| 113171. |
- Larsson Ivanov, Oskar, et al.
(författare)
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Framtagande av temperaturlaster i broar med hjälp av allmänt tillgängliga klimatdata
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To study and evaluate temperature distributions and subsequent load cases in concrete structures it is common to use thermal simulations. Such simulations have been performed in multiple previous studies using weather data measured in the vicinity of the studied object. However, this method has limitations, since important factors such as solar radiation and longwave heat radiation are only measured in a few places in Sweden. This means that thermal simulations can only be performed for structures located close to the measuring locations, if local measurements is to be avoided. This, in turn, limits the possibility of including all parts of the country when e.g. evaluating the load levels for various cases.An alternative is to use models for estimating solar radiation and longwave heat radiation, such as STRÅNG, provided by SMHI, the Swedish Radiation Safety Authority (Strålsäkerhetsmyndigheten, SSM) and the Swedish Environmental Protection Agency (Naturvårdsverket), for solar radiation and models based on cloud cover and air temperature. With this kind of methodology, it would be possible to simulate the temperature in most places in Sweden without having to perform local measurements, i.e. the simulation can be made with easily accessible public data only. There is however an uncertainty related to the accuracy of STRÅNG and other possible models for estimating radiation.In this study, the possibility of using easily accessible public data in thermal simulations is evaluated. The temperature has been simulated with easily accessible public data for three reference objects where the temperature in the structures has been measured in previous studies. Comparisons are made between the new simulations and measured temperatures, as well as with simulations using local data as input.The results show that if the general trend and maximum and minimum values over time is of interest, the simulations using easily accessible public data give adequate results. If, however, the temperature at a specific point in time is sought, the new simulations may be unreliable. If the input data are taken from a location with a different climate than the location of the object, the results may differ significantly which is the result in one of the reference cases. The results presented here creates the possibility of e.g. producing isotherm maps for thermal gradients and differences in temperature between structural parts, since local variations can be included all over Sweden with the use of easily accessible public data.
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| 113172. |
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| 113173. |
- Larsson Ivanov, Oskar, et al.
(författare)
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Prolca—treatment of uncertainty in infrastructure LCA
- 2019
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Ingår i: Life-Cycle Analysis and Assessment in Civil Engineering. - : CRC Press/Balkema. - 9781138626331 - 9781351857574 ; , s. 2923-2930
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Konferensbidrag (refereegranskat)abstract
- The construction, operation and maintenance of transportation infrastructure require energy and materials which impact the environment. Large infrastructure projects thus use resources intensively and leave a significant environmental footprint. To demonstrate and support the sustainability of such large-scale projects, life cycle assessment (LCA) has become a common tool to evaluate environmental impacts in all stages of infrastructure life cycle, from raw material production through end-of-life management. However, the various phases of the assessment are all associated with uncertainties. If decisions are made without consideration of these uncertainties, they might be misleading and suboptimal. In this paper, results are presentedwhere variations associated with different parameters and tools for life cycle assessment have been considered using probabilistic methods. A categorization of common uncertainties in LCA is also included. The most influential parameters can be identified with sensitivity analysis methods, since for LCA with a large number of parameters it may be unreasonable to incorporate all in a probabilistic simulation. For a limited amount of influential variables, Monte Carlo simulation has been used to assess the effects of uncertainties on the results.A bridge has been used as a case study to find important aspects in infrastructure LCA. The results indicate that if the most influential parameters are considered as random variables, it is possible to estimate the uncertainty and increase the validity of the life cycle assessment.
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| 113174. |
- Larsson Ivanov, Oskar, et al.
