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较高温度下混凝土的一般应力-应变关系曲线

钢结构(中英文) 2008年第5期 77-78页

作者： youssef, m.a. moftah, m.

提供高温混凝土的应力-应变关系曲线是很必要的,因为它可以允许将结构设计为符合特殊的防火标准,并且改善这些结构在火灾中的行为。基于对无约束混凝土样本的火灾试验发展出现有的关系曲线,但是由于每一个关系曲线的独特性和用于计算控... 详细信息

提供高温混凝土的应力-应变关系曲线是很必要的,因为它可以允许将结构设计为符合特殊的防火标准,并且改善这些结构在火灾中的行为。基于对无约束混凝土样本的火灾试验发展出现有的关系曲线,但是由于每一个关系曲线的独特性和用于计算控制参数的大量公式的存在,他们显然提供了不同的预测。本文提出了可以预估参数的公式这些参数可以影响无约束和有约束混凝土的行为。这些参数是混凝土抗压强度、混凝土抗拉强度、峰值应力下混凝土的压应变,混凝土的初始弹性模量、瞬时蠕变应变、热应变、屈服应力和配筋的粘结强度。基于精确性、普遍性和简易性,推荐选择特定的公式。较高温度下适当的拉压力应力-应变关系利用了推荐的公式,这个公式是基于与周围温度一致的有约束混凝土提出的。提议的关系与现有的应力-应变关系曲线,以及现有的试验数据相比较,他们可以捕捉到因温度和约束而产生的混凝土的力学性质,并且被证实优于现有关系曲线。然而,还需要另外的试验来进一步验证和改进新提议的关系曲线。

关键词：混凝土应力-应变关系曲线温度火灾瞬时蠕变初始应力热应变屈服强度抗拉强度抗压强度

Engineering of efficient visible light photocatalysts:Ti_(1-x+y)Cu_(x)La_(y)O_(2)(x=0.03;y=0,0.005,0.01) compositions

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Journal of Rare Earths 2024年第3期42卷 497-505,I0003页

作者： S.m.Yakout A.m.youssef Inorganic Chemistry Department National Research Centre(NRC)El Buhouth StDokkiCairo12622Egypt

In dye-photocatalysis, widening the wavelengths absorption range of catalysts as well as aborting the recombination of the photoexcited charge carriers(electrons-holes pairs) are of paramount *** the current study, we report the photocatalytic characteristics of four compositions composed of TiO_(2),Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders for two harmful dyes(Congo red and methylene blue). The X-ray diffraction technique verified the configuration of mixed anatase and rutile phases in pure TiO_(2)and Ti_(0.97)Cu_(0.03)O_(2)powders while Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders possess anatase phase only. The changes of the band gap structure and dimensions of the unit cell volume of TiO_(2)confirm the substitution of Ti^(4+)sites by Cu^(2+)and La^(3+)ions. Remarkable widening of wavelengths absorption with formation of long absorption tails were found in TiO_(2)(3.13 e V) through insertion of La^(3+)plus Cu^(2+)ions. Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)samples exhibit a visible light band gap of 2.3 and 2.7 e V, respectively. Based on SEm images, incorporation of Cu^(2+)and La^(3+)ions influences the surface morphology of TiO_(2). The resulting Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders present enhanced photocatalytic activity towards Congo red dye degradation com.a.ed to pure one under natural solar spectrum. The best Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst exhibits superior photocatalytic activity of 96% for 10 ppm CR dye in 20 min as well as above average photocatalytic efficiency of 63% for 30 ppm CR dye in 120 min. As well, it showed acceptable photodegradation activity of 52% for 30 ppm mB solution in 140 min of sunlight irradiation. The heightened photodegradation efficiency of Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst can be clarified in terms of higher ch

关键词： Semiconductor TiO_(2) Rare earths Congo red methylene blue Solar spectrum Photodegradation

DEPENDENCE OF mODULUS OF ELASTICITY AND THERmAL CONDUCTIVITY ON REFERENCE TEmPERATURE IN GENERALIZED THERmOELASTICITY FOR AN INFINITE mATERIAL WITH A SPHERICAL CAVITY

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Applied mathematics and mechanics(English Edition) 2005年第4期26卷 470-475页

作者： Hamdy m.youssef mathematical Department Faculty of Engineering Umm Al_Qura UniversityMakkah Al_Mokaramah P.5555 Saudi Arabia

The equations of generalized thermoelasticity with one relaxation time with variable modulus of elasticity and the thermal conductivity were used to solve a problem of an infinite material with a spherical *** inner surface of the cavity was taken to be traction free and acted upon by a thermal shock to the surface. Laplace transforms techniques were used to obtain the solution by a direct *** inverse Laplace transforms was obtained *** temperature,displacement and stress distributions are represented graphically.

