Constant Coupling Research Articles

Omnidirectional Wireless Power Transfer Based on Constant Coupling Polarity Concept

Omnidirectional Wireless Power Transfer Based on Constant Coupling Polarity Concept

Reconfigurable dual-mode meta-waveguide

With the rapid growth of information flux, integrating more channels in limited spaces has been a critical requirement for highly-integrated long-range parallel transmissions. Although meta-waveguides, such as spoof surface plasmon polariton (SSPP) waveguides, can suppress crosstalk between adjacent channels, it is still urgent to seek new methods to further increase the number of channels without occupying additional space. Here, we propose a reconfigurable dual-mode meta-waveguide (RDMMW) by integrating diodes into meta-units, which supports two independent channels using two orthogonal modes. The RDMMW can be switched among dual-mode, even-mode, odd-mode and cutoff states by controlling the diodes, which provides more freedom to manipulate the channel features. The RDMMW possess two outstanding merits in highly-integrated long-range parallel transmissions, including lower coupling between two channels than conventional single-mode waveguides and constant mode coupling in longer waveguides. Thus the proposed RDMMW has advantages of multi-mode, reconfiguration, low coupling and high integration density, providing a new avenue to realize highly-integrated multi-functional systems.

Freestanding Metamaterial with Constant Coupling Response for Terahertz Flexible Functional Devices

Freestanding Metamaterial with Constant Coupling Response for Terahertz Flexible Functional Devices

Effect of Constant Cyclic Stress Coupling on the Fatigue Behavior of 304LN Stainless Steel.

The stress state of the primary circuit main pipeline is very complex mixed constant stress and periodic cyclic stress during the operation of nuclear power plants, which often affects the failure behavior of the stainless steel (SS) pipe. The fatigue behavior of 304LN SS under mixed constant stress and cyclic stress was investigated, and it was found that the coupling effect of constant stress and cyclic stress has a significant collaborative acceleration on the fatigue behavior. The research results showed that the cracks in the 304LN SS did not propagate even after 78 days under both constant load conditions of 5 KN and 7.5 KN, while the crack growth rate (CGR) of the specimen increased by about an order of magnitude when coupled with a cyclic fatigue load. The fatigue life of 304LN SS was the longest under 200 °C high-temperature water, and its life was roughly the same under 250 °C and 300 °C water. In a 300 °C high-temperature water environment, the fatigue life under the coupling of constant stress and cyclic fatigue stress is significantly lower than that under symmetric cyclic stress alone. There is a synergistic acceleration effect on the fatigue life of 304LN SS when constant stress is coupled with periodic cyclic stress, which is attributed to the combined effect of a corrosion environment and mechanical factors.

Two‐Streams Revisited: General Equations, Exact Coefficients, and Optimized Closures

AbstractTwo‐Stream Equations are the most parsimonious general models for radiative flux transfer with one equation to model each of upward and downward fluxes; these are coupled due to the transfer of fluxes between hemispheres. Standard two‐stream approximation of the Radiative Transfer Equation assumes that the ratios of flux transferred (coupling coefficients) are both invariant with optical depth and symmetric with respect to upwelling and downwelling radiation. Two‐stream closures are derived by making additional assumptions about the angular distribution of the intensity field, but none currently works well for all parts of the optical parameter space. We determine the exact values of the two‐stream coupling coefficients from multi‐stream numerical solutions to the Radiative Transfer Equation for shortwave radiation. The resulting unique coefficients accurately reconstruct entire flux profiles but depend on optical depth. More importantly, they generally take on unphysical values when symmetry is assumed. We derive a general form of the Two‐Stream Equations for which the four coupling coefficients are guaranteed to be physically explicable. While non‐constant coupling coefficients are required to reconstruct entire flux profiles, numerically optimized constant coupling coefficients (which admit analytic solutions) reproduced shortwave reflectance and transmittance with relative errors no greater than over a large range of optical parameters. The optimized coefficients show a dependence on solar zenith angle and total optical depth that diminishes as the latter increases. This explains why existing coupling coefficients, which often omit the former and mostly neglect the latter, tend to work well for only thin or only thick atmospheres.

