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排序方式: 共有231条查询结果,搜索用时 15 毫秒
111.
Muhammad Taher Abuelma’atti Zainulabideen Jamal Khalifa 《Analog Integrated Circuits and Signal Processing》2014,80(3):577-584
Since its inception many proposals and attempts have been reported on using the memristor in digital signal processing (DSP) circuits. Memristor-based DSP applications are mainly focusing on improving the performance of memories and in realizing synapses in neural networks. In most of the reported applications the verification of the proposed DSP circuits is made using mathematical-based memristor models. In this paper a new circuit for practical emulation of the memristor and its applications in memristor-based digital modulation is experimentally investigated. 相似文献
112.
Collaborative tools typically employ linear threading for representing and organizing the contributions of the discussants. We argue that linear representations provide little support for the conceptualization, contextualization, and visualization of the discussion. To address these drawbacks, we propose the usage of semantic networks for representing discussions. In this paper, we demonstrate the applicability of semantic network representation to discussions through the development of a prototype named CollectiveThought. We also test some of the potential benefits of semantic network discussion representation with an empirical study. More specifically, we compare these two modes of discussion representation (i.e., linear versus semantic network) in terms of effects on the communication process as measured by perceived contextualization and on the communication outcome as measured by mutual understanding, using both subjective and objective indicators. The results show that semantic network discussion representation leads to a higher level of perceived contextualization and better mutual understanding. 相似文献
113.
Khalifa Aguir Dave B. B. Lollman Herv Carchano 《Materials Science and Engineering: B》1997,50(1-3):157-160
This work concerns investigations on electrical properties of amorphous GaAs1−xNx thin films grown on GaAs substrates. Film deposition was carried out by RF sputtering of a GaAs target by adding a nitrogen carrier gas (NH3) to an Ar plasma. Chemical etching of substrates followed by different plasma treatments (like reverse bias and/or NH3 glow discharge) prior to film deposition have been studied. The effects of substrate and growth temperature and of total pressure in the reactor have been analysed. Electrical characteristics (C–V and C–V(T)) have enabled us to put in evidence the evolution of interface states of the a-GaAs1−xNx/c-GaAs junctions. The amorphous GaAs1−xNx thin films are potentially interesting to be considered for GaAs-based MIS structures, due to their relatively high resistivity values, or as passivating layers on GaAs devices. 相似文献
114.
Some toxins from scorpion venoms, much more toxic to insects than to other animal classes, possess high affinity to Na+ channels. These anti-insect scorpion toxins have been divided into: 1) alpha toxins which lack strict selectivity for insects, do not compete with following groups of anti-insect toxins, resemble other alpha scorpion toxins by their structure and their ability, as alpha anemone toxins, to prolong insect axonal action potential durations through a drastic slowing down of the Na+ current inactivation, 2) excitatory insect selective scorpion toxins which induce in blowfly larvae an immediate fast paralysis; in isolated cockroach axons, they depolarize and induce a sustained repetitive activity of short (normal) action potentials through a shift of Na+ activation mechanism towards more negative potentials and some decrease of inactivation at these potential values, 3) depressant insect selective neurotoxins which cause a slow progressive flaccid paralysis of larvae, depolarize insect axons and reduce or even suppress evoked action potentials; resting depolarizations which are antagonized by a post-application of TTX, are due to the opening of sodium channels at very negative potential values and to the suppression of their inactivation mechanism. The decrease of the maximal Na+ conductance following flaccid toxin action may be understood if toxin-modified channels opened at very negative potentials values remain open (or re-open) for much longer times than in control conditions and pass by substate less conductant states. Anti-insect scorpion toxins become of major interest into insect neurophysiology and also into insect pest control, due to their specific target sites and to the recent constructions of insecticidal baculovirus expressions of several of these toxins. 相似文献
115.
W. Khalifa F. H. Samuel J. E. Gruzleski 《Metallurgical and Materials Transactions A》2003,34(13):807-825
The iron intermetallics observed in six dilute Al-Si-Fe alloys were studied using thermal analysis, optical microscopy, and
image, scanning electron microscopy/energy dispersive X-ray, and electron probe microanalysis/wavelength dispersive spectroscopy
(EPMA/WDS) analyses. The alloys were solidified in two different molds, a preheated graphite mold (600°C) and a cylindrical
metallic mold (at room temperature), to obtain slow (}0.2 °C/s) and rapid (}15 °C/s) cooling rates. The results show that
the volume fraction of iron intermetallics obtained increases with the increase in the amount of Fe and Si added, as well
as with the decrease in cooling rate. The low cooling rate produces larger-sized intermetallics, whereas the high cooling
rate results in a higher density of intermetallics. Iron addition alone is more effective than either Si or Fe+Si additions
in producing intermetallics. The alloy composition and cooling rate control the stability of the intermetallic phases: binary
Al-Fe phases predominate at low cooling rates and a high Fe:Si ratio; the β-Al5FeSi phase is dominant at a high Si content and low cooling rate; the α-iron intermetallics (e.g., α-Al8Fe2Si) exist between these two; while Si-rich ternary phases such as the δ-iron Al4FeSi2 intermetallic are stabilized at high cooling rates and Si contents of 0.9 wt pct and higher. Calculations of the solidification
paths representing segregations of Fe and Si to the liquid using the Scheil equation did not conform to the actual solidification
paths, due to the fact that solid diffusion is not taken into account in the equation. The theoretical models of Brody and
Flemings[44] and Clyne and Kurz[45] also fail to explain the observed departure from the Scheil behavior, because these models give less weight to the effect
of solid back-diffusion. An adjusted 500°C metastable isothermal section of the Al-Si-Fe phase diagram has been proposed (in
place of the equilibrium one), which correctly predicts the intermetallic phases that occur in this part of the system at
low cooling rates (}0.2 °C/s). 相似文献
116.
