john mccoy - Academia.edu (original) (raw)

Papers by john mccoy

Research paper thumbnail of On the relationship between the geometric and parabolic propagation models and an extension of both

Journal of the Acoustical Society of America, Dec 1, 1977

Research paper thumbnail of Transverse Horizontal Coherence and Low-Frequency Array Gain Limits in the Deep Ocean

Naval Research Lab. Report, Aug 9, 1983

Research paper thumbnail of Correcting the Kirchhoff rough boundary. Interaction model for scattering

Journal of the Acoustical Society of America, Nov 1, 1987

DDD12. High-resolution acoustic bottom roughness measurement in support of bottom echo interactio... more DDD12. High-resolution acoustic bottom roughness measurement in support of bottom echo interaction modeling. W. P. Dammann and C. A. Lauter (Ocean Acoustics Division, NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149) A high-resolution acoustic bottom profiler using an extremely narrow-beam, 3-MHz echo sounder was developed at the Ocean Acoustic Division of NOAA/AOML. The device was used to measure bottom 2:43 DDD18. Sound scattering from a randomly rough fluid-solid interface.

Research paper thumbnail of Propagation of radiation from a finite beam or source through an anisotropic random medium

Journal of the Acoustical Society of America, Dec 1, 1974

The long-range propagation of explosive signals and of 14and 111-Hz CW signals were studied exper... more The long-range propagation of explosive signals and of 14and 111-Hz CW signals were studied experimentally. The tow ran from a point near Antigua to the Grand Banks, a distance of about 2800 kin. The detonations were shallow and nearly turbation solution to become invalid. The coherence function for cylindrically spreading waves is compared with the corresponding solution for the plane wave case. Both the cylindrical and plane wave solutions are shown to have essentially the same range of validity.

Research paper thumbnail of On using dispersion characteristics to actively control transient broadband signals

Journal of the Acoustical Society of America, Oct 1, 1992

Research paper thumbnail of Pulsed signal coherence propagation in one‐dimensional dispersive waveguides

Journal of the Acoustical Society of America, Oct 1, 1991

Published by the Acoustical Society of America only. An ultrasonic attenuation spectroscopy syste... more Published by the Acoustical Society of America only. An ultrasonic attenuation spectroscopy system for the study of ultrasonic properties of food dispersion has been developed. The results of tests on castor oil are in good agreement with the literature values. Experiments on skimmed milk, semi-skimmed milk, full fat milk, and homogenized milk's ultrasonic attenuation spectra have been performed. The results demonstrate the effects of both fat content and fat globule particle size on the ultrasonic attenuation characteristics of milk.

Research paper thumbnail of Propagation through an anisotropic random medium. An integro–differential formulation

Journal of Mathematical Physics, Jul 1, 1976

In a previous paper [J. Math. Phys. 15, 1901 (1975)] we derived an equation governing the mutual ... more In a previous paper [J. Math. Phys. 15, 1901 (1975)] we derived an equation governing the mutual coherence function, {Γ̂}, of an initial plane wave signal propagating in an anisotropic random medium. In Eq. (49) of that paper we made a strong narrow-angle approximation which allowed us to derive an ordinary differential equation for {Γ̂}. Here we derive an integro–differential equation for {Γ̂} in which this approximation is not made. We show that for the horizontal scattering cases considered in the previous paper the approximation is valid. The vertical spectrum, however, is changed somewhat.

