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Effect of Conductive Fillers on the Cyclic Stress-Strain and Nano-Scale Free Volume Properties of Silicone Rubber

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Chinese Journal of Polymer Science 2014年第5期32卷 558-567页

作者： M.H.Abd-el Salam S.el-Gamal M.Mohsen D.M.Abd el-Maqsoud Physics Department Faculty of Education Ain Shams University Physics Department Faculty of Science Ain Shams University

The effect of carbon black （CB） and graphite （G） powders on the macroscopic and nano-scale free volume properties of silicone rubber based on poly（di-methylsiloxane）（PDMS） was studied through thermal and cyclic mechanical measurements, as well as with positron annihilation lifetime spectroscopy （PALS）. The melting temperature of the composites （Tm） and the endothermic enthalpy of melting （ΔHm） were estimated by differential scanning calorimetry （DSC）. Tm and the degree of crystallinity （χc） of PDMS composites were found to decrease with increasing the CB content. This can be explained due to the increase in physical cross-linking which results in a decrease in the crystallite thickness. Besides, χc was found to be dependent on the filler type. Cyclic stress-strain behavior of PDMS loaded with different contents of filler has been studied. Mullins ratio （RM） was found to be dependent on the filler type and content. It was found that, RM increases with increasing the filler content due to the increase in physical cross-linking which results in a decrease in the size of free volume, as observed through a decrease of the o-Ps lifetime τ3 measured by PALS. Moreover, the hysteresis in PDMS-CB composites was more pronounced than in PDMS-G composites. Furthermore, a correlation was established between the free volume Vf and the mechanical properties of PDMS composites containing different fillers. A negative correlation was observed between Vf and RM.

关键词： Positron annihilation Positronium Free volume Si-rubber Composite Cyclic mechanical properties.

Calculation of photon shielding properties for some neutron shielding materials

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Nuclear Science and Techniques 2017年第5期28卷 74-80页

作者： A. M. el-Khayatt Physics Department College of Science Al Imam Mohammad Ibn Saud Islamic University (IMSIU) RiyadhSaudi Arabia Reactor Physics Department NRC Atomic Energy Authority 13759 Cairo Egypt

The objective of the present study is to calculate photon shielding parameters for seven polyethylene-based neutron shielding materials. The parameters include the effective atomic number(Z_(eff)), the effective electron density(N_(eff)) for photon interaction and photon energy absorption,and gamma-ray kerma coefficient(kc). The calculations of Z_(eff)are presented as a single-valued and are energy dependent. While Z_(eff)values were calculated via simplistic powerlaw method, the energy-dependent Z_(eff)for photon interaction(Z_(PI-eff)) and photon energy absorption(Z_(PEA-eff)) are obtained via the direct method for energy ranges of 1 keV–100 GeV and 1 keV–20 Me V, respectively. The kccoefficients are calculated by summing the contributions of the major partial photon interactions for energy range of 1 keV–100 MeV. In most cases, data are presented relative to pure polyethylene to allow direct comparison over a range of energy. The results show that combination of polyethylene with other elements such as lithium and aluminum leads to neutron shielding material with more ability to absorb neutron and crays. Also, the kerma coefficient first increases with Z of the additive element at low photon energies and then converges with pure polyethylene at energies greater than 100 keV.

关键词： Neutron shielding materials Effective atomic number Kerma coefficient c-rays

Hepatoprotective activity of Dypsis lutescens against D-galactosamine-induced hepatotoxicity in rats and its phytoconstituents

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Asian Pacific Journal of Tropical Biomedicine 2019年第11期9卷 467-473页

作者： Mai M.el-Ghonemy Walaa A.el-Kashak Tahia K.Mohamed Enayat A.Omara Jihan Hussein Abdel-Razik H.Farrag Mahmoud I.Nassar Mohamed y.el-Kady Chemistry of Natural Compounds Department National Research Centre33 El-Bohouth St.Dokki12622CairoEgypt Department of Pathology National Research Centre33 El Bohouth St.Dokki12622CairoEgypt Medical Biochemistry Department National Research Centre33 El Bohouth St.Dokki12622CairoEgypt Chemistry Department Faculty of ScienceAin Shams UniversityCairoEgypt

Objective:To isolate and identify the polyphenolic constituents of Dypsis lutescens,and evaluate the hepatoprotective activity of the ethanolic extract of Dypsis lutescens ***:Hepatoprotective,antioxidant and anti-inflammatory effects of two doses of Dypsis lutescens ethanolic leaf extract were investigated in five groups of six rats each administered with the ethanolic extract of Dypsis lutescens *** function parameters were assessed,histopathological study was carried out,the anti-inflammatory mediators and the antioxidant potential in the liver tissues were *** addition,the total ethanolic extract of Dypsis lutescens leaves was subjected to different chromatographic separation techniques to yield ten phenolic *** isolated compounds structures were spectroscopically ***:Hepatoprotective activity of Dypsis lutescens ethanolic extract was estimated for the first time and showed significant activity against histopathological changes induced by D-galactosamine in *** extract improved the liver *** to the D-galactosamine group,the architecture of the liver in the treated groups was improved in the histopathological *** results proved the hepatoprotective activity of Dypsis lutescens and its ability in attenuating liver oxidative damage and *** investigations of the total extract afforded ten compounds from the genus ***:The alcoholic extract of Dypsis lutescens exerted potential hepatoprotective action,maintaining liver health and functions.

