• Polymer(Korea)
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• v.34 no.4
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• pp.326-332
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• 2010

Nanocomposite films were prepared by blending poly(amic acid)(PAA), poly(o-hydroxyamide)( PHA) and organically modified montmorillonite (OMMT) that has a layered structure. XRD, SEM and TEM were used to study the morphology of PAA/PHA nanocomposites, and DMA, TGA, UTM, LOI and PCFC techniques were used to characterize the mechanical and thermal properties, and flame retardancy of the nanocomposites. TEM images revealed that OMMT layers were well dispersed in the PAA/PHA matrix and showed exfoliation and intercalation behavior. The addition of 3 wt% OMMT to the PAA/PHA blend increased the initial modulus of PAA/ PHA blend to 3.68 GPa that was ca. 48% higher than that of the control PAA/PHA blend. Above 4 wt%, however, both the initial modulus and the tensile strength were found to decrease, which might be due to the aggregation of OMMT in PAA/PHA matrix. When the OMMT content was below 3 wt%, the thermal stability and flame retardancy of the PAA/PHA nanocomposites increased with increasing OMMT content.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.51-57
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• 2021

This paper analyzed the effects of the concentration of nano-silica particles contained in epoxy resin on the thermomechanical properties of the composite materials. The 12nm sized nanoparticles were mixed with epoxy polymer by 5 different weight ratios for the test samples. The glass transition temperature, stress relaxation, and thermal expansion behaviors were measured using dymanic mechanical analyzer (DMA) and thermomechanical analyzer (TMA). It was shown that the nano particle mixing ratios had significant influences on the viscoelastic behaviors of the materials. As the content of the silica particles was increased, the elastic modulus was also increased, while the glass transition temperatures were decreased. Fourier Transform Infrared Spectroscopy (FTIR) results played an important role in determining the causes of the property changes by the filler contents in terms of the molecular structures, enabling the interpretations on the material behaviors based on the chemical structure changes.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.168-177
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• 1987

The equilibria of chemical reaction between $\alpha$-Ni(rac-[14]-decane)$^{2+}$ and polar solvents(L; ANT, MFA, DMSO, DMF, and DMA) have been investigated by the spectrophotometric method at $25^{\circ}C$. (The equilibrium constants($K_1$) of) the first step in ANT, MFA, DMSO, DMF, and DMA were 31.0, 27.5, 21.3 15.9, and 6.4, respectively. The smallness of equilibrium constants ($K_2$) of the second step compared with $K_1$, was observed. $\alpha$-Ni(rac-[14]-dacane)$^{2+}$ + L $\leftrightharpoons$ [$\alpha$-Ni(rac-[14]-decane){\cdot}L]$^{2+}$ : $K_1$.[$\alpha$-Ni(rac-[14]-decane){\cdot}L)$^{2+}$+ L $\leftrightharpoons$ [$\alpha$-Ni(rac-[14]-decane){\cdot}$L_2$)$^{2+}$ :$K_2$. The relationship between d-d absorption energy and half-wave potential of complex ions at ACT was considered. Macrocyclic ligands increasing d-d transition energy caused half-wave potentials of Ni(II)-macrocycle to be shifted more positively. The half-wave potentials for Ni(rac-1[14]7-diene)$^{2+}$, Ni(meso-1[14]7-diene)$^{2+}$, Ni(1[14]4-diene)$^{2+}$, $\alpha$-Ni(rac-[14]-decane)$^{2+}$, ${\beta}-Ni(rac-[14]-decane)$^{2+}$, and Ni(meso-[14]-decane)$^{2+}$ reductions were -1.419, -1.431, -1.450, -1.473, and -1.480 (V vs. SCE), respectively. The d-d transition energies ($\nu_{max},\;cm^{-1}$) of the Ni(meso-[14]-decane)$^{2+}$ isomer were discussed with the dielectric constant (${\varepsilon}/{\varepsilon}_0$) of the various solvents, $\nu_{max}(cm^{-1})$ increased with increasing ${\varepsilon}/{\varepsilon}_0$.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.33-46
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• 2010

