Interface Conditions Research Articles

Effect of the Cooling Liquid on the Milled Interface in the Combined Process of Milling and Direct Metal Deposition.

The combination of Direct Metal Deposition (DMD) with milling offers numerous advantages for the manufacturing of complex geometry parts demanding high dimensional accuracy and surface quality. To reach this, a process strategy alternation between both processes is often required, leaving the milled surface with a layer of cooling fluid before adding material by DMD. This paper investigates the effect of cooling liquid on the milled interface in the combined process of milling and DMD. Five different interface conditions were examined, employing four distinct cleaning techniques to assess their impact on the quality of the interface. Key metrics analysed included hydrogen content, carbon content, and porosity levels at the interface. Cleaning techniques were evaluated to determine their necessity in enhancing the interface quality in the combined DMD and milling production process. Results from this study provide essential insights into the optimal cleaning requirements for improving the interface integrity in hybrid manufacturing processes, which could lead to more reliable and efficient production methods in industrial applications.

Uncertainty quantification of turbine endwall aero-thermal performance under combustor-turbine interface louver coolant and cavity

The uncertainty characteristics have a significant influence on turbine cooling performance and its reliability, especially for the combustor-turbine interface region which faces more complicated flow interactions. Previous researches under the certainty framework are not able to reflect the realistic cooling characteristics of the interface region under real operation circumstances. Considering the random fluctuations of the major structure and flow parameters, uncertainty quantification of turbine endwall cooling performance under realistic combustor-turbine interface conditions is conducted in this paper using the polynomial chaos expansion method. The mix characteristic of combustor louver coolant and interface cavity leakage in the turbine endwall region is investigated, and the influences of parameter uncertainties on endwall cooling, vane phantom cooling, and cascade aerodynamic characteristics are analyzed. The results indicate that the uncertainties at the combustor-turbine interface largely influence the endwall cooling by modifying the strength and position of the secondary flows. Under the random fluctuations of interface geometry parameters, the local mean value of endwall cooling effectiveness can reach up to 0.25, and the standard deviation of endwall cooling effectiveness can reach 0.1. The geometrical parameters of interface width and misalignment height are the decisive factors for endwall cooling uncertainty. The random fluctuations of interface width and misalignment height separately cause great cooling effectiveness uncertainties on the pressure side endwall and suction side hot ring. The uncertainties in mainstream and structure parameters exhibit a reduced propensity to propagate onto vane phantom cooling. The decisive factors for vane phantom cooling uncertainty are interface width and misalignment height, and the major influenced area is the vane middle part. Four mainstream and structure parameters all make great contributions to the aerodynamic uncertainty at the strong secondary flow region and vane wake flow region. This paper can provide a theoretical basis for the design of combustor-turbine interface cooling structures to accommodate the actual turbine operation uncertainty conditions.

Preparation of Al@FTCS/P(VDF-HFP) Composite Energetic Materials and Their Reaction Properties.

Strengthening the interfacial contact between the reactive components effectively boosts the energy release of energetic materials. In this study, we aimed to create a close-knit interfacial contact condition between aluminum nanoparticles (Al NPs) and Polyvinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) through hydrolytic adsorption and assembling 1H, 1H, 2H, 2H-Perfluorododecyltrichlorosilane (FTCS) on the surface of Al NPs. Leveraging hydrogen bonding between -CF and -CH and the interaction between C-F⋯F-C groups, the adsorbed FTCS directly leads to the growth of the P(VDF-HFP) coating layer around the treated Al NPs, yielding Al@FTCS/P(VDF-HFP) energetic composites. In comparison with the ultrasonically processed Al/P(VDF-HFP) mixture, thermal analysis reveals that Al@FTCS/P(VDF-HFP) exhibits a 57 °C lower reaction onset temperature and a 1646 J/g increase in heat release. Associated combustion tests demonstrate a 52% shorter ignition delay, 62% shorter combustion time, and a 288% faster pressurization rate. These improvements in energetic characteristics stem from the reactivity activation of FTCS towards Al NPs by the etching effect to the surface Al2O3. Moreover, enhanced interfacial contact facilitated by the FTCS-directed growth of P(VDF-HFP) around Al NPs further accelerates the whole reaction process.

