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Refinement calculus is a powerful and expressive tool for reasoning about sequential programs in a compositional manner. In this paper we present an extension of refinement calculus for reactive systems. Refinement calculus is based on monotonic predicate transformers, which transform sets of post-states into sets of pre-states. To model reactive systems, we introduce monotonic property transformers, which transform sets of output traces into sets of input traces. We show how to model in this semantics refinement, sequential composition, demonic choice, and other semantic operations on reactive systems. We use primarily higher order logic to express our results, but we also show how property transformers can be defined using other formalisms more amenable to automation, such as linear temporal logic (suitable for specifications) and symbolic transition systems (suitable for implementations). Finally, we show how this framework generalizes previous work on relational interfaces so as to be able to express systems with infinite behaviors and liveness properties.

We are interested in verifying dynamic properties of finite state reactive systems under fairness assumptions by model checking. The systems we want to verify are specified through a top-down refinement process. In order to deal with the state explosion problem, we have proposed in previous works to partition the reachability graph, and to perform the verification on each part separately. Moreover, we have defined a class, called Bmod, of dynamic properties that are verifiable by parts, whatever the partition. We decide if a property P belongs to Bmod by looking at the form of the Buchi automaton that accepts the negation of P. However, when a property P belongs to Bmod, the property f => P, where f is a fairness assumption, does not necessarily belong to Bmod. In this paper, we propose to use the refinement process in order to build the parts on which the verification has to be performed. We then show that with such a partition, if a property P is verifiable by parts and if f is the expression of the fairness assumptions on a system, then the property f => P is still verifiable by parts. This approach is illustrated by its application to the chip card protocol T=1 using the B engineering design language.

This is the final technical report tor the project. It presents an enumeration of the research results of the effort, including a list of papers published and a brief summary of the content or the papers. The results were primarily in the area of compiler validation, formal methods, and verification. Applications or the work include reactive systems, as mentioned in the title of the effort, as well as more general software Systems.

The goals of this research are to produce intelligent, flexible, reactive behaviors and methods for specifying and communicating information between multiagent teams. In particular we have been studying three closely related subjects: * Formation Control - to allow teams of robotic agents to move in a coordinated manner through a potentially hostile environment without interfering with other active navigational behaviors. * Teleautonomous Control of Multi-agent Teams - to allow a massive reduction in cognitive workload for the control of a group of robotic vehicles by permitting commands to be specified at the team level rather than at the individual agent level. * Team Mission Specification Methods - to provide robust and flexible mission specification for reactive team military scenarios. (KAR) p. 4

The 18tb International Colloquium on the Dynamics of Explosions and Reactive Systems was held at the University of Washington from 29 July through 3 August 2001. Two hundred and twenty nine participants from 21 countries gathered to discuss the latest advances in experimental investigation and mathematical modeling of explosions and reactive systems. Two minisymposia focused on pulsed detonation engines and ram accelerators, while 186 podium presentations and 40 posters covered a broad range of theoretical and experimental topics.

This project aims to develop a novel three-stage coupled multi-scale QM-MD-SPH approach for modeling and simulation of complex heterogeneous multicomponent reactive systems, considering both high explosive (HE) explosion effects. The novelty of our approach is that the unified particle-based approaches couples the dynamic events over nine orders of magnitude length scales (nm-m) and twelve orders of magnitude timescales (ps-s). This is achieved by using ab initio quantum mechanics (QM) approaches at the nano scale, molecular dynamics (MD) at the micro scale and smoothed particle hydrodynamics (SPH) at the continuum scale.

This final report summarizes progress realized in the development and utilization of a gas diagnostics system for use in evaluating ramjet combustor performance. The work accomplished is described in four sections. In the first section, the results of several series of cold flow sampling tests are presented. Several detailed simulated fuel concentration profiles were determined for the flowfield of the ramjet combustor which was studied. This ramjet combustor can be operated in both dump combustor and ducted rocket combustor configurations. The second section of the report reviews progress achieved in the development of methodology and calibration procedures for monitoring several compounds of interest in an active combustion environment, including O2, CO, CO2, H2O, and hydrocarbon fuels. The third section describes the construction of a flat flame burner system and its application for flame species profiles measurements. Detailed profiles of several stable flame species, including N2, O2, CO, CO2, CH4, H2O, and AR, were obtained for both methane/air and methane/oxygen flames. Finally, the fourth section of this report is concerned with the design and construction of an innovative sample probe which consists of a quartz microprobe tip for gas sampling and a water-cooled stainless steel probe body to provide the required physical support and protection for the tip.

