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排序方式: 共有1078条查询结果,搜索用时 15 毫秒
81.
Magdy El-Hagary Said H. Moustafa Hany Hashem Essam R. Shaaban Mohamed Emam-Ismail 《Journal of the American Ceramic Society》2019,102(8):4737-4747
Mn-doped HgO nanostructured thin films (Hg1-xMnxO) have been prepared using electron beam evaporation technique on Corning glass (1022) substrate at room temperature with different concentrations x = 0, 0.015, 0.05, 0.1, 0.15, and 0.2. The microstructural, morphological, semiconducting, and optoelectronic properties of the films have been investigated. The X-ray diffraction spectra suggest a hexagonal wurtzite type structure with lattice parameters decreased with increasing Mn content. It was found that the average particle size of the films decreases with increasing Mn doping which is confirmed by FE-SEM and AFM micrographs. The optical band gap of the investigated Mn-doped HgO nanocrystalline films is determined from the absorption coefficient and found to increase with the increase of Mn concentration which is attributed to the sp-d exchange interaction and/or the quantum confinement effect. The refractive index and extinction coefficient of the Mn-doped HgO films are also reported. The refractive index dispersion n(λ) is analyzed by single-effective-oscillator dispersion model proposed by the Wemple–DiDomenico (WDD). The oscillator parameters were estimated. The obtained dispersion values are suitable for the design of optoelectronic devices. 相似文献
82.
Saad Ahmed Muhammad Ali Yangben Cai Yunhua Lu Zaheer Ahmad Santosh Khannal Shiai Xu 《应用聚合物科学杂志》2019,136(22):47603
In the present study, multi-walled carbon nanotubes (MWCNTs) were sulfonated by 1,3-propane sultone and distillation–precipitation polymerization, respectively, and then incorporated into chitosan (CS) to prepare CS/MWCNTs composite membranes for fuel cell applications. CS/MWCNTs membranes show better thermal and mechanical stability than pure CS membrane due to the strong electrostatic interaction between the SO3H groups of MWCNTs and the NH2 groups of CS, which can restrict the mobility of CS chain. The sulfonated MWCNTs provide efficient proton hopping sites ( SO3H, SO3− …. 3+HN ), thereby resulting in the formation of continuous proton conducting channels. The composite membranes with 5 wt % of MWCNTs modified by two different ways show a proton conductivity of 0.026 and 0.025 S·cm−1, respectively. In conclusion, CS/MWCNTs membrane is a promising proton exchange membrane for fuel-cell applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47603. 相似文献
83.
Selma Ben Saad Caroline Gentric Jean-François Fourmigué Patrice Clément Jean-Pierre Leclerc 《Chemical Engineering Research and Design》2014
High performance of compact heat exchangers is conditioned by correct fluid distribution. This is especially true for gas–liquid heat exchangers where a uniform distribution is particularly delicate to obtain and where maldistribution entails significant performance deterioration. Several phenomena can lead to phase distribution problems: the fins may be subject to manufacturing defects or fouling, leading to shortcuts or dead zones. But the first source of maldistribution may be a poor distribution at the outlet of the entrance distributor. This distributor aims at mixing the phases and distributing them across the channels. 相似文献
84.
Mustafa S. Nasser Mohammed J. Al-Marri Abdelbaki Benamor Sagheer A. Onaizi Majeda Khraisheh Mohammed A. Saad 《Korean Journal of Chemical Engineering》2016,33(2):448-455
The effects of the surface charge type and density C496, C492 and A130LMW polyacrylamides (PAMs) on the rheological behavior of real industrial papermaking suspensions were quantitatively related to the degree of flocculation for the same industrial papermaking suspensions. The floc sizes were larger but less dense when anionic PAM was used, and this due to the repulsive forces between the anionic PAM and colloidal particles, leading to the development of open structure flocs of less density. On the other hand, rheological measurements showed that the papermaking suspension is thixotropic with a measurable yield stress. The results showed that the magnitude of the critical stress, τ c , complex viscosity, η*, elastic modulus, G′, and viscous modulus, G″, depend on the number of interactions between the PAM chains and particle surface and the strength of those interactions. Cationic PAM showed higher values of η*, G′, G″ and τ c compared to anionic PAM. This behavior is in good agreement with Bingham yield stress, τ B , adsorption and effective floc density results. Similar to oscillatory measurements, creep measurements also showed that the deformation was much lower for the cationic PAM based suspensions than for the anionic PAM based suspensions. Furthermore, the results revealed that increasing the cationic PAM surface charge decreases the floc size but increases the adsorption rate, elasticity and effective floc density proposing differences in the floc structures, which are not revealed clearly in the Bingham yield stress measurements. 相似文献
85.
D. Fink A. Chandra W.R. Fahrner K. Hoppe H. Winkelmann A. Saad P. Alegaonkar A. Berdinsky D. Grasser R. Lorenz 《Vacuum》2008,82(9):900-905
In the past years, fundaments were set for a new type of electronics which is based on tracks in insulators formed by individual or multiple swift heavy ions. Due to the possibility of inserting any (semi)conducting material into these tracks, various active and passive electronic devices can be created. Among them are also transistor-like and Esaki diode-like elements. As many of these structures have sensing properties and the capability to undergo logic decisions, autonomous intelligent sensors appear to be a favourite field for future application. The use of liquid conductors may even expand the range of applicability towards medical implants. 相似文献
86.
