High Power Characteristics Research Articles

Design of a High-Voltage Miniaturized Control System for Macro Fiber Composites Actuators

Macro Fiber Composites (MFCs) exhibit significant potential in active control applications. These include vibration control for unmanned aerial vehicle wings and helicopter rotors. However, the high-voltage drive requirements of MFCs present challenges. The miniaturization of the controller is a mandatory condition in order not to affect the overall space utilization. Thus, this paper presents a specialized miniaturized high-voltage control system designed specifically for MFC actuators. The proposed system employs a mixed analog-digital modulation method (ADM). This method precisely regulates a discontinuous conduction mode flyback switch-mode power supply operating in current mode. The system achieves an adjustable high-voltage output range of -500 V to 1500 V. The mixed control system consists of several components. These include a switching power supply, a voltage divider circuit, a bleeder circuit, and a digital controller. Additionally, this high-voltage control system integrates with a Simulink software environment. The system is compact and lightweight. It also features high load capacity, high power, and excellent dynamic response. Moreover, it offers real-time control capabilities. Experimental validation on a high-aspect-ratio wing demonstrates that this control system achieves a vibration reduction effect of 65%. The miniaturized control system provides a valuable research base for vibration control studies.

A novel horizontal self-tuning piezoelectric energy harvester based on a beam-slider system

Abstract With the rapid development of piezoelectric energy harvesting technologies, this approach is emerging as a promising power source for smart sensors. Despite this progress, a significant challenge remains in achieving a wider bandwidth while increasing the output power. In response to this challenge, this paper introduces a horizontal self-tuning beam-slider piezoelectric energy harvester (STBS-PEH). This innovative harvester employs a unilateral beam-slider mechanism to enable self-tuning of the energy harvesting by adjusting its resonant frequency to match the external excitation frequency. The electromechanical coupled dynamic model of this harvester has been established. Comprehensive simulations and experimental analysis have been conducted to demonstrate the wide bandwidth and high output power characteristics of the proposed harvester. Notably, the simulation results exhibit strong agreement with the experimental findings. The resonance response bandwidth of the STBS-PEH is particularly noteworthy, which is twice that of a conventional cantilever beam piezoelectric energy harvester. The root mean square (RMS) voltage and output power of the developed STBS-PEH can reach 23.54 V and 194.61 µW, respectively, at a frequency of 21 Hz, with an excitation amplitude of 0.5 g. These results demonstrate that the STBS-PEH is capable of powering low-power electronic devices in a broadband vibrational environment.

Ruddlesden-Popper Type Intercalation Cathode with High Capacity Involving O-O Bond Formation for All-Solid-State Fluoride-Ion Batteries

