• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1244-1250
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• 2014

The temperature of the main engine cabin of commercial vessel is very high. The material SS-316L undergoes creep damage at temperatures exceeding $450^{\circ}C$. It is essential to maintain the highly stressed engine cabin below the creep regime. Hence, seawater is employed in this kind of maritime vehicles as cooling liquid. It obtains the thermal energy at the cooling pipe line after passing through main engine cooling system. To harness the energy in the seawater, a turbine can be installed to absorb the energy in the seawater before being released into the sea. In this study, a cooling pipe line is selected to apply the tubular type hydro turbine for transferring the energy. Numerical analysis for investigating the performance and the internal flow characteristics of the tubular turbine is conducted. The results show that the maximum efficiency of 85.8% is achieved although the efficiency drops rapidly at partial flow rate condition. The efficiency descends slowly at the condition of excess flow rate. There is a relatively wide operating range of flow rate of this turbine to keep high efficiency at the excess flow rate condition. For the internal flow of the turbine, there is uniform streamline on the suction and pressure sides of the blade at the design point. However, the secondary flow appears at the suction and pressure sidesat the excess flow rate.In addition, it appears only at pressure side at the partial flow rate condition.

• Textile Coloration and Finishing
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• v.27 no.3
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• pp.175-183
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• 2015

Weight loss treatment of a fiber leads an improvement of its handle and drape properties. Hydrolysis of a fiber is commonly known as a method to reduce its weight of 5-40%. Most of the studies on the weight loss treatment are mainly based on polyester fibers and there has been almost no study on the weight reduction of nylon fibers. In this study, however, in order to develop a use of nylon 6 fiber for the industrial applications such as toothbrush, underwear, carpet and more, weight loss treatment of a nylon 6 fiber was carried out. Under various treatment conditions, morphological analysis were done to observe the change in the structure of the surface and analysis. From the observation of formic acid treated nylon 6 fiber, there were many etched and deformed morphologies. Thermal and crystalline properties were analyzed to find the changes in the crystal structure caused by the weight loss treatment. There were little differences in the crystalline properties of nylon 6 fiber by formic acid treatment. Tensile strength of nylon 6 fiber decreases with acid concentration. The FITR peak intensity of the amide bond decreases with formic acid concentration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.553-561
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• 2010

A medium-scale helium loop that can simulate a VHTR (very-high-temperature reactor) is now under construction at the Korea Atomic Energy Research Institute. The heaters of the test helium loop electrically heat helium fluid up to $950^{\circ}C$ at pressures of 1 to 9 MPa. To optimize the design specifications of the experimental helium loop, the conjugate heat transfer in the high-temperature helium heater was analyzed by performing a CFD simulation. The analysis results indicate that the maximum temperature does not exceed the allowable limit. It is confirmed that the thermal characteristics of the loop with the given geometry satisfy the design requirements.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.349-358
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• 2005

In this study, analysis of the disposal tunnel spacing and disposal pit pitch was carried out, as a factor of the design to estimate the scale and layout of the repository. To do this, based on the reference repository concept and the engineered barrier concept, several cross sections of the disposal tunnel and disposal pit were established. After then, the mechanical and thermal stabilities of the established tunnels were analyzed. Also, an optimized disposal tunnel spacing and the disposal pit pitch reducing the excavation volume was proposed. The results of these analyses can be used in the deep geological repository design. The detailed analyses by the exact site characteristics data to reduce the uncertainty of the site and the modification for the optimization are required.

• Journal of Powder Materials
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• v.23 no.2
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.518-529
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• 1996

To develope chemical heat pump using available energy sources such as solar heat and many kinds of waste thermal energy we have studied the enhancement effect of inserted fins in cylindical packed bed reactor. Two dimensionnal(radial and circumferential) partial differential eqaetions, concerning heat and masstransfer in CaO packed bad, are solved numerically to describe the characteristics of the reaction of fins inserted reactor and heat transfer. The results obtained by numerical analysis about two dimensional profiles of temperature and conversion in the reactant in the packed bed and exothermic heat amount released from the reactor are follows; -. The insertion of fins in reactor can redue the reaction completion time by half. -. The rate of thermochemical reaction depends of the temperature and concentration and it is also governed by the boundary conditions and heat transfer rate in the particle packed bed.

