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Chinese Journal of Polymer Science 2008年第6期26卷 669-678页

作者： R.Rajasekaran C.Karikalchozhan m.Alagar Department of Chemistry St.Joseph's College of EngineeringChennai-600 119.India Department of Chemical Engineering Anna UniversityChennai-600 025India

Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (om-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (ommT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDm) as curing *** mechanical properties like tensile strength,tensile modulus,flexural strength,flexural modulus and impact properties of the nanocomposites were studied as per ASTm ***...

关键词： Nanocomposites Glass transition temperature Impact strength Interpenetrating networks (IPN) Polysulfone.

Effect of storage conditions on long-term stability of Ag nanoparticles formed via green synthesis

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International Journal of minerals,metallurgy and materials 2017年第10期24卷 1177-1182页

作者： Oksana Velgosova Elena Cizmarova jaroslav málek jana Kavulicova Institute of materials Faculty of Metallurgy Technical University of Kosice Letna 9 042 00 Kosice Slovakia Department of materials Engineering Faculty of Mechanical Engineering Czech Technical University in Prague Karlovo nám. 13 121 32 Prague 2 Czech Republic Institute of metallurgy Faculty of Metallurgy Technical University of Kosice Letna 9 042 00 Kosice Slovakia

Spherical Ag nanoparticles(AgNPs) with a diameter of 20 nm or smaller were biologically synthesized using algae Parachlorella kessleri. The effect of storage conditions on the long-term stability of AgNPs was investigated. UV/Vis spectrophotometry, transmission electron microscopy, and dynamic light scattering measurements revealed that the long-term stability of AgNPs was influenced by light and temperature conditions. The most significant loss of stability was observed for the AgNPs stored in daylight at room temperature. The AgNPs stored under these conditions began to lose their stability after approximately 30 d; after 100 d, a substantial amount of agglomerated particles settled to the bottom of the Erlenmeyer flask. The AgNPs stored in the dark at room temperature exhibited better long-term stability. Weak particle agglomeration began at approximately the 100 th day. The AgNPs stored in the dark at about 5℃ exhibited the best long-term stability; the AgNPs stored under such conditions remained spherical, with a narrow size distribution, and stable(no agglomeration) even after 6 months. Zeta-potential measurements confirmed better dispersity and stability of AgNPs stored under these conditions.

关键词： silver nanoparticles stability storage conditions green synthesis Parachlorella kessleri

Preliminary Study of a Hybrid Helicon-ECR Plasma Source

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Plasma Science and Technology 2016年第8期18卷 832-836页

作者： A.m.HALA L.OKSUZ ZHU Ximing The National Center for Applied Physics Material Science Research InstituteKing Abdul Aziz City for Science and Technology(KACST) Süleyman Demirel University Science and Literature FacultyPhysics Department Institute for Plasma and Atomic Physics Ruhr University

A new type of hybrid discharge is experimentally investigated in this work. A helicon source and an electron cyclotron resonance（ECR） source were combined to produce plasma. As a preliminary study of this type of plasma, the optical emission spectroscopy（OES） method was used to obtain values of electron temperature and density under a series of typical conditions. Generally,it was observed that the electron temperature decreases and the electron density increases as the pressure increased. When increasing the applied power at a certain pressure, the average electron density at certain positions in the discharge does not increase significantly possibly due to the high degree of neutral depletion. Electron temperature increased with power in the hybrid *** mechanisms of these preliminary observations are discussed.

