Pusat Pengajian Kejuruteraan Mekanikal - Tesis

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Ageing treatment effect on the bending behaviour of nickel-titanium archwires in orthodontic bracket systems
(2024-08-01)
Asad, Munir
Superelastic nickel-titanium (NiTi) archwires have gained popularity as the archwire of choice during the orthodontic alignment and levelling stages because of their capacity to apply light force to the teeth. Generally, orthodontic treatment starts with round archwires and subsequently progresses to rectangular archwires within 4- 6 weeks, ensuring a consistent bending force of approximately 1.0 N. However, commercial NiTi archwires may cause discomfort because of their greater bending force, which exceeds the recommended force for tooth movement. In this study, a novel ageing treatment approach was used to alter the magnitude of the bending force in commercially available superelastic NiTi archwires of various sizes. This study examined three archwires with dimensions of 0.30, 0.40, and 0.40 × 0.56 mm. Subsequently, these archwires were subjected to various ageing temperatures ranging fr om 370 to 550 °C for durations of 15, 30, and 45 min. The archwires underwent thermal analysis, tensile testing, three-point bending testing, and three-bracket bending testing after the ageing treatment. The study used the force deflection curve of aged archwires to evaluate force delivery parameters, and regression models was created to predict the bending force of aged NiTi archwires in orthodontic bracket assemblies. Differential scanning calorimetry (DSC) analysis shows that the ageing treatment effectively alters the thermal transformation temperature of commercial NiTi archwire, with longer durations leading to higher Af temperatures. Furthermore, with ageing treatment, the unloading forces of the commercial NiTi archwire during the three-point and three-bracket tests were reduced to lower magnitudes. The study found that ageing treatment reduced the maximum unloading force of commercial archwire from 2.79 N to 0.21 N for aged rectangular geometry during three-bracket bending, with less impact on round-shaped geometries. The suitable ageing conditions for these archwires were 430–550 °C for 15 min for 0.30 mm, 370–550 °C for 30 min for 0.40 mm, and 400–550 °C for 45 minutes 0.40 × 0.56 mm, respectively. The developed regression models yielded high R-squared values of 0.9677, 0.7207, and 0.7083 and p-values < 0.05 for the loading force, unloading force, and force difference, respectively. The ageing treatment could be employed to improve the force delivery trends of commercial grade NiTi archwire by reducing the magnitude of the force exerted on the teeth during the entire course of orthodontic treatment.
Analysis Of Piston Secondary Motion
(2014-04)
April 2014
In an internal combustion engme, the piston performs secondary motion besides the primary reciprocating motion. The clearance between the piston skirt and cylinder liner allows the piston to move in the lateral direction and rotational motion about the piston pin axis. The piston secondary motion created impact between the piston skirt and the cylinder liner that radiates unwanted engine noise and increases friction loss. A measurement system consists of three laser displacements sensors are developed to capture the instantaneous piston motion and posture directly from the piston assembly under motorized condition. The laser spots aimed at the piston crown with machined profile in order to obtain the rotational and lateral motion of the piston. The instantaneous piston motion showed that the likelihood of contact between the piston skirt and the cylinder liner increases with the occurrence of the piston secondary motion. In addition, a non-linear model of the piston with reciprocating, lateral and rotational degree of freedom is developed to investigate the piston secondary motion and the piston slap induced vibration behavior of the single cylinder engine.
Cascaded cylindrical micro-perforated panel for noise broadband attenuation
(2023-04-01)
Mohamad Izudin Bin Alisah
This research presents an analysis of cascaded cylindrical micro-perforated panel (MPP) for absorbing the sound of a flow system in a circular duct application. This is important for the cases where the noise source comes from multi direction as actual application would not in single direction. Since the typical MPP has limited narrow band attenuation, it is necessary to have a specific MPP to radiate noise from circular direction and broadband attenuation. The aim of this study is to model using simplified transfer matrix method, optimized via genetic algorithm and demonstrate the effectiveness of cascaded cylindrical micro-perforated panel on vacuum cleaner. Cascaded cylindrical MPP is a special class of cylindrical MPP, where two cylindrical MPPs are arranged in series to improve sound attenuation. The manufacturing of MPP primarily involves the machining of micro perforations because the small holes are not readily made using injection moulding due to the complexity of the die, flow control of the molten polymer through the small orifices and dimensional stability, making it unsuitable for mass production. This limitation can be overcome with the use of additive manufacturing (AM) technology based fused deposition method (FDM), where the micro perforations can be designed and manufactured, with relatively larger tolerances. Moreover, parametric studies on basis of perforation diameter, perforation ratio, depth of air cavity on the diameter of the duct and length ratio are carried out. Result shows that the transmission loss performance of cascaded cylindrical MPP can be improved by reducing the perforation diameter and by correct selection of perforation ratio and air cavity depth value. Experimental validation ensures that the manufactured cascaded cylindrical MPP is performed according to design. The application of transfer TMM framework was aligned with similar trend with boundary element method (BEM) and measured result via two-load method measurement. Small shift of the transmission loss peak values attributed to perforations in printed structures that were not perfectly circular in shape. The average Root Mean Square Error (RMSE) obtained was 3.04 dB. A case study is demonstrated here in the design and additive manufacturing of cascaded cylindrical MPP to attenuate peak noise at 1650 Hz. The manufactured cascaded cylindrical MPP is installed on a vacuum cleaner duct, and the measurement of sound power level shows a reduction of 5.2 dB (A).
