# Projects

I have more ideas than time, and am happy to share! If you are interested in these projects, email me and we'll talk about it. If you have a project idea of your own, we can talk about that, too.

### Learning to Cluster

networks

Algorithms for community detection (aka graph clustering) seek strongly-connected subgraphs inside a larger graph. While this problem is often posed in terms of a fixed network, possibly with edge weights, we often construct the network (and weights) from much richer relational information. In this project, we consider a semi-supervised approach in which edge weights can be computed as a parametric function of edge information, and the appropriate parameters chosen based on training data indicating pairs that should (or should not) be clustered together.

You should have a course in linear algebra to tackle this project. A course in ML or networks may be helpful, but is probably not required.

### BTG: TNG

rbf tools statistics

The Bayesian Transformed Gaussian method is a Bayesian method for prediction in spatio-temporal random fields modeled as an underlying Gaussian process composed with a parametric nonlinearity. I wrote a fast (for the time) implementation of the BTG method as an undergraduate project in 1997, but our tools (both in terms of algorithms and software) have advanced significantly sinice then. For this project, we propose to combine the original BTG approach with recent work on fast linear algebra in order to scale the method to larger data sets, with a particular emphasis on one-dimensional data sets (time series analysis).

You should ideally have a course in numerical computing and some mathematical maturity to take on this project.

### Continuation Methods for Optimization on Surrogates

rbf tools

Surrogate methods for global optimization of expensive functions
alternately sample the expensive function, update a model
(a *surrogate* to the expensive function), and use the model to
determine where to sample next. This last step frequently
involves an inner global optimization problem that may be somewhat
expensive in its own right. In this project, we propose to use a
parameter continuation approach to solve this global optimization
on the surrogate through a sequence of optimizations on smoother
and simpler surrogates.

You should ideally have a course in numerical computing to take on this project.

### Preconditioning Radial Basis Functions with Clustered Centers

rbf

Radial basis function interpolation is a standard method of interpolating data in more than one space dimension. It has many attractive features, but the problem can become unstable when posed in the normal basis, particularly for very smooth basis functions or when the basis function centers are clustered. Recently-developed methods address the former case, but the latter is more of a concern when RBF interpolants are used for optimization, as is the case in some of my projects. I have an idea for a formally equivalent method that gets around this stability issue by a preconditioning strategy, and would like help implementing it.

You should have a course in numerical computing and some mathematical maturity to take on this project.

### JuliaFEM

physics tools

The Finite Element Method (FEM) is a standard algorithm for the solution of certain partial differential equations, and is particularly popular in mechanical engineering applications. In this project, we will implement a literate finite element code for simple problems in the Julia programming language.

You should ideally have a course in numerical computing to take on this project.

### Resonances in Quantum Graphs

physics eigen

A quantum graph is a graph with differential equations on the edges and compatibility conditions at the nodes. I am interested in the case of infinite quantum graphs, where a local irregular region (a scatterer) is surrounded by a regular lattice extending off to infinity. I want to build a tool that will compute the spectral properties of such an object – bound states and resonance poles – given a description of the far-field lattice structure and the local irregular region.

You should have a course in differential equations and a course in linear algebra to tackle this project, and ideally a course in analysis and a course in numerics. But if you don’t have these courses and think the project sounds fun anyhow, do come talk to me!

### Evans Functions and Nonlinear Eigenvalue Problems

physics eigen

The Evans function is a Wronskian-type construction that plays a role similar to the characteristic polynomial in the unbounded-domain spectral problems that arise in the analysis of 1D solitary wave stability. This construction has been used computationally to good effect for some problems; however, some preliminary results (and analogy to more conventional eigenvalue problems) suggests that this should be less numerically stable than an alternate method based on a nonlinear eigenvalue computation. I have coded variants of this before, and now have some nice theory to back up my favored algorithm. But I would love to have help in doing a systematic comparison between my favored algorithm and methods based on the Evans function. Ideally, I would also love to have a numerical error analysis of both methods, too.

You should have a course in differential equations and a course in linear algebra to tackle this project, and ideally a course in analysis and a course in numerics.

### Model Reduction of Buckling Lattices

physics

Three-dimensional printing lets us make elaborately microstructured materials, but our understanding of how to model these microstructures is still young. The mechanics of microtruss structures can be analyzed by mostly-standard methods when the strains are small and the truss structure is periodic; but the picture becomes more complex even at small strains when the truss is not quite periodic, and it becomes very complicated at large strains when the individual elements can buckle. I have some ideas about how to use a type of model reduction to simulate the behavior of such structures quickly, and would like to try them out – but given the background required, and given that I don’t have a code to do it at hand, I would be delighted to have some help first putting together a code to do the analysis in the simple case.

You should have a course in numerical computing to tackle this project. Prior exposure to finite element analysis or structural analysis will also be helpful.