Coupling Conditions Research Articles

Sound Mitigation by Metamaterials With Low-Transmission Flat Band

Abstract Space-coiling acoustic metamaterials dominated by the Fano resonance are being widely exploited for simultaneous control of sound isolation and air ventilation, and they usually achieve complete sound mitigation at multiple isolated frequencies. Here, we theoretically discover and experimentally demonstrate the low-transmission flat-band phenomenon in channeling-type acoustic metamaterials. The metamaterial is constructed with coupled coiling and straight channels, both working in acoustic resonant states. An analytic coupled-mode model is established to capture the coupling interaction between resonant states supported by two channels. A critical coupling condition is derived from the model, which can lead to sextremely low sound transmission in a finite band rather than at isolated frequencies, as validated by both numerical simulations and experiments. We then demonstrate the generality of the flat-band behavior of low transmission by a systematic survey of the coupling of different order resonant modes. Finally, the flat-band effect is also found to exist in the extended model with the side-loaded coiling channel as verified experimentally.

Co-vulcanization of natural rubber and Eucommia ulmoides gum for mediation of the nonlinear rheology behaviors

Co-vulcanization of natural rubber (NR) and high-moduli Eucommia ulmoides gum (EUG) is promising while the reduction in crystallinity of crosslinked EUG is adverse for developing high-performance materials. Proposed herein is a novel method to prepare high-strength and high-stretchability NR/EUG vulcanizates with rapid vulcanization of EUG into slightly crosslinked particles, followed by further vulcanization of NR to form crosslinked matrix network. Deep eutectic solvents (DESs) are employed to facilitate the vulcanization of EUG during its blending with NR. The two-step vulcanization results in vulcanizates exhibiting superior mechanical properties under shear, tensile, and compressive conditions, significantly exceeding those of vulcanizates prepared by traditional processing methods. The reinforcement mechanism is elucidated by controlling thermomechanical coupling conditions and is supported by comprehensive structural characterizations. It is suggested that the EUG crystalline regions, maintained through the special processing method, work in conjunction with the stress-induced crystallization of the matrix to enhance the vulcanizates, nearly doubling the deformation stress at 800% strain. The crystalline regions can mediate the deformation stress during shear and compression and weaken nonlinear rheological behavior. The established structure-performance relationship is guidable for preparing high-performance NR/EUG blend vulcanizates.

3D package thermal analysis and thermal optimization

3D packaging mainly uses TSVs (Through Silicon via) to vertically interconnect multiple chips, achieving the purpose of signal transmission and electrical connection. As a popular advanced packaging method, its research is of great significance. Although stacked chips can achieve stronger performance in smaller spaces, they can also cause a series of reliability issues, among which thermal stress and warping due to differences in the thermal expansion coefficients of materials can even lead to chip failure. Therefore, it is highly valuable to simulate and analyze the entire 3D packaging model.In this study, the thermal stress and deformation of the whole three-dimensional package model were simulated by finite element analysis. The results showed that there were significant stress and deformation effects at the joint of the TSV structure at normal temperature, and the stress and deformation reached 209.99MPa and 0.0018519mm, respectively. After that, the temperature of the double-sided package system containing 3D package under electrothermal coupling conditions was optimized by heat dissipation design, which verified the ‘quantity first’ scheme of heat dissipation fins and reduced the temperature by 40%.

Culturing 3D chitosan/gelatin/nano-hydroxyapatite and bone-derived scaffolds in a dynamic environment enhances osteochondral reconstruction.

