• Korean Journal of Materials Research
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• v.4 no.4
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• pp.406-415
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• 1994

The effects of fabrication method and condition on critical current density of Ag sheathed Bi- 2223 superconducting tapes by powder-in-tube method were studied. The highest critical current density (Jc) in the whole process was measured in the repeative heat treatment of 250 hour and mechanical deformation of 2 times. These results are suggested that the high-Tc phase at the heat treatment of 250 hour was superior and the good grain alignment at the mechanical deformation of 2 times was analyzed by XRD pattern. The highest critical current density obtained by pressing method was $1.05\times 10^4A/\textrm{cm}^2$ and $0.78\times 10^4A/\textrm{cm}^2$ in case of rolling method. The multifilamentary wires with 7 and 49 filaments were fabricated to check the applicability of pressing and rolling method for preparing multifilaments wire. The critical current density of 7 filaments tapes prepared by pressing showed $0.45 \times 10^{4}A/\textrm{cm}^2$ and $0.20 \times 10^{4}A/\textrm{cm}^2$ for 49 filaments tapes prepared by rolling.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.495-504
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• 2015

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the ${\gamma}$-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.231-239
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• 2006

In this study, we evaluated the efficiency of using sulfur-$CaCO_3$ complex pellet in the sulfur oxidizing autotrophic denitrification process for synthetic wastewater with high $CaCO_3$ concentration. The sulfur-$CaCO_3$ complex pellet was packed in reactor(R4). Influent ${NO_3}^--N$ loading rate was from 200 to $1,000g/m^3{\cdot}day$. During the operation, average denitrification efficiency of R4 was above 95%. Particularly, the denitrififation rate at $1,000g/m^3{\cdot}day$ loading was 98.96% for R4. High ${NO_3}^--N$ removal efficiency was determined in R4 compared with other reactors. Through $Ca^{2+}$ and alkalinity analyses, we calculated the supplied alkalinity from the packed $CaCO_3$ in the reactor. Sulfur-$CaCO_3$ complex pellet more effectively supplied alkalinity through the dissociation of $CaCO_3$ as compared with other media. Based on these results, sulfur-$CaCO_3$ complex pellet increased the pH buffering capacity while also providing the carbon source to the denitrifying bacteria. Denitrification efficiency of R4 was also higher than other reactors. ESEM pictures of sulfur-$CaCO_3$ complex pellet show higher porosity than that of the granular sulfur. Hence, more denitrifying bacteria attached on the sulfur-$CaCO_3$ complex pellet than on granular sulfur. It can be concluded that the sulfur-$CaCO_3$ complex pellet is a more suitable media for a sulfur oxidizing autotrophic denitrification process as it provides high denitrification efficiency.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.796-805
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• 2009

In this paper, a fabrication process for PZT preform of 1-3 type piezo-composite were studied using powder injection molding (PIM). The viscosity and the Pressure-Volume-Temperature (PVT) characteristics of the fabricated PZT feedstock were analyzed. The filling patterns, pressure, temperature distributions, and forming defects of the preform were analyzed with 3D TIMON commercial packages during PIM process. Also the fabrication conditions and the delivery system of the preform were optimized during the entire PIM process. Based on the simulated results, the preform having uniform distributions of the PZT rod was fabricated with the PIM process.

• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Membrane Journal
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• v.25 no.2
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• pp.152-161
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• 2015

In this study, novel pore-filled anion-exchange membranes (PFAEMs) with low electrical resistance, high permselectivity, and low water-splitting flux property under a concentration polarization condition have been developed for the enhancement in the efficiency of electrochemical water treatment processes. The base membranes have been prepared by filling a copolymer containing quaternary ammonium groups with an excellent ion-exchange capability into a porous polyolefin substrate, showing a high performance superior to that of a commercial membrane. In addition, it was confirmed that the electrochemical membrane performances are preserved while the water-splitting flux is effectively controlled by coating an imidazolium polymer onto the surface of the base membrane. The prepared PFAEMs revealed remarkably low electrical resistances of about 1/6~1/8 compared to those of a commercial membrane, and simultaneously low water-splitting flux comparable with that of cation-exchange membranes under a concentration polarization condition.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.527-534
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• 2012

