This talk investigates the role of feedback in a network of amplifiers. We start by revisiting the theory of the individual feedback amplifier. Then, taking inspiration from neuronal behaviors, we present a simple architecture that makes the network amplification zoomable, allowing for a versatile modulation of the resolution of the network ampl...

Creator:

Sepulchre, Rodolphe (University of Cambridge)

Created:

2015-09-30

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

In this talk, I will discuss some issues and recent results related to the viscous boundary layer theory. In particular, I will present a global existence result on classical soluition to the 2-dimensional unsteady Prandtl's boundary system; some convergence results on viscous solutions when the viscosity becomes small. Both non-slip and Navier-...

Creator:

Xin, Zhouping (Chinese University of Hong Kong)

Created:

2010-02-24

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

For a zero-sum stochastic game which does not satisfy the Isaacs condition, we provide a value function representation for an Isaacs-type equation whose Hamiltonian lies in between the lower and upper Hamiltonians, as a convex combination of the two. For the general case (i.e. the convex combination is time and state dependent) our representatio...

Creator:

Hernandez-Hernandez, Daniel (Center of Investigations in Mathematics (CIMAT))

Created:

2018-05-07

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

In joint work with Carla Savage, we studied the inversion sequence representation of Eulerian polynomials and their generalizations. This led us to new recurrences for the generalized Eulerian polynomials and their refinements. These recurrences, combined with a relaxed notion of interlacing polynomials, called compatible polynomials, can be use...

Creator:

Visontai, Mirkà³ (Google Inc.)

Created:

2014-11-10

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

This lecture will focus on the situation when gradients of the objective function are not available to an optimization algorithm. We summarize algorithms for local optimization of a deterministic function, with particular attention directed to model-based trust-region methods. We provide foundations for the theory underlying these algorithms and...

Creator:

Wild, Stefan (Argonne National Laboratory)

Created:

2016-08-05

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

We discuss properties of distributions that are multivariate totally positive of order two (MTP2). Such distributions appear in the context of positive dependence, ferromagnetism in the Ising model, and various latent models. We show that maximum likelihood estimation for MPT2 exponential families is a convex problem. Hence, if the MLE exists, i...

Creator:

Uhler, Caroline (Massachusetts Institute of Technology)

Created:

2016-01-26

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

The property enhancements associated with dispersion of nanoparticles in polymers will depend not only on the state of dispersion achieved during the synthesis or formulation of the nanocomposite, but also on the degree and direction of particle alignment induced during subsequent processing. Here we present data on flow-induced orientation in t...

Creator:

Burghardt, Wesley R. (Northwestern University)

Created:

2009-09-16

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Ptychography comprises sampling and analyzing the object's spatial spectrogram by windowed (or "short-space") Fourier transforms. Its capability to reconstruct both image and illumination, as well as other experimental conditions including instabilities has proven promising for high-resolution X-ray microscopy. Practical implementation of X-ray ...

Creator:

Menzel, Andreas (Paul Scherrer Institute)

Created:

2017-08-14

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Recent experiments by Kantsler et al. [Phys. Rev. Lett. 99, 178102 (2007)] have shown that the relaxational dynamics of a vesicle in external elongation flow is accompanied by the formation of wrinkles on a membrane. Motivated by these experiments we present a theory describing the dynamics of a wrinkled membrane. The formation of wrinkles is re...

Creator:

Turitsyn, Konstantin (University of Chicago)

Created:

2008-07-23

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

The mechanics of a thin elastic sheet can be explored variationally, by minimizing the sum of 'membrane' and 'bending' energy. For some loading conditions, the minimizer develops increasingly fine-scale wrinkles as the sheet thickness tends to 0. While the optimal wrinkle pattern is probably available only numerically, the qualitative features o...

Creator:

Kohn, Robert V. (New York University)

Created:

2011-05-16

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

It is well known that elastic sheets loaded in tension will wrinkle, with the length scale of wrinkles tending to zero with vanishing thickness of the sheet [Cerda and Mahadevan, Phys. Rev. Lett. 90, 074302 (2003)]. We give the firstmathematically rigorous analysis of such a problem. Since our methods require an explicit understanding of the und...

