• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.606-616
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• 2003

Purpose : The purpose of this study was to research the properties of some chemically cured methacrylate polymers such as MMA, HEMA, TEG-DMA, bis-GMA, GMA. Material and Method : 5 kinds of methacrylates were selected and added 2% tertiary amine and benzoyl peroxide to make a chemically curable polymer 25 micron crushed silicas which are treated with silane were selected as filler, they were added into methacrylate monomer until the consistency did not changed by the load of 500gram. All of the experimental resins were 5 kinds, and a serial test was done with 3 kinds of items including the filler contents, the tensile strength, and the bond strength. The number of specimen were 10 for each group. Filler contents were obtained by reducing the specimens to ashes at $600^{\circ}C$ for 1 hour. The specimens with the dimension of 6mm in diameter and 3mm thick were immersed in $37{\pm}1^{\circ}C$ distilled water for 24 hours before test, and tensile strength were measured with cross-head speed 1mm/min. Shear bond strength were mea sured on the specimens attached to bovine enamel etched with 37% phosphoric acid for 1 minute. Results : 1. Maximum filler incorporation was the highest as 75.5% on MMA, and the least as 53.4% on bis- GMA(p<0.0001). 2. The tensile stregth were MMA 141.3, GMA 154.3, TEG-DMA 157.4, bis-GMA 161.4 MPa, and HEMA showed the highest value, 226.9MPa(p = 0.0004). 3. The bond strength were GMA 10.1, TEG-DMA 11.7, HEMA 12.2, bis-GMA 13.3 MPa, and MMA showed the highest value, 15.3MPa, however statistical significances were not (p =0.3838), 4. TEG-DMA and HEMA were not different on the aspect of maximum filler contents and shear bond strength(p>0.05). Conclusion : HEMA can be used as an another diluent substituting TEG-DMA with the increased strength and with the constant bond strength and the constant filler contents.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.1
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• pp.7-14
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• 1981

Secondary amines are known as one of the precursors of nitrosamines which are potent carcinogenic compounds for human being and animals. In this study, trimethylamine and dimethylamine contents of salted, hot-air dried and sun dried samples of two commercial fishes, mackerel pike and seerfish were analyzed and quantitatively compared at three different temperature conditions. The formation of both secondary amines was more rapid at$10^{\circ}C\;and\;15^{\circ}C\;than\;at\;2^{\circ}C$. Residual amounts of trimethylamine oxide of salted samples were relatively higher than those of the other samples. Trimethylamine contents of hot-air dried mackerel pike and sun dried seerfish were relatively higher than those in the other samples, while those of salted samples were comparatively lower than those of others. Dimethylamine contents of hot-air dried samples were higher than those of the other samples, whereas those of salted samples were comparatively lower than those of the other samples.

• Journal of Food Hygiene and Safety
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• v.13 no.4
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• pp.332-336
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• 1998

The effect of ripening temperature, pH and salinity on the formation of Nnitrosamine (NA) during Kimchi fermentation and in vitro was studied, respectively. During Kimchi fermentation for six weeks at cold storage temperature ($4^{\circ}C$) and room temperature ($16{\pm}2^{\circ}C$), the contents of nitrite and dimethylamine (DMA) showed variation at room temperature but no variation at cold storage temperature. The maximum generation of nitrosodimethylamine (NDMA) resulted low content ($2.69\;\mu\textrm{g}/kg$) at cold storage temperature but started to increase after one week fermentation and reached to the 18-fold higher generation ($49.6\;\mu\textrm{g}/kg$) at room temperature. During Kimchi fermentation, no correlation was observed between the variation of nitrite and DMA content and the generation of NDMA. However, pH showed effective relation to NDMA generation such as the highest NDMA generation was obtained at lowest pH 4. During in vitro test, higher temperature and lower pH resulted more NDMA generation and generation amount was affected more by pH. Also, the salinity of Kimchi provided inhibitory effects on the formation of NDMA. NDMA was produced $5.86\;\mu\textrm{g}/kg$ at normal salinity (2.5%) but $90.9\;\mu\textrm{g}/kg$ at lower salinity (15%) after three week. The higher salinity showed lower formation of NDMA in vitro test, too.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.156-163
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• 1989