Research paper thumbnail of A Statistical Theory for Predicting Response of Materials That Possess a Disordered Structure

J iwvmmmm^mmmwmmwmmmmmmmmmmmmmm «w m^*™amimm9*™*mmmGm*mmmimmmm{ UNCLASSIFIED Security CI«i«ific»t... more J iwvmmmm^mmmwmmwmmmmmmmmmmmmmm «w m^*™amimm9*™*mmmGm*mmmimmmm{ UNCLASSIFIED Security CI«i«ific»tion fä'l&tWO DOCUMENT CONTROL DATA R&D fS»cur>(y ttmtaill (ion ol litt», body ol mhnracl mnd Indrth.g mnnoitilor muti b* tnftmd wh»r< ih» ovtrstl ftp.>f> It clmnltlmd) I. ORiaiNATiN« ACTIVITY (Ccq/onf author) It«. nrPORT •RCWKIT« CLAMICICATION Army Materials and Mechanics Research Center Watertown ; Massachusetts 021''2 i RtPONT TITLE Unclassified 26. cnoup

Research paper thumbnail of On the calculation of bulk properties of heterogeneous materials

Quarterly of Applied Mathematics, 1979

Research paper thumbnail of Effects of random heterogeneity on wave fields

The Journal of the Acoustical Society of America, 1988

A theory of wave propagation in random media must actually refer to a suite of predictive models ... more A theory of wave propagation in random media must actually refer to a suite of predictive models of the effects of a random heterogeneity. This is because a single general formalism, suitable for all stochastic experiments, would be too complicated for realistic scenarios to have any computational capability. Thus predictive models expressed in partial descriptors of a propagating radiation field, intended for specific experiments are acceptable. In this talk, a number of thought experiments for the propagation of waves in random media will be presented. The point of this is to highlight a richness in the observations one might expect to obtain as a result of random heterogeneity, and to provide a discussion of the possible physical bases for these observations. Appropriate descriptors of the radiation field for each of the thought experiments will be considered, as will be the derivation of prediction models expressed in these measures. A number of specific issues to be addressed a...

Research paper thumbnail of Scattering at a rough boundary to an inhomogeneous ocean

The Journal of the Acoustical Society of America, 1977

The development of randomly rough boundary interaction models formulated in terms of the (average... more The development of randomly rough boundary interaction models formulated in terms of the (averaged) acoustic intensity angular spectral density is considered. The principal advantage of these models is that they are completely compatible with a previously presented propagation model, which in turn is applicable for a general inhomogeneous medium and is well suited for numerical computation. Thus, taken together, the boundary interaction models and the propagation model provide a general wave theoretic approach to experiments containing both a rough boundary and an inhomogeneous sound-speed profile. Heretofore, such a general approach has been limited either to geometric theory analysis on to a perturbation analysis that is suitable for slightly rough boundaries. Two specific boundary interaction models are considered in some detail; one being a phenomenological model that can be termed a linear filter model, and one being a structural model based on Kirchhoff scattering theory. Any ...

Research paper thumbnail of Propagation of torsional waves in a circular elastic rod

Zeitschrift füur angewandte Mathematik und Physik ZAMP, 1964

Es werden unter Beniitzung der N~herung yon Berger vereinfachte Differentialgleichungen fiir gros... more Es werden unter Beniitzung der N~herung yon Berger vereinfachte Differentialgleichungen fiir grosse Deformationen elastischer Schalen hergeleitet und auf kreiszylindrische Schalen spezialisiert. Der rechtwinklige Streifen mit beliebigem Seitenverhgltnis und der unendlich lange Streifen werden, beide mit Randauflage, im Detail behandelt. Die numerischen Ergebnisse fiir den quadratischen Aussehnitt werden mit ~nderen be kannten L6sungen verglichen.

Research paper thumbnail of A new class of propagation models based on a factorization of the Helmholtz equation

Geophysical Journal of the Royal …, 1985

A new class of propagation models, which is based on a factorization of the Helmholtz equation, t... more A new class of propagation models, which is based on a factorization of the Helmholtz equation, that is, in principle, exact for rangeindependent environments, is presented. A numerical algorithm which makes use of the forward propagation feature of the propagation models and 'marches' the radiation field over a sequence of incremented range planes is derived and implemented. Numerical results of transmission loss as a function of range are obtained for a number of sample wave speed profiles for two members of the class of propagation models, one being an often-used parabolic wave theory and one being a high-frequency model that is new to our study. These results are compared to each other, to results obtained from an 'exact' numerical integration of the complete Helmholtz theory, and to results obtained using a WKB approximation to the Helmholtz equation formulation. The results demonstrate both the computational viability of the class of propagation models using the derived marching algorithm and very promising numerical agreement between the 'exact' results and those obtained using the high-frequency model.

