• Journal of Energy Engineering
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• v.10 no.3
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• pp.223-232
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• 2001

To study the stabilization characteristics of diffusion flame formed in the wake of a cylindrical bluff body with fuel injection, the flame stability limits, length and temperature of recirculation zone of flame, turbulence intensity distribution near the recirculation zone of flame were measured and analyzed. The length of recirculation zone is independent on main fuel injection quantity, but it is dependent on fuel injection angles, air stream velocity, and auxiliary fuel injection into recirculation zone. For diffusion flame, in general, the flame stabilization is deteriorated with increase of he length of recirculation zone, but if the turbulence generator is installed, the flame stabilization is improved with increase of the length of recirculation zone. The temperature of recirculation zone is dependent on fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators, and it dependent on fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators, and it has a maximum value at the condition of each theoretical mixture. In general, the more temperature of recirculation zone is low, the more flame is stable. But when the turbulence generator is installed, the more temperature of recirculation zone is low, the more flame is unstable. The turbulence intensity in the wake of bluff body is increased with increase of diameter or blockage ratio of grid. The more turbulence intensity is increased by installation of turbulence generator, the more flame is unstable. Finally, It is clear that the stabilization characteristics of diffuser flame can be controlled by some parameters such as fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.31-38
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• 1991

Effect of thermal cycling on shape memory effect and stabilization of austenite was investigated in Fe-21%Mn alloy. The thermal cyclic treatment was carried out with two types, room temperature${\leftrightarrow}215^{\circ}C$ and room temperature${\leftrightarrow}260^{\circ}C$. In case of the room temperature${\leftrightarrow}215^{\circ}C$, the SME was rapidly increased up to 3 cycles and maintained nearly constant value regardless of further cycles. In case of the room temperature${\leftrightarrow}260^{\circ}C$, however, the SME was increased with increasing the thermal cycle up to 5 cycles and decreased gradually with further cycle. The variation of the ${\varepsilon}$ martensite volume pet with the thermal cycle was in good agreement with the variation of the SME. Therefore, the change of the SME due to the cyclic treatment was explained with the change of the ${\varepsilon}$ martensite content. As the thermal cycle was increased, the $M_s$ temperature was decreased, and the $A_s$ and $A_f$ temperatures were increased, respectively.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.93-99
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• 2015

This test focuses on the correlations between joining axial force at non-room temperature and at room temperature according to the surface treatment (Geomet, Dacro, Green Kote, Armore Galv.). The quality characteristics of the fastening axial force required by the KSB 2819 and EN14399-10 standards were discussed. Surface treatment was implemented to S10T and 10.9HRC sets of bolts under the same environmental factors. Development for the stabilization of the fastening axial force required by each standard should continually be enforced, and the fastening and storage in the field should be maintained at room temperature. Managing stabilization of torque enumerated data is required after application of surface treatment. It is concluded that, by conducting the test of applying surface treatment to effectively manage, each lot-specific rate of axial force at room temperature conditions should be maintained below the maximum 4.47%. The decline rate of axial force should be maintained under 2.15% maximum, and the standard deviation of the room temperature condition should be maintained below 0.5.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.217-221
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• 2005

The evaporation amounts of volatile Cd, Pb and Zn were characterized by measuring their total concentrations in the EAF dust-clay bodies with various mixing ratio and heat treatment temperature. TCLP test was conducted for evaluating the chemical stabilities of the heavy metal elements. Evaporation amounts and leaching concentrations of heavy metal components were strongly dependent on the mixing ratio and heat treatment temperature. The evaporation of the heavy metal components in EAF dust was effectively suppressed by increasing the clay content. The leaching concentrations of heavy metal components were decreased with increasing clay content and temperature. 20 wt% EAF dust-80 wt% clay sample shows nearly zero evaporation and leaching concentrations of heavy metal components. XRD analysis showed that peak intensities of major crystalline phases such as franklinite and quartz were decreased with increasing the heat treatment temperature which means that the stabilization mechanism of the heavy metals was related with the vitrification process of the $SiO_2$ in the clay.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2253-2258
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• 2009

wet spun polyacrylonitrile (PAN) fiber precursors. The process variables chosen were treatment temperature, applied tension in stabilization process. The temperature profile of the stabilization was set on the basis of exothermic peaks of the differential scanning calorimetry (DSC) result. Both tensile strength and modulus increased with holding at onset temperatures of the exothermic peaks for extended duration, and with a higher heating rate up to the onset temperatures at a given applied tension among the experimental conditions. The increase in load monotonously increased the tensile modulus, on the other hand, the tensile strength was maximum at the load of 15 mg/filament (T15). The load 20 mg/ filament (T20) was considered to be exceeded to form oriented crystalline structure, possibly introducing more defects in the fiber than under load of T15. The sample CP3-T15 O5 H30 showed the best tensile properties among the samples experimented whose tensile properties are compatible with the commercialized grade of general purpose carbon fibers even at low carbonization temperature such as $800\;{^{\circ}C}$ (the carbonization temperature in the commercial process. 1300∼$1500\;{^{\circ}C}$).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.717-718
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• 2011

