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Electro-osmotic flow of a second-grade fluid in a porous microchannel subject to an AC electric field

journal of Hydrodynamics 2013年第2期25卷 309-316页

作者： MIsRA j. C. CHANDRA s. Department of Mathematics Institute of Technical Education and Research Siksha O Anusandhan University Department of Physics Sabang S. K. Mahavidyalaya Vidyasagar University

studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field. In the case of viscoelastic fluids, the volumetric flow rate differs significantly from that of Newtonian fluids, even when the flow takes place under the same pressure gradient and the same electric field. With this end in view, this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel, which is under the action of an alternating electric field. The influence of various rheological and electro-osmotic parameters, e.g., the Reynolds number, Debye-Huckel parameter, shape factor and fluid viscoelasticity on the kinematics of the fluid, has been investigated for a secondgrade viscoelastic fluid. The problem is first treated by using analytical methods, but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA. The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the stern and diffuse layers. The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced. The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number. The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations, where electro-osmotic flows come into the picture, as in blood flow in the micro-circulatory system subject to an elect

关键词： electrical double layer Debye length second-grade fluid Ionic energy

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Adaptive optics in laser processing

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Light(science & Applications) 2019年第1期8卷 140-155页

作者： Patrick s.salter Martin j.Booth Department of Engineering science University of OxfordParks RoadOxford OX13PJUK

Adaptive optics are becoming a valuable tool for laser processing,providing enhanced functionality and flexibility for a range of *** a single adaptive element,it is possible to correct for aberrations introduced when focusing inside the workpiece,tailor the focal intensity distribution for the particular fabrication task and/or provide parallelisation to reduce processing *** is particularly promising for applications using ultrafast lasers for threedimensional *** review recent developments in adaptive laser processing,including methods and applications,before discussing prospects for the future.

关键词： laser optics workpiece

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Difference in the Hot Compressive Behavior and Processing Maps between the As-cast and Homogenized Al-Zn-Mg-Cu(7075) Alloys

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journal of Materials science & Technology 2016年第7期32卷 660-670页

作者： s.Y. Park W.j. Kim Department of Materials science and Engineering Hongik University 72-1 Sangsu-dong Mapo-gu Seoul 121-791 Republic of Korea Advanced Fusion Process R&D Group Korea Institute of Industrial Technology 994-32 Dongchun-dong Yeonsu-gu Incheon 406-130 Republic of Korea

The deformation mechanisms and processing maps of the as-cast Al-Zn-Mg-Cu （？0？5） aluminum （AI） alloy were studied and compared with those of the homogenized 7075 Al alloy in the temperature range of 573-723 K and in the strain rate range of 10 3-10 s-1 to explore a possibility for directly using the as- cast 7075 Al alloy as a billet for hot working. The as-cast and homogenized 7075 A1 alloys had similar grain sizes and showed similar high-temperature deformation behaviors. The as-cast 7075 Al alloy, however, exhibited higher power efficiencies and smaller unstable flow regions compared to the homogenized 7075 AI alloy because of the presence of secondary phases （MgZn2） segregated at the dendritic interfaces in the as-cast microstructure, which were formed during non-equilibrium solidification. These segregated phases provided nucleation sites for dynamic recovery or continuous dynamic recrystallization, and as a result a fine and more homogeneous （sub）grain structure could be obtained from the as-cast micro- structure compared to the homogenized microstructure. The current work suggested the possibility and advantage of using as-cast microstructures for hot working of aluminum alloys with high content of solutes.

关键词： Al-based alloysProcessing mapHot compressionAs-cast microstructuresegregationRecrystallization

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Combustion synthesis of Ce^(3+), Eu^(3+) and Dy^(3+) activated NaCaPO_4 phosphors

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journal of Rare Earths 2011年第6期29卷 527-535页

作者： K N shinde s j Dhoble Animesh Kumar Department of Physics RTM Nagpur University National Environmental Engineering Research Institute

The preparation of NaCaPO4 doped with rare earth （RE） ions Ce3＋, Eu3＋ and Dy3＋ by combustion method was described. Under UV excitation （251 nm） of NaCaPO4：Ce3＋ showsd emission （367 nm） in UV range. When NaCaPO4：Dy3＋ phosphor was excited at 349 nm, the emission spectrum showed intense bands at 482 nm （blue） and 576 nm （yellow）. In Eu activated NaCaPO4 phosphor, the emission spectrum showed a dominant peak at 594 nm （orange） while others were at 614 and 621 nm （red） when excited at 393 nm. The prepared phosphor was characterized by X-ray diffraction （XRD）, scanning electron microscope （sEM） and photoluminescence （PL） measurement. Thus, the photoluminescence behavior of NaCaPO4：Ce3＋ was strongly suggested for scintillator. Likewise, Eu3＋ and Dy3＋ activated NaCaPO4 phosphors were recommended for near-UV white light-emitting diodes （LEDs）.

