Grid-connected inverter for wind power generation system

In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation (SVPWM) is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on PI-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.     

Global dynamics near the resonance in the sine-gordon equation

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浅析JK触发器的一次变化现象

本从JK触发器输入状态发生跳变,引起输出状态发生变化,分析其产生的一次变化现象。     

基于 Labview 的脉冲激励法电涡流厚度测量系统设计

虚拟仪器在其数据采集、信号调理等硬件支持下,用软件编程就能开发出各种用户需要的测控系统。本设计硬件系统包括传感器、调理电路、PCI-6221数据采集卡及计算机,软件系统是用Labview进行编程,完成输出脉冲信号,采集信号,数据处理以及结果表达与输出,发现瞬态响应电压的特征值与厚度有明显的对应关系,取特征值中变化最明显的峰值与厚度进行拟合,两者呈指数对应关系,最后通过实验验证了系统的可行性。     

脉冲核磁共振实验自由衰减信号分析

学生学习脉冲核磁共振实验时对自由衰减信号的形成较难理解,本文从布洛赫方程出发详细地分析分析了自由衰减信号的产生,加深学生对磁共振技术的理解。     

Ti基Hg膜电极微分脉冲伏安法测定磺胺嘧啶和甲氧苄啶

建立了一种微分脉冲伏安法检测磺胺嘧啶和甲氧苄啶的方法．采用光化学沉积Hg膜Ti基电极以及微分脉冲伏安法使得检测灵敏度大幅度提高,磺胺嘧啶的检测限为3．68×10^-11mol／L,回收率范围为96．87％-110．3％;甲氧苄啶的检测限3．25×10^-11mol／L,回收率范围为94．18％-103．3％．     

Physical Characteristics and Oxygen Utilization of Male and Female Marathon Runners

Verbal and nonverbal communication is a critical mediator of performance in team sports and yet there is little extant research in sports that involves direct measures of communication. Our study explored communication within NCAA Division I female tennis doubles teams. Video and audio recordings of players during doubles tennis matches captured the communications that took place between and during points. These recordings were coded and sequential analysis computed using the Discussion Analysis Tool software (Jeong, 2003). Results indicated that most communications were emotional (i.e., > 50%) or action statements (i.e., > 25%). Winning teams exhibited significantly different communication sequences than losing teams. In particular, winning teams had a more homogeneous model of communication, which perhaps makes message interpretation more reliable. Finally, winning teams exchanged twice as many messages as losing teams.     

基于多模激光器的超短脉冲产生技术

针对窄脉冲、高峰值功率的光脉冲难以产生的问题,研究了基于多模激光器的超短脉冲产生技术。由于没有锁模的多模激光器的输出呈现不规则变化,故难以产生超短脉冲。通过对主动锁模和被动锁模的相关理论及方法分析,详细阐述了锁模激光器产生超短激光脉冲的原理,并重点研究了基于主动锁模和被动锁模的几种超短脉冲产生方法。     

双通道PWM实现LED动态光源混色控制模型

充分利用发光二极管（LED）光源的可控性,采用冷暖白光LED和两通道脉冲宽度调制PWM法,从人们关心的照明光源参数出发,依据选用冷白LED光源和暖白LED光源光度色度参数,建立了给定光度量输出时冷暖白光LED光源控制占空比计算的模型,并探讨了基于色温目标控制参数占空比的约束条件．实际设计混色光源参数分析过程和人们选择光源性能指标参数的一致性,为实现分档或连续调光调色提供了直观实用的混色控制模型．     

超声波收发及电子开关电路的设计

超声波在金属测厚中有广泛的应用,本文设计了一种超声波收发及电子开关电路,该电路经分析及实验证明在超声波测厚时可以较好完成超声波信号的激励,能够完成信号收发,为超声波测厚奠定基础.