Inhomogeneous Interface Research Articles

A Zener-Stroh crack along the interface of a rigid elliptical inhomogeneity in an anisotropic elastic matrix

A Zener-Stroh crack along the interface of a rigid elliptical inhomogeneity in an anisotropic elastic matrix

Applicability of polypropylene/polyethylene glycol/molecular sieve composites as desiccant pharmaceutical packaging materials

Pharmaceutical oral dosage forms are vulnerable to moisture-induced damage during transport and storage. This paper investigates the applicability of polypropylene (PP), polyethylene glycol (PEG), and molecular sieve (MS) as packaging materials, focusing on their moisture-absorbing properties, to mitigate this issue. PP/PEG/MS composites were developed in this study to replace conventional desiccants. These composites absorb moisture via hydrophilic channels, physically formed by PEG and MS. The efficacy of moisture absorption is influenced by the number of these PEG channels, functioning as molecular sieves. Increasing MS content in the composites led to decreased mechanical strength, attributed to an inhomogeneous interface with the PP. In storage tests, the composites effectively reduced moisture content and water activity, particularly in multivitamin tablet packaging. These results indicate that the PP/PEG/MS combination efficiently protects the hydration of pharmaceutical products and can be used as a packaging material.

Cooling Effects of Interface Heat Control for Wide Permafrost Subgrades

Quantitative studies of the heat transfer mechanism of permafrost subgrades and its effect on the permafrost under the subgrade are crucial for the study of permafrost subgrade disposal measures; however, few studies have been conducted in this area. In the present work, by quantitatively analyzing the permafrost subgrade heat transfer mechanism and the variations in the underlying permafrost, the preliminary parameters of the interface heat control method—such as the application period, position, and imported cold energy quantity—are determined. The cooling effects of the ideal interface heat control method for different application schemes are analyzed. Finally, by determining the optimized temporal inhomogeneous interface energy control strategy, the required inlet velocity and artificial permafrost table for a mechanical ventilation permafrost subgrade are calculated and compared. The results show that (1) the suitable cold energy application position and period are a 0.5 m interface above the subgrade bottom and the lower thaw season, respectively, and that the imported cold energy needs to vary within the subgrade service life; (2) by adopting interface heat control measures, the maximum difference between the artificial permafrost table under the subgrade and the nearby natural ground table is only 0.097 m, and the temperature of the underlying permafrost and the area of the thawing bowl are significantly reduced; and (3) the mechanical ventilation subgrade employing the cold energy importing strategy of the interface heat control parameter also achieves a protection effect for permafrost, but as the cold air inside the ventilation pipe is gradually heated, it is necessary to amplify the inlet air speed to a certain extent for a better cooling effect.

Microgel particle deposition patterns after impinging on nanofiber-based coatings

The study focuses on predicting the hydrodynamics of sodium alginate-based microgel “liquid core–gel shell” particles for droplet-based bioprinting. Hydrophobic polytetrafluoroethylene nanofiber-based coating (NBC #1) and hydrophilic polycaprolactone–polyvinylpyrrolidone NBC #2 are manufactured to serve as the basis for microgel deposition. An approach is proposed to model the flow of a Maxwell gel-like liquid with different fluidity, surface tension, and initial velocity along an inhomogeneous interface after microgel particle–NBC collision. Wetting and anti-wetting pressure differences allow estimating liquid impalement into NBCs at We = 10–50. For NBC #2, the initial particle velocity plays mainly a decisive role in predicting the contact diameter and height at maximum spreading and receding. For NBC #1, the pinning is considered by introducing the complex parameter resolving particle inertia, microgel rheology and surface tension, and NBC characteristics. The flow along the porous interface physically correlates with the extended Freundlich model, explaining the surface inhomogeneity caused by multilayer adsorption.

Bandwidth of quantized surface plasmons: competition between radiative and nonradiative damping effects.