Heat transfer in shear flow over a still nanofluid: A direct integration approach

Heat transfer in a two-layer fluid system, including shear-driven viscous fluid in the upper layer and still nanofluid in the lower layer, is investigated in this work. Following single phase model for nanofluid, three different types of nanofluids are considered. Different from existing literatures on two-layer fluid flow problem, this work introduces the heat transfer of shear-driven viscous fluid over a still nanofluid which makes this investigation new. The main equations which are partial in nature are reduced to a set of coupled nonlinear ordinary differential equation (ODE) by employing suitable similarity transformations. These ODEs together with the coupled interfacial boundary conditions are supplied to MATLAB software to get the solution numerically. Comparing the results obtained in this study with the previous authoritative research results, the accuracy and correctness of the present research methodology are ensured. The results show that the temperature of the upper fluid and the lower fluid are controlled by the thermophysical properties of different types of nanofluids. Also, opposite behavior of temperature distribution for the upper and the lower fluid are observed.

Dynamic responses of a plate on layered transversely isotropic poroelastic subgrade under moving thermal and mechanical loads

In this paper, the dynamic responses of a plate on layered transversely isotropic (TI) poroelastic subgrade under moving thermo-mechanical loads are investigated. Based on the thermodynamics, poroelastic mechanics and the Kirchhoff's thin plate theory, the governing equations of the plate and layered TI saturated subgrade are derived in the wavenumber domain. Then, by introducing the flexibility coefficient of the layered TI poroelastic subgrade and the plate-subgrade interface condition, the solution of the plate-subgrade dynamic interaction is obtained through the extended precise integration method. After the presented method is validated, parametric studies are carried out to confirm the influences of the thermal load, plate-subgrade modulus ratio, plate thickness, and the speed of moving load. Parametric analysis shows that the effect of the thermal load cannot be ignored when considering the plate-subgrade dynamic interaction. In addition, the plate-subgrade modulus ratio, plate thickness, and the speed of moving load have a significant effect on the plate-subgrade dynamic interaction.

Mendelian segregation and high recombination rates facilitate genetic analyses in Cryptosporidium parvum.

Very little is known about the process of meiosis in the apicomplexan parasite Cryptosporidium despite the essentiality of sex in its life cycle. Most cell lines only support asexual growth of Cryptosporidium parvum (C. parvum), but stem cell derived intestinal epithelial cells grown under air-liquid interface (ALI) conditions support the sexual cycle. To examine chromosomal dynamics during meiosis in C. parvum, we generated two transgenic lines of parasites that were fluorescently tagged with mCherry or GFP on chromosomes 1 or 5, respectively. Infection of ALI cultures or Ifngr1-/- mice with mCherry and GFP parasites resulted in cross-fertilization and the formation of "yellow" oocysts, which contain 4 haploid sporozoites that are the product of meiosis. Recombinant oocysts from the F1 generation were purified and used to infect HCT-8 cultures, and phenotypes of the progeny were observed by microscopy. All possible phenotypes predicted by independent segregation were represented equally (~25%) in the population, indicating that C. parvum chromosomes exhibit a Mendelian inheritance pattern. The most common pattern observed from the outgrowth of single oocysts included all possible parental and recombinant phenotypes derived from a single meiotic event, suggesting a high rate of crossover. To estimate the frequency of crossover, additional loci on chromosomes 1 and 5 were tagged and used to monitor intrachromosomal crosses in Ifngr1-/- mice. Both chromosomes showed a high frequency of crossover compared to other apicomplexans with map distances (i.e., 1% recombination) of 3-12 kb. Overall, a high recombination rate may explain many unique characteristics observed in Cryptosporidium spp. such as high rates of speciation, wide variation in host range, and rapid evolution of host-specific virulence factors.

Intrinsic Elastomer with Remarkable Dielectric Constant via Elastification of Relaxor Ferroelectric Polymer.

High-dielectric-constant elastomers always play a critical role in the development of wearable electronics for actuation, energy storage, and sensing; therefore, there is an urgent need for effective strategies to enhance dielectric constants. The present methods mainly involve adding inorganic or conductive fillers to the polymer elastomers, however, the addition of fillers causes a series of problems, such as large dielectric loss, increased modulus, and deteriorating interface conditions. Here, the elastification of relaxor ferroelectric polymers is investigated through slight cross-linking, aiming to obtain intrinsic elastomers with high-dielectric constants. By cross-linking of the relaxor ferroelectric polymer poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorofluoroethylene) with a long soft chain cross-linker, a relaxor ferroelectric elastomer with an enhanced dielectric constant is obtained, twice that of the pristine relaxor ferroelectric polymer and surpassing all reported intrinsic elastomers. This elastomer maintains its high-dielectric constant over a wide temperature range and exhibits robust mechanical fatigue resistance, chemical stability, and thermal stability. Moreover, the ferroelectricity of the elastomer remains stable under strains up to 80%. This study offers a simple and effective way to enhance the dielectric constant of intrinsic elastomers, thus facilitating advancements in soft robots, biosensors, and wearable electronics.