Bioreactor can provide a dynamic culture environment for the in vitro construction of osteochondral tissue engineering. They facilitate more efficient exchange of nutrients and provide mechanical and other beneficial stimulation. Previous findings demonstrated that rotary flask (RF) bioreactor, rotary cell culture system (RCCS), or electromagnetic field (EMF) mediated scaffold culture could create a favorable dynamic environment for osteochondral tissue engineering. However, it is still unclear whether there is an optimal bioreactor or if bioreactors under multi-parameter coupling conditions are conducive to osteochondral tissue engineering. Based on this, the application of static T-flask (TF), RF, RCCS, and coupling environment of RCCS and EMF for osteochondral tissue engineering were systematically compared. The results showed that the RCCS/EMF culture system achieved the highest level of cellular proliferation and directed differentiation. Compared with the static culture group, the expression levels of chondrogenic factors of Sox9, Col II, and ACAN and osteogenic factors of Runx2, OCN, and Col I in RCCS/EMF culture system were 2.90±0.10, 3.53±0.05, 3.15±0.08, 7.16±0.15, 5.01±0.21 and 3.99±0.17 folds, respectively. The 'Active osteochondral' constructs (The construct is composed of chitosan/gelatin/nano-hydroxyapatite and bone-derived scaffolds) were prepared under different culture modes in vitro and implanted into the femoral condylar defect of New Zealand rabbits. After 12weeks, all culture modes could effectively promote the repair of osteochondral defects, in which the RCCS/EMF intervention had the best effect on the in vivo in-situ repair of osteochondral tissues. Furthermore, the fabricated cartilage and subchondral bone in the RCCS/EMF treatment group were most similar to the surrounding natural tissues, providing a new therapeutic idea for osteochondral tissue engineering.

Numerical study of underwater oil spill diffusion in complex hydrodynamic environments

Waves and currents are key dynamic factors that influence the diffusion of underwater oil spills. To study the behavior of such spills under complex hydrodynamic conditions, an oil spill diffusion numerical model was established and physically verified by model test data. The drift and diffusion of crude oil from seabed to surface under current, wave, and wave–current coupling conditions were analyzed. The results reveal that under the wave–current coupling condition, the oil spill diffusion exhibits the movement characteristics of oil particles influenced by both currents and waves. The oil particles oscillate with water particles while simultaneously diffusing in the direction of the water flow. The rising speed of oil droplets is fastest in still water but slows significantly under the influence of waves and currents. The shape of the oil slick at the leakage point is related to the hydrodynamic conditions. The oil slick diffuses vertically upwards in still water. While in current and wave conditions, it takes on “C” and “Z” shapes, respectively. Under the influence of the wave–current coupling, the slick spreads in an “S” shape. Moreover, the faster the oil spill, the more significant the entrainment effect, leading to an intensified lateral and vertical diffusion of the oil particles. These research findings offer valuable insights for tracking underwater oil spill trajectories during accidents.

Mechanical properties and multiscale structure evolution of cement mortars under temperature cycling and low-humidity coupled condition

The degradation of concrete induced by wide temperature differences and drying significantly impacts the durability of constructions in plateau regions. This study systematically investigated the mechanical properties, the structure evolution from nanoscale to macroscale, and the hydration product changes under temperature cycling with low relative humidity (5–60°C cycling, 30±5 % RH). Damage gradients were meticulously discussed based on the experimental measured thermal gradient and mechanical failure modes. Pore coarsening and microcracks which increased with w/c mainly occurred between 50 nm and 50 μm, becoming key factors contributing to the mechanical degradation. Nevertheless, the relatively small damages enable the mortar to maintain much stable mechanical properties than cement paste and concrete. The hydration and the small amount of decomposition had little effect on the structure. Overall, the strength increased until a certain time window followed by a decreasing trend because of two contradictory factors: enhancement led by the increase of capillary pressure and surface energy and degradation driven by the gradient damage.

Dynamic in-situ CT imaging to study meso-structure evolution and fracture mechanism of shale during thermal-mechanical coupling condition

