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9 results on '"Aebischer, Philippe"'

1. Herbage biomass predictions from UAV data using a derived digital terrain model and machine learning.

Author

Aebischer, Philippe, Sutter, Michael, Birkinshaw, Amy, Nussbaum, Madlene, and Reidy, Beat

Subjects
*BIOMASS estimation, *MACHINE learning, *RANDOM forest algorithms, *DIGITAL elevation models, *AGRICULTURE
Abstract

More than 70% of Switzerland's agricultural area is covered by grasslands that often exhibit highly diverse species compositions and heterogeneous growth patterns. An essential requirement for efficient and effective pasture management is the regular estimation of herbage biomass. While various methods exist for estimating herbage biomass, they are often time‐consuming and may not accurately capture the variability within pastures. This highlights the need for more efficient, accurate estimation techniques. To help improve herbage biomass estimation, we present estiGrass3D+, a Random Forest model. This model predicts pasture biomass using a digital terrain model (DTM) derived from a digital surface model (DSM) for sward height modelling, along with vegetation indices and agronomic variables from UAV images only. The model was successfully evaluated with independent test data from different sites on the Swiss central plateau, including both grazed and mown areas. Model performance on an independent validation dataset achieved a NRMSE of 20.3%, while the training dataset had an NRMSE of 21.5%. These consistent results confirm that estiGrass3D+ is both transferable and applicable to unseen data while maintaining accuracy and reliability across different datasets. The wide applicability of our method demonstrates its practicality for predicting herbage biomass under different pasture management scenarios. Additionally, our method of deriving a DTM directly from a DSM simplifies the measurement of grass sward height by UAVs, eliminating the need for prior ground control point (GCP) marking and subsequent aligning, enhancing the efficiency of herbage biomass estimation. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Antragsformular Forschungsprojekt: Folgenabschätzung der mechanischen Beikrautregulierung auf Umwelt und Ertrag

Author

Grosse, Meike, Krauss, Maike, Gelencsér, Tobias, Dierauer, Hansueli, Mäder, Paul, Reidy, Beat, and Aebischer, Philippe

Subjects
Soil, Nutrient turnover, Weed management, Soil tillage
Abstract

Die gesellschaftliche Forderung nach einer nachhaltigen und produktiven Pflanzenproduktion bei gleichzei-tig zunehmenden Wetterextremen setzt die Betriebe stark unter Druck. Der pfluglose biologische Ackerbau bietet hier viel Potential, muss aber in Punkto Beikrautregulierung und Stickstoffverfügbarkeit optimiert wer-den, um für die Bio-, IP- und ÖLN-Praxis attraktiv zu sein. Das Projektziel ist zu untersuchen, ob mit geziel-tem Hacken die Stickstoffernährung der Pflanzen und die Beikrautregulierung auch bei reduzierter Dünger-menge effizient gesteuert werden kann und der dabei angeregte Humusabbau auf einem akzeptablen Niveau bleibt. In einem 12-jährigen Langzeitversuch zur reduzierten Bodenbearbeitung und Düngung wer-den im Projekt verschiedene Hackintensitäten in den Kulturen Silomais und Winterweizen zusätzlich inte-griert. Die N-Mineralisierung wird über Nmin-Analysen und der Humusabbau über CO2 Gasmessungen ver-folgt. Die N-Aufnahme wird über Orthofotos sowie N-Analysen in der Trockenmasse und die Produktivität über den Biomasseertrag ermittelt. Die Messung der Beikrautbiomasse wird als Indikator für die Effektivität des Hackens verwendet und die Qualität des Mais mittels Silierversuchen bestimmt. Daneben werden auf Praxisbetrieben in Streifenversuchen mit verschiedenen Hackintensitäten Ertragsbestimmungen und N-Analysen in der Trockenmasse bei Mais und Weizen durchgeführt. Die ökonomische Einschätzung erfolgt über Deckungsbeitragsrechnungen. Die Versuchs- und Praxisdaten helfen die Nachhaltigkeit der Pflanzen-produktion im Bereich der Pestizid- und Düngerreduktion, sowie die Anpassung an den Klimawandel zu op-timieren.

Published
2022

4. Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Author

Conley, Gaurasundar M., Aebischer, Philippe, Nöjd, Sofi, Schurtenberger, Peter, Scheffold, Frank, Conley, Gaurasundar M., Aebischer, Philippe, Nöjd, Sofi, Schurtenberger, Peter, and Scheffold, Frank

Abstract

Tuning the solubility of fuzzy polymer microgels by external triggers, such as temperature or pH, provides a unique mechanism for controlling the porosity and size of colloidal particles on the nanoscale. As a consequence, these smart microgel particles are being considered for applications ranging from viscosity modifiers and sensing to drug delivery and as models for the glass and the jamming transition. Despite their widespread use, little is known about how these soft particles adapt their shape and size under strong mechanical compression. We use a combination of precise labeling protocols and two-color superresolution microscopy to unravel the behavior of tracer microgels inside densely packed soft solids. We find that interpenetration and shape deformation are dominant until, in the highly overpacked state, this mechanism saturates and the only remaining way to further densify the system is by isotropic compression.

Published
2018

8. Relationship between rheology and structure of interpenetrating, deforming and compressing microgels

Author

Conley, Gaurasundar M., Zhang, Chi, Aebischer, Philippe, Harden, James L., Scheffold, Frank, Conley, Gaurasundar M., Zhang, Chi, Aebischer, Philippe, Harden, James L., and Scheffold, Frank

Abstract

Thermosensitive microgels are widely studied hybrid systems combining properties of polymers and colloidal particles in a unique way. Due to their complex morphology, their interactions and packing, and consequentially the viscoelasticity of suspensions made from microgels, are still not fully understood, in particular under dense packing conditions. Here we study the frequency-dependent linear viscoelastic properties of dense suspensions of micron sized soft particles in conjunction with an analysis of the local particle structure and morphology based on superresolution microscopy. By identifying the dominating mechanisms that control the elastic and dissipative response, we can explain the rheology of these widely studied soft particle assemblies from the onset of elasticity deep into the overpacked regime. Interestingly, our results suggest that the friction between the microgels is reduced due to lubrification mediated by the polymer brush-like corona before the onset of interpenetration.

9. Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Author

Conley, Gaurasundar M., Aebischer, Philippe, Nöjd, Sofi, Schurtenberger, Peter, Scheffold, Frank, Conley, Gaurasundar M., Aebischer, Philippe, Nöjd, Sofi, Schurtenberger, Peter, and Scheffold, Frank

Abstract

Tuning the solubility of fuzzy polymer microgels by external triggers, such as temperature or pH, provides a unique mechanism for controlling the porosity and size of colloidal particles on the nanoscale. As a consequence, these smart microgel particles are being considered for applications ranging from viscosity modifiers and sensing to drug delivery and as models for the glass and the jamming transition. Despite their widespread use, little is known about how these soft particles adapt their shape and size under strong mechanical compression. We use a combination of precise labeling protocols and two-color superresolution microscopy to unravel the behavior of tracer microgels inside densely packed soft solids. We find that interpenetration and shape deformation are dominant until, in the highly overpacked state, this mechanism saturates and the only remaining way to further densify the system is by isotropic compression.

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