Search

Albert Einstein’s assertion that we cannot solve our problems with the same thinking that we used to create them has never been truer than it is today as the world grapples with the global health crisis of the COVID-19 pandemic. In July 2019, representatives from 142 countries gathered for the High-Level Political Forum for Sustainable Development (HLPF) to review progress towards the United Nations’ 2030 Agenda for Sustainable Development and to identify areas in urgent need of attention. Progress towards achieving the Agenda’s sustainable development goals (SDGs) had been uneven prior to the pandemic, but its outbreak abruptly disrupted implementation towards many of these goals and, in some cases, reversed decades of progress. The crisis has affected every segment of society and has rocked economies around the world. Unsurprisingly, it is the poorest and most vulnerable populations that will suffer the most. The pandemic has exposed harsh and profound inequalities in societies and is further exacerbating disparities within and between countries. Although the SDGs are broad global goals, their implementation is rooted in action at the local level. The authors of this publication collectively represent the Global South and their expertise touches on some of the key challenges facing us today: water and sanitation (SDG 6), biodiversity (SDG 15), energy (SDG 7), economics (SDG 8), poverty (SDG 1), inequality (SDG 10), urban sustainability (SDG 11), climate action (SDG 13) and more. The challenges presented by the pandemic are without precedent in our lifetimes. Robbed of our equilibrium, we decided to focus our thoughts on achieving a deeper understanding of the implications of this crisis for sustainable development, climate protection, and our respective areas of focus. This led us to consider how we could work together and help to forge pathways towards a more sustainable and equitable world., Albert Einsteins Erkenntnis, dass man Probleme niemals mit derselben Denkweise lösen kann, durch die sie entstanden sind, war nie wahrer als heute, da die Welt mit der globalen Gesundheitskrise der Covid-19-Pandemie zu kämpfen hat. Im Juli 2019 versammelten sich Vertreterinnen und Vertreter von 142 Ländern beim Hochrangigen Politischen Forum für Nachhaltige Entwicklung (HLPF), um die Fortschritte bei der Umsetzung der Agenda 2030 für Nachhaltige Entwicklung der Vereinten Nationen zu überprüfen und Bereiche zu identifizieren, die dringend der Aufmerksamkeit bedürfen. Die Fortschritte bei der Erreichung der UN-Nachhaltigkeitsziele (SDGs) waren schon vor der Pandemie uneinheitlich, aber der Ausbruch der Pandemie hat die Umsetzung vieler dieser Ziele abrupt unterbrochen und in einigen Fällen Jahrzehnte des Fortschritts rückgängig gemacht. Die Krise hat alle Bereiche der Gesellschaft erfasst und Volkswirtschaften auf der ganzen Welt erschüttert. Es überrascht nicht, dass die ärmsten und verletzlichsten Bevölkerungsgruppen am meisten leiden. Die Pandemie hat tiefgreifende gesellschaftliche Ungleichheiten offengelegt und verschärft die Unterschiede innerhalb von und zwischen den Ländern weiter. Obwohl es sich bei den SDGs um breit angelegte globale Ziele handelt, findet ihre Umsetzung ganz wesentlich auf lokaler Ebene statt. Die Autorinnen und Autoren dieser Publikation repräsentieren gemeinsam den Globalen Süden und bringen Fachwissen zu einigen der wichtigsten Herausforderungen mit, vor denen wir heute stehen: Wasser und Sanitäreinrichtungen (SDG 6), Biodiversität (SDG 15), Energie (SDG 7), Wirtschaft (SDG 8), Armut (SDG 1), Ungleichheit (SDG 10), nachhaltige Städte und Gemeinden (SDG 11), Klimaschutz (SDG 13) und mehr. Die Herausforderungen, die die Pandemie mit sich bringt, sind zu unseren Lebzeiten ohne Beispiel. Als die Welt aus den Fugen geriet, beschlossen die Autorinnen und Autoren dieser Publikation, ein tieferes Verständnis für die Auswirkungen dieser Krise auf die nachhaltige Entwicklung, den Klimaschutz und unsere jeweiligen Forschungsschwerpunkte zu erlangen. Sie überlegten, wie sie zusammenarbeiten und dazu beitragen können, Wege zu einer nachhaltigeren und gerechteren Welt zu entdecken.

