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排序方式: 共有649条查询结果,搜索用时 635 毫秒
51.
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
52.
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
53.
54.
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
55.
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
56.
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
57.
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
58.
Subbarama Kousik Suraparaju Arivazhagan Sampathkumar Sendhil Kumar Natarajan 《亚洲传热研究》2021,50(6):5516-5537
The paucity of drinking water is an alarming glitch across the globe. The conversion of available seawater into drinking water by utilizing renewable energy is the best way to surmount this challenge. Desalination through solar still is one of the notable, monetary, and viable processes among various desalination approaches. The current research aims to augment the potable water yield of single-slope solar still by using a hollow-finned absorber basin inserted into paraffin wax—phase change material (PCM). The effect of hollow-finned absorber basin on the yield of solar still is investigated separately, with and without PCM, and compared with the results of conventional solar still (CSS). In the first set of experiments, the CSS and solar still with a hollow-finned absorber basin without PCM (SSHF) are investigated. In the second set of experiments, the CSS and solar still with a hollow-finned absorber basin inserted into PCM (SSHFP) are investigated. The experimental results reported that the CSS is having almost the same yield on the 2 days of testing. The yield of SSHF and SSHFP is increased by 15.7% and 52.4%, respectively, when compared with CSS. The results of the economic analysis proved that the payback period and cost per liter of freshwater produced from SSHFP are comparatively better than SSHF and CSS. 相似文献
59.
Duraiswami Divakar Dhanagopal Manikandan Valentine Rupa Esther Leena Preethi Revathi Chandrasekar Thiripuranthagan Sivakumar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(3):253-258
Palladium nanoparticles were generated in the interlamellar region of swelling 2:1 type vermiculite clay using an adsorption excess isotherm. An adsorption excess isotherm was constructed for vermiculite after exchanging the exchangeable Na+ ions in the interlamellar region using a binary liquid mixture (ethanol:toluene). Based on adsorption excess isotherm, 1% w/w palladium was intercalated into the interlamellar space of vermiculite. The Pd‐intercalated vermiculite was characterized by X‐ray diffraction, transmission electron microscopy and atomic absorption spectroscopy. The 1% w/w Pd‐intercalated vermiculite was tested for its catalytic activity towards selective hydrogenation reactions involving some α,β‐unsaturated carbonyl compounds using a pulse reactor and its catalytic activity was compared with commercial 1% Pd/C. The intercalated catalyst was found to be very selective towards the desired product of unsaturated alcohols. Copyright © 2007 Society of Chemical Industry 相似文献
60.
Abhay K. Jha D. Sivakumar K. Sreekumar M.C. Mittal 《Engineering Failure Analysis》2008,15(8):1042-1051
Austenitic stainless steel AISI 321 is used to fabricate plumbing lines to transfer cryogens from storage to output collector of propulsion system. Cracks were found in some of such tubes during one of the qualification tests of pipelines. The crack occurred at the bent region of the fuel feed pipeline along its neutral axis. Detailed metallographic investigations revealed presence of numerous longitudinal fine cracks on the inner surface of the tube that resulted from improper extrusion of the tube. Further, deformation induced martensitic transformation occurred, as the tube was bent at liquid nitrogen temperature. The transformed martensite, in presence of fine cracks on inner surface of the tube, due to improper extrusion, resulted in crack opening. This paper highlights the details of investigations carried out. 相似文献