
• 2011

In this paper, we consider Hammerstein-Wiener nonlinear model for solid oxide fuel cell (SOFC). A nonlinear model predictive control (MPC) is proposed to trace the constant stack terminal power by Hydrogen flow as control input. After the stability of the closed-loop system with static output feedback controller is analysed by Lyapunov method, a nonlinear model predictive control based on the Hammerstein-Wiener model is developed to control the stack terminal power of the SOFC system. Simulation results verify the effectiveness of the proposed control method based on the Hammerstein-Wiener model for SOFC system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.528-531
• /
• 2004

For a simple one-dimensional ignition problem a mathematical model is described to investigate the difficulties in numerical simulations. Some computation results are obtained and comparison is made with analytical solution. Discussions are made on topics such as 1) coordinate transformation, 2) gas-phase and solid-phase analysis; (divergence form of the governing system, a finite-volume discretization, implicit time integration, upwind split flux, spatial accuracy improvement are described. Mass, reagent mass, and energy conservations are solved.), and 3) method to determine quantities on the burning surface (matching). Results obtained for small values of the non-dimensional pressure show a steady-combustion and good agreement with the analytical solution. Numerical instability appeared for larger values of the pressure, discussion on the cause of the problem is made. This effort is a part of a study of flame spread phenomena on solid propellant surface.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.2
• /
• pp.37-45
• /
• 2015

Typically, water quality sampling takes place intermittently since sample collection and following analysis requires substantial cost and efforts. Therefore regression models (or rating curves) are often used to interpolate water quality data. LOADEST has nine regression models to estimate water quality data, and one regression model needs to be selected automatically or manually. The nine regression models in LOADEST and auto-selection by LOADEST were evaluated in the study. Suspended solids data were collected from forty-nine stations from the Water Information System of the Ministry of Environment. Suspended solid data from each station was divided into two groups for calibration and validation. Nash-Stucliffe efficiency (NSE) and coefficient of determination ($R_2$) were used to evaluate estimated suspended solid loads. The regression models numbered 1 and 3 in LOADEST provided higher NSE and $R_2$, compared to the other regression models. The regression modes numbered 2, 5, 6, 8, and 9 in LOADEST provided low NSE. In addition, the regression model selected by LOADEST did not necessarily provide better suspended solid estimations than the other regression models did.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.7 s.184
• /
• pp.168-176
• /
• 2006

Nowadays, Three dimensional printing (3DP) technique that is one of solid freeform fabrication (SFF) technology has been notable issue, and has been applied by various fields. The SFF system can fabricate three dimensional objects of solid freeform with high speed and low cost using ink jet printing technology. In this research, a SFF system to analyze 3DP process technology is developed. We applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm and minimized position error to the developed SFF system. We analyzed and optimized process variables such as jetted volume, layer thickness, powder bed and so on experimentally. Also. the dimensional error of a developed SFF system is evaluated. Finally, the feasibility of application to bio manufacturing is presented through successful fabrication of teeth and cranium model.

• Journal of Industrial Technology
• /
• v.21 no.B
• /
• pp.281-286
• /
• 2001

In this study, product design and prototype manufacturing of a plastic water-pump pulley has been tried. The designed model is supposed to be made of 33 % glass reinforced resin of which the tensile strength is 180 MPa, and has 24 ribs on each side to increase its structural strength. Structural analysis under a static load of 300 kgf acting on both edges of the belt has been carried out using a commercial finite element code, MARC. The analysis result showed the maximum effective stress near a rib of designed model would be at most 35 MPa (less than 20% of the tensile strength), therefore, the plastic product would be sufficiently safe under that loading condition. On the basis of the structural analysis, a prototype of the designed model has been manufactured by using the fused deposition modelling (FDM) method which is one of the rapid prototyping (RP) methods, using ABS resin and support materials. The CAD data exported to the RP system in STL format was prepared by a commercial solid modeling software, SolidWorks. It has been proved that the plastic pulley can successfully replace the existing flow-formed steel product.