Single-stage, single-phase, ac–dc buck–boost converter for low-voltage applications

The suitability of a single-stage ac–dc buck–boost converter for low-voltage applications is investigated. In-depth discussion and analysis of the converter's operating principle, basic relationships that govern converter steady-state operation and details of the necessary control structures needed to comply with the grid code are provided. The validity of the proposed system is confirmed using power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) simulations, and is substantiated experimentally. The buck–boost converter under investigation has good dynamic performance in both buck and boost modes, and ensures near unity input power factor over the full operating range, whilst having fewer devices and passive elements than other published versions of the buck–boost converter

Economic crisis and the construction of a neo-liberal regulatory regime in Korea

A consistent theme of the literature on the ontology of the 1997 South Korean crisis is the key role played by regulatory failures and the growing weakness of the state. This paper seeks to briefly highlight both the insights and the limitations of this approach to understanding the crisis. Having done so, we shall set out the argument that the crisis created an opportunity for reformist Korean élites to advance their longstanding, but previously frustrated, project to create a comprehensive unambiguously neo-liberal regulatory regime. This paper will also seek to highlight the implications of our reading of the development of the Korean political economy for broader debates on economic liberalisation, crisis and the future of the developmental state

First Sagittarius A* Event Horizon Telescope results. I. The shadow of the supermassive black hole in the center of the Milky Way

Galaxie

Planktic foraminiferal turnover across the Aptian/Albian boundary and new criteria to define the GSSP for the base of the Albian Stage

Apart from the terminal Cretaceous extinction, the planktic foraminiferal turnover across the Aptian/Albian boundary interval is the most dramatic event in the Cretaceous evolutionary history of planktic foraminifera, with a change from large-sized and heavily ornamented species in the latest Aptian to small-sized, globigeriniform specimens in the earliest Albian. The detailed documentation of planktic foraminiferal species content and abundance across a continuous Aptian\u2013Albian sedimentary sequence exposed at the Col de Pr\ue9-Guittard section in the Vocontian Basin (southeast France) permits a reliable description of the magnitude and rate of planktic foraminiferal turnover at the Niveau Kilian organic rich bed. The latest Aptian assemblage is dominated by few long-ranging Hedbergella and large-sized Paraticinella that completely disappear near the base of the Niveau Kilian organic-rich level. Planktic foraminiferal assemblages from across the Niveau Kilian to the top of the studied section are composed of minute, but very distinctive smooth-surfaced species of Microhedbergella miniglobularis and Mi. renilaevis. The appearance of Mi. renilaevis in the middle part of the Niveau Kilian represents a major step in the evolution and diversification of the Albian planktic fauna. The lowest occurrence of this taxon is recorded immediately above the extinction level of the Aptian hedbergellids and corresponds with a dramatic decrease in the number of planktic and benthic foraminifera specimens and with a 1\u2030 negative \u3b413C excursion in bulk carbonate. The same sequence of events was reported from several deep-sea sites in the north and south Atlantic and Indian Oceans. Understanding the causes of the major planktic foraminiferal extinction event will require the study of additional biostratigraphically complete sections yielding well-preserved calcareous plankton assemblages. Nevertheless, the extinction of Paraticinella eubejaouaensis, the planktic foraminiferal turnover, the appearance of Microhedbergella renilaevis and the negative carbon-isotope shift in the Pr\ue9-Guittard section are globally identifiable events that could be used as primary and secondary criteria for defining the Global Boundary Stratotype Section and Point for the base of the Albian Stage