Influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel

The influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel is investigated.The DarcyBrinkman model is used to characterize the fluid flow dynamics in porous materials.The analytical solutions are obtained for the unidirectional and completely developed flow.Based on a normal mode analysis,the generalized eigenvalue problem under a perturbed state is solved.The eigenvalue problem is then solved by the spectral method.Finally,the critical Rayleigh number with the corresponding wavenumber is evaluated at the assigned values of the other flow-governing parameters.The results show that increasing the Darcy number,the Lewis number,the Dufour parameter,or the Soret parameter increases the stability of the system,whereas increasing the inclination angle of the channel destabilizes the flow.Besides,the flow is the most unstable when the channel is vertically oriented.

Mechanism of Thermally Radiative Prandtl Nanofluids and Double-Diffusive Convection in Tapered Channel on Peristaltic Flow with Viscous Dissipation and Induced Magnetic Field

The application of mathematical modeling to biological fluids is of utmost importance, as it has diverse applicationsin medicine. The peristaltic mechanism plays a crucial role in understanding numerous biological flows. In thispaper, we present a theoretical investigation of the double diffusion convection in the peristaltic transport of aPrandtl nanofluid through an asymmetric tapered channel under the combined action of thermal radiation andan induced magnetic field. The equations for the current flow scenario are developed, incorporating relevantassumptions, and considering the effect of viscous dissipation. The impact of thermal radiation and doublediffusion on public health is of particular interest. For instance, infrared radiation techniques have been used totreat various skin-related diseases and can also be employed as a measure of thermotherapy for some bones toenhance blood circulation, with radiation increasing blood flow by approximately 80%. To solve the governingequations, we employ a numerical method with the aid of symbolic software such as Mathematica and MATLAB.The velocity, magnetic force function, pressure rise, temperature, solute (species) concentration, and nanoparticlevolume fraction profiles are analytically derived and graphically displayed. The results outcomes are compared withthe findings of limiting situations for verification.

Microstructural Evolution and Thermal Stability of Ultra-fine Grained Al-4Mg Alloy by Equal Channel Angular Pressing

Experiments were conducted to evaluate the grain refinement and thermal stability of ultra-fine grained Al-4Mgalloy introduced by equal-channel angular pressing (ECAP) at 473 K. The results show that the intensities of X-ray(111/222) and (200/400) peaks for the alloy processed by ECAP decrease significantly and the peak widths of halfheight become broadening compared with the corresponding value in the annealed alloy. The microstructure of 2passes ECAPed alloy consists of both elongated and equiaxed subgrains. The residual strain in the alloy increaseswith increasing passes numbers, that appears as increasing dislocation density and lattice constant of matrix. Anequiaxed ultra-fine grained structure of～0.2μm is obtained in the present alloy after 8 passes. The ultra-fine grainsare stable below 523 K, because the alloy retains extremely fine grain size of～1μm after static annealing at 523 Kfor 1 h.

Application of a Cleaning System Made up of a Centrifugal Fan with Double Channel and One Sieve to Combine

In this paper the application of a cleaning system which was made up of a centrifugal fan with double channel and one sieve to 4LZ-3.5 combine was introduced. This cleaning system with double channel compared with the traditional air-sieve cleaning system of combines may omit one two sieves and simplify the transmission mechanism. It is also compared with the present cleaning system with double channel applied to some combines, such as the Commandor 112CS/ 228CS combines of Claas Corporation in Germany and the MAXIMIZERTMombincs of John Deerc company in U.S.A. It may omit one sieve and the preclcaner and simlify the transmission mechanism. The measuring results indicated that the cleaning ratio of wheat grain is 99.1% and the cleaning loss ratio of wheat is 0.17% when the feed rate is 4.01 kg/ s.

Importance of Double Layer Force between a Plat and a Nano-Particle in Restricting Fines Migration in Porous Media

Fines migration is defined as separation of a Nano-sized particle by fluid flow in porous media and its migration along some distances and its entrapment in a narrow pore throat or its settlement on pore wall. Although this phenomenon happens in scales of Nano-meters, it can lead to sever irretrievable damages. This damage includes permeability reduction that causes drastic oil recovery reduction. There are several forces impacting a fine that is placed on a pore wall. Some of most important forces affecting settlement of a fine in porous media in presence of a fluid are electrical forces. Electrical forces consist of several long and short range forces. This study focuses on a long range force called Double Layer Force (DLF) that beside Van der Waals is one of most powerful electrical forces. DLF is a repulsive force that can repel a particle from pore wall and result separation of a Nano-sized solid which subsequently moves along with flowing fluid and clogs a throat. The DLF depends on the solid material (reservoir rock and fine) and fluid properties (i.e. ionic strength, pH). This study investigates how each of these parameters affects DLF and introduces proper conditions for reservoir water flooding for controlling fines migration.

