85 research outputs found
Analysis of rate-dependent deformation and fracture phenomena during cutting of viscoelastic materials
The cutting of foods is characterized by deformation, fracture and friction processes, and the viscoelastic properties of the cutting materials determine their rate-dependent cutting behavior. This is responsible for uncontrolled fracture and deformation events with increasing cutting velocity. There is a significant information deficit regarding the assignment of material properties and cutting parameters, as well as regarding a process description for industrial high-speed cutting.
The aim of the work is the analysis of the velocity-dependent cutting behavior of foods up to the high-speed range. The focus is on the deformation and fracture phenomena, analysed by methods of classical material analysis but also associated cutting experiments performed in the range from low to high cutting velocities. For high-speed analyses, a test station enabling cutting velocities of up to 10 m/s was designed. To identify relevant material and cutting parameters and to establish a systematic experimental program, elastomer-based model systems with controllable viscoelastic profiles were developed. The results of the respective investigations were further verified for foods. The velocity-dependent deformation behavior during cutting could be described by dynamic-mechanical material analyses in the frequency range. Cutting force slopes at the beginning of the cutting process correlated with the complex moduli and were furthermore dependent on the cutting velocity; this dependency corresponded to the frequency behavior from material analysis. The fracture properties could be attributed to ductile (polymeric systems) or brittle behavior (cellular plant systems). Confectionary products had a strong temperature- and time-dependent behavior with ductile-brittle transition within the experimental conditions.
The results obtained demonstrate that there is a significant relationship between viscoelasticity and velocity-dependent cutting behavior. They allow a phenomenological process description of high-speed cutting and can be used as a basis for the balancing of cutting forces and as input parameters for numerical analyses of the cutting process.Das Schneiden von Lebensmitteln ist geprĂ€gt durch Deformations-, Bruch- und ReibvorgĂ€nge. Dabei bestimmen die viskoelastischen Eigenschaften der SchneidgĂŒter deren geschwindigkeitsabhĂ€ngiges Schneidverhalten. Dies fĂŒhrt mit zunehmender Schneidgeschwindigkeit zu unkontrollierten Bruch- und Deformationsereignissen. Dabei besteht ein Informationsdefizit bei der konkreten Zuweisung von Materialeigenschaften und Schneidparametern sowie einer Verfahrensbeschreibung fĂŒr das industrielle Hochgeschwindigkeitsschneiden.
Ziel der Arbeit ist die Analyse des geschwindigkeitsabhĂ€ngigen Schneidverhaltens von Lebensmitteln bis in den Hochgeschwindigkeitsbereich. Der Fokus richtet sich auf die Untersuchung der TeilphĂ€nomene Deformation und Bruch durch Methoden der klassischen Materialanalyse sowie zugeordnete Schneidexperimente im Bereich von niedrigen bis hohen Schneidgeschwindigkeiten. FĂŒr entsprechende Hochgeschwindigkeitsanalysen wurde ein Versuchsstand mit Schneidgeschwindigkeiten von bis zu 10 m/s konzipiert. Zur Identifikation relevanter Material- und Schneidparameter und zur Aufstellung des systematischen Versuchsprogramms wurden Modellsysteme auf Elastomerbasis mit steuerbarem viskoelastischen Profil entwickelt. Die Ergebnisse wurden fĂŒr Lebensmittel verifiziert. Das geschwindigkeitsabhĂ€ngige Deformationsverhalten beim Schneiden konnte durch dynamisch-mechanische Materialanalysen im Frequenzbereich beschrieben werden. Dabei korrelierten Kraftanstiege zu Beginn des Schneidvorganges mit den Komplexmoduln. Die Anstiege zeigten eine AbhĂ€ngigkeit von der Geschwindigkeit; diese entsprach dem Frequenzverhalten aus der Materialanalyse. Die Brucheigenschaften konnten produktspezifisch duktilem (polymere Systeme) oder sprödem Verhalten (zellulĂ€re, pflanzliche Systeme) zugeordnet werden. Zuckerwaren zeigten ein stark temperatur - und zeitabhĂ€ngiges Verhalten mit duktil-sprödem Ăbergang innerhalb der Versuchsbedingungen.