(författare)
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The practical value of structural health information for time dependence in bridge maintenance
- 2021
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; , s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- For practical decisions on common recurring maintenance actions, the information from routine inspections form a decision basis for the bridge manager. It is often difficult to assess whether this information is sufficient for deciding on a repair action, or if more information is needed. For many bridges the information for supporting decisions may be limited, although those bridges cause large yearly maintenance costs for the society. The purpose of the study presented in this paper is to show how two different models for decision making based on Bayesian decision theory, a point-in-time decision model and a sequential updating decision model, can be used to improve the decision-making process for common maintenance decisions. The models use information from routine inspections and incorporates time dependent aspects such as material degradation and time value of money to improve the decision-making process. The focus is on presenting the methodology with a case study of a concrete bridge in Sweden where the edge beams may have to be replaced. Three assessment approaches are considered: (i) no assessment, (ii) desktop evaluation and (iii) measurements. The main finding is that sequential updating decision making will provide a higher benefit than a point-in-time decision, and thus give higher Value of Information. This value becomes even higher when the measurements are selected for the assessment. The results also show that the edge beams should be replaced. The general approach presented can be applicable to many decision scenarios related to maintenance of deteriorating structures.
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| 113175. |
- Larsson Ivanov, Oskar, et al.
(författare)
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Uncertainty and variation in LCA - Implementation of probabilistic methods to assess environmental impacts of infrastructures
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- For most applications trying to interpret the real world uncertainties will be an important factor to consider, which is also true for Life-Cycle Assessment used for estimating total environmental impact during the life-cycle of products, services, buildings, structures, roads etc. The construction and usage of infrastructure are major causes of emissions and energy use, thus making it even more important for society to aim at reducing this impact. One way of reducing environmental impact is by using LCA to show improvements for specific items and/or benefits of using a specific solution over another. To be able to use LCA, or any other calculated estimation, for comparisons it is of great importance to incorporate effects of uncertainties and to understand where such uncertainties have their sources. Otherwise, any attempt on comparing two solutions will be flawed and there is a risk for bias towards a specific solution. The aim of the work presented in this report have been to describe and discuss the types of uncertainties present in a LCA, and to discuss their importance, source and influence. An extensive review of the current state of the art of both uncertainties in general and specifically for LCA have been performed to find the most common ways of including uncertainties in LCA, with focus on the possibilities and limitations of different types of methods. It was found that many previous attempts on including uncertainties in LCA exists, and they showed that it is now possible to using probabilistic methods such as Monte Carlo simulations to incorporate uncertainties in LCA-tools, since the computational capacity have increased. The common problem for all previous studies and the study presented here is the availability of validated input data including uncertainty estimations. Initiatives exist for data quality control; however, they do not fully consider the effect of uncertainties, and typically have been limited to the consideration of variations in emission factors only. Other factors such as system boundaries and choices made by the user have a much larger influence on the result than a small variation in the emission factor itself.To evaluate this, the basis for a methodology considering uncertainties in LCA and possibilities for controlling these uncertainties is presented. The methodology is based on general definitions of uncertainties to be able to understand the source and characteristics of each affecting parameter and for making informed decisions on how to reduce the uncertainty depending on the purpose of the LCA. This kind of methodology will especially be valuable for raising awareness of uncertainties in LCA for different stages of the building process.The possibility of including uncertainties in a LCA-tool for infrastructures in also presented, showing possibilities for studying the sensitivity of the input parameters and the propagation of uncertainties. A case study is used to demonstrate these possibilities, showing the importance of considering uncertainties in all input parameters. It is shown that the influence of other factors apart from the emission factors can be large, such as material amounts and expected service life, and that they have to be considered if reasonable results are sought. It should be noted, however, that the case study presented in this report serves illustrative purposes and includes significant simplifications.
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| 113176. |
- Larsson, Jim, et al.
(författare)
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A 3-D printed phantom for optical techniques in medicine
- 2017
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Ingår i: CLEO: Applications and Technology, CLEO_AT 2017. - 9781943580279 ; Part F43-CLEO_AT 2017
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Konferensbidrag (refereegranskat)abstract
- Development of optical techniques in medical applications can be difficult due to limited access to realistic phantoms. Here a 3-D printed model based on CT-images of the thorax of an infant is developed and tested.
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| 113177. |
- Larsson, Johan, et al.
