Two-dimensional (2D) materials have demonstrated great performance and good application prospects in a variety of photodetectors, including photoelectrochemical (PEC)-type photodetectors, due to ...their superior optical and electrical properties. Among these, 2D Bi
2
Se
3
materials have drawn a lot of attention from scientists due to their special physical characteristics, such as a topological insulator, strong carrier mobility, and narrow bulk bandgap of 0.3 eV. Among the many methods for preparing Bi
2
Se
3
, the electrodeposition method stands out for its high adaptability and compatibility with PEC systems. Herein, through a simple electrodeposition method based on an electrochemical system, a Bi
2
Se
3
film-based PEC-type photodetector was constructed, which exhibits good and tunable photoresponse properties, as well as excellent cycle and time stability. This research demonstrates the potential of the Bi
2
Se
3
film created by electrodeposition as a photoanode material for photodetectors and offers a practical and prolongable method for creating photoanodes for PEC photodetectors.
•An advanced computational approach for simulating multi-pass welding process was developed.•The influence of groove shape on welding residual stress distribution was studied.•The influence of groove ...shape on angular distortion was examined.•Groove shape has significant influence on residual stress, deformation and sensitization zone.
To join a medium or thick plate weldment with a full penetration, a groove is usually prepared in the space between two sections of metal. Because weld metal needs to be deposited within the groove to form the joint, it is expected that different groove type will require different heat input, which may consequently have influence on welding residual stress and deformation. Generally, different groove corresponds to different bead layout, so it can be foreseen that the groove type has a significant effect on temperature history, shape and size of heat affected zone, and region of sensitization in certain alloys such as austenitic stainless steel. The influences of groove type on residual stress, angular distortion and width of sensitization region in a SUS304 butt-welded joint were investigated by means of numerical simulation and experiment. Based on ABAQUS code, a computational approach with considering thermo-mechanical coupling behaviors, moving heat source, strain hardening and annealing effect was developed to simulate temperature profile, stress field and deformation in multi-pass joint. Welding temperature cycles, residual stress distributions and deformations in V, K and X groove joints were calculated through using the proposed computational procedure. Meanwhile, experiments were carried out to obtain residual stress distributions and angular distortions. Through comparing the numerical results and the measured data, the effectiveness and accuracy of the developed computational approach were verified. The simulation results show that groove type has a significant influence on welding residual stress distribution, angular distortion and width of sensitization region.
A novel real-time monitoring system for photovoltaic (PV) generation is presented in this paper. Internet of Things (IoT) integrated with cloud servers and terminal applications allow the remote ...monitoring of centralized or distributed photovoltaic systems. The proposed system could realize the networking communication of multiple nodes based on ZigBee, and upload the operational data to the cloud server via a 4G communications network. Then, the server selects three-phase current as the sample sets from the uploaded data to set up a composite current characteristic combining wavelet packet energy with waveform parameter, and establishes a fault diagnosis model based on the probabilistic neural network to analyze the health status of the PV inverter online. This method requires little sampling frequency without an extra signal and saves the cost of local devices by placing online diagnostics on the server-side. In addition, the user could query and store the running information of the PV systems through the personal computer-side web or mobile phone with remote control. This article presents the hardware design of ZigBee and the 4G module, and composition of the diagnosis model for open circuit failure of the PV inverter through the cloud server, building the user software at the application layer. The final experimental results show that the proposed system has better communication performance and higher diagnostic accuracy in real-time monitoring.
The commutation torque ripple of a brushless dc motor (BLDCM) in a six-step driving mode generates vibration noise. To minimize the commutation torque ripple of the BLDCM, this article analyzes the ...cause of torque ripple and establishes the model of torque ripple suppression by using the phase current predictive method based on the trapezoidal back electromotive force (EMF). In addition, based on the prediction model of the non-commutation phase current, the pulsewidth modulation model predictive control (PWM-MPC) algorithm is proposed. By changing the duty cycle with prior evaluation, the predictive control avoids commutation current hopping, thereby reducing torque ripple during commutation. This control approach is more accessible to be implemented, because it does not require changing the topology of the motor driving circuit. Simulation models of the proposed control scheme constructed in the MATLAB/Simulink environment are given, compared with the conventional square-wave driving method. Moreover, experiments are performed to verify the feasibility. The output torque during experiments is transmitted to the computer software through the torque transducer. Compared with the traditional driving methods, the simulation and experimental results show that the proposed novel algorithm in this article could suppress the torque ripple efficiently.
Bi 2 Se 3 has a unique surface state and excellent electron transport performance, but because of its narrow band gap, Bi 2 Se 3 ‐based photodetectors are difficult to achieve high response to ...ultraviolet (UV) light. In this paper, the TiO 2 /Bi 2 Se 3 heterostructure was constructed by spin‐coating TiO 2 on Bi 2 Se 3 film, and TiO 2 /Bi 2 Se 3 heterostructure‐based photoelectrochemical (PEC) photodetector was constructed, and a series of measurements were carried out. The measure results showed that the photoresponse performance of TiO 2 /Bi 2 Se 3 heterostructure‐based photodetector was improved in the visible region, and the performance in the UV was further improved. This is because the type ii band alignment between TiO 2 and Bi 2 Se 3 is beneficial for the effective separation and transfer of photogenerated electron‐hole pairs, reducing recombination losses and enhancing the overall photoresponse. In addition, under the action of the built‐in electric field formed by the heterostructure, the photogenerated electrons and holes are easier to separate, which reduces the recombination probability of the photogenerated electron‐hole pair and improves the photoelectric conversion efficiency. In the UV, TiO 2 /Bi 2 Se 3 heterostructure can make more efficient use of the light absorption characteristics of TiO 2 and absorb more photons, resulting in a larger photocurrent. These results indicate that TiO 2 /Bi 2 Se 3 heterostructure‐based photodetector has great application potential in the UV.
A new steering mechanical structure and an improved control method of the manned self-balanced vehicle are presented in this Letter. An effective method is introduced to calculate the real-time ...inclination of the vehicle. Then, the integrating inclination of the vehicle could be obtained by the complementary filter and proportional derivative (PD) algorithm. In addition, the control system could be regarded as a linear superposition of three parts, including the balance control, the speed control and the steering control. Moreover, the proportional, integral and derivative (PID) parameters of the whole control system are different under different operational conditions. Furthermore, the pressure sensors placed on the left and right pedals could detect the change of the weight, which simplifies the mechanical structure and improves the flexibility of the manned steering. The experiments in the prototype are designed to prove the steering structure and the improved method.
To minimize the commutation torque ripple of brushless DC motor (BLDCM), the Pulse Width Modulation Model Predictive Control (PWM-MPC) algorithm is proposed based on predictive models of the current ...in non-commutation phase. The purpose of the predictive control is to avoid current jumping during the commutation interval by changing the duty cycle with prior evaluation. The simulation of the proposed new method established in MATLAB/Simulink environment is given compared with conventional driving method. The results show that the proposed novel methods could suppress the torque ripple efficiently.
This paper will introduce a self-identification method to measure the motor key parameters through its own drive or motor controller. These key parameters include the motor line resistance and ...inductance at operating frequency as well as back EMF constant or torque constant, which are very important to design motor close-loop control gains. The proposed method does not utilize the special meters or instruments, such as, multirneters, LCR meters or motor testing system, but do apply the phase current and voltage terminal detecting channels of a motor controller. It will provide the bases to the auto-tuning of motor control and motor health online dialogue without extra cost except the bigger size of flash or RAM memory for more codes.
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