We describe several techniques for verifying infinite-state systems via finite-state abstractions. Diagrams are top-down property-driven abstractions, which are especially suited for compositional, assume-guarantee reasoning. Predicate abstraction uses a bottom-up approach for generating abstractions; invariant generation techniques are applied to automatically generate the required predicates. Extended finite-state abstractions allow inclusion of extra information produced by the deductive abstraction, which can be used by the model checker to reduce the number of spurious counterexamples. These methods have been or currently are being implemented in the Stanford Temporal Prover. The methods have been applied in the analysis of a medical device.

We describe several techniques for verifying infinite-state systems via finite-state abstractions. Diagrams are top-down property-driven abstractions, which are especially suited for compositional, assume-guarantee reasoning. Predicate abstraction uses a bottom-up approach for generating abstractions; invariant generation techniques are applied to automatically generate the required predicates. Extended finite-state abstractions allow inclusion of extra information produced by the deductive abstraction, which can be used by the model checker to reduce the number of spurious counterexamples. These methods have been or currently are being implemented in the Stanford Temporal Prover. The methods have been applied in the analysis of a medical device.

Philip Morris Records; publication

Philip Morris Records; publication

An approach to evaluating reactive airborne windshear detection systems was developed to support a deployment study for future FAA ground-based windshear detection systems. The deployment study methodology assesses potential future safety enhancements beyond planned capabilities. The reactive airborne systems will be an integral part of planned windshear safety enhancements. The approach to evaluating reactive airborne systems involves separate analyses for both landing and take-off scenario. The analysis estimates the probability of effective warning considering several factors including NASA energy height loss characteristics, reactive alert timing, and a probability distribution for microburst strength.

The research involved investigation of process parameter growth environment film property relationships for various binary oxide and nitride films grown on unheated substrates by reactive sputter deposition using an elemental target. In situ optical emission spectroscopy and glow discharge mass spectrometry were used to determine gas phase species in the plasma volume. A battery of techniques were used to characterize (post-deposition) film crystallography, chemistry, microstructure, electrical resistivity, and optical behavior. Keywords: Sputter deposition, Glow discharges, Glow discharge diagnostics, Optical emission, Mass spectrometry, Aluminum oxide, Vanadium, Pentoxide, Gold oxide, Tungsten nitride, Aluminum nitride, Germanium dioxide.

The research involved investigation of process parameter growth environment film property relationships for various binary oxide and nitride films grown on unheated substrates by reactive sputter deposition using an elemental target. In situ optical emission spectroscopy and glow discharge mass spectrometry were used to determine gas phase species in the plasma volume. A battery of techniques were used to characterize (post-deposition) film crystallography, chemistry, microstructure, electrical resistivity, and optical behavior. Keywords: Sputter deposition, Glow discharges, Glow discharge diagnostics, Optical emission, Mass spectrometry, Aluminum oxide, Vanadium, Pentoxide, Gold oxide, Tungsten nitride, Aluminum nitride, Germanium dioxide.

The goal of software testing is to expose as many faults as possible. Often one can increase the number of faults detected by running large amounts of test cases, therefore the ability to automatically generate applicable test cases for a System Under Test (SUT), would be a valuable tool. In this thesis an attributed event grammar is designed and used to build a model that describes the environment a SUT must operate in. This event grammar captures events, their precedence or inclusion relation to other events, and attributes of the events. An event is defined as an observable action that has a distinct beginning and end. The high level environment model is then used by a test generator to produce an event trace from which input for the SUT is extracted. Thousands of event traces can be generated. For reactive systems the event trace will have the appropriate time delays between inputs. The feasibility of this approach is proven by implementing a prototype of an automated test generator based on environment models.

