Flat Interface Research Articles

Impact of the Interband Transitions in Gold and Silver on the Dynamics of Propagating and Localized Surface Plasmons.

Understanding and modeling of a surface-plasmon phenomenon on lossy metals interfaces based on simplified models of dielectric function lead to problems when confronted with reality. For a realistic description of lossy metals, such as gold and silver, in the optical range of the electromagnetic spectrum and in the adjacent spectral ranges it is necessary to account not only for ohmic losses but also for the radiative losses resulting from the frequency-dependent interband transitions. We give a detailed analysis of Surface Plasmon Polaritons (SPPs) and Localized Surface Plasmons (LPSs) supported by such realistic metal/dielectric interfaces based on the dispersion relations both for flat and spherical gold and silver interfaces in the extended frequency and nanoparticle size ranges. The study reveals the region of anomalous dispersion for a silver flat interface in the near UV spectral range and high-quality factors for larger nanoparticles. We show that the frequency-dependent interband transition accounted in the dielectric function in a way allowing reproducing well the experimentally measured indexes of refraction does exert the pronounced impact not only on the properties of SPP and LSP for gold interfaces but also, with the weaker but not negligible impact, on the corresponding silver interfaces in the optical ranges and the adjacent spectral ranges.

Telescope objective with tunable field of view

We report an electrically controlled telescope objective which can obtain tunable field of view. The proposed telescope objective consists of three main parts: a telescopic objective, a liquid prism and CMOS. The liquid prism is the essential part which composes of two immiscible liquids and makes the system more stable. In particular, there is a transparent partition sheet between liquid–liquid (L–L) interface in the liquid prism which helps to obtain perfect flat interface. When a voltage is applied on the device, the flat interface tilts and field of view (FOV) is deflected. To prove the concept, we fabricate an electrically controlled telescope objective whose tunable FOV is ∼5.8°. The response time is about 480 ms. Application in imaging system to deflect FOV is also demonstrated. The proposed telescope objective has potential applications in surveillance system, unmanned aerial vehicle system, military field and so on.

Radar Sounding Confirms a Hydrologically Active Deep-Water Subglacial Lake in East Antarctica

Lake CookE2, upstream of Cook Glacier in East Antarctica is an ‘active’ subglacial lake, which experiences episodic discharge and recharge of basal water. Although around 130 active lakes are known to exist, the majority are not able to be identified by radar sounding techniques, suggesting they are ephemeral and/or distributed stores of small amounts of water rather than permanent significant singular features. Airborne ice-sounding radar data from Lake CookE2, a known ‘active’ subglacial lake, reveal a bright and flat ice-bed interface, providing clear evidence of deep (>10 m) water surrounded by elevated topography, however. The data reveal the lake area is ~46 km2; 3 times less than a previous estimated (145 km2) from ICESat surface altimetry, indicating a possible bias in identifying subglacial lake area from surface depressions. Using time-series altimetry from ICESat, Cryosat-2 data, and the Reference Elevation Model of Antarctica, we re-estimate the lake discharged ~2.93 km3 of water (or ~63.8 m in lake level) between February 2006 and January 2011. Subsequently, the ice surface over the lake rose steadily and experienced a mean uplift of ~11 m between January 2011 and November 2016, indicating continuous recharge with total volume increase of ~0.51 km3. The lake is recharging at a rate of ~1.33 m/year, which means it will take another ~39 years to reach the lake level that triggered the previous discharge.

