单模光纤耦合器的传输光谱温度特性

在温变条件下,对光纤光源发出光波经单模光纤耦合器传输后的输出光谱进行了测试.借助测试结果,仿真计算了耦合器的透射光波和耦合光波分别进入Sagnac干涉仪后干涉仪输出信号的误差随温度的变化情况.结果表明:当环境温度发生变化时,耦合器透射光波和耦合光波的平均波长和功率都会发生变化,且透射光波的平均波长和功率的温度稳定性远远高于耦合光波的稳定性;当透射光波作为干涉仪输入光波时,由温变引起的干涉仪输出误差比耦合光波作为输入光波时的误差小一个数量级.     

频率分集阵列对干涉仪的角度欺骗效果

针对干涉仪的测向隐蔽性问题,提出了一种基于频率分集阵列（FDA）对干涉仪的角度欺骗方法。干涉仪通过求取各天线接收到信号的相位差确定信号到达角,而FDA由于各阵元具有微小频偏造成其相位差并不满足求解关系,从而实现角度欺骗。首先,利用模型建立法和欧拉公式法2种方法建立了FDA波束相位模型;然后,从建立的2种模型出发,论证了FDA发出信号对干涉仪具有角度欺骗效果;最后,仿真分析了干扰距离、阵元间距、发射频率、频率增量等因素的影响。理论分析与仿真结果表明,FDA对处于远场的干涉仪目标有良好的欺骗效果。      

Strong magnetic field effect on the dissolution process of tetragonal lysozyme crystals.

Either a homogeneous or inhomogeneous magnetic field has been known to dampen the protein crystal growth. To date the mechanism is not clear. However, it was generally proposed that the magnetic field may dampen the convection in the solution, resulting in a reduced crystal growth rate and possibly a good crystal quality, similar to the case of protein crystal growth in space. To understand the mechanism of the magnetic field effect on protein crystal growth, further explorations on the magnetic field effect on protein solution, on the processes of crystal growth and dissolution, and on different crystallization (solution) systems, should be valuable. In this paper we present our recent efforts to study magnetic field effects on the dissolution processes of tetragonal lysozyme crystals under a strong magnetic field. A layer of oriented tetragonal lysozyme crystals was prepared under a temperature gradient and magnetic field, after that the crystals were dissolved by increasing the temperature of the solution. The lysozyme molecules will diffuse upwards due to the steep concentration gradient at the lower side of the cell caused by the dissolution. The evolution of the concentration in the solution was measured in-situ using a Mach-Zehnder interferometer. The results confirmed that the dissolution process of the crystals was slowed by the magnetic field. Judging from the concentration evolution versus time at different positions in the solution, we concluded that the apparent diffusion coefficient of lysozyme molecules was decreased by the magnetic field. The results were discussed using a suspended crystal model in the initial dissolution stage.     

冷原子干涉重力仪在深空环境下的微重力探测

主要介绍了冷原子干涉的基本概念和原子干涉重力仪的发展;介绍了原子干涉的基本原理和在微重力环境下原子干涉重力仪的优势;阐述了国际上微重力环境下原子干涉重力仪的研究现状及其可能的应用。相对其他重力仪而言,原子干涉重力仪成为深空重力场测量的上佳选择,并且深空微重力环境可以有效延长原子干涉仪的干涉时间,提高仪器灵敏度。     

光纤Sagnac温度传感器信号检测技术

利用光纤Sagnac干涉仪的偏振非互易性PNR(Polarization Non-Reciprocity)可以实现对单温度点的高精度测量.传感头周围温度场的变化引起干涉仪光路中两相干光的相位差变化.通过分析温度传感器的测温原理,得到其输出的线性化模型.采用方波调制解调技术实现了对温度传感器光路系统输出的全数字信号检测.设计了以C8051F060混合信号微控制器为核心的全数字信号检测系统,实现其采样信号和调制信号的相位关系保持.16位高精度模/数转换器的电压采样值通过数字滤波及分段函数解算处理,得到测量温度值的数字输出.这种技术具有实现方便,便于数字化处理及时序控制等优点.通过-15~55℃的全温扫描实验得到的实验数据和理论曲线近乎重合,系统输入/输出成很好的线性关系,线性度达到了10-3量级.实验研究表明这种温度传感器可以实现高精度的温度测量.      

