• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.963-972
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• 2003

Performance characteristics of the planar-type solid oxide fuel cell (SOFC) are investigated by the analysis of flow fields coupled with heat and mass transfer phenomena in anode and cathode channels. For these purposes, performance analysis of the SOFC is conducted based on electrochemical reaction phenomena in electrodes and electrolyte coupled with flow fields in anode and cathode channels. In the present study, the isothermal model adopted in the previous paper prepared by the same authors is extended to the non-isothermal model by solving energy equation additionally with momentum and mass transfer equations using CFD technique. It is found that the difference between isothermal and non-isothermal models come from non-uniform temperature distribution along anode and cathode electrodes by solving energy equation in non-isothermal model. Non-uniform temperature distribution in non-isothermal model contributes to the increase of average temperature of the fuel cell and influences its performance characteristics.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.3-13
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• 1999

The diffusion characteristics of the high temperature and salinity water discharged in Chinhae Bay under BMP(Barge-Mounted Plants) desalination processes were simulated to access environmental impact. The 3-D baroclinic flow model is formulated by integrating the basic equations with respect to each control volume and by transforming them into a finite difference form using the space-staggered grid system. With a 3-D baroclinic flow model, the tide-induced and density-induced current was computed and confirmed by comparing with observed data. From the results of numerical experiment, it is expected that the maximum diffusion lengths of the high temperature and salinity which increase $0.6^{circ}C$ and 0.2 after discharging are 1 km and 3.5km, respectively. It may be expected that the discharge has an effect on surrounding area of discharge, but not an effect on whole area of Chinhae Bay.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1895-1899
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• 2006

Seawater intrusion phenomenons of coastal area happen by natural or artificial factor. For example, density difference of seawater and fresh water, surface of the water change by tidal current, pumping, aggregate picking from mouth of a river, large scale reclamation in water area business etc. This research analyzed effect that groundwater TDS changed by pumping.As a result, it was expose that TDS density increases by sudden inflow of seawater when do pumping up more than $200m^3/day$. Finally, We are expected to prevent calamity by seawater intrusion in coastal area through this study and propose optimum pumping amount to use groundwater safety.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.685-692
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• 1995

The effect of five different surface treatments on the shear bond strength of the resin bond to Type IV Gold alloy was studied by bonding resin to metal. The metal surface was subjected to one of the following treatments and bonded ;(1) air abraded with $50{\mu}m$ alumina particles,(2) beads(3) beads and tin-plated at curreant density of 300mA/$cm^2$,(4) tin-plated at current density of 300mA/$cm^2$,(5) silicacoating with sililink, and bonded with an MDP Opaque primer, CESEAD resin system. The bonded specimens were immersed in water for 23 hours after 1 hour resin curing and shear bond strength were recorded. On the basis of this study, the following conclusions can be drawn; 1. Difference were found in the shear bond strength among all experimental groups. And bead glroup exihibited the highest shear bond strength and sand blasting group exhibited the lowest shear bond strength on five groups. 2. Bead group, mechanical bonding was significantly higher than that obtained with the samples, tinplating, silicacoating, and chemical bonding. 3. No statistically signiflcant difference was found between the shear bond strengths obtained with bead and bead-tinplating, and between tinplating and sili cacoating.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.535-541
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• 1997

The effect of concentration of each solution( HCI, $H_2SO_4$ and $HNO_3$), scan rate and polished surface condition on the corrosion of AISI 304 Stainless Steel were investigated, utilizing the Method ASTM G5 - 87. It can be concluded that: 1) For the same concentration(i.e. 1N) of each solution the corrosion rate is the highest in HCI and lowest in $HNO_3$. Also, the difference of values of $i_{cirt}$ generated for each solution is significant. 2) As the concentration of the solution $H_2SO_4$ is increased (O.5N, 1N, 2N) the values of $E_{cor}$ $i_{crit}$ and $i_{p}$ are increased. 3) In case of existence of SCN ion of O.OlN, the values of iCTIt and ip generated are approximately 100 times and 1.4 times higher respectively, than in the case of non - existence of $SCN^{-}$. However the existence of $SCN^{-}$ doesn't affect the value of $E_{cor}$ and $E_{p}$. 4) The values of $i_{crit}$ and $i_{p}$ are increased due to the increase of scan rate. But the values of $E_{cor}$ and $E_{p}$ do not depend on the scan rate. 5) The $i_{p}$ value depends greatly on oxygen in the solution, but the changes in values of $E_{cor}$ $i_{crit}$ and $E_{b}$ due to the oxygen are insignificant. 6) If a component is polished using #400, #600 and #800 wet polish paper, the effect of surface condition on variations of values of $i_{crit}$ and $i_{p}$ is slightly significant.