(författare)
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A case study in fitting area-proportional euler diagrams with ellipses using eulerr
- 2018
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Ingår i: CEUR Workshop Proceedings : Proceedings of International Workshop on Set Visualization and Reasoning (SetVR 2018) - Proceedings of International Workshop on Set Visualization and Reasoning (SetVR 2018). - 1613-0073. ; 2116, s. 84-91
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Konferensbidrag (refereegranskat)abstract
- Euler diagrams are common and user-friendly visualizations for set relationships. Most Euler diagrams use circles, but circles do not always yield accurate diagrams. A promising alternative is ellipses, which, in theory, enable accurate diagrams for a wider range of input. Elliptical diagrams, however, have not yet been implemented for more than three sets or three-set diagrams where there are disjoint or subset relationships. The aim of this paper is to present eulerr: a software package for elliptical Euler diagrams for, in theory, any number of sets. It fits Euler diagrams using numerical optimization and exact-area algorithms through a two-step procedure, first generating an initial layout using pairwise relationships and then finalizing this layout using all set relationships.
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| 113178. |
- Larsson, Josefin, et al.
(författare)
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A new constraint for gamma-ray burst progenitor mass
- 2007
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 376:3, s. 1285-1290
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Tidskriftsartikel (refereegranskat)abstract
- Recent comparative observations of long-duration gamma-ray bursts (LGRBs) and core collapse supernova (cc SN) host galaxies demonstrate that these two, highly energetic transient events are distributed very differently upon their hosts. LGRBs are much more concentrated on their host galaxy light than cc SN. Here we explore the suggestion that this differing distribution reflects different progenitor masses for LGRBs and cc SN. Using a simple model we show that, assuming cc SN arise from stars with main-sequence masses > 8 M-circle dot, GRBs are likely to arise from stars with initial masses > 20 M-circle dot. This difference can naturally be explained by the requirement that stars which create a LGRB must also create a black hole.
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| 113179. |
- Larsson, Jonas, et al.
(författare)
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Abnormal angiogenesis but intact hematopoietic potential in TGF-beta type I receptor-deficient mice
- 2001
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Ingår i: EMBO Journal. - : Wiley. - 1460-2075. ; 20:7, s. 1663-1673
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Tidskriftsartikel (refereegranskat)abstract
- Deletion of the transforming growth factor beta1 (TGF-beta1) gene in mice has previously suggested that it regulates both hematopoiesis and angiogenesis. To define the function of TGF-beta more precisely, we inactivated the TGF-beta type I receptor (T beta RI) gene by gene targeting. Mice lacking T beta RI die at midgestation, exhibiting severe defects in vascular development of the yolk sac and placenta, and an absence of circulating red blood cells. However, despite obvious anemia in the T beta RI-/- yolk sacs, clonogenic assays on yolk sac-derived hematopoietic precursors in vitro revealed that T beta RI-/- mice exhibit normal hematopoietic potential compared with wild-type and heterozygous siblings, Endothelial cells derived from T beta RI-deficient embryos show enhanced cell proliferation, improper migratory behavior and impaired fibronectin production in vitro, defects that are associated with the vascular defects seen in vivo. We thus demonstrate here that, while T beta RI is crucial for the function of TGF-beta during vascular development and can not be compensated for by the activin receptor-like kinase-1 (ALK-1), functional hematopoiesis and development of hematopoietic progenitors is not dependent on TGF-beta signaling via T beta RI.
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| 113180. |
- Larsson, Jim, et al.
(författare)
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Atmospheric CO2 sensing using Scheimpflug-lidar based on a 1.57-mu m fiber source
- 2019
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 27:12, s. 17348-17358
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Tidskriftsartikel (refereegranskat)abstract
- A molecular laser-radar system, based on the Scheimpflug principle, has been constructed and demonstrated for remote sensing of atmospheric CO2 concentrations using Differential Absorption Lidar (DIAL) in the (30012 <- 00001) absorption band. The laser source is a Continues Wave (CW) Distributed-FeedBack (DFB) diode laser seeding an Erbium-doped fiber amplifier, emitting narrowband (3 MHz) tunable radiation with an output power of 1.3 W at 1.57 mu m. The laser beam is expanded and transmitted to the atmosphere. The atmospheric backscattered signal is collected with a Newtonian telescope and detected with a linear InGaAs array detector satisfying the Scheimpflug condition. We present range-resolved measurements of atmospheric CO2 concentration from a test range of 2 km located in the city of Lund, Sweden. We discuss and provide scalable results for CO2 profiling with the Scheimpflug-lidar method.
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