Thursday, October 29, 2020

2020-11-03 / 16:30 ~ 17:30

학과 세미나/콜로퀴엄 - 계산수학 세미나: How do flagellated bacteria swim?: Modeling, Simulations & Analysis

by 임숙경(University of Cincinnati)

Swimming bacteria with helical flagella are self-propelled micro-swimmers in nature, and the swimming strategies of such bacteria vary depending on the number and the position of flagella on the cell body. In this talk, I will introduce some microorganisms such as E. coli, Vibrio A and P putida. The Kirchhoff rod theory is used to model the elastic helical flagella and the cell body is represented by a hollow ellipsoid that can translate and rotate as a neutrally buoyant rigid body interacting with a surrounding fluid. The hydrodynamic interaction between the fluid and the bacteria is described by the regularized version of Stokes flow. I will focus on how bacteria can swim and reorient swimming course for survival and how Mathematics can help to understand the swimming mechanism of such bacteria.

2020-11-03 / 15:00 ~ 16:30

학과 세미나/콜로퀴엄 - 정수론:

by ()

Let $E$ be an elliptic curve over the rational number field $\mathbb{Q}$. Selmer Groups and Ideal Class Groups are important and widely-studied objects in number theory. Brumer and Kramer studied relations between these two objects in their paper in 1977. They actually found an upper bound for the $2$-Selmer rank of $E$ in terms of the ideal class group of a certain cubic field extension of $\mathbb{Q}$. As an application, they determined the Mordell-Weil ranks of (most) elliptic curves of prime conductor assuming the BSD conjecture. In this talk, we will talk about a generalization of Brumer-Kramer's work to the case of elliptic curves over an arbitary number field. We will give both upper and lower bounds for the $2$-Selmer rank in terms of a (modified) ideal class group, and the bounds turn out to be sharp in many cases. This is joint work with Hwajong Yoo. (If you would like to join the seminar, please let me(Bo-Hae Im) know so that I can send you the Zoom link.)

2020-11-05 / 16:30 ~ 17:30

학과 세미나/콜로퀴엄 - 콜로퀴엄: Image Segmentation : old fashioned ways are still worthy

by 김윤호(UNIST)

In this talk, I will present a recent work in collaboration with physicists on the analysis of real time Transmission Electron Microscopy (TEM) images to understand molecular transition from crystal solid state to liquid state. Molecules are deposited on graphene with multilayer structures, which are projected and overlaid in noisy 2d TEM images. The problem is to find all the molecular centers in the extremely noisy 2d images where projected molecules are overlaid and to track the centers across the image frames. Before discussing the method that we considered, I will give a brief history in the development of image segmentation techniques with some theoretical and numerical details of old fashioned methods. Then, our method of image segmentation for molecular center identification follows.

Events for the 취소된 행사 포함