• Applied Chemistry for Engineering
• /
• v.20 no.3
• /
• pp.313-316
• /
• 2009

Synthesis of porous $CeO_2$ particles was investigated using various ionic liquids (ILs) as an effective template. The pore structure and crystalline phase of $CeO_2$ particles was affected significantly by the composition of ionic liquids. The strength of the hydrogen bonds on the anion part of ionic liquid was an essential factor to form the pore architecture of $CeO_2$ particles. Moreover, the length of alkyl group on the cation part of ionic liquid determined the pore size and surface area of $CeO_2$ particles. Among the ionic liquids, it was found that 1-Buthyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) was the most effective ionic liquid to synthesize the porous $CeO_2$ particle.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.6 s.177
• /
• pp.1565-1574
• /
• 2000

Surface edge crack subjected to contact stresses is analysed. A punch with corner radii is considered to press the semi-infinite plane. Partial slip problem is solved when a shear force is applied to the punch. Dislocation density function method is used to solve the present mixed mode crack problem. The crack length of positive K1 is examined, which is affected by the ratio of the flat portion to the total width of the punch. Surface traction during one cycle of the shear force is evaluated to simulate the fretting condition. The compliance change of the contact surface is also investigated during the shear cycle. It is found that the crack grows during only a part of the cycle, which may be termed as effective period of crack growing. A design method for restraining the fretting failure is discussed, from which recommendable geometry of the punch is suggested.

• Journal of computational fluids engineering
• /
• v.21 no.3
• /
• pp.110-117
• /
• 2016

It is a essential to minimize production of by-products for economically effective petrochemical process. In order to find key factor to achieve the effective process, 2-dimensional computational fluid dynamics considering a variety of physics such as convective and radiative heat transfer and thermal cracking of ethane are carried out. The reactor is modeled as an isothermal tube, whose length is 1.2 m and radius is 0.01 m, respectively. At first, the axial distribution of representative by-products in ethane thermal cracking are investigated in each inner wall temperature conditions. Then the comparison between concentration of propene($C_3H_6$) and ethane conversion is discussed with respect to inner wall temperature conditions too. Finally, both reaction rate and turbulent kinetic energy are used to identify the production mechanism of $C_3H_6$ under the intersection point in the plot for $C_3H_6$ molar concentration and ethane conversion.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.2
• /
• pp.141-152
• /
• 2011

In this study, we extracted effective factors of pipe burst from the status data of water asset, operating data of pressure, volume and etc. and 7 years' pipe burst and repair records. The extracted factors were sorted by each attribution and then a statistical analysis was performed to generate a pipe burst probability function using the logistic regression model. As the result, material, diameter, length, laying year, pressure and road width affected to pipe burst significantly. Especially, in case of small diameter, laying year was most effective factor and in case of steel pipe, external loading was main cause of burst, and in case of cast iron, PE, PC, HP pipes, the deterioration of joint was main cause. The other side, as a result of Hosmer-Lemeshow goodness of fit test the models are turned out significant statistically. Also the classification criteria were determined to minimize the total cost from classification errors, when the predicted probability was more than 18% this pipe could have a chance of burst.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.5 no.2
• /
• pp.42-48
• /
• 2006

In order to assess the validity of fatigue crack arrest design charts obtained from our previous numerical approach to fatigue crack arrest condition, an extensive fatigue crack growth/arrest test was performed using CT-type integrally stiffened panels. The results are presented as fatigue crack growth rate and non-dimensional crack length relationship, and these are compared with numerically simulated crack growth rates. The measured values of da/dN at the moment of fatigue crack arrest occurred in stiffened panels are good agreement with those numerically simulated crack growth rates.

• Structural Engineering and Mechanics
• /
• v.10 no.1
• /
• pp.27-36
• /
• 2000

The Oktalok nodal connection system is an aesthetic and efficient system. It has been widely used throughout Australia. The paper will briefly introduce the concept and application of the Oktalok nodal system. The existing design method is based on the assumption that the joints are pin-ended, i.e., the rotational stiffness of the joints is zero. However the ultimate capacity of the frame may increase significantly depending on the rotational stiffness of the joints. Stiffness tests and finite element simulations were carried out to determine the rotational stiffness of the Oktalok joints. Column buckling tests and non-linear finite element analyses were performed to determine the member capacity of columns with semi-rigid end conditions. A simple formulae for the effective length factor of column buckling is derived based on the above experimental and theoretical investigations.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.653-658
• /
• 1999

Bond between reinforcing bars and the surrounding concrete is supposed to safely transfer load in the design process of reinforced concrete structures. Bond failure of reinforcing bars generally take place by splitting of concrete cover as bond force between concrete and reinforcing bars exceeds the resistance by the confinement of the concrete cover and transverse reinforcement. Confinement, concrete cover and transverse reinforcement, on bond are the key factor of current provision to determine development length of reinforcing bars to concrete. In this study, previous available data are analyzed with respect to the current provisions for development and splice of reinforcement. From this study, the new provision for the design are proposed, which will be efficient and effective with some specific limit value.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2001.04a
• /
• pp.28-33
• /
• 2001

Screw conveyors are used extensively in industrial for conveying and elevating materials. Despite their apparent simplicity, the mechanics of the conveying action is very complex. so many engineers depend on experiential data. Capacities of screw are pumping, steady flow of polymer melts, steady volumetric throughput etc. they are affected by geometry of screw, heat flux, pressure on inside barrel, rotating velocity, friction coefficient at screw surface etc. by computation volumetric efficiency increases as rotating velocity increases and decreases as friction coefficient increases. also it decreases with short pitch length. and double flight screw is more effective than single flight screw. The temperature of polymer melts by heating pad and injection pressure play a very important role in the injection molding machine. so in this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand what design factors influence on volumetric throughput efficiency of the screw and thermo-mechanical characteristics of screw.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.182-187
• /
• 2000

The application of fracture mechanics have traditionally concentrated on cracks leaded by tensile stresses, and growing under an opening or mode I mechanism. However, many cases of failures occur from growth of cracks subjected to mixed mode loading. Several criteria have been proposed regarding the crack growth direction under mixed mode loadings. This paper is aimed at prediction of fatigue crack growth behaviour under mixed mode(I+II) in two dimensional branched type precrack. In this paper, the maximum tangential stress(MTS) criterion was used to predict crack growth direction. Not only experiment but also finite element analysis(FEA) was carried out. The theoretical predictions were compared with experimental results in this paper

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.1
• /
• pp.113-118
• /
• 2010

In This Paper, at the PSPICE model is presented by Piezoelectric Transformer and CCFL and equivalent circuit of fluorescent light. Highly effective fluorescent light release for next generation is developed for 35W supremacy model three wave length T5 fluorescent lamps. Lighting a candle experiment of T5 fluorescent lamps is carried out by employing Piezoelectric Transformer power-factor improvement circuit and inverter. PLL method is used for supplying a correct frequency of Piezoelectric Transformer operating.