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Samuel Graham

Bio: Samuel Graham is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Thermal conductivity & Thermal resistance. The author has an hindex of 48, co-authored 347 publications receiving 9774 citations. Previous affiliations of Samuel Graham include Merck & Co. & United States Military Academy.


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TL;DR: In this article, a new paradigm is presented for the direct generation of self-sustaining millimeter-wave oscillations, based on the piezo and ferroelectric properties of wurtzite III-nitride materials.
Abstract: A new paradigm is presented for the direct generation of self-sustaining millimeter-wave oscillations, based on the piezo- and ferroelectric properties of wurtzite III-nitride materials. In contrast to Gunn diodes which exploit a bulk-like active region, periodic oscillation is achieved in the proposed structures through the creation, propagation and collection of traveling dipole domains supported by fixed polarization charge and the associated two-dimensional electron gas along the plane of a polar heterojunction. State-of-the-art numerical simulation based on the synchronous full-band ensemble Monte Carlo method is applied to study induced oscillations in a simple triode structure commonly used for AlGaN/GaN high electron mobility transistors. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

3 citations

07 Jun 1999
TL;DR: In this paper, the authors used an IR camera to capture thermal transients during electrical breakdown of ZnO varistors and to freeze the rotation of an automobile disk brake in order to study thermoplastic instability in the braking system.
Abstract: The high-speed, snap-shot mode, and the external triggering capability of an IR camera allows thermal transients to be captured. These advanced features were used to capture thermal transients during electrical breakdown of ZnO varistors and to freeze the rotation of an automobile disk brake in order to study thermoplastic instability in the braking system. The IR camera also showed the thermoplastic effect during cyclic fatigue testing of a glass matrix composite.

3 citations

14 May 2017
TL;DR: In this paper, a ground-level integrated diverse energy storage (GLIDES) is proposed to store energy by compressing/expanding a gas (air) using a liquid (water) piston.
Abstract: 1 This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ABSTRACT Increased generation capacity from intermittent renewable electricity sources being brought on-line combined with an electrical grid ill-equipped to handle the mismatch between electricity generation and use, necessitates advanced bulk energy storage technologies. This paper introduces once such technology, GLIDES (Ground-Level Integrated Diverse Energy Storage), which stores energy by compressing/expanding a gas (air) using a liquid (water) piston. A Pelton turbine is utilized as the energy extraction machine through which high head water is passed. This paper is the first to report on experimental system performance of the GLIDES technology.

3 citations


Cited by
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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
01 Aug 2014-Science
TL;DR: Perovskite films received a boost in photovoltaic efficiency through controlled formation of charge-generating films and improved current transfer to the electrodes and low-temperature processing steps allowed the use of materials that draw current out of the perovskites layer more efficiently.
Abstract: Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

5,789 citations

Journal ArticleDOI
TL;DR: A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized.
Abstract: A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized. Fullerene-free polymer solar cells (PSCs) based on the ITIC acceptor are demonstrated to exhibit power conversion effi ciencies of up to 6.8%, a record for fullerene-free PSCs.

3,048 citations