A reactive system is characterized by a control program that interacts with an environment (or controlled program). The control program monitors the environment and reacts to significant events by sending commands to the environment. This structure is quite general. Not only are most embedded real time systems reactive systems, but so are monitoring and debugging systems and distributed application management systems. Since reactive systems are usually long running and may control physical equipment, fault tolerance is vital. The research tries to understand the principal issues of fault tolerance in real time reactive systems and to build tools that allow a programmer to design reliable, real time reactive systems. In order to make real time reactive systems reliable, several issues must be addressed: (1) How can a control program be built to tolerate failures of sensors and actuators. To achieve this, a methodology was developed for transforming a control program that references physical value into one that tolerates sensors that can fail and can return inaccurate values; (2) How can the real time reactive system be built to tolerate failures of the control program. Towards this goal, whether the techniques presented can be extended to real time reactive systems is investigated; and (3) How can the environment be specified in a way that is useful for writing a control program. Towards this goal, whether a system with real time constraints can be expressed as an equivalent system without such constraints is also investigated.

We study a reaction diffusion system where we consider a non-gaussian process instead of a standard diffusion. If the process increments follow a probability distribution with tails approaching to zero faster than a power law, the usual qualitative behaviours of the standard reaction diffusion system, i.e., exponential tails for the reacting field and a constant front speed, are recovered. On the contrary if the process has power law tails, also the reacting field shows power law tail and the front speed increases exponentially with time. The comparison with other reaction-transport systems which exhibit anomalous diffusion shows that, not only the presence of anomalous diffusion, but also the detailed mechanism, is relevant for the front propagation.

The bigraph embedding problem is crucial for many results and tools about bigraphs and bigraphical reactive systems (BRS). Current algorithms for computing bigraphical embeddings are centralized, i.e. designed to run locally with a complete view of the guest and host bigraphs. In order to deal with large bigraphs, and to parallelize reactions, we present a decentralized algorithm, which distributes both state and computation over several concurrent processes. This allows for distributed, parallel simulations where non-interfering reactions can be carried out concurrently; nevertheless, even in the worst case the complexity of this distributed algorithm is no worse than that of a centralized algorithm.

Reactive Rayleigh-Taylor systems are characterized by the competition between the growth of the instability and the rate of reaction between cold (heavy) and hot (light) phases. We present results from state-of-the-art numerical simulations performed at high resolution in 2d by means of a self-consistent lattice Boltzmann method which evolves the coupled momentum and thermal equations and includes a reactive term. We tune the parameters affecting flame properties, in order to address the competition between turbulent mixing and reaction, ranging from slow to fast-reaction rates. We also study the mutual feedback between turbulence evolution driven by the Rayleigh-Taylor instability and front propagation against gravitational acceleration. We quantify both the enhancement of flame propagation due to turbulent mixing for the case of slow reaction-rate as well as the slowing down of turbulence growth for the fast reaction case, when the flame quickly burns the gravitationally unstable phase. An increase of intermittency at small scales for temperature characterizes the case of fast reaction, associated to the formation of sharp wrinkled fronts separating pure hot/cold fluids regions.

Reactive Rayleigh-Taylor systems are characterized by the competition between the growth of the instability and the rate of reaction between cold (heavy) and hot (light) phases. We present results from state-of-the-art numerical simulations performed at high resolution in 2d by means of a self-consistent lattice Boltzmann method which evolves the coupled momentum and thermal equations and includes a reactive term. We tune the parameters affecting flame properties, in order to address the competition between turbulent mixing and reaction, ranging from slow to fast-reaction rates. We also study the mutual feedback between turbulence evolution driven by the Rayleigh-Taylor instability and front propagation against gravitational acceleration. We quantify both the enhancement of flame propagation due to turbulent mixing for the case of slow reaction-rate as well as the slowing down of turbulence growth for the fast reaction case, when the flame quickly burns the gravitationally unstable phase. An increase of intermittency at small scales for temperature characterizes the case of fast reaction, associated to the formation of sharp wrinkled fronts separating pure hot/cold fluids regions.

Reactive Rayleigh-Taylor systems are characterized by the competition between the growth of the instability and the rate of reaction between cold (heavy) and hot (light) phases. We present results from state-of-the-art numerical simulations performed at high resolution in 2d by means of a self-consistent lattice Boltzmann method which evolves the coupled momentum and thermal equations and includes a reactive term. We tune the parameters affecting flame properties, in order to address the competition between turbulent mixing and reaction, ranging from slow to fast-reaction rates. We also study the mutual feedback between turbulence evolution driven by the Rayleigh-Taylor instability and front propagation against gravitational acceleration. We quantify both the enhancement of flame propagation due to turbulent mixing for the case of slow reaction-rate as well as the slowing down of turbulence growth for the fast reaction case, when the flame quickly burns the gravitationally unstable phase. An increase of intermittency at small scales for temperature characterizes the case of fast reaction, associated to the formation of sharp wrinkled fronts separating pure hot/cold fluids regions.

