A global model of intensity autocorrelation to determine laser pulse duration

We present a new global model of collinear autocorrelation based on second harmonic generation nonlinearity.The model is rigorously derived from the nonlinear coupled wave equation specific to the autocorrelation measurement configuration,without requiring a specific form of the incident pulse function.A rigorous solution of the nonlinear coupled wave equation is obtained in the time domain and expressed in a general analytical form.The global model fully accounts for the nonlinear interaction and propagation effects within nonlinear crystals,which are not captured by the classical local model.To assess the performance of the global model compared to the classic local model,we investigate the autocorrelation signals obtained from both models for different incident pulse waveforms and different full-widthes at half-maximum(FWHMs).When the incident pulse waveform is Lorentzian with an FWHM of 200 fs,the global model predicts an autocorrelation signal FWHM of 399.9 fs,while the classic local model predicts an FWHM of 331.4 fs.The difference between the two models is 68.6 fs,corresponding to an error of 17.2%.Similarly,for a sech-type incident pulse with an FWHM of 200 fs,the global model predicts an autocorrelation signal FWHM of 343.9 fs,while the local model predicts an FWHM of 308.8 fs.The difference between the two models is 35.1 fs,with an error of 10.2%.We further examine the behavior of the models for Lorentzian pulses with FWHMs of 100 fs,200 fs and 500 fs.The differences between the global and local models are 17.1 fs,68.6 fs and 86.0 fs,respectively,with errors approximately around 17%.These comparative analyses clearly demonstrate the superior accuracy of the global model in intensity autocorrelation modeling.

Pulse-Width Pulse-Frequency Based Optimal Controller Design for Kinetic Kill Vehicle Attitude Tracking Control

The attitude control problem of the kinetic kill vehicle is studied in this work. A new mathematical model of the kinetic kill vehicle is proposed, the linear quadratic regulator technique is used to design the optimal attitude controller, and the pulse-width pulse-frequency modulator is used to shape the continuous control command to pulse or on-off signals to meet the requirements of the reaction thrusters. The methods to select the appropriate parameters of pulse-width pulse-frequency are presented in detail. Numerical simulations show that the performance of the LQR/PWPF approach can achieve good control performance such as pseudo-linear operation, high accuracy, and fast enough tracking speed.

Radio-frequency compressed electron pulse-width characterization by cross-correlation between electron bunches and laser-induced plasma

A method is proposed to determine the temporal width of high-brightness radio-frequency compressed electron pulses based on cross-correlation technique involving electron bunches and laser-induced plasma. The temporal evolution of 2-dimensional transverse profile of ultrafast electron bunches repelled by the formed transient electric field of laser-induced plasma on a silver needle is investigated, and the pulse-width can be obtained by analyzing these time-dependent images.This approach can characterize radio-frequency compressed ultrafast electron bunches with picosecond or sub-picosecond timescale and up to 105 electron numbers.

基于STM32 PWM的正弦信号发生器设计

文章阐述了基于STM32应用PWM方式产生幅度频率可调的模拟正弦波的一种方法。原理是在产生某一频率信号时,让采样脉冲的周期保持不变,在每个采样周期内改变1次占空比,改变的规律按正弦表变化,这样输出的信号经过滤波电路滤掉高次谐波以后就变换成相应的正弦波。设计经可编程芯片实现功能,实验结果表明设计系统的输出信号具有以下特点:稳定性和平滑性都很好,且相应的参数调节方便;这种信号产生方式与传统的信号相比具有较高的频率分辨率,且易于实现频率相位幅度的数控调制。相比于DDS技术,PWM方式的主要优点是从处理器到被控系统信号都是数字形式的,无需进行数模转换,能进一步提高信号的抗干扰能力,可广泛应用在测量、通信及功率控制与变换等领域中。

抑制BLDCM换相转矩脉动的超前换相控制策略

为了抑制无刷直流电机的换相转矩脉动,该论文从引起换相转矩脉动的主要原因——电流滞后入手,提出了一种新颖的超前换相的电机控制策略。该策略是通过让电机提前一段时间进入换相状态并且在换相过程对三相电压同时进行PWM调制来实现的。根据所提出的换相策略详细分析了换相过程中的不同阶段的电流流向,理论上推导了电机提前换相时间的解析式。通过实验给出了在不同转速和负载下运用所提方法进行换相的电流波形,将其与传统的换相方法比较,分析两者电流在换相期间的波动值。实验结果表明传统换相方法的电流波动值远远高于该论文提出的方法的电流波动值,验证了这种方法在抑制换相转矩脉动上的有效性。

