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31.
爆炸冲击震动模拟平台的研制 总被引：1，自引：0，他引：1
为了模拟核爆、化爆冲击震动环境,根据能量守恒和弹性碰撞原理,研制了悬挂式爆炸冲击震动模拟平台。该平台能够完成水平向和垂直向冲击试验,通过对锤重、锤高和垫层厚度等参数的合理选择,性能指标可达到:水平向冲击加速度峰值5~1 500 m/s2,作用时间50~4 ms;垂直向冲击加速度峰值10~1 000 m/s2,作用时间60~4 ms。性能试验表明,该平台能够为防护工程结构抗震及其他有关冲击振动问题的研究提供安全、方便、经济、可靠的试验手段。 相似文献
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为实现正电子发射断层成像（PositronEmissionTomography,PET）探测器的作用深度（DepthOfInteraction,DOI）信息获取,本文提出一种基于分光技术的探测器设计方案.探测器采用晶体单元与硅光电倍增管（SiliconPhotomultiplier,SiPM）一对一耦合、蛇形光路的设计和单端Anger加权读出方法进行DOI解码.基于GATE软件进行蒙特卡罗模拟,建立8×1的LSO晶体阵列（单根晶体尺寸3.1×3.1×20mm 相似文献
34.
HE Kuikui;DAI Yutang;YAN Chaofan 《光子学报》2022,51(11):142-152
Hard and brittle dielectric materials represented by quartz are widely used in aerospace, consumer electronics, weapons and other fields. In view of the defects such as re-condensation and micro-cracks in the process of femtosecond laser machining such materials, the ultrasonic gas jet assisted femtosecond laser machining technology is proposed. The steady-state jet is transformed into pulsating jet through the coupling of ultrasonic and gas jet. With the help of the purging effect of gas jet and the high-frequency scouring and crushing effect of pulsating jet, the re-condensate produced in the machining process is taken away, which reduces the adhesion of re-condensate on the machined wall, improves the machining efficiency and improves the machining quality. Firstly, this paper proposes an ultrasonic gas jet device and analyzes the coupling mechanism of ultrasonic and gas jet. The coupling effect of ultrasonic and gas jet is mainly manifested in two aspects. One is that the local shock wave structure is formed by the direct coupling of ultrasonic and inlet jet. The formation of shock wave structure originates from the combination of sound pressure and jet pressure. Due to the alternating propagation of ultrasonic sound pressure with time, the combination of sound pressure and jet pressure makes the gas jet change from a steady jet to pulsating jet with alternating high and low pressure. Second, the ultrasonic transducer is mechanically fixed with the jet nozzle, and the high-frequency micro-displacement generated by the transducer is transmitted to the nozzle. The high-frequency displacement of the nozzle drives the whole flow field to generate high-frequency vibration, thus high-frequency scouring the machined surface. The coupling effect of ultrasonic sound pressure and jet pressure is deduced theoretically, and simulated with ANSYS Fluent software. The theoretical analysis and simulation results show that the steady-state jet is transformed into a pulsating jet, alternating high and low pressure under the action of ultrasound. Secondly, the AT tangential quartz wafers were etched by femtosecond laser with a wavelength of 1 030 nm, pulse width of 290 fs and repetition rate of 20 kHz under the condition of 45 ° between the central axis of the jet nozzle and the laser axis. The effects of ultrasonic frequency, ultrasonic power and gas inlet pressure on the depth and width ratio of femtosecond laser etching quartz microgrooves were investigated, and the morphology of femtosecond laser etching quartz microgrooves with or without ultrasonic gas jet was compared and analyzed. The experimental results show that： 1） Under the assistance of gas jet and ultrasonic gas jet, the depth and aspect ratio of femtosecond laser etching quartz microgrooves have been greatly improved. Under the same conditions, the gas jet and ultrasonic gas jet have little change in the depth and aspect ratio of etching. 