A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators

A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings

Electron acceleration associated with the magnetic flux pileup regions in the near-Earth plasma sheet: A multicase study

Using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we study electron acceleration (<30 keV) in the magnetic flux pileup regions (FPRs) in the near-Earth plasma sheet (X ~ –10 RE). We present three cases of FRPs associated with dipolarization fronts and substorm dipolarization. Based on the characteristics of the magnetic field, we defined the magnetic field enhancement region (MFER) as the magnetic field with significant ramp that is usually observed near the dipolarization front boundary layer. On the other side, the increased magnetic field without a significant ramp is the rest of a FPR. Our results show that betatron acceleration dominates for 10–30 keV electrons inside the MFER, whereas Fermi acceleration dominates for 10–30 keV electrons inside the rest of the FPR. Betatron acceleration is caused by the enhancement of the local magnetic field, whereas Fermi acceleration is related to the shrinking length of magnetic field line. These accelerated electrons inside the FPRs in the near-Earth tail play a potentially important role in the evolution of the Earth's electron radiation belt and substorms

Introduction to the thematic series "Coupling of the magnetosphere–ionosphere system"

This thematic series contains 4 papers mostly presented at the 2016 AOGS meeting in Beijing. The four papers investigate four key regions in the magnetosphere–ionosphere coupling process: mid-tail magnetosphere, near-Earth magnetosphere, inner magnetosphere, and the polar ground region. Guo et al. (Geosci Lett 4:18, 2017) study the current system in reconnection region using 2.5D particle-in-cell simulations. Yao et al. (Geosci Lett 4:8, 2017) use conjugate measurements from ground auroral imagers and in situ THEMIS spacecraft to reveal the mechanism for the wave-like auroral structures prior to substorm onset. Zhang et al. (Geosci Lett 4:20, 2017) investigate the profiles of resonance zone and resonant frequency in the Landau resonance between radiation belt electrons and magnetosonic waves and between protons and cyclotron waves. Rae et al. (Geosci Lett 4:23, 2017) determine the relative timing between sudden increases in amplitude, or onsets, of different ultra-low-frequency wave bands during substorms

A flicker-free electrolytic capacitor-less AC-DC LED driver

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Properties of plasmoids observed in Saturn’s dayside and nightside magnetodisc

Plasmoid is a key structure for transferring magnetic flux and plasma in planetary magnetospheres. At Earth, plasmoids are key media which transfer energy and mass in the "Dungey Cycle". For giant planets, plasmoids are primarily generated by the dynamic processes associated with “Vasyliunas Cycle”. It is generally believed that planetary magnetotails are favorable for producing plasmoids. Nevertheless, recent studies reveal that magnetic field lines could be sufficiently stretched to allow magnetic reconnection in Saturn’s dayside magnetodisc. In the study, we report direct observations of plasmoids in Saturn’s dayside magnetodisc for the first time. Moreover, we perform a statistical investigation on the global plasmoid electron density distribution. The results show an inverse correlation between the nightside plasmoid electron density and local time, and the maximum plasmoid electron density around prenoon local time on the dayside. These results are consistent with the magnetospheric circulation picture associated with the "Vasyliunas Cycle"

Zero-bias anomaly in two-dimensional electron layers and multiwall nanotubes

The zero-bias anomaly in the dependence of the tunneling density of states $\nu (\epsilon)$ on the energy $\epsilon$ of the tunneling particle for two- and one-dimensional multilayered structures is studied. We show that for a ballistic two-dimensional (2D) system the first order interaction correction to DOS due to the plasmon excitations studied by Khveshchenko and Reizer is partly compensated by the contribution of electron-hole pairs which is twice as small and has the opposite sign. For multilayered systems the total correction to the density of states near the Fermi energy has the form $\delta \nu/\nu_0 = {max} (| \epsilon |, \epsilon^*)/4\epsilon_F$, where $\epsilon^*$ is the plasmon energy gap of the multilayered 2D system. In the case of one-dimensional conductors we study multiwall nanotubes with the elastic mean free path exceeding the radius of the nanotube. The dependence of the tunneling density of states energy, temperature and on the number of shells is found.Comment: 8 pages, 3 figure

Two fundamentally different drivers of dipolarizations at Saturn

Solar wind energy is transferred to planetary magnetospheres via magnetopause reconnection, driving magnetospheric dynamics. At giant planets like Saturn, rapid rotation and internal plasma sources from geologically active moons also drive magnetospheric dynamics. In both cases, magnetic energy is regularly released via magnetospheric current redistributions that usually result in a change of the global magnetic field topology (named substorm dipolarization at Earth). Besides this substorm dipolarization, the front boundary of the reconnection outflow can also lead to a strong but localized magnetic dipolarization, named a reconnection front. The enhancement of the north-south magnetic component is usually adopted as the indicator of magnetic dipolarization. However, this field increase alone cannot distinguish between the two fundamentally different mechanisms. Using measurements from Cassini, we present multiple cases whereby we identify the two distinct types of dipolarization at Saturn. A comparison between Earth and Saturn provides new insight to revealing the energy dissipation in planetary magnetospheres

Observation of aerosol size distribution and new particle formation at a mountain site in subtropical Hong Kong

Author name used in this publication: Guo, H.Author name used in this publication: Wang, D. W.2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A study of Pt4+ -adsorption and its reduction by Bacillus megaterium D01

The properties of Pt4+-adsorption and its reduction by Bacillus megaterium D01 were studied by means of ICP, anode-stripping voltammetry, TEM, IR and XPS. The results of ICP analyses showed that the Pt4+-adsorptive efficiency of the strain D01 was as high as 94.3% under the conditions of 100 mg Pt4+/L, 1 g biomass/L, pH 3.5 and at 30 degreesC for 24 h. Moreover, it was confirmed from anode stripping voltammetry that the strain D01 possessed a strong reducibility. The TEM analysis indicated that the strain D01 was able to adsorb and reduce Pt4+ to Pt-0, small particles. The XPS result further supported the reduction of Pt4+ to Pt2+, followed by the further recuction to Pt-0. The IR spectrum implied that D01 biomass adsorption of Pt4+ may result in the complexation of the C = O bond to the Pt species

On the Relation Between Jupiter's Aurora and the Dawnside Current Sheet

Jupiter's auroral emission is a spectacular phenomenon that provides insight into energy release processes related to the coupling of its magnetosphere and ionosphere. This energy release is influenced by solar wind conditions. Using joint observations from Juno and the Hubble Space Telescope (HST), we statistically investigate the relationship between auroral power and current sheet variations under different solar wind conditions. In this study, we reveal that during global main auroral brightening events that are closely connected to solar wind compressions, the dawn side current sheet is substantially thinner than during times when a quiet auroral morphology is present. Furthermore, the total current intensity in the current sheet is found to increase under solar wind compression conditions compared to the quiet period. These findings provide important observational evidence for how magnetospheric dynamics driven by solar wind behavior affect auroral activity, deepening our understanding of the coupling between Jupiter's magnetosphere and ionosphere