关键词： combustion synthesis photoluminescence phosphor scintillator solid state lighting rare earths

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Effects of bottom shear stresses on the wave-induced dynamic response in a porous seabed:PORO-WssI (shear) model

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Acta Mechanica sinica 2011年第6期27卷 898-910页

作者： j.Ye D.-s.jeng Division of Civil Engineering University of Dundee Center for Marine Geotechnical Engineering State Key Laboratory of Ocean EngineeringShanghai Jiao Tong University

When ocean waves propagate over the sea floor,dynamic wave pressures and bottom shear stresses exert on the surface of *** bottom shear stresses provide a horizontal loading in the wave-seabed interaction system,while dynamic wave pressures provide a vertical loading in the ***,the bottom shear stresses have been ignored in most previous studies in the *** this study,the effects of the bottom shear stresses on the dynamic response in a seabed of finite thickness under wave loading will be examined,based on Biot＇s dynamic poro-elastic *** the model,an ＂u-p＂ approximation will be adopted instead of quasi-static model that have been used in most previous *** results indicate that the bottom shear stresses has certain influences on the wave-induced seabed dynamic ***,wave and soil characteristics have considerable influences on the relative difference of seabed response between the previous model（without shear stresses） and the present model（with shear stresses）.As shown in the parametric study,the relative differences between two models could up to 10% of p0,depending on the amplitude of bottom shear stresses.

关键词： Bottom shear stresses Wave-induced dynamicresponse Porous seabed - "u-p" approximation - Biot's the-ory

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synthesis and photoluminescence studies of Ba(Gd,Ln)B_9O_(16):Eu^(3+)(Ln=La,Y) phosphors for n-UV LED lighting and display devices

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journal of Rare Earths 2015年第2期33卷 140-147页

作者： V.V.Rangari s.j.Dhoble Department of Physics RTM Nagpur University

BaGdB9O16：Eu^3＋ and Ba（Gd,Ln）B9O16：Eu^3＋（Ln=La, Y） phosphors were synthesized by solid state diffusion method. The X-ray diffraction, scanning electron microscopy（sEM） and photoluminescence properties were investigated. The as-synthesized BaGdB9O16：Eu^3＋ and Ba（Gd,Ln）B9O16：Eu^3＋（Ln=La, Y） phosphors showed strong red emission under ultraviolet light excitation. By partially substituting Gd^3＋ by La^3＋ and Y^3＋ ions in the host BaGdB9O16：Eu^3＋ materials, the maximum emission intensity was observed for the optimum composition of BaGd0.91La0.8B9O16Eu0.01 phosphor. The experimental results indicated that the Eu doped BaGdB9O16 and Ba（Gd,Ln）B9O16（Ln=La, Y） phosphors were promising red phosphors, which might find potential applications in near-UV excited LED lighting as well as display devices. Comparison of as-synthesized phosphors with standard phosphor used in CFL（compact fluorescent lamp） was also done. Energy transfer mechanism of Gd^3＋ to Eu^3＋ was also discussed in this paper.

关键词： phosphor solid state diffusion display devices photoluminescence rare earths

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Performance of inclined pillars with a major discontinuity

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International journal of Mining science and Technology 2019年第3期29卷 437-443页

作者： K.V.jessu A.j.s.spearing Western Australia school of Mines Kalgoorlie Curtin University

Discontinuities are an inherent part of the rock mass and majorly affect the stability of the excavation skin and *** dip of the discontinuities and their properties also have a significant effect on the strength of the *** approaches are commonly used to determine the pillar strength but can overestimate the strength and don’t consider the inclination of the pillars and the strength reduction caused by *** modeling is a powerful tool and if calibrated can be used to evaluate the strength of the pillars with discontinuities having a range of *** effect of a discontinuity on inclined pillars was conducted which has been seldom considered in evaluating the pillar ***-dimensional vertical pillars were simulated,and the pillar strength was calibrated to accepted theoretical results and then the discontinuities were introduced in different pillar inclinations with distinct width to height ratios to gain an insight into the effective pillar strength *** upon the results,it was found that the discontinuities have a significant effect with the increase in the inclination of the pillars even at a higher width to height ratios.