Creator:

Bella, Peter (New York University)

Created:

2011-05-16

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

This lecture provides an introduction to the IMA Workshop onLarge-scale Inverse Problems and Quantification of Uncertainty. Wepresent context and motivation for the workshop topic along with adiscussion of open research challenges. We will discuss workshop goalsand provide a brief overview of the workshop schedule.

Creator:

Ghattas, Omar (The University of Texas at Austin)

Created:

2011-06-06

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

I'll discuss a method for approximating the super-level set persistent homology of a Gaussian kernel density estimator for a point cloud data set, which is related to the witness complex. Instead of selecting elements of the data set, the witnesses are generated using quadratic programming, and the shifted Voronoi diagram (aka the power diagram)...

Creator:

Carlsson, Erik (University of California, Davis)

Created:

2022-08-02

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Optimization of energy by large aquatic animals (e.g., dolphins, whales, manta) requires adaptations that control hydrodynamic flow to reduce drag, and improve thrust production and efficiency. Although streamlining of the body and appendages minimizes drag, highly derived aquatic animals utilize mechanisms of propulsion and control based on lif...

Creator:

Fish, Frank E. (West Chester University)

Created:

2010-06-05

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

In contrast to the positive definite Helmholtz equation, thedeceivingly similar looking indefinite Helmholtz equation is difficultto solve using classical iterative methods. Applying directly a Krylovmethod to the discretized equations without preconditioning leads ingeneral to stagnation and very large iteration counts. Using classicalincomplet...

Creator:

Gander, Martin J. (Universite de Geneve)

Created:

2010-11-29

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Vacant taxi driversâ€™ cruising behavior to seek the next potential passenger in a road network generates additional vehicle traveled miles, adding congestion and pollution into the road network and the environment. This study aims to employ reinforcement learning to model idle e-hailing driversâ€™ optimal sequential decisions in passenger-seeki...

Creator:

Di, Sharon (Columbia University)

Created:

2018-10-05

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

It is now well understood that there is a minimal requirement on the channelquality in feedback stabilization via a communication channel. In the case of SISO plant and SISO channel. This minimal channel quality is given in terms of the degree of instability of the plant to be stabilized. For a MIMO system controlled via a MIMO communication cha...

Creator:

Qiu, Li (Hong Kong University of Science and Technology)

Created:

2015-10-08

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

We develop computational and experimental methods to gain insights into visual functions and psychiatric disorders. We also build deep learning models that predict human behaviors and identify people with disorders. In this talk, I will share our recent innovations on data and models, aiming at understanding and predicting visual attention in na...

Creator:

Zhao, Catherine Qi (University of Minnesota, Twin Cities)

Created:

2017-02-03

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

We explore a geometric and topological approach to understanding the structural significance of edges in a complex network. To do so, we embed the complex network (or the graph $G(V, E)$ representing it) into a Euclidean space determined by the eigen-space of the Moore-Penrose pseudo-inverse of the combinatorial laplacian (denoted by $\bb L^+(G)...

Creator:

Ranjan, Gyan (University of Minnesota, Twin Cities)

Created:

2012-09-07

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Sequential quadratic programming (SQP)methods a powerful and effective class of methods for awide range of nonlinearly constrained optimizationproblems. Given the scope and utility of nonlinearoptimization, it is not surprising that SQP methods arestill a subject of active research. Recentdevelopments in methods for mixed integer nonlinearprogra...

Creator:

Gill, Philip E. (University of California, San Diego)

Created:

2008-11-19

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Cellular structures coarsen according to a local evolution law,a gradient flow or curvature driven growth, for example,limited by space filling constraints, which give rise to randomchanges in configuration. Composed of volumes, facets, theirboundaries, and so forth, they are ensembles of singlularstructures. Among the most challenging and ancie...

Creator:

Kinderlehrer, David (Carnegie Mellon University)

Created:

2008-07-21

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

It has been approximately twenty years since the initial germination ofnumerical continuation as an approach to finding solution points of systemsof polynomial equations and ten years since its flowering into numericalalgebraic geometry, which facilitates description of solution sets of anydimension and operations on these, such as intersection ...

Creator:

Wampler, Charles W. (General Motors Company)

Created:

2006-10-23

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

We study the influence of individual neuronal dynamics and network topology on synchronization of bursting neurons. We demonstrate that the type and duration of bursting are the critical characteristics that determine the synchronization properties of the network. We show that the onset of synchrony in an excitatory-inhibitory network with any c...

