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Träfflista för sökning "WFRF:(Ólafsdóttir Kristín) srt2:(2017)"

Search: WFRF:(Ólafsdóttir Kristín) > (2017)

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1.
  • Olafsdottir, Helga Kristin, et al. (author)
  • Exact Gradients Improve Parameter Estimation in Nonlinear Mixed Effects Models with Stochastic Dynamics
  • 2017
  • In: Journal of Pharmacokinetics and Pharmacodynamics. 44(Suppl 1): 11. - : Springer Science and Business Media LLC. - 1567-567X .- 1573-8744.
  • Conference paper (other academic/artistic)abstract
    • Nonlinear mixed effects (NLME) models based on stochastic differential equations (SDEs) have evolved into a mature approach for analysis of PKPD data [1-3], but parameter estimation remains challenging. We present an exact-gradient version of the first order conditional estimation (FOCE) method for SDE-NLME models, and investigate whether it enables faster estimation and better gradient precision/accuracy compared to finite difference gradients.
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3.
  • Ragnarsdottir, Kristin Vala, et al. (author)
  • Time of scarcity horizons for technology metals, precious metals, base metals, superalloy metals, battery technology metals and infrastructure materials.
  • 2017
  • In: Accelerating the Resource Revolution - WRF 2017 Meeting Report : Geneva, October 24 – 25, 2017 - Geneva, October 24 – 25, 2017. - 9783906177182
  • Conference paper (peer-reviewed)abstract
    • We have built a system dynamics model, WORLD6, that takes into account population, energy extraction, production and need, aspects social behaviour, material and metals recycling and important links to the economy. The model is ground-truthed by comparing with actual supply per person from 1900 till 2015 and run until 2400. Primary scarcity metrics are supply per person and year and stock-in-use per person. Results show that technology metals (antimony, bismuth, selenium, indium, gallium and germanium) will all peak in production before 2100. Precious metals will peak in production earlier, or before 2050. The base metals (copper, zinc) will have a roughly stable supply from 2050 till 2300, whereas the production of lead will be approximately the same from 1960 till 2400 and that of nickel will peak before 2050. The superalloy metals (molybdenum, niobium) will have a stable supply from around 2050 till 2400, but cobalt will be stable from 2100 till 2300 and then decline. The battery metal lithium will peak in production 2010, cobalt will be stable (as stated above) and rare earth´s will rise in use, particularly after 2100. When considering service capital per person (concrete, iron, aluminium, copper) the model predicts steady rise throughout the 21st century, with stabilization in the 22nd century. Our dynamic WORLD6 modelling results give clear indications that for the most important metals that are used in modern technology and in societal infrastructure there are limits and therefore careful circular economy programmes are necessary at the level of every nation so that metals do not become the centre of future conflicts.
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4.
  • Sverdrup, Harald, et al. (author)
  • The WORLD6 model for evaluation of natural resource sustainability considering metals, materials, energy, population and food.
  • 2017
  • In: Accelerating the Resource Revolution : WRF 2017 Meeting Report, Geneva, October 24 – 25, 2017 - WRF 2017 Meeting Report, Geneva, October 24 – 25, 2017. - 9783906177182
  • Conference paper (peer-reviewed)abstract
    • A new model; WORLD6 was developed. WORLD6 differs from the earlier system dynamics world models in several aspects. Several modules link the economy, materials, metals, energy, population and politics in a dynamic system. The present version is a result of a dismantling of the World3 model (Meadows et al., 1972, 1992, 2004) with an extension and substitution of its resource module and economy module. The WORLD6 model has several sub-modules at present which are all dynamically linked: 1. Population and food module: The module contains the original World3 model from 1972 model and used again in 1992 and 2004. This was enhanced with a new module for phosphate rock extraction, fertilizer production and an agricultural unit of WORLD6. 2. Materials and metals module a. Materials: Phosphorus, cement, sand, gravel and cut stone. b. Metals: Copper, zinc, lead, silver, gold, Iron, chromium, manganese, nickel, aluminium, stainless steel, antimony, bismuth, cobalt, gallium, germanium, indium, cadmium, tellurium, selenium, lithium, platinum, palladium, rhodium, molybdenum, rhenium, niobium, tantalum, tin, wolfram (tungsten), titanium, zirconium, hafnium and rare earth metals.3. Economy module: The model has a new simplified global economy module, considering the major actors like households, businesses, and government. Disposable funds, investments and market price for every resource is simulated endogenously in the model for every resource: metals, materials, food and commodities. 4. Energy module: An energy model including the extraction of fossil fuels. Different types of oil, gas, and coal as well as the extraction dynamics and reprocessing of uranium and thorium, used in conventional and breeder reactor technologies, technological energy harvests and renewable energy. 5. Climate and biosphere module: A simplified CLIMATE change module, converting CO2 emissions to CO2 in the atmosphere, with increase in temperature and sea level rise.
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