• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.71-80
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• 2012

To improve the $NO_X$ conversion over a SCR (selective catalytic reduction) catalyst, the DOC (diesel oxidation catalyst) is usually placed upstream of the SCR catalyst to enhance the fast SCR reaction ($4NH_3+2NO+2NO_2{\rightarrow}4N_2+6H_2O$) using equimolar amounts of NO and $NO_2$. Here, a ratio of $NO_2/NO_X$ above 50% should be avoided, because the reaction with $NO_2$ only ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$) is slower than the standard SCR reaction ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$). In order to accurately predict the performance characteristics of SCR catalysts, it is therefore desired to develop a more simple and reliable mathematical and kinetic models on the oxidation kinetics of nitric oxide over a DOC. In the present work, the prediction accuracy and limit of three different chemical reaction kinetics models are presented to describe the chemicophysical characteristics and conversion performance of DOCs. Steady-state experiments with DOCs mounted on a light-duty four-cylinder 2.0-L turbocharged diesel engine then are performed, using an engine-dynamometer system to calibrate the kinetic parameters such as activation energies and preexponential factors of heterogeneous reactions. The reaction kinetics for NO oxidation over Pt-based catalysts is determined in conjunction with a transient one-dimensional (1D) heterogeneous plug flow reactor (PFR) model with diesel exhaust gas temperatures in the range of 115~$525^{\circ}C$ and space velocities in the range of $(0.4{\sim}6.5){\times}10^5\;h^{-1}$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.20-28
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• 2002

In this paper, the aerodynamic performance prediction of a 30kW counter-rotating (C/R) wind turbine system has been made by using the momentum theory as well as the two-dimensional quasi-steady strip theory with special care on the wake and the post-stall effects. In order to take into account the wake effects in the performance analysis, the wind tunnel test data obtained for a scaled blade are used. Both the axial and rotational inductions behind the auxiliary rotors are determined through the wake model. In addition, the optimum chord and twist distributions along the blades are obtained from the Glauert's optimum actuator disk model considering the Prandtl's tip loss effect. The performance results of the counter-rotating wind turbine system are compared with those of the conventional single rotor system and demonstrated the effectiveness of the counter-rotating wind turbine system.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.4
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• pp.134-139
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• 2008

A spirally arrayed nano-pattern is designed as a model pattern for the next generation optical storage media. The pattern consists off types of embossed rectangular dot, which are 50nm, 100nm, 150nm and 200nm in length and 50nm in width. The height of the dot is designed to be 50nm. The pitch of the spiral track of the pattern is 100nm. A ER(Electron resist) master for this pattern is fabricated by e-beam lithography process. The ER is first spin-coated to be 50nm thick on a Si wafer and then the model pattern is written on the coated ER layer by e-beam. After developing this pattern written wafer in the solution, a ER pattern master is fabricated. The most conventional e-beam machine can write patterns in orthogonal way, so we made our own pattern generator which can write the pattern in circular or spiral way. This program generates the patterns to be compatible with the e-beam machine from Raith(Raith 150). To fabricate 50nm pattern master precisely, a series of experiments were done including the design compensation for the pattern size, optimization of the dose, acceleration voltage, aperture size and developing. Through these experiments, we conclude that the higher accelerating voltages and smaller aperture size are better for mastering the nano pattern which is in order of 50nm. With the optimized e-beam lithography process, a spiral arrayed 50nm pattern master adopting PMMA resist was fabricated to have dimensional accuracy over 95% compared to the designed. Using this pattern master, a metal pattern stamp will be fabricated by Ni electro plating for injection molding of the patterned plastic substrate.

• The Korean Journal of Nuclear Medicine
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• v.39 no.2
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• pp.94-99
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• 2005

Electrocardiogram-gated single photon omission computed tomography (SPECT) provides valuable information in the assessment of both myocardial perfusion and ventricular function. Tl-201 is a suboptimal isotope for gating. Tl-201 images are more blurred compared with Tc-99m tracers due to the increased amount of scattered photons and use of a smooth filter. The average myocardial count densities are approximately one-half those of conventional technetium tracers. However, Tl-201 is still widely used because of its well-established utility for assessing myocardial perfusion, viability and risk stratification. Gated SPECT with Tl-201 enables us to assess both post-stress and rest left ventricular volume and function. Previous studies with gated Tl-201 SPECT measurements of ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV) have shown high correlation with first-pass radionuclide angiography, gated blood pool scan, Tc-99m-MIBI gated SPECT, contrast ventriculography, echocardiography, and 3-dimensional magnetic resonance imaging. However, problems related to these studies include few agreement data of EDV and ESV, use of a reference method that is likely to have the same systemic errors (gated Tc-99m-MIBI SPECT), and other technical factors related to the count density of gated SPECT. With optimization of gated imaging protocols and more validation studies, gated Tl-201 SPECT would be an accurate method to provide perfusion and function information in patients with coronary artery disease.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.51-59
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• 2006

The physical characteristics of autonomic microcapsules manufactured with various agitation speeds in a stirred tank were observed experimentally by a particle size analyzer and an optical microscope. The flow characteristics in a stirred tank were also investigated through a 3-dimensional numerical simulation to understand the manufacturing process of autonomic microcapsules. According to the results, we found that the agitation speed was the important factor to determine the sizes of microcapsules. The impeller-induced flow allowed the jet and tip-vortex pair components in the mixed fluid of a stirred tank. The vorticity around the blades in the impeller was increased as increasing the agitation speed. In addition, the size of autonomic microcapsules was strongly affected on the small scale mixing pattern such as a tip-vortex pair.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.3
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• pp.201-208
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• 2015

