The bionic navigation system composed of polarization sensor (PS)-aided inertial measurement unit could provide high-accuracy attitude and heading for unmanned vehicles in GNSS rejection or magnetic interference environments. However, the existing loosely coupled (LC) method is vulnerable to occlusion interference and atmospheric depolarization. Therefore, this article proposes the tightly coupled (TC) attitude and heading measurement method based on full-sky polarization mode. First, the TC system model is constructed, in which the sun azimuth error and zenith error are added to the state vector, and the angle of polarization (AOP) deviation of multiple observation channels are taken as the measurement. On this basis, a robust fusion mechanism based on the sequential cubature Kalman filter is proposed. And the linear gravity measurement update and the nonlinear polarization measurement update are carried out in turn to improves the system robustness. In the rotation test, the slight interference vehicle test, and the serious interference vehicle test, the heading root-mean-square error (RMSE) of the proposed method compared with that of the LC method are reduced by 32.5%, 32.3%, and 70.2%, respectively, which verifies the great advantages in practical unmanned driving applications.

Cold atom gravimeters are used to measure the absolute value of the gravitational acceleration. To mitigate the influence of seismic noise on the mirror, a vibration correction system is used. A commercial seismometer CMG-3ESPC is employed to measure the mirror vibration. The transfer function between the mirror vibration and the output of the seismometer is regarded as a proportional element with a time delay. The best proportional element and the best time delay are obtained by minimizing the standard deviation of the fitting residuals of the interference fringe α − P with vibration correction. This system not only exhibits excellent environmental adaptability but also eliminates the need for rough estimation of local gravitational acceleration during the vibration correction process. The system was built on the homemade cold atom gravimeter to carry out experiments in the laboratory. Compared with the measurement results without vibration correction, the standard deviation of the gravity measurement results was reduced from 120.5 μ Gal to 4.2 μ Gal, resulting in a significant reduction by a factor of 28.7. Meanwhile, its sensitivity was significantly improved from 330.8 μ Gal Hz − 1 to 18.0 μ Gal Hz − 1 by performing vibration correction. In the future, this system is expected to carry out comprehensive verification experiments in more complex noisy environments.

We have theoretically and experimentally studied the dispersive signal of the Rydberg atomic electromagnetically-induced transparency (EIT) Autler–Townes (AT) splitting spectra obtained using amplitude modulation of the microwave (MW) electric field. In addition to the two zero-crossing points interval Δf zeros, the dispersion signal has two positive maxima with an interval defined as the shoulder interval Δf sho, which is theoretically expected to be used to measure a much weaker MW electric field. The relationship of the MW field strength E MW and Δf sho is experimentally studied at the MW frequencies of 31.6 GHz and 9.2 GHz respectively. The results show that Δf sho can be used to characterize the much weaker E MW than that of Δf zeros and the traditional EIT–AT splitting interval Δf m; the minimum E MW measured by Δf sho is about 30 times smaller than that by Δf m. As an example, the minimum E MW at 9.2 GHz that can be characterized by Δf sho is 0.056 mV/cm, which is the minimum value characterized by the frequency interval using a vapor cell without adding any auxiliary fields. The proposed method can improve the weak limit and sensitivity of E MW measured by the spectral frequency interval, which is important in the direct measurement of weak E MW.

<p>Zircon, a stable paragenetic mineral in various geological environments, has been recognized as a great tool to study the ages of primary rocks. Trace elements of zircons thus can record the geological evolution processes. Zircon-associated trace elements have been long studied for zircon classification and formation traditionally using binary diagram technique, classical examples including Th-U and La<sub>N</sub>-(Sm/La)<sub>N</sub> diagrams. However, with the massive increase of zircon research, the traditional binary diagrams currently cannot precisely classify zircon types because the binary plot cannot demonstrate the higher dimensional information. It therefore significantly restricts a clear understanding of zircon formation. To address the research gap, we performed the machine-learning-based approaches on 3498 zircon trace-element data of different zircon genetic types, producing high-dimensional zircon-classification diagram plots. We applied and tested four machine learning methods (random forest, support vector machine, artificial neural network, and k-nearest neighbor) and proposed that support vector machine can best contribute to zircon genetic classification study, with an 86.8% accuracy in the prediction of zircon type and formation. In addition to the high-dimensional zircon classification diagram, this work massively improves the accuracy of zircon formation analyses by trace elements, which benefit future studies in zircons. Using the machine learning approach on zircon trace element big data is an effective multidisciplinary exploration of the modern data science technique in the geochemistry study.</p>

原子重力仪是测量重力加速度的高精度仪器,振动噪声是原子重力仪灵敏度受限的一个主要因素,故需对振动噪声进行抑制.详细介绍了用于原子重力仪的各个隔振技术,分析了以弹簧和阻尼结构组成的被动隔振、以主动反馈元件作动的主动隔振和通过算法剔除振动噪声影响的补偿隔振技术的原理、特点及应用领域,讨论了隔振技术的发展趋势,为原子重力仪的隔振技术研究提供参考.

