2D Raman band splitting in graphene: charge screening and lifting of the K-point Kohn anomaly

Pristine graphene encapsulated in hexagonal boron nitride has transport properties rivalling suspended graphene, while being protected from contamination and mechanical damage. For high quality devices, it is important to avoid and monitor accidental doping and charge fluctuations. The 2D Raman double peak in intrinsic graphene can be used to optically determine charge density, with decreasing peak split corresponding to increasing charge density. We find strong correlations between the 2D 1 and 2D 2 split vs 2D line widths, intensities, and peak positions. Charge density fluctuations can be measured with orders of magnitude higher precision than previously accomplished using the G-band shift with charge. The two 2D intrinsic peaks can be associated with the “inner” and “outer” Raman scattering processes, with the counterintuitive assignment of the phonon closer to the K point in the KM direction (outer process) as the higher energy peak. Even low charge screening lifts the phonon Kohn anomaly near the K point for graphene encapsulated in hBN, and shifts the dominant intensity from the lower to the higher energy peak.This work was supported by the United States National Science Foundation (DMR 1411008, DMR 1308659). J.C. thanks the Department of Defence (DoD), Air Force Office of Scientific Research for its support through the National Defence Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. The authors would like to thank Cory Dean and Carlos Forsythe for the graphene encapsulated hBN sample. (DMR 1411008 - United States National Science Foundation; DMR 1308659 - United States National Science Foundation; 32 CFR 168a - Department of Defence (DoD), Air Force Office of Scientific Research through the National Defence Science and Engineering Graduate (NDSEG) Fellowship

Paper_Uniaxial Compressive Behavior of “Solidified” Synthetic Lightweight Aggregates

This paper presents results from uniaxial compression tests on a synthetic lightweight aggregate (SLA) created from high carbon fly ash and mixed waste plastics. Since their invention in the late 1990’s, SLA has represented an innovative and potentially novel construction material created solely from the co-extrusion of these two, high volume, waste streams. This current effort involved testing specimens created as “solidified” SLA cylinders. Three types of cylindrical specimen were created from ‘loose’ SLA that existed at the following grain-size ranges: Coarse (between U.S. sieve No. 4 and No. 8 or between 2.36 to 4.75mm), Medium (between No. 8 and No. 16 or between 1.18 to 2.36mm), and Fine (between No. 16 to No. 30 or between 0.6 to 1.18mm). Though the initial porosity of loose SLA was between 0.4 to 0.5, compression led to final specimen porosities of 0.05 to 0.2; creating cylinders competent enough to be subjected to uniaxial compression tests (i.e., no lateral support needed during testing). Final cylinders were nominally 5.1cm (~2in) high and 3.6cm (~1.4in) in diameter. Uniaxial compressive tests were performed for the various types of test specimens created. Additionally, an on-specimen yoke system was used during testing to capture small strain compressive behaviors (e.g., Young’s moduli) of the various “solidified” SLA specimens. Results from the uniaxial compression tests showed the ultimate strength of the cylinders increased as the “solidified” specimen’s compressed porosity decreased. Also, the initial Young’s modulus of the “solidified” specimens increased as the specimen’s compressed porosity decreased. What is of interest is that there was only a small, if any, difference between the three types of SLA cylinders – Coarse, Medium, and Fine – indicating that the properties measured do represent that of the micro-SLA regardless of its initial, loose size range

Ecotypic Differentiation of Mid-Atlantic \u3ci\u3eQuercus\u3c/i\u3e Species in Response to Ultramafic Soils

Spatial heterogeneity of soil conditions combined with intraspecific variation confer site-specific edaphic tolerance, resulting in local adaptation and speciation. To understand the geoecological processes controlling community assembly of woodland tree species on serpentine and mafic soils, we investigated resource gradients and provenance (geographic area of propagule collection) as variables affecting typical representative upland oak (Quercus) species distribution. Accordingly, we conducted a year-long reciprocal transplant experiment in the greenhouse with serpentine and mafic soils, using seedlings of five oak species (Quercus marilandica, Q. stellata, Q. montana, Q. michauxii and Q. alba). All seedlings, regardless of provenance or soil depth, displayed more robust growth in the mafic soils. Soil depth was an important determinant, with all species exhibiting increased growth in the deeper-soil treatments. Fitness surrogates such as stem height, relative growth rate, and leaves per plant were greater when seedlings were grown in their home soil than when they were grown in the non-resident soil, suggesting an ecotypic effect. Mean stomatal conductance and stem growth were positively correlated with soil depth in all treatments. Taken together, the study showed provenance-specific growth responses of oak seedlings to soil type and depth, providing a better understanding of the mechanisms controlling species assembly in woodland communities

Symmetry breaking and friction in few layer phosphorene

National Defense Science and Engineering Graduate Fellowshi

Physical mechanisms controlling the strength and deformation behavior of unfrozen and frozen Manchester fine sand

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1994.Includes bibliographical references (v. 4, leaves 721-743).by Christopher Wayne Swan.Sc.D

Metaheuristic Design Patterns: New Perspectives for Larger-Scale Search Architectures

Design patterns capture the essentials of recurring best practice in an abstract form. Their merits are well established in domains as diverse as architecture and software development. They offer significant benefits, not least a common conceptual vocabulary for designers, enabling greater communication of high-level concerns and increased software reuse. Inspired by the success of software design patterns, this chapter seeks to promote the merits of a pattern-based method to the development of metaheuristic search software components. To achieve this, a catalog of patterns is presented, organized into the families of structural, behavioral, methodological and component-based patterns. As an alternative to the increasing specialization associated with individual metaheuristic search components, the authors encourage computer scientists to embrace the ‘cross cutting' benefits of a pattern-based perspective to optimization algorithms. Some ways in which the patterns might form the basis of further larger-scale metaheuristic component design automation are also discussed

Grain Sorghum Variety Trial Archive

This report features the available sorghum data from 2003-2017. Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU

Monolayer MoS2 strained to 1.3% with a microelectromechanical system

We report on a modified transfer technique for atomically thin materials integrated onto microelectromechanical systems (MEMS) for studying strain physics and creating strain-based devices. Our method tolerates the non-planar structures and fragility of MEMS, while still providing precise positioning and crack free transfer of flakes. Further, our method used the transfer polymer to anchor the 2D crystal to the MEMS, which reduces the fabrication time, increases the yield, and allowed us to exploit the strong mechanical coupling between 2D crystal and polymer to strain the atomically thin system. We successfully strained single atomic layers of molybdenum disulfide (MoS2) with MEMS devices for the first time and achieved greater than 1.3% strain, marking a major milestone for incorporating 2D materials with MEMS We used the established strain response of MoS2 Raman and Photoluminescence spectra to deduce the strain in our crystals and provide a consistency check. We found good comparison between our experiment and literature.Published versio