镁铝富燃料推进剂燃烧残渣影响因素理论分析

用最小自由能法计算了镁铝富燃料推进剂一次燃烧室产物的成分,分析了凝聚相C、Mg和A l产物含量的变化对燃烧残渣的影响;主要探讨了AP含量、Mg/A l比例、HTPB粘合剂含量、燃烧室压强对凝聚相C、Mg、A l燃烧产物含量的影响。计算结果表明,增加AP含量、设计Mg/A l比小于3/5、减小HTPB粘合剂含量、降低燃烧室压强均能减少凝聚相产物含量,有利于降低燃烧残渣。燃气发生器实验结果表明,Mg/A l比例对燃烧残渣影响的实验数据与理论分析一致。     

N2O-C2H2火焰原子吸收光谱法测定纯镍中硅含量

为简化纯镍中硅含量的测定过程,提高测量精度,研究了一种N2O-C2H2火焰原子吸收光谱法用于检测。介绍了方法的原理、工作参数和测定条件,并确定最佳工作条件,讨论了燃烧温度、共存离子等干扰因素的影响。实验结果表明,该法的灵敏度高、干扰小、选择性和重现性好,操作简单,分析周期短。其测定结果的相对标准偏差均小于1.0%,标准加入回收率大于97.0%(样本数n=6),可满足实验室仪器分析质量与控制的要求。     

Topological defects and highest energy cosmic and gamma rays

In this paper we review the hypothesis that a substantial part of the cosmic ray flux observed above about 10¹⁹ eV may be produced by decaying or annihilating topological defects left over from phase transitions in the early universe at grand unification energy scales ( 10¹⁶ GeV). Possible signatures of cosmic ray producing defect models are discussed which could be tested experimentally in the near future. We thereby focus on model independent universal spectral properties of the predicted particle fluxes.     

Symmetry and asymmetry of ionospheric weather at magnetic conjugate points for two midlatitude observatories

Variations of the ionospheric weather W-index for two midlatitude observatories, namely, Grahamstown and Hermanus, and their conjugate counterpart locations in Africa are studied for a period from October 2010 to December 2011. The observatories are located in the longitude sector, which has consistent magnetic equator and geographic equator so that geomagnetic latitudes of the line of force are very close to the corresponding geographic latitudes providing opportunity to ignore the impact of the difference of the gravitational field and the geomagnetic field at the conjugate points on the ionosphere structure and dynamics. The ionosondes of Grahamstown and Hermanus provide data of the critical frequency (foF2), and Global Ionospheric Maps (GIM) provide the total electron content (TECgps) along the magnetic field line up to the conjugate point in the opposite hemisphere. The global model of the ionosphere, International Reference Ionosphere, extended to the plasmasphere altitude of 20,200 km (IRI-Plas) is used to deliver the F2 layer peak parameters from TECgps at the magnetic conjugate area. The evidence is obtained that the electron gas heated by day and cooled by night at the summer hemisphere as compared with the opposite features in the conjugate winter hemisphere testifies on a reversal of plasma fluxes along the magnetic field line by the solar terminator. The ionospheric weather W-index is derived from NmF2 (related with foF2) and TECgps data. It is found that symmetry of W-index behavior in the magnetic conjugate hemispheres is dominant for the equinoxes when plasma movement along the magnetic line of force is imposed on symmetrical background electron density and electron content. Asymmetry of the ionospheric storm effects is observed for solstices when the plasma diffuse down more slowly into the colder winter hemisphere than into the warmer summer hemisphere inducing either plasma increase (positive phase) or decrease (negative phase of W-index) in the ionospheric and plasmaspheric plasma density.     

Deformation of the ionosphere structure during the space weather events on October–November 2003

We present the spatial maps of the ionosphere–plasmasphere slab thickness τ (ratio of the vertical total electron content, TEC, to the F-region peak electron density, NmF2) during the intense ionospheric storms of October–November 2003. The model-assisted technology for estimate of the upper boundary of the ionosphere, hup, from the slab thickness components in the bottomside and topside ionosphere – eliminating the plasmasphere contribution of τ – is applied at latitudes 35° to 70°N and longitudes −10° to 40°E, from the data of 20 observatories of GPS-TEC and ionosonde networks, for selected days and hours of October and November 2003. The daily–hourly values of NmF2, hmF2 and TECgps are used as the constrained parameters for the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, during the ionospheric quiet days, positive and negative storm phases for estimate of τ and hup. Good correlation has been found between the slab thickness and the upper boundary of the ionosphere for the intense ionospheric storms at October–November 2003. During the negative phase of the ionospheric storm, when the ionospheric plasma density is exhausted, the nighttime upper boundary of the ionosphere is greatly uplifted towards the magnetosphere tail, while the daytime upper boundary of the ionosphere is reduced below 500 km over the Earth.     

H型球粒陨石TL灵敏度与冲击相和钾含量的研究

测定了坠落在我国武安、枣阳、信阳等地的10个H型球粒陨石的热释光(TL)灵敏度、自然热释光峰温和峰半高宽温度,同时对它们的K含量进行了测定.将测得的H型球粒陨石的TL灵敏度与它们的钾含量和所属冲击相进行比较.结果表明,H型球粒陨石的TL灵敏度与其钾含量和冲击相之间存在着规律性的关系.      

