Calculating WCET Estimates from Timed Traces

© The Author(s) 2015. This article is published with open access at Springerlink.comReal-time systems engineers face a daunting duty: They must ensure that each task in their system can always meet its deadline. To analyse schedulability they must know the worst-case execution time (WCET) of each task. However, determining exact WCETs is practically infeasible in cost-constrained industrial settings involving real-life code and COTS hardware. Static analysis tools that could yield sufficiently tight WCET bounds are often unavailable. As a result, interest in portable analysis approaches like measurement-based timing analysis (MBTA) is growing. We present an approach based on integer linear programming (ILP) for calculating a WCET estimate from a given database of timed execution traces. Unlike previous work, our method specifically aims at reducing overestimation, by means of an automatic classification of code executions into scenarios with differing worst-case behaviour. To ease the integration into existing analysis tool chains, our method is based on the implicit path enumeration technique (IPET). It can thus reuse flow facts from other analysis tools and produces ILP problems that can be solved by off-the-shelf solvers.Peer reviewe

Denitrification, dehydration and ozone loss during the 2015/2016 Arctic winter

The 2015/2016 Arctic winter was one of the coldest stratospheric winters in recent years. A stable vortex formed by early December and the early winter was exceptionally cold. Cold pool temperatures dropped below the nitric acid trihydrate (NAT) existence temperature of about 195 K, thus allowing polar stratospheric clouds (PSCs) to form. The low temperatures in the polar stratosphere persisted until early March, allowing chlorine activation and catalytic ozone destruction. Satellite observations indicate that sedimentation of PSC particles led to denitrification as well as dehydration of stratospheric layers. Model simulations of the 2015/2016 Arctic winter nudged toward European Centre for Medium-Range Weather Forecasts (ECMWF) analysis data were performed with the atmospheric chemistry–climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) for the Polar Stratosphere in a Changing Climate (POLSTRACC) campaign. POLSTRACC is a High Altitude and Long Range Research Aircraft (HALO) mission aimed at the investigation of the structure, composition and evolution of the Arctic upper troposphere and lower stratosphere (UTLS). The chemical and physical processes involved in Arctic stratospheric ozone depletion, transport and mixing processes in the UTLS at high latitudes, PSCs and cirrus clouds are investigated. In this study, an overview of the chemistry and dynamics of the 2015/2016 Arctic winter as simulated with EMAC is given. Further, chemical–dynamical processes such as denitrification, dehydration and ozone loss during the 2015/2016 Arctic winter are investigated. Comparisons to satellite observations by the Aura Microwave Limb Sounder (Aura/MLS) as well as to airborne measurements with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) performed aboard HALO during the POLSTRACC campaign show that the EMAC simulations nudged toward ECMWF analysis generally agree well with observations. We derive a maximum polar stratospheric O3 loss of ∼ 2 ppmv or 117 DU in terms of column ozone in mid-March. The stratosphere was denitrified by about 4–8 ppbv HNO3 and dehydrated by about 0.6–1 ppmv H2O from the middle to the end of February. While ozone loss was quite strong, but not as strong as in 2010/2011, denitrification and dehydration were so far the strongest observed in the Arctic stratosphere in at least the past 10 years

Trunk anatomical features and essential oils composition of woody-shrub species of the ecotone and steppe from the Northwestern region of Chubut Province

