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排序方式: 共有292条查询结果,搜索用时 15 毫秒
41.
Atallah Hany A. El Negm Yousef Mahmoud Mohamed Ahmed Abdel-Rahman Adel B. 《Wireless Personal Communications》2021,116(3):2083-2109
Wireless Personal Communications - The ceaseless increase in the number of the wireless Internet of Things (IoT) devices has resulted in the need of different traffic engineering techniques to... 相似文献
42.
Ehab Ellobody 《Journal of Constructional Steel Research》2007,63(2):145-155
This paper investigates the buckling behaviour of cold-formed high strength stainless steel stiffened and unstiffened slender square and rectangular hollow section columns. The high strength duplex material is austenitic-ferritic stainless steel approximately equivalent to EN 1.4462 and UNS S31803. The columns were compressed between fixed ends at different column lengths. A nonlinear finite element model has been developed to investigate the behaviour of stiffened slender square and rectangular hollow section columns. The column strengths, load-shortening curves as well as failure modes were predicted for the stiffened and unstiffened slender hollow section columns. An extensive parametric study was conducted to study the effects of cross-section geometries on the strength and behaviour of the stiffened and unstiffened columns. The investigation has shown that the high strength stainless steel stiffened slender hollow section columns offer a considerable increase in the column strength over that of the unstiffened slender hollow section columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the three specifications are generally conservative for the cold-formed stainless steel unstiffened slender square and rectangular hollow section columns, but slightly unconservative for the stiffened slender square and rectangular hollow section columns. 相似文献
43.
Texture evolution in 1050 commercial purity aluminum severely deformed by equal channel angular pressing (ECAP) is investigated by electron back scattered diffraction (EBSD). Pole figures and orientation distribution function (ODF) plots are generated for samples processed to 1, 2, 4, 8, 12 and 16 passes. The processing was done using route BC, in which the samples were rotated by 90° in the same sense between subsequent pressings. Two different sized scans were performed on the flow plane of the processed samples. The orientations constituting the favorably oriented fibers are depicted and crystal orientation maps are generated. The spatial distribution of grains having these orientations are revealed through these maps. The fraction of the main texture fibers for a 5° spread around the specified orientations is experimentally calculated and a quantitative idea on the evolution of texture is presented. The results ascertained that the texture intensity around the main fibers generally weakens with number of ECAP passes. 相似文献
44.
Ehab A. Ahmed Ehab F. El-Salakawy Brahim Benmokrane 《Canadian Metallurgical Quarterly》2008,12(6):596-607
This paper presents the results of an experimental study conducted on the pullout capacity of glass fiber reinforced polymer (GFRP) postinstalled adhesive anchors embedded in concrete. A total of 90 adhesive anchors were installed using sand-coated GFRP reinforcing bars and tested under monotonic tension loading in accordance with ASTM E-488-96 in 1996. The test parameters were: (1) the GFRP bar diameter (25.4, 15.9, and 6.4?mm); (2) the embedment depth (5, 10, and 15 db where db=bar diameter); (3) the adhesive type (epoxy-based and cement-based adhesives); and (4) installation conditions (wet or partially submerged and dry holes). The tested GFRP adhesive anchors were installed in concrete slabs measuring 3,750?mm long, 1,750?mm wide, and 400?mm deep. The test specimens were kept outdoors for 7?months to be subjected to real environmental conditions including freeze-thaw cycles, wet and dry cycles, and temperature variations. The experimental results indicated the adequate performance of GFRP adhesive anchors installed in wet or partially submerged condition using epoxy-based adhesive. Similar behavior was observed for those installed with cement-based adhesive in dry conditions as well. The capacity of the GFRP bars installed with both adhesive types was achieved at an embedment depth ranging from 10 to 15 db. 相似文献
45.
Peter Corkery Kayley E. Waltz Patrick M. Eckhert Mueed Ahmad Andrea Kraetz Yurun Miao Dennis T. Lee Mohammed K. Abdel-Rahman Yucheng Lan Paul Haghi-Ashtiani Aaron Stein J. Anibal Boscoboinik Michael Tsapatsis D. Howard Fairbrother 《Advanced functional materials》2024,34(12):2311149
Motivated by the drawbacks of solution phase processing, an all-dry resist formation process is presented that utilizes amorphous zinc-imidazolate (aZnMIm) films deposited by atomic/molecular layer deposition (ALD/MLD), patterned with electron beam lithography (EBL), and developed by novel low temperature (120 °C) gas phase etching using 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH) to achieve well-resolved 22 nm lines with a pitch of 30 nm. The effects of electron beam irradiation on the chemical structure and hfacH etch resistance of aZnMIm films are investigated, and it is found that electron irradiation degrades the 2-methylimidazolate ligands and transforms aZnMIm into a more dense material that is resistant to etching by hfacH and has a C:N:Zn ratio effectively identical to that of unmodified aZnMIm. These findings showcase the potential for aZnMIm films to function in a dry resist technology. Sensitivity, contrast, and critical dimensions of the patterns are determined to be 37 mC cm−2, 0.87, and 29 nm, respectively, for aZnMIm deposited on silicon substrates and patterned at 30 keV. This work introduces a new direction for solvent-free resist processing, offering the prospect of scalable, high-resolution patterning techniques for advanced semiconductor fabrication processes. 相似文献
46.
