• Tribology and Lubricants
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• v.33 no.6
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• pp.282-287
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• 2017

SU-8 is an epoxy-type photoresist widely used for the fabrication of high-aspect-ratio (HAR) micro-structures in micro-electro-mechanical systems (MEMS). To fabricate highly integrated structures, chemical mechanical polishing (CMP) has emerged as the preferred manufacturing process for planarizing the MEMS structure. In SU-8 CMP, an oxidizer decomposes organic impurities and particles in the CMP slurry remove the chemically reacted surface of SU-8. To fabricate HAR microstructures using the CMP process, the adhesion between SU-8 and substrate material is important to avoid the delamination of the SU-8 film caused by the mechanical-dominant material removal characteristic. In this study, the friction force during the CMP process is measured with a CMP monitoring system to detect the delamination phenomenon and investigate the delamination of the SU-8 film from the silicon substrate under various pressure conditions. The increase in applied pressure causes an increase in the frictional force and wafer-edge stress concentration. The frictional force measurement shows that the friction force changes according to the delamination phenomenon of the SU-8 film, and that it is possible to monitor the delamination phenomenon during the SU-8 CMP process. The delamination at a high applied pressure is explained by the effect of stress distribution and pad deformation. Consequently, it is necessary to control the pressure of polishing, which can avoid the delamination in SU-8 CMP.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.441-442
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• 2002

Chemical mechanical polishing (CMP) is a manufacturing process that uses controlled wear to planarize dielectric and metallic layers on silicon wafers. CMP experiments revealed that a sub-ambient film pressure developed at the wafer/pad interface. Additionally, dishing occurs in CMP processes when the copper-in-trench lines are removed at a rate higher than the barrier layer. In order to study dishing across a stationary wafer during polishing, dishing maps were created. Since dishing is a function of the total contact pressure resulting from the applied load and the fluid pressure, the hydrodynamic pressure model was refined and used in an existing model to study copper dishing. Density maps, highlighting varying levels of dishing across the wafer face at different radial positions, were developed. This work will present the results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.842-846
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• 2005

A brake disk and a pad are important parts that affect the braking stability of a railway vehicle. Especially, because a brake disk stops the vehicle using conversion of the kinetic energy to frictional energy, thermal fatigue cracks are generated by the cyclic thermal load, as frictional heat, on a frictional surface and these cracks cause the fracture of a brake disk. Therefore, many researches for the thermal stress must be performed to improve the efficiency of brake disk and ensure the braking stability. In this study, we performed the thermal stress analysis for a ventilated brake disk with 3-D analysis model. For that, we simplified the shape of a ventilated hole to minimize problems that could be occurred in analysis process. Thermal stress analysis was performed in case that pressure distributions on a frictional surface is constant and is not. To determine pressure distributions of irregular case, pressure distribution analysis for a frictional surface was carried out. Finally using the results that were obtained through pressure distribution analysis, we carried out thermal stress analysis of each case and investigated the results of thermal stress analysis.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06a
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• pp.21-27
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• 1994

본 연구에서는 대형 틸팅패드 저어널베어링의 성능에 관한 보다 정확한 설계 자료를 제시하기 위해서 선단압력을 고려한 이론해석을 수행하여 선단압력이동 베어링의 THD 성능에 미치는 영향을 제시하고자 한다. 그리고, 이론해석 결과와 실험 결과를 비교하여 이론해석 결과의 타당성을 제시하고자 한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.80-84
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• 1996

The effects of guide pads on burnishing action and accuracy of machined hole are investigated in drilling with burnishing drill using a speciaaly designed tool experimentally. The cutting forces are balanced at the small forward regions of guide pads. The burnishing action takes place under a high contact pressure between the bore wall and those regions. The over size mechanism of machined hole by the guide pads is discussed.

• YAKHAK HOEJI
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• v.37 no.1
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• pp.76-83
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• 1993

The changes in discharge current, emission and/or oscillation frequency of the electric oscillation of a glow discharge are the potential sensitive measure of the concentration of an impurity in the argon plasma supporting gas. A single jet enhanced glow discharge has been interfaced with the gas chromatograph via 1/8" O.D. tube with a heating pad to study the changes in discharge current. To investigate the optimum operating conditions of the glow discharge system as detector for gas chromatography, pressure, gas flow rate, discharge current, distance between the anode and the cathode have been studied.

