Publications by authors named "Sang-Kwan Lee"

This study was conducted on titanium diboride (TiB) reinforced Al metal matrix composites (MMCs) with improved properties using a TiB and aluminum (Al) 1050 alloy. Al composites reinforced with fine TiB at volume ratios of more than 60% were successfully fabricated via the liquid pressing infiltration (LPI) process, which can be used to apply gas pressure at a high temperature. The microstructure of the TiB-Al composite fabricated at 1000 °C with pressurization of 10 bar for 1 h showed that molten Al effectively infiltrated into the high volume-fraction TiB preform due to the improved wettability and external gas pressurization.

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Aluminum alloy (Al7075) composites reinforced with a high volume fraction of silicon carbide (SiC) were produced by a liquid-pressing process. The characterization of their microstructure showed that SiC particles corresponding to a volume fraction greater than 60% were uniformly distributed in the composite, and MgSi precipitates were present at the interface between the matrix and the reinforcement. A superior compressive strength (1130 MPa) was obtained by an effective load transfer to the hard ceramic particles.

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Repositioning of plant extracts and chemical drugs can accelerate drug development. However, its success rate may depend on what the clue is for the repositioning. Recently, repositioning based on correction of unwarranted gene expression pattern has suggested the possibility of new drug development.

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Background: Extracts derived from natural products have been used to produce health supplements or therapeutic agents in oriental medicine. Although these extracts contain various bioactive compounds, their applications are generally limited to a few previously known diseases. To effectively expand their use for the treatment of other conditions, systematic analysis should be conducted for repurposing.

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Myrrh essential oil (MEO) is widely used as remedies for the different human ailment in different parts of the world. The misuse of this natural product in higher doses may lead to fever, inflammation, and liver and kidney problems. In this study, we performed the acute and subacute toxicity analysis of MEO in mice model after subcutaneous injection and evaluated the safe dose to prevent the possible risk and side effects.

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Here, we report a novel highly sensitive wearable strain sensor based on a highly stretchable multi-walled carbon nanotube (MWCNT)/Thermoplastic Polyurethane (TPU) fiber obtained via a wet spinning process. The MWCNT/TPU fiber showed the highest tensile strength and ultra-high sensitivity with a gauge factor (GF) of approximately 2800 in the strain range of 5-100%. Due to its high strain sensitivity of conductivity, this CNT-reinforced composite fiber was able to be used to monitor the weight and shape of an object based on the 2D mapping of resistance changes.

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In order to explore the possibility of using carbon nanotube (CNT) to introduce and control the temperature coefficient of resistance (TCR) of metal matrix composite, relatively thick and short multi-walled CNTs (MWCNTs) were introduced in the metal matrix with in-situ formation of chromium carbide (CrC) at the CNT/copper (Cu) interface. We demonstrate that incompatible properties such as electrical conductivity and TCR can be achieved simultaneously by introducing MWCNTs in the Cu matrix, with control of the interfacial resistivity using the MWCNT/CrC-Cu system. High electrical conductivity of 94.

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Recently, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) have become serious problems due to the growth of electronic device and next generation telecommunication. It is necessary to develop new electromagnetic wave absorbing material to overcome the limitation of electromagnetic wave shielding materials. The EMI attenuation is normally related to magnetic loss and dielectric loss.

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In this study, we fabricated Fe nanofibers that had a high aspect ratio and were coated by an oxidation protection layer, because electromagnetic properties are affected by the aspect ratio and oxidized layers. PVP/Fe salt nanofibers were prepared by an electrospinning method using an optimized concentration of PVP solution with Iron(lll) nitrate nonahydrate (Fe (NO3)3.9H2O) solution to apply a high voltage.

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Vapor-grown graphite nanofibers (GNFs) were modified by plasma treatments using low-pressure plasmas with different gases (Ar gas only and/or Ar/O2 gases), flow rates, pressures, and powers. Surface characterizations and morphologies of the GNFs after plasma treatment were investigated by X-ray photoelectron spectroscopy (XPS), contact angle, titration, and transmission electron microscopy (TEM) measurements. Also, the investigation of thermomechanical behavior and impact strengths of the GNFs/epoxy composites was performed by dynamic-mechanical thermal analysis (DMTA) and Izod impact testing, respectively.

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