Pusat Pengajian Kejuruteraan Mekanikal - Tesis

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A Model For The Fuzzy Front End Of New Product Development Process
(2016-01)
Abd Rahman, Md Nizam
In general, New Product Development (NPD) methodology can be broken down into five phases, Strategic Planning. Idea Generation, Pretechnical Evaluation, Technical Development, and Commercialization. The first three steps are known as the front end and the last two are known as the back-end of the NPD methodology. The scope of this research work is limited to the first two steps of the NPD methodology, which are strategic planning and idea generation. The objectives of this research work are I) to piece together the various steps required in executing strategic planning process to ensure its effectiveness and 2) to define guidelines in selecting idea generation techniques that are suitable for a given set of conditions. Through analyzing case studies on thirty cornpapies that have been proven successful in NPD programs, the main factors that have significant impact on the success of NPD strategic planning process are verified and guidelines for selecting suitable idea generation techniques for a given set of conditions are developed.
A study of punch-die misalignment in square cup deep drawing process using experiment and finite element analysis
(2022-09-01)
Abdul Ghafar, Alimi
Square deep drawing is a forming process that transforms a flat sheet metal to a seamless vessel by using a set of punch and die. Any misalignment in the punch -die assembly during the process can cause thinning, which can result in the tearing of the drawn part. The onset of thinning due to punch-die misalignment is yet to be explored fully, thus understanding the thinning initiation will be useful for process optimization. In this study, a series of comprehensive methods to identify the presence of punch-die misalignment in square cup deep drawing process is implemented. These methods are deployed at the pre-drawing, during the drawing process and at the post drawing stage. In the pre-drawing stage, an image processing technique is utilized forpre-drawiing inspection. The captured images are analysed to identify the severity of misalignment between the punch and the die. At the second stage (during forming), an in-situ method is used to observe the presence of punch-die misalignment. For this purpose, a customised die rig is fabricated and installed on a universal tensile machine (UTM). A Commercial Electrolytic Zinc-Coated Steel Sheet (SECC) was used as the specimen for the deep drawing process, and the effect of misalignment severity on drawing force and wall thickness distribution are investigated. For comparison, a finite element (FE) simulation is utilized as an early prediction of the punch-die misalignment. The simulation was conducted using Abaqus/Explicit FEA software, utilitising the Hill’48 model, to determine the stress-strain diagram and forming limit diagram (FLD) of the SECC material. Two conditions of misalignment were simulated, 1) single axis punch-die misalignment and 2) multi axes punch-die misalignment with the misalignment severity of 0.1 mm to 0.5 mm. At the post-drawing stage, the wall thickness distributions of the cup for each misalignment conditions were investigated. Variations in wall thickness distributions would indicate the severity of misalignment between the punch and die. Specifically, a novel methods are introduced for detecting the presence of punch-die misalignment in square cup deep drawing process. Both the FE and experimental results were in good agreement with regard to the drawing forces and thinning patterns due to punch-die misalignment. Greater misalignment severity was observed to increase the drawing force and thinning in the wall of the drawn cup. For both misalignment conditions, similar wall thickness distribution patterns were observed, with the maximum thinning occurring in the cup sidewall and minimal thinning at the bottom of the cup. For single axis misalignment, the maximum thickening up to 18% has occured at the lowest misalignment severity of 0.1 mm. On the other hand, for misalignment severity of 0.3 mm and above, the maximum thinning in the x-axis was higher as compared to the y-axis by average of 0.53% and 1.72% based on FE and experimental results, respectively. For multi axes misalignment, the maximum thickening averages at 15%, while the thinning was more pronounced in the rolling direction as compared to the transverse direction. As a conclusion, this study had contribute a positive signification implication in die making, especially punch-die alignment issue in deep drawing process. Alignment punch-die is essential in square cup deep drawing process. A series of comprehensive approach for identifying punch-die misalignment issue according to this study can be referred by researcher and industrial practioner in making high quality square cup deep drawn product.
