RAHIZAR RAMLI | University of Malaya, Malaysia (original) (raw)

Papers by RAHIZAR RAMLI

Polymers, Oct 6, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Materials, Apr 30, 2022

Springer eBooks, 2011

Lung cancer has become one of most killing disease in 20 th century. There are various external a... more Lung cancer has become one of most killing disease in 20 th century. There are various external and internal causes identified by experts to be the causes of this disease. Various type of treatments have been developed taking account on the stage and condition of cancer itself, such as Radiation Therapy, Chemotherapy and Surgery. In this paper, a method called Thoracoscopy is focused for improvement by investigating a possibility of using finite element method (FEM) to predict deformation and movement of tumor during lung lethargy process as a preparation stage for this surgery method to be deployed. Thoracoscopy is suitable for stage-I cancer, as it will only create a small incisions on the skin and has high possibility to cure by removing the tumor. This paper used a commercial FEM tool to model lung in 3dimension and by using tested data of material properties, a simulated result of lung lethargy process was compared with experimental data. Results revealed a few promising points to further develop this virtual capability and use it to predict deformation prior the surgery.

PLOS ONE, Jan 20, 2023

The inerter is a two-terminal component that can be added to the spring-and-damper configuration ... more The inerter is a two-terminal component that can be added to the spring-and-damper configuration of a suspension system. It has the property that the force exerted is proportional to the relative acceleration at its terminals. Studies have demonstrated the inerter's benefit of providing superior vibration isolation when it is used in the vehicle suspension of passenger cars. However, similar benefit on another common vehicle class on the roads, namely heavy vehicles, remain to be shown, as these vehicles have vastly different parameter values than passenger cars. This study is an investigation on the performance improvement brought by an inerter in the suspension of common heavy vehicles. In the study, the parameter values of a truck and a bus were adopted in the quarter vehicle model with two different spring-damper-inerter configurations (parallel and serial inerter), and the improvements in vibration isolation and road holding capability were determined by optimization of inertance. Results show that the inerter is similarly effective in providing the said improvements when implemented on heavy vehicles instead of on passenger cars, judging from reductions in sprung mass acceleration and dynamic tire load. It is also observed that the performance benefit is associated with larger optimum inertance than that for passenger cars. Overall, the inerter has been shown to be beneficial in the parallel and serial configurations, both of which are common and can be practically implemented in the suspension of heavy vehicles.

Journal of Simulation, Aug 1, 2015

Background: This paper presents parametric modelling of flexible plate structures using ant colon... more Background: This paper presents parametric modelling of flexible plate structures using ant colony optimization (ACO). The global optimization technique of ACO is utilized to obtain a dynamic model of a flexible plate structure based on one-step-ahead (OSA) prediction. Objective: The structure is subjected to three different disturbance signal types, namely random, pseudo random binary sequence (PRBS), and finite duration step. The fitness function for the ACO optimization is the mean-squared error (MSE) between the measured and estimated outputs of the plate. Results: The validation of the algorithm is presented in both time and frequency domains. The developed ACO modelling approach will be used for active vibration control systems design and development in future work. Conclusion The performance of ACO2 has been shown to outperform ACO1 in minimizing the prediction error, resulting in a good level of accuracy of the estimated model.

2009 17th Mediterranean Conference on Control and Automation, 2009

This paper presents parametric modelling of flexible plate structures using ant colony optimizati... more This paper presents parametric modelling of flexible plate structures using ant colony optimization (ACO). The global optimization technique of ACO is utilized to obtain a dynamic model of a flexible plate structure based on one-step-ahead prediction. In this paper a proposed ACO with roulette wheel selection known as ACO2 is compared with a previous modified ACO which is denoted as ACO1. The comparison is to recognize the optimum performance and to enhance the fast convergence. The flexible plate structure is subjected to random disturbance signal types. Fitness function for the ACO optimization is the mean-squared error between the measured and estimated output of the plate. The validation of the algorithm is presented in both time and frequency domains. Simulation results show that the proposed approachis better and has a fast convergence rate than ACO1. The developed ACO modelling approach will be used for active vibration control systems design and development in future work.