Microstructure and Mechanical Properties of Ultrafine Grained Mg15Al Alloy Processed by Equal-channel Angular Pressing

An as-cast magnesium alloy with high Al content Mg15Al was subjected to equal-channel angular pressing （ECAP） through a die with an angle of φ= 90？ at 553 K following route Bc. It is found that the network β-Mg17Al12 phases in the as-cast Mg15Al alloy are broken into small blocks and dispersed uniformly with increasing numbers of pressing passes. Moreover, many nano-sized Mg17Al12 particles precipitate in the ultra-fine α-Mg matrix. The grains are obviously refined. However, the grain structure is inhomogeneous in different areas of the alloy. The average size of the primary phase α-Mg is reduced to about 1 μm while grains of around 0.1-0.2 μm are obtained in some two-phase areas. With additional ECAP passes （up to 8）, coarsening of the grains occurs by dynamic recovery. Room temperature tensile tests show that the mechanical properties of Mg15Al alloys are markedly improved after 4 ECAP passes. The ultimate tensile strength and elongation to failure increase from 150 MPa to 269.3 MPa and from 0.05% to 7.4%, respectively. Compared with that after 4 passes, the elongation to failure of the alloy increases but the strength of the alloy slightly decreases after 8 ECAP passes. Fracture morphology of the ECAP-processed alloy exhibits dimple-like fracture characteristics while the as-cast alloy shows quasi-cleavage fractures.

IGZO/ZTO TFTs with Modulated Double Channel of Thickness Structures

The device characteristics of IGZO/ZTO(indium-gallium-zinc oxide/zinc-tin oxide)TFTs(thin film transistors)with modulated channels were investigated.The field effect mobility was enhanced to 20.4 cm2/Vs in the channel-modulated TFT.The electrical performance of the TFT device was improved by the insertion of a high carrier concentration layer at the channel/gate insulator interfaces.It was due to the enhancement of carrier accumulation and the reduction of parasitic resistance via channel modulation.The threshold voltage was controlled at appropriate value.These results indicate that the device characteristic of TFTs can be enhanced by the modulated channel structure.

Microstructures of ultra-fine grained FeCoV alloys processed by ECAP plus cold rolling and their evolutions during tempering

A new processing method,equal channel angular pressing(ECAP)plus cold rolling(CR),was applied to producing ultra-fine grained FeCoV alloy.The microstructures of ultra-fine grained FeCoV alloy after ECAP,ECAP plus CR,and the effect of tempering treatment on the microstructure of FeCoV alloy produced by ECAP plus CR were investigated.The results show that an elongated substructure with a width of about 0.3μm is obtained after four-pass ECAP using Route A.Cold rolling after ECAP cannot change the morphologies of elongated substructure,and it results in higher fraction of high-angle boundaries and higher dislocation density compared with the identical ECAP without rolling.Subsequent tempering for 30 min at 853 K brings about many nano-phases precipitating at subgrain boundaries and insides the grains,and the size of precipitated phase is measured to be about 10 nm.Nano-phases grow up with increasing tempering temperature and equiaxed structure forms at 883 K.

Hydraulic Optimization of a Double-channel Pump's Impeller Based on Multi-objective Genetic Algorithm

Computational fluid dynamics（CFD） can give a lot of potentially very useful information for hydraulic optimization design of pumps, however, it cannot directly state what kind of modification should be made to improve such hydrodynamic performance. In this paper, a more convenient and effective approach is proposed by combined using of CFD, multi-objective genetic algorithm（MOGA） and artificial neural networks（ANN） for a double-channel pump＇s impeller, with maximum head and efficiency set as optimization objectives, four key geometrical parameters including inlet diameter, outlet diameter, exit width and midline wrap angle chosen as optimization parameters. Firstly, a multi-fidelity fitness assignment system in which fitness of impellers serving as training and comparison samples for ANN is evaluated by CFD, meanwhile fitness of impellers generated by MOGA is evaluated by ANN, is established and dramatically reduces the computational expense. Then, a modified MOGA optimization process, in which selection is performed independently in two sub-populations according to two optimization objectives, crossover and mutation is performed afterword in the merged population, is developed to ensure the global optimal solution to be found. Finally, Pareto optimal frontier is found after 500 steps of iterations, and two optimal design schemes are chosen according to the design requirements. The preliminary and optimal design schemes are compared, and the comparing results show that hydraulic performances of both pumps 1 and 2 are improved, with the head and efficiency of pump 1 increased by 5.7% and 5.2%, respectively in the design working conditions, meanwhile shaft power decreased in all working conditions, the head and efficiency of pump 2 increased by 11.7% and 5.9%, respectively while shaft power increased by 5.5%. Inner flow field analyses also show that the backflow phenomenon significantly diminishes at the entrance of the optimal impellers 1 and 2, both the area of vortex and intensity of vortex decreases in the whole flow channel. This paper provides a promising tool to solve the hydraulic optimization problem of pumps＇ impellers.

