Coupling Mode Research Articles

Unfolding Electrolyzer Characteristics to Reveal Solar-to-Chemical Efficiency Potential: Rapid Analysis Method Bridging Electrochemistry and Photovoltaics.

Development of photovoltaic-electrochemical (PV-EC) systems for energy storage and industry decarbonization requires multidisciplinary collaborative efforts of different research groups from both photovoltaic and electrochemical research communities. Consequently, the evaluation of the solar-to-chemical or solar-to-fuel efficiency of a new electrolyzer (EC) as a part of a PV-EC system is a time-consuming task that is challenging in a routine optimization loop. To address this issue, a new rapid assessment method is proposed. This method employs power balance requirements to unfold the input EC characteristics into the parameter space of PV-EC systems. The system parameters, composed with the EC output characteristics, yield the solar-to-chemical efficiency attainable by the electrolyzer in combination with any PV device under any irradiance at any relative PV-to-EC scaling and any mode of power coupling. This comprehensive overview is achieved via a mathematically simple conversion of the EC characteristics in any spreadsheet software. The method, designed to streamline the development and minimize the efforts of both the photovoltaic and electrochemical communities, is demonstrated via the analysis of CO2-reduction electrolyzer characteristics and verified with dedicated PV-EC experiments.

Flexible magnetoelectric systems: Types, principles, materials, preparation and application

Recently, the rapid development of flexible electronic materials and devices has profoundly influenced various aspects of social development. Flexible magnetoelectric systems (FMESs), leveraging magnetoelectric coupling, hold vast potential applications in the fields of flexible sensing, memory storage, biomedicine, energy harvesting, and soft robotics. Consequently, they have emerged as a significant branch within the realm of flexible electronic devices. According to its working principle, FMES are divided into three categories: FMES based on magnetodeformation and piezoelectric effects, FMES based on giant magnetoresistive effect, and FMES based on electromagnetic induction. Although some articles have reviewed the first two types of FMES, there is a lack of systematic introduction of the FMES based on electromagnetic induction in existing studies, especially the development history and research status of the three types of FMES. Therefore, this paper systematically reviews the development history and research status of these three kinds of FMES and reveals the working principle and mode of the flexible magnetoelectric system from the perspective of the force-electricity-magnetism coupling mode. In addition, the material selection criteria, device manufacturing methods, and application fields of the FMES are also introduced. Finally, this review delves into the challenges and opportunities confronting the development of FMES, exploring the future development directions. This review aims to establish a theoretical foundation and provide methodological strategies for future research on FMES. It is anticipated to promptly address the current gap in this research field and facilitate the development of the flexible electronic family.

Research on the Sensing Properties and Vibration Reduction Performance of Self-Sensing Self-Tuning Magnetic Fluid Damper

Abstract The semi-active control damping system has gained popularity due to its quick response time and versatility. However, external sensors are susceptible to environmental interference, affecting system reliability and increasing complexity and maintenance costs, restricting their use. To address this, a self-sensing self-tuning magnetic fluid damper is proposed. The vibration-measuring induction coil is wound on the damper to sense the magnetic fluid vibration information in real time, and the vibration signal is communicated to the self-tuning control circuit. The control circuit calculates and determines the dominant frequency of structural vibration, then outputs the relevant current signal to set the damper's natural frequency to track the excitation frequency, resulting in self-tuning vibration reduction. First, the self-sensing unit's output induced electromotive force model is created, followed by an expression of the damper's natural frequency, indicating that the self-sensing unit can achieve self-tuning vibration reduction by tracking the excitation frequency. The multi-field coupling simulation model of the magnetic fluid damper is generated, and the induction coil coupling mode and damper excitation angle are defined to obtain the maximum induced voltage.
Finally, an experimental platform was developed to assess the damper's self-sensing and self-tuning vibration reduction performance. The experimental results demonstrate that the suggested self-tuning magnetic fluid damper exhibits excellent self-sensing capabilities and effectively reduces vibrations. This offers an innovative research concept for using magnetic fluid in self-sensing technology and vibration reduction domains.

