检索结果-南通市图书馆

Investigation of nanocrystalline structure in selected carbonaceous materials

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

International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 940-946页

作者： Manoj b Department of Physics Christ University

The structural parameters of nine Indian coals were determined by X-ray diffraction （XRD） and Kaman spectroscopy. The study revealed that the coals contain crystalline carbon of turbostratic structure with amorphous carbon. The stacking height （Lc） and interlayer spacing （rico2） of the crystallite structure of the coals ranged from 1.986 to 2.373 nm and from 0.334 to 0.340 nm, respectively. The degree of graphitization was calculated to range from 42% to 99%, thereby confirming the ordering of the carbon layers with the increase in coal rank. An exponential correlation was observed among the aromaticity （fa）, the lateral size （La）, and the rank （I20/I26）, suggesting that the coal crystallites are nanocrystalline in nature. A very strong correlation was observed between the structural parameters （fa, d002, Lc, the H/C ratio, and I20/I26）, the volatile matter content, and the elemental carbon content, indicating the structures of coals are controlled by the degree of contact metamorphism. The Raman spectra exhibited two prominent bands： the graphitic band （G） and the fn＇st-order characteristic defect band （D）. The deconvolufion resulted in five peaks： G, D1, D2, D3, and D4. The intense D1 band, which appeared at -1350 cm^-1, corresponds to a lattice vibration mode with Alg symmetry. The D2 mode, which appeared at -1610 cm^-1, arises from the structural disorder as a shoulder on the G band.

关键词： nanocrystals graphitization aromaticity carbonaceous materials

Rethinking the solar flare paradigm

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2018年第7期20卷 15-21页

作者： d b melrose SIfA School of PhysicsThe University of SydneyNSW 2006Australi

It is widely accepted that solar flares involve release of magnetic energy stored in the solar corona above an active region, but existing models do not include the explicitly time-dependent electrodynamics needed to describe such energy release. A flare paradigm is discussed that includes the electromotive force （EMF） as the driver of the flare, and the flare-associated current that links different regions where magnetic reconnection, electron acceleration, the acceleration of mass motions and current closure occur. The EMF becomes localized across regions where energy conversion occurs, and is involved in energy propagation between these regions.

关键词： solar flares electrodynamics time-dependence

在线全文

学校读者我要写书评

暂无评论

热带大豆的指数选择

大豆科学 1992年第3期11卷 198-203页

作者： P. T. Dao hari Har Ram G.b.Pant农业技术大学植物育种系印度Pantnagar

本试验采用25个新的大豆品系为材料,用Robinson等的公式计算了选择指数的遗传进展;用Johnson等的公式计算了直接选择产量的遗传进展;用选择指数的遗传进展占直接选择产量的遗传进展的百分率表示选择指数的相对选择效率;用判别函数求得... 详细信息

本试验采用25个新的大豆品系为材料,用Robinson等的公式计算了选择指数的遗传进展;用Johnson等的公式计算了直接选择产量的遗传进展;用选择指数的遗传进展占直接选择产量的遗传进展的百分率表示选择指数的相对选择效率;用判别函数求得选择指数的公式。试验结果表明:除了单因子指数选择的效率低于直接选择产量的效率外,所有的指数选择效率都高于直接选择产量。包括所有10个性状的指数选择效的相对效率最高(115.25％)。从经济和简便的角度出发,我们认为包括5个性状(小区产量,熟期,株高,每株荚数,百粒重)的指数选择是可行的。它的相对选择效率是114.07％。

关键词：大豆指数选择

Oil spill model development and application for emergency response system

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2001年第2期13卷 252-256页

作者： b Qiao Environmental Science Center Peking University Beijing 100871 China.

The paper introduces systematically the developing principle of CWCM 1.0 oil spill model based on Lagrange system and oil spill fate processes in environment, reviews two oil spill incidents of "East Ambassador" in Jiaozhou bay and "Min Fuel 2" in the mouth of Pearl River, and designs the predictable system simulating oil spill applied in contingency plans. It is indicated that CWCM 1.0 has met preliminarily the demands for functions of precision simulating and predicting oil spill, and can plan an important role to support oil spill response.

关键词： Oil spill model development and application for emergency response system

Analysis of non-symmetrical flapping airfoils

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第4期25卷 433-450页

作者： W.b.Tay K.b.Lim Department of Mechanical Engineering National University of Singapore

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. by using non- symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil＇s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interac- tions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter＇s wing.

关键词： Flapping Non-symmetrical Design ofexperiments Ornithopter Airfoil

Microstructure and Mechanical Properties of Mg–7.4% Al Alloy Matrix Composites Reinforced by Nanocrystalline Al–Ca Intermetallic Particles

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 444-448页

作者： A.K.Chaubey b.b.Jha b.K.Mishra Institute of Minerals and Materials Technology (IMMT)

Mg-7.6% Al （in mass fraction） alloy matrix composites reinforced with different volume fractions of nano- crystalline Al3Cas particles were synthesized by powder metallurgy, and the effect of the volume fraction of reinforcement on the mechanical properties was studied. Room temperature compression test reveals considerable improvement on mechanical properties as compared to unreinforced matrix. The compressive strength increases from 683 MPa for unre- inforced alloy matrix to about 767 and 823 MPa for the samples having 20 and 40 vol% of reinforcement, respectively, while retaining appreciable plastic deformation ranging between 12 and 24%. The specific strength of the composites increased significantly, demonstrating the effectiveness of the low-density AlaCas reinforcement.

