An Axiomatic Approach to Liveness for Differential Equations

This paper presents an approach for deductive liveness verification for ordinary differential equations (ODEs) with differential dynamic logic. Numerous subtleties complicate the generalization of well-known discrete liveness verification techniques, such as loop variants, to the continuous setting. For example, ODE solutions may blow up in finite time or their progress towards the goal may converge to zero. Our approach handles these subtleties by successively refining ODE liveness properties using ODE invariance properties which have a well-understood deductive proof theory. This approach is widely applicable: we survey several liveness arguments in the literature and derive them all as special instances of our axiomatic refinement approach. We also correct several soundness errors in the surveyed arguments, which further highlights the subtlety of ODE liveness reasoning and the utility of our deductive approach. The library of common refinement steps identified through our approach enables both the sound development and justification of new ODE liveness proof rules from our axioms.Comment: FM 2019: 23rd International Symposium on Formal Methods, Porto, Portugal, October 9-11, 201

Dynamic airfoil stall investigations

Experimental and computational investigations of the dynamic stall phenomenon continue to attract the attention of various research groups in the major aeronautical research laboratories. There are two reasons for this continued research interest. First, the occurrence of dynamic stall on the retreating blade of helicopters imposes a severe performance limitation and thus suggests to search for ways to delay the onset of dynamic stall. Second, the lift enhancement prior to dynamic stall presents an opportunity to achieve enhanced maneuverability of fighter aircraft. A description of the major parameters affecting dynamic stall and lift and an evaluation of research efforts prior to 1988 has been given by Carr. In this paper the authors' recent progress in the development of experimental and computational methods to analyze the dynamic stall phenomena occurring on NACA 0112 airfoils is reviewed. First, the major experimental and computational approaches and results are summarized. This is followed by an assessment of our results and an outlook toward the future

Towards Physical Hybrid Systems

Some hybrid systems models are unsafe for mathematically correct but physically unrealistic reasons. For example, mathematical models can classify a system as being unsafe on a set that is too small to have physical importance. In particular, differences in measure zero sets in models of cyber-physical systems (CPS) have significant mathematical impact on the mathematical safety of these models even though differences on measure zero sets have no tangible physical effect in a real system. We develop the concept of "physical hybrid systems" (PHS) to help reunite mathematical models with physical reality. We modify a hybrid systems logic (differential temporal dynamic logic) by adding a first-class operator to elide distinctions on measure zero sets of time within CPS models. This approach facilitates modeling since it admits the verification of a wider class of models, including some physically realistic models that would otherwise be classified as mathematically unsafe. We also develop a proof calculus to help with the verification of PHS.Comment: CADE 201

Climate Variability and Change: Implications for Malaria Control and Elimination in Africa

In Ethiopia, malaria continues to be a major public health concern with an estimated two thirds of the national population at risk of infection. Tackling a key driver, this workshop was convened to advance the understanding of the impact of climate variability and change in relation to the malaria burden to better inform policy decisions related to current control and future elimination strategies. To achieve this, the workshop explored data, methodologies and tools that could be used by national public health researchers to improve malaria risk assessments. The motivation for the workshop came from an NIH funded project entitled “Climate Variability and Change: Implications for Malaria Control and Elimination in Africa” with the goal of supporting malaria researchers in affected countries in East Africa to identify opportunities for improving the effectiveness of prevention, control and elimination strategies by incorporating an understanding of likely short and longer term changes in the climate in their analysis. In particular, the workshop aimed to address the challenge of varied drivers of the climate, acting at multiple timescales including year to year variability, 10-20 year climate shifts and long term trends associated with climate change. Data sources explored during the workshop included the newly developed Enhanced National Climate Services (ENACTS) rainfall and temperature products disseminated by the Ethiopian National Meteorological Agency (NMA), as well as globally available climate products freely distributed online. The Climate Predictability Tool (CPT), developed by the International Research Institute for Climate and Society (IRI), to assist climatologists in making robust predictions was tested for the first time as a potential tool for the malaria research community to assess the relationship of malaria to large-scale climate processes. In addition, a multi-model malaria platform (MMMP) was presented during the workshop to explore uncertainty associated with the predictability of malaria over time using a series of process-based models

