Sandia National Laboratories

About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Combustion. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

Electrically resonant terahertz metamaterials: Theoretical and experimental investigations

Abstract: We present a class of artificial materials that exhibit a tailored response to the electrical component of electromagnetic radiation. These electric metamaterials are investigated theoretically, computationally, and experimentally using terahertz time-domain spectroscopy. These structures display a resonant response including regions of negative permittivity ${ϵ}_{1}(\ensuremath{\omega})l0$ ranging from $\ensuremath{\sim}500\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}1\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$. Conventional electric media such as distributed wires are difficult to incorporate into metamaterials. In contrast, these localized structures will simplify the construction of future metamaterials, including those with negative index of refraction. As these structures generalize to three dimensions in a straightforward manner, they will significantly enhance the design and fabrication of functional terahertz devices.

The Ulysses solar wind plasma experiment

Abstract: The scientific objectives of the Ulysses solar wind plasma experiment, termed the Solar Wind Observations Over the Poles of the Sun (SWOOPS) include measurements of the solar-wind global properties, the nonlinear MHD disturbances in the solar wind, the internal state of the solar wind plasma, and the solar-wind interaction with Jupiter's magnetic field. In this paper, special attention is given to the two instrumental packages of SWOOPS experiment that will simultaneously perform measurements on electrons and ions of solar plasma: the ion analyzer and the electron analyzer. Results obtained in the initial phases of the SWOOPS experiment are presented.

A split Hopkinson pressure bar technique to determine compressive stress-strain data for rock materials

Abstract: This paper presents a split Hopkinson pressure bar technique to obtain compressive stress-strain data for rock materials. This technique modifies the conventional split Hopkinson bar apparatus by placing a thin copper disk on the impact surface of the incident bar. When the striker bar impacts the copper disk, a nondispersive ramp pulse propagates in the incident bar and produces a nearly constant strain rate in a rock sample. Data from experiments with limestone show that the samples are in dynamic stress equilibrium and have constant strain rates over most of the test durations. In addition, the ramp pulse durations can be controlled such that samples are unloaded just prior to failure. Thus, intact samples that experience strains beyond the elastic region and postpeak stresses can be retrieved for microstructural evaluations. The paper also presents analytical models that predict the time durations for sample equilibrium and constant strain rate. Model predictions are in good agreement with measurements.

Exascale computing technology challenges

Abstract: High Performance Computing architectures are expected to change dramatically in the next decade as power and cooling constraints limit increases in microprocessor clock speeds. Consequently computer companies are dramatically increasing on-chip parallelism to improve performance. The traditional doubling of clock speeds every 18-24 months is being replaced by a doubling of cores or other parallelism mechanisms. During the next decade the amount of parallelism on a single microprocessor will rival the number of nodes in early massively parallel supercomputers that were built in the 1980s. Applications and algorithms will need to change and adapt as node architectures evolve. In particular, they will need to manage locality to achieve performance. A key element of the strategy as we move forward is the co-design of applications, architectures and programming environments. There is an unprecedented opportunity for application and algorithm developers to influence the direction of future architectures so that they meet DOE mission needs. This article will describe the technology challenges on the road to exascale, their underlying causes, and their effect on the future of HPC system design.

Research challenges to ultra-efficient inorganic solid-state lighting

Abstract: Solid-state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next several years. This efficiency is significantly higher than that of traditional lighting technologies, giving solid-state lighting the potential to enable significant reduction in the rate of world energy consumption. Further, there is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even more significant reduction in world energy usage. In this article, we discuss in some detail: (a) the several approaches to inorganic solid-state lighting that could conceivably achieve “ultra-high,” 70% or greater, efficiency, and (b) the significant research questions and challenges that would need to be addressed if one or more of these approaches were to be realized.