On the detection of anomalous seismo-ionospheric behavior in the presence of space weather stimuli for large earthquakes

Anomalous behavior of ionospheric total electron content (TEC) prior to earthquake has been observed in many studies. Evidence of such seismo-ionospheric coupling effects suggests that it is plausible to rely on TEC signatures for early earthquake warning. However, the detection of pre-earthquake TEC anomalies (PETA) has not been adopted in practice due to two pertinent issues. Firstly, the effects of space weather activity can affect TEC levels and cause anomalous behavior in the TEC. Usually arbitrary thresholds are set for space weather indices to eliminate TEC anomaly due to space weather effects. Secondly, the choice regarding moving time-window length used to characterise background variation of TEC within the statistical envelope approach has an effect on detection of PETA. While the rule-of-thumb in selecting the moving window length is to have a time window capable of capturing background variability and short-term fluctuations, the length of the time window used in the literature varies with little justification. In this study, a critical examination is conducted on the statistical envelope approach and in particular, to eliminate the effect of space weather activity without the use of arbitrary space indices to detect PETA. A two-part PETA identification procedure is proposed, consisting of wavelet analyses isolating non-earthquake TEC contributions, followed by the statistical envelope method using a moving window length standardized based on observed periodicities and statistical implications is suggested. The approach is tested on a database of 30 large earthquakes (M?≥?7.0). The proposed procedure shows that PETA can be detected prior to earthquakes at higher confidence levels without the need to separately check for space weather activity. More importantly, the procedure was able to detect PETA for studies where it was previously reported that PETA could not be detected or detected convincingly.     

Differential code bias estimation based on uncombined PPP with LEO onboard GPS observations

Differential Code Bias (DCB) is an essential correction that must be provided to the Global Navigation Satellite System (GNSS) users for precise position determination. With the continuous deployment of Low Earth Orbit (LEO) satellites, DCB estimation using observations from GNSS receivers onboard the LEO satellites is drawing increasing interests in order to meet the growing demands on high-quality DCB products from LEO-based applications, such as LEO-based GNSS signal augmentation and space weather research. Previous studies on LEO-based DCB estimation are usually using the geometry-free combination of GNSS observations, and it may suffer from significant leveling errors due to non-zero mean of multipath errors and short-term variations of receiver code and phase biases. In this study, we utilize the uncombined Precise Point Positioning (PPP) model for LEO DCB estimation. The models for uncombined PPP-based LEO DCB estimation are presented and GPS observations acquired from receivers onboard three identical Swarm satellites from February 1 to 28, 2019 are used for the validation. The results show that the average Root Mean Square errors (RMS) of the GPS satellite DCBs estimated with onboard data from each of the three Swarm satellites using the uncombined PPP model are less than 0.18 ns when compared to the GPS satellite DCBs obtained from IGS final daily Global Ionospheric Map (GIM) products. Meanwhile, the corresponding average RMS of GPS satellite DCBs estimated with the conventional geometry-free model are 0.290, 0.210, 0.281 ns, respectively, which are significantly larger than those obtained with the uncombined PPP model. It is also noted that the estimated GPS satellite DCBs by Swarm A and C satellites are highly correlated, likely attributed to their similar orbit type and space environment. On the other hand, the Swarm receiver DCBs estimated with uncombined PPP model, with Standard Deviation (STD) of 0.065, 0.037 and 0.071 ns, are more stable than those obtained from the official Swarm Level 2 products with corresponding STD values of 0.115, 0.101, and 0.109 ns, respectively. The above indicates that high-quality DCB products can be estimated based on uncombined PPP with LEO onboard observations.     

Near real-time PPP-based monitoring of the ionosphere using dual-frequency GPS/BDS/Galileo data

Ionosphere delay is very important to GNSS observations, since it is one of the main error sources which have to be mitigated even eliminated in order to determine reliable and precise positions. The ionosphere is a dispersive medium to radio signal, so the value of the group delay or phase advance of GNSS radio signal depends on the signal frequency. Ground-based GNSS stations have been used for ionosphere monitoring and modeling for a long time. In this paper we will introduce a novel approach suitable for single-receiver operation based on the precise point positioning (PPP) technique. One of the main characteristic is that only carrier-phase observations are used to avoid particular effects of pseudorange observations. The technique consists of introducing ionosphere ambiguity parameters obtained from PPP filter into the geometry-free combination of observations to estimate ionospheric delays. Observational data from stations that are capable of tracking the GPS/BDS/GALILEO from the International GNSS Service (IGS) Multi-GNSS Experiments (MGEX) network are processed. For the purpose of performance validation, ionospheric delays series derived from the novel approach are compared with the global ionospheric map (GIM) from Ionospheric Associate Analysis Centers (IAACs). The results are encouraging and offer potential solutions to the near real-time ionosphere monitoring.     

Temporal evolution analysis of storm-enhanced density during an intense magnetic storm on March 2015

An intense Storm Enhancement Density (SED) event with the magnetic storm occurred on 17–24 March 2015 has been investigated. The morphological character of the SED during different phase of the magnetic storm is examined and compared with the non-storm time. Three intensity indexes, i.e., “general” SED index, “heavy” SED index and “severe” SED index, are defined to represent the intensity of SED respectively represented by the numbers of the ionospheric total electron content (TEC) grids with TEC > 60 TECu, TEC > 80 TECu and TEC > 100 TECu. The temporal evolution of the SED intensity indexes during a time span covering the non-storm time and the magnetic storm time have also been investigated. The SED exhibits a shape with two parallel slender troughs in the middle and low latitudes during the non-storm time and then gradually develops into an ellipse structure as the development of magnetic storm. The intensity of SED and the fluctuation of the TEC evolution are generally corresponding to the fluctuation of Dst index. The analyzing results enrich our understanding of the temporal and spatial evolution of the ionospheric SED.