A reaction-diffusion model for population dynamics in patchy landscapes

We address the linear eigenvalue problem associated with reaction-diffusion models for patchy linear domains with any finite number of unique patches. Interface conditions between adjacent patches may be chosen independently to accurately reflect organism behavior. We show that there exists a real principal eigenvalue with a corresponding non-negative eigenfunction that is non-zero interior to the domain. We demonstrate that our model is a generalization of several existing two-patch models. We consider simple three- and four-patch landscapes representing fragmented reserves to illustrate how our model can be used to analyze population persistence, spatial distribution, and migration dynamics. Fragmented landscapes with increased heterogeneity capture migration dynamics not found in landscapes with only two patch types, such as favorable habitat patches that experience net immigration. Conditions for the existence and non-existence of zero-flux conditions interior to three-patch systems are shown, which provide insight to the location of sources and direction(s) of migration.

Relaxed and Bonded Interfacial Conditions for the Axial Interaction of a Flexible Plate with a Transversely Isotropic Half-Space

Relaxed and Bonded Interfacial Conditions for the Axial Interaction of a Flexible Plate with a Transversely Isotropic Half-Space

Passivation of 1D@3D perovskite ferroelectric film with hydrophobic molecules for ferro-pyro-phototronic effect-based self-driven photodetector

High-performance, self-driven photodetectors in commercial and public applications show promising prospects. The pyro-phototronic effect is a promising method for building these detectors, but limitations in interfacial contact conditions hinder the use of the ferro-pyro-phototronic effect. By modifying the surface of 1D@3D perovskite ferroelectric film with tetra-ethyl ammonium (TEAI) molecules, the interfacial defect density is reduced, resulting in a high-performance, stable photodetector. Moreover, the passivation can greatly enhance the ferro-pyro-phototronic effect, which can be explained by the increased band bending and decreased trap states at the SnS/perovskite interface resulting in less re-distribution of charge carriers directly across the interface. Our work offers a feasible and effective method for producing pyro-phototronic responses in perovskite films-based devices, and thus presents a feasible solution for high-performance, self-driven and flexible photodetection.

Equivalent analytical model for liquid sloshing in a 2-D rectangular container with multiple vertical baffles by subdomain partition approach

An equivalent analytical model of sloshing in a two-dimensional (2-D) rigid rectangular container equipped with multiple vertical baffles is presented. Firstly, according to the subdomain partition approach, the total liquid domain is partitioned into subdomains with the pure interface and boundary conditions. The separation of variables is utilized to achieve the velocity potential for subdomains. Then, sloshing characteristics are solved according to continuity and free surface conditions. According to the mode orthogonality of sloshing, the governing motion equation for sloshing under horizontal excitation is given by introducing generalized time coordinates. Besides, by producing the same hydrodynamic shear and overturning moment as those from the original container-liquid-baffle system, a mass-spring analytical model of the continuous liquid sloshing is established. The equivalent masses and corresponding locations are presented in the model. The feasibility of the present approach is verified by conducting comparative investigations. Finally, by utilizing normalized equivalent model parameters, the sloshing behaviors of the baffled container are investigated regarding baffle positions and heights as well as the liquid height, respectively.

Homogenized moduli and local multiphysics fields of unidirectional piezoelectric nanocomposites with energetic surfaces

The study extends the locally-exact homogenization theory (LEHT) to determine the effective parameters and localized multiphysics fields of unidirectional piezoelectric nanocomposites with energetic surfaces. The interface is simulated using the generalized Gurtin-Murdoch model for piezoelectric nanocomposites, taking into account the discontinuities between surface stresses and electrical displacement. By characterizing hexagonal and square repeating unit cells (RUC), the interactions across a fiber's or pore's interface in piezoelectric nanocomposites with energetic surfaces have been analyzed. The extended LEHT possesses the advantages of fast convergence, excellent stability, and computational efficiency due to its avoidance of mesh discretization and pointwise satisfaction of interfacial conditions. To verify the validity of the present theory, this paper also derives the Eshelby solution for piezoelectric nanocomposite with energetic surfaces. The reliability and accuracy of the present theory are demonstrated by comparing the present results from the Eshelby solution and the finite element method (FEM) with generally good agreement. On this basis, the influence of microstructural effects, such as phase volume fractions and geometrical arrangement, on the effective and local responses of piezoelectric nanocomposites with energetic surfaces are investigated. The results show that effective piezoelectric/dielectric moduli and electric displacement field for piezoelectric nanocomposites are significantly affected by the size effect, along with several other parameters such as unit cell arrays and fiber/pore volume fractions. Those results highlight the significance of neighboring pore or fiber interactions for piezoelectric nanocomposites, which are often overlooked in traditional micromechanics models and are challenging to be captured using numerical methods.

