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Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiberreinforced concrete railway sleepers

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Frontiers of Structural and Civil Engineering 2023年第3期17卷 411-428页

作者： sayed AHMED Hossam ATEF mohamed HUSAIN Department of Structural Engineering Faculty of EngineeringZagazig UniversityZagazig 44519Egypt Track Work Department National Authority for TunnelsCairo 11522Egypt

In this study,ultrahigh-performance fiber-reinforced concrete(UHPFRC)used in a type B70 concrete sleeper is investigated experimentally and *** main parameters investigated are the steel fiber volume fractions(0%,0.5%,1%,and 1.5%).Under European standards,35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections,and the screw on the fastening system is pulled *** first cracking load,failure load,failure mode,crack propagation,load–deflection curve,load–crack width,and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete *** accuracy of the parametric study is verified ***,the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their *** and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is *** manufactured using UHPFRC with a steel fiber volume fraction of 1%and a concrete volume less than 25%that of standard sleeper B70 can be used under the same loads and requirements,which contributes positively to the cost and surrounding environment.

关键词： pre-stressed concrete sleeper ultrahigh performance fiber-reinforced concrete pull-out test static bending test steel fiber aspect ratio volume fraction

Seismic performance of high-rise buildings in selected regions in Saudi Arabia according to different seismic codes

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Earthquake Engineering and Engineering Vibration 2021年第1期20卷 179-191页

作者： sayed Mahmoud mohamed Alsearheed Waleed Abdallah Department of Civil and Construction Engineering College of EngineeringImam Abdulrahman Bin Faisal UniversitySaudi Arabia Department of Building Engineering College of ArchitectureImam Abdulrahman Bin Faisal UniversitySaudi Arabia Department of Civil Engineering College of Engineering at MatariaHelwan UniversityCairoEgypt

The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order to provide more realistic considerations of seismic demand,seismic response,and seismic *** on the aforementioned provisions,structures designed according to different seismic codes may yield different performances for the same level of *** study aims to investigate and compare the induced responses related to the earthquake-resistant design of reinforced concrete(RC)buildings according to the Saudi building code(SBC-301),American code(ASCE-7),uniform building code(UBC-97),and European code(EC-8).In order to account for the provision regarding the hazard specification and its effect on the induced seismic responses,four regions in the Kingdom of Saudi Arabia with different seismic levels are *** code provisions related to the specification of site classification and its effect on the induced design base shear are investigated as *** differences are observed in the induced responses with the variation in seismic design codes for the considered seismic hazards and site classifications.

关键词： high-rise building SBC-301 international seismic codes seismic zones site classifications

Effects of Nickel Distribution on the Strengthening and Toughening of Alumina Ceramics

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Journal of Materials Science & Technology 2008年第5期24卷 723-728页

作者： mohamed.M.El-sayed Seleman Department of Materials and Metallurgical Eng. Faculty of Petroleum and Mining Eng.Post Code 43721SuezEgypt

Three types of composite materials were designed and fabricated by hot pressing powder blends of alumina with 20 vol. pct nickel particles. The composites differ in the shape, size and distribution of the nickel particles. Composite microstructures are described and measurements of density, hardness, flexure strength, and fracture toughness are reported. The results showed that the fracture strength of the composite with dispersed nickel particles is higher than the other two composites （network microstructure and mixed microstructure） and the alumina matrix. For all the composites studied, tougher materials than the monolithic alumina were produced. The fracture toughness of the composite with a network microstructure is much higher than that of the other composites. The toughening mechanisms were described based on the observation of the fracture surfaces and the crack-particle interactions. Moreover, the parameters for microstructural tailoring of these materials have been deduced. The toughening of the produced composites was explained in light of the interracial bond strength.

关键词： Alumina-nickel composites Nickel morphology Interfacial bonding Fracturetoughness Flexure strength

Processing of Ceramic Based Nanocomposite Usingα-Al_2O_3 Powder and FeCl_2 Solution as Starting Materials

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Journal of Materials Science & Technology 2007年第6期23卷 837-842页

作者： mohamed M.EL-sayed Seleman Department of Materials and Metallurgical Engineering Faculty of Petroleum and Mining EngineeringPost Code 43721SuezEgypt