Chronic nerve health following implantation of femoral nerve cuff electrodes

BackgroundPeripheral nerve stimulation with implanted nerve cuff electrodes can restore standing, stepping and other functions to individuals with spinal cord injury (SCI). We performed the first study to evaluate the clinical electrodiagnostic changes due to electrode implantation acutely, chronic presence on the nerve peri- and post-operatively, and long-term delivery of electrical stimulation.MethodsA man with bilateral lower extremity paralysis secondary to cervical SCI sustained 5 years prior to enrollment received an implanted standing neuroprosthesis including composite flat interface nerve electrodes (C-FINEs) electrodes implanted around the proximal femoral nerves near the inguinal ligaments. Electromyography quantified neurophysiology preoperatively, intraoperatively, and through 1 year postoperatively. Stimulation charge thresholds, evoked knee extension moments, and weight distribution during standing quantified neuroprosthesis function over the same interval.ResultsFemoral compound motor unit action potentials increased 31% in amplitude and 34% in area while evoked knee extension moments increased significantly (p < 0.01) by 79% over 1 year of rehabilitation with standing and quadriceps exercises. Charge thresholds were low and stable, averaging 19.7 nC ± 6.2 (SEM). Changes in saphenous nerve action potentials and needle electromyography suggested minor nerve irritation perioperatively.ConclusionsThis is the first human trial reporting acute and chronic neurophysiologic changes due to application of and stimulation through nerve cuff electrodes. Electrodiagnostics indicated preserved nerve health with strengthened responses following stimulated exercise. Temporary electrodiagnostic changes suggest minor nerve irritation only intra- and peri-operatively, not continuing chronically nor impacting function. These outcomes follow implantation of a neuroprosthesis enabling standing and demonstrate the ability to safely implant electrodes on the proximal femoral nerve close to the inguinal ligament. We demonstrate the electrodiagnostic findings that can be expected from implanting nerve cuff electrodes and their time-course for resolution, potentially applicable to prostheses modulating other peripheral nerves and functions.Trial registrationClinicalTrials.govNCT01923662, retrospectively registered August 15, 2013.

The effect of astigmatism induced by refraction on the orbital angular momentum of light

We use the Fourier transform and Snell’s law to demonstrate how refraction at a flat interface induces astigmatism and transforms the spatial distribution of a stigmatic beam. Refraction makes the beam parameters for the transverse dimensions perpendicular and parallel to the plane of incidence grow differently and gives rise astigmatism. The decompositions of the orbital angular momentum of the beam before and after refraction are different. A single-value state of orbital angular momentum of the incident photon in a Laguerre–Gaussian mode is transformed into a superposition state.

Modelling of the circular edge-clamped interface of a hydraulic pressure energy harvester to determine power, efficiency and bandwidth

There is an increasing desire to monitor and control hydraulic systems in an autonomous and battery-free manner. One solution to this challenge is to harvest hydraulic pressure ripples and noise by exploiting the piezoelectric effect. This paper develops a new generalized model of a hydraulic piezoelectric harvester based on a circular edge-clamped flat plate interface with a central piezoelectric stack. Such a model allows the relationships between harvesting performance and structure to be assessed in detail. It is demonstrated that the force-deflection relationship of a circular edge-clamped plate with a central lumped mass follows a cubic hardening Duffing equation. A single degree of freedom (SDOF) lumped-parameter model of the system is established where the nonlinear frequency response resulting from hardening nonlinearities are explored. The input mechanical energy and the output electrical energy both exhibit a quadratic nonlinear relationship with vibration amplitude. The maximum output occurs at the jump-down frequency and the overall energy conversion efficiency of the system is determined. The optimum resistance load for maximum output energy and energy efficiency are obtained as non-dimensional excitation frequency. Experimental validation is performed and good agreement is observed between model results and experimental measurements. The developed model provides important insights into the optimization of power output and response of future hydraulic energy harvesting devices.

Thermophoresis of a spherical particle straddling the interface of a semi-infinite micropolar fluid

The quasi-steady thermophoretic motion of a spherical particle straddling the flat interface of a semi-infinite micropolar fluid flow is investigated. The Reynolds numbers of the micropolar fluid and also the capillary number are assumed to be small. The case of 90° contact angle with flat surface is considered. The Knudsen number is assumed to be in the slip-flow regime. Various types of slip conditions are considered on the immersed portion of the particle surface: frictional and thermal slip for linear velocity and also microrotation slip. The cases of axisymmetric and asymmetric motions are studied. Expressions for thermophoretic velocities, forces and couples on the half-submerged sphere are obtained and their variations represented graphically as functions of the Fourier thermal conductivities, Knudsen number, micropolarity parameter, frictional slip parameter and the thermal stress slip parameter. The limiting cases of classical viscous fluid with thermophoresis are also discussed.

Ferroelectric, ferromagnetic, and magnetoelectric properties of Bi3.15Nd0.85Ti2.9Zr0.1O12–CoFe2O4 composite films with large magnetoelectric coupling effect

The magnetoelectric composite films of Bi3.15Nd0.85Ti2.9Zr0.1O12 (BNTZO)–CoFe2O4 (CFO) were deposited on the substrates of Pt/Ti/SiO2/Si (111) by means of the sol–gel method. The results show that, in the composite films, there are tri-axial compressive stresses in the CFO films. Nevertheless, there are bi-axial tensile stresses and uniaxial compressive stress in the BNTZO films. The composite films possess compact microstructure and flat interface without forming intermediate layer. The composite films have good magnetoelectric properties besides both good ferroelectric and ferromagnetic properties. When Hdc is 738 Oe, the composite film of BNTZO-CFO possesses the maximum of αE, 114 mV cm−1 Oe−1, which is helpful for the application in multi-functional devices.