General decay anti-synchronization and [formula omitted] anti-synchronization of derivative coupled delayed memristive neural networks with constant and delayed state coupling

In this article, we explore the general decay anti-synchronization (GDAS) and general decay H∞ anti-synchronization (GDHAS) of derivative coupled delayed memristive neural networks (DCDMNNs) with constant and delayed state coupling, respectively. To begin with, on account of the definitions of ψ-type function as well as ψ-type stability, we present the GDAS and GDHAS concepts for the considered DCDMNNs. What is more, several sufficient conditions are derived for reaching GDAS and GDHAS of DCDMNNs with constant and delayed state coupling by selecting correct Lyapunov functionals and devising a proper controller. Moreover, numerical simulations examples are provided to demonstrate the feasibility of the obtained conclusions.

Study on the Structure, Morphology, Dielectric, and Piezoelectric Properties of Large-Grain (Ba0.85Sr0.15)1-x Pb x TiO3 Ceramic System for 0.02 ≤ x ≤ 0.08.

Barium strontium lead titanate ((Ba0.85Sr0.15)1-x Pb x TiO3), along with various compositions (x(mol %) = 0, 2, 4, and 8), was synthesized through the conventional sol-gel reaction method. Following this, the resultant powders underwent a carefully controlled calcination process at 1000 °C for a period of 4 h. The examination of the crystalline phase of the calcined ceramics was conducted at room temperature using X-ray diffraction. Rietveld refinement of the XRD data, performed using FullProf, revealed that the samples exhibited a tetragonal structure within the space group P4mm. The impact of Pb doping on the lattice structure of BaSr1-x TiO3 was explored by analyzing the charge density distribution. The FTIR analysis unveiled a distinct absorptive band within the 450-600 cm-1 range, indicative of the stretching and bending vibrations associated with TiO6 octahedra. Notably, sintering the material at 1150 °C for 4 h resulted in improved densification, as observed in scanning electron microscopy images showcasing a nearly uniform distribution of densely packed grains. Through the utilization of Williamson-Hall plots derived from XRD data, the average particle diameter was estimated to fall within the range of 131.87-141 nm, with an associated uncertainty ranging from 5 to 10%. Additionally, the dielectric characteristics unveiled the presence of a negative dielectric constant (εr) spanning the frequency range from 1 kHz to 2 MHz. The (Ba0.85Sr0.15)1-x Pb x TiO3 ceramic displayed a widespread occurrence of negative permittivity, emphasizing the influence of dielectric resonance. The investigation revealed that the sintered ceramic with the formula (Ba0.85Sr0.15)1-x Pb x TiO3 exhibited exceptional piezoelectric properties, achieving the highest piezoelectric constant (d33 = 137 pC/N) and electromechanical coupling factor (k p = 0.49).

An Optimized Operation Method for Integrated Energy System Based on Variable Operating Condition Characteristics

Abstract An integrated energy system (IES), functioning as a multi-input, multi-output apparatus, incorporates diverse power conversion and storage device. Typically, the energy hub visually demonstrates its multi-energy coupling. However, traditional energy hub models tend to ignore the variable operating condition characteristics of conversion device, that is, the actual operation efficiency fluctuates with the load rate. Consequently, it results in constant coupling coefficients in the energy hub coupling matrix, causing discrepancies between the IES operating state and actual conditions, affecting the operation scheme’s economy. Therefore, this study focuses on IES optimized operation method, which is based on variable operating condition characteristics, incorporating conversion device operating efficiency and load rate relationships into EH models. Development of a dynamic energy hub (DEH) model that takes into account the variable operating condition characteristics of the conversion device, operational efficiency of the device is corrected in real time, and an optimal scheduling model is built with the objective of optimal IES economy, designing different scenarios for simulation and verification with an IES as an example. The study demonstrates that incorporating device operating condition dynamics into scheduling scheme effectively minimizes system expenses and enhances the system’s integrity and feasibility.

Compact silicon photonic-lantern mode (de)multiplexer based on tilt slot waveguide.