We investigate the damping effects of coherent electron oscillations on the bandwidth of a quantized nanoparticle plasmon resonance. The nanoparticle (NP) is treated as a two-level quantum system, and the total relaxation time involves both the population relaxation time associated with radiative processes and the collisional relaxation time associated with nonradiative processes that result in dephasing/decoherence of electron oscillations. We describe the optical response of NPs to an external electromagnetic field by the optical Bloch equations employing the density matrix formalism to capture the quantum description nature of dipolar plasmon resonance and suggest a generalized criterion for the validity of dipole approximation. Then we explore the competition between the radiative and nonradiative damping in determining the plasmon bandwidth of two typical NP models; metallic nanospheres and dielectric core-metal shell NPs (nanoshells). We show that the frequency of plasmon resonance, in addition to the NP size, plays an important role in the competition between the damping mechanisms. Consequently, the damping processes are significantly influenced by the factors that determine the resonance frequency, such as the core size, the dielectric constant of the medium, and the shell thickness (for nanoshells). For both models of NPs, we identify the optimum parameters that achieve a narrower plasmon bandwidth (minimal damping), which is a prerequisite for advanced sensing and medical applications. We demonstrate excellent agreement of the simulated spectral features of the plasmon resonance with previously reported experimental results for a single NP where the inhomogeneous broadening of the plasmon line is excluded. For NP ensembles where inhomogeneous broadenings and interface chemical effects are significant, our theoretical approach successfully predicts the overall trend of size-dependent damping rates.

Ultrawide linear range, high sensitivity, and large-area pressure sensor arrays enabled by pneumatic spraying broccoli-like microstructures.

Large-area pressure sensor arrays with a wide linear response range and high sensitivity are beneficial to map the inhomogeneous interface pressure, which is significant in practical applications. Here, we demonstrate a pneumatic spraying method to prepare large-area microstructure films (PSMF) for high performance pressure sensor arrays. The sprayed surface morphology is designable by controlling the spraying parameters. It is worth noting that the constructed "broccoli" like morphology with a swollen top and shrunken bottom inspired a new mechanism to enlarge the linear response range by decreasing the series resistance with pressure increasing. At the same time, the pneumatic sprayed "broccoli" has a rough surface due to droplet stacking, which reduces the initial current effectively. Hence, the sensor achieves a 10 000 kPa ultrawide linear response range with a high sensitivity (98.71 kPa-1), and low detection (5 Pa). The prepared sensor has a small static response error (4.4%) and 5000 cycle full-range dynamic response durability. Finally, the constructed sensor arrays can distinguish the pressure distribution in different ranges clearly, which indicates a great potential in health care, motion detection, and the tire industry.

A three-dimensional Petrov-Galerkin finite element interface method for solving inhomogeneous anisotropic Maxwell's equations in irregular regions

In this paper, a three-dimensional Petrov-Galerkin finite element interface (3D PGFEI) method with non-body-fitted grids is proposed for solving the inhomogeneous anisotropic time-harmonic Maxwell's equations in irregular regions. We derive the weak variational form of the anisotropic Maxwell interface problem. The irregular region is discretized by uniform tetrahedral grids while the media interface is not aligned with the grids. The level-set functions are applied to capture the discontinuity on the anisotropic media interface. Meanwhile, we construct the special basis functions according to the jump conditions across the inhomogeneous interface, where the permittivity and permeability are discontinuous three-dimensional tensors. The resulting linear system is a banded sparse matrix and demands fewer memory resources than dense matrix. Numerical experiments illustrate the efficiency and accuracy of the proposed 3D PGFEI method and the solutions can achieve second-order accuracy in terms of the relative L∞(Ω) and relative L2(Ω) error norms.

Spectral widths and Stokes shifts in InP-based quantum dots.