Simulation and experimental study of high power microwave damage effect on AlGaAs/InGaAs pseudomorphic high electron mobility transistor

The high power microwave （HPM） damage effect on the AIGaAs/InGaAs pseudomorphic high electron mobility transistor （pHEMT） is studied by simulation and experiments. Simulated results suggest that the HPM damage to pHEMT is due to device burn-out caused by the emerging current path and strong electric field beneath the gate. Besides, the results demonstrate that the damage power threshold decreases but the energy threshold slightly increases with the increase of pulse-width, indicating that HPM with longer pulse-width requires lower power density but more energy to cause the damage to pHEMT. The empirical formulas are proposed to describe the pulse-width dependence. Then the experimental data validate the pulse-width dependence and verify that the proposed formula P = 55τ^-0.06 is capable of quickly and accurately estimating the HPM damage susceptibility of pHEMT. Finally the interior observation of damaged samples by scanning electron microscopy （SEM） illustrates that the failure mechanism of the HPM damage to pHEMT is indeed device bum-out and the location beneath the gate near the source side is most susceptible to bum-out, which is in accordance with the simulated results.

Damage effects and mechanism of the silicon NPN monolithic composite transistor induced by high-power microwaves

A two-dimensional model of the silicon NPN monolithic composite transistor is established for the first time by utilizing the semiconductor device simulator, Sentaurus-TCAD. By analyzing the internal distributions of electric field, current density, and temperature of the device, a detailed investigation on the damage process and mechanism induced by high-power microwaves （HPM） is performed. The results indicate that the temperature elevation occurs in the negative half-period and the temperature drop process is in the positive half-period under the HPM injection from the output port. The damage point is located near the edge of the base-emitter junction of T2, while with the input injection it exists between the base and the emitter of T2. Comparing these two kinds of injection, the input injection is more likely to damage the device than the output injection. The dependences of the damage energy threshold and the damage power threshold causing the device failure on the pulse-width are obtained, and the formulas obtained have the same form as the experimental equations, which demonstrates that more power is required to destroy the device if the pulse-width is shorter. Furthermore, the simulation result in this paper has a good coincidence with the experimental result.

Experiment Research on Fine Regulation of Wheel Cylinder Pressure Using PWM Technology

A test bench of ABS/ASR integrated hydraulic system is developed by using pulse-width modulation （PWM） technology. The effective duty ratio range of ABS outlet valve has been tested in PWM control. With 50 Hz carrier wave frequency, the tests are performed to determine the correspondence between duty ratio and the wheel cylinder pressure variation. The duty ratio range of ABS outlet valve in PWM control is determined and an experimental model of pressure reduction velocity （PRV） of wheel cylinder using PWM control is established. By comparison and test of the experimental model and realization of controlling the duty ratio of ABS outlet valves, the fine regulation of wheel cylinder PRV is realized in the working of ABS/ASR braking regulation, which is important and valuable to the improvement of the ABS/ASR controlling effect.

A Comparison of Control Methods for Z-Source Inverter

In recent years, Z-source inverters (ZSI) have been proposed as an replacement power conversion concept which it has both voltage buck and boost abilities. In addition, ZSI doesn’t require dead-time to protection short circuit at two switches any of the same phase leg in the inverter bridge and to achieve optimal harmonic of current, voltage. This paper presents two different control methods (CM) for ZSI. The aim of this study to compare between two modulation methods, there are modi?ed space vector pulse width modulation method (MSVM) and the simple boost control (SBC) about the unique harmonic performance features, the total average and peak switching device power of the inverter system. In addition, this paper also analyzes about the ability exceed modulation index in linear region of two CM using MATLAB/Simulink.

FIXED POINTS AND STABILITY FOR QUARTIC MAPPINGS IN β-NORMED LEFT BANACH MODULES ON BANACH ALGEBRAS

The goal of the present paper is to investigate some new HUR-stability results by applying the alternative fixed point of generalized quartic functional equationin β-Banach modules on Banach algebras. The concept of Ulam-Hyers-Rassias stability （briefly, HUR-stability） originated from Th. M. Rassias stability theorem that appeared in his paper： On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 （1978）, 297-300.

