Centre for Mathematical Sciences - Wilberforce Road
CB3 0WA Cambridge, United Kingdom
Thursday, 05 May 2016
from 14:00 to 18:00
Schlumberger are currently recruiting for an intern this summer. Find the role here.
14:10 – Carola Schönlieb (DAMTP, University of Cambridge)
14:50 – Simon Godsill (Department of Engineering, University of Cambridge)
15:30 – Ray Goldstein (DAMTP, University of Cambridge)
16:10 – Coffee
16:30 – Richard Pinch (GCHQ)
17:10 – Nigel Peake (DAMTP, University of Cambridge)
17:50 – Thanks (SIAM Cambridge Student Chapter Committee)
Nigel Peake (DAMTP)
The aeroacoustics of the owl
Many species of owl can hunt in acoustic stealth. The question of precisely how the owl actually manages to fly so quietly has remained open. However, it has long been appreciated that owls which need to hunt silently possess two unique features, which are not found on any other bird, and indeed are not even found on owls which do not need to hunt silently (e.g. on small owls which feed on insects, or Fish owls). First, the microstructure of the feathers on the upper wing surface is exceedingly complex, with an array of hairs and barbs which form a thick canopy just above the nominal wing surface. Second, the wing trailing edge possesses a small flexible and porous fringe. Our research objective is to answer the following two questions: First, how do these two features of the owl actually work to suppress noise? And second, can we learn something form the owl which can be applied in engineering practice? The first question is exceedingly complex, and as I will describe has only been partially answered to date. However, we have made definite progress with the second question, and I will present very promising test results for an owl-inspired trailing-edge noise reduction device. The research I am going to describe is part of an ongoing theoretical and experimental program between Cambridge, Virginia Tech, Lehigh University and Florida Atlantic University.
Richard Pinch (GCHQ)
Traditional (symmetric or secret key) cryptography has historically been the province of government, diplomatic and military users with a requirement for confidentiality. Modern (asymmetric or public key) cryptography has been developed and taken up to meet the requirements of life in cyberspace. Businesses and private individuals are now using it, often unknowingly, to achieve authentication as well as confidentiality. New threats and opportunities are emerging with the advent of novel challenges, such as quantum computing, and novel requirements such as distributed data. The talk will describe how cryptography is being used today and some of the challenges for the future.
Ray Goldstein (DAMTP)
Upside Down and Inside Out: The Biomechanics of Cell Sheet Folding
Deformations of cell sheets are ubiquitous in early animal development, often arising from a complex and poorly understood interplay of cell shape changes, division, and migration. In this lecture I will describe our experimental and theoretical studies of perhaps the simplest example of cell sheet folding: the “inversion” process of the algal genus Volvox, during which spherical embryos turn themselves inside out through a process hypothesized to arise from cell shape changes alone. We use light sheet microscopy to obtain the first three-dimensional visualizations of
inversion in vivo, and develop the first theory of this process, in which cell shape changes appear as local variations of intrinsic curvature, contraction and stretching of an elastic shell. Our results support a scenario in which these active processes function in a defined spatiotemporal manner to enable inversion.
Simon Godsill (Cambridge Engineering)
Sequential inference for dynamically evolving points, groups and clusters
In this talk I will describe recent advances in methods and applications for sequential inference about dynamically evolving structures such as stochastically linked groups, networks and multiple interacting objects. The problems are posed within a Bayesian framework and inference is carried out using modern computational methods such as sequential Monte Carlo, Markov chain Monte Carlo and combinations of the two. Examples will be discussed in which we learn the dynamic structures of small groups from noisy tracking data, learn automatically the network structure of brain communications and learn behaviioural models for groups of moving animals.
Carola Schönlieb (DAMTP)
Mathematical image analysis — from mitotic cells into the woods and to medieval art works
We humans are visual creatures. An image aims to depict reality to us, but also invokes our imagination. It speaks more than a thousand words. We live in a world saturated with images and images allows us to see this world – from brain cells to distant galaxies – as never before. This wealth of images and the information they carry is overwhelming in its size and complexity. Automated image analysis methods are required to process them, find patterns and extract meaningful, essential information.
In this talk we will discuss variational models for image analysis and their connection to partial differential equations, and go all the way to the challenges of their mathematical analysis as well as the hurdles for solving these – typically non-smooth- models computationally. Images are a rich source of beautiful mathematical formalism and analysis. The associated mathematical problems we will encounter in this talk arise in functional and non-smooth analysis, the theory and numerical analysis of partial differential equations, harmonic, stochastic and statistical analysis, and optimisation. The talk is furnished with applications to the analysis of mitotic cells in cancer research, automated delineation of trees from airborne image data, and the digital restoration of frescoes, painting and illuminated manuscripts.