InP-based quantum dots (QDs) have Stokes shifts and photoluminescence (PL) line widths that are larger than in II-VI semiconductor QDs with comparable exciton energies. The mechanisms responsible for these spectral characteristics are investigated in this paper. Upon comparing different semiconductors, we find the Stokes shift decreases in the following order: InP > CdTe > CdSe. We also find that the Stokes shift decreases with core size and decreases upon deposition of a ZnSe shell. We suggest that the Stokes shift is largely due to different absorption and luminescent states in the angular momentum fine structure. The energy difference between the fine structure levels, and hence the Stokes shifts, are controlled by the electron-hole exchange interaction. Luminescence polarization results are reported and are consistent with this assignment. Spectral widths are controlled by the extent of homogeneous and inhomogeneous broadening. We report PL and PL excitation (PLE) spectra that facilitate assessing the roles of homogeneous and different inhomogeneous broadening mechanisms in the spectra of zinc-treated InP and InP/ZnSe/ZnS particles. There are two distinct types of inhomogeneous broadening: size inhomogeneity and core-shell interface inhomogeneity. The latter results in a distribution of core-shell band offsets and is caused by interfacial dipoles associated with In-Se or P-Zn bonding. Quantitative modeling of the spectra shows that the offset inhomogeneity is comparable to but somewhat smaller than the size inhomogeneity. The combination of these two types of inhomogeneity also explains several aspects of reversible hole trapping dynamics involving localized In3+/VZn2- impurity states in the ZnSe shells.

Study on the slip characteristics of rock inhomogeneous friction interface

Theory assumes that the friction along the discontinuous interface is uniform, and the selection of uniform distribution of friction resistance along the interface is a simplification of the actual physical process. This assumption leads to unsafe design. Therefore, the numerical simulation and experimental methods are used to study the slip of the discontinuous interface with non-uniform friction. This study used a numerical model comprised of two blocks with completely matching contact interfaces. The friction coefficient of one part of the contact surface differed from that of the other, resulting in a non-uniform friction interface. The model was simulated under biaxial compression. First, a normal load of 3 MPa was applied, followed by a shear load until the contact interface slipped. The initiation and propagation of slippage at the contact interface and the changes in the stress field at the slippage contact interface were monitored. The slip started from the area with low frictional strength and gradually expanded to the area with high frictional strength with increasing shear load. The transfer of the slip from an interface with a small friction coefficient to a high friction strength resulted in stress concentration at the interface of the non-uniform friction interface. Engraving using an engraving machine produces a discontinuous interface in which one part of the interface has high friction strength, whereas the other part has low friction strength. The shear load is applied using a shear instrument to cause the discontinuous interface to slip. At the same time, DIC monitored the displacement of the discontinuous interface. The comparison found that the rule of the experimental results is the same as that of the numerical simulation. Reinforcement measures (enhanced friction strength) for areas with low friction strength can effectively prevent slip damage. Based on the distribution of shear stiffness of the rock discontinuous interface, the friction properties of the entire fracture interface can be obtained to accurately identify areas with low frictional strength, and targeted reinforcement measures should be carried out to prevent slip damage.

Evaluation of Radiation Treatment Planning Algorithms in IMRT and VMAT: A Comparative Dosimetric Study in Lung Equivalent Heterogeneous Medium.

In Radiotherapy, computation of dose is important since in a small field with heterogeneity, dose is usually computed with discrepancies. The present study was aimed to evaluate the dosimetry of treatment planning algorithms in lung equivalent heterogeneous medium for Volumetric Modulated Arc Therapy (VMAT) with step and shoot Intensity-Modulated Radiation Therapy (ss-IMRT), and dynamic Intensity-Modulated Radiation Therapy (d-IMRT). In this experimental study, Computerized Imaging Reference System (CIRS) phantom was used with an inhomogeneous Racemosa wood cylinder for two types of tumors, namely, Left Lung Central Tumor (LCT) and Left Lung Peripheral Tumor (LPT) in the CIRS left lung cavity. The computed tomography (CT) datasets were employed with the generation of VMAT, d-IMRT and ss-IMRT plans for the LCT and LPT irradiated with 6 MV photon beams. In this study, the accuracy and efficacy of two algorithms: Monte Carlo (MC) and the Pencil Beam (PB), from the Monaco treatment planning system (TPS), were tested by using Gafchromic EBT3 films and CIRS thorax phantom. Regardless of treatment techniques, both algorithms exhibited higher divergence in LPT than LCT. In both LCT and LPT, the highest deviation was near the tumor-lung junction. However, the deviation was higher in the PB algorithm than MC algorithm, with a minimally acceptable variation of -0.8%. The MC algorithm shows more consistency for EBT3 measured dose in lung equivalent heterogeneous medium. However, accurate dose predictions are complicated due to electronic disequilibrium within and at the interface of inhomogeneity. These constraints may cause variations from the anticipated outcomes of the treatments.

