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Friction stir alloying of immiscible magnesium alloy and mild steel with aluminium and carbon nanotubes as additives / Sufian Raja
No full textWith growing environmental concerns, the need for more energy-efficient vehicles is bigger today than ever, and producing lighter vehicle support structures is a promising way to increase efficiency. Magnesium alloys welded with steel propose the possibility of weight-efficient structures, with the stronger steel in critical locations and magnesium alloy in locations where a stronger material (usually heavier) is not required. Friction stir alloying (FSA), as a solid-state process, is shown to be a promising method for joining dissimilar/ immiscible metals by using additives to improve joint properties. Dissimilar materials joining AZ31-mild steel using Al-Mg additives and AZ61 magnesium alloy-mild steel using Al-CNT additives were successfully produced by the friction stir alloying process. Al-Mg powder additives were injected in a gap between AZ31 and the mild steel specimen’s butt prior to welding. The experiments were performed for different weight percentages of Al-Mg powder additives at welding speeds of 25 mm/min, 50 mm/min and 100 mm/min with a constant tool rotational speed of 500 rpm. The effect of powder additives and welding speed on tensile strength, microhardness, characterisation across welding interface and fracture morphology were investigated. Tensile test results showed significant enhancement of tensile strength of 150 MPa for 10% Al and Mg (balance) powder additives welded joint compared to the tensile strength of 125 MPa obtained for welded joint without powder additives. The loss of aluminium in the alloy is compensated by Al-Mg powder addition during welding under a suitable heat input condition identified by varying welding speeds. Microstructural analysis revealed that the Al-Mg powder was well mixed and dispersed at the interface of the joint at a welding speed of 50 mm/min. Intermetallic compounds detected in the welding interface contributed to the welding strength. In other material combinations, another promising magnesium alloy, AZ61 used to join with mild steel with Al-CNT additives by the friction stir alloying. Before welding, Al-CNT additives were too injected in a gap between the AZ61 and steel specimens. The experimentation was performed using different welding speeds while tool rotational speed was kept constant for varying weight percentages of carbon nanotubes (CNT) in Al powder. The influence of additives and welding speed on tensile strength and characterisation across the welding interface was studied. Tensile strength of joint with 3% CNT improved up to 222 Mpa. In terms of improving joint strength qualities, CNT has a significant impact. Al-rich Intermetallic compounds were found at the welding contact, while the formation of Al2MgC2 carbide was detected, which contributed to CNT strengthening effects all to improved welding strength
Design and development of mechanical amplifier structure for piezoelectric harvester in high force environment / Long Su Xian
No full textIn recent years, harvesting electrical energy from mechanical vibration by using piezoelectric material has become the main focus of many researchers in developing a sustainable energy harvester. This is useful for Wireless Sensor Network (WSN), where a replacement or replenishment of energy source, such as a battery is unpractical. From previous studies, the amount of energy generated by piezoelectric energy harvester (PEH) is very limited even in a high force environment. To solve this issue, a mechanical amplifier structure such as the Rectangular Cymbal structure is implemented to amplify the tensile loading force towards the piezoelectric. From the material strength perspective, this performance can be further enhanced by using a compressive-typed mechanical amplifier structure, as the compressive yield strength of piezoelectric material is 10 times higher than its tensile yield strength. In this study, a novel compressive Hull PEH is designed and developed. A coupled piezoelectric-circuit finite element model (CPC-FEM) is developed to evaluate the energy harvesting performance based on the power output and stress analysis. Parametric optimization has been carried out to further enhance the amplification effect and determine the relationship of each parameter on the power output. An improved FEA power output of 11.34 mW is obtained for the optimized Hull PEH under 1 kN of sinusoidal force at 2 Hz. It is 178% larger than the unoptimized Hull PEH and 308% larger than the benchmarking tensile-typed Rectangular Cymbal PEH. The developed Hull PEH has a volume power density of 1.817 kW/m3. An analytical force amplification factor of 9.72 is proven based on the kinematic theorem and the deformation of the frame. In the experiment, it exhibits at least 5 times larger voltage output than the benchmark case and at least 14 times greater than the standalone piezoelectric plate under impact force from a range of 10 N to 1 kN, with less than 5.2% of deviation to the FEA result. A maximum peak power output of 7.16 W is produced across a 50 kΩ of optimum load resistance. It is 37.68 times higher than that of the benchmark PEH under 1 kN of impact force. Meanwhile, 84.38% of energy conversion efficiency is achieved by the Hull PEH based on the average input and output energies. It shows a power output of 54 μW at 180 kΩ and 5.28 times higher voltage output than the Rectangular Cymbal structure under 10 N of sinusoidal force at 50 Hz. It has a slight deviation of 3.8% from the FEA result. Therefore, the reliability of the developed CPC-FEM has been proven. The Hull PEH is concluded to have better harvesting performance in both simulation and experiment despite the loading environment either in high or low force. Hence, a higher power output PEH with enhanced load capacity and amplification effect has been realized. It has a lower stress concentration and is more cost-effective than the benchmark case. The developed PEH holds great potential to act as a sustainable energy source for some microcontroller applications with an LTC-3588 energy harvesting circuit