We investigated and estimated at the characteristics of decomposition and by-products of N-Nitrosodimethylamine (NDMA) using a design of experiment (DOE) based on the Box-Behken design in an UV process, and also the main factors (variables) with UV intensity($X_2$) (range: $1.5{\sim}4.5\;mW/cm^2$), NDMA concentration ($X_2$) (range: 100~300 uM) and pH ($X_2$) (rang: 3~9) which consisted of 3 levels in each factor and 4 responses ($Y_1$ (% of NDMA removal), $Y_2$ (dimethylamine (DMA) reformation (uM)), $Y_3$ (dimethylformamide (DMF) reformation (uM), $Y_4$ ($NO_2$-N reformation (uM)) were set up to estimate the prediction model and the optimization conditions. The results of prediction model and optimization point using the canonical analysis in order to obtain the optimal operation conditions were $Y_1$ [% of NDMA removal] = $117+21X_1-0.3X_2-17.2X_3+{2.43X_1}^2+{0.001X_2}^2+{3.2X_3}^2-0.08X_1X_2-1.6X_1X_3-0.05X_2X_3$ ($R^2$= 96%, Adjusted $R^2$ = 88%) and 99.3% ($X_1:\;4.5\;mW/cm^2$, $X_2:\;190\;uM$, $X_3:\;3.2$), $Y_2$ [DMA conc] = $-101+18.5X_1+0.4X_2+21X_3-{3.3X_1}^2-{0.01X_2}^2-{1.5X_3}^2-0.01X_1X_2+0.07X_1X_3-0.01X_2X_3$ ($R^2$= 99.4%, 수정 $R^2$ = 95.7%) and 35.2 uM ($X_1$: 3 $mW/cm^2$, $X_2$: 220 uM, $X_3$: 6.3), $Y_3$ [DMF conc] = $-6.2+0.2X_1+0.02X_2+2X_3-0.26X_1^2-0.01X_2^2-0.2X_3^2-0.004X_1X_2+0.1X_1X_3-0.02X_2X_3$ ($R^2$= 98%, Adjusted $R^2$ = 94.4%) and 3.7 uM ($X_1:\;4.5\;$mW/cm^2$, $X_2:\;290\;uM$, $X_3:\;6.2$) and $Y_4$ [$NO_2$-N conc] = $-25+12.2X_1+0.15X_2+7.8X_3+{1.1X_1}^2+{0.001X_2}^2-{0.34X_3}^2+0.01X_1X_2+0.08X_1X_3-3.4X_2X_3$ ($R^2$= 98.5%, Adjusted $R^2$ = 95.7%) and 74.5 uM ($X_1:\;4.5\;mW/cm^2$, $X_2:\;220\;uM$, $X_3:\;3.1$). This study has demonstrated that the response surface methodology and the Box-Behnken statistical experiment design can provide statistically reliable results for decomposition and by-products of NDMA by the UV photolysis and also for determination of optimum conditions. Predictions obtained from the response functions were in good agreement with the experimental results indicating the reliability of the methodology used.

• The Magazine of the IEIE
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• v.22 no.9
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• pp.14-27
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• 1995

KAICUBE/한빛-1호는 하이퍼큐브 형태의 연결망을 가진 병렬 컴퓨터이고 각 노드는 i860프로세서와 통신용의 i82380 DMA 콘트롤러를 탑재하고 있다. 40Mh2 CPU클럭을 사용하는 32노드로 구성되어 있고 컴퓨터의 최고 속도는 2.5G-flops 정도로써 이것은 국내 최초의 Giga급 컴퓨터이다. DMA콘트롤러에 의해 구동되는 노드간 통신은 채널 대역폭이 100Mbps정도이다. 0번 노드는 UNIX를 탑재한 호스트 컴퓨터와 연결되어 있고 호스트 컴퓨터는 병렬 프로그래밍 환경과 각 노드를 관리하는 역할을 한다. 익스프레스는 호스트 컴퓨터에 탑재된 병렬 운영 체제이고 사용하기 간편한 사용자 환경과 프로그래밍 방법에 따라 호스트-노드방법과 cubits 프로그래밍 환경을 각각 제공한다. 그밖에 고수준의 병렬 프로그래밍 환경으로써 기존의 순차 프로그램에 기초한 입력 프로그램을 병렬 프로그램으로 자동 변환 해주는 KAPPA가 있다. 여러 분야의 과학 계산용 프로그램이 수행되고 있으며 그의 성능 측정을 통하여 탁월한 성능을 보여 주었다. 보다 편리한 병렬 프로그래밍 환경의 개발과 범용 계산 전응 서버로써 자유로이 사용할 수 있도록 네트워크 기능을 강화하는 일이 남아있다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.885-888
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• 2000