Journal of Applied Fluid Mechanics, 2019

Two-phase flow happens widely in the industrial plants and certain equipment. This paper attempts... more Two-phase flow happens widely in the industrial plants and certain equipment. This paper attempts to study the characteristics of two-phase flow in a vertical piping system. This was achieved by comparing the void fraction, in the working fluid, by employing Constant Electric Current Method (CECM) with the actual observation using high-speed camera. The experiment requires a complete set of two-phase flow system information and was conducted based on various flow conditions. In order to carry out this experiment, the two-phase flow loop was constructed using a specific experimental apparatus and components. The flow channels were constructed using three pipes with three different inner diameters of 21.0 mm, 47.0 mm and 95.0 mm. The flow direction was vertical upward co-current flow with liquid superficial velocity range of 0.025 m/s to 3.0 m/s and gas superficial velocity range of 0.025 m/s to 3.0 m/s, depending on the size of the pipe. The flow pattern investigation focuses on experimental work, which was based on systematic observation and measurements using a high-speed camera and some measuring apparatus. The void fraction measurement using the CECM sensor was integrated into twophase flow system with constant electric current running in the pipe and data acquisition system controlled virtually via LabVIEW software. Both result of the flow pattern and void fraction graph were then compared to determine the type of flow pattern from the void fraction graph. Information from the previous studies and experiments were collected and the assumption of any theoretical simplifications were used as a reference. According to the result, the flow pattern in pipe can be easily determined using CECM.

International Journal of Advanced Mechatronic Systems, 2021

The vehicle suspension is an important system in a vehicle which provides ride comfort and handli... more The vehicle suspension is an important system in a vehicle which provides ride comfort and handling capability, albeit with a compromise between the two. Semi-active suspension system, which solves this compromise, has been studied frequently with well-known control strategies. However, many of these strategies are designed based on vertical dynamics, focusing on ride improvement. This study evaluates any potential improvement in handling performance brought by a semi-active suspension system with these ride-oriented control strategies. In this study, these were implemented independently on the four wheel stations of a 10-degree-of-freedom full vehicle model which was subjected to step-steering and sine-steering manoeuvres, and the relevant handling performance criteria were evaluated. Results from the simulations indicated that, despite these control strategies mostly being designed for ride comfort, some of them are actually capable of bringing improvement in the handling aspect also, judging from the improvement in a few handling performance criteria.

IEEE Access, 2021

Longitudinal vibrations due to different external excitations are omnipresent in almost every mac... more Longitudinal vibrations due to different external excitations are omnipresent in almost every machine, eventually leading to unplanned downtime, and in some cases, catastrophic failures. The passive approach to isolate such vibration has some limitations. Magnetorheological elastomers (MREs) typically consist of micron-sized ferrous particles dispersed in an elastomeric matrix. Its rheological properties, such as the viscosity and dynamic modulus, can be altered when subjected to a magnetic field. Thus, magnetorheological elastomers have drawn significant attention from researchers due to their versatility in vibration control applications. In this study, an MRE-based metamaterial coupler is fabricated for broadband vibration attenuation. The vibration control performance of the proposed model is investigated in terms of its transmissibility factor. Sine sweep vibration testing is used to examine the transmissibility factor for single, double, and triple-layer MRE metamaterial couplers accompanied by different activation scenarios. The results reveal that the stiffness of the MRE layers increases with the strength of the applied magnetic field. Utilizing more than one layer of MRE increases the ability to isolate longitudinal vibration at different frequency bands. The maximum reduction curves achieved by single, double, and triple-layer MREs are approximately 84.5%, 97%, and 99.6%, respectively. The findings of this study demonstrate that the proposed MRE-based metamaterial couplers can attenuate vibrations at broadband frequencies.

Lecture Notes in Mechanical Engineering, 2018

Failures in a reciprocating compressor are often caused by the valves, as they are the major movi... more Failures in a reciprocating compressor are often caused by the valves, as they are the major moving components in the reciprocating compressor. The acoustic emission (AE) technique has been employed by condition-based monitoring personnel to detect valve problems prior to failure. However, the extent to which the valve should be replaced, or more specifically, the relationship between AE measurement and valve severity remains unclear. This study attempted to establish a method to quantify the severity of valve problems in a reciprocating compressor by examining the relationship between AE root-mean-square (rms) value and the rotational speed at increasing severity. The study involved the acquisition of AE signals in different simulated valve conditions with increasing severity and the correlation of these signals with valve severity at its corresponding valve events. The results of the study showed that AE signal is linearly related to the 4th power of speed. Besides, the signal showed large decrement at increasing severity. It is believed that the study can help to quantify valve severity level with AE signal in the near future.

