Parallel To Surface Research Articles

Hall current and morphological effects on MHD micropolar non-Newtonian tri-hybrid nanofluid flow between two parallel surfaces

In the present work, the magnetohydrodynamic flow and heat transfer of a micropolar tri-hybrid nanofluid between two porous surfaces inside a rotating system has been examined. A tri-hybrid nanofluid is a new idea in the research area, which gives a better heat transfer rate as compared to hybrid nanofluid and nanofluid. We also incorporated the thermal radiation effects and Hall current in this article. The similarity techniques are used to reduce the governing nonlinear PDEs to a set of ODEs. For the numerical solution of the considered problem, we have used the MATLAB-based Bvp4c method. The results are presented for tri-hybrid Fe3O4-Al2O3-TiO2/H2O nanofluid. The main focus of this study is to examine the magnetohydrodynamic heat transfer and tri-hybrid nanofluid flow in a rotating system between two orthogonal permeable plates by taking into account the Hall current and thermal radiation effects. The obtained results have been explained with the help of graphical illustrations and tables. It is observed that the heat transfer rate of tri-hybrid nanofluid is greater than as compared to hybrid nanofluid and nanofluid. The increasing behavior is also noticed in micro rotational velocity for augmented values of {R}_{0}, Ha, and beta. The larger values of {phi }_{1}, {phi }_{2}, and {phi }_{3} result in the decrement of SFC and increment in Nusselt number in both (suction and injection) cases.

Two case studies in approach to the renovation of volumetrically challenged music rehearsal spaces

A music rehearsal room renovation can be acoustically challenging in that there is often limited room volume, lack of loudness control, and budget constraints. Two case studies detail these challenges. (1) The University of North Texas’ choral rehearsal room was due for renovation and with a volume of only 44,000 cubic feet, the room had to accommodate choral ensembles varying from 20–85 people for daily use, over 100 voices for an annual festival, and an added recital use. At an appropriate budget, the renovation used room shaping to simultaneously break up parallel surfaces and support voices while also adding adjustable acoustics to allow for tuning of the room for each rehearsal or performance. (2) The University of Texas at San Antonio’s large band, orchestra, and jazz rehearsal room lacked loudness control even with an approximate volume of 73,500 cubic feet to serve 30 – 70 + musicians. At a much more limited budget, the solution was to flip the orientation of the musician layout in the room to take advantage of the existing room geometry and to introduce variable absorption stored exposed to the room which increased the overall absorption while also giving the ensembles an opportunity to tune the room.

In Situ Co-modification Strategy for Achieving High-Capacity and Durable Ni-Rich Cathodes for High-Temperature Li-Ion Batteries

Operating Li-ion batteries in a harsh environment will greatly degrade the cyclic performance and safety of Ni-rich layered cathodes, which challenges the current modification approaches to form a more stable interface with the electrolyte and a robust crystal structure. Herein, we demonstrate the surface engineering enabling V-doped and ZrV2O7-coated Ni-rich layered cathodes (V-NCM@ZVO), where stoichiometric ZVO generates on the surface of oxides and tailorable V subsequently diffuses into the bulk phase during high-temperature lithiation. The introduction of high-energy V–O bonds vastly refrains the lattice oxygen escape, and meantime, ionic conductive and electrochemically inert ZVO ensures a robust interphase on the Ni-rich cathode, greatly enhancing the thermal stability. At 55 °C, the modified cathode displays a high reversible capacity of 220.3 mAh g–1 at 0.2 C and 183.0 mAh g–1 at 10 C. More impressively, the assembled V-NCM@ZVO//graphite pouch-type cell exhibits a capacity retention of 90.2% at 1 C after 400 cycles at 55 °C. This work exhibits a feasible modification strategy to strengthen the surface and crystal stability in parallel of Ni-rich cathodes to meet high-temperature Li-ion batteries.

