We introduce the empirical mode decomposition algorithm and applied low‐frequency filtering and high‐frequency noise reduction to the waveform of the electric field changes recorded in 1‐ms segments. This algorithm greatly improved the accuracy of the peak time extraction and the number of pulses in the low and very low frequency band, which enhanced the accuracy in positioning the pulse of the electric field change. Compared with the previous algorithm, the algorithm can significantly reduce the time error, giving a better positioning result. With a time error estimate of 100 ns and a limit of goodness of fit less than 5, the number of pulse locations is increased by nearly 7 times. The goodness‐of‐fit distribution of the pulse location results had a normal distribution, and the 95% confidence interval of goodness of fit was 0–4; the corresponding positioning space error was <60 m. The continuity of the lightning channel was significantly improved, and the development characteristics and fine structure of the lightning channel were clearly distinguished. The low‐frequency electric field detection array system gave detailed positioning results for a bolt from the blue lightning strike. By comparing the results from the low‐frequency electric field detection array with the actual lightning strike point, we objectively demonstrated the positioning performance of the new algorithm. The system gave positioning results for the lightning for all seven return strokes. The maximum horizontal distance between the locating point and the real lightning strike point was 57 m, the minimum horizontal distance between them was 3 m, and the mean distance was 27 m.

in all storm intensity change categories: rapid intensification (RI), average intensity change (AIC), and rapid weakening (RW). The differences in LD between RI and RW are largest in the inner core, and the LD for RI cases is larger than for RW cases in the inner core (0-100 km). Lightning activity there, rather than in the outer rainbands, may be a better indicator for RI prediction in northwest Pacific storms. There was a marked increase in the lightning density of inner core during the RI stage for Super Typhoon Rammasun (2008). Satellite data for this storm show that the RI stage had the highest cloud top height and coldest cloud top temperatures, with all the minimum black body temperature values being below 200 K in the inner core.

Observations have been obtained of the initial stage of a rocket‐and‐wire‐triggered lightning flash with a high‐resolution broadband VHF interferometer. The discharge produced 54 precursor current pulses (PCPs) over 883 ms during the rocket's ascent. The interferometer observations show that the PCPs were produced by breakdown at the ascending tip of the rocket, and that individual PCPs were produced by weak upward positive breakdown over meters‐scale distances, followed by more energetic, fast downward negative breakdown over several tens of meters distance. The average propagation speeds were ~5 × 106 m s−1 and ~3 × 107 m s−1, respectively. The sustained upward positive leader (UPL) was initiated by a rapid, repetitive burst of 14 precursor pulses. Upon initiation, the VHF radiation abruptly became continuous with time. Significantly, breakdown during the UPL appeared to extend the discharge in a similar manner to that of the precursor pulses.

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More than three dozen red sprites were captured above Hurricane Matthew on the nights of 1 and 2 October 2016 as it passed to the north of Venezuela after undergoing rapid intensification. Analyses using broadband magnetic fields indicate that all of the sprites were produced by positive cloud‐to‐ground (CG) strokes located within the outer rainbands as defined by relatively cold cloud top brightness temperatures (≤194 K). Negative CG strokes with impulse charge transfers exceeding the threshold of sprite production also existed, but the timescale of the charge transfer was not sufficiently long to develop streamers. The reported observations are contrary to the finding of the Imager of Sprites/Upper Atmospheric Lightning showing that sprites are preferentially produced by negative strokes in the same geographic region. Further ground‐based observations are desired to obtain additional insights into the convective regimes associated with the dominance of negative sprites in many oceanic and coastal thunderstorms.

It is of importance to image electrical activity and properties of biological tissues. Recently hybrid imaging modality combing ultrasound scanning and source imaging through the acousto-electric (AE) effect has generated considerable interest. Such modality has the potential to provide high spatial resolution current density imaging by utilizing the pressure induced AE resistivity change confined at the ultrasound focus. In this study, we investigate a novel 3-dimensional (3D) ultrasound current source density imaging (UCSDI) approach using unipolar ultrasound pulses. Utilizing specially designed unipolar ultrasound pulses and by combining AE signals associated to the local resistivity changes at the focusing point, we are able to reconstruct the 3D current density distribution with the boundary voltage measurements obtained while performing a 3D ultrasound scan. We have shown in computer simulation that using the present method, it is feasible to image with high spatial resolution an arbitrary 3D current density distribution in an inhomogeneous conductive media.

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Synthesizing chemically recyclable solid polymeric materials is a significant strategy to potentially achieve carbon neutral production of new polymers and alleviate plastic pollution, especially when the synthesis is based on CO 2 and inexpensive co-feedstocks available in large scales. Additionally, polymeric materials should have high enough molecular weight to exhibit distinguished properties from low molar mass polymers to serve for a broader range of application scenarios. However, up to now, strategies for developing solid-state CO 2 -based chemically recyclable polyesters with both high molecular weight and facile property tunability are still unprecedented. Herein, a brand-new synthetic route is developed to synthesize chemically recyclable CO 2 -based solid polyesters with high molecular weight (M n up to 587.7 kg mol −1 ) and narrow dispersity (Ð < 1.2), which should further broaden the potential application scenarios of new CO 2 -based polyesters. Additionally, complete monomer recovery from poly(𝜹LH 2 ) material is also achieved. The preserved terminal alkene groups allow facile property tuning of the polyesters via photo-initiated thiol-ene click reactions, enabling more potential utilities and further functionalizations.