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11.
N. Nada 《Desalination》1982,41(1):57-69
In Saudi Arabia, the largest producer of water by MSF (500 mgd),for scale control 28% of the units use acid and 60% use additive. It is critical to study and modify operating paremeters affecting corrosion since life-time can be reduced to 1/3 or 1/4 if not cared for.External aeration should be used with <20 ppb dissolved oxygen in the deaerator effluent for an acid treated unit. Low CO2 in the decarbonator effluent is recommended to reduce corrosion in the Cu-Ni alloy and unit internals. 相似文献
12.
F. Abd El-Salam L. A. Wahab R. H. Nada H. Y. Zahran 《Journal of Materials Science》2007,42(10):3661-3669
The hardness of Al–5wt%Zn (alloy A) and Al–5wt%Zn–0.25wt%In (alloy B) was measured at room temperature for samples heat treated
in the range 300–453 K and dwell times in the range 30–300 s under 50 gm load. Softening was observed for all the samples
and the hardness decreased with increasing temperature and/or dwell time. Hardness drop was larger for alloy (B), which in
general showed higher hardness than alloy (A). The stress exponent n increased with increasing temperature and showed high values falling in the power law breakdown region. The parameters deduced
from the analysis of X-rays data and micrographs were found to be consistant with the calculated mechanical data. 相似文献
13.
LaBO3 (B = Ni, Co, Fe and Mn) were prepared by microwave-assisted citrate method. The electrocatalytic activity toward hydrogen evolution reaction (HER) was investigated. XRD characterization showed that pure perovskite crystals were indeed formed. SEM images showed that changing the type of the B-site metal ion affected the morphology of the prepared perovskites. The influence of the type of B-cation on the catalytic activity toward hydrogen evolution was studied and the order of the electrocatalytic activity was LaFeO3 > LaCoO3 > LaNiO3 > LaMnO3, that was related to the calculated values of the activation energy 51.61, 45.37, 41.15 and 55.05 kJ mol−1 for LaBO3 (B = Ni, Co, Fe and Mn), respectively. The reaction order and the reaction mechanism for all the prepared perovskites were identified. In addition, the effect of the partial substitution at the B-site in LaNi1 − xCoxO3 was also studied. It was found that among ternary perovskites, the catalytic activity of LaNiO3 decreased by increasing the fraction of doped-Co. 相似文献
14.
Granules containing indomethacin crystals are coated with Eudragit solutions of different RL/RS ratios using a pan coating technique. The process is reproducible with regard to drug content, inexpensive and the formed granules were directly compressed into tablets. In vitro release of indomethacin from coated granules, tablets and capsules was studied as a function of different ratios of Eudragit RL/RS in the coating solution. The release of the drug was significantly reduced by the coating process in comparison with a formulation made from uncoated granules, prepared using 10 per cent gelatin solution as a binder. Release data were found to follow a diffusion-controlled model. 相似文献
15.
Next-generation wireless networks should be able to coordinate and integrate different communication systems. It has been a challenging problem to support a seamless handover in these diverse wireless network environments. Link level triggers can provide information about events which can help handover decision and layer 3 entities better streamline their handover related activities. In most conventional layer 2 triggering approaches, a pre-defined threshold for a specific perspective such as the received signal strength is used. This may cause too late or too early handover executions. In this paper we propose a new predictive handover framework that uses the neighbor network information to generate timely the link triggers so that the required handover procedures can appropriately finish before the current link goes down. First we estimate a required handover time for the given neighbor network conditions, then using a predictive link triggering mechanism the handover start time is dynamically determined to minimize handover costs. The handover costs are analyzed in terms of the total required handover time and the service disruption time. The numerical analysis and simulation results show that the proposed method significantly enhances the handover performance in heterogeneous wireless networks. 相似文献
16.
Martini Maria G. Istepanian Robert S. H. Mazzotti Matteo Philip Nada 《Mobile Computing, IEEE Transactions on》2010,9(1):5-16
M-health is an emerging area of research and one of the key challenges in future research in this area is medical video streaming over wireless channels. Contrasting requirements of almost lossless compression and low available bandwidth have to be tackled in medical quality video streaming in ultrasound and radiology applications. On one side, compression techniques need to be conservative, in order to avoid removing perceptively important information; on the other side, error resilience and correction should be provided, with the constraint of a limited bandwidth. A quality-driven, network-aware approach for joint source and channel coding based on a controller structure specifically designed for enhanced video streaming in a robotic teleultrasonography system is presented. The designed application based on robotic teleultrasonography is described and the proposed method is simulated in a wireless environment in two different scenarios; the video quality improvement achievable through the proposed scheme in such an application is remarkable, resulting in a peak signal-to-noise ratio (PSNR) improvement of more than 4 dB in both scenarios. 相似文献
17.
18.
Ahmed Galal Nada F. Atta Soher A. Darwish Ahmed Abdel Fatah Shimaa M. Ali 《Journal of power sources》2010,195(12):3806-3809
SrPdO3 was prepared for the first time by the citrate method. XRD, SEM and TGA characterizations were carried out. The catalytic activity toward hydrogen evolution reaction (HER) was investigated, the activation energy, and reaction order and reaction mechanism have been determined using Tafel polarization and impedance techniques. The modified surface showed up to 100 times more efficiency towards electrocatalytic production of hydrogen. Adsorption of hydrogen on the catalyst was the rate-determining step and the reaction order at the surface of the catalyst is 0.86. The molar magnetic susceptibility was measured using Faraday's method and anti-ferromagnetic character was observed. 相似文献
19.
20.
Preciptated solid materials (PSM) from waste black liquor (WBL), at pH 8·5–9·0, produced from cooking of rice straw in paper
mill factories were thermally treated. The cooking process led to decrease in organic material and partial substitution in
silica structure. During this cooking process, three probable stages of mass loss comprise removal of moisture, volatile release,
and combustion.
The chemical analysis depicts the cooking effect on leaching either the high percentage elements (Ca, Na, and K) or some metallic
cations (Mn, Cd, Zn and Cu) in the parent rice straw. Silica hydrate, amorphous silica and crystalline silica were obtained
at <600°C, 600–700°C and at>800°C, respectively. The infrared spectra show gradual removal of the hydrocarbon bond (C–H),
molecular H2O, and sianol group (Si-OH) with temperature. TG, DTA, XRD and SEM were used in this study. 相似文献