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1.
M. H. El-Fouly A. F. Maged H. H. Amer M. A. Morsy 《Journal of Materials Science》1990,25(4):2264-2266
Temperature-induced transformations are considered to be interesting characteristic properties of amorphous materials including the Si
x
Te60–x
As30Ge10 system, withx=5, 10, 12 and 20. Density (), X-ray diffraction and differential thermal analysis (DTA) were used to characterize the compositions. DTA traces of each glass composition at different heating rates from 5 to 30° C min–1 were obtained and interpreted. Fast and slow cooling cycles were used to determine the rate of structure formation. Cycling studies of materials show no memory effect but only ovonic switching action. The compositional dependence of the crystallization activation energy (E) and the coefficient of glass-forming tendency (K
gl) have been calculated. The thermal transition temperatures and associated changes in specific heat have been examined as a function of the Te/Si ratio by differential scanning calorimetry. It was found that andE increase linearly with increasing tellurium content, while the heat capacity (c
p) andK
gl, decrease with increasing tellurium content.E=1.54 eV andc
p=0.246 J g–1 K–1 forx=20 whileE=2.74eV andc
p=0.22 J g–1 K–1 forx=5. 相似文献
2.
M. H. El-Fouly A. M. Morsy A. H. Ammar A. F. Maged H. H. Amer 《Journal of Materials Science》1989,24(7):2444-2448
The effect of composition on amorphous chalcogenide threshold switches of the system Si
x
Te60-x
As30Ge10, wherex = 5, 10, 12 and 20, has been studied. The compositionx = 5 shows the best switching characteristics, e.g. the smallest holding voltage (V
h = 0.4V), the highest ON state current (I
h = 45A) and smallest threshold voltage (V
s = 1.5V). Applying the three mechanisms of conductance of Mottet al. (Phil. Mag.
37 (1975) 961), it is found that for a particular composition
2 <
1 <
0 (the pre-exponential factors) andW
2 < (E
a –E
1 +W
1) < (E
c –E
f) (whereE
a,E
c andE
e = activation energies at band edge, fermi level and conduction band;W
1 andW
2 = activation energy for hopping). It was found that the density of states at the fermi levelN(E
f) increases with the decrease of silicon content. The results provided further evidence against thermal interpretations and thereby support electronic models of threshold switching for these glass systems. 相似文献
3.
Nabel?A.?NegmEmail author Salwa?M.?I.?Morsy 《Journal of surfactants and detergents》2005,8(3):283-287
A weight loss technique was used to determine the corrosion inhibition efficiency of synthesized alkyl mono-and dibenzoate
triethanolammonium bromide derivatives (TEAMB, TEADB) in an acidic medium (2 N HCl) at different doses (50, 100, and 200 ppm).
The results showed that monoderivatives had a higher corrosion inhibition efficiency than diderivatives. The results were
correlated with several factors, including the alkyl chain length of the hydrophobic chains, interfacial tension (IT), critical
micelle concentration (CMC), and adsorption free energy of these inhibitors. Increasing the geometric length of the alkyl
chains in the synthesized inhibitors had an increasing effect on their corrosion inhibition efficiency, whereas decreasing
the CMC and IT had an increasing effect on their tendency toward corrosion inhibition. The number of hydrophobic chains attached
to the inhibitor molecules had a vital influence on their efficiency as corrosion inhibitors. 相似文献
4.
Wail Mardini Yaser Khamayseh Abdalrhman Abdalkareem Almodawar Ehab Elmallah 《Peer-to-Peer Networking and Applications》2016,9(6):991-1004
Range of applications for Wireless Sensor Networks (WSNs) is increasing rapidly. One class of such applications is Energy-Aware Wireless Positioning Systems for situation awareness. Localization deals with determining a target node’s position in WSN by analyzing signals exchanged between nodes. Received Signal Strength Indicator (RSSI) represents the ratio between received signal power and a reference power, and is typically used to estimate distances between nodes. RSSI distance estimations are affected by many factors. This paper aims to enhance the accuracy of RSSI-based localization techniques in ZigBee Networks through studying the communication channel status between two nodes. As the network nodes are exposed to high noise levels, position estimation accuracy deteriorates. A novel adaptive localization scheme is proposed; Two-State Markov model with moving average is employed to detect unpredictable RSSI readings that may reflect badly on the estimation. The proposed scheme achieves better estimation accuracy, for example, the estimation error was reduced from 11.7 m to just 3 m using the proposed scheme. 相似文献
5.
A new mesoporous adsorbent for uranium removal from waste effluents was prepared, characterized, and impregnated with trioctylamine. The adsorption efficiency was investigated as a function of pH, contact time, initial uranium concentration, competing ions, solid/liquid ratio, and temperature using batch sorption techniques. The maximum adsorption capacity was 21.9 mg g–1 at pH 5. The equilibrium data fit well with the Langmuir adsorption isotherm. Kinetic study showed that the process was fast and reached equilibrium within 60 min. The kinetic data fit well with the pseudo-second-order law. Thermodynamic data show that the process is spontaneous and exothermic. 相似文献
6.
Solvent extraction of uranium ions with 4-methylpentan-2-one was examined. The diluent, extractant concentration, aqueous to organic phase ratio, and contact time were varied. Different stripping agents were examined to reach the optimum stripping conditions. The results obtained show that uranium can be quantitatively extracted from 5 M nitric acid with 7% 4-methylpentan-2-one dissolved in refined kerosene and stripped from the organic phase with 5% Na2CO3. The equilibrium is attained within 10 min. Uranium can be efficiently separated from a large number of elements by adding EDTA salt to the stripping solution before uranium precipitation. 相似文献
7.
8.
Active Management Framework for Distributed Multimedia Systems 总被引:17,自引:0,他引:17
Ehab Al-Shaer 《Journal of Network and Systems Management》2000,8(1):49-72
9.
Ehab A. Sobhy Ahmed M. Soliman 《International Journal of Circuit Theory and Applications》2010,38(5):441-452
Three novel CMOS realizations for the fully differential voltage second‐generation inverting current conveyor (FDVCCII‐) are proposed in this paper. The first realization has a limited input range, and the other two realizations have a rail to rail input range and show excellent features in linearity and bandwidth. As an application to the FDVCCII‐, a floating gyrator is proposed. A floating inductor is realized using the floating gyrator and it is used in realizing a second‐order low‐pass filter, which is simulated and compared with the ideal result. All circuits are simulated with SPICE using CMOS 0.35µm technology and supply voltages ±1.5V to verify the theoretical results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
10.
This paper addresses the optimal distributed generation sizing and siting for voltage profile improvement, power losses, and total harmonic distortion (THD) reduction in a distribution network with high penetration of non-linear loads. The proposed planning methodology takes into consideration the load profile, the frequency spectrum of non-linear loads, and the technical constraints such as voltage limits at different buses (slack and load buses) of the system, feeder capacity, THD limits, and maximum penetration limit of DG units. The optimization process is based on the Genetic Algorithm (GA) method with three scenarios of objective function: system power losses, THD, and multi-objective function-based power losses and THD. This method is executed on the IEEE 31-bus system under sinusoidal and non-sinusoidal (harmonics) operating conditions including load variations within the 24-hr period. The simulation results using Matlab environment show the robustness of this method in optimal sizing and siting of DG, efficiency for improvement of voltage profile, reduction of power losses, and THD. A comparison with particle swarm optimization (PSO) method shows that the proposed method is better than PSO in reducing the power losses and THD in all suggested scenarios. 相似文献