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31.
The use of a scanning Fabry-Perot interferometer of variable length (variable resolution) for investigating the output of a cw CO laser is reported. Under experimental conditions required to achieve maximum power it was found that the laser output consisted of two or more simultaneously occuring transitions due to the overlapping nature of the vibration- rotation bands. The frequency differences between these transitions were measured to an accuracy of 0.01 cm-1. Operation of the CO laser on a single vibration-rotation transition was obtained by controlling the laser gain with the experimental variables of discharge pressure, gas temperature, and optical alignment. An alternative approach of obtaining monochromatic radiation, by using a Fabry-Perot interferometer as a frequency selective filter external to the CO laser, is reported. 相似文献
32.
Dr. M. H. Hamza 《Mathematical Methods of Operations Research》1968,12(1):121-132
Zusammenfassung An Hand von einfachen Modellen wird gezeigt, daß man die Theorie der Automatik auf das Gebiet der Lagerhaltung anwenden kann. Ein kontinuierliches lineares System und ein diskretes System werden untersucht. Für das erste System wird dieLaplace-Transformation verwendet, für das zweite diez- und modifiziertez-Transformation. Schließlich wird die Zeitbereichmethode eingeführt und eine Anwendung davon gezeigt.
Summary By means of simple models, it is shown that control theory can be applied to inventory control problems. TheLaplace transform is used in the study of a linear continuous system. Thez and modifiedz transforms are employed in the study of a discrete system. Finally, the state space approach is introduced and is applied to a model with multirate sampling.相似文献
33.
M'Hamed Ali Hamza Guy Serratrice Jean-Jacques Delpuech 《Magnetic resonance in chemistry : MRC》1981,16(2):98-102
Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors are reported for five polyfluoroaromatic compounds at 28°C. In all cases the relaxation of the fluorine bearing carbon is predominantly dipolar. Effective correlation times are smaller than those of the analogous benzene derivatives by a factor of 3–4, in qualitative agreement with predictions from the Stokes–Einstein diffusion theory. The T1 values for the para-carbon of monosubstituted fluorobenzenes is clearly shorter than the T1 values for the ortho- and meta-carbons. This phenomenon was traced to anisotropic tumbling, and D∥ and D⊥ diffusion coefficients were computed using Woessner's equations for molecules assumed to behave like symmetric rotors about their C2 in-plane principal symmetry axis. Equal tumbling ratios, D∥/D⊥, were found in this way for toluene and perfluorotoluene. 相似文献
34.
Bugarcić ZD Nandibewoor ST Hamza MS Heinemann F van Eldik R 《Dalton transactions (Cambridge, England : 2003)》2006,(24):2984-2990
Substitution reactions of the complexes [Pd(bpma)(H2O)]2+, [Pd(bpma)Cl]+, [Pd(dien)(H2O)]2+ and [Pd(dien)Cl]+, where bpma = bis(2-pyridylmethyl)amine and dien = diethylentriamine or 1,5-diamino-3-azapentane, with some nitrogen-donor ligands such as triazole, pyrazole, pyrimidine, pyrazine and pyridazine, were studied in an aqueous 0.10 M NaClO4 at pH 2.8 using variable-temperature and -pressure stopped-flow spectrophotometry. The second-order rate constants indicate that the Pd(II) complexes of bpma, viz. [Pd(bpma)(H2O)]2+ and [Pd(bpma)Cl]+, are more reactive than the complexes of dien, viz. [Pd(dien)(H2O)]2+ and [Pd(dien)Cl]+. Also, the aqua complexes, [Pd(bpma)(H2O)]2+ and [Pd(dien)(H2O)]2+, are much more reactive than the corresponding chloro complexes. The most reactive nucleophile of the five-membered rings is triazole and for the six-membered rings the most reactive one is pyridazine. Activation parameters were determined for all reactions and the negative entropies and volumes of activation (Delta S++, Delta V++) support an associative ligand substitution mechanism. The crystal structure of [Pd(bpma)(H2O)](ClO4)2.2H2O was determined by X-ray diffraction. Crystals are monoclinic with the space group P2(1)/c. The coordination geometry of [Pd(bpma)(H2O)]2+ is distorted square-planar. The Pd-N (central) bond distance, 1.958(5) A, is shorter than the other two Pd-N distances, 2.007(5) and 2.009(5) A. The Pd-O distance is 2.043(5) A. 相似文献
35.