关键词： Dypsis lutescens Flavonoid glycosides Phenolic acids Hepatoprotective Antioxidant Anti-inflammatory

Radionuclides measurements and mineralogical studies on beach sands, East Rosetta Estuary, Egypt

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Chinese Journal Of Geochemistry 2013年第2期32卷 146-156页

作者： Abd el Wahab M. el Nahas H.A. Physics Department Faculty of Women for Arts Science and Education Ain Shams University Cairo P.O 11757 Egypt Nuclear Materials Authority Cairo P.O. Box 530 Egypt

Radiometric measurements were carried out for the beach sands from East Rosetta estuary to determine the activity concentrations of 238 U, 226 Ra, 232 Th, and 40 K, using a Hyper Pure Germanium spectrometer, to estimate the dose rates and radiation hazard indices. The average specific activities are 778.20 Bq/kg for 238 U; 646.89 Bq/kg for 226 Ra; 621.92 and 627.85 Bq/kg for the 222 Rn daughters 214 Pb and 214 Bi respectively. The average specific activity of 232 Th is 1510.25 Bq/kg, while the calculated specific activity for 40 K has an average of 8.41 Bq/kg. The average specific activity of 235 U is 38.61 Bq/kg. The average absorbed dose rate is 1211.36 nGy/h, 20 times higher than the estimated average global primordial radiation of 60 nGy/h and 6 times higher than that of the world range (10-200 nGy/h). The radium equivalent (Ra eq ) values are from 6 to 9 times the recommended value. The internal and external hazard indices (H int , H ex ) indicate that their values are from 6 to 11 times the permissible values of these indices. These higher values may be due to the presence of economic heavy minerals containing radionuclides as zircon and monazite as well as some trace minerals, thorite and uranothorite. The mineralogical study indicates the beach sands contain heavy minerals, zircon, monazite, rutile, ilmenite, leucoxene, magnetite and garnet. The average abundance of zircon is 0.175 wt% ranging from 0.125 wt% to 0.239 wt%, while it is 0.004wt% ranging from 0.001 wt% to 0.007 wt% for monazite. The average abundance is 0.087 wt% for rutile; 2.029 wt% for ilmenite; 1.084 wt% for magnetite; 0.384 wt% for leucoxene and 0.295 wt% for garnet.

关键词：放射性核素海滩砂矿物学核素测量河口平均丰度埃及辐射测量

Use of genetic algorithm in new approach to modeling of flood routing

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Journal of Oceanology and Limnology 2019年第1期37卷 72-78页

作者： el ALAOUI el FelS Abdelhafid ALAA Noureddine BACHNOU Ali Laboratory of Geosciences and Environnement Department of Earth Sciences Faculty of Science and Technics Gueliz (P. B. 549) Cadi Ayyad University Laboratory Applied Mathematics and Informatics Department of Math and Informatics Faculty of Science and Technics Gueliz (P. B. 549) Cadi Ayyad University

The hydrological models and simpli?ed methods of Saint-venant equations are used extensively in hydrological modeling, in particular for the simulation of the ?ood routing. These models require speci?c and extensive data that usually makes the study of ?ood propagation an arduous practice. We present in this work a new model, based on a transfer function, this function is a function of parametric probability density, having a physical meaning with respect to the propagation of a hydrological signal. The inversion of the model is carried out by an optimization technique called Genetic Algorithm. It consists of evolving a population of parameters based primarily on genetic recombination operators and natural selection to?nd the minimum of an objective function that measures the distance between observed and simulated data. The precision of the simulations of the proposed model is compared with the response of the Hayami model and the applicability of the model is tested on a real case, the N'Fis basin river, located in the High Atlas Occidental, which presents elements that appear favorable to the study of the propagation. The results obtained are very satisfactory and the simulation of the proposed model is very close to the response of the Hayami model.

关键词： Genetic Algorithm flood routing Hayami model simulation propagation

Magnetocaloric Effect in Anisotropic Mixed Spin1/2–1 System: Pair Approximation Method

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Communications in Theoretical Physics 2019年第11期71卷 1370-1378页

作者： Abderrazak Boubekri Moulay youssef el Hafidi Mohamed el Hafidi Laboratory of Condensed Matter Physics Faculty of Sciences Ben M’sik Hassan II University of Casablanca

We use the Pair Approximation method to analyze the magnetic and magnetocaloric behaviors of diluted mixed spin SA=1 and spin SB=1/2 with the anisotropic Heisenberg model, on a cubic lattice with coordination number z=6. Our system is described in presence of an external magnetic field;the phase diagram and thermodynamic properties related to the concentration of magnetic atom(A or B) and the single ion anisotropy are constructed and *** attention is paid to magnetocaloric properties provided by isothermal entropy change as well as the cooling capacity. These cooling power keys are plotted and discussed as a function of interaction anisotropy and magnetic component concentration of two sublattices ions A and B. Numerical results show a double peak structure in the entropy change curve and the inverse magnetocaloric effect related to the presence of the negative single-ion anisotropy.

