• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.481-488
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• 1998

In recently, lots of researcher have been attached to develope various alternative fuels and to use renewable fuels for solution of the exhaust emission problems. In this study, the usability of used vegetable oil as alternative fuel for diesel engines has been investigated. This paper was compared with the exhaust emissions and performance in diesel engine with used vegetable oil and conventional diesel fuel. Since the vegetable oil includes oxygen of about 10%, it influenced the combustion process strongly. So, the smoke emissions of used vegetable oil were exhausted to be lower than those of diesel fuel. Also, the used vegetable oil was much the same cycle to cycle variation with diesel fuel except $P_{(dP}$d.theta.)max/, but the cycle to cycle variation of used vegetable oil was reduced significantly by preheating of the fuel and swirling of the intake air. It was concluded that used vegetable oil could be utilized effectively as renewable fuel for diesel engine.e.

• Journal of the Korean Society of Safety
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• v.12 no.1
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• pp.77-93
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• 1997

The natural convection and combined heat transfer induced by fire in a rectangular enclosure is numerically studied. The model for this numerical analysis is partially opened, it is divided by a vertical baffle projecting from ceiling. The solution procedure Includes the standard k- $\varepsilon$ model for turbulent flow and the discrete ordinates method (DOM ) is used for the calculation of radiative heat transfer equation. In this study, numerical simulation on the combined naturnal convection and radiation is carried out in a partial enclosure filled with absorbed-emitted gray media, but is not considered scattering problem. The velocity vectors, streamlines, and isothermal lines are compared the results of pure convection with those of the combined convection-radiation, the combined heat transfer. Comparing the results of pure convection with those of the combined convection-radiation, the combined heat transfer analysis shows the stronger circulation than those of the pure convection. Three different locations of heat source are considered to observe the effect of heat source location on the heat transfer phenomena. As the results, the circulation and the heat transfer In the left region from heating block are much more influenced than those in the right region. It is also founded that the radiation effect cannot be neglected in analyzing the building in fire.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1428-1437
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• 1988

An analysis of radiative heat transfer has been conducted on axisymmetric finite cylindrical media. It is assumed that the temperature in the media is uniformly distributed and the boundaries are diffusely emitting and reflecting at a constant temperature. The scattering phase function is represented by the delta-Eddington approximation to account for highly forward scattering by particulates just as in the combustion system. Exact numerical solutions are obtained by Gaussian quadrature method and compared with P-1 and P-3 approximation solutions to verify their engineering application limit. The effects of optical thickness, scattering albedo, wall emissivity and aspect ratio are investigated. The results show that P-3 approximation is found to be in good agreement with the exact solution.

• 대한공업교육학회지
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• v.32 no.2
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• pp.188-198
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• 2007

Platinum nanoparticles loading on carbon nanotube was carried out by impregnation of hexachloro platinate(IV) from hydrogen hexachloro platinate(IV) hydrate dissolved solution without using reduction agents, and heating the hexachloro platinate(IV) impregnated carbon nanotube up to $400^{\circ}C$. The amounts of impregnated hexachloro platinate(IV) on to carbon nanotube were measured with UV-visible spectrophotometer. The TG, XRD, and TEM analysis were performed to confirm the platinum particles loading and distribution on carbon nanotube. The average platinum particles size on carbon nanotube was under 2 nm by heating the hexachloro platinate(IV) up to $400^{\circ}C$ in spite of non-using reduction agents, while the average size increased due to the agglomeration of some particles by heating them up to $800^{\circ}C$. Therefore, uniformly distributed platinum nanoparticles loading on carbon nanotube can be obtained from simple impregnation of hexachloro platinate(IV) from solution and heating it up to $400^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.128-136
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• 2007

It is well known that two representative methods satisfy EURO-IV regulation from EURO-III. The first method is to achieve the regulation through the reduction of NOx in an engine by utilizing relatively high EGR rate and the elimination of subsequently increased PM by DPF. However, it results in the deterioration of fuel economy due to relatively high EGR rate. The second is to use the high combustion strategy to reduce PM emission by high oxidation rate and trap the high NOx emissions with DeNOx catalysts such as Urea-SCR. While it has good fuel economy relative to the first method mentioned above, its infrastructure is demanded. In this paper, the number distribution of nano PM has been evaluated by Electrical Low Pressure Impactor(ELPI) and CPC in case of Urea-SCR system in second method. From the results, the particle number was increased slightly in proportion to the amount of urea injection on Fine Particle Region, whether AOC is used or not. Especially, in case of different urea injection pressure, the trends of increasing was distinguished from low and high injection pressure. As low injection pressure, the particle number was increased largely in accordance with the amount of injected urea solution on Fine Particle Region. But Nano Particle Region was not. The other side, in case of high pressure, increasing rate of particle number was larger than low pressure injection on Nano Particle Region. From the results, the reason of particle number increase due to urea injection is supposed that new products are composited from HCNO, sulfate, NH3 on urea decomposition process.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.8-13
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• 1999