Chemical surface cleaning procedures for metals using oxidation/reduction cycles by exposure to oxidizing (oxygen, nitric oxide) and reducing (Hydrogen, Ammonia) gases are summarized and are briefly discussed for iron, nickel, palladium, copper and silver surfaces. We also present data on the reduction of gaseous contaminants in a stainless steel UHV system by flowing nitric oxide through the system during bake-out Keywords: Vacuum chambers.

This report discusses the development of formal methods for monitoring safety-critical real-time and reactive systems. This project centers on building on expertise in the area of process-algebra-based specification and analysis of real-time systems as well as the paradigm of program checking which allows one to make rigorous statements about the correctness of program behavior rather than of the program itself. To integrate these ideas a prototype system (JavaMAC) for monitoring and checking Java programs has been implemented. MAC takes a monitoring script provided by the user, the program, and a requirement specification and produces a) an instrumentation of the program to send variable update information to the monitoring and checking unit b) a script for transforming low level program variable values to abstract events and c) a script for checking whether a sequence of events is consistent with the desired property. These scripts written in new languages are defined (PEDL and MEDL respectively) and are then used to produce other components that extract low-level information from the program, convert it to events and check that the sequence of events represents correct behavior. The prototype has been successfully tested on two applications --- micro air vehicles attaining a desired formation, and convergence of a network routing protocol. Performance measurements have been done on JavaMAC in an attempt to breakdown the overhead introduced by JavaMAC into its various components. Subsequently several optimizations in JavaMAC have been introduced to improve the performance. Other research funded by this grant includes papers on probabilistic bisimulation and on low-overhead checking of the correctness of the output produced by programs for sorting and other mathematically well-defined' tasks.

The pulsed electrical excitation of reactive metals like aluminum in water triggers a fast and highly energetic chemical reaction generating gaseous products. For applications such as fuses, safe explosives or fast gas generation, it is desirable to maximize the ratio of conductor mass to stored electrical energy while rapidly attaining a high resistive state. Various techniques have been used to partly meet this requirement. These techniques included double pulse application, pre-dispersion of metallic material prior to pulse application, and coaxial metallic system in which a metal of lower boiling point is surrounded by a metal of higher boiling point. The preliminary test results demonstrated that the efficiency of the pulsed power in deriving the chemical action can be greatly improved by these techniques.

Formal methods are being considered for the description of many systems including systems with real time constraints and multiple concurrently executing processes. This report develops a set of evaluation criteria and evaluates Communicating Sequential Processes (CSP), the Vienna Development Method (VDM), and temporal logic. The evaluation is based on specifications, written with each of the techniques, of an example avionics system. The term reactive systems is used in this report to describe systems that do not terminate but instead maintain continuing interaction with the environment. Examples of reactive systems are operating systems and industrial control systems. The report classifies each specification technique using criteria based on the characteristics and development of reactive systems. We also provide an evaluation of the applicability of the techniques to the specification of reactive systems. The report also includes a summary of our discussions with developers and practitioners of formal specification techniques.

Formal methods are being considered for the description of many systems including systems with real time constraints and multiple concurrently executing processes. This report develops a set of evaluation criteria and evaluates Communicating Sequential Processes (CSP), the Vienna Development Method (VDM), and temporal logic. The evaluation is based on specifications, written with each of the techniques, of an example avionics system. The term reactive systems is used in this report to describe systems that do not terminate but instead maintain continuing interaction with the environment. Examples of reactive systems are operating systems and industrial control systems. The report classifies each specification technique using criteria based on the characteristics and development of reactive systems. We also provide an evaluation of the applicability of the techniques to the specification of reactive systems. The report also includes a summary of our discussions with developers and practitioners of formal specification techniques.

