Dynamic Polarization Research Articles

On‐Demand Dynamic Polarization Meta‐transformer

AbstractPolarization is one of the key characteristics of light; hence its versatile manipulation plays a pivotal role in wave‐matter interaction, communication, detection, etc. Although metasurfaces have emerged as a promising platform for polarization optics, most of them only support limited polarization controls even in reconfigurable fashion. Here, an on‐demand dynamic polarization meta‐transformer operating for full Poincaré sphere by means of an ultrathin transmissive time‐varying metasurface is proposed. By temporally and independently modulating co‐polarized transmission coefficients of the metasurface for a pair of orthogonal linearly polarized incidence, the effective transmission metasurface anisotropy can be modified to mimic the desired arbitrary birefringence, thus enacting the polarization transformation between incidence and transmission waves with arbitrary polarization states. Experiments have been conducted in the microwave region to verify the design theory. This study may provide a new architecture in polarization optics and may advance the applications in vectorial polarimetry imaging, polarimetry radars, and optical/wireless communications.

Siloxane-based epoxy coatings through cationic photopolymerization for corrosion protection

In order to effectively prevent the hull of the ship from being corroded in the seawater environment, in this study, we prepared organic coating films (SAE-0, SAE-5, SAE-10 and SAE-15) that contain various amount of siloxane epoxy resins (1,3-bis[2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane, BETMS) and bisphenol A epoxy resin (BE-188) in the presence of Doublecure®1172 photoinitiator for the cationic photopolymerization under UV light as the irradiation source. All the photocured polymers afforded good-quality films and had the 5 wt% thermal decomposition temperatures of above 335 °C. In addition, the contact angle decreases in the order of SAE-15 > SAE-10 > SAE-5 > SAE-0 related to the siloxane content. Finally, the potential dynamic polarization curve of the coated film on the galvanized steel surface was also studied to investigate its protection performance in a 3 M NaCl solution. Among all examined films, SAE-15 coated film showed the lowest corrosion current density (Icorr), corrosion rate (Rcorr) and the highest corrosion resistance (Rp). As a result, the highest protection ability of this sample can reach up to 97.3 % and even superior better than the control sample (SAE-0, 90.6 %). Furthermore, SAE-15 coated film shows the best protection capability after immersing into the 3 M NaCl and seawater solution at 28 days. The siloxane-based photocured hybrid film prepared in this study exhibits excellent potential for the marine corrosion protection fields.

Effect of Hydrogen on Corrosion Behavior of 321 Stainless Steel in NH4Cl Solution.

For a hydrogenation heat exchanger operating under severe working conditions such as high temperature, high pressure and a hydrogen environment, perforation accidents caused by NH4Cl corrosion occur frequently. However, few reports on the effect of hydrogen on the corrosion behavior of metal materials in NH4Cl aqueous solution have been published. In this paper, X-ray photoelectron spectroscopy (XPS), electrochemical dynamic potential polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky (M-S) curves and scanning electron microscopy (SEM) were used to study the effect of electrochemical hydrogen charging (EHC) on the corrosion behavior of 321 stainless steel in an NH4Cl solution environment. The results show that: (1) hydrogen can change the structure and chemical composition of 321 stainless steel passive film and promote the conversion of metal oxide to hydroxide. At the same time, it can reduce the stability of the passive film. (2) Hydrogen can increase the thermodynamic and kinetic tendency of corrosion reaction and cooperate with Cl− to promote the occurrence of pitting corrosion.

