• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1960-1964
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• 2008

The roles of coordinating ligands (TOPO, OA, HDA, and TDPA) for the synthesis of ZnO nanoparticles are investigated. Various shapes (hexagonal cone, hexagonal plate, and rod) and sizes (5-100 nm) of ZnO nanoparticles are prepared in relation to the coordinating ligands. The hexagonal shapes ($\leq$ 100 nm) are synthesized with TOPO and OA, while smaller size nanorods (5 ${\times}$ 30 nm) are with TOPO and TDPA. The relative intensities of two distinctive emission bands centered at 385 and 500 nm, which are related to the exciton and defect states, respectively, depend on the crystal qualities of ZnO nanoparticles affected by the coordinating ligands. The intense UV emissions with the reduced visible emissions are found in the monodisperse nanoparticles such as hexagonal cones and nanorods, suggesting that the monodispersity as well as the crystallinity is closely related to the coordinating ligands. The blue-shift of photoluminescence and absorption edge is observed in the nanorods, because the sizes of the nanorods are in the quantum confinement regime.

• Elastomers and Composites
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• 제53권1호
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• pp.6-12
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• 2018

Styrene-butadiene Rubber (SBR) Latex composites, incorporated with cellulose/starch-silica hybrids synthesized by gel-adsorption method, were filled into rubber by the latex compounding method. The structure morphology, mechanical properties, and thermodynamic properties of gel-silica hybrids were characterized. The states of hybrids which used as fillers were also characterized by SEM. As the fillers ratio increased, the difference for storage modulus of samples had been morphology by rubber process analyzer (RPA). Then, as more fillers ratio was filled into the matrix, the best tensile strength result, and the largest modulus value were also proved by UTM and RPA. As for thermal stability, increase in the ratio of fillers led to higher initial decomposition temperature, which was also proved by TGA. The swelling ratio of samples has also been characterized. From the results of all the tests, cellulose-silica hybrid showed the best results as a filler, and the best filling ratio of this hybrid is about 10 phr, which has the best storage modulus and great tensile strength.

• 대한화학회지
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• 제27권3호
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• pp.224-232
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• 1983

$Fe_2O_3$와 $BaCO_3$ 분체를 철제 ball-mill로 각각 5, 15, 30, 80, 200시간 혼합분쇄하여 얻어진 $BaCO_3-Fe_2O_3$계에서 고체반응 및 생성 Ba-ferrite의 자기적 성질에 미치는 분쇄시간의 영향을 조사하였다. 열천칭, X-선 회절기, 주사형전자현미경 및 B-H 이력곡선기 등을 사용하여 조사한 결과 일정시간 이상 분쇄시켰을 때 입자의 응집현상과 함께 초상자성을 띄는 미립자가 생기게 되어 Ba-ferrite의 생성 및 자기적 성질에 중요한 영향을 미친다는 사실을 확인했다.

• 대한화학회지
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• 제12권3호
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• pp.89-92
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• 1968

基底狀態의 Porphin 核과 Phthalocyanine 核의 電子狀態와 反應性을 理論的으로 考察하였다. 이때 各 ${\pi}$軌道의 energy量과 superdelocalizability 및 結合次數(bond order)는 單純分子軌道法에 依據해서 算出하였다. 이 두 化合物의 경우, 最高被占軌道와 最底空軌道 사이의 energy 差가 一般的인 다른 有機化合物보다 상당히 적었는데, 이것은 곧 이 두 化合物이 勵起되기 쉬운 狀態에 놓여 있음을 뜻한다. 또한 superdelocalizability와 結合次數로서 이 두 化合物의 各 原子位置에서의 親電子的, 親核的 및 radical 反應의 反應性과 結合强度를 各各 決定하였다.

• 한국의류학회지
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• 제25권5호
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• pp.868-879
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• 2001

The purpose of this study is to scan the textiles having been used for Hanbok since the 1945 Liberation. This paper states the situation of textile industry related to Hanbok. On the basis of this, the popularized textiles of each term and their characteristics are arranged. From 1945 to 1950, in the middle of disorder of this Liberation term, the clothing situation was very bad, so the majority of people wore clothing of Moomyung or Kwangmok. In the 50s, Moomyung, Kwangmok, Okyangmok, and Poplin were popularized. People could use more different kinds of textile then such as Chokyundan, Hobakdan, Newttong, Mobondan, Popdan, and Nylon. In the 60s, Chemical fibers, beginning to come in from the 50s, were their favorites, with which they made Hanbok and Western style dresses as well. Their characteristics were to have an cubic and ornamental effect on the surface. In the 70s, Yangdan, Newttong and other typical fabrics for Hanbok were manufactured with chemical fibers. they intended to give the ornamental effect by putting gold foil, embroidery, printing, and pictures on the surface of the fabrics. In the 80s, there were no seasonable fabrics for Hanbok during this term, as all-year-round fabric like Nobangzu was in common use. In the 90s, seasonable fabrics reappeared. Owing to the increasing interest in our typical fabrics like Mosi, Mobondan, and Hangra began to be in use again.