A study on low temperature synthesis of silicon carbide thermionic cathode and its electron emission analysis for thermionic energy converter
(2020-07-01)
Leong, Thye Jien
Energy conversion of renewable and clean energy such as thermal energy is often related to solar cell and photovoltaic cell. These are the rising technology devices that generate electrical energy for the use in industrial and residential sectors. In order to seek for an alternative approach in meeting the growing energy demand and reducing the dependency on conventional energy resources such as biomass energy, another direct thermal energy to electricity conversion device namely Thermionic Energy Converter (TEC) is being studied. However, the technology involved in this device has one major limitation which is the unavailability of low cost cathode materials with low work function yet easily-obtained. This drawback has motivated the study of cathode material in term of lowering the work function by surface nanostructuring the thermionic cathode for TEC in the mentioned research direction. By using atmospheric pressure chemical vapor deposition (APCVD) method, a low temperature (600°C) synthesis thermionic cathode was developed, as validated by the literature (Xi et al., 2006). In this approach, silicon carbide (SiC) nanostructures were synthesized on the silicon substrate. This method was optimized based on two parameters which are controlling the thickness of catalyst (Magnesium) and the amount of precursors (silicon tetrachloride and 2-ethoxyethanol) used in the experiments. Some material characterization techniques, such as SEM, EDX, and FESEM were performed to the thermionic cathode to support the proposed synthesis method. Besides, a new in-house built TEC system that is equipped with a vacuum chamber, CO2 laser heating system, turbomolecular pump, and digital nanoammeter was developed, which can manipulate temperature of the thermionic cathode. The electron emission analysis of thermionic cathode was performed at different temperature ranges where a copper plate (4.7eV) was used as the anode. Based on the results, a total reduction of ~0.36 eV to the work function of the p-type silicon (111) with ~4.84 eV is achieved by the as-synthesized SiC nanowires thermionic cathode using M200SC3 - ~4.48 eV sample. Lastly, the Schottky effect is proven showing an enhancement to the current density of the SiC nanowires thermionic cathode by compromising a small deviation of the work function of ~0.02 eV. These findings prove that the presence of SiC nanostructures on the thermionic cathode has achieved higher current density, 87 nA cm-2 with the presence of applied voltage at 4000 V/cm and 71.8 nA cm-2 at zero field effect, as compared to 14.4 nA cm-2 for the control sample in this TEC study.
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.
Analysis of void formation for no-flow underfill process using numerical simulation and machine learning-based methods
(2022-09-01)
Nashrudin, Muhammad Naqib
The no-flow underfill process has been developed as an alternative to the conventional capillary flow underfill. It offers low cost and lead time production effectively due to the integration of simultaneous reflow of solder interconnect and cure of underfill material. Somehow, no-flow underfill also faces the same reliability issue which is the potential void formation during the process. The research on the void formation issue in no-flow underfill has been found scarce. In addition, the research works on no-flow underfill focused on the experimental method which is costly and very limited to study the root cause of the issue. Therefore, this research presents a numerical simulation study of the no-flow underfill which has the ability to track dynamically the movement of the flow of underfill in real time during the process. This research investigates and predicts the possible void formation of no-flow underfill. Three major parameters were selected to align with industry requirements which are chip placement speed, bump pitches and viscosity of underfill. Subsequently, previous literature of no-flow underfill experiment, industrial no-flow underfill experiment and current scaled-up imitated flip-chip experiment were compared in term of flow and void formation percentage to validate with the current numerical simulation. Overall, the current numerical simulation produced low discrepancy which is less than 15% error among all the experiments and affirmed the capability and accuracy of the numerical simulation model. It was found that the void formation rate increases with the chip placement speed but decreases with the increase in bump pitch. The highest chip placement speed of 14 mm/s produces 4-6% meanwhile, the low chip placement speed (2-5 mm/s) produces around 2-3.5% of void formation. Moreover, several supervised machine learning prediction-based methods such as linear regression, decision forest regression and neural network regression were implemented to train the numerical values and to investigate further the most significant parameter that affects the void formation in the chip. It is observed that linear regression, decision forest regression and neural network regression produced mean absolute errors between 0.1588, 0.176375, and 0.1818, respectively. The neural network regression is the preferred algorithm method of machine learning in the study since it shows the least error with a high R2 value of 0.95159. Based on permutation feature importance, the most significant parameter that affect the formation of void in the no-flow underfill was chip placement speed compared to bump pitches and underfill’s viscosity with a score of 1.7916, 0.2962 and 0.000878, respectively. This research provided engineers in the microelectronic industry with a deep understanding of the void formation and expected to provide an appropriate guide to minimize the failure for the development of no-flow underfill in the future.