Fluoride ion batteries, which utilize fluoride ions as carriers, have gained attention as a candidate for the next generation of secondary batteries due to their high energy density and low resource risk independent of lithium metal. The basic operating principle is to achieve high capacity by utilizing multivalent reactions of metals during fluoride/defluoride reactions.[1] However, there are difficulties in ensuring cycling performance and rate characteristics due to significant changes in crystal structure, electronic conductivity, and ion conductivity during fluorination/defluorination. To address these challenges, we are considering the application of intercalation reactions, which are also utilized as electrode reactions in lithium-ion secondary batteries. In this presentation, we focus on Ruddlesden-Popper type La1.2Sr1.8Mn2O7F2 oxyfluoride and report on its detailed charge-discharge mechanism, as we have found that it can intercalate and deintercalate more than two fluoride ions contained in its structure.[2] La1.2Sr1.8Mn2O7F2 was synthesized using a topochemical fluorination method with PVDF. It was mixed with La0.9Ba0.1F2.9 and VGCF to form the composite electrode, and a solid-state cell was constructed using La0.9Ba0.1F2.9 as the solid electrolyte and PbF2/AB composite electrode and Pb foil as the counter electrode. Charge-discharge reactions were carried out at 140°C in the voltage range of -1.5 to 3.0 V, and after evaluation, X-ray diffraction (XRD) measurement, scanning transmission electron microscope (STEM) observation, X-ray absorption spectroscopy (XAS) measurement, and resonant inelastic X-ray scattering (RIXS) measurement of O K-edge were performed.The initial discharge capacity of La1.2Sr1.8Mn2O7F2 showed 91 mAh/g, confirming that almost all of the fluoride ions in the structure were topochemically defluorinated. In the charge reaction, it was confirmed that reversible insertion of fluoride ions occurred mainly due to charge compensation of manganese, the transition metal, up to 1.5 V. Furthermore, at higher potentials, a new plateau appeared around 2.0 V, indicating further insertion of fluoride ions into the structure, and it exhibited a high capacity of nearly 200 mAh/g even during subsequent discharge. XAS and RIXS measurements of O K-edge revealed that charge compensation was achieved by oxide ions, and the formation of O-O bonds, as which is reported in lithium-excess cathode material[3], was observed. These results demonstrate the potential of intercalation materials to achieve high capacity, high cycling performance, and high power characteristics. Reference s : [1] M. A. Reddy, M. Fichtner, J. Mater. Chem. 2011, 21, 17059–17062.[2] H. Miki, K. Yamamoto, Y. Uchimoto, et al., J. Am. Chem. Soc. 2024, 146, 3844–3853[3] R. A. House, P. G. Bruce, et al., Nat. Energy 2020, 5, 777–785.Acknowledgement: This research was financially supported by JST-Mirai program (JPMJMI18E2), JSPS Grant-in-Aid for Scientific Research on Innovative Areas, “Mixed-Anion” (JP16H06438, JP16H06440, JP16H6441), JSPS Grant-in-Aid for Transformative Research Areas (A) “Supra-ceramics” (JP22H05148, JP22H05146) and JSPS Grant-in-Aid for Scientific Research (B) (JP21H02048).

Enhanced Specific Capacitance of Lithium Ion Capacitors By Effective Surface Functionalization for Lithiophilic Activated Carbon

Lithium Ion Capacitor (LIC) is a hybrid energy storage device that combines high power characteristics of Electric Double Layer Capacitors (EDLC) with high energy density features of Lithium Ion Batteries (LIB). In LICs, a graphite electrode from LIBs serves as the anode, while an activated carbon electrode from EDLCs functions as the cathode. This configuration results in higher energy density than EDLCs, improved power and cycling characteristics compared to LIBs. To supply lithium ions internally or externally as the energy source, LICs may employ techniques such as (1) Li pre-doping, (2) the use of sacrificial anodes made from Li transition metal oxides, or (3) electrodes embedded with lithium ions.Significant research efforts are underway to enhance the resistance components and performance metrics, including energy density and output of LICs. Although methods like adding Li transition metal oxide, sintering salts, or blending with activated carbon are employed to increase internal capacity, challenges such as decreased energy density per unit weight, increased resistance from reaction by-products, or gas formation persist. During discharge, the desolvation energy of cations is higher than that of anions, and an increase in resistance components occurs at the 3 V point where ion exchange between lithium ions and anions happens.This study focuses on minimizing resistance components in LICs by synthesizing a Li/activated carbon (Li/AC) hybrid material, which provides a Li source within the activated carbon matrix. Acid treatment introduces oxygen functional groups on the surface of the activated carbon, followed by the synthesis of lithium compounds using a Li precursor. The crystallization and growth conditions of Li ions were optimized using the thermal treatment temperatures established in previous studies. The study also conducted concentration-dependent synthesis experiments to optimize the molar concentration of the Li precursor solution. The manufactured Li/AC active materials were tested for charge and discharge cycles, Nyquist plots, and rate capability. To analyze these properties, techniques such as Brunauer Emmett Teller (BET) analysis, Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), and Thermogravimetric Analyzers (TGA) were employed.