Supramammillary Theta Oscillations in Water Maze Learning.

The supramammillary nucleus (SuM) in the hypothalamus, in conjunction with the hippocampus (HPC), has been implicated through theta oscillations in various brain functions ranging from locomotion to learning and memory. While the indispensable role of the SuM in HPC theta generation in anesthetized animals is well-characterized, the SuM is not always necessary for HPC theta in awake animals. This raises questions on the precise behavioral relevance of SuM theta activity and its interaction with HPC theta activity. We used simultaneously recorded SuM and HPC local field potentials (LFPs) in a one-day water maze (WM) learning paradigm in rats (n = 8), to show that theta activities recorded from the SuM itself were not positively correlated with locomotor (swimming) speed nor acceleration, but the individual relationship between acceleration and SuM theta frequency is correlated with WM learning rates. In contrast, we found that SuM-HPC theta phase coherence is strongly correlated with swimming speed and acceleration, but these do not relate to WM learning. SuM-HPC-directed coherence analysis demonstrated no swimming kinetics nor learning rate associations, but revealed that periods of high SuM-HPC theta phase coherence are driven by the SuM at relatively low (~6.2 Hz) frequencies. Additionally, we demonstrate that the SuM and the HPC also engage in non-random, non-coherent phase coupling modes where either structure preferentially displays a ± 2 Hz difference with the other. Our data indicate SuM theta LFPs do not appear to be related to either speed coding or spatial learning in swimming rats and display non-random out-of-phase theta frequency coupling with the HPC.

Three perspectives on entropy dynamics in a non-Hermitian two-state system

Abstract A comparative study of entropy dynamics as an indicator of physical behavior in an open two-state system with balanced gain and loss is presented. To begin with, we illustrate the phase portrait of this non-Hermitian model on the Bloch sphere, elucidating the changes in behavior as one moves across the phase transition boundary, as well as the emergent feature of unidirectional state evolution in the spontaneously broken PT-symmetry regime. This is followed by an examination of the purity and entropy dynamics. Here we distinguish the perspective taken in utilizing the conventional framework of Hermitian-adjoint states from an approach that is based on biorthogonal-adjoint states and a third case based on an isospectral mapping. In this it is demonstrated that their differences are rooted in the treatment of the environmental coupling mode. For unbroken PT symmetry of the system, a notable characteristic feature of the perspective taken is the presence or absence of purity oscillations, with an associated entropy revival. The description of the system is then continued from its PT-symmetric pseudo-Hermitian phase into the regime of spontaneously broken symmetry, in the latter two approaches through a non-analytic operator-based continuation, yielding a Lindblad master equation based on the PT charge operator C. This phase transition indicates a general connection between the pseudo-Hermitian closed-system and the Lindbladian open-system formalism through a spontaneous breakdown of the underlying physical reflection symmetry.

Study on runoff forecasting and error correction driven by atmosphere–ocean-land dataset

Accurate runoff forecasting results can not only provide an important basis for flood control scheduling, but also provide scientific support for water resources optimization, which promotes the maximization of the overall benefits of the basin. To further explore the inherent mechanisms of the atmosphere–ocean-land factors driving runoff changes, this study proposes the factors dimension reduction and interpretation framework based on Pearson, eXtreme Gradient Boosting and SHapley Additive exPlanations (P-XGBoost-SHAP). Base on this, the Gaussian Process Regression (GPR), Long Short-Term Memory neural network (LSTM) and Support Vector Machine (SVM) models are used to construct the atmospheric-ocean-land data-driven runoff prediction model. Meanwhile, for the runoff prediction residuals, this paper proposes an error multi-step correction framework based on ensemble empirical mode decomposition and autoregressive model (EEMD-AR). The case study of Lianghekou hydrological station shows that the factor dimension reduction and interpretation framework can greatly reduce the input dimension of the model, and explain the factors globally and locally by using SHAP Value. Compared with the traditional Random Forest (RF) dimension reduction method, it shows higher prediction accuracy. The Nash-Sutcliffe efficiency coefficient (NSE) can be increased to about 0.93, which is 4.91 % and 1.97 % higher than the series–parallel coupling (AR-Parallel) and empirical mode decomposition-autoregressive (EMD-AR) correction methods, respectively. The accuracy of the runoff forecasting prediction is improved while reducing the input dimension of the model.

