共查询到20条相似文献,搜索用时 140 毫秒
1.
随着微推进技术的快速发展,微推力器推力的测试与标定也日益困难。为实现微推力的精密测量和动态特性测试,通过分析超导重力梯度仪的差分加速度测量原理、仪器的构成和原理电路等,提出了一种基于高温超导差分加速度测量原理和SQUID检测技术微推力测量方案,其推力测量范围为10^-7-10^-2N、测量频带从直流至4Hz。根据检验质量的动力学方程和超导回路磁通量守恒方程,导出了推力与输出差分电流的传递函数,分析了影响测量的主要噪声。方案可应用于微推力的测量,并有进一步提高推力测量精度的潜力。 相似文献
2.
为获取激光推力器在重复脉冲激光作用下产生推力的变化情况,在对聚偏氟乙烯(PolyVinylidene Flouride,PVDF)进行动态标定的基础上,建立了一套基于PVDF的重复脉冲推力测量装置.在单脉冲能量40 J,重复频率10 Hz的条件下进行了实验,并与半导体应变片的测量结果进行了比较分析,实验结果表明,该测量装置响应速度块、精度高,并有较强的噪音抑制能力,能充分获得脉冲推力在时间上的细微变化;同时发现,在双脉冲激光作用下,实验测量的冲量耦合系数有所减小,这一现象需要进一步的实验研究. 相似文献
3.
为解决法布里?珀罗(Fabry?Perot, F?P)干涉仪锁频方法响应速度、抗干扰能力、长期稳定性方面存在不足的问题,提出了F?P干涉仪差分锁频方案,将存在频差的双频激光耦合入F?P谐振腔,当激光频差足够小时,两光强信号曲线存在交叉,以两光强信号的差值作为被控量,在交叉点附近构建单调过零函数,作为闭环控制系统的反馈量,实现动态差分锁频控制。基于该方案,搭建了一套F?P干涉仪微位移测量装置并开展实验验证,结果表明该装置能够实现0 ~ 300 nm范围内的微位移测量,位移测量分辨力达到23 pm,验证了F?P干涉仪差分锁频方案的有效性,为推动微位移测量领域的发展提供了重要借鉴。 相似文献
4.
5.
6.
7.
8.
基于声表面波传感技术的微液滴检测方法 总被引:1,自引:0,他引:1
为了提高声表面波(SAW)技术用于微液滴体积测量的精度,提出了一种差分面积拟合法.根据声表面波信号的特点分析了差分面积拟合法的合理性,在自行研制的声表面波液滴体积检测系统上对该方法的应用进行了验证.采用两种黏性不同的微液滴,分别为5~9μL的微水滴和微油滴进行了测量.对测得的信号分别采用曲线峰值法和差分面积拟合法与微液滴大小进行回归.实验结果表明,采用差分面积拟合法进行回归得到的模型的相关系数相比采用峰值法提高了4%以上,同时对两种微液滴的预测均方根误差(RMSEP)减小了37%以上,从而证明了该方法的有效性. 相似文献
9.
针对脉冲爆轰发动机的脉动流动特性设计加工了塞式收敛扩张喷管,并对其增推性能和增推机理进行了研究。研究结果表明,塞式收敛扩张喷管可以大幅增加推力,10Hz和15Hz时塞式收敛扩张喷管对发动机的推力增益分别为32.4%和29.52%;塞式收敛扩张喷管扩张段对爆轰室排出的高温高压气体有减压加速作用;塞式收敛扩张喷管塞式结构增加推力壁平台压力值和平台压力持续时间,从而增加发动机推力。 相似文献
10.
11.
We propose a fully enclosed hybrid nanogenerator consisting of five electromagnetic generators (EMGs) and four triboelectric nanogenerators (TENGs).Under a vibration frequency of 15.5 Hz,one TENG can deliver a high output voltage of approximately 24 V and a low output current of approximately 24 μA,whereas one EMG can deliver a low output voltage of approximately 0.8 V and a high output current of approximately 0.5 mA.By integrating five rectified EMGs in series and four rectified TENGs in parallel,the hybrid nanogenerator can be used to charge a home-made Li-ion battery from 1 to 1.9 V in 6.3 h.By using the hybrid nanogenerator to scavenge the vibrational energy produced by human hands,a temperature-humidity sensor can be sustainably powered by the nanogenerator,which is capable of charging the 200 μF system power capacitor from 0 to 2 V in 15 s,and sustainably power the sensor in 29 s. 相似文献
12.
A laser-diode-pumped Nd:YVO(4) microchip laser was built and actively frequency stabilized relative to a Fabry-Perot cavity with the frequency-modulated sideband technique. The error signal reaches the shot-noise level of 7.4 mHz/√Hz around 1 kHz. Excess intensity noise sets a lower limit of16.5 mHz/√Hz for the relative frequency noise, corresponding to a spectral linewidth of 860 μHz. We discuss the method for reconstructing the actual frequency deviation from the observed error signal. 相似文献
13.
依据菊花(Dendranthema morifolium)植物电信号小波软阈值消噪后的数据,进行了其电信号时间序列的高斯径向基函数(RBF)神经网络预测.菊花植物电信号是一种微弱低频非平稳信号,最大幅值1 093.44μV,最小为-605.35μV,均值-11.94μV;功率谱分布为0-0.2 Hz.该结果说明,利用RBF人工神经网络对植物微弱电信号进行短期预测是可行的,其预测数据可作为以节能为目标依据植物自适应电信号特性建立温室和/或塑料大棚智能自动化控制系统的重要参数. 相似文献
14.