Bio-based and hybrid based polymer composites for enclosures of memory storage device application
(2022-08-01)
Janakiraman, Vishnu Chandar
A large proportion of consumer electrical and electronic packaging applications were made up of thermoplastics. Casings or enclosures are generally used in circuit boards, and data storage which is made up of plastic to ensure the appliances are mobile, lightweight while being tough and durable and at the same time, the plastics used in these applications are very high and also not biodegradable. This research aims to reduce the usage of plastics in storage applications via two approaches, i.e., bio-based and hybrid-based polymer composites. In this work, pure polymer [polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), cellulose acetate (CA)] and its bio-based composite ((PLA/Aluminium oxide (Al2O3)/Boron Nitride (BN)), PLA/BN/Graphene tubes (GT), PHBV/Al2O3/BN, PHBV/BN/GT, CA/Al2O3/BN, CA/BN/GT) sheets with different concentration of hybrid filler [(Aluminium oxide (Al2O3)/Boron nitride (BN), BN/Graphene tubes (GT)] were fabricated. Similarly, pure thermoplastics (polyoxymethylene (POM), polypropylene(PP), polycarbonate (PC)) and its hybrid-based composite POM/PHBV/Al2O3/BN, POM/PHBV/BN/GT, PP/cellulose fiber (CF)/Al2O3/BN, PP/CF/BN/GT, PC/basalt fiber (BF)/Al2O3/BN, PC/BF/BN/GT) sheets with different concentration of hybrid fillers were fabricated using internal mixer equipment and compression molding method. The effect of fillers on the structural, optical, thermal, thermophysical, mechanical, surface, electrical properties of the pure polymer and its bio-based and hybrid-based polymer composite sheets were studied, compared, and suggested for electronic packaging applications. XRD results confirm the presence of polymers and fillers (ceramic, carbon, and natural) in the prepared bio-based and hybrid-based composites. The prepared bio-based (PLA/BN/GT, PHBV/BN/GT, CA/BN/GT) and hybrid-based (POM/PHBV/BN/GT, PP/CF/BN/GT, PC/BF/BN/GT) polymer composites exhibit high UV-VIS-NIR absorption, thermal conductivity (0.29 - 0.51 W/mK and 0.35 – 0.53 W/mK), flexural strength (34.2 – 66.4 MPa and 59.1 –74.8 MPa), flexural modulus (1088 – 3239 MPa and 1313 – 3424 MPa), storage modulus (726 – 2130 MPa and 1492 – 3132 MPa), scratch hardness (0.43 – 0.73 GPa and 0.44 – 1.19 GPa), and low CTE (17 - 42.9 µm/m ºC and 38.6 – 114 µm/m ºC), ESD (<10V to <100V and <10V) compared to composites with Al2O3/BN filler and pure polymer that may be due to the high thermal conductivity, mechanical strength and synergetic effect of BN and GT filler. As for dielectric permittivity, Al2O3/BN reinforced composites exhibit favourable dielectric constant (3.02 - 4.74 and 2.72 –3.37) and loss (< 0.02), whereas BN/GT reinforced polymer composites shows higher values at a lower frequency. Like bio-based, hybrid-based polymer composites also follows the same trend in dielectric permittivity. On comparing the bio-based composites, CA/BN/GT polymer composites are suitable for USB products with high storage capacity as per the obtained melting, glass transition temperature, CTE, ESD, mechanical, and scratch performance, whereas PLA/BN/GT and PHBV/BN/GT polymer composites are suitable for USB products with very low storage capacity and can ultimately reduce 98% of plastics. Similarly, the prepared hybrid-based polymer composites (POM/PHBV, PP/CF, PC/BF) with BN/GT filler are suitable for USB, SSD, and HDD products with both low and high capacity as per the obtained thermal, ESD, mechanical, and scratch performance and can ultimately reduce 15-40% of plastics in enclosure applications.
Design and implementation of six rotors unmanned aerial vehicle
(2010-04-01)
Mohamed Aziyen, Mohamed Afique
The control of a helicopter is complex, and includes the interaction of forces and the balancing of them. Although a stable condition can be achieved with sophisticated control system, good mechanical design can reduce the problem of instability of a helicopter. One of the designs is the coaxial types of blade system. Nevertheless, a good control system is still needed since a helicopter control involves many parameters. PIC16F876A microcontroller has been used to measured the input from sensor, do the calculation and control the actuators). In this project, ultrasonic sensor is used to control the height of the helicopter. The force that been produce by the helicopter must be the same to make sure that the helicopter is stable.
Development and documentation on use of completely randomised design
(2010-04-01)
Hamid, Zulkharnain
This project presents the development and documentation of actual engineering examples on the use of the Completely Randomized Design (CRD) in PPKEE. The examples involve a single factor experiment that uses the analysis of variance (ANOVA) technique to analyze the data. Basically the project is to understand the single factor analysis on use of the Completely Randomised Design. The other objective of this project are to search the actual use completely Randomized Design final year students of EE School. After searching, the actual examples of potential use of the Completely Randomised Design are developed based on type of research conducted by the EE students. Minitab is using to analysis the data from the previous final year report. There are a two phase in this project are literature review and develop the examples. The parts reviews and searching of the examples involve the three major courses in school of electrical engineering which is Electrical, Electronic and Mechatronic engineering. From the review of the previous final year report, three examples are developed in the project. The evaluation form was designed to get a feedback from engineering student regarding the examples that have been given. From the analysis of the evaluation form, the performance of the examples were developed are at a good level.
