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Sökning: LAR1:lu > Odefinierat språk

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1.
  • Blok, Daan, et al. (författare)
  • The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature
  • 2011
  • Ingår i: Environmental Research Letters. - IOP Publishing. - 1748-9326. ; 6:3, s. 035502-035502
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000–10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.
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  • Ducoing, Cristián, et al. (författare)
  • Natural Resources Curse in the Long Run? Bolivia, Chile and Peru in the Nordic Countries’ Mirror
  • 2018
  • Ingår i: Sustainability. - Formas. - 2071-1050. ; 10:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The new estimates of the Maddison Project show that GDP per capita ratio at purchasing power parity (ppp) between Bolivia and Finland has changed from 0.68 ca. 1850 to 0.16 in 2015; similarly, that between Chile and Norway from 0.65 to 0.28. The aim of this article is to present a review of the literature and available quantitative evidence to understand how these extreme differences became possible between countries with similarly enormous natural resource endowments. Specifically, the article seeks to: (a) identify some stylized facts that may help understand the divergence between Andean and Nordic countries; (b) identify key historical processes that explain the divergent effect of natural resource abundance in Andean and Nordic economies. In order to achieve these objectives, four topics are covered: GDPpc, population, trade and taxation. The analysis comprises three Nordic countries (Finland, Norway and Sweden) and three Andean countries (Bolivia, Chile and Peru) from the mid-Nineteenth Century to present day. The sample size, time span covered and thematic approach provide new evidence regarding previous work.
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5.
  • Fecchio, Alan, et al. (författare)
  • Host associations and turnover of haemosporidian parasites in manakins (Aves: Pipridae)
  • 2017
  • Ingår i: Parasitology. - Cambridge University Press. - 1469-8161.
  • Tidskriftsartikel (refereegranskat)abstract
    • Parasites of the genera Plasmodium and Haemoproteus (Apicomplexa: Haemosporida) are a diverse group of pathogens that infect birds nearly worldwide. Despite their ubiquity, the ecological and evolutionary factors that shape the diversity and distribution of these protozoan parasites among avian communities and geographic regions are poorly understood. Based on a survey throughout the Neotropics of the haemosporidian parasites infecting manakins (Pipridae), a family of Passerine birds endemic to this region, we asked whether host relatedness, ecological similarity and geographic proximity structure parasite turnover between manakin species and local manakin assemblages. We used molecular methods to screen 1343 individuals of 30 manakin species for the presence of parasites. We found no significant correlations between manakin parasite lineage turnover and both manakin species turnover and geographic distance. Climate differences, species turnover in the larger bird community and parasite lineage turnover in non-manakin hosts did not correlate with manakin parasite lineage turnover. We also found no evidence that manakin parasite lineage turnover among host species correlates with range overlap and genetic divergence among hosts. Our analyses indicate that host switching (turnover among host species) and dispersal (turnover among locations) of haemosporidian parasites in manakins are not constrained at this scale.
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  • Grbac, Tihana Galinac, et al. (författare)
  • Plug-in Software Engineering Case Studies
  • 2016
  • Ingår i: Proceedings 4th International Workshop on Conducting Empirical Studies in Industry (CESI@ICSE16). - ACM. - 978-1-4503-4154-7 ; s. 21-24
  • Konferensbidrag (refereegranskat)abstract
    • Empirical software engineering is a growing research area. Industrial experience gathered by systematic empirical case studies is extremely important for further evolution of the software engineering discipline. Scientific theory cannot provide effective means for software industry without fundamental understanding of the evolutionary development of complex software systems. However, there are certain limitations in performing observational quantitative case studies in real software engineering environments, and to enable their replication. In this paper, we propose a framework that would allow plug-in case studies for industries, aiming to overcome obstacles of engagement and wide replications of industrial empirical studies.
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8.
  • Javed, Saqib, 1978-, et al. (författare)
  • New Analytical and Numerical Solutions for the Short-term Analysis of Vertical Ground Heat Exchangers
  • 2011
  • Ingår i: ASHRAE Transactions. - ASHRAE. - 2378-2129. ; 117:1, s. 3-12
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the background, development and the validation of new analytical and numerical solutions for the modeling of short-term response of borehole heat exchangers. The new analytical solution studies the borehole's heat transfer and the related boundary conditions in the Laplace domain. A set of equations for the Laplace transforms for the boundary temperatures and heat-fluxes is obtained. These equations are represented by a thermal network. The use of the thermal network enables swift and precise evaluation of any thermal or physical setting of the borehole. Finally, very concise formulas of the inversion integrals are developed to obtain the time-dependent solutions. The new analytical solution considers the thermal capacities, the thermal resistances and the thermal properties of all the borehole elements and provides a complete solution to the radial heat transfer problem in vertical boreholes. The numerical solution uses a special coordinate transformation. The new solutions can either be used as autonomous models or easily be incorporated in any building energy simulation software.
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10.
  • Javed, Saqib, 1978-, et al. (författare)
  • Recovery times after thermal response tests on vertical borehole heat exchangers
  • 2011
  • Ingår i: Proceedings of 23rd IIR International Congress of Refrigeration (ICR2011), Prague, Czech Republic..
  • Konferensbidrag (refereegranskat)abstract
    • The design of a ground source heat pump system requires accurate knowledge of properties, such as ground thermal conductivity and borehole thermal resistance. These properties are often determined using an in-situ thermal response test of a pilot borehole. These tests are sometimes interrupted by unexpected circumstances and occasionally a retest is required. For a retest to be conducted, the ground temperature must return to within 0.1-0.3 K of the initial undisturbed ground temperature. This paper addresses the issue of borehole retesting and reports on a systematic series of thermal response tests conducted to study the times needed for the ground temperature to return to within 0.3 K of the pre-test ground temperature. Tests were conducted using various heat injection rates and different time durations. Following a test, the development of ground temperature was studied for up to 2-3 months. A mathematical model was used to validate the experimentally measured ground temperatures and to extend the results to other testing conditions.
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