As the key component in on-chip mode-division multiplexing systems, a compact silicon photonic-lantern mode (de)multiplexer is proposed and demonstrated using the shallow-etched tilt slot waveguide. The proposed six-mode (de)multiplexer is designed as a constant coupling length of 11.7 µm for each mode conversion and eliminates the adiabatic transition tapers for cascaded asymmetric directional couplers, which have an ultra-short total length of 69 µm. The measured peak insertion losses of the fabricated device for all mode channels are less than 1.2 dB, and the crosstalk is below -12.6 dB in a 60 nm waveband. Additionally, the simulation results indicate that the device has a good fabrication tolerance. The proposed mode (de)multiplexer is scalable and could provide a feasible solution for the dense integration of on-chip mode division multiplexing systems.

TTEP: A code for efficient calculation of the thermal transport from constant electron-phonon coupling approximation

A Fortran code named TTEP (Thermal Transport from constant Electron-Phonon coupling approximation) is presented in this work. Within the framework of first-principles calculation, this code utilizes the deformation potential approximation to replace the electron–phonon (EP) coupling matrix element in the phonon scattering due to EP interaction. By adopting this approximation, our method achieves a balance between computational efficiency and accuracy, enabling the exploration of the thermal transport from EP interaction with much reduced computational consumption. One of the key features of TTEP is its versatility in handling a broad range of carrier concentration, including both hole and electron doping. We also extend the applicability of TTEP to actual doping case and capture EP effect over a wide temperature range. Other scattering mechanisms, such as grain boundary scattering and phonon–phonon interaction, have been included in the calculation of lattice thermal conductivity through the Matthiessen’s rule. Several test cases are presented in this work to demonstrate the above features.

Cosmological fluids with boundary term couplings

Cosmological models can be studied effectively using dynamical systems techniques. Starting from Brown’s formulation of the variational principle for relativistic fluids, we introduce new types of couplings involving a perfect fluid, a scalar field, and boundary terms. We describe three different coupling models, one of which turns out to be particularly relevant for cosmology. Its behaviour is similar to that of models in which dark matter decays into dark energy. In particular, for a constant coupling, the model mimics well-known dynamical dark energy models while the non-constant couplings offer a rich dynamical structure, unseen before. We are able to achieve this richness whilst working in a two-dimensional phase space. This is a significant advantage which allows us to provide a clear physical interpretation of the key features and draw analogies with previously studied models.

An NJL model analysis of a magnetised nonextensive QCD medium

We investigate the effect of a background magnetic field when applied to a nonextensive QCD medium in a 2+1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2+1$$\\end{document} flavour Nambu— Jona-Lasinio model. The effect of a constant as well as an eB-dependent coupling is considered. For the constant coupling, the well-known magnetic catalysis effect is observed with reduced strength in both the condensates and the transition temperatures compared to the standard extensive medium. In the case of a field-dependent coupling, we observe a competition between the nonextensive parameter, q and eB. With sufficiently high q-values, the phenomenon of inverse magnetic catalysis —, a well-known trait in effective models featuring eB-dependent coupling, appears to be eliminated within the range of magnetic fields examined in our present study.

High-throughput discovery of metal oxides with high thermoelectric performance via interpretable feature engineering on small data

In this work, we have proposed a data-driven screening framework combining the interpretable machine learning with high-throughput calculations to identify a series of metal oxides that exhibit both high-temperature tolerance and high power factors. Aiming at the problem of weak generalization ability of small data with power factors at high temperatures, we employ symbolic regression for feature creation which enhances the robustness of the model while preserving the physical meaning of features. 33 candidate metal oxides are finally targeted for high-temperature thermoelectric applications from a pool of 48,694 compounds in the Materials Project database. The Boltzmann transport theory is utilized to perform electrical transport properties calculations at 1,000 K. The relaxation time is approximated by employing constant electron-phonon coupling based on the deformation potential theory. Considering band degeneracy, the electron group velocity is obtained using the momentum matrix element method, yielding 28 materials with power factors greater than 50 μWcm−1K−2. The high-throughput framework we proposed is instrumental in the selection of metal oxides for high-temperature thermoelectric applications. Furthermore, our data-driven analysis and transport calculation suggest that metal oxides rich in elements such as cerium (Ce), tin (Sn), and lead (Pb) tend to exhibit high power factors at high temperatures.