Development and performance analysis of hydraulic hybrid regenerative braking system for passenger vehicle
(2022-01-01)
Idris, Khairul Anuar
The global fuel consumption of passenger vehicles has been rising dramatically over time. Since fossil fuel is non-renewable energy, there is a need to improve the passenger vehicles efficiency. Therefore, the hydraulic regenerative braking system (HRBS) is introduced to recapture the lost energy during the deceleration. This study aims to develop HRBS and determine its performances. The experimental work involved designing and fabricating a test rig of the HRBS in a parallel configuration. The performance of the developed system was determined in terms of efficiencies of hydraulic motor and pump. The study findings developed a mechanical efficiency map for the hydraulic motor for different pressures. It was found that the efficiency gradually increased with the increase in pressure from 20 to 80 bar, but a slight drop was seen with further increase in pressure above 80 bar. The highest efficiency recorded by pump and motor were 83 % and 74 %, respectively. Meanwhile, hydraulic pump’s mechanical efficiency maps in terms of pressure were determined for four different speeds. The efficiency was steadily increasing from the pressure 20 to 75 bar. The optimum operating pressure was 65 bar for both the pump and motor. The optimum operation also played a crucial role in establishing the higher mechanical efficiency for the motor and pump, subsequently affecting the overall performance of the developed HRBS system.
Development of finger-based computer mouse by using wiimote
(2009-04-01)
Lee, Wee Chuen
This report presents the project of finger-based computer mouse by using a game controller of Nintendo Wii, Wiimote. This project is focusing on developing an alternative computer mouse which is cost-effective, real-time application, user-friendly and can be used at a further distance from computer. It consists of a hardware setup for sending infrared (IR) light to Wiimote and a Graphical User Interface (GUI) that is built by using Microsoft Visual C++. A C++ library, “WiiYourself!”, is being used to obtain three IR dots’ coordinates from Wiimote, which are implemented for computer mouse’s functions. From the experiment, it is found that the user can successfully move the mouse pointer and perform clicking at a maximum distance about 2 meters away from Wiimote, which is good for presentation. The main drawback is the batteries of the glove with IR LED need to be changed after four hours of usage as its voltage dropped to a level that would worsen its performance. Besides, as the user used this system for long time, the users hand started to be uncomfortable. At this moment, the user can successfully move and perform clicking just like a conventional computer mouse with some limitations.
Discrete phase model simulation and optimization of different types nano-reinforced solder fillet using taguchi analysis and neural network method
(2021-12-01)
Muhamed Mukhtar, Muhamed Abdul Fatah
Recently, the electronic industry required electronic components to become reliable, lightweight, and miniature. In order to ensure the functionality of electronic devices, advanced joining through the nano-reinforced solder material was required. In previous studies, the addition of different types of nanoparticles to lead-free solders has been studied. One of the strengthened elements added, such as NiO and TiO2, helps the solder fillet to have better mechanical properties. Nevertheless, there is still a large research gap in the miniaturized part assembly processes through nano-reinforced solder paste on the actual surface mount devices. Hence, this research aims to investigate the advanced joining of ultra-fine packages using the nano-reinforced solder paste. Nanoparticles material name, TiO2, Fe2O3, and NiO with (0.01wt. %, 0.05 wt. %, and 0.15 wt. %) were selected to be reinforced with lead-free solder paste (SAC 305 type 5) to form three different types of nanoparticles samples. The nano-reinforced solder paste was contrasted with the pure SAC305 solder paste in terms of material and mechanical properties. In the current analysis, a two-way interaction is implemented using both the fluid volume method (VOF) and the disperse phase method (DPM) to account for the interaction between both the nanoparticles and the molten solder. DPM simulation is capable of viewing the comprehensive trajectory of nanoparticles as it undergoes thermal reflow from SAC305 based on the comparison of the simulation the experimental result. Additionally, for all cases of nanoparticles being used, strong agreement can be seen between both experimental and simulation data collected. By using different experimental techniques, the microstructure, fillet height, hardness and Modulus Young were investigated. The experimental results showed that the presence of nanoparticles generally strengthened the ultra-fine solder joint's material and mechanical properties. The reflow soldering process parameters were optimized by Taguchi technique based on Taguchi’s L16 orthogonal array. The optimum weighted percentage and nanoparticle material types were determined, and their percentage of contribution was estimated by applying the signal-to-noise ratio and analysis of variance. By adding 0.15 wt. % of TiO2, Fe2O3, and NiO, respectively, it increased the hardness and shear strength of the solder joint. The optimal configuration and the highest mean value of hardness and the modulus Young were obtained by 0.15 wt. % of SAC305+TiO2 nanoparticles were0.2875GPa and 89.65GPa. Meanwhile, optimal configuration and the highest mean for fillet height were obtained by 0.05 wt. % of SAC305+NiO nanoparticles was 0.1719mm. Quasi Newton method of Neural Network (NN) was used to train the experimental values. In comparison between experimental and neural network model results, the percentage error of predictive models for fillet height, hardness, and modulus Young were -0.046% , 1.077% ,and 20.420 %. This research provides engineers with a deep understanding of the ultra-fine package features of the nano-reinforced solder joint in the microelectronics industry. The results are expected to provide an appropriate guide and reference for the electronics industries in order to develop nano-reinforced solder joints of miniaturized electronic packages in the future.
