• Journal of Advanced Marine Engineering and Technology
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• v.34 no.3
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• pp.360-368
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• 2010

A SCR catalytic filter system is used for reducing $NO_x$ and soot emissions simultaneously from diesel combustors. The amount of ammonia (as a reducing agent) must be controlled with the amount of $NO_x$ to obtain an optimal $NO_x$ conversion. Hence, gas mixing between ammonia and exhaust gases is vital to ensure that the SCR catalyst is optimally used. If ammonia mass distribution is not uniform, slip potential will occur in rich concentration areas. At lean areas, on the other hand, the catalyst is not fully active. The better mixing is indicated by the higher uniformity of ammonia mass distribution which is necessary to be considered in SCR catalytic filter system. The ammonia mass distributions are depended on the flow field of fluids. In this study, the velocity field of gaseous flow is investigated to characterize the transport of ammonia in SCR catalytic filter system. The influence of different injection placements on the ammonia mass distribution is also discussed. The results show that the ammonia mass distribution is more uniform for the injector directed radially perpendicular to the main flow of inlet at the gravitational direction than that at the side wall for both laminar (Re = 640) and turbulent flows (Re = 4255). It is also found that the mixing index decreases as increasing the heating temperature in the case of ammonia injected at the side wall.

• Analytical Science and Technology
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• v.6 no.2
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• pp.217-223
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• 1993

Thin films of the Au/Cr, Au/Ni/Cr and Au/Pd/Cr systems were deposited on alumina substrates at ambient temperature and $250^{\circ}C$ in a high-vacuum resistance heating evaporator and annealed at $300^{\circ}C$, $450^{\circ}C$ and $600^{\circ}C$ for 1 hour in air, respectively. The film thicknesses of Au, Ni(or pd), and Cr were $1000{\AA}$, $300{\AA}$, and $50{\AA}$, respectively. The substrate temperature during deposition and the post-deposition annealing temperature affected the sheet resistance of thin-films due to the inter-diffusion of each layer. As a result of Auger depth profile analysis, in the Au/Cr system Cr already diffused out to Au surface during deposition at the substrate temperature of $250^{\circ}C$ and Au distribution changed after heat treatment. In the Au/Ni/Cr and Au/Pd/Cr systems, diffusion phenomena of Ni and Pd were found and especially Ni (approximately 45 at.%) diffused out to Au surface and oxidized.

• Journal of the Korean Solar Energy Society
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• v.35 no.4
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• pp.67-75
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• 2015

PV module is conventionally connected in series with some solar cell to adjust the output of module. Some bypass diodes in module are installed to prevent module from hot spot and mismatch power loss. However, bypass diode in module exposed outdoor is easily damaged by surge voltage. In this paper, we study the thermal and electrical characteristics change of module with damaged bypass diode to easily find module with damaged bypass diode in photovoltaic system consisting of many modules. Firstly, the temperature change of bypass diode is measured according to forward and reverse bias current flowing through bypass diode. The maximum surface temperature of damaged bypass diode applied reverse bias is higher than that of normal bypass diode despite flowing equal current. Also, the output change of module with and without damaged bypass diode is observed. The output of module with damaged bypass diode is proportionally reduced by the total number of connected solar cells per one bypass diode. Lastly, the distribution temperature of module with damaged bypass diode is confirmed by IR camera. Temperature of all solar cells connected with damaged bypass diode rises and even hot spot of some solar cells is observed. We confirm that damaged bypass diodes in module lead to power drop of module, temperature rise of module and temperature rise of bypass diode. Those results are used to find module with a damaged bypass diode in system.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.571-580
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• 2020

In this study, an experimental study on storage media for thermal energy storage system was conducted. For thermal energy storage medium, concrete has excellent thermal and mechanical properties and also has various advantages due to its low cost. In addition, the ultra-high strength concrete reinforced by steel fibers exhibits excellent durability against exposure to high temperatures due to its high toughness and high strength characteristics. Moreover, the high thermal conductivity of steel fibers has an advantageous effect on heat storage and heat dissipation. Therefore, to investigate the temperature distribution characteristics of ultra-high-strength concrete, concrete blocks were fabricated and a heating test was performed by applying high-temperature thermal cycles. The heat transfer pipe was buried in the center of the concrete block for heat transfer by heat fluid flow. In order to explore the temperature distribution characteristics according to different shapes of the heat transfer pipe, a round pipe and a longitudinal fin pipe were used. The temperature distribution at the differnent thermal cycles were analyzed, and the thermal energy and the cumulated thermal energy over time were calculated and analyzed for comparison based on test results.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1520-1532
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• 2003