An atomistic-based finite deformation continuum membrane model for monolayer Transition Metal Dichalcogenides

A finite-deformation crystal-elasticity membrane model for Transition Metal Dichalcogenide (TMD) monolayers is presented. Monolayer TMDs are multi-atom-thick two-dimensional (2D) crystalline membranes having atoms arranged on three parallel surfaces. In the present formulation, the deformed configuration of a TMD-membrane is represented through the deformation map of its middle surface and two stretches normal to the middle surface. Crystal-elasticity-based kinematic rules are employed to express the deformed bond lengths and bond angles of TMDs in terms of the continuum strains. The continuum hyper-elastic strain energy of the TMD membrane is formulated from its inter-atomic potential. The relative shifts between two simple lattices of TMDs are also considered in the constitutive relation. A smooth finite element framework using B-splines is developed to numerically implement the present continuum membrane model. The proposed model generalizes the crystal-elasticity-based membrane theory of purely 2D membranes, such as graphene, to the multi-atom-thick TMD crystalline membranes. The significance of relative shifts and two normal stretches are demonstrated through numerical results. The proposed atomistic-based continuum model accurately matches the material moduli, complex post-buckling deformations, and the equilibrium energies predicted by the purely atomistic simulations. It also accurately reproduces the experimental results for large-area TMD samples containing tens of millions of atoms.

Towards merged-element transmons using silicon fins: The FinMET

A merged-element transmon (MET) device based on silicon (Si) fins is proposed, and the first steps to form such a “FinMET” are demonstrated. This new application of fin technology capitalizes on the anisotropic etch of Si(111) relative to Si(110) to define atomically flat, high aspect ratio Si tunnel barriers with epitaxial superconductor contacts on parallel sidewall surfaces. This process circumvents the challenges associated with the growth of low-loss insulating barriers on lattice matched superconductors. By implementing low-loss, intrinsic float-zone Si as the barrier material rather than commonly used, potentially lossy AlOx, the FinMET is expected to overcome problems with standard transmons by (1) reducing dielectric losses; (2) minimizing the formation of two-level system spectral features; (3) exhibiting greater control over barrier thickness and qubit frequency spread, especially when combined with commercial fin fabrication and atomic-layer or digital etching; (4) potentially reducing the footprint by several orders of magnitude; and (5) allowing scalable fabrication. Here, as a first step to making such a device, the fabrication of Si fin capacitors on Si(110) substrates with shadow-deposited Al electrodes is demonstrated. These fin capacitors are then fabricated into lumped element resonator circuits and probed using low-temperature microwave measurements. Further thinning of silicon junctions toward the tunneling regime will enable the scalable fabrication of FinMET devices based on existing silicon technology while simultaneously avoiding lossy amorphous dielectrics for the tunnel barriers.

Impedance Control on Arbitrary Surfaces for Ultrasound Scanning Using Discrete Differential Geometry

We propose an approach to robotic ultrasound scanning and interaction control with arbitrary surfaces using a passivity-based impedance control scheme. First, we introduce task coordinates depending on the geometry of the surface, which enable hands-on guidance of the robot along the surface, as well as teleoperated and autonomous ultrasound image acquisition. Our coordinates allow controlling the signed distance of the robot to the surface and alignment of the tool to the surface normal using classical impedance control. This corresponds to implicitly obtaining a foliation of parallel surfaces. By setting the desired signed distance negative, i.e., into the surface, we obtain passive contact forces and simultaneously provide an intuitive way to control the maximum penetration depth into the surface. We extend the approach to also incorporate coordinates allowing to control the specific point on the surface and, automatically, on all parallel surfaces. Finally, we demonstrate the performance of the controller on the seven degrees of freedom lightweight robot DLR <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Miro</small> : the robot tracks complex trajectories while accurately keeping the desired distance to the surface and applying an almost constant contact force. Finally, we compare the approach to the state of the art.

