| 1. |
- Ahlberg, Erik, et al.
(författare)
-
"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
-
Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Martinsson, Johan, et al.
(författare)
-
Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol
- 2015
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:24, s. 14663-14671
-
Tidskriftsartikel (refereegranskat)abstract
- The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Angstrom exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Eriksson, Axel, et al.
(författare)
-
Diesel soot aging in urban plumes within hours under cold dark and humid conditions
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322.
-
Tidskriftsartikel (refereegranskat)abstract
- Fresh and aged diesel soot particles have different impacts on climate and human health. While fresh diesel soot particles are highly aspherical and non-hygroscopic, aged particles are spherical and hygroscopic. Aging and its effect on water uptake also controls the dispersion of diesel soot in the atmosphere. Understanding the timescales on which diesel soot ages in the atmosphere is thus important, yet knowledge thereof is lacking. We show that under cold, dark and humid conditions the atmospheric transformation from fresh to aged soot occurs on a timescale of less than five hours. Under dry conditions in the laboratory, diesel soot transformation is much less efficient. While photochemistry drives soot aging, our data show it is not always a limiting factor. Field observations together with aerosol process model simulations show that the rapid ambient diesel soot aging in urban plumes is caused by coupled ammonium nitrate formation and water uptake.
|
|
| 9. |
|
|
| 10. |
- Mark, Andreas, 1980, et al.
(författare)
-
Microstructure Simulation of Early Paper Forming Using Immersed Boundary Methods
- 2011
-
Ingår i: Paper360. - 1933-3684. ; 10:11, s. 23-30
-
Tidskriftsartikel (refereegranskat)abstract
- Paper forming is the first step in the paper machine where a fibersuspension leaves the headbox and flows through a forming fabric.Complex physical phenomena occur during paper forming due to theinteraction between fibers, fillers and fines as well as chemicalsadded to the suspension. Understanding this process is important forthe development of improved paper products because the configurationof the fibers during this step has a large influence on the finalpaper quality. Since the effective paper properties depend on themicro-structure of the fiber web, a continuum model is inadequate andthe properties of each fiber need to be accounted for in thesimulations.In the present work, a framework for microstructure simulation ofearly paper forming has been developed. The simulation frameworkincludes a Navier-Stokes solver and immersed boundary methods are usedto resolve the flow around the fibers. The fibers are modeled with afinite element discretization of the Euler-Bernoulli beam equation ina co-rotational formulation. The contact model is based on a penaltymethod and includes friction as well as elastic and inelasticcollisions.The fiber model and the contact model are validated against demandingtest cases from the literature with excellent results. Thefluid-structure interaction in the model is examined by simulating anelastic beam oscillating in a cross flow. Finally, a simulation ofearly paper forming is performed to demonstrate the potential of theproposed framework. The unique modeling approach can be used toincrease the fundamental understanding of paper forming and supportprocess optimization.
|
|