Temperature has a significant impact on the occurrence characteristics and flow properties of oil and gas in shale reservoirs at in-situ conditions. Under thermal–mechanical coupling conditions, the macroscopic deformation instability characteristics and the evolution of the internal microstructure of shale are of great importance for the exploitation of shale oil and gas. However, most studies on the macroscopic and microscopic characteristics of shale only analyze the deformation and instability mechanisms of shale from observations of the post-failure microscopic structures. This paper employs a self-developed THM-CT coupling test system to study the macroscopic deformation characteristics of shale under triaxial compression at real-time temperatures, and simultaneously uses in-situ CT imaging technology to characterize the internal microstructure of shale under different stress levels. Real-time CT porosity obtained via in-situ CT imaging technology represents the mesoscopic structural parameters, together with macroscopic deformation characteristics, delineate the four stages of the entire deformation process in shale: initial compression, linear elastic deformation, yielding deformation, and post-failure. The deformation after peak-stress (σf) in shale is 1–3 times that before peak-stress (σf). The dissolution and softening of clay minerals within the internal micro-lamination of shale, along with the weakening of the internal structure, result in a decline in mechanical parameters such as stress strength (σf) and elastic modulus (E) with increasing temperature. The reconstruction of three-dimensional μCT digital volumes further reconstructs the internal fracture spatial structure under different stress levels during the deformation process, precisely characterizing the dynamic evolution of internal fracture nucleation, expansion, and coalescence during the whole test process. The failure characteristics of shales display notable heterogeneity and anisotropy. Internally, fractures experience a sequence of initiation, formation of vertical and oblique main fractures along the axial direction, and crossing connections between fractures. During test process, multiple occurrences of horizontal secondary micro-fractures extend along weakly cemented lamination, playing a connecting role between the main fractures. Importantly, a real-time quantitative relationship between the macroscopic and microscopic mechanics of rock has been established by linking the mesoscopic damage factor with the applied stress. It was found that the damage factor increases according to a power-law relationship with stress in the yield deformation phase. The variation in the mesoscopic damage factor serves as an intuitive index reflecting the systematic failure of rock, providing an early warning for the impending failure of shale.

Mechanism of microfracture propagation under mechanical–chemical coupling conditions considering dissolution

Microfracture propagation is well known to significantly impact the stability of well bores in shale formations; however, there is a lack of research on the role of dissolution. Herein, a shale microfracture propagation model is constructed that couples mechanics and chemistry by considering hydration, capillary, strength weakening, and dissolution effects. Combining relevant experiments with the model reveals the mechanism of microfracture propagation. Results indicate that ΔK(stress intensity factor) shows an upward trend with increasing hydration micromechanical forces and when hydration time exceeds 30 h, the rate of increase in ΔK gradually slows down. ΔK increases linearly with tensile strength. When the yield zone length “a” remains constant, ΔK first decreases and then increases with increasing a/b ratio, reaching its minimum value when the a/b ratio is 0.6. ΔK shows a linear increase with interfacial tension and decreases with increasing wetting angle and initiation angle of cracking. The dissolution of carbonate minerals can considerably influence the propagation of microcracks. Initially, the impact of this dissolution may not be pronounced; however, as the duration of the rock samples' exposure to the dissolution process exceeds 100 h, the increase in the stress intensity factor becomes substantial. The increase in ΔK accelerates the propagation of microcracks within rocks. Constructing a shale microfracture propagation model based on dissolution effects is crucial for elucidating the microscopic mechanisms of mechanical–chemical coupled changes in shale microfractures, which is significant for analyzing wellbore stability.

Influx ratio preserving coupling conditions for the networked Lighthill–Whitham–Richards model

AbstractA new coupling rule for the Lighthill–Whitham—Richards model at merging junctions is introduced that imposes the preservation of the ratio between inflow from a given road to the total inflow into the junction. This rule is considered both in the context of the original traffic flow model and a relaxation setting giving rise to two different Riemann solvers that are discussed for merging 2‐to‐1 junctions. Numerical experiments are shown, suggesting that the relaxation based Riemann solver is capable of suitable predictions of both free‐flow and congestion scenarios without relying on flow maximization.

A new semi–analytical method for elastic–strain softening circular tunnel with hydraulic–mechanical coupling

