Wan Nor Liza Mahadi - Academia.edu (original) (raw)

Papers by Wan Nor Liza Mahadi

In the past few decades, passive suspension system has been widely used in passenger vehicle susp... more In the past few decades, passive suspension system has been widely used in passenger vehicle suspension system. The needs of improving ride and handling performance has fueled up significant researches into controllable suspension which provide variable damping and controllable force to stabilize the vehicle motions. This study reviews various research outcomes carried out in the advancement of controllable suspension system and the prospect of energy regeneration within the suspension system. There have been numerous studies being conducted on controllable suspension and most of them were proven to improve ride and handling performance of a vehicle. Nonetheless, it requires the use of external energy to power-up the suspension system. To overcome this, energy regeneration concept has been introduced to supply additional power within the suspension system by harvesting energy from road surface excitations. In realizing this concept, a suitable control scheme should be developed. The review will cover the design aspect of energy regenerating controllable suspension and the development of its control strategy. It is intended for future prospect of developing a new electromagnetic suspension with energy regeneration capability.

Journal of Manufacturing Processes, 2021

Abstract The electrospinning process is a simple and versatile method for the fabrication of nano... more Abstract The electrospinning process is a simple and versatile method for the fabrication of nanofibers. The low production rate of fibers in a conventional single-nozzle setup inhibits the commercialization of the process for large-scale applications. Multiple-nozzle electrospinning is a straightforward approach in the efforts of increasing fiber yield. The installation of multiple nozzles in a single setup alters the electric field in the working space, affecting the process and fiber quality. In this study, the effects of varying the distance between adjacent nozzles are investigated in terms of the jet behavior and fiber distribution, comparing between equally-spaced and unequally-spaced nozzles. The simulation of the electric field shows a more uniform electric field distribution near the nozzle tips for the unequally-spaced nozzles. The unequally-spaced setup also resulted in a more uniform distribution of fiber diameter and deposited fiber mats. Additionally, electrospinnability was also improved by using unequally-spaced nozzles.

Proceedings of International Technical Postgraduate Conference 2022

This research project presented an improved in house calibration procedure for electrostatic fiel... more This research project presented an improved in house calibration procedure for electrostatic field meter. The proposed improved arrangement is by using copper parallel plates with the optimum separation distance of 6.01 mm between plates. The material properties test, repeatability test and reproducibility test have been conducted throughout the project. The material properties test shows that copper is the suitable material to be used as the calibration plate due to its behaviour that can withstand high voltage up to 8 kV. The repeatability test conducted shows that the arrangement produces consistent results in five cycles of measurements. As for the reproducibility test where taken into account that the arrangement has been dismantled before undergoes the reproducibility test shows that the arrangement is reproducible. This study is conducted for the improvement electrostatic discharge (ESD) protection monitoring in the production line. ESD protection can prevent from any hazard ...

This paper present a circular patch microstrip array antenna operate in KU-band (10.9GHz – 17.25G... more This paper present a circular patch microstrip array antenna operate in KU-band (10.9GHz – 17.25GHz). The proposed circular patch array antenna will be in light weight, flexible, slim and compact unit compare with current antenna used in KU-band. The paper also presents the detail steps of designing the circular patch microstrip array antenna. An Advance Design System (ADS) software is used to compute the gain, power, radiation pattern, and S11 of the antenna. The proposed Circular patch microstrip array antenna basically is a phased array consisting of 'n' elements (circular patch antennas) arranged in a rectangular grid. The size of each element is determined by the operating frequency. The incident wave from satellite arrives at the plane of the antenna with equal phase across the surface of the array. Each 'n' element receives a small amount of power in phase with the others. There are feed network connects each element to the microstrip lines with an equal lengt...

Evaluation of magnetic properties of electrical steel is vital in improving the quality of electr... more Evaluation of magnetic properties of electrical steel is vital in improving the quality of electrical machinery since it is used as magnetic cores for transformers, motors and generators. A double yoke single sheet tester (SST) was modeled using two identical C-cores wound with copper wires at limb side in horizontal arrangement. The magnetic properties for electrical steels, grade M4 and M19 were tested under a frequency of 50 Hz with the current ranging from 0.2 to 2.4A. The effects of the sample dimension and anisotropy on magnetic measurements were investigated. Evaluation on specimen dimensions indicate that the non-uniformity of sample magnetization in overhang sample can attribute to the flux leakage between the yoke legs. The stray flux is also increased with the overhang sample. However, the so-called fit-in sample which is fitted nicely between the yoke end poles can minimize the effect of stray flux. One way ANOVA and T-test were used as statistical methods and executed a...

