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Lau S.T.W.,Multimedia University | Said M.R.,University Technical Malaysia Melaka | Yaakob M.Y.,University Technical Malaysia Melaka
Composite Structures | Year: 2012

Composite materials have been known for its low density, ease in fabrication, high structural rigidity, and wide range applications, i.e. aeronautic applications and automotive industry. Due to this, extensive studies had been conducted to evaluate its axial crushing ability to replace metallic materials. In this paper, it reviewed the usage of fibre reinforced plastic composite (FRP) as an energy absorption application device. Failure modes and geometrical designs such as shapes, geometry and triggering effect have been studied where these factors affected on peak load and specific energy absorption significantly. Accordingly, numerical analysis for axial crushing of affected factors had been simulated to predict the failure mechanisms of FRP composites. © 2011 Elsevier Ltd.


Khamis A.,National University of Malaysia | Khamis A.,University Technical Malaysia Melaka | Shareef H.,National University of Malaysia | Bizkevelci E.,Tubitak Uzay | Khatib T.,National University of Malaysia
Renewable and Sustainable Energy Reviews | Year: 2013

Islanding detection of distributed generations (DGs) is one of the most important aspects of interconnecting DGs to the distribution system. Islanding detection techniques can generally be classified as remote methods, which are associated with islanding detection on the utility sides, and local methods, which are associated with islanding detection on the DG side. This paper presents a survey of various islanding detection techniques and their advantages and disadvantages. The paper focused on islanding detection using a conventional and intelligent technique. A summary table that compares and contrasts the existing methods is also presented. © 2013 Elsevier Ltd. All rights reserved.


Anand T.J.S.,University Technical Malaysia Melaka | Shariza S.,University Technical Malaysia Melaka
Electrochimica Acta | Year: 2012

Thin films of molybdenum sulphoselenide, MoS xSe 2-x, (0 ≤ x ≤ 2) have been electrosynthesized on indium-tin-oxide (ITO)-coated glass and stainless steel substrates. The films were characterized for their structural, morphological and compositional characteristics. Their optical and semiconducting parameters were also analysed in order to determine the suitability of the thin films for photoelectrochemical (PEC)/solar cell applications. Structural analysis via X-ray diffraction (XRD) analysis reveals that the films are polycrystalline in nature. Scanning electron microscope (SEM) studies reveals the films were adherent to the substrate with uniform in nature which also confirmed by Transmission electron microscope (TEM). Compositional analysis via energy dispersive X-ray (EDX) technique confirms the presence of Mo, S and Se elements in the films. The optical studies show that the films are of direct bandgap. Results on the semiconductor parameters analysis of the films showed that the nature of the Mott-Schottky plots indicates that the films obtained are of n-type material. For all films, the semiconductor parameter values come in the better range of other transition metal chalcogenides which has proven that MoSSe thin films are capable as solar/PEC cell materials. © 2012 Elsevier Ltd. All rights reserved.


Shukor A.Z.,Yokohama National University | Shukor A.Z.,University Technical Malaysia Melaka | Fujimoto Y.,Yokohama National University
IEEE Transactions on Industrial Electronics | Year: 2014

This paper presents the direct-drive position control verification of a spiral motor in monoarticular configuration. The spiral motor is a newly developed high-thrust high-backdrivable direct-drive three-phase permanent-magnet motor with a unique 3-D structure. One of the possible uses of the spiral motor is to actuate musculoskeletal-like structure which is shown in animals and humans. This is achieved by indirectly actuating the elbow/shoulder joints via pulling/pushing the links by using a linear actuator. We describe the control methods for the direct drive of the spiral motor which are the decoupling control and independent control. Next, simulations were performed to assess the control parameter variation effects. Then, the experimental results confirm the validity of the control method in monoarticular position. The key element of the linear motion control of the spiral motor is the magnetic levitation (air gap between the stator and rotor) control and simultaneous angular motion control via vector d- and q-axis currents. © 1982-2012 IEEE.


Ifayefunmi O.,University Technical Malaysia Melaka
Thin-Walled Structures | Year: 2016

This paper examines the buckling of short mild steel cylindrical shells subjected to axial compression. Cylinders were joined together using Metal Inert Gas (MIG) welding process with radius-to-thickness ratio, R/t, ranging from 25 to 100. The axial length of the specimens were assumed to be 111.8 mm. Past result on axially compressed cylinder machined using Computer Numerically Controlled (CNC) machining is compared with fresh experimental results on MIG manufactured axially compressed cylinder. The paper contains a comparison between theoretical predictions, ABAQUS FE results and experimental data for axially compressed cylinder. Details about material testing and collapse test are provided. As compared to the CNC machined specimen, results indicates that there is a good agreement between theoretical prediction, ABAQUS FE results and experimental data for MIG manufactured cylinder with radius-to-thickness ratio, R/t ranging from 25 to 100, with difference ranging between -7% and +2%. © 2015 Elsevier Ltd. All rights reserved.


