Advances in Mechanical and Manufacturing Engineering

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Authors: Harijono Djojodihardjo, Muljo Widodo Kartidjo
Abstract: Flapping Wing Micro Air Vehicles (FWMAV) and Quad-Rotor Micro Air Vehicles (QRMAV) are strategic for many applications, applications, ranging from control device test bed to perform difficult tasks as well as to perform surveillance mission to unreachable places. While salient features and functional significance of the various components in the flying bio-systems can be synthesized into a simplified and generic and simplified model of a flapping Bi-Wing and Quad-Wing Ornithopter; Quad-Rotor Micro Air Vehicle could be utilized for developing emerging Personal Air Vehicle (PAV) technologies. Theoretical development of Bio-Inspired Bi-Wing and Quad-Wing Flapping Wing Micro Air Vehicles is outlined by considering the motion of a three-dimensional rigid and thin wing in flapping and pitching motion with phase lag. Basic Unsteady Aerodynamic Approach incorporating viscous effect and leading-edge suction is utilized. Theoretical and experimental development of a new variant of Quad-Rotor Micro Air Vehicles is also outlined. The theoretical development of these potential MAVs is carried out using a first principle approach starting from the Euler-Newton equations of motion.
Authors: Harijono Djojodihardjo
Abstract: Flow control for enhanced aerodynamic performance have been utilized for enhanced lift, reduced drag and delay of stall at higher angle of attack. To this end, techniques such as continuous, synthetic and pulsed jets, compliant surface, vortex-cell, Coănda jet and the like have been developed and applied to alter the behavior of airfoils, wings, and bodies and other aerodynamic components. Two such techniques are here assessed as potentially promising technique in the framework of airfoil surface blowing circulation enhancement, i.e. Coănda-jet circulation enhancement and vortex-cell. Their progress and development in influencing the effectiveness and configuration of airfoil surface blowing for circulation enhancement of aerodynamic surfaces are discussed, using fundamental principles and CFD technique.
Authors: Abdul Hakim Abdullah, Zamir A. Zulkefli
Abstract: This study presents the assessment of the quality of speech intelligibility of two Malaysian mosques and the results are used to develop a set of general acoustical guidelines to be used in the design of a mosque. Two mosques were selected for the research: Masjid UPM and the Masjid Jamek. The objective of the research is to enable the comparison of the acoustics and speech intelligibility between the mosques as function of the size, volume, occupancy and other parameters of the main prayer hall on the acoustic and speech intelligibility of the respective mosques. The reverberation time (RT60), speech level (SL), background noise (BN), signal-to-noise ratio (S/N ratio) were determined and are used to develop the speech transmission index (STI) and rapid transmission index (RASTI) prediction models for both mosques. It was observed from the results that the RT60, STI and RASTI values shows better performance over number of occupancy for both mosques. Furthermore, the BN and SL results were visualized using the spatial distribution patterns (SDP) of the main hall. The results of the analysis show that the overall acoustic and speech quality of Masjid Jamek is better when compared to the overall acoustic and speech quality of Masjid UPM. These results are then used to develop a set of design recommendations to ensure adequate speech intelligibility quality a mosque.
Authors: Muhammad Kusni, Benjamin Soenarko, Harijono Djojodihardjo
Abstract: The commercial feasibility of active noise control (ANC) is very promising due to its capability beyond passive noise control (PNC). To some extent ANC becomes a complement of PNC. The active noise reduction is also capable and beneficial in reducing noise selectively. However, the active noise reduction using a conventional secondary source can become very complicated if a significant noise level reduction is required, since a large number of secondary sources will be needed. The active noise reduction is also less effective for reducing high-frequency noise. With such perspectives, a novel approach has been developed using a multipole secondary source to addressthe problems mentioned. In addition, the multipole secondary source will be used for numerical simulation of noise reduction in of propeller noise source in a free field.
Authors: Teng Sheng Su, Chen Far Hung, Shu Hua Chang, Ting Hao Wu, Luh Maan Chang
Abstract: In this paper a new type of semi-active vibration absorber has been developed. The vibration absorber consists of mass block, cantilever beam, magnet lock system, vibration and distance sensors, controller and servo motor. The mass block is fixed on the tip of cantilever beam, and the control process is driven by a servo motor and a transmit gears. Portion of cantilever was cut in form of gear tracks, which can be driven by servo motor through transmit gear to regulate the length of the cantilever beam, and the natural frequency of absorber will also be regulated. After the mass locates in right position (i.e. the natural frequency of absorber is in assigned condition), the magnetic lock will clamp the cantilever beam. The design has the benefit of simplified control system, and extra unknown vibration modes will be averted. A fabrication prototype of the proposed semi-active vibration absorber is constructed and tested to demonstrate the application and modeling of the new cantilever beam damper. By performing the experimental work, the semi-active vibration control system is designed not only for reduce vibration level in resonant condition, but also considered for vibration attenuation in non-resonant conditions.
