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61.
Jin Sung Choi Sang Hyuk Im Min Young Song O Ok Park Hansol Cho Jin Taek Hwang 《应用聚合物科学杂志》2005,95(5):1100-1104
A gradient refractive index rod was successfully prepared by a new fabrication method using laminar shear mixing, and a graded index polymer optical fiber that satisfied IEEE1394b was obtained from the method. To fabricate the gradient refractive index rod, a liquid monomer mixture with a relatively low refractive index was placed in a prepared cylindrical glass reactor and a transparent polymer rod with a higher refractive index was introduced at the center of the reactor. The reactor and the polymer rod were then rotated concurrently with a small rotating speed difference to generate a Couette flow in the liquid phase. The centrifugal force generated by rotation and the polymer diffusion into the liquid monomer mixture developed a graded concentration profile in a radial direction. The Couette flow could reduce the concentration fluctuation in a tangential direction. In addition, the graded index profile could be controlled by the copolymer composition of the rod and its diameter. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1100–1104, 2005 相似文献
62.
Jongseong Park Dae‐Hyeon Kim Su‐Jin Park Tae‐gon Lee Mir Im Jeong‐Seog Kim Sahn Nahm 《Journal of the American Ceramic Society》2016,99(7):2229-2232
A specimen having a stoichiometric composition of KSbO3·(KSb) calcined at 800°C has an R rhombohedral structure (RS), and changes to a Pn cubic structure (CS) when calcined at 1100°C. Finally, a <111>‐oriented rhombohedral phase is formed in the specimen calcined at 1230°C. K/Sb ratio decreases from 1.0 in RS, 0.93 in CS, and finally to 0.85 in <111>‐oriented rhombohedral phases. On the other hand, a specimen having a K‐excess composition of K1.1SbO3 calcined at 800°C shows a RS that is maintained in the K‐excess specimen calcined at 1230°C. The composition of these specimens is very close to KSb. Therefore, the RS with a space group of R is a stable form of KSbO3. The formation of Pn cubic and <111>‐oriented R phases can be explained by the evaporation of K2O during the calcination process at temperatures above 1100°C. 相似文献
63.
Jyh-Dar Fan L. James Lee Junil Kim Yong-Taek Im 《Polymer Engineering and Science》1989,29(11):740-748
The effects of material flow, heat transfer, part geometry, and curing agents on the cure of sheet molding compounds (SMC) in molds with substructures were analyzed both experimentally and numerically. It was found that heat transfer during mold filling has a profound effect on the cure pattern, especially for fastcure resins molded for parts with thin dimensions. 相似文献
64.
Jun Wuk Park Seung Soon Im Soo Hyun Kim Young Ha Kim 《Polymer Engineering and Science》2000,40(12):2539-2550
Gelatinized starches were prepared with various content of glycerol and were investigated in terms of the effect of the glycerol addition on characteristics of starch and its blends. Poly (L‐lactic acid) (PLA) with various ratios of linear/star shaped PLA and starch gelatinized with various ratios of water/glycerol were melt‐blended by using twin screw mixer. The blends were characterized by DSC thermal analysis, tensile test and morphological analysis. Gelatinization of starch was found to lead to destruction or diminution of hydrogen bonding in granules and a decrease of crystallinity of starch. DSC data showed that starch played a role as a nucleating agent and glycerol as plasticizer contributed to an improvement in crystallinity in PLA blends. When the content of starch increased, the size of spherulites in PLA blends was smaller and less regular. In the case of PLA/pure starch blends, the voids appeared, which were formed by the separation of starch particles from the matrix. But for PLA/gelainized starch blends, these voids were not observed. In the case of blends with linear PLA and starch gelatinized with water/glycerol ratio of 100/40, the greatest superiority of mechanical properties was shown and the toughness was improved compared with PLA/pure starch blends. 相似文献
65.
Rajkumar Patel Se Jun Im Yun Taek Ko Jong Hak Kim Byoung Ryul Min 《Journal of Industrial and Engineering Chemistry》2009,15(3):299-303
The syntheses of series of proton conducting comb copolymer membrane involving polysulfone back bone as main chain and poly(styrene sulfonic acid) (PSSA) being side chain, i.e. polysulfone grafted poly(styrene sulfonic acid) (PSU-g-PSSA) are presented. Chloromethylation of the polysulfone backbone was done by Fridel Craft alkylation reaction. Atom transfer radical polymerization was used for control grafting from the chloromethylated positions. The successful substitution of the chloromethyl group and its grafting with PSSA was characterized by elemental analysis and proton nuclear magnetic resonance. Water uptake, electrochemical properties like ion exchange capacity (IEC) and proton conductivities increase with increase in PSSA contents. Thermal gravimetric analysis (TGA) showed the thermal stability of membranes up to 250 °C. Proton conductivity for maximum amount of grafting is 0.02 S/cm. 相似文献
66.