Cutting design for oil palm frond analysis of circular saw
(2024-08-01)
Sun, Qun
This study develop a model to assess energy consumption, cutting force associated with the use of circular saw in the cutting of oil palm fronds. The energy consumption model is formulated based on kinematic equations and a simplified cutting process model, incorporating Ernst and Merchant's force circle. The final cutting power equation considers sawing and clamping, dependent on circular saw geometry, tooth shear angle, disc thickness, feed rate, speed, frond rupture modulus, and friction coefficient between the saw and frond. This model is validated against experimental data (38
Development and impact of customised serious game system in stable-sitting trunk control exercises among stroke survivors
(2024-08-01)
Tan, Alexander Wai Teng
This study presents a custom Serious Game (SG) system designed for stable sitting trunk exercises. The system incorporates three key features: (1) measurement of the Centre of Pressure (CoP) using a custom force plate, (2) real-time translation of CoP shifts into game avatar control, and (3) recording of CoP trajectories during gameplay. This approach provides an engaging game-based rehabilitation therapy that offers valuable insights into users' functional movements. The study assesses the impact of this SG system on trunk rehabilitation in stroke survivors through a two phase approach. Initially, a within-participant, repeated measures pilot study involved 12 stroke subjects who undertook both conventional trunk exercises (CTE) and SG based trunk exercises (SGTE) in a stable-sitting posture was carried out, aiming to compare the physiological and postural responses. ANOVA results revealed low muscle activity and light-intensity cardiovascular responses across exercises, with game-paced SGTE yielding marginally higher CoP velocity in Anterior-Posterior (AP) and Medio-Lateral (ML) axes compared to CTE (AP: 4.40 ± 1.80 vs. 4.02 ± 1.20 cm/s; ML: 6.40 ± 2.54 vs. 5.42 ± 2.21 cm/s). However, self-paced SGTE had a lesser impact on postural control. Subsequently, a larger cohort of 25 stroke subjects participated in SGTE to explore the relationship between in-game CoP measures and clinical assessment outcomes. Spearman correlation analysis found significant correlations, particularly in the ML axis, with the TIS2.0 score showing a strong association with CoP range (ρ = 0.78; p < 0.001) and mean CoP velocity (ρ = 0.75; p < 0.001). The novelty of this thesis lies in developing a custom SG system specifically designed for trunk rehabilitation in a sitting position for stroke survivors, combining the motivational aspects of games with the clinical relevance of force plate measurements. This study compares the impacts of SGTE on physiological and postural responses with those of CTE in stroke survivors. Additionally, it establishes correlations between in-game CoP measures and clinical assessments among stroke survivors. The findings indicate that the SG system provides impacts comparable to CTE and shows potential as an adjunct to existing rehabilitation protocols and assessment tools for stroke survivors, suggesting further investigation into its utility.