La Provincia del Chubut tiene una superficie aproximada de 224.686 km2, donde los bosques subantárticos se extienden hacia el oeste y el noroeste. Están compuestos por árboles nativos como la lenga, el coihue, el alerce o lahuán, el ciprés, el maitén, el ñire y el radal, entre otros. En el ecotono bosque-estepa incursionan algunas de estas especies arbóreas, pero existe mayor predominancia de arbustos de muy bajo porte. El objetivo de este trabajo fue analizar, sobre la base de los caracteres anatómicos del leño secundario, aspectos xeromórficos de arbustos patagónicos y determinar la presencia y la composición de los aceites esenciales en sus follajes. Se realizó el estudio anatómico de algunas especies arbustivas, comprendidas en las siguientes familias botánicas: Apiaceae, Asteraceae, Fabaceae, Lamiaceae, Malvaceae, Rhamnaceae, Solanaceae y Verbenaceae. Se realizó el estudio anatómico de: Adesmia boronioides (Fabaceae), Ameghinoa patagonica (Asteraceae), B. obovata, B. salicifolia, (Asteraceae), Clinopodium darwinii (Lamiaceae), Corynabutilon bicolor (Malvaceae), Diostea juncea (Verbenaceae), Discaria chacaye (Rhamnaceae), Fabiana imbricata (Solanaceae), Mulinum spinosum (Apiaceae), Ochetophila trinervis (Rhamnaceae), Schinus johnstonii y S. patagonicus (Anacardiaceae). Los elementos observados, analizados y medidos permitieron obtener resultados y establecer analogías y diferencias entre las especies. La mayoría de los arbustos presenta: porosidad de circular a semicircular en xilema temprano, y porosidad difusa, disposición dendrítica, ulmoide, en racimos, y oblicua en zigzag, en xilema tardío. En sección transversal, los poros se distribuyen solitarios, múltiples radiales cortos, largos y en cadena; en sección tangencial se observaron radios uni a multiseriados, homocelulares y heterocelulares. El sistema de radios es heterogéneo. Los espesamientos helicoidales están presentes en las paredes de los vasos y las traqueidas vasculares de varias especies. En el leño de otras, se hallaron traqueidas vasicéntricas y fibrotraqueidas. Las perforaciones reticuladas solo fueron halladas en algunos vasos de Ochetophila trinervis; y perforaciones radiovasculares, en D. chacaye. Las demás especies tienen vasos con perforaciones simples. Los valores de índice de vulnerabilidad, mesomorfismo, índice de fibras/vasos y frecuencia promedio de poros/mm2 obtenidos, demuestran que los arbustos estudiados habitan en sitios de xerófitos a extremadamente xéricos del ecotono-estepa del Chubut. El 64% de las especies mostró contenidos importantes de aceites esenciales. Este resultado estaría en concordancia con algunas hipótesis que plantean la presencia de estos metabolitos secundarios como adaptación a las condiciones xerófitas.Chubut Province has an area of about 224.686 km², and therein the sub Antarctic forest extends to the West and Northwest. Native trees such as lenga, coihue, alerce or lahuán, cypress, maitén, ñire and radal, among others, are the most frequent species present. Meanwhile in the forest-steppe of the ecotone some of these tree species are also present but with a greater predominance of very low bearing shrubs. The objective of this study was to analyze the xeromorphic aspects of patagonian shrubs based on the anatomical characters of the secondary wood and on the presence and composition of essential oils in their foliage. The anatomical study was conducted on: Adesmia boronioides (Fabaceae), Ameghinoa patagonica (Asteraceae), Baccharis linearis, B. obovata, B. salicifolia, (Asteraceae), Clinopodium darwinii (Lamiaceae), Corynabutilon bicolor (Malvaceae), Diostea juncea (Verbenaceae), Discaria chacaye (Rhamnaceae), Fabiana imbricata (Solanaceae), Mulinum spinosum (Apiaceae), Ochetophila trinervis (Rhamnaceae), Schinus johnstonii y S. patagonicus (Anacardiaceae). The anatomical elements observed, analyzed and measured, allowed establishing analogies and differences between the species. Most of the bushes presented: circular to semicircular porosity in spring wood, and diffuse-porous, dendritic provision, ulmoid, in clusters, and oblique zigzag in autumn-winter wood. In cross section, the pores were solitare, multiple radial short, long and chain; uni multiseriate, homocellular and heterocellular rays were observed in the tangential section. The radio system was heterogeneous. The helical thickening was present in the vessel walls and vascular tracheids, of several species. Fibrotracheids and vasicentric tracheids were found in the others woods. The reticulate perforations were only found in some vessels of Ochetophila trinervis; and radiovasculars drillings in D. chacaye. Other species had vessels with simple perforations. Index values of vulnerability, mesomorphism, index of fibers/vessels and frequency average pores/mm² obtained, demonstrated that the shrubs under study live in xerophytic to extremely xeric conditions in the ecotone-steppe in Chubut. About 64% of the species showed essential oils content. These results would be consistent with some hypotheses posed that the presence of these secondary metabolites constitutes a possible adaptation to xerophytic conditions.Fil: Guerra, Pedro E.. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ingeniería - Sede Esquel; ArgentinaFil: González, Silvia Beatriz. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel; ArgentinaFil: Kirner, Helga J.. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ingeniería - Sede Esquel; ArgentinaFil: Retta, Daiana Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Di Leo Lira, Paola Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Gómez, Mariano F.. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentin

Diurnal variations of reactive chlorine and nitrogen oxides observed by MIPAS-B inside the January 2010 Arctic vortex

The winter 2009/2010 was characterized by a strong Arctic vortex with extremely cold mid-winter temperatures in the lower stratosphere associated with an intense activation of reactive chlorine compounds (ClOx) from reservoir species. Stratospheric limb emission spectra were recorded during a flight of the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 24 January 2010 inside the Arctic vortex. Several fast limb sequences of spectra (in time steps of about 10 min) were measured from nighttime photochemical equilibrium to local noon allowing the retrieval of chlorine- and nitrogen-containing species which change rapidly their concentration around the terminator between night and day. Mixing ratios of species like ClO, NO2, and N2O5 show significant changes around sunrise, which are temporally delayed due to polar stratospheric clouds reducing the direct radiative flux from the sun. ClO variations were derived for the first time from MIPAS-B spectra. Daytime ClO values of up to 1.6 ppbv are visible in a broad chlorine activated layer below 26 km correlated with low values (below 0.1 ppbv) of the chlorine reservoir species ClONO2. Observations are compared and discussed with calculations performed with the 3-dimensional Chemistry Climate Model EMAC (ECHAM5/MESSy Atmospheric Chemistry). Mixing ratios of the species ClO, NO2, and N2O5 are well reproduced by the model during night and noon. However, the onset of ClO production and NO2 loss around the terminator in the model is not consistent with the measurements. The MIPAS-B observations along with Tropospheric Ultraviolet-Visible (TUV) radiation model calculations suggest that polar stratospheric clouds lead to a delayed start followed by a faster increase of the photodissoziation of ClOOCl and NO2 near the morning terminator since stratospheric clouds alter the direct and the diffuse flux of solar radiation. These effects are not considered in the EMAC model simulations which assume a cloudless atmosphere

Partitioning and budget of inorganic and organic chlorine species observed by MIPAS-B and TELIS in the Arctic in March 2011

The Arctic winter 2010/11 was characterized by a persisting vortex with extremely cold temperatures in the lower stratosphere above northern Scandinavia leading to a strong activation of chlorine compounds (ClOx) like Cl, Cl2, ClO, ClOOCl, OClO, and HOCl which rapidly destroyed ozone when sunlight returned after winter solstice. MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and TELIS (Terahertz and submillimeter Limb Sounder) balloon measurements obtained in northern Sweden on 31 March 2011 inside the polar vortex have provided vertical profiles of inorganic and organic chlorine species as well as diurnal variations of ClO around sunrise over the whole altitude range in which chlorine is undergoing activation and deactivation. This flight was performed at the end of the winter during the last phase of ClOx deactivation. The complete inorganic and organic chlorine partitioning and budget in the stratosphere has been derived by combining MIPAS-B and TELIS simultaneously observed molecules. A total chlorine amount of 3.41 ± 0.30 ppbv is inferred from the measurements. This value is in line with previously carried out stratospheric observations confirming the slightly decreasing chlorine trend in the stratosphere. Observations are compared and discussed with the output of a multi-year simulation performed with the Chemistry Climate Model EMAC (ECHAM5/MESSy Atmospheric Chemistry). The simulated stratospheric total chlorine amount is in accordance with the MIPAS-B/TELIS observation taking into account the fact that some chlorine source gases and very short lived species are not included in the model