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Rethinking the solar flare paradigm

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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

Oil spill model development and application for emergency response system

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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

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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

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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

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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

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

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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

Dedicated to Professor Dr.-Ing. ***.h.c. Jurgen Zierep for his 80^(th) birthday Pattern Formation in Rotating Fluids

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Journal of Thermal Science 2009年第2期18卷 109-118页

作者： Karl bühler Department of Mechanical and Process Engineering University of Applied Sciences

Flows in nature and technology are often associated with specific structures and pattern. This paper deals with thedevelopment and behaviour of such flow pattern. Flow structures are important for the mass, momentum and energytransport. The behaviour of different flow pattern is used by engineers to obtain an efficient mass and energyconsumption. Mechanical power is transmitted via the momentum of rotating machine parts. Therefore thephysical and mathematical knowledge of these basic concepts is important. Theoretical and experimental investigationsof principle experiments are described in the following. We start with the classical problem of the flowbetween two concentric cylinders where the inner cylinder rotates. Periodic instabilities occur which are calledTaylor vortices. The analogy between the cylindrical gap flow, the heat transfer in a horizontal fluid layer exposedto the gravity field and the boundary layer flow along concave boundaries concerning their stability behaviour isaddressed. The vortex breakdown phenomenon in a cylinder with rotating cover is also described. A generalizationto spherical sectors leads then to investigations with different boundary conditions. The spherical gap flowexhibits interesting phenomena concerning the nonlinear character of the Navier-Stokes equations. Multiple solutionsin the nonlinear regime give rise to different routes during the laminar-turbulent transition. The interactionof two rotating spheres results in flow structures with separation and stagnation lines. Experimental results areconfirmed by numerical simulations.

关键词： Rotating Fluids Stability behaviour bifurcation Vortices Laminar-turbulent Transition

Irreversibility investigation of Casson fluid flow in an inclined channel subject to a Darcy-Forchheimer porous medium:a numerical study

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 95-108页

作者： A.ROJA b.J.GIREESHA b.NAGARAJA Department of PG Studies and Research in Mathematics Kuvempu UniversityShankaraghattaShimoga 577451KarnatakaIndia

The heat transfer and entropy generation characteristics of the magnetohydrodynamic Casson fluid flow through an inclined microchannel with convective boundary conditions are ***,the effects of the viscous forces,Joule heating,heat source/sink,and radiation on the flow are taken into *** non-dimensional transformations are used to solve the governing ***,the reduced system is resolved by the fourth-fifth order Runge-Kutta-Fehlberg method along with the shooting *** effects of different physical parameters on the heat transfer and entropy generation are discussed in detail through *** the perspective of numerical results,it is recognized that the production of entropy can be improved with the Joule heating,viscous dissipation,and convective heating *** is concluded that the production of entropy is the maximum with increases in the Casson parameter,the angle of inclination,and the Hartmann *** the Reynolds number and the radiation parameter cause the dual impact on entropy generation.

关键词： inclined channel Casson fluid magnetism radiation entropy generation bejan number

How relevant are engineering samples in the management of personal dust exposure?

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International Journal of Mining Science and Technology 2018年第4期28卷 697-703页

作者： b.belle Anglo American Coal BrisbaneQueenslandAustralia Department of Mining Engineering UNSWSydneyNSW 2052Australia

A directive, legislated by the South African Department of Minerals and Energy(DME) in 1997, was introduced to reduce the dust exposures of continuous miner(CM) operators to below 5 mg/m3, when measured at the operator's cab position. The focus of this paper is to review the effectiveness of observing this rule for almost two decades and discuss industry perceptions arising from the application of this rule. The results have demonstrated that the engineering sample cannot predict the personal shift dust exposure of a CM operator. Therefore, it is recommended that the engineering sampling, as currently practiced,should be reviewed with the objective to discontinue and replace it by the approved PDM3700 realtime dust monitor.

关键词： Continuous miner (CM) Dust exposure Personal Engineering sample