Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “mill”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Anisotropic N=4 Super-Yang-Mills Plasma and Its Instabilities

We present a type-IIB supergravity solution dual to a spatially anisotropic finite-temperature N=4 super-Yang-Mills plasma. The solution is static and completely regular. The full geometry can be viewed as a renormalization group flow from an ultraviolet anti-de Sitter geometry to an infrared Lifshitz-like geometry. The anisotropy can be equivalently understood as resulting from a position-dependent {theta} term or from a nonzero number density of dissolved D7-branes. The holographic stress tensor is conserved and anisotropic. The presence of a conformal anomaly plays an important role in the thermodynamics. The phase diagram exhibits homogeneous and inhomogeneous (i.e., mixed) phases. In some regions the homogeneous phase displays instabilities reminiscent of those of weakly coupled plasmas. We comment on similarities with QCD at finite baryon density and with the phenomenon of cavitation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Vacuum Pyrolysis of Hybrid Poplar Milled Wood Lignin with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry Analysis of Feedstock and Products for the Elucidation of Reaction Mechanisms

The pyrolysis of lignocellulosic materials is a promising technique to produce fuels and chemicals. It is well known that the most abundant products of lignin pyrolysis are oligomeric molecules, known as pyrolytic lignin (PL). The chemical composition of PL has been extensively studied; however, there is still an important debate whether these oligomers are produced directly from the lignin or from the recombination of monomeric pyrolytic products. Existing theories are unable to describe the effect of vacuum on the distribution of pyrolysis products. Hybrid poplar milled wood lignin (MWL) was initially isolated and thoroughly characterized by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Chemical formulas were assigned to each oligomeric compound detected. The MWL was also subjected to vacuum pyrolysis in a modified pyroprobe at 250, 750, and 1000 mbar (absolute pressure), and the resulting liquid products were analyzed by FT-ICR MS. A new strategy to assign structural representations to the oligomeric PL products is proposed, based on the plausible pyrolysis reaction mechanisms of depolymerization/fragmentation applied to original MWL oligomer formulas. Our results support the hypothesis that PL is formed from the removal of moieties from primary lignin pyrolysis products with between three and five aromatic rings. This depolymerization/fragmentation allows the oligomers to reduce their molecular weights to the point where they can be removed from the reaction zone by direct vaporization. Furthermore, this phenomenon highlights the importance of pressure on removal mechanisms and their impact on the molecular weight of the resulting products from lignin pyrolysis.

09 BIOMASS FUELS↗
DOE OSTI2015

Atomic-scale thermocapillary flow in focused ion beam milling

Focused ion beams provide a means of nanometer-scale manufacturing and material processing, which is used for applications such as forming nanometer-scale pores in thin films for DNA sequencing. We investigate such a configuration with Ga{sup +} bombardment of a Si thin-film target using molecular dynamics simulation. For a range of ion intensities in a realistic configuration, a recirculating melt region develops, which is seen to flow with a symmetrical pattern, counter to how it would flow were it driven by the ion momentum flux. Such flow is potentially important for the shape and composition of the formed structures. Relevant stress scales and estimated physical properties of silicon under these extreme conditions support the importance thermocapillary effects. A flow model with Marangoni forcing, based upon the temperature gradient and geometry from the atomistic simulation, indeed reproduces the flow and thus could be used to anticipate such flows and their influence in applications.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Six-point next-to-maximally helicity-violating amplitude in maximally supersymmetric Yang-Mills theory

We present an integral representation for the parity-even part of the two-loop six-point planar next-to-maximally helicity-violating amplitude in terms of Feynman integrals which have simple transformation properties under the dual conformal symmetry. We probe the dual conformal properties of the amplitude numerically, subtracting the known infrared divergences. We find that the subtracted amplitude is invariant under dual conformal transformations, confirming existing conjectures through two-loop order. We also discuss the all-loop structure of the six-point next-to-maximally helicity-violating amplitude and give a parametrization whose dual conformal invariant building blocks have a simple physical interpretation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Effect of sintering in ball-milled K{sub 2}Bi{sub 8}Se{sub 13} thermoelectric nano-composites

K{sub 2}Bi{sub 8}Se{sub 13} has many attractive features for thermoelectric applications. Recently, K{sub 2}Bi{sub 8}Se{sub 13}-based nanocomposite materials, consisting of nano-crystalline, micro-crystalline and amorphous phases, have been fabricated based on powder technology techniques. The Seebeck coefficient has been enhanced while the thermal conductivity has been decreased presenting, thus, interesting behavior. The behavior of the materials under heat treatment conditions is now of interest, as the application of sintering process is necessary for the development of thermoelectric modules. In this work, the crystallization of the K{sub 2}Bi{sub 8}Se{sub 13}-based nano-composites is studied using Differential Scanning Calorimetry. The results show that crystallization follows a multiple-step process with different activation energies. The thermoelectric properties are also discussed in the range that crystallization occurs. - Graphical Abstract: {beta}-K{sub 2}Bi{sub 8}Se{sub 13}-based nanocomposites follow a multiple-step crystallization process. Highlights: Black-Right-Pointing-Pointer K{sub 2}Bi{sub 8}Se{sub 13}-based composites consisting of nanocrystalline and amorphous phases. Black-Right-Pointing-Pointer Sintering results multiple-step crystallization with variable activation energies. Black-Right-Pointing-Pointer Thermoelectric properties follow a step-like behavior during sintering. Black-Right-Pointing-Pointer Properties are attributed to the strain relaxation, nucleation and grain growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