一种综合孔径微波辐射计成像处理算法

综合孔径成像是基于干涉仪成像原理实现的一种成像方式,其通过对干涉测量结果进行逆傅里叶变换得到场景的亮温分布,利用小波增强去噪算法在时域和频域同时对图像进行处理,增强需求信息抑制非必要信息,并附加特定的窗函数滤除杂波,提高重建的微波辐射计图像的清晰度和平滑感。采用盲解卷的Lorentzian超分辨率算法提高成像的分辨力,较好的解决了天线口面尺寸与分辨力矛盾的问题。     

一种综合孔径微波辐射计成像处理算法

综合孔径成像是基于干涉仪成像原理实现的一种成像方式,其通过对干涉测量结果进行逆傅里叶变换得到场景的亮温分布,利用小波增强去噪算法在时域和频域同时对图像进行处理,增强需求信息抑制非必要信息,并附加特定的窗函数滤除杂波,提高重建的微波辐射计图像的清晰度和平滑感。采用盲解卷的Lorentzian超分辨率算法提高成像的分辨力,较好的解决了天线口面尺寸与分辨力矛盾的问题。     

中高层大气风场和温度场星载探测技术研究进展

中高层大气风场和温度场是重要的大气基本参数, 其全球高精度测量具有广泛的应用前景, 探测需求日趋强烈. 干涉光谱仪由于其多通道、高通量和高光谱分辨率等优点而成为本项目的首选. 目前被成功应用的干涉式测风/测温仪器主要有Fabry-Perot 干涉仪和广角Michelson 干涉仪两大类. 本文对干涉光谱仪用于中高层大气风场和温度场探测的发展状况进行了分析, 同时比较了几种干涉仪测风和测温的可行性及优缺点, 为中国开展中高层大气风场和温度场星载探测打下基础.      

星载FPI探测低热层温度的研究

80～350km高度区域的大气温度与风场探测研究对于认识全球性空间动力学和日地耦合机制具有重要科学意义.法布里-珀罗干涉仪(FPI)能够通过分析接收光的干涉环反演计算出一定高度大气层的风场和温度.近年来,中国利用多种地基探测设备对中高层大气进行了观测研究,对于温度反演和星载探测技术的研究开始起步.本文基于系统传输函数和发射谱线函数的卷积,讨论了利用FPI探测高空大气温度反演计算的原理;分析了星载FPI探测的方法,根据星载FPI探测与地基探测的不同点,仿真了星载探测干涉图;结合中国观测技术现况及空间探测需要,讨论了发展星载空间环境探测仪的可行性.      

Finding the suitable drag-free acceleration noise level for future low-low satellite-to-satellite tracking geodesy missions

This paper evaluates the impact of residual acceleration noise on the estimation of the Earth’s time-varying gravity field for future low-low satellite-to-satellite tracking missions. The goal is to determine the maximum level of residual acceleration noise that does not adversely affect the estimation error. The Gravity Recovery And Climate Experiment (GRACE) has provided monthly average gravity field solutions in spherical harmonic coefficients for more than a decade. It provides information about land and ocean mass variations with a spatial resolution of ～350?km and with an accuracy within 2?cm throughout the entire Earth. GRACE Follow-on was launched in May 2018 to advance the work of GRACE and to test a new laser ranging interferometer, which measures the range between the two satellites with higher precision than the K-Band ranging system used in GRACE. Moreover, there have been simulation studies that show, an additional pair of satellites in an inclined orbit increases the sampling frequency and reduces temporal aliasing errors. Given the fact that future missions will likely continue to use the low-low satellite-to-satellite tracking formation with laser ranging interferometry, it is expected that the residual acceleration noise will become one of the largest error contributor for the time-variable gravity field solution. We evaluate three different levels of residual acceleration noise based on demonstrated drag-free systems to find a suitable drag-free performance target for upcoming geodesy missions. We analyze both a single collinear polar pair and the optimal double collinear pair of drag-free satellites and assume the use of a laser ranging interferometer. A partitioned best linear unbiased estimator that was developed, incorporating several novel features from the ground up is used to compute the solutions in terms of spherical harmonics. It was found that the suitable residual acceleration noise level is around 2?×?10^?12?ms^?2?Hz^?1/2. Decreasing the acceleration noise below this level did not result in more accurate gravity field solutions for the chosen mission architecture.     