• Journal of Adhesion and Interface
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• v.11 no.1
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• pp.15-25
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• 2010

In the present study, isothermal stabilization processes for rayon fabrics were performed at two relatively low temperatures $180^{\circ}C$ and $200^{\circ}C$ for a long period of time. The results of weight loss, dimensional shrinkage, X-ray diffraction and scanning electron microscopic observations studied with the rayon fabrics before and after the isothermal stabilization indicated that the chemical and physical changes of rayon precursor fibers proceeded continuously and slowly at the stabilization temperature below $200^{\circ}C$. And the pre-treatment with four different chemical compounds done prior to stabilization process influenced differently the characteristics of rayon fabrics. As a result, it was noticed that under the given stabilization conditions, $H_3PO_4$ and $Na_3PO_4$ played a role in catalyzing the stabilization reaction of rayon fabric whereas $NH_4Cl$ and $ZnCl_2$ played a role in delaying or retarding the reaction. $H_3PO_4$ showed the lowest percent weight loss of the fabric in the second stabilization conducted at $350^{\circ}C$. It was considered that phosphoric acid, which has a function of flame retardant, contributed to retarding somewhat the subsequent reaction even in the second stabilization step.

• Carbon letters
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• v.14 no.2
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• pp.94-98
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• 2013

Isotropic pitch fibers were stabilized and carbonized for preparing carbon fibers. To optimize the duration and temperature during the stabilization process, a thermogravimetric analysis was conducted. Stabilized fibers were carbonized at 1000, 1500, and $2000^{\circ}C$ in a furnace under a nitrogen atmosphere. An elemental analysis confirmed that the carbon content increased with an increase in the carbonization temperature. Although short graphitic-like layers were observed with carbon fibers heat-treated at 1500 and $2000^{\circ}C$, Raman spectroscopy and X-ray diffraction revealed no significant effect of the carbonization temperature on the crystalline structure of the carbon fibers, indicating the limit of developing an ordered structure of isotropic pitch-based carbon fibers. The electrical conductivity of the carbonized fiber reached $3.9{\times}10^4$ S/m with the carbonization temperature increasing to $2000^{\circ}C$ using a four-point method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.11
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• pp.2981-2994
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• 1995

In order to elucidate the effects of positive pressure gradient on flame properties, structure and stabilization, an experimental study is made on turbulent diffusion flame stabilized by a circular cylinder in a divergent duct flow. A commercial grade gaseous propane is injected from two slits on the rod as fuel. In this paper, stabilization, characteristics and flame structure are examined by varying the divergent angle of duct. Temperature, ion current and Schlieren photographs were measured. It is found that critical divergent angle is expected to be about 8 ~ 12 degree through blow-off velocity pattern to divergent angle and the positive pressure gradient influences the flame temperature, intensity of ion current and eddy structure behind the rod. With the increase of divergent angle, typical temperature of recirculation zone is low but intensity of ion current is high in shear layer behind rod. Energy distributions of fluctuating temperature and ion current signals turn up low frequency corresponding to large scale eddies but high frequency corresponding to small scale eddies as well as low with the increase of divergent angle. Therefore the flame structure becomes a typical distributed-reacting flame.

• Current Applied Physics
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• v.18 no.12
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• pp.1600-1604
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• 2018

This paper reports on a systematic and quantitative assessment of light induced degradation (LID) and regeneration in full Al-BSF and passivated emitter rear contact cells (PERC) along with the fundamental understanding of the difference between the two. After LID, PERC cells showed a much greater loss in cell efficiency than full Al-BSF cells (~0.9% vs ~0.6%) because the degradation in bulk lifetime also erodes the benefit of superior BSRV in PERC cells. Three main regeneration conditions involving the combination of heat and light ($75^{\circ}C/1\;Sun/48h$, $130^{\circ}C/2\;Suns/1.5h$ and $200^{\circ}C/3\;Suns/30s$) were implemented to eliminate LID loss due to BO defects. Low temperature/long time ($75^{\circ}C/48h$) and high temperature/short time ($200^{\circ}C/30s$) regeneration process was unable to reach 100% stabilization. The intermediate temperature/time ($130^{\circ}C/1.5h$) generation achieved nearly full recovery and stabilization (over 99%) for both full Al-BSF and PERC cells. We discussed the effect of temperature, time and suns in regeneration mechanism for two cells.