Pusat Pengajian Kejuruteraan Mekanikal - Tesis

Browse

Now showing 1 - 5 of 282

Performance characterization of bag-valve-mask (BVM) compression using machine learning
(2024-02)
Sanjivan Muthu Kumar
Medical staff face issues when ventilating patients manually using the Bag-Valve-Mask (BVM) for long periods to resuscitate patients unable to breathe properly on their own. As for ICU mechanical ventilators in hospitals, medical specialists must check on patients frequently and adjust settings manually. Currently, there are portable ventilators available in the market that aid in supplying oxygen to patients, however the usage of ML is rare, and they do not take into account various variables which are deemed important in patient recovery. In this research, the BVM was used to perform ventilation using manual and automated methods, after which machine learning (ML) study was done. The first objective was to predict the average tidal volume using artificial neural network (ANN) and boosted decision tree regression algorithms. The R2 value obtained from manual ventilation using ANN was 0.738861, whereas the boosted decision tree model scored 0.600049. Thus, ANN was used on the automated ventilation system to compare its performance with the manual, where an R2 value of 0.978604 was obtained after removing unwanted features. When compared with the manual model, a 32% increase in R2 was obtained. K-fold cross validation was carried out to test the manual and automated models in a bigger data space, where the standard deviation of the automated model was significantly lower, indicating lower variability within its dataset. The outcome of the study suggests that the automated system predicts the experiment data better than the manual system when utilizing ANN. Another objective of this research included conducting ML study using data collected from an ICU mechanical ventilator to provide a setting recommendation for a particular patient using linear and Poisson regression, where linear regression scored a R2 value of 0.936, whereas the Poisson model scored 0.836 when tested on tidal volume (TV) setting. Thus, linear regression was used to perform ML on the TV setting, fraction of inspired oxygen (FiO2) setting, and positive end-expiratory pressure (PEEP) setting, where TV setting scored the highest R2 values overall. To validate the TV setting formula obtained through Microsoft (MS) Azure, three experiments were conducted using a ventilator prototype on an artificial test lung for validation. The experiments yielded error results ranging from 53% to 79%, indicating that the TV setting values obtained from the prototype were incomparable to mechanical ventilator data. Extensive research is needed to compare the results between BVM ventilators and ICU mechanical ventilators.
Optimization of wire-bonding process parameters for gold wire and aluminium substrate using response surface methodology
(2024-09-01)
Megat Sufi Aniq, Mohamad Rosli
Wire bonding is a connecting technique that uses a combination of temperature, force, ultrasonic power, and time to attach two metallic materials, a wire, and a bond pad. In electronics, gold-aluminium (Au-Al) contact wire bonds are widespread due to corrosion resistance and great conductivity of both metals. However, the intermetallic compound growth at the metal’s interaction boundary has considerably worsened the advantageous properties of Au-Al intermetallic system due to the large contact- potential difference. These intermetallics exhibit low toughness, and possibly low corrosion resistance, which would result poor bonding quality. This study aims to investigate the most optimized set of parameters to be used in Au-Al wire bond system. During the initial study, this research’s starting point is to identify the dependent and independent parameters within the wire bonding process by using the two fractional factorial method. After conducting the experiments, data has shown that there are 4 dependent and 4 independent parameters. The four dependent parameters are time of bond at first bonding site, wire looping height, Y-axis length and ultrasonic force at second bonding site. These four dependent parameters are brought into extended study for further analysis. In the extended study, the experimental array was created using a response surface methodology (RSM)-based design of experiments. The effect of parameters and their significance to bonding quality in the Au-Al bond system were studied using analysis of variance (ANOVA). A correlation model was created for the wire bond strength data. The findings suggest that, within the range of parameters examined, the proposed correlation model can be utilized to predict performance measures. The optimum value of Au-Al wire bond system parameters was established at time of bond at first bonding site selected for 300 milliseconds (ms), wire looping height selected for 1200 micrometre (μm), wire bond Y-axis length selected for 996 micrometre (μm), and ultrasonic force at second bonding site selected for 300 milli Newton (mN). A validation test was conducted to verify the adequacy of the developed regression model, and the percentage errors between the predicted and experimental data were calculated as 0.91% to 7.05%. Thus, the regression model created for this study are capable of being reasonable accurate. The outcomes of this research add to our understanding of the Au-Al wire bonding contact for the engineers in the microelectronics industry and to enhance the wire bond’s quality during the electronic packaging process.
