• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.134-134
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• 2010

Fuel cell is a device that directly converts chemical energy in the form of a fuel into electrical energy by way of an electrochemical reaction. In the anode for a high temperature fuel cell, nickel or nickel alloy has been used in consideration of the cost, oxidation catalystic ability of hydrogen which is used as fuel, electron conductivity, and high temperature stability in reducing atmosphere. Most MCFC stacks currently operate at an average temperature of $650^{\circ}C$. There is some gains with decreased temperature in MCFC to diminish the electrolyte loss from evaporation and the material corrosion, which could improve the MCFC life. However, operating temperature has a strong related on a number of electrode reaction rates and ohmic losses. Baker et al. reported the effect of temperature (575 to $650^{\circ}C$). The rates of cell voltage loss were 1.4mV/$^{\circ}C$ for a reduction in temperature from 650 to $600^{\circ}C$, and 2.16mV/$^{\circ}C$ for a decrease from 600 to $575^{\circ}C$. The two major contributors responsible for the change in cell voltage with reducing operation temperature are the ohmic polarization and electrode polarization. It appears that in the temperature range of 550 to $650^{\circ}C$, about 1/3 of the total change in cell voltage with decreasing temperature is due to an increase in ohmic polarization, and the electrode polarization at the anode and cathode. In addition, the oxidation reaction of hydrogen on an ordinary nickel alloy anode in MCFC is generally considered to take place in the three phase zone, but anyway the area contributing to this reaction is limited. Therefore, in order to maintain a high performance of the fuel cell, it is necessary to keep this reaction responsible area as wide as possible, that is, it is needed to keep the porosity and specific surface area of the anode at a high level. In this study effective anodes are prepared for low temperature MCFC capable of enhancing the cell performance by using zirconium hydride at least in part of anode material.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.59.1-59.1
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• 2010

Aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) is studied with the structure of a glass/Al/$SiO_2$/a-Si, in which the $SiO_2$ layer has micron-sized laser holes in the stack. An oxide layer between aluminum and a-Si thin films plays a significant role in the metal-induced crystallization (MIC) process determining the properties such as grain size and preferential orientation. In our case, the crystallization of a-Si is carried out only through the key hole because the $SiO_2$ layer is substantially thick enough to prevent a-Si from contacting aluminum. The crystal growth is successfully realized toward the only vertical direction, resulting a crystalline silicon grain with a size of $3{\sim}4{\mu}m$ under the hole. Lateral growth seems to be not occurred. For the AIC experiment, the glass/Al/$SiO_2$/a-Si stacks were prepared where an Al layer was deposited on glass substrate by DC sputter, $SiO_2$ and a-Si films by PECVD method, respectively. Prior to the a-Si deposition, a $30{\times}30$ micron-sized hole array with a diameter of $1{\sim}2{\mu}m$ was fabricated utilizing the femtosecond laser pulses to induce the AIC process through the key holes and the prepared workpieces were annealed in a thermal chamber for 2 hours. After heat treatment, the surface morphology, grain size, and crystal orientation of the polycrystalline silicon (pc-Si) film were evaluated by scanning electron microscope, transmission electron microscope, and energy dispersive spectrometer. In conclusion, we observed that the vertical crystal growth was occurred in the case of the crystallization of a-Si with aluminum by the MIC process in a small area. The pc-Si grain grew under the key hole up to a size of $3{\sim}4{\mu}m$ with the workpiece.

• Journal of Environmental Science International
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• v.17 no.4
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• pp.423-437
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• 2008

Until comparatively lately, the annual time series of the $SO_2$ concentration had been shown in a decreasing trend in Ulsan as well as other Korean cities. However, the high concentration of $SO_2$ was frequently found in the specific countermeasure region including the national industrial complex such as Mipo and Onsan in the Ulsan city for the period of $2001{\sim}2004$. There are many conditions that can influence the high concentration of $SO_2$ at monitoring sites in Ulsan, such as: First, annual usage of the fuel including sulfur increased in comparison with the year before in spite of the fuel conversion policy which wants to use low sulfur oil less than 3% and LNG. Second, point source, such as the power plants and the petroleum and chemistry stacks, was the biggest contributor in $SO_2$ emission, as a analyzed result of both the air quality modeling and the stack tole-monitoring system (TMS) data. And third, the air pollutants that occurred in processes of homing and manufacturing of the fuel including sulfur were transported slow into a special monitoring site by accumulating along the frontal area of see-breeze. It was concluded that Ulsan's current environmental policy together with control methods should be changed into the regulation on total amount of emission, including a market-based emission trading with calculating of atmospheric environmental critical loads, for the $SO_2$ reduction like the specific countermeasure for the $O_3$ and PM10 reduction in the Seoul metropolitan area. And this change should be started in the big point sources of $1{\sim}3$ species because they are big contributors of Ulsan's $SO_2$ pollution. Especially it is necessary to revitalize of the self-regulation environmental management. Other control methods for sustaining the $SO_2$ reduction are as follows: maintenance of the fuel conversion policy, reinforcement of the regional stationary source emission standard, and enlargement of the stack TMS.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.979-988
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• 2012