关键词： Intermetallics Consolidation Dispersion strengthening Powder metallurgy Mechanicalproperty Electron microscopy

Numerical analysis of the s1020 airfoils in tandem under different flapping configurations

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2010年第2期26卷 191-207页

作者： K.b.Lim W.b.Tay Department of Mechanical Engineering National University of Singapore21 Lower Kent Ridge RoadSingapore 119077Singapore

The objective of this project is to improve the performance of the efficiency, thrust and lift of flapping wings in tandem arrangement. This research investigates the effect of the arrangement of the airfoils in tandem on the performance of the airfoils by varying the phase difference and distance between the airfoils. Three flapping configurations from an earlier phase of a research which gives high efficiency, thrust and lift are used in the tandem simulation. It is found all the different flapping configurations show improvement in the efficiency, thrust or lift when the distance between the two airfoils and the phase angle between the heaving positions of the two airfoils are optimal. The average thrust coefficient of the tandem arrangement managed to attain more than twice that of the single one （4.84 vs. 2.05）. On the other hand, the average lift coefficient of the tandem arrangement also increased to 4.59, as compared to the original single airfoil value of 3.04. All these results obtained will aid in the design of a better ornithopter with tandem wing arrangement.

关键词： Tandem Flapping· Airfoils Ornithopter·Immersed boundary

Generating a New Higher-Dimensional Coupled Integrable Dispersionless System:Algebraic Structures,bcklund Transformation and Hidden Structural Symmetries

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2013年第8期60卷 145-149页

作者： Souleymanou Abbagari Thomas b.bouetou Timoleon C.Kofane National Advanced School of Engineering University of Yaounde IP.O.Box 8390Cameroon Department of Physics Faculty of ScienceUniversity of Yaounde IP.O.Box 812Cameroon The Max Planck Institute for the Physics of Complex Systems Nthnitzer Strasse 3801187 DresdenGermany

The prolongation structure methodologies of Wahlquist-Estabrook [H.D. Wahlquist and F.b. Estabrook, J. Math. Phys. 16 （1975） 1] for nonlinear differential equations are applied to a more general set of coupled integrable dispersionless system. based on the obtained prolongation structure, a Lie-Algebra valued connection of a closed ideal of exterior differential forms related to the above system is constructed. A Lie-Algebra representation of some hidden structural symmetries of the previous system, its biicklund transformation using the Riccati form of the linear eigenvalue problem and their general corresponding Lax-representation are derived. In the wake of the previous results, we extend the above prolongation scheme to higher-dimensional systems from which a new （2 ＋ 1）-dimensional coupled integrable dispersionless system is unveiled along with its inverse scattering formulation, which applications are straightforward in nonlinear optics where additional propagating dimension deserves some attention.

关键词： coupled integrable dispersionless system algebraic structures b^cklund transformation Hiddenstructural symmetries

Evaluation of gravimetric sampler bias, effect on measured concentration, and proposal for the use of harmonised performance based dust sampler for exposure assessment

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2019年第3期29卷 445-452页

作者： b.belle Anglo American Coal UNSW SydneyAustralia

The last three years has brought about alarming news of re-identification of coal worker’s pneumoconiosis(CWP)or‘black lung’in Australia after reporting nearly being absent for over five ***,the CWP statistics in South Africa(SA)are unverifiable,but certainly CWP has not been *** events have re-kindled the need for better understanding of the dust monitoring,performance of sampling devices,and compliance *** the last half century,gravimetric sampling has been the fundamental means for dust exposure monitoring using recognised respirable size-selective *** both South Africa and Australia,the gravimetric sampling technique in coal mines has been followed since 1988 and 1983 respectively using samplers of original Higgins-Dewell(HD)type *** paper provides the evaluation results of currently used South African and Australian gravimetric samplers compared against the original UK SIMPEDS‘true reference’*** results consistently suggested that the South African and Australian cyclones do not conform to the required size selective curve or even the‘true’reference *** results show that the currently used SA and Australian samplers showed a D50 sampling bias as high as 59%and 47%respectively against the size-selective ***,under the controlled laboratory coal dust test conditions measuring the same coal mine dust level in a chamber,the South African,Australian and UK standard SIMPEDS sampler were 7.87,9.79 and 6.71 mg/m3 respectively,which aligned with the sampling *** differences can in part be attributed to the‘un-auditable’inherent design and manufacturing quality,or unverifiable data on sizeselective sampling *** finding has significant implications towards exposure data collected over the last 25 years and their subsequent use in the arrival of the dose-response ***,it is strongly recommended that the harmonised use of‘true reference’SIMPEDS cyclone that meets the IS

关键词： Dust Respirable Sampling