Fe ions of dose 8×1016 cm−2 are implanted into a ZnO single crystal at 180 keV. Annealing at 1073 K leads to the formation of zinc ferrite (ZnFe2O4), which is verified by synchrotron radiation X-ray diffraction (SR-XRD) and X-ray photoelectron spectroscopy (XPS). The crystallographically oriented ZnFe2O4 is formed inside the ZnO with the orientation relationship of ZnFe2O4 (111)//ZnO (0001). Superconducting quantum interference device (SQUID) measurements show that the as-implanted and post-annealing samples are both ferromagnetic at 5 K. The synthesized ZnFe2O4 is superparamagnetic, with a blocking temperature (TB = 25 K), indicated by zero field cooling and field cooling (ZFC/FC) measurements.
By implanting B+ and O+ ions respectively into polycarbonate (PC) plates, the sur-face mechanical properties of PC have been improved. Measurement by Nano IndenterⅡ showed that the hardness of samples increased 7-25 times than that before implan-tation; and the modulus of elasticity raised 2-5 times. The wear-resistance was testedby ball crusher; the width and depth of the wear-streak decreased by 1/3-1/2 or evenmore. The structure, deformation and appearance were analyzed by using Micro-FTIR Spectra, ESCA method and the steps instrument. These analyses showed thatthe structure of PC had been modified: a series of new cross-linking yielded, it de-pends on the Linear Energy Transition (LET) of implanted ions in the high polymercompounds.
The fluctuating magnetic helicity is considered an important parameter in diagnosing the characteristic modes of solar wind turbulence. Among them is the Alfvén-cyclotron wave, which is probably responsible for the solar wind plasma heating, but has not yet been identified from the magnetic helicity of solar wind turbulence. Here, we present the possible signatures of Alfvén-cyclotron waves in the distribution of magnetic helicity as a function of θVB, which is the angle between the solar wind velocity and local mean magnetic field. We use magnetic field data from the STEREO spacecraft to calculate the θVB distribution of the normalized reduced fluctuating magnetic helicity σm. We find a dominant negative σm for 1 s < p < 4 s (p is time period) and for θVB < 30° in the solar wind outward magnetic sector, and a dominant positive σm for 0.4 s < p < 4 s and for θVB>150° in the solar wind inward magnetic sector. These features of σm appearing around the Doppler-shifted ion-cyclotron frequencies may be consistent with the existence of Alfvén-cyclotron waves among the outward propagating fluctuations. Moreover, right-handed polarized waves at larger propagation angles, which might be kinetic Alfvén waves or whistler waves, have also been identified on the basis of the σm features in the angular range 40° < θVB < 140°. Our findings suggest that Alfvén-cyclotron waves (together with other wave modes) play a prominent role in turbulence cascading and plasma heating of the solar wind.
Lunar shallow subsurface structure is important in revealing the formation and evolution of the Moon. Therefore, a review of key issues in the lunar shallow subsurface structure will help deepen our understanding of the Moon. From a global perspective, lunar shallow subsurface structure is formed by endogenic and exogenic geological processes such as volcanic activities, tectonic activities, meteorite impacts, and space weathering. Its morphological characteristics and stratigraphic structure record the evolution of these geological processes. Recent lunar exploration missions have returned new samples and high-resolution data that have greatly enriched our knowledge. On the basis of reviewing the research progress of radar detection, crater-based excavation analysis, material inversion, and heat flow measurement, we also discuss the processes that contribute to the formation of the lunar shallow surface structure, such as volcanoes, impacts, tectonics, and space weathering. The main hot issues were sorted out and focused on 3 areas: transformation of lunar shallow subsurface structure by geological processes, environment and material composition of the lunar shallow surface structure, and physical properties of lunar shallow surface structure. Overall, existing research on the lunar subsurface has made significant progress, but it has also brought more new unsolved mysteries. It is necessary to introduce new applied payloads such as synthetic aperture radar (SAR), orbiter subsurface investigation radar (OSIR), or time-domain electromagnetic sounding (TDEM) to provide higher-resolution subsurface data, and develop better interpretation methodologies, to further deepen the understanding of the lunar shallow subsurface structure and indeed reveal the mechanism of lunar geological evolution.
Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4–5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne VIII is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne VIII is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.
The observational data of Magnetotelluric(MT) sounding is necessary to be corrected of distortion because of the effect of small,shallow,local inhomogeneous 3D body.The purpose of this research is to get more reliable regional geo-electric strike and MT sounding data under the assumption that the regional conductivity structure is 2D.We extended Groom-Bailey(GB) decomposition method under the constraints of phase tensor which was independent of local distortion from 'galvanic effect'.Subsurface conductivity information such as regional strike could be obtained from analysis of phase tensor,and which was considered as constraints to get better initial model for GB decomposition in order to improve the stability and reliability.In addition,different with traditional algorithm,we took anisotropy factor into the objective function and solved the optimization problem with Conjugate Gradient(CG) strategy.We added different Gaussian noise into synthetic data to test the sensitivity of each item in the initial model.The results showed that the reliability of GB decomposition of MT impedance tensor was strongly dependent on initial value of strike and impedance tensor.And the GB decomposition under the constraints of phase tensor was demonstrated to improve validity a lot.Moreover,the study showed GB algorithm with anisotropy factor performed well than the traditional way in terms of accuracy and computational cost,although there was no way to calculate the anisotropy parameters without any assumption.We compared decomposition results of our method with the classic multisite,multi-frequency way with real MT data from north-west china.And the results showed our study could get reliable conductivity analysis information.Further study into getting anisotropy parameters under special constraints is necessary.On the other hand,research of multisite,multi-frequency decomposition with the constraints from phase tensor should be further studied in relation to the too complicated statistical result when MT data is not good because of influence of noise.
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