Public concerns on Extremely Low Frequency (ELF) Electromagnetic Field (EMF) exposure have been e... more Public concerns on Extremely Low Frequency (ELF) Electromagnetic Field (EMF) exposure have been elongated since the last few decades. Electrical substations and high tension rooms in commercial buildings were among the contributing factors emanating ELF magnetic fields. This paper discussed various shielding methods conventionally used in mitigating the ELF exposure. Nevertheless, the standard methods were found to be impractical and incapable of meeting currents shielding demands. In response to that, remarkable researches were conducted in effort to invent novel methods which is more convenient and efficient such as magnetic aqueous shielding or paint, textiles and papers shielding. A magnetic aqueous substrate, Manganese Zinc Ferrite was used as shielding material. The magnetic field and flux distribution inside the aqueous magnetic material are evaluated to optimize shielding against ELFEMF exposure, as to mitigate its exposure.

Electromagnetics, 2020

A metamaterial (MTM) inspired star-slot planar microstrip line fed ultrawideband (UWB) antenna ha... more A metamaterial (MTM) inspired star-slot planar microstrip line fed ultrawideband (UWB) antenna having a soft-surface ground structure is presented in this paper. The proposed antenna comprises periodically repeated star-slot unit cells on patch (radiating) side. This feature helps achieve an UWB from 4.0 to 16.2 GHz. Back lobe radiation is suppressed when the ground metallic part is partially replaced by periodic squareshaped cross-slot soft-surface unit cells. The dispersion relation exhibits a wide bandgap in the resonance frequency regions. The backward wave displays a balanced condition when series and shunt frequencies are equivalent (ω se = ω sh), whereas it displays an unbalanced condition when they are not (ω se ≠ ω sh). The periodic star rings etched on the metal patch enhance bore sight gain to a maximum of 8 dBi at 9.2 GHz. The antenna is fabricated on a Duroid substrate with overall dimensions of 27.00 × 31.40 × 1.57 mm 3 with a 10.0 GHz of the resonant frequency. The numerical and experimental results verify the proposed artificial metamaterial design structure that matches the theory.

Materials and Manufacturing Processes, 2017

ABSTRACT Electrospinning is a versatile method of producing continuous nanofibers through the app... more ABSTRACT Electrospinning is a versatile method of producing continuous nanofibers through the application of an electric field. The simplest and earliest form of electrospinning involves the use of a single-needle spinneret to draw the solution out and form fibers. The process, however, is very time consuming, limiting the potential wide-scale application of electrospun nanofibers. Many multiple-jet electrospinning methods have been proposed to overcome the problem of low productivity, but the generation of multiple jets brought about other problems such as jet repulsion, lower process controllability, and deterioration of fiber quality. Thus, continuous development is necessary for the optimization of the process. The aim of this review is to provide an overview of the recent electrospinning technologies reported in the literature, particularly on various multiple-jet electrospinning methods from both nozzles and free surfaces. The general principle underlying the electrospinning process, as well as important parameters involved are also presented in this paper.

International Journal of Circuit Theory and Applications, 2016

Enhancing electromagnetic research on prior light bend mechanisms is a significant issue for comp... more Enhancing electromagnetic research on prior light bend mechanisms is a significant issue for composite material phenomena, and one that is not available in nature. The unit cell of metamaterial can be revised, such that it is significantly smaller than the free space of the wavelength. It is essential to extend the appropriate retrieval process to measure electrical and magnetic responses to the backward wave propagation and dispersion diagram characteristics. In this paper, we propose a retrieval process inversion response between known and unknown parameters of the lumped unit‐cell circuits that optimizes the best fit parameters. By utilizing the optimization of particle swarm techniques, we provide appropriate values of periodic unit cells of CRLH transmission line circuits that matched with the microstrip implementation model. The group velocity of the wave is indicated in the parallel direction, whereas the phase velocity is in the anti‐parallel direction. The dispersion diagram displayed a specifically left‐handed and right‐handed medium, and a tiny band gap appeared in the attenuation medium. The constitutive parameters of dielectric permittivity, permeability, and refractive index were obtained from the periodic composite transmission line circuits.

