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Introduction

**Skills and Expertise**

## Publications

Publications (66)

William Rede Hawthorne was a pioneer in gas turbine aerodynamics and thermodynamics, a sought-after technology advisor to industry and government, and a generous and enthusiastic teacher who encouraged students to excel. His outstanding contributions included resolution of combustion problems that limited the operation of the original Whittle jet e...

R. E. D. Bishop was one of the founders of the Journal of Mechanical Engineering Science (JMES). He was a member of the journal's Editorial Panel for 27 years. This is an appreciation of his contribution to the formation and success of the Journal.

Introduction Wavelet Transforms Dilation Wavelets Malvar Wavelets Meyer Wavelets Harmonic Wavelets Discrete Harmonic Wavelet Transform Mean-Square Wavelet Maps Construction of Time-Frequency Maps Example of Time-Frequency Analysis References

Introduction Summary of Statistical Concepts Summary of Applied Mechanics Concepts Input–Output Response Relationships for Linear Systems Input–Output Response Relationships for other Systems Applications of Random Vibration Theory References

IntroductionProbability Distributions and AveragesCorrelation FunctionsSpectral AnalysisResponse of Linear SystemsNarrow-Band ProcessesFailure Due to Random VibrationResponse of Nonlinear SystemsReferences

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1963. MICROFICHE COPY AVAILABLE IN ENGINEERING. Vita. Includes bibliographical references (leaves 152-154). by D. E. Newland. Sc.D.

The unexpected pedestrian-excited vibration of London's Millennium Bridge was caused by its low damping and high live load. Several other examples of bridges which vibrate significantly when carrying a crowd of people have since come to light. This paper reviews results for the dynamic loading caused by moving pedestrians, for both vertical and lat...

Harmonic wavelet analysis is a tool that has been developed over the past 15 years for the analysis of non-stationary signals in the time–frequency domain. This paper discusses the use of this technique and its application to the problems of soil dynamics and earthquake engineering. Specific reference is made to the use of this technique in investi...

The feasibility of protecting tall buildings against progressive downwards collapse following catastrophic structural failure at high level is explored and various design suggestions made.

Centrifuge model experiments have generated complex transient vibration data. New algorithms for time-frequency analysis using harmonic wavelets provide a good method of analyzing these data. We describe how the experimental data have been collected and show typical time-frequency maps obtained by the harmonic wavelet algorithm. Some preliminary co...

Experimental records of acceleration time-history at several different heights in a centrifuged soil model have been analysed by the harmonic wavelet method to generate time-varying cross-spectra. These cross-spectra are compared with simulated results for a linear model. Local changes in the experimental cross-spectra, both amplitude and phase cha...

Four practical examples from mechanical engineering illustrate how wavelet theory has improved procedures for the spectra analysis of transient signals. New wavelet–based algorithms generate better time–frequency maps which trace how the spectra content of a signal changes with time. The methods are applicable to multi–channel data and time–varying...

It is difficult to generate high-definition time-frequency maps for rapidly changing transient signals. New details of the theory of harmonic wavelet analysis are described which provide the basis for computational algorithms designed to improve map definition. Features of these algorithms include the use of ridge identification and phase gradient...

New details of the theory of harmonic wavelets are described and provide the basis for computational algorithms designed to compute high-definition time-frequency maps. Examples of the computation of phase using the complex harmonic wavelet and methods of signal segmentation based on amplitude and phase are described.

This paper shows that there are three main categories of factors that make the optimum mechanical design of micro-systems different from macro-systems: scale effects, a limited range of materials, and a limited range of production processes. The combined effect of these factors can make the optimum configuration of a micro-system potentially very d...

Signal decomposition by time-frequency and time-scale mapping is an essential element of most diagnostic signal analysis. Is the wavelet method of decomposition any better than the short-time Fourier transform and Wigner-Ville methods? This paper explores the effectiveness of wavelets for diagnostic signal analysis. The author has found that harmon...

For vibration signal analysis, the objective is usually to extract frequency data from a signal and study how the signal's frequency content changes with time. Because wavelets are local functions of time, each with a predetermined frequency content, wavelet analysis provides a good means of doing this. As a result, practical wavelet analysis is gr...

The applications of wavelet transforms in vibrations and acoustics discussed in the Symposium on Transient Signal Processing and Wavelets in Vibrations and Acoustics are presented. Fast wavelet transform algorithms become as readily available and as effective as fast Fourier transform algorithms used in inverse filtering and wavelet analysis. These...

The discrete wavelet transform provides a new method for the analysis of vibration signals. It allows specific features of a signal to be localized in time by decomposing the signal into a family of basis functions of finite length, called wavelets. A particular property of the method is its ability to identify and isolate the fine structure of a s...