An experiment was performed to obtain the local heat transfer coefficient and Nusselt number in a circular duct with a 180$^{\circ}$ bend for Re=6 x 10$^4$, 8 x 10$^4$ and 1 x 10$\^$5/ under swirling flow and non-swirling flow conditions. The test tube with a circular section was made from stainless steel having a curvature ration of 9.4. Current heat flux of 5.11 kW/㎡ was applied to the test tube by electrical power and the swirling motion of air was produced by a tangential inlet to the pipe axis at 180$^{\circ}$. Measurements of local wall temperatures and the bulk mean temperatures of air were made at four circumferential positions at 16 stations. The wall temperatures showed a reduced distribution curve at the bend for the non-swirling flow, but this effect did not appear for the swirling flow. The Nusselt number distributions for the swirling flow, which was calculated from the measured wall and the bulk temperatures, were higher than that of the non-swirling flow. The average Nusselt number of the swirling flow increased by about 90-100%, compared to that of the non-swirling flow. The Nu/Nu$\_$DB/ values at the 90$^{\circ}$ station for non-swirling flow and swirling flow were approximately 2.5 and 4.8 at Re=6x10$^4$ respectively. The values agree well with Said's results for non-swirling flow.

• Journal of Welding and Joining
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• v.4 no.2
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• pp.30-39
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• 1986

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthal's equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05b
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• pp.126-126
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• 1992

Solid and liquid sintering behaviors of mechanically alloyed 75W-25Cu powders have been studied by using a dilatometry technique. The sintering was performed under hydrogen atmosphere of 1 atm with a heating rate of 3 $^{\circ}C$/min. The mechanically alloyed 75W-25Cu powders were prepared by high energy ball milling process under argon atmosphere of 1 atm with alloying times of 0 to 400 h. To compare with the sintering behaviors of mechanically alloyed powders, pure Cu and W powders were also sintered under the above conditions, As the mechanical alloying time increased from 0 to 400 h, the shrinkage behavior of the alloyed powders was enhanced during the sintering, and staring temperature of liquid sintering decreased from 1083 to 1068 $^{\circ}C$. The saturation temperature, above which the shrinkage was completed, of liquid phase sintering decreased from 1248 to 1148 $^{\circ}C$ with increasing mechanical alloying time from 200 to 400 h. The residual stress of the mechanically alloyed powder was measured by X-raydiffractometer. The microstructure of sintered spcimen was observed by optical and scanning electron microscope. From these results, variations of solid and liquid sintering behaviors with mechanical alloying time were discussed in terms of the amount of residual stress and the distribution of W and Cu powders in the mechanically alloyed powder.

• Culinary science and hospitality research
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• v.7 no.3
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• pp.85-98
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• 2001

This study was performed to describe the overall sanitation of baking utensils and equipments, employees, and environment in 9 bakeries. Microbiological tests on employees, utensils and equipments, were done according to standard procedure and included total plate count, coliforms, fungi and Staphylococcus aureus.. Microbiological testing is a value in determining hazards for developing a HACCP plan but were not detected throat and employee's hands before use. Staphylococcus aureus was detected nasal cavity and employees's hands after use. Employee's apron after use was detected fungi and coliform and was risk factor of cross-contamination to bread or cookies et al. Generally hygienic conditions of pan, kitchen board, knife, brush, and wooden scoop were worse than those of other baking utensils such as tray, bread tweezers, dusting brush and dish cloth. And refrigerator, freezer and fermentation chamber were detected fungi and coliforms. Total plate count of heating table, working table, distribution table, washbowl and refrigerator was increased in 2nd period. Temperature of refrigerator was 10.43$^{\circ}C$ and strict temperature control of refrigerations needs. Therefore, baking utensils and equipments were reguraly need to sterilize and clean. Additionary, it need to practice the effective sanitation education and training program for the bakery managers and employees.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.29-37
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• 1999

Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room, numerical simulation with standard k-${\epsilon}$ model was carried out. In the present study, the marine engine room is separated to two floors with porus horizontal partition and considered as a closed space with a heat source and forced ventilation ducts. The porosity of horizontal partition is found to be important. For the engine room with 2 supply ports & 2 exhaust ports, the increasing of the porosity of horizontal partition is effective to reduce the recirculation flow zone in the second floor. When the engine room is ventilated with three supply air ports & one exhaust port, the increasing of the porosity of horizontal partition is effective to reduce the recirculating flow zone in the exhaust air area, but there is a possibility of local extreme heating at the lower side of engine near bottom.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1282-1284
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• 1998

ZnO Varistor is an electronic ceramic device for controlling the surge voltage from low level to high. In this study, the puncture mechanism occurring in ZnO varistor is investigated, and the simulation for restraining the puncture by formulating the relation between the applied voltage and the increase of the inside temperature of grain is applied. In order to simulate the cause of the current localization which is the primary factor causing the puncture, the localization phenomenon and the temperature distribution induced by the localized current, the Voronoi network is applied, which can realize the structure of the practical varistor better than the established simple network. Using the current through each grain and the voltage applied to the grain boundary obtained from that simulation, the Joule heating energy is calculated and the phenomenon that the puncture occurs can be analyzed quantitatively by simulating the electric and thermal characteristics according to the externally applied pulsed voltage.