Development and optimization ofmicro gas turbine combustor fueled by refined palm oil
(2024-03-01)
Mohammed Raad, Abdulwahab
Investigations on alternative renewable liquid biofuels to replace petroleum oils have drastically increased in the past decades to mitigate the energy crisis and global warming issues. In Malaysia, the abundance of liquid palm oil waste that can be used directly as fuel or converted into biodiesel (B100) to replace diesel fuel. However, these fuels suffer from high viscosity and lower heating value compared to diesel which presents a major challenge towards achieving clean and complete combustion. This research optimized a new combustion chamber alternative design for micro gas turbine (MGT) applications that can provide clean combustion of low-grade liquid biofuels without the need of fuel preheating or blending with fossil fuels. Chamber design optimization was performed in three stages Design of Experiment (DoE), while combustion and flow hydrodynamics were evaluated using CFD simulation in ANSYS-FLUENT program. Cold-flow spray atomization tests were experimentally performed for refined bleached deodorized palm oil (RBD), B100 and diesel, where spray pictures were analyzed using IC-measure software. RBD oil showed long liquid film extension before breaking down to large droplets resulting in low spray angle <10°, while B100 performed significantly better at lower flow. Increasing the flow increased the spray angle to 21°. The optimum combustion design was then fabricated and tested with Garrett GT-25 turbocharger in single stage MGT test rig. Modifications were then performed to optimize the MGT start-up process with RBD oil. Finally, MGT performance was characterized in the pressure range of 0.2-0.7 bar gauge pressure using RBD oil and palm biodiesel. The performance was compared to diesel as the benchmark fuel. The trend lines of turbine power against compressor pressure using diesel were similar to those of B100 and RBD oil at same pressure range. Minimum CO emission in the range of 132-135 ppm for diesel and B100 were achieved at the higher operating pressures, while RBD oil showed slightly higher value of 207 ppm. NOx emission showed comparable values in the range of 32-39 ppm for all the fuels. Finally, diesel suffered from its higher TIT value that reached 800°C at 0.7 bar compared to 785°C and 762°C for RBD oil and B100 respectively. Chamber efficiency was comparable for all fuel used with low values at low operation pressure and low flame intensity with the range about 85% to 92%. The CFD model was verified with experimental findings at 0.7 bar with low error of 1.6% for TIT, 2.6% for CO and 0.8% for NOx.
Development and validation of the lateral material shift (lms) ratio method for surface finish quality assessment in machining with palm oils as cutting fluids
(2024-09-01)
Mohd Naqib, Derani
Surface texture plays a crucial role in various applications, including optical, electrical, thermal performance, and appearance. In order to produce the desired surface texture in machining, several measures such as cutting zone temperature, tool wear, cutting forces, surface roughness of workpiece, vibration, chip formation, etc have been used in the past to investigate the effectiveness of machining. Among these the two most common parameters investigated in the past are tool flank wear and average surface roughness (Ra). The use of flank wear and average roughness, however, have resulted in confusing and contradicting findings in some of the published literature, such as improvement in surface roughness in spite of increase in flank wear. This is mainly due to the poor correlation between flank wear and surface roughness. Moreover, since Ra is a measure of the average absolute height of the roughness profile and, therefore, is insenstive to lateral changes in the topography of the surface profile of the workpiece as a consequence of tool wear. The use of Ra as the sole roughness measure could potentially lead to errorneous conclusions. No previous attempt has been made to analyze surface finish quality other than looking at two common parameters which are tool flank wear and current roughness parameters. In this research, a new and more effective method of measuring surface finish quality has been developed to assess the effectiveness of palm oils as cutting fluids. Three methods of workpiece surface analysis, namely autocorrelation, cross-correlation, and lateral material shift (LMS) ratio are investigated. Machining experiments were carried out on AISI 316 stainless steel. Images of tool nose and workpiece profiles were captured using digital camera, and the edges were extracted using sub-pixel edge detection. In the autocorrelation approach, each workpiece profile was correlated with a shifted version of the same profile. In the cross-correlation approach, the workpiece profiles at different stages of machining were correlated with a reference profile generated using the unworn tool edge. In the LMS ratio method, the material shift ratios were determined from each waveform on the workpiece profile at various stages of tool wear. Among the three methods, the LMS ratio method produced the best correlation with tool flank wear with the maximum R-squared value of 0.9466, while average roughness Ra showed no correlation at all with both major and nose flank wear. The proposed LMS ratio method provides a novel method of measuring the workpiece surface deterioration thus giving correlation result in assessing the workpiece surface deterioration.
