LTL Parameter Synthesis of Parametric Timed Automata

The parameter synthesis problem for parametric timed automata is undecidable in general even for very simple reachability properties. In this paper we introduce restrictions on parameter valuations under which the parameter synthesis problem is decidable for LTL properties. The investigated bounded integer parameter synthesis problem could be solved using an explicit enumeration of all possible parameter valuations. We propose an alternative symbolic zone-based method for this problem which results in a faster computation. Our technique extends the ideas of the automata-based approach to LTL model checking of timed automata. To justify the usefulness of our approach, we provide experimental evaluation and compare our method with explicit enumeration technique.Comment: 23 pages, extended versio

Ground track density considerations on the resolvability of gravity field harmonics in a repeat orbit

One of the limiting factors in the determination of global gravity field parameters is the spatial sampling, namely during phases when the satellite is in an orbit with few revolutions for each repeat cycle. This often happens when it is freely passing (drifting) through the atmosphere and encountering a fair number of such deficient repeat orbits. This research was triggered in 2004 by the significant but only temporary, 2–3 months long, decrease of the accuracy of monthly solutions for the gravity field variations derived from GRACE. The reason for the dip was the 61/4 resonance in the GRACE orbits in autumn 2004. At this resonance, the ground track density dramatically decreased and large (mainly longitude) gaps appeared in the data-coverage of the globe. The problem of spatial sampling has been studied repeatedly (Wagner et al., 2006; Klokočník et al., 2008; Weigelt et al., 2009) and simple rules have been derived to limit the maximum order for unconstrained solutions (inversions) for the gravity field parameters or their variations from observations of a single satellite. Here we work with the latest rule from Weigelt et al. (2013) which distinguishes the maximum attainable order according to the parity of the two parameters defining the repeat orbit or orbital resonance, β the number of nodal satellite’s revolutions in α nodal days (α, β co-prime integers, the ratio β/α irreducible). This rule, that the resolvable order (in a repeat near polar orbit) should be β for odd parity (β − α) and β/2 for even parity (β − α) orbits, arose from the discovery that the number of distinct and equally spaced equatorial crossings (ascending and descending passes) for odd parity (β − α) is 2β while for even parity orbits it is only β. We extend this insight over all achievable latitudes and assess the ground track density (or coverage) by way of the maximum distances between subsatellite points at arbitrary latitude, specifically for the nearly polar (drifting) orbits of CHAMP, GRACE, and the repeat tuned GOCE. We demonstrate clearly how latitude (and also the orbital inclination) is important and affects the choice of an order resolution limit. A new rule, compromising between β and β/2 for each specific repeat orbit, is proposed, based on the average maximum distance between subsatellite points over the achievable latitudes. Although these findings allow an initial estimate of recoverability based solely on the global spatial sampling of the ground track, a more refined analysis involving the inversion of specific observations is still outstanding.Web of Science5661160114

Methodology for the digitalization of analog film records by trick projector and digital camera:Coordination of the work of the digital restorer and its expert or research groups in the specialized photographic conversion of analogue 35mm and 16mm cinematographic image into a digital form on Oxberry optical film printer according to the DRA (Digitally Restored Autorizate) method

Coordination of the work of the digital restorer and its expert or research groups in the specialized photographic conversion of analogue 35mm and 16mm cinematographic image into a digital form on Oxberry optical film printer according to the DRA (Digitally Restored Autorizate) metho