Authors: Khairil Anas Md Rezali, Michael J. Griffin
Abstract: In International Standard 10819 (1996), the requirements for a glove to be considered an anti-vibration glove are determined by the transmission of vibration to the palm of the hand. The transmission of vibration to a finger is very different from the transmission of vibration to the palm, but there are currently no requirements to measure the transmission of vibration through gloves to the fingers. This study investigated the effects of material dynamic properties on the transmission of vibration to the palm of the hand and to the fingers. Two materials (foam material from one anti-vibration glove and gel material from another anti-vibration glove) were investigated. Subjects placed their palms or index fingers on the material and pushed down with a force of 10 N while the transmission of random vibration was measured over the frequency range 5 to 500 Hz. At frequencies greater than 20 Hz, both materials attenuated vibration to the palm of the hand but amplified vibration to the finger. The study shows that the materials in gloves can both attenuate and amplify the transmission of vibration, depending on the material, the frequency of vibration, and the location on the hand (palm or finger).
Authors: A. Hamdan, Faizal Mustapha, Kamarul Arifin Ahmad, A.S.M. Rafie, Mohamed Thariq Hameed Sultan, M.R. Ishak
Abstract: Wind energy is one of the renewable energy sources which the trend is positive and increasing year by year. This technology applied widely in several regions in the world and already has maturity in technology, good infrastructure and relative cost competitiveness. The application of structural health monitoring (SHM) is crucial especially to evaluate the performance of wind turbine in real time assessment. Furthermore, the smart material in SHM can be utilized as micro energy harvester as well. However, the application of SHM and micro energy harvester for wind turbine is still premature especially in SHM embedded or bonded strategy. Several issues are highlighted such as SHM material selection, wind turbine selection and the issue in micro energy harvester. The issues are discussed and compared with the recent finding in this review. Several recommendations are suggested for future study especially on the application of micro energy harverster.
Authors: Nikolaos Dervilis, A.C.W. Creech, A.E. Maguire, Ifigeneia Antoniadou, R.J. Barthorpe, Keith Worden
Abstract: Reliability of offshore wind farms is one of the key areas for the successful implementation of these renewable power plants in the energy arena. Failure of the wind turbine (WT) in general could cause massive financial losses but especially for structures that are operating in offshore sites. Structural Health Monitoring (SHM) of WTs is essential in order to ensure not only structural safety but also avoidance of overdesign of components that could lead to economic and structural inefficiency. A preliminary analysis of a machine learning approach in the context of WT SHM is presented here; it is based on results from a Computational Fluid Dynamics (CFD) model of Lillgrund Wind farm. The analysis is based on neural network regression and is used to predict the measurement of each WT from the measurements of other WTs in the farm. Regression model error is used as an index of abnormal response.
Authors: Ifigeneia Antoniadou, Thomas P. Howard, R.S. Dwyer-Joyce, Matthew B. Marshall, Jack Naumann, Nikolaos Dervilis, Keith Worden
Abstract: Different signal processing methods are applied to experimental data obtained from a rolling element bearing rig in order to perform damage detection. Among these methods the Teager-Kaiser energy operator is also proposed as a more novel approach. This energy operator is an amplitude-frequency demodulation method used in this paper as an alternative to the Hilbert Transform in order to perform envelope analysis on the datasets analysed.
Authors: S.T. Cheng, Nawal Aswan Abdul Jalil, Zamir A. Zulkefli
Abstract: Vibration based technique have so far been focused on the identification of structural damage. However, not many studies have been conducted on the corrosion identification on pipes. The objective of this paper is to identify corrosion on pipes from vibration measurements. A hollow pipe, 500 mm in length with 63.5 mm in diameter was subjected to impact loading using an impact hammer to identify the natural frequency of the tube in two conditions i) without any corrosion and ii) with an induced localized 40 mm by 40 mm corrosion at the middle of the pipe. The shift of natural frequencies of the structures under free boundary conditions was examined for each node of excitation. The results showed that there is a shift in natural frequency of the pipe, between 3 and 4 Hz near to the corrosion area. It can suggested that that the impact vibration is capable of identifying of localized corrosion on a hollow tube.

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