HTS pulse-stretcher and second order modulator: design and first results

One of the remaining challenges in the application of superconducting electronics is the interfacing between superconducting and semiconducting environments. The voltage and speed mismatch between RSFQ pulses and semiconducting read-out electronics makes it necessary to amplify as well as stretch the RSFQ pulses. Moreover, circuits based on HTS (High Temperature Superconductor) technology are very attractive since they can operate under considerably relaxed cooling effort, which is one of the main problems with LTS (Low Temperature Superconductor) circuits. Within the European project SuperADC, a HTS second order sigma delta modulator and a pulse stretcher, used as an interface between the modulator and the first semi-conducting amplifier stage, have been designed at Twente University and will be presented here

A Feasibility Study on Using the Blockchain to Build a Credit Register for Individuals Who Do Not Have Access to Traditional Credit Scores

In South Africa and many other countries, credit registers and credit scores are used to determine how much credit a person can get access to, as well as the interest rate which they will be charged. In addition to this, some companies (such as insurance companies and rental agencies), use this data as part of the process to vet potential clients before allowing them to sign a contract. Part of the problem with this approach is that only certain records are stored on these credit registers. This excludes a large number of individuals, specifically those who are unbanked, those who have not got access to credit from formal institutions or those who do not own property and therefore pay their landlord for utilities. The purpose of this research is to determine the feasibility of using blockchain to store payment histories from small businesses to give their clients access to a credit record. The case study for this research will look specifically at a business which offers insurance to individuals living in informal settlements. This could be extended to many other businesses who work within informal settlements which allow cash payments on a regular basis for services offered. Shops in informal marketplaces which allow people to take products on credit and only pay later could also be included. By storing these transactions on the blockchain, individuals who would not usually have access to a credit history will have access to records of transactions that they have made and will be able to use these to show their ability and willingness to meet their financial obligations. This paper provides insight into existing credit registers and the process followed to build an informal credit register on the blockchain. The research covers an investigation into the feasibility of the project and it was found that this could is feasible and could add a lot of value, especially to those who do not have a credit history. There are many considerations, such as speed, security and costs which need to be taken into account, but these are outweighed by the benefits of the blockchain

A record of three cases of human infection in Southern Africa with a common tapeworm of rats

No Abstrac

RSFQ Circuitry Using Intrinsic π-Phase Shifts

The latching of temporary data is essential in the rapid single flux quantum (RSFQ) electronics family. Its pulse-driven nature requires two or more stable states in almost all cells. Storage loops must be designed to have exactly two stable states for binary data representation. In conventional RSFQ such loops are constructed to have two stable states, e.g. by using asymmetric bias currents. This bistability naturally occurs when phase-shifting elements are included in the circuitry, such as pi-Josephson junctions or a pi-phase shift associated with an unconventional (d-wave) order parameter symmetry. Both approaches can be treated completely analogously, giving the same results. We have demonstrated for the first time the correct operation of a logic circuit, a toggle-flip-flop, using rings with an intrinsic pi-phase shift (pi-rings) based on hybrid high-Tc to low-Tc Josephson junctions. Because of their natural bistability these pi-rings improve the device symmetry, enhance operation margins and alleviate the need for bias current lines.\ud \u

Feasibility study of the dual active bridge as a low-frequency sine wave inverter

A dissertation submitted n fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, 2018The conventional Sinusoidal PulseWidth Modulation (SPWM) inverter is limited by the fact that it does not allow for Zero Voltage Switching. This means that the switching frequency is kept low to reduce the switching losses. As a consequence of holding these switching frequencies low, the distribution of power over the frequency spectrum is kept closer to the fundamental frequency (compared to higher switching frequencies) leading to larger reactive components to filter out these harmonics. The use of high-frequency switching, Zero Voltage Switching, and different modulation schemes can lead to higher power densities. This research investigates under what conditions the use of these techniques in a Dual Active Bridge (DAB) inverter might lead to a higher power density than the SPWM. Volumetric approximations for the different circuit components in the investigated inverter topologies are demonstrated. These approximations are used to design circuits using physical volume as the cost function where possible. Additionally, a loss model is derived to determine the expected efficiency of each topology being investigated. This model is related to the power density since it is directly proportional to the size of heat sink required to cool the inverter. The techniques for improving power density mentioned above are presented, and the impact that they have on power density is shown using the volumetric approximation function. From this approximation, the volumes between the DAB and the SPWM are compared and investigations into where the DAB may have a higher power density have been performed. It was found that the DAB was not smaller than the SPWM for frequencies less than 72kHz. When simulating the converters operating at different frequencies, the general trend is that the SPWM increases in volume as the frequency increases, whereas, the DAB decreases in volume as the frequency increases. An exact frequency at which the DAB would be smaller than the SPWM was not found in this research. However, many conclusions have been drawn around the use of a DAB as an inverter and the strengths and shortcomings it provides. The modulation scheme would need to be modified to reduce the losses and provide a more competitive volume. Additionally, multi-level and multi-stage techniques could be used to reduce the volume further.MT 201

