ALBERT

Description: EAST has been equipped with two high power lower hybrid current drive (LHCD) systems with operating frequencies of 2.45 GHz and 4.6 GHz. Comparative LHCD experiments with the two different frequencies were performed in the same conditions of plasma for the first time. It was found that current drive (CD) efficiency and plasma heating effect are much better for 4.6 GHz LH waves than for the one with 2.45 GHz. High confinement mode (H-mode) discharges with 4.6 GHz LHCD as the sole auxiliary heating source have been obtained in EAST and the confinement is higher with respect to that produced previously by 2.45 GHz. A combination of ray-tracing and Fokker-Planck calculations by using the C3PO/LUKE codes was performed in order to explain the different experimental observations between the two waves. In addition, the frequency spectral broadening of the two LH wave operating frequencies was surveyed by using a radio frequency probe.

Description: One-dimensional (1D) nanotubes of Nd 0.1 Bi 0.9 FeO 3 (NBFO) with an inner diameter of ∼50 nm were synthesized via sol-gel based electrospinning without template assistant. The phases, morphologies, crystalline structures, and magnetic properties of these 1D nanostructures were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and SQUID, respectively. It was found that the calcination condition plays a crucial role in determining the morphologies and the magnetic properties. Interestingly, these 1D NBFO nanotubes exhibit wasp-waisted magnetic hysteresis with a lower coercivity and larger saturation magnetization, which were prevalent in natural rocks and artificial composite materials. The origin of these wasp-waisted hysteresis loops was discussed.

Description: P-type Cu 2 O is a promising CMOS-compatible candidate to fabricate memristive devices for next-generation memory, logic and neuromorphic computing. In this letter, the microscopic switching and conducting mechanisms in TiW/Cu 2 O/Cu memristive devices have been thoroughly investigated. The bipolar resistive switching behaviors without an electro-forming process are ascribed to the formation and rupture of the conducting filaments composed of copper vacancies. In the low resistive state, the transport of electrons in the filaments follows Mott's variable range hopping theory. When the devices switch back to high resistive state, the coexistence of Schottky emission at the Cu/Cu 2 O interface and electron hopping between the residual filaments is found to dominate the conducting process. Our results will contribute to the further understanding and optimization of p-type memristive materials.

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: The description of quantum lidar in the presence of photon loss and phase noise is presented. Taylor series is directly exploited to expand the interference signal to separate the detected phase and the phase noise. The analytical expression of interference signal and its sensitivity are illustrated by binary outcome homodyne, parity photon counting, and zero-nonzero photon counting detection. Numerical calculation indicates that homodyne detection has the best sensitivity and resolution and should be considered as the optimal detection strategy for quantum lidar in the diffusion region of κ 〈 10 − 2 . However, parity detection should be the best detection scheme for resolution, and zero-nonzero detection represents the optimal detection for sensitivity in the rest region. Finally, zero-nonzero detection produces better sensitivity than parity detection.

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: We demonstrate the impacts of Ag doping on the local atomic structure of amorphous GeTe phase-change material. The variations of phonon vibrational modes, boding nature, and atomic structure are shown by Raman, X-ray photoelectron spectroscopy, and ab initio calculation. Combining the experiments and simulations, we observe that the number of Ge atoms in octahedral site decreases and that in tetrahedral site increases. This modification in local order of GeTe originating from the low valence element will affect the crystallization behavior of amorphous GeTe, which is verified by differential scanning calorimetry and transmission electron microscope results. This work not only gives the analysis on the structural change of GeTe with Ag dopants but also provides a method to enhance the thermal stability of amorphous phase-change materials for memory and brain-inspired computing applications.

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: 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: Biofuels from microalgae are potentially important sources of liquid renewable energy. Algae are not yet produced on a large scale, but research shows promising results. This study assesses the blue water footprint (WF) and land use of algae-based biofuels. It combines the WF concept with an energy balance approach to determine the blue WF of net energy. The study considers open ponds and closed photobioreactors (PBRs). All systems have a positive energy balance, ranging from output-input ratios between 1.13 and 1.98. This study shows that the WF of algae-based biofuels lies between 8 and 193 m 3 per GJ net energy provided. The land use of micro-algal biofuels ranges from 20 to 200 m 2 per GJ net energy. For a scenario in which algae-based biofuels provide 3.5% of the transportation fuels in the European Union in 2030, the system with the highest land productivity needs 3,300 km 2 to produce the 850 PJ per year. Producing all algae-based biofuels through the system with the highest water productivity, would lead to a blue WF of 7 Gm 3 per year, which is equivalent to 15% of the present blue WF in the EU28. However, a complete transition to algae-based transportation fuels will cause increased competition over water and land resources.