Yoon Taik Goh Rajkumar Patel Se Jun Im Jong Hak Kim Byoung Ryul Min 《Korean Journal of Chemical Engineering》2009,26(2):518-522
Two-step synthesis of proton-conducting poly(ether sulfone) (PES) graft copolymer electrolyte membrane is proposed. Fridel
Craft alkylation reaction was used to introduce chloromethyl pendant group onto the PES polymer backbone. Later on, atom transfer
radical polymerization (ATRP) was applied to synthesize a series of poly(ether sulfone) grafted poly(styrene sulfonic acid)
(PES-g-PSSA). Successful chloromethyl substitution and grafting of the pendant group was characterized by the 1H-NMR and elemental analysis. Electrochemical properties such as ion exchange capacity (IEC), water uptake and proton conductivity
increased with increasing PSSA contents. Thermal gravimetric analysis (TGA) showed the thermal stability of membranes up to
270 °C. Proton conductivity for maximum amount of grafting was 0.00297 S/cm. 相似文献
67.
Fractionation of the MeOH extract of Homaxinella sp., a marine sponge, led to the isolation of a sodium salt of a new brominated FA (1), two new MG (2 and 4), and a new lysoPC (6). The geometry of the double bonds in 1 and 2 was defined by comparison of the NMR chemical shifts of the allylic carbons, nuclear Overhauser effect spectroscopy correlations
of the allylic protons, and coupling constants of the vinylic protons with those reported. Evidence mainly from NMR and MS
analyses established the planar structures of the compounds. Compounds 1, 2, 4, and 6 were evaluated for cytotoxicity against a panel of five human solid tumor cell lines. Only compound 1 showed moderate activity. 相似文献
68.
Ji Sun Im Ohseob Kwon Young Ho Kim Soo-Jin Park Young-Seak Lee 《Microporous and mesoporous materials》2008,115(3):514-521
In this paper, the effect of embedding vanadium pentoxide in electrospun carbon fiber was investigated in relation to textural properties and hydrogen storage behavior. Electrospun carbon fibers involving vanadium were prepared from polyacrylonitrile/N,N-dimethyl formamide/vanadium pentoxide through electrospinning method and heat treatment. Chemical activation of electrospun carbon fibers was carried out in order to generate the pore by using potassium hydroxide as a chemical agent. Eventually, vanadium embedded activated electrospun carbon fibers (AECFs) with high specific surface area 2780 m2/g were prepared as a hydrogen storage medium. As the effects of vanadium pentoxide, it was found that dissociated oxygen from vanadium pentoxide in electrospun fibers would generate the ultra-micropore (0.6 nm) by forming carbon monoxide and carbon dioxide during the carbonization. Also, vanadium in electrospun carbon fibers is considered to act as a catalyst for the improved capacity of hydrogen adsorption. Vanadium embedded AECFs have the high capacity of hydrogen storage, about 2.5 wt% at room temperature and 100 bar. 相似文献
69.
Yonghyun Kim Huiwen Liu Yi Liu Boa Jin Hao Zhang Wenjing Tian Chan Im 《Frontiers of Chemical Science and Engineering》2021,15(1):187-197
Cesium lead halide perovskite(CsPbX3,X=Cl,Br,I)quantum dots(QDs)and their partly Mn2+-substituted QDs(CsPb1–xMnxX3)attract considerable attention owing to their unique photoluminescence(PL)efficiencies.The two types of QDs,having different PL decay dynamics,needed to be further investigated in a form of aggregates to understand their solid-state-induced exciton dynamics in conjunction with their behaviors upon degradation to achieve practical applications of those promising QDs.However,thus far,these QDs have not been sufficiently investigated to obtain deep insights related to the long-term stability of their PL properties as aggregated solid-states.Therefore,in this study,we comparatively examined CsPbX3-and CsPb1–xMnxX3-type QDs stocked for>50 d under dark ambient conditions by using excitation wavelength-dependent PL quantum yield and time-resolved PL spectroscopy.These investigations were performed with powder samples in addition to solutions to determine the influence of the inter-QD interaction of the aged QD aggregates on their radiative decays.It turns out that the Mn2+-substituted QDs exhibited long-lasting PL quantum efficiencies,while the unsubstituted CsPbX3-type QDs exhibited a drastic reduction of their PL efficiencies.And the obtained PL traces were clearly sensitive to the sample status.This is discussed with the possible interaction depending on the size and distance of the QD aggregates. 相似文献
70.
Youri Oh Hoyong Jung Hyejin Kim Jihyun Baek Joonhong Jun Hyunwook Cho Daseul Im Jung-Mi Hah 《International journal of molecular sciences》2021,22(8)
Polo-like kinase 1 (PLK1) plays an important role in cell cycle progression and proliferation in cancer cells. PLK1 also contributes to anticancer drug resistance and is a valuable target in anticancer therapeutics. To identify additional effective PLK1 inhibitors, we performed QSAR studies of two series of known PLK1 inhibitors and proposed a new structure based on a hybridized 3D-QSAR model. Given the hybridized 3D-QSAR models, we designed and synthesized 4-benzyloxy-1-(2-arylaminopyridin-4-yl)-1H-pyrazole-3-carboxamides, and we inspected its inhibitory activities to identify novel PLK1 inhibitors with decent potency and selectivity. 相似文献