The Optimization/Waves seminar is now part of the Imaging and Sensing track course credit !

## Fall 2020

For the Fall 2020 semester, seminars will take place on **Thursdays** from **10:30am to 11:30am**, with alternate topics, **via Zoom**.

Contact Prof. Petra (npetra@ucmerced.edu) for the Optimization, Prof. Carvalho (ccarvalho3@ucmerced.edu) for the Waves.

## Optimization Seminar

## Waves seminar

## Spring 2020

### January 30: Optimization

Speakers: Jacky Alvarez, Roummel Marcia

### February 6: Waves

Dr. Nicki Boardman, 2pm-3pm in Granite Pass 120-125

### February 13: Optimization

Teaching demo at 3pm

### February 20: Waves

Speaker: Matthias Bussonnier

Title: How to use Python: an overview

### February 27: Optimization

Speakers: Toshi

### March 5: Waves

Speaker: Camille Carvalho

Title: Subtraction tecnhiques for the close evaluation of layer potentials

Abstract: Close evaluation of layer potentials reffer to large errors occured at evaluation points near (but not on) the boundary. This is due to peaked behaviors of the integrands near the boundary. There exist subtraction techniques to smooth out the peaked behavior for Laplace's problems. In this talk we present how to extend those ideas to waves problems.

Speaker: Arnold D. Kim

Title: Optical imaging of colloids

Abstract: A colloidal suspension is a collection of nanometer to micron scaled particles in a fluid used to study self-assembly. A key to studying colloids lies in imaging these particles accurately and efficiently within a standard microscope setup. In this talk, we introduce this imaging problem, propose an imaging method that uses space, angle or wavelength diversity at the source to compensate for the intensity-only measurements, and demonstrate its effectiveness through numerical simulations.

### March 12: Optimization

Cancelled

### March 19: Waves

Cancelled

### April 2: Optimization

Cancelled

### April 9: Waves (Virtual)

Speaker: Lori Lewis

Title: Asymptotic approximations for boundary integral equations with regions of high curvature

### April 16 : Optimization

Cancelled

### April 23: Waves (Virtual)

Speaker: Ben Latham

Title: Introduction to Surface Plasmons on a Planar Interface

Speaker: Zoïs Moitier

Title: Where are the plasmons: asymptotics for the cavity case

### April 30 : Optimization

Cancelled

## Optimization Seminars

## Waves Seminars

## Fall 2019

For the Fall 2019 semester, seminars will take place on **Thursdays** in **ACS 362B** from **10am to 11am**, with alternate topics.

#### September 19th: Optimization

Alex Ho (grad student, Applied Mathematics, University of California, Merced)

Title Talk: TBA

Ki-Tae Kim (postdoc, Applied Mathematics, University of California, Merced)

Title Talk: TBA

#### September 26th: Waves

Arnold D. Kim, (Full Professor, Applied Mathematics, University of California, Merced)

Title Talk: Research projects about the multiple scattering of light

Abstract: In this talk I give an overview of my research projects about the multiple scattering of light. Then I discuss two specific projects in detail. First, I discuss modeling nano cloaking structures in collaboration with Prof. Ghosh's lab. Then I discuss some recent work in the diffuse optical imaging of tissues using spatially modulated light.

#### October 3rd: Optimization

Noemi Petra (Assistant Professor, Applied Mathematics, University of California, Merced)

#### Title Talk: Introduction to hIPPYlib

#### October 10th: Waves

Chrysoula Tsogka, (Full Professor, Applied Mathematics, University of California, Merced)

Title Talk: Imaging in waveguides

Boaz Ilan, (Full Professor, Applied Mathematics, University of California, Merced)

Title Talk: Nonlinear eigenvalue problems in nonlinear waves

#### October 17th: Optimization

Omar DeGuchy (grad student, Applied Mathematics, University of California, Merced)

Title Talk: TBA

#### October 24th: Waves

Jay Sharping, (Professor, Physics, University of California, Merced)

