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STEM Graduate Student Summer Colloquium Series

Monday, June 10, 2013 at 4:00pm to 5:00pm

Clark Hall, 700
Central Campus

This is a weekly colloquium series featuring Cornell graduate students in STEM fields giving short talks about their research.  The speakers this week are:

Benjamin Reinhardt, Mechanical and Aerospace Engineering, "How to Build a Tractor Beam"

abstract: In space, contact-based manipulation bears numerous risks for both the chaser and target spacecraft. Magnetic eddy currents have demonstrated the ability to produce non-contacting forces that could be used in a contactless actuator. This talk will outline the motivations for the development of such an actuator and the experimental characterization experiments that will lead to the design and demonstration of an EC actuator.

Yang Yuan, Computer Science, "A General Framework for Combinatorial Multi-Armed Bandit Problem"

abstract: Multi-armed bandit (MAB) is a good model for decision-making based on previous exploration (e.g., creating a list of the best restaurants in Ithaca). The classical version of MAB is formulated as a system of m arms (or machines, or restaurants), each having an unknown distribution of the reward with an unknown mean. The task is to choose and play one arm in each round so that the difference between the total expected reward and the reward of the optimal arm (which is defined as regret in literature) is minimized. In many real-world applications, the setting has a combinatorial nature (CMAB). Instead of playing one arm, the player can play a set of arms in each round. Using classical MAB algorithm, there will be exponentially many arms due to the combinatorial explosion. Under reasonable assumptions, we propose a CUCB algorithm that achieves O(log n) regret for CMAB. Our regret analysis is tight in the sense that it matches the bound for classical MAB problem up to a constant factor, and also improves the regret bound in a recent paper. We apply the CMAB framework to two new applications.

Veronica Pillar, Physics, "Diffuse X-Ray Scattering in Protein Crystals"

abstract: X-ray crystallography is a well-established and powerful technique for determining the atomic structure of proteins. Bragg peaks, or small bright spots, in an X-ray diffraction image reveal the static molecular structure of the protein and are usually the focus of a researcher's attention. However, the X-ray images of many proteins contain additional diffuse, anisotropic features that reveal the dynamic fluctuations of the protein, which are critical to understanding how a protein functions. Though it has long been known that analysis of diffuse X-ray scattering can reveal the amplitudes and directions of molecular fluctuations, nobody has yet extracted such dynamical information from diffuse x-ray data because collecting a usable diffuse scattering signal is extremely technically challenging. In this talk, I will give an overview of how to obtain dynamical information from diffuse X-ray scattering and discuss the recent technological advances that finally enable us to do the relevant experiments.

Please join us at 3:45 for refreshments.

More information:
The Physics Graduate Society is sponsoring eleven weekly colloquia, beginning June 10.  These talks are intended to be given by graduate students, for graduate students. The goal is to provide a unique, interdisciplinary environment for grads in all science and engineering fields to talk about their research and get a glimpse into the work of their peers.  Talks are around 15 minutes each.  If you would like to give a talk please contact Jennifer Chu (jyc72@cornell.edu). The colloquium series is funded by the Physics Department and the GPSAFC and is open to the graduate community.

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