This study presents a novel coupled hydraulic–mechanical algorithm for analysing nonlinear seepage in circular tunnels with elastic strain softening characteristics. The model integrates porosity changes with permeability coefficients to formulate a set of nonlinear seepage equations. The Mohr–Coulomb criterion is used to determine the of rock stress yielding state, and the plastic strain εθp is used as a softening parameter to assess the degradation of rock strength. The proposed model is validated through a comparison with established numerical and analytical solutions. The pore water pressure distribution exhibits a distinctive three-stage curve under coupling conditions, with the seepage behaviour transitioning to a classical Laplace-type equation as the coupling coefficient weights diminish. Parametric analysis reveals that the brittleness index β is a pivotal factor governing the extent of the softening region. A decrease in residual strength σc∗ intensifies strain softening, leading to a more extensive softening zone. Conversely, a reduction in the angle of internal friction φ affects only the rock's strength without altering the softening intensity. The study also demonstrated that the pore water pressure diminishes the effective stress within the rock mass, resulting in a larger plastic zone than that under dry conditions. Finally, internal reinforcement and external support can effectively mitigate the effects of strain softening and seepage on the stability of the surrounding rock.

Redox-active a pyrene-4,5,9,10-tetraone and thienyltriazine-based conjugated microporous polymers for boosting faradaic supercapacitor energy storage

Conventional supercapacitor electrodes typically suffer from drawbacks such as low energy density, short cycle life, and poor conductivity. In contrast, conjugated microporous polymers (CMPs) present a more advantageous option, providing higher surface area, greater cycle stability, and enhanced electrical properties. Utilizing pyrene-4,5,9,10-tetraone (PyTE) as a key redox-active component, we successfully prepare pyrene-4,5,9,10-tetraone-thiophene polymer (PyTE-Th Polymer) and Thienyltriazine-pyrene-4,5,9,10-tetraone conjugated microporous polymer (TTh-Ph-PyTE CMP). This particular set of materials has been tailored for supercapacitor applications, employing a nitrogen-rich triazine, conductive thiophene (Th), and redox-active pyrene-4,5,9,10-tetraone (PyTE), a creation through simple Suzuki coupling conditions. PyTE-Th Polymer and TTh-Ph-PyTE CMP exhibit comparable BET surface areas and demonstrate good thermal stability, with char yields exceeding 62 wt% for each material. Electrochemical measurements reveal that TTh-Ph-PyTE CMP, featuring a triazine group with abundant heteroatoms, exhibited exceptional cycle stability of 90 % after 5000 cycles at 10 A g−1 and a specific capacitance of 1041 F g−1 (1 A g−1). Notably, TTh-Ph-PyTE CMP portrays the maximum specific capacitance at 1 A g−1 compared to PyTE-Th polymer (486 F g−1) and other porous materials, suggesting a synergistic effect of redox-active units and abundant heteroatoms.

An analytical method for effective dynamic properties of SH wave in piezoelectric nanocomposites with coated nano-fibers

In this paper, a generalized self-consistent model of nanocoated fiber composite material considering interface effect is established by using the Gurtin-Murdoch surface/interface elasticity theory, elastic wave theory and micromechanics methods, and the propagation of anti-plane shear electroelastic wave in infinite nano-piezoelectric material is analyzed. Based on the wave function expansion method, the displacement potential and electric potential functions of each phase medium in composite materials are described, and the function expressions of displacement, electric potential, stress and electric displacement are obtained. The dynamic effective shear modulus of piezoelectric reinforced composites is obtained by satisfying the boundary conditions of the electroelastic coupling surface/interface theory and the multiple scattering formulas. The effects of coating thickness, coating material parameters, interfacial shear modulus and piezoelectric properties on dynamic effective shear modulus at different incident frequencies are discussed. The results show that the effective shear modulus fluctuates obviously with the increase of frequency. The effective shear modulus increases with the increase of interfacial shear modulus and piezoelectric constant, and is more sensitive to the change of interfacial shear modulus. The effective shear modulus is more affected by the interface effect on the outer surface of the coating than the inner interface, and the effect of interface mechanical properties decreases with the increase of coating stiffness. The larger the parameter of the coating material, the larger the dynamic effective shear modulus and the smaller the influence of the interface effect.