The Effect of Surface Finish on the Proper Functioning of Underplatform Dampers

Abstract Underplatform dampers are used to limit the resonant vibration of turbine blades. In recent years, various strategies have been implemented to maximize their damping capability. Curved-flat dampers are preferred to ensure a predictable bilateral contact, while a pre-optimization procedure was developed to exclude all those cross-sectional shapes that will bring the damper to roll and thus limit the amount of dissipated energy. The pre-optimization bases its predictions on the assumption that the effective width of the flat contact interface corresponds to the nominal one. It is shown here that this hypothesis cannot be relied upon: the energy dissipated by two nominally identical dampers, machined according to the usual industrial standards, may differ by a factor up to three due to the morphology of the flat-to-flat contact interface. Five dampers have been tested on two dedicated test rigs, available in the AERMEC laboratory, specially designed to reveal the details of the damper behavior during operation. Their contact interfaces are scanned by means of a profilometer. In each case, the mechanics, the kinematics, and the effectiveness of the dampers in terms of cycle shape and dissipated energy are correlated to the morphology of the specific contact surface. To complete the picture, a state-of-the-art numerical simulation tool is used to show how this tribo-mechanic phenomenon, in turn, influences the damper effect on the dynamic response of the turbine.

Negligible Substrate‐Induced Strain Effects on Magnetic Properties of SrRuO3 Thin Films

SrRuO3 is known to exhibit strong magnetocrystalline effect, which enables us to control its magnetic properties using lattice engineering. The magnetocrystalline effect of SrRuO3 is systematically investigated under both compressive and tensile strain by depositing SrRuO3 thin films on various oxide substrates with different in‐plane lattice mismatch. All SrRuO3 films have high crystallinity with flat interface and surface. It is found that out‐of‐plane lattice constant is decreased with increasing strain. Moreover, unit cell volume decreases with strain due to structural distortion attributable to RuO6 octahedral distortion as theoretically expected. However, magnetization does not match to any of the theoretical models only considering structural changes; at current stage, internal interactions rather than structural changes seem critical in determining the magnetization of the SrRuO3 films. This study can play a crucial role in understanding internal correlations of magnetic properties in ruthenate films and can trigger research on magnetic functionality.

Influence of Constrained High-Pressure Torsion on Microstructure and Mechanical Properties of an Aluminum-Based Metal Matrix Composite

Multilayered Al-Cu composites were fabricated successfully by constrained high-pressure torsion (HPT) in a Bridgeman anvil type unit under an applied pressure of 6.0 GPa after ten turns. Due to the good strain compatibility of Al and Cu, achieved during HPT, separate discs bonded without pores and cracks. Microstructural characterization of the processed disks showed that the originally flat interface between Al and Cu layers transforms, and some bindings and vortice-like folding are formed in a submicron multilayered structure embedded in an Al-rich matrix in almost all volumes. This led to an exceptional increase of ultimate strength. The tensile tests showed the value of the tensile strength reached 485 MPa at room temperature, which is several times higher than in pure aluminum (80 MPa) and copper (190 MPa) subjected to the same processing. Such an increase in the ultimate strength is associated with hardening due to formation of a multiphase fine-grained structure. This study indicates a high potential for the application of high-pressure torsion in bonding of Al and Cu to produce composites with enhanced mechanical properties.

Large spin Hall effect and increase in perpendicular magnetic anisotropy in artificially synthesized amorphous W/Hf multilayer/CoFeB system

We studied the spin-Hall effect and perpendicular magnetic anisotropy in W/Hf multilayer/CoFeB/MgO and W80Ta20/Hf multilayer/CoFeB/MgO systems and compared them with those in the β-W/CoFeB/MgO system. From the cross-sectional high-resolution transmission electron microscopy images, (i) the amorphous structure of W/Hf and W80Ta20/Hf multilayers, (ii) the flat interface between heavy metals and CoFeB, and (iii) highly (100) texture of MgO (1.0 nm) on CoFeB were observed in those multilayer systems. A higher spin-Hall effect and enhancement of perpendicular magnetic anisotropy in the W/Hf multilayer/CoFeB/MgO system can be achieved compared to the β-W/CoFeB/MgO system. In addition, we found that the resistivity in amorphous W/Hf multilayers is low compared to that in β-W. These results suggest that the artificially synthesized multilayer system is one of the avenues for realizing the heavy metal with a large spin-Hall effect and low resistivity.