• Journal of Nutrition and Health
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• v.38 no.6
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• pp.475-486
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• 2005

This study was intended to investigate the nutritional status between lactating and non- lactating women, especially calcium and iron. The subjects were 84 lactating women and 20 non-lactating women visiting a public health center and hospital in Daegu. Each subject was interviewed to collect the information on dietary intake for 2 consecutive days. Biochemical assessment of iron status and bone mineral density (BMD) measurement were conducted. Dietary intake of carbohydrate, potassium, Vit $B_1,\;B_2$, Vit C were significantly higher in women during lactating period (p<0.05). However, relative intake as expressed by percentage of Korean Recommended Dietary Allowances (RDA) was not significantly different between the two groups. The dietary intake of iron and calcium were 58.8%, 60.4% of Korean RDA respectively in women during lactating period. The current food habit score of these women was significantly higher than that of non-lactating women (p<0.05). When we compared the quality of nutritional status, the Index of nutritional quality (INQ) was significantly higher for vitamin $B_2$, P in lactating women than in non-lactating women (p<0.1). Mean adequacy ratio (MAR) was not significantly different between two groups. Dietary variety score (DVS) was significantly higher in women during the lactating period (p<0.05). There was no significant difference in biomarkers (Hb, Hct, Serum ferritin, Transferrin) related to iron status between the two groups. No significant difference in bone mineral density (BMD) T-score was not observed. However, it appeared that BMD of lactating women was lower than that of non-lactating women.

• The Journal of Korean Medicine
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• v.43 no.2
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• pp.27-41
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• 2022

Objectives: There should be an objective analysis on the academic competency for incorporating Computer-based Test (CBT) in the education of traditional Korean medicine (TKM). However, the Item Response Theory (IRT) for analyzing latent competency has not been introduced for its difficulty in calculation, interpretation and utilization. Methods: The current study analyzed responses of 390 students of 8 years to the herbology test with 14 items by utilizing Rasch model, and the characteristics of test and items were evaluated by using characteristic curve, information curve, difficulty, academic competency, and test score. The academic competency of the students across gender and years were presented with scale characteristic curve, Kernel density map, and Wright map, and examined based on T-test and ANOVA. Results: The estimated item, test, and ability parameters based on Rasch model provided reliable information on academic competency, and organized insights on students, test and items not available with test score calculated by the summation of item scores. The test showed acceptable validity for analyzing academic competency, but some of items revealed difficulty parameters to be modified with Wright map. The gender difference was not distinctive, however the differences between test years were obvious with Kernel density map. Conclusion: The current study analyzed the responses in the herbology test for measuring academic competency in the education of TKM using Rasch model, and structured analysis for competency-based Teaching in the e-learning era was suggested. It would provide the foundation for the learning analytics essential for self-directed learning and competency adaptive learning in TKM.

• Journal of Digital Convergence
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• v.11 no.8
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• pp.199-204
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• 2013

Computational fluid dynamics (CFD) is used to reduce number of experiments. The CFD tools are widely used for engine design and flow pattern analysis to reduce experiments. In this study the performance of a PEMFC single cell was analyzed by using STAR-CD, product of CD-ADAPCO. The effect of cell design and flow pattern on the performance of a PEMFC was analyzed with the 3-D simulation. As a result the performance of rectangular cell was the higher than that of square cell, while the flow direction scarcely affected on the performance of a PEMFC. Also the current density according to different excess ratio of air flow rate was compared and analyzed. The difference between maximum and minimum current density of flip-flow was lower than that of co-flow.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.371-375
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• 2014

In this paper, the solutions of TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential magnetic field and the induced surface current density on the resistive strip. The induced surface current density of resistive strip is obtained by difference of the up and down of the magnetic field in two boundary areas of the resistive strip. The numerical results for reflected power of zeroth order mode analyzed by according as the resistivity, the width and spacing of resistive strip, the relative permittivity and thickness of dielectric layer, and incident angles. The numerical results shown in good agreement compared to those of the existing papers using FGMM(fourier galerkin moment method).

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.1
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• pp.35-44
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• 2000

The winter case of the near-field dilution at the Masan outfalls has been studied by field measurements and CORMIX model simulations. Dilution rates of the wastewater discharge in winter were obtained by a salinity deficit method using the field data observed in the neap tidal period of February, 1999. The observed dilution rates in winter season were found to be very high in the range of 90～130 due to the isopycnal mixing of ambient density compared with the summer range of 30～40 under weak neap tidal currents. The results of CORMIX model simulations also show that the winter dilution rates under a weak ambient current(Ua=6.0ms/s) were increased by 3-fold of the summer dilution rates. However, the difference between two seasons becomes small by 30% under a strong current(Ua=15.5cm/s). This result indicates that the dilution and hydrodynamic mixing process of the effluents are more influenced by ambient crossflow condition than by ambient density stratification at the outfalls site.