基于TCP/IP&DMX512协议的LED装饰照明系统

本文介绍品能光电技术(上海)有限公司近两年来运用TCP/IP&DMX512协议的LED装饰照明控制系统。本系统可轻松将文字、FLASH动画、视频、图像等媒体信息方式表现于基于LED装饰照明的建筑等景观中,表现出丰富多样的变化效果。广泛应用于工程建筑景观、舞台灯光、大型活动、节庆场所等场合的灯光装饰。用户可在世界各地用IE或Nescap等现有的Web浏览器,对LED装饰照明系统进行控制。

Design of low-power high-frequency digital controlled DC-DC switching power converter

This paper models a low-power high-frequency digitally controlled synchronous rectifier （SR） OUCK converter. The converter is a hybrid system with three operation modes. Digital PID controler is used. Key problems such as quantization resolution of digital pulse-width modulation （DPWM） and steady-state limit cycles of digital control switching model power supply （SMPS） are discussed, with corresponding solutions presented. Simulation of a digital control synchronous buck is performed with a fixed-point algorithm. The results show that the described approach enables high-speed dynamic performance.

Application of Internet of Things Micropower Smart Switch in Temperature Monitoring

This study uses the smart phone with the Android system to construct a cloud-side smart switch system in the client-server architecture with the Android open platform system, using microprocessors(MCU 16F690) as the thermostat controller and combined with Raspberry Pi. The computing technology extends the control of the constant temperature from the local to the cloud, allowing the user to view the temperature status recorded by the cloud server using the smart phone application(App) or web browser. It can even remotely control the heating power of the smart switch for the heating device in the Internet control environment and use the proportional-integral-derivative(PID) control and the pulse-width modulation(PWM) technology to achieve intelligent constant temperature control.The proposed control system uses the expert PID control as the core to calculate the duty cycle of the PWM signal to control the power output of the smart switch for the constant temperature water tank. The experiment results verify the effectiveness of the proposed system.

A type of inverter power supply based on harmonic elimination PWM control

In order to output sine wave with small degree of distortion and improve stability,a type of inverter power supply is designed based on harmonic elimination pulse-width modulation(PWM)control.The rectifier and filter are added to input circuit of the inverter.Single-phrase full-bridge inverter performs the function of converting direct current into alternating current(DC/AC).In the control circuit,single chip micyoco(SCM)AT89C2051 is used for main control chip to accomplish the hardware design of the control system.A given value of output frequency of the inverter is input in the way of coding.According to the output frequency code which is read,SCM AT89C2051 defined harmonic elimination PWM control data which will be selected.Through internal timing control,the switches are switched under this provision of PWM control data.Then the driving signals of the switches in the inverter are output from I/O of SCM AT89C2051 to realize harmonic elimination PWM control.The results show that adding Newton homotopic algorithm of harmonic elimination PWM control to corresponding software of the control system can make the quality of output voltage of the inverter higher and it will have broad application prospects.

Anycast Transmission in Routing Modulation Level Spectrum Assignment (RMLSA) Problem on Space Division Multiplexing (SDM) Elastic Optical Networks (EON)

With the rise of cloud computing in recent years, a large number of streaming media has yielded an exponential growth in network traffic. With the now present 5G and future 6G, the development of the Internet of Things (IoT), social networks, video on demand, and mobile multimedia platforms, the backbone network is bound to bear more traffic. The transmission capacity of Single Core Fiber (SCFs) may be limited in the future and Spatial Division Multiplexing (SDM) leveraging multi-core fibers promises to be one of the solutions for the future. Currently, Elastic optical networks (EONs) with multi-core fibers (MCFs) are a kind of SDM-enabled EONs (SDM-EON) used to enhance the capacity of transmission. The resource assignment in MCFs, however, will be subject to Inter-Core Crosstalk (IC-XT), hence, reducing the effectiveness of transmission. This research highlights the routing, modulation level, and spectrum assignment (RMLSA) problems with anycast traffic mode in SDM-EON. A multipath routing scheme is used to reduce the blocking rate of anycast traffic in SDM-EON with the limit of inter-core crosstalk. Hence, an integer linear programming (ILP) problem is formulated and a heuristic algorithm is proposed. Two core-assignment strategies: First-Fit (FF) and Random-Fit (RF) are used and their performance is evaluated through simulations. The simulation results show that the multipath routing method is better than the single-path routing method in terms of blocking ratio and spectrum utilization ratio. Moreover, the FF is better than the RF in low traffic load in terms of blocking ratio (BR), and the opposite in high traffic load. The FF is better than the RF in terms of a spectrum utilization ratio. In an anycast protection problem, the proposed algorithm has a lower BR than previous works.

