激光诱导击穿光谱在冶金在线分析中的应用研究进展

化学成分在线直接测量是冶金分析长久以来的追求,也被誉为冶金分析面临的三大难题之一。激光诱导击穿光谱技术因其在无需复杂样品制备、直接快速、非接触等方面展现的独有技术优势,备受研究上的关注。文章综述了激光诱导击穿光谱在选矿、熔融金属在线检测方面的研究进展,总结了当前存在的主要问题,并对未来发展进行了展望。     

现浇混凝土水池的渗漏问题与防水措施研究

现浇混凝土水池受诸多因素的影响,容易引发水池渗漏现象,极大程度降低了水池的使用期限,因此,提高水池施工技术,对于降低水池渗漏、延长水池使用寿命都具有重要的意义。结合长江口中华鲟自然保护区基地项目珍稀鱼类抢救暂养车间的D水池建设过程,分析了现浇混凝土水池的渗漏问题,并详细地论述了相应的渗漏处理方案与技术要点,所研究的成果可以为相关工程项目与研究提供参考。     

A method of laser focusing control in microlaser-induced breakdown spectroscopy

This paper presents a method for the automatic adjustment of the laser defocusing amount in micro-laser-induced breakdown spectroscopy. A microscopic optical imaging system consisting of a CCD camera and a 20× objective lens was adopted to realize the method. The real-time auto-focusing of the system was achieved by detecting the effective pixels of the light spot generated by the laser pointer. The focusing accuracy of the method could achieve 3 μm. The element concentrations of Mn and Ni in low-alloy steels were analyzed at a crater diameter of about 35 μm using the presented method. After using the presented method, the determination coefficients of Mn and Ni both exceeded 0.997, with the root-mean-square errors being 0.0133 and 0.0395, respectively. Scanning analysis was performed on the inclined plane and the curved surface by means of focusing control and non-focusing control. Ten characteristic spectral lines of Fe were selected as the analysis lines. With the focusing control, the average relative standard deviations obtained on the inclined plane and curved surface were both less than 5%, and much less than the values without focusing control, 14.6% and 40.39%.     

快速瞬态响应交错并联DCM Boost PFC变换器

分析了实现单位功率因数的四通道交错并联DCM Boost PFC变换器的变占空比控制方法,基于变占空比控制,研究了一种具有快速瞬态响应的改进型变占空比控制方法。改进型变占空比控制交错并联DCM Boost PFC变换器不仅实现了单位功率因数,还具有快速的输入和负载瞬态响应速度。MATLAB/Simulink仿真及试验结果验证了理论分析的正确性。     

箝位网络对峰值电流控制有源箝位正激变换器稳定性影响研究

文章研究了开关频率较高、占空比较大时,箝位网络参数对峰值电流模式 (PCM)控制有源箝位正激变换器 (ACFC)稳定性的影响;分析了箝位网络引起 ACFC 低频振荡的原理,得到出现低频振荡时箝位网络参数的边界;阐述了给出励磁电感参数给定时,根据箝位电压纹波和稳定性设计箝位电容的条件.结果表明,减小箝位电容值,箝位电容与励磁电感之间的谐振有利于变压器磁芯复位,使变换器在较高开关频率和较大占空比时仍能稳定工 作。