Lee Kee Quen

The effectiveness of two-versus three-start helical strakes in suppressing VIV of flexible cylinder

The proposed paper investigates experimentally the effectiveness of strakes in suppressing the vortex-induced vibration (VIV) of a long flexible cylinder by varying the number of helix of the strakes, which differ from the previous studies that only focus on short rigid cylinder. The experiment was conducted in the towing tank with constant velocity under subcritical Reynolds number (0.14x104 - 1.37x104) by using a poly vinyl chloride cylinder with aspect ratio of 162. CCD cameras were installed to capture the amplitude vibration while the variation of tension was measured by using tension load-cell. The drag force coefficient and the cross-flow and in-line frequency response were obtained from the strain gauges. The purpose of the present study is to identify the main deficiency and advantage of a two-start helical strakes compare to a three-start helical strakes in reducing the VIV of a low mass ratio flexible riser. The experimental result shows that the two-start helical strakes perform well in mitigating the VIV in low reduced velocity range. However, its effectiveness in suppressing the vibration amplitude of flexible cylinder is far smaller than the three-start helical strakes. Substantial amplitude mitigation is found for the three-start helical strakes, but with significant amplification of drag at high reduced velocity, which is unfavourable. On the other hand, although the mean drag coefficient is slightly higher for the two-start helical strakes in the lock-in region, the drag force response is more consistent and independent to the velocity changes at high reduced velocity.

On Theoretical of Transmission Loss in Exhaust Muffler System

Exhaust muffler system iscommonly used to reduce noise associated with internal combustion engine exhausts.This paper presents a numerical analysis of transmission loss for exhaust muffler by using transfer matrix method. The objective of this study is to develop the computer program to predict the transmission loss of muffler.The influence of cross sectional area of pipe, effect of muffler length and temperature towards the transmission loss of muffler is discussed as well in present study. The efficiency and capabilities of the computing transmission loss is compared to the experiment results obtained from the previous established research paper.

Flat electroencephalography’s cluster centers movement tracking during epileptic seizure

Epilepsy is a term used for a chronic disorder caused by excessive and abnormal nerve cell activity within the brain. This dynamic process is often associated with electroencephalography (EEG), which is an electrophysical method to record the electrical activity of the brain. For epilepsy patients, their EEG signals are characterized by abnormal signal flow and large spikes. This shows the excessive electrical activity within the brain can be extracted thus locating problematic cells of epilepsy is possible. However, it is very challenging due to the complexity of the signals to be analyzed. Through fEEG, the signals can be viewed in a Cartesian plane which consists of EEG’s channels and cluster center of electrical potential during epilepsy. To date, no research has been done on across time-frame of fEEG. In order to gain better insight into the dynamic process of epilepsy, a dynamic study on the cluster center movement across time-frame is necessary. Therefore, this study to shows the tracking of cluster centers movements across time-frame of fEEG. This movement tracking is essentials to understand the behavior of epilepsy such as the patterns of electrical potential. Further studies on the model could potentially assist in locating the problematic cells caused by epilepsy.

Underwater Target Tracking of Offshore Crane System in Subsea Operations

Accurate underwater target tracking during subsea lowering is a complex technological problem in offshore installation and deep ocean mining. It involves the real-time motion compensation of both combined effects from flow-induced vibration on the cable-payload and wave-induced motions on the host vessel. A target tracking mechanism for a planar motion was theoretically derived and simulated in this paper under both regular and irregular wave motions. The simulation results have shown that the proposed target tracking system, by using PID controller integrated with hydrodynamic effects of both surface vessel and subsea payload, has followed the movable subsea target with small vicinity. The findings of this paper can be further implemented in the development of automatizing the subsea operations of the offshore crane system.

A study on structural system identification and damage detection for free vibration response using the wavelet transform

This paper presents a wavelet-based method of identification modal parameter and damage detection in a free vibration response. An algorithm for modal parameter identification and damage detection is purposed and complex Morlet wavelet is chosen as an analysis wavelet function. This paper only focuses on identification of natural frequencies of the structural system. The method utilizes both undamaged and damage experiment data of free vibration response of the truss structure system. Wavelet scalogram is utilizes for damage detection. The change of energy components for undamaged and damage structure is investigated from the plot of wavelet scalogram which corresponded to the detection of damage.

Analysis of Baffle Effect for Measuring Transmission Loss

Exhaust noise is one of the noise pollution to the environment and it will cause interference that may harm the activity or balance of human. A muffler is designed to minimize transmission caused by exhaust gases. In this paper, the principle of transfer matrix method is used to analyze the transmission loss. The method is used for developed source code programming to predict muffler performance. The result from programming show excellent agreement with the previous established research paper. This programming is applied for baffle effect to determine transmission loss.