Improving BDD Based Symbolic Model Checking with Isomorphism Exploiting Transition Relations

Symbolic model checking by using BDDs has greatly improved the applicability of model checking. Nevertheless, BDD based symbolic model checking can still be very memory and time consuming. One main reason is the complex transition relation of systems. Sometimes, it is even not possible to generate the transition relation, due to its exhaustive memory requirements. To diminish this problem, the use of partitioned transition relations has been proposed. However, there are still systems which can not be verified at all. Furthermore, if the granularity of the partitions is too fine, the time required for verification may increase. In this paper we target the symbolic verification of asynchronous concurrent systems. For such systems we present an approach which uses similarities in the transition relation to get further memory reductions and runtime improvements. By applying our approach, even the verification of systems with an previously intractable transition relation becomes feasible.Comment: In Proceedings GandALF 2011, arXiv:1106.081

Industry agglomeration, sub-national institutions and the profitability of foreign subsidiaries

This study investigates the impact of agglomeration and its interaction with subnational institutions on the profitability of multinational enterprises (MNEs) subsidiaries operating in an emerging economy. We argue that in an emerging economy like China, competition in product and factor markets is more intense between foreign firms than between foreign and domestic firms owing to market segmentation. Consequently, agglomerating with other foreign firms has negative impact on the profitability of foreign subsidiaries. In contrast, foreign firms agglomerating with domestic firms may reap gains owing to less competition and improved access to local resources and knowledge. We find that these effects are more pronounced to domestic-market-oriented foreign firms. Furthermore, sub-national institutions moderate the above relationships. Our arguments are supported by the empirical analysis based on a comprehensive dataset of foreign firms operating in China over the period of 1999-2005

Women on boards of Malaysian firms: Impact on market and accounting performance

We seek to offer some reconciliation for the conflicting theoretical arguments and empirical findings regarding the impact of women’s participation in boards on firms’ performance.We suggest that this impact differs in relation to market- and accounting-performance, and it is firm-specific, and varies by firms’ ownership type and the composition of their boards.These arguments find theoretical underpinnings in agency and resource-dependency theories, combined with behavioral and discrimination theories that articulate women behavior in the workplace and market perception of gender equality.The empirical analysis is based on a dataset of 841 publicly-listed firms in Malaysia.The results show positive impact of women’s participation on accounting-performance and negative impact on market-performance, suggesting that women directors create economic value, which is undervalued by the market. We interpret the findings with reference to the perception of women’s role in society and business in Malaysia, and the nature of corporate governance and ownership types prevalent among Malaysian firms.We suggest that the relationships might be context-specific, and hence the desired level of women’s participation varies across countries.We discuss the normative implications of the findings for government authorities considering legislation of gender-quota on boards, and for firms

The 'long' 16th century : a key period of animal husbandry change in England

Although many historians have extensively discussed the agricultural history of England between the Late Middle Ages and the Modern Era, this period of crucial changes has received less attention by archaeologists. In this paper, zooarchaeological evidence dated between the Late Middle Ages and the Early Modern period is analysed to investigate changes in animal husbandry during the ‘long’ sixteenth century. The size and shape of the main domestic animals (cattle, sheep, pig and chicken) is explored through biometrical data and discussed in line with evidence of taxonomic frequencies, ageing and sex ratios. Data from 12 sites with relevant chronologies and located in different areas of the country are considered. The results show that, although a remarkable size increase of animals occurred in England throughout the post-medieval period, much of this improvement occurred as early as the sixteenth century. The nature and causes of such improvement are discussed, with the aim of understanding the development of Early Modern farming and the foundations of the so-called Agricultural Revolution

Investigation of the Effect of Injected CO₂ on the Morrow B Sandstone through Laboratory Batch Reaction Experiments: Implications for CO₂ Sequestration in the Farnsworth Unit, Northern Texas, USA

About one million tons of CO2 have been injected into the Farnsworth unit to date. The target reservoir for CO2 injection is the Morrow B Sandstone, which is primarily made of quartz with lesser amounts of albite, calcite, chlorite, and clay minerals. The impact of CO2 injection on the mineralogy, porosity, and pore water composition of the Morrow B Sandstone is a major concern. Although numerical modeling studies suggest that porosity changes will be minimal, significant alterations to mineralogy and pore water composition are expected. Given the implications for CO2 storage effectiveness and risk assessment, it is crucial to verify the accuracy of theoretical model predictions through laboratory experiments. To this end, batch reaction experiments were conducted to model conditions near an injection well in the Morrow B Sandstone and at locations further away, where the CO2 has been diluted by formation water. The laboratory experiments involved submerging thin sections of both coarse- and fine-grained facies of the Morrow B Sandstone in formation water samples with varying levels of CO2. The experiments were conducted at the reservoir temperature of 75 °C. Two experimental runs were conducted, one lasting for 61 days and the other for 72 days. The initial fluid composition used in the second run was the same as in the first. The mineralogy changes in the thin sections were analyzed using SEM and the Tescan Integrated Mineral Analyzer (TIMA), while changes in the composition of the formation water were determined using ICP-AES. During each experiment, a thin layer of white fine-grained particles consisting mainly of dolomite and silica formed on the surface of the thin sections, leading to significant reductions in Ca, Mg, and Sr in the formation water. This outcome is consistent with numerical model predictions that dolomite would be the primary mineral that would react with injected CO2 and that silica would be oversaturated in the formation water. Changes in mineral abundance in the thin sections themselves were much less systematic than in the theoretical modeling experiments, perhaps reflecting heterogeneities in the mineral grain size surface area to volume ratios and mineral distributions in the thin sections not considered in the numerical models

Numerical Modeling of CO2 Sequestration within a Five-Spot Well Pattern in the Morrow B Sandstone of the Farnsworth Hydrocarbon Field: Comparison of the TOUGHREACT, STOMP-EOR, and GEM Simulators

The objectives of this study were (1) to assess the fate and impact of CO2 injected into the Morrow B Sandstone in the Farnsworth Unit (FWU) through numerical non-isothermal reactive transport modeling, and (2) to compare the performance of three major reactive solute transport simulators, TOUGHREACT, STOMP-EOR, and GEM, under the same input conditions. The models were based on a quarter of a five-spot well pattern where CO2 was injected on a water-alternating-gas schedule for the first 25 years of the 1000 year simulation. The reservoir pore fluid consisted of water with or without petroleum. The results of the models have numerous broad similarities, such as the pattern of reservoir cooling caused by the injected fluids, a large initial pH drop followed by gradual pH neutralization, the long-term persistence of an immiscible CO2 gas phase, the continuous dissolution of calcite, very small decreases in porosity, and the increasing importance over time of carbonate mineral CO2 sequestration. The models differed in their predicted fluid pressure evolutions; amounts of mineral precipitation and dissolution; and distribution of CO2 among immiscible gas, petroleum, formation water, and carbonate minerals. The results of the study show the usefulness of numerical simulations in identifying broad patterns of behavior associated with CO2 injection, but also point to significant uncertainties in the numerical values of many model output parameters