Khalid Al‐Osaimi Abdulmohsen Alheraish Saad Haj Bakry 《International Journal of Network Management》2008,18(1):65-75
The STOPE‐based approach is used here for practical e‐readiness assessment case studies. The approach integrates and evaluates the various e‐readiness assessment issues, over its well‐structured domains: strategy, technology, organization, people, and environment. The case studies considered concern three Saudi organizations: a government organization, a bank, and a private sector company. The results obtained provide e‐readiness indicators that illustrate the strengths and weaknesses of each organization with regard to e‐readiness strategic development issues, information and communication technology (ICT) issues, management and organization issues, people issues, and environment issues within which the organization operates. The work shows how the approach can be practically used, and it also provides practical results that direct the organizations concerned toward enhancing their e‐readiness in response to the current trend of globalizing e‐business. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
87.
Probiotic potential and sensory properties of coconut flan supplemented with Lactobacillus paracasei and Bifidobacterium lactis 总被引:1,自引:1,他引:0
Sabrina B. M. Corrêa Inar A. Castro & Susana M. I. Saad 《International Journal of Food Science & Technology》2008,43(9):1560-1568
The effect of probiotic cultures on sensory performance of coconut flan during storage at 5 °C and the viability of these micro organisms for up to 28 days were investigated. Sensory analyses of the product were performed after 7, 14 and 21 days of storage. Coconut flans were produced with no addition of cultures (T1, control), or supplemented with Bifidobacterium lactis (T2), Lactobacillus paracasei (T3) and B. lactis + L. paracasei (T4). Populations of L. paracasei and B. lactis as single or in co-culture remained above 7 log CFU g−1 during the entire storage period. Viability of L. paracasei was higher for T3. All products were well accepted and no significant differences ( P > 0.05) were detected between the coconut flans studied. The addition of L. paracasei and B. lactis to coconut flan resulted in its having great potential as a functional food, which has high sensory acceptability. 相似文献
88.
Siddiqui MR Alshehri S Warad IKh Abd El-Salam NM Mahfouz RM 《International journal of molecular sciences》2010,11(9):3600-3609
Kinetic studies for the non-isothermal decomposition of unirradiated and γ-irradiated silver acetate with 10(3) kGy total γ-ray doses were carried out in air. The results showed that the decomposition proceeds in one major step in the temperature range of (180-270 °C) with the formation of Ag(2)O as solid residue. The non-isothermal data for un-irradiated and γ-irradiated silver acetate were analyzed using Flynn-Wall-Ozawa (FWO) and nonlinear Vyazovkin (VYZ) iso-conversional methods. These free models on the investigated data showed a systematic dependence of Ea on α indicating a simple decomposition process. No significant changes in the thermal decomposition behavior of silver acetate were recorded as a result of γ-irradiation. Calcinations of γ-irradiated silver acetate (CH(3)COOAg) at 200 °C for 2 hours only led to the formation of pure Ag(2)O mono-dispersed nanoparticles. X-ray diffraction, FTIR and SEM techniques were employed for characterization of the synthesized nanoparticles. 相似文献
89.
Tina Tin Benjamin K. Sovacool David Blake Peter Magill Saad El Naggar Sven Lidstrom Kenji Ishizawa Johan Berte 《Renewable Energy》2010,35(8):1715-1723
This article showcases a range of small and large scale energy efficiency and renewable energy deployments at Antarctic research stations and field camps. Due to the cold and harsh environment, significant amounts of fuel are needed to support humans working and living in Antarctica. The purchase, transportation and storage of large amounts of fossil fuel entail significant economic costs and environmental risks and have motivated developments in energy efficiency and renewable energy deployment. Over the past three decades, improved building design, behavioral change, cogeneration, solar collectors, solar panels and wind turbines have been found to be effective in Antarctica, demonstrating that harsh environmental conditions and technological barriers do not have to limit the deployment of energy efficiency and renewable energy. The ambition to run entire stations or field camps on 100% renewable energy is increasingly common and feasible. While the power requirements of Antarctic research stations are small compared to urban installations on other continents, these case studies clearly demonstrate that if energy efficiency and renewable energy can be deployed widely on the coldest, darkest and most remote continent of the world, their deployment should be more widespread and encouraged on other continents. 相似文献
90.
M. H. Moh Y. B. Che Man B. S. Badlishah S. Jinap M. S. Saad W. J. W. Abdullah 《Journal of the American Oil Chemists' Society》1999,76(2):249-254
β-Carotene content is usually determined by using ultraviolet (UV)-visible spectrophotometry at 446 nm. In this study, two
spectroscopic techniques, namely, Fourier transform infrared (FTIR) and near infrared (NIR) spectroscopy, have been investigated
and compared to UV-visible spectrophotometry to measure the β-carotene content of crude palm oil (CPO). Calibration curves
ranging from 200 to 800 ppm were prepared by extracting β-carotene from original CPO using open-column chromatography. Separate
partial least squares calibration models were developed for predicting β-carotene based on the spectral region from 976 to
926 cm−1 for FTIR spectroscopy and 546 to 819 nm for NIR spectroscopy. The correlation coefficient (R
2) and standard error of calibration obtained were 0.972 and 25.2 for FTIR and 0.952 and 23.6 for NIR techniques, respectively.
The validation set gave R
2 of 0.951 with standard error of performance (SEP) of 25.78 for FTIR technique and R
2 of 0.979 with SEP of 19.96 for NIR technique. The overall reproducibility and accuracy did not give comparable results to
that of spectrophotometric method; however, the standard deviation of prediction was still within ±5% β-carotene content over
the range tested. Because of their rapidness and simplicity, both FTIR and NIR techniques provide alternative means of measuring
β-carotene content in CPO. In addition, these two spectroscopic techniques are environmentally friendly since no solvent is
involved. 相似文献