Hamza Guebbai 《Numerical Functional Analysis & Optimization》2018,39(1):1-10
To compute an approximate solution, of a weakly singular integral equation, we first regularize the kernel, and then truncate the associated Fourier series. An application to an astrophysical transfer equation is presented. 相似文献
36.
S. A. Agamy M. Y. Khalil M. Y. Hamza W. A. Abou-Taleb 《Isotopes in environmental and health studies》2013,49(6):287-291
Microstructure defects play a very important role in the swelling of irradiated stainless steel. This work is a parametric study of the effects of microstructural defects on the swelling of ion-irradiated steel. For simplicity, vacancy loop effects were neglected. Cold working was found to play a complicated role in the swelling behavior. On one hand, it increase the bias to interstitial absorption due to the increase in dislocation density. On the other hand, it decreases the total flux of point defects to voids by the decrease of the point defect concentrations. Grain size has also a strong effect on swelling. It was found that large gain sizes produces higher swelling and vise versa, i.e. the larger the surface of grain boundaries the less the irradiation-produced swelling. Similar effects were found for precipitates. 相似文献
37.
J. A. Carlisle L. J. Terminello A. V. Hamza E. A. Hudson E. L. Shirley F. J. Himpsel 《Molecular Crystals and Liquid Crystals》2013,570(1):819-824
Abstract The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C60, C70, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C60 and C70, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations. 相似文献
38.
Mohamed G. Assy Hassan A. El‐Sayed Nabil H. Ouf Ahmed Hamza Hesham A. Morsy 《Journal of heterocyclic chemistry》2019,56(10):2954-2959
A simple and direct synthetic methodology for a novel series of azines and their annulated systems was performed. Heterocyclization of acyl isothiocyanate 2 with urea or malononitrile gave s‐triazine 4 and 1,3‐oxazine 7 derivatives, respectively. The reaction of heteroallene 1 with acetylacetone tolerated 2‐thioxopyridine derivative 9 . The latter compound underwent heterocyclization with urea, hydrazine hydrate, or phenyl hydrazine to give the annulated pyridines 10 – 12 . Pyrimidinethione 14 was resulted from reaction of acylisothiocyanate with enamine 13 . Condensation of compound 14 with hydrazine hydrate, phenyl hydrazine, urea, and 3‐nitrobenzaldehyde in the presence of ethyl cyanoacetate or sodium hydroxide afforded 15 – 20 , respectively. 相似文献
39.
40.
Soumaya Touzani Hamada Imtara Shankar Katekhaye Hamza Mechchate Hayat Ouassou Ali S. Alqahtani Omar M. Noman Fahd A. Nasr Hugo Fearnley James Fearnley Anant Paradkar Ilham ElArabi Badiaa Lyoussi 《Molecules (Basel, Switzerland)》2021,26(15)
The biological activities of propolis samples are the result of many bioactive compounds present in the propolis. The aim of the present study was to determine the various chemical compounds of some selected propolis samples collected from Palestine and Morocco by the High-Performance Liquid Chromatography–Photodiode Array Detection (HPLC-PDA) method, as well as the antioxidant and antibacterial activities of this bee product. The chemical analysis of propolis samples by HPLC-PDA shows the cinnamic acid content in the Palestinian sample is higher compared to that in Moroccan propolis. The results of antioxidant activity demonstrated an important free radical scavenging activity (2,2-Diphenyl-1-picrylhydrazyl (DPPH); 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and reducing power assays) with EC50 values ranging between 0.02 ± 0.001 and 0.14 ± 0.01 mg/mL. Additionally, all tested propolis samples possessed a moderate antibacterial activity against bacterial strains. Notably, Minimum Inhibitory Concentrations (MICs) values ranged from 0.31 to 2.50 mg/mL for Gram-negative bacterial strains and from 0.09 to 0.125 mg/mL for Gram-positive bacterial strains. The S2 sample from Morocco and the S4 sample from Palestine had the highest content of polyphenol level. Thus, the strong antioxidant and antibacterial properties were apparently due to the high total phenolic and flavone/flavonol contents in the samples. As a conclusion, the activities of propolis samples collected from both countries are similar, while the cinnamic acid in the Palestinian samples was more than that of the Moroccan samples. 相似文献