Enhancing the Spectral Sensitivity of Prism-Based SPR Sensors: The Role of Analyte RI

A theoretical approach is presented to significantly enhance the spectral sensitivity of prism-based SPR sensors. The spectral sensitivity of prism-based SPR sensors is derived based on the coupling conditions of SPR and might exceed 105 nm/RIU for analytes with large RI values when other sensor parameters are carefully considered, including the RI of the prism, the angle of incidence, and the SPR active material. The spectral sensitivity could be markedly enhanced, reaching up to 10,000 nm/RIU by fine-tuning the effective RI of the incident light to be slightly larger, specifically 0.01~0.02 RIU, than the RI of the analyte, which is attributed to the large dielectric permittivity of the SPR active material, the key factor for achieving high sensitivity. The dynamic range is 0.040 RIU in the case of high sensitivity, which is sufficient in most applications. Moreover, the spectral sensitivity could be pushed even higher, into the range of 106~108 nm/RIU, by positioning the effective RI of the incident light closer to that of the analyte. However, it requires a careful balance between optimizing the sensitivity and maintaining an acceptable dynamic range.

Static voltage stability analysis of integrated smart energy systems

The analysis of multi-energy flows forms the cornerstone for the study of state estimation, safety assessment, and optimization in integrated smart energy systems (ISES). The interactions between various energy flows and the inherent variability of renewable energy sources often lead to significant challenges to the static stability of ISES. This paper investigates the static voltage stability of ISES under multi-energy coupling conditions through multi-energy flow analysis in electric-gas-thermal energy systems. First, a steady-state model of the ISES is constructed by representing the interconnected energy subsystems as equivalent sources and loads in the power grid. Subsequently, through the coupling elements of ISES, the power flows of the natural gas system (NGS) and the district heating system (DHS) are converted into active power in the electrical power system (EPS), resulting in an equivalent power flow equation for the ISES. Then, using Brouwer’s fixed-point theorem, the analytical sufficient conditions for solving the equivalent power flow equation are derived. Finally, a simulation model based on MATLAB/Simulink is established. The steady-state criterion for ISES is obtained in this paper, and the correctness and effectiveness of the proposed conclusions are verified by the simulation results.

Role of cavity strong coupling on single electron transfer reaction rate at electrode-electrolyte interface.

The physicochemical properties of molecules can be modulated through polariton formation under strong electromagnetic confinement. Here, we discuss the possibility of exploiting this phenomenon to increase the electron transfer rate at an electrode-electrolyte interface. Electron transfer theory under strong electromagnetic confinement can be extended to the electrode-electrolyte interface, and single-electron transfer reactions can be simulated using Gerischer's theory. Although single electron transfer in free space is well described using Marcus theory, the vacuum electric field can facilitate an additional electron transfer pathway via virtual photon excitation under cavity strong coupling conditions. Therefore, this binary reaction pathway for single electron transfer can yield a quasi-two-particle electron transfer process. This quantum behavior can dominate when the mode volume is small and when there are a large number of molecules in the vacuum electric field. Exploitation of polaritons in single electron transfer reactions can lead to enhanced electrochemical energy conversion systems.

The First Decade of SuFEx Chemistry: Advancements in SuFEx Polymerization, Non-Canonical SuFEx Reactions, and SuFEx Radiochemistry

AbstractThis year marks the 10th anniversary of SuFEx chemistry, a field that has witnessed significant advancements over the past decade. These include efficient synthetic strategies toward polymerization via the SuFEx approach leading to diverse polymers, alongside the discovery of new SuFExable hubs and coupling conditions. Non-canonical reactions, such as deoxyfluorination and on-water reactions, have also emerged. Furthermore, there have been substantial strides in the radiosynthesis of [18F] SuFExable hubs. This review provides an overview of these developments, focusing on polymerization, non-canonical reaction, and radiochemistry in SuFEx chemistry.1 Introduction2 SuFEx Polymerization3 Non-Canonical SuFEx Reactions4 Fluorine-18 SuFEx Radiochemistry5 Conclusions and Outlook

Influences of thickness and coupled water-temperature-load effects on adhesion/cohesion properties of mastic and mortar in porous asphalt mixtures

