A possible flyby anomaly for Juno at Jupiter

In the last decades there have been an increasing interest in improving the accuracy of spacecraft navigation and trajectory data. In the course of this plan some anomalies have been found that cannot, in principle, be explained in the context of the most accurate orbital models including all known effects from classical dynamics and general relativity. Of particular interest for its puzzling nature, and the lack of any accepted explanation for the moment, is the flyby anomaly discovered in some spacecraft flybys of the Earth over the course of twenty years. This anomaly manifest itself as the impossibility of matching the pre and post-encounter Doppler tracking and ranging data within a single orbit but, on the contrary, a difference of a few mm/s in the asymptotic velocities is required to perform the fitting.Nevertheless, no dedicated missions have been carried out to elucidate the origin of this phenomenon with the objective either of revising our understanding of gravity or to improve the accuracy of spacecraft Doppler tracking by revealing a conventional origin.With the occasion of the Juno mission arrival at Jupiter and the close flybys of this planet, that are currently been performed, we have developed an orbital model suited to the time window close to the perijove. This model shows that an anomalous acceleration of a few mm/s² is also present in this case. The chance for overlooked conventional or possible unconventional explanations is discussed.     

A critique of reliability prediction techniques for avionics applications

Avionics (aeronautics and aerospace) industries must rely on components and systems of demonstrated high reliability. For this, handbook-based methods have been traditionally used to design for reliability, develop test plans, and define maintenance requirements and sustainment logistics. However, these methods have been criticized as flawed and leading to inaccurate and misleading results. In its recent report on enhancing defense system reliability, the U.S. National Academy of Sciences has recently discredited these methods, judging the Military Handbook (MIL-HDBK-217) and its progeny as invalid and inaccurate. This paper discusses the issues that arise with the use of handbook-based methods in commercial and military avionics applications. Alternative approaches to reliability design (and its demonstration) are also discussed, including similarity analysis, testing, physics-of-failure, and data analytics for prognostics and systems health management.     

全面视角下“法律面前人人平等原则”的探讨

本文以全面视角审视了法律面前人人平等是什么，并就我们为什么需要法律面前人人平等原则，以及如何实现法律面前人人平等等问题进行了探讨。     

基于华氏宏观经济数学模型的高等职业教育动态投入产出模型

伴随着经济的发展和产业结构的变化,高等职业教育越来越受重视,高职教育的投入产出关系也引起了人们的关注。通过分析高职教育的投入产出关系,应用华氏宏观经济数学模型建立了高等职业教育动态投入产出模型。它对分析高职教育各项投入的效率具有实际意义。     

Fringe fitting and group delay determination for geodetic VLBI observations of DOR tones

Extracting the group and phase delays of interferometric observations produced in the Very Long Baseline Interferometry (VLBI) measurement concept requires a special fringe fitting and delay search algorithm for the recorded bandwidth. While fringe fitting is in use routinely for several megahertz wide channels in geodetic and astrometric VLBI with quasar observations, fringe fitting for artificial tones of very small bandwidth of artificial signals for Differential One-way Ranging (DOR) requires a different way of handling. In a project called Observing the Chang’E-3 Lander with VLBI (OCEL), the DOR tones emitted by the Chang’E-3 lander were observed in a standard geodetic VLBI mode with 8 or 4?MHz wide channels to maintain compatibility with the corresponding quasar observations. For these observations, we modified the existing fringe fitting program of the Haystack Observatory Processing Software (HOPS), fourfit, to properly handle narrow band DOR tones. The main motivations are that through this modification, the data of quasars and artificial radio sources can be processed in the existing geodetic analysis pipeline, and that the algorithm can be used for similar projects as well. In this paper, we describe the algorithm and show that the new algorithm produces much more reliable group delay results than using the standard fourfit algorithm. This is done by a simulation test and in particular by processing of real observations. It is shown that in many cases, systematic deviations of several nanoseconds, which are seen with the standard fourfit algorithm, can be avoided. The ultimate benefit of the new procedure is demonstrated by reducing the errors in delay triangle closures by at least a factor of 3, which, in the OCEL case, is from ～300 to ～100?ps.     

