Publications

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The Technical Reachback (TRB) project analyzes data and builds tools to enhance the capability for interdiction of illicit nuclear material at U.S. border crossings. The work done by TRB allows for a more precise classification of radioactive isotopes, pattern detection in traffic, and formulation of effective defenses.

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Advances in node-level architecture and interconnect technology needed to reach extreme scale necessitate a reevaluation of long-standing models of computation, in particular bulk synchronous processing. The end of Dennard-scaling and subsequent increases in CPU core counts each successive generation of general purpose processor has made the ability to leverage parallelism for communication an increasingly critical aspect for future extreme-scale application performance. But the use of massive multithreading in combination with MPI is an open research area, with many proposed approaches requiring code changes that can be unfeasible for important large legacy applications already written in MPI. This paper covers the design and initial evaluation of an extension of a massive multithreading runtime system supporting dynamic parallelism to interface with MPI to handle fine-grain parallel communication and communication-computation overlap. Our initial evaluation of the approach uses the ubiquitous stencil computation, in three dimensions, with the halo exchange as the driving example that has a demonstrated tie to real code bases. The preliminary results suggest that even for a very well-studied and balanced workload and message exchange pattern, co-scheduling work and communication tasks is effective at significant levels of decomposition using up to 131,072 cores. Furthermore, we demonstrate useful communication-computation overlap when handling blocking send and receive calls, and show evidence suggesting that we can decrease the burstiness of network traffic, with a corresponding decrease in the rate of stalls (congestion) seen on the host link and network.

Visible light laser voltage probing (LVP) for improved backside optical spatial resolution is demonstrated on ultra-thinned samples. A prototype system for data acquisition, a method to produce ultra-thinned SOI samples, and LVP signal, imaging, and waveform acquisition are described on early and advanced SOI technology nodes. Spatial resolution and signal comparison with conventional, infrared LVP analysis is discussed.

This final report summarizes ATA Engineering Inc.'s experimental dynamic characterization of the Sandia National Laboratories (SNL) Scaled Wind Farm Technology (SWIFT) Vestas 27 (V27) wind turbine components and fully assembled turbines. Testing was performed at SNL's SWIFT facility in Lubbock, Texas, from October 2012 through June 2013.Dynamic testing consisted of modal testing of the individual blades, the towers in a free-free boundary condition, the towers bolted to the foundations, and the fully assembled wind turbines. Additionally, modal testing was performed on a hub and two nacelles to determine the mass and inertia properties of these components. Details on these tests can be found in their respective reports.

Berry and Wang [Phys. Rev. A 83, 042317 (2011)] show numerically that a discrete-time quan- tum random walk of two noninteracting particles is able to distinguish some non-isomorphic strongly regular graphs from the same family. Here we analytically demonstrate how it is possible for these walks to distinguish such graphs, while continuous-time quantum walks of two noninteracting parti- cles cannot. We show analytically and numerically that even single-particle discrete-time quantum random walks can distinguish some strongly regular graphs, though not as many as two-particle noninteracting discrete-time walks. Additionally, we demonstrate how, given the same quantum random walk, subtle di erences in the graph certi cate construction algorithm can nontrivially im- pact the walk's distinguishing power. We also show that no continuous-time walk of a xed number of particles can distinguish all strongly regular graphs when used in conjunction with any of the graph certi cates we consider. We extend this constraint to discrete-time walks of xed numbers of noninteracting particles for one kind of graph certi cate; it remains an open question as to whether or not this constraint applies to the other graph certi cates we consider.

We introduce a quantum dot qubit architecture that has an attractive combination of speed and fabrication simplicity. It consists of a double quantum dot with one electron in one dot and two electrons in the other. The qubit itself is a set of two states with total spin quantum numbers S² = 3/4 (S = 1/2) and S_z = - 1/2, with the two different states being singlet and triplet in the doubly occupied dot. Gate operations can be implemented electrically and the qubit is highly tunable, enabling fast implementation of one- and two-qubit gates in a simpler geometry and with fewer operations than in other proposed quantum dot qubit architectures with fast operations. Additionally, the system has potentially long decoherence times. These are all extremely attractive properties for use in quantum information processing devices.