• 한국응용과학기술학회지
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• 제12권2호
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• pp.29-39
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• 1995

The phase separated structure and the electro-optical properties of the (polymer/liquid) crystal : LC) composite film strongly depended on the weight fraction of LC in it. The continuous LC phase was formed in a three-dimensional polymer network when the LC weight fraction was above 40wt%. The aggregation structure of the composite film could be controlled by controlling the solvent evaporation velocity during the film preparation process. The smaller LC domains or channels were formed in the case of the faster solvent evaporation velocity. The composite film exhibited reversible light scattering-light transmission switching upon electric field -OFF and -ON states, respectiverly. The light scattering properties of the composite film strongly depended on the spatial distortion of the nematic directors as well as the mismatch in refractive indices between matrix polymer and LC.

• 한국환경농학회지
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• 제26권4호
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• pp.294-299
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• 2007

Natural gypsum has been used as a soil amendment in the United States. However, flue gas desulfurization (FGD)-gypsum has not traditionally been used for agricultural purpose although it has potential benefit as a soil amendment. To expand use of FGD-gypsum for agricultural purpose, the effect of FGD-gypsum on soil chemical properties was investigated in the field scales. Application rates for this study were 0 (control), 1.1, and 2.2 Mg ha-1 of FGD-gypsum. After two year application, the soil samples were taken to 110 cm depth and sub-sampled at 10 cm intervals. The heavy metal contents in FGD-gypsum were lower than ceiling levels allowed by regulations for land-applied biosolids. Soil pH was not largely affected by FGD-gypsum application. Although degree of calcium (Ca) saturation in surface horizons increases only slightly with respect to the control, there is a clear decrease in exchangeable aluminum (Al). FGD-gypsum clearly increases the soil electrical conductivity (EC) with increasing application rate. Water-soluble Ca and sulfate is increased with FGD-gypsum application and these ions moved to a depth of at least 80 cm after only 2 years. We conclude that surface application of FGD-gypsum can mitigate toxicity of Al and deficiency of Ca in subsoil of acid soil.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.124-127
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• 2005

Rewritable optical memory devices such as an CD-RW and DVD+RW are data storage media, which take advantage of the different optical properties in the amorphous and crystalline states of phase change materials. The switching property, structural transformation, transformation kinetics and chemical bindings of $Ge_xSb_{100-x}$($6{\le}x{\le}$34) were studied to investigate the feasibility of applying $Ge_xSb_{100-x}$ alloys in optical memory. The $Ge_xSb_{100-x}$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, inductively coupled plasma atomic emission spectrometer (ICP-AES) and atomic force microscopy (AEM). Optimum fiim composition of $Ge_xSb_{100-x}$ was studied and its minimum time fur laser induced crystallization and optical contrast fur phase transition was performed. These results might be correlated with the binding energies between Ge and Sb, and indicate that $Ge_xSb_{100-x}$ have an potential far optical memory applications.

• 대한화학회지
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• 제38권6호
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• pp.405-410
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• 1994

들뜬상태의 소랄렌 유도체와 바닥상태의 티민 사이에 형성되는 분자착물의 형태를 분자궤도 함수법으로 고찰하였다. PM3-CI-UHF법으로 계산한 결과는 메틸소랄렌 및 하이드록시소랄렌의 C3-C4 이중결합과 C4'-C5' 이중결합과 티민의 C5-C6 이중결합과 광고리화 반응이 일어남을 프론티어궤도의 상호작용으로 설명하고, 이들 화합물의 들뜬상태에서 전자구조를 구조-활성화 관계로 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제29권3호
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• pp.641-646
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• 2008

Equilibrium molecular dynamics simulations in a canonical ensemble are performed to evaluate the transport coefficients of several Lennard-Jones (LJ) mixtures at a liquid argon states of 94.4 K and 1 atm via modified Green-Kubo formulas. Two component mixture of A and B is built by considering the interaction between A and A as the attractive (A) potential, that between A and B as the attractive potential (A), and that between B and B as the repulsive potential (R), labelled as AAR mixture. Three more mixtures - ARA, ARR, and RAR are created in the same way. The behavior of the LJ energy and the transport properties for all the mixtures is easily understood in terms of the portion of attractive potential (A %). The behavior of the thermal conductivities by the translational energy transport due to molecular motion exactly coincides with that of diffusion constant while that of the thermal conductivities by the potential energy transport due to molecular motion is easily understood from the fact that the LJ energy of AAR, ARR, and RAR mixtures increases negatively with the increase of A % from that of the pure repulsive system while that of ARA changes rarely.