检索结果-南通市图书馆

International Journal of Minerals,Metallurgy and Materials 2018年第3期25卷 339-349页

作者： sayed Ghafar hashemi B.Eghbali Department of Materials Engineering Sahand University of Technology

The characteristics of nanosized precipitates in steels depend on the heat-treatment parameters. The effects of characteristics of vanadium precipitates formed during isothermal heat treatment on the hardness of the ferrite matrix in low-carbon vanadium-alloyed steel were investigated through analysis of transmission electron microscopy images and microhardness measurements. The results show that, during isothermal holding in the temperature range from 675 to 750℃, only interphase precipitation occurs, whereas only random precipitation occurs in the ferrite matrix during holding at 600℃. Furthermore, during isothermal heat treatment between 600 and 675℃, both random and interphase precipitates occurred in the ferrite. Nanoscale vanadium carbides with different atomic ratios of vanadium(V) and carbon(C) were the dominant precipitates in the random and interphase precipitates. The sizes of random precipitation carbides were smaller than those of interphase ones. Also, the sample isothermally heat treated at 650℃ for 900s exhibited a higher hardness with a narrower hardness distribution.

关键词： low carbon steel vanadium carbide precipitation heat treatment microhardness

FIRST-ORDER METhODS FOR SOLVING ThE OPTIMAL STATIC h∞-SYNThESIS PROBLEM

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2007年第6期25卷 672-689页

作者： El-sayed M.E. Mostafa Department of Mathematics Faculty of Science Alexandria University Alexandria Egypt

In this paper, we consider the static output feedback （SOF） h∞-synthesis problem posed as a nonlinear semi-definite programming （NSDP） problem. Two numerical algorithms are developed to tackle the NSDP problem by solving the corresponding Karush- Kuhn-Tucker first-order necessary optimality conditions iteratively. Numerical results for various benchmark problems illustrating the performance of the proposed methods are given.

关键词： Static output feedback h∞-synthesis Semi-definite programming Nonlinear programming.

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

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

The Release Behavior,Biocompatibility and Physical Properties of Aid-loaded Strontium Doped Calcium Phosphate Cement

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2020年第6期17卷 1209-1223页

作者： Maryam Mohammadi sayed Mahmood Rabiee Saeed hesaraki Department of Materials Engineering Babol Noshirvani University of TechmologyBabol 71167-47148Iran Nanotechnologv and Advanced Materials Materials and Energy Research CenterKaraj ***AlborzIran

The effect of concurrent attendance of two inhibitors of bone degradation,namely Alendronate(Aid)sodium trihydrate and Strontium(Sr),on Calcium Phosphate Cement(CPC)characteristics was *** this aim,5 wt%Strontium and 21 mM Alendronate sodium trihydrate were used in calcium phosphate cement and setting time,ion and drug release were ***264.7 and G cell were cultured on cement samples and Tartrate-Resistant Acid Phosphatase(TRAP),Alkaline phosphatase(ALP)activity and MTT assay were *** results of structural analysis indicated that 21 mM Aid did not let the cement ***,colloidal silica was added to the cement formula and successfully decreased the setting *** vitro tests showed Sr-loaded sample had a greater inhibitory effect on biocompatibility of G cells than Aid-loaded and Sr-Ald-loaded *** addition,the findings about osteoblast MTT and ALP activity indicated that Sr was more effective in osteogenic activity of G *** simultaneous presence of Aid and Sr in Calcium Phosphate Cement(CPC)was not as effective in its biocompatibility as the presence of Sr alone.

关键词： calcium phosphate cements drug release alendronate sodium trihydrate strontium RAW264.7 cell G cell

high temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2014年第2期24卷 163-170页

作者： Fahamsyah h.Latief Koji Kakehi El-sayed M.Sherif Department of Mechanical Engineering Tokyo Metropolitan University Center of Excellence for Research in Engineering Materials (CEREM) Advanced Manufacturing Institute King Saud University Electrochemistry and Corrosion Laboratory Department of Physical Chemistry National Research Centre (NRC)

An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at1100 ℃. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.

关键词： Ni-based superalloy Oxidation behavior Microstructure Aluminide coating Crystallographic orientation

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

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

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

Amplitude Variation with Offset Responses Modeling Study of Walkaway Vertical Seismic Profile Data at CO_2 Geological Storage Site,Ketzin,Germany

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2011年第5期85卷 1118-1126页

作者： sayed hesammoddin KAZEMEINI Christopher JUhLIN Department of Earth Sciences Uppsala University

An important component of any CO_2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties,such as velocity and *** reservoirs have different amplitude variation with offset(AVO) responses,which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile(VSP) AVO response to CO_2 injection at the Ketzin site,the first European onshore CO_2 sequestration pilot study dealing with research on geological storage of CO_***,we performed rock physics analysis to evaluate the effect of injected CO_2 on seismic velocity using the Biot-Gassmann *** the basis of this model,the seismic response for different CO_2 injection saturation was studied using ray tracing *** then created synthetic walkaway VSP data,which we then *** contrast,synthetic seismic traces were created from borehole ***,we found that the amplitude of CO_2 injected sand layer with different gas saturations were increased with the offset when compared with the original brine target *** is the typical classⅢAVO anomaly for gas sand *** AVO responses matched the synthetic seismic traces very ***,walkaway VSP AVO response can monitor CO_2 distribution in the Ketzin area.

