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71.
Hydroconversion of n-hexane was studied on catalysts containing 0.25% Pt supported on H-mordenite (H-M) and NH4-M. The H-M containing catalysts were Pt/H-M, Pt on steamed H-M (Pt/St H-M) and steamed Pt/H-M (StPt/H-M), whereas the NH4-M containing catalysts were Pt/NH4-M and StPt/NH4-M. Steam-treatment of H-M containing catalysts enhanced the hydroconversion activity, whereas such treatment decreased the activity of the Pt/NH4-M catalyst. The diffusion resistance parameter, i.e., the Thiele modulus, ΦL, estimated for the reaction on the catalysts under study was found to increase with the increase in the catalytic activity, and both were found to decrease in the order:Pt dispersion in the zeolite was not comparable with the catalytic activities of the H-M containing catalysts. The higher activity of the Pt/NH4-M catalyst could be attributed to a higher Pt dispersion in the zeolitic channels, higher strength of the acid sites (determined by temperature programmed desorption (TPD) of ammonia) and higher diffusion limitation of the reactant in the catalyst pores. 相似文献
72.
MA Ghoneim 《Canadian Metallurgical Quarterly》1997,49(7):17-23
Since 1986 we have used the orthotopic substitution technique on some 280 male patients suffering from bladder carcinoma and 38 females. There is minimal morbidity and mortality, though patients are generally younger than those seen in Europe and the USA. Postoperative daytime continence is experienced by about 94% of patients and night-time continence by around 78%. Since some complications were encountered using the hemi-Kock's pouch, we devised an orthotopic bladder substitute from 40 cm of ileum, using no staples and without creating a nipple. The ileum is arranged in a W formation, the ante-mesenteric border is incised and the serosa of the two lateral limbs joined together. Two troughs are created on either side of the neo-bladder and each ureter is laid into its respective trough. The mucosa on either side is sutured in front of the ureter creating a tunnel. Some 87 male patients have undergone this revised procedure, and female patients, when the urethra can be utilised. 相似文献
73.
74.
Ethylene-propylene-diene terpolymer rubberlnatural rubber blends (EPDM/NR) in different proportions (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) reinforced with 20 phr semireinforcing furnace carbon black have been studied. The permittivity ?' and dielectric loss ?″ for these samples were determined in the frequency range 102–107 Hz. Also, their physico-mechanical properties were investigated. The EPDM/NR blend (75 : 25) possessed the best mechanical properties and stability against aging. Thus, it was chosen to explore the effect of adding carbon black in different quantities up to 50 phr on its electrical and mechanical properties. Three different types of carbon black. namely high-abrasion furnace black, fast-extrusion furnace black, and medium thermal black, were used. At a certain concentration of carbon black, referred to as the threshold percolation concentration, an abrupt increase in ?′ and ?″, which depends on its type, was detected. This could be attributed to some sort of interaction between the blend and the carbon black at higher concentrations. 相似文献
75.
The polarographic behaviour of eosin and erythrosin in buffer solutions of pH 4–11 is discussed. The observed waves are assigned to the reduction of furan and pyrone rings of the molecule of erythrosin at pH 4–11 and for eosin at pH ?7. The nature of the waves is also investigated. In alkaline media the electrode reaction is essentially diffusion controlled whereas at pH < 8 adsorption of the reduction products contributes in the electrodes process. 相似文献
76.
An attempt to capture software aging and specify when to do preventive maintenance (PM) is presented in this paper. A composite measure termed the DRM, Deteriorating Response Measure, is defined. It is based on the analysis of the deteriorating speed of the software against time and load. This speed is characterized as follows: (1) It decays with increased load. (2) It does not increase again when the load decreases, this indicates loss of elasticity. The DRM is mathematically formulated based on a queueing system model.Specifying when to do preventive maintenance depends on the decision maker's perspective of the manifestation of aging. It is tried here to formalize this dependence. Three degrading performance metrics are defined for a DRM: (1) Decaying restored speed value. (2) Increasing speed offset ratio (recoverability index). (3) Increasing operation interval offset. These metrics can be used singly or aggregately in a DRM to specify when to do preventive maintenance. Results of model testing are also shown.This work can be part of an on-line procedure that calculates performance indexes for a server type software system like a web browser, an operating system, a database, and helps in the decision to do preventive maintenance for aging software. 相似文献
77.
Lakes Roderic S. Korttila K. Eltoft D. Derose A. Ghoneim M. 《IEEE transactions on bio-medical engineering》1981,(10):725-729
A force platform has been developed, which is capable of measuring postural sway in humans in two orthogonal directions. For each direction, output data consist of total average sway in two frequency bands centered on 0.57 and 2.9 Hz. The device is suitable for use in research or in a clinical setting. 相似文献
78.
The Shuttle Radar Topographic Mission (SRTM) elevation data reveal segments of inactive drainage channel systems in the eastern Sahara. Four sites are investigated and their drainage networks are delineated and compared with processed Synthetic Aperture Radar (SAR) and Enhanced Thematic Mapper Plus (ETM+) images. These include parts of the drainage lines that lead to the Kufra Oasis in Libya; the eastern Gilf Kebir drainage system that straddles the border region between Egypt and Sudan; the lower reach of Wadi Howar, the extinct western Nile tributary in Sudan; and a reversed flow channel of Wadi Kubbaniya northwest of Aswan in Egypt. These features are delineated using SRTM data and a Geographic Information System (GIS) hydrologic routine. The results show that the SRTM signals penetrate the desert‐sandy surfaces and map ancient drainage systems in the same way as SAR. The study also demonstrates that SRTM data can be used to confirm or modify pathways of channel courses mapped from radar images alone. Because of this capability, it is also recommended that SRTM data be used in place of GTOPO30 elevation data in hydrologic modelling of sand‐covered deserts. 相似文献
79.
ElBatal H. A. El-Kheshen A. A. Ghoneim N. A. Marzouk M. A. ElBatal F. H. Fayad A. M. Abdelghany A. M. El-Beih A. A. 《SILICON》2019,11(1):197-208
Silicon - Glasses based on the soda lime borophosphate system together with samples doped with SrO, ZnO or CuO were prepared. Glass – ceramic derivatives were prepared by controlled thermal... 相似文献
80.
The sintering of lime doped with up to 2 mol% La2O3 as well as CeO2 was followed on firing at 1400, 1500 and 1600°C. X-ray diffraction and reflected-light microscopy techniques have been used to investigate the phase composition and texture of the fired samples. The load bearing capacity and the rate of hydration of the obtained dense lime samples have also been determined to assess its quality. It is found that doping lime with 0·5–1·0 mol% of either La2O3 or CeO2 and firing up to 1600°C leads to dense and hydration-resistant lime with uniform texture. At this level of the dopant oxides, normal grain growth occurred with the increase in the degree of direct bonding. Doping with less than 0·5 mol% La2O3 or CeO2 is insufficient for inhibiting the discontinuous grain growth of the lime grains. On the other hand, increase in the dopant content above 1·0 mol% showed finer grain sizes at the expense of the degree of direct bonding. 相似文献