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We report an in-well and barrier coupling pump scheme of semiconductor disk laser (SDL). An in-well-absorbed (940 nm) and a barrier-absorbed (808 nm) pump source were used to measure laser output characteristics. The output power of the coupling pump can be significantly improved compared to the in-well pump only scheme under similar thermal load conditions. The power scaling of the coupling pump SDL is caused by the interaction dynamics of the photoexcited carrier between quantum-well and barrier. The results are discussed with a rate equation model that considers the injected into the quantum-well carrier and the barrier carrier in the active region. [ABSTRACT FROM AUTHOR]

To improve the thrust performance of permanent magnet synchronous linear motor (PMSLM), novel deep adaptive ridge regression with embedded analytical mapping function (EAMF-RR) is proposed to calculate the thrust performance of PMSLM quickly and accurately, and combined with the EAMF-RR, a whale optimization algorithm (WOA) is introduced to optimize the PMSLM structure. First, the PMSLM's thrust is analyzed by the analytical modeling (AM) to determine the variation range of structural design parameters. Based on the variation range, a finite-element sample database is established for the EAMF-RR. Then, EAMF derived from AM, k-nearest neighbor algorithm, and WOA are integrated into RR to establish deep adaptive EAMF-RR model. Comparative simulation experiments conducted by using another two machine learning methods, i.e., extreme learning machine and weighted random forest, confirm the superiority of the EAMF-RR. Finally, WOA is reused to optimize the thrust performance of PMSLM, and prototype experiments prove the effectiveness of the proposed optimization method. [ABSTRACT FROM AUTHOR]

In this article, we proposed a discrete-time sliding mode load thrust observer to reduce the influence of load thrust mutation on the linear motor and improve the antiinterference ability and speed tracking performance of the system. First, the electrical and dynamic models of linear motor are established, and the limitation of conventional double-closed-loop control based on proportional integral (PI) algorithm is analyzed. Second, the extended state equation of velocity and load thrust is given and an improved sliding mode reaching law is designed to establish the discrete-time load thrust observer. Based on Lyapunov theory, the stability of the observer is proved. The observed load thrust is compensated to the controller in the form of feedforward. Finally, a series of comparative experiments were carried out. The experimental results show that compared with the PI control, the maximum speed fluctuation of this method is reduced by about 18.1% when the load changes between no-load and rated load. This means that the method in this article can effectively improve the antidisturbance ability of the system. [ABSTRACT FROM AUTHOR]

High-power terahertz frequency quantum cascade lasers operating in both pulsed and continuous wave (CW) modes are demonstrated. High Al composition four quantum wells active region based on diagonal structure are employed to suppress the escape of electrons into continuum and thermally activated LO-phonon scattering, as evidenced by the activation energy value of ~14.4 meV extracted from the experimental data. The devices operate in a frequency range of 3.8 - 4.05 THz and have a pulsed maximum operating temperature of ~119 K. The total optical output power from an uncoated laser is 1.57 W and the maximum single-facet emission power from an HR coated one is 1.03 W in pulsed mode at 7 K. The maximum output power of ~256 mW is obtained by a 2.5-mm-long device operating in CW mode with a low threshold current density of 188.6 A/cm2 at 15 K. [ABSTRACT FROM AUTHOR]

Existing self-supervised methods pose one-shot video object segmentation (O-VOS) as pixel-level matching to enable segmentation mask propagation across frames. However, the two tasks are not fully equivalent since O-VOS is more reliant on semantic correspondence rather than accurate pixel matching. To remedy this issue, we explore a new self-supervised framework that integrates pixel-level correspondence learning with semantic-level adaptation. The pixel-level correspondence learning is performed through photometric reconstruction of adjacent RGB frames during offline training, while semantic-level adaption operates at test-time by enforcing a bi-directional agreement of the predicted segmentation masks. In addition, we further propose a new network architecture with multi-perspective feature mining mechanism which can not only enhance reliable features but also suppress noisy ones to facilitate more robust image matching. By training the network using the proposed self-supervised framework, we achieve state-of-the-art performance on widely adopted datasets, further closing up the gap between self-supervised learning methods and their fully supervised counterparts. [ABSTRACT FROM AUTHOR]