Understanding intra-pore electrolyte resistances and distributed capacitances in carbon electrodes used in supercapacitors using a robust modeling process to separate the charge-storage occurring into macro-, meso-, and micro-pore structures

In this study, a Modified Generic Electrochemical (MGE) model is introduced for studying rough/porous carbon-based electrode materials employed in electrical double-layer capacitors (EDLC) which contain different types of surface defects. Instead of adopting the common theoretical approach involving the use of transmission line models or ad hoc equivalent circuits, a rational equivalent circuit model has been devised, which permitted us to derive the different equations for each electrochemical technique. The MGE representing the overall electrochemical behavior of EDLCs obtained using the different techniques (e.g., cyclic voltammetry, chronoamperometry, chronopotentiometry, and impedance) is formally derived based on a simple premise considering that the different inhomogeneous surface defects, which are geometrically arranged under equipotential conditions, are not electrochemically equivalent. In this sense, the presence of hierarchically distributed charge-storage processes with different time constants, accounting for the ionic accumulation at the electrode/solution interface, can be ascertained. We verified that is imperative to avoid the determination of the specific capacitances and resistances in EDLCs using a single electrochemical technique or several techniques whose model equations are based on different theoretical premises. The use of the MGE model unequivocally revealed that isolated measurements of the specific capacitance in the absence of the associated intra-pore resistances are not sufficient to ensure the presence of rapid charge storage allied with high-power characteristics. With the appropriate choice of carbon-based materials with very low intra-pore resistances, substantial progress can be made in ushering in the next generation of EDCLs with very high-power characteristics.

Layered Structure Modification of Sodium Vanadate through Ca/F Co‐Doping for Enhanced Energy Storage Performance

AbstractVanadate materials are promising for sodium‐ion batteries (SIBs) due to their low cost, high capacity, and high power characteristics enabled by vanadium's multiple oxidation states. However, their development is hindered by poor conductivity, suboptimal high‐rate performance, and limited cycle life. In this work, a layered structure modification strategy involving Ca/F co‐doping in sodium vanadate Na2CaV2O6F (CVF) is proposed to address these issues. Through a combination of experiments and density functional theory calculations, it is demonstrated that Ca/F synergies enhance the Na layer spacing in CVF, resulting in reduced crystal water content and volume shrinkage compared to Na2V2O6 (NVO). Additionally, Ca/F incorporation significantly mitigates the diffusion potential of Na+ within the material framework. The unmodified CVF sample exhibits a high reversible capacity of 220 mAh g−1 at 10 mA g−1 and an excellent rate capacity of 65.78 mAh g−1 at 400 mA g−1. Furthermore, the cathode material maintains a capacity of up to 138 mAh g−1 at 200 mA g−1 and retains 104.88 mAh g−1 after 100 cycles within the voltage range of 1.5−4.0 V. These findings enhance the understanding of the crystal structure of NVO cathode materials and pave the way for the rational design of high‐quality vanadate cathodes for SIBs.

Stoichiometric and non-stoichiometric Mn modification on high-power properties in PYN-PZT piezoelectric ceramics

The types of dopants lead to distinctive microstructural evolution behavior and physical properties in materials. In this study, the effect of stoichiometric and non-stoichiometric Mn modification, namely Pb(Mn1/3Nb2/3)O3 (PMnN) and MnO2, on the microstructure and properties of Pb(Yb1/2Nb1/2)O3-PbZrO3-PbTiO3 (PYN-PZT) piezoelectric ceramics are systematically investigated. It was found that stoichiometric PMnN modification inhibits the grain growth while non-stoichiometric MnO2 modification promotes it, and thus the former yields stronger high-power characteristics (higher internal bias field Ei and larger mechanical quality factor Qm) than the latter. Specifically, with an equivalent amount of Mn modification (2 mol%), PMnN and MnO2 modification PYN-PZT ceramics exhibit significantly different values for average grain size (1.21 μm vs. 14.12 μm), Ei (8.5 kV/cm vs. 5 kV/cm), and Qm (2376 vs.1134). To further evaluate high-power performance, the vibration velocity v of these two modified PYN-PZT under high driving conditions was measured. Under an AC electric field of 3.5 V/mm, the PYN-PZT+6PMnN ceramics exhibit a v of up to 0.95 m s−1, larger than both MnO2-doped PYN-PZT (0.72 m s−1) and unmodified PYN-PZT ceramics (0.1 m s−1), and far outperformance than both PZT-4 and PZT-8 ceramics. Furthermore, to elucidate the origin of the exceptional high-power performance of PMnN-modified PYN-PZT, we performed phase-field simulations revealing a pinning effect of the grain boundary on domain wall motion. Consequently, the small grain size (high grain boundary density) in PMnN-modified PYN-PZT exhibits a strong pinning effect, resulting in a large Qm and outstanding high-power performance.