能取湖の底生動物群集と底質中の全硫化物

It is of great interest to numerous geophysical studies that the time series of global gravity field models derived from Gravity Recovery and Climate Experiment (GRACE) data remains uninterrupted after the end of this mission. With this in mind, some institutes have been spending efforts to estimate gravity field models from alternative sources of gravimetric data. This study focuses on the gravity field solutions estimated from Swarm global positioning system (GPS) data, produced by the Astronomical Institute of the University of Bern, the Astronomical Institute (ASU, Czech Academy of Sciences) and Institute of Geodesy (IfG, Graz University of Technology). The three sets of solutions are based on different approaches, namely the celestial mechanics approach, the acceleration approach and the short-arc approach, respectively. We derive the maximum spatial resolution of the time-varying gravity signal in the Swarm gravity field models to be degree 12, in comparison with the more accurate models obtained from K-band ranging data of GRACE. We demonstrate that the combination of the GPS-driven models produced with the three different approaches improves the accuracy in all analysed monthly solutions, with respect to any of them. In other words, the combined gravity field model consistently benefits from the individual strengths of each separate solution. The improved accuracy of the combined model is expected to bring benefits to the geophysical studies during the period when no dedicated gravimetric mission is operational.</p

New implications for Tunguska explosion based on magnetic, dendrological, and lacustrine records

Introduction: Evenkia is a district in Krasnoyarsk Krai, Russia, characteristic of preserved areas of East Siberian continental taiga. In 1908, this region experienced catastrophe (Tunguska event = TE). Over 2,000 km2 of boreal forest were felled and burned [1,2]. The exact cause of this event is not known but this event has often been associated with either an asteroid or comet encounter [3,4,5]. Material and Methods: We collected tree samples that survived the explosion within the tree collapse area. Most of the tree is Siberian larix. Samples were analyzed for elemental composition (XRF and similar). We collected sediment from three lakes, Zapoviednoe, Cheko, and Gin. Lake Zapoviednoe and Cheko varved sediment came from similar depth of about 35-40 m with conical bottom bachymetry. Lake Gin was shallow (50-60 cm) and had no varves. Chronology of the sediment was already established in Cheko lake using 210Pb, 137Cs, and 226Ra radioactive isotopes analysis [6]. An increase in 137Cs corresponded to 1961 [6]. We ran similar analysis for the two new lakes, Gin and Zapoviednoe and established the sediment chronology. Zapoviednoe lake sediment was exposed to 0-50 keV X-Ray Fluorescence and major element data, including magnetic susceptibility, were obtained across the TE containing sediment. We plotted aeromagnetic data from the world magnetic map flown at ~4 km [7,8] over the tree fall area. Magnetic paleointensity was obtained from the samples collected from Mount Stoikovich and Farrington near epicentre. Results: Tree samples provided an evidence that the ovepressure wave compressed the floem fluid rich in Ca, Sr, Mn into the xylem at the time of TE. This compression had strong anisotropy with maximum compression directed towards the epicenter. We detected that after TE, during the past 40 years the Larix trees in Tunguska have anomalous increase in Hg concentration. Lake sediment revealed 2-4 mm thick clay layer deposited at the time of TE. The layer has anomalous decrease in Fe, while magnetic susceptibility increased. In addition the TE layer has significant increase in Pa, Mo, Th, Cd, Nb, Y, Cu, Cr, Sr, Ti, and V. Aeromagnetic data showed negative magnetic anomaly covering the toppled forest area around the epicenter. Samples from Mount Farrington indicated magnetic paleofields exceeding 1 mT. Four samples from Mount Stoikovitch detected paleofields consistent with geomagnetic field intensity while two samples indicated magnetic paleofield exceeding 0.1 mT. Discussion and Conclusion: TE was shown to leave a biochemical signature in the wood of Larix Sibirica sensitive to explosion direction. TE area was subjected to large energy pulse that may have compromised the permafrost in the area. This was indicated here by an excess of Hg detected in the last 40 years of tree ring material. Tunguska layer in the Zapoviednoe lake is of very fine nature, resembling the clay. While the content of Fe dropped from 160 ppm to 19 ppm the magnetic susceptibility increased two fold. This is an evidence of quick and intense burst of energy, melting vapourizing the dust, causing agglutination of the dust material. This resulted in a ubiquitous presence of nanophase iron with large magnetic susceptibility that became part of molten dust particulates and deposited in the lake sediment. Anomalous elemental increase in lake suggested possible allochtonous material. Paleomagnetic data revealed presence of plasma during the TE near rock surfaces.Web of Science5