Spontaneously Self‐Assembly of a 2D/3D Heterostructure Enhances the Efficiency and Stability in Printed Perovskite Solar Cells

AbstractAs perovskite solar cells (PSCs) are highly efficient, demonstration of high‐performance printed devices becomes important. 2D/3D heterostructures have recently emerged as an attractive way to relieving the film inhomogeneity and instability in perovskite devices. In this work, a 2D/3D ensemble with 2D perovskites self‐assembled atop 3D methylammonium lead triiodide (MAPbI3) via a one‐step printing process is shown. A clean and flat interface is observed in the 2D/3D bilayer heterostructure for the first time. The 2D perovskite capping layer significantly suppresses nonradiative charge recombination, resulting in a marked increase in open‐circuit voltage (VOC) of the devices by up to 100 mV. An ultrahigh VOC of 1.20 V is achieved for MAPbI3 PSCs, corresponding to 91% of the Shockley–Queisser limit. Moreover, notable enhancement in light, thermal, and moisture stability is obtained as a result of the protective barrier of the 2D perovskites. These results suggest a viable approach for scalable fabrication of highly efficient perovskite solar cells with enhanced environmental stability.

Theoretical and numerical analysis of density perturbation development induced by high velocity impact

The problem of high velocity impact between two solid plates where one of them has a non-uniformly disturbed density field is studied. The nature of an initial perturbation here differs from one considered in the classical Richtmyer–Meshkov instability (RMI). We consider the instability that develops from the initial perturbations of the density field with a flat interface between plates, while RMI is triggered by a shock passing through the corrugated interface. The structure of perturbation fields generated in the plates due to impact and the interface evolution are studied via the analytic linear and nonlinear models for normal modes using the Euler equations for compressible fluids and appropriate boundary conditions. Such analysis reveals three different regimes in which the generated disturbances can develop depending on the direction of the perturbation wave vector. The obtained theoretical findings are in good quantitative agreement with our detailed numerical simulations.

High interfacial quality metal-oxide-semiconductor capacitor on (111) oriented 3C-SiC with Al2O3 interlayer and its internal charge analysis

Metal-oxide-semiconductor (MOS) capacitors with various gate dielectrics were fabricated on (111) oriented n-type 3C-SiC. Deposited SiO2 by sputtering without an interlayer (IL) and thermally grown SiO2 show deteriorated capacitance–voltage (C–V) characteristics and high interface trap density (Dit) over 1011–1012 cm−2 eV−1. By inserting an IL, C–V and leakage current characteristics are improved. In particular, an atomic layer deposited (ALD) Al2O3-IL is suitable for 3C-SiC, which successfully achieved low Dit in the order of 1010 cm−2 eV−1. MOS capacitor with the same gate dielectric on n-Si shows contradictory characteristics. Structural analysis shows it is considered the flat and uniform interface at Al2O3/3C-SiC leads good electrical characteristics. The 3C-SiC MOS capacitor with Al2O3-IL showed slightly negative flatband voltage and it is induced by negative interfacial dipole generated at the Al2O3/3C-SiC interface. This 3C-SiC MOS structure can be fabricated at low process temperature (<600 °C), which means the overall process for device application can be designed more flexibly.

Numerical Simulation of Flow Field and Ion Transport for Different Ion Source Sampling Interfaces of a Mass Spectrometer.

Understanding ion transport mechanisms in the flow expansion section of the first vacuum region of a mass spectrometer (MS) with an atmospheric pressure ionization source is essential for optimizing the MS sampling interface design. In this study, numerical simulations of three types of ions in two different MS interface designs have been carried out. In contrast to previously reported numerical studies, nonequilibrium gas dynamics due to rarefied gas effects has been considered in modeling the flow expansion and a realistic space charge effect has been considered in a continuous ion injection mode. Numerical simulations reveal that a flat plate interface has a higher peak buffer gas velocity but a narrower zone of silence compared to the conical interface. Shock wave structures are clearly captured, and the Knudsen number distribution is displayed. Simulation results show that in the axial direction the buffer gas effect is much stronger than the electric force effect in the current configuration. The conical interface leads to both a strong ion acceleration in the zone of silence and a strong ion deceleration downstream. In the radial direction, both the electric force and buffer gas drag force play an important role. The conical interface introduces a relatively stronger ion focusing effect from the radial buffer gas effect and a stronger ion dispersion from the radial electric force than the flat plate interface. The net effect for the current configuration is an increase in ion losses for the conical interface. Nanoelectrospray ionization experiments were carried out to validate the ion transmission efficiency.