Plasma-Fluid Energy Transfers in Plasma Assisted Ignition

ABSTRACT A three-dimensional model of plasma-fluid coupling is developed, including the Navier-Stokes, the drift-diffusion, and the radiative transfer equations, to investigate the energy transfers between plasma and fluid in repetitive-pulsed discharge ignition. A modal decomposition of the energy transfer is performed to determine the contributions of plasma to the mechanical coupling and pressure losses during ignition. The detailed model is validated against experiments and compared against a well-known empirical approximation. The main findings are that the modal coupling is dependent on the geometry of the electrodes and flat electrodes provide the strongest mechanical transfer into the acoustic modes. Uniform flow conditions decrease the extent of the mechanical coupling due to the decreased pressure velocity correlations in shear flows. Water vapor production reduces the entropic mode of the energy coupling.

Advanced Peak Phase of ENSO under Global Warming

Abstract El Niño–Southern Oscillation (ENSO) is the leading mode of interannual ocean–atmosphere coupling in the tropical Pacific, greatly influencing the global climate system. Seasonal phase locking, which means that ENSO events usually peak in boreal winter, is a distinctive feature of ENSO. In model future projections, the ENSO sea surface temperature (SST) amplitude in winter shows no significant change with a large intermodel spread. However, whether and how ENSO phase locking will respond to global warming are not fully understood. In this study, using Community Earth System Model Large Ensemble (CESM-LE) projections, we found that the seasonality of ENSO events, especially its peak phase, has advanced under global warming. This phenomenon corresponds to the seasonal difference in the changes in the ENSO SST amplitude with an enhanced (weakened) amplitude from boreal summer to autumn (winter). Mixed layer ocean heat budget analysis revealed that the advanced ENSO seasonality is due to intensified positive meridional advective and thermocline feedback during the ENSO developing phase and intensified negative thermal damping during the ENSO peak phase. Furthermore, the seasonal variation in the mean El Niño–like SST warming in the tropical Pacific favors a weakened zonal advective feedback in boreal autumn–winter and earlier decay of ENSO. The advance of the ENSO peak phase is also found in most CMIP5/6 models that simulate the seasonal phase locking of ENSO well in the present climate. Thus, even though the amplitude response in the winter shows no model consensus, ENSO also significantly changes during different stages under global warming.

Theory and application of temporal coupling mode for a SiC/CaF2/Ag cell-based grating.

Tailoring spectral thermal radiation properties via multiple resonances excited by micro/nanoscale-patterned structures plays a vital role in designing functional emitters and devices. However, predicting thermal radiation properties of a structure with multiple resonances-via a fast and accurate algorithm-is still challenging because of the complex mode coupling effects of different resonances. Herein, we establish a temporal coupling mode (TCM) model for a SiC/CaF2/Ag cell-based grating by extracting the intrinsic parameters and coupling constants of the resonances. The accuracy and efficiency of the established TCM model for predicting absorption spectra of SiC/CaF2/Ag gratings with multiple resonances in each unit cell is verified. Results indicate that the narrowband absorption of the SiC/CaF2/Ag cell-based grating can be enhanced via the multiple-resonance coupling effects. This work provides an alternative tool for predicting absorption characteristics of complex structures with multiple-resonance coupling effects.

