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Effect of cooling rate and composition on microstructure and mechanical properties of ultrahigh-strength steels

Journal of Iron and Steel Research International 2019年第12期26卷 1350-1365页

作者： Mohammed Ali David Porter Jukka Komi Mamdouh Eissa Hoda El Faramawy taha mattar Materials and Mechanical Engineering Centre for Advanced Steels ResearchUniversity of OuluOulu 90014Finland Steel Technology Department Central Metallurgical Research and Development InstituteHelwanCairo 11421Egypt

The influence of cooling rate on the microstructure and mechanical properties of two new ultrahigh-strength steels(UHSSs)with different levels of C,Cr and Ni has been evaluated for the as-cooled and untempered *** UHSS had higher contents of C and Cr,while the other one had a higher Ni *** the basis of dilatation curves,microstructures,macrohardness and microhardness,continuous cooling transformation diagrams were constructed as a guide to heat treatment *** rates(CRs)of 60,1 and 0.01°C/s were selected for more detailed *** characterization was made by laser scanning confocal microscopy,field emission scanning electron microscopy combined with electron backscatter diffraction,electron probe microanalysis and X-ray *** properties were characterized using macrohardness,tensile and Charpy V-notch impact *** with the higher C and Cr contents showed lower transformation temperatures and slower bainite formation kinetics than that with the higher Ni *** cooling rates led to lower volume fractions and carbon contents of retained austenite together with finer prior austenite grain size,as well as effective final grain size and lath *** changes were accompanied by higher yield and tensile *** best combinations of strength and toughness were obtained with martensitic microstructures and by avoiding the formation of granular bainite accompanied by proeutectoid carbides at low *** the cooling rates studied,UHSS with the higher C and Cr contents showed the higher hardness and strength but at the cost of toughness.

关键词： Ultrahigh-strength steel Electroslag remelting Continuous cooling transformation diagram Microstructure feature Mechanical property

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Effect of Tempcore Processing on Mitigating Problems of Tramp Elements in Low C Steel Produced from Recycled Material

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Journal of Iron and Steel Research International 2015年第7期22卷 582-589页

作者： Ahmed RAMADAN A.Y.SHASH I.S.EL-MAHALLAWI D.SENK taha mattar Quality Department Faculty of Engineering Cairo University Institute of Ferrous Metallurgy RWTH-Aachen University Central Metallurgical Research and Development Institute

The effect of tramp elements in the steel was intensively studied. It was found that the solubility of tramp elements decreased as the temperature decreased under normal cooling conditions. The tramp elements （Cu, Pb, and Sn） diffused toward the grain boundaries, and intermetallic compounds or rich phases which have low melting points were formed, causing reduction in ductility and failure during the bending test. Rebars with Cu content which were left to air cooling after the last step showed drop in elongation, up to 32 %. On contrast, the samples with high per- centage of tramp elements （Cu, Pb, and Sn） in the billet, which were rolled and subjected to Tempcore process, did not show drop in elongation or failure in bending test （especially for rebar with diameter less than 32 mm）; however, copper must be less than 0.35 mass% to prevent the precipitation of Cu-rich zones of critical size in 32 mm. When quench- ing was applied, the tramp elements remained in the interstitial supersaturated solid solution positions inside the grains and would not have the chance to diffuse and form precipitates, hindering the copper precipitates from reac- hing the critical size necessary for impairing the properties. This would hinder the occurrence of the harmful effect of the tramp elements on the elongation or the hot shortness after rolling.

关键词： recycled steel hot shortness crack susceptibility Tempcore process tramp element residual melt

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Validation of Calculated Thermal Parameters with Experimental Results in SOFCs

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Journal of Minerals and Materials Characterization and Engineering 2018年第2期6卷 193-202页

作者： Saeed Ghali Azza Ahmed taha mattar Steel Technology Department Central Metallurgical Research & Development Institute (CMRDI) Cairo Egypt

Eleven steel grades were designed to be used as metallic interconnects for Solid Oxide Fuel Cells (SOFC). Low carbon, high chromium steel with different additives of niobium, vanadium, aluminum, molybdenum, silicon, manganese and titanium were produced. Phase transformation temperatures;eutectoid temperature (Ac1) and temperature at which transformation of ferrite to austenite is completed during heating (Ac3) were measured by L75-76 dilatometer. The influence of the alloying elements on transformation temperatures was analyzed using MATLab. Considering the interaction between different alloying elements two equations for predicting Ac1 & Ac3 were obtained. The obtained Ac1 & Ac3 by these equations showed more compatibility than that obtained by traditional ones. In addition, the coefficients of thermal expansion of these steel grades were detected. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed;the obtained equations were verified to certain extent by using several kinds of steels. The predicted values were in good accordance with the experimental results which proof the validation of calculation model.

