• Journal of Energy Engineering
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• v.23 no.1
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• pp.1-6
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• 2014

We have surveyed on microcalorimetry which we can treat with energy dispersive spectrometer(EDS) as wavelength dispersive spectrometer(WDS), to be developed in order to make higher energy resolution as to detect X-ray peak as high as wavelength dispersive spectrometer(WDS). When we take into consideration about energy resolution, Wavelength dispersive spectrometer is 2~20eV and energy dispersive spectrometer is 140~180eV.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.174-180
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• 1996

For the investigation of the influence of microstructure of optical thin films on the in-plane thermal diffusivity of glass substrate coated by that films, we constructed the AC calorimeter which uses argon-ion laser as a thermal source and measured several kinds of ZnS optical thin films which prepared by the changing of thermal evaporation speed such as 5$\AA$/s, 10$\AA$/s, 20$\AA$/s, 40$\AA$/s, 60$\AA$/s. The result showed that the thermal diffusivity decreases as the temperature increases. Also, when the evaporation speed is 20$\AA$/s, the thermal diffusivity has maximum value, and the variation of the thermal diffusivities are 27% at maximum.

• Food Science and Preservation
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• v.9 no.3
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• pp.261-266
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• 2002

A transpiration model was selected and tested experimentally to predict transpiration into of Fuji apple stored in a normal air and controlled atmospheres (l∼3% O$_2$+ l∼3% CO$_2$) at 0$\^{C}$ and 98% RH for 6weeks. CA storage decreased the respiration rate of Fuji apple by 50% when compared with normal air storage. The transpiration rates of apple showed 50∼70% higher in normal air storage than those in CA storage and were decreased by increasing CO$_2$concentration under same concentration of O$_2$. The transpiration rates estimated by the selected model were in good agreement with experimental data for Fuji apples under controlled atmosphere conditions and normal air. When the respiratory heat generation rate u of Fuji apple increased with storage conditions, the evaporating surface temperature and transpiration rate also increased. But since some portion of respiratory heat was used as latent heat in the evaporating surface, the change of u value had a little effect on the determination of the evaporation temperature and the transpiration rate.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.31-37
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• 2014

The aim of this work is to provide new experimental data on the pyrolysis characteristics and the minimum ignition energy (MIE) by using the same high-density polyethylene (HDPE) powder in domestic HDPE dust explosion accident. To evaluate the explosion sensitivity of HDPE, thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC) and MIE apparatus (MIKE-3, K$\ddot{u}$hner) was conducted. The measurements showed the volume median diameter of $61.6{\mu}m$ but the particle number density of 98 % in the range $0.4{\sim}4{\mu}m$. The ignition temperature from the results of TGA and DSC in HDPE dust layers was observed in the range of $380{\sim}490^{\circ}C$. MIE was measured under 1 mJ in the HDPE dust concentration of $1200{\sim}1800g/m^3$, it was found that the ratio of particle number density in the range $0.4{\sim}4{\mu}m$ was very high (98%).

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.206-210
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• 2011

We fabricated rod-like poly(lactic acid)(PLA) specimens through applying various methods of equal-channel angular extrusion(ECAE) process and investigated the change of thermal and mechanical properties of specimens before and after each ECAE process. Combining three re-injection routes(A, BC, and C) and three pass counts(1, 2 and 4) allowed us to fabricate 7 different PLA specimens. Thermal properties of each specimen were measured by both differential scanning calorimeter and thermo-gravimetric analyzer. Shear strains of each specimen with respect to applied loads were measured by indentation hardness tester. Field emmision scanning electron microscopy was used to observe internal microstructure of cross-section of each specimen. The observed microstructures qualitatively supported the explanation of hardness test results. Among 7 specimens, PLA-P2A showed the biggest shear strain probably due to its dense microstructure.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.92-100
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• 1997

Weld repair of ASTM A-470 class 8 high pressure (HP) steam turbine rotor steel has been performed to extend the service life of older fossil units. Microhardness measurements were conducted across the weldment from unaffected base metal (BM) to weld metal (WM). The hardness of the BM was VHN 253, however it dropped up to VHN 227 at the heat affected zone (HAZ) close to unaffected BM for multipass SAW. This area of hardness drop is called "siftening zone" and has a width of 0.5-0.6mm. During creep rupture test, failure occurred around the softening zone and rupture time was 772.4hr at 19Ksi (132 Mpa) and 593.deg. C. Multipass MIG and TIG welding have been employed to reduce the softening zone width. The softening zone width for MIG was 0.3-0.4mm and for TIG was zero-0.4mm depending on heat inputs. However creep rupture time was decreased as softening zone width reduced. Creep rupture time also showed a close relationship with heat inputs in TIG process. The higher heat input, the longer rupture time. Most failure occurred at intercritical HAZ (ICHAZ), however rupture location was shifted to coarse grained HAZ (CGHAZ) as heat input decreased. The rupture surface showed tearing and dimple which indicated transgranular fracture. fracture.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.660-667
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• 2017

