飞机客舱内病菌传播的数值仿真研究进展

飞机客舱内病菌传播规律的数值模拟主要包括2个阶段,先模拟密闭空间内部空气流场,然后再在该 流场基础上,研究呼吸液滴在其中的扩散。大多数研究采用湍流模型来仿真内流场,文中对比分析了各类湍流模型的特点及适用条件。离散相模型分析呼吸液滴在内流场内的扩散传播轨迹,欧拉模型分析呼吸液滴在内流场内随时间的扩散浓度变化,综述了离散相模型和欧拉模型的研究进展和应用现状。同时综述了解决旅客在客舱中移动影响病原体液滴传播规律的动网格技术,最后提出了数值仿真分析过程中亟待解决的问题。     

激光绝对测距中相位信号的数字处理方法综述

随着工业4. 0时代的来临,精密测量的技术发展变得越来越重要。绝对距离测量作为精密测量的一个重要组成部分,其测量精度离不开对信号相位信息的分析,而相位信息一般可以通过数字处理方法来获得。本文介绍了激光绝对距离测量中涉及到的相位信号数字处理方法的相关原理及应用。     

北斗GEO卫星CEI相时延解算方法研究

连线端站干涉测量(connected element interferometry,CEI)是高精度测角技术,在中高轨卫星、月球及深空航天器定轨定位中有良好的应用前景。基于CEI技术特点,提出了一种新的测量方法,即在相干测距模式下利用测距音和载波信号作为信号源进行连线端站干涉测量。构建了CEI试验系统对北斗GEO卫星进行观测,利用相干测距模式下的下行信号解算群时延、相时延。利用北斗GEO卫星精密星历计算的时延理论值,对北斗GEO卫星CEI群时延和相时延结果进行评估。结果表明,相干测距模式下CEI群时延和相时延残差均值分别为0.47 ns、0.08 ns,标准差(3σ)分别4.2 ns、0.13 ns。该项研究验证了相干测距模式下CEI相时延解算的可行性,可为共位地球同步卫星精密相对定位、月球探测器CEI测量提供技术参考。     

An experimental method for squealer tip flow field considering relative casing motion

Squealer tip is widely used in turbines to reduce tip leakage loss. In typical turbine environment, the squealer tip leakage flow is affected by multiple factors such as the relative casing motion and the wide range of variable incidence angles. The development of experimental methods which can accurately model the real turbine environment and influencing factors is of great significance to study the squealer tip leakage flow mechanism. In the present paper, a low-speed turbine cascade test faci...     

外挂式飞机定位系统在型号试飞中的运用

飞机定位数据在诸多试飞任务中不可或缺.为实现飞机定位系统易于在机上装卸且精度足够,提出了一种先进的外挂式飞机定位系统的技术解决方案,同时凝炼出外挂式飞机定位系统的运用程序,且在差分定位解算时,优选载波相位定位方法(差分法),从而确保系统拥有较高的定位精度.该系统已成功运用于诸如雷达精度考核等型号试飞任务,满足用户较高标...     

Fast calibration of between-receiver GPS/Galileo/BDS differential phase bias with millimeter accuracy based on short baseline mode

The differential code and phase biases induced by the receiver hardware (including receiver, antenna, firmware, etc.) of the Global Navigation Satellite System (GNSS) have significant effects on precise timing and ionosphere sensing, thus deserve careful treatment. In this contribution, we propose an approach to fast fix the single-difference ambiguity to finally obtain the unbiased estimates of between-receiver differential phase bias (BR-DPB) and between-receiver differential code-phase bias (BR-DCPB) based on the short baseline mode. The key to this method is that the error sources can be significantly eliminated due to the length of the baseline is very short. At the same time, the empirical constraints and random characteristics of BR-DPB/BR-DCPB were considered, which is conducive to the resolution of single-difference ambiguity. Several sets of GNSS data (GPS L1/L2, Galileo E1/E5b, and BDS B1/B3), recorded by the short baselines in an interval of 30 s and covered a broad range of receiver/antenna types (JAVA, SEPT, LEIC, and TRIM), were used to verify the effectiveness of the proposed method. The numerical tests show that the proposed method is capable of fast fixing the single-difference ambiguity successfully within a few epochs and then providing the unbiased estimates of BR-DPB and BR-DCPB in an epoch-by-epoch manner. Experiments show that the estimated BR-DPB is in millimeter accuracy, which is of great significance for the millimeter-accuracy phase time transfer and ionospheric delay estimation. Furthermore, the calibrated BR-DPB/BR-DCPB can be treated as the known products for long-distance precise timing and ionosphere sensing based on the inter-station single-difference model.     

