ALBERT

Description: The ionosphere scale height is one of the most significant ionospheric parameters, which contains information about the ion and electron temperatures and dynamics in upper ionosphere. In this paper, an empirical orthogonal function (EOF) analysis method is applied to process all the ionospheric radio occultations of GPS/COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) from the year 2007 to 2011 to reconstruct a global ionospheric scale height model. This monthly medium model has spatial resolution of 5° in geomagnetic latitude (-87.5° ~ 87.5°), and temporal resolution of 2 hours in local time. EOF analysis preserves the characteristics of scale height quite well in the geomagnetic latitudinal, anural, seasonal and diurnal variations. In comparison with COSMIC measurements of the year of 2012, the reconstructed model indicates a reasonable accuracy. In order to improve the topside model of International Reference Ionosphere (IRI), we attempted to adopt the scale height model in the Bent topside model by applying a scale factor q as an additional constraint. With the factor q functioning in the exponent profile of topside ionosphere, the IRI scale height should be forced equal to the precise COSMIC measurements. In this way, the IRI topside profile can be improved to get closer to the realistic density profiles. Internal quality check of this approach is carried out by comparing COSMIC realistic measurements and IRI with or without correction respectively. In general, the initial IRI model overestimates the topside electron density to some extent, and with the correction introduced by COSMIC scale height model, the deviation of vertical total electron content (VTEC) between them is reduced. Furthermore, independent validation with Global Ionospheric Maps (GIM) VTEC implies a reasonable improvement in the IRI VTEC with the topside model correction.

Description: Author(s): X. L. Xu, C.-H. Pai, C. J. Zhang, F. Li, Y. Wan, Y. P. Wu, J. F. Hua, W. Lu, W. An, P. Yu, C. Joshi, and W. B. Mori Ionization injection is attractive as a controllable injection scheme for generating high quality electron beams using plasma-based wakefield acceleration. Because of the phase-dependent tunneling ionization rate and the trapping dynamics within a nonlinear wake, the discrete injection of electrons … [Phys. Rev. Lett. 117, 034801] Published Fri Jul 15, 2016

Description: Increasing total electron content (TEC) measurements from the low earth orbiting (LEO) satellites to Global Positioning System (GPS) satellites flourish the exploration of the ionosphere and plasmasphere for decades. This paper indicates a method that 3-D Var is applied to assimilate precise orbit determination (POD) antenna TEC measurements of Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites into the background Global Core Plasma Model (GCPM). The slant TEC data archived in the COSMIC Data Analysis and Archive Center (CDAAC) from 500 km to 20,200 km are used to reconstruct a new electron density model. This model has temporal resolution of 2 hours and spatial resolution of 2.5° in geomagnetic latitude, 5° in longitude, 50 km in the upper ionosphere and several hundred kilometers in the plasmasphere. Preliminary results show that the data assimilation modifies the initial GCPM forecast to be better coincident with actual COSMIC measurements in internal quality check. Furthermore, independent validation with upper ionosphere retrieved electron density, and TEC of Global Ionosphere Maps (GIM) implies a reasonable improvement in the estimation of plasmaspheric electron density after the assimilation.

Description: Author(s): J. Shan, W. Shi, L. Y. Liu, Y. R. Shen, and L. Xu Gold nanoparticles deposited on the windows of a liquid crystal (LC) cell were found to be able to reduce the surface anchoring energy of the LC, and hence the threshold for its reorientation phase transition, by 1 to 2 orders of magnitude when a cw pump light was used to excite the local plasmon re... [Phys. Rev. Lett. 109, 147801] Published Tue Oct 02, 2012