The Influence of LOS Components on the Statistical Properties of the Capacity of Amplify-and-Forward Channels

Amplify-and-forward channels in cooperative networks provide a promising improvement in the network coverage and system throughput. Under line-of-sight (LOS) propagation conditions in such cooperative networks, the overall fading channel can be modeled by a double Rice process. In this article, we have stud-ied the statistical properties of the capacity of double Rice fading channels. We have derived the analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level- crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. The obtained results are studied for different values of the amplitudes of the LOS components in the two links of double Rice fading channels. It has been observed that the statistics of the capacity of double Rice fading channels are quite dif-ferent from those of double Rayleigh and classical Rice fading channels. Moreover, the presence of an LOS component in any of the two links increases the mean channel capacity and the LCR of the channel capacity. The validity of the theoretical results is confirmed by simulations. The results presented in this article can be very useful for communication system designers to optimize the performance of cooperative networks in wireless communication systems.

Influences of double diffusion upon radiative flow of thin film Maxwell fluid through a stretching channel

This work explores the influence of double diffusion over thermally radiative flow of thin film hybrid nanofluid and irreversibility generation through a stretching channel.The nanoparticles of silver and alumina have mixed in the Maxwell fluid(base fluid).Magnetic field influence has been employed to channel in normal direction.Equations that are going to administer the fluid flow have been converted to dimension-free notations by using appropriate variables.Homotopy analysis method is used for the solution of the resultant equations.In this investigation it has pointed out that motion of fluid has declined with growth in magnetic effects,thin film thickness,and unsteadiness factor.Temperature of fluid has grown up with upsurge in Brownian motion,radiation factor,and thermophoresis effects,while it has declined with greater values of thermal Maxwell factor and thickness factor of the thin film.Concentration distribution has grown up with higher values of thermophoresis effects and has declined for augmentation in Brownian motion.

Study on characteristics of a double-conductible channel organic thin-film transistor with an ultra-thin hole-blocking layer

The properties of top-contact organic thin-film transistors （TC-OTFTs） using ultra-thin 2, 9-dimethyl-4, 7- diphenyl-1, 10-phenanthroline （BCP） as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers arc limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate insulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at VDS = --20 V showed excellent hole mobility μFE and threshold voltage VTH of 0.58 cm^2/（V-s） and -4.6 V, respectively.

Effects of supersonic fine particles bombarding on thermal barrier coatings after isothermal oxidation

This work was attempted to modify the current technology for thermal barrier coatings（TBCs） by adding an additional step of surface modification,namely,supersonic fine particles bombarding（SFPB） process,on bond coat before applying the topcoat.After isothermal oxidation at 1000 °C for different time,the surface state of the bond coat and its phase transformation were investigated using X-ray diffraction（XRD）,scanning electron microscopy（SEM） equipped with energy-dispersive X-ray spectrometry（EDS）,transmission electron microscopy（TEM） and Cr3＋ luminescence spectroscopy.The dislocation density significantly increases after SFPB process,which can generate a large number of diffusion channels in the area of the surface of the bond coat.At the initial stage of isothermal oxidation,the diffusion velocity of Al in the bond coat significantly increases,leading to the formation of a layer of stable α-Al2O3 phase.A great number of Cr3＋ positive ions can diffuse via diffusion channels during the transient state of isothermal oxidation,which can lead to the presence of（Al0.9Cr0.1）2O3 phase and accelerate the γ→θ→α phase transformation.Cr3＋ luminescence spectroscopy measurement shows that the residual stress increases at the initial stage of isothermal oxidation and then decreases.The residual stress after isothermal oxidation for 310 h reduces to 0.63 GPa compared with 0.93 GPa after isothermal oxidation for 26 h.In order to prolong the lifespan of TBCs,a layer of continuous,dense and pure α-Al2O3 with high oxidation resistance at the interface between topcoat and bond coat can be obtained due to additional SFPB process.