Development of a triaxial biomechanical force plate based on uniaxial load cells and deep learning
(2024-08-01)
Yeo, Ying Heng
Custom force plate developed from half-bridge strain gauge load cells is a potential low-cost alternative to expensive laboratory-grade force plates. Nevertheless, the measurement accuracy has not been thoroughly validated. The inability to quantify bilateral ground reaction force (GRF) prevents the utilization of the low-cost force plate in biomechanical analysis. In this study, a low-cost custom force plate has been developed by using uniaxial half-bridge strain gauge load cells. Based on Poisson effect, the load cells could produce readings even when the off-axis bilateral GRF which was orthogonal to the primary axis vertical GRF was applied. These readings were used as features to infer the bilateral GRF measured with laboratory-grade force plate. The mapping of uniaxial load cell readings to bilateral GRF was carried out using deep learning models. The validity of the custom force plate in measuring three-dimensional GRF, centre of pressure (CoP), and clinical metrics derived from vertical GRF and CoP was evaluated. The custom force plate validity in vertical GRF and CoP measurement for all tasks was indicated by mean absolute error of lower than 9.90 N and 6.29 mm, and high Pearson correlations (ρ), coefficient of determinations (R2), and intraclass correlation coefficients (ICC) of more than 0.94, 0.88, and 0.94 respectively. In acquiring clinical metrics, the custom force plate achieved ρ, R2, and ICC of greater than 0.98, 0.96, and 0.98 respectively. The recorded ρ and ICC were higher than that achieved in five previous studies which investigated other low-cost force plates. Autoencoder and U-net models were trained to receive time series or Short-Time Fourier Transformed (STFT) vertical GRF (acquired from the individual single-axis load cells of a custom force plate) as input and generate bilateral GRF as output. Different models were trained with Adam optimizer under the implementation of early stopping and hyperparameter tuning. The most accurate model was U-net model that accepted STFT-transformed input. Apart from the mediolateral GRF measured during sit-to-stand, the model predicted the bilateral GRF in the test dataset with root mean squared error (RMSE), and relative RMSE of less than 1.95% of body weight and 14.17%, and ρ, R2, and ICC of more than 0.89, 0.79, and 0.88, respectively. The values of ρ were greater than that obtained in six previous works that studied the bilateral GRF prediction methods with devices other than low-cost force plate. The result comparison with previous works highlighted the good measurement performance of the custom force plate. Hence, the custom force plate could potentially be a low-cost solution to measure GRF, CoP, and clinical metrics.
Fabrication and molecular dynamics analysis of polydimethylsiloxane antimicrobial nanostructure
(2023-04-01)
Nur Liyana Binti Mohd Shamsuddin
The topographically surface modification using lithography techniques is an alternative approach to create antimicrobial surfaces. The micro/nano structure surfaces mimic the naturally-occur surfaces that are able to repel bacterial attachment or rupture the bacterial cell wall once attached to the surfaces. Nevertheless, the conventional photolithography technique has limits on light diffraction. An electron beam lithography (EBL) the being explored in fabricating the desired micro-and nanofeatures on large areas. This study aimed to fabricate micro/nanostructured of polydimethylsiloxane (PDMS) with antimicrobial properties. The pattern definition process produce the micro/nanohole array on the PMMA/Si mould and the pattern was transferred onto the PDMS using replica moulding (soft lithography) technique. Large-scale Atomic/Molecules Parallel Simulator (LAMMPS) was employed for molecular dynamics (MD) simulation to determine stress-strain response under compression. The adhesion of the Methicillin-resistant Staphylococcus aureus (MRSA) cells was observed and bactericidal efficiency count via the viable plate count method. The PDMS micro/nanostructures arrays of 200 to 300 nm in base diameter and 30-160 nm in height successfully fabricated. The simulated compressive modulus and ultimate compressive strength of PDMS nanostructure was decreased with the increase in simulated temperature. The cell viability diminished by almost 80% and FESEM images showed the cells were deformed and ruptured once attached to the PDMS surface. The topographic features of the PDMS micro/nanostructured surface enhanced the bactericidal properties of the film, which effectively inhibit bacterial attachment and cell proliferation.
Flow characteristics and heat transfer enhancement of synthetic jet impinging on heated plate
(2023-02-01)
Azmi Bin Husin
Downsizing electronic components while increasing their performance will increase heat generation exponentially. The excessive heat produced in electronic components can cause premature failure. Hence, maintaining the operating temperature at optimal conditions becomes more challenging. A synthetic jet is one of the under-developing forced cooling systems. The capability to produce continuous high fluid flow without additional fluid supply systems, high reliability and simple construction are the synthetic jet device's main advantages to be considered as a future active cooling system. The present research work was focused on enhancing the flow and the heat transfer rate by synthetic jet. The effect of the straight, nozzle and diffuser-shaped orifices were studied to see the flow characteristic of the speaker-driven synthetic jet. Additionally, the exit velocity was investigated to see the opening angle effect of the diffuser-shaped orifice. Then, the cooling performance of synthetic jet impinges on a flat heated surface was further investigated in the numerical work. Moreover, the effect of various heat source inputs, the gap between the orifice to the cooling surface, the opening angle of the diffuser shape orifice and the speaker’s diaphragm amplitude were extensively studied. The flow and heat transfer characteristics of the synthetic jet were numerically simulated using commercial computational fluid dynamic software. A three-dimension model with a moving boundary method was developed to achieve the objective of the current study. The flow is assumed to be incompressible and turbulent. The Unsteady Reynolds-averaged Navier-Stokes equations with Shear Stress Transport k-ω model are chosen to solve the governing equations for the synthetic jet flow. The user-defined functions that represent the movement of the speaker's diaphragm were utilized to increase the accuracy of the numerical model. In the flow study, the numerical model successfully captured the streamline of the synthetic jet flow generated by the speaker actuator. The ejection centreline velocity from the diffuser shape orifices was higher than straight and nozzle shape orifices. The most significant change in centreline velocity was observed when the opening angle switched from 0o to 30o. The maximum acceptable opening angle was 60o because the change of the centreline velocity at the opening angle of 90o and 120o were almost insignificant. The location of vortex formation near the centreline of the orifice help to increase the velocity during the ejection of the synthetic jet. In the heat transfer study, the distance between the orifice and the heated surface has significant heat transfer characteristics. The smaller gap (H=10mm) is suitable for centred or point cooling while the greater gap (H=30mm) shows a more uniform temperature distribution on the heated surface. Considering the opening angle of the diffuser shape orifice with suitable speaker diaphragm amplitude improved the cooling performance of the speaker-driven synthetic jet impinging on the flat heated surface. The heat transfer performance for the opening angle of 90o is better than 45o at a higher diaphragm amplitude.
