Advanced High Power Research Articles

Impact of Advanced High-Power Pain Threshold Static Ultrasound and Muscle Energy Technique on Pain Thresholds and Functional Improvement in Myofascial Trigger Points

bands and hypersensitive Trigger Points (TrPs), contributing to musculoskeletal pain. The objective of this study is to investigate and assess the effectiveness of Advanced High-Power Pain Threshold Static Ultrasound (AHPPTSU) and Muscle Energy Technique (MET) in altering pain thresholds and enhancing functional outcomes in individuals with myofascial trigger points. Methods: In this randomized clinical trial involving 86 individuals with TrPs in the upper trapezius muscle, the participants were divided into experimental and control groups. 33 males and 53 females, underwent six sessions of treatment over two weeks. A repeated measure Analysis of variance was used to compare baseline values and altered values at 1 and 2 weeks. Results: The study demonstrated that the Pressure Pain Threshold (PPT) and the Neck Pain Disability Index (NPDI) score, showed a significant improvements in participants receiving AHPPTUS in experimental group compared to the other group. Experimental group showed a significantly greater improvement in PPT (p=0.001) and both groups experienced a significant enhancement in function. However, when comparing the two groups, experimental group showed a significantly greater improvement (p=0.001). Importantly, no adverse effects were reported in either group. Conclusion: In the treatment of myofascial trigger point, AHPPTSU can be considered as an alternative therapy method, which is more effective than previously used High-Power Pain Threshold Static Ultrasound (HPPTSU) therapy and it also shortens the total treatment protocol to 2 weeks.

509 nm high power wide-tuned external cavity surface emitting laser

High power widely tunable green lasers have potential applications in many fields such as biomedicine, lidar, laser spectroscopy, laser display, underwater wireless optical communication, and fine processing of nonferrous metals. Vertical-external-cavity surface-emitting lasers, also known as semiconductor disk lasers, have the advantages of high power, good beam quality, and wide bandwidth of gain medium. In this work, a gain chip with a reverse-growth epitaxy structure and an emitting wavelength of 1018 nm is designed. In the DBR reflection spectrum, a bandwidth of 74 nm is achieved above a reflectivity of greater than 99.1%, laying a solid foundation for achieving high-power widely tunable output. The laser cavity combines a 1018 nm semiconductor gain chip, a folded mirror, and a plane mirror to construct a compact V-type resonant cavity. A class-I phase-matched LBO nonlinear crystal with a length of 10 mm is placed at the beam waist of the cavity to realize an efficient frequency doubling process to produce a 509 nm green laser. To meet the requirement for the polarization during frequency conversion and to tune the oscillating wavelength of the laser, a birefringent filter (BRF) is employed in the laser resonant cavity. When the thickness of the used BRF is 1 mm, the obtained wavelength tuning range of the fundamental laser and the frequency doubled green laser are 47.1 nm and 20.1 nm, respectively, showing a good tuning capability of the laser. The laser’s performance varies with the thickness of the BRF. When using a 2 mm BRF, a maximum power output of the frequency-doubled green laser reaches 8.23 W during continuous tuning, indicating an ideal compatibility of wide tuning characteristics with a high power output. Meanwhile, its beam quality <i>M</i> <sup>2</sup> factors are 1.00 and 1.03 in the <i>x</i>- and <i>y</i>-direction, respectively, demonstrating a near diffraction-limited excellent beam quality. This green laser also possesses a frequency doubling conversion efficiency of up to 68.2%, which can efficiently converse the fundamental laser into the frequency doubled green laser. The optical-to-optical conversion efficiency from the absorbed pump light to the frequency-doubled green light also reaches 16.6%. Meanwhile, from the spectral linewidths of the green lasers under different thickness values of BRFs it is found that the thicker the BRF, the narrower the laser line width is, which is consistent with the theoretical result.

