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SHS法制备Al_3Ti/Al复合材料的研究

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稀有金属材料与工程 2000年第3期29卷 145-148页

作者：介万奇 E.G.Kandalova 张瑞杰 V.I.nikitin 西北工业大学西安710072 萨马拉国立工业大学

介绍了高熔点化合物颗粒增强的铝基复合材料的一种先进制备方法 ,即自蔓延高温合成法 (SHS法 ) ,并以Al3Ti/ Al为例进行了实验研究。结果表明 ,将 Ti粉与 Al粉混合 ,在铝合金液中进行自蔓延高温合成 ,可有效地控制 Al3Ti的形态。其中 Al... 详细信息

介绍了高熔点化合物颗粒增强的铝基复合材料的一种先进制备方法 ,即自蔓延高温合成法 (SHS法 ) ,并以Al3Ti/ Al为例进行了实验研究。结果表明 ,将 Ti粉与 Al粉混合 ,在铝合金液中进行自蔓延高温合成 ,可有效地控制 Al3Ti的形态。其中 Al∶Ti比是控制 Al3Ti形态的关键参数。当 Al∶Ti比远小于理论化学计量比 3∶ 1时 ,获得针状 Al3Ti组织。而当该比值等于或大于 3∶ 1时则获得块状 Al3Ti组织 ,其分布也更均匀。但该比值太大 (大于约3.75∶ 1)时 ,则因 Al粉升温和熔化吸热 ,将使得自蔓延合成反应终止。

关键词： SHS法复合材料 A13Ti/Al 制备

on Inherent Irreversibility in a Reactive Hydromagnetic Channel Flow

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Journal of Thermal Science 2010年第1期19卷 72-79页

作者： o.D.Makinde o.Anwar Bég Faculty of Engineering Cape Peninsula University of TechnologyP.O.Box 1906Bellville 7535South Africa. Mechanical Engineering Department Harmer BuildingSheffield Hallam UniversitySheffieldS1 1WB EnglandUK.

This study is devoted to investigate the inherent irreversibility and thermal stability in a reactive electrically conducting fluid flowing steadily through a channel with isothermal walls under the influence of a transversely imposed magnetic *** a perturbation method coupled with a special type of Hermite-Pade' approximation technique,the simplified governing non-linear equation is solved and the important properties of overall flow structure including velocity field,temperature field and thermal criticality conditions are derived which essentially expedite to obtain expressions for volumetric entropy generation numbers,irreversibility distribution ratio and the Bejan number in the flow field.

关键词： Hydromagnetic channel flow Entropy analysis Thermal criticality Arrhenius kinetics Hermite-Pade approximants

Estimation of drift limits for different seismic damage states of RC frame staging in elevated water tanks using Park and Ang damage index

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Earthquake Engineering and Engineering Vibration 2020年第1期19卷 161-177页

作者： Suraj o.Lakhade Ratnesh Kumar o.R.Jaiswal Department of Applied Mechanics Visvesvaraya National Institute of Technology

Damage to elevated water tanks in past earthquakes can be attributed to the poor performance of their supporting frame staging. In order to ascertain the performance of these elevated water tanks, it is crucial to categorize the damage in quantifiable damage states. Among various parameters to quantify the damage states, the top drift of frame staging can be conveniently correlated to the different damage levels. In literature, drift limits corresponding to different damage states of the frame staging of the elevated water tank are not available. In the present study, drift limits for RC frame staging in elevated water tanks corresponding to different seismic damage states have been proposed. Various damage states of the elevated water tank have been determined using the Park and Ang damage index. The Park and Ang damage index utilizes results of both pushover analysis and incremental dynamic analysis. Twelve models of elevated water tanks have been developed considering variation in staging height and tank capacity. Incremental dynamic analysis has been performed using the suite of twelve actual earthquake ground motions. Based on the regression analysis between damage indexes and drift, limiting drift values for each damage state are proposed.

关键词： elevated water tank frame staging damage states drift limit 3D modelling incremental dynamic analysis pushover analysis

Zinc In CCl_4 Toxicity

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Biomedical and Environmental Sciences 2002年第3期15卷 187-195页

作者： o·ADEMUYIWA o·oNITILo 等 DepartmentofBiochemistryandDepartmentofChemicalPathology OgunStateUniversityAgo－IwoyeNigeriaand

objective To investigate the protective effect of zinc in CCl4-induced hepatotoxicity. Methods Rats were treated with zinc acetate for four days. The zinc doses were 5 mg Zn/kg and 10 mg Zn/kg body weight respectively. Two groups of the zinc acetate-treated rats were later challenged with a single dose of CCl4 (1.5 mL/kg body weight). Results Compared to control animals, the plasma of rats treated with CCl4 showed hyperbilirubinaemia, hypoglycaemia, hypercreatinaemia and hypoproteinaemia. When the animals were however supplemented with zinc in form of zinc acetate before being dosed with CCl4, the 5 mg Zn/kg body weight of zinc acetate reversed the hypoproteinaemia induced by CCl4, whereas the 10mg Zn/kg body weight of zinc acetate reversed the hypoglycaemia, hyperbilirubinaemia and hypercreatinaemia induced by CCl4. Conclusion The 10mg Zn/kg body weight of zinc acetate is more consistent in protecting against CCl4 hepatotoxicity. The possible mechanisms of protection are highlighted.

关键词： CCl4 Zinc Plasma Hypoglycaemia Hyperbilirubinaemia Hypercreatinaemia

Vapour-diffusion assisted growth of oriented α-cobalt hydroxide thin films

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Particuology 2010年第3期8卷 188-191页

作者： Dermot o’Hare Chemistry Research Laboratory Department of Chemistry University of Oxford Mansfield Road Oxford OX1 3TA United Kingdom

Layered α-cobalt hydroxides Co（oH1.65 Cl0.***.0.5H2o （1）, Co（oH）1.75（No3）0.***.0.1H2o（2） with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-diffusion method. The materials have thin film morphologies and were characterized by X-ray powder diffraction （XRD） and field emission scanning electron microscopy （FESEM）.

