• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1072-1075
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• 2001

$Al_2O_3$ ceramics are generally used as components in processing equipment, devices or machinery because it can perform some functions better than competing metals or polymers. Many of these applications rely on $Al_2O_3$ ceramics special electromagnetic properties, its relative chemical inertness, hardness, strength and its temperature capabilities. But $Al_2O_3$ ceramics are brittle materials, a fact that may cause problems and at the same time be helpful while machining with laser. This study described a basic study of the input parameters effect on the dimension of the microhole at the $Al_2O_3$ ceramics using Excimer laser. In the laser microhole machining of $Al_2O_3$ ceramics, major input parameters are pulse energy, pulse power, pulse frequency and pulse numbers. In conclusion, we can get a smaller microhole and diameter rate by an appropriate pulse energy, pulse frequency and pulse number.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.525-529
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• 2003

Biotribological properties, such as wear rate and friction coefficient, of 3Y-TZP and Low Temperature Degradation (LTD) free materials were investigated via a ball(SiC)-on-plate sliding wear test to evaluate the relationship between wear mechanism and phase transformation. Wear test was conducted with a sliding speed of 0.035 m/s at room temperature and at 25$0^{\circ}C$ in air under a normal load of 49 N, respectively. Although friction coefficient of 3Y-TZP was the lowest due to the fine grain size, the highest wear loss and rate were observed due to the debris of monoclinic grains introduced during sliding and their values increased drastically with raising temperature. However, the biotribological properties of LTD-free materials were insensitive to temperature due to the inertness of the phase transformation, suggesting that they may be applicable to the biomechanical parts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.350-350
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• 2010

Silicon carbide (SiC), one of the well known wide band gap semiconductors, shows high thermal conductivities, chemical inertness and breakdown energies. The design of normally-off 4H-SiC VJFETs [1] has been reported and 4H-SiC VJFETs with different lateral JFET channel opening dimensions have been studied [2]. In this work, 4H-SiC based VJFETs has been designed using the device simulator (ATLAS, Silvaco Data System, Inc). We varied the n-epi layer thickness (from $6\;{\mu}m$ to $10\;{\mu}m$) and the channel width (from $0.9\;{\mu}m$ to $1.2\;{\mu}m$), and investigated the static characteristics as blocking voltages, threshold voltages, on-resistances. We have shown that silicon carbide JFET structures of highly intensified blocking voltages with optimized figures of merit can thus be achieved by adjusting the epi layer thickness and channel width.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.618-623
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• 2014

This study, analyzed the waveform and mechanical properties of flux cored arc Welding on SM45C. $CO_2$ 10% + Ar 90% shows the lowest standard deviation and shunt ratio at which the arc was most stable. $CO_2$ 10% + Ar 90% is equal to $CO_2$ 20% + Ar 80%. therefore, $CO_2$ 20% + Ar 80% is the best of mixture gases. The hardness test result for the gas mixture ratio of $CO_2$ 10% + Ar 90% was HV 249.7 which is the highest measured value. According to tensile test results, the tensile strength increased with increasing Ar in the mixture gas. This was because of the inertness of the argon, which does not combine with other elements, causing $CO_2$ to combine with pearlite and ferrite and decreasing the maximum tensile strength. Microstructural examination results show that with increasing Ar, ferrite generation decreases while the mild microstructure increases which influences the hardness.

• Korean Journal of Materials Research
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• v.27 no.4
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• pp.229-235
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• 2017

Through density functional theory calculations, to provide insight into the origins of the catalytic activity of Au nanoparticles (NPs) toward oxidation reactions, we have scrutinized the oxygen adsorption chemistry of 9 types of small unsupported Au NPs of around 1 nm in size (Au13, Au19, Au20, Au25, Au38, and Au55) looking at several factors (size, shape, and coordination number). We found that these NPs, except for the icosahedral Au13, do not strongly bind to $O_2$ molecules. Energetically most feasible $O_2$ adsorption that potentially provides high CO oxidation activity is observed in the icosahedral Au13, our smallest Au NP. In spite of the chemical inertness of bulk Au, the structural fluxionality of such very small Au NP enables strong $O_2$ adsorption. Our results can support recent experimental findings that the exceptional catalytic activity of Au NPs comes from very small Au species consisting of around 10 atoms each.

• Journal of the Korean institute of surface engineering
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• v.39 no.3
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• pp.129-136
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• 2006

The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and $1100^{\circ}C$ in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was $Ni_3Al$. The oxides formed on the coatings consisted primarily of ${\alpha}-Al_2O_3$, together with some $CoCr_2O_4,\;CoAl_2O_4$, and $Al_5Y_3O_{12}$. Tantalum oxidized to $Ta_2O_5$ and $Ta_2O_{22}$. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.