Numerical investigation on natural convection and optimization of the fin design on a bus duct conductor
(2024-01-01)
Mark Selvan, Anthony Rogers Louis
In the field of electrical power systems, the efficient transfer of heat is essential in ensuring high thermal performance. One critical component that requires efficient heat dissipation is the bus duct casing. The bus duct casing is an electrical power distribution system that transports electrical energy from one location to another. It is essential that the bus duct casing operates within the thermal limits to ensure its reliability and prevent electrical failures. However, often times the bus duct conductor operates at very high temperatures border lining the maximum allowable temperature in accordance to IEC 60439-1 and IEC 60439-2 standards. Hence, it is imperative that a more efficient and effective heat sink design is employed to guarantee peak current carrying capacity. The design optimization of a three-dimensional natural convection heat sink used on the bus duct conductor's casing was examined in this study. Four design variables, fin length, fin pitch, fin thickness, and number of fin valleys, were analysed to improve the thermal performance of the heat sink. Each design variables were investigated one-factor-at-a-time . The Average Surface Temperature and Nusselt number were used as the performance criterion. Upon completion of the OFAT analysis, a statistical optimization method known as Definitive Screening Design was carried out to determine the best combination of the 4 design variables. The Definitive Screening Design method suggested thirteen optimized test conditions and the outcome of the parametric study showed that the fin length was the most influential factor, followed by the number of fin valley, fin pitch and fin thickness. Fin pitch of 4mm, fin length of 6.5mm, fin thickness of 1mm, and 6 fin valleys were the most optimal combination, resulting in an average surface temperature of 72.05°C and a Nusselt number of 21.59. The results were benchmarked against the experimental study and showed a deviation of 2.97% and 6.25% from the predicted values, respectively. This study investigated the effects of each design variable on the thermal performance of the heat sink, providing insights into improving the design of the heat sink used on the bus duct conductor.
Finite element analysis of deformation and fracture of cortical bone in vibration-assisted bone cutting
(2024-11-01)
Du, Qianrui
The use of vibration-assisted cutting (VAC) technology has made its way from industrial applications to the medical field, particularly in bone cutting for orthopaedic surgery. Nevertheless, the bone cutting process can be quite complex because of the bone’s anisotropic properties, which contribute to its intrinsic toughening mechanism and vulnerability to surface damage. Therefore, it is important to take into account the impact of microstructure on the efficiency of the bone cutting process, which can be accurately evaluated using the finite element method. Yet, simulating tool-bone contact is seldom done because of the large deformation of the bone model, which can cause convergence issues, thereby adding complexity to the analysis. Hence, to simplify the modelling process, this study creates Python code for building a bone micro-model that includes bone microstructure considerations. The code allows for creating a micro-model with a user-defined distribution of bone microstructure constituents, enabling adjustable porosity. Two bone models with different microstructure properties and porosity are created using the code to represent young and aged bones. The models have been validated through a comparison of the stress intensity factor with the analytical results for a single-edge notch bending (SENB) specimen, revealing a deviation of just 4.5%. By incorporating the extended finite element method (XFEM), these models are utilised to analyse how amplitude and cutting depth impact the performance of vibration-assisted bone cutting. This analysis involves quantitatively assessing the resulting cutting force, stress, strain rate, crack initiation and propagation, and comparing them to conventional cutting methods. According to the results, VAC consistently decreases cutting force and stress in both models for various cutting depths and shows improved control of crack extension direction with smoother crack curves. It has been noted that the impact of amplitude variation on the resulting cutting force varies between the two models. In aged bones, increasing the amplitude decreases the cutting force, whereas in young bones, it has a negligible effect. In terms of bone strain rate, vibration-assisted cutting can significantly increase the cutting strain rate, thus reducing toughness damage and cumulative damage. VAC temperature is observed to be higher than conventional cutting. At the area of high temperature, which is near the tool, the cutting chips are smaller.
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.

Browse

Recent Submissions