Observation and theory of strong circular dichroism in angle-revolved photoemission from graphite

Experimental angle-resolved photoemission spectra (ARPES) and its circular dichroism (CD) from a graphite surface are reported together with calculations in the one-step model of photoemission. For photoelectrons emitted with surface parallel momentum k∥ perpendicular to the incoming light, a strong and complex CD signal is observed and analyzed along the Γ-K and Γ-M lines of the Brillouin zone. Calculations using real-space multiple scattering theory agree well with the data both for the total ARPES and the CD intensity maps. In the independent atomic approximation, i.e. when photoelectron scattering is neglected, the total ARPES intensity map is still well described, but not the CD. We find that photoelectron scattering makes a large contribution to the CD signal and may change its sign. Moreover, the CD of the bands depends strongly on photon energy, while this is much less the case for the total ARPES intensity. The present findings show that an accurate description of the photoemission final state, including photoelectron scattering effects, is crucial for understanding the CD in ARPES from surfaces and two-dimensional materials.

Experimental Investigation on the Effect of Surface Shape and Orientation in Magnetic Field Assisted Mass Polishing.

Magnetic field assisted finishing (MFAF) technology has been widely used in industries such as aerospace, biomedical, and the optical field for both external and internal surface finishing due to its high conformability to complex surfaces and nanometric surface finishing. However, most of the MFAF methods only allow polishing piece-by-piece, leading to high post-processing costs and long processing times with the increasing demand for high precision products. Hence, a magnetic field-assisted mass polishing (MAMP) method was recently proposed, and an experimental investigation on the effect of surface posture is presented in this paper. Two groups of experiments were conducted with different workpiece shapes, including the square bar and roller bar, to examine the effect of surface orientation and polishing performance on different regions. A simulation of magnetic field distribution and computational fluid dynamics was also performed to support the results. Experimental results show that areas near the chamber wall experience better polishing performance, and the surface parallel or inclined to polishing direction generally allows better shearing and thus higher polishing efficiency. Both types of workpieces show notable polishing performance where an 80% surface roughness improvement was achieved after 20-min of rough polishing and 20-min of fine polishing reaching approximately 20 nm.

Cylindrical Panel Like Response of Fully Surface Parallel Restrained Simply Supported Hyperbolic Paraboloidal Thick General Cross-ply Panels

An analytical (exact in the limit) solution to the boundary-value problem of deformation of a finite-dimensional general cross-ply thick hyperbolic-paraboloidal panel, modeled using a third order shear deformation theory, is presented. Of special interest is the issue of cylindrical panel-like response, in the presence of full surface-parallel constraints at all four edges of a thick antisymmetric cross-ply panel of negative Gaussian curvature.

Intentionally created localized bridges for electron transport through graphene monolayer between two metals

Monolayer graphene (1LG) is frequently unpredictably modified by supporting material so that it limits development of devices. Van der Waals interaction is dominant in the models describing the in-plane processes, including the electrical charge transport. However, the current flow perpendicular to the plane of the graphene is still less understood. This report analysed specific aspect of the perpendicular current and disclosed an original way to create transport bridges perpendicular to the plane across the 1LG. The most extraordinary finding is that the electron transport between two parallel metal surfaces can be shut down and opened if the metals are separated by the 1LG. The electron transmission can be intentionally varied in this metal–1LG–metal (M–G–M) system by pressure. In the experimental study the AFM force curve and tunnelling current measurements were combined when the external load force (0–1200 nN) and electrical potential (−1.5 V to +1.5 V) were used. It is proved that for low voltages (<±9 mV) a bridge is opened perpendicular to the graphene across the M–G–M systems by the external force, if the compression dependent Fermi level crosses electronic states in the interfaces and graphene. The localised bridges with diameter about 10–40 nm can be opened and kept continuously by the stabilised force in separated points of the system. However, the predictable changes can be produced in the system if the voltage and the force exceeded critical magnitudes. A combined model was proposed acceptable to explain the bridging and predictably modify the characteristics.

Microscale Confinement and Wetting Contrast Enable Enhanced and Tunable Condensation.

