Surface roughness (R_a ) is an important parameter in determining the quality of surface finishing of any products obtained from the machining process. Surface roughness can be affected by several factors such as machining parameters, workpiece material properties, cutting tool parameters and machine tool conditions. In this study, the effects of machining parameters such as feed rate and cutting speed on the surface roughness was investigated for aluminium, mild steel and brass materials during the turning process using CNC Lathe machine. The experimental R_a values obtained were compared with the theoretical values with discrepancy ranging from 1.14 % to 113.71 %. From the study, it can be concluded that the surface roughness of materials will increases as the feed rate increases and decrease when higher cutting speed is applied.

This research work aims to investigate the presence of four nonlinear characteristics (i.e., hysteresis, saturation, creep, and uncertainty vibration) when a piezoelectric patch material acts as an actuator and sensor for the active vibration suppression of a cantilever beam. The parameters such as different operating frequencies and voltages are taken into account for the piezoelectric patch material characterization and the vibration before and after activation of a proportional–derivative–integral controller in an active vibration suppression system are measured. The effect of different proportional–derivative–integral controller tuning methods, frequency independent, and frequency dependency excitations are the three main contributions to evaluate the performance of active vibration suppression system. From the results, the piezoelectric actuator posed all the four nonlinearity effects while only three are observed in the sensor characteristics, and these effects increased significantly with the increase of operating frequencies and voltages. For the frequency-independent excitation of the active vibration suppression system, the vibration attenuation of the beam shows an improvement from low to higher excitation frequency, except at 500 Hz because of the saturation effect. In terms of controller performances, the proportional gain step-up method shows the best performance by scoring 3/5 of highest vibration attenuation percentages compared with manual and Ziegler–Nichols methods. For the frequency-dependent excitation, the effective frequency range for the active vibration suppression system is determined between 75 and 245 Hz with the highest vibration attenuation of 79.60% occurred at the second natural frequency of the beam.

Prolonged exposure to the orbital sander with high vibration level can lead to the Hand-arm Vibration Syndrome (HAVs). In order to attenuate the vibration when using the orbital sander, dynamic analysis of the orbital sander is carried out using coupled orbital sander-hand-arm model subjected to the Active Vibration Control (AVC). The orbital sander is modelled as a three-degree-of-freedom system where the values of the dynamic mass, stiffness and damping are derived from the experimental modal analysis and the single-degree-of-freedom of Reynolds and Soedel model is chosen to represent the hand-arm system. Various control schemes are applied in the AVC system including Proportional-Derivative (PD) and Active Force Control (AFC) techniques. Two disturbances are created for the system where the first disturbance is measured from the orbital sander operating condition and the second disturbance is modelled as a sine wave to test the robustness of the control schemes. The simulation result shows that the control scheme with AFC produced a superior result compared to the classical PD controller, even though under the influence of external disturbance with a vibration reduction of 99% and 88%, respectively.

In this paper, the vibration analysis in terms of modal and harmonic responses are investigated for the power station structure of Kenyir Dam in Terengganu, Malaysia. Modal analysis is carried out to provide the dynamic characteristics of the power station which includes the natural frequencies and mode shapes. Meanwhile, the harmonic response analysis is performed by applying the force to the structure to obtain the Frequency Response Function (FRF) in certain range of frequencies. A real scale three-dimensional (3D) model of the Kenyir Dam power station is constructed using SolidWorks software and imported to ANSYS software for the Finite Element (FE) analysis. A proper boundary condition is taken into consideration to demonstrate the real behaviour of the power station structure. From the results, six most significant natural frequencies and mode shapes including the FRF in all three axes are selected. The highest natural frequency value occurred at 5.4 Hz with the maximum deflection of 0.90361 m in the z axis direction. This value is important in order to verify whether the structure can overcome the resonance phenomenon from the external disturbance forces in the future.

Aeration is an important parameter in water filtration system as it allows the transfer of oxygen to water through turbulence effect which subsequently increases air entrainment in the water. For water treatment application, aeration efficiency is measured to ensure continuous re-oxygenation of the unfiltered water. Aside from aeration, this paper also studies the flow patterns through the use of particle image velocimetry (PIV) setup. Through the use of real scale down physical model laboratory study is performed using PIV to obtain the velocity profile. These velocity profiles will then be used to calculate the aeration efficiency of the water in a cascade aerator system. Based on the findings, the aeration efficiency obtained from the PIV experiment has a maximum value at the lowest point of the cascade aerator system with a value of 0.0139 due to increase in mass flow rate as it moves through the steps with velocity of 0.418 m/s. Therefore, in the design of a cascade aerator system, it is advisable to increase the number of steps since it will increase the aeration efficiency of the system.