• Macromolecular Research
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• v.10 no.4
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• pp.187-193
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• 2002

Several methods have been used to synthesize polymer-clay nanocomposites. In-situ polymerization with clay belongs to a classical way to develop nano-structured materials, while melt intercalation is being recognized as another useful approach due to its versatility and environmentally benign character. In this research, we prepared polymer-clay nanocomposites based on the poly (methyl methacrylate) and organically modified montmorillonite via two-stage sonication process. According to the unique mode of power ultrasonic wave, the sonication during processing led to enhanced breakup of the clay agglomerates and reduction in size of the dispersed phase. Optimum conditions to form stable exfoliated nanocomposites were studied for various compositions and conditions. It was found that a novel attempt carried out in this study yielded further improvement in the mechanical performance of the nanocomposites compared to those produced by the conventional melt mixing process, as revealed by DMA, XRD and TEM. And rheological properties of nanocomposites were measured by ARES. As a result, sonicated PMMA-clay nanocomposites exhibits enhanced properties such as storage modulus and thermal stability than that of neat PMMA.

• Journal of the Korea Society of Computer and Information
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• v.5 no.4
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• pp.62-68
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• 2000

It was designed a high-speed analog input card that is a important device of ultrasonic testing flaw detector in the middle of non-destructive testing in this Paper. The A/D Board is inquired high-speed sampling rate and fast data acquisition system. This pater shows a design that has a function of Peak- Detection for ultrasonic testing by ISA Bus type and a 50MHz of A/D converter in order to do sampling more than quadruple frequency of transducer frequency.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.793-798
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• 2007

During May of 2003, smoke from fires in the Yucatan Peninsula was transported across the Gulf of Mexico and into Texas where it caused significant enhancement in measured aerosol concentrations and reduced visibility. During this event, the formation and growth of aerosol particles has been observed by a differential mobility analyzer (DMA) / tandem differential mobility analyzer (TDMA) system to characterize the size distribution and size-resolved hygroscopicity of the aerosol. The most number concentration is by the particles smaller than 100 nm, but the integrated number concentrations for over 100 nm increased due to the aerosol growth. Hygroscopic growth factor increase from 1.2 to 1.4 for 25, 50, and 100 nm particles during the nucleating period. This distribution and the aerosol properties derived from the TDMA data were used to calculate the growth rate. Particle growth rates were in the range 1-12 nm/hr.

• Advanced Composite Materials
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• v.17 no.1
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• pp.89-99
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• 2008

Using a Dynamic Mechanical Analyzer (DMA), mechanical properties like modulus and phase transition temperature of polyester composites of banana fibers (treated and untreated) are measured simultaneously. The shifting of phase transition temperature is observed in some treatments. The performance of the composite depends to a large extent on the adhesion between polymer matrix and the reinforcement. This is often achieved by surface modification of the matrix or the filler. Banana fiber was modified chemically to achieve improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkalies were used to modify the fiber surface. Chemical modification was found to have a profound effect on the fiber/matrix interaction, which is evident from the values of phase transition temperatures. Of the various chemical treatments, simple alkali treatment with 1% NaOH was found to be the most effective.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1298-1303
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• 2004

The characteristics of soot near the soot inception point for an ethene-air flame was carried out in a WSR (well-stirred reactor). The new sampling tool like the temperature controlled filter system was introduced to minimize the condensation during sampling. The new analysis tools applied include the real time size distribution analysis with the Nano-DMA, particle size by transmission electron microscopy, C/H analysis, g filter analysis, and thermogravimetric analysis using both non-oxidative and oxidative pyrolysis. The WSR can generate young soot particles that can be collected and examined to gain insight into inception. For the current conditions, soot does not form for ${\Phi}=1.9$, inception occurs at or before ${\Phi}=2.0$, and inception combined with soot surface growth and/or coagulation occurs for ${\Phi=2.1}$. The filter samples for ${\Phi}$=1.9 are composed of volatile compounds that evolve at relatively low temperatures when heated in the presence or absence of $O_2$. The samples collected from the WSR at ${\Phi}=2.0$ and ${\Phi}=2.1$ are precursor-like in morphology and size. They have higher C/H ratios and lower organic percentages than precursor particles, but they are clearly not fully carbonized soot. The WSR PAH distribution is similar to that in young soot from inverse flames.