Some aspects of temperature sounding of the atmosphere

Based on measurements with the interferometer spectrometer SI-1 on board of Meteor satellites the following problems are investigated: the systematic effect of the spectral response function in deriving effective radiation temperatures; the selection of ‘optimal’ spectral channels within the 15 μm region, and effects of additional molecular absorbers on the determination of the temperature profile. It can be shown that using broad-band window channels (half width ?20cm^?1) the derived surface temperature is significantly different from the surface temperature derived from narrow spectral band channels (e.g. for the HIRS window channel 8 this difference is about 1° C). Simulations of some combinations of spectral channels including one proposed as an optimal approach show no significant difference in the derived temperature profile. Neglecting the ozone absorption of the 14.1 μm band leads to a change in radiance of about 1.5 mW/m²sr cm^?1 and to a systematic error of the derived temperature of about ?2° C in the troposphere.     

气体在矿物油中扩散现象的可视化研究

介绍了利用马赫-泽德干涉仪法实现气体-矿物油扩散过程的可视化测量的原理、作用与意义。由于运用马赫-泽德干涉仪法获得的图像干涉条纹数及其图像的形状变化与折射率n直接与液体介质折射率相关,用马赫-泽德干涉仪法可获得十分清晰的影像。在N2,O2-矿物油扩散过程中,干涉条纹式样并未发生显著的紊乱变化,表明N2与O2气体在矿物油中发生扩散后,所引起的矿物油折射率变化过程较为缓慢。在CO2-矿物油扩散过程中,由于溶解的作用,矿物油近表面层中的气体溶解度增加,导致自然对流的出现。通过可视化测量,成功地观测到这一重要实验现象。同时,利用可视化技术,还可很好地判明对流出现的时间,从而确保扩散研究的有效性。     

龙卷风维持特性的探索

利用计算流体力学（CFD）方法建立了模拟龙卷风的装置模型。基于龙卷风在平面上的速度型,拟合成函数关系式,在三维CFD程序中设置初始速度场以及相关的边界条件,匹配不同的初始温度场进行了关于龙卷风维持和发展的一系列数值模拟。重现并利用漩涡管的Ranque-Hilsch效应以及汇流换热原理分析了本文2种不同的温度型对龙卷风内部流场变量随时间推移所发生的变化,同时揭示了龙卷风产生并维持下去的一种可能性,即冷热气流汇流换热生成温度场可能是产生和维持龙卷风的直接原因,并在此基础上提出使龙卷风削弱甚至消亡的方法,即破坏温度场。      

Using LASCO-C1 spectroscopy for coronal diagnostics

The LASCO-C1 telescope was designed to perform spectral analysis of coronal structures by means of a tunable Fabry–Pérot interferometer acquiring images at different wavelengths. Results from spectral scans of the Fe xiv 5303 Å green coronal emission line are presented. Physical quantities like the ion temperature (line widths), and the flow velocity along the line of sight (Doppler shifts) are obtained over the entire corona.     