The 3D structure of GDL for fuel cells was measured using high-resolution X-ray tomography in order to study material transport in the GDL. A computational algorithm has been developed to remove noise in the 3D image and construct 3D elements representing carbon fibers of GDL, which were used for both structural and fluid analyses. Changes in the pore structure of GDL under various compression levels were calculated, and the corresponding volume meshes were generated to evaluate the anisotropic permeability of gas within GDL as a function of compression. Furthermore, the transfer of liquid water and reactant gases was simulated by using the volume of fluid (VOF) and pore-network model (PNM) techniques. In addition, the simulation results of liquid water transport in GDL were validated by analogous experiments to visualize the diffusion of fluid in porous media. Through this research, a procedure for simulating the material transport in deformed GDL has been developed; this will help in optimizing the clamping force of fuel cell stacks as well as in determining the design parameters of GDL, such as thickness and porosity.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.1
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• pp.11-21
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• 1986

The study was performed to investigate the effects of gaseous imission of sulfur dioxide and hydrogen fluoride on the growth of rice plant under stressed field conditions. The plants were cultivated in normal paddy fields where are 88 industrial plants operating with 285 smoke stacks emitting pollutants. There has been a number of reported studies (1, 3, 11, 19, 20) which deal with rice plant damages by air pollution under a simulated exposure experimental condition. Furthermore, these experiments were conducted to examine effects of a single pollutant on the plant. Furthermore, these experiments were conducted to examine effects of a single pollutant on the plant. In korea, however, there is no study reported in literature with respect to the in-situ dose-response relationship between rice pant reduction in yields and air pollution. This study is specifically dealt with multiple effects of sulfur dioxde and hydrogen fluoride on various plant growth indicators such as leaf damage, culm height, weight of grain, panicles per hill, spikelets per panicle and percent fertility.It appears that there is a good correlation between ambient concentrations of sulfur oxides and sulfur contents found in leaves with an average correlation coefficient of 0.868 within a 1% significance level. It is interesting to note that a better multiple correlation was found between percent leaf damage and sulfur and fluoride contentd found in leaf with a significance of 1% level. The yearly correlation coefficient ranges from 0.963 to 0.987 with an average being 0.971. It is, therefore, believed that a percent leaf damage may serve as a single indicator of pollutional damages to rice plant cultivating in fields. Regarding other factors to the diminution of rice plant growth in polluted atmosphere, it appears that a significant correlation to culm length and dry weight of grain with a 1% significance level whereas T/R ratio has a good correlation with lead damage within 5% significance level. An evaluation of data observed has demonstrated that both panicles per hill and percent fertility are significantly affected by air pollutants. As expected, hydrogen fluoride has more effects than sulfur oxide. It is, however, interesting to note that spikelets per panicles has slightly been affected while no indication of effects on 1000-grain-weight has been observed. This may lead to a conclusion that a reduction in yield of rice under polluted field conditions may have more been caused by the diminution of panicles per hill and percent fertility rather than by the diminution of spikelets per panicle and grain weight.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1205-1214
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• 2005

This study was carried out to investigate the emission characteristics of volatile metals(Hg, As, Se) and semi volatile metals such as Pb from small and medium size municipal solid waste incinerators(MSWIs). The concentrations of Hg, Pb, As and Se in emission gas from small size waste incinerators were higher than those of medium size waste incinerators. This is probably due to less air pollutant control devices and high emission gas temperature of the small size waste incinerators relative to the medium size waste incinerators. Emission gas temperature from small and medium size waste incinerators were divided into 2 groups. The first group was about $100^{\circ}C$ and the second roup in the range of $400{\sim}700^{\circ}C$. The concentrations of emission gas at the second group were Hg $70.43\;{\mu}g/Sm^3$, Pb $0.94\;{\mu}g/Sm^3$, As $9.83\;{\mu}g/Sm^3$ and Se $5.05\;{\mu}g/Sm^3$. The concentrations of Hg, Pb, As and Se at the first group were lower than those found at the second group. Besides, the removal efficiencies of Hg in medium size waste incinerators were $55.2{\sim}95.9%$. Emission gas temperature reduction from waste heat boiler(WHB) contribute to control of Hg. Based on above results, we postulate that the temperature of flue gas should play a very important role in volatile metal control in small and medium size MSWIs. In order to improve the volatile metals removal efficiency, the temperature of cooling system must be controlled and the air pollution control device should be operated properly.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.2
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• pp.173-180
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• 2017

