• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.811-820
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• 2007

A Study on the optimal design of the AIG(Ammonia Injection Grid) to improve the performance of DeNOx facilities in the HRSG(Heat Recovery Steam Generator) was performed using the CFD analysis. On the basis of the flow analysis results in the case that the AIG in the HRSG was not installed, the numerical analyses according to the positions of AIG, injection angles of nozzle and the control of ammonia injection quantity were carried out. The standard deviation according to factors was calculated for quantitative comparison. As the results, the AIG in the HRSG should be installed in the position that the uniform flow field shows through the exact flow analysis in the previous of the AIG design and installation. In the case the AIG has already been installed and non uniform flow distribution shows, it is recommended that flow correction device or KoNOx catalyst should be used. Otherwise, the control of ammonia injection angle or the ammonia injection quantity using the velocity profile analysis is demanded to accomplish the optimal performance.

• Corrosion Science and Technology
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• v.17 no.4
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• pp.183-192
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• 2018

Stainless steel can be classified into three categories depending on the microstructure as austenitic stainless steel, ferritic stainless steel and martensitic stainless steel. Generally, stainless steel is extremely resistant to corrosion as the name implies. However, under specific environments, susceptibility to localized corrosion such as pitting, intergranular corrosion and stress corrosion cracking increases. This paper reviewed the state of arts on intergranular corrosion mechanisms, countermeasures on intergranular corrosion and intergranular corrosion test methods. Intergranular corrosion is mostly related with chromium depletion at the grain boundary and sometimes with segregation of electroactive elements in solution annealed stainless steel. Countermeasures on intergranular corrosion include avoiding chromium depletion by heat treatment and the addition of alloying elements. Sensitization evaluation of stainless steel was performed either through acid immersion test or electrochemical test. The methods were standardized in (Japanese Industrial Standards). Even though are useful in evaluating the degree of sensitization for industrial purpose but do not provide detailed information about sensitization mechanism, cause and chromium profile.

• Transactions of Materials Processing
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• v.13 no.8
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• pp.723-730
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• 2004

This paper describes the analysis of extrusion process and integrity for a condenser tube which is a component of the heat exchanger in automobile and all conditioning apparatus. Recently, according to the development of analysis method using the computer, the numerical simulation have been applied to the 3-dimensional hot extrusion process with complex section area of the non-steady statement and then results of the analysis have been applied to optimal die design and process design. In this paper, firstly, the die design was performed for a condenser tube with a multi-hole section and the rigid-plasticity FE analysis performed of extrusion process. Secondly, we estimated metal flow of billet, extrusion load, welding pressure in chamber etc. and evaluated the pressure and elastic strain of the die land and mandrel tooth profile through a stress analysis of the die. Finally, the extrusion test was performed to estimate the validity of FE analysis. This paper confirmed that the designed extrusion die of the research is satisfactorily designed fur integrity of condenser tube.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.75-79
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• 2006

Recently, more highly effective construction materials are needed for the reasonable and economical structure system is required as the construction structures become more multi storied, large-sized and diversified. That is to say, the highly qualified concrete is positively promoted as a part of plan to establish the effective space according to the dead load of structures and diminish of segment profile and to build up the economic structures. However, the high strength concrete has the problems such high brittleness and low ductility. Specially, for the high strength concrete, it has different strength from normal concrete as the internal temperature goes up steadily due to high heat of hydration by the quantities of highly level of cement, so the concrete which is mixed with various miscible materials is used. As the development and study for high strength concrete (more than $100N/mm^2$) is under way actively and the strength of high strength concrete increases, the strength different from the existing high strength concrete of ten than $100N/mm^2$, but the study for this is not adequate and indefinite. In addition, the study and report to apply the strength expression and analysis results of internal structure. Therefore, this study is an experiment about using the miscible materials affects what happens to the longitudinal physical property.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1737-1741
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• 2008

The electrochemical and thermal stability of $LiNi_{0.8}Co_{0.16}Al_{0.04}O_2$ were studied before and after $Co_3(PO_4)_2$ coating. Different to conventional coating material such as $ZrO_2$ or AlPO4, the coating layer was not detected clearly by TEM analysis, indicating that the $Co_3(PO_4)_2$ nanoparticles effectively reacted with surface impurities such as $Li_2CO_3$. The coated sample showed similar capacity at a low C rate condition. However, the rate capability was significantly improved by the coating effect. It is associated with a decrease of impedance after coating because impedance can act as a major barrier for overall cell performances in high C rate cycling. In the DSC profile of the charged sample, exothermic peaks were shifted to high temperatures and heat generation was reduced after coating, indicating the thermal reaction between electrode and electrolyte was sucessfully suppressed by $Co_3(PO_4)_2$ nanoparticle coating.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.841-855
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• 1999

