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81.
Effects of operating parameters in the thermal gradient chemical vapor infiltration of propane such as thermal gradient, diffusion, infiltrations time, and concentration of propane were studied by focusing on the visualizations of the intrinsic effects of these parameters. A uniform deposition in the preform was obtained with a gradually increasing temperature along the gas flow. The uniformity of deposition through the preform got improved with increasing deposition time. Results of numerical modeling estimated the experimental data very well when the pre-exponential factor of the overall rate of carbon deposition from propane reported by Vaidyaraman[1] was multiplied by 4. The average density of a preform increased by about 3 times from 0.38 to 1.15 g/cm3 after 60 hr deposition with a thermal gradient under the conditions of 3% propane in nitrogen and 840 to 900 ℃. 相似文献
82.
Kwang Joo Kim Kwang-Young Lim Young-Wook Kim 《Journal of the European Ceramic Society》2012,32(16):4401-4406
The influence of Y2O3 addition on electrical properties of β-SiC ceramics has been investigated. Polycrystalline SiC samples obtained by hot-pressing SiC–Y2O3 powder mixtures in nitrogen (N) atmosphere contain Y2O3 clusters segregated between SiC grains. Y2O3 forms a Y–Si-oxycarbonitride phase during sintering by reacting with SiO2 and SiC and by dissolution of N from the atmosphere; this induces N doping into the SiC grains during the process of grain growth. The SiC samples exhibit an electrical resistivity of ~10?3 Ω cm and a carrier density of ~1020 cm?3, which are ascribed to donor states derived from N impurities. The increase in defect density with increasing Y2O3 content is likely to be a main limiting factor of the electrical conductivity of SiC ceramics. 相似文献
83.
84.
The high‐temperature sous‐vide (HTSV) method was developed to prepare carrots with a soft texture at the appropriate degree of pasteurization. The effect of heating conditions, such as temperature and time, was investigated on various package sizes. Heating temperatures of 70, 80, and 90 °C and heating times of 10 and 20 min were used to evaluate the HTSV method. A 3‐dimensional conduction model and numerical simulations were used to estimate the temperature distribution and the rate of heat transfer to samples with various geometries. Four different‐sized packages were prepared by stacking carrot sticks of identical size (9.6 × 9.6 × 90 mm) in a row. The sizes of the packages used were as follows: (1) 9.6 × 86.4 × 90, (2) 19.2 × 163.2 × 90, (3) 28.8 × 86.4 × 90, and (4) 38.4 × 86.4 × 90 mm. Although only a moderate change in color (L*, a*, and b*) was observed following HTSV cooking, there was a significant decrease in carrot hardness. The geometry of the package and the heating conditions significantly influenced the degree of pasteurization and the final texture of the carrots. Numerical simulations successfully described the effect of geometry on samples at different heating conditions. 相似文献
85.
A synthetic method to prepare a novel double spirobifluorene core structure was developed and a hole transport type exciton blocking material with the double spirobifluorene core was synthesized. A two step ring closing method was used to synthesize the double spirobifluorene core. The double spirobifluorene core based hole transport material showed high glass transition temperature due to rigid structure, and high quantum efficiency in green phosphorescent organic light emitting diodes because of efficient hole injection and triplet exciton blocking properties. 相似文献
86.
Joo Hee Kim Seok Hyun Nam Catherine W. Rico Mi Young Kang 《International Journal of Food Science & Technology》2012,47(6):1176-1182
The antioxidative and anti‐allergic activities of fresh and aged black garlic extracts were investigated. The garlic samples were extracted with 70% ethanol (v/v) and the total phenolic content was measured. The antioxidant capacity of extracts was assessed by determining the scavenging activities on 1,1‐diphenyl‐2‐picrylhydrazyl and hydroxyl radicals, ferricyanide reducing power, ferrous ion‐chelating ability and inhibitory effect on linoleic acid peroxidation. The anti‐allergic activity of extracts was analysed by measuring their inhibitory effects against β‐hexosaminidase release. The aged black garlic exhibited significantly higher phenolic content and greater antioxidative activity than fresh garlic. Both garlic extracts showed strong antioxidant capacity in a dose‐dependent manner. On the other hand, a considerably higher suppression of β‐hexosaminidase release was found in fresh garlic extract at lower concentration compared with that of the black garlic. Results of this study illustrate that ageing of garlic could enhance its antioxidant capacity, but could decrease its anti‐allergic activity. 相似文献
87.
Sung Chul Jee Ho Jae Lee Young Hoon Joo 《International Journal of Control, Automation and Systems》2012,10(4):841-848
This paper addresses sensor fault detection and isolation problems for continuous- and discrete-time linear time-invariant systems. To that end, we employ a bank consisting of the same number of observers as there are sensors. Both the observer gain and the residual gain are considered. Unlike earlier work, the design conditions with H ?/H ∞ performance are derived in terms of linear, rather than nonlinear, matrix inequalities. An illustrative example is provided to show the effectiveness of the proposed methodology. 相似文献
88.
Phosphorescent OLEDs: Sky‐Blue Phosphorescent OLEDs with 34.1% External Quantum Efficiency Using a Low Refractive Index Electron Transporting Layer (Adv. Mater. 24/2016) 下载免费PDF全文
89.
90.
Wonsang Kwon Yecheol Rho Kensuke Kamoshida Kyung Ho Kwon Youn Cheol Jeong Jonghyun Kim Hideki Misaka Tae Joo Shin Jehan Kim Kwang‐Woo Kim Kyeong Sik Jin Taihyun Chang Heesoo Kim Toshifumi Satoh Toyoji Kakuchi Moonhor Ree 《Advanced functional materials》2012,22(24):5194-5208
Low‐temperature anionic ring‐opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal‐free catalyst system, 3‐phenyl‐1‐propanol (PPA) (an initiator) and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris‐(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4) (a promoter) in order to obtain well‐defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring‐opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well‐defined linear AGE‐homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE‐homopolymer in a unimodal narrow molecular‐weight distribution. In this case, however, a side reaction (i.e., chain‐transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well‐defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post‐modification products are examined. Overall, this study demonstrates that a low‐temperature metal‐free anionic ROP using the PPA/t‐Bu‐P4 catalyst system is suitable for the production of well‐defined linear AGE‐homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post‐modifications, nanostructures, and their applications. 相似文献