Hydrogen absorption and diffusion in niti shape memory alloy
(2023-05-01)
Ng Ching Wei
Nickel titanium (NiTi) alloy is a popular biomaterial in biomedical implants and orthodontic applications. In orthodontic treatment, the usage of NiTi archwire in combination with dental bracket is capable of delivering constant force on the treated tooth, to induce tooth movement. The contact between NiTi archwire and stainless steel brackets could form a galvanic couple in the oral cavity, while giving rise to hydrogen absorption into archwire. The absorption of hydrogen atoms impairs its shape memory behavior and functionality in orthodontic treatment. The deterioration of shape memory behavior of NiTi archwire may persist and worsen over the treatment duration, owing to the inner diffusion of hydrogen interstitial atoms into deeper core of the matrix. This study investigated the effect of hydrogen absorption and diffusion over time toward shape memory and load-deflection behavior of NiTi alloy wires. Two different NiTi wires were use, the industrial round wire, and the commercial rectangular orthodontic wire. At room temperature, the round wire was at martensitic phase, and the rectangular wire was at austenite phase. The absorption of hydrogen into wire specimens was induced via electrolytic charging. The inward diffusion of hydrogen over time was achieved via aging at room temperature. The differential scanning calorimetry showed that the absorption and diffusion of hydrogen in martensitic NiTi round wire suppressed the size of thermal martensite phase transformation peaks. Furthermore, the additional hydrogen-related phase transformation peaks were also observed after hydrogenation, while its peak size and enthalpies increased over the aging duration. The tensile deformation behavior was also largely affected, of which the stress-induced martensitic phase transformation exhibited a non-flat plateau with the formation of force curvatures at the onset and ending stages, respectively. The loading force, as deduced from its load-deflection behavior via three-point bending deformation also increased slightly. This impaired its strain recovery. The effect of hydrogen charging towards load-deflection behavior of rectangular austenitic NiTi wire via three-point bending test was only detected after charging for 16 and 24 hours. The strain recovery of the wire deteriorated over aging time in the unloading stage of load-deflection curve. The largest residual deflection was 0.65 mm for the 24-hour-charged and 7-day-aged wire specimen, as compared to 0.03 mm for the as-received specimen. In a three-bracket bending test, the hydrogen charging caused the wire to fracture during the loading stage. Likewise, the hydrogen diffusion via aging led to the large residual deflections upon complete unloading, of which its magnitude increased from 0.12 mm for the as-received specimen, to 0.70 mm after charging for 24 hours and aging for 7 days, at a maximum deflection of 4 mm. After prolonged aging, the effect of inner diffusion of hydrogen has caused obstruction towards the reverse stress-induced martensite phase transformation, thus causing the unloading force curve to occur at lower force levels.