关键词： anisotropic Heisenberg model dilution entropy change mixed spin system inverse magnetocaloric effect pair approximation magnetic Gruneisen ratio

Implementing Effective Learning with Ubiquitous Learning Technology During Coronavirus Pandemic

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Computer Systems Science & Engineering 2022年第1期40卷 389-404页

作者： Hosam F.el-Sofany Samir A.el-Seoud King Khalid University AbhaKingdom of Saudi Arabia Cairo Higher Institute for Engineering Computer Science and ManagementCairoEgypt British University in Egypt—BUE Faculty of Informatics and Computer ScienceCairoEgypt

Ubiquitous computing supports U-learning to develop and implement a new educational environment that provides effective and interactive learning to students wherever they *** study aims to present a qualitative evaluation for using U-learning instead of traditional education to avoid the spread of the Coronavirus *** authors introduce a UTAUT(Unified Theory of Acceptance and Use of Technology)model to assess the capability of the given factors that are expected to affect the learners’intention and behavior for accepting the U-learning technology for full *** research study shows a promising impact on the use of U-learning apps for implementing their learning activities in both the present and coming *** study also presents the descriptive statistics that affect the students’answers by using U-learning while implementing learning assignments including exams,projects,forums,essays,presentations,and *** research experiments demonstrate both the composite reliability(CR)and the average variance extracted(AVE)of the presented *** experimental results have shown that(1)the factor loadings≥0.75,CR≥0.9,and AVE≥0.75,which present appropriate proof for the validity and reliability of the proposed model,and(2)the total average of students that accept the U-learning is 82.99%,and who disagree is 8.13%,while who neither agree nor disagree is 6.44%.

关键词： Ubiquitous learning U-learning E-learning M-learning COVID-19 pandemic coronavirus UTAUT model

Comparison between seismic analysis of twisting and regular 52-story towers considering soil-structure interaction

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Earthquake Engineering and Engineering Vibration 2024年第3期23卷 663-675页

作者： Mohamed Naguib Abouelsaad Mohammed Shaaban Salah el Bagalaty Mohamed E.el Madawy Structural Engineering Department Faculty of EngineeringMansura UniversityMansoura 35511Egypt Faculty of Engineering Delta University for Science and TechnologyGamasa 35712Egypt

A dynamic analysis of both twisting and regular towers is carried out to determine the results of considering soil-structure interaction(SSI)on high-rise *** addition,the difference between the seismic performance of using twisting towers over regular ones is *** twisting tower is a simulation of the Evolution Tower(Moscow).The towers’skeletons consist of RC elements and rest on a reinforced concrete piled-raft *** soil model is considered as multi-layered with the same soil properties as the zone chosen for the analysis(New Mansoura City,Egypt).The only difference between both towers is their shape in *** whole system is modelled and analyzed in a single step as one full 3D model,which is known as the direct approach in *** analyses are carried out using finite-element software(Midas GTS NX).Dynamic output responses due to three records of seismic loads are proposed and presented in some *** on the results,it is concluded that SSI has a considerable effect on the dynamic response of tall buildings mainly because of the foundation flexibility,as it leads to lengthening the vibration period,increasing the story drift and the base shear for both cases.

关键词： soil-structure interaction seismic analysis twisting towers base shear story drift finite element method Midas GTS NX

Synthesis and comparative study of reactivities of δ-lactone,estor group and oxazinone ring in coumarin derivatives towards carbon or nitrogen nucleophiles

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Chinese Journal of Chemistry 1990年第5期8卷 469-473页

作者： el-KAFRAWy,A.F. SOLIMAN,A.y. BAKER,H.M. MOHAMED,F.K. el-KADy,M.y.Department of Chemistry,Faculty of Science,Ain Shams University and Faculty of Education at el-Fayoum,Cairo.Egypt Department of Chemistry Faculty of Science Ain Shams University and Faculty of Education at El‐Fayoum Cairo Egypt

Condensation of methyl 7-methylcoumarin-4-acetate(2)with primary amines and with an- thranilic acid gave 7-methyl-2-oxo-N-aryl-2H-[1]-benzopyran-4--acetamide(4a—d)and(7),respectively. Compound 7 underwent cyclization to give 2-(7-methyl-2-oxo-2H-[1]-benzopyran-4-yl)-methyl-4H-3,1- benzoxazin-4-one(3).The reaction of 3 with aromatic amines gave the corresponding quinazolone derivatives 5 which tautomerises to the thermodynamically more stable isomer 6,whereas its reaction with Grignard reagents and aromatic aldehydes gave 8a,8b,and 9a,9b,respectively.

关键词： Synthesis and comparative study of reactivities of lactone,estor group and oxazinone ring in coumarin derivatives towards carbon or nitrogen nucleophiles ring