Research paper thumbnail of The use of strain gradient theory for analysis of random media

International Journal of Solids and Structures

In this paper we consider the equations governing the response to a forcing field of an infinite ... more In this paper we consider the equations governing the response to a forcing field of an infinite statistically homogeneous medium with small fluctuations in the constants of elasticity. These equations were previously derived by Beran and McCoy [l]. The solution is obtained for the problem of a point force in an infinite medium and an analysis is presented to determine the ability of first strain gradient theory to approximate this solution. It is shown that a valid approximation can be obtained for the "slowfy" varying (in space) portion of the solution only if the square of the lengths introduced in gradient theory for an isotropic centrosymmetric material are negative. This requirement violates the requirement that the strain energy density of the gradient theory be positive definite. Further consequences of choosing these lengths to be imaginary are considered. The value of going to higher order gradient theories is also discussed.

Research paper thumbnail of Active Control of Flexible Space Structures Using the Nitinol Shape Memory Actuators

Research paper thumbnail of A study of the effective properties of mass and stiffness microstructures—a multiresolution approach

Quarterly of Applied Mathematics

Research paper thumbnail of Extensional Waves Along the Edge of an Elastic Plate

A solution of second-order equations of extensional motion of plates is obtained for waves travel... more A solution of second-order equations of extensional motion of plates is obtained for waves traveling along a free edge. The usual Rayleigh-type wave is found to become more and more confined to the edge of the plate as the frequency increases. Above a certain frequency another edge wave is found.

Research paper thumbnail of Another interpretation and derivation of one-way wave theories

Wave Motion, May 31, 1990

An alternative interpretation of one-way wave theory equivalents to a governing two-way formulati... more An alternative interpretation of one-way wave theory equivalents to a governing two-way formulation, which can be argued for range-independent environments, shows the equivalence requires a detailed specification of a boundary value problem. Thus, a distinction is to be made with the more common interpretation in which the equivalence appears to be based in terms of the governing two-way equation alone. The alternative interpretation is argued to he significant for extending one-way scalar wave theory equivalents to the Helmholtz equation, to obtain one-way seismic wave theory equivalents to the equations of linear elastodynamics. The alternative interpretation also provides a framework for the construction of approximate one-way wave theories and two such theories are considered for the Helmholtz equation.

Research paper thumbnail of Mean Field Variations in Random Media

UnclassifjNrt-15a. DECLASSIFICATION/DOWNGRADING SCHEDULE »A 16. DISTRIBUT|b{LJl»*TE1»eW Approved ... more UnclassifjNrt-15a. DECLASSIFICATION/DOWNGRADING SCHEDULE »A 16. DISTRIBUT|b{LJl»*TE1»eW Approved for public release; distribution unlimited. 17. DISTRIBUTION STATEMENT (ol the abstract entered In Block 10, it dltlarent horn Repon D D C qpSEtmOEE MAY 24 19TT " ; LUlESElHrDTSlB 5"-3i KA cy D 18. SUPPLEMENTARY NOTES The findings in this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents. 19. KEY WORDS (Continue on reverse aide it neceaaary and identity by block number) Composite Materials, Statistical Continuum Theory, Random Media aO".-ABSTRACT (Continue on reverse aide It necessary and identity by block number) A brief review is provided of research to incorporate more detailed information of substructure geometry, when compared to volume fraction information, in bounds on the effective property measures of composite materials. This review motivates i^ome of the work carried out during the tenure of the grants under discussionT"*In addition, we discuss., the need for a coherence function formulation of stress waves in randomly heterogeneous materials, and some steps taken toward developing this formulation.