关键词： helicon plasma ECR hybrid discharge

PVC nanocomposites for cable insulation with enhanced dielectric properties,partial discharge resistance and mechanical performance

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High Voltage 2020年第4期5卷 463-471页

作者： Nagat m.K.Abdel-Gawad Adel Z.El Dein Diaa-Eldin A.mansour Hanaa m.Ahmed mohamed m.F.Darwish matti Lehtonen Department of Electrical Power and machines Engineering Faculty of Engineering at ShoubraBenha UniversityCairoEgypt Department of High Voltage Networks Faculty of Energy EngineeringAswan UniversityAswanEgypt High Voltage and Superconductivity Laboratory Department of Electrical Power and Machines EngineeringFaculty of EngineeringTanta UniversityTantaEgypt Department of mathematics and Engineering Physics Faculty of Engineering at ShoubraBenha UniversityCairoEgypt Department of Electrical Engineering and Automation School of Electrical EngineeringAalto UniversityEspooFinland

The current study aims to develop polyvinyl chloride(PVC)nanocomposites with enhanced electrical and mechanical properties by incorporating titanium oxide(TiO_(2))nanoparticles within PVC *** loading of nanoparticles and different nanoparticle surface states were *** surface states are unfunctionalised,functionalised using vinyl silane and functionalised using amino *** choice of a most suitable surface state was a critical factor that guarantees a good dispersion of nanoparticles and consequently enhances the compatibility between TiO_(2)and PVC *** process followed in the PVC/TiO_(2)nanocomposites preparation,loaded with different wt.%of TiO_(2)nanoparticles,was the solvent *** dielectric properties measured here were the relative permittivity(ɛr),dielectric loss(tanδ),breakdown strength(AC and DC under uniform field)and the internal partial discharges(PDs)within insulation *** measurements have been performed under room temperature and at frequency ranged from 20 to 1.0 ***,the mechanical properties of the samples like elongation,elasticity modulus and tensile strength were also *** silane showed better improvements in both electrical and mechanical performances compared to the amino silane,especially in cases of high weight fractions of TiO_(2).This is because of the improvement in the PVC-TiO_(2)interfacial region arise from the similarity of polarity and surface tension values of vinyl silane with that of PVC matrix and TiO_(2)nanoparticles.

关键词： dielectric insulation resistance

Some novel integration techniques to explore the conformable m-fractional Schrödinger-Hirota equation

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Journal of Ocean Engineering and Science 2022年第4期7卷 337-344页

作者： Asim Zafar m.Raheel m.Asif Kamyar Hosseini mohammad mirzazadeh Lanre Akinyemi Department of mathematics COMSATS University IslamabadVehari CampusPakistan Department of mathematics and Statistics ISP MultanPakistan Department of mathematics Rasht BranchIslamic Azad UniversityRashtIran Department of Engineering Sciences Faculty of Technology and EngineeringEast of GuilanUniversity of GuilanVajargah P.C.44891-63157RudsarIran Department of mathematics Lafayette CollegeEastonPAUSA

The current study deals with exact soliton solutions for Schrödinger-Hirota(SH)equation via two modi-fied integration *** methods are known as the improved(G/G)-expansion method and the Kudryashov *** model is a generalized version of the nonlinear Schrödinger(NLS)equation with higher order dispersion and cubic *** can be considered as a more accurate approximation than the NLS equation in explaining wave propagation in the ocean and optical fibers.A novel deriva-tive operator named as the conformable truncated m-fractional is used to study the above mentioned *** obtained results can be used in describing the Schrödinger-Hirota equation in some better *** the obtained results are verified through symbolic computational ***,the ob-tained results show that the suggested approaches have broaden capacity to secure some new soliton type solutions for the fractional differential equations in an effective *** the end,the results are also explained through their graphical representations.

关键词： Shrödinger-Hirota equation Truncated m-fractional derivative Soliton solutions

Simultaneous approximation of a function and its derivatives by Sobolev polynomials: Applications in satellite geodesy and precise orbit determination for LEO CubeSats

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Geodesy and Geodynamics 2020年第5期11卷 376-390页

作者： m.Kiani Graduated from Department of Geodesy School of Surveying and Geospatial Data EngineeringUniversity of TehranTehranIran