• Archives of Pharmacal Research
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• v.20 no.3
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• pp.239-246
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• 1997

In the present study, liver regeneration rate (%) was increased up to 70% 3 days after partial hepatectomy (PH). Nitric oxide synthase (NOS) activity in liver tissue as well as serum nitrite/ nitrate content had no timed response, revealing no significant difference between shamoperated and partially hepatectomized rat liver. Contents of free methylarginines in liver tissue were increased biphasically in a time-dependent manner after PH. However, those in serum did not exhibit the same patterns as in liver. Taken together, the results suggest that $N^{G}$-monomethyl-L-arginine (MMA) and $ N^{G}, N^{G}$-dimethylarginine (DMA) play a role in inhibiting nitric oxide (NO) synthesis in regenerating rat liver because the increase of their contents was synchronized with NOS expression.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.61-66
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• 2009

An analytical method based on solid-phase extraction and gas chromatography / mass spectrometry has been developed for measurement of acaricides (amitraz, bromopropylate, coumaphos, cymiazole, and tetradifon) in honey sample. In the stability test of acaricides in honey, amitraz underwent a rapid degradation into 2,4-dimethylaniline (DMA), 2,4-dimethylphenylformamide (DMPF), and N-(2,4-dimethylphenyl)-N'-methylformamidine (DMPMF), whileas other acaricides were found to be stable even for over three months. Extraction of five acaricides from 5g of honey sample was carried out by liquid-liquid extraction using 20mL of ethylacetate. For purification, Florisil-SPE cartridge with elution of 5mL of n-hexane/ acetone (55:45, v/v) was found to remove interferences effectively. Quantification was performed using gas chromatography / mass spectrometry in the selected ion monitoring mode. Spiking experiments were carried out to determine the recovery, precision, and limits of detection (LODs) of the method. The overall recovery values from honey spiked at 0.02 and 0.20 ${\mu}g/g$ levels, respectively, were found to be greater than 75% for all acaricides. The method detection limits for acaricides were ranged from 0.1 to 3 ppb. The developed method in this study was applied for the monitoring of acaricides in honey products collected from urban markets in Korea.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.2
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• pp.39-45
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• 2010

In the recent years, it is important to evaluate the durability and the reliability of the vehicle, aircraft, and structure. Especially, in case of the vehicle, the durability and reliability are tested by driving test after making prototype vehicles. However, these methods require many costs and efforts for the experiment are needed to react the defects of product. This problems can be settled by simulator which supplies the realistic environments. In this parer, four-axial road simulator with hydraulic power and driving program to operate are made up. The displacement road profile is realized by accelerometers. For the verification the real-vehicle experiment is executed and road profile obtained from the experiment is verified by four-axial road simulator.

• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.287-293
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• 2013

Purpose: This study is to provide basic data of the dental acrylic denture base resin in the mechanical property difference investigation according to the monomer composition weight ratio of the acrylic denture base resin. Methods: The monomer composition of the acrylic denture base resin and weight ratio makes the different specimen. It measured the mechanical property with the specimens through Hardness Test, Tensile Test, Flexural Test, Flexural Modulus, FT-IR Test. Results: The control group Vertex was 18.4 Hv and the experimental group MED was 14.46~19.07Hv in the hardness test. Vertex was 364N, MED-3 was lowest in the tensile strength test and the Head of a family cursor declination was big. The result declination of the experimental specimens showed. Vertex and MED-2 was the highestest in the flexural test and after coming MED-6, MED-5, MED-1, MED-3, MED-4. Vertex and MED-2, as to a spectrum for $500{\sim}1800cm^{-1}$ peak can show the excellent degree of polymerization in the FT-IR Test. Conclusion: The ideal weight ratio of the monomer of the acrylic denture base resin of which the mechanical property is the highestest was MMA 100g, EDGMA 5g, DMA 0.2g, of MED-2.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.1107-1111
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• 2005

The DVR system realization with watermarking and MPEG-4 for real time processing speed improvement is presented in this paper. For the real time processing the system is used the DSP processor, Quick DMA for data transmission, watermarking for security and MPEG-4 compression for facility. The algorithms are that the operational structure has the internal memory of processor, and the optimal realization is suitable to form the DSP processor structure r processed for the iterative operations. The experimental result shows the real time processing is improved 12% over for the D1 image in comparison with the other system.