Dropwise condensation represents the upper limit of thermal transport efficiency for liquid-to-vapor phase transition. A century of research has focused on promoting dropwise condensation by attempting to overcome limitations associated with thermal resistance and poor surface-modifier durability. Here, we show that condensation in a microscale gap formed by surfaces having a wetting contrast can overcome these limitations. Spontaneous out-of-plane condensate transfer between the contrasting parallel surfaces decouples the nanoscale nucleation behavior, droplet growth dynamics, and shedding processes to enable minimization of thermal resistance and elimination of surface modification. Experiments on pure steam combined with theoretical analysis and numerical simulation confirm the breaking of intrinsic limits to classical condensation and demonstrate a gap-dependent heat-transfer coefficient with up to 240% enhancement compared to dropwise condensation. Our study presents a promising mechanism and technology for compact energy and water applications where high, tunable, gravity-independent, and durable phase-change heat transfer is required.

Effect of Tb diffusion anisotropy on mechanical and magnetic properties of Nd-Fe-B magnet

The surfaces parallel and perpendicular to c-axis of commercial N52 Nd-Fe-B magnet were coated with Tb by magnetron sputtering, respectively. The effect of Tb diffusion anisotropy on magnetic and mechanical properties was investigated. The coercivity increased from original 13.66 kOe to 21.90 kOe for the magnet diffusing parallel to c-axis and 19.68 kOe for the perpendicular diffusion, mainly resulting from the formation of (Nd, Tb)2Fe14B shells. The bending strength σb of original magnet revealed obvious anisotropy. The σb of diffused magnets for parallel to c-axis and perpendicular to c-axis showed a decrease by 1.76% and 6.14%, respectively. The deterioration in mechanical properties was related to internal stress resulting in transgranular fracture near surface of diffused magnet. The difference of magnetic and mechanical properties for the magnets with diverse diffusion direction was mainly caused by anisotropy of Tb diffusion in magnet.

Micromanipulation and Automatic Data Analysis to Determine the Mechanical Strength of Microparticles.

Microparticles are widely used in many industrial sectors. A micromanipulation technique has been widely used to quantify the mechanical properties of individual microparticles, which is crucial to the optimization of their functionality and performance in end-use applications. The principle of this technique is to compress single particles between two parallel surfaces, and the force versus displacement data are obtained simultaneously. Previously, analysis of the experimental data had to be done manually to calculate the rupture strength parameters of each individual particle, which is time-consuming. The aim of this study is to develop a software package that enables automatic analysis of the rupture strength parameters from the experimental data to enhance the capability of the micromanipulation technique. Three algorithms based on the combination of the “three-sigma rule”, a moving window, and the Hertz model were developed to locate the starting point where onset of compression occurs, and one algorithm based on the maximum deceleration was developed to identify the rupture point where a single particle is ruptured. Fifty microcapsules each with a liquid core and fifty porous polystyrene (PS) microspheres were tested in order to produce statistically representative results of each sample, and the experimental data were analysed using the developed software package. It is found that the results obtained from the combination of the “3σ + window” algorithm or the “3σ + window + Hertz” algorithm with the “maximum-deceleration” algorithm do not show any significant difference from the manual results. The data analysis time for each sample has been shortened from 2 to 3 h manually to within 20 min automatically.

Exploring the limits of condensation heat transfer: A numerical study of microscale-confined condensation between parallel surfaces having wetting contrast

