• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• Communications of Mathematical Education
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• v.20 no.3 s.27
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• pp.425-441
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• 2006

Entering upon 21th, the internet which bring the digital era, are changing the paradigm of education and cultivating creative and challenging person, which is the core of competitive power in knowledge-information society, is more emphasized than ever. To meet the needs of the present times, it has been concentrating its effort to improve learning-environment using e-Learning in the field of teaching. E-schoolbooks that were introduced recently by way of showing an example are representative case of this intention. Though many e-learning contents are being developed, the more speedily a society grow, the shorter the life of contents are. Moreover, the contents developed are impossible to use directly for tele-education system, so standard types adjusted for various kind of system are showing up. Among them the leading standard type is SCORM(Sharable Content Object Reference Medel) made in ADL(Advanced Distributed Learning) Corporation. The KERIS' Cyber Home Education System adopted this and is using it. So, in this study, we set the goal at designing and developing an e-learning contents and an experiment-focused mathematics that suit the KERIS' Cyber Home Education System on the basis of SCORM.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.118-125
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• 2002

Hydration is the main reason for the growth of the material properties. An exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development of all material properties and the formation of microstructure should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of W/C ratio on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The tatter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration. In this study, the effects of chemical composition of cement, W/C ratio, temperature, and moisture conditions on the degree of hydration are considered. Parameters that can be used to indicate or approximate the real degree of hydration are liberated heat of hydration, amount of chemically bound water, and chemical shrinkage, etc. Thus, the degree of heat liberation and adiabatic temperature rise could be determined by prediction of degree of hydration.

• Communications of Mathematical Education
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• v.33 no.3
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• pp.163-180
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• 2019

This study introduces a development of calculus contents which makes to understand the main concepts of calculus in a short period of time and to enhance problem solving and computational thinking for complex problems encountered in the real world for college freshmen with diverse backgrounds. As a concrete measure, we developed 'Teaching and Learning' contents and Python-based code for Calculus I and II which was used in actual classroom. In other words, the entire process of teaching and learning, action plan, and evaluation method for calculus class with Python based coding are reported and shared. In anytime and anywhere, our students were able to freely practice and effectively exercise calculus problems. By using the given code, students could gain meaningful understanding of calculus contents and were able to expand their computational thinking skills. In addition, we share a way that it motivated student activities, and evaluated students fairly based on data which they generated, but still instructor's work load is less than before. Therefore, it can be a teaching and learning model for college mathematics which shows a possibility to cover calculus concepts and computational thinking at once in a innovative way for the 21st century.

• Journal of Aquaculture
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• v.6 no.1
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• pp.13-27
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• 1993

In order to determine the protein requirements of the Korean rockfish Sebastes schlegeli six isocaloric diets containing crude protein level from 20\%\;to\;60\%$ were fed to two groups of fish, small and large size, with the initial average body weight of 8 g and 220 g respectively. White fish meal was used as a sole protein source. Daily weight gain, daily protein retention. daily energy retention, feed efficiency, protein retention efficiency and energy retention efficiency were significantly affected by the dietary protein content (p< 0.05). The growth parameters (that is, daily weight gain, daily protein retention and daily energy retention) increased up to $44\%$ protein level with no additional response above this point. The protein requirements were determined from daily weight gain using two different mathematical models. Second order polynomial regression analysis showed that maximum daily weight gain occurred at $56.7\%\;and\;50.6\%$ protein levels for the small size group and the large size group, respectively. However the protein requirements, determined by the broken line model, appeared to be about $40\%$ for both groups. Nutrient utilization also suggested that the protein requirements of both groups were close to $40\%$. When daily protein intake was considered, daily protein requirements per 100g of fish, estimated by the broken line model, were 0.99g and 0.35g for the small and large size groups respectively. Based on these results, a $40\%$ dietary crude protein level could be recommended for the optimum growth and efficient nutrient utilization of the Korean rockfish weighing between 8g and 300g.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.833-843
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• 2016

Recently, in the field of rail freight transportation, the number of trains dedicated for shippers has been increasing. These dedicated trains, which run on the basis of a contract with shippers, had been restricted to the transportation of containers, or so called block trains. Nowadays, such commodities have extended to cement, hard coal, etc. Most full freight cars are transported by dedicated trains. But, for empty car distribution, the efficiency still remains questionable because the distribution plan is manually developed by dispatchers. In this study, we investigated distribution models delineated in the KTOCS system which was developed by KORAIL as well as mathematical models considered in the state-of-the-art. The models are based on optimization models, especially the network flow model. Here we suggest a new optimization model with a framework of the column generation approach. The master problem can be formulated into a transportation problem with additional constraints. The master problem is improved by adding a new edge between the supply node and the demand node; this edge can be found using a simple shorted path in the time-space network. Finally, we applied our algorithm to the Korean freight train network and were able to find the total number of empty car kilometers decreased.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.381-387
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• 2013

