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.
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.