Research paper thumbnail of The factorized Helmholtz equation - The construction of direct and inverse wave propagation theories

Research paper thumbnail of On the relationship between the geometric and parabolic propagation models and an extension of both

Journal of the Acoustical Society of America, Dec 1, 1977

Research paper thumbnail of Transverse Horizontal Coherence and Low-Frequency Array Gain Limits in the Deep Ocean

Naval Research Lab. Report, Aug 9, 1983

Research paper thumbnail of Correcting the Kirchhoff rough boundary. Interaction model for scattering

Journal of the Acoustical Society of America, Nov 1, 1987

DDD12. High-resolution acoustic bottom roughness measurement in support of bottom echo interactio... more DDD12. High-resolution acoustic bottom roughness measurement in support of bottom echo interaction modeling. W. P. Dammann and C. A. Lauter (Ocean Acoustics Division, NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149) A high-resolution acoustic bottom profiler using an extremely narrow-beam, 3-MHz echo sounder was developed at the Ocean Acoustic Division of NOAA/AOML. The device was used to measure bottom 2:43 DDD18. Sound scattering from a randomly rough fluid-solid interface.

Research paper thumbnail of Propagation of radiation from a finite beam or source through an anisotropic random medium

Journal of the Acoustical Society of America, Dec 1, 1974

The long-range propagation of explosive signals and of 14and 111-Hz CW signals were studied exper... more The long-range propagation of explosive signals and of 14and 111-Hz CW signals were studied experimentally. The tow ran from a point near Antigua to the Grand Banks, a distance of about 2800 kin. The detonations were shallow and nearly turbation solution to become invalid. The coherence function for cylindrically spreading waves is compared with the corresponding solution for the plane wave case. Both the cylindrical and plane wave solutions are shown to have essentially the same range of validity.

Research paper thumbnail of On using dispersion characteristics to actively control transient broadband signals

Journal of the Acoustical Society of America, Oct 1, 1992

Research paper thumbnail of Pulsed signal coherence propagation in one‐dimensional dispersive waveguides

Journal of the Acoustical Society of America, Oct 1, 1991

Published by the Acoustical Society of America only. An ultrasonic attenuation spectroscopy syste... more Published by the Acoustical Society of America only. An ultrasonic attenuation spectroscopy system for the study of ultrasonic properties of food dispersion has been developed. The results of tests on castor oil are in good agreement with the literature values. Experiments on skimmed milk, semi-skimmed milk, full fat milk, and homogenized milk's ultrasonic attenuation spectra have been performed. The results demonstrate the effects of both fat content and fat globule particle size on the ultrasonic attenuation characteristics of milk.

Research paper thumbnail of Propagation through an anisotropic random medium. An integro–differential formulation

Journal of Mathematical Physics, Jul 1, 1976

In a previous paper [J. Math. Phys. 15, 1901 (1975)] we derived an equation governing the mutual ... more In a previous paper [J. Math. Phys. 15, 1901 (1975)] we derived an equation governing the mutual coherence function, {Γ̂}, of an initial plane wave signal propagating in an anisotropic random medium. In Eq. (49) of that paper we made a strong narrow-angle approximation which allowed us to derive an ordinary differential equation for {Γ̂}. Here we derive an integro–differential equation for {Γ̂} in which this approximation is not made. We show that for the horizontal scattering cases considered in the previous paper the approximation is valid. The vertical spectrum, however, is changed somewhat.

Research paper thumbnail of A Statistical Theory for Predicting Response of Materials That Possess a Disordered Structure

J iwvmmmm^mmmwmmwmmmmmmmmmmmmmm «w m^*™amimm9*™*mmmGm*mmmimmmm{ UNCLASSIFIED Security CI«i«ific»t... more J iwvmmmm^mmmwmmwmmmmmmmmmmmmmm «w m^*™amimm9*™*mmmGm*mmmimmmm{ UNCLASSIFIED Security CI«i«ific»tion fä'l&tWO DOCUMENT CONTROL DATA R&D fS»cur>(y ttmtaill (ion ol litt», body ol mhnracl mnd Indrth.g mnnoitilor muti b* tnftmd wh»r< ih» ovtrstl ftp.>f> It clmnltlmd) I. ORiaiNATiN« ACTIVITY (Ccq/onf author) It«. nrPORT •RCWKIT« CLAMICICATION Army Materials and Mechanics Research Center Watertown ; Massachusetts 021''2 i RtPONT TITLE Unclassified 26. cnoup