月面无人自主采样返回任务动力下降点确定及验证

动力下降点确定是实施月面软着陆的重要环节，是多系统间复杂迭代的过程，涉及轨道设计、制导律设计、着陆目标的采样区确定、着陆及起飞安全分析。其设计结果直接影响了最终着陆点的位置和着陆过程的着陆安全，也间接影响采样安全和采样工程目标的实现结果。针对嫦娥五号在实施月面软着陆前确定动力下降点的任务需求，提出了通过多次轨道控制与最优标称制导轨迹搜索联合控制策略的动力下降点确定方法。首先，根据月面无人自主采样返回任务设计总结了动力下降点确定原理和约束条件；然后，详细论述了月面无人自主采样返回任务软着陆过程动力下降点确定方法；最后，通过嫦娥五号在着陆前主要的几次轨控实施结果分析了其对动力下降点的影响，同时综合了着陆区地形分析及着陆、起飞安全性分析，对动力下降点进行确定并根据最终在轨飞行结果进行验证。验证结果表明，基于“逐次逼近寻优方法”的月面软着陆环节动力下降点的确定方法有效，可以为后续地外天体软着陆等任务提供参考和借鉴。     

飞机健康状况量化分析方法浅析

提出与飞机健康状况相关的事件参数、风险参数的概念，具体阐述了建立量化模型的思路和方法。该方法简单可靠，具有较强的可扩展性，可为飞机的技术派遣提供决策支持。     

Some peculiarities of longitudinal distribution of proton fluxes at high latitudes

Dynamical features of proton fluxes at high and middle latitudes were studied based on data measured by Sun-synchronous low-altitude (800 km height) polar-orbiting three NOAA series satellites: POES 15, 16, and 17 during the geomagnetic storm on January, 21–22, 2005. Data from three satellites that passed the Northern hemisphere along different MLTs allow reconstructing the longitudinal distribution of the proton fluxes. Measurements of protons with energies of 30–80 keV and 80–240 keV (the ring current energy range) by 0- and 90-detectors were used to evaluate and compare the longitudinal asymmetry of proton flux distribution measured in the regions equatorward and poleward of the isotropic boundary. It was found that during all the phases of the geomagnetic storm distribution of the maximum flux of precipitating protons (0-detector data) is sufficiently asymmetric. The maximal flux position along MLT is moving from pre-midnight sector in quiet time to post-midnight one before and during SSC and moving back during recovery phase. The longitudinal distribution of precipitation maxima demonstrates the local increase in afternoon sector (approximately at 13:30 MLT) and decrease in the dusk one during SSC. These features are evident consequence of the magnetosphere compression. To identify the origin of the particles, the locations of maximum fluxes have been projected to the magnetosphere. It was determined that during geomagnetic storm main and recovery phases maximum fluxes were measured at latitudes poleward of the isotropic boundary. To evaluate the trapped particle flux asymmetry, the particle fluences (90-detector data) were calculated along the satellite orbit from L = 2 to the isotropic boundary. The total fluences of trapped particles calculated along the satellite orbit show regular asymmetry between dusk and dawn during main and recovery phases. The maximal intensity of proton fluxes of both investigated populations located poleward and equatorward of the isotropic boundary is achieved during SSC. The total flux measured during crossing the anisotropic region can be considered as a proxy for ring current injection rate.     

A data-driven health indicator extraction method for aircraft air conditioning system health monitoring

Prognostics and Health Management (PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model, one of the challenges for airborne system health monitoring is to find an appropriate health indicator that is highly related to the actual degradation state of the system. This paper proposed a novel health indicator extraction method based on the available sensor parameters for the health monitoring of Air Conditioning System (ACS) of a legacy commercial aircraft model. Firstly, a specific Airplane Condition Monitoring System (ACMS) report for ACS health monitoring is defined. Then a non-parametric modeling technique is adopted to calculate the health indicator based on the raw ACMS report data. The proposed method is validated on a single-aisle commercial aircraft widely used for short and medium-haul routes, using more than 6000 ACMS reports collected from a fleet of aircraft during one year. The case study result shows that the proposed health indicator can effectively characterize the degradation state of the ACS, which can provide valuable information for proactive maintenance plan in advance.     

载机武器舱盖表面压力计算研究

对带有内埋武器舱盖的载机,采用结构重叠网格方法保证各舱盖与载机网格质量,通过求解三维定常、非定常Navier-Stokes方程,得到内埋武器舱盖开启过程的静态、动态复杂流场,分析了内埋舱盖开启过程中其内外壁的气动特性,通过分析发现内外壁分布压力变化各有特点,动态压力分布居于静态压力分布包络中,舱盖结构强度设计宜采取"动-静结合"方式。