• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.466-470
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• 2000

Externally pressurized air journal bearing has been widely used in high-speed spindle system and precision machinery because of its characteristics such as substantially low frictional loss, low heat generation and averaging effect leading better running accuracy. But air journal bearing have a disadvantage of the low load capacity due to the low viscosity. In this paper, The air journal bearing design to overcome the defects of air bearing such as low stiffness and dimping coefficients was investigated theoretically.

• Journal of Korea Foundry Society
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• v.13 no.6
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• pp.563-573
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• 1993

The wear resistance of Hyper-eutectic Al-Si alloy, have recently been noticed as a new automobile material, was investigated. For the purpose of developing wear resistant Al-Si alloy, some factors which attribute to wear resistance are examined as follows; refinement of primary Si particle during solidification, and effect of refinement on wear resistance and other mechanical properties. The most effective refinement was accomplished by adding both NaF and S, and this improve wear-resistance in abrasive wear type. The wear losses of specimens cast in metal mold were ruduced to 80% of those in sand mold. T6 heat treatment increases hardness, which resulted in reduction of wear loss about $3{\sim}18%$.

• Proceedings of the Korean Fiber Society Conference
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• 1996.04a
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• pp.158-161
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• 1996

Microfibers of Poly(ethylene terephthalate)(PET)/Nylon 6 (P/N) was heat set at 170C in a fixed state and then treated with hydrazine at 30C for 5, 10, 15, 20, 30 and 40 h. Weight loss from the hydrazine treatment increased according to the hydrazine concentration(Fig.1). In order to investigate in detail the effect of the electrostatic attraction between the dye anion and hydrazide groups in cooperated by hydrazinolysis, -potential of P/N fiber was measured by streaming potential method. The surface charge density, o, of the fiber was evaluated from the -potential.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.2
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• pp.181-189
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• 2000

The scroll compressor used for heat pump has a wide range of operation condition. To cover both heating and cooling modes, the operating Pressure ratio ranges from 1.5 to 6.8. Since the scroll compressor, however, is a type of compressor whose pressure ratio is fixed, some loss in the compression work is caused by the operation at the pressure ratio different from the built-in pressure ratio. A way of avoiding this problem is to introduce by-Pass holes in compression chambers, so that the compressed gas of pressure higher than the discharge pressure, yet not reached to the discharge port can be released earlier through the by-Pass holes. In this paper, an optimum Positioning of the by-Pass hole and the effect of the by-pass valve on the compressor performance are studied.

• Elastomers and Composites
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• v.57 no.2
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• pp.29-39
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• 2022

In this research, the relationships between the chemical structures of 10 different acrylate monomers with 3 different cross-linking monomers were evaluated. The thermal stabilities of the prepared copolymers were evaluated by their weight-loss percentage through thermogravimetric analysis, and their glass-transition temperatures were analyzed using differential scanning calorimetry. Based on the results, some relationships between the chemical structures of the monomers and their properties were derived and are discussed herein.

• Food Science and Preservation
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• v.16 no.5
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• pp.623-628
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• 2009

Fresh ginger rhizomes were heat-treated for 10 min, 30 min, or 60 min using hot air ($40^{\circ}C$, $50^{\circ}C$, or $60^{\circ}C$), and stored in low-density polyethylene (0.04 mm thickness) bags for 2 months at $12{\pm}1^{\circ}C$. We studied the effects of heat pretreatment on changes in gas levels after packaging, and quality characteristics of the rhizomes. Oxygen and carbon dioxide levels progressively fell and rose, respectively, as the temperature of heat treatment rose and the duration of such treatment was extended. The sprouting rate of ginger rhizomes treated at $40^{\circ}C$ was higher than that of other samples. Rotting, softening, and increasing pH of rhizomes were accelerated by treatment at higher temperature for a longer time. Weight loss and soluble solid levels were not affected by heat treatment. Sensory qualities such as appearance, odor, and overall acceptability of rhizomes fell with treatment at a higher temperature for a longer time. These results suggest that heat pretreatment has a detrimental effect on the quality of fresh ginger rhizomes.

• Transactions of the KSME C: Technology and Education
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• v.4 no.2
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• pp.123-130
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• 2016

Unitex is widely used for the floor structure of urban railway vehicles because it shows good structural safety and heat insulation, has long life, and lowers the cost owing to easy installation. However, in spite of these merits, Unitex has a limit to the sound insulation performance, which is very important in vehicle structure. It shows a sound transmission loss considerably lower than the mass law value, which indicates the sound insulation performance per unit weight. Recently, railway vehicle manufacturers and Unitex supplier have tried to improve the sound insulation performance of Unitex, but meaningful results have not been achieved yet. Through the industry-university collaborative research, we propose structural improvement methods to increase the sound transmission loss by more than 5dB and we then verify the effect by performing experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1183-1188
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• 2013

The reliability of hydraulic equipment used in power plants is especially important because failures that occur in the power plant can have a great ripple effect on human lives and financial losses. In this study, specimens using the materials used in the spool and sleeve of hydraulic valves of power plants have been produced, heat-treated, and tested under the precipitation conditions of phosphate ester hydraulic fluid with a variety of conditions. 23 full factorial designs have been applied to evaluate the significance of factors that affect the wear loss of the specimen, specifically, the load, velocity, and temperature. The significance evaluation was performed on the main effects and two-way interactions for wear loss based on the experiment results, and the mathematical equations between the wear loss and the three factors were derived from the analysis results.

• Journal of Convergence for Information Technology
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• v.12 no.5
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• pp.298-304
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• 2022

In this study, it is intended to provide basic research data on hair loss and problematic scalp that is expanding to lower age groups and women. When using Company B's hair ampoule containing L-Menthol, Salicylic acid, and Dexpanthenol daily for women in their 20s with problematic scalp, the effect on the scalp and hair after 4 weeks was investigated. As a result of this study, when using Company B's ampoule containing L-Menthol, Salicylic acid, and Dexpanthenol, the subjects showed improvement effects such as relieving inflammation, reducing scalp fever and erythema, reducing itching and hair loss, and increasing hair thickness. In addition, it was confirmed that the scalp self-diagnosis of the subjects showed improvement effects on scalp satisfaction, scalp vitality and elasticity, heat generation, scalp pulling after cleaning, and itching. Through these research results, it is believed that products containing L-Menthol, Salicylic acid, and Dexpanthenol will help improve problematic scalp and hair.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.117-125
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• 2014

The temperature distribution of steady state rolling tires with detailed tread blocks is numerically predicted using the three dimensional full patterned tire model. A three dimensional periodic patterned tire model is constructed by copying 1-sector mesh in the circumferential direction. Using the static tire contact analysis, the strain cycles during one revolution are approximated with the strains at Guassian points of the elements which are sector-wise repeated within the same circular ring of elements, by neglecting the tire rolling effect. Based upon the multi-axial fatigue theory, the maximum principal strain is used to represent the combined effect of six strain components on the hysteretic loss. In the following, the deformation due to the inflation and vertical load is calculated using ABAQUS. Then heat generation rate in each element is calculated using an in-house code. Lastly, temperature distribution is calculated using ABAQUS again. Through the numerical experiments, the validity of the proposed prediction method is examined by comparing with the experiment and the temperature distribution of a patterned tire model is compared with those of the main-grooved simple tire model.