Creator:

Belykh, Igor (Georgia State University)

Created:

2012-09-06

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Consider the Vietoris-Rips complex for n evenly-spaced points around a circle. For small choices of the connectivity parameter, this complex is homotopy equivalent to a circle. For n even and for a connectivity parameter slightly less than the diameter of the circle, this complex is the boundary of a cross-polytope and is homeomorphic to the (n/...

Creator:

Adams, Henry (University of Minnesota, Twin Cities)

Created:

2013-10-01

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

The importance of spatial and spatio-temporal data mining is growing with the increasing incidence and importance of large datasets such as trajectories, maps, remote-sensing images, census and geo-social media. Applications include Public Health (e.g. monitoring spread of disease, spatial disparity, food deserts), Public Safety (e.g. crime hot ...

Creator:

Shekhar, Shashi (University of Minnesota, Twin Cities)

Created:

2017-01-24

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

A National Research Council report has called attention tomathematicians the problem of protein folding. Here we will give a settingfor the problem by putting a geometrical structure on the space of proteins.A significant question in the understanding of the folding process is this.Which pairs of positions in a linear string representing the pro...

Creator:

Smale, Stephen (City University of Hong Kong)

Created:

2013-10-09

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

There are many different queueing policies, and they tend to be defined inmodel-specific ways that differ in form from policy to policy. While eachform is suitable for the task at hand (e.g. steady-state derivation,scaling-limit theorem, or proof of some other property), the specificity ofthe policy definition can sometimes limit the scope of wh...

Creator:

Gromoll, Christian (University of Virginia)

Created:

2015-06-26

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Economists have traditionally viewed futures prices as fully informative about future economic activity and asset prices. We argue that open interest could be more informative than futures prices in the presence of hedging demand and limited risk absorption capacity in futures markets. We find that movements in open interest are highly pro-cycli...

Creator:

Yogo, Motohiro (Federal Reserve Bank of Minneapolis)

Created:

2012-05-17

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Microseismic imaging is an important technology for tracking fracture creation and reactivation of pre-existing fractures occurring during various industrial operations, particularly hydraulic fracture treatments of unconventional reservoirs. Often microseismic locations are used to interpret the fracture geometry, although additional insights i...

Creator:

Maxwell, Shawn (Itasca Image)

Created:

2015-05-11

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Two types of wetting phenomena will be discussed: (i) Morphological wettingtransitions at chemically patterned or topographically structured substrates; and(ii) Wetting of flexible membranes such as lipid bilayers by aqueous phases.Morphological wetting transitions between different droplet shapes occur, e.g., as onevaries the amount of liquid d...

Creator:

Lipowsky, Reinhard (Max Planck Institute for Colloids and Interfaces)

Created:

2009-12-07

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

The talk will be based on a joint work with L. Ambrosio, G. Crippa and A.Figalli. First, some new well-posedness results for continuity andtransport equations with weakly differentiable velocity fields will bediscussed. These results can be applied to the analysis of a 2 x 2 systemof conservation laws in one space dimension known as the chromato...

Creator:

Spinolo, Laura Valentina (Scuola Normale Superiore)

Created:

2009-07-25

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

We consider the question of global in time existence and uniqueness of solutions of the infinite depth full water wave problem. We show that the nature of the nonlinearity of the water wave equation is essentially of cubic and higher orders. For any initial data that is small in its kinetic energy and height, we show that the 2-D full water wave...

Creator:

Wu, Sijue (University of Michigan)

Created:

2010-02-23

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

Given a model based on a conservation law, we study how the solutiondepends from the initial/boundary datum, from the flow and fromvarious constraints. With this tool, several control problems can beaddressed and the existence of an optimal control can beproved. Models describing escape dynamics of pedestrians, traffic attoll gates, open canals ...

Creator:

Colombo, Rinaldo Mario (Università di Brescia)

Created:

2009-07-31

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.

The form of accurate semiclassical surface hopping propagators and wave functions for processes involving more than one electronic quantum state is discussed. It is shown that conditions, which define the required non-classical events along trajectories, can be derived from the Schrödinger equation. These conditions also uniquely specify the dir...

Creator:

Herman, Michael F. (Tulane University)

Created:

2009-01-16

Contributed By:

University of Minnesota, Institute for Mathematics and its Applications.