Dropwise condensation has received extensive interest due to its potential to enhance the efficiency of power generation, water harvesting, and thermal management systems. The degree of heat transfer enhancement during dropwise condensation is hindered by the delicate balance between nucleation, droplet growth rate, and condensate shedding. Condensation between parallel surfaces having wetting contrast, termed microscale-confined condensation (MCC), presents a promising method to break the fundamental limits of dropwise condensation by decoupling droplet nucleation and growth from condensate removal. The key mechanisms governing MCC enable spontaneous condensate transfer from the condensing surface to a highly wetting absorbing surface to limit the maximum droplet size. Here, we developed and explored numerical simulations of MCC to elucidate the upper limits of the condensation heat transfer rate. To optimize MCC with respect to heat transfer, we examined the effects of surface gap or maximum droplet size, and condensing surface contact angle on droplet size distribution and overall condensation heat flux. We then developed a regime map in terms of surface wettability and shedding droplet size, and showed that smaller surface gaps and smaller condensing surface contact angles are preferential to achieve a higher heat flux in pure vapor condensation conditions. The optimized MCC outperforms state-of-art condensation including classic dropwise condensation and jumping-droplet condensation, with a 250% enhancement of heat transfer coefficient at a steam temperature of 100 °C. Through numerical simulations, our study not only calculates the upper bound of condensation heat transfer, but also provides guidelines for further enhancement of condensation via decoupling droplet shedding from nucleation.

Analytical Treatment of Unsteady Fluid Flow of Nonhomogeneous Nanofluids among Two Infinite Parallel Surfaces: Collocation Method-Based Study

Fluid flow and heat transfer of nanofluids have gained a lot of attention due to their wide application in industry. In this context, the appropriate solution to such phenomena is the study of this exciting and challenging field by the research community. This paper presents an extension of a well-known collocation method (CM) to investigate the accurate solutions to unsteady flow and heat transfer among two parallel plates. First, a mathematical model is developed for the discussed phenomena, then this model is converted into a non-dimensional form using viable similarity variables. In order to inspect the accurate solutions of the accomplished set of nonlinear ordinary differential equations, a collocation method is proposed and applied successfully. Various simulations are performed to analyze the behavior of non-dimensional velocity, temperature, and concentration profiles alongside the deviation of physical parameters present in the model, and then plotted graphically. It is important to mention that the velocity is enhanced due to the higher impact of the parameter Ha. The parameter Nt caused an efficient enhancement in the temperature distribution while the parameters Nt provided a drop in the temperature that actually affected the rate of heat transmission. Dual behavior of concentration is noted for parameter b, while it can be noted that mixed increasing behavior is available for the concentration against Le. The behavior of skin friction, the Nusselt number, and the Sherwood number were also investigated in addition to the physical parameters. It was observed that the Nusselt number increases with the enhancement of the effects of the magnetic field parameter and the Prandtl number. A comparative study shows that the proposed scheme is very effective and reliable in investigating the solutions of the discussed phenomena and can be extended to find the solutions to more nonlinear physical problems with complex geometry.

Magnetic Domain Structure of Galfenol at Elevated Temperatures

Galfenol (iron&#x2013;gallium) has a great potential in MEMS applications owing to its high magnetostriction constant, low saturation field, and resilience to bending, compressive, and tensile loading. Here, we report on the expansion/shift of the topography and the expansion/shift of the magnetic domain structure of galfenol observed at high temperatures via atomic force microscopy (AFM) and magnetic force microscopy (MFM). The maze-like domain pattern and stripe-like domain pattern are observed in the perpendicular and parallel surfaces. The spike and reverse domains are observed in 3-D view via XEI imaging software. A MATLAB-based stereological method was used to obtain the domain width and domain wall energy density. An increase in domain width and decrease in domain wall energy density was identified when temperature increased from room temperature to 150 &#x00B0;C.

Interaction between surfaces decorated with like-charged pendants: Unravelling the interplay between energy and entropy leading to attraction

HypothesisThe stronger motional coupling between monovalent counterions neutralizing homogeneously like-charged surfaces induced by an increase in charge density is known to foster inter–surface attraction. Compared to a uniformly distributed charge, point-like charges generate locally more intense fields, so that the correlation induced between counterions may be even stronger despite an identical total charge. It should thus be possible to induce surface attraction at lower charge densities than commonly expected. ExperimentsMonte Carlo simulations on primitive electrolyte models have been exploited to compute potential of mean force profiles and mobile ion densities for systems composed of two parallel surfaces bearing surface-tethered monovalent like-charged pendants as a function of the surface distance and pendant densities. FindingsSurfaces bearing like-charged pendants are found to attract each other over a wide range of distances despite the presence of very low charge densities. Notwithstanding the attractive contribution to the inter-surface forces provided by electrostatic interactions, the entropic component of the system Helmholtz energy is found to play the key role in defining the overall magnitude. The latter finding appears justified by an increase in the relative delocalization of counterions upon decreasing the surface distance.

