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- 저자 : M.S. Sheikh (검색결과 19 건)
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S. M. Abdelbasir,S. M. El-Sheikh,M.M. Rashad,D.A. Rayan 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.4
Cuprous oxide Cu2Onanopowders were purposefully synthesised from waste electric cables (WECs) via a simple precipitationroute at room temperature using lactose as a reducing agent. In this regard, dimethyl sulfoxide (DMSO) was first appliedas an organic solvent for the dissolution of the cable insulating materials. Several parameters were investigated during dissolutionof WECs such as dissolution temperature, time and solid/liquid ratio to determine the dissolution percentage of theinsulating materials in DMSO. The morphology and the optical properties of the formed Cu2Oparticles were investigatedusing X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopyand UV–visible–near IR spectrophotometer. XRD data confirmed the presence of single crystalline phase of Cu2Onanoparticles. FE-SEM and TEM images revealed spherical, cubic and octahedral shapes with the various particle sizesranged from 16 to 57 nm depending on the synthesis conditions. A possible mechanism explaining the Cu2Onanostructuresformation was proposed. The band gap energies of the Cu2Onanostructures were estimated and the values were locatedbetween 1.5 and 2.08 eV. Photoluminescence spectroscopy analysis clearly showed a noticeably blue-shifted emission forthe synthesized samples compared to spectrum of the bulk. Eventually, magnetic properties of the synthesized nanoparticleshave been measured by vibrating sample magnetometer and the attained results implied that the synthesized particles areweakly ferromagnetic in nature at normal temperature.
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Sheikh, F.A.,Barakat, N.A.M.,Kim, B.S.,Aryal, S.,Khil, M.S.,Kim, H.Y. Elsevier 2009 Materials Science and Engineering C Vol.29 No.3
In the present study, spherical nanoparticles (NPs) containing polyhedral oligosilsesquioxane (POSS) as an inner hydrophobic core and poly(vinyl alcohol) PVA as a hydrophilic outer shell were prepared by dialysis approach. Preparation of amphiphilic POSS-grafted-PVA co-polymer was characterized by <SUP>1</SUP>H NMR and FT-IR. The results indicated urethane linkage between monoisocyanate group of POSS macromer and the hydroxyl groups of PVA. The dynamic light scattering (DLS) and electrophoretic light scattering (ELS) of the NPs revealed that they have an average hydrodynamic diameter and negative zeta (ζ)-potential of 215 nm and -161 mV, respectively. Atomic force microscopy (AFM) and bio-transmission electron microscope (BIO-TEM) have shown unagglomerated NPs within a diameter range of 60-90 nm. The prepared NPs were investigated to improve the control release of anticancer drug; paclitaxel as a model drug. Due to drug loading, the hydrodynamic diameter and negative zeta (ζ)-potential have changed to 325 nm and -14 mV, respectively. In addition, in-vitro drug release experiments were conducted; the obtained results explicated continuous release for over 40 days. However, in case of using pure drug only, the drug completely released within 1 h.
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On stability and bifurcation of periodic solutions of delay differential equations
M. M. A. El-Sheikh,S. A. A. El-Mahrouf 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.19 No.1-2
The purpose of this paper is to study a class of delay differential equations with two delays. First, we consider the existence of periodic solutions for some delay differential equations. Second, we investigate the local stability of the zero solution of the equation by analyzing the corresponding characteristic equation of the linearized equation. The exponential stability of a perturbed delay differential system with a bounded lag is studied. Finally, by choosing one of the delays as a bifurcation parameter, we show that the equation exhibits Hopf and saddle-node bifurcations.
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ON STABILITY AND BIFURCATION OF PERIODIC SOLUTIONS OF DELAY DIFFERENTIAL EQUATIONS
EL-SHEIKH, M. M. A.,EL-MAHROUF, S. A. A. 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.19 No.1
The purpose of this paper is to study a class of delay differential equations with two delays. First, we consider the existence of periodic solutions for some delay differential equations. Second, we investigate the local stability of the zero solution of the equation by analyzing the corresponding characteristic equation of the linearized equation. The exponential stability of a perturbed delay differential system with a bounded lag is studied. Finally, by choosing one of the delays as a bifurcation parameter, we show that the equation exhibits Hopf and saddle-node bifurcations.
