On the Uniform Random Generation of Non Deterministic Automata Up to Isomorphism

In this paper we address the problem of the uniform random generation of non deterministic automata (NFA) up to isomorphism. First, we show how to use a Monte-Carlo approach to uniformly sample a NFA. Secondly, we show how to use the Metropolis-Hastings Algorithm to uniformly generate NFAs up to isomorphism. Using labeling techniques, we show that in practice it is possible to move into the modified Markov Chain efficiently, allowing the random generation of NFAs up to isomorphism with dozens of states. This general approach is also applied to several interesting subclasses of NFAs (up to isomorphism), such as NFAs having a unique initial states and a bounded output degree. Finally, we prove that for these interesting subclasses of NFAs, moving into the Metropolis Markov chain can be done in polynomial time. Promising experimental results constitute a practical contribution.Comment: Frank Drewes. CIAA 2015, Aug 2015, Umea, Sweden. Springer, 9223, pp.12, 2015, Implementation and Application of Automata - 20th International Conferenc

SAT-based Explicit LTL Reasoning

We present here a new explicit reasoning framework for linear temporal logic (LTL), which is built on top of propositional satisfiability (SAT) solving. As a proof-of-concept of this framework, we describe a new LTL satisfiability tool, Aalta\_v2.0, which is built on top of the MiniSAT SAT solver. We test the effectiveness of this approach by demonnstrating that Aalta\_v2.0 significantly outperforms all existing LTL satisfiability solvers. Furthermore, we show that the framework can be extended from propositional LTL to assertional LTL (where we allow theory atoms), by replacing MiniSAT with the Z3 SMT solver, and demonstrating that this can yield an exponential improvement in performance

Influence of Cabling on Photovoltaic System Performance: Wire Length, Diameter, and Material

Despite advancements in solar PV technology, significant challenges remain in the Global South, including financial, human resource, environmental, and technological constraints. System losses—caused by reflection, temperature effects, inverter inefficiency, cabling losses, shading, and degradation—are a major concern. This study examines how cabling parameters—wire length, diameter, and material—affect PV system performance and energy losses. Using a computational model, it evaluates a 3 kWp PV system in Durban, South Africa, analyzing efficiency, specific annual yield, and avoidable CO₂ emissions across various cabling configurations. The study’s key findings include: at a constant wire diameter of 4 mm, specific annual yield decreases as wire length increases, dropping from 977.36 kWh/kW at 5 m to 966.32 kWh/kW at 50 m, reflecting efficiency losses; at a constant wire length of 20 m, yield improves with increasing diameter, rising from 970.71 kWh/kWp at 2.5 mm to 977.81 kWh/kWp at 20 mm. Beyond 25 mm, yield gains diminish, stabilizing around 978.39 kWh/kW at 90 mm; at a fixed wire length of 20 m, avoided CO₂ emissions increase with wire diameter up to 25 mm, after which gains level off from 30 mm to 90 mm; at a constant diameter of 4 mm, avoided CO₂ emissions increase from 1,378 kg/year at a wire length of 5 m to 1,363 kg/year at 50 m. These findings highlight the importance of optimizing cabling parameters to minimize system losses and enhance the overall efficiency and sustainability of PV systems

e-Learning development in medical physics and engineering

Medical Physics and Engineering was among the first professions to develop and apply e-Learning (e-L). The profession provides excellent background for application of simulations and other e-L materials. The paper describes several layers for e-L development: Programming specific simulations; Building e-L modules; Development of e-L web-based programmes. The paper shows examples from these layers and outlines their specificities. At the end, the newest e-L development (project EMITEL) is briefly introduced and the necessity of a regularly updated list of e-L activities is emphasised

Floating Photovoltaic Systems: Expanding Renewable Alternatives to Combat Greenhouse Gas Emissions

