• Restorative Dentistry and Endodontics
• /
• v.28 no.2
• /
• pp.156-161
• /
• 2003

The purpose of this study is to evaluate the polymerization ability of three different light sources by microhardness test. Stainless steel molds of 1, 2, 3, 4 and 5 mm in thickness of 7 mm in diameter were prepared. The hybrid composite Z100 was packed into the hole of the mold and curing light was activated for designated time. Three different light sources, conventional halogen, light emitting diode, and plasma arc, were used for curing of composite. Two different curing times applied ; one is to follow the manufacturers recommendation and the other is to extend the curing time of LED and plasma arc for balancing the light energy with halogen. Immediately after curing, the Vickers hardness was measured at the bottom of specimen. The results were as follows. 1 The composite cured with LED showed equal to higher microhardnesss than halogen. 2. The composite was cured with plasma arc by manufacturers recommendation showed lowest micro-hardness at all thickness. However, when curing time was extended, microhardness was higher than the others. In conclusion, this study suggested that plasma arc needs properly extended curing time.

• Korean Journal of Materials Research
• /
• v.33 no.7
• /
• pp.309-314
• /
• 2023

This study aimed to address the limitations of traditional plasma nitriding methods by implementing a short-term plasma oxy-nitriding treatment on the surface of AISI 420 martensitic stainless steel. This treatment involved the sequential formation of nitride and oxide layers, to enhance surface hardness and corrosion resistance, respectively. The process resulted in the formation of a 20 ㎛-thick nitride layer and a 3 ㎛-thick oxide layer on the steel surface. Initially, the hardness increased by 2.2 times after nitriding, followed by a subsequent decrease of approximately 31 % after oxidation. While the nitriding process reduced corrosion resistance, the subsequent oxidation process led to the formation of a passive oxide film, effectively resolving this issue. The pitting corrosion of the oxide passive film started at 82.6 mVssc, providing better corrosion resistance characteristics than the nitride layer. Consequently, the trade-off between surface hardness and corrosion resistance in plasma oxy-nitrided AISI 420 martensitic stainless steel is anticipated to be recognized as an innovative and comprehensive surface treatment process for biomedical components.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.5
• /
• pp.424-429
• /
• 2008

Surface wettability in terms of the size of the micro nano structures has been examined. To evaluate the influence of the nano structures on the contact angles, we fabricated two different kinds of structures: squarepillar-type microstructure with nano-protrusions and without nano-protrusions. Microstructure and nanostructure arrays were fabricated by deep reactive ion etching (DRIE) and reactive ion etching (RIE) processes, respectively. And plasma polymerized fluorocarbon (PPFC) was finally deposited onto the fabricated structures. Average value of the measured contact angles from microstructures with nanoprotrusions was $6.37^{\circ}$ higher than that from microstructures without nano-protrusions. This result indicates that the nano-protrusions give a crucial effect to increase the contact angle.

• Tuberculosis and Respiratory Diseases
• /
• v.77 no.2
• /
• pp.60-64
• /
• 2014

MicroRNAs (miRNAs) are a class of small noncoding RNAs that modulate target gene activity, and are aberrantly expressed in most types of cancer as well in lung cancer. A miRNA can potentially target a diverse set of mRNAs; further, it plays a critical role in lung tumorigenesis as well as affects patient outcome. Previous studies focused mainly on abnormal miRNAs expressions in lung cancer tissues. Interestingly, circulating miRNAs were identified in human plasma and serum in 2008. Since then, considerable effort has been directed to the study of circulating miRNAs as one of the biomarkers of lung cancer. miRNAs expression of tissues and blood in lung cancer patients is being analyzed by more researchers. Recently, to overcome the high false-positivity of low-dose chest computed tomography scan, miRNAs in lung cancer screening are being investigated. This article summarizes the recent researches regarding clinical applications of miRNAs in the diagnosis and management of lung cancer.

• Proceedings of the KIEE Conference
• /
• 1994.11a
• /
• pp.267-269
• /
• 1994

Various types of plasma display panels(PDPs) have been developed to realize the flat panel display device. But, many of its characteristics must be improved before it can be commercialized. In order to investigate tile characteristics of micro discharge in a PDP ceil, we have constructed a micro-gap discharge system whose electrode gap can be adjustable between $100-1000{\mu}m$ within $0.1{\mu}m$ accuracy. We measured the minimum sustain voltage, current, delay time of discharge while changing parameters(electrode gap distance, electrode surface area, pressure) which influence discharge characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.05a
• /
• pp.1375-1376
• /
• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.185-186
• /
• 2007

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.354-356
• /
• 2007

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1998.08a
• /
• pp.151.1-151
• /
• 1998

• Korean Journal of Materials Research
• /
• v.11 no.12
• /
• pp.1063-1067
• /
• 2001

The effect of the pulse parameters(pulse ratio and frequency) on the characteristics of the nitrided layer in the pulsed plasma nitrified SCM435 Steels was investigated. Material properties of the nitrided layer were analysed by employing optical microscope, scanning electron microscope(SEM), X-ray diffractometer(XRD) and micro-Vickers hardness tester. It was found that both the compound layer thickness and the surface hardness decreased with decreasing of pulse ratios. At high pulse ratio, the compound layer thickness and the surface hardness were rapidly decreased with decreasing frequency compared to lower pulse ratios.