An Analysis of the Kinematics and Dynamics Performance of a New Type of Three-Pronged Sliding Universal Coupling

The three-pronged sliding universal coupling is a new kind of three-pronged coupling. The purpose of this study is to demonstrate that, compared with a traditional unequal angular velocity universal coupling (such as the Hooke universal coupling), the universal coupling has the superior characteristics of constant angular speed transmission, simple structure and strong transmission capacity by performing kinematic and dynamic analysis of the new three-pronged sliding constant angular velocity universal coupling. It provides a broad prospect for applications in automotive and other fields. To study its kinematic and dynamic characteristics, directional cosine matrices are utilized as tools to analyze the coordinate systems by establishing simplified geometric models and corresponding motions. Through the analysis of the motions of the input and output shafts and employing the method of single-force element, a set of equilibrium equations for the forces acting on the output shaft and the input shaft are formulated for solution analysis. The research indicates that during the rotation process, there exists a small angular difference between the input shaft and the intermediate shaft, demonstrating the quasi-constant angular velocity characteristics of the new tripod sliding universal coupling. The curves of the forces and force moment acting on each component of the coupling approximate sinusoidal curves. The optimal operating angle range for the new tripod universal coupling is at angle , during which the system exhibits good transmission and mechanical performance. It can be widely used in the automobile industry, tie steel industry and other occasions that require angular transmission. It is especially used in high-speed operation and large transmission capacity.

An adaptive fluid-solid coupling time step control algorithm for unsteady conjugate heat transfer

Unsteady simulation with conjugate heat transfer has to tackle the stiffness issue that originates from the wide disparate time scales between fluid and solid heat transfer. In the loosely coupled framework, challenges remain in determining the optimal coupling time step between the fluid and solid solvers, in terms of efficiency and accuracy. This study formulates a correlation for the coupling error, together with the Proportional-Integral-Derivative (PID) control method, to propose an adaptive fluid-solid coupling time step algorithm, which dynamically adjusts the coupling time step such that the computational efficiency can be improved without sacrificing accuracy. The proposed algorithm has been tested in a 1D conjugate heat transfer application with typical operating conditions of a real engine, and the performance of different controllers (I, PI, PID) has been analyzed and compared. Results show that with the closed-loop control, all controllers can ensure the error control below the user specified tolerance at the cost of reducing efficiency. Meanwhile, with the open-loop control which is of more interest to practical applications, controllers suffer from instability issues when a conventional algorithm based on integration error is employed. The proposed coupling-error-based algorithm successfully tackles the instability issues. Compared with the baseline algorithm of the constant coupling time step, the proposed algorithm can reduce approximately 40%–90% computational cost for the 1D cases considered.

Extending the lower bound of attainable load-independent voltage gain values range in contactless, feedbackless and sensorless power delivery links

It is well-known that series(capacitive)-series(capacitive) compensated inductive wireless power transfer links (SS(CC)-IWPTL) operating at fixed frequency with constant coupling coefficient may be designed to attain arbitrary load independent voltage gain (LIVG) value, residing within a region defined only by loosely coupled transformer (LCT) parameters. Such a characteristic allows designing the system to be sensorless and operate without feedback, which is an extremely useful feature in hostile environment applications. Unfortunately, LCT parameters are not selected arbitrarily in practice; hence, the desired LIVG value may reside outside the attainable region, calling for an additional power conversion stage. In particular, region of attainable LIVG values is especially narrow when LCT inductances ratio is imposed by the application and thus cannot be freely selected. One of existing challenges is regulating the system output to low DC voltage while it is being fed from a much higher valued voltage source, i.e. calling for an extremely low LIVG value. The paper demonstrates that adopting an inductor rather than a capacitor as primary series compensation element allows to extend the lower bound of attainable LIVG values region for given LCT and operating frequency, potentially eliminating the need for an additional step-down power converter. Resulting coil-to-coil efficiency is quantified and guidelines for sizing corresponding compensation elements pair are established as well. Simulations and experiments accurately verify the proposed methodology.

