S. Braun

Altered heart rate variability in panic disorder patients

Resting electrocardiographic recordings were obtained from 10 patients with panic disorder (PD) and 14 normal controls. Signal analysis of the beat-to-beat heart rate variability was performed by means of power spectrum analysis. The analysis revealed that patients with PD had marked reduction in the high-frequency peaks of the power spectrum densities. An Energy Ratio Index (ERI), which accurately differentiated between patients and controls, was calculated. In PD patients, a significant correlation was demonstrated between the clinical ratings and the energy ratios. Our findings suggest that decreased heart rate variability may be a characteristic of PD. The importance of this finding as a diagnostic marker and the underlying pathophysiological mechanisms need to be further explored.

The Signature Analysis of Sonic Bearing Vibrations

Those aspects of roller bearing vibrations are addressed which are of importance in machinery health monitoring. Mechanisms of signal generation and the signal modification introduced by struc- tural paths and instrumentation are reviewed. Examples of various vibration analyses show how correct interpretation of results neces- sitates knowledge about such modifications. The main signal processing methods, including some recently developed ones, are described, and their relationship to the signals generating mechanism and various modification mechanisms are discussed.

Analysis of repetitive mechanism signatures

Abstract A new signal decomposition for repetitive signatures is introduced. This is based on the concept of derived time series, produced by rearranging the original signal by using points one period apart. Time domain averaging is shown to be a special case of such rearrangement, and a second technique of variance analysis is presented. Applications to rotating machinery show that the decomposition can be very sensitive to various generating mechanisms, making them suitable for signature analysis of mechanical systems.

Signature Analysis Applied to Drilling

This paper investigates the relationship between drill life, the sound, and the drift forces produced by the drilling process. Tests were performed while drilling steel with 38 in. twist drills. As a tool life criterion, the wear of the drill lips was monitored. Typical signals are described, and various signal processing techniques presented in view of characterizing them. These include time, frequency, and amplitude domain techniques. It is shown that specific signal patterns that occur with increasing lip wear show definite trends which can be followed by some analysis techniques. A discrete point process, derived from the signal’s spectrum, has been found specifically valuable. Results shown for actual data using these signal analysis techniques seem to support a theory of drill wear mechanism which was reported recently.

Left Eigenvectors: Extraction From Measurements and Physical Interpretation

In this paper the extraction of left eigenvectors from measured frequency response functions is presented and discussed. It is shown that contrary to the extraction of right eigenvectors from measured response data, the extraction of left eigenvectors is inherently ill-posed when the same measured information is being used. The ill-posedness can result in a spatially oscillating additive component (short wavelength) appearing in the identified left eigenvectors, a property which is not described in existing literature on structural dynamics. Some well-known regularization methods are hence used to reduce the inaccuracies appearing in the extracted left eigenvectors. It is also shown that a further improvement in the accuracy of the solution can be achieved by making use of an approximation of the mass distribution combined with regularization. Throughout this paper, an attempt is made to provide a physical insight to the various aspects related to the left eigenvectors and their extraction. This includes (a) the interpretation of left eigenvectors as internal force distributions; (b) the inherent reason for the ill-conditioning, and (c) the spatial filtering of short wavelength achieved by regularization, yielding an improved estimate of the left eigenvectors.

Time and frequency identification methods in over-determined systems

Abstract An integrated discussion of time and frequency domain identification method is presented. A least square is sought in both cases, but an iterative procedure is used in the frequency domain in order to ‘unweight’ the least square problem. Over-determination is of value for both domains, and the theoretical background of the over-determination is given. A perturbation based procedure, using singular values is shown to enable the differentiation between true and mathematical parameters.

Crack Detection in Beams by Rank-Ordering of Eigen-Frequency Shifts

Abstract A method for non-destructive detection and location of slots and cracks in a beam using rank ordering of the reduction of natural frequencies is studied. It is shown theoretically and using computer simulation that the rank ordering of the eigen- frequency shifts is a function of the damage location but does not depend on the damage magnitude. This property is used to detect the damage location. Experimental results are presented from tests on perspex and aluminum beams damaged at different locations and different magnitudes. Good agreement is obtained between the theoretical and the experimental results.

Eigenproblem error bounds with application to symmetric dynamic system modification

Suppose A and B are two

Structural modifications in truncated systems by the Rayleigh-Ritz method

m \times m

Structural dynamic modifications using truncated data: Bounds for the eigenvalues

symmetric matrices. Let