• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.286-290
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• 2003

The high temperature superconducting bulk can be used as the bearing of induction motors. This paper presents the fabrication and test results of an induction motor with superconducting bearings using HTS bulks. The bearing had eight hexahedron type YBCO bulks. Height, width and thickness of the HTS bulk were 30mm, 30mm and 10mm, respectively. Single phase induction motor was used to drive the shaft made of aluminum and the rotor of a conventional induction motor. To estimate the performance of the HTS bulk magnetic bearing, no load test, load test and Impact test were carried out. Load tests were performed by using air resistance caused by the shaft-mounted thin cylinder with buckets. Impact tests by axial direction and vertical direction impact showed that the vibration of the shaft gradually decayed. The induction motor with HTS bulk magnetic bearing rotated silently and smoothly throughout the tests. According to the test results, conventional bearings can be replaced with superconducting magnetic bearings made of HTS bulks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.477-482
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• 2002

This research is concerned with the study of an active vibration absorber using piezoelectric actuators and Isolation pad. The active isolation system consists of 4-pairs of PZT actuators bonded on the surface of an aluminum plate and a passive damping material. The active system is connected to the passive system in series. The Signals of the accelerometers are fed into the PZT actuator through the controller. We proposed a new control technique which can deal with the shock as well as the base excitation in this study. The Positive Acceleration Feedback(PAE) tuned to the natural frequency of the vibration isolation system is used to suppress the vibrations caused by the shock using the top accelerometer signal. The Negative Acceleration Feedback (NAF) based on the base acceleration signal is used to counteract the base motion. Experimental results show that the proposed active vibration isolation system can suppress vibrations.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1835-1838
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• 2013

Polypyrrole-Gold (PPy/Au) segment nanowires are prepared using anodized aluminum oxide (AAO) templates and assembled into a curved superstructure. Since the shape of the obtained superstructures can be designed to be capsule-like with inner space for containing materials, and their openings and closures can be controlled with external stimuli, these structures can be useful for a large variety of applications. Inner space of capsule-like superstructures is an important factor for their applications, and the volume of the inner space can be assessed using the generalized equation suggested by J. K. Lim (Bull. Korean Chem. Soc. 33, 2699 (2012)). In this paper, we introduce a new approach to obtain correct and simplified equation without redundant assumption which was used to induce the previous equations, and recalculate the volume of the inner space in the capsule-like superstructure using a new equation.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.5
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• pp.1-10
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• 2008

Synthetic mineral microparticles (SMM) is a patented system which has been developed to promote drainage of water and retention of fine particles during papermaking. It is shown in patents that the SMM system can have advantages in both of drainage and retention, compared with montmorillonite (bentonite), which is one of the most popular materials presently used in this kind of application. Turbidity and gravity drainage time were measured using a Britt-Jar test with representative SMM formulations, in order to confirm the efficacy of SMM covering a wide range of compositions and discover effects of some key variables that have the potential to lead to unexpected advantages in terms of the effectiveness of the microparticles, when used in combination with a cationic polyacrylamide treatment of papermaking furnish. An iron silicate showed highest retention performance, as well as suitably fast drainage time relative to other metal silicate and bentonite. Zinc silicate improved retention and drainage. SMM synthesized from aluminum sulfate ($Al_2(SO_4){_3}$) did not show a benefit in retention and drainage, relative to bentonite. SMM synthesized from aluminum chloride ($AlCl_3$) performed better in drainage and retention than bentonite when the Al/Si ratios were 0.76 and 1.00. It was found that when the Al/Si ratio and neutralization are considered, pH variation due to the change of Al/Si ratio can be a key factor to control the size of primary metal silicate particles and the degree of coagulation of the primary particles.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.549-553
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• 2014

$CoSb_3$-based skutterudite compounds are candidate materials for thermoelectric power generation in the mid-temperature range (600 - 900 K) because their thermoelectric properties can be enhanced by doping and filling. The joining property of thermoelectric module electrodes containing thermoelectric materials is of great importance because it can dominate the efficiency of the thermoelectric module. This study examined the properties of $CoSb_3$/Al/Ti/CuMo joined by the spark plasma sintering technique. Titanium thin foil was used to prevent the diffusion of copper into $CoSb_3$ and Aluminum thin foil was used to improve the adhesion between $CoSb_3$ and Ti. The insertion of an Aluminum interlayer between the Ti and $CoSb_3$ was effective for joining $CoSb_3$ to Ti by forming an intermediate layer at the Al-$CoSb_3$ boundary without any micro cracks. Specifically, the adhesion strength of the Ti/Al/$CoSb_3$ joining interface showed a remarkable improvement compared with our previous results, without deterioration of electrical property in the interface.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.58-63
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• 2005