Rapid Automatized Naming (RAN) is a powerful tool for pre- dicting future reading skill. A person’s ability to quickly name symbols as they scan a table is related to higher-level reading proficiency in adults and is predictive of future literacy gains in children. However, noticeable differences are present in the strategies or patterns within groups having similar task comple- tion times. Thus, a further stratification of RAN dynamics may lead to better characterization and later intervention to support reading skill acquisition. In this work, we analyze the dynamics of the eyes, voice, and the coordination between the two during performance. It is shown that fast performers are more similar to each other than to slow performers in their patterns, but not vice versa. Further insights are provided about the patterns of more proficient subjects. For instance, fast performers tended to exhibit smoother behavior contours, suggesting a more sta- ble perception-production process.

Active-clamp dc-dc converters are pulsewidth-modulated converters having two switches featuring zero-voltage switching at frequencies beyond 100 kHz. Generalized equivalent circuits valid for steady-state and dynamic performance have been proposed for the family of active-clamp converters. The active-clamp converter is analyzed for its dynamic behavior under current control in this paper. The steady-state stability analysis is presented. On account of the lossless damping inherent in the active-clamp converters, it appears that the stability region in the current-controlled active-clamp converters get extended for duty ratios, a little greater than 0.5 unlike in conventional hard-switched converters. The conventional graphical approach fails to assess the stability of current-controlled active-clamp converters, due to the coupling between the filter inductor current and resonant inductor current. An analysis that takes into account the presence of the resonant elements is presented to establish the condition for stability. This method correctly predicts the stability of the current-controlled active-clamp converters. A simple expression for the maximum duty cycle for subharmonic-free operation is obtained. The results are verified experimentally.

Active-clamp dc-dc converters are pulsewidth-modulated converters having two switches featuring zero-voltage switching at frequencies beyond 100 kHz. Generalized equivalent circuits valid for steady-state and dynamic performance have been proposed for the family of active-clamp converters. The active-clamp converter is analyzed for its dynamic behavior under current control in this paper. The steady-state stability analysis is presented. On account of the lossless damping inherent in the active-clamp converters, it appears that the stability region in the current-controlled active-clamp converters get extended for duty ratios, a little greater than 0.5, unlike in conventional hard-switched converters. The conventional graphical approach fails to assess the stability of current-controlled active-clamp converters due to the coupling between the filter inductor current and resonant inductor current. An analysis that takes into account the presence of the resonant elements is presented to establish the condition for stability. This method correctly predicts the stability of the current-controlled active-clamp converters. A simple expression for the maximum duty cycle for subharmonic free operation is obtained. The results are verified experimentally.

The soft switching converters evolved through the resonant load, resonant switch, resonant transition and active clamp converters to eliminate switching losses in power converters. This paper briefly presents the operating principle of the new family of soft transition converters; the methodology of design of these converters is presented through an example. In the proposed family of converters, the switching transitions of both the main switch and auxiliary switch are lossless.When these converters are analysed in terms of the pole current and throw voltage, the defining equations of all converters belonging to this family become identical.Such a description allows one to define simple circuit oriented model for these converters. These circuit models help in evaluating the steady state and dynamic model of these converters. The standard dynamic performance functions of the converters are readily obtainable from this model. This paper presents these dynamic models and verifies the same through measurements on a prototype converter.

In hard-switched converters, the switching frequency is limited by switching losses and EMI problems. However, high-switching frequency is necessary to reduce the converter size. Hence, soft switching is imperative at high switching frequency to obtain good efficiency. Push-pull converter is a preferred topology at medium power level. This paper proposes a novel resonant transition topology for push-pull converter. The proposed topology uses two additional switches and two diodes when compared to hard-switched push-pull converter. These extra switches introduce freewheeling in the primary circuit and thus enable loss-less switching. In classical push-pull converters, the transformer primary is left open during two sub-intervals in a period making the turn-on of the switch hard. The new circuit topology converts these open circuit intervals into freewheeling ones. With such a modification, all trapped energy in the core is conserved to achieve zero-voltage switching during the entire transition. Switch stress, control and small signal model are similar to hard-switched PWM converter. Idealized analysis and design methodology are explained for the push-pull converter. A prototype-300 kHz, 200 W push-pull converter validates the design method. Dynamic analysis of the push-pull converter is presented. The proposed topology can be extended to half-bridge converter also. Its circuit diagram is presented.

In developing countries, the demand for electricity in rural communities is increasing day-by-day. Stand alone micro hydro generator installations provide an inexpensive and reliable solution to the demand for electrical energy, in rural and remote sites. Such installations in order to be useful, must incorporate an appropriate voltage control facility. This article describes a few approaches, through electronic means, to control the generator terminal voltage, namely, using mechanical relays for switching, synchronised thyristor switching, and high frequency chopping of the generator output to vary the effective ballast load (0 refs.)