A 5 V Ultrahigh Energy Density Lithium Metal Capacitor Enabled by the Fluorinated Electrolyte

Lithium metal capacitor (LMC), incorporating a redox-type lithium metal anode and a capacitive-type carbon cathode, delivers a combination of high energy and power characteristics, which is regarded as a promising electrochemical energy storage system. However, the unstable interface stability of lithium anode and the unclear capacitive mechanism of carbon cathode seriously restrict the advancement of LMC. Herein, an all-fluorinated electrolyte with high voltage stability has been designed for engineering 5 V LMC. It is noticed that a high-quality LiF-rich solid electrolyte interphase derived from all-fluorinated electrolyte effectively improves the interfacial stability of lithium metal anode, boosting the reversible Li plating/stripping behavior and suppressing dendrite growth. Moreover, analyzed by the thermodynamic perspective, the stable PF6−(FEC)2(FEMC)4 configuration with the lowest solvation energy mainly exists in the all-fluorinated electrolyte, which reveals that the suitable pore size distribution (1.3–4.6 nm) can ensure the strong adsorption/desorption process. Endowed by the all-fluorinated electrolyte, the established 5 V LMC paired with an optimized porous carbon sheet cathode manifests excellent electrochemical performances with an ultrahigh energy density of 537.6 Wh kgcathode−1 and a large power density of 17500 W kgcathode−1. This elaborate work affords in-depth insights based on fluorinated electrolyte strategy into the fabrication guidance of LMC.

Simultaneously enhanced electrical properties and high-power characteristics of (K,Na)NbO3 lead-free piezoceramics by hot-pressing

Piezoelectric materials enabling direct conversion between electrical and mechanical energies are ubiquitously implemented in high-power apparatuses, where both superior piezoelectricity and high-power performance are demanded. However, it remains a challenge to simultaneously achieve the two goals, which are hindered by their antagonistic relationship. Herein, hot-pressing is employed to address this dilemma, as exemplified in lead-free (K,Na)NbO3 (KNN) piezoceramics. In contrast to the samples prepared using normal sintering (NS–KNN), hot-pressed KNN (HP–KNN) polycrystals show higher density, lager piezoelectricity (d33∼129 pC/N), and more active domain wall movement. In particular, the normalized strain d33* of HP-KNN piezoceramics exhibits high thermal stability (variation of d33*<10 %) in a broad temperature range from ambient temperature up to 150 °C. Moreover, the HP-KNN samples show superior high-power characteristics with a maximum vibration speed of 1.1 m/s, which is almost 78 % larger than that of NS-KNN. This study not only demonstrates that the HP-KNN lead-free piezoceramics hold great potential for high-power implements, but also opens a new avenue for integrating antagonistic properties for the enhancement of the collective performance in functional materials.

Advances in the development of few-cycle gigawatt-peak-power mid-IR optical parametric amplifiers pumped by Cr:Forsterite laser using non-oxide nonlinear crystals

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics.

