Measurement, Decoherence and Chaos in Quantum Pinball

The effect of introducing measuring devices in a ``quantum pinball'' system is shown to lead to a chaotic evolution for the particle position as defined in Bohm's approach to Quantum Mechanics.Comment: Latex, uses ioplppt style, two figures. Also can be ftp'd anonymously from: ftp://zaphod.phys.port.ac.uk/pub/papers/paper2

Conflicts and projections

This paper studies abstraction methods suitable to verify very large models of discrete-event systems to be nonconflicting. It compares the observer property to methods known from process algebra, namely to conflict equivalence and observation equivalence. The observer property is shown to be the property that corresponds to conflict equivalence in the case where natural projection is used for abstraction. In this case, the observer property turns out to be the least restrictive condition that can be imposed on natural projection to enable compositional reasoning about conflicts. The observer property is also shown to be closely related to observation equivalence. Several examples and propositions are presented to relate different aspects of these methods of abstraction

Is there Evidence of Shift-Contagion in International Housing Markets?

The paper attempts to provide, for housing markets, evidence of "shift-contagion" at the international level, i. e. regime shifts in the transmission of asset prices during crisis periods. The focus is in particular on UK and Spain. We use a Markov Switching FAVAR framework and regime-dependent impulse response functions. The `Crisis' regime which we identify endogenously is shown to also correspond to an exogenously determined index of frequency of financial crises in OECD countries, which peaked in the early 1990s and in the more recent Subprime crisis. Furthermore, we find that the response of domestic house price to a shock to a common (global) house price factor during a `Crisis' regime is relatively more amplified than in a `Normal' (more tranquil) regime. Less compelling evidence is found for France.contagion, housing market, regime shifts, FAVAR model

Variable abstraction and approximations in supervisory control synthesis

This paper proposes a method to simplify Extended Finite-state Automata (EFA) in such a way the least restrictive controllable supervisor is preserved. The method is based on variable abstraction, which involves the identification and removal of irrelevant variables from a model. Variable abstraction preserves controllability, and the paper shows how approximations can be used to ascertain least restrictiveness of the synthesis result. The approach has the modelling benefits of Extended Finite-state Automata, leads to optimal control solutions, and reduces the synthesis cost. An example of a manufacturing system illustrates the contributions

Compositional nonblocking verification with always enabled events and selfloop-only events

This paper proposes to improve compositional nonblocking verification through the use of always enabled and selfloop-only events. Compositional verification involves abstraction to simplify parts of a system during verification. Normally, this abstraction is based on the set of events not used in the remainder of the system, i.e., in the part of the system not being simplified. Here, it is proposed to exploit more knowledge about the system and abstract events even though they are used in the remainder of the system. Abstraction rules from previous work are generalised, and experimental results demonstrate the applicability of the resulting algorithm to verify several industrial-scale discrete event system models, while achieving better state-space reduction than before

Chapter 12 Social distance, teachers’ beliefs and teaching practices in a context of social disadvantage

"This chapter analyses the widening inequalities within the government primary schooling systems in India and Pakistan and the implications of the emerging social distance between teachers and students. Social distance is a significant factor impacting student–teacher interaction in classrooms. How, and to what extent, does social distance shape teachers’ beliefs and practices? What is the likely effect of social distance on the education or learning of children from disadvantaged backgrounds? Using teacher interviews and classroom observation data, the chapter describes teachers’ beliefs and observed teacher–student interaction for high- and low-performing children. The empirical analysis is grounded in a conceptual frame linking teachers’ beliefs, practices and learning outcomes. Most teachers included in the study believe family background is the most significant determinant of learning. Teachers’ conceptualisation of a good student comprises a set of characteristics that are much more likely to be present in children from families where parents are educated and in stable economic circumstances or naturally gifted children. Teachers tend to favour the good students and can rarely adapt practice to help remove disadvantages for low-performing children or those from marginalized backgrounds. As a result, government schools are sites for the social reproduction of inequalities.

Magnetic phases evolution in the LaMn1-xFexO3+y system

We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange (SE) interaction between Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82% of the usual Mn^{3+} ions, with possible double exchange interaction between them. The Fe doping in this system is known to produce only stable Fe^{3+} ions. We find an evolution from a fairly strong FM phase with a Curie temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2 < x < 0.7. A model based on the expected exchange interaction among the various magnetic-ion types, accounts very well for the saturation-magnetization dependence on Fe doping.Comment: 27 pages, 9 figure

A Proactive-Restoration Technique for SDNs

Failure incidents result in temporarily preventing the network from delivering services properly. Such a deterioration in services called service unavailability. The traditional fault management techniques, i.e. protection and restoration, are inevitably concerned with service unavailability due to the convergence time that is required to achieve the recovery when a failure occurs. However, with the global view feature of software-defined networking a failure prediction is becoming attainable, which in turn reduces the service interruptions that originated by failures. In this paper, we propose a proactive restoration technique that reconfigure the vulnerable routes which are likely to be affected if the predicted failure indeed occurs. The proposed approach allocates the alternative routes based on the probability of failure. Experimental evaluation on real-world and synthetic topologies demonstrates that the network service availability can be improved with the proposed technique to reach up to 97%. Based on the obtained results, further directions are suggested towards achieving further advances in this research area

Graph Modeling for OpenFlow Switch Monitoring

Network monitoring allows network administrators to facilitate network activities and to resolve issues in a timely fashion. Monitoring techniques in software-defined networks are either (i) active, where probing packets are sent periodically, or (ii) passive, where traffic statistics are collected from the network forwarding elements. The centralized nature of software-defined networking implies the implementation of monitoring techniques imposes additional overhead on the network controller. We propose Graph Modeling for OpenFlow Switch Monitoring (GMSM), which is a lightweight monitoring technique. GMSM constructs a flow-graph overview using two types of asynchronous OpenFlow messages: packet-in and flow-removed, which improve monitoring and decision making. It classifies new flows based on the class of service. Experimental findings suggest that using GMSM leads to a decrease in network overhead resulting from the communication between the controller and the switches, with a reduction of 5.7% and 6.7% compared to state-of-the-art approaches. GMSM reduces the controller’s CPU utilization by more than 2% compared to other monitoring methods. Overhead reduction comes with a slight reduction of approximately 0.17 units in the estimation accuracy of links utilization because GMSM allows the user to monitor the network subject to a selected class of service, as opposed to having an exact view of the network utilization