Efficient compression of reduced impedance matrices for trimmed structural models: a novel methodology and industrial validation

In response to increasingly strict vibration and noise regulations, software frameworks such as Nastran and Actran have stepped up to the challenge, providing sophisticated solutions to efficiently model damping treatments within numerical methods. One of the available techniques is the representation of trim components as frequency-dependent reduced impedance matrices (RIM) in a frequency response analysis of fully trimmed models. While RIM enables coupling between physical or modal-based components, challenges arise due to large dense matrices. Each matrix is reduced either on physical coupling DOFs or modes of vibration of the component and stored on disk. Since each matrix is dense and large in industrial models, it leads to storage and efficiency issues related to computational and input/output (I/O) operations. This paper introduces a methodology to compress RIMs, particularly for modal components, by selecting the most contributing modes to represent the coupling relationship of each surface. Numerical results on an industrial car body model demonstrate that this approach effectively eliminates low-effect contributions, minimizes storage requirements, and reduces computational time. General Motors' involvement in validating the method adds real-world applicability and reliability to the findings, enhancing its practical engineering value.

Magnetization States and Coupled Spin-Wave Modes in Concentric Double Nanorings.

Concentric multiple nanorings have previously been fabricated and investigated mainly for their different static magnetization states. Here, we present a theoretical analysis for the magnetization dynamics in double nanorings arranged concentrically, where there is coupling across a nonmagnetic spacer due to the long-range dipole-dipole interactions. We employ a microscopic, or Hamiltonian-based, formalism to study the discrete spin waves that exist in the magnetic states where the individual rings may be in either a vortex or an onion state. Numerical results are shown for the frequencies and the spatial amplitudes (with relative phase included) of the spin-wave modes. Cases are considered in which the magnetic materials of the rings are the same (taken to be permalloy) or two different materials such as permalloy and cobalt. The dependence of these properties on the mean radial position of the spacer were studied, showing, in most cases, the existence of two distinct transition fields. The special cases, where the radial spacer width becomes very small (less than 1 nm) were analyzed to study direct interfaces between dissimilar materials and/or effects of interfacial exchange interactions such as Ruderman-Kittel-Kasuya-Yoshida coupling. These spin-wave properties may be of importance for magnetic switching devices and sensors.

Revealing various change characteristics and drivers of ecological vulnerability in the mountains of southwest China

Ecological vulnerability (EV) assessment is an important means of reflecting the evolutionary process of the local ecological environment, which is crucial for ecological security. The current EV assessment still faces challenges in comprehensively revealing its spatio-temporal change characteristics due to diversity, multi-scale complexity and non-linearity of ecosystems. In this study, we comprehensively revealed the spatio-temporal change features and driver mechanisms of EV in Yunnan Province (YP) using methods such as breaks for additive seasonal and trend (BFAST) and Geodetector. According to the findings, (1) the ecological vulnerability index (EVI) in YP decreased by 0.0265 on the raster scale between 2000 and 2018, and the ecological vulnerability level (EVL) was mainly dominated by level III. At the city scale, EVL in YP was dominated by level IV. At the basin scale, the average EV of the Jinsha River basin was much greater other basins. (2) The linear trend of EV in the YP mainly showed an insignificant decrease, mostly concentrated in the YP’s eastern region. The non-linear trend mainly showed a monotonous decrease, with the mutation time concentrated in 2009. The future persistence trend of EV under different coupling modes was dominated by anti-persistence decrease (Sen-MK + Hurst) and anti-persistence monotonous decrease (BFAST + Hurst), with an area percentage of 40.19 % and 25.13 %, respectively. (3) Gross primary productivity was the priority factor influencing YP’s EV (q = 0.4137). This study not only enriches the cases of EV assessment studies in the high mountain valley area but also bridges the gap of analysing the multi-spatial scale characteristics and change trends of regional EV.

