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81.
Ali Ali Arafa Ibrahim Sayed Shafie Fathi Sultan Ahmed Sultan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1956,7(3):256-264
The thermoelectric power of natural specimens of lead sulphide crystals has been measured between room temperature and 700° K. Specimens which are of then-type remain as such throughout the temperature range. Thep-type specimens, however, show an initial small rise followed by a gradual decrease and a subsequent change of sign ata temperature which, in some specimens, is well defined. Further increase of temperature results in a negative extremum. From this stage onwards there seems to develop a common behaviour for both types of specimens. Some crystals which were initially of thep-type changed over to then-type and remained as such throughout subsequent investigation. Among the crystals one showed a metallic conduction and an extraordinary large thermoelectric power. 相似文献
82.
A perturbed hard-sphere equation of state (EOS) has been previously employed to predict pressure–volume–temperature properties
of some ionic liquids (ILs) with phosphonium-, pyridinium-, and pyrrolidinium cations. In this work, we have extended the
considered EOS to another class of ILs in compressed states. This class consists of 14 imidazolium-based ILs. The predicted
densities were compared with those obtained from the experiment, over a broad pressure range from 0.1 to 200 MPa. From 1,122
data points examined for the aforementioned ILs, the total average absolute deviation was found to be 1.05%. 相似文献
83.
The optical properties of ethylene vinyl acetate (EVA) film have been studied. The effects of gamma irradiations on the optical spectrum of EVA films have been investigated using spectrophotometric measurements of reflectance and transmittance in the wavelength range 200–1100 nm. The absorption spectra were recorded in the UV–vis region for the unirradiated and irradiated films (from 0 to 50 kGy). Optical constants such as refractive index (n), extinction coefficient (K), and complex dielectric constant have been determined, as well as the optical dispersion parameters and high frequency dielectric constants. A large dependence of the fundamental optical constants on the irradiation dose was noticed. On irradiation, a higher refractive index was obtained as compared with that for unirradiated film. The dispersion parameters, such as E 0 (single‐oscillator energy), E d (dispersive energy), and M ?1 and M ?3 (moments), are discussed in terms of the single‐oscillator Wemple–DiDomenico model. 相似文献
84.
A new transparent bulk glass from the system 76TeO2?·?10ZnO?·?9.0PbO?·?1.0PbF2?·?3.0Na2O doped with Er3+ (TZPPN doped with Er3+) has been prepared using the conventional melt-quenching method. Results of differential thermal analysis (DTA) measurements indicate good thermal stability of this glass. The refractive indices at different wavelengths, the optical energy gap, the Sellmeier gap energy and the dispersion energy have been estimated. The Judd–Ofelt parameters, Ω t (t?=?2,?4,?6) of Er3+ were evaluated from optical absorption spectra. Electric dipole, magnetic dipole type transition probabilities, spectroscopic quality factors, branching ratio and radiative lifetimes of several excited states of Er3+ have been predicted using intensity Judd–Ofelt parameters. The spectroscopic properties indicate that TZPPN glass doped with Er3+ is a promising candidate for laser applications and may be suitable for upconversion fibre optical devices. 相似文献
85.
The synthesis of a new series of annulated thieno[2,3‐b]pyridines was performed. Ester compound 1 underwent heterocyclization upon reaction with phenylisothiocyanate and formamide to afford pyrimidines 2 and 3 , respectively. Thienopyrimidine 5 was resulted via reaction of amino derivative 1 with triethyl orthoformate to afford the non‐isolable intermediate 4 , which allowed hydrazinolysis with hydrazine hydrate to afford the target compound. Pyrimidine type 5 was condensed with p‐nitrobenzaldehyde to afford Schiff base 6 . Refluxing of ester 1 with ethyl cyanoacetate and diethyl malonate followed by base‐mediated heterocyclization afforded condensed pyridines 8 and 9 , respectively. The tetracyclic pyrazine derivative 14 was obtained from the reaction of amino compound 1 with 2,5‐dimethoxytetrahydrofuran followed by hydrazinolysis to give carbohydrazide 11 , which undergo diazotization followed by Curtius rearrangement. The antibacterial results illustrated no significant results for the investigated compounds except compound 5 , which has moderate activity against Gram‐positive bacteria. 相似文献
86.