The objectives of this paper are twofold:(1) to present a new method of approximation such that the function and some of its derivatives are simultaneously approximated;and(2) to investigate the potential applications of this new method in the field of satellite geodesy by deriving a numerical solver of ordinary differential equations. To fulfill both the objectives, Sobolev polynomials are used. Explicit formulas for these polynomials are presented. A quadrature rule is derived based on the explicit forms of these polynomials. Solution of first order ordinary differential equations is presented based on the numerical integration method by the new quadrature rule. To present the applications of the results, three problems are investigated in the field of satellite geodesy. In the first application, orbit propagated by the numerical solution of orbital equations is compared with the Keplerian motion. It is shown that the new method for solving ordinary differential equations can be used alongside any other method, including the adaptive Runge-Kutta and Adams-Bashforth-moulton integration methods. The comparison of this new method with the adaptive Runge-Kutta, Adams-Bashforth-moulton, and the powerful and newly established adaptive Gaussian numerical integration methods reveals that it is at least 580, 666667, and72 times more accurate than the mentioned methods, respectively, in any given absolute tolerance and time increment. The method is fast, stable, consistent, and capable of handling high accuracy, even with large time increment and low absolute tolerance, which is shown in this application. In the second application, the Gravity Recovery and Climate Experiment(GRACE) satellites’ orbits are propagated using both the Ensemble Kalman Filter(EnKF) with stochastic updates and smoothing for the position and the Sobolev numerical integration. The orbits are then compared with the observed positions of the satellites. It is shown that the Sobolev polynomials work bet

关键词： numerical approximation ordinary

Antibiotic Resistance Profile of Enterococcus faecalis and Enterococcus faecium Isolates from Urine and Pleural Fluid in Two Hospitals of Cameroon

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Open Journal of medical microbiology 2024年第1期14卷 39-49页

作者： Cécile Ingrid Djuikoue Farid Wega Grace Yemina Kombeu Cedric Seugnou Nana Christiane Possi Kiyang Lussabella Pohoko medzam Erica megane Noubissi makougoum Nellie mbianga Nkuigoua Herman Koyouo Tagne mérimé Joël Tchinda Talokou Yvonne Valérie Yolande mavoungou Ashu michel Agbor microbiology Department of the Faculty of Health Sciences of the Université des montagnes Bangangté Cameroon Faculty of medicine and Pharmaceutical Sciences University of Douala Douala Cameroon microbiology Department of the Faculty of Health Sciences of Institut Universitaire du Golf de Guinée Douala Cameroon Centre Hospitalier Dominicain St martin de Porres Yaoundé Cameroun Faculté des Sciences de la Santé Université Marien Ngouabi Brazzaville République du Congo

Enterococcus faecalis and Enterococcus faecium rank among the leading causes of nosocomial bacteremia and urinary tract infections. They often persist on hospital surfaces due to their ability to withstand adverse environmental conditions (low or high temperatures, high pH, and high salinity). The global Enterococcus faecalis-Enterococcus faecium ratio is currently shifting towards Enterococcus faecium. Enterococci present variable levels of resistance to certain families of antibiotics. This is the case for aminoglycosides, beta-lactams and cephalosporins. In 2017, WHO ranked Enterococci among priority pathogens for research and development of new antibiotics. The objective of our study was to determine the antibiotic resistance profile of Enterococcus faecalis and Enterococcus faecium isolates from urine and pleural fluid in two hospitals in Cameroon. This cross-sectional and analytic study was carried out between June to August 2023 on hospitalized and day patients in which a cytobacteriological test of urine and pleural fluid was done. The samples were inoculated on CLED Agar for urine and on Chocolate + polyvitex and blood agar (prepared from Columbia agar) for pleural fluid samples and incubated at 37℃ for 18 to 24 hours. Identification of isolates was carried out using the API 20 STREP micro gallery (Biomerieux, France) and tested for antimicrobial susceptibility. The data on socio-demographical and potential risk factors were recorded using self-administered questionnaires and data from laboratory analyses of the specimen were collected in a data capture sheet. Potential risk factors associated with the presence of Enterococci, were evaluated using the logistic regression in univariate and multivariate analysis. P value minantly females. Enterococcus spp were isolated in 27.79% of our samples with Enterococcus faecalis mostly encountered. Enterococcus spp showed a high