Research paper thumbnail of On the calculation of bulk properties of heterogeneous materials

Quarterly of Applied Mathematics, 1979

Research paper thumbnail of Effects of random heterogeneity on wave fields

The Journal of the Acoustical Society of America, 1988

A theory of wave propagation in random media must actually refer to a suite of predictive models ... more A theory of wave propagation in random media must actually refer to a suite of predictive models of the effects of a random heterogeneity. This is because a single general formalism, suitable for all stochastic experiments, would be too complicated for realistic scenarios to have any computational capability. Thus predictive models expressed in partial descriptors of a propagating radiation field, intended for specific experiments are acceptable. In this talk, a number of thought experiments for the propagation of waves in random media will be presented. The point of this is to highlight a richness in the observations one might expect to obtain as a result of random heterogeneity, and to provide a discussion of the possible physical bases for these observations. Appropriate descriptors of the radiation field for each of the thought experiments will be considered, as will be the derivation of prediction models expressed in these measures. A number of specific issues to be addressed a...

Research paper thumbnail of Scattering at a rough boundary to an inhomogeneous ocean

The Journal of the Acoustical Society of America, 1977

The development of randomly rough boundary interaction models formulated in terms of the (average... more The development of randomly rough boundary interaction models formulated in terms of the (averaged) acoustic intensity angular spectral density is considered. The principal advantage of these models is that they are completely compatible with a previously presented propagation model, which in turn is applicable for a general inhomogeneous medium and is well suited for numerical computation. Thus, taken together, the boundary interaction models and the propagation model provide a general wave theoretic approach to experiments containing both a rough boundary and an inhomogeneous sound-speed profile. Heretofore, such a general approach has been limited either to geometric theory analysis on to a perturbation analysis that is suitable for slightly rough boundaries. Two specific boundary interaction models are considered in some detail; one being a phenomenological model that can be termed a linear filter model, and one being a structural model based on Kirchhoff scattering theory. Any ...

Research paper thumbnail of Propagation of torsional waves in a circular elastic rod

Zeitschrift füur angewandte Mathematik und Physik ZAMP, 1964

Es werden unter Beniitzung der N~herung yon Berger vereinfachte Differentialgleichungen fiir gros... more Es werden unter Beniitzung der N~herung yon Berger vereinfachte Differentialgleichungen fiir grosse Deformationen elastischer Schalen hergeleitet und auf kreiszylindrische Schalen spezialisiert. Der rechtwinklige Streifen mit beliebigem Seitenverhgltnis und der unendlich lange Streifen werden, beide mit Randauflage, im Detail behandelt. Die numerischen Ergebnisse fiir den quadratischen Aussehnitt werden mit ~nderen be kannten L6sungen verglichen.

Research paper thumbnail of A new class of propagation models based on a factorization of the Helmholtz equation

Geophysical Journal of the Royal …, 1985

A new class of propagation models, which is based on a factorization of the Helmholtz equation, t... more A new class of propagation models, which is based on a factorization of the Helmholtz equation, that is, in principle, exact for rangeindependent environments, is presented. A numerical algorithm which makes use of the forward propagation feature of the propagation models and 'marches' the radiation field over a sequence of incremented range planes is derived and implemented. Numerical results of transmission loss as a function of range are obtained for a number of sample wave speed profiles for two members of the class of propagation models, one being an often-used parabolic wave theory and one being a high-frequency model that is new to our study. These results are compared to each other, to results obtained from an 'exact' numerical integration of the complete Helmholtz theory, and to results obtained using a WKB approximation to the Helmholtz equation formulation. The results demonstrate both the computational viability of the class of propagation models using the derived marching algorithm and very promising numerical agreement between the 'exact' results and those obtained using the high-frequency model.

