| 1. |
- Köppl, Christian Josef, et al.
(författare)
-
Hyperspectral reflectance measurements from UAS under intermittent clouds: Correcting irradiance measurements for sensor tilt
- 2021
-
Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 267, s. 1-1
-
Tidskriftsartikel (refereegranskat)abstract
- One great advantage of optical hyperspectral remote sensing from unmanned aerial systems (UAS) compared to satellite missions is the possibility to fly and collect data below clouds. The most typical scenario is flying below intermittent clouds and under turbulent conditions, which causes tilting of the platform. This study aims to advance hyperspectral imaging from UAS in most weather conditions by addressing two challenges: (i) the radiometric and spectral calibrations of miniaturized hyperspectral sensors; and (ii) tilting effects on measured downwelling irradiance. We developed a novel method to correct the downwelling irradiance data for tilting effects. It uses a hybrid approach of minimizing measured irradiance variations for constant irradiance periods and spectral unmixing, to calculate the spectral diffuse irradiance fraction for all irradiance measurements within a flight. It only requires the platform's attitude data and a standard incoming light sensor. We demonstrated the method at the Palo Verde National Park wetlands in Costa Rica, a highly biodiverse area. Our results showed that the downwelling irradiance correction method reduced systematic shifts caused by a change in flight direction of the UAS, by 87% and achieving a deviation of 2.78% relative to a on ground reference in terms of broadband irradiance. High frequency (< 3 s) irradiance variations caused by high-frequency tilting movements of the UAS were reduced by up to 71%. Our complete spectral and radiometric calibration and irradiance correction can significantly remove typical striped illumination artifacts in the surface reflectance-factor map product. The possibility of collecting precise hyperspectral reflectance-factor data from UAS under varying cloud cover makes it more operational for environmental monitoring or precision agriculture applications, being an important step in advancing hyperspectral imaging from UAS.
|
|
| 2. |
- Gosselink, Richard J. A., et al.
(författare)
-
Lignin depolymerisation in supercritical carbon dioxide/acetone/water fluid for the production of aromatic chemicals
- 2012
-
Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 106, s. 173-177
-
Tidskriftsartikel (refereegranskat)abstract
- Valorisation of lignin plays a key role in further development of lignocellulosic biorefinery processes the production of biofuels and bio-based materials. In the present study, organosolv hardwood and wheat straw lignins were converted in a supercritical fluid consisting of carbon dioxide/acetone/water (300-370 degrees C, 100 bar) to a phenolic oil consisting of oligomeric fragments and monomeric aromatic compounds with a total yield of 10-12% based on lignin. These yields are similar to the state-of-the-art technologies such as base-catalysed thermal processes applied for lignin depolymerisation. Addition of formic acid increases the yield of monomeric aromatic species by stabilizing aromatic radicals. Supercritical depolymerisation of wheat straw and hardwood lignin yielded monomeric compounds in different compositions with a maximum yield of 2.0% for syringic acid and 3.6% for syringol, respectively. The results of the present study showed that under the applied conditions competition occurred between lignin depolymerisation and recondensation of fragments.
|
|
| 3. |
|
|
| 4. |
- Pelkmans, Luc, et al.
(författare)
-
The role of sustainability requirements in international bioenergy markets
- 2014
-
Ingår i: Lecture Notes in Energy. - Dordrecht : Springer Netherlands. - 2195-1292 .- 2195-1284. ; 17:1, s. 125-149
-
Tidskriftsartikel (refereegranskat)abstract
- As the main driver for bioenergy is to enable society to transform to more sustainable fuel and energy production systems, it is important to safeguard that bioenergy deployment happens within certain sustainability constraints. There is currently a high number of initiatives, including binding regulations and several voluntary sustainability standards for biomass, bioenergy and/or biofuels. Within IEA Bioenergy studies were performed to monitor the actual implementation process of sustainability regulations and certification, evaluate how stakeholders are affected and envisage the anticipated impact on worldwide markets and trade. On the basis of these studies, recommendations were made on how sustainability requirements could actually support further bioenergy deployment. Markets would gain from more harmonization and cross-compliance. A common language is needed as 'sustainability' of biomass involves different policy arenas and legal settings. Policy pathways should be clear and predictable, and future revisions of sustainability requirements should be open and transparent. Sustainability assurance systems (both through binding regulations and voluntary certification) should take into account how markets work, in relation to different biomass applications (avoiding discrimination among end-uses and users). It should also take into account the way investment decisions are taken, administrative requirements for smallholders, and the position of developing countries.
|
|
| 5. |
- Yeung, Sing Yee, et al.
(författare)
-
Reversible Self-Assembled Monolayers with Tunable Surface Dynamics for Controlling Cell Adhesion Behavior.
- 2022
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:37, s. 41790-41799
-
Tidskriftsartikel (refereegranskat)abstract
- Cells adhering onto surfaces sense and respond to chemical and physical surface features. The control over cell adhesion behavior influences cell migration, proliferation, and differentiation, which are important considerations in biomaterial design for cell culture, tissue engineering, and regenerative medicine. Here, we report on a supramolecular-based approach to prepare reversible self-assembled monolayers (rSAMs) with tunable lateral mobility and dynamic control over surface composition to regulate cell adhesion behavior. These layers were prepared by incubating oxoacid-terminated thiol SAMs on gold in a pH 8 HEPES buffer solution containing different mole fractions of ω-(ethylene glycol)2-4- and ω-(GRGDS)-, α-benzamidino bolaamphiphiles. Cell shape and morphology were influenced by the strength of the interactions between the amidine-functionalized amphiphiles and the oxoacid of the underlying SAMs. Dynamic control over surface composition, achieved by the addition of inert filler amphiphiles to the RGD-functionalized rSAMs, reversed the cell adhesion process. In summary, rSAMs featuring mobile bioactive ligands offer unique capabilities to influence and control cell adhesion behavior, suggesting a broad use in biomaterial design, tissue engineering, and regenerative medicine.
|
|