关键词： CO_2 injection rock physics amplitude variation with offset walkaway vertical seismic profile seismic modeling

Modeling of shear wave velocity in limestone by soft computing methods

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2017年第3期27卷 423-430页

作者： Behnia Danial Ahangari Kaveh Moeinossadat sayed Rahim Department of Mining Engineering Science and Research Branch Islamic Azad University Tehran *** Iran

The main purpose of current study is development of an intelligent model for estimation of shear wave velocity in limestone. Shear wave velocity is one of the most important rock dynamic parameters. Because rocks have complicated structure, direct determination of this parameter takes time, spends expenditure and requires accuracy. On the other hand, there are no precise equations for indirect determination of it; most of them are empirical. By using data sets of several dams of Iran and neuro-genetic, adaptive neuro-fuzzy inference system （ANFIS）, and gene expression programming （GEP） methods, models are rendered for prediction of shear wave velocity in limestone. Totally, 516 sets of data has been used for modeling. From these data sets, 413 ones have been utilized for building the intelligent model, and 103 have been used for their performance evaluation. Compressional wave velocity （Vp）, density （7） and porosity （.n）, were considered as input parameters. Respectively, the amount of R for neuro-genetic and ANFIS networks was 0.959 and 0.963. In addition, by using GEP, three equations are obtained; the best of them has 0.958R. ANFIS shows the best prediction results, whereas GEP indicates proper equations. Because these equations have accuracy, they could be used for prediction of shear wave velocity for limestone in the future.

关键词： Shear wave velocity Limestone Neuro-genetic Adaptive neuro-fuzzy inference system Gene expression programming

Characterization of porous Ti-bioglass composite produced by mechanical milling and space holder sintering

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2015年第9期34卷 638-644页

作者： Saeed Riahi Mohammad Rajabi sayed Mahmood Rabiee Department of Mechanical Engineering Babol Noshirvani University of Technology

In this study, porous titanium-10 wt% bioglass(BG) composites were fabricated by the process of combining mechanical alloying with space holder sintering. The pore morphology and phase constituents of the milled powders and porous compacts were characterized by scanning electron microscopy(SEM), X-ray diffractometry(XRD), and Fourier transform infrared spectroscopy(FT-IR). The mechanical properties were determined by running compression test. The porosity of the sintered samples shows a downward trend with the increase of milling time. As the porosity increases, both the compressive strength and elastic modulus decrease. The results illustrate that the fabricated porous compacts with high porosity and suitable mechanical properties have the potential application in bone tissue engineering.

关键词： Titanium Bioglass Porous material Mechanical milli

Oldest Basement(ca.462 Ma)in Indonesian Borneo and its Implication for Early Paleozoic Tectonic Evolution of SE Asia

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2022年第6期96卷 2093-2104页

作者： ZhU Junbin LI Shan sayed MURTADhA Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Geology Syiah Kuala UniversityBanda Aceh 23111Indonesia

The lack of preserved basement results in uncertain placements of many terranes in Southeast ***,we flag the first evidence of the oldest basement in Indonesian Borneo,which can help locate terranes in Borneo on the northern margin of Gondwana in the early Paleozoic and explain the regional tectonic setting of the *** schist samples from the Embuoi Complex in the Semitau Block,Northwest Kalimantan yielded zircon U-Pb dates of 453.3±1.9 Ma and 462.4±2.6 Ma,respectively,representing the formation time of the ***,internal structural and high Th/U ratios of zircons indicate that the protolith of schists is of magmatic *** zircons haveεhf(t)values of−4.1 to+1.1 and hf model ages of 1.37–1.69 Ga,indicating they were derived from a mixed source of juvenile crust with old *** comparison of zircon age distribution,two-stage hf model ages andεhf(t)variations of the early Paleozoic igneous rocks from Semitau with those of South China,Tengchong–Baoshan,and Indochina,the Semitau Block was most likely a part of or placed next to the Indochina Block of northern Gondwana during the early *** a similar tectono-magmatic pattern on northern Gondwana formed a prolonged early Paleozoic arc-related belt associated with subduction of the Proto-Tethyan Ocean.

关键词： basement N Gondwana Proto-Tethys Embuoi Complex early Paleozoic Borneo