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排序方式: 共有551条查询结果,搜索用时 31 毫秒
31.
The dissolution of kaolinite clay in hydrochloric acid solutions has been carried out in the presence of fluoride ions. Leaching in the presence of fluoride ions activates the clay for leaching, making higher extractions possible at lower roasting and leaching temperatures. The activation energy for the leaching of clay calcined at 540°C is decreased from 71 kJ/mol to 23 kJ/mol in the presence of fluoride ions. Dissolution in the presence of fluoride appears to fit a second-order reaction mechanism. 相似文献
32.
Five malonanilide derivatives (M1-M5) were prepared by the reaction of ethyl malonate with aniline derivatives. These compounds were investigated as new stabilizers for double-base propellants (DBPs). The evaluation process has been performed through thermal stability tests, thermal analyses measurements (TGA and DSC) and kinetic parameters calculations (E(a)). The results of the new stabilizers were compared with the results of the classical stabilizer N, N-diethyldiphenyl urea. It has been found that o- and p-dinitromalonanilides, in particular, showed better stability effect for DBPs than the classical one. 相似文献
33.
Soliman A. Mahmoud 《Analog Integrated Circuits and Signal Processing》2007,50(3):195-203
This paper presents a new CMOS fully differential second-generation current conveyor (FDCCII). The proposed FDCCII is based
on a fully differential difference transconductor as an input stage and two class AB output stages. Besides the proposed FDCCII
circuit is operating at supply voltages of ±1.5 V, it has a total standby current of 380 μA. The application of the FDCCII
to realize variable gain amplifier, fully differential integrator, and fully differential second order bandpass filter are
given. The proposed FDCII and its applications are simulated using CMOS 0.35 μm technology. 相似文献
34.
Rasha Mohamed Soliman Medhat Awad El-Hadek Shaban Ibrahim Abdu 《International Journal of Mechanics and Materials in Design》2010,6(4):359-365
Detailed micro electronic and mechanical systems (MEMS) for a mobile microprocessor complex shape were modeled using Finite
Element (FE) processing. Fatigue and impact conditions were performed on the Ball Grid Array (BGA) Integrated Circuit (IC)
using Abaqus\CAE finite element analysis software. The main objective of this research is to make sure that BGA products can
endure the roughness of the daily usage, where a portable electronic product is habitually coupled with potential damage of
functional failure when the device falls. 相似文献
35.
K.A. Soliman 《Electrochimica acta》2007,52(18):5654-5658
The potential of zero charge (PZC) of a pseudomorphic silver monolayer electrodeposited onto Au(1 1 1), Pt(1 1 1), Pd(1 1 1), Ir(1 1 1) and Rh(1 1 1) has been determined in diluted perchlorate solution by measuring capacitance-potential curves. The PZC of these Ag overlayers varies in the potential range between −0.8 V and −0.45 V versus SCE depending on the nature of the substrate material and thus reveals significant shifts compared to −0.7 V versus SCE for a massive Ag(1 1 1) electrode. This bulk value for the PZC has also been obtained for two monolayer thick Ag overlayers, demonstrating that mainly the first monolayers are electronically altered by an underlying foreign substrate. In addition, the PZC of thicker deposits has always been found to be identical to the PZC of Ag(1 1 1), showing an epitaxial growth of Ag on the electrodes under study. While no dependence on the lattice constants of the substrates for the PZC of the pseudomorphic Ag monolayers was found, it has been observed that calculated shifts in the d-band centre show the same systematic variation. Work function data for Ag monolayers on Au(1 1 1) and Pt(1 1 1) are in good agreement with the measured PZC values. Consequences of altered double-layer properties on electrocatalytic reactions are briefly addressed. 相似文献
36.
A novel low distortion CMOS linearized transconductor circuit is developed for analogue signal processing. The circuit gives a very low distortion level and a wide linearity range when compared with other reported topologies. Simulation results based on using the 0.5 µm CMOS process show that this approach gives an exceptional linearity and an excellent performance. 相似文献
37.