In this study, nanosecond-pulse lasing was achieved using a vertical-external-cavity surface-emitting laser (VECSEL) with only a single gain chip. A simple linear-cavity setup was used for the VECSEL, and pulsed lasing with a pulse width of ∼9 ns and a repetition frequency of ∼54 MHz was achieved. Dual-wavelength lasing at 974 and 978 nm was observed. The average output power during pulsed operation exceeded 100 mW. As the pumping power was increased, the laser output power could be switched off. However, stable dual-wavelength emission was maintained. The maximum output power under dual-wavelength operation could reach 455 mW. [ABSTRACT FROM AUTHOR]

This work investigates the dynamic characteristics of vacuum arc in the initial expansion process of a direct current (dc) circuit breaker. Based on the commercial cup-type axial magnetic field (AMF) contact, a 3-D transient magnetohydrodynamic (MHD) model is established. In the model, transient equations are used to study the transient characteristics of the vacuum arc. The effect of magnetic field hysteresis is also considered in the method. The dynamic mesh technique is adopted to simulate the electrode separation, which can make the simulation results more accurate. The simulation results show that, during the initial expansion process, with the increase in the current, the arc gradually expands in the electrode gap. The ion pressure, ion number density, axial current density, and energy flux density to the anode gradually decrease. Ion rotation can be observed under the influence of the magnetic field, and the rotation speed will increase with the increase in the current. Two different arc ignition positions are also compared. The result shows that igniting the arc at the contact center is more helpful to the success of the interruption of the dc circuit breaker. The appearance of the arc predicted by the model is consistent with the experimental results. [ABSTRACT FROM AUTHOR]

To solve the problem that both analytical model (AM) and finite element model are difficult to give consideration to the calculation accuracy and efficiency at the same time in motor optimization work, a novel Lasso regression with the embedded AM, called EAM-LR, is proposed to quickly and accurately calculate the thrust performance of the permanent magnet synchronous linear motor (PMSLM) in this article. First, the thrust performances of PMSLM are analyzed by the AM to determine the variation range of structural design parameters. Based on the variation range, a finite-element sample database is established. Then, combined with the finite-element sample database, the analytical mapping functions derived from AM, are integrated into Lasso regression to establish EAM-LR. The accuracy of EAM-LR was verified by comparison with AM, traditional lasso regression, and well-known extreme learning machine. Finally, combined with the EAM-LR, the chaotic golden section algorithm is introduced to search the optimal structure parameters of PMSLM, and the control simulation and prototype experiment prove the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Time delay estimation (TDE) is an important step in identifying and locating vibration sources. The TDE result can be obtained by the cross-correlation method through seeking the maximum correlation peak of two signals. However, the cross-correlation method will induce random error when dealing with the nonstationary signal. We propose a novel time shifting deviation (TSDEV) method to solve this problem, which has been proven to achieve ultrahigh-precision localization results in the fiber vibration monitoring system. This paper compares the TSDEV method with cross-correlation in detail by simulating the TDE process in different conditions, such as signals with arbitrary intercepted length, nonstationary drift and correlated noise. In addition, an experimental demonstration was carried out on a 60 km fiber to localize a wide band vibration signal. The typical localization error is 3.0 m with a standard deviation of 23.0 m using the TSDEV method. It stands in clear contrast to the result of cross-correlation method, whose localization error is 76.3 m and the standard deviation is 216.5 m. Compared with cross-correlation method, TSDEV has the same resistance to white noise, but has fewer boundary conditions and better suppression effect on linear drift or common noise, which leads to more precise TDE results. [ABSTRACT FROM AUTHOR]

This work investigates the effect of oxygen (O2) as gas admixture on hydrodynamic characteristics of a coaxial double-ring electrode helium plasma jet by a “Z-type” shadowgraphy system. The shadowgraphy images and visual optical photographs show that the addition of O2 will slow down the transition of gas flow from the laminar region to the turbulent region regardless of the plasma is ignited or not. The hydrodynamic behaviors of the plasma jet at the impact region for epoxy resin (EP) and aluminum substrates are also researched. The addition of oxygen reduces the vortex on the surface of both EP and aluminum surface. As a result, with the increase of O2, the decrease of gas temperature caused by reduction of electrons and the reduction of the density difference between the mixed gas and the ambient air weaken the gas velocity and results in a weaker collision between the gas and the substrate, which is the main factor for less vortex on the substrate surface. [ABSTRACT FROM AUTHOR]