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
87.
The study of γ‐neutrons attenuation and mechanical characteristics of modified concrete are vital and crucial parameters for the construction of civilian radiological, nuclear shielding, and/or shelters. In this work, fifteen samples of ordinary concretes with five different additives; steel fibers, polypropylene, silica fume, and fly ash, with variation of cement percentages, were prepared and used for performing the mechanical and radiation attenuation investigations. The compressive strength, tensile strength, slump test, bulk density, and water permeability were also carried out for the prepared concrete mixes. Collimated coherent beams from 60Co and Pu‐Be fast neutron sources were used to check the radiation penetrability through the syntheized mixed concrete‐additives. Very sensitive and well calibrated gamma‐neutron pulse shape discriminating spectrometer with its electronic componenets and stilbene organic detector and 3′′ × 3′′ NaI scintillation crystal was used to measure the radiation before and after attenuation and transmission. The integrated fast neutron removal macroscopic cross section (Σr) and linear attenuation coefficient of total gamma rays (μ) were calculated for all the analysed concrete mixes. The results of measurements, tests, analyses and calculations are given and explained. The investigated modified concrete mixes show good workability and properties from the view point of mechanical loads and γ‐fast neutrons penetrability and resistance. These results can be used for shielding and sheltering design. 相似文献
88.
El Sayed Moustafa Yasser B. Saddeek Essam R. Shaaban 《Journal of Physics and Chemistry of Solids》2008,69(9):2281-2287
Glasses with compositions 25Li2O-(75−x)Bi2O3-x B2O3, with 0?x?30 mol%, have been prepared using the melt quenching technique. The density and the molar volume have been determined. IR spectroscopy is used as a structural probe of the nearest neighbor environment in the glass network. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400-1100 nm. The values of the optical band gap Egopt for indirect transition and refractive index have been determined for 0?x?30 mol%. The average electronic polarizability of the oxide ion αo2− and the optical basicity have been estimated from the calculated values of the refractive indices. Variations in the different physical parameters such as the density, molar volume, optical band gap, refractive index, average electronic polarizability of the oxide ion and optical basicity with B2O3 content have been analyzed and discussed in terms of the changes in the glass structure. 相似文献
89.
Gholam Reza Gordani Reza ShojaRazavi Sayed Hamid Hashemi Ali Reza Nasr Isfahani 《Optics and Lasers in Engineering》2008,46(7):550-557
Laser surface alloying of an electroless plating Ni–P coatings on an Al-356 aluminium alloy was carried out using a 1-kW pulsed Nd:YAG laser. The microstructure, chemical composition and phase identification of the alloyed layer were determined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD), respectively. It was shown that laser surface treatment produced a relatively smooth, crack-free and hard surface layer. The hardness of the surface significantly increased due to the formation of the uniformly distributed fine Ni–Al intermetallic phases. The corrosion behaviour of the surface alloyed specimens in 3.5% NaCl solution at 23 °C was also determined by electrochemical techniques. The laser-alloyed surface showed an improved corrosion and pitting potential compared to the substrate as well as the plated Ni–P coating. 相似文献
90.
Glasses in the system TeO2/Nb2O5/ZnO/CdS were studied with respect to the density, molar volume, refractive index, polarizability, molar refraction, metallization and third order non-linear optical susceptibility. The third order non-linear optical susceptibilities, χ(3), were measured using degenerate four-wave mixing (DFWM). The addition of CdS to TeO2-based glasses leads to increasing refractive as well as the non-linear refractive indices. The largest measured value of the third order non-linear optical susceptibility was 7.8 × 10?13 esu and has been found in the 90TeO2 · 5Nb2O5 · 5ZnO · 0.4 CdS glass. The non-linear optical susceptibility increased with increasing CdS-concentration. In order to estimate the third order non-linear optical susceptibility, the theoretical model of Lines and the empirical equation of Miller were used. 相似文献