On the origin of Minnaert resonances

It is well known that the presence, in a homogeneous acoustic medium, of a small inhomogeneity (of size ε), enjoying a high contrast of both its mass density and bulk modulus, amplifies the generated total fields. This amplification is more pronounced when the incident frequency is close to the Minnaert frequency ωM. Here we provide an interpretation of such a phenomenon: at first we show that the scattering of an incident wave of frequency ω is described by a self-adjoint ω-dependent Schrödinger operator with a singular δ-like potential supported at the inhomogeneity interface. Then we show that, in the low energy regime (corresponding in our setting to ε≪1) such an operator has a non-trivial limit (i.e., it asymptotically differs from the Laplacian) if and only if ω=ωM. The limit operator describing the non-trivial scattering process is explicitly determined and belongs to the class of point perturbations of the Laplacian. When the frequency of the incident wave approaches ωM, the scattering process undergoes a transition between an asymptotically trivial behavior and a non-trivial one.

Enhanced Long‐Term Cathode Stability by Tuning Interfacial Nanocomposite for Intermediate Temperature Solid Oxide Fuel Cells

AbstractPerformance durability is one of the essential requirements for solid oxide fuel cell materials operating in the intermediate temperature range (500–700 °C). The trade‐off between desirable catalytic activity and long‐term stability challenges the development and commercialization of electrode materials. Here an oxygen cathode material, Ba0.5Sr0.5(Co0.7Fe0.3)0.69−xMgxW0.31O3−δ (BSCFW‐xMg), that exhibits excellent electrocatalytic performance through the addition of an optimized amount of Mg to the self‐assembled nanocomposite Ba0.5Sr0.5(Co0.7Fe0.3)0.69W0.31O3−δ (BSCFW) by simple solid‐state reaction is reported. Distinct from the bulk and surface approaches to introduce vacancies and defects in materials design, here the Mg2+ ions concentrate at the single perovskite/double perovskite interface of BSCFW with dislocations and Mg2+‐rich nanolayers, resulting in stressed and compositionally inhomogeneous interface regions. The interfacial chemistry within these nanocomposites provides an additional degree of freedom to enable performance optimization over single phase materials and promotes the durability of alkaline‐earth based fuel cell materials.

Effect of Anode Material on the Sensitivity of GaN Schottky Barrier Diode Temperature Sensor

GaN Schottky barrier diode (SBD) temperature sensors with TiN, Ni, and NiN anodes were fabricated in this study to evaluate the effect of anode material and inhomogeneous interface on the sensitivity. The temperature-dependent current–voltage curves negatively shift with the increasing temperature, presenting a slight inhomogeneous barrier behavior. Compared with the Ni anode, the TiN and NiN anodes suppress the inhomogeneity. The sensitivity obtained from the sub-threshold region follows the same tendency for all the SBDs, which increases with the decreasing current level. Furthermore, the NiN anode temperature sensor shows slightly higher sensitivity and better linearity compared with the Ni and TiN anodes, with the highest sensitivity of 2.54 mV/K. The discrepancy between the measured sensitivity and the theoretical value is ascribed to the inhomogeneous interface barrier.