\u3ci\u3eEchinococcus\u3c/i\u3e from Dogs in Pretoria and Vicinity

Discusses the discovery of Echinococcus granulosus (Batsch, 1786), Rud., 1805; Echinococcus cameroni n. sp. syn. E. granulosus of Cameron, 1926, from Vulpes vulpes; not E. granulosus (Batsch) Rud. 1805; and Echinococcus lycaontis sp. n. from stray dogs in Pretori, South Africa

The design and performance of a stand-alone solar and wind powered RTM House

This research project investigates the viability of using renewable energy sources and passive solar design in Saskatchewan, with its harsh climate, abundant energy resources, and absence of financial incentives for residential renewable energy systems. An experimental Ready-To-Move (RTM) house, using passive solar design and stand-alone solar and wind power with gas generator backup, was designed and built and has been tested for a one year period from January to December, 2006.The design methodology was based on well established design procedures for passive solar homes and renewable energy systems that are documented in the literature. A data collection system was used to record solar and wind charging currents, and battery status and temperature data was recorded on a daily basis. Average household loads were estimated from this data. For 2006, the power generation of the solar array was 990 kWh, which was better than the expected output of 927 kWh. However, the wind generator produced only 475 kWh, which was substantially less the expected output of 1430 kWh. Average wind speeds were lower than the normal for 2006 and power production was less than the manufacturer’s projections for the specified wind speeds. Financial analysis showed that the lack of incentives and net metering made an off-grid system economically feasible only in remote locations where the cost of grid connection is over $20,000

Textilbeton in Theorie und Praxis: Tagungsband zum 6. Kolloquium zu textilbewehrten Tragwerken (CTRS6); Gemeinsames Abschlusskolloquium der Sonderforschungsbereiche 528 (Dresden) und 532 (Aachen) Berlin, 19.9.2011 – 20.9.2011

Seit nunmehr über einem Jahrzehnt arbeiten die beiden Sonderforschungsbereiche 528 und 532 der Deutschen Forschungsgemeinschaft (DFG) an der Verwendung technischer Textilien im Bauwesen. An der RWTH Aachen (SFB 532) wurde in erster Linie der innovative Verbundwerkstoff „Textilbewehrter Beton“ untersucht, wobei das Ziel dünnwandige und hochbelastbare Betonbauteile waren. An der TU Dresden (SFB 528) wurde in erster Linie die Verwendung von technischen Textilien für die Verstärkung und Instandsetzung von Stahlbetontragwerken oder Holzbauteilen erforscht, um eine wirtschaftlich und technisch attraktive Alternative für die aktuellen Herausforderungen im Bauwesen anbieten zu können. Das 6. Kolloquium zu textilbewehrten Tragwerken (CTRS6) ist Teil einer Serie von Kolloquien, die seit 2001 von den beiden Sonderforschungsbereichen 528 (Dresden) und 532 (Aachen) abwechselnd organisiert werden. Das gemeinsame Abschlusskolloquium der beiden Sonderforschungsbereiche nach dem Ende der Förderung durch die DFG ist das sechste in dieser Reihe und wurde vom Dresdner SFB 528, allerdings diesmal zentral gelegen in Berlin, organisiert. Die Wissenschaftlerinnen und Wissenschaftler der beiden Sonderforschungsbereiche stellten ihre aktuellen Ergebnisse vor, wobei diese von Nachwuchswissenschaftlern aus den einzelnen Teilprojekten präsentiert wurden. Ergänzt wurde das Programm durch Vorträge renommierter internationaler Gastredner auf den Gebieten der Fasern und Textilien.For more than a decade, the collaborative research centres 528 and 532 of the Deutsche For-schungsgemeinschaft (DFG) have worked on the application of textile fabrics in civil engi-neering. The RWTH Aachen (CRC 532) first and foremost dealt with the innovative composite “textile reinforced concrete” with the aim of developing thin-walled concrete components with a heavy-load capacity. The TU Dresden (SFB 528) concentrated on re-search into the strengthening and restoration of reinforced concrete load-bearing structures or timber components to provide an economically and technically attractive alternative for the current challenges in civil engineering. The sixth colloquium on textile reinforced structures (CTRS 6) is part of a series of colloquia which has been alternately organized by the collaborative research centre 528 (Dresden) and 532 (Aachen).After the DFG’s grant had come to an end, the joint sixth and final colloquium of both collaborative research centres, which was this time organized by the CRC 528 from Dresden, took place in Berlin due to its more central location. The scientists from both col-laborative research centres presented their current results which were explained by young scientists from the individual subprojects. The programme was complemented by presenta-tions by renowned international guest lecturers from the field of fibres and textiles