关键词： Enterococcus faecalis Enterococcus faecium Healthcare-Associated Infections Antimicrobial Resistance Cameroon

Chemically reactive and radiative von Kármán swirling flow due to a rotating disk

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Applied mathematics and mechanics(English Edition) 2018年第9期39卷 1295-1310页

作者： m.KHAN J.AHmED L.AHmAD Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan Department of mathematics Shaheed Benazir Bhutto UniversitySheringal Upper Dir 18000Pakistan

A new mathematical model is presented to study the heat and mass transfer characteristics of magnetohydrodynamic(mHD) maxwell fluid flow over a convectively heated stretchable rotating disk. To regulate the fluid temperature at the surface, a simple isothermal model of homogeneous-heterogeneous reactions is employed. The impact of nonlinear thermal radiative heat flux on thermal transport features is studied. The transformed nonlinear system of ordinary differential equations is solved numerically with an efficient method, namely, the Runge-Kutta-Felberg fourth-order and fifth-order(RKF45)integration scheme using the mAPLE software. Achieved results are validated with previous studies in an excellent way. major outcomes reveal that the magnetic flux reduces the velocity components in the radial, angular, and axial directions, and enhances the fluid temperature. Also, the presence of radiative heat flux is to raise the temperature of fluid. Further, the strength of homogeneous-heterogeneous reactions is useful to diminish the concentration of reaction.

关键词： rotating stretchable disk magnetic field nonlinear radiative heat flux homogeneous-heterogeneous chemical reaction

Annealing Effects on the Structural, Optical, and UV Photoresponse Properties of ZnO Nanostructures Prepared by RF-magnetron Sputtering at Different Deposition Temperatures

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Acta metallurgica Sinica(English Letters) 2015年第2期28卷 230-242页

作者： Husam S.Al-Salman m.J.Abdullah School of Physics University Sains Malaysia Department of Physics College of Science University of Basrah

Undoped ZnO nanostructures were deposited on SiO2/Si substrates via radio 11：equency magnetron sputtenng at different deposition temperatures （room temperature, 200, 300, and 400 ℃）. The prepared samples were annealed at 500 ℃ for 2 h under an N2 flow. The structural, surface morphological, optical, and photoresponse characteristics of ZnO nanostructures as deposited and after annealing were then investigated. The energy bandgaps of all samples after annealing （3.22-3.28 eV） decreased compared with those of the as-deposited specimens. The barrier height increased when the deposition temperature increased and reached 0.77 eV at 400 ℃ after annealing with a leakage current of 0.17 gA at a 5 V bias. The UV photodetector device which was deposited at the optimal temperature of 300 ℃, has 12.51 × 10^3% pho- tosensitivity, 2.259 pA dark current, 0.508 s response time, and 0.466 s recovery time. The dark current significantly decreased for all samples after annealing. The proposed UV photodetectors exhibit high performance, high photosensi- tivity, shorter response and recovery times, and excellent stability at lower bias voltages of 5 and 2 V.

关键词： Undoped ZnO UV photoresponse Deposition temperatures Annealing effect

A cavitation aggressiveness index within the Reynolds averaged Navier Stokes methodology for cavitating flows

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Journal of Hydrodynamics 2015年第4期27卷 579-586页

作者： KOUKOUVINIS P. BERGELES G. GAVAISES m. Department of Engineering and mathematical Science City University London

The paper proposes a methodology within the Reynolds averaged Navier Stokes（RANS） solvers for cavitating flows capable of predicting the flow regions of bubble collapse and the potential aggressiveness to material damage. An aggressiveness index is introduced, called cavitation aggressiveness index（CAI） based on the total derivative of pressure which identifies surface areas exposed to bubble collapses, the index is tested in two known cases documented in the open literature and seems to identify regions of potential cavitation damage.

关键词： cavitation aggressiveness index(CAI) cavitation erosion multiphase cavitating flows