Saturation of a spin 1/2 particle by generalized Local control

We show how to apply a generalization of Local control design to the problem of saturation of a spin 1/2 particle by magnetic fields in Nuclear Magnetic Resonance. The generalization of local or Lyapunov control arises from the fact that the derivative of the Lyapunov function does not depend explicitly on the control field. The second derivative is used to determine the local control field. We compare the efficiency of this approach with respect to the time-optimal solution which has been recently derived using geometric methods.Comment: 12 pages, 4 figures, submitted to new journal of physics (2011

Sharper and Simpler Nonlinear Interpolants for Program Verification

Interpolation of jointly infeasible predicates plays important roles in various program verification techniques such as invariant synthesis and CEGAR. Intrigued by the recent result by Dai et al.\ that combines real algebraic geometry and SDP optimization in synthesis of polynomial interpolants, the current paper contributes its enhancement that yields sharper and simpler interpolants. The enhancement is made possible by: theoretical observations in real algebraic geometry; and our continued fraction-based algorithm that rounds off (potentially erroneous) numerical solutions of SDP solvers. Experiment results support our tool's effectiveness; we also demonstrate the benefit of sharp and simple interpolants in program verification examples

Home country advantage? The influence of Italian, German and Austrian employee representatives in the UniCredit European Works Council

This article examines the first European Works Council (EWC) to be established in the Italian banking sector, at UniCredit. It focuses on the interaction between Italian, German and Austrian delegations of employee representatives and on the perspectives and practices that reflect their different cultural and institutional backgrounds in industrial relations. Much of the literature suggests that employee representatives from the home country of a multinational company are likely to mould EWC structures in accordance with their own national backgrounds and have greater confidence in dealing with central management in EWC meetings. Our findings partly substantiate this argument, but also suggest that minority delegations, when they have the benefit of strong national institutional arrangements and less fragmented union patterns, are more likely to be cohesive and experienced and therefore able to challenge management and sometimes win significant arguments over strategy

South Korea's automotive labour regime, Hyundai Motors’ global production network and trade‐based integration with the European Union

This article explores the interrelationship between global production networks(GPNs) and free trade agreements (FTAs) in the South Korean auto industry and its employment relations. It focuses on the production network of the Hyundai Motor Group (HMG) — the third biggest automobile manufacturer in the world — and the FTA between the EU and South Korea. This was the first of the EU’s ‘new generation’ FTAs, which among other things contained provisions designed to protect and promote labour standards. The article’s argument is twofold. First, that HMG’s production network and Korea’s political economy (of which HMG is a crucial part) limited the possibilities for the FTA’s labour provisions to take effect. Second, that the commercial provisions in this same FTA simultaneously eroded HMG’s domestic market and corporate profitability, leading to adverse consequences for auto workers in the more insecure and low-paid jobs. In making this argument, the article advances a multiscalar conceptualization of the labour regime as an analytical intermediary between GPNs and FTAs. It also provides one of the first empirical studies of the EU–South Korea FTA in terms of employment relations, drawing on 105 interviews with trade unions, employer associations, automobile companies and state officials across both parties

Verifying Hybrid Systems Involving Transcendental Functions

Abstract. We explore uses of a link we have constructed between the KeYmaera hybrid systems theorem prover and the MetiTarski proof en-gine for problems involving special functions such as sin, cos, exp, etc. Transcendental functions arise in the specification of hybrid systems and often occur in the solutions of the differential equations that govern how the states of hybrid systems evolve over time. To date, formulas ex-changed between KeYmaera and external tools have involved polynomi-als over the reals, but not transcendental functions, chiefly because of the lack of tools capable of proving such goals.