$ZrB _2$ was prepared from a mixture of $ZrO_2$, $B_2$$O_3$and Mg by SHS method. The combustion products were successfully obtained from a mixture of $Zro_2$:$B_2$$O_3$:Mg=1:2.0:8.5(molar ratio). MgO, by-product, was removed to 92.7% by leaching with 1M HCl solution at 9$0^{\circ}C$, for 10 hours. After leaching, the mean particle size of the resultant $ZrB_2$powders was 23.6$\mu\textrm{m}$. $ZrB_2$-ZrC composite was suitably obtained from a mixture of C/Zr=1.2 molar ratio by arc-melting method. The density of arc-melted specimen increased by adding excess zirconium content(x). The bulk density was 6.17g/㎤ for x=0, and 6.37g/㎤ x=4. Vickers hardness of arc-melted specimen was /$1290kg\textrm{mm}^2$ for x=0, and fracture toughness increased to 4.2MPa.m\ulcornerforx=4 compared to 3.4MPa.m\ulcornerfor x=0.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.12
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• pp.1639-1644
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• 2018

Unlike internal combustion engines, electric cars have little engine sound and very quiet, causing the following problems to occur. First of all, pedestrians are a threat to safety because they can't feel the car approaching. The driver is also unable to recognize how fast his car is driving at a certain speed. To solve these problems, electric cars should be artificially created and reused. This paper examines the problems of the Sampling engine sound currently being used and uses the engine sound to produce a sound engine sound for the solution. The sampling engine sound has some limitations in making natural engine sounds. To overcome this problem, we studied two methods of using software synthesizers. They found subtractive synthsizing and wavetable synthsizing, which compared wavetabe synthsizing with actual engine, sampling and subtractive methods to find the most similar to real engine sound. We found that data usage and production cost are more advantageous than sampling method and subtractive syndication method.

• Journal of the Korean Society of Radiology
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• v.2 no.3
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• pp.11-18
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• 2008

In this study, the particle properties and luminescence properties of Gd2O3 nano powder with various Eu content were studied. Gd2O3:Eu nano powder was fabricated using special solvent which mixed the alcohol and the distilled water at specific ratio. This solvent by the solution method showed short fabrication time because solution time of Gd and Eu was reduced. From this experiment with Gd2O3:Eu, the particle properties og nano powder phosphor way analysed using SEM (scanning electron microscope) and EDX(Energy Dispersive X-ray). Also the luminescence properties of nano powder was measured using PL(Photoluminescence) and CL (CathodeLuminescence). The size of powder was 30nm~40nm. The magnitude of powder showed the best peak at 620nm. Among 1,3,5wt% of Eu content, the more Eu content was added in powder, the more photons wre generated. Also it shows luminescence efficiency was improved adding 5% of Eu content.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.18-24
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• 2013

This study was conducted to recycle fly ash containing an abundance of CaO generated from combustion in a circulating layer as a carbon storage medium. The study utilized XRD, TG-DTA and XRF analyses during the hydration of fly ash and identified calcium substances within fly ash that could be used in a carbonation process. $Ca^{2+}$ ions in the calcium substances were easily converted to hydrates. A carbonation experiment was done, which used the method of $CO_2$ gas injection to produce suspensions by mixing fly ash with distilled water. The results were analyzed using TG-DTA, XRD, and pH meter measurements. The study was able to verify that the reaction was completed at a $CO_2$ flow rate of 300cc/min approximately 30 minutes after an injection into a solution with a solid-liquid ratio of 1 : 10 of fly ash and distilled water. Moreover, the stirring time of the suspensions did not influence the reaction, and the reaction time was found to diminish as the portion of the fly ash became smaller. Thus, this study produced carbon storage fly ash having a $CO_2$ storage rate of about 71% through the utilization of the CaO content contained within fly ash.