663 research outputs found
A fully coupled regularized mortar-type finite element approach for embedding one-dimensional fibers into three-dimensional fluid flow
The present article proposes a partitioned Dirichlet-Neumann algorithm, that
allows to address unique challenges arising from a novel mixed-dimensional
coupling of very slender fibers embedded in fluid flow using a regularized
mortar-type finite element discretization. The fibers are modeled via
one-dimensional (1D) partial differential equations based on geometrically
exact nonlinear beam theory, while the flow is described by the
three-dimensional (3D) incompressible Navier-Stokes equations. The arising
truly mixed-dimensional 1D-3D coupling scheme constitutes a novel approximate
model and numerical strategy, that naturally necessitates specifically tailored
solution schemes to ensure an accurate and efficient computational treatment.
In particular, we present a strongly coupled partitioned solution algorithm
based on a Quasi-Newton method for applications involving fibers with high
slenderness ratios that usually present a challenge with regard to the
well-known added mass effect. The influence of all employed algorithmic and
numerical parameters, namely the applied acceleration technique, the employed
constraint regularization parameter as well as shape functions, on efficiency
and results of the solution procedure is studied through appropriate examples.
Finally, the convergence of the two-way coupled mixed-dimensional problem
solution under uniform mesh refinement is demonstrated, a comparison to a 3D
reference solution is performed, and the method's capabilities in capturing
flow phenomena at large geometric scale separation is illustrated by the
example of a submersed vegetation canopy
Quantum Response of Human Skin to Hydrogen Peroxide Stimulation
Visible range photon signals emitted after applying five concentrations of hydrogen peroxide (H2O2) on both sides of the left hand were measured and called response signals. Their quantum nature was ascertained in two analyses. The first analysis determined decay parameters of signals in two models - quantum and two exponential decays - and checked the robustness of decay parameters. The analysis established hyperbolic decay of response signals and showed that signals were in evolving squeezed states. The second analysis split response signal in small sections and determined the properties of the signal in each section from mean, variance and photon count distribution in the section. The properties showed that every section was a high strength biophoton signal having a core quantum component in squeezed state and a peripheral classical component. The properties further suggested the involvement of same or similar quantum entities in the emission of response and biophoton signals
Determination of Lamb Wave Modes on Lithium-Ion Batteries Using Piezoelectric Transducers
This work presents a method to determine the type of Lamb mode (antisymmetric or symmetric) that propagates through a lithium-ion pouch cell. To determine the type of mode and the group velocity at a specific frequency, two- and three-transducer setups were created. For these setups, it is important that all transducers have the same polarization direction. Two transducers are affixed to the center of the cell at a distance of several centimeters from each other so that the group velocity can be determined. Using cross-correlation, the group velocity of the emerging mode can be calculated. The measurement setup and the processing method was first validated with experiments on acrylic glass and aluminum plates. The measurements were supported with FEM simulations and a numerically calculated model. The output voltages of the receiving piezo-elements obtained in the FEM simulation are in agreement with the underlying theories. The phase shift, which results from the output voltage of the piezo-elements mounted one above the other on different sides of the plate, shows the type of mode. The results of the experimental determination of the Lamb mode that propagates through a lithium-ion pouch cell were validated with a numerically calculated multi-layer model and therefore validate this novel experimental approach
Why Farmers Don\u27t Always Practice \u27Optimum\u27 Management: Case Study of Small Stock Ranching Systems in Southern Namibia
Isogeometric dual mortar methods for computational contact mechanics
International audienceIn recent years, isogeometric analysis (IGA) has received great attention in many fields of computational mechanics research. Especially for computational contact mechanics, an exact and smooth surface representation is highly desirable. As a consequence, many well-known finite e lement m ethods a nd a lgorithms f or c ontact m echanics h ave b een t ransferred t o I GA. I n t he present contribution, the so-called dual mortar method is investigated for both contact mechanics and classical domain decomposition using NURBS basis functions. In contrast to standard mortar methods, the use of dual basis functions for the Lagrange multiplier based on the mathematical concept of biorthogonality enables an easy elimination of the additional Lagrange multiplier degrees of freedom from the global system. This condensed system is smaller in size, and no longer of saddle point type but positive definite. A very simple and commonly used element-wise construction of the dual basis functions is directly transferred to the IGA case. The resulting Lagrange multiplier interpolation satisfies discrete inf–sup stability and biorthogonality, however, the reproduction order is limited to one. In the domain decomposition case, this results in a limitation of the spatial convergence order to O(h 3 /2) in the energy norm, whereas for unilateral contact, due to the lower regularity of the solution, optimal convergence rates are still met. Numerical examples are presented that illustrate these theoretical considerations on convergence rates and compare the newly developed isogeometric dual mortar contact formulation with its standard mortar counterpart as well as classical finite elements based on first and second order Lagrange polynomials
Rare variants in IFFO1, DTNB, NLRC3 and SLC22A10 associate with Alzheimer's disease CSF profile of neuronal injury and inflammation
Alzheimer's disease (AD) biomarkers represent several neurodegenerative processes, such as synaptic dysfunction, neuronal inflammation and injury, as well as amyloid pathology. We performed an exome-wide rare variant analysis of six AD biomarkers (β-amyloid, total/phosphorylated tau, NfL, YKL-40, and Neurogranin) to discover genes associated with these markers. Genetic and biomarker information was available for 480 participants from two studies: EMIF-AD and ADNI. We applied a principal component (PC) analysis to derive biomarkers combinations, which represent statistically independent biological processes. We then tested whether rare variants in 9576 protein-coding genes associate with these PCs using a Meta-SKAT test. We also tested whether the PCs are intermediary to gene effects on AD symptoms with a SMUT test. One PC loaded on NfL and YKL-40, indicators of neuronal injury and inflammation. Four genes were associated with this PC: IFFO1, DTNB, NLRC3, and SLC22A10. Mediation tests suggest, that these genes also affect dementia symptoms via inflammation/injury. We also observed an association between a PC loading on Neurogranin, a marker for synaptic functioning, with GABBR2 and CASZ1, but no mediation effects. The results suggest that rare variants in IFFO1, DTNB, NLRC3, and SLC22A10 heighten susceptibility to neuronal injury and inflammation, potentially by altering cytoskeleton structure and immune activity disinhibition, resulting in an elevated dementia risk. GABBR2 and CASZ1 were associated with synaptic functioning, but mediation analyses suggest that the effect of these two genes on synaptic functioning is not consequential for AD development
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