Numerical Investigation of Evaluating the Degree of Damage in Concrete Plate Cold Joints through Surface Wave Dispersion Velocity Profiles

This study aims to develop a technology for assessing the interfacial condition of cold joints in concrete plates, focusing on the dispersion velocity profile of surface waves. The methodology employs a small impact hammer embedded with a piezoelectric element and a displacement receiver strategically positioned on either side of the seam. In this initial investigation, numerical models were constructed using ANSYS LS-DYNA. The cold joint zone was simulated by randomly removing elements with a predetermined void ratio. Displacement waveforms at the sensor node underwent analysis using a short-time Fourier Transform and the reassigned method to derive the dispersive velocity profile of surface waves. The study delves into the impacts of varying test-line lengths, impact durations, and void distributions. Numerical findings indicate that cold joints are detectable with a void ratio of 40% or greater. For the 60% and 80% void ratios, surface wave velocities register notably lower for wavelengths below 0.1 m and 0.2 m, respectively. Under the same porosity ratio for surface-observable cold joints, if their extension depth is smaller, the wave velocity on the dispersion curve will be lower than that of a fully penetrated cold joint. The current study reveals that a contact duration of 60 μs and an impactor-receiver distance of 0.82 m yield the most distinguishable results for detecting the extension and porosity ratio of a cold joint. Accompanied by tests with a hammer with a contact duration of 20 μs, additional information about the joint can be unveiled. Finally, various void distributions in the cold joint predominantly influence the wave velocity at shorter wavelengths.

First-principles-based machine learning interatomic potential for molecular dynamics simulations of 2D lateral MoS2/WS2 heterostructures

Understanding the mechanical and thermodynamic properties of transition-metal dichalcogenides (TMDs) and their heterostructures is pivotal for advancing the development of flexible semiconductor devices, and molecular dynamics (MD) simulation is widely applied to study these properties. However, current uncertainties persist regarding the efficacy of empirical potentials in MD simulations to accurately describe the intricate performance of complex interfaces within heterostructures. This study addresses these challenges by developing an interatomic potential based on deep neural networks and first-principles calculations. Specifically focusing on MoS2/WS2 heterostructures, our approach aims to predict Young's modulus and thermal conductivities. The potential's effectiveness is demonstrated through the validation of structural features, mechanical properties, and thermodynamic characteristics, revealing close alignment with values derived from first-principles calculations. A noteworthy finding is the substantial influence of the load direction on Young's modulus of heterostructures. Furthermore, our results highlight that the interfacial thermal conductance of the MoS2/WS2 heterostructures is considerably larger than that of graphene-based interfaces. The potential developed in this work facilitates large-scale material simulations, bridging the gap with first-principles calculations. Notably, it outperforms empirical potentials under interface conditions, establishing its significant competitiveness in simulation computations. Our approach not only contributes to a deeper understanding of TMDs and heterostructures but also presents a robust tool for the simulation of their mechanical and thermal behaviors, paving the way for advancements in flexible semiconductor device manufacturing.

Multiple scattering of local nonlinear resonators on a thin plate

Developing nonlinear resonant metamaterial plates requires an effective wave simulation method to analyze the wave interactions between multiple nonlinear scatterers. The multiple scattering method has the advantages of high computational efficiency and closed-form displacement solutions in modeling the finitely periodic scatterer array. However, the multiple scattering method of nonlinear scatterers is absent in the available studies of plate structures. In this paper, a nonlinear multiple scattering approach is formulated and analyzed for thin plates with nonlinear resonant scatterers. The resonant scatterer consists of an inner plate with a local resonator modeled by the nonlinear mass-spring system. The motion equation of resonant scatterers is solved using the perturbation technology and wave expansion method. The T-matrix of the resonant scatterer of each order is then derived at the arbitrary harmonic frequency from continuous interfacial conditions of resonant scatterers. Finally, the multiple scattering is formulated for a finitely periodic array of resonant scatterers on a thin plate. Numerical simulations capture the scattering characteristics and stop-band formations of fundamental and second-harmonic waves. Furthermore, the finitely periodic array of nonlinear and linear resonant scatterers achieves the nonreciprocal transmission of flexural waves. These numerical results demonstrate the potential applications of the proposed method in designing metamaterial-based plates with complex transmission properties.