Editorial: Advanced high power solid-state laser technology

Editorial: Advanced high power solid-state laser technology

An Advanced High Dimensional Power System of Optimization Problems Algorithm

New Evolutionary Algorithm-based for High-Dimensional Power System Optimization Problems and Modern power system optimization problems face growing challenges as there are numerous decision variables and unbiased functions. Multi-objective evolutionary algorithms (MOEAs) basically are popularly applied for solving and dealing with such complicated problems in substantial power systems that have several objective functions. However, customary MOEAs works appropriately when the number of objective features comes to be less than three. Generally, the effectiveness of MOEAs begins to decrease apparently with an increase in the number of unbiased functions. This study is devoted to applying an authentic gradable evolutionary algorithm for the purpose of solving power system optimization issues which manifest numerous objective functions. In particular, this seeks an algorithm based upon NSGA-II algorithm dedicated for an efficient solution of multi-objective optimization problems. Here, we attempt to modify NSGA-II algorithm to effectively solve many target optimization problems. A novel effective grouping method is applied in the proposed algorithm in similar to the non-dominant grouping method of NSGA-II algorithm to accelerate decision convergence action in POF. The recommended algorithm is compared with modern numerous objective optimization algorithms following three test problems. The findings reveal that as the number of unbiased functions is noticeably large, the algorithm that we propose is significantly superior to other algorithms.

Fast charge induced phase evolution and element contribution of nickel-rich layered cathode for lithium-ion batteries

In nickel-rich layered cathode materials, three transition metals (TM = Ni, Co and Mn) play critical roles in Li storage performance. However, rate-dependent phase evolution and elemental contribution of nickel-rich cathode materials are not well understood, but very important for further design and development of these cathodes in high-power applications. Here, the rate-dependent phase evolution and elemental contribution of LiNi0.5Mn0.3Co0.2O2 (NMC532) cathode are investigated thoroughly by using time-resolved synchrotron-based in situ X-ray diffraction and absorption techniques. The increase of Ni content in NMC532 has been found to be the main cause of the complex structural changes, resulting in distortion of TM-O6 octahedron and strong static vibration between TM and O coordination. It is revealed that the fast charge (10 and 30C) of NMC532 leads to intermediate Li-poor phases, shrinking of H2 phase region, and prolonged O1 phase. During high-rate charging, Co is oxidized easily in low voltage region, while Ni mainly dominates charge compensation in high voltage region. It is found that delithiation-induced local structure distortion transfers from Ni to Co sites in fast kinetic process. These findings provide in-depth understanding for the fast charge behavior of Ni-rich layered cathode materials, and help to guide further development of advanced high power lithium-ion batteries.

Application and development direction of fiber laser

A fiber laser is a kind of laser emitting device based on fiber technology, which has the advantages of high power, high efficiency, and high beam quality. Therefore, fiber laser has wide application prospects in communication, medical treatment, material processing, and other fields. In the future, with the continuous progress of technology and the increasing demand, the application field of fiber lasers will be further expanded, and the development direction will be more diversified and specialized. In this paper, through the study of the application of fiber lasers, the development of fiber lasers in recent years is introduced, and its application status and development trend in communication, medical treatment, material processing, military, and other fields are summarized.

The Temporal Measurement of Infrared Femtosecond Fiber Laser Pulse with Complex Spectra: SPIDER and FROG

Femtosecond fiber laser pulse (FFLP) is very suitable for precision laser processing (PLP) with the advantages of high power, compact integrated structure, and easy installation. However, with the power increasing, nonlinear optical effects (NOE) of fiber, such as self-phase modulation (SPM), will be greatly enhanced, and the spectra of the output pulse will be very complex, which considerably increases the temporal complexity of FFLP and takes an immeasurable influence on PLP, so it is of great significance to accurately measure the temporal property of FFLP for higher accuracy of PLP. This paper presents a self-referencing spectral phase interferometry for direct electric-field reconstruction based on a single grating stretcher (SGS-SPIDER) with the two-step phase shift (TSPS) method for measuring FFLP with complex and infrared spectra. Meanwhile, we present a modified pulse-retrieval algorithm called an adaptive pulse-retrieval algorithm (APRA) of frequency-resolved optical gating (FROG) to reconstruct the measured pulse accurately. The duration of the reconstructed pulse measured by FROG is 162 fs, whose autocorrelation curve is similar to the measured autocorrelation curve including the picosecond background. The error of the reconstructed FROG trace is 0.42%, which is reliable enough according to the literature experience. Finally, the unique advantages of FROG for measuring complex ultrashort pulses such as FFLP are compared with SPIDER; that is, FROG has a wider spectral phase measuring range than SPIDER. These studies provide a new diagnostic technique for the complete temporal characterization of FFLP with complex spectra and extend the measurement range and application of SPIDER at the infrared wavelength band, which is significant for improving the accuracy of PLP using FFLP.