关键词： Transformation Temperature Thermal Expansion Coefficient SOFCs Steel Matlab

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Electroslag Refining of CrNiMoWMnV Ultrahigh-Strength Steel

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Journal of Minerals and Materials Characterization and Engineering 2017年第6期5卷 385-407页

作者： Mohammed Ali Mamdouh Eissa Hoda El Faramawy David Porter Jukka Kö mi M. F. El-Shahat taha mattar Materials Engineering and Production Technology University of Oulu Oulu Finland Steel Technology Department Central Metallurgical Research and Development Institute Cairo Egypt Chemistry Department Ain Shams University Cairo Egypt

Increasing demands for ultrahigh-strength steels in commercial as well as military applications have raised interest in finding alternatives to the high-cost high-alloyed steel and super-alloys currently used, e.g. the use of economic low-alloy compositions processed via low-cost air induction melting and electroslag refining (ESR). In this work the yield of alloying elements and the removal of the impurities nitrogen, sulphur and phosphorus as a result of electroslag refining (ESR) in a newly developed CrNiMoWMnV ultrahigh-strength steel (UHSS) have been studied in relation to their activities in the molten metal pool. Six experimental heats of CrNiMoWMnV UHSS with different chemical compositions were designed, melted in an induction furnace (IF) and refined using ESR. This was followed by hot forging of the ingots at 1100°C to 950°C. ESR using a CaF2-CaO-Al2O3 slag system led to a high yield in Cr, Ni, Mo, W, Mn and V, while the yield of Si is low. The desulphurization of all six UHSS grades was pronounced with most of the sulphur removed either to the slag or by gas reactions. The degree of dephosphorization was only 5% irrespective of the steel composition. On the other hand, denitrification (removal of nitrogen) was achieved. It ranged from 8% to 63% depending on the steel composition. The yield of the alloying elements and removal of impurities from the steel during ESR depends on the chemical and physical properties of the ESR slag and the activity of the elements in the molten state, taking into account elemental interactions.

关键词： Ultrahigh-Strength Steel Electroslag Refining Alloying Elements Impurities Activity

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Biomarker bust:meta-analyses reveal unreliability of neuronal extracellular vesicles for diagnosing parkinsonian disorders

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Neural Regeneration Research 2025年第1期20卷 201-202页

作者： Hash Brown taha Leonard Davis School of Gerontology University of Southern CaliforniaLos AngelesCAUSA

A range of neurodegenerative disorders,collectively termed parkinsonian disorders,present with a complex array of both motor and non-motor *** in this group are Parkinson’s disease(PD),dementia with Lewy bodies(DLB),multiple system atrophy(MSA),corticobasal syndrome(CBS),and progressive supranuclear palsy(PSP).These disorders are differentiated neuropathologically by their dominant protein pathologies involvingα-synuclein(α-syn)and/or tau,the types of brain cells affected,such as neurons,oligodendroglia,and astrocytes,and the specific brain regions involved(Tolosa et al.,2021).

关键词： disorders parkin

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Immunoassay development guidelines for neurodegenerative disorders:lessons from a failed pS129-α-synuclein electrochemiluminescence immunoassay

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Neural Regeneration Research 2025年第10期20卷 2906-2908页

作者： Hash Brown taha Alanna Morris Leonard Davis School of Gerontology University of Southern CaliforniaLos AngelesCAUSA Deparmtent of Neurobiology David Geffen School of MedicineUniversity of California Los AngelesLos AngelesCAUSA

An aging population is a double-edged *** one hand,advancements in biotechnology and healthcare allow more people to enjoy longer *** the other hand,increases in the aging population accompany a surge in age-associated diseases,particularly neurodegenerative *** aging is the primary risk factor for many neurodegenerative disorders,living longer does not necessarily equate to maintaining a reasonable quality of life(Feigin et al.,2020).