디지털 기술의 급속한 발전으로 디지털 방송을 위한 DTV가 곧 상용화 될 것으로 보인다. DTV는 단순한 TV수상기 기능 외에 여러 가지 응용 제품으로 발전할 수 있다는 장점이 있다. 그 응용 제품으로 현재 각 국에서 앞 다투어 개발중인 것에는 WEB TV 나 PVR 등을 들 수 있다. 본 논문은 대용량 하드디스크를 이용하여 HD 급 방송 스트림에서도 성능을 발휘하는 DTV의 PVR 기능 추가를 위한 Time-Shifter보드 설계에 관한 것이다. HD급 방송 스트림을 위한 PVR을 개발 할때의 문제점은 읽기와 쓰기가 동시에 발생할 때 최대 40Mbps에 달하는 데이터 엑세스 속도인데 본 논문에서는 현재 시판중인 하드디스크(HDD)를 이용하여 위 속도를 나타내기 위한 효율적인 DMA방식과 버퍼 제어 방법을 제시한다 더불어 저장되었던 스트림을 다시 재생 할 때 문제 될 수 있는 bit rate 제어는 time-stamp방식을 이용하여 해결하였으며 VCR에서의 트릭 모드 재생 기능을 위해 Index 추출 방식을 적용하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.147-150
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• 2002

The cure kinetics of blends of epoxy (DGEBA:diglycidyl ether of bisphenol A)/anhydride (NMA:nadic methyl anhydride) resin with synthesized amino terminated polyetherimide (AT-PEI) were studied using differential scanning calorimetry (DSC) and Dynamic Mechanical Analysizer(DMA) under isothermal condition to determine the reaction parameters and gel-vitrification behavior. The fracture toughness of AT-PEI 20phr/epoxy resin system was improved over 224% and 42.5% more than neat epoxy resin and commercial PEI/Epoxy Resin System.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.11b
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• pp.261-266
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• 1999

본 논문에서는 인터넷 폰이나 디지털 이동통신에서와 같이 낮은 비트율이 요구되는 응용분야에서 사용될 수 있는 HVXC 부호화 및 복호화 알고리즘을 TMS320C6701 160MHz DSP를 사용하여 실시간 동작을 구현한 내용을 기술한다. 사용한 최적화 방법으로는 기본적으로 연산 시간이 많이 소요되는 함수 루틴에 대한 C 언어레벨의 최적화 및 어셈블리어 레벨의 최적화를 수행하였고, TMS320C6701 DSP 내부 프로그램 메모리를 프로그램 캐쉬로 사용하였다. 또한, 계산량이 많은 부분과 테이블 참조가 필요한 연산을DSP의 내부 데이터 메모리 영역에서 수행하여 소요시간을 단축하였으며, 음성신호 및 비트스트림의 입출력에는 background DMA(direct memory access) 방식을 이용하였다. 이와 같은 최적화결과 2kbps 및 4kbps의 비트율에서 압축 및 복원을 실시간으로 수행할 수 있다.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.470-473
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• 2010

Graphene, consisting of a single layer of carbon in a two-dimensional lattice, has been emerging as a fascinating material with many unique physical, chemical and mechanical properties. In this study, graphenes were prepared by a chemical method. To develop high performance polymer nanocomposites reinforced by graphenes, adequate dispersion of the fillers and strong interfacial bonding between the fillers and the polymer matrix are essential. The purpose of this study was to examine the influence of introducing amine groups on the surfaces of graphenes. FT-IR spectroscopy, SEM were used to confirm the functionalization. Epoxy nanocomposites comprising the graphenes were prepared and their characteristics were investigated by DSC, DMA and TMA. Fracture surfaces of the nanocomposites were investigated by SEM. The functionalized graphenes induced strong interfacial bonding than the pristine graphenes and resulted in considerable improvements in the performance of the nanocomposites.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.65-71
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• 2004

A fat body-specific glutathione S-transferase cDMA was cloned from the spider, Araneus ventricosus. The cDNA encoding A. ventricosus glutathione S-transferase (AvGST) is 645 base pairs long with an open reading frame of 215 amino acid residues with a calculated molecular weight of approximately 24 kDa. Northern blot analysis showed the tissue-specifically expression of AvGST in the A. ventricosus fat body.