In the present work, the effect of a flow maldistribution on the thermal and conversion response of 8 monolith catalytic converter is Investigated. To achieve this goal, a combined chemical reaction and multi-dimensional fluid dynamic mathematical model has been developed. The present results show that flow uniformity within the monolith brick has 8 great impact on light-off performance of the catalytic converter. In the case of lower flow uniformity, large portions of the monolith remain cold due to locally concentrated high velocities and CO, HC are unconverted during warm-up period, which loads to retardation of light-off. It has been also found that the heat-up pattern of the monolith ill similar to the flow distribution profile, In the early stage of the reaction. It may be concluded that flow maldistribution can cause a significant retardation of the light-off and hence can eventually worsen tho conversion efficiency of automotive catalytic converter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.693-699
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• 2009

This paper shows mechanical properties and behaviors of macro- and micro-structures on friction stir welded specimen with 6061-T6 aluminum alloy plate. It apparently results in defect-free weld zone jointed at welding conditions like the traverse speed of 267mm/min, tool rotation speed of 2500rpm, pin inserted depth of 4.5mm and tilting angle of $2^{\circ}$ with tool dimensions such as tool pin diameter of 5mm, shoulder diameter of 15mm and pin length of 4.5mm. The tensile stress ${\sigma}_T=228MPa$ and the yield point ${\sigma}Y=141MPa$ are obtained at the condition of traverse speed of 267mm/min and tool rotation speed of 2500rpm. With the constant rotation speed, the higher traverse speed become, the higher tensile stress and yielding point become. Vickers hardness for welding zone profile were also presented.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.22-28
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• 2008

Friction stir welding(FSW) is an relatively new solid state joining process. A1606l-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process(FSP) uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile playa major role in deciding FSP zone formation in A16061-T6 aluminium alloy. Tow different tool pin profiles have been used to fabricate the joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.19-31
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• 1996

To invetigate the impurity distribution in GaAs crystal grown by horizontal Bridgman method, we constructd the mathematical model describing heat transfer, mass transfer and fluid flow n transient growth of GaAs. Galerkin finite element method and implicit time integration were used to solve the equations and simulate the transient growth. The concentration distribution is similar to the case of diffusion controlled growth when Gr - 0. With the increase of Gr the concentration profile is distroted and the minimum solute concentration appears near the interface. As solidification prosceeds, interface deflection increases steadily and transverse segregation increases until mixing by flow becomes steady. The axial segregation increases with solidification. But, with high intensity of flow axial segregation becomes steady after short transient. At small and large Gr the result showed a good agreememt with the prediction Smith and Scheil.

• International Journal of Industrial Entomology and Biomaterials
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• v.29 no.2
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• pp.145-152
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• 2014

The variation in the level of immune response related gene expression in silkworm, Bombyx mori following infection with Bombyx mori nucleopolyhedrovirus (BmNPV) was analyzed at different time intervals. The occlusion bodies of BmNPV orally inoculated to the two most divergent silkworm races viz., Sarupat (resistant to BmNPV infection) and CSR2 (susceptible to BmNPV infection) were subjected to oral BmNPV inoculation. The expression profile of gp 41 gene of BmNPV in the Sarupat and CSR2 races revealed that the virus could invade the midguts of both susceptible and resistant races. However, its multiplication was significantly less in the midgut of resistant race, while, in the susceptible race, the viral multiplication reached maximum level within 12 h. These findings indicate that potential host genes are involved in the inhibition of viral multiplication within larval midgut. The immune response genes arylphorin, cathepsin B, gloverin, lebocin, serpin, Hsp 19.9, Hsp 20.1, Hsp 20.4, Hsp 20.8, Hsp 21.4, Hsp 23.7, Hsp 40, Hsp 70, Hsp90 revealed differential level of expression on NPV infection. The gloverin, serpin, Hsp 23.7 and Hsp 40 genes are significantly up-regulated in the resistant race after NPV infection. The early up-regulation of these genes suggests that these genes could play an important role in baculovirus resistance in the silkworm, B. mori.