240 research outputs found
Discussant\u27s response to Using and evaluating audit decision aids
https://egrove.olemiss.edu/dl_proceedings/1034/thumbnail.jp
Acme Financial Statement Insurance Company Inc.: A case study
https://egrove.olemiss.edu/dl_proceedings/1056/thumbnail.jp
Assertion based approach to auditing
https://egrove.olemiss.edu/dl_proceedings/1174/thumbnail.jp
Boundary terms and their Hamiltonian dynamics
It is described how the standard Poisson bracket formulas should be modified
in order to incorporate integrals of divergences into the Hamiltonian formalism
and why this is necessary. Examples from Einstein gravity and Yang-Mills gauge
field theory are given.Comment: Talk at 29th Ahrenshoop Symposium in Buckow 1995, 6 pages,
espcrc2.sty, twoside.sty, fleqn.sty, amssymb.sty, no figure
Variational Principles for Natural Divergence-free Tensors in Metric Field Theories
Let be a system of differential equations for the
components of a metric tensor on . Suppose that transforms
tensorially under the action of the diffeomorphism group on metrics and that
the covariant divergence of vanishes. We then prove that is
the Euler-Lagrange expression some Lagrangian density provided that is
of third order. Our result extends the classical works of Cartan, Weyl,
Vermeil, Lovelock, and Takens on identifying field equations for the metric
tensor with the symmetries and conservation laws of the Einstein equations
Machine Learning based Extraction of Boundary Conditions from Doppler Echo Images for Patient Specific Coarctation of the Aorta: Computational Fluid Dynamics Study
Purpose- Coarctation of the Aorta (CoA) patient-specific computational fluid
dynamics (CFD) studies in resource constrained settings are limited by the
available imaging modalities for geometry and velocity data acquisition.
Doppler echocardiography has been seen as a suitable velocity acquisition
modality due to its higher availability and safety. This study aimed to
investigate the application of classical machine learning (ML) methods to
create an adequate and robust approach for obtaining boundary conditions (BCs)
from Doppler Echocardiography images, for haemodynamic modeling using CFD.
Methods- Our proposed approach combines ML and CFD to model haemodynamic flow
within the region of interest. With the key feature of the approach being the
use of ML models to calibrate the inlet and outlet boundary conditions (BCs) of
the CFD model. The key input variable for the ML model was the patients heart
rate as this was the parameter that varied in time across the measured vessels
within the study. ANSYS Fluent was used for the CFD component of the study
whilst the scikit-learn python library was used for the ML component.
Results- We validated our approach against a real clinical case of severe CoA
before intervention. The maximum coarctation velocity of our simulations were
compared to the measured maximum coarctation velocity obtained from the patient
whose geometry is used within the study. Of the 5 ML models used to obtain BCs
the top model was within 5\% of the measured maximum coarctation velocity.
Conclusion- The framework demonstrated that it was capable of taking
variations of the patients heart rate between measurements into account. Thus,
enabling the calculation of BCs that were physiologically realistic when the
heart rate was scaled across each vessel whilst providing a reasonably accurate
solution.Comment: Article to be submitted to Springer Nature Cardiovascular Engineering
and Technology Journa
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