Die gewonnenen Erkenntnisse demonstrieren den Zusammenhang von ViskoelastizitĂ€t und geschwindigkeitsabhĂ€ngigem Schneidverhalten. Sie erlauben eine phĂ€nomen ologische Verfahrensbeschreibung des Hochgeschwindigkeitsschneidens und können als Basis fĂŒr die Bilanzierung von SchneidkrĂ€ften und als Eingangsparameter fĂŒr numerische Analysen des Schneidvorganges dienen
Analysis of rate-dependent deformation and fracture phenomena during cutting of viscoelastic materials
The cutting of foods is characterized by deformation, fracture and friction processes, and the viscoelastic properties of the cutting materials determine their rate-dependent cutting behavior. This is responsible for uncontrolled fracture and deformation events with increasing cutting velocity. There is a significant information deficit regarding the assignment of material properties and cutting parameters, as well as regarding a process description for industrial high-speed cutting.
The aim of the work is the analysis of the velocity-dependent cutting behavior of foods up to the high-speed range. The focus is on the deformation and fracture phenomena, analysed by methods of classical material analysis but also associated cutting experiments performed in the range from low to high cutting velocities. For high-speed analyses, a test station enabling cutting velocities of up to 10 m/s was designed. To identify relevant material and cutting parameters and to establish a systematic experimental program, elastomer-based model systems with controllable viscoelastic profiles were developed. The results of the respective investigations were further verified for foods. The velocity-dependent deformation behavior during cutting could be described by dynamic-mechanical material analyses in the frequency range. Cutting force slopes at the beginning of the cutting process correlated with the complex moduli and were furthermore dependent on the cutting velocity; this dependency corresponded to the frequency behavior from material analysis. The fracture properties could be attributed to ductile (polymeric systems) or brittle behavior (cellular plant systems). Confectionary products had a strong temperature- and time-dependent behavior with ductile-brittle transition within the experimental conditions.
The results obtained demonstrate that there is a significant relationship between viscoelasticity and velocity-dependent cutting behavior. They allow a phenomenological process description of high-speed cutting and can be used as a basis for the balancing of cutting forces and as input parameters for numerical analyses of the cutting process.Das Schneiden von Lebensmitteln ist geprĂ€gt durch Deformations-, Bruch- und ReibvorgĂ€nge. Dabei bestimmen die viskoelastischen Eigenschaften der SchneidgĂŒter deren geschwindigkeitsabhĂ€ngiges Schneidverhalten. Dies fĂŒhrt mit zunehmender Schneidgeschwindigkeit zu unkontrollierten Bruch- und Deformationsereignissen. Dabei besteht ein Informationsdefizit bei der konkreten Zuweisung von Materialeigenschaften und Schneidparametern sowie einer Verfahrensbeschreibung fĂŒr das industrielle Hochgeschwindigkeitsschneiden.
Ziel der Arbeit ist die Analyse des geschwindigkeitsabhĂ€ngigen Schneidverhaltens von Lebensmitteln bis in den Hochgeschwindigkeitsbereich. Der Fokus richtet sich auf die Untersuchung der TeilphĂ€nomene Deformation und Bruch durch Methoden der klassischen Materialanalyse sowie zugeordnete Schneidexperimente im Bereich von niedrigen bis hohen Schneidgeschwindigkeiten. FĂŒr entsprechende Hochgeschwindigkeitsanalysen wurde ein Versuchsstand mit Schneidgeschwindigkeiten von bis zu 10 m/s konzipiert. Zur Identifikation relevanter Material- und Schneidparameter und zur Aufstellung des systematischen Versuchsprogramms wurden Modellsysteme auf Elastomerbasis mit steuerbarem viskoelastischen Profil entwickelt. Die Ergebnisse wurden fĂŒr Lebensmittel verifiziert. Das geschwindigkeitsabhĂ€ngige Deformationsverhalten beim Schneiden konnte durch dynamisch-mechanische Materialanalysen im Frequenzbereich beschrieben werden. Dabei korrelierten Kraftanstiege zu Beginn des Schneidvorganges mit den Komplexmoduln. Die Anstiege zeigten eine AbhĂ€ngigkeit von der Geschwindigkeit; diese entsprach dem Frequenzverhalten aus der Materialanalyse. Die Brucheigenschaften konnten produktspezifisch duktilem (polymere Systeme) oder sprödem Verhalten (zellulĂ€re, pflanzliche Systeme) zugeordnet werden. Zuckerwaren zeigten ein stark temperatur - und zeitabhĂ€ngiges Verhalten mit duktil-sprödem Ăbergang innerhalb der Versuchsbedingungen.