The adsorption dynamics of activated carbon (AC) and carbon molecular sieve (CMS) beds were studied to recover ethylene from FCC fuel gas. In this study, the FCC fuel gas used consisted of six-component mixture ($CH_4/C_2H_4/C_2H_6/C_3H_6/N_2/H_2$,32:15:14:2:12:25 vol.%). And the breakthrough experiments of adsorption and desorption were carried out. The breakthrough sequence in the AC bed was $H_2$ < $N_2$ < $CH_4$ < $C_2H_4$ < $C_2H_6$ while the sequence in the CMS bed was $H_2$ < $CH_4$ < $N_2$ < $C_2H_6$ < $C_2H_4$. The separation performance of the CMS bed during the adsorption step was lower than that of the AC bed. However, due to the characteristics of kinetic separation, the CMS bed could remove $CH_4/N_2$ as well asthe molecules that are larger than $C_2H_6$, which was not easy to be done by the AC bed. Since it was hard to regenerate the adsorption bed by simple depressurization, vacuum regeneration should be adopted. As a result, the pressure vacuum swing adsorption (PVSA) process, consisting of CMS pretreatment process and AC main process, was suggested to recover ethylene efficiently.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.201-209
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• 2006

Various desorption methods were investigated for an activated carbon and zeolite 13X packed bed after benzene adsorption. Desorption experiments using hot steam, purge gas, and evacuation were performed. As a result, the desorption with hot steam showed the best performance. Hot steam makes the temperature in the adsorption column increase and gives arise to the desorption. Drying process should be accompanied to increase the efficiency because steam vapor prevents the adsorption later. The vacuum desorption showed poor performance and it reveals that temperature swing operation is more effective than pressure swing operation. In the purge gas desorption, good performance was achieved using evacuation.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.174-178
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• 2001

In order to reduce the lead-time and cost, recently the technology of rapid protoyping and manufacturing(RPM)has been widely used. Machining process is still considered as one of the effective RPM methods that have been developed and currently available in the industry. It also offers practical advantages such as precision and versatility. Some considerations are still required during the machining process. One of the most important points is fixturing. There should be an effective method of fixturing since the fixturing time depends on the complexity of geometry of the part to be machined. In this paper, the rapid manufacturing process has been developed combining machining with automatic filling. The proposed fixturing technique using automatic filling can be widely applicable to free surface type of product such as a fan. In the filling stage, remeltable material is chosen for the filling process. An automatic set-up device attachable to the table of the machine has also been developed. The device ensures the quality during a series of machining operations. This proposed process has shown to be a useful method to manufacture the required products with the reduced the response-time and cost.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.28-31
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• 2001

Recently, in order to satisfy the consumer's demand the life cycle and the lead-time of a product is to be shortened. It is thus important to reduce the time and cost in manufacturing trial products. Several techniques have been developed and successfully commercialized in the market RPM(Rapid Prototyping and Manufacturing). However, most commercial systems currently use resins or waxes as the raw materials. So, the limited mechanical strength for functional testing is regarded as an obstacle towards broader application of rapid prototyping techniques. To overcome this problems, high-speed machining technology is being investigated worldwide for rapid manufacturing and even for direct rapid tooling application. In this paper, some fundamental experiments and analyses are carried out to obtain the filling time, materials, method, and process parameters for HisRP process. HisRP is a combination process using high-speed machining technology with automatic filling. In filling process, Bi58-Sn alloy is chosen because of the properties of los-melting point, low coefficient of thermal expansion and enviromental friendship. Also the use of filling wire is of advantage in term of simple and flexible mechanism. Then the rapid manufacturing product, for example a skull, is machined for aluminum material by HisRP process with an automatic set-up device of 4-faces machining.