H. F. Aly M. M. El Dessouky S. M. Khalifa J. D. Navratil F. A. Shehata 《溶剂提取与离子交换》2013,31(6):867-879
ABSTRACT Cobalt (II) was extracted from perchlorate aqueous media by thenoyltrifluoroacetone (HTTA)alone and mixed with 12-Crown-4 (12C4) 15-Crown-5 (15C5) 18-Crown-6 (18C6)dibenzo-18-Crown-6 (Dbl8C6)dicyclohexyl-18-Crown-6 (Dchl8C6) or dicyclohexyl-24-Crown-8 (Dch24C8), in chloroform. The extraction constant of the chelate (K20) the extraction constant of the mixed species (K21), the synergic factor (S.F.) and the formation constant of the extracted adducts (β21) were evaluated. The adduct stoichiometry was found to have the general formula Co(TTA)2CE, irrespective of the crown ether (CE) used. It was found that no specific cavity size is required for the adduct formation. The synergic values K21, S.F., and β21as related to the crown ether took the order Dch24C8 > 18C6 > Dchl8C6 > 15C5 > Dbl8C6 > 12C4, which could be explained in terms of the crown ether basicity rather than the correspondence between the cavity size of the crown ether and the cobalt(II) crystal radii. The sequence 18C6 > Dchl8C6 > Dbl8C6 was interpreted in terms of the withdrawing ability of Dch and Db as substitutes in reducing the basic character of the adjacent crown ether oxygen donors. 相似文献
117.
Islam Shayla Khalifa Othman O. Hashim Aisha-Hassan Abdalla Hasan Mohammad Kamrul Razzaque Md. Abdur Pandey Biswajeet 《Wireless Personal Communications》2020,114(2):1133-1153
Wireless Personal Communications - Handoff management is an indispensable component in supporting network mobility. The handoff situation raises while the Mobile Router (MR) or Mobile Node (MN)... 相似文献
118.
Fatiha Benmahdi Safia Semra Djemal Haddad Philippe Mandin Mounira Kolli Mohammed Bouhelassa 《化学工程与技术》2019,42(2):355-369
Activated carbon was used as an adsorbent for the removal of phenol from aqueous solution under various operating conditions. Statistical design using MATLAB® tools was employed to study the effects of three variables on six different response factors. MATLAB® software was employed to solve proposed quadratic model equations and for fitting a quadratic response surface. All the models with a very high adjusted R‐square predicted the experimental data well. The Thomas, the Yoon‐Nelson, the Wolborska, the bed depth service time, and the linear driving force models were used to predict breakthrough curves for experimental data. The results showed that the linear driving force model was suitable for the prediction of the breakthrough curve data. 相似文献
119.
Russian Engineering Research - This paper presents a finite element method for the modeling of the hard turning of (AISI) 4340 steel. Abaqus/Explicit software was used for the numerical simulation.... 相似文献
120.
A comparative study was made of the fracture behavior of austenitic and duplex stainless steel weldments at cryogenic temperatures by impact testing. The investigated materials were two austenitic (304L and 316L) and one duplex (2505) stainless steel weldments. Shielded metal arc welding (SMAW) and tungsten inert gas welding (TIG) were employed as joining techniques. Instrumented impact testing was performed between room and liquid nitrogen (?196 °C) test temperatures. The results showed a slight decrease in the impact energy of the 304L and 316L base metals with decreasing test temperature. However, their corresponding SMAW and TIG weld metals displayed much greater drop in their impact energy values. A remarkable decrease (higher than 95%) was observed for the duplex stainless steel base and weld metals impact energy with apparent ductile to brittle transition behavior. Examination of fracture surface of tested specimens revealed complete ductile fracture morphology for the austenitic base and weld metals characterized by wide and narrow deep and shallow dimples. On the contrary, the duplex stainless steel base and weld metals fracture surface displayed complete brittle fracture morphology with extended large and small stepped cleavage facets. The ductile and brittle fracture behavior of both austenitic and duplex stainless steels was supplemented by the instrumented load–time traces. The distinct variation in the behavior of the two stainless steel categories was discussed in light of the main parameters that control the deformation mechanisms of stainless steels at low temperatures; stacking fault energy, strain induced martensite transformation and delta ferrite phase deformation. 相似文献