关键词： thermoelasticity generalized thermoelasticity modulus of elasticity thermal conductivity

State-space approach to two-temperature generalized thermoelasticity without energy dissipation of medium subjected to moving heat source

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Applied mathematics and mechanics(English Edition) 2013年第1期34卷 63-74页

作者： H.m.youssef Department of mathematical Faculty of EducationAlexandria UniversityAlexandria 21527Egypt

In this work, a model of two-temperature generalized thermoelasticity without energy dissipation for an elastic half-space with constant elastic parameters is constructed. The Laplace transform.a.d state-space techniques are used to obtain the general solution for any set of boundary conditions. The general solutions are applied to a specific problem of a half-space subjected to a moving heat source with a constant velocity. The inverse Laplace transforms are computed numerically, and the com.a.isons are shown in figures to estimate the effects of the heat source velocity and the two-temperature parameter.

关键词： generalized thermoelasticity energy dissipation two-temperature heat source

Preliminary performance analysis and optimization based on 1D neutronics model for Indian DEmO HCCB blanket

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Plasma Science and Technology 2020年第8期22卷 184-191页

作者： D AGGARWAL C DANANI m Z youssef Institute for Plasma Research GandhinagarGujarat 382428India Homi Bhabha National Institute(HBNI) AnushaktinagarMumbai 400094India University of California-Los Angeles Los AngelesCA 90095United States of America

India,under its breeding blanket R&D program for DEmO,is focusing on the development of two tritium breeding blanket concepts;namely the lead-lithium-cooled ceramic breeder and the helium-cooled ceramic breeder(HCCB).The study presented in this paper focuses on the neutronic design analysis and optimization from the tritium breeding perspective of the HCCB *** Indian concept has an edge-on configuration and is one of the variants of the helium-cooled solid breeder blanket concepts proposed by several partner countries in *** Indian HCCB blanket having lithium titanate(Li2TiO3)as the tritium breeder and beryllium(Be)as the neutron multiplier with reduced-activation ferritic/martensitic steel structure aims at utilizing the low-energy neutrons at the rear part of the *** aim of the optimization study is to minimize the radial blanket thickness while ensuring tritium self-sufficiency and provide data for further neutronic design and thermal-hydraulic layout of the HCCB *** is found that inboard and outboard blanket thicknesses of 40 cm.a.d 60 cm,respectively,can give a tritium breeding ratio(TBR)>1.3,with 60%6Li enrichment,which is assumed to be sufficient to cover potential tritium losses and associated *** results also demonstrated that the Be packing fraction(PF)has a more profound im.a.t on the TBR as com.a.ed to 6Li enrichment and the PF of Li2TiO3.

关键词： DEmO helium-cooled ceramic breeder blanket neutronic optimization study tritium breeding ratio

State-space approach to vibration of gold nano-beam induced by ramp type heating

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Nano-micro Letters 2010年第3期2卷 139-147页

作者： Hamdy m.youssef Khaled A.Elsibai mathematical Department-Faculty of Education-Alexandria University-Egypt mathematics Department Faculty of ScienceMansoura University

In the nanoscale beam,two effects become *** is the non-Fourier effect in heat conduction and the other is the coupling effect between temperature and strain *** the present study,a generalized solution for the generalized thermoelastic vibration of gold nano-beam resonator induced by ramp type heating is *** solution takes into account the above two ***-space and Laplace transform methods are used to determine the lateral vibration,the temperature,the displacement,the stress and the strain energy of the *** effects of the relaxation time and the ramping time parameters have been studied.

关键词： Thermoelasticity Euler-Bernoulli equation Gold nano-beam Ramp type heating

Radiolarian and Planktic Foraminifera Biostratigraphy of the Early Albian Organic Rich Beds of Fahdene Formation,Northern Tunisia

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Journal of Earth Science 2014年第1期25卷 45-63页

作者： m Ben Fadhel T Zouaghi A Amri m Ben youssef Département de Géologie Faculté des Sciences de Gafsa-Campus Universitaire Sidi Ahmed Zarrouk–2112 Département des Géoressources CERTE–Technopole de Borj Cédria