Salam Z.,University of Technology Malaysia | Ramli M.Z.,University Technical Malaysia Melaka
2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 | Year: 2012

In a typical photovoltaic (PV) power system, when part of the PV module is shaded, the bypass diode is activated to protect the module from hot-spot damages. As a result, the output power is reduced significantly because the power generated from the shaded module is totally unusable. In this paper, a simple circuit is proposed to increase the power yield of PV system under partial shading condition. The idea is to recover the power generated by the shaded module and then process it using power electronics circuit to become part of the output power. Consequently, the inclusion of the circuit enables the system to deliver more power compared to the bypass diode method. The concept is evaluated using Matlab-Simulink simulation and proven using an experimental test rig. The performance of the proposed circuit is compared with (1) PV system with bypass diode and (2) micro-inverter. The results show marked improvement in the efficiency, especially under heavy partial shading condition © 2012 IEEE.


Zhu Z.Q.,University of Sheffield | Mohd Jamil M.L.,University Technical Malaysia Melaka | Wu L.J.,University of Sheffield
IEEE Transactions on Industry Applications | Year: 2013

Unbalanced magnetic forces (UMFs) exist in permanent magnet machines with diametrically asymmetric windings, e.g., machines having pole and slot numbers differed by one and two, even when there is no rotor eccentricity. In machines having pole and slot numbers differed by two, the on-load UMF results only when the single-layer winding is employed and the number of coils is odd. This paper investigates the influence of slot and pole number combinations on the UMF by using an analytical method based on the finite-element predicted airgap flux densities. A UMF may be divided into two components due to the radial and circumferential traveling stresses. It is found that they are additive for machines having pole number 2p = 3k - 1, e.g., 8-pole/9-slot and 8-pole/6-slot, but partially canceling for machines having 2p = 3k + 1, e.g., 16-pole/15-slot and 16-pole/18-slot. Furthermore, due to the additive and canceling effects, for the same slot number, the machine having a smaller pole number exhibits a larger UMF when the slot/pole numbers differ by one, whereas the machine having a larger pole number exhibits a larger UMF when the slot/pole numbers differ by two and the slot number is higher than 6. For the same pole number, machines having slot/pole numbers differed by two exhibit a smaller UMF than machines having slot/pole numbers differed by one. It is also found that, if 2p = 3k + 1, the UMF gradually diminishes to 0 with the increase in pole number. On the other hand, when 2p = 3k - 1 , it reduces to a certain value with the increase in pole number. The experimental results are provided to verify the analysis. © 2012 IEEE.


The plastic buckling of thick steel conical shells subjected to combined action of axial compression and external pressure is of considerable interest in the offshore and the nuclear industries. However, design information on this subject area is limited. At present, only the ASME B&PV code case 2286-2 provides design information for cones subjected to axial and hoop compressions acting simultaneously. This design rule has not been validated both experimentally and numerically, especially in the elastic–plastic region. Past results on interactive buckling tests carried out at the University of Liverpool, Liverpool, UK on 13 computer numerically controlled (CNC)-machined cones having r2/r1 = 2.02, r2/t = 34.3, h/r2 = 1.01, and β = 26.56° were compared with predictions of design loads obtained from ASME code case 2286-2. This was done in order to check the applicability of this design rule and suggest a safe operating region. The paper consider the general procedure adopted by the ASME case code 2286-2 to predict the interactive buckling curve and identifies some discrepancies in the predictions. It further suggests region of safe operational design level. Combined stability plots for the master cone and equivalent cylinder have also been derived. Results of this study show that ‘the equivalent cylinders’ do not represent a safe design substitute for a relatively thick cone under combined loading. © 2013, © 2013 Taylor & Francis.


Ramli M.Z.,University Technical Malaysia Melaka | Salam Z.,University of Technology Malaysia
IEEE Transactions on Power Electronics | Year: 2014

This paper proposes a simple circuit to recover the energy that otherwise would be lost due to the partial shadings on photovoltaic (PV) modules. Since the circuit can be readily retrofitted to an existing PV system, no modification on the central inverter is required. The main idea of the scheme is that, during partial shading, parts of the current from the nonshaded modules are harvested by an energy recovery circuit using power electronic switches and storage components. In doing so, the current of the PV string is maintained at the level generated by the shaded module. There is no need for the shaded module to be short-circuited; as a result, it can still actively produce output power (despite being partially shaded). To investigate the idea, the proposed circuit is retrofitted to a prototype PV system using eight modules. The partial shading conditions are emulated using a solar simulator with a controllable irradiance capability. The results are validated by a good agreement between the experimental and simulation works. © 2014 IEEE.


Omar R.,University Technical Malaysia Melaka | Rahim N.A.,University of Malaya
International Journal of Electrical Power and Energy Systems | Year: 2012

This paper presents the analysis and design of a three phase four wire Dynamic Voltage Restorer (DVR) based on supercapacitor as energy storage for power quality improvement in electrical distribution system. The proposed system comprises of a supercapacitor as energy storage, DC-DC converter, and the power circuit of the DVR. It involves the construction of the proposed DVR topologies consists of filtering scheme, isolation or distribution transformer, injection transformer and Voltage Source Inverter (VSI). The main aims of this paper covers design, modeling, construction and testing of a laboratory DVR prototype for a three phase four wire system. This system is capable to mitigate voltage disturbances at low voltage distribution system. The implementation of supercapacitor as an energy storage is to supply real power to the inverter during disturbances. The experimental results of the prototype were also illustrated. The controllers based on d-q-0 transformation technique and Proportional Integral (PI) was applied to the DVR. The proposed controller was then coded into a digital signal processor (DSP) TMS320F2812 board. The proposed system is verified through simulation and is implemented in a prototype, and the experimental results are compared. © 2012 Elsevier Ltd. All rights reserved.

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