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排序方式: 共有275条查询结果,搜索用时 31 毫秒
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Continuous solution copolymerization of methyl methacrylate with ethyl methacrylate or n-butyl methacrylate was carried out
in a continuous stirred tank reactor. Solvent and initiator used were toluene and benzoyl peroxide, respectively. Reaction
volume was 1.2 litters, residence time 3 hours and polymerization temperature 80°C. The copolymerization conversions were
analyzed by UV spectrophotometry and confirmed by measuring the solid weights of copolymers obtained after evaporating solvent.
The copolymerization of methyl methacrylate and alkyl methacrylates followed the second order kinetics. The simulated conversions
and copolymerization rates were compared with the experimental results. The average time to reach dynamic steady-state was
three and half times of the residence time. 相似文献
3.
The resonant excitation of metal-clad modes, including fundamental and higher-order modes, in a multilayer structure deposited on the polished cladding of a single-mode optical fiber is theoretically analyzed and experimentally demonstrated. The excitation of metal-clad modes is shown as a resonant power transfer from the fiber to the metal-clad mode that takes place for an external refractive-index value such that the effective index of the metal-clad mode reaches the cladding level. The observed attenuation on the TM polarization provides a suitable transducing mechanism for refractive-index sensor devices as well as the principle for developing tunable wavelength-polarized filters with a wide range of optical performance characteristics. 相似文献
4.
ZnO thin films were prepared on Si(0 0 1) substrates using a pulsed laser deposition (PLD) technique and then their growth and properties were investigated particularly as a function of ambient O2 pressure during film growth. It was found that the microstructure, crystallinity, orientation and optical properties of the films grown are strongly dependent on the O2 pressures used. Completely c-axis oriented ZnO films are grown in a low O2 pressure regime (5×10−4-5×10−2 Torr), whereas a randomly oriented film with a much lower crystallinity and a rougher grained-surface is grown at an O2 pressure of 5×10−1 Torr. This deterioration in film quality may be associated with the kinetics of atomic arrangements during deposition. Our results suggest that ambient O2 pressure is an important processing parameter and should be optimized in a narrow regime in order to grow a ZnO film of good properties in PLD process. 相似文献
5.
张积忠 《广东输电与变电技术》2004,(4):56-59
本文研究各种电网事故发生的原因,提出综合性的应对策略,从地区电网的角度加强继电保护和安全稳定自动装置的优化配置;采用先进可靠的调度自动化系统对电网进行密切监控;保证正常情况下系统的安全稳定运行和事故时能够及时正确地切除故障,防止事故扩大。 相似文献
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Chung Sub Kim Oh Wook Kwon Sun Yeou Kim Sang Un Choi Ki Hyun Kim Kang Ro Lee 《Lipids》2014,49(11):1151-1159
In the course of our continuing search for bioactive constituents of Korean medicinal plants, we isolated five new oxylipins, chaenomic acid A–E ( 1 – 5 ), and six known ones ( 6 – 11 ) from the twigs of Chaenomeles sinensis. The structures of the new compounds ( 1 – 5 ) were determined by spectroscopic methods, including 1D and 2D NMR (1H and 13C NMR, 1H–1H COSY, HMQC, HMBC, and NOESY), olefin cross‐metathesis, and LC/MS analysis. The known compounds ( 6 – 11 ) were identified by comparison of their spectroscopic data and specific optical rotation with the reported data. The isolated compounds ( 1 – 11 ) were tested for their inhibitory effects on nitric oxide production in lipopolysaccharide‐activated murine microglial cells and for their cytotoxic activities against four human cancer cell lines (A549, SK‐OV‐3, A498, and HCT‐15). 相似文献
8.