Effect of aperture filling parameters of solder paste on stencil printing process
(2020-05-01)
Rusdi, Mohd Syakirin
The stage that causes major concern compared to the other stages in Surface Mount Technology (SMT) is known as the stencil printing stage. The study of pre-stencil printing is performed using simulation software to minimize fabrication costs and time. Therefore, this research focuses on the 3D simulation of aperture filling using lead-free solder during the stencil printing process via the usage of CFD simulation. The aperture filling of a solder paste at a varying squeegee pressure, squeegee speed and separation speed were studied using a commercial solder paste printer (DEK 265), and a 3D solder paste scanner (KOH YOUNG Aspire 2). A PCB that measures at 183 mm × 133 mm with 2 mm thickness was used in the experiment. Optimization of the process was done via Response Surface Methodology (RSM) where optimum solder filling volume, solder paste height and solder area coverage were obtained during the printing process. The optimum values suggested by RSM were squeegee pressure = 0.69 MPa, squeegee speed = 35 mm/s, and separation speed = 0.498 mm/s, and the optimal responses were volume = 0.783 mm3, height = 0.121 mm, and area = 6.481 mm2. The optimized parameters then were used as the validating data to carry out other extending studies. Anton Parr Physica MCR 301 Rotary Rheometer machine was used to conduct experiments on solder paste rheology (shear rate and viscosity). Parallel-plate (PP) and Cone-plate (CP) spindle were used to carry out five different tests consisting of different spindle type and setting. The volume filled under different squeegee speeds found that PP of 0.5mm gap exhibited the lowest average discrepancy value at 5.4% while CP1° and PP 0.5mm at 11.6% for different aperture sizes. The average discrepancy was the comparison between experiments and simulations results. Then, the studies were further extended to simulate the stencil printing process by using ANSYS Fluent 19. VOF method with Cross viscosity model was selected to undergo the numerical simulation. The volume filled by the solder paste at different aperture size according to the experiment and simulation results were compared. For different aperture size, all the results showed a similar trend with an average discrepancy of 11.6%. Furthermore, another study was added to investigate the stencil printing process efficiency at different squeegee speed and aperture size. The performance of the solder pastes for stencil printing is then compared with different lead-free solder paste (SAC105, SAC307, SAC305, SAC405 and SN100C). Leaded solder paste (Sn62Pb36Ag2) was also included in the analysis to demonstrate how well the lead-free solder pastes perform in comparison to the leaded solder paste. The research results were analyzed by comparing the effects of different angles, stencil thickness and aperture size. Results showed that the SAC305 gives the best result compared to other lead-free solder pastes and also leaded solder paste.
