A new ZVT–ZCT quasi-resonant DC link for soft switching inverters

In this article, the new ZVT–ZCT Quasi-Resonant DC Link, which ensures zero crossings at any time required for soft switching (SS) and provides zero voltage transition (ZVT) turn-on and zero current transition (ZCT) turn-off together for the main switch of active snubber cell in pulse width modulated or space vector modulated operation of inverter is presented. The new circuit combines the most desirable features of the circuits presented previously and overcomes most drawbacks of these circuits by using only one auxiliary switch with fewer other components. Consequently, new ZVT–ZCT Quasi-Resonant DC Link, which is verified by a prototype of a 1.2 kW and 50 kHz circuit, is analysed in detail. All semiconductor devices operate under SS, the main switch is subjected to no additional voltage and current stresses, and the stress on the auxiliary switch is very low in the proposed new inverter.     

Integrating multiple calendars using τ ZAMAN

Programmers are increasingly interested in developing applications that can be used internationally. Part of the internationalization effort is the ability to engineer applications to use dates and times that conform to local calendars yet can inter‐operate with dates and times in other calendars, for instance between the Gregorian and Islamic calendars. ZAMAN is a system that provides a natural language‐ and calendar‐independent framework for integrating multiple calendars. ZAMAN performs ‘runtime‐binding’ of calendars and language support. A running ZAMAN system dynamically loads calendars and language support tables from XML‐formatted files. Loading a calendar integrates it with other, already loaded calendars, enabling users of ZAMAN to add, compare, and convert times between multiple calendars. ZAMAN also provides a flexible, calendar‐independent framework for parsing temporal literals. Literals can be input and output in XML or plain text, using user‐defined formats, and in different languages and character sets. Finally, ZAMAN is a client/server system, enabling shared access to calendar servers spread throughout the Web. This paper describes the architecture of ZAMAN and experimentally quantifies the cost of using a calendar server to translate and manipulate dates. Copyright © 2006 John Wiley & Sons, Ltd.