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排序方式: 共有477条查询结果,搜索用时 15 毫秒
1.
Maher M. Osman Mounir M. Abd El-Malek Aida B. Tadros Atef M. Michael 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):46-52
4-Amino-3-thio-1,24-triazolidine (L1) and 4-amino-5-thio-1,3,4-thiadiazole (LII) as well as their metal complexes of the general formulae MLI·2H2O and MLIICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(LI)2·2H2O and SnLIICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae. 相似文献
2.
Mahmoud M. Abou el Leil Frank A. Camaratta Rocco R. DiGenova 《Journal of the American Ceramic Society》1985,68(1):18-C-
In-service fracture of helicopter windshields was studied. Simulated catastrophic fracture tests were conducted by firing alumina and steel spheres onto stationary tempered and as-received glass panels. The results were studied by Hertzian analysis and modified Auerbach's relations. Thermally tempered glass shows much higher impact resistance than that estimated from superposition of residual stresses. Subcritical impact sites exhibit slow crack growth in tempered plates, eventually leading to fracture of the entire plate. 相似文献
3.
Abd El-Shafy A. Nafeh Faten H. Fahmy Essam M. Abou El-Zahab 《Solar Energy Materials & Solar Cells》2003,75(3-4):723-728
In this paper the implementation of a suggested stand-alone PV system, for maximum-power point tracking (MPPT), is carried out. Also, this paper presents a comparative study, through experimental work, between the conventional PI controller and the fuzzy logic controller (FLC) under different atmospheric conditions. The implemented system with both the PI controller and the FLC gives a good maximum-power operation of the PV array, but the tracking capability for different optimum operating points is better and faster for the case of using the FLC compared to the case of using the PI controller. 相似文献
4.
Lasserre S Hernando J Hill S Schümann F Anasagasti Pde M Jaoudé GA Markram H 《IEEE transactions on visualization and computer graphics》2012,18(2):214-227
We present a process to automatically generate three-dimensional mesh representations of the complex, arborized cell membrane surface of cortical neurons (the principal information processing cells of the brain) from nonuniform morphological measurements. Starting from manually sampled morphological points (3D points and diameters) from neurons in a brain slice preparation, we construct a polygonal mesh representation that realistically represents the continuous membrane surface, closely matching the original experimental data. A mapping between the original morphological points and the newly generated mesh enables simulations of electrophysiolgical activity to be visualized on this new membrane representation. We compare the new mesh representation with the state of the art and present a series of use cases and applications of this technique to visualize simulations of single neurons and networks of multiple neurons. 相似文献
5.
El Nahrawy Amany M. Hemdan Bahaa A. Abou Hammad Ali B. Othman Abdelmageed M. Abouelnaga Amal M. Mansour A. M. 《SILICON》2021,13(9):2979-2991
Silicon - Magnesium calcium silicate nanostructures (MCSNS) loaded with (0.0, 0.6, 0.9, and 1.2 wt%) of Cephradine-drug consisting of mesoporous particles were functionally prepared by sol-gel... 相似文献
6.
A. Daoud M. T. Abou El-Khair A. N. Abdel-Azim 《Journal of Materials Engineering and Performance》2004,13(2):135-143
Aluminum (Al) alloy 7075 reinforced with Al2O3 particles was prepared using the stir casting method. The microstructure of the cast composites showed some degree of porosity
and sites of Al2O3 particle clustering, especially at high-volume fractions of Al2O3 particles. Different squeeze pressures (25 and 50 MPa) were applied to the cast composite during solidification to reduce
porosity and particle clusters. Microstructure examinations of the squeeze cast composites showed remarkable grain refining
compared with that of the matrix alloy. As the volume fraction of particles and applied squeeze pressure increased, the hardness
linearly increased. This increase was related to the modified structure and the decrease in the porosity. The effect of particle
volume fraction and squeeze pressure on the dry-sliding wear of the composites was studied. Experiments were performed at
10, 30, and 50 N with a sliding speed of 1 m/s using a pin-on-ring apparatus. Increasing the particle volume fraction and
squeeze pressure improved the wear resistance of the composite compared with that of the monolithic alloy, because the Al2O3 particles acted as load-bearing constituents. Also, these results can be attributed to the fact that the application of squeeze
pressure during solidification led to a reduction in the porosity, and an increase in the solidification rate, leading to
a finer structure. Moreover, the application of squeeze pressure improved the interface strength between the matrix and Al2O3 particles by elimination of the porosity at the interface, thereby providing better mechanical locking. 相似文献
7.
Atef Eldenfria 《International journal of human-computer interaction》2013,29(20):1960-1974
ABSTRACTIndividual preferences for learning environments can be linked to a specific behavior. The tendency of such behavior can somehow be associated with an individual’s ability to cognitively engage in the learning process without being distracted by other stimuli. An online continuous adaptation mechanism (OCAM) of learning contents was developed in order to regulate the presentation of learning contents based on changes in the learner’s aptitude level. This was claimed to stimulate a better cognitive and emotional response among learners, thus stimulating their engagement. A total of 41 students (36 male and 5 female; age 20–25 years) participated in this study. The results revealed that learners’ levels of concentration and cognitive load were positively influenced by the OCAM, which significantly increased their engagement. Our findings can be used to inform designers and developers of online learning systems about the importance of regulating the presentation of learning contents according to the aptitude level of individual learners. The proposed OCAM can improve learners’ ability to process specific information meaningfully and make the inferences necessary for understanding the learning content. 相似文献
8.
Muhammad Saeed Ji-Yang Yu Aniseh Ahmed Atef Abdalla Xian-Ping Zhong Mahmood Ahmad Ghazanfar 《核技术(英文版)》2017,28(10)
This paper presents the gas distribution analysis by injecting air fountain into the containment and simulations with the HYDRAGON code. Turbulence models of standard k-ε(SKE), re-normalization group k-ε(RNG) and a realizable k-ε(RLZ) are used to assess the effects on the gas distribution analysis during a severe accident in a nuclear power plant. By comparing with experimental data,the simulation results of the RNG and SKE turbulence models agree well with the experimental data on the prediction of dimensionless density distributions. The results illustrate that the turbulence model choice had a small effect on the simulation results, particularly the region near to the air fountain source. 相似文献
9.
Complex structural contribution of the morphotropic phase boundary in Na0.5Bi0.5TiO3 - CaTiO3 system
Roy Roukos Sara Abou Dargham Jimmy Romanos Fatima Barakat Denis Chaumont 《Ceramics International》2019,45(4):4467-4473
The correlation between structure and dielectric properties of lead-free (1-x)Na0.5Bi0.5TiO3 - xCaTiO3 ((1-x)NBT - xCT) polycrystalline ceramics was investigated systematically by X-ray diffraction, combined with impedance spectroscopy for dielectric characterizations. The system shows high miscibility in the entire composition range. A morphotropic phase boundary (MPB), at 0.09?≤?x?<?0.15 was identified where rhombohedral and orthorhombic symmetries coexist at room temperature. The fraction of orthorhombic phase increases gradually with x in the MPB region. Dielectric measurements reveal that the relative permittivity increase with addition of Ca2+. This behavior is unusual with this kind of doping. A thermal hysteresis occurred only in the MPB composition which varies in a non-monotonically manner with x, detected by dielectric properties. This phenomenon is related to the crystalline microstructure by a linear relationship between the fraction of each phase and dielectric properties, and, more precisely, to the strong interaction between rhombohedral and orthorhombic phases. 相似文献
10.