(Invited) Dynamic Electrochemical Responses of "Dead Li" during Battery Operations

The increasing demand for next-generation energy storage systems necessitates the development of high-performance lithium batteries. Unfortunately, current Li anodes exhibit rapid capacity decay and a short cycle life, owing to the continuous generation of solid electrolyte interface and isolated Li (i-Li). The formation of i-Li during the nonuniform dissolution of Li dendrites leads to a substantial capacity loss in lithium batteries under most testing conditions. Because i-Li loses electrical connection with the current collector, it has been considered electrochemically inactive or ‘dead’ in batteries. Contradicting this commonly accepted presumption, here we show that i-Li is highly responsive to battery operations, owing to its dynamic polarization to the electric field in the electrolyte. Simultaneous Li deposition and dissolution occurs on two ends of the i-Li, leading to its spatial progression toward the cathode (anode) during charge (discharge). Revealed by our simulation results, the progression rate of i-Li is mainly affected by its length, orientation, and the applied current density. Moreover, we successfully demonstrate the recovery of i-Li in Cu–Li cells with >100% Coulombic efficiency and realize LiNi0.5Mn0.3Co0.2O2 (NMC)–Li full cells with extended cycle life.

Dynamic Polarization Behaviors of Equimolar CoCrFeNi High-Entropy Alloy Compared with 304 Stainless Steel in 0.5 M H2SO4 Aerated Aqueous Solution.

Three corrosion potentials and three corrosion current densities are clearly identified before the passivation for both dynamic polarization curves of equimolar CoCrFeNi high-entropy alloy (HEA) and 304 stainless steel (304SS) in 0.5 M H2SO4 aerated aqueous solution, by decomposing anodic and cathodic polarization curves. The passivated current density of the former is greater than the latter, compliant with not only the constant of solubility product (ksp) and redox equilibrium potential (Eeq) of each metal hydroxide but also the sequence of bond energy (Eb) for monolayer hydroxide on their facets derived from the first principle founded on density function theory. However, the total amount of ion releasing from HEA is less than 304SS, since the hydroxide/oxide film formed in the air of the latter containing greater amounts of Fe(Ⅱ) and Mn(Ⅱ) is less stable around corrosion potentials while they are further oxidized into more stable Fe(Ⅲ) and Mn(ⅢorⅣ) with much lower ksp, leading to the much less increasing ratios of ion releases from 0.25 to 0.6 V.

Robustness of helical edge states under edge reconstruction

The helical edge states of time-reversal invariant two-dimensional topological insulators are protected against backscattering in idealized models. In more realistic scenarios with a shallow confining potential at the sample boundary, additional strongly interacting edge states may arise, that could interfere with the topological protection of edge conduction. We find that interaction effects within the reconstructed edges are well described by the Luttinger liquid model. While interactions between this Luttinger liquid and the helical edge states can in principle give rise to dynamical spin polarization and the breaking of time-reversal symmetry, we demonstrate that random spin-orbit coupling strongly suppresses such dynamical spin polarization, resulting in the persistence of near quantized edge conduction.

Asymmetric terahertz polarizer based on VO2 composite metasurface

• We proposed a terahertz asymmetric reflection polarization device based on VO 2 composite metasurface . • The unit cell has two concentric oblique-split-ring-resonators (OSRRs) connected by patterned VO 2 . • When VO 2 is in insulating state, linear-circular polarization conversion is realized at 0.48 and 1.31 THz. • When VO 2 is in metallic state, linear-circular polarization conversion is realized at 0.52 and 0.91 THz. • A new method is proposed for dynamic polarization regulation of THz wave.

Influence of voltage modes on microstructure and corrosion resistance of micro-arc oxidation coating on magnesium alloy

Micro-arc oxidation (MAO) technology, as an efficient and widely used technology, can fabricate a ceramic film on magnesium (Mg) alloys in situ to significantly improve corrosion resistance. The study aims to investigate the effect of voltage modes on the preparation and performance of MAO coating on Mg alloys. The scanning electron microscope, X-ray diffractometer, potential dynamic polarization, and electrochemical impedance spectroscopy measurements were applied for characterizing the microstructure, composition, and corrosion resistance of the MAO film, respectively. The results revealed that employed 300/350 V step-up mode, the MAO film showed a more uniform distribution of surface micro-pores, fewer micro-cracks and denser inner layer, lower corrosion current density (1.871 × 10−3 mA·cm−2), and higher electrochemical impedance value, compared to other voltage treated parameters. Therefore, it could be concluded that the step-up voltage parameters are conducive to the optimization of microstructure, improvement of corrosion resistance of MAO coating, and reduction of the energy consumption during processing.

