Petri net equivalence

Determining whether two Petri nets are equivalent is an interesting problem from both practical and theoretical standpoints. Although it is undecidable in the general case, for many interesting nets the equivalence problem is solvable. This paper explores, mostly from a theoretical point of view, some of the issues of Petri net equivalence, including both reachability sets and languages. Some new definitions of reachability set equivalence are described which allow the markings of some places to be treated identically or ignored, analogous to the Petri net languages in which multiple transitions may be labeled with the same symbol or with the empty string. The complexity of some decidable Petri net equivalence problems is analyzed

Now: Music from the musicals 1975 - 2018

Musical Theatre performance at The Meteor Theatre Gwen is an opera singer and is joined for an evening of song, by special guests; Courteney Mayall, Alex Pelham-Waerea, Scot Hall, Hannah MacFarlane and Michaela Gilling Accompanied by the incomparable David Sidwell, Gwen and guests will be singing from musical theatre canon of 1975 through to 2018 Let them take you on a journey through the best pieces Broadway has to offer

Here I am: Wallace Gallery

Performance of " HERE I AM" for Soprano, Piano & Cello at the Wallace Gallery. Music by David Sidwell and Lyrics by Wayne Senior. Pamela Wallace - Soprano, Alexandra Wiltshire - Piano, Yotam Levy - Cello. SHIFT Exhibition Concer

PAN AIR summary document (version 1.0)

The capabilities and limitations of the panel aerodynamics (PAN AIR) computer program system are summarized. This program uses a higher order panel method to solve boundary value problems involving the Prandtl-Glauert equation for subsonic and supersonic potential flows. Both aerodynamic and hydrodynamic problems can be solved using this modular software which is written for the CDC 6600 and 7600, and the CYBER 170 series computers

Results of the 1978 NASA/JPL balloon flight solar cell calibration program

The 1978 scheduled solar cell calibration balloon flight was successfully completed. Thirty six modules were carried to an altitude of above 36 kilometers. Recovery of telemetry and flight packages was without incident. These calibrated standard cells are used as reference standards in simulator testing of cells and arrays with similar spectral response characteristics. The factors affecting the spectral transmission of the atmosphere at various altitudes are summarized

Analysis of co-firing biomass with South African coal in pulverised coal boilers

In this study, the effect on the extent of emissions reduction with co-combustion of small proportions (0-20%) of biomass with coal in a pulverised fuel combustor, is investigated. Such emissions include CO2, SO2 and NOx. South African coal has high ash content and low volatile content that affects its ignitability. The effect of biomass co-firing on ignitability and slagging is also investigated. While higher percentages of biomass could reduce emissions more and improve ignitability, biomass tends to increase the undesirable fouling and slagging propensities, hence limiting the amount of biomass that can be co-fired. Two types of biomass, namely grass and sawdust (calorific value 16-18 MJ/kg), and one coal (calorific value 21 MJ/kg) were used in this study. Combustion tests were carried out using the Eskom 1 MW Pilot Scale combustion Test Facility (PSCTF). The coal chosen was representative of an average coal burned at the Eskom’s coalfired power stations. For each of the types of biomass, three blends of biomass and coal were used, resulting in seven different feed fuels including coal alone. The ratios of biomass to coal, on an energy basis, in the three blends were 10%:90%, 15%:85% and 20%:80%. Seven tests were also carried out with the same fuels using a drop tube furnace (DTF) to determine the reaction kinetics of the baseline coal and its three different blends with each type of biomass. The reaction parameters obtained from these tests were used as input data in numerical simulations of the tests. Simulation using CFD software was used to predict combustion characteristics of each fuel in the PSCTF, which in turn can be extrapolated to predict the performance in a full scale commercial boiler. The simulation results were validated by the experimental data from the PSCTF; comparison of the combustion and emissions characteristics with experimental data from the PSCTF showed that the simulation procedure was capable of predicting these characteristics with generally good accuracy. The results coming out of this work are positive. Co-firing with grass at the PSCTF was found to reduce the emissions by between 13% and 50% for NOX, between 12% and 23% for CO2 and between 21% and 29% for SO2 as the proportion of biomass increased from 10% to 20%. The maximum emissions reduction for sawdust occurred at 20% co-firing ratio; these are, 29% for NOx, 17% for CO2 and 15% for SO2. For grass based co-firing, the combustion efficiency of the coal used was improved by 0.55% and 0.62% for 15% and 20% co-firing ratios respectively; whereas that of sawdust was between 0.78% and 0.38% as co-firing ratio was increased from 10% to 20%. Combustion efficiency for 10% grass dropped by 0.65%. The DTF results indicate that both grass and sawdust were able to improve the ignitability of the coal used in a temperature range of 1000°C to 1200°C. The combustion efficiency determined from DTF results for this range indicate an improvement of between 0.1% and 1.4% for grass and between 0.8% and 2.45% for sawdust. The QEMSCAN analysis of slag deposits when co-firing biomass indicated that they should generally be weak enough to be handled by soot blowing equipment. In conclusion grass (herbaceous) biomass resulted in greater emissions reductions than sawdust (ligneous). It was also found that slagging would be less of a problem when using grass, because the slag deposits are more friable than those of sawdust. At higher co-firing ratios grass based co-firing was found to improve coal ignitability better than that can be achieved with sawdust. The optimum co-firing ratio with grass would appear to be about 15% on an energy basis. This project was carried out to obtain fundamental technical information on some of the salient effects of using biomass co-firing with pulverised power station coal. Before any implementation can be carried out, the next step would be to conduct a detailed technical and economic feasibility study into possible large-scale applications, using full systems engineering principles

Accuracy of furan analysis in estimating the degree of polymerization in power transformers

MSc (Eng), School of Electrical and Information Engineering, Faculty of Engineering and the Built Environmen

Review of Peter K. Norquest, A Phonological Reconstruction of Proto-Hlai (Leiden/Boston, Brill, ISBN 978-9004-30052-1 (E-Book)), 2016

This recent addition to the Brill “The Languages of Asia” series, although outwardly rather arcane, makes an important contribution to the wider field of SEAsian linguistic history that bridges mainland and insular languages at a cross-roads of multiple language families (and especially relates to the Kra-Dai language family). The book is derived essentially unchanged from Norquest’s 2007 University of Arizona PhD dissertation, and I congratulate Brill for rendering it into print - this will ensure it now begins to appear up in academic libraries and online databases worldwide. The e-book edition was provided for this review, but for those who prefer the tactile there is a handsome hardback available. The book is accompanied also by a separate PDF index of “Hlai Language Data and Proto-Hlai Reconstructions” which runs to 192 pages (regrettably the entries are not numbered but there are over 1,000) and this constitutes a fundamental resource for Kra-Dai historical studies that has previously been difficult to access