Surface waves on the inhomogeneous interface between radiative electron–ion plasma and vacuum

The impact of temperature inhomogeneity, surface charge and surface mass densities on the stability analysis of charged surface waves at the interface between dense, incompressible, radiative, self-gravitating magnetized electron–ion plasma and vacuum is investigated. For such an incompressible plasma system, the temperature inhomogeneity is governed by an energy balance equation. Adopting the one-fluid magnetohydrodynamic (MHD) approximation, a general dispersion relation is obtained for capillary surface waves, which takes into account gravitational, radiative and magnetic field effects. The dispersion relation is analysed to obtain the conditions under which the plasma–vacuum interface may become unstable. In the absence of electromagnetic (EM) pressure, astrophysical objects undergo gravitational collapse through Jeans surface oscillations in contrast to the usual central contraction of massive objects due to enhanced gravity. EM radiation does not affect the dispersion relation much, but actually tends to stabilize the Jeans surface instability. In certain particular cases, pure gravitational radiation may propagate on the plasma vacuum interface. The growth rate of radiative dissipative instability is obtained in terms of the wavevector. Our theoretical model of the Jeans surface instability is applicable in astrophysical environments and also in laboratory plasmas.

A screw dislocation located outside, inside or on the interface of a parabolic elastic inhomogeneity

Using conformal mapping techniques, superposition and analytic continuation, we derive analytic solutions to the problem of a screw dislocation interacting with a parabolic elastic inhomogeneity. The screw dislocation can be located anywhere either in the surrounding matrix or in the parabolic inhomogeneity or simply on the parabolic interface itself. We obtain explicit expressions for the two analytic functions in the image plane characterizing the elastic fields describing displacement and stresses in the two-phase composite. Using the Peach-Koehler formula, we also obtain the image force acting on the screw dislocation. The analytic function defined in the parabolic inhomogeneity in the physical plane can be interpreted in terms of real and image screw dislocations for any location of the real screw dislocation.

Molecular dynamics simulation on (001) interfacial fracture of Fe/Ni and Fe/Pd/Ni and deformation mode analysis by eigenvector of atomic elastic stiffness matrix

Tensile fracture simulations are performed on the (001) interfaces of Fe/Ni and Fe/Pd/Ni by molecular dynamics method, in order to discuss the interfacial strength by means of the eigenvalue and eigenvector of atomic elastic stiffness, Baij=Δσai/Δεj. Three models are considered, Fe/Ni stacked layers (Bimetal), 2 atomic interlayers of Pd between Fe and Ni phases (Pd 2layer) and same thickness Fe/Pd/Ni/Pd blocks (Trimetal). Before tensile simulation, distribution of ηa(1) < 0 atoms (ηa(1) is the 1st eigenvalue of the solution of BaijΔεj=ηaΔεi) and residual atomic stress in each atomic layers are discussed. Then tensile simulations are implemented; the peak strain and stress of Pd2layer are significantly reduced from that of Bimetal. Trimetal shows slightly lower maximum stress at slightly higher strain than Bimetal. Bimetal shows fracture in Ni phase near the interface, while Pd2layer and Trimetal do in Pd phase near the Ni/Pd and Fe/Pd interface, respectively. Void generation process or the initial stage of the fracture is then discussed with the distribution of ηa(1) < 0 atoms and corresponding eigenvector, {Δε1,Δε2,・・・,Δε6} ={Δεxx,Δεyy,・・・,Δγxy}. In all models the void is formed at the intersection between the interface and slip deformation, so that we can’t find clear mode for atomic plane opening but complicated modes for plastic deformation and inhomogeneous heterometal interface. However, large deformation modes or large negative ηa(1) definitely emerge at the opening void edges.

