智能阀门定位器的控制设计

针对工业过程控制中阀门定位器阀位控制不精确,易造成阀门阀位往复波动不稳定现象,设计了一款气动智能阀门定位控制电路板。其中硬件设计以微处理STC12C5A60S2为核心并输出双极性PWM(脉宽调制)脉冲驱动压电阀,外围电路包括电源转换电路、I/V转换电路、A/D采样电路、按键和液晶显示电路等;软件设计由于阀门控制及执行过程是非线性时变的系统,很难建立精确数学模型,所以控制系统采用模糊PID(比例积分微分)控制算法替代常规PID控制。通过软件硬件两方面改进设计,可以有效避免阀位波动不稳定现象,稳定过渡时间只需1.2 s且系统无超调量;在Matlab中,采用阀门各机构所建立数学模型的传递函数及阀位实测数据进行仿真。通过波形对比,得出所设计的阀门定位器控制电路板,能使阀门控制更加稳定、快速、准确。     

可调谐垂直腔面发射激光器

近年来国内外在可调谐垂直腔面发射激光器这一研究领域取得了极大的进步。叙述了可调谐垂直腔面发射激光器的结构原理和发展历程,对不同结构的优缺点作了对比介绍,展望了可调谐激光器的发展前景。这种器件在光传输、光互连及光并行信息处理等方面有着良好的应用前景。     

"烯-二炔"模型化合物前体--6-硫杂-13-氧杂双环[9.3.0]-3,8-十四二炔的合成(Ⅱ)

以顺-1,2,3,6-四氢邻苯二甲酸酐为原料,经还原、环化、臭氧化、Wittig羰基烯化、酯化、二醇化和硫化等8步反应,合成了新型抗癌抗菌素"烯-二炔"的双环前体:6-硫杂-13-氧杂双环[9.3.0]-3,8-十四二炔.该合成路线步骤少,收率高,反应条件温和.6个新化合物4-9的结构均经元素分析、核磁共振、红外光谱和质谱确证.     

Hysteresis effects of the interaction between serum albumins and silver nanoparticles

In recent years, nanomaterials have wide-ranging implications to a variety of areas, including chemistry and biology sciences, and the emerged new fields, nanochemistry and nanobiology, have received considerable attention. The latest studies show that the unique optical, electronic and magnetic properties make nanoparticles useful for applications in the fields of bio-analysis, diseases diagnosis and medicine[1—9]. With particular optoelectronic properties, the silver nanoparticles have…     

引信计层信号调理电路设计

当硬目标侵彻武器对目标进行打击时,加速度传感器会采集到不同的模拟信号,本文主要研究一信号调理电路,通过该电路对信号进行过滤校正处理,使信号能够有效准确地反馈到主CPU中,从而进行后续的控制。     

UHF频段抗金属标签天线的分析与设计

抗金属标签天线设计是 RFID研究的热点及难点,文中设计并研究了一种UHF频段陶瓷基片抗金属标签天线,对天线的回波损耗和阻抗进行了测量,在905～925 MHz内, S11<-20 dB,在良好匹配的同时还具有全向性辐射的特性,与仿真结果相吻合,而且陶瓷基片保证了良好的耐热性,这意味着天线在恶劣环境下仍能保持良好的性能。     

Chloride-based fast homoepitaxial growth of 4H-SiC films in a vertical hot-wall CVD

Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition (CVD) system using H₂-SiH₄-C₂H₄-HCl. The effect of the SiH₄/H₂ ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively. The growth rate increase in proportion to the SiH₄/H₂ ratio and the influence mechanism of chlorine has been investigated. With the reactor pressure increasing from 40 to 100 Torr, the growth rate increased to 52 μm/h and then decreased to 47 μm/h, which is due to the joint effect of H₂ and HCl etching as well as the formation of Si clusters at higher reactor pressure. The surface root mean square (RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h. The scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved. These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy.     

Alpha Power广义指数分布

研究了一种新的寿命分布,称为Alpha power广义指数分布.新分布的危险率函数具有单调、浴盆和单峰形状,更加灵活地适用于可靠性分析中寿命数据拟合.讨论了新分布的统计特征,包括分位数、矩和矩母函数、熵、次序统计量,并讨论了参数的最大似然估计.通过两组真实寿命数据拟合分析说明了新分布的优越性.     

Absorption measurement of optical thin films under high power density with a Closed Cavity

A Closed Cavity measuring platform is built on the basis of a 1000 W-class direct current(DC)-discharge drived continuous-wave(CW) HF/DF chemical laser. On this platform, the absorption coefficients of optical thin films coated on the surfaces of monocrystalline silicon substrates, at the wavelength of 3.6–4.1 μm, is measured, when the power density on the surfaces of optical thin films reaches about 3.16 kW ∕cm2. The measuring principle and structure of the Closed Cavity is introduced. The temperature curves and balanced temperature rises of the film-substrate systems under test measured through the experiment is presented in this Letter. The experiments show high reliability, good repeatability and strong practicality. The Closed Cavity measuring platform is applicable for not only absorption measurement but other performance measurement of optical thin films under high power density.     

Advances and prospects in nitrides based light-emitting-diodes

Due to their low power consumption, long lifetime and high efficiency, nitrides based white light-emitting-diodes (LEDs) have long been considered to be a promising technology for next generation illumination. In this work, we provide a brief review of the development of GaN based LEDs. Some pioneering and significant experiment results of our group and the overview of the recent progress in this field are presented. We hope it can provide some meaningful information for the development of high efficiency GaN based LEDs and solid-state-lighting.