Synthesis and characterization of lead and cadmium hexaborates doped with Cr3+

Borates doped with transition metals (Mn, Cu, Cr) exhibit a significant and long-lasting luminescence at room temperature, high power, and other outstanding characteristics. Therefore, the purpose of the study was to establish the possibility of the formation of borate materials containing chromium and the determination of their structure and thermal properties. New phases of variable composition were synthesized in the PbCd2–xB6O12:xCr3+ system by heterovalent substitution of Cd2+ions with Cr3+ ions using solid-phase reactions at 640 °C. The phases were isolated in the concentration range 0 ≤ x ≤ 7.0 mol % and characterized by X-ray phase analysis (XRD), differential scanning calorimetry (DSC) and IR spectroscopy. According to XRD and IR spectra, the resulting borates crystallize in a monoclinic cell and are assigned to one structural type (space group P21/n, Z = 4). The crystallographic characteristics of the new phases have been determined. The crystal lattice parameters and their volumes decrease monotonically, indicating the formation of a continuous series of substitutional solid solutions in the studied concentration range. According to the DSC results, the sample PbCd2–xB6O12: 0.03 Cr3+melts incongruently at 729 °C

Monolithic beam combined quantum cascade laser arrays with integrated arrayed waveguide gratings.

Quantum cascade lasers (QCLs) are ubiquitous mid-infrared sources owing to their flexible designs and compact footprints. Manufacturing multiwavelength QCL chips with high power levels and good beam quality is highly desirable for many applications. In this study, we demonstrate an λ ∼ 4.9 µm monolithic, wavelength beam-combined (WBC) infrared laser source by integrating on a single chip array of five QCL gain sections with an arrayed waveguide grating (AWG). Optical feedback from the cleaved facets enables lasing, whereas the integrated AWG locks the emission spectrum of each gain section to its corresponding input channel wavelength and spatially combines their signals into a single-output waveguide. Our chip features high peak power from the common aperture exceeding 0.6 W for each input channel, with a side-mode suppression ratio (SMSR) of over 27 dB when operated in pulsed mode. Our active/passive integration approach allows for a seamless transition from the QCL ridges to the AWG without requiring regrowth or evanescent coupling schemes, leading to a robust design. These results pave the way for the development of highly compact mid-IR sources suitable for applications such as hyperspectral imaging.

Rayleigh wave excitation with an elliptical reflector for high-power ultrasound

This study proposes a Rayleigh wave transducer with an elliptical reflector for high-power ultrasound (ELIPS). In contrast to conventional transducers using IDT with single crystal piezoelectric plates or wedge transducers, our ELIPS enables high-power Rayleigh wave excitation in the megahertz range, which will be useful for applications such as surface acoustic wave (SAW) motors, SAW tactile devices, and SAW atomizers. The driving principles of the transducer are Rayleigh wave excitation with a transverse wave source and transverse wave focusing with a dilatational wave source and an elliptical reflection surface. The effectiveness of this mechanism was confirmed with an FEM simulation, and the Rayleigh wave excitation was validated using a prototype transducer. Finally, the high-power characteristics were examined, and a maximum vibration amplitude of 15.5 nm at 1.0 MHz was successfully obtained. It should be noted that this vibration amplitude is not a saturated value, and a much higher value could be realized with higher input power.

Efficient nonlinear pulse compression to 20 fs based on an all-solid-state periodic self-focusing system

Ultrafast lasers with high average power and excellent spatial characteristics have been sought after in the ultrafast optics field. In this work, we propose and experimentally demonstrate a simple Gaussian beam optics model to realize the configuration of periodic self-focusing systems for generating intense ultrashort pulse with high spatial quality. An efficient 17-fold nonlinear pulse compression is implemented by a two-stage solid-thin-plates periodic self-focusing system based on this model, delivering 20 fs (full-width-at-half-maximum, FWHM) pulses with a pulse energy of 155 µJ at a repetition rate of 200 kHz. The waveguide-like self-consistent stationary spatial mode propagation achieved in the system enables the high efficiency of 94 %, good beam quality and spectral homogeneity across the beam profile. The solid-thin-plates in three different materials are used in the first stage, which manifests the model can be widely applied in many kinds of nonlinear medium. In the second stage, a simple and compact double-pass architecture is demonstrated, indirectly proving the accuracy of model. The beam propagations under non-stationary modes are also investigated and a more precise quasi-stable oscillatory region is suggested based on the Gaussian beam optics model. These results underline that the Gaussian beam optics model is a practical solution for identifying the self-consistent stationary mode of the periodic self-focusing system and show the potential of the periodic self-focusing system for efficient few-cycle pulses generation which is demand by many applications.

