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Search Publications by: Ward L. Johnson (Fed)

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Displaying 51 - 75 of 103

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

Surface-plasmon-enhanced electric fields in two-dimensional arrays of gold nanodisks

August 4, 2008
Author(s)
Ward L. Johnson, Sudook A. Kim, Zhandos Utegulov, B. T. Draine
Electric-field distributions in two-dimensional arrays of gold nanodisks on Si3N4 membranes are modeled, using the discrete-dipole approximation, as a function of nanodisk diameter (20 − 50 nm), height (10 − 100 nm), ratio of the array spacing to diameter

Mode-selective acoustic spectroscopy of trigonal piezoelectric crystals

May 1, 2008
Author(s)
Ward L. Johnson, Carlos F. Martino, Sudook A. Kim, Paul R. Heyliger
A noncontacting electromagnetic-acoustic-resonance technique is presented for generating and detecting vibrational modes with prescribed symmetries in piezoelectric trigonal crystals with cylindrical geometry. This technique provides the experimental basis

Vibrational modes of nanolines

March 5, 2008
Author(s)
Paul R. Heyliger, Colm Flannery, Ward L. Johnson
Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a