Distribution systems (DSs) are highly stressed with addition of newer loads like electric vehicle charging stations and lower scope for expansion due to urbanization. Any line outage could cause interruption to major loads. Reliability studies have gained importance for lowering the frequency and lowering the duration of interruption for supply systems. In this paper a bi-stage method for optimum placement of reactive power compensation devices and distributed generations (DGs) for enhancing voltage stability and system reliability. A new method named delta analysis method is used to optimally locate the reactive power compensation devices and DGs. IEEE-33 radial DS, which is taken as experimental system. Based on the study, the fixing of reactive power compensation devices and DGs are to increase voltage outline of buses and decrease power fatalities. After the placement of DGs, the enhancement in reliability indices following line contingency is studied using MATLAB simulation.

viii, 659 pages : 24 cm

An approach to provably-correct design of reactive algorithms is described, that has been developed at the Glushkov Institute of Cybernetics of the Ukrainian Academy of Sciences. The basic problems arising in the design of reactive algorithms specified in the logical language L, and methods to solve them are considered. 

Forward-looking windshear systems are developing to a point (particularly the infrared sensors) where their interface with the cockpit and reactive windshear systems needs to be defined. As airlines retrofit their aircraft with reactive windshear systems, it is important to recognize that onboard windshear systems of the future will be a combination of both forward-looking and reactive elements. Today's reactive systems need to be built with the capability to interface with the forward-looking systems of tomorrow. This presentation is a first step at looking at the requirements and defining interface standards for integrated forward-looking and reactive windshear systems. Undoubtedly the requirements for interfacing these types of windshear systems will change as the technology changes.

A mathematical model was obtained, on the basis of the method of mixed coordinates, of a generalized flexible spacecraft at one end of which was appended the directive action of a system of gas reactive nozzles. Various structural forms were obtained functionally describing flexible spacecraft, as systems consisting of a solid central body with flexible structural elements joined to it.

Real-time embedded software development is recognized as a significant cost and schedule driver for many of today's advanced-and highly software-centric-military systems. This project targets these issues directly by developing techniques to enable rapid construction and greater reuse in embedded systems while also delivering reliability and performance improvements. In particular, these benefits are a result of the ability to analyze the behavior and correctness of real-time software; the ability to construct individual software components or to develop large configurations of multiple components more rapidly by leveraging high-level, domain-specific abstractions (a productivity benefit); the ability to enforce predictable and graceful degradation behavior during overload (a reliability benefit); and the ability to operate closer to resource saturation (a performance benefit due to support for graceful degradation).

This study focuses on reactive power planning in the IEEE30-bus test system, specifically involving the integration of flexible AC transmission systems (FACTS) within the utility system. The primary objective is to minimize power loss and voltage deviation. To address this, a recently developed optimization algorithm called modified ant-lion optimizer (MALO) is applied to solve the optimal reactive power dispatch (ORPD) problem on the IEEE 30-bus system. A comparative analysis is conducted between the results obtained with and without FACTS devices. The findings reveal that the utilization of FACTS devices leads to significantly improved outcomes compared to scenarios without FACTS devices. Among the FACTS devices studied, the unified power flow controller (UPFC) demonstrates superior performance compared to the static synchronous compensator (STATCOM) and interline power flow controller (IPFC).

Significant scientific progress was made during the final year of this grant. The primary accomplishment was improving the performance of the Probabilistic I/O Automata (PIOA) Tool and comparing its performance to the PRISM model checker. The authors also designed and implemented the Aristotle runtime verification tool suite and applied it to the Linux kernel, as well as the GMC software model checker for GCC. They also developed and implemented a generic, on-the-fly technique for checking the correctness of real-time systems. This report contains a list of 13 papers submitted or published under ARO sponsorship; the names of scientific personnel supported by the project; a summary of scientific progress and accomplishments with regard to process-algebraic language for PIOA, Monte Carlo model checking, efficient modeling of excitable biological cells using hybrid automata, and safety/liveness semantics for UML 2.0 sequence diagrams; architectural system modeling; and technology transfer.

The initial vibrational energy distribution of molecules that collide with a hot surface has been varied. The effect on the collisional reaction probability has been studied under single collision conditions. These experiments provide a more sensitive test of the relative suitability of various analytical forms for the collisional transition probability matrix, (CTPM). The reaction system is the isomerization of cyclobutene to 1,3 butadiene. A seasoned fused quartz surface was used over the temperature range 600 K - 900 K. Variation of the initial vibrational energy population vector of cyclobutene molecules was made by change of their initial temperature in the range 273 K - 620 K. Gaussian or Boltzmann exponential forms of (CTPM) prove to be the most suitable to fit the data.