Effect of sintering temperature on the properties of magnesium substituted biphasic calcium phosphate
(2020-05-01)
Marahat, Muhammad Hanif
Biphasic calcium phosphate (BCP) is a bioceramic material which are known to have two distinguish phases which is hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). The aim of this research is to improve the limitation in mechanical properties of BCP by the addition of 0.025 wt% of Mg. The addition of Mg was able to increase the densification of BCP by stabilizing the β-TCP phase and delay the formation of α-TCP at high sintering temperature. Therefore, this study emphasizes on the effect of Mg substitution on BCP upon densification through sintering process. BCP and MgBCP powder was synthesized via wet precipitation method using the ratio of (Ca+Mg)/P 1.61. The obtained as-synthesized powder was pressed in pellet shape and sinter at temperature 900oC, 1000oC and 1100oC. The analysis is separated into two part which covers the unsintered as-synthesized powder and sintered pellet. The as-synthesized powder shows that Mg substitution improved the crystallinity peak from XRD analysis. For sintered pellet, the result for porosity of BCP have shown that the porosity of BCP have decreases from 40% at 900oC to 25% at 1100oC respectively. The trend also decreases as Mg was added, from 39% (900oC) to 22% (1100oC). Moreover, the result for mechanical testing shows that the MgBCP pellet is having higher mechanical strength compared to BCP pellet. The highest compressive strength for BCP pellet is at 5.02 MPa and MgBCP is at 9.41 MPa. The same trend with Vickers hardness testing which record BCP (0.82 GPa) and MgBCP (0.93 GPa). Overall trend shows that sintering at 1100oC gives better mechanical strength. Moreover, in term of biological analysis, MgBCP pellet gives more formation of apatite layer on its surface under FESEM observation due to more dissolution process for apatite to growth.
Encapsulation process of polymer for led packaging
(2021-12-01)
Alim, Md. Abdul
Several developments and innovations have reported strengthening the reliability and efficiency of these devices to speed up the LED packaging industry for the past few years. To develop a sustainable LED packaging process, die attachment and encapsulation shape are key factors. Epoxy based non-conductive adhesive (NCA) is popular die attachment material. Though NCA have many benefits so, an investigation on the suitable shear strength, adhesive thickness, and adhesion area are essential for die attachment process. Normally, high viscous epoxy resin is used as encapsulation material. A proposed low viscosity epoxy encapsulation shape can represent a new milestone for low-cost LED fabrication. In this work, the relationship between adhesive thickness and shear strength developed in chip and substrate joint is evaluated by using different adhesive applicator. Surface morphology of chip and substrate are also studied by using the SEM, EDS, and image processing software. The result indicated that the suitable shear strength 37.42 N/mm2 obtains at 24 µm thickness of the adhesive layer. A new moldless dispensing method for forming dome shaped encapsulation is studied. Luminous intensity of LED is determined by mixing verity of weight % of phosphor with the epoxy and variation in shape of encapsulation The results show that this method can produce the lenses with high aspect ratio (height over radius) on substrates of different sizes. The improvement of light output was found about 2.37% for dome shaped (average H/R value 0.71) encapsulation. This experimental work is a good guideline to master the geometric shape of encapsulation for further development and to choose technological criteria for LED packaging.
Enhanced liquid mixing in 2d channel with different fin configurations
(2022-08-01)
Tan, Sak Jie
In microfluidic devices, narrow channels lead to low Reynolds number flows, thereby restricting the fluid flow in a laminar flow condition, a long mixing channel length is thus needed to achieve a complete mixing. The research on liquid mixing enhancement in the channel shall be explored to reduce the required mixing length. The assessment of liquid mixing in the channel was performed to investigate the fluid flow in the channel with augmented design. The experiment on channels with the augmented designs was performed in the study to mimic the mixing behavior in the channel. The combination of different inlet designs, for example, Cross-inlet and T-inlet integrated with staggered fins, were modelled to numerically investigate the mixing performance. It is found that the implementation of obstacles within the channel can significantly enhance the mixing performance. The numerical investigation on the effects of geometric parameters and flow parameters on the Cross-mixer and T-mixer were performed in this study. Several fin arrangements, such as staggered fin arrangement, in-line fin arrangement, and Tri-fin arrangement on T-mixer, were proposed to enhance the mixing performance on the mixer. At 𝑥/𝐻 = 10, 𝑀 of 0.8905 is attained with staggered fin arrangement. Meanwhile, 𝑀 = 0.8509, 0.8498, and 0.7443 are yielded with in-line fin, Tri-fin and basic mixer, respectively, at the same axial position. Among these designs, T-mixer with staggered fin arrangement yielded the best mixing performance, in the practical range of Reynolds numberinvestigated. Besides, the comparison between Cross-mixer and conventional mixers was also examined. The results show that well-mixed fluid can be achieved with only a one-quarter channel length using Cross-mixer as compared with conventional mixers (T-mixer and Y-mixer) under the same flow condition. The correlation equation for T-mixer and Cross-mixer is proposed to predict the mixing length based on the Péclet number. The correlations are in good agreement with the simulation results. The effect on Péclet number and the validity of 3D mixers were also presented to validate the proposed correlations. Apart from that, the proposed correlation equation for Cross-mixer is validated by comparing the experimental results of the Cross-mixer at Re = 12 to 67. The correlation formulation proposed is found to be in good agreement with the experimental results. The deviation between numerical simulation and proposed correlation for T-mixer and Cross-mixer are 1.69 % and 0.89 %, respectively. These correlations shall be useful for researchers in predicting the mixing length without the need to perform numerical simulation.