Influence of 8-hydroxyquinoline addition on the corrosion behavior of commercial Al and Al-HO411 alloys in NaOH aqueous media 总被引:1,自引:0,他引:1
H.N. Soliman 《Corrosion Science》2011,(9):2994-3006
The effect of 8-hydroxyquinoline (8HQ) on the corrosion inhibition of commercial Al and Al-HO411 alloys has been investigated in NaOH solutions. Results showed that the inhibition efficiency was increased with increasing concentration of 8HQ. Al-HO411 alloy exhibited higher corrosion resistance and inhibition efficiency than the commercial Al. Examination of both samples was studied by means of optical microscope as well as energy-dispersive X-ray spectrometer. The crystallographic structure of both samples was analyzed by means of X-ray diffractometry. It was observed that protective films are formed on the surfaces that play an essential role in the corrosion inhibition of the alloys under investigation. 相似文献
38.
Xavier Chaud Tatiana Prikhna Yaroslav Savchuk Anne Joulain Evert Haanappel Pavel Diko Laureline Porcar Mahmoud Soliman 《Materials Science and Engineering: B》2008,151(1):53
Oxygen high pressure (up to 16 MPa) has been introduced in the oxygen-annealing step necessary to make the YBa2Cu3Ox phase superconducting (change x from 6 to about 7). It enables a displacement in the equilibrium phase diagram towards higher temperatures, which means the possibility to achieve the same final oxygen content as the one at low temperature, but with the benefit of higher diffusion rates. Initial development made on thin bars (1.5–3 mm thick) has confirmed the interest of using a high pressure of oxygen. TEM observations have shown an increase of twin density associated with higher Jc. This is in agreement with other works claiming the possibility of higher Jc by twin engineering, and more precisely by twin refinement while annealing at high temperature. We report the successful application of this process without any adjustment to so-called thin-wall single-domain samples. These samples are obtained by growing a crystal on a pellet already shaped with an array of holes. The advantage is that, as far as diffusion processes are concerned, the typical length is not anymore the diameter of the sample, but the thickness of the walls between holes. The trapped field of 16 mm diameter Y123 thin-wall single-domain samples was doubled (0.6 T vs. 0.3 T at 77 K) in a rather short annealing time (about 3 days). Microstructures as well as magneto-optical observations of plain and thin-wall samples evidenced a reduction of cracks in the thin-wall samples. Improved performances were confirmed by further characterizations performed from 77 down to 20 K using the pulse-field facilities of the LNCMP at Toulouse. 相似文献
39.
Polyaniline (PANI) has been blended with cellulose triacetate (CTA) to obtain both good mechanical properties and good electrical
properties. The effects of PANI weight percentage on the optical, structural, morphological and electrical properties in the
blend films of polyaniline and cellulose triacetate (PANI/CTA) have been investigated. The phenomenon of percolation was observed
in these blend films. It is found that the electrical conductivity of the blend films increases with the increase of polyaniline
content up to a value of 10−4 S cm−1 at 84 weight percentage of PANI. The experimental percolation threshold of the dried blend films is obtained at 9.5 wt% of
polyaniline. The values of Mott’s temperature, density of states at the Fermi level [N (E
f)], hopping distance (R
hop), and barrier height (W
hop) for PANI/CTA blend films are calculated. By applying Mott’s theory, it is found that the PANI/CTA blend films obey the three
dimensional variable range hopping mechanism. 相似文献
40.
Beef tallow and cottonseed oil were mixed with a pure butterfat in the ratios of 2%, 4% and 6% to obtain admixtures of beef
tallow with butterfat and cottonseed oil with butterfat. The hydrolysis of individual triglycerides was carried out using
the lipase to obtain 2-monoglycerides. The results indicated that butterfat had a higher percentage of C14:0 and C16:0 acids
than found in the triglycerides and 2-monoglycerides of beef tallow and cottonseed oil.
Beef tallow contained a higher proportion of C18:0 and C18:1 acids than butterfat and cottonseed oil triglycerides or 2-monoglycerides.
Cottonseed oil had a higher percentage of C18:2 acid located in triglyceride or 2-monoglyceride than found in butterfat or
beef tallow triglycerides and 2-monoglycerides.
The analysis of the samples of butterfat containing 2%, 4% and 6% beef tallow revealed that the addition of beef tallow to
butterfat affected the fatty acid composition of butterfat triglycerides and 2-monoglycerides with C18:0 and C18:1 acids;
the effect was increased with increasing percentages of beef tallow.
The addition of cottonseed oil to butterfat in the ratios of 2%, 4% and 6% affected the fatty acid composition of butterfat
triglycerides and 2-monoglycerides. It was found that both C18:1 and C18:2 increased as the added cottonseed oil percentages
increased. 相似文献