2） There is little difference between the etching depth and aspect ratio of quartz microgrooves under different ultrasonic frequencies, but the etching depth increases slightly with the increase of ultrasonic frequency. There is no significant difference in ultrasonic power （ultrasonic amplitude） etching. Ultrasonic power has little effect on the etching depth and aspect ratio of femtosecond laser etching quartz microgrooves. Under the same laser processing parameters, the depth and depth-width ratio of microgrooves increase with the increase of inlet pressure. When the inlet pressure reaches a certain value （about 0.4 MPa）, the depth and depth-width ratio of microgrooves reach the maximum value. When the pressure is above the value, the depth and depth-width ratio of quartz microgrooves change little. 3） Under the single laser etching, the particles on the surface of quartz microgrooves are disorderly and irregular, and the size is large. The particle size of quartz microgrooves tends to be consistent under the assistance of jet. Compared with the single laser etching, the particle size of quartz microgrooves is reduced. Under the assistance of ultrasonic gas jet, the particle size of quartz microgrooves further decreases and tends to be consistent, and the wall quality is significantly improved and improved. The reason is that the high-speed pulsating jet formed by the coupling of ultrasonic and gas jet breaks and forms an impact in the laser action zone. The impact takes away the laser removal near the molten pool and accelerates the melt injection, thereby reducing the adhesion of laser removal on the machined surface. In addition, under the high-frequency impact of pulsating jet, the large particle slag generated in the laser action zone is decomposed into small particles. Some of these small particle slags are brought out with the gas, and even some are attached to the machining surface. Compared with the attachment of large particle slag, the quality of the machining surface is improved. 相似文献
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为了满足测量的高分辨率和灵敏度,基于光栅为关键元件的光学测量方法要求光栅有很高的频率。在已有的高折射率介质制栅方法的基础上提出了一种新的制作超高频全息光栅的方法,该方法制栅准确、简单、方便,其特点是所制光栅的频率与激光波长及介质的折射率无直接关系,而是等于制栅光路所得频率与两倍母栅频率之和。实验表明,利用该方法制得１００００线／ｍｍ的光栅是完全可能的 相似文献
36.
运用２４８ｎｍ激光光解瞬态吸收光谱研究了ＳＯ４·－与ＤＮＡ及其核苷酸和多聚核苷酸ｐｏｌｙ［Ｇ］、ｐｏｌｙ［Ａ］和ｐｏｌｙ［Ｃ］的相互作用,观察了各体系的作用过程,结果表明,ｐｏｌｙ［Ｇ］、ｐｏｌｙ［Ａ］与ＳＯ４·－发生单电子氧化反应生成嘌呤端基自由基;ｄＣＭＰ与ＳＯ４·－单电子氧化生成阳离子自由基,随后与水反应生成５－羟基－６Ｃ自由基;而ｐｏｌｙ［Ｃ］,ＳＯ４·－先在碱基上加成,生成的加成自由基再从核糖上抽氢生成Ｃ２’－糖自由基;ＤＮＡ与ＳＯ４·－作用生成的主要瞬态产物是鸟嘌呤端基自由基。 相似文献
37.
本文对电热原子吸收光谱法机理研究的常用方法,特别是多种物理测试手段进行介绍。 相似文献
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气相分子吸收光谱法测定地下水中亚硝酸盐氮、氨氮、硝酸盐氮 总被引：4，自引：0，他引：4
采用气相分子吸收光谱法测定地下水中的亚硝酸盐氮(NO2^-)、氨氮(NH4^+)、硝酸盐氮(NO3^-)。考察NO2^-,NH4^+和NO3^-测定时的相互干扰,并给出了相应的消除方法。研究结果表明,测定NO2^-时,NH4^+和NO3^-无干扰;NO2^-对测定NH4^+和NO3^-产生干扰,可分别采用分段法和加入2滴10%氨基磺酸溶液的方法消除干扰;对于不含NO2^-或NO2-含量不高的地下水样品,可简化操作步骤直接测定NO3^-。该方法测定结果的相对标准偏差为0.73%~2.74%(n=12),样品加标回收率为97.67%~100.28%。所用检测仪器具有流动注射、自动进样及在线绘制标准曲线的功能,简化了标准方法中的样品前处理过程,减少了样品的损失,实现了自动化分析,大幅提高了检测结果的准确度和工作效率。 相似文献