Equilibrium data of the mixture is essential in the design and operation of separation equipment such as distillation or extraction in chemical processes. These equilibrium data can be obtained through experiments or by calculations using the known binary parameters and the thermodynamic models. Generally, to obtain these parameters, phase equilibrium experimental data such as gas-liquid and liquid-liquid are used. In this study, the excess enthalpy of the mixture was measured using the flow type microcalorimeter which is a simpler method than phase equilibria experiments, and the parameters of various theories were obtained by using this data. In order to investigate the relationship between carbon chain length, enthalpy and binary parameters in the alkane system, excess enthalpies for the n-hexane + alkane (n-pentane, n-heptane, n-octane and n-dodecane) were measured at 298.15 K and the banary interaction parameters of Wilson, NRTL, and UNIQUAC were obtained from the experimental data. In addition, we wanted to obtain basic information on the interaction and association phenomena of the system including electrolyte applicable to various fields by using the excess enthalpy experimental data and the existing theory. First, we investigated the excess enthalpy for the NaOH / Water / Ethanol system as a basic experiment and examined the applicability using the electrolyte-NRTL (eNRTL) theory.

• Fire Science and Engineering
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• v.13 no.2
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• pp.26-32
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• 1999

We had investigated combustion pro야$\pi$ies of rice bran dusts. Decomposition of rice bran d dusts with temperature were investigated using DSC and the weight loss according to t temperature using TGA in order to find the thermal hazard of rice bran dusts, and the p properties of dust explosion in variation of their dust with the same particle size. Using H Hartman's dust explosion apparatus which estimate dust explosion by electric ignition after m making dust disperse by compressed air, dust explosion experiments have been conducted by v varying concen$\sigma$ation and size of rice br뻐 dust. According to the results for thermodynamic stability of rice bran dust, there are little change of initiation temperature of heat generation 때d heating value for used particle size. But i initiation temperature of heat generation decreased with high heating rate whereas d decomposition heat increased with particle size. Also, the explosion pressure was increased as t the ignition energy increased and average maximum explosion pressure was 13.5 kgv'cnt for 5 BJ/60 mesh and 1.5 뼈Ie미 dust concentration.

• Polymer(Korea)
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• v.25 no.1
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• pp.56-62
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• 2001

When polyethylene terephthalate(PET) film specimen were stepwise elongated under tension with various speeds of about 0.5~500 mm/min, the necking area, consisted of transparent and opaque bands, was formed during plastic deformation. Stress oscillation was apparently obtained in the stress-strain curve of above specimen. However, stress oscillation was not obtained in the stress-strain curve of annealing specimen. Microstructure was examined dynamically using an optical microscopy and thermal analysis was carried out in a differential scanning calorimeter at a heating rate of 10${\circ}$/min. Also, orientation and crystallization were examined using monochromatic-pinhole technique and elastic modulus was measured by a dynamic mechanical analyzer in the temperature range of -150~70 ${\circ}$ with the frequency of 1 Hz. Transparent PET products were fabricated by use of the PET pellets annealed at 83${\circ}$ for 30 min in an electric furnace.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.124-129
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• 2017

In this study, we report characteristics of friction stir welding (FSW) technique applied to Al-6005-T6 extruded sheets, which is a common material for railway car bodies. With the welding speed fixed at 300 mm/min, the revolution per minute (RPM) of the rotating tool was varied from 600 to 1800 RPM, with the aim at evaluating the resultant microstructure and mechanical behaviors. Comparison is also made with the conventional Metal Inert Gas (MIG) welding technique. Unlike MIG, no micro-voids were observed for FSW specimens. Hardness measurement revealed that the increased heat input by increasing RPM results in widened heat affected zone (HAZ) and decreased hardness for HAZ due to grain coarsening. Hardness results for the nugget do no show difference. During tensile tests, specimens fractured at HAZ, and increasing rpm led to decrease of the yield stress and tensile stress for the selected RPM range, which is considered to be due to the grain coarsening for HAZ.