A symbolic algorithm for the synthesis of bounded Petri nets

This paper presents an algorithm for the synthesis of bounded Petri nets from transition systems. A bounded Petri net is always provided in case it exists. Otherwise, the events are split into several transitions to guarantee the synthesis of a Petri net with bisimilar behavior. The algorithm uses symbolic representations of multisets of states to efficiently generate all the minimal regions. The algorithm has been implemented in a tool. Experimental results show a significant net reduction when compared with approaches for the synthesis of safe Petri nets.Peer ReviewedPostprint (author's final draft

A Comparison of Petri Net Semantics under the Collective Token Philosophy

In recent years, several semantics for place/transition Petri nets have been proposed that adopt the collective token philosophy. We investigate distinctions and similarities between three such models, namely configuration structures, concurrent transition systems, and (strictly) symmetric (strict) monoidal categories. We use the notion of adjunction to express each connection. We also present a purely logical description of the collective token interpretation of net behaviours in terms of theories and theory morphisms in partial membership equational logic

Incorporation of stochastic chemistry on dust grains in the PDR code using moment equations

Unlike gas-phase reactions, chemical reactions taking place on interstellar dust grain surfaces cannot always be modeled by rate equations. Due to the small grain sizes and low flux,these reactions may exhibit large fluctuations and thus require stochastic methods such as the moment equations. We evaluate the formation rates of H2, HD and D2 molecules on dust grain surfaces and their abundances in the gas phase under interstellar conditions. We incorporate the moment equations into the Meudon PDR code and compare the results with those obtained from the rate equations. We find that within the experimental constraints on the energy barriers for diffusion and desorption and for the density of adsorption sites on the grain surface, H2, HD and D2 molecules can be formed efficiently on dust grains. Under a broad range of conditions, the moment equation results coincide with those obtained from the rate equations. However, in a range of relatively high grain temperatures, there are significant deviations. In this range, the rate equations fail while the moment equations provide accurate results. The incorporation of the moment equations into the PDR code can be extended to other reactions taking place on grain surfaces

Enhanced production of HD and D_2 molecules on small dust grains in diffuse clouds

Motivated by recent observations of deuterated molecules in the interstellar medium, we examine the production of HD and D$_2$ molecules on dust grain surfaces. A mechanism for the enhanced production of these deuterated molecules is studied. This mechanism applies on grain surfaces on which D atoms stick more strongly than H atoms, under conditions of low flux and within a suitable range of temperatures. It is shown that under these conditions the production rates of HD and D$_2$ are greatly enhanced (vs. the H$_2$ production rate) compared with the expected rates based on the adsorption of gas-phase atomic abundances of D and H. The enhancement in the formation rate of HD is comparable with the enhancement due to gas-phase ion-molecule reactions in diffuse clouds.Comment: This is a preprint of an article accepted for publication in Monthly Notices of The Royal Astromnomical Societ

Teacher-to-Parent Communication: What Parents Want from Alternative Educators

This study was conducted to determine teacher-to-parent communication preferences among parents of students, grades 9-12, attending a rural Iowa alternative education program. Thirty-seven parents were chosen to participate in the study. Twenty volunteered to complete the Parent Communication Survey (PCS). Data analysis of the PCS indicated most parents preferred regular progress updates to be sent bi-weekly via U.S. mail. Parents preferred that teachers contact them about more specific issues via phone call home. Over half of parents surveyed said they would read a classroom newsletter and website. An analysis of parent comments yielded four themes: honesty, timeliness, sensitivity, and partnership. Knowledge of these trends will be used to improve communication with parents, develop parental involvement programs, and guide future research

Replication, refinement & reachability: complexity in dynamic condition-response graphs

We explore the complexity of reachability and run-time refinement under safety and liveness constraints in event-based process models. Our study is framed in the DCR? process language, which supports modular specification through a compositional operational semantics. DCR?encompasses the “Dynamic Condition Response (DCR) graphs” declarative process model for analysis, execution and safe run-time refinement of process-aware information systems;including replication of sub-processes. We prove that event-reachability and refinement are np-hard for DCR? processes without replication, and that these finite state processes recognise exactly the languages that are the union of a regular and an ω-regular language. Moreover, we prove that eventreachability and refinement are undecidable in general for DCR? processes with replication and local events, and we provide a tractable approximation for refinement. A prototype implementation of the DCR ⋆ language is available at http://dcr.tools/acta16<br/

Diageo Strategic Audit: A Deep Dive into the Management Strategies of Diageo

Diageo is a multinational premium drink producer and supplier with over 200 brands and sales in over 180 countries. A conglomerate since its founding, Diageo controls and operates some of the world’s well-known and loved drinks, like Guinness, Johnnie Walker, Smirnoff, Bailey’s, Captain Morgan, and Crown Royal. The firm is an industry leader in consumer insight, innovation and creativity, and sustainability efforts. Diageo believes pursuing sustainability, efficiency, and positive drinking allows them to compete, now and in the future. This audit analyzes the history, leadership, business model, mission, external environment, internal environment, core competencies, recent performance, competitive dynamics, business level strategies, corporate level strategies, merger/acquisition strategies, corporate governance, and organizational controls of Diageo. The combination of ethical, innovative, and sustainable management strategies across all of these areas paints a vivid picture that explains the decades of success Diageo has had and continues to have in a fast-paced and ever-changing industry