Organogels are semi-solid systems that consist of an apolar solvent as the liquid phase within a three-dimensional networked structure. In this study, we developed a stable and skin penetration-enhanced Lecithin Organogel (LO) containing genistein, which is one of the poorly soluble active ingredients in both polar and apolar phase. After screening of various components (type of gelators, organic and aqueous phase), hydrogenated lecithin (HL), sunflower oil (SO), dipropylene glycol (DPG), and polyethylene glycol (PEG) were mainly used in this formulation. Phase ternary diagram was employed for optimization of the composition in the LO. The formulated LO were evaluated for its organoleptic characteristics, stability, pH, rheology, phase transition temperatures, microscopic analysis and skin penetration. The optimized stable LO system can be utilized as an effective and stable cosmetic formulation that can carry poorly soluble active ingredients at high concentration for topical dermal delivery.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.675-691
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• 2002

The focus of this work is on the development of large-scale numerical optimization methods for optimal control of steady incompressible Navier-Stokes flows. The control is affected by the suction or injection of fluid on portions of the boundary, and the objective function of fluid on portions of the boundary, and the objective function represents the rate at which energy is dissipated in the fluid. We develop reduced Hessian sequential quadratic programming. Both quasi-Newton and Newton variants are developed and compared to the approach of eliminating the flow equations and variables, which is effectively the generalized reduced gradient method. Optimal control problems we solved for two-dimensional flow around a cylinder. The examples demonstrate at least an order-of-magnitude reduction in time taken, allowing the optimal solution of flow control problems in as little as half an hour on a desktop workstation.

• Korean Business Review
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• v.11
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• pp.101-122
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• 1998

This study is to analyze the effect of product involvement on consumer purchase process. From review on previous involvement literatures, enduring product involvement can be defined as "a person's arousal and motivational state activated by product on the basis of his basic value, objective and ego-relevance." To evaluate the effect of involvement on product purchase process, 11 hyphotheses concerning behavioral aspects which is expected to comprise consumer purchase process and to be influenced by degree of involvement were constructed: prepurchase information search, alternative brand comparision, utilization of product attribute, brand differentiation, brand commitment, product knowledge, influence of reference group, dependence on price, price awareness, cognitive dissonance and purchase optimization. Hyphotheses are tested with data from 388 housewives through 20 item involvement scale developed with multi-dimensional perspective on involvement. The scale successfully provides rank order of 8 selected products expected to cover the spectrum of product involvement: formal clothes, coffee, washing machine, shampoo, perfume, detergent, soft drink, pain-reliever as the order of product involvement. Major findings of this study are as follow. First of all, incresed differences were found in hihg involvement product like formal clothes with respect to the degree of prepurchase information search, alternative brand comparision, utilization of product attribute, influence of reference group in any method of analysis. Secondly, invlovement should be interpreted as a consumer characteristic rather than a product one. This means that consumers involve themselves with products, instead products themselves do not have any involvement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1911-1918
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• 2014

The increase of input resources, such as labor and equipment, in a construction project causes workspace interference between activities and it influences on the productivity and quality of construction activities. To solve this problem, many studies related to the workspace interference have been performed, however they verified the workspace concerning with only the geometric location of activities or generated the shape of workspace by a whole object concept not separated units of detailed operations. It is difficult for project manager to reasonably analyze the workspace conflict, because the size of workspace cannot reflect the characteristics of an activity and input time of a resource. This paper presents a methodology that can generate three-dimensional models in order to optimize the workspace shape and size by considering with the characteristics of each activity and input time of each resource. The suggested method can be used for the active BIM system that optimizes the workspace conflict without additional construction duration and for the searching algorithm of optimized moving path for construction equipment.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.5 no.1
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• pp.22-28
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• 2002

A New concept for the LNG-FPSO ship, with moonpool and bilge step in bottom, is proposed. This concept is investigated with regard to motion reduction and sloshing phenomena of the cargo and operation tanks. The principal dimensions of the ship are $L\timesb B\times D\times t(design)=270.0\times51.0\times32.32\times13.7(m)$, with a total cargo capacity of 161KT; a 98% loading condition is considered for this study. The moonpools and rectangular step at the bilge have been designed for the purpose of decreasing the motion within the tank. For the motion analysis, linearized three-dimensional diffraction theory, with the simplified boundary condition was used. The six-degree of freedom coupled motion responses were calculated for the LNG-FPSO ship. Viscous effects on the roll motion responses of a vessel were taken into account in this calculation program, using an empirical formula suggested by Himeno(1981). The case study for the moonpool size has been conducted using theoretical estimation and the experimental method. For the optimization of the moonpool size and effect of the bilge step, 9 cases of its size, both with and without bilge step, were involved in the study. no motion responses, especially roll motion, for the designed LNG-FPSO ships are much lower than those of other drill ships and shuttle tankers. The limit criterions are satisfied. To check the cargo tank and operation tank sizes, we performed a sloshing analysis in the irregular waves which focuses on the pressure distribution on the tank wall and the time history of pressure and free surface for No.2 and 5 tanks of LNG-FPSO with chamfers. Finally, optimum tank sire was estimated.