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Search Publications by: Ward L. Johnson (Fed)

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Displaying 26 - 50 of 88

High-Temperature Electromechanical Properties of CTGS

December 1, 2013
Author(s)
Ward L. Johnson, Michal Schulz, Holger Fritze
CTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting

Continuum-based free vibration of circular trigonal and isotropic plates

May 28, 2013
Author(s)
Ward L. Johnson, Paul R. Heyliger
The free vibration behavior of completely unrestrained elastic circular plates with trig- onal and isotropic material symmetry is studied using approximate solutions to the three- dimensional theory of linear elasticity. Of primary interest are 1) the

Nonlinear acoustic effects in multilayer ceramic capacitors

January 25, 2013
Author(s)
Ward L. Johnson, Sudook A. Kim, Timothy P. Quinn, Grady S. White
Nonlinear resonant acoustics was explored as an approach for nondestructively evaluating the susceptibility of BaTiO3-based multilayer ceramic capacitors to electrical failure during service. The acoustic nonlinearity was characterized through measurements

Vibrational modes of GaN nanowires in the gigahertz range

November 13, 2012
Author(s)
Ward L. Johnson, Sudook A. Kim, Roy H. Geiss, Colm Flannery, Kristine A. Bertness, Paul R. Heyliger
Monocrystalline nanowires offer an attractive basis for resonant nanoelectromechanical systems (NEMS) for a variety of applications, including mass and force sensing, and, in each of these applications, there are advantages to operation at frequencies

Thermogravimetric Analysis with a Heated Quartz Crystal Microbalance

August 11, 2012
Author(s)
Ward L. Johnson, Elisabeth Mansfield
Thermogravimetric analysis with an SC-cut quartz crystal microbalance (QCM) were demonstrated at temperatures in the range from 20 C to 450 C. A measurement system was built around a crystal sensor head that was mounted in a small tube furnace. Changes in

A thickness-shear MEMS resonator employing electromechanical transduction through a coplanar waveguide

May 21, 2012
Author(s)
Ward L. Johnson, Thomas M. Wallis, Pavel Kabos, Eduard Rocas, Juan C. Collado Gomez, Li-Anne Liew, Albert Davydov, Alivia Plankis, Paul R. Heyliger
The design, modeling, fabrication, and characterization of a vibrationally trapped thickness-shear MEMS resonator is presented. This device is intended to avoid various limitations of flexural MEMS resonators, including nonlinearity, clamping losses

Contributions to anelasticity in langasite and langatate

December 30, 2011
Author(s)
Ward L. Johnson, Sudook A. Kim, Christine F. Rivenbark, Satoshi Uda
Maximization of the quality factors Q of langasite (LGS) and langatate (LGT) is necessary for optimal performance of acoustic resonators of these materials in frequency-control and high-temperature sensing applications. In this report, measurements and

Effects of shape distortions and imperfections on mode frequencies and collective linewidths in nanomagnets

March 28, 2011
Author(s)
Hans T. Nembach, Justin M. Shaw, Thomas J. Silva, Ward L. Johnson, Sudook A. Kim, Robert D. McMichael, Pavel Kabos
We used Brillouin light scattering to show that shape distortions in Ni80Fe20 nanoelements can have a dramatic effect on the measured linewidth of certain modes. By intentionally introducing an amount of “egg-like” shape distortion to an ideal elliptical

Workshop on Quantitative Tools for Condition Assessment of Aging Infrastructure

October 14, 2010
Author(s)
Ward L. Johnson, Thomas A. Siewert, Jessica Terry, Dat Duthinh, Mark Iadicola, William E. Luecke, Joseph D. McColskey
The Quantitative Tools for Condition Assessment of Aging Infrastructure Workshop was held May 4-5, 2010, in Boulder, Colorado. It was organized by a team of researchers within the National Institute of Standards and Technology s (NIST) Materials Science

Elastic constants and dimensions of imprinted polymeric nanolines determined from Brillouin light scattering

January 18, 2010
Author(s)
Ward L. Johnson, Sudook A. Kim, Roy H. Geiss, Colm Flannery, Paul R. Heyliger, Christopher L. Soles, Wen-Li Wu, Chengqing C. Wang, Christopher M. Stafford, B D. Vogt
Elastic constants and cross-sectional dimensions of imprinted nanolines of poly(methyl methacrylate) (PMMA) on silicon are determined nondestructively from finite-element inversion analysis of dispersion curves of hypersonic acoustic modes of these