• Herbal Formula Science
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• v.13 no.1
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• pp.49-69
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• 2005

This Study was designed to investigate the effect of Sunkihwalhyul -Tang extract(SHT) on the change of cerebral hemodynamics [regional cerebral blood flow(rCBF), pial arterial diameter(PAD) and mean arterial blood pressure(MABP)] in normal and cerebral ischemic rats, and further to determine the mechanisms of action of SHT on hemodynamics. In addition, this study was designed to investigate whether SHT inhibits lactate dehydrog enase(LDH) activity in neuronal cells and cytokines production in serum of cerebral ischemic rats. The results were as follows 1. SHT significantly increased rCBF and PAD in a dose-dependent manner, but MABP was not changed by injecting SHT. These results suggest that SHT significantly increases rCBF by dilating PAD. 2. The SHT-induced increase in rCBF was significantly inhibited by pretreatment with indomethacin(IDN, 1 mg/kg, i.p.), an inhibitor of cyclooxygenase and methylene blue(MTB, $10{\mu}g/kg$, i.p.), an inhibitor of guanylate cyclase. 3. The SHT-induced dilation in PAD was significantly inhibited by pretreatment with IDN and MTB. 4. The SHT-induced some increase in MABP was significantly increased by pretreatment with IDN. These results suggest that the mechanism of action of SBT is mediated by guanylate cyclase. 5. Both rCBF and PAD were significantly and stably increased by SHT(10 mg/kg, i.p.) during the period of cerebral reperfusion, which contrasted with the findings of rapid and marked increase in control group. 6. SBH significantly inhibited LDH activity in neuronal cells. These results suggest that SHT prevents the neuronal death. 7. In cytokine production in the senlm drawn from femoral artery 1 hr after middlecerebral arterial occlusion, sample group showed significantly decreased production of IL-1$\beta$ production, decreased production TNF-$\alpha$ and increased Production of IL-10 compared with control group. 8. In cytokine production in the serum drawn femoral artery 1 hr after reperfusion, sample group showed significantly decreased production of IL-1$\beta$ and TNF-$\alpha$ as wellas significantly increased production of IL10 compared with control group. These results suggest that SHT mediated by guanylate cyclase has inhibitive effect on the brain damage by inhibiting LDH activity, IL-1$\beta$ and TNF-$\alpha$ production, and by accelerating IL-10 production. The present author thinks that SHT has an anti-ischemic effects through the improvement of cerebral hemodynamics and inhibitive enects on the brain damage.

• The Journal of Korean Medicine
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• v.26 no.3 s.63
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• pp.188-203
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• 2005

Objectives : This study was designed to investigate the effects of Jayun-tang extract (JYT) on the change of cerebral hemodynamics [regional cerebral blood flow (rCBF), pial arterial diameter (PAD) and mean arterial blood pressure (MABP)] in normal and cerebral ischemic rats, na to determine the mechanisms of action of JYT. Methods : We investigated whether JYT inhibits lactate dehydrogenase activity in neuronal cells and cytokines production in serum of cerebral ischemic rats. Results : 1. JYT significantly increased rCBF and PAD in a dose-dependent manner, but MABP was not changed by injecting JYT. These results suggested JYT significantly increased rCBF by dilating PAD. 2. The JYT-induced increase in rCBF was significantly inhibited from pretreatment with indomethacin (1mg/kg, i.p.), an inhibitor of cyclooxygenase and methylene blue $(10{\mu}g/kg, i.p.)$, an inhibitor of guanylate cyclase. 3. The JYT-induced dilation in PAD was significantly inhibited from pretreatment with indomethacin, but was increased by pretreatment with methylene blue. 4 The JYT-induced increase in MABP was reduced by pretreatment with indomethacin and methylene blue. 5. JYT significantly inhibited lactate dehydrogenase activity in neuronal cells. These results suggest that JYT prevented the neuronal death. 6. Both rCBF and PAD were significantly and stably increased by JYT $(10{\mu}g/kg,\;i.p.)$ during the Period or cerebral reperfusion, which contrasted with the findings of rapid and marked increase in the control group. 7. In cytokine production in the serum drawn from femoral artery 1hr after middle cerebral artery occlusion, the sample group showed significantly decreased production of $IL-1\beta$ and $TNF-\alpha$ as well as increased production of IL-10 and $TGF-\beta$ compared with rho control group. 8. In cytokine production in the serum drawn from femoral artery 1hr after reperfusion, the sample group showed significantly decreased production of $IL-1\beta$ and $TNF-\alpha$ as well as significantly increased production of IL-10 and $TGF-\beta$ compared with the control group. Conclusions : JYT mediated by cyclooxygenase had an inhibitive effect on brain damage by inhibiting lactate dehydrogenase activity, $IL-1\beta$ and $TNF-\alpha$ production, and by accelerating IL-10 and $TGF-\beta$ production. The author feels that JYT had anti-ischemic effects through the improvement of cerebral hemodynamics and inhibitive effects on brain damage.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.689-692
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• 2006

In this study, an implementation of a system for measuring more accurate blood pressure by non-invasive methods of oscillometric was performed to reduce errors and weaknesses of the existing invasive blood pressure measurement methods. The system is composed of pressure control, signal measurement and blood pressure signal processing units. To verify the validity of the system, tests of characteristics evaluations for pressure measurement unit, extraction of characteristic ratios for blood pressure estimation, blood pressure tracking by oscillometric method were performed. A group of five adult male was selected for the clinical test of the implemented system. The results of the oscillometric method in comparison with auscultatory method are that the maximum ratios of PAD of average, systolic and diastolic arterial pressure are 1.38%, 1.63% and 2.97% with SEP of 5.00, 3.72 and 4.34.