Flowing Heating System for Pipeline of Electromagnetic Coupling of Power Frequency Without the Iron Core and Its Structure Optimization

Abstract In response to the current problems such as electromagnetic coupling heating equipment relying on the limitations of electronic devices mostly and difficulty in achieving uniform heating of flowing material, this paper proposed a flowing heating system for pipelines of electromagnetic coupling of power frequency without the iron core. Using the heating system of 500 kW/10.5 kV, structural and electrical parameters were obtained from theoretical calculations, and a finite element simulation model was established. Aiming at the problems of voltage waveform distortion and low power factor, the factors affecting the heating system such as pipe wall thickness and coupling gap were analyzed, and the influence laws on the heating system were obtained. The structure of the conductive ring was proposed for system optimization. In the case of the no-iron heart, the heat efficiency can reach 89.01%, the power factor increased to 0.915, and the voltage distortion was also significantly reduced. Based on the finite element simulation results, the structure of the spoiler ball was proposed to address the problem of uneven heating, and the simulation showed that the spoiler balls can optimize the heating uniformity of the heating system. This system can realize the uniform heating of material without the cost of the iron core and has the characteristics of high voltage and high power, which can provide an effective way of thinking for the electric heating of hot water, steam, hot air, etc.

Hierarchical NiCo-LDH layered composite on PANI coated Ni foam for highly efficient supercapattery applications

Supercapatteries combine the high-power density characteristic of supercapacitors with the high energy density typically found in batteries, offering a promising solution for advanced energy storage applications.

Improving PEMFC Performance with Customized Catalyst Combinations and Advanced Mixing Techniques

Proton Exchange Membrane Fuel Cells (PEMFCs) are a popular choice for use in vehicles and buildings because they can operate at relatively low temperatures and have a simpler system compared to other types of fuel cells. The performance and durability of PEMFCs are influenced by the membrane electrode assembly (MEA).The cathode, where the oxygen reduction reaction occurs, is the component of the MEA that has the greatest influence on performance. The factors that affect high power performance are catalyst activity, proton conductivity, and mass transport resistance of fuels and products.Pt catalysts and PtCo catalysts have advantages and disadvantages at different current densities in PEMFCs. In low current density conditions, PtCo catalysts have been shown to exhibit higher catalytic activity compared to Pt catalysts for the oxygen reduction reaction (ORR). This can result in a more efficient fuel cell operation. However, in high current density conditions, the activity of PtCo catalysts can be reduced compared to Pt catalysts because of their larger particle sizes, which can limit their performance.The properties of the carbon support, such as its hydrophobicity and surface area, can also play an important role in determining the performance of the fuel cell. Hydrophobic carbon supports can facilitate gas diffusion and prevent flooding which can occur when water accumulates in the pores of the electrode and limits reactant transport. Moreover, such supports can limit the contact area between the water and catalyst, leading to prolonged catalyst activity and lifespan. On the other hand, high surface area supports can increase the number of sites available for catalyst anchoring and enlarge the electrode's effective surface area. However, achieving both hydrophobicity and high surface area can be challenging due to the trade-off between these properties.Because each catalyst has advantages and disadvantages at different current densities or operating conditions in PEMFCs, combining different catalystscan achieve improved performance across a wider range of operating conditions. However, each catalyst and carbon support has different affinity with ionomer. Therefore, it is impossible to achieve even ionomer distribution through simple mixing. This means that it is difficult to express the advantages of each catalyst through simple mixing because the transport properties of protons can be influenced by the distribution of the ionomer.To address this, two catalysts were mixed into thecathode electrodes separately, and it was confirmed that this approach improved their performance across a range of current densities. In particular, their high power characteristics were enhanced. To confirm these results, the MEA was tested using H2/air polarization curves, EIS analysis, and limit current density tests, and the porosity in the electrode structure was measured by the BET method and Mercury intrusion porosimetry (MIP).In conclusion, Pt and PtCo catalysts have unique advantages and disadvantages at different current densities in PEMFCs. The properties of the carbon support also play a crucial role in determining the fuel cell performance. Combining different catalysts can enhance the fuel cell's performance but achieving even ionomer distribution through simple mixing is challenging. Applying the two catalysts separately through a distribution process improved the fuel cell's performance across different current densities, especially high power characteristics.