Fuzzy energy-based dual contours model for automated coronal hole detection in SDO/AIA solar disk images

The presence of coronal holes in solar disk plays an important role in influencing the space weather and generation of the solar wind. As such there lies a requirement in proper study and prediction of coronal holes occurs in the solar disk. This, in turn, arises the necessity of detection of coronal holes present in the solar disk. In this work, a Hough transformed inspired fuzzy-energy simulated dual contours-based segmentation technique has been proposed for the detection and extraction of holes in solar disk. In the proposed method Hough transform has been induced to initialize the contour for the contour-based method of segmentation. In the algorithm, two contours (active and static) have been initiated and made to evolve based on the energy function by incorporating the gray-scale intensity. Here in the work one contour is made to deform its shape while the other contour is kept static for the coronal holes detection purpose. The experiment has been carried out on few benchmark datasets and the corresponding outcomes have been compared with the results of other existing algorithms. The comparison results highlight the performance of the proposed technique in detection of coronal holes in solar disk.     

一种新型铁电移相器材料的第一性原理计算

铁电薄膜移相器是基于铁电材料的新型移相器,被广泛应用于相控阵天线中。对于这类移相器组成材料的性能改进一直是雷达系统在军事、航天等领域的研究热点之一。基于第一性原理密度泛函理论,综合分析了ABi₂Nb₂O₉(A=Ba, Pb, Sr, Ca)材料的电子属性、化学键和极化属性。结果表明:这种体系有着类似的铁电性起源；Nb—O和Bi—O间的杂化对于系统的畸变和铁电相的稳定起着重要作用；随着A位离子半径的增大,体系的畸变参数也随之增大,导致材料有更大的自发极化,增强了铁电移相器的性能。实验结果验证了理论计算的正确性,为新型铁电移相器的研发奠定了基础。     

Integrated method of guidance,control and morphing for hypersonic morphing vehicle in glide phase

The morphing technology of hypersonic vehicle improved the flight performance by changing aerodynamic characteristics with shape deformations, but the design of guidance and control system with morphing laws remained to be explored. An Integrated of Guidance, Control and Morphing (IGCM) method for Hypersonic Morphing Vehicle (HMV) was developed in this paper. The IGCM method contributed to an effective solution of morphing characteristic to improve flight performance and reject the disturbance for guidance and control system caused by the morphing system for HMV in gliding phase. The IGCM models were established based on the motion models and aerodynamic models of the variable span vehicle. Then the IGCM method was designed by adaptive block dynamic surface back-stepping method with stability proof. The parallel controlled simulations’ results showed the effectiveness in accomplishing the flight mission of IGCM method in glide phase with smaller terminal errors. The velocity loss of HMV was reduced by 32.8% which inferred less flight time and larger terminal flight velocity than invariable span vehicle. Under the condition of large deviations of aerodynamic parameters and atmospheric density, the robustness of IGCM method with variable span was verified.     

小数偏差产品质量评估及固定性能分析

为了评估不同小数偏差产品的数据质量和模糊度固定效果，比较了2016年全年的SGG FCB产品和CNES产品，结果表明两种产品具有很高的一致性，SGG FCB产品的数据完整性更好。应用两种产品进行精密单点定位(PPP)固定解的静态结果平面位置精度可以达到1 cm以内，高程位置精度可以达到1~2 cm，采用两种产品获得的PPP模糊度固定率十分接近，动态模式下处理静态数据的位置结果可以达到平面2~3 cm，高程5 cm以内的精度，两组固定解的位置误差结果差异不超过5 mm，模糊度固定成功率分别为92.37%和92.14%，两种小数偏差产品在23分钟左右完成首次固定，能够有效提高PPP的收敛速度。使用两种小数偏差产品得到的机载动态数据结果也非常相近。