Research paper thumbnail of The use of strain gradient theory for analysis of random media

International Journal of Solids and Structures

In this paper we consider the equations governing the response to a forcing field of an infinite ... more In this paper we consider the equations governing the response to a forcing field of an infinite statistically homogeneous medium with small fluctuations in the constants of elasticity. These equations were previously derived by Beran and McCoy [l]. The solution is obtained for the problem of a point force in an infinite medium and an analysis is presented to determine the ability of first strain gradient theory to approximate this solution. It is shown that a valid approximation can be obtained for the "slowfy" varying (in space) portion of the solution only if the square of the lengths introduced in gradient theory for an isotropic centrosymmetric material are negative. This requirement violates the requirement that the strain energy density of the gradient theory be positive definite. Further consequences of choosing these lengths to be imaginary are considered. The value of going to higher order gradient theories is also discussed.

Research paper thumbnail of Active Control of Flexible Space Structures Using the Nitinol Shape Memory Actuators

Research paper thumbnail of A study of the effective properties of mass and stiffness microstructures—a multiresolution approach

Quarterly of Applied Mathematics

Research paper thumbnail of Extensional Waves Along the Edge of an Elastic Plate

A solution of second-order equations of extensional motion of plates is obtained for waves travel... more A solution of second-order equations of extensional motion of plates is obtained for waves traveling along a free edge. The usual Rayleigh-type wave is found to become more and more confined to the edge of the plate as the frequency increases. Above a certain frequency another edge wave is found.

Research paper thumbnail of Another interpretation and derivation of one-way wave theories

Wave Motion, May 31, 1990

An alternative interpretation of one-way wave theory equivalents to a governing two-way formulati... more An alternative interpretation of one-way wave theory equivalents to a governing two-way formulation, which can be argued for range-independent environments, shows the equivalence requires a detailed specification of a boundary value problem. Thus, a distinction is to be made with the more common interpretation in which the equivalence appears to be based in terms of the governing two-way equation alone. The alternative interpretation is argued to he significant for extending one-way scalar wave theory equivalents to the Helmholtz equation, to obtain one-way seismic wave theory equivalents to the equations of linear elastodynamics. The alternative interpretation also provides a framework for the construction of approximate one-way wave theories and two such theories are considered for the Helmholtz equation.

Research paper thumbnail of Mean Field Variations in Random Media

UnclassifjNrt-15a. DECLASSIFICATION/DOWNGRADING SCHEDULE »A 16. DISTRIBUT|b{LJl»*TE1»eW Approved ... more UnclassifjNrt-15a. DECLASSIFICATION/DOWNGRADING SCHEDULE »A 16. DISTRIBUT|b{LJl»*TE1»eW Approved for public release; distribution unlimited. 17. DISTRIBUTION STATEMENT (ol the abstract entered In Block 10, it dltlarent horn Repon D D C qpSEtmOEE MAY 24 19TT " ; LUlESElHrDTSlB 5"-3i KA cy D 18. SUPPLEMENTARY NOTES The findings in this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents. 19. KEY WORDS (Continue on reverse aide it neceaaary and identity by block number) Composite Materials, Statistical Continuum Theory, Random Media aO".-ABSTRACT (Continue on reverse aide It necessary and identity by block number) A brief review is provided of research to incorporate more detailed information of substructure geometry, when compared to volume fraction information, in bounds on the effective property measures of composite materials. This review motivates i^ome of the work carried out during the tenure of the grants under discussionT"*In addition, we discuss., the need for a coherence function formulation of stress waves in randomly heterogeneous materials, and some steps taken toward developing this formulation.

Research paper thumbnail of The factorized Helmholtz equation - The construction of direct and inverse wave propagation theories