## Research Seminars in the School of Mathematical Sciences

The School of Mathematical Sciences host regular research seminars delivered by internal and external researchers on topics across mathematical sciences. Seminars take place on the Kevin Street campus and are open to all.

## Seminar 27/4/18: On mathematical models for microelectromechanical systems

On mathematical models for microelectromechanical systems

Prof Joachim Escher

Leibniz University Hannover

Friday 27 April 2018

1pm, Blue Room, 4th floor, Main Building, DIT Kevin Street

Abstract:

A review of some recent results on mathematical models for microelectromechanical systems with general permittivity profile will be presented. These models consist of a quasilinear parabolic evolution problem for the displacement of an elastic membrane coupled with an elliptic moving boundary problem that determines the electrostatic potential in the region occupied by the elastic membrane and a rigid ground plate.

Local well-posedness, global existence, the occurrence of finite-time singularities, and convergence of solutions to those of the so-called small-aspect ratio model, respectively, are addressed. Furthermore, a topic is addressed that is of note not till non-constant permittivity profiles are taken into account — the direction of the membrane's deflection or, in mathematical parlance, the sign of the solution to the evolution problem.

## Seminar 9/3/18: A numerical study of in-plane wave propagation in mooring cables

A numerical study of in-plane wave propagation in mooring cables

Biswajit Basu

Trinity College Dublin

Friday 9 March 2018

2.15pm, Blue Room, 4th floor, Main Building, DIT Kevin Street

Abstract:

This talk focuses on wave propagation in mooring cables. For cables in ocean applications, there are three sources of nonlinearities affecting the cable response: the hydrodynamic effect, geometric stiffening effect, and seabed effect. To this end, numerical solutions are pursued, where the partial differential equations describing the dynamics of the submerged mooring cable are formulated in Lagrangian coordinates and solved using space-time finite difference methods. Specifically, a two-dimensional cable is considered and the wave propagation is studied when the cable is subjected to harmonic excitation at the fairlead. The wave propagation with seabed effects is also compared to that in a fully suspended cable. The nonlinear mechanisms governing the propagation of waves are discussed based on the numerical results. Further, some results on hydrodynamic analysis using Lagrangian based smooth particle hydrodynamics (SPH) are presented. Comparisons are made with some recent results and the impact of nonlinear hydrodynamics on offshore applications is emphasized.

## Seminar 27/10/17: Theoreticholesterol

Theoreticholesterol

Steven Watterson

University of Ulster

Friday 27 October 2017

1pm, Blue Room, 4th floor, Main Building, DIT Kevin Street

Abstract:

Cardiovascular disease is the leading cause of death globally. The majority of cardiovascular disease can be attributed to atherosclerosis, a chronic condition akin to swelling in the artery wall that impedes blood flow either directly or by thrombosis after rupture. Atherosclerosis develops as a result of the interplay between blood flow dynamics, innate immune responses and cholesterol metabolism and many of the pharmaceutical industries blockbuster drugs of the last twenty years have targeted cholesterol metabolism, making this a field of significant commercial as well as clinical interest. Despite this, relatively little quantitative work has been done modelling cholesterol metabolism, atherosclerosis and their physiological regulation. I will describe work undertaken recently at the Northern Ireland Centre for Stratified Medicine modelling cholesterol metabolism and atherosclerosis. I will describe how we can learn from nature to better improve preventative treatments for cardiovascular disease and how we should be able to use computational approaches to create treatments that are tailored to an individual's genetics in the future.

## Seminar 8/12/17: Trends in undergraduate students' basic mathematical skills on entry to third level education over the past two decades

Trends in undergraduate students' basic mathematical skills on entry to third level education over the past two decades

Fiona Faulkner

Dublin Institute of Technology

Friday 8 December 2017

1pm, KE3-008, 3rd floor, Main Building, DIT Kevin Street

Abstract:

In 1997 diagnostic testing was first implemented in the University of Limerick due to service mathematics lecturers' anxiety regarding Science and Technology students' mathematical competency levels. The test is a tool to identify those who are struggling with the basic mathematical concepts needed for third level education. An examination of over 8,000 students involved in the diagnostic testing in UL between 1998 and 2008 highlighted a steady decline in students' basic mathematical competency levels on entry to third level education. This data was also used to explore the role of prior mathematics achievement in predicting performance in third level mathematics (Faulkner et al 2010). Later examinations of the diagnostic test data, between 2003 and 2013, found that the proportion of students tested that are predicted to be at risk of failing their service mathematics end-of-semester examinations had continued to increased. Furthermore, when students' performance in secondary level mathematics was controlled, it was determined that the performance of beginning undergraduates in 2013 was statistically significantly below that of the performance of the beginning undergraduates recorded 10 years previously (Treacy and Faulkner 2015). This research also examines the declining standard in basic mathematics skills in light of curriculum changes in second level education (Treacy, Faulkner and Prendergast 2016).

## Seminar 6/10/17: Formation and Growth of the first Black Holes

Formation and Growth of the first Black Holes

John Regan

Dublin City University

Friday 6 October 2017

1pm, Blue Room, 4th floor, Main Building, DIT Kevin Street

Abstract:

The discovery of supermassive black holes (SMBHs) at high-z (z ≥ 6) is a direct challenge to our understanding of the formation of the structure at small scales in the Universe (first stars, galaxies and black holes). The first stars are expected to form in mini-haloes where a combination of gravity and gas chemistry result in the first runaway collapse. These first stars may be massive with characteristic masses in the region of 50 Msolar. However, the observations of SMBHs with masses of 1 billion solar masses shortly after when we expect the first stars to form is perplexing.

I will discuss possible solutions to this problem. In particular I will discuss forming unusually massive stars in the early Universe which could explain the high-z SMBHs and also importantly the growth requirements subsequently (from either PopIII stars or supermassive stars) – which will likely require periods of super-critical growth.

### More Articles...

- Seminar 31/03/17: Geometric aspects of fluid models with vorticity
- Seminar 31/03/17: Breeding new methods for finding first order saddle points
- Seminar 31/03/17: Integrable nonlocal multi-component equations with PT and CPT symmetries
- Seminar 31/03/17: Modelling of the stratified flow circulation in Greenland fjords