The $ν_a+amide II$ combination band of thiopropionamide has been recorded for investigation of Hydrogen bonding between thiopropionamide (TPA) and N,N-dimethylalkylamide (DMF, DMA and DMP) in carbon tetrachloride over the range of $5^{\circ}$ to $55^{\circ}$. The combination band of monomeric TPA and hydrogen-bonded TPA can be resolved by Lorentzian-Gaussian product function into monomeric TPA and hydrogen-bonded TPA with amides. The association constants ($K_1$) for the hydrogen-bonded TPA were calculated by the concentrations of the monomeric TPA and the hydrogen-bonded TPA obtained from the computer resolved absorption bands. Thermodynamic parameters for the Hydrogen bonding have been evaluated by the analysis of the temperature dependent spectra. The ${\Delta}$$H^{\circ}$ of hydrogen-bonded TPA with DMF, DMA and DMP have been found to be-12.5, -13.5 and -14.1 kJ/mol, respectively. The corresponding ${\Delta}$$S^{\circ}$for the above system were -15.2, -17.9 and -22.3 J/mol${\cdot}$deg, respectively.

• Elastomers and Composites
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• v.48 no.1
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• pp.18-23
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• 2013

Nylon 12 elastomer was slightly crosslinked in molten state by the addition of small amount of dicumyl peroxide (DCP) as a crosslink agent and triallycyanuate (TAC) as a co-agent during melt compounding at $160^{\circ}C$ in an internal mixer. The effect of the peroxide crosslinking on mechanical, dynamic mechanical and rheological properties of the nylon 12 elastomer was investigated by means of tensile testing, dynamic mechanical analysis (DMA) and small amplitude oscillating rheometer, respectively. With modification, there is an improvement in tensile modulus and Young's modulus with decease in elongation at break. DMA results for peroxide modified nylon 12 elastomers demonstrated that the glass transiaiton temperature of PTMG segment shifted to higher temperature and the storage modulus remained constant above the melting temperature of nylon 12 segments. Melt rheological studies revealed that the peroxide modified nylon 12 elastomer exhibited a more solid like behavior and stronger shear thinning behavior compared to neat nylon 12 elastomer, which was more prominent at higher TAC content in the polymer matrix. The peroxide modified nylon 12 elastomer exhibited good elastic recoverability and improved mechanical properties without sacrificing melt processibilty, and especially the service temperature range increased as compared to neat nylon 12 elastomer.

• Journal of Food Hygiene and Safety
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• v.13 no.3
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• pp.274-277
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• 1998

The study was focused to investigate the effect of nitrosodimethylamine (NDMA) formation due to nitrosamine (NA) precursor and/or inhibitor addition to Kimchi during the fermentation of Kimchi at room temperature ($16{\pm}2^{\circ}C$). The addition of nitrite and dimethylamine (DMA) to Kimchi showed the average 32-fold ($21.3{\sim}113.9\;\mu\textrm{g}/kg$) and 9-fold ($1.3{\sim}40.3\;\mu\textrm{g}/kg$) higher NDMA formation than control ($O{\sim}5.6\;\mu\textrm{g}/kg$), respectively. Also, the addition of both nitrite and DMA resulted in the increase of NDMA formation to average 42-fold ($39.4{\sim}155.7\;\mu\textrm{g}/kg$) higher than control. On the other hand, the addition of 4 ruM ascorbic acid to Kimchi with nitrite and DMA inhibited the formation of NDMA down to 71.3% of control. However, the addition of cysteine and erythorbic acid affected no inhibition to NDMA formation during the test. The addition of sodium sulfite increased NDMA formation. Accordingly, this showed that the amount of ascorbic acid generated during Kimchi fermentation played an important inhibition role for NA formation.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.377-384
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• 2010