Research on the inhomogeneity and joint interface of in situ oriented TiBw/TA15 composites fabricated by vacuum hot-pressing sintering and canned extrusion

Abstract TiBw/TA15 composite bars with in situ synthesized TiBw were successfully manufactured by the hot-pressing sintering and subsequent hot canned extrusion. Microstructure evolution and mechanical behavior of as-sintered and as-extruded composites had been systematically investigated. After extrusion, due to the large deformation degree, significant grain refinement occurred and the long axes of whiskers were almost parallel to the extrusion direction. Almost no micro-voids were caused by the fractured TiBw as a consequence of three-dimensional compressive stress during the extrusion process. The mechanical properties results demonstrated that the ultimate tensile strength, elongation and Vickers hardness of the as-extruded composites all increased compared with that of the as-sintered composites. Moreover, there was an inhomogeneous microstructure in the as-extruded composites. The edge part possessed stronger grain refinement and much weaker texture than that of the central part owing to the different deformation degree. The interface between the titanium matrix composites and the capsule (45# steel) was relatively flat with no interfacial reaction, which showed the superiority of the 45# steel as the capsule for hot canned extrusion. Oxygen content result illustrated that there was no significant oxidation of titanium matrix during the sintering and extrusion process.

Surface Evolution of Aluminum Electrodes in Non-Aqueous Aluminum Batteries

Aluminum batteries are considered as novel devices for safe energy storage. However, there is still a lack of understanding of the operation mechanism and evolution behaviors inside the cells of the current aluminum batteries, which limits the rational design and fabrication of high-performance aluminum batteries. To address the issue, systematical studies were applied to understand the surface evolution of the aluminum electrode in the aluminum batteries. Using in situ optical observation and simulation methods, the results suggest that dendrite growth and deposition on the aluminum electrode surface is critical to the aluminum deposition/corrosion evolution during following cycles, which leads to uneven current distribution on the electrode and inhomogeneous ion concentration interface. Additionally, the activity of the aluminum dendrites suggests that the nanosized aggregation would present less activity than the pristine aluminum, which in turn impacts the uniform evolution of the electrode surface. The aluminum-graphite full cells also exhibit a similar trend that is found in the in situ symmetric cells. The combined results from in situ optical observation, simulation, and full cell evaluation provide a deep insight into the aluminum batteries, which would be meaningful to guide research on their life cycle and evolution.

Existence and two-scale convergence of the generalised Poisson–Nernst–Planck problem with non-linear interface conditions

The paper is devoted to the existence and rigorous homogenisation of the generalised Poisson–Nernst–Planck problem describing the transport of charged species in a two-phase domain. By this, inhomogeneous conditions are supposed at the interface between the pore and solid phases. The solution of the doubly non-linear cross-diffusion model is discontinuous and allows a jump across the phase interface. To prove an averaged problem, the two-scale convergence method over periodic cells is applied and formulated simultaneously in the two phases and at the interface. In the limit, we obtain a non-linear system of equations with averaged matrices of the coefficients, which are based on cell problems due to diffusivity, permittivity and interface electric flux. The first-order corrector due to the inhomogeneous interface condition is derived as the solution to a non-local problem.

Stable Fano-like plasmonic resonance: its impact on the reversal of far- and near-field optical binding force

Even for a 100 nm interparticle distance or a small change in particle shape, optical Fano-like plasmonic resonance mode usually vanishes completely. It would be remarkable if stable Fano-like resonance could somehow be achieved in distinctly shaped nanoparticles for more than 1 μm interparticle distance, which corresponds to the far electromagnetic field region. If such far-field Fano-like plasmonic resonance can be achieved, controlling the reversal of the far-field binding force can be attained, like the currently reported reversals for near-field cases. In this work, we have proposed an optical set-up to achieve such a robust and stable Fano-like plasmonic resonance, and comparatively studied its remarkable impact on controlling the reversal of near- and far-field optical binding forces. In our proposed set-up, the distinctly shaped plasmonic tetramers are half immersed (i.e. air–benzene) in an inhomogeneous dielectric interface and illuminated by circular polarized light. We have demonstrated significant differences between near- and far-field optical binding forces along with the Lorentz force field, which partially depends on the object’s shape. A clear connection is shown between the far-field binding force and the resonant modes, along with a generic mechanism to achieve controllable Fano-like plasmonic resonance and the reversal of the optical binding force in both far- and near-field configurations.