Generating Non-Linear Interpolants by Semidefinite Programming

Interpolation-based techniques have been widely and successfully applied in the verification of hardware and software, e.g., in bounded-model check- ing, CEGAR, SMT, etc., whose hardest part is how to synthesize interpolants. Various work for discovering interpolants for propositional logic, quantifier-free fragments of first-order theories and their combinations have been proposed. However, little work focuses on discovering polynomial interpolants in the literature. In this paper, we provide an approach for constructing non-linear interpolants based on semidefinite programming, and show how to apply such results to the verification of programs by examples.Comment: 22 pages, 4 figure

Subsumer-First: Steering Symbolic Reachability Analysis

Abstract. Symbolic reachability analysis provides a basis for the veri-fication of software systems by offering algorithmic support for the ex-ploration of the program state space when searching for proofs or coun-terexamples. The choice of exploration strategy employed by the anal-ysis has direct impact on its success, whereas the ability to find short counterexamples quickly and—as a complementary task—to efficiently perform the exhaustive state space traversal are of utmost importance for the majority of verification efforts. Existing exploration strategies can optimize only one of these objectives which leads to a sub-optimal reach-ability analysis, e.g., breadth-first search may sacrifice the exploration ef-ficiency and chaotic iteration can miss minimal counterexamples. In this paper we present subsumer-first, a new approach for steering symbolic reachability analysis that targets both minimal counterexample discovery and efficiency of exhaustive exploration. Our approach leverages the re-sult of fixpoint checks performed during symbolic reachability analysis to bias the exploration strategy towards its objectives, and does not require any additional computation. We demonstrate how the subsumer-first ap-proach can be applied to improve efficiency of software verification tools based on predicate abstraction. Our experimental evaluation indicates the practical usefulness of the approach: we observe significant efficiency improvements (median value 40%) on difficult verification benchmarks from the transportation domain.

Abstraction Refinement for Quantified Array Assertions

We present an abstraction refinement technique for the verification of universally quantified array assertions such as “all elements in the array are sorted”. Our technique can be seamlessly combined with existing software model checking algorithms. We implemented our technique in the ACSAR software model checker and successfully verified quantified array assertions for both text book examples and real-life examples taken from the Linux operating system kernel

Outstanding challenges in the transferability of ecological models

Predictive models are central to many scientific disciplines and vital for informing management in a rapidly changing world. However, limited understanding of the accuracy and precision of models transferred to novel conditions (their 'transferability') undermines confidence in their predictions. Here, 50 experts identified priority knowledge gaps which, if filled, will most improve model transfers. These are summarized into six technical and six fundamental challenges, which underlie the combined need to intensify research on the determinants of ecological predictability, including species traits and data quality, and develop best practices for transferring models. Of high importance is the identification of a widely applicable set of transferability metrics, with appropriate tools to quantify the sources and impacts of prediction uncertainty under novel conditions.Katherine L. Yates ... Alice R. Jones ... et al

Linear Collider Physics Resource Book for Snowmass 2001, 3: Studies of Exotic and Standard Model Physics

This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 3 reviews the possible experiments on that can be done at a linear collider on strongly coupled electroweak symmetry breaking, exotic particles, and extra dimensions, and on the top quark, QCD, and two-photon physics. It also discusses the improved precision electroweak measurements that this collider will make available.This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 3 reviews the possible experiments on that can be done at a linear collider on strongly coupled electroweak symmetry breaking, exotic particles, and extra dimensions, and on the top quark, QCD, and two-photon physics. It also discusses the improved precision electroweak measurements that this collider will make available

Long recovery VLF perturbations associated with lightning discharges

Long D-region ionospheric recovery perturbations are a recently discovered and poorly understood subcategory of early VLF events, distinguished by exceptionally long ionospheric recovery times of up to 20 min (compared to more typical �1 min recovery times). Characteristics and occurrence rates of long ionospheric recovery events on the NWC transmitter signal recorded at Malaysia are presented. 48 long recovery events were observed. The location of the causative lightning discharge for each event is determined from GLD360 and WWLLN data, and each discharge is categorized as being over land or sea. Results provide strong evidence that long recovery events are attributed predominately to lightning discharges occurring over the sea, despite the fact that lightning activity in the region is more prevalent over land. Of the 48 long recovery events, 42 were attributed to lightning activity over water. Analysis of the causative lightning of long recovery events in comparison to all early VLF events reveals that these long recovery events are detectable for lighting discharges at larger distances from the signal path, indicating a different scattering pattern for long recovery events

On the relationship between lightning peak current and early VLF perturbations

Lightning strokes are known to cause direct heating and ionization of the D region, some of which are detected via scattering of VLF transmitter signals and are known as Early VLF events. The disturbed ionosphere typically recovers in many tens of seconds. New experimental evidence is presented demonstrating that the scattering pattern and onset amplitude of Early VLF events are strongly related to both the magnitude and polarity of causative lightning peak current. Observations of Early VLF events at nine Stanford VLF receiver sites across the continental United States are combined with lightning geolocation data from the National Lightning Detection Network (NLDN). During January and March 2011, NLDN recorded 7769 intense lightning discharges with high peak currents (>100 kA) generating 1250 detected Early VLF events. We show that the size of the scattered field due to the ionospheric disturbance increases with the peak current intensity of the causative lightning discharge. The most intense peak currents of >+200 and <−250 kA disturb VLF transmitter signals as far as ∼400 km away from the lightning stroke. Early VLF event detection probability also increases rapidly with peak current intensity. On the other hand, the observed VLF amplitude change is not significantly dependent on the peak current intensity. Stroke polarity is also important, with positive strokes being ∼5 times more likely to generate Early VLF disturbances than negative strokes of the same intensity. Intense positive cloud-to-ground lightning discharges, especially when occurring over the sea, are also more likely to produce Early VLF events with long recovery (many minutes)

Azurmendi, Joxe. Espainolak eta euskaldunak

Reseña bibliográfica de la obra de Joxe Azurmendi "Espainolak eta euskaldunak"

DEMETER observations of transmitter-induced precipitation of inner radiation belt electrons

International audienceNear loss cone energetic electron flux increases induced by ground-based very low frequency (VLF) transmissions are observed directly via satellite-based detection. In 2 years of experiments ranging from 27 March 2006 through 2 April 2008 with the 21.4-kHz transmitter NPM in Lualualei, Hawaii, and the French satellite DEMETER (detection of electromagnetic emissions transmitted from earthquake regions), only a few cases of detection of individual pulses of transmitter-induced precipitation of inner radiation belt electrons have been realized. Analysis of the specific cases of detection allow comparison of precipitating flux with predictions based on ray-tracing analyses of wave propagation and test particle modeling of the wave-particle interaction. Results indicate that the precipitated flux of >100 keV electrons induced by the NPM transmitter peaks at L ' 1.9 and, in the rare cases of detection, may be at higher energies than the $100 keV peak predicted by the model. The low detection rate is attributed to the orientation of the DEMETER particle detector, which is mostly overwhelmed by the trapped population at the location of detection