Title Talk: Tunable SRF cavities for 3D optomechanics

Abstract: Quantum mechanics is real! If you took a physics class on Quantum Mechanics, they (should have) told you to consider a mass on a spring and (should have) showed that the energy spectrum for that thing is quantized. Over the past 10 years or so we have finally been able to do just that in the lab. One of my research goals is to combine low loss oscillators such as optical or microwave cavities with mechanical oscillators in hopes of one day recognizing quantum behavior in large oscillators. In this talk I will (hopefully) get you excited about the prospects of this effort and then share designs, simulations and experiments with high-Q 3-dimensional cavities. I’ll give you a status report on my group’s journey to coupling these cavities to mechanical oscillators.

#### October 31st: Optimization

Amalia Kokkinaki (PhD, Assistant Professor, Environmental Science, Environmental Engineering, University of San Francisco)

Title Talk: Large-scale inverse problems and data assimilation in hydrogeology: developments and challenges

Abstract: In hydrogeology, inverse problems and data assimilation are used to estimate the properties of the subsurface using noisy, indirect measurements, as well as to track fluid movement through the soil or rock matrix. Applications include characterization for improved site cleanup, water resources management, and identification of contaminant sources. The corresponding inverse problems range from weakly nonlinear, such as pressure dissipation in mildly heterogeneous formations, to strongly nonlinear, such as multiphase flow in heterogeneous formations. A variety of techniques have been used over the last two decades to tackle such inverse problems, including deterministic/regularization based techniques to stochastic Bayesian estimation techniques. In this talk, a review of these methods will be presented, focusing on methods that are applicable for large scale systems with thousands to millions of unknowns, and specifically addressing the tradeoff between computational efficiency and estimation accuracy. The challenges associated with strongly non-linear problems, and Kalman Filtering variants that can address such problems will be discussed. The talk will close with an overview of current research needs for inverse modeling methods in the field of hydrogeology.

#### November 7th: Waves

Zoïs Moitier, (Postdoc, Applied Mathematics, University of California, Merced)

Title : Asymptotic expansions of Whispering Gallery Modes optical micro-cavities

Abstract: In this talk we study the resonance frequencies of bidimensional optical cavities. More specifically, we are interested in whispering-gallery modes (modes localized along the cavity boundary with a large number of oscillations). The first part deals with the numerical computation of resonances by the finite element method using perfectly matched layers, and with a sensibility analysis in the three following situations: an unidimensional problem, a reduction of the rotationally invariant bidimensional case, and the general case. The second part focuses on the construction of asymptotic expansions of whispering-gallery modes as the number of oscillations along of boundary goes to infinity. We start by considering the case of a rotationally invariant problem for which the number of oscillations can be interpreted as a semiclassical parameter by means of an angular Fourier transform. Next, for the general case, the construction uses a phase-amplitude ansatz of WKB type which leads to a generalized Schrödinger operator. Finally, the numerically computed resonances obtained in the first part are compared to the asymptotic expansions made explicit by the use of a computer algebra software.

#### November 14th: Optimization

Omar DeGuchy (grad student, Applied Mathematics, University of California, Merced)

Title Talk: Deep Learning with Pytorch (Part II)

#### November 21st: Waves

Cory MacCullough, (graduate student, Applied Mathematics, University of California, Merced)

Imran Khan, (graduate student, Physics, University of California, Merced)

December 5th: Optimization

Tucker Hartland, (grad student, Applied Mathematics, University of California, Merced)

Title Talk: Hierarchical Off-Diagonal Low-Rank Approximation forHessians in Inverse Problems

Radoslav Vuchkov (grad student, Applied Mathematics, University of California, Merced)

Title Talk: Quasi-Newton Methods for Infinite-Dimensional Inverse Problems Governed by PDEs

#### December 12th: end of the semester seminar

We'll conclude our seminar series with light refreshments, and discuss next semester's agenda.