Die gewonnenen Erkenntnisse demonstrieren den Zusammenhang von ViskoelastizitĂ€t und geschwindigkeitsabhĂ€ngigem Schneidverhalten. Sie erlauben eine phĂ€nomen ologische Verfahrensbeschreibung des Hochgeschwindigkeitsschneidens und können als Basis fĂŒr die Bilanzierung von SchneidkrĂ€ften und als Eingangsparameter fĂŒr numerische Analysen des Schneidvorganges dienen
Distributed Co-Simulation of Networked Hardware-in-the-Loop Power Systems
The paper presents a method to extend existing
co-simulation frameworks to emulate quasi-dynamic behavior of
real grid components in a grid simulator using a distributed networked co-simulation platform. The platform uses generic socket
communication to exchange data between real grid components
and the grid simulator. The framework utilizes event triggered
models to enable data exchange between grid components and
the platform over user datagram protocol (UDP)/IP interface.
This framework has its use-case in smart grids as well as
microgrids for analyzing, monitoring and control applications
where it is impractical to model each component separately inside
the grid simulator. Intrinsic communication delays including
jitter is handled using built-in fallback strategies inside the
framework itself. As a proof-of-concept, a co-simulation between
a simulated low-voltage (LV) grid model and an emulation of
a simplified Photovoltaic (PV) model is presented. The behavior
of PV emulator is integrated in the grid simulator using socket
communication. The primary focus of this work is to validate the
extended framework. The effect of network delays on the stability
of the distributed co-simulation setup are also investigated
The puzzling properties of the MACS1149-JD1 galaxy at z=9.11
We analyze new JWST NIRCam and NIRSpec data on the redshift 9.11 galaxy
MACS1149-JD1. Our NIRCam imaging data reveal that JD1 comprises three spatially
distinct components. Our spectroscopic data indicate that JD1 appears dust-free
but is already enriched, . We
also find that the Carbon and Neon abundances in JD1 are below the solar
abundance ratio. Particularly the Carbon under-abundance is suggestive of
recent star formation where Type~II supernovae have already enriched the ISM in
Oxygen but intermediate mass stars have not yet enriched the ISM in Carbon. A
recent burst of star formation is also revealed by the star formation history
derived from NIRCam photometry. Our data do not reveal the presence of a
significant amount of old populations, resulting in a factor of
smaller stellar mass than previous estimates. Thus, our data support the view
that JD1 is a young galaxy.Comment: Accepted for publicatio
Streamlined Lensed Quasar Identification in Multiband Images via Ensemble Networks
Quasars experiencing strong lensing offer unique viewpoints on subjects
related to the cosmic expansion rate, the dark matter profile within the
foreground deflectors, and the quasar host galaxies. Unfortunately, identifying
them in astronomical images is challenging since they are overwhelmed by the
abundance of non-lenses. To address this, we have developed a novel approach by
ensembling cutting-edge convolutional networks (CNNs) -- for instance, ResNet,
Inception, NASNet, MobileNet, EfficientNet, and RegNet -- along with vision
transformers (ViTs) trained on realistic galaxy-quasar lens simulations based
on the Hyper Suprime-Cam (HSC) multiband images. While the individual model
exhibits remarkable performance when evaluated against the test dataset,
achieving an area under the receiver operating characteristic curve of 97.3%
and a median false positive rate of 3.6%, it struggles to generalize in real
data, indicated by numerous spurious sources picked by each classifier. A
significant improvement is achieved by averaging these CNNs and ViTs, resulting
in the impurities being downsized by factors up to 50. Subsequently, combining
the HSC images with the UKIRT, VISTA, and unWISE data, we retrieve
approximately 60 million sources as parent samples and reduce this to 892,609
after employing a photometry preselection to discover lensed quasars
with Einstein radii of arcsec. Afterward, the ensemble
classifier indicates 3080 sources with a high probability of being lenses, for
which we visually inspect, yielding 210 prevailing candidates awaiting
spectroscopic confirmation. These outcomes suggest that automated deep learning
pipelines hold great potential in effectively detecting strong lenses in vast
datasets with minimal manual visual inspection involved.Comment: Accepted for publication in the Astronomy & Astrophysics journal. 28
pages, 11 figures, and 3 tables. We welcome comments from the reade
Tree phylogenetic diversity structures multitrophic communities
1. Plant diversity begets diversity at other trophic levels. While species richness is
the most commonly used measure for plant diversity, the number of evolutionary
lineages (i.e. phylogenetic diversity) could theoretically have a stronger influence
on the community structure of co-occurring organisms. However, this prediction
has only rarely been tested in complex real-world ecosystems.