High-Performance Aqueous Zinc-Ion Battery Based on Laser-Induced Graphene

Zn-ion batteries (ZIBs) have a broad application prospect because of their advantages of high power, large capacity, and high energy density. However, the development of high-capacity, long-lifespan ZIBs is challenging because of the faster dendrite growth and the occurrence of the hydrogen evolution reaction. Laser-induced graphene (LIG) is a material with many defects and heteroatoms. Because of these characteristics, it plays an important role in improving nucleation. A simple and effective method for preparing LIG was proposed in this paper, and the LIG was covered on the surface of Zn foil to form a composite structure. This structure substantially reduces the nucleation overpotential of Zn and slows down the dendrite growth of Zn by improving the nucleation behavior of Zn2+. Simultaneously, the three-dimensional porous structure increases the specific surface area of the electrode, so the battery has a larger specific capacity. Compared with the bare Zn electrode, the composite electrode possesses lower overpotential and longer cycle life. In addition, the full battery using activated carbon as the active material exhibits great rate and cycle performance. This facile and scalable approach may solve the problem of Zn dendrite growth, which is crucial for the large-scale application of ZIBs.

A novel honey authenticity detection system based on external cavity quantum cascade laser

Limited by the flexibility of the detection instrument, the current research reports on rapid detection of honey authenticity are mainly about algorithm research under the laboratory conditions. External cavity quantum cascade laser (EC-QCL) is a new sensor technology, has the advantages of high power, high flux and high flexibility, which is very suitable for the development of in-situ detection instrument. In this study, we developed a novel miniaturized detection system based on EC-QCL for detecting sweeteners in Vitex honey, and established the discrimination model of honey authenticity based on the EC-QCL detection system combined with partial least squares discriminant analysis (PLS-DA) and support vector machine (SVM), respectively. The accuracy, sensitivity and specificity of the validation set of the best model were both 100%, and the area under the receiver operating characteristic curves (AUROC) is greater than 0.99. In addition, the performance of the discrimination model trained using data obtained by EC-QCL system are better than that established by traditional detection equipment under the same conditions. The results show that EC-QCL detection system provides a potential solution for the rapid in-situ detection of honey authenticity.

A Bidirectional Fast EV Charger for Wide Voltage Range Using Three-Level DAB Based on Current and Voltage Stress Optimization

Converter cost is the crucial concern while designing off-board electric vehicle (EV) chargers for high-voltage charging applications using advanced high breakover voltage power semiconductor switches. To solve this problem, multilevel topology is used with the typical dual active bridge (DAB) for the development of high-voltage and high-power EV charging. It offers low cost, compact, less complex control, highly efficient, and reliable development. This article presents the design and development of bidirectional off-board fast EV charger with voltage and current stress optimization for wide voltage range. It is designed with two-stage power conversion. Here, active front-end converter is connected to three phase grid and controlled through synchronous reference frame (SRF) d-q control approach for active rectification. The large range of power and voltage variation in off-board EV charger design makes it challenging to develop a controller that allows the converter to operate inside the zero voltage switching (ZVS) operating region. In this context, a detailed circuit analysis of dc–dc stage with dual phase shift (DPS) control under different operating conditions is presented to identify the coordinates of safe operating region with reduced voltage stress. To select the converter control parameters with optimum current stress in conjunction with reduced voltage stress, particle-swarm-optimization technique is applied to the identified operating regions. This provides a unique selection criterion for both control parameters over wide voltage conversion ratio. A coordinated control is designed based on the identified boundaries for easy implementation and less computation burden on microcontroller units (MCUs). A 7.2-kW system is designed and simulated on MATLAB/Simulink. A 3.3-kW laboratory prototype is designed to validate the identified operating points with wide battery voltage range under varying source and loading scenarios.