Springer Proceedings in Physics, 2019

Non-intrusive measurement technique, namely, the acoustic emission (AE) technique, is often emplo... more Non-intrusive measurement technique, namely, the acoustic emission (AE) technique, is often employed to provide an early detection of valve failures in reciprocating compressor. Past researchers often relate the root-mean-square (RMS) value of AE signal to valve leakages. However, the amount of valve leakage is often unknown. In other words, the degree of valve deterioration to the extent that valve should be replaced is unknown. This study examined the effect of increasing valve impacts on AE signal and flow rate of fluid flowing through the suction valve correspondingly, with the intention to relate AE signal to the mass flow rate of fluid. It involves measurement of both suction mass flow rate and AE signal at different compressor speeds and valve conditions and statistical test to investigate the significance of compressor speed on AE signal and mass flow rate of suction valve. It is believed that the study can help to establish an empirical relationship for AE signal and valve ...

Acoustic emission (AE) technique is often employed by condition monitoring personnel to detect ab... more Acoustic emission (AE) technique is often employed by condition monitoring personnel to detect abnormalities in moving components of machines. Due to its low signal-to-noise ratio at high-frequency range, it often requires certain signal processing technique to extract valuable information from machine parts. This study intends to obtain the characteristic frequency segments of AE signals that correspond to the physical movement of valves in reciprocating compressor. It involves acquisition of AE signals at various simulated valve conditions and rotating speeds, decomposition of these signals through wavelet packet transform (WPT), and computation of crest factor (CF) of WPT coefficients at a specific crank angle. The characteristic frequency segments that indicate valve problems are often accompanied by an extra high or low CF value. By relating the CF value to valve events, the condition of valve can be predicted. It is hoped that this study can provide a methodology to obtain val...

INTERNATIONAL JOURNAL OF AUTOMOTIVE AND MECHANICAL ENGINEERING, 2016

Recent experiences have shown that one of the main causes of heavy vehicle crashes is the braking... more Recent experiences have shown that one of the main causes of heavy vehicle crashes is the braking performance. In particular, when having to decelerate in an emergency situation, such as when an unexpected object is in the road. Thus, the capability of a vehicle to come to a safe stop is one of the most important factors in preventing more accidents. Safe braking distance is influenced by many factors, such as brake pedal force, the vehicle's loading conditions, the travel speed and the road surface conditions. The aim of this study was to analyse the effect of the driver's brake pedal force on braking distance during an emergency situation, allowed for a wide range of heavy vehicle's GVW and speed. This study is carried out by using a multi-body dynamics simulation of a Single Unit Truck based on the validated vehicle model. Braking performance was estimated in terms of braking distance on a straight road with a wet surface. The findings from the braking distance simulation suggest a non-linear relationship between brake pedal force and braking distance. Finally, it reveals that, depending on the wheel lock-up situation, braking distance increases with increasing brake pedal force, and that the braking distance on a wet road is significantly affected by both the heavy vehicle's GVW and speed.

International Journal of Technology and Design Education, 2011

World Academy of Science, Engineering and Technology, International Journal of Transport and Vehicle Engineering, 2015

RSC Adv., 2015

Correction for ‘Impact of aluminium addition on the corrosion behaviour of Sn–1.0Ag–0.5Cu lead-fr... more Correction for ‘Impact of aluminium addition on the corrosion behaviour of Sn–1.0Ag–0.5Cu lead-free solder’ by N. I. M. Nordin et al., RSC Adv., 2015, 5, 99058–99064.

Sustainability

Heavy vehicles make up a relatively small percentage of traffic volume on Malaysian roads compare... more Heavy vehicles make up a relatively small percentage of traffic volume on Malaysian roads compared to other vehicle types. However, heavy vehicles have been reported to be involved in 30,000–40,000 accidents yearly and caused significantly more fatalities. Rollover accidents may also incur cargo damages and cause environmental or human disasters for vehicles that carry hazardous cargos if these contents are spilled. Thus, in this paper, a comprehensive study was conducted to investigate the effects of vehicle and road conditions on rollover of commercial heavy vehicles during cornering at curved road sections. Vehicle conditions include the heavy vehicle class (based on the axle number and vehicle type), speed and gross vehicle weight, while road conditions include the cornering radius and coefficient of friction values. In order to reduce the risks involved in usage of actual heavy vehicles in crash experiments, a simulation approach using a multi-body vehicle dynamic software was ...

The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly fo... more The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly for improvement in ride and handling, over the passive system. However, the durability of the suspension components resulting from this implementation received very little attention. Therefore, this research aims to examine the effect of employing a selection of semi-active control strategies on the components' durability. To achieve this early in the design cycle, accurate representations of the load histories must be generated as these histories are the prerequisite in predicting fatigue life. This requires an alternative modelling and simulation approach capable of combining the complexity of vehicle suspensions with semi-active controller models, and at the same time capable of maintaining accurate dynamic responses. In realizing this objective, a multi-body cosimulation approach has been proposed to predict these loads. Initially, efforts are centred on verifying the proposed meth...