关键词： Thin films Cobalt hydroxide Hydrotalcite Morphology control

Population distribution and threats to sustainable management of selected non-timber forest products in tropical lowland rainforests of south western Nigeria

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Journal of Forestry Research 2013年第1期24卷 75-82页

作者： Jimoh S.o. Amusa T.o. I.o. Azeez Department of Forest Resources Management University of IbadanNigeria. Department of Forest Resources Management University of IlorinNigeria.

Uncontrolled harvesting of non-timber forest products （NTFPs） poses a serious risk of extermination to several of these species in Nigeria. Yet, there is a paucity of information on the distribution, population status and sustainable management of NTFPs in most of the tropical lowland rainforests. We, therefore, assessed the population, distribution and threats to sustainable management of NTFPs within the tropical lowland rainforests of omo and Shasha Forest Reserves, south western Nigeria. Data were obtained through inventory surveys on five top priority species including： bush mango （Irvingia gabonensis （Aubry-Lecomte ex o’Rorke） Baill）, African walnut （Tetracarpidium conophorum （Mull. Arg.） Hutch. ＆ Dalziel syn. Plukenetia conophora）, chew-stick （Massularia acuminata （G. Don） Bullock）, fever bark （Annickia chlorantha Setten ＆ *** syn. Enantia chloranta） and bush pepper （Piper guineense Schumach. ＆ Thonn.）. Purposive and stratified random sampling techniques were used for the inventory. Each forest reserve was stratified into three, viz： less disturbed natural forest （for areas that have been rested for at least ten years）, recently disturbed natural forest （for areas that have suffered one form of human perturbation or the other in the last five years）, and plantation forest （for areas carrying forest plantation）. Data were collected from eighteen 10 m × 500 m belt transects located in the above strata. The species were generally fewer in both plantation and recently disturbed natural forest than the less disturbed natural forest, suggesting that forest disturbances （habitat modification） for other uses may have an effect on the occurrence and densities of the NTFPs. Exceptions to this trend were found for P. guineense and T. conophorum, which were fairly common in both plantation and recently disturbed natural forest. Among three tree NTFP species （i.e. I. gabonensis, M. acuminata and A. chlorantha）, only I. gabonensis showed a significant difference in ov

关键词： Tropical rainforest non-timber forest products (NTFP) population density distribution forest management

Current self-limitation in a transverse nanosecond discharge with a slotted cathode

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Plasma Science and Technology 2017年第3期19卷 69-74页

作者： N A ASHURBEKoV K o IMINoV o A PoPoV G S SHAKHSINoV Dagestan State University Faculty of Physics 43a Gadjieva Street Makhachkala 367002 Russia Moscow Power Engineering Institute Krasnokazal'mennaya 14 Moscow 111250 Russia

A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy （few kV） ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed.

关键词： nanosecond discharge electron beams upper current limitation slotted cathode

Weibull approach to brake pad wear analysis in the Nigerian market

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Friction 2015年第3期3卷 228-233页

作者： R.S.FoNo-TAMo o.o.oSUNBoR o.A.KoYA Department of Mechanical and Biomedical Engineering Bells University of TechnologyOtaNigeria Department of Mechanical Engineering Obafemi Awolowo UniversityIle-IfeNigeria

In this study,we evaluated the wear properties of four brands of brake pad available in the Nigerian *** particular,we assessed the tribo performance and service life of the brake *** purchased four commercial brands of brake pads used in light duty cars and coded them as AU,SN,TY and SM,respectively.A small piece of the brake pad lining materials was carefully chiseled from the back plates to obtain samples for the *** conducted Brinell hardness tests using a tensometer and a pin-on-disc test rig to determine the coefficient of friction and the wear characteristics of the *** then correlated the wear on each set of brake pads with the running time and used Weibull’s equation to determine average service *** TY exhibited the highest hardness value(29.09)and sample SN the lowest(10.05).The determined coefficients of friction ranged between 0.3-0.36,with sample AU exhibiting the lowest value and sample SM the *** SN showed the lowest wear rate of 3.53×10^(9) g/min,while the wear rates of samples TY,AU,and SM were 5.64×10^(8),8.19×10^(9),and 2.10×10^(8) g/min,*** relative service life of samples SN,TY,and AU were similar,with average values of 2778.09,2725.41,and 2717.34 min,respectively,and SM had a relatively low service life(2017.82 min).We conclude that the overall performances of Nigerian brake pads do not meet all the specifications for friction materials used in road vehicle brake linings and pads.

关键词： Weibull wear rate service life brake pads friction composite

SPECTRA oF CoMPoSITIoN GRoUPS oN THE WEIGHTED DIRICHLET SPACE oF THE UPPER HALF-PLANE

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Acta Mathematica Scientia 2020年第6期40卷 1739-1752页

作者： M.o.AGWANG J.o.BoNYo Department of Pure and Applied Mathematics Maseno UniversityP.O.BOX 333-40105MasenoKenya

We prove that the group of weighted composition operators induced by continuous automorphism groups of the upper half plane U is strongly continuous on the weighted Dirichlet space of U,Dα(U).Further,we investigate when they are isometries on Dα(U).In each case,we determine the semigroup properties while in the case that the induced composition group is an isometry,we apply similarity theory to determine the spectral properties of the group.

关键词： one-parameter semigroup composition operator semigroups strong continuity infinitesimal generator spectra