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排序方式: 共有592条查询结果,搜索用时 15 毫秒
141.
Walaa Mahmoud Shehata Mohamed Fathy Mohamed Fatma Khalifa Gad 《Egyptian Journal of Petroleum》2018,27(4)
Petroleum refineries are now facing much tighter and stricter transportation and fuel specification standards, as well as environmental regulations, than in previous years. Therefore, tough rules have been applied on gasoline specifications. Octane number is a key variable of gasoline quality. Isomerization is one of many processes that generate profit by increasing low gasoline octane numbers, with better environmental impacts compared to other processes. Here we analyzed and optimized the various variables affecting the isomerate octane numbers produced by isomerization. Feed composition (naphthenes and benzene content in the feed) and operating conditions (temperature, hydrogen consumption and liquid hourly space velocity) data were collected from the Midor isomerization plant (Egypt) over a 4-year period based on the catalyst lifetime. These data were then used to predict the influence of feed composition and operating conditions on isomerate research octane number using a Response Surface Methodology (RSM) approach (Design Expert software). Thus, we were able to predict isomerate research octane number under various operating conditions. All of the studied variables were found to influence octane number. 相似文献
142.
In situ preparation of magnetic Fe3O4.Cu2O.Fe3O4/cryogel nanocomposite powder via a reduction–coprecipitation method as adsorbent for methylene blue water pollutant
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Ayman M Atta Hamad A Al‐Lohedan Ahmed M Tawfeek Mona A Ahmed 《Polymer International》2018,67(7):925-935
Magnetic nanocomposites have attracted great attention as adsorbents for the removal of water pollutants, which respond to an external magnet that is used to remove both pollutants and composite nanomaterial traces from water. They are environmentally friendly and effective adsorbents for water treatment. In this respect, a simple in situ preparation method was used to prepare cryogel powder composite based on Fe3O4.Cu2O.Fe3O4 nanomaterials. The ionic cryogel based on 2‐acrylamido‐2‐methylpropane sulfonate sodium salt and styrene sulfonate sodium salt was prepared by crosslinking polymerization at low temperature. The new magnetic nanoparticles based on Fe3O4.Cu2O.Fe3O4 were successfully prepared inside the cryogel networks by a simple reduction–coprecipitation method based on reaction of Fe3+ with sodium sulfite and Cu2+ in the presence of hydroxylamine and ammonia solution. The thermal stability, accurate Fe3O4.Cu2O.Fe3O4 content, magnetic properties, crystal lattice structure, particle sizes and morphology of the prepared cryogel composite were evaluated. The optimum conditions such as pH, contact time, adsorbate concentrations, adsorption equilibrium and adsorption kinetics were investigated to determine the efficiency of the prepared composite as an adsorbent to remove toxic methylene blue (MB) pollutant from aqueous solution. The data for MB adsorption confirmed the high ability of the prepared composite to remove more than 4.696 mmol L?1 of MB from water during 6 min. The regeneration and reuse experiments showed excellent data for the synthesized new dye as an effective adsorbent for water treatment. © 2018 Society of Chemical Industry 相似文献
143.
Khalifeh Ala’ F. Al-Taee Majid A. Murshed Ayman N. 《Multimedia Tools and Applications》2017,76(24):26129-26152
Multimedia Tools and Applications - Video streaming over Internet has been gaining momentum and several quality adaptation schemes have been reported to improve quality of the streamed videos. Most... 相似文献
144.
Ali Osman Ayman El Agha Dimitris P. Makris Panagiotis Kefalas 《Food and Bioprocess Technology》2012,5(1):243-251
Plant food residues including trimmings and peels might contain a range of enzymes capable of transforming bio-organic molecules,
and thus they may have potential uses in several biocatalytic processes, including green organic synthesis, modification of
food physicochemical properties, bioremediation, etc. Although the use of bacterial and fungal enzymes has gained interest
in studies pertaining to biocatalytic applications, plant enzymes have been given less attention or even disregarded. In this
view, this study aimed at investigating the use of a crude peroxidase (POD) preparation from onion solid by-products for oxidizing
chlorogenic acid (CGA), a widespread phenolic acid, various derivatives of which may occur in foods and food wastes. The highest
enzyme activity was observed at a pH value of 4, but considerable activity was also observed at pH 2. Favorable temperatures
for increased activity varied between 5 and 20 °C. Liquid chromatography–mass spectrometry analysis of a POD-treated CGA solution
showed the formation of two major oxidation products, which were tentatively identified as CGA dimers. 相似文献
145.
A new dynamic accumulation method for measuring the oxygen transmission rate (OTR) of packages and packaging films using robust and inexpensive fluorescence oxygen sensing technology has been developed. The method allows for oxygen to transfer through a given area of packaging or sample film and accumulate over time. The test volume incorporates a fluorescence‐based oxygen sensor that does not consume oxygen and therefore does not interfere with the real‐time measurement of oxygen concentration. The new method was tested against a widely used, commercially available instrument (Mocon Oxtran 2/20; Mocon, Inc., Minneapolis, MN, USA) designed around the steady‐state gas permeation measurement approach described by ASTM D3985. Sample films were chosen to provide comparison over several orders of magnitude of OTR. Specifically, sample films with OTR values in the range of 101, 103 and 104 ml O2/m2/day were measured, and results using the two methods were compared. Results showed that the new dynamic accumulation method provides comparable results with the steady‐state method (ASTM D3985). Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
146.