Mechanical and formability analysis of low power laser welded dissimilar aa5052-h32 and aa6061-t6 aluminium alloys
(2024-08-01)
Mohd.Fadzil, Jamaludin
Laser welding of aluminium alloys using high-power lasers presents significant challenges, such as the high energy requirements needed to overcome the material’s high reflectivity and thermal conductivity, the formation of porosity due to keyhole instability, and embrittlement in the weld or heat affected zone resulting from rapid cooling rates. Low power laser welding offers a potential solution to these issues by operating below the keyhole formation threshold, resulting in reduced energy consumption, decreased porosity, improved weld quality, and enhanced process stability. However, its limited penetration depth necessitates strategic approaches for welding sheet metal applications, particularly for automotive tailor welded blank (TWB) fabrications. This study investigates the feasibility of low power welding for joining similar AA5052-H32 as well as dissimilar AA5052-H32 and AA6061-T6 aluminium alloys in a butt-weld configuration. The influence of laser power (270 W to 310 W) and welding speed (10 mm/s to 20 mm/s) on weld characteristics, including penetration depth, weld zone geometry, mechanical strength, springback behaviour, and formability, is examined using specimens with thicknesses of 1.0 mm, 1.5 mm, and 2.0 mm. A full factorial design of experiments (DoE) was employed to evaluate the effects of these parameters on similar alloys with different thicknesses, different alloys with similar thicknesses, and different alloys with different thicknesses. Achieving an average weld penetration depth of only 0.77 mm, a double-sided welding strategy was employed for full penetration. This resulted in successful full penetration for 1 mm thick weld interfaces, while partial penetration occurred for 1.5 mm and 2.0 mm interfaces. Weld strength increased with higher laser power and lower welding speeds for thicker specimens and interfaces, while minimal variation was observed for thinner specimens. Results showed that weld strength increases with higher laser power and lower welding speeds for thicker specimens, while thinner specimens exhibited minimal variations. Response surface methodology (RSM) was utilized to optimize the laser power and welding speed for maximum tensile strength in the most varied joint configuration of 1.0 mm (AA6061-T6) to 1.5 mm (AA5052-H32). The optimized parameters of 302 W laser power and 22 mm/s welding speed resulted in a very low heat input of 13.7 J/mm. Post-weld assessments revealed springback angles of 3° to 4° for similar AA5052-H32 alloy welds, while dissimilar alloy combinations displayed values between the respective base metals. TWB dome heights were 52-62% of the base metal values, indicating significantly lower formability for welded blanks. This research demonstrates the potential of low-power laser technology for joining dissimilar aluminium alloys in TWBs using a double-sided welding strategy for full penetration, particularly for applications requiring thin metal sheet forming.
Performance analysis of concentrated solar power flash desalination system and optimization of process variables using response surface methodology
(2024-06-01)
Faizan, Ahmed
The demand for fresh water supply across the globe is on the rise and is projected to keep rising in the future due to its heavy utilization across various sectors such as agriculture, industry, aquatic life and human consumption. To meet this demand, focus is placed on improving the existing desalination systems and exploring ways in which renewable energy components can be integrated into desalination systems to make them more efficient and sustainable. The present thesis explores a novel single-stage spray flash desalination system integrated with concentrating solar-powered technology. The work involves performing experimental investigations, energy and exergy analysis, mathematical models development, statistical analysis (Analysis of Variance-ANOVA, Fit Statistics) of developed models, optimization of system performance using Response Surface Methodology (RSM), and evaluation of various performance metrics such as gain output ratio (GOR), energy utilization factor (EUF), and specific energy consumption (SEC) for the proposed system. The experimental setup was designed, manufactured, assembled and tested at Prince Mohammed Bin Fahd University in Al-Khobar city of Saudi Arabia. The influence of four critical process parameters on system performance was examined, namely, feed temperature, flow rate, salinity, and vacuum pressure. Results reveal that feed temperature and vacuum pressure positively impact distillate production, while salinity negatively influences productivity. However, the flow rate was found to have an optimum setting. The optimum factor setting for the flow rate is 0.016 kg/s, feed temperature is 55 °C, salinity is 15 g/kg, and vacuum pressure is 70 kPa, for which the system exhibits an optimum distillate production of 0.0025 kg/s. The maximum energy efficiency of the brine heater is 67.2%, while the maximum exergy efficiencies of the condenser, brine heater, and flash chamber are 89.2%, 17.4%, and 44.3%, respectively. Results indicate that the proposed system is capable of attaining a maximum GOR of 19.2, a maximum EUF of 4.8, and a minimum SEC of 100.8 kWh/m 3. The device does not use any fossil fuels or other non-renewable sources to heat the brine, thus caters for zero emissions and a cleaner environment. Moreover, with the integration of concentrating solar power technology in the proposed system, the device is expected to contribute significantly towards cleaner and sustainable water production.