Call for Papers: Special Section on Advanced High Frequency Medium Voltage Power Electronic Systems and Control for Distributed Energy Resources (DER)

Call for Papers: Special Section on Advanced High Frequency Medium Voltage Power Electronic Systems and Control for Distributed Energy Resources (DER)

Design choices in randomization tests that affect power

We consider the problem of evaluating designs for a small-sample two-arm randomized experiment using the power of the one-sided randomization test as a criterion. Our evaluation assumes a linear response in one observed covariate, an unobserved component and an additive treatment effect where the model's randomness is due to different treatment allocations. It is well-known that the power depends on the allocations’ imbalance in the observed covariate. We show that power is additionally affected by two other design choices: the number of allocations and the degree of the allocations’ dependence. We prove that the more allocations, the higher the power and the lower the variability in power. Our theoretical findings and simulation studies show that the designs with the highest power provide thousands of highly independent allocations each providing nominal imbalance in the observed covariates. These high-powered designs exhibit less randomness than complete randomization and more randomness than recently proposed designs that employ numerical optimization. This advantage of high power is easily accessible to practicing experimenters via the popular rerandomization design and a greedy pair switching design, where both outperform complete randomization and numerical optimization. The tradeoff we find also provides a means to specify rerandomization’s imbalance threshold parameter.

A New Type of Transverse Flux Permanent Magnet Rim Motor and Its Modeling Analysis

In this paper, a new type of transverse flux permanent magnet rim motor is obtained by combining transverse flux permanent magnet motor with shaftless rim motor. When a sinusoidal current is passed through the stator of the motor, a rotating magnetic field will be generated. The rotating magnetic field interacts with the constant magnetic field generated by the rotor magnet, and the interaction will drive the motor to rotate. The new motor has the advantages of high power, low noise, small vibration and small volume, and is suitable for marine propulsion and other fields. This paper introduces the special magnetic field distribution of the new motor, and uses the 3D finite element analysis method to analyze the electromagnetic field of the motor’s no-load and load conditions. The paper will verify the correctness and superiority of the model.

Ultrahigh Energy Storage Density and High Efficiency in Lead-Free (Bi0.9Na0.1)(Fe0.8Ti0.2)O3-Modified NaNbO3 Ceramics via Stabilizing the Antiferroelectric Phase and Enhancing Relaxor Behavior.

Dielectric capacitors have attracted growing attention because of their important applications in advanced high power and/or pulsed power electronic devices. Nevertheless, the synergistic enhancement of recoverable energy storage density (Wrec > 10 J/cm3) and efficiency (η > 80%) is still a great challenge for lead-free dielectric bulk ceramics. Herein, by introducing complex perovskite compound (Bi0.9Na0.1)(Fe0.8Ti0.2)O3 with a smaller tolerance factor into an NaNbO3 matrix (NN-BNFT), we have achieved and explored stable relaxor antiferroelectric ceramics with enhanced relaxor behavior. Of particular importance is the composition of 0.88NN-0.12BNFT, which exhibits a large electric breakdown strength Eb of 87.3 kV/mm, an ultrahigh Wrec of 12.7 J/cm3, and a high efficiency η of 82.5%, as well as excellent thermal reliability and an ultrafast discharge speed, resulting from the dense microstructure, the moderate dielectric constant, the reduced grain size, the dielectric loss, and the sample thickness. The outstanding energy storage properties of NN-BNFT display great promise in advanced dielectric capacitors for energy storage applications.