Double quantum dot spin resonances with a time-dependent spin-orbit coupling

Two-spin resonances in double quantum dots with a constant spin-orbit coupling (SOC) can be induced by an ac field which periodically modulates the energy detuning. But a large ac field amplitude may unintentionally trigger an ac modulation in the SOC, which in turn can alter the frequency of the resonances and the form of the current peaks. Here, we demonstrate that depending on the applied magnetic field and the double quantum dot parameters a weak time dependence in the SOC can have a completely different effect on the resonant peaks; in particular, it can enhance the peaks, but it can also completely suppress them.

Effective orientifolds from broken supersymmetry

We recently proposed a class of type IIB vacua that yield, at low energies, four–dimensional Minkowski spaces with broken supersymmetry and a constant string coupling. They are compactifications with an internal five-torus bearing a five–form flux Φ and warp factors depending on a single coordinate. The breaking of supersymmetry occurs when the internal space includes a finite interval. A probe-brane analysis revealed a gravitational repulsion and a charge attraction of equal magnitude from the left end of the interval, together with a singularity at the other end. Here we complete the analysis revealing the presence, at one end, of an effective of negative tension and positive five–form charge. We also determine the values of these quantities, showing that , and characterize the singularity present at the other end of the interval, which hosts an opposite charge. Finally, we discuss various forms of the gravity action in the presence of a boundary and identify a self–adjoint form for its fluctuations. Invited contribution to the special issue of Journal of Physics A: Mathematical and Theoretical on ‘Fields, Gravity, Strings and Beyond: In Memory of Stanley Deser’

Strength characteristics of foamed concrete under coupling effect of constant compressive loading and freeze-thaw cycles

In cold regions, foamed concrete used for the tunnel reserved deformation layer is usually subjected to environmental factors, such as the groundwater erosion, peristaltic pressure of surrounding rock, and freeze-thaw cycles. In this research, experiments considering single-factor (i.e., water immersion, constant compressive loading, and freeze-thaw cycles) and coupled multi-factor effects (the coupling of water saturated - constant loading and constant loading - freeze thaw cycles) were conducted on foamed concretes with different densities to examine the strength variation under different conditions. The results show that under the effect of single-factor environment, the average compressive strength of saturated foamed concrete is about 10% lower than the dry foamed concrete. The compressive strength of foamed concrete significantly decreases at the beginning of constant compressive loading but gradually increases with the loading time. Furthermore, the strength loss of foamed concrete after 30 freeze-thaw cycles can exceed 10%. Under the multi-factor coupled environment, the hydraulic effect accelerates the degradation of foamed concrete, particularly in terms of water saturation - constant loading coupling. Furthermore, for loading - freeze thaw cycles coupling, the compressive loading of 0.3 fc (fc is the unconfined compressive strength at 28 days) can improves the frost resistance of foamed concrete. In addition, the results of orthogonal analysis prove that the density has the most important influence, followed by the freeze-thaw cycle and the slightest effect of constant compressive loading. Additionally, a prediction equation of compressive strength as a function of density, freeze-thaw cycles, and the constant pressure value was established to describe the strength variation of foamed concretes under coupled-loading effects.

Improved electromechanical properties of Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 ferroelectric ceramics via Sm-modification

Sm-modification has recently attracted widespread attention as an optimized method for enhancing the electromechanical properties of Pb-based perovskite ferroelectrics. The present study extends the application of Sm-modification to the Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 (PNN-PZT) ceramics, aiming to improve their electromechanical properties. The impact of Sm-doping on the phase structure, microstructure, domain morphology, dielectric and piezoelectric properties was comprehensively investigated. The results demonstrate that the Sm-doping enhances the dielectric and piezoelectric properties while retaining competitive ferroelectric-paraelectric phase transition temperature (Tm). Notably, for the 2 mol% Sm-doped samples, a significant piezoelectric coefficient d33 of 1130 pC/N and a high Tm of 130 °C were achieved, accompanied by an improved dielectric constant (εr) and electromechanical coupling factor (kp). The comprehensive properties of Sm-doped PNN-PZT ceramics exceed the general trend observed in current Pb-based ferroelectric ceramics. This research confirms the effectiveness of the Sm-modification method in PNN-PZT systems, establishing it as a promising candidate for high-performance electromechanical applications.