Multiconfigurational SCF and Short-Range DFT Combined with Polarizable Density Embedding: Comparison of Linear-Response and State-Specific Solvatochromic Shifts of Acrolein and Para-nitrophenolate in Water.

The polarizable density embedding model is combined with the multiconfigurational self-consistent field and MC-srDFT electronic structure methods to calculate solvatochromic shifts of the n-π* absorption of acrolein and the π-π* absorption of the para-nitrophenolate anion in aqueous solution. Differences between linear-response (LR) and state-specific (SS) solvent shifts are analyzed by assessing the contributions of different terms in the solvent potential. This comparison shows that the differences are not only due to the intrinsically different response of LR and SS excitation energies to the polarizability of the environment but also due to a different response to the static part of the environment potential. These observations show that even in nonpolarizable environments, LR and SS calculations based on SCF (orbital optimization) methods do not necessarily agree on the spectral shift. The difference can be as large as, or even dominate, the difference due to dynamical polarization.

Circular RNA ACTR2 activates M2 polarization of macrophages through activating Yes-associated protein signalling and contributes to renal fibrosis.

Macrophages, associated with their heterogenous and dynamic polarization status, actively shape the development of renal fibrosis (RF). In this study, we revealed the significance of a signalling axis, circular RNA ACTR2 (circACTR2)/miR-200c/Yes-associated protein (YAP), in regulating macrophage polarization and the development of RF. A unilateral urethral obstruction (UUO)-induced RF model was established in vivo. In vitro, interferon-γ (IFNγ) and interleukin (IL)-4 were applied to induce M1 and M2 polarization, respectively. The abundance of M1 and M2 macrophages were examined by immunofluorescence (IF) or flow cytrometry on markers specific for each subtype. Expressions of circACTR2, miR-200c and YAP were measured by quantitative real-time-polymerase chain reaction and/or Western blotting. Interactions between circACTR2, miR-200c and YAP were examined by combining luciferase assay, RNA immunoprecipitation and IF. Impact of targeting circACTR2 on RF and macrophage polarization was also examined in vivo. UUO-induced RF was associated with increased M1 and M2 macrophages, up-regulations of circACTR2 and YAP and the down-regulation of miR-200c in the obstructed kidney. circACTR2 was essential for IL-4-induced M2 polarization, but not IFNγ-induced M1 polarization. This activity of circACTR2 was mediated by sponging miR-200c and activating the downstream YAP signalling. In vivo, knocking down circACTR2 boosted miR-200c expression, reduced YAP level, lowered M2 macrophages in obstructed kidney and ameliorated UUO-induced RF. circACTR2, by targeting and sponging miR-200c, activates YAP signalling, stimulates M2 macrophage polarization and promotes the development of RF. Therefore, targeting circACTR2 may benefit the treatment of RF.

A Resonant Cavity Based on Capacitively Loaded Coaxial Structure for Overhauser Magnetic Sensors

The RF excitation coil is an important component of the Overhauser magnetic sensor, which determines whether the dynamic nucleation polarization of the free radical solution can be carried out smoothly. A capacitance-loaded resonant cavity structure is proposed as the RF excitation of the Overhauser magnetic sensor. The structure and equivalent circuit of the capacitance-loaded coaxial resonant cavity are analyzed and improved on the conventional structure, and the resonant frequency is verified to be consistent with the excitation frequency of the free radical solution by modeling and simulation using COMSOL software. The resonant cavity solid was fabricated, and the cavity was tested by using a vector network analyzer. The results show that the initial resonance point of the homemade resonant cavity is 60.55MHz, and the frequency point can be adjusted to 60.7MHz by adjusting the loading capacitor and tuning capacitor; the resonant cavity return loss S11 is about -19dB, and the quality factor Q value is about 506.