• The Journal of Advanced Prosthodontics
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• v.6 no.3
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• pp.207-214
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• 2014

PURPOSE. This study characterized the synthesis of a modified PMMA (Polymethyl methacrylate) denture acrylic loading platinum nanoparticles (PtN) and assessed its bacterial inhibitory efficacy to produce novel antimicrobial denture base material. MATERIALS AND METHODS. Polymerized PMMA denture acrylic disc ($20mm{\times}2mm$) specimens containing 0 (control), 10, 50, 100 and 200 mg/L of PtN were fabricated respectively. The obtained platinum-PMMA nanocomposite (PtNC) was characterized by TEM (transmission electron microscopy), SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), thermogravimetric and atomic absorption spectrophotometer analysis. In antimicrobial assay, specimens were placed on the cell culture plate, and $100{\mu}L$ of microbial suspensions of S. mutans (Streptococcus mutans) and S. sobrinus (Streptococcus sobrinus) were inoculated then incubated at $37^{\circ}C$ for 24 hours. The bacterial attachment was tested by FACS (fluorescence-activated cell sorting) analysis after staining with fluorescent probe. RESULTS. PtN were successfully loaded and uniformly immobilized into PMMA denture acrylic with a proper thermal stability and similar surface morphology as compared to control. PtNC expressed significant bacterial anti-adherent effect rather than bactericidal effect above 50 mg/L PtN loaded when compared to pristine PMMA (P=.01) with no or extremely small amounts of Pt ion eluted. CONCLUSION. This is the first report on the synthesis and its antibacterial activity of Pt-PMMA nanocomposite. PMMA denture acrylic loading PtN could be a possible intrinsic antimicrobial denture material with proper mechanical characteristics, meeting those specified for denture bases. For clinical application, future studies including biocompatibility, color stability and warranting the long-term effect were still required.

• Clean Technology
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• v.2 no.1
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• pp.60-68
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• 1996

The oxidation of carbon monoxide of low concentration on the natural manganese dioxide (NMD) has been investigated in a fixed bed reactor. The experimental variables were concentration of oxygen (500ppm~99.8%) and carbon monoxide (500ppm~10000ppm) and catalyst temperature ($50{\sim}750^{\circ}C$). The NMD(Natural Manganese Dioxide) has been characterized by temperature - program reduction(TPR) using 2.4% $CO/H_2$ as a reducing agent, thermogravimetric analysis (TGA), and reduction of NMD by 2.4% $CO/H_2$. It was found that the NMD catalyst activity on the unit area was greater than the $MnO_2$ catalyst for oxidation of CO at the same temperature. The thermal stability of oxidation activity was considered to be maintained when the NMD was heated to $750^{\circ}C$. The TGA, reduction by CO, and TPR of the NMD showed that the NMD had active lattice oxygen which was easily liberated on heating in the absence and low concentration of oxygen. The reaction order in CO is 0.701 between 500~3500ppm and almost zero between 3500~10000ppm of CO.

• Journal of Environmental Science International
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• v.27 no.2
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• pp.83-90
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• 2018

In this study, zeolite (Z-C2) was synthesized using a fusion/hydrothermal method on coal fly ash (FA) discharged from a thermal power plant in the Ulsan area and then analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Z-C2 was characterized in terms of mineralogical composition and morphological analysis. The XRD results showed that its peaks had the characteristics of Na-A zeolite in the range of $2{\theta}$ of 7.18~34.18. The SEM images confirmed that the Na-A zeolite crystals had a chamfered-edge crystal structure almost identical to that of the commercial zeolite. The adsorption kinetics of Cu, Co, Mn and Zn ions by Z-C2 were described better by the pseudo-second-order kinetic model more than by the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model did. The maximum adsorption capacities of Cu, Co, Mn and Zn ions obtained from the Langmuir model were in the following order : Cu (94.7 mg/g) > Co (77.7 mg/g) > Mn (57.6 mg/g) > Zn (51.1 mg/g). These adsorption capacities are regarded as excellent compared to those of commercial zeolite.

• Journal of Hydrogen and New Energy
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• v.21 no.3
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• pp.193-200
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• 2010

Anode off-gas of high temperature fuel cell still contains combustible components such as hydrogen, carbon monoxide and hydrocarbon. In this study, a catalytic combustor has been applied to the high temperature fuel cell so that the combustion of anode-off gas can be boosted up. Since the performance of catalytic combustor directly depends on the combustion catalyst, this study is designed to perform the experimental investigation on the combustion characteristics of the three commercial catalysts with a different composition. Screening tests with three catalysts are preceded before the performance examination since it is necessary to determine the most suitable catalyst for design configuration of the catalytic combustor. The performance analysis shows that methane conversion rate strongly depends on gas hourly space velocity (GHSV) as well as inlet gas temperature. Additionally, the GSHV optimization results show that the optimum GHSV will be in the range between 18,000 $hr^{-1}$ and 36,000 $hr^{-1}$. It is also shown that the minimum inlet temperature of catalytic reaction of methane is from $100^{\circ}C$ to $150^{\circ}C$.