Wavelets provide a new tool for the analysis of vibration records. They allow the changing spectral composition of a nonstationary signal to be measured and presented in the form of a time-frequency map. The purpose of this paper, which is Part 1 of a pair, is to introduce and review the theory of orthogonal wavelets and their application to signal...

Wavelet maps provide a graphical picture of the frequency composition of a vibration signal. This paper, which is Part 2 of a pair, describes their construction and properties. In the case of harmonic wavelets, there are close similarities between wavelet maps and sonograms. A range of practical examples illustrate how the wavelet method may be app...

Wavelet analysis allows a signal f(x) to be decomposed into a family of orthogonal functions whose members have different scales and different positions along the x axis. There has been a great deal of research into the theory of dilation wavelets, which arise from the recursive solution of a special class of difference equation, and which cannot b...

A two-dimensional model for computing contacts and motions of granular particles of different shapes, sizes and material properties is presented. The primary aim of this model is to achieve a high degree of computational efficiency, to allow simulations to be performed very rapidly on a modest sequential machine. The important features of the model...

A new harmonic wavelet is suggested. Unlike wavelets generated by
discrete dilation equations, whose shape cannot be expressed in
functional form, harmonic wavelets have the simple structure w(x) =
{exp(i4π x)-exp(i2π x)}/i2π x. This function w(x) is
concentrated locally around x = 0, and is orthogonal to its own unit
translations and octave dilati...

Fundamental concepts frequency response of linear systems general response properties matrix analysis natural frequencies and mode shapes singular and defective matrices numerical methods for modal analysis response functions application of response functions - Fourier transforms discrete response calculations systems with symmetric matrices - Lang...

Many buildings near railways are mounted on rubber springs to isolate them from ground vibration. This paper reviews the theory of resiliently mounted buildings and discusses recent calculations of the effects of (a) different damping models and (b) piled foundations. The paper also describes site measurements in London and laboratory tests in Camb...

As part of a study of the road forces generated by commercial vehicles, the authors have been concerned with numerical models of road surface topography. The objective is to provide realistic road inputs for numerical vehicle models in order to simulate wheel-road interaction.

This paper describes two theoretical calculations of the fluctuating spin creep of a railway wheel rolling on straight track. The first calculation is of the transient spin moment which occurs when a constant spin creep angular velocity is applied suddenly to a rolling wheel. This may occur, for example, when a wheel passes over a discontinuity in...

The cause of the Flixborough explosion was traced to some temporary pipework. A bypass pipe assembly collapsed, allowing large quantities of volatile cyclohexane to escape. At an early stage in the accident investigation, it was realized that this pipework must have failed, but the mechanism by which it had done so was not apparent. A detailed expe...

The deflection equation for the buckling of an initially straight elastic column subjected to external or internal pressure is derived for the case when the pressure and the area of the column may vary along its length. Appar-ently this equation has not been reported in the literature previously.

This paper is a theoretical study of the whirling of a cantilever elastic shaft subjected to external pressure. The whirling speeds are shown to depend on the variation of pressure and area along the shaft and the lowest whirling speed is solved approximately by an energy method for a number of cases. When the external pressure is high enough., its...

It is shown that an unstable bending wave may be excited in an elastically supported beam by a travelling inertia load. Since the occurrence of this dynamic instability reduces the axial buckling load of the beam, the result is relevant to present studies of the temperature buckling of continuous welded railway track.

The equation of mean power flow between two groups of randomly excited oscillators is derived from first principles. Subject to the coupling satisfying certain requirements, it is shown that a new parameter—the average natural frequency shift of the oscillators owing to the coupling—determines the power flow between the two groups. Power flow is di...

The definition and use of coupling‐loss factors in the calculation of power flow between randomly excited systems is discussed, with particular reference to the paper cited.

If small non-linear terms couple the (linear) modes of a multidegree-of-freedom system, energy can flow from one mode to another and vice versa. In this paper a perturbation method is used to calculate the average rate of energy transfer between nonlinearly coupled modes. Each mode is assumed to be subjected to an independent source of stationary,...

Corrugated bellows expansion joints may buckle under internal pressure in the same way as an elastic strut may buckle under an axial load. This paper is concerned with the analysis of this phenomenon for the 'universal expansion joint' which incorporates two bellows joined by a length of rigid pipe. The principal conclusion is that, by providing a...

Centrifugal pendulums have been used for many years to limit the torsional vibration of reciprocating engines. Recently small pendulums, designed to swing through amplitudes of about 45 deg, have been tested for lightweight aircraft engines. These have not functioned properly, and have been found to swing through much larger angles than expected, d...

This thesis is in two parts. Part 1 is a comparative study of methods for the analysis of nonlinear vibrations. It is primarily concerned with forced vibrations, and is restricted to lumped parameter systems (systems with a finite number of degrees-of-freedom). Part 2 is the application of the most suitable of these methods to problems occurring in...