A highly efficient power block with series connection of power SiC MOSFETs‐design, characterization and assessment in MV converters

Implementation of the series connection of the SiC MOSFETs in medium voltage (MV) high power converters faces a series of challenges, including the electrical/thermal stress imbalance, insulation coordination design, high dv/dt elimination and robustness under variable operating conditions. This paper stresses these challenges and proposes a comprehensive design of a 9.6 kV/200 A power block based on the series connection of SiC MOSFETs. The power block has been verified under the continuous operation, which demonstrates the highly efficient and reliable operation under the variable switching current condition. Afterward, performance screening in a 5 kV/1 MW inverter is conducted to assess the efficiency in MV converters. Compared with the advanced high voltage high power devices, the proposed power block demonstrates fast switching speed and low switching loss, which indicates that the series connection of SiC MOSFETs is a promising technique to expand the operation voltage/power of the SiC MOSFETs to the MV megawatt level. The proposed design can be expanded to other specifications as well.

γ-MnOOH-graphene nanocomposite as promising anode material for Li-ion capacitors

Developing environmentally benign electrode materials with faster Li-ion kinetics is an essential requirement for high-performance Li-based energy storage devices. Here we report the large-scale synthesis of γ-MnOOH-graphene (γ-MnOOH-rGO) nanocomposite, through a simple hydrothermal route, for their application as potential anode material in Li-ion batteries. As-synthesized nanocomposite with the γ-MnOOH nanorods uniformly anchored on the graphene sheets exhibits enhanced electrochemical performance and achieves a very high specific capacity of ∼435 mAh g−1 at a current density of 1.0 A g−1. Detailed electrochemical studies reveal faster Li-ion kinetics in γ-MnOOH-rGO nanocomposite electrode, dominated by non-diffusion controlled processes (∼ 80% at 1.0 mV s−1). Further, the full-cell Li-ion capacitor fabricated with γ-MnOOH-rGO nanocomposite as the anode and activated carbon as the cathode exhibits a maximum energy density of ∼51 Wh kg−1 and a maximum power density of ∼ 6.3 kW kg−1, with excellent capacity retention of more than ∼87% upon 8500 cycles. The present work thus demonstrates γ-MnOOH-graphene nanocomposite as promising anode material for advanced Li-ion batteries and high power Li-ion capacitors.

Study of the Influence of Power Supply Ripple on Magnetron’s Output Spectrum

Magnetron is an important microwave device because of its advantages of high power, small size, lightweight, and low cost. However, due to the instability of magnetron spectrum, it is difficult to use magnetron when we need high-stability spectrum. In order to improve the output spectrum of the magnetron, many efforts have been made and we find that the ripple of magnetron power supply has a great influence on the spectrum. So this article studies this influence systematically. First, we start from the equivalent circuit of magnetron, from which we can derive the equation of high-voltage power supply ripple and magnetron's time-domain output. Then we obtain the relationship between power supply ripple and magnetron's frequency-domain output spectrum by fast Fourier transform. Through theoretical derivation, numerical simulation analysis and experiment, we find that with the increase of ripple, the spectrum is gradually disordered, noise frequency point appears, center frequency point remains unchanged, and output energy reduces. The research results of this article provide theoretical guidance for the realization of high-stability spectrum magnetron.

Design and experiment of light field shaping system for three-dimensional extended light source used in photoacoustic spectrometer