Dual-Polarized RSMA for Massive MIMO Systems

This letter proposes a novel dual-polarized rate-splitting multiple access (RSMA) technique for massive multiple-input multiple-output (MIMO) networks. The proposed strategy transmits common and private symbols in parallel through dynamic polarization multiplexing, and it does not require successive interference cancellation (SIC) in the reception. For assisting the design of dual-polarized MIMO-RSMA systems, we propose a deep neural network (DNN) framework for predicting the ergodic sum-rates. An efficient DNN-aided adaptive power allocation policy is also developed for maximizing the ergodic sum-rates. Simulation results validate the effectiveness of the DNNs for sum-rate prediction and power allocation and reveal that the dual-polarized MIMO-RSMA strategy can impressively outperform conventional baseline schemes.

Vectorial sculpturing of spatiotemporal wavepackets

Spatiotemporal vectorial pulse shaping can produce ultrafast optical pulses that enable unprecedented coherent control for light–matter interactions. A traditional pulse shaper produces ultrafast pulses with scalar programmable waveforms for various quantum control applications. However, quantum systems are three dimensional in nature; thus, the interactions are inevitability vectorial. Existing polarization pulse shaping techniques, which are often difficult to align and cumbersome to handle, can only produce dynamic polarization modulation in the temporal domain. Through simply introducing a quarter-wave plate in a pulse shaper using a two-dimensional spatial light modulator, we show that wavepackets with much more sophisticated spatiotemporal vectorial structures such as spatiotemporal spin grating, spatiotemporal spin lattice, and spatiotemporally twisting polarization can be generated, significantly expanding our ability in coherently controlling light–matter interactions that may find broad applications.

Wire Arc Additive Manufactured CuMn13Al7 High-Manganese Aluminium Bronze

In this work, high-manganese aluminium bronze CuMn13Al7 samples were prepared by arc additive manufacturing technology. The phase composition, microstructure, and crystal structure of the high-manganese aluminium bronze CuMn13Al7 arc additive manufactured samples were analysed using direct-reading spectrometer, metallographic microscope, scanning electron microscope, and transmission electron microscope. The micro-hardness tester, tensile tester, impact tester, and electrochemical workstation were also used to test the performance of the CuMn13Al7 samples. By studying the microstructure and properties of the CuMn13Al7 samples, it was found that preparation of the samples by the arc additive manufacturing technology ensured good forming quality, almost no defects, and good metallurgical bonding inside the sample. The metallographic structure (α + β + point phase) mainly comprises the following: the metallographic structure in the equiaxed grain region has an obvious grain boundary α; the metallographic structure in the remelting region has no obvious grain boundary α; the thermal influence on the metallographic structure produced a weaker grain boundary α than the equiaxed grain region. The transverse and longitudinal cross sections of the sample had uniform microhardness distributions, and the average microhardness values were 190.5 HV0.1 and 192.7 HV0.1, respectively. The sample also had excellent mechanical properties: yield strength of 301 MPa, tensile strength of 633 MPa, elongation of 43.5%, reduction of area by 58%, Charpy impact value of 68 J/cm2 at – 20 ℃, and dynamic potential polarisation curve test results. Further, it was shown that the average corrosion potential of the sample was – 284.5 mV, and the average corrosion current density was 4.1×10–3 mA/cm2.

Effect of the Applied Voltages on the Corrosion–Wear Behavior of Thermal Spray Al Coating

In this work, an Al coating prepared using the arc spray process was carried out with a corrosion–wear analysis by a block-on-ring system. The interaction of corrosion and wear of coatings in seawater was also investigated. The effect of different corrosion potentials on the corrosion and wear of the coating was discussed, and the structure and corrosion products of the coating were observed by SEM. The results of dynamic potential polarization curves and friction coefficient measurements were used to clarify the corrosion and wear behavior of aluminum coatings in seawater. After quantitative analysis of a corrosion and wear test, it was found that with the increase in polarization potential, the total weight loss of corrosion and wear (Wtotal) of the aluminum coating increased significantly. This means that the corrosion–wear interaction accounts for most of the weight loss of the coating.