Extreme weather events like droughts, floods, heatwaves, and cyclones are increasingly linked to climate change, leading to fatalities, infrastructure damage, and the displacement of thousands. CO2 emissions primarily drive this climate change from burning fossil fuels. South Africa (SA), the highest CO2 emitter in Africa, heavily relies on coal, which accounts for nearly 85% of its emissions. However, SA also has significant but underdeveloped solar energy potential. Expanding solar PV is crucial for SA and other African nations to address energy shortages, reduce GHG emissions, enhance energy security, stimulate economic growth, create jobs, and achieve long-term cost savings. The study includes a computational modelling case study to evaluate PV potential and system performance, comparing onshore and offshore scenarios. It reports a Global Tilted Irradiance (GTI) of 1866 kWh/m² for land-based PV (LPV) and 1797 kWh/m² for FPV, with a Levelised Cost of Energy (LCOE) of $0.04612/kWh for LPV and$0.05664/kWh for FPV, respectively. The results suggest that the 10-kWp LPV system slightly outperforms the FPV system, though both are within acceptable performance ranges because of harsher offshore conditions. The paper proposes hybrid RE systems including FPV to improve SA's grid stability and efficiency.

Advanced Automata Minimization

We present an efficient algorithm to reduce the size of nondeterministic Buchi word automata, while retaining their language. Additionally, we describe methods to solve PSPACE-complete automata problems like universality, equivalence and inclusion for much larger instances (1-3 orders of magnitude) than before. This can be used to scale up applications of automata in formal verification tools and decision procedures for logical theories. The algorithm is based on new transition pruning techniques. These use criteria based on combinations of backward and forward trace inclusions. Since these relations are themselves PSPACE-complete, we describe methods to compute good approximations of them in polynomial time. Extensive experiments show that the average-case complexity of our algorithm scales quadratically. The size reduction of the automata depends very much on the class of instances, but our algorithm consistently outperforms all previous techniques by a wide margin. We tested our algorithm on Buchi automata derived from LTL-formulae, many classes of random automata and automata derived from mutual exclusion protocols, and compared its performance to the well-known automata tool GOAL.Comment: 15 page

Antichain Algorithms for Finite Automata

We present a general theory that exploits simulation relations on transition systems to obtain antichain algorithms for solving the reachability and repeated reachability problems. Antichains are more succinct than the sets of states manipulated by the traditional fixpoint algorithms. The theory justifies the correctness of the antichain algorithms, and applications such as the universality problem for finite automata illustrate efficiency improvements. Finally, we show that new and provably better antichain algorithms can be obtained for the emptiness problem of alternating automata over finite and infinite words

Power Supply and the Role Hydropower Plays in Sub-Saharan Africa's Modern Energy System and Socioeconomic Wellbeing

This study overviews the status of the power supply; implications of the inadequate power supply; and the significance of hydropower in the socioeconomic wellbeing of sub-Saharan Africa (SSA). This study noted that despite the large presence of energy potentials across the entire region, the power supply is grossly inadequate. Currently, the world's highest population without access to electricity live in SSA and the number, which was 585 million in 2009 is expected to increase to 645 million in 2030. The supply of clean, affordable and adequate power in the region is compounded by the global energy trends, described as energy trilemma by the World Energy Council (WEC). These attributes are anchored in three pillars -energy equity, energy security and environmental sustainability. This article sees hydropower technology, which has been revolutionised over the years into different categories, as a vital modern energy source for clean power generation. The hydropower technologies discussed are large hydropower, small hydropower (SHP) and pumped storage hydropower. Hydropower provides clean, relatively cheap electricity, reliable and sustainable power supply. The study identifies SHP as a system that satisfies the modern energy attributes of low CO2 emissions and environmentally friendly scheme, suitable for standalone and rural electrification. Keywords: Hydropower; Small hydropower; Renewable energy; Power; Electricity; sub-Saharan Africa JEL Classifications: Q2, Q4, Q5, Q420 DOI: https://doi.org/10.32479/ijeep.718

Thyroglossal duct cyst carcinoma

Not required for Clinical Vignette