ABSTRACT The thickness of the mastic and mortar is randomly distributed in porous asphalt mixtures and has a critical influence on the adhesion/cohesion properties of the mastic and mortar. An advanced pull-off test, combined with a coupled effect tester, was designed to evaluate the adhesion/cohesion properties of mastic and mortar. Pull-off tensile strength (POTS) of mastic and mortar firstly increased then decreased with the increasing thickness of mastic and mortar. The failure mode of mastic changed from brittle adhesive failure to adhesive failure, while the failure mode of mortar changed from cohesive failure to adhesive failure with increasing thickness under dry conditions. However, adhesive failure was found in all thicknesses under coupled effects. As coupled effects increased, POTS and fracture energy of mastic and mortar prominently decreased. The failure modes of mastic and mortar changed from adhesive failure to cohesive failure with temperature increase. A water pressure of 0.2 MPa is critical where POTS dramatically decreases. With increasing coupled effect duration, failure modes of mastic changed from adhesive failure to brittle adhesive failure, while failure modes of mortar show brittle adhesive failure. High-viscosity modified asphalt greatly improved the POTS of mastic and mortar under dry and coupled effect conditions.

Numerical investigation on the polarization-dependent light extraction of 275-nm AlGaN based nanowire with bowtie antenna array or passivation layer

Abstract The low light extraction efficiency (LEE) is one of the major factors hindering the application of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs). Here we investigate the LEE of AlGaN based nanowire (NW) DUV LEDs emitting at 275 nm for bare NW, NW integrated with aluminum (Al) bowtie antenna array, and NW with passivation layer under transverse-electric (TE) and transverse-magnetic (TM) polarization. It is observed that by integrating plasmonic Al bowtie antenna array with AlGaN based NW, the LEE up to 83% and 74% can be achieved under TE and TM polarization. In addition, the effect of the three different passivation layer SiO2, SiNx and AlN on the LEE of AlGaN based NW is also analysed, the results suggests that SiO2, which has smaller refractive index than NW core, could extract more photons from the NW and lead to large enhancement of LEE. For SiNx and AlN passivation layer, which has refractive index similar to the NW core, have strong coupling with the NW core, when the thickness of passivation layer satisfy resonance coupling conditions, the LEE could be achieved more than 80% for both TE and TM polarization. These integrated NW/antenna array and NW with passivation layer system can provide guidelines for designing other nano-photonic devices.

A dual‐excitation inductive power transfer system with decoupled transformer for high misalignment tolerance

AbstractThis study delves into the design and optimization of a 4 kW dual‐excitation inductive power transfer system designed to accommodate large misalignments. The system utilizes a bipolar‐solenoid inductive coupled transformer as its coupling mechanism. Detailed simulation and analysis of this coupling mechanism are conducted. Additionally, the system employs a control strategy aimed at optimizing the coordination between output power and efficiency. This control strategy dynamically adjusts the power of the two transmitters, aiming to enhance system efficiency to the maximum extent possible under favourable coupling conditions. Moreover, it ensures that the system's output power remains at or above the rated value even when coupling conditions deteriorate. During the experiment, the system can optimize the output power and efficiency at the same time by using a suitable control strategy when the coils are misaligned. Meanwhile, the system can achieve a minimum efficiency of 81.5% even when the misalignment distance reaches 300 mm (60% of per transmitting coil size). The system and control strategy proposed in this paper can effectively overcome the deterioration of the output characteristics of the wireless power transfer system when misalignment occurs.

The simplest transformation model of deformation of a rod-strip fixed on a double-sided support element through elastic interlayers

An extremely simplified transformation model of dynamic deformation of a rod-strip consisting of two sections along its length is constructed. It is based on the classical geometrically nonlinear Kirchhoff-Love model on an unfixed section, and the fixed section of finite length is considered to be connected to a rigid and fixed support element through elastic layers. On the fixed section, the deflections of the rod and interlayers are considered zero, and for displacements in the axial direction within the thicknesses of the rod and interlayers, approximations are adopted according to the shear model of S.P. Timoshenko, subject to the conditions of continuity at the points of their connection with each other and immobility at the points of connection of the interlayers with the support element. The conditions for the kinematic coupling of the unfixed and fixed sections of the rod are formulated, and based on these, using the d’Alembert-Lagrange variational principle, the corresponding equations of motion and boundary conditions, as well as the force conditions for coupling of the sections, are derived for the sections introduced into consideration.