Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract: The Neutral Atom Image System with High energetic particles (NAIS-H) developed for a Chinese mission of Magnetosphere Ionosphere and Thermosphere (MIT) capable to obtain the global map of the plasma distribution with a high temporal-spatial resolution in support this mission. The calibration of detector was an important technical task in the development, which is the fundamental basis of data analysis and inversions.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract: Long term high energy electron irradiation may affect performance of the Si-PIN semiconductor detector (SSD).In order to assess the life of the detector in space radiation environment, electron irradiation source was used to simulate space electron environment, and the irradiation experiments were carried out on the semiconductor detector. Experiment results show that under the radiation dose of 7.64×1014, the SSD’s energy response capability had not changed, and the counting efficiency slightly decreased. As the radiation dose increased, the leakage current of the SSD increased, but the noise was relatively stable, and the performance of the detector did not affect the work index of the load.
Peer Review Status:Awaiting Review
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract:镁作为一种典型的密排六方结构(Hexagonal Close-packed)金属,其枝晶形貌和生长取向受到多种因素的影响,目前针对镁合金中α-Mg 枝晶生长模型的描述以及多样性的起源等问题的研究都比较缺乏,基于此,本文综述了本课题组在镁合金凝固微观组织结构三维表征方面取得的研究成果。借助同步辐射X射线微观断层扫描技术以及相场数值模型,研究了镁合金凝固过程中α-Mg(X)枝晶生长选择多样性的形成机理以及固溶合金元素(Al,Ca,Zn 和Sn 等)、固溶元素含量(溶质浓度)等因素对α-Mg 枝晶生长选择和演化的影响。研究结果表明,固溶元素、固溶元素含量等因素都会对镁合金中α-Mg三维枝晶形貌和择优取向产生重要影响。在Mg-Ca和Mg-Al(hcp-fcc)合金中,枝晶倾向于以或为择优方向生长。在Mg-Sn(hcp-bct)合金中,等轴生长的枝晶沿着基面上和偏离基面的(X≈2)方向形成一种18次分支的结构,在Mg-Zn(hcp-hcp)合金中,α-Mg枝晶的择优取向会随着Zn含量的增加从方向朝偏离基面的方向发生连续转变,并在转变的过渡区,发现了超支化的藻状枝晶结构,其原因可能是高各向异性Zn元素的引入带来的固液界面自由能各向异性的变化。研究结果从一定程度上揭示了镁合金凝固过程α-Mg枝晶生长形貌和分支结构选择多样性的规律。同时基于快速X射线成像技术率先开展了镁合金凝固过程三维微观结构演化原位表征研究,并获得了Mg合金凝固过程三维枝晶的生长演化过程。
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract: By utilizing data obtained on Chinese satellite in the middle Earth orbit from solar activity descending phase to solar activity ascending phase, the properties of high energy electron environment in the middle Earth orbit are analyzed, such as spatial distribution, flux intensity, temporal variations, and response to geomagnetic storms. The investigating results indicate that the spatial distribution of high energy electron in the middle Earth orbit is stable;the fluxes of electrons decrease with energy increasing;the high energy electron environment is a dynamical system which disturbs evidently on different timescales;the evolvement of this system is stimulated by geomagnetic storms, but the correlation between the evolvement and the storms is nonlinear.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract: FY-3A satellite can measure the radiation dose data from different directions during the missions from 2008 to 2012. In this paper, we describe total radiation dose from two directions, and dose rate variation with energetic particle flux. The result shows that different sections of the spacecraft receive different amounts of radiation dose, which is always consistent with space distribution of energetic particles. Absorbed dose rate changed greatly from several rad (Si).d~(-1) during quite time to even more than tenfold during disturbances. The increased high energy electrons in polar regions during disturbances are responsible for significant increase of radiation dose. At last, FY-3A radiation dose during the operational period of the mission is compared with the results calculated by SPENVIS. It is obvious that observation data is more realistic to reflect the real space radiation environment.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract: This paper introduces the structure and working principle of the Neutral Atom Imaging System-High (NAIS-H) which is in the MIT project. Based on the testing needs of the instrument, we have designed ground test equipment, including the circuit system and the host computer system. In this paper, we show the structure and working principle of the ground test for NAIS-H, and tell structure and java programming of the sub modules of the host computer system in detail, such as API communicating system, data analyzing system and data saving system. At last, we test the equipment, and the result shows the ground test system has good performance and achieves the design requirement.
Peer Review Status:Awaiting Review