Wind Energy Conversion System from Electrical Perspective—A Survey

This paper focuses on the wind energy conversion system (WECS) with the three main electrical aspects: 1) wind turbine generators (WTGs), 2) power electronics converters (PECs) and 3) grid-connection issues. The current state of wind turbine generators are discussed and compared in some criteria along with the trends in the current WECS market, which are ‘Variable Speed’, ‘Multi-MW’ and ‘Offshore’. In addition, the other crucial component in the WECS, PECs will be discussed with its topologies available in the current WECS market along with their modulation strategies. Moreover, three main issues of the WECS associating with the grid-connection, fault-ride through (FRT) capability, harmonics/interharmonics emission and flicker, which are the power quality issues, will be discussed due to the increasing responsibility of WECS as utility power station. Some key findings from the review such as the attractiveness of BDFRG are presented in the conclusion of this paper.

A Dual-Mode Step-up DC/DC Converter IC with Current-Limiting and EMI Reduction Techniques

This paper presents a novel dual-mode step-up （boost） DC/DC converter. Pulse-frequency modulation （PFM） is used to improve the efficiency at light load. This converter can operate between pulse-width modulation （PWM） and pulse-frequency modulation. The converter will operate in PFM mode at light load and in PWM mode at heavy load. The maximum conversion efficiency of this converter is 96%. The conversion efficiency is greatly improved when load current is below 100 mA. Additionally, a soft-start circuit and a variable-sawtooth frequency circuit are proposed in this paper. The former is used to avoid the large switching current at the start up of the converter and the latter is utilized to reduce the EMI of the converter.

Fuel cell stack design and modelling with a double-stage boost converter coupled to a single-phase inverter

A comprehensive proton-exchange membrane fuel cell stack model was developed and integrated with a two-stage DC/DC boost converter.It was directly coupled to a single-phase(two levels-four pulses)inverter without a transformer.The pulse-width modu-lation signal was used to independently regulate every converter phase.The converter was modelled using a MATLAB®/Simulink®environment and an appropriate voltage control method.The analysis features of the suggested circuit were created and,through established experiments,the simulation results were verified.A single-phase(two levels-four pulses)inverter control circuit was tested and it produced a pure sinusoidal waveform with voltage control.It matches the voltage of the network in terms of amplitude and frequency.A sinusoidal pulse-width modulation approach was performed using a single-phase(two levels-four pulses)pulse-width modulation inverter.The results demonstrated an enhancement in the standard of the output wave and tuned the dead time with a reduction of 63μs compared with 180μs in conventional techniques.

Modeling and analysis of the HPM pulse-width upset effect on CMOS inverter

We derive analytical models of the excess carrier density distribution and the HPM （high-power mi- crowave） upset susceptibility with dependence of pulse-width, which are validated by the simulated results and experimental data. Mechanism analysis and model derivation verify that the excess carriers dominate the current amplification process of the latch-up. Our results reveal that the excess carrier density distribution in P-substrate behaves as pulse-width dependence. The HPM upset voltage threshold Vp decreases with the incremental pulse- width, while there is an inflection point which is caused because the excess carrier accumulation in the P-substrate will be suppressed over time. For the first time, the physical essence of the HPM pulse-width upset effect is pro- posed to be the excess carrier accumulation effect. Validation concludes that the lip model is capable of giving a reliable and accurate prediction to the HPM upset susceptibility of a CMOS inverter, which simultaneously consid- ers technology information, ambient temperature, and layout parameters. From the model, the layout parameter LB has been demonstrated to have a significant impact on the pulse-width upset effect： a CMOS inverter with minor LB is more susceptible to HPM, which enables us to put forward hardening measures for inverters that are immune from the HPM upset.

Spray drift characteristics of pulse-width modulation sprays in wind tunnel

Pulse-width modulation(PWM)sprays can improve flow accuracy by adjusting duty cycle and frequency signal which accurately controls the relative proportion of opening time of solenoid valve.The objective of this research was to determine the impacts of PWM duty cycle and frequency on spray drift characteristic.Spray tests were conducted in a wind tunnel with a PWM variable-rate spraying system.The airborne drift and sediment drift were determined with tracer method,and the drift potential reduction(DPR)compared with reference condition of 100%duty cycle at vertical profile and horizontal planes were calculated,respectively.The results show that,at a given frequency,droplet size decreases with the increase of duty cycle,the main reason is that the liquid does not reach full pattern development at lower duty cycle.Duty cycle has a greater impact than the frequency on spray drift,the influence weights of duty cycle on airborne drift and sediment drift were 88.32%and 77.89%,respectively.At a lower PWM frequency,in addition to the droplet size,the spray drift may be affected by the pulsed spray pattern.From the perspective of reducing spray drift,it is recommended that the PWM duty cycle should be set in the range of 20%-70%to reduce the potential drift in PWM sprays.This research provides a pesticide drift reduction scheme for variable spraying technology,which can serve as a theoretical basis for PWM parameter selection.