This research is directed towards the implementation of a comprehensive deductive-algorithmic environment (toolkit) for the development and verification of high assurance reactive systems, especially concurrent, real-time, and hybrid systems. For this, we have designed and implemented the STCP (Stanford Temporal Prover) verification system. Reactive systems have an ongoing interaction with their environment, and their computations are infinite sequences of states. A large number of systems can be seen as reactive systems, including hardware, concurrent programs, network protocols, and embedded systems. Temporal logic provides a convenient language for expressing properties of reactive systems. A temporal verification methodology provides procedures for proving that a given system satisfies a given temporal property. The research covered necessary theoretical foundations as well as implementation and application issues.

As a result of the growing wind power penetration especially of Type-1 and Type-2 wind turbine technology that requires reactive power from the electricity grid rather than producing reactive power and with the current trend in the infrastructure of functional wind power plants in nowadays electric-power systems

As a result of the growing wind power penetration especially of Type-1 and Type-2 wind turbine technology that requires reactive power from the electricity grid rather than producing reactive power and with the current trend in the infrastructure of functional wind power plants in nowadays electric-power systems

We show in this paper how managed multi-context systems (mMCSs) can be turned into a reactive formalism suitable for continuous reasoning in dynamic environments. We extend mMCSs with (abstract) sensors and define the notion of a run of the extended systems. We then show how typical problems arising in online reasoning can be addressed: handling potentially inconsistent sensor input, modeling intelligent forms of forgetting, selective integration of knowledge, and controlling the reasoning effort spent by contexts, like setting contexts to an idle mode. We also investigate the complexity of some important related decision problems and discuss different design choices which are given to the knowledge engineer.

Accurate quantum mechanical transition probabilities and rate constants for vibrational deactivation via reactive and nonreactive collisions in collinear H + FH(v), D + FD(v), H + FD(v), and D + FH(v) are presented. In all cases, the reactive inelastic rate constants are larger than the nonreactive ones for the same initial and final vibrational states, but the ratios of these reactive and nonreactive rate constants depend strongly on the vibrational quantum number v and on isotopic composition of the reagents. Nonreactive and reactive transition probabilities for multiquantum jump transitions are generally comparable to those for single quantum transitions. This vibrationally nonadiabatic behavior is a direct consequence of the severe distortion of the diatomic that occurs in a collision on a reactive potential surface, and makes H or D more efficient deactivators of HF or DF than are nonreactive collision partners. Most conclusions are in qualitative and even quantitative agreement with those of Wilkins' three-dimensional quasi-classical trajectory study on the same systems. (Author)

The applicability of objects architecture for designing real-time reactive operating systems is examined through a model of its elements, their relationships and operations. The requirements of creation, deletion and manipulation of objects in a distributed system with a high degree of fault tolerance are introduced and analyzed. Then, the imposition of time constraints is introduced, and its influence on the objects architecture is analyzed. Relationships with other objects and additional fault tolerance relations are considered. Finally, examples of some solutions to fundamental real-time problems are proposed. Keywords: Systems engineering; Embedding; Computer programming.

SOL (Secure Operations Language) is a synchronous programming language for implementing reactive systems. The utility of SOL hinges upon the fact that it is a secure language, i.e., most programs in SOL are amenable to fully automated static analysis techniques, such as automatic theorem proving using decision procedures or model checking. Among the unique features of SOL is the ability to express a wide class of enforceable safety and security policies (including the temporal aspects of software component interfaces) in the language itself, thereby opening up the possibility of eliminating runaway computations and malicious code, such as worms and viruses.

From the bitsavers.org collection, a scanned-in computer-related document. memorex :: 7x00 processor :: Reactive Computer Systems RPG II System Design Specification 197108

From the bitsavers.org collection, a scanned-in computer-related document. memorex :: 7x00 processor :: Reactive Computer Systems RPG II System Design Specification 197108

Larsen and Skou characterized probabilistic bisimilarity over reactive probabilistic systems with a logic including true, negation, conjunction, and a diamond modality decorated with a probabilistic lower bound. Later on, Desharnais, Edalat, and Panangaden showed that negation is not necessary to characterize the same equivalence. In this paper, we prove that the logical characterization holds also when conjunction is replaced by disjunction, with negation still being not necessary. To this end, we introduce reactive probabilistic trees, a fully abstract model for reactive probabilistic systems that allows us to demonstrate expressiveness of the disjunctive probabilistic modal logic, as well as of the previously mentioned logics, by means of a compactness argument.