Experimental Study on the Mobility of Channelized Granular Mass Flow

Granular mass flows （e.g., debris flows/avalanches） in landslide-prone areas are of great concern because they often cause catastrophic disasters as a result of their long run-out distances and large impact forces. To investigate the factors influencing granular mass flow mobility, experimental tests were conducted in a flume model. Granular materials consisting of homogeneous sand and non- homogeneous sandy soil were used for studying particle size effects. Run-out tests with variable flow masses, water contents, and sloping channel confinement parameters were conducted as well. The results indicated that granular mass flow mobility was significantly influenced by the initial water content; a critical water content corresponding to the smallest flow mobility exists for different granular materials. An increase in the total flow mass generally induced a reduction in the travel angle （an increase in flow mobility）. Consistent with field observations, the travel angles for different granular materials decreased roughly in proportion to the logarithm of mass. The flume model tests illustrate that the measured travel angles increase as the proportion of fine particles increases. Interestingly, natural terrain possesses critical confinement characteristics for different granular mass flows.

Influence of Fine Sediment on the Fluidity of Debris Flows

Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments： assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other eases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.

A FINE GRANULAR JOINT SOURCE CHANNEL CODING METHOD

An improved FGS (Fine Granular Scalability) coding method is proposed in this letter, which is based on human visual characteristics. This method adjusts FGS coding frame rate according to the evaluation of video sequences so as to improve the coding efficiency and subject perceived quality of reconstructed images. Finally, a fine granular joint source channel coding is proposed based on the source coding method, which not only utilizes the network resources efficiently, but guarantees the reliable transmission of video information.

Corrosion behavior of ultra-fine grained industrial pure Al fabricated by ECAP

Corrosion behavior of ultra-fine grained(UFG) industrial Al fabricated by equal channel angular pressing(ECAP) for 16 pass times was investigated by potentiodynamic polarization test,potentiostatic polarization test,electrochemical impedance spectroscopy(EIS) measurement,immersion test and surface analyses (OM and SEM). The microstructures including grain size,grain boundaries and dislocations were also observed by TEM. The results show that the UFG industrial pure Al has more positive pitting potential,less corrosion current density and five times larger passive film resistance compared with the coarse grained(CG) one. It was found that the increased pitting resistance is profited from the more stable passive film kept in the Cl-aggressive solution due to more grain boundaries,larger fraction of non-equilibrium grain boundaries and residual stress of the UFG industrial pure Al.

Reversal current observed in micro-and submicro-channel flow under non-continuous DC electric field

In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.

Fang-Howard wave function modelling of electron mobility in AlInGaN/AlN/InGaN/GaN double heterostructures

To study the electron transport properties in InGaN channel-based heterostructures,a revised Fang-Howard wave function is proposed by combining the effect of GaN back barrier.Various scattering mechanisms,such as dislocation impurity(DIS)scattering,polar optical phonon(POP)scattering,piezoelectric field(PE)scattering,interface roughness(IFR)scattering,deformation potential(DP)scattering,alloy disorder(ADO)scattering from InGaN channel layer,and temperature-dependent energy bandgaps are considered in the calculation model.A contrast of AlInGaN/AlN/InGaN/GaN double heterostructure(DH)to the theoretical AlInGaN/AlN/InGaN single heterostructure(SH)is made and analyzed with a full range of barrier alloy composition.The effect of channel alloy composition on InGaN channel-based DH with technologically important Al(In,Ga)N barrier is estimated and optimal indium mole fraction is 0.04 for higher mobility in DH with Al_(0.4)In_(0.07)Ga_(0.53)N barrier.Finally,the temperature-dependent two-dimensional electron gas(2DEG)density and mobility in InGaN channel-based DH with Al_(0.83)In_(0.13)Ga_(0.04)N and Al_(0.4)In_(0.07)Ga_(0.53)N barrier are investigated.Our results are expected to conduce to the practical application of InGaN channel-based heterostructures.

Control of Beam Halo-Chaos for an Intense Charged-Particle Beam Propagating Through Double Periodic Focusing Field by Soliton

We study an intense beam propagating through the double periodic focusing channel by the particle-coremodel,and obtain the beam envelope equation.According to the Poincare-Lyapunov theorem,we analyze the stabilityof beam envelope equation and find the beam halo.The soliton control method for controlling the beam halo-chaos isput forward based on mechanism of halo formation and strategy of controlling beam halo-chaos,and we also prove thevalidity of the control method,and furthermore,the feasible experimental project is given.We perform multiparticlesimulation to control the halo by using the soliton controller.It is shown that our control method is effective.We alsofind the radial ion density changes when the ion beam is in the channel,not only the halo-chaos and its regeneration canbe eliminated by using the nonlinear control method,but also the density uniformity can be found at beam's centre aslong as an appropriate control method is chosen.