Hatem A. El-Batal Moenis A. Azooz Fathy M. Ezz-El-Din Nagia A. El-Alaily 《Journal of the American Ceramic Society》2001,84(9):2065-2072
The optical absorption spectra of nominally pure and rare-earth-ion-doped (Ho3+ or Er3+ ) calcium aluminoborate (cabal) glasses were measured from 190 to 900 nm before and after γ-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradiated glasses, exhibit the characteristic absorption bands caused by the respective rare-earth ions. The intensity of the induced bands depends on the rare-earth oxide content. The response of the cabal glass to γ-ray irradiation is related to the formation of color centers associated with the intrinsic defects in the lattice structure of the cabal glass. The rates of formation and annihilation of the color centers are believed to approach saturation or equilibrium with prolonged irradiation. 相似文献
147.
Hybrid Nanoparticle–Polymer Brush Composites for Detection of Low‐Level Radiostrontium in Water
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Valery N. Bliznyuk Ayman F. Seliman Scott M. Husson Yuri M. Lvov Timothy A. DeVol 《大分子材料与工程》2018,303(6)
Combining extraction and scintillation properties within the same material is a relatively new approach in development of sensors for detection of radioactive elements. Structural organization of such materials at a nanoscale typically offers higher efficiency of detection and shorter response time. In this contribution, several new protocols are discussed for fabrication of stable extractive scintillating systems based on commercial Superlig 620 (SL) material with high affinity to radiostrontium. Application of hybrid organic–inorganic beads with SL particles used as core and halloysite clay nanotubes (HNT) modified with a polyvinyltoluene (PVT) brush as a permeable shell combines high‐performance extracting properties of the SL material with efficient light emission properties of the polymer scintillator. The developed SL–HNT–PVT hybrid extractive scintillating material allows real‐time detection of low‐level concentrations of radiostrontium in water. Moreover, the suggested approach is not limited to detection of Sr but can find broader application in development of chemical, biological, or radioluminescent sensors and multifunctional materials. 相似文献
148.
The infrastructure of a country is a principal factor for its development, welfare and prosperity. Electricity is considered nowadays to be one of the most important components of a country's infrastructure and a key indicator of the standard of living of the population. 相似文献
149.
Oral Cenk Aktas Wolfgang Metzger Lisa Mees Marina Miro Martinez Ayman Haidar Martin Oberringer Gunther Wennemuth Norbert Pütz Muhammad Zubair Ghori Tim Pohlemann Michael Veith 《IET nanobiotechnology / IET》2019,13(6):621
The fibrotic encapsulation, which is mainly accompanied by an excessive proliferation of fibroblasts, is an undesired phenomenon after the implantation of various medical devices. Beside the surface chemistry, the topography plays also a major role in the fibroblast–surface interaction. In the present study, one‐dimensional aluminium oxide (1D Al2 O3) nanostructures with different distribution densities were prepared to reveal the response of human fibroblasts to the surface topography. The cell size, the cell number and the ability to form well‐defined actin fibres and focal adhesions were significantly impaired with increasing distribution density of the 1D Al2 O3 nanostructures on the substratum.Inspec keywords: biomechanics, adhesion, surface chemistry, biomedical materials, cellular biophysics, surface topography, nanostructured materials, alumina, nanomedicineOther keywords: fibrotic encapsulation, medical devices, surface chemistry, human fibroblasts, surface topography, cell size, cell number, well‐defined actin fibres, focal adhesions, distribution density, fibroblast adhesion, 1D nanostructures, distribution densities, fibroblast proliferation, fibroblast‐surface interaction, one‐dimensional aluminium oxide nanostructures, Al2 O3 相似文献
150.
Ayman M. Okeil Yilmaz Bingol Md. Rubiat Ferdous 《Canadian Metallurgical Quarterly》2009,13(6):547-557
The use of composite materials for strengthening the ailing infrastructure has been steadily gaining acceptance and market share. It can even be stated that this strengthening technique has become main stream in some applications such as strengthening concrete structures. The same cannot be said about steel structures; for which research on composite material strengthening is relatively new. Several challenges face strengthening steel structures using composite materials such as the need for high-modulus composites to improve the effectiveness of the strengthening system. This paper explores a new approach for strengthening steel structures by introducing additional stiffness to buckling-prone regions. The proposed technique relies on improving the out-of-plane stiffness of buckling-prone members by bonding pultruded fiber-reinforced polymer (FRP) sections as opposed to the commonly used approach that relies on in-plane FRP contribution. The paper presents results from an experimental investigation where shear-controlled beam specimens were tested to explore the feasibility of the proposed technique. Bar specimens were also tested in tension to compare between in-plane and out-of-plane contributions of FRP to the behavior and strength of thin steel plates. Based on the results, it can be concluded that this strengthening technique has great potential for altering failure modes by delaying the initiation of undesirable local buckling of thin steel plates. Recommendations for future research efforts are made to expand the knowledge base about this unexplored strengthening technique. 相似文献