In this paper, we introduce reactive multi-context systems (rMCSs), a framework for reactive reasoning in the presence of heterogeneous knowledge sources. In particular, we show how to integrate data streams into multi-context systems (MCSs) and how to model the dynamics of the systems, based on two types of bridge rules. We illustrate how several typical problems arising in the context of stream reasoning can be handled using our framework. Reasoning based on multiple knowledge sources that need to be integrated faces the problem of potential inconsistencies. We discuss various methods for handling inconsistencies, with a special focus on non-existence of equilibria. In particular, we show how methods developed for managed MCSs can be generalized to rMCSs. We also study the issue of nondeterminism in rMCSs. One way of avoiding nondeterminism is by applying an alternative, skeptical semantics. We show how such a semantics, called well-founded semantics, can be defined for rMCSs, and what the effect of using this semantics instead of the original one is. We investigate the complexity of various reasoning problems related to rMCSs. Finally, we discuss related work, with a special focus on two of the most relevant approaches w.r.t. stream reasoning, namely LARS and STARQL.

Synchronous programming is a paradigm of choice for the design of safety-critical reactive systems. Runtime enforcement is a technique to ensure that the output of a black-box system satisfies some desired properties. This paper deals with the problem of runtime enforcement in the context of synchronous programs. We propose a framework where an enforcer monitors both the inputs and the outputs of a synchronous program and (minimally) edits erroneous inputs/outputs in order to guarantee that a given property holds. We define enforceability conditions, develop an online enforcement algorithm, and prove its correctness. We also report on an implementation of the algorithm on top of the KIELER framework for the SCCharts synchronous language. Experimental results show that enforcement has minimal execution time overhead, which decreases proportionally with larger benchmarks.

We study polar molecule scattering in quasi-one-dimensional geometries. Elastic and reactive collision rates are computed as a function of collision energy and electric dipole moment for different confinement strengths. The numerical results are interpreted in terms of first order scattering and of adiabatic models. Universal dipolar scattering is also discussed. Our results are relevant to experiments where control of the collision dynamics through one dimensional confinement and an applied electric field is envisioned.

This paper studies the problem of receiver modeling in molecular communication systems. We consider the diffusive molecular communication channel between a transmitter nano-machine and a receiver nano-machine in a fluid environment. The information molecules released by the transmitter nano-machine into the environment can degrade in the channel via a first-order degradation reaction and those that reach the receiver nano-machine can participate in a reversible bimolecular reaction with receiver receptor proteins. Thereby, we distinguish between two scenarios. In the first scenario, we assume that the entire surface of the receiver is covered by receptor molecules. We derive a closed-form analytical expression for the expected received signal at the receiver, i.e., the expected number of activated receptors on the surface of the receiver. Then, in the second scenario, we consider the case where the number of receptor molecules is finite and the uniformly distributed receptor molecules cover the receiver surface only partially. We show that the expected received signal for this scenario can be accurately approximated by the expected received signal for the first scenario after appropriately modifying the forward reaction rate constant. The accuracy of the derived analytical results is verified by Brownian motion particle-based simulations of the considered environment, where we also show the impact of the effect of receptor occupancy on the derived analytical results.

The goal of software testing is to expose as many faults as possible. Often one can increase the number of faults detected by running large amounts of test cases, therefore the ability to automatically generate applicable test cases for a System Under Test (SUT), would be a valuable tool. In this thesis an attributed event grammar is designed and used to build a model that describes the environment a SUT must operate in. This event grammar captures events, their precedence or inclusion relation to other events, and attributes of the events. An event is defined as an observable action that has a distinct beginning and end. The high level environment model is then used by a test generator to produce an event trace from which input for the SUT is extracted. Thousands of event traces can be generated. For reactive systems the event trace will have the appropriate time delays between inputs. The feasibility of this approach is proven by implementing a prototype of an automated test generator based on environment models.