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排序方式: 共有769条查询结果,搜索用时 15 毫秒
61.
Muthuraj Esther Leena Preethi Thiripuranthagan Sivakumar Muthiahpillai Palanichami 《Catalysis communications》2010,11(10):876-879
Fe/Al-MCM-41 (Si/Al = 25, 50, 75 and 100) were synthesized. Their catalytic activity was evaluated towards benzylation of benzene with benzyl chloride in liquid phase. The catalytic activity of Fe/Al-MCM-41(25) was higher than the other catalysts. Diphenylmethane(DPM) was obtained as the major product with 100% selectivity and with 100% conversion of benzyl chloride under optimum condition. The effect of temperature and the feed ratio, on the activity of Fe/Al-MCM-41(25) and selectivity towards DPM was studied and a possible reaction mechanism was proposed. 相似文献
62.
63.
Shuqi Guo Ramasamy Sivakumar Hideaki Kitazawa Yutaka Kagawa 《Journal of the American Ceramic Society》2007,90(5):1667-1670
Fully dense multiwall carbon nanotubes (MWCNT)/SiO2 nanocomposites with MWCNTs contents of 5 and 10 vol% have been processed by spark plasma sintering, and the electrical conductivities of the nanocomposites were evaluated at temperatures ranging from 5 to 300 K. It has been found that the incorporation of MWCNTs converted an insulating silica nanoceramic into metallically conductive composites. The room-temperature conductivities of the nanocomposites, with over 14 orders of magnitude compared with pure silica, are in the range of 8 and 65 S/m. Also, it was interestingly found that the conductivity increased linearly with temperature from 5 to 300 K. 相似文献
64.
In this paper a new approach to simultaneously tuning the power system stabilizer (PSS) settings in a multimachine electric utility system is presented. The approach is based on eigenvalue assignment, which is treated as a problem of solving a set of non-linear equations. The possibility of meeting additional specified performance criteria is discussed. The flexibility of the proposed method is demonstrated using an operating utility system. 相似文献
65.
66.
There are numerous researcher-developed mathematical models for single slope passive solar stills which considered the effect of heat capacities of basin and glass cover as negligible. The negligence parameter also plays a vital role in the prediction of the thermal performance of the system. In this paper, an effort has been made to evaluate the cumulative yield, energy efficiency and exergy efficiency of a single slope passive solar still with and without considering the heat capacities of basin and glass cover by using various thermal models such as Dunkle’s model, Zheng Hongfei et al.’s model and Tsilingiris model. These models were studied and compared with and without considering the heat capacity of solar components such as basin and glass cover. The thermodynamic model of this system is developed, and executed in a MATLAB code. By comparing the theoretical values of the cumulative yield, energy efficiency and exergy efficiency, it was found that consideration of the heat capacities of glass cover and basin gives a higher output in all the thermal models. 相似文献
67.
Structural and Electrical Properties of Ni‐Substituted Mg‐Mn Nanoferrite by Coprecipitation Route
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Subbiah Rammohan Chitra Sechasalom Sendhilnathan 《International Journal of Applied Ceramic Technology》2015,12(3):643-651
Ni2+ ions doped on Mg0.40Mn0.60‐xNixFe2O4 compositions with 0.00 ≤ x ≤ 0.60 have been synthesized by coprecipitation method and taken for the present work to study the dielectric properties and impedance characterization using the XRD and electrical measurements. The X‐ray diffraction and FT‐IR revealed that the ferrite has single‐phase cubic spinel structure. The calculated particle size from XRD data verified using SEM as well as AFM. These photographs show that the ferrites have crystalline size in the range of 20–50 nm. It was observed that the particle size decreased and Ni concentration increased. The dielectric constant and dielectric loss decreased with increase in nonmagnetic Ni2+ ions. Electrical properties indicate that synthesized nanoferrite particles have high resistivity. 相似文献
68.
We report a unique growth of platelet-shaped nanoscale tips of transparent dielectric using femtosecond laser radiation at
MHz pulse repetition rate with nitrogen background gas flow under ambient condition. The tips grew with sharp nanoscale apex
while their base and lengths are of the order of few hundred nanometers. In the absence of nitrogen, the irradiation leads
to nanofibrous structure formation. The collision between the nitrogen gas atoms and the vapor species slows down plume expansion
and lead to an increase of nanoparticles size. This prevents the fibrous structure formation and provides appropriate condition
for nanoscale tips growth. 相似文献
69.
Silicon - In this study, heterojunction photocatalysts made up of Arundo donax L. plant leaves are used to synthesized SiO2 nanosheets and ZnO nanoparticles were prepared by wet impregnation... 相似文献
70.
Growing vegetables under shade nets is currently becoming popular in summer to provide protection from high intensities of light. High temperatures and light quality affect postharvest quality and storage life of vegetables. Photo-selective shade netting technology is an emerging agro-technological concept that aims at the improvement of crop quality by the modification of spectral light and provides physical protection of the crop. Incorporation of various light-dispersive and reflective chromatic additives in the photo-selective nets is responsible for the modification of spectral quality, especially in the UV 200–400 nm, visible (400–700 nm), or far-red (FR; also known as “near infrared”; 705–740 nm) in the infrared region of the spectral region. Altered light-quality changes under the photo-selective nets were shown to improve the accumulation of phytochemicals and aroma compounds, and ultimately, the growth, yield, and quality of the selected vegetables such as tomatoes, sweet peppers, lettuce, and aromatic herbs. The postharvest quality of fresh produce is also influenced by environmental conditions such as light, average temperature, minimum temperature, and day-night temperature differences. During production, light quality under the photo-selective shade nets had a positive effect on the quality parameters and phytochemical content in fresh produce after postharvest storage.
The review includes the use of photo-selective netting in protected agriculture as a preharvest tool to improve aroma volatiles, antioxidants, and overall quality of fresh produce after postharvest storage. 相似文献