Applied/ACMS: Difference between revisions

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*'''When:''' Fridays at 2:25pm (except as otherwise indicated)
*'''When:''' Fridays at 2:25pm (except as otherwise indicated)
*'''Where:''' 901 Van Vleck Hall
*'''Where:''' 901 Van Vleck Hall
*'''Organizers:''' [https://math.wisc.edu/staff/fabien-maurice/ Maurice Fabien], [https://people.math.wisc.edu/~rycroft/ Chris Rycroft], and [https://www.math.wisc.edu/~spagnolie/ Saverio Spagnolie],
*'''Organizers:''' [https://www.math.wisc.edu/~spagnolie/ Saverio Spagnolie], [https://people.math.wisc.edu/~rycroft/ Chris Rycroft], and [https://sites.google.com/view/laurel-ohm-math Laurel Ohm]  
*'''To join the ACMS mailing list:''' Send mail to [mailto:acms+join@g-groups.wisc.edu acms+subscribe@g-groups.wisc.edu].
*'''To join the ACMS mailing list:''' Send mail to [mailto:acms+join@g-groups.wisc.edu acms+subscribe@g-groups.wisc.edu].


<br>   
<br>   


== '''Fall 2024''' ==
== '''Fall 2025''' ==
{| class="wikitable"
{| cellpadding="8"
|+
! align="left" |Date
!Date
! align="left" |Speaker
!Speaker
! align="left" |Title
!Title
! align="left" |Host(s)
!Host(s)
|-
|-
|Sep 13
|Sep 19*
|[https://people.math.wisc.edu/~nchen29/ Nan Chen] (UW)
|[https://www.anl.gov/profile/zichao-di Zichao (Wendy) Di] (Argonne National Laboratory)
|Uncertainty Quantification (UQ) for Beginners
|[[#Di|Multimodal Inverse Problems and Multilevel Optimization for X-ray Imaging Science]]
|Rycroft/Li
|-
|Sep 26
|[https://scholar.google.com/citations?user=Imuw5CMAAAAJ&hl=en&oi=ao Pouria Behnoudfar] (UW)
|[[#Behnoudfar|Bridging Conceptual and Operational Models: A Physics-Guided Machine Learning Framework for Enhanced Climate Simulation]]
|Spagnolie
|Spagnolie
|-
|-
|Sep 20
|Oct 3
|[https://knewhall.web.unc.edu Katie Newhall] (UNC Chapel Hill)
|
|
|Rycroft
|-
|Sep 27
|[https://ptg.ukzn.ac.za Indresan Govender] (Mintek / Univ. of KwaZulu-Natal, South Africa)
|
|
|Rycroft
|-
|Oct 4*
|[https://sse.tulane.edu/math/people/hongfei-chen Hongfei Chen] (Tulane)
|
|
|Jean-Luc
|-
|-
|Oct 11 '''Colloquium in B239 at 4:00pm'''
|Oct 10*
|[https://people.math.ethz.ch/~imikaela/ Mikaela Iacobelli] (ETH/IAS)
|[https://www.alexandriavolkening.com Alexandria Volkening] (Purdue)
|[[# TBA|  TBA  ]]
|TBD
|Li
|Rycroft
|-
|-
|Oct 18 '''Colloquium in B239 at 4:00pm'''
|Oct 17*
|[https://galton.uchicago.edu/~guillaumebal/ Guillaume Bal] (U Chicago)
|[https://www.nickderr.me/ Nick Derr] (UW)
|[[# TBA|  TBA  ]]
|TBD
| Li, Stechmann
|Spagnolie
|-
|-
|Oct 25
|Oct 24
|[https://www.cs.cornell.edu/~damle/ Anil Damle] (Cornell)
|[https://cims.nyu.edu/~oneil/ Mike O'Neil] (Courant)
|
|TBD
|Li
|Spagnolie
|-
|-
| Nov 1
|Oct 31
|[https://research-hub.nrel.gov/en/persons/michael-sprague Michael Sprague] (NREL)
|[https://people.math.wisc.edu/~hhong78/ Hyukpyo Hong] (UW)
|[[# TBA|  TBA  ]]
|TBD
|Spagnolie
|Spagnolie
|-
|-
| Nov 8
|Nov 7*
|[https://personal.math.ubc.ca/~holmescerfon/ Miranda Holmes-Cerfon] (UBC)
|[https://thales.mit.edu/bush/ John Bush] (MIT)
|
|TBD
|Stechmann
|Spagnolie
|-
|-
| Nov 15*
|Nov 14
| Yue Sun (UW–Madison)
|[https://sites.google.com/andrew.cmu.edu/yukunyue/home Yukun Yue] (UW)
|
|TBD
| Rycroft
|Spagnolie
|-
|-
| Nov 22
|Nov 21*
|[https://ibd.uchicago.edu/joinus/yenfellowship/ Ondrej Maxian] (U Chicago)
|[https://jesnial.github.io/ Jessie Levillain] (CNES/INSA Toulouse)
|[[# TBA|  TBA  ]]
|TBD
|Ohm & Spagnolie
|Ohm
|-
|-
| Nov 29*
|Nov 28
|''Thanksgiving''
|Thanksgiving
|
|
|
|
|-
|-
| Dec 6
|Dec 5
|[https://www.simonsfoundation.org/people/ido-lavi/ Ido Lavi] (Flatiron)
|[https://mesomod.weebly.com/ Jiamian Hu] (UW)
|[[# TBA|  TBA  ]]
|TBD
|Spagnolie
|Chen
|-
|-
|
|Dec 12
|[https://sites.google.com/a/brandeis.edu/tfai/home Thomas Fai] (Brandeis)
|TBD
|Rycroft
|}
|}
''[Dates marked with an asterisk are close to weekends with a home game for the [https://uwbadgers.com/sports/football/schedule UW Badgers football team]. Hotel availability around these dates is often limited if booked on short notice.]''
==Abstract==
<div id="Di">
'''Zichao (Wendy) Di (Argonne National Laboratory)'''
Title: Multimodal Inverse Problems and Multilevel Optimization for X-ray Imaging Science