• BMB Reports
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• v.47 no.3
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• pp.130-134
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• 2014

The combination of a high-affinity antibody to a hapten, and hapten-conjugated compounds, can provide an alternative to the direct chemical cross-linking of the antibody and compounds. An optimal hapten for in vitro use is one that is absent in biological systems. For in vivo applications, additional characteristics such as pharmacological safety and physiological inertness would be beneficial. Additionally, methods for cross-linking the hapten to various chemical compounds should be available. Cotinine, a major metabolite of nicotine, is considered advantageous in these aspects. A high-affinity anti-cotinine recombinant antibody has recently become available, and can be converted into various formats, including a bispecific antibody. The bispecific anti-cotinine antibody was successfully applied to immunoblot, enzyme immunoassay, immunoaffinity purification, and pre-targeted in vivo radioimmunoimaging. The anti-cotinine IgG molecule could be complexed with aptamers to form a novel affinity unit, and extended the in vivo half-life of aptamers, opening up the possibility of applying the same strategy to therapeutic peptides and chemical compounds.

• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.127-131
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• 2010

Adhesion of DLC film is very significant property that exhibits wear resistance, chemical inertness and high hardness when being deposited to metal substrate. This study was considered that change adhesion of DLC film produced by Plasma Enhanced Chemical Vapor Deposition can be presented through inserting interlayer (Cr, Si-C:H). The thickness of interlayer was result of changing adhesion and residual stress. It was showed that the maximum 12 N of adhesion is on DLC film of Cr interlayer, and that a tendency is to be increased residual stress depend on the thickness. DLC film of Si-C:H interlayer represented 16 N of adhesion at $1{\mu}m$, whereas adhesion is decreased when the thickness is increased. For the interlayer at multi-layer, it was the best that adhesion of Cr/Si-C:H/DLC film was 33 N. Si-C:H interlayer at DLC film controled adhesion of the whole film. It was relaxed the internal stress of DLC film produced by inserting Cr, Si-C:H interlayer.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.249-254
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• 2014

Due to their unique properties, tungsten borides are good candidates for the industrial applications where certain features such as high hardness, chemical inertness, resistance to high temperatures, thermal shock and corrosion. In this study, conditions were investigated for producing tungsten boride powder from tungsten oxide($WO_3$) by self-propagating high-temperature synthesis (SHS) followed by HCl leaching techniques. In the first stage of the study, the exothermicity of the $WO_3$-Mg reaction was investigated by computer simulation. Based on the simulation experimental study was conducted and the SHS products consisting of borides and other compounds were obtained starting with different initial molar ratios of $WO_3$, Mg and $B_2O_3$. It was found that $WO_3$, Mg and $B_2O_3$ reaction system produced high combustion temperature and radical reaction so that diffusion between W and B was not properly occurred. Addition of NaCl and replacement of $B_2O_3$ with B successfully solved the diffusion problem. From the optimum condition tungsten boride($W_2B$ and WB) powders which has 0.1~0.9 um particle size were synthesized.

• Korean Journal of Acupuncture
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• v.35 no.2
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• pp.47-55
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• 2018

Objectives: Clinical improvements can be observed following placebo administrations in clinical trials. Randomized controlled trials have been conducted to disentangle the specific effects of therapeutic interventions over the past decade. In acupuncture trials, non-penetrating placebo needles offer the opportunity to determine the specific effects of needling. Methods: The present review provides an overview of the concept of the placebo effect and the characteristics of the placebo needles. Results: Placebo control can contribute to minimize for bias and the contextual and psychological components of therapeutic interventions. Placebo control should meet two criteria: blinding efficacy (indistinguishable from active treatment) and physiological inertness. In the case of acupuncture, however, it is difficult to meet both criteria simultaneously. The dilemma of placebo needles suggests that placebo needles do not constitute proper control in acupuncture research. Considering the characteristics of placebo needles, patients are more likely to perceive placebo needles as active treatment in acupuncture trials compared to placebo pills in pharmaceutical trials. Placebo response might be observed more frequently to placebo needles than to placebo pills. When acupuncture treatments are utilized in clinical use, placebo effects can be enhanced by exploiting patients' expectations in the contextual or environmental cues that surround medical intervention. Conclusions: We have to consider these unique characteristics of placebo needles in order to avoid drawing premature conclusions that acupuncture itself is just a placebo.