Changho Lee Raehyun Kim Jong Sub Lee Woojin Lee 《Bulletin of Engineering Geology and the Environment》2013,72(1):3-13
The measurements of a strain gauge type cone penetrometer are influenced by the temperature change during penetration. A real-time temperature compensation technique using a fiber Bragg grating (FBG) sensor is suggested to correct the effect of temperature on cone tip resistance. A 7-mm micro cone penetrometer equipped with FBG sensors and electrical strain gauges was developed to evaluate the suggested technique. Design concepts include the cone configuration, sensor installation and the temperature compensation process. It is shown that the measured cone tip resistance is significantly affected by the temperature; the error increasing with increasing temperature change. The cone tip resistance measured by the FBG sensor is effectively corrected by the real-time compensation method. The q c profile of the strain gauge indirectly corrected by the re-penetration test is quite similar to the real-time compensated profile. It is concluded that the proposed real-time temperature compensation using the FBG sensor is an effective technique to obtain reliable cone tip resistance profiles. 相似文献
9.
Structural and Piezoelectric Properties of (Na1−xKx)NbO3 Platelets and Their Application for Piezoelectric Nanogenerator 下载免费PDF全文
HaiBo Xu Young‐Jin Ko Tae‐Gon Lee Su‐Jin Park Myoung‐Sub Noh Bo‐Yun Kim Jeong Seog Kim Sahn Nahm 《Journal of the American Ceramic Society》2016,99(10):3476-3484
(Na1?xKx)NbO3 (NKN) platelets synthesized at 600°C for 12 h have an Amm2 orthorhombic structure. However, the structure of NKN platelets synthesized at 500°C is a mixture of R3m rhombohedral and Amm2 orthorhombic structures. The formation of a rhombohedral structure is attributed to the presence of OH? and H2O defects in the NKN platelets. The piezoelectric strain constant (d33) of NKN platelets synthesized at 600°C for 12 h is 100 pmV?1, whereas that of NKN platelets synthesized at 500°C is lesser (50 pmV?1) due to the presence of these defects. Piezoelectric nanogenerators (PNGs) are fabricated using composites consisting of NKN platelets and polydimethylsiloxane. A large output voltage of 25 V and output current of 2.7 μA were obtained for the PNG with NKN platelets synthesized at 600°C for 6 h. This PNG shows a high output electrical energy of 3.0 μW at an external load of 5.1 MΩ. 相似文献
10.
Sung Ho Oh Jae Gun Han Young Kim Ji Hye Ha Seung Seop Kim Myoung Hoon Jeong Hyang Suk Jeong Na Young Kim Jeong Sub Cho Won Byong Yoon Shin Young Lee Do Hyung Kang Hyeon Yong Lee 《Journal of Bioscience and Bioengineering》2009,108(5):429-434
Autotrophic growth of Porphyridium cruentum under 18:12 h and 12:12 h light:dark cycles showed the maximum cell concentration of 2.1 g-dry wt./L, whereas the specific growth rate, 0.042 (1/h), at 18:6 h is faster than that of 12:12 h, 0.031 (1/h), respectively. The highest lipid accumulation level, 19.3 (%, w/w), was achieved at 12:12 h cycle. Under dark cultivation condition with 10 g/L of glucose, the lipid accumulation in the cell was 10.9 (%, w/w), whereas the heterotrophic growth with glycerol as the carbon resource showed low level of cell concentration and lipid production, compared to that of glucose. The glucose was decided to be a suitable carbon resource for the heterotrophic growth of P. cruentum. The lipids from P. cruentum seemed be feasible for biodiesel production, because over 30% of the lipid was C16–C18:1. The cultivation time and temperature were important factors to increase the maximum cell concentration. Extending the cultivation time helps maintain the maximum cell concentration, and higher lipid accumulation was achieved at 25 °C, compared to 35 °C. The fed-batch cultures showed that, under the light condition, the specific production rate was slightly decreased to 0.4% lipid/g-dry wt./day at the later stage, whereas, under the dark condition, the specific production rate was maintained to be a maximum value of 1.1% lipid/g-dry wt./day, even in the later stage of cultivation. The results indicate that the heterotrophic or 12:12 h cyclic mixotrophic growth of P. cruentum could be used for the production of biodiesel in long-term fed-batch cultivation of P. cruentum. 相似文献