Finite element modeling of warpage molded printed circuit board in a reflow process
(2022-05-01)
Sek, Chun Hei
A printed circuit board (PCB) consists of multi-layer materials that allow electrical current flow. Each material layer has its own specific coefficient thermal expansion (CTE), such as Young’s modulus, Poisson’s ratio, etc. A conventional PCB board consists of polymer, silicon, copper, and dielectric. With each layers having different CTE values, this causes PCB to warp.In the semiconductor industry, PCB warpage has greatly impacted assembly process yield and solder joint reliability. The present study explores the warpage changes of molded PCB during the reflow process. Warpage behavior on molded PCB models has been investigated experimentally and numerically. Experimental set-up employs Shadow Moiré technique to measure real-time warpage measurement for a benchmark model with the size of 10 × 10 ×1 mm. Temperature profile with progressive heating from 25 ℃ to 300 ℃ with an interval of 50 ℃ is employed. Then, the sample undergoes a cooling process until it reaches the room temperature. Numerically, ANSYS FEA simulation was carried out to investigate the warpage on different sizes of PCB models. In addition, thermal stress induced by CTE mismatch is studied to understand its impact on PCB warpage. The results revealed that the experiment and the FEA simulation results are in a good agreement, in particularly at the peak temperature of 300 ℃, with less than 5 % deviation between both results. Moreover, the overall package warpage had also been influenced by package size in the reflow temperature. In addition, the results lead to the suggestion that the thermal stress exerted on the contact surface between different material types could lead to PCB warpages. The present research has established FEA that obtaining good warpage prediction model. The insights attained from this study would be beneficial for PCB design improvement, by optimizing materials and dimensions of PCB, in the attempt to minimize the warpage occurrence.
Fpga based iris detection and recognition system
(2010-03-01)
Lee, Hoon Hoon
Iris detection and recognition is widely applied in areas that require high security requirements. The iris can be used as a living passport in national border control system or applied as a living password, birth certificates, driving licenses, credit card authentication and enforcing internet security where controlled access to certain web pages is necessary. Iris recognition is considered as one of the ideal biometric recognition component. This project basically explains the iris recognition system implemented using Digital Camera and Multimedia Development Platform consisting of the Altera DE2-70 board, 4.3” LCD Touch Panel Kit(LTM), 5 Mega Pixel Digital Camera Module(D5M). This project involves finding out the best way to capture the best iris image taking the lighting condition and the object distance into consideration. The hardware control of the camera, display panel and DE2-70 board is written in verilog codes. Then, image pre-processing is performed followed by extracting the iris portion of the eye image. The extracted iris part is then normalized, and iris code is constructed using cumulative-sum method. Finally two iris codes are compared to find the Hamming Distance, which is a fractional measure of the dissimilarity.
Gripper design of an underwater manipulator
(2010-04-01)
Ooi, Yuh Sheng
Gripper is an important part of a manipulator. Emulating the motion of a human hand is deemed to be challenging. This project proposes a same-sized and light-weight robotic hand designed and concerned with the feasibility of using control system to control 5 fingers robot hand. The mechanics of five-fingered robot hand is designed in way to mimic the human hand. Each finger of the robot hand has 1 degree of freedom which is actuated by only 1 servomotor and almost acts like a human finger. The function of tactile sensor is to provide the feedback signal to the microcontroller when the gripper holds an object. The Servo Motor chain drive is used to drive the sector of each robot hand’s finger. Furthermore, the servo motor can only provide a low torque for the finger, so the robot hand can only generate a suitable force for each finger. All the behavior and movement of the robot are processed by an FPGA. With further research and development, the robot hand can be used to implement in humanoid robot.