Parents’ perspectives of the transition to independent living for young adults with autism spectrum disorder / Nik Nadia Nik Nazri
No full textAim: This present study aims to explore parents’ perspectives on the transition to independent living of young adults with ASD in Malaysia, particularly in the domains that define transitioning, namely; social participation, school and work opportunities. Methodology: Semi-structured interviews were conducted with 4 parents of young adults with ASD where they expressed their views and elaborate on the various challenges faced during the period of transitioning for their children related to these domains. Findings: All the parents held the view that the young adults with ASD were not ready for transition to independent living despite being of the age expected to. This is attributed to various factors including lack of public awareness, teachers’ limited knowledge of strategies for dealing with children with ASD, financial limitations to consider other alternatives and the limited number of centres that provide long term support were the issues raised by parents of young adults diagnosed with autism. As for parents of the young adult diagnosed with Asperger’s Syndrome, difficulty in social communication was consistently highlighted. However, they are hopeful for the future if there is an improvement in the awareness among society, schoolteachers and professionals, as well as increased efforts to create a more conducive and supportive school and working environment for your adults with ASD. Limitations: Repeating this study in rural areas and with more participants may increase generalizability of stud
Behavioural output of ahand goal-directed aiming task during rapid learning and neuromuscular fatigue / Elaheh Amini
No full textGoal-directed aiming task requires a highly accurate movement of the limb from the onset to the desired target. This aiming movement consists of two components, (i) the initial adjustment of a rapid phase that regulates limb direction and velocity to the vicinity of the target, and (ii) late error correction phase, where visual and other forms of feedback are utilized to reduce aiming errors. The integration of sensory information from visual, proprioceptive, tactile, spatial etc. to the brain for precision of movement planning transforms into speed, accuracy, and energy optimization. When confronting changes to these sensory inputs and external related factors occur (i.e., neuromuscular fatigue), subsequent alteration to movement planning occurs, which in turn affects behavioural output. Thus, these adaptations could affect internal model of governing goal-directed aiming. The aim of this thesis was to investigate the processes of sensorimotor adaptation of a hand goal-directed aiming task, confronting (i) changes in spatial (i.e., hand orientation) with and without directional visual feedback during and following rapid-learning phase, and (ii) challenges to neuromuscular fatigue during low and high force production.
It has been established that directional errors in a goal-directed aiming task are not consistent towards different targets in a workspace, which are commonly regarded as inherent bias. However, when there is a hand rotation, it is unknown whether the inherent bias shifts according to joint, muscle, and/or visual space in different component of goal-directed aiming task. In Chapter 3, the shift in inherent bias was analysed from neutral to pronated hand position at every 22.5 o and vice-versa. It was discovered that the shift in inherent bias is dominantly according to joint space rather than muscle or extrinsic reference frame.
Short-term adaptation is also known to have a distinct mechanism upstream to primary motor cortex (M1) which is evident through visuomotor and force-field tasks. In Chapter 4, this adaptation in a goal-directed aiming task was tested by manipulating hand orientations (neutral and pronated) during rapid learning phase (familiarisation) with visual feedback. Then, the directional errors and learning rate were compared between different hand orientations. It was discovered that it is highly probable for a goal-directed aiming task to have similar mechanisms to short-term adaptation, generally observed in motor adaptations. When visual feedback was removed, there was no additional learning for both hand orientations and errors remain consistent with subsequent trials, alternating between with and without visual feedback. Hence, it was concluded that higher centres are likely governing the internal model that controls the aiming task without visual feedback.
