Recent ozone investigations over Bulgaria by remote sensing: Ground-based and satellite data

This presentation deals with the recent investigations of the dynamics of the total ozone content (TOC) and of the lower troposphere ozone over Bulgaria, South-Eastern Europe.     

Estimation and analysis of GPS receiver differential code biases using KGN in Korean Peninsula

The total electron content (TEC) estimation by the Global Positioning System (GPS) can be seriously affected by the differential code biases (DCB), referred to as inter-frequency biases (IFB), of the satellite and receiver so that an accuracy of GPS–TEC value is dependent on the error of DCBs estimation. In this paper, we proposed the singular value decomposition (SVD) method to estimate the DCB of GPS satellites and receivers using the Korean GPS network (KGN) in South Korea. The receiver DCBs of about 49 GPS reference stations in KGN were determined for the accurate estimation of the regional ionospheric TEC. They obtained from the daily solution have large biases ranging from +5 to +27 ns for geomagnetic quiet days. The receiver DCB of SUWN reference station was compared with the estimates of IGS and JPL global ionosphere map (GIM). The results have shown comparatively good agreement at the level within 0.2 ns. After correction of receiver DCBs and knowing the satellite DCBs, the comparison between the behavior of the estimated TEC and that of GIMs was performed for consecutive three days. We showed that there is a good agreement between KASI model and GIMs.     

Change in refractivity of the atmosphere and large variation in TEC associated with some earthquakes,observed from GPS receiver

The present study reports the analysis of GPS based TEC for our station Surat (21.16°N, 72.78°E) located at the northern crest of equatorial anomaly region in India at times close to some earthquake events (M ? 5) during the year 2009 in India and its neighbouring regions. The TEC data used in the study are obtained from GPS Ionospheric Scintillation and TEC Monitoring (GISTM) system. The TEC data has been analysed corresponding to 11 earthquakes in low solar activity period and quiet geomagnetic condition. We found that, out of 11 cases of earthquakes (M > 5) there were seven cases in which enhancement in TEC occurred on earthquake day and in other four cases there was depletion in TEC on earthquake day. The variation in refractivity prior to earthquake was significant for the cases in which the epicentre lied within a distance of 600 km from the receiving station. By looking into the features on temporal enhancement and depletion of TEC a prediction was made 3–2 days prior to an earthquake (on 28 October 2009 in Bhuj – India). The paper includes a brief discussion on the method of potentially identifying an impending earthquake from ionospheric data.     

神舟3号返回舱内的LET分布及吸收剂量

为了测量进入航天器舱内重电离粒子引起的辐射剂量,在神舟3号返回舱的内壁上安装了一个由CR-39片和铝片叠合组成的固体核径迹探测器.对回收的CR-39片进行化学蚀刻处理后,进行扫描并测量了由重电离粒子在CR-39片上形成的径迹斑.参照由重离子加速器的各种离子给出的标定值,在扣除由地面对照样本提供的本底值后,得出了返回舱内的线性能量传递（LET）值的分布,线性能量传递大于探测器记录阈值的总吸收剂量和总等效剂量,以及总等效剂量随屏蔽物厚度的变化.     

木星系探测中多层材料的辐射屏蔽优化设计方法

与地球辐射环境相比,木星辐射带中的粒子辐射环境有能量高、通量大、能谱硬等特点,对木星探测器的辐射防护要求更高。航天器设计中常用的多层金属材料的防护效果取决于辐射环境、屏蔽层数量与厚度、屏蔽层叠放顺序等众多因素,因此采用数值方法进行设计十分困难,有必要开发智能屏蔽优化算法。文章结合遗传算法和MULASSIS多层屏蔽仿真程序,以屏蔽后的吸收剂量为优化目标,开发了多层材料辐射防护优化设计方法。利用该方法,得到一定重量指标约束下的最优屏蔽结构,其特点是将高低原子序数材料相结合,多为双层或三层结构,并把高原子序数材料放置在外侧。以远木点和近木点分别为25个和10个木星半径的赤道面轨道为例,当面密度为1 g/cm2时,最优屏蔽结构为0.829 mm铅和0.158 mm镁的双层结构,可将辐射造成的总剂量降低至120.3 krad(Si)/a,与传统铝屏蔽材料相比,可节省近43.6%的重量资源。本方法可用于指导未来木星探测的辐射防护设计。     

Experimental investigation of flow and distortion mitigation by mechanical vortex generators in a coupled serpentine inlet-turbofan engine system

The performance of compact,aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow distortions at the duct exit.An experimental investigation was conducted to study the flow field and passive suppression of flow separation and Aerodynamic Interface Plane (AIP) distortion in a serpentine air inlet duct.Tests were performed by a turbofan engine at several Engine Ope...     

Simulation of plasma behavior for medium propellant mass and pulsed energy of small scale pulsed inductive thruster

The pulsed inductive thruster is characterized of no electrode corruption and wide propellant choice. To give insight into the propulsion mechanism of small scale thruster at different propellant mass(m) and energy(E) levels, the transient Magneto Hydro Dynamics(MHD) method,completed by high temperature thermodynamic and transport, and plasma electrical models, is developed to study argon plasma response under the excitation of current of high rise rate. By calculating the two-dimensional expans...     

紫外后向散射探测臭氧总量的反演误差研究

通过探测紫外后向散射获取臭氧总量目前已经成为臭氧总量探测的主要方法之一. 本文以模拟计算为主要方法, 从模式计算误差, 反演算法误差和仪器误差三方面着手, 对影响臭氧总量反演精度的各个参数进行分析研究, 并对由其引起的臭氧总量反演误差进行定量计算, 研究结果对臭氧总量反演精度的提高和实际观测资料的处理有着重要的指导意义.     

月球表面次级中子辐射环境仿真研究

由于缺少磁场和大气,宇宙线高能粒子轰击月壤可以形成月球特有的强中子辐射环境,并对航天员和电子设备造成潜在威胁。文章采用蒙特卡罗方法仿真研究宇宙线高能粒子辐射与月壤成分核反应产生的次级中子能谱特征,给出不同太阳活动、不同月壤深度下月球中子能谱特征和空间分布特征。仿真结果表明,宇宙线高能粒子导致的次级中子随着月壤深度的增加先增大后减小,大约在1 m深度达到最大值,深度越深银河宇宙线诱发的中子贡献越大。相关结果可为我国后续载人月球探测任务的辐射防护设计提供参考。     

Improved model of ionosphere variability and study for long-term statistical characteristics

Ionospheric variability is influenced by many factors, such as solar radiation, neutral atmosphere composition, and geomagnetic disturbances. Mainly characterized by the total electron content (TEC) and electron density, the climatology of the ionosphere features temporal and spatial changes. Establishing a multivariant regression model helps substantially in better understanding the ionosphere characteristics and their long-term variability. In this paper, an improvement of the existing ionosphere multivariate linear fitting regression model is proposed and investigated using data from both the ionosonde and the global ionosphere map (GIM) derived from ground-based Global Navigation Satellite System (GNSS) observations. The proposed method gives more consideration to the impact of the solar activity and adds modeling of the annual periodic fluctuations and half-year periodic fluctuations for the F10.7 index. The improved model is verified to have a better correlation with the real observations and can help reduce the calculation uncertainty. Moreover, the proposed model is used to evaluate the fitting accuracy of the GIMs produced by five authorized data analysis centers from the International GNSS Service (IGS). The results show that there is a fixing hole in the North America region for the GIM model where the correlation between the GIM and the proposed model always returns lower values compared to other places.