Identifying harmful pollutants from conventional energy system
(2000-01-01)
Projek ini adalah mengenai mengenalpasti bahan tercemar yang berbahaya yang terhasil dari sistem kuasa yang menggunakan jenis bahan api dan prinsip kerja yang berlainan. Pendekatan yang digunakan adalah mengenalpasti tahap pencemaran bahan yang terhasil dan semua parameter yang berkaitan menghasilkan bahan tercemar tersebut. Projek ini juga akan mengupas bagaimana jenis bahan api yang berlainan dalam sistem kuasa lazim akan memberi kesan kepada tahap pencemaran yang terhasil. Rangka projek ini ialah berdasarkan pencemaran yang terhasil dari stesen janakuasa yang menggunakan tiga jenis bahan api yang berbeza iaitu arang batu, minyak dan gas. Daripada stesen janakuasa yang berbeza, jenis bahan tercemar yang terhasil dari stesen janakuasa akan dikaji dan kaedah untuk mengawal tahap pencemaran akan dikupas. Semua parameter yang berkaitan dengan penghasilan bahan tercemar akan dikaji dan mencari alternatif untuk mengawal dan mengurangkan tahap pencemaran tanpa memberi kesan kepada kuasa yang akan dihasilkan oleh stesen janakuasa tersebut. Metodology bagi projek ini ialah dengan mendapatkan data dari setiap stesen janakuasa yang dipilih, mengkaji data, banding dan mengaitkan data yang diperolehi dengan teori. Projek ini juga akan melihat kepada aspek kerja rekabentuk bagi setiap stesen janakuasa bagi mencadangkan satu rekabentuk rujukan untuk stesen janakuasa yang akan menghasilkan tahap pencemaran yang rendah. Semasa proses tersebut, satu perhubungan relatif diantara jenis bahan api dalam sistem kuasa dan jenis bahan tercemar yang dihasilkan oleh stesen janakuasa. Pada akhir projek, apa yang diharapkan agar tercapai ialah satu rujukan rekabentuk bagi stesen janakuasa yang menggunakan sumber lazim dan menghasilkan pencemaran pada tahap rendah.
Inversed unnormalized distance-weighted k-nn: a kinect human motion classification model based on skeletal joints features
(2021-12-01)
Lee, Pui Yi
Human motion (HM) classification remains an active research field due to its wide applications in surveillance, robotics and medical disciplines. HM is commonly recognized from skeletal joint (SJ) coordinates extracted from videos, images sequence, or marker-based motion capture devices. Microsoft Kinect V1 (MKV1) is among the frequently used tool for its low-cost and capable marker-less motion tracks via sensors. Its datasets were captured in image sequence or video output at 30 fps recorded in RGB (red, green, blue) format, depth images, and SJ data (text file) forms. The SJ data includes coordinates for 45 (3D 15 joints) or 60 (3D 20 joints) (features × the total action captured). Previous studies have revealed that MKV1 is a reliable tool having excellent test-retest reliability, and valid for HM patterns assessments based on SJ detection. MKV1 dataset’s big dimensionality requires efficient Feature Selection (FS) analysis to achieve high classification efficiency in a short running time. Nevertheless, no study has applied FS based on Cronbach’s alpha analysis despite wide growth in FS algorithms’ applications. Additionally, previous works which considered the human SJ suffers from low classification accuracy and inconsistent performances across MKV1 datasets. Therefore, the present study aims to assess the reliable SJ indicators captured in MKV1, to determine the optimal subset of SJ for human motion FS, and to develop a human motion classification model of high accuracy and lowest running time. Each dataset’s reliability analysis was established on three indicators: internal consistency, inter-rater reliability, and intra-rater reliability. FS (FSSJFCA) was performed using the exhaustive search strategy and hybrid method. Filter was initially applied to obtained SJ feature combination based on Cronbach’s alpha reliability indicator for subsequent cross-validation mode classification. The Inversed Unnormalized Distance-Weighted k-NN classification algorithm was developed to segregate Kinect SJ data into motions’ classes. The strategy was deployed on three case studies: two datasets from public domains (UTKinect-Action3D and Florence 3D Actions) and an experimental dataset (USMKinect) involving nine to 16 simple daily HM activities. Findings show that the FSSJFCA improves classification accuracy (reduces total runtime) by 0% (54.63%), 0.1% (25.56%) and 0% (52.69%) in UTKinect-Action3D, Florence 3D Actions, and USMKinect dataset, respectively. The Inversed Unnormalized Distance-Weighted k NN developed achieved classification accuracy above 98% at a low total runtime ((2 - 3 seconds) and (40 seconds) for (31 × 6028) and (31 x 30693) dimension Kinect HM dataset respectively). The newly developed model, a combination of FSSJFCA and Inversed Unnormalized Distance-Weighted k-NN, outperformed 11 existing algorithms applied to UTKinect-Action3D and/or Florence 3D Actions datasets by 0.49% to 17.87% classification accuracy. The newly developed model has high practicability to classify human motion applicable in Artificial Intelligence, Machine Vision, Biomechanics, Image Processing, and Pattern Recognition.

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