Coupling effect of impact and in-layer voltage on flexoelectricity of PDMS laminated structures

The low flexoelectric coefficients of polymers are the key problem that limit their application. In this paper, electret-like PDMS/metal conductive layer/PDMS laminated structures have been prepared, an internal electric field are applied on the metal conductive layer aimed at improving electromechanical response. Experiments on the flexoelectric responses of polymer laminated structures under impact are performed based on SHPB, in-layer voltage supply system and polarization voltage measuring system. Numerical simulations are also conducted to investigate the dynamic stress-strain relationship and polarization characteristics of polymer laminated structure under different in-layer voltages. The results show that maximum stress increases with decreasing in-layer voltage; the maximum polarization voltage increases first and then decreases with absolute value of in-layer voltage; the minimum polarization voltage decreases with absolute value of in-layer voltage. Specimen with negative voltage has advantage of conversing electric energy and transferring charges. The impact induced strain gradients have been investigated based on numerical simulation and the related flexoelectricity coefficients are obtained. Addition of metal conductive layer and application of in-layer voltage are effective ways to enhance flexoelectricity.

Dynamic Evaluation of Transformation Ability for Emergency Scientific Research Achievements Based on an Improved Minimum Distance-Maximum Entropy Combination Weighting Method: A Case Study of COVID-19 Epidemic Data.

In the process of responding to major public health emergencies, the transformation of emergency scientific research results often faces many unfavourable factors such as limited resources, tight time, changes in needs, and lack of results. It is necessary to evaluate and analyze the ability to transform emergency scientific research results under public health emergencies, so as to rationally allocate emergency scientific research resources between subjects and regions, improve the efficiency of emergency results transformation, enhance emergency scientific research capabilities, and efficiently support incident prevention, control, and treatment. Starting from the patent level, this paper constructs an indicator system to evaluate the transformation ability of emergency scientific research results under major public health emergencies. It improves the minimum distance-maximum entropy combination weighting method to realize the static evaluation of transformation ability for emergency scientific research results from the perspective of patents, then constructs the dynamic evaluation model of transformation ability for emergency scientific research results in public health emergencies from the perspective of patents, and carries out the dynamic evaluation of the emergency scientific research achievements transformation ability of different subjects and different regions. We also improve the ER index, measure the static polarization effect of the transformation ability for regional emergency scientific research results, and consider the time factor to construct a dynamic polarization effect measurement model for the transformation ability of emergency scientific research achievement. Furthermore, this paper improves the measurement model of contribution degree to the polarization effect, and analyzes the contribution degree to polarization of the transformation ability for regional emergency scientific research results.

Frontispiz: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

Elektronentransfer. In ihrem Forschungsartikel (e202203758) untersuchen Jianzhang Zhao et al. den langlebigen Ladungstransferzustand in Spiro-Donor-Akzeptor-Dyaden auf der Grundlage von Pyromellitimid-abgeleitetem Rhodamin.

Frontispiece: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

Frontispiece: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

Impact of structure on the vibrational properties of Ag8SnSe6 crystal: Experimental and theoretical studies

The crystal structure of Ag8SnSe6 argyrodite, grown by the direct melting from the elemental Ag, Sn, and Se in the ampoule, was determined by the powder X-ray diffraction and shown to be the orthorhombic structure with the space group Pmn21 (no. 31). Structure data, atomic coordinates, and interatomic distances have been obtained by the Rietveld method. Lattice dynamics of Ag8SnSe6 argyrodite are studied by the Raman scattering excited at high absorbance spectral range and first-principles calculations. Based on the comparison of frequencies from results of density functional lattice dynamics calculations and polarization properties observed in the spectra the vibrational modes are assigned to the lattice eigenmodes. A satisfactory agreement between theoretical calculations and experimental measurements is established. The SnSe4 tetrahedral groups were found to be responsible for the main (highest intensity) phonon vibration.