# Spring 2016 Colloquia

# Upcoming Events › STOR Colloquium

## September 2016

### STOR Colloquium: Bin Hu, University of North Carolina at Chapel Hill

Bin Hu University of North Carolina at Chapel Hill, Kenan-Flagler Business School Is Reshoring Better than Offshoring? The Effect of Offshore Supply Dependence In this paper we investigate the effect of offshore supply dependence (OSD) on offshoring-reshoring profit comparisons. We find that OSD hampers a reshoring manufacturer's responsiveness to demand information updates and may significantly affect offshoring-reshoring comparisons, such that reshoring may yield lower profits than offshoring in many cases, including when offshoring has no baseline-cost advantage. We then show…

Find out more »## October 2016

### STOR colloquium: Nelson Antunes, CEMAT/University of Lisbon

Nelson Antunes CEMAT/University of Lisbon and University of Algarve Sampling Internet traffic: estimation of flow distributions In this talk, the focus is on recovering the flow (sequence of packets sharing common attributes) size and duration distributions from sampled Internet traffic using a number of previously introduced packet sampling algorithms. Assuming a basic probabilistic flow model, the distribution of flow durations is expressed in terms of the distributions of flow sizes and flow IATs (interarrival times between packets). The available estimation…

Find out more »### STOR colloquium: Joe Guinness, North Carolina State University

Joe Guinness North Carolina State University Permutation methods for sharpening Gaussian process approximations Vecchia's approximate likelihood for Gaussian process parameters depends on how the observations are ordered, which can be viewed as a deficiency because the exact likelihood is permutation-invariant. I take the alternative standpoint that the ordering of the observations is an aspect that can be tuned to sharpen the approximations. I show that advantageously chosen orderings of the observations can drastically improve the approximations. In addition to…

Find out more »### STOR colloquium: Dirk Lorenz, Braunschweig Technical University

Dirk Lorenz Braunschweig Technical University Probabilistic Image Models and Extensions of the Perona-Malik Filter The Perona-Malik model has been very successful at restoring images from noisy input. In this paper, we show how the Perona-Malik model can be reinterpreted and extended using the language of Gaussian scale mixtures. Specifically, we show how the expectation-maximization EM algorithm applied to Gaussian scale mixtures leads to the lagged-diffusivity algorithm for computing stationary points of the Perona-Malik diffusion equations. Moreover, we show how mean…

Find out more »### STOR colloquium: Seyed Emadi, University of North Carolina at Chapel Hill

Impact of Delay Announcements in Call Centers: An Empirical Approach We undertake an empirical study of the impact of delay announcements on callers' abandonment behavior and the performance of a call center with two priority classes. A Cox regression analysis reveals that in this call center, callers' abandonment behavior is affected by the announcement messages heard. To account for this, we formulate a structural estimation model of callers' (endogenous) abandonment decisions. In this model, callers are forward-looking utility maximizers…

Find out more »## November 2016

### STOR colloquium: Ivo Adan, Eindhoven University of Technology

Ivo Adan Technical University of Eindhoven and EURANDOM The Netherlands A rate balance principle We introduce a rate balance principle for general (not necessarily Markovian) stochastic processes, with special attention to birth-death like processes. This principle appears to be useful in deriving well-known, as well as new results for various queueing systems. Refreshments will be served at 3:00pm in the 3rd floor lounge of Hanes Hall

Find out more »### STOR colloquium: CANCELLED

This colloquium has been cancelled. We apologize for any inconvenience. STOR colloquium: Vanja Dukic, University of Colorado-Boulder

Find out more »### STOR colloquium: Stephen Becker, University of Colorado-Boulder

Stephen Becker University of Colorado Boulder Efficient robust PCA algorithms for the GPU We introduce the matrix completion problem and the similar robust PCA (RPCA) problem and discuss their relation to compressed sensing and some of their applications to collaborative filtering, background detection in videos, and neuroscience. We cover some standard algorithms to solve these problems, including proximal gradient descent, Frank-Wolfe/conditional-gradient, and Burer-Monteiro splitting. A natural idea to speed up the algorithms is to run them on the GPU…

Find out more »## December 2016

### STOR colloquium: Elaine McVey, TransLoc/Insightus

Title: Commuting, voting, and the off-label use of data Abstract: The modern practice of data science often involves approaching datasets differently than in traditional statistics. Two analyses will be presented, both of which use combinations of public datasets in expected and "off-label" ways. One addresses the need to simulate realistic commuting patterns, and the other evaluates the effects of North Carolina voting site decisions. In the process of telling the stories of these two data science projects, we'll have…

Find out more »## January 2017

### STOR Colloquium: Santiago Balseiro, Duke University

Santiago Balseiro Duke University Dynamic Mechanisms with Martingale Utilities We study the dynamic mechanism design problem of a seller who repeatedly sells independent items to a buyer with private values. In this setting, the seller could potentially extract the entire buyer surplus by running efficient auctions and charging an upfront participation fee at the beginning of the horizon. In some markets, such as internet advertising, participation fees are not practical since buyers expect to inspect items before purchasing them. This…

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