Low- and high-force fatiguing task are believed to be governed by different mechanisms (varying central and peripheral contributions). In Chapter 5, a goal-directed aiming was assessed following fatiguing tasks to determine the movement accuracy. The findings indicate that low-force fatiguing contraction (15% MVC) until task failure induces greater errors in goal-directed aiming task compared to high-force ones, even when the high neural drive before task failure were eliminated by inducing low-force fatiguing contraction for 70% of the time to task failure until task failure occurs. Hence, a goal-directed aiming requires greater central contribution and affects the control systems that are involved in task execution.
In summary, mechanisms involved in goal-directed aiming short-term adaptation are likely similar to other motor tasks i.e., visuomotor rotation. Central fatigue is also found to negatively affect the goal-directed aiming task performance. In addition, the inherent bias seen in a goal-directed aiming task shifts according to joint-space with hand rotation. The findings collectively provide insights to the factors contributing to the goal-directed aiming task models and in addition to better design of a motor control aiming task for rehabilitation purposes
Motivation for participating in continuous professional development among selected general practitioners in Kuala Lumpur, Malaysia: An exploratory case study / Low Kien Yong
No full textContinues Professional Development (CPD) activities are life-long learning
engagements for general practitioners. It can enhance their medical competencies across
cognition, psychomotor and affection domains, hence upholding safety and quality of
healthcare services. Literature reported that motivation drives learning among general
practitioners. However, limited studies explored the motivation from an educational lens.
This study explored motivation(s) from the Andragogy and Self-Determination Theory
perspectives in promoting active learning among general practitioners. This study also
explored their perceptions of the amended law enforcement in Malaysia that mandates
CPD participation. Three private general practitioners in Kuala Lumpur consented to
participate in this study. In-depth interviews were conducted using a semi-structured
interview guide. The participants were prompted to elaborate on their opinions and
provide examples. Recorded interviews were transcribed verbatim. The data were
analysed using thematic analysis to generate themes and codes. No new theme emerged
after the third interviewee. Private general practitioners were motivated when given the
freedom to choose their preferred learning style(s), coupled with a flexible learning
schedule and self-identified learning needs. Motivated general practitioners looked for
resonance by relating learnt knowledge with their daily practice. They enjoyed socialising
and professional networking elements of these learning activities. Their learning was
driven by internalised value and personal interest. They continuously improved their
competency to solve real-life problems at their workplace by learning. They perceived
the mandate as a positive reinforcement that acting as external motivation. However,
iv
measures on competence indicators after learning were desired. This study reported that
understanding motivation from an Andragogy perspective could promote learning among
general practitioners towards learning activities. Fulfilment of their autonomy,
relatedness and competency need could enhance learning motivations. Recommendations
are made for the CPD organisers on how to apply Andragogy and Self-Determination
Theory in curriculum development.
Keywords: Continuous Professional Development (CPD), Adult Learners, General
Practitioners (GPs), Andragogy, Self-Determination Theory (SDT
Commuting additive maps on tensor products of matrix algebras / Wong Jian Yong
No full textLet k ⩾ 1 and n1, . . . , nk ⩾ 2 be integers. Let F be a field and letMni be the algebra of ni × ni matrices over F for i = 1, . . . , k. Let
⊗ki=1Mni be the tensor product of Mn1 , . . . ,Mnk . In this dissertation, we obtain a complete structural characterization of additive maps ψ :
⊗k
i=1
Mni
→
⊗k
i=1
Mni satisfying
ψ(⊗k
i=1Ai)(⊗ki
=1Ai) = (⊗ki
=1Ai) ψ(⊗ki
=1Ai)
for all A1 ∈ S1,n1 , . . . ,Ak ∈ Sk,nk , where
Si,ni =
{
E(ni)
st + αE(ni)
pq : α ∈ F and 1 ⩽ p, q, s, t ⩽ ni are not all distinct integers
}
and E(ni)
st is the standard matrix unit inMni for i = 1, . . . , k. In particular, we show that
ψ :Mn1
→Mn1 is an additive map commuting on S1,n1 if and only if there exist a scalar
λ ∈ F and an additive map μ :Mn1
→ F such that
ψ(A) = λA + μ(A)In1
for all A ∈ Mn1 , where In1
∈ Mn1 is the identity matrix. As an application, we
classify additive maps ψ :
⊗k
i=1
Mni
→
⊗k
i=1
Mni satisfying ψ(⊗ki
=1Ai)(⊗ki
=1Ai) =
(⊗ki
=1Ai) ψ(⊗ki=1Ai) for all A1 ∈ Rn1
r1 , . . . ,Ak ∈ Rnk
rk . Here, Rni
ri denotes the set of rank