The paper describes a new approach to characterize metallic materials by a novel instrumented notch impact test for samples with small specimen size. A piezo‐electric sensor mounted on the pendulum hammer provides force information during the fracture process. By numerical integration of the signal the absorbed impact energy can be calculated very exactly. Further information about the fracture behavior can be extracted from the resulting force‐displacement‐diagram. Several duplex stainless steels in different heat treatment conditions were tested and compared to standard Charpy impact testing specimen. It is concluded that different grades of embrittlement of duplex materials can be detected with high accuracy. Due to a data acquisition rate of 250 kilo‐samples/second and limited stiffness of the pendulum hammer impact energies of less than 7% of maximum energy materials with high brittleness can only be characterized qualitatively. 相似文献
15.
三种菊科植物电信号的分析 总被引:2,自引:7,他引:2
对测得的瓜叶菊(Senecio cruentus)、雏菊(Bellis perennis)和茼蒿(Chrysanthemum coronarium)三种盆栽菊科植物的电信号进行了短时傅立叶变换分析.三种菊科植物的电信号幅值的变化范围分别为-34.07~35.15μV、-94.37~25.03μV和-22.92~21.71μV,能量谱分别主要分布在约0.15 Hz、0.08 Hz和0.11 Hz以下.据此表明三种菊科植物的电信号均为微弱低频信号.另外,还发现三种菊科植物的电信号中于不同时刻出现频率范围不同的“动作电波”成分. 相似文献
16.
A microscale biosensor for methane containing methanotrophic bacteria and an internal oxygen reservoir 总被引:1,自引:0,他引:1
A microscale biosensor for continuous measurement of methane partial pressure based on a novel counterdiffusion principle is presented. Methane-oxidizing bacteria placed in the microsensor utilize oxygen from an internal oxygen reservoir when methane from the exterior diffuses through the tip membrane. The transducer is an internal oxygen microsensor with its tip positioned between the oxygen reservoir and the sensor tip membrane. The external partial pressure of methane determines the rate of bacterial oxygen consumption within the sensor, which in turn is reflected by the signal from the transducer. Tip diameters were down to 20 μm, enabling us to study methane distribution on a microscale. The microscale construction also results in a low stirring sensitivity and a 95% response time down to 20 s. By tailoring the geometry, sensors can be made to exhibit a linear response in the full range of 0-1 atm partial pressure of methane or, alternatively, to exhibit a linear response only at lower concentrations, improving the sensitivity to below 0.1 kPa, corresponding to ~1 μM in aqueous solution. Temperature, oxygen, and H(2)S interfere with the signal; no interferences were detected from H(2), NH(3), CO(2), or acetate. 相似文献
17.
基于商用坐标测量机的3D微纳米计量 总被引:1,自引:0,他引:1
以测量精度为1μm的商用坐标测量机(CMM)为基础,构建了测量范围为25mm×40mm×25mm、测量不确定度约为O.15μm的PTB微纳米专用坐标测量机.研究了CMM的运动控制系统、恒温室的空调系统以及CMM的被动隔振系统等对测量结果的影响.由测量结果可以看出,CMM的运动控制系统产生的噪声水平约为其他误差源的2倍.通过FFT运算,发现未优化系统的短时最大漂移量发生频率为750Hz,对应为运动控制的工作频率.文中还介绍了测量力为1州光纤探针的测量原理,并给出了对2.5mm短轴的测量结果. 相似文献
18.
本文从原理和实验两方面提出了一种明显提高相位测距分辨率的方法.应用差频模拟锁相环(APLL)专用集成电路KD080H,作者设计制作出一种环路噪声带宽小于1Hz的晶体分频APLL,并成功用于相位检测频率1.5kHz的相位测距系统.实验表明,在光电信号频率为15MHz,晶体滤波器带宽500Hz,所得信号信噪比仅为40dB的条件下,测距分辨率可优于0.5mm,比应用中心频率1.5kHz带宽50Hz的有源滤波器测距系统的分辨率提高约7倍.该方法还具有结构简单,成本低,使用方便等优点. 相似文献
19.
基于直接数字频率合成芯片AD9959、锁相环芯片ADF4351,结合开源电子平台Arduino(基于微处理器ATmega328),建立参考到同一个外部频率参考的多路信号源,能够输出频率为0 Hz~4.4 GHz的正弦波,频率、相位、幅度可以通过USB端口和控制面板灵活控制,通过混频和叠加等手段,产生边带调制PDH激光稳频需要的调制信号和解调信号。该信号源集成度高、成本低且能在实验室条件下替代商品仪器应用于边带调制PDH激光稳频等实验,解决了限制边带调制PDH激光稳频推广应用的一个重要障碍。 相似文献
20.
Z. J. Yang 《Journal of Superconductivity》1992,5(1):47-53
The quasistatic magnetic field responses (typically 0.8 Hz) of fluxoids in ac-axis oriented Y1Ba2Cu3O7– (Y123) film have been studied using a computerized mechanical pendulum at 77 K. The resonance frequence of the pendulum is significantly shifted to higher values due to the interaction between the Y123 film and a magnet mounted on the pendulum. The contribution of the magnet-superconductor interaction to the shift of the squared resonance frequency shows, in a certain range, a logarithmic dependence on the driving force (proportional to the amplitude). The present results are consistent with the previous studies on the bulk Y123 materials for different configuration. 相似文献