Results 151 to 160 of about 1,440 (216)

Friction‐Corrected In‐Situ Viscosity Measurement in Material Extrusion: A Force‐Based Method Validated Against Capillary Rheometry Using Identical Nozzle Geometry

Polymer Engineering &Science, EarlyView.
In the filament force measurement (FFM), the friction of the solid filament, determined in an open‐bore reference, is subtracted from the measured extrusion force to obtain the capillary force. The resulting apparent viscosity is compared with high‐pressure capillary rheometry (HPCR) using the identical printer nozzle in both instruments.
Philipp Beier, Ivica Ðuretek, Stephan Schuschnigg, Thomas Lucyshyn, Viktoria Gruber, Clemens Holzer   +5 more
wiley   +1 more source

Propagation of internal gravity waves: Optimal vertical discretisation and grid design based on numerical error analysis

Quarterly Journal of the Royal Meteorological Society, EarlyView.
An energy‐conserving discrete framework for the vertical discretisation of stratified ocean models is developed using internal gravity‐wave theory. A β$$ \beta $$‐indexed family of schemes is analysed through perturbation theory, revealing optimal parameter choices and grid designs that reduce truncation errors significantly.
Gabriel Derrida, Laurent Debreu, Florian Lemarié, Jérome Chanut   +3 more
wiley   +1 more source

Evaluation of a stochastically perturbed parametrisations scheme for sea ice in sub‐seasonal forecasts

Quarterly Journal of the Royal Meteorological Society, EarlyView.
Overconfident sea ice forecasts pose a challenge in subseasonal prediction. To test a potential way to address this issue and account for sea ice model uncertainty, this article investigates a stochastically perturbed parametrisations (SPP) scheme for sea ice in a prototype CY49R2 configuration of the coupled IFS‐NEMO4‐SI3 system. The results show that
Jonas Spaeth, Steffen Tietsche, Kristian Strommen, Michael Mayer, Andrea Storto, Christopher D. Roberts, Sarah‐Jane Lock, Sarah Keeley   +7 more
wiley   +1 more source

Calibration of medium‐range temperature ensemble forecasts dependent on the time horizon: An assessment

Quarterly Journal of the Royal Meteorological Society, EarlyView.
Numerical weather prediction output necessitates calibration, as weather model systems are unable to replicate the correct statistics of observations. Such processing is especially important when predicting extreme weather. Calibration methods function by learning from prediction inadequacies during a training phase and by exploiting this information ...
Dmitrij Japs, Oleksiy Boyko, Paolo Reggiani, Ezio Todini   +3 more
wiley   +1 more source

Data‐driven emulation of flow‐dependent background‐error variance in variational data assimilation

Quarterly Journal of the Royal Meteorological Society, EarlyView.
A machine‐learning approach is developed to emulate flow‐dependent background‐error variance within a variational data assimilation framework. The method reproduces uncertainty information that would normally require a 50‐member ensemble using only five members, while maintaining comparable observation fit and forecast performance.
Wei Pan, Massimo Bonavita, Marcin Chrust, Elías Hólm   +3 more
wiley   +1 more source

Adaptive Sliding‐Mode Control of a Perturbed Diffusion Process With Pointwise In‐Domain Actuation

International Journal of Robust and Nonlinear Control, EarlyView.
ABSTRACT A sliding mode–based adaptive control law is proposed for a class of diffusion processes featuring a spatially‐varying uncertain diffusivity and equipped with several point‐wise actuators located at the two boundaries of the spatial domain as well as in its interior.
Paul Mayr, Alessandro Pisano, Stefan Koch, Markus Reichhartinger   +3 more
wiley   +1 more source

Optimal Homogeneous ℒp$$ {\boldsymbol{\mathcal{L}}}_{\boldsymbol{p}} $$‐Gain Controller

International Journal of Robust and Nonlinear Control, EarlyView.
ABSTRACT Nonlinear ℋ∞$$ {\mathscr{H}}_{\infty } $$‐controllers are designed for arbitrarily weighted, continuous homogeneous systems with a focus on systems affine in the control input. Based on the homogeneous ℒp$$ {\mathcal{L}}_p $$‐norm, the input–output behavior is quantified in terms of the homogeneous ℒp$$ {\mathcal{L}}_p $$‐gain as a ...
Daipeng Zhang, Benjamin Calmbach, Jaime A. Moreno, Johann Reger   +3 more
wiley   +1 more source

Optimal Gain Selection for the Arbitrary‐Order Homogeneous Differentiator

International Journal of Robust and Nonlinear Control, EarlyView.
ABSTRACT Differentiation of noisy signals is a relevant and challenging task. Widespread approaches are the linear high‐gain observer acting as a differentiator and Levant's robust exact differentiator with a discontinuous right‐hand side. We consider the family of arbitrary‐order homogeneous differentiators, which includes these special cases.
Benjamin Calmbach, Jaime A. Moreno, Johann Reger   +2 more
wiley   +1 more source

Discrete Implementations Modify the Intuition of Final Set Adjustment in Barrier Function Based Control

International Journal of Robust and Nonlinear Control, EarlyView.
ABSTRACT This paper establishes an implementation‐aware framework for Barrier Function Adaptation (BFA) and shows that discrete‐time realizations fundamentally alter the logic of final‐set adjustment. In particular, sufficient conditions are derived to preserve the key benefits of BFA (predefined performance, gain adaptation with uncertain perturbation
Luis Ovalle, Andrés González, Leonid Fridman, Meléndez Alfredo   +3 more
wiley   +1 more source

Exact Robust Filtering and Differentiation Based on Sliding Modes and Homogeneity

International Journal of Robust and Nonlinear Control, EarlyView.
ABSTRACT This article addresses the problem of online estimation of the derivatives of a signal corrupted by measurement noise. The measured signal is modeled as the sum of a smooth nominal component and a uniformly bounded noise term. A key objective is to attenuate the effect of high‐frequency noise.
Jaime A. Moreno, Arie Levant
wiley   +1 more source