2. Using a comprehensive multitrophic dataset of arthropods and fungi from a
species-rich subtropical forest, we tested whether tree species richness or tree
phylogenetic diversity relates to the diversity and composition of organisms.
3. We show that tree phylogenetic diversity but not tree species richness determines
arthropod and fungi community composition across trophic levels and increases
the diversity of predatory arthropods but decreases herbivorous arthropod diver-
sity. The effect of tree phylogenetic diversity was not mediated by changed abun-
dances of associated organisms, indicating that evolutionarily more diverse plant
communities increase niche opportunities (resource diversity) but not necessarily
niche amplitudes (resource amount).
4. Our findings suggest that plant evolutionary relatedness structures multitrophic
communities in the studied species-rich forests and possibly other ecosystems
at large. As global change non-randomly threatens phylogenetically distinct plant
species, far-reaching consequences on associated communities are expected
Motor-free force generation in biological systems
A central part of soft matter physics is the investigation of effects in an active environment. These systems are driven out of equilibrium by a constant energy consumption. In biological systems, for instance, energy is consumed in the dynamic polymerization process of cytoskeletal filaments or by motor-filament interactions. These active processes convert chemical energy into mechanical work and impede a trapping of cellular structures in thermodynamically frozen states. Thus, active soft matter is crucial for biological systems to fulfill a broad range of tasks. Inherent physical principles relying on entropy maximizing arguments, however, cannot be easily switched off even in active systems. Cells might even employ these principles to accomplish certain tasks without the need to arrange elaborate, energy dissipating structures. Within the presented studies we demonstrate possibilities how biological relevant forces can be generated in the absence of any active accessory proteins. The presented studies are based on the cytoskeletal key components actin and microtubules. We demonstrate different approaches ranging from light induced softening to cross-linker expansion, which realize entropy driven contractions of the according system
Designing forest biodiversity experiments : general considerations illustrated by a new large experiment in subtropical China
Funded by German Research Foundation. Grant Number: DFG FOR 891/1 and 2 National Natural Science Foundation of China. Grant Numbers: NSFC 30710103907, 30930005, 31170457 , 31210103910 Swiss National Science Foundation (SNSF) Sino-German Centre for Research Promotion in BeijingPeer reviewedPublisher PD
Carbonâbiodiversity relationships in a highly diverse subtropical forest
Carbonâfocused climate mitigation strategies are becoming increasingly important in forests. However, with ongoing biodiversity declines we require better knowledge of how much such strategies account for biodiversity. We particularly lack information across multiple trophic levels and on established forests, where the interplay between carbon stocks, stand age, and tree diversity might influence carbonâbiodiversity relationships. Using a large dataset (>4600 heterotrophic species of 23 taxonomic groups) from secondary, subtropical forests, we tested how multitrophic diversity and diversity within trophic groups relate to aboveground, belowground, and total carbon stocks at different levels of tree species richness and stand age. Our study revealed that aboveground carbon, the key component of climateâbased management, was largely unrelated to multitrophic diversity. By contrast, total carbon stocksâthat is, including belowground carbonâemerged as a significant predictor of multitrophic diversity. Relationships were nonlinear and strongest for lower trophic levels, but nonsignificant for higher trophic level diversity. Tree species richness and stand age moderated these relationships, suggesting longâterm regeneration of forests may be particularly effective in reconciling carbon and biodiversity targets. Our findings highlight that biodiversity benefits of climateâoriented management need to be evaluated carefully, and only maximizing aboveground carbon may fail to account for biodiversity conservation requirements
Towards a methodical framework for comprehensively assessing forest multifunctionality
Funded by Deutsche Forschungsgemeinschaft. Grant Number: DFG FOR 891/1-3 National Natural Science Foundation of China. Grant Numbers: 30710103907, 30930005, 31170457, 31210103910 Swiss National Science Foundation (SNSF) Sino-German Centre for Research Promotion in Beijing. Grant Number: GZ 986Peer reviewedPublisher PD
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