Jedol Dayou - Profile on Academia.edu (original) (raw)

Papers by Jedol Dayou

Journal of Sound and Vibration, 2002

Tunable vibration absorbers are used to control vibration due to time-varying harmonic disturbanc... more Tunable vibration absorbers are used to control vibration due to time-varying harmonic disturbances. Either vibration which is local to the neutralizer, or global vibration of the host structure can be chosen as the quantity to be suppressed. In this paper, the latter is the subject of investigation, but using multiple neutralizers rather than a single device. It is shown that by positioning these devices carefully, the global vibration of a structure (as characterized by its kinetic energy) can be effectively reduced at each single frequency in the frequency range of interest, and is comparable to the performance of active control. A methodology on how to correctly position the devices, an on how to determine their optimum mass is suggested.

A comparison between active and semi-active global vibration control of structures

Journal of The Acoustical Society of America, 1999

Journal of Sound and Vibration, 2000

Noise & Vibration Worldwide, 2001

Applied Acoustics, 2003

A theoretical method has been previously proposed by the authors to optimize a tunable vibration ... more A theoretical method has been previously proposed by the authors to optimize a tunable vibration neutralizer for global vibration control. However, experimental verification of the tuning method has yet to be presented. This paper aims to do this. It is shown that by using the proposed optimization method, the tunable vibration neutralizer can be as effective as an active control device in reducing global vibration of a structure. One particularly interesting finding is that although the vibration neutralizer is a passive device which is incapable of supplying energy to a system, it appears to be as effective as active control in reducing the global vibration of a structure, even in the frequency range where the control device is required to supply energy. # .my (J. Dayou), mjb@isvr.soton.ac.uk (M.J. Brennan).

Proceedings of The Institution of Mechanical Engineers Part C-journal of Mechanical Engineering Science, 2001

Journal of Sound and Vibration, 2006

The vibration neutralizer has been used in many applications since invented. In many cases, an in... more The vibration neutralizer has been used in many applications since invented. In many cases, an ingenious design law called fixed-points theory was utilized in determining the optimum tuning and damping ratios of the device. However, those applications are limited to point response control of a relatively simple structure. There are some applications related to continuous structures but the purpose is for point response control, collocated or non-collocated. In this paper, the fixed-points theory is examined for global vibration control namely the control of the kinetic energy of a continuous structure. It is proven in this paper that the same design law is applicable for a more complicated purpose. The results presented in this paper may offer new ways of using the device. r

Review of Scientific Instruments, 2008

For vibration testing, discrete types of scanning laser Doppler vibrometer (SLDV) have been devel... more For vibration testing, discrete types of scanning laser Doppler vibrometer (SLDV) have been developed and have proven to be very useful. For complex structures, however, SLDV takes considerable time to scan the surface of structures and require large amounts of data storage. To overcome these problems, a continuous scan was introduced as an alternative. In this continuous method, the Chebyshev demodulation (or polynomial) technique and the Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. As an alternative, in this paper, the Hilbert-Huang transform approach is applied to impact excitation cases in terms of a numerical approach, where the vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a clamped-clamped beam was chosen as the test rig in the numerical simulation and real experiment. This paper shows that with additional innovative steps of using ideal bandpass filters and nodal point determination in the postprocessing, the Hilbert-Huang transformation can be used to create a better mode shape reconstruction even in the impact excitation case.

Journal of Nondestructive Evaluation, 2011

Operating Deflection Shapes (ODS) has emerged as one of the powerful techniques in vibration anal... more Operating Deflection Shapes (ODS) has emerged as one of the powerful techniques in vibration analysis to understand and to evaluate the absolute dynamic behaviour of a machine, component or an entire structure. Traditionally, accelerometers have been used to get the ODS of a structure. However, recent development shows that certain situation may not allow direct contact with the structure under investigation. Therefore, Scanning Laser Doppler Vibrometer (SLDV) has become popular in the investigation. In this paper, a new ODS Frequency Response Function (ODS FRF) for investigations using SLDV is formulated. The ODS FRF is used to construct the ODS of the structure. A new form of scale factor for the ODS FRF is also introduced to normalize the effects from variable excitation force. The importance of this scale factor is demonstrated on a beam and plate under the excitation of varying forces. It is found that the suggested ODS FRF and the scale factor give the desired result in comparison with theory.

Mechanics Based Design of Structures and Machines, 2006

A new hybrid method for automated frog sound identification by incorporating entropy and spectral... more A new hybrid method for automated frog sound identification by incorporating entropy and spectral centroid concept is proposed. Entropy has important physical implications as the amount of "disorder" of a system. This study explores the use of various definitions of entropies such as the Shannon entropy, Kolmogorov-Rényi entropy and Tsallis entropy as measure of information contents or complexity for the purpose of the pattern recognition of bioacoustics signal. Each of these definitions of entropies characterizes different aspects of the signal. The entropies are combined with other standard pattern recognition tools such as the Fourier spectral analysis to form a hybrid spectral-entropic classification scheme. The efficiency of the system is tested using a database of sound syllables are obtained from a number of species of Microhylidae frogs. Nonparametric k-NN classifier is used to recognize the frog species based on the spectral-entropic features. The result showed that the k-NN classifier based on the selected features is able to identify the species of the frogs with relativity good accuracy compared to features relying on spectral contents alone. The robustness of the developed system is also tested for different noise levels.

Applied Acoustics, 2011

A new hybrid method for automated frog sound identification, using spectral centroid, Shannon ent... more A new hybrid method for automated frog sound identification, using spectral centroid, Shannon entropy and Rényi entropy is proposed. The advantage of using entropy based information theoretic approach for analyzing complexity of bioacoustics signals in animal vocalization is discussed. Sound samples from nine species of Microhylidae frogs are first segmented into syllables. Fourier spectral centroid, Shannon entropy and Rényi entropy of the syllables are then determined. Finally, nonparametric k-th nearest neighbour (k-NN) classifier is used to recognize the frog species based on these three extracted features. Result shows that the k-NN classifier based on these selected features is capable to identify the species of the frogs with an average accuracy of 98%. It is found that the accuracy reduces significantly only when the noise levels higher than À20 dB.