Description: Cracks are widely developed along the edge of loess platforms in NW China. Field surveys reveal that these cracks can be grouped into shallow and deeply penetrating ones. The former occur at a small distance from platform edge, normally penetrate into the top unsaturated loess with the penetration depth being controlled by the joints in loess. The latter penetrate deeper into the saturated loess farther away from the platform edge. These cracks control the inflow and drainage of irrigation water. The shallow penetrating crack can fail as a slide or fall with a volume of up to hundreds of cubic meters. The deeply penetrating crack can fail as a flow-like landslide with a volume of thousands of cubic meters or more. A full-scale field test simulating irrigation on the platform surface was conducted. The two types of crack can be interconnected so that the water applied in the test finally flowed into the deep crack and was discharged from the platform. Analysis of soil stress states and the results of field test show that the deeply-penetrating cracks could have both positive as well as negative effects on slope stability. On the one hand, water can flow more freely in the cracks, and the loess could be saturated and triggered landslide. On the other hand, the water can drain more easily along the crack and slope stability could be enhanced as the groundwater level is suppressed. Copyright © 2012 John Wiley & Sons, Ltd.

Description: Author(s): J. D. Mar, J. J. Baumberg, X. L. Xu, A. C. Irvine, and D. A. Williams We demonstrate electrical control of the neutral exciton fine-structure splitting in a single InAs/GaAs self-assembled quantum dot by significantly reducing the splitting to near zero through the application of a vertical electric field in the fast electron tunneling regime. This is verified by perf… [Phys. Rev. B 93, 045316] Published Wed Jan 27, 2016

Description: Author(s): J. D. Mar, X. L. Xu, J. J. Baumberg, F. S. F. Brossard, A. C. Irvine, C. Stanley, and D. A. Williams We present bias-dependent micro-photoluminescence (μ-PL) spectroscopy of the neutral (X^{0} ) and singly negatively-charged (X^{-} ) excitons in single InAs/GaAs self-assembled quantum dots (QDs) embedded in the intrinsic region of an n-i-Schottky diode based on a two-dimensional electron gas (2DEG... [Phys. Rev. B 83, 075306] Published Mon Feb 14, 2011

Description: Author(s): X. L. Xu, J. F. Hua, F. Li, C. J. Zhang, L. X. Yan, Y. C. Du, W. H. Huang, H. B. Chen, C. X. Tang, W. Lu, P. Yu, W. An, C. Joshi, and W. B. Mori The evolution of beam phase space in ionization injection into plasma wakefields is studied using theory and particle-in-cell simulations. The injection process involves both longitudinal and transverse phase mixing, leading initially to a rapid emittance growth followed by oscillation, decay, and a... [Phys. Rev. Lett. 112, 035003] Published Thu Jan 23, 2014

Description: Author(s): A. Manchon, Q. Li, L. Xu, and S. Zhang Laser-induced demagnetization is theoretically studied by explicitly taking into account interactions among electrons, spins, and lattice. Assuming that the demagnetization processes take place during the thermalization of the subsystems, the temperature dynamics is given by the energy transfer betw... [Phys. Rev. B 85, 064408] Published Fri Feb 17, 2012

Description: Cracks are widely developed along the edge of loess platforms in NW China. Field surveys reveal that these cracks can be grouped into shallow and deeply penetrating ones. The former occur at a small distance from platform edge, normally penetrate into the top unsaturated loess with the penetration depth being controlled by the joints in loess. The latter penetrate deeper into the saturated loess farther away from the platform edge. These cracks control the inflow and drainage of irrigation water. The shallow penetrating crack can fail as a slide or fall with a volume of up to hundreds of cubic meters. The deeply penetrating crack can fail as a flow-like landslide with a volume of thousands of cubic meters or more. A full-scale field test simulating irrigation on the platform surface was conducted. The two types of crack can be interconnected so that the water applied in the test finally flowed into the deep crack and was discharged from the platform. Analysis of soil stress states and the results of field test show that the deeply-penetrating cracks could have both positive as well as negative effects on slope stability. On the one hand, water can flow more freely in the cracks, and the loess could be saturated and triggered landslide. On the other hand, the water can drain more easily along the crack and slope stability could be enhanced as the groundwater level is suppressed. Copyright © 2012 John Wiley & Sons, Ltd.