2008–2009

Distinguished Lectures Series

The ECE Distinguished Lectures Series brings world-class researchers to the University to share their research and discoveries.

High Performance Throughput Computing

Mark Tremblay

High-Performance Throughput Computing, achieved through designed-from-scratch processors composed of multiple multithreaded cores, offers an unprecedented opportunity to create a new generation of pipelines that deliver both high throughput performance and high single-thread performance.

A checkpoint-based architecture that offers a new execution model, perhaps the only novel one in over a decade, forms the cornerstone of the Rock microprocessor. Hardware threads are spawned and they speculatively execute and retire
instructions out-of-order. Power efficiency is emphasized by maximizing the utilization of pipeline stages, through temporal threading, and functional units, through spatial threading and speculation. This pipeline is organized in an hierarchical manner in the 16-core 65nm Rock microprocessor.

As important as the Throughput Computing paradigm, is the enablement of parallel software. Rock should be the first processor to support Transactional Memory, a leading candidate to deliver high-performance scalable parallel applications through composable software.

 

Design & Control of Autonomous Systems

Raffaell D’Andrea

The commoditization of computation, sensing technology, and communication has enabled the conceptualization of new physical systems with large levels of autonomy. In many instances, we are no longer limited by physical hardware, but rather our ability to design and deploy reliable systems that take advantage of these new capabilities. In this talk I will discuss some of our contributions in the area of control and system design, and our attempts to tame and manage the complexity inherent in high performance autonomous systems. Examples include soccer playing robots, self-assembling chairs, and warehouses with hundreds of autonomous mobile vehicles. For more information, please visit www.raffaello.name.

 

Magnetic Nanoparticles:  Current Trends & Future Directions

Sara Majetich

The magnetic behavior of a monodomain nanoparticle was first described by Stoner and Wohlfarth nearly sixty years ago, yet this simple system is frequently invoked in discussions of high-density magnetic recording media, magnetic refrigeration materials, and a host of biomedical applications. Here we examine the unique features of magnetic nanoparticles, relative to bulk materials, and discuss three case studies that highlight these differences.

Surfactant-coated nanoparticles can self-assemble into ordered arrays that have no exchange coupling between particles. Future composite materials like these could be beneficial as high frequency inductors because they can have high permeability but low power losses. The ability to make magnetic nanostructures creates a need for new tools that enable us to visualize their magnetization patterns. Here we apply electron holography and Fresnel Lorentz microscopy to visualize the domain structures within the films and to monitor their dynamics.

Because a magnetic nanoparticle is small, its motion can be controlled with external field gradients, and it can be used for medical imaging and drug delivery. Here we will present results for particles designed for in vitro studies, where simultaneous optical imaging and magnetic guidance is desired. These magnetic particles are coated with gold for dark field imaging using the surface plasmon resonance, or with fluorophore tags for fluorescence microscopy. Microscopic magnetically guided collection of particles is demonstrated.

Finally, if the magnetization of the nanoparticle is stable, it can be used to store information. Here we examine a new approach to magnetic recording media that uses nanoparticles as an etch mask for patterning an underlying thin film. After describing the pattern transfer process, we discuss electronic measurements on individual 10 nm wide magnetic tunnel junction nanopillars using conducting atomic force microscopy (C-AFM). Scanning probe techniques have the potential to read and write the magnetization state of the nanopillar.

 

Soft Errors Make Hard Problems for Chip Designers

John Hayes

The steady shrinking of the transistors used in integrated circuit (IC) chips makes them increasingly vulnerable to transient upsets caused by external radiation such as cosmic rays, or by internal effects such as electrical noise. Usually no permanent damage is done to the chips, but the resulting soft errors may lead to serious system failures. Moreover, many of the nanotechnologies being proposed to replace or supplement conventional ICs have behavior, both normal and faulty, that is inherently prone to random errors. To deal with such errors requires probabilistic methods that are not easily incorporated into the traditional chip design flow. In this talk, I will review the sources and impact of soft errors. I will describe some recent methods to model them and analyze their effects on digital circuit behavior and reliability. In particular, I will discuss a computational framework based on probabilistic transfer matrices (PTMs) to estimate soft error rates, noting the central role played by the tensor product and related algebraic operations. Finally, I will discuss some design techniques to make circuits fault-tolerant in the presence of soft errors.

 

Cooling and Amplifying Mico-Mechanical Motion with Light

Kerry Vahala

Recent years have witnessed a series of developments at the intersection of two, previously distinct subjects. Optical (micro-) cavities and micro (nano-) mechanical resonators, each a subject in their own right with a rich scientific and technological history, have, in a sense, become entangled experimentally by the underlying mechanism of optical, radiation pressure forces. These forces and their related physics have been of major interest in the field of atomic physics for over 5 decades, and the emerging optomechanical context for these forces has many parallels with this field. There is also a rich theoretical history that considers the implications of optical forces in this new context. Despite this theoretical promise, the manifestations of these forces on micromechanical objects have only recently become an experimental reality. We will review recent demonstrations of both mechanical amplification and cooling by radiation pressure forces in a micron-scale toroidal resonator. These devises contain high-Q optical modes (Q factors as high as 500 million) in coexistence with high-Q mechanical breathing modes. Resonantly enhanced optical forces couple these mechanical and optical degrees of freedom, creating two distinct dynamical regimes. In the first, mechanical amplification can overcome intrinsic loss to induce regenerative oscillation up to microwave rates. In the second, mechanical cooling to low temperatures is possible (milli-Kelvins from room temperature has been demonstrated). We conclude by discussing current progress in this field directed to attaining the ground-state cooling of a macroscale mechanical oscillator.

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