Inerter is an additional suspension element to spring and damper with the property that the force... more Inerter is an additional suspension element to spring and damper with the property that the force generated is proportional to the relative acceleration between its two terminals. This study investigates the effectiveness of a parallel inerter in various vehicle suspension systems to provide superior vibration isolation. In the study, the inerter was paired in parallel to passive, semi-active and active vehicle suspension systems, and the systems were solved with a quarter vehicle model to obtain suspension responses due to ground excitations in the form of step and random road profiles. From the analysis, it was observed that inerter force and spring force were anti-phase to each other, and in parallel layout the cancellation of the two forces gave better vibration isolation to a sprung mass. This provided superior ride performance in vehicle suspension application as indicated by the reduction in vertical sprung mass acceleration. It was also found that the effectiveness brought by parallel inerter was independent on the various vehicle suspension systems; however, the improvement was only slight as the cancellation of forces was insignificant relative to the damping force associated with the specific vehicle model used in the study.

2014 4th International Conference on Engineering Technology and Technopreneuship (ICE2T), 2014

ABSTRACT Due to variation of environmental condition, power generated from a renewable source of ... more ABSTRACT Due to variation of environmental condition, power generated from a renewable source of energy always fluctuates. In the same way, by injection of wind power into the electric grid some power quality may varies because of a wind fluctuating inherent and relatively new types of generators. The measurements and the guidelines indicated in International Electro Technical Commission 61400 Standards the quality of power generated and the performance of wind turbines are derived. As far as the measurements of the generated power quality is concerned while the turbine is connected to an electrical grid there are certain associated powers such as active and reactive powers, flicker, the switching function’s electrical behavior, voltage swell, harmonics and voltage sag. Their measurements are done according to national and international guidelines. Nowadays, grid connected doubly fed induction generator becomes an interesting topic for power engineers to focus on. Moreover, voltage stability becomes an important factor to maintain the DFIG-based wind farm functioning during disturbances. This paper studies the static synchronous compensator implementation in order to address the issue of voltage stability in wind farms connected to the distribution network. STATCOM is used as a dynamic reactive power compensator to stable the voltage at the point of common coupling by protecting DFIG-based wind farm interconnected to the distribution system from going offline throughout and after the disturbances. Results obtain shows that, during the voltage sag voltage drops to 0.7pu and after connection of STATCOM voltage will improve to 0.89pu.The developed system is simulated in MATLAB/Simulink and the results show that STATCOM mitigates the effects of transient disturbances such as, voltage sag in the system and hence improves the stability and performance of wind farm.

2013 IEEE Conference on Clean Energy and Technology (CEAT), 2013

ABSTRACT With growing electricity demand and environmental concerns, renewable energy especially ... more ABSTRACT With growing electricity demand and environmental concerns, renewable energy especially wind energy has been moved into the center of concentration recently. The wind energy conversion system has connected to the power grid to provide the consumer electricity demand. The various area where researchers have contributed could be classified in various ways. The major concern of most of the previous researches deals with power quality improvement such as reactive power compensation, voltage regulation, total harmonic distortion reduction and stability of the system. Various proposed control schemes and techniques are reviewed in this paper which focused on grid integration of large wind turbines in order to keep the power quality in acceptable limit.

Science and Engineering of Composite Materials, 2015

The design analysis and prototype of a compact 8×10-mm2 planar microstrip line-fed patch antenna ... more The design analysis and prototype of a compact 8×10-mm2 planar microstrip line-fed patch antenna on a readily available, low-cost, reinforced-fiberglass polymer resin composite material substrate is presented in this article. The proposed compact-size antenna has been configured and numerically analyzed using the finite element method-based three-dimensional full-wave electromagnetic field simulator. The optimized design of the antenna has been fabricated on a printed circuit board (PCB), and experimental results have been collected for further analysis. The measurement results affirm the fractional impedance bandwidths of (return loss of less than -10 dB) of 38.78% (2.03–2.98 GHZ) and 16.3% (5.38–6.35 GHz), with average gains of 2.52 and 3.94 dBi at both lower and upper bands, respectively. The proposed dual resonant antenna shows the radiation efficiencies of 91.3% at 2.45 GHz and 87.7% at 5.95 GHz. The stable and almost symmetric radiation patterns and performance criteria of the...