Alumina-iron nanocomposite powders were prepared by a two-step process. In the first step, α-Al2O3-FeCl2 powder mixture was formed by mixing α-Al2O3 powders with FeCl2 solution followed by drying. In the second step, the FeCl2 in the dry power mixture was selectively reduced to iron particles. A reduction temperature of 750℃ for 15 min in dry H2 was chosen based on the thermodynamic calculations. The concentration of iron in FeCl2 solution was calculated to be 20 vol. pct in the final composite. Two techniques were used to produce composite bulk materials. The Al2O3 nanocomposite powders were divided to two batches. The first batch of the produced mixture was hot pressed at 1400℃ and 27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface bonding and mechanical properties of the composite, the second batch was heat treated in air at 700℃ for 20 min to partially oxidize the iron particles before hot pressing. Characterization of the composites was undertaken by conventional density measurements, X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electron probe micro analysis （EPMA）. The suggested processing route （mixing, reduction and hot pressing） produces ceramic-metal nanocomposite much tougher than the pure Al2O3. The fracture strength of the produced Al2O3/Fe nanocomposite is nearly twice that of the pure Al2O3. The presence of spinel phase, FeAl204, as thick layer around the Fe particles in the Al2O3 matrix has a detrimental effect on interfacial bonding between Fe and AI203 and the fracture properties of the composite.

关键词： Ferrous chloride Reduction Alumina-iron nanocomposite Spinel phase

Position Control of Synchronous Motor Drive by Modified Adaptive Two-phase Sliding Mode Controller

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International Journal of Automation and computing 2008年第4期5卷 406-412页

作者： mohamed Said sayed Ahmed Automation Science and Electrical Engineering School Beijing University of Aeronautics and Astronautics

A modified adaptive two-phase sliding mode controller for the synchronous motor drive that is highly robust to uncertain- ties and external disturbances is proposed in this *** proposed controller uses two-phase sliding mode control (SMC) where the 1st phase mainly controls the system in steady states and disturbed states-it is a smoothing *** 2nd phase is used mainly in the case of disturbed ***,it is an autotuning phase and uses a simple adaptive algorithm to tune the gain of conventional variable structure control (VSC).The modified controller is useful in position control of a permanent magnet synchronous drive.

关键词： Reaching law adaptive control sliding mode control (SMC) chattering.

Microstructure and mechanical properties of hot extruded 6016 aluminum alloy/graphite composites

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Journal of Materials Science & Technology 2018年第9期34卷 1580-1591页

作者： mohamed M.El-sayed Seleman mohamed M.Z.Ahmed Sabbah Ataya Department of Metallurgical and Materials Engineering Faculty of Petroleum and Mining Engineering Suez University 43518 Suez Egypt Suez and Sinai Metallurgical and Materials Research Center of Scientific Excellence (SSMMR-CSE) 43518 Suez Egypt The British University in Egypt Mechanical Engineering Deportment El-Sherouk City 11837 Cairo Egypt Department of Mechanical Engineering College of Engineering AI Imam Mohammad Ibn Saud Islamic University Riyadh 11432 saudi Arabia

The incorporation of graphite particles into AA6016 aluminum alloy matrix to fabricate metal/ceramic composites is still a great challenge and various parameters should be considered. In this study, dense AA6016 aluminum alloy/（0-20 wt%） graphite composites have successfully been fabricated by powder metallurgy process. At first, the mixed aluminum and graphite powders were cold compacted at 200 MPa and then sintered at 500 ℃ for 1 h followed by hot extrusion at 450 ℃. The influence of ceramic phases（free graphite and in-situ formed carbides） on microstructure, physical and mechanical properties of the produced composites were finally investigated. The results show that the fabricated composites have a relative density of over 98%. SEM observations indicate that the graphite has a good dispersion in the alloy matrix even at high graphite content. Hardness of all the produced composites was higher than that of aluminum alloy matrix. No cracks were observed at strain less than 23% for all hot extruded *** strength, reduction in height, ultimate tensile stress, fracture stress, yield stress, and fracture strain of all Al/graphite composites were determined by high precision second order equations. Both compressive and ultimate tensile strengths have been correlated to microstructure constituents with focusing on the in-situ formed ceramic phases, silicon carbide（SiC） and aluminum carbide（Al4 C3）. The ductile fracture mode of the produced composites became less dominant with increasing free graphite content and in-situ formed carbides. Wear resistance of Al/graphite composites was increased with increasing graphite content. Aluminum/20 wt% graphite composite exhibited superior wear resistance over that of AA6016 aluminum alloy.

