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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://people.math.wisc.edu/~lzepeda/ Leonardo Zepeda-Núñez], [http://www.math.wisc.edu/~spagnolie/ Saverio Spagnolie] and [http://www.math.wisc.edu/~jeanluc Jean-Luc Thiffeault]
*'''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+join@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 2021  ==
== '''Fall 2025''' ==
 
{| cellpadding="8"
{| cellpadding="8"
!align="left" | date
! align="left" |Date
!align="left" | virtual/in-person
! align="left" |Speaker
!align="left" | speaker
! align="left" |Title
!align="left" | title
! align="left" |Host(s)
!align="left" | host(s)
|-
|-
| Sept 10
|Sep 19*
| Virtual
|[https://www.anl.gov/profile/zichao-di Zichao (Wendy) Di] (Argonne National Laboratory)
|[https://www.math.tamu.edu/~jhu/ Jiuhua Hu] (Texas A&M / UW)
|[[#Di|Multimodal Inverse Problems and Multilevel Optimization for X-ray Imaging Science]]
|''[[Applied/ACMS/absF21#Jiuhua Hu (Texas A&M / UW)|Wavelet-based Edge Multiscale Parareal Algorithm for Parabolic Equations with Heterogeneous Coefficients]]''
|Rycroft/Li
|Chen and Stechmann
|-
|-
| Sept 17
|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
|-
|Oct 3
|
|
|[https://math.berkeley.edu/~difang/ Di Fang] (Berkeley)
|''[[Applied/ACMS/absF21#Di Fang (Berkeley)|Time-dependent unbounded Hamiltonian simulation with vector norm scaling]]''
|Li
|-
| Sept 24
|
|
|[https://www.pnnl.gov/people/lai-yung-ruby-leung/ Ruby Leung] (PNNL)
|''[[Applied/ACMS/absF21#Ruby Leung  (PNNL)|TBA]]''
|Chen and Stechmann
|-
| Oct 1
| Virtual
|[https://gauss.math.yale.edu/~ya248/ Yariv Aizenbud] (Yale)
|''[[Applied/ACMS/absF21#Yariv Aizenbud (Yale)|TBA]]''
|Saverio, Shamgar
|-
| Oct 8
|
|
|[https://mathematics.stanford.edu/people/yuhua-zhu Yuhua Zhu] (Stanford)
|''[[Applied/ACMS/absF21#Yuhua Zhu (Stanford)|TBA]]''
|Zepeda-Núñez
|-
|-
| '''Oct 8, 4-5pm'''
|Oct 10*
|Virtual
|[https://www.alexandriavolkening.com Alexandria Volkening] (Purdue)
|[https://www.maths.ox.ac.uk/people/jon.chapman Jon Chapman] (Oxford)
|TBD
|'''Wasow Lecture''': ''[https://hilbert.math.wisc.edu/wiki/index.php/Colloquia#Fall_2021 Asymptotics beyond all orders: the devil's invention?]''
|Rycroft
|Jean-Luc
|-
|-
| Oct 15
|Oct 17*
|
|[https://www.nickderr.me/ Nick Derr] (UW)
|TBA
|TBD
|TBA
|Spagnolie
|
|-
|-
| Oct 22
|Oct 24
| Virtual
|[https://cims.nyu.edu/~oneil/ Mike O'Neil] (Courant)
||[https://www.rjh.io Russell Hewett] (Virginia Tech)
|TBD
|''[[Applied/ACMS/absF21#Russell Hewett (Virginia Tech)|TBA]]''
|Spagnolie
|Zepeda-Núñez
|
|-
|-
| Oct 29
|Oct 31
|
|[https://people.math.wisc.edu/~hhong78/ Hyukpyo Hong] (UW)
|TBA
|TBD
|TBA
|Spagnolie
|
|-
|-
| Nov 5
|Nov 7*
|Virtual
|[https://thales.mit.edu/bush/ John Bush] (MIT)
|[https://people.maths.ox.ac.uk/vella/ Dominic Vella] (Oxford)
|TBD
|''[[Applied/ACMS/absF21#Dominic Vella (Oxford)|TBA]]''
|Spagnolie
|Saverio
|-
|-
| Nov 12
|Nov 14
|Virtual
|[https://sites.google.com/andrew.cmu.edu/yukunyue/home Yukun Yue] (UW)
|[https://www.mfarazmand.com/ Mohammad Farazmand] (NCSU)
|TBD
|''[[Applied/ACMS/absF21#Mohammad Farazmand (NCSU)|TBA]]''
|Spagnolie
|Chen
|
|-
|-
| Nov 19
|Nov 21*
|
|[https://jesnial.github.io/ Jessie Levillain] (CNES/INSA Toulouse)
|TBA
|TBD
|''[[Applied/ACMS/absF21#|TBA]]''
|Ohm
|
|-
|-
| Nov 26
|Nov 28
|
|Thanksgiving
|Thanksgiving
|
|
|
|
|-
|-
| Dec 3
|Dec 5
|Virtual
|[https://mesomod.weebly.com/ Jiamian Hu] (UW)
|[https://scholar.google.com/citations?user=LlBckhUAAAAJ&hl=en Aseel Farhat] (Florida State University)
|TBD
|''[[Applied/ACMS/absF21#Aseel Farhat (Florida State University)|TBA]]''
|Chen
|Smith
|-
|-
| Dec 10
|Dec 12
|
|[https://sites.google.com/a/brandeis.edu/tfai/home Thomas Fai] (Brandeis)
|TBA
|TBD
|''[[Applied/ACMS/absF21#|TBA]]''
|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.]''


== Future semesters ==
==Abstract==


*[[Applied/ACMS/Spring2022|Spring 2022]]
<div id="Di">
'''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.
 
<div id="Behnoudfar">
'''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 ==
== Archived semesters ==


*[[Applied/ACMS/Spring2025|Spring 2025]]
*[[Applied/ACMS/Fall2024|Fall 2024]]
*[[Applied/ACMS/Spring2024|Spring 2024]]
*[[Applied/ACMS/Fall2023|Fall 2023]]
*[[Applied/ACMS/Spring2023|Spring 2023]]
*[[Applied/ACMS/Fall2022|Fall 2022]]
*[[Applied/ACMS/Spring2022|Spring 2022]]
*[[Applied/ACMS/Fall2021|Fall 2021]]
*[[Applied/ACMS/Spring2021|Spring 2021]]
*[[Applied/ACMS/Spring2021|Spring 2021]]
*[[Applied/ACMS/Fall2020|Fall 2020]]
*[[Applied/ACMS/Fall2020|Fall 2020]]

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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