Self-Decoupled Multiantennas With Coupling Modes Identification and Suppression

Self-Decoupled Multiantennas With Coupling Modes Identification and Suppression

Evaluation of the Polypyrrole Coupling Mode for High-Performance Dual-Ion Batteries.

Due to the advantages of large interstitial sites, antisolubility, and reversible insertion and extraction of anions, polypyrrole (PPy) has become an excellent P-type electrode material for dual-ion batteries. Unfortunately, PPy electrodes inevitably suffer from low specific capacity and poor cycle stability because of structural disintegration during repeated cycling as well as poor doping ability brought on by aggregation or cross-linking within the PPy chain. In this work, PPy with different proportions of coupling mode (α-α, α-β, or β-β coupling) was derived from different preparation methods. Among them, PPy derived from the interfacial frozen polymerization method (I-PPy) is dominated by the α-α coupling mode and possesses the best anion doping ability and the highest specific capacity of 119 mAh g-1 at 100 mA g-1 compared with PPy derived from electrochemical deposition (E-PPy) and chemical oxidation method (C-PPy) (both less than 40 mAh g-1). This work verifies that increasing the proportion of the α-α coupling mode in the PPy electrode is a useful strategy to enhance the anion doping ability and capacity of dual-ion batteries.

Coupled modes analysis of stimulated Brillouin scattering in the regimes of nonlinear ion acoustic waves

The nonlinear saturation of stimulated Brillouin scattering (SBS) in long scale length plasmas is studied in detail through coupled mode equations. Our model incorporates harmonic and subharmonic generation of ion acoustic waves (IAWs), as well as nonlinear Landau damping and the nonlinear frequency shift of IAWs induced by particle trapping. Numerical simulations are carried out across various IAW wavenumbers (k a λ De ) and electron-ion temperature ratios (Z i T e /T i ) within different SBS instability regimes. The results demonstrate that our model can distinguish the importance of each effect contributing to the nonlinear behavior in SBS under different plasma conditions. Furthermore, we examine the scaling of SBS reflectivity with laser intensity under conditions relevant to inertial confinement fusion.

Coupled mode theory-based analytical model of a ring resonator refractive index sensor incorporating bending loss and dispersion

This paper presents an analytical model of a silicon nitride-based 2D ring resonator refractive index (RI) sensor using coupled mode theory (CMT). The proposed model decomposes the ring resonator into two coupling regions and employs coupled-mode equations to describe input and output amplitudes via scattering matrix analysis. The proposed sensor, operating with varying refractive indices in the background cladding, demonstrates a sensitivity of 218 nm/RIU and a total quality factor of 1198. A comprehensive analysis of the bending loss in the proposed sensor is conducted, elucidating its impact on sensitivity, coupling quality factor, and intrinsic quality factor. This analysis aids in the selection of optimal ring resonator parameters, including radius, width, and gap, to achieve superior sensing performance. Furthermore, the paper examines the effect of dispersion on sensitivity and quality and compares the results with those obtained from CMT-based silicon core ring resonator and disk resonator RI sensors. This study provides valuable insights for the design and optimization of high-performance silicon nitride-based RI sensors for various applications.

Triple plasmon induced transparency based on multilayer graphene metamaterials

In this study, a novel multilayer terahertz metamaterial with four graphene sub-structures is designed to achieve dynamically tunable triple plasmon-induced transparency (PIT) due to interference among bright-bright modes. Coupled mode theory (CMT) and finite-difference time-domain (FDTD) simulations show a high degree of consistency in their results. Interestingly, enhanced transmission dips are observed when various graphene structures couple with the two longitudinal graphene strips at the bottom layer. Based on the dynamic modulation characteristics of graphene, the metamaterial demonstrates seven-band optical switching capabilities, achieving modulation depths (MD) of 94.6%, 88.1%, 90.8%, 90.8%, 90.4%, 86.6%, and 87.5%. Additionally, the proposed graphene metamaterial also shows excellent slow-light effects, with a group index reaching up to 1034. This proposed terahertz metamaterial holds significant theoretical implications for the development of dynamically integrated terahertz optoelectronic devices.