We perform a comparative study to investigate the properties of the new energetic chain extender (AzPD). A series of poly(glycidyl azide)/poly(tetramethylene oxide)-based energetic segmented polyurethane (GAP/PTMG ESPU) with different chain extender, which is 3-azidopropane-1,2-diol (AzPD), 1,4-butane diol (1,4-BD), or 1,5 pentane diol (1,5-PD), was synthesized by solution polymerization in dimethyl formamide (DMF) and their phase behaviors were investigated. The ESPUs were characterized with Fourier transform infrared-attenuated total reflection spectroscopy (ATR FT-IR), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The results of the ATR FT-IR analysis of the urethane carbonyl group region showed that the 'free' C=O fraction was higher in GAP/PTMG AzESPU (0.5) than GAP/PTMG BDESPU (0.44) and GAP/PTMG PDESPU (0.41) for 7 days samples after preparation and that it was similar in the range of 0.26~0.29 for three 60 days ESPU samples. DMA curves of the GAP/PTMG AzESPU for 7 days samples showed amorphous polymers, but GAP/PTMG BDESPU and GAP/PTMG PDESPU showed viscoelastic behaviors with rubbery plateau and the flow region. However, DMA curves of the GAP/PTMG AzESPU for 60 days samples showed viscoelastic behaviors with rubbery plateau and the flow region like GAP/PTMG PDESPU, but GAP/PTMG BDESPU did not show the flow region. From phase behaviors with ATR FT-IR, DSC and DMA analysis, GAP/PTMG AzESPU showed good phase-mixing between components. However, it represented viscoelastic behavior of TPE similar to GAP/PTMG PDESPM according to phase equilibrium progress with aging time.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.305-313
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• 2013

In this study, we investigated effects of thermal annealing on the thermal properties and microphase separation behaviors of glycidyl azide-based thermoplastic polyurethane elastomers (ETPE). The GAP-based ETPEs were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and gel permeation chromatography (GPC). The effects of annealing temperature conditions ($80{\sim}130^{\circ}C$, 1 h or 24 h) on the properties of the ETPEs were investigated. The intensity of azide group absorption peak of ATR-FTIR spectra and the solubility of ETPE for methylene chloride and dimethylformamide solvent decreased after the annealing at $130^{\circ}C$ for 1 h and at $105^{\circ}C$ for 24 h. With increasing the annealing temperature from $80^{\circ}C$ to $110^{\circ}C$, the high temperature rubbery plateau region of storage modulus curves from DMA thermogram for GAP-based ETPEs was extended to the higher temperature.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.63-66
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• 2001

본 논문에서는 TI사의 TMS320C6201 DSP를 이용하여 H.263 동영상 부호화기를 실시간 구현하고자 한다. 구현한 부호화기는 QCIF 형식의 영상을 사용하여 ITU-T H.263 권고안의 기본 모드를 따라 주로 C 언어와 intrinsics를 사용하여 구현하였다. 특히, 속도 향상을 위해서 고속 메모리의 사용을 극대화하는데 중점을 두었고, 연산량이 많은 모듈에 대한 최적화와 데이터의 병렬 처리 및 DMA (Direct Memory Access) 전송 등을 고려하여 구현하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.683-686
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• 2001

The thermomechanical characteristics of NITINOL shape memory alloy were evaluated using DSC with small samples and DMA with three-point bending specimens. The shape memory alloy of 54.4Ni/45.5Ti wt.% was used so that the austenite finish temperature was in the range of $50~100^{\circ}C$. Two types of sample were tested in the experiments corresponding to as-received and annealed conditions. Simple beam bending theory was used to calculate the dynamic moduli of the shape memory alloy. According to the results, a large discrepancy in transformation temperatures was found between DSC and DMA techniques. Annealing treatment was found to suppress the R-phase transformation during cooling and the secondary plateau in the austenite transformation. Such a heat treatment was also significantly influenced to raise the transformation temperatures and the moduli of the shape memory alloy.