The experimental setup is primarily consisted of fire source, glazing system and measurement system, as shown in Fig. 2.1. The specific introduction of measurement tools are in following sections.

Cold atom interferometer based on two-photon stimulated Raman transition has been proved to be a promising way to measure g with higher precision. In this work, we first introduce the principle of atomic interference gravimetry, including the interaction between the atoms and light, the interferometry with the Raman beams and the measure of the g. Then our gravity acceleration measurement system will be introduced, including atomic fountain, Raman system and detection system. With this device, we can get the value of the g, with the uncertainty in the order of ten minus seven.

Femtosecond laser has been demonstrated to be a prominent tool to manufacture micro scale structure. In the processing, the focusing lens is usually used as the concentrated tool to assemble the original beam to the tiny spot to provide enough energy for ablation. What is more, different focal length means the diverse scale of the focused spot. In common use, various sizes of the spot are required to adjust to the multifarious profiles and substituting the focus lens is the general method. There is no doubt that changing the lens is a fussy job and frequent replacing the lens may cause the lack of stability. In this paper, we report the defocus of the lens to modify the scale of the spot and it is proved to be an effective way to vary the diameter of the focused spot without changing the focus lens.

In order to choose appropriate frequency stabilization method in the atom gravimeter system under construction, Doppler-free dichroic atomic vapor laser lock (Doppler-free DAVLL) and saturated absorption spectroscopy (SAS) method were implemented on Rubidium atomic vapor. Basic principle and experimental details of both frequency stabilization methods were introduced. With restructuring of optical path and applying of self-made low noise photoelectric detector as well as digital lock module, excellent error signal was obtained. For each method, two sets of locking system were built and kept locked during 3000 s′ data acquisition . A frequency fluctuation of 629 kHz when the laser is free running and of 16.2 kHz & 31.4 kHz after locked by SAS and Doppler-free DAVLL were calculated respectively, corresponding to a frequency stability of 1.64 ×10-9 in the condition of free running and 4.21 ×10-11 &8.18 ×10-11 after locked for averaging time of 10 s. The strength and weakness of both methods were elaborated with the demand of system miniaturization. After compared with SAS, Doppler-free DAVLL isconsidered to be a promising choice for miniaturization and modularization in atom interferometry gravimeter.

黑硅材料具有良好的光学吸收特性,广泛用于太阳能电池和红外探测器的制备中.基于黑硅材料制备的探测器具有光谱响应度大、响应范围宽、响应曲线较为平直等优点,介绍了黑硅红外探测器国内外的研究进展,其中涉及的黑硅制备方法包括飞秒激光辐照、皮秒激光辐照、湿法腐蚀、离子注入结合准分子纳秒激光辐照.讨论了目前黑硅红外探测器制备中存在的问题,包括黑硅在退火过程中吸收率下降严重以及黑硅表面电极制备难、载流子横向输运能力差等问题.对存在的问题进行了分析,总结了当前的解决方法,展望了黑硅红外探测器的发展趋势和应用前景.

Atom Interferometry is proved to be a potential method for measuring the acceleration of atoms due to Gravity, we are now building a feasible system of cold atom gravimeter. In this paper development and the important applications of laser cooling and trapping atoms are introduced, some key techniques which are used to obtain 87Rb cold atoms in our experiments are also discussed.

Atom interferometry gravimeter with stimulated Raman transitions is realized by atom matter wave, it is now widely used in gravity measurements. We are now building a feasible system of cold atom gravimeter, it is based on the atom interferometry technology by coherently manipulating the cold atoms in a fountain with specific Raman lasers, the cold atom wave packet is splitted, combined, and then re-splitted in the process. Then the atomic wave packet will acquire different phase because of the different evolution path. The precise acceleration can be deduced through the precision measurement of atomic interference fringes phase, and this will be a high precision standard of acceleration. At present, the preparation of Raman laser and the precise control of the laser Frequency have been finished, and they have been proved to meet the requirements of the experiment.