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991.
Ali El-Shekeil Khalid Y. Abid Omar Al-Shuja''a 《Journal of Inorganic and Organometallic Polymers》2001,11(4):217-234
Oligo[aromatic diimidoselenium] (PADIS) is prepared from the reaction of the disubstituted aromatic compounds, namely, 1,4-phenylenediamine, 4,4-thiodianiline, 1,1-biphenylene-4,4-diamine, and 2,2-dithiodianiline, with selenium dioxide in refluxing absolute ethanol. The four materials are investigated by elemental analysis, electronic spectra, Fourier Transform-infrared spectroscopy, and [1H]NMR spectroscopy. The DC electrical conductivity variation with temperature in the range 300–500 K of the materials after annealing for 24 h at 100°C and after doping with 10% I2 is determined for comparison. 相似文献
992.
Khalid Abidi 《国际强度与非线性控制杂志
》2014,24(1):166-178
》2014,24(1):166-178
A periodic adaptive control approach is proposed for a class of nonlinear discrete‐time systems with time‐varying parametric uncertainties which are almost periodic, and the only prior knowledge is the periodicity. The new adaptive controller updates the parameters and the control signal periodically in a pointwise manner over one entire period, in the sequel that achieves a bounded tracking convergence. The result is further extended to scenarios with unknown input gain, higher order dynamics, and tracking. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
993.
994.
David Sánchez-hernández Ulun Karacaoglu Tacar Gokdemir Ata H. Khalid Ali A. Rezazadeh Miguel Ferrando Elias de los Reyes Ian D. Robertson 《电信纪事》1997,52(3-4):164-173
It is well known that mm-waves have an important role to play in the rapid expansion of mobile and personal communications, mmic technology is an important factor since it can provide a means of mass producing the user terminal rf subsystems. Millimetre-wave integrated circuits do not yet however offer the high packing density and functionality which is now possible for lower frequency applications where lumped elements are used. This problem is influenced most of all by the extreme modelling difficulties encountered at frequencies above 30 GHz. This paper reviews the current state-of-the-art for cad techniques used in mmic design. It describes some limitations of the standard Smarttm library approach and looks at the application of commercial electromagnetic simulators in the design of both microstrip and cpw circuits. 相似文献
995.
The bituminous impurity incorporated with the elemental sulphur in the Mishraq deposit was separated by solvent extraction. The extract was further fractionated by column chromatography and the fractions were studied spectroscopically (i.r. u.v., and p.m.r.) The observation that the bituminous material is basically asphaltic (ca. 80% of the total weight, precipitated by straight-chain pentane) with no detection of light components, coupled with the p.m.r. results on carbon type distribution, may add support to the existing theories about the origin of elemental sulphur in the Mishraq region. Elemental analysis of bitumen samples isolated from Frasch sulphur when compared with those isolated from borehole samples using identical isolation techniques may indicate that a reaction between elemental sulphur and the bituminous impurity is taking place under the thermal conditions of the Frasch Process. 相似文献
996.
Blending of poly (lactic acid) (PLA)/functionalized gum arabic (FG) in presence of dicumyl peroxide (DCP) presents a simple process to produce film using melt extrusion (recycle time ~ 4 min, screw speed ~60 rpm) at 180°C with tailored characteristics. The FTIR investigation shows that the confirmation of grafting of PLA chains on FG through formation of new C─C linkage. Properties of fabricated films such as morphological, mechanical, UV barrier and contact angle are examined to develop film with improved interfacial interaction, increased toughness, UV–C blocking effect (~95%) and hydrophobicity (~14%). Polarized optical microscopy (POM) studies reveal that PLA/1FG with and without DCP has more crystal density as compared to PLA at 120°C. This melt extrusion permits straightforward, feasible bionanocomposite film and has great potential as a modification with DCP assists to overcome particular drawbacks of FG. 相似文献
997.
Chaudhry Shehzad Ashraf Naqvi Husnain Mahmood Khalid Ahmad Hafiz Farooq Khan Muhammad Khurram 《Wireless Personal Communications》2017,96(4):5355-5373
Wireless Personal Communications - Internet of Things has drastically expanded the global network for information exchange, because thousands of communication devices are becoming part of the... 相似文献
998.
Khalid Muzaffar 《Drying Technology》2016,34(1):142-148
The present study aimed to investigate the effect of adding soya protein isolate (SPI) as a complementary drying aid of maltodextrin (MD) on spray drying of tamarind pulp. Tamarind pulp powders were prepared by spray drying of tamarind pulp, adding 0, 5, 10, 15, and 20% of SPI together with maltodextrin as the drying aids. The results showed that the addition of SPI resulted in a significant increase in powder recovery from 9.35 to 70.04%, thereby reducing the requirement of higher levels of maltodextrin for the production of quality tamarind pulp powder. The powders were evaluated for moisture content, bulk density, particle size, morphological characteristics, cohesiveness, and glass transition temperature. With the addition of SPI in the feed material, the powder samples showed a significant variation in their properties. Addition of SPI decreased the cohesion index of the powders from 14.21 to 9.29 mm, thereby increasing the flowability of the powders. Surface morphology of the powders showed that the addition of SPI resulted in an indented and wrinkled particle surface, a characteristic feature of powders produced with protein as the drying aid. 相似文献
999.
This paper examines the effects of composite constituents and geometry on the energy absorption capability of composite hemispherical shells. To examine the effects of matrix types on their energy absorption capability, glass fibre/epoxy and glass fibre/polyester hemispherical shells were fabricated. While glass fibre/epoxy and carbon fibre/epoxy hemispherical shells were fabricated to investigate the effect of fibre reinforcements. Effect of aspect ratio (R/t) was also examined and the results were presented. The results obtained showed that the energy absorption capability of the hemispherical shells significantly affected by the composite constituents as well as R/t ratio. 相似文献
1000.