检索结果-南通市图书馆

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

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

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

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

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

Microstructural Features of Spray-Deposited Immiscible Bearing Alloys Al-43Sn and Al-7Sn-1.3Cu-1.3Ni

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2003年第5期19卷 437-443页

作者： o.P.Pandey Thapar Institute of Engineering & Technology Deemed University Patiala-147004 India

Two commercial grade aluminum based immiscible bearing alloys were spray-deposited using convergent-divergent type of nozzle. The processing parameters for spray-deposition were adjusted in such a way that most of the droplets arrived on the deposition substrate in either liquid or semi-liquid state. The microstructural features of spray-formed and as-cast alloys are compared. In spray-formed alloys equiaxed grains were observed. The cell boundaries and intercellular regions were observed to be decorated with sub-micron sized particles whereas in normal casting the second phase was observed to be segregated along grain boundaries. The morphology and distribution of second phase were observed to have similarity with those in over-spread and atomized powders produced under similar processing conditions. The microstructural features observed with variation in spray conditions are discussed in detail.

关键词： Spray deposition Immiscible bearing alloys Microstructure Atomization

Computer Simulation of the Multiphase Flow in a Peirce-Smith Copper Converter

在线全文

学校读者我要写书评

暂无评论

open Journal of Applied Sciences 2018年第7期8卷 296-303页

作者： oscar Barrios Miguel A. Barron Dulce Y. Medina isaias hiler.o Departamento de Materiales Universidad Autonoma Metropolitana Azcapotzalco Ciudad de Mexico Mexico

The multiphase flow in a Peirce-Smith copper converter is numerically explored in this work. Molten matte, molten slag and air are the phases considered. The transient partial differential equations that constitute the mathematical model are discretized using a two-dimensional computational mesh. The Computational Fluid Dynamics technique is employed to numerically solve the discretized equations. The aim of the numerical analysis is to study the influence of the nozzle height on the phase distributions inside the converter. Three values of the nozzle heights are considered.

关键词： Computational Fluid Dynamics Copper Converter Multiphase Flow Nozzle Height Peirce-Smith Converter

Development，Application，Markets，and　Patent　Situation　of　Magnetostrictive　TERFENoL－D

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 Rare Earths 1995年第4期13卷 295-301页

作者： McMasters, o.D. ETREMA Products Inc. 2500 North Loop Drive Ames Iowa 50010

The development of the giant magnetostrictive rare earth-iron materials is reported from their discovery in the early 1970's to their present use in transducer and sensor applications. Fifteen broad market areas, ranging from miniature devices in the medical industry to high powder sonar and seismic sources have been identified. A world-wide customer base in these high technology fields has been established and the superior properties of these materials are responsible for the rapid growth of the magnetostrictive transducer industries. The critical design criteria that lead to efficient devices are reported and the performance of several of these products is presented. The key patents associated with these giant magnetostrictive materials and devices using these materials are reviewed. The present and future of these technologies in reference to commercialization, market growth and the impact on the many transduction industries are discussed. (Author abstract) 9 Refs.

关键词： Magnetostrictive Situation Patent TERFENoL and Development Application

Breakage of drops and bubbles in a stirred tank： A review ofexperimental studies

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2017年第6期25卷 698-711页

作者： Basim o. Hasan Department of Chemical Engineering Technical University of Berlin 6ermany Department of Chemical Engineering AI-Nahrain University lraq

The rate of breakage of drops and bubbles(fluid particles) in stirred systems is of great consequence on mass,heat, and momentum transport phenomena. Therefore, over the years, the topic has gained a considerable attention from the researchers to study and characterize this phenomenon. In present work, the experimental studies of breakage phenomenon in a stirred tank in the last four decades were reviewed. The review highlighted the investigated experimental conditions and the major findings concerning the breakage mechanism and the effect of operating conditions. The discrepancy and contradictions of the outcomes of those studies were specified and discussed. Experimental observations and conclusions concerning the breakage characterization parameters,such as deformation, breakage probability, breakage time, and breakage location were presented and commented on. Possible future refinements and prospective were recommended. The review indicated that there are clear discrepancies and contradictions between previous studies regarding the effect of some operating parameters and the values of breakage time, breakage probability, number of daughter particles, and breakage location relative to the impeller. In addition, there are still many scientific gaps that need to be studied and characterized in future by overcoming specific experimental difficulties and uncertainties.

关键词： Drop Bubble Breakage Stirred tank Review Breakage rate