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Past Seminars in Fall 2012:

Parametric and topological inference for masked system lifetime data

Speaker: Simon Wilson, School of Computer Science and Statistics Trinity College, Dublin, Ireland

Abstract:

Commonly, reliability data consists of lifetimes (or censoring information) on all components and systems under examination. However, masked system lifetime data represents an important class of problems where the information available for statistical analysis is more limited: one only has failure times for the system as a whole, but no data on the component lifetimes directly, or even which components were failed. For example, such data can arise when system autopsy is impractical or cost prohibitive. A novel signature based data augmentation scheme is presented which enables inference for a wide class of component lifetime models for an exchangeable population of systems. It is shown that the approach can be extended to enable topological inference of the underlying system design. A number of illustrative examples are included such as the usual iid exponential case, an exchangeable case and phase-type component reliability case.

Friday, November 30th, 3:30PM-4:30PM

Location: Duques 553 (2201 G Street, NW)

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Efficient Distribution of Water Between Head-Reach and Tail-End Farms in Developing Countries

Dr Srinagesh Gavirneni, Associate Professor, Cornell University

Abstract:

The necessity of surface water for irrigation and its increasing scarcity in developing economies motivate the need for its efficient distribution. The inequity in the distribution of surface water arises due to the relative physical locations of the farms. Head-reach (primary) farms are close to the source while tail-end(secondary) farms are relatively farther. The lack of physical infrastructure implies that water allocated to secondary farms must pass through primary farms. Left to their individual incentives, primary farmers use more than their fair share of water by denying its release to secondary farmers. Such an inequitable sharing results in significantly sub-optimal productivity of the farming community as a whole. We propose decentralized, individually-rational mechanisms to achieve socially-optimal distribution of surface water for a farming community under uncertainty in rainfall, choice of multiple crops, and differing risk-bearing abilities of primary and secondary farmers. We show that the mechanisms can be efficiently computed and highlight the impact of the improved sharing of surface water. We also study the movement of the price of water with its scarcity. Ideas that can help administer the mechanisms in practice are briefly discussed.

Monday, November 12th, 1:30PM-2:30PM

Location: Duques 453 (2201 G Street, NW)

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Extropy: XColony - A Paper Game. An Exotic Tool for Intuitive Decision Making

Speaker: Dr. Sorin Alexe

Abstract:

XColony is a hierarchical modular construction game that aims to train the brain for today's careers: researcher, scientist, data analyst, or manager. Concepts like abstract thinking, structure, modular approach, duality and isomorphism are emerging from a toy, using a visual language rather than mathematical or formal notations. The game-like environment would make it easier to understand problems in computational architecture, robotics, 3D perception and combinatorial geometry. The open-end features are challenging the limits of intuition and creativity, setting up the stage for puzzle solving. This environment is used to detect structural problems together with and their solutions using non-digital computations, which could inspire a decision making process based on Monte Carlo like simulations, intuition and creativity.

Friday, November 9th, 11:00AM-12:00PM

Location: Duques 652 (2201 G Street, NW)

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Kolmogorov Stories

Speaker: Academician Asaf Hajiev, Azerbaijan National Academy of Sciences and Baku State University.

Abstract:

Asaf Hajiev is a Professor of Mathematics at Baku State University and is a Corresponding Member of the Azerbaijan National Academy of Sciences. He received his doctorate in probability theory from Moscow State University under the supervision of Yuri Belyaev with a specialization in queueing and reliability. His current interests are in probability modeling and statistical inference. He has been a visiting professor at many institutions, including UC Berkeley and Bogacizi University in Istanbul. During his student days at Moscow State University he had first hand interactions with Kolmogorov, as a teacher, a mentor, an advisor, and a friend. In this talk Asaf will relate his experiences with Kolmogorov with a slant towards the personal and the non-academic, and give us some interesting stories about Kolmogorov's modus operandus with his colleagues, students, and a bevy of scientists and mathematicians who visited him. Academician Hajiev is unusual among us. Besides his teaching and research duties he is also in public service as a Member of Parliament in Azerbaijan, representing his home district of Ganja. Science education is one among his many portfolios.

Friday, October 19th 4:00 PM - 5:00 PM

Location: Duques 651 (2201 G Street, NW)


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Extropy: A complementary dual of entropy

Speaker: Frank Lad, University of Canterbury

Abstract:

Asaf Hajiev is a Professor of Mathematics at Baku State University and is a Corresponding Member of the Azerbaijan National Academy of Sciences. He received his doctorate in probability theory from Moscow State University under the supervision of Yuri Belyaev with a specialization in queueing and reliability. His current interests are in probability modeling and statistical inference. He has been a visiting professor at many institutions, including UC Berkeley and Bogacizi University in Istanbul. During his student days at Moscow State University he had first hand interactions with Kolmogorov, as a teacher, a mentor, an advisor, and a friend. In this talk Asaf will relate his experiences with Kolmogorov with a slant towards the personal and the non-academic, and give us some interesting stories about Kolmogorov's modus operandus with his colleagues, students, and a bevy of scientists and mathematicians who visited him. Academician Hajiev is unusual among us. Besides his teaching and research duties he is also in public service as a Member of Parliament in Azerbaijan, representing his home district of Ganja. Science education is one among his many portfolios.

Thursday, October 18th 11:00 am - 12:00 noon

Location: Duques 553 (2201 G Street, NW)


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Hospitals clustering via semiparametric Bayesian models: Model based methods for assessing healthcare performance

Speaker: Francesca Ieva, Dipartimento di Matematica "F.Brioschi", Politecnico di Milano

Abstract:

A Bayesian semiparametric mixed effects models is presented for the analysis of binary survival data coming from a clinical survey on STEMI (ST segment Elevation Myocardial Infarction), where statistical units (i.e., patients) are grouped by hospital of admission. The idea is to exploit the flexibility and potential of such models for carrying out model-based clustering of the random effects in order to profile hospitals according to their effects on patient's outcome. Our focus is on the advantages of "modelbased" clustering of the hospitals provided by the semiparametric assumption on random effects and on prediction of the binary patient's outcome (in-hospital survival) in case of the strongly unbalanced share. The optimal clustering is obtained by minimising suitable loss functions which improves the capability of the model in predicting failures in presence of strongly unbalanced shares. The proposed Bayesian approach provides a new way for classifying patients by taking advantage of the posterior predictive credibility intervals of the outcome. The methods have been applied to a real dataset from the STEMI Archive, a clinical survey on patients affected by STEMI and admitted to hospitals in Regione Lombardia, whose capital is Milano.

Friday, September 21, 3:30 PM - 4:30 PM

Location: Duques 553 (2201 G Street, NW)