Reducing work-related injuries: a comparative analysis of patient transfer devices for healthcare professional
(2023-09-01)
Mitchelle Law Jyy Jinn
Work-related musculoskeletal disorders (WMSDs) are a common problem among healthcare workers. For WMSDs risks assessment, the Rapid Entire Body Assessment (REBA) is widely used. However, previous studies have used a constant estimated external force as load input in REBA, which does not consider the load variations due to patient and nurse postural changes. A method to input the actual load to REBA through instantaneous measurement is needed. Despite the risk-reducing benefits, the adoption rates for patient transfer devices are still low. Surveys are prone to cognitive judgement and biases and cannot capture instantaneous user emotions. Emotional evaluation of patient transfer devices has not been done before. Whether an evaluation tool of the National Aeronautics and Space Administration Task Load Index (NASA-TLX) can capture both perceived workload and instantaneous emotions, or whether facial expression analysis is necessary to quantify emotions, is unknown. This thesis aimed to identify the WMSDs risks of patient transfer devices through REBA with instantaneous measured force, to quantify the nurses' perceived workload, technology acceptance, and instantaneous emotional states during the use of patient transfer devices, and to quantify the relationship between the perceived workloads and instantaneous emotions via facial expression. Seven nurses were recruited to carry out tasks using a sliding board, motorised transfer, walking belt, and floor lift. The postural and ground reaction force data were used for the calculation of external load as load input for the REBA system. User experience was obtained through a technology acceptance questionnaire, NASA-TLX, and facial expression analysis. Motorised transfer obtained the lowest REBA score (3.33 ± 0.56), and floor lift as an intervention, still reported high REBA scores (7.73 ± 0.51). The motorised transfer had a higher technological acceptance (p = 0.016) and lower perceived workload (p = 0.004) than the sliding board. The floor lift significantly reduced perceived workload compared to the walking belt (p = 0.018), but acceptance scores did not significantly differ (p= 0.098). Despite good feedback on the interventions for the NASA-TLX and technology acceptance surveys, all devices, including the motorised transfer and floor lift, showed a high negative valence of over 80 in facial expression analysis. The motorised transfer had relatively better valence scores (82.87 ±12.60), while the floor lift had the highest negative valence (99.16±1.93). This study contributes to WMSDs risk assessment by using REBA with instantaneous measured force and introducing facial expression analysis to understand user emotions while using patient transfer assistive devices.
Residential building electrical appliances’ identification through current profiling using machine learning
(2024-11-01)
Tan, Jia Xiang
In the face of global challenges such as climate change and the effort on sustainable energy practices, innovations such as non-intrusive load monitoring (NILM) are playing an important role in providing understanding to revolutionize the usage and conserving of energy. In energy monitoring and management field, NILM has become a vital technology due to the ability to offer detailed insights into the energy consumption patterns of individual appliances with only main power entry. NILM provides better understanding of their energy consumption and potential energy saving opportunities to the consumer compared to intrusive load monitoring (ILM). The advancement of smart meters and machine learning approaches immediately gets the researchers’ attention in NILM. In this study, a real time NILM system is proposed. The proposed system can process and identify the individual appliances in real time with only measure current data from main electric meter. The Arduino UNO acts as the data collection tool to collect current data in real time and the SCT-013-000 Non-Invasive CT current sensor is responsible for measuring the current. Low voltage data will be generated with the help of CT sensor while burden resistor and EmonLib library is used to convert low voltage data into current waveform. Python software is integrated to preprocess, detect and identify the appliances. In event detection, the proposed system identifies steady state and transient state events. In the training process, the dataset for steady state event and transient state event are trained separately. In the recognition process, the system identifies the appliance and its usage in real time. Random Forest applied for steady state events, LSTM combined with Attention mechanism for transient state events and Library Matching for post processing. Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) are used to assist in the prediction. Ten appliances are selected to setup the dataset which include three major types of appliances which is single state, multi state and finite state machine (FSM). The proposed system can recognize nearly simultaneous and appliances on concurrently condition in real time and manage to identify the changing state on active appliance. A comparative analysis with existing NILM approaches demonstrates that the proposed system offers superior accuracy and efficiency, particularly in handling nearly simultaneous and concurrently operating appliances in real-time. The overall system stands out with 100% accuracy and extremely low MAE of 0.0305 in case study four that indicate superior performance compared to other models particularly in recognizing appliances in real-time.