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Rasool Aatifa,Bhat K. M.,Mir M. A.,Sundouri A. S.,ALshamrani Salha Mesfer,Aloufi Abeer S.,El Moneim Diaa Abd,Mansoor Sheikh,정용석 한국식물생명공학회 2024 Plant biotechnology reports Vol.18 No.1
In recent years, there has been significant progress in enhancing the genetic foundation underlying important agricultural traits such as resistance to scab and the development of a columnar growth habit. V. inaequalis is a hemibiotrophic fungus widely distributed in temperate regions where apples are grown on commercial scale. The present investigation was undertaken to identify Vf gene and Co gene, which, respectively, confer resistance against apple scab disease and columnar phenotype in apple cultivar ‘Rosalie’ and introgression of both the genes in commercially important cultivar ‘Fuji’. Polymorphism sur- vey was carried out between the two parents using 22 simple sequence repeat (SSR) and sequence-characterized amplified region (SCAR) markers. The observations revealed that almost 50% hybrids fall in resistant category and 50% in susceptible category. The results of marker-assisted screening confirmed 38 F1s carrying resistance gene for scab while the remain- ing 32 F1 plants were found to be lacking the gene. The 38 genotypically scab-resistant hybrids were selected for further characterization as columnar and non-columnar plants. Based on the selection criteria, 21 individuals were categorized as columnar and the remaining 17 were categorized as non-columnar. The phenotypic screening was followed by screening of F1 s using molecular markers for Co gene. The amplification of Co-specific markers yielded columnar-specific fragments in the population and fitted the expected 1:1 Mendelian ratio. 18 scab-resistant F1 hybrids were found to carry Co gene and the remaining 20 did not possess the gene for columnar growth habit. Gene-specific primers identified in the present study can be directly used for screening large apple germplasm in a short period of time for developing resistant varieties against apple scab as well as varieties with columnar growth habit. Hybrids with verified scab resistance and columnar growth can be swiftly utilized as scab-resistant columnar cultivars.
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Gallium Arsenide (GaAs) Nanofibers by Electrospinning Technique as Future Energy Server Materials
Sheikh, Faheem A.,Barakat, Nasser A.M.,Kanjwal, Muzafar A.,Park, S.J.,Kim, Hern,Kim, Hak-Yong 한국섬유공학회 2010 FIBERS AND POLYMERS Vol.11 No.3
Gallium arsenide (GaAs) does have superior electronic properties compared with silicon. For instant, it has a higher saturated electron velocity and higher electron mobility. Weak mechanical properties and high production cost are the main drawbacks of this interesting semiconductor. In this study, we are introducing production of GaAs nanofibers by electrospinning methodology as a very low cost and yielding distinct product technique. In general, nano-fibrous shape is strongly improving the physical properties due to the high surface area to volume ratio of this nanostructure. The mechanical and environmental properties of the GaAs compound have been modified since GaAs nanofibers have been produced as a core inside a poly(vinyl alcohol) (PVA) shell. GaAs/PVA nanofibers were prepared by electrospinning of gallium nitrate/PVA solution in presence of arsenic vapor. The whole process was carried out in a closed hood equipped with nitrogen environment. FT-IR, XPS, TGA and UV-Vis spectroscopy analyses were utilized to confirm formation of GaAs compound. Transmission electron microscope (TEM) analysis has revealed that the synthesized GaAs compound is crystalline and does have nano-fibrous shape as a core inside PVA nanofibers. To precisely recommend the prepared GaAs nanofiber mats to be utilized in different applications, we have measured the electric conductivity and the band gap energies of the prepared nanofiber mats. Overall, the obtained results affirmed that the proposed strategy successfully remedied the drawbacks of the reported GaAs structures and did not affect the main physical properties of this important semiconductor.
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Axial compressive behaviour of circular CFFT: Experimental database and design-oriented model
Qasim S. Khan,M. Neaz Sheikh,Muhammad N.S. Hadi 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.4
Concrete Filled Fibre Reinforced Polymer Tube (CFFT) for new columns construction has attracted significant research attention in recent years. The CFFT acts as a formwork for new columns and a barrier to corrosion accelerating agents. It significantly increases both the strength capacity (Strength enhancement ratio) and the ductility (Strain enhancement ratio) of reinforced concrete columns. In this study, based on predefined selection criteria, experimental investigation results of 134 circular CFFT columns under axial compression have been compiled and analysed from 599 CFFT specimens available in the literature. It has been observed that actual confinement ratio (expressed as a function of material properties of fibres, diameter of CFFT and compressive strength of concrete) has significant influence on the strength and ductility of circular CFFT columns. Design oriented models have been proposed to compute the strength and strain enhancement ratios of circular CFFT columns. The proposed strength and strain enhancement ratio models have significantly reduced Average Absolute Error (AAE), Mean Square Error (MSE), Relative Standard Error of Estimate (RSEE) and Standard Deviation (SD) as compared to other available strength and strain enhancement ratios of circular CFFT column models. The predictions of the proposed strength and strain enhancement ratio models match well with the experimental strength and strain enhancement ratios investigation results in the compiled database.
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Qasim S. Khan,M. Neaz Sheikh,Muhammad N.S. Hadi 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.6
This research study investigates experimentally and analytically the axial compressive behaviour of Concrete Filled Fiber Reinforced Polymer Tube (CFFT) columns with and without Fiber Reinforced Polymer (FRP) bars. The experimental program comprises five circular columns of 204-206 mm outer diameter and 800-812 mm height. All columns were tested under concentric axial compressive loads. It was found that CFFT columns with and without FRP bars achieved higher peak axial compressive loads and corresponding axial deformations than conventional steel reinforced concrete (RC) column. The contribution of FRP bars was about 12.1% of the axial compressive loads carried by CFFT columns reinforced with FRP bars. Axial load-axial deformation (P ‒ δ) curves of CFFT columns were analytically constructed, which mapped well with the experimental P ‒ δ curves. Also, an equation was proposed to predict the axial compressive load capacity of CFFT columns with and without FRP bars, which adequately considers the contributions of the circumferential confinement provided by FRP tubes and lower ultimate strength of FRP bars in compression than in tension.
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