A New Dual Polarity Direct AC-AC Voltage Regulator Ensuring Voltage Step-Up and Step-Down Capabilities

The problem of voltage sag and swell is one of the major reasons for low-quality power in the distribution system. Normally, it results from the system’s faults, including line-to-ground and line-to-line, non-linear characteristics of loads and sources. Its effect is very serious for the critical loads as their performance is very sensitive to the variation in voltage. The stabilization of voltage is a mandatory requirement in such a situation. The correction of such problems requires the addition and subtraction of the voltage once the line voltage is decreased and increased. This behavior of the correcting voltage is ensured by the use of voltage controllers that can convert a constant input voltage into a non-inverted and inverted variable form. Their voltage gains depend on the depth level of the problem. The voltage buck and boost capabilities of the AC voltage stabilizers can tackle the problems having any depth level. The smartness of such a system depends on the number of electronic devices as they are the key elements in the power conversion system. Therefore, this research proposes a new AC voltage controller with fewer solid-state devices. Its overall impact is low volume and cost. The validation of the introduced approach is ensured with the help of simulation modeling and results gained from the practical setup.

Dual polarity voltage imaging reveals subthreshold dynamics and concurrent spiking patterns of multiple neuron-types

Genetically encoded fluorescent voltage indicators are ideally suited to reveal the millisecond-scale interactions among and between distinct, targeted cell populations. However, current indicator families lack the requisite sensitivity for in vivo multipopulation imaging. We describe high-performance green and red sensors, Ace-mNeon2 and VARNAM2, and their reverse response-polarity variants, pAce and pAceR. Our indicators enable 0.4-1 kHz voltage recordings from >50 neurons per field-of-view in awake mice and ~30-min continuous imaging in flies. Using dual-polarity multiplexed imaging, we uncovered behavioral state-dependent interactions between distinct neocortical subclasses, as well as contributions to hippocampal field potentials from non-overlapping projection neuronal ensembles. By combining three mutually compatible indicators, we demonstrate concurrent triple-population voltage imaging. Our approach will empower investigations of the dynamic interplay between neuronal subclasses at single-spike resolution.

A Study of Fast Front Transients of an HVDC Mixed Transmission Line Exposed to Bipolar Lightning Strokes

Bipolar lightning strokes are associated with multiple polarity electrical discharge with no current intervals in between, making their behavior quite peculiar. This work presents a fast front analysis of a mixed high voltage direct current (HVDC) transmission link, evaluating the factors that influence the line transients due to shielding failures and back flashovers (BFOs), considering both overvoltage and repeated polarity reversal at the cable sending terminal. The research process includes a detailed modeling of a bipolar lightning stroke, frequency-dependent HVDC overhead, and underground transmission line sections. Noticeable findings include the occurrence of only a positive polarity insulator BFO for the adjacent and subsequent tower, despite the dual polarity of the lightning stroke with relatively small values for the lightning parameters. The influence of traveling waves on the insulator flashover performance of the line with varying parameters (such as the riser section length, the tower grounding impedance, and the location of the lightning stroke) is recorded and explained.

Parameters Affecting the Polarity Inversion of the Vertical Electric Lightning Field to the CN-Tower

The aim of this paper is to perform a parametric study in order to analyze factors having an effect on the vertical lightning field polarization to the CN-Tower in Canada, and estimate with numerical simulation, the horizontal distance for which the reversed polarity will occur. The calculation is performed using the Finite-Difference-Time-Domain technique in two dimensions (2D-FDTD), the spatial-temporal current propagation through the lightning channel and through the high structure is represented by the lumped-series voltage-source model. The obtained results show that the vertical electric lightning field behavior has a dual polarity, the transition from a negative waveform to a positive one is observed at different observation points localized near the elevated object influencing by each modification made to the tower-parameters, the medium conductivity and the return stroke speed value. These results can contribute to the understanding of the lightning-phenomenon and allow to solve the problems of electromagnetic compatibility.

Middle–Late Permian magnetostratigraphy and the onset of the Illawarra Reversals in the northeastern Parana Basin, South America

SUMMARY Recent compilations of the Illawarra Reversals show remarkable differences in the onset age (265 Ma versus 269 Ma) and the magnetic polarity pattern, hampering the establishment of a reference geomagnetic timescale for the Middle–Late Permian. The Parana Basin hosts a 7-km-thick, discontinuous sedimentary succession spanning the Palaeozoic to the Mesozoic, including the Gondwana 1 supersequence which extends from Late Carboniferous to the Triassic or Jurassic. We provide the magnetostratigraphy of the middle and upper Permian part of this sequence of a ca. 300-m-long core, pertaining to the Passa Dois Group and the Piramboia Formation. Sample demagnetization of NRM revealed two magnetic overprints ascribed to the Brunhes chron and to the emplacement of Parana Large Igneous Province in the Early Cretaceous, respectively. Stable, dual polarity characteristic components (ChRM) were isolated at temperatures higher than 450 °C and interpreted as a primary detrital magnetic remanence (DRM), acquired during or soon after sediment deposition. Available U-Pb dating on volcanic zircons from the literature provided independent chronologic constraints for our magnetostratigraphy. A total of 8 reverse polarity intervals were identified, the lowermost of which (up to 110 m thick) correlates to the Kiaman Superchron. The overlying Illawarra is dominated by a reverse polarity magnetization with thin (4–5 m thick) normal polarity intervals. This pattern agrees with the Illawarra sequence from the Karoo Basin and other proposed timescales for the Permian. The onset of the Illawarra reversals is interpolated to ca. 270 Ma, close to the age of 269 Ma from the Karoo Basin. Combined magnetostratigraphy and geochronology yielded sediment accumulation rates of ca. 8 m Myr–1 for the Passa Dois Group in the northeastern (marginal) sector of the Parana Basin, indicating that Serra Alta and Teresina Formations span 279–274 Ma and 274–254 Ma, respectively.