Simulation-guided optimization and experimental validation of a new end cap for tire strain piezoelectric energy harvesters
(2024-09-01)
Alnajati Ibrahim, Ali Hameed
Vehicle accidents are often caused by tire-related issues, particularly improper tire pressure. To address this, many countries mandate the installation of battery powered Tire Pressure Monitoring Systems (TPMS). Nonetheless, concerns over the environmental and safety impacts of batteries have led to research into sustainable energy sources. Piezoelectric energy harvesters, particularly those utilizing PZT-5X, have emerged as promising alternatives. The primary objective of this study is to design and optimize a supporting aluminum end-cap structure to enhance the functionality of PZT-5X for inner tire energy harvesting applications. The study comprises three main stages: development, optimization, and experimental investigation. The development process involves analyzing tire models using ABAQUS software to identify crucial strain distribution patterns and numerically constructing the harvester structure using COMSOL Multiphysics software. Findings from the development stage revealed a maximum tire deflection of 16.71 mm for a tire size of 175/65 R14, with corresponding tire footprint dimensions of 53.62 mm × 50.20 mm. The initial energy generated by the single end-cap harvester (M1) is 32.64 µJ/rev, while for the dual end-cap harvester (M2), it is 11.66 µJ/rev. Meanwhile, findings from the pre-optimization phase identified PZT-5X as the most efficient material, with an optimal thickness of 2 mm and an ideal end-cap rotation angle (Θ) of 5º. Transitioning to the optimization stage, a Taguchi L9 plan and Analysis of Variance (ANOVA) are employed. The optimal combination of geometrical parameters was determined to be 11 for end-cap height (hd), 1 for end-cap thickness (ts), and 3 for the adhered length of PZT-5X (Alp). As a result, the optimized harvester (M3) produced an energy output of 5.44 mJ/rev and 138 mW max power at 3 MΩ and a vehicle speed of 80 km/h. The experimental work commences with strain measurements using three strain sensors. At speeds of 20, 40, and 80 km/h, the strain values remained consistent. In other words, maximum strain occurs at the tire footprint and is not affected by vehicular speed, as confirmed during numerical analysis. Additionally, three (M3) harvesters were mounted inside a traveling tire with identical conditions. The results revealed that changing vehicle speeds do not affect the voltage output. However, it does alter the frequency of that voltage, enabling faster charging of capacitors when the speed increases. The accumulated energy for the (M3) ranged from 24.04 mJ to 28.47 mJ, with a power range from 65.52 mW to 67.54 mW at a 3 kΩ resistance and 80 km/h vehicle speed. Based on a 30 km road test, the electric lifespan ranged from 5,300 km to 8,250 km.
Study On The Effect Of Tool Nose Wear On Surface Roughness And Dimensional Deviation Of Workpiece In Finish Turning Using Machine Vision
(2009-02)
Haghighi, Hamidreza Shahabi
The aim of this research is to study the effect of tool nose wear, which is in contact with the surface profile of workpiece directly, on Ra using a developed machine vision in finish turning operation.
Synthesis of stretchable conductive polymer for electronics circuit application
(2023-04-01)
Sana Zulfiqar
Stretchable electronic circuits (SECs) have become very popular nowadays in various mechanical, electrical and biomedical engineering applications. They are comprised of flexible and stretchable substrate as well as conductive ink, and electronic components. The stretchability and flexibility of SECs can be controlled by the proper selection of materials and designs for the substrate and conductive ink. Moreover, the material used to develop the conductive ink must exhibit high electrical conductivity and good adhesion with the substrate to obtain a high quality of stretchable printed circuit. This study focussed on the synthesis, material modelling and the examination of various properties of polymeric substrate and conductive ink by different thermal, mechanical and electrical testing. For synthesis, PDMS-OH was used as a binder or elastomer in both the formulations and silver powder as a conductive filler for silver-based conductive ink. The mechanical properties of these materials were evaluated by simple UTM under tensile loading. The modulus of elasticity and tensile strength of the substrate and ink were found as 0.48 MPa and 2.18 MPa at 300% stretchability, and 5.72 MPa and 1.195 MPa with the yield stress of 0.86 MPa at 137% stretchability before rupture, respectively. Afterwards, the thermal analysis of the conductive ink was carried out by DSC and TGA. From DSC, the glass transition and melting temperatures of the cured ink were found as 130°C and 297.43°C, correspondingly. The thermal degradation was studied by TGA in which the weight loss occurred at different ranges of temperature. The residue of silver particles was obtained as 82.62% after complete analysis. This proves that the current formulation of the ink becomes more viscous at higher temperatures. Moreover, the storage modulus, loss modulus and damping ratio of the ink were calculated using DMA analysis. As a result, the silver ink exhibited low loss modulus value than the storage modulus, which proves that the current formulation of the ink was more elastic in nature rather viscous. Farther the micro mechanical analysis, the hardness and reduced modulus of the conductive were computed by nanoindentation technique. In addition, the surface analysis of the ink was done by OM and SEM. As a result, the silver particles were homogeneously spread throughout the surface of the ink. The electrical conductivity was measured by 2-point multi-meter before and after application of load. It was found as 1002 S/cm without loading, while, the resistance of the ink increased from 0.042 Ω to 25 Ω at 60% strain during loading and decreased from 25 Ω to 0.0767 Ω at 0% after unloading. Finally, the stress-strain data of respective material were utilized to characterize the material properties using hyper-elastic constitutive models for the substrate and multi-linear plastic models for the conductive ink. The curve fitting was done using three solvers, Abaqus, GRG and C-PSO algorithm. As a consequence, the Reduced Polynomial (𝑁=6) model under C-PSO algorithm was considered as the best fit hyper-elastic model than others. The validation of this hyper-elastic model was then executed through FE analysis. Consequently, the experimental results were in a good agreement with the simulated results.

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