Compared with infrared laser sources, the three-dimensional incoherent extended light source has the advantages of high power, wide spectral range, and low cost. It has extremely wide applications in high-precision and multi-component photoacoustic spectrometers. However, it encounters some problems about poor directivity, low energy density, irregular shape, light field shaping needed in the design of optical system. The photoacoustic spectrometer is required to collect and optimize the radiation of the centimeter-level three-dimensional extended light source to the whole space in a small volume. Through using a series of wavelength and frequency modulation elements, the final cylindrical light field distribution with millimeter-level radius and centimeter-level length is realized. According to the concept of optical expansion and the principle of edge light, this paper breaks through the traditional design mode based on point light source in the process of optical system design and optimization. The concept of extended light source is used throughout the design process. The luminous characteristics of the three-dimensional extended light source are directly acquired by the self-designed measurement method and device which is accurately reflected in the three-dimensional extended light source model in the form of micro-element. The design of the light field shaping system of the three-dimensional extended light source for the photoacoustic spectrometer is realized by the aspheric surface, and the relevant experimental verification is carried out. Taking the Hawkeye IR-Si272 light source for example, the experimental value of the light power at the entrance of the photoacoustic cell and the sidewall noise rate of the photoacoustic spectrometer have a small deviation from their corresponding simulation values. Compared with the original condenser system, the self-designed photoacoustic spectrometer light source system increases the value of the light power at the entrance of the photoacoustic cell from 0.86W to 1.32W, and reduces the value of the sidewall noise rate from 50.3% to 19.7%. The lower limit of detection of the concentration of trace gas in the order of ppm (parts per million) is also achieved.

Thermally conductive, mechanically strong dielectric film made from aramid nanofiber and edge-hydroxylated boron nitride nanosheet for thermal management applications

ABSTRACT Polymer-based dielectric films with desirable heat dissipation property hold great promise as thermal management materials in advanced electronics and high power devices. Herein, we report a new strategy for preparing thermally conductive films by synergistically combining one-dimensional (1D) aramid nanofiber (ANF) with 2D edge-hydroxylated boron nitride nanosheet (OH-BNNS) via a vacuum-assisted self-assembly technique. The obtained ANF/OH-BNNS film exhibits an ultrahigh in-plane thermal conductivity of 32.3 W m−1K−1 at 40 wt% BNNS-OH loading, which is 3530% greater than that of the pure ANF film. The excellent thermal conductivity results from the special ‘brick-and-mortar’ layered structure of ANF/OH-BNNS, in which the increased contacting and overlapping of OH-BNNS promotes the formation of the thermal conduction pathways. In addition, the rigid ANFs act as bridges linking OH-BNNS by favorable hydrogen bonding interactions, which efficiently enhance phonon propagation and stress transfer in the film. Moreover, the ANF/OH-BNNS film simultaneously shows low dielectric loss (~0.03), high tensile strength (~88 MPa), and a high decomposition temperature (>510 °C). We believe that these findings are of great importance for the fabrication and practical application of thermal management materials in high-temperature electronics and devices.

Significantly enhanced dielectric breakdown strength of ferroelectric energy-storage ceramics via grain size uniformity control: Phase-field simulation and experimental realization

The utilization of ferroelectric ceramics in electrical energy storage has become a hot topic due to the urgent need for advanced pulsed power and high power energy storage applications. Much attention has been paid to achieving nanograined ferroelectric ceramics but little to the effect of grain size uniformity, which is critical for dielectric breakdown and reliability. We first investigated this effect via a model based on virtually constructed ceramic samples solved with the phase-field method. Ferroelectric ceramic samples with the same average grain size of typically 100 nm but different uniformity degrees by the variation of the standard deviation values of 83.7, 81.9, 80.1, and 78.7 were constructed via Voronoi tessellation based on a controlled seeding method. The effect of grain size uniformity on the dielectric breakdown was studied through a phase-field dielectric breakdown model. The results indicate that with the standard deviation decreasing, the dielectric breakdown strength is distinctly enhanced. Experimentally, BaTiO3-based ceramics with the same average grain size of 100 nm but different uniformity degrees were realized via conventional sintering and two-step sintering methods. The grain size uniformity of two-step sintered ceramics is greatly improved, which leads to the breakdown strength and discharge energy density of the two-step sintered ceramics about 50% and 100% larger than those of the conventionally sintered ones. This work demonstrates that significant enhancement in dielectric breakdown strength of ferroelectric energy-storage ceramics can be achieved via grain size uniformity control, shedding light on the meticulous design and fine tuning of the energy-storage properties of ferroelectric ceramics.