A network model to predict ionic transport in porous materials

Understanding the dynamics of electric-double-layer (EDL) charging in porous media is essential for advancements in next-generation energy storage devices. Due to the high computational demands of direct numerical simulations and a lack of interfacial boundary conditions for reduced-order models, the current understanding of EDL charging is limited to simple geometries. Here, we present a network model to predict EDL charging in arbitrary networks of long pores in the Debye-Hückel limit without restrictions on EDL thickness and pore radii. We demonstrate that electrolyte transport is described by Kirchhoff's laws in terms of the electrochemical potential of charge (the valence-weighted average of the ion electrochemical potentials) instead of the electric potential. By employing the equivalent circuit representation suggested by these modified Kirchhoff's laws, our methodology accurately captures the spatial and temporal dependencies of charge density and electric potential, matching results obtained from computationally intensive direct numerical simulations. Our network model provides results up to six orders of magnitude faster, enabling the efficient simulation of a triangular lattice of five thousand pores in 6 min. We employ the framework to study the impact of pore connectivity and polydispersity on electrode charging dynamics for pore networks and discuss how these factors affect the time scale, energy density, and power density of capacitive charging. The scalability and versatility of our methodology make it a rational tool for designing 3D-printed electrodes and for interpreting geometric effects on electrode impedance spectroscopy measurements.

Local Spectral Multiplicity of Selfadjoint Couplings with General Interface Conditions

We consider selfadjoint operators obtained by pasting a finite number of boundary relations with one-dimensional boundary space. A typical example of such an operator is the Schrödinger operator on a star-graph with a finite number of finite or infinite edges and an interface condition at the common vertex. A wide class of “selfadjoint” interface conditions, subject to an assumption which is generically satisfied, is considered. We determine the spectral multiplicity function on the singular spectrum (continuous as well as point) in terms of the spectral data of decoupled operators.

Mathematical Modeling and Numerical Approximation of Heat Conduction in Three-Phase-Lag Solid

In this article, we propose a mathematical model for one-dimensional heat conduction in a three-layered solid considering that an interfacial condition is present for the temperature and heat flux conditions between the layers. The numerical approach is developed by constructing a finite difference scheme to solve the initial boundary–interface problem. The numerical scheme is designed by considering the accuracy of the model on the inner part of each layer, then extending to the interfaces and boundaries by incorporating the continuous interfacial conditions. The finite difference scheme is unconditionally stable, convergent, and easy to implement since it consists of the solution of two algebraic systems. We provide three numerical examples to confirm that our numerical approximation is consistent with the analytical solution and the physical phenomenon.

Study of the shear bond behavior of a hybrid fiber-reinforced concrete (HyFRC) composite slab

In this study, a new composite slab consisting of a prefabricated hybrid fiber-reinforced concrete (HyFRC) formwork and a cast-in-place ordinary concrete (OC) topping was proposed. The HyFRC was comprised of steel and PVA fibers. The compressive strength and bending strength of the HyFRC were 111.4 MPa and 15.6 MPa, respectively, and the toughness coefficient was 12.1 MPa. Seven full-scale composite slabs including six simply-supported slabs and one two-span continuous slab were tested under four-point bending to study the shear bond behavior. Three different contact surface conditions were considered for the simply supported slabs. Despite the different interface conditions, results showed that the interfacial bond strength between the HyFRC formwork and the OC topping was sufficient to achieve flexural failure. Numerical simulation was used to analyze the interfacial force transfer mechanism and was validated by the experimental data. The validated numerical model was used to study the influence of concrete topping depth and amount of reinforcement on the load-carrying capacity and longitudinal shear stress at the joint surface. The numerical results identified a critical condition of positive effect between reinforcement ratio and OC topping thickness. The peak load of a properly designed composite slab was almost two times that of the corresponding slab with ordinary concrete only, and the deformation capability was also larger. A procedure for calculating the flexural capacity of the composite slab was proposed.

Developing organs-on-chips for biomedical applications.

In recent years, organs-on-chips have been arousing great interest for their bionic and stable construction of crucial human organs in vitro. Compared with traditional animal models and two-dimensional cell models, organs-on-chips could not only overcome the limitations of species difference and poor predict ability but also be capable of reappearing the complex cell-cell interaction, tissue interface, biofluid and other physiological conditions of humans. Therefore, organs-on-chips have been regarded as promising and powerful tools in diverse fields such as biology, chemistry, medicine and so on. In this perspective, we present a review of organs-on-chips for biomedical applications. After introducing the key elements and manufacturing craft of organs-on-chips, we intend to review their cut-edging applications in biomedical fields, incorporating biological analysis, drug development, robotics and so on. Finally, the emphasis is focused on the perspectives of organs-on-chips.