关键词： AA6016/graphite composites Hot extrusion In-situ carbides Mechanical properties Wear resistance Fracture behavior

Cuticular hydrocarbons in two parapatric species of ants and their hybrid

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Integrative Zoology 2011年第3期6卷 259-265页

作者： mohamed EL-SHEHABY mohamed sayed SALAMA Elisabeth BRUNNER Jürgen HEINZE Biologie I University of RegensburgRegensburgGermany Department of Entomology Ain Shams UniversityCairoEgypt

Discrimination between nestmates and non-nestmates in social insects is thought to rely on the pattern of cuticular *** investigated the cuticular hydrocarbon profiles of 2 parapatric sibling ant species,Temnothorax nylanderi(Förster,1850)and Temnothorax crassispinus(Karavaiev,1926),and their *** found that although the profiles show considerable similarities,a discriminant analysis based on the relative peak areas of cuticular hydrocarbons separates the 3 *** profiles of hybrids were not consistently intermediate between those of the paternal species,suggesting either non-additive interactions among the parental biosynthetic pathways or systematic differ-ences in environment-derived odor cues.

关键词： colony odor cuticular hydrocarbons hybridization Temnothorax

Toxoplasma gondii infection can induce retinal DNA damage: an experimental study

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International Journal of Ophthalmology(English edition) 2014年第3期7卷 431-436页

作者： Nagwa Mostafa El-sayed Eman mohamed Aly Department of Medical Parasitology Research Institute of Ophthalmology Department of Basic Science Biophysics and Laser Science Unit Research Institute of Ophthalmology

AIM:To detect whether Toxoplasma gondii(***)infection of mice can induce retinal DNA ***:A total of 20 laboratory-bred male Swiss albino mice were used and divided into four groups:control group(non-infected animals);*** infected group;immunosuppressed infected group;and infected group treated with sulfadiazine and *** eyes were collected 6wk post infection and retinas were *** retina was immediately processed for comet assay and the frequency of tailed nuclei(DNA damage)was *** addition,retinal DNA damage was revealed by various comet assay parameters that were provided by the image analysis software including tail length,percentage of DNA in the tail,percentage of tailed cells and tail ***:The obtained results showed that *** infection induced a statistically significant increase in the frequency of tailed nuclei,tail length,percentage of DNA in the tail,and tail moment in mice retinal cells compared to the control group(which showed some degree of DNA damage).In immunosuppressed infected group,retinal DNA damage was severing and there was significant increase in various comet assay parameters compared to both control and infected *** treatment with sulfadiazine and pyrimethamine,retinal DNA damage decreased and all comet assay parameters showed a statistical significant decrease compared to infected ***:*** infection can induce DNA damage in mice retinal cells.

关键词： Toxoplasma gondii retinochoroiditis DNA damage comet assay

Co-combustion of RDF and biomass mixture with bituminous coal:a case study of clinker production plant in Egypt

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Waste Disposal and Sustainable Energy 2021年第4期3卷 257-266页

作者： Osayed sayed mohamed Abu‑Elyazeed mohamed Nofal Khalaf Ibrahim Junfeng Yang Mechanical Power Engineering Department Faculty of EngineeringMatariaHelwan UniversityMasaken El-HelmiyaP.O.11718CairoEgypt School of Mechanical Engineering University of LeedsLeeds LS29JTUK

Cement clinker production in Egypt till 2013 relied mainly on fossil fuel as a primary energy ***,with multiple fossil fuel shortages,the utilization of biomass wastes was initiated by multiple cement *** the current work,and to present an industrial-scale biomass and coal co-combustion study,the utilization of multiple biomass fuels to substitute a portion of bituminous coal was studied in an Egyptian clinker production *** of biomass fuels were used to reduce the consumption of bituminous coal and to investigate the diminishing of the environmental impact of the clinker production *** current study was conducted during 8 days of the stable clinker production process by replacing 14%of bituminous coal with biomass mixtures while monitoring the major process control parameters and resulting *** results were compared to the nation’s regulations.A conclusion can be made that using biomass mixtures as alternative fuels minimized the dependency on coal as the main fuel and reduced the CO_(2)burden of the cement produc-tion *** addition,NO_(x)and SO_(2)emissions were declined while CO emissions were increased by utilizing biomass mixtures as alternative fuels;all emissions,however,were below the allowable limits stated by the Egyptian environmental ***,the heavy elements,dioxins,and furans were not changed significantly compared to those produced using coal only.

关键词： Refuse derived fuel Biomass Co-Combustion Clinker