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51.
The main contribution of this paper shows that distributed simulation of timed Petri nets (TPN) can take advantage of their structure to obtain a significant lookahead which is usually difficult to compute with other models. In this paper, we introduce a conservative-distributed simulation with a reduced number of control messages and without deadlock resolution. This approach is based on a part of optimism computed on the prediction time each logical process can determine for its advancement. Obviously this prediction time must be computed easily according to the structure of the simulated logical process. Timed Petri nets meet these requirements and we use their structure to evaluate the depth of the prediction. In conservative-distributed simulation, it is known that the deeper the prediction, the better the efficiency of the simulation. We present a method we have devised based on channel time prediction. We compare its performance to the Chandy–Misra method and to some related Petri nets approaches (Chiola). Experiments carried out on Sun stations show that there is more parallelism and a reduced number of null messages in the cases of deadlock avoidance. Moreover, considering deadlock detection and resolution technique we observe that in many cases no deadlock occurs with less control messages. 相似文献
52.
M. M. El-Nahass B. A. Khalifa A. M. Abd El-Rahman R. El-Ariny 《Applied Physics A: Materials Science & Processing》1996,63(1):81-86
Solid solutions of ZnSe
x
Te1–x
(0. 1 x 1) were synthesized by vacuum fusion of stoichiometric proportions of ZnSe and ZnTe. X-ray diffraction data revealed that they have polycrystalline cubic zinc-blende structure. The calculated unit cell lattice constant (a) for the different compositions in powder form vary linearly, with molecular fractionx following Vegard's law:a(x) = 6.165 – 0.485x. Thin films of ZnSe
x
Te1–x
(0.1 x 1) solid solutions deposited onto glass or quartz substrates by thermal evaporation in a vacuum of 10–4 Pa were found to be polycrystalline with a preferred (1 1 1) orientation. The obtained data were confirmed by electron diffraction. The optical studies showed that ZnSe
x
Te1–x
polycrystalline films of different compositions have two direct transitions with corresponding energy gapsE
g andE
g +
so The variations in bothE
g andE
g +
so, withx indicate that ZnSe
x
Te1–x
solid solution belongs to an amalgamation-type following quadratic equations with bowing parameters 1.251 and 1.275, respectively. 相似文献
53.
H. A. Dessouky M. M. Abdel-Badei S. M. Khalifa H. M. Aly 《Journal of Radioanalytical and Nuclear Chemistry》1988,126(2):165-172
Chromatographic column investigations were performed for the recovery of uranium from aqueous medium of pH 1.0 and ionic strength of 0.6M/NaNO3/, which is comparable /in its chemical activity/ to certain high active waste solutions. Six different active beds were tested and compared in terms of their capacity for uranium, height equivalent to theoretical plate and their numbers. The main uranium species present in the medium were elucidated. 相似文献
54.
Esam Khalifa Abhoy N. Ganguly Jost H. Bieri Max Viscontini 《Helvetica chimica acta》1980,63(8):2554-2558
A Convenient Synthesis of Leucovorin The synthesis of leucovorin, a 5-formyl-(6R or S)-5,6,7,8-tetrahydropteroyl-L -glutamic acid (II) is described. The L -folic acid was first reduced to (6R, S)-tetrahy-dro-L -folic acid (I); formylation with methyl-formate in DMSO gave directly leucovorin (as a diastereomeric mixture) in good yields. To demonstrate, that the formylation occurred regiospecifically at N (5) and not at N (10), N (10)-nitroso-(6 R, S)-tetrahydro-L -folic acid was formylated under the same conditions. Reductive elimination of the N (10)-nitrosogroup gave the identical leucovorin as in the previous case. The synthetic leucovorin was biologically as active as the natural product with Streptococcus faecalis ATCC 8043 and Pediococcus cerevisiae ATCC 8081. 相似文献
55.
Summary Massive gold because of the passivity of the oxide formed on its surface can be used as a substitute for platinum in electrometric titrations including acid-base and oxidation-reduction systems. The end points are attended with large jumps on the curves and coincide satisfactorily with those obtained using the hydrogen or platinum electrode or by other method. 相似文献
56.
H. Khalifa A. M. Amin Farouk A. Osman 《Fresenius' Journal of Analytical Chemistry》1960,172(3):167-175
Summary The acid-base properties of Fast Grey R. A. have been studied with reference to the mode of chelation of the dye with different valent metals. The pK values of 3.83, 10.53 and 10.70 corresponding to the three steps of ionization of the free acid were evaluated by the aid of the relation between log [acid]/[salt] and pH values obtained during the course of the potentiometric titration of the free acid with a free base. 相似文献
57.
Interfacial condensation of decamethylenediamine and acid chlorides I, II, and III yielded polyamides the thermal stability of which decreased in the order III, I, II, a finding reasserted by calculating activation energy decomposition temperatures. Irradiation of these polyamides does not appreciably affect their properties, and thus they can be considered satisfactorily γ-irradiation resistant. It appears that there are only few papers dealing with syntheses and properties of polyamidoarylates. Cleaver and Pratt [1] prepared polyamidoesters by the polymerization of bisoxazolones with glycols. Korshak and others [2], however, obtained a polyamidoester by the aminolysis of polyethylene-sebacate with hexamethylenediamine. In a previous investigation [3] a few polyamidoarylates were obtained by the condensation of aminophenols with aromatic acid chlorides. In this work we obtained some new polyamidoarylates by the inter-facial condensation of equimolar ratios of decamethylenediamine with 相似文献
58.
Khalifa N. M. El-Sayed A. S. Abd El-Karim S. S. Hassan E. S. Nossier E. S. Shalaby A. G. 《Russian Journal of General Chemistry》2018,88(12):2646-2652
Russian Journal of General Chemistry - A group of new analogs of 1,3,4-trisubstituted pyrazoles functionalized 2-thioxoimidazolidinones and fused heterocyclic systems are synthesized. Their tests... 相似文献
59.
Physics of Particles and Nuclei Letters - The spectrum of spinless modes in a model with the $$SU{{(2)}_{L}} \times U{{(1)}_{R}}$$ symmetrical four-quark-interaction proposed by Miransky,... 相似文献
60.
Khalifa N. M. Haiba M. E. Taha M. M. Al-Omar M. A. 《Russian Journal of General Chemistry》2019,89(2):319-323
Russian Journal of General Chemistry - Novel polycyclic compounds, 1-pyrene-based pyridone derivatives, are synthesized by treatment of pyrenyl acetohydtazide with several arylidenemalononitriles... 相似文献