Distinct modes of coupling between VCP, an essential unfoldase, and deubiquitinases.

Errors in proteostasis, which requires regulated degradation and recycling of diverse proteins, are linked to aging, cancer and neurodegenerative disease (1). In particular, recycling proteins from multiprotein complexes, organelles and membranes is initiated by ubiquitylation, extraction and unfolding by the essential mechanoenzyme VCP (2-4), and ubiquitin removal by deubiquitinases (DUBs), a class of ∼100 ubiquitin-specific proteases in humans (5, 6). As VCP's substrate recognition requires ubiquitylation, the removal of ubiquitins from substrates for recycling must follow extraction and unfolding. How the activities of VCP and different DUBs are coordinated for protein recycling or other fates is unclear. Here, we employ a photochemistry-based approach to profile proteome-wide domain-specific VCP interactions in living cells (7). We identify DUBs that bind near the entry, exit, or both sites of VCP's central pore, the channel for ATP-dependent substrate translocation (8-10). From this set of DUBs, we focus on VCPIP1, required for organelle assembly and DNA repair (11-13), that our chemical proteomics workflow indicates binds the central pore's entry and exit sites. We determine a ∼3Å cryo-EM structure of the VCP-VCPIP1 complex and find up to 3 VCPIP1 protomers interact with the VCP hexamer. VCPIP1's UBX-L domain binds VCP's N-domain in a 'down' conformation, linked to VCP's ADP-bound state (2, 14), and the deubiquitinase domain is positioned at the central pore's exit site, poised to remove ubiquitin following substrate unfolding. We find that VCP stimulates VCPIP1's DUB activity and use mutagenesis and single-molecule mass photometry assays to test the structural model. Together, our data suggest that DUBs bind VCP at distinct sites and reveal how the two enzyme activities can be coordinated to achieve specific downstream outcomes for ubiquitylated proteins.

Multiple Valley Modulations in Noncollinear Antiferromagnets.

Two-dimensional valleys and magnetism are rising areas with intriguing properties and practical uses in advanced information technology. By coupling valleys to collinear magnetism, valley degeneracy is lifted in a large number of magnetic valley materials to exploit the valley degree of freedom. Beyond collinear magnetism, new coupling modes between valley and magnetism are few but highly desirable. By tight-binding calculations of a breathing Kagome lattice, we demonstrate a tunable valley structure and valley-contrasting physical properties in noncollinear antiferromagnets. Distinct from collinear magnetism, noncollinear antiferromagnetic order enables valley splittings even without spin-orbit coupling. Both the canting and azimuthal angles of magnetic moments can be used as experimentally accessible knobs to tune valley splittings. Our first-principles calculations of the Fe3C6O6-silicene-Fe3C6O6 heterostructure also exhibit tunable valley splittings in noncollinear antiferromagnetism, agreeing with our tight-binding results. Our work paves avenues for designing novel magnetic valley materials and energy-efficient valleytronic devices based on noncollinear magnetism.

Long-distance strong coupling of magnon and photon: Effect of multi-mode waveguide

Coupled mode theory predicts that the long-distance coupling between two distant harmonic oscillators is in the weak coupling regime. However, a recent experimental measurement observed strong coupling of magnon and critically-driven photon with a distance of over two meters. To explain the discrepancy between theory and experiment, we study long-distance coupling of magnon and photon mediated by a multi-mode waveguide. Our results show that strong coupling is achieved only when both critical coupling and multi-mode waveguide are involved. The former reduces the damping while the latter enhances the coupling strength by increasing the pathways of coupling magnon and photon. Our theory and results pave the way for understanding the long-distance coherence and designing the magnon-based distributed quantum networks.