ri matrices inMni and 1 < ri ⩽ ni is a fixed integer such that ri ̸= ni when ni = 2 and
|F| = 2 for i = 1, . . . , k
Centralizing additive maps on rank Rblock triangular matrices / Muhammad Hazim Abdul Mutalib
No full textIn this dissertation, we study centralizing additive maps on block triangular matrix algebras. The main focus of this research is to classify centralizing additive maps on rank r block triangular matrices over an arbitrary field. Let k, n1, nk be positive integers with n1 + · · · + nk = n ! 2. Let Tn1,...,nk be the n1, . . . ,nk block triangular matrix algebra over a field F with center Z(Tn1,...,nk) and unity In. We first obtain a characterization of centralizing additive maps on Tn1,...,nk . Then, by using this preliminary result together with the classification of rank factorization of block triangular matrices, we characterize centralizing additive maps : Tn1,...,nk !Tn1,...,nk on rank r block triangular matrices, i.e, additive maps satisfying A (A) − (A)A 2 Z(Tn1,...,nk) for all rank r matrices A 2 Tn1,...,nk , where r is a fixed integer 1 1 upper triangular matrices
Characteristics study of carbon fibre material for BioApps RoMicP® foot prosthesis / Shen Wenhui
No full textIn this research project, to study the characteristics of materials used in BioApps RoMicP® Foot Prothesis and improve its performance in diferrent parts which are in different positions and can withstand different types of force. The material studies is the composite including Onyx and Carbon Fiber(CF) which were utilized in markforged Mark-Two 3-D printer to produce a light foot prosthesis with high performance and low cost. To investigate the mechanical properties, samples with different CF contribution way and with different components of carbon fiber were produced. Three types of mechanical test involving tensile test, compression test and 3-point bending test were conducted. Then, through calculation and analysis of the yield strenght, yield modulus respectively to get the most excellent design of each part. In tensile test, the testing sample with 80% Onyx and 20% carbon fiber embedded in the middle behaves best, its yield strength is 117.1 MPa and yield modulus in 2.065 GPa. In compression test, the specimenwith 10% carbon fiber printed in the middle showed the best performance, its yield strength is 5.03 MPa and yield modulus is 23.0 MPa. In 3-point bending test, the results of testing sample with 20% carbon fiber distributed at the both ends is most excellent, its flexural strength is 81.68 MPa and flexural modulus is 4.464 GPa. Therefore, according to the above results, we can design and print different parts in foot prosthesis to optimiza their performance
Phenotypic and genotypic characterisation of Klebsiella pneumoniae isolated from veterinary and clinical sources / Golnaz Mobasseri
No full textMultidrug-resistant (MDR) Klebsiella pneumoniae (K. pneumoniae) poses a serious public health threat. Strains that produce extended-spectrum beta-lactamases (ESBL) are becoming increasingly prevalent among hospital and community-acquired infections. More recently, MDR K. pneumoniae has been isolated from animal sources and potential transmissions between animal and human have also been reported. For better understanding of the importance of “one health” approach, this study described the antimicrobial susceptibility and resistance mechanisms of K. pneumoniae strains isolated from swine farms and a tertiary hospital in Malaysia. The genetic linkages of the strains from different sources were also determined. Swabs from pigs, farmers and environment as well as the feed were collected from 7 swine farms in Peninsular Malaysia. A total of 63 K. pneumoniae strains were isolated with the majority (79.3%) showed resistance to tetracycline. Twenty-two (35%) and 19 (30%) strains were identified as MDR and ESBL-producers, respectively. Among the ESBL producers, the presence of blaTEM (15/19), blaSHV (15/19), blaCTX-M-1 group (7/19) and blaCTX-M-2 group (2/19) have been detected. However, only class 1 integron-encoded integrase was detected. In addition, high resistance to colistin was detected (n=13), where 11 of them were resistant to at least one carbapenem antibiotic. Based on the PCR-sequencing analysis, majority of the colistin-resistant strains harboured blaTEM gene (92.3%), followed by blaSHV (69.23%), blaCTXM-1 (38.46%) and mcr-1 (23.1%). Three colistin-resistant strains had transferable plasmids and colistin-resistant gene, mcr-1. Based on the clustering analysis using Pulsed-Field Gel Electrophoresis (PFGE) and Repetitive Extragenic Palindrome-Polymerase Chain Reaction (REP-PCR), the 63 strains were genetically diverse. However, the clonal relationships of the strains from same sources have been identified. On the other hand, 97 clinical K. pneumoniae strains were analysed for antimicrobial susceptibility, all of which were sensitive to amikacin and colistin (except one strain), while 31.9 % and 27.8 % were MDR and ESBL-producers, respectively. The majority of MDR strains (26/27) were positive for blaTEM, followed by blaSHV (24/27), blaCTX-M-1 group (23/27), blaCTX-M-9 group (2/27) and mcr-1 (1/27). Thirty-seven strains were hypervirulent, and PCR detection of virulence genes showed 38.1 %, 22.7 % and 16.5 % of the strains were positive for K1, wabG and uge genes, respectively. Generally, all the strains were genetically diverse and heterogenous based on clustering analysis. Only seven clusters which comprised of 3-7 strains with high similarity (>80%) have been identified. Finally, one strain each from animal (KP2013Z28) and human (KP2014C46) sources were selected and subjected to whole-genome sequencing. The final draft genome sequences consist of the combined 5,718,777 and 5,455,584 bases with 56.9% and 57.7% G+C content in KP2013Z28 and KP2014C46, respectively. Antimicrobial susceptibility profile of these two K. pneumoniae strains showed resistance to several classes of antibiotics which correlated with genomic analysis that it indicated various antimicrobial resistance genes associated with resistance to various antibiotics. This study has drawn attention to emergence of antimicrobial resistance in clinical setting and animal husbandry which should be taken seriously to prevent the spread and treatment failure due to antimicrobial resistance
Assessment of slope bioengineering practice on soil hydrological regimes at Guthrie Corridor Expressway, Selangor / Aimee Halim
No full textThe removal of vegetation and cutting of hillslopes for development has radically disturbed the balance of soil hydrological networks and resulted in slope instability or susceptibility to failure. Meanwhile, the oversupply of water flow into soils during intense or prolonged rainfall could lead to surface runoffs, which wear away the topsoil and ensue accelerated soil erosion. Accordingly, this calls for more effective slope management and bioengineering practice; hence, this study aims to address the influence of vegetation on soil hydrological components and identify the key parameters related to hydrological performances in combating slope erosion. In this study, three experimental plots were set up on the eroded cut slope at the Guthrie Corridor Expressway, Selangor, Malaysia, comprising three coverage treatments: bare (control), less dense (50% of plant coverage), and dense (80% of plant coverage) with potential pioneers of Lantana camara, Melastoma malabathricum, and Bauhinia pupurea. The study area entails sandy clay loam soil derived from the meta sedimentary rock with more quartz and weathering grade III to IV. Based on the electrical resistivity survey, the study area could contribute to slope failure due to its highly conductive characteristic, especially during intense rainfall when the water inputs into the soil are high. After two years of revegetation practice, the dense plot exhibited the highest reduction in bulk density by 52% and the highest increment in total porosity by 45.8%, thus enhancing the infiltration capacity of the slope soil. The dense plot had also positively increased the hydraulic conductivity by 73.8%, followed by the less dense plot with 30.85%. Besides, the right plant species selection and mix- culture practice displayed the best performance in soil moisture, organic matter, carbon storage, microbial abundance, and cation exchange capacity, thereby representing positive effects on soil quality and fertility. The measured erosion rate was also reduced between 10 to 15 t h-1 year−1 and this verifies a positive interaction between plant and soil, besides providing a better perspective towards the changes of soil hydrological properties. Based on the findings, L. camara in the dense plot recorded the highest photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency, followed by M. malabathricum and B. purpurea. Hence, this implies the light utilization efficiency of plants’ leaves during the photosynthesis process, which further influences the growth performance of the plants. In terms of plant hydraulic pattern, the shoot hydraulic conductance was lower than the root hydraulic conductance for all species, thereby indicating the plants’ strategy in dealing with the conflicting balance between evaporative demand and protection from hydraulic failure. Furthermore, the significant key parameters to control slope erosion through a bioengineering practice include soil porosity, fungal/bacterial ratio, soil respiration rate, soil organic matter, and plant shoot hydraulic conductance. Overall, based on the interpretation of the research results, the selection of the right pioneer species and dense vegetation coverages are decisive for the improvement of the soil-plant hydrological cycle on the selected slope, which features a notable capacity for the provision of a better slope ecosystem and promotes a promising alternative solution for slope soil reinforcement and stabilization