In order to minimize weight of vehicle seat, an optimum design of aluminum seat is presented while satisfying stress and fatigue life constraints. In this study, the analysis model is validated by comparing it's stress with that of test. Then, two-level orthogonal array is used to estimate the design sensitivity for 7 design variables. Finally, the sequential approximate optimization (SAO) is performed using the constructed RSM models. The approximate RSM models are sequentially updated using the analysis results corresponding to the approximate optimum obtained during the SAO. After 14 analyses, the SAO gives an optimal design that can reduce 16.7$\%$ of weight while increasing 369$\%$ of fatigue life and satisfying stress constraint.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2650-2656
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• 2013

Mesoporous alumina was synthesized using bayberry tannin (BT) as template. This novel synthesis strategy was based on a precipitation method associated with aluminum nitrate as the source of aluminum in an aqueous system. $N_2$ adsorption/desorption, XRD, SEM and TEM were used to characterize the as-prepared mesoporous alumina. The results showed that the mesoporous alumina possessed crystalline pore wall, high specific surface area, narrow pore distribution and excellent thermal stability. Moreover, the surface area and pore size of the mesoporous alumina can be tuned by changing the experimental parameters. Further, the mesoporous alumina was investigated as the support of palladium catalyst ($Pd-Al_2O_3{^*}$) for the hydrogenation of propenyl, styrene and linoleic acid. For comparison, the reference catalyst ($Pd-Al_2O_3$) prepared without barberry tannin was also employed for the catalytic hydrogenation. The experimental results showed that $Pd-Al_2O_3{^*}$ exhibited the superior catalytic performance than $Pd-Al_2O_3$ for all the investigated substrates, especially for the hydrogenation of linoleic acid with larger molecular.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.319-324
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• 2001

A finite element model for the process of squeeze casting for metal matrix composites (MMCs) in cylindrical mold is developed. The fluid flow and the heat transfer are the fundamental phenomena in the squeeze casing process. To describe heat transfer with solidification of molten aluminum, the energy equation in terms of temperature and enthalpy are applied to two dimensional axisymmetric model which is similar to the experimental system. And one dimensional flow model is employed to simulate the transient metal flow. The direct iteration technique was used to solve the resulting nonlinear algebraic equations. A computer program is developed to calculate the enthalpy, temperature and fluid velocity. Cooling curves and temperature distribution during infiltration and solidification are calculated for pure aluminum. The temperature is measured and recorded experimentally. At two points of the perform inside and one point of the mold outside, thermocouple wire are installed. The time-temperature data are compared with the calculated cooling curves. The experimental results show that the finite element model can estimate the solidification time and predict the cooling process.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.498-509
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• 2009

Present study is concerned with the simulation of plasticity models for the cyclic stressstrain behavior of aluminum alloy AC4C-T6 that can be used for primary materials of LNG cargo pump. Material model of cyclic hardening and plasticity for aluminum alloy AC4C-T6 was investigated through experiments and numerical simulations. Monotonic tensile and cyclic tension-compression test under symmetric load cycles was performed at both room temperature and cryogenic temperature of $-165^{\circ}C$. Based on the experimental data plastic hardening models were evaluated for isotropic/kinematic/combined hardening. FEA (Finite Element Analysis) models which describe the cyclic stress-strain relationship were evaluated for the simulation of plasticity. An appropriate hardening model is proposed comparing the results of FEA with those of experiments.

• Membrane Journal
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• v.19 no.1
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• pp.19-24
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• 2009

Sol-gel process is relatively simple, easy to use, cheap to install, and results in thin coating layers with superior physical and gas barrier properties. Films coated by the sol-gel process can be used as insulating films or packaging films for foods, chemicals, drugs, and beverages, etc. In this study, alumina sol was synthesized from aluminum isopropoxide and silane coupling agent was added to make coating solutions. In addition, biaxially oriented polypropylene (BOPP) was coated using several alumina sol solutions and their oxygen permeabilities were measured. The experimental results indicate that in the best case, the oxygen permeability of coated film was reduced by 85% compared to that of pure BOPP.