High-Performance Supercapacitors Using Hierarchical And Sulfur-Doped Trimetallic NiCo/NiMn Layered Double Hydroxides.

A supercapacitor features high power density and long cycling life. However, its energy density is low. To ensemble a supercapacitor with high power- and energy-densities, the applied capacitor electrodes play the key roles. Herein, a high-performance capacitive electrode is designed and grown on a flexible carbon cloth (CC) substrate via a hydrothermal reaction and a subsequent ion exchange sulfuration process. It has a 3D heterostructure, consisting of sulfur-doped NiMn-layered double hydroxide (LDH) nanosheets (NMLS) and sulfur-doped NiCo-LDH nanowires (NCLS). The electrode with sheet-shaped NMLS and wire-shaped NCLS on their top (NMLS@NCLS/CC) increases the available surface area, providing more pseudocapacitive sites. It exhibits a gravimetric capacity of 555.2 C g-1 at a current density of 1 A g-1 , the retention rate of 75.1% when the current density reaches up to 20 A g-1 , as well as superior cyclic stability. The assembled asymmetric supercapacitor that is composed of a NMLS@NCLS/CC positive electrode and a sulfurized activated carbon negative electrode presents a maximum energy density of 24.2Wh kg-1 and a maximum power density of 16000W kg-1 . In this study, a facile strategy for designing hierarchical LDH materials is demonstrated as well as their applications in advanced energy storage systems.

An exact projection pursuit-based algorithm for multivariate two-sample nonparametric testing applicable to retrospective and group sequential studies

Nonparametric tests for equality of multivariate distributions are frequently desired in research. It is commonly required that test-procedures based on relatively small samples of vectors accurately control the corresponding Type I Error (TIE) rates. Often, in the multivariate testing, extensions of null-distribution-free univariate methods, e.g., Kolmogorov-Smirnov and Cramér-von Mises type schemes, are not exact, since their null distributions depend on underlying data distributions. The present paper extends the density-based empirical likelihood technique in order to nonparametrically approximate the most powerful test for the multivariate two-sample (MTS) problem, yielding an exact finite-sample test statistic. We rigorously apply one-to-one-mapping between the equality of vectors' distributions and the equality of distributions of relevant univariate linear projections. We establish a general algorithm that simplifies the use of projection pursuit, employing only a few of the infinitely many linear combinations of observed vectors' components. The displayed distribution-free strategy is employed in retrospective and group sequential manners. A novel MTS nonparametric procedure in the group sequential manner is proposed. The asymptotic consistency of the proposed technique is shown. Monte Carlo studies demonstrate that the proposed procedures exhibit extremely high and stable power characteristics across a variety of settings. Supplementary materials for this article are available online.

Permanent Magnet Motors in Energy Storage Flywheels

Flywheel energy storage system stores energy in the form of mechanical energy and can convert mechanical energy into electrical energy. Flywheel energy storage is a mechanical energy storage system. Due to its high energy storage density, high power, high efficiency, long life, no pollution and other characteristics, it has a broad application prospect in the field of aerospace, power peaking, UPS, electric vehicles, high-power electromagnetic guns and so on. With the continuous development of magnetic levitation, composite materials, vacuum and other technologies, the current flywheel energy storage technology is mainly through the increase in the speed of the flywheel rotor to achieve energy storage, the continuous development of various technologies, so that the research of flywheel energy storage technology has stepped into the "high-speed" development period, and has been widely used in many fields. Application, and gradually become the focus of research in various countries.