大型客机驾驶舱气流热仿真及舒适性评价

驾驶舱的空气速度场和温度场直接影响驾驶员的热舒适和工效,是驾驶舱结构和环境控制系统设计中考虑的重要内容.对B737-800驾驶舱进行全尺寸三维建模,以高空夜航工作情况为例,采用商用CFD(Computational Fluid Dynamics)软件Fluent计算该驾驶舱的流场和温度场,再用平均温度评价指标和热环境综合评价指标PMV(Predicted Mean Vote)来对驾驶舱进行温度环境客观评价,并采用问卷调查法对飞行员进行驾驶舱内部空气流速和温度舒适度的主观评价.数值仿真结果与主观评价结果都得出B737-800驾驶舱在高空夜航时基本处于舒适的环境,除躯干和脚部由于偏凉而略感不舒适.数值仿真结果与客观评价结果的一致性,验证了大型客机驾驶舱气流热仿真的准确性.     

冷原子干涉技术原理及其在深空探测中的应用展望

简要介绍了基于冷原子干涉技术的陀螺仪与重力仪的特点以及国内外研究现状,重点介绍冷原子制备、冷原子分束、反射以及原子内态探测等冷原子干涉关键技术的基本原理及其实现方法。结合深空探测特点,冷原子干涉技术在深空探测领域潜在的应用有两个方面:一方面可应用于深空探测器在飞行、交互、对接以及着陆过程中的自主导航;另一方面可应用于深空探测器引力助推过程中的重力以及加速度的精密测量。     

基于EFPI-FBG结构的光纤复合传感器研究

研究了一种基于非本征型Fabry-Perot干涉仪(EFPI)和光纤Bragg光栅(FBG)串联结构构成的EFPI-FBG光纤复合传感器,用于实现对压力和温度信号的同步测量。传感器选用熔融石英作为压力敏感材料,利用飞秒激光焊接技术实现传感器探头结构的封装。对传感器的工作原理进行了分析,制作并封装传感器工程样机,搭建测试系统,对传感器的性能进行了灵敏度及交叉敏感性分析。结果表明,该传感器在0.8 MPa范围内的灵敏度约为-0.729μm/MPa,在50℃~200℃范围的温度灵敏度为0.009 nm/℃,传感器压力测量最大允许误差为±4.12%FS。该EFPI-FBG复合传感器有望应用于压力—温度双参数测量需求的技术领域。     

全光纤M-Z干涉仪激光器鉴频系统

研究了不等臂M-Z干涉仪鉴频的基本原理,对采用三角波调制改变干涉仪臂长获得鉴频信号的过程进行了定量分析.在此基础上,仿真计算了线性改变干涉仪臂长和频率漂移对鉴频信号输出的影响,采用LiNbO₃相位调制器取代PZT(Piezo-Electric Transducer)调制方式,设计实现了鉴频实验装置,获得的实验结果与理论和仿真结果吻合.对驱动信号和环境扰动对该方案的影响进行了实验验证和理论分析,与 PZT调制方式相比,无需高精度温控装置,系统工作稳定可靠,信号调制动态范围可以从PZT调制方式下的几十Hz扩大到GHz.同时可以在该方案中采用lock-in确定相位-频率响应度,从而测定激光器的频率波动范围.     

基于光场成像技术的散射性火焰温度场重建

光场成像是一项新兴的非接触式测温技术,针对传统辐射成像温度场重构效率低的问题,开展了基于光场成像的散射性火焰温度场重建研究。在火焰光场成像模型的基础上,以广义源项多流法为正问题模型,利用Landweber算法重构吸收散射性火焰的三维温度场,同时引入最小二乘QR（LSQR）分解算法作为对比以衡量Landweber算法的性能。分析了测量误差对于重建精度的影响,重建结果表明,即使在添加5%测量误差的情况下温度场的平均重建相对误差也仅为0.91%和0.92%,重建结果仍然是合理的。Landweber算法和LSQR算法具有相当的计算精度,但Landweber算法的计算时间是LSQR算法的1/10,其计算效率明显优于LSQR算法。