In this study, air sampling locations in the stack of the Advanced Fuel Science Building (AFSB) at the Korea Atomic Energy Research Institute (KAERI) were assessed according to the ANSI/HPS N13.1-1999 specification. The velocity profile, flow angle and $10{\mu}m$ aerosol particle profile at the cross-section as functions of stack height L and stack diameter D (L/D) were assessed according to the sampling location criteria using COMSOL. The criteria for the velocity profile were found to be met at 5 L/D or more for the height, and the criteria for the average flow angle were met at all locations through this assessment. The criteria for the particle profile were met at 5 L/D and 9 L/D. However, the particle profile at the cross-section of each sampling location was found to be non-uniform. In order to establish uniformity of the particle profile, a static mixer and a perimeter ring were modeled, after which the degrees of effectiveness of these components were compared. Modeling using the static mixer indicated that the sampling locations that met the criteria for the particle profile were 5-10 L/D. When modeling using the perimeter ring, the sampling locations that met the criteria for particle profile were 5 L/D and 7-10 L/D. The criteria for the velocity profile and the average flow angle were also met at the sampling locations that met the criteria for the particle profile. The methodologies used in this study can also be applied during assessments of air sampling locations when monitoring stacks at new nuclear facilities as well as existing nuclear facilities.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.657-665
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• 2010

Carbon dioxide ($CO_2$) is known to be a major greenhouse gas partially emitted from waste combustion facilities. According to the greenhouse gas emission inventory in Korea, the quantity of the gas emitted from waste sector in 2005 represents approximately 2.5 percent of all domestic greenhouse gas emission. Currently, the emission rate of greenhouse gas from the waste sector is relatively constant partly because of both the reduced waste disposal in landfills and the increased amounts of waste materials for recycling. However, the greenhouse gas emission rate in waste sectors is anticipated to continually increase, mainly due to increased incineration of solid waste. The objective of this study was to analyze the property of Municipal Solid Waste (MSW) and estimate $CO_2$ emissions from domestic MSW incineration facilities. The $CO_2$ emission rates obtained from the facilities were surveyed, along with other two methods, including Tier 2a based on 2006 IPCC Guideline default emission factor and Tier 3 based on facility specific value. The $CO_2$ emission rates were calculated by using $CO_2$ concentrations and gas flows measured from the stacks. Other parameters such as waste composition, dry matter content, carbon content, oxidation coefficient of waste were included for the calculation. The $CO_2$ average emission rate by the Tier 2a was 34,545 ton/y, while Tier 3 was 31,066 ton/y. Based on this study, we conclude that Tier 2a was overestimated by 11.2 percent for the $CO_2$ emission observed by Tier 3. Further study is still needed to determine accurate $CO_2$ emission rates from municipal solid waste incineration facilities and other various combustion facilities by obtaining country-specific emission factor, rather than relying on IPCC default emission factor.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.3
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• pp.231-242
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• 2004

Remote control and monitoring of information appliances require RTOS and TCP/IP network module to communicate each other. Traditional TCP/IP protocol stacks, however, require relatively large resources to be useful in small 8 or 16-bit systems both in terms of code size and memory usage. It motivates design and implementation of micro TCP/IP that is lightweight for embedded systems. Micro embedded web server is also required to control and monitor information appliances through the Web. In this paper, we design and implement micro TCP/IP and Web server for information appliances. For this goal, we investigate requirements for the interoperability of embedded systems with the Internet and the Web-based control of embedded systems. Next, we compare our micro TCP/IP protocol stack with that of RTIP and QPlus in terms of object code size and performance. The size of micro TCP/IP protocol stack can be reduced by 3/2 and 1/4, respectively, comparing with that of RTIP and QPlus. We also show that the performance of our micro TCP/IP is similar to that of RTIP and QPlus since it handles 2.9Mbps when delayed ACK is not adapted.

• Membrane Journal
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• v.4 no.3
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• pp.163-170
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• 1994

The separation of inorganic salt from amino acid solution using was performed electrodialysis. In order to review the availability of electrodialysis using isoelectric point of amino acid as a bio-separation technique, electrodialysis stacks were designed using ion exchange membrane. Separation of NaCl from amino acid solution was performed in the condition similar to amino acid fermentation process. To obtain otimum conditions of separation, leakage of amino acid depending of pH and limiting current density were measured. On the basis of optimum condition, removal of NaCl and leakage of amino acid were investigated quantitatively in batch and continuous process, and current efficiencies were also obtained. As a result of batch experiment for 11 hours each amino acid solution, removal efficiencies of NaCl were in the ranges of 96.1~96.2%. Amino acid leakage rate of glycine, methionine, alanine were 2.5, 1.7, 2.0% respectively. Current efficiencies were in the ranges of 44.5~44.6%. As a result of continuous experiment in various flow rate of each amino acid solution, it took 120 ~ 150 min to reach to steady state. Removal efficiency of NaCl was increased as the flow rate was decreased, but current efficiency was decreased. At the steady states, there were no leakage of amino acid.