Evaluation of Double-Sided Plasma Vortex Generator in Comparison with Vane Vortex Generator on Separation Control

The present research has introduced a new type of Plasma Vortex Generator named as Double-Sided Plasma Vortex Generator (DSPVG) that has dual expose electrodes on both sides. This DSPVG is placed normal to the surface parallel to incoming air and creates vortices on it’s both sides. As conventional VG has an angle with flow direction which introduce device drag, to overcome this, DSPVG is placed with zero angle with flow direction; besides due to the smaller thickness and frontal area with incoming air than VGs, the drag penalty due to its geometry is minimised. Furthermore, as vortices are created on both sides, DSPVG is expected to reduce the number of Plasma Vortex Generator (PVG) with respect to the conventional embedded PVGs or VGs on the flow controlling surface. Hence, it is able to take advantage of height like conventional VGs and active control systems of PVGs with dual vortices on both sides. The impact of DSPVG on separation control has been investigated experimentally and compared its effectiveness with conventional vane VGs. Three different types of flow measurement techniques have been used to confirm the repeatability and consistency of the experimental results. Numerical investigations have been carried out to evaluate the experimental results. These findings show that the DSPVG is capable to eliminate the separation similarly to the conventional VGs but with higher momentum injection and more effective in minimizing drag penalty in the uncontrolled case as in OFF condition of DSPVG, there is no alternation of local flow which is generally affected in case of VGs that adds drag penalty.

Contact With Circles and Euclidean Invariants of Smooth Surfaces in ℝ3

Abstract We investigate the vertex curve, that is the set of points in the hyperbolic region of a smooth surface in real 3-space at which there is a circle in the tangent plane having at least 5-point contact with the surface. The vertex curve is related to the differential geometry of planar sections of the surface parallel to and close to the tangent planes, and to the symmetry sets of isophote curves, that is level sets of intensity in a 2-dimensional image. We investigate also the relationship of the vertex curve with the parabolic and flecnodal curves, and the evolution of the vertex curve in a generic 1-parameter family of smooth surfaces.

Effects of C-factor on dentin bonding using various adhesive systems.

This study evaluated the effect of C-factor on the bond strength of a resin composite to floor and wall dentin using various adhesive systems. Four dentin substrates (flat wall, flat floor, cavity wall, or cavity floor) were prepared on human molars. Each specimen was restored with one of three adhesives; Clearfil SE Bond, Single Bond, or Clearfil tri-S Bond followed by buildup or filling using Z100 resin composite. The specimen was cut perpendicular to the bonded surface parallel to the floor or wall to obtain beams after light curing at 24,000 mJ/cm2. The microtensile bond strength to wall specimens or the cavity floor was determined. Data were analyzed. All adhesive systems exhibited the highest bond strength to flat wall group (p < 0.05). The bond strength to the cavity group was significantly lower than that to the respective flat group regardless of the bonding system (p < 0.05). There was no significant difference in bond strength with Clearfil SE Bond and Clearfil tri-S Bond between the cavity wall and cavity floor (p > 0.05). The findings suggested that the strength of bonding to the cavity floor and cavity wall was affected by C-factor regardless of the adhesive system. Bonding to flat wall was higher than flat floor regardless of the adhesive system. Self-etching system provided uniform bond to the cavity wall and cavity floor dentin. However, total etching system reduced bond to the cavity floor than to the cavity wall.