Advanced Materials Research, 2014

Advancement in computational technologies has accelerated the research effort in exploring the po... more Advancement in computational technologies has accelerated the research effort in exploring the possibility of semi-active and active suspension. Computational simulations were used widely in the studies of the controller strategies. Among them are PID controllers. Studies from previous work suggested that PID controllers are capable of improving ride comfort and road holding capability. However, very little emphasis is given to examine the whole state of the vehicle suspension system resulted from this implementation. Therefore this study will examine the application of a basic PID controller to an active suspension system (ASS) to determine the requirement of active force that should be delivered in stabilizing the whole system. Two different configurations of electromagnetic suspension system (EMS) will be considered. One variable in the vehicle system will be selected to be the controlled output of PID controller and its effect to overall vehicle state will be observed. In the ca...

2008 IEEE International RF and Microwave Conference, 2008

This paper presents an initial investigation for breast cancer detection using a special mode of ... more This paper presents an initial investigation for breast cancer detection using a special mode of bistatic radar system known as forward scattering radar (FSR). The proposed method analyzes the Doppler frequency in the received signal scattered from the tumor for cancer detection and localization. Three systems of architectures were analyzed which determined by the mechanical movement of transmitter or receiver or both. This paper also discusses an initial simulated result by using CST Microwave Studio as a feasibility study of utilizing FSR for breast cancer detection. It is shown that by investigating the unique character of Radar Cross Section (RCS) for breast tissue and tumor of FSR a cancer can be predicted. Electromagnetic model including fatty tissue and a tumor were simulated to obtain RCS parameter and analyzed as well as compared with whose fatty tissue without cancerous lesion to pinpoint the presence of tumor from its FSR signature. The result shows a significant different between these two models in FS RCS.

2013 IEEE International Conference on Space Science and Communication (IconSpace), 2013

Metamaterial are a special class of material which have negative permittivity and permeability. D... more Metamaterial are a special class of material which have negative permittivity and permeability. Due to their unique negative properties they are known to increase the gain and directivity of the antenna. To simulate metamaterial structure CST Computer simulation technology software is used. Simulation setup is matched to free space extraction model which measures permittivity and permeability of the material based on S-Parameter. This paper presents a simulation analysis of several of metamaterial structure in X-band for space communication application. A comparison is made based on simulation result to analyze several structures in terms of tune ability, size and ease of use.

Journal of Vibration and Control, 2013

A passive vehicle suspension has constant spring and damper properties that compromise either rid... more A passive vehicle suspension has constant spring and damper properties that compromise either ride or road holding ability, depending on whether the suspension is designed to be hard or soft. This study examines the implementation of a gear mechanism in a vehicle suspension system to alter its suspension characteristic while keeping the same spring and damper properties. In the study, a rack-and-pinion mechanism was used to modify the suspension force which acted between the sprung and unsprung masses of a quarter vehicle model. The system with proposed suspension layout was modeled mathematically and solved to obtain the vehicle response due to step excitation for various gear ratios. Results indicated that the use of such a mechanism was capable of changing the equivalent suspension force of the system. It was noted that different gear ratios would amplify or reduce the equivalent suspension force, hence emulating a harder or softer suspension setting compared to that of the origi...

International Journal of Emerging Electric Power Systems, 2009

There is an attempt to correlate the public health risk with strong magnetic fields from high vol... more There is an attempt to correlate the public health risk with strong magnetic fields from high voltage multiple transmission lines. The statement is based on the public perception that multiple sources of two and three tower lines can generate more radiated fields as compared to single tower. This paper evaluates the fact and figures on realistic situation cases about radiated field exposures based on measurements and simulation models of two and three transmission lines. The case study sites which consist of several towers of 132kV and 275kV lines were located in Melaka district, Malaysia. Measurement procedures of magnetic fields were conducted based on the IEEE/ANSI 644 standard while the dose exposure reference value was based on the public exposures of the ICNIRP limits. The results obtained from this analysis are then compared with the ICNIRP standard for assessing the significance of dose exposure between actual conditions in TNB systems with optimum simulated models of phase ...