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Search Publications by: Ward L. Johnson (Fed)

Displaying 76 - 100 of 105

Elastic constants and internal friction of martensitic steel, ferritic-pearlitic steel, and a-iron

April 15, 2007

Author(s)

Sudook A. Kim, Ward L. Johnson

The elastic constants and internal friction of induction hardened and unhardened SAE 1050 plain-carbon steel were determined by acoustic resonance spectroscopy. The hardened specimen contained only martensite and the unhardened specimen was ferrite

Elastic constants and internal friction of martensitic steel, ferritic-pearlitic steel, and a-iron

January 2, 2007

Author(s)

Sudook A. Kim, Ward L. Johnson

Surface-plasmon enhancement of Brillouin light scattering from gold-nanodisk arrays on glass

January 1, 2007

Author(s)

Zhandos Utegulov, B. T. Draine, Sudook A. Kim, J. M. Shaw, Ward L. Johnson

Enhancement of Brillouin light scattering (BLS) at 532 nm was observed from Rayleigh-like and Sezawa-like acoustic modes of alkaline-earth boro-aluminosilicate glass covered with periodic arrays of gold nanodisks. This enhancement is larger than that

Characterization of Magnetic Properties at Edges by Edge Mode Dynamics

April 21, 2006

Author(s)

Brian B. Maranville, Robert McMichael, Sudook A. Kim, Ward L. Johnson, C A. Ross, J Cheng

We have used trapped spinwave or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field

Elastodynamic characterization of imprinted nanolines

April 3, 2006

Author(s)

Ward L. Johnson, Colm Flannery, Sudook A. Kim, Roy H. Geiss, Christopher Soles, Paul R. Heyliger

Experimental techniques employing Brillouin light scattering (BLS) and analytical techniques employing finite-element (FE) and Farnell-Adler models are being developed for characterizing acoustic modes and determining elastic moduli and dimensions of

Acoustic Modes and Elastic Properties of Polymeric Nanostructures

October 21, 2005

Author(s)

R Hartschuh, A Kisliuk, V N. Novikov, Alexei Sokolov, Paul R. Heyliger, Colm Flannery, Ward L. Johnson, Christopher Soles, Wen-Li Wu

Fabricating mechanically robust polymer structures with nanoscale dimensions is critical for a wide range of emerging technologies. The rigidity of such structures is expected to change as the feature sizes approach the characteristic dimensions of the

Brillouin light scattering from pumped uniform-precession and low-k magnons in Ni81Fe19

March 4, 2005

Author(s)

Ward L. Johnson, Sudook A. Kim, Stephen E. Russek, Pavel Kabos

A method is presented for performing Brillouin-light-scattering measurements on uniform-precession and low-wave-number (Iow-k) magnons excited by a microwave magnetic field in opaque magnetic specimens. The optical configuration is similar to that employed

ProfIles of material properties in inductlon-hardened steel determined through inversion of resonant acoustic measurements

January 3, 2005

Author(s)

Ward L. Johnson, Sudook A. Kim, S J. Norton

Electromagnetic-acoustic measurements of resonant frequencies of induction-hardened steel shafts were used in an inverse calculation to determine parameters of the radial variations in the shear constant and density, including the effects of material

Acoustic Loss in Langasite and Langanite

March 1, 2004

Author(s)

Ward L. Johnson, K Sudook, U Satoshi

Resonant ultrasonic loss 1/Q in plano-convex unplated Y-cut disks of langasite and langanite were measured as a function of freqeuncy and temperature with the aim of identifying dominant internal mechanisms that will degrade electronic oscillator

Analysis of Anelastic Dislocation Effects in the Presence of an Unknown Background

August 12, 2003

Author(s)

Ward L. Johnson

The general problem of analyzin- acoustic measurements of dislocation anelasticity in the presence of unknown background contributions is addressed for situations where material treatments induce changes in the physical parameters governing dislocation

Symmetrization of Ritz Approximation Functions for Vibrational Analysis of Trigonal Cylinders

April 1, 2003

Author(s)

Ward L. Johnson, Paul R. Heyliger

In the Ritz method of calculating vibrational normal modes, a set of finite series approximation functions provides a matrix eigenvalue equation for the coefficients in the series and the resonant frequency. The matrix problem usually can be block

Traction-Free Vibrations of Finite Trigonal Elastic Cylinders

April 1, 2003

Author(s)

Paul R. Heyliger, Ward L. Johnson

The unrestrained, traction-free vibrations of finite elastic cylinders with trigonal material symmetry are studied using two approaches, based on the Ritz method, which formulate the weak form of the equations of motion in cylindrical and retangular

Acoustic Damping in Langatate as a Function of Temperature, Frequency, and Mechanical Contact

October 1, 2002

Author(s)

Ward L. Johnson, Sudook A. Kim, Damian S. Lauria, R C. Smyth

Resonant acoustic damping in plano-convex (trapped-mode) langatate (La 3Ga 5.5Ta0 0.50 14) discs was measured at frequencies from 2 MHz to 18 MHz and temperatures from 130 K to 450 K. A broad anelastic relaxation peak was observed in the temperature