Lefschetz Center for Dynamical Systems Seminar
Brown University
Joint Materials/Solid Mechanics Seminar Series
Lawrence Livermore National Lab | |
Abstract: Lawrence Livermore is a key driver in meeting the emerging National security needs in Chem- and Bio-Sensors. I will argue that sensing will probably be the first killer app for the revolution in Nanoscience that has occurred over the last few years. This talk will overview some key developments in the implementation of nanotechnology-based sensors at LLNL. Recent developments in nanoscience enable both directed synthesis and controlled manipulation of bioactivity in inorganic materials. Specific technologies to be described include synthetic antibodies, functionalized porous materials, protein-templated sensor materials, nanotube-based separation, and viral-fragmentation signatures. This impressive toolbox is being rapidly deployed to support the need for a range of application- specific sensors around the world.
Brown University
Cognitive & Linguistic Sciences Colloquium Series
Abstract: The silver anniversary of Jim McCawley's classical paper "Conversational Implicature and the Lexicon" provides a natural springboard for an exploration of the state of the art in lexical pragmatics. A century before McCawley's investigation of how Gricean inference informs our understanding of the structure and use of lexical items, Hermann Paul (1880) had surveyed a range of constructions whose form and distribution reflect the interplay of two functional principles governing conversation, the tendency to reduce expression (later formulated by G. K. Zipf as the linguistic correlate of a more general Principle of Least Effort) and the contextually determined communicative requirements on sufficiency of information. The descendants of this functional dialectic include the speaker's vs. hearer's economies of Zipf and Martinet and the opposed halves of Grice's Maxim of Quantity ("Make your contribution {as informative as is required/no more informative than is required} for the current purpose of the exchange"), grounded within a general theory of rationality and co-operation. From these Gricean submaxims, in turn, derive the Q and R Principles of Horn 1984 (essentially = "Say enough"/"Don't say too much") and the interplay of effort and effect within Relevance Theory (Sperber & Wilson 1986). While the interaction of the Paul/Grice principles pervades the entire linguistic system--as emerges notably in the minimax between articulatory "laziness" vs. perceptual distinctness in functional phonetics and the corresponding violable constraints in Optimality Theory--it is the consequences of this interaction for the lexicon that provide the focus for this presentation.
Since McCawley's seminal paper, it has become gradually evident that choices among lexical alternatives is guided to a large extent by pragmatic principles; work by Elizabeth Traugott and others has examined the role of these principles in semantic change. After comparing pragmatic and semantic approaches to asymmetries in lexicalization and the inference from {\it most} to {\it not all}, I will survey the role of speaker- and hearer-based economy principles in motivating syntagmatic reduction, euphemism and negative strengthening, lexical clones ({\it No, I wanted a SALAD salad}) and the productive formation of "un-nouns" (from the {\it un-cola} to the {\it un-politician}). Finally, drawing on the complementary tendencies of Avoid Synonymy and Avoid Homonymy, I will argue that synchronic, diachronic, and developmental aspects of lexical pragmatics provide support for a neo-Gricean view of the division of labor in natural language meaning.
Refreshments will be served before the talk in Room 124-125
Please contact Christie Crozier at (401) 863-2616 if you would like to meet with Dr. Horn.
Special Brown Applied Mathematics Pattern Theory and Vision Seminar
Center for Fluid Mechanics Seminar
Abstract: Microfluidic devices offer the possibilities of precision control over fluid flow. They are typically used to control the flow of single fluids or mixtures of miscible mixtures. However, they also offer the potential of producing more complex fluid structures. This talk will discuss the use of microfluidic devices to produce and study droplets of one fluid in a second. The droplets can be produced and studied one by one, enabling precision control over the structure and make-up of each drop, and allowing the formation of new complex fluid structures.
Stochastic Systems Seminar
Abstract: Several basic examples of parabolic stochastic partial differential equations (SPDEs) will be presented in a Hilbert space setting. Various notions of existence and uniqueness of solutions along with the convergence schemes that lead to the solutions will be given. Asymptotic behavior, ergodicity, and large deviations of certain SPDEs will be shown.
Brown Applied Mathematics Pattern Theory and Vision Seminar
If you would like to meet with Lior Wolf please e-mail Eitan Sharon at eitans@dam.brown.edu if you would like to meet with Lior Wolf. |
Abstract:
We address the problem of selecting a subset of the most
relevant features from a set of sample data in cases where
there are multiple (equally reasonable) solutions. In
particular, this topic includes on one hand the introduction
of hand-crafted kernels which emphasize certain desirable
aspects of the data and, on the other hand, the suppression
of one of the solutions given ``side'' data, i.e., when one
is given information about undesired aspects of the data.
Such situations often arise when there are several, even
conflicting, dimensions to the data. For example, documents
can be clustered based on topic, authorship or writing style;
images of human faces can be clustered based on illumination
conditions, facial expressions or by person identity, and so
forth.
Starting from a spectral method for feature selection, known
as Q \alpha, we introduce first a kernel version of the
approach thereby adding the power of non-linearity to the
underlying representations and the choice to emphasize certain
kernel-dependent aspects of the data. As an alternative to the
use of a kernel we introduce a principled manner for making
use of auxiliary data within a spectral approach for handling
situations where multiple subsets of relevant features exist
in the data. The algorithm we will introduce allows for
inhibition of relevant features of the auxiliary dataset and
allows for creating a topological model of all relevant
feature subsets in the dataset.
Joint work with Prof. A. Shashua
Brown University
Joint Materials/Slid Mechanics Seminar Series
University of Illinois at Urbana-Champaign | |
Abstract: The folding of thin films is an old research subject that has a way of coming up time and again under ever changing guises. Early in the Nineteenth Century, a misguided theory of mountain building lead to a flurry of work on the folding of a thin film (the lithosphere) subjected to compressive stresses by a shrinking spherical substrate (the cooling earth). More recently, the proposal of novel applications for microfabricated thin-film diaphragms, including diaphragms in which folding patterns tailored for a particular end are induced by design, has lead to a renewed interest in the folding of thin films. Here we study the folding of elastic thin-film diaphragms under in-plane compressive strains by means of theoretical and experimental work. In our theoretical work we use a constrained von Karman plate theory to obtain an energy functional for folded diaphragms. The perturbative character of the bending energy leads us to adopt a two-step minimization strategy: Fold to release membraneous energy, then let bending select one out of a number of alternative foldings. In the case when the compressive strain is isotropic, we find foldings which satisfy the boundary conditions and minimize the membraneous energy. In the case when the compressive strain is anisotropic, no such foldings exist, but we are able to construct sequences of increasingly fine foldings which satisfy the boundary conditions and whose membraneous energies converge to the infimum. In both cases we obtain solutions by allowing bending to select a preferred folding. The preferred folding depends on the shape, thickness, and size of the diaphragm in differing forms depending on whether the strain be isotropic or anisotropic. To verify this prediction, we perform simple experiments aimed at documenting the foldings associated with different diaphragms and strains. To verify other predictions of our theoretical work, we use shadow Moire interferometry to measure the deflection fields of folded thin-film diaphragms and compute the attendant bending and membraneous energies. The experimental results are in good agreement with the predictions.
Special Lecture Series
Special Lecture Series
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