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Articles 1 - 7 of 7

Full-Text Articles in Physics

Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao Dec 2018

Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao

Aerospace Engineering Publications

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from 25-340 K. For ...


Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer Jul 2018

Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer

Ames Laboratory Accepted Manuscripts

Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as ...


Theoretical And Experimental Investigation Of Forward Spatter Of Blood From A Gunshot, P. M. Comiskey, A. L. Yarin, Daniel Attinger Jun 2018

Theoretical And Experimental Investigation Of Forward Spatter Of Blood From A Gunshot, P. M. Comiskey, A. L. Yarin, Daniel Attinger

Mechanical Engineering Publications

A theoretical model predicting forward blood spatter patterns resulting from a round nose bullet gunshot wound is proposed. The chaotic disintegration of a blood layer located ahead and aside of the bullet is considered in the framework of percolation theory. The size distribution of blood drops is determined, which allows for the prediction of a blood spatter cloud being ejected from the rear side of the target where the bullet exits. Then, droplet trajectories are numerically predicted accounting for gravity and air drag, which is affected by the collective aerodynamic interaction of drops through air. The model predicts the number ...


An Instrument For In Situ Time-Resolved X-Ray Imaging And Diffraction Of Laser Powder Bed Fusion Additive Manufacturing Processes, Nicholas P. Calta, Jenny Wang, Andrew M. Kiss, Aiden A. Martin, Philip J. Depond, Gabriel M. Guss, Vivek Thampy, Anthony Y. Fong, Johanna Nelson Weker, Kevin H. Stone, Christopher J. Tassone, Matthew J. Kramer, Michael F. Toney, Anthony Van Buuren, Manyalibo J. Matthews May 2018

An Instrument For In Situ Time-Resolved X-Ray Imaging And Diffraction Of Laser Powder Bed Fusion Additive Manufacturing Processes, Nicholas P. Calta, Jenny Wang, Andrew M. Kiss, Aiden A. Martin, Philip J. Depond, Gabriel M. Guss, Vivek Thampy, Anthony Y. Fong, Johanna Nelson Weker, Kevin H. Stone, Christopher J. Tassone, Matthew J. Kramer, Michael F. Toney, Anthony Van Buuren, Manyalibo J. Matthews

Ames Laboratory Accepted Manuscripts

In situ X-ray-based measurements of the laser powder bed fusion (LPBF) additive manufacturing process produce unique data for model validation and improved process understanding. Synchrotron X-ray imaging and diffraction provide high resolution, bulk sensitive information with sufficient sampling rates to probe melt pool dynamics as well as phase and microstructure evolution. Here, we describe a laboratory-scale LPBF test bed designed to accommodate diffraction and imaging experiments at a synchrotron X-ray source during LPBF operation. We also present experimental results using Ti-6Al-4V, a widely used aerospace alloy, as a model system. Both imaging and diffraction experiments were carried out at the ...


Tip-Enhanced Raman Scattering Of Dna Aptamers For Listeria Monocytogenes, Siyu He, Hongyuan Li, Carmen L. Gomes, Dmitri V. Voronine May 2018

Tip-Enhanced Raman Scattering Of Dna Aptamers For Listeria Monocytogenes, Siyu He, Hongyuan Li, Carmen L. Gomes, Dmitri V. Voronine

Mechanical Engineering Publications

Optical detection and conformational mapping of aptamers are important for improving medical and biosensing technologies and for better understanding of biological processes at the molecular level. The authors investigate the vibrational signals of deoxyribonucleic acid aptamers specific to Listeria monocytogenes immobilized on gold substrates using tip-enhanced Raman scattering (TERS) spectroscopy and nanoscale imaging. The authors compare topographic and nano-optical signals and investigate the fluctuations of the position-dependent TERS spectra. They perform spatial TERS mapping with 3 nm step size and discuss the limitation of the resulting spatial resolution under the ambient conditions. TERS mapping provides information about the chemical composition ...


An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox Feb 2018

An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox

Chemical and Biological Engineering Publications

The extended quadrature method of moments (EQMOM) for the solution of population balance equations (PBE) is implemented in the open-source computational fluid dynamic (CFD) toolbox OpenFOAM as part of the OpenQBMM project. The moment inversion procedure was designed (Nguyen et al., 2016) to maximize the number of conserved moments in the transported moment set. The algorithm is implemented in a general structure to allow the addition of other kernel density functions defined on R+, and arbitrary kernels to describe physical phenomena involved in the evolution of the number density function. The implementation is verified with a set of zero-dimensional cases ...


Deformation, Lattice Instability, And Metallization During Solid-Solid Structural Transformations Under General Applied Stress Tensor: Example Of Si I -> Si Ii, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson Jan 2018

Deformation, Lattice Instability, And Metallization During Solid-Solid Structural Transformations Under General Applied Stress Tensor: Example Of Si I -> Si Ii, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson

Materials Science and Engineering Publications

Density functional theory (DFT) was employed to study the stress-strain behavior, elastic instabilities, and metallization during a solid-solid phase transformation (PT) between semiconducting Si I (cubic A4) and metallic Si II (tetragonal A5 structure) when subjected to a general stress tensor. With normal stresses (σ1, σ2, σ3) acting along ⟨110⟩, ⟨11¯0⟩, and ⟨001⟩, respectively, dictating the simulation cell, we determine combinations of 6 independent stresses that drive a lattice instability for the Si I→Si II PT, and a semiconductor-metal electronic transition. Metallization precedes the structural PT, hence, a stressed Si I can be a metal. Surprisingly, a stress-free ...