Abdel-Rahman El-Sayed Hossnia S. Mohran Hany M. Abd El-Lateef 《Journal of power sources》2011,196(15):6573-6582
The corrosion of zinc and Zn-0.5Ni alloy in strong alkaline solution (7 M KOH) in the absence and presence of [Fe(CN)6]3− complex anion (1 × 10−3-1 × 10−2 M) as inhibitor has been studied. Tafel plot, potentiodynamic, potentiostatic and electrochemical impedance spectroscopy (EIS) techniques were used, and complementary by EDX and SEM investigation. It is observed that, the corrosion current density (Icorr) decreases, and the inhibition efficiency (IE%) increases as the concentration of inhibitor is increased. The shift of breakdown potential to less positive direction, indicating that the reduction of oxide layer on the alloy surface occurs somewhat easier in the presence of [Fe(CN)6]3− complex anion. The impedance measurements have shown that the increase of the inhibitor concentration in the alkaline solution reduces the corrosion rate in the active region. Accordingly, addition of [Fe(CN)6]3− complex anion to KOH solution can be considered as an important criteria for a good battery anodes. This behavior is due to its high negative open-circuit potential, less corrosion rate and higher self-catalysis in the passive region compared with those in its absence. 相似文献
47.
Abdel-Rahman El-Sayed Hossnia S. Mohran Hany M. Abd El-Lateef 《Metallurgical and Materials Transactions A》2012,43(2):619-632
The article describes the use of Tafel plot and electrochemical impedance spectroscopy (EIS) techniques, in order to study
the corrosion process of pure zinc, nickel, and synthetic Zn-Ni alloys in various concentrations (0.25 to 1 M) of KOH solution
in a temperature range 298 K to 328 K (25 °C to 55 °C). The corrosion rate increases with increasing both concentration of
KOH and temperature for all investigated electrodes. The results showed that the increase in Ni content improves the corrosion
resistance and increases the barrier of activation energy, and the higher value of corrosion resistance is obtained at 10 pct Ni.
The electrochemical measurements using two mentioned techniques are in good agreement with the results of microhardness in
that the microhardness gradually increases with increasing Ni content in the alloy. Thus, the corrosion rate of these alloys
is significantly reduced compared with that of pure zinc. It is observed that the Warburg tail at low frequency completely
disappears at the applied potentials in the case of alloy IV (10 pct Ni) only. This indicates that the diffusion of Zn ion
species is strongly reduced. Therefore, addition of Ni to Zn has a beneficial effect, because it leads to lower loss of anode
material. The results obtained at certain positive potential (+420 mV vs SCE) exhibited that the semicircle diameter in the case of alloys is lower compared with that of pure zinc. This result means
that the values of the charge transfer resistance (R
ct
) in the case of alloys are decreased, due to the breakdown of the oxide layer at this potential. This behavior can be considered
as an important criterion for a good battery anode, due to reactivation of the alloy surface at certain positive potential
(+0.420 V vs SCE) and suppression of hydrogen gas compared with those of pure zinc. 相似文献
48.
Aiman E. Al-Rawajfeh Ehab M. Al-Shamaileh Khaldoon Al-Whoosh Ala’a Al-Ma’abrah Ramzi Al-Zorqan Rana Zanoon Khalid Rawajfeh Saleh Al-Jufout 《Journal of Industrial and Engineering Chemistry》2013,19(6):1895-1902
The release of chlorine in the electrodeionization (EDI) unit causes corrosion in the EDI unit, damaging ion exchange membranes and creating a safety risk for the workers. In this work, adsorption desalination of Cl? ions on low-cost composite synthetic–natural Jordanian materials were investigated as an approach to prevent the release of corrosive chlorine gas at the positive electrode. The percentage removal reaches 25% at 25 min shaking time to 55% at 120 min, in a single batch experiment. The values of ΔH0, ΔS0, and ΔG0 indicate the favorability of physisorption. Zeolite and Pozzolana represent potential adsorbents of chloride. 相似文献
49.
Abeer Dagher Hanadi G. Salem Tarek M. Moustafa Eman Bellah Mettawee Ehab Abdel-Rahman 《International Journal of Hydrogen Energy》2014
A first investigation into the production of amorphous and nanostructured Ti-based alloys with nominal compositions Ti41.5Zr41.5Ni17, Ti61Zr22Ni17, Ti41.5V41.5Ni17 and Ti61V22Ni17 by mechanical alloying (MA) technique is presented. This technique was adopted to produce alloys' powders with high fresh surface area that were active for hydrogen storage. Hydrogen absorption characteristics and structure changes in the alloys after hydrogenation were investigated. Gas phase hydrogenation of the Ti–Zr–Ni alloys, at 573 K and an initial hydrogen pressure of 2 MPa, exhibited good hydriding properties and started at a maximal rate without induction period with a hydrogenation capacity up to 1.2 wt%. However, hydriding of Ti–V–Ni alloys at the same conditions exhibited slower rates. The Ti61V22Ni17 composition showed high hydrogen absorption capacity of 1.8 wt% and exceeded 4 wt% at 345 K. In addition, the Ti–V–Ni alloys showed structure stability after hydrogenation and retained the amorphous structure. 相似文献
50.
Hesham H. Sokker Sayed M. Badawy Ehab M. Zayed Faten A. Nour Eldien Ahmad M. Farag 《Journal of hazardous materials》2009
Ion exchange adsorbents based on cellulosic fabric wastes carrying sulfonic acid and amine functional groups were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) with subsequent chemical modification of the epoxy groups of poly-GMA graft chains with sodium sulfite/H2SO4 and triethylamine, respectively. The conversion of epoxy groups into the functional groups was investigated. Factors affecting on grafting process such as radiation dose, monomer concentration and solvent were studied. The synthesized adsorbent and its applications in the removal of different types of hazardous pollutants e.g. acidic dye, cobalt, dichromate and phenols from aqueous solution were also studied. 相似文献