关键词： Numerical modelling Pillar Discontinuities Inclination Width to height ratios

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spin synthesis of monolayer of siO_2 thin films

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journal of semiconductors 2015年第4期36卷 16-25页

作者： s.s.shinde s.Park j.shin Korea Research Institute of standards and science

The highly ordered monolayer of submicron size silica （siO2） particles （235 nm） is developed on p-silicon by using three-step spin-coating in colloidal suspension, which has significant potential in various applications. The influence of three-step spin speeds, spinning time, acceleration time between different steps, concentration of siO2 particles in the solution, solution quantity, and the ambient humidity （relative humidity） on the properties ofmonolayer siO2 are studied in order to achieve a large area monolayer film. A relatively high surface coverage and uniform monolayer film of siO2 particles in the range of 85%-90% are achieved by appropriate control of the preparative parameters. We conclude that this method can be useful in industrial applications, because of the fabrication speed, surface coverage and cost of the process.

关键词： thin films spin synthesis electron microscopy

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Prediction of flow patterns during silo discharges using a finite element approach and its preliminary experimental verification

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Particuology 2015年第1期13卷 42-49页

作者： s.Ding H.Li j.Y.Ooi j.M.Rotter Faculty of science and Engineering University of AgderGrimstadand Tel-TekPorsgrunnNorway school of Material & Mineral Resources Xi'an University of Architecture & Technology Institute for Infrastructure and Environment School of EngineeringUniversity of Edinburgh

Obtaining a reliable discharge of particulate solids from a storage silo is a prerequisite to securing oper- ational adequacy in solids handling processes. If a silo is poorly designed, an unreliable interrupted discharge often occurs. In this study, an in-house finite element （FE） program was modified to predict the particulate solids flow patterns during discharges from silos, and the effect of a double-cone insert on such flow patterns. In FE modeling, a Eulerian approach was adopted with an assumption of steady-state flow-a state that greatly facilitated investigations on the effects of double-cone inserts on the flow of particulate solids. Predictions were carried out on whether the discharge was in mass flow or funnel flow, associated with the inclination angle of the silo＇s hopper. Predicted results were in agreement with the jenike Chart, and proved that an upper lateral pressure ratio value gave a better critical hopper half angle to achieve mass flow （EN 1991-4, 2006）. The shape and size of the stagnant zone were further discussed to address the flow channel boundary between the flowing and static solids if the discharge was in a funnel pattern. Results also showed the effects of a double-cone insert on the flow patterns which con- verted silos from funnel flow to mass flow up to a certain hopper inclination angle and would improve the flow pattern even for shallower angles. Experiments were carried out to verify some of the predicted results. some qualitative comparisons were made between the predicted results and experimental mea- surements, which indicated that further efforts are needed in predicting the shape of the stagnant zone （flow channel boundary） during funnel flow discharges.

关键词： Discharge pattern Flow boundary Double-cone insert FE analysis Preliminary verification

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Electrochemical studies on interplay of mineralogical variation and particle size on bioleaching low grade complex sulphide ores

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中国有色金属学会会刊：英文版 2009年第5期19卷 1312-1325页

作者： P.A.OLUBAMBI j.H.POTGIETER s.NDLOVU j.O.BORODE Department of Chemical and Metallurgical Engineering Tshwane University of TechnologyPretoriaSouth Africa Chemistry and Materials Division School of BiologyChemistry and Health SciencesManchester Metropolitan UniversityUK school of Chemical and Metallurgical Engineering University of the WitwatersrandJohannesburgSouth Africa Department of Metallurgical and Materials Engineering Federal University of TechnologyAkureNigeria

The interplay of mineralogical variation and mineral phase distribution within varying particle sizes on the dissolution behaviour of a low grade complex sulphide ore was investigated through bioleaching experiments and electrochemical technique. Investigations were carried out utilizing mineralogical data on the variations in mineral and phase distribution within particle sizes of sophilic cultures of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum *** behaviour was studied using particulate electrodes from the four varying particle sizes and from massive electrodes prepared from the two major sulphide mineral rich phases(sphalerite-rich and galena-rich)and a complex mineralogical phase of the bulk *** studies reveal the highest recoveries at a particle size of 75μm,while electrochemical investigations reveal the highest dissolution at particle size of 106μ*** results show that sphalerite rich phase has the highest dissolution rate while galena-rich complex phase has the *** studies confirm the highest bacterial attack at the sphalerite-rich *** discrepancies between the dissolutions within particle sizes obtained from bioleaching experiments and electrochemical studies are consistent with and attributed both to the physical and mineralogical *** behaviour is influenced and controlled by galvanic interaction resulting from mineralogical variation, while bioleaching behaviour is influenced by mineralogical variation as well as physical effect of particle size.

关键词：复杂硫化矿化学研究颗粒大小低品位浸出用电互作矿物

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