In compiling flood hazard maps for the case of dam-failure, a scenario-based numerical modeling approach is commonly used, involving the modeling of important parameters that capture peak discharge, such as breach formation and progress. In this study, an earth-dam-break model is constructed assuming an identical mechanism and hydraulic process for all dam-break processes. A focus of the analysis is estimation of the hydrograph at the outlet as a function of time. The constructed hydrograph then serves as an upper boundary condition in running the flood routing model downstream, although flood routing is not considered here. Validation was performed using the record of the Tangjishan dam-break in China. The results were satisfactory, with a coefficient of determination of 0.974, Nash-Sutcliffe Coefficient of Efficiency (NSC) of 0.94, and Root Mean Square Error (RMSE) of $610m^3/sec$. The proposed model will contribute to assessments of potential flood hazards caused by dam-break.

• Journal of Korea Multimedia Society
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• v.15 no.5
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• pp.595-605
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• 2012

Various methods for measuring strabismus have been developed and used in clinical diagnosis. However, most of them are based on the visual inspection by clinicians. For this reason, there is a high possibility of subjective evaluation in clinical decisions and they are only useful for cooperative patients. Therefore, the development of a more objective and reproducible method for measuring strabismus is needed. In this paper, we introduce a new software to complement the limitations of previous diagnostic methods. Firstly, we simply obtained facial images of patients and performed several preprocessing steps based on the spherical RGB color model with them. Then, the measurement of strabismus was performed automatically by using our 3D eye model and mathematical algorithm. To evaluate the validity of our software, we performed statistical correlation analysis of the results of the proposed method and the Krimsky test by two clinicians for ten patients. The coefficients of correlation for two clinicians were very high, 0.955 and 0.969, respectively. The coefficient of correlation between two clinicians also showed 0.968. We found a statistically significant correlation between two methods from our results. The newly developed software showed a possibility that it can be used as an alternative or effective assistant tool of previous diagnostic methods for strabismus.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.304-310
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• 2015

The moisture content of sawdust must be measured accurately and controlled appropriately during storage and transportation because biological degradation could be caused by improper moisture. In this study, to measure the moisture contents of Larix kaempferi sawdust, the near-infrared reflectance spectra (Wavelength 1000-2400 nm) of sawdust were used as detection parameter. After acquiring the NIR reflection spectrum of specimens which were humidified at each relative humidity condition ($25^{\circ}C$, RH 30~99%), moisture content prediction model was developed using mathematical preprocessings (e.g. smoothing, standard normal variate) and partial least squares (PLS) analysis with the acquired spectrum data. High reliability of the MC regression model with NIR spectroscopy was verified by cross validation test ($R^2$ = 0.94, RMSEP = 1.544). The results of this study show that NIR spectroscopy could be used as a convenient and accurate method for the nondestructive determination of moisture content of sawdust, which could lead to optimize wood utilization.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.2
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• pp.20-30
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• 1999

To improve water quality particularly for sea bathers along the Fylde coastal zone near Blackpool, North West England, waste water from a sewage outfall is studied using a mathematical model. The explicit second order accurate central scheme and the third order accurate QUICKEST scheme are used to represent the diffusion terms and the advection terms of the advective-diffusion equation, respectively. Hydrodynamic model is run for a coarse and fine grid, of 1km and 200m, respectively, obtaining good agreement with measured data. Water quality model is then used to predict faecal coliform levels in the region for four different scenarios, including discharges from: - (i) Fleetwood outfall, (ii)River Ribble for summer condition, (iii)River Ribble for winter condition, and (iv)combined sewer overflows for the Blackpool and Fleetwood communities. Main findings from the simulations are:- (i) Fleetwood outfall has a negligible impact on the beaches with respect to pathogen levels; (ii) Discharge from River Ribble for both summer and winter conditions is predicted in the range of coliform levels 10 -500 counts/100ml along the beach at Lytham St. Annes; and (iii) The CSO effluent discharges are predicted not to advect out into offshore by stronger tidal currents.