The lower part of Fahdene Formation outcropping in northeastern Tunisia is repre- sented by pelagic sequences and characterized by an important siliciclastic fraction that includes ra- diolarian and organic-rich beds of Allam member. Litho-biostratigraphic analysis based on planktic foraminifera and radiolaria shows that deposition of organic-rich beds of Allam member is confined to the microhedbergella rischi Zone through the lower part of Ticinella primula Zone. Age diagnostic radiolaria recovered from these beds has been identified to constrain a direct age of black shale depo- sition. The assemblages can be correlated with the radiolarian biochronozone U.A.10-11 indicating an Early Albian to early middle Albian in age. Radiolarian assemblages composed of species characteris- tic of U.A.10 biochronozone （A. montisserei, D. gracilis） are associated with radiolarian taxa belonging to Costata Zone （U.A.9 Pseudoeucyrtis hanni and Thanarla pseudodecora）, which can be correlated with Dercourt member in the Ionian Zone and Paquier level of the Vocontian Basin （southeast of France）. Biostratigraphic and abundance curves analysis has demonstrated significant diversification of cryptocephalic Nassellaria and Archaeodictyomitrae, probably adapted to eutrophic conditions that characterized the Aptian-Albian transition. Ecological conditions may have governed the stratigraphic range of many cosmopolitan taxa （i.e., Pseudodictyomitrae lodogaensis） com.a.ed with stratigraphic distributions schemes reported from other domains. The timing of black shales deposition was dia- chronic due to local geodynamic conditions and upwelling currents distribution. The Allam black shales are correlative with the oceanic anoxic event OAElb which is characterized by the widespread of supraregionnally organic-rich beds in the mediterranean Tethys basins across the Aptian-Albian transition.

关键词： northeastern Tunisia Albian Allam member black shale radiolaria planktic foraminifera.

Bimodal imaging of proliferative diabetic retinopathy vascular features using swept source optical coherence tomography angiography

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International Journal of Ophthalmology(English edition) 2018年第9期11卷 1528-1533页

作者： Amal m Elbendary Hossam youssef Abouelkheir mansoura Ophthalmic Center Mansoura University

AIm： To categorize neovessels morphology and to detect response to anti-angiogenic therapy by using structural and angiographic modes of swept source optical coherence tomography（SS-OCT）.mETHODS： Thirty-two eyes with neovessels at disc（NVD） and neovessels elsewhere（NVE）-as diagnosed by fluorescein angiography-were included. Cross sectional OCT images of disc and macular regions were registered to enface OCT angiography（OCTA）, B-scan blood flow over lay and density maps. Three eyes received antiangiogenic ***： Pin point registration of cross-sectional OCT and OCTA images differentiated active NVD with vascular elements from fibrous or equivalent fibrovascular elements. En face images delineated NVE as vascular tufts or area of filling while cross-sectional images differentiated NVE from microvascular intraretinal abnormality（IRmA）. All cases were associated with enlargement of foveal avascular zone and or areas of capillary non perfusion. Regressed NVD appeared as ghost vessel or pruned vascular loops after ***： Structural and angiographic modes of SS-OCT can detect, characterize and categorize the pattern of wide spectrum of neovessels based on blood flow data and density maps. It is potentially useful to detect ischemic changes in the vascular bed and regression of NVD after therapeutic regimens providing substitute for invasive techniques.

关键词： optical coherence tomography angiography swept proliferative diabetic retinopathy

Fabrication,characterization,and electrical conductivity properties of Pr_6O_(11) nanoparticles

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Journal of Rare Earths 2013年第7期31卷 701-708页

作者： Bahaa m.a.u-Zied youssef A.mohamed Abdullah m.a.iri Chemistry Department Faculty of ScienceKing Abdulaziz UniversityP.O.Box 80203Jeddah 21589Saudi Arabia Chemistry Department Faculty of ScienceAssiut University71516 AssiutEgypt Center of Excellence for Advanced materials Research(CEAmR) King Abdulaziz UniversityP.O.Box 80203Jeddah 21589Saudi Arabia

PrrOll nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant. The calcination process was affected, for 1 h in static air atmosphere, at 400-700 ℃ temperature range. The different samples were characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEm）, field emission scanning electron microscopy （FE-SEm）, thermogravimetric analysis （TGA）, in situ electrical conductivity, and N2 adsorption/desorption. The obtained results demonstrated that nano-crystalline Pr6O11, with crystallites size of 6-12 nm, started to form.a. 500 ℃. Such value increased to 20-33 nm for the sample calcined at 700℃. The as-synthesized PrrOll nanoparticles presented high electrical conductivity due to electron hopping between Pr（III）-Pr（IV） pairs.

关键词： nanocrystalline praseodymium oxide Pr6O11 nano structured materials electrical conductivity rare earths