To realize the demagnetization fault diagnosis and degree estimation of permanent-magnet synchronous linear motors in linear motion applications with high precision and multiple working conditions, a novel double closed-loop control with an adaptive linear neuron (ALN) model reference adaptive system (MRAS) flux linkage observer is proposed in this article. First, a sliding-mode control (SMC) is introduced to design the velocity loop to obtain good speed adaptability. Then, the MRAS flux observer is established, and the ALN algorithm for modifying the MRAS adaptive law online is designed combining with MRAS flux observer. In addition, the finite element models of normal, weak (F1), mild (F2), moderate (F3), and severe (F4) demagnetization faults are established, and the accurate values of flux linkage under different demagnetization degrees are simulated. Furthermore, the demagnetization fault diagnosis algorithm is introduced with an SMC-ALN-MRAS flux observer. Finally, a prototype motor experimental platform is built, and comparative experiments are designed to confirm the correctness and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) model for multispecies vacuum arc considering ionization and recombination process has been built in this article. With the model, the arc behaviors and species characteristics subjected to actual spatial magnetic fields of cup-shaped axial magnetic field (AMF) contact and transverse magnetic field-axial magnetic field (TMF-AMF) contact are investigated and compared. Furthermore, the validity of the model is verified by comparing with the experiments. Simulation results show that contact structures affect the species distributions of the arc by changing magnetic field and current density distributions. More triple charged ions are generated through ionization under higher electron temperature so that the triple charged ions gather where current constricts. The heat flux density is large in the current contraction region, where the contribution from triple charged ions is large as well. Spatial magnetic field distribution affects the Lorentz force acting on ion components. The force distribution is relatively uniform and the species are subject to inward force on the arc edge under cup-shaped AMF contact. For TMF-AMF contact, the double charged ions are subject to the force pointing to the TMF contact arms, whereas the triple charged ions are subject to the force pointing to the arc center. In addition, the consideration of arc species can improve the accuracy of the simulation results of the heat flux distribution, leading to a good agreement of the erosion condition between experiments and simulation. [ABSTRACT FROM AUTHOR]

Battery energy storage system (BESS) plays an important role in solving problems in which the intermittency has to be considered while operating distribution network (DN) penetrated with renewable energy. Aiming at this problem, this paper proposes a global centralized dispatch model that applies BESS technology to DN with renewable energy source (RES). The method proposed in this paper aims to minimize the power purchase cost considering network active loss cost as well as voltage deviation penalty cost. Later, second-order cone programming (SOCP) method as well as big M method are applied to make the problem tractable. Last, the method illustrated in this paper is applied and validated on a modified IEEE 33-bus benchmark system to verify the effectiveness of the proposed scheduling model. [ABSTRACT FROM AUTHOR]

As a special phenomenon under transverse magnetic field (TMF) contacts, vacuum arc rotation deserves more attention. In this article, rotation characteristics of three typical TMF contacts, i.e., swastika-type, cup-shaped, and double-TMF contacts, are systematically studied. According to arc images, recorded by a high-speed camera, physical terms related to arc rotation such as rotation duration and rotation speed are clearly defined. The magnetic field and Lorentz force are calculated and the force balance of the moving arc is analyzed. On this basis, the effects of arc ignition mode, peak current, and contact type on arc rotation are investigated. Arc voltage noise as well as arc splashing outside caused by rotation is also discussed. The results show that the duration from ignition to rotation in two-point arc ignition (TPAI) mode is usually the shortest because of the rapidest constructed column formation. As the peak current increases, arc rotation becomes easier. Due to stronger TMF, the arc under double-TMF contacts has the longest rotation duration and the highest rotation speed. [ABSTRACT FROM AUTHOR]

The modeling and reconstruction of radar sea clutter (RSC) based on fractal theory is studied in this article. With theoretical derivation and quantitative analysis, the radar clutter reconstruction model based on singularity power spectrum (SPS) and instantaneous singularity exponent (ISE) distribution is proposed. The proposed ISE–SPS model consists of two coupling channels: power measure channel and dimension measure channel. The former is controlled by SPS to characterize the power distribution of signals in the SE domain, while the latter is determined by ISE function to characterize the statistical distribution of ISE. The multiscale wavelet coefficients are estimated based on the coupling of the two channels to reconstruct the RSC. The proposed ISE–SPS method is tested on RSC data in different sea state, from the ice multiparameter imaging X-band (IPIX) radar. Experimental and simulation based on the IPIX radar data set indicates that the proposed method performs better than the N-partitioned random multiplicative model (NRMM) method and SPS-multifractal spectrum (MFS) method, and exceeds the traditional methods by nearly 35% in terms of correlation coefficient and normalized mean square error of MFS and SPS. [ABSTRACT FROM AUTHOR]