一种基于DSP的便携式光纤EFPI传感器解调仪

介绍了一种利用数字信号处理(DSP)芯片的便携式光纤外腔式法珀干涉型(EFPI)传感器解调系统。为了实现高速度、高精度的光纤EFPI传感器的解调,提出了一种测量EFPI透射波长的算法。利用DSP通过对EFPI反射波形的实时跟踪,计算透射出的波长值,并根据标定转换为被测量。实验结果表明,解调系统的波长分辨率可达到2pm,动态测量范围高达50nm。     

高灵敏度光纤温度传感器

针对深井温度变化小,提出了一种可用于深井温度测量的高灵敏度光纤温度传感器。两根陶瓷插芯从铝管的两端插入构成外腔式光纤法珀干涉仪(EFPI)结构,用螺钉固定插芯,再用高强度的环氧树脂密封该结构,达到防水防尘效果。金属铝和陶瓷插芯具有不同的热膨胀系数,温度的变化将引起EFPI腔长变化,采用高灵敏度光纤白光干涉测量技术,就可以通过测量EFPI腔长获得被测温度。分别在固定温度和不同温度下,对腔长为146.5μm的EFPI光纤温度传感器进行了连续测量。测量结果表明,高灵敏度EFPI光纤温度传感器的腔长-温度灵敏度为260nm/℃,温度测量分辨率为0.002℃。     

高温光子晶体光纤温度传感器

针对大于500℃的高温环境,提出了一种可用于高温温度测量的高温光子晶体光纤(PCF)温度传感器。在光子晶体光纤末端熔接一段纯石英无芯光纤构成外腔式光纤法珀腔(EFPI)结构。纯石英无芯光纤在高温下的热膨胀和热光效应使得EFPI的光学腔长发生变化。结合光纤白光干涉测量技术,通过测量EFPI的腔长得到被测温度。在不同温度环境下,对腔长为175μm的EFPI光纤温度传感器进行连续测量。测量结果显示,设计的高温光纤温度传感器在27~1100℃范围内,腔长-温度三阶拟合精度达到99.95%,腔长-温度灵敏度为(0.851+0.0023T-0.000000957T2)nm/℃,其中在1100℃时,温度测量分辨率为0.225℃。     

测量光纤外腔Fabry-Perot干涉仪的白光干涉术

提出了一种基于白光干涉术测量低锐度光纤外腔Fabry Perot干涉仪（EFPI）的方法用宽带光源注入F P腔,在接收端用一高锐度的可调谐光纤F P滤波器对EFPI的反射光谱进行扫描,获得了周期性变化的光谱输出为了测量出EFPI的腔长,对光谱信号进行傅里叶变换,得到光谱的周期,由此求出EFPI的绝对腔长证明了用低锐度EFPI的测量准确度由腔长决定F P腔越长,测量准确度越高在腔长分别是200 μm,400 μm和600 μm时,测量的腔长与实际腔长相同.     

基于非本征光纤法布里-珀罗干涉仪的局放声发射传感器设计EI北大核心CSCD

采用耦合石英膜和光纤接头构成非本征法布里-珀罗干涉仪(EFPI)传感器,检测液-固复合绝缘电介质中的局部放电声发射信号。为解决目前EFPI传感器灵敏度低的问题,依据弹性力学原理和有限元分析方法确定EFPI膜片结构设计方法,并制作传感器样品。建立以分布式反馈(DFB)激光器为光源的EFPI正交强度解调系统。以绝缘油针-板电极局部放电为信号源,利用压电陶瓷(PZT)传感器与EFPI样品进行对比测试。结果表明,EFPI传感器局放检测灵敏度取决于传感器频响带宽和静压灵敏度,完善了EFPI膜片设计方法,获得局放检测灵敏度与PZT相近的EFPI传感器。     

基于非本征光纤法布里-珀罗干涉仪的局放声发射传感器设计

采用耦合石英膜和光纤接头构成非本征法布里-珀罗干涉仪(EFPI)传感器,检测液-固复合绝缘电介质中的局部放电声发射信号。为解决目前EFPI传感器灵敏度低的问题,依据弹性力学原理和有限元分析方法确定EFPI膜片结构设计方法,并制作传感器样品。建立以分布式反馈(DFB)激光器为光源的EFPI正交强度解调系统。以绝缘油针-板电极局部放电为信号源,利用压电陶瓷(PZT)传感器与EFPI样品进行对比测试。结果表明,EFPI传感器局放检测灵敏度取决于传感器频响带宽和静压灵敏度,完善了EFPI膜片设计方法,获得局放检测灵敏度与PZT相近的EFPI传感器。     

外腔式光纤Fabry-Perot干涉型高温应变传感器

介绍了一种外腔式光纤Fabry-Perot干涉型(EFPI)高温应变传感器,传感器是在两段切割平整的单模光纤之间熔接一段空心光纤构成。实验证明,传感器在1000℃以下时能够稳定工作,腔长变化灵敏度为0.17nm/με,应变测量灵敏度可达±1με,线性度高达0.99998。EFPI高温应变传感器结构紧凑,工艺简洁,成本低廉,是一种可靠、优秀的高温应变传感器。     

基于宽谱光源的光纤传感波长解调系统的研究

研究制作了基于宽谱光源的光纤传感波长解调系统, 以多光纤光栅作为波长参考基准、采用可调谐光纤法布里-珀罗(F-P)滤波器作为波长扫描器件。系统中采用三次多项式拟合的方法对滤波器锯齿波的扫描电压与透射波长关系曲线进行非线性拟合, 解决可调谐光纤F-P滤波器的电压—波长非线性关系对系统测量带来的较大误差问题, 实现波长的高精度解调。采用五光纤光栅做波长参考, 单根光纤光栅传感器的解调实验结果表明：待测光纤光栅布拉格波长短期测量分辨率为3.5 pm, 长期测量稳定性为7 pm。采用该系统对光纤非本征法布里-珀罗干涉型(EFPI)应变传感器的测试结果表明, 测量应变灵敏度为2.41 nm/με, 并且应变和波长之间存在良好的线性关系, 线性相关度达到0.99991。     

光纤应变、温度、振动同时测量新技术的研究

本文介绍了集成式Bragg光纤光栅(FBG)和非本征型Fabry-Perot干涉腔(EFPI)复合传感器的结构及应用该传感器同时测量静态应变、温度和振动的原理.利用FBG、EFPI和低相干性干涉信号解调方法实现了用一个传感器同时测量三个参量.实验结果表明温度精度达±1℃,应变精度为±20με,振幅分辨率达1nm,测量重复性好.     

光纤复合型油气井下压力温度测量系统

针对目前广泛使用的电子式油气井下压力温度测量系统可靠性低、高温环境漂移大的不足,设计了一种基于非本征型F-P干涉仪(EFPI)和光纤布喇格光栅(FBG)的复合型油气井下压力、温度测量系统,详细说明了其工作原理、传感器组成和信号解调方法,初步试验结果表明,该测量系统不仅克服了电子测量方式的不足,而且具有复用性好、测量精度高等优点.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...