Birkhoff Normal form for Gravity Water Waves

We consider the gravity water waves system with a one-dimensional periodic interface in infinite depth, and present the proof of the rigorous reduction of these equations to their cubic Birkhoff normal form (Berti et al. in Birkhoff normal form and long-time existence for periodic gravity Water Waves. arXiv:1810.11549, 2018). This confirms a conjecture of Zakharov–Dyachenko (Phys Lett A 190:144–148, 1994) based on the formal Birkhoff integrability of the water waves Hamiltonian truncated at degree four. As a consequence, we also obtain a long-time stability result: periodic perturbations of a flat interface that are of size $$\varepsilon $$ in a sufficiently smooth Sobolev space lead to solutions that remain regular and small up to times of order $$\varepsilon ^{-3}$$ .

Numeric input operation on electronic devices among individuals with visuospatial working memory impairment

ABSTRACT In human–computer interactions, higher-level visuospatial function is likely needed to effectively use the interface. The aim of this study is to clarify whether individuals with visuospatial defects can use electronic devices effectively. We quantitatively and qualitatively analyzed the ability of seven individuals with Bálint syndrome and seven individuals with left-unilateral spatial neglect (USN) to input a digit sequence into a flat touch interface. Control groups consisted of seven individuals with memory deficits and 11 healthy individuals. Participants with Bálint syndrome took longer and had more hesitations than the USN group and the two control groups to input numerical sequences (Steel-Dwass test, p < .01). In addition, participants with Bálint syndrome had a high percentage of hesitations for exploration of the button array on the interface relative to USN and the memory deficit group (Fisher’s exact test, p < .05). Regarding neuropsychological data, participants with Bálint syndrome had a lower score for visuospatial working memory than participants with USN and the memory deficits control group (Steel-Dwass test, p < .01). The results shed some light on the relation between visuospatial working memory deficits and the spatial perception of interface layouts and spatial control during electronic device operation.

Prediction of pressure drop for segregated oil-water flows in small diameter pipe using modified two-fluid model

Horizontal segregated oil-water two-phase flows are widely encountered in oil wells. The pressure drop is an important parameter to evaluate the productivity of the horizontal oil well. In this study, through introducing dynamic contact angle, we calculate the oil-water interface shape by solving Young-Laplace equation. The oil-water interface shapes and the wave characteristics are considered to modify the closure relations of the two-fluid model (TFM), and consequently the pressure drop of horizontal oil-water flows is predicted using the modified TFM. In addition, we predict the pressure drop of horizontal oil-water flows using the TFM with flat interface. Through comparing the prediction results of the pressure drop, it is found that the TFM modified with dynamic contact angle allows for higher accuracy in pressure drop prediction, and it is not dependent on the flow pattern discrimination.

Enhanced Dynamics of Confined Polymers near the Immiscible Polymer-Polymer Interface: Neutron Reflectivity Studies.

For polymer-blend films, local dynamics in confined polymer domains tend to differ from the bulk because of significant contributions from the polymer-polymer interface. Herein, we investigated the diffusion dynamics of entangled polymer thin films confined between different polymers in a direction perpendicular to the surface using neutron reflectivity. We found that a bilayer of poly(methyl methacrylate) (PMMA) and deuterated PMMA (dPMMA) sandwiched between polystyrene (PS) layers exhibited significant increase in mobility near the polymer-polymer interface with decreasing PMMA thickness. This indicates that the contribution of repulsive interactions at the immiscible polymer-polymer interface becomes more significant as the film thickness decreases. We also found that the interfacial roughness between PMMA and PS (28 Å at equilibrium) and soft confinement of PS layers did not significantly affect the change in the diffusion dynamics of the adjacent PMMA. This was evidenced by comparison with the diffusion results of multilayers with a flat interface (8 Å at equilibrium) between PMMA and hard PS by UV cross-linking.