关键词： aging degenerative necessarily

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Using 3-D magnetic modeling to evaluate subsurface structures of the Siwa Oasis,Western Desert,Egypt

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Science China Earth Sciences 2012年第2期55卷 279-289页

作者： taha RABEH National Research Institute of Astronomy and Geophysics CairoEgypt IDL Faculty of ScienceLisbon UniversityPortugal

This work was designed to study the subsurface structures in the Siwa Oasis area of the Western Desert in Egypt and to determine their effects on surface geologic structures. A detailed land magnetic survey was performed in traverses covering about 400 km2 of the study area. The measured total magnetic field was corrected and reduced to the north magnetic pole. The reduction-to-pole aeromagnetic and Bouguer anomaly maps were used to obtain regional extensions of these subsurface structures, study the continuation of these structures in sedimentary rocks, and delineate the depths to the basement rocks. Data analysis was performed using trend analysis, Euler deconvolution, Werner deconvolution, the Hilbert transform of the analytical signal, and 3-dimensional magnetic modeling methods. The results indicate that the area is affected by tectonic forces in the E-W, N45°-65°E, and N35°-45°W trends, which are correlated with the directions of surface geologic lineaments. The depth to the basement rocks increases from 3.2 km in the southern part to about 3.6 km in the northern part of the area. The results are in good agreement with depths obtained from drill hole data in the area.

关键词： land magnetic survey aeromagnetic data gravity data fault and dyke parameters

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Dark count rate and band to band tunneling optimization for single photon avalanche diode topologies

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Chinese Physics B 2019年第6期28卷 458-464页

作者： taha Haddadifam Mohammad Azim Karami Iran University of Science and Technology

This paper proposes two optimal designs of single photon avalanche diodes(SPADs) minimizing dark count rate(DCR). The first structure is introduced as p^+/pwell/nwell, in which a specific shallow pwell layer is added between p^+and nwell layers to decrease the electric field below a certain threshold. The simulation results show on average 19.7%and 8.5% reduction of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. Moreover, a new structure is introduced as n+/nwell/pwell, in which a specific shallow nwell layer is added between n+and pwell layers to lower the electric field below a certain threshold. The simulation results show on average 29.2% and 5.5% decrement of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. It is shown that in higher excess biases(about 6 volts), the n+/nwell/pwell structure is proper to be integrated as digital silicon photomultiplier(dSiPM) due to low DCR. On the other hand, the p^+/pwell/nwell structure is appropriate to be utilized in dSiPM in high temperatures(above 50?C) due to lower DCR value.

关键词： single-photon avalanche diode digital silicon photomultiplier dark count rate

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Identification and control of a small-scale helicopter

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第12期11卷 978-985页

作者： Abdelhakim DEBOUCHA Zahari taha Centre for Product Design and Manufacturing University of Malaya Faculty of Manufacturing Engineering and Management Technology University Malaysia Pahang

Designing reliable flight control for an autonomous helicopter requires a high performance dynamics *** this paper,a nonlinear autoregressive with exogenous inputs (NLARX) model is selected as the mathematical structure for identifying and controlling the flight of a small-scale helicopter.A neural network learning algorithm is combined with the NLARX model to identify the dynamic component of the rotorcraft unmanned aerial vehicle (RUAV).This identification process is based on the well-known gradient descent learning *** a case study,the multiple-input multiple-output (MIMO) model predictive control (MPC) is applied to control the pitch motion of the *** of the neural network output model are closely match with the real flight *** MPC also shows good performance under various conditions.

关键词： Dynamics model System identification Black box Small-scale helicopter Neural networks (NNs) Control design

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Variational approach for the flow of Ree–Eyring and Casson fluids in pipes

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International Journal of Modeling, Simulation, and Scientific Computing 2016年第2期7卷 126-138页

作者： taha Sochi University College London Department of Physics&Astronomy Gower Street LondonWC1E 6BTUK

The flow of Ree–Eyring and Casson non-Newtonian fluids is investigated using a variational principle to optimize the total *** variationally obtained solutions are compared to the analytical solutions derived from the Weissenberg–Rabinowitsch–Mooney equation and the results are found to be identical within acceptable numerical errors and modeling approximations.

关键词： Fluid mechanics tube flow Ree-Eyring Casson Weissenberg-Rabinowitsch-Mooney variational method total stress optimization.

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