Dates marked with an asterisk correspond to [https://uwbadgers.com/sports/football/schedule home football games of the UW–Madison Badgers]. On these dates it can be difficult to get a hotel room close to campus at short notice.
X-ray imaging experiments generate vast datasets that are often incomplete or ill-posed when considered in isolation. One way forward is multimodal data analysis, where complementary measurement modalities are fused to reduce ambiguity and improve reconstructions. A key question, both mathematically and practically, is how to identify which modalities to combine and how best to integrate them within an inverse problem framework.


== Abstracts ==
A second line of work focuses on the computational challenge: even for single-modality inverse problems, the resulting optimization problems are large-scale, nonlinear, and nonconvex. Here, I will discuss multilevel optimization and stochastic sampling strategies that accelerate convergence by exploiting hierarchical structure in both parameter and data spaces.
====Nan Chen (UW–Madison)====
Title: Taming Uncertainty in a Complex World: The Rise of Uncertainty Quantification -- A Tutorial for Beginners


I will provide a tutorial about uncertainty quantification (UQ) for those who have no background but are interested in learning more about this area. The talk will exploit many elementary examples, which are understandable to graduate students and senior undergraduates, to present the ideas of UQ. Topics include characterizing uncertainties using information theory, UQ in linear and nonlinear dynamical systems, UQ via data assimilation, the role of uncertainty in diagnostics, and UQ in advancing efficient modeling. The surprisingly simple examples in each topic explain why and how UQ is essential. Both Matlab and Python codes have been made available for these simple examples.
Although developed separately, these two directions point toward a common goal: building scalable, optimization-based frameworks that make the best use of diverse data to enable new discoveries in X-ray imaging science.
== Future semesters ==


*[[Applied/ACMS/Fall2024|Fall 2024]]
<div id="Behnoudfar">
'''Pouria Behnoudfar (UW Madison)'''
 
Title: Bridging Conceptual and Operational Models: A Physics-Guided Machine Learning Framework for Enhanced Climate Simulation


*[[Applied/ACMS/Spring2025|Spring 2025]]
Operational models are high-resolution and contain many crucial variables. Despite numerous successes, biases persist in most of these models, particularly in identifying extreme events and accurately reproducing statistics. However, it is challenging to directly modify these models to improve their performance. Conceptual and intermediate coupled models accurately characterize certain features of nature. Yet, these coarse-grained models contain only a subset of variables within a specific domain. By leveraging the strengths of models of varying complexities, we develop a robust physics-driven machine learning modeling framework as the next-generation climate emulator, which bridges the model hierarchy through effective latent space data assimilation. The resulting bridging model not only inherits the benefits of the operational models, including their high resolution and comprehensive set of variables, but also globally enhances the accuracy through local dynamical and statistical improvements provided by the simpler models.  Our developed latent space technique identifies the dominant nonlinear features, which facilitates effective communication between models. The machine learning representation of the bridging model significantly enhances simulation efficiency, providing high-quality datasets and advancing the quantification of uncertainty in extreme events. The framework is applied to improve the performance of CMIP6 simulations in characterizing ENSO complexity by exploiting simpler yet statistically accurate models. 


== Archived semesters ==
== Archived semesters ==


*[[Applied/ACMS/Spring2025|Spring 2025]]
*[[Applied/ACMS/Fall2024|Fall 2024]]
*[[Applied/ACMS/Spring2024|Spring 2024]]
*[[Applied/ACMS/Spring2024|Spring 2024]]
*[[Applied/ACMS/Fall2023|Fall 2023]]
*[[Applied/ACMS/Fall2023|Fall 2023]]

Latest revision as of 03:51, 9 September 2025


Applied and Computational Mathematics Seminar


Fall 2025

Date Speaker Title Host(s)
Sep 19* Zichao (Wendy) Di (Argonne National Laboratory) Multimodal Inverse Problems and Multilevel Optimization for X-ray Imaging Science Rycroft/Li
Sep 26 Pouria Behnoudfar (UW) Bridging Conceptual and Operational Models: A Physics-Guided Machine Learning Framework for Enhanced Climate Simulation Spagnolie
Oct 3
Oct 10* Alexandria Volkening (Purdue) TBD Rycroft
Oct 17* Nick Derr (UW) TBD Spagnolie
Oct 24 Mike O'Neil (Courant) TBD Spagnolie
Oct 31 Hyukpyo Hong (UW) TBD Spagnolie
Nov 7* John Bush (MIT) TBD Spagnolie
Nov 14 Yukun Yue (UW) TBD Spagnolie
Nov 21* Jessie Levillain (CNES/INSA Toulouse) TBD Ohm
Nov 28 Thanksgiving
Dec 5 Jiamian Hu (UW) TBD Chen
Dec 12 Thomas Fai (Brandeis) TBD Rycroft

[Dates marked with an asterisk are close to weekends with a home game for the UW Badgers football team. Hotel availability around these dates is often limited if booked on short notice.]

Abstract

Zichao (Wendy) Di (Argonne National Laboratory)

Title: Multimodal Inverse Problems and Multilevel Optimization for X-ray Imaging Science

X-ray imaging experiments generate vast datasets that are often incomplete or ill-posed when considered in isolation. One way forward is multimodal data analysis, where complementary measurement modalities are fused to reduce ambiguity and improve reconstructions. A key question, both mathematically and practically, is how to identify which modalities to combine and how best to integrate them within an inverse problem framework.

A second line of work focuses on the computational challenge: even for single-modality inverse problems, the resulting optimization problems are large-scale, nonlinear, and nonconvex. Here, I will discuss multilevel optimization and stochastic sampling strategies that accelerate convergence by exploiting hierarchical structure in both parameter and data spaces.

Although developed separately, these two directions point toward a common goal: building scalable, optimization-based frameworks that make the best use of diverse data to enable new discoveries in X-ray imaging science.

Pouria Behnoudfar (UW Madison)

Title: Bridging Conceptual and Operational Models: A Physics-Guided Machine Learning Framework for Enhanced Climate Simulation

Operational models are high-resolution and contain many crucial variables. Despite numerous successes, biases persist in most of these models, particularly in identifying extreme events and accurately reproducing statistics. However, it is challenging to directly modify these models to improve their performance. Conceptual and intermediate coupled models accurately characterize certain features of nature. Yet, these coarse-grained models contain only a subset of variables within a specific domain. By leveraging the strengths of models of varying complexities, we develop a robust physics-driven machine learning modeling framework as the next-generation climate emulator, which bridges the model hierarchy through effective latent space data assimilation. The resulting bridging model not only inherits the benefits of the operational models, including their high resolution and comprehensive set of variables, but also globally enhances the accuracy through local dynamical and statistical improvements provided by the simpler models.  Our developed latent space technique identifies the dominant nonlinear features, which facilitates effective communication between models. The machine learning representation of the bridging model significantly enhances simulation efficiency, providing